FLOW OF WATER. 11 



By this same simple means, he settles by actual 

 trial, and measures (what had been foreseen by 

 theory) the deviation of the form of the earth from 

 that of a sphere ; and by its aid he values, both 

 as to kind and as to amount, the attractive power 

 that governs the particles of earth, and binds them 

 together as a whole, which no force from without 

 can sunder. 



The same cause which gives rise to the swinging 

 of the pendulum, forces every moveable body to 

 strive for such a position as shall place its centre 

 of gravity as low as possible, and as shall ensure 

 as far as possible its remaining in a state of rest. 

 First then we see that water runs down from 

 mountains and sloping land, till it can find a basin 

 which allows of no escape, in which it can take 

 for itself a level surface, that is, one agreeing 

 with the curvature of the earth, and in which it 

 thus can come to rest. The surface of flowing 

 water in brooks and rivers is not level ; if it were 

 so, that is, if the direction of the gravitation of the 

 moving particles were perpendicular to the surface, 

 the force that draws them onward would cease, 

 and the motion which they had already would 

 quickly be stopped by the resistance of the river's 

 bed. The slope of the surface of running water, 

 or its fally agrees in general with that of the bed 

 on which it moves, and is therefore usually greater 

 in highlands than in plains. The speed of the 



