relating to the Mountains of the Moon. 515 
January 13, 1780, 7 o’clock, I examined the moun- 
tains in the Moon ; but there was not one of them that 
was fairly placed on level ground, which is a condition 
very neceffary for an exaCt meafurement of the projec- 
tion. If there fhould be a declivity on the Moon before 
the mountains, or a trad; of hills placed fo as to caft a 
fhadow on that part before them which would other- 
wife be illuminated, it is plain that the projection would 
appear too large ; and, on the contrary, fhould there be a 
riling ground before them, it would appear too little. 
As far as I was able to judge of the direction of the 
line of illumination, the higheft hill projected 2 5 // 3 1 , or 
30,36 miles : from thence we find, as before that the 
perpendicular height is (.42 mile) lefs than half a 
mile. 
January 14, 1 1 o’clock, I took the projection of the 
higheft mountain which was fituated at the Weftern 
edge. It meafured 24", 68, or about 27 miles ; and the 
perpendicular height comes out lefs than half a mile. 
There was not one mountain in the edge of the difk fo 
high as this. 
January 17, 7 o’clock, a very high mountain pro- 
jected n.o lefs than 40", 625. Its fituation is in the South - 
eaft quadrant. The Moon’s femi-diameter, at the time of 
Vol, LXX. Y y y obfervation, 
