706 



WINDS OF THE GLOBE 



southern hemisphere, -which ore very strong mid prevail all around the globe, 

 especially from 40° to 60° S. In Puerto Montt these winds also prevail, especially 

 in the cold season, June to August, while the quantity of southerly (cold polar) 

 winds increases in December and February. 



In Central Chili (Valparaiso and Santiago) we meet opposing winds in winter 

 and summer. They are northerly in the cold season, soiitherly in the warm. 

 This is a feature of the sub-tropical belt, which is especially well developed in the 

 southern hemisphere, owing to the great extent of sea. But in Chili the winds 

 are S. and S. W. from December to February, instead of S. E., the direction of the 

 true trades. But this is easily explained by the high chain of the Andes, which 

 does not permit an extensive circulation of air from the S. E. Besides this, air is 

 drawn towards the land from the sea, which is to the westward. The seasons of 

 Central Chili are in keeping with the sub-tropical winds ; the summer months are 

 rainless. The further we advance to the N. the greater time the polar winds 

 (S. E., S., S. W.) blow and the longer is the rainless season. About 27° S. the rain 

 ceases altogether, and this belt stretches along the coast of Bolivia and Peru to 5° S. 

 Santiago has regular sea and land Avinds, especially from December to March, as 

 is shown by the tri-horary observations of the U. S. expedition under Capt. Wilkes. 

 (See tables, Zone 25.) At midnight, 3, and 6 A. M., the winds are nearly N., from 

 9 A. M. to 9 P. INI. they are nearly S. W. There is no gradual passage of one 

 into the other, but a calm separates them in the morning and evening. 



From the latitude of Central Chili to the Isthmus . of Panama Ave can supply 

 the deficiency of land-observations by those made at sea, near the coast. The 

 prevailing wind in zones 25 and 2-4 (25°-35° S.) is S., especially in the last, where 

 from that quarter more than half of all the winds blow. As we advance towards 

 the north the wind is deflected to the S. E. by the influence of the earth's rotation. 

 Between 5° and 10° S. (Zone 20) 90 per cent, of all the winds blow from the S. E. in 

 the cold months of the year, giving the ratio of resultant 96. This gradual change 

 in the direction of the wind is clearly seen on Plates 5 and 6. There is scarcely 

 any trade-wind region in the southern hemisphere where they are so largely pre- 

 vailing, and none in the northern hemispliere. Yet it is necessary to remember that 

 the observations between 5° and 10° S. were taken further from the coast (85°-98° 

 W.) than on the other parallels, and thus the proportion of S. E. Avinds is greater, 

 and of S. less. The nearer to the coast, the less frequent are the S. E. winds, 

 because of the proximity of the Andes on the E., and also because the land is here 

 much Avarmcr than the sea, on account of the extremely cold Peruvian current. 



As Ave approach the equator, the S. winds again increase. BetAveen 0° and 5° S. 

 this increase is probably caused by the position of the cold marine current, Avhich 

 is deflected to the AvestAvard. But southerly winds here cross the equator, and are 

 by the earth's rotation deflected to the S. W. Already between 0° and 5° N. there 

 is a great proportion of S. W. Avinds, though the S. Avinds still prevail. The mean 

 direction is to the W. of S., as shoAvn on Plates 5 and 6. BetAveen 5° and 10° 

 N., even southerly Avinds prevail during nine months, especially from June to 

 August. Only in the Avinter of the northern hemisphere the Avind is N. W., and 

 then even with a small ratio of resultant. The equatorial boundary of the northern 



