MICROSCOPE AND OPTICAL APPARATUS 1 3 



simple and greatly cheaper stands already men- 

 tioned. If the possessor of these but put 

 his heart into the work and make the best 

 use of his tools, he can depend upon results 

 which will compare favorably with any, no 

 matter what microscope they may have been 

 made with. 



A Bulls-eye condensing lens mounted on 

 stand, with universal movements, will be neces- 

 sary for the illumination of opaque objects, 

 and for throwing partially parallel rays upon 

 the substage condenser. The latter should 

 be achromatic and provided with either iris 

 diaphragms or a series of stops. The usual 

 form of chromatic Abbe condenser, supplied 

 with all of the microscopes I have named, is 

 not suitable for photo-micrography, if the 

 best work is expected; indeed, for critical 

 lighting and resolution it is utterly useless. 

 It can be made to answer fairly well with 

 medium powers, but I would strongly advise 

 that it be discarded altogether when purchas- 

 ing a stand, and an achromatic form procured 

 at the outset. A suitable lens for accurately 

 focusing an object upon the screen is necessary. 

 The most simple form is that known as a 

 three-legged microscope, a double-convex lens 

 mounted in a frame of that description, with 



