Evening star. [volume] (Washington, D.C.) 1854-1972, 1878-05-06
The Transit Of Mercury.

An InTEhEsTlNG ASTRONOMICAL EVENT.
The planet Mercury is passing between the
earth and the sun to-day from the east to the
west. The transit began at four minutes past
10 this morning, and will be completed at 54
this afternoon. These transits of Mercury
occur at intervals of three, seven and ten years,
the last one being in 1868, and the one before
in 1861. The next one will occur i'm 1881. There
is regularity in the intervals between each,
but none in the tranSitS themselves. The tran
sit today or the 'transit of 1875" as it will be
known in the future furnishes exceptional
advantages for astronomical observations, the
passage OF the planet between the earth and
the sun occupying, as before stated. the time
from l0:C4 In the morning until 5:34 i'm the af-
ternOon, being the longest period of time so
occupied in hundred years. The time usual
hands
AT THE NATIONAL OBSERVATORY
IN this city are busy day making observa-
tnSHSr lions irGm which to deduee calculations Pro-
Professor Hall is experimenting the taking
or photographs of the passing planet as
1t appears on the surface Of the sun. These
Photographs are produced by means of the
horizontal telescope and reflector.
OTHER OBSERVATIONS ARE BEING MADE
elsewhere, under the auspices of the ObServa-
tin, Texas: Observer Paul is at Hanover, N.
d. ! while Mr.. Pritchard is at the Georgetown
college observatory: Observations are also
being made by the different colleges and by
private establishments throughout the coun-
try, who will report the result to the Observa-
tory here. Having plenty of time, excellent
weather, and more than enough people at
work, the observations are expected to be i'm
every way complete.
1T IS EXPECTED
by t0-day'S labor to ascertain definitely the
the sun and earth, the exact diameter of Mer-
curry which is not now wellknOwn, and the
motion OF Mercury in its orbit around the sum-
The suppositiOn that the calculation of the
in I.nts,, ,folx,
the distance from the earth to the sun is errO-
neOus: What it is expected to ascertain today
viii, 1t is thought, also decide the correctness
or lncOrrectneSS of
LIE vERRIERs THEORY,
that there is another planet between Mercury
and the sun. In one of his calculations that
astronomer concluded that there We're certain
irregularities in the motion of Mercury
which he supposed to have been due to the
presence of some other disturbing body inter
yening between it and the sun. Onceit was
thought that his SuppOSitOn had been verified
and this disturbing body was called Vulcan
Subsequently LIE Verrier thought he might be
mistaken, and inclined somewhat to the Opin-
ion OF other astronomers that mistake in his
hgureS had caused what he had ascribed to
lrreeularltles in Mercury's motion. He never,
however, wholly abandoned his idea that there
is an Intervening planet. This theory will be
verIhed or dlSproved by tO-day,s observation,
and the result is one of great interest to the
astronomical world.
GLIMPsEs OF THE PLANET
AS Mercury crossed the eastern edge of
the sun this morning, it was plainly visible
through the telescope. AS it passes beyond the
sun to the west it can also be seen, but not so
distinctly Between the two points a telescope,
even small one, or a strong pair OF opera
glasses. enable the curious ones to catch a
glimpse of the planet. Through the instru-
ments at the observatory, it looked like
small round black Speck little larger than a
ten cent piece on the bright surface of the sun
The photographs taken of the sun and Mercury
III their various positions, will add greatly to
the value of tO-dayS work.