366 On the PROGRESS of HEAT 
17. Let us then fuppofe, that the ftrata of the atmofphere 
have a capacity for heat, which increafes as the air becomes 
r 
rarer, fo as to be proportional to mb *,% denoting, as be- 
fore, the diftance from the centre of the earth, 7 the radius 
of the earth, m and 6 determinate, but unknown quan- 
oe vet m1 : : 
tities, fuch that mé ors, exprefles the capacity of air for 
heat, when of its ordinary denfity, at the furface of the earth. 
The formula thus aflumed, agrees with the extreme cafes ; 
, m ; 
for, when. x=7, the capacity of heat = za finite 
3 : GSR 
quantity ; when w increafes, ze diminifhes, and fo alfo does 
r 
¥. . : m =. F, 
b”, if b is greater than unity, and therefore — increafes conti- 
bF 
nually. It does not, however, increafe beyond a certain limit, 
for when x is infinite — becomes +> OF m. 
bz 
18. HENCE, 
~~ —_. 
