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"force of the steam to the top of the tube, the bolt of another piston could immediately be removed, the force of which in "its descent would continue the motion of the axis; and so,

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again, yet another piston could be lowered, and exert its "force on the same axis, while the pistons first pressed down were again being raised to the top by the force of heat, "and so were gaining new force to move the said axis, in the manner above described. But one grate, containing a "moderate fire, would be sufficient to raise all of those pistons in succession.

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Perhaps, however, some one may object, that the teeth of "the piston-rods, fitting into the teeth of the wheels, must in "their ascent and descent communicate opposite movements "to my axis; and that so the ascending pistons would hinder "the movement of the descending ones, and the descending pistons would hinder that of the ascending ones. But this objection is a very trifling one; for machine-makers are "well acquainted with a method whereby toothed wheels are so fixed to an axis, that when moved round in one direction they carry the axis round with them, but when going round "in the other direction they communicate no movement to the "same axis, but allow it to be very freely turned round with "an opposite movement. The principal difficulty, therefore, "consists in finding the manufactory for easily making very large tubes, as I have more fully stated in the Acta Eru"ditorum for September, 1688. And for preparing that, this "new machine ought to supply no small additional induce

ment; inasmuch as it very clearly shows that such very "large tubes can be most advantageously employed for "several important purposes."

CHAPTER XII.

THOMAS SAVERY

ENGINE

'THE MINER'S FRIEND

DESCRIPTION OF HIS STEAM

USES TO WHICH IT COULD BE APPLIED PAPIN'S INFERIOR IMITATION OF IT ESTIMATE BY HORSE-POWER-SIR SAMUEL MORENEWCOMEN AND CAWLEY THEIR GREAT IMPROVEMENTS DESAGULIERS AMONTONS AND DALESME -SMEATON.

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IN the contrivance which has thus made the name of Papin, to say the least, quite as famous as it deserves, the vessel in which the steam was tediously generated, and then allowed slowly to condense, was at once boiler and cylinder; and, so long as it continued to fulfil alternately the functions of both of those vessels, it was necessarily unfit to do any really effective work. In order to the accomplishment of that desideratum, it was essential that the steam should, on the one hand, be steadily, continuously, and abundantly produced, and, on the other, that it should from time to time be condensed with at least tolerable rapidity. The honour of making this great step in advance,-the first that in fact led to the attainment of any really useful results from the employment of steam as a motive power of machinery, and which, therefore, it seems impossible too highly to commend,-belongs entirely to an Englishman, Captain Thomas Savery. Of his life and private history but little appears to be known; and an enquiry made several years ago of a gentleman of the same name at Bristol, (who acknowledged relationship), did not produce any information or papers.

But of his steam-engine Savery has luckily left us a very particular description, in a work entitled The Miner's Friend, or an Engine to raise Water by Fire described, ' and the Manner of fixing it in Mines, with an Account of 'the several other uses it is applicable unto; and an Answer 'to the objections made against it. By Tho. Savery, Gent. Pigri est ingenii contentum esse his quae ab aliis inventa sunt.

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Seneca. London, printed by S. Crouch at the corner of 'Pope's-head Alley in Cornhill. 1702.' The edition from which we copy this title is of that date; but Mr. Robert Stuart, at p. 34 of his History of the Steam-engine,' published in 1824, says, quoting from Robison, "The fact is, Savery obtained his patent in 1698, after a hearing of "objections; * *but, besides this, he had erected several "of his engines before he obtained his patent;" "and," continues Mr. Stuart,"published an account of his engine in 1696, under the title of The Miner's Friend, and a Dialogue "by way of answer to the objections which had been made "against it, in 1699; both were printed in one volume in "1702." We have not seen the publication of 1696; but we observe that in that of 1702, he says he worked a small model before some members of the Royal Society, on the 14th of June, 1699; and also, that, previous to the Royal Assent being obtained to the Patent and Act of Parliament, (i. e. in 1698), he had performed an experiment with a small model of the engine before the King at Hampton Court, to his Majesty's "seeming satisfaction of the power and use of it." And he adds, that it is "now fully compleated, and put in "practice in his dominions, with that repeated success and applause that it is not to be doubted but that it will be of "universal benefit and use to all his Majesty's subjects." What is most important is, that the letter-press of The 'Miner's Friend' is accompanied by a very clear and sufficiently well-executed engraving, including two figures, each of about twelve inches in height, of which the first represents "The Engine for raising Water by Fire," and the second represents the same engine "working in a mine." In the former, the various parts are all delineated on such a scale, that, with the aid of the particular description accompanying it, it is impossible to mistake either their proportion or their mode of action; and of both figures it may with perfect confidence be asserted, that they are the first representations to be met with in the publications of any country, of a real steam-engine doing useful work.

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Savery's engine, as so described and delineated, acted by

two distinct principles; raising water, in the first place, by the pressure of the atmosphere forcing it into a vacuum formed by the condensation of steam; and, in the second, by the expansive power of steam. The steam from the detached boiler was let into a vessel called a receiver, and, having driven out the air, was condensed by the affusion of cold water, and a partial vacuum formed. A communication being then opened with a suction pipe, twenty-four feet in height, the lower end of which was placed in a cistern or reservoir of water, that water was forced upwards, by the pressure of the atmosphere, into the receiver. When this was nearly filled, the communication with the suction-pipe was shut off, the steam was readmitted into the receiver, and by its expansive power forced the water contained in it up an ascending, or, as he called it, a force-pipe. This second operation is similar to one of those experimentally tried by Porta, and indicated by Solomon de Caus; and not only indicated, but perhaps practised, by the Marquis of Worcester. The prior operation,—that of raising the water into a vacuum formed by the condensation of steam, we believe to have been original with Savery. For, although both Porta and Papin had described the principle, they applied it in a different manner; and there is no proof, or even surmise, of its having been known to Savery when he invented his engine in 1696, or perhaps sooner. Indeed, Papin, with praiseworthy candour, as quoted by Belidor, (Arch. Hyd.,' tome ii. p. 309), writes, "What I say here is not "to give room for believing, that Mr. Savery, who has since published this invention at London, is not actually the in"ventor. I do not doubt that the same thought may have "occurred to him, as well as to others, without having learnt "it elsewhere." When we consider the whole of the contrivances invented by Savery, as described by himself in The Miner's Friend,' we cannot but accord him the praise of very great ingenuity, independent of the merit of having made THE FIRST WORKING STEAM-ENGINE, (if he was not preceded in that by the Marquis of Worcester); but at all events, of having been the first who introduced it into use. drawing and description in The Miner's Friend,' apply to an

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His

engine with two receivers; but it was soon altered, in practice, to one receiver, as we have described it.

Switzer, in his 'System of Hydrostatics and Hydraulics,' published in 1729, says, p. 325, "Among the several engines "which have been contrived for the raising of water for the

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supply of houses and gardens, none has been more justly "surprising than that for the raising of water by fire, the par"ticular contrivance and sole invention of a gentleman with "whom I had the honour long since to be well acquainted; "I mean the ingenious Captain Savery, some time since de"ceased, but then a most noted engineer, and one of the "Commissioners of the sick and wounded.

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"It was a considerable time before this curious person, who "has been so great an honour to his country, could, (as he "himself tells us), bring this his design to perfection, on "account of the awkwardness of the workmen who were ne"cessarily to be employed in the affair; but at last he conquered all difficulties, and procured a recommendation of it "from the Royal Society, in Trans. No. 252, and soon after, a patent from the Crown, for the sole making this engine. "And I have heard him say myself, that the very first time "he played it, was in a potter's house at Lambeth, where, though it was a small engine, it forced its way through the "roof."

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We think it right to add that the language used by Savery in his Miner's Friend,' in treating of the advantages, whether ascertained or prospective, of his invention, presents a great contrast, in point of plainness, simplicity, and modesty, to the more high-flown and extravagant phrases in which the Marquis of Worcester so unhesitatingly magnifies the wonderful performance of his "semi-omnipotent" engine. Savery was evidently a practical man, possessed of great common sense as well as ingenuity; and although it would probably be wrong to deny to Lord Worcester the possession of a good deal of the second of those qualities, it may well be doubted how far he is entitled to claim any very considerable share of the first.

Savery, in the second chapter of his Miner's Friend,'