30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. /O 



ferences between the different land stations which Meinardus has 

 chosen, for these may he along- nearly the same isobars. (This was, 

 for example, the case in February, 1899, in 1904 and at other times, 

 when the chosen air pressure differences were very small, the 

 air circulation over the North Atlantic Ocean, however, very active, 

 and this with very diff'erent consequences on the temperature of 

 Europe.) Meinardus neglects to' consider the effect of the pos- 

 sible changes in the wind directions in the different parts of the 

 ocean. He supposes that, for example, an increased velocity of the 

 wind over the Gulf Stream would increase its heat transportation 

 and make the ocean warmer without considering that the increased 

 wind might take a more westerly or northwesterly direction than is 

 common. 



Meinardus considers the variations of the surface temperatures 

 on the Norwegian coast near the lighthouses Utsire, Helliso and 

 Ona, where the coast waters are fairly mixed with the waters of 

 the Baltic currents, and near Horns Riff on the west coast of Shet- 

 land where the intermixture of coast water is yet more strongly 

 marked, in both cases to be due to the greater or less transportation 

 of warm water by the Gulf Stream. 



Although as we shall show later we cannot accept these assump- 

 tions, yet Meinardus' proofs of the dependence of the variations 

 of the air pressure differences, the variations in the surface tem- 

 peratures on the Norwegian coast, the heat of the upper layer of 

 the ocean at Horns Riff", and also the variations in the transporta- 

 tion of ice by the Labrador stream are of great interest. 



The relation between the air pressure distribution over the Atlan- 

 tic Ocean, with its Icelandic minimum, and the variations in the 

 velocity of the Gulf Stream or in the ocean circulation generally, 

 Meinardus considers to be a closed chain of cause and effect. A 

 more active Gulf Stream drift would make the ocean in the north 

 warmer and a depression of the Icelandic air pressure minimum 

 would be the conse(|uence. This again would increase the air 

 circulation and increase the velocity of the Gulf Stream, and vice 

 versa. By these self-inductions he thinks that the tendency to steadi- 

 ness in the temjjerature deviations, either positive or negative, 

 thro'ugh several months may be explained. But the secondary conse- 

 quence is that cold ocean currents, particularly the Laborador cur- 

 rent, will l)e increased by increased air circulation, or vice versa, and 

 thereby the Gulf Stream will be cooled, or vice versa, and hence 

 after the lapse of the necessary time the sea in the east and the north 



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