THE PKOFESSIONAL MICROSCOPE. 53 



THE PROFESSIONAL MICROSCOPE. 



This is the largest and most expensive instrument 

 made by the company, and may be described as follows : 

 Heavy brass foot and pillars, both highly finished, 

 carrying the axis for inclination of the body, which 

 movement can be easily tightened or loosened by two 

 strong milled-head screws. Coarse adjustment by rack 

 and pinion, moving along prismatic slide, of first-class 

 workmanship, attached to the body; fine adjustment by 

 a new and patented frictionless motion. The object 

 slide rests upon a newly devised carrier; the body tube 

 has an inner draw tube, with society screw to which ob- 

 jectives of very long focal distance can be attached ; large 

 plane and concave mirrors ; sub-stage for receiving acces- 

 sories of standard size, and two revolving diaphragms, 

 one of the latter belonging to the condenser ; all attached 

 to the swinging mirror bar, the axis of which is placed on 

 the level of the object so that the diaphragm and mirror 

 swing concentrically around it. The mirror as well as the 

 sub-stage can be moved on the iniiror-bar to and from 

 the object, and both can be removed, the latter by a hor- 

 izontal prismatic slide. The sub-stage ring is provided 

 with internal " society screw" for objectives, condenser, 

 etc. There are also two slot diaphragms of different 

 widths, covering the whole surface of the mirror, and 

 only allowing light to pass through the slot in such a 

 direction that very sharp shadows by oblique light will 

 be produced. 



