THE MICKOSCOPE. 
As the effect of the illuminators varies not only with their 
distance from the object, but also with the direction in which the 
light directed from them falls upon the object, provisions are 
made in mounting the microscope, by which various positions may 
be given to them, so that the light may fall upon the object in any 
desired manner. 
In the frame in which the illuminator, M M, is mounted, it is 
customary to place two reflectors, one at each side, one concave 
and the other plane. By the former a converging, and by the 
latter a parallel pencil of light is reflected towards the object. 
In this general illustration we have supposed the axis of the 
instrument to be vertical; it may, however, have any direction 
whatever; but whatever be its direction, the stage, s s, must 
always be at right angles and concentric with it. The eye-piece 
and object-piece are also supposed to be set in the same straight 
tube, with their axes set in the same straight line. This arrange¬ 
ment, though most commonly adopted, is neither necessarily nor 
always so. The tube which carries the eye-piece may, on the 
contrary, be inclined, at any desired angle, with that which 
carries the object-piece; for this purpose it is only necessary to 
place in the angle formed by the two tubes a reflector, so inclined 
that the rays coming from the object-piece shall be reflected along 
the axis of the tube which carries the eye-piece. 
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