410 REV. E. HILL ON THE ROCKS OF GUERNSEY. 
If the explanations of these appearances here given can be 
established they remove the only objection to the igneous origin of 
these rocks. Some bedded structures at two localities on Bellegreve 
Bay belong to the group described in the following section. In a 
paper in the Cambr. Phil. Soc. Proce. (vol. i. p. 76) these rocks are 
said to be visible underlying the gneiss below Fort George. How- 
ever, an inspection of the whole shore, hasty but under favourable 
circumstances, showed no such appearance, and as above mentioned 
the rock seems to join the gneiss intrusively at Castle Cornet. 
When all these considerations are taken into account, I think that 
most observers will agree to abandon the metamorphic theory of 
these syenites and diorites. 
In the group are included rocks of very various aspects, and 
perhaps of different ages. The most prevalent is perhaps a compact 
bluish rock as fine in grain as an ordinary sandstone. This is the 
variety at the junction with the gneiss: it is quarried in the town 
and by St. John’s Church to some extent, and very largely north of 
St. Sampson’s as well as in the neighbourhood of Cobo Bay. This 
furnishes the best kerbstones and “sets” for street-paving. A 
coarser rock of greyer colour with well-marked crystals of horn- 
blende and felspar is also abundant. Occasionally it contains a good 
amount of black mica and sometimes a little quartz, so that some 
specimens approach rather closely to granite. The felspar when 
coarsely crystallized often shows plagioclase striping. A very 
beautiful rock, of well-shaped black hornblende and white felspar 
erystals about + inch long, is quarried west of St. Sampson’s near the 
‘‘Saltpans” and near Vale. The Baubigny quarry also yields a rock 
resembling these, but with so much quartz that 1t must be ranked 
as a granite. Different varieties may, as 1 have said, occasionally 
be seen very close to each other. The rocks of Fort Doyle belong 
to the second variety above mentioned, and are mixed with rock 
belonging to the first. In the mass they look quite distinct, but it 
is difficult to find any decided separation. 
West of Vale Church a true syenite occurs. To its east and north 
the rock quarried contains much mica. I have made no attempt to 
work out the limits of this variety, but I am much inclined to think 
it really a separate mass. A black hornblendic rock on the coast 
about half a mile south of Fort Doyle decomposes and exfoliates 
spheroidally. At one time I thought this a dyke, but no clear line 
of separation from the normal rock seemed to exist. 
4, Tar HornepLENDE-GABBRO. 
The curious rocks included in this section occupy an oval area 
extending from the outskirts of St. Peter’s Port to Vale Castle beyond 
St. Sampson’s, and from the shore to the hummock called Hougue des 
Quartiers. The quarry called Bouetis their southernmost extension, 
while they occupy the sea-shore from Hougue 4a la Perre Battery 
nearly to Bordeaux Harbour. Their boundary inland includes 
Delancy Hill, on which stands the Saumarez monument. They 
have hardly been noticed by previous writers; but the quarrymen 
