NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 79 



full drawn lines and the March curve in a weak dotted line. These 

 curves have on the whole considerable less similarity with ours 

 though the February curve for the years 1900 to 1905 has the 

 same great features as shown in our curves. The curves for 

 these Dutch fields show on the whole after the year 1904 uncom- 

 monly low temperatures. 



The lowest curve of figure 39 gives the yearly temperatures of 

 the air in San Juan, Porto Rico. Between this curve and the yearly 

 curve September to August for the Dutch field 15° to 25° north 

 latitude and 35° to 45° west longitude there exists clear similarity, 

 though with some exceptions, particularly in the year 1905. But 

 in this year the February curve for the same field shows a rise simi- 

 lar to that which we found in several other curves. The curve for 

 Porto Rico shows in a still more marked degree the tendency to 

 sink from 1901 to 1910. 



DIFFERENCE OF TEMPERATURE VARIATIONS IN THE WESTERN, 

 MIDDLE, AND EASTERN PARTS OF THE NORTH ATLANTIC 



If we consider the run of the temperature anomalies in the dif- 

 ferent 10° fields from west towards east in the course of the period 

 of observation, we find on the whole a great regularity. Figure 

 40 gives an assembly of the yearly curves for the temperature 

 anomalies of the surface water for both decade groups for the 

 whole ocean stretch from the Channel to New York. The same 

 curves for the different years are also given in plates 16 to 40, 

 which also include the corresponding curves for the more southerly 

 region between Portugal and New York shown on the left. The 

 minimum years 1899, 1903, and 1904 give curves with well marked 

 concavity (see fig. 40) whereas the maximum years, for example 

 1901 and 1908, show convex curves. This holds particularly for 

 the month of February. This circumstance finds its natural ex- 

 planation in the fact that the yearly variations in the middle part 

 of the ocean are relatively much greater than those of the more 

 eastern part. There happens, in other words, in minimum years 

 a rise of the curves towards the eastern fields, starting from the 

 middle fields. If we take the difference between the anomalies for 

 one of the middle fields and the most easterly fields, we find there- 

 fore a negative value in the minimum years and a positive one in 

 the maximum years. For the month of February we have obtained 

 the anomalies of such differences of the surface temperatures for 

 one of the fields 30° to 39° west longitude minus the surface tem- 



