CHAP. VII.] VEEP-SEA TEMPBRArVHES. 311 



At this point, therefore, the ice-cold Avater of the 

 Arctic current filling up the bottom of the trough 

 is nearly 2,000 feet deep, while the temperate water 

 above has nearly an equal depth. The lower half of 

 the latter, however, has its temperature considerably 

 reduced by intermixture and diifusion. Pig. 55 

 represents diagrammatically the general result of 

 temperature observations in the cold area. The 

 depth at the next Station, No. 65, was 354 fathoms, 

 showing that the channel had begun to shoal towards 

 Shetland; the temperature was, however, still low, 

 almost exactly 0° C. The next Station, No. 66, 

 eighteen miles further on towards the Shetland 

 banks, gave a depth of 267 fathoms, Avith a bottom 

 temperature of 7°"6 C, the temperature at the surface 

 beiag ll°-3 C. We had therefore got beyond the 

 edge of the trough filled by the cold stream, and 

 passed into lesser depths occupied from the surface to 

 the bottom by the warm southern stratum. 



The next series of soundings, Nos. 67 to 75, are either 

 in shallow water round Shetland, or in water on the 

 shelving edge of the plateau, not deep enough to reach 

 the frigid stream. It is of some interest that the 

 tM^o soundings, Nos. 68 and 69, in 75 and 67 fathoms 

 respectively, to the east of Shetland, show a bottom 

 temperature of 6°-6 C, while a serial sounding in the 

 warm area at the western entrance of the Teeroe 

 Channel gives for the same depth a temperature of 

 about 8°-8 C. This circumstance, along with others 

 to be mentioned hereafter, would seem to show that 

 a considerable indraught of cold water spreads over 

 the bottom of the shallow north sea. 



At Stations 76 to 86, which are along the southern 



