470 AisrisruAL report Smithsonian- institution, 192 8 



to the Baltic. Subtropical seas, as, for instance, the Eed Sea and 

 the Persian Gulf, have water above the normal salinity, while Hud- 

 son Bay and the Baltic Sea are below normal in salinity. 



The Gulf Stream in the North Atlantic undergoes a periodical 

 expansion and contraction, and the flooding which accompanies these 

 gigantic pulsations periodically influences hydrographic conditions 

 in the waters bordering northern Europe. The maximum flooding 

 of the North Atlantic by the Gulf Stream, according to Jenkins 

 (1921, p. 75), occurs in August. The ice-chilled Nova Scotian 

 current which floods westward into the Gulf of Maine every spring 

 is an overflow of the pool that develops from Cabot Strait out over 

 Banquereau Bank with the melting of field ice from the Gulf of St. 

 Lawrence, and this surface drift, which flows past Cape Sable into 

 the Gulf of Maine, originates some 300 miles eastward- (Bigelow, 

 1927, pp. 681, 832.) Between Cape Sable and Cape Cod the surface 

 water is chilled to its minimum for the year in the last week of 

 February and the first few days of March. At this time the surface 

 temperature of the coastal belt is as low as 35.6°, while the central 

 and offshore reaches 36.5° and 38.3° F. In mid-August the surface 

 readings may reach 68° F. During the month of February the 

 surface temperatures of the Irish Sea range from 40.6° to 46.7° F. 

 and in August from 55.6° to 62.2° F. (Jenkins, 1921, pp. 64-65.) 

 According to the chart of isotherms of surface temperatures pre- 

 pared by Fowler (1912, chart 4), the surface temperature of the 

 Caribbean Sea is 80.6°, the Mediterranean 62.6° to 69.8°, Gulf of 

 Biscay 59°, Norwegian coast 48.2° to 41°, Iceland 41° to 42.8°, and 

 Spitzbergen 32° to 30.2° F. 



From these data it would appear that neither salinity nor tem- 

 perature by themselves interpose any appreciable barrier to the 

 migration routes of whales, for in the North Atlantic whales leave 

 the Caribbean Sea with its surface temperature of 80° F. and 

 journey northward toward Greenland waters, where the surface 

 temperatures of the water range from 32° to 30.2° F. On the North 

 American side they enter water chilled by pack ice and icebergs 

 issuing from Davis Strait, and on the European side they reach 

 the icy waters in the vicinity of Spitzbergen. These physical factors, 

 however, do indirectly determine to some extent the migration routes 

 of whales, for unless hydrographic conditions are favorable plankton 

 wi^l be too scant to feed the animals that are dependent upon it 

 for their sustenance. The Gulf Stream is bounded on the left by 

 cold water, the temperatures of which are reported to be from 

 60° to 57° below that of the Gulf Stream, Favorable conditions 

 for growth of plankton are created where the cold polar current 

 mixes with water of higher temperature. And it is along the 

 border layers of these great currents of icy water that the produc- 



