THE ELECTRIC LIGHT. 673 
The following table gives in standard candles the perform- 
ance of the respective machines: * 
Name of Machines. Maximums. Minimum. 
Holmes 1,523 1,523 
Alliance 1,953 1,953 
Gramme (No. 1) . . . . 6,663 4,016 
Gramme (No. 2) . . . . 6,663 4,016 
Siemens (Large) . . . 14,818 8,932 
Siemens (Small, No. 1) . . 5.539 3,339 
Siemens (Small, No. 2) . . 6,864 4,138 
Two Holmes' Coupled . . 2,811 2,811 
Two Gramme's (Nos. land 2) . 11,396 6,869 
Two Siemens' (Nos. 1 and 2) . 14,134 8,520 
These determinations were made with extreme care and 
accuracy by Mr. Douglass, the engineer-in-chief, and Mr. 
Ay res, the assistant engineer of the Trinity House. It is 
practically impossible to compare photometrically and 
directly the flame of the candle with these sunlike lights. 
A light of intermediate intensity that of the six- wick 
Trinity oil lamp was therefore in the first instance com- 
pared with the electric light. The candle power of the oil 
lamp being afterward determined, the intensity of the 
electric light became known. The numbers given in the 
table prove the superiority 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 
coupling of two Grammes, or of two Siemens together, 
here effected for the first time, was followed by a very 
great augmentation of the light, rising in the one case 
from 6,663 candles to 11,396, and in the other case from 
6,864 candles to 14,134. Where the arc is single and the 
external resistance small, great advantages attach to the 
Siemens light. After this contest, which was conducted 
* 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. 
