The winds appear to be caused by partial changes in the density of the
atmosphere in a great measure arising from a diverse distribution of
heat. When air is warmed it becomes less dense, or, in other words, it
occupies a greater space. If an adjacent stratum of air be cooler, it
will on coming in contact with the warmer air expand and pour into
space occupied by the latter, thus forming a current. The greater the
difference between the temperature of the one or other portion, the
greater will be the force which the cold portion will rush into the
space occupied by the warm portion, or, in other terms, the more violent
will be the wind. In temperate climates the winds are variable; but in
some parts of the world they blow with great regularity, and in others
are subject to periodical changes.