Page:Popular Science Monthly Volume 23.djvu/859

Rh pulverization. Deep dark-blue smalt can be converted into a perfectly colorless powder by being pulverized and washed, and no one would recognize it as being identical with the coarsely grained original article. Gold-powder, in its most minute division, does not possess the known yellow color of the metal, but a bluish-green shade, and at first glance would not be held to be metallic gold until the blue-green powder, when fused, reassumes its yellow color. When we introduce a film of gold between two transparent pieces of glass, and hold it against the sun, the rays of the latter will shine through with a bluish-green color; this transparency of gold, however, only occurs when the film is of a line, or less, in thickness. It is indisputable that in the two instances mentioned here the appearance of color depends upon the minute mechanical division of the pigment, and with this is also connected the alteration in the color of solid bodies, when converted into gas or air. In a gaseous (therefore a very minutely divided) condition, black iodine becomes violet, yellow sulphur red, blue indigo purple. All these instances, to which numerous others might easily be added, prove the intimate connection between color and form. According to my opinion, some similar process, as far as regards form and division, possibly occurs in vegetable nature, and exerts its influence upon the multiplicity of color-shades.

Flower pigments, almost without an exception, are so inconstant and transient that they can not be employed in our industries. They, the children of light, separated from a vital union with the plant, no longer resist the effect of light—they wither and bleach in it. This is unhappily true with the most universally found of all—the leaf-green (chlorophyl). If this pigment could by some means be changed into a fast dye, the poisonous Swinefurt, or Paris-green, would have seen its last days. What an incomparable color is contained in the safflower (Carthamus tinctorius), which, although used as a beautiful rose in the dyeing of silk, is unhappily of an unstable nature! The same is true of the splendid yellow of the flowers of the wild Reseda luteola. This plant, in spite of the instability of its color, is cultivated in France, England, and different parts of Germany. The white color of various flowers—lilies, roses, and others—is generally produced by a white cellular juice, but may also be due to a white pigment, artholeucine, suspended in the colorless cell-juice. These white flowers would offer most suitable material for researches, if the experimental conversion of colors were undertaken. When undecomposed light is reflected by a body, its color appears to us as white. White, therefore, is no actual color, but simply a union of all colors, or the collective rays of light in an unseparated combination. By an alteration of the chemical combination in the plant, by means of an appropriate manure, it becomes possible to cause the fibers of the white petals no longer to reflect upon our eye an undivided white, but a divided colored ray. The yellow or orange coloring-matter of flowers,