on the Atmosphere of Venus. 317 
a very peculiar kind of faintness, verging towards a pale 
greyish hue. 
The limb of the planet at this small part of its dark moiety, 
appeared with as faint a light, and, compared with the ex- 
tremity of the southern cusp, as pale as the dark limb of the 
moon three days before and after the new moon, when it is 
faintly illuminated by the reflected rays from the earth : and 
it appeared to me, that towards the farther extremity c, 
where it was actually inflected, according to the circular limb 
of the dark hemisphere, its light vanished into a pale bluish 
tint, in the same manner as the more vivid light of the lu- 
minous hemisphere dwindles away towards the terminating 
border and the extremities of the cusps. The 3d fig. represents 
this striking phaenomenon only in its projection, it being im- 
possible to give a just representation of it in a drawing. Sur- 
prised at this new and singular appearance, I pointed it out 
to Mr. Tischbein, an ingenious artist, who was then with me 
engraving the plates for my Selenotopographic Fragments, 
and desired him to attend particularly to all its circumstances. 
He found and described the whole just as I had seen it. I 
made the drawing, fig. 3, under his eye ; and we viewed the 
object together very attentively for about an hour, when the 
planet descended too low to be distinctly seen. 
The apparent diameter of Venus was, by means of the pro- 
jecting table, and the mean of several observations, all of which 
agreed to within 1", found to measure 59" ; but the greatest 
breadth of the illuminated part did not exceed 2,6". 
On the following evening, the air being as calm and serene 
as the preceding one, I observed the planet from 6 h to 6 h 40', 
but on account of some necessary alterations in the apparatus 
T t 
MDCCXCII, 
