22 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 70 



AlEAN TEMPERATURE FOR EACH DECADE. 

 A. Water. 



II 



III 



V 



VI 



VII 



10-30° W 

 30-50° W 

 50-70° W 



Mean. . 



10-30° W 

 30-50° W 

 50-70° w 



Mean.. 



1 1. 19 

 13-36 

 11-59 



12.05 



11.42 



13-23 



12.06 

 12.24 



B. Air. 



II. 12 

 II. 71 



9.83 



10.89 



C. Water Minus Air. 



half of February and in the greater part of March form a trust- 

 worthy indication of the temperatures of the great water-masses. 

 At the end of March the surface temperature begins to rise rather 

 rapidly. There soon comes about a warm layer in the water, so 

 that !he surface temperature can no longer be regarded as an index 

 of the temperature relations of the great water-masses lying beneath. 

 The air temperatures for the whole region show a sharply marked 

 minimum in the middle of February, after which they rise rather 

 rapidly to the first of March ; but after that up to March 20, only 

 small changes occur. Later the temperature rises again very rapidly. 

 The peculiar form which the curve takes, (see fig. ii-L) with its 

 horizontal course through the first three weeks of March, may be 

 due to several causes. One might well suppose that our mean values 

 are not good enough to give a very regular curve. And it is indeed 

 possible that this is a reasonable explanation, for we are consider- 

 ing only a few tenths of a degree for the third and fifth decades. 

 One cannot suppose that satisfactory decade values for the air 

 temperature can be obtained from so short a series of observations 

 as eleven years, and especially not when many of the decade mean 

 values for the single years rest upon so few and so unsatisfactory 



