Rockall. 65 
Of its geology we have only the accounts of Vidal and 
Captain Hall. 
My friend Mr John Cordeaux of Great Cétes, Uleeby, 
Lincolnshire, who at my request has assisted me in preparing 
the materials for this paper, and who has good opportunities 
of interviewing the Grimsby smacksmen and owners, sent me, 
amongst other items, a small piece of stone which was 
obtained near Rockall, and concerning which he writes to me 
as follows :—“ With regard to your question as to where I 
got the rock and from whom? It was given to me by a man 
who had been line-fishing off Rockall for cod. I had several 
pieces, with a branching coral attached, brought up entangled 
on the cod-lines. I cannot remember the man’s name now, 
but believe that it was one by name Frederick Barr, formerly 
of this parish, and drowned at sea some few yearsago. There 
was a good deal of the coral and rock brought to Grimsby 
about the same time. The little bit I sent to you was the 
only piece I could find, although I had several pieces on the 
chimney-piece when at Eaton.” 
You will, from the above notes, observe that this piece of 
rock was not obtained zn situ from Rockall, but from the floor 
of the ocean in its vicinity. Nevertheless I considered it 
worthy of a specialist’s examination. 
It was therefore forwarded to Professor Heddle,’ with a 
request to report upon its character, which he has done as 
follows :—“ I have cut a slice out of Rockall rock, and now 
return the rest. I cannot finish the section here, so have sent 
it to London to be finished, and on receipt of it will report.” 
He goes on to say—“ If this comes from there, it is none of 
the rocks mentioned before, but (unless possibly, but not 
probably, a hornblende band of old gneiss) a volcanic rock. 
This would make Rockall a plugged volcanic throat, which 
its form makes very probable.” 
After a later and more exhaustive examination, Professor 
Heddle writes :—“ It is an olivine-dolerite of an unusually 
close-grained or dense character. It has an unusual structure, as 
containing very little augite. Olivine and labradorite crystals 
occur porphyritically disposed; and also in what Professor 
Judd calls glomero-porphyritic clusters; and here both the 
VOL. XIII. E 
