28 THE OCEAN. 



higher elevation. The empty space thus left is in- 

 stantly filled by the surrounding air rushing in, 

 pressed by the weight of the atmosphere above: this 

 motion communicated to the air, has been supposed 

 to constitute a wind blowing in the direction of 

 the spot where the heat was generated. It must 

 be confessed, however, that the cause thus adduced 

 does not seem adequate to produce the effects at- 

 tributed to it; though probably some of the cur- 

 rents of the air are owing to variations of its tem- 

 perature. And as these variations are perpetually 

 occurring, dependent on causes which are difficult 

 to detect, and as the aerial currents resulting from 

 them act and react on each other, variously modi- 

 fying their direction, force, and duration, the or- 

 dinary winds are irregular and inconstant even to 

 a proverb. Some observations, however, recently 

 made, have revealed some particulars of a highly- 

 interesting character, concerning the winds of the 

 temperate zones: one of which is, that they blow 

 in a circular direction ; that is, the course which 

 a storm has taken, if marked out on a map or 

 globe, would describe a circle, often of many de- 

 grees in diameter. The direction of the gale in 

 the circle is not arbitrary but seems to be inva- 

 riably from north to west, south, and east, in the 

 northern hemisphere, and in the opposite course 

 in the southern. These winds appear to be inti- 

 mately connected with magnetism : it is a curious 

 fact, that, in the midst of the southern Atlantic, 

 where magnetic influence is at the lowest degree 

 of intensity, storms are unknown, while the mcri- 



