PREFACE. Vll 



pursued, and many of the results arrived at in my 

 laboratory during many years of patient inquiry. In 

 the compilation of the Analytical Guide I have received 

 much valuable help from my esteemed assistants, Mr. 

 F. J. M. Page, and Mr. C. G. Stewart, for which I 

 here express to them my sincere thanks. 



THE AUTHOR. 



3, PEMBROKE ROAD, KENSINGTON, W. ; 

 April, 1872. 



