Ch. XV.] 



FOEMED BY RAIN 



337 



water. 



matrix 



from the decomposition of the red porphyry, of which the 

 whole of this country is made up, 



numerous 



and largest of the capping-stones consist of the same por- 

 phyry ; but blocks of granite, two or three feet in diameter, 



must have come from 



immediate 



neighbourhood, are also scattered sparingly through the 

 reddish matrix. The Finsterbach, besides cutting through 



mass 



of several yards through the underlying porphyry, or at one 

 point through a sandstone of the Lower Trias which occasion- 

 ally appears in this region. The series of geological events 

 of which we have evidence both in this ravine and in that of 



Katzenbach 



ram 



will be better understood by reference to 

 .17. First a valley ah c was excavated in 

 a country consisting almost entirely of red porphyry. 

 Secondly, this original valley was filled up in its lower part by 



Fig. 17 









4^ 









r >V> 



/ 



Diagram illustrative of the Formation of Earth-pillars. 



a be. Outline of original valley hollowed out of porphyry. 

 dbed. Moraine left by glacier as it receded up the valley. 



/. Chasm cut by torrent through the moraine before the first earth- 

 pillars were formed. 

 bi. Channel of torrent excavated in porphyry below the level of 



the original valley. 

 gih. Outline of the present valley, the earth-pillars marked by dark 



lines being still standing. The faint outlines between g and h 



represent portions of earth-pillars and their capping-stones 

 now destroyed. 



moraine matter, dbed, probably left by a large glacier as it 

 retreated up the valley at the close of the Glacial Period. 



VOL. I. 



z 



