50 VIEWS OF NATURE. 



mination of the ship's place during the days in which Colum- 

 bus was crossing the great bank is the more important, 

 because it shews us that for three centuries and a half the 

 total accumulation of these socially-living thalassophytes, 

 (whether consequent on the local character of the sea's bottom 

 or on the direction of the recurrent Gulf stream,) has re- 

 mained at the same point. Such evidences of the persistence 

 of great natural phenomena doubly arrest the attention of the 

 natural philosopher, when they occur in the ever-moving 

 oceanic element. Although the limits of the fucus banks 

 oscillate considerably, in accordance with the strength and 

 direction of long predominating winds, yet we may still, in the 

 middle of the nineteenth century, take the meridian of 41 

 west of Paris (or 8 38' west of Greenwich) as the principal 

 axis of the great bank. Columbus, with his vivid imaginative 

 force, associated the idea of the position of this bank with the 

 great physical line of demarcation, which according to him, 

 " separated the globe into two parts, and was intimately con- 

 nected with the changes of magnetic deviation and of climatic 

 erlations." Columbus when he was uncertain regarding the 

 longitude, attempted to determine his place (February, 1493,) 

 by the appearance of the first floating masses of tangled weed 

 (de la primer a yerva} on the eastern border of the great Corvo 

 bank. The physical line of demarcation was, by the pow- 

 erful influence of the Admiral, converted on the 4th of May, 

 1493, into a political one, in the celebrated line of demar- 

 cation between the Spanish and Portuguese rights of pos- 

 session*. 



(8) p. 3" The Nomadic Tribes of Tibbos and Tuaryks" 



These two nations, which inhabit the desert between 

 Bornou, Fezzan, and Lower Egypt, were first made more 

 accurately known to us by the travels of Hornemann and 

 Lyon. The Tibbos or Tibbous occupy the eastern, and the 

 Tuaryks (Tueregs) the western portion of the great sandy 

 ocean. The former, from their habits of constant moving, 

 were named by the other tribes "birds." The Tuaryks are 

 subdivided into two tribes the Aghadez and the Tagazi. 

 These are often caravan leaders and merchants. They speak 



* See my Examen Critique, t. iii. pp. 6499 ; and Cosmos, vol. ii. 

 P. 655. Bolm's edition. 



