The positive electrode consists of a carbon rod placed in the center of the cup; the space between is filled with carbon--ground coke and dioxide of manganese mixed with an absorbent material. This filling is moistened with a liquid, generally sal-ammoniac. The top of the cell is closed with pitch to prevent leakage and evaporation. A binding post for holding the wire connections is attached to each electrode and each cell is placed in a paper box to protect the zincs of adjacent cells from coming into contact with each other when finally connected together to form a battery. =Points Relating to Dry Cells.=--The following instructions on the care and operation of dry cells should be carefully noted and followed to get the best results: [Illustration: FIGS. 56 and 57.--Round and rectangular types of the so-called “dry” cell.] 1. In renewing dry cells (or any other kind of cell), a greater number should never be put in series than was originally required to do the work, because the additional cells increase the voltage beyond that required, which causes more current than is necessary to flow through the coil. This increased current flow shortens the life of the battery. 2. In connecting dry cells in places where there is vibration, heavy copper wire should not be used, because vibration will cause it to break. 3. Water should not be allowed to come in contact with the paper covers of the cells because they form the insulation, hence, when moist, current will leak across from one cell to another, resulting in running down the battery. 4. Dry cells will deteriorate when not in use, making it necessary to renew them about every sixty days. The reason dry cells deteriorate is because the moisture evaporates. Freezing, exposure to heat, and vibration which loosens the sealing, causes the evaporation. 5. Weak cells can be strengthened somewhat by removing the paper jacket, punching the metal cup full of small holes, and then placing in a weak solution of sal-ammoniac, allowing the cells to absorb all they will take up. This is only to be recommended in cases of emergency when they are hard to get. [Illustration: FIGS. 58 to 63.--Various zincs; fig. 58 Fuller; fig. 59 Daniell; fig. 60 Leclanche square; fig. 61 Leclanche round; fig. 62 Sampson; fig. 63, bottle.] 6. The average voltage of a dry cell when new is one and one-half volts, while the amperage ranges from about twenty-five to fifty amperes according to size. 7. A dry cell when fresh should show from =20= to =25= amperes when tested; the date of manufacture should also be noted as fresh cells are most efficient.