R. M. Beeley — Mountain Building. 119 



However, the bending of the rock stratum, although resulting in 

 a general stretching, would also produce local compression. That 

 a mountain range may be resting upon a liquid or very plastic base, 

 as would appear to have been the case with the old mountain range 

 the "roots" of which are now the Canadian shield, leads to some 

 important consequences. 



My chief endeavour has been to show that there are other ways 

 of accounting for anticlines and synclines than by compression. 

 To further illustrate the suggestion some remarks will be made 

 concerning the history of the Swiss Alps. 



The structure of the Swiss Alps was for many years an enigma ; 

 but there seems every reason to believe that the broad outlines of 

 their architecture are now known. 



At the base we have crystalline gneisses, schists, and granites. 

 They form the lofty massifs of Mont Blanc, the Aiguilles Eonglies, 

 the Bernese and Gothard Alps, etc. They once formed a highly 

 worn or much denuded surface, upon which the newer rocks were 

 deposited. The older rocks are chiefly crystalline masses and some 

 Carboniferous strata, while the overlying bedded series range in age 

 from Permian and Triassic down to early Cainozoic. These sediments 

 filled up the valleys and submerged the mountains of the old land. 

 The area over which they wei-e deposited was a subsiding one. We 

 are told that after the deposition of these sediments the sea bottom 

 was raised and a low flat undulating land area was formed ; and that 

 great rock-sheets from the north and south were then thrust up 

 gentle inclines over this land. The chief of these sheets are the 

 Helvetian, Lepontine, East-Alpine, and South-Alpine. That these 

 sheets could have been thrust up and over each other and over a 

 rising land seems quite impossible. That they are there, and have 

 travelled great distances, is certain ; but the conditions under which 

 they have travelled require further elucidation. 



It may be that the sea in which these early sediments were 

 deposited became very deep, and that the rock-sheets slowly slid into 

 this deep sea one after the other; for in most instances the upper 

 sheets are formed of older rocks than the lower ones. The covering 

 of the sea bed by cold rock-sheets instead of water would deepen the 

 sea, whilst the removal from the shallow water or land of the cold 

 rock-sheets would be replaced by rising warmer rock. This would 

 increase the gradient and result in further slides. 



The whole mass was then raised and folded. It is very doubtful 

 if this folding was the result of pressure: rather may it have been 

 due to the differential vertical earth movements resulting from 

 denudation. During the rising of the Alps great deposits were 

 formed along the margins of the mountains. It is a peculiar fact 

 that some of tlie rock folds have moved outwards and been thrown 

 over these deposits. Indeed, it may be that overfolds are not due to 

 thrust ; but are due to the flow of the elevated rocks near the margins 

 of the mountains towards or even over the surrounding low lands. 



It is rather a rash thing perhaps to suggest that compression has 

 not been a prime factor in earth movements ; but the difiiculties that 

 can be urged against the idea are so very great, that it cannot be 



