Mr. Spalding is of opinion, that one air barrel, capable of containing thirty gal lons, is sufficient for an ordinary machine.
In fig. 1 and 2, are shewn representa tions of a frame for supporting a diving bell, and transporting it from. place to place upon the water Fig. 1, is a side elevation, and fig. 2, a section of it. The same letters refer to both figures. A B fig. 2, are sections of two barges, such as are used upon the Thames, at Lon don : D E F, is a frame laying across the barges, and supporting a beam, G, frond which hangs I strong block for the rope by which the bell, H, is suspended ; the other end of the rope goes round a wind lass, a, with a ratchet wheel and Click, to raise and lower the bell as occasion re quires b d are smaller blocks, for the ropes to draw up the air barrels ; ef are rollers, turned by winches, fixed on the opposite barge to the windlass a; the ropes are wound round these rollers in I contrary directions, and the winches come close together, so that one man can turn them both at once, and when one rope descends, the other ascends, so as to give a constant supply of air to the divers under the bell, H. 'When the divers wish to come up, they give a sig nal to that purpose, and the windlass is turned by men until the bottom of the bell is brought above water ; a small boat or raft is rowed under the bell, to take the divers out : the same method is to be used to get them in, and this will be done without wetting them, or any other inconvenience. Several small bells of very different tones should be fixed to the beam C, and strings fastened to them should go into the bell, for the divers to ring as signals to the work men in the barges above. The barges should be well secured ,together by cross beams.
Several other machines have been con trived to answer the purposes of the div ingbell ; one of which, fig. 4, was invent-, ed in 1753, by — Rowe, Esq. and pub lished in the Univeisal Magazine.
The engine is a trunk, or hollow ves sel, of copper or brass, of sufficient strength to resist the pressures of deep waters, and dimensions to contain the body of a man, supposed to enter there- in feet foremost at t, bent at the bearing of his knees at t, for the more convenient goidg between rocks and great stones ; at k, and on the other side, are holes for his arms to pass through, and a glass for his sight at n. h represents a sleeve
made of soft leather, lined with fine cloth, exactly to fit the diver, and fas tened to the body of the engine at k, where the arms come through ; which is h likewise defended by a soft quilting, to prevent the arms from being hurt by pressure, and the sleeves from being thrust into the engine ; d d represents ,a. cover to fit the head of the engine, fas- tened down with screws, and leather be- : tween the borders, so as to prevent leak- ing in any depth of water ; a 6 , sents a plate of lead, to be fastened t fore the engine, in a straight line, pass between the arms, not only as a pro per weight to sink the engine, but as a balance thereto ; whereby the diver will always be kept in a proper posture for working, and the more so by means of a I block, or cradle, supposed to be fastened over the lead, by which means the di , ver has not only the power of handling 1 what is at the bottom, but may at any time rest his arms from work ; g is the engine-rope, by which it is let down and hauled up again from the bottom ; z y u is called the life-line, with a knot at y, so as the handle at z may always remain at a due distance for the diver to take r hold thereof, in 'order to give any notice ! to the persons above, as, by agreement, by giving a certain number of pulls, or sudden twitches, which is immediately felt by the person that holds the line. The diver can tarry under water at least half an hour at one time, without the help of pipes, or any other air than what the en gine contains. At i and w are two brass screw caps, or plugs, both which are to be opened as soon as the diver gets from the bottom to the water's surface, in or der to give him fresh air by help of a pair of bellows blowing at the latter ; at which, when the engine leaks, we likewise pump out the water. In deep water the diver is forced to make use of a sad dle on his hack, with a ridge touching the upper part of the engine, whereby he can keep his arms at a due distance out of the engine, which otherwise would be thrust in by the column of water pressing thereon equal to the weight thereof.