rade-wind.

The more detailed circumstances usually met with in that part of a
voyage to India which lies between 30 deg. north and 30 deg. south, and which
I am about to describe, will now, I imagine, be readily understood.
Before setting out, however, I must strongly recommend any one wishing
to see these matters clearly, to have them fixed in his mind to useful
purpose, to follow both the theoretical and the practical parts of
this explanation with the assistance of a terrestrial globe.

Most ships touch at Madeira, either to take in a stock of wine, to get
fruit and vegetables, or to form a pleasant break in the early and
most disagreeable part of the voyage. Some ships pass barely in sight
of the high mountain which rises above the town of Funchal, and
satisfy themselves with taking sights for verifying the rates of their
chronometers when on the meridian of the island; while others
tantalise their passengers still more by sweeping through the roads,
without anchoring, or communicating with the shore. The captains by
such ships are pretty deeply, if not very loudly, abused by all hands,
passengers especially, who are perhaps the most dissatisfied, because
the most idle, of mortals. Shortly after leaving Madeira, which is in
32-1/2 deg. north latitude, a ship may expect to meet the Trades; but she
cannot calculate with any certainty upon catching them till she
arrives at the parallel of 28 deg.. On first reaching the Trade-wind it
will be found to blow very nearly from due east, and with this a
course is easily steered past or amongst the Canaries, and thence for
the Cape de Verdes. Some navigators pass within this group, others
keep so far out as barely to make San Antonio; and this, I think, is
considered the best route. As the ship proceeds to the southward, the
wind draws gradually round from the east to north-east, and eventually
to north-north-east, and even to north, at the southern margin of the
north-east Trade-wind.

The position of this margin or southern edge, which in technical
language is called the equatorial limit of the Trade, varies
considerably with the season of the year. From December to May
inclusive it frequently reaches as far as the 3rd degree of north
latitude, though it ranges about 5 deg. and 6 deg. north. From June to
November it is shifted back as far, sometimes, as 13 deg. north, but it
seldom extends as far south as 8 deg. north. Subjects which are treated of
in a series of tables