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.