S50 THEORIES OF WERNER AND BUTTON. ALPINE VALLEYS. 



neath, it seems to follow as a necessary corollary, that the surface 

 would be unequally elevated and broken into inequalities by the same 

 cause ; unless we suppose, that every part presented an equal degree 

 of resistance to the moving force. There must, therefore, have 

 been originally, inequalities or valleys, which determined the direc- 

 tion of the water-courses in the first instance, though the form of 

 these valleys may have been subsequently modified by the action of 

 water. That all valleys have been excavated by the rivers that flow 

 through them, is opposed by many decisive facts. Before their ex- 

 cavation, the water must have had less force than at present, as the 

 fall would be gentle ; and the present effect of rivers in Igrge valleys, 

 is not to excavate them deeper, but to fill them with alluvial de- 

 positions. 



There are numerous deep valleys in the Alps, that are closed at 

 one end by steep mountains or perpendicular walls of rock, and 

 which were originally closed, and are now nearly closed, at the other 

 end also. Such are the valley of Thones, near Annecy, the valley 

 of Chamouni, and on a larger scale, the valley of Geneva. It is 

 evident that the valley of Thones, and that of Geneva, have once 

 been filled with water, and formed lakes : by an earthquake, or by 

 the erosion of water, a fissure has been made, which has drained the 

 greater part of these valleys ; but it is obvious that the valleys could 

 not have been formed by the original lakes, or by the rivers that 

 flowed into them. If valleys were formed by the erosion of rivers, 

 the lakes through which these rivers flow, must have long since been 

 filled up by the materials brought into them. To say that the lakes 

 were once deeper than at present, is giving up the theory ; for lakes 

 are only the deeper parts of valleys. 



Had the valley of Borrowdale, in Cumberland, been excavated 

 by the water that flows from it, the lake of Keswick, at its entrance, 

 must have received all the materials, and been long since choked up. 

 Or had the valley of the Rhone, ten thousand feet deep and sixty 

 miles in length, been excavated by the Rhone, the quantity of matter 

 brought down by this river, would not only have filled the lake of 

 Geneva, into which it empties itself, but the broad valley in which 

 the lake lies, must also have been filled up, and raised to the height 

 of the Jura. That the Lake of Geneva, and all lakes into which 

 large rivers flow, are gradually filling up, has been before stated ; 

 but the valley of the Rhone is not, nor are other valleys becoming 

 deeper. The upper part of this valley, as before stated, has evi- 

 dently been itself a lake, closed in, or nearly so, by the rocks at 

 Martigny. 



The action of torrents in Alpine districts may have been sufficient 

 to widen fissures already made, or to scoop out glens, in the softer | 

 beds on the sides of mountains; but they appear inadequate to the I 

 original formation of large longitudinal valleys. Water-courses run- 

 ning on the edges of nearly vertical beds, may scoop out a portion 



