WHO can sum up the benefits we derive from coal? It warms and lights our dwellings, cooks our food, illuminates our streets. Coal develops and sustains the force which propels the locomotive along the railway and the ship across the sea; works the printing press, wields the hammer, lifts the weight, draws the load, moves the machinery, grinds the corn, spins the cotton, weaves the cloth, pumps the mine, deepens the river, covers the land with a network of railways, forges the electric wire, and, submerging the ocean telegraph, "will put agirdle round about the Earth in forty minutes."bounds to the power of Coal, Iron, and Steam?
Who shall set
The economical and industrial importance of the union of coal and iron in the British Isles cannot be over-estimated. To the abundance of these minerals in the deposits of the coal formation are owing the increase and prosperity of the British people, their wide-spread mercantile enterprise, their rapid intercourse with all parts of the world, their boundless territories abroad, their opulence and influence at home.
From its proximity to a mere patch of the English coal measures-a detached portion not exceeding the area of one of the larger Scottish lakes-Birmingham has risen to the rank of the first iron manufacturing town in the world. Manchesterand Glasgow have equally derived their manufacturing and commercial importance from being placed each in the centre of a great coal basin.
The vegetable origin of coal is no longer a matter of doubt. The leaves of ferns, reeds, and other plants, are frequently found between layers of shale or slaty clay, beautifully perfect, but converted into coal. And in many kinds of coal, by means of very thin sections, and by the employment of the microscope, the cells of a vegetable structure become visible; thus affording us a distinct proof that coal is really a vegetable substance, and produced by vegetable decay.
The coal plants flourished in the widely extended forests of the primeval world; and as they fell and decayed, they left theirremains imbedded in sandstone and shales,accumulatingin lakes and the deltas and estuaries of rivers, to become transformed into coal in the lapse of ages, by the united influences of heat and pressure.
The trunks of the trees, being covered with water, were kept from contact with the air, and gradually decayed, until they were converted into a blackish-brown substance resembling peat, but which still retained more or less of the fibrous structure of wood. The decomposed mass became gradually covered with a deposit of sediment, the great pressure of which, when accumulated into beds of clay or sand of some thickness, gave to this substance the hardness and density of a true mineral. It thus became stored up for future employment in the service of man.
The trees which grew in the swamps and forests of the coalperiod derived their carbonaceoussubstance from carbonic
acid gas and water, existing in the soil and floating in invisible currents in the air. They imbibed the gas by their fronds, leaves, and roots; and separating the solid carbon from the oxygen gas with which it was combined, they appropriated the former for the purposes of their nourishment and growth, and restored the latter to the atmosphere. But the plant can only decompose carbonic acid and water with the aid of the light and heat of the sun-the process ceases in the dark.
In helping the plant to appropriate and deposit carbon inits tissues, the sun parted with so much of its light and beat, which became latent in the vegetable. This long dormant light and heat are set free by the process of combustion.
When the Yule log is laid on the blazing hearth of thebaron"s hall, and the fagots are piled on the peasant"s fire, they shed upon the radiant faces of the festive circle light and heat which were borrowed from the sun while the seed sprang into a sapling, and at length became a goodly tree, a century or two old.
But the coal glowing in the cheerful fires of our town dwellings, and diffusing light by means of the gas-pipes of our streets, is composed of vegetables in which are stored up, in another form, light and heat originally derived from the sunshine of distant ages. In the grate we liberate this ancient heat for our comfort; in the gasometer we take advantage of the light for our convenience; in our boilers and engines we convert the latent heat into mechanical force.IDEAL VIEW OF A MARSHY FOREST OF THE COAL PERIOD"Wood fires," says a distinguished philosopher, "give us heat and light which have been got from the sun a few years ago. Our coal fires and gas lamps bring out, for our present comfort, heat and light of the primeval sun, which have lain dormant beneath seas and mountains for countless ages."- Sketches in Natural History -ELLIS"S Chemistry .
QUESTIONS
Mention some of the great things done by means of coal. What other mineral is generally found near coal? Mention great cities which owe their importance to coal. What is the origin of coal? How is this proved? How have the coal plants been transformed into coal? Whence did they derive their carbonaceous properties? What are latent or dormant in coal? Whence were they derived? When do they again become active?
