shafts or axles, in such a way that being impelled towards one side they necessarily cause the axle to turn with them, but towards the opposite side, they can turn freely without giving any motion to the axle, which may thus have a motion entirely opposite to that of the said wheels. The greatest difficulty then merely consists in erecting a manufactory for making tight tubes, thick and equal from one end to the other, etc."

Papin proposed then, in print, to propel ships by means of the steam engine, forty-two years before Jonathan Hull, who is looked upon as the inventor of steam navigation in England.*

The process explained by Papin for changing the rectilinear motion of the piston into a continuous rotary motion, is not inferior, I think, to that of the English machinist; for according to the latter, the wheels attached to the principal axis and the paddle wheels, only communicate with each other by cords.

The two cylinders, acting alternately, which Papin thought of making use of to regulate the motion of the wheels, are not so despicable as one might think them. Mr. Maudsley, one of the most able English constructors, has used them lately in many of his large boats to supply the place of the fly wheel, which cannot be used without great difficulty in a confined space.t

The substitution of a paddle wheel for ordinary oars, belongs neither to Papin nor to Hull; to say nothing of Prince Rupert's sloop cited by the former, we shall find in very old authors evident proofs of the employment of wheels. As to the first exact experiments upon which any judgment could be formed of the relative advantages of these two methods of impulsion, they can be hardly traced higher than the year 1699, and we are indebted for them to Mr. Quet, ‡ (see, mach. appr. par l'acad, t. 1st.)

* What a step from the proposal to propel ships to its execution!-TRANS.

† The plan adopted long since by Mr. Stevens of two cranks at right angles connected with the same piston is much more eligible. But M. Arago seems not to have turned his attention to American mechanics or their devices, or to American writings on the subject of the steam engine.-TRANS.

† Mr. Robert Stuart's work (see page 83, 3d edition,) contains the following passage; "Jonathan Hull ought to be honorably mentioned for having pointed out paddle wheels, moved by a steam engine, as a means of propelling vessels without wind and sails. This proposition requires a change in the rectilinear and alternate motion of the rod of the piston into a rotary motion. Hull showed that a crank gave an ingenious solution of the problem. We now see rightly in this invention the origin of the introduction of the steam engine in the manufactories as impellents of every kind of mechanical operations." Thus, in the opinion of Mr. Stuart, Jonathan Hull has the double merit of having invented steam vessels, and of having shewn that the steam engine might be substituted for the mechanical agents hitherto employed in manufactories of every kind. I have but one objection to oppose to these conclusions; which is, that Papin's work, in which the idea of boats, and that of a continuous rotary motion communicated to a wheel by a steam pump, preceded the work of the engineer, Hull, by 42 years.

An English Savant, a friend of mine, to whom I communicated verbally the results contained in this memoir, told me that if I ever should publish it, he would confute all my assertions by passages taken from French authors. "It will be," added he laughing, "a war of quotations." Begging him to explain himself farther, I discovered that the arguments which he meant to array against me would be derived either from a biographical article upon Newcomen, from the pen of one of the most illustrious philosophers of our day, or in a memorial concerning steam vessels drawn up by the celebrated professor of mechanics in the Conservatory, and approved by the Academy of Sciences. In these two articles, I am compelled to admit, the opinions of English authors upon the inventors of the steam engine have been unreservedly adopted. The objection has therefore some weight, but it does not appear to me to be conIn speaking of steam engines in general, I have endeavoured to give a share of the notice to the inventors, properly so called, and another to the engineers, who have been the first to turn the invention to account. If we continue to follow the same plan we shall find:

That M. Perier was the first, in 1775 to build a steam vessel, (a work of M. Ducrest, printed in 1777, contains the discussion of the experiments which this engineer witnessed; their date is therefore authentically verified);

That experiments on a larger scale were made in 1778, at Baume les Dames, by the Marquis de Jouffroy;

That in 1781, M. de Jouffroy, putting his plans into execution, actually established a large boat of the same kind, upon the Saône, which was not less than 46 metres long, with 4.5 metres beam.

That the minister of that time addressed the report of the favorable results given by this vessel, to the Academy of Sciences in 1783, with the view of deciding whether M. de Joffroy had a right to the exclusive privilege

clusive. As to what respects the memoir of Newcomen, I will remark in the first place that it is evidently copied from Robison's history; that the distinguished writer to whom we are indebted for it, no where announces that he has made particular research upon this occasion, or, that he has consulted original documents. If he had cited Solomon de Caus, I should have doubtless entertained scruples as to the importance which it appeared right to me to give to the researches of the French machinist; but his name is not found once in the biography, although, we find in large letters, those of Worcester and Savery. From this I think I may conclude with certainty, that the works of Solomon de Caus, and I presume those of Papin also, were unknown to my learned brother; (confrère)-his opinion ought not therefore to be opposed to mine, since I shall have the right, like an ancient Greek philosopher, to appeal from Philip to Philip better informed.* In reference to the second objection, I shall easily set aside the authority of the Academy of Sciences by remarking that its invariable rule is only to decide upon the conclusions of the reports presented to it. The developments, be they more or less extensive, which accompany these conclusions, do not give rise, on its part, to any deliberation, the reporter alone is responsible for them. Now the very minute report respecting steain vessels, which was read before the Academy on the 27th of January, 1823, winds up with conclusions in which I do not find a single word in relation to the inventors of the steam engine. The Academy has therefore decided nothing that can be brought in opposition to my views. As to the text of the report itself, I find in it, it is true, that the English were the first to employ steam power for raising water; that Worcester is the inventor, whose ideas Savery developed; that Jonathan Hull was the first who thought of propelling vessels by means of the steam engine, but as I neither see there the name of Solomon de Caus nor that of Papin, although, whether for good or evil, they were occupied with these same questions before the English mechanicians, I may claim the right to reproduce here the reflections which the article in the Universal Biography suggested to me some time ago. Besides, the authorities, however respectable, are in this place of no importance. The question is reduced to the simple point, whether the works by which I have supported my argument really bear the date assigned to them, and whether my extracts are faithfully made. Though all the Academies in the world should decide, by common consent, that Worcester first conceived the idea of impelling water by the elastic power of steam, it would not be less an established fact that the idea belonged to Solomon de Caus, since 1615 preceded 1663. As long as it has not been proved, in like manner, that the year 1695 followed 1736, Papin, in spite of all reports past, present, and to come, will have the merit of having proposed steam vessels 42 years before his competitor Jonathan Hull.

* For the same reason on the subject of the high pressure engine, and of the Steam Boat, we appeal from M. Arago to M. Arago better informed.

TRANS.

which he claimed,* (Messrs. Borda and Perier, were appointed a committee on it);

That the trials made in England by Mr. Miller, Lord Stanhope and Mr. Symington are of a much later date, (the first should be referred to the year 1791; Lord Stanhope's, to 1795, and the experiment made by Symington in a canal in Scotland, to the year 1801);

Lastly, that the attempts of Messrs. Livingston and Fulton at Paris, not taking place until 1803, could with so much the less propriety give title to the invention, in that Fulton had had a minute acquaintance in England with the experiments of Messrs. Miller and Symington, and because many of his countrymen, Mr. Fitch, among others, had devoted themselves to the subject by public experiments from the year 1786.* Let it be observed, however, that the first steam vessel, which was not given up after being tried; the first which was applied to the transportation of men and merchandize, was that which Fulton constructed at New York, in 1807, and which made a trip from that city to Albany. In England the first steam vessel established for the convenience of commerce and travellers, dates as far back only as 1812; it navigated the Clyde, and was called the Comet. The second began to run in 1813; it made trips between Yarmouth and Norwich.

Contrivances which render the Steam Engine self-acting.

The first of Newcomen's engines required the constant attention of a workman who opened and closed, alternately, various valves, sometimes to let steam into the cylinder, and sometimes to admit the water required to condense it. Tradition attributes the first invention of the contrivance, by means of which the engine itself opens the valves at the proper time, to a boy named Humphrey Potter. It is said that Potter, disconcerted one day at not being able to go and play with his companions, took it into his head to tie the ends of a piece of pack-thread to the handles of the two cocks which he was stationed to open and shut; the other ends being fastened to the working beam, the pull which it occasioned in rising or descending, did the office which had been performed by hand. Beighton, the engineer, improved very much upon this idea, by fixing a bar of wood called a plug-frame, vertically, to the working frame. This bar was provided with various plugs, which bore upon the stems of the different valves, at convenient times determined by the vibration of the beam. Beighton's mechanism was adopted by Watt with some advantageous modifications. The distribution of steam into the various parts of the cylinder, is now effected by simpler means which have entirely superceded the use of the plug-frame, at least in engines in which the power is not excessively great, and which are intended to communicate a rotary motion. This contrivance, which I will not here attempt to describe, as without drawings it would perhaps be unintelligible, is called an eccentric. An eccentric wheel attached to an axis turned by the engine, gives two opposite motions to the slide, during each of its revolutions; these two motions suffice to admit the steam from the boiler above and below the piston suc

* The vessel tried at Lyons, contained two distinct steam engines. The events of the French revolution compelled M. de Jouffroy to emigrate, and all his efforts were consequently without result.

† Rumsey's name is not even mentioned by M. Arago, nor is he acquainted with the claims of Stevens, Evans, and others. It is highly desirable that some one acquainted fully with this subject would take up the assertion of our countryman's claims against the manifest injustice ice here and elsewhere done to them. The tardy admission made in the next sentence is not justice. TRANS.

cessively, and to provide a convenient outlet towards the condenser for that which has already acted.

The mechanism of the slide and its eccentric, was contrived by Mr. Murray, of Leeds, in 1801.

In high pressure and double acting engines the steam is let in successively above and below the piston, and as soon as it has produced its effect is let off into the air. All this only requires a quarter of a turn of one and the same cock, called the four way cock. This very ingenious apparatus is uniformly employed at present in all the large water-engines made in Gen many. Its invention belongs to Papin: it may be seen in the high pressure engine of this machinist, a figure of which is given by Leopold, and in that which Leopold himself subsequently proposed, in the year 1724.

The Crank and Fly Wheel.

Mr. Keane Fitzgerald published in the Philosophical Transactions, for 1758, p. 727, et seq., the description of a process for transforming the rectilinear motion of the piston of a steam engine into a continuous rotary motion. For this purpose he made use of a rather complicated system of toothed wheels, several of which were ratchet-wheels. Thus far the method of this engineer agrees with that of Papin; but he improved upon it by adding to this mechanism, a fly-wheel, a valuable contrivance for regulating the motion of steam engines, now in general use, and the honour of which justly belongs to Mr. Keane Fitzgerald.

While the oscillating motion of the working beam of a steam engine was transmitted to the revolving axis by the intervention of toothed-wheels, it was exposed to fractures, very vexatious in themselves, and the more so on account of the interruptions of work which they occasioned. In 1778 Mr. Washborough of Bristol, proposed to make this communication by means of a crank connected with the revolving axis. This, it will be perceived, was simply to make use of an expedient found in all spinning wheels, and in the apparatus of every knife grinder.

Nevertheless a patent having been taken out, a contrivance which every body was at liberty to make use of when the motive power was either the foot of a man or a current of water, was interdicted to the engineer whose engine operated by steam. In order to avoid the tax which he would have been obliged to pay to Mr. Washborough for each one of his engines, Watt made use of a communication of motion slightly different, until the expiration of the patent right which the former possessed; this operated by means of a toothed-wheel fastened to the revolving axis, which he called the sun wheel, because its centre remained fixed, and another wheel also furnished with cogs attached to a rod from the working beam, and which, as it revolves round the other wheel, he called the planet wheel. It would be of no use to describe this piece of mechanism more particularly, since Watt himself used the crank as soon as he could.

The Parallel Motion.

In Newcomen's or Watt's single acting engine, the working beam terminated in the arc of a circle, and a flexible chain, attached to the upper extremity of that arc was the means of communicating between these two parts of the apparatus. When the piston descended by the pressure of the atmosphere, it pulled the beam. When the beam rose again by the action of a counterpoise placed at the opposite extremity, it pulled the piston. Now VOL. XXV.-No. 2-FEBRUARY, 1840.

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though a chain, however flexible it may be, is always excellent for a pull, it will not answer to push, and hence the double acting engine requires a different connection. In the descending motion of the piston it draws the beam; but in the succeeding motion, or when the beam rests again, it ought to be propelled from below upwards: which the chain cannot do. The first contrivance, therefore, required modification.

The first modification adopted consisted in cogging a part of the rod of the piston, to make a rack of it, which caught in a circular arc, also cogged, and fixed to the extremity of the working beam. This is what Papin proposed in 1695.

Subsequently, Watt devised a much preferable method, which is now generally adopted wherever there is no want of room; it is called the parallel motion. It would be very difficult for me to give a complete description of it here, without figures. Suffice it to say that a parallelogram the four angles of which have four pivots, and which consequently may assume all sorts of angles without ceasing to be a parallelogram, is attached by its two upper angles to the working frame of the engine; that the piston rod is fixed to one of the lower angles, and that the fourth angle is fastened to a stiff radius rod, movable round a fixed centre. Whatever the position of this centre, if the lever attached to it remain of invariable length, the parallelogram changes its shape during the vibrations of the beam, being sometimes a rectangle and sometimes a rhomboid. But when the centre to which the lever is attached is suitably chosen (herein the discovery of Watt consists) the angle of the movable parallelogram of variable form, to which the piston rod is attached, does not sensibly depart from the vertical during the vibration of the working frame. The motion of the piston is in this manner perfectly regulated and its communication with the working beam taking place by the intervention of an inflexible system, it can with the same ease draw the beam downwards during the descending motion of the piston as force it upward when the piston rises. The jointed parallelogram attracts the strongest attention from persons who witness the operation of a steam engine for the first time. To the eyes of the practised machinist, it presents itself as an apparatus of easy construction, entirely exempt from concussion, and susceptable of indefinite duration. It is evidently one of Watt's most ingenious inventions. The patent in which it is described is dated in the month of April, 1784.

The Governor.

The pipe which, in Watt's engines, lets the steam from the boiler into the cylinder, contains a thin plate, or valve, similar to the dampers which are fitted in our stove pipes. In a certain position, the plate leaves the opening of the pipe almost entirely free; in another it is entirely closed, and in the intermediate positions of the valve, the opening is greater or less according to its approach to the two limits just mentioned. The valve may be moved by a handle attached to the axis which is prolonged to the outside of the pipe.

If the valve is entirely open the steam fills the cylinder very rapidly; if it is nearly closed, it requires, on the contrary, a considerable time to effect the efflux of the same same quantity of steam. Now the number of seconds occupied by the strokes of the piston depends evidently upon the rapidity of the pressure of the steam upon one or other of its surfaces. The turning valve in the tube gives, therefore, in a certain degree, the means of regulating this rapidity.