360 J. H. Collins — Cornish Serpentinous Rocks. 



examined the Lizard Coast with any degree of detail. De la Beetle's 

 description of that seen near the Lizard Town is as follows, and it 

 would apply equally well to the others. " The hornblende slate," 

 he says, "supports the great mass of the Lizard serpentine with an 

 apparent passage of the one into the other in many places — an ap- 

 parent. passage somewhat embarrassing," that is, from his point of view ; 

 from mine it is perfectly natural. He goes on to say : " Whatever 

 the cause of this apparent passage may have been, it is very readily 

 seen at Mullion Cove, at Pradanack Point, at the coast west of 

 Lizard Town, and at several places on the east coast between Lan- 

 dewednack and Kennick Cove, more especially under the Balk .... 

 and at the remarkable cavern and open cavity named the Frying- 

 Pan, near Cadgwith." ] At Kynance some of the laminae of serpentine 

 are not more than one-tenth of an inch in thickness for considerable 

 distances. It would not be easy to explain how such thin plates of 

 molten intrusive matter could be forced between the laminae of an 

 already consolidated stratified rock for many feet together. Now, 

 although thin films of remarkably pure serpentinous matter are 

 often found deposited from aqueous solution in thin fissures in certain 

 parts of the Lizard district, yet in such cases as those referred to at 

 Kynance I do not think such an explanation will apply, and I see 

 no alternative but to believe that these thin bands consist of altered 

 material originally stratified and forming part of the same series as 

 the containing l'ocks. 



It seems to me that those who deny the origin of serpentine from 

 certain beds of stratified rock are ready enough to invoke Sir H. 

 De la Beche when his views support theirs. If, on the contrary, they 

 happen to clash with their views, or, which is here the same thing, 

 to support mine, they are very ready to explain away his conclusions. 



The popular idea that the Lizard Peninsula is composed almost 

 entirely of serpentine or serpentinous rocks is far indeed from the 

 truth. Considerably less than half the area is so coloured on the 

 Geological Survey Map, and there is good reason to doubt whether 

 the whole of this is actually serpentine. Inland, the excavations are 

 few and far between; on the coasts, many of the cliffs are inac- 

 cessible ; and it may very well be that large areas of hornblende- 

 schist, mica-schist, gabbro, or even of ordinary clay-slate exist, within 

 the area hitherto regarded as wholly serpentinous, the tendency 

 having been hitherto to mark as serpentine whatever is covered by 

 a soil containing fragments of that rock. 



II. The Extra-Lizard Serpentines. 

 Whatever may have been the origin of the Lizard serpentines, it 

 is certain that serpentinous change in the West of England is not 

 confined to the Lizard District. Serpentinous rocks exist in many 

 other parts of Cornwall and Devon ; and probably the total area of 

 what may be called the "Extra-Lizard " serpentines is not less than 

 that of the serpentines of the Lizard Peninsula. Some of these 

 rocks have been described by various writers, and in considerable 

 1 Report on Cornwall, etc. See also Memoirs of the Geological Survey. 



