in Architecture, the largest piece of wood in a building, which lies cross the walls, and serves to support the principal rafters of the roof, and into which the feet of these rafters are framed. No building has less than two of these beams, viz. one at each end; and into these the girders of the garret roof are also framed. The proportions of beams in or near London, are fixed by statute, as follows: a beam 15 feet long, must be 7 inches on one side its square, and 5 on the other; if it be 16 feet long, one side must be 8 inches, the other 6, and so proportionally to their lengths. In the country, where wood is more plenty, they usually make their beams stronger.

BEAMS of a Ship are the great main cross timbers which hold the sides of the ship from falling together, and which also support the decks and orlops: the main beam is next the main-mast, and from it they are reckoned by first, second, third beam, &c. the greatest beam of all is called the midship beam.

BEAM-Compass, an instrument consisting of a square wooden or brafs beam, having sliding sockets, that carry steel or pencil points; they are used for describing large circles, where the common compasses are useless.

BEAN-Bird, or Petty chaps. See MOTACILLA.

Beam also denotes the lath, or iron, of a pair of scales; sometimes the whole apparatus for weighing of goods is so called: Thus we say, it weighs so much at the king's beam.

BEAM of a Plough, that in which all the parts of the plough-tail are fixed. See PLough, AGRICULTURE Index.

or Roller, among weavers, a long and thick wooden cylinder, placed lengthwise on the back part of the loom of those who work with a shuttle. That cylinder, on which the stuff is rolled as it is weaved, is also called the beam or roller, and is placed on the forepart of the loom.