Currents of air, and winds, are the result of convection. The air, heated by the high temperature of the tropics, ascends, while the colder air of the temperate and the frigid zones blows towards the equator to supply its place.
"Give unto the Lord the glory due unto his name; worship the Lord in the beauty of holiness."—Psalm xxix.
235. What is the cause of sea breezes?
Sea breezes are also the result of convection. The land, under the heat of the day's sunshine, becomes of a high temperature, and the expanded air on its surface flies away towards the ocean. As the sun goes down, the earth cools again, and the air flies back to find its equilibrium.
Many countries by the sea are subjected to these periodical breezes, known as either "land" or "sea breezes," according to their direction. About eight o'clock in the morning an ærial current begins to flow from the sea towards the land, and continues until about three o'clock in the day; then the current takes a reverse direction, flowing from the land to the sea. This it continues to do throughout the night, until the time of sunrise, when a temporary calm ensues.
236. Why does a soap bubble ascend in the air?
Because, being filled with warm air, it is lighter than the surrounding medium, and therefore ascends.