Year: 1874




with that coming from the great dis
tance of the sun. But although inn
possible to measure its intensity it is
not so with its quantity, as emitted
in given time the standard is the
quantity of heat required TO heat one
pound of water one degree or to melt
pound of ice. Sir John Herschell
and NJ PouilIet showed that if the
SUMS surface could be covered with
al envelope Of ice forty feet thick it
would melt in a minute Herschell
also said that if a cylinder of ice
10000 miles in diameter could be
darted at the sun it would me as fast
as it came. Many opinions have
been held as to the scource of this
tremendous temperature as to whether
or not it was gradually growing less.
There is no evidence in regard to the
latter question, but, if falling off at
all, it is imperoepible, the same vege>
tation growing now on the earth it
grew 1000 years ago; and geology
shows that though the world has at
times been hotter than it now is, yet
it has also been colder. AS to the
scource of its heat. all is yet con-
lecture; it can hardly be chemical
combination, for a ball of coal as big
as the sun would burn out in 5000
years; the heat is also held to be
from meteors impinging on the body,
and doubtless this has its effect, yet
it seems probable that the true cause
is the gradual contraction Of its mass,
sice a contraction Of t20 feet Of its
radius per year would account for all
the heat given off. Touching the
physical appearance and condition Of
the sun, it is a great mass of gas, on
the outer portions of which there
are metallic vap0rs ever Condensing
and forming clouds. It's appearace
warrants this assertion; its granula-
tions, facula. and spots all cary out
the belief. The spots rotate with
the sun, which performs It's axial
rotation at the equator once in about
twenty-five days, although when great
numbers oe them are IN process of
formations they seem to leap forward,
d fact readily explained on the sup
position that they are motions of
mobile gases. These spOts-many
illustrations Of which were here cast
upon the screen-have 4 dark centre
or nucleus, and are generally de-
pressed towards this centre below the
8 rfacc; this fact is certain, although
It does not justify the belief that they
are holes in tie cnrOm0sphere throgh
which the sun itself can be seen.
They change in form far more swiftly
as do clouds on summers day, show
ing beyond peradventure that they
are not composed Of dense matter
which could not be subject to such
viciSsitudes sometimes they change
at the rate of 1000 miles an hour.
Spots are not alike numerous on all
parts of the solar surface; they are
not common at the equator, but are
seen mostly in what might be called
the temperate zones. NCr are they
equally frequent in different years;
first there will b, numbers of them ;
then for about three years they will
diminish again to reach their maxi>
mum at ten years from their first ap
pearance. De la Rue and Darlington
thought that their frequency depends
on certain positions of the planets
Mars. Jupiter, and Venus, but this
neds cOnfrmations, and it is probable
tLat they are only period cal boillngs-
over from below As to their nature,
Father Secchi and French physicists
have thought they we're mere cavities
though which gas was blown upwards {,
attended consequently by draughts
inward, buc spectroscOpic examlna-
lion shows no evolution from the
centre while it does from the edges.
Zollner believed them to be made by
the throwing up of Stag; and as to
whether they are caused by an iurush
or an outrush it is not now possible
to say. Mr.. Lockyer being inclined, a
few years ago, to accept the latter
explanation. During a total eclipse
of the sun the dark body of the moon
is seen to be surrounded by halo,
the nature and origin of which have
long been discussed, as to whether it
was caused by the suns atmosphere
or a thin atmosphere of the earth eX-
tending to the moon and suddenly
made visible by the solar rays Strik-
ing through it. the latter being the
belief entertained by Professor Airy.
During the eclipse of 1869, Professor
WinlOck's observations showed that it
was of solar Origin since its spectrum
presented bright lines. In 1870
photographs of the sun in eclipse
taken in Spain and Sicily SO fully
conceded with each other and es-
tablished the solar origin of the
phenomena, which was so character
lied by the photographs of Lord
Lindsay in India during the succeed
ing year, that even Mr.. Lockyer,
formerly Of different opinion, ac>
cepted the matter as settled. The
material of the corona is not known.
Mr.. Proctor thought it meteOrs seca
falling into the sun, but its spectrum
shows it to be partly of hydrogen and
some unknown substance giving
green light in the spectrum. 1t may
be matter similar to that illuminated
in the aurora bOrealis. as it has at
least one line like that given by the
aurora. Solar prOminences were
noticed first in 1872. and in 1860
Father Secchi showed them to belong
to the sun. They are of hydrogen
and part of the chromosphere DART
ing outwards sometimes 100000
miles. They are of course, intensely
hot, but they do not burn, since they
do not unite with oxygen. Dir. Proc