CONSTRUCTION OF THE MICROSCOPE. 61 



object on the stage, an advantage which every real worker with a simple 

 instrument of this class will appreciate. 1 



59. Ross's (Zentmayer} Student's Microscope. Another instrument 

 of superior make. (Fig. 43), has lately been introduced by Messrs. Ross, 

 with the view of affording to the Student the ad vantage of the ' swinging 

 tail-piece for oblique illumination/ devised by Mr. Zentmayer; of which 

 a fuller description will be given in its application to their First-class 

 Microscope ( 72). This tail-piece swings round a pivot which serves for 

 the attachment of the stage to the limb; and at the back of the limb is a 

 milled-head working on the projecting end of this pivot, by tightening 

 which the stage may be firmly fixed in its ordinary horizontal position, 

 whilst by loosening it the stage may be made to incline to one side or the 

 other. The ' tail-piece ' carries, between the mirror and the stage, a ' sub- 

 stage,' fitting into which may be screwed an ordinary 1 inch, 1J inch, or 2 

 inch Objective, which answers the purpose of an Achromatic condenser; 

 and when a pencil of light reflected from the mirror has been made by it to 

 focus in the object, the swinging of the ' tail-piece ' to one side or the 

 other will give any degree of obliquity to the illuminating pencil that 

 may be desired, without throwing its focus off the object, as this lies in 

 the plane of the centre round which it turns. The ' tail-piece' may even 

 be carried round above the stage, so that light of various degrees of 

 obliquity may be concentrated upon opaque objects. The object-plat- 

 form of the stage is of glass, and rotates round the optic axis of the 

 microscope; so that the object may be illuminated by oblique rays from 

 any azimuth. A mechanical stage may be added, if desired. The work- 

 manship of this simple model is of the highest class; and there is little 

 real work, of which, in the hands of an observer who knows how to turn 

 the instrument to the best account, it may not be made capable, by the 

 addition of a Polariscope, Paraboloid, and other accessories, which its 

 Sub-stage adapts it to receive. 2 



60. Wale's New Working Microscope. A Student's Microscope lately 

 brought out by Mr. George Wale (IT. S.), deserves special notice, on 

 account of several ingenious improvements which he has introduced into 

 its construction. In the first place, the 'limb ' which carries the body 

 and the stage, instead of being swung by pivots as ordinarily on the 

 two lateral supports (so that the balance of the Microscope is greatly 

 altered when it is much inclined), has a circular groove cut on either 

 side, into which fits a circular ridge cast on the inner side of each sup- 

 port. The two supports, each having its own fore-foot, are cast separately 

 (in iron), so as to meet to form the hinder foot, where they are held 

 together by a strong pin; while by turning the milled-head on the right 

 support, the two are drawn together by a screw, which thus regulates 

 the pressure made by the two ridges that work into the two grooves on 

 the limb. When this pressure is moderate, nothing can be more satis- 

 factory than either the smoothness of the inclining movement, or the 

 balancing of the instrument in all positions; while, by a slight tighten- 



1 The cost of the above Microscope, with two Eye-pieces (B and C), and two 

 Objectives (5-8ths and l-7th inch) giving with the Draw-tube a range of powers 

 from 50 to 420 diameters, packed in a very compact Case, is only 7 10s. Od. , or, 

 with the addition of an A Eye-piece, a 1^ or 2-inch Objective, Polarizing 

 Apparatus, and Beale's Drawing Camera, 10 guineas. 



2 The price of the Microscope, as above figured, in Case, is 10 guineas. None 

 but first-class Objectives are supplied by Messrs. Ross; but the Student who finds 

 these too costly may obtain elsewhere such as suit his requirements. 



