of the Sun and fixed Stars. 51 
earth there may be refraction enough to bring some of the 
solar rays to a shorter focus. The distance of the moon at the 
time of the eclipse would require a refraction of 54/ 6 " equal 
to its horizontal parallax at that time, to bring them to a focus 
so as to throw light on the moon. 
The unenlightened part of the planet Venus has also been 
seen by different persons, and not having a satellite, those re- 
gions that are turned from the sun cannot possibly shine by a 
borrowed light ; so that this faint illumination must denote 
some phosphoric quality of the atmosphere of Venus. 
In the instance of our large spot on the sun, I concluded 
from appearances that I viewed the real solid body of the sun 
itself, of which we rarely see more than its shining atmosphere. 
In the year 1783, I observed a fine large spot, and followed 
it up to the edge of the sun's limb. Here I took notice that 
the spot was plainly depressed below the surface of the sun ; 
and that it had very broad shelving sides. I also suspected 
some part, at least, of the shelving sides to be elevated above 
the surface of the sun ; and observed that, contrary to what 
usually happens, the margin of that side of the spot, which was 
farthest from the limb, was the broadest. 
The luminous shelving sides of a spot may be explained by a 
gentle and gradual removal of the shining fluid, which permits 
us to see the globe of the sun. As to the uncommon appearance 
of the broadest margin being on that side of the spot which 
was farthest from the limb when the spot came near the edge 
of it, we may surmise that the sun has inequalities on its sur- 
face, which may possibly be the cause of it. For, when moun- 
tainous countries are exposed, if it should chance that the 
highest parts of the landscape are situated so as to be near that 
He 
