agascar, Teneriffe,
&c., show marked differences of this sort. The eastern coasts of Guiana,
Central America, south-eastern Brazil, south-eastern Africa, and eastern
Australia are well watered, while the interiors are dry. The eastern
highland of Australia constitutes a more effective barrier than that in
South Africa; hence the Australian interior has a more extended desert.
South America in the south-east trade belt is not well enclosed on the
east, and the most arid portion is an interior district close to the
eastern base of the Andes where the land is low. Even far inland the
Andes again provoke precipitation along their eastern base, and the
narrow Pacific coastal strip, to leeward of the Andes, is a very
pronounced desert from near the equator to about lat. 30 deg. S. The cold
ocean waters, with prevailing southerly (drying) winds alongshore, are
additional factors causing this aridity. Highlands in the trade belts
are therefore moist on their windward slopes, and become oases of
luxuriant plant growth, while close at hand, on the leeward sides, dry
savannas or deserts may be found. The damp, rainy and forested windward
side of Central America was from the earliest days of European
occupation left to the natives, while the centre of civilization was
naturally established on the more open and sunny south-western side.

The rainfall associated with the conditions just described is known as
the _trade type_. These rains have a maximum in winter, when the trades
are most active. In cases where the trade blows steadily throughout the
year against mountains or bold coasts, as on the Atlantic coast of
Central America, there is no real dry season. The curve for Hilo (mean
annual rainfall 145.24 in.) on the windward side of the Hawaiian
Islands, shows typical conditions (see fig. 5). The trade type of
rainfall is often much complicated by the combination with it of the
_tropical_ type and of the _monsoon_ type. In the Malay archipelago
there are also complications of equatorial and trade rains; likewise in
the West Indies.

3. _Monsoon Belts._--In a typical monsoon region the rains follow the
vertical sun, and therefore have a simple annual period much like that
of the tropical type above described. This monsoon type of rainfall is
well illustrated in the curve for Port Darwin (mean annual rainfall
62.72 in.), in Australia (see fig. 5). This summer monsoon rainfall
results from the inflow of a body of warm, moist air fro