70 STEPPES AND DESERTS. 



World. (Cosmos, vol. ii. p. 259, and note 405, English ed.) The 

 determination of the ship's place, while Columbus was engaged in 

 traversing the great meadows of sea-weed, is the more important, 

 because we learn from it that for three centuries and a half the situ- 

 ation of this great accumulation of thalassophytes, whether resulting 

 from the local character of the bottom of the sea, or from the direc- 

 tion of the Grulf Stream, has remained the same. Such evidences 

 of the permanency of great natural phenomena arrest the attention 

 of the physical inquirer with double force, when they present them- 

 selves in the ever-moving oceanic element. Although the limits of 

 the fucus banks oscillate considerably, in correspondence with the 

 variations of the strength and direction of the prevailing winds, yet 

 we may still in the middle of the 19th century take the meridian of 

 41 W. from Paris (38 38' W. from Greenwich) as the principal 

 axis of the "great bank." In the vivid imagination of Columbus, 

 the idea of the position of this bank was intimately connected with 

 the great physical line of demarcation, which, according to him, di- 

 vided the globe into two parts, with the changes of magnetic varia- 

 tion, and with climatic relations. Columbus, when uncertain re- 

 specting his longitude, (February 1493,) directed himself by the 

 appearance of the first floating streamers of weed (de la primera 

 yerba) on the eastern margin of the great Corvo bank. The phy- 

 sical line of demarcation was, by the powerful influence of the Ad- 

 miral, converted on the 4th of May, 1493, into a political line, being 

 made the celebrated "line of demarcation' ' between the Spanish and 

 Portuguese rights of possession. (Compare my Examen Critique, 

 torn. iii. pp. 64-99, and Cosmos, English ed. vol. ii. pp. 279-280.) 



( s ) p. 27. " The Nomadic Tibbos and Tuaricks." 

 These two nations inhabit the Deserts between Bornou, Fezzan, and 

 Lower Egypt. They were first made known to us with some exact- 

 ness by Hornemann's and Lyon's travels. The Tibbos or Tibbous 

 roam through the eastern, and the Tuaticks (Tueregs) through the 

 western, parts of the Great Desert. The first are called by the other 

 tribes, from being in continual movement, " birds." The Tuaricks 

 are distinguished into those of Aghadez and those of Tagazi. , They 

 are often engaged as conductors of caravans, and in trade. Their 



