64 THE PHYSICAL GEOGRAPHY OF THE SEA. 



it was made, the Gulf Stream was altogether insidious in its ef- 

 fects. By it, vessels wea'e often drifted many miles out of their 

 course without knowing it ; and in bad and cloudy weather, when 

 many days would intervene from one observation to another, the 

 set of the current, though really felt for but a few hours during 

 the interval, could only be proportioned out equally among the 

 whole number of days. Therefore navigators could have only 

 very vague ideas either as to the strength or the actual limits of 

 the Gulf Stream, until they were marked out to the Nantucket 

 fishermen by the whales, or made known by Captain Folger to 

 Dr. Franklin. The discovery, therefore, of its high temperature, 

 assured the navigator of the presence of a current of surprising 

 velocity, and which, now turned to certain account, would hasten, 

 as it had retarded his voyage in a wonderful degree. 



84. Such, at the present day, is the degree of perfection to 

 which nautical tables and instruments have been brought, that 

 the navigator may now detect, and with great certainty, every 

 current that thwarts his way. He makes great use of them. 

 Colonel Sabine, in his passage, a few years ago, from Sierra Le- 

 one to New York, was drifted one thousand six hundred miles of 

 his way by the force of currents alone ; and, since the application 

 of the thermometer to the Gulf Stream, the average passage from 

 England has been reduced from upward of eight weeks to a little 

 more than four. 



85. Some political economists of America have ascribed the 

 great decline of Southern commerce which followed the adoption 

 of the Constitution of the United States to the protection given 

 by legislation to Northern interests. But I think these statements 

 and figures show^ that this decline was in no small degree owing 

 to the Gulf Stream and the water thermometer ; for they changed 

 the relations of Charleston — the great Southern emporium of the 

 times — removing it from its position as a half-way house, and 

 placing it in the category of an outside station. 



86. The plan of our work takes us necessarily into the air, for 

 the sea derives from the winds some of the most striking features 

 in its physical geography. Without a knowledge of the winds, we 

 can neither understand the navigation of the ocean, nor make our- 

 selves inteUigently acquainted with the great highways across it. 

 As with the land, so with the sea ; some parts of it are as un- 



