A second alteration consists in the suppression of the dilated sheet of water which terminates the ascending jet. I confess, that having no argument to offer upon the length of these tubes; I did not enjoin the person who copied the figure to preserve the proportions of the original drawing. As to the sheet of water, the engraver suppressed it to simplify his work. Mr. Ainger might have added that he has not figured the water in the ball and that the burning sticks placed under it do not perfectly resemble those of Solomon de Caus. I recommend these observations to his attention in case his pamphlet reaches a second edition. The extreme futility of the criticism just noticed ought not to prevent me from making a brief remark. I have no where announced either that Hiero's figure, or that of Solomon de Caus, were copied minutely or in exact geometrical proportion; thus Mr. Ainger exposed himself to severe observations when he said: "M. Arago gives the figure as an extract from the same work (that of Solomon de Caus)."

Observing that Mr. Ainger, in the article Savery, returns a second time to this lengthening of the tube, which he presents as an important alteration, and one made on purpose, I have had the curiosity to apply a compass to the tube in the figure given in the Annuaire, and to the jet figured in the work of Solomon de Caus; and it appears that the jet is nearly a third larger than the tube. Thus Mr. Ainger has reduced himself to the choice of an alternative, either to retract his abusive insinuations or to maintain that the power in virtue of which a jet of water rises in the air would not carry the liquid the same height in a tube. I would charitably persuade him not to make this choice until after having consulted a treatise upon hydraulics.

This elongation of the tube appears to have been a real windfall in Mr. Ainger's eyes. He makes the best of it in every way; he would not cut off a millemetre of it for a treasure, and yet the whole amounted to this, that it appeared to him very long, since he declares, page 330, that the two tubes are indefinitely elongated. I have just said that the tube is shorter than the jet in the original; thus, whatever malice may be exercised in the case, this fact must be recognized, that the alteration, if alteration there be, has not been made with the intention of adding to the power of the engine. If I had thought and I ought to insist upon the great height to which steam, in the apparatus of de Caus, could raise water, I should have shewn it not by a figure without a scale, but by reference to this phrase, already cited: "The violence is great when the water is converted into air by means of fire it is certain that if the said ball (a copper ball containing water) is placed upon a large fire so that it may get very hot, it will cause so violent a compression that the ball will split in pieces."

...

In writing the history of the steam engine, I thought that the best way of fixing the attention of the reader would be to show, step by step, in what respect each new plan improved the engine already existing. It is in this way, for instance, that I have analysed all the improvements which Savery made in Solomon de Caus' engine. This method appears to have singularly displeased Mr. Ainger; to explain Savery's engine, and to explain it clearly without finding it necessary to resort to a figure, is quite shameful in his eyes; he does not say that the description is inaccurate or that it appears to him insufficient, and the sin of omission, therefore, with which he reproaches me was only conjured up by way of a make weight.

Whoever should entertain the idea of not limiting his responsibility to the strict signification of his words, and should be imprudent enought to extend it to the consequences which might be deduced from them, would find certain commentators who would soon make him repent his rashness. Two little illustrations having appeared to me necessary to explain the ideas which directed Papin in the various attempts to which he devoted himself before he contrived the atmospheric steam engine, I placed them in the memoir published in the Annuaire at the head of the arguments of which they were, in some degree, the illustration. What does Mr. Ainger on this occasion? He says that these illustration being immediately under the title, Denis Papin, "the reader of course concludes are the description of Papin's invention; but," adds he, it will hardly be believed that they are nothing of the sort, they are the descriptions of the apparatus of the Englishman, Newcomen, made fifteen years afterwards."

My answer will be very simple: as a general position I do not accept of the conclusions which the first-comer takes a fancy to draw from my words; I do not feel myself strong enough to resist this sort of attack; I will add in this particular case, that having nowhere said: "the two figures which I make use of are taken from Papin's works," it should affect me but little to have my critic cry out that they are not to be found there; but I have a perfect right to maintain that they are there, for the engine in which Papin proposed to cause a vacuum under the piston by the aid of a separate hydraulic wheel, is no other than that which I have given a drawing of, excepting this single modification; that the valve, or rather the cock, intended to admit the air, instead of being situated under the metallic plate which supports the cylinder, as in my drawing, is on one side at the end of a little horizontal tube issuing from the bottom of this same cylinder. If, profiting by the inexperience which the readers of a journal may have in the contrivances of mechanists, Mr. Ainger has pretended to establish the belief that such a displacement of the valve or cock had been made with the view of improving Papin's plan, I will remark that in modern engines the valve is never at the bottom of the cylinder and that it is always, as in the genuine illustration of Papin, upon the nearly horizontal tube which supplies the steam. M. Arago, says Mr. Ainger, "gives six pages to the description of this apparatus (Papin's,) in which he brings the steam into the cylinder from the boiler, through the valve a," (that of the lower plate.) I am really sorry that my antagonist so often obliges me to answer him by a simple denial; but in truth I cannot admit his version, as I said: "the water which furnished the steam in these first attempts, was not contained in a separate boiler, it was deposited in the cylinder upon the metallic plate which stopped it below." In the whole of the remainder of the article nothing more is said about the production of steam.

Papin proposed two kinds of steam engines. The first, that of 1690, is the engine with a piston, known, since its improved construction by Newcomen, by the name of the atmospheric engine; the other, described in 1707, depended upon different principles, and was simply intended for raising water. I have not room here to discuss the different criticisms of which this last engine has been the subject; I will grant then, if it is desired, that they are all well founded; but what of that? We can only conclude that Papin was more clever or more fortunate in 1690 that in 1707; that his mind was enfeebled by age; that at the second period of time the whole merit of the discovery which he had made seventeen years before, had ceased to be as vividly impressed upon his memory; but in what does all this weaken his right to the invention. Did Newton cease to be author of the Principia or of his Optics after he had witten an inferior treatise upon chronology.

The trouble, therefore, that Mr. Ainger and other writers have given themselves to criticise the second engine (invented in 1707) is thrown away

Though Papin should have been crazy at the time, though he should have been confined in a mad house, his engine of 1690 would, nevertheless, remain the germ of all the steam engines in existence. Besides, it is not difficult perhaps to find a plausible motive for Papin's abandonment of his first project: it probably lay in the difficulty in casting and boring out the cylinders which he would have required. In 1695 this difficulty, which in our days has entirely disappeared, seemed to him so great that he proposed to establish a manufactory expressly for the purpose of making the tubes intended to compose the cylinders of such of his engines as should be made use of to propel vessels.

Mr. Ainger does not admit the doubts which I have raised respecting the interpretation hitherto given to a passage relative to the boiler which Worcester proposed to make use of. Want of space obliges me to submit to judgment by default in this case, although, if it were worth the trouble, I could cite one of the most celebrated English engineers in support of my opinion. The same motive prevents me from correcting one or two really singular mistakes into which Mr. Ainger has fallen in an irrelevant display of erudition on the subject of an experiment of Otto de Guerike.* I hasten then to come to his great objections.

However slight the attention which may have been given to the working of a steam engine, two things of capital importance are apparent: in the first place the idea of employing the elastic power of steam as a principle of motion; secondly, the idea, not less important, of getting rid of this steam by condensation, as soon as it has operated.

Should the person, who first reflecting upon the prodigious elasticity which steam acquires when it is produced at a high temperature, have shewn that it might be used to raise great weights; he who has been the first to propose and describe an engine in which the elasticity of steam was the sole priciple of useful operation in the arts; should this person, I repeat, be considered as the inventor of the steam engine? Such is the first question to which the history of this engine gives birth; and one which has been answered affirmatively in all the works with which I am acquainted. Thomas Young, Robison, Partington, Tredgold, Millington, Lardner, Nicholson, etc., are unanimous in this respect. For my part I have only adhered to the opinion of so many able natural philosophers and engineers, and differ from them but in one point: in England the discovery is generally attributed to the Marquis of Worcester, I maintain that it is due to Solomon de Caus, because this engineer's work contains the figure and the description of an engine intended to raise water by the action of steam; because the Marquis of Worcester's, of which moreover the form is not known, had precisely the same object, and because the little which is known with regard to it did not appear until 1663, forty-eight years after the publication of La Raison des Forces Mouvantes.

Here Mr. Ainger enters the lists, who also discovers an engine intended for raising water, in J. B. Porta, an author older than Solomon de Caus. If this be the case, the name of Solomon de Caus, which I have substituted for that of Worcester, ought, without doubt, to make way in turn for the name of Porta. Therefore I proceed at once to verify Mr. Ainger's assertion, without dwelling upon the singularity of the circumstance that the

* We cannot consider this as an irrelevant display of erudition on the part of Mr. Ainger, as Otto de Guerike certainly did raise a weight by the descent of a piston before Papin had any such idea. That he made a vacuum under the piston by an air pump does not invalidate this claim.-TRANS.

name of the Neapolitan savant should never have been mentioned as long as Worcester enjoyed, without dispute, the title of inventor, and that it should have been called to mind as soon as it seemed to militate against the rights of a French author.

The Neapolitan philosopher's engine is found, says Mr. Ainger, "in a translation of the work of Hiero of Alexandria, which was published in Italian by Baptista Porta, in 1606," (pages 326 and 327.) I read further on (page 344,) "The reader who wishes to verify the statements here given may consult the different editions of Hiero's Spiritalia, and especially the translation in 1606, by Porta, entitled: I tre libri Spiritalia, of which a copy is in the British museum."

When the article in the Quarterly Journal reached me, I had glanced over various editions of Hiero's work, but I did not know that of Porta which Mr. Ainger cites. At first I reproached myself for this negligence, but, upon investigation, assisted by our most celebrated bibliographers, it was discovered that the work in question does not exist; that, in fact, there is no translation of Hiero by Porta. This author, it is true, has published a work, in latin entitled, like that of the Greek mechanician, (Pneumaticorum libri tres, Naples, 1601, in quarto) but it is no more the work of Hiero than Buffon's natural history is a translation of Aristotle's. The Pneumatics of Porta, translated into Italian and Spanish by a person called Juan Escrivano, were published in 1606 with the title of: I tre libri de Spiritali de Giovam. Battista della Porta Napolitano, in a small quarto volume. This is the book which Mr. Ainger has taken for an Italian translation made by Porta, while it is actually by Juan Escrivano; for a translation of the Greek work by Hiero, while it is a translation of a Latin work by Porta. Mr. Ainger has succeeded in uniting upon this point all the errors into which it was possible to fall.

In the seventy-fifth page of Porta's Spiritali, published by Escrivano, is found the apparatus which Mr. Ainger cites as an engine for raising water by means of the elastic power of steam, as a great improvement of an engine by Hiero, of which I shall soon have occasion to speak. I will here give a translation of the chapter of Porta, or rather of the chapter of Escrivano, for it does not exist in the original, and it will then appear how far Mr. Ainger has brought his inventive genius into play.

"CHAPTER VII.-To know into how many parts a simple portion of water is transformed.

C

"Make a box of glass or tin, the bottom of which should be pierced with a hole, through which shall pass the neck of a bottle used for distilling, containing one or two ounces of water. The neck shall be soldered to the bottom of the box, so that nothing can escape there. From the same bottom shall proceed a pipe, the opening of which shall almost touch it, leaving just room enough between them for the water to run. This pipe shall pass through an opening in the lid of the box, and extend itself on the outside to a small distance from its surface, (passi per lo coverchio fuori poco lontano dalla sua superficia.) The box must be filled with water by a funnel, which is afterwards to be well closed, so as not to allow the air to escape, (che non

posso respirare); finally, the bottle must be placed upon the fire and heated a little, then the water, changed into steam, will act violently upon the water in the box, and will make it pass through the pipe c and flow off on the outside. The water must be kept heated, in this way, until no more of it remains; and as long as the water shall smoke (sfumera) the air will press the water in the box, and the water will flow off on the outside. The evaporation being finished, you may measure how much water has gone out of the box, and there will remain in it as much water as shall have passed out of it, (the bottle) and from that you can conclude how much water has run out, and into how much air it has been changed. You may also easily calculate how many parts of lighter air an ounce of air of ordinary consistence is capable of giving."

Let us now recall the manner in which Mr. Ainger announces this passage.

"A translation, says he, of the work of Hiero's, was published in Italian, by Baptista Porta, in 1606, he repeats Hiero's invention, and adds the following of his own, illustrated by a diagram, in which is shewn the furnace for heating the water."

The truth is, that Porta does not speak at all of Hiero's machine; that he had no kind of intention of improving it; that he did not even dream of making an engine; that his aim, his whole aim, was to determine experimentally, and by a method, all the faults of which it is useless here to point out, the relative bulk of a given quantity of water, and of the steam into which it is transformed by heat. Porta had so little idea of proposing his apparatus as a fit one for raising water, that he says in formal terms that the pipe by which the water flows off passes to a small distance from the lid of the small box. I have no wish to deny that Porta was not ignorant that steam could propel a liquid in the same way as air; but nothing, absolutely nothing, proves that he had the least idea of the great power which steam is susceptible of acquiring, and of the possibility of employing it as an effective moving power. Porta, the most enthusiastic of contrivers mentioned in the history of the sciences, would not certainly have neglected to speak of this particular motion if he had ever entertained it. Moreover, the whole effect of Porta's experiment would have been equally produced, if his large bottle in lieu of water had only contained air.*

The double idea that steam properly enclosed, raises water above its level, and that it is capable of producing the greatest effect; that therefore, it might be used in the construction of useful engines, is found, for the first time to my knowledge, in the work of Solomon de Caus. Perhaps something analogous to it may be found in older authors. Very well! in that case, the name of Solomon de Caus, I repeat, must disappear from the history of the steam engine, as I have erased from it the Marquis of Worcester; but, unless this new name belongs to some personage born in the British isles, there will be still room for correcting this assertion so often reproduced. "The steam engine has been the invention of a few individuals, all Englishmen."

Many enlightened men of science and mechanicians attach small importance to the first idea of the application of steam as a motive power. The ancients, say they, who attributed earthquakes to the instantaneous develop

*Notwithstanding this laboured argument, it appears to me, that if the figure given of Porta's machine is correct, it is the true germ of the engine for raising water, afterwards used by Savery; without, however, using the principle of condensation.

TRANS.