GULT' STnEAM, CLIMATES, AND COMMERCE. 71 



Delaware in winter to be blown off and to go the West Indies, 

 and there wait for the return of spring before they would 

 attempt another approach to this part of the coast. 



1S6. Thermal navigation. — Accordingly, Dr. Franklin's dis- 

 covery with regard to the Gulf Stream temperature was looked 

 upon as one of great importance, not only on account of its 

 affording to the frosted mariner in winter a convenient refuge 

 from the snow-storm, but because of its serving the navigator 

 with an excellent land-mark or beacon for our coast in all 

 weathers. And so viewing it, the doctor, through political 

 considerations, concealed his discovery for a while.. The prize 

 of 20,000Z., which had been offered, and partly paid, by the 

 British government, to Harrison, the chronometer maker, for 

 improving the means of finding longitude at sea, was fresh in 

 the minds of navigators. And here it was thought a solution of 

 the grand problem — for longitude at sea was a grand problem — 

 had been stumbled upon by chance; for, on approaching the 

 coast, the current of warm water in the Gulf Stream, and of 

 cold water on this side of it, if tried with the thermometer, 

 would enable the mariner to judge witii great certainty, and in 

 the worst of weather, as to his position. Jonathan Williams 

 afterwards, in speaking of the importance which the thermal 

 use of these warm and cold currents would prove to navigation, 

 pertinently asked the question, " If these stripes of water had 

 been distinguished by the colours of red, white, and blue, could 

 they be more distinctly discovered than they are by the constant 

 use of the fnermometer ?" And he might have added, could 

 they have marked the position of the ship more clearly ? 



187. Commodore Truxton. — 'When his work on Thermometrical 

 Navigation appeared, Commodore Truxton wrote to him: " Your 

 publication will be of use to navigation by rendering sea-voyages 

 secure far beyond what even you yourself will immediately 

 calculate, for I have proved the utility of the thermometer very 

 often since we sailed together. It will be found a most valuable 

 instrument in the hands of mariners, and particularly as to those 

 who are unacquainted with astronomical observations; * * * * 

 these particularl}' stand in need of a simple method of ascertain- 

 ing their approach to or distance from the coast, especially in the 

 winter season ; for it is then that passages are often prolonged, 

 and ships blown off the coast by hard westerly winds, and 

 vessels get into the Gulf Stream without its being known ; on 

 which account they are often hove to by the captains suj^posing 



