224 Messrs. Rosa and. Smith on a Calorimetric 



and the other coiled ahont and soldered to the jacket 







ne 



end of each pipe is closed and the other connected to one end 

 of the U-tube, G, shown on the outside of the calorimeter in 

 fig. 1. The U-tube, which we call the gauge, contains kero- 

 sene oil, and serves to indicate any difference of temperature 

 between the two copper walls. The zero-mark is fixed after 



Fig. 2. 

 E F 



maintaining the whole calorimeter at a constant temperature 

 for some hours. In order to keep the gauge reading sensibly 

 zero, and thus keep the two copper walls very closely at the 

 same temperature, a coil of wire through which an electric 

 current of any desired strength can be passed is wound about 

 the jacket in the space B. And in order to make the regulation 

 more perfect a second coil is wound about the second box in 



