Now if we suppose the force of the Moon's Attaction to decrease as the Square of the Distance from its Center increases (as in the Earth and other Cœlestial Bodies) we shall find, that where the Moon is perpendicularly either above or below the Horizon, either in Zenith or Nadir, there the force of Gravity is most of all diminished, and consequently that there the Ocean must necessarily swell by the coming in of the Water from those parts where the Pressure is greatest, _viz._ in those places where the Moon is near the Horizon: But that this may be the better understood, I thought it needful to add the following Figure, (_Vide Fig. 1. Plate 1._) where _M_ is the Moon, _E_ the Earth, _C_ its Center, and _Z_ the place where the Moon is in the Zenith, _N_ where in the Nadir. Now by the Hypothesis it is evident, that the Water in _Z_, being nearer, is more drawn by the Moon, than the Center of the Earth _C_, and that again more than the Water in _N_; wherefore the Water in _Z_ hath a tendency towards the Moon, contrary to that of Gravity, being equal to the excess of the Gravitation in _Z_, above that in _C_: And in the other case, the Water in _N_, tending less towards the Moon than the Center _C_, will be less pressed, by as much as is the difference of the Gravitation towards the Moon in _C_ and _N_. This rightly understood, it follows plainly, that the Sea, which otherwise would be Spherical, upon the Pressure of the Moon, must form it self into a Spheroidal or Oval Figure, whose longest Diameter is where the Moon is vertical, and shortest where she is in the Horizon; and that the Moon shifting her Position as she turns round the Earth once a Day, this Oval of Water shifts with her, occasioning thereby the two Floods and Ebbs observable in each 25 Hours. And this may suffice, as to the general Cause of the Tides; it remains now to shew how naturally this Motion accounts for all the Particulars that have been observ'd about them; so that there can be no room left to doubt, but that this is the true cause thereof. The Spring Tides upon the New and Full Moons, and Neap Tides on the Quarters, are occasion'd by the attractive Force of the Sun in the New and Full, conspiring with the Attraction of the Moon, and producing a Tide by their united Forces: Whereas in the Quarters, the Sun raises the Water where the Moon depresses it, and the contrary; so as the Tides are made only by the difference of their Attractions. That the force of the Sun is no greater in this Case, proceeds from the very small Proportion the Semi-diameter of the Earth bears to the vast distance of the Sun.