A Treatise on Rocks, Rock-weathering and Soils |
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abundant action alkalies alumina Alumina Al2O3 amount analyses andesites apatite augite basalt beds black mica boulders calcareous calcite carbonic acid chemical composition chlorite clay color compact condition containing County crystalline crystals débris decomposed decomposition deposits depth derived described diabase dikes diorite disintegration dolomite epidote eruptive rocks essential constituents feet feldspar feldspathic ferruginous formation fragments fresh gabbros geological given glacial glassy gneiss grains granite granular granules gravel hornblende hydration inches insoluble iron oxides kaolin less leucite Lime CaO limestone loess magnesia Magnesia MgO mainly material metamorphic mica microscope mineral nature nepheline occurs olivine organic matter original orthoclase particles percentage plagioclase plant porphyritic portions potash Potash K2O proportion pyroxene quartz regions residual rock masses sand sandstone schists serpentine sesquioxide Silica SiO2 silicates silt Soda Na2O soil soluble stone structure surface syenite tion U. S. Geol varieties varying volcanic weathering wholly
Popular passages
Page 398 - 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 v - THE ruins of an older world are visible in the present structure of our planet ; and the strata which now compose our continents have been once beneath the sea, and were formed out of the waste of pre-existing continents.
Page 398 - 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 10 - ... considerable numbers, but minute quantities. It is customary to speak of those minerals which form the chief ingredients of any rock, and which may be regarded as characteristic of any particular variety, as the essential constituents, while those which occur in but small quantities, and whose presence or absence does not fundamentally affect its character, are called accessory constituents. The accessory mineral which predominates, and which is, as a rule, present in such quantities as to be...
Page 398 - ... with an equable distribution of rain through the seasons, and a moderate and regular inclination of surface — the whole earth, unless rescued by human art from the physical degradation to which it tends, becomes am assemblage of bald mountains, of barren, ttirfless hills, and of swampy and malarious plains.
Page 397 - 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 56 - 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 211 - 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.
Page 124 - State, each square mile would, in that case, yield 7,500,000 barrels, or one-fortieth of the total product of the entire oil field. These figures pass at once beyond clear comprehension, but they serve to give us some idea of the vast stock of petroleum contained in the earth's crust. If petroleum is generally distributed through a considerable series of rocks in any appreciable percentage, it is easy to see that the aggregate amount must be immense. Even...