Year: 1873

own estimate must give way !; the tenn
perature of the solar spots must be
marked down at once, and that OF the
suns average surface with them. Let
us bear in mind that the higher and
more astonishing estimates are based
upon certain theories of radiation which
may have been revised.


Leaving the question of the solar tenn
perature, let us ask the quantity OF heat
which is given out by the sun. Here
we have to deal with subject which is
essentially different from that OF tenn
perature, and much easier to handle.
The data are more simple and more GER
tain. Knowing the distance OF the sun
from our planet, and assuming that II
radiates heat equally in all directions,
we are able TO calculate how large pro-
portion of the energy emitted is received
by the earth. This being determined,
we can ascertain by experiment the
quantity of heat which we actually re-
ceive, and by a simple multiplication
learn how much the sun gives out Now,
it has been found that, of the total heat
emitted, our planet receives but the
1-2138000 part. That which falls upon
one quarter of the terrestrial surface at
the equator at noon, is sufficient to melt
26. 900 tons of ice per hour. And that
which falls upon the whole surface of
the earth in year would be able to
liouefv q layer of ice 100 feet thick,
wholly enveloping the planet. This is
the heat which is manifested in the
evaporation of oceans. 1t raises their
waters to the mountain tops, thence to
flow down to the sea in rivers. The
water powers of the world, from the
great Falls of Niagara down to the pet
tiest ripple in rivulet, are products of
this energy. 1t enables plants to grow
and animals to breathe it governs
glaciers and avalanches it stored up,
ages ago, our beds of coal. And yet it
is but the 1-213S000 part of the total
heat radiated by the sun. The total can
be expressed in a variety of striking
forms, which, though not absolutely
exact, give us admirable approximate
ideas of the immensity of our great
luminary.


The total heat emitted by the sun,
then, would melt stratum of ice COM
pletely surrounding it, at the rate of
2,400 feet of thickness per hour. Her
schel says that if column of ice forty
five miles in diamter were TO be darted
into the gun with the velocity of light
| Q92,0 miles per second), the heat
radiated from the solar surface would be
Just consumed in melting it, while the
actual temperature of the vast globe
would be unaltered. The constant ex-
penditufe of the sun would be balanced,
and no more. Tyndall gives us still an
other expression of this wonderful
amount of power. He says that the
heat given out by the sun is sufficient
to raise 700, 0,0O0,00 of cubic
miles of ice cold water to boil
ing, every hour The heat necessary to
elevate the temperature of single
pound of water in single degree, if
converted into work, would lift weight
of 772 pounds one foot high. What
stupendous weight, therefore, would be
raised by the whole thermal energy of
the sun No wonder that the planets
keep obediently in their places under
the influence of so vast a power. Yet
the sun, grand as it is, is comparatively
but small star, and is rushing onward
through space with vast velocity, re-
spending to some attractive agency still
mightier than it's own.


From what source is this astonishing
amount of solar energy supplied? =? The
sun cannot create force. All its loss
must be made good, or else in time it
will cool down to a dead globe, unable
to warm or light us. That some source
of supply must exist is evident for the
sun has been shining upon our planet
for thousands of years of historical
time, during which period our climate
has not appreciably changed. Century
after century, the solar expenditure of
heat goes on, and the mighty orb shows
yet no signs of exhaustion. Some how
or other its waste has been repaired, and
its store of force replenished. If the
sun were merely body which radiated
heat during the process of cooling, its
temperature would be lowered about
$1,000 deg. Fair. in 5000 years At
this rate our climate would probably
have undergone considerable change
since the building of the Pyramids. A
crust would soon form over the surface
of the sun, and radiation would cease
If the heat were due TO combustion, and
the sun were a solid block of coal,
in about 5000 years it would be entirely
consumed And if, as has been sug-
gested, the solar heat were due to the
friction of the sun against some resist
ing medium as it revolved upon its axis,
its entire motive power would be used
up in little less than two centuries.
We must look yet farther for our source
of energy And, though we may never
solve the vast problem, the speculations
will hardly be useless. Even failure in
such work is beneficial, since it teaches
the mind more fully the limits of its
powers. But repeated failures need
not make us despair of attaiGng to some
measure of success in the end.


Two prominent theories of the suns
heat are now before the scientific world
The first of these is due to DIR. Julius
Robert Mayer, a physician of Heilbroun,
who published in 1S4S his famous essay
upon Celestial Dynamics. Calling
attention to the great numbers of me-
teors which flash through our sky, he
suggested that these, or bodies like
them, might furnish the sun with its
heat. He knew that motion, suddenly
arrested, was converted into heat. When
cannon ball strikes a target, it becomes
heated. A weight, falling to the ground,
underOOes a rise of temDerature By n