CHAPTER XL 



GOUGES AND RAVINES. 



IN Great Britain and Ireland most of the valleys 

 are more or less wide, with sloping sides, and have 

 evidently suffered from various denudants since they 

 were first formed, having been probably two or 

 three times submerged and exposed to marine 

 denudation, and as many times raised up, so as to 

 come within the influence of the atmospheric agencies 

 or ice. In tropical climates this does not seem to be 

 so often the case, as many gorges and ravines are 

 well developed, and apparently the only denudant 

 that has acted on them is meteoric abrasion. To 

 those in Abyssinia we may draw attention, as they 

 have been lately described by Mr W. J. Blanford. 1 

 This observer has stated that no faults seem to exist 

 in the ravines, and that they could not possibly have 

 been excavated by either the sea or ice action ; but as 

 he does not take into consideration the contraction of 

 rocks as they come to the surface of the earth, he is 

 led to believe the valleys were formed solely by 

 meteoric abrasion. Such a theory would require an 



1 "Geology of Abyssinia," pp. 86 and 87, 154 and 155. 



