we find that movable belt of
continual or daily rains, and comparative calms, particularly _near its
center_, about four hundred and fifty miles in width upon the Atlantic,
and over Africa, and the eastern portions of the Pacific, and something
more over South America and the West Indies, the western portion of the
Pacific and the Indian Ocean, to which we have already alluded. This belt
of rains and calms follows the trades and sun, in their transit north and
south, from one tropic to the other--its width and extension depending
upon the volume of trade-winds existing on the sides of it. Its southern
edge, when the sun is at the southern solstice, extends to 7 deg. south in the
Atlantic, to 10 deg. south in the Indian Ocean, and still further, probably,
over South America: on this point I do not pretend to be accurate, for
accuracy is not essential. When the sun is at the northern solstice the
southern edge is carried up as far as 12 deg. north, over the Atlantic, and
still further over the northern portions of South America, the West
Indies, and Mexico. It travels, therefore, from south to north, over from
twenty to forty degrees of latitude. The presence of this belt of rains
over any given portion of the inter-tropics, gives that portion its rainy
season, and its absence, as it moves to the north, or the south, gives the
portion from which it has moved, its dry season. It passes in its transit
twice each year over some portions of the country, Bogota, for instance,
and two corresponding rainy and dry seasons result. Its presence, and
character, and movements, are as fixed and regular, over from twenty-five
to forty degrees of the earth's surface, _and all around it_, as the
presence and movements of the sun over the same area.

At the northern edge of this movable belt of rain, and extending in some
places, particularly in the Pacific Ocean, north about 20 deg., or about one
thousand four hundred miles, and in other places a less distance, the N.
E. trade winds prevail, blowing toward and into it from N. N. E., N. E.,
and E. N. E., averaging about N. E. At the south line of this belt of
rains, extending south from twenty-five to thirty degrees, or from sixteen
hundred to two thousand miles, the S. E. trades blow toward and into it,
from the S. E., S. S. E., or E. S. E., averaging about S. E. Of course the
northern limit of the N. E. trades travels north and south with the belt
of rain, toward which it blows; and so t