on the Mountain Chains of Europe and Asia. li 



abruptness which he likewise believed to prevail in the southern 

 escarpments of such chains as run east and west, he ascribed 

 to a tendency of the tidal currents towards vast abysses 

 which he fancied to exist in the southern hemisphere. As 

 the substance of Kirwan's Essay is given at much length in 

 the Encyclopaedia Britannica, (Article Geology,) I am sur- 

 prised that a theory detailed in so popular a work should have 

 escaped Mr. Walker's notice. 



Having shown that such speculations were familiar at a 

 much earlier period of geology, it can only be necessary for 

 me to explain the reasons why they have been generally neg- 

 lected, in the more advanced state of the science, as founded 

 on a hasty and often erroneous induction. 



The circumstance which invariably determines the position 

 of the more abrupt escarpments of hilly chains, is really the 

 direction of the great anticlinal lines of elevation. All the 

 lateral chains have necessarily — to borrow expressive terms, 

 commonly understood, from the art of fortification, — an abrupt 

 counterscarp facing towards the central anticlinal ridge, and 

 the gentle slope of a glacis, as it were, declining outwards. If, 

 therefore, the anticlinal ridge range north and south, the lateral 

 chains on the eastern side will have their steepest escarpment 

 towards the west, and, vice versa, the western lateral chains 

 will have it towards the east; or if the anticlinal ridge should 

 range east and west, the steep escarpments will face respect- 

 ively to the south in the northern lateral chains, and to the north 

 in the southern chains. This being the case, it is easy to find 

 examples enough of steep escarpments in any direction to fill 

 up a sufficient induction in favour of any hypothesis. Stukeley, 

 we see, favoured the north and west; Kirwan the south and 

 west. Both were equally confident, and I believe both equally 

 well or rather ill founded. Thus, it is certainly true that the 

 general configuration of America, of India, of Great Britain 

 and of Norway, favours the idea of the greatest line of elevation 

 being towards the west ; but if we look at the great chain of 

 the Ural, we see the Asiatic valley of the Tobol and Oby far 

 nearer to its base than the European valley of the Volga. It 

 is clear also that the chains skirting the north-east of Asia, 

 and extending to the borders of the Chinese empire, in which 

 the Lena and Yenisee have their source, are most abrupt 

 towards the east, where along the sea of Ohkotsk they nearly 

 line the coast. Little as we know of the interior of Africa, 

 enough has been ascertained to show that there the principal 

 elevations certainly do not tend towards the west; and the 

 same remark may be made concerning the vast continent, 

 B2 



