394 THE PHYSICAL GEOGRAPHY OF THE SEA. 



ecliptic, they travel up and down the sea in declination, and serve 

 the monsters of the deep for signs and for seasons. 



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

 The meeting of cool <irawn on Plate IX., between the cool and warm 

 and warm waters, ^^tcrs. Or, more propcrlj speaking, between the 

 channels representing the great polar and equatorial flux and re- 

 flux, are not so sharp in nature as this plate would represent 

 them. In the first place, the plate represents the mean or average 

 limits of these constant flows — polar and equatorial ; whereas, with 

 almost every wind that blows, and at every change of season, the 

 line of meeting between their waters is shifted. In the next place, 

 this line of meeting is drawn with a free hand on the plate, as if 

 to represent an average ; whereas there is reason to believe that 

 this line in nature is variable and unstable as to position, and 

 as to shape rough and jagged, and oftentimes deeply articulated. 

 In the sea, the line of meeting betw^een waters of different tem- 

 peratures and density is not unlike the sutures .of the skull-bone 

 on a grand scale — very rough and jagged; but on the plate it is 

 a line drawn with a free hand, for the purpose of showing the 

 general direction and position of the channels in the sea, through 

 which its great polar and equatorial circulation is carried on. 



735. Now, continuing for a moment our examination of Plate 

 The direction of aque- lY WO are struck wlth the fact that most of the 



ous isotherms on op- tit -i -\ 



posite sides of the sea. thermal Imcs thcrc drawn run from the western 

 side of the Atlantic toward the eastern, in a northeastwardly di- 

 rection, and that, as they approach the shores of this ocean on 

 the east, they again turn down for lower latitudes and warmer 

 climates. This feature in them indicates, more surely than any 

 direct observations upon the currents can do, the presence, along 

 the African shores in the North Atlantic, of a large volume of 

 cooler waters. These are the waters which, having been first 

 heated up in the caldron (§ 726) of St. Koque, in the Caribbean 

 Sea, and Gulf of Mexico, have been made to run to the north, 

 charged with heat and electricity to temper and regulate climates 

 there. Having performed their offices, they have cooled down ; 

 but, obedient still to the " Mighty Yoice" which the winds and the 

 waves obey, they now return by this channel along the African 

 shore to be again replenished with warmth, and to keep up the 

 system of beneficent and wholesome circulation designed for the 

 ocean. 



