The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1900-11-04
ADVANCE in ASTRONOMY
MARVELLOUS ACHIEVEMENTS DURING
THE CLOSING CENTURY.
PrfncfpI>. of Instrument Making Per-
fected-RcsuIts OF Spectroscoptc
Observation.


the nineteenth century have been little
short of marvellous Not only have the
classic methods OF research been expended
and developed. but in the latter half OF
the century new instruments OF unex-
pected power have been perfected and re-
suits obtained by their use In fields utterly
closed to the astronomers OF hundred
years ago.
Mathematical analysis reached high
state OF perfection in the researches Of
Iaplace and Lagrange at the century's be-
ginning; the labors OF profound analysts
like Gauss Adams, lie Verrier, Gylden,
Hill. Newcomb and many others, have
placed mathematical astronomy on an
entirely footing 1t Is impossible. in
popular paper, TO give any account Of the
triumphs of mathematicians. IL must suffice
90 say that the advances in the theory of
tic motions Of the heavenly bodies are as
important and far-reaching the results
obtained by the spectroscope, the photo
meter and the Photographic plate. One
signal result stands out as a brilliant type
OF the power Of analysis.
DISCOVERY OF NEPTUNE.
The planet Neptune was discovered with
the telescope in 1916 in consequence of
laborious calculations by lie Verrier (and
Adams) upon the materials OF the planet
Uranus. Uranus had been discovered by
chance, by Sir William Herschel in 1871. A
body OF unusual appearance was seen in
his telescope Examination showed that it
was a major planet revolving about the
sun in eighty-fOur years. Careful observa-
lions gave the shape and size Of its orbit.
Calculations OF the perturbing forces ex-
erted by the other known major planets
Mercury, Venus, the earth, Mars, Jupiter,
Saturn-showed that its course in space
would be along a certain line If these
planets, and only these. affected its motion.
Renewed observations showed very slight.
yet obvious deviations from the predicted
course. 1t occurred to several astronomers
to Arago, Bessel, Strive. lie Verrier,
Adams-that these deviations were pro-
duced by the attraction of a major planet
as yet unknown. Sir John Herschel wrote
OF the new planet a few weeks before its
discovery in memorable words: I'VE see it
as Columbus saw America from the shores
of Spain. Its movements have been felt
trembling along the far-reaching line of our
analysis with a certainty hardly inferior
20 ocular demonstration" The axtraordi-
narily complex problem of inverse pertur-
bations was worked out by lie Verrier and
by Adams and the place where the new
planet would be found was foretold. When
the telescope was directed to the predicted
place the unknown planet was there; the
mathematician, in his study, had directed
the observers telescope. other achieve
ments OF the same order Of merit, though
far less striking, have distinguished the
present century.
INSTRUMENT MAKING.
In the mathematical processes relating to
spherical and 10 practical astronomy also
this century has made its mark in history.
Bessel. Strive and their successors in Eu-
rope and in America have reconstructed
these branches of the science from the
foundations Every pupil in our colleges
Is now familiar with the highest refine
nents OF observation and calculation. and
the principles of instrument making have
been carried well nigh to perfection In
some departments the instruments fur
nished are so perfect that the outstanding
errors OF observation are due chiefly to
the human being who uses the apparatus,
not TO the apparatus itself. The distances
OF the sun and of many of the stars have
been fixed with exactness. Telescopes are
now made of great size and power. In 1924
Sir John Herschel became possessed of a
very good refractor of five inches aper-
ture. then the largest of its kind in the
world An instrument of equal power is
now attached alongside the thirty-six-inch
telescope of the Lick Observatory to serve
rs a mere finder-like the sight of a rifle
10 direct the giant tube of the main instru-
LlEaa az
much improved. though not greatly in
creased in size. since the days of the elder
HerscheI well-equipped observatories are
now scattered all over the earth. The
heavens are assiduously watched, by pro-
fessionaIs and by amateurs. in all the
length and breadth of the globe. and no
change of Importance can take place with
out being Neutrality-suspicious. by photogra-
phy-and reported by the electric telegraph
Co every interested watcher in all the con-
tinents
RESULTS IN PHOTOGRAPHY.
The advent of photography as the hand
maid OF astronomy marks a distinct ad-
vance in the processes of observation. The
sensitive plate partially records all rays of
light that fall upon its surface. Such a
plate directed at the heavens shows thou
sands upon thousands of stars, each reg
fstered In it's proper position and of its
proper brightness. second plate. taken
upon succeeding night. records all
changes, either OF position OF of brilliancy
It is In this way that new minor planets
are discovered, by their change OF posi-
ton; new variable stars detected. By their
change of brilliancy. Maps of the whole
sky are now made by photography, and
they record millions upon millions of stars
The inventory OF the stellar universe will
soon be completed, a magnificent gift of
this century 20 the next. Photography has
proved 10 be of immense importance in
the study Of the moon. a satisfactory pic
fure OF the full moon can be made in less
than second OF time which will show
more than is contained IN the best lunar
maps that required lifetime 10 construct
by the old methods. The study OF the
solar corona would have been impossible
without the Photographic plate.
The mysterious world OF the nebulae, too
s. depicted by means of photography with
extraordinary faithfulness, the work of
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