The stage as a whole is a mobile picture in light, shade, and color with the addition of words and music.  Excepting the latter, it is an expression of light worthy of the same care and consideration that the painting, which is also an expression of light, receives from the artist.  The scenery and costumes should be considered in terms of the lighting effects because they are affected by changes in the color of the light.  In fact, the author showed a number of years ago that by carefully relating the colors of the light with the colors used in painting the scenery, a complete change of scene can be obtained by merely changing the color of the light.  Rather wonderful dissolving effects can be produced in this manner without shifting scenery.  For example, a warm summer scene with trees in full foliage under a yellow light may be changed under a bluish light to a winter scene with ground covered with snow and trees barren of leaves.  But before such accomplishments can be realized upon the stage, scientific knowledge must be available behind the scenes.

The art museum affords a multitude of opportunities for utilizing the expressiveness of light.  This is more generally true of sculptured objects than of paintings because the latter may be treated as a whole.  The artist almost invariably paints a picture by daylight and unless it is illuminated by daylight it is altered in appearance, that is, it becomes another picture.  The great difference in the appearance of a painting under daylight and ordinary artificial light is quite startling, when demonstrated by means of apparatus in which the two effects may be rapidly alternated.  Art museums are supposed to exhibit the works of artists and, therefore, no changes in these works should be tolerated if they can be avoided.  The modern artificial-daylight lamps make it possible to illuminate galleries with light at night which approximates daylight.  A further advantage of artificial light is that it may be easily controlled and a more satisfactory lighting may be obtained than with natural light.  Considering the cost of daylight in museums and its disadvantages it appears possible that artificial daylight with its advantages may replace it eventually in the large galleries.  If the works of artists are really prized for their appearance, the lighting of them is very important.

Sculpture is modeled by light and although it is impossible to ascertain the lighting under which the sculptor viewed his completed work with pride and satisfaction, it is possible to give the best consideration to its lighting in its final place of exhibition.  The appearance of a sculpture depends upon the dominant direction of the light, the solid-angle subtended by the light-source (skylight, area of sky, etc.) and the amount of scattered light.  The direction of dominant light determines the general direction of the shadows; the solid-angle of the light-source affects the character of the edges of the shadows;