192 PHYSICAL GEOar.APHY OF THE SEA, AND ITS 3IETE0E0L0GY. 



up from it again as vapour, this would give two hundred and fifty- 

 five cubic miles as the quantity of water which is daily lifted up 

 and poured back again into this expanse. It is taken up at one 

 place and rained down at another, and in this process, therefore, we 

 have agencies for multitudes of partial and conflicting currents — all 

 in their set and strength, apparently as uncertain as the Tsinds. 



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

 The influence of ^ produciug currcuts in the sea, now here, now there, 

 tbn\ipon cul?mts. first this Way, and then that, let us, by way of illus- 

 ti'ation, imagine a district of two hundred and filty-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-fom- hom's, all the 

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

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

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

 some other place. Noav here is a force for creating cmTents that is 

 equivalent in its results to the eftect that would be produced by 

 baling up, in twenty-fom' hom'S, two hundred and fifty-five cubic 

 miles of water fr^om one part of the • Pacific Ocean, and emptying- 

 it out again upon another part. The cm-rents that would be created 

 by such an operation would overwhelm na^dgation and desolate 

 the sea ; and, happily for the human race, the great atmospherical 

 machine which actually does perform every day, on the average, 

 all this lifting up, transporting, and letting d.o^YD. 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 thi^ee hmidi^ed 

 thousand times as great ; yet, nevertheless, the same quantity of 

 water is kept in motion, and the cm-rents, in the aggregate, trans- 

 port as much water to restore the equilibrium as they would have 

 to do were all the distm-bance to take place upon our h}q3othetical 

 area of one mile deep over the space of two hmidred and fifty-five 

 square miles. Now when we come to recollect that evaporation is 

 lifting up, that the winds are transporting, and that the clouds are 

 letting down every day actually such a body of water, we are re- 

 minded 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 natm-e a force perhaps quite sufficient to give 

 rise to just such a system of cmTents as that which mariners find in 



