DESCRIPTION OF THE ACHROMATIC MICROSCOPE. 113 



beautiful effects visible to the natural sight, requires both 

 the talent of an artist and the experience of a workman. 

 Enlist, however, hut the microscope into this interesting 

 service, and the result will be that you will be supplied 

 at once, without a shade of difficulty, with an almost 

 endless variety of natural forms clothed in the most bril- 

 liant tints, and that too by the ordinary crystallization of 

 common salts. Thus, the application of a polarizing 

 apparatus to a microscope must be considered as being 

 highly desirable. 



In a small pamphlet, entitled " A List of 2000 Micro- 

 scopic Objects," I have given a brief description of a 

 polarizer of my own contrivance, suggested to me 

 through being informed that Mr. FoxTalbot had applied 

 one to a compound microscope. To this gentleman is 

 due the merit of having first brought this arrangement 

 before the public ; as also the application to the engi- 

 scope of that beautiful invention of Mr. Nicol the 

 single-image calc prism. It appears, however, that 

 Sir D. Brewster had for years attached tourmalines to 

 single magnifiers for the purpose of making experiments 

 on polarization by crystals. He did this by cement- 

 ing the tourmaline to a plano-convex lens, and then illu- 

 minating the object by polarized light reflected from a 

 glass or japanned surface*. Professor Amici, also, has 

 introduced the ordinary rhombs of Iceland spar into the 

 compound microscope for a similar purpose. He has, 



* Vide treatise on Microscopes, Encyclopaedia Britannica, p. 95. t 

 I 



