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 — 
sc[ueezed, 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 working 
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, 
suflicient 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- 
