\ 



61 



was almost as rapid as from 20° 8' to 10° 46 y ; 

 but it slackened extremely on the limits of the 

 torrid zone, from 29° 10 to 20° 8'. This in- 

 ' equality is no doubt caused by the currents, 

 that mingle the waters of different latitudes, 

 and which, according as we approach the Ca- 

 nary islands or the coasts of Guyana, set either 

 to the south-east or the north-north-west. Mr. 

 de Churruca, who crossed the equator in his 

 voyage to the straits of Magellan, in the twenty- 

 fifth degree of west longitude *, found the maxi- 

 mum of the temperature of the Atlantic Ocean 

 at it's surface in six degrees north latitude. In 

 those parts, in latitudes equally distant from 

 the equator, the water of the sea was colder to 

 the south than the north. We shall soon see, 

 that this phenomenon varies with the seasons, 

 and that it depends in a great measure on the 

 impetuosity, with which the waters run toward 

 the north and north-west, across the channel 

 formed between Brazil and the coasts of Africa. 

 If the motion of these waters did not modify the 

 temperature of the ocean, the increment of heat 

 under the torrid zone would be enormous, be- 

 cause the surface of the water reflects infinitely 

 fewer of those rays which approach the perpen- 

 dicular, than of those which fall in a more ob- 

 lique direction. 



I have observed in the Atlantic Ocean, as well 



* In the month of October, 1788. 



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