CURRENTS OF THE SEA. 199 



precipitation is in excess. Here, being cooled, and ao-itated, 

 and mixed up with waters that are less salt, these over-heated 

 and over-salted waters from the tropics are replenished and 

 restored to their rounds in the wonderful system of oceanic 

 navigation. 



401. Equatorial currents. — There are also about the equator in 

 this ocean some curious currents, which I have called the 

 " Doldnim Currents " of the Pacific, but which I do not under- 

 stand, and as to which observations are not sufficient yet to 

 afford the proper explanation or description. There are many 

 of them, some of which at times run with great force. On a 

 voyage from the Society to the Sandwich Islands I encountered 

 one running at the rate of ninety-six miles a day. These cun-ents 

 are generally found setting to the west. They are often, but 

 not always, encountered in the equatorial Doldrums on the 

 voyage between the Society and the Sandwich Islands. In Cap- 

 tain Pichon's abstract log of the French corvette "L'Eurydice," 

 from Honolulu to Tahiti, in August, 1857, a " doldrum " current 

 is recorded at 79 miles a day west by north. Pie encountered it 

 between 1° N. and 4° S., w^here it was 300 miles broad. On the 

 voyage to Honolulu in July of the same year, he experienced no 

 such current ; but in 6° N. he encountered one of 36 miles, 

 setting south-east, or nearly in the opposite direction. This 

 current does not appear to have been more than 60 miles broad. 

 What else should we expect in this ocean but a system of currents 

 and counter-currents apparently the most uncertain and comj)li- 

 cated ? The Pacific Ocean and the Indian Ocean may, in the 

 view we are about to take, be considered as one sheet of watei . 

 This sheet of water covers an area quite equal in extent 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 eailh's surface is one hundred and 

 eighty-six thousand two hundred and forty cubic imperial miles. 

 Not less than three-fourths of the vapour which makes this rain 

 comes from this waste of w^aters ; 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 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 



