Since direct rays of the sun give more light than those reflected, it is desirable to admit them to the house as much as possible rather than to depend upon reflected light from the surfaces outside, such as the trees and buildings. There is a certain loss of light as it passes through window glass. This loss is about 8% through plate glass while through double glass the loss is 10%, and through milk glass there is a loss of 50%. The amount of light in a room may be increased by the use of prism or ribbed glass which results in a more even distribution of light over the room. The window area of rooms in a home should be not less than 10% of the floor area, or not less than one square foot of glass surface for every seventy cubic feet of interior to be lighted. This is not sufficient, however, for a schoolroom or for factories. The schoolroom should have a window area not less than one-fourth of the floor space. Windows should be placed so as to admit direct rays of the sun and should extend within six inches of the ceiling. Window shades may be used to regulate the amount of light admitted, but care should be exercised in keeping down the dust, since it accumulates on the shades and is disturbed when they are adjusted. The dust then gets into the breathing zone and becomes objectionable from a hygienic standpoint. Artificial Lighting With the present day modern methods of artificial lighting it seems there would be little difficulty in lighting our homes and other buildings; but the question is not alone one of how they are to be lighted, but also how this can best be accomplished and not interfere with health and produce eye strain and other conditions that are likely to follow improper lighting. It is interesting to note the evolution of the lighting systems from the primitive man who carried a burning stick from the campfire into his cave and thus realized the pleasure of the privacy of his own dwelling, up to the modern lighting systems. For centuries man burned wood and other materials in their natural state and depended upon these for his illumination. Then it was discovered that by dipping this raw material in animal fat more light could be obtained. Later the oil was placed in a container and a wick used. Then from this crude grease lamp with its wick evolved the candle, which was a great improvement over the former method. And so mankind groped in comparative darkness through centuries. It was not until the closing years of the nineteenth century that he found a better means of illumination. In 1879 Edison brought out his wonderful invention, the electric light. Even the evolution of this light would be interesting for there have been many improvements over the original. It is very obvious that the best method of lighting is by the use of the incandescent electric light. It produces the desired intensity, does not vitiate the air, requires little attention, and is operated at a minimum expense.