;68 



SCIENTIFIC NEWS. 



[Oct. 5, iS 



is irresistible unless — and this is a very important con- 

 sideration which is only beginning to receive the atten- 

 tion it deserves — unless, I sa} r , the compound of zinc 

 formed by the action of the battery can be reduced again 

 to metallic zinc by a comparatively inexpensive process, 

 and the zinc used over and over again in the battery. If 

 the compound of zinc obtained from the battery be re- 

 garded as a waste product then it would be much too 

 expensive to work even theoretically perfect electro- 

 motors if they were existent by consuming zinc. Sup- 

 pose, however, a process be devised by means of which 

 burnt zinc can be unburnt with an expenditure com- 

 parable with the burning of the same weight of coal, 

 then it might be that although coal would still form the 

 basis of our supply of energy the consumption of zinc in 

 batteries might be an important intermediary in trans- 

 forming the energy of coal economically into mechanical 

 energy. 



While then some experimenters are aiming at possibly 

 increasing the working power of a ton of coal to eight 

 times its present value by earnestly seeking for a method 

 of converting the energy it contains directly into electric 

 energy without the intervention of a wasteful heat 

 engine, it should not be forgotten that in the cheap un- 

 burning of oxidised metal may lie another solution. 



The solution of this latter problem is quite consistent 

 with the principles of the conservation and dissipation 

 of energy since the heat required to theoretically unburn 

 i lb. of zinc is only one seventh of that given out by the 

 burning of I lb. of coal. Further, it involves no com- 

 mercial absurdity like that found in the calculations 

 given in the prospectuses of many primary battery 

 companies which are based on zinc oxide, a material 

 used in the manufacture of paint, maintaining its present 

 price, even if thousands of tons were produced. Unless 

 all those who use primary batteries on this expectation 

 intend to have the painters doing up their houses all the 

 year round, they will find themselves possessed of the 

 stock-in-trade of an oil and colourman on a scale only 

 justified by a roaring business in paint. 



Now about waste No. 3 — the waste of power at the 

 motor. That also was gone into fully in the discussion 

 in Mr. Hunt's paper, and Mr. Robert Stevenson con- 

 cluded that discussion by remarking " That there could 

 be no doubt from what had been said, that the applica- 

 tion of voltaic electricity, in whatever shape it might be 

 developed, was entirely out of the question, com- 

 mercially speaking. . . . The power exhibited by 

 electro-magnets extended through so small a space as to 

 be practically useless. A powerful electro-magnet might 

 be compared, for the sake of illustration, to a steam 

 engine with an enormous piston but with an exceedingly 

 short stroke. Such an arrangement was well known to 

 be very undesirable." 



And this objection made with perfect justice against 

 the electro-motors of thirty years ago, might also have 

 been made to all the machines then existing for the 

 mechanical production of electric currents. I have two 

 coils of wire at the two sides of the platform joined to- 

 gether with two wires. I move this magnet backwards 

 and forwards in front of this coil, and you observe the 

 magnet suspended near the coils begins to swing in time 

 with my hand. Here you have, in its most rudimentary 

 form, the conversion of mechanical power into electro 

 power, and the re-conversion of electric power into 

 mechanical power; but the apparatus at both ends has 

 the defects pointed out by Mr. Hunt and all the speakers 



in the discussion on his paper — the effect diminishes very 

 rapidly as the distance separating the coil from the 

 moving magnet increases. 



As long as electro-motors as well as the machines for 

 the production of electric currents had this defect, the 

 electric transmission of power was like carrying coals to 

 Newcastle in a leaky wagon. You would pay at least 

 sixteen shillings for your coals in Bath, lose most of 

 them on the way, and sell any small portion that had 

 not tumbled out of the wagon for say two shillings a 

 ton at Newcastle — a commercial speculation not to 

 be recommended. 



A very great improvement in electro-motors was 

 made by Pacinotti in i860, but although his new form 

 of electro-motor was described in 1864 it attracted but 

 little attention, probably because any form of electro- 

 motor, no matter how perfect, was commercially almost 

 useless until some much more economical method of pro- 

 ducing electric currents had been devised than the 

 consumption of zinc and acids. Pacinotti's invention 

 removed from motors that great defect that had been so 

 fully emphasized by the various speakers at the reading 

 of Mr. Hunt's paper in 1857. When describing his 

 motor in the Nuovo Cimento in 1864 he pointed out that 

 his principle was reversible, and that it might be used 

 in a mechanical current generator. This idea was 

 utilised by Gramme in 1870, who constructed the well- 

 known Gramme dynamo for converting mechanical into 

 electrical power, a machine far more efficient that even 

 Pacinotti had contemplated, and gave the whole subject 

 of electrical engineering a vigorous forward impulse. 

 Every subsequent maker of direct-current dynamo, or 

 motors, has followed Gramme's example in utilising the 

 principle devised by Pacinotti, which was as follows : — ■ 

 In all the early forms of dynamos or motors there were 

 a number of magnets and a number of coils of wire, the 

 magnets moving relatively to the coils, or the coils rela- 

 tively to the magnets, as you see in this rather old 

 specimen of alternate current dynamo. To produce 

 magnetism by a large number of little magnets is not 

 economical, and Pacinotti's device consisted in arranging 

 a number of coils round a ring in the way shown in 

 the large wooden model, so that they could all be 

 acted on by one large magnet. Instead of frittering 

 away his magnetism, Pacinotti showed how it could be 

 concentrated, and thus he led the way to dynamos and 

 motors becoming commercial machines. Pacinotti's 

 science engineered by Gramme not only made electric 

 lighting commercially possible, but led to electricity being 

 used as a valuable motive power. It was in their work 

 that the electrical transmission of power in its modern 

 sense sprang into existence. 



Quite recently an improvement in the same direction 

 has been introduced into alternate current dynamos by 

 Mr. W. N. Mordey, for he has replaced the many magnets 

 of the ordinary alternate current dynamos with one large 

 magnet, and so with his alternator, weighing 41 cwt., 

 which you see in this hall, he has succeeded in obtaining 

 at a speed of 650 revolutions per minute an output of 

 53'6 horse-power with a high efficiency. 



It may be convenient to mention at this stage the very 

 valuable work done by the Doctors Hopkinson, Cromp- 

 ton, Kapp, and others in the improving dynamos and 

 motors by applying scientific principles in the construc- 

 tion of these machines. Were I lecturing on dynamos 

 and motors instead of on the electric transmission of 

 power, I would explain to you how by putting more iron 



