PREFACE. 



TREATISES on Electrolysis are fewer in France than in 

 England, in the United States, and in Germany. This is not 

 because the subject has been less studied in France than in 

 other countries, but because French authors have published 

 their works in the columns of scientific journals instead of 

 publishing them in book shape. 



Amongst the best known works, those of Sprague, Napier, 

 AYatt, Urquhart, Gore, and Wilson have passed through many 

 editions in England ; and those of Kafelowski, Scelhorft, Van 

 Kress, Julius Weiss, Japing, Hans Jahn, and Pfanhauser are 

 held in great estimation in Austria and Germany. Italy is 

 beginning to enrich herself with some remarkable works upon 

 the subject. 



In France, only two practical treatises on Electrolysis are 

 known which are of a real value : ' Guide du doreur, de 

 1'argenteur et du galvanoplaste ' (Guide for Gilding, Silvering, 

 and Electro-depositing), byKoseleur; and 'Elements d'electro- 

 chimie ' (Elements of Electro-chemistry), by Becquerel. 



These two treatises complete each other, but are antiquated, 

 having been written long before the recent progress made in 

 electric generators, so that French technological literature, 

 although so rich in theoretical and practical documents con- 

 cerning almost every other branch of industry, shows in the 

 speciality with which we are now dealing, a lamentable 

 deficiency. 



Our object in publishing this work is to make up for this 

 deficiency to the best of our ability. 



In order to facilitate the study of the subject, we have 

 divided the work into four sections. 



a 2 



