138 , MR. J. BALL ON THE BOTAIVY 



were confirmed by my own brief experience on finding at Buena- 

 ventura, on open ground clear of the forest, an abundant growth 

 of Cyperacece with a minute TltricuJaria^ while, under a nearly 

 vertical sun and a clear sky, the soil was everywhere moi^t. 



The maximum of rainfall appears to lie some three or four 

 degrees nortli of the equator, for tlie aspect of the coast at Tu- 

 maco, on tbe frontier of Ecuador, indicates a distinct cliange of 

 climate: open spaces of grass-covered ])lain, afiording good pas- 

 ture to borned cattle, could not exist amid the perpetual moisture 

 of the coast only 100 miles farther to the north. So far as I can 

 learn, the low country of Ecuador between the Andes and the 

 sea has what maybe called the normal equatorial climate* — a 

 rainy sea>on extending through more than lialf the year, with an 

 interval of comparative cessation of rainfall. Tliere is reason, 

 bowever, to conjecture that some projecting points on the 

 coast, especially the Capes San Lorenzo and Santa Elena, are 

 affected by the southerly currents of the air and ocean that main- 

 tain the exceptional aridity of tbe coasts of Northern Chili and 

 Peru, and I shall have occasion to adduce some evidence to that 

 effect. 



The coasts of tbe Gulf of Gruayaquil possess, as might be ex- 

 pected, an equatorial climate- — an average temperature of about 

 82° Fabr., subject to very sligbt variation, with considerable 

 though not excessive moisture. On the southern side of the 

 gulf, at Tumbez, the frontier port of Peru, the same climate is 

 £>aid to prevail; but on issuing from the gulf and rounding the 

 headland of Cape Blanco, little over 4° S. lat., an abrupt change 

 of climate and vegetation is encountered. Under the influence 

 of the cold Humboldt current which, issuins: from the southern 

 ocean, sets along tbe west coast of S. America, and of tbe breeze 

 wbieb constantly flows in the same direction, the mean tempera- 

 ture is reduced by more than ten degrees of Pahrenbeit, and, the 

 land being almost always warmer than tbe sea-breeze, rain falls 

 very rarely and at long intervals. 



The same conditions, with scarce any variation, prevail along 

 the coast from Cape Blanco to Copiapd, or somewhat south of 

 that place, over more than 23 degrees of latitude and a coast- 

 line of about 1700 miles. The maximum of aridity appears to be 

 reached a little north of the Tropic of Capricorn ; but the mean 



In some places near the equator there appear to be two rainy seasons in the 

 year, with intervening dry seasons; but there are few indications of this phe- 

 nomenon in equatorial America. 



