The home journal. (Winchester, Tenn.) 1858-188?, 1875-12-30
Study of the solar Surface.

At the recent meeting Of the Amcn-
can Association, Professor :. 7, Langley,
of Allcghany observatory, detailed some
Of the conclusions at which he had ar
rived after years Of study Of the solar
surface. Professor Langley first showed
bv comparative experiments that IN alb
sorptiyc atmosphere surrounds the sun.
Little attention has in recent years been
paid to the study Of this atmosphere.
The earlier efforts to tabulatc its absorp-
tive power, produced with different OBJ
servers, though men of cmincncc,
strangely discordant results. Their
methods and reductions were given III
detail. Sccchi's results, making the
ncichborhood of the edge of the sun
about half the brightness Of the center,
are probably near the fact Professor
Langlv applied well known photomctric
methods to the problem, by attaching
circle of cardboard to the equatorial tcIc-
scope, a solar image is received ON the
board. plainly showing spots, penumbrr,
etc. if the image bc one foot i'll diameter.
From holes in this cardboard pencils of
rays issue, which being caught on 4
screen rive second series OF images.
If these images are caught upon sep
aratc mirrors, instead Of Il screen,
their relative light can he made
the subject of comparison with that
of a disc of fame from Hunscns
apparatus, and thereby their relative in
tensity determined. Between each aper-
ture and It's respective mirror lens was
interpOscd which concentrated the pencil
of rays. BY suitable additions this ap-
paratus can be converted to Il Rumford
pbotomctcr, and in this form it proved
most available in Professor Langley,s
hands He found Il value for the bril-
liancy of the umbra in sun spots consld-
erably higher than that hitherto com
putcd. The bIackest umbra, he finds, is
between 5000 and 10000 times as bright
as the full moon. The light Of the sun
is absorbed by its atmosphere not IN the
same, but in greater proportion than its
heat. A long series of experiments
shows that not much more or less than
onc-halr of the radiant heat of the sun
is absorbed or suffers internal reflection
by the atmosphere of the sun itself. OBJ
scrvations indicate that this atmosphere
is (spcaking comparatively extremely
thin; Professor Langley is inclined to re-
card it as identical with the reversing
laycr" observed by DR.. Young, OF Dart
mouth, at the base of the chromosphere,
though the chromospheric shadow should
perhaps be taken into the account. The
importance of study of this absorbant
atmosphere becomes evident If we adj
nit that the greater part of the 300
which separate the temperature of the
temperate zone from absolute zero is
principally due to the suns radiation.
To this atmosphere new matter is CON
stantly being added and taken away by
the continual changes of the interior sur
face. Any alteration in the capacity fol
absorption-say II difference OF % pc
cent which could hardly be recognized
bv obsrryation-would alter the temper
ature of our globe by 1902. The exist
ence of life on the earth is clearly dc
pendent on the cOnstancy OF the depth an
absorption of this solar envelope, ll.tl
erto we have chiefly confined calculation
to the diminuton of solar heat by con
traction of the suns mGSS--;ln operation
likely to 20 on with great uniformity
But here is an element Of far more ripl'
variation. If changes in the depth o
this solar envelope are cyc!lcal, the!
would be accompanied by eycllcaI aIIe! Ill.,,
ations on the earth's temperature. lhl
NAV serve alike to explain the character
/ i.iics of variable stars and the vast sect
I lar change, on earth indicated by g
J. ology.