CHEVALIER S MOUNTING. 



square piece r, 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 having a milled head 

 at Q. 



To the square piece M is attached the illuminator H, on one side, 

 K, 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 D F G, 

 into which that bar enters when it is vertical as represented in the 

 figure, and in which it is held by the pin at G. 



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 B, 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 R, 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 r. 



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 B, 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 u, 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 



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