IH) THE rilYSICAL GEOGRAPHY OF THE SEA. 



They turn inth the cle froni the southwest, and that, consequently, there 



iitinJs of a watch iiiii i i t -t 



ubuiit the south pole, should 06 aoout the poles a disc or circular space 



aiai7ist them about r> i • i • i i • n i 



thcnorth. 01 caims, lu which the air ceases to move lorward 



as wind, and ascends as in a calm ; about this calm disc, there- 

 fore, there sh.ould be a whirl, in which the ascending column of 

 air revolves from right to left, or against the hands of a watch. 

 At the south pole the winds come from the northwest (§ 213), 

 and consequently there they revolve about it with the hands of a 

 watch. That this should be so will be obvious to any one who 

 will look at the arrows on the polar sides of the calms of Cancer 

 and Capricorn (Plate I., § 215). These arrows are intended to 

 represent the prevailing direction of the wind at the surface of 

 the earth on the polar side of these calms. 



259. The arrows that are drawn about the axis of this diagram 

 The arrows in the di- ^^^ intended to rcprcscnt, by their flight, the mean 

 rgram of the winds, ^ifectiou of thc wiud, and by their length and their 

 feathers the mean annual duration from each quadrant. Only 

 the arrows nearest to the axis in each belt of 5° of latitude are 

 drawn with such nicety. The largest arrow indicates that the 

 wind in that belt blows annually, on the average, for ten months 

 as the arrow flies. The arrow from the next most prevalent 

 quarter is half-feathered, provided the average annual duration 

 of the wind represented is not less than four months. The un- 

 feathered arrows represent winds having an average duration of 

 less than three months. The arrows are on the ^decimal scale; 

 the longest arrow — which is that representing the southeast trade- 

 winds between 5° and 10° S., where their average duration is 

 ten months — being half an inch. Winds that blow five months 

 are represented by an arrow half this length, and so on. The half- 

 bearded arrows are on a scale of two for one. It appears, at first, 

 as a singular coincidence that the wind should whirl in these discs 

 about the poles as it does in cyclones, viz., against the hands of a 

 watch in the northern, with them in the southern hemisphere. 



260. To act and react upon each other, to distribute moisture 

 The offices of sea and over the surfacc of the earth, and to temper the cli- 

 eJonomy. matc of different latitudes, it would seem, are two of 

 the many offices assigned by their Creator to the ocean and the air. 

 When the northeast and southeast trades meet and produce the 

 equatorial -calms (§ 212), the air, by the time it reaches this calm 



