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

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pressure in such a boiler will never exceed the weight of column of water, equal in height to the elevation of the cistern.

bc represent two vessels, which communicate with the boiler a, by means of the pipes ƒƒ, and three-way cocks m n, and with the reservoir from which the water is to be drawn by the pipes ll. gg are two tubes, through which the water is elevated to the cistern; they reach nearly to the bottom of the vessels b c, and are open at each end. The pipe l, also ff, communicate with the vessels b c, by means of the three-way cocks m n, which, by moving the handles o p, can be so placed that either the steam from the boiler, or the water from the reservoir, shall instantly have access to the vessels b c.

Fire having been kindled under the boiler a, in the furnace d, “the man who tends the work" places the cock n, in the position represented in the drawing, when the water will have free access from the reservoir to the vessel c, which being filled, the handle p is turned back, so that the cock shall be relatively in the position shown at m; the steam then fairly enters through the pipe ƒ, into the vessel C, and having no other mode of escape, presses on the surface of the water, which it forces up through the pipe g. During this operation, (the cock m having been placed as shewn at n,) the vessel b is filling from the reservoir through the pipe l; so that the water in the vessel c, being consumed, the man turns the handle o, of the cock p, and admits the steam on the surface of the water in b, shutting off, by the same operation, the communication between b and the reservoir; the other then begins to repeat the act of filling the cistern, "and so successively, the fire being tended and kept constant."

This apparatus, we submit, approaches nearer than any to the idea which we of the present day might form from the Marquis's description; but it should be observed, that, by such a modification, we may be giving him credit for arrangement to an extent which he himself never contemplated. In fact, though there can be no doubt but that he meant to describe a machine actuated by the force of steam, yet the absurdity of many of the remaining nine

ty-nine of his projects and the ambiguity of this, warrant us to hazard a conjecture that he intended to gain his object by some arrangement of mechanism equally absurd with them. That his description is ambiguous and contradictory, none can deny; in fact, the strongest evidence of this, is the very different manner in which ingenious men have attempted to represent his machine.

But, whatever value may be set on the Marquis's merit as an inventor, we have not the slightest evidence of his having carried any of his projects into execution. In truth, judging by the character of the man, many have been led to question his title to their invention; for, according to Walpole, "He appears in a very different light in his public character, and in that of an author. In the former, he was an active zealot; and in the latter, a fantastic mechanic: in both, very credulous."-" We find him taking oath upon oath to the Pope's nuncio, with promises of unlimited obedience both to his holiness and to his delegate; and begging five hundred pounds of the Irish clergy, to enable him to embark and fetch fifty thousand pounds; like an alchymist who begs a trifle of money, for the secret of making gold;" -when, according to another author," he had not a groat in his purse, or as much gunpowder as would scare a corbie.”

About twenty years after this, (1682 and 1683), we find Sir Samuel Moreland, in France, endeavouring to promote a project for raising water by steam. His invention was exhibited to the French King, at St. Germains; but, unfortunately, no record remains of the experiment. An account of some of his experiments on the force of steam, however, is preserved among the Harleian Manuscripts in the British Museum, which is evidently the result of great care, and exhibits much correctness in the calculations.

About the year 1680, Dr. Denys Papin, a native of Blois, commenced a series of experiments on the power of steam, which terminated in the construction of an useful and ingenious machine, a description of which we will speedily give. In 1684 he had discovered the method of dissolving bones by steam of a very high pressure and temperature, and in

* No. 5771.

this invention introduced that simple but inseparable accom paniment of every steam engine, THE SAFETY VALVE. This invention (without which steam would, long ere this, have been abandoned as a most dangerous and ungovernable agent,) entitles Papin to universal admiration ; since it has contributed more than any single addition or improvement to the maturity of the steam engine.

The course of Papin's experiments occupied a number of years, and in their progress many ideas occurred to him, which have since been adopted as important improvements. His earliest project was that of using an air pump, for the purpose of transmitting power to some distance, in order to raise water where the first mover could not be conveniently applied. For instance, where a fall of water could be obtained, he proposed to erect a water wheel, which should work an air pump. This air pump he intended to connect by pipes with another pump at the place where the mine was situated. When by the crank on the water wheel the piston of one pump was depressed, the air in the pipes would be condensed, and force up the piston of the other cylinder; and when the piston of the first cylinder was elevated, that of the second would be drawn down by partial vacuum which the elevation produced. This experiment failed even in a model, owing to the great compressibility of the air, and Papin directed his studies to the discovery of some means of forming a vacuum under his piston. In 1688 he described a method of effecting this, by first displacing the air by exploding gunpowder. This he abandoned as dangerous; and, finally, after various experiments and failures, in 1690 he suggested the employment of steam for raising the piston, and afterwards forming a vacuum in the cylinder by its condensation. He states-" that in a little water, changed into steam by means of fire, we can have an elastic power like air; but that it totally disappears when chilled, and changes into water, by which means he perceived, that he could contrive a machine in such a manner that with a small fire he could be able, at a trifling expense, to have a perfect vacuum." After noticing the difficulty of making a vacuum by gun

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powder, he observes, "where there may not be the conveniency of a near river to turn the aforesaid engine, I propose alternately turning a small surface of water into vapour by fire, applied to the bottom of the cylinder which contains it which vapour forces up the plug or piston in the cylinder to a considerable height, and which, as the water cools when taken from the fire, descends again by air's pressure, and is applied to raise water out of the mine."

This, as far as discovery goes, entitles Papin to the merit of having first invented the well-known Atmospheric Steam Engine: and, probably, had he followed up the idea by actual experiment, we would have had to record him as the man who first brought it into successful operation. But the greatest merit is not always due to the inventor; thousands of the most brilliant discoveries have perished for want of industry or talent to foster them. The man who first invents and afterwards struggles through every difficulty, and by the greatest sacrifices and perseverance brings it into actual practice, perhaps outsteps the projector of the most refined contrivance of which history can boast.

Whilst Papin was prosecuting these interesting experiments, a sea-faring man, named Thomas Savery, or, as he is commonly called, Captain Savery, was engaged in England, in endeavouring to bring into notice an engine of his invention, which possessed great merit. The description of his machine was published in a work of his, called “The Miner's Friend." This work is dated 1702, and contains, besides a candid detail of the principle, much useful instruction relative to the proper management of his machine. The liberality and honest appeal to experiment which pervades he whole work, forms a rare and striking contrast with the self-sufficiency and conceit which are too generally to be found in productions of this nature. Savery exhibited his model before King William, who warmly interested himself in the project. In June, 1699, he obtained a patent, granting him the exclusive privilege of manufacture. We subjoin a description nearly in the words of the inventor.