OCTOB^ 19, 1905] 



NA TURE 



in working, this high, prcssiire must be transformed down 

 into a low one at the distant end of the transmission 

 system. '■ 



' But what did high pressure — produced with a dynamo- — 

 mean twenty-six years ago? Why, three or four hundred 

 volts — ^what, in fact, is called low pressure to-day — a pressure 

 less than is now often used for lifts in buildings, pumps in 

 mines, and tramcars in streets. And how was it proposed 

 to' transform this so-called high pressure into a low one? 

 Why, 1 suggested mechanically coupling a 400-volt dircct- 

 rtf^rent motor to a 50-volt direct-current dynamo — the 

 de\-ice that has since been called a " motor generator " — 

 and such a combination was shown in operation at that 

 lecture. 



But it was in Paris, at the Palais de I'lndustrie, the 

 home of that electrical exhibition of 1881 which has now 

 become classical, that modern electrical engineering was 

 born, and shortly afterwards Punch exhibited the young 

 infant thriving, and imbibing liquid nourishment from a 

 storage cell. 



" VV'hat win he grow to? " says the picture. What has 

 he grown to? Aladdin's ring, Aladdin's lamp — whose 

 slaves brought a fortune to him, and a fainting fit to his 

 mother — were but poor magic makers compared with the 

 ring evolved by Gramme and that boy, Paccinotti — com- 

 pared with the lamp constructed by those veterans Edison 

 and Swan. 



In the " Arabian Nights " it is stated that Aladdin's 

 would-be uncle, the noled and learned African magician, 

 knew that the wonderful lamp was not fed with oil, and 

 he anticipated by many centuries the plan for reconciling 

 the inhabitants of Johannesburg to having the electric 

 pressure in their houses raised from no to 230 volts — 

 for did not he, like the municipal African magician, offer 

 '" new lamps for old? " 



U is also described how the lamp enabled Aladdin to 

 carry off the Princess Badroulboudour, and the wicked 

 uncle to transport the palace. But electric traction has 

 carried off whole neighbourhqods out of cities into suburbs, 

 and, by transporting hundreds of thousands daily, has 

 helped to solve the problem of housing the working class ; 

 while electric distribution of power has discovered, not 

 caves of . buried jewels, but waterfalls of ever-fjpwing 

 wealth. 



At the mines near Silver City, Idaho, for example, coal 

 had reached ■ seventy shillings a ton, wood thirty-six 

 shillings a cord. ■ For years the distribution of power was 

 by donkeys, or by long teams of horses slowly hauling 

 heavy loads of wood up the mountain road ; and then the 

 magician of this, the electric age, came to Idaho, and 

 what those mines need — power, clean, dustless, weightless 

 power, now courses up the mountain side from Swan Falls 

 on Snake River in the valley below. What fairy of old, 

 who could change dead leaves into jewels, ever worked 

 such beneficent wonder? See how proudly those posts look 

 down upon their conquest Of the past. For have they not 

 brought an end, not merely to wasteful extravagance in 

 lifting fuel up to those mines, but also to needless toil 

 for tired cattle? ■ 



In 1.SS6, when the boy Electricity was five, the babe 

 Johannesburg was born, and the two youngsters have raced 

 along neck and neck. To-night I will tell you something 

 of their lives. 



N'ine years after that first lec-ture, the British Association 

 honoured me by asking for another. In 1888, however, 

 it was beginning to be realised that a pressure of 2000 

 volts between electric mains might not make too great a 

 call on the 'funds of life insurance companies. Alternate 

 current transformers had come into use ; Ferranti was 

 employing them practically, for distributing electric current 

 from the Grosvenor Gallery, Bond Street. A " transform- 

 ation scene " Lord Kelvin called the apparatus at that 

 lecture. The male white population of Johannesburg was 

 now — 2000. 



But, although current, at 100 volts pressure, was 

 beginning to be distributed for electric lighting, the dis- 

 tribution of power for working electro-motors was still 

 but a dream of the future. 



In exactly a decade after the Paris Electrical Exhibition 

 of tSSi came the Frankfort Exhibition of 1891. More 

 than ten times 2000 volts was there used to transmit more 



with 



than 100 horse-power, more than 100 

 than 75 per cent, efficiency. 



A death's-head and cross-bones were painted on every 

 post along that 109 miles of railway line, Lauffen to 

 Frankfort, for he who should touch these bare wires, with 

 a pressure of 25,000 volts between them, secured electrocu- 

 tion ; and a similar suggestion of mortality greets the way- 

 farer — in his own language, be he English or Dutch — on 

 the posts of the Rand Central Electric Works. 



The table shows that the use of higher and higher 

 pressures has enabled larger and larger amounts of power 

 to be transmitted longer and longer distances, with greater 

 and greater effieiency, that is, with less and less waste. 

 Now, why is this? 



The electric current, as you know, is used for lighting 

 buildings, driving machinery, propelling cars and trains. 

 But throw away the notion, if any of you still have it, 

 that electricity is a kind of gas, or oil, or fuel that is used 

 up in these operations. The common expressions, buying 

 electricity, consuming electric current, are most mislead- 

 ing, for just as much electricity flows away per minute — 

 through the return conductor — from your electrically lighted 

 house as flows to it through the coming conductor. If, 

 therefore, it were electricity that you had undertaken to 

 pay for, you must have made a very bad bargain, because 

 you do not retain the striallest portion of what you would 

 have agreed to purchase. 



The electric current is like a butcher's cart carrying 

 round meat — you no more consume current than you con- 

 suinc cart. It is not the vehicle, but what it leaves behind 

 that the consumers buy — meat in the case of the butcher's 

 cart, and energy in the case of the electric current. 



Exactly the same considerations apply to the distribu- 

 tion' of power, with air at 70 lb. pressure per square 

 inch, to the thousands of rock drills on the Rand, to the 

 distribution of power with water at 425 lb. pressure per 

 square inch down, the shaft of the Rietfontein Mine, and 

 at 750 lb. pressure in the workshops of the Central South 

 African Railways at Pretoria. 



The energy conveyed with air, with electricity, or with 

 water is made up of three factors — (i) the current, (2) the 

 time during which it flows, and (3) the pressure under 

 which it flows ; while power depends on the current and 

 the pressure only. 



Few words are used more vaguely than this one 

 "power." Before starting for South Africa some of us 

 gave someone a. power of attorney ; we cariie on a ship 

 of 12,000 horse-power; the voyage did us a power of good; 

 at the concert on board we sang of the power of love. 



In engineering, however, power has one very definite 

 meaning — the rate of doing work — and a stream of air, of 

 electricity, or of water exerts much power, that is, works 

 rapidlv, when it quickly loses pressure, or head. Quickly 

 losing one's head, however, is not characteristic of large 

 brain-power, and the power exercised by those who sit in 

 high places is often much in excess of their rate of doing 

 any kind of work. 



■When water has but a few feet of head, the quantity 

 flowing over a water-wheel inust be large if much work 

 has to be done. But since the water usually comes to a 



NO. 1S77, VOL. 72] 



