330 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



This cause seems to have been the flooding 

 of the English Channel and Irish Sea by water of 

 Mediterranean origin. It is well known that a current 

 of water of high salinity flows from the Mediterranean 

 through the Straits of Gibraltar below the inflowing 

 current of Atlantic water. 



It was shown by Professor H. N. Dickson,* from the 

 results of cruises made by Dr. Wolfenden in 1903-1905, 

 that this Mediterranean water spreads westwards and 

 northwards at a depth of between about 500 and 1,000 

 metres below the less salt and specifically lighter Atlantic 

 water. His figures, and those of the German " Planet " 

 (1906) and Danish " Thor " (1904-1905)t expeditions, 

 show that the Mediterranean water can be traced outside 

 the Continental shelf as far North as about Latitude 53°. 



Dickson also suggested that this Mediterranean 

 water might sometimes rise to the surface and enter the 

 English Channel. This is just what seems to have 

 happened during 1912. 



In my paper to the Royal Meteorological Society 

 already referred to, I have pointed out that the oceanic 

 circulation in the North Atlantic is composed of two 

 main circulations — one centred about the Sargasso Sea, 

 with the Gulf Stream forming its north-western portion ; 

 the other centred about Iceland and fringing the Arctic 

 regions, with the Labrador Current forming its western 

 section. 



The Gulf Stream Drift is, so to say, a composite 

 current partly derived from the southern circulation and 

 partly from the northern. 



The southern and northern circulations are probably 

 largely independent of one another and can vary in 



* Memoirs of the Challenger Society, No. 1, p. 107 (1909). 

 t Krummel. Handbuch der Oceanograpkie, Vol. II, p. 610. 



