108 Odbjervations on the Flux and Reflux 
peculiarly common to elaflic fluids; and it is obferyed, ae~ 
cording to thefe principles, that the winds during ftorms 
change their courfe, and blow exacétly from thofe points to 
which the current was before directed. 
. The fpecific gravity of the air is 800 times lefs than that 
of water, and its elafticity is infinitely greater. The attrac- 
tive power of the fun and moon leffens the gravity and pref- 
fure of the atmofphere towards the earth, as it draws it to- 
wards thefe bodies in the fame manner as it does the water 
of the ocean. But this power of attraction does not extend 
the water of the ocean, which is deftitute of elafticity, as it 
does the whole mafs of the atmofphere (poffeffed of it, and 
expofed to the action of this power) in the ratio of the de- 
creafe of gravity, and of the preffure of the atmofphere to-— 
wards the earth. Adopting, therefore, the inadmiffible fup- 
pofition, that-water, air, and quickfilver would be raifed to 
nearly the fame height, and be moved in the fame manner 
by the attractive force of the fun and moon; this much at 
any rate is proved, that the extenfion of the air, in proportion 
to the leflening of, the gravity of the atmofphere towards the 
earth, muft always take place, and produce a confiderable 
atmofpheric flux, while this effect cannot occur in regard to 
the flux of the ocean, It is certain that fluids are more or — 
lefs fubjeét to the effects of any power acting upon them, ~ 
-according as they have more or lefs mobility, which is in — 
the direct ratio of their rarity and elafticity. Now, as air 
poffeffes thefe properties in a degree 800 times greater than 
water, the flux of the atmafphere muft very perceptibly ex- — 
ceed in magnitude that of water. This, therefore, is a fe- 
cond certain argument againft thofe who pretend that the — 
flux and reflux: of the atmofphere are fimilar to thofe of the | F 
ocean. Not only niuft the attractive power of the fun and 
moon, on account of the greater elafticity and mobility of — 
the air compared with water, produce a greater effect on the © 
atmofphere than on the ocean, but the component parts of 
the atmofphere, as they are nearer the moon by about a 
ninetieth part of the femidiameter of the earth, muft be ~ 
"more ftrongly attraGted than the watery particles of the 
-gcean; in the fame manner as thofe which are go degrees _ 
diftant 
