A System of Mineralogy Comprising the Most Recent Discoveries


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Seite 143 - Let a mass of matter be supposed to consist of spherical particles all of the same size, but of two different kinds in equal numbers, represented by black and white balls; and let it be required that, in their perfect intermixture, every black ball shall be equally distant from all surrounding white balls, and that all adjacent balls of the same denomination shall also be equidistant from each other.
Seite 28 - A Report to the Navy Department of the United States on American Coals, Applicable to Steam Navigation, and to other purposes.
Seite 98 - Is the projection of crystals, the eye is supposed to be at an infinite distance, so that the rays of light fall from it on the crystal in parallel lines. The plane on which the crystal is projected is termed the plane of projection.
Seite 12 - ... reduced to a manageable quantity the gold is amalgamated with clean mercury ; the amalgam is next strained to separate any excess of mercury, and finally is heated and the mercury expelled, leaving the gold.* In this way by successive trials with the rock, the proportion of gold is quite accurately ascertained.
Seite 148 - a flinty slate, black, grey or white,"8 but a "velvet black siliceous stone or flinty jasper used on account of its hardness and black color for trying the purity of precious metals. The color left on the stone after rubbing the metal across it indicates to the experienced eye the amount of the alloy.
Seite 168 - CD is the sine of the angle CED, which is the angle of refraction. This principle may therefore be thus stated : The sine of the angle of incidence bears a constant ratio to the sine of tlw angle of refraction.
Seite 167 - AE ; or, if we consider the ray as passing from the water into the air, the part, AE, is farther from the same perpendicular than if it had proceeded in the original direction DE. We have therefore this important principle : Light, in passing from a rarer to a denser medium, is refracted TOWARDS the perpendicular ; if from a denser to a rarer, it is refracted FROM the perpendicular.
Seite 147 - Milky quartz, as the name implies, has a milk-white color. It is a massive vitreous variety, and one of the most common. It has sometimes a greasy lustre, and is then called greasy quartz.

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