216 winds; 



that it is blowing there we know from the little 

 white clouds, which are sometimes seen at great 

 heights coming up, as it were, against the lower 

 trade wind. Several times, too, more distinct 

 evidence of them has been obtained from the 

 ashes, which they have carried with them imme- 

 diately after volcanic discharges. Thus, on the 

 occasion of the outburst of Cosiguina, which I 

 have before mentioned, as taking place on the 20th 

 of January 1835, the ashes were borne in a north- 

 easterly direction as far as Jamaica, and at the 

 same time were driven in a south-westerly direction 

 into the Pacific Ocean, where at a distance of about 

 nine hundred and sixty miles from the volcano, 

 the Ship ' Conway' fell in with a shower of ashes. 

 Hence, the ashes were carried by the rising current 

 of air partly in a northerly, and partly in a southerly 

 direction. 



At the limits of the torrid zone the upper trade- 

 wind blows very much lower; it is found, for 

 instance, on the Peak of Teneriffe even in 

 summer. Beyond the tropics it comes gradually 

 lower, reaching the surface in summer in some- 

 what higher latitudes than in winter, and appears 

 as the south-west wind so prevalent in the tempe- 

 rate zone. 



The trade-winds, and, indeed, especially those 

 of the Atlantic Ocean, have been known, as we 

 learn from the history of the discovery of America, 



