14 WRITINGS OF JOSEPH HENRY. [1855- 



materially altered. Heated water is constantly carried from 

 the equatorial regions towards the poles, and streams of cold 

 water returned, by means of which the temperature of the 

 earth is modified and the extremes reduced in intensity. The 

 great currents of the ocean are seven in number, and may 

 be best and most clearly described in connection with an 

 hypothesis as to their origin. For this purpose let us sup- 

 pose the earth at rest and the equatorial regions continually 

 heated by the sun. In this condition a continuous current 

 of air from the north and another from the south would 

 blow towards the equator, there ascend and flow backward 

 in the upper regions towards the poles. If we next suppose 

 the earth to be in motion on its axis from west to east, and 

 compound the effects of this motion with that of the winds 

 towards the equator on either side, they will not meet di- 

 rectly opposite each other, as in the previous supposition, 

 but at an acute angle, and produce a belt of wind from east 

 to west entirely around the earth in the region of the equator. 

 The continued action of this wind on the surface of the 

 water would evidently give rise to a current of the ocean in 

 the belt over which the wind passed. If now instead of 

 considering the earth entirely covered with water, we sup- 

 pose the existence of two continents extending from north to 

 south, forming barriers across the current we have described, 

 and establishing two separate oceans, similar to the Atlantic 

 and Pacific, then the continuous current to the west would 

 be deflected right and left or north and south at the western 

 shore of each ocean, and would form four immense whirlpools, 

 namely, two in the Atlantic, one north and the other south 

 of the equator, and two in the Pacific, similar in situation 

 and direction of motion. The regularity of the outline of 

 these whirls will be disturbed by the configuration of the 

 deflecting coasts, and the form of the bottom of the sea, as 

 well as by islands and irregular winds. For a like reason 

 a similar whirlpool will tend to be produced in the Indian 

 Ocean, the current from the east being deflected down the 

 coast of Africa, and returning again into itself along a 

 southern latitude on the western side of Australia. A fifth 



