The operation was delicate and required great care. The iron, previously made into long and thin bars, with tapering ends, having been introduced into the largest hole of the drawing-plate, was drawn out by the main shaft of the mill, rolled out to a length of 25 or 30 feet, then unrolled, and pulled, in turn, through the smaller holes; and at length, the engineer obtained wires 30 or 40 feet long, which it was easy to join together and place along the five miles between the corral and Granite House. It took but a little while to get this work under way, and then, Smith, making his companions the wire-drawers, busied himself in the construction of his battery. It was necessary to make a battery with a constant circuit. We know that modern batteries are usually made of a certain kind of coke, zinc, and copper. Copper the engineer was without, since, in spite of all his efforts, he had been unable to find a trace of it on the island. The coke, which is that hard deposit obtained from gas retorts could be procured, but it would be necessary to arrange a special apparatus—a difficult thing to do. As to the zinc, it will be remembered that the box found on Jetsam Point, was lined with a sheet of that metal, which could not be better utilized than at present. Smith, after deep reflection, resolved to make a very simple battery, something like that which Becquerel invented in 1820, in which zinc alone is used. The other substances, nitric-acid and potash, he had at hand. The manner in which he made this battery, in which the current was produced by the action of the acid and the potash on each other, was as follows:— A certain number of glass vessels were made and filled with nitric-acid. They were corked with perforated corks, containing glass tubes reaching into the acid, and stopped: with clay plugs, connected with threads. Into these tubes the engineer poured a solution of potash—obtained from burnt plants—and thus the acid and the potash reacted on each other through the clay. Then Smith plunged two plates of zinc, the one in the nitric acid, the other in the solution, and thus produced a circuit between the tube and jar, and as these plates had been connected by a bit of wire, the one in the tube became the positive and the other the negative pole of the apparatus. Each jar produced its currents, which, together, were sufficient to cause all the phenomena of the electric telegraph. On the 6th of February they began to erect the poles, furnished with glass insulators, and some days later the wire was stretched, ready to produce the electric current, which travels with the speed of 100,000 kilometres a second. Two batteries had been made, one for Granite House, and the other for the corral, as, if the corral had to communicate with Granite House, it might, also, be needful for Granite House to communicate with the corral.