110 DISSERTATION SECOND. [pabtu. 



philosophy of Plato and Aristotle were never more per- 

 fect than when they came from the hands of their respec- 

 tive authors, and a legion of commentators, with all their 

 efforts, did nothing but run round perpetually in the same 

 circle. Even Descartes, though he had recourse to phy- 

 sical principles, and tried to fix his system on a firmer 

 basis than the mere abstractions of the mind, left behind 

 him a work which not only could not be improved, but 

 was such, that every addition attempted to be made de- 

 stroyed the equilibrium of the mass, and pulled away 

 the part to which it was intended that it should be at- 

 tached. The philosophy of Newton has proved suscep- 

 tible of continual improvement 5 its theories have explain- 

 ed facts quite unknown to the author of it ; and the ex- 

 ertions of La Grange and La Place, at the distance of 

 an hundred years, have perfected a work which it was 

 not for any of the human race to begin and to complete. 

 Newton next turned his attention to the phenomena of 

 the Tides, the dependence of which on the moon, and in 

 part also on the sun, was sufficiently obvious even from 

 common observation. That the moon is the prime ruler 

 of the tide, is evident from the fact, that the high water, 

 at any given place, occurs always nearly at the moment 

 when the moon is on the same meridian, and that the 

 retardation of the tide from day to day, is the same with 

 the retardation of the moon in her diurnal revolution. — 

 That the sun is also concerned in the production of the 

 tides is evident from this, that the highest tides happen 

 when the sun, the moon, and the earth, are all three in 

 the same straight line ; and that the lowest, or neap tides, 

 happen when the lines drawn from the sun and moon to 

 the earth make right angles with one another. The eye 

 of Newton, accustomed to generalize and to penetrate 

 beyond th^ surface of things, saw that the waters of the 



