CURRENTS OF THE SEA. 167 



description. There are many of them, some of whicli, at times, 

 run with great force. On a voyage from the Society to the Sand- 

 wich Islands, I encountered one running at the rate of ninety-six 

 miles a day. 



459. And what else should we expect in this ocean but a sys- 

 tem of currents and counter-currents apparently the most uncer- 

 tain and complicated ? The Pacific Ocean and the Indian Ocean 

 may, in the view we are about to take, be considered as one sheet 

 of water. This sheet of water covers an area quite equal in ex- 

 tent to one half of that embraced by the whole surface of the 

 earth ; and, according to Professor Alexander Keith Johnston, 

 who so states it in the new edition of his splendid Physical Atlas, 

 the total annual fall of rain on the earth's surface is one hundred 

 and eighty-six thousand, two hundred and forty cubic imperial 

 miles. Not less than three fourths of the vapor which makes this 

 rain comes from this waste of waters ; but supposing that only 

 half of this quantity, i. e., ninety-three thousand, one hundred and 

 twenty cubic miles of rain falls upon this sea, and that that much, 

 at least, is taken up from it again as vapor, this would give two 

 hundred and fifty-fi.ve 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 winds. 



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

 producing currents in the sea, now here, 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 effects that would be produced by bailing up, in 



