00 THE MICROSCOPE. 



worthy character. My observations will therefore be 

 almost exclusively confined to points of excellence in 

 workmanship, to mechanical difficulties successfully 

 overcome, and new forms introduced since the publica- 

 tion of my ninth edition. 



The Improved Koss-Zentmayer Microscope is a 

 thoroughly substantial and practical instrument, com- 

 bining elegance of appearance with facility in the 

 attainment of everything the microscope can at present 

 be expected to accomplish. 



The stand is on the well-known Jackson model, with 

 extra wide slides for the rack-and-pinion movement. 

 The slow movement is obtained by a second slide 

 close behind the first, but to avoid the friction of rub- 

 bing surfaces, hardened steel rollers are inserted between 

 them, which gives a frictionless fine motion, amenable 

 to the slightest touch of the milled-head screw, situated 

 conveniently at the back of the limb, through which 

 a steel lever passes which actuates the slow motion 

 slide. The body of the instrument is therefore not 

 touched during the fine focussing, so that all lateral 

 movement is avoided. The mechanical stage is made to 

 rotate axially, and the outer edge of the lower plat? 

 is divided into degrees, in order to register the angles, 

 and a simple mode of adjustment is provided, for 

 setting the centre of rotation exactly coincident with 

 the focal point of the object-glass. As the plates of 

 the stage have no screw or rack work between them 

 (these being placed externally), they are brought close 

 together, giving the advantage of a very thin sub- 

 stantial stage, and ensuring rigidity where required ; 

 phosphor bronze being used in its construction. The 

 stage is attached to the limb by a conical stem, with a 

 screw and clamp nut at the back, so that it can 

 be easily removed for the substitution of a simple 

 plate, or other stage, and by turning the stem in the 

 socket the stage may be tilted sideways at any angle 

 required. One special feature in the Ross-Zentmayer 

 stand is a swinging sub- stage and bar, carrying the 

 mirror, having its axis of rotation situated from an 

 axial point in the plane of the object, which conse- 



