46 SELECTION ANb USE 



and good binoculars are common, this form of instrument has 

 become a great favorite with all the noted microscopists, and 

 we refer not merely to men who own microscopes as a means 

 of amusement, but to those, who, like Carpenter and others, 

 have enlarged the boundaries of knowledge by their re- 

 searches. 



There are, of course, certain limits to the range of usefulness 

 of the binocular microscope. As at present constructed, it is 

 most efficient in the use of the low powers, and hence, there 

 are certain classes of work to which it is peculiarly applicable, 

 while in other branches, particularly certain departments of 

 histology, it is of comparatively slight advantage. And it will 

 in general be found that the principal opposition to the binoc- 

 ular has come from continental histologists, who, because they 

 found it of little use to themselves, concluded that it could not 

 possibly be of use to any one else. 



Attempts have been made, and with partial success, to apply 

 the binocular feature to instruments used with high powers. 

 Messrs. Powell & Lealand have produced an instrument of this 

 kind which has been highly praised by some. Not having seen 

 it, however, we cannot speak of its merits. 



The advantages presented by binocular instruments are two 

 fold ; the relief to the observer arising from the ability to use 

 both eyes is very great, and the view which is obtained of 

 any object is so much clearer and more realistic, that we at 

 once perceive, by our mere sense of vision, those features which 

 we would otherwise have to work out by tedious mental pro- 

 cesses. It has been said by some, that the binocular is apt to 

 exaggerate the stereoscopic effects, and give false views. This 

 is certainly not the case under ordinary circumstances, and we 

 doubt much if it ever occurs. 



We have chosen as an illustration of the binocular micro- 

 scope, one of moderate cost, made by Mr. Crouch, of London. 

 The stand is designed after the Jackson model, and the two 

 bodies are furnished with draw-tubes, which may be moved out 

 or in simultaneously by racks and pinions, the milled heads of 

 which are seen at the upper part of the instrument. The fitting 

 of the Wenham prism which produces the binocular effect, is 

 seen just above the nose-piece; by withdrawing it slightly, the 



