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Extensive deposits of lignite are met with both in the Dominion and in the United States, whilst true coal-measures flank both sides of the Rocky Mountains. Coal-seams are often encountered in the Arctic archipelago. The principal areas of deposit in South America are in Brazil, Uruguay, and Peru.
None of the reptiles obtained from the coal-measures of the South Joggins are of a higher grade than the Labyrinthodonts, but some of these were of very great size, two caudal vertebrae found by Mr. Marsh in 1862 measuring two and a half inches in diameter, and implying a gigantic aquatic reptile with a powerful swimming tail. Except some obscure traces of an insect found by Dr.
We have supplemented, but hardly given more life to, his picture of the first beginnings, by evidence drawn from a thousand sources then unknown or unexplored from coal-measures and mud-deposits, Pictish barrows and lacustrine middensteads, remote tribes of hidden Africa and islands of the Pacific Sea.
This is about three times the thickness contained in the South Wales coal-field, in a similar thickness of coal-measures. There are single seams up to 60 feet thick, but much of the coal is covered by more recent rocks of New Red and Cretaceous age.
Another engineering device, very necessary in a land where foundations are so frequently built under water, is the enclosed caisson with compressed air, as shown in detail in this exhibit. It was originally invented by M. Triger to keep the water expelled from the sheet-iron cylinders which he sunk through quick-sands in reaching the coal-measures in the vicinity of the river Loire in France.
Occasionally the layers of matter in the inside of the tree are more numerous than those without; but it is more common in the coal-measures of all countries to find a cylinder of pure sandstone the cast of the interior of a tree intersecting a great many alternating beds of shale and sandstone, which originally enveloped the trunk as it stood erect in the water.
Yet it is on the strength of community of fossils, that the whole Devonian series of the United States is assumed to be contemporaneous with the whole Devonian series of England. And it is partly on the ground that the Devonian of the United States corresponds in time with our own Devonian, that Sir Charles Lyell concludes the superjacent coal-measures of the two countries to be of the same age.
Dawson states that they are very similar to both taxus and salisburia.. They are abundant in some coal-measures, and are contained, not only in the coal itself, but also in the sandstones and shales.
Owing to the great igneous and volcanic activity at the close of the deposition of the carboniferous system of strata, the coal-measures exhibit what are known as faults in abundance. The mountain limestone, where it outcrops at the surface, is observed to be much jointed, so much so that the work of quarrying the limestone is greatly assisted by the jointed structure of the rock.
Upon the whole, it is evident that the Permian plants approach much nearer to the Carboniferous flora than to the Triassic; and the same may be said of the Permian fauna. Principal Subdivisions of the Carboniferous Group. Different Thickness of the sedimentary and calcareous Members in Scotland and the South of England. Coal-measures. Terrestrial Nature of the Growth of Coal. Erect fossil Trees.
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