in order to af certain the height of Mountains. 5 6-g 
8°. 50, and confequently ^=31°. 24 the temperature re- 
quired: which, if it fhould be thought convenient, may 
be confidered as the freezing point. 
In the whole of-hhe above inquiry I have taken no 
notice of the effedt of gravity upon the particles of the 
air at different diftanees from the earth’s center, which 
fhould douhtlefs enter into the account, and which would 
occafion the denfity of the atmofphere to decreafe in a 
ratio fomething greater than the prefent theory admits 
of. In a height of four Englifh miles Dr. hoesley finds 
(Phil. Tranf. vol. LXIV.) that the diminution of denfity 
or volume from the accelerative force of gravity would be 
only ~ part of the whole, or about 48 feet; and I may 
add to this, that this eflfedt will be in the duplicate ratio 
of the heights, fo that at one mile high it becomes only 
three feet. A like effedl takes place alfo below the fur- 
face of the earth, as in meafuring the depths of mines, 
8 cc. with this difference, that here it is but half the quan- 
tity; in the former inftance gravity within the earth 
being limply as the diftance from the center; they are 
both of them, however, circumftances that deferve no 
attention in practice. 
This would be the place for me to enumerate the 
many defiderata, befides thofe already hinted at, that ftill 
remain for the perfection of this theory ; fuch as the 
Tol. LXVII. 4 E laves 
