An apparatus in which persons may be let down and remain for a considerable time under water without much inconvenience or danger. It is a large vessel, closed at the top and sides, but open at the bottom. It takes its name from having been originally shaped somewhat like a bell; but it is now generally made square at the top and bottom, the bottom being somewhat larger than the top. The bell is used in blasting rocks under water, in examining the foundations of piers and bridges, and in recovering stores and treasures from sunken vessels. A code of signals has been arranged by which those below can make known their wishes to others stationed at the top. Dresses have now been devised which enable divers to work under water without the aid of a diving-bell. The dress is made of india-rubber cloth, and covers the entire body. The head is covered by a helmet provided with eye-holes covered with strong glass. Air is supplied through a tube which enters the head-piece, and is connected with an air-pump above. A dress of this kind is now much used by those who dive for pearls, sponges, and coral.