The Atlantic Telegraph (1865)

by Sir William Howard Russell

Messrs. Glass, Elliot, & Co. had long successfully manufactured Cables in accordance with all the improvements that had taken place in machinery, as well as in the manufacture of gutta percha, since the laying of the Cable of 1858. Their experience as contractors in laying lines might be estimated by the report of the Jurors of the Exhibition of 1862. They had been identified with the history of submarine telegraphy from its earliest existence, and now, having previously incorporated the Gutta Percha Company, they accepted the offer made by capitalists of influence and became absorbed in “The Telegraph Construction and Maintenance Company,” of which Mr. Pender, M.P., was chairman, and Mr. Glass managing director.

The British Government were willing to assist by subsidy and guarantee, and there lay the Great Eastern, the only vessel in the world suited for the undertaking, seeking for a purchaser. The huge ship, which cost £640,000, was chartered by the Directors of the Telegraph Construction and Maintenance Company, who seemed bent upon solving the problem of its existence, and on showing what great things it was destined to accomplish. Captain James Anderson, an accomplished officer of the Cunard line, was asked to take the command, and received leave to do so, and it was with satisfaction the Directors learned his willingness to undertake the task.

In May, 1864, a contract previously entered into was ratified, providing that all profit should be contingent on success, and that all payments were to be made in unissued shares of the Atlantic Telegraph Company. A resolution was also passed, authorising the raising of additional capital by the issue of 8 per cent. guaranteed shares, of which Glass, Elliot, & Co., were to receive 250,000l., and also 100,000l. in debentures. The form of the Cable selected was similar in its component parts to that of 1858, but widely different in the construction and quality of the materials. It had been reported on most favourably by the Committee of Selection, and was at once accepted by the contractors; the Directors of the Company recognising the assiduity and skill of Mr. Glass in the investigations as to the best description of Cable.

The following official account[3] states so minutely every particular connected with the Cable during the process of formation, down to its shipment on board the Great Eastern, that no better description can be given:—

It differed from the Cable of 1857-8, as to its size, as to the weight and method of application of the materials of which it was composed, as to its specific gravity, and as to the mode adopted for its external protection.

For the same reason as before, the copper conductor employed in the Cable was not a solid rod, but a strand, composed of seven wires, each of which gauged ·048 parts of an inch. It was found practically that this form of conductor, in which six of the wires were laid in a spiral direction around the seventh, was a most effectual protection against the sudden or complete severance of the copper wire.

The severance, or “breach of continuity,” as it is usually called, is one of the most serious accidents that can happen to a submerged Cable, when unaccompanied by loss of insulation—owing to the great difficulty in discovering the locality of such a fault. Even the best description of copper wire can seldom be relied upon for equality of strength throughout, and in some instances an inch or even a less portion of the wire will prove to be slightly crystallised, and consequently incapable of resisting the effects of coiling or paying out if brought to bear upon the part, though no external difference be at all apparent between the weak portion and the remainder of the sample. By proceeding, however, as in the present case, the conductor was divided into seven sections, and the risk of seven weak places occurring in the same spot being exceedingly remote, the probability of a breach of continuity in a strand conductor was almost nil.

The weight of the new conductor was nearly three times that of the former one—being 300 pounds to the nautical mile against 107 pounds per knot to the conductor of 1857. The adoption of this increased weight had reference to the increase of commercial speed in the working of the new Cable expected to accrue therefrom, and was founded upon the principles of conduction and induction, now well understood, which consist in the law that the conductivity of the conductor is as its sectional area, while its inductive capacity (whereby speed of transmission is retarded) is as its circumference only; and, as the maximum speed at which the original Cable was ever worked did not exceed two and a-half words per minute, it would follow by calculation, taking into account the thickness of the dielectric surrounding the present conductor, that, using the same instruments as in 1858, a speed of three and a-half to four words per minute might be expected from the new Cable; but it was stated by the electricians that owing to the improved modes of working long Cables that have been discovered since 1858, an increase of speed up to six or even more words per minute might be secured by the adoption of suitable apparatus.

The purity of the copper employed, a very important item, affecting the rate of transmission, had been carefully provided for. Every portion of the conductor was submitted to a searching test, and all copper of a lower conductivity than 85 per cent. of that of pure copper was carefully rejected.