242 THE PHYSICAL GEOGRAPHY OF THE SEA. 



as they come down from the Arctic Ocean through Davis's Straits, 

 press upon the warm waters of the Gulf Stream, and curve their 

 channel into a horse-shoe. Navigators have often been struck 

 with the great and sudden changes in the temperature of the wa- 

 ter hereabouts. In the course of a single day's sail in this part 

 of the ocean, changes of 15°, or 20°, and even of 30°, have been 

 observed to take place in the temperature of the sea. The cause 

 has puzzled navigators long, but how obvious is it not now made to 

 appear ! This " bend" is the great receptacle of the icebergs which 

 drift down from the north ; covering frequently an area of hund- 

 reds of miles in extent, its waters differ as much as 20°, 25°, and 

 in rare cases even as much as 30° of temperature from those about 

 it. Its shape and place are variable. Sometimes it is like a pen- 

 insula, or tongue of cold water projected far down into the waters 

 of the Gulf Stream. Sometimes the meridian upon which it is 

 inserted into these is to the east of 40°, sometimes to the west 

 of 50° longitude. By its discovery we have clearly unmasked 

 the very seat of that agent which produces the Newfoundland fogs. 

 It is spread out over an area frequently embracing several thou- 

 sand square miles in extent, covered with cold water, and sur- 

 rounded on three sides, at least, with an immense body of w^arm. 

 May it not be that the proximity to each other of these two very 

 unequally heated surfaces out upon the ocean would be attended 

 by atmospherical phenomena not unlike those of the land and sea 

 breezes ? These warm currents of the sea are powerful meteoro- 

 logical agents. I have been enabled to trace, in thunder and lights 

 ning, the influence of the Gulf Stream in the eastern half of the 

 Atlantic, as far north as the parallel of 55° north ; for there, in 

 the dead of winter, a thunder-storm is not unusual. 



523. These isothermal lines of 50°, 60°, 70°, 80°, &c., may 

 illustrate for us the manner in which the climates in the ocean are 

 regulated. Like the sun in the ecliptic, they travel up and down 

 the sea in declination, and serve the monsters of the deep for signs 

 and for seasons. 



524. It should be borne in mind that the lines of separation, as 

 drawn on Plate IX., between the cool and warm waters, or, more 

 properly speaking, between the channels representing the great 

 polar and equatorial flux and reflux, are not so sharp in nature as 

 this plate would represent them. In the first place, the plate rep- 



