TRACES OF A GREAT POST-GLACIAL FLOOD IN CORNWALL. 



Br NICHOLAS WHITLEY, C.E. 



One of the greatest of the physical changes, and probahly 

 the last in the geological history of our county, must be described 

 as that of a great post-glacial flood; which, could we have 

 witnessed it, would have impressed us as a great catastrophe ; 

 and yet the results have conferred untold blessings on unknown 

 generations. 



There is absolute geological evidence that the whole of the 

 solid frame- work of our County at no very distant geological 

 period sank wholly and completely under the surface of the 

 ocean ; and that after its baptism it rose again refreshed and 

 regenerated, adapted and furnished for the fit and enjoyable 

 abode of intellectual man ; with a treasury of stream-tin de- 

 posited and assorted in our valleys, the traffic of which brought 

 civilization to our shores and enriched successive generations. 



My present object is to give a brief outline of the evidence 

 in support of this hypothesis. That a great denudation of 

 the surface of our County has taken place, is shown by the 

 granite tors which stand up far above the crests of our highest 

 hiU-S, as at Carn-brea, — The Cheese-wring, — Eoughtor; and on 

 a larger scale on the hill tops of Dartmoor, at heights of from 

 1400 to 2000 feet above the sea. Large masses of solid granite 

 have been severed from their native bed and swept down the 

 slopes of the hills and rest now on the surface of the less 

 elevated beds of Killas. The surface of these slopes for a 

 depth of from 4 to 6 feet has been in a semi-fluid state, and the 

 denuded upturned beds of slate have been pressed and curved 

 down the hill side towards the valleys. 



The evidence of an overwhelming flood is further shown 

 by our valleys having been swept out to their base, and the 

 stream tin. deposited immediately on the bare rock and in its 

 fissures and pockets, above which is a thin vegetable stratum 

 composed of the ruin of forests with an abundance of hazel 

 nuts — and from thence to the present surface nothing but turbid 

 river deposits of from 6 to 30 feet in depth. Conclusively 



