206 PHYSICAL GEOGRAPHY OF THE SEA : 



great currents of circulation over the globe, which we know 

 must be the certain effect of differences of temperature, but 

 which may in part also depend on the diurnal rotation of the 

 earth, affecting the rate of motion and direction of such 

 currents as they flow through different latitudes. The Arctic 

 current setting into the Atlantic from Baffin's Bay, and 

 transporting huge icebergs to be dissolved by the warmer 

 seas of the South, is well known as a branch of one of these 

 circuits. The existence of a similar circulation of waters in 

 the Pacific -the other great ocean which stretches from 

 pole to pole of the globe though less defined in its details, 

 comes in confirmation of this view. It is more directly cor- 

 roborated by the old experiment of casting bottles into the 

 sea containing dates of place and time; which transported 

 in silent, slow, but certain course, give information to 

 watchful observers on distant seas or shores. These mute 

 interpreters of natural phenomena often render better service 

 to science than the thoughts or theories of man. The chart 

 drawn up by Admiral Beechy, representing the tracks of 

 more than a hundred bottles, shows that all the equatorial 

 waters of the Atlantic tend westwards towards the Mexican 

 Gulf, to issue thence in the Gulf-stream. Those thrown 

 overboard in mid-ocean, or on any part of the African coast, 

 have been found after a certain lapse of time either in the 

 West Indies, or on the British shores, or floating in the course 

 of the Gulf-stream between. There is even reason to believe 

 that some of these bottles have been discovered on their 

 second circuit ; arrested probably on the coasts of Spain by 

 the drift southwards, carried along the African coast into 

 the equatorial seas, and thence againacross the Atlantic to 

 the Gulf of Mexico. The first among the valuable plates 

 appended to Captain Maury's work, clearly shows the course 

 thus indicated, and illustrates the whole scheme of the 

 mighty currents we have been describing. 



