107 



On the comparative Merits of the new refracting, reflecting, 

 and single Microscopes ; with a Vindication of Microscopic 

 Science, and its Votaries. By C. R. Goring, M. D. 



[Communicated by the Author.] 



Refracting and reflecting microscopes do not stand in the 

 same relation to each other that telescopes of similar construc- 

 tion do, though it is true that the ratio of their natural illuminat- 

 ing power and light is not very different : the light of the Ami- 

 cian microscope is equivalent to that of the Newtonian tele- 

 scope, (if we do not reckon the quantity lost by the interposition 

 of the small diagonal metal, which from its larger proportional 

 diameter amounting to about one-third of the aperture of the 

 elliptic one, is much more considerable in the microscope than 

 in the telescope.) 



The light of the Newtonian construction is said to be in the 

 ratio of 5* to 8", or perhaps 7*, compared with that of an achro- 

 matic object-glass of the same aperture; but the small metal in 

 the microscope causes a greater loss, and perhaps reduces its 

 light to the ratio of only 5* to 8", or even 9^ compared with that 

 of a refractor of the same calibre. This difference would make 

 a very serious defalcation in the performance of a telescope^ 

 but it by no means operates in the same manner on a micro- 

 scope, for reasons I have frequently alluded to, viz., because we 

 can brighten a microscopic object artificially, and thus com- 

 pensate for almost any mere loss of light. Moreover it has 

 always appeared to me, nay I believe it may be positively 

 demonstrated, that a certain perfect angle of aperture is 

 exactly/ as penetrating and effectual in metal as in glass, exhi- 

 biting all the objects within its reach, even if no care is taken 

 to compensate the want of light by artificial illumination ; the 

 only difference seems to be, that the picture of the reflector 

 is much darker than that of the refractor, but equally developed 

 and evident. 



To this issue, therefore, I think the case between the two 

 kinds of microscopes may be committed. There are, however, 

 other circumstances which require discussion. The depth of 

 the curves of the small aplanatic lenses precludes the extension 

 of the aperture, of the best triple ones, beyond a certain 

 point ; whereas that of the metals may be carried a great deal 



