Essex County herald. [volume] (Guildhall, Vt.) 1873-1964, 1876-11-25
The Heat Of the Sun.

At meeting of the academy of sci
ences, Prof. Roses naval experiments
were discussed. A paper was read as
follows On no one of the unsettled
questions of science is there so wide a
discrepancy as in respect to the values
set on the actual heat of the surface of
the sun. Estimates have been furnished
by Herschel and Secchi that place it at
100000 deg; by Ericsson at 4,000,-
600; and on the other hand, by French
physicists of repute at point little
over that of blast furnace-say 1900
degrees centigrade. This is a monstrous
discrepancy for skilled experimenters.
The difference in results depends upon
the mode of working the problem, and
the assumption involved. The large
estimates come from following Newton's 8
law that temperature increases as radia-
tion does. The smaller estimates come
from applying Dulong and Petit's law.
in which temperature is function of
radiation; function that reaches its
practical extreme when it is pushed be-
yond temperature of two thousand de-
grees.
Strange to say, the direct and stimuli
taneous comparison of the suns heat
and that from terrestrial sources has not
yet been made. AS an approximate
mode of inquiry, Prof. s. P. Langley
determined to compare the light of the
sun with that from the molten iron
poured out of the Bessemer converter.
The experiments we're made at the Edgar
Thomson steel works, where every fa-
cility was given. The galvanometer
could not be used for measuring COM
parative heats, because that instrument
is at once affected by the movement of
large masses of iron in its vicinity. The
Ritchie type of photometer was en-
ployed; Prof. Langley described its
construction and merits. In using it
he was placed under great disadvantage
from the continuous changes i'll the posi-
tion of the Bessemer converter. The
heliostat arrangement to give beam of
the sun for comparison, had to be as
continually shifted; the observer sat on
window sill in uncomfortable proxi-
nifty to the furnace operations. The
details of the experiment need not be
given here. The first conclusion reached
was that the suns light, which turns the
light from the molten steel into black
spot, must be at least fifty times the
greater. Then the spectroscope was
employed and the two rays compared.
The steel rays were again blotted out.
Hence the suns rays must have been at
least sixty-four times brighter. Next
Prof. Langley made comparisons of the
suns rays with those from the fame
above the converter, when the latter
We're at their brightest. This was less
difficult proceeding, and furnished more
specific results. The photometric COM
parison could be made directly. 1t is
admitted, however, that the fame light
may not be quite so bright as that of the
molten steel. The arrangement was
somewhat like that of camera obscurs.
It gave tho image of the sun so accurate
ly that sun spots could be easily exam
ined; it also gave an exact representa-
ton of the furnace fame. Each was
alternately superposed on the other.
The conclusion is that the sunlight is at
least 2, 1853 times brighter than the fur
mace fame. AS the heat is presumably
of the same relative order, the result is
adverse to the law of Dulong and Petit.
The actual heat of the sun is probably
among the higher values that have been
suggested.