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steam; as much steam, therefore, as will fill a gallon vessel may, by the application of cold, be resolved again into the two hundred and sixteenth part of a pint of water.

Now let us take our "pop-gun” for an illustration. Let us magnify the pop-gun, and call the tube a cylinder, and the handle or rammer a piston. Suppose a jet of steam is let into the bottom of the cylinder while the piston remains in it; the steam expands; and, of course, up goes the piston. Now, hon application of cold, the steam becomes a little drop of me then down drops the handle: all the faster and heavier beca the steam baving shut out the air, there is not even the resistance of that to oppose it.

Repeat this up-and-down movement as often as you like. By rods and cranks it is easy to make this up-and-down movement turn a wheel or shaft; and that is the principle of the steamengine.

Now, in Newcomen's engine, when the cylinder was full of steam, and the piston raised, some cold water was thrown into the cylinder, which, of course, condensed the steam, and the piston fell. But the scheme had this great disadvantage. The cold water not only cooled the steam, but the cylinder too. The consequence was, that the vessel had to be made hot again, before the steam, as steam, would remain in it. Watt saw that this caused an expenditure of four times the necessary fuel ; or, in other words, that three-fourths of the fuel employed for the engine was wasted in making the cylinder hot after each application of cold water. After much consideration, Watt remedied this great defect. It struck him that the steam, having raised the piston, might be drawn off for condensation. He bad, therefore, a condenser placed at the side of the cylinder, into which the steam, when used, was made to pass instantly; and the piston fell as before. The cylinder was thus kept continually liot; and it was found that it took only a quarter of the fuel to make enough steam to fill it.

This was James Watt's first great improvement. Then came another. It occurred to him that if steam admitted into the bottom of the cylinder would send the piston up, steam admitted into the upper part would send the piston down, instead of simply allowing it to fall. To do this would almost double the power of

t.be engine; and insure greater regularity in the working. This most important object was easily accomplished when once conceived. Bring a pipe from the boiler to the top of the cylinder, to convey the steam; and carry another from it to the condenser, to condense the steam, as in the lower parts, the thing is done; and the principle of the steam-engine, as we now work it, was established. The steam is admitted alternately at the top and at the bottom of the piston; now forcing it up, now forcing it down.

Watt was the great improver of the steam-engine; but, in truth, as to all that is admirable in its structure, or vast in its utility, he should rather be described as its inventor. It was by his inventions that its action was so regulated, as to make it capable of being applied to the finest and most delicate manufactures, and its power so increased as to set weight and solidity at defiance. By his admirable contrivance it has become a thing stupendous alike for its force and its flexibility; for the prodigious power which it can exert, and the ease, and precision, and ductility, with which that power can be varied, distributed, and applied. The trunk of an elephant, that can pick up a pin or rend an oak, is as nothing to it. It can engrave a seal, and crush masses of obdurate metal before it; draw out, without breaking, a thread as fine as gossamer, and lift a ship of war like a bauble in the air. It can embroider muslin and forge anchors, -cut steel into ribands, and impel loaded vessels against the fury of the winds and waves.

It would be difficult to estimate the value of the benefits which these inventions have conferred upon this country. There is no branch of industry that has not been indebted to them; and, in all the most material, they have not only widened most magnificently the field of its exertions, but multiplied a thousand-fold the amount of its productions.

It has increased indefinitely the mass of human comforts and enjoyments; and rendered cheap and accessible, all over the world, the materials of wealth and prosperity. It has armed the feeble hand of man, in short, with a power to which no limits can be assigned ; completed the dominion of mind over the most refractory qualities of matter; and laid a sure foundation for all those future miracles of mechanic power which are to aid and reward the labors of after generations. It is to the genius of one man, too, that all this is mainly owing! And certainly no man ever bestowed such a gift on his kind. The blessing is not only universal, but unbounded; and the fabled inventors of the plough and the loom, who were deified by the erring gratitude of their rude contemporaries, conferred less important benefits mankind than the inventor of our present steam-engine

Various.

GEORGE STEPHENSON AND THE LOCOMOTIVE. The locomotive engine was then known to the world as a new toy, curious and costly. Stephenson had a perception of what might be done with it, and was beginning to make it the subject of his thoughts.

George Stephenson was thirty-two years old, and however little he may by that time have achieved, one sees that he had accumulated in himself a store of power that would inevitably carry him on, upon his own plan of inch-by.inch advance, to new successes. Various experiments had been made with the new locomotive engines. One had been tried upon the Wylam tram-road, which went past the cottage in which Stephenson was born. George Stephenson brooded upon the subject, watched their failures, worked at the theory of their construction, and made it his business to see one. He felt his way to the manufacture of a better engine, and proceeded to bring the subject under the notice of the lessees of the colliery. He had acquired a reputation not only as an ingenious, but as a safe and prudent man. He had instituted already many improvements in the collieries. Lord Ravensworth, the principal partner, therefore authorised him to fulfil his wish; and with the greatest difficulty, making workmen of some of the colliery hands, and having the colliery blacksmith for his head assistant, he built his first locomotive in the workshops at Westmoor, and called it “My Lord.” It was the first engine constructed with smooth wheels; for Stephenson never admitted the prevailing notion that contrivances were

necessary to secure adhesion.* “My Lord” was called “Blutcher" by the people round about. It was first placed on the Killing. worth railway, on the 25th July, 1814, and, though a cumbrous machine, was the most successful that had, up to that date, been constructed.

At the end of a year it was found that the work done by Blutcher cost about as much as the same work would have cost if done by horses. Then it occurred to Stephenson to turn the steam-pipe into the chimney, and carry the smoke up with the draught of a steam-blast. That would add to the intensity of the fire and to the rapidity with which steam could be generated. The power of the engine was, by this expedient, doubled.

At about the same time some frightful accidents, caused by explosion in the pits of his district, set Stephenson to exercise his ingenuity for the discovery of a miner's safety-lamp. By a mechanical theory of his own, tested by experiments made boldly at the peril of his life, he arrived at the construction of a lamp less simple, though perhaps safer, than that of Sir Humphrey Davy, and with the same method of defence. The practical man and the philosopher worked independently in the same year on the same problem. Stephenson's solution was arrived at a few weeks earlier than Davy's, and upon this fact a great controversy afterwards was founded. One material result of it was, that Stephenson eventually received as a public testimonial a thousand pounds, which he used later in life as capital for the founding at Newcastle of his famous locornotive factory. At the Killingworth pits the “Geordy” lamp is still in use, being there, of course, considered to be better than the Davy.

Locomotives had been used only on the tram-roads of the collieries, and by the time when Stephenson built his second engine, were generally abandoned as failures. Stephenson alone stayed in the field, and did not care who said that there would be at Killingworth “a terrible blow-up some day.” He turned his attention to the perfection of the rail, as an essential point; and his contrivances for the improvement of the locomotive always

* Adhesion, sticking. It was supposed that, without some additional contrivance, the wheels of a steam-carriage would simply revolve on the rail (as may be observed at the start of a train on a frosty-night), and never advance.

went hand in hand with his contrivances for the improvement of the road on which it ran. We need not follow the mechanical details. In his work at the rail and engine, he made progress in his own way, inch by inch. Every new locomotive built by him contained improvements on its predecessor; every time he laid down a fresh rail he added some new element of strength and firmness to it. The Killingworth Colliery Railway was the seed from which sprang the whole system of railway intercourse.

The Darlington line was constructed in accordance with his survey. His travelling engine ran upon it for the first time on the 27th of September, 1825, in sight of an immense concourse of people, and attained, in some parts of its course, a speed, then unexampled, of twelve miles an hour.

With what determined perseverance Mr. Stephenson upheld the cause of the locomotive in connection with the proposed Liverpool and Manchester line: how he did cheaply what all the regular engineers declared impossible or ruinous-in carrying that line over Chat-Moss, * persevering, when all who were about him had confessed despair ; and, because he had made good bis boldest promises in every one case, how he was at last trusted in the face of public ridicule, upon the merits of the locomotive also : how after the line was built, at the public competition of light engines constructed in accordance with certain strict conditions, his little Rocket won the prize : how the fulfilment of his utmost assertions raised Stephenson to the position of an oracle in the eyes of the public: how he nevertheless went on improving the construction of both rails and locomotives : how the great railway system, of which the foundations were laid patiently by him, was rapidly developed: how, when success begot a mania, he was as conspicuous for his determined moderation as he had before been for his determined zeal : how he attained honor and fortune ; and retired from public life, again to grow enormous fruits or vegetables in his garden, pineapples instead of leeks, again to pet animals, and watch birds'-nests—we cannot here detail.t

* Chat-Moss : he succeeded by throwing in hurdles and all sorts of buoyant rubbish.

+ See his “ Life,” by Mr. Smiles.

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