S. G :: 1. _n_. Hence, S = G/_n_. And that the Force of the Moon to raise the Sea is to Gravity, as 1 to 2031821. Let this be L. G :: 1. _s_. Hence, L = G/_s_. And since the Centrifugal force of the Parts of the Earth arising from its Diurnal Motion is to Gravity, as 1 to 291. Let this be C. G :: 1. C. Then C = G/_e_. Hence, (S + L). C :: (G/_n_ + G/_s_). G/_e_ :: (1/_n_ + 1/_s_). 1/_e_ :: 1. _sn_/((_s + n_) × _e_) :: 1. 6031. The same Philosopher has taught us[22] that the Centrifugal force raises the Water at the Equator above the Water at the Poles, to the height of 85200 Feet. Wherefore if that Force which is as 6031, raise the Ocean to 85200 Feet, the United forces of the Sun and Moon, which are as 1. will raise the same to 14 Feet, for 85200/6031 = 14. _Proximé_. Now we know that the more easily the Waters can obey the Attraction, with the more Force are the Tides moved; but since, as Mr. _Halley_ has determin'd it,[23] our Atmosphere is extended to 45 Miles, whereas the middle depth of the Ocean is but about half a Mile; it is plain, that the Air revolving in a Sphere about 100 times larger than that of the Ocean, will have a proportionably greater Agitation. Besides, Rocks, Shelves, and the inequality of Shoars are a great stop to the Access and Recess of the Sea: But nothing repels the rising Air, which is also of such thinness and fluidity, that it is easily driven, and runs every way. Nor ought we to omit, that it is the universal Law of Bodies Attracted, that the Force of Attraction is reciprocally as the Squares of their Distances; so that the Action of the Sun and Moon will be greater upon the Air than upon the Water, upon the Account of its Nearness. But the Consideration of the Elasticity is still of greater Moment here, of which this is the nature, that it is reciprocally as the Pressure, so that the incumbent Weight being diminished by the Attraction, the Air underneath will upon this score be mightily expanded. These and such like Causes will make the Tides in the Air to be much greater than those of the Ocean; nor is it necessary to our purpose to determine, by nice Calculations, their particular Forces; it is sufficient to have proved that these Motions must both be Universal, and also return at certain Intervals.