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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 22, 



In places where the slope of the land is at a small angle, the " head " 

 is mostly earthy, and of small amount ; where it is steep, or rocky, it 

 becomes in proportion thick and fragmentary : the component frag- 

 ments will, in this case, be seen to have been derived in every instance 

 from the masses of rock immediately overhanging — the materials are 

 always strictly local as to origin. 



These accumulations, as seen in cliff sections and at short distances, 

 present an appearance of horizontal arrangement ; closer examination, 

 however, shows that this has nothing of the character of subaqueous 

 arrangement : another very obvious feature is, that the fragments 

 are all perfectly sharp and angular — no specimens of included water- 

 worn rock are ever to be found. 



A few localities at wide intervals, but at which these accumulations 

 may be observed, and presenting their most instructive features, as 

 to age and origin, may perhaps suffice. The blocks and fragments 

 included in the mass west of Pendennis Point consist exclusively of the 

 peculiar slates and included harder bands of that locality ; the like 

 occurs in the St. Austle Bay sections, particularly in the coarse beds 

 at Polkerris. The accumulations about the bold headlands from the 

 Bolt-head to the Start (and which when seen from the sea, at short 

 distances from the coast, might be easily mistaken for horizontal stra- 

 tified deposits) consist only of the waste of the hard fibrous and chlo- 

 ride rocks of that part of the coast. To the west of Dartmouth the 

 high slate hills contain intrusive veins of greenstone, and in the beds 

 of debris which have been derived from them, we accordingly find 

 greenstone fragments with those of the slate. In the limestone district 

 of Torbay, as at Hope's Nose, as also in the Brixham side, the "head" 

 is exclusively of limestone fragments. 



Fig. 3. — Section of " the Head" and old Marine Shingle at Tor- 

 nanven. (After Borlase.) 



The accumulations which I have here noticed were long since so 

 well described by Borlase in his ' Natural History of Cornwall,' that 

 I cannot do better than refer to his representations of cliff sections, 



