Ratio of the Specific Heats for Air and Steam, 

 Table I. 



231 



Resistance 



Resistance 



Kick of 



galvr. in 



micrometer 



divisions. 



Change of 



(R) 

 before open- 



(R) 

 after open- 



Resistance 



ing vessel. 



ing vessel. 



K. 





651-00 



64054 



no kick 



10-46 



651-19 



640-84 



3 



10-35 



651-27 



64104 



5 



1023 



651-38 



641-24 



10 



1014 



651-61 



641-44 



10 



10-17 



65162 



651-34 



5 



10-28 



651-82 



641-49 



4 



10-33 



651-97 



641-54 



2 



10-43 



Barometric pressure = 767*G mm. mercury at 0° C. 

 = 1044 cms. o£ water at 0° C. 



Excess pressure = 67*l cms. oil at 18° C. = 58*3 cms. water. 

 The coefficient of the platinum wire used in the thermometer 

 was '003835 and its resistance at 0° C. was 610*58. Hence 



2*34 units of resistance correspond 

 shift of 10*47 units corresponds to 

 of 4°*48pt. = 4 c *43 C. 



1102*3 

 1044 



to 1° pt. ; therefor 



e a 

 i change of temperature 



log 



7 = 



, 1102*3 

 lo -T044 



, 289*83 



Jqo- 



° 285*4 



= 1-396. 



For this experiment t = *76 second. 



6. Corrections and Results. 



To the value of 7 found above there are two corrections to 

 he applied : — 



(1) The air in the immediate neighbourhood of the ther- 

 mometer has risen in temperature by conduction and con- 

 vection during the time (t) which elapses between opening 

 the stopper b and closing the battery circuit. 



(2) The final temperature as indicated by the thermometer 

 will be higher than the temperature of the air surrounding ir 

 on account of direct radiation from the walls of the vessel. 



(1) In order to find how much the air had heated up before 

 the battery-circuit was closed by the automatic key. a number 

 of observations were taken similar to those given above, but 

 with different values of t. A series of values of 7 was thus 

 obtained for different values of r, from which it was possible 

 to deduce the value 7 which would have been obtained had 



