CORNISH POST-TERTIARY GEOLOGY. 43 



fragments of earth and soil, through, the wedging of frosts and 

 melting snows, might be temporarily succeeded by a finer talus, 

 containing smaller and fewer stones, during milder seasons. 



The frequent cliff-sections, composed of a thick masking film of 

 Head resting, as no modern talus could rest, against a rock-face a 

 few feet from its cliffs, coupled with occasional instances of its 

 isolation from the main cliffs, upon rocky reefs on the foreshore, as 

 at Godrevy and Cape Cornwall, point to a very much greater exten- 

 sion of land during its accumulation. 

 Next as to its age : 



1st. It is more recent than the Kaised Beaches, because, as Mr. 

 Carne pointed out, where both are present in the same cliff, 

 it invariably rests upon them. A possible exception may 

 be furnished by the Greenway Cliff section, mentioned in 

 the supplementary paper on Padstow. 

 2nd. It is older than the commencement of the forest growth, for 

 the following reasons : 

 (a) The Head evidences a period of great subaerial waste, a 

 more rigid climate; both likely to occur when the old 

 beaches attained their maximum elevation, possibly pro- 

 ducing continental conditions. The submerged forests 

 must have flourished on a much more extended, though 

 subsiding, area, and that subsidence must have been going 

 on for some time prior to their growth, as the flora does 

 not indicate any marked change of climate from the 

 present : a greater extent of area is also indicated by the 

 depth of the stream-tin gravels at Par, Pentuan, Carnon, 

 etc., below the sea-level. 

 (h) The Head rests upon the old plane of marine denudation, 

 whilst the forest ground seems to occupy tracts eroded in 

 its surface, as on Dunbar Sands, near Padstow, etc., so that 

 we may infer that a considerable amount of denudation had 

 taken place posterior to the accumulation of the Head, and 

 prior to the growth of the forests, 

 (f) The Head is never found resting on traces of submerged 

 forest, as we might expect to find it near the old cliff, had 

 their growth been prior to its accumulation. 

 (d) The Kaised Beaches furnish proofs of elevation, and the 



