According to my researches, Columbus crossed the great fucus bank in 1492, in lat. 28-1/2°, and in 1493, in lat. 37°, both times in the long. of from 38° to 41° W. This is deducible with tolerable certainty from Columbus’s recorded 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 Magellan’s Voyage 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 position 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, when uncertain respecting his longitude, (February 1493), directed himself by the appearance of the first floating streamers of weed (de la primera yerva) on the eastern margin of the great Corvo bank. The physical line of demarcation was, by the powerful influence of the Admiral, 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, tom. iii. p. 64-99, and Cosmos, English ed. vol. ii. p. 279-280.) [8] p. 3.--“_The Nomadic Tibbos and Tuaricks._”