6 Dixon, huxugiiral Address. * 



of the mode in which carbon compounds burn at high 

 temperature has, I think, been justified. But who has 

 not had to suffer that great tragedy of Science, as Huxley- 

 calls it, the slaying of a beautiful hypothesis by an ugly 

 fact? In this case the increase of the specific heats of 

 gases at high temperature is an ugly fact. I assumed it 

 to be constant : my own experiments have convinced me 

 that it is not. My formula, therefore, though parallel to 

 the truth, is obviously not truth itself ! 



Again, I pointed out that the formula did not account 

 for the curious fact that an increase in the initial 

 temperature of the gases was accompanied by a diminu- 

 tion in the rate of the explosion. M. Jouguet's formula, 

 founded on Hugoniot's equation, does account for this 

 diminution. M. Jouguet argues that the heated products 

 of combustion follow the wave front with great velocity, 

 and I have abundant photographic evidence that this is 

 the case : he states that the explosion-wave travels with 

 the velocity of sound through this rapidly moving gas, 

 and therefore has an absolute velocity (relatively to the 

 unburnt gas) of both motions added together. The 

 important question remains, can we calculate backwards 

 by Jouguet's equations from the easily-measured rates of 

 explosion to the unknown specific heats ? M. Crussard * 

 claims that this is an important new application. Apart 

 from the consideration that Hugoniot's theory has 

 not been experimentally established, I must point out 

 that if we calculate backwards from the rates of explosion 

 we get different values for the specific heats according as 

 the condensation in the wave is assumed to be more or 

 less. These values, however, lie between certain limits, 

 and the method therefore promises to be useful. 1 must 



* L. Crussard, " Ondes de choc et onde explosive." Bull. Soc. de 

 f Industrie Miniralc, Salni-Elleiine, 1907. 



