66 STEPPES AND DESERTS. 



deducible with tolerable certainty from Columbus's re- 

 corded estimation of the ship's rate, and the " distance daily 

 sailed over " derived indeed, not from casting the log, but 

 from data afforded by the running out of half-hour sand- 

 glasses (ampolletas) . The first certain and definite mention 

 of a log (catena della poppa) which I have been able to 

 discover, is in the year 1521, in Pigafetta's journal of Ma- 

 gellan's Yoyage round the "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 situation 

 of this great accumulation of thalassophytes, whether resulting 

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

 from the direction of the Gulf 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 themselves 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 posi- 

 tion of this bank was intimately connected with the 

 great physical line of demarcation, which, according to him, 

 divided the globe into two parts, with the changes of 

 magnetic variation, and with climatic relations. Columbus, 



