xxxii THE COAST OF ECUADOR 491 



view generally held that the aridity of this extensive coast region, 

 stretching from the thirtieth parallel of south latitude to the 

 equator, arises from the loss by the trade-winds of all their 

 moisture in the interior of the continent before reaching the 

 western countries of Chile and Peru. Mr. Ball, in his book on 

 South America, opposed this view, though from reasons only par- 

 tially valid, since he instanced the Ecuador coast as being, contrary 

 to the theory, a wet coast, whereas we know that a large stretch of 

 it is arid and not unlike Peru. The parting of the ways in this 

 discussion lies in the answer to the query. Why should the south- 

 east trade carry so much moisture to the east side of South 

 America, whilst the south-west winds, that are equally prevalent on 

 the west coast of the continent, are drying winds which convert the 

 sea-border into a desert, as in Northern Chile, or into a region of 

 semi-sterility, as in the instance of Peru ? Other things being 

 equal, we should expect both sea-borders of the continent in these 

 latitudes to be well watered. In the answer to the question why the 

 south-east trade should be a wet wind and the south-west wind a 

 dry one lies a fatal objection to the prevailing view. 



When Professor Davis, in his article on North America in the 

 Encyclopedia Britannica (vol. 25), observes in connection with the 

 arid coast regions on the west side of the continent that the 

 southerly flow of the winds along the Pacific coast gives them a 

 drying] quality, thus causing the extension to the coast in South 

 California and in North Mexico of the arid regions of the interior, 

 he seems to imply that these winds acquire their drying capacity 

 in flowing from cooler to warmer latitudes. On this view all 

 trade-winds should be drying winds, whereas the reverse would 

 appear to be the case. 



There is some condition, present on one coast of the South 

 American continent and absent on the other, which determines why 

 a southerly wind, blowing landward, is in the one case moist and in 

 the other dry. According to my own view the winds of the arid 

 coast regions of western North America cross the cool waters of 

 the Californian current, and thus acquire their drying quality on 

 striking a sea-border more highly heated than the winds them- 

 selves. On the tropical west coast of South America the winds 

 also become drying winds by passing over the cold waters of the 

 Peruvian or Humboldt current, where mists are in consequence of 

 frequent occurrence ; and on striking the more highly heated land- 

 surface at the sea-border the moving air does not part with any 

 more moisture until an altitude of some thousands of feet above 



