The semi-weekly messenger. [volume] (Wilmington, N.C.) 1897-1908, 1901-07-05
COMET.
u In Expected to Return In seDteA-
Der of the Present Year.

Der OF the Present Year.
Among the periodic comets due in 1901
is Encke's comet, which is expected to
return to ~perihelion about the middle of
September. Its last return to perihelion
took place on May "a, 1898, the same day
on which il also occurred at the first pre-
dicted return in 1922. The prediction
was made by Johann Franz Encke, after
whom the comet has been named, and he
detected the periodicity OF the comet in
1919.
The comet had been frequently observ-
ed during the preceding so years, and as
soon as the elements Of its orbit had been
computed and compared with the eie-
ments Of the orbits of comets which had
previously appeared il was found to be
the same comet which had been observed
in 1855. 1795 and 1905. Having thus
identified the comet at four different re-
turns to perihelion, Encke was enabled to
ascertain the period Of its revolution
with great precision. the result being 3h
years, the comet having the shortest
known time of revolution and being the
first of the short period comets.
Encke predicted its return for 1922,
making due allowance for planetary per-
turbations, and on account Of it's posi-
ton in the heavens he announced that the
comet would only be visible in the south
ern heavens. The return of the comet
was therefore looked for by astronomers
living in that part of the world and dur
ing the month Of June was sighted by
O watcher at Paramatta, in New South
Wales. The next return was predicted
to take place in 1925, and on the 18th of
July. true to its appointed time, the
nnynn - r-nz nhonr-a1 h- VAL - N:.-z-
The next return took place in 1923,
when it was first seen by Strive at Dor
pat, in Russia, ON Oct. ID of that year,
and remained under observation at the
European observatories until Dec. 25.
On Nov. Z, 1928, Professor Strive made
q series OF observations of the comet, and
he noticed a star of the eleventh magni-
tude SO near the center of brightness in
the comet that he mistook it at first for
the nucleus. The brightness of the star
was not in the least percsptible degree
diminished by the mass of cometary mat
ter through which Its light had passed.
By Nov. 80 the comet had greatly in
creased in brightness, and this must be
ascribed to the contraction and conse-
quent condensation Of the nebulous mat
ter Of which it i composed as it receded
from the sun.
In 1882 the comet again returned to its
perihelion, but, being ~unfavorably stu
ated for observation, it was only seen by
Harding at Gottingen on Aug. 81. How
ever, it was observed by Henderson at
the Cape of Good Hope during the entire
month of June and was also seen at Bue-
nos Ayres. In 1885 it was observed from
July ~ till Aug. 6, and in 1888 it was
seen at Breslau on Aug. IA as a very
faint. i'll defined object. 1t subsequently
increased in brilliancy and continued yisi-
BILE until the middle of December.
In combining all the observations which
had been made from 1856 to 1888 inclu-
sive, Encke found that the period of revo-
luton of the comet was regularly dimin-
ishing by about 212 hours at each return
to perihelion.
This effect he attributed to the retard-
ing action of a C~esisting medium in space.
This theory seemed to be confirmed by
observations made at the return of the
comet in 1912, 1S4S. 1852, 1855. 1853.
1862 and up to 1868, but at it's return in
1868 the acceleration had fallen to one
half its customary and until then constant
value. The change has proved perma-
nent. and accumulated facts bid fair to
Danish the theory of a resisting medium"
out of existence.
The comet has been seen at every re-
turn to perihelion lately. the dates of its
visits being 1895, 1898. and it is now look
ed for in 1901. 1t has been described as
irregular in form and 'lumpy" in appear
ance, seldom showing a well defined nu-
cleus. Under very favorable circum-
stances it can be seen with the unaided
eye. but is usually visible only in the tele-
scope. 1t does not exhibit much in the
way Of jets and envelopes, and the train.
when visible, is but a degree or two in
length.-M. Proctor in Scientific Ameri-
can.