According to my researches, Columbus made his way through the great fucus bank in the year 1492, in latitude 28½°, and in 1493, in latitude 37°, and both times in the longitude of 38°–41°. This can be established with tolerable certainty from the estimation of the velocity recorded by Columbus, and “the distance daily sailed over;” not indeed by dropping the log, but by the information afforded by the running out of half-hour sand-glasses (_ampolletas_). The first certain and distinct account of the log, (_catena della poppa_,) which I have found, is in the year 1521, in Pigafetta’s Journal of Magellan’s Circumnavigation of the World.[AQ] The determination of the ship’s place during the days in which Columbus 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 remained 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 connected with the changes of magnetic deviation and of climatic relations.” 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 primera yerva_) on the eastern border 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 one, in the celebrated _line of demarcation_ between the Spanish and Portuguese rights of possession[AR]. Footnote 8: p. 3—“_The Nomadic Tribes of Tibbos and Tuaryks_.”