482 SCIENCE PROGRESS 



the neighbourhood of Norway are therefore of very great 

 importance. To Otto Pettersson belongs the credit of first 

 attempting to demonstrate the intimate relationship between 

 the hydrographic conditions in the sea off the coasts of 

 Norway, and the climatic conditions in that country. He 

 showed that an unusually strong Gulf Stream flow led to an 

 accumulation of relatively warm water in the Norwegian Sea. 

 As this cooled it gave up its heat to the atmosphere, setting 

 up ascending air-currents, which gave rise to cyclonic atmos- 

 pheric disturbances, with all the consequences resulting from 

 these eddies. He also showed that there was an intimate 

 relationship between the air-temperature over Norway and 

 the sea-temperature near the land ; and that the earlier or 

 later ploughing or sowing seasons might be associated with 

 earlier or later maxima of the Gulf Stream flow. Pettersson's 

 suggestions have had the greatest possible influence on 

 methods of oceanographical and fishery research : indeed, 

 it is largely owing to them that the International Fishery 

 Investigations were initiated. 



The Gulf Stream in High Latitudes 1 



The dotted lines on fig. i show the lines along which the 

 hydrographic observations are being systematically taken. 

 Along each of these lines there is a series of "stations," and 

 at each station the temperature of the sea is determined, by 

 means of insulated, or reversing thermometers, at the surface 

 and sea-bottom, and at a number of intermediate levels ; 

 while, at the same time, samples of the water are taken for 

 the purpose of salinity determinations, or of analyses of gas- 

 contents, etc. A " hydrographic section " of the sea under 

 the line of observations is constructed by drawing isohalines 

 and isotherms, representing the condition of the water, as 

 regards the distribution of temperature and salt-contents, by 

 means of contour lines. Such a section shows that the water 

 nearer the land is usually low-salinity water, while that near 



1 The most recent and authoritative work on the oceanography of the Norwegian 

 Sea is that by Bjorn Helland-Hansen and Fridjof Nansen, " The Norwegian 

 Sea : its Physical Oceanography, based on the Norwegian researches 1900- 1904," 

 Report on Norwegian Fishery and Marine Investigations, vol. ii., pt. 1, No. 2, 

 pp. i.-xx. + 1-390 ; tables and 28 plates. Kristiania, 1909. 



