TIDE-RIPS AND SEA DRIFT. 



395 



sails so nicely trimmed to the breeze ? Who 'pilots them, and 

 what master hand holds the helm ? AVhat compass, and of whose 

 workmanship, is that which guides these delicate and graceful 

 little argonauts from sea to sea ? x^niving off the " Stormy 

 Capes," the flotilla is separated, one division holding its way for 

 the racific,'the other hauling up for the Atlantic, each bound on 

 its high and secret mission. They build, equip, and repair as 

 ikey go ; the fleet is imperishable, but individual life in it is 

 ephemeral. The}^ die, these tiny " men o' war," one after another, 

 but the same watchful Providence .that cared for them while 

 living, now provides for their burial being dead. The inanimate 

 shell, drawn to distant seas by under currents, descends like 

 autumnal leaves from depth to depth by an insensible fall. In 

 future times the seaman's sounding-rod may reach the bottom on 

 which it has fallen, and thus reveal to man the secret paths of 

 the sea, — or when the geological clock next strikes the hour, the 

 same little shell may, by some throe of nature, be brought up to 

 the surface, and spread out in its marl bed, to fertilize and make 

 fruitful unknown lands. 



741. Drift described. — There is a movement of the waters of 

 the ocean which, though it be a translation, yet it does not 

 amount to what is known to the mariner as " current," for our 

 nautical instruments and the art of navigation have not been 

 brought to that state of 'perfection which will enable navigators 

 generally to detect as currents the flow to which I allude as drift. 

 If an object be set afloat in the ocean, as at the equator, it would, 

 in the course of time, even though it should not be caught up b}' 

 any of the known currents, find its way to the icy barriers about 

 the poles, and again back among the tepid waters of the tropics. 

 Such an object would illustrate the drift of the sea, and by its 

 course would indicate the route w^hich the surface-waters of the 

 sea follow in their general channels of circulation to and fro 

 between the equator and the poles. 



742. Plate IX.— The object of Plate JX., therefore, is to illus- 

 trate, as far as the present state of my researches enable me to do, 

 the circulation of the ocean as influenced by heat and cold, and 

 to indicate, on one hand, the routes by which the overheated 

 waters of the torrid zone escape to cooler regions, and to point 

 out, on the other, the great channel-ways through which the 

 same waters, after having been deprived of this heat in the extra- 

 tropical or polar regions, return again towards the equator; it 



