PKBPACE. IX 



mucli that might otherwise appear strange. Tlie Author has 

 thought it particularly needful to restrain himself, in treating of 

 certain very important subjects which are fully discussed in trea- 

 tisesi expressly devoted to them (such, for example, as the struc- 

 ture of Insects, and the Primary Tissues of Vertebrata), in order 

 that he might give more space to those on which no such sources 

 of information are readily accessible. For the same reason he 

 has omitted all reference to the applications of the Microscope 

 to Pathological inquiry; a subject which would interest only 

 cue division of his readers, and on which it would have been 

 impossible for him to compress, within a sufficiently narrow 

 compass, a really useful summary of what such readers can 

 readily learn elsewhere. So again, the application of the Micro- 

 scope to the detection of Adulterations in Food, &c., is a topic 

 of such a purely special character, and must be so entirely based 

 on detailed descriptions of the substances in question, that he 

 has thought it better to leave this also untouched. 



It has been the Author's object throughout, to guide the pos- 

 sessor of a Microscope to the intelligent study of any department 

 of Natural History, that his individual tastes may lead him to 

 follow out, and his particular circumstances may give him faci- 

 lities for pursuing. And he has particularly aimed to show, 

 under each head, how small is the amount of reliable knowledge 

 already acquired, compared with that which remains to be 

 attained by the zealous and persevering student. Being satis- 

 fied that there is a large quantity of valuable Microscope-power 

 at present running to waste in this country, — being applied in 

 such desultory observations as are of no service whatever to 

 science, and of very little to the mind of the observer, — he will 

 consider the labor he has bestowed upon the production of this 

 Manual as well repaid, if it should tend to direct this power to 

 more systematic labors, in those fertile fields which only await 

 the cultivator to bear abundant fruit. 



In all that concerns the working of the Microscope, the Author 

 has mainly drawn upon his own experience, which dates back 

 almost to the time when Achromatic Object-glasses were first 

 constructed in this country. He would be ungrateful, however, 

 if he were not to acknowledge that he has derived many valu- 

 able hints from the Practical Treatises of Mr. Quekett and Dr. 

 Beale, and from the Micrographic Dictionary of Messrs. Griffith 

 and Henfrey. And among the works by which he has been 



