ASSOCIATED ROCKS OF PORTHALLA COVE. A471 
of the one into the other in many places—an apparent 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 Mul- 
lion Cove, at Pradanack Cove, at the coast west of the Lizard Town, 
and at several places on the east coast between Landewednack and 
Kennick Cove, more particularly under the Balk . .. . and at the 
remarkable cavern and open cavity named the Frying Pan, near 
Cadgwith.” He goes on to say that at such places there is a good 
deal of calcareous matter, and a tendency to more red colour in the 
serpentine near its base than elsewhere *, and this is certainly the 
case at Porthalla also. . 
Finally, I cannot see any sufficient reason for referring these 
metamorphosed rocks to any Archean series. I believe, indeed, 
that they are older than the rocks nearer the village (which there 
seems good reason, indeed, to regard as Post-Silurian); but, as I have 
said before, their strike and chief dip are the same as those of the 
Lower Silurians forming the greater part of the south coast of West 
Cornwall, and at present the evidence, such as it is, points to their 
being of the same age. 
Discussron. 
Professor Bonney said that it must be remembered that the rock 
in dispute was the one form of the many rocks bearing the name of 
serpentine, of which that at the Lizard was a typical example. 
Some general considerations Mr. Collins had failed to notice, which 
to him it seemed impossible to neglect in considering the question, 
viz. that there was abundant evidence that this kind of serpentine 
resulted from the metamorphism of olivine rock; that rocks of iden- 
tical structure generally had but one origin; and that there was no 
well-authenticated instance of an olivine rock not igneous, for, even 
as a mineral, olivine was rare in sedimentary rocks. Further, it 
was idle to appeal to testimony which was not substantiated by the 
microscope. Coming, however, to Cornwall, we could not separate 
the Porthalla serpentine from that of the Lizard: what was the 
origin of the one must also have been the origin of the other. Now, 
if there were any signs which proved the intrusive character of a 
rock, these were exhibited by the serpentine of the Lizard. Further, 
it cut transversely across the ends not only of the hornblendic but 
also of the granulitic series. He asserted, however, that even at 
Porthalla the evidence was clear in several places. Mr. Collins had 
‘mistaken a serpentine in one case for a hornblende-schist, as might 
be seen by the specimen on the table. The streaky structure, if he 
would examine it microscopically, would be found to have nothing 
to do with bedding; and his asserted proofs were of the vaguest 
nature. As for the schists, the hornblende-schist of the Porthalla- 
Porthoustock district closely resembled that of the Lizard district ; if 
the one were Archean the other must be. The strikes over the two 
*olibid: 
