DEEP SEA SOUNDING.

New Zealand Times, Volume XXIX, Issue 4295, 25 December 1874, Page 3

DEEP SEA SOUNDING.

(From the Kew Yorh Herald.) Washington, D. C., Sept. 12, 1874. The general interest shown toward all that is connected with the aeries of deep sea soundings in the Pacific, just completed by Commander Belknap, of the navy, prompts a detailed description of the machinery used by him so successfully. The subject of the contour or “profile” of ocean beds has long interested geologists and scientists engaged in the study of the sea, and when about 1854 Passed Midshipman Brooke (afterward of the Confederate navy) invented an apparatus which brought up in a small quill specimens of the ocean bottom, scientific men all over the world rushed to see and study the new field opened to them. The apparatus of Brooke has been variously improved upon by that gentleman and others, until now Commander Belknap has fully tested its capacity for sounding at a depth of more than five miles, with the Belknap sounding cups, invented by himself. A rod about two feet long has the lower end cone-shaped for two inches, and in the next eight is shaped exactly like a carpenter’s large augur ; above this is a sliding cup which drops close over the spiral portion, fitting tightly on tho shoulder which the point presents. This cup, during the descent to the bottom, is held at the upper part of the rod, and, being detached, as hereafter shown, when the bottom is reached, drops down upon the shoulder and retains along the spiral all the mud, ooze, sand, or gravel which is collected. An eight-inch round shot has bored through the centre a hole two and three-quarter inches in diameter, and has attached a net work of wire, with two handles which terminate in rings. This shot, weighing about fifty-five pounds, is passed over the sounding rod and the rings hung on a short arm or trigger, which holds the shot in position just so long as the cord or wire which connects it, is pendant. To the ring at the top of the rounding rod trigger, a rod formed of five or six strands of wire twisted together, is attached, and to the cud of this, connecting with the piano wire which is used, is twenty-five fathoms of albaeore line. These form the whole apparatus at the bottom, the wire rod and albaeore line having been found necessary to avoid “kinking” the wire and thereby incurring risk of loss. THE MACHINE USED IN SOUNDING Is known as the Thomson Machine, having been invented by Sir William Thomson, of London, and Commander Belknap’s work is the first important work in which it has been thoroughly tested, the British Government declining to place it on board their own ships. The material used for lowering and raising the sounding rod is wire, known as No. 22 piano wire, and weighs but fourteen pounds to the mile. By using this, the casts are made with greater rapidity, and less room is required than for the old-fashioned one and a-half inch and two inch rope. The Thomson machine consist of a drum or wheel thirty inches in diameter, on the edge of which is a Y-shaped flange on which the wire is wound. The drum is mounted on a platform extending over the ship’s side, and has on the axle a register or counter, on the principle of the odometer, which shows the number of revolutions made by the drum ; over a disk at one side of the drum runs a cord, which, when making a cast, is turned once round a stationary wheel ten inches in diameter, just in rear, attached to the dynamometer; this cord, which slips around the dynamometer wheel, runs thence thirty feet to a pully block, which is connected from an upright post to a pendant, to which are attached weights of various sizes, to control the running out of the wire. Another wheel, near the weighted pendant, is used in reeling in the wire after bottom is reached ; and this, which is four feet in diameter, is fitted with handles on each side for that purpose. When the wire is to be reeled in, the cord or belt attached from the drum to the dynamometer is removed, and another leading to the large wheel is substituted. With this brief and imperfect description of the apparatus used, the operation of making a sounding may be perhaps better understood, and no description of a cast can be better than that contained in a report just received from Commander Belknap, which is as follows : REPORT OF COMMANDER BELKNAP. In getting ready for a cast, half an hour’s notice is given to rig the machine. The pendant attached to the pulley line is well weighted before the machine takes the weight of the sinker. The stray line is always unbent at the end of a cast, and in rigging the machine, the counter is put on before the albaeore line is attached; thus, of course, the counter registers backwards as the line is round on the drum—and the line being of a known length, twenty-five fathoms —the revolutions of the counter are not noted until the wire begins to run down. The wire is made to run slowly at first, the velocity being gradually increased by taking off some of the weights hooked on to the pendant. Equal weights on the pendant do not always show equal indications on the dynamometer—due to different conditions of the line, whether wet or dry, the wet line slipping round the dynamometer wheel so easily as to require more weight to render its action effective. Upon nearing the bottom the weights on the pendant are of course increased to bring more strain on the dynamometer and to reduce the revolutions of the drum. When bottom is reached the drum stops turning, but with the motion of the ship will start again, and make three or four turns in a sluggish way, which to the experienced is a sure sign that tho sinker is on the bottom. Sometimes, when the ship is rolling badly, the drum will come almost to a dead stop, and those unaccustomed to the machine would think that the sinker had struck, but in a moment the dram starts again, and runs more rapidly than ever. In such cases it is a safe plan to press the hand down on the pulley line so as to check the too rapid running out, as the wire might kink and break. The sinker being on the bottom, a few turns more are allowed to run out to make assurance doubly sure and to allow a little slack for the rolling of the ship, but care must bo had not to allow enough to run out to let the wire touch bottom, as in that case it would be almost certain to “ kink.” Then the check line is cast off from the dynamometer wheel, so that tho latter can now turn. The officer in charge takes hold of the pulley line and hauls in until he thinks tho cylinder is off the bottom, minus the sinker. The men then man the line and reel in fifty fathoms, when the officer again tries the line himself, and, if still satisfied that the sinker has been detached, the wire is clamped and tho order given to “ shift belts,” and the men go to the pulley wheel. The dynamometer wheel is unshipped and the large bolt is passed, and when all is ready the wire is undamped and the reeling in is begun, slowly at first, but after a little while as fast as the men can do it. The men are relieved at every 150 turns, which makes easy work of it. Whether running out or coming in, petty officers—and always tho same ones—stand on the platform outside the ship on each side of tho drum, with round sticks in their hands, to guide tho wire fair. When the cast is completed the machine is unrigged and the draw holding the wire put into the tank containing a solution of caustic soda to prevent rust. This solution should bo renewed from time to time. Both in running down and hauling back the clerk is stationed to note the time of every one hundred revolutions, and also the number of splices in tho wire. Tho wire comes in different lengths, and as it is spliced it is carefully measured, and the number of fathoms between tho splices and

the number of revolutions of the drum, as indicated by the counter, between the splices, and also the corresponding gain in fathoms noted. “The revolutions must not be confounded with fathoms, for though the first turns on the drum will be a fathom for each one, the diameter is constantly increasing, and therefore after the first layer or two of wire is on there is a slight gain in the length of the wire for each turn. THE SOUNDINGS have been principally taken from the starboard gangway, the ship’s stern to wind and sea, the engines backing as required. Sometimes in a strong breeze and heavy seaway it is necessary to keep the jib hoisted, either fully up, or part way, the headyards square and the afteryards braced on the port tack. In that case the ship generally keeps steady, though at times she will come to, two or three points, but soon fall off again. Soundings have been made with the ship laid in that position, when the force of the wind was not less than eight. I have never been able to hold this ship head on to the wind and sea in making deep casts, though the plan of keeping all the yards square might work well. But being well satisfied with the action of the ship before the wind, I have experimented but little in any other direction, fearing the loss of wire. The machine itself is so simple, and occupies so little room, that any cruiser might carry one as part of her outfit, and make soundings from time to time, when getting up steam in calm weather, or for the purpose of going into port. In conclusion, I beg to remark that an. officer undertaking deep sea soundings with wire will constantly find new and interesting points of experience, and will never cease to wonder at the ease with which perfect results are obtained ; but a strict attention to details is essential to success, and any act of carelessness will most likely lead to disaster.—Very respectfully your obedient servant, George E. Belknap. Commodore Daniel Ammen, United States Navy, head of Bureau of Navigation, Navy Department. Commodore Ammen is now having manufactured some piano wire, weighing twenty pounds to the statute mile, which is designed for use in the upper splices, where the depth is 2000 fathoms or more. This will decrease the liability of breaking, and consequently loss of large amounts of wire. The total amount of wire lost through uuadvoidable accidents by Commander Belknap was about eighteen miles. Since beginning the recently-completed cable soundings, Commander Belknap has invented several improvements in the Thomson machine, which Sir William Thomson has complimented him for and adopted in his own work. The Challenger, engaged in soundings in the Antarctic and Indian Ooeahs, still uses the one-and-a-half and two inch lines.