98 THK president's address. 



Every microscopist whose eyes are equal, recognises at once and 

 without difficulty the stereoscopic projection and apparent solid- 

 arity, and the infinitely greater beauty and perfection of form 

 which certain objects consequently present when viewed through 

 the "Wenham Binocular. Every one, also, who tries the experi- 

 ment readily becomes conscious of the fact that it is much more com- 

 fortable, — much less tiring to the eyes and brain, — to watch an ob- 

 ject for any length of time under the binocular than under the mon- 

 ocular microscope. The pleasure derived from increased perfection 

 of view, and the comfort arising from less urgent sense of fatigue, 

 are immediate advantages readily appreciated. The ulterior and, 

 as I think, greater advantage of the binocular, depends upon the 

 comparative safety with which it may be used. Frequent and, 

 from time to time, continuous use of the monocular microscope is 

 much more liable to result in permanent damage to the eyesight 

 than a corresponding use of the binocular. That it must be so is 

 obvious. Every one accustomed to the use of both eyes, who by 

 accident is for a time dependent upon one eye, or any one who, for 

 the sake of experiment, may choose to make himself thus dependent, 

 speedily finds out that one eye serves him less than half as Avell as 

 two, and much sooner becomes tired. In order that they may be 

 maintained in well-nourished, healthy condition, the eyes, like all 

 other organs of the body, must be used and exercised. Now exer- 

 cise and use may be continued with advantage and safety up to a 

 certain point. Beyond such point, which may be called the fatigue 

 point, exercise tends to exhaustion ; use becomes abuse ; and more 

 or less lasting damage is liable to result. Experience teaches us 

 that the fatigue point is reached much sooner when we use 

 the eyes singly, or either eye by itself, than when we use both to- 

 gether. But this is not all. We can see very well with one eye ; 

 we can see best, however, not simply when we use both eyes, but 

 when both eyes act precisely in unison. To preserve perfect 

 vision, therefore, the integrity of each eye must be maintained ; 

 and more than this, the natural sympathy and consentaneity of 

 action of the two must be kept up. Now, when we look at an 

 object under the monocular microscope the eye which we use is sub- 

 jected to very different conditions to the other. The eye which we 

 use " accommodates" and "adjusts" itself to the requirements of its 

 present purpose. The other eye at fii-st sympathises to a certain 

 extent ; but its external circumstances are altogether different ; 



