PEEFACE. 



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 recrea- 

 tion, has naturally led to a demand for information, both as to the mode 

 of employing the Instrument and its appurtenances, and as to the Objects 

 for whose minute examination it is most appropriate. This information 

 the Author has endeavored 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 essen- 

 tial to the working Microscopist, with such an account of the Objects 

 best fitted for his study as may qualify him to comprehend what he ob- 

 serves, and thus prepare him to benefit Science whilst expanding and 

 refreshing his own mind. The sale of five large Editions of this Manual, 

 with the many spontaneous 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 prepa- 

 ration of the new Edition now called -for, therefore, he has found no rea- 

 son to deviate from his original plan, whilst he has endeavored to improve 

 its execution as to every point which seemed capable of amended treat- 

 ment. 



In his account of the various forms of Microscopes and Accessory 

 Apparatus., the Author has not attempted to describe everything 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 the optical arrangements of their 

 instruments, the chief English Microscope-makers are quite on a level 

 with, if not in advance of, their Continental rivals; but, on the other 

 hand, the latter have supplied instruments which are adequate to all the 

 ordinary purposes of scientific research, at a lower price than such could 

 until recently be obtained in this country. Several British makers, how- 

 ever, are now devoting themselves to the production of Microscopes which 

 shall be really good though cheap; and the Author cannot but view with 

 great satisfaction the extension of the manufacture in this direction. In 

 the selection of Instruments for description which it was necessary for 

 Mm to make, he trusts that he will be found to have done adequate jus- 



