Balance

Apparatus for weighing bodies, i.e., comparing their ma es with that of a standard. It consists of a lever called the "beam,” usually of metal, and having the fulcrum vertically above and near to the center of gravity. At the extremities of the beam. scale-pans are suspended in which to Improved Short Beam Analytical Balance. put the body on one side and the weights on the other. The axis of rotation of all the movable parts are steel or agate "knife-edges" bearing on plates of the same material. A needle or pointer, called the index, is fixed to the beam and oscillates with it in front of a graduated scale. When the beam is horizontal the index points to zero. As a means of subdividing the smallest weight, e.g. , a milligram, a little bent platinum wire, called the “rider,” is sometimes set astride the beam, the effect being equal to its weight and to its distance from the fulcrum. The sensitivene of the balance is given by the formula, tan d in which L is the length of each Lx Mh' arm, M the ma of the beam, h the distance from its center of support to its center of gravity, x a small exce of weight on one side, and 8 the angle of deflection from the horizontal.