DIVING. 826 DIVING BEETLE. ami from these a suj>|)l.v of air was drawn by ineaus of a hose. The form of iliving-bell now in use was lirst constructed l)y Sincaton for the works at Kams^atc Harbor, EuyUind. 178S. It was of cast-iron, and weighed oO cwt.; its height, 4',>> feet; U^nglh, the same; and width, 3 feet. It sank hy its own weight, and was lighted by stout jjieces of bull'scye ghiss tirmly cemented by brass rings near the top. The prin- ciple of the diving-bell will be easily understood by floating a piece of lighted candle or a wax match on a cork, and then covering it with an inverted tumbler, and jjressing downward: the candle will descend Indow the level of the sur- rounding water, and continue burning for a short time, although the tumbler be entirely innnersed. The reason is obvious- enough : the air in the tumbler, having no vent, remains in it. and pre- vents the water from occupying its place, so that the cork and candle, though apparently under water, are still floating, and surrounded by the air in the tumbler; the candle continues burning until the oxygen of the air is exhausted, and then it goes out, as would the life of a man under similar circumstances. If vessels full of air. like the barrels of Dr. llalley, were sub- merged, and their contents poured into the tumbler, the light might be maintained : but this could better be done if a tube i)asse(l through the tumbler, and air were j)uni|)ed from above through the tul)e into the tumbler. An account of early diving-bells and apparatus will be found in 'cJerland and Trauniiiller's Oeschichle der Physikalischen Expcrimentier- kunst (Leipzig. ISM). The modern diving-bell, which is made of cast- iron like Snieaton's, is supplied with air in this manner. It must bo remembered that air is compressible, and diminishes in bulk in propor- tion to the ])ressure. so that at a depth of about 33 feet iu water it would occujiy half the space it tilled at the surface; if the inverted tumbler were carried to this depth, it would be half filled with water. A considerable quantity of air has, therefore, to I>c pumped into the diving- bell, merely to keep it full as it descend? : the air thus compresM>d exerts a corresponding pres- sure, and would rush up with great force if the tube were open ami free. This is prevented by a valve 0|>ening downward only, ^^■hen the diving-bell has reached its full depth, the pump- ing is continued to supply air for respiration; and the redundant air overflows, or rather under- flows, by the open mouth, and ascends to the surface in bubbles. The diving-bell is provided with a platform or seat for the workmen, and susiK-ndcd from a suitable crane or beams pro- jecting from a barge or pier: men above are sta- tioned to work the pumps and attend to the signals of the bellman. These signals are simply made by striking the sides of the iron diving- bell with a han.mer, and as sound is so freely communicated through water, they are easily heard above. Owing to their great weight and clumsy operation, diving-bells are now seldom used in -iubaipieons operations, the modern ap- pliance being the diving-dress or diving-armor. DiviNO-DiiE.ss. In Sehott's Technica Curioaa, publi-hcd in lfil!4. is described a lorica aquatica, or aqimlic armor, which consisted of a leathern dress, to protect the diver from the water, and a helmet. In 1721 llalley describes a contrivance of his own of nearly the same kind; its object was to enable the diver to go out from the bell and walk about; he was to be provided with a waterproof dress, and a small diving-bell, with glass front, as a helmet over his head, which was to be suj>plied with air by means of a tube from the diving-bell. In IT'.'S Kleingcrt of IJrcslau in- vented a diving-dress available for depths up to 20 feel. The head and body of the diver wer>j encased iu cylindrical tin-plate armor, and his legs in leather breeches. Fresh air was con- veyed to him and the vitiated air was removed by means of pij)es. In 182il August Sielie de- vised an open-helmet diving-dress, having a copper helmet and breastplate, with attached canvas jacket below which the air was allowed to escape, bvit to avoid the admission of water the diver was forced to kecj) a vertical position. In 183!) .Siebe improved his dress, which now is a waterproof costume with helmet of tinned cop- per, having circular glasses in front, valves to admit and discharge air, and a signal-line to allow conununication with those above water. The weight of the dress is about 275 jwunds. In 1880 I'leuss invented a dress weighing only 20 pounds. This has a copper cylinder fastened to the back, carrying a supply of compressed oxy- gen. The carbonic acid exhaled by the diver is absorbed by caustic soda in a recci>tacle fixed above the copper cylinder, while the nitrogen is breathed over and over again. In this dress the diver may remain several hours Ik-Iow the sur- face. For lighting, arc and incandescent lights are used, as well as improved oil-lamps supplied with air by force-pumps. Slates and signal-lines are used for purposes of comnuniication. Accord- ing to SiclK" the greatest depth to which a man has ever descended is 204 feet ; equivalent to a pressure of 88 '^ pounds per square inch. On all ships of the United States Xavy. except very small ones, there is a complete diver's out- fit. Nearly all ginmcrs' mates are now instructed in diving and all recently appointed ginners and boatswains are thoroughly conversant with the work, as are also the carpenters. Divers are used for examining the bottom, or cleaning it, overhauling the strainers of submerged i>i|M's. scraping the iirojiellers. examining chains, look- ing for articles lost overboard, etc. Men who are qiialified divers are given $1.25 for each hour actually spent in diving in addition to the or- dinary pay of their rating. DIVING BEETLE. An aquatic predaceons beetle of the family D.vtiscidiC. These beefles are flat. oval. and. when not disturtx'd. hang head downward in the water with only the tip of the abdomen touching the surface. They may be distinguished by the threadlike antennir. They are brownish black in color, sometimes with indistinct yellow markings. These beet'es are very voracious and feed on other insects, worms, and even small fish: (ly at night with ease, and frequently congregate aboit electric lights, and some forms make a sound both in and out of water. Their eggs are laid in the water and the larv;r are known as water-tigers. The frnns- formation of the larva- is undergone in a cell in the earth. Nearly 300 species of this family arc known. The two genera to which the largest .merican diving beefles l>elong are C>bister and nytis<>ns. distingni-^hed by the disks on the tarsvis, which are in four rows and similar in Cybister, while they are variable in Dyti-cus.
