me ee 
of the Atmo/phere. 209 
diftant from the place where the moon is vertical, muft oc~ 
cafion a greater preffure on the earth on account of the 
greater obliquity of the attraction, and this in proportion to 
the greater height of the atmofphere above that of the fea. 
This is the third phyfical caufe which makes the flux and 
reflux of the atmofphere more confiderable than that of the 
ocean, To this we may add the immenfe {pace occupied by 
the atmofphere in comparifon of the ocean ; for if the whole 
globe were covered with water, this general ocean would not — 
occupy the fiftieth part of the fpace actually filled by the at- 
mofphere; and in my opinion the extenfion effected in elaftic 
fluids, by the fame power of attraction, is in proportion to 
their maffes. Suppofing this to be the cafe, the flux of air 
in an atmofphere of ten miles height, would be much more 
confiderable than in another amounting to only a tenth part 
of that height: though this difference cannot take place in 
the flux and reflux of the ocean, becaufe water is deftitute of 
elafticity. Befides, lands, iflands, ftraits, bays, the fituation 
_of the coafts, fand-banks, fhoals, &c. throw a great many 
impediments in the way of the water in regard to its mo- 
tion; whereas the atmofphere, which rifes to a height ten or 
twelve times greater than the fummits of the higheft moun- 
tains, is in no manner prevented from moving according to 
the effects of the power of attraction, unlefs fomething very 
particular takes place in its loweft ftrata. It is more than 
probable that each of thefe caufes contributes its part to make 
the movement of the atmofphere far more ronficérable than 
that of the ocean. 
It. is therefore certain that the united effects of the attrac- 
_ tion of the fun and moon on the atmofphere of the earth 
~ mutt raife and extend it in the inverfe ratio of the fquare of 
the diftance fo as to make it aflume the form of a lengthened 
fpheroid, the greater diameter of which, from the fame 
grounds and with the fame variations as the aqueous fphe- 
roid, muft nearly follow the direction of the line of attrac- 
tion. 
Befides, the heat of the fun, which has no fenfible influ- 
_ence in raifing or extending the water of the ocean, will pro- 
duce an effect on that part of the atmofphere ¢xpofed. to , its 
rays 
