Captain Kater on a lunar volcano. 131 
for two friends, who remarked the same phenomena as the 
night before, but in an inferior degree, partly perhaps in 
consequence of the evening not being so favourable. 
On the 6th I again observed it ; it had certainly become 
more faint, and the star-like appearance less frequent. I 
could see it very distinctly with a power of 40. As the 
moon approached the horizon, it was visible only at intervals 
when the star-like appearance took place. On the same even- 
ing I had the pleasure of showing it to Mr. Henry Browne, 
F. R. S. 
I regret that I had no micrometer adapted to my tele- 
scope ; but I have reason to believe the distance of the vol- 
cano from the edge of the moon was about one tenth of 
her diameter, and the angle it formed this evening with a 
line joining the cusps was about $o‘°. 
I remarked near the edge of the moon, a well known 
dark spot, from which the volcano was distant, as nearly as 
I could estimate, three times its distance from the edge of 
the moon. 
In a map of the moon published by Dr. Kitchener (and 
which is the best small map with which I am acquainted), 
there is a mountain sufficiently near the situation of the 
volcano, to authorize the supposition that they may be iden- 
tical. 
On the 7th I could still see the volcano, and the occasional 
star-like appearance ; but I do not think it was sufficiently 
perceptible to have been discovered by a person ignorant 
of its precise situation. I am inclined however to think, that 
the difficulty of seeing it is rather to be attributed to the 
