Mr Hugh Miller on River -Terracing. 265 



Subsequent History and Literature of the Subject. 



The literature of the subject, after l*layfair's time, if not 

 voluminous, is at least extensive. In this country it chieiiy 

 consists of passing references in text-books and local memoirs. 

 In America and in Norway, terrace-formations, existing upon 

 a grander scale, have received more attention. The pro- 

 gress of opinion during the last eighty years has been slow 

 enough. There has been the usual search after other causes 

 to account for the same effects; but, now-a-days, alluvial 

 terraces in valleys are almost everywhere recognised as the 

 work of the rivers. Among many working geologists there 

 exists an almost tacit understanding as to the methods by 

 which river-terracing has been accomplished. But there is 

 still not a little misapprehension abroad, and less, perhaps, 

 has been added to Playfair's original outline than might have 

 been expected. 



I need only allude to the old cataclysmal views which 

 stood in the way of the Huttonian theory, — waves of transla- 

 tion, for instance, and other suppositious floods, — sudden 

 emergence of countries from the sea, whereby the waters 

 were thrown violently off, — earthquake-formation of valleys 

 and lakes, whose waters were drained from level to level by 

 ruptures in the rock below. The fragile and uninjured land 

 shells contained in the terrace-alluvia, proved them to be 

 ordinary deposits ; and it came to be better understood that 

 geology and common sense, alike, cannot exist if rare or 

 imaginary accidents are to be accepted as the explanations of 

 what is universal, only because they might act swiftly. 



Many of the early geologists were carried insensibly from 

 the terraces of the old coast lines into those of the rivers in 

 the interior. This transition was found by Darwin * in 

 South America, and by Robert Chambers f in parts of Britain. 



they sometimes lead us further, and make it certain that the great mass of 

 gravel which form the successive terraces on each side of the river was de- 

 posited in the bottom of a lake " (p. 355). This statement, Avhich may apply 

 to pre-existing valley-deposits of any kind, has been kept in mind in di-awing 

 the diagram, Fig. 1, 



* Geological Observations in South America, 1844. 



t Ancient Sea Mar^fins, 1846. 



