CHAP. IV. | THE CRUISES OF THE ‘ PORCUPINE’ 165 
living among the recent chalk-mud of the Atlantic 
sea-bed, will be discussed in a future chapter. 
While we were examining our wonderful dredge- 
load the little ‘ Porcupine’ was steaming slowly 
southwards—past the island of Rona, and Cape Wrath 
looking out into the north cold and blue, with the 
waves now curled up asleep at its feet, as if they 
never did any harm; past the welcome Butt of the 
Lews, and into the little harbour of Stornoway. Here 
we remained some days; not sorry—even although 
our cruise had been thoroughly pleasant—to exchange 
the somewhat cramped routine of life in a gun-boat 
for the genial hospitalities of Stornoway Castle. 
The fauna of the ‘warm area’ is under circum- 
stances altogether special and peculiar, which must 
be discussed in full hereafter. While the cold area 
is sharply restricted, the warm area extends con- 
tinuously from the Féroes to the Strait of Gibraltar. 
At all events the same conditions are continuous; 
but as will be explained more fully hereafter, the 
whole 600 or 700 fathoms of water down to the 
bottom at the mouth of the Féroe Channel, corre- 
sponds with the surface layer only to a like depth in 
the Rockall Channel or in the Atlantic basin. The 
first 700 to 800 fathoms in all cases are actually 
warm, but where the depth greatly exceeds 800 
fathoms, there is a mass of cold water beneath sink- 
ing slowly to nearly the freezing-point. The bottom 
therefore, the habitation of the fauna, is only warm 
where the depth is not greater than 800 fathoms, 
and in such a case only can the term ‘warm area’ 
be correctly applied. Such are the conditions off 
Feéroe, and it is this which makes the contrast 
