along a Pipe through which Gas is Flowing. Ill 



was continued into a copper tube 0*8 mm. in diameter, which 

 passed through the wall of the heating bath and into a vessel 

 o£ cold water which corresponded to the calorimeter of 

 Regnault's experiment. The length of the pipe from heater 

 to calorimeter was 10 cm., and the portion near the heater was 

 surrounded by cork. The object of the experiment was to 



measure — •( k— J , the temperature gradient in the pipe in the 

 vicinity of the heater when gas flowed, and the gradient 

 £— ) when no gas flowed through the pipe. Apart from 

 certain minor considerations which will be referred to later, 

 (a~) K^t) re P resen ^ s the fraction of the measured heat 



conduction which should be taken if the apparatus were used 

 for a specific heat determination with the corresponding rate 

 of flow, and the heat conduction were measured in the manner 

 adopted by Regnault. 



If two german-silver wires are soldered to the copper tube 

 near the heater, and connected to a galvanometer, we have a 

 complete thermoelectric circuit, the german-silver being one 

 element and the copper tube itself the other. The ratio of 

 the deflexion £ : when gas flows to the deflexion 8 2 when no 

 gas flows, gives the ratio of the temperature gradients referred 

 to above. As a matter of fact, seven german-silver wires 

 were soldered at different points extending to the end of the 

 cork, i. e., about half-way along the tube, and the deflexion 

 corresponding to each adjacent pair was measured under the 

 two conditions. The results were found not to vary very 

 much with the rate of the flow, when that rate exceeded a 

 certain minimum. The following results represent the mean 

 for two experiments which agreed very well with each othei\ 

 and corresponded to a rate of flow of about 0*5 litre per 

 second. The numbers in the top line represent the various 

 pairs of german-silver wires (counting from the heater) 

 between which the temperatures were measured. 



1,2 



2,3 



3,4 



4,5 



5,6 



6,7 



Values of d Q ... 



54-1 



41-7 



415 



18-7 



40-2 



33-2 



36-7 



Values of d l ... 



33o 



21-0 



230 



17-5 



22-2 



Values of d x /d 2 . 



0621 



0503 



0-450 



0-572 



0-527 



0-605 



