time at sea, "That the longest way round is often the shortest
way there," as the saying is. In tropical latitudes, winds from
different quarters blow with great regularity in different places at
certain seasons of the year. The great object of a master is, to find
where the wind is blowing which will be fair for him. The two most
regular winds are the north-east and south-east trade-winds which blow
from either side of the equator, and meet in a wide belt of calms found
under it. There are currents in the air as well as in the ocean; and
Silas told me that he has more than once passed ships at sea right
before the wind--steering north, for instance, while his ship, with an
equally fair breeze, has been standing to the south. Formerly, ships
used to be steered as far south as they could get before the
trade-winds; and then often found themselves baffled for days, if not
weeks together, in the calm latitudes off the coast of Africa, when, if
they had stood boldly across the ocean, as we were now doing, they would
never have wanted a wind move or less fair. Thus it will be seen that
in navigation there are currents in the sea and currents in the air to
be considered, and that it requires a great deal of forethought, and
knowledge, and experience, to take a ship in safety and with speed round
the world. We were bowling along in grand style before the north-east
trade-wind, when Gerard stopped his father in his morning walk on deck.

"I say, father, can you tell Harry and me all about this trade-wind,
which we have got hold of it seems?" said he with a grave look, as if he
wished to become very learned.

"Which has got hold of us rather, I should say, by the way it is
carrying us along," answered the captain, smiling. No one knew Jerry so
well as he did, though he often pretended not to understand at what he
was driving. "You ask a question to which it is rather difficult to
reply in a brief way. Take a piece of paper; draw a circle on it; now,
draw three parallel belts across it--one in the centre, and one on each
side of the centre. Write on the centre belt, `Equatorial Calms;' on
the upper, `Calms of Cancer;' on the lower, `Calms of Capricorn.' The
circle represents the globe; the ends of a line drawn at right angles to
the belts where it reaches the circle, mark the poles. The globe moves
from west to east. Now, suppose a mass of air sent off from the north
pole towards the equator in a straight line, it