534 



NATURE 



{Sept. 27, 1888 



a steam, gas, or water engine, I am working them both by 

 electromotors, since a steam-engine or a water-wheel would be an 

 unsuitable occupant of the Drill Hall. Practically, then, a 

 steam-engine on the land belonging to the Midland Railway 

 Company, on the other side of the Lower Bristol Road, is driving 

 a Thomson- Houston dynamo; this is sending a small current 

 working these high-voltage constant-current Immisch motors. 

 The motors being geared with low-voltage dynamos the potential 

 •difference is transformed down, the first alternate-current trans- 

 former transforms it up again, and the second alternate-current 

 transformer ttansforms it down again, so that there are in fact 

 three transformations taking place in this experiment on the 

 platform before you. For the benefit of the electricians present, 

 I may mention that the two motors are running in series, and 

 that their speed is kept constant by means of a centrifugal 

 governor which automatically varies the number of the convolu- 

 tions of the field magnet that are being utilized at any moment. 

 In fact, since the dynamo maintains the current constant that is 

 passing through each motor, the function of the governor may 

 be regarded as that of proportioning the potential difference 

 maintained at the terminals of either motor to the load on the 

 motor at any moment. 



A vast 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 we>t, has over 20,000 in- 

 candescent lamps scattered over it all worked from the Grosvenor 

 Gallery in Bond Street by meins of alternate-current trans- 

 formers which convert the 2000 volts maintained 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 sixty-eight 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 transformer is 

 very high, being no less than 96*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 motive 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, or, lastly, electrical power into motive 

 power, in each case with an efficiency of not less than 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 current even a few yards would be attended with a great 

 •waste of power ; consequently, while an enormous current 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 Prof. 

 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 % of an inch, 

 and the operation is, as you see, entirely completed in some 

 fifteen seconds. For this experiment an alternate current of 20 

 amperes will be produced 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 9000 amperes, large 

 enough for 12,000 of these incandescent lamps if they 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 ends of the bars plastic long 

 before it even warms the whole bar, so that I can, as you see, 

 hold the bar at a distance of three or four inches from where 

 the weld has been made without experiencing any marked sense 

 of warmth. The heat is, in fact, applied exactly where we 

 require it, the temperature can be adjusted with the greatest 



nicety so as not to burn the steel, and the softening of the bar is 

 effected throughout its entire cross-section. Hence a very good 

 weld indeed can be made by end pressure. We have to thank 

 Mr. Fish, not merely for showing us these most interesting 

 experiments on electric welding, but for supplying the electric 

 power for many of the experiments I have been showing you, 

 and for the electric lighting of the Drill Hall. 



To Mr. Snell, the representative of Mr. Immisch, our best 

 thanks are clue for his having devoted several days in arranging the 

 two high- voltage, constant-current motors, to drive the dynamos 

 with that constancy of speed which you observe. This ingenious 

 telpher model, to which I shall refer presently, is the handi- 

 work of Mr. Bourne, and considering that it has had to be 

 hastily taken to pieces, and hastily put together again, it is 

 surprising that it works as well as it does. An ordinary watch 

 is a very trustworthy, steady-going machine, but if one had to 

 take it to pieces hastily, and as hastily to put it together again, 

 one might expect it to lose. Indeed, if you or I had to do it, 

 we should not be surprised if it did not go at all, and so was 

 only right twice every twenty-four hours. 



For the arrangements of the models and the smaller experi- 

 ments, as well as for the admirable execution of many of the 

 diagrams, our best thanks are due to Mr. Raine. 



Did time allow I should like to describe to you to what per- 

 fection the system of economical distribution with accumulators, 

 originally proposed by Sir William Thomson in 188 1 and shown 

 in its very simplest form in the wall diagram, has been brought 

 by Mr. King, the engineer to the Electrical Power Storage 

 Company ; how the cells when they are fully charged are 

 automatically disconnected from the charging circuit, and elec- 

 trically connected with the discharging circuit ; how the electric 

 pressure on the discharging or house mains is automatically 

 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 "alternate-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 clustered 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 electromotors 

 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 

 users, from the apparent fickleness of their complex chemical ac- 

 tion, 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 work, for 12^ 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 re- 

 sponsibility. 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 a hundred yeirs ago, in his 

 " Life of Richard Nash, Esquire ": " People of fashion at Bath, 

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

 which are frequently taught in a pretty superficial manner, so as 

 not to tease the understanding, while they afford the imagina- 

 tion some amusement." I want not to be superficial, yet I 

 must not tease your understanding, and so we will not lose our- 

 selves in technical details. If, however, my remarks have led 



