234 MR. W. F. G. SWANN ON THE SPECIFIC HEATS OF AIR AND 



pressures in the reservoir ; the value for each case was, however, easily deduced from 

 REGNAULT'S observations. The expression for Q in terms of H and P was found 

 to be 



Q = 0-0071081{l + 0'0089(P-78)} 



the equation applying when the temperature of the tubes was 167 C. 



(26) ABRIDGED Table for the Calibration of the Fine Tubes for CO 2 . 



As in the case of the experiments on air, the percentage decrease in the flow per 

 degree increase in t was measured. It was found to amount to 0'299 per cent, for 

 H = 26-82, and 0'518 per cent, for H = 8'984. 



(27) The Calorimetric Experiments. The method of performing the experiments 

 was similar to that employed in the case of air ; only the leads Qp were, however, 

 used for carrying the current. The values of the " quantity (a) involved in the 

 correction for the heating effect of the leads were assumed to be the same as those for 

 air, both in the cases of the large and small flows, this assumption being justified by 

 the fact that the temperature conditions were the same, and the quantities of energy 

 supplied per second in the corresponding flows for air and C0 2 were practically 

 the same. 



In view of the large variation of the specific heat of CO 2 with temperature, the 

 correction to be applied when the two runs from which a value of the specific heat 

 was deduced were performed at slightly different temperatures was more important 



