132 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



eleven years. The sun spot curve itself is given below in figure 8 

 but inverted. 



The two-year period is of small importance for the temperature 

 of the North Atlantic Ocean. It is inconceivable but that periods of 

 so short an interval must entirely disappear in that great region, 

 for they would be found in different places in consequence of dif- 

 ferent climatic conditions. The three-year period is more strongly 

 brought out, but the period of five or five and a half years is particu- 

 larly marked. This is the half of the sun spot period and is shown 

 by the curve b-d. This is obtained with the help of the difference 

 between the values which are given in the curves h and d and there- 

 fore relates alone to the five-year period. 



It may appear arbitrary to assume that real periods for tempera- 

 ture variations at the surface of the Atlantic Ocean can exist, but 

 such periods obviously need not be primarily for the surface tem- 

 perature of the ocean, but can be called forth by the same causes 

 as for example periods in the air pressure distribution. However, 

 as we have before said, our series of observations is all too short 

 to draw certain conclusions with regard to the matter. 



It is to be noted that in the above analysis we have used only 

 observations of February, but as stated already it appears as if 

 the temperature of the surface of the Altantic Ocean in February 

 is significant of the whole year and the changes which we observe 

 then closely represent the changes for the whole year. In other 

 parts of the Atlantic Ocean we have carried on the investigations 

 for each month in the whole year for about the same period of 

 time, which we have treated above. This has been done for the 

 Danish fields north of 50° north latitude and by the aid of the 

 International Central Bureau in Copenhagen, tables of monthly 

 mean temperatures for the period 1900 to 1913 have been obtained 

 for three fields in the southerly North Atlantic Ocean between 36° 

 and 37° north, between 20° and 21° north, and between 0° and i° 

 north. 



In figure 55 we give yearly curves for the four northerly Danish 

 fields (see curves I to IV), as well as curves for the three fields of 

 the Central Bureau (curves V to VII) according to the results of 

 twelve-month consecutive means. 



We find here the same opposition that we have earlier called 

 attention to between the curve for the easterly Danish field 0° to 9° 

 west longitude (curve I) and the curves for the westerly Danish 

 fields 20° to 29° west longitude and 30° to 39° west longitude, 



