APPENDIX C: KNUDSEN — 4 — 



The proof is as follows: when the cyclonic centre is so placed, that the wind 

 which blows over the Fseroes, undoubtedly comes from the Kast Icelandic Polar 

 Stream, a regular fall of the air-temperature below the average will ensue, and 

 this will be the case more in winter and spring than in summer and autumn. It 

 is therefore of interest, to observe the variations caused in the temperature of the 

 air by the reciprocal action of the warm water of the Atlantic Ocean and the 

 cold East Icelandic Polar stream. 



For this purpose, I have noted down the observations for each single day, 

 over the period from December 1883 to November 1892, and divided the whole 

 material into two groups. In the first group, I have placed all the days on which 

 it could be determined with certainty, that the wind' came from the region of the 

 Gulf Stream, whilst the second group comprise the days when the wind came 

 from the Polar Stream. Those days have been excluded, on which it could not 

 be concluded with absolute certainty, from the direction, of the winds and isobars 

 alone, whether the wind blew from the cold or warm region, even when the 

 temperature of the air left no doubt about the matter. Further, the days of no 

 wind and those on which the wind had changed its direction from the one region 

 to the other, have also been left out of consideration in this investigation. Lastly, 

 those days are also excluded on which the wind had remained weak for one or 

 more days after changing its direction. Experience has shown that the wind, 

 after changing its direction, must blow for some time with a certain force in 

 order to effect any change in the temperature. As a rule, but a few hours are 

 sufficient. 



On separating the material in this way, 987 out of the total 3288 days fall 

 into the first group and 849 into the second. If we now take the monthly averages 

 for the temperature of the air, we having the following table: 



Difference between 

 Temperature of the air the air-temperature 



with the wind from 



Wind from the Wmd from the tjjg Gulf Stream and 



1883 — 1892 Gulf Stream Polar Stream the wind from the 



Polar Stream 



December 6-2° o-o° 6-2° 



January 5-3° — 0-4° 57° 



February 5-8° — o-6" 6-4° 



March .' 5-6° — i-i° 67° 



April 7-2° 2-5° 47° 



May 8-3° 4-4° 3-9° 



June 10-3° 77° 2-6° 



July 10-9° 9-4° 1-5= 



August 11-4° 9-0° 2-4° 



September .... 10-2" 6-8° 3-4" 



October 8-8" 4-2° 4-6" 



November 7-4° i-8° 5-6° 



Average 8-i° 3-6° 4-5° 



