1404. The regular motion of the atmosphere, known by the name of land and sea breezes, may be explained by the effects of rarefaction: the air heated over the land rises up, because rarefied, and its place is supplied by the cooler air which flows in from the sea; this produces the sea breeze; at sunset, the equilibrium is first restored; but as the earth cools faster by radiation than the water, the air over it becomes cooler than that over the sea, especially if there be mountains in the vicinity; the air over the land then displaces the light air from the sea, and thus the land breeze is formed. Granting that the attraction of the moon, and the diurnal movement of the sun, affect our atmosphere, there cannot be a doubt but a westward motion of the air must prevail within the boundaries of the trade-winds, the consequence of which is an easterly current on each side: from this, then, it proceeds that south-west winds are so frequent in the western parts of Europe, and over the Atlantic Ocean. Kirwan attributes our constant south-west winds, particularly during winter, to an opposite current prevailing between the coast of Malabar and the Moluccas at the same period: this, he adds, must be supplied from regions close to the pole, which must be recruited in its turn from the countries to the south of it, in the western parts of our hemisphere.
