The Scranton tribune. [volume] (Scranton, Pa.) 1891-1910, 1900-05-26

elRnt lnCnes 10 Illuminate u Sneet VI
white paper as brightly as the sun.
Bond found that sunlight Is 100000
times as bright as the light OF the full
moon.
NOT ALL RAYS VISIBLE
BY measuring the heat OF the sun
the energy of all its rays is determined
that OF the dark heat rays as well
as of the visible rays. There Is no
real difference in the nature Of the
visible rays we call light ard those
which can be detected merely by their
heating effect or by means OF photo
graphy. The difference lies in our
sense organs, which respond tD some
rays more readily than to others.
One of the simplest ways for de-
terminating the heat effect Of the sun
is to expose to its rays hollow cop
per disk covered on the side oward the
sun with lampblack, so as to absorb
all the heat, and filled with water In
which is immersed a delicate ther-
mometer. The rise in the temperature
of the water after exposing the disk
for q given time is measured, and this
with the weight OF the water heated,
enabl es one to measure the quantity
Of heat BY such means it is found
that the heat annually received by
the earth would melt a layer Of ice
1856 feet deep all over Its surface, II
the sunlight were equally distributed
in all latitudcs; or using the known
relation between heat and work, the
heat received by each square yard
when the sun is overhead is equal to
about one and one-fourth horsepower
OF which about one-eight rs mechari-
cally available by the use of machines
such as those constructed by Ericks-
son and Mondrot. 1t is found, how
ever, that the cost Of the machine for
the power obtained makes it cCm-
mercially impracticable.
MEASURING THE SUNLIGHT.
We live, however, at the bottom of
sea OF air through which the sun
light must penetrate to the earth. II Y
much of the sunlight which falls on the
upper regions of the atmosphere pene-
trates to its depths? To make such
measurements we cannot pass above
the atmosphere, but we can ascend
some high mountain. and leaving half
the mass of the air below, measure
the suns light and heat, and then de-
ternine the total effect of atmospheric
absorption by computation.
A few years ago the director OF the
Allegheny observatory, Professor S. z.
Langley organized an expedition to
Mount Whitney, Cal. for the purpose OF
making such measurements. Mount
Whitney, which is $4,000 feet above
the level Of the sea, rises abruptly from
a desert plane. in an atmosphere pc
culiarly dry and clear. By making
measurements at the foot OF the noun
tain and on its heights the absorptive
power of the atmosphere could be
determined. Professor Langley found
that the atmosphere has a sitting ac-
ton on sunlight, absorbing more OF
the blue and violet rays than of the
red, so that should the air be removed
the sun would appear blue.
1t was also found that the atmos-
phere permits only half Of the suns
heat to penetrate to the surface of the
earth, while at the same time it acts
as blanket to prevent the heat from
being Immediately radiated into space
On the mountain top the members
of the expedition, when not exposed to
the direct rays of the sun, suffered con-
siderably from cold, but in the SUMS
light they suffered still more from its
burning and blistering rays. Professor
Langley estimated tnat, if the at
mosphere We're removed, the tempera-
ture even at noon would be far below
freezing.
Having thus found that the heat
which reaches the upper regions OF
the atmosphere is about 40 per cent.
more than that which penetrates the
surface of the EARTH or about Ia
horse power for every square yard it
can be calculated how much heat Is
radiated at the surface OF the sun.
DIMENSIONS OF OLD SOL.
Now we know that the sun Is a globe
S66,50 miles in diameter, having a sur
face 1900 times and a volume 1,SO0,-
600 times as great as the earth. The
earth might be placed at the center OF
the sun, the moon still revolve about
it as now at a mean distance OF 239, 900
miles and be but little more than hall
way toward the solar surface. About
the sun the earth revolves in a nearly
circular orbit. at a mean distance of
930OO,000. Imagine a sphere OF this
radius surrounding the sun. The earth
will, of course, be on the surface OF
this sphere. We know the heat which
falls on each square foot of the earth,
when the sun is directly overhead, con-
sequently we know how much heat
falls on our imaginary sphere.
Now suppose this sphere ishrlnks un-
til it touches the sun; there now falls
on it's surface the same total amount
of heat as before, but euch square foot
receives more heat. as much more as
the area OF the sphere with the earth's