d, e, are two leaden or iron vessels, containing a certain quantity of water, which may be computed to be about four gallons each.

f, g, h, i, k, l, are leaden vessels, each holding about two quarts.

o, p, two cocks, each of which passes through two pipes, opening the one and closing the other.

q, r, is a water-balance, that moves on its centre 8, and by which the two cocks o and p are alternately turned.

t, u, and w, x, are two air-pipes of lead, both internally 1 inch in diameter.

y, z; y, z; y, z; are water-pipes, each being one inch in diameter.

The pipe b, e, c, is always full from the stream a, b: the small cisterns g, i, l, and the large one d, are supposed to have been previously filled with water. The fluid may then be admitted by turning the cock o, through the pipe c, e, into the large cistern e. This water will press the air confined in the cistern e up the air-pipe w, x, and will force the fluid out of the cisterns g, i, l, into those marked h, k, and C.-At the same time, by opening B, the water and condensed air, which previously existed in the large cistern d, and in the smaller ones marked f, h, k, will be discharged at B. After a short time, the water-balance, q, r, s, will turn the cocks, and exclude the water, while it opens the opposite ones: the cisterns f, h, k, are emptied in their turns by the condensed air from the cistern d, as the water progressively enters the latter from the pipe b, c.

8. A very ingenious application of the same principle has been made in the celebrated Hungarian machine, at Chemnitz. The best account we have been able to obtain of this is the following:

In fig. 213, A represents the source of water elevated 136 feet above the mouth of the pit. From this there runs down a pipe D of four inches diameter, which enters the top of a copper cylinder B, 84 feet high, 5 feet diameter, and 2 inches thick, and reaches to within 4 inches of the bottom: it has a cock at I.

This cylinder has a cock at Q, and a very large one at N. From its top proceeds a pipe V EC, two inches in diameter, which goes 96 feet down the pit, and is inserted into the top of another brass cylinder C, which is 64 feet high, four feet diameter, and two inches thick: the latter containing about 83 cubic feet, which is nearly one half of the capacity of the former, viz. 170 cubic feet. There is another pipe FO of four inches diameter, which rises from within four inches of the bottom of this lower cylinder, is soldered into its top, and rises to the trough Z which carries off the water from the mouth of the pit. This lower cylinder communicates at the bottom with the water O, which collects in the drains of the mines. A large cock P serves to exclude or admit this water: another cock M at the top of this cylinder communicates with the external air.

Now, suppose the cock I shut, and all the rest open: the upper cylinder will contain air, and the lower cylinder will be filled with water, because it is sunk so deep that its top is below the usual surface of the mine-waters. Shut the cocks Q, N, M, P, and open the cock I. The water of the source A must run in by the orifice J, and rise in the upper cylinder, compressing the air above it and along the pipe V E C, and thus acting on the surface of the water in the lower cylinder. It will therefore cause it to rise gradually in the pipe OF, where it will always be of such a height that its weight balances the elasticity of the compressed air. Suppose no issue given to the air from the upper cylinder, it would be compressed into one-fifth of its bulk by the column of 136 feet high; for a column of 34 feet nearly

balances the ordinary elasticity of the 'air. Therefore, when there is an issue given to it through the pipe V EC, it will drive the compressed air along this pipe, and it will expel water from the lower cylinder. When the upper cylinder is full of water, there will be 34 cubic feet of water expelled from the lower cylinder. If the pipe OP had been more than 136 feet long, the water would have risen 136 feet, being then in equilibrio with the water in the feeding pipe D by the intervention of the elastic air; but no more water would have been expelled from the lower cylinder than what fills this pipe. But the pipe being only 96 feet high, the water will be thrown out at Z with a considerable velocity. If it were not for the great obstructions which water and air must meet with in their passage along pipes, it would issue at Z with a velocity of more than 50 feet per second. It issues however much more slowly, and at last the upper cylinder is full of water, and the water would enter the pipe V E and enter the lower cylinder, and, without displacing the air in it, would rise through the discharging pipe OP, and run off to waste. To prevent this there hangs in the pipe V E a cork ball or double cone, by a brass wire which is guided by holes in two cross pieces in that pipe. When the upper cylinder is filled with water, this cork plugs up the orifice V, and no water is wasted; the influx at J now stops. But the lower cylinder contains compressed air, which would balance water in a discharging pipe 126 feet high, whereas OP is only 96. Therefore the water will continue to flow at Z till the air has so far expanded as to balance only 96 feet of water, that is, till it occupies one-half of its ordinary bulk, that is, one-fourth of the capacity of the upper cylinder, or 424 cubic feet. Therefore 424 cubic feet will be expelled, and the efflux at Z will cease; and the lower cylinder is about one-half full of water. When the attending workman observes this, he shuts the cock I. He might have done this before, had he known when the orifice V was stopped; but no loss ensues from the delay. At the same time the attendant opens the cock N the water issues with great violence, being pressed by the condensed air from the lower cylinder. It therefore issues with the sum of its own weight and of this compression. These gradually decrease together, by the efflux of the water and the expansion of the air; but this efflux stops before all the water has flowed out; for there is 424 feet of the lower cylinder occupied by air. This quantity of water remains, therefore, in the upper cylinder nearly the workman knows this, because the discharged water is received first of all into a vessel containing three-fourths of the capacity of the upper cylinder. Whenever this is filled, the attendant opens the cock P by a long rod which goes down the shaft; this allows the water of the mine to fill the lower cylinder, and the air to get into the upper cylinder, which permits the remaining water to run out of it. Thus every thing is brought into its first condition; and when the attendant sees no more water come out at N, he shuts the cocks N and M, and opens the cock I, and the operation is repeated.

There is a very surprising appearance in the working of this engine. When the efflux at Z has stopped, if the cock Q be opened, the water and air rush out together with prodigious violence, and the drops of water are changed into hail or lumps of ice. It is a sight usually shown to strangers, who are desired to hold their hats to receive the blasts of air: the ice comes out with such violence as frequently to pierce the hat like a pistol bullet. This rapid congelation is a remarkable instance of the general fact, that air by suddenly expanding generates cold, its capacity for heat being increased. The above account of the procedure in working this engine shows that the efflux both at Z and N becomes very slow near the end. It is found convenient therefore not to wait for the complete discharges, but to turn

the cocks when about 30 cubic feet of water have been discharged at Z: more work is done in this way. A gentleman of great accuracy and knowledge of these subjects took the trouble of noticing particularly the performance of the machine. He observed that each stroke, as it may be called, took up about three minutes and one-eighth; and that 32 cubic feet of water were discharged at Z, and 66 were expended at N. The expense therefore is 66 feet of water falling 136 feet, and the performance is 32 raised 96, and they are in the proportion of 66 × 136 to 32 × 96, or of 1 to 0,3422, or nearly as 3 to 1. This is superior to the performance of the most perfect undershot mill, even when all friction and irregular obstructions are neglected; and is not much inferior to any overshot pump-mill that has yet been erected. When we reflect on the great obstructions which water meets with in its passage through long pipes, we may be assured, that, by doubling the size of the feeder and discharger, the performance of the machine will be greatly improved; we do not hesitate to say, that it would be increased one-third: it is true that it will expend more water; but this will not be nearly in the same proportion, for most of the deficiency of the machine arises from the needless velocity of the first efflux at Z, The discharging pipe ought to be 110 feet high, and not give sensibly less water. Then it must be considered how inferior in original expense this simple machine must be to a mill of any kind which would raise 10 cubic feet 96 feet high in a minute; and how small the repairs on it need be, when compared with a mill. And, lastly, let it be noticed, that such a machine can be used where no mill whatever can be put in motion. A small stream of water, which would not move any kind of wheel, will here raise one-third of its own quantity to the same height, working as fast as it is supplied.

For these reasons, the Hungarian machine eminently deserves the attention of mathematicians and engineers, to bring it to its utmost perfection, and into general use, There are situations where this kind of machine may be very useful. Thus, where the tide rises 17 feet, it may be used for compressing air to seven-eighths of its bulk; and a pipe leading from a very large vessel inverted in it may be used for raising the water from a vessel of one-eighth of its capacity 17 feet high; or if this vessel has only one-tenth of the capacity of the large one set in the tide-way, two pipes may be led from it, one into the small vessel, and the other into an equal vessel 16 feet higher, which receives the water from the first. Thus one-sixteenth of the water may be raised 34 feet, and a smaller quantity to a still greater height; and this with a kind of power that can hardly be applied any other way. Machines of this kind are described by Schottus, Sturmius, Leupold, and other old writers; and they should not be forgotten, because opportunities may offer of making them highly beneficial.

9. Mr. John Whitley Boswell has devised an apparatus which when attached to such a machine as that at Chemnitz will enable it to work itself without attendance. The

description of this will be presented to the reader in Mr Boswell's own words.

Fig. 213. A is the reservoir, or upper level of water.

B, a chamber made of sufficient strength to bear the internal pressure of a column of water the height of A above it, multiplied by its own base. C, a chamber of the same strength as B, but of a smaller size; it is placed at the bottom of the pit from which the water is to be raised, and under the level of the water.

These chambers would be stronger with the same materials, if of a globular or cylindrical form; but the square shape is used in the drawing merely for the facility of representing the position of the parts.

D, a pipe from the reservoir A which passes through the top of B and ends near its bottom, to convey water from A to B.

E, a pipe from the top of B to the top of C, to convey air from B to C. F, a pipe from the bottom of C to the level of the ground at the top of the pit, to carry off the water from the pit.

G, a pipe from the bottom of B to carry off the water from it.

H, a vessel to contain the water used in working the cocks; it is only placed on the top of B to save the construction of a stand on purpose for it.

I, a cock, or movable valve, (worked by the lever there represented,) in the large pipe D.

K, a stop-cock in the small pipe which conveys water from D to H. Its use is to make the engine work faster or slower, by letting water more or less quick into H; or to stop it altogether from working when required.

L, a movable valve, or cock in the small pipe LK. The lever which works it is connected by a strong wire with the lever which works I, and is balanced by a weight at its opposite extremity, sufficient to open both these cocks and shut N, when not prevented by a counter weight. N, a cock in the pipe G to open and shut it as wanted.

O, a self-moving valve in the pipe F, which permits the water to pass upwards, but prevents its return.

P, a self-moving valve at the bottom of C, which permits the water to pass into C, but prevents any from passing out of it; it is furnished with a grating, to prevent dirt getting in.

R, a vessel suspended from the levers of I and L, capable of containing a weight of water sufficient to shut them.

S, a vessel suspended from the lever of N: it must contain water enough by its weight to open N: it is connected by a chain to R, to keep it down as long as N is open.

T, a syphon passing from the bottom of H, near its upper edge, and down again to the mouth of R.

V, a self-moving valve of a sufficient levity to rise, when the water in B comes up to it, and close the pipe E; into which no water would else pass from B. A ball-cock, such as used in common water cisterns, would do here.

X, a syphon from the bottom of R rising within an inch of its top, and passing down again to the mouth of S.

Y, a small pipe at the bottom of S; this may have a stop-cock to regulate it, which, when stopped, will also stop the engine.

The mode of this engine's working is as follows: suppose the vessels V, H, R, and S empty of water, and the cocks K and Y open, and the vessel C full of water. The weight on the lever of L will then open the cocks L and I, on which the water from A will flow into B and H. As

the water rises in B, it will force the air through E into C, which_strongly pressing on the water in C, will force it up through the pipe F, till the water in B rises to the level of V and closes it, at which time H will be full of water, (the quantity flowing in being so regulated by the cock K,) and the water will flow from it through the syphon T into the vessel R, which as it fills shuts the cock I and L, and prevents any more water coming into B and H. When R is full, the water flows through its syphon X, which fills S, and by it opens N, which empties B of water, and keeps N open as long as there is any water in H.

When H is empty, B will be so too, (being so regulated by the cock K,) on which, in a moment or two, R and S will also be empty, which will cause the cocks I and L to open, and all things will be again in the state first supposed, for a repetition of the operations described.

To stop the engine, the cocks at K and Y should be shut, while S is full of water. To set it working, they should be open; and this is all the attendance it will require. As no one but an engineer should attempt to construct such an engine as this, it was useless to represent the manner of connecting the pipes by flaches or otherwise, or the proper methods of fastening and closing the parts, which are all well known to such as have made this art their study.

In No. 5, of the New Series of Nicholson's Journal, Mr. Boswell has made some further improvements in the application of the Hungarian machine.

10. The spiral pump is a very curious hydraulic engine, which operates on nearly the same principle as the Hungarian machine. The first engine of this kind, of which we have seen any account, was invented and erected by H. Andreas Wirtz, a tinplate-worker of Zurich, at a dye-house in Limmat, in the vicinity of that city. It consists of a hollow cylinder, like a very large grindstone, turning on a horizontal axis, and partly plunged in a cistern of water. The axis is hollow at one end, and communicates with a vertical pipe. This cylinder or drum is formed into a spiral canal, by a plate coiled up within it like the main spring of a watch in its box; only the spires at a distance from each other, so as to form a conduit for the water of uniform width. This spiral partition is well joined to the two ends of the cylinder, and no water escapes between them. The outermost turn of the spiral begins to widen about three-fourths of a circumference from the end, and this gradual enlargement continues nearly a semicircle, this part being called the horn: it then widens suddenly, forming a scoop or shovel. The cylinder is so supported that this shovel may, in the course of a rotation, dip several inches into the water. As the cylinder turns upon its axis, the scoop dips and takes up a certain quantity of water before it emerges again. This quantity is sufficient to fill the horn; and this again is nearly equal in capacity to the outer most uniform spiral round.