350 On the Gulf Stream and contiguous currents. 



tion of temperature on leaving the margin of the stream is most re- 

 markable, and is almost unparalleled except in the immediate vicia- 

 ity of ice. 



We shall in vain attempt to explain this extraordinary change of 

 temperature by the proximity of shallows or soundings, for this can- 

 not avail if the water itself be derived from the gulf current, to say 

 nothing here of the general unsoundness of this explanation. 



I have long since become satisfied that the current in question is 

 neither more nor less than a direct continuation of the polar or Lab- 

 rador current, which bears to the southward the great stream of drift 

 ice from Davis' strait, and which, in its progress to the lower lati- 

 tudes, is kept in constant proximity to the American coast by the 

 dynamical law or influence which, in the northern hemisphere, causes 

 all currents which pass in a southerly direction to incline towards 

 the west, in consequence of the increasing rotative motion of the 

 earth's crust in the opposite direction, as in the case of the trade- 

 winds in the lower latitudes. 



In collating the observations of various navigators which have been 

 published, we find reason to conclude that, in ordinary states of 

 weather, this current may be traced from the coast of Newfoundland 

 to Cape Hatteras, and perhaps to Florida, the reflux influence which 

 follows a violent gale being of but short duration. 



According to this view of the case, the Gulf Stream, in its course 

 from Florida to the Bank of Newfoundland, is for the most part im- 

 bedded or stratified upon a current which is setting in the opposite 

 direction in its progress from the polar regions. The impulses by 

 which these diverse currents are maintained being, however, as per- 

 manent and unchanging as the diurnal rotation of our planet, their 

 opposite courses on this coast while in contact with each other, are 

 no more surprising or inexplicable than the case of two opposite cur- 

 rents of the atmosphere, and the latter are often known to maintain 

 opposite courses for a long period, and at high velocities, while thus 

 superimposed one upon the other. 



From the fact that these great currents have their origin, one in 

 the tropical and the other in the polar seas, their presence can be 

 unfailingly identified by means of the thermometer ; and with the 

 aid of good chronometers their position and extent may be determin- 

 ed with greater certainty than has yet been done, particularly in the 

 latitudes between Nantucket and Florida. In this department of 

 hydrology, every navigator may contribute something of value to his^ 

 profession and to science, for which no other qualifications are requi- 



