Astronomical and Nautical Collections. 297 
the monthly revolution of the moon, which does not affect the 
velocity of its mean annual revolution round the sun, together with 
the earth. 
*< It is therefore so far from being true, that the inequality of the 
centrifugal force, at different parts, gives rise to any part of the 
phenomena of the tides, that, on the contrary, the perfect uniformity 
of this force is the basis of the determination of the powers imme- 
diately concerned in these phenomena. The Atlantic and the Pa- 
cific oceans are subjected to a centrifugal force precisely equal to 
that which affects the solid parts of the earth; but when the lumi- 
nary is over the Atlantic, its attraction for that ocean is greater 
than for the central part, and consequently greater than the centri- 
fugal force, so that this differential attraction tends to elevate the 
Atlantic ; at the same time that its attraction for the Pacific ocean is 
less than the mean attraction, and less than the centrifugal force, 
which therefore prevails over the attraction, and the differential 
force tends to raise the Pacific ocean almost as much as it tends to 
raise the Atlantic in the opposite direction. 
“ There is also an additional force, derived from the obliquity 
of the action of the luminary on the parts of the earth not imme- 
diately below it, which tends to compress the lateral parts, and to 
increase the elevation at the ends of the diameter pointing to the 
luminary. 
“The readiest way of calculating the operation of all these 
forces is, to reduce them to ahorizontal direction, and to determine 
what inclination of each part of the surface of the sea, considered 
as an inclined plane, will cause such a tendency, in a particle 
situated on it, to move in acontrary direction, as precisely to coun- 
terbalance, not only these forces, but also the new disturbing force, 
derived from the attraction of the parts thus elevated ; and it may 
easily be shown, that all these conditions will be fulfilled, if we at- 
tribute to the surface of the sea the form of an oblong elliptic sphe- 
roid, differing but little from a sphere.” 
Now, “ we have only to recollect, with respect to the first ob- 
jection” already mentioned, ‘“ that we are by no means required 
to imagine that the moon repels the remoter parts of the earth and 
