March 3, 1910J 



NATURE 



27 



and though it carried a very heavy sinker, the resistance 

 to its motion through the water was so great that it took 

 a long time to reach the bottom. For the same reason 

 the ship had to be stopped while the line ran out, and, 

 except in shallow water, while it was being heaved in. 

 Many hands were needed, and much time was spent in 

 making a cast. Hence it came about that the operation of 

 sounding, beyond the use of the hand-lead in quite shallow 

 ■water, was but little resorted to as an aid to navigation, 

 notwithstanding the importance of the indications it could 

 give in such cases as when a ship was approaching land 

 in a fog or in circumstances which made the exact position 

 uncertain, when the depth might be anything up to, say, 

 one or two hundred fathoms. 



I have spoken already of Thomson's study of the forces 

 acting on a cable during its submersion. Applying these 

 principles to the sounding-line, he recognised that to make 

 the line slip down quickly it should have the smallest 

 possible and the smoothest possible surface, and this led 

 him to use a single wire of steel — the ateel of high tensile 

 strength used in pianofortes. In 1872 he demonstrated the 

 practicability of using wire by taking a sounding and find- 

 ing bottom at 2700 fathoms in the Bay of Biscay with a 

 30-lb. sinker and a single wire of No. 22 gauge. He soon 

 devised a suitable drum and winding-in wheel for deep- 

 sea use, and from this was developed later a compact form 

 of navigational sounding machine by which flying sound- 

 ings are taken without stopping the ship. 



In a flying sounding the wire streams out behind, taking 

 an oblique course to the bottom, and the length of wire 

 that runs out is greatly in excess of the depth. To read 

 the depth directly, Thomson invented several forms of 

 depth gauge, the simplest of which is a long narrow glass 

 tube, closed at the top, and coated inside with chromate 

 of silver or some other chemical which is discoloured by 

 the action of sea-water. This tube is put in a protecting 

 case, which is attached near the sinker, and as it descends 

 the increased pressure forces the sea-water up into it, com- 

 pressing the air, and indicating the depth by the height to 

 which the chemical lining is discoloured. Accordingly, the 

 depth is read off by laying the tube against a scale, when 

 the line is again drawn on board. 



This machine has become a standard navigational appli- 

 ance. The length of wire in common use is 300 fathoms. 

 A strand of seven fine steel wires, which gives greater 

 flexibility, is now substituted for the single wire. It runs 

 out under a regulated tension, supplied by a rope brake, 

 which retards the rotation of the drum on which the wire 

 is wound. When the sinker touches bottom the tension is 

 at once seen to slacken, or rather felt to slacken by a 

 sailor who keeps a little rod of wood lightly pressed against 

 the wire while it runs out ; the drum is stopped, and the 

 wire is slowly wound in again by hand, or in the latest 

 naval type by electric motor. Lord Kelvin's final improve- 

 rnents in the machine were made only a year or so before 

 his death ; they were, in fact, his last serious inventive 

 tycrk. They include a large horizontal dial for reading 

 the number of fathoms of wire out, and with this it is 

 jften practicable to tell the depth very closely without 

 -esorting to a depth gauge at all ; for in the modern 

 nachine the action is so uniform that, at any given speed 

 Jf ship, a definite relation holds between the depth and the 

 length of wire out, and by finding this relation once for 

 ill a table can be prepared by which the speed is known, 

 md so when the length of wire out is observed the depth 

 nay be at once inferred. This system is now in regular 

 ise in the Navy. A pair of the Kelvin machines stand on 

 he bridge ; the wire runs out along a boom at either side 

 md over an ingeniously designed pulley or fair-lead ; when- 

 ;ver soundings are wanted, they can be taken systematically 

 ind in quick succession while the ship proceeds at un- 

 iiminished speed, and the depth is called out for the in- 

 ormation of the navigating officer almost as soon as the 

 vire has stopped running out. Alike in the Navy and the 

 nerchant service, there is no difficulty in making it a 

 natter of routine to keep the sounding machines going 

 ncessantly when near shore or within, say, a hundred 

 athoms in thick weather. 



(Dr. Ewing then went on to speak of Lord Kelvin's 

 idvocacy of the Sumner or " position-line " method of 

 vorking out sights at sea, and his tables for facilitating 

 NO. 2105, VOL. 83] 



Sumner's method ; also his harmonic analysis of the tides 

 and his. tide-predicting machine.) 



In attempting this account of the work of Kelvin in 

 telegraphy and navigation, I am embarrassed by its volume 

 and its range. The time has proved far too short for a 

 fitting notice of discoveries and inventions so various, so 

 fundamental, so far-reaching in their practical effects. 

 Yet we have dealt only with a very small part of the 

 whole achievement of a man not less remarkable for 

 sustained industry' than for outstanding originality — a man 

 incessant in action and in thought — of whom it may be 

 truly said that there is no department of physics on which 

 he has not left an abiding impress. 



I have said nothing to-night of the lofty flights of scien- 

 tific imagination, which are, perhaps, his highest title to 

 fame ; but I have said enough to show that Kelvin was 

 no mere philosopher with head in the clouds. He was 

 quick to recognise a real need, quick also to see how 

 the need should be met. He found material for invention 

 in the most commonplace appliances, because his mental 

 habit was in everything to seek for the how and the why 

 and to ask himself in what wa}' the thing might be done 

 better. He had an infinite faculty of taking pains, of 

 adhering to a purpose until he secured its full accomplish- 

 ment, of going on from improvement to improvement in 

 pursuit of the more perfect result, and with all this a 

 courage and hopefulness that no opposition could damp, 

 that never accepted defeat. 



UMVERSITY AXD EDUCATIONAL 

 INTELLIGENCE. 



Cambridge. — Dr. E. W. Hobson, F.R.S., fellow, tutor, 

 and lecturer in mathematics at Christ's College, has been 

 elected Sadlerian professor of pure mathematics. Dr. 

 Hobson was senior wrangler in 1878, and has been mathe- 

 matical lecturer in the University since 1884, a lecturer in 

 Christ's College since 1879, and for the last few years 

 Stokes lecturer. His earlier published work related prin- 

 cipally to spherical harmonics, Bessel's functions, and 

 other allied functions, together with the cognate subject of 

 the theory of the potential. On these subjects he published 

 a memoir in the Philosophical Transactions of the Royal 

 Society-, two memoirs in the Cambridge Philosophical 

 Transactions, and a series of papers in the Proceedings of 

 the London Mathematical Society. About the year 1900 

 Dr. Hobson began to publish a series of papers dealing 

 with the theory of aggregates, that of functions of real 

 variables, the theories of G. Cantor, and the fundamental 

 principles of mathematical analysis ; and in 1907 his 

 treatise on the theory of functions of a real variable, and 

 on Fourier's series, was published by the L'niversity 

 Press. Since the appearance of this book he has, during 

 the last two years, published several papers, in which he 

 has given a general convergence theorem, and applied it 

 to questions connected with the representation of functions 

 by means of series of Sturm-Liouville functions, Legendre's 

 and Bessel's functions, and to the elucidation and extension 

 of the theory of Hamilton's fluctuating functions. He has 

 also quite recently published papers dealing with Lebesgue's 

 new theorv of integration, in relation to the fundamental 

 processes of the integral calculus. 



London. — ^The first annual report of the Military Educa- 

 tion Committee on the work of the university contingent 

 of the Officers' Training Corps, which was presented to 

 the Senate on February 23, has been issued. The con- 

 tingent, which was formed under the authority of a War 

 Office letter dated January 7, 1909, numbered 24 officers 

 and 783 enrolled cadets at the end of the year. Three 

 units are included, an engineer unit of one company, an 

 infantrv unit of a battalion of six companies, and a 

 medical unit of three sections of a field ambulance. An 

 application has been submitted to the War Office for per- 

 mission to organise Artillery and Army Service Corps units, 

 and to augment the medical unit. University College has 

 the largest number of cadets (160), King's College coming 

 second with 132 ; and the medical schools, especially Guy's 

 (67) and Middlesex (64). are well represented. The report 

 contains much statistical information throwing light on the 



