CUBRENTS OF THE SEA. 191 



that botli tlie north-east and the south-east trade-winds can take 

 up and cany off. I have marked on Plate IX. the dhection of the 

 supposed warm-water cuiTent which conducts these overheated and 

 briny waters from the tropics in mid ocean to the extra-tropical 

 regions where precipitation is in excess. Here, being cooled, and 

 agitated, and mixed up mth 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 navi- 

 gation. 



401. There are also about the equator in this ocean some curious 

 Equatorial currents. cmTonts, wliich I have Called the " Doldrimi Cur- 

 rents " of the Pacific, but which I do not understand, and as to 

 which observations are not sufficient yet to afford the proper ex- 

 planation or description. There are many of them, some of which 

 at times run with great force. On a voyage from the Society to 

 the Sandmch Islands I encountered one running at the rate of 

 ninety-six miles a day. These cm-rents 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 

 Sandvdch Islands. In Captain Pichon's abstract log of the French 

 corvette " L'Eurydice," from Honolulu to Tahiti, in August, 1857, 

 a " doldrum " cmTont is recorded at 79 miles a day, west by north. 

 He encountered it between 1° N. and 4° S., where 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 

 cmTents and counter-cmTents apparently the most uncertain and 

 comphcated ? 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 extent 

 to one half of that embraced by the whole smface 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 smface is one hundred and 

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

 Not less than three fomihs of the vapom^ which makes this rain 

 comes irom this waste of waters ; but supposing that only half of this 

 quantity, i. e., ninety-tliree thousand one huncbed and twenty cubic 

 miles of rain falls upon this sea, and that that much, at least, is taken 



