so well as those
of Irving: "The wind suddenly fell, and a dead sultry calm commenced,
which lasted for eight days. The air was like a furnace; the tar melted,
the seams of the ship yawned; the salt meat became putrid; the wheat was
parched as if with fire; the hoops shrank from the wine and water casks,
some of which leaked and others burst, while the heat in the holds of
the vessels was so suffocating that no one could remain below a
sufficient time to prevent the damage that was taking place. The
mariners lost all strength and spirits, and sank under the oppressive
heat. It seemed as if the old fable of the torrid zone was about to be
realized; and that they were approaching a fiery region where it would
be impossible to exist."[593]

[Footnote 591: Humboldt in 1799 did just this thing, starting
from Teneriffe and reaching Trinidad in nineteen days. See
Bruhn's _Life of Humboldt_, vol. i. p. 263.]

[Footnote 592: "The strength of the trade-winds depends
entirely upon the difference in temperature between the equator
and the pole; the greater the difference, the stronger the
wind. Now, at the present time, the south pole is much colder
than the north pole, and the southern trades are consequently
much stronger than the northern, so that the neutral zone in
which they meet lies some five degrees north of the equator."
_Excursions of an Evolutionist_, p. 64.]

[Footnote 593: Irving's _Columbus_, vol. ii. p. 137. One is
reminded of a scene in the _Rime of the Ancient Mariner_:--

"All in a hot and copper sky
The bloody sun, at noon,
Right up above the mast did stand,
No bigger than the moon.

"Day after day, day after day,
We stuck,--nor breath nor motion;
As idle as a painted ship
Upon a painted ocean."]

Fortunately, they were in a region where the ocean is comparatively
narrow. The longitude reached by Columbus on July 13, when the wind died
away, must have been about 36 deg. or 37 deg. W., and a run of only 800 miles
west from that point would have brought him to Cayenne. His course
between the 13th and 21st of July must have intersected the thermal
equator, or line of greatest mean annual heat on the globe,--an
irregular curve which is here deflected as much as five degrees north of
the equinoctia