( 39 ) 
COEEESPONDENCE. 
Optical Curiosities of Literature. 
To the Editor of the * Monthly Microscopical Journal 
Boston, May 24, 1872. 
Mr. Editor, — In your May issue the Kev. S. Leslie Brakey, A.M., 
takes notice of the reply that I gave to the question of B. in the 
November, 1871, number, in regard to the angular aperture of the 
famous -^th Tolies’ objective belonging to the United States. The 
notice requires a rejoinder from me, if I will not submit to the impu- 
tation of a want of instruction, or in another word ignorance. 
The notice reads, “ In three of the cases the figures are no doubt 
correct ; in the remaining one — the object immersed, uncovered— 
prompted by Mr. Tolies, he reports the aperture as 140° ! ! ! Colonel 
Woodward .... also answers for the four cases, but better in- 
structed than his countrymen on coming to the critical case, he leaves 
out the figures.” There are several things involved in the above pas- 
sages to which I ask the attention of yourself and of your readers. 
First, he asserts what it was impossible for him to know, if it had been 
true, and which he had no reason or right to assert, that I was 
“ prompted ” by Mr. Tolies. In fact, the figures were taken from the 
record of the sale, July 19th, 1871, and were made from the original 
memorandum (now before me) of the maker, June 27th, and corre- 
spond with those of Colonel Woodward’s measurement communicated 
to me in July. The three exclamation marks are original interpola- 
tions of Mr. Brakey, I surmise, intended to signify his “ surprise.” 
We will examine further on the equity of that surprise. Mr. Brakey 
does not assign any reason for doubting the angle, he leaves that to be 
guessed at. Now I will assure him again that the angular aperture 
of the lens at uncovered immersion is 140°, and 175° at maximum. 
And what will “surprise” him again, perhaps, is that Colonel Wood- 
ward’s own answer, to which Mr Brakey pays a compliment, says 
precisely the same thing. Colonel Woodward’s words are,* “ on 
coming to the critical case ” “ Its angle is then 140°. Without 
further change of adjustment a drop of water may be introduced, and 
it is fitted for the study of uncovered objects wet.” This is exactly 
what the reverend gentleman says Colonel Woodward left out, and 
precisely what I gave, taken from the original record of the maker, 
not prompted by Mr. Tolies after November. Does Mr. Brakey 
know that immersion objectives can be used on objects mounted 
dry as well as on those in balsam ? 
These quotations show the animus that prompted the gentleman’s 
paper : but there is more yet. The original question of B., now 
acknowledged to be Mr. Brakey,! reads thus : — “ It would not sur- 
prise me to hear that Mr. Tolies’ fifth has an aperture of 150° or 
160°.” In November he would not be “ surprised” by an aperture of 
160°. In April he is astonished to the extent of three exclamation 
* ‘M. M. J.,’ January, 1872, p. 28. j ‘M. M. J.,’ Nov. 1871, p. 241, 
