Phenix gazette. [volume] (Alexandria [D.C.]) 1825-1833, 1826-06-10
VOLCANIC APPEARANCE IN THE MOON.
en- Copta;n Henry Kater, ER.S.J

[ DY CuptsHU Jlc"J <A"'e',
On Sunday evening, the 4th OF February, !
observed luminous spot in the dark part OF
of the moon, which was inclined to ascribe to
the eruption of volcano.
The telescope used was an excellent Newto-
nian, OF ST inches aperture, with power OF "a.
The moon was exactly two days old, and the
evening so clear that was able TO discern the
general outlines in the dark part OF her disc
Her western azimuih was about 70 degrees, and
her altitude about 10 degrees. In this position,
at hours and 80 minutes, the volcano (esti-
mating by the eye> appeared distant from the
northern limb of the moon about l-l0th OF her
diameter. LIS appearance was that of a small
ue5ula. subtending an angle Of about three or
four seconds. Its brightness yer! variable; a
luminous point like small star Of the sixth or
seventh magnitude, would suddenly appear in
its centre, and as suddenly disappear, and these
changes would sometimes take place in the
course of few seconds. On the evening OF
the 5th, having an engagement which prevent
ed me from observing it myself, arranged the
telescope for two friends, who marked the
same phenomena as the night before, but in an
inferior degree, partly, perhaps, on consequence
of the evening not being SO favorable. On the
9th again observed it: it had certainly become
more feint, and the star-like appearance less
frequent. could see it very distinctly with a
power of 40: as the moon approached the horl-
ION, it was visible only at intervals, when tn.
star-like appearance took place. On the same
evening had the pleasure OF showing II 10 Mr..
Henry Browne, FRS. Iregret that had no
micrometer adapted to my telescope, but have
reason to believe he distance Of the volcano
from the edge Of the moon was about l-loth Of
her diameter; and the angle it formed this eve.
ming with the line Joining the cusps, was about
50 degrees. remarked near the edge Of the
moon, wel-known dark spot, from which the
volcano was distant, as nearly as could esti-
mate, three times its distance from the edge OF
the moon. In map Of the moon, published
by Dr. Kitchener, (Which is the best small map
with which am acquainted, there is noun
tain sufficiently near the situation Of the volca-
no, to authorize the supposition that they may
be Identical On the 18th, could still see the
Volcano, and the occasional star-like appear
ance, but do not think it was sufficiently per-
ceptible to have been discovered by person
ignorant Of its precise situation. l am inclin-
ed however, to think, that the di fliculty Of see
ing it is rather to be attributed to the increased
light of he moon, than 10 the diminished &C
ton of the volcano. The spot in which l OBJ
served the volcanic appearance is that named
Aristarchus. This spot was particularly exam
ined by Hevelius, who calls il Mons Porphorifes,
and who considers il 10 be volcanic. If his
drawings are to be relied upon, it has under
gone considerable change in its appearance
since his time. Sir William Herschell has re-.
corded in his Philosophical Transactions, an
observation Of three volcanoes which he per-
ceivcd in the moon, April 10th, 1887, at loh
som sidereal time. One of these. which he
said showed an actual eruption Of fire or lumi-
nous NATTER was dislan. from the northern
limb of the moon 3h. SIM. IS. the diameter OF
the burning part being not less ;han SIN. find
that this observation was made about nine o.
clock in the evening, when the moon was not
quite two days old; and from The situation Of
the spot described by Sir William Herschcll, l
have no doubt Of its being the same that have
noticed"