334? OUTLINES OF NATURAL PHILOSOPHY. 



which the equilibrium of the forces acting on 

 them would require ; so that they oscillate con- 

 tinually, alternately approaching to that figure, 

 and receding from it. 



To resolve the problem of the tides, including the 

 condition of the diurnal motion, is a matter of 

 great difficulty, and requires all the latest improve- 

 ments of the Calculus. LA PLACE is the only one 

 who has ventured to undertake it, and he calls it 

 " le Probleme leplus epineux de toutc la Mecanique 

 " Celeste" Exposition du Syst. du Monde, chap. 

 JO. p. 248. edit. 2<fc. His solption agrees with the 

 phenomena more nearly than could be expected, 

 considering that the continuity of the Ocean is 

 much interrupted by the land, and that this, toge- 

 ther with the inequalities in the depth of the sea, 

 the friction against the bottom and sides, &c. are 

 all causes impossible to be submitted to analysis. 



339. The oscillations excited in the Sea, by 

 the force of the Sun, and by that of the Moon, 

 are similar to one another, and are so combined, 

 that each effect takes place in its full amount, 

 independent of the other. 



The law which connects the rise and fall of the tide 

 with the time at any place, is expressed by a geo- 

 metrical construction. 



340. Let 



