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abundant accessory action alumina amount analyses andesites apatite augite basalt beds biotite black mica calcareous calcite carbonic acid Chemical Composition chlorite clay color common compact condition County crystalline crystals debris decomposed decomposition deposits described diabase dikes diorite disintegration dolomite earth's crust epidote eruptive rocks essential constituents feet feldspar feldspathic ferruginous fragmental gabbros geological given glassy gneiss grains granite granular gray ground-mass hornblende hydration igneous rocks inches iron oxides kaolin known lava less leucite lime limestone Liparite magma magnesia magnetite mainly material metamorphic mica microscope Mineral Composition nature nepheline occurs olivine organic matter original orthoclase particles peridotites plagioclase Plate porphyritic portions potash proportion pyrite pyroxene quartz quartz porphyries rarely regions residual rock masses sand sandstone schists secondary serpentine sesquioxide silicates silt soda soil soluble stone structure surface syenite tion trachyte U. S. Geol varieties varying volcanic weathering wholly
Page 387 - The earth is fast becoming an unfit home for its noblest inhabitant, and another era of equal human crime and human improvidence, and of like duration with that through which traces...
Page 381 - In many parts of England a weight of more than ten tons of dry earth annually passes through their bodies and is brought to the surface on each acre of land; so that the whole superficial bed of vegetable mould passes through their bodies in the course of every few years.
Page 387 - There are parts of Asia Minor, of Northern Africa, of Greece, and even of Alpine Europe, where the operation of causes set in action by man has brought the face of the earth to a desolation almost as complete as that of the moon ; and though, within that brief space of time which we call
Page 387 - When the forest is gone, the great reservoir of moisture stored up in its vegetable mold is evaporated, and returns only in deluges of rain to wash away the parched dust into which that mold has been converted.
Page 52 - Air-castle — and they have a' their different turns, and some can clink verses, wi' their tale, as weel as Rob Burns or Allan Ramsay — and some rin up hill and down dale, knapping the chucky stanes to pieces wi...
Page 386 - The high road has been several times turned to avoid this cavity, the enlargement of which is still proceeding, and the old line of road may be seen to have held its course directly over what is now the widest part of the ravine. In the perpendicular walls of this great chasm appear beds of clay and sand, r.ed, white, yellow, and green, produced by the decomposition in situ of hornblendic gneiss, with layers and veins of quartz, as before-mentioned, and of a rock consisting of quartz and felspar,...
Page 302 - ... which root at the bottom of the basins or swamps and send up their stems and leaves to the surface of the water or above it, where their substance becomes in the sunshine hard and woody. As these plants periodically decay, their remains, of course, drop to the bottom of the water ; and each year the process is repeated, with a more or less marked variation in the species of the plants. After a time the basins become filled by these successive accumulations of years or even centuries, and then...
Page 190 - The finest silt, when treated with a diluted acid to remove the iron stains, shows the remaining granules of quartz, feldspar and epidote beautifully fresh and with sharp, angular borders, the mica being, however, almost completely decolorized and resembling sericite more than biotite.