di Halfa; A, Alice Springs; H, Honolulu; J, Jamestown, St Helena; N,
Nagpur.]

The so-called _tropical_ type of temperature variation, with one maximum
and one minimum, is illustrated in the accompanying curves for Wadi
Halfa, in upper Egypt; Alice Springs, Australia; Nagpur, India;
Honolulu, Hawaii; and Jamestown, St Helena (fig. 7). The effect of the
rainy season is often shown in a displacement of the time of maximum
temperature to an earlier month than the usual one.

2. _Trade-Wind Belts._--The trade belts near sea-level are characterized
by fair weather, steady winds, infrequent light rains or even an almost
complete absence of rain, very regular, although slight, annual and
diurnal ranges of temperature, and a constancy and regularity of
weather. The climate of the ocean areas in the trade-wind belts is
indeed the simplest and most equable in the world, the greatest extremes
over these oceans being found to leeward of the larger lands. On the
lowlands swept over by the trades, beyond the polar limits of the
equatorial rain belt (roughly between lats. 20 deg. and 30 deg.), are
most of the great deserts of the world. These deserts extend directly to
the water's edge on the leeward western coasts of Australia, South
Africa and South America.

The ranges and extremes of temperature are much greater over the
continental interiors than over the oceans of the trade-wind belts.
Minima of 32 deg. or less occur during clear, quiet nights, and daily
ranges of over 50 deg. are common. The midsummer mean temperature rises
above 90 deg., with noon maxima of 110 deg. or more in the non-cloudy,
dry air of a desert day. The days, with high, dry winds, carrying dust
and sand, with extreme heat, accentuated by the absence of vegetation,
are disagreeable, but the calmer nights, with active radiation under
clear skies, are much more comfortable. The nocturnal temperatures are
even not seldom too low for comfort in the cooler season, when thin
sheets of ice may form.

While the trades are drying winds as long as they blow strongly over the
oceans, or over lowlands, they readily become rainy if they are cooled
by ascent over a mountain or highland. Hence the windward (eastern)
sides of mountains or bold coasts in the trade-wind belts are well
watered, while the leeward sides, or interiors, are dry. Mountainous
islands in the trades, like the Hawaiian islands, many of the East and
West Indies, the Philippines, Borneo, Ceylon, Mad