Sept. 20, 1888] 



NATURE 



5" 



the heat required to theoretically unburn 1 pound of zinc is only 

 one-seventh ot' that given out by the burning of 1 pound of coal. 

 Further, it involves no commercial 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 is gone into fully in the discussion on Mr. Hunt's paper, 

 and Mr. Robert Stephenson concluded that discussion by 

 remarking "that there could be no doubt, from what had been 

 said, that the application of voltaic electricity in what ever 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 

 electromotors 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 together with two wires. I move this magnet 

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

 the magnet suspended near the coil begins to swing in time with 

 my hand. [Experiment shown.] Here you have in its most 

 rudimentary form the conversion of mechanical power into 

 electric 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 electromotors as well as the machines for the pro- 

 duction of electric currents had this defect, the electric transmis- 

 sion of power was like carrying coals to Newcastle in a leaky 

 waggon. You would pay at least i6j. a ton for your coals in Bath, 

 lose most of them on the way, and sell any small portion that 

 had not tumbled out of the wagg6n for, say, Is. a ton at Newcastle 

 — a commercial speculation not to be recommended. 



A very great improvement in electromotors was made by 

 Pacinotti in i860, but although his new form of electromotor 

 was described in 1864 it attracted but little attention, probably 

 because any form of electromotor, no matter how perfect, was 

 commercially almost useless until some much more economical 

 method of producing 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 

 utilized by Gramme in 1870, who constructed the well-known 

 Gramme dynamo for converting mechanical into electric power — 

 a machine far more efficient than even Pacinotti had contemplated 

 — and gave the whole subject of electrical engineering a vigorous 

 forward impulse. Every subsequent maker of direct-current 

 dynamos, or motors, has followed Gramme's example in utilizing 

 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 re- 

 latively to the coils, or the coils relatively 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 [model shown], 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 electric 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. \V. N. Mordey, 

 for he has replaced the many magnets of the ordinary alternate- 

 current dynamos with one large magnet, and so with his alter- 

 nator weighing 41 hundredweight, 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 that has been done by the Drs. Hopkinson, Mr. Crompton, 

 Mr. Kapp, and others, in the improving of dynamos and motors 

 by applying scientific principles in the construction 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 into the rotating armature, as it is 

 called, and less wire on it, by shortening the stationary magnet, 

 and generally by concentrating the magnetic action, these con- 

 structors have raised the commercial efficiency of these machines 

 to actually as high as between 93 and 94 per cent. ; further, 

 how, by recognizing the force of the general principles laid down 

 by Prof. Perry and myself, as to the difference that should exist in 

 the construction of a motor and a dynamo, Messrs. Immisch 

 have succeeded in constructing strong, durable electromotors 

 weighing not more than 62 pounds per effective horse- power 

 developed. 



The subject is so entrancing to me, the results commercially 

 so important, that I am strongly tempted to branch off, but the 

 inexorable clock warns me that I mu t concentrate my remarks 

 as they have concentrated the magnetic action. 



87^ per cent, of the power put into an Edison- Hopkinson 

 dynamo has actually been given out by the motor spindle when 

 50 horse-power was being transmitted. How does this compare 

 with the combined efficiencies of an air-pump and an air-motor, 

 or of a water-pump and a water-motor ? I understand that in 

 either of these cases 60 per cent, is considered a very satis- 

 factory result. As far, then, as the terminal losses are concerned, 

 electric transmission of power is certainly superior to air or water 

 transmission. 



{To be continued.) 



SCIENTIFIC SERIALS. 



The Proceedings of the American Academy of Arts and 

 Sciences for the year May 1887-88 contains many important papers. 

 Among them we may mention one on the relative values of the 

 atomic weights of hydrogen and oxygen, by Prof. J. P. Cooke 

 and Mr. Richards, and a catalogue of. all recorded meteorites, by 

 Prof. Huntington. The volume also contains papers on the 

 existence of oxygen, carbon, and certain other elements in the 

 sun ; the first two of these papers are chiefly remarkable for the 

 absence of reference to the literature of the subjects, and it is 

 charitable to suppose that this proceeds from the authors' 

 ignorance. 



Bulletin de VAcademie Royale dc Belgique, June 30. — On the 

 physical aspect of Mars during the opposition of 1888, by L. 

 Niesten. An image of the planet taken by the author on May 5 

 shows that the so-called continent was again visible, which M. 

 Perrotin had reported as having disappeared during the opposi- 

 tion of 1886. Analogous though less marked modifications in 

 the form and colour of the spots seem to imply that these 

 changes are periodical. The paper is illustrated by two success- 

 ful photographs of the planetary disk, showing its appearance on 

 April 29 and May 5, 1888. — Fresh researches on the optic origin 

 of the spectral rays in connection with the undulatory theory of 

 light, by C. Fievez. A new interpretation of the spectral rays 

 is here offered by the author, who regards spectral phenomena as 

 a particular case of optical interferences. According to this view 

 luminous rays would produce at a given point of the spectrum a 

 vibratory movement, whose intensity might be maximum or 

 minimum according as one of the rays follows another by an even 

 or uneven number of half wave-lengths. A spectrum presenting 

 dark or bright rays would always proceed, not from a luminous 

 source, but from at least two different sources. It would thus 

 indicate the nature of the rays, whose undulatory movement was 

 disturbed by the simultaneous action of the various luminous 

 sources. M. Fievez concludes that Kirchhoff s absorption theory 

 does not alone suffice to explain the observed facts, which may 

 also be interpreted by means of the undulatory theory of light. 

 His views are supported by a number of ingenious and skilfully 

 executed experiments in spectral analysis. 



