Prichard; To this latter point we would solicit special attention.
The manner in which large proportion of coast effects the developemen of civilization is two fold. First, its influence on the temperature of the land; secondly, the facility it affords for the intercourse of those variously endowed by various climatic influences.
Large bodies of water have the power of equalising, or rendering less excessive, the temperature of whatever land may be in their vicinity. Water remains fluid and coherent under a range of 180 Fahr., from 32°, the freezing to 212°, the boiling or gaseous point. When heat falls upon the surface of water, it is not all absorbed therein; for a large portion is thrown off said surface, in the vapor of water. This vapor is extremely small globules of water kept at a distance from each other by the expansive power of the heat, which they carry off from the surface of the water, which is left nearly as cool as the heat found it; and this vapor requires so much heat for the purpose of maintaining itself a vapor, that its actual temperature, measured by a thermometer, is very little greater than the surface of the water forsaken by it; and any sudden abstraction of this vaporizing heat, is followed by condensation of the vapor into—rain for example.
If the calorific rays of the sun, capable of raising the temperature of the air to 128°, fall upon the subjacent surface of the ocean at a temperature of 70°, this latter surface will not be raised to the temperature of the air; because, of the heat falling upon it a large proportion would be incessantly occupied in converting the surface of the water into vapor; and this vapor, cooler than the surrounding air into which it rises, would actually cool the air; and the remainder of the heat would raise the surface of the ocean only 5° or 6° in temperature. And this would be the case, were the heat of the sun constantly applied to the surface of the water. But as solar heat falls on any given portion of the globe, only 12 out of 24 hours, and as the vapor of water rises up and is driven off by currents of air, the surface of the ocean cools again during the intermission of solar heat.
Let calorific rays of the intensity 128° fall upon a surface of land. Land, having no cooling apparatus, such as water is furnished with, admits this intense heat into its surface, upon and immediately beneath which this heat accumulates, gaining more by day as it loses by radiation at night, until at length it becomes as hot as the superincumbent air, during the extreme heat of the day.
Assuming the same temperature of the air, 128° Fahr., if we place beneath it land and water adjacent, the surface of the land will of necessity be hotter than the surface of the ocean adjoining. And, moreover, vast superficies of land, such as the desert of Sahara, and the Plains of Hindustan, will reach a much higher temperature than strips of land environed with water in the same latitudes, as Central America and the Indian Islands; for, in these latter instances, particularly at night, the hot air rising from the surface of the land is replaced by the cool air from the neighboring water surface.
The converse of these phenomena occur in the low temperatures of the high latitudes, where the land cools more rapidly than the water, and where, consequently, vast superficies of land are colder by many degrees than strips of land environed by large surfaces of water. The land, during the night, (which is long), parts with more heat, by direct radiation from its surface, than it received from the sun during the day. The water-surface only parts with its heat by vaporization; the colder the air, the slower the vaporization. And further, the cold water on the surface sinks to the bottom and is replaced by the water from the depths of the ocean, which is
