34$ -Mr. Schroeter’s Observations 
which reflects so much of the solar light into its dark he- 
misphere as produces a twilight, more luminous than the 
light reflected upon its surface from the earth, when it is 
only 31 0 47' 9" from its opposition to the moon, when, 
consequently, it shews the greatest part of its disk illumi- 
nated, and affords some degree of light to the nights in the 
moon. 
A cursory survey of these computations, shews that they 
not only contribute to illustrate the observations, but also that 
they coincide so fully with the collateral circumstances, as still 
farther to confirm those observations. 
1. I was well aware, even at the time I made the observa- 
tions, that the lunar twilight must, as it actually did, appear in 
the form of a lengthened pyramid. And indeed the 7th fig. 
Tab. VI. which represents the twilight c k, gf, F h, before the 
conjunction, projecting from the cusps towards the west, 
clearly points out, that only its pyramidal part c f k could 
be visible at T, whilst the whole remainder of it F g c fh ex- 
tended over the whole hemisphere of the moon AFDEC, 
which was turned away from the eye of the observer. 
2. It appeared to me, on the other hand, before I had suffi- 
ciently reflected on these collateral circumstances, that it could 
not well be reconciled to theory, that this twilight, whose length 
from c to/ measured 20 lines, should at c k, where its breadth 
was the greatest, not be broader than or at most — of 
a line. I soon, however, removed the difficulty by the follow- 
ing deduction. From the above computation, it appears that 
the sid ef g = k c, or the distance of f k, the farther edge of 
the twilight from the terminator g c, was — 105 lines, or an 
arc of 2 0 34' 12". But the arc k c —f g } or the greatest visible 
