Page:Popular Science Monthly Volume 44.djvu/373

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the color of light can be found in more prosaic subjects. Buildings offer examples. Ordinary brick and stone often have more influence than is imagined upon the light that enters windows. A brilliant although exceptional example of this occurred once in the writer's office. It has an eastern exposure and nearly opposite, at a distance of over one hundred feet, is a large red-brick building. The sky area exceeds all others, and ordinarily the amount of gray or light-blue light entering is enough to entirely overcome the effect of the red surface. On this special occasion, however, after a rainy day the sun suddenly burst through the clouds. The face of the building was illuminated by clear white sunlight, and stood out brilliantly against a backing of heavy, dark clouds. The effect in the office was most noticeable. Where had been nothing but a cold gray light in an instant a glare of red was cast over everything. Table and book that had been dull looked warm in color, and the walls appeared, as if by magic, in the most delicate rose tint fit for a fairy's boudoir. True, these were conditions most admirably adapted to illustrate the point that surfaces opposite windows can affect the quality as well as the intensity of the light reflected, but others more common lead to the same conclusion.

An excellent opportunity for alternating contrast is offered by a ride on an elevated city railway. Let one select a time in the afternoon when the eastern sky is not so bright as to obliterate the effect, and seat himself on the right-hand side of a down-town train in New York city. If the buildings are not too far removed from the track, a very decided change is noticed as each block is passed. Where the opening of the street brings a considerable sky area into view an ordinary gray light is cast upon the newspaper. This is succeeded by a sudden flush of rose as a high block of red-brick buildings is passed, and again a street opening allows the western sky to assert itself. Moreover, let it be noted that this may occur not with a bright sunlight pouring upon the buildings, but when they are in shadow, except as the eastern sky illuminates them.

Occasionally the effect of surfaces opposite the windows upon the color of the light can be noticed inside of buildings, even with no exceptional atmospheric conditions existing. On any clear day, by limiting the rays striking a marble slab in a certain room chiefly to those from a brick building opposite, one can change the white marble to a deep rose tint of a most beautiful shade.

These various illustrations have many corroborations in experience. They show that the light entering windows must be considerably influenced in color by reflecting surfaces opposite, even though the effect be not noticeable. Usually this is not a