238 Scientific Intelligence. 
Soon after these experiments, Mr. B. O. Peirce, now Shek it 
in the Physical Laboratory of Harvard College, ma e fol- 
a thermopile. He used a large Bunsen burner provided with 
an air valve, so that the non-luminous could be at once changed 
a lumi He placed the burner wide ay between 
circular aperture admitted the rays and where the 
reflecting surface of the cover set obliquely enabled the observer 
to count the revolutions of the radiomet Tn front of the 
, an 
also took the readings of the galvanometer ; then, after rendering 
the flame luminous (by oe the air valve), t the same observa- 
tions were repeated, mparison of the similar values ee 
of cou beste —— Brie aa of the non-luminous and the 
feta nous us ay — ba the radiometer on the one side 
and the cheetaicile on the o 
Psat Thermopile. 
1 0°342 028% 
2 07309 0°380 
3 0°248 0°283 
4 0°267 0°325 
5 0-277 0-350 
6 0°367 0°250 
7 0°394 0°304 
Mean, "315 ll 
While, therefore, there was A eg a large variation between the 
several observations, as might be expected with such a variable 
source as a Bunsen flame, yet the close agreement of the averages 
showed conclusively that with the radiometer, as with the thermo- 
pile, the effect caused by the rays of light must arise solely from 
the change of temperature thus produced. It will be noticed that— 
as measured by either instrument— the radiation of the. Juminous 
the same time showed that the illuminating power of the first was 
at least a thousand times greater than that of the second. wo 
separate experiments gave 1080 and 1079 times greater respec 
tive 
In ‘ this notice we have been able to refer to only a few of the 
‘omit sane presented in recent articles on the radiometer, and 
t wi e be understood that our limits prevent us 
even sitidiigy t we a large number of other very eras t ere 
vations bearing on the “subject. 
Ne August 3d, 1877. 
