PREFACE TO SECOND EDITION. 



The demand for this book having considerably 

 exceeded the expectations of its author, and the 

 comments on its utility having been so favorable 

 leads to the view that it fills a gap in microscopi- 

 cal literature. 



In preparing for a new edition an opportunity has 

 been given for enlarging on some of the subjects and 

 rewriting others, so as to make them conform to the 

 changes which the last five years have brought about 

 in the construction of apparatus. 



While it may be true that many of the subjects 

 might be treated much more extensively, the writer 

 has purposely refrained from doing so, because he 

 has considered it beyond the province of his inten- 

 tion and because books giving more extensive infor- 

 mation are available. 



An intending purchaser of a microscope finds it 

 more or less difficult to make a suitable selection, 

 and while it is always best to consult an exper- 

 ienced microscopist, the writer has endeavored to 

 convey information which, he hopes, will aid in 

 this direction. 



May, 1891. THE AUTHOR. 



