Q. How can hills and mountains alter the course of the wind?
A. Suppose a wind, blowing from the north, comes to a mountain, as it cannot pass through it, it must either rush back again, or fly off at one side (as a marble when it strikes against a wall).
Q. Do mountains affect the wind in any other way?
A. Yes; many mountains are capped with snow, and the warm air is condensed as it comes in contact with them; but as soon as the temperature of the wind is changed, its direction may be changed also.
Suppose A B C to be three columns of air. A, the column of air which is cooling down; B, the column to which the sun is vertical; and C, the column which is to be heated next. In this case the cold air of A will rush towards B C, because the air of B and C is hotter than A. But suppose now C to be a snow-capped mountain. As the hot air of B reaches C, it is chilled; and (being now colder than the air behind) it rushes back again towards A, instead of following the sun.
Q. How can the ocean affect the direction of the wind?
A. When the ocean rolls beneath the vertical sun, the water is not made so hot as the land; and (as another change of temperature is produced) another obstacle is offered to the uniform direction of the wind.
Q. Why is not the water of the sea made so hot by the vertical sun, as the surface of the land?
A. 1st—Because the evaporation of the sea is greater than that of the land: