The principal cause of the winds, as we have observed, is the heat of the sun; on this subject we refer to Halley's Treatise in Phil. Trans. All causes which occasion rarefaction or condensation in the air will produce winds, whose directions will be opposite to the places where is the greatest rarefaction or condensation. The pressure of the clouds, the exhalations of the earth, the inflammation of meteors, &c. are causes which also produce considerable agitations in the atmosphere. Each of these causes combining in different manners, produces different effects. It appears to me, therefore, a vain attempt to assign a theory of the winds, for which reason I shall limit myself to the study of their history. If we could have a course of observations on the direction, power, and variation of the wind in different climates; if this course of observations was exact and extensive enough for us to perceive the result of these vicissitudes of the air in every country, we should arrive at that degree of knowledge, from which at present we are very remote; but a short time has passed since meteorological observations have been made, and possibly much more will pass before we know how to employ the results of them, although they are the only means that we have to arrive at some positive knowledge on this subject. On the sea the winds are more regular than on land, because the sea is an open space, in which nothing opposes their direction, while on land mountains, forests, and towns, form obstacles which change their course. Winds reflected by the mountains are often as impetuous as in their first direction: these winds are very irregular, because their course depends on the size, height, and situation of the mountains which reflect them. The sea winds blow with greater power than the land winds, are not so variable, and last longer. Land winds, however violent, have moments of remission, and sometimes of quiet, but at sea their currents are constant and continual, without any interruption.