ASSOCIATED ROCKS OF THE LIZARD DISTRICT. 885 



in mineral composition. As neither of these works is now very 

 readily accessible, and I wish to make my paper as complete as 

 possible, I have occasionally described phenomena noticed by them, 

 although it has added slightly to the length of the communication. 

 The microscope has, I hope, enabled me to explain several of those 

 phenomena with which the appliances at their command could not 

 deal. Where I differ from them, as I do occasionally, it is with 

 diffidence, and only because, after careful consideration, I am 

 unable to adopt any other conclusion. The remaining works are 

 generally too vague in their terminology to be of much use at the 

 present day*. 



Por the general features of the Lizard peninsula I must refer, for 

 the sake of brevity, to Sir H. De la Beche's admirable memoir; 

 suffice it to say here that the district of which I more particularly 

 treat may be described as a plateau, partly cultivated, partly wild 

 moorland, which, as a rule, descends precipitously to the sea, except 

 where it is furrowed by small coves and gullies. The cliffs often 

 rise vertically from 100 to 200 feet above the sea ; of beach beyond 

 the high- tide mark there is but little, the base of the cliffs being 

 then often washed by the waves for hundreds of yards together. 

 In not a few places the cliffs are totally impracticable from above, 

 and could only be examined (without a hope of landing) from a 

 boat below in the calmest weather. This, of course, adds greatly to 

 the difficulty of investigating the district ; for, even at low water, 

 progress at the base of the cliffs, where possible, is often laborious, 

 and the state of the tide has to be carefully watched. 



The district described in this paper forms the southern part of 

 the Lizard peninsula. I have examined the coast of this from 

 Lizard Head to Mullion Cove on the west side, and from the same 

 to Manacle Point on the east, as carefully as circumstances admitted, 

 and have also traversed the interior in two or three directions. 



The following rocks, the positions of which may be seen on the 

 geological map, occur in the above district : — (1) hornblende schist ; 

 (2) serpentine; (3) gabbro ; (4) granite (restricted, as will be 

 shown, to the west coast) ; (5) greenstone, i. e. dark augitic or 

 hornblendic traps, described hereafter in detail, restricted, so far as 

 I know, to the east coast. 



The most convenient arrangement will be to commence with a 

 few remarks on the hornblende schist, next to describe the petrology 

 and stratigraphy of the two coast- sections in detail, and then the 

 inland sections, reserving to the end all details of the microscopic 

 structure of the serpentine. 



The Hornblende Schist. — Under this title are included an extensive 

 group of rocks which I do not profess to have minutely investigated, 

 as I was chiefly occupied with the rocks of presumed igneous origin. 

 The following description, however, will be fairly accurate : — This 



* Mr. Smyth, in his Presidential Address, Quart. Journ. Geol. Soc. xxiii. 

 p. lxiii, calls attention to a distinct case of intrusion of the serpentine, and 

 doubts the evidence of a passage into gabbro. He also mentions some inter- 

 esting facts supporting the theory of a peridotic origin for the serpentine. 



Q. J. G. S. No. 132. 3 m 



