Page:Popular Science Monthly Volume 67.djvu/750

744 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 instruments 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 developmentally 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 thinking is in visual terms, and the sine qua non of civilization, the alphabet, is only a series of conventionalized pictures of things seen. The problem of our being here, the primal conditions of organic and social evolution, have depended and will always depend upon visual function. Is it then to be wondered at that our difficulties, bodily and social, our diseases, 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 technical 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