Coming into the latitude of 18° N. we found that part of the sea which is generally so covered with grass that it looks at a distance like a meadow. This grass has a yellowish cast, being hollow within, and on being pressed it yields a clammy viscous juice. In some years none of this grass appears, while in other years it is found in prodigious quantities. Some imagine that it comes from the bottom of the sea, as divers report that the bottom is in many places covered with grass and flowers. Others conceive that it comes from the coast of Africa: But our author disapproves both of these opinions, because, if it came from the bottom, there is no reason why the same appearance should not be found elsewhere; whereas, if it came from the coast of Africa, it ought to be found in other situations, especially near that coast. His opinion, therefore, is, that it comes from the coast of America, and particularly from the Gulf of Bahama, or Mexico, where it is known to grow in great abundance, and where, when it comes to maturity, it breaks off; and is carried away by the currents.[2] [Footnote 2. In the old Portuguese maps and voyages, this part of the Atlantic is called _Mar de Sargasso_, or the _Sea of Cresses_; Sargasso signifying water-cresses, which these weeds which spread over the sea nearly resemble.--Harris.] Nothing is more difficult than to account for the motion and course of currents in the ocean, which, in some places, run for six months in one direction, and six in another, while in other places they run always one way. There are instances also where they run one way for a day or two after full moon, and then run strongly in the opposite direction till next full moon. Seamen also observe, that in places where the trade-winds blow, the currents are generally influenced by them, moving the same way with the winds, but not with equal force in all places; neither are they so discernible in the wide ocean, but chiefly about islands, where their effects are more or less felt according as they are influenced by being more or less in the way of the trade-winds. It would be of great service to navigation if sensible men would take notice of these currents, and enquire into the reason of their appearances. In old books of voyages we find many more wonders than in those of later date, not because the course of nature is at all changed, but because nature was not then so well understood. A thousand things were prodigious a century ago, which are not now at all strange. Thus the storms at the Cape of Good Hope, which make so great a figure in the histories of the Portuguese discoveries, are now known to have been merely the effect of endeavouring to double that Cape at a wrong season of the year.