266 
PROCEEDINGS OF SOCIETIES. 
The thanks of the meeting were voted to Mr. Beck for his com- 
munication. 
A paper by Dr. G. W. Eoyston - Pigott, " On the Identical 
Characters of Chromatic and Spherical Aberration," was read by the 
Secretary. 
The President thought that some of the statements in the paper 
appeared to require a little limit ; for he imagined it would be quite 
possible to produce a lens having the spherical aberration correct for 
each ray, and yet still having a different focus for each ray. 
Mr. Slack suggested that the paper obviously opened up a very 
important question as to the finest possible point of correction for 
lenses ; and this reminded him that Herr Hasert, of Eisenach, adverr 
tised a new objective, which he said magnified 2000 or 3000 diameters, 
required no corrections for covering glasses of different thicknesses, 
and with which, it was stated, Amphipleura pellucida could be seen 
" without the use of oblique light." Now if he had done this, he had 
certainly done a most astounding thing ; but whether it was all true 
or not, it showed the direction in which foreign makers were moving. 
Mr. Beck said he had tried to understand Dr. Pigott's paper, but 
could not do so at all ; perhaps when printed he might be able to 
comprehend the meaning of it. 
Dr. Lawson said he had received a letter from Mr. Hickie respect- 
ing the objective referred to by Mr. Slack, to the effect that he had 
examined it, and had found it produced very remarkable effects ; also 
that it was perfectly true that it did not matter within certain limits 
what covering glass was used with it. 
Mr. Curties said that Mr. Hickie would be very happy to send this 
lens to the Society for examination. 
Dr. Pigott said he had not much to say in reply. The matter 
seemed very simple. He had lately been studying Professor Litrow's 
remarks on the achromatism of lenses for telescopes, and he there 
shows that he has calculated the marginal, central, violet, and red 
rays, and carried them out to five places of decimals, and found that 
they all came to the same point. 
Dr. C. T. Hudson gave a highly interesting communication " On 
a New Species of Melicerta," illustrating the subject by a large 
number of very beautiful diagrams in coloured chalk, and by drawings 
on the board. 
The President felt sure that all would unite in passing a cordial 
vote of thanks to Dr. Hudson for his very interesting paper, and he 
could not himself refrain from complimenting him upon the very 
great artistic taste displayed in the drawings exhibited in the room. 
He had not studied that class of objects much, but felt there were 
many persons in the room who would be glad to say something on the 
subject. 
Dr. Pigott said he should like to ask Dr. Hudson what power he 
used in making these investigations ? 
Dr. Hudson replied that he usually worked with a ^ inch and a 
B eye-piece, but ho preferred A. When looking at the objects with 
a I inch through the side of a trough, he often found that he could 
