[Fr. ballon.] A large bag made of silk, and filled with light gas, coal gas being now generally used. It rises in the atmosphere, because its weight is less than the weight of air which it displaces. A car, supported by a network attached to the balloon, carries the aeronauts; when they wish to ascend more quickly, they throw out some of the ballast, which consists of bags of sand ; when they wish to descend, they open a valve at the top, which allows some of the gas to escape. Ascents have been made to determine the pressure and temperature of the air at different heights. In some cases balloons have risen to a height of five miles, and in one instance to seven miles. Balloons have been used as aids in war, and are now being applied in flying machines.

Bal'sam [Arab.] or Balm [Gk.] A liquid aromatic substance, of resinous character, which under the name of Balm of Gilead has long been famous in the East for its fragrance and medicinal virtues. It is the product of a shrub growing in Arabia and Egypt. The word balsam, when used alone, now signifies the balsams of Peru and Tolu, a viscid and very fragrant liquid, obtained from two species of South American trees. They are used to flavor confectionery, also in perfumery, and as stimulants and tonics in medicine. Balsam of Canada is the liquid resin of Abies balsamea, a species of fir. There is also a genus of trees in the East Indies and Japan known as balsam, of which some species are of great beauty and are widely grown elsewhere. |See Gums, Resins.)