450 
ON THERMAL RADIATION IN ABSOLUTE MEASURE. 
The Edison lamp was now opened, and, the filament having been removed, it was 
re-“ flashed ” in such a way as to give it a beautiful polished metallic-looking surface. 
It was then placed in a fresh globe, and was exhausted down to the same point as 
before and sealed off from the pump; and the new lamp was re-tested against the 
Swan lamp and standard candle. The result of these experiments was as follows :— 
Incandescent Lamp at same candle-power in two cases. 
(1.) 
(2.) 
Oriainal Edison filament— 
Same filament re-“ flashed,” 
dull lustreless surface. 
to have brilliant surface. 
Potential (volts). 
777 
58'5 
Current (amperes) . 
0745 
0-680 
Watts. 
57-9 
39-8 
It thus appears that to maintain the same carbon in these two conditions, at the 
same candle-power, there is required 30 per cent, less energy in the second case than 
in the first. 
On this important subject, of the influence on radiation of the nature of the 
surface, I hope at an early date to make a more complete investigation : and I propose, 
also, as soon as may be, to repeat and extend the observations of Macfarlane, to 
which I have already more than once referred. The increase in the rate of loss of 
heat due to diminution of the radiating surface demands further examination. 
