348 HOW TO SEE WITH THE MICROSCOPE. 



Since the chapter on stands was written we have received the 

 following description of 



BECK'S INTERNATIONAL MICROSCOPE STAND. 



The improved large best or international microscope stand 

 has a tripod (A) for its base, upon which is placed a revolving 

 fitting (B), graduated to degrees, by which means the micro- 

 scope can be turned round without its being lifted from the 

 table, and the amount of such rotation registered ; upon this 

 fitting two pillars are firmly fixed, and between them the limb 

 <C) can be elevated or depressed to any angle, and tightened in 

 its position by the lever (D). The limb carries at one end the 

 body (E) (binocular or monocular) with eye-pieces and object- 

 glasses; in its centre the compound stage (F), beneath which is 

 the circular plate, sliding on a dove- tailed fitting, and moved up 

 and down by the lever (Z), and cariying the supplementary body 

 or sub-stage (G); and at the lower end a triangular bar carrying 

 the mirror (H). Each of these parts requires a separate 

 description. 



The binocular body consists of two tubes, the one fitted in the 

 optical axis of the microscope, and the other oblique. At thek 

 lower end and immediately above the object-glass there is an 

 opening, into which a small brass box or fitting (I) slides ; this 

 box holds a prism so constructed that when slid in it intercepts 

 half the rays from the object-glass, diverts them from their 

 direct course, and reflects them into the additonal or oblique 

 tube. To the prism-box is attached a spring-catch, which,when 

 pressed in, permits of the removal of the prism-box ; but this is 

 only needed for cleaning, as, when the box is drawn back to the 

 distance allowed by this spring, the prism in no way interferes 

 with the field of view, and all the rays pass up the direct body, 

 and the microscope is converted into a monocular one. 



The upper or eye-piece ends of the tubes are fitted with racks 

 and pinion for varying the distances between the two eye-pieces 

 to suit the differences between the eyes of various persons ; and 

 arrangements are made for racking out one tube more than the 

 other, to suit irregularities or inequalities between the eyes of 

 the observer. 

 This body is moved up and down with a quick movement by 



