térité regardera, sans doute, comme le premier inventeur de la machine à feu."

This case, as far as regards the claim made in behalf of France and De Caus, may now be left to the reader; but it remains to consider it in reference to M. Arago's protestation, "mes citations seront exactes, on peut y compter."

The diagram, Fig. 4, is accurately copied from the work of De Caus; the diagram given by M. Arago as an extract from the same work is represented in Fig. 5, where it will be seen that the tubes b and c are indefinitely elongated, and the jet of water omitted. This is, of course, an accidental variation, but it renders the assertion of M. Arago, that the apparatus is a "proper machine for draining," a little less amusing than it would have been without this example of the exactness of the citations.

Fig. 6 describes an apparatus proposed in 1629, by Branca, an Italian. The boiler a terminates with a bent tube b, from which the steam issues, and impinges upon the vanes of a wheel c, which receives motion in the direction of the arrow. There is very little novelty in this contrivance; the principle does not differ from the first apparatus of Hero, and the practical effect would probably be inferior.

In 1663 appeared the "Century of Inventions," by the Marquis of Worcester; the following is a copy of that numbered 68.

“An admirable and most forcible way to drive up water by

fire, not by drawing it or sucking it upwards, for that must be, as the philosopher calleth it, intra sphæram activitatis, which is but at such a distance. But this way hath no bounder, if the vessels be strong enough: for I have taken a piece of a whole cannon, whereof the end was burst, and filled it three-quarters full of water, stopping and screwing up the broken end, and also the touch-hole, and making a constant fire under it, within twenty-four hours it burst, and made a great crack; so that having a way to make my vessels so that they are strengthened by the force within them, and the one to fill after the other, I have seen the water run like a constant fountain-stream forty feet high; one vessel of water rarefied by fire driveth up forty of cold water. And a man that tends the work is but to turn two cocks, that one vessel of water being consumed, another begins to force and refill with cold water, and so successively the fire being tended and kept constant, which the self-same person may likewise abundantly perform in the interim between the necessity of turning the said cocks."

This apparatus is, in principle, the same as Porta's. The merit of the Marquis of Worcester consists in having suggested the use of highly elastic steam, in exceedingly strong vessels, so as to raise water to a useful height, as forty feet. He has also the merit of urging the adoption of this plan on the large scale, whereas the schemes of Hero and Porta were mere experimental toys. It is most probable that the Marquis never tried this apparatus on a large scale, notwithstanding his assertion to the contrary; but that his description may easily be realized there is no doubt, though M. Arago denies it, and although he says that Mr. Stuart could not realize it, otherwise than by grouping together two of the vessels of Salomon De Caus, and working them alternately. Mr. Stuart's description is very incorrect if it be as M. Arrago states; for the globe of De Caus ejects hot water, whereas the Marquis of Worcester proposes that one vessel of heated water shall raise forty of cold water. This M. Arago insinuates it is impossible to do by adhering strictly to the description of Lord Worcester. The annexed diagram appears, however, to realize all the conditions. Let a (Fig. 7,) represent the boiler communicating by the pipes b and c, with the cold water vessels d

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and e, which latter communicate by the pipe ff, with the water to be raised, gg. The pipes h and k ascend to the reservoir, forty feet above, and their lower ends enter the cold water vessels e and d. The two cocks, b and c, are those which are described to be opened and shut alternately. The four valves in the pipes f, h, and k, are precisely such as had been used for nearly two thousand years in pumps. The vessels d and è are in fact forcing-pumps, in which steam is substituted for a solid piston." The cock e is in the diagram open, the steam is therefore for cing the water out of e, and up the pipe h. The cock b is closed, and the vessel d is cooling; the water tends therefore to enter it both from the cistern g g, and from the pipe k; the arrangement of the valves, exactly like those of a pump, prevents the latter and permits the former: therefore, the vessel d as it cools is filled from the cistern g g. This action would no doubt go on alternately, by maintaining the fire, and alternately opening and shutting the cocks bc; and it is quite certain that this proposal more nearly resembles the first steam-engine known to have been made, than any prior invention. In this diagram, the most unfavourablé case is taken for the Marquis, because there is nothing in his description to forbid our concluding that he would have availed himself of what was then

well known, the vacuum formed by the condensation of the steam. He would then have placed the vessels d and e twenty. or thirty feet above the water g, and in this shape it would be very nearly a perfect anticipation of the first working steamengine.

On the whole, very little credit is due to the Marquis of Worcester. The majority of his hundred projects are either absurd or puerile: some are impossible to realize, many are not worth realizing, many contain no novelty, and several have a taint of the perpetual motion. All this is so evident, that it would hardly have been thought worth while to mistranslate the Marquis, in order to make his one rational project as absurd as many of the others, yet this M. Arago does.

The Marquis says, "my vessels are strengthened by the force within them." This has been usually translated by French writers," mes vaisseaux sont fortifiés intérieurement." M. Arago translates it, "des vases qui se fortifient par le dévet loppement de la force intérieure." He says that he is aware! that the rendering of former translators is more reasonable than » his own, but that it ought to be made extravagant to corre spond with the other projects of the Marquis. M. Arago has certainly succeeded in making the Marquis absurd, for he supposes him to mean that the stronger the steam, that is to say, the greater the strain to which they are exposed, the stronger will be the vessels; and, in order to bear out this assumption, he alters the whole passage. Lord Worcester says, “the vessels are strengthened." M. Arago translates it, "des vases qui se fortifient." Lord Worcester says, "by the force within them." M. Arago translates this, par le développement de la · force intérieure ;" the word "développement" is gratuitously introduced to assist the first misrepresentation, and to help. the insinuation that it was proposed to strengthen the vessels by the strength of the steam; for the word développement is unintelligible as applied to a constant source of strength; it must mean something which fluctuates in the vessel, and there is nothing which does this but the steam.

To proceed with the historical series, it may be mentioned, that about this time Otto Guericke was engaged in those experiments and speculations which led to the invention of the

APRIL-JUNE, 1829.

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air-pump, to a better knowledge than had hitherto been obtained of the air's weight and elasticity, and particularly of the powerful effects of that weight and elasticity when excited by an exhausted, or partially exhausted, space,

Otto Guericke, in his work on the subject, published in 1672, describes numerous contrivances for exhibiting or using mechanically the weight of the air. One apparatus he describes similar to that in Fig. 8, where a a is a cylinder, to

which is fitted a piston, b, attached to a chain, c, which passes over the pulleys, d d, and supports a loaded scale, e. A pipe, f, enters the cylinder near the bottom, and to this pipe a pump is to be attached, by whose means the air may be withdrawn from the lower part of the cylinder, which will, of course, cause the piston to be forced downwards by the unbalanced pressure of the atmosphere. In this way Guericke says that a boy of twelve or fifteen years old, acting on the pump at f may raise a weight, however large, in the scale, e, provided only that the diameters of the pump and the cylinder, a, be properly proportioned.

This, it will be perceived, is an anticipation of the principle of Bramah's hydrostatic press; not that it at all interferes with the credit due to Mr. Bramah for that beautiful invention, because he claimed no discovery of new principles, but a better application of those which were old.

In this apparatus of Otto Guericke, which is fully described by a very large picturesque engraving in his work of 1672, we have a complete explanation of the principle of obtaining power from a vacuum formed under a movable piston. It is quite clear, also, that the mode of producing a vacuum, by