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Many of the latter are magnetite, while the others are hornblende and various ferromagnesian silicates. I did not detect any fragments of volcanic origin. The specimen of argillaceous sandstone is made up of thin layers of fine-grained sand of the same sort as the first, alternating with others containing considerable clay.
The procedure given below applies to silicates undecomposable by acids, of which the mineral feldspar is taken as a typical example. The sieve may be made by placing a piece of the bolting cloth over the top of a small beaker in which the ground mineral is placed, holding the cloth in place by means of a rubber band below the lip of the beaker.
If, however, the silica is removed and the filtrates are again evaporated and the residue heated, the amount of silica remaining in solution is usually negligible, although several evaporations and filtrations are required with some silicates to insure absolute accuracy.
Let us get out of this before there's another avalanche or we shall be globular silicates and isometric crystals in spite of ourselves," whispered Steve with a panic-stricken air, and they fled from the hailstorm of hard words that rattled about their ears, leaving Mac to enjoy himself in his own way.
However, as you will remember, your soil is distinctly acid and consequently markedly in need of lime, the magnesium and calcium evidently being contained in part in the form of acid silicates with no carbonates; whereas, our brown silt loam is a neutral soil and our black clay loam contains much calcium carbonate, the same compound as pure limestone."
Thus the granite of Corsica degenerates into a powder in a time which scarcely suffices to deprive the polished granite of Heidelberg of its lustre. Some soils abound in silicates so readily decomposable, that in every one or two years, as much silicate of potash becomes soluble and fitted for assimilation as is required by the leaves and straw of a crop of wheat.
The two were standing now before the cylindrical furnace containing the mixture of silicates and other ingredients from which Tom Swift hoped would emerge a glass as flexible as rubber and as strong as steel. The thermometer on the front stood at twenty-one degrees Centigrade. "She's just right," muttered the inventor, consulting a complicated chart hanging on the wall. "Now we'll see!"
That store of silicates and alkalies which is the principal condition of their success is obtained, if potatoes or turnips are grown upon the same fields in the intermediate periods, since these crops do not abstract a particle of silica, and therefore leave the field equally fertile for the following crop of wheat.
The first table contains a very attractive collection of minerals, including the varieties of jasper; all kinds of opals the sun opal, the semi-opal, wood opal, and wood partially opalised. The second table is covered with varieties of Silicates of Lime, magnesia, and alumina; also soapstone, keffekil, or the meerschaum, highly esteemed by smokers, serpentine, chrysolite, &c.
Out of these numerous improvements, we select two that appear peculiarly attractive. The first is the method of precipitating the copper, in our second process, from the fused silicates containing it, by the action of the electric current the negative pole of the battery terminating in an iron plate, which replaces the copper in the liquid mass. The second method is an improvement on this.
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