NOTICES OF MEETINGS. 283 
admit, but cannot agree, that a circle consists of 360 degrees, and 
by drawing lines through it we can cut off any number of these 
degrees, constitutes a performance of this simple task. Surely for 
the “younger members” who might need such milk as this, some- 
thing more would be required also. The reader did not apply 
these elements of geometry to his subject at all, and of the principles 
of numerical aperture left us profoundly ignorant. Perhaps this is 
not to be wondered at when considered in connection with an in- 
ference which he drew from a fact mentioned in the N. M. of last 
month. The fact was that a better image was produced with an 
inch of 35° and the C eyepiece than with a half-inch of 40° and the 
A ocular; the inference was that this proved the superiority of low 
angled glasses, as a better result was obtained from 35° than 40°. 
Is not this mere sophistry, and intended for effect upon a mixed 
audience, or was the reader really unaware that 35° in a one inch 
lens corresponds to considerably more than 40° in a half-inch? or 
does he argue upon the number of degrees only, and leave the lens 
entirely out of consideration? Moreover, has he not made a slight 
mistake upon the above point? and were not the photos. in last 
month’s N. M. given as test results shewing what migA¢ rather than 
what should always be done? On one point I think that all those 
who heard the paper will agree with its reader, namely, that “ideas 
upon aperture are sometimes rather vague, and this is occasionally 
betrayed where least expected.” 
I am, etc., 
ONE WHO WAS PRESENT. 

NOTICES OF MEETINGS. 
BOLTON MICROSCOPICAL SOCIETY.—The members of this Society 
met on Friday the 1st of September, after the summer recess. The meeting 
was fairly well attended, a very interesting evening was spent, chiefly in 
examining living organisms brought by various members. Mr. A. S. Penning- 
ton, in the absence of the President, occupied the chair. During the recess two 
out-door meetings have been held,—Chequerbent being the hunting ground in 
the first instance, and Hulton Park, at the invitation of of W. W. B. Hulton, 
Esq., the second. Both rambles were very pleasant, and the find in each case 
_— Great service was rendered to the Society by Mr. Tonge, agent to Mr. 
ulton, who spared no pains in making each of the meetings a success. 
MANCHESTER MICROSCOPICAL SOCIETY. 
— monthly meeting of the members of the Manchester eg ao So- 
ciety was held on Thursda a Sept. 7th, 1882, at the Mechanics’ 
Institution, Manchester. Mr. THOMAS BRITTAIN, F.R.M.S., the President, 
in the Chair. / 
The Secretary, Mr. Charles L. Cooke, read the minutes of the previous 
meeting. 

