Li THE DEPTHS OF THE SEA. [CHAP. III. 
over that region we had found a great uniformity of 
conditions. As already mentioned, the average bottom 
temperature throughout was a little below the freezing- 
point of fresh water, and it sometimes fell to nearly 
2° C. below the zero of the centigrade scale. The 
bottom was uniformly gravel and clay, the gravel on 
the Scottish side of the channel consisting chiefly of 
the débris of the laurentian gneiss and the other 
metamorphic rocks of the North of Scotland, and the 
devonian beds of Caithness and Orkney. On the 
Fiéroe side of the channel, on the other hand, the 
pebbles were chiefly basaltic. This difference shows 
itself very markedly in the colour and composition of 
the tubes of annelids, and the tests of sundry fora- 
minifera. The pebbles are all rounded, and the 
varying size of the pebbles and roughness of the 
eravel in different places give evidence of a certain 
amount of movement of material along the bottom. 
There seems to be but little doubt, from the 
direction of the series of depressions in the isothermal 
lines of the region (PI. 7), that there is a direct move- 
ment of cold water from the Spitzbergen Sea into the 
North Sea, and that a branch of this cold indraught 
passes into the Fzeroe Channel. The fauna of the cold 
area is certainly characteristic, although many of its 
most marked species are common to the deep water 
of the warm area whenever the temperature sinks 
below 2° or 3° C. 
Over a considerable district in the Féroe Channel 
there is a large quantity of a sponge which is pro- 
bably identical with Cladorhiza abyssicola, SARs, 
dredged by G. O. Sars in deep water off the 
Loffoten Islands. This sponge forms a kind of 
