The herald and mail. [volume] (Columbia, Tenn.) 1873-188?, 1875-07-02
Reflnements in Modern Astronomical
Observations.

The tools used by the modern astrono-
mer are clocks to measure time, gradu-
ated circles to measure degrees and
their subdivisions, telescopes to mag
nifty distant objects, Photographic ap-
paratus to make permanent records of
ephemeral phenomena, photometers to
measure the comparative intensity of
light, polariscopes to reveal the nature
of certain luminous rays, and spectre
scopes to reveal the chemical compost
ton of the heavenly bodies.
The invention of the clock is of great
antiquity; but it is to the wants of
modern astronomy and other sciences
to which it is applied navigation, for
instance) that the perfection with which
they are now made is due. So with the
graduated circles, which are applied to
quadrants, sextants, octants, and as
trolabes.
The telescope, invented by Jansen in
Holland. about 1909. was successfully
improved by Gallileo, Herschel, Dol
lond, Fraunhofer, and others, while
lately Lord Rose and our own Alvan
Clark have surpassed all former efforts.
But who can say what improvements the
future has in store for the telescope,
especially as liberal monetary compen-
sation has become a stimulus to the
ablest opticians, and the making of
million dollar instruments has been
discussed?
Photography is now largely used in
astronomy, and the work done by it
during the recent transit of Venus. in
different parts of the earth, has enrich
ed astronomical science with records of
the highest value and permanency.
One amateur astronomer, Mr.. Ruther-
ford of New York city, has for several
years past applied this science to max
ing records of the position of the stars,
so as ultimately to obtain knowledge of
their distance from us, and their mo-
tions in space and in connection with
this branch of the subject, he has in
vented instruments of measurement, to
be applied to the Photographic impress
sions, which have already given results
superior in precision to the measurment
by direct observation of the stars re-
presented.
Photometric observations on heavenly
bodies, comparing their relative lumin-
osity and determining changes in the
nature or distance, have been brought
to a high degree of perfection. espe-
cially by Zollner, who3used for this pur-
pose the following apparatus The
polariscope, an ingenious tool invented
by Malus in France in 1903. is based
on certain peculiar properties of re-
fected light, by which it may be ascer-
tanned what light or portions of light
belonged to a luminous body itself and
which are borrowed from other sources;
while it also shows the direction
whence the borrowed light arrived be-
fore it was reflected by the body under
investigation. Zollner applied to this
instrument several ingenious devices,
making it the most perfect measures of
the intensity of light, and has thus
founded a new branch of astronomical
research, called astrO photometry.
The spectroscOpe, based on dis
covery made in 1890 by Fraunhofer, and
in 1910 by John W. Draper of New
York city, is the invention of Bunsen in
Germany, and, next to the telescope, is
the greatest gift astronomy has ever re-
ceived. BY mems of this instrument,
Secchi, in Rome, has so successfully
investigated the light of the stars that
he has classified them by their tempera-
lures, which may be distinguished by
the number of dark lines or bands in
their spectra the hottest stars show
the least number, the next class Ito
which our sun belongs showing a great
er number, and the third class having
so many dark lines, Obscuring portions
of their spectra, that peculiar color
prevails in them; while fourth class.
of a still lower temperature, are still
more obscure. Next come the dark
globes, so cool that they have no light
of their own, and cannot be seen except
when they are so near to a luminous
star as to shine by reflected light. This
is the case with most of our planets, as
well as with we do not know how many,
perhaps much larger, darker bodies,
floating in the infnity of space, and tC
which the disappearance and reappear-
ance or changes in luminosity of some
stars are ascribed, these phenomena
taking place when their light is inter
cepted by an intervening dark body.
Secchi has just published some of his
recent observations on Coggia's comet.
He combined the spectroscope and pO-
lariscope with his telescope the spec
troscOpe showed that there we're two
spectra, one continuous, and the other
consisting OF luminous bands, agreeing
with those of oxide of carbon; while
the polariscope showed that the latter
spectrum was original light, while the
continuous spectrum was reflected light,
also showing that the latter came from
the direction of the sun consequently
that the continuous spectrum was re-
fected sunlight. He proved thus that
this comet shone not only with reflected
sunlight, but by its own light also,
thereby revealing the nature of it's orig
inal luminosity. This is an instance of
the highest degree of refinement as yet
obtained in modern astronomical re-
search.