46 Transaction?. 



daring one, and if it rested nierel}? on tlic grounds that we 

 cannot understand how tliis lioUow could be produced in any 

 other way, it would indeed have rather a precarious founda- 

 tion. Fortunately, liowever, there is evidence of a more 

 positive nature, which goes far to substantiate it. Allow me, 

 shortly, to draw your attention to this evidence, which we 

 will consider under three heads — (a) ice as a lake-forming 

 agent, (6) proofs of glacial conditions about the commence- 

 ment of the Permian Era, (c) tlie favourable contour of the 

 STOund for the formation of a mass of ice. 



o 



(5.) Evidence in Favour of a Glacial Origin. 



(a) Ice AS A Lake-forming Agent. 

 By the great majority of our most eminent living geolo- 

 gists, amongst whom I need only mention Kamsay and 

 Geikie, the theory is held that most existing lake basins 

 were first formed during the Glacial Epoch, and were due 

 not to elevation or subsidence, but to actual erosion by 

 glaciers, in proof of which it is shown that lakes are exceed- 

 ingly numerous in those countries where erratic and 

 other signs of glacial action exist ; and that they are com- 

 paratively rare in tropical and subtropical where no signs 

 of ice action exist. That is to say that beyond glaciated 

 countries lakes almost abruptly <;ease. This is a coincidence 

 Avhich could hardly be accidental, and the well-known 

 erosive action of glaciers makes it all the more probable that 

 they were the principal if npt the sole agents in producing 

 our present lake basins. Without, however, going so far as 

 to suppose that even most existing lake basins ha,ve origi- 

 nated in this manner, it is sufficient for our purpose to un- 

 derstand that ice is a great lake-forming agent. 



(b) Proofs of Glacial Conditions during Permian 

 Times. 



Passing now to the direct evidence bearing on the 

 subject, let us consider, in the second place, the proofs of 

 glacial conditions existing during the time when this basin, 

 was scooped out. 



