88 
THE PHYSICAL GEOGRAPHY OF THE SEA. 
ot, rather, to have so much of it taken from them as to reduce their 
dew-point below the Desert temperature ; for the air can never de- 
posit its moisture when its temperature is higher than its clew-point. 
135. We have a rainless region about the Red Sea, because the 
Red Sea, for the most part, lies within the northeast trade-wind 
region, and these winds, when they reach that region, are dry 
winds, for they have as yet, in their course, crossed no wide sheets 
of water from which they could take up a supply of vapor. 
136. Most of New Holland lies within the southeast trade-wind 
region ; so does most of inter-tropical South America. But inter- 
tropical South America is the land of showers. The largest riv- 
ers and most copiously watered country in the world are to be 
found there, whereas almost exactly the reverse is the case in 
Austraha. Whence this dilFerence ? Examine the direction of 
the winds with regard to the shore-hne of these two regions, and 
the explanation will at once be suggested. In Australia — east 
coast — the shore-line is stretched out in the direction of the trades ; 
in South America — east coast — it is perpendicular to their direc- 
tion. In Australia, they fringe this shore only with their vapor, 
and so stint that thirsty land with showers that the trees can not 
afford to spread their leaves out to the sun, for it evaporates all 
the moisture from them ; their instincts, therefore, teach them to 
turn their edges to his rays. In America, they blow perpendicu- 
larly upon the shore, penetrating the very heart of the country 
with their moisture. Here the leaves — as the plantain, &c. — turn 
their broad sides up to the sun, and court his rays. 
137. Why there is more rain on one side of a mountain than on 
the other. 
We may now, from what has been said, see why the Andes and 
all other mountains which run north and south have a dry and a 
rainy side, and how the prevailing winds of the latitude determine 
which is the rainy and which the dry side. 
Thus, let us take the southern coast of Chili for illustration. 
In our summer time, when the sun comes north, and drags after 
him his belts of perpetual winds and calms, that coast is left with- 
in the regions of the northwest winds — the winds that are counter 
to the southeast trades— which, cooled by the winter temperature 
of the highlands of Chili, deposit their moisture copiously. Dur- 
ing the rest of the year, the most of Chili is in the region of the 
