498 
PROCEEDINGS OF THE SOCIETY. 
Meeting of 19th June, 1895, at 20 Hanover Square, W. 
E. M. Nelson, Esq., Vice-President, in the Chair. 
The Minutes of the Meeting of 15th May last were read and 
confirmed, and were signed by the Chairman. 
The following Donation was reported, and the thanks of the Society 
were given to the donor. 
From 
J. Pereira, Lectures on Polarised Light (8vo, London, 1843) .. Mr. W. H. Brown 
Messrs. Watson and Sons exhibited a simple Centering Underfitting 
for use with any ordinary Student’s Microscope. It was well known 
that very few instruments of this class did centre accurately, and the 
fitting exhibited was a contrivance for providing a means of accurate 
centering at a small expense to such Microscopes. 
The Chairman thought this was a very good thing indeed, and one 
which he was extremely glad to welcome, for he had long felt that the 
most elementary student’s Microscope should have some kind of centering 
gear fitted to the substage condenser. The one before them met the 
two essential requirements of efficiency and cheapness. 
The Chairman exhibited a new low-power lens by Zeiss, which he 
thought would be found very acceptable. It was the first of its kind 
made in Germany, for hitherto all German low powers had consisted of 
single combinations, except one made by Seibert of 36 mm. Zeiss had 
now remedied this by making one with optical index of 31, which so 
far as he had yet tried it gave very excellent results. 
He also brought another lens for exhibition which was not ex- 
actly microscopical, but was such a new advance in optics that it was 
not possible yet to tell how it might affect the construction of Microscope 
lenses intended for photography. This was an ordinary photographic 
camera lens which consisted of two symmetrical, but uncorrected lenses ; 
its chemical focus was therefore not coincident with its visual focus. 
It was 8J in. in focus, and it covered a half plate sharply to the edge. 
In fact, it was the most anastigmatic lens he had ever seen. 
A few years ago a lens capable of taking pictures that size would 
have cost 81. or 91., whereas this cost only 25s., with an iris diaphragm 
included. The point was, Could this principle be applied to Microscope 
objectives ? The method of working of this lens was very simple. The 
visual rays were first focused in the ordinary manner, the lens was then 
pushed nearer the ground glass by means of the bayonet-shaped slot in 
the mount, and then the photograph was taken. 
He further brought an improved form of his little reflector lamp, 
exhibited at a former meeting of the Society ; it had now been achro- 
matised, and was found to act remarkably well. 
