PROPER LIGHT.
3. The illumination should always be sufficient. Nothing is more injurious to the eyes than reading by a poor light. Many persons strain their eyes by reading on into the twilight as long as they possibly can. They become interested and do not like to leave off. Some read in the evening at too great a distance from the source of light, forgetting that the quantity of light diminishes as the square of the distance from the source of light increases. Thus, at four feet, one gets only one-sixteenth part of the light upon his page that he would at one foot. It is the duty of parents and others who have charge of children to see to it that they do not injure their eyes by reading by insufficient light, either daylight or artificial light. There is a common notion that electric light is bad for the eyes. The only foundation I can think of for such a notion is that it is trying to the eyes to gaze directly at the bright electric light. It is bad to gaze long at any source of light, and the brighter the source of light gazed at, the worse for the eyes, the sun being the worst of all. I have seen more than one person whose eyes were permanently injured by gazing at the sun, during an eclipse or otherwise. As a matter of fact, nothing short of sunlight is better than the incandescent electric light to read by or to work by.