THE ELECTRIC LIGHT. 435 



ard candles the performance of the respective ma- 

 chines: * 



These determinations were made with extreme care 

 and accuracy by Mr. Douglass, the engineer-in-chief, 

 and Mr. Ayres, the assistant engineer of the Trinity 

 House. It is practically impossible to compare photo- 

 metrically and directly the flame of the candle with 

 these sun-like lights. A light of intermediate intensity 

 that of the six-wick Trinity oil-lamp was therefore 

 in the first instance compared with the electric light. 

 The candle power of the oil lamp being afterwards 

 determined, the intensity of the electric light became 

 known. The numbers given in the table prove the su- 

 periority of the Alliance machine over that of Holmes. 

 They prove the great superiority both of the Gramme 

 machine and of the small Siemens machine over the 

 Alliance. The large Siemens machine is shown to 

 yield a light far exceeding all the others, while the 



* Observations from the sea on the night of November 21, 

 1876, made the Gramme and small Siemens practically equal to 

 the Alliance. But the photometric observations, in which the 

 external resistance was abolished, and previous to which the 

 light-keepers had become more skilled in the management of the 

 direct current, showed the differences recorded in the table. A 

 close inspection of these powerful lights at the South Foreland 

 caused my face to peel, as if it had been irritated by an Alpine sun. 



