elevation of about 2,000 feet above the sea up the mountainsides nearly
to timber-line, and flourishes alike in the hot, arid valleys and in
regions bordering on perpetual snow and ice. One beautiful feature of
the silver-pine forests is their open, park-like character. The trees
stand far apart, and thus have room to reach not only a great size,
but a remarkable degree of perfection of form. Between the
islands of shade on the sunlit ground there is usually but little
undergrowth, and the far-extending natural pastures permit one to ride
in any direction without inconvenience.

One other pine of the widely extended Pacific forest demands attention
even from the passing traveller, not on account of its size, for it is a
dwarf in a land of giants, but for its wide distribution and the food
its large, oily seeds furnish for birds, squirrels, and even for man. I
refer to the piñon pine, of which there are several species. They are
seldom over 35 or 40 feet high, and are not remarkable for beauty,
although they furnish an agreeable feature in the sparsely
forest-clothed and semiarid region where they thrive best, but they bear
a profusion of small cones, each of which contains perhaps a dozen
edible and nutritious seeds. These seeds were formerly used by the
Indians for food on an extensive scale, and are still gathered in large
quantities, and may be found in the markets of our cities. The Indian
encampments in the piñon forests in the fall of the year are among the
most picturesque features of these degenerate days of the aborigines.

In the southwest portions of the United States the forests are confined
to the mountains and the higher table-lands, the hot, arid valleys being
without trees other than the larger growths of cacti and yucca. Similar
conditions are present in northern Mexico, but on the western side of
that republic and throughout practically the whole of the peninsula of
Lower California the mountains and valleys alike are treeless and
desolate.

As stated by C. S. Sargent, the forests of North America, exclusive of
Mexico, Central America, and the West Indies, contain arboreal
representatives of 158 genera of plants, of which 94 genera occur in the
Atlantic and 59 in the Pacific side of the continent, and 48 genera in
the tropical portion of southern Florida. Of the number of genera of
trees in the Caribbean forest we have no reliable census.

                PRAIRIES, TREELESS PLAINS, AND PLATEAUS

To the west of the Atlantic forest lie the broad natural meadows termed
prairies, and still farther west the yet more extensive pasture-lands of
the great plateaus which reach the eastern base of the Rocky Mountains
(Fig. 28). The transition from the luxuriant and varied forest on the
east to the treeless, thinly grass-covered plateaus on the west side of
the interior Continental basin is gradual. The change occurs in the
prairie region, where a struggle has been in progress for thousands of
years between the conditions favouring and those adverse to tree growth.
The balance of power, so to speak, is the amount of rain or of
soil-stored moisture during the summer season. The gradual decrease in
the mean annual precipitation from east to west on the inland border of
the Atlantic forest continues westward, and on the plateaus adjacent to
the Rocky Mountains the aridity is such that no trees can grow except
along the immediate border of the stream, unless artificially irrigated.

The explanation of the absence of trees in the central and western
portions of the interior Continental basin is found in the mean annual
rainfall and the manner in which it is distributed throughout the year,
together with variations in the texture and composition of the soil, and
the disturbances in the natural conditions brought about by fires. The
question, "Why are the prairies treeless?" has been variously answered
by different observers. The outcome of a long discussion in this
connection seems to be that the main cause of the absence of trees lies
in the climatic conditions and principally in the lack of sufficient
rain during the long, hot summers. Arid regions the world over are
without forests, but the Prairie plains cannot be said to be arid; in
fact, the mean annual rainfall over the greater portion of this region
is equal to or exceeds that of many well-forested countries, averaging
as it does in general about 30 inches. But the prairies lie between the
more humid forest-covered regions on the east and the less humid or
subarid plateaus on the west, and during the summer season
droughts and hot, scorching winds are of common occurrence. It is the
long dry summer that establishes the critical conditions, particularly
about the eastern and northern borders of the prairies. Of secondary
importance is the character of the soil. An exceedingly fine soil, like
that of the prairies, as has been pointed out by J. D. Whitney, by
excluding the air from the roots of trees is detrimental to their
growth. Where the dryness of the summers make the lives of trees
precarious the nature of the soil, whether coarse or fine, becomes the
controlling factor. In the prairie region where the soil is more open
and porous than usual, although other conditions remain the same, as in
the Cross Timbers of Texas, trees flourish; while intervening areas
where the soil is fine are typical prairies. Again, where the climatic
conditions become critical, as during long, dry summers, the grass and
other vegetation burns readily, fire spreads rapidly and widely, and
young trees are destroyed. In the prairie region, as pointed out by J.
W. Powell, the Indians were formerly in the habit of burning the grass
each summer in order to insure more favorable pasturage for game during
the succeeding spring. This annual burning kept back the forest and led
to the eastward extension of the prairie.

During the past decade many groves have been planted on the prairies,
and have flourished, especially when the adjacent fields are cultivated
so as to allow the earth to store a larger share of the winter rain; the
success of this tree planting, it has been claimed, is evidence that the
nature of the soil is not a determining factor in the problem, because
trees will grow if protected from fire. The success of arboriculture on
the formerly treeless plains and plateaus, however, decreases as one
travels westward. On the western border of the prairies and on the great
plateaus, remote from streams, trees can be made to grow only by the aid
of irrigation. If this region had never been swept by fire it is safe to
say it would still be treeless. Each of the explanations referred to
above to account for the treeless condition of the prairies--one
referring it to soil conditions, and the other to the former prevalence
of fires--certainly has much in its favour, and for certain localities
seems satisfactory, but each point of view should include a broader
range and recognise the fact that the requisite critical conditions have
been furnished by wide-reaching climatic causes. The Prairie plains
furnish but one phase of the gradual change that occurs in the natural
mantle of vegetation when traced from the dense, well-watered forests of
the Appalachians and the Alleghany plateau westward to the semiarid and
truly arid lands of the great plateaus and Rocky Mountain region, where
only such plants as are able to withstand long-continued drought can
grow. This same broad conclusion is sustained also at the north, where
the prairie dovetails, as it were, with the subarctic forest.

The general or underlying reason for the treeless condition of the vast
central portion of the continent is doubtless a lack of sufficient rain.
The precipitation that does occur comes mainly during the winter season,
when the land is colder than the ocean; in summer the land becomes
highly heated and imparts its temperature to the air, which thus has its
capacity for moisture increased, and prolonged droughts occur. At the
south, in Mexico and the adjacent portion of the United States, the
trade-winds blow over a region which is more highly heated than the
ocean from which they come, and are hence drying winds. To the west of
the Great plateaus rise the Rocky Mountains, where climatic conditions
are different on account of elevation, and, as we have seen, forests
occur at considerable elevations, but not in the broader valleys. The
conditions unfavourable for tree growth are continued and even
intensified in the valleys of the central portion of the Pacific
mountain region, and culminate in the deserts of the Great Basin and
western Mexico. Throughout all of this vast treeless region the
controlling condition is deficiency of moisture, particularly during the
summer or growing season.

The nearest approach to desert conditions to be found in North America
occur in the valley of Utah and Nevada and the southern portion
of the Great Basin region in Arizona and Mexico. The bottoms of these
valleys are, in some instances, occupied by shallow lakes in winter,
when scanty rains occur, but during the long, hot summers they become
completely desiccated, and are then broad expanses of hard mud, cracked
by drying so as to resemble a tessellated pavement of cream-coloured
marble. These mud-flats or _playas_ are frequently absolutely without
plant life. Excepting the playas, however, and, in numerous instances, a
narrow belt of ground encircling them, which is white with efflorescent
salts, the valleys of even the most arid portion of the Great Basin
region are generally plant-covered. The most common and most widely
spread of the shrubs on these shadeless plains is the sage-brush. So
characteristic is this plant of countless valleys from Canada to Mexico
within the general region of the Pacific mountains that to one familiar
with the country the term "sage-brush land" brings to mind the leading
features of the region designated. The sage-brush lands are far from
being desert areas, however, for in early spring a profusion of low,
sweet-scented flowers bloom beneath the gray-green _Artemisia_, and
sufficient bunch-grass to sustain considerable herds may be expected in
the same localities.

The vast, irregular belt of forest encircling the central treeless
portion of the continent also dies out on its northern border, where the
subarctic forest is succeeded northward by the Barren Grounds and tundra
plains. Clearly the explanation of the absence of trees in the prairie
region and the adjacent plateaus cannot be applied to scarcely less
extensive treeless plains at the far north, where rain falls in summer
and the soil is always abundantly charged with moisture. It needs no
argument to show that the control among the conditions governing tree
growth at the north passes to the temperate element of climate, and that
the timber-line is there determined, as it is on high mountains, by the
severity of the winters' storms and frosts and the shortness of the
summers.

                       THE TREELESS MOUNTAIN TOPS

On the higher mountains of North America above the upper limit at which
trees are able to grow there are picturesque regions carpeted and
garlanded in late spring and summer with lovely flowers, the
indescribable charms of which are only known to those who rejoice in
climbing rugged peaks and in following the trails of the mountain-goat
along sharp-crested ridges. The gorgeous blossoms of these roof-gardens
of the world are much the same on all high mountains in temperate
latitudes, but from having become first widely known to civilized man on
the mountains of Switzerland, are generally termed alpine flowers. The
most attractive features of an alpine flora, which springs into bloom as
soon as the snow melts and forms a rapidly widening belt of colour as
the margins of the snow-fields recede higher and higher, is the great
profusion of brilliantly coloured blossoms. No sooner does the snow of
winter melt than the moist ground becomes enamelled in brilliant colours
on account of the springing up and quick blossoming of millions of hardy
plants. The growing season on mountain heights is short, but the sun's
energy is there more intense and the hours of light each day longer than
in the valleys below, and the plants adapted to such conditions pass
through their annual circle of changes from sprouting seed to mature
fruit with remarkable rapidity. In many instances the mountain-climber
finds beautiful lilies unfolding their sun-dyed blossoms at the bottom
of well-like depressions in lingering snow-banks. The gleaming
mountain-peaks when seen from afar are said to be crowned with snow, but
the mountaineer rejoices in the knowledge that their cold diadems are
wreathed and festooned about their lower margins with lovely blossoms.
Many mountains less ambitious than their neighbours have the garlands
without the crown. An alpine flora is present on the Pacific mountains
from Mexico northward to Alaska. Like the "timber-line" and the
"snow-line," the intermediate belt of profusely flowering herbaceous
plants descends lower and lower with decrease in latitude; on the great
volcanic cones of Mexico it has an elevation of over 15,000 feet;
on the Sierra Nevada the greatest wealth of flowers occurs at about
12,000 feet; on Mount Rainier widely extended gardens resplendent with
rainbow tints occur at 7,000 to 8,000 feet; and about the foot-hills
near Mount St. Elias, at an elevation of 2,500 feet or less above the
sea, every knoll and island-like area in the vast ice-fields is so
densely overgrown with brilliantly flowered plants that one has to part
the rank growths with his hands and press them aside with his alpenstick
in order to force a way through the fields of bloom. Admirers of
nature's loveliness who have not climbed to aspiring heights will find a
new and beautiful world in the public alpine garden on the summit and
about the snow-fields of the higher portions of the Pacific mountains,
where no sign-boards forbid entry and no fences obstruct the way. In
these regions nearest the sun and stars there are few, if any, plants of
utility to man, but marvellous beauty and lavish profusion fill the
foreground in every view. These glorious mountain heights have their
use, however, although as yet known to but few; rest and recreation amid
scenes at the same time novel and most inspiring may there be found by
the toilers in our crowded cities.

Among the Atlantic mountains only a few summits attain a sufficient
elevation to claim a wreath of alpine flowers. Something of the nature
of the gorgeous fields of bloom about the great peaks of the Pacific
mountains is suggested on the treeless summits of the White Mountains,
but although classed by botanists among alpine floras, the plants
growing there fail to give a true idea of the display characteristic of
the mountains which make a nearer approach to the lower limit of
perennial snow. In the southern Appalachians the absence of a luxuriant
alpine flora is perhaps more than counterbalanced by the profusion of
rhododendrons, azaleas, and laurels.

One instructive lesson suggested by this hasty glance at the plant life
of North America is furnished by the quick response that vegetation
gives to conditions of environment. Throughout the greater
divisions of the forest, prairies, grass-covered plains and valleys, and
flower-decked mountain heights there are constant variations from
locality to locality in the plant life to meet seemingly obscure or but
slight changes in the conditions of temperature, humidity, exposure to
sunlight, soil composition, soil texture, etc.; and besides there is a
never-ceasing struggle for existence among the plants themselves which
leads to important modifications of a flora. These changes occur from
locality to locality, frequently within a short radius, but more than
this, the resultant of the various modifying conditions on which plant
life depends are not constant even for a given locality. The study of
extinct floras has shown that during the preceding ages in the earth's
history marvellous changes in the plants of many regions, and, in fact,
of the entire earth's surface, have taken place. The distinct
impressions of palm-leaves, for example, are commonly found in the rocks
of the Cascade Mountains, where spruces, firs, and cedars now dominate
the landscape. Still more striking is the fact that even treeless
Greenland and the largely ice-covered islands of the arctic archipelago
were formerly clothed with forests as luxuriant and varied as those now
growing in the southern Appalachian region. Although the migrations of
existing forests during the few centuries of which we have historic
records have been too slow to be appreciated by man, yet it is safe to
conclude that changes similar to, and in fact a continuation of, those
known by geologists to have taken place in the distribution of the
vegetation of the continent since the Tertiary period are still in
progress. With far-reaching and exceedingly slow changes in climatic
conditions and in elevation above the sea due to upheaval and
denudation, the plants of our forests, prairies, and mountainsides, are
being moved here and there, in ever-changing combinations. Nature thus
secures a rotation in the vegetation of a region, as the careful
husbandman varies his crops from year to year. The suggestion in this
connection furnished by geologists is that we are living in a
spring-time following the great winter, known as the Glacial epoch, and
that the tropical, temperate, and subarctic forests are migrating
northward in an orderly march, and each in turn ascending higher and
higher on the more lofty mountains.

                               LITERATURE

  MUIR, JOHN. _The Mountains of California._ T. Fisher Unwin,
    London, 1894.

  PINCHOT, GIFFORD. _A Primer of Forestry._ United States Department
    of Agriculture, Bulletin No. 24, Washington, D. C., 1899.

  SARGENT, C. S. _Report on the Forests of North America._ Tenth
    Census of the United States, vol. ix, Washington, D. C., 1884.

  United States Geological Survey. Reports on Forestry.

                                CHAPTER V

                               ANIMAL LIFE

A common ground to zoologists and geographers in the exploration of
which they derive mutual pleasure from assisting each other, is the
geographical distribution of animals. In this connection the fauna of
North America presents perhaps even more interesting problems than does
its flora.

             GENERAL PRINCIPLES OF GEOGRAPHICAL DISTRIBUTION

In the study of the distribution of animals over a continent, the
discovery of the laws determining the intangible boundaries which the
members of a species may not pass is even more difficult than the
similar task in the case of plants. Plant species for the most part
advance and retreat slowly as conditions change, and, with minor
exceptions, there is no freedom of movement for the individual; but
animals, and especially the higher forms, are sensitive to even slight
changes in their environment, and there is more or less individual
freedom to travel over the land, to fly through the air, or to swim
through the water. Why the members of a given species which have
apparently unlimited power to travel should be confined to a certain and
frequently a narrowly circumscribed area has excited the curiosity of
man for many centuries.

A point is gained in reference to the distribution of animal species
when it is remembered that animals are either directly or indirectly
dependent on plants for food, and it follows that if plants, as we have
seen, are so largely controlled in their distribution by climate, the
secret of the distribution of animals is to be sought in the same
direction. When a thoroughly satisfactory classification of
climatic provinces is arrived at, it will no doubt be found to agree
with the larger features of plant distribution, and should coincide,
although perhaps less definitely, with the major divisions into which
the zoologist partitions the earth's surface. This principle has been
recognised by C. Hart Merriam in subdividing the United States into
"life-zones and crop-zones," and in the following pages his view will be
discernible, although losing much of their clearness by reflection.

_The Place of North America in the Life Realms of the Earth._--The
geological distribution of animals has been critically studied by P. L.
Sclater, A. R. Wallace, T. H. Huxley, and others, and the entire land
area of the earth subdivided into realms, regions, etc., in such a
manner as to indicate the present grouping of animals. One of the latest
of these broad views of the life of the earth is presented by Richard
Lydekker, who, from the evidence furnished by both living and extinct
mammals, has divided the world into three great "realms," two of which
are again subdivided into "regions," as follows:

                    { 1. Australian region.
    Notogæic realm  { 2. Polynesian region.
                    { 3. Hawaiian region.
                    { 4. Austro-Malayan region.

    Neogæic realm        Neotropical region.

                    { 1. Malagasy region.
                    { 2. Ethiopian region.
    Arctogæic realm { 3. Oriental region.
                    { 4. Holarctic region.
                    { 5. Sonoran region.

In this classification, North America falls in part in two realms, the
_Arctogæic_ and _Neogæic_, the former embracing the table-land of
north-central Mexico and all of that portion of the continent lying to
the northward, while the lowland of Mexico, together with Central
America and the West Indies, falls in the latter realm. The Arctogæic
includes also nearly the whole of the eastern hemisphere. The
relationship expressed in this classification of both the living and
extinct mammalia of North America to that of Eurasia, is supposed to be
due to a former land connection between the Old and the New World
at Bering Strait, and is most clearly marked by northern species, the
intercontinental bridge being too far north to be available for southern
forms. The mammals and many of the other animals of the low, hot borders
of Mexico and of Central America are a northward extension of the fauna
of South America--that continent constituting nearly the entire Neogæic
realm. The mammals of the West Indies are few in species, and have their
nearest relationship with the fauna of the continent to the southward.

                      LIFE-REGIONS AND LIFE-ZONES

The detailed study of the zoology of North America is far from complete,
but the voluminous results reached have led to several attempts at broad
generalization in reference to geographical distribution. Important and
highly instructive memoirs have been presented in this connection by J.
A. Allen, Angelo Heilprin, E. D. Cope, and others, who have in the main
attempted to correlate the distribution of animal species, but
principally the mammals, with variations in mean annual temperature.
Among the latest of these contributions, and marking the advance made at
the close of the nineteenth century, is the classification proposed by
C. Hart Merriam, already referred to in the sketches that have been
given of the climate and of the flora of the continent. The basis for
this classification is the seemingly well-determined law that the
northward distribution of terrestrial animals and plants is controlled
by the sum of the positive temperatures for the entire season of growth
and reproduction, and that the southward distribution is governed by the
mean temperature of a brief period during the hotter portion of the
year. By "positive temperatures" is meant the sum of the mean daily
temperature above that which determines the period of physiological
activity in plants and of reproductive activity in animals, assumed to
be 6° C. or 43° F. The exact length of the period to be taken as the
hottest portion of the year has not been definitely determined, but
must be short enough to fall within the hottest part of the
summer in high northern latitudes, and probably increases in length from
north to south; the time assumed is the six hottest consecutive weeks of
the year.

On the basis just stated, Merriam has divided North America into the
following life-regions and life-zones:

 +--------+---------+---------------+---------------------------------+
 |        |         |               |      Governing Temperatures     |
 |        |         |               +-----------------+---------------+
 |        |         |               | NORTHERN LIMIT  |SOUTHERN LIMIT |
 |        |         |               +-----------------+---------------+
 | Realms | Regions |    Zones      |  Sum of normal  |Normal mean    |
 |  of    |         |               |   mean daily    |temperature of |
 |  Ly-   |         |               |  temperatures   |the six hottest|
 | dekker |         |               |   above 6° C.   |consecutive    |
 |        |         |               |    or 43° F.    |   weeks       |
 +--------+---------+---------------+--------+--------+-------+-------+
 |        |         |               | Deg. C.| Deg. F.|Deg. C.|Deg F. |
 |        |         |{Arctic        |        |        | 10[3] | 50[3] |
 |        |{Boreal  |{Hudsonian     |        |        | 14[3] |57.2[3]|
 |Arcto-  |{        |{Canadian      |        |        | 18    | 64.4  |
 |  gæic  |{        |{Transition    |  5,500 | 10,000 | 22    | 71.6  |
 |        |{Austral |{Upper austral |  6,400 | 11,500 | 26    | 78.8  |
 |        |         |{Lower austral | 10,000 | 18,000 |       |       |
 |Neogæic |Tropical |(At present    |        |        |       |       |
 |        |         | unclassified) | 14,500 | 26,000 |       |       |
 +--------+---------+---------------+--------+--------+-------+-------+

[3] Estimated from insufficient data.

The boundaries of the regions and zones given in the above table are
shown on the map facing page 173, but for detailed information
concerning the basis of the classification the reader is referred to the
monographs by Merriam mentioned at the end of this chapter. In the
publications referred to lists are presented of the resident mammals and
birds characteristic of each region and of its subdivisions to the north
of Mexico. While the boundaries shown on the accompanying map can be
recognised in nature by the naturalist and serve a useful purpose, to
the unskilled observer each region would appear to blend with its
neighbours by intangible gradations. In fact, in this, as in the case of
so many other similar instances in nature, there is an absence of
definite, or what may be termed hard and fast lines. The significance of
the boundaries referred to, to the unskilled observer, is still more
obscure by the fact that the migratory birds, and to some extent the
mammals, annually pass from one zone to another, and besides,
several conspicuous mammals and birds are permanent residents in more
than one zone.

                              THE MAMMALS

The relation of the mammals of North America to the similar animals now
inhabiting other portions of the earth may be briefly shown by
indicating the distribution of the orders into which the mammalia are
divided. It will be remembered that in general each order is subdivided
into families, these again into genera, the genera into species, and a
species may contain several varieties. The classification here adopted
is the one used by Lydekker in his Manual of Palæontology. An order when
represented in the fauna of a continent is indicated in the following
table by a plus, and when absent by a minus sign.

                            CLASS--MAMMALIA

 +-------+-------------+--------------------+--------------------------+
 |       |             |                    |    DISTRIBUTION          |
 | Sub-  |             |                    +---+---+----+------+------+
 |Classes|     Orders  |      Examples      | N.| S.|Eur-|      |Aus-  |
 |       |             |                    |Am.|Am.|asia|Africa|tralia|
 +-------+-------------+--------------------+---+---+----+------+------+
 |      {|1. Primates  |Man, lemurs,        | + | + | +  |  +   |(Man) |
 |      {|             |apes, monkeys.      |   |   |    |      |      |
 |      {|2. Chiroptera|Bats.               | + | + | +  |  +   |  +   |
 |      {|3. Insecti-  |Moles, shrews,      | + | + | +  |  +   |  -   |
 |      {|     vora    |hedgehogs.          |   |   |    |      |      |
 |      {|4. Carnivora |Lions, tigers, cats,| + | + | +  |  +   |  -   |
 |      {|             |dogs, seals, etc.   |   |   |    |      |      |
 |      {|5. Rodentia  |Beavers,  rats,     | + | + | +  |  +   |  +   |
 |      {|             |mice, squirrels,    |   |   |    |      |      |
 |      {|             |rabbits.            |   |   |    |      |      |
 |Eu-   {|6. Ungulata  |Ox, horse, elephant,| + | + | +  |  +   |  -   |
 |theria{|             |tapir, etc.         |   |   |    |      |      |
 |      {|7. Sirenia   |Dugong and          | + | + | +  |  +   |  +   |
 |      {|             |manatee.            |   |   |    |      |      |
 |      {|8. Cetacea   |Whales, dolphins,   | + | + | +  |  +   |  +   |
 |      {|             |narwhals.           |   |   |    |      |      |
 |      {|9. Edentata  |Sloths, armadillos, | + | + | +  |  +   |  -   |
 |       |             |ant-eaters.         |   |   |    |      |      |
 +-------+-------------+--------------------+---+---+----+------+------+
 |Meta-  |10. Marsu-   |Kangaroos, opossums,| + | + | -  |  -   |  +   |
 |theria |     pialia  |etc.                |   |   |    |      |      |
 +-------+-------------+--------------------+---+---+----+------+------+
 |Proto- |11. Monotre- |Ornithorhynchus,    | - | - | -  |  -   |  +   |
 |theria |      mata   |echidna             |   |   |    |      |      |
 +-------+-------------+--------------------+---+---+----+------+------+

1. Of the _primates_, exclusive of man, the monkeys are the only
representatives in North America. Several species are common in Central
America, but they are absent from the West Indies, and do not occur
north of the _terra caliente_ of Mexico.

2. The bats are world-wide in their distribution, and several genera and
species occur on this continent, their northern limit being in central
Canada; during the winter in the United States and Canada they hibernate
largely in caverns. One family of the _Chiroptera_, the leaf-nosed bats
(_Phyllostomatidæ_), are strictly American, having their principal
habitat in the southern continent, but ranging as far north as the West
Indies, Mexico, and southern California. These are the vampires of which
many harrowing tales are told. The Central American species are small,
not larger than an English sparrow, but do not hesitate to attack
cattle, and even men.

3. The insect-eating mammals are represented by a large number of genera
and species, of moles and shrews, but hedgehogs are absent.

4. The flesh-eating animals are well represented by the cats (jaguars,
panthers, and lynxes), wolves, bears, racoons, martens, etc. Many
species of the seal family occur about the entire coast-line from Panama
to the Arctic Ocean. The lion, tiger, leopard, hyena, are absent.

5. The rodents are present in great numbers not only of individuals, but
of species and genera; as rats, mice, jumping-mice, squirrels,
porcupines, beavers, rabbits, etc.

6. The hoofed animals, _ungulates_, are represented by the bison,
musk-ox, several deer, antelope, mountain-sheep and mountain-goat,
tapir, and swine (peccary). Abundant remains of extinct species of the
horse family have been found, ranging far back in geological time, but
native horses are not known to have existed since the coming of
Europeans. The most notable vacancies in this order in the living fauna
are the rhinoceros, hippopotamus, camel, giraffe, and elephant, although
these are abundantly represented by fossil forms.

7. The _Sirenia_, which includes certain large herbivorous marine
mammals of wide distribution, are represented on the borders of the Gulf
of Mexico and the Caribbean Sea by the manatee.

8. The _Cetacea_ are present in the marine waters adjacent to the coast,
more especially in the north, where whales of several species, dolphins,
the narwhal, etc., are found.

9. Of the _Edentata_, which are so characteristic of the fauna of South
America, and with one exception (the scaly ant-eater, not found in
America) do not occur in the Old World, only the armadillo can be
credited to North America; of this, two species occur from Texas
southward.

10. The marsupials, found nowhere else in the world to-day except in
Australia and America, are represented by the opossum, of which two
species are common in the United States.

11. The lowest known order of the mammalia, the _Monotremata_,
represented in Australia by the duck-billed platypus (Ornithorhynchus)
and the _Echidna_, is unknown in America.

Considered in reference to their abundance, large size of individuals,
and number of species, in comparison with the other orders present,
North America may be said to be the home of _herbivores_. The only
continent in rivalry with it in this respect is Africa. More abundant in
individuals and species than the herbivorous mammals, however, but
smaller in size and frequently diminutive, are the rodents. The
carnivores are fortunately limited in number of species, although the
individuals of certain species are at times numerous, but not in general
dangerous to man.

                       SOME REPRESENTATIVE MAMMALS

To the general reader the animals of greatest interest are no doubt the
mammals, and particularly those which attract the sportsman, are of
value for food, or furnish fur and skins for clothing. Of such animals
the northern portion of North America and the mountains extending
southward into the austral region furnish a large number.

_The Musk-Ox._--In the far north, mostly beyond the arctic circle, lives
the musk-ox, the hardiest of herbivores, in which, as expressed in its
generic name, _Ovibos_, there is a curious mingling of the
characteristics of the sheep and the ox. The teeth are similar to those
of the sheep, the female has but two mammæ, and beneath the long
yellowish-brown hair of the outer coat there is a thick wool-like
growth. Its gentle, inoffensive nature is also similar to that of the
sheep. The large feet and the horns, however, are like those of the ox
tribe. The horns resemble those of the Cape buffalo, being broad at the
base and covering nearly the entire forehead. They slope downward at the
sides, and then curve forward and outward, at the same time tapering to
a sharp point, which renders them efficient weapons. These
characteristics, although intermediate between those of the sheep and
the ox, are more strongly inclined to the former. In reality, however,
the musk-ox is more goat-like than sheep-like, as is indicated by its
covering of hair, its short sturdy legs, the cannon-bone being
remarkably short, and its ability as a climber.

A full-grown musk-ox measures about 8 feet in length, inclusive of the
short tail, and is 3 feet, 8 or 9 inches in height at the shoulders. The
thick-set, shaggy body is supported on short stout legs, and the feet
are broad, to serve both as scrapers in clearing away the snow from the
moss and herbage on which it lives and in climbing ice-covered slopes.

Its range is over the Barren Grounds of Canada, the islands of the
arctic archipelago, and the border of Greenland. Peary found it grazing
in herds in the far north of Greenland beyond the inland ice, and was
saved from starvation by the food it furnished. Although hardy and well
adapted by nature to withstand the most severe cold, it moves southward
over the Barren Grounds in winter and to some extent at least seeks
shelter in the subarctic forest, but apparently does not pass to the
southward of latitude 59°. Like certain other animals of the northern
portion of the continent, its habitat is to the northeastward and it is
unknown in Alaska.

Bones of the musk-ox found in the frozen soil of Siberia indicate that
it formerly had a circumpolar distribution. A skull obtained near Salt
Lake City, Utah, in 1871, and the presence of its bones in the
superficial deposit of Europe as far south as the Pyrenees, show that it
formerly lived far to the southward of its present southern limit. This
was during the Pleistocene division of geological history, when glacial
ice covered all of Canada and the arctic animals were crowded southward.
As the ice melted and its southern margin receded, the musk-ox moved
northward. The absence of this species in northern Europe and Asia,
where the climatic conditions, nature of the vegetation, etc., are
similar to those of its present home, is perhaps due to the influence of
man. The successful introduction of the domesticated reindeer into
Alaska suggests that beneficial results would follow the transplanting
of the musk-ox to northern Siberia.

_The Polar Bear._--About all of the northern coast-line of America,
including the shore of Bering Sea and Baffin Bay, lives the well-known
polar bear, which is circumpolar in its distribution. The wide range of
this the most northern of the bear tribe is due not only to its strength
and ability to make long journeys over rough ice-floes and the wide
distribution of the animals it feeds upon, principally the hair-seal,
but is aided by the fact that it takes to the water readily and is a
good swimmer. It has also been known to make long journeys on floating
ice.

_The Eskimo Dog._--Another animal of circumpolar distribution, the
original home of which is unknown, is the Eskimo dog, the range of which
has no doubt been extended while the distribution of many other animals
has been curtailed, owing to human influences.

_The Caribou._--The neighbour of the musk-ox in the desolate solitudes
of the far north, and in part ranging over the same ground, is the
caribou, the American representative of the reindeer. Indeed the caribou
and the reindeer have been considered as belonging to the same species
by some naturalists, but recently the American division of the genus has
been shown to consist of at least five species, each of which
differs from the one found in Europe and Asia. Among hunters and
sportsmen, two divisions have long been known, namely, the woodland
caribou and the Barren Ground caribou. The former includes the larger
species, or the caribou proper, as it may be termed, and the recently
described species from Newfoundland and Alaska; while the latter is
represented by a single species, the _Rangifer articus_.

The woodland caribou is in general about twice the size of the species
inhabiting the Barren Grounds, has a height of 4½ feet at the
shoulder, and weighs some 250 pounds, although the males sometimes reach
a weight of 400 pounds. Its range is from Nova Scotia and Newfoundland
northwestward through the subarctic forest to British Columbia and
northeastern Alaska. As its popular name signifies, its home is in the
forest, and although meeting the smaller form during the latter's
southward migrations, it does not extend its range to the Barren
Grounds. On the south, it was formerly found in northern Michigan and in
southern New York, and thence eastward through Vermont, New Hampshire,
and Maine. Owing to the activity with which it has been hunted, it has
for the most part been crowded to the north of the St. Lawrence, and is
reported to be greatly diminished in numbers even in the wilds of
Labrador. It still wanders into the woods of New Hampshire and Maine,
and occurs somewhat abundantly in Nova Scotia and Newfoundland. It is
the caribou of Newfoundland, etc., which comes nearest the reindeer in
size and in the shape of its magnificent antlers, but none of the
American species has been domesticated.

The Barren-Ground caribou still occurs in large herds in northern
Labrador, on the treeless region to the west of Hudson Bay, and in
winter migrates southward into the shelter of the subarctic forest. In
its northern range it reaches the shore of the Arctic Ocean and the
islands adjacent, and on the west follows the tundra to the Bering Sea
coast. In Alaska it formerly occurred in immense herds, especially in
winter, when it made long inland journeys through the forest and across
the frozen rivers, but the invasion of the region by miners and
the supplying of the natives with firearms has led to a great reduction
in its numbers. In the barren and but seldom traversed region to the
west and north of Hudson Bay the caribou is still in its primitive
condition and moves in bands numbering several thousand. In this
connection an extract from the journal of J. B. Tyrrell, of the Canadian
Geological Survey, is of interest: "All day [July 30, 1893] the caribou
have been around us in vast numbers, many thousands being assembled in a
single herd. One herd collected on the hill behind our camp, and another
remained for hours in the wet bog on the point in front of us. The
little fawns were running about everywhere, often coming up to within a
yard or two of us, uttering their sharp grunts as they stood and looked
at us or as they turned and ran back to the does. About noon a large
herd had collected on the sides and summit of the hill behind us. Taking
a small hand-camera with which we were supplied, we walked quietly among
them. As we approached to within a few yards of the dense herd, it
opened to let us in and then formed a circle around us, so that we were
able to stand for a couple of hours and watch the deer as they stood in
the light breeze or rubbed slowly past each other to keep off the black
flies. The bucks, with their beautiful branching antlers, kept well to
the background. Later in the afternoon a herd of bucks trotted up to us
and stood at about 40 yards distant. This was a most beautiful sight,
for their horns were fully grown, though still soft at the tips, but
unfortunately we had no camera with us. We did no shooting to-day." The
herd of caribou just described was estimated to contain between 100,000
and 200,000 animals.

The destruction of the woodland caribou in the eastern portion of Canada
has been so great that it is in danger of being exterminated, and great
suffering, and even starvation has overtaken the Indians of that region
in consequence. Similar, but even more alarming results have followed
the thoughtless slaughter of the Barren-Ground caribou in Alaska, and to
prevent the suffering and even threatened extermination of the
natives, reindeer from Siberia and northern Europe have been introduced
by the United States Government[4] and are thriving under the care of
herders from Lapland. The moss on which the reindeer feed is abundant in
Alaska, and there seems no good reason why they should not become as
numerous and useful in their new home as they were in the boreal portion
of the Old World. The first reindeer were introduced in Alaska in 1881,
and the several herds, collectively, now number 3,323.

[4] The introduction of domesticated reindeer into North America is a
very important matter, and one which if properly conducted will add
vastly to the food supply and resources for clothing for both native and
white people. The civilization of the natives in the northern portion of
the continent and the securing for them of a source of subsistence which
will depend on their own care and industry hinges on the success of this
undertaking. Much information in this connection may be found in the
reports of Sheldon Jackson, published by the Bureau of Education at
Washington between 1893 and 1900.

_The Moose._--This, the largest living representative of the deer tribe,
and with the exception of the bison the largest existing land mammal of
North America, formerly inhabited the continent throughout its entire
breadth from the forty-third to the seventieth degree of latitude, or
from the mouth of the Ohio to the mouth of the Mackenzie. Although
crowded northward and now found only sparingly in the United States, as,
for example, in the extensive forests of Maine and in the still larger
forests clothing the mountains of Montana and Idaho, it has held its own
in the wildest and most remote portions of the Pacific mountains in
Canada and Alaska, where its numbers are perhaps nearly as great as they
were a century ago. Its preservation is due not only to its shyness,
remarkably quick hearing, and keen sense of smell, but to its solitary
habits and the fact that it does not gather in herds during the
breeding season, like most other deer.

A full-grown male moose is from 7 to 8 feet high at the shoulder, and
from 10 to 12 feet high at the tip of the magnificent antlers when
standing erect, and is from 800 to 1,200 pounds in weight. The
broad palmate antlers with numerous sharp points sometimes measure 8½
feet or more from tip to tip. The does are without antlers, and are
still more ungainly than the long-legged and apparently awkward males.
Stringent laws are now enforced for the protection of the moose in all
of the inhabited portions of its range, and it is likely to survive and
to continue to tempt the sportsman to traverse the wild regions it
inhabits for several generations to come.

_The Wapiti._--Next in size to the moose, and in many ways the grandest
of the deer tribe not only of America, but of the world, is the wapiti
or American elk. In language not pedantic, W. A. Perry speaks as follows
of this noble animal: "Monarch of the wilderness, lord of the mountain,
king of the plain, what hunter who has sought thee in thy pine-embowered
home whose heart-beat does not quicken and whose eye does not brighten
at the mention of thy name! For with it comes the recollection of
boundless prairies, grass-robed and flower-decked; of pine-clad,
snow-capped mountains; of sweet breezes, gentle melodies, and grand
trophies. I once heard an Indian speak his last words, and they were
these: 'To-morrow, in the Spirit Land, again shall I chase the wapiti.'"

Although the wapiti is one of the typical animals of the boreal region,
in its primitive freedom it overstepped the boundaries of the life-zones
which science seeks to define, and marched southward far into the
austral region. It was found at the coming of the white man in nearly
all parts of what is now the United States, and extended from the
table-land of north-central Mexico northward to the fifty-sixth or
fifty-seventh degree of latitude, or about the position of Lake
Athabasca. Its northern range thus overlapped the region inhabited by
the moose and caribou, while at the south it was exposed to the attacks
of the jaguar. As civilization advanced across the continent, the wapiti
slowly retreated, and in diminished numbers it now lives in the wildest
portion of the Pacific mountains to the north of Snake River and the
Columbia. It is still abundant in the Olympic Mountains of Washington,
the Bitter Root Mountains of Idaho, and in Montana. A large herd
finds protection in the Yellowstone National Park, but in winter, when
migrating southward, is exposed to most destructive attacks from both
white and Indian hunters. Among the mountains of the mainland in British
Columbia and the central and more rugged portion of Vancouver Island it
is still the "king of the wilderness."

The male wapiti at maturity is some 7 or 8 feet high at the shoulders,
and lifts its wide-spreading antlers fully 11 feet from the ground. Its
weight is from 800 to possibly 1,100 pounds. The colour is, in general,
dark brown, with lighter shades on the thighs, and changing to black
beneath the body; there are stripes of light brown on either side of the
tail which join an area of similar colour beneath the hind legs; the
colour varies, however, at different seasons and in different
individuals. The head is small, well formed, and beautiful. The carriage
of the animal and its bold, undaunted mien, when roaming its native
mountains and glens, is all and more than poets ascribe to the stag of
the Old World.

Stringent laws are now on the statute-books for the protection of the
wapiti, both in the United States and Canada, but the difficulties in
the way of enforcing them in regions remote from civilization are great.
The wapiti does not extend into the most forbidding wilds of the far
north, where its safety as a species, as in the case of the moose, would
be insured, and besides, congregates in bands, which facilitates its
slaughter. Its range has been steadily decreasing since the coming of
the white man, and particularly since the introduction of firearms among
the Indians, and its extinction, outside of reservations and parks, is
to be expected in the near future.

_The Smaller Deer._--Besides the caribou, moose, and wapiti, there are
half a dozen or more members of the deer family (_Cervidæ_) represented
in the fauna of North America. Of these the Virginia deer is best known,
as its range embraces the most thickly settled portion of the continent
between Maine and the Gulf States, and from the Atlantic coast to the
Rocky Mountains. In spite of indiscriminate slaughter and poorly
enforced game laws, this species has not only held its own, but in
recent years has greatly increased in number in certain localities. To
the west of the range of the Virginia deer and merging with it in part,
in the Pacific mountain region occur the white-tailed, black-tailed
mule, and sonora deer, and perhaps other species. The combined ranges of
these several species embrace the larger part of the continent and
extend from eastern Canada to the Pacific coast, and from southern
Alaska to Panama.

Next to the deer comes the antelope, formerly so common on the Great
plateaus. This, the pronghorn antelope, as it is usually termed, is
about the size of the domestic sheep, but with long slim legs, and is a
most active and exceedingly graceful animal. Its true home is on the
treeless plateaus east of the Rocky Mountains, but its range extends
from Saskatchewan to northern Mexico, and from the Prairie plains to the
Cascade Mountains in Oregon. It has steadily decreased in number,
especially during the last quarter of a century, and is now no longer
seen in the large bands that were formerly an attractive feature of the
sea-like plains over which it travels seemingly with the freedom of a
bird.

The animals thus far referred to have their range determined mainly by
the broader features of climate, but not in a conspicuous way by the
relief of surface. They inhabit mountains, plateaus, and plains alike,
as is shown most conspicuously in the case of the wapiti, which formerly
grazed in large herds on the prairies of the Mississippi Valley, and has
been killed at an elevation of over 10,000 feet in the Pacific
mountains. Not so, however, with the mountain-climbers whose names
follow, which have their chosen "station" on the mountains at
timber-line and ascend as far above that horizon as vegetation grows.

_The Bighorn or Mountain-Sheep._--The bighorn, of which three species
are now recognised, has its home in the Pacific mountains from northern
Mexico to central and northern Alaska. Its vertical range is also great,
as it has been seen on the precipitous walls of the Grand Cañon of
the Colorado, but a few hundred feet above sea-level, and about
the summits of the peaks of Colorado and in the Sierra Nevada and
Cascade Mountains at elevations of from 10,000 to 13,000 feet. An
exception to the fact that the bighorn is usually found on rugged
mountains and is most at home on seemingly inaccessible cliffs is
furnished by bands which live and appear to thrive amid the Bad Lands
along the Missouri River, some 400 miles to the eastward of the Stony
Mountains.

The bighorn resembles the wapiti in colour, although it is of a lighter
brown, especially in winter. It is clothed with wool beneath the stiff
outer coat of hair, and is a true sheep, but larger than any
domesticated variety of _Ovis_. The rams attain a height of at least 3
feet 6 inches at the shoulder, and weigh some 300 or 400 pounds. Both
sexes are provided with horns, but those of the male are much the
larger, and in the finest examples attain a length of 30 inches,
measured along the outer curve, and a circumference at the base of 15 or
16 inches. The most magnificent head ever obtained, so far as the writer
has been able to learn, is that of a ram shot in the Selkirk Mountains,
the horns of which are 52½ inches in length, measured along the outer
curve, and 18½ inches in circumference at the base. These immense
horns are used, as in the case of the domestic ram, in fighting, but the
widely current statement in reference to the animals alighting on them
when jumping from precipices is entirely mythical. The bighorn is a
fearless and skilful mountaineer, and will climb or descend precipices
by bounding from ledge to ledge where the most reckless hunter dares not
follow. Its ability to find a sure footing on even smoothly glaciated
rocks is due to the peculiar structure of the feet, which have a
rubber-like pad beneath the sharp-pointed and sharp-edged hoofs.

_The Mazama or Mountain-Goat._--The companion of the bighorn on the
lofty mountains, but even more thoroughly a mountaineer, is the
so-called mountain-goat, _Aplocerus montanus_, which, in spite of its
long hair, short curved horns, sturdy legs, bearded chin, and general
goat-like appearance, and more than the goat's ability to climb,
is in reality more nearly related to the antelope than it is to the
sheep. This alpine antelope, unlike its cousin of the plains, is only at
home on dizzy heights, and summer and winter alike lives at timber-line
on the mountains or in the alpine gardens adjacent to perpetual snow.

One of the earliest generic names under which it is assumed this alpine
antelope was included, namely, _Mazama_, although rejected by
naturalists, has recently been revived and adopted by an enthusiastic
mountaineering club in Portland, Oregon, as their name, and is likely to
become widely known. Among the hunters and the inhabitants generally of
the region where the animal under consideration lives it is termed the
mountain-goat, and no protest from naturalists, however well founded, is
likely to bring about a change in this connection.

The mazama is entirely white, excepting its hoofs, horns, and narrow
lines about the eyes and nostrils, which are black. In general, it is
smaller than the bighorn, but bucks have been reported to attain a
length of nearly 6 feet and a weight of some 300 or 400 pounds. Its
habitat is not only higher on the mountains but more restricted in
geographical extent than that of the bighorn. It is said to live about
Mount Whitney, the highest summit in the Sierra Nevada, but is unknown
farther south; in Colorado it is reported to have been seen on a few of
the higher peaks, but its main range begins well to the north of these
outlying localities, in the mountains of Montana and Idaho and in the
Cascades. To the north of the United States it occurs throughout the
higher ranges of British Columbia and in the mountains of southern
Alaska as far west at least as Cook Inlet. It is plentiful and as yet
undisturbed by hunters on the foot-hills about Mount St. Elias, where
the alpine conditions congenial to it occur at an elevation of from
2,000 to 3,000 feet above the sea. Like all of the larger animals, and
especially the herbivores, the bighorn and the mazama are sought by
sportsmen, but on account of the ruggedness of the regions they inhabit
and their wariness they are likely to survive when most other examples
of "big game" shall have been exterminated. Both the bighorn and
the mazama are sought by Indians for food and for their pelts, and their
horns are frequently used, especially in Alaska, in the manufacture of
spoons. They are practically of no economic importance to white men,
although their flesh when young is excellent food, and their fleeces
would be of value to the weaver if they could be obtained in sufficient
quantity. They serve, however, to entice the sportsman, who is usually
an ardent lover of nature, into some of the wildest and grandest regions
the continent affords. Their value in this connection is not to be
measured in dollars, and strenuous efforts should be made to insure
their continuance.

[Illustration: FIG. 31.--Bison at Silver Heights, Winnipeg. (Photograph
by William Notman & Son.)]

_The Bison._--Of all the larger mammals of North America, none was more
numerous at the time Europeans advanced over the continent than the
bison or "buffalo" (_Bos americanus_), and none more important alike to
the Indian and the white man. The part played by this relative of the
domestic ox in the history of the country is not only instructive, but
one of the best illustrations that can be furnished of the practical
extermination of a species through the greed and lack of forethought of
so-called civilized man.

The bison is a shaggy, brown animal, about the size of the well-known
Durham breed of cattle, but with a larger head and a prominent hump on
the shoulders (Fig. 31). The hind quarters are small in comparison with
the massive head and shoulders, and appear weak. The head, neck,
shoulders, and fore legs are covered with thick matted hair, at times 16
inches long and of a dark-brown colour merging into black. The straight
black hair beneath the chin of the bull is usually some 10 inches in
length, and as the animal carries its head low, frequently sweeps the
ground. Back of the medial portion of the body the hair is short and of
a yellowish-brown colour, or "between dark umber and a living-liver
brown," as Audubon says. There is much variation in colour, however, and
distinct varieties have been stated to exist. The horns, hoofs,
and a bare space about the nostrils and mouth are black.

The weight of a fully grown bull is about 2,000 pounds, and of a cow
1,200 pounds.

[Illustration: FIG. 32.--Range of the Bison.]

The boundaries of the region in which the bison has been seen by white
men, together with the dates of its extermination in various sections of
the country, etc., are shown in Fig. 32. In about 1870 the vast herd
which ranged over the treeless plateaus and Prairie plains between the
Rio Grande and Great Slave Lake was divided, owing to the great
slaughter that occurred in the vicinity of the Central Pacific Railroad,
into two herds, one of which had its summer range in Montana and
neighbouring territory, but moved northward in summer into
Canada, while the other fed on the plains of the west Texas region in
winter and moved northward in summer as far as southern Nebraska. In
each case a southward movement was begun as winter approached, but these
seasonal changes scarcely warrant the name of migrations.

The number of these large animals living between the Mississippi and
Rocky Mountains previous to 1872, even after being hunted for centuries
by the Indians and killed in constantly increasing numbers each year by
white men for half a century, can only be reckoned in millions. Many
trustworthy observations are on record, however, from which the vastness
of the herds can be approximately judged. For example, R. I. Dodge thus
refers to a herd which he passed through in the Arkansas Valley in May,
1871, when it was moving northward: "The great herd could not have
averaged, _at rest_, over 15 or 20 individuals to the acre, but was not
less than 25 miles wide, and from reports of hunters and others it was
about five days in passing a given point, or not less than 50 miles
deep. From the top of Pawnee Rock I could see from 6 to 10 miles in
almost every direction. This whole vast space was covered with buffalo,
looking at a distance like one compact mass, the visual angle not
permitting the ground to be seen." From this and other observations, W.
T. Hornaday has estimated that the herd referred to numbered not less
than 4,000,000 individuals. From the records kept by railroad companies
of the number of skins shipped over their lines and other evidences, it
has been computed that of the southern herd mentioned above over
3,500,000 individuals were killed during the years 1872, 1873, and 1874.
The northern herd seems to have been at least as large as the southern
one, so that the entire number on the Great plateaus in any one year for
the decade preceding 1870 was not less than 8,000,000, and even this
vast number seems to be an underestimate.

The great slaughter of the southern herd occurred from 1872 to 1874, and
of the northern herd ten years later. In 1889, as stated by Hornaday,
the bisons running at large in North America numbered but 635. In
1902 the number of bison in the United States was reported to be 800,
the increase being due to protection extended to the herds, and perhaps
also to a more accurate count.

_Fur-Bearing Animals._--Of the animals of North America which are taken
for their fur, the seal and sea-otter have already been referred to in
connection with the brief review presented of the life of the
continental shelf. As is well known, the colder regions of the earth are
the ones which yield the most valuable furs, and in the fur trade of the
world this continent, on account of its wide expansion at the north, has
taken the leading place as a producer. In fact, the fur trade is a
prominent feature in the history of America, and one whose followers
experienced great vicissitudes and countless adventures.

The animals that tempted the tireless and fearless sons particularly of
France, England, Scotland, and Russia to build their fortified
trading-posts throughout the subarctic forest from the St. Lawrence to
the Mackenzie and Yukon, were principally the beaver, sable, ermine,
fox, mink, wolverene, bear, otter, wolf, lynx, musk-rat, skunk, marmot,
etc. Nearly all of these animals are forest dwellers, and several of
them, as the beaver, otter, mink, and musk-rat, haunt the shores of
streams and lakes. Of the sable, there are two species, known as the
marten and the fisher. The bears are represented by at least four
species. The foxes number at least a dozen species, of which four are
especially prized for the beauty of their fur, namely, the arctic, red,
cross, and silver.

While the fur-bearing animals named above are characteristic of the life
of the boreal region of North America, a number of the species, and, in
fact, nearly all of them, range southward into the austral region,
especially in the more humid and generally forest-covered portions of
both the Pacific and Atlantic mountains, while one of the most important
as regards the beauty of its fur--the otter (_Lutra canadensis_),
frequently termed the land-otter, in order not to confound it with its
larger and far more valuable cousin, the sea-otter (_Enhydra
marina_)--reaches the torrid region and is still living in
Florida, and has been reported as occurring in Central America.

Of all the fur-bearing animals referred to above, the most valuable when
the total number of skins that have been taken is considered, and in
many ways the most interesting, is the beaver, of which but one living
species (_Castor canadensis_), closely allied to the beaver of northern
Europe, is known in America. Fully grown individuals are about 3 feet in
length, one-third of which is to be credited to the broad, flat,
scale-covered tail, and weighs some 50 or 60 pounds. The outer coat of
its pelage consists of rather coarse brown hair, beneath which there is
a fine, soft, dark fur, which makes its skin of commercial value. In
dressing the skins the hair is plucked, the fine fur beneath being
clipped to a uniform length and usually dyed. The formerly well-known
beaver hat was made from this fur, but in recent years silk has taken
its place. The importance of the American beaver is illustrated by the
fact that some 7,000,000 skins have been sold in London by the Hudson's
Bay Company since the year 1752. Not only is the fur of the beaver in
demand, but its flesh, and especially the muscles of the tail, are
prized for food by hunters and others who live the free, open-air life
of the frontier, although it is seldom exposed for sale in the markets
of cities.

The beaver is of interest to the geographer not only on account of its
wide distribution, which embraced the entire continent wherever the
willow, birch, alder, etc., on which it subsisted, could grow, from
northern Mexico to the Arctic Ocean, but for the reason that it made
more conspicuous and lasting changes in the minor features of the
surface of the land than any other mammal. One of its peculiar habits is
that it gnaws down trees frequently 6 or 8 inches in diameter, and after
cutting them into sticks a few feet in length, uses them in making dams
across small streams. These dams were built in thousands and tens of
thousands all through the forested regions, and being plastered with
mud, and still further enlarged and strengthened by the accumulation of
driftwood and leaves, held the waters of the streams in check and
caused them to expand so as to form small lakes, ponds, and swamps.
These beaver-dam lakes are common even at the present day, and many of
them which have been filled with sediment or drained furnish rich lands,
now utilized for gardens and cultivated fields. In Michigan these
beaver-dam lakes furnish the rich black soil so favourable for the
raising of celery and other vegetables. The beaver has disappeared from
all but the wilder and more inaccessible portions of the continent, but
the influence of the changes it made in the drainage of the land will
endure for many generations to come.

Of the fur-bearing animals mentioned above, none are more definitely
American than the skunks, or, to use a more felicitous name, _Mephitis_,
which ranges from central Canada to central Mexico, and is represented
by four or five species. As stated by Elliott Coues in his instructive
monograph on the North America _Mustelidæ_, the skunks are closely
related to the badgers, being heavy-bodied, short-legged, stout in
build, with hairy tails and generally loose pelage. They neither climb
trees nor swim in water; their gait is slow, and they do not allow
themselves to be hurried, even in the face of danger; their retreats are
burrows in the ground or dens in rocks and hollow logs, and sometimes in
the nooks and corners of dwellings and outhouses. Their most common
representative, _Mephitis mephitica_, is a beautiful animal some 15 or
20 inches in length, exclusive of its bushy tail, which is usually 12 to
15 inches long. The head is small, the ears low and short, and the hair
of a glossy black, relieved by conspicuous white markings which are not
only irregular in shape, but vary with individuals. The most marked
characteristic of the skunks is their ability to emit at will a fluid
which has the most disagreeable and sickening odour known. This fluid is
secreted in two glands, each about one inch in diameter, situated at the
base of the tail and opening into the rectum, but has no connection with
the secretions of the kidneys, and is probably seldom discharged except
when the animal is annoyed. It is a unique and most efficient
means of defence. In this connection it is to be remembered, however,
that the skunks belong to the family _Mustelidæ_, which is characterized
in part by the odoriferous secretions present in its various species,
but, above all others, the odours emitted by the genera under
consideration are the most dreadful. The stench produced by these
animals when startled or enraged is not only horrible beyond
description, but endures for months and even a year or more. The yellow
liquid which is ejected is squirted in a fine spray for a distance of
some 6 or 8 feet, but its odour may sometimes be perceived, even when
the wind is still, for a distance of a quarter of a mile.

The skunk having this one unconquerable means of defence from all its
enemies except man, exhibits evidence of degeneration in other respects.
When discharging its odoriferous fluid it faces its enemy, who is held
at bay or retreats, and hence, not being compelled to run, has acquired
a slow, wavering gait and deliberate movements; having no occasion to
ascend trees for safety, it has lost or failed to develop the ability to
climb; and its lack of other powers which are highly developed in its
near of kin may be used in illustration in a similar way. It is
practically removed from the attacks of enemies excepting dogs and other
canines and some birds of prey, but has to adapt itself to conditions of
climate and food supply. In winter in the northern portion of its
habitat it becomes more or less torpid, and during the coldest weather
usually hibernates, thus lessening the exertion required to procure
sustenance. When the temperature is not excessively low it seeks its
food, which consists of insects, birds' eggs, small reptiles, mice,
etc., and in settled regions visits the poultry-yards, and thus
increases the enmity extended to it by all mankind, who have ever been
disgusted by its odours. Another objectionable fact in reference to this
despised yet, we may perhaps say, respectfully treated animal, is that
its bite sometimes produces hydrophobia.

The skunks are not only widely distributed in North America, occupying
perhaps a larger area in the austral than they do in the boreal region,
but are influenced to a less extent by climatic and topographic
conditions than probably any other genera among our mammals. It lives
among mountains and on plateaus and plains, and in forests as well as on
the open prairies, and extends from humid regions like eastern Canada
and New England to the dry, semi-desert valley of New Mexico, and from
the cold shores of the Great Lakes and central Canada to the warm Gulf
States. Although offensive, and everywhere declared a nuisance, and
persecuted as such, as well as trapped and hunted for its pelt, its
range has been decreased but little since the settlement of the country
by Europeans, although its numbers are greatly reduced. Its beautiful
fur when deodorized and dyed of a uniform black is sold under the name
"Alaskan sable," "black marten," "American sable," etc., and is
extensively worn even by the most fashionably attired dames of every
land.

_The Bears._--Of the bears native to North America, as was stated by S.
F. Baird in 1857, the number of species is somewhat indefinite, but four
are commonly recognised and mention is sometimes made of two others.
This uncertainty as to the number of species of the genus _Ursus_, I
believe, still exists, and in itself is significant. If the bears have
not been satisfactorily classified, as is apparently the case, it
suggests that they exhibit great variations and that the drawing of hard
and fast specific boundaries among them is difficult, and perhaps
impossible.

The species which are usually recognised are the polar bear, the
grizzly, the cinnamon, and the black. Of the black and brown or cinnamon
bears there seems to be several varieties, some of which are perhaps
worthy of being considered species. On the other hand, it must be
remembered that Baird and others makes the cinnamon a variety of the
black bear. Again the grizzly and cinnamon intergrade in such a manner
that an experienced naturalist has considered them to be but extremes of
a single species.

The polar bear is distinguished from its kindred, at least in a general
way, by its large size and white or yellowish-white colour. These and
other differences from its relatives have led naturalists to place it in
a distinct genus, of which it is the only species. It is
circumpolar in its distribution, and in America occurs along the coast,
seldom travelling inland except during the breeding season, when it is
sometimes met with 25 miles from the ocean. Its southern range on the
Atlantic coast is in northern Labrador, but it is occasionally carried
on floating ice as far south as Newfoundland. It inhabits the shores of
Hudson Bay and the Arctic Ocean. On the west coast it reaches Bering
Strait, and is carried on floating ice to the islands in the northern
part of Bering Sea, and at rare intervals reaches the Pribilof Islands.
It is probably strictly carnivorous, and lives principally on the seal.
It is supposed to be the largest of the bear tribe, but is certainly
approached if not rivalled in size by the brown bear of southern Alaska.
As many arctic explorers testify, it is dangerous to man and will lead
in an attack.

The famous grizzly or "silver tip" inhabits the Pacific mountains, but
is best known in the Rocky Mountains and Sierra Nevada. Although like
all kindred species presenting conspicuous individual variations, it is
usually dark in colour, with white tips to some of the hairs. The pelage
is long, almost shaggy, and gives the animal even a more formidable
appearance than its great size and strength justifies. It is not only
one of the largest of the American bears, ranking in this respect with
the polar bear and the largest of the huge brown bears, but is also
probably the fiercest, and not infrequently has been known to attack
man, although it will usually retreat from the presence of human beings
if an opportunity is available. Full-grown individuals are about 8 feet
in length and weigh in the neighbourhood of 1,000 to 1,200 pounds.

The brown bear, of which there are perhaps three species, including the
Barren-Ground bear of the north-central part of Canada, are, as their
name signifies, of a brown or cinnamon colour, but present great
variation in this respect. Some are of a decided yellow, while others
become dark and are scarcely distinguishable from the true grizzly. They
reach a great size, particularly in southern Alaska, and possibly in
certain instances even exceed the polar bear in dimensions and
weight. The tracks of one which I measured near Mount St. Elias were 16
inches long by 8 inches wide, and the stride was 64 inches. The range of
the brown bear is confined principally to the Pacific mountains, but is
of greater extent than that of the true grizzlies and includes central
Canada.

The black bears are of almost continental distribution and occurred in
all or nearly all wooded districts before the balance of natural
conditions was disturbed by the coming of the white man. They are the
smallest of the bear tribe on this continent and are usually harmless,
but at times when attacked or approached suddenly, especially if
accompanied by their young, become formidable enemies. Their colour is
usually a glossy black, but much variation occurs, especially about the
head, and this and other differences are thought by some to indicate
specific distinctions. A seemingly well-marked variety occurring in
southern Alaska, which has a thick bluish-black under-fur, has recently
been described as a distinct species.

Near relatives of the bear are the racoons, of which several species are
present, one being abundant in the eastern portion of the United States
and the other in the Pacific mountains.

_The Cats._--The _Felidæ_ are represented by two genera, _Felis_ and
_Lynx_, each of which contains several species.

Of the true cats, the largest is the beautiful jaguar, or American
tiger, _Felis onza_, which is nearly as large, and by some said to be
equal in size to its Asiatic relative. It more nearly approaches the
leopard, however, in the character of its spots as well as in its
arboreal habit, but exceeds it in size. The jaguar is some 4 feet or
more in length to the base of the tail, and the tail is about 3 feet
long. Its general colour is a soft-yellowish passing into dark brown and
black, with large rosette- or somewhat lozenge-shaped spots, which take
the form of indefinite rings of dark fur with lighter centres, within
which there are one or two dark dots or eyes. The skins are fully as
beautiful as those of the tiger or leopard, and are highly prized for
rugs, and in some cases have been used for clothing. A dark,
nearly black variety (or perhaps more properly, examples of melanism)
has been described as a distinct species, and is sometimes spoken of as
the black tiger.

The centre of distribution of the jaguar is probably in the great
Amazonian forest, but it ranges over nearly all of South America,
throughout Central America, and extends northward to Texas and perhaps
Louisiana.

Next to the jaguar in importance is the widely known panther. Unlike
most of its relatives, this species has an essentially uniform colour.
The fur on the back, head, and tail is of a tawny brownish-yellow, but
varies somewhat with changes in seasons. The under parts are of a dirty
white. The animal when full-grown is of a formidable size, the larger
examples being nearly 5 feet long from the tip of the nose to the base
of the tail. The stout cylindrical tail is from 20 to over 30 inches
long. In spite of its size and great strength the panther is not to be
feared so long as room for its escape is open, as it is a great coward.
One of the most interesting facts concerning this species is its
unusually great range. Before being disturbed by white men it inhabited
practically the entire width of both North and South America, from
Hudson Bay to Patagonia, an extreme range of some 110 degrees of
latitude. It is most at home in the mountains and is seldom seen on open
plains. It is still common in the Pacific mountains of the United States
and Canada.

Of the smaller cats, several of which are beautifully marked, mention
may be made of the ocelot of the Texas region and the lynx or American
wildcat. The latter, of which there are at least three varieties, is yet
common, and maintains approximately its original range, which embraces
the entire width of the continent from the subarctic forest at least as
far south as northern Mexico.

_The Wolves._--In the history of the establishment of English colonies
in this country, and throughout the spread of civilization across the
continent, many accounts are given of encounters with wolves. These
stories as they have been handed down have probably in many instances
been magnified, but there is no doubt but that the larger wolves,
such as the gray timber-wolf, once common in the northern portion of the
United States, when assembled in packs and pressed by hunger, were
formidable antagonists.

Of the wolves, four species are usually recognised, but their great
variation, in each instance, has led to the description of numerous
varieties, some of which have by certain writers been given the dignity
of distinct species. The largest is the gray wolf, which is white or
grizzly gray in colour, and frequently 5 feet or more in length and
weighs 50 to 60 pounds. Individuals have been killed, however, which
exceed these measures. The range of this species, or group of species as
the case may be, was originally continental, but more particularly in
the forested regions. Its hair, which is frequently 4 inches or more in
length, and the fine thick under-fur make the skins valuable for robes,
but they are seldom used for clothing, except by the Indians and
Eskimos. The hood of the outer garment worn by Eskimos, termed a parkie,
is frequently fringed about the face-opening with the long warm hair of
the wolf.

A smaller species, the coyote, is still common on the western plains,
and is termed the prairie-wolf. It is a comparatively small animal,
although frequently 3 feet in length of body with a bushy tail
two-thirds as long, and is of a skulking, cowardly nature. Its colour is
usually a yellowish gray, and its skin, although used for robes, is much
inferior to that of the gray wolf. Its range is from northern Mexico
northward throughout the great plateaus, and in the valleys of the
Pacific mountains into Canada. It is usually the first of the larger
mammals the traveller in that region learns the existence of, even at
the present day. Several individuals frequently gather together just
after sunset and make their presence known by barking and howling in
concert. These serenades last but a short time, however, and are likely
to be repeated in the morning just before sunrise. During the night the
animals composing these bands seem to scatter and hunt for food
singly, but reunite in the early morning, after which they again
separate and seek secluded individual retreats.

_Brief Mention of Other Mammals._--In order to convey an adequate idea
of the large variety and richness of the North American mammalian fauna
far more space would be required than is at present available. Indeed,
of the smaller mammals much more research is evidently needed before
even the number of genera and species can be enumerated, much less their
life histories and economic importance made known, as is indicated by
the fact that a large number of species previously recognised has been
described during the past two or three years.

Of the abundant smaller mammals, none are more attractive or beautiful
than the arboreal squirrels, of which several species are widely known.
One of these, the common red squirrel, is remarkable for its wide range
and adaptability to a great variety of conditions. It is abundant in the
valley of the Yukon and even north of the arctic circle, throughout the
forest-covered portions of Canada, and as far south as the South
Atlantic States. Of less extensive range is the gray squirrel and the
black squirrel, common in New England, and the somewhat larger and yet
more beautiful fox squirrel of the central part of the continental
basin. There are also a large number of species of ground squirrels, and
several species of flying-squirrels. The rodents are also represented by
the marmots, certain species of which are exceedingly numerous near
timber-line in many of the ranges of the Pacific mountains as far north
at least as Mount St. Elias, and by gophers, chipmunks, lemmings, the
musk-rat, porcupines, rabbits, hares, rats, mice, etc. The list might
also be extended by enumerating the bats, shrews, and moles, but we are
compelled to cut short this most interesting portion of our review.

_Mammalian Families Peculiar to America._--While there are many genera
and species of mammals found only on this continent, the number of
families that are peculiar to it is small. Among the characteristic
families, most of which, however, extend into South America, none are of
greater interest in the study of geographical distribution than
the opossums, of which there are 3 genera and some 22 species, all of
them confined to the New World. Of these, two species are common in
North America: one, the Virginia opossum, abundant throughout the
eastern portion of the United States to the south of New York, and the
other and smaller species, which inhabits Mexico and extends northward
into southern California and Texas. Many representatives of this same
family occur in Central and South America, some of which are notable on
account of their diminutive size. The opossums are of peculiar interest
owing to the fact that they are the only representatives of the
marsupials now living outside of Australia. Fossil species occur,
however, in the Tertiary rock of Europe, so that the American forms
cannot be considered as indicating a recent land connection between this
continent and Australia.

The porcupines are also representative of the New World fauna, although
not strictly confined to it, and belong mostly in the northern
continent. The Canadian porcupine is found throughout nearly the entire
forested portion of the boreal region and extends as far south as the
Middle Atlantic States, and an allied species, but of larger size,
inhabits a portion of the same region and extends to the Pacific
mountains and occurs in Alaska.

The racoons are strictly American and inhabit both continents. They are
common in the forests of Central America and Mexico, and extend as far
north as central Canada.

Of the several families of smaller and less well-known mammals peculiar
to this continent, mention may be made of the pouched rats of
California.

All of the animals to which attention has thus far been directed are now
living; should one attempt to describe the great number of fossil forms
whose bones have been discovered in the rocks, the menagerie would be
vastly enlarged, and many exceedingly strange species, genera, families,
and even larger divisions of the animal kingdom, added to the extended
procession.

                               THE BIRDS

When one attempts to write an account of the birds of North America, the
heavens seem darkened with such a multitude of varied and beautiful
forms and the air filled with such a discordant clamour mingled with the
sweetest of music that failure to convey an adequate idea of the
countless numbers and diversity of the feathered throng within the
compass of a few pages must be recognised from the start.

The important place held by the birds of North America in the avifauna
of the world, may perhaps be best indicated by noting first of all what
orders and families are without representatives among them.

The orders under which the birds of the world are arranged in the scheme
of classification adopted by Wallace in his great work on the
geographical distribution of animals are as follows:

                              CLASS--AVES

 ORDERS.                       EXAMPLES.

 1. Passeres     Includes the greater number of the smaller birds, such
                   as kingbirds, flycatchers, larks, jays, crows,
                   blackbirds, finches, sparrows, warblers, chickadees,
                   swallows, thrushes, etc., numbering in North America
                   some 328 species and many subspecies.

 2. Picariæ      Woodpeckers, cuckoos, toucans, kingfishers, swifts,
                   goat-suckers, humming-birds, etc.

 3. Psittaci     Parrots only.

 4. Columbæ      Pigeons and the dodo.

 5. Gallinæ      Grouse, pheasants, quail, jungle-fowl, turkeys,
                   guinea-fowl, etc.

 6. Opisthocomi  The hoazin of Guiana and Brazil only.

 7. Accipitres   Eagles, owls, vultures, hawks, buzzards, falcons, etc.

 8. Grallæ       Rails, snipes, plovers, cranes, herons, storks,
                   flamingoes, etc.

 9. Anseres      Ducks, geese, gulls, petrels, pelicans, penguins,
                   loons, auks, etc.

 10. Struthiones Ostrich, rhea, cassowaries, emeus, apteryx.

Of these ten orders, all but two are abundantly represented in North
America. The missing orders include the ostrich-like birds, of which the
only species in the New World is the rhea, of the southern portion of
South America, and the peculiar hoazin, represented by a single
species found in Guiana and Brazil.

The eight orders under which the birds of North America have been
arranged (other classifications, however, have been adopted by various
naturalists) have again been subdivided into families, genera, species,
etc. According to Wallace's summary, the 8 orders referred to contain
124 families, of which 75 are not represented in North America to the
north of the lowlands of Mexico, while 47 families are present. Of these
47 families, 25 are essentially of world-wide distribution, and only 1,
containing a single species, a small wren-like bird of the genus
_Chamæa_, found in California, is peculiar to the fauna of the
continent.

As the North American continent under the arrangement adopted for the
series of books of which the one in hand forms a part, is considered as
including the West Indies, Mexico, and Central America, the above
summary does not represent its entire bird fauna, but presents, perhaps,
the best general idea of it that is at present attainable. To include
the birds of the tropical portion of the continent would add greatly to
the number of species, but I believe not materially to the number of
families and orders, as given above.

In reviewing the distribution of the land birds of North America to the
north of Mexico, but including lower California, J. A. Allen places the
total number of genera, as given in the check-list of the American
Ornithologists' Union, at 181. Of these, 55, or 30 per cent, are
circumpolar or otherwise wide-ranging Old World forms; 126 genera, or 70
per cent, are American, of which 35, or 28 per cent, are essentially
tropical, leaving 91 genera, or about 50 per cent, as distinctly North
American.

The number of species in the avifauna of the continent, according to the
latest check-list published by the American Ornithologists' Union
(1895), is 768, together with a large number of subspecies. If the
tropical portion of the continent were included, this number would be
greatly increased and possibly doubled.

A further generalization has been advanced by Allen, who states that in
the arctic portion of the continent the number of genera of birds
present during the breeding season is 65, of which only 5 are
exclusively American. In the cold temperate belt 120 genera are
represented, of which 98 are circumpolar and 22 American. In the warm
temperate belt 95 genera occur which do not range into the cold
temperate belt, and of these only 12 are Old World forms, while 83 are
exclusively American, and in addition 60 genera are common to both the
cold and the warm temperate zone, of which 46 are represented in the
fauna of the Old World, while 14 are American. This gives 155 genera for
the warm temperate zone, of which 58 are Old World and 97 exclusively
American. There are besides 50 essentially tropical genera which extend
into the warm temperate zone, of which 43 are American and 7
tropicopolitan. The avifauna of the warm temperate zone thus contains a
total of 205 genera.

The above enumeration indicates the rapid increase in the variety of
bird life met with as one travels from the arctic to the Gulf coast of
the continent, and in this connection it is to be remembered that the
land contracts in breadth towards the south. In number of individuals,
however, it is doubtful if there are less per square mile at the north
than at the south during the breeding season.

There is a decrease in the number of Old World forms inhabiting North
America from north to south. A similar decrease in mammalian species
common to America and Eurasia has previously been referred to, and the
same explanation applies in each case, namely, the near approach of the
land areas of the Old and the New World at the north, and the actual
union of the two continents in late geological time.

As has been shown by Allen, the species of birds of the temperate and
boreal zones of North America were derived in part from the Old World,
in part from types almost universally distributed throughout the warmer
latitudes, and in part from tropical America, but to a marked extent the
species present developed where they are now found. This
generalization is in harmony with the geographical relations of the
continent to other land areas, and with the fundamental principles of
evolution.

_Migrations._--Among the many facts of interest to the geographer in
connection with the bird life, none present a more fascinating field for
study than the annual migrations in which a very large number of the
species participate.

As one travels northward from Mexico or the Gulf States, the number of
species of birds which remain in essentially the same area throughout
the year, or the _residents_ as they are termed, becomes less and less.
In New England and about the southern shores of the Great Lakes there
are about 30 species which remain all winter and may justly claim to be
citizens. Besides these, there are several visitors that come from the
north and belong to the vast army of migrants, but which are contented
with a comparatively small change of position during the periods of
greatest cold or heaviest snow. In the far north the number of residents
is still more restricted. On the tundras fringing the arctic coast even
the snow-owls, snow-buntings, and the ptarmigans, the hardiest of birds,
move southward during the winter to the shelter of the subarctic forest,
and bird life on the vast frozen morasses is practically, if not
absolutely, wanting.

The millions of birds that journey southward each fall begin their
return migrations at the first promise of spring. Even during unusually
mild spells of weather in winter, temporary northward movements occur.
The migratory birds are actuated by such a strong desire to regain their
nesting places and summer homes that they embrace every opportunity to
journey towards them, and not infrequently suffer severely for the risks
they take. In some instances species which have begun their northward
flight too soon are killed by thousands owing to a return of severely
cold weather or die for lack of food.

The first definite northward migration in the southern portion of the
Mississippi Valley begins during exceptionally favourable years as early
as the end of January, but the great movement of the feathered
hosts is not usually at its height before the middle of March or the
first of April. In New England the current of migration begins between
the middle of February and the first of March, and increases in strength
until the middle of May, when it is at its height, and then rapidly
declines and is practically over by the beginning of June. In the far
north, the first arrival from the southward, and that a species which
does not make a long annual journey, usually appears early in April. At
Point Barrow, the most northern portion of Alaska, as was observed by
John Murdock in 1882 and 1883, the first harbinger of spring was a
snow-bunting, which arrived the first year on April 9th. The
northward-flowing tide of bird life ends early in July in the region of
the Yukon, and by the middle of that month the vast flocks have been
separated and the many mates have found their nesting places. The time
taken for the general movement is thus in the neighbourhood of four
months.

The northward flight of the birds is seldom, if ever, one continuous
journey, but like many other movements in nature, progresses by
pulsations. Well-defined "bird-waves" have been recognised especially in
the Mississippi Valley. The direct or immediate cause of the starting of
these waves of life is the coming of a wave of heat. Secondary or
modifying conditions are furnished by strength and direction of the
wind, cloudiness, rain, etc. As the weather in spring-time is fickle,
and its variations not the same for any two consecutive years, so the
gathering of the birds into flocks and their northward flights vary,
although for a term of years the arrival of a given species at a
particular station does not depart far from a mean date. With the
northward sweep of the waves of bird life over the temperate and boreal
portions of the continent comes the awakening of plant life, but the
birds, to a marked extent, precede the unfolding of the flowers. This
marvellous renewal of the life of the land after the long cold winter
makes the budding and nesting spring-time the most joyous portion of the
year, and one which exerts a marked effect on human thought and
activities. The spring-time awakening in all nature is like a
resurrection, and has apparently exerted an influence on the religions
of the world.

The bird-waves referred to above are characterized at the start by the
presence of great numbers of a single species, but as they progress,
scattering occurs, and at the time of the greatest movements in the
northern portion of the United States a large number of species
frequently arrive at a given locality in a single night. At sunset the
groves may be nearly tenantless and silent, while at sunrise they are
alive with the flitting of wings of many colours, and the air pulsates
with many different songs.

Judging from extended observations on migrations made in the Mississippi
Valley, the definite waves of bird life which sweep northward with the
spring-tide of temperature are in some instances 100 or 200 miles long
and have a breadth of perhaps a score of miles. The distance between the
waves varies with variations in the weather and perhaps other causes,
and as they progress they apparently become less definite and at the
north have yet to be recognised.

The migrations of the birds are performed principally at night. In the
northern part of the United States during the hours of darkness in early
spring, even when cloudiness prevails or the land is veiled in mist, the
voices of geese may frequently be heard overhead, proving that unseen
flocks are then winging their way northward. About the lighthouses along
the coast and on the shores of the Great Lakes, when migration is in
progress, dead birds are frequently found in considerable numbers and of
various species. In these cases the birds are evidently attracted by the
lights and killed on striking the windows that protect them. This occurs
particularly on stormy or cloudy nights, when the birds fly low. Several
of the larger species of birds, as the geese, ducks, cranes, etc., which
are strong of wing, make long flights without resting. In many instances
a single stage in a journey may include 500 or 600 miles. Most of the
smaller birds, however, fly comparatively short distances between the
pauses made for rest and food.

A species on reaching the northern portion of the route over which it
usually migrates scatters, and the individuals mate, nests are built,
and young reared. At the approach of cold weather reassemblage occurs,
frequently great flocks being formed, and the southern movement begins.
The southward migration is less conspicuous in most instances than the
movement _en masse_ of the birds in the spring, and so far as now seems
to be recognised is not divided into definite waves.

While the winter habitat of most birds in the temperate and boreal
portions of the continent is to the south of their summer homes, the
annual migration is not in all cases great in amount. Some species move
only a few hundred, or possibly a few score, miles. Even the winter
residents make short migrations, dependent on weather conditions. The
greater part of the migratory birds, however, pass the winter in the
Gulf States, Mexico, the West Indies, and Central and South America. In
some cases they go well to the south of the equator. The annual flight
going and coming measured in a straight line, between the nesting place
and the winter home, cannot be less in many instances than from 8,000 to
10,000 or 12,000 miles. An interesting fact in this connection is that
certain species follow definite routes. The region moved over annually,
if marked on a map, would resemble two open or partially opened fans,
with their handles pointing towards each other and connected by a narrow
band.

The causes of the annual migrations of birds have received much study
and been the subject of much speculation. The general consensus of
opinion in this connection seems to be that the birds are controlled
largely by what we in our ignorance term instinct. The true beginning of
the migration seems to be in the fall, when the birds are driven from
their homes by cold or, perhaps more accurately in most cases, by
scarcity of food. This, however, is not the whole story, since many
species start southward before cold weather approaches and while food is
yet abundant. Then, too, crippled individuals have been known to survive
the winter in regions from which their summer companions have
departed. Instinct, therefore, plays a part in even the fall migration,
where at first glance sufficient physical reasons may seemingly be
claimed for it. During the spring migration the birds are moved by a
strong impulse to regain their breeding-grounds. Each species seems to
have adapted itself to certain conditions of temperature, food, etc.,
through long ages of development, and acquired a subtle faculty of
regaining the environment to which it is best adapted, as soon as the
adverse conditions that caused it to leave its home are ameliorated. How
a particular bird is enabled to return to the nest it built the year
previous is not known. The study of the homing instinct of pigeons
assists in this direction, however, and suggests that birds are endowed
with something answering to a sixth sense--that is, a sense of direction
or of orientation.

_Spring-time Music._--The northward-flowing tide of life each spring
brings to the temperate zone of North America a marvellous change not
only in colour and movements, but in sound. This is the season of bird
courtship and more than usual happiness among the feathered millions.
From shore to shore of the continent a chorus more seductive than
sirens' songs pulsates on the breezes.

The winter is characteristically a season of silence. The sounds heard
at a distance from human habitations are mainly those produced by
inanimate nature. The wind causes varied discords amid the bare branches
of the deciduous trees or sings weird melodies in the pines. Strange
muffled roars come from the frozen lakes, as the ice contracts and
breaks during periods of excessive cold. The frost in tree trunks causes
sharp explosions. The ice-covered streams are still except where
cataracts interrupt their even flow. In the profound silence of a calm
winter night the distant dismal howl of a wolf, the cry of an owl, or
the bark of a fox alone reminds one that life still continues, but these
animate sounds are far more frequently absent than present. With the
coming of the spring there is a marvellous awakening and unfolding. The
brooks, swollen to overflowing by the melting of the snow, make
music as they run. The northward flight of the birds brings to every
grove a chorus of song. A host of batrachians and reptiles bestir
themselves after a long winter sleep and vociferously proclaim their
presence. The insect world, with its unnumbered legions, takes wing. The
air vibrates with millions of voices. The trees put forth their leaves,
each a harp-string which responds to the touch of the fingers of the
wind. The organ-notes of the thunder again startle the hibernating
echoes. As the winter is the silent season, so the spring is the time of
music.

One of the most charming of the many phases of nature's concert season
is the matin songs of the birds. Ere the eastern sky along the New
England coast becomes roseate with the first blush of morn, the twitter
of birds may be heard amid the shadowy branches of the trees. Soon a
thrush or a warbler awakens in full song, and is followed by a host of
other voices, until the air pulsates with music. As the sun rises and
his first level rays reveal the varied tints of the tree tops, the
many-voiced chorus passes the height of its ecstasy and the music
gradually subsides. But the glad tidings of the coming of the day are
passed westward from grove to grove and from meadow to meadow, and a
wave of song sweeps on ahead of the wave of light, induced by its
coming. The song-wave spreads to the north and south and flows steadily
westward over the forest-covered mountains, across the great central
basin of the continent, breaking on the treeless plateaus into many
streams which follow the grove-fringed rivers, passes through the
depressions in the Rocky Mountains, and although weakened in the arid
valleys beyond, is not checked. The larks there listen for its coming
and pass the joyful message westward. The timid dwellers in the great
forests of Oregon awaken at the magic sound and the lofty tree tops are
made to thrill with the voices of unseen choirs while it is yet night in
the silent aisles below. The onward rush of sound is not reflected or
turned back by the lofty Cascades, but flows through their passes and
only ceases when the sea-birds of the Pacific renew a note that
was dropped on the distant Atlantic coast.

One of the most fascinating incidents in the life of the explorer in his
lonely camps in the great forests or amid the solemn mountains is the
coming of the wave of song in the spring and early summer-time which
precedes and accompanies the rising of the sun.

The fascination of the field of study touched upon in this chapter
invites an attempt to present an account of some of the more
characteristic birds of North America, and to endeavour to convey to the
reader some idea of the varied reptilian, fish, and invertebrate life of
the continent, but the limitations of space prohibit such a review. Even
the great problems dealing with the intimate relation that exists
between geographical conditions and the distribution of animals cannot
be given more attention than the suggestions already offered.

                              LITERATURE

  ALLEN, J. A. _The Geographical Distribution of Animals_, in
    Bulletin of the United States Geological and Geographical Survey
    of the Territories, vol. iv, Washington, 1878, pp. 313-377; _The
    Geographical Distribution of North American Mammals_, in
    Bulletin of the American Museum of Natural History, vol. iv, New
    York, 1892, pp. 199-243.

  HEILPRIN, ANGELO. _The Geographical and Geological Distribution of
    Animals_. International Scientific Series, London and New York,
    1897.

  OSBORN, H. F. _The Rise of the Mammalia in North America._ New
    York, 1893.

  COPE, E. D. _Geographical Distribution._ In the Annual Report of
    the Smithsonian Institution for the year ending June 30, 1898,
    Washington, 1900, pp. 1199-1234.

  MERRIAM, C. HART. _Life-Zones and Crop-Zones of the United
    States_, United States Department of Agriculture, Division of
    Biological Survey, Bulletin No. 10, Washington, 1898; _Results
    of a Biological Survey of the San Francisco Mountain Region and
    Desert of the Little Colorado, Arizona_, United States
    Department of Agriculture, Division of Ornithology and Mammalogy
    [Bulletin] No. 3, Washington, 1890; _The Geographical
    Distribution of Life in North America_, in Proceedings of the
    Biological Society of Washington, vol. vii, 1892, pp. 1-64.

                              CHAPTER VI

                               GEOLOGY

                           _Introduction_

In the preceding chapters an attempt has been made to present outline
sketches of the geography, fauna, and flora of North America as they
exist now. Yesterday, we may say for the sake of emphasis, there were
differences from what exists to-day in each of these great groups of
facts. That is, changes are everywhere in progress. With the recognition
of this idea comes logically the conclusion that similar changes must
have taken place in the past, and that the geography of the earth's
surface, and its flora and fauna, at no very distant time must have been
markedly different from what they are to-day. To test this hypothesis
the geologist studies the records preserved in the rocks in much the
same manner that the historian searches the papyri or the monuments of
Egypt to discover what changes in the affairs of men have occurred since
the days of the Pharaohs. The changes referred to are not essentially
different from those now in progress, but in reality the two are parts
of a single series. For a very long time there have been continents and
oceans, lakes and rivers, and the land has been diversified by mountains
and hills, plains and valleys, in the same general way as at the present
time. When once the idea is grasped that we are living in a geological
age, and that there is no break between the present and the past, it is
evident that the history of the past can be interpreted by means of the
results produced by known causes. Familiar formulas which express this
idea are: "The present is the key to the past"; "Geography is the
geology of to-day," etc. The forces or agencies which are now modifying
the earth's surface, such as the rending of rocks by changes of
temperature and the action of frost, erosion and deposition by streams,
the dash of ocean waves against the land, volcanic eruption, the
chemical action of organic acids, movements producing upheaval and
subsidence, etc., have been in action for geological eras, but their
intensity has varied from time to time and from place to place.

                      THE GROWTH OF THE CONTINENT

The geological history of North America is, in general, the same as that
of other continents, but claims attention in certain particulars,
largely for the reason that with the exception of Europe it has been
studied more thoroughly than any other comparable land area. In Europe,
throughout much of geological time, there have been numerous islands,
and as a large portion of the records of past changes which have been
presented were formed in the ocean, the results are complex. But in
North America there has been a comparatively steady growth from one main
continental centre or nucleus, and the records of the principal changes
that have occurred are, to a greater degree, simple. Not only in the
major features of the relief of the continent, as already described, but
in its growth and geological history, it is, so far as can be judged
from the present state of our knowledge of the various land areas, the
most typical of all the continents.

Changes in the outlines and area of a continent are brought about
principally by movements of elevation or depression in the earth's
crust. Of less importance is the erosion of the margin of the land by
waves and currents and the deposition of material brought from the land
by streams, together with the spits, bars, and embankments made by waves
and currents. By these and other and less conspicuous processes the
shape of North America has undergone numerous changes in outline and is
still being modified.

General maps have been prepared by J. D. Dana and others, showing the
outlines of North America at various stages in the course of its
development, and from a series of such maps recently compiled by D. C.
Schaffner those here reproduced (Fig. 33) have been selected to
illustrate the growth of the continent. As has been shown by various
geologists, the outlines of the present continents and ocean-basins had
their major features determined at a very early stage in the history of
the earth, and at a time preceding the existence of the oldest known
sedimentary rocks. At the close of the Archean, the earliest geological
era now recognised, and, so far as has been determined, before life
existed on the earth, the principal nucleus of North America was a land
mass some 2,000,000 square miles in area, situated mainly in what is now
the eastern half of Canada, from which there was a southward
prolongation represented by the Adirondack hills of New York (Fig. 33,
A).

The rocks forming this earliest known land in the Western Hemisphere
consist of crystalline schists, gneisses, and granite, which are
considered by some geologists at least as having resulted from the
metamorphism of sedimentary beds. Penetrating and intimately
intermingled with these greatly altered rocks, some of them perhaps
metamorphosed lavas and allied terranes, are many rocks that were forced
upward from deep in the earth into fissures in a molten condition and
have since cooled and crystallized. More than one epoch of metamorphism
has perhaps occurred, and the entire record now accessible is
exceedingly complicated.

The physical conditions at the earth's surface at the close of the
Archean period, as may reasonably be inferred, were not essentially
different from what they are now. The land areas were eroded by streams,
and the _débris_ carried to the sea and deposited, the coarser near
shore and the finer farther seaward. Upward movements in the earth's
crust in various places subsequently laid bare a portion of the
sea-floor adjacent to the former land, and the continent was enlarged.
The outline of the land as it existed previous to the upheaval which
exposed this portion of the ocean's bottom would be defined by the
landward margin of the material deposited. The exposed sediments
would be coarsest near the former coast-line and become finer and finer
seaward from it, and the fossils contained in the consolidated sands and
clays would also supply evidence bearing on the origin of the rocks. It
is by such interpretation of the ancient records in the light of what is
now taking place that the geologist is enabled to map approximately the
outline of North America at several stages in its growth in the manner
shown on the series of maps here presented. Information in this
connection, however, concerning both the northern and southern portions
of the continent is too meagre at present to be largely utilized in
these outline sketches.[5]

[5] The relations of the eras referred to on these maps and the
positions they occupy on the geological time-scale are shown a few pages
later on a chart of the geological history of North America.

The next system thus far recognised, following the Archean, is the
Algonkian, at the close of whose deposition some additions had been made
to the Archean or pre-Algonkian land. Succeeding the Algonkian system
come, in succession, the Cambrian, Ordovician, and Silurian systems. At
the close of the Silurian there was a decided increase in the size of
the main nucleus of the continent. Owing principally to an excess of
elevation over subsidence in the portion of the earth's crust beneath
the northeastern part of the region now occupied by the United States,
portions of the sediments deposited previous to the close of the
Silurian were upraised and important additions made to the extent of the
land southward from the Archean area of Canada. This "Appalachian
peninsula" would be conspicuous in a map representing the outline of the
continent at the close of the Silurian. The eastern margin of the
growing continent was then well to the eastward of its present position,
but how far beyond the present coast we have no means of determining.
Although at the close of the Silurian the continent had greatly
increased in area over that of the nucleus at the close of the Archean,
it bore but little resemblance to its present form. It is worthy
of note, however, that with the exception of the eastward extension of
the land at the time referred to, the growth had been within the present
continental outline.

A later stage in the growth of the continent is shown in Fig. 33, B,
when its eastern margin had much of its present general outline and the
Appalachian Mountains were in their prime. The time indicated is at the
close of the Paleozoic era, and after the great coal-fields extending
from Pennsylvania southward to Alabama and westward to beyond the
Mississippi were formed. The eastern half of the continent was
approximately completed at the time just referred to, and is older than
the western half.

During the Cretaceous period great changes took place in the geography
of the still growing continent, as may be seen by the map illustrating
that period. The conspicuous features in the geography are the submerged
Atlantic and Gulf borders, and the presence of a broad belt of ocean
water in the continental basin which reached from the then much expanded
Gulf of Mexico to the Arctic Ocean, and divided the land into an eastern
and a western continental island.

Following the Cretaceous period came the Tertiary period, during which
the continent assumed very nearly its present outline. During this
period, however, as is indicated in Fig. 33, D, the Atlantic border of
the United States from New England southward and a wide area about the
Gulf of Mexico, were submerged and had deep layers of sediment deposited
on them. During the Tertiary, bodies of fresh water became for the first
time a conspicuous feature on the land, and large lakes and broad
silt-depositing rivers existed particularly in the Pacific mountain
region of the United States, and at its close the continent was
practically completed as we now know it, but several important
oscillations, particularly at the north, have since occurred.

[Illustration: FIG. 33.--Maps showing the growth of the North American
continent.]

With the growth of the continent, briefly outlined above, came greater
and greater diversity in its relief, due principally to the
upraising of various mountains in a somewhat orderly succession from
east to west.

The oldest mountains on the continent are the Laurentian Highlands of
eastern Canada. Although the region referred to--the one mentioned above
as being composed of Archean crystalline rocks--is not now of sufficient
elevation or ruggedness to be termed mountainous, it shows in the nature
and structure of its rocks that deep erosion has taken place. The
inference is that truly great mountains have been removed, but the
evidence may also sustain the interpretation that slow upheaval has been
accompanied by erosion, and that at no time was the land conspicuously
elevated.

Next in age after the Laurentian Highlands come the mountains of New
England and the maritime province of Canada, which were upraised at the
close of the Silurian period. The next great step was the crumpling into
folds and upheaval of the rocks in the Appalachian region at the close
of the Paleozoic era. The Park and Stony Mountains were upraised at the
close of the Mesozoic era, and later came the Sierra Nevada and
Cascades, followed by the Coast Ranges. Youngest of all, and in part for
that reason the boldest and most lofty, are the magnificent mountains of
southern Alaska, with a host of sublime peaks, like Mounts Fairweather,
Logan, St. Elias, and perhaps McKinley. The last-named and highest peak
of all, however, may be of volcanic origin.

In the above list showing the progressive westward movement of the birth
of mountain systems, account is taken only of the elevations produced by
upheaval. The mountains due to volcanic eruptions, which are still
conspicuous, are all young, in comparison with the mountains situated to
the eastward of the Sierra Nevada. The majestic cones of the
northwestern portion of the United States, of which Mounts Shasta, Hood,
Adams, Rainier, Baker, etc., are the most glorious, are of Tertiary or
later age. The same is true, so far as known, of the still more lofty
volcanoes in Mexico. The "pine-tree" forms of steam rising from the
volcanoes of the Caribbees, Central America, southern Mexico, and
southwestern Alaska, proclaim the recency of the birth of the frequently
magnificent craters built of rocks that were once molten, from which
they emerge.

             THE ROCKS OF WHICH THE CONTINENT IS COMPOSED

The rocks of which North America is built belong to three classes, which
are world-wide in their distribution. These are: First, rocks produced
by the cooling and crystallizing of formerly molten magmas; second,
those deposited by water; and third, those which previously belonged to
either of the two classes just referred to, but have been recrystallized
and so greatly changed that their preceding condition is no longer
clearly recognisable.

These three classes or subkingdoms, as perhaps they might be termed from
analogy with systems of biological classifications, are in technical
language:

     1. _Igneous rocks_, such as the lava of Vesuvius.

     2. _Sedimentary rocks_, such as sandstone, shale, limestone,
     coal, etc.

     3. _Metamorphic rocks_, such as gneiss, schist, some granites,
     etc.

These major divisions are based principally on mode of origin, but do
not indicate relative age. While theoretically at least, and in a
general way, the rocks of these three great classes came into existence
on the earth in the order named, it is convenient to consider first
those of sedimentary origin.

[Illustration: PLATE IV.--Leading geological features.]

_The Sedimentary Rocks_ (Plate IV).--Whenever land exists or the waves
and currents of the ocean come in contact with the rocks denudation
occurs. That is, the rocks are broken through the action of mechanical
or chemical agencies, such as the friction of the gravel and sand swept
along by streams, the solvent power of water, etc., and the fragments
thus produced are removed principally through the action of flowing
water and deposited. Resulting from this general process of rock decay
and disintegration, combined with transportation and deposition,
there result mechanically formed sedimentary beds, such as shale,
sandstone, conglomerate, etc.; chemically formed sedimentary beds, such
as the deposits of springs, the saline precipitates from inclosed lakes,
etc.; and organically formed sedimentary beds, as, for example, peat,
coal, and limestone.

Since the first appearance of land in the region now occupied by North
America, sedimentary rocks have been in process of formation, and in
this way the growth of the continent, with the aid of movements in the
earth's crust, has been produced.

The superficial extent of the sedimentary beds in North America is very
great, as is indicated on the map referred to above. By far the larger
portion of the surface of the continent is underlain by them. Their
thickness varies from place to place, but probably reaches a maximum in
the Appalachian region, where a depth of some 40,000 feet has been
measured. Throughout the continental basin their depth is in general
from 3,000 to 4,000 feet. In the Pacific mountains their thickness
embraces tens of thousands of feet, and the same is true in Mexico,
Cuba, and Jamaica. These sedimentary rocks contain fossils which, with
comparatively few exceptions, show that they were deposited in the
ocean; thus sustaining in an important manner the conclusion already
presented in reference to the growth of the continent.

Great as is the area of the sedimentary beds at the present time, it
does not show the entire extent to which what is now land has at some
time been submerged beneath the sea. In certain broad regions,
sedimentary beds which formerly existed have been removed by erosion; in
other extensive areas they are covered by volcanic rocks, and in still
other portions of the continent, embracing thousands of square miles,
they have been metamorphosed and their original characteristics
obliterated.

The system of classification of the sedimentary beds that has been
adopted, as is well known, is based on the relative age of the
formations, determined primarily by the occurrence of one formation
above another, in regions where but moderate disturbances in
position have occurred. Many of the stratified rocks contain
fossils--that is, records of the life of the time they were deposited,
and after the order of succession of a large number of formations has
been ascertained, the life records they contain may be used as a means
of determining the age of a newly discovered terrane.

By grouping the information obtained from the study of the vertical
sequence of the formations in many regions, and also the records of life
contained in them, a composite geological column has been constructed
which shows the relative age of all known formations. The larger
divisions of such a scheme of classification are world-wide in their
application, but the smaller divisions are usually of restricted
geographical extent.

The scheme of classification of general application in North America is
shown in the chart on page 308. The arrangement is in order of age, the
oldest formation being at the bottom. There is some lack of uniformity
among American geologists as to certain of the terms used, more
especially in the lower portion of the column, and in part the scheme is
provisional, but in general it may be taken as expressing the progress
made in the study of the geology of North America up to the present
time.

The names of the larger divisions in this scheme of classification, or
those designating the groups and systems and the eras and periods, have
for the most part been adopted from European geologists. Two important
ones, however--namely, Archean and Algonkian--are of American birth.

While this scheme of classification is based on the succession of
sedimentary beds, igneous and metamorphic rocks have a place in it,
providing their age can be determined.

The Archean period includes the time previous to the deposition of the
oldest known sedimentary beds, and its lower limit is as yet undefined.
The Archean system, or the rocks formed during the Archean period, are
without known fossils, and consist largely of gneisses and foliated
schists, which are metamorphosed sedimentary or igneous terranes,
together with various eruptives. The typical area where these rocks are
exposed at the surface is in the Laurentian Highlands of eastern Canada,
the main Archean nucleus of the continent, but rocks of the same age and
same general character occur in several of the mountain systems of both
the Atlantic and Pacific cordilleras, and underlie the sedimentary beds
throughout a large part of the Continental basin. The Archean system was
named by J. D. Dana, and divided into two portions, namely, the
Laurentian below and the Huronian above. More recent studies, especially
by C. R. Van Hise, have shown the necessity of removing from the system
many of the terranes formerly referred to it, and of placing them in the
Algonkian. The Archean as it remains after this adjustment is termed by
Van Hise the _Basement Complex_. This term, although thus far not
generally adopted, has much to commend it, since the terranes designated
by it are highly complex, and may perhaps be ultimately subdivided into
two or more systems, and besides occupy a basal position lower than any
known sedimentary formation that has escaped metamorphism.

      _Outline Chart of the Geological History of North America_

 +----------------------------------------+-----------+-----------------+
 |                         Rock-Scale. -->|   Group.  |   System.       |
 |                         Time-Scale. -->|    Era.   |   Period.       |
 +------------+------------+--------------+-----------+-----------------+
 |Zoic time:  |  Time of   |   Time of    |Psychozoic.|Human.           |
 |embracing   |  Mammals.  |  Palms and   +-----------+-----------------+
 |the history +------------+ Angiosperms. |           |Pleistocene.     |
 |of the      |            +--------------+Cenozoic.  +-----------------+
 |earth since |            |              |           |Tertiary.        |
 |the         |  Time of   |              +-----------+-----------------+
 |appearance  | Reptiles.  |   Time of    |           |Cretaceous.      |
 |of life.    |            |   Cycads.    |Mesozoic.  +-----------------+
 |            +------------+--------------+           |Jura-Trias.      |
 |            |  Time of   |              +-----------+-----------------+
 |            |Amphibians. |   Time of    |           |Carboniferous.   |
 |            |            |   Acrogens   |           +-----------------+
 |            +------------+(Ferns, club- |           |Devonian.        |
 |            |  Time of   |mosses, etc.).|           +-----------------+
 |            |  Fishes.   |              |Paleozoic. |Silurian.        |
 |            +------------+              |           +-----------------+
 |            |            +--------------+           |Ordovician.      |
 |            |  Time of   |              |           +-----------------+
 |            |Molluscs and|              |           |Cambrian.        |
 |            |Crustaceans.|              +-----------+-----------------+
 |            |            |   Time of    |           |Algonkian.       |
 |            +------------+    Algæ.     |           +-----------------+
 |            |            |              |Eozoic.    |(As yet unknown  |
 |            |  Time of   |              |           |pre-Algonkian    |
 |            | Protozoa?  |              |           |sediments.)      |
 +------------+------------+--------------+-----------+-----------------+
 |Azoic time: preceding the dawn of life. |Azoic.     |Archean or       |
 |                                        |           |Basement Complex.|