Structure of the Eastern Alps. 415 



pended. This, at least, is proved by every torrent descending from the chain 

 to the levels of the tertiary plains. 



Considered on a great scale the tertiary sand and conglomerates of south- 

 western Bavaria may be described as a series of inclined planes, down which 

 the rivers roll, in nearly undeviating lines, till they mingle themselves with 

 the Danube, presenting, in this respect, a striking contrast to the old sinuous 

 channels and gorges through which the waters struggle to escape from the 

 higher Alps. Some of these rivers run brawling over the surface like the 

 waters of a great land-flood, not having found any well defined course ; and 

 ages must yet elapse before they have worked for themselves anything like 

 permanent channels. Under such circumstances the alluvial deposits are 

 coarse in texture, and are spread far and wide, and, in future ages, should the 

 rivers ever change their channels, may be mistaken for diluvial formations. 



We do not mean by this remark to assert, that there is no distinction 

 between alluvium and diluvium (to adopt the technical language now in use, 

 though not perhaps well chosen), or to confound the detritus of river channels 

 with the masses of incoherent matter left on the surface of the land by seas 

 retiring after some period of elevation. What we contend for is, that on the 

 confines of the Bavarian Alps (and the same remark applies to the outskirts of 

 many other mountain chains), the two classes of deposits cannot be easily 

 separated from each other : and in proof of this we may add, that in the parts 

 of Bavaria above described, as well as in other tertiary regions of the flanks 

 of the Alps, bosses of decomposing tertiary conglomerates are often mistaken 

 for patches of diluvial gravel — that where the beds are horizontal, and even 

 in some places where they are considerably inclined, we find it difficult to 

 draw a line between the diluvial gravel and the newer tertiary conglomerates 

 — and that the recent gravel on the banks of the rivers often differs very little 

 from the incoherent matter which caps the neighbouring hills. 



That such must be the case is obvious, when we further consider the 

 manner in which the forces of degradation have acted on the newest deposits 

 on the north flanks of the Alps. By a movement of elevation the sea has been 

 driven from the whole region, and the retiring waters have left traces of their 

 ravages on the edges of the uplifted strata. It is to this very action that we 

 have referred the horizontal conglomerates of the Arzt and Untersberg sec- 

 tions*, and other phenomena above noticed. But every movement of eleva- 

 tion must produce a destruction of equilibrium among the waters of inland 

 drainage, and must, in mountain chains, have been necessarily followed by 

 debacles, capable perhaps of producing such horizontal masses as those above 



* Plate XXXVI. liir. 6. & 9. 



