March 3, 19 10] 



NATURE 



23 



accompanied by a large coloured map of the Antarctic and 

 sub-Antarctic regions, showing the ocean depths as ascer- 

 tained by recent expeditions. 



Valuable scientific and economic work in botany has 

 been carried on by Dr. Cockayne during the past two 

 years. Although a great deal has been done in the way 

 of establishing sanctuaries and national parks in order that 

 the native fauna may be preserved for all time, the import- 

 ance of placing on record their present ecological condition 

 can hardly be overestimated. It is hoped that at some 

 early date the Government may see its way to authorise 

 Dr. Cockayne to proceed further with the botanical survey 

 of the Dominion. 



Largely owing to the representations of the institute, 

 combined with those of the Otago Institute, the position of 

 the memorial to the late Sir James Hector has been 

 made satisfactory. Owing to the action of the Govern- 

 ment in granting a generous subsidy, ample funds will 

 be at the disposal of the committee for establishing a 

 memorial that will be worthy of Sir James Hector's long 

 and distinguished services to the cause of science in New 

 Zealand. Observations in connection with the Arthur's 

 Pass Tunnel were continued throughout the year. 

 Temperature readings have been taken every ten chains 

 and specimens collected. Early last year a committee was 

 formed for the purpose of investigating systematically the 

 artesian system of Christchurch and the neighbourhood. 

 The committee has held several meetings, and has taken 

 preliminarv steps for ascertaining the extent, depth, and 

 geological relations of the water-bearing strata, and for 

 the examination of physical, chemical, and biological 

 proj>erties of the water obtained from them. Two papers 

 by Dr. Farr and Mr. D. C. H. Florance, on the radium 

 emanation contained in the artesian water and on the 

 effect of the water as it comes direct from the well on 

 trout and other fish, have already been laid before the 

 institute. 



-A committee was appointed to consider the Animals' 

 Protection Act, and to suggest amendments with the 

 view of giving more effective protection to the native 

 fauna of the Dominion. A conference was held with a 

 similar committee appointed by the Canterbury Acclimatisa- 

 tion Society, and a number of recommendations were made 

 which received the approval of the council. It is intended 

 to submit the proposals to other institutes for their con- 

 sideration, and if they meet with approval to bring the 

 matter under the notice of members of Parliament and of 

 the Minister for Internal .\ffairs. It is hoped later to 

 send a party to the Chatham Islands for purposes of 

 scientific investigation. 



It is evident that the institute is not only encouraging 

 interest in science by its monthly meetings, but is also 

 actively engaged in promoting the progress of natural 

 knowledge. 



THE WORK OF LORD KELVIN IN TELE- 

 GRAPHY AND NAVIGATIONA 

 T ORD KELVIN'S work was great and many-sided. We 

 -*-' might compare it to the cathedral in some crowded 

 mediaeval city, where no place can be found commanding 

 a general view. You approach by one narrow street or 

 another, seeing from each only some portion of a particular 

 face of the building. The Kelvin lecturer has, as it were, 

 to select his view-point, conscious that he must concentrate 

 his attention on what is, after all, but a small part of a 

 gigantic whole. The lecturer might, for instance, take up 

 the mathematical work of Kelvin in the theory of electro- 

 statics, in the theory of magnetism, in the theory of 

 elasticity, in hydrodynamics, in the wave theory of light ; 

 his contributions to thermodynamics, which included the 

 establishment of an absolute scale of temperature and the 

 enunciation of the principle of the dissipation of energy, 

 his experimental work on the electrodynamic quality of 

 metals, his speculations on the structure of matter, his 

 views on the age of the earth, his share in fixing the elec- 

 trical units ; or, on the riiore practical side, his electrical 

 measuring instruments, from the electrometers of the early 

 days to the ampere balances and wattmeters which he 



1 From the second Kelvin lecture, delivered at the Institution of Electrical 

 Engineers on January 13, by Prof. J. A. Ewing, C.B., F.R.S. 



NO. 2105, VOL. 83] 



designed when the need for such instruments became 

 apparent with the growth of electrical engineering. Any 

 one of these subjects, or others that might be named, 

 would provide a more than ample text. To-night I have 

 selected two portions of Lord Kelvin's work as the most 

 suitable to bring before you, namely, his work in sub- 

 marine telegraphy and in navigation. Both of these are 

 practical matters which appeal to members of this institu- 

 tion. They illustrate well the bent of his genius as an 

 engineer. In both of them he made inventions of first- 

 rate importance — inventions which not only met an 

 immediate requirement, but have stood the test of time ; 

 and an additional reason for the selection is the personal 

 one that both in telegraphy and navigation it was my 

 good fortune, as one of his young assistants, to see some 

 of his inventions in the making. 



His connection with telegraphy had begun long before, 

 when he was only thirty years of age. It dates from 1854, 

 and to appreciate rightly the part he began to play then 

 I must ask you to go back as far as 1850, the year of 

 the earliest submarine telegraph. It was in August, 1850, 

 that a line consisting of a single copper wire, insulated by 

 gutta-percha, wound on a great reel on the deck of a steam 

 tug in Dover Harbour, was laid from Dover to Calais. 

 There was no sheathing or protection of any sort ; the line 

 was what we should now call a bare core, and so light 

 was it that lead sinkers were attached at every hundred 

 yards to ensure its going to the bottom. In a few hours 

 it was cut by the anchor of a fisherman, who took home 

 a piece to show to his family as a curious new kind of 

 seaweed ; but during its brief life it gave the operators 

 much food for thought. Accustomed only to the clear, 

 sharp signals of land lines, they could make nothing of 

 those got from the cable, and Mr. Willoughby Smith tells 

 us how at each end of the line it was regretfully concluded 

 that the operator at the other end must have been lunch- 

 ing, not w-isely, but too well. This was the earliest 

 experience of the effects of electrostatic induction in retard- 

 ing the signals and altering their character. The cable is 

 equivalent to an extended Leyden jar of large capacity, 

 and at every application of the sending battery there is a 

 gradual charging up, so that the signal current which 

 arrives at the distant end does not at once reach its full 

 strength ; and, further, when the contact with the sending 

 battery stops the current does not at once cease, but tails 

 off slowly as the cable discharges the electricity it has 

 accumulated. The current accordingly arrives in the 

 character of a wave, slowly rising to a maximum value 

 and then slowly subsiding each time a signal is sent. 



In a short cable this causes little trouble; it only makes 

 the process of signalling a little slower, but the instruments 

 which serve on land lines may still be used. .\ successful 

 Dover-Calais cable properly covered with a protecting 

 sheath was laid in 185 1, and was soon followed by other 

 short lines. The general character of the electrostatic 

 charge in a cable was explained by Faraday, and it was 

 experimented on by Latimer Clark in a cable, no miles 

 long, laid to connect England with Holland ; but no one 

 knew then in what manner the retardation of signals to 

 which it gives rise depended on the electrical characteristics 

 or how it would be affected in cables of different lengths 

 or with different dimensions of core. It was in 18^4 that 

 Thomson's attention was directed to the subject by Stokes, 

 following on a conversation at the British Association, and 

 in this wav began the connection with submarine tele- 

 graohv which was to prove of momentous import. 



Thomson attacked the problem with characteristic 

 ardour, and in less than twelve days he sent a comolete 

 solution to Stokes, which was published in fuller form 

 in the Proceedings of the Royal Societ>- for May. 18.:;;. 

 In this paoer he points out that the effect of electrostatic 

 induction is to make the flow of electricity in a cable 

 corresoond to the flow of heat in a solid conductor as 

 investigated mathematically by Fourier. He formulates th^ 

 equations and draws what is called the curve of arrival, 

 the curve, namely, which shows in what manner the 

 current graduallv reaches its full value, at the distant end 

 of the cable, w^hen contact with the battery is made at 

 the sending end. He shows how the current falls away 

 when the batterv is removed and the cable is put to earth ; 

 and how, in cables of different lengths but of the same 



