Table of the Diameter and Length of Steam Cylinders; with the Number of Pounds Weight to be raised.

In 1695, Papin, then resident at Cassel, published a work, describing a variety of methods for raising water, in

a greater space (near two thousand times) than the water occupied before; and was it to be always confined, would burst a piece of cannon. But being well-regulated according to the laws of gravity, and reduced by science to measure, to the weights and balance, then they carry their burdens peaceably, (like good horses,) and thus become of great use to mankind, particularly for the elevation of water, according to the following table, which marks the number of pounds that may be raised 1800 times per hour, by cylinders half full of water, as well as the different diameters and depths of the said cylinders.

which he enumerates the above invention. Being unable to procure this tract, we insert the following translation of that part which relates to the steam engine. It occurs in the Transactions of the Royal Society, for 1697. After alluding to the inconvenience of forming a vacuum by means of gunpowder, which was one of his early propositions, he recommends "the alternately turning a small surface of water into vapour, by fire applied to the bottom of the cylinder that contains it, which vapour forces up the plug in the cylinder to a considerable height, and which (as the vapour condenses, as the water cools when taken from the fire) descends again by the air's pressure, and is applied to raise the water out of the mine."

In 1698, Captain Savery obtained a patent for a new mode of raising water, and communicating motion to a variety of machines by the force of steam; and in the following year a working model of the above engine, was submitted to the Royal Society, who then held their sittings in Arundel House.* Savery's engine was employed to raise water to a given height by the pressure of the atmosphere, and then to force the fluid up the remaining elevation, by the power of steam acting on the surface.

The engine suggested by Savery, for the purpose of raising water, consisted of a boiler o, furnished with a safety-valve m. The steam vessel s was connected with the well c by a suction-pipe h, and when water was to be raised, the vessels was filled with steam, which, rushing in, soon expelled the air. When that was completely

*The following notice of this machine is inserted in their Transactions for that year.

"Mr. Savery, June 14, 1699, entertained the Royal Society, with shewing a small model of his engine for raising water by the help of fire, which he set to work before them. The experiment succeeded according to expectation, and to their satisfaction."

effected, the communication with the boiler was closed by the handle, and the steam condensed by the introduction of water at e, i, which, diminishing its bulk,

formed a vacuous space

within the vessel; the pressure of the atmosphere then operating upon the surface of the water at c, drove it up the pipe. In this form of the арраratus, the inventor was seldom able to raise water more than thirty feet; and when a greater altitude was required, it was effected by the impellent force of the steam. This was accomplished by the ascending pipe a d, which was sometimes carried sixty feet higher than the steam vessel s. After condensing the steam, and filling the vessel s with water, a new supply of steam was then introduced, which pressing on the surface of the water, drove it up the pipe d; and it will be evident that the pressure on the internal surface of the boiler must be proportioned to the height of the column of water thus raised by the steam.

The principal objection to this form of the engine arises from the great consumption of fuel,-a considerable portion of the caloric employed in the generation of the steam being absorbed in heating the new surface of cold water last raised from the well; and where great heights are required, there appears no mode of completely obviating this objection. Should it, however, be required merely to raise water about thirty feet, there are few contrivances more

economical, or better adapted for general use. While speaking of Savery's apparatus, it may be advisable to notice the very ingenious adoption of the same principle to the construction of a gas engine by Mr. Brown. In the latter case a vacuum is formed by the introduction of an inflamed jet of carburetted hydrogen gas, which consumes the oxygen, and rarefies the nitrogen by the increase of temperature which ensues. The vacuum thus produced is much more perfect than would at first view have been supposed, from the nature of the process resorted to by the patentee; but the economy of employing hydrogen gas, as a substitute for condensable vapour, is still somewhat problematic.

In the engines constructed under the authority of Savery's patent, it was necessary for a labourer to be in constant attendance for the purpose of turning the cocks, which alternately admitted the steam and condensing water. M. de Moura however effected a considerable improvement in this part of the engine, by constructing a self-acting apparatus for this purpose.

From the above facts it will be seen, that Savery's engine was not adapted either for the supply of towns or the draining of mines, (two of the patentee's principal objects,) the latter of which were often of considerable depth; but a number of small ones were erected for the raising of water in gentlemen's pleasure grounds, in different parts of England. Dr. Desaguliers tells us that he made seven of these engines: the first was for the Czar, Peter the Great, for his garden at Petersburgh, where it was set up. The boiler was made spherical, and held between five and six hogsheads. The receiver held one hogshead, and was filled and emptied four times in a minute. The water was drawn up by suction, or the pressure of the atmosphere, twentynine feet high out of the well, and then pressed up eleven

feet higher. The pipes were all of copper, but soldered to the suction piece with soft solder, which held very well for that height. Had, however, the amount of pressure been greater, it must have burst the metal, and produced the most mischievous effects.

It was soon found that the mode of producing a vacuum in these engines was liable to the most serious objections, not the least of which was the unnecessary waste of steam; and an improvement on the original construction was shortly effected, which, although not capable of completely correcting this defect, produced a considerable saving in the amount of fuel employed.

It has been already stated, that Savery's first mode of condensation consisted in throwing a quantity of cold water on the outside of the steam vessel employed to form a vacuum in the pipes; and on the re-admission of steam it was found necessary to restore the heat previously absorbed. To prevent this, a small jet was inserted, which striking against the steam, converted it into water without sensibly lowering the temperature of the vessel. When the repellent force of steam was employed in this engine, the waste of fuel was still more considerable; great part of the steam being condensed upon coming in contact with the surface of the water, so that it could not be brought into action till a large portion of the cold fluid was raised to the boiling point. As a further improvement on this engine, Papin introduced a moveable disk or float, which was interposed between the water and steam, and, by being pressed upon the former, forced it up the connecting pipe without the steam coming into actual contact with the water.

An ingenious combination of Savery's and Papin's apparatus was proposed in 1805, by Mr. James Boaz of Glasgow, by which water can be raised without condensing the steam. a, is the steam cylinder, i, the pipe from the boiler,