50 PEOCEEBINGS OF THE GEOLOGICAL SOCIETY. 



slopes, may in the Subalpine region have proceeded until there were 

 left only detached remnants of the upraised Lower Molasse, which 

 were saved from total removal by the encroaching deposition of the 

 torrential detritus forming the Upper Molasse. Subsequent com- 

 pression coincident with a sinking of the mountain- mass, which 

 also seems to have gone to greater lengths in the Alps than in the 

 Himalayas, might in such a case obliterate any clue to such an 

 original relation. The necessity for suggesting this interpretation 

 is the more surprising, since almost all Alpine geologists agree that 

 the actual boundary of the Molasse is approximately in the position 

 of the original limit of deposition. None state explicitly what is 

 supposed to have become of the original contact. 



The much debated question of the formation of the great Alpine 

 lakes at once finds a place in the hypothesis I am proposing. This 

 hypothesis assimilates the main feature of the explanation given by 

 Sir Charles Lyell, as already noticed, and is free from the discre- 

 pancy I have pointed out in that explanation. The presence of 

 these lakes is corroborative evidence of the sinking of the mountain- 

 mass and the rising of the fringing zone, of which more direct proof 

 has been sought in the structural features. I think that the formation 

 of these lakes was more or less coincident with the contortion of the 

 Molasse, and with the concurrent partial elevation of the zone at the 

 base of the mountains, both results being due to the depression of 

 the central region. A period of continental elevation, such as the 

 tuberance of M. de Beaumont's theory, succeeding to a period of 

 tranquillity, would have arrested the deposition of the Molasse, and 

 brought on a period of denudation, just as was supposed by M. 

 Kaufmann. The great valleys then received their final clearing out, 

 preparatory to their conversion into lake-basins. In due time de- 

 pression of the culminating regions of elevation, and compression, 

 with reflex partial rising of the border-zone would supeiwene. 

 Although adopting the maxim that the original main drainage of 

 any area of elevation must be transverse to the axis of that area, 

 since any such drainage must pari passu develope secondary 

 drainage, transverse to itself, and therefore longitudinal with refe- 

 rence to the axis of elevation, one may admit with M. Kaufmann 

 some small influence to these secondary lines in guiding the lines of 

 contortion (which are essentially longitudinal) when the compressing 

 action began to operate. The chief objection to this mode of relation 

 of the actual general coincidence of these features is, that the reg-u- 

 larity and continuity of the lines of flexure seem incompatible with 

 so very accidental and superficial an influence as that of secondary 

 lines of drainage. 



It may be said that the Himalayan parallel fails to support me 

 here ; there are no great lakes along the base of this range. Sir 

 Charles Lyell has suggested that the absence of glaciers in the sub- 

 tropical latitudes may account for the want in that position of lakes 

 analogous to those of the Alps. It might have been known from 

 the first that this removal of an admitted obstacle to his theory was 

 of little avail ; for alluvial flats holding the place of the lakes in the 



