THE DRIFT OF THE SEA. 253 



and its tail in the midst of the ocean (^ 492), is wedge-shaped ; 

 its waters chng together {^ 28), and are pushed to and fro — 

 squeezed, if you please — by a pressure (§ 53), now from the right, 

 then from the left, so as to work the whole wedge along between 

 the cold liquid walls which contain it. May not the velocity of 

 this stream, therefore, be in some sort the result of this workinjr 

 and twisting, this peristaltic force in the sea ? 



549. In carrying out the views suggested by the idea of pulsa- 

 tions in the sea, and their effects in giving dynamical force to the 

 circulation of its waters, attention may be called to the two lobes 

 of polar waters that stretch up from the south into the Indian 

 Ocean, and which are separated by a feeble flow of tropical wa- 

 ters. Icebergs are sometimes met with in these polar waters as 

 high up as the parallel of the fortieth degree of latitude. Now, 

 considering that this tropical flow in mid ocean is not constant — 

 that many navigators cross the path assigned to it in the plate 

 without finding their thermometer to indicate any increase of heat 

 in the sea ; and considering, therefore, that any unusual flow of 

 polar waters, any sudden and extensive disruption of the ice there, 

 sufficient to cause a rush of waters thence, would have the effect 

 of closing for the time this mid-ocean flow of tropical waters, we 

 are entitled to infer that there is a sort of conflict, at times, go- 

 ing on in this ocean between its polar and equatorial flows of wa- 

 ter. For instance, a rush of waters takes place from the poles 

 toward the equator. The two lobes close, cut off" the equatorial 

 flow between them, and crowd the Indian Ocean with polar wa- 

 ters. They press out the overheated waters ; hence the great 

 equatorial flow encountered by Captain Grant. 



Thus this opening between the cold-water lobes appears to 

 hold to the chambers of the Indian Ocean, with their heated wa- 

 ters, the relations which the valves and the ventricles of the hu- 

 man heart hold to the circulation of the blood. The closing of 

 these lobes at certain times prevents regurgitation of the warm 

 waters, and compels them to pass through their appointed chan- 

 nels. 



550. From this point of view, how many new beauties do not 

 now begin to present themselves in the machinery of the ocean ! 

 its great heart not only beating time to the seasons, but palpitat- 

 ing also to the winds and the rains, to the cloud and the sun- 



