Hydrostatics and pneumatics / [Dionysius Lardner].

  • Lardner, Dionysius, 1793-1859.
Date:
1831
Catalogue details

Licence: Public Domain Mark

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

    364/376 (page 348)
    capacity of the machine, the air contained in it being con- densed. It is necessary, therefore, in order to maintain sufficient room for the diver free from water, to supply such a quantity of air, as that in its condensed state it will keep the surface of the water near the mouth of the machine. Thus, at the depth of 34 feet, it will be neces- sary to supply as much air as would fill the bell in its natural state. At double that depth, as much more will he necessary, and so on. The air necessary for these purposes is supplied by one or more large condensing syringes, constructed on the principle explained in (162.). These syringes or pumps are placed above the surface of the water into which the bell is let down, and they communicate with the interior of the bell by a flexible tube carried through the water and under the mouth of the bell. Through this tube any quantity of fresh air, which may be requi- site for either of the purposes already mentioned, may be supplied. A tube furnished with a stopcock is placed in the top of the hell, by which the diver can let any quantity of impure air escape to make room for the fresh air which is admitted. The impure air will rise by its levity in bubbles to the surface. The diving bell received its name from the shape originally given to it. It was constructed with a round top, increasing in magnitude towards the mouth, thus resembling the shape of a bell. It is now, however, usually constructed square at the top and bottom, the bottom being a little larger than the top, and the sides slightly diverging from above. The material is some- times cast iron, the whole machine being cast in one piece, and made very thick, so that there is no danger either from leakage or fracture. In this case the weight of the machine itself is sufficient to sink it. Diving bells, however, are also sometimes constructed of close grained wood, two planks being connected together with sheet lead between them. In the top of the machine are placed several strong