Systems of Lighting Direct lighting is secured by fixtures which throw the light downward into the room from which the eyes are protected by properly adjusted shades. Indirect lighting is from bowl-like fixtures in which electric lights are placed and the light rays are reflected upward toward the ceiling with no light penetrating the bowl. Semi-indirect is accomplished by using a bowl which will permit some of the light rays to penetrate. The best results are obtained by a combination of the direct and indirect methods of lighting and in some cases by a semi-indirect way. It has been observed that the direct rays of light should not fall squarely into the eyes. It is also quite essential that in some cases there should be direct rays on the work or object under observation. To accomplish this and at the same time to keep the light out of the eyes there must be a judicial use of shades and other means of softening the light. There are some objections to the indirect method in that all the light is thrown on the ceiling. This gives a very soft light in the room, but is not sufficiently bright and faces lose their expression; there is insufficient modeling of objects, and the interior will be almost devoid of character. This form of lighting, therefore, is undesirable for home and offices, but is not objectionable for places of amusement. There are also objections to the direct system since the strong direct light makes too harsh shadows and a light glare which is very objectionable. By properly diffusing this direct light and adding sufficient upward light we get a much more effective and pleasing illumination. By using the two systems, or better still, by combining the two systems into the semi-indirect, a method is obtained which will furnish an abundance of light and at the same time give one that is so perfectly diffused there will be no objectionable shadows and no harmful glare. Insufficient light may be quite as injurious to the eyes as too much light. As a matter of fact it is not so much a question of too great an intensity as it is of the proper light direction; it is hardly possible to get a light of greater intensity than that of the sun, but we are very careful that the sun’s direct rays do not enter the unprotected eye; neither is it good to permit the reflection of the rays into the eyes, as from a printed page. (For schoolroom lighting see chapter on School Hygiene.) CHAPTER VII WATER WATER GENERAL CONSIDERATIONS NECESSITY FOR PROPER SUPPLY HISTORY OF PUBLIC SUPPLY COMPOSITION OF WATER CHEMICAL ELEMENTS FOREIGN INGREDIENTS STATES OF AGGREGATION UNIVERSAL SOLVENT NECESSITY FOR WATER IN BODY CHEMICALLY PURE WATER HOW OBTAINED TASTE OF WATER HARD AND SOFT WATER PERMANENT TEMPORARY ELIMINATION OF WATER FROM BODY AMOUNT OF WATER NEEDED FOR ALL PURPOSES FOR THE BODY FOR DOMESTIC PURPOSES FOR CITY USE