Hemp Rope Research Articles

IV.—On a Navigational Sounding Machine. THE machine before you is designed for the purpose of obtaining soundings from a ship running at full speed in water of any depth not exceeding 100 or 150 fathoms. The difficulties to be overcome are twofold: first, to get the lead or sinker to the bottom; and, secondly, to get sure evidence as to the depth to which it has gone down. For practical navigation a third difficulty must also be met, and that is to bring the sinker up again; for, although in deep-sea surveys in water of more than 3,000 fathoms' depth it is advisable, even when pianoforte wire is used, to leave the thirty or forty pounds' sinker at the bottom, and bring back only the wire with attached instruments, it would never do in practical navigation to throw away a sinker every time a cast is taken, and the loss of a sinker, whether with or without any portion of the line, ought to be a rare occurrence in many casts. The first and third of these difficulties seem insuperable—at all events they have not hitherto been overcome—with hemp rope for the sounding-line; except for very moderate depths, and for speeds much under the full speed of a modern fast steamer. It may indeed be said to be a practical impossibility to take a sounding in twenty fathoms from a ship running at sixteen knots with the best and best-managed ordinary deep-sea lead. Taking advantage of the great strength and the small and smooth area for resistance to motion through the water, presented by pianoforte wire, I have succeeded in overcoming all these difficulties; and with such a sounding machine as that before .you the White Star liner Britannic (Messrs. Ismay, Imrie, and Co., Liverpool) now takes soundings regularly, running at sixteen knots over the Banks of Newfoundland and in the English and Irish Channels in depths sometimes as much as 130 fathoms. In this ship, perhaps the fastest ocean-going steamer in existence, the sounding machine was carefully tried for several voyages in the hands of Capt. Thompson, who succeeded perfectly in using it to advantage; and under him it was finally introduced into the service of the White Star Line.