THE FORMS OF ENERGY. 



127 



Experiment of Schuster and Gannon. Another determination by the 

 method of electrical heating was described by Schuster and Gannon in the 

 Phil. Trans., 185, A., 1895, p. 415. They immersed a coil in a calori- 

 meter containing about 1500 gms. of water, and passed a current through 

 it. The energy supplied was EC ergs in time t. By passing the 

 current through a silver voltameter, and using the known electro- 

 chemical equivalent of silver the value of Gt was determined, while E 

 was measured by comparison with a Clark's cell. The temperature was 

 measured by a mercury thermometer, which was standardised in terms 

 of the nitrogen and the hydrogen scales. It is interesting to observe 

 the difference in the result expressed in ergs per calory at 19*1 on 

 these three scales 



4*1804 x 10 7 on mercury thermometer of hard French glass. 

 4-1905 x 10 r on nitrogen scale. 

 4' 19 17 x 10 7 on hydrogen scale. 



The results below, taken from Schuster and Gannon's paper, give the 



099 . . 



0' 20' 40' 60' SO' 100' 



+ Temperature 



FIG. 60. Kesults of Different Experiments on the Specific Heat of Water. 



values obtained by different observers in foot-lbs. at Greenwich, and 

 Fahrenheit degrees of the nitrogen thermometer at 15 0. ; the values 

 in ergs and Centigrade degrees of the same thermometer are added : 



Foot-lbs. F 



Joule (1878) ... 775 



Rowland .... 778*3 



Miculescu .... 776*6 



Griffiths . . . . 780-2 



Schuster and Gannon . 779*2 



And in terms of the mean calory : 



Reynolds and Morby . . 776*94 



Ergs. C. 

 4*178 xlO 7 

 4*1895 xlO 7 

 4*180 xlO 7 

 4-199 xlO 7 

 4*194 xlO 7 



4-1832 x 107 



The values given in terms of the nitrogen scale must be increased by 

 1 in 2500 to bring them to the hydrogen scale. In Fig. 60 the results 



