THE MICROSCOPE. 



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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