NATURE 



333 



THURSDAY, AUGUST 7, 1SS4 



ELECTRIC LIGHTING 

 A Practical Treatise on Electric Lighting. By J. E. 



H. Gordon. (London : Sampson Low and Co., 



18S4.) 

 "PRACTICAL treatises on this subject are very nume- 

 ■*- rous, but they do not emanate from the right men. 

 We want a book from a perfectly independent authority, 

 unflavoured with the taint of invention, the result of prac- 

 tical experience. Mr. Gordon is in many respects well 

 qualified for the task, but he is an inventor, and his book 

 is strongly impregnated with prejudice and a green-spec- 

 tacle view of the subject. He is, however, a staunch 

 believer in the immediate future of successful electric 

 lighting, and is very hopeful that the dark clouds that now 

 envelop it will be dispelled by the enlightenment of 

 steady progress. 



After an introductory chapter on the general principles 

 of artificial lighting, he deals with the conversion of elec- 

 tric currents into heat, and shows how carbon, when 

 raised to incandescence, fulfils all the conditions required 

 t<> give the maximum light with the minimum expenditure 

 of heat. The problem is to concentrate the heat in a 

 solid of the smallest possible size or with the smallest 

 possible cooling surface. Electrical units — amperes, volts, 

 ohms, coulombs — and their relation to each other and to 

 the ordinary heat and work units are explained, though, 

 curiously enough, that most useful and much employed 

 unit the iua.lt is not even mentioned. The rules that 

 regulate derived currents lead to an investigation of the 

 method of calculating the power wasted in a network of 

 conductors — a matter of very serious consequence in the 

 commercial aspect of electric lighting, though Mr. Gordon 

 does not touch on any of the recent methods devised to 

 reduce the excessive cost of mains. We then have a dis_ 

 quisition on the experimental measurements of currents, 

 electromotive forces, resistances, and power developed, 

 with a description of various indicators and measurers 

 employed. No reliable instrument has yet been intro- 

 duced for ordinary practical use, and there are many 

 instruments now undergoing trial which Mr. Gordon has 

 not touched upon— particularly those of Marcel Deprez 

 in use on the Continent, and which were exhibited at 

 Munich and Vienna. 



A capital chapter is devoted to glow lamps. "The 

 first public exhibition of incandescent lamps that was 

 made in this country was made by Mr. Swan before the 

 Society of Telegraph Engineers on November 24, 1880. 

 The first exhibition in America was made by Mr. Edison" 

 (p. 62). Mr. Gordon does not give the date ! Arc lamps 

 follow, Mr. Crompton's admirable lamp being that selected 

 for description. 



Perhaps the most valuable and certainly the most novel 

 chapter in the book is that written by Mr. Crompton on 

 carbons used in arc lamps. The following information is 

 useful (p. 105) : — 



" The diameters most commonly used have been as 

 follows : 



Vol.. x\x- No. 771 



For currents horn 7-12 ampere: 

 12-18 



18-25 „ 

 25-40 

 ,, 40 upwards 



And the following is startling: — 

 Illuminating Fewer per Electrical H.P. of 13 mm. (.'■ 



different Makers. Currents from 15 to 20 amperes 



9 mm. to 1 1 mm. diameter. 

 11 mm. to 13 mm. 

 13 mm. to 15 mm. 

 15 mm. to 18 mm. 

 18 mm. to 20 mm. ,, 



N.-ime.i . 

 Siemens (cored), pos. ) 

 Cane (cored), neg. J 



Siemens (cored) 



Bainsley Co 



Johnson and Phil 

 Sautter and Lemonnier 



Cane (not cored) 



Silvertown (Gray's) 

 Carre (cored) 



per H.P. 

 ... 4270 



•■• 3514 



■ 3500 



... 29S6 



2 



... 2773 



... 2580 



... 1072 



We then have a chapter on magnets and electro ti 

 netic induction, which leads to the general principles and 

 of electric generators, including a very admirable 

 account of that important subject, self-induction. 



"// is found experimentally, ami can be proved mathe- 

 matically, that if a coil a wire forms part of a circuit, 

 m alternating E.M.F. semis a current through it. 

 that the current will he much less than it \ 

 been had the same resistance been interposed in the form 

 af a straight wire. 



"Further, the proportional dim i nut:, 

 as the current is increased by the reduction af the 

 an-c; and finally, for a given E.M.F. , a given late 0/ 

 alternation, and a coil of given shape, a limit is readied 

 beyond which even re, ice ing the resistance to zero does not 

 increase the current" (p. 123). 



" This diminution, however, does not, to the best of my 

 belief, -waste energy or diminish the efficiency of the 

 machine. ; it only diminishes its output. Thus self- 

 induction increases the size of a mac/line required to feea 

 a certain number of lamps, but it docs not per, . 

 increase the H.P. required to drive the machin • with that 

 number of lamps on it. 



" The effect of self-induction increases as the current 

 increases, and therefore short-circuiting a. coil of an 

 alto nature: machine does not indefinitely increase the 

 current in that coil, and seldom increases it enough to 

 injure the insulation " (p. 137). 1 



Of course we have a good description of alternate-cur- 

 rent machines, and after some adverse criticism of the 

 Ferranti type (which is imperfectly described), and not 

 justified by the performance of the latter, Mr. Gordon 

 describes his own form, which is chiefly distinguished by- 

 its size and weight. A few direct-current machines are 

 described — not the best— and their regulation briefly re- 

 ferred to, with the curious conclusion (p. 1831 : — 

 " Conclusion. 



" The true secret of successful regulation is to far, 

 very targe dynamos, because then, as we have said before, 

 the maximum number of lamps that can be turned out at 

 one time is a -aery small percentage of the whole, and 

 when there are a great number of lamps on one machine. 

 the cost per lamp of regulating, either by hand or by an 

 elaborate mechanical contrivance, is very trifling." 



Goulard and Gibbs' secondary generators and the 

 various secondary batteries are briefly despatched. 

 Apropos of the latter he says (p. 191) : — 



" There is no doubt that the interest and depreciation 

 on a set of secondary batteries large enough to enable ai, 

 electric tight plant to work day ami night, and so givt 



