[8] See Silliman’s Journal, vol. 35, 1839, pages 258-267.
CONDUCTING POWER AND GALVANIC ACTION OF THE EARTH.
After the close of the session of Congress in the spring, 1844, a series of experiments were commenced by the request of Prof. Morse, under the direction of Mr. Vail, for the purpose of ascertaining what amount of battery was absolutely required for the practical operation of the telegraph. From the first commencement of its operations to the close of the session, so anxious were the public to witness its almost magic performances, that time could not be taken to put it in a state to test either the size of the battery required, or bring into use all the machinery of the register. On that account, but _one wire_ was used during that period for transmitting and receiving intelligence, and the capabilities of the instrument were shown to some disadvantage; requiring the constant attendance of those having charge of the two termini.
This first experiment made was to ascertain the number of cups absolutely required for operating the telegraph. Eighty cups had been the number in use. Upon experiment, it was found, that two cups would operate the telegraph from Washington to Baltimore. This success was more than had been anticipated and urged on further experiments, which eventually proved that the earth itself furnished sufficient galvanic power to operate the electro magnet without the aid of a battery. In the first experiment, a copper plate was buried in the ground, and about three hundred yards from it, a zinc plate was also buried in the ground. To each of these plates a wire was soldered, and the ends brought into the telegraph office, and properly connected with the key and electro magnet of the register. The battery not being in connection. Upon manipulating at the key, it was found that the electro magnet was operated upon and the pen of the register recorded. This led to another experiment upon a more magnificent scale, and nothing less than that of using the copper plate at Washington, and the zinc plate at Baltimore, with the single wire, connecting those distant points, and the battery thrown out. Here, too, success followed the experiment, though with diminished effect. By the application of a more delicate apparatus the _Electro Magnet_[9] was operated upon, and the pen of the _registering instrument recorded_ its success. From these experiments, the fact appears conclusive, that the ground can, through the agency of metallic plates, constantly generate the galvanic fluid.