378 TAYLOR POST-GLACIAL CHANGES IN ITALIAN AND SWISS LAKES 



relatively higher levels than formerly ; but this kind of change is not so 

 evident on ordinary examination, and its amount is sometimes hard to 

 determine. The only one of these lakes examined was lake Lucerne. 

 No evidence of a higher lake level was found, but, on the other hand, 

 no very certain evidences of submergence were seen. Descriptions of 

 lakes Zurich and Constance indicate the same conditions as for lake 

 Lucerne. It seems probable that these lakes were affected in the same 

 way, and that more detailed study would show .southward submergence 

 in all of them. 



Conclusions 



The observations here recorded were not sufficiently accurate to deter- 

 mine the exact direction of tilting for the lakes mentioned, but they seem 

 to show a differential elevation having a generally northerly direction. 



In another part of his work Forel discusses the origin of lake Geneva. 

 He rejects the glacial theory and regards the basin of the lake as merely 

 a prolongation of the Rhone valley, made when the mountains stood 

 1,000 meters higher than now. The lake he regards as having origi- 

 nated by a more recent general depression of the mountains to this 

 amount, while the Swiss plain remained relatively unaffected. It 

 would seem natural for one holding Forel's view to explain the Italian 

 lake basins in the same way. If this be done, then the deformation 

 here recorded is due to a resilience of later date than Forel's depression* 

 and would seem to indicate that both depression and resilience were 

 confined mainly to the central region of the Alps. To the present writer 

 glacial agencies seem to have been, perhaps not the sole, but at least the 

 main, cause of all the deeper Alpine lake basins. On this view Forel's 

 recent depression of 1,000 meters would be eliminated, and a cause of 

 tilting must be sought elsewhere. 



In " Das Antlitz der Erde " Suess holds that the Adriatic and Black 

 Sea depressions are of recent origin. The shores of the gulf of Genoa 

 suggest a similarly recent depression. A study of the slopes of the Po 

 valley and the floor of the Adriatic sea shows that if the modern delta 

 of the Po, reaching 40 or 50 miles westward from the present mouth of 

 the river, be eliminated, the slope from Pavia to the head of the delta 

 and thence on the Adriatic sea floor out to the bathymetrical line of 100 

 meters is so nearly uniform as to strongly suggest a subaerial or fluvial 

 origin for the whole of it. If the recent movement of depression sup- 

 posed by Suess took place, it may have produced as one of its mani- 

 festations the observed deformation of the Italian and Swiss lakes. This 

 seems to the writer a more likely cause than that suggested along the 

 lines laid down by Forel, and it agrees with the fact that the Swiss lakes 

 appear to have been tilted in the same general direction as the Italian. 



