The Story of a Piece of Coal - What It Is, Whence It Comes, and Whither It Goes by Edward A. Martin
page 26 of 147 (17%)
page 26 of 147 (17%)
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strata.
In South Wales the coal-bearing strata have been estimated at between 11,000 and 12,000 feet, yet amongst this enormous thickness of strata, the whole of the various coal-seams, if taken together, probably does not amount to more than 120 feet. This great disproportion between the total thickness and the thickness of coal itself shows itself in every coal-field that has been worked, and when a single seam of coal is discovered attaining a thickness of 9 or 10 feet, it is so unusual a thing in Great Britain as to cause it to be known as the "nine" or "ten-foot seam," as the case may be. Although abroad many seams are found which are of greater thicknesses, yet similarly the other portions of the formation are proportionately greater. It is not possible therefore to realise completely the significance of the coal-beds themselves unless there is also a knowledge of the remaining constituents of the whole formation. The strata found in the various coal-fields differ considerably amongst themselves in character. There are, however, certain well-defined characteristics which find representation in most of the principal coal-fields, whether British or European. Professor Hull classifies these carboniferous beds as follows:-- UPPER CARBONIFEROUS. _Upper coal-measures._ Reddish and purple sandstones, red and grey clays and shales, thin bands of coal, ironstone and limestone, with _spirorbis_ and fish. _Middle coal-measures._ |
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