744 POPULAR SCIENCE MONTHLY. 



whereby the direction of the parts of the rays making the image are 

 so modified as to restore the picture about to be formed to normality. 

 Plus is met by minus, minus by plus, astigmatic one-sidedness by its 

 reverse. If the living eye were a dead mechanical one, if it were not 

 subject to many diseases, if the results of eyestrain did not end in a 

 multitude of diseases of the entire body and mind, then the optician 

 might learn to prescribe glasses. But even for the highest medical 

 intellect the work is a science and art demanding his best powers. 

 Some one said that there are nine and forty distinct and separate ways 

 of achieving damnation, while there is but one of salvation. There are 

 twice that number of separate ways of failing to get right spectacles, 

 and seventy-eight of them are set forth by an American oculist, reasons 

 being given why, if any one is neglected, there will be no relief of 

 eyestrain. Even if the physician's prescription is right, even if the 

 lenses are properly ground and mounted, even if the spectacles are 

 properly adjusted to the wearer's peculiarities of face, etc. — and these 

 are all hazardous suppositions — there remains the wearer's carelessness, 

 prejudices and ignorances, to thwart the entire proceeding. There are 

 microscopists, and astronomers who will spend lifetimes of self and 

 others, in care to correct the optical inaccuracies of their microscopes 

 and telescopes, and yet whose own eyes that look through the instru- 

 ments have far more glaring optical defects than Clark eliminated from 

 his objectives by years of patient labor. The eye that sees everything 

 can not see itself. So slow is man to study the student, himself. He 

 will even investigate the brain and its functions before he will the eye : 

 although embryology demonstrates that it was the brain which develop- 

 mentally came out to see ; the eye did not at first exist apart from the 

 brain, and then send in to the mind the message of its discoveries. 

 When once the million threads of brain substance were pushed out to 

 the surface, the product called intellect resulted. For all useful think- 

 ing is in visual terms, and the sine qua non of civilization, the alphabet, 

 is only a series of conventionalized pictures of things seen. The prob- 

 lem of our being here, the primal conditions of organic and social evolu- 

 tion, have depended and will always depend upon visual function. Is it 

 then to be wondered at that our difficulties, bodily and social, our dis- 

 eases, imperfections, our wants, failures and miseries, most frequently 

 have also their source in visual difficulties and imperfections? Error 

 is the softest and best word we have for human failure to reach the best 

 attainable aims and ideals. It is more than an accident that the tech- 

 nical name for the great mass of ocular woes, and for the causes of 

 multitudes of others, is ' errors of refraction.' The compulsion of fate 

 as well as an error of evolution has brought it about that the unaided 

 eye must persistently struggle against the astonishing difficulties and 

 errors inevitable in its structure, function and circumstance. This 

 struggle wrecks health, happiness and life, because by no device can the 



