Determination of Energy Dissipated in Condensers. 225 



the space C, so as to maintain the temperature of this space 

 nearly constant. The temperature of the chamber A is 

 usually kept a little higher than the external temperature, so 

 that no cooling is required ; and by varying the currents in 

 the two heating-coils the temperature in B can be made to 

 follow that in A so closely that the gauge-readings are always 

 small, and their algebraic sum during any experiment zero. 

 This eliminates all correction for radiation. In rare cases 

 when the temperature of the room has risen considerably, we 

 have found it necessary to hang a wet cloth about the box to 

 prevent the temperature of C rising above that of B and A. 

 We intend to coil a small copper pipe in C so that a stream of 

 cool water may be sent through it, and then no difficulty will 

 be encountered in the hottest weather. 



In addition to the gauge four thermometers (fig. 1) indicate 

 the temperatures of A, a, b, and C: that is, A' shows the tem- 

 perature of the air in the calorimeter chamber A ; a! has its 

 bulb in a pocket of the lining a, and hence indicates the tem- 

 perature of the wall a; V similarly extends down into a 

 pocket of the copper jacket b, and shows its temperature. 

 Finally, C 7 gives the temperature of the outer air-space C. 

 A' is an accurate thermometer reading from i0° to 25° C, 

 graduated to 0°*01 and read to o> 001 C. If A 7 shows the 

 temperature to be constant during the whole period of an 

 experiment, or the same for a considerable time near the end 

 of an experiment that it was at the beginning, then there will 

 be no correction for heat absorbed or given up by the appa- 

 ratus. With both the " cooling correction " and the capacity 

 correction eliminated, it remains to carry away and measure 

 the entire heat generated by a condenser in A, or by any other 

 source of heat within the calorimeter. 



2. Carrying away and Measuring the, Heat. 



In order to carry away the heat generated a stream of 

 water, which enters at 1 (figs. 1 and 3), is made to flow 

 through a coiled copper pipe (fig. 3), where it absorbs heat, 

 and then leaves the calorimeter at 0. In order to increase its 

 absorbing capacity the pipe is soldered to a sheet of copper, 

 L L, both pipe and copper being painted black. Three such 

 sheets, each with 4 metres of pipe attached, are joined 

 together and placed side by side in the chamber A, the con- 

 densers being slipped in between them. The rate of absorption 

 of heat depends upon the difference of temperature between 

 the absorbers and the air surrounding them. If a large 



