SUBMARINE TELEGRAPH BETWEEN ENGLAND AND FRANCE.

The project of constructing a submarine telegraph between England and France, across the Straits of Dover, first announced during the year 1349,[A] has been in part accomplished. The following description of the laying down of the wire, we copy from an English Journal:—

At one o'clock the steamer Goliath was ready to start across the Channel, with all the necessary apparatus on board, and a crew of about thirty men. Between the paddle-wheels, in the centre of the vessel, was a gigantic drum, or wheel, nearly fifteen feet long and seven feet in diameter, weighing seven tons, and fixed on a strong framework. Upon it was coiled up, in careful, close convulsions, about thirty miles of telegraphic wire, one-tenth of an inch in diameter, incased in a covering of gutta-percha, the thickness of the little finger. The point proposed to be reached, Cape Grinez, the nearest landmark to the English coast, and between Calais and Boulogne, is a distance of twenty-one miles, so that a surplus supply of nine miles of wire was held in reserve for the purpose of slackening. The connecting wires were placed in readiness at the Government pier in the harbor, and likewise at the Cape, where they run up the face of the acclivity, which is 194 feet above the sea-mark.

Some interesting experiments were first made upon a small scale to show the practicability of the plan. A mile of wire was paid out off the deck, from the pier to Shakspeare's Cliff, and the sinking process was proved to be a practicable performance. A communication was also sent through twenty four miles of wire. On Wednesday morning the experiment of sinking submarinely was practically commenced. The Goliath put out to the pier, with her telegraphic tackle and apparatus on board, under a calm sea and sky and a favoring wind. The connection between the thirty miles of telegraphic wire was then made good to 300 yards of the same wire inclosed in a leaden tube on shore, to prevent it being bruised by the shingle on the beach, and to enable the experimenters, as they proceeded out to sea, to send communications on shore. The vessel steamed out at the rate of three or four miles an hour into the open sea, in a direct track for Cape Grinez. The wire weighed five tons and the cylinder two. The operation of paying out the thirty miles of wire commenced on a signal to the sailors to "Go-ahead with the wheel, and pay out the wire," which was continuously streamed out over a roller at the stern of the vessel, the men at every 16th of a mile being busily engaged in riveting on to the wire, square leaden clamps, or weights of iron, from 14 lbs. to 24 lbs. in weight, which had the effect of sinking the wire to the bottom, which, on the English coast commences at a depth of 30 feet, and goes on varying from that to 100 and 180 feet, which latter, or 30 fathoms, is the greatest depth.

The whole of the casting out and sinking was accomplished with great precision and success, owing to the favorable state of the day. The only conjectured difficulty on the route was at a point in midchannel, called the Ridge, between which and another inequality called the Varne, both well known and dreaded by navigators, there is a deep submarine valley, surrounded by shifting sands, the one being seventeen miles in length, and the other twelve, and in their vortex, not unlike the voracious one of Godwin Sands, ships encounter danger and lose their anchors, and trolling nets of fishermen are frequently lost. Over this, however, the wire was successfully submerged, below the reach, it is believed, of either ship's anchors, sea-animals, or fishing nets. The remainder of the route, though rougher on approaching the coast of France, was accomplished cleverly, but slowly. A communication, dated Cape Grinez, Coast of France, half past eight, P. M., and received at Dover by submarine telegraph, was as follows:—"The Goliath has just arrived in safety, and the complete connection of the under-water wire with that left at Dover this morning is being run up the face of the cliff; complimentary interchanges are passing between France and England, under the strait and through it, for the first time."

Notwithstanding this apparently successful result of the work, the line was cut asunder soon after the connection was completed on the rocks near Cape Grinez, the physical configuration of the French coast being very unfavorable. The precise point where the breakage took place was about two hundred yards out to sea, just where the twenty miles of electric line that had been laid down from Dover joins on to a leaden tube designed to protect it from the surge beating against the beach, and which also serves a similar purpose up the front of the cliff to the station upon the top. The leaden conductor, it would appear, was of too soft a texture to resist the oscillation of the sea, and thereby became detached from the coil of gutta-percha wire that was thought to have been safely encased in it. The occurrence was, of course, quickly detected by the sudden cessation of the series of communications, though it was at first a perplexing point to discover at what precise spot the wire was broken or at fault. This, however, was done by hauling up the line at intervals, a process which disclosed the gratifying fact, that, since its first sinking, it had remained in situ at the bottom of the sea, inconsequence of the leaden weights or clamps that were strung to it at every sixteenth of a mile. The experiment, as far as it has gone, proves the possibility of the gutta percha wire resisting the action of the salt water, of the fact of its being a perfect waterproof insulator, and that the weights on the wire are sufficient to prevent it being drifted away by the currents, and for sinking it in the sands.

The work at present has been suspended, but will be resumed again during the spring of 1851; a somewhat different plan, however, has been proposed to be followed from that at first adopted. Instead of one slender wire, it is intended to lay down cables inclosing four lines. These cables will be composed of gutta-percha, four or five inches in thickness, the whole encased in wire rope, chemically prepared, to protect it from rot, and kyanized. There will be two of these cables, each twenty miles long, and three miles apart, the whole weight representing 400 tons; and it is expected, when chained down in the bottom of the sea, they will be of sufficient consistency and strength to resist the anchor of a 120-gun ship. The expense of the cables is estimated at £40,000. It is thought that the whole work may be accomplished by May, 1851.—Annual of Scientific Discovery.