These depend upon the same general principle that causes and regulates all other wind. Heat acting upon air rarefies it, by which it becomes specifically lighter, and mounts upward. The denser parts of the atmosphere which surround that so rarefied, rush into the vacuity from their superior weight; endeavouring, as the laws of gravity require, to restore the equilibrium. Thus in the round buildings where the manufactory of glass is carried on, the heat of the furnace in the centre being intense, a violent current of air may be perceived to force its way in, through doors or crevices, on opposite sides of the house. As the general winds are caused by the DIRECT influence of the sun's rays upon the atmosphere, that particular deviation of the current distinguished by the name of land and sea breezes is caused by the influence of his REFLECTED rays, returned from the earth or sea on which they strike. The surface of the earth is more suddenly heated by the rays of the sun than that of the sea, from its greater density and state of rest; consequently it reflects those rays sooner and with more power: but, owing also to its density, the heat is more superficial than that imbibed by the sea, which becomes more intimately warmed by its transparency and by its motion, continually presenting a fresh surface to the sun. I shall now endeavour to apply these principles. By the time the rising sun has ascended to the height of thirty or forty degrees above the horizon the earth has acquired, and reflected on the body of air situated over it, a degree of heat sufficient to rarefy it and destroy its equilibrium; in consequence of which the body of air above the sea, not being equally, or scarcely at all, rarefied, rushes towards the land and the same causes operating so long as the sun continues above the horizon, a constant sea-breeze, or current of air from sea to land, prevails during that time. From about an hour before sunset the surface of the earth begins to lose the heat it has acquired from the more perpendicular rays. That influence of course ceases, and a calm succeeds. The warmth imparted to the sea, not so violent as that of the land but more deeply imbibed, and consequently more permanent, now acts in turn, and by the rarefaction it causes draws towards its region the land air, grown cooler, more dense, and heavier, which continues thus to flow back till the earth, by a renovation of its heat in the morning, once more obtains the ascendancy. Such is the general rule, conformable with experience, and founded, as it seems to me, in the laws of motion and the nature of things. The following observations will serve to corroborate what I have advanced, and to throw additional light on the subject for the information and guidance of any future investigator.