168 THE PHYSICAL GEOGRAPHY OF THE SEA. 



twenty-four hours, two hundred and fifty-five cubic miles of wa- 

 ter 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 atmospherical machine 

 which 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 hund- 

 red and fifty-five square miles, but to an area three hundred thou- 

 sand 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 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 hair's 

 breadths at a time, not by parallelopijDcdons one mile thick — that 

 the evaporation is most rapid and the rains most copious, not al- 

 ways 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 — currents which appear to rise in mid ocean, run at 

 unequal rates, sometimes east, sometimes west, but which always 

 lose themselves where they rise, viz., in mid ocean. 



461. Under Cureents. — Lieutenant J. C.Walsh, in the U. S. 

 schooner "Taney," and Lieutenant S. P. Lee, in the U. S. brig 

 " Dolphin," both, while they were carrying on a system of obser- 

 vations in connection with the Wind and Current Charts, had 

 their attention directed to the subject of submarine currents. 



462. They made some interesting experiments upon the sub- 

 ject. A block of wood was loaded to sinking, and, by means of 

 a fishing-line or a bit of twine, let down to the depth of one hund- 

 red or five hundred fathoms, at the will of the experimenter. A 

 small barrel as a float, just sufficient to keep the block from sinking 

 farther, was then tied to the line, and the whole let go from the boat. 



