458 RESEARCHES IN SOUND. 



tilde of about 35°, and then turning gradually to the eastward, crosses the 

 Atlantic and impinges against the coast of Northern Europe. Through- 

 out its entire course, on account of the immense capacity of water for 

 heat, the tem])erature of the stream is greater than that of the ocean on 

 either side. In addition to this stream, the Atlantic Ocean is traversed 

 by another current of an entirely opposite character, one of cold water, 

 which, coming from the arctic regions down Davis's Strait, is thrown, by 

 the rotation of the earth, against our coast, passing between it and the 

 Gulf-stream, and sinking under the latter as it approaches the southerij 

 extremity of the United States. 



These conditions are those most favorable to the production of fogs, 

 since whenever the warm air, surcharged with moisture, is blown from 

 the Gulf-stream over the arctic current and mingles with the cold air 

 of the latter, a precipitation of its vapor takes place in the form of fog. 

 Hence, especially in summer, when the wind in the eastern part of the 

 United States is in a southeasterly direction, fogs prevail. As we pro- 

 ceed southerly along the coast, the fog-producing winds take a more 

 easterly direction. 



A somewhat similar circulation in the Pacific Ocean produces fogs on 

 the western coast of the United States. In this ocean a current of warm 

 water, starting from the equatorial regions, passes along the shores of 

 China and Japan, and, following the general trend of the coast, turns 

 eastward and continues along our shore. The northern part of this 

 current being waruier than the ocean through which it passes, tends to 

 produce dense fogs in the region of the Aleutian Islands and the coast 

 of Alaska. As this current descends along the American coast into 

 lower latitudes it gradually loses its warmth, and soon assumes the 

 character, in regard to the water through which it j^asses, of a compara- 

 tively colder stream; and to this cause we would attribute the preva- 

 lence of fogs on the coast of Oregon and California, which are most 

 prevalent during the spring and early summer, with wind from the 

 northwest and west. 



From what has been said, it is evident that the fogs in the Aleutian 

 Islands occur chiefly in summer, when southwesterly winds prevail and 

 mingle the moist air from the warm current with the colder air of the 

 more northerly latitude. In winter, the wind being from the north 

 chiefly, the moist air is driven in an opposite direction, and dense fogs 

 therefore at this season do not prevail. 



In regard to the fogs on the coast of Maine, the following interesting 

 facts were furnished me by the late Dr. Stimpson, formerly of the Smith- 

 sonian Institution and of the Chicago Academy of Sciences, who had 

 much experience as to the weather during his dredging for marine speci- 

 mens of natural history in the region of Grand Manan Island, at the 

 entrance of the Bay of ^und5^ 



"So shaq)ly marked," says Dr. Stimpson, "is the diiference of tem- 

 perature of the warm water from the Gulf-stream and that of the polar 



