on the Climate of the Canary Islands. 95^ 



est elevation a month after the summer solstice. The Canary- 

 Islands, also, no longer experience any thing resembling tropi- 

 cal rains ; or such as, in the language of seamen, are said to fol- 

 low the sun, and set in when he has reached the zenith. The 

 rains of these climates first make their appearance when the > 

 temperature in winter sinks perceptibly, and has become consi- 

 derably lower than that of the equatorial regions. The cause 

 of the rains, then, appears to be nothing else than that which 

 produces them in all countries towards the pole ; the cooling of 

 the warm south-west winds coming from the tropics and lower 

 latitudes. But since these winds, by the temperature of the har- 

 vest months in the Canary islands, are not immediately cooled 

 down to the point where the condensation of vapour takes place ; 

 the reason is obvious, why the rains should here begin much 

 later than in Spain and Italy, and still more so than in France 

 and Germany. Rain does not often fall on the coast, before the 

 beginning of November, nor later than the end of March. In 

 Italy, the rainy season lasts from the first half of October till 

 the middle of April. 



On the other hand, the summer of the Canary Islands iden- 

 tifies the climate with that of the tropics ; so that, in these lati- 

 tudes, both zones pass into each other. For, from April to October 

 the north east trade-wind blows without intermission, just as it 

 does all the way down to the Mexican Gulf. The trade-wind in 

 summer always stretches farther north, till at last it reaches the 

 coasts of Portugal. In like manner, it recedes back towards the 

 equator, in proportion as the sun advances southward, and the 

 temperature falls. But how far do they proceed ? Do even 

 the south-west winds, if only for a few weeks in December and 

 January, descend on the Cape-Verd Islands ? And is this po- 

 sition, on the boundaries as it were, of the tropical and winter 

 rains, which proves so beneficial and fertilizing to their respec- 

 tive countries, perhaps the cause why these unfortunate islands, 

 in the midst of the ocean, frequently, for many years together, 

 are never blessed with a single drop of rain ? 



The invariableness of the trade-wind during summer is such, 

 that it interrupts, like an insurmountable barrier, all communica- 

 tion at this season, in the direction of south-west to north-east. 

 In two days, one can conveniently reach Teneriff*e from Madeira ; 



