As far back as 1795, Francisco Salva had recommended to the Academy of Sciences, Barcelona, the covering of subaqueous wires by resin, which is both impenetrable by water and a non-conductor of electricity. Insulators, indeed, of one kind and another, were common enough, but each of them was defective in some quality indispensable for success. Neither glass nor porcelain is flexible, and therefore to lay a continuous line of one or the other was out of the question. Resin and pitch were even more faulty, because extremely brittle and friable. What of such fibres as hemp or silk, if saturated with tar or some other good non-conductor? For very short distances under still water they served fairly well, but any exposure to a rocky beach with its chafing action, any rub by a passing anchor, was fatal to them. What the copper wire needed was a covering impervious to water, unchangeable in composition by time, tough of texture, and non-conducting in the highest degree. Fortunately all these properties are united in gutta-percha: they exist in nothing else known to art. Gutta-percha is the hardened juice of a large tree (Isonandra gutta) common in the Malay Archipelago; it is tough and strong, easily moulded when moderately heated. In comparison with copper it is but one 60,000,000,000,000,000,000th as conductive. As without gutta-percha there could be no ocean telegraphy, it is worth while recalling how it came within the purview of the electrical engineer.
In 1843 José d'Almeida, a Portuguese engineer, presented to the Royal Asiatic Society, London, the first specimens of gutta-percha brought to Europe. A few months later, Dr. W. Montgomerie, a surgeon, gave other specimens to the Society of Arts, of London, which exhibited them; but it was four years before the chief characteristic of the gum was recognized. In 1847 Mr. S. T. Armstrong of New York, during a visit to London, inspected a pound or two of gutta-percha, and found it to be twice as good a non-conductor as glass. The next year, through his instrumentality, a cable covered with this new insulator was laid between New York and Jersey City; its success prompted Mr Armstrong to suggest that a similarly protected cable be submerged between America and Europe. Eighteen years of untiring effort, impeded by the errors inevitable to the pioneer, stood between the proposal and its fulfilment. In 1848 the Messrs. Siemens laid under water in the port of Kiel a wire covered with seamless gutta-percha, such as, beginning with 1847, they had employed for subterranean conductors. This particular wire was not used for telegraphy, but formed part of a submarine-mine system. In 1849 Mr. C. V. Walker laid an experimental line in the English Channel; he proved the possibility of signalling for two miles through a wire covered with gutta-percha, and so prepared the way for a venture which joined the shores of France and England.
Fig. 58.—Calais-Dover cable, 1851
In 1850 a cable twenty-five miles in length was laid from Dover to Calais, only to prove worthless from faulty insulation and the lack of armour against dragging anchors and fretting rocks. In 1851 the experiment was repeated with success. The conductor now was not a single wire of copper, but four wires, wound spirally, so as to combine strength with flexibility; these were covered with gutta-percha and surrounded with tarred hemp. As a means of imparting additional strength, ten iron wires were wound round the hemp—a feature which has been copied in every subsequent cable ([Fig. 58]). The engineers were fast learning the rigorous conditions of submarine telegraphy; in its essentials the Dover-Calais line continues to be the type of deep-sea cables to-day. The success of the wire laid across the British Channel incited other ventures of the kind. Many of them, through careless construction or unskilful laying, were utter failures. At last, in 1855, a submarine line 171 miles in length gave excellent service, as it united Varna with Constantinople; this was the greatest length of satisfactory cable until the submergence of an Atlantic line.
In 1854 Cyrus W. Field of New York opened a new chapter in electrical enterprise as he resolved to lay a cable between Ireland and Newfoundland, along the shortest line that joins Europe to America. He chose Valentia and Heart's Content, a little more than 1,600 miles apart, as his termini, and at once began to enlist the co-operation of his friends. Although an unfaltering enthusiast when once his great idea had possession of him, Mr. Field was a man of strong common sense. From first to last he went upon well-ascertained facts; when he failed he did so simply because other facts, which he could not possibly know, had to be disclosed by costly experience. Messrs. Whitehouse and Bright, electricians to his company, were instructed to begin a preliminary series of experiments. They united a continuous stretch of wires laid beneath land and water for a distance of 2,000 miles, and found that through this extraordinary circuit they could transmit as many as four signals per second. They inferred that an Atlantic cable would offer but little more resistance, and would therefore be electrically workable and commercially lucrative.
In 1857 a cable was forthwith manufactured, divided in halves, and stowed in the holds of the Niagara of the United States navy, and the Agamemnon of the British fleet. The Niagara sailed from Ireland; the sister ship proceeded to Newfoundland, and was to meet her in mid-ocean. When the Niagara had run out 335 miles of her cable it snapped under a sudden increase of strain at the paying-out machinery; all attempts at recovery were unavailing, and the work for that year was abandoned. The next year it was resumed, a liberal supply of new cable having been manufactured to replace the lost section, and to meet any fresh emergency that might arise. A new plan of voyages was adopted: the vessels now sailed together to mid-sea, uniting there both portions of the cable; then one ship steamed off to Ireland, the other to the Newfoundland coast. Both reached their destinations on the same day, August 5, 1858, and, feeble and irregular though it was, an electric pulse for the first time now bore a message from hemisphere to hemisphere. After 732 despatches had passed through the wire it became silent forever. In one of these despatches from London, the War Office countermanded the departure of two regiments about to leave Canada for England, which saved an outlay of about $250,000. This widely quoted fact demonstrated with telling effect the value of cable telegraphy.
Now followed years of struggle which would have dismayed any less resolute soul than Mr. Field. The Civil War had broken out, with its perils to the Union, its alarms and anxieties for every American heart. But while battleships and cruisers were patrolling the coast from Maine to Florida, and regiments were marching through Washington on their way to battle, there was no remission of effort on the part of the great projector.
Indeed, in the misunderstandings which grew out of the war, and that at one time threatened international conflict, he plainly saw how a cable would have been a peace-maker. A single word of explanation through its wire, and angry feelings on both sides of the ocean would have been allayed at the time of the Trent affair. In this conviction he was confirmed by the English press; the London Times said: “We nearly went to war with America because we had no telegraph across the Atlantic.” In 1859 the British government had appointed a committee of eminent engineers to inquire into the feasibility of an Atlantic telegraph, with a view to ascertaining what was wanting for success, and with the intention of adding to its original aid in case the enterprise were revived. In July, 1863, this committee presented a report entirely favourable in its terms, affirming “that a well-insulated cable, properly protected, of suitable specific gravity, made with care, tested under water throughout its progress with the best-known apparatus, and paid into the ocean with the most improved machinery, possesses every prospect of not only being successfully laid in the first instance, but may reasonably be relied upon to continue for many years in an efficient state for the transmission of signals.”