104 TRAVELS IN BRAZIL. 



19* and ^0° W. of Greenwich ; and, during the 

 months in which the sun is in the south, find it 

 advantageous to hold near the continent, where 

 northerly winds usually blow. By this means they 

 avoid the shoal called Banco de Porgas, the ex- 

 istence of which, however, has lately been called in 

 question ; as also, the dangerous reef (query, of co- 

 ral?) Boneta, which is said to lie two miles E. by 

 N. of the most northern point of Boa Vista. 



The nearer we approached the Cape Verd 

 Islands, the more different did the character of 

 the elements become. Even in the latitude of the 

 Canaries, we experienced rapid changes in the 

 temperature of the air, and those sudden distinct 

 gusts and whirlwinds which are here frequently ob- 

 served. It was not tQl about the 11th or 12th of 

 June, in the longitude of 21° 51' W. of Paris, 

 when we crossed the tropic of Cancer, beyond 

 those islands, that the N. and E. wind which had 

 hitherto alternated, united in a N.E., and after- 

 wards in a N.N.E. wind, which blew day and 

 night with equal strength towards the equator ; 

 with this steady N. E. wind we made a hundred 

 and fifty miles in four and twenty hours. We 

 perceived a similar change in the temperature of 

 the air and water, as in the saltness of the sea, and 

 otiier natural phenomena. North of the tropic 

 the temperature of the air changed day and 

 night, always differing at least one degree from 

 that of the water ; but now there was a smaller 



