Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1876-11-15
Heat of the Sun.

On no one of the unsettled questions
of science is there SO wide diScrep-
ancy 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
l0,000,00O degrees; by Ericsson at
100000 degrees; and, Oh the other
hand, by French physicists of repute
at a point little over that of a blast
furnace-say, 1900 degrees cent?
grade. This is monstrOuS discrep-
ancy for skilled experimenters. The
difference in results depends upon the
mode of working the problem. and the
assumption involved. The large esti-
mates come from following Newton S
law that temperature increases as IA
diation does. The smaller estimates
come from applying Dulong and Petit s
law, in which temperature is a fuuc-
ton of radiation; function that
reaches its practical extreme when it
is pushed beyond temperature of
1000 degrees.
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 approx
mate 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 BESSIE
mer converter. The experiments We're
made at the Edgar Thompson Steel
Works, where every facility was given.
The galvanometer could not be used
for measuring comparative heats, be-
cause that instrument is at once af-
tected by the movement of large
masses of iron III its vicinity. The
Richie type of photometer was en-
ployed; Prof. Langley described its
construction and merits. In using it
he was placed under great disadvan-
tageS from the continuous changes in
the position of the BesSemer converter
The heliostat arrangement to give a
beam of the sun for comparison, had
| To be as continually shifted; the OBJ
server sat on window-sill in uncom-
Portable proximity to the furnace
operations. The details of the
experiment need not he given
here. The first copclusion reached
was that the suns light, which turns
! the light from the molten steel into a
| black spot must be at least fifty times
the greater. Then the spectroscope
was employed and the two RAYS com
pared. The steel rays We're again
blotted out. Hence the sun RAYS must
have been at least siXty-four times
brighter. Next, Prof. Langley made
comparisons of the suns RAYS with
| those from the flame above the con-
Nerter. when the latter were at their
brightest. This was less difficult
proceeding and furnished more specific
results. The photometrIc comparison
could be made directly. Its admitted
that the flame light may not be quite
as bright as that of the molten steel.
| The arrangement was somewhat like
thai OF camera obscura. 1t gave the
! image of the sun SO accurately that
sun spots could be easily examined ; il
also gave an exact representation of
the furnace flame. Each was alter
nately superposed on the other. The
| conclusion is that the sunlight is at
least 2.16S times brighter than the
furnace flame. As the heat is preSum-
| ably 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. -PhIQdel-
phja Letter 20 n. Y. Tribune.