THE SOUNDINGS FOR THE ATLANTIC TELEGRAPH.

New Zealand Spectator and Cook's Strait Guardian, Volume XII, Issue 1288, 5 December 1857, Page 4

THE SOUNDINGS FOR THE ATLANTIC TELEGRAPH.

[From the New York Times.] Years ago people asked “ Cui Bono when thousands were expended on expeditions the only returns of which were a handful of shells and a few casts of the deep sea lead ;—yet it is on the accuracy of these returns that the project is now being hazarded. The bottom of the sea has been carefully surveyed and mapped, with all its variety of mountain and prairie land, its telegraphic plateau, and its deep hollows, where no lead has ever found bottom. The soil, too, from the bottom has been brought up and analyzed, and has revealed many curious phenomena pertaining to these sunless depths. The ocean bed of the North Atlantic is a curious study ; in some parts furrowed by currents, in others presenting banks, the accumulations, perhaps, of the debris of these ocean rivers during countless ages. To the west, the Gulf stream pours along in a bed from one mile to a mile and a half in depth. To the cast of this, and south of the Great Banks, is a basin eight or ten degrees square, where the bottom attains a greater depression than perhaps the highest peaks of the Andes or Himalaya, •—six miles of line have faded to reach the bottom ; but of this more presently. Taking a profile of the Atlantic basin in our own latitude, we find a far greater depression than any mountain elevation on our own continent. Four or five Allegbunies would have to be piled on each other, and on them added Fremont’s peak, before their point would show itself above the surface. Between the Azores and the mouth of the Tagus this decreases to about three miles. Further north there is an apparent decrease of depth, with increasing regularity of bottom, though it is problemmatical whether this is not owing to tho greater accuracy with which these observations have been conducted. This apparent rise has been called the “ Telegraphic Plateau ” or, as articles emanating from the Observatory would have it, “ Maury’s Plateau ” (lucus a non, &c.) This appears to bo the natural route for the Transatlantic Telegraph. Other plans have been proposed—one a northing circuit, between the several points of Scotland, Iceland, Greenland, and the Labrador coast, each span being some 500 miles, or to use one or two of the island groups of the Atlantic. In the route selected we have many advantages—convenient harbours at either terminus ; a depth of water at every point sufficient to place the wire beyond the reaclt of any surface causes, such as ice or the anchor of any ship, yet not at an impracticable depth, being at the shoalesl several hundred feet, and in mid-Atlantic not materially over two miles. During a thousand miles of its course the gradual depression of the occan-bed does not exceed 500 fathoms, On either side lie Ireland and Newfoundland, the breastworks of either continent, approaching within seventeen hundred miles, and forming the natural terminus of its route, Trinity Bay is its western head, and Valentin Bay, on the south-western point of lieland, its eastern. This, then, is the bed on which tlto telegraphic cable is to lie, an unbroken prairie land, extending from continent to continent. Let us now see the nature of this bed.

Specimens of the bottom, when subjected to a powerful glass, exhibit delicate shells and infusoria, fragile as if carved in eggshell, and yet as perfect in all their delicate formation as any of

I the more d urable works of nature. The least attrition would crumble all this to powder. The inference is, that all agitation of winds and currents is confined to the surface, and that at these sunless depths the great mass of water remains in almost a quiescent state, and that the electric telegraph, if once laid in safety, would lie for ever beyond the reach of harm, sinking among and covered by these fleecy particles. All this may be incorrect, but we have strong reasons for the supposition. If so, can it ever be laid in safely ? Some abortive efforts at deep-sea soundings furnish curious data for our belief in its practicability. Miles of n small iron wire not thicker than a child’s little finger were actually laid at the bottom of the ocean, and recovered unbroken at a considerably greater depth than any found on the plateau. The modus operands of laying the cable was here perfotmed with a wire of but a fractional part of the strength and fitness of that proposed. The wire laid bv the British in the Black Sea was, however, not of greater size or strength than thia. The experiment of laying the wire is performed in deep-sea sounding whenever a wire is substituted for the ordinary sounding line. With the depth known, with the character of the bottom known, with a cable as plastic os rope, yet with a tenacity capable of sustaining four miles of its length in air, and almost any extent in water, with four of the finect ships in the world for laying it, and aided by the dearly-bought experience gained in the submersion of half-a-dozen other lines, We have every reason for our belief that the Atlantic Telegraph will be a success.

Let us now see by whom, and in wbr.t manner, were these explorations made, and whether they are worthy of the confidence placed in their accuracy by the Telegraph Company. Lieutenant Manry has up to this time enjoyed a monopoly of the reputation derivable from them, and his own name has been linked to the Telegraphic Plateau, the existence of which was first rendered probable and afterwards certain by the labours of other persons. Thia rather questionable reputation would now be left undisturbed did he not now essay to knock away the scaffolding by which he has risen, and to throw discredit on those very researches the fruit of which be has so abundantly reaped. Lieutenant Maury has only been the medium by which the labours of other officers have been made public. The only explorations made by our own Government at all bearing on this field are those of Lieutenant Berryman in the Dolphin in 1853, and in the Arctic during the past autumn, when sent out by the Navy Department to examine the telegraphic route, That the surveys of the Dolphin were as accurate as the imperfect apparatus then in use would permit is admitted by Maury, who bestowed on them the highest praise. It only remains, then, to examine the returns of the Arctic which have been questioned by him, both officially in scientific lectures, and in the public press. Before doing this the public must understand the several modes of making deepsea soundings, on the relative merits of which the whole question binges. The old system is, with a small line marked at distances of 100 fathoms, and with a weight of 30 or 50 pounds, the depth being told by the length of line run out. This is, of course, the most natural apparatus that suggests itself, and has been io use from the earliest ages. Experience has given directions for its use, avoiding some of the grosser causes of error from driftage and other causes. Yet its success in immense ocean depths is problematical, and a problem decided in the negative by very many of the first scientific authorities at home and abroad. In the mechanical improvements of the last half century, substitutes for this simple but rather uncertain method began to be devised. It was proposed to ascertain the depth by the amount of pressure, or by explosions under water, with other equally impracticable plans. At last was noticed the perfect regularity of the movements of a spirally-shaped wheel, on being drawn through the water. Experiments proved that this regularity, when unaffected by other causes, could be relied on with perfect accuracy, and that an arrangement of cog-wheels would register its revolutions with mathematical precision. Very soon it came in use as a ship’s log. So perfect was their precision that they were even introduced in scientific surveys. Base lines, where the nicest accuracy is required, were run with them, and we have the highest authority of the Royal Navy for believing that they never failed. At this point it was proponed to apply them in a perpendicular as well as in a horizontal motion through the water, Massey’s apparatus promising to solve those problems of submarine geography left unsolved by the old method of obtaining depth with a simple line and sinker, and this moro especially as some causes of error considerable on the surface, disappear in the still water below.

After a more thorough trial of the old method than, perhaps, any officer in the service, Lieutenant Berryman proposed to explore the Telegraphic Plateau with the use of Massey's apparatus, in opposition to the opinion of Lieutenant Maury, who, following the traditions of the service, was attached to the old system of line and ball. Many traditions are stubborn things, and the new method has met, of course, with all that opposition unavoidable on the introduction of an improvement which, though known for years abroad, is a novelty among our own people. But, though its use was new, its principle was no novelty to Lieutenant Maury, who years ago was quite in love with its beautiful simplicity, and copied it as bis own invention into a late edition of bis Sailing Directions, with the assurance that it 11 works beautifully.” This would not be referred to did not Maury’s present attack on the soundings made with Massey’s apparatus now make it necessary to quote him among the many authorities in its favour.

The manner of obtainingdepth from the Arctic was with the two methods used in conjunction, —to sound with a simple line and ball, giving an approximation to the depth, but trusting for the nicer shades of accuracy to the readiness of Massey's indicator, which sank appended to the lead, the one being a check on the other, so that no error of moment could avoid detection. In no event could the depth be greater than the amount of line out, while, owing to deflecting causes affecting the line alone, Massey’s indicator might with perfect accuracy rend considerably less. During the first half of the cruise care was taken to obtain the precise depth with the line, with the most gratifying agreement of its returns with the readiness of the self-registering sounding apparatus. As in every case, however, the readings of the latter were preferred, it was found convenient to throw out a superabundance of line to assure the descent of the lead to the

bottom ; the amount of line out was thus often in considerable excess of the recorded depth. Two sets of soundings were thus obtained ; one with Massey’s apparatus, and tbe other with the old method of simple line and sinker. That the former is to be preferred is argued by the fact that specimens from tbe bottom being obtained every time, the depth could not have been in excess of the length of line out, while it might have been as much less as tbe readings on Massey’s apparatus, the sounding line being deflected from tbe perpendicular by driltage and currents, and that these causes of error really exist is admitted by Maury in a dozen places. The imperfections of the system he advises are prodigious, and when overcome are the exceptional cases; not one-tenth of the deep-sea soundings obtained under it are considered reliable by Maury himself. At a depth of one mile or two miles, with no currents or driftings, it may be trusted. These conditions were apparently perfectly obtained by Captain Platt, of tbe Albany, in the Gulf of Mexico ; yet, sounding twice at tbe same point, the returns differed one-half. But these conditions are hardly ever obtained. The ocean is full of currents, which will carry offthe sounding line in immense loops; and in the immense ocean depths, where the shock of tbe sinker striking bottom cannot be conveyed through two or three miles of line, it becomes almost impossible to arrive at an approximation of the true depth. Two soundings at the same spot will differ 50 and 100 per cent. It is this impotent manner of obtaining soundings that has fostered the vulgar belief in the unfathomable depth of the sea. However great are these causes of error, they are not applicable to the little seif-registering sounding apparatus used on board of the Arctic. It may have errors of its own, but it escapes these ; and on the precision of its returns will depend, io no small degree, the success or failure of the Atlantic Telegraph.