INFLUENCE OF THE GULF STREAM UPON COMMERCE. 59 
the influence of these high temperatures, philosophers have not 
been able to explain. ' - 
76. The injiuence of the Gulf Stream upon commerce and navi- 
gation. , ' 
Formerly the Gulf Stream controlled commerce across the At- 
lantic by governing vessels in their routes through this ocean to 
a greater extent than it does now, and simply for the reason that 
ships are faster, instruments better, and navigators are more skill- 
ful now than formerly they were. 
Up to the close of the last century, the navigator guessed as 
much as he calculated the place of his ship : vessels from Europe 
to Boston frequently made New York, and thought the land-fall 
by no means bad. Chronometers, now so accurate, were then an 
experiment. The Nautical Ephemeris itself was faulty, and gave 
tables which involved errors of thirty miles in the longitude. The 
instruments of navigation erred by degrees quite as much as they 
now do by minutes ; for the rude " cross staiF" and " back staff," 
the " sea-ririg" and "mariner's bow," had not yet given place to 
the nicer sextant and circle of reflection of the present day. In- 
stances are numerous of vessels navigating the Atlantic in those 
times being 6°, 8°, and even 10° of longitude out of their reckon- 
ing in as many days from port. 
77. Though navigators had been in the habit of crossing and 
recrossing the Gulf Stream almost daily for three centuries, it 
never occurred to them to make use of it as a means of giving 
them their longitude, and of warning them of their approach to 
the shores of this continent. 
Dr. Franklin was the first to suggest this use of it. The con- 
trast afforded by the temperature of its waters and that of the sea 
between the Stream and the shores of America was striking. The 
dividing line between the warm and the cool waters was sharp 
2) ; and this dividing line, especially that on the western side 
of the stream, never changed its position as much in longitude as 
mariners erred in their reckoning. 
78. When he was in London in 1770, he happened to be con- 
sulted as to a memorial which the Board of Customs at Boston 
sent to the Lords of the Treasury, stating that the Falmouth 
packets were generally a fortnight longer to Boston than com- 
mon traders were from London to Providence, Rhode Island, 
