ree hundred miles in searching for a wind;
but, if they really knew what they were about, they would be sure to
catch it at last, and to turn it to their purpose.

From April to October, when the sun's rays fall with greatest effect
on Arabia, India, and China, and the several interjacent seas to which
these immense countries give their name, the air in contact with them,
becoming heated, rises, and gives place to fresh supplies drawn from
the equator. But this equatorial mass of air has had imparted to it by
the earth's rotation a greater degree of velocity in the direction
from west to east than belongs to the countries and seas just
mentioned; and this additional velocity, combined with its motion from
the equator, in rushing to fill up the vacuum caused by the
rarefaction of the air over those regions intersected by the tropic,
causes the south-west monsoon. "This wind," says Horsburgh, "prevails
from April to October, between the equator and the tropic of Cancer,
and it reaches from the east coast of Africa to the coasts of India,
China, and the Philippine Islands; its influence extends sometimes
into the Pacific Ocean as far as the Marian Islands, on to longitude
about 145 deg. east, and it reaches as far north as the Japan Islands."

The late Captain Horsburgh thus describes what takes place in the
winter months:--"The north-east monsoon," he says, "prevails from
October to May, throughout nearly the same space that the south-west
monsoon prevails in the opposite season mentioned above. But the
monsoons are subject to great obstructions by land; and in contracted
places, such as Malacca Strait, they are changed into variable winds.
Their limits are not everywhere the same, nor do they always shift
exactly at the same period."

During this last named period, when the north-east monsoon is blowing,
viz. from October to May, the sun is acting with its greatest energy
on the regions about the equator, and the seas lying between it and
the southern tropic, while the countries formerly mentioned (Arabia,
India, and China), lying under the northern tropic, become
comparatively cool. The air over these regions becomes relatively more
dense than the rarefied air near the line; consequently the cool air
rushes to the southward to interchange places with that which has been
heated; and as the cool air comes from slower-moving to quicker-moving
parallels of latitude, that is, from the tropical to the equatorial
regions, t