rays, a part of them enters the intervals between the trees, and their reflection upwards is intercepted by the leaves and boughs.  The rest fall on the trees, the leaves of which being generally inclined towards the horizon, reflect the rays downwards.  The atmosphere here, then, receives little or no heat by reflection.  Again, these leaves having a power of keeping themselves cool by their own transpiration, they impart no heat to the air by contact.  Reflection and contact, then, two of the three modes before-mentioned, of communicating heat, are wanting here; and, of course, the air over a country covered by forest must be colder than that over cultivated grounds.

The sea being pellucid, the sun’s rays penetrate it to a considerable depth.  Being also fluid, and in perpetual agitation, its parts are constantly mixed together; so that instead of its heat being all accumulated in its surface, as in the case of a solid, opaque body, it is diffused through its whole mass.  Its surface, therefore, is comparatively cool, for these reasons; to which may be added that of evaporation.  The small degree of reflection which might otherwise take place, is generally prevented by the rippled state of its surface.  The air resting on the sea, then, like that resting on a forest, receives little or no heat by reflection or contact; and is therefore colder than that which lies over a cultivated country.

To apply these observations to the phenomena under consideration.  The first settlements of Virginia were made along the sea coast, bearing from the south, towards the north, a little eastwardly.  These settlements formed a zone, in which, though every point was not cleared of its forest, yet a good proportion was cleared and cultivated.  The cultivated earth, as the sun advances above the horizon in the morning, acquires from it an intense heat, which is retained and increased through the warm parts of the day.  The air resting on it becomes warm in proportion, and rises.  On one side is a country still covered with forest:  on the other is the ocean.  The colder air from both of these, then rushes towards the heated zone, to supply the place left vacant there by the ascent of its warm air.  The breeze from the west is light and feeble; because it traverses a country covered with mountains and forests, which retard its current.  That from the east is strong; as passing over the ocean, wherein there is no obstacle to its motion.  It is probable, therefore, that this easterly breeze forces itself far into, or perhaps beyond, the zone which produces it.  This zone is, by the increase of population, continually widening into the interior country.  The line of equilibrium between the easterly and westerly breezes is, therefore, progressive.