114 CORRESPONDENCE. One ae ano 
that Mr. Tolles produces the very best lenses in the world. I am not 
willing toyield to either of these gentlemen in the disinterestedness of 
my desire for the success of American opticians, but am of the opinion 
that our progress will be hindered rather than helped if we shut our 
eyes to the few cases in which English or other manufacturers excel 
ours. In fact, where this is the case a recognition of the reality 
appears to me necessary to our progress. 
Mr. Stodder’s complaint that his paper in the ‘American Natu- 
ralist’ has been ignored, certainly cannot apply to me. In my first 
essay on the Nobert’s plate,* I quoted from it, and gave the reasons 
why I thought Messrs. Stodder and Greenleaf had been misled by 
spurious lines. At that time I had not been able to resolve any band 
beyond the 15th, and I did not succeed with the 19th until I obtained 
the immersion ;!,th of Powell and Lealand in the spring of 1869. So 
that if Messrs. Stodder and Greenleaf’s original claims were really 
well founded, they certainly ante-dated mine. Nevertheless, I still 
think they were at that time mistaken, and do not now believe that the 
joth, with which they at present claim to have resolved the lines, has 
really succeeded in doing so. I will endeavour to state very briefly 
my reasons for this opinion. 
In my judgment it cannot be said that one of the bands of the 
Nobert’s plate is resolved unless the lines are shown in such a manner 
that they can be correctly counted from one edge of the band to the 
other. Objectives of inadequate defining power can easily be made 
to show lines in the higher bands which would deceive even an expe- 
rienced eye, and the lower the power the more readily the observer 
will be misled; but if such spurious lines are counted, they will be 
found too few in number, and their nature is thus shown. Now, not 
only did Mr. Stodder in his original paper admit that he had not 
counted the lines, but he fell into a grave error on the subject of 
counting fine lines, which he expressed in the following words :—“ In 
counting lines of such exquisite fineness either the micrometer or the 
stage must be moved, and it is next to impossible to construct apparatus 
that can be moved at once the ;gp/ggpth part of an inch and no more.” 
In consequence of this error, Mr. Stodder had omitted the only reli- 
able mode of demonstrating that he had not been misled. My paper 
led to some correspondence between him and myself, in the course of 
which I endeavoured to borrow the lens in question for the purpose 
of testing it. I then learned that it had been unfortunately broken. 
Other iths and ths, made by Mr. Tolles, which from time to time I 
had an opportunity of testing, did not in my opinion justify the claims 
made. In the latter part of May, 1869, I received for inspection the 
so-called j1,th, with which Mr. Stodder now claims that he has resolved 
the 19th band. I was, however, unable to push it beyond the 16th. 
Mr. Stodder had requested me to send it, in case I did not succeed 
with it, to Mr. W. 8. Sullivant, of Columbus, Ohio, a gentleman whose 
reputation for skill as a microscopical manipulator stands deservedly 
high in this country. Mr. Sullivant wrote me, July 11, 1869 :—* The 
Tolles’ immersion ,1,th I returned to Mr. Stodder, who wrote me about 
* “Quarterly Journal of Microscopical Science’ for October, 1868, p. 225. 
