viii PREFACE 



forces the banlv water back, especially in the Labrador channel (at depths of 75 to 

 100 in.), where also the Atlantic water of high salinity, 35°, penetrates farther in 

 towards the channel in the spring at a depth of 100 to 200 m. As to temperature, the 

 turface of the gulf is warmer in summer than in spring, owing to the (fresher) 

 coastal water and the Gulf Stream. In the straits of Northumberland it is as high as 

 18-5° C. (about 65° F.), while the lowest record is 11-65° C. close up to the north 

 "shore. In the inner parts of the gulf at 10 m. depth the temperature ranges about 

 10° C, but in the outer parts at 20 m. an extremely low temperature prevails at 50 

 to 80 m., especially in the northern parts. There must be a constant inflow of frigid 

 Arctic water through the deeper parts of Belle Isle straits, as the cold water layers 

 are more extended in summer than in spring, though this cold influence appears, off 

 the Newfoundland banks, to decrease in summer. The influence of the Labrador 

 current and the Gulf Stream introduces many complications, as Mr. Bjerkan shows, 

 an(| the water-masses of continental origin, of low salinity, add to the complexity, 

 both superficial and at greater depths. The effects potently influence the breeding, 

 hatching, and larval development of important food-fishes, and throw light on the 

 migrations and the distribution of the schools of adult-fish on which our great Atlantic 

 fishing industries depend. 



