BEAM

, in Architecture, a large timber laid across a building, into which the principal rafters are framed. Several ingenious authors have considered the force or strength of beams, as supporting their own weight and any other additional weight; particularly Varignon, and Parent in the Memoir. Acad. R. Scien. an. 1708, and Mr. Emerson, on the Strength and Stress of Timber, in his Mechanics. Mr. Parent makes the proportion of the depth to the breadth of a beam to be as 7 to 5 when it is strongest.

Beams of a ship, are the large, main, cross timbers, stretched from side to side, to support the decks, and keep the sides of the ship from falling together.

Beam of a balance, is the horizontal piece of wood or iron supported on a pivot in the middle, and at the extremities of which the two scales are suspended, for weighing any thing.

Beam-Compass, an instrument consisting of a wooden or brass square beam, having sliding sockets carrying steel or pencil points; and are used for describing large circles, the radii of which are beyond the extent of the common compasses.