THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. XI. OCTOBER, 1890. No. 10. 



All coinmunicatiotis for this Jou7-nal, whether relating to business or to editorial 

 ^natters, and all books, pamphlets, exchanges, etc., should be addressed to Ameri- 

 can Monthly Microscopical Journal, lVashi7igton, D. C. 



Europea7i subscriptions may be sent directly to the above address accompanied 

 by International Postal Order for $1.13 per annum, or they 7nay be sent to iMessrs. 

 Triibner &^ Co., jy Lttdgate Hill, London, or to Mr. IV. P. Collins, 13 j Great 

 Portland street, London, accompanied by the yearly price of fizie shillings. 



Microscopy for Amateurs. 



By t. charters white, 



QUEKETT CLUB. 



The Microscope Described. — ^Microscopes may be divided into 

 two classes — simple and compound. The simple microscope may be 

 exemplified by the ordinary hand magnifier, generally consisting of one 

 lens, or a set of three, which may be used singly or in conjunction. A 

 simple microscope of this class is useful, and should be the pocket com- 

 panion of every microscopist ; not onlv will it be found of value in the 

 examination of any object which mav casually offer its attractions in his 

 walks in the country, but it will also aid in his recognition of infusorial 

 forms in his pond explorations ; it will furnish a most valuable adjunct 

 in mounting objects as well as in insect dissection. But for more ex- 

 tended observation, recourse must be had to the second class — the com- 

 pound microscope. The essential parts of this may require a word of 

 explanation. Firstly, the objective, or as it is sometimes called, the 

 object glass, is the lens or series of lenses placed at the end of the mi- 

 croscope tube next to the object to be examined. It is generally com- 

 pounded of several lenses of varying curvature, and different refractive 

 powers, ceinented together and securely adjusted in a brass mount. 

 When successfully mounted, they should give clear definition, a flat 

 field, and entire freedom from color ; all of which characters ma}' be 

 found in the achromatic objectives sold by good makers. Objectives 

 are of different focal lengths, ranging from four inches from the object 

 examined to one-fiftieth of an inch. The lenses sold with the student's 

 microscope are usually one inch focus, magnifying fifty diameters, and 

 a quarter of an inch giving 250 diameters. These have been most judi- 

 ciously selected for the beginner as giving amplifications which will be 

 found sufficient for all ordinary work he may be likely to attempt at 



Copyright, 1890, by C. W. Smiley. 



