Abstract

This paper may be regarded as a continuation of two which I have already had the honour to communicate to the Geological Society; and with a view of preventing misapprehension, I think it will be well to state clearly what I am seeking to demonstrate, and the mode in which I am endeavouring to effect my purpose.

As I have already stated, I am unable to accept the theory which was put forward by Professor Ramsay in a paper communicated to this Society, a theory which attributes the existence of the various Alpine lake-basins mainly to the erosive action of the glaciers by which they were once occupied. I do not deny the possibility of some lake-basins being the result of glacial erosion, or of others being considerably modified by it; the position which I am endeavouring to maintain is that none of the greater Alpine lake-basins has been primarily so formed, or indeed has undergone any important secondary modification. I will add that all the opportunities which I have had of examination of lake-basins in this and other countries have suggested to me serious doubts as to the excavating power of glaciers; and, notwithstanding the weighty arguments which have been advanced in favour of this theory in more northern regions, I am still disposed to believe, from what I have seen, that it is only under very exceptional circumstances that they can in any proper sense of the word excavate a rock-basin.