INFLUENCE OF THE GULF STREAM UPON COMMERCE. 59 



the influence of these high temperatures, philosophers have not 

 been able to explain. 



76. The injiiience 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 w^ere. 



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, wxre then an 

 experiment. The Nautical Ephemeris itself w^as 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 staff" and " back staff," 

 the "sea-ring" 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 w^as 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 w^hich 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. 



