Hydrostatics and pneumatics / [Dionysius Lardner].

  • Dionysius Lardner
Date:
1831
Catalogue details

Licence: Public Domain Mark

Credit: Hydrostatics and pneumatics / [Dionysius Lardner]. Source: Wellcome Collection.

    350/376 (page 334)
    The magazine of condensed air may receive different shapes and be differently arranged, but that which is now described is one of the best forms for it. The Air Balloon. (172.) The physical conditions under which a solid body immersed in a liquid will rise to the surface, sink to the bottom, or remain suspended, have been fully detailed in a former part of this volume. (Hydrostatics, Chapter V.) If a body be heavier than the quantity of liquid, the place of which it occupies, it will sink by that prepon- derance. If it be equal in weight to the liquid it dis- places, it will remain suspended, as the liquid itself would; but, if it be lighter than the liquid which is displaced, the superior weight of the surrounding liquid will press it upwards, and will cause it to ascend to the surface. Liquids being incompressible, all their strata have the same density, or nearly so; and, consequently, a solid which at one depth is lighter than the liquid which it displaces, will also be lighter at every depth. Con- sequently, if a solid has a tendency to rise towards the surface at any depth, it will continue so to rise until it reach the surface. If, however, the strata of liquid approaching the surface had gradually decreased in den- sity, then the solid, which was lighter, bulk for bulk, than an inferior stratum, might be equal in weight, bulk for bulk, to a superior one, and heavier, bulk for bulk, than others nearer to the surface. Thus, such a body would rise at certain depths, but at other lesser depths it would sink; and at the depth of a certain stratum it would remain suspended. The property of liquids, which is the cause of these phenomena, is their power of freely transmitting pres- sure. This will be plainly perceived by referring to (55.), where it is shown that the solid rises to the sur- face by the pressure of the column of the liquid whose base is contiguous to it, and rests on the same level, and