CHAPTER XXVIII 

 PHOTOGRAPHY AND THE CHEMICAL ACTION OF LIGHT 



The magic of the sun. Ribbons and dresses washed and 

 hung in the sun fade; when washed and hung in the shade, 

 they are not so apt to lose their color. Clothes are laid away 

 in drawers and hung in closets not only for protection against 

 dust, but also against the well-known power of light to weakei 

 color. 



Many housewives lower the window shades that the wall 

 paper may not lose its brilliancy, that the beautiful hues of 

 velvet, satin, and plush tapestry may not be marred by loss in 

 brilliancy and sheen. Bright carpets and rugs are sometim< 

 bought in preference to more delicately tinted ones, becaus 

 the purchaser knows that the latter will fade quickly if used 

 in a sunny room, and will soon acquire a dull mellow tone. 

 The bright and gay colors and the dull and somber colors are all ! 

 affected by the sun, but why one should be affected more 

 than another we do not know. Thousands of brilliant and 

 dainty hues catch our eye in the shop and on the street, but 

 not one of them is absolutely permanent ; some may last for 

 years, but there is always more or less fading in time. 



Sunlight causes many strange, unexplained effects. If the 

 two substances, chlorine and hydrogen, are mixed in a dark 

 room, nothing remarkable occurs any more than though water 

 and milk were mixed, but if a mixture of these substances is 

 exposed to sunlight, a violent explosion occurs and an entirely 

 new . substance is formed, a compound entirely different in 

 character from either of its components. 



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