50 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



about 30° at the bottom in 640 fathoms, while in the warm 

 area which stretches S.W. from the line of demarcation the 

 temperature is 47° F. at 250 fathoms, and 42° at the bottom 

 in 600 fathoms. The warm area was found to have 216 species, 

 while the cold had 217, and of these only 48 species were 

 common to both. 



Sir Wyville Thomson (see " Nature," Sept. 2nd, 1880), 

 as a result of his consideration of the " Challenger " tempera- 

 tures, came to the conclusion that the cold and warm areas 

 of the Faroe Channel must be separated by a very considerable 

 submarine ridge rising to within 200 or 300 fathoms of the 

 surface. He therefore addressed a letter in June, 1880, to the 

 Hydrographer of the Admiralty, pointing out these facts, 

 and asking for the use of a surveying vessel for a few weeks 

 for the purpose of sounding the Faroe Channel with a view 

 of testing his prediction. That was the origin of the " Knight 

 Errant " expedition conducted by Captain Tizard and 

 Dr. John Murray, under the general direction of Sir Wyville 

 Thomson, who remained at Stornoway in the Outer Hebrides, 

 during the four traverses of the region in question. The results* 

 completely justified Sir Wyville Thomson's prediction, and 

 showed that a ridge rising to within 300 fathoms of the surface 

 runs from the N.W. of Scotland by the Island of Rona to the 

 southern end of the Faroe fishing banks. 



This was followed by a further expedition in H.M.S. 

 " Triton," in the summer of 1882, again under Murray and 

 Tizard, which was very fruitful of zoological results. The 

 discovery of two very different assemblages of animals living 

 on the two sides of the Wyville Thomson ridge — arctic forms 

 to the North and atlantic forms to the South — gives us 

 a notable example of the effect of the environment on the 

 distribution of marine forms of life. 



Sir Wyville Thomson, however, did not live to see the 



* Published in the Proc. Roy. Soc. Edin. for 1882 (Vol. XI). 



