The herald and mail. [volume] (Columbia, Tenn.) 1873-188?, 1874-11-27
TRANsIFs OF VENUS.
Their ImpOrtaMce-The Great Asaronona-
Ical Event of the Century.

1
A large portion of the astronomical
world has for two years been busy with
preparations to, observe one of the
rarest of celestial phenomena. When
Venus last passed over the face of the
sun the infants Napoleon and Yelling
ton were sleeping in the arms of their
nurses, all unconscious of the parts
they were TO play in the world history
| Washington, loyal subject of King
George, lived quietly on his Virginia
plantation; and American independence
was dream Of few enthusiasts. Now,
after the lapse of more than century,
the present generation is to witness two
occurrences of the phenomenon, the one
during the present year. and the other
eight years later. Then the rest of the
nineteenth century and the whole of
the twentieth are to pass away without
its again being seen. Finally, on June
8, 1904, our posterity vill have an op-
portunity of again observing il.
We know from our astronomical Ia
bles that this phenomenon has required
in its regular cycle four times every 243
years for many centuries past. But it
has been only in times comparatively
recent that it could be predicted and
observed. In the years 1918 and 1926
the idea of looking for such a thing
does not seem to have occurred to any
one. The following century gave birth
to Kepler, who SO far improved the
planetary tables as to predict that a
transit would occur on December 6,
1851. But it did not commence until
after sunset in Europe, and was over
before sunrise next morning, so that it
passed entii ely unObserved. Unfortu-
nately the tables were so far from accu-
rate that they failed to indicate the tran
sit which occurred eight years later, and
led Kepler to announce that the phe-
nomenom would not recur till 1761.
The transit of 1889 would, therefore,
like all former ones, have passed en-
tirely unobserved had it not been for
the talent and enthusiasm of young
Englishman. jeremiah Horrox was
then young curate of eighteen, resid-
ing in the north of England, but who,
even at that early age, was master of
the astronomy of his times. Compar-
ing different tables with his own obser-
vations of Venus, he found that tran
sit might be expected to occur on De-
cember 4, and prepared to observe it af-
ter the fashion then in vogue, by letting
the image of the sun passing through
his telescope fall on a screen behind it.
Unfortunately the day was Sunday, and
his clerical duties prevented his seeing
the ingress of the planet upon the solar
disk-a circumstance which science has
mourned for a century past, and will
have reason to mourn for century to
come. When he returned from church
he was overioyed to see the planet upon
the face of the sun, but after following
it half an hour the approach of sun
set compelled him to suspend observing.
During the interval between this and
the next transit, which occurred in 1851, !
exact astronomy made enormous strides,
through the discovery of the law of |
gravitation and the application of the |
telescope to celestial measurement. A
great additional interest was lent to the |
by Hailey's discovery that |
observations of it made in distant por-
tions of the earth could be used to de-
termine the distance of the sun-an |
element of which scarcely any thing |
ancient observations of eclipses it had |
been concluded by Ptolemy that the
distance of the sun was about l 100 !
semi diameters, and this value was
adopted with few notifications for
more thon thousand years. When the
telescope enabled more accurate obser-
vations to be made, it was found that |
this estimate must be far too small and |
from observations on Mars in 1872 Cas-
SIM concluded that the solar parallax
was between nine and ten seconds, and |
consequently that the sun must be dis
tant more than 10000 semi diameters
of the earth. But this result was nee
very uncertain, and, with the
means then known, the only feasible
way of attaining certainty seemed to be
to adopt Halley's plan of observing
Venus. -H0rDer's.