622 THE POPULAR SCIENCE MONTHLY. 



direction apparently parallel to the horizon, I am now having an 

 object-lesson in optics with bodies whose apparent motion is at an 

 angle to the horizontal line. In both these cases the explanation 

 of the observed phenomena is precisely the same. The body of 

 the mountain represents the most distant objects on the level 

 desert, its base is the point of fixation, while the near objects are 

 between it and the receding train. 



The rails, sleepers, and the gravel fly past with a velocity 

 which apparently diminishes in the distance ; the mountain-base 

 is practically at a standstill, but beyond it is the prominent bulk 

 of the mountain itself, which appears to advance in obedience to 

 the laws we have just been considering. 



But my cerebral convolutions refuse to accept such evidence. 

 They insist, these maturer products of the evolutionary force, 

 that the organism has never had any experience of mountains 

 chasing railway trains. And so it happens that I, placing my 

 trust in an enlightened experience rather than in a report from 

 my childish optical centers, feel assured that this particular 

 mountain is not following us. 



The prevailing idea that the organ of vision is practically a 

 perfect piece of optical and nervous mechanism has done not a 

 little to discourage attempts to develop those wonderful powers 

 which it undoubtedly possesses. 



One may, by judicious education, train and improve an unde- 

 veloped sense, but what improvement can be wrought in a per- 

 fected organism ? 



Far too little has been done in this direction, not only among 

 children during school life, but in after-years spent at literary, 

 technical, or other institutions. Of course, it may be asserted that 

 the sense of sight, in conjunction with the other senses, receives 

 its due share of developmental training in the ordinary course of 

 general and sj)ecial instruction. But, as opposed to this, may be 

 urged, in the first place, the natural deficiencies of the eye, a few 

 of which have just been referred to ; and, in the second instance, 

 the splendid results which, despite these innate defects, are ob- 

 tainable by judicious training — results richer far than any other 

 sense is capable of attaining. 



This plea for a systematic exercise of the visual functions does 

 not exclude the payment of proper attention to the other senses. 

 It is asserted merely that our knowledge would be more complete 

 if a larger proportion of the time and attention given to the culti- 

 vation of the special senses were devoted to the development of 

 the capable but congenitally deficient organ of vision. 



As a preliminary to this there should never be forgotten the 

 care of sight. A great deal has been said (and too much, perhaps, 

 can not be said) about the importance of ocular hygiene, especial- 



