PROCEEDINGS OF SOCIETIES. 133 
La 
definition can be obtained by this method when the speculum is 
of the proper curvature. This contrivance can always remain 
attached to the microscope without interfering with the general 
appearance of the instrument, and when the use of the speculum 
is not required it can be withdrawn or turned aside out of the 
field of view, and the aperture at the side of the body may be 
closed by a small shutter. It is obvious that the use of the 
binocular body is not interfered with by this arrangement. 
A binocular and a monocular microscope with this arrange- 
ment were exhibited to the members at the close of the meeting. 
December 18th, 1865. 
J. B. Dancnr, F.R.A.S., in the Chair. 
Mr. Parry exhibited some sections of fossil wood and Echinus 
spines, most beautifully cut by Mr. John Butterworth, of Oldham, 
and presented some of the slides to the Section. 
Mr. Parry also presented to the meeting, for distribution among 
the members, mounted slides of the contents of a shark’s stomach, 
from the Madras coast, consisting almost entirely of Diatomacez. 
Mr. Hurst then made a few remarks on late improvements in 
illuminating opaque objects under the higher powers of the micro- 
scope. He said they consisted of three different methods. Firstly 
that of H. E. Smith, of Kenyon College, America, described in 
the English ‘ Mechanics’ Magazine’ of the 20th October, 1865, 
in an extract from the ‘American Journal of Science and Arts.’ 
This gentleman employed a box, or adaptor, between the object- 
glass and the Wenham’s prism of the binocular, with a side 
perforation, opposite to which was a small silver reflector or a 
common thin glass cover, acting as a mirror and capable of adjust- 
ment to any angle, thus enabling it to throw the rays of light 
admitted by the side aperture through the object-glass down on 
to the object itself. 
The disadvantage of this method is that all adaptors cause 
unsteadiness, and, however skilfully constructed, injure the accu- 
rate centering of the object-glass ; and while, on the one hand, the 
thin glass cover appears to produce some distortion of the image, 
the reflector so near the object necessarily casts off a number of 
the rays proceeding from it. This plan also seems to require 
lamp-light and the use of a condenser. Messrs. Smith and Beck 
appear to have patented the use of the thin glass cover. 
Secondly, a modification of the foregoing by Mr. Dancer, of 
this Section, who places the thin glass or reflector between the 
eye-piece and the Wenbam prism, cutting an aperture in the 
body of the microscope to admit the light. This dispenses with 
the objection inherent to adapters, and theoretically seems the 
most perfect of these new methods; but Mr. Hurst’s experience 
