36 
January lOth, 1866. 
An extract from a letter from Professor H. L. Smith, of 
Kenyon College, Gambia, Ohio, U.S., was read by Mr. E. G. 
Lobb, giving a description of the method of using a new 
illuminator for opaque objects. The apparatus sent over by 
Professor Smith was exhibited by Mr. Lobb, a description of 
which is given in ^ Silliman^s Journal^ for September, 1865. 
The apparatus of Professor Smith, which consisted of a 
metallic reflector to be fitted between the object-glass and 
the compound body, he requested might be placed in the 
hands of Messrs. Powell and Lealand, as he had no doubt 
they might improve upon it, and these gentlemen, as well as 
Messrs. Smith, Beck and Beck, have invented a plan for sub- 
stituting a glass plate for the metallic reflector, which obviates 
many of the difficulties in the illumination to which the 
metallic reflector is subject. 
The Object-Glass Us own Condenser; or, a new kind of 
Illumination for Opaque Objects under High Powers. 
By BicHARD Beck. 
(Read January 10th, 1866.) 
This method of illumination has been recently introduced 
by Mr. Smith, of Kenyon College, U.S.;^ but I believe the 
best effect may be obtained by the following exceedingly 
simple plan : — 
A piece of thin glass (fig. 3, b)y attached to a small brass 
milled head, fits into the side of an adapter (fig. 1), and 
when in position, as in figs. 1 and 2, the light coming 
through a small circular aperture [a) may be refiected down 
and through the object-glass, by the thin glass which makes 
no obstruction to the rays passing upwards again from the 
object-glass to the eye-piece, nor even affects the definition 
to any perceptible degree. 
The adapter (fig. 1) is used, as shown in section (fig. 2), 
between the nose-piece (c) and the object-glass {d) ; it has a 
rotating fitting at the milled ring, and this movement, in 
combination with that of the small milled head to which the 
thin glass is attached, is sufficient for the nicest adjustment 
of the illumination. 
* *Silliman*s Journal,* Sept., 1865. 
