Oct. 12, 1 888.] 



SCIENTIFIC NEWS. 



395 



THE ELECTRICAL TRANSMISSION OF 

 POWER. 



A Lecture Delivered by Professor Ayrton, F.R.S., etc., 



BEFORE THE BRITISH ASSOCIATION, ON SEPTEMBER 8TH, 

 AND Re-DeLIVERED TO THE WORKING-CLASSES OF 



Bath, on September 13TH, 1888. 

 ( Continued from p. 370.J 



AVAST district in London, extending from Regent's 

 Park on the north to the Thames on the south, from 

 the Law Courts on the east to Hyde Park on the west, has 

 over 20,000 incandescent lamps scattered over it, all 

 worked from the Grosvenor Gallery in Bond Street by 

 means of alternate current transformers, which convert 

 the 2,000 volts contained between the street mains into 

 100 volts in the houses ; and this London Electric Supply 

 Company have arranged for a vast extension of this 

 system to be worked from Deptford. 



In America alternate current transformers are due to 

 the remarkable enterprise of Mr. Westinghouse, used to 

 light 120,000 incandescent lamps in 68 towns. In fact, 

 the electric lighting of a whole town from a central 

 station begins to excite less astonishment than the 

 electric lighting of a single house did ten years ago. 



The efficiency of a well-made alternate current trans- 

 former is very high, being no less than g6'2 per cent, 

 when the transformer is doing its full work, and 89/5 

 per cent, when it is doing one quarter of its full work, 

 according to the experiments made by our students. 

 It certainly does seem most remarkable, and it reflects the 

 highest praise on the constructors of electrical machinery, 

 that motor power can be converted into electrical power, 

 electrical power at low pressure into electrical power at 

 high pressure, or electrical power at high pressure into 

 electrical power at low pressure, and lastly, electrical 

 power into motor power in each case with an efficiency 

 of 94 per cent. 



As a further illustration of the commercial importance 

 of this electric transformation, I will show you some 

 experiments on electric welding, one of the latest 

 developments in electrical engineering. To weld a bar 

 of iron one square inch in section requires a gigantic 

 current of some 13,000 amperes. To convey this cur- 

 rent even a few yards would be attended with a great 

 waste of power, consequently while an enormous cur- 

 rent is passed through the iron to be welded, only a 

 comparatively small current is transmitted along the 

 circuit from the dynamo to the welding apparatus. Mr. 

 Fish, the representative of Professor Elihu Thomson, of 

 America, to whom this apparatus is due, will be so kind 

 as to first show us the welding together of two bars of 

 square tool steel, the edge of each bar being three- 

 quarters of an inch, and the operation is entirely 

 completed in some fifteen seconds. For this experi- 

 ment an alternate current of 20 amperes will be pro- 

 duced by the dynamo at the other side of the lower 

 Bristol road, and this current will be converted by the 

 transformer on the platform into one of 9,000 amperes, 

 large enough for 12,000 of those incandescent lamps, if 

 these were placed in parallel and the current divided 

 among them. He will next try welding some thicker 

 bars ; and lastly, he proposes welding together two 

 pieces of aluminium, which it is extremely difficult, if 

 not impossible, to weld in any other way. The bars, as 

 you see, are in each case pressed together end on, and, 

 in consequence of the electric resistance of the very 

 small gap between the bars being much higher than 



that of the bars themselves, the current makes the end 

 of the bars plastic long before it softens the whole bar. 

 Hence a very good weld indeed can be made by end 

 pressure. 



Did time allow, I should like to describe to you what 

 perfection the system of economical distribution with 

 accumulators originally proposed by Sir William Thom- 

 son in 1881, and shown in its very simplest form in the 

 wall diagram, has been brought by Mr. King, the engi- 

 neer to the Electrical Power Storage Company, how the 

 cells when they are fully charged are automatically dis- 

 connected from the charging circuit and electrically con- 

 nected with the discharging circuit, how the electric 

 pressure on the discharging or house mains is automati- 

 cally kept constant, so that the brightness of the lamps 

 is unaffected by the number turned on, and how cells 

 that are too energetic have their ardour automatically 

 handicapped and not allowed to give more current than 

 is being supplied by the less active ones. 



During the last few months fierce has been the battle 

 raging among the electricians, the war-cry being alter- 

 nate current transformers versus accumulators, while the 

 lookers-on with that better view of the contest that they 

 are proverbially said to possess, have decided that the 

 battle is a drawn one. Neither system is the better 

 under all circumstances; if the district to be lighted be 

 a very scattered one, use alternate current transformers 

 by all means, but if the houses to be lighted are clus- 

 tered together at a distance from the supply of power, 

 then the storing property possessed by accumulators, 

 which enables the supply of electric power to far exceed 

 the capacity of the dynamos and engines in the busiest 

 part of the twenty-four hours, will win the battle for 

 accumulators. Any direct current system of distribution 

 such as is furnished by accumulators has also the very 

 great advantage that it lends itself to the use of the very 

 efficient electro-motors which I have been using this 

 evening. Alternate current motors do exist, but they 

 are still in the experimental stage and are not yet 

 articles of commerce. 



Secondary batteries have caused much heart-burning 

 for their uses, from the apparent fickleness of their com- 

 plex chemical action, yet but imperfectly understood. 

 But we have at length been taught what is good and 

 what is bad treatment for them, and after years of brave 

 persevering application on the part of the Electrical 

 Power Storage Company, that forlorn hope, the 

 secondary battery, has become one of the most useful 

 tools of the electrical engineers, and secondary cells, 

 some of which, thanks to the kindness of that company, 

 I am using here to-night to supply power for lamps and 

 motors, may now be trusted to have a vigorous long 

 life. That company, I learn, undertake henceforth to 

 keep their cells in order, when used for central station 

 works, for I2| per cent, per annum, and I understand 

 that they have such confidence in them that they anticipate 

 making no little money by incurring this insurance office 

 responsibility. It is not then surprising that the Chelsea 

 Supply Company have decided to use secondary batteries 

 on a large scale for the economical distribution of light 

 and power in their district. 



Oliver Goldsmith said more than 100 years ago in his 

 life of Richard Nash, Esq., " People of fashion at Bath. 

 . . . .when so disposed attend lectures on the arts and 

 sciences, which are frequently taught in a pretty, super- 

 ficial manner so as not to tease the understanding, while 

 they afford the imagination some amusement." I want 



