Year: 1869




1t would scarcely be thought by
most persons says our contemporary
that the stars supply the earth with
an appreciable amount of heat. Even
on the darkest and elearest night,
when the whole heavens seem lit up
! by a multitude of sparkling Orbs, the
idea OF heat is not suggested by their
splendOr. twill, therefore, seem sur
prising to many that men of science
should assign no ineOnsiderable pOr-
ton of our terrestrial heat suppIy to
those distant twinkling lamps. it is
not many years since Professor Hon
kins, of Cambridge, went even farther,
and expressed his belief that if the
earth's atmosphere were but increased
some 1900 yards in height, so as to
have an increased power of retaining
the warmth poured upon it from outer
space, we might do without the sun
altogether so far as heat supply is con-
eerned. As a glass-hOuse collects the
suns heat and renders it available
during the time that the sun is below
the horizon, so we held that the addi-
tiOnal layer of air would serve to gar
ner the warmth'Of the stars in quanti-
AAE1 0AAAANAGAAD AOL ali Va OAL IG4uAAC-
ments. But until lately all these views,
however plausible they might have
seemed, had not been founded upon
facts actually observed. 1t has been
reserved for these days in which dis
coveries of the most unexpected kind
are daily rewarding the labors Of our
physicists to see that established as a
certainty which had before been foun-
ded merely upon considerations of
probability. Mr.. Higgins, the phys
icist and astronomer, has Just publish
ed the results of a series of inquiries
addressed to the actual measurement
of the heat which we receive from the
leading brilliants of the nocturnal sky.
The instrument called the galvanOme-
ter, which has been made more or less
familiar to many of us by the re-
searches and lectures of Mr.. Tyndall,
was made use of by Mr.. Higgins in
these Investigations. The instrument
was fixed by Mr.. Higgins large re-
tractor, so that the image of star
formed by the eight-inch Object-glass
might fall upon the surface of the
thermOpile. 1t will give some token
of the care required in researches of
the sort TO mention that the apparatus
had to be left attached to the telescope
for hours, sometimes for days, until
the needle, whose motion marks the
action of heat, had come to perfect
rest. When the time came for making
anObseryatiOn, the shutterOf the dome
which covers the telescope was opened,
and the telescope was turned upon a
part of the sky near to some bright
star, but not actually under the star
Then the needle was watched to de-
termine whether the change of posi-
ton had produced any effect. If in
four or five minutes no signs of change
were shown, the telescope was moved
the small distance necessary to bring
the image of the star directly on the
face of the pole. Almost always the
needle began to move as soon as the
image of the star fell upon it. The
telescope was then moved slightly
away again from the star; the needle
was then seen to return to its place
In this way from twelve to twenty
observations would be made upon the
same star, so that no doubt might re-
main as TO the motion being really due
to the stars heat. In this way it was
found that the bright Arcturus moved
the needle three degrees in about a
quarter of an hour. So did Regulus,
the leading brilliant of Leo, the con-
stellation at present adorned by the
splendOr of ruddy Mars. POllux gave
a DETECTION Of one degree and half;
but, singularly enough, his twin broth
er Castor produced no effect at all upon
the needle. The splendid Sirius gave
q detection of only two degrees; but
as this star is always low down, and
so shines through greater proportion
of the denser atmospheric strata, it is
not surprising that its heat should not
be propOrtiOned to its brillianey.