Year: 1872

q1,o nreseut state Of knowledge concerning the
SIM as modified by the progress Of physical research
during the last few years Is hero setforth with rc
narkable clearness of exposition and fecityo ol mus
tration Within the compass of brief essay gie"V
amouut of information is communicated, ana IN
manner which needs only an attentive perusal, even
without the discipline ola scientific training, ior Us
intelligent comprehension by the general reader,


According 70 the most advanced views OF nlouern
b,scs the Sun the central material force through
which vitality and power are diSPenSeu 10 tne
universe in the form of light ana neat ana
of the subtle mysterious influences whose
nqture and operation have not as yet Deeh
fully explored The winds the rivers, the
1avcs and currents of the ocean all driven and
moiutaiped by the Sun. The wonderful energy of
soon Is derived at secondhand from the treasures
of solar force that have been garnered in combusi-
be materials By the processes of vegetable and an
inal vitality the power of the Sun is stored away IN
ya1ious organic products, by the consumption OF
which alone our human life and activity are MAIN
taned We may recognize the transformation OF
solar energy in our mechanical actions, IN the mo-
tions of our limbs and the sound of our voices, ana
in the higher functions of thought and passion 90
long as the mind works through the medium Oh the
brain and uses the nerves and muscles as i'S ser
wants so long is il true that all energy ol 'nous"'
allintensty of feeling all vigor OF action OF "Aa
III.


Tho FIRST element to be taken into account, IN
determining our relations to the sun is its distance
from the Garth Without the knowledge of this, we
cannot verify its magnitude and weight, and tney
are essential to an accurate idea Of its physical con-
stitutiOn and modes of action. Less than twenty
Years ago there was an of more than three per
cent in the universally received computation OF the
SIMS distance. The number was then stated to be
about 90 millions of miles, but it is actually less than
o. This is the average distance, although the sun is
some three millions Of miles nearer on the first Of
January than oil the first of June. Still there is
large margin of possible error perhaps half million
Of miles one way the other. Hence astronomers
are looking forward with great interest to the tran
sits of yenUs in 1874 and 1882 as the means Of adding
TO the precision Of our knowledge on the subject


In stating the distance of the Sun as 92 millions Of
miles TO real notion is conveyed The number might
inst as well have been declared to be 90 billions. The
conception is too vast to be grasped by the human
intellect. An illustration may help TO comprehend
the fact. II railway had been established between
the earth and the Sun ON which the Pilgrim
Fathers had started at the time when they left
England and travelled at the rate of 40 miles an
hour they would not have arrived until 1883, a
period Of SG3 years upon the road. cannon ball,
moving with its greatest speed, could not make the
tourney to the sun in nine years. If sounds could
travel through the celestial spaces at the same rate
as in atmosphere, the report of a solar thunder
storm might reach US in little more than fourteen
years Yet across this illimtable chasm, the Sun
exercises his Influence and performs his service.
Every pulsation Of the solar surface is Instantly
responded to upon the earth.


Having determined the distance of the Sun we
find the magnitude by simple process. The diam
eter proves to be 100000 miles, about 100 times as
great as that Of the earth. If we represent the
earth by q bali two inches in diameter, the Sun, or
III the same scale, would be little more than Is feet
" through In bulk it would take than million
and quarter earths to make a globe of equal size
If the earth were placed at the center of the SUI
the moon would be so far within his surface thai
there would be within il for another moon al
most as far again from the earth.


The mass of the Sun, ia weight, is about 325, ,0OC
times much the earth. But it is $50 600 time
ac bulky it follows that bulk for bulk it is much
lighter than the EARTH that is to say, its density is
only about quarter that of the earth, and about
one and half times that of water. Hence the solar
gravity or the force which attracts bodies To the
surface of the Sun is nearly 2S times great as ter
restrial gravity weight let fall on the earth drops
about feet in the first second on the Sun would fall
$50 feet. The ponderous swing of the pendulum of
an astronomical clock would at the Sun become a
culver more rapid than the vibration of the most
delicate watch balance. A lady whose 1.-THE form
would here weigh hardly 100 pounds if earned to the
Sun would become as unwieldy as an elephant, or
rather would be crushed by her own weight. Her
airy head alone would weigh as much as a stout
man, nearly $50 pounds. 1t has been supposed that
the singular lightness of the solar substance and
the great power Of solar gravity may be reconcied
by considering the Sun a cloud of gaseous
matter This is the view of Secclii, and of the
French astronomer Faye. But the theory needs con-
frmation. 1t is rejected by many eminent astrOno-
mers. At present, indeed il must be admitted that
we lave precise knowledge of the condition
of the central of the SUM- than we have of that
Of the earth.


The intensity Of the Suns temperature may he de-
1uced from the most elementary principles of the
science of heat Many attempts have been made to
reduce il 10 an exact measures but although the ex-
periments are simple and uniform in their results
we can place little confidence in the numerical con-
illusions. But while the temperature of the Sun is
uncertain, the quantity of heat emitted can be de-
terDined with considerable accuracy. The methods
are various, but the principle is the They
all based upon the measurement of the elevation of
temperature produced in given quantity Of water
by the action Of a sunbeam Of known diameter in a
measured time. BY experiments of this kind at the
Cape Of Good Hope Sir John Herschel discovered
that the heat received by the surface Of the earth
from the Sun in the zenith would be sufficient TO
melt layer of ice one inch thick in about 9 hours
and ~ minutes. But as more heat falls upon the
earth than upon any other surface Of equal size at
the same distance it follows that if the Sun were
surrounded by complete shell Of ice having the
same diameter the eaTths orbitand one n ch thick
it would all be melted in the time. The same
result in substance has been arrived at by several
other observers.


In order to produce this effect by the burning of