PHYSICAL OCEANOGRAPHY 



243 



are all very much alike in these two places, nearly 2000 

 nautical miles distant from each other. There is thus a 

 marked difference as far as the upper layers are concerned, 

 both salinity and temperature decreasing northwards, while in 

 the deep layers below 500 fathoms the conditions are the same 

 throughout the middle and north-eastern part of the North 

 Atlantic. Northwards from Station 65 to Station loi the 

 decrease of temperature in the upper layers is more marked 

 than that of the salinity, so that the density of the surface-layer 

 increases from 1.0254 at Station 65 to 1.0266 at Station loi. 

 As a general rule, the upper water- layers, on being cooled, 

 become gradually heavier from the tropics toward the poles. 



Fig. 169 shows the conditions at Station 106, loth August Faroe 

 19 10, in the Faroe- Shetland Channel to the north of the ^^^""^^• 



Station 106 



Fig. 169.— Temperature, Salinity, and Density at Station 106, in the 

 Faroe-Shetland Channel (loth August 1910). Depth in metres. 



Wyville Thomson Ridge, about 300 miles north-east of 

 Station loi. At Station 106 some fresher water was found at 

 the surface, but otherwise the salinity, temperature, and density 

 were the same at both stations as far down as 500 metres ; the 

 water had grown slightly colder and heavier in these 300 miles, 

 but the difference was very small. Below 500 metres, however, 

 there is a great contrast, the temperature of the deep water 

 being, as already indicated, much lower north of the Wyville 

 Thomson Ridge than south of it, and the density is therefore 

 greater on the north side. The deep water of the Norwegian 

 Sea is thus colder and heavier than that of the Atlantic, but, 

 strange to say, there is no difference in the salinity of the 

 deepest layers of the two regions. 



At all three stations the surface -layers are occupied by a 

 warm, comparatively saline, northerly current. On proceeding 

 northwards, there is a fall of temperature and of salinity and 



