CHAP. TV.] THE CRUISES OF THE 'PORCUPINES 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 J 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 Faeroes 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 Fseroe 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 

 Faeroe, and it is this which makes the contrast 



