=B. & S. W-G.= Abbreviations for Brown & Sharp and wire-gauge, and referring to the sizes of wire and sheet-metal thicknesses that are considered standards in America. =Bar-armature.= An armature in which the conductors are constructed of bars. =Bar-magnet.= One whose core presents the appearance of a straight bar, or rod, without curve or bend. =Bare-carbons.= Electric light carbons whose surfaces are not electro-plated with copper. =Barometer.= An apparatus for measuring the pressure exerted by the atmosphere. It consists of a glass tube 31 inches long, closed at one end, filled with mercury, and then inverted, with its open end immersed in a cistern of mercury. The column of mercury falls to a height proportional to the pressure of the atmosphere. At the sea-level it ranges from 30 to 31 inches. =Bar-windings.= The windings of an armature constructed of copper bars. =Bath.= In electro-plating, the solution or electrolyte used for depositing metal on the object to be plated. It may be a solution of copper, silver, nickel, or other metal. In electro-therapeutics it is a bath of water with suitable electrodes and connections for treating patients with electricity. =Bath-stripping.= A solution used for stripping or removing the metal plating from an object. =Batten.= A strip of wood grooved longitudinally, in which electric light or power wires are set. The grooved strip is screwed to the wall, the wires being laid in the grooves, and then covered with a thin wooden strip fastened on with small nails. =Battery.= A combination of parts, or elements, for the production of electrical action. A number of cells connected parallel or in series for the generation of electricity. Under this heading there are at least one hundred different kinds. Nowadays the dynamo is the cheap and efficient generator of electricity. =Battery Cell, Elements of.= The plates of zinc and carbon, or of zinc and copper, in a cell are called elements. The plate unattacked by the solution, such as the carbon or copper, is the negative element, while the one attacked and corroded by the electrolyte is the positive. =Battery, Dry.= A form of open circuit cell in which the electrolyte is made practically solid, so that the cell may be placed in any position. A zinc cup is filled with the electrolyte and a carbon-rod placed in the middle, care being taken to avoid contact between cup and carbon at the bottom of the cell. The gelatinous chemical mass is then packed in closely about the carbon, so as to nearly fill the cup. A capping of asphaltum, wax, or other non-conducting and sealing material is placed over the electrolyte, and this hardens about the carbon and around the top inner edge of the zinc cup. The latter becomes the positive pole, the carbon the negative. Binding-posts, or connections, may be attached to the zinc and carbon to facilitate connections. =Battery, Galvanic.= The old name for a voltaic battery.