TRANSLATOR'S NOTE 



I BEG to offer my sincere thanks to Dr. Aders-Plimmer 

 for his kind help in the translation of the chemical 

 section of this volume : and to Mr. W. L. Symes for 

 assistance in many other technical difficulties. 



FKANCES A. WELBY. 



LONDON, October 1910. 



vii 



