BRIDGE

n. Brit A.-S., brycg._ Gr., yépupa. Lat., pons. Fr., pont. Ger., Briicke. It., ponte. Sp., puente. In general, a structure extending like a roadway from one part to another; of the nose, the anterior and upper, salient portion — B. of Varolius. See Pons Varolii—Intercellular. Slender proce es of cell substance connecting neighboring cells. [J.]—-Jugal b. See Zygomatic ArcH.—Wheat stone’s b. An apparatus for determining the resistance encountered by a galvanic current by comparing or balancing it with a known resistance. It consists of four wires, AB, BC, CD, and DA, forming the sides of a parailelogram and constituting a closed circuit, two opposite points of which, A and C, are connected with the poles of a galvanic battery, and two other opposite points, B and D, with a galvanometer. There are four breaks, a, b, c, and d, one at the middle of each wire. At two of these points connection is made by wires of a known degree of resistance; at the third is insert a rheostat by which a known resistance variable at will can be interposed in the circuit; at the fourth is inserted the substance the resistance of which is to be ascertained. If now a current from the battery enters the circuit at A, it will divide and pa partly along AB and BC to C. and partly along AD and DC; and, if the combined effect of the resistances at a and b is equal to-that of those at c and d, the two currents will neutralize each other and the galvanometer needle will not be defiected. In this condition of equilibrium the four resistances are in proportion to each other, and, three of them being known, the fourth can be determined. Hence, to find the unknown resistance it is only nece ary to alter the resistance in the rheostat until the galvanometer needle no longer deviates. [B, 21.]