f 
90 THE PHYSICAL GEOGRAPHY OF THE SEA. 
times reaches the enormous depth of twelve or fifteen inches in 
one day.* 
140. These winds then continue their course to the Himalaya 
range as dry winds. In crossing this range, they are subjected to a 
lower temperature than that to which they were exposed in cross- 
ing the Ghauts. Here they drop more of their moisture in the 
shape of snow and rain, and then pass over into the thirsty lands 
beyond with scarcely enough vapor in them to make even a cloud. 
Thence they ascend into the upper air, there to become counter- 
currents in the general system of atmospherical circulation. By 
studying Plate VHI., where the rainless regions and inland basins, 
as w^ell as the course of the prevailing winds, are shown, these 
facts will become obvious. 
141. The Regions of Greatest Precipitation. — We shall now 
be enabled to determine, if the views which I have been en- 
deavoring to present be correct, what parts of the earth are sub- 
ject to the greatest fall of rain. They should be on the slopes of 
those mountains which the trade-winds first strike, after having 
blown across the greatest tract of ocean. The more Abrupt the 
elevation, and the shorter the distance between the mountain top 
and the ocean, the greater the amount of precipitation. 
If, therefore, we commence at the parallel of about 30° north 
in the Pacific, where the northeast trade-winds first strike that 
ocean, and trace them through their circuits till they first strike 
high mountains, we ought to find such a place of heavy rains. 
Commencing at this parallel of 30°, therefore, in the North Pa- 
cific, and tracing thence the course of the northeast trade-winds, 
we shall find that they blow thence, and reach the region of equa- 
torial calms near the Caroline Islands. Here they rise up ; but, 
instead of pursuing the same course in the upper stratum of winds 
through the southern hemisphere, they, in consequence of the ro- 
tation of the earth 98), are made to take a southeast course. 
They keep in this upper stratum until they reach the calms of 
Capricorn, between the parallels of 30° and 40° ; after which 
they become the prevailing northwest winds of the southern hemi- 
sphere, which correspond to the southwest of the northern. Con- 
tinuing on to the southeast, they are now the surface winds ; they 
are going from warmer to cooler latitiides ; they become as the 
* Keith Johnston. 
