ZINCS FOR FIRE ALARMS.
When ordinary zincs are used, there immediately begins to form a hard scale, impenetrable by the solution in the jars, rendering the parts so scaled inoperative, reducing the amount of surface exposed to the action of the solution, and, relatively, thestrength of the current. This process goes on until the current is so reduced that the zincs have to be removed and cleaned, or the battery would become inoperative This must be repeated from time to time, until the value of the time required to clean them is more than the value of the zinc remaining In the Beattie zinc, mercury is thoroughly incorporated with the zinc when cast, and it impregnates every part, with the result that no scale can form. A corrosion forms as they dissolve, which, being porous, allows the solution to act on every part of the zinc, and offers but a slight resistance to its action. This corrosion is easily brushed off and the time required to clean them is small. The absence of scale allows the amalgamated zincs to be almost totally consumed; the weight, when discarded, need not exceed half a pound, most of which is in the binding post, which is not submerged in the solution. The electromotive force is greater, and the internal resistance less in the Beattie zincs than any others. They require three-quarters, two-thirds, and, in some cases, only one-half the number of cells to produce a given current. The Beattie zincs are in use in fire alarm and police telephone signals in every State in the Union.