360 SUMMARY OF CAREER CHAP, xi 



graphy of the region, when the streams descended 

 from a central, still unremoved dome or ridge of 

 chalk. Extending this process of reasoning, he after- 

 wards discussed the main causes whereby the rivers of 

 England had been led to flow in the courses which 

 they now follow. There was undoubtedly a good deal 

 of speculation in this discussion, but his treatment of 

 the subject was full of suggestiveness, and pointed out 

 the direction in which, with perhaps a larger array of 

 facts, the question might eventually be solved. 



Subsequently he attacked the history of individual 

 rivers, working it out in more detail along the same 

 lines as he had already followed. In this manner he 

 traced the successive stages which, in his opinion, had 

 led to the excavation of the present valley of the 

 Rhine, showing that in Miocene time the flow of the 

 drainage between the Black Forest and the Vosges 

 had been from north to south, or towards the great 

 hollow lying to the north of the Alps, that subsequent 

 disturbance and elevation of the Alpine chain tilted 

 the ground in such a manner that the drainage was 

 reversed, and the streams from the tract of the Alps 

 were collected into a river which found its way 

 northward, and gradually excavated the valley and 

 gorge in which the present Rhine still flows. Though 

 it cannot be demonstrated that such have been the 

 successive stages in the history of the course of this 

 river, the available evidence makes Ramsay's explana- 

 tion highly probable. 



The later application of the same principles of 

 interpretation to the history of the valley of the Dee 

 in Wales led him into still ampler fields of speculation, 

 because dealing with a vaster and dimmer geological 

 past. He could not claim to have proved every step 



