584 SUPPLEMENTARY REMARKS ON WINDS, ETC. 



Currents. — The North African Current (see pages 312—324) sets down 

 upon the Cape Verde Islands, in a south-westerly direction, at the rate of 

 about 12 miles a day, influenced by the prevailing wind. This sot is more 

 uncertain and irregular among the eastern islands, and has been the cause 

 of several wrecks. Rollers are frequent in July, August, and September, 

 most violent generally at full and change of the moon. 



The channels between the islands, and between them and the coast, are 

 deep and clear, with the exception of the dangerous Leton Rock, between 

 Boavista and Maio, but all precautions must be taken in approaching, 

 owing to the frequent fogs and the uncertainty of the currents. To the 

 eastward and N.E. the water is frequently much discoloured. Sailing 

 vessels will find it advisable to approach from the North ; from the 

 South, they will experience calms and squalls, and the Trade Wind blows 

 strongly between the islands, and causes a rough sea. If not bound to 

 any port in the islands, it is advisable to pass westward of the group. 



Instances have occurred of vessels coming from the Canaries being set 

 far to the eastward or westward of their supposed position, even though 

 the passage is so short. 



Mr. Finlaison states that, " In leaving Tenerife for the Cape Verde 

 Islands, you will certainly have the wind from E. by S. to N.E. as you 

 approach the islands." He also adds, that in the passage a current 

 was generally found setting from S.S.W. at the rate of half a mile an 

 hour, which is contrary to the current on the African coast. (See 

 pages 312—324). 



Bonetta Rock (?). — In April, 1835, the ship Madeline was reported to 

 have been wrecked on a reef, at about 8 leagues E.N.E. from Boavista, 

 or in lat. 16° 17' 20" N., long. 22° 23' 50" W. Other reefs have also been 

 reported far to the eastward and N.E. of Boavista. Captain Vidal, by 

 his researches in the Mtna, satisfactorily proved that no such dangers as 

 the Madeline or Bonetta Reefs have any existence. These imaginary 

 dangers were also sought for in vain by the American Exploring squadron, 

 and the result seems to be, that the Madeline was impelled to the S.W. by 

 the current, and wrecked on Hartwell Reef off Boavista. Lieutenant Lee, 

 U.S.N. , on the cruise of the Dolphin, found a depth of 1,580 fathoms on 

 one spot, in about lat. 17° N., long. 21° 40' W., near the reported site of 

 Emily Rock, and great depths close up to the islands. 



