62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. JO 



If we consider now the different parts of this great region of 

 investigation more closely, it is apparent that the difference in the 

 geographical relations comes to an expression in these curves. Par- 

 ticularly the curves for those fields which adjoin the continental 

 coast in the east, that is, between io° and 20° west longitude, and 

 those similarly lying on the west, that is, between 60° and 70° west 

 longitude, differ from the curves for the fields in the middle of the 

 ocean. This holds not only for the region Channel to New York 

 (see fig. 20) but also for the southern region Portugal to Azores, 

 figure 28. 



The curves for the most easterly 2° fields of the northern region 

 have in general about the same type, between 10° and 20° (see 

 fig. 16) as is also shown by these 10° fields in figure 20. These 

 curves are distinguished by several well marked features from 

 the curve of more westerly fields. Particularly the curves for the 

 first decade groups in figure 20 show as a distinguishing character- 

 istic a symmetrical depression from the year 1898 to 1902, then 

 two secon4ary maxima in the year 1903 and 1905 and a minimum 

 in the year 1904. In the year 1906 there came a small depression. 

 In the curves for the second decade group these characteristic 

 features were somewhat altered. 



A similarity with the curves for the first decade group is found 

 also in the curve for the most northerly 10° field for the northern 

 region, that is, from 10° to 19° west longitude and from 43° to 44° 

 north latitude, as shown in figure 28. This is yet more apparent in 

 the curve for the field westward of it, 20° to 29° west longitude 

 and 43° to 44° north latitude. 



All of these curves belong, as one may say, to the same type and are 

 distinguished from the curves for the fields further out toward the 

 middle of the ocean. Closely related to them are the curves for 

 the three southerly 10° fields between 10° and 20° west longitude 

 and between 27° and 43° north latitude as shown in figure 28, which 

 also present different characters from the more westerly curves. 

 Indeed their features are at times inverted. 



The curves for the most westerly field of the ocean between 60° 

 and 70° west longitude show great features which are completely 

 different from those which we find in all the rest and they form a 

 type completely distinct from them. In part they go inversely as 

 the others. They have for example minima in the years 1901 and 

 1902 and in the year 1905. The curve for the first decade group has 

 besides this a strong minimum in the year 1898. Furthermore they 



