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COMPARISON OF ENGINES.

objections which were made against his invention, before he got a grant of a monopoly of the profit which might arise froin his permission to construct and use this povel apparatus.

The line between the engines of Worcester and Savery might, conjecturally, be easily drawn, so as to define, with the greatest probability, the merits and claims of both. Lord Worcester expressly says, his machine did not draw or suck upwards ; that is, it did not produce any part of its effect by the aid of atmospheric pressure. This is à material point; for this agency was one of the most distinguishing features in Savery's machine, He combined the elastic force of steam with that which was derived by condensing the vapour to form a vacuum; and thus availed himself of the pressure of the atmosphere not only to increase the power, but even to form the sole means by which he produced the effect in his engine. In all his descriptions, it is remarkable that he never once produces the entire effect by the elasticity alone of the vapour; but in describing an arrangement for draining fens, he says, this could be done solely by condensation. The opinion, therefore, that Lord Worcester's apparatus was similar to a high-pressure engine, receives a strong corroboration from the circumstance of its not having heen an effective bar to Savery's privilege of monopoly; and on the other hand, the total difference in the construction of each, places Savery's merit in a new and more interesting view, and on a broader basis.

Even, therefore, admitting, in the fullest and most unequivocal terms, that Savery was intimately acquainted with his predecessors' labours in this particular species of mechanism, his merit in the formation of his apparatus was as great as that of COMPARISON OF INVENTIONS. 127 any of his rivals’. Lord Worcester could not be ignorant of Porta's, Decaus's, and Kircher's schemes. Savery, probably, did not throw away the advantage he had of adding the marquess's, and Hautefeuille's, and Papin's experience to these; for his machine certainly embodies nearly all their ideas. Hero, Porta, and Decaus mention the condensation of steam by the cold from the air, and the means of replenishing the vacuum by the pressure of the atmosphere; Porta and Decaus raised water through a pipe by the elasticity of steam pressing upon its surface. Hautefeuille and Papin describe similar contrivances, and the latter, particularly, made wonderful strides in improvement on his predecessors. Yet, bow prodigious the difference between the most refined of these and the celebrated machine of Savery! How many essential parts were to be supplied from the stores of his own comprehensive and fertile imagination! How many difficulties were to be overcome! And how many original and masterly connecting ideas may no be traced in the imperishable monument of his genius, his

engine for raising water by fire." Among these may be named, raising the steam in a boiler, conducting it into a separate vessel ; condensing it there by artificial means, and with instantaneous rapidity; making the production of the vacuum from an auxiliary become à principal cause of its wonderful effects; producing a continuity in its action by the arrangement of the parts of his machine; in aid of this latter purpose, replenishing his larger boiler with waler, without lowering the temperature of that which it already contained; the use of small pipes to know when it was necessary to introduce the supply of water; the fine mechanism of the sliding

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AMONTONS, valves'; the ingenious construction of the coldwater pipe; the precision with which all the parts were adjusted to aid in the action of each other; and though last in the enumeration, not least in merit, his admirable arrangement of the parts, and sagacious selection of forms, and their effective connection;-all these, which were the achievements of his own genius, have left to suc. ceeding mechanics but few opportunities of supplying omissions, or remedying defects; and this admirable machine, in form and construction, is now nearly the same as when it first proceeded from the masterly hand of its excellent inventor.

At this period the exertions of mechanics in France to derive a power from the action of heat, discovered the usual refined ingenuity of that accomplished people; but the results of their la. bours are considered to have been, on the whole, unsuccessful, inasmuch as they wanted the merit of fitness for practice, which was possessed in so eminent a degree by the machine produced among their insular rivals. The inventor of a steamwheel is found in the ranks of its most distinguished and industrious philosophers.

Guillaume Amontons, the son of a Norman advo. cate, who settled at Paris, was afflicted, from child. hood, with so great a deafness as nearly to deprive him of the society and conversation of mankind. He began the study of machines for his amusement, and his first essay was an attempt to construct an apparatus to produce a perpetual motion; a perseverance in this research taught him, that he had lost the time he had expended on it, and thrown away his care. The family of Amontons was opposed to these studies from their beginning, as leading neither to distinction nor to fortune ; but the student despairing, after the

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failure of a course of medical and surgical experiments, of ever obtaining his hearing, redoubled bis attention to mathematical and mechanical pursuits. He designed buildings with taste, and in works of carpentry introduced some theoretical refinements to improve its practice; he invented an ingenious telegraph for conveying a message from Rome to Paris in three or four hours, and the experiment was tried with success in the suburbs of Paris. His works on hygrometers and barometers are of great merit; and his theory and experiments on friction are still appealed to for their ingenuity as well as accuracy : for his invention of the “moulin à feu,” he ranks as an early improver of the steam-engine. But the amiable qualities of his mind exceeded even the ingenuity of his spirit. Amontons was proverbial for the frankness, and simplicity, and polish of his manners, and for the almost infantine benevolence of his disposition.

The scheme of Amontons, totally different from the idea of Savery, and unique of its kind, thus early attracted the attention of mechanics to supply a desideratum of a continuous rotary motion from the elasticity of steam. The machine was called, by its inventor, a fire-wheel, and described as operating by the action of heated air, forcing a quantity of water up one side of a wheel and producing a rotary motion by its differing weight from the other side.

Like some of his contemporaries, Amontons appears partial to the expansion of air, * and to have forced it into his service in the construction of his engine. Upon the authority of his own drawing it would appear, that the presence of air in his

• Memoires de l'Académie des Sciences, p, 208. 1699 Bossut, Hydrodynamique, tome įi, p. 307.

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FIRE-WHEEL. apparatas was more to be avoided than introduced, and that, in fact, all its effective power would be derived from steam. A cursory inspection of his “moulin à feu” will show us, that the water in the inner range of chambers would soon become intensely heated and form vapour, which could not, by any mechanism he has shown, be prevented from filling what may be designated the air-chamber

The fire-wheel, as described by its author, consists of two concentric ungulas or rings, connected and communicating by means of small pipes, 1, 2, 3, 4, &c. The outer ring of the wheel is divided into a certain number of compartments, a, b, c, d, e, f, &c. Amoutons describes his as having twelve, and perfectly closed, so as to have no connection with each other. The inner ring is divided into the same number of compartments, marked a, b, c, d, e, f, &c.; each of these communicates with the adjoining chamber by a valve made in each compartment moving on a hinge, and only opening in one direction, and that upwards. Although the two rings and their series of compartments are placed at a distance, each compartment of the one communicates with a corresponding division of the other by small pipes, 1, 2, 3, 4, &c. The wheel is placed so as to have one side of its periphery exposed to the action of a fire, and the other side is immersed in a cistern, y, of cold water. Four or five of the lower chambers of the inner series are filled with water,

A fire is then, says Amontons, to be made in the furnace: this will heat the air in the chamber (for example, marked a) of the outer series, which is exposed to its influence, and the air which it contains is rarefied, and flowing through the pipe

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