ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



593 



groovo works a knob projecting from the under surface of the vertical 

 axis of the object-carrier. When the knife-carrier moves, the object- 

 holder is borne along the groove towards the edge of the knife. Ac- 

 cording to the relative positions of the knife and the groove, so is the 



length of the movement of the object-carrier— indeed this movement may 

 be reduced to zero. To the micrometer screw is attached a toothed 

 wheel which is actuated by a hook fixed to the grooved plate. This 

 arrangement effects the automatic raising of the preparation, and may 

 be made to vary from 0-005 mm. to 0- 1 mm. The gape of the jaws of 



