itias_, 108; cf. the notion of a
viscous sea in Plutarch, _De facie in Orbe Luna_, 26), Plato's
fancy has furnished a theme for much wild speculation. See, for
example, Bailly, _Lettres sur l'Atlantide de Platon_, Paris,
1779. The belief that there can ever have been such an island
in that part of the Atlantic is disposed of by the fact that
the ocean there is nowhere less than two miles in depth. See
the beautiful map of the Atlantic sea-bottom in Alexander
Agassiz's _Three Cruises of the Blake_, Boston, 1888, vol. i.p.
108, and compare chap. vi. of that noble work, on "The
Permanence of Continents and of Oceanic Basins;" see also
Wallace's _Island Life_, chap. vi. It was formerly supposed
that the Sargasso plants grow on the sea-bottom, and becoming
detached rise to the surface (Peter Martyr, _De rebus
oceanicis_, dec. iii. lib. v. p. 53; Humboldt, _Personal
Narrative_, book i. chap, i.); but it is now known that they
are simply rooted in the surface water itself. "L'accumulation
de ces plantes marines est l'exemple le plus frappant de
plantes congeneres reunies sur le meme point. Ni les forets
colossales de l'Himalaya, ni les graminees qui s'etendent a
perte de vue dans les savanes americaines ou les steppes
siberiens ne rivalisent avec ces prairies oceaniques. Jamais
sur un espace aussi etendu, ne se rencontrent de telles masses
de plantes semblables. Quand on a vu la mer des Sargasses, on
n'oublie point un pareil spectacle." Paul Gaffarel, "La Mer des
Sargasses," _Bulletin de Geographie_, Paris, 1872, 6e serie,
tom. iv. p. 622.]

[Sidenote: The trade wind.]

On September 22 the journal reports "no more grass." They were in clear
water again, and more than 1,400 geographical miles from the Canaries.
A third source of alarm had already begun to disturb the sailors. They
were discovering much more than they had bargained for. They were in the
belt of the trade winds, and as the gentle but unfailing breeze wafted
them steadily westward, doubts began to arise as to whether it would
ever be possible to return. Fortunately soon after this question began
to be discussed, the wind, jealous of its character for capriciousness
even there, veered into the southwest.

[Sidenote: Impatience of th