M. E. Wiedemann on the Specific Heats of Gases. 87 



temperature of the gas as it entered the balloon. The time 

 allowed to elapse between the filling of Q and the carrying- 

 out of the experiment never exceeded half an hour ; in this 

 short time the temperature of the surroundings and of the 

 gas itself altered but slightly : the thermometer F indicated 

 very nearly the true temperature of the gas in the balloon as 

 that gas for the second time passed over its surface. 



When a new gas was to be examined, the balloon Q, having 

 been emptied, was only partially filled with this gas and again 

 emptied before being finally filled ; in this way the last traces 

 of the gas originally in the balloon were removed. 



In filling Q the gas was allowed to stream through until 

 the walls of the balloon were stiffly distended. On account 

 of their weight the walls of the balloon then pressed upon the 

 contained gas with a force equal to 1 centim. of water, as 

 determined by the manometer k. 



The stopcock V being closed the calorimeter was connected 

 in its place. B and C were connected and the pinchcock E 

 was removed ; b and c in the balloon B were then connected, 

 D w T as removed, and water was allowed to flow from A until 

 the manometers k and e showed the pressure at which the gas 

 was to be allowed to issue from Q. 



S having been then closed, D and E replaced, and A and 

 B and B and C disconnected, the balloon was weighed in the 

 balance W. A, B, and were then once more connected, D 

 and E were again removed, and T was opened ; S and V 

 remained meanwhile closed. 



The temperature of the calorimeter was noticed as the ap- 

 paratus was placed in position. The telescope, through which 

 the temperature of the calorimeter was read off, was so placed 

 that one could look through it and at the same time open the 

 stopcocks V and S wdth the hand. 



The position of the thermometer in the calorimeter was read 

 off from minute to minute. Five or ten minutes after the 

 beginning of the experiment V and S were opened at the 

 same moment (marked by means of a second stop-watch), and 

 the gas was allowed to flow through the heating -vessel and 

 calorimeter. By carefully regulating the stopcock S the 

 manometers k and e could be readily maintained constant ; 

 the gas in Q was therefore maintained at the same pressure 

 throughout the experiment, and consequently flowed through 

 the calorimeter at a constant rate. The temperature of the 

 calorimeter was determined each minute as the gas passed 

 through it. So soon as the rise of temperature had attained 

 to a certain amount (between 5° and 12°), the flows of gas 

 and of water into B were simultaneouslv checked by suddenlv 



