Fresh fuel is perpetually being pushed on in front, and by alternate
movement of the fire bars the fire is kept in perpetual motion till the
ashes drop out at the back. To such an arrangement as this a steady air
supply can be adjusted, and if the boiler demand is constant there is no
need for smoke, and an inferior fuel may be used. The other plan is to vary
the air supply to suit the stoking. This is effected by Prideaux automatic
furnace doors, which have louvers to remain open for a certain time after
the doors are shut, and so to admit extra air immediately after coal has
been put on, the supply gradually decreasing as distillation ceases. The
worst of air admitted through chinks in the doors, or through partly open
doors, is that it is admitted cold, and scarcely gets thoroughly warm
before it is among the stuff it has to burn. Still this is not a fatal
objection, though a hot blast would be better. Nothing can be worse than
shoveling on a quantity of coal and shutting it up completely. Every
condition of combustion is thus violated, and the intended furnace is a
mere gas retort.

_Gas Producers_.--Suppose the conditions of combustion are purposely
violated; we at once have a gas producer. That is all gas producers are,
extra bad stoves or furnaces, not always much worse than things which
pretend to serve for combustion. Consider how ordinary gas is made. There
is a red-hot retort or cylinder plunged in a furnace. Into this tube you
shovel a quantity of coal, which flames vigorously as long as the door is
open, but when it is full you shut the door, thus cutting off the supply of
air and extinguishing the flame. Gas is now simply distilled, and passes
along pipes to be purified and stored. You perceive at once that the
difference between a gas retort and an ordinary furnace with closed doors
and half choked fire bars is not very great. Consumption of smoke! It is
not smoke consumers you really want, it is fuel consumers. You distill your
fuel instead of burning it, in fully one-half, might I not say nine-tenths,
of existing furnaces and close stoves. But in an ordinary gas retort the
heat required to distill the gas is furnished by an outside fire; this is
only necessary when you require lighting gas, with no admixture of carbonic
acid and as little carbonic oxide as possible. If you wish for heating gas,
you need no outside fire; a small fire at the bottom of a mass of coal will
serve to distill it, and you will have most of the carbon also converted
into gas. Here, for instance, is Siemens' gas producer. The mass of coal is
burning at the bottom, with a very limited supply of air. The carbonic acid
formed rises over the glowing coke, and takes up another atom of carbon to
form the combustible gas carbonic oxide. This and the hot nitrogen passing
over and through the coal above distill away its volatile constituents, and
the whole mass of gas leaves by the exit pipe. Some art is needed in
adjusting the path of the gases distilled from the fresh coal with
reference to the hot mass below. If they pass too readily, and at too low a
temperature, to the exit pipe, this is apt to get choked with tar and dense
hydrocarbons. If it is carried down near or through the hot fuel below, the
hydrocarbons are decomposed over much, and the quality of the gas becomes
poor. Moreover, it is not possible to make the gases pass freely through a
mass of hot coke; it is apt to get clogged. The best plan is to make the
hydrocarbon gas pass over and near a red-hot surface, so as to have its
heaviest hydrocarbons decomposed, but so as to leave all those which are
able to pass away as gas uninjured, for it is to the presence of these that
the gas will owe its richness as a combustible material, especially when
radiant heat is made use of.

The only inert and useless gas in an arrangement like this is the nitrogen
of the air, which being in large quantities does act as a serious diluent.
To diminish the proportion of nitrogen, steam is often injected as well as
air. The glowing coke can decompose the steam, forming carbonic oxide and
hydrogen, both combustible. But of course no extra energy can be gained by
the use of steam in this way; all the energy must come from the coke, the
steam being already a perfectly burned product; the use of steam is merely
to serve as a vehicle for converting the carbon into a convenient gaseous
equivalent. Moreover, steam injected into coke cannot keep up the
combustion; it would soon put the fire out unless air is introduced too.
Some air is necessary to keep up the combustion, and therefore some
nitrogen is unavoidable. But some steam is advisable in every gas producer,
unless pure oxygen could be used instead of air; or unless some substance
like quicklime, which holds its oxygen with less vigor than carbon does,
were mixed with the coke and used to maintain the heat necessary for
distillation. A well known gas producer for small scale use is Dowson's.
Steam is superheated in a coil of pipe, and blown through glowing
anthracite along with air. The gas which comes off consists of 20 per cent.
hydrogen, 30 per cent. carbonic oxide, 3 per cent. carbonic acid, and 47
per cent. nitrogen. It is a weak gas, but it serves for gas engines, and is
used, I believe, by Thompson, of Leeds, for firing glass and pottery in a
gas kiln. It is said to cost 4d. per 1,000 ft., and to be half as good as
coal gas.

For furnace work, where gas is needed in large quantities, it must be made
on the spot. And what I want to insist upon is this, that all
well-regulated furnaces are gas retorts and combustion chambers combined.
You may talk of burning coal, but you can't do it; you must distill it
first, and you may either waste the gas so formed or you may burn it
properly. The thing is to let in not too much air, but just air enough.
Look, for instance, at Minton's oven for firing pottery. Round the central
chamber are the coal hoppers, and from each of these gas is distilled,
passes into the central chamber, where the ware is stacked, and meeting
with an adjusted supply of air as it rises, it burns in a large flame,
which extends through the whole space and swathes the material to be
heated. It makes its exit by a central hole in the floor, and thence rises
by flues to a common opening above. When these ovens are in thorough
action, nothing visible escapes. The smoke from ordinary potters' ovens is
in Staffordshire a familiar nuisance. In the Siemens gas producer and
furnace, of which Mr. Frederick Siemens has been good enough to lend me
this diagram, the gas is not made so closely on the spot, the gas retort
and furnace being separated by a hundred yards or so in order to give the
required propelling force. But the principle is the same; the coal is first
distilled, then burnt. But to get high temperature, the air supply to the
furnace must be heated, and there must be no excess. If this is carried on
by means of otherwise waste heat we have the regenerative principle, so
admirably applied by the Brothers Siemens, where the waste heat of the
products of combustion is used to heat the incoming air and gas supply. The
reversing arrangement by which the temperature of such a furnace can be
gradually worked up from ordinary flame temperature to something near the
dissociation point of gases, far above the melting point of steel, is well
known, and has already been described in this place. Mr. Siemens has lent
me this beautiful model of the most recent form of his furnace, showing its
application to steel making and to glass working.

The most remarkable and, at first sight, astounding thing about this
furnace is, however, that it works solely by radiation. The flames do not
touch the material to be heated; they burn above it, and radiate their heat
down to it. This I regard as one of the most important discoveries in the
whole subject, viz., that to get the highest temperature and greatest
economy out of the combustion of coal, one must work directly by radiant
heat only, all other heat being utilized indirectly to warm the air and gas
supply, and thus to raise the flame to an intensely high temperature.

It is easy to show the effect of supplying a common gas flame with warm air
by holding it over a cylinder packed with wire gauze which has been made
red hot. A common burner held over such a hot air shaft burns far more
brightly and whitely. There is no question but that this is the plan to get
good illumination out of gas combustion; and many regenerative burners are
now in the market, all depending on this principle, and utilizing the waste
heat to make a high temperature flame. But although it is evidently the
right way to get light, it was by no means evidently the right way to get
heat. Yet so it turns out, not by warming solid objects or by dull warm
surfaces, but by the brilliant radiation of the hottest flame that can be
procured, will rooms be warmed in the future. And if one wants to boil a
kettle, it will be done, not by putting it into a non-luminous flame, and
so interfering with the combustion, but by holding it near to a freely
burning regenerated flame, and using the radiation only. Making toast is
the symbol of all the heating of the future, provided we regard Mr.
Siemens' view as well established.

The ideas are founded on something like the following considerations: Flame
cannot touch a cold surface, i.e., one below the temperature of combustion,
because by the contact it would be put out. Hence, between a flame and the
surface to be heated by it there always intervenes a comparatively cool
space, across which heat must pass by radiation. It is by radiation
ultimately, therefore, that all bodies get heated. This being so, it is
well to increase the radiating power of flame as much as possible. Now,
radiating power depends on two things: the presence of solid matter in the
flame in a fine state of subdivision, and the temperature to which it is
heated. Solid matter is most easily provided by burning a gas rich in dense
hydrocarbons, not a poor and non-luminous gas. To mix the gas with air so
as to destroy and burn up these hydrocarbons seems therefore to be a
retrograde step, useful undoubtedly in certain cases, as in the Bunsen
flame of the laboratory, but not the ideal method of combustion. The ideal
method looks to the use of a very rich gas, and the burning of it with a
maximum of luminosity. The hot products of combustion must give up their
heat by contact. It is for them that cross tubes in boilers are useful.
They have no combustion to be interfered with by cold contacts. The _flame_
only should be free.

The second condition of radiation was high temperature. What limits the
temperature of a flame? Dissociation or splitting up of a compound by heat.
So soon as the temperature reaches the dissociation point at which the
compound can no longer exist, combustion ceases. Anything short of this may
theoretically be obtained.

But Mr. Siemens believes, and adduces some evidence to prove, that the
dissociation point is not a constant and definite temperature for a given
compound; it depends entirely upon whether solid or foreign surfaces are
present or not. These it is which appear to be an efficient cause of
dissociation, and which, therefore, limit the temperature of flame. In the
absence of all solid contact, Mr. Siemens believes that dissociation, if it
occur at all, occurs at an enormously higher temperature, and that the
temperature of free flame can be raised to almost any extent. Whether this
be so or not, his radiating flames are most successful, and the fact that
large quantities of steel are now melted by mere flame radiation speaks
well for the correctness of the theory upon which his practice has been
based.

_Use of Small Coal_.--Meanwhile, we may just consider how we ought to deal
with solid fuel, whether for the purpose of making gas from it or for
burning it _in situ_. The question arises, In what form ought solid fuel to
be--ought it to be in lumps or in powder? Universal practice says lumps,
but some theoretical considerations would have suggested powder. Remember,
combustion is a chemical action, and when a chemist wishes to act on a
solid easily, he always pulverizes it as a first step.

Is it not possible that compacting small coal into lumps is a wrong
operation, and that we ought rather to think of breaking big coal down into
slack? The idea was suggested to me by Sir W. Thomson in a chance
conversation, and it struck me at once as a brilliant one. The amount of
coal wasted by being in the form of slack is very great. Thousands of tons
are never raised from the pits because the price is too low to pay for the
raising--in some places it is only 1s. 6d. a ton. Mr. McMillan calculates
that 130,000 tons of breeze, or powdered coke, is produced every year by
the Gas Light and Coke Company alone, and its price is 3s. a ton at the
works, or 5s. delivered.

The low price and refuse character of small coal is, of course, owing to
the fact that no ordinary furnace can burn it. But picture to yourself a
blast of hot air into which powdered coal is sifted from above like ground
coffee, or like chaff in a thrashing mill, and see how rapidly and
completely it might burn. Fine dust in a flour mill is so combustible as to
be explosive and dangerous, and Mr. Galloway has shown that many colliery
explosions are due not to the presence of gas so much as the presence of
fine coal-dust suspended in the air. If only fine enough, then such dust is
eminently combustible, and a blast containing it might become a veritable
sheet of flame. (Blow lycopodium through a flame.) Feed the coal into a
sort of coffee-mill, there let it be ground and carried forward by a blast
to the furnace where it is to be burned. If the thing would work at all,
almost any kind of refuse fuel could be burned--sawdust, tan, cinder heaps,
organic rubbish of all kinds. The only condition is that it be fine enough.

Attempts in this direction have been made by Mr. T.R. Crampton, by Messrs.
Whelpley and Storer, and by Mr. G.K. Stephenson; but a difficulty has
presented itself which seems at present to be insuperable, that the slag
fluxes the walls of the furnace, and at that high temperature destroys
them. If it be feasible to keep the flame out of contact with solid
surfaces, however, perhaps even this difficulty can be overcome.

Some success in blast burning of dust fuel has been attained in the more
commonplace method of the blacksmith's forge, and a boiler furnace is
arranged at Messrs. Donkin's works at Bermondsey on this principle. A
pressure of about half an inch of water is produced by a fan and used to
drive air through the bars into a chimney draw of another half-inch. The
fire bars are protected from the high temperatures by having blades which
dip into water, and so keep fairly cool. A totally different method of
burning dust fuel by smouldering is attained in M. Ferret's low temperature
furnace by exposing the fuel in a series of broad, shallow trays to a
gentle draught of air. The fuel is fed into the top of such a furnace, and
either by raking or by shaking it descends occasionally, stage by stage,
till it arrives at the bottom, where it is utterly inorganic and mere
refuse. A beautiful earthworm economy of the last dregs of combustible
matter in any kind of refuse can thus be attained. Such methods of
combustion as this, though valuable, are plainly of limited application;
but for the great bulk of fuel consumption some gas-making process must be
looked to. No crude combustion of solid fuel can give ultimate perfection.

Coal tar products, though not so expensive as they were some time back, are
still too valuable entirely to waste, and the importance of exceedingly
cheap and fertilizing manure in the reclamation of waste lands and the
improvement of soil is a question likely to become of most supreme
importance in this overcrowded island. Indeed, if we are to believe the
social philosophers, the naturally fertile lands of the earth may before
long become insufficient for the needs of the human race; and posterity may
then be largely dependent for their daily bread upon the fertilizing
essences of the stored-up plants of the carboniferous epoch, just as we are
largely dependent on the stored-up sunlight of that period for our light,
our warmth, and our power. They will not then burn crude coal, therefore.
They will carefully distill it--extract its valuable juices--and will
supply for combustion only its carbureted hydrogen and its carbon in some
gaseous or finely divided form.

Gaseous fuel is more manageable in every way than solid fuel, and is far
more easily and reliably conveyed from place to place. Dr. Siemens, you
remember, expected that coal would not even be raised, but turned into gas
in the pits, to rise by its own buoyancy to be burnt on the surface
wherever wanted. And not only will the useful products be first removed and
saved, its sulphur will be removed too; not because it is valuable, but
because its product of combustion is a poisonous nuisance. Depend upon it,
the cities of the future will not allow people to turn sulphurous acid
wholesale into the air, there to oxidize and become oil of vitriol. Even if
it entails a slight strain upon the purse they will, I hope, be wise enough
to prefer it to the more serious strain upon their lungs. We forbid sulphur
as much as possible in our lighting gas, because we find it is deleterious
in our rooms. But what is London but one huge room packed with over four
millions of inhabitants? The air of a city is limited, fearfully limited,
and we allow all this horrible stuff to be belched out of hundreds of
thousands of chimneys all day long.

Get up and see London at four or five in the morning, and compare it with
four or five in the afternoon; the contrast is painful. A city might be
delightful, but you make it loathsome; not only by smoke, indeed, but still
greatly by smoke. When no one is about, then the air is almost pure; have
it well fouled before you rise to enjoy it. Where no one lives, the breeze
of heaven still blows; where human life is thickest, there it is not fit to
live. Is it not an anomaly, is it not farcical? What term is strong enough
to stigmatize such suicidal folly? But we will not be in earnest, and our
rulers will talk, and our lives will go on and go out, and next century
will be soon upon us, and here is a reform gigantic, ready to our hands,
easy to accomplish, really easy to accomplish if the right heads and
vigorous means were devoted to it. Surely something will be done.

The following references may be found useful in seeking for more detailed
information: Report of the Smoke Abatement Committee for 1882, by Chandler
Roberts and D.K. Clark. "How to Use Gas," by F.T. Bond; Sanitary
Association, Gloucester. "Recovery of Volatile Constituents of Coal," by
T.B. Lightfoot; Journal Society of Arts, May, 1883. "Manufacture of Gas
from Oil," by H.E. Armstrong; Journal Society of Chemical Industry,
September, 1884. "Coking Coal," by H.E. Armstrong; Iron and Steel
Institute, 1885. "Modified Siemens Producer," by John Head; Iron and Steel
Institute, 1885. "Utilization of Dust Fuel," by W.G. McMillan; Journal
Society of Arts, April. 1886. "Gas Producers," by Rowan; Proc. Inst. C.E.,
January, 1886. "Regenerative Furnaces with Radiation," and "On Producers,"
by F. Siemens; Journal Soc. Chem. Industry, July, 1885, and November, 1885.
"Fireplace Construction," by Pridgin Teale; the _Builder_, February, 1886.
"On Dissociation Temperatures," by Frederick Siemens; Royal Institution,
May 7, 1886.

Near Colorados, in the Argentine Republic, a large bed of superior coal has
been opened, and to the west of the Province of Buenos Ayres extensive
borax deposits have been discovered.

THE ANTI-FRICTION CONVEYER.

The accompanying engraving illustrates a remarkable invention. For ages,
screw conveyers for corn and meal have been employed, and in spite of the
power consumed and the rubbing of the material conveyed, they have
remained, with little exception, unimproved and without a rival. Now we
have a new conveyer, which, says _The Engineer_, in its simplicity excels
anything brought out for many years, and, until it is seen at work, makes a
heavier demand upon one's credulity than is often made by new mechanical
inventions. As will be seen from the engravings, the new conveyer consists
simply of a spiral of round steel rod mounted upon a quickly revolving
spindle by means of suitable clamps and arms. The spiral as made for
England is of 5/8 in. steel rod, because English people would not be
inclined to try what is really sufficient in most cases, namely, a mere
wire. The working of this spiral as a conveyer is simply magical. A 6 in.
spiral delivers 800 bushels per hour at 100 revolutions per minute, and
more in proportion at higher speeds. A little 4 in. spiral delivers 200
bushels per hour at 100 revolutions per minute. It seems to act as a mere
persuader. The spiral moves a small quantity, and sets the whole contents
of the trough in motion. In fact, it embodies the great essentials of
success, namely, simplicity, great capacity for work, and cheapness. It is
the invention of Mr. J. Little, and is made by the Anti-friction Conveyer
Company, of 59 Mark Lane, London.

[Illustration: THE ANTI-FRICTION CONVEYER WITH CASING OR TROUGH--END
VIEW WITH HANGER.]

Since the days of Archimedes, who is credited with being the inventor of
the screw, there has not been any improvement in the principle of the worm
conveyer. There have been several patents taken out for improved methods of
manufacturing the old-fashioned continuous and paddle-blade worms, but Mr.
Little's patent is the first for an entirely new kind of conveyer.

STUDIES IN PYROTECHNY.

[Footnote: Continued from SUPPLEMENT, No. 583, page 9303.]

II. METHODS OF ILLUMINATION.

_Torches_ consist of a bundle of loosely twisted threads which has been
immersed in a mixture formed of two parts, by weight, of beeswax, eight of
resin, and one of tallow. In warm, dry weather, these torches when lighted
last for two hours when at rest, and for an hour and a quarter on a march.
A good light is obtained by spacing them 20 or 30 yards apart.

Another style of torch consists of a cardboard cylinder fitted with a
composition consisting of 100 parts of saltpeter, 60 of sulphur, 8 of
priming powder, and 30 of pulverized glass, the whole sifted and well
mixed. This torch, which burns for a quarter of an hour, illuminates a
space within a radius of 180 or 200 yards very well.

The _tourteau goudronné_ (lit. "tarred coke") is merely a ring formed of
old lunt or of cords well beaten with a mallet (Fig. 10). This ring is
first impregnated with a composition formed of 20 parts of black pitch
and 1 of tallow, and then with another one formed of equal parts of
black pitch and resin. One of these torches will burn for an hour in
calm weather, and half an hour in the wind. Rain does not affect the
burning of it. These rings are usually arranged in pairs on brackets
with two branches and an upper circle, the whole of iron, and these
brackets are spaced a hundred yards apart.

[Illustration: FIGS. 9 TO 16.--VARIOUS PYROTECHNIC DEVICES.]

[Illustration: FIGS. 17.--ILLUMINATING ROCKET.]

A _tarred fascine_ consists of a small fagot of dry wood, 20 inches in
length by 4 in diameter, covered with the same composition as the preceding
(Fig. 11). Fascines thus prepared burn for about half an hour. They are
placed upright in supports, and these latter are located at intervals of
twenty yards.

The _Lamarre compositions_ are all formed of a combustible substance, such
as boiled oil,[1] of a substance that burns, such as chlorate of potash,
and of various coloring salts.

[Footnote 1: For preparation see page 9304 of SUPPLEMENT.]

The _white composition_ used for charging fire balls and 1½ inch flambeaux
is formed of 500 parts of powdered chlorate of potash, 1,500 of nitrate of
baryta, 120 of light wood charcoal, and 250 of boiled oil. Another white
composition, used for charging ¾ inch flambeaux, consists of 1,000 parts of
chlorate of potash, 1,000 of nitrate of baryta, and 175 of boiled oil.

The _red composition_ used for making red flambeaux and percussion signals
consists of 1,800 parts of chlorate of potash, 300 of oxalate of strontia,
300 of carbonate of strontia, 48 of whitewood charcoal, 240 of boiled oil,
6 of oil, and 14 of gum lac.

A red or white _Lamarre flambeau_ consists of a sheet rubber tube filled
with one of the above-named compositions. The lower extremity of this tube
is closed with a cork. When the charging has been effected, the flambeau is
primed by inserting a quickmatch in the composition. This is simply lighted
with a match or a live coal. The composition of the Lamarre quickmatch will
be given hereafter.

A Lamarre flambeau 1½ inch in diameter and 3 inches in length will burn for
about thirty-five minutes. One of the same length, and ¾ inch in diameter,
lasts but a quarter of an hour.

A _fire ball_ consists of an open work sack internally strengthened with a
sheet iron shell, and fitted with the Lamarre white composition. After the
charging has been done, the sphere is wound with string, which is made to
adhere by means of tar, and canvas is then wrapped around the whole.
Projectiles of this kind, which have diameters of 6, 8, 11, and 13 inches,
are shot from mortars.

The _illuminating grenade_ (Fig. 13) consists of a sphere of vulcanized
rubber, two inches in diameter, charged with the Lamarre white composition.
The sphere contains an aperture to allow of the insertion of a fuse. The
priming is effected by means of a tin tube filled with a composition
consisting of three parts of priming powder, two of sulphur, and one of
saltpeter. These grenades are thrown either by hand or with a sling, and
they may likewise be shot from mortars. Each of these projectiles
illuminates a circle thirty feet in diameter for a space of time that
varies, according to the wind, from sixty to eighty seconds.

The _percussion signal_ (Fig. 14) consists of a cylinder of zinc, one inch
in diameter and one and a quarter inch in length, filled with Lamarre red
composition. It is provided with a wooden handle, and the fuse consists of
a capsule which is exploded by striking it against some rough object. This
signal burns for nearly a minute.

_Belgian illuminating balls and cylinders_ are canvas bags filled with
certain compositions. The cylinders, five inches in diameter and seven in
length, are charged with a mixture of six parts of sulphur, two of priming
powder, one of antimony, and two of beeswax cut up into thin slices. They
are primed with a quickmatch. The balls, one and a half inch in diameter,
are charged with a composition consisting of twelve parts of saltpeter,
eight of sulphur, four of priming powder, two of sawdust, two of beeswax,
and two of tallow. They are thrown by hand. They burn for six minutes.

_Illuminating kegs_ (Fig. 15) consist of powder kegs filled with shavings
covered with pitch. An aperture two or three inches in diameter is made in
each head, and then a large number of holes, half an inch in diameter, and
arranged quincuncially, are bored in the staves and heads. All these
apertures are filled with port-fires.

The _illuminating rocket_ (Fig. 17) consists of a sheet iron cartridge,
_a_, containing a composition designed to give it motion, of a cylinder,
_b_, of sheet iron, capped with a cone of the same material and containing
illuminating stars of Lamarre composition and an explosive for expelling
them, and, finally, of a directing stick, _c_. Priming is effected by means
of a bunch of quickmatches inclosed in a cardboard tube placed in contact
with the propelling composition. This latter is the same as that used in
signal rockets. As in the case of the latter, a space is left in the axis
of the cartridges. These rockets are fired from a trough placed at an
inclination of fifty or sixty degrees. Those of three inches illuminate the
earth for a distance of 900 yards. They may be used to advantage in the
operation of signaling.

A _parachute fire_ is a device designed to be ejected from a pot at the end
of the rocket's travel, and to emit a bright light during its slow descent.
It consists of a small cylindrical cardboard box (Fig. 16) filled with
common star paste or Lamarre stars, and attached to a parachute, _e_, by
means of a small brass chain, _d_.

To make this parachute, we cut a circle ten feet in diameter out of a piece
of calico, and divide its circumference into ten or twelve equal parts. At
each point of division we attach a piece of fine hempen cord about three
feet in length, and connect these cords with each other, as well as with
the suspension chain, by ligatures that are protected against the fire by
means of balls of sized paper.

In rockets designed to receive these parachutes, a small cavity is reserved
at the extremity of the cartridge for the reception of 225 grains of
powder. To fill the pot, the chain, _d_, is rolled spirally around the box,
_c_, and the latter is covered with the parachute, _e_, which has been
folded in plaits, and then folded lengthwise alternately in one direction
and the other.

The _parachute port-fire_ consists of a cardboard tube of from quarter to
half an inch in diameter, and from four to five inches in length, closed at
one extremity and filled with star paste. This is connected by a brass wire
with a cotton parachute eight inches in diameter. A rocket pot is capable
of holding twenty of these port-fires.

Parachute fires and port-fires are used to advantage in the operation of
signaling.--_La Nature_.

IMPROVEMENT IN LAYING OUT FRAMES OF VESSELS--THE FRAME TRACER.

By GUSTAVE SONNENBURG.

To avoid the long and time-consuming laying out of a boat by ordinates and
abscissas, I have constructed a handy apparatus, by which it is possible
without much trouble to obtain the sections of a vessel graphically and
sufficiently accurate. The description of its construction is given with
reference to the accompanying cut. A is a wooden rod of rectangular
section, to which are adapted two brackets, a_{1} a_{2}, lined with India
rubber or leather; a_{1} is fixed to the wood, a_{2} is of metal, and, like
the movable block of a slide gauge, moves along A. In the same plane is a
second rod, perpendicular to A, and attached thereto, which is perforated
by a number of holes. A revolving pin, C, is adapted to pass through these
holes, to which a socket, D, is pivoted, C acting as its axis. To prevent
this pin from falling out, it is secured by a nut behind the rod. Through
the socket, D, runs a rod, E, which carries the guide point, s_{1}, and
pencil, s_{2}. Over s_{1} a rubber band is stretched, to prevent injury to
the varnish of the boat. Back of and to A and B a drawing board is
attached, over which a sheet of paper is stretched.

[Illustration: THE FRAME TRACER.]

The method of obtaining a section line is as follows: The rod, A, is placed
across the gunwale and perpendicular to the axis of the boat, and its
anterior vertical face is adjusted to each frame of the boat which it is
desired to reproduce. By means of the brackets, a_{1} and a_{2}, A is fixed
in place. The bolt, C, is now placed in the perforations already alluded
to, which are recognized as most available for producing the constructional
diagram. At the same time the position of the pencil point, s_{2}, must be
chosen for obtaining the best results.

Next the operator moves along the side of the boat the sharpened end,
s_{1}, of the rod, E, and thus for the curve from keel to gunwale, s_{2}
describes a construction line. It is at once evident that a_{2}, for
example, corresponds to the point, a_{1}. The apparatus is now removed and
placed on the working floor. If, reversing things, the point, s_{1}, is
carried around the construction curve, the point, s_{2}, will inscribe the
desired section in its natural dimensions. This operation is best conducted
after one has chosen and described all the construction curves of the
boat. Next, the different section lines are determined, one by one, by the
reversed method above described. The result is a half section of the boat;
the other symmetrical half is easily obtained.

If the whole process is repeated for the other side of the boat, tracing
paper being used instead of drawing paper, the boat may be tested for
symmetry of building, a good control for the value of the ship. For
measuring boats, as for clubs and regattas, for seamen, and often for the
so-called _Spranzen_ (copying) of English models, my apparatus, I doubt
not, will be very useful.--_Neuste Erfindungen und Erfahrungen_.

TAR FOR FIRING RETORTS.

The attention of gas engineers has been forcibly directed to the use of tar
as a fuel for the firing of retorts, now that this once high-priced
material is suffering, like everything else (but, perhaps, to a more marked
extent), by what is called "depression in trade." In fact, it has in many
places reached so low a commercial value that it is profitable to burn it
as a fuel. Happily, this is not the case at Nottingham; and our interest in
tar as a fuel is more experimental, in view of what may happen if a further
fall in tar products sets in. I have abandoned the use of steam injection
for our experimental tar fires in favor of another system. The steam
injectors produce excellent heats, but are rather intermittent in their
action, and the steam they require is a serious item, and not always
available.

Tar being a _pseudo_ liquid fuel, in arranging for its combustion one has
to provide for the 20 to 25 per cent. of solid carbon which it contains,
and which is deposited in the furnace as a kind of coke or breeze on the
distillation of the volatile portions, which are much more easily consumed
than the tar coke.

THE TAR FIRE

I have adopted is one that can be readily adapted to an ordinary coke
furnace, and be as readily removed, leaving the furnace as before. The
diagram conveys some idea of the method adopted. An iron frame, d, standing
on legs on the floor just in front of the furnace door, carries three fire
tiles on iron bearers. The top one, a, is not moved, and serves to shield
the upper face of the tile, b, from the fierce heat radiated from the
furnace, and also causes the air that rushes into the furnace between the
tiles, a and b, to travel over the upper face of the tile, b, on which the
tar flows, thereby keeping it cool, and preventing the tar from bursting
into flame until it reaches the edge of the tile, b, over the whole edge of
which it is made to run fairly well by a distributing arrangement. A rapid
combustion takes place here, but some unconsumed tar falls on to the bed
below. About one-third of the grate area is filled up by a fire tile, and
on this the tar coke falls. The tile, c, is moved away from time to time,
and the tar coke that accumulates in front of it is pushed back on to the
fire bars, e, at the back of the furnace, to be there consumed. Air is thus
admitted, by three narrow slot-like openings, to the front of the furnace
between the tiles, a, b, and c, and under c and through the fire bars, e.
The air openings below are about three times the area of the openings in
the front of the furnace; but as the openings between the fire bars and the
tiles are always more or less covered by tar coke, it is impossible to say
what the effective openings are. This disposition answers admirably, and
requires little attention. Three minutes per hour per fire seems to be the
average, and the labor is of a very light kind, consisting of clearing the
passages between the tiles, and occasionally pushing back the coke on to
the fire bars. These latter are not interfered with, and will not require
cleaning unless any bricks in the furnace have been melted, when a bed of
slag will be found on them.

THE AMOUNT OF DRAUGHT

required for these fires is very small, and less than with coke firing. I
find that 0.08 in. vacuum is sufficient with tar fires, and 0.25 in. for
coke fires. The fires would require less attention with more draught and
larger tar supply, as the apertures do not so easily close with a sharp
draught, and the tar is better carried forward into the furnace. A regular
feed of tar is required, and considerable difficulty seems to have been
experienced in obtaining this. So long as we employed ordinary forms of
taps or valves, so long (even with filtration) did we experience
difficulties with the flow of viscous tar. But on the construction of
valves specially designed for the regulation of its flow, the difficulty
immediately disappeared, and there is no longer the slightest trouble on
this account. The labor connected with the feeding of furnaces with coke
and cleaning fires from clinker is of a very arduous and heavy nature.
Eight coke fires are normally considered to be work for one man. A lad
could work sixteen of these tar fires.

COMPOSITION OF FURNACE GASES.

Considerable attention has been paid to the composition of the furnace
gases from the tar fires. The slightest deficiency in the air supply, of
course, results in the immediate production of smoke, so that the damper
must be set to provide always a sufficient air supply. Under these
circumstances of damper, the following analyses of combustion gases from
tar fires have been obtained:

                  No Smoke.
                  CO_{2}.    O.           CO.
                  11.7      5.0      Not determined.
                  13.3      3.7           "
                  10.8      5.4           "
                  14.8      2.5           "
                  13.5      3.0           "
                  12.4      5.6           "
                  12.4      4.6           "
                  13.1      5.9           "
                  15.3      1.0           "
                  10.8      4.0           "
                  14.0      2.8           "
                 ______    ______
   Average        12.9      3.9
(11 analyses)    ______    ______
                  11.5    Not determined.
                  14.3          "
                  14.6          "

Damper adjusted so that a slight smoke was observable in the combustion
gases.

                CO_{2}.     O.          CO.
                 17.30     None.    Not determined.
                 16.60      "            "
                 16.50     0.1           "
                 15.80     0.1           "
                 16.20     1.8          0.7
                _______   _____        _____
Average          16.48     0.4          0.7

--_Gas Engineer_.

A NEW MERCURY PUMP.

The mercury pumps now in use, whether those of Geissler, Alvergniat,
Toepler, or Sprengel, although possessed of considerable advantages, have
also serious defects. For instance, Geissler's pump requires a considerable
number of taps, that of Alvergniat and Toepler is very fragile in
consequence of its complicated system of tubes connected together, and that
of Sprengel is only suitable for certain purposes.

The new mercury pump constructed by Messrs. Greisser and Friedrichs, at
Stutzerbach, is remarkable for simplicity of construction and for the ease
with which it is manipulated, and also because it enables us to arrive at a
perfect vacuum.

The characteristic of this pump is, according to _La Lumiere Electrique_, a
tap of peculiar construction. It has two tubes placed obliquely in respect
to its axis, which, when we turn this tap 90 or 180 degrees, are brought
opposite one of the three openings in the body of the tap.

Thus the striæ that are formed between the hollowed-out parts of the tap do
not affect its tightness; and, besides, the turns of the tap have for their
principal positions 90 and 180 degrees, instead of 45 and 90 degrees, as in
Geissler's pump.

The working of the apparatus, which only requires the manipulation of a
single tap, is very simple. When the mercury is raised, the tap is turned
in such a manner that the surplus of the liquid can pass into the enlarged
appendage, a, placed above the tap, and communication is then cut off by
turning the tap to 90 degrees.

The mercury reservoir having descended, the bulb empties itself, and then
the tap is turned on again, in order to establish communication with the
exhausting tube. The tap is then closed, the mercury ascends again, and
this action keeps on repeating.

NO ELECTRICITY FROM THE CONDENSATION OF VAPOR.--It has been maintained by
Palmieri and others that the condensation of vapor results in the
production of an electrical charge. Herr S. Kalischer has renewed his
investigations upon this point, and believes that he has proved that no
electricity results from such condensation. Atmospheric vapor was condensed
upon a vessel coated with tin foil, filled with ice, carefully insulated,
and connected with a very sensitive electrometer. No evidence could be
obtained of electricity.--_Ann. der Physik und Chemie_.

THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.

An interesting contribution was made by M. Mercadier in a recent number of
the _Comptes Rendus de l'Academie Francaise_. On the ground of some novel
and some already accepted experimental evidence, M. Mercadier holds that
the mechanism by virtue of which the telephonic diaphragms execute their
movements is analogous to, if not identical with, that by which solid
bodies of any form, a wall for instance, transmit to one of their surfaces
all the vibratory movements of any kind which are produced in the air in
contact with the other surface. It is a phenomenon or resonance. Movements
corresponding to particular sounds may be superposed in slender diaphragms,
but this superposition must necessarily be disturbing under all but
exceptional circumstances. In proof of this view, it is cited that
diaphragms much too rigid, or charged with irregularly distributed masses
over the surface, or pierced with holes, or otherwise evidently unfitted
for the purpose, are available for transmission. They will likewise serve
when feathers, wool, wood, metals, mica, and other substances to the
thickness of four inches are placed between the diaphragm and the source of
vibratory movement. The magnetic field does not alter these relations in
any way. The real diaphragm may be removed altogether. It is sufficient to
replace it by a few grains of iron filings thrown on the pole covered with
a piece of pasteboard or paper. Such a telephone works distinctly although
feebly; but any slender flexible disk, metallic or not, spread over across
the opening of the cover of the instrument, with one or two tenths of a
gramme (three grains) of iron filings, will yield results of increased and
even ordinary intensity. This is the iron filing telephone, which is
reversible; for a given magnetic field there is a certain weight of iron
filings for maximum intensity. It appears thus that the advantage of the
iron diaphragm over iron filings reduces itself to presenting in a certain
volume a much more considerable number of magnetic molecules to the action
of the field. The iron diaphragm increases the telephonic intensity, but it
is by no means indispensable.

ON ELECTRO-DISSOLUTION, AND ITS USE AS REGARDS ANALYSIS.

By H.N. WARREN, Research Analyst.

On the same principle that electro-dissolution is used for the estimation
of combined carbon in steel, etc., I have lately varied the experiment by
introducing, instead of steel, iron containing a certain percentage of
boron, and, having connected the respective boride with the positive pole
of a powerful battery, and to the negative a plate of platinum, using as a
solvent dilute sulphuric acid, I observed, after the lapse of about twelve
hours, the iron had entirely passed into solution, and a considerable
amount of brownish precipitate had collected at the bottom of the vessel,
intercepted by flakes of graphite and carbon; the precipitate, having been
collected on a filter paper, washed, and dried, on examination proved to be
amorphous boron, containing graphite and other impurities, which had become
chemically introduced during the preparation of the boron compound. The
boron was next introduced into a small clay crucible, and intensely heated
in a current of hydrogen gas, for the purpose of rendering it more dense
and destroying its pyrophoric properties, and was lastly introduced into a
combustion tubing, heated to bright redness, and a stream of dry carbonic
anhydride passed over it, in order to separate the carbon, finally pure
boron being obtained.

In like manner silicon-eisen, containing 9 per cent. of silicon, was
treated, but not giving so satisfactory a result. A small quantity only of
silicon separates in the uncombined form, the greater quantity separating
in the form of silica, SiO_{2}, the amorphous silicon so obtained
apparently being more prone to oxidation than the boron so obtained.

Ferrous sulphide was next similarly treated, and gave, after the lapse of a
few hours, a copious blackish precipitation of sulphur, and possessing
properties similar to the sulphur obtained by dissolving sulphides such as
cupric sulphide in dilute nitric acid, in all other respects resembling
common sulphur.

Phosphides of iron, zinc, etc., were next introduced, and gave, besides
carbon and other impurities, a residue containing a large percentage of
phosphorus, which differed from ordinary phosphorus with respect to its
insolubility in carbon disulphide, and which resembled the reaction in the
case with silicon-eisen rather than that of the boron compound, insomuch
that a large quantity of the phosphorus had passed into solution.

A rod of impure copper, containing arsenic, iron, zinc, and other
impurities, was next substituted, using hydrochloric acid as a solvent in
place of sulphuric acid. In the course of a day the copper had entirely
dissolved and precipitated itself on the negative electrode, the impurities
remaining in solution. The copper, after having been washed, dried, and
weighed, gave identical results with regard to percentage with a careful
gravimetric estimation. I have lately used this method, and obtained
excellent results with respect to the analysis of commercial copper,
especially in the estimation of small quantities of arsenic, thus enabling
the experimenter to perform his investigation on a much larger quantity
than when precipitation is resorted to, at the same time avoiding the
precipitated copper carrying down with it the arsenic. I have in this
manner detected arsenic in commercial copper when all other methods have
totally failed. I have also found the above method especially applicable
with respect to the analysis of brass.

With respect to ammoniacal dissolution, which I will briefly mention, a rod
composed of an alloy of copper and silver was experimented upon, the copper
becoming entirely dissolved and precipitating itself on the platinum
electrode, the whole of the silver remaining suspended to the positive
electrode in an aborescent form. Arsenide of zinc was similarly treated,
the arsenic becoming precipitated in like manner on the platinum electrode.
Various other alloys, being experimented upon, gave similar results.

I may also, in the last instance, mention that I have found the above
methods of electro-dissolution peculiarly adapted for the preparation of
unstable compounds such as stannic nitrate, potassic ferrate, ferric
acetate, which are decomposed on the application of heat, and in some
instances have succeeded by the following means of crystallizing the
resulting compound obtained.--_Chem. News_.

A NEWLY DISCOVERED SUBSTANCE IN URINE.

Dr. Leo's researches on sugar in urine are interesting, and tend to correct
the commonly accepted views on the subject. Professor Scheibler, a chemist
well known for his researches on sugar, has observed that the determination
of the quantity of that substance contained in a liquid gives different
results, according as it is done by Trommer's method or with the
polariscope. As sugar nowadays is exclusively dealt with according to the
degree of polarization, this fact is of enormous value in trade. Scheibler
has isolated a substance that is more powerful in that respect than grape
sugar. Dr. Leo's researches yield analogous results, though in a different
field. He has examined a great quantity of diabetic urine after three
different methods, namely, Trommer's (alkaline solution of copper); by
fermentation; and with the polarization apparatus. In many cases the
results agreed, while in others there was a considerable difference.

He succeeded in isolating a substance corresponding in its chemical
composition to grape sugar, and also a carbo-hydrate differing considerably
from grape sugar, and turning the plane of polarization to the left. The
power of reduction of this newly discovered substance is to that of grape
sugar as 1:2.48. Dr. Leo found this substance in three specimens of
diabetic urine, but it was absent in normal urine, although a great amount
was examined for that purpose. From this it may be concluded that the
substance does not originate outside the organism, and that it is a
pathological product. The theory of Dr. Jaques Meyer, of Carlsbad, that it
may be connected with obesity, is negatived by the fact that of the three
persons in whom this substance was found, only one was corpulent.

FURNACE FOR DECOMPOSING CHLORIDE OF MAGNESIUM.

The problem of decomposing chloride of magnesium is one which has attracted
the attention of technical chemists for many years. The solution of this
problem would be of great importance to the alkali trade, and,
consequently, to nearly every industry. The late Mr. Weldon made many
experiments on this subject, but without any particular success. Of late a
furnace has been patented in Germany, by A. Vogt, which is worked on a
principle similar to that applied to salt cake furnaces; but with this
difference, that in place of the pot it has a revolving drum, and instead
of the roaster a furnace with a number of shelves. The heating gases are
furnished by a producer, and pass from below upward over the shelves, S,
then through the channel, C, into the drum, D, which contains the
concentrated chloride of magnesium. When the latter has solidified, but
before being to any extent decomposed, it is removed from the drum and
placed on the top shelf of the furnace. It is then gradually removed one
shelf lower as the decomposition increases, until it arrives at the bottom
shelf, where it is completely decomposed in the state of magnesia, which is
emptied through, E. The drum, D, after being emptied, is again filled with
concentrated solution of chloride of magnesium. The hydrochloric acid
leaves through F and G. If, instead of hydrochloric acid, chlorine is to be
evolved, it is necessary to heat the furnace by means of hot air, as
otherwise the carbonic acid in the gases from the generator would prevent
the formation of bleaching powder. The air is heated in two regenerating
chambers, which are placed below the furnace.--_Industries_.

THE FILTRATION AND THE SECRETION THEORY.

At a recent meeting of the Physiological Society, Dr. J. Munk reported on
experiments instituted by him in the course of the last two years with a
view of arriving at an experimental decision between the two theories of
the secretion of urine--the filtration theory of Ludwig and the secretion
theory of Heidenhain. According to the first theory, the blood pressure
prescribed the measure for the urine secretion; according to the second
theory, the urine got secreted from the secretory epithelial cells of the
kidneys, and the quantity of the matter secreted was dependent on the rate
of movement of the circulation of the blood. The speaker had instituted his
experiments on excided but living kidneys, through which he conducted
defibrinized blood of the same animals, under pressures which he was able
to vary at pleasure between 80 mm. and 190 mm. Fifty experiments on dogs
whose blood and kidneys were, during the experiment, kept at 40° C.,
yielded the result that the blood of starving animals induced no secretion
of urine, which on the other hand showed itself in copious quantities where
normal blood was conducted through the kidney. If to the famished blood was
added one of the substances contained as ultimate products of digestion in
the blood, such, for example, as urea, then did the secretion ensue.

The fluid dropping from the ureter contained more urea than did the blood.
That fluid was therefore no filtrate, but a secretion. An enhancement of
the pressure of the blood flowing through the kidney had no influence on
the quantity of the secretion passing away. An increased rate of movement
on the part of the blood, on the other hand, increased in equal degree the
quantity of urine. On a solution of common salt or of mere serum sanguinis
being poured through the kidney, no secretion followed. All these facts,
involving the exclusion of the possibility of a central influence being
exercised from, the heart or from the nervous system on the kidneys, were
deemed by the speaker arguments proving that the urine was secreted by the
renal epithelial cells. A series of diuretics was next tried, in order to
establish whether they operated in the way of stimulus centrally on the
heart or peripherally on the renal cells. Digitalis was a central diuretic.
Common salt, on the other hand, was a peripheral diuretic. Added in the
portion of 2 per cent. to the blood, it increased the quantity of urine
eight to fifteen fold. Even in much less doses, it was a powerful diuretic.
In a similar manner, if yet not so intensely, operated saltpeter and
coffeine, as also urea and pilocarpine. On the introduction, however, of
the last substance into the blood, the rate of circulation was accelerated
in an equal measure as was the quantity of urine increased, so that in this
case the increase in the quantity of urine was, perhaps, exclusively
conditioned by the greater speed in the movement of the blood. On the other
hand, the quantity of secreted urine was reduced when morphine or strychine
was administered to the blood. In the case of the application of
strychnine, the rate in the current of the blood was retarded in a
proportion equal to the reduction in the secretion of the urine.

The speaker had, finally, demonstrated the synthesis of hippuric acid and
sulphate of phenol in the excided kidney as a function of its cells, by
adding to the blood pouring through the kidney, in the first place, benzoic
acid and glycol; in the second place, phenol and sulphate of soda. In order
that these syntheses might make their appearance in the excided kidney, the
presence of the blood corpuscles was not necessary, though, indeed, the
presence of oxygen in the blood was indispensable.

VARYING CYLINDRICAL LENS.

By TEMPEST ANDERSON, M.D., B. Sc.

The author has had constructed a cylindrical lens in which the axis remains
constant in direction and amount of refraction, while the refraction in the
meridian at right angles to this varies continuously.

A cone may be regarded as a succession of cylinders of different diameters
graduating into one another by exceedingly small steps, so that if a short
enough portion be considered, its curvature at any point may be regarded as
cylindrical. A lens with one side plane and the other ground on a conical
tool is therefore a concave cylindrical lens varying in concavity at
different parts according to the diameter of the cone at the corresponding
part. Two such lenses mounted with axes parallel and with curvatures
varying in opposite directions produce a compound cylindrical lens, whose
refraction in the direction of the axes is zero, and whose refraction in
the meridian at right angles to this is at any point the sum of the
refractions of the two lenses. This sum is nearly constant for a
considerable distance along the axis so long as the same position of the
lenses is maintained. If the lenses be slid one over the other in the
direction of their axes, this sum changes, and we have a varying
cylindrical lens. The lens is graduated by marking on the frame the
relative position of the lenses when cylindrical lenses of known power are
neutralized.

Lenses were exhibited to the Royal Society, London, varying from to -6 DCy,
and from to +6 DCy.

THE LAWS OF THE ABSORPTION OF LIGHT IN CRYSTALS.

By H. BECQUEREL.

1. The absorption spectrum observed through a crystal varies with the
direction of the rectilinear luminous vibration which propagates itself in
this crystal. 2. The bands or rays observed through the same crystal have,
in the spectrum, fixed positions, their intensity alone varying. 3. For a
given band or ray there exist in the crystal three rectangular directions
of symmetry, according to one of which the band generally disappears, so
that for a suitable direction of the luminous vibrations the crystal no
longer absorbs the radiations corresponding to the region of the spectrum
where the band question appeared. These three directions may be called the
principal directions of absorption, relative to this band. 4. In the
orthorhombic crystals, by a necessary consequence of crystalline symmetry,
the principal directions of absorption of all the bands coincide with the
three axes of symmetry. We may thus observe three principal absorption
spectra. In uniaxial crystals the number of absorption spectra is reduced
to two. 5. In clinorhombic crystals one of the principal directions of
absorption of each crystal coincides with the only axis of symmetry; the
two other principal rectangular directions of each band may be found
variously disposed in the plane normal to this axis. Most commonly these
principal directions are very near to the principal corresponding
directions of optical elasticity. 6. In various crystals the characters of
the absorption phenomena differ strikingly from those which we might expect
to find after an examination of the optical properties of the crystal. We
have just seen that in clinorhombic crystals the principal absorption
directions of certain bands were completely different from the axis of
optical elasticity of the crystal for the corresponding radiations. If we
examine this anomaly, we perceive that the crystals manifesting these
effects are complex bodies, formed of various matters, one, or sometimes
several, of which absorb light and give each different absorption bands.
Now, M. De Senarmont has shown that the geometric isomorphism of certain
substances does not necessarily involve identity of optical properties, and
in particular in the directions of the axes of optical elasticity in
relation to the geometric directions of the crystal. In a crystal
containing a mixture of isomorphous substances, each substance brings its
own influence, which may be made to predominate in turn according to the
proportions of the mixture. We may, therefore, admit that the molecules of
each substance enter into the crystal retaining all the optical properties
which they would have if each crystallized separately. The principal
directions of optical elasticity are given by the resultant of the actions
which each of the component substances exerts on the propagation of light,
while the absorption of a given region of the spectrum is due to a single
one of these substances, and may have for its directions of symmetry the
directions which it would have in the absorbing molecule supposing it
isolated. It may happen that these directions do not coincide with the axes
of optical elasticity of the compound crystal. If such is the cause of the
anomaly of certain principal directions of absorption, the bands which
present these anomalies must belong to substances different from those
which yield bands having other principal directions of absorption. If so,
we are in possession of a novel method of spectral analysis, which permits
us to distinguish in certain crystals bands belonging to different matters,
isomorphous, but not having the same optical properties. Two bands
appearing in a crystal with common characters, but presenting in another
crystal characters essentially different, must also be ascribed to two
different bodies.

[Continued from SUPPLEMENT, No. 585, page 9345.]

HISTORY OF THE WORLD'S POSTAL SERVICE.

It is commonly believed in Europe that the mail is chiefly forwarded by the
railroads; but this is only partially the case, as the largest portion of
the mails is intrusted now, as formerly, to foot messengers. How long this
will last is of course uncertain, as the present postal service seems
suitable enough for the needs of the people. The first task of the mail is
naturally the collection of letters. Fig. 17 represents a letter box in a
level country.

[Illustration: FIG. 17.--COUNTRY LETTER BOX.]

By way of example, it is not uninteresting to know that the inhabitants of
Hanover in Germany made great opposition to the introduction of letter
boxes, for the moral reason that they could be used to carry on forbidden
correspondence, and that consequently all letters should be delivered
personally to the post master.

After the letters are collected, the sorting for the place of destination
follows, and Fig. 18 represents the sorting room in the Berlin Post Office.
A feverish sort of life is led here day and night, as deficient addresses
must be completed, and the illegible ones deciphered.

It may here be mentioned that the delivery of letters to each floor of
apartment houses is limited chiefly to Austria and Germany. In France and
England, the letters are delivered to the janitor or else thrown into the
letter box placed in the hall.

After the letters are arranged, then comes the transportation of them by
means of the railroad, the chaise, or gig, and finally the dog mail, as
seen in Fig. 19. It is hard to believe that this primitive vehicle is
useful for sending mail that is especially urgent, and yet it is used in
the northern part of Canada. Drawn by three or four dogs, it glides swiftly
over the snow.

It is indeed a large jump from free America, the home of the most unlimited
progress, into the Flowery Kingdom, where cues are worn, but we hope our
readers are willing to accompany us, in order to have the pleasure of
seeing how rapidly a Chinese mail carrier (Fig. 20) trots along his route
under his sun umbrella.

Only the largest and most robust pedestrians are chosen for service, and
they are obliged to pass through a severe course of training before they
can lay any claim to the dignified name, "Thousand Mile Horse."

[Illustration: FIG. 18.--SORTING ROOM IN BERLIN POST OFFICE.]

But even the Chinese carrier may not strike us so curiously as another
associate, given in our next picture, Fig. 21, and yet he is a European
employe from the Landes department of highly cultivated France. The
inhabitants of this country buckle stilts on to their feet, so as to make
their way faster through brambles and underbrush which surrounds them. The
mail carrier copied them in his equipment, and thus he goes around on
stilts, provided with a large cane to help him keep his balance, and
furnishes a correct example of a post office official suiting the demands
of every district.

While the mail in Europe has but little to do with the transportation of
passengers, it is important in its activity in this respect in the large
Russian empire.

[Illustration: FIG. 19.--DOG POST AT LAKE SUPERIOR.]

The tarantass (Fig. 22), drawn by three nimble horses, flies through the
endless deserts with wind-like rapidity.

The next illustration (Fig. 23) leads us to a much more remote and deserted
country, "Post office on the Booby Island," occupied only by birds, and a
hut containing a box in which are pens, paper, ink, and wafers. The
mariners put their letters in the box, and look in to see if there is
anything there addressed to them, then they continue their journey.

Postage stamps are not demanded in this ideal post office, but provision is
made for the shipwrecked, by a notice informing them where they can find
means of nourishment.

Once again we make a leap. The Bosnian mail carrier's equipment (Fig. 24)
is, or rather was, quite singular, for our picture was taken before the
occupation.

This mounted mail carrier with his weapons gives one the impression of a
robber.

The task of conducting the mail through the Alps of Switzerland (Fig. 25)
must be uncomfortable in winter, when the sledges glide by fearful
precipices and over snow-covered passes.

Since the tariff union mail developed from the Prussian mail, and the
world's mail from the tariff union, it seems suitable to close our series
of pictures by representing the old Prussian postal service (Fig. 26)
carried on by soldier postmen in the eighteenth century during the reign of
Frederick the Great.

[Illustration: FIG. 20.--CHINESE POSTMAN.]

[Illustration: FIG. 21.--DELIVERING LETTERS IN LANDES DEPARTMENT,
FRANCE.]

[Illustration: FIG. 22.--RUSSIAN EXTRA POST.]

The complaint is made that poetry is wanting in our era, and it has
certainly disappeared from the postal service. One remembers that the
postilion was for quite a while the favorite hero of our poets, the best of
whom have sung to his praises, and given space to his melancholy thoughts
of modern times in which he is pushed aside. It is too true that the post
horn, formerly blown by a postilion, is now silenced, that the horse has
not been able to keep up in the race with the world in its use of the
steam horse, and yet how much poetry there is in that little post office
all alone by itself on the Booby Island, that we have described--the
sublimest poetry, that of love for mankind!

The poet of the modern postal system has not yet appeared; but he will find
plenty of material. He will be able to depict the dangers a postman passes
through in discharging his duty on the field, he will sing the praises of
those who are injured in a railroad disaster, and yet continue their good
work.

[Illustration: FIG. 23.--POST OFFICE ON BOOBY ISLAND.]

[Illustration: FIG. 24.--BOSNIAN POST.]

[Illustration: FIG. 25.--SWISS ALPINE POST IN WINTER.]

[Illustration: FIG. 26.--SOLDIER POSTMAN OF THE EIGHTEENTH CENTURY.]

He can also praise the noble thought of uniting the nations, which assumed
its first tangible form in the world's mail. It will not be a sentimental
song, but one full of power and indicative of our own time, in spite of
those who scorn it.--_Translated for the Scientific American Supplement by
Jenny H. Beach, from Neue Illustrirte Zeitung_.

ON NICKEL PLATING.

By THOMAS T.P. BRUCE WARREN.

The compound used principally for the electro-deposition of nickel is a
double sulphate of nickel and ammonia. The silvery appearance of the
deposit depends mainly on the purity of the salt as well as the anodes. The
condition of the bath, as to age, temperature, and degree of saturation,
position of anodes, strength of current, and other details of manipulation,
which require care, cleanliness, and experience, such as may be met with in
any intelligent workman fairly acquainted with his business, are easily
acquired.

In the present paper I shall deal principally with the chemical department
of this subject, and shall briefly introduce, where necessary, allusion to
the mechanical and electrical details connected with the process. At a
future time I shall be glad to enlarge upon this part of the subject, with
a view of making the article complete.

A short time ago nickel plating was nearly as expensive as silver plating.
This is explained by the fact that only a few people, at least in this
country, were expert in the mechanical portions of the process, and only a
very few chemists gave attention to the matter. To this must be added that
our text-books were fearfully deficient in information bearing on this
subject.

The salt used, and also the anodes, were originally introduced into this
country from America, and latterly from Germany. I am not aware of any
English manufacturer who makes a specialty in the way of anodes. This is a
matter on which we can hardly congratulate ourselves, as a well known
London firm some time ago supplied me with my first experimental anodes,
which were in every way very superior to the German or American
productions. Although the price paid per pound was greater, the plates
themselves were cheaper on account of their lesser thickness.

The texture of the inner portions of these foreign anodes would lead one to
infer that the metallurgy of nickel was very primitive. A good homogeneous
plate can be produced, still the spongy, rotten plates of foreign
manufacture were allowed the free run of our markets. The German plates
are, in my opinion, more compact than the American. A serious fault with
plates of earlier manufacture was their crumpled condition after a little
use. This involved a difficulty in cleaning them when necessary. The
English plates were not open to this objection; in fact, when the outer
surfaces were planed away, they remained perfectly smooth and compact.

Large plates have been known to disintegrate and fall to pieces after being
used for some time. A large anode surface, compared with that of the
article to be plated, is of paramount importance. The tank should be
sufficiently wide to take the largest article for plating, and to admit of
the anodes being moved nearer to or further from the article. In this way
the necessary electrical resistance can very conveniently be inserted
between the anode and cathode surfaces. The elimination of hydrogen from
the cathode must be avoided, or at any rate must not accumulate. Moving the
article being plated, while in the bath, taking care not to break the
electrical contacts, is a good security against a streaky or foggy
appearance in the deposit.

At one time a mechanical arrangement was made, by which the cathodes were
kept in motion. The addition of a little borax to the bath is a great
advantage in mitigating the appearance of gas. Its behavior is electrical
rather than chemical. If the anode surface is too great, a few plates
should be transferred to the cathode bars.

When an article has been nickel plated, it generally presents a dull
appearance, resembling frosted silver. To get over this I tried, some time
ago, the use of bisulphide of carbon in the same way as used for obtaining
a bright silver deposit. Curiously the deposit was very dark, almost black,
which could not be buffed or polished bright. But by using a very small
quantity of the bisulphide mixture, the plated surfaces were so bright that
the use of polishing mops or buffs could be almost dispensed with. When we
consider the amount of labor required in polishing a nickel plated article,
and the impossibility of finishing off bright an undercut surface, this
becomes an important addendum to the nickel plater's list of odds and ends.

This mixture is made precisely in the same way as for bright silvering, but
a great deal less is to be added to the bath, about one pint per 100
gallons. It should be well stirred in, after the day's work is done, when
the bath will be in proper condition for working next day. The mixture is
made by shaking together, in a glass bottle, one ounce bisulphide and one
gallon of the plating liquid, allow to stand until excess of bisulphide has
settled, and decant the clear liquid for use as required. It is better to
add this by degrees than to run the risk of overdoing. If too much is
added, the bath is not of necessity spoiled, but it takes a great deal of
working to bring it in order again.

About eight ounces of the double sulphate to each gallon of distilled or
rain water is a good proportion to use when making up a bath. There is a
slight excess with this. It is a mistake to add the salt afterward, when
the bath is in good condition. The chloride and cyanide are said to give
good results. I can only say that the use of either of these salts has not
led to promising results in my hands.

In preparing the double sulphate, English grain nickel is decidedly the
best form of metal to use. In practice, old anodes are generally used.

The metal is dissolved in a mixture of nitric and dilute sulphuric acid,
with the application of a gentle heat. When sufficient metal has been
dissolved, and the unused nitric acid expelled, the salt may be
precipitated by a strong solution sulphate of ammonia, or, if much free
acid is present, carbonate of ammonia is better to use.

Tin, lead, and portion of the iron, if present, are removed by this method.
The silica, carbon, and portions of copper are left behind with the
undissolved fragments of metals.

The precipitated salt, after slight washing, is dissolved in water and
strong solution ammonia added. A clean iron plate is immersed in the
solution to remove any trace of copper. This plate must be cleaned
occasionally so as to remove any reduced copper, which will impede its
action. As soon as the liquid is free from copper, it is left alkaline and
well stirred so as to facilitate peroxidation and removal of iron, which
forms a film on the bath. When this ceases, the liquid is rendered neutral
by addition of sulphuric acid, and filtered or decanted. The solution, when
properly diluted, has sp. gr. about 1.06 at 60° F. It is best to work the
bath with a weak current for a short time until the liquid yields a fine
white deposit. Too strong a current must be avoided.

If the copper has not been removed, it will deposit on the anodes when the
bath is at rest. It should then be removed by scouring.

Copper produces a reddish tinge, which is by no means unpleasant compared
with the dazzling whiteness of the nickel deposit. If this is desired, it
is far better to use a separate bath, using anodes of suitable composition.

The want of adhesion between the deposited coating and the article need not
be feared if cleanliness be attended to and the article, while in the bath,
be not touched by the hands.

The bath should be neutral, or nearly so, slightly acid rather than
alkaline. It is obvious that, as such a liquid has no detergent action on a
soiled surface, scrupulous care must be taken in scouring and rinsing.
Boiling alkaline solutions and a free use of powdered pumice and the
scrubbing brush must on no account be neglected.

A few words on the construction of the tanks. A stout wood box, which need
not be water-tight, is lined with sheet lead, the joints being blown, _not
soldered_. An inner casing of wood which projects a few inches above the
lead lining is necessary in order to avoid any chance of "short circuiting"
or damage to the lead from the accidental falling of anodes or any article
which might cut the lead. It is by no means a necessity that the lining
should be such as to prevent the liquid getting to the lead.

On a future occasion I hope to supplement this paper with the analysis of
the double sulphates used, and an account of the behavior of
electrolytically prepared crucibles and dishes as compared with those now
in the market.--_Chem. News_.

CHILLED CAST IRON.

At a recent meeting of the engineering section of the Bristol Naturalists'
Society a paper on "Chilled Iron" was read by Mr. Morgans, of which we give
an abstract. Among the descriptions of chilled castings in common use the
author instanced the following: Sheet, corn milling, and sugar rolls; tilt
hammer anvils and bits, plowshares, "brasses" and bushes, cart-wheel boxes,
serrated cones and cups for grinding mills, railway and tramway wheels and
crossings, artillery shot and bolts, stone-breaker jaws, circular cutters,
etc. Mr. Morgans then spoke of the high reputation of sheet mill rolls and
wheel axle boxes made in Bristol. Of the latter in combination with wrought
iron wheels and steeled axles, the local wagon works company are exporting
large numbers. With respect to the strength and fatigue resistance of
chilled castings, details were given of some impact tests made in July,
1864, at Pontypool, in the presence of Captain Palliser, upon some of his
chilled bolts, 12¾ in. long by 4 in. diameter, made from Pontypool
cold-blast pig iron. Those made from No. 1 pig iron--the most graphitic and
costly--broke more easily than those from No. 2, and so on until those made
from No. 4 were tested, when the maximum strength was reached. No. 4 pig
iron was in fracture a pale gray, bordering on mottled. Several points
regarding foundry operations in the production of chilled castings were
raised for discussion. They embraced the depth of chill to be imparted to
chilled rolls and railway wheels, and in the case of traction wheels, the
width of chill in the tread; preparation of the chills--by coating with
various carbonaceous matters, lime, beer grounds, or, occasionally, some
mysterious compost--and moulds, selection and mixture of pig irons, methods
and plant for melting, suitable heat for pouring, prevention of
honeycombing, ferrostatic pressure of head, etc. Melting for rolls being
mostly conducted in reverberatories, the variations in the condition of the
furnace atmosphere, altering from reducing to oxidizing, and _vice versa_,
in cases of bad stoking and different fuels, were referred to as
occasionally affecting results. Siemens' method of melting by radiant heat
was mentioned for discussion. For promoting the success of a chilled roll
in its work, lathing or turning it to perfect circularity in the necks
first, and then turning the body while the necks bear in steady brasses,
are matters of the utmost importance.

The author next referred to the great excellence for chilling purposes
possessed by some American pig irons, and to the fact that iron of a given
carbon content derived from some ores and fluxes differed much in chilling
properties from iron holding a similar proportion of carbon--free and
combined--derived from other ores and materials. Those irons are best which
develop the hardest possible chill most uniformly to the desired depth
without producing a too abrupt line of division between the hard white skin
and the softer gray body. A medium shading off both ways is wanted here, as
in all things. The impossibility of securing a uniform quality and chemical
composition in any number grade of any brand of pig iron over a lengthened
period was adverted to. Consequent from this a too resolute faith in any
particular make of pig iron is likely to be at times ill-requited.
Occasional physical tests, accompanied with chemical analysis of irons used
for chilling, were advocated; and the author was of opinion it would be
well whenever a chilled casting had enjoyed a good reputation for standing
up to its work, that when it was retired from work some portions of it
should be chemically analyzed so as to obtain clews to compositions of
excellence. Some of the physical characteristics of chilled iron, as well
as the surprising locomotive properties of carbon present in heated iron,
were noticed.

Attention was called to some German data, published by Dr. Percy in 1864,
concerning an iron which before melting weighed--approximately--448¼ lb.
per cubic foot, and contained--approximately--4 per cent. of carbon--3¼
being graphitic and ¾ combined. The chilled portion of a casting from this
had a specific gravity equivalent to 471 lb. per cubic foot, and contained
5 per cent. of carbon, all combined. The soft portion of the same casting
weighed 447¾ lb. per cubic foot, and contained 34.5 per cent. of
carbon--31.5 being graphitic and 3.5 combined. Mr. Morgans doubted whether
so great an increase in density often arises from chilling. Tool steel,
when hardened by being chilled in cold water, does not become condensed,
but slightly expanded from its bulk when annealed and soft. Here an
increase of hardness is accompanied by a decrease of density. The gradual
development of a network of cracks over the face of a chilled anvil orbit
while being used in tilt hammers was mentioned. Such minute cleavages
became more marked as the chill is worn down by work and from grinding.
Traces of the same occurrence are observable over the surface of much worn
chilled rolls used in sheet mills. In such cases the sheets get a faint
diaper pattern impressed upon them. The opening of crack spaces points to
lateral shrinkage of the portions of chilled material they surround, and to
some release from a state of involuntary tension. If this action is
accompanied by some actual densification of the fissured chill, then we
have a result that possibly conflicts with the example of condensation from
chilling cited by Dr. Percy.

SNOW HALL.

The recent dedication of Snow Hall, at Lawrence, Kansas, is an event in the
history of the State, both historic and prophetic. Since the incorporation
of the University of Kansas, and before that event, there has been a steady
growth of science in the State, which has culminated in Snow Hall, a
building set apart for the increase and diffusion of the knowledge of
natural science, as long as its massive walls shall stand. It is named in
honor of the man who has been the inspiration and guiding spirit of the
whole enterprise, and some incidents in his life may be of interest to the
public.

Twenty years ago Professor Frank H. Snow, a recent graduate of Williams
College, came to Kansas, to become a member of the faculty of the State
University. His election to the chair of natural science was unexpected, as
he first taught mathematics in the university, and expected in due time to
become professor of Greek. As professor of the mellifluous and most plastic
of all the ancient tongues, he would undoubtedly have been proficient, as
his college classics still remain fresh in his warm and retentive memory,
and his literary taste is so severe and chaste as to make some of his
scientific papers read like a psalm. But nature designed him for another,
and some think a better, field, and endowed him with powers as a naturalist
that have won for him recognition among the highest living authorities of
his profession.

Upon being elected to the chair of natural history, Prof. Snow entered upon
his life work with an enthusiasm that charmed his associates and inspired
his pupils. The true naturalist must possess large and accurate powers of
observation and a love for his chosen profession that carries him over all
obstacles and renders him oblivious to everything else except the specimen
upon which he has set his heart. Years ago the writer was walking in the
hall of the new university building in company with General Fraser and
Professor Snow, when the latter suddenly darted forward up the stairs and
captured an insect in its flight, that had evidently just dug its way out
of the pine of the new building. In a few moments he returned with such a
glow on his countenance and such a satisfied air at having captured a rare
but familiar specimen, whose name was on his lips, that we both felt
"Surely here is a genuine naturalist."

Some years ago an incident occurred in connection with his scientific
excursions in Colorado that is quite characteristic, showing his
obliviousness to self and everything else save the object of his scientific
pursuit, and a fertility in overcoming danger when it meets him face to
face. He was descending alone from one of the highest peaks of the Rockies,
when he thought he could leave the path and reach the foot of the mountain
by passing directly down its side over an immense glacier of snow and ice,
and thus save time and a journey of several miles. After a while his way
down the glacier grew steeper and more difficult, until he reached a point
where he could not advance any further, and found, to his consternation,
that he could not return by the way he had come. There he clung to the side
of the immense glacier, ready, should he miss his hold, to be plunged
hundreds of feet into a deep chasm. The situation flashed over him, and he
knew now it was, indeed, a struggle for dear life. With a precarious
foothold, he clung to the glacier with one hand, while with his pocket
knife he cut a safer foothold with the other. Resting a little, he cut
another foothold lower down in the hard snow, and so worked his way after a
severe struggle of several hours amid constant danger to the foot of the
mountain in safety. "But," continued the professor, speaking of this
incident to some of his friends, "I was richly repaid for all my trouble
and peril, for when I reached the foot of the mountain I captured a new and
very rare species of butterfly." Multitudes of practical men cannot
appreciate such devotion to pure science, but it is this absorbing passion
and pure grit that enable the devotees of science to enlarge its boundaries
year by year.

Once, while on a scientific excursion on the great plains, with the
lamented Prof. Mudge, he nearly lost his life. He had captured a
rattlesnake, and, in trying to introduce it into a jar filled with alcohol,
the snake managed to bite him on the hand. The arm was immediately bound
tightly with a handkerchief, and the wound enlarged with a pocket knife,
and both professors took turns in sucking it as clean as possible, and
ejecting the poison from their mouths. This and a heavy dose of spirits
brought the professor through in safety, although the poison remaining in
the wound caused considerable swelling and pain in the hand and arm. When
this incident was mentioned in the Kansas Academy of Science that year,
some one said, "Now we know the effect of the bite of the prairie
rattlesnake on the human system. Let some one, in the interests of pure
science, try the effect of the timber rattlesnake on the human system." But
like the mice in the fable, no one was found who cared to put the bell on
the cat.

Professors Mudge and Snow, because scientists were so few in the State at
that early day, divided the field of natural science between themselves,
the former taking geology and the latter living forms. Professor Mudge
built up at the agricultural college a royal cabinet, easily worth $10,000,
and Professor Snow has made a collection at the State University whose
value cannot be readily estimated until it is catalogued and placed in
cases in Snow Hall.

As a scientist, Professor Snow is an indefatigable worker, conscientious
and painstaking to the last degree, never neglecting anything that can be
discovered by the microscope, and when he describes and names a new
species, he gives the absolute facts, without regard to theories or
philosophies. For accuracy his descriptions of animal and vegetable life
resemble photographs, and are received by scientists with unquestioned
authority. He possesses another quality, which may be called honesty. Some
scientists, whose reputation has reached other continents, cannot be
trusted alone in the cabinet with the keys, for they are liable to borrow
valuable specimens, and forget afterward to return them.

It is possible only to glance at the immense amount of work performed by
Professor Snow during the last twenty years. Neglecting the small fry that
can only be taken in nets with very fine meshes, he ascertained that there
are twenty-seven species of fish in the Kansas River at Lawrence. Work on
this paper occupied the leisure time of two summers, as much time in such
investigations only produces negative results. For several years he worked
on a catalogue of the birds of Kansas, inspiring several persons in
different parts of the State to assist him. Later this work was turned over
to Colonel N.S. Gross, of Topeka, an enthusiast in ornithology. Colonel
Goss has a very fine collection of mounted birds in the capitol building at
Topeka, and he has recently published a catalogue of the "Birds of Kansas,"
which contains 335 species. Professor Snow has worked faithfully on the
plants of Kansas, but as other botanists came into the State, he turned the
work over to their hands. For several years he has given a large share of
his time and strength to entomology. Nearly every year he has led
scientific excursions to different points in Colorado, New Mexico, Arizona,
etc., where he might reap the best results.

Once, during a meeting of the Kansas Academy of Science, at Lawrence,
Professor Snow was advertised to read a paper on some rare species of
butterflies. As the hour approached, the hall in the university building
was thronged, principally by ladies from the city, when Professor Snow
brought out piles of his trays of butterflies, and without a note gave such
an exhibit and description of his specimens as charmed the whole audience.

In meteorology, Professor Snow is an acknowledged authority, wherever this
science is studied, and he has, probably, all things considered, the best
meteorological record in the State.

Personally, Professor Snow possesses qualities that are worth more,
perhaps, to his pupils, in forming character, than the knowledge derived
from him as an instructor. His life is pure and ennobling, his presence
inspiring, and many young men have gone from his lecture room to hold good
positions in the scientific world. When one sees him in his own home,
surrounded by his family, with books and specimens and instruments all
around, he feels that the ideal home has not lost everything in the fall.

Snow Hall is the natural resultant of twenty years of earnest and faithful
labor on the part of this eminent scientist. The regents displayed the rare
good sense of committing everything regarding the plans of the building,
and the form and arrangement of the cases, to Professor Snow, which has
resulted in giving to Kansas the model building of its kind in the West, if
not in this country. Very large collections have accumulated at the State
University, under the labors of Professor Snow and his assistants, which
need to be classified, arranged, and labeled; and when the legislature
appropriates the money to furnish cases to display this collection in
almost every department of natural science, Kansas will possess a hall of
natural science whose influence will be felt throughout the State, and be
an attraction to scientists everywhere.--_Chaplain J.D. Parker, in Kansas
City Journal_.

ELIMINATION OF POISONS.

A study of the means by which nature rids the economy of what is harmful
has been made by Sanquirico, of Siena, and his experiments and conclusions
are as follows:

He finds that the vessels of the body, without undergoing extensive
structural alteration, can by exosmosis rid themselves of fluid to an
amount of eight per cent. of the body weight of the subject of the
experiment.

Through the injection of neutral fluids a great increase in the vascular
tension is effected, which is relieved by elimination through the kidneys.

With reference to this fact, the author, in 1885, made experiments with
alcohol and strychnine, and continued his researches in the use of chloral
and aconitine with results favorable to the method employed, which is as
follows:

The minimal fatal dose of a given poison was selected, and found to be in a
certain relation to the body weight.

Immediately upon the injection of the poison a solution of sodium chloride,
0.75 per cent. in strength, was injected into the subcutaneous tissues of
the neck, in quantities being eight per cent. of the body weight of the
animal.

In the case of those poisons whose effect is not instantaneous, the
injection of saline solution was made on the first appearance of toxic
symptoms. In other poisons the injection was made at once.

The result of the use of salines was a diuresis varying in the promptness
of its appearance and in its amount.

Those animals in which diuresis was limited at first and then increased
generally recovered, while those in which diuresis was not established
perished. The poison used was found in the urine of those which died and
also those which recovered.

The author succeeded in rescuing animals poisoned by alcohol, strychnine,
chloral, and aconitine. With morphine, curare, and hypnone, the method of
elimination failed, although ten per cent. in quantity of the body weight
of the animal was used in the saline injection. With aconitine, diuresis
was not always established, and when it failed the animal died in
convulsions.--_Centralblatt fur die Medicinischen Wissenschaften, December_
18, 1886.

A catalogue, containing brief notices of many important scientific papers
heretofore published in the SUPPLEMENT, may be had gratis at this office.

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