Lesley.] J^QQ [March 



nian and Silurian lakes, to the original shores of the Laurentian Con- 

 tinent. 



We cannot regard, therefore, without some natural chagrin, the 

 latest treatment of the subject by Professor Tyndale and Professor 

 Ramsay, of England ; for these accomplished observers not only take 

 up our own old views with all the empressement of new discoveries, 

 but make what seems to us the very absurd attempt to carry the 

 petty energies of mountain floods and local glaciers up to the 

 work of excavating, not merely lakes like those of Como, Constance, 

 and Geneva, but such seas as Lake Huron and Lake Superior. It 

 is gratifying, however, to see that such views can be refuted by 

 European observers, who have never encountered the phenomenal 

 problems of America. The impossibility that a moving glacier after 

 descending to sea level, should excavate the bed of a lake, and con- 

 tinue to move up and over its farther end, even taking the smallest 

 Alpine lake known for an example, is admirably demonstrated by Mr. 

 Ball in the February number of the London, Edinburgh, and Dublin 

 Philosophical Magazine for 1863. If this be not possible for the 

 tarns among the valleys where glaciers are at home, how can it be 

 possible for lakes and seas, where the existence of glaciers at any 

 epoch is a theory ? And how reckless of all consequences must that 

 theory be, which reads an incantation to these icy demons, to accom- 

 plish the symmetrical erosion of a triangular area of earth-surface a 

 thousand miles on each side long, the southern angle of which touches 

 the parallel of 33° ! 



Professor Ramsay calls attention to the remarkable fact that the 

 lakes of Europe and America seem to be confined to the scratched 

 and grooved portion of the hemisphere, and that they are not found 

 further south than the drift, except in Alpine, that is to say, in gla- 

 cial regions. This is a coincidence, indeed, which ought to harmonize 

 the two phenomena under some theory ; but not necessarily subordi- 

 nate the one to the other as effect and cause. I have no satisfactory 

 explanation to give for the coincidence. The special reasons for the 

 existence of each separate lake can be easily pointed out. The dam- 

 ming back of the waters of the New York Devonian lakes, including 

 Erie and Huron, are due to the gentle northward rise of their floor- 

 rock. Lakes in the same soft Devonian measures, are numerous 

 along the valley of Pennsylvania, at the foot of the Alleghany Moun- 

 tain, but only where the measures are gently inclined. Lakes dis- 

 appear from the map as the eye passes southeastward over the more 

 upturned regions. Steepness of dip is hostile to deep excavation. 



