LOCAL WINDS. 321 



hundred miles is necessary to enable vessels to 

 reach Barbadoes from St. Vincent, a quantity 

 of volcanic ashes fell on the island of Barbadoes, 

 which undoubtedly had their origin in the 

 eruption at St. Vincent. The only explanation 

 of this singular event was upon the supposed 

 existence of this upper or back current. The 

 power of the volcano had projected these ashes 

 entirely through the lower current into the 

 upper, and after being carried by it, they were 

 dropped in Barbadoes. Another curious con- 

 firmation of its existence is recorded by Messrs. 

 Humboldt and Bonpland. They set out on an 

 expeditibn to ascend the Peak of Teneriffe; at 

 its base the trade wind was blowing strongly in 

 its customary direction, but upon reaching the 

 summit they found they had actually penetrated 

 through the lower stratum of air and got into 

 the upper, and they now felt a strong wind 

 blowing in a precisely opposite direction ! 



A variety of local winds, receiving their 

 peculiar modifications from the circumstances 

 in which they originate, are to be found treated 

 of in works upon meteorology. Many of these, 

 together with those here mentioned, appear to 

 be easily explained upon the great principle of 

 the inequalities of temperature. But many cir- 

 cumstances render it at least probable that other 

 causes of motion in air exist beside, or perhaps 



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