On Mia^oscopes and Microscopy. 57 



Mr 



attainments in this department have of late been so often dis- 

 cussed in print, that It is unnecessary for me to mention who he 

 is and what he has been doing. The capabilities of his lenses 

 are well known to our first microscopists, and the occasional arti- 

 cles of Prof. Bailey within the past two years, have shown the 

 opinion of one of our first authorities on this subject. But, with 

 all this, I do not recollect to have seen the result of a comparative 

 trial between Spencer's and the best foreign glasses.* It is to this 

 point that I wish to ask your attention. *" 



Last summer I had the, good fortune to obtain from him a set 

 of lenses, which he acknowledged, he would be pleased to have 

 brought into competition with those of Europe. I considered 

 this particularly fortunate, not only on my own account, but 

 because I was then just ready to leave for Europe and should 

 shortly enjoy the opportunity of comparing them, as he desired. 



The best foreign instruments seldom reach this country. The 

 makers have always friends at hand who immediately seize upon 

 whatever may be wrought in an eminently superior manner. I 

 therefore thought that if I could reach and address the makers 

 themselves, it Avould ensure a fair trial to all. 



I regret that I was not long enough in London, or sufficiently 

 favorably situated, to take advantage of the many kind induce- 

 ments offered me to have a comparison there. 



In Paris, however, many circumstances tended to hasten a 

 trial, and particularly the presence there at that time of some 

 of the latest, and reputedly the best English lenses. Moreover 

 there were there many amateur microscopists. 



The lenses on trial were as follows: those of Mr. Ross, of 

 Messrs. Powell and Lealand, of Messrs. Smith and Beck, of Lon- 

 don; those of M. Nachet of Paris; and those of Mr. Spencer of 

 America. I regretted that none of the lenses of M. Oberhauser 



I mean his best — could be obtained at that time. 



To secure perfect fairness, the lenses were all adapted to one 

 mounting (a small one of Amici's pattern), and M. Nachet kindly 

 superintended its correct adjustment. 



The tests used were the most difficult that could be obtained, 

 and that are now known — Noherfs lines, the Gran 



Ni 



t 



and having markings more difficult to resolve than any other shell 

 as yet discovered, if we perhaps except a Grammatophora, lately 

 lound at Providence, R. I. Now it is well known that the mark- 

 ings on the most difficult of orsanic test-objects can be made 



out by oblique light only, this obliquity was obtained to almost 



* The notice o 

 ^"18 Journal, had 



» 



.It 



I 



1 



the trials at Paris, given by Dr. J. L. Smith in toL xi, p, 277 of \ 



not been seen by the author when this Was writtei^j-Ei>s. 



S£Ei£s, Vol XI^ No- 34.— July, 185L "* 8 '*' 



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4 •" ¥ 



