DIVING APPARATUS 381 DIVISIBILITY Sinclair in his work on gravitation (1669), mentions the diving-bell which was used in 1588, 1665, and 1687 to res- cue the treasures of the Spanish Arma- da. The diving bell then used was similar to those used at the present time, though of much more clumsy con- OUTFIT FOR DEEP-SEA DIVING struction. Dr. Smeaton was the first to use an air pump for the supply of air, about 1788. He constructed a cast iron diving-bell which sank by its own weight and afforded room for two men. Diving-dress, water-proof dress, or armor, was described as early as 1664 The diving-dress used at the present time may be independent of any connec- tion with persons above. The most common one is a rubber cloth dress, with a copper helmet, having air-tight connections, and supplied by a reser- voir, attached to the back and contain- ing air, compressed to a number of atmospheres, which is supplied to the diver by means of a proper apparatus. Among the best known diving appara- tus are those called by the name of Skaphander and those of Rouquairol- Denayrouze; in the United States, the Morse and the Schroder. By means of this apparatus the diver can remain from four to five hours under water with perfect freedom of motion. The diving apparatus most generally used in the United States is the rubber suit, copper helmet, with face plates of glass, and air pump. The diver is connected by rubber hose with the air pump which is constantly worked by an experienced man. Another man called the "tender" holds the air hose and a life line by which the diver signals his require- ments. When the diver has to go into dark places, where the sunlight cannot reach, he is equipped with an incandes- cent electric light. DIVINING ROD, a forked rod or branch, generally, but not necessarily, of hazel, by means of which it is pre- tended to the foolish and superstitious that the presence of water, minerals, etc., underground can be detected. When used, the rod, which is carried slowly along in suspension, will, as is affirmed, dip and point toward the ground when brought over the spot where the con- cealed water or mineral is to be found. DIVISIBILITY, that general property of bodies by which their parts or component particles are capable of sep- aration. Numerous examples of the division of matter, to a degree almost exceeding belief, may be easily in- stanced. Thus glass test-plates for mi- croscopes have been ruled so fine as to have 225,000 spaces to the inch. Cotton yarn has been spun so fine that one pound of it extended upward of 1,000 miles, and a Manchester spinner is said to have attained such a marvelous fineness that one pound would extend 4,770 miles. One grain of gold has been beaten out to a surface of 52 square inches, and leaves have been made 367,500 of which would go to the inch of thickness. Iron has been reduced to wonderfully thin sheets. Fine tissue paper is about the 1,200th part of an inch m thickness, but sheets of iron have been rolled mu h thinner than this, and "s fine as one 4,800th part of an inch 25— Vol. Ill— Cyc
