CAPTAIN TUCKEY'S NARRATIVE. 11 



the vicinity of soundings. Here I may observe, that should 

 this discolouration of the sea at such a distance from the 

 land be a constant circumstance, it may serve to guide 

 ships which have no means of correcting their reckonings, 

 and thereby prevent the shipwrecks that so often happen 

 on the coast of the Desart in the vicinity of cape Blanco, 

 by their not allowing for the easterly current that seems 

 invariably to set quite from the English Channel to the 

 Canaries, and the effect of which we found to be, in that 

 distance, equal to one degree and a half of longitude. 



The towing-net was now become tolerably successful, 

 taking up from time to time various species of mollusca, 

 such as Portuguese men of war, (Holothuria physalis), 

 Vellela mutica, (La Marc) Thalis trilineata, (ib.) besides some 

 testacea, viz. the Helix ianthina, with the living animal ; 

 many dead shells of the Nautilus spiralis, &c. specimens of 

 all which were preserved by Mr. Cranch. 



The holothuria made its first appearance on the 4th in- 

 stant in latitude 24° 13', longitude 18° 31', temperature of 

 the atmosphere at noon being 68°, of the surface of the sea 

 Q5°. These animals continued more or less abundant until 

 past the Cape Verde islands, when they entirely disappear- 

 ed. The greatest abundance of them was however on the 



