CORRESPONDENCE. 
245 
admiration, that he ought to have known this was absurd and impos- 
sible. Bringing these two together, Mr. S. announces his discovery of 
a fatal contradiction. — “ In November he would not be surprised by 
an aperture of 160° ; in April he is astonished by an aperture of 
140°.” Upon this he proceeds to comment with severe irony that I 
must have made progress in the study of Coptics, and then dismisses 
my contribution as a “ ridiculous lucubration.” 
Now the thing — the one thing — asserted in this controversy from 
the beginning is this, that an aperture, whatever it may be when the 
object is in air, is abruptly changed when the object is immersed : so 
that the angle of a glass, the same glass, is totally different when used 
in one way from its angle when used in another way. Entirely 
unconscious that this is itself the “ thesis,” Mr. Stodder writes to 
announce his discovery, — that he has detected a contradiction. He is 
ready at a moment’s notice to decide the controversy ; — that he does 
not know, and has never asked, what it is about, does not seem to have 
given him the smallest concern. 
This is Mr. Stodder’s contribution to the discussion. It is his own 
contribution, written without prompting ; as from another passage we 
learn incidentally that Mr. Tolies was absent, and had no share in it. 
I have thought it worth while calling attention to this episode, 
because it is instructive beyond the immediate question concerned. 
Mr. S. has the pen of a very ready writer. His name is familiar to 
the readers of many journals in many lands. From his many appear- 
ances he has come to be looked on by casual readers, latterly also by 
himself, as an authority on the more recondite questions of optical 
science ; and has performed the difficult feat of building up a reputa- 
tion for profound learning on a knowledge derived from the perusal 
of printed catalogues. His creed is, that on every disputed point Mr. 
Tolies is right, and the other side wrong : a fidelity the more to be 
admired when we find him ready to prove his position not only with- 
out being able to understand the question, but without even knowing 
what it is. 
As I observe from your editorial notice that Mr. Wenham declines 
any further controversy with Mr. Tolies, I add a few observations on 
his lately-published table, the last probably I shall have occasion to 
make in connection with it. This table Mr. Tolies offers as “ proof 
enough ” of the position he has maintained. Now assuming for a 
moment the accuracy of his figures, of what are they a proof ? The 
position which he undertook, which he attempted by diagrams to 
prove, and which now in this his latest paper he reasserts in express 
words, is this, that by an immersion lens the whole angular pencil can 
he transmitted . In proof of this we are offered measurements of nine 
glasses ; and how much do they give ? They differ a little, but taking 
them on the average we find just 90° for each. And this is offered as 
“ proof enough” that the whole pencil, or 170°, can be transmitted. 
90° however is something greater than 82°, the limit scientifically 
assigned. And what this extra 8° shows is only this, that Mr. Tolies 
cannot be trusted to take an observation correctly. Of this we shall 
know more when the glass which he has so kindly sent over shall 
