8 Dixon, Inaugural Address. 



became difficult at 400° and the margin of safety was 

 small. On the other hand the velocity of sound in CO2 

 can be measured in a heated tube and compared with 

 that in air or nitrogen under the same conditions; by 

 this method I have found the rise in specific heat of CO. 

 up to 400° on the assumption that air has a constant 

 value. This experiment gives the specific heat at 4oo°C., 

 and not, as in the cooling method, the mean specific heat 

 between 20° and 400X, Quite recently Holborn, at 

 Charlottenburg, has succeeded in pushing Regnault's 

 calorimeter method to high temperatures. I am glad to 

 find that our curves for CO., run, as far as they go, nearly 

 parallel with one another : — 



Specific Heats of CO., at constant pressure. 



At 0°. 100°. 200°. 300°. 400°. 600°. 800°. 



Holborn.. "203 ... '216 ... "228 ... ... "250 ... "268 ... "281 



Dixon ... 'igd ... -208 ... "220 ... "232 ... "244 ... ... 



The rise in the specific heat from 0° to 100" agrees 

 with the experiments of VVullner ; it is much less than 

 that found in the old determinations of Regnault and of 

 Wiedemann. The new values would "join up" fairly 

 with the high temperature values deduced by Le Chatelier 

 from the explosion pressures. Holborn, also, this sum- 

 mer has determined the specific heat of steam, and shown 

 that it rises regularly. Dugald Clerk, too, by an entirely 

 different method, has shown the rise in the specific heats 

 of gases in the gas-engine cylinder. 



There is, therefore, a satisfactory consensus of opinion 

 as to the fact of the increase in the specific heats of the 

 triatomic gases ; the rate of the rise has still to be deter- 

 mined with precision. 



Another point connected with gases that has recently 

 occupied attention is the temperature of their ignition 

 points. The methods that have been used, mainly on the 



