340 Philip Lake — 



much smaller force may be sufficient, for the movements imagined 

 are imperceptibly slow and the time allowed indefinitely long. 

 Wegener believes that the predominant movements have been 

 towards the Equator and towards the west, and he offers some 

 suggestions to account for this, but he does not profess that the 

 problem has been solved. His contention is that whether the cause 

 is known or not the movements have actually taken place. 



Much of his evidence is superficial. Pie supposes, as others have 

 supposed, that South America was connected with the Antarctic 

 continent through Graham Land. As the whole mass was pushed 

 westward through the resistant Sima, the narrow isthmus bent and 

 broke, and the fragments trailing behind formed the island arc of 

 South Georgia, the Sandwich Group, and the South Orkneys. 



Similarly, he attributes the elbow of the Malay Peninsula and 

 the eastward curve of the Malay Islands to the resistance of the Sima. 

 In connexion with this example it is interesting to notice a suggestion 

 made by Osmond Fisher. ^ He is considering Sir George Darwin's 

 idea that the Pacific depression may be the scar left where the moon 

 separated from the earth, and he frankly admits that he is indulging 

 in a far-fetched speculation. He thinks it possible, however, that the 

 islands of this part of the world may be fragments of the broken 

 crust which have floated slowly towards the cavity left when the 

 moon was thrown off.^ But this belongs to an early period of the 

 earth's existence. He never supposed that such movements were 

 taking place now, and he did not consider the geological history of 

 the islands in question, a matter which Wegener also entirely ignores. 



But Wegener has evidence more impressive than this. According 

 to him, if we take the masses of Sal as they exist to-day and allow 

 movement, they may be fitted together like the pieces of a puzzle, 

 and when this is done correctly the tectonic structures of each piece 

 are continued into the piece which has been fitted to it. If this can 

 be proved, few geologists will doubt the truth of his conclusions. 



It is necessary, first, to determine the present shapes of the existing 

 masses, and it should be remembered that he is not concerned with 

 the division bet»veen land and water, but with the division between 

 Sal and Sima. Here he is inconsistent. According to his own idea 

 the masses of Sal float in the Sima and the surface of the Sima forms 

 the floor of the ocean. The boundary of the Sal should therefore 

 be drawn at the foot of the continental slope, where the continental 

 masses begiu to rise from the ocean-floor. Instead, he takes the edge 

 of the continental shelf as the margin of the Sal, though, as he says, 

 he allows himself a certain freedom. This can only be correct if the 

 surface of the Sima rises several thousands of feet as it approaches 

 the masses of Sal, and he gives no reason for such a rise. 



1 Physics of the Earth's Crust, 2nd ed., 1889, p. 339. 



^ Pickering's idea {Journ. of Geol., vol. xv, p. 23) is similar to tliis, but he 

 imagines much more extensive effects. He supposes the separation of Africa 

 from South America to be due to the same cause. 



