PREFACE. Vll 



striven to attain. If I have not always been successful in 

 doing so if here and there I may have underestimated the 

 merits of some and unduly asserted those of others- this has 

 been unintentional. If I have been severe in my judgment, I 

 have at least been free from any personal feeling, and it has 

 always been the matter alone that I have attacked. Should I have 

 approached in some cases too closely to the limits of historical 

 accuracy, or should I not have succeeded in representing fairly 

 the claims of every one, I am fully prepared to rectify my error 

 as soon as I am convinced of it. 



If my colleagues are interested in the subject, and assist 

 me with their knowledge and advice, it may soon be possible, 

 perhaps, to obtain an objective picture of the chemical theories 

 of the last hundred years. I desire that this book may be 

 regarded as an attempt in that direction, and that it may be 



judged indulgently. 



A. LADENBURG. 



KIEL, December 1886. 



