In remarking that the fucus and the mud or mire, (πηλός), the shallowness of the sea, and the perpetual calms, are always spoken of by the ancients as characteristics of the western ocean beyond the Pillars of Hercules, one is disposed, more particularly on account of the mention of the _calms_, to ascribe something to Punic artifice,--to the desire of a great trading people to deter others, by the apprehension of dangers and difficulties, from entering into competition with them in western navigation and commerce. But even in the genuine writings of Aristotle (Meteorol. ii. p. 1, 14,) he maintains this same opinion of the absence of wind in those regions, and seeks the explanation of what he erroneously supposes to be a fact of observation, but which is more properly a fabulous mariner’s tale, in an hypothesis concerning the depth of the sea. In reality, the stormy sea between Gades and the islands of the Blest or Fortunate Islands, (between Cadix and the Canaries), is very unlike the sea farther to the south between the tropics, where the gentle trade winds blow, and which is called very characteristically by the Spaniards, el Golfo de las Damas, the Ladies’ Gulf. (Acosta Historia natural y moral de las Indias, lib. iii. cap. 4.) From very careful researches by myself, and from the comparison of the logs or journals of many English and French vessels, I infer that the old and indefinite expression, Mar de Sargasso, includes two banks of fucus, of which the greater and easternmost one, of a lengthened shape, is situated between the parallels of 19° and 34° N. lat., in a meridian of 7 degrees to the west of the Island of Corvo, one of the Azores; while the lesser and westernmost bank, of a roundish form, is situated between the Bermudas and the Bahamas, (lat. 25°-31°, long. 66°-74°.) The longer axis of the small bank which is crossed by ships going from Baxo de Plata (Caye d’Argent, Silver Cay) on the north of St. Domingo, to the Bermudas, appears to have a N. 60° E. direction. A transverse band of Fucus natans, running in an East and West direction between the parallels of 25° and 30°, connects the greater and lesser banks. I have had the gratification of seeing these inferences approved by my honoured friend Major Rennell, and adopted by him in his great work on Currents, where he has further supported and confirmed them by many new and additional observations. (Compare Humboldt, Relation Historique, tom. i. p. 202, and Examen critique, tom. iii. p. 68-99, with Rennell’s Investigation of the Currents of the Atlantic Ocean, 1832, p. 184.) The two groups of sea-weed, included together with the transverse connecting band under the old general name of the Sargasso Sea, occupy altogether a space exceeding six or seven times the area of Germany.