77ie Stage 11 



the front edge of the bench it will remain firm, where a 

 tripod instrument would fall completely over. These are 

 just demands. 



While an instrument mounted on the horseshoe is in 

 a vertical position it stands firmly ; but if the body be 

 inclined at an angle, as an amateur usually employs it, 

 even with a large and heavy foot there is a tendency to 

 side-falling. All considered, the tripod has so many 

 advantageous points that it is to be recommended in 

 preference to any other. Our selection of a foot for a 

 microscope would therefore be in the following order : 



1. The tripod foot, as shown fitted to instruments on 

 pages 8, 25, 32, and frontispiece. 



2. The Jackson forin of foot, as fitted to the instrument 

 illustrated on pages 37 and 41. 



3. The Continental or horseshoe form, as shown on 

 page 12. 



THE STAGE. 



The stage of the microscope on which the object is 

 placed for examination may be divided into two classes : 

 (1) mechanical, and (2) plain. 



The Mechanical Stage. — The instruments figured on 

 page 25 and frontispiece are provided with this type of 

 stage, in which, by the turning of two milled heads which are 

 attached to screws, plates are moved in dove-tailed grooves 

 one over the other, in rectangular directions, carrying the 

 object with them. A first-class microscope should be pro- 

 vided with this form of stage ; in fact, there is no means so 

 suitable for systematically examining an object as is afforded 

 by it. In addition to these mechanical movements, if a 

 bar be fitted to slide in a vertical direction on the top plate 

 the efficiency of the stage will be greatly increased. The 

 mechanical stage lends itself to the adaptation of further 

 important movements. A means of rotating the object is 

 an essential in most classes of work. For this purpose the 

 lowest plate of the stage is usually fitted to rotate on the 



