14 GRAVITY, AND ITS EFFECTS. 



are, therefore, truly governors of the water-level of 

 a river. Thus, the great lakes of Switzerland, all 

 but one of which pour off their waters through the 

 Rhine, gather during the spring a great part of 

 the snow-water from the mountains, and letting 

 it off slowly, usually keep plenty of water in the 

 Rhine till the summer is pretty far advanced. 



The stock of water in the mountains would be 

 thus soon drained off, were it not that the heat 

 returns it to the air in the state of vapour, which 

 is then set down again on the high lands as rain 

 and snow. Thus the waters travel in an ever- 

 lasting round, which it seems must end at last in 

 making smooth every unevenness on the face of 

 the earth. 



By the solvent power of water, some parts of the 

 solid surface of the earth are always being made 

 liquid; others, laid open to the combined influ- 

 ences of water and air, are changed in their nature, 

 and, becoming weathered, moulder away. Thus 

 the higher parts of the earth are brought, by 

 degrees, into a moveable condition, and are carried 

 down, partly by their own weight, partly by the 

 force of running water, to the valleys, the plains, 

 and the sea. We see this levelling going on 

 everywhere on the solid land. Stones, and masses 

 of rock, get loosened from the hill-sides, and are 

 slowly filling up the hollows. Even the very 

 mountain-peaks, slowly undermined by the trick- 



