The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1870-03-05
Measuring Star-Heat.


Last year the scientific world hailed with
interest the discovery that heat comes to us
from beyond the infinite depths which sepa-
rate our earth from the fixed stars bringing
us message not less full of interest than
that conveyed by the stellar hght-rays. 1t
seemed wonderful indeed that any contrivance
man could devise should enable him to rem
der sensible the heat sent forth on all sides
! from those distant suns. We know that at
midday the summer sun pours his beams so
! fercely on the earth that we compare their
! heat with that of a fire near at hand. But
we recognize the fact that even within the
known bounds of the solar system
the sensible heat his direct rays can
produce is diminished more than thou
sandfold. And knowing this, it seems
as though the physicist in Neptune-suppos-
ing that arctic world to be the abode of rea-
soniag creatures-would have problem of
some difficulty on the measurement of the
warmth received from the tiny sun which
rules the Neptunian day. But the distance
which separates Neptune from the central
luminary of the planetary scheme sinks into
utter nothingness beside the vast gap which
lies between that scheme and the nearest of
the fixed stars. Seven thousand times farther
from the sun than Neptune stands the ad-
vanced guard of the stellar host, the famous
star which marks the raised fore-foot of the
Centaur. Light and heat from beyond that
enormous distance are reduced fifty million
times more than the solar light and heat which
she'd their faint rays over the Neptunian ice
fields.
Strange, indeed, and difficult was the prob
lem which had thus been mastered. And yet
the lesson taught us was one which, in another
form, we had already learned. We had been
able, by the aid of a new and wonderful in
strument-the spectroscope-to assure our
selves that the stars are suns in all essential
respects resembling our own. We know that
around them hang suspended the vapors of
metals which only the fiercest heat can melt,
for we saw that the light which came to us
from them had been robbed of the waves
which those metallic vapors alone have the
power of selectively absorbing.
But now new and more difficult task has
been achieved. Astronomy has not been con
tent with the discovery that the stellar heal
can be felt, but has faced the more -arduous
problem of measuring that heat. Worthy of the
task has been the instrument with which it
has been undertaken. The great equatorial
of the Greenwich Observatory is perhaps
surpassed by no telescope in the world as
regards the optical qualities which the astro
nomer delights in. Constructed by the same
eminent opticians who made both the famous
Poulkova refractor and the telescope which
has done such distinguished service in the
cause of science at Cambridge, United States
. and not inferior to either of those tele
scopes either in size or quality, thi
splendid instrument has been mounted
in a manner which does infinite credit to the
mechanical ingenuity of our Astronomer
Royal. corps of observers and mathema
ticiaGs unsurpassed perhaps in the world gar
risons the noble observatory in which it il
placed. With a liberality which cannot be
too highly praised (and which might with ad-
vantage perhaps be extended more widely
!, Government has taken care that the CHIEF
national observatory shall so be provided for
in all respects, as worthily to support th'
! national reputation. Future ages will doubt
less record long list of physical researches
in which the powers of the noble equatoria
of our nobly furnished observatory shal
have been employed by the skilful and pra c
tised astronomers now gathered at Greenwich
Its first great achievement in this specia
J direction is one of which our country ma
we'll be proud. Many months since, MI
Stone, +. II. S., the chief assistant at Green
wicb, and already known to fame for his suC
y cessful attacks upon the problem of the sun
distance, turned his thoughts towards til
application of the powers of the great equf
toral to the determination of stellar hea
II The results he then attained, though highl
interesting, did not become widely knowI
Mr.. Higgins having anticipated their publ
cation by communicating to the Royal Societ
his own successful treatment of the san
problem. But, as we have said, it was IL
simple fact that we do receive heat from ii
stars, not quantitative estimate of the
heating powers which was then laid befo