AUTHOR'S PREFACE. 



Notwithstanding the magnitude which the manufacture of 

 Chemical Manures has assumed m France, no author has 

 hitherto attempted to make it the subject of a special treatise 

 in the French language. The author has endeavoured to 

 fill this gap in spite of the difficulties inherent to the subject. 

 From a technical point of view% French hterature supphes 

 but little material for such a purpose. French chemists and 

 works managers rarely write. They are tied down by pro- 

 fessional secrecy, and when they do risk writing their prose is 

 comphcated by an embarrassed reticence which deprives it of 

 all practical interest. Foreign publications, German especially, 

 are better equipped in this respect. In addition to numerous 

 special treatises, annual reports on the progress of different 

 industries are available, edited most often by retired practical 

 . men or bv old works managers, knowing everything, calhng 

 things by" their names, discussing the value of the new pro- 

 cesses recommended or apphed, pointing out their merits and 



defects. • u i. u 



The numerous and valuable data which the author has 

 thus collected have largely recompensed him for the ill-will 

 which he encountered elsewhere. Certain constructors, it is 

 true that they are not precisely at the head of mechanical 

 progress, made a wry face. Others omitted to reply to our 

 letters. This explains why French engineering firms are but 

 little represented in this treatise. This explanation is due to 

 the reader : it is for him to draw^ the moral. 



The author, however, hastens to add that he met with 

 the best reception from specialists eminent by their know^- 

 ledge and long experience, and obtained from them the most 

 complete information. He here returns them his smcere 

 thanks, as well as to the scientists who have aided him by 

 their counsel and encouragement. 



The author makes no pretension of presenting a pertect 

 treatise, yet he is confident that it will be useful to every one 

 in any way connected with chemical manures. 



Paris, March, 1909. 



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