434 DEPTHS OF THE OCEAN 



and southern series. The hydrographical conditions prevailing 

 along the east side of the Atlantic at these depths are well seen 

 in the chart for 500 fathoms (see Fig. 202, p. 296), which shows 

 that the temperature at 500 fathoms to the south of the Faroe 

 Islands is above 7.0° C, and south of the Canaries, 8.0° C. 

 Only outside of the Mediterranean do we find a higher tempera- 

 ture. On the western side of the Atlantic the temperature at 

 the same depth is only 4.0" C. These facts seem to me to 

 throw much new light on the geographical distribution of the 

 deep-sea fauna. 



The conditions in the deep basin of the Norwegian Sea, which 

 has been described in Chapter IV., are no less interesting. In 

 the little chart (Fig. 309) the contour-lines for 600 and 2000 

 metres are shown. The 2000 metres isobath encloses the 

 abyssal plain of the Norwegian Sea, the central parts of which 

 are covered by 3000 and 3500 metres of water. The area 

 between the 2000 and the 600 metres isobaths shows the region 

 of the slopes, which are steep all the way from Spitzbergen to 

 the Wyville Thomson Ridge, a deep channel (the Faroe- 

 Shetland channel) running from the deep basin right down to 

 the ridge. The hydrographical conditions in the Norwegian 

 Sea are indicated in the vertical section (Fig. 310), which runs 

 through the points a, b, <;, from the east coast of Greenland 

 across Jan Mayen to Vesteraalen in Norway. In this section 

 the "Atlantic water," with a salinity above 35 per thousand, is 

 shaded, and is seen to be limited to the eastern side, the 

 depth of the layer not exceeding 600 to 700 metres (or 350 

 to 400 fathoms). All the water to the west, and beneath this 

 " Atlantic water," is quite cold, most of it below 0° C, the 

 abyssal plain itself being covered by water having a temperature 

 below — 1° C. 



The fauna of this cold deep basin has been extensively 

 studied during the Norwegian expeditions on board the 

 " Voringen " and the "Michael Sars," during the Danish 

 expeditions on board the " Ingolf" and the " Thor," and also by 

 Swedish and French expeditions (Duke of Orleans, etc.). On 

 the chart (Fig. 309) small circles denote localities where 

 Norwegian expeditions have employed dredges or trawls, the 

 captures everywhere being remarkably poor in species. 



The abyssal plain and the slopes of the Norwegian Sea do 

 not show a single species in common with the Atlantic. While 

 in the Atlantic the genus Macrurus plays an important part in 



