THE STEAM ENGINE.

Mr. Phillips, the eminent Professor of Geology, in the University of Oxford, remarks that, "coal, since it has been applied to the steam-engine, is really hoarded power applicable to almost every purpose which human labor, directed by ingenuity, can accomplish.' He then goes on to remark, with the pride of a genuine Briton, "It is the possession of her coal-mines which has rendered Britain in relation to the whole world, what a city is to the rural district which surrounds it-the producer and dispenser of the various products of art and industry. Our coal-fields are vastly more precious to us than would have been mines of the precious metals, like those of Peru and Mexico." If the latter statement be true of Britain it must be true of the United States also, even to a much greater extent.

According to Mr. Hunt, the keeper of the Mining Records of Britain, the coal area of the British Islands is 12,800 square miles, or one-tenth of the whole surface; according to the same author. ity, the proportion in the United States is still greater; the coal area being two-ninths of the whole surface. Scotland possesses the largest coal-field in Britain — 1,600 square miles in the basin of the Forth and Clyde; this field is very rich in iron as well as coal. Between the Tweed and the Trent, in the north of England, there are nearly 10,000 square miles.

WHO DEVELOPED STEAM-POWER?

It was in one of these districts that Watt brought forth his almost, if not quite, perfect condensing engine. On the Forth and Clyde Canal was the theater for Symington's steam-boat. Near Newcastle the Newcastle of coals-the Stevensons grew to maturity, connected with those great collieries; and there, too, grew to full development of monstrous power and bird-like speed, their giant pet, the locomotive. On the Schuylkill and the Delaware successfully experimented Oliver Evans and John Fitch; here, too, on or near the great anthracite coal-fields of Pennsylvania, Robert Fulton first saw the light, and noted the development of steam-power, to which he has allied his name for all time.

We propose now to see what the steam-engine, well fed and watered, can do. In the language of Dr. Lardner, "Coals are by the steam-engine, made to spin, weave, dye, print, and dress silks,

cottons, woolens, and other cloths; to make paper and print books upon it when made; to express oil from the olive [aye, we may add, and from cotton seed too, which is largely taking the place of the oil from the olive, for which it is sold in all the markets of the world], and wine from the grape; to draw up metals from the bowels of the earth; to pound and smelt it, to melt and mold it, to forge it, to roll it, and fashion it into every desirable form; to transport these manifold products of its own labor to the doors of those for whose convenience they are produced; to carry persons and goods over water and land, from town to town, and country to country, with a speed as much exceeding the ordinary wind, as the ordinary wind exceeds that of a common pedestrian."

INTERESTING FACTS.

"Such are the virtues, such the powers, which the steamengine, with its rotary or continuously circular motion, as brought into being by Watt, has conferred upon COALS. The means of calling these powers into activity are supplied by a substance which nature has happily provided in unbounded quantity in every part of the earth; and though it has no price, it has inestimable value. This substance is water. A pint of water may be evaporated by two ounces of coals. In its evaporation it

swells into two hundred and sixteen gallons of steam, with a meIchanical force sufficient to raise a weight of thirty-seven tons a foot high. The steam thus produced has a pressure equal to that of common atmospheric air; and by allowing it to expand by virtue of its elasticity, a further mechanical force may be obtained at least equal in amount to the former. A pint of water, therefore, and two ounces of common coal, are thus rendered capable of doing as much work as is equivalent to seventy-four tons raised a foot high.

"The circumstances under which the steam-engine is worked on a railway are not favorable to the economy of fuel; nevertheless, a pound of coke burned in a locomotive-engine will evaporate about five pints of water. In their evaporation they will exert a mechanical force sufficient to draw two tons weight on the railway a distance of one mile in two minutes. Four horses, working in a stage-coach on a common road, are necessary to draw the same weight the same distance in six minutes.

"A train of cars, weighing about eighty tons, and transporting 240 passengers with their luggage, has been taken from Liverpool to Birmingham, and thence back to Liverpool, the trip each way taking about four and a half hours, stoppages included—the distance being 95 miles. This double journey of 190 miles is effected by the mechanical force produced from the combustion of four tons of coke, valued at 57. To carry, in England, the same num

ber of passengers daily between the same places, by stage coaches, would require 20 vehicles and an establishment of 3,800 horses, with which the journey would be performed both ways in about twelve hours, stoppages included.

"The circumference of the earth measures 25,000 miles; and if it were begirt with an iron railway, such a train as that described carrying 240 passengers would be drawn round it by the combu tion of about thirty tons of coke, and the circuit would be accomplished in five weeks."

Capt. Savery contrived his engine, in 1698, with especial reference to the drainage by pumping of the deep mines of England, and it was used mainly for this purpose. Indeed, it is necessary to recollect that, notwithstanding the extensive and various applications of steam-power in the arts and manufactures, up to the time when Watt got his patent extended in 1775, the steam-engine had never been employed for any other purpose than that of raising water by working pumps.

The water of streams was used over and over again, in the manufacturing districts of England, by being pumped up, and thus re-supplied to water-wheels driving machinery. The motion required, therefore, was merely an upward force, such as is necessary to elevate the piston of a pump.

"In the drainage of the Cornish mines now, the economy of fuel is much attended to, and coal is made to do more there than elsewhere. A bushel of coal usually raises 40,000 tons of water a foot high; but on some occasions it has raised 60,000 tons a foot high. Let us take its labor at 50,000 tons. A horse worked in a fast stage coach, pulls against an average resistance of about a quarter of a ton weight. Against this he is able to work at the usual speed through about 8 miles daily; his work is, therefore, equivalent to about five hundred tons raised one foot. A bushel of coals, as used in Cornwall, therefore, performs as much labor as a day's work of one hundred such horses."

"When steam-engines were first brought into use, they were commonly applied to work pumps for mills, which had previously been worked or driven by horses. In forming their contracts, the first steam-engine builders found themselves called upon to supply engines for executing the same work as before had been executed by a certain number of horses. It was, therefore, convenient, and indeed necessary, to be able to express the performance of these machines by comparison with the animal power to which manufacturers, miners, and others, had been so long accustomed. When an engine, therefore, was capable of performing the same work, in a given time, as any given number of horses of average strength usually performed, it was said to be an engine of so many horses' power. It was, however, a considerable period before this term came to have a definite meaning. Mr. Smeaton estimated that

a horse of average strength, working for eight hours a day, was capable of performing a quantity of work equal in its mechanical effect to 22,916 tons raised one foot per minute, while Desaguliers estimated the same power at 27,500 tons. The difference between these estimates probably arose from their being made from the performances of different classes of horses."

"Messrs. Boulton and Watt caused experiments to be madewith the strong horses used in the breweries of London, and from the results of these trials they assigned 33,000 pounds, raised one foot per minute, as the value of a horse's power. This is the unit of engine power now universally adopted. The steam-engine is no longer used to replace the power of horses, and, therefore, no contracts are based upon this comparison. The term horse-power, then, means simply the ability of the engine to move 33,000 pounds. through one foot per minute."

"The conversion of a given volume of water into steam is productive of a certain definite amount of mechanical force, this amount depending on the pressure under which this water is evaporated, and the extent to which the expansive principle is used in working the steam. It is evident that this amount of mechanical effect is a major limit, which cannot be exceeded by the power of the engine.

"What is known as the duty or service of engines varies according to their form and magnitude, the circumstances under which they are worked, and the purposes to which they are applied. In double-acting engines, working without expansion, the coal consumed per nominal horse-power per hour varies from 7 to 12 lbs. An examination of the steam-logs of several government steamers, made a few years since, gave as the average consumption of fuel at that time, of the best class of marine engines, about 8 lbs. per nominal horse-power per hour. Out of fifteen atmospheric engines working at Newcastle-on-Tyne, in 1769the date of Watt's earliest discoveries the yearly duty of the poorest was shown to be 3,220,000 lbs., and of the best 7,440,000 lbs. In 1772, Smeaton began his improvements on the atmospheric engine, and raised the duty to 9,450,000, but when Watt, in 1776, had obtained a duty of 21,600,000, Smeaton acknowledged that Watt's engines gave a duty double that of his own. From 1779 to 1798, Watt increased that of his engines from 23,400,000 to 27,000,000. The engine which accomplished the last was under the care of Mr. Murdock, at Cornwall, and was by Mr. Watt pronounced perfect. [Mr. Murdock will be remembered as the ingenious producer of a model locomotive heated by a spiritlamp, which so frightened the village parson upon a dark evening, as it moved rapidly down upon him on the side-walk.] Mr. Watt thought further improvement in the duty of his steam-engine could not be expected. Yet in twenty years afterward the best.

engine had attained to an average duty of 40,000,000 lbs., and in forty years it was about 84,000,000 lbs. per year. How impossible, then, for even the most sagacious to foresee the results of mechanical improvement."

COAL CONSUMED.

We now revert again to fuel, or the food of what the men of the Newcastle collieries originally called the "Iron Horse." For this home of the Stephensons, near the close of the thirteenth century Henry III. gave a charter, granting license to the burgesses of Newcastle to dig for coal. In 1281-just five hundred years before George Stevenson was born, at Wylam CollieryNewcastle is said to have had a considerable trade in this article, and about this time the use of coal had commenced in London, by smiths, brewers, dyers, soap-boilers, etc. A notion got abroad that the smoke was highly injurious to the public, and in 1316, on petition of parliament his majesty Edward I. issued a proclamation prohibiting its use, on the ground of its being an intolerable nuisance. Notwithstanding this, and the fact that more rigorous means were resorted to, its use continued progressively to gain ground. Since the reign of Charles I., the use of coal in London has been universal, to the exclusion of nearly all other articles of fuel. The coals of Britain are almost wholly bituminous, similar to the coals taken out of the Western Alleghanies and generally mined in the Mississippi Valley. The anthracite coal of Pennsylvania is nearly pure carbon, igniting with some difficulty, and giving out intense heat during combustion. It is almost exclusively used in the cities and towns of the Northern Atlantic States, and wherever wood is not cheaper, in that part of the Union. Its adaptation for use in blast furnaces makes it immensely valuable to the great home interest in iron, of the Keystone State; and it yields a rich revenue to her citizens from the demand for it in the large manufacturing and commercial districts of the Eastern States, while it is in growing request wherever in the South and West a cleaner fuel is preferred to the smoky and sooty coals of the great central valley. Strangely enough, it was scarcely known to exist in this country fifty years ago, and now the tonnage engaged in transporting it to a minor extent by the old canals on the railroads of the East is of enormous magnitude, as will appear from the reports of the Philadelphia and Reading Railroad, the Lehigh Valley, the Delaware and Lackawanna, the New Jersey Central, the Pennsylvania Central, and other roads. A half century ago, this coal, as discovered in Ireland, and in South Wales, was considered to be incombustible refuse and was thrown away, but now it is there thought to be of the very highest value for furnace purposes.

In this running and brief history of coal, we not only discover