358 Prof. B. Studer on the Slow Elevation 



to have been deposited in water of a uniform and generally 

 slight depth, in a locality where marine and freshwater con- 

 ditions occasionally replaced each other. 



The molasse without doubt suffered a slow and continuous 

 downward movement, so as to maintain the moderate depth 

 above indicated, notwithstanding the continual filling up by 

 new depositions. Hence we conclude that a fissure existed 

 between the molasse and the secondary rocks of the Alps 

 (which have not participated in the subsidence), without doubt 

 in consequence of the previous elevation of the latter. 



2. The Aar near Berne, the Sarine near Freiburg, and other 

 rivers, have serpentine courses, like rivers of low plains with 

 little fall, although their deeply-cut channels, traversing an 

 undulating country, have steep banks, thirty or forty metres 

 high. The stair-like terraces of the river beds show that 

 their erosive operations alternated with periods of rest. The 

 material thus cut through generally consists of " old alluvia," 

 i.e., gravel and sand, with indistinct horizontal stratification ; 

 but often in the lower portion of the channel, and to the 

 height of ten metres, the perpendicular banks are composed 

 of molasse. 



A stream, however, that has force and fall enough to ex- 

 cavate so deep a channel, can no longer describe a serpen- 

 tine; hence, these rivers must at first have flowed over 

 ground having only a slight declivity, but which, after the 

 serpentine course was formed, became more and more steep, 

 thus giving rise to the deep cuttings above mentioned. These 

 conditions may have simply happened thus : — the^upper part 

 of these river courses has been gradually raised by the 

 elevation of the continent; and this is proved: — 1. By the 

 traces of a previous filling up of the alpine valleys, some 

 hundred feet above the present surface of the rivers, and, 

 2. by the preservation of the horizontality of the strata, — in 

 contrast with the verticality and folding of the molasse beds 

 previously caused by secondary alpine strata. 



The elevation of these alluvia can only have taken place 

 subsequently to the distribution of the erratic boulders, as the 

 serpentine river-courses cut through gravel and loam,inclosing 

 large alpine blocks, which, however, are never found on the 



