e
direction, and prevail in most parts of the Atlantic and Pacific Oceans,
between the latitudes of twenty-eight degrees north and twenty-eight
degrees south. In northern latitudes the trade wind blows from
north-east, or varies but a few points from that direction. South of
the equator it blows constantly from the south-east; and the "south-east
trade" is more steady than the trade wind north of the line.

It often happens that vessels bound to the United States from India,
after passing the Cape of Good Hope, steer a course nearly north-west,
carrying studding-sails on both sides, uninterruptedly, through fifteen
or twenty degrees of latitude.

The cause of the trade winds is supposed to be the joint influence of
the higher temperature of the torrid zone and the rotation of the earth
on its axis. On the equator, and extending sometimes a few degrees on
either side, is a tract where light easterly winds, calms, and squalls,
with thunder, lightning, and inundating rains, prevail.

From what I have said, it will be seen that vessels bound from the
American coast to the West Indies or Guiana should steer to the eastward
in the early part of their passage, while they have the advantage of
variable winds. And this precaution is the more important, as these
vessels, being generally dull sailers and deeply laden, will fail to
reach their port if they fall to leeward, unless by returning north into
the latitude of the variable winds, and making another trial, with the
benefit of more experience.

In those days there were no chronometers in use, and but few of our West
India captains were in possession of a sextant, or indeed able to work
a lunar observation. The latitude was accurately determined every day
by measuring the altitude of the sun as it passed the meridian. To
ascertain the longitude was a more difficult matter. They were obliged
to rely mainly on their dead reckoning; that is, to make a calculation
of the course and distance run daily, from the points steered by the
compass and the rate as indicated by the log-line and half-glass. A
reckoning on such a basis, where unknown currents prevail, where
a vessel is steered wildly, or where the rate of sailing may be
inaccurately recorded, is liable to many errors; therefore it was
customary with all prudent masters, in those days, especially if they
distrusted their own skill or judgment in keeping a reckoning to KEEP
WELL TO THE EASTWARD. This was a general rule, an