iNLEER + 
52 Description of an improved Microscope. — [JAN. 
only an ephemeral existence. It is very easy to form it, merely 
by blowing out air from the lungs through a glass tube in lime 
water. Carbonate of magnesia seems to form the same kind of 
combination ; for, according to Bucholz, it is capable of existing 
in the state of three different compounds. 
ARTICLE IX. 
Description of an improved Microscope. (See Pl. LXXXVIII.) 
Fic. 1. The instrument mounted for viewing an opaque 
object. A B is the body of the microscope ; it consists of five 
lenses, and differs from that commonly used for microscopes. 
The instrument-maker will comprehend how to make it when he 
is told that the lenses 1 and 2 at the bottom are similar to 
those used for the eye-pieces of refracting telescopes ; the lenses 
3, 4, and 5, are the field-glass, and double eye-glass used in 
compound microscopes. To increase the magnifying power, 
there are three astronomical eye-pieces of different powers, 
which are made to fix on at A. This body is eight inches long, 
the bottom is tapered a little, as may be seen at B, for the purpose 
of allowing the rays to pass more freely from the mirror g to the 
object to be examined.. At the top, A, a shoulder is made 
which is screwed for a purpose hereafter to be mentioned. If it 
is asked why I have rejected the old body for viewing opaque 
objects, and what is the advantage of this new one, I answer as 
follows. Every one accustomed to common compound micro- 
scopes may have observed a kind of milkiness in the field, so 
that the object appears as if seen through a kind of mist, or as 
if the glasses were dimmed by moisture. The greater the aper- 
tures of the little glasses are at the bottom, the more perceptible 
this becomes ; but it can never be removed altogether, as I know 
from experience, by any reduction of the apertures: when an 
opaque object is viewed, the defect is still more striking; besides 
opaque objects require a great deal more light to be seen pro- 
perly than transparent ones, and this kind of microscope gives 
very little, especially if the apertures are reduced to a proper 
_ standard. Our microscope labours under none of these defects ; 
the image is quite clear, as if produced by a single lens, and 
there is abundance of light. The body of the instrument is made 
to ¢wist into the socket of the arm C C, which is made to slide 
backwards and forwards in the case represented at O. The 
stage, D D, travels up and down with a rack and pinion, as seen 
in the Plate; it is five inches in length, reckoning from 
the brass bar, O O O; the hole E is 2, inches diameter ; that 
at F one inch, and has a small notch in it. There are two holes 
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