[9] These live near the surface of the ocean in myriads upon myriads, incessantly sinking to the bottom as their short life is ended. Thus, in the course of ages, there grows constantly upward a formation similar to the chalk cliffs of England, which contain the identical shells, deposited when this country was submerged far below sea-level thousands of years ago. [10] In the present day, however, soundings are taken at intervals of about ten miles along the proposed route, and even then submarine hills and valleys are frequently encountered. This is effected by means of the Thomson steam sounding-apparatus, the great feature of which is a fine steel wire (the same as that in the treble notes of a piano) in place of a hempen line of enormous bulk. Nowadays, taking a sounding in the Atlantic occupies well under an hour of time, where by the old method it took at least six hours. [11] The full particulars of the agreement with the English Government were embodied in a letter from the Treasury (see Life Story of Sir Charles Bright) and form instructive reading even at the present time. [12] Submarine Telegraphs. [13] The Pirate, p. 2. [14] Valentia is the Irish terminus of several of the present Atlantic lines. [15] N.M.--Nautical miles. [16] Though such a core would have been a great novelty at the time, it closely approximates to present-day practise. [17] Mins. Proc. Inst. C. E., vol. xvi. [18] An Atlantic cable of the present day runs into about half a million sterling. Gutta-percha was, in those days, less scarce; on the other hand, its manufacture was more of a novelty, and there was comparatively little competition in cable-making. [19] Professor Morse (who held a sort of watching brief for the United States Government) also took passage, but had to retire to his berth as soon as the elements asserted themselves, and was scarcely visible again till all was over. [20] The sheaves had several grooves which the cable fitted into in its passage. Though possessing some merits, this plan was never again adopted, owing partly to the above risk. [21] This was owing to the two halves of the cable being made at different factories, without any communication passing between them on the subject. [22] This apparatus first gained its name from the nature of the part it plays in machinery, being similar to that of a human jockey. [23] So called on account of the form of grooving adopted for taking the under side of the table. [24] Submarine Telegraphs. [25] It is partly for this reason that so full an account is given here. [26] In those days all such instruments were spoken of as galvanometers, no matter for what purpose they were employed. Moreover, this instrument was also used sometimes for testing. That which goes by the name of the marine galvanometer in the present day was not invented by Lord Kelvin till some years later.