502 PASSAGES OVER THE ATLANTIC. 



North to N.B. If the course to the Westward of Madeira be adopted, a 

 'vessel will make the Westernmost of the Canaries only, and her position 

 may be rectified by a sight of Palma or Ferro. / 



But a sight of the coast of Africa is by no means necessary for vessels 

 bound to the Senegal or Goree. What has been said of the currents and 

 prevailing winds in this navigation, leaves no doubt that it is perfectly 

 useless to make the land more than 50 or 60 miles to the Northward of 

 the Senegal, when bound to the Bar anchorage. This digression is the 

 utmost which should be made from the above course ; and by means of 

 the lead, and some few latitudes carefully observed, it might even be 

 made a direct one. On leaving Teneriffe, the course from its South point 

 should be S.W. by S. as far as the parallel of 21°, then S. by W. f W. as 

 far as 20°, and from thence S. by E. J E. without any further alteration. 



The first course will carry a vessel 85 miles from the nearest point on 

 the African coast, and in a track where no danger has been found. The 

 second will conduct her nearly 100 miles to the Westward of the Western- 

 most point of the Bank of Arguin. By the third she will make the coast 

 in the neighbourhood of the Marigot or Lagoon of Mosquitos (lat, 16° 36^'), 

 from whence she may coast the shore until abreast the Senegal. 



If it be found necessary to make the land during the night, the lead, 

 being the only means of correcting the estimated run, should be used 

 frequently and with great care. At about 25 miles N.W. by N. from the 

 Senegal, a bottom of white sand will be found, with 70 fathoms. From 

 thence the depth gradually decreases towards the shore, and at 1 mile from 

 it there is 7 or 8 fathoms. When in 15 fathoms of water, it is advisable 

 to anchor until daylight. 



There is a source of error attached to the navigation of the African 

 coast, which must be carefully guarded against. It is the optical illusion 

 caused by the great horizontal refraction, which renders any correct 

 estimation of distance almost impossible. Numerous instances of it might 

 be cited which would hardly be credited ; therefore the moment the coast 

 is seen, the lead only should be trusted to determine the distance from it. 



Track from Senegal to Goree. — The Almadies of Cape Verde (described 

 hereafter) are 94 miles S.W. f W. from the roadstead of the Senegal, and 

 the prevailing currents set nearly on that bearing ; it is, therefore, the 

 course to be steered from the Senegal to Cape Verde during the day ; 

 during the night steer a quarter of a point or more Westerly. From 

 Cape Verde to Goree the course is direct ; it is merely to coast the shore 

 at the distance of 2 miles. From 6 miles off Cape Verde to Cape St. 

 Mary, at the mouth of the Gambia, the direct course and distance are 

 S. by E. ^ E. 93 miles, in all which space soundings may be found. 



If bound to a port South of Goree, vessels should steer to sight Cape 

 Verde, as the winds are fresher near the cape than at the islands. Hence 

 the navigation is easy in the fine season, with the prevalent N.E. winds, 

 but in the rainy season the S.W. winds make it difficult. After rounding 

 Cape Palmas the land should be kept in sight, at a distance of 10 to 15 

 miles, and when 30 or 40 miles Westward of the destination the land 

 should be anproachod more closely, to avoid being carried to the East- 

 ward of the place. 



