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DETAILS OF ENGINE. descend from above, and here will be a perpetual circulation of the air, and with that swiftness as is hardly to be believed." He also describes an arrangement by which it could be applied to the extinction of fires, “ without the hand labour of pumping or bailing with buckets."
The directions he gives for the erection of his engine, and also the description of its parts, are minute and circumstantial; but of the dimensions he says but little. The furnace was so contrived, that the flame took a turn or two round each of the boilers, “which,” he says, “any bricklayer used to furnaces could manage, it being performed by running a row of bricks round them both like a screw or worm, which being contiguous to the wall of the fumaces and the boilers, makes it, as it were, a worm-funnel round them both.” The greatest boiler belonging to his engine was between twenty-four and thirty inches diameter, and was, when occasion required, made much narrower and deeper. An engine having a pipe of delivery of three-inch bore, working the water sixty feet high, had a fire-place of not above twenty inches deep, and fourteen or fifteen inches wide: but he said, that "the quantity of coals used for one engine in a year could not easily be ascertained, because of the different nature of the several sorts of coals."
The valves of his engines were constructed of brass, as were also the screws. The boilers, receivers, and the pipes, communicating from the pit to the receivers, were made of copper; the discharge pipes, in his engravings, are shown as made of wood.
The five engravings marked Savery, which are given, it is hoped, will fully explain the construction of his machine; and, with a brief enume
ration of the various parts of which it is composed, will be sufficient, to explain the principle as well as the mode of its action. The inventor's own account, given in his treatise, which he entitled the * Miner's Friend,” will be found as amusing, lively, and original in the manner, as it is candid, ingenuous, and circumstantial in the points connected with the principle and operation of his exquisite mechanism. To understand fully the great merit of Savery as an inventor, it is necessary to peruse his celebrated treatise ; and as the original edition has now become of exceeding rarity, and great price, it has been reprinted in the same size with these Anecdotes, and is sold at a price which makes it accessible to all: we gladly, therefore, refer to this interesting record of his genius for the most ample details.
Here our space limits us to a brief abstract only of part of his description.
The engraving numbered JI. is an elevation of this apparatus; IV.a section of the same; Ill. contains some of the parts more in detail; and the engraving having the title Savery, without any distinguishing number, is a side view of the same apparatus. With one exception, which we have noticed in its place, the same letter, in all the figures of the plates marked Savery, refers to the same parts of the mechanism : a, the furnaces; b, B, the fireplaces; C, the chimney; d, the small boiler; e, its pipe and cock, closed by the screw, f; the small pipe, 9, goes within eight inches of the bottom of the boiler; h, a pipe of greater diameter, is inserted to the same depth, having a valve or clack, i, opening upwards; the pipe, k, may be considered a continuation of the box containing this valve, and is inserted about an inch below the roof of the larger boiler, l; m, screws which adjust the
118 DESCRIPTION OF ENGINE. regulator; n, a small cock and pipe going somewhat more than half way into the larger boiler; 0, 0, steam pipes, one end of each being inserted into the roof of the large boiler, and the other end of each being inserted into one of the receivers, p, P, forms communications between each of those vessels and the boilers; 9,q, are the screws by which the pipes are fastened together; 7,7, R, R, valves or clacks of brass, constructed so that they may be opened and inspected at pleasure ; , the pipe through which the water that is forced from the receiver, is conveyed into the cis. tern at the required height; t, the pipe connecting the cistern from which the water is to be raised with the receivers; x, a cistern with a buoy cock proceeding from the forcing-pipe, s, having a pipe, y, constructed so as to be easily moved round upon each of the receivers, p, P; %, the handle of the regulator.
The boilers being previously filled to the necessary height with water, all the cocks being shut : the valves in their proper positions : and the receivers empty, a fire being made under the large boiler: and the water it contains being made to boil: and steam raised of a temperature, as much higher than 112° as may be necessary,(to balance a column of water, equal to the height between the bottom of the receivers and the upper surface of the water in the cistern into which it is to be elevated,) then turning the handle, x, of the regulator, will open a communication between one of the cylinders and the boiler. Suppose a passage for the steam opened through the pipe, o, into the receiver, p, the orifice of the other pipe, O, in the roof of the boiler, will be closed by the sliding valve; by the influx of the steam all the air which was contained in the receiver, p, will be expelled through the valve, r', DESCRIPTION OF ENGINE. 119 into the empty pipe, 8.' If the handle of the regulator be now turned, the further flow of steam from the boiler is prevented; the pipe, y, is then to be moved so as to allow a quantity of cold water to fall upon the vessel, p; this almost instantaneously cools that vessel, and thus condenses the vapour which it contained into a very small portion of water, about the eighteen hundredth part of the quantity of steam which formed it: a vacuum is thus produced nearly perfect within the receiver. The pressure of the atmosphere upon the water in the cistern now forces it up the pipe into the receiver, and fills it; the same operation takes place with the steam and water in the other receiver, and both vessels are thus filled with water.
The handle of the regulator is again turned into its first position, by which the steam is shut off from the pipe, 0, and allowed to flow through o into the receiver, p; the elastic vapour pressing upon the surface of the water in the receiver, forces it (as it did the air) through the valve, or clack, r, up the pipe, s, into the cistern or reservoir at the required height. When all the water has been expelled from this receiver, by turning the handle, 2, the further supply of steam is cut off, and it now flows into the other receiver, and impels the water it contains also up the pipe, s; but while this operation is going on, the water pipe, y, is again brought over the receiver, p, which is filled with steam, and a jet of cold water falling upon it, the vapour it contains is a second time condensed, and the pressure of the atmosphere, as before, forces the water from the cistern to replenish the vacuum in the receiver. When the steam has forced all the water from the other receiver, P, the fall of cold water from the movable pipe, y, also condenses the vapour with which it is filled, a
SUPPLYING BOILER. vacuum is formed, and this versel is also replenished by the pressure of the atmosphere : the same process is alternately repeated, and may obviously be continued as long as there is any steam generated in the boiler, and water in the cistern to be forced up the pipe, s, to replenish the vacuum produced in the receiver by the condensation of the vapour.
The action of this apparatus would cease after all the water had been evaporated from the large boiler, and during the time it was replenishing, and until the fresh supply had received the necessary temperature; this, in practice, would have been a serious obstacle to its use in a great many situations. The mode by which Savery replenished his large boiler, without lowering its temperature, and thus ensuring a perfect continuity in its action, almost exceeded in ingenuity the invention of the engine for raising water by fire itself. In the figures, the two boilers are shown as connected by a pipe, (marked n, in fig. 12, and k, in fig. 5, Plate III.) When the water has evaporated to a certain quantity in the large boiler, a fire is made under the smaller one; and as no part of, the steam is permitted to escape from this vessel, its elasticity or temperature quickly exceeds that in the larger boiler, which is constantly flowing into one or other of the receivers. The vapour, therefore, in the boiler, d, will force the water up the pipe, h, and raising the valve, i, and flowing along the pipe, k, into the large boiler, will replenish the waste which has arisen from evaporation. When the water has been expelled from the small boiler to the level of the pipe, h, cold water is introduced through the cock, e, which communicates by a pipe, e, with the rising pipe, s, to be again introduced at a high temperature into the larger vessel ; the valve, i, by