Wegener's Displacement Theory. 845 



It is evident, then, that Wegener's reconstruction implies much 

 more than fracturing of the masses of Sal. They must have 

 altered their shapes. No one knows how much they have altered, 

 or which of them have altered ; and to deduce their original forms 

 would require a much greater knowledge of their geological structure 

 than we possess, and a much more critical examination than Wegener 

 has bestowed upon the question. 



It will be useful now to summarize the evidence with regard to the 

 Atlantic. If east and west are to be brought together both in the 

 north and in the south, there must be great distortion. One side 

 or the other, or both, must be plastic. If they are moulded so as 

 to fit, as Wegener fits them, the following points may be noticed. 

 If we accept Wegener's statement about the gneiss of Labrador, 

 then we know, from the Memoir on the North-west Highlands, that 

 there must be a sudden change of strike at the junction. At the 

 junction, too, the violent Caledonian movements of the British 

 Isles must suddenly die down into the less conspicuous movements 

 of the sanie age in Newfoundland. The Armorican folds fit very well. 



Again, if we accept Wegener's statements about South America, 

 and assume that both in Africa and South America there is a definite 

 line where a change of strike occurs, then the position of that line 

 on one side of the junction lies hundreds of miles away from its 

 position on the other. Lastly, in South Africa the folds bend north- 

 ward near the western coast, and there is no evidence that they were 

 ever continued farther west. It may be noted in passing that the 

 ranges in Buenos Aires have not yet been closely examined. 



We may now turn to a few general considerations. Apart 

 altogether from mountain-building movements, due to crumpling, 

 it is certain that large areas of the Sal have sunk beneath the sea 

 and have risen again, not only once but many times. If we admit 

 the presence of deep-sea deposits, their surfaces must have reached 

 the level of the Sima. We know, at least, that they sank below the 

 . hundred-fathom line, which Wegener takes as the general boundary 

 between Sal and Sima. Some of these movements have been 

 oscillations, one portion of the mass rising while another fell. Others, 

 such as the Cenonianian transgression, have been almost world-wide 

 in their effects. The former, perhaps, may be ascribed to tilting of the 

 blocks. The sunken areas would then be subjected to an upward 

 hydrostatic pressure, and if the Sal is as plastic as Wegener's recon- 

 struction requires, it is not easy to understand why it did not bend 

 instead of sinking so deeply into the Sima as it must have done. 

 The widespread movements are still more difficult to explain. Some 

 cause is required which would press all the masses more deeply into 

 the Sima ; and it must have been a temporary cause, for they rose 

 again. 



A problem which Wegener scarcely touches is the fornaation of 

 the separate masses of Sal. He imagines that at one time the Sal 

 formed a thin skin completely covering the globe. The sea was then 



