208 



M:H. T. HOPKINS ON THE INFLUENCE OP SUN-HEATED LAND 



which is the reverse of what would take place if heated air 

 over the desert were ascending to the higher regions, and 

 overflowing to adjoining countries. 



Teneriffe, one of the Canary Islands, is to the north of the 

 locality where the Harmattan blows, and Humboldt says that 

 when he was on the Peak of that island, a west wind blew 

 with violence, though the island below was under the ordinary 

 influence of the north-east trade wind. But this shows a state 

 of things just the reverse of what would be found if heated 

 air ascended from the desert. Under such circumstances there 

 would be a west wind blowing below from the cool sea and 

 towards the heated land, and the air which rose from the 

 desert would overflow, and if towards the sea, in the upper 

 regions. Thus all the facts of the case that have been passed 

 under our view, are at variance with the common theory of 

 ascending currents from sun-heated land. The water of the 

 sea in this part of the Atlantic Ocean, it may be observed, 

 comes from the north, it being the place of termination of the 

 great gulf stream that flows from Newfoundland by Ireland ; 

 but no continued wind can be traced, even in the summer, 

 blowing from this cool sea to the heated desert. Captain 

 Fitzroy, when writing of this part, says — " At St. Jago, the 

 wind being always from the north or east from December to 

 June, a ship can moor as close to the weather shore as may be 

 convenient ; but from July to October no vessel should deem 

 the bay of Porto Praya secure, or anchor near the shore, 

 because southerly gales sometimes blow with great strength."* 

 Thus we see that all winds are found to blow in this part 

 except westerly, which would be the principal, if not the only 

 one, if air ascended from the desert and overflowed in the 

 upper regions. 



There is another wind which must not be passed unnoticed, 

 as it may possibly be thought to countenance the ideas here 

 combatted. It blows more or less throughout the year from 



* Fitzroy, p. 51. 



