smaller at the top A than at the bottom, and of the same height; the pressure upon the bottom BC is as great as the pressure upon the bottom of the vessel DEFG, when they are filled with water, or any other liquid, notwithstanding that there will be a much greater quantity of water in the cylindrical than in the conical vessel; or, in other words, the bottom BC will sustain a pressure equal to what it would be if the vessel were as wide at the top as at the bottom. In like manner, the bottom of the vessel HIKL, Fig. 3, sustains a pressure only equal to the column whose base is KL, and height KM, and not as the whole quantity of fluid contained in the vessel; all the rest of the fluid being supported by the sides. The demonstration of these positions would occupy too much room, and to many readers would appear too abstract and uninteresting; but they will be found satisfactorily demonstrated in most books which treat of the doctrines of hydrostatics.

2. The positions now stated form the foundation of the hydrostatical paradox, namely, "that a quantity of fluid, however small, may be made to counterpoise a quantity however great." Thus, if to a wide vessel AB we attach a tube CD, communicating with the vessel, and pour water into it, the water will run into the larger vessel AB, and will stand at the same height C and G in both. If we affix an inclined tube EF, likewise communicating with the large vessel, the water will also stand at E at the same height as in the other two; the perpendicular altitude being the same in all the three tubes, however small the one may be in proportion to the other. This experiment clearly proves that the small column of water balances and supports the large column, which it could not do if the lateral pressures at bottom were not equal to each other. Whatever be the inclination of the tube EF, still the perpendicular altitude will be the same as that of the other tubes, although the column of water must be much longer than those in the upright tubes. Hence it is evident, that a small quantity of a fluid may, under certain circumstances, counterbalance any quantity of the same fluid. Hence also the truth of the principle in hydrostatics, that "in tubes which have a communication, whether they be equal or unequal, short or oblique, the fluid always rises to the same height." From these facts it follows, that water cannot be conveyed by means of a pipe that is laid in a reservoir to any place that is higher than the reservoir.

These principles point out the mode of conveying water across valleys without those expensive aqueducts which were erected by the ancients for this purpose. A pipe, conforming to the shape of the valley, will answer every purpose of an aqueduct. Suppose the spring at A, Fig. 5, and water is wanted on the other side of the valley to supply the house H, a pipe of lead or iron laid from the spring-head across the valley will convey the water up to the level of the spring-head; and if the house stand a little lower than the spring-head, a constant stream will pour into the cisterns and ponds where it is required, as if the house had stood on the other side of the valley; and, consequently, will save the expense of the arches BB, by which the ancient Romans conducted water from one hill to another. But, if the valley be very deep, the pipes must be made very strong near its bottom, otherwise they will be apt to burst; as the pres

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And if he put his finger on the top of the pipe, he may sup port himself as long as he pleases.

The uses to which this power may be applied are of great variety and extent; and the branches of art dependent upon it appear to be yet in their infancy. By the application of this power the late Mr. Bramah formed what is called the Hydrostatic Press, by which a prodigious force is obtained, and by the help of which, hay, straw, wool, and other light substances may be forced into a very small bulk, so as to be taken in large quantities on board a ship. With a machine, on this principle, of the size of a tea-pot, standing before him on a table, a man is enabled to cut through a thick bar of iron as easily as he could clip a piece of pasteboard with a pair of shears. By this machine a pressure of 500 or 600 tons may be brought to bear upon any substances which it is wished to press, to tear up, to cut in pieces, or to pull asunder.

Upon the same principle, the tun or hogshead HI, Fig. 7, when filled with water, may be burst, by pressing it with some pounds additional weight of the fluid through the small tube KL, which may be supposed to be from 25 to 30 feet in height. From what has been already stated, it necessarily follows, that the small quantity of water which the tube KL contains presses upon the bottom of the tun with as much force as if a column of water had been added as wide as the tun itself, and as long as the tube, which would evidently be an enormous weight. A few years ago, a friend of mine, when in Ireland, performed this experiment to convince an English gentleman, who called in question the principle, and who laid a bet of fifty pounds that it would not succeed. A hogshead, above 3 feet high, and above 2 feet wide, was filled with water; a leaden tube, with a narrow bore, between 20 and 30 feet long, was firmly inserted into the top of the hogshead; a person, from the upper window of a house, poured in a decanter of water into the tube, and, before the decanter was quite emptied, the hogshead began to swell, and, in two or three seconds, burst into pieces, while the water was scattered about with immense force.

Hence, we may easily perceive what mischief may sometimes be done by a very small quantity of water, when it happens to act according to its perpendicular height. Sup