232 SEC. 8. HEAT. 



In a box protected against draught there are placed two calorimeters one 

 filled with water, the other with the liquid to be tested. An electric current is 

 passed through the two spiral wires, both of equal power of resistance, which 

 are inserted in the fluids. 



Two paddles stir, and two thermometers measure, the temperature of the 

 liquids. 



The respective capacities of heat are calculated from the proportion of the 

 increment of heat. 



106 3a. Original Apparatus of M. Regnault for ascer- 

 taining Specific Heat by observing Refrigeration. 



College of France, Paris. 



1064. The original Lavoisier Calorimeter. Fabre and 

 Silbermann's original calorimeter for measuring the heat disengaged 

 in combustion. Conservatoire dcs Arts et Metiers, Paris. 



1064a. Original Vessel, by Dulong, for measuring Specific 

 Heat by Refrigeration. Polytechnic School, Paris. 



10G4b. Original Apparatus, by M. Regnault, for ascer- 

 taining the latent Heat of Steam at different pressures. 



College of France, Paris. 



106 5 a. A Calorimeter. M. Laurent, Paris. 



IV. RADIATION. 



1056. Hargreaves's Thermo-radiometer, for measuring 

 losses of heat by radiation from walls of furnaces, sides of steam 

 boilers, &c. James Hargreaves. 



The silver-plated copper vessel is filled with water and enclosed in the 

 case, the blackened face then being exposed for a given time (say five 

 minutes) to the radiating surface, while a thermometer inserted in the neck 

 of the vessel shows the elevation of temperature due to radiation. The 

 heat is calculated as follows, either in calorics or British thermal units. 



^ . -f = x. Where WS = weight and average specific heat of vessel 



a in 



and its contents ; t, temperature of the same before exposure ; T, temperature 

 of the same after exposure ; a, area of blackened face of vessel ; and m, time 

 of exposure, whence may be calculated the amount of fuel necessary to 

 replace the heat lost by radiation. 



1059. Diacalorimeter. To measure the resistance which 

 liquids oifer to the passage of heat. Frederick Guthrie, F.R.S. 



Two conical platinum vessels, having their bases accurately plane, are sup- 

 ported so that their bases are parallel, horizontal, and nearly touching. The 

 lower cone is fixed, and, being provided with an air-tight fitting vertical tube 

 in which water stands at a known height, serves as an air thermometer and 

 calorimeter. The upper cone can be adjusted by a micrometer screw at any 



