MODERN VIEWS OF DENUDATION. 
461 
conditions. I cannot, however, assent to the views of some 
of my own colleagues and other eminent geologists, at least 
until the objections here advanced — I trust fairly and can- 
didly — have been fully answered. In the formation of valleys, 
as well as plains, terraces, and escarpments, the sea has been, 
as it seems to me, the great artificer. In many minor valleys, 
the rivers have been the agents of denudation, but every 
special district requires the application of special principles in 
order to account for its physical features. 
