1882.] Mr. Swan on Electric Lighting hij Incandescence. 33 



WEEKLY EVENING MEETING, 



Friday, March 10, 1882. 



Sir Frederick Bramwell, F.R.S. Vice-President, in the Chair. 



Joseph W. Swan, Esq. 



Electric Lighting hy Incandescence. 



Speaking in this place on electric light, I can neither forget, nor for- 

 bear to mention, as insej)arably associated with the subject and with 

 the Royal Institution, the familiar, illustrious, names of Davy and 

 Faraday. It was in connection with this Institution that, eighty years 

 ago, the first electric light experiments were made by Davy, and it 

 was also in connection with this Institution that, forty years later, the 

 foundations of the methods, by means of which electric lighting has 

 been made useful, were strongly laid by Faraday. 



I do not propose to describe at any length the method of Davy. I 

 must, however, describe it slightly, if only to make clear the differ- 

 ence between it and the newer method which I wish more particularly 

 to bring under your notice. 



The method of Davy consists, as almost all of you know, in pro- 

 ducing electrically a stream of white-hot gas between two pieces of 

 carbon. 



"When electric light is produced in this manner, the conditions, 

 which surround the process are such as render it impossible to obtain 

 a small light with proportionally small expenditure of power. In 

 order to sustain the arc in a state approaching stability, a high 

 electro-motive force and a strong current are necessary ; in fact, such 

 electro-motive force and such current as correspond to the jDroduction 

 of a luminous centre of at least several hundred candle-power. When 

 an attempt is made to produce a smaller centre of light by the em- 

 ployment of a proportionally small amount of electrical energy, the 

 mechanical difiiculties of maintaining a stable arc, and the diminution 

 in the amount of light (far beyond the diminished power employed), 

 put a stop to reduction at a point at which much too large a light is 

 produced for common purposes. 



The often-repeated question, " Will electricity supersede gas?" 

 could be promptly answered if we were confined to this method of 

 producing electric light ; and for the simple reason that it is im- 

 possible, by this method, to produce individual lights of moderate 

 power. 



The electric arc does very well for street lighting, as you all 

 know from what is to be seen in the City. It also does very well for 



Vol. X. (No. 75.) d 



