194 THE TARNS OF THE CANTON TICINO. [May I906, 



It struck him as curious that the soluble rocks should be dissolved 

 only at some spots, and not at others where the active movement 

 of streams would make one expect solution to be more rapid. Such 

 irregularity pointed to some additional local agency, such as gas- 

 laden springs, in determining the site of some of these lakes. Their 

 occurrence also at the junction of different rocks would be partly 

 explained by the crushing produced in earth-movement by differential 

 shearing at such junctions. He quite agreed that glacier-action 

 did not explain their origin. He would also remark that the 

 minerals of the mica-group were much more soluble in a solution 

 of carbon-dioxide than was usually supposed. 



The Author thanked the President and Prof. Bonney for their 

 kind remarks. In reply to the latter, he said that he thought the 

 division on Dr.K. von Fritsch's map, between the rauchwacke and the 

 calcareous schist at the western end of Lake Eitom, rather an artificial 

 one, at all events so far as solubility was concerned ; and there may 

 have been no really-insoluble ridge, as he had traced massive 

 calcareous rocks round that end of the lake as far as the gully 

 shown in the photograph, while dolomite came in again still farther 

 round at the lake-level. With this exception, he quite agreed with 

 Prof. Bonney as to the difficulties in accounting for everything by 

 solution. In regard to the excavation of Lago Tremorgio by ice, he 

 had set out fully in the paper the difficulties that he found in 

 accepting this explanation. He thought that the reversal of the 

 Eitom drainage had begun at a much higher level. The lakes, 

 however, did not depend on this. 



