George Eugene Belknap

“ When sounding, serial temperatures are taken at the same time from the topgallant forecastle with a duplicate Thomson machine. For instance, if the temperature is desired for every 100 fathoms below the surface down to 500 fathoms, a 7 lb. lead and a Miller-Casella thermometer is attached to the wire. Then the wire is allowed to rim out slowly till the 100 fathom mark is reached and another thermometer is attached, and so on, till the desired depth is reached, and thus, at one serial sounding, the several temperatures are taken. ”

“ The motion of the drum is regulated by an exceedingly simple friction break, which is so adjusted that when the lower and heavier weight has nearly reached the bottom the retarding force is a little less than the total strain on the wire, but much greater than that strain becomes when the lower weight rests on the bottom, consequently the moment the bed of the ocean is reached the paying out gear automatically stops,—the wire hangs practically vertical without slack, and the total amount run out indicates the true depth. ”

“ When the machine is in operation, the pulley line, or endless rope, runs freely round with the drum and pulley wheel, but the dynamometer wheel being held fast by the small cord attached to the spring balance, the friction of the turns of the rope running round the wheel expends itself in bringing a strain on the balance, the index of which registers the number of pounds of that strain; it is needless to say the strain is in proportion to the amount of weight on the pendant. ”

“ The total time occupied in sounding to that great depth and bringing back a bottom specimen, was 1 hour, 56 minutes, 32 seconds. The quickest time was made, when sounding at a depth of 3009 fathoms, which occupied 1 hour, 29 minutes, 32 seconds only.
The soundings are made at night as well as by day, and the incomparable working of the Thomson machine is a source of never ending wonder and admiration to all who witness it. ”

“ The Thomson machine consists of a reel or drum six feet in circumference, made of galvanized sheet iron. The drum is about four inches in width and has a rim on each side from one and a half inches to two inches in height. Around the right side of the drum runs a V groove which takes the endless rope or pulley line which controls the revolutions of the drum in sounding.
The drum weighs about 60 lbs., and will readily hold five miles of the piano wire. It rests on a light iron frame bolted to a wooden bed and can be readily unshipped when not required for use. ”

“ The sinkers used are 8-inch shot with holes bored through their centres 21/4 inches, and 23/4 inches in diameter, through which the Brooke detaching rod and the specimen cylinders are passed; their weight is 55 lbs. and 51 lbs. Sir William Thomson used a lead sinker weighing 30 lbs. which he hauled back with the wire, but that plan put too much stress on the machine in reeling in, and the heavier sinker to be detached by Brooke’s apparatus was adopted on board the Tuscarora. ”

“ When it is required to sound, supposing the ship to be under sail, the fires, which have been banked, are spread, and when steam is ready, say in half an hour, the usual time, all sails are furled, and kept in that position by the backing of the engines. ”

“ In calm or light weather, the use of the engines is only required at intervals, at other times, when the wind is fresh and the sea heavy, they are kept backing all the time, and sometimes at full speed. ”

“ The piano wire No. 22 in size, weighs, in water, about 12 lbs. to the statute mile, and will bear a strain of from 200 lbs to 230 lbs. The wire comes in lengths of from 200 fathoms to about 400 fathoms, and has to be spliced to make it available for sounding purposes. The splices are made some three feet in length, the parts being put together with a long jawed twist, and the ends and three or four intermediate points secured with solder. The whole length of the splice is then served with fine waxed thread and the splice is complete. ”