Vlll PREFACE 



optimism and love for research with which this indefatigable in- 

 vestigator is ever surrounded that the author was originally led 

 to enter the field of applied microscopy when first a student. 



To Professor Louis Munroe Dennis, Head of the Department 

 of Chemistry of Cornell University, the writer is even more in- 

 debted in later years for his unflagging enthusiasm and confidence 

 in the possibilities of a neglected field. Without his encourage- 

 ment and support, the development of laboratories and equipment 

 would have been impossible and the preparation of this little book 

 impracticable. 



The author also wishes to express his indebtedness to Dr. 

 E. Mace of the University of Nancy, France, and to colleagues 

 in the Cornell University departments of chemistry, physics, 

 and mineralogy for valuable advice and suggestions. His thanks 

 are also due to his assistants Dr. C. M. Sherwood and Mr. H. I. 

 Cole for reading manuscript and testing methods. 



E. M. C. 



ITHACA, N. Y., June, 1914. 



