Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 13, MAT-MIC

Chap. V METEOR
Me;eon ally taking place in different parts ot the atxnofphere,
'•'““’V ■'*“*' which will occafion winds varying in dire6tion, violence,
and continuance, according to the fuddennefs and the
quantity of air deitroyed or produced. Belides thefe,
there are many other ingredients conftantly mixing
with the atmofphere, and many partial caufes of conden-
fation and rarefadlion in particular places. 1 o thefe,
and probably to other caufes hitherto unknown, are to
be afcribed all thofe winds which blow in any place
befides the general ones already explained } and which,
as they depend on caufes hitherto at leatt reckoned
contingent, will probably for ever prevent uniformity
and regularity in the winds. All thefe caules, how¬
ever, may, and probably will, be difcovered : the cir-
cmnitances in which they will take place, and the ef-
fedls they will produce, may be knowm ; and when¬
ever this is the cafe, the winds of any place may in
fome meafure be reduced to calculation.
7*9
Meteors.
75
Metaors,
Chap. V. Of Meteors.
The principal luminous phenomena denominated
meteors, have been fully confidered under Atmo¬
spheric Electricity. Thofe meteors that burft in
the air, and are followed by the falling of ftones or
other mineral fubftances, have been fully defcribed and
accounted for under Meteorolite. We have here
only to notice briefly the meteors ceXitA. falling Jiars^
and i^nes fatm.
Falling The falling or (hooting ftar is a very common pheno-
ftar. menon, and takes place more efpecially at thofe fea-
fons and in thofe fituations where the aurora borealis is
mod frequently obferved. Indeed they are confidered by
mod philofophers as modifications of the lame pheno¬
menon, and depending on the fame caufe. We have
feen good reafon to conclude that the aurora borealis is
an electrical meteor; and if the falling flar is fo nearly
allied to the aurora as is fuppofed, it mud alfo be pro¬
duced by electricity. Mr G. Morgan feems to have
no doubt of the eleCtrical nature of this meteor, and
remarks that if u'hat appears as an undulating flaih in
the aurora, could be concentrated or confined within
fmaller dimenfions, it would probably affume the ap¬
pearance of a falling flar. He founds this opinion
chiefly on the following experiment.
Into a tube 48 inches long, and \ inch diameter,
Mr Morgan conveyed as much air, as, under the com¬
mon preflure of the atmofphere, would fill two inches in
length of the fame tube. (The tube we prefume
was previoufly exhaufted of air.) One extremity of
the tube he connected with the ground by means of
good conductors, and faftened to the other a metallic ball.
Through the tube thus filled with rarefied air, he fent
eleftric fparks of different magnitudes, bv bringing the
ball within the ftriking diftance of different fixed con-
duftors. When the fparks were fmall, a flafli like that
of the aurora borealis, feemed to fill the whole tube •,
but when the fpark was what might be made to ftrike
through 10 inches in the open air, it appeared to ftrike
through the whole length of the tube, with all the
brilliancy and ftraightnefs of a falling ftar. If, how¬
ever, he extrafted part of the air out of the tube, by
the air-pump, he could never make the eleftric fluid
•affiime anv form excepting that of a flafti; but by
exchanging the tube for another with a thermometrical
V-OL. XIII. Part II.
O L O G Y.
ball, and treating it in the fame manner as the preced¬
ing, the flaih never appeared, but the fluid in its pallage ^
affumed all the brilliancy of a tailing ftar.
It is eafy to trace the iimilarity of circumftances that
take place in this experiment, ami in the natural pheno¬
menon of the falling ftar. Both take place in rarefied
air; both are remarkable for the brighenefs of their
light, and for the ftraightnefs of their direflion. That
falling liars are frequently, if not always, the concen¬
tration of an aurora borealis, may be inferred from
their being the conftant attendants of a very electrical
ftate of the atmofphere-, and from their frequent appear¬
ance near that portion of the heavens which is illu¬
mined by the northern lights at the time of their ap¬
pearance.
Mr Morgan was riding towards Norwich late at
night, when to the north-eaft of the town he beheld a
fine conical ftream of the aurora borealis. The whole
body every now and then flaftied, as if an additional
quantity of eleftric fluid were thrown into it, and
nearly at the fame inftant he perceived what is vulgarly
called a falling ftar, darting from its fummit. This
appearance he obferved twice fuccefiively. 77
The ignis fatuus, or will-with-tke-wifp, that appears Ignis fa
fo often in boggy, marihy and damp fituations, decoy-tuus*
ing the unwary traveller, and terrifying the fuperfti-
tious vulgar, feems to be rather of a phofphoric than an
eleftric nature, fimilar to the light which is emitted
by ftale fifti, rotten wood, and other putrefeent fub¬
ftances. Sir Ifaac Newton defined it to be a vapour
fliining without heat.
A remarkable ignis fatuus was obferved by Mr
Derham, in fome boggy ground, between two rocky
hills. He was fo fortunate as to be able to approach it
within two or three yards. It moved with a brifle and
defultory motion about a dead thiftle, till a flight agita¬
tion of the air, occafioned, as lie fuppofed, by his near
approach to it, oecafioned it to jump to another place j
and as he approached, it kept flying before him. He
was near enough to fatisfy himfelf, that it could not be
the (Inning of glow-ivurms or other infedts—it was one
uniform body of light.
M. Beccaria mentions two of thefe luminous appear¬
ances, which were frequently obferved in the neigh¬
bourhood of Bologna, and which emitted a light equal
to that of an ordinary faggot. Their motiom were
unequal, fometimes rifing, and fomedmes finking to¬
wards the earth ; fometimes totally difappearing, though
in general they continued hovering about fix feet from
the ground. They differed in fize and figure and in¬
deed, the form of each was flutluating, fometimes
floating like waves, and dropping fparks of fire. He
was affured there was not a "dark night in the whole
year in which they did not appear nor was their appear¬
ance at all affedled by the weather, whether cold or
hot, fnow or rain. They have been known to change
their colour from red to yellow and generally grew
fainter as any perfon approached, vanifliing entirely
when the obferver came very near to them, and appear¬
ing again at fome diftance.
Dr Shaw alfo deferibes a Angular ignis fatuus^
which he faw in the Holy Land. It was fometimes
globular, or in the form of the flame of a candle and
immediately afterwards fpread itfilf fo much, as to
involve the whole company in a pale inoffenfive light,
4 Z and