338 Mr, Schroeter’s Observations 
the calculations and inferences I there made, to some appear- 
ances I had already noticed on this satellite. It occurred to me, 
that if in fact there were a twilight on the moon, as there is 
on Venus and our earth, it could not, considering the greater 
rarity of its atmosphere, be so considerable: and that the 
vestiges of it, allowing for the brightness of the luminous part 
of the moon, the strong light that is thence thrown upon the 
field of the telescope, and in some measure the reflected light 
of our earth, could only be traced on the limb, particularly at 
the cusps ; and even this only at the time when our own twi- 
light is not strong, but the air very clear, and when the moon, 
in one of its least phases, is in a high altitude, either in the 
spring, following the sun two days after a new moon, or in 
the autumn, preceding the sun in the morning, with the same 
aspect: in a word, that the projection of this twilight will 
be the greater and more perceptible the more falcated the 
phase, and the higher the moon above the horizon, and out of 
our own twilight. This struck me the more, as I recollected 
having, two years ago, perceived such an appearance at the 
outward edge, near the points of the cusps, though I did not 
then reflect on the cause of it. 
As all the requisite circumstances, however, do not often 
coincide, I thought myself particularly fortunate when, on the 
24th of February, I was favoured with a lucky combination 
of them. Although this be as yet only a single observation 
of the sort, it is, however, in every respect so complete, and 
the inferences it leads to are, to me at least, so new and in- 
teresting, that I cannot withhold it from those liberal minded 
men, who are zealous in the pursuit of genuine philosophical 
knowledge. 
