Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/62

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58

TRANSITION SERIES.

The strata in which these vegetable remains have been collected together in such vast abundance have been justly designated by the name of the carboniferous order, or great coal formation. (See Conybeare and Phillips's Geology of England and Wales, book iii.) It is in this formation chiefly, that the remains of plants of a former world have been preserved and converted into beds of mineral coal; having been transported to the bottom of former seas and estuaries, or lakes, and buried in beds of sand and mud, which have since been changed into sandstone and shale. (See Pl. 1, sec. 14.)^[1]

↑ The most characteristic type that exists in this country of the general condition and circumstances of the strata composing the great carhoniferous order, is found in the north of England. It appears from Mr. Forster's section of the strata from Newcastle-upon-Tyne to Cross Fell, in Cumberland, that their united thickness along this line exceeds 4,000 feet. This enormous mass is composed of alternating beds of shale or indurated clay, sandstone, limestone, and coal: the coal is most abundant in the upper part of the series, near Newcastle and Durham, and the limestone predominates towards the lower part; the individual strata enumerated by Forster, are thirty-two beds of coal, sixty-two of sandstone, seventeen of limestone, one intruding bed of trap, and one hundred and twenty-eight beds of shale and clay. The animal remains hitherto noticed in the limestone beds are almost exclusively marine; hence we infer that these strata were deposited at the bottom of the sea. The fresh-water shells that occur occasionally in the upper regions of this great series show that these more recent portions of the coal formation were deposited in water that was either brackish or entirely fresh. It has lately been shown that fresh water deposites occur also occasionally in the lower regions of the carboniferous series. (See Dr. Hibbert's account of the limestone of Burdie House, near Edinburgh; Transactions of the Royal Society of Edinburgh, vol. xiii.; and Professor Phillips's Notice of fresh-water shells of the genus Unio, in the lower part of the coal series of Yorkshire; London Phil. Mag. Nov. 1832, 349.) The causes which collected these vegetables in beds thus piled above each other, and separated by strata of vast thickness, composed of drilled sand and clay, receive illustration from the manner in which drifted timber from the existing forests of America is now accumulated in the estuaries of the great rivers of that continent, particularly in the estuary of the Mississippi, and on the River Mackenzie. See Lyell's Principles of Geology, 3d edit.

[p58r1-1] The most characteristic type that exists in this country of the general condition and circumstances of the strata composing the great carhoniferous order, is found in the north of England. It appears from Mr. Forster's section of the strata from Newcastle-upon-Tyne to Cross Fell, in Cumberland, that their united thickness along this line exceeds 4,000 feet. This enormous mass is composed of alternating beds of shale or indurated clay, sandstone, limestone, and coal: the coal is most abundant in the upper part of the series, near Newcastle and Durham, and the limestone predominates towards the lower part; the individual strata enumerated by Forster, are thirty-two beds of coal, sixty-two of sandstone, seventeen of limestone, one intruding bed of trap, and one hundred and twenty-eight beds of shale and clay. The animal remains hitherto noticed in the limestone beds are almost exclusively marine; hence we infer that these strata were deposited at the bottom of the sea. The fresh-water shells that occur occasionally in the upper regions of this great series show that these more recent portions of the coal formation were deposited in water that was either brackish or entirely fresh. It has lately been shown that fresh water deposites occur also occasionally in the lower regions of the carboniferous series. (See Dr. Hibbert's account of the limestone of Burdie House, near Edinburgh; Transactions of the Royal Society of Edinburgh, vol. xiii.; and Professor Phillips's Notice of fresh-water shells of the genus Unio, in the lower part of the coal series of Yorkshire; London Phil. Mag. Nov. 1832, 349.) The causes which collected these vegetables in beds thus piled above each other, and separated by strata of vast thickness, composed of drilled sand and clay, receive illustration from the manner in which drifted timber from the existing forests of America is now accumulated in the estuaries of the great rivers of that continent, particularly in the estuary of the Mississippi, and on the River Mackenzie. See Lyell's Principles of Geology, 3d edit.

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