which (lie moves; whence arife feveral Irregu- 

 larities in her Motion, of all which, the Author 

 in this Book, with no lefs Subtility than Indu- 

 ftry, has griven a full account. And though by 

 reafbn of the great Complication of the Pn> 

 blem, he has not yet been able to make it pure- 

 ly Geometrical, 'tis to be hoped, that in fbme 

 farther Effay he may furmounc the difficulty : 

 And having perfected the Theory of the Moon, 

 the long defir'd Difcovery of the Longitude 

 (which at Sea is only practicable this way) may 

 at length be brought to light, to the great Ho- 

 nour of your Majefty, and Advantage of your 

 Subjects. 



All the furprifing Phenomena of the Flux 

 and Reflux of the Sea, are in like manner 

 fhewn to proceed from the fame Principle; 

 which I defign more largely to infill on, fince 

 the Matter of Fact is in this Cafe much bet- 

 ter known to your Majefty than in the fore- 

 going. 



If the Earth were alone, that is to (ay, not 

 affected by the Actions of the Sun and Moon, 

 at is not to be doubced, but the Ocean, being 

 equally prefs'd by the force of Gravity towards 

 the Center, would continue in a perfect Stagna- 

 tion, always at the fame height, without either 

 Ebbing or Flowing; but it being here demon- 

 flrated, that the Sun and Moon have a like Prin- 

 ciple of Gravitation towards their Centers, and 

 that the Earth is within the Activity of their At- 

 tractions, it will plainly follow, that the Equali- 

 ty of the prcffure of Gravity towards the Cen- 

 ter will thereby be difturb'd ; and though the 

 fmal'nefs of thefe Forces, in refpect of the Gravita- 

 tion towards the Earth's Center, renders them al- 

 together imperceptible by any Experiments we 



can 



