Within the tropics the land and sea breezes are more gentle; and though the night scenes there are not so suggestive as those just described, yet they are exceedingly delightful, and altogether lovely. The oppressive heat of the sun is mitigated, and the climate of the sea-shore is made both refreshing and healthful, by the alternation of those winds, which invariably come from the cooler place;-from the sea, which is the coolerby day; and from the land, which is the cooler by night.
About ten in the morning the heat of the sun has played upon the land with sufficient intensity to raise its temperature above that of the water. A portion of this heat being imparted to the air above it, causes it to rise; when the air, first from the beach, then from the sea, to the distance of several miles, begins to flow in with a most delightful and invigorating freshness.
When a fire is kindled on the hearth, we may see, if we observe the motes floating in the room, that those nearest to the chimney are the first to feel the draught and to obey it-they are drawn into the blaze. The circle of inflowing air is gradually enlarged, until it is scarcely perceived in the remote parts of the room. Now, the land is the hearth; the rays of the sun the fire; and the sea, with its cool and calm air, the room; and thus have we at our firesides the sea breeze in miniature.
When the sun goes down the fire ceases; then the dry⑦land commences to give off its surplusheat by radiation, so
that by dew-fall it and the air above it are cooled below the sea temperature. The atmosphere on the land thus becomes heavier than that on the sea, and, consequently, there is a wind sea-ward, which we call the land breeze.
- MAURY
NOTES
① Tropical countries, countries between the tropics, or within the torrid zone. The tropics [Gr. trepo, I turn] are the parallels of latitude drawn through the points in the ecliptic at which the sun appears to turn in his course.
② Extra-tropical, immediately beyond the tropics, north or south.
③ Trade-winds, constant winds that blow in the tropical regions of the great oceans, especially of the Atlantic, where they are most regular. Currents of cold air are always flowing from the poles to the equator, to supply the place of the hot air which rises there from the surface of the globe. If the globe were at rest, these would be due north and south winds; but as the globe turns from west to east more quickly than the surrounding air, these lagging currents become a north-east and a south-east wind respectively. They are called "trade-winds" because of their great advantage to navigators in sailing from east to west.
④ Rarefaction, the distending or separating of the atoms of the atmosphere, which makesit lighter, and therefore causes it to rise. The air from the sea then rushes in to fill its place.
⑤ Valparaiso (Valpah-ri-so ), "Vale of Paradise," the chief sea-port of Chili, on the west of South America.
⑥ Andes, the great mountain chain of South America. They "seem to draw near," because the clearness of the atmosphere makes them appear nearer.
⑦ Surplus, lit. overmuch; more than enough.
QUESTIONS
Where do the sea and the land breezes blow with the greatest regularity? When does the sea breeze set in? When does the land breeze? When do these breezes blow in extra-tropical countries? Where has the writer seen the sea breeze most powerfully developed? By what is it followed there? What is the character of these breezes within the tropics? What is their effect upon the climate? What is the cause of their alternation? Illustrate this by a fire on a hearth?
