PREFACE. V 



But of all these recent advances the germs may be found in 

 M. Berthelot's work, not necessarily in all cases originated by 

 him, but more or less worked out, examined, and compared, 

 and having, so to speak, the soil prepared for their subsequent 

 growth. As previously stated, a certain amount of omission 

 and condensation has been exercised, for the original volumes 

 consist rather of a series of essays than one connected work, 

 and this condensation became, to avoid repetition, not only 

 advisable, but necessary. Several portions, consisting of matter 

 of merely historical interest, such as the history and origin of 

 explosives, and the history of methods of extraction of saltpetre 

 in France, have been omitted. 



M. Berthelot adheres to the older chemical notation; this 

 has been replaced by that more recently introduced and now 

 most commonly in use. 



It should be added that this book has been produced with 

 the full consent of M. Berthelot, who has also suggested what 

 Mr. Macnab has carried out, viz. the addition of abstracts of 

 some of M. Berthelot's essays published since the appearance 

 of the main work, and principally relating to the propagation 

 of detonation in explosive gaseous mixtures, with further 

 studies on the " explosive wave " in solid and liquid bodies. 



J. P. C. 



