March 14, 1878] 



NATURE 



I'^l 



of which dynamic electricity presents numerous examples, 

 and which tends to facilitate the flow of water from an 

 electrified cloud. The agitation of the liquid, the boiling 

 of the waters at the point where these meteors encounter 

 the surface of the sea, are explained not only by the 

 descending movement itself, but also by the action of the 

 electric current, which may repel or raise liquid masses 

 like a breeze or an impetuous wind. If we support, in 



FjG. 20. — Electric bore or formation of litjuid waves by the flow of a 

 powerful current of dynamic electricity. 



fact, the positive electrode against the sides of the vessel 

 of salt-water communicating with the negative pole, we 

 observe, besides the luminous streaks and jets abounding 

 in vapour, a violent whirling of the liquid forming a sort of 

 electric bore, which raises the water to the height of i^ 

 centimetre above its level (Fig. 19). When the current 

 rneets at certain points inequalities of resistance, it is 

 divided and gives rise to several aqueous hillocks, as seen 

 in Fig. 20. 



ON COMPASS ADJUSTMENT IN IRON SHIPS 



AND ON NAVIGATIONAL SOUNDINGS^ 



IV. — On a Navigational Sounding Machine. 



nPHE machine before you is designed for the purpose of obtain- 

 ■^ ing 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 diffi- 

 culty 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 in- 

 superable — at all events they have not hitherto been overcome — 

 wiih 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 Impos- 

 sibility 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, pre- 

 sented 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 somelimes 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 per- 

 fectly in using it to advantage; and under him it was finally 

 introduced into the service of the White Star Line. 



• Report of paper read to the Royal United Service Institution, February 

 4, by ^ir Wm. Thomson, LL.D., F.R.S., P.R.S.E., Professor of Natural 

 Philosophy in the University of Glasgow, and Fellow of St. Peter's College, 

 Cambridge. Ke vised by the Author, [the Council of the R. U.S.I, have 

 kindly permitted us to pablish Sir W. Thomson's paper in advance, and have 

 granted us the use of the illustrations.— Ed.] Continued from p. 354. 



The steel wire which I use weighs nearly i4 lbs. per 100 

 fathoms, and bears when fresh, from 230 to 240 lbs. without 

 breaking ; its circumference is only -03 of an inch. By carefully 

 keeping it always, when out of use, under lime water in the 

 galvanised iron tank prepared for the purpose, which you see 

 before you, it is preserved quite free from rust, and, accidents 

 excepted, this sounding line might outlive the iron plates and 

 frames of the ship. If the sinker gets jammed in a cleft of rock 

 at the bottom, or against the side of a boulder, the wire is 

 inevitably lost. Such an accident must obviously be very rare 

 indeed, and there does not seem to be any other kind of accident 

 which is altogether inevitable by care in the use of the instru- 

 ment. The main care in respect to avoidance of breakage of the 

 wire may be stated in three words— beware of kinks. A certain 

 amount of what I may call internal molecular wear and tear will 

 probably occur through the wire bending round the iron guard 

 rod which you see in the after part of the instrument, when, in 

 hauling in, the wire does not lead fair aft in the plane of the 

 wheel, as is often the ca?e even with very careful steering of the 

 ship, but from all we know of the elastic properties of metals, 

 it seems that thousands of casts might be taken with the same 

 wire before it would be sensibly weakened by internal molecular 

 friction. Practice has altogether confirmed these theoretical anti- 

 cipat'ons so far as one year of experience can go. My sounding 

 machine has been in regular use in charge of Captams Munro 

 and Hedderwick in the Anchor liners Anchoria and Devonia. 

 ( Messrs. Henderson Brothers, Glasgo *) for eleven months and 

 seven months respectively, and in neither ship has a fathonv o 

 wire been lost hitherto, though soundings have been taken at all 

 hours of day and night, at full speed, in depths sometimes as great 

 as 1 2a fathoms. No break not explicable by a kink in the wire 

 has hitherto taken place in any ship provided with the sounding 

 machine. That it will bear much rough usage is well illustrated 

 by one incident which happened in a cast taken from the Devonia 

 running at thirteen knots. The sinker in falling from the wheel 

 into the water accidentally fell between the rudder chain and the 

 ship, and fifty fathoms or so had gone out before it was noticed 

 that the wire was running down vertically from the wheel instead 

 of nearly horizontally as it ought to have been by that time. 

 The handles were immediately applied to the sounding wheel, 

 and it was turned round to haul in without reducing the speed 

 of the ship. Though the wire was bent almost at right angles 

 round the chain until it was nearly all in, it was all got safely on 

 board, as was also the cod-line with attached depth gauge, and 

 the sinker at the end of it. 



When soundings are being taken every hour or more frequently 

 (as in the case ol a ship feeling her way up channel from the 100 

 fathom line when the position is not known with sufficient 

 certainty by sights and chronometers) the sounding wheel should 

 be kept on its bearings in position ; with the cod-line, depth 

 gauge, and sinker, all bent on and ready for use. But in all 

 other cases the wheel should be kept in its tank under lime 

 water, and the cod-line with sinker and depth gauge attached 

 should be kept at hand in a convenient place near the stand of 

 the machine, which should be always fixed in position ready for 

 vTse. With such arrangements, and methodical practice, as part 

 of regular naval drill in the use of the sounding machine, one 

 minute of time should suffice to take the sounding wheel out of 

 its tank, place it on its bearings, adjust the brake cord, bend on 

 the cod-line, and be quite ready for a cast. When the machine 

 is to be shown to an inspecting officer the wheel ought to be in 

 Its tank of lime water when he asks to see a cast. It should be 

 carefully noticed that the ring at the end of the wire is securely 

 lashed by small cord to the hole provided for it in the ring of the 

 wheel whenever the cod-line is unbent from the ring. If the 

 wire and ring are allowed at any time to knock about slack on 

 the wheel when the wheel is being moved to be set up for use or 

 to be replaced under the lime-water there is a liability to some 

 part of the wire getting a turn which may be pulled into a kink. 

 One accident, at least, has happened in this way : the sinker 

 dropped off carrying the cod-line and ring with it just as it was 

 being let down from the taffrail for a cast. If the sinker had 

 weighed 400 lbs. ^ it could not have broken the double wire next 

 the ling witliout a kink. 



A description of the machine and rules for its use are given 

 in the accompanying printed paper of instructions, to which I 

 have only now to add a few words regarding the depth gauge. 

 Erichsen's self-registering sounding lead (patented in 1836), 

 depending on the compression of air, might be used with my 

 machine, but the simpler form before you is preferable as being 



'It weighs 22 lbs. 



