170 



On a Swinging Sub-stage for the Microscope. 

 By James Mackenzie. 



C Communicated June 25th, 1880J 



Plate XII., Upper Fart. 



In the sketch, A shows a portion of the fixed stage-plate of a 

 microscope, B is an angular plate fixed to under part of A, and hav- 

 ing a swivel joint at C, on which the stem with rack F swings, and 

 can be tightened by the nut or screw G. A pinion D, works on 

 the rack, and carries an arm, H, with either a single or compound 

 lens, E, which should be so adjusted as to be central with the optical 

 axis of the objective of the microscope. I is an ordinary small 

 concave mirror. 



It is obvious that the condensing lens E maybe of any convenient 

 focal length, (I have used i inch,) and it may be raised or lowered 

 at pleasure by the pinion D, and can be swung aside to any angle 

 either below or above the stage. The angle-plate B should be made 

 and fixed so that the centre of the moveable joint or swivel coincides 

 with tlie top of an ordinary object-slide when it lies on the stage. 



