254 
PROCEEDINGS OF THE SOCIETY. 
Mr. E. M. Kelson exhibited and described an apochromatic con- 
denser fitted with a correction collar worked by a lever ; he also 
exhibited a new magnifying lens illuminator, or lens mirror, in which 
the upper surface of a plano-convex lens was silvered, excepting a 
circular aperture in the centre, above which was placed another lens 
arranged so that the foci of the loup and the lens mirror were identical, 
and thus the advantages of a loup and a lieberkuhn were combined. 
Dr. W. H. Dallinger said that Mr. Nelson had done so much in 
making and suggesting improvements in matters of detail to assist them 
in carrying out the higher microscopical work, that any fresh communi- 
cation from him was sure to be received with attention and interest. 
Unfortunately he had himself not yet had an opportunity of discussing 
the subject before them with him, nor of seeing the arrangement until 
that moment, but he anticipated the pleasure of doing so, and from what 
they had heard he thought that the improvement in the condenser was 
likely to prove of great value. He was of course not able to say more 
about it, for the reason mentioned, but he felt he could not sit still and 
allow the matter to pass without a note of thanks to Mr. Nelson for his 
communication. 
Mr. R. Smith said he should like to mention that Mr. Nelson was 
not quite correct as to the impossibility of registering the aperture of 
the iris diaphragm, for he had one made a short time ago which worked 
admirably and enabled him to register the aperture quite accurately, so 
that at any future time he could set it to precisely the same condition 
if desired. 
Mr. T. Charters White thought the addition of the lever to the cor- 
rection collar would get over a great difficulty if it could be applied to 
objectives, as the stiffness with which these collars generally worked, 
made them very inconvenient to manipulate. 
The President said that this arrangement was likely to be specially 
useful to those who required fine definition ; whether in practice it would 
be found too loose or not, he could not say, but the apparatus itself was 
a very ingenious application of a well-known principle to the improve- 
ment of the condenser, and was sure to be of great service. As regarded 
the iris diaphragm, he did not quite see why they could not register the 
aperture if it was desirable to do so. 
The thanks of the Society were voted to Mr. Nelson for his commu- 
nication. 
Mr. E. E. Hill said he had brought for exhibition a very small 
Microscope made by Nachet, which fitted in a small brass case, and 
would, he thought, be found even smaller than the portable Microscope 
by Zentmayer, described by Mr. Nelson in the last number of the 
Journal. 
The President said this was certainly a remarkable instance of ex- 
treme portability, and for those who wanted to carry a very small instru- 
ment about with them, as for instance a traveller or explorer, who was 
obliged to reduce his outfit to what could be carried on a horse’s back, 
so small a Microscope would be very useful. He did not think how- 
ever that it need be quite so heavy as this one was ; there was no need to 
