relative to the application of steam, excepting what we have already stated. We are unable, at this period, to form any idea as to the originality of the plans which have been named. It is impossible to state whether they were descriptions of what was generally known, or they were the invention of those by whom they were claimed. Nor should our readers be surprised at the obscurity in which these matters are involved, when they reflect, that there is frequently great difficulty in deciding who are the inventors of the most meritorious productions of our own times.

Having briefly stated what is recorded respecting the earlier history of the steam engine, when it had merely the character of a philosophic toy, we come to speak of the first attempt towards its adoption as a powerful agent.

It is described in a work by Solomon de Caus, an eminent French mathematician and engineer, published in 1615, entitled, "Les Raisons des Force mouvantes avec divers Desseins de Fontains."

The following description will explain the principle of his invention.

a is a spherical vessel, placed over a fire; it is furnished with two pipes, b, e. The pipe e is open at the top, and reaches down to the bottom of the vessel a. The pipe b is furnished with a cock d, and funnel c. The vessel being filled with water, and fire applied, steam is speedily generated upon the surface of the water, and having no other way to escape, the cock d being stopped, presses on the surface, and so forces it up

the tube e into the air, causing (De Caus's Engine. 1615.)

a jet, which varies in proportion to the elasticity of the steam within.

De Caus appears, also, to have been aware that a vacuum could be obtained by the condensation of steam, but we have no opportunity of knowing whether he ever thought of using it as a means of increasing the power of his machine.

The engine which next demands our attention, both on account of its importance and date, is that invented by Giovanni Branca, an Italian mathematician, who resided at Rome, at the commencement of the seventeenth century. We are indebted for our knowledge of this machine to his own account, published in 1629.* The drawing which he there furnishes must be understood rather as an ornamental illustration of his plan, than as the form in which it was actually constructed: we have, therefore, given one which we conceive to be more consistent with the end he proposed to effect by its use.

The boiler of this engine is represented by a; b is the fire grate; c a small pipe, provided with a stop cock f; d is a wheel furnished with vanes; e is a crank which gives motion, through the medium of the suspended rod, to a

stamper for pounding drugs. The principle of action isthat steam is generated in the boiler, and rushes violently against the vanes, which causes the wheel to revolve, and thus produces a reciprocation of the rod and stamper.

This invention had remained unnoticed but by the learned, until the last few years. It is described by Partington, in his History of the Steam Engine, who goes so far as to allow Branca the merit of the first idea. We believe our readers will perceive that to this honour Branca has no claim. His engine is on the same principle as Hero's, only differently modified. Its ingenuity is decidedly inferior to its prototype, both in simplicity and effect.

But of all the various applications of the elastic force of steam, nothing of this period has stood so high in public estimation as a brief description of "a fire-water work," contained in the Marquis of Worcester's celebrated "Century of Inventions," dated 1663; the original manuscript of which is preserved in the British Museum. The following is the Marquis's own description :—

"An admirable and most forcible way to drive up water by fire, not by drawing or sucking it upwards, for that must be, as the philosopher calls it, infra 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, stopping and screwing up the broken end, as 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 found 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, rarified 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."

From this account Dr. Robinson founds an opinion, that "the steam engine was, beyond all doubt, the invention of the Marquis of Worcester." It is probable that the learned doctor was unacquainted with De Caus and Branca's previous experiments, or he could not have come to this conclusion. But whilst we cannot admit the Marquis to be entitled to the extravagant encomiums which have been lavished upon him, we are far from disallowing his invention to possess merit and originality. The annexed drawing we consider to embody the Marquis's idea more perfectly than any we have seen, although there must be several parts unexplained.

The most difficult and unintelligible seems to have been the "forcing and refilling," which (but for its being a mechanical impossibility) one should imagine to mean that both these operations were going on at the same time, in the same vessel. The easiest way of getting over this difficulty seems to be by supposing the "refilling" to allude to the filling of the cistern, to which the water must be elevated. So that, instead of saying, "the other begins to force and refill," we should say, the other begins to force and refill the cistern. This, we confess, is a straining of the text, but at the same time much less so than Dr. Brewster's corrections, who reads: "One vessel of water being consumed, another begins to force, and then to fill itself with cold water;" or than the author of Stewart's History of the Steam Engine, who, in order to accommodate the text to his idea of the engine, makes an emendation by saying, "to force and empty of cold water."-The strengthening of a vessel by the force within, also appears to be a mechanical impossibility; but we conceive that, to an extent equal to any force required for raising water, a boiler, of the form represented in the figure, would be strengthened by the internal pressure.

In the above figure, a represents the boiler, composed of arched iron plates, with their convex sides turned inwards, they are fastened at the joinings by bolts passing through holes in their sides, which also pass through the ends of the rods i ii. A series of which rods extend from end to end of the boiler, being a few inches apart. The ends of this boiler are hemispherical, and are fastened to flanges on the plates hhhh. It will appear evident that, each plate being an arch, before the boiler can burst, several, if not nearly all the rods i i, must either be pulled asunder, or torn from the bolts at the points of junction; and as the strength of the rods and bolts may be increased to any extent, without interrupting the action of the fire, there can be no doubt but that a boiler might be so constructed as to be perfectly safe under any pressure, which could be required for raising water to a given height, because the