| 
Ad58 J. H. COLLINS ON THE SERPENTINE AND 
32. On the SERPENTINE and associated Rocks of PortHatta Cove, 
By J. H. Cottus, Esq., F.G.S. (Read January 23, 1884.) 
Introduction. 
Turse rocks were briefly described by me in a paper communicated 
to the Royal Geological Society of Cornwall, in the year 1879 *, as 
‘‘ much-contorted strata of slaty green and red serpentine and 
hornblende rocks in numerous alternations, all, however, having a 
strike to the N.N.E.” 
In the same paper I stated my belief that the whole series con- 
sisted of ‘‘ highly altered Lower Silurian stratified rocks.” 
The Cove has been more recently visited by Prof. Bonney, and 
his remarks thereon were published in the Quarterly Journal 
of the Geological Society for February 1883. A brief reference is 
therein made to my paper, and the Professor considers that I have 
‘completely mistaken the relations of, the rocks to each other”. 
Iam glad therefore to be permitted to bring my views on this 
subject under the notice of the Society in sufficient detail to enable 
me to justify the opinions so distinctly controverted, so far at least 
as to show that the hornblende schist, serpentine, and other rocks 
described are distinctly interstratified, and that there is a real 
“‘ passage ” from one to the other. I am more especially glad of 
this opportunity, because the real question at issue is that of the 
origin of certain masses of serpentine rock, than which there are 
few more interesting or more important in the whole range of 
chemical geology. With much of what Prof. Bonney has written 
concerning the rocks of the Lizard district I very cordially agree, and 
I can from personal observation corroborate what he says as regards 
the present condition of the rocks; but when he goes on to say 
(loc. cit. p. 16), ‘‘There is no appearance whatever of a ‘ passage’ 
(i.e. of the hornblende schist) into the serpentine,” I think that he is 
entirely wrong, and that the rock specimens which accompany this 
paper will suffice to show that heis sot. ‘To me they seem veritable 
‘‘ passage ” specimens, and similar ones may be collected by hundreds 
on the beach at low water. 
Stratigraphy of the Porthalla Rocks. 
The following distinct succession of different kinds of rock is 
observable within a space of little more than a hundred yards at the 
* Trans. Roy. Geol. Soc. Cornw. vol. ix. 
t The Professor continues “and not to add any thing to the work of De la 
Beche, which he criticises.” I hope it will never be thought improper for a 
local geologist well acquainted with a particular district to criticise the published 
statements of previous writers. In the particular case referred to, however, I 
have merely referred to the criticisms of other geologists on the views of Sir H. De 
la Beche, and intimated my concurrence with the very opposite ideas entertained 
by Prof. Sedgwick, Mr. W. J. Henwood, and Mr. Budge. 
{ These specimens are described in detail further on. 
