August io, 1882] 



XATURE 



359 



power is available, electric lighting is in a position of still 

 greater advantage, and, in point of cost, altogether beyond 

 comparison with other means of producing light. 



To complete the comparison between the cost of electric light 

 and gas light, we must consider not only the amount of coal 

 required to yield a certain product of light in the one case and in 

 the other, but also the cost of converting the coal into electric 

 current and into gas ; that is to say, the cost of manu- 

 facture of electricity and the cost of manufacture of gas. I 

 cannot speak with the same exactness of detail on this point as I 

 did on the comparative cost of the raw material. But if you 

 consider the nature of the process of gas manufacture, and that 

 it is a process, in so far as the lifting of coal by manual labour is 

 concerned, not very unlike the stoking of a steam boiler, and if 

 electricity is generated by means of steam, then the manual 

 labour chiefly involved in both processes is not unlike. It is 

 evident that in gas manufacture it would be necessary to shovel 

 into the furnaces and retorts five or six times as much coal to 

 yield the same light product as would be obtainable through the 

 steam engine and incandescent lamps. But here again it is 

 necessary to allow for the value of the labour in connection with 

 the products other than gas, and hence it is right to cut down 

 the difference I have mentioned to half — i.e. debit gas with only 

 half the cost of manufacture, in the same way as in our calcula- 

 tion we have charged gas with only one-half the coal actually 

 used. But when that is done there is still a difference of pro- 

 bably three to one in respect of labour in favour of electric 

 lighting. 



I have made these large allowances of material and labour in 

 favour of the cost of gas, but it is well known that the bye 

 products are but rarely of the value I have assumed. I desire, 

 however, to allow all that can be claimed for gas. 



With regard to the cost of tlant, I think there will be a 

 more even balance in the two cases. In a gasworks you have 

 retorts and furnaces, purifying chambers and gasometers, engines, 

 boilers, and appliances for distributing the gas and regulating 

 its pressure. Plant for generating electricity on a large scale 

 would consist principally of boilers, steam-engines, dynamo- 

 electric machines, and batteries for storage. 



No such electrical station, on the scale and in the complete 

 form I am supposing, has yet been put into actual operation ; 

 but several small stations for the manufacture of electricity 

 already exist in England, and a large station designed by Mr. 

 Edison is, if I am rightly informed, almost completed in 

 America. We are therefore on the point of ascertaining by 

 actual experience, what the cost of the works for generating 

 electricity will be. Meanwhile, we know precisely the cost of 

 boilers and engines, and we know approximately w4iat ought to 

 be the cost of dynamo-electric machines of suitably large size. 

 We have, therefore, sufficient grounds for concluding that to 

 produce a given quantity of light electrically the cost of plant 

 would not exceed greatly, if at all, the cost of equivalent gas- 

 plant. 



There remains to be considered, in connection with this part 

 of the subject, the cost of distribution. Can electricity be distri- 

 buted as widely and cheaply as gas? On one condition, which 

 I fully hope can be complied with, this may be answered in the 

 affirmative. The condition is that it may be found practicable 

 and safe to distribute electricity of comparatively high ten-ion. 



The importance of this condition will be understood when it 

 is remembered that to effectively utilise electricity in the produc- 

 tion of light in the manner I have been explaining, it is necessary 

 that the resistance in the carbon of the lamps should be relatively 

 great to the resistance in the wires which convey the current to 

 them. When lamps are so united with the conducting wire, that 

 the current which it conveys is divided amongst them, you have 

 a condition of things in which the aggregate resistance of the 

 lamp* w ill be very small, aud the conducting wire, to have a 

 relatively small resistance, must either be very short, or, if it be 

 long, it must be very thick, otherwise there will be excessive 

 waste of energy ; in fact, it will not be a practical condition of 

 things. 



In order to supply the current to the lamps economically, 

 there should be comparatively little resistance in the line. A 

 waste of energy through the resistance of the wire of 10 or 

 perhaps 20 per cent, might be allowable, but if the current is 

 supplied to the lamps in the manner I have described— that of 

 multiple arc, each lamp being as it were a crossing between two 

 main -vires, then— and even if the individual lamps offered a 

 somewhat higher degree of resistance than the lamps now in 



actual use — the thickness of the conductor would become exces- 

 sive if the line was far extended. In a line of half a mile, for 

 instance, the weight of copper in the conductor would become 

 so great, in proportion to the number of lamps supplied through 

 it, as to be a serious charge on the light. On the other hand, if 

 a smaller conducting wire were used, the waste of energy and 

 consequent cost would greatly exceed that I have mentioned as 

 the permissive limit. 



Distribution in this manner has the merit of simplicity, it 

 involves no danger to life from accidental shock ; and it does 

 not demand great care in the insulation of the conductor. But 

 it has the great defect of limiting within comparatively small 

 bounds the area over which the power for lighting could be dis- 

 tributed from one centre. In order to light a large town electri- 

 cally on this system, it would be necessary to have a number of 

 supply stations, perhaps half a mile or a mile apart. It is 

 evidently desirable to be able to effect a wider distribution than 

 this, and I hope that either by arranging the lamps in series, so 

 that the same current passes through several lamps in succession, 

 or by means of secondary voltaic cells, placed as electric reservoirs 

 in each house, it may be possible to economically obtain a much 

 wider distribution. 



Whether by the method of multiple arc (illustrated by Diagram 

 I.) which necessitates the multiplication of electrical stations; or 

 by means of the simple series (illustrated by Diagram II.), or by 

 means of secondary batteries connected with each other from 

 house to house in single series, the lamps being fed from these 

 in multiple arc (as illustrated by Diagram III.), I am quite 

 satisfied that comparatively with the distribution of gas, the 

 distribution of electricity is sufficiently economical to permit of 

 its v radical application on a large scale. 



As to the cost of laying wires in a house, I have it on the 

 authority of Sir Wm. Thomson, who has just had his house com- 

 pletely fitted with incandescent lamrs from attics to cellars — to 

 the entire banishment of gas — that the cost of internal wires for 

 the electric lamps is less than the cost of plumbing in connection 

 with gas-pipes. 



I bave expended an amount of time on the question of cost 

 which I fear must have been tedious ; but I have done so from 

 the conviction that the practical interest of the matter depends 

 on this point. If electric lighting by incandescence is not an 

 economical process, it is unimportant ; but if it can be esta- 

 blished — and I have no doubt that it can — that this mode of 

 producing light is economical, the subject assumes an aspect of 

 the greatest importance. 



Although at the present moment there may be deficiencies in 

 the apparatus for generating and storing electricity on a very 

 large scale, and but little experience in distributing it for 

 lighting purposes over wide areas, and consequently much yet to 

 be learnt in these respects ; yet, if once it can be clearly esta- 

 blished that, light for light, electricity is as cheap as gas, and 

 that it can be made applicable to all the purposes for which arti- 

 ficial light is required, electric light possesses such marked 

 advantages in connection with health, with the preservation of 

 property, and in respect of safety, as to leave it as nearly certain 

 as anything in this world can be, that the wide substitution of 

 the one form of light for the other is only a question of time. 



SCIENTIFIC SERIALS 



Bulletin de V Academic Roy ale des Sciences de Belgique, No. 6. 

 — Resistance of the air in guns ; letter by M. Colladon. — Note 

 on experimental ballistics, by M. Melsens. — Experimental re- 

 rearches on the respiratory movements of insects, by M. Plateau. 

 — Existence and amount of diurnal precession and nutation, on the 

 hypothesis of a solid earth, by M. Folie. — Fundamental principle 

 relative to contact of two surfaces having a common generatrix, 

 by M. Mansion. — On a geometrical representation of two uni- 

 form transformations, by M. Le Paige.— On bibrominated 

 camphor, by M. Swarts. — Action of trichloride and tribromide 

 of phosphorus on gaseous phosphuretted hydrogen, by M. de 

 Wilde. — Action of trichloride of phosphorus on iodide of 

 phosphonium, by the same. — Researches on the structure and 

 signification of the respiratory apparatus of Arachuida, by Mr. 

 MacLeod. 



Annalen der Physik und Chemie, No. 8.— On development of 

 electricity as equivalent of chemical processes, by F. Braun. — 

 The theory of the micro-telephone, by V. Wietlisbach. — On 

 prism-observation with obliquely-incident light, and on a modi- 



