200 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY. 



tukeri up at one place and rained down at another, and in tbis 

 process, therefore, we have agencies for multitudes of partial and 

 conflicting currents — all in their set and strength, apparently a« 

 uncertain as the winds. 



402. Tlie influence of rains and evaporation tijyon currents. — The 

 better to appreciate the operation of such agencies in producing 

 currents in the sea, nowhere, now there, first this way, and then 

 that, let us, by way of illustration, 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 effect that would be produced by baling 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 atmo- 

 spherical machine wdiich 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. Now when we come to 

 recollect that evaporation is lifting up, that the winds are trans- 

 porting, 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 hairs' breadths at a time, not by 

 parallelopipedons 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 sufficient to give rise to just such 

 a system of currents as that which mariners find in the Pacific 



