Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 3, ASS-BOO

Part II. ASTRO
Apparent ter, but confined to a imall fpace. Thefe nodules, and
Motions of ridges, on account of their being brighter than the ge-
tiieHeaven-nerai furface of the fun, and alfo differing a little from
,ly Ew*‘es- ^ in colour, have been called faculae, and luculi.
“ Corrugations, I call that very particular and re¬
markable unevennefs, ruggednefs, or afperity, which is
peculiar to the luminous folar clouds, and extends all
over the furface of the globe of the fun. As the de-
preffed parts of the corrugations are lefs luminous than
the elevated ones, the difk of the fun has an appearance
which may be called mottled.
Indentations are the depreffed or low parts of the cor¬
rugations ; they alfo extend over the whole furface of
the luminous folar clouds.
Pores are very fmall holes or openings, about the
middle of the indentations.
From the numerous obfervations of this philofopher he
-72 has drawn the following conclufions :—
Openings. 1. Openings are places where the luminous clouds
of the fun are removed : large openings have generally
(hallows about them ; but fmall openings are generally
without (hallows. They have generally ridges and
nodules about them, and they have a tendency to run
into each other. New openings often break out near
other openings. Hence he fuppofes that the openings
are occafioned by an elaftic but not luminous gas, which
comes up through the pores and incipient openings,
and fpreads itfelf on the luminous clouds, forcing them
out of its way, and widening its paffage. Openings
fometimes differ in colour j they divide when decayed j
fometimes they increafe again *, but when divided they
ufually decreafe and vanilh *, fometimes they become
large indentations, and fometimes they turn into
73 pores.
Shallows. 2. Shallows are depreffed below the general furface
of the fun, and are places from which the luminous fo¬
lar clouds of the upper regions are removed. Their
thicknefs is vifible •, fometimes they exift without open¬
ings in them. Incipient (hallows come from the open¬
ings, or branch out from (hallows already formed, and
go forward. He fuppofes that the (hallows are occa¬
fioned by fomething coming out of the openings, which,
by its propelling motion, drives away the luminous
clouds from the place where it meets with the lead re-
fiftance ; or which, by its nature, diffolves them as it
comes up to them. If it be an elaftic gas, its levity
muft be fuch as to make it afcend through the inferior
region of the folar clouds, and diffufe itfelf among the
^ fuperior luminous matter.
Ridges. 3. Ridges are elevations above the general furface of
the luminous clouds of the fun. One of them, which he
meafured, extended over an angular fpace of 2' 4jw*9,
which is nearly 75,000 miles.
Ridges generally accompany openings: but they
often alfo exift in places where there are no openings.
They ufually difperfe very foon. He fuppofes, that
the openings permit a tranfparent elaftic fluid to come
out, which dirturbs the luminous matter on the top, fo
as to occafion ridges and nodules ; or, more precife-
ly, that fome elaftic gas, afting below the luminous
clouds, lifts them up, or increafes them ; and at laft
forces itfelf a paffage through them, by throwing them
afide.
4. Nodules are fmall, but highly elevated luminous
Vol. III. Part I.
„ 75
Nodules.
N O M Y. 33
places. He thinks that they may be ridges fore-(hort- Apparent
ened. # Motions of
5. Corrugations confift of elevations and depreflions.'*”
They extend all over the furtace of the fun} they change 2. v-— <
their (hape and fituation ; they increafe, diminifh, divide,
and vanilh quickly. Difperfed ridges and nodules form
corrugations. 76
6. The dark places of corrugations are indentations. P°res*
Indentations are ufually without openings, though in
fome places they contain fmall ones. They change to
openings, and are of the fame nature as (hallows. I hey
are low places, which often contain very fmall open¬
ings. They are of different fizes, and are extended all
over the furt. With low magnifying powers they appear
like points. The low places of indentations are pores.
Pores increafe fometimes, and become openings : they
vanifh quickly.
“ It muft be fufficiently evident,” fays Dr Herf-
chel, “ from what we have (hown of the nature of
openings, (hallows, ridges, nodules, corrugations, in¬
dentations, and pores, that thefe phenomena could not
appear, if the (hining matter of the fun were a liquid ;
fince, by the laws of hydroftatics, the openings, (hal¬
lows, indentations, and pores, would inftantly be fill¬
ed up ; nor could ridges and nodules preferve their
elevation for a (Tngle moment. Whereas, many open¬
ings have been known to laft for a whole revolution
of the fun ; and fextenfive elevations have remained
fupported for feveral days. Much lefs can it be an
elaftic fluid of an atmofpheric nature : this would be
ftill more ready to fill up the low places, and to ex¬
pand itfelf to a level at the top. It remains, therefore,
only for us to admit this (hining matter to exift in the
manner of empyreal, luminous, or phofphoric clouds,
refiding in the higher regions of the fdlar atmo-
fphere,” 77
From his obfervations, Dr Herfchel concludes, that Two re-
there are two different regions of folar clouds j that theSl0ns lo”
inferior clouds are opaque, and probably not unlike i‘l1 c oa
thofe of our planet j while the fuperior are luminous, and
emit a vaft quantity of light : that the opaque inferior
clouds probably fuffer but little of the light of the
felf-luminous fuperior clouds to come to the body of
the fun. “ The (hallows about large openings,” he
obferves, “ are generally of fuch a fize, as hardly to
permit any direft illumination from the fuperior clouds
to pafs over them into the openings •, and the great
height and clofenefs of the (ides of fmall ones, though
not often guarded by (hallows, muft alfo have nearly
the fame effeft. By this it appears, that the planetary
clouds are indeed a moft effeftual curtain, to keep the
brightnefs of the fuperior regions from the body of
the fun.
“ Another advantage arifing from the planetary
clouds of the fun, is of no lefs importance to the whole
folar fyftem. Corrugations are everywhere difperfed
over the fun j and their indentations may be called
(hallows in miniature. From this we may conclude,
that the immenfe curtain of the planetary folar clouds
is everywhere clofely drawn ; and, as our photometri-
cal experiments have proved that thefe clouds refleft
no lefs than 469 rays out of 1000, it is evident that
they muft add a moft capital fupport to the fplendour
of the fun, by throwing back fo great a (hare of the
E brightne&