V. HAPIATIOX. 273 



into the " mouffles." The divisions on the stem of the thermometer are read 

 by means of a micrometer. To protect the large bulb of the thermometer 

 from the influence of the temperature of the exterior, it is surrounded by a 

 wooden box, in which is placed flannel and swan's down. 



1060. Thermometric Tube for determining the calorific capa- 

 cities of different liquids. Elie Wartmann, Geneva. 



A thermometric tube, being part of the exhibitor's apparatus for the 

 determination of calorific capacities in liquids. A full description of the 

 method is printed in the number for May 1870 of the " Archives des Sciences 

 physiques et naturelles." An electric chronoscope, such as Sir Charles 

 Wheatstone's, expresses in thousandth parts of a second the time necessary 

 for the cooling between two constant temperatures of the same body (the ther- 

 mometric tube) when immersed in equal volumes of different liquids, at the 

 same initial degree of heat. 



1061. Apparatus made by De la Rive and Marcet for 

 measuring the specific heat of Gases. A small copper calori- 

 meter, containing a very thin serpentine gold pipe. 



Lucien de la Rive, Geneva. 



1O63. Drawing of an Apparatus for determining the calo- 

 rific capacity of liquids. 



Dr. Leopold Pfaundler, Professor of Physics at Innsbruck. 



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, of equal resistance, which are inserted in 

 the fluids. 



Two paddles stir the liquids, and two thermometers measure the tempera- 

 ture. 



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

 increment of heat. 



V. RADIATION. 



1O56. Hargreaves's Thermo-radiometer, for measuring 

 loss 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, a thermometer inserted in the neck 

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

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



WS(T-t) _ x ^rh ere -y^g _ we ight and average specific heat of vessel 



a m 



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. 



40075. S 



