February 2, 1893] 



NATURE 



;29 



of peace to Ireland as solid and substantial as any promised 

 political proposal. 



The New York and Chicago trunk line is 950 miles long, 

 and it is built with 435 lbs. (or No. 8 S.W.G.) copper wire. 

 This wire gives a resistance of 2 '06 ohms per mile, which is 

 easily verified ; but it is said by Mr. Wetzler to have a capacity 

 ■ f 0"0I58 microfarad per mile, which cannot be verified, and 

 uhich is absurdly high. 00158 microfarad was a measuremenc 

 made by me in England on an old line, but I have frequently 

 pointed out that owing to the use of earth wires the capacity of 

 nur English lines is very much greater than that of American 

 Wnes. Mr. Edison discovered this in 1872 when he came to 

 lingland to introduce his automatic system. Moreover, I have 

 also pointed out that induction still further diminishes 

 iliis capacity. The Paris circuit does not exceed 0005 

 microfarad per mile, I should estimate the Chicago circuit 

 .Tt 0004 microfarad per mile, and the K R at 7500, 

 which gives a result that quite accords with the opinions 

 that I nave heard expressed by those who have tried the two 

 circuits as to the relative efficiency of the Paris and Chicago 

 lines. My American friends would have done better if they 

 had used thicker wire. I should have specified 600 lbs. per 

 mile ; but if it had been in England I should have used 1000 lbs., 

 for we cannot dispense entirely with cables and underground 

 work as they have done in the States, and the increased capacity 

 introduced must be compensated for by reduced resistance. As 

 a matter of fact, i once proposed 1200 lbs. wire for a circuit 

 between London and Berlin— a distance of 760 miles, including 

 a cable 55 miles long. 



The beneficial ettect of induction as a negative capacity is 

 observed when working a circuit telegraphically with automatic 

 high-speed apparatus. Thus, on two copper wires 450 miles 

 long, making 900 miles altogether, the speed on each single v\ire 

 was 120 words per minute, and on metallic circuit — 



Loop z^fJ different routes ... 120 words per minute. 

 ,, on same poles 150 ,, ,, 



So that the improvement effected by induction was 25 per cent. 



There is no difficulty in measuring R of a metallic loop The 

 Wheatstone bridge determines it at onee. There is more diffi- 

 culty in obtaining K. It cannot be measured directly. But 

 with a metallic loop of copper, partly overhead and partly under- 

 ground, there are several modifications required, due to electro- 

 static and electro-magnetic induction, which are at present 

 beyond the reach of formulae, and render it difficult to determine 

 the capacity except approximately from the telephonic effects 

 themselves. Thus the capacity on the London-Paris circuit 

 proved to be only one-half of that obtained by calculation, and 

 every long circuit will require its own K to be determined by 

 comparison with an empirical K R scale. Such a scale I have 

 determined by careful experiment on artificial cables. 



I have recently devised a new form of cable which will pro- 

 bably quadruple the rale of telegraph working to America ; 

 and 1 may say with all confidence that there is no theoretical 

 reason whatever why we should not converse between London 

 and every capital in Europe, while it is not impossible to speak 

 even across the Atlantic. 



With regard to electric lighting, Mr. Preece said that many 

 efforts are being made to utilise the waste forces of nature in 

 producing electric currents for the economical supply' of the 

 light. In America, Scotland, Switzerland, Italy, and, indeed, 

 wherever waterfalls are available, electric plant is being installed 

 to convert the energy of the fall into the useful form of electricity. 

 At Tivoli, near Rome, a fall of 165 feet is used to work six 

 turbines of 350 horse- power each, giving 21CO horse-power in 

 all. Six high-pressure alternators working in parallel send 

 electrical energy at over 5000 volts pressure to Porta Pia, near 

 Rome, 14-8 miles from Tivoli, through four stranded copper 

 conductors, each having a diameter of 13mm., and bunched into 

 one metallic loop, givm;4 a total resistance of 4 ohms. At Porta 

 Pia the 5000 volts are reduced to 2000, and the currents are dis- 

 tributed to several substations spread over the city, where they 

 are again lowered to the safe pressure of 102 volts, at which 

 voltage the current is supplied to the consumer on the three-wire 

 system. There are 600 arcs and 30,000 glow lamps in use in 

 Rome, but they are not all supplied from Tivoli. Mr. Preece 

 in.-pected this installation only a few days ago, and found every- 

 thing working smoothly and efficiently under the able guidance 

 of Prof. Mengarini. 



Water power abolishes the coal bill, but it must be remembered 



NO. 12 14, VOL. 47] 



that the cost of maintenance of machinery and of the erection 

 and upkeep of conductors limits the distance to which the enerjiy 

 of falling water can be economically transmitted. The proposal 

 to light New York by currents generated at Niagara is at pre- 

 sent financially absurd. It is doubtful whether it will l)e 

 commercially advantageous at Buffalo, 30 miles away, but it 

 is certain that at Tivoli it can be so applied with advantage and 

 profit. 



There is much water power in this country that might be use- 

 fully employed. At Worcester it is proposed to use the water 

 of the Teme, a tributary of the Severn, to supply electrical 

 energy to the city— an experiment that will be watched with con- 

 siderable interest, for the use of water power will solve the 

 difficulty occasioned by light loads during the small hours and 

 daylight. Keswick and Lynton have already been so served, 

 but on a small scale only. There are many towns whose public 

 streets could be brilliantly illuminated by the streams running 

 past them, but there is much fear and distrust to be removed 

 from the minds of our local magnates, and a considerable amount 

 of education necessary before the public will receive the full 

 value of the gifts that nature so freely places at its disposal, and 

 the engineer so thoroughly converts into a utilitarian form. 



The following are some extracts from the passage in which 

 theoretical views of electricity are discussed : — 



In the Presidential address which I delivered to the Society 

 of Telegraph Engineers and Electricians in 1880, I took the 

 opportunity to formulate the theoretical views of electricity that 

 I had acquired at the feet of Faraday. It is not given to evei;y 

 boy to have his great ambitions realised. One of my ambitions 

 as an earnest listener to Faraday's simple and delightful lectures 

 was to be his assistant, and in almost the last investigation he 

 undertook on electric induction in underground wires it was my 

 privilege to see much of him, and to prepare many experiments 

 for him. Early in 1854, at his wish, I carried out for Mr. 

 Latimer Clerk certain experiments on the comparative effect of 

 increments of voltage in increasing the rate of transmission of 

 signals through long telegraph circuits. It was found that 

 variation of voltage nad no effect. Currents from 31 and from 

 500 cells sent through 768 miles of gutta-percha-covered under- 

 ground wire showed precisely the same velocity. Theseexperi- 

 ments were sent by Faraday to Mellon), who had prompted the 

 wish, and Melloni ("Faraday's Researches," vol. iii. page 577) 

 remarked : " The equal velocity of currents of various tensions 

 offers a fine argument in favour of the opinion of those who sup- 

 pose the electric current to be analogous to the vibrations of air 

 under the action of sonorous bodies." This is to be found in 

 the very last contribution inserted in the greatest work ever 

 published on ourscience, "Faraday's Experimental Researches 

 in Electricity." 



Faraday's views were subsequently expounded and extended 

 by Maxwell, who said : " Faraday, in his mind's eye, saw lines 

 of force traversing all space, where the mathematician saw 

 centres of force attracting at a distance ; Faraday saw a 

 medium where they saw nothing but distance ; Faraday sought 

 the seat of the phenomena in real actions going on in the 

 medium, they were satisfied that they had found it in a power 

 of action at a distance impressed on the electric fluids" (Max- 

 well, "Electricity," vol. i. page 10). 



Since that peiiod I have never regarded electricity as any- 

 thing else but as a form of energy, and its effects as modes of 

 motion of the molecules of matter and of the ether that fills 

 all space ; and daring my long apprenticeship of forty years I 

 have never examined one experiment or considered one fact 

 that was not explicable on this theory. . . . 



Electricity is energy which is transmitted by matter and 

 through space by certain disturbances the result and the 

 equivalent of work done, and in certain orderly and law regu- 

 lated forms, called "electromagnetic waves." It is not 

 difficult to conceive the ether carved or the molecules of 

 matter swayed or excited in definite periodic waves. A 

 molecule is subject to all kinds of motion — translation, oscilla- 

 tion, rotation upon its own axis, and revolution about some 

 external axis. Clausius {Pogg. Ann., clvi. p. 618) suggested 

 that the atoms or groups of atoms constituting a molecule 

 revolve around one another similarly to planets, and are 

 sometimes nearer to and sometimes further from each 

 other. The difference between the infinitely great and 

 the infinitely little is only one of degree. The motions 

 of the solar system and that of a molecule of water 

 are similar. These motions are imparted to and transmitted by 



