第137章

The iron of Lincoln Island, as has been said, was of excellent quality, and consequently very fit for being drawn out.Harding commenced by manufacturing a drawplate, that is to say, a plate of steel, pierced with conical holes of different sizes, which would successively bring the wire to the wished-for tenacity.This piece of steel, after having been tempered, was fixed in as firm a way as possible in a solid framework planted in the ground, only a few feet from the great fall, the motive power of which the engineer intended to utilize.In fact as the fulling-mill was there, although not then in use, its beam moved with extreme power would serve to stretch out the wire by rolling it round itself.It was a delicate operation, and required much care.The iron, prepared previously in long thin rods, the ends of which were sharpened with the file, having been introduced into the largest hole of the drawplate, was drawn out by the beam which wound it round itself, to a length of twenty-five or thirty feet, then unrolled, and the same operation was performed successively through the holes of a less size.Finally, the engineer obtained wires from forty to fifty feet long, which could be easily fastened together and stretched over the distance of five miles, which separated the corral from the bounds of Granite House.

It did not take more than a few days to perform this work, and indeed as soon as the machine had been commenced, Cyrus Harding left his companions to follow the trade of wiredrawers, and occupied himself with manufacturing his battery.

It was necessary to obtain a battery with a constant current.It is known that the elements of modern batteries are generally composed of retort coal, zinc, and copper.Copper was absolutely wanting to the engineer, who, notwithstanding all his researches, had never been able to find any trace of it in Lincoln Island, and was therefore obliged to do without it.Retort coal, that is to say, the hard graphite which is found in the retorts of gas manufactories, after the coal has been dehydrogenized, could have been obtained, but it would have been necessary to establish a special apparatus, involving great labor.As to zinc, it may be remembered that the case found at Flotsam Point was lined with this metal, which could not be better utilized than for this purpose.

Cyrus Harding, after mature consideration, decided to manufacture a very simple battery, resembling as nearly as possible that invented by Becquerel in 1820, and in which zinc only is employed.The other substances, azotic acid and potash, were all at his disposal.

The way in which the battery was composed was as follows, and the results were to be attained by the reaction of acid and potash on each other.Anumber of glass bottles were made and filled with azotic acid.The engineer corked them by means of a stopper through which passed a glass tube, bored at its lower extremity, and intended to be plunged into the acid by means of a clay stopper secured by a rag.Into this tube, through its upper extremity, he poured a solution of potash, previously obtained by burning and reducing to ashes various plants, and in this way the acid and potash could act on each other through the clay.

Cyrus Harding then took two slips of zinc, one of which was plunged into azotic acid, the other into a solution of potash.A current was immediately produced, which was transmitted from the slip of zinc in the bottle to that in the tube, and the two slips having been connected by a metallic wire the slip in the tube became the positive pole, and that in the bottle the negative pole of the apparatus.Each bottle, therefore, produced as many currents as united would be sufficient to produce all the phenomena of the electric telegraph.Such was the ingenious and very simple apparatus constructed by Cyrus Harding, an apparatus which would allow them to establish a telegraphic communication between Granite House and the corral.

On the 6th of February was commenced the planting along the road to the corral, of posts furnished with glass insulators, and intended to support the wire.A few days after, the wire was extended, ready to produce the electric current at a rate of twenty thousand miles a second.

Two batteries had been manufactured, one for Granite House, the other for the corral; for if it was necessary the corral should be able to communicate with Granite House it might also be useful that Granite House should be able to communicate with the corral.

As to the receiver and manipulator, they were very simple.At the two stations the wire was wound round a magnet, that is to say, round a piece of soft iron surrounded with a wire.The communication was thus established between the two poles; the current, starting from the positive pole, traversed the wire, passed through the magnet which was temporarily magnetized, and returned through the earth to the negative pole.If the current was interrupted, the magnet immediately became unmagnetized.It was sufficient to place a plate of soft iron before the magnet, which, attracted during the passage of the current, would fall back when the current was interrupted.This movement of the plate thus obtained, Harding could easily fasten to it a needle arranged on a dial, bearing the letters of the alphabet, and in this way communicate from one station to the other.

All was completely arranged by the 12th of February.On this day, Harding, having sent the current through the wire, asked if all was going on well at the corral, and received in a few moments a satisfactory reply from Ayrton.Pencroft was wild with joy, and every morning and evening he sent a telegram to the corral, which always received an answer.