444 ON THE ACTION OF RUNNING WATEttS. 



tated which they held in suspension. Besides, we have 

 shown that many rivers, on leaving the mountains, tra- 

 verse lakes, in which they deposit all the earthy matters 

 suspended in their waters. This deposition is particularly 

 striking in all the considerable rivers, which descend from 

 the ridge of the Alps toward the north-west and south-east 

 of that chain of mountains. These rivers meet, at the 

 opening of the valleys they flow through, lakes, which they 

 traverse, and which seem intended for their purification. 

 Thus, on the northern side, we see the Rhone traversing 

 the lake of Geneva ; the Aar, the Lakes of Brientz and 

 Thun ; the Reuss, the Lake of the Four Cantons ; the 

 Linth, the Lake of Zurich ; the Rhine, the Lake of Con- 

 stance. On the south side, the Lac Majeur is traversed 

 by the Tessin, the Lake of Como by the Adda, the Lake 

 Disco by the Oglio ; the Lake of Guarda by the Mincio, 

 Sec. Now, these lakes, which are only themselves deeper 

 parts of the valley, would have been filled up by the 

 debris conveyed to the valley, if this valley had the 

 origin attributed to it. Proceeding from one hypothesis 

 to another, it might perhaps be supposed that these lakes 

 may have been sufficiently deep to swallow up all the de- 

 bris of the valley, without being chocked up. But, ra- 

 ther than admit such suppositions, why not grant that 

 the same unknown cause which has scooped out the 

 lake, has also scooped out the valley which is only a 

 continuation of it ? 



4. But if facts had proved that the waters degrade the 

 rocks, scoop them out, and perpetually remove their de- 

 bris, we might perhaps be induced to admit that un- 

 known causes, of which we are absolutely ignorant, and 

 of which we can form no idea, have given to the original 



