« PreviousContinue »
the vegetable mass had undergone before it was finally covered by other strata; and the porous or retentive nature of the strata between which it is imbedded. All these and other causes have tended to create the differences that now exist among the different members of the Coal Family—the graphites and anthracites burning like charcoal, without smoke or flame; the ordinary bituminous coals burning with varying degrees of smoke and flame; the lignites burning with stifling odour, and expelling much watery vapour and smoke; and the peats scarcely combustible till dried in the sun or by hydraulic pressure, and then burning with little flame but with much smoke and their own peculiar odour. But whatever their peculiarities in these respects, they are all highly important substances, and stand along with iron as the most valuable that human industry obtains from the crust of the earth. Indeed the coals are altogether indispensable to modern civilisation, the peculiar mechanical phases of which are mainly of their own creating. So long as man depends upon the forests for his fuel, his mastery over the metals is limited, and his mechanical appliances restricted. But when he has once learned the uses of coal, and can obtain it in fair supplies, his metal-working powers expand, and his forges, factories, steam-engines, steamships, gas-works, railroads, and electric telegraphs become the necessary developments of this new acquirement. Once acquainted with these and similar appliances, man takes his stand on a higher platform, gains new ascendancy over the forces of nature, and overcomes in a great measure the obstacles which time and space oppose to his operations.
Where and at what time man first began to employ coal as a fuel iS unknown. The Chinese and Japanese have evidently been long acquainted with its uses, but their chronology is uncertain. The Hindoos, Egyptians, and other Oriental nations never seem to have searched for any variety of mineral coal, but laboriously prepared woodcharcoal for their metallurgical processes. The Greeks and Eomans were acquainted with its properties, though they appear to have seldom employed it, and this on the most limited scale.* In our own country some ancient cropworkings, with stone hammers and hatchets still remaining, date back perhaps to the Eoman invasion, and "coal" is mentioned in Saxon records of the ninth century; but it was not till the twelfth and thirteenth centuries that the value of the substance began to be fairly recognised. And in connection with these facts it is a circumstance worth noting, that no savage race has ever yet been discovered that seemed to be aware of its nature and uses. It may crop out along the ravines and sea-cliffs, as it does in North America, in Eastern Africa, in Farther India, in Australia and New Zealand, but the savage never bends to dig while the twigs and branches around him can be broken. The use of certain minerals and metals are, in truth, as satisfactory tests of man's progress in civilisation as the cultivation of certain plants or the domestication of certain animals. The possession of the 'one may largely increase his comforts; a knowledge of the other invests him with new and higher powers.
As a nation we cannot exalt too highly the importance of our coals and coal-fields. Our mechanical, manufacturing, and commercial greatness is intimately bound up with their existence; and whatever tends to disseminate a knowledge
* It is thus referred to by Theophrastus, a Greek author, who wrote about 240 years B.C. :—" Those fossile substances that are called Coals, and are broken for use, are earthy; they kindle, however, and burn like wood coals. These are found in Liguria, where there also is amber, and in Elis in the way to Olympias over the mountains. These are used by the smiths."—Sir John Hill's Translation, 1774. The Ligurian coal would appear, from its connection with amber, to have been lignitic; the Olympian coal, now being worked by a modern company, is bituminous, and of older date.
of their nature, to develop their resources, or economise their products, is worthy of our encouragement and attention. Commercially, we may have no immediate interest in the substances called coals, but indirectly every man is less or more indebted to their applications; and it must be a dull or indifferent mind that cannot be induced to take some interest in products to which his country owes so much of her power and greatness, himself so many, of the comforts and amenities he is daily enjoying, and the world in general so much of its newer life and civilisation.
THE OLD COAL-MEASURES.
THE CARBONIFEROUS OR COAL SYSTEM—ITS PLACE IN GEOLOGYNATURE AND COMPOSITION OF ITS STRATA—ITS UPPER, MIDDLE, AND LOWER DIVISIONS—-VARIETIES OF ITS COALS—APPARENT CAUSES OF—IGNEOUS ROCKS ASSOCIATED WITH ITS STRATA—ITS FOSSIL FLORA AND FAUNA—EXUBERANCE OF ITS PLANT-LIFE— GENERAL GEOGRAPHICAL CONDITIONS OF THE PERIOD—THE COALMEASURES AS AN ECONOMIC REPOSITORY—VARIETY AND VALUE OF ITS PRODUCTS—THEIR INFLUENCE ON HUMAN CIVILISATION AND PROGRESS—EXTENT AND DURATION OF PALAEOZOIC COAL-FIELDS.
The reader who has perused the preceding sketch will have seen that coal is a product of every geological epoch, from the peat now accumulating on the earth's surface down through the lignites of the tertiary, the true coals of the secondary, and the harder coals and anthracites of the primary periods. But though thus occurring in all stages of the earth's history, it is in the so-called " Carboniferous System" that it appears in numerous seams, in many varieties, and in great thickness and continuity over extensive areas. It is from this old system that Britain, France, Belgium, Eussia, China, Australia, and the United States of America obtain their main supplies; hence the familiar terms "Coal-Formation" and " Coal-Measures," as if it were the only series of coal-yielding strata in the crust of the globe. In Britain it generally rests on a series of reddish sandstones, and is in turn overlaid by another series of red sandstones; the former being naturally designated the '; Old Eed," and the latter the "New Eed," by the systematic geologist. It thus holds a sort of middle place in chronological classification, being younger than the Cambrian, Silurian, and Old Eed systems, and older by far than the Chalks, Oolites, and New Eed Sandstones. Its position is well defined, and may be seen at a glance in the following sequential arrangement:—
Cainozoio ( Quaternary or Recent.
(Recent). ( Tertiary.
Cretaceous or Chalk.
'l e'' \ Triassic—(Upper New Red).
. Permian—(Lower New Red).
PALiEOzoic j Carboniferous—The Old Coal-measures.
(Ancient). \ Old Red Sandstone and Devonian.
Eozoic i Cambrian.
(Dawn). ( Laurentian.
It is to these palaeozoic or ancient coal-measures, in contradistinction to all others, that we direct the present sketch, dwelling more especially on their geological aspects, and only incidentally alluding to their industrial applications and importance. We say "incidentally alluding;" for their building-stones, fire-clays, oil and alum shales, limestones, ironstones, and coals—the labour and skill expended in mining them, the innumerable uses to which they are applied, and their bearings on the industrial and social conditions of a people—are subjects which of themselves would require the consideration of half-a-dozen sketches.
Perhaps the most intelligible way of treating any geological system is to consider it first as a Eock-formation, second as a Life-period, and third as an Economic repository. In this way we get an insight into the nature of the strata of which it is composed, and the agencies concerned