PREFACE 



TO THE SECOND EDITION. 



THE rapid sale of the first edition of this work, both in 

 England and the United States, proves its adaptation to the 

 wants of the scientific community, and justifies the care and 

 extra expense with which this second edition has been prepared. 



Although the first edition was unusually large, it is not at 

 all probable that the demand has been exhausted. But a little 

 more than a year has elapsed since its appearance, yet sufficient 

 time has been afforded for the author to make a number of 

 important additions, which increase the value of the work to 

 the student of nature. 



The facts relating to microscopic science are not the result 

 of one man's labors, or of a single generation, but have been 

 gradually accumulating for many years ; yet at the present the 

 number of indefatigable observers is very considerable, and the 

 author is presumptuous enough to think that the preparation 

 of this manual has increased that number, by diminishing the 

 difficulty of the study, and pointing out the most judicious 

 methods of observation. 



