38 
MECHANICAL PORTION OF THE MICROSCOPE. 
55. Clieniical or Inverted Microscopes. The chemical 
microscopist frequently has occasion to perform manipulations 
which are rendered difficult by the close proximity of the 
object-glass to the object, or to apply heat, or chemical reagents, 
the fumes of which might injure the lenses. To avoid these 
difficulties, Prof. J. Lawrence Smith has invented the inverted 
microscope, which he presented to the Societe de Biologic of 
Paris, in 1850. 
In this microscope the object-glass is placed below the stage, 
and the arrangement of the several parts are such that the eye 
can observe the object, and, almost, at the same time, with ease, 
guide the hands in performing any required manipulation on 
the stage. 
The optical arrangement of the inverted microscope is shown 
in Fig. 15. 
15. E represents the stage 
with the object upon it, 
C is the object-glass placed 
below the stage, A is a 
prism so constructed that 
the light entering it at 
right angles to the face 
after undergoing total re- 
flection at h and c, emerges 
at right angles to the face 
and is viewed by means 
of the eye-piece placed at 
D. The prism A, wdiich 
is the most important part 
of the instrument of this form, has its angles ah^h c d^ and 
d respectively 55°, 107 52^°, and 145°, consequently the 
body of the microscope is inclined to the perpendicular 35°, 
which is found to be the most convenient position for steady 
and protracted observation. The illuminating apparatus for 
the inverted microscope is placed above the stage, and consists 
of a reflecting prism and condensing lenses. 
J. & W. GRUNOW & GO’S ILLUSTRATED 
