190 THE PHYSICAL GEOGRAPHY OF THE SEA. 



multitudes of partial and conflicting currents — all, in their set and 

 strength, apparently as uncertain as the winds. 



402. The better to appreciate the operation of such agencies in 

 The influence of rains producing currcuts iu the sca, now here, now there, 

 currents, first this waj, and then that, let us, by way of illus- 



tration, imagine a district of two hundred and fifty-five square 

 miles in extent to be set apart, in the midst of the Pacific Ocean, 

 as the scene of operations for one day. We must now conceive a 

 machine capable of pumping up, in the twenty-four hours, all the 

 water to the depth of one mile in this district. The machine must 

 not only pump up and bear off this immense' quantity of water, 

 but it must discharge it again into the sea on the same day, but 

 at some other place. Now here is a force for creating currents 

 that is equivalent in its results to the effects that would be pro- 

 duced by bailing up, in twenty -four hours, two hundred and fifty- 

 five cubic miles of water from one part of the Pacific Ocean, and 

 emptying it out again upon another part. The currents that would 

 be created by such an operation would overwhelm navigation and 

 desolate the sea ; and, happily for the human race, the great at- 

 mospherical machine which actually does perform every day, on 

 the average, all this lifting up, transporting, and letting down of 

 water upon the face of the grand ocean, does not confine itself to 

 an area of two hundred and fifty-five square miles, but to an area 

 three hundred thousand times as great ; yet, nevertheless, the 

 same quantity of water is kept in motion, and the currents, in the 

 aggregate, transport as much water to restore the equilibrium as 

 they would have to do were all the disturbance to take place upon 

 our hypothetical area of one mile deep over the space of two 

 hundred and fifty -five square miles. ISTow when we come to rec- 

 ollect that evaporation is lifting up, that the winds are transport- 

 ing, and that the clouds are letting down every day actually such 

 a body of water, we are reminded that it is done by little and little 

 at a place, and by hair's breadths at a time, not by parallelopip- 

 edons one mile thick, and that the evaporation is most rapid and 

 the rains most copious, not always at the same place, but now 

 here, now there. We thus see actually existing in nature a force 

 perhaps quite suf&cient to give i^ise to just such a system of cur- 

 rents as that which mariners find in the Pacific (§ 401) — currents 

 which appear to rise in mid ocean, run at unequal rates, sometimes 



