21 



(although against direct evidence) the existence of such ancient 

 lakes, we shall not, by that hypothesis, introduce an agent 

 capable of producing the diluvial debris which is exhibited on 

 almost every part of the earth's surface which has been well 

 examined. 



In illustration of the first of these two assertions, I need only 

 state, after Prof. Auckland, that in none of the higher parts of 

 England out of the reach of ordinary floods, have any traces 

 been yet discovered of lacustrine terraces, such as those which 

 arc seen in one or two of the glens of Scotland, or of any other 

 deposits indicating the former presence of extensive tracts of 

 stagnant water. The hypothesis which ascribes the distribution 

 of the enormous masses of diluvial gravel existing in so many 

 parts of our island to the agency of a series of lakes, which 

 from time to time have burst their barriers and descended to 

 lower levels, may, therefore, at once be rejected as gratuitous. 



Diluvian Actiojt proved from the Form of main/ Valleys of 



Denudation. 

 There is another independent reason for rejecting the hypo- 

 thesis, which may be properly stated in this place. That most 

 of our secondary valleys have been formed by denudation, and 

 that by the action of water many portions of the earth's surface 

 have been greatly changed in form since the solid strata assumed 

 their present elevation is universally admitted; the only ques- 

 tion is respecting the manner in which such changes have been 

 brought about. Now we may venture to assert, that in number- 

 less instances the present drainage of the earth's surface could 

 never have been effected, either by the long continued erosion 

 of the elements, or by the bursting of any series of lakes oncn 

 pent up among its higher regions ; and if this statement be true, 

 the present modifications in the external contour of the earth 

 must have been effected by the action of water put in motion by 

 powers which differ altogether with those with which we are 

 acquainted. It is impossible in this place to enter on a detailed 

 proof of the preceding assertion. By way of illustration, I shall 

 only refer to two examples of the kind alluded to, though many 

 others equally decisive of the question at issue, might be derived 

 from various parts of our island.* 



Wealds of Kent. 

 The first example to which I shall refer is supplied by the 



• Some excellent observations connected with this subject may be found in the 

 " Geological Survey of the Yorkshire Coast;" by Young and liird, p. 279, 286. 

 Many valleys appear to have been formed by an actual disruption of the strata produced 

 at the time of their first elevation. Valleys of this kind are of course excepted from the 

 remarks in the text, which apply exclusively to true valleys of denudation, such as those 

 by which the greater part of the secondary strata of England are intcrteeted. 



