276

Hydrostatic Press.

[Book III.

also vol. xxxii, Phil. Transactions, and Abridg. vol. vi, 352. Desaguliers ’Phil. vol. ii, 491. In Jamieson’s Dictionary , p. 852, a mereurial pump inthe form of a wheel is described.

The hydrostatic press is simply a cylindrical forcing pump, whose pistonis moved by the water, instead of the latter by it. A platen, on which areplaced the articles to be pressed, is connected to the upper end of the pistonrod; water is then injected into the cylinder by a much smaller pump,and as this liquid is, to all practical purposes, incompressible, the piston isnecessarily raised, and the articles brought against an immoveable plate,between which and the platen they are compressed. The degree of pres-sure thus excited depends upon the difference between the area of thepistons of the pump and of the press. The apparatus exhibits in anotherform, the celebrated hydrostatic paradox by which the pressure of a liquidcolumn however small, is made to counterbalance that of another howeverlarge. Hydrostatic presses have been applied with advantage in nume-rous operations, as, expressing oil from seeds, pressing paper, books, hayand cotton ; tearing up trees by the roots, proving the strength of steamboilers, metallic water-pipes, and even cannon. In this city (New-York )ships of a thousand tons are raised out of the water to repair, by one ofthese machines erected at the head of one of the docks. The cylinderis secured in a horizontal position, and the pumps are worked by a steam-engine. The frame on which the vessel floats, and by which it is raised,is suspended by a number of chains on each side that pass over pulleys andterminate at the end of the piston.

There is a very interesting and beautiful Illustration of the principleof Bramah ’s hydrostatic press in the contrivance by which bees störetheir honey. The cells, open at one end and closed at the other, are ar-ranged horizontally over each other, and in that position are fitted withthe liquid treasure. Now suppose a series of glass tumblers or tubes laidon their sides and piled upon one another in like manner were requiredto be then filled with water, it certainly would require some reflection todevise a plan by which the Operation could be performed; but whatevermode were hit upon, it could not be more ingenious and effective than thatadopted by these diminutive engineers. At the further or closed extre-mity of each cell, they fabricate a moveable piston of wax which is fittedair tight to the sides, and when a bee arrives laden with honey, (which iscontained in a liquid form, in a sack or stomach,) she penetrates the pistonwith her proboscis and through it injects the honey between the closedend of the cell and the piston, and then stops the aperture with her feet.The piston is therefore pushed forward as the honey aceumulates behindit, tili at last it reaches the open end of the cell, where it remains, herme-tically sealing the vessel and excluding the air. a As soon as one cellis thus charged, the industrious owners commence with another. Itwill be perceived that these pistons are propelled precisely as in the hy-drostatic press, the liquid honey being incompressible, (with any force towhich it is there subjected,) every additional particle forced in necessa-rily moves the piston forward to afford the required room. Without sucha contrivance the cells could no more be filled, and kept so, than a bücketcould be, with water, while laying on one side. Were the Organization

a To keep the honey pure, and preserve it from evaporation, in the high temperatureof a liive, the air must be kept from it. Could human ingenuity have devised a moreperfect mode of accomplishing the object? The fact is, bees in this matter, might long agohave taught man the practice which is now pursued of preserving both liquid and solidaliment fresh for years—in tin cases impervious to the air, and from which it has beertexcluded.