WINDOW LIGHTS AND THEIR VALUE. 355 



power, he will probably speak of the sky first as the great source 

 of light to the window. Tlien, if he does not ignore them alto- 

 gether, the objects on the earth are grouped in one class of com- 

 paratively little importance. This is not Nature's method. There 

 is no sharp division between the strong reflecting surfaces and 

 the weak, between the sky and the earth. "We are prone to such 

 a distinction, because the sky seems prominent as a reflecting sur- 

 face, but it can be shown that circumstances arise when this is by 

 no means true. 



Imagine the window to look out upon a landscape. Earth, foli- 

 age, and sky all combine to reflect light into the room. The 

 water may be very dark, from the shadow of overhanging trees, 

 reflecting less than ten per cent as much light as comes from the 

 sky, but there is a path across it where the sunlight is cast back 

 far more brilliant than the sky itself. The beaten highway gleams 

 in the sun so that it is a relief to look away from it into the blue 

 above. Even the foliage, delightfully dark and cool in the shad- 

 ows, may have a brightness where the sunlight strikes it which is 

 fifty or eighty per cent of the intensity of sky light. 



On turning from the country to the city view we find the less- 

 ened importance of the sky as a source of light especially empha- 

 sized. There the great value of space causes one building to en- 

 croach upon the sky light of another until frequently the patch of 

 blue visible from the windows is limited to a mere streak, or may 

 be cut off entirely. If the sky were the only means of lighting, 

 the windows would be useless in such cases; but the fronts of 

 buildings, the paved streets, and other surfaces combine to throw 

 much light into them, and give a reason for their existence. 



The reflecting power of the sky dome is due almost entirely to 

 the particles of vapor contained in the atmosphere, and hence must 

 be considerably affected by changes in its aqueous condition. Con- 

 trary to what might be imagined, the clearer the sky the less valu- 

 able is it as a reflector. The more haze that it contains within 

 limits the more intense the light obtained from it. An observer 

 will recall dreamy summer days when the sun has seemed to shine 

 softly as through a gauze cast over its face and the shadows were 

 mellowed and diffused, yet the sky was white with a radiance 

 painful to the eye. There was little suggestion of ethereal blue 

 in the white light sent down from this atmosphere charged with 

 particles of moisture. Again, a clear day comes ; the air fairly 

 dances with brilliancy, and distant objects stand out in the sun- 

 light as clear-cut as a silhouette. The sky is a beautiful Italian 

 blue, but does it occur to one how really dark it is except in the 

 immediate vicinity of the sun ? Try to match it with a sheet of 

 blue paper, and it is almost startling to discover what a somber 

 surface the sky dome is. Its value as a source of light is greatly 



