# Popular Science Monthly/Volume 53/September 1898/Minor Paragraphs

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By availing himself of the properties of surface tension, M. Charles Henry has discovered a method of producing permanent coloration by the use of light-colors, without the aid of any pigment. Liquids having a superficial tension less than that of water are deposited on water in thin layers, where they reflect the colors of the spectrum. By whistling over this layer we obtain for each tone a vibration which is responded to by a special coloration, and a kind of molecular landscape is produced. The liquid, however, soon evaporates, and the play of colors vanishes. In order to preserve the colors, a fixed excipient is introduced into the liquid, which will retain the thickness of the pellicular layer, and the colors as well, after the essence has evaporated. Some resin or coal-tar substance is used for this, giving permanence to the pellicle and the picture. M. Henry has further devised a process for producing this pellicle and picture upon a solid foundation, as of wood, glass, or paper, and even for accomplishing it by mechanical processes. The nature of the ground in which the picture-pellicle is laid has much to do with its character. Dark grounds give intense colors, white grounds lighter ones, and grounds of intermediate colors various shades. The process is called iri chromatime.
The images left by uranium upon a sensitive plate locked up with it in the dark may be regarded as an effect of the fluorescent property that metal is known to possess. Dr. Russell has, however, described to the Royal Society experiments from which it appears that mercury, zinc, magnesium, cadmium, aluminum, nickel, pewter, bismuth, lead, tin, antimony, and cobalt give out radiations capable of affecting the sensitive plate, and will leave images of themselves after standing upon one in the dark for about a week, although they possess no evident luminosity. Gold, platinum, and iron exhibit little or no power of the kind. A figure scratched upon the polished face of a sheet of zinc repeated itself. The interposition of a coat of varnish between the metal and the plate served to increase the effect, while glass, which makes no difference when uranium is applied, stopped the action with the other metals. Some non-metallic substances, such as straw, wood, charcoal, and printer's ink, presented the same property of leaving images. A section of young larch wood printed its formation clearly on a plate, so that the rings and bark could be made out. In many cases the activity was increased by heating the body, and diminished by cooling it.
A silicified tree is described by Lewis Woolman in the Report of the Geological Survey of New Jersey which lies in the orange-colored sand near Lindenwold in that State. The farmer of the land having regularly plowed up pieces of silicified wood, Mr. Woolman and his friends dug for the ​stump. It measured seven feet six inches across at the base, which had been much broken by the plow, tapering to five feet two inches twelve feet higher up. Beyond this the central part of the trunk was missing, but the outer parts continued as two parallel arms, in line with the lower part of the trunk, to a total length of twenty-six feet. The silicification was perfect, and the rings of annual growth were plainly shown. An average of seventeen annual rings to the inch was determined, and the age of the tree when it fell was approximately estimated at six hundred years. Fragments split lengthwise and those broken directly across showed beautifully the structure of wood, and this is more minutely defined under the microscope. The orange-colored sand bed in which the trunk was buried, and the grounds of lighter yellow that overlie it near by, are known to have at least a local wide distribution.