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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.
Were our present forests uprooted and overthrown, to be covered by sedimentary deposits such as those which cover our coal-seams, the amount of coal which would be thereby formed for use in some future age, would amount to a thickness of perhaps two or three inches at most, and yet, in one coal-field alone, that of Westphalia, the 117 most important seams, if placed one above the other in immediate succession, would amount to no less than 294 feet of coal.
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.
Yet so minute are the shells of which it is composed, that one square inch of rock is said to contain about four thousand millions of them. Each one of these millions is a separate distinct fossil.... a. Sandstone, b. Shales, c. Coal-seams, d. If you examine carefully a piece of coal, you will find, more or less clearly, markings like those which are seen in a piece of wood.
Some of them seem to be still hopeful that it will follow as a necessary consequence from week-day services, ecclesiastical decoration, and improved hymn-books; others apparently trust to descanting on self-culture in general, or to raising a general sense of faulty circumstances; and meanwhile lax, make-shift work, from the high conspicuous kind to the average and obscure, is allowed to pass unstamped with the disgrace of immorality, though there is not a member of society who is not daily suffering from it materially and spiritually, and though it is the fatal cause that must degrade our national rank and our commerce in spite of all open markets and discovery of available coal-seams.
In Stafford-shire, too, which is now almost the middle of England, another small coal-field tells the same story, while in South Wales the deep coal-mines and number of coal-seams remind us how for centuries and centuries forests must have flourished and have disappeared over and over again under the sand of the sea. But what is it that has changed these beds of dead plants into hard, stony coal?
In the United States there are about 120,000 square miles underlaid by known workable coal-beds, besides what yet remains to be discovered; while on the cliffs of Nova Scotia the coal-seams can be seen one over the other for many hundred feet, and showing how the coal was originally formed.
Both in the coal-fields of Europe and America the association of fresh, brackish-water, and marine strata with coal-seams of terrestrial origin is frequently recognised.
Great as is the diversity in the horizontal extent of individual coal-seams, they all present one characteristic feature, in having, each of them, what is called its UNDERCLAY. These underclays, co-extensive with every layer of coal, consist of arenaceous shale, sometimes called fire-stone, because it can be made into bricks which stand the fire of a furnace.
The coal-seams are few in number, six to twelve inches thick, very confused and distorted, and full of elliptic nodules, or spheroids of quartzy slate, covered with concentric scaly layers of coal: they overlie the sandstones mentioned above.
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