Year: 1865

Prof. E. L. YoumuDs, 10 his eSsays
recently published, indulges in the fol.
lowing curious speculstions:


Another essential question a, regards
the future Of our planetary system bus
reference to its future temperature and
Illumination: AS the internal heat Of
the earth has butlittle influence on the
temperature Of the surface, the heat Of
tho sun is the only thing which essen.
TALLY affects tho question. The quantity
Of heat falling. from, the sun during u
given time upon a given portion OF the
earth's surface may be measured, md
from this it can be calculated how much
heat in given time is sent out from the
entire sun. Such measurements have
been made by the French physicist
Pouilles, aud it has been found that the
sun gives out a quantity Of heat per
hour equal to which layer Of the den
sest coal ton feet thick would give out
by its combustion; md hence in year
a quantity equal to the combustion Of
layer Of seventeen miles. If this heat
were drawn uniformly from the entire
mass Of the suu, its temperature would
only be diminished thereby one and one
third Of a degree centigrade per year,
assuming it's capacity for heat to be equal
to that Of water. These results can give
US an idea of the magnitude of the
emission, in relation to the surface aud
mass Of the sun; but they cannot in-
form us whether the sun radiates heat
as a glowing body which since its for.
nation has its heat accumulated within
it, or whether n new generation OF heat
BY chemical processes takes place at the
suns 8 surface. At all events, the law Of
the conversation Of force teaches US that
no process analogous to those known ut
the surfacc Of the earth, eau supply for
eternity an inexhaustible amount Of heat
and light to the SUI. But the same law
alBo teaches that the store Of force q;
present existing, us heat, or as what may
become heat, is sufficient for an immeas'
urable time. With regard 10 the store
Of chemical force in the sun, We can
form no conjecture, and the store of heat
there existing can only be determined
by very uncertain cS,imations. II, how
ever, We adopt the very probable view.
tha, The remarkably small density Of 50
large body is caused by its high tenn
pcrature, and may become greater in
time, it may be calculated that if the
diameter Of tho sun were diminished
only the ten. thousandth part Of its
present length, by this act a sufficient
quantity of heat would be generated to
cover the total emission for 2,l00 years.
Such small change, besides, i, would
be difficult to dclect even by the finest
astronomical observations.


Indeed, from the commencement Of
the period during which VIC possess his.
toric accounts, that is, for period Of
about 1000 years, the temperature Of
the earth has not sensibly diminished.
From these old ages we have certainly
no thermometric observations, but we
have information regarding the distribu-
ton Of certain cultivated plants, the
vine, tho olive tree, which are very sen.
si.ive to the changes of the mean annual
temperature, and We find that these
plants at the present moment have the
same limits Of distribution that they
had in the times Of Abraham and Flo.
mer, from which We may infer backwards
the constaucy Of the climate.