relating to the Mountains of the Moon . 517 
January 28, 6 o’clock in the morning, the higheft 
mountain in the difk meafured 30", 937 ; the Moon’s 
femi-diameter at that time 15' 40"; and on therefore 
equal 31,37 miles : but as the Moon is within four hours 
of her quadrature we may be affured that this mountain 
is lefs than half a mile high. 
February 19, Mons Sinopium projected 5 // ,7 8 1 ; 
therefore on - 6,26 miles, and the quantity lm 56,54 
miles ; and confequently the height of this mountain, 
which it feems proves to be a very high one, is not much 
lefs than a mile and a half. However, my journal ob- 
ferves, that the meafure was very full ; therefore the 
mountain in all probability does not exceed a mile and a 
quarter. Moreover, I think that obfervations made fo 
near the full or new Moon are lefs to be depended upon, 
becaufe a fmall error in meafuring will produce a great 
one in the height of a mountain. 
From thefe obfervations I believe it is evident, that 
the height of the lunar mountains in general is greatly 
over-rated ; and that, when we have excepted a few, the 
generality do not exceed half a mile in their perpendi- 
cular elevation. It is not fo eafy to find any certain 
mountain exadlly in the fame fituation it has been mea- 
fured in before ; therefore fome little difference muft be 
expected in thefe meafures. Hitherto I have not had an 
Y y y 2 ■ oppor- 
