A History of Inventions, Discoveries, and Origins (Vol. 1&2). Johann Beckmann

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Another improvement of the diving-bell was effected by the well-known Triewald, a Swede, in 1732. His bell, which was much smaller and more commodious, was made of copper, tinned in the inside. On the top there were panes of glass, which, for the greater security, were fixed in a frame of the same metal. The stool below was placed in such a manner, that the head only of the diver, when he stood upon it, rose above the surface of the water in the bell. This situation is much better than when the whole body is raised above the water in the bell, because near the surface of the water the air is much cooler and fitter to breathe in than at the top of the machine. That the diver also might remain conveniently in the upper part of the bell, Triewald arranged his apparatus so that when the diver had breathed as long as possible in the upper air, he found at the side of the bell a spiral pipe, through which he could draw in the lower cool air which was over the surface of the water. To the upper end of this copper pipe was affixed a pliable leather one, with an ivory mouth-piece, which the diver put into his mouth, and could thus inspire fresh air, in whatever position his body might be298.

      [In 1776, Mr. Spalding of Edinburgh made some improvements in Dr. Halley’s diving-bell, for which he was rewarded by the Society of Arts. His diving-bell was made of wood, and was so light, that, with the divers and the weights attached to its rim, it would not sink; the weight necessary to counteract its buoyancy being added in the form of a large balance-weight, suspended from its centre by a rope, which was so mounted on pulleys that the divers could either draw the balance-weight up to the mouth of the bell or allow it to fall a considerable depth below it. Thus by letting the weight down to the bottom, the divers could, as it were, anchor the bell at any required level, or prevent its further descent if they perceived a rock or part of a wreck beneath it, which might otherwise overturn it. Also, by hauling in the rope while the weight was at the bottom, the persons in the bell might lower themselves at pleasure. Another improvement consisted in the addition of a horizontal partition near the top of the bell, which divided off a chamber, that might, by suitable openings and valves, be filled either with water or with air from the lower part of the bell, so as to alter the specific gravity of the whole machine, and thereby cause it to ascend or descend at pleasure. The bell was supplied with air by an apparatus resembling that of Dr. Halley, and ropes stretched across the bell were used instead of seats and platforms for standing on. Thus the persons in the diving-bell were enabled, in case of accident, to raise themselves to the surface without any assistance from above, and it was rendered so perfectly manageable, that it might be removed to a considerable distance from the point at which it descended; its outward motion and its return to the vessel for the purpose of being hauled up, being assisted by a long boat, which carried the signal lines and the tackle for working the air-barrels.

Mr. John Farey, junior, made an improvement in Spalding’s apparatus299. The upper chamber of the diving-bell is very strong and air-tight, without any openings for the admission of water. Two pumps are fixed in the partition, by which air may be forced into the upper chamber, whenever, during a pause in the descent, the lower chamber or the cavity of the bell is replenished with air. By this means, the upper chamber is made a reservoir of condensed air, from which the bell may be replenished with air, when it is desired to increase its buoyancy, by forcing out the water from the lower part. Hence also, the buoyancy of the bell may be at any time diminished, by pumping some of the air from it into the upper chamber, whereby the water will be allowed to enter to a greater height; and as this is effected without wasting the air, there is no danger of diminishing the buoyancy of the machine to a degree which would prevent it from rising, in case the suspending rope or chain should break.

Smeaton first employed the diving-bell in civil engineering operations in repairing the foundations of Hexham bridge in 1779. The bell was made of wood, and was supplied with air by means of a forcing-pump, which was fixed to the top, and threw in a gallon of air at a time; the river being shallow, the top of the bell was not covered with water300. In 1788 he used a cast-iron one in repairing Ramsgate harbour; a forcing-pump in a boat supplied air through a flexible tube. Since that time it has been frequently used by Rennie and others in submarine operations, recovering property from wrecks, blasting, &c. Mr. Rennie has moreover constructed apparatus for moving the bell in any direction.

In addition to the various forms of diving-bell, different water- and air-tight dresses have been invented to enable divers to remain in the water and perform various operations. Thus, Dr. Halley invented a leaden cap which covered the diver’s head; it had glass before it, and contained as much air as was sufficient for two minutes, and had affixed to it a thick pliable pipe, with the other end fastened to the bell, and which, at the cap, was furnished with a valve to convey fresh air to the diver from the bell. This pipe, which the diver was obliged to wind round his arm, served him also as a guide to find his way back to the bell301.

Mr. Martin states that a gentleman at Newton-Bushel, in Devonshire, invented an apparatus consisting of a large case of strong leather, holding about half a hogshead of air, made perfectly water-tight, and adapted to the legs and arms, with a glass in the anterior part, so that when the case was put on, he could walk about very easily at the bottom of the sea, and go into the cabin and other parts of a ship in a wreck, and deliver out the goods; and that he practised this method for forty years, and thereby acquired a large fortune and equal fame302.

      M. Klingert also invented a similar kind of apparatus, and described it in a pamphlet published at Breslau in 1798. The armour was made of tin-plate, in the form of a cylinder, with a round end to enclose the head and body; also, a leather jacket with short sleeves, and a pair of water-tight drawers of the same, buttoned on the metal part, where they joined, and were made tight by brass hoops. Two distinct flexible pipes terminated in the helmet, and rose to the surface of the water; one was for inhaling, and terminated in an ivory mouth-piece, the other was for the escape of foul air. The body was kept down by weights.

Another method of supplying air to the apparatus was used by Mr. Tonkin in 1804. This consisted in the application of a bellows or pump, until the elastic force of the air was equal to the pressure of the water, the foul air being allowed to escape into the water through a valve, or conducted to the surface by a pipe303.]

      FOOTNOTES

274 Instances of the dexterity of the savages in diving and swimming may be seen in J. Kraft, Sitten der Wilden, Kopenhagen, 1766, 8vo, p. 39. To which may be added the account given by Maffæus of the Brasilians: “They are,” says he, “wonderfully skilled in the art of diving, and can remain sometimes for hours under water, with their eyes open, in order to search for any thing at the bottom.”—Hist. Indic. lib. ii.

275 Lucanus, iii. 697.

276 Livius, xliv. c. 10. Manilii Astronom. v. 449.

277 A Latin translation of these laws may be found in Marquard de Jure Mercatorum, p. 338. “If gold or silver, or any other article be brought up from the depth of eight cubits, the person who saves it shall receive one-third. If from fifteen cubits, the person who saves it shall, on account of the danger of the depth, receive one-half. If goods are cast up by the waves towards the shore, and found sunk at the depth of one cubit, the person who carries them out safe shall receive a tenth part.” See also Scheffer De Militia Navali, Upsaliæ, 1654, 4to, p. 110.

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