32 
MECHANICAL PORTION OF THE MICROSCOPE. 
stage is a plate, carefully centered, and adapted for receiving 
achromatic condenser, and other apparatus. A strong trian- 
gular bar, moved by a rack and pinion, b}" two large milled 
heads, gives the quick motion of the body, while the delicate 
fine adjustment is effected by a screw on the left of the instru- 
ment, acting upon a lever, which gives a slow movement to the 
stage, as in the instrument last described. 
The arm which carries the body can be turned away from over 
the stage ; this is a great convenience in changing the object- 
glasses, or in performing any manipulation on the object upon 
the stage. 
The body of the instrument, which is attached by a bayonet 
joint to the arm that supports it, can be easily removed, for 
packing in a small case, and the instrument can be readjusted 
for use with great facility. When the body is removed, this 
microscope can be used for dissecting, by inserting a single lens 
into the end of the movable arm in place of the body. 
Chevalier’s Prismatic Body, shown in the next figure, can 
be attached to this instrument. 
51. Chevalier’s Prismatic Body, shown in Fig. 12, as it 
is attached to the microscope, consists of a tube with an elbow 
in which is inserted a rectangular reflecting prism. The light 
from the object-glass enters the prism perpendicular to the first 
surface, and falling upon the second surface at an angle of 45° 
sufl[ers total reflection, and emerges perpendicular to the third 
surface of the prism, which makes a right angle with the first. 
This addition is particularly useful in examining living animal- 
cules and other objects in water, and in all other cases where 
the horizontal position of the stage is either necessary or desira- 
ble ; and when otherwise the continued posture of the observ- 
er, in looking down vertically, would be attended with great 
fatigue to the eye. 
This apparatus can be applied to microscopes Nos. 5 and G. 
A short elbow tube, (containing a rectangular prism,) one 
end to be inserted in the draw-tube and the other to hold the 
eye-piece, is furnished to order with any of our microscopes. 
It is used for the same purpose as the prismatic body. 
J. & W. GRUNOW & GO’S ILLUSTRATED 
