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Updated: June 20, 2025
The trade gradually increased, until we find as many as 150 pots and kettles cast in a week. An abundance of coals existed in the neighbourhood: by rejecting those of inferior quality, and coking the others with great care, a combustible was obtained better fitted even than charcoal itself for the fusion of that particular kind of ore which is found in the coal-measures.
But what I should like you to remember is that geologists of our own time tell us that the lowest layer of the earth's crust which has yet been explored appears to be made of vegetable remains, so crushed and altered by time and by the tremendous pressure of rocky layers lying above it, that though it is probably of the same material as that which forms the coal-measures, it resembles the blacklead of which pencils are made much more than the coal which you know is what has been formed by the decay of buried forests and jungles.
Dawson to 120, to which we may add about 80 from the European flora of the same age, so that already the vegetation of this period is beginning to be nearly half as rich as that of the coal-measures which have been studied for so much longer a time and over so much wider an area. The Psilophyton above alluded to is believed by Dr.
It is from these measures that almost all our commercial coals are obtained. This list of beds might be further curtailed for all practical purposes of the geologist, and the three great divisions of the system would thus stand: Upper Carboniferous, or Coal-measures proper. Millstone grit. Lower Carboniferous, or Mountain limestone.
It usually comprises two very distinct members: first, the sedimentary beds, usually called the Coal-measures, of mixed fresh-water, terrestrial, and marine origin, often including seams of coal; secondly, that named in England the Mountain or Carboniferous Limestone, of purely marine origin, and made up chiefly of corals, shells, and encrinites, and resting on shales called the shales of the Mountain Limestone.
In the south-western part of our island, in Somersetshire and South Wales, the three divisions usually spoken of are: 1. Coal-measures: strata of shale, sandstone, and grit, from 600 to 12,000 feet thick, with occasional seams of coal.
The imbedded fragments are both rounded and angular, some consisting of sandstone from the coal-measures, being of vast size, and weighing nearly a ton.
Such beds as there remain undoubtedly belong to the base of the coal-measures, and observations all go to show that the surface suffered such extreme denudation subsequent to the growth of the coal-forests, that the wealth which once lay there, has been swept away from the surface which formerly boasted of it.
Numerous specimens proper to the extinct order of labyrinthodontia have been arranged into at least a score of genera, these having been drawn from the coal-measures of Newcastle, Edinburgh, Kilkenny, Saärbruck, Bavaria, Pennsylvania, and elsewhere.
A core of old red sandstone, which occasionally crops out at the surface, and through which in one spot, near Downhead, a vein of igneous rock has forced its way, is thickly coated with a crust of mountain limestone. The once superincumbent coal-measures are huddled together on one side in a confused heap near Radstock, and on the other are probably buried beneath the Glastonbury marshes.
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