64 
THE PHYSICAL GEOGRAPHY OF THE SEA. 
it was made, the Gulf Stream was altogether insidious in its ef- 
fects. By it, vessels were 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 intelligently acquainted with the great highways across it. 
As with the land, so with the sea ; some parts of it are as un- 
4k. 
