CHAP. X.] CONTINUITY OF THE CHALK. el We 
From 1,263 FaTHoms (STATION 22). 
A single rounded pebble, weighing 18 grains, chiefly quartz, 
with a little of a black mineral hornblende or tourmaline, prob- 
ably from a metamorphic schist. 
GRAVEL FROM 1,366 FATHOMS (STATION 19). 
Consisted of 51 small subangular pieces of rock, all less than 
$ grain in weight, excepting only one fragment angular) of 
quartz, which weighed 2 grains; they consisted of— 
19 Fragments of quartz, all of which appeared to have pro- 
ceeded from the disintegration of crystalline schists, and 
not from granite. 
9 Hornblende schist. 
8 Mica schist. 
7 Loose, dirty-white tufaceous limestone. 
3 Small fragments of augite or tourmaline (? which). 
1 Fragment of quartz, with tourmaline. 
4+ Fragments of indistinct and uncertain character. 
GRAVEL FROM 1,476 Fatnoms (STATION 21). 
Six small subangular fragments, the largest of which did not 
exceed two grains in weight ; they were respectively— 
1 Yellow quartz 
1 Quartzose chlorite schist. 
3 Mica schist. 
1 Small fragment, apparently of volcanic lava. 
6 
The specimen from Rockall is not a fragment of any normal 
rock, but is only a brecciaform aggregate, principally consisting 
of quartz, felspar, and crystals of green hornblende, held to- 
gether by a silicious cement. It has evidently been broken 
from the projecting edge of a fault or vein fissure; and although 
it cannot settle the matter definitely as to what rocks this islet 
may really be composed of, it would indicate that it most 
