Page:The American Cyclopædia (1879) Volume III.djvu/633

 CALORIC ENGINE CALOVIUS 627 pistons to a maximum, which takes place when they have attained their greatest velocity ; from this point to the end of the stroke the tension is reduced to about the atmospheric pressure. It is seen that the latter motion, produced by inward pressure on the piston D, is the power which drives the engine. Many modifications have been made of the principles on which this arrangement is founded, but the high expectations entertained in regard to its economy, where a considerable power is re- quired, have by no means been realized. About 1853 a large ship was built in New York, called the Ericsson, provided with caloric engines of the most colossal size, constructed under the supervision of the inventor; but the experi- ment was unsuccessful, and the owners were compelled to substitute steam for the caloric engine. At present such engines are only used where a small power, say two or one horse or less, is required. For such purposes the second kind of caloric engines above referred to, in which the expansion of the products of com- bustion is utilized, has been the most successful. An engine of this class, that of Roper, is repre- sented in section in fig, 3, and in perspective in fig. 4. The cold air is drawn in by the air pump at the left, through the opening A, its FIG. 8. Roper's Caloric Engine (section). return being prevented by the valve B, and forced into the furnace through the valve D. Two dampers, E and H, serve to pass the air either under the grate through the fire or par- tially over the fire. This air, being heated and mingled with the products of combustion, car- bonic acid, watery vapor, &c., passes by the channels indicated by the arrows under the working piston, raising it by the difference in pressure on its large surface, with the small surface of the air pump ; by the return or down stroke the air is expelled by the opening of the proper valves through the upward chim- ney seen at the right hand. This return stroke is made by the momentum of a large fly wheel. The piston consists of a long hollow drum, of which the packing is only at the top around the portion marked 1, in order to keep it at a dis- Fto. 4. Koper's Caloric Engine (In perspective). tance from the fire and heat, which otherwise would soon destroy it. CALORIMETER (Lat. calor, heat, and Gr. pirpov, measure), an instrument for measuring quanti- ties of heat, without making any assumption as to what heat is. One of the first employed for this purpose was contrived by Lavoisier and Laplace, and was directed to determining the comparative quantity of heat developed by the combustion of definite amounts of fuel. The combustion was effected in a cylinder, which was let down into a larger one filled around with pounded ice. Another cylinder outside of all also contained ice, which prevented that in the middle cylinder from being affected by the external temperature. The heat from the innermost vessel caused the ice to melt in the cylinder next to it, and the water thus pro- duced ran off through a pipe passing through the bottom. The practical application of this principle, however, did not give correct results, all the water not leaving the ice, and on ac- count of the relatively large quantity required of the material to be examined and the conse- quent impossibility of determining the specific heat of many rare substances. Bunsen in 1871 modified the apparatus in a way that enabled him to measure the volume of ice melted by the contraction which this ice undergoes on liquefaction. Count Rumford's method was to substitute water for ice, and to determine by delicate thermometers the increase of tem- perature in a definite weight of this liquid by the absorption of the heat. Other forms of apparatus have been invented by Dulong, Favre, Silbermann, Regnault, Despretz, and others. CALOVIUS (originally KALATJ), Abraham, a German Lutheran divine, born at Mohrungen, in Prussia, April 16, 1612, died in Wittenberg, Feb. 25, 1686. He was first a teacher in Ros- tock, in 1637 a professor at Konigsberg, in 1643 rector at Dantzic, and after 1650 profes-