EXPLOSIVES 389 



been evidence of some degree of exaggeration in the reports 

 which have appeared in the press concerning the advantages of 

 soil explosions. 



There can be no doubt that the aeration of the soil, the breaking 

 up of the subsoil, especially when hard, the destruction of vermin, 

 and the saving of labour are advantages generally recognised. 

 The two questions in respect to soil improvement by explosion 

 which must be considered are first whether it is effectual in all 

 cases, and secondly does it pay ? There seem on both these 

 points to be as yet a lack of unanimity, which perhaps is due to 

 want of experience, as the method is so new. The experiments 

 on limes, bananas, and other crops in the West Indian Islands 

 as reported in the Agricultural News published by the Imperial 

 Department of Agriculture, Barbados (March 11, 1916), show 

 that much further experience is necessary before a definite 

 conclusion can be reached, as it appears that in these islands and 

 for the crops referred to the results obtained have not been 

 encouraging. 



The phenomena of combustion and explosion in gases have an 

 interest both for the scientific man and for the coal miner, ex- 

 posed as he is in the majority of pits to imminent risk in his 

 daily work. 



During the last forty years great advances have been made 

 in the theory of gaseous explosion, and in a knowledge of the 

 rate of transmission of an explosion wave. The first steps in 

 this direction were taken by the famous French chemist, M. 

 Berthelot. At the time of the siege of Paris in 1870, Berthelot, 

 then Professor in the College de France, became President of 

 the Scientific Committee of National Defence. The superinten- 

 dence of the manufacture of explosives to be used against the 

 enemy naturally led him, after the war, to turn his attention to 

 the systematic investigation of the phenomena of explosions. 

 In the result he was able to connect the maximum velocity of 

 the flame in a mixture of gases with the mean velocity of the 

 molecules, according to the kinetic theory of gases. A long 

 series of researches on the propagation of flame through mixtures 

 of gases and on cognate subjects was begun by Messieurs Mallard 

 and Le Chatelier in 1879, and the work of these distinguished 

 French investigators is still frequently referred to. 



Another very important discovery was made in 1880 by Mr. 

 Harold B. Dixon, a few years later Professor of Chemistry in the 



