PREFACE 



AMEEICAN EDITION 



IN presenting this book to the American scientific 

 public, I need only, as an excuse, refer to the success 

 which it has met in Germany, as indicated by the 

 appearance of eight editions in rapid sequence. 



The grounds of its success may, in part, be looked 

 for in the fact that it is adapted as well to the use of 

 beginners as to that of those advanced in the science. 



o 



The beginner will find a simple principle of classifica 

 tion, carefully carried out, eminently fitted to his first 

 object of obtaining a general view of the subject; the 

 advanced will find it exceedingly rich in statements of 

 facts with which he has constantly to deal. 



The year that has elapsed since the appearance of 

 the last German edition, with its quota of investiga 

 tions in this branch of science, has caused the neces 

 sity of a revision in order that the work might be 

 equal to its avowed object. The additions and correc 

 tions have been made as nearly as possible in the spirit 

 of the original, with the view merely of rendering 

 the book a representative of the science at the date of 

 publication. 



An introductory chapter on the &quot;Constitution ot 

 Chemical Compounds&quot; has been prefixed in order to 



