Evening star. [volume] (Washington, D.C.) 1854-1972, 1890-03-22
A SLAVE TRADE IN THE HEAVENS.
Some wonderful Facts Regarding
Comets-Prok. Searle's Lecture.

Prof. George n. Searls lectured ct the
Catholic university yesterday afternoon on the
movements and physical appearance Of comets.
He began by saying that the movements OF
comets, 20 far from being erratc, O. IL COM
monty supposed, ere perfectly definite, and
their orbits are more easily calculated than
those of the planets. The only reason why
they do not become members Of our solar
system is simply that they usually travel in a
curve called parabola, which Is an infinite
curve in its own nature and never returns into
ITSELF Comets In general are supposed TO drop
from space into the solar system, and, after
passing around the sun, to leave IL never to re-
turn. There are some comets, however, which
are permanent members OF the solar system
and are periodic. These are supposed to have
been brought into the system BY the disturb
ing action Of one or more of the great planets
as they were entering or attempting to leave.
An account was given Of the remarkable
comet OF Lexell, which was made a member Of
our system in 1857 by Jupiter as it was enter
ing, probably for the first time. It passed hear
the earth In ITO and made one complete revolu-
ton around the sun; then, a. it passed near
Jupiter again, in l779, it was caught by its in
fusnce and thrown into different orbit. What
that orbit was was not known until last year, in
which the wanderer was again picked up and
found TO have probably been thrown into a
twenfy-six-year period by Jupiter in 1779, and
again meeting 1t in 1886 to have changed its
period to one Of eight years. In that orbit it
is now travelling, but probably will underg
some further change from its next meeting
with Jupiter in 1928.
He went on to describe Donati's comet of
1883, the specimen comet of this century, as
far as regular development was concerned and
one OF the most beautiful that have been seen,
as many who are now living will remember.
Views OF this comet were given in various
stages OF its development as it appears to the
naked eye, and also as the head appears in the
telescope. In the views Of the latter the
formation Of the envelopes and Of the tail was
shown.
The question of the physical constitution Of
comets, as shown BY the spectroscope, was then
brought up. and illustrated by views. The
gone, shows principally in comets gas similar
to our Illuminating gas. When they approach
near the sun and are subjected to great heat
the spectrum lines of some metals appear,
principally sodium and magnesium and pos
sibly iron. Views and descriptions were also
given OF the wonderful comet of 1882, probably
the most extraordinary that has appeared in
modern times The lecturer concluded with
an allusion to the connection of comets with
meteor streams
The next lecture of the public astronomical
course will be given on the 18th of April.
There will be no public lectures at the Catholic
university during the next three weeks. and
those announced for the coming week will be
postponed until Wednesday, April l5 and the
Friday following. This change in the an
nouncements Is necessitated by the devotion Of
holy week and the Easter vacation.