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and the state of cultivation in different countries create some variation in the temperature of the climate.  Sand is susceptible of a much higher degree of heat from the rays of the sun, and retains it longer than clay or loam ; and an uncultivated region, shaded with forests, and filled with undrained marshes, is more frigid in northern, and more temperate in southern latitudes than countries laid open to the full action of the solar influence.*  In winter the moisture of the atmosphere is congealed into more abundant snows, and in summer descends in more frequent and copious showers of rain.  When the North of Europe lay almost buried in its native forests, 

[[footnote]]* Notwithstanding this general fact, it is equally true that, in a new country, like that of the United States, when only a few plantations are opened here and there in the midst of the woods, the inhabitants are subjected to a more oppressive heat in the summer season than they will be when the country shall be entirely disforested.  When a small plantation is opened in a forest, the surrounding woods obstruct those breezes which would refresh the inhabitants, while they are exposed to the direct and scorching rays of the sun.  To this we may add, that the moist vapor, with which the atmosphere is generally filled in a region that is not yet cleared and drained, settling down more copiously on the few spots which are opened, where there is not vegetation sufficient, as in the woods, to adsorb it, renders the heat more oppressive, and at the same time the atmosphere more unwholesome.[[/footnote]]

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and was inhabited only by various tribes of barbarians and savages, there are several facts recorded in history which demonstrate that cold prevailed in a much higher degree than at present.  In the age of Horace hail and snow were frequent phenomena at Rome; and the light wines of Italy were sometimes frozen in their cellars.  And Trajan, in his Dacian wars, is said to have transported his armies across the Danube on the ice.  But since those barbarous regions, from the Adriatic to the White Sea, have been civilized, and those extensive forests have been cleared away, and the earth subjected to tillage, hail or snow are rarely seen at Rome, and their wines, at present, never suffer from congelation. 

From the preceding observations this conclusion results; that there is a general ratio of temperature prevailing over the whole globe according to the degree of latitude from the equator, which forms what is usually denominated climate.*  And a general re-

[[footnote]]* Besides the effects resulting from temperature, or the direct action of the sun's rays, when we consider the various elements, or gases, which enter into the constitution of our atmosphere, and the different proportions of these principles which exist in the various regions of the globe, according to their[[/footnote]

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