334 } 
Mr . Schroeter's Observations 
of the twilight. And the side d c being to ec as rad. is to the 
cosin. of the angle c , subtract from this b c , the semidiameter of 
Venus, and the remainder, db, will be the height of the atmo- 
sphere. Now, taking 834 geogr. miles = 3178874 toises for 
the semidiameter, we have 
Log. 3178874 = L. 6,5022632 
Log. cos. 2 0 19' 15" = L. 9,9996436 
Log. dc = L. 6,5026196 = 3181400 
— be — 3 1 78874 
db — 2526 
Hence it appears that the perpendicular height of the in- 
ferior and more dense part of the atmosphere of Venus, which 
has the power of reflecting the solar light to such a degree, as, 
under favourable circumstances, to be visible on our globe, 
where, with a good telescope, it assumes the appearance of a 
faint ash-coloured light, measures 2526 toises, or 15156 Paris 
feet. 
As we are not acquainted, with the laws of the inflection of 
light at the atmosphere of Venus, and are as much in the dark, 
concerning that as well as our own twilight, whether it be 
produced by a simple or compound reflection, this computation, 
it must be owned, is somewhat conjectural, and at best, condi- 
tional ; and yet it supplies us with some farther means of esti- 
mating the height and density of the atmosphere of Venus with 
a somewhat greater precision. 
If, according to the above principles and computations, it be 
determined that the twilight of Venus extends, at least in a 
considerable proportion, as far as ours ; and if the inferior part 
