chevalier’s mounting. 
square piece P, to which it is attached by turning the milled 
head o, and that a slower motion, to give more exact adjust¬ 
ment, is imparted to it by a fine screw haying a milled head 
at Q. 
To the square piece it is attached the illuminator h, on one side, 
x, of which is a concave reflector, and on the other, I, a smaller 
plane reflector. This illuminator has two motions, a horizontal 
or lateral one upon a joint at M, by which it can be placed at 
pleasure either vertically under the centre of the stage z, or at a 
limited distance on one side or other of the vertical through the 
centre of the stage. The circular illuminator is suspended at two 
points diametrically opposite in a semicircular piece, and may be 
placed at any desired inclination to the vertical, and with either 
reflector upwards by means of the milled head i. 
From the lowest part of the pillar c c a piece projects, having a 
cavity corresponding with the size and form of the bar dfg, 
into which that bar enters when it is vertical as represented in the 
figure, and in which it is held by the pin at a . 
The body of the microscope, as shown in the figure, is rect¬ 
angular. The eye-tube t is moved backwards and forwards in the 
body s by a pinion u working in a rack. The eye-piece s is 
inserted in this tube, and the eye is protected from the light by a 
circular blackened screen, seen edgeways in the figure. The 
rectangular tube v x is inserted by a bayonet-joint in the remote 
end of the body K, in which it is capable of being turned, so 
that the object-tube x shall be horizontal, to enable the observer 
with greater facility to screw on or to change the object-glasses 
at Y. 
The body is attached to the bar E c by a joint at c, upon which 
it can be turned, by which means other positions can be given to 
the instrument, as will presently be explained. 
An assortment of object-glasses is supplied, which may be 
screwed at pleasure upon Y. They are adapted to each other in 
sets of three, so that one, two, or three may be attached to Y 
according to the power required. 
In the angle b of the body, a rectangular prism is fixed, by 
which the rays proceeding upwards from y are reflected horizontally 
along the axis of n to the eye-piece, on the principle explained 
in 30. 
Several eye-pieces of different powers are supplied with the 
instrument. 
The magnifying power may be varied within certain narrow 
limits by moving the eye-tube in or out by the pinion 1 1 , and at 
the same time adjusting the focus by the pinions o and Q, which 
move the stage z. When it is desired to augment the power, the 
73 
