PREFACE TO THE TENTH EDITION 



WITH the general progress of Science, the Microscope and its Accessor- 

 ies have not only kept pace, but have added their full share to the 

 momentum of that progress. With the increased usefulness and 

 consequent use of the microscope it has steadily advanced in excellence and 

 efficiency ; and the means of applying it to the solution of the problems con- 

 fronting the workers in various fields are becoming more simple and exact 

 every year. 



In rewriting this book the aim has been to represent the microscope of the 

 present day, and to serve as a helpful introduction to the microscopic world. 

 Constant reference has been made to original sources in books and periodicals 

 so that the investigator, the teacher and the ambitious student might find 

 fuller treatment of any subject in which he is especially interested. 



Grateful acknowledgement is made to the opticians, and the manufacturers 

 of laboratory supplies for the loan of cuts, and for courteous and complete 

 answers to numerous questions ; to the directors of laboratories for helpful 

 suggestions; to my colleagues in Cornell University and to my pupils; to 

 Henry Phelps Gage for help in optics, micro-chemistry and photography ; to 

 Susannna Phelps Gage for a critical revision of the whole work, for proof 

 reading and the preparation of the index. And finally to Professor Burt 

 Green Wilder who encouraged me when a student to undertake work with the 

 microscope, and gave me every facility in his power, I wish to express special 

 feelings of gratitude. 



SIMON HENRY GAGE, 



CORNELL UNIVERSITY, 

 October i, 1908 ITHACA, N. Y., U. S. A. 



