on the Atmosphere of Venus. 319 
jection of this glimmering strip of pale light, and to ascertain 
whether in fact it only belongs to the northern cusp. 
The very next, or the fourth evening, gave me a favourable 
opportunity for this purpose, and this was the more fortunate, 
as, on account of the hazy weather that immediately suc- 
ceeded, of the increased twilight into which the planet ad- 
vanced, and of its decreasing declination, this was the last 
evening in which such an observation could be made with 
some precision. At six o’clock, the atmosphere being uncom- 
monly clear, I looked at Venus with the seven-feet reflector, 
magnifying 95 and 74, times. It appeared very distinct, and I 
ascertained, beyond the possibility of doubt, that the southern 
cusp projected somewhat into the dark hemisphere, and that 
from the point of the northern one, the very faint narrow 
streak of pale bluish light, intermittent in intensity on ac- 
count of its faintness, but yet permanent as to duration, ex- 
tended several degrees along the limb of the dark hemisphere 
of the planet. I strained all my visual powers, but could ac- 
tually see this appearance only at the northern point. As the 
planet descended towards the horizon, the light of the very 
sharp southern, as well as that of the bright part of the 
northern point began to glimmer with gradual diminution, the 
latter more faintly than the former ; but not the least appear- 
ance of a pale bluish prolongation could be traced at the 
southern cusp. 
I had immediate recourse to the projection machine, and 
though I found it very difficult to measure, with the greatest 
accuracy, the very faint light at the northern, as well as the 
bright prolongation at the southern cusp, I succeeded, how- 
ever, to ascertain 
Tt 2 
