PREFACE. 



The rapid increase which has recently taken place in the use of 

 the Microscope, — both as an instrument of scientific research, and 

 as a means of gratifying a laudable curiosity and of obtaining a 

 healthful recreation, — has naturally led to a demand for infor- 

 mation, both as to the mode of employing the Instrument and its 

 appurtenances, and as to the Objects for whose minute examination 

 St is most appropriate. This information the Author has endea- 

 voured to supply in the following Treatise ; in which he has aimed 

 to combine, within a moderate compass, that information in regard 

 to the use of his Instrument and its Appliances which is most 

 essential to the working Microscopist, with such an account of the 

 Objects best fitted for his study as may qualify him to comprehend 

 what he observes, and thus prepare him to benefit Science whilst 

 expanding and refreshing his own mind. The sale of three large 

 Editions of this Manual, notwithstanding the competition of 

 several cheaper and more popular treatises, with the numerous 

 unsought testimonies to its usefulness which the Author has 

 received from persons previously unknown to him, justify the 

 belief that it has not inadequately supplied an existing want ; and 

 in the preparation of the new Edition now called-for, therefore, 

 he has found no reason to deviate from his original plan, whilst 

 he has endeavoured to improve its execution as to every point 

 which seemed capable of amended treatment. 



In his account of the various forms of Microscopes and Acces- 

 sory Apparatus, the Author has not attempted to describe every 

 thing which is used in this country ; still less, to go into minute 

 details respecting the construction of foreign instruments. He is 

 satisfied that in nearly all which relates both to the mechanical and 



