1884.] on the Building of the Alps. 67 



proceed south of the lake of Geneva, changing rapidly in the neighbour- 

 hood of Grenoble from a strike N.E. to S.W. to one from N.W. to S.E. 

 This subject, however, is too complicated to be followed further on the 

 present occasion. I will only add that the singular trough-like 

 upland valleys, forming the upper parts of some of the best-known 

 road passes — as, for instance, the Maloya — which descend so gently to 

 the north, and are cut off so abruptly on the south, seem to me most 

 readily explained as the remnants of a comparatively disused drainage 

 system of the Alps. 



It remains only to say a few words on the post-tertiary history of 

 the Alps. We enter here upon a troubled sea of controversy, upon 

 which more than the time during which I have spoken might easily be 

 spent; so you will perhaps allow me to conclude with a simple 

 expression of my own opinion, without entering into the arguments. 

 That the glaciers of the Alps were once vastly greater than at the 

 present time is beyond all dispute ; they covered the fertile lowlands of 

 Switzerland, they welled up against the flanks of the Jura above Neuf- 

 chatel, they crept over the orange gardens of Sirmio, and projected 

 into the plains of Piedmont. By their means great piles of broken 

 rock must have been transported into the lowlands; but did they 

 greatly modify the peaks, deepen the valleys, or excavate the lake 

 basins ? My reply would be, " To no very material extent." I regard 

 the glacier as the file rather than as the chisel of nature. The Alpine 

 lakes appear to be more easily explained, as the Dead Sea can only bo 

 explained — as the result of subsidence along zones roughly parallel 

 with the Alpine ranges, athwart the general directions of valleys 

 which already existed and had been in the main completed in pre- 

 glacial times. To produce these lake basins we should require earth 

 movements on no greater scale than have taken place in our own 

 country since the furthermost extension of the ice-fields. This 

 opinion as to the origin of the lakes is, I believe, generally held 

 to be a heresy, but it is a heresy which has been ingrained in me by 

 some twenty years of study of the physiography of the Alps. 



[T. G. B.] 



F 2 



