CHAPTER V 

 THE MONOCULAR MICROSCOPE 



Advantages. — Doubtless monocular microscopes will long 

 continue to be employed, notwithstanding the deserved 

 popularity of the binocular instruments. Although monoc- 

 ular microscopes have several disadvantages connected 

 with their use, yet they possess the following advantages: 

 The tube length, when not fixed, can be increased (by per- 

 haps 5 centimeters), and to a less degree (about 1 centi- 

 meter) shortened, to compensate for thinner or thicker 

 cover-glasses, or for mounting media of different refrangi- 

 bilities. There is doubtless in the binocular microscope 

 some slight loss of definition, due to the use of prisms ; and 

 though more can be seen with two eyes than with one for 

 long periods of observation, yet for the best vision for short 

 periods the monocular must probably be used. The 

 monocular has physically double the brightness (ceteris 

 paribus). It thus allows the use of denser color screens, 

 which give light more nearly monochromatic. The monoc- 

 ular alone is suited for photography. 



The Unoccupied Eye. — The monocular microscope, in 

 the writer's opinion, is best used with a frame fitted below 

 the eyepiece, bearing a disc of ground glass to compensate 

 the unemployed eye (see Chap. I). The training of the 

 unused eye to ignore what it sees, is, in the writer's view, 

 a mistake. The absence of discomfort on this account 

 seems to be one of the factors which make the monobjective 

 binocular superior in comfort to the ordinary monocular. 

 In fact, after practice, a microscope in which the unoccupied 

 eye is compensated by being allowed sufficient light, but 

 prevented from focusing on (accommodating for) any 

 object, so that it is led to follow- the other eye in this, may 

 be, to some observers, nearly as comfortable as the binocu- 



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