Sept. 8, 1881] 



NA TURE 



435 



rain. We may or may not look f 01 ward ho;e^ullyto the lime 

 when windmills will again "lend revolving animation" to a 

 dull flat counli7 ; but we certainly need not I e afraid that the 

 ;cene will be marred by forests of iron columns tal.ing the place 

 of natural trees, and gigantic tanks overshadowing the fields and 

 blackening the horizon. 



To use rain-power economically on any considerable scale %\ e 

 must look to the natural drainage of hill country and take the 

 water whei-e we find it tither actually falling or stored up and 

 ready to fall when a >hort artificial ihannel or j ipe can be pro- 

 vided for it at moderate cust. The expense of aqutducts, (.r of 

 underground water-pipes, to carry water to any great distance — 

 any distance of mote than a few miles or a few hundred yards — 

 is n.ULh too great for economy when the yield to be provided fcr 

 is power; and such works can cjnly te undertaken when the 

 ■water itself \s what is wanted. Ii.cidentally, in connection with 

 the water supply of towns, some pait of ihe energy due to the 

 head at which it is supplied may Le u:ed for power. There are 

 however but kw cases (I know of noi.e except Giecnock) in 

 which the energy to spare over and above that clev. ted to bring- 

 ing the water to where it is wanted, and can in g it to flow fast 

 enough fcr convenience at every opened tap in every hou-e or 

 factory, is enough to make it wcrth while to make ariangements 

 for letting the water-power be used without wasting the water- 

 substance. The ca-es in which water-power is taken from, a 

 town supply are generally very smal', such as w. rl ing the bellows 

 of an organ, or " hair-bru-hing by machinery," and involve 

 simply throwing away the used » ater. 1 he cost of energy thus 

 obtained must be something enorm< us in pro] orticnto the actual 

 quantity of the energy, and it isonly thesmallnessof the quantity 

 that allows the convenience of havirg it when wanted at any 

 moment, to be so dearly bought. 



For anything of great work by rain-power, the water-wheels 

 must be in the very place where the water supply v.ith natural 

 fall is found. Such places are -generally far from great towns, 

 and the time is not yet come when great towns grow by 

 natural selection beside waterfall*, for power ; as they glow 

 beside navigable rivers, for shipping. Thus hitherto the use •. f 

 water-power has been confined cbiefly to isolated factories which 

 can be conveniently placed and economically worked in the 

 neighbourhood of natural wa'erfalls. But the splendid sugges- 

 tion made about three years ago by Mr. Siemens in his presiden- 

 tial address to the Insiituti ,n of Mechanical Engineers, that the 

 pcwer of Niagara might be uiilised, by transmitting it el ctri- 

 cally to great distances, has given quite a fresh departure fcir 

 design in respect to economy of rain-power. FVom the time of 

 Joule's experimental electroma;;nt tic engir.es developing 90 per 

 cent, of the energy of a Voltaic battery in the form of w eights 

 raised, and the theory of the electromagnetic transmission of 

 energy completed thirty years ago on theft undai ion afforded by 

 the train of experimental and theoretical mvestigaticns by which 

 he established his dynamical equivalent of heat in m.echanical, 

 electric, electro chtmical, chemical, eleclro-magneic, and ihcrmo- 

 elastic phenomena, it had been known that ] otential energy 

 from any available source can be transmitted electromngnetically 

 by means of an electric current through a wire, and directed to 

 raise weights at a distance, with unlimitidly perfect economy. 

 The first large-scale practicd application of electro-nagnetic 

 machines was proposed by Holmes in 1854, to produce the 

 electric light for lighth uses, and perevered in by him till he 

 proved the availability of his machine to the satisfactii n of the 

 Trinity House and the delight of Faraday in trials at Elackwall 

 in Ajril, 1S57, and it was applied to light the South Fore- 

 land lighthouse on December 8, 1S58. This gave the impulse 

 to invention ; by which the electro-magnetic machine has been 

 brought from the physical labor: t iry into the province of ergi- 

 neering, and has sent back to the realm of pure science a 

 beautiful discovery, that of the fundamental principle of the 

 dynamo, made triply and independently, and as nearly as may 

 he simultaneously in 1S67 by Dr. AA'erner Sien en=, Mr. S. A. 

 Varley, and Sir Charles Wheatstone ; a discovery which consti- 

 tutes an electro magnttic analogue to the fundamental electro- 

 static principle of Nichi Ison's revolving doubler, resuscitated by 

 Mr. C. F. Varley in his instrument "for generating electricity " 

 patented in 1S60 ; and by Holtz in his celehratul electric machine ; 

 and by myself in my " replenisher " for multiplying and main- 

 taining charges in Leyden jars for heterostatic electrometers, 

 and in the electrifier for the siphon of my recorder for sub- 

 marine cables. 



The dynamos of Gramme and Siemcn--, invented r.nd made in 



the course of these fourteen years since the discovery of the 

 fundamental principle, give now a ready means of realising 

 economically on a large scale for many important practical 

 applications, the old ihermo-dynamics of Joule in electrc- 

 magnetism ; and, what particularly concerns us now in connec- 

 tion w ith my present subject, they make it possible to transmit 

 electro-magreiitally the work of waterfalls through long insulated 

 conducting v ires, and use it at distances of fifties or hundreds of 

 miles from the source, with excellent economy — better economy, 

 indeed, in respect to proportion of energy used to energy dissi- 

 pated than almost ai.ything known in ordinary mechanics and 

 hydraulics for distances of hundreds of yards instead of hundreds 

 of miles. 



In answer to questions put to me in May, 1879,' by the Par- 

 liamentary Cominittee c n Electric Lighting, I gave a formula 

 for calculating the amount of energy transmitted, and the 

 amount disipa'ed by being converted into heat on the way, 

 through an in-ulated copper conductor of any length, with a;iy 

 given electromi live force applied to produce the current. Taking 

 Niagara as example, and with the idea of bringirg its energy 

 usefully to Moi,trea!, Bo.'ton, New Voik, and Philadelphia, I 

 calculated the formula for a distance of 300 British s'atute miles 

 (which is greater than the dislrnceof any of those four cities from 

 Niagara, and is the ladius of a circle covering a large and very 

 important part of the United States and British North America), 

 I found almost to my surprise that even with so great a di.-tance 

 to be pi'Gvided for, the conditions are thoroughly practicable with 

 good economy, all aspects of the case carefully considered. The 

 formula itself will be the subject of a technical communication 

 to Section A in the course of the Meeting on which we are new 

 entering. I therefore at present restrict myself to a slight 

 statement of results. 



1. Apply dynamos driven by Niagara to produce a difference 

 of potential of So,oco vol's between a good earth-connection 

 and the near end of a solid copper wire of half an inch {r27 

 centimetres) diameter, and 300 statute miles (483 kilometres) 

 length. 



2. Let resistance by driven dynamos doing work, or by elec- 

 tric liiihts, or, as I can now say, by a Faure battery takir^ in a 

 charge, be applied to keep the remote end at a potential differ- 

 ing by 64,000 volts from a good earth-plate there. 



3. The result will 1 e a current of 240 webers through the wire 

 taking energy from the Niagara end at the rate of 26,250 horse- 

 power, losing 5250 (or 20 per cent.) of this by the generation 

 and dissipation of heat through the conductor and 21,000 horse- 

 power (or 80 per cent, of the whole) on the recipients at the far 

 end. 



4. The elevation of temperature above the surrounding atmo- 

 sphere, to allow the heat generated in it to escape by radiation 

 and be carried away by convection is only abcut 20° Centigrade ; 

 the wire being hung fi eely exposed to an- like an ordinary tele- 

 graph wire supported on posts. 



5. The striking distance between flat metallic surfaces with 

 difference of potentials of 80,000 volts (or 5,oco Daniell's) is 

 (Thomscii's " Electrostatics and Magneti.-m," § 340) only 18 

 millimetres, and therefore there is no difliculty about the insula- 

 tion. 



6. The cost of the copper wire, reckoned at id. per lb., is 

 37,rco/. ; the interest on which at 5 per cent, is igcx)/. a year. 

 If 5250 horse-power at the Niagara end costs more than 1900/. 

 a year, it would be better economy to put more copper into the 

 conductor ; if less, less. I say no more on this poii t at present, 

 as the economy of copper for electric conduction will be the 

 subject of a special communication to the Section. 



I shall only say in conclusion that one great difficulty in the 

 way of economising the rlectrical tran mitting power to great 

 distanecs (or even to moelerate distances of a few ki'ometres) 's 

 now overcome by Faure's splendid invention. Hi^jh potential, 

 as Siemens, I believe, first pointed cut, is the essential for good 

 dynamical economy in the electric transmission of power. 

 But what are we to do wi h So,coo volts when we have them at 

 the civili- ed end of the wire ? Imagine a doirestic servant going 

 to dus; an electric lamp with So,coo volts on one of its meals ! 

 Nothing above 200 volts ought on any account ever to be ad- 

 mitteel into a house or ship or other pilace where safeguards 

 against accident cannot be made tbsclutely a d for ever trust- 

 worthy against -all possibility cf accident. In an electric work- 

 shop 8o,coo volts is no more dangerous than a circular saw. 



'■ Printed in the Parliamentary Blue Eook Rep.rt of the Committee on 

 Electric Lighting. 1879. 



