302 DEPTHS OF THE OCEAN 



in the temperature of the sea-surface off the Norwegian light- 

 houses for the month of February, while the upper curve shows 

 the variations of the date at which the coltsfoot {Ttissilago far- 

 fara) began to blossom in central Sweden (Upsala). This plant 

 begins to blossom, on the average, about the 9th April, the 

 exact date varying in different years from the i8th March to 

 the 28th April. The two curves agree in many points ; when 

 the water off the lighthouses was relatively warm in February 

 the flowering commenced early, and when it was cold the 

 blossoming was late. 



Pettersson had at his disposal only observations from the 

 water in the immediate vicinity of these coast stations, but since 



7^ 75 76 77 7a 79 SO 61 82 83 8H 85 86 87 68 89 90 9/ 92 93 9^ 95 96 



^ 



13 - 



9 — 



30mrf5 



zo — 



6' 



Fig. 207. 

 The upper curve shows the time of blossoming of Tz/ssi/ago /ar/ara at Upsala during a series of 

 years. The lower curve shows the surface-temperature of the sea off the west coast of Norway, 

 in the month of February of the same years. 



regular investigations were started in the Norwegian Sea in 

 1 900, we have excellent series of observations during a succession 

 of years, not only in the coast-water, but also in that branch of 

 the Gulf Stream which flows into the Norwegian Sea. Nansen 

 and the writer have found, by going through all the observations 

 made in the years 1900 to 1905, that there are great variations 

 in the temperature-conditions of this Atlantic current, and that 

 these variations are apparently followed by corresponding 

 variations in many other conditions ; for example, the temper- 

 ature of the air, the year's harvest, the growth of the trees, and 

 various circumstances touching the appearance of great shoals 

 of fish. One or two instances may be referred to here. 



During the Norwegian investigations a section was run 



