ANNOTATIONS AND ADDITIONS. 61 



a west wind often takes the place of the general east or 

 trade-wind of the tropics. It is the wide expanse of the 

 desert of Sahara which causes this westerly wind. The air 

 over the heated sandy plain becomes rarefied and ascends, 

 the air from the sea rushes in to supply the void so formed, 

 and thus there sometimes arises a west wind, adverse to 

 ships bound to the American coast, which are made in this 

 manner to feel the vicinity of the heat-radiating desert 

 without even seeing the continent to which it belongs. 

 The changes of land and sea breezes, which blow alternately 

 at certain hours of the day or night on all coasts, are due 

 to the same causes. 



The accumulation of sea-weed in the neighbourhood of 

 the African coast has been often spoken of by ancient 

 writers. The locality of this accumulation is a problem 

 which is intimately connected with our conjectures respecting 

 the extent of Phrenician navigation. The Periplus, which 

 has been ascribed to Scylax of Caryanda, and which, 

 according to the researches of Niebuhr and Letronne, was 

 very probably compiled in the time of Philip of Macedon, 

 describes beyond Cerne a quantity of fucus forming a weed- 

 covered sea a kind of " Mar de Sargasso ;" but the locality 

 indicated appears to me to differ very much from that 

 assigned in the work entitled " De Mirabilibus Auscultationi- 

 bus," which long bore, unduly, the great name of Aristotle. 

 (Co-mpare Scyl. Caryand. Peripl. in Hudson, vol. ii. p. 53, 

 with Aristot. de Mirab.' Auscult. in opp. omnia ex. rec. 

 Bekkeri, p. 844, 136.) The pseudo- Aristotle says, 

 " Phoenician mariners, driven by the east wind, came in four 

 days' sail from Gades to a nart where they found the sea 



