174 FOUNDERS OF OCEANOGRAPHY 



land its rate is only IJ miles an hour. Though thus 

 changing in cross-section and speed, it is said to preserve 

 its individuality and distinctive character for over 3,000 

 miles. Off the coast of North Carolina the edge of the stream 

 is still sharply marked, the clear indigo blue of the warmer 

 water abutting against the dull green of the coastal water 

 of the United States and forming a line that is visible to 

 the eye of the passing sailor. Even as far north as the Banks 

 of Newfoundland the temperature of the Gulf Stream water is 

 from 20° to 30° F. higher than that of the surrounding sea. 



The Gulf Stream, however, is not constant in volume 

 and in position. It shows seasonal and even annual varia- 

 tions. Petermann (1870) insisted on the seasonal variations 

 in the strength of the Gulf Stream, and this has been fully 

 established since by H. N. Dickson. The limit of its 

 northern edge off Cape Race, Newfoundland, is in March 

 about latitude 40° to 41°, and in September about latitude 

 45° to 46°. It is pushed down to the south by the colder 

 water in winter, and then expands to the north in summer. 

 Its drift eastward across the Atlantic towards Europe is 

 strongest in summer. It shows, moreover, pulsations 

 extending over periods of years, the effects of which 

 in the north of Europe can be traced, according to the 

 Scandinavian investigators, in their weather, their harvests 

 and their sea-fisheries. 



Benjamin Franklin attributed the Gulf Stream to the 

 action of the trade -winds, and this was the prevalent view 

 amongst seafaring men until Captain Maury in 1860 put 

 forward the view that the winds were insufficient to produce 

 the effect, and that the true cause of the strong current of 

 tropical water of high salinity was to be found in the difference 

 of specific gravity and of temperature between the water 

 in the Gulf of Mexico and in the Atlantic outside. But the 

 high salinity would render the Gulf water heavier and the 

 high temperature causes it to be lighter, so these two 

 characteristics would tend to counteract, and the resulting 



