Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/64

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SECONDARY SERIES.

forms and extinct species, which were swept from the earth ere the formation of the transition strata was completed Our instruments of cutlery, the tools of our mechanics, and the countless machines which we construct, by the infinitely varied applications of iron, are derived from ore, for the most part coeval with, or more ancient than the fuel, by the aid of which we reduce it to its metallic state, and apply it to innumerable uses in the economy of human life. Thus, from the wreck of forests that waved upon the surface of the primeval lands, and from ferruginous mud that was lodged at the bottom of the primeval waters, we derive our chief supplies of coal and iron; those two fundamental elements of art and industry, which contribute more than any other mineral production of the earth, tot increase the riches, and multiply the comforts, and ameliorate the condition of mankind.





CHAPTER VIII.


Strata of the Secondary Series.

We may consider the history of secondary, and also of tertiary strata, in two points of view: the one, respecting their actual state as dry land, destined to be the habitation of man; the other, regarding their prior condition, whilst in progress of formation at the bottom of the waters, and occupied by crowds of organic beings in the enjoyment of life.[1]

  1.  The secondary strata are composed of extensive beds of sand and sandstone, mixed occasionally with pebbles, and alternating with deposites of clay, and marl, and limestone. The materials of most of these strata appear to have been derived from the detritus of primary and transition rocks; and the larger fragments, which are preserved in the form of pebbles,