THE GULF STREAM. 43 



tlie Gulf Stream leaves the coasts of the United States, it begins to 

 vary its position according to the seasons ; the limit of its northern 

 edge, as it passes the meridian of Cape Eace (Plate YI.), being in 

 wnter about latitude 40-41°, and in September, when the sea is 

 hottest, about latitude 45-46^. The trough of the Gulf Stream, 

 therefore, may be supposed to waver about in the ocean not unlike 

 a peimon in the breeze. Its head is confined between the shoals of 

 the Bahamas and the Carolinas ; but that part of it which stretches 

 over towards the Grand BanlvS of Ne^^foundland is, as the tem- 

 peratm-e of the waters of the ocean changes, fii^st pressed down to- 

 wards the south, and then again up towards the north, accordmg to 

 the season of the year, 



125. To appreciate the extent of the force by which it is so 

 The phenomenon prcsscd, Ict US imagine thc watcTS of the Gulf 

 ractof "^ ^ ^ '^ ' ■ Stream to extend all the way to the bottom of the 

 sea, so as completely to separate, by an impenetrable liquid wall, 

 if you please, the waters of the ocean on the right from the waters 

 in the ocean on the left of the stream. It is the height of sum- 

 mer : the waters of the sea on either hand are for the most part in 

 a Hquid state, and the GuK Stream, let it be supposed, has as- 

 sumed a normal condition between the two divisions, adjusting itself 

 to the pressm^e on either side so as to balance them exactly and 

 be in equilibriimi. Now, again, it is the dead of winter, and the 

 temperatm^e of the waters over an area of millions of square miles 

 in the North Atlantic has been changed many degrees, and this 

 change of temperatm^e has been folloAved likewise by a change in 

 volume of those waters, amounting, no doubt, in the aggregate, 

 to many hundi'ed miUions of tons, over the whole ocean ; for sea- 

 water, unlike fresh (§ 103), contracts to freezing, and below. Now 

 is it probable that, in passing fi'om then' summer to their winter 

 temperatm^e, the sea-waters to the right of the GuK Stream should 

 change their specific gi-avity exactly as much in the aggregate as 

 do the waters in the whole ocean to the left of it ? If not, the 

 difference must be compensated by some means. Sparks are not 

 more prone to fly upward, nor water to seek its level, than Nature 

 is sure with her efforts to restore equilibrium in both sea and ah* 

 whenever, wherever, and by whatever it be disturbed. Therefore, 

 though the waters of the GuK Stream do not extend to the bottom, 

 and though they be not impenetrable to the waters on either hand, 

 yet, seeing that they have a w^aste of waters on the right and a 

 waste of waters on the left, to which (§ 70) they offer a sort of 



