I slipped my letter into the bosom of my dress, turned down the lane which ran at right angles with that leading from the cottage, and walked swiftly on. On I went, without thinking whither; yielding to the impulse upon me, without pausing to ask myself how far I should have to go, or what I should find to do in those silent lanes. Was some subtle influence at work with me, of which at the time I was not conscious? Was some guardian spirit leading me towards an end it was not necessary for me to see? I only know that I shall never believe it was only chance which led me to a certain spot that night!
Twenty-seven years ago the first submarine cable was laid across the Strait of Dover. This was a single copper wire covered in gutta-percha, which parted next day; and the first practicable submarine cable was laid in 1851, on the same route. Since then the progress of ocean telegraphy has been extraordinary; no fewer than six cables spanning the Atlantic bed--five to North America (although these are not all working), and one to South America by way of Madeira and Pernambuco. And so extensive is the already existing network of foreign cables, that when Asia is united to America by cabling the Pacific, the electric girdle round the world will be complete from east to west, as it now is between north and south.
In this great development of telegraphy our countrymen have unquestionably furnished both the lion's share of the work and the capital. The cables have nearly all been manufactured in London, which is the headquarters of telegraphy.
The principal parts of a submarine cable are: the _conductor_; the _insulator_; and the _protector_ or sheathing. The conductor, as its name implies, is the wire which conducts or conveys the electric current from one place to another. It corresponds to the iron wire of our ordinary open air or land lines of telegraph. Along this wire, as is well known, the current from the battery at the station from which the message is being sent travels to the station receiving the message, where it passes to the earth, and appears to return through the earth to the battery again; thus _completing its circuit_. There are two distinct parts of the circuit which the current has to traverse--namely, the outgoing part, represented by the wire or _conductor_; and the return part, represented by the earth itself; and inasmuch as these two parts must be kept distinct and apart throughout their length, the wire which is laid along the earth's surface must be kept apart from the earth, to secure which the conductor is entirely surrounded with an _insulator_. In land lines, erected on posts overhead, the wire is separated or insulated from the earth by the air, which is, when dry, the most perfect insulator known; and at the points of support, contact with the earth is prevented by the use of porcelain, stoneware, or vulcanite 'insulators,' to which the conducting wire is fastened.