430 On a Pheenomenon 
- they were formed of newer granite, and, if properly ex 
amined, would be found to cut the old granite as well ag 
the rock which rested on it. This opinion was once very 
strenuously supported in this country; but as facts could 
not bear it out, it was abandoned. J find however, im a 
recent publication, something similar to it maintained by 
De Luc, who asserts that the veins at St. Michael’s Mount 
are not granite, but mere quartz, which traverses the 
granite as well as the stratified rock. 1 cannot compre- 
hend how De Luc has been so much deceived in this piace, 
as simple inspection of the smallest specimen will prove 
that he was mistaken.—I have only a few specimens to lay 
before the Society, from the veins of St. Michael’s Mount, 
but they are really interesting and satisfactory. One ex- 
hibits a portion of kedlas, bounded on each side by granite ; 
another of two granite veins, traversing kellas included in 
granite. The simple inspection is sufficient, in the first 
place, to show that the opinion ef De Luc is groundless, 
with respect to the snbstance of these veims. One of the 
specimens also contains two small veins of quartz, which 
are of the kind called contemporaneous: these keep the di- 
rection of the seams of the stratified rock, and are cut off 
by granite in the same line without any interruption.” 
This, sir, is what you have extracted from Mr. Allan’s 
work concerning me: he says he has found it iz @ recené 
publication, without mentioning which : it must be in the 
account of some inattentive Reviewer; and if this answer 
comes to his knowledge, he will be sorry to have thus been 
deceived himself ; while he could have seen what I have 
yeally described in my Geological Travels, published in 
London, in 1811, by Messrs. Rivington, in two volumes. 
This is the authentic document to which I shall refer for 
what J have really described. It was in July 1806 that I 
visited St. Michael’s Mount; and as, in all my observations, 
I endeavoured to have the company of some gentlemen of 
the country, I had the satisfaction, in these, to be conducted 
by two gentlemen as desirous as myself to observe that 
island, because they had read Mr. Playfair’s account of it. 
One of these gentlemen was Davies Giddy, Esq. M.P. who 
lives in the neighbourhood at Tredrw, an estate of his 
family ; the other Mr.Winicombe, of Oxford, who, used for 
many years to spend the vacations with one of his friends 
near Mount’s Bay, to which belongs St. Michael’s Island. 
Thus, if Mr. Allan had known my work, he would have 
seen that I was not the only obseryer of the phenomena 
which I described. 
The 
