Evening star. [volume] (Washington, D.C.) 1854-1972, 1900-11-03
Achievements Of Astronomy in the
Nineteenth Century.
LITTLE SHORT OF MARVELLOUS
Important Results of Observation
and Calculation.
DISCO VERIES


Holden, formerly director of Lick Observatory,
California.
The achievements of astronomy during
the nineteenth century have been little
short of marvellous. Not only have the
classic methods of research been expanded
and developed, but in the latter half of the
century new instruments of unexpected
power have been perfected and results OBJ
tanned by their use in fields utterly closed
to the astronomers of hundred years ago.
Mathematical analysis reached a high
state Of perfection in the researches of La
place and Lagrange at the century's begin
ming; the labors Of profound analysts like
Gauss. Adams, LIE Verrier, Gylden. Hill,
Newcomb and many others have placed
mathematical astronomy on an entirely
new footing
1t is impossible in a popular paper to
give any account Of the triumphs Of mathe-
maticians. 1t must suffice to say that the
advances in the theory of the motions OF
the heavenly bodies are as important and
far reaching as the results obtained by the
spectroscope, the photometer and the pho
tographic plate. One signal result stands
out as brilliant type Of the power Of anal
ySis.
Discovery of Neptune.
The planet Neptune was discovered with
the telescope in 1916 in consequence Of la
borious calculations by LIE Verrier (and
Adams) upon the materials of the planet
Uranus. Uranus had been discovered by
chance by Sir William Herschel in 1881.
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 it's orbit.
Calculations of the perturbing forces ex-
erted by the other known major planets
Saturn-showed that it's course in space
would be along a certain line If these plan
cts, 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
at yet unknown. Sir John Herschel wrote
of the new planet a few weeks before its
discovery in memorable words: I'VE see it
Columbus saw America from the shores
Of Spain. Its movements have been felt
trembling along the far-reaching line of our
analysis with certainty hardly inferior to
ocular demonstration" The extraordinarily
complex problem of inverse perturbations
was worked out by LIE Verrier and by
Adams and the place where the new planet
would be found foretold When the tel
escope was directed to the predicted place
the unknown planet was there; the mathe-
matician, in his study, had directed the OBJ
servers telescope Other achievements of
the same order of merit, though far less
striking, have distinguished the present
century.
Instrument Making Perfected.
In the mathematical processes relating to
spherical and to 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
ments Of observation and calculation; and
the principles of instrument making have
been carried we'll 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 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 aperture,
then the largest of its kind in the world
An instrument of equal power is now at
tached alongside the thirty-six-inch tele-
scope of the Lick observatory to serve as
mere fnder-like the sights of a rifle
to direct the giant tube Of the main in
stlUment.
Rejecting telescopes. too. have been
much improved, though not greatly in
creased in size, since the days Of the elder
Herschel Well-equipped observatories are
now scattered all over the EARTH The
heavens are assiduously watched by pro-
fessionals and by amateurs in all the length
and breadth of the globe, and no change Of
importance can take place without being de-
tected-perhaps by photography-and re-
ported by the electric telegraph to every
interested watcher in all the continents
Results in Photography.
The advent of photography as the hand
maid Of astronomy marks distinct advance
in the processes Of observation. The sensi-
tive plate partially records all rays of light
that fall upon its surface. Such a plate d.
rected at the heavens shows thousands upon
thousands Of stars. each registered in its
proper position and of its proper bright
ness A second plate taken upon succeed
ing night records all changes. either of po-
that new minor planets are discovered (by
their change of position), new variable
stars detected (by their change Of bril-
liancy). Maps of the whole sky are now
made by photography and they record mil
lions upon millions of stars. The inventory
of the stellar universe will soon be COM
pleted, a magnificent gift of this century to
the next.
Photography has proved to be of i'm
mense Importance in the study of the
moon. A satisfactory picture Of the full
neon can be made In less than a second
of time which will show more than is con-
tanned in the best lunar maps that re-
quired a lifetime to 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 is depicted by means of photography
with extraordinary faithfulness, the work
of years of observation being compressed
into hours. Up to this time little success
has been attained, however, in the study
of planetary features by photography, and
the old methods Of telescope examination
and pictorial representation by drawing
are still employed 1t is partly for this
reason that so much remained doubtful