18 25.1 
[ 241] 
SPIRIT OF PHILOSOPHICAL DISCOVERY, AND ‘OF THE 
VARIOUS SCIENTIFIC JOURNALS. 
» gargs Y-Moving Images of the Fired 
Stars, similar in effect to the well-known 
image of a firebrand, or other incalescent 
body, whirled rapidly round, or else moved 
quickly to and fro in the same line, have 
been exhibited and carefully examined by 
Dr. T: Forster: this he effected in the 
field of a telescope, causing either circular 
or rectilinear streaks of light to appear there- 
in, according as the object-end of the 
telescope was made to revolve rapidly in a 
small circle, or else vibrate backwards and 
forwards, by the action of mechanism ap- 
plied to the stand of the telescope, whilst 
observing therewith the stars, the moon, 
and the planets. 
The star Arcturus, the planets and the 
moon, were each found to afford continuous 
and uniform streaks of light; but the lu- 
Iinous images occasioned by several others 
of the larger fixed stars, under the same 
circumstances, instead of such streaks of 
light, uniform in colour throughout, con- 
sisted of separated portions or sectors of 
differently colowred light, arranged prismati- 
cally round the circle, when the telescope 
had a quick reyolving motion, or else along 
_astraight line, when the object end of the 
instrument reciprocated. 
In the circular image occasioned by the 
star Lyra, the blue colour was not only 
the most intense, but occupied a consider- 
ably larger sector than any others of the 
coloured sectors, which were red, yellow, 
green and indigo, in this succession :— 
Spica Virginius shewed nearly the same 
phenomena as Lyra, only the blue was 
still more preponderating ; 2 Cygni shewed 
a preponderance of indigo, with less yellow 
and blue; Betalgeus produced yellow, in- 
tense red, and green sectors; Sirius 
shewed much indigo violet, and portions 
of bright white light; Capella, much 
orange, red, green, and less of the more 
refrangible colours ; d/debaran, principally 
red, with some green, and very faint 
orange. 
In very rapid revolutions of the tele- 
scope, the circle appeared broken, and 
small sectors of darkness intervened be- 
tween the coloured sectors; which dark 
arts. were soon bordered, next the colours, 
y narrow sectors of rather intense white 
light, except in viewing Arcturus, when no 
separation of the circle of light, by inter- 
yening dark and light patches, could be pro- 
duced; and so, also, with Aldebaran and 
Betalyeus, the dark patches were but faixtly 
indicated. In concluding his account of 
these noyel and curious experiments in the 
Pil. Mag. No. 313, Dr. Foster asks, 
“ Does the fact, that Arcturus resembles 
the planets, in not affording the colours in 
any great degree, afford grounds for con- 
sidering him as the nearest of the fixed stars, 
Montuty Mac. No. 407. 
and that distance of the stars is one cause 
of the disposition of the light to be easily 
separated ?”” 
A Meteor, on? of the Satellitule of our 
planet, was observed by several persons, 
near London, on the evening of the 16th 
of November last, about seven o’clock, 
moving upwards from the eastern part of 
the horizon; it would seem from the ob- 
servations made in this instance, and from 
what has been inferred from numerous 
former observations on this class cf satel- 
litic bodies, that this satellitula’s course 
through the higher region of our atmo- 
sphere was such, that, for two or three 
seconds, after it became visible (through 
the air’s resistance to motion, and its oxi- 
genous action upon it) it was advancing so 
nearly towards the eye of the-spectator, as 
to appear almost stationary at about 15° of 
elevation ; from which position it shot up- 
wards with an apparently accelerated ve- 
locity, and in clear sky instantly vanished 
on passing again without the oxigenous 
limits of the atmosphere, to continue, un- 
seen, its elliptical course: it does not ap- 
pear that, during this perigeic visit, any 
meteoric fragments were thrown off by 
this body. It is much to be regretted, 
that observations are not made on a con- 
certed plan, at two or three places suffi- 
ciently distant, and perseveringly carried 
on, to ascertain the periodic times of some 
of these satellitule : the plane of the orbit 
of the one above-mentioned seems to lie so 
nearly parallel to that of the earth’s equa- 
tor, that a series of recorded observations, 
of no very long duration, would, it is be- 
lieved, suffice, for approximately determin- 
ing its periodic time of revolution about 
the earth. See our 54th vol. p. 301; vol. 
56, p- 270; vol. 58,p. 239; and p. 58, 
herein. 
Tolcanic Islands seem unfitted for Pendu- 
lum Observations, having in view the de- 
termination of the ellipsoid form and propor- 
tion of the earth’s mass ; because the basis of 
such an island, especially-a small one, may 
be presumed to contain large caverns, as 
compared with the bulk of the island, either 
now wholly or partially empty (except as 
to air or some gaseous fluid), from which 
caverns the materials had been vomited, 
which raised such island from the ocean’s 
bottom, to its present elevation above its 
surface ; or at most, as to the attractive 
force acting beneath such an island, sea- 
water now, in no inconsiderable part, oc- 
cupies the place of the former substrata of 
the island. Yet the pendulum observa- 
tions, lately made by Captain Basil Hall 
and Mr. Henry Forster, on Abingdon 
Island, one of the Galapagos group in 
the Pacific, near to the Equator, in lat. 
0° 32’ 19’ N., and Jong. 90° 30’ W., which 
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