MICROSCOPIC OBJECTS. 



167 



as a lever ; by this all the motions are obtained in a very- 

 simple manner, as shown in the annexed figm?e. 



The end C, which is cylindrical, fits into the stage of 

 the microscope, or the lower immoveable plate A may 

 be the stage. This plate A is fixed to the part C ; it has 

 a circular aperture in the middle, and a small hole at o, 

 which acts as the centre of motion for the plate B to turn 

 about ; on the top of this plate is another, e, which carries 

 the slider-holder and object F. This plate is moveable 

 to and fro by turning the screw by the milled head D ; 

 and at the same time a cross motion may be communicated 

 to the object by moving the head D laterally, which 

 carries along with it the plate B, the centre of motion 

 being o. The plates A, B,e, must be fastened together; 

 which, however, it is not necessary to show. 



By this contrivance a traversing motion in any direc- 

 tion is obtained with the milled head D, by one hand 

 only. No part of it is in the way of the illumination, nor 

 is it liable to derangement. 



In Mr. Pritchard's standard microscope, described in 

 another part of this work, this method of obtaining a 

 traversing motion is adopted with complete success. 



q2 



