PS 
414 REV. E. HILL ON THE ROCKS OF GUERNSEY. 
Another important area occupied by granite is that which sur- 
rounds the bay called Lancresse. The sand hills which form Lan- 
cresse common make its inland boundary somewhat uncertain; but 
the road may probably without much error be taken as marking 
this. On the west the boundary on the shore lies about midway 
between the bays called Jaonneuse and Grand Camp, to the north 
of Mont Cuet; but I have not noticed any actual contact with the 
rock of Mont Cuet. On the west the boundary can be roughly 
traced across the heath by comparison of outcrops, and on the shore 
about 300 yards south of Fort Le Marchant the contact with the 
neighbouring rock is well seen. This is a blue diorite, weathering 
bluish-white, while the granite weathers into a pinkish white. This 
difference of colouring markedly distinguishes between the rocks. 
There can be no doubt that this granite is also igneous and intrusive 
into the rock which surrounds it. 
This granite bears no resemblance to that of Cobo. It is a grey 
rock with a faint shade of pink that increases with weathering, and 
sometimes becomes the predominant colour. It is well crystallized, 
but the crystals are uniformly small, averaging, I think, about -05 
inch in length. The constituents are white felspar, quartz slightly 
stained, and black mica to the extent perhaps of one sixth of the 
whole. I noticed that there was very little quartz near the eastern 
boundary, and that there was a decided increase in the amount to 
the southward and westward, till it reached an equality with the 
felspar. 
In the hollow of the bay between Forts Doyle and Le Marchant 
occurs a pink quartzose rock which was to me for long a perplexity. 
Not much can be seen above high-water mark, as it is covered by 
the turf, but a good deal is disclosed at low tide. It consists of 
much stained quartz, some felspar, and a good deal of black mica. 
It has a granulitic look, and a structure, caused by a tendency to a 
parallel arrangement of the constituents, that approaches a foliation. 
This is most noticeable on its eastern boundary. For some time I 
thought this an altered rock, probably belonging to the gneisses. 
But chancing one day to reverse my usual direction of survey along 
the shore, this rock suddenly reminded me of the granite I had just 
been traversing, the granite of Lancresse. Prof. Bonney indepen- 
dently sent the suggestion that this looked like a crushed granite. 
On a later visit I found a rock undistinguishable from this a little 
to its west, forming a clear dyke running up into the east side of 
the Fort-Le-Marchant peninsula, while on the west side similar 
dykes pass without break into the main Lancresse mass already 
described. . 
An oval area of granite, about half a mile long, lies south-west of 
Vale church, just south of the inmost extension of Grand Havre. 
I have preserved no specimen. Half a mile further to the south-west, 
by the mill on the Rue Maingy Road, is a small quarry in a rock 
very similar to that of Lancresse. . | 
A granite entirely different from both that of Cobo and that of 
Lancresse is found on the promontory which forms the west side of 
