432 On a Phenomenon 
the veins and the granite of the mount, as did three ob- 
servers on the spot. : 
There is another remarkable phenomenon I have de- 
scribed as belonging to these veins, which excludes the idea 
of an injection of soft granite, and places them in the rank 
of all the mineral veins; an object of which I shall speak 
more hereafter; but here it will be sufficient to describe 
that character. All these veins have what is called Sale- 
banque by the mineralogists of the continent, and Capel in 
Cornwall. This is a first crust produced on the sides of 
the fissures in the strata, before they were filled with the 
substances which distinguish the different kinds of mineral 
veins. Now, the veins of psendo-granite in St. Michael’s 
Mount which pervade the granite of the mount, have their 
capel of pure white quartz, but in the kellas their capel is 
of mica of a very singular kind; its thickness is about 727 
of an inch, and its very brilliant lamine are at right-angles 
to its direction. This capel belongs so essentially to the 
veins, that, when they become very narrow, it fills them en- 
tirely, without pseudo-granite between the two crusts. 
Another object of my observations in St. Michael’s 
Island, more important to geology than that of the veis 
above described, concerns the manner in which our conti- 
nents, after having evidently been a part of the bed of the 
sea, are become dry land. The main point of my contro- 
versy with Mr. Playfair was this: whether our continents 
have been lifted up from the bottom of the sea, which is his 
opinion; or, what [ maintained, that, such a part of the 
bed of the sea having sunk so low that the sea had retired 
on it, another part having been left dry, is become our con- 
tinents. In my works already published, I have demon- 
strated the last proposition by a great number of phzeno- 
mena, and in particular by the situation of the strata along 
the coasts and in the led of the sea near them. ‘To this 
subject relate the following observations on St. Michael’s 
Island, bezinning at p. 267. ; 
‘© We followed all the western side of the island, with- 
out finding any point by which we could ascend to the foot 
of the granite rock; it being everywhere rendered inacces+ 
sible by heaps of large blocks of granite. But the seene 
changed on the south side; where the bed of the sea instead 
of being formed of schistus (which ought to have been the 
uppermost) consists of sunken masses of granite, which are 
in part covered by the high tides. Here we saw the same 
veins of pseudo-granite and of quartz as in the mount..... 
| . Continuing 
