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used for burning, for making ointment, etc. C. calaba is a West Indian species whose oil is used for illuminating purposes.

Calores'cence, the phenomenon of the transmutation of heat rays into light rays; a peculiar transmutation of the invisible calorific rays, observable beyond the red rays of the spectrum of solar and electric light, into visible luminous rays, by passing them through a solution of iodine in bisulphide of carbon, which intercepts the luminous rays and transmits the calorific. The latter, when brought to a focus, produce a heat strong enough to ignite combustible substances, and to heat up metals to incandescence; the less refrangible calorific rays being converted into rays of higher refrangibility, whereby they become luminous.


Calor'ic (Latin, calor, "heat"), a formerly given to a hypothetical, imponderable fluid, whose existence was postulated in order to explain the observed phenomena of heat. It is known that no such fluid exists, and the word is now practically obsolete, except as an adjective in such expressions as "caloric effect," "caloric engine," etc., where it stands for the words "thermal," or "heat," though sometimes in a special sense. (For a statement of the principles of the old caloric theory, consult Preston, Theory of Heat,' p. 34.) See also HEAT;


Caloric Engine, a name originally given by Ericsson to a form of hot-air engine invented by him, in order to distinguish it from other engines whose operation depends upon the same general principles; but now commonly applied to every form of hot-air engine in which the source of the motive power is a furnace external to the working cylinder, but associated with it. In these engines air is admitted to the working cylinder, where it is heated by contact with the hot cylinder wall. Its pressure at once rises, and it is then allowed to expand, pushing a piston before it. A new supply of

air is next admitted, and the process is repeated indefinitely. Hot-air engines are useful for pumping and other small work, especially because they do not need a skilled engineer. They have also been thoroughly tried upon a large scale, but without lasting success. Doubtless the inventors who have striven to overcome the immense practical difficulties that appear to be inherent in the hot-air engine have been stimulated by the knowledge that in the steam-engine an enormous quantity of heat is required merely to evaporate the water that is used, before a single pound of pressure can be exerted upon the piston of the engine. The heat so expended appears to be largely wasted, and hence it might be hoped that some form of air-engine can be devised that will avoid this apparent source of loss, and be correspondingly more efficient. (See THERMODYNAMICS.) It does not appear that this hope is likely to be fulfilled by the hot-air engine; and the gas-engine (q.v.) must be regarded as a far more promising subject for the exercise of inventive genius, and a far more formidable rival of the steam-engine. (For more detailed accounts of the hot-air engines now in use, consult Hutton, Heat and Heat Engines, and Carpenter, Text-Book of Experimental Engineering.' The latter volume contains useful directions for testing such engines. For the general theory of the hot-air engine, see

Wood, Thermodynamics,' and Rankine, (The Steam-Engine and Other Prime Movers.'

Cal'orie, or Cal'ory, the unit of heat; the amount of heat necessary to raise the temperature of a kilogram of water one degree Centigrade, or from o° to 1° C. It is used as a standard of heat by physicists as the term "foot-pound" is employed as the unit of energy. It is also known as the "greater calorie," to distinguish it from the "small calorie," in which the unit of mass is the gram instead of the kilogram. See CALORIMETRY.

Calorimeter, Respiration. The respiration calorimeter is an instrument which has proved of great value for studying the fundamental laws of nutrition, as well as more practical problems. It takes its name from the fact that it is used to measure and study the products of respiration and to measure energy in the form of heat. The apparatus was devised (1896– 1903) by Professors W. O. Atwater and E. B. Rosa, under the auspices of the United States Department of Agriculture, co-operating with the Storrs (Connecticut) Experiment Station and the Wesleyan University, some of the features being suggested by the respiration apparatus elaborated a number of years ago by Pettenkofer of Munich.

The apparatus includes a copper walled and six and one-half feet high, in which the chamber about seven feet long, four feet wide, lives one or more days and nights, usually at man who served as subject of the experiment least four. An opening in the front of the apparatus, sealed during an experiment, serves as both door and window. A smaller opening in the side, called the food aperture, having tightlyfitting caps on both ends, is used for passing food, drink, excreta, and other materials into and out of the chamber. There is a telephone by which the subject may communicate with those outside. The chamber is furnished with a folding chair, table and bed. Air is kept in circulation through the chamber at the rate of not far from two and one-half cubic feet? Thus, while the dimensions of the chamber are rather small, the subject finds nothing particularly disagreeable or uncomfortable in his sojourn within it, save for the restricted space and the monotony of the prescribed daily routine.


The circulation of air is effected by a special pump, which measures the volume of the ventilating current and at regular intervals draws measured samples of the outgoing air for analysis. At the same time samples of the incoming air are also taken for analysis. From these determinations the amounts of respiratory products-carbon dioxid and water - given off by the subject may be computed.

The diet during an experiment is uniform from day to day. All food and drink, and all solid and liquid excreta are carefully weighed, sampled and analyzed. By comparing the chemical elements and compounds received by the body in food, drink and inhaled air with those given off in the solid, liquid and gaseous excretions, it is possible to strike a balance between the total income and total outgo of matter in the body and to determine whether it has increased or diminished its store of material. In this way a gain or loss of even a small

fraction of an ounce of body fat or protein during a period of one or several days can be detected and measured.

At the same time it is desirable to study the metabolism of energy. This is done likewise by determining the balance of income and outgo. The measurements made in these investigations are in terms of heat, since other forms of energy may be transformed into it. To this end it is necessary to know how much energy is taken into the body in food and drink, how much is given off unused in the solid and liquid excreta, and how much is transformed in the body and given off in the forms of heat and external muscular work.

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A. Device for regulating temperature of ingoing air cur


burned outside the body, that is by their heats of combustion, as learned by burning samples of them with oxygen in an apparatus called the bomb calorimeter.

B. Tank for compressed air used to drive valves of meter
pump and operate brine pump of freezing apparatus.
C. Shaft for driving meter pump and other mechanism.
F. Feed pump bringing ammonia to freezing apparatus.
R. Return pipe conveying ammonia from freezing appar-


As regards the outgo of energy it must be remembered that heat is constantly given off within the chamber of the man's body, whether he is at work or at rest. When he is at rest, i. e., doing no external muscular work, there is nevertheless a great deal of muscular work going on within his body. Even when he is asleep the organs of respiration, circulation and digestion are active. The energy of the internal work is transformed into heat in the body and leaves the body as heat. In rest ex

O. Food aperture.

Pr. Pipe bringing air to freezing tank.

P2. Pipe conveying air from freezing tank to respiration chamber.

D. Freezer used to remove moisture from ingoing air.


So far as we know the only energy received by the body is the potential energy of the food, and the only forms in which it leaves the body are (1) partly in the potential energy of the unoxidized residues of food and body material which are eliminated in the solid and liquid excreta, but (2) chiefly in the kinetic energy resulting from the oxidation of material in the body, and leaving the body, so far as is known, only as heat and external muscular work.

The potential energy of the food and excretory products is measured by the amount of heat generated when these substances


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P3. P4.






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Pipe conveying air from respiration chamber to freezer. Pipe conveying air from freezer to meter pump. Freezer used to remove moisture from outgoing air. Pipe conveying air for analysis from chamber to aspira


Pipe conveying sample of ingoing air for analysis to


Small meter used to measure samples of ingoing air. Secondary shaft connecting main power shaft with

meter pump.


Box where galvanometer is read.

T1, T2, T3, and T4. Balances, drying oven, sink, and tables used for analytical operations.

periments, practically all the kinetic energy leaves the body as heat. In work experiments part is put forth as muscular power applied to the pedals of a bicycle-dynamo, which transforms this external muscular energy into heat and as an ergometer, measures its amount. The problem is to measure the whole heat including that which left the body as heat and that which resulted from the transformation of the muscular work. The method consists in collecting this heat, for measurement, and at the same time providing that there shall be no gain or loss in the amount.

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The chamber of the calorimeter is enclosed by double metal walls, which are surrounded on all sides by walls of wood with air spaces between, so that the temperature within the chamber is not greatly affected by changes in the temperature of the room outside. Very delicate thermo-electric elements arranged in series and connected with a galvanometer, show changes in the temperature of the metal walls; and devices for heating and cooling the walls are arranged so that their temperature may be kept as near that of the interior of the chamber as desired and the very small amounts of heat that may pass through them into or out of the calorimeter may be made to counterbalance each other. The temperature of the ventilating air current is also regulated so that neither more nor less heat is taken in than is brought out. Accordingly there is no gain or loss of heat either through the walls of the chamber or by the ventilating air current.

The heat produced within the chamber is that from the energy of the material oxidized in the man's body. The only way this heat can escape is by the proper agencies for carrying it out and measuring it, two in number. A small portion of the heat generated within the chamber is carried out by water vapor in the ventilating air current. The excess of vapor in the air leaving the chamber over that in the air entering it represents the amount given off as vapor from the body of the subject, and has required heat to vaporize it. The amount of this heat is computed by factor from the amount of water vapor and the temperature at which it leaves the chamber.

The larger part of the heat generated within the chamber is absorbed and carried out of it by a current of cold water, flowing through a copper pipe around the interior. The cooling surface of the pipe is increased by thin disks of copper fastened at close intervals along the coil. The water enters the chamber at a low temperature, passes through the copper coil, absorbs heat from the chamber and passes out at a higher temperature. The quantity of water and the difference between the temperatures at which it enters and leaves the coil are carefully determined and show how much heat was thus brought out of the chamber. Adding the heat brought out by the water vapor in the ventilating air current to this heat we have the whole heat produced.

By regulating the temperature and rate of flow of the water current, the heat is absorbed and carried out of the chamber as fast as generated, at the same time keeping the temperature within the chamber at a point agreeable to the subject and almost absolutely constant. So delicate are the measurements of temperature of the air within the chamber, and of the metal walls, that the observer sitting outside the apparatus and noting the changes every two or four minutes, immediately detects a rise or fall of even one one-hundredth of a degree. The accuracy of the respiration calorimeter is shown by the fact that in check experiments in which large quantities of alcohol were burned in a lamp in the chamber 99.8 per cent of the theoretical amount of carbon-dioxid, 100.1 per cent of the theoretical water, and 99.9 per cent of the energy were measured. In the average of 32 experiments with man, covering 107 days,

the energy measured was 99.9 per cent of the theoretical amount, and the value for carbon and hydrogen was equally satisfactory. Fig. A. shows the general plan of the apparatus and accessories.

The data for the matabolism of matter and of energy, obtained as heretofore explained, taken in connection with what is known of the physiological processes that go on in the body, give more accurate information than can be otherwise obtained regarding the ways in which food is used in the body, the quantities of different food ingredients that are needed to supply the demands of the body, the different conditions of rest and work, and the comparative nutritive value of different food materials. A respiration calorimeter, like that described, has been built, under government auspices, at Bonn, Germany, and a form adapted for experiments with steers has just been completed at the Pennsylvania Experiment Station, in cooperation with the United States Department of Agriculture.

C. F. LANGWORTHY, U. S. Agricultural Dept., Washington, D. C.

Calorimetry, ("heat measurement"), the art of measuring the quantity of heat that a body absorbs or emits when it passes from one temperature to another, or when it undergoes some definite change of state. In order to execute such measurements it is first necessary to adopt some convenient and accurate unit, in terms of which the quantities of heat that are to be measured can be expressed. Several such units have been proposed, but none has yet met with universal favor among physicists. One of the simplest that has been suggested (at least so far as the principles involved are concerned) is the quantity of heat that is required to melt a kilogram or a pound of ice. Evidently it will require precisely 10 times as much heat to melt 10 pounds of ice as to melt one pound, and hence, if the quantity of heat required to melt one pound of ice is taken as the unit of heat, the measurement of any given quantity of heat becomes reduced to the simple operation of observing how many pounds of ice the proposed quantity of heat can melt. The earliest form of heat-measuring device (or "calorimeter") based upon this idea is that invented by Dr. Joseph Black about the year 1760. It consists simply of a block of clear ice, in which a cavity is made, the cavity being closed by a slab of ice laid upon the main block. To make the use of this device plain, let us suppose that it is desired to determine the quantity of heat that is given out by a certain fragment of platinum in cooling from 100° F. to the freezing-point. The chamber in the block of ice is first carefully wiped dry, and the platinum, heated accurately to 100°, is quickly introduced, and the covering lid of ice is laid in place. The platinum gives up its heat to the ice about it, with the result that a certain weight of the ice is melted, and a corresponding weight of water collects within the chamber. When it is certain that the platinum has attained the temperature of the ice, the slab covering the excavation in the main block is lifted off, and the water that has collected about the platinum is removed and weighed. The quantity of heat given out by the platinum is then known at once, if the


accepted unit of heat is the quantity required to melt one pound of ice. Lavoisier and Laplace improved Black's calorimeter in certain respects, while retaining its main features. Their instrument consists essentially of three distinct concentric chambers. The object upon which the experiment is to be performed is placed in the inner chamber, and the ice whose melting is to serve as a measure of the heat given out is placed, in the form of broken lumps, in the intermediate chamber, surrounding the object to be investigated. In the outer chamber, which encloses the other two as completely as possible, broken ice is also introduced, to prevent the conduction of heat into the apparatus from the outside. The quantity of ice melted is determined by observing the amount of water that is formed in the middle chamber, this being drawn off by a conveniently situated tube and tap. This apparatus has been described as an improvement upon that of Black; but the only way in which it can be said to be an improvement is in the respect that it does not call for large blocks of pure, clear ice. In other particulars it is somewhat inferior to the simpler apparatus of Black. The quantity of water that is produced, for example, cannot be determined with the same degree of accuracy in Lavoisier and Laplace's instrument. The ice calorimeter of Bunsen was a far greater advance. This ingenious apparatus consists of an inner chamber, for the reception of the object to be studied, and an outer enveloping one, which is entirely filled with a mixture of ice and water, and from which a graduated capillary tube is led away. The whole instrument is surrounded by broken ice, as in Lavoisier and Laplace's form, in order to protect the interior parts from the effect of external thermal influences. When the apparatus is in perfect working order, the mixture of ice and water in the intermediate chamber should be neither melting nor freezing, but should be in exact equilibrium in this respect. Upon the introduction of the object to be studied into the central chamber, the ice in the intermediate chamber begins to melt, just as in the types of calorimeter already considered; but the essential peculiarity of Bunsen's instrument consists in deducing the quantity of ice that is melted by observing the change of volume of the contents of the intermediate chamber, as shown by the motion of the water in the graduated capillary tube that leads away from that chamber; advantage being taken, for this purpose, of the known fact that ice diminishes in volume upon melting, so that when the exact diminution in the volume of the contents of the intermediate chamber is known, we can calculate with a considerable degree of precision the quantity of ice that has been melted. Bunsen's calorimeter is an admirable instrument, capable of giving results of great accuracy when intelligently handled.

Another unit of heat that suggests itself quite naturally is the quantity of heat given out by a pound of steam when it condenses into a pound of water at the same temperature. A calorimeter based upon this idea was also used by Bunsen, but the steam calorimeter was brought to its present excellent form largely through the labors of Dr. J. Joly. In his type of the instrument the object to be studied is suspended from one arm of a delicate balance. After being accurately counterpoised, the object

is bathed in an atmosphere of steam, with the result that it absorbs a certain amount of heat as its temperature rises to that of the steam. But the heat thus absorbed by the body under examination can be obtained only from the steam itself; and, since saturated steam cannot part with heat in this way without condensing, it follows that there is deposited upon the body a weight of condensed moisture that corresponds precisely to the quantity of heat that has been absorbed. The amount of this moisture is determined by careful weighing; and it is evident that the quantity of heat absorbed by the experimental body in passing from its original temperature to the temperature of the steam is then immediately known, if we take, as the unit of heat, the quantity of heat that is given out by a pound of steam in condensing into a pound of water at the same temperature. In practice, numerous corrections are of course necessary, as with all other instruments of precision. It may be added that although the ice and the steam calorimeters are primarily intended to determine the heat emitted or absorbed by a body in passing from any given temperature to some one particular temperature that is always the same (that is, the freezing-point in the one case and the boiling-point in the other), yet it is always possible to determine the quantity of heat emitted or absorbed by the body between any two temperatures, by performing two experiments in succession, the body having these respective temperatures as its initial temperatures in the respective experiments. It is plain that the quantity of heat emitted or absorbed between the proposed initial and terminal temperatures can then be obtained by simply subtracting one of these results from the other.

Another and more familiar unit of heat is the quantity of heat required to warm a given weight of water by one degree on a given thermometric scale. (See CALORIC.) Thus in general engineering practice in the United States and in England, it is customary to define a heat unit as the quantity of heat that is required in order to raise the temperature of a pound of water one degree on the Fahrenheit scale. This definition is good enough for rough purposes, because it conveniently happens that there is no great difference between the quantity of heat required to warm a pound of water from 32° to 33° and the quantity required (for example) to warm it from 99° to 100°. This, however, we can only regard as a fortunate accident; and for accurate scientific purposes we must recognize that the equality is only approximate, and we must adopt some particular temperature range as a part of our definition. Thus it is common to define the British heat unit, when great accuracy is desired, as the quantity of heat required to raise the temperature of a pound of water from 59° to 60°; although some authorities, apparently without sufficient reason, make the temperature range from 32° to 33°, and others have chosen other positions on the temperature scale for the defining degree. It is unfortunate that no general agreement has yet been reached on this point. In accurate scientific work the unit of heat is usually taken as the quantity of heat required to warm a kilogram of water from 15° C. to 16° C., or (which is practically the same thing) from 14.5° to 15.5° C. It would appear that several very good reasons could be assigned for selecting 40° C.


as the standard temperature to be used in defining the heat unit. For example, the specific heat of water has its minimum value not far from that point; or, in other words, any small uncertainty in the actual realization of the temperature contained in the definition would have little or no effect if that temperature were 40° C. Again, 40° C. is the temperature at or near which the differences between the various thermometric scales that are in practical use reach their maximum; and this means that at or near this temperature a slight error in the standardization of the thermometer that is used would have the least effect upon the verification of the heat unit. Moreover, 40° C. (104° F.) is a temperature that is likely to be always greater than the general temperature of the laboratory in which work is being carried out; and it is well known to be easier to realize a temperature that is higher than that of the surrounding air, than it is to realize one that is lower. From every point of view, therefore, 40° C. (or thereabouts) would appear to be the best temperature to assume in establishing the definition of the heat unit; a unit of heat being then defined as the quantity of heat required to raise the temperature of a kilogram of water from (say) 39° C. to 40° C. Yet, cogent as these reasons would appear, no authority has yet suggested this particular temperature as the standard.

In measuring the quantity of heat emitted by a body by observing the change of temperature produced in a given mass of water when the water absorbs the heat so emitted, a great variety of forms of apparatus may be used. In some cases the heated body may be plunged into the water directly, the water being kept well stirred, and its temperature taken at the beginning and end of the experiment. In other cases, and especially when the body under examination cannot be allowed to come in contact with the water, it is necessary to adopt some more elaborate method, such as enclosing the experimental body in a water-tight envelope of some kind, and afterward making due allowance for the heat capacity of the envelope. In cases, for example, in which the heat generated by the combustion of fuel is to be measured, the fuel must be enclosed in an air-tight crucible, to which oxygen is admitted by one tube, and from which the products of combustion are drawn off by another. The crucible is surrounded by a mass of water that is disposed in such a way as to intercept and absorb as much of the heat that is produced as possible. direct observation of the temperature of the


water in the calorimeter is made before and after the combustion, and the change of temperature so obtained gives a first approximation

to the amount of heat that has been liberated.

This result has to be corrected, however, for the thermal capacity of each part of the calorimeter that has been warmed during the experiment, and for that of the gases admitted and drawn off, and also for any loss of heat that may have occurred through radiation. The precise details of the corrections will vary, however, with the design of the calorimeter, and with the mode of conducting the experiments.

For a discussion of the relations of the different units of heat that have been mentioned above, and for an account of the experiments that have been made for determining the differences in the heat capacities of water at

different temperatures, see HEAT. A very good account of the subject of calorimetry in general will be found in Preston's Theory of Heat,' which also contains valuable references to original papers. The various forms of calorimeter that are used in practical engineering are explained and illustrated in Carpenter's 'TextBook of Experimental Engineering.'

Calotropis, a genus of asclepiads forming shrubs or small trees, natives of the tropics of Asia and Africa. There are three species, and their flowers have a somewhat bell-shaped corolla, expanding into five divisions. C. gigantea, the largest of the genus, forms a branching shrub or small tree about 15 feet high, with a short trunk four or five inches in diameter. Its flowers are of a pretty rose-purple color. Cloth and paper have been made from the silky down of the seeds. The bark of the roots of several of the species furnishes the substance called mudar, which is used in India as a diaphoretic. The juice has been found very efficacious in the cure of elephantiasis, in syphilis, and anasarca. From the bark of the plant is made a substance called mudarine. The bark of the young branches also yields a valuable fibre. The leaves warmed and moistened with oil are applied as a dry fomentation in pains of the stomach; they are a valuable rubefacient. The root, reduced to powder, is given in India to horses. An intoxicating liquor, called bar, is made from the mudar by the hillmen about Mahabuleshwar, in the western Ghauts.

Calot'tists (French, Calottistes, ka-lō-test'), or the RÉGIMENT DE LA CALOTTE, a society which sprang up at Paris in the last years of the reign of Louis XIV., and took their name from the priests, which was the symbol of the society. word calotte, a flat cap formerly worn by the

All were admitted whose odd behavior or cha


racter, foolish opinions, etc., had exposed them self particularly ridiculous received lettersto public criticism. Every one who made himpatent, authorizing him to wear the calotte. They had a singular coat of arms, on which was the sceptre of Momus, with bells, apes, rattles, On their principal standard were the words, Favet Momus, luna influit. On the death of Torsac, the colonel of the Calottists, the éloge (a spirited satire on the academical style), which the Calottists pronounced on this occasion, was suppressed. Aimon, colonel of the guards, hastened to Marshal Villars with their complaints, and concluded with the words, "My lord, since the death of Alexander and Cæsar, the Calottists have not had any protector besides you," and the order was retracted. They became, however, too bold, attacked the ministers and even the king himself; and the regiment was in consequence dissolved. After the restoration the epithet Régime de la Calotte, was applied to the clerical influence in politics.

Cal'otype, a photographic process invented by Talbot. Paper saturated with iodide of silver is exposed to the action of light, the latent image being subsequently developed and fixed by hyposulphite of soda.

Calo'vius (Latinized form of original German name, KALAU), Abraham, German polemic: b. Mohrungen, Prussia, 16 April 1612; d. 25 Feb. 1686. He was the chief representative of controversial Lutheran orthodoxy in the 17th century, and waged war

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