ime, there is no cause in
operation, that I can discover, to alter the direction of the
meridional motion, as it may be called, of the Trade-winds, or that
by which they are impelled directly towards the equator.

At first starting from the temperate zone, on its voyage to the
equator, the cold air of that slow-moving region is impressed with a
rotatory velocity of only 800 miles per hour to the eastward, but it
soon comes over parts of the earth moving more than 100 miles per hour
faster to the eastward than itself. The difference of velocity in the
earth's rotation between latitudes 30 deg. and 20 deg. is 74 miles an hour,
while between 20 deg. and 10 deg. it is only 45 miles, and in the next ten
degrees the difference in rate per hour is reduced to 15 miles.

The velocity with which the air drawn from beyond the tropics travels
along the sea towards the equator is probably not above twenty miles
an hour, a rate slow enough to allow time for the
constantly-increasing friction of the earth's rotation to act upon it,
and draw it more and more entirely to the east. By the time it has
reached the equatorial regions, the friction of the earth's surface
has operated long enough to carry the air completely along with it;
and, of course, all relative motion being done away with, everything
easterly in the character of the Trade-winds will be at an end.

But, although this constantly-increasing friction of the earth's
rotation has thus annihilated all relative easterly motion between the
air and earth, that air still retains its motion towards the equator;
and accordingly we do find the Trade-winds, at their equatorial
limits, blowing, not from the east, as Hadley, Dr. Young, and others,
conceived, but directly from the north and from the south
respectively. The strength and velocity of the Trades at these places
is, in general, considerably diminished, chiefly, perhaps, by the air
becoming heated, and rising up rather than flowing along; and also, no
doubt, by the meeting of the two opposite currents of air--one from
the north, the other from the south--which produces the intermediate
space called the Calms, or the Variables.

In strict conformity with these theoretical views, the clouds above
the Trades are almost invariably observed to proceed in the contrary
direction to the winds below. On the top of the Peak of Teneriffe I
found a gentle breeze blowing from the south-westward, directly
opposite to the course of the T