78 THE MICROSCOPE. 



In this way, I have been able to see points which I have 

 failed to bring out in any other way." J 



Magnifying power, as we have already explained, has to 

 do with size only, and only expresses the magnitude of the 

 angle subtended by the enlarged image, at the eye, as com- 

 pared with that subtended by the object itself under the 

 circumstances of ordinary standard vision; namely, at a 

 distance of ten inches from the eye. 



The Kelner eye-piece, while it increases the magnifica- 

 tion, detracts from the definition ; on this account, it is 

 only used when desirous to show the whole of an object 

 at once, as an insect, or in viewing the series of rings 

 formed by different crystals with polarized light. This 

 differs from the ordinary Huyghenian eye-piece in having 

 a double-convex field-glass, and an achromatic meniscus 



COMPOUND MICROSCOPES. 



It should be understood that the descriptions we are 

 about to give of Compound Microscopes cannot embrace 

 that of every manufacturer. Want of space forbids this, 

 and therefore we particularly wish to disclaim any inten- 

 tion of instituting invidious comparisons ; our desire is 

 solely that of giving, as concisely as possible, a description 

 of those instruments that have more immediately fallen 

 under our notice, or have been the companions of our 

 microscopical pursuits. At the head of our list stands 



Eoss's microscope, an instrument of which the aim is 

 not simplicity, but perfection not the production of the 

 best effect compatible with limited means, but the attain- 

 ment of everything that the microscope can accomplish, 

 without regard to cost or complexity. Without any un- 

 due preference, the first place may fairly be assigned to 

 this large Compound Microscope of Mr. Eoss, as the one 

 which was earliest brought (in all essential features, at 

 least) to its present form. The general plan of Mr. Eoss's 

 microscope will be seen to be essentially that which has 

 been adopted in a simpler form by many other makers ; 

 but it is carried out with the greatest attention to solidity 



(1) Beale, " How to Work with the Microscope." 



