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Updated: June 6, 2025
By far the most abundant was the little bundle of silicious rods, fastened together loosely at one end, separating from one another at the other end, and the whole bundle loosely twisted into a spindle. The rods are hollow, and contain the characteristic endochrome of the Diatomaceoe.
The purity and fineness of the material thus employed is very remarkable, as well as its strength, of which advantage was taken to make the cylinders hollow, and thus at once to render them cheaper and more portable. The terra cotta of the cylinders and tablets is sometimes unglazed; sometimes the natural surface has been covered with a "vitreous silicious glaze or white coating."
The fantastic helmets of the chiefs glittered with gold and precious stones, and their plumes were set with emeralds. The Mexicans carved the obdurate jade and emerald with wonderful skill, using, like the Peruvians, nothing but silicious powder and copper instruments alloyed with tin.
Iron in the early times is seemingly unknown, and when it first appears is wrought into ornaments for the person. They indicate some practical knowledge of the cleavage of silicious rocks, but they show no power of producing even such finish as the celts frequently exhibit. In one case only has a flint instrument been discovered perfectly regular in form, and presenting a sharp angular exactness.
When the embryo has become partly developed, it detaches itself from the parent sponge, and, issuing from the oscula, propels itself through the water by means of a number of flagella. Silicious spicules next appear in its structure, and it then attaches itself to a rock and assumes its mature form.
Associated with the geysers are numerous hot springs, some clear, some turbid, and variously impregnated with iron, sulphur or alum. In Nevada the Steamboat Springs, as they are designated, exist in Washoe Valley, east of the Virginian range. They come nearer in character to the Yellowstone geysers, their waters depositing true geyserite, or silicious concretions.
In situations where the sand is driven through depressions in rock-beds, or over deposits of silicious pebbles, the surface of the stone is worn and smoothed much more effectually than it could be by running water, and I have picked up, in such localities, rounded, irregularly broken fragments of agate, which had received from the attrition of the sand as fine a polish as could be given them by the wheel of the lapidary.
In the great intermediate zone, occupying some 110° of latitude, which separates the circumpolar Arctic and Antarctic areas of silicious deposit, the Diatoms and Radiolaria of the surface water and the sponges of the bottom do not die out, and, so far as some forms are concerned, do not even appear to diminish in total number; though, on a rough estimate, it would appear that the proportion of Radiolaria to Diatoms is much greater than in the colder seas.
It is nothing less than flint, which the roots of the maple absorbed, while it was dissolved in water in the soil. The sap, still holding the flint in solution, flows out, clear as water, when the tree is tapped; but when it is concentrated by boiling, the silicious mineral is deposited in little crystals, so that the bottom of the pan appears to be covered with sand.
These silicious bodies belong partly to the lowly vegetable organisms which are called Diatomaceæ, and partly to the minute, and extremely simple, animals, termed Radiolaria. It is quite certain that these creatures do not live at the bottom of the ocean, but at its surface where they may be obtained in prodigious numbers by the use of a properly constructed net.
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