68 



THE MICROSCOPE AND ITS REVELATIONS. 



among those who value first-rate workmanship, with all convenient appli- 

 ances for ordinary Biological research. A Sub-stage (not shown in the 

 figure) carrying every kind of illuminating apparatus, can be attached 

 beneath the stage; and the large angular aperture now given by Messrs. 

 Powell and Lealand to their Immersion Achromatic Condenser, enables 

 this instrument to resolve the most difficult test-objects. The stand is 



well suited to carry a Bino- 

 cular body; which may be 

 fitted not "only with the or- 

 dinary stereoscopic < Wen- 

 ham' prism, but also with 

 the non-stereoscopic arrange- 

 ment of these Makers (81), 

 which enables even the 

 highest powers to be used 

 binocularly, though not ste- 

 reoscopically. 



66. The value of Stereo- 

 scopic Binocular vision in 

 Scientific investigation be- 

 ing now admitted by all 

 who have really worked with 

 it upon suitable objects, the 

 Author would earnestly re- 

 commend every one about to 

 provide himself with even a 

 Second-class Microscope, to 

 incur the small expense of 

 the Binocular addition. 

 This addition, however, will 

 lose an important element of 

 its value, if the Stage of the 

 instrument be not adapted 

 to rotate in the optic axis of 

 the Body; so that objects 

 which are being viewed by 

 incident light may be pre- 

 sented to the illuminating 

 rays in every direction. 

 Among the first to recog- 

 nize this principle, and to 



it in practice, were Messrs. Beck; whose Popular Microscope 

 Late iv. ), devised by the late Mr. R. Beck, will be found very suitable 

 to the wants of such as work with low and moderate powers upon objects 

 for the study of which Binocular vision is peculiarly advantageous; and 

 especially serviceable to Travellers, as the ingenious way in which it is 

 framed and supported enables it to bear a good deal of rough usage 

 without injury. The original Ross model here adopted in the support 

 and movement of the body, is sufficiently steady when only moderate 

 powers are employed; and the stem that forms the centre of the whole, is 

 swung immediately behind the stage on a broad stay G, which, again, is 

 attached by a pair of centres at its lower angles to the triangular base F. 

 The lower end H of the stem carries a stout projecting pin, which fits 

 into various holes along the median line of the base; whereby the instru- 



Powell and Lealand's Smaller Microscope. 



apply 

 (Pla 



