42 Mr, Joseph W. Swan [March 10, 



resistance in the wires tvhich 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 lamps will be very small, and 

 the conducting wire, to have a relatively small resistance, must either 

 be very short, or, if it be long, it must be vei^y 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 ivires, 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 excessive 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 i^roportion 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 distributed from one centre. 

 In order to light a large town electrically 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 

 comj)aratively with the distribution of gas, the distribution of 

 electricity is sufficiently economical to permit of its practical aj)plica- 

 tion 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 lamps from attics to cellars— to the 



