426 
PROCEEDINGS OF THE SOCIETY. 
were shown to explain the use of large aperture objectives for viewing 
minute structure. 
Mr. E. M. Nelson said he had been much delighted by the very 
beautiful exhibition which they had just witnessed. Some of the experi- 
ments had been of very great rarity on account of the extreme scarcity 
of good specimens of some of the crystals employed. 
The President said the Society was extremely indebted to Sir David 
Salomons for the very admirable and interesting exhibition which he 
had given them, the value of which was not only on account of the 
refraction phenomena which had been so well shown, but because of the 
advance which was indicated in the construction of the apparatus. The 
lantern was increasingly becoming a means of illustration, and in con- 
nection with it the projection Microscope was coming to the front. 
Lantern illustration was undoubtedly the most attractive method for 
class purposes and for large audiences, but where the ordinary lantern 
was used it involved the trouble of the preparation of lantern-slides, so 
that every step in the direction of the improvement of the projection 
Microscope was to be welcomed as most important, since it enabled the 
actual objects to be shown. Their thanks were, therefore, due to any one 
who helped to improve the instrument. He could not help observing, 
as the exhibition proceeded, that there was a remarkable flatness of field 
not generally seen under similar circumstances ; the difficulty, of course, 
was always to get sufficient light for the purpose, and when this was 
obtained it was usually at the sacrifice of some degree of flatness. 
There was one point on which he should like to ask for information : 
it sometimes arose that the great concentration of light produced also 
a great concentration of heat, and that consequently objects in balsam 
if exposed for too long a time were apt to get spoilt through the 
softening of the medium. Was this difficulty got over in the present 
instance by using the electric arc light as an illuminant ? 
Sir David Salomons said this question was one very much to the 
point, because the difficulty mentioned was one of the first met with. 
He obviated it very much by using lenses cemented with balsam. The 
customary alum and water he found to be rather troublesome and so he 
used distilled water and found that it answered every purpose. He 
should have been glad had it been possible to have used a larger cur- 
rent -for the arc lamp to increase the brilliancy of the disc, but for 
the reason already mentioned he had been unable to do so. 
A hearty vote of thanks was then passed to Sir David Salomons on 
the motion of the President. 
The following Instruments, Objects, &c., were exhibited 
Mr. C. Lees Curties : — New form of Camera Lucida by Herr Leitz of 
Wetzlar. 
Mr. C. Rousselet: — Rotifers. 
Sir David L. Salomons : — Exhibition with the Projection Micro- 
scope. 
Mr. W. H. Youdale : — Diseased Beard-hairs. 
New Fellows: — -The following were elected Ordinary Fellows: — 
Messrs. James Adams and Joseph Gritton, Prof. James W. Hartigan, 
Dr. Walter Cairns Johnson, Messrs. George Mellors, and Frank S. 
Morton. 
