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          ENCYCLOPAEDIA BRITANNICA

  A DICTIONARY OF ARTS, SCIENCES, LITERATURE
           AND GENERAL INFORMATION

              ELEVENTH EDITION

             VOLUME V, SLICE VI

         Celtes, Konrad to Ceramics

ARTICLES IN THIS SLICE:

  CELTES, KONRAD         CENTO (town of Italy)
  CELTIBERIA             CENTO (composition)
  CEMENT                 CENTRAL AMERICA
  CEMETERY               CENTRAL FALLS
  CENCI, BEATRICE        CENTRALIA
  CENOBITES              CENTRAL INDIA
  CENOMANI               CENTRAL PROVINCES AND BERAR
  CENOTAPH               CENTUMVIRI
  CENSOR                 CENTURION
  CENSORINUS             CENTURIPE
  CENSUS                 CENTURY
  CENTAUREA              CEOS
  CENTAURS               CEPHALIC INDEX
  CENTAURUS              CEPHALONIA
  CENTAURY               CEPHALOPODA
  CENTENARY              CEPHEUS
  CENTERVILLE            CEPHISODOTUS
  CENTIPEDE              CERAM
  CENTLIVRE, SUSANNA     CERAMICS

CELTES, KONRAD (1459-1508), German humanist and Latin poet, the son of a
vintner named Pickel (of which Celtes is the Greek translation), was
born at Wipfeld near Schweinfurt. He early ran away from home to avoid
being set to his father's trade, and at Heidelberg was lucky enough to
find a generous patron in Johann von Dalberg and a teacher in Agricola.
After the death of the latter (1485) Celtes led the wandering life of a
scholar of the Renaissance, visiting most of the countries of the
continent, teaching in various universities, and everywhere establishing
learned societies on the model of the academy of Pomponius Laetus at
Rome. Among these was the _Sodalitas litteraria Rhenana_ or _Celtica_ at
Mainz (1491). In 1486 he published his first book, _Ars versificandi et
carminum_, which created an immense sensation and gained him the honour
of being crowned as the first poet laureate of Germany, the ceremony
being performed by the emperor Frederick III. at the diet of Nuremberg
in 1487. In 1497 he was appointed by the emperor Maximilian I. professor
of poetry and rhetoric at Vienna, and in 1502 was made head of the new
Collegium Poetarum et Mathematicorum, with the right of conferring the
laureateship. He did much to introduce system into the methods of
teaching, to purify the Latin of learned intercourse, and to further the
study of the classics, especially the Greek. But he was more than a mere
classicist of the Renaissance. He was keenly interested in history and
topography, especially in that of his native country. It was he who
first unearthed (in the convent of St Emmeran at Regensburg) the
remarkable Latin poems of the nun Hrosvitha of Gandersheim, of which he
published an edition (Nuremberg, 1501), the historical poem _Ligurinus
sive de rebus gestis Frederici primi imperatoris libri x._ (Augsburg,
1507), and the celebrated map of the Roman empire known as the _Tabula
Peutingeriana_ (after Konrad Peutinger, to whom he left it). He
projected a great work on Germany; but of this only the _Germania
generalis_ and an historical work in prose, _De origine, situ, moribus
et institutis Nurimbergae libettus_, saw the light. As a writer of Latin
verse Celtes far surpassed any of his predecessors. He composed odes,
elegies, epigrams, dramatic pieces and an unfinished epic, the
_Theodoriceis_. His epigrams, edited by Hartfelder, were published at
Berlin in 1881. His editions of the classics are now, of course, out of
date. He died at Vienna on the 4th of February 1508.

  For a full list of Celtes's works see Engelbert Klüpfel, _De vita et
  scriptis Conradi Celtis_ (2 vols., Freiburg, 1827); also Johann
  Aschbach, _Die früheren Wanderjahre des Conrad Celtes_ (Vienna, 1869);
  Hartmann, _Konrad Celtes in Nürnberg _(Nuremberg, 1889).

CELTIBERIA, a term used by Greek and Roman writers to denote, sometimes
the whole north-east of Spain, and sometimes the north-east part of the
central plateau of the peninsula. The latter was probably the correct
use. The Celtiberi, in this narrower sense, were not so much one tribe
as a group of cantons--Arevaci, Pelendones, Berones and four or five
others. They were the most warlike people in Spain, and for a long time
offered a stubborn resistance to the Romans. Originally Carthaginian
mercenaries, they were induced to serve the Romans in a similar
capacity, and Livy (xxiv. 49) distinctly states that they were the first
mercenaries in the Roman army. They did not, however, keep faith, and
several campaigns were undertaken against them. In 179 B.C. the whole
country was subdued by T. Sempronius Gracchus, who by his generous
treatment of the vanquished gained their esteem and affection. In 153
they again revolted, and were not finally overcome until the capture of
Numantia (133). The twenty years' war waged round this city, and its
siege and destruction by Scipio the Younger (133 B.C.) form only the
most famous episode in the long struggle, which has left its mark in
entrenchments near Numantia excavated in 1906-1907 by German
archaeologists. After the fall of Numantia, and still more after the
death of Sertorius (72 B.C.), the Celtiberians became gradually
romanized, and town life grew up among their valleys; Clunia, for
instance, became a Roman municipality, and ruins of its walls, gates and
theatre testify to its civilization; while Bilbilis (Bambola), another
municipality, was the birthplace of the eminently Roman poet Martial.
The Celtiberians may have been so called because they were thought to
be the descendants of Celtic immigrants from Gaul into Iberia (Spain),
or because they were regarded (cf. Lucan iv. 9) as a mixed race of Celts
and Spaniards (Iberians); in either case the name represents a
geographer's theory rather than an ascertained fact. That a strong
Celtic element existed in Spain is proved both by numerous traditions
and by the more trustworthy evidence of place-names. The Celtic
place-names of Spain, however, are not confined to Celtiberia or even to
the north and east; they occur even in the south and west.

  A long description of the manners and customs of the Celtiberi is
  given by Diodorus Siculus (v. 33, 34). Their country was rough and
  unfruitful as a whole (barley, however, was cultivated), being chiefly
  used for the pasture of sheep. Its inhabitants either led a nomadic
  life or occupied small villages; large towns were few. Their infantry
  and cavalry were both excellent. In battle, they adopted the
  wedge-shaped formation of the column. They carried double-edged swords
  and short daggers for use hand to hand, the steel of which was
  hardened by being buried underground; their defensive armour was a
  light Gallic shield or a round wicker buckler, and greaves of felt
  round their legs. They wore brazen helmets with purple crests, and
  rough-haired black cloaks, in which they slept on the bare ground.
  Like the Cantabri, they washed themselves with urine instead of water.
  They were said to offer sacrifice to a nameless god (Strabo iii. p.
  164) at the time of the full moon when all the household danced
  together before the doors of the houses. Although cruel to their
  enemies, they were hospitable to strangers. They ate meat of all
  kinds, and drank a kind of mead. E. Hübner's article in
  Pauly-Wissowa's _Realencyclopadie_, iii. (1886-1893), collects all the
  ancient references, which are almost all brief. Strabo's notice (bk.
  iii.), based perhaps on Poseidonius, is fullest.     (F. J. H.)

CEMENT (from Lat. _caementum_, rough pieces of stone, a shortened form
of _caedimentum_, from _caedere_, to cut), apparently first used of a
mixture of broken stone, tiles, &c., with some binding material, and
hence of any material capable of adhering to, and uniting into a
coherent mass, fragments of a substance not in itself adhesive. The term
is often applied to adhesive mixtures employed to unite objects or parts
of objects (see below), but in engineering, when used without
qualification, it means Portland cement, its modifications and
congeners; these are all hydraulic cements, i.e. when set they resist
the action of water, and can, under favourable conditions, be allowed to
set under water.

_Hydraulic Cements_.--It was well known to builders in the earliest
historic times that certain limes would, when set, resist the action of
water, i.e. were hydraulic; it was also known that this property could
be conferred on ordinary lime by admixture of silicious materials such
as pozzuolana or tufa. We have here the two classes into which hydraulic
cements are divided.

  Pozzuolanic cement.

When pure chalk or limestone is "burned," i.e. heated in a kiln until
its carbonic acid has been driven off, it yields pure lime. This slakes
violently with water, giving slaked lime, which can be made into a
smooth paste with water and mixed with sand to form common mortar. The
setting of the mortar is due to the drying of the lime (a purely
physical phenomenon, no chemical action occurring between the lime and
the sand). The function of the sand is simply that of a diluent to
prevent undue shrinkage and cracking in drying. Subsequent hardening of
the mortar is caused by the gradual absorption of carbonic acid from the
air by the lime, a skin of carbonate of lime being formed; but the
action is superficial. Mortar made from pure or "fat" lime cannot
withstand the action of water, and is only used for work done above
water-level. If, however, such "fat" lime is mixed in the presence of
water, not with sand but with silica in an active form, i.e. amorphous
and (generally) hydrated, or with a silicate containing silica in an
active condition, it will unite with the silica and form a silicate of
lime capable of resisting the action of water. The mixture of the lime
and active silica or silicate is a pozzuolanic cement. The simplest of
all pozzuolanic cements would be a mixture of pure lime and hydrated
silica, but though the latter is prepared artificially for various
purposes, it is too expensive to be used as a cement material. A similar
obstacle lies in the way of using a certain native form of active
silica, viz. kieselguhr, for it is too valuable as an absorbent of
nitroglycerine, for the manufacture of dynamite, to be available for
making pozzuolanic cement. There are, however, many silicious
substances occurring abundantly in nature which can thus be used. They
are mostly of volcanic origin, and include pumice, tufa, santorin earth,
trass and pozzuolana itself. The following analyses show their general
composition:--

  +-----------------------------+-----------+-----------+-----------+
  |                             |Neapolitan |   Roman   |           |
  |                             |  Pozzuo-  |  Pozzuo-  |   Trass   |
  |                             |   lana    |   lana    |(per cent) |
  |                             |(per cent) |(per cent) |           |
  +-----------------------------+-----------+-----------+-----------|
  | Soluble silica (SiO2)       |   27.80   |   32.64   |   19.32   |
  | Insoluble silicious residue |   35.38   |   25.94   |   50.40   |
  | Alumina (Al2O3)             | / 19.80   | / 22.74   |   13.86   |
  | Ferric oxide (Fe2O3)        | \         | \         |    3.10   |
  | Lime (CaO)                  |    5.68   |    4.06   |   · ·     |
  | Magnesia (MgO)              |    0.35   |    1.37   |    0.13   |
  | Sulphuric anhydride (SO3)   |   Trace   |   Trace   |   · ·     |
  | Combined water (H2O)        | /  4.27   | /  8.92   |    7.57   |
  | Carbonic anhydride (CO2)    | \         | \         |   · ·     |
  | Moisture                    |    · ·    |    · ·    |    5.04   |
  | Alkalis and loss            |    6.72   |    4.33   |    0.58   |
  |                             +-----------+-----------+-----------+
  |                             |  100.00   | 100.00    |   100.0   |
  +-----------------------------+-----------+-----------+-----------+

An artificial product which serves perfectly as a pozzuolana is
granulated blast-furnace slag. The slag, which must contain a high
percentage of lime, is granulated by being run while fused into
abundance of water. This granulated slag differs from the same slag
allowed to cool slowly, in that a portion of the energy which it
possesses while fused is retained after it has solidified. It bears to
ordinary slowly-cooled slag a similar relation to that borne by plastic
sulphur to ordinary crystalline sulphur. This potential energy becomes
kinetic when the slag is brought into contact with lime in the presence
of water, and causes the formation of a true hydraulic silicate of lime.
The following analysis shows the composition of a typical slag:--

                                       Per Cent.
  Insoluble residue                      1.04
  Silica (SiO2)                         31.50
  Alumina (Al2O3)                       18.56
  Manganous oxide (MnO)                  0.44
  Lime (CaO)                            42.22
  Magnesia (MgO)                         3.18
  Soda (Na2O)                            0.70
  Sulphuric anhydride (SO3)              0.45
  Sulphur (S)                            2.21
                                       100.30
  Deduct oxygen equivalent to sulphur    1.10
                                        99.20

Granulated slag of this character is ground with slaked lime until both
materials are in a state of fine division and intimately mixed. The
usual proportions are three of slag to one of slaked lime by weight. The
product termed slag cement sets slowly, but ultimately attains a
strength scarcely inferior to that of Portland cement. Although it is
cheap and suitable for many purposes, its use is not large and tends to
decrease. Pozzuolanic cements are little used in England. Generally
speaking, they are only of local importance, their cheapness depending
largely on the nearness and abundance of some suitable volcanic deposit
of the trass or tufa class. They are not usually manufactured by the
careful grinding together of the pozzuolana and the lime, but are mixed
roughly, a great excess of pozzuolana being employed. This excess does
no harm, for that part which fails to unite with the lime serves as a
diluent, much as does sand in mortar. In fact, ordinary pozzuolanic
cement made on the spot where it is to be used may be regarded as a
better kind of common mortar having hydraulic qualities. Good hydraulic
mortars may be made from lime mixed with furnace ashes or burnt clay as
the pozzuolanic constituent.

  Portland Cement

Cements of the Portland type differ in kind from those of the
pozzuolanic class; they are not mechanical mixtures of lime and active
silica ready to unite under suitable conditions, but consist of definite
chemical compounds of lime and silica and lime and alumina, which, when
mixed with water, combine therewith, forming crystalline substances of
great mechanical strength, and capable of adhering firmly to clean inert
material, such as stone and sand. They are made by heating to a high
temperature an intimate mixture of a calcareous substance and an
argillaceous substance. The commonest of such substances in England are
chalk and clay, but where local conditions demand it, limestone, marl,
shale, slag or any similar material may be used, provided that the
correct proportions of lime, silica and alumina are maintained. The
earliest forms of cements of the Portland class were the hydraulic
limes. These are still largely used, and are prepared by burning
limestones containing clayey matter. Some of these naturally possess a
composition differing but little from that of the mixture of raw
materials artificially prepared for the manufacture of Portland cement
itself. Although hydraulic limes have been in use from the most ancient
times, their true nature and the reason of their resistance to water
have only become known since 1791. Next in antiquity to hydraulic lime
is Roman cement, prepared by heating an indurated marl occurring
naturally in nodules. Its name must not be taken to imply that it was
used by the ancients; in point of fact the manufacture of this substance
dates back only to 1796.

With the growth of engineering in the early part of the 19th century
arose a great demand for hydraulic cement. The supply of materials
containing naturally suitable proportions of calcium carbonate and clay
being limited, attempts were made to produce artificial mixtures which
would serve a similar end. Among those who experimented in this
direction was Joseph Aspdin, of Leeds, who added clay to finely ground
limestone, calcined the mixture, and ground the product, which he called
Portland cement. The only connexion between Portland cement and the
place Portland is that the cement when set somewhat resembles Portland
stone in colour. True, it is possible to manufacture Portland cement
from Portland stone (after adding a suitable quantity of clay), but this
is merely because Portland stone is substantially carbonate of lime; any
other limestone would serve equally well. Although Portland cement is
later in date than either Roman cement or hydraulic lime, yet on account
of its greater industrial importance, and of the fact that, being an
artificial product, it is of approximately uniform composition and
properties, it may conveniently be treated of first. The greater part of
the Portland cement made in England is manufactured on the Thames and
Medway. The materials are chalk and Medway mud; in a few works the
latter is replaced by gault.

  The composition of typical samples of chalk and clay is shown in the
  following  analyses:--

  +-----------------------------------+----------------------------------------------------------------------------+
  |              Chalk.               |                                   Clay.                                    |
  +-------------------------+---------+----------------------------+---------+------------------+-------+----------+
  |                         |Per cent.|                            |Per cent.|                  |       |          |
  |Silica (SiO2)            |   0.92  | Insoluble silicious matter |  26.67  |Consisting of     |       |          |
  |Alumina+ferric oxide     |         | Silica (SiO2)              |  31.24  |  Quartz (SiO2)   | 19.33 |          |
  |  (Al2O2 + Fe2O3)        |   0.24  | Alumina (Al2O3)            |  16.60  |  Silica (SiO2)   |  5.19 |\         |
  |Lime (CaO)               |  55.00  | Ferric Oxide (Fe2O3)       |   8.66  |  Alumina (Al2O3) |  1.47 | >Feldspar|
  |Magnesia (MgO)           |   0.36  | Lime (CaO)                 |   0.25  |  Magnesia (MgO)  |  0.03 | | 7.34%  |
  |Carbonic anhydride (CO2) |  43.40  | Magnesia (MgO)             |   1.91  |  Soda (Na20)     |  0.65 |/         |
  |                         |  -----  | Soda (Na2O)                |   1.00  |                  | ----- |          |
  |                         |  99.92  | Potash (K2O)               |   0.45  |                  | 26.67 |          |
  |                         |         | Sodium Chloride (NaCl)     |   1.86  |                  |       |          |
  |                         |         | Combined water, organic    |         |                  |       |          |
  |                         |         |   matter, and loss         |  11.36  |                  |       |          |
  |                         |         |                            | ------  |                  |       |          |
  |                         |         |                            | 100.00  |                  |       |          |
  +-------------------------+---------+----------------------------+---------+------------------+-------+----------+

    Mixing.

    Loading the kiln.

  [Illustration: FIG. 1]

  These materials are mixed in the proportion of about 3:1 by weight so
  that the dried mixture contains approximately 75% of calcium
  carbonate, the balance being clay. The mixing may be effected in
  several ways. The method once exclusively used consists in mixing the
  raw materials with a large quantity of water in a wash mill, a machine
  having radial horizontal arms driven from a central vertical spindle
  and carrying harrows which stir up and intermix any soft material
  placed in the pit in which the apparatus revolves. The raw materials
  in the correct proportion are fed into this mill together with a large
  quantity of water. The thin watery "slip" or slurry flows into large
  settling tanks ("backs") where the solids in suspension are deposited;
  the water is drawn off, leaving behind an intimate mixture of chalk
  and clay in the form of a wet paste. This is dug out, and after being
  dried on floors heated by flues is ready for burning. This process is
  now almost obsolete. According to present practice the raw materials
  are mixed in a wash mill with so much water that the resulting slurry
  contains 40 to 50% of water. The slurry, which is wet enough to flow,
  is ground between millstones so as to complete the process of
  comminution begun in the wash mill. Thorough grinding and mixing are
  of the utmost importance, as otherwise the cement ultimately produced
  will be unsound and of inferior quality. The drying of the slurry is
  generally effected by the waste heat of the kilns, so that while one
  charge is burning another is drying ready for the next loading of the
  kilns. The kilns commonly employed are "chamber kilns," circular
  structures not unlike an ordinary running lime kiln, but having the
  top closed and connected at the side with a wide flue in which the
  slurry is exposed to the hot products of combustion from the kiln. The
  farther ends of the flues of several such kilns are connected with a
  chimney shaft. The slurry, in drying on the floor of the flue, forms a
  fairly tough cake which cracks spontaneously in the process of drying
  into rough blocks suitable for loading into the kiln. At the bottom of
  the kiln is a grate of iron bars, and on this wood and coke are piled
  to start the fire. A layer of dried slurry is loaded on this, then a
  layer of coke, then a layer of slurry, and so on until the kiln is
  filled with coke and slurry evenly distributed. Fresh slurry is run on
  to the drying floors, and the kiln is started. The construction of an
  ordinary chamber kiln may be gathered from the accompanying diagram
  (fig. l). The operation of burning is a slow one. An ordinary kiln,
  which will contain about 50 tons of slurry and 12 tons of coke, will
  take two days to get fairly alight, and will be another two or three
  days in burning out. Therefore, allowing adequate time for loading and
  unloading, each kiln will require about one week for a complete run.
  The output will be about 30 tons of "clinker" ready to be ground into
  cement. The grinding of the hard rock-like masses of clinker is
  effected between millstones, or in modern plants in ball-mills,
  tube-mills and edge-runners. It is an important part of the
  manufacture, because the finished cement should be as fine and
  "floury" as possible. The foregoing description represents the
  procedure in use in many English factories. There are various
  modifications in practice according to local conditions: a few of
  these may be described. In all cases, however, the main operations are
  the same, viz. intimately mixing the raw materials, drying the
  mixture, if necessary, and burning it at a clinkering temperature
  (about 1500° C. =2732° F.). Thus when hard limestone is the form of
  calcium carbonate locally available, it is ground dry and mixed with
  the correct proportion of clay also dried and ground. The mixture is
  slightly damped, moulded into rough bricks, dried and burned. A
  possible alternative is to burn the limestone first and mix the
  resulting lime with clay, the mixture being burned as before. By this
  method grinding the hard limestone is avoided, but there is an extra
  expenditure of fuel in the double burning.

    Other kilns.

  Many different forms of kiln are used for burning Portland cement.
  Besides the chamber kilns which have been described, there are the
  old-fashioned bottle kilns, which are similar to the chamber kilns,
  but are bottle-shaped and open at the top; they do not dry the slurry
  for their next charge. Their use is becoming obsolete. There are also
  stage kilns of the Dietzsch type, which consist of two vertical
  shafts, one above the other, but not in the same vertical line,
  connected by a horizontal channel. At this middle portion and in the
  upper part of the lower shaft the burning proper proceeds; the upper
  shaft is full of unburnt raw material which is heated by the hot gases
  coming from the burning zone, and the lower shaft contains clinker
  already burned and hot enough to heat the incoming air which supplies
  that necessary for combustion at the clinkering zone. A pair of
  Dietzsch kilns, built back to back, are shown in fig. 2. There are
  other forms of shaft kiln, such as the Schneider, in which there is a
  burning zone, a heating and cooling zone as in the Dietzsch, but no
  horizontal stage, the whole shaft being in the same vertical plane.
  Another form is the Hoffmann or ring kiln, made up of a number of
  compartments arranged in a ring and connected with a central chimney;
  in these compartments rough brick-shaped masses of the raw materials
  are stacked, and between these bricks fuel is sprinkled. At a given
  moment one of these compartments is burning and at its full
  temperature; the air for combustion is drawn in through one or more
  compartments behind it which have just finished burning, and is
  thereby strongly heated; the products of combustion pass away through
  one or more compartments in front of it and heat their contents before
  they are subjected to actual combustion. It will be seen that the
  principle of the ring kiln is similar to that of the stage kiln. In
  each case the clinker which has just been burned and is fully hot
  serves to heat the air-supply to the compartment where combustion is
  actually proceeding; in like manner the raw materials about to be
  burned are well heated by the waste gases from the compartment in full
  activity before they themselves are burned. (It may be noted that here
  and generally in this article "burn" is used in the technical sense;
  it is technically correct to speak of cement clinker being "burned",
  although it is not a fuel; in accurate terms it is the fuel which is
  burned, and it is the heat it generates which raises the clinker to a
  high temperature, i.e. technically "burns" it.) By this device a great
  part of the heat is regenerated and a saving of fuel is effected.

  [Illustration: FIG. 2.]

    Rotatory kilns.

  The methods of burning cement described above are obsolescent. They
  are being replaced by the rotatory process, so called because the
  cement is burned in rotating cylinders instead of in fixed kilns.
  These cylinders vary from 60 to 150 ft. in length, an ordinary length
  in modern practice being 100 to 120 ft.; their diameter
  correspondingly varies from 6 ft. to 7 ft. 6 in. The cylinders are
  made of steel plate, lined with refractory bricks, are carried on
  rollers at a slight angle with the horizontal, and are rotated by
  power. At the upper end the raw material is fed in either as a dry
  powder or as a slurry; at the lower end is a powerful burner. In the
  early days of rotatory kilns producer gas was used as a fuel, but with
  little success; about 1895 petroleum was used in the United States
  with complete success, but at a relatively heavy cost. At the present
  time, finely powdered coal injected by a blast of air is almost
  universally employed, petroleum being used only where it is actually
  cheaper than coal. In the working of this type of kiln the rotation
  and slight inclination of the cylinder cause the raw material to
  descend towards the lower end. At the upper end the raw material is
  dried and heated moderately. As it descends it reaches a part of the
  kiln where the temperature is higher; here the carbonic acid of the
  carbonate of lime, and the combined water of the clay are driven off,
  and the resulting lime begins to act chemically on the dehydrated
  clay. The material is then in a partially burnt and slightly sintered
  state, but it is not fully clinkered and would not make Portland
  cement. The material continues to descend by the rotation of the kiln
  and reaches the lower end nearest the burner where the temperature is
  highest, and is there heated so highly that the union of the lime,
  silica and alumina is complete, and fully burnt clinker falls out of
  the kiln. It is extremely hot, and is cooled usually by being passed
  down one or more rotating cylinders, similar to the first, but
  smaller, and acting as coolers instead of kilns. On its way down the
  cylinders the clinker meets a current of cold air and is cooled, the
  air being correspondingly warmed and passing on to aid in the
  combustion of the fuel used in heating the kiln. This regenerative
  heating is similar in principle and effect to that obtained by means
  of the shaft and ring kilns described above. The output of these kilns
  varies from 200 to 400 tons per kiln per week according to their size
  and the nature of the raw materials burned, as against 30 tons per
  week for an ordinary chamber kiln. A large saving in labour is also
  secured. The rotatory system presents many advantages and is rapidly
  replacing the older methods of cement making. Fig. 3 represents
  diagrammatically a rotatory cement plant on the Hurry & Seaman system,
  which was one of the first to make cement by the rotatory process
  successfully on a large scale, using powdered coal as fuel. Rotatory
  kilns of various other makes are now in use, but the same principles
  are embodied, namely, the employment of a rotating inclined cylinder
  for burning the raw materials, a burner fed with powdered coal and a
  blast of air, and some device such as a cooling cylinder or cooling
  tower by which the clinker may be cooled and the air correspondingly
  heated on its way to the burner.

  [Illustration: FIG. 3.]

  Another method of making Portland cement which has been proposed and
  tried with some success consists in fusing the raw materials together
  in an apparatus of the type of a blast furnace. The high temperature
  necessary to fuse cement clinker makes this process difficult to
  accomplish commercially, but it has many inherent merits and may be
  the process of the future, displacing the rotatory method.

    Cement clinker.

  Portland cement clinker, however produced, is a hard, rock-like
  substance of semi-vitrified appearance and very dark colour. The
  product from a well-run rotatory kiln is all evenly burnt and properly
  vitrified; that from an ordinary fixed kiln of whatever type is apt to
  contain a certain amount (5 to 15%) of underburnt material, which is
  yellowish and friable and is not properly clinkered. This material
  must be picked out, as such underburnt stuff contains free lime or
  unsaturated lime compounds. These may slake slowly in the finished
  cement and cause such expansion as may destroy the work of which it
  forms part. Well-burnt, well-picked clinker when ground yields good
  Portland cement. Nothing is added during or after grinding save a
  small amount (1 to 2%) of calcium sulphate in the form either of
  gypsum or of plaster of Paris, which is sometimes needed to make the
  cement slower-setting. For the same purpose a small quantity of water
  (up to 2%) may be added either by moistening the clinker or by blowing
  steam into the mills in which the clinker is ground. This small
  addition for this specified purpose is recognized as legitimate, but
  the employment of various cheap materials such as ragstone and
  blast-furnace slag, sometimes added as diluents or make-weights, is
  adulteration and therefore fraudulent.

    Composition.

  The composition of Portland cement varies within comparatively narrow
  limits, and for given raw materials the variations are tending to
  become smaller as regularity and skill in manufacture increase. The
  following analysis may be taken as typical of cements made from chalk
  and clay on the Thames and Medway:--

                             Per cent.
    Silica (SiO2)              22.0
    Insoluble residue           1.0
    Alumina (Al2O3)             7.5
    Ferric oxide (Fe2O3)        3.5
    Lime (CaO)                 62.0
    Magnesia (MgO)              1.0
    Sulphuric anhydride (SO3)   1.5
    Carbonic anhydride (CO2)    0.5
    Water (H2O)                 0.5
    Alkalis                     0.5
                              -----
                              100.0

  There may be variations from this composition according to the nature
  of the raw materials employed. Thus the silica may range from 19 to
  27%, the alumina and ferric oxide jointly from 7 to 14%, the lime from
  60 to 67%. All such variations are permissible provided that the
  quantity of silica and alumina is sufficient to saturate the whole of
  the lime and to leave none of it in a "free" condition, likely to
  cause the cement to expand after setting. Other things being equal,
  the higher the percentage of lime within the limits indicated above
  the stronger is the cement, but such highly limed cement is less easy
  to burn than cement containing about 62% of lime; and unless the
  burning is thorough and the raw materials are intimately mixed, the
  cement is apt to be unsound. Although the ultimate composition of
  cement, that is, the percentage of each base and acid present, can be
  accurately determined by analysis, its proximate composition, i.e. the
  nature and amount of the compounds formed from these acids and bases,
  can only be ascertained indirectly and with difficulty. The
  foundations of our knowledge on this subject were laid by H. le
  Chatelier, whose work has since been supplemented by that of Spenser
  B. Newberry, W.B. Newberry and Clifford Richardson. As the outcome of
  these inquiries it has been established that tricalcium silicate
  3CaO·SiO2 is the essential constituent of Portland cement. The
  constituent of next importance is an aluminate, but whether this is
  dicalcium aluminate, 2CaO·Al2O3, or tricalcium aluminate, 3CaO·Al2O3,
  is still in doubt. In the following description it is assumed to be
  the tricalcium aluminate. The remaining silicates and aluminates
  present, and ferric oxide and magnesia, if existing in the moderate
  quantities which are usual in Portland cement of good quality, are of
  minor importance and may be regarded as little more than impurities.
  The silicates and aluminates of which Portland cement is composed are
  believed to exist not as individual units but as solid solutions of
  each other, these solid solutions taking the form of minerals
  recognizable as individuals. The two principal minerals are termed
  alite and celite; according to the best opinion, alite consists of a
  solid solution of tricalcium aluminate in tricalcium silicate, and
  celite of a solid solution of dicalcium aluminate in dicalcium
  silicate. Celite is little affected by water, and has but small
  influence on the setting; alite is decomposed and hydrated, this
  action constituting the main part of the setting of Portland cement.
  Both the components of alite react, and for simplicity their reactions
  may be stated in separate equations, thus:--

    (1)  2(3CaO·SiO2) + 9H2O = 2(CaO·SiO2)·5H2O + 4Ca(OH)2
        Tricalcium silicate.    Hydrated mono-     Calcium
                               calcium silicate.  hydroxide.

    (2)  3CaO·Al2O3 + 12H2O = 3CaO·Al2O3·12H2O
        Tricalcium aluminate.  Hydrated tricalcium
                                 aluminate.

  Since alite is a solid solution and, although an individual mineral,
  is not a chemical unit, the proportion of tricalcium silicate to
  tricalcium aluminate in a given specimen of alite will vary; but,
  whatever the proportions, each of these substances will react in its
  characteristic manner according to the equations given above.

  The precise mechanism of the process of setting of Portland cement is
  not known with certainty, but it is probably analogous to that of the
  setting of plaster of Paris, consisting in the dissolution of the
  compounds produced by hydration while they are in a more soluble form,
  their transition to a less soluble form, the consequent
  supersaturation of the solution, and the deposition of the surplus of
  the dissolved substance in crystals which interlock and form a
  coherent mass. This theory being accepted, it is evident that a small
  quantity of water, by successive dissolution and deposition of a
  substance capable of existing in a more soluble and in a less soluble
  form, is able to bring about the crystallization of an indefinitely
  large quantity of material. It is not necessary that there should be
  present sufficient water to dissolve the whole of the reacting
  substance at any one time; it is sufficient if there is enough for
  hydration and a small surplus for the crystallization by successive
  stages as above described. It is generally admitted that the aluminate
  is the chief agent in the first setting of the cement, and that its
  ultimate hardening and attainment of strength are due to the
  tricalcium silicate.

  As mentioned above, the constituents other than the tricalcium
  silicate and tricalcium aluminate of which alite is composed, are of
  minor importance. The function of the ferric oxide present in ordinary
  cement is little more than that of a flux to aid the union of silica,
  alumina and lime in the clinker; its role in the setting of the cement
  is altogether secondary. In fact, excellent Portland cement can be
  prepared from materials free from iron. Such cement, if free also from
  manganese, is white, and its manufacture has been proposed for
  exterior decorative use. Magnesia, if present in Portland cement in
  quantity not exceeding 5%, appears to be inert, but there is evidence
  that in larger proportion, e.g. 10-15%, it may hydrate and set after
  the general setting of the cement, and may give rise to disruptive
  strains causing the cement to "blow" and fail. In so-called natural
  cement which is comparatively lightly burnt, the magnesia appears to
  be inert, and as much as 20 to 30% may be present. Another constituent
  of Portland cement which influences its setting time is calcium
  sulphate, naturally formed from the sulphur in the raw materials or
  fuel, or intentionally added to the finished cement as gypsum or
  plaster of Paris. It has a remarkable retarding effect on the
  hydration of the calcium aluminate, and consequently on the setting of
  the cement; thus it is that a little gypsum is often added to convert
  a naturally quick-setting cement into one which sets slowly. It will
  be observed that in the hydration of tricalcium silicate, the main
  constituent of Portland cement, a large portion of the lime appears as
  calcium hydroxide, i.e. slaked lime. It is evident that this will form
  a pozzuolanic cement if a suitable silicious material such as trass is
  added to the cement. The ultimate product when set may be regarded as
  a mixed Portland and pozzuolanic cement. The use of trass in this
  manner as an adjunct to Portland cement has been advocated by W.
  Michaelis, and undoubtedly increases the strength of the material, but
  it has not become general.

    Testing.

  The quality of Portland cement is ascertained by its analysis and by
  determining its specific gravity, fineness, mechanical strength and
  soundness. A good sample will usually have a composition within the
  limits cited above and approximating to the typical figures given
  above. It will be ground so finely that not more than 3% will be left
  on a sieve of 76 × 76 meshes per sq. in., the wires of the sieve being
  0.005 in. in diameter. It will have, when freshly burned, a specific
  gravity not lower than 3.15, and briquettes made from it and kept in
  water will possess a tensile strength of 400-500 lb. per sq. in. seven
  days after they are made, while briquettes made from a mixture of 3
  parts by weight of sand and 1 of cement will give about 225 lb. per sq.
  in. at twenty-eight days. Formerly the soundness of cement was
  determined by keeping thin pats of the cement in cold water for
  twenty-eight days, or in warm water (110°-120° F.) for twenty-four
  hours, and examining for cracks or other signs of expansion. Modern
  practice is to measure the expansion of a test piece of cement kept in
  water at a temperature of 212° F. The simplest and most generally used
  method is due to H.L. le Châtelier, and consists in measuring the
  increase in circumference of a cylinder of cement 30 mm. in diameter
  by means of a split ring encircling the cylinder, the motion of which
  is magnified by two light rods extending radially. Another
  quantitative test for soundness is that formulated by L. Deval, who
  has shown that briquettes of 3 of sand and 1 of cement kept in water
  for two days at 80° C. = 176° F. attain approximately the same
  strength as similar briquettes attain at seven days in water at the
  ordinary temperature. In like manner briquettes kept at 176° F. for
  seven days are approximately equal in strength to those kept at the
  ordinary temperature for twenty-eight days. A cement not perfectly
  sound will give low results in the hot test, and a cement of
  indifferent soundness will crack and go to pieces. The test is
  admittedly severe, but can be passed without difficulty by cement made
  with proper care and skill. There are many modifications and
  elaborations of all the tests which have been mentioned. Cement for
  all important work is submitted to a rigorous system of testing and
  analysis before it is accepted and used.

_Hydraulic Lime_ is a cement of the Portland as distinct from the
pozzuolanic class. The most typical hydraulic lime is that known as
Chaux du Theil, made from a limestone found at Ardèche in France. This
limestone consists of calcium carbonate most intimately intermixed with
very finely divided silica. It contains but little alumina and oxide of
iron, which are the constituents generally necessary to bring about the
union of silica and lime to form a cement, but in spite of this the
silica is so finely divided and so well distributed that it unites
readily with the lime when the limestone is burned at a sufficiently
high temperature. English hydraulic limes are of a different class; they
contain a good deal of alumina and ferric oxide, and in composition
resemble somewhat irregular Portland cement.

  Analyses of the two classes of hydraulic lime are as follows:--

                                Chaux de Theil.    Blue Lias.
                                   Per cent.        Per cent.

    Insoluble silicious matter       0.3              2.39
    Silica (SiO2)                   21.7             14.17
    Alumina (Al2O3)                  1.8              6.79
    Ferric oxide (Fe2O3)             0.6              2.34
    Lime (CaO)                      74.0             63.43
    Magnesia (MgO)                   0.7              1.54
    Sulphuric anhydride (SO3)        0.3              1.63
    Carbonic anhydride (CO2) \       0.6            / 3.64
    Water (H20)              /                      \ 2.69
    Alkalis and loss                 · ·              1.38
                                   -----            ------
                                   100.0            100.00

  Hydraulic lime contains a good deal of uncombined lime, and has to be
  slaked before it is used as a cement. In France this slaking is
  conducted systematically by the makers, the freshly burned lime being
  sprinkled with water and stored in large bins where slaking proceeds
  slowly and regularly until the whole of the surplus uncombined lime
  is slaked and rendered harmless, while the cementitious compounds,
  notably tricalcium silicate, remain untouched. In English practice
  hydraulic lime is slaked by the user. Seeing that regular and perfect
  slaking is more easily attained when working systematically on a large
  scale and by storing the material for a long period, the French method
  is the better and more rational. The product may then be regarded as a
  cement of the Portland class mixed with slaked lime. When gauged with
  water and made into a mortar it sets slowly, but ultimately becomes
  almost as strong as Portland cement. Its slow setting is an advantage
  for some purposes, e.g. for foundations and abutments where
  settlements may occur. The structure is free to take its permanent
  position before the lime sets, and cracks are thus avoided. A case in
  point is the employment of hydraulic lime in place of Portland cement
  as grouting outside the cast-iron tubes used for lining tunnels made
  by the shield system.

_Roman Cement_ is another cement of the Portland class which came into
use shortly before the manufacture of artificial Portland cement was
attempted. It is still in use, though only for special purposes where a
quick-setting material is required. It is made from septaria nodules
which are dredged up on the Kent and Essex coasts and consist of about
60% of calcium carbonate mixed with clay, the mass being sufficiently
indurated to remain coherent under water. The nodules are not prepared
in any way, but simply burned at a moderate red heat.

  The resulting cement varies somewhat in composition, but approximates
  to the following figures:--

                                   Per cent.
    Insoluble silicious matter       5.86
    Silica (SiO2)                   19.62
    Alumina (Al203)                 10.30
    Ferric oxide (Fe2O3)             7.44
    Manganese dioxide (MnO2)         1.57
    Lime (CaO)                      44.54
    Magnesia (MgO)                   2.92
    Sulphuric anhydride (SO3)        2.61
    Carbonic anhydride (CO2)         3.43
    Water (H2O)                      0.25
    Alkalis and loss                 1.46
                                   100.00

  The most characteristic constituent is the oxide of iron, which gives
  the cement a reddish colour, and the presence of manganese also
  differentiates Roman from Portland cement, which rarely contains
  appreciable quantities of that element. The high percentage of alumina
  causes the cement to be quick-setting, and it becomes hard in about
  five minutes. It resists the action of water, salt or fresh, very
  well, and is therefore useful in situations where the work is likely
  to be submerged immediately after it has been put in place.

The term _Natural Cements_ is applied to cements made by burning
mixtures of clay and carbonate of lime naturally occurring in
approximately suitable proportions. They may be regarded as badly-mixed
Portland cements, and need no special description. American "natural"
cements are of a somewhat different class. They are usually made from a
silicious limestone containing magnesia, and are comparatively lightly
burned.

  The following analysis is typical of a cement of this kind:--

                                        Per cent.
    Silica (SiO2)                         24.30
    Alumina (Al203)                        7.22
    Ferric oxide (Fe2O3)                   5.06
    Lime (CaO)                            33.70
    Magnesia (MgO)                        20.94
    Water, carbonic anhydride, and loss    8.78
                                         100.00

  These irregular cements of the Portland class are good building
  materials for ordinary purposes, but are not so suitable as good
  artificial Portland cement for heavy and important undertakings.

_Passow Cement _is a recent product which is in a class by itself. It is
made by granulating blast furnace slag of suitable composition and
finely grinding the product, either alone or with an admixture of about
10% of Portland cement clinker. It differs from ordinary slag cement
(see above) in that it is not a pozzuolanic cement depending on the
interaction of granulated slag and lime. The particular method of
granulating slag for Passow cement produces a material which sets _per
se_ and attains a strength comparable with that of Portland cement.
Passow cement has been successfully made from slag of different
compositions in Germany, England and America.

  Uses of hydraulic cements.

The chief use of hydraulic cements, whether of the pozzuolanic or
Portland class, is to act as an adhesive material in work which is to be
exposed to water. No doubt in times of remote antiquity it was found
that the jointing of masonry which was to be immersed required the use
of a cement indifferent to the action of water. Ordinary mortar failed
in such positions; mortar made from lime prepared from limestones or
chalks containing a little clay was found to stand; mortar made from
lime mixed with trass or similar active silicious material was also
found to stand. On this observation rests the whole of the present
enormous employment of hydraulic cements. It was a natural transition to
utilize these cements not merely for jointing masonry but also for
making concrete, and the only reason why hydraulic cements, as distinct
from cements which are not hydraulic (e.g. ordinary mortar), are used
for the latter purpose is their great mechanical strength. Their use in
above-water work is checked by the low price of common brick. Even in
such work, where it would be thought that masses of burnt clay would be
the cheapest conceivable material, concrete is at least on level terms
with its rival. It must be remembered that one of the great advantages
of concrete is that five-sixths of its total mass may be provided from
local sand and gravel, on which no carriage has to be paid. The cement,
on which alone freight is to be reckoned, converts these from loose
incoherent material into a solid stone. Thus it comes about that the
largest use of cement is for manufacturing concrete for dock and harbour
work, and for the making of foundations. It is also employed for the
building of light bridges, floors, and pipes constructed of cement
mortar disposed round a skeleton of iron rods. Such composite structures
take advantage at once of the high tensile strength of iron and of the
high compressive strength of cement mortar. (See also CONCRETE.)

Good hydraulic cements are highly permanent materials provided certain
conditions be observed. It might be supposed that hydraulic cements from
their nature would be indifferent to the action of water, but this is
only true if the structures of which they form part are sufficiently
compact. In this case the action of the water is checked by the film of
carbonate of lime which eventually forms oh the surface of calcareous
cement. This, together with the compactness of the mortar, hinders the
ingress and egress of water, and prevents the dissolution and ultimate
destruction of the cement. But where the concrete or mortar is not well
made and is porous, the continual passage of water through it will
gradually break up and dissolve away the calcareous constituents of the
cement until its strength is utterly destroyed. This destructive action
is increased if the water contains sulphates or magnesium salts, both of
which act chemically on the calcareous constituents of the cement. As
sea-water contains both sulphates and magnesium salts, it is especially
necessary in concrete for harbour work to take every care to produce an
impervious structure. There are various minor external causes for the
failure and ultimate destruction of cement mortar and concrete, but
their discussion is a matter for the specialist. Failure from inherent
vice in the cement has been already touched on; it can always be traced
to want of skill and care in manufacture.

_Calcium Sulphate Cements._--Under this term are comprehended all
cements whose setting properties primarily depend on the hydration of
calcium sulphate. They include plaster of Paris, Keene's cement and many
variants of these two types. The raw material is gypsum (q.v.). This may
be almost chemically pure, when it is generally used for Keene's cement;
or it may contain smaller or greater quantities of impurities, in which
case it is suitable for the preparation of cements of the plaster of
Paris class. The mode of preparation is to calcine the gypsum at
temperatures which depend on the class of cement to be produced. If
plaster of Paris is to be made, calcination is carried out at about 204°
C. (=400° F.); at this temperature, gypsum, CaS04.2H20, loses
three-quarters of its combined water and becomes 2CaSO4.H20. If a cement
of the Keene's cement class is to be prepared the temperature used is
higher, e.g. 500° C. (=932° F.), and the whole of the combined water of
the gypsum is expelled, the anhydrous sulphate CaSO4 being obtained.

    Plaster of Paris; Keene's cement.

  To produce plaster of Paris European practice consists in baking the
  mineral in ovens, and in America in heating it in kettles. Both
  processes are inferior in economy to calcination in rotatory kilns, a
  process which may be regarded as the method of the present and the
  immediate future. Keene's cement and its congeners are made in fixed
  kilns so constructed that only the gaseous products of combustion come
  into contact with the gypsum to be burnt, in order to avoid
  contamination with the ash of the fuel.

  The setting of plaster of Paris depends on the fact that when
  2CaSO4·H2O is treated with water it dissolves, forming a
  supersaturated solution of CaSO4·2H2O. The excess held temporarily in
  solution is then deposited in crystals of CaSO4·2H2O. In the light of
  this knowledge the mode of setting of plaster of Paris becomes clear.
  The plaster is mixed with a quantity of water sufficient to make it
  into a smooth paste; this quantity of water is quite insufficient to
  dissolve the whole of it, but it dissolves a small part, and gives a
  supersaturated solution of CaSO4.2H2O. In a few minutes the surplus
  hydrated calcium sulphate is deposited from the solution, and the
  water is capable again of dissolving 2CaSO4·H2O, which in turn is
  fully hydrated and deposited as CaSO4·2H2O. The process goes on until
  a relatively small quantity of water has by instalments dissolved and
  hydrated the 2CaSO4·H2O, and has deposited CaSO4·2H2O in felted
  crystals forming a solid mass well cemented together. The setting is
  rapid, occupying only a few minutes, and is accompanied by a
  considerable expansion of the mass. There is reason to suppose that
  the change described takes place in two stages, the gypsum first
  forming orthorhombic crystals and then crystallizing in the
  monosymmetric system. Gypsum thus crystallized is in its normal
  monosymmetric form, more stable under ordinary conditions than the
  orthorhombic form. Correlatively in its process of dehydration to form
  plaster of Paris, monosymmetric gypsum is converted into the
  orthorhombic form before it begins to be dehydrated.

  The principles which govern the preparation and setting of the other
  class of calcium sulphate cements, that is, cements of the Keene
  class, are not fully understood, but there is a fair amount of
  knowledge on the subject, both empirical and scientific. The essential
  difference between the setting of Keene's cement and that of plaster
  of Paris is that the former takes place much more slowly, occupying
  hours instead of minutes, and the considerable heating and expansion
  which characterize the setting of plaster of Paris are much less
  marked.

  It is the practice in Great Britain to burn pure gypsum at a low
  temperature so as to convert it into the hydrate 2CaSO4·H2O, to soak
  the lumps in a solution of alum or of aluminium sulphate, and to
  recalcine them at about 500° C. On grinding they give Keene's cement.
  Instead of alum various other salts, e.g. borax, may be used. The
  quantity of these materials is so small that analyses of Keene's
  cement show it to be almost pure anhydrous calcium sulphate, and make
  it difficult to explain what, if any, influence these minute amounts
  of alum and the like can exert on the setting of the cement. It seems
  probable that the effect of the salts is inconsiderable, and that the
  governing condition is the temperature at which the cement has been
  burnt. The setting of Keene's cement takes place by the same sort of
  process which has been described for the setting of plaster of Paris,
  the chief differences being that the substance dissolved is anhydrous
  calcium sulphate and that the operation takes a longer time.

  All cements having calcium sulphate as their base are suitable only
  for indoor work because of the solubility of this substance. They form
  excellent decorative plasters on account of their clean white colour
  and the sharpness of castings made from them, this latter quantity
  being due to their expansion when setting.

  See D.B. Butler, _Portland Cement_ (London, 1905); E.C. Eckel,
  _Cements, Limes and Plasters_ (New York, 1905); G.R. Redgrave and
  Charles Spackman, _Calcareous Cements_ (London, 1905); F.H. Lewis,
  "Manufacture of Hydraulic Cements in the United States," _The Mineral
  Industry_ (New York, 1898); W.H. Stanger and Bertram Blount, "Cement
  Manufacture in Great Britain," _The Mineral Industry_, New York, 1897
  and 1905; _Id_. "The Testing of Hydraulic Cements," _Journ. Soc. Chem.
  Ind.,_ 1894, 13, p. 455; _Id., Proc. Inst. Civ. Eng._, 1901; B.
  Blount, "Recent Progress in the Cement Industry," _Journ. Soc. Chem.
  Ind.,_ 1906, 25, p. 1020; H.L. le Chatelier, _Recherrhes
  experimenlales sur la constitution des mortiers hydrauliques;_ Desch,
  _Concrete_, No. 2, pp. 101-102; Davis, _Journ. Soc. Chem. Ind.,_ 1905,
  26, p. 727.     (B. Bl.)

  _Adhesive Cements._--Mixtures of animal, vegetable and mineral
  substances are employed in great variety in the arts for making
  joints, mending broken china and other objects, &c. A strong cement
  for alabaster and marble, which sets in a day, may be prepared by
  mixing 12 parts of Portland cement, 8 of fine sand and 1 of infusorial
  earth, and making them into a thick paste with silicate of soda; the
  object to be cemented need not be heated. For stone, marble, and
  earthenware a strong cement, insoluble in water, can be made as
  follows:--skimmed-milk cheese is boiled in water till of a gluey
  consistency, washed, kneaded well in cold water, and incorporated
  with quicklime; the composition is warmed for use. A similar cement
  is a mixture of dried fresh curd with 1/10th of its weight of
  quicklime and a little camphor; it is made into a paste with water
  when employed. A cement for Derbyshire spar and china, &c., is
  composed of 7 parts of rosin and 1 of wax, with a little plaster of
  Paris; a small quantity only should be applied to the surfaces to be
  united, for, as a general rule, the thinner the stratum of a cement,
  the more powerful its action. Quicklime mixed with white of egg,
  hardened Canada balsam, and thick copal or mastic varnish are also
  useful for cementing broken china, which should be warmed before their
  application. For small articles, shellac dissolved in spirits of wine
  is a very convenient cement. Cements such as marine glue are solutions
  of shellac, india-rubber or asphaltum in benzene or naphtha. For use
  with wood which is exposed to moisture, as in the case of wooden
  cisterns, a mixture may be made of 4 parts of linseed oil boiled with
  litharge, and 8 parts of melted glue; other strong cements for the
  same purpose are prepared by softening gelatine in cold water and
  dissolving it by heat in linseed oil, or by mixing glue with
  one-fourth of its weight of turpentine, or with a little bichromate of
  potash. _Mahogany cement_, for filling up cracks in wood, consists of
  4 parts of beeswax, 1 of Indian red and yellow-ochre to give colour.
  _Cutler's cement_, used for fixing knife-blades in their hafts, is
  made of equal parts of brick-dust and melted rosin, or of 4 parts of
  rosin with 1 each of beeswax and brick-dust. For covering bottle-corks
  a mixture of pitch, brick-dust and rosin is employed. A cheap cement,
  sometimes employed to fix iron rails in stone-work, is melted
  brimstone, or brimstone and brick-dust. For pipe-joints, a mixture of
  iron turnings, sulphur and sal ammoniac, moistened with water, is
  employed. _Japanese cement_, for uniting surfaces of paper, is made by
  mixing rice-flour with water and boiling it. _Jewellers'_ or _Armenian
  cement_ consists of isinglass with mastic and gum ammoniac dissolved
  in spirit. Gold and silver chasers keep their work firm by means of a
  cement of pitch and rosin, a little tallow, and brick-dust to thicken.
  _Temporary cement_ for lathe-work, such as the polishing and grinding
  of jewelry and optical glasses, is compounded thus:--rosin, 4 oz.;
  whitening previously made red-hot, 4 oz.; wax, ¼ oz.

CEMETERY (Gr. [Greek: koimêtêrion], from [Greek: koiman], to sleep),
literally a sleeping-place, the name applied by the early Christians to
the places set apart for the burial of their dead. These were generally
extra-mural and unconnected with churches, the practice of interment in
churches or churchyards being unknown in the first centuries of the
Christian era. The term cemetery has, therefore, been appropriately
applied in modern times to the burial-grounds, generally extra-mural,
which have been substituted for the overcrowded churchyards (q.v.) of
populous parishes both urban and rural.

From 1840 to 1855, attention was repeatedly called to the condition of
the London churchyards by correspondence in the press and by the reports
of parliamentary committees, the first of which, that of Mr Chadwick,
appeared in 1843. The vaults under the pavement of the churches, and the
small spaces of open ground surrounding them, were crammed with coffins.
In many of the buildings the air was so tainted with the products of
corruption as to be a direct and palpable source of disease and death to
those who frequented them. In the churchyards coffins were placed tier
above tier in the graves until they were within a few feet (or sometimes
even a few inches) of the surface, and the level of the ground was often
raised to that of the lower windows of the church. To make room for
fresh interments the sextons had recourse to the surreptitious removal
of bones and partially-decayed remains, and in some cases the contents
of the graves were systematically transferred to pits adjacent to the
site, the grave-diggers appropriating the coffin-plates, handles and
nails to be sold as waste metal. The neighbourhood of the churchyards
was always unhealthy, the air being vitiated by the gaseous emanations
from the graves, and the water, wherever it was obtained from wells,
containing organic matter, the source of which could not be mistaken. In
all the large towns the evil prevailed in a greater or less degree, but
in London, on account of the immense population and the consequent
mortality, it forced itself more readily upon public attention, and
after more than one partial measure of relief had been passed the
churchyards were, with a few exceptions, finally closed by the act of
1855, and the cemeteries which now occupy a large extent of ground to
the north, south, east and west became henceforth the burial-places of
the metropolis. Several of them had been already established by private
enterprise before the passing of the Burial Act of 1855 (Kensal Green
cemetery dates from 1832), but that enactment forms the epoch from
which the general development of cemeteries in Great Britain and Ireland
began. Burial within the limits of cities and towns is now almost
everywhere abolished, and where it is still in use it is surrounded by
such safeguards as make it practically innocuous. This tendency has been
conspicuous both in the United Kingdom and the United States. The
increasing practice of cremation (q.v.) has assisted in the movement for
disposing of the dead in more sanitary conditions; and the proposals of
Sir Seymour Haden and others for burying the dead in more open coffins,
and abandoning the old system of family graves, have had considerable
effect. The tendency has therefore been, while improving the sanitary
aspects of the disposal of the dead, to make the cemeteries themselves
as fit as possible for this purpose, and beautiful in arrangement and
decoration.

The chief cemeteries of London are Kensal Green cemetery on the Harrow
Road; Highgate cemetery on the slope of Highgate Hill; the cemetery at
Abney Park (once the residence of Dr Watts); the Norwood and Nunhead
cemeteries to the south of London; the West London cemetery at Brompton;
the cemeteries at Ilford and Leytonstone in Essex; the Victoria cemetery
and the Tower Hamlets cemetery in East London; and at a greater
distance, accessible by railway, the great cemetery at Brookwood near
Woking in Surrey, and the cemetery at New Southgate. The general plan of
all these cemeteries is the same, a park with broad paths either laid
out in curved lines as at Kensal Green and Highgate, or crossing each
other at right angles as in the case of the West London cemetery. The
ground on each side of these paths is marked off into grave spaces, and
trees and shrubs are planted in the intervals between them. The
buildings consist of a curator's residence and one or more chapels, and
usually there is also a range of family graves with imposing tombs,
massive structures containing in their corridors recesses for the
reception of coffins, generally closed only by an iron grating. The
provincial cemeteries in the main features of their arrangements
resemble those of the metropolis. One of the most remarkable is St
James's cemetery at Liverpool, which occupies a deserted quarry. The
face of the eastern side of the quarry is traversed by ascending
gradients off which open catacombs formed in the living rock,--a soft
sandstone; the ground below is planted with trees, amongst which stand
hundreds of gravestones. The main approach on the north side is through
a tunnel, above which, on a projecting rock, stands the cemetery chapel,
built in the form of a small Doric temple with tetrastyle porticos.

Many of the cities of America possess very fine cemeteries. One of the
largest, and also the oldest, is that of Mount Auburn near Boston.
Others of importance are the Laurel Hill cemetery (1836) at
Philadelphia; the Greenwood cemetery (1838) at Brooklyn (New York); the
Lake View cemetery at Cleveland, Ohio; while the cemeteries at New
Orleans (q.v.) are famous for their beauty.

The chief cemetery of Paris is that of Père la Chaise, the prototype of
the garden cemeteries of western Europe. It takes its name from the
celebrated confessor of Louis XIV., to whom as rector of the Jesuits of
Paris it once belonged. It was laid out as a cemetery in 1804. It has an
area of about 200 acres, and contains about 20,000 monuments, including
those of all the great men of France of the 19th century--marshals,
generals, ministers, poets, painters, men of science and letters, actors
and musicians. Twice the cemetery and the adjacent heights have been the
scene of a desperate struggle; in 1814 they were stormed by a Russian
column during the attack on Paris by the allies, and in 1871 the
Communists made their last stand among the tombs of Père la Chaise; 900
of them fell in the defence of the cemetery or were shot there after its
capture, and 200 of them were buried in quicklime in one huge grave and
700 in another. There are other cemeteries at Mont Parnasse and
Montmartre, besides the minor burying-grounds at Auteuil, Batignolles,
Passy, La Villette, &c. In consequence of all these cemeteries being
more or less crowded, a great cemetery was laid out in 1874 on the
plateau of Méry sur Oise, 16 m. to the north of Paris, with which it is
connected by a railway line. It includes within its circuit fully 2 sq.
m. of ground. The French cemetery system differs in many respects from
the English. Every city and town is required by law to provide a
burial-ground beyond its barriers, properly laid out and planted, and
situated if possible on a rising ground. Each interment must take place
in a separate grave. This, however, does not apply to Paris, where the
dead are buried, forty or fifty at a time, in the _fosses communes_, the
poor being interred gratuitously, and a charge of 20 francs being made
in all other cases. The _fosse_ is filled and left undisturbed for five
years, then all crosses and other memorials are removed, the level of
the ground is raised 4 or 5 ft. by fresh earth, and interments begin
again. For a fee of 50 francs a _concession temporaire_ for ten years
can be obtained, but where it is desired to erect a permanent monument
the ground must be bought by the executors of the deceased. In Paris the
undertakers' trade is the monopoly of a company, the _Société des pompes
funèbres_, which in return for its privileges is required to give a free
burial to the poor.

The _Leichenhäuser_, or dead-houses, of Frankfort and Munich form a
remarkable feature of the cemeteries of these cities. The object of
their founders was twofold--(1) to obviate even the remotest danger of
premature interment, and (2) to offer a respectable place for the
reception of the dead, in order to remove the corpse from the confined
dwellings of the survivors. At Frankfort the dead-house occupies one of
the wings of the propylaeum, which forms the main entrance to the
cemetery. It consists of the warder's room, where an attendant is always
on duty, on each side of which there are five rooms, well ventilated,
kept at an even temperature, and each provided with a bier on which a
corpse can be laid. On one of the fingers is placed a ring connected by
a light cord with a bell which hangs outside in the warder's room. The
use of the dead-house is voluntary. The bodies deposited there are
inspected at regular intervals by a medical officer, and the warder is
always on the watch for the ringing of the warning bell. One revival,
that of a child, has been known to take place at Frankfort. The
Leichenhaus of Munich is situated in the southern cemetery outside the
Sendling Gate. At one end of the cemetery there is a semicircular
building with an open colonnade in front and a projection behind, which
contains three large rooms for the reception of the dead. At both
Frankfort and Munich great care is taken that the attendants receive the
dead confided to them with respect, and no interment is permitted until
the first signs of decomposition appear; the relatives then assemble in
one of the halls adjoining the Leichenhaus, and the funeral takes place.
In any case there is, with ordinary care, little fear of premature
interment, but in another way such places of deposit for the dead are of
great use in large towns, as they prevent the evil effects which result
from the prolonged retention of the dead among the living. Mortuaries
for this purpose have also been established in many places in England.

In Italy the _Campo Santo_ (Holy Field) is best illustrated by the
famous one at Pisa, from which the name has been given to other Italian
burying-grounds. Of the cemeteries still in use in southern Europe the
catacombs (q.v.) of Sicily are the most curious. There is one of these
under the old Capuchin monastery of Ziza near Palermo, where in four
large airy subterranean corridors 2000 corpses are ranged in niches in
the wall, many of them shrunk up into the most grotesque attitudes, or
hanging with pendent limbs and head from their places. As a preparation
for the niche, the body is desiccated in a kind of oven, and then
dressed as in life and raised into its place in the wall. At the end of
the principal corridor at Ziza there is an altar strangely ornamented
with a kind of mosaic of human skulls and bones.

Cemeteries have been in use among many Eastern nations from time
immemorial. In China, the high grounds near Canton and Macao are crowded
with tombs, many of them being in the form of small tumuli, with a low
encircling wall, forcibly recalling the ringed barrows of western
Europe. But the most picturesque cemeteries in the world are those of
the Turks. From them it was, perhaps, that the first idea of the modern
cemetery, with its ornamental plantations, was derived. Around
Constantinople the cemeteries form vast tracts of cypress woods under
whose branches stand thousands of tombstones. A grave is never reopened;
a new resting-place is formed for every one, and so the dead now occupy
a wider territory than that which is covered by the homes of the living.
The Turks believe that till the body is buried the soul is in a state of
discomfort, and the funeral, therefore, takes place as soon as possible
after death. No coffin is used, the body is laid in the grave, a few
boards are arranged round it, and then the earth is shovelled in, care
being taken to leave a small opening extending from the head of the
corpse to the surface of the ground, an opening not unfrequently
enlarged by dogs and other beasts which plunder the grave. A tombstone
of white marble is then erected, surmounted by a carved turban in the
case of a man, and ornamented by a palm branch in low relief if the
grave is that of a woman. The turban by its varying form indicates not
only the rank of the sleeper below but also the period of his death, for
the fashion of the Turkish head-dress is always changing. A cypress is
usually planted beside the grave, its odour being supposed to neutralize
any noxious exhalations from the ground, and thus every cemetery is a
forest, where by day hundreds of turtle doves are on the wing or
perching on the trees, and where bats and owls swarm undisturbed at
night. Especially for the Turkish women the cemeteries are a favourite
resort, and some of them are always to be seen praying beside the narrow
openings that lead down into a parent's, a husband's, or a brother's
grave. Some of the other cemeteries of Constantinople contrast rather
unfavourably with the simple dignity of those which belong to the Turks.
That of the Armenians abounds with bas-reliefs which show the manner of
the death of whoever is buried below, and on these singular tombstones
there are frequent representations of men being decapitated or hanging
on the gallows.

  See also the articles BURIAL AND BURIAL ACTS; CREMATION; FUNERAL
  RITES; CHURCHYARD.

CENCI, BEATRICE (1577-1599), a Roman woman, famous for her tragic story;
poetic fancy has woven a halo of romance about her, which modern
historic research has to a large extent destroyed. Born at Rome, she was
the daughter of Francesco Cenci (1549-1598), the bastard son of a
priest, and a man of great wealth but dissolute habits and violent
temper. He seems to have been guilty of various offences and to have got
off with short terms of imprisonment by bribery; but the monstrous
cruelty which popular tradition has attributed to him is purely
legendary. His first wife, Ersilia Santa Croce, bore him twelve
children, and nine years after her death he married Lucrezia Petroni, a
widow with three daughters, by whom he had no offspring. He was very
quarrelsome and lived on the worst possible terms with his children,
who, however, were all of them more or less disreputable. He kept
various mistresses and was even prosecuted for unnatural vice, but his
sons were equally dissolute. His harsh treatment of his daughter
Beatrice was probably due to his discovery that she had had an
illegitimate child as the result of an intrigue with one of his stewards
(A. Bertolotti, in his _Francesco Cenci_, publishes Beatrice's will in
which she provides for this child), but there is no evidence that he
tried to commit incest with her, as has been alleged. The eldest son
Giacomo was a riotous, dishonest young scoundrel, who cheated his own
father and even attempted to murder him (1595). Two other sons, Rocco
and Cristoforo, both of them notorious rakes, were killed in brawls.
Finally Francesco's wife Lucrezia and his children Giacomo, Bernardo and
Beatrice, assisted by a certain Monsignor Guerra, plotted to murder him.
Two bravos were hired (one of them named Olimpio, according to
Bertolotti, was probably Beatrice's lover), and Francesco was
assassinated while asleep in his castle of Petrella in the kingdom of
Naples (1598). Giacomo afterwards had one of the bravos murdered, but
the other was arrested by the Neapolitan authorities and confessed
everything. Information having been communicated to Rome, the whole of
the Cenci family were arrested early in 1599; but the story of the
hardships they underwent in prison is greatly exaggerated. Guerra
escaped; Lucrezia, Giacomo and Bernardo confessed the crime; and
Beatrice, who at first denied everything, even under torture, also ended
by confessing. Great efforts were made to obtain mercy for the accused,
but the crime was considered too heinous, and the pope (Clement VIII.)
refused to grant a pardon; on the 11th of September 1599, Beatrice and
Lucrezia were beheaded, and Giacomo, after having been tortured with
red-hot pincers, was killed with a mace, drawn and quartered. Bernardo's
penalty, on account of his youth, was commuted to perpetual
imprisonment, and after a year's confinement he was pardoned. The
property of the family was confiscated.

  The romantic character of the history of this family has been the
  subject of poems, dramas and novels. Shelley's tragedy is well known
  as a magnificent piece of writing, although the author adopts a purely
  fictitious version of the story. Nor is F.D. Guerrazzi's novel,
  _Beatrice Cenci_ (Milan, 1872), more trustworthy. The first attempt to
  deal with the subject on documentary evidence is A. Bertolotti's
  _Francesco Cenci e la sua famiglia_ (2nd ed., Florence, 1879),
  containing a number of interesting documents which place the events in
  their true light; cf. Labruzzi's article in the _Nuova Antologia_,
  1879, vol. xiv., and another in the _Edinburgh Review_, January 1879.

CENOBITES (from Gr. [Greek: koinos], common, and [Greek: bios], life),
monks who lived together in a convent or community under a rule and a
superior,--in contrast to hermits or anchorets who live in isolation.
The Basilians (q.v.) in the East and the Benedictines (q.v.) in the West
are the chief cenobitical orders (see MONASTICISM).

CENOMANI, a branch of the Aulerci in Gallia Celtica, whose territory
corresponded generally to Maine in the modern department of Sarthe.
Their chief town was Vindinum or Suindinum (corrupted into Subdinnum),
afterwards Civitas Cenomanorum (whence Le Mans), the original name of
the town, as usual in the case of Gallic cities, being replaced by that
of the people. According to Caesar (_Bell. Gall._ vii. 75. 3), they
assisted Vercingetorix in the great rising (52 B.C.) with a force of
5000 men. Under Augustus they formed a _civitas stipendiaria_ of Gallia
Lugdunensis, and in the 4th century part of Gallia Lugdunensis iii.
About 400 B.C., under the leadership of Elitovius (Livy v. 35), a large
number of the Cenomani crossed into Italy, drove the Etruscans
southwards, and occupied their territory. The statement of Cato (in
Pliny, _Nat. Hist._ iii. 130), that some of them settled near Massilia
in the territory of the Volcae, may indicate the route taken by them.
The limits of their territory are not clearly defined, but were probably
the Athesis (Adige or Etsch) on the east, the Ollius (Oglio, or perhaps
the Addua) on the west, and the Padus on the south. Livy gives their
chief towns as Brixia (Brescia) and Verona; Pliny, Brixia and Cremona.
The Cenomani nearly always appear in history as loyal friends and allies
of the Romans, whom they assisted in the Gallic war (225 B.C.), when the
Boii and Insubres took up arms against Rome, and during the war against
Hannibal. They certainly joined in the revolt of the Gauls under
Hamilcar (200), but after they had been defeated by the consul Gaius
Cornelius (197) they finally submitted. In 49, with the rest of Gallia
Transpadana, they acquired the rights of citizenship.

The orthography and the quantity of the penultimate vowel of Cenomani
have given rise to discussion. According to Arbois de Jubainville, the
Cenom[)a]ni of Italy are not identical with the Cenom[=a]ni (or
Cenomanni) of Gaul. In the case of the latter, the survival of the
syllable "man" in Le Mans is due to the stress laid on the vowel; had
the vowel been short and unaccented, it would have disappeared. In
Italy, Cenomani is the name of a people; in Gaul, merely a surname of
the Aulerci.

  See A. Voisin, _Les Cénomans anciens et modernes_ (Le Mans, 1862); A.
  Desjardins, _Géographic historique de la Gaule romaine,_ ii.
  (1876-1893); Arbois de Jubainville, _Les Premiers Habitants de
  l'Europe_ (1889-1894); article and authorities in _La Grande
  Encyclopédie_; C. Hulsen in Pauly-Wissowa's _Realencyclopadie_, iii.
  pt. 2 (1899); full ancient authorities in A. Holder, _Alt-celtischer
  Sprachschatz_, i. (1896).

CENOTAPH (Gr. [Greek: kenos], empty, [Greek: taphos], tomb), a monument
or tablet to the memory of a person whose body is buried elsewhere. The
custom arose from the erection of monuments to those whose bodies could
not be recovered, as in the case of drowning.

CENSOR (from Lat. _censere_, assess, estimate; in Gr. [Greek:
timaetaes]). I. _In ancient Rome_, the title of the two Roman officials
who presided over the census, the registration of individual citizens
for the purpose of determining the duties which they owed to the
community. In the etymology of the word lurks the idea of the arbitrary
assignment of burdens or duties. Varro defines _census_ as _arbitrium_,
and derives the name _censores_ from the position of these magistrates
as _arbitri populi_ (Varro, _de Ling. Lat._ v. 81; _ap._ Non. p. 519).
This original idea of "discretionary power" was never entirely lost;
although ultimately it came to be more intimately associated with the
appreciation of morals than with the assignment of burdens. From the
point of view of its moral significance the censorship was the Roman
manifestation of that state control of conduct which was a not unusual
feature of ancient societies. It is true that Rome possessed sumptuary
laws, and laws dealing with moral offences, which it was the duty of
other magistrates to enforce; but the organization for the control of
conduct was mainly exhibited in the censorship, and, as thus exhibited,
was at once simple and comprehensive.

The censorship was believed to have been instituted in 443 B.C. to
relieve the consuls of the duties of registration. Since the periods of
registration were quinquennial, it was not a continuous office; but its
tenure does not seem to have been fixed until 434 B.C., when a _lex
Aemilia_ provided that the censors should hold office for eighteen
months. This magistracy was at first confined to patricians; a plebeian
censor is first mentioned in 351 B.C. A _lex Publilia_ of 339 B.C. is
said to have enacted that one censor must be a plebeian. Two plebeian
censors were for the first time elected in 131 B.C. The election always
took place in the Comitia Centuriata (see COMITIA). The censorship,
although lacking the powers implied in the imperium and the right of
summoning the senate and the people, was not only one of the higher
magistracies, but was regarded as the crown of a political career. It
was an irresponsible office; and the only limitations on its powers were
created by the restriction of tenure to a year and a half, the fact that
re-election was forbidden, and the restraint imposed on each censor by
the fact that no act of his was valid without the assent of his
colleague.

The original functions of the censors were (1) the registration of
citizens in the state-divisions, such as tribes and centuries; (2) the
taxation of such citizens based on an estimate of their property; (3)
the right of exclusion from public functions on moral grounds, known as
the _regimen morum_; (4) the solemn act of purification (_lustrum_)
which closed the census. Two other functions were subsequently
added:--(5) the selection of the senate (_lectio senatus_, see SENATE),
and (6) certain financial duties such as the leasing of the contracts
for tax-collecting and for the repair of public buildings. The first
four of these functions were those of the census, which was a detailed
examination of the citizen body as represented by heads of families
(_patres familiarum_) in the Campus Martius. The equites were a select
portion of this citizen body; but the review of these knights took
place, not in the Campus, but in the Forum (see EQUITES). It was in
connexion with this review of the ordinary citizens and the knights, as
well as with the choice of senators, that the censors published their
edicts stating the moral rules which they intended to enforce. The
offences which they punished were sometimes concerned with family life
and private relations, sometimes with breaches of political duty.
Certain professions, such as that of an actor or gladiator, also invoked
their stigma, and at times the disqualifications they pronounced were
the consequence of a previous judicial condemnation. _Infamia_ was the
general name given to the disabilities pronounced by the censor. These
varied in degree from the deprivation of a senator of his seat, or a
knight's loss of his horse, to exclusion from the tribes or centuries,
an exclusion which entailed the loss of voting power. All the
disabilities pronounced by one pair of censors might be removed by their
successors.

The censorship, although its control over the senate came to be
weakened (see SENATE), lasted as long as the republic; and it was only
suspended, not abolished, during the principate. Although the princeps
exercised censorial functions, he was seldom censor. Yet the office
itself was held by Claudius I. and Vespasian. Domitian assumed the title
of life censor (_censor perpetuus_), but the precedent was not followed.
A fruitless attempt to galvanize the republican office into new life was
made in A.D. 251, during the reign of the emperor Decius.

  AUTHORITIES.--Mommsen, _Romisches Staatsrecht_, ii. 331 foll. (3rd
  ed., Leipzig, 1887); Daremberg-Saglio, _Dictionnaire des antiquités
  grecques et romaines_, i. 990 foll. (1875, &c.); Lange, _Romische
  Alterthumer_, i. 572 foll. (Berlin, 1856, &c.); de Boor, _Fasti
  Censorii_ (Berlin, 1873); Gerlach, _Die romische Censur in ihrem
  Verhaltnisse zur Verfassung_ (Basel, 1842); Nitzsch, "Über die Census"
  in _Neues Jahrbuch f. Phil._ lxxiii. 730 (Leipzig, 1856); Zumpt, "Die
  Lustra der Römer" in _Rhein. Museum_, xxv. 465, xxvi. i.
       (A. H. J. G.)

II. In modern times the word "censor" is used generally for one who
exercises supervision over, or criticizes, the conduct of other persons.
In the universities of Oxford and Cambridge it is the title of the
official head or supervisor of the non-collegiate students (i.e. those
who are not attached to a college, hall or hostel). In Oxford the censor
is nominated by the vice-chancellor and the proctors, and holds office
for five years; in Cambridge he is similarly appointed, and holds office
for life. The censors of the Royal College of Physicians are the
officials who grant licences.

_Council of Censors_, in American constitutional history, is the name
given to a council provided by the constitution of Pennsylvania from
1776 to 1790, and by the constitution of Vermont from 1777 to 1870.
Under both constitutions the council of censors was elected once in
seven years, for the purpose of inquiring into the working of the
governmental departments, the conduct of the state officers, and the
working of the laws, and as to whether the constitution had been
violated in any particular. The Vermont council of censors, limited in
number to thirteen, had power, if they thought the constitution required
amending in any particular, to call a convention for the purpose. A
convention summoned by the council in 1870 amended the constitution by
abolishing the censors.

  For the censorship of the press, see PRESS LAWS; for the censorship of
  plays, THEATRE: _Law_, and LORD CHAMBERLAIN.

CENSORINUS, Roman grammarian and miscellaneous writer, flourished during
the 3rd century A.D. He was the author of a lost work _De Accentibus_,
and of an extant treatise _De Die Natali_, written in 238, and dedicated
to his patron Quintus Caerellius as a birthday gift. The contents are of
a varied character: the natural history of man, the influence of the
stars and genii, music, religious rites, astronomy, the doctrines of the
Greek philosophers. The second part deals with chronological and
mathematical questions, and has been of great service in determining the
principal epochs of ancient history. The whole is full of curious and
interesting information. The style is clear and concise, although
somewhat rhetorical, and the Latinity, for the period, good. The chief
authorities used were Varro and Suetonius. Some scholars, indeed, hold
that the entire work is practically an adaptation of the lost _Pratum_
of Suetonius. The fragments of a work _De Natali Institutione_, dealing
with astronomy, geometry, music and versification, and usually printed
with the _De Die Natali_ of Censorinus, are not by him. Part of the
original MS., containing the end of the genuine work, and the title and
name of the author of the fragment are lost.

  The only good edition with commentary is still that of H. Lindenbrog
  (1614); the most recent critical editions are by O. Jahn (1845), F.
  Hultsch (1867), and J. Cholodniak (1889). There is an English
  translation of the _De Die Natali_ (the first eleven chapters being
  omitted) with notes by W. Maude (New York, 1900).

CENSUS (from Lat. _censere_, to estimate or assess; connected by some
with _centum, i.e._ a count by hundreds), a term used to denote a
periodical enumeration restricted, in modern times, to population, and
occasionally to industries and agricultural resources, but formerly
extending to property of all kinds, for the purpose of assessment.

Operations of this character have been conducted with different objects
from very ancient times. The fighting strength of the children of Israel
at the Exodus was ascertained by a count of all males of twenty years
old and upwards, made by enumerators appointed for each clan. The
Levites, who were exempted from military duties, were separately
enumerated from the age of thirty upwards, and a similar process was
ordained subsequently by Solomon, in order to distribute amongst them
the functions assigned to the priestly body in connexion with the
temple. The census unwillingly carried out by Joab at the behest of
David related exclusively to the fighting men of the community, and the
dire consequences ascribed to it were quoted in reprobation of such
inquiries as late as the middle of the 18th century. It appears, too,
that a register of the population of each clan was kept during the
Babylonian captivity and its totals were published on their return to
Jerusalem. In the Persian empire there was apparently some method in
force by which the resources of each province were ascertained for the
purpose of fixing the tribute. In China, moreover, an enumeration of
somewhat the same nature was an ancient institution in connexion with
the provincial revenues and military liabilities. In Egypt, Amasis had
the occupation of each individual annually registered, nominally to aid
the official supervision of morals by discouraging disreputable means of
subsistence; and this ordinance, according to Herodotus, was introduced
by Solon into the Athenian scheme of administration, where it developed
later into an electoral record.

It was in Rome, however, that the system from which the name of the
inquiry is derived was first established upon a regular footing. The
original census was ascribed to Servius Tullius, and in the constitution
which goes by his name it was decreed that every fifth year the
population should be enumerated along with the property of each
family--land, live-stock, slaves and freedmen. The main object was to
ensure the accurate division of the people into the six main classes and
their respective centuries, which were based upon considerations of
combined numbers and wealth. With the increase of the city the operation
grew in importance, and was followed by an official _lustrum_, or
purificatory sacrifice, offered on behalf of the people by the censors
or functionaries in charge of the classification. Hence the name of
lustrum came to denote the intercensal term, or a period of five years.
The word census, too, came to mean the property qualification of the
class, as well as the process of registering the resources of the
individual. Later, it was used in the sense of the imposition itself, in
which it has survived in the contracted form of _cess_. Unfortunately
the statistics of population thus collected were subordinated to the
fiscal interests of the inquiry, and no record has been handed down
relating to the population of the city and its neighbourhood. In the
time of Augustus the census was extended to the whole empire. In the
words of the Gospel of St Luke, he ordered "the whole world to be
_taxed_," or, according to the revised version, to be _enrolled_. The
compilation of the results of this the most comprehensive enumeration
till then attempted was engaging the attention of the emperor, it is
said, just before his death, but was never completed. The various
inquiries instituted during the middle ages, such as the Domesday Book
and the Breviary of Charlemagne, were so far on the Roman model that
they took little or no account of the population, the feudal system
probably rendering information regarding it unnecessary for the purposes
of taxation or military service.

The foundations of the census on the modern system were laid in Europe
towards the middle or end of the 17th century. Sweden led the way, by
making compulsory the parish record of births, deaths and marriages,
kept by the clergy, and extending it to include the whole of the
domiciled population of the parish. In France, Colbert, in 1670, ordered
the extension to the rural communes of the system which had for many
years been in force in Paris of registering and periodically publishing
the domestic occurrences of the locality. Five years before this,
however, a periodical enumeration by families and individuals had been
established in the colony of New France, and was continued in Quebec
from 1665 till 1754. This, therefore, may be considered to be the
earliest of modern censuses.

Efforts have been almost unceasingly made since 1872 by statistical
experts in periodical conference to bring about a general understanding,
first, as to the subjects which may be considered most likely to be
ascertained with approximate accuracy at a census, and secondly--a point
of scarcely less importance--as to the form in which the results of the
inquiry should be compiled in order to render comparison possible
between the facts recorded in the different areas. In regard to the
scope of the inquiry, it is recognized that much is practicable in a
country where the agency of trained officials is employed throughout the
operation which cannot be expected to be adequately recorded where the
responsibility for the correctness of the replies is thrown upon the
householder. The standard set up by eminent statisticians, therefore,
may be taken to represent an ideal, not likely to be attained anywhere
under present conditions, but towards which each successive census may
be expected to advance. The subjects to which most importance is
attached from the international standpoint are age, sex, civil
condition, birthplace, illiteracy and certain infirmities. Occupation,
too, should be included, but the record of so detailed a subject is
usually considered to be better obtained by a special inquiry, rather
than by the rough and ready methods of a synchronous enumeration. This
course has been adopted in Germany, Belgium and France, and an approach
to it is made in the decennial census of Canada and the United States.
Religious denomination, another of the general subjects suggested, is of
considerably more importance in some countries than in others, and the
same may be said of nationality, which is often usefully supplemented by
the return of mother-tongue. Nor should it be forgotten that the
internal classification and the combinations of the above subjects are
also matters to be treated upon some uniform plan, if the full value of
the statistics is to be extracted from the raw material. On the whole,
the progress towards a general understanding on many, if not most, of
the questions here mentioned which has been made in the present
generation, is a gratifying tribute to those who have long laboured in
the cause of efficient enumeration.

THE BRITISH EMPIRE

_England and Wales._--Up to the beginning of the 19th century the number
of the population was a matter of estimate and conjecture. In 1753 a
bill was introduced by a private member of the House of Commons, backed
by official support, to provide for the annual enumeration of the people
and of the persons in receipt of parochial relief. It was violently
opposed as "subversive of the last remains of English liberty" and as
likely to result in "some public misfortune or an epidemical distemper."
After passing that House, however, the bill was thrown out by the House
of Lords. The fear of disclosing to the enemies of England the weakness
of the country in fighting-material was one of the main objections
offered to the proposal. By the end of the century, however, owing to a
great extent to the publication of the essays of Malthus, the pendulum
had swung far in the opposite direction, it was thought desirable to
possess the means of judging from time to time the relations between an
increasing population and the means of subsistence. A census bill,
accordingly, again brought in by a private member, became law without
opposition at the end of 1800, and the first enumeration under it took
place in March of the following year, the operations being confined to
Great Britain. The inquiry was entrusted in England to the overseers,
acting under the justices of the peace and the high constables, and in
Scotland, to village schoolmasters, under the sheriffs. A supplementary
statement of births, deaths and marriages for each parish was required
from the clergy, who transmitted it to parliament through the bishops
and primates successively. There was no central office or control. The
schedule required the number of houses, inhabited and otherwise, the
population of each family, by sex, and the occupation, under one of the
three heads, (a) agriculture, (b) trade, manufacture or industry, or (c)
other than these two. The results, which were not satisfactory, were
published without comment. Ten years later, the chief alteration in the
inquiry was the substitution of the main occupation of the family for
that of the individual. The report on this census contained a very
valuable exposition of the difficulties involved in such operations and
the numerous sources of error latent in an apparently simple set of
questions. In 1821 an attempt to get a return of ages was made, but it
was not repeated in 1831, when the attention of the enumerators was
concentrated upon greater detail in the occupation record. Their efforts
were successful in getting a better, but still far from complete result.
The creation, in 1834, of poor law unions, and the establishment, in
1836, of civil registration districts, as a rule coterminous with them,
provided a new basis for the taking of a census, and the operations in
1841 were made over accordingly to the supervision of the
registrar-general and his staff. The inquiry was extended to the sex,
age and occupation of every individual; those born in the district were
distinguished from others, foreigners being also separately returned.
The number of houses inhabited, uninhabited and under construction
respectively, was noted in the return. The parish statement of births,
deaths and marriages was sent up by the clergy for the last time. The
most important innovation, however, was the transfer of the
responsibility for filling up the schedule from the overseers to the
householders, thereby rendering possible a synchronous record.

With some modification in detail, the system then inaugurated has been
since maintained. In 1851 the relationship to the head of the family,
civil condition, and the blind and deaf-mute were included in the
inquiry. On this occasion, the act providing for the census was
interpreted to authorize the collection of details regarding
accommodation in places of public worship and the attendance thereat, as
well as corresponding information about educational establishments. A
separate report was published on the former subject which proved
something of a storm centre. The census of 1871 obtained for the first
time a return of persons of unsound mind not confined in asylums. During
the next ten years, the separate areas for which population returns had
to be prepared were seriously multiplied by the creation of sanitary
districts, to the number of 966. The necessity, for administrative or
other purposes, of tabulating separately the returns for so many
cross-divisions of the country constitutes one of the main difficulties
of the English census operations, more particularly as the boundaries of
these areas are frequently altered. In anticipation of the census of
1891, a treasury committee was appointed to consider the various
suggestions made in regard to the form and scope of the inquiry. Its
proposals were adopted as to the subdivision of the occupation column
into employer, employed and independent worker, and as to the record
upon the schedule of the number of rooms occupied by the family, where
not more than five. Separate entry was also made of the persons living
upon property or resources, but not following any occupation. No action
was taken, however, upon the more important recommendation that midway
between two censuses a simple enumeration by sex and age should be
effected. A return was also prepared in 1891, for Wales, of those who
could speak only Welsh, only English, and both languages, but, owing to
the inclusion of infants, the results were of little value. In 1901 the
same information was called for, excluding all under three years of age.
The term tenement, too, was substituted for that of storey, as the
subdivision of a house, whilst in addition to inhabited and uninhabited
houses, those occupied by day, but not by night, were separately
recorded. The nationality of those born abroad, which used to be
returned only for British subjects, was called for from all not born
within the kingdom.

_Scotland._--In the acts relating to the census from 1801 to 1851,
provision for the enumeration of Scotland was made with that for England
and Wales, allowance being made for the differences in procedure, which
mainly concerned the agency to be employed. In 1855, however, civil
registration of births and deaths was established in Scotland, and the
conduct of the census of 1861 was, by a separate act, entrusted to the
registrar-general of that country. The same course was followed at the
three succeeding enumerations, but in 1901 the former practice was
resumed. The complexity of administrative areas, though far less than in
England, was simplified, and the census compilation proportionately
facilitated, by the passing of the Local Government Act for Scotland, in
1889. In 1881, the definition of a house in Scotland was made identical
with that in England, since previously what was called a house in the
northern portion of Great Britain was known as a tenement in the south,
and vice versa. Since 1861 a return has been called for in Scotland of
the number of rooms with one or more windows, and that of children of
school-age under instruction is also included in the inquiry. The number
of persons speaking Gaelic was recorded for the first time in 1881. The
question was somewhat expanded at the next census, and in 1901 was
brought into harmony with the similar inquiry as to Welsh and Manx.

_Ireland_.--An estimate of the population of Ireland was made as early
as 1672, by Sir W. Petty, and another in 1712, in connexion with the
hearth-money, but the first attempt to take a regular census was made in
1811, through the Grand Juries. It was not successful, and in 1821
again, the inquiry was considered to be but little more satisfactory.
The census of 1831 was better, but the results were considered
exaggerated, owing to the system of paying enumerators according to the
numbers they returned. The census, therefore, was supplemented by a
revisional inquiry three years afterwards, in order to get a good basis
for the newly introduced system of public instruction. The completion of
the ordnance survey and the establishment of an educated constabulary
force brought the operations of 1841 up to the level of those of the
sister kingdom. The main difference in procedure between the two
inquiries is that in Ireland the schedule is filled in by the
enumerator, a member of the constabulary, or, in Dublin, of the
metropolitan police, instead of being left to the householder. The
tabulation of the returns, again, is carried out at the central office
from the original schedule, and not, as in England, from the book into
which the former has been copied by the enumerating agency. The inquiry
in Ireland is more extensive than that in Great Britain. It includes,
for instance, a considerable amount of information regarding holdings
and stock. The details of house accommodation are fuller. A column is
provided for the degree of education, and another for religious
denomination, an addition which has always been successfully resisted in
England. This last information was made voluntary in 1881 and the
following enumerations without materially affecting the extent of the
record. The inquiry as to infirmities, too, is made to extend to those
_temporarily_ incapacitated from work, whether at home or in a hospital.
There is also a column for the entry of persons speaking the Irish
language only or able to speak both that and English. In the report of
1901 for England and Wales (p. 170) a table is given showing, for the
three divisions of the United Kingdom, the relative number of persons
speaking the ancient languages either exclusively or in addition to
English.

_British Colonies and Dependencies._--A simultaneous and uniform census
of the British empire is an ideal which appeals to many, but its
practical advantages are by no means commensurate with the difficulties
to be surmounted. Scattered as are the colonies and dependencies over
the world, the date found most suitable for the inquiry in the mother
country and the temperate regions of the north is the opposite in the
tropics and inconvenient at the antipodes. Then, again, as to the scope
of the inquiry, the administrative purposes for which information is
thus collected vary greatly in the different countries, and the inquiry,
too, has to be limited to what the conditions of the locality allow, and
the population dealt with is likely to be able and willing to answer. By
prearrangement, no doubt, uniformity may be obtained in regard to most
of the main statistical facts ascertainable at a census, at all events
in the more advanced units of the empire, and proposals to this effect
were made by the registrar-general of England and Wales in his report
upon the figures for 1901. Previous to that date, the only step towards
compilation of the census results of the empire had been a bare
statement of area and population, appended without analysis; comparison
or comment, to the reports for England and Wales, from the year 1861
onwards. In 1905, however, the returns published in the colonial reports
were combined with those of the United Kingdom, and the subjects of
house-room, sex, age, civil condition, birthplace, occupation, and,
where available, instruction, religion and infirmities, were reviewed as
fully as the want of uniformity in the material permitted (Command
paper, 2860, 1906). The measures taken by the principal states, colonies
and dependencies for the periodical enumeration of their population are
set forth below.

_Canada_.--The first enumeration of what was afterwards called Lower
Canada, took place, as above stated, in 1665, and dealt with the legal,
or domiciled, population, not with that actually present at the time of
the census, a practice still maintained, in contrast to that prevailing
in the rest of the empire. The record was by families, and included the
sex, age and civil condition of each individual, with a partial return
of profession or trade. Later on, the last item was abandoned in favour
of a fuller return of agricultural resources, a feature which has
remained a prominent part of the inquiry. After the British occupation,
a census was taken in 1765 and 1784, and annually from 1824 to 1842, the
information asked for differing from time to time. Enumerations were
conducted independently by the different states until 1871, when the
first federal census was taken of the older parts of the Dominion. Since
then, the enumeration has been decennial, except in the case of the more
recently colonized territories of Manitoba and the North-West, where an
intermediate census was found necessary in 1885-1886. The census of
Canada is organized on the plan adopted in the United States rather than
in accordance with British practice, and includes much which is the
subject of annual returns in the latter country, or is not officially
collected at all. The details of deaths in the year preceding the
census, for instance, are called for, there being no registration of
such occurrences in the rural tracts. In consideration of the large
immigrant population again, the birthplace of each parent is recorded,
with details as to nationality, naturalization and date of immigration.
Occupation is dealt with minutely, in conjunction with temporary
unemployment, average wage or salary earned, and other particulars. No
less than eleven schedules are employed, most of them relating to
details of industries and production. The duty of filling up so
comprehensive a return, involving an answer to 561 questions, is not
left to the householder, but entrusted to enumerators specially engaged,
working under the supervision of the Department of Agriculture. Owing to
the sparse population and difficulties of communication in a great part
of the dominion, the inquiry, though referred to a single date, is not
completed on that day, a month being allowed to the enumerator for the
collection of his returns and their revision and transmission to the
central office. A special feature in the operations is the provision,
necessitated by the record of the _legal_ population, for the inclusion
in the local return of the persons temporarily absent on the date of the
census, and their adjustment in the general aggregates, a matter to
which considerable attention is paid. The very large mass of detail
collected at these inquiries entails an unusually long time spent in
compilation; the statistics of population, accordingly, are available
considerably in advance of those relating to production and industries.

_Australasia_.--As the sphere of the census operations in Canada has
been gradually spreading from the small beginnings on the east coast to
the immense territories of the north-west, so, in the island continent,
colonization, first concentrated in the south-east, has extended along
the coasts and thence into the interior, except in the northern region.
The first act of effective occupation of the country having been the
establishment of a penal settlement, the only population to be dealt
with in the earlier years of British administration was that under
restraint, with its guardians and a few scattered immigrants in the
immediate neighbourhood of Sydney Cove. This was enumerated from 1788
onwards by official "musters," at first weekly, and afterwards at
lengthening intervals. The record was so inaccurate that it had no
statistical value until 1820, when the muster was taken after due
preparation and with greater care, approximating to the system of a
regular census. The first operation, however, called by the latter name,
was the enumeration of 1828, when an act was passed providing for the
enumeration of the whole population, the occupied area and the
live-stock. The details of population included sex, children and adults
respectively, religion and _status_, that is whether free (immigrants or
liberated convicts), on ticket-of-leave, or under restraint. A similar
inquiry was made in 1833 and again in 1836. In 1841 a separate census
was taken of New Zealand and Tasmania respectively. The scope of the
inquiry in New South Wales was somewhat extended and made to include
occupations other than agriculture and stock-breeding. Five years later,
the increase of the population justified the further addition of
particulars regarding birthplace and education. The record of _status_,
too, was made optional, and in 1856 was omitted from the schedule. In
that year, moreover, Victoria, which had become a separate colony, took
its own census. South Australia, too, was enumerated in 1846, ten years
after its foundation as a colony. From 1861 the census has been taken
decennially by all the states except Queensland, where, as in New
Zealand, it has been quinquennial since 1875 and 1881 respectively. Up
to and including the census of 1901 each state conducted separately its
own inquiries. The scheme of enumeration is based on that of Great
Britain, modified to suit the conditions of a thin and widely scattered
population. The schedules are distributed by enumerators acting under
district supervisors; but it is found impossible to collect the whole
number in a single day, nor does the mobility of the population in the
rural tracts make such expedition necessary. In more than one state the
police are employed as enumerators, but elsewhere, a staff has to be
specially recruited for the purpose. The operations were improved and
facilitated by means of an interstatal conference held before the census
of 1891, at which a standard schedule was adopted and a series of
general tables agreed upon, to be supplemented in greater detail
according to the requirements of each state. The standard schedule, in
addition to the leading facts of sex, age, civil condition, birthplace,
occupation and house-room, includes education and sickness as well as
infirmities, and leaves the return of religious denomination optional
with the householder. Under the head of occupation, the bread-winner is
distinguished from his dependants and is returned as employer, employed,
or working on his own account, as is now the usual practice in
census-taking. Each state issues its own report, in which the returns
are worked up in the detail required for both local administrative
purposes, and for comparison with the corresponding returns for the
neighbouring territory. The reports for New South Wales and Victoria are
especially valuable in their statistical aspect from the analysis they
contain of the vital conditions of a comparatively young community under
modern conditions of progress.

_South Africa._--Almost from the date of their taking possession of the
Cape of Good Hope and its vicinity, the Netherlands East Indian Company
instituted annual returns of population, live-stock and agricultural
produce. The results from 1687 for nearly a century were recorded, but
do not appear to have been more accurate than those subsequently
obtained on the same method by the British government, by whom they were
discontinued in 1856. The information was collected by district
officials, unguided by any general instructions as to form or procedure.
The first synchronous census of the colony, as it was then constituted,
took place in 1865, on a fairly comprehensive schedule. Ten years later
the inquiry was extended to religion and civil condition, and for the
census of 1891, again, a rather more elaborate schedule was used. The
next census was deferred till 1904, in consequence of the
disorganization produced by the Boer war. The inquiry was on the same
lines as its predecessors, with a little more detail as to industries
and religious denomination. Speaking generally, the administration of
the operations is conducted upon the Australian plan, with special
attention to allaying the distrust of the native and more ignorant
classes, for which purpose the influence of the clergy was enlisted. In
some tracts it was found advisable to substitute a less elaborate
schedule for that generally prescribed. In Natal, indeed, where the
first independent census was taken in 1891, the Kaffir population was
not on that occasion enumerated at all. In 1904, however, they were
counted on a very simple schedule, by sex and by large age-groups up to
40 years old, with a return of birthplace, in a form affording a fair
indication of race. Natives of India, an element of considerable extent
and importance in this colony, are enumerated apart from the white
population, but in full detail, recognizing the remarkable difference
between the European and the Oriental in the matter of age distribution
and civil condition. The Transvaal and the Orange River colonies were
enumerated in 1904. In the latter, a census had been taken in 1890, in
considerable detail, but that of the Transvaal, in 1896, seems to have
been far from complete or accurate even in regard to the white
population. In Southern Rhodesia the white residents were enumerated in
1891, but it was not until 1904 that the whole population was included
in the census. The difficulty in all these cases is that of procuring a
sufficient quantity of efficient agency, especially where a large and
illiterate native population has to be taken into account. For this
reason, amongst others, no census had been taken up to 1906 of Northern
Rhodesia, the British possessions and protectorates of eastern Africa,
or, again, of Nigeria and the protectorates attached to the West African
colonies of Gambia, Sierra Leone and Lagos.

_The West Indies._--Each of the small administrative groups here
included takes its census independently of the rest, though since 1871
all take it about the date fixed for that of the United Kingdom. The
information required differs in each group, but the schedule is, as a
rule, of a simple character, and the results of the inquiry are usually
set forth with comparatively little comment or analysis. In some of the
groups distinctions of colour are returned in general terms; in others,
not at all. On the other hand, considerable detail is included regarding
the indentured labourers recruited from India, and those of this class
who are permanently settled on the land in Guiana and Trinidad. No
census was taken in the former, or in Jamaica and Barbados, in 1901.

_Ceylon_.--Here the census is taken decennially, on the same date as in
India, in consideration of the constant stream of migration between the
two countries. The schedule is much the same as in India with the
substitution of race for caste. Until 1901, however, it was not filled
in by the enumerator, as in India, but was distributed before and
collected after the appointed date as in Great Britain.

_India_.--The population of India is the largest aggregate yet brought
within the scope of a synchronous and uniform enumeration. It amounts to
three-fourths of that of the British Empire, and but little less than a
fifth of the estimated population of the world. Between 1853 and 1881
each province conducted its own census operations independently, with
little or no attempt at uniformity in date, schedule or tabulation. In
the latter year the operations were placed for the first time under
central administration, and the like procedure was adopted in 1891 and
1901, with such modification of detail as was suggested by the
experience of the preceding census. On each occasion new areas had to be
brought within the sphere of enumeration, whilst the necessity for the
use in the wilder tracts of a schedule simpler in its demands than the
standard, grew less as the country got more accustomed to the inquiry,
and the efficiency of the administrative agency increased. Not more than
5% of the householders in India can read and write, and the proportion
capable of fully understanding the schedule and of making the entries in
it correctly is still lower. From the literate minority, therefore,
agency has to be drawn in sufficient strength to take down every
particle of the information dictated by the heads of families. As it
would be impossible for an enumerator to get through this task in the
course of the census night for more than a comparatively small number of
houses, the operation is divided into two processes. First a preliminary
record is made a short time before the night in question, of the persons
ordinarily residing in each house. Then, on that night, the enumerator,
reinforced if necessary by aid drafted from outside, revisits his beat,
and brings the record up to date by striking out the absent and entering
the new arrivals. The average extent of each beat is arranged to include
about 300 persons. Thus, in 1901, not far from a million men were
required for enumeration alone. To this army must be added the
controlling agency, of at least a tenth of the above number, charged
with the instruction of their subordinates, the inspection and
correction of the preliminary record, and the transmission of the
schedule books to the local centre after the census has been taken. The
supply of agency for these duties is, fortunately, not deficient.
Irrespective of the large number of clerks, village scribes and state
and municipal employés which can be drawn upon with but slight
interruption of official routine, there is a fair supply of casual
literary labour up to the moderate standard required. The services, too,
of the educated public are often voluntarily placed at the disposal of
the local authorities for the census night, with no desire for
remuneration beyond out-of-pocket expenses, and the addition, perhaps,
of a personal letter of thanks from the chief official of the district.
By means of a well-organized chain of tabulating centres, the
preliminary totals, by sexes, of the 294 millions enumerated in 1901
were given to the public within a fortnight of the census, and differed
from the final results by no more than 94,000, or .03%. The schedule
adopted contains in addition to the standard subjects of sex, age, civil
condition, birthplace, occupation and infirmities, columns for
mother-tongue, religion and sect, and caste and sub-caste. It is printed
in about 20 languages. The results for each province or large state are
tabulated locally, by districts or linguistic divisions. The final
compilation is done by a provincial superintendent, who prepares his own
report upon the operations and results. This work has usually an
interest not found in corresponding reports elsewhere, in the prominent
place necessarily occupied in it by the ethnographical variety of the
population.

FOREIGN COUNTRIES

Inquiries by local officials in connexion with measures of taxation,
such as the hearth-tax in France, were instituted in continental Europe
as early as the 14th century; but as the basis of an estimate of
population they were intrinsically untrustworthy. Going outside Europe,
an extreme instance of the results of combining a census with more
definite administrative objects may be found in the census of China in
1711, when the population enumerated in connexion with a poll-tax and
liability to military service, was returned as 28 millions; but forty
years later, when the question was that of the measures for the relief
of widespread distress, the corresponding total rose to 103 millions!
The notion of obtaining a periodical record of population and its
movement, dissociated from fiscal or other liabilities, originated, as
stated above, in Sweden, where, in 1686, the birth and death registers,
till then kept voluntarily by the parish clergy, were made compulsory
and general, the results for each year being communicated to a central
office. A census, as a special undertaking, was not, however, carried
out in that country until 1749. The example of Sweden was followed in
the next year by Finland, and twenty years later, by Norway, where the
parish register was an existing institution, as in the neighbouring
state. Several other countries followed suit in the course of the 18th
century, though the results were either partial or inaccurate. Amongst
them was Spain, though here a trustworthy census was not obtained until
1857, or perhaps 1887. Some of the small states of Italy, too, recorded
their population in the middle of the above century, but the first
general census of that country took place in 1861, after its
unification. In Austria, a census was taken in 1754 by the parish
clergy, concurrently with the civil authorities and the military
commandants. Hungary was in part enumerated thirty years later. The
starting-point of the modern census, however, in either part of the dual
monarchy, was not until 1857. Speaking generally, most of the principal
countries began the current series of their censuses between 1825 and
1860. The German empire has taken its census quinquennially since its
foundation, but long before 1871 a census at short intervals used to be
taken in all the states of the Zollverein, for the purpose of
ascertaining the contribution to the federal revenue, the amount of
which was revisable every three years. The last great country to enter
the census field was Russia. From 1721, what are known as revisions of
the population were periodically carried out, for military, fiscal and
police purposes; but these were conducted by local officials without
central direction or systematic organization. In 1897 a general census
was taken as synchronously throughout the empire as was found possible.
It embraced a population second to that of India alone, as China,
probably the most populous country in the world, has not yet been
subjected to this test. The inquiry was made in great detail, under
central control, and on a plan sufficiently elastic to suit the
requirements of so varied a country and population. As in India, the
schedules had to be issued in an unusual number of languages, and were
dealt with locally in the earlier stages of tabulation. The principal
regions of which the population is still a matter of mere conjecture are
the Turkish empire, Persia, Afghanistan, China and the Indo-Chinese
peninsula, in Asia, nearly nine-tenths of Africa, and a considerable