RECENT HYDROBIOLOGICAL INVESTIGATIONS 489 



formed. His measurements of the growth of the trees were 

 made at eleven places in eastern Norway, and are represented 

 graphically by Helland-Hansen and Nansen. I reproduce their 

 diagram as fig. 5. The thick line represents the mean surface 

 temperature of the sea over the Sognefjord line, and the thin 

 line the mean summer growth of the Fir in eastern Norway. 

 The degree of correlation is so good that one cannot doubt that 

 the two series of events are associated. 



Meinardus associated two groups of conditions : 



A. Weak Atlantic Circulation (August to February). 



Low sea-temperature off European coast (November to 



April). 

 Low air-temperature in Middle Europe (February to 



April). 

 Not much ice round Newfoundland (Spring). 

 Much ice round Iceland (Spring). 

 Bad wheat and rye crops in Western Europe and 



Northern Germany. 



B. Strong Atlantic Circulation (August to February). 



High sea-temperature off European coast (November 



to April). 

 High air-temperature in Middle Europe (February to 



April). 

 Much ice round Newfoundland (Spring). 

 Not much ice round Iceland (Spring). 

 Good wheat and rye crops in Western Europe and 



Northern Germany. 



A similar parallelism between the physical conditions in the 

 sea and the yield of the land crops has been demonstrated for 

 Norway by Helland-Hansen and Nansen. This is shown in 

 fig. 6, where the thick continuous line I. represents the surface 

 temperature of the Atlantic water on the Sognefjord line in 

 the May of each of the years considered; and the thin line II. 

 represents the mean annual deviation of the air-temperature 

 of June of the same year from the mean of the preceding thirty 

 3 r ears. The crop of peas, lentils, and beans of the same year 

 is represented by the line III.; that of cereals in general by 

 the line IV. ; potatoes by the line V. ; and hay by the line VI. 



