96 The Rev. W. Buckland on the Excavation of Valleys, &;c. 



subsequent to the deposition and consolidation of the most recent of the regu- 

 lar strata ; for rocks and strata of all ages bear on those portions of their sur- 

 face which are not covered by other strata^ the marks of aqueous excavation ; 

 and are strewed over with the mingled fragments of the most recent^ as well 

 as of the most ancient beds. 



The diluvian waters to which these effects must be referred, (if we except the 

 very limited and partial action of modern causes, such as of torrents in cutting 

 ravines, of rivers in forming deltas, of the sea in eroding its cliffs, and of vol- 

 canos in ejecting and accumulating their exuviae,) appear to have been the 

 last agents that have operated in any extensive degree to change the form of 

 the earth's surface. 



When one or more sides of a valley are formed by abrupt escarpments, 

 such as usually terminate the outgoings of our secondary strata, it is difficult 

 to say to what extent the discontinuity of the strata, and the formation of the 

 valley beyond the limits of the escarpment, are attributable to diluvian exca- 

 vation ; for we know not how far the strata originally extended beyond their 

 present frontier, nor how much of the subjacent valley is referable to other 

 causes than the most recent diluvial agency : for example, it is not possible 

 to determine how far the escarpment, which may be seen in the annexed map 

 to terminate the green sand-hills of Blackdown towards the vale of Taun- 

 ton, might have extended northward beyond its present boundary towards 

 the Quantock hills ; nor how much of this vale is to be attributed to excavation 

 by water, or to originally low position : and we are equally without data for 

 judging to what distance the same green sand might have originally extended 

 on the west of Haldon towards Dartmoor ; or over any spaces exterior to its 

 present escarpments. 



But when a valley originates and has almost its whole extent within the 

 escarpment of strata that are horizontal or nearly so, and which bear no mark 

 of having been moved from their original position by elevation, depression, or 

 disturbance of any kind; and when such valley is inclosed along its whole 

 course by hills that afford an exact correspondence of opposite parts, it must 

 be referred exclusively to the removal of the substance that once filled it ; and 

 the cause of that removal appears to have been a violent and transient inun- 

 dation*. 



* For a well-digested statement of the arguments in support of the theory of the formation of 

 valleys by aqueous excavations, I beg to refer to the works of Dr. Richardson on the coast of 

 Antrim, in the Philosophical Transactions ; to Mr. Greenough's Geology ; and Mr. Catcott's 

 Treatise on the Deluge : Mr. Catcott, however, has carried his doctrine of denudation too far, 

 and has applied it to explain phenomena that must be referred to other causes. 



