THE GULF STREAM. 45 



tlie seasons; the limit of its northern edge, as it passes the 

 meridian of Cape Eace (Plate YI.), being in winter about lati- 

 tude 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 pennon 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 Banks of Newfoundland is, as the tem- 

 perature of the waters of the ocean changes, first pressed down 

 towards the south, and then again up towards the north, accord- 

 ing to the season of the year. 



125. The j^lienomenon thermal in its character. — To appreciate the 

 extent of the force by which it is so pressed, let us imagine the 

 waters of the Gulf 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 

 summer : the waters of the sea on either hand are for the most 

 part in a liquid state, and the Gulf Stream, let it be supposed, 

 li;^s assumed a normal condition between the two divisions, 

 adjusting itself to the pressure on either side so as to balance 

 them exactly and be in equilibrium, Now, again, it is the dead 

 of winter, and the temperature of the waters over an area of 

 millions of square miles in the North Atlantic has been changed 

 man}^ degrees, and this change of temperature has been followed 

 likewise by a change in volume of those waters, amounting, no 

 doubt, in the aggregate, to many hundred millions of tons, over 

 the whole ocean ; for sea-w^ater, unlike fresh (§ 103), contracts 

 to freezing, and below. Now is it probable that, in passing from 

 their summer to their winter temperature, the sea-waters to the 

 right of the Gulf Stream should change their specific gravity 

 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 com- 

 pensated 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 air whenever, 

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

 the waters of the Gulf 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 waste of waters on the right and a 

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



