Louis Émile Javal

“ It is not enough to lay down a rule establishing the proportion which the surface of glass should bear to the number of pupils; attention must also be given to the direction whence the light comes to each pupil. The darkest point in the room must be light enough, and for this it is necessary that each desk shall receive a sufficiency of light direct from the sky. Every one who has practiced photography knows that the sky acts more strongly than any terrestrial body upon the sensitive surface. The least favored place in the room should be within the reach of this light. ”

“ Still, we must not demand of our organs the maximum of adaptation of which they are susceptible. If we read a book with the sun shining directly upon it, even if we do not injure the eyesight, we will disarrange the rate of adaptation, so that we will not be able for some time to see in a demi-obscurity. On the other hand, if we stay long in the dark, we may increase the sensibility of the retina so that a sudden return to daylight will be painful. ”

“ Even after we have properly proportioned the height of the windows to the size of the room, if there is a neighboring building the height of which is precisely half the distance between its base and the middle of the schoolroom, the worst situated scholars will receive the light from only the upper half of the windows, and not enough of it. ”

“ In consequence of this remarkable aptitude, the eye is the reverse of a good photometric apparatus. Enormous changes in the intensity of light pass unperceived by it, and we are able to attend to our occupations undisturbed by the fluctuations which are constantly taking place. ”

“ Bearing these facts in mind, we should keep the direct rays of the sun out from workshops and schoolrooms, where the place of each person is fixed, and should not make our bedrooms too dark, lest the eye be worried by sudden changes. ”

“ Adults are less liable than children to suffer injury from insufficient light, for several reasons: 1. Their pupils being less dilatable, they are obliged to desist from their work sooner when the light diminishes; 2. They make more frequent use of glasses; 3. They are less often confined, like school-children, and compelled to continue their labors after the light has become insufficient ”

“ Less perfect eyes, on the other hand, not being able to perform their functions with ease, have to make fatiguing efforts to accommodate themselves to the situation, which tend to increase existing defects or to induce short-sightedness. ”

“ We have, then, to establish the rule that a free space must be reserved on either side of the schoolroom, the width of which, measuring from the middle of the room, shall not be less than twice the height of the largest building that is likely to be put up near it. ”