History of the Atlantic Cable & Undersea Communications
The Recent Soundings for the Atlantic Telegraph
Illustrated London News: 13 September 1856
THE RECENT SOUNDINGS FOR THE ATLANTIC TELEGRAPH
On application being made to the American Government they, with a most laudable zeal for the promotion of this great national work, expressed their readiness to render to the projectors of the Atlantic Telegraph every possible assistance; and the Secretary of the United States' Navy, Mr. Dobbin, courteously placed at their disposal the Arctic, the vessel most fitted for the purpose, and a selection of officers whose known talents and experience in this particular department of nautical science leaves nothing to be desired. Lieutenant Berryman, who had already once taken soundings across the Atlantic, was appointed to command this expedition, with the object of repeating and enlarging his former observations; Lieutenant Strain, whose zeal and energy in command of the perilous Darien Expedition, as well as his love for, and attainments in, science, qualified him for this office; and Mr. Mitchell, as acting master, who had accompanied Lieut. Berryman on the former occasion: these, with a full complement of other officers, and men specially chosen for the purpose, have done their work nobly. All, from the highest to the lowest, have thrown their hearts fully into the work, and it has indeed been well done—even those of the seamen who should have been below, have been seen creeping from their hammocks at midnight, to watch the return of the lead, and to learn the result in some of the deepest soundings. The track thus subjected to repeated and critical survey, extends from St. John's, Newfoundland, to Valentia Bay, at the south-western extremity of Ireland, a distance of 1640 nautical, or 1900 statute miles.
Within these limits, on a course corresponding to the line of the great-circle sailing, soundings have been taken at intervals of about thirty miles, and in each instance (by means of quills affixed to the bottom of the sounding apparatus) a sample or specimen of the ocean bed has been obtained.
These samples are now undergoing close microscopical examination ; but even the first cursory glance disclosed an abundance of the most fragile forms of shell, either of recent or of fossil infusoria, so delicate, and yet so perfect, as to afford a guarantee of the entire absence of any current or movement of the water at these great depths ; thus confirming in the most satisfactory manner the results of the previous soundings. Not a single rock has been met with, not a particle of gravel or sand has been brought up, but it appears as if nature had provided a bed "soft as a snowbank," to use Maury's own words, for the express purpose of receiving a telegraphic cable.
Lieut. Berryman says that he is satisfied that the lead, with the sounding apparatus, has frequently buried itself ten or fifteen feet deep in this soft material, and he doubts not that the cable will likewise sink and imbed itself in a similar manner. The greatest depth attained has been two thousand and seventy fathoms (about two and one-third miles); but perhaps the most remarkable, and at the same time the most satisfactory result is the perfect confirmation which these soundings give of the opinion expressed by Lieut. Maury as to the existence of a great flat or level at the bottom of the ocean, unparalleled by anything on the surface of the earth, and which he proposed to name "the Telegraph Plateau." For more than thirteen hundred miles the bed of the Atlantic in the direct line of our track is found by these soundings to present an almost unbroken level plain. Nature has thus placed no obstacle in the way of this great undertaking, which may not, by cautious perseverance, be overcome; nay, rather (if we except the enormous length of cable which will be required), it would seem that the line to be followed by the Atlantic cable presents absolutely fewer engineering difficulties than the shorter route (though more complex, from the nature of the bottom) on which the Mediterranean cable must be laid.
As many of your readers may be interested in the nature of the process and mechanism by which these soundings are obtained, I will briefly describe it, inclosing you at the same time an illustrative Sketch.
The vessel being "hove to," and made to remain as stationary as possible, the lead is dropped into the water from a pulley on the fore-yard arm, and carries with it the line, which in its descent it rapidly unwinds from the large reel seen in the Sketch. The descent, at first very rapid, gradually diminishes in speed, in consequence, not of the enormously-increased density of the water, as is usually supposed, but of the gradually-increasing friction due to the length of line to be drawn through the water. This diminution of speed at different depths has been accurately noted by Lieutenant Berryman, and is remarkably uniform. The descent in the deepest soundings usually occupied about three hours. The arrangement of the mechanism is such that the moment the rod (e) carrying the quill touches the bottom, the wires (c), which were previously supported by hooks (b b), become detached, and allow the escape of the lead, while the quills and the register, which are attached to the rod, thus relieved of its load, are more easily drawn up again Still the process of raising, though facilitated by discarding the leaden weight (of 60 lb. to 120 lb.) would be tedious and laborious for human hands, There is,therefore, a small steam-engine attached to the reel, having two oscillating cylinders, whose piston-rods work direct upon a crank on the axle of the reel; by this means the raising of the apparatus occupies less time than its descent. Still it is a slow process, and, occasionally, from the occurrence of a knot or twist in the line, it has been snapped at the pulley when nearly raised, and the whole labour of the sounding, together with the apparatus and specimens, have been lost.
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Last revised: 25 January, 2015