DRY BATTERIES.--Instead of using cells with liquid in them, as the electrolyte, a dry cell is made which acts efficiently. This is usually made in the form of a zinc cup, within which is centrally held a carbon rod, and the space around the rod is filled with ground carbon and dioxide of manganese, and moistened with sal ammoniac. CELL CONSTRUCTION.--The zinc cell and the carbon have upwardly-projecting posts to which the wires are attached, and when thus made the top of the cup is closed with pitch, or some suitable preparation to prevent evaporation and to retain the substances within, and the whole is then inclosed in a jacket, usually of pasteboard. Usually these cells give one and a half volts, and are very durable. This is, of course, a very low voltage, and it is necessary, for this reason, to use at least a half dozen, to operate the coil used in an ignition system. CONNECTING UP CELLS.--If we have a number of cells they can be connected with each other so as to get an additional voltage as well as greater amperage. This statement must be understood in a definite way. Supposing we have six cells, each with an output of 1-1/2 volts, and an ampere flow of 25 in each. Multiplying 25 by 9 makes 225 watts. [Illustration: Fig. 84. Series Wiring.] We may connect up the six cells in such a way that we can get First: 9 volts, and 25 amperes, equal to 225 watts, or, Second: 1-1/2 volts and 150 amperes, equal to 225 watts, or, Third: 4-1/2 volts and 50 amperes, also equal to 225 watts. In either case, you will see we have 225 watts. These three windings are designated as _series_, _parallel_, and series _multiple_. THE SERIES CONNECTION.--The illustration, Fig. 84, shows the series winding. Here the positive wire B is connected with the carbon pole C, and the wire D, wired up with the zinc pole, E, the connections being made directly through each cell, to the outlet wire F. Now, as we have six cells, the combined voltage is 1-1/2 × 6 = 9 volts. As, however, all the cells now act as one cell, the amperage is just the same as of one cell, namely, 25. [Illustration: Fig. 85. Parallel Wiring.] THE PARALLEL CONNECTION.--Fig. 85 shows the parallel connection. Here all the carbon terminals A are connected together in series by a wire B, and all the zinc terminals C by a wire D. In this method the voltage of the battery is the same as that of a single cell, but the amperage is the same as that of a single cell multiplied by the number of cells, namely, 25 amperes × 6. SERIES MULTIPLE CONNECTION.--The series multiple, Fig. 86, is so arranged as to form two distinct batteries, 1 and 2. Each battery is connected up in series, by means of the wires A, which join the carbon and zinc. In this way we have at one end a pair of carbon terminals which are joined by a wire B, and at the other end a pair of zinc terminals, joined by a wire C. [Illustration: Fig. 86. Multiple Wiring.]