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# Influence of the Sea on the Distribution of Climate

INFLUENCE OF THE SEA ON THE DISTRIBUTION OF CLIMATE Water, of all known substances, has the highest specific heat, or, in other words, has the greatest capacity for heat ; that is, it requires more heat to raise the temperature of a given quantity of water to a certain degree than it does to raise the temperature of equal quantities of any other sub stance to the same degree. For instance, taking the specific heat of water as 1, that of mercury is 0.0333, so that 30 times as much heat would be required to raise the temperature of a given quantity of water as of an equal quantity of mercury.' Again, the heat required to raise the temperature of one pound of water one degree, would raise to the same degree four pounds of chalk or nine pounds of iron. As water, then, requires more heat to raise its temperature than any other substance, so much the more heat is liberated when its temperature is reduced. A reduction of one degree in the temperature of a given quantity of water, would effect the liberation of four times as much heat as a similar reduction of the temperature of an equal quantity of chalk, or nine times that of an equal quantity of iron. The earth's outer crust is composed of materials widely different as regards their capacity for heat ; but, generally speaking, it requires four times as much heat to raise the temperature of water as it does that of land to the same degree. Land, therefore, is heated and cooled much more rapidly than water. Land and water absorb solar heat differently ; thus, while the heat falling on the land is communicated by conduction, that falling on water is dis tributed by convection,—that is, on land the same particles are exposed to the sun's heat, while at sea the sulfate particles first heated are displaced by colder particles from below, which are in turn heated and similarly displaced. It follows, then, that the heat gained by the land during the day is conducted downwards very slowly, inasmuch as its particles are, generally speaking, immovable. The particles of water, on the contrary, are incessantly in motion, and thus the heat gained is widely diffused. The heat falling on the land consequently accu mulates on the surface, while that falling on the ocean penetrates to a considerable depth. Where the surface of the land is sandy and barren, the heat accumulates more rapidly than where it is covered with vegetation. But whatever the nature of the soil, the conductivity of its particles is so limited that the solar heat penetrates to the depth of scarcely four feet. Given the same initial temperature, the land will be more quickly heated than the sea ; but while the heat of the former is soon dissipated, that of the water is retained for some considerable time.

The difference between the temperature of the land and the sea during the day and night, is the cause of the well known land and sea breezes, common in all the warmer mari time countries, and a most important element in the climate of the tropics. During the day the temperature of the land, and, consequently, that of the overlying air also, is above that of the sea and superincumbent air. The air over the land, being heated, expands and ascends, and is replaced by a current of cooler air from the sea,—that is, a "sea-breeze." During the night, on the contrary, the temperature of the land and that of the air over it is quickly reduced below that of the sea, con sequently the air over the sea rises, and is replaced by a cur rent which sets in from the land,—that is, a "land-breeze." The surface of the land, according to its position, nature of soil, elevation, &c., varies exceedingly as regards heat, one part being constantly parched under a fiery sun, while another is mantled with perpetual snow. The sea, on the contrary, has, on the whole, a more even climate ; its vast thermal cur rents pouring the heated tropical waters into remote colder areas; while the icy-cold water of the poles, creeping as a vast under-current towards the equator, limits the warm layer of the tropics to a few hundred fathoms. Land and sea breezes illustrate on a small scale the mutual reaction of the unequal distribution of heat on sea and land. There is, as we have seen, a difference in the day and night temperatures of the sea and land sufficient to originate land and sea breezes. But the difference in summer and winter is still more marked. On land, in summer, more heat is gained in the long day than is lost in the short night ; but in winter more heat is lost in the long night than is gained in the short day. Hence the heat of summer, and the cold of winter. The ocean, in sum mer, does not absorb the heat so rapidly as the land ; but in winter it does not part with it so readily. Hence its com parative coolness in summer, and warmth in winter. The influence of air-currents from the sea to the land, and vice versa, is thus easily explained. In summer, winds from the sea cool, and in winter, warm the land. This being the case, the climate of those countries bordering on the sea will be more equable than those removed from its influences. In the former the heat of summer will be tempered, and the cold of winter moderated, by the winds sweeping over them from the sea ; but in the latter, the heat of summer and cold of winter will be excessive.

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