We can now understand what extensive and sometimes irremediable injury may arise from the collection of a small but lofty column of water, opening into a wide but confined space below. This sometimes occurs when water gets into a narrow chink between buildings, and, finding its way down, opens finally into some cavity under the floor. The pressure exerted here is immense, and there are few bodies able to resist it. It is owing to this that the pipes for conveying water are burst, on account of the pressure exerted on the insides of the pipes; and this occurs the more frequently, the higher the source from which they are filled. In practice, every vessel containing liquid should increase in strength in proportion to its depth. We have no doubt that a process similar to this takes place on the large scale in nature, which is capable of uprooting trees, rending rocks, producing earthquakes; for if we suppose that some collections of water on the surface of a hill have found their way down through crevices into a cavity in the body of the mountain which has no external opening, as long as this cavity remains unfilled no evil arises, but when it and the crevices also are completely filled, the pressure exercised here is so immense, that even the sides of the hill cannot withstand it. Perhaps this occurrence has not been sufficiently noticed in explaining natural phenomena. It is usual to consider earthquakes and volcanoes as solely the result of chemical action, excluding entirely physical agency. The pressure of water may be rendered visible by blowing through a tube under water into a tall glass jar. The bubble of air, small at the bottom, as it rises, gradually enlarges from the diminution of the pressure. The hydrostatic bellows, formed upon this principle, consists of nothing more than a water-tight bellows, with a long pipe fixed into the valve aperture. If this pipe be three feet long, and hold a quarter of a pint of fluid, it will exert a pressure sufficient to raise three cwt. laid upon a bellows, the area of the upper side of which is equal to about a square foot and a half. Many are the uses to which this principle might be applied in the several arts. Bramah’s Press is almost the only machine which has been extensively used. By its means solid bars of iron can be cut through with ease. Hay and cotton have been compressed by its means into a very small compass. In the East Indies, where water-power is used, bales of cotton are compressed into one-half the size of those from the West Indies. By its means power may be multiplied, or rather concentrated, a thousand-fold. As commonly made, a man working it may, by using the same force that would raise half a cwt., apply a force amounting to twenty tons to the work in hand; and by varying the proportions of the machine, pressure might be brought to bear upon any body which would be perfectly irresistible.