■*y2 ASTRO 
An atmofphere, with its natural changes, will explain fuch 
belts. The fpot in the Sun may be accounted for on the 
lame principles. The Earth is furrounded by an atmof¬ 
phere compofed of various elaftic fluids. The Sun alfo 
lias its atmofphere, and if fome of the fluids which enter 
into its competition fliou’ld be of a fhining brilliancy, while 
others are merely tranfparent, any temporary caul'e which 
may remove the lucid fluid, will permitus to fee the body 
of the Sun through the tranfparent ones. If an obferver 
were placed on the Moon, lie would fee the folid body of 
our Earth only In thofe places where the tranfparent fluids 
of our atmofphere would permit him. In others, the 
opaque vapours would refieft the light of rhe Sun, with¬ 
out permitting his view to penetrate to the furface of our 
globe. He would probably alfo find that our planet had 
occafionally fome fiiining fluids in its atmofphere ; as, not 
unlikely, fome of our northern lights might not efcape his 
notice, if they happened in the unenlightened part of the 
Earth, and were feen by him in his long dark night. Nay, 
we have pretty good reafon to believe, that probably all 
the planets emit light in fome degree ; for the illumination 
which remains on the Moon in a total eclipfe cannot be 
entirely afcribed to the light which may reach it by the re- 
fYa£tion of the Earth’s atmofphere. For inftance, in the 
eclipfe of the Moon, wdiich happened Oiftober 22, 1790, 
tire rays of the Sun ref rafted by the atmofphere of tiie 
Earth towards the Moon, admitting the mean horizontal 
refraction to be 30' 3o"-8, would meet in a. focus above 
j89thoufand miles beyond the Moon; fo that confequently 
there could be no illumination from rays refrafted by our 
atmofphere. It is however not improbable that about 
the polar regions of the Earth there may be refraction 
enough to bring fome of the folar rays to a (horter focus. 
The diftance of the Moon at the time of the eclipfe would 
require a refraCtion of 54' 6" equal to its horizontal pa¬ 
rallax at that time, to bring them to a focus fo as to throw 
light on the Moon. The unenlightened part of the pla¬ 
net Venus has alfo been feen by different perfons, and, not 
^having a fatellite, thofe regions that are turned from the 
Sun cannot poffibly fhine by a borrowed light; fo that this 
faint illumination mud denote fome phofphoric quality of 
the atmofphere of Venus. In the inftance of the above 
large fpot on the Sun, I concluded from appearances that 
I viewed the real folid body of the Sun itfelf, of which we 
rarely fee more than its (hining atmofphere. 
“ In the year 1783, I obferved a fine large fpot, and 
followed it up to the edge of the Sun’s limb. Here I took 
notice that the fpot was plainly depreffed below the furface 
of the Sun ; and that it had very broad fhelving Tides. I 
alfo fufpeCted fome part at lead of the fhelving (ides to be 
elevated above the furface of the Sun ; and obferved that, 
contrary to what ufually happens, tire margin of that fide 
of the fpot, which was fart he ft from the limb, was the 
broadeft. The luminous fhelving (ides of a fpot may be 
explained by a gentle and gradual removal of the fhining 
fluid, which permits us to fee tire globe of the fun. As 
so the uncommon appearance of the broadeft margin being 
on that fide of the fpot which was fartheft from the limb 
when the fpot came near the edge of it, we may furmife 
that the Sun has inequalities on its furface, which may 
poffibly be the caufe of it. For, when mountainous coun¬ 
tries are expofed, if it ftiould chance that the higheft parts 
of the landfcape are fituated fo as to be near that fide of 
the margin, or penumbra of the fpot, which is towards 
the limb, it may partly intercept our view of it, when 
the fpot is feen very obliquely. This would require ele¬ 
vations at lead five or fix hundred miles high ; but con- 
fidering the great attraction exerted by the Sun upon bo¬ 
dies at its furface, and the flow revolution it has upon its 
axis, we may readily admit inequalities to that amount. 
From the centrifugal force at the Sun’s equator, and the 
weight of bodies at its furface, I compute that the power 
of throwing down a mountain by the exertion of tire for¬ 
mer, balanced by the fuperior force of keeping it in its 
fkuation of the latter, is near fix and a half times lefs on 
1 
N O M Y. 
the Sun than on our equatorial regions; and as an eleva¬ 
tion fimilar to one of three miles on the Earth would not 
be lefs than 334 miles on the Sun, there can be no doubt 
but that a mountain much higher would (land very firmly. 
The little denfity of the folar body feems alfo to be in fa¬ 
vour of the height of its mountains ; for, cateris parabus , 
denle bodies will fooner come to their level than rare ones. 
The difference in the vanifhing of the fhelving fide, in- 
ftead of explaining it by mountains, may alfo, and perhaps 
more fatisfaflorily, be accounted for from the real diffe¬ 
rence of the extent, the arrangement, the height, and the 
intenfity of the fhining fluid, added to tlieoccafional changes 
that may happen in thefe particulars, during the time in 
which the fpot approaches to the edge of the dilk. How¬ 
ever, by admitting large mountains on the furface of the 
Sun, we fhall account for the different opinions of the two 
eminent aftronomers ; one of whom believed the fpots de¬ 
preffed below the Sun, while the other fuppofed them ele¬ 
vated above it. For it is not improbable that fome of the 
folar mountains may be high enough occafionally to project 
above the ftiining elaftic fluid, when, by fome agitation 
or other caufe, it is not of the ufual height; and this opi¬ 
nion is much ftrengthened by the return of fome remark¬ 
able fpots, which lerved Caffini to afeertain the period of 
theSun’s rotation. A very high country or chain of moun¬ 
tains may oftener become vilible, by the Vemoval of the 
obftrufting fluid, than the lower regions, on account of 
its not being fo deeply covered with it. 
“ In the year 1791, I examined a large fpot in the Sun, 
and found it evidently depreffed below the level of the 
furface ; about the dark part was a broad margin, or plane 
of confiderable extent, lefs bright than the Sun, and alfo 
lower than its furface. This plane feemed to rife, with 
fhelving fides, up to the place where it joined the level of 
the furface. In confirmation of thefe appearances, I care¬ 
fully remarked that the difk of the Sun was vifibly con¬ 
vex ; and the reafon of my attention to this particular, 
was my being already long acquainted with a certain op¬ 
tical deception, that takes place now and then when we 
view the Moon; which is, that all the elevated fpots on 
its furface will feem to be cavities, and all cavities will 
alfume the fliape of mountains. But then at the fame 
time the Moon, inftead of having the convex appearance 
of a globe, will feem to be a large concave poition of an 
hollow fphere. As foon as, by the force of imagination, 
you drive away the fallacious appearance of a concave 
Moon, you reftore the mountains to their protuberance, 
and fink the cavities again below the level of the furface. 
Now, when I faw the fpot lower than the ftiining matter 
of the Sun, and an extended plane alfo deprelied, with 
fhelving fides riling up to the level, I alfo found that the 
Sun was convex, and appeared in its natural globular (fate. 
Hence 1 conclude that there could be no deception in thofe 
appearances. How very ill would this obfervation agree 
with the ideas of folid bodies bobbing up and down in a 
fiery liquid? with the fmoke of volcanoes, or feum upon 
an ocean ? And how eafily is it explained upon the forego¬ 
ing theory ! The removal of the fhining atmofphere, which 
permits us to fee the Sun, muft naturally be attended with 
a gradual diminution on its borders ; an inftance of a fitni- 
lar kind we have daily before us, when through the open¬ 
ing of a cloud we fee the fky, which generally is attended 
by a furrounding hazinefs of fome fhort extent; and fcl- 
dom tranfits, from a perfect clearnefs, at once to the great- 
eft obfeurity. 
“ Auguft 26, 1792, I examined the Sun with feveral 
powers, from 90 to 300. It appears evidently that the 
black fpots are the opaque ground, or body of the Sun; 
and that the luminous part is an atmofphere, which, be¬ 
ing interrupted or broken, gives us a tranfient glimpfe of 
the Sun itfelf. My 7-feet reflector reprefents the fpots, as 
it always ufed to do, much depreffed below the furface of 
the luminous part. 
“September 2, 1792. I faw two fpots in the Sun with 
the naked eye. In the telefcope I found they were cl lif¬ 
ters 
