RAMBLES IN CORNWALL. 47 



district, where it may be seen in the high cliffs, 

 intruding into the slates, and sometimes itself 

 invaded by another igneous rock called Gabbro. 

 It is curious that this Serpentine, forming a kind 

 of plateau in a basin of surrounding hornblendic 

 schists, may be identified by means of the pretty 

 Cornish heath, Erica vagans, which grows on the 

 Serpentine in great profusion, and scarcely any- 

 where else. De la Beche supposed that the 

 Serpentine appeared during the deposition of the 

 Killas or Devonian clay-slates ; and it is clearly an 

 eruptive rock like the granite. It is impossible to 

 describe the delight we experienced in rambling 

 over this peninsula, climbing the Logan Rock, 

 which, though hundreds of tons in weight, could 

 yet be made to swing by a mere push ; gazing at 

 the white and golden sands of Kynance Cove, and 

 exploring the wondrous caves which the devouring 

 sea has eaten out of the hard cliffs in many a 

 place. 



Igneous and metalliferous rocks are so general 

 and so important in Cornwall that no apology need 

 be offered for this somewhat lengthy, yet all too 

 scanty, description of them ; for, indeed, very little 

 else remains to be remarked in the geology of this 

 county, the stratified rocks being rarely met with. 



CAMBRIAN. Mr. Collins has described the old 

 slates which are seen near Camborne, Ponsanooth, 

 etc., as Cambrian ; but no fossils have been found 

 in them. 



SILURIAN. In the Fowey beds, ichthyolites are 

 found, while at Gorran Haven several species of 



