106 



THE ART OF MAKING MICROSCOPE SLIDES 



Casting block 



1""-/ ^ W"*^' ' ' " !^ " '- " ^ ^ " " - ' ■" ' ■,' , -*i^ 



Fig. 52. Filling with wax an embedding box which has been attached with water to a 



glass slide. 



which slides up and down has, at the end 

 opposite to the block, a rectangular plate 

 of hardened steel inclined at an angle of 

 about 45°. This plate bears, under the 

 pressure of a powerful spring, against a 

 hardened steel knob which is itself con- 

 nected to a micrometer screw. As the han- 

 dle is rotated a pawl works against a 

 ratchet to move the micrometer screw, 

 and thus the knob connected with it, 



through a given distance for each rotation. 

 As the knob moves forward, it moves the 

 block the required distance forward at 

 each revolution by bearing on the diag- 

 onal plate. This mechanism is very costly 

 to make and is liable to a large number of 

 minor defects which are not always appar- 

 ent until one has started section cutting. 

 One of the most important things that 

 must be watched is that the knob which 



