1092. Elevation, or the height of the soil above the level of the sea, affects climate much in the same manner as latitude ; while, at the same time, it occasions a material difference in atmospheric pressure. This diminished pressure is thought by Professor Dobereiner, and some other botanists, to be the chief cause of the diminutive size of plants grown in elevated situations. Experiments have been made to prove this, by causing seeds of barley to germinate in soil placed in vessels under different degrees of atmospheric pressure; and the result has been, that where the pressure was greatest, the vigour of the plant was greatest also. With respect to the influence of elevation on temperature, as the altitude increases, the temperature lessens in regular gradation, in the same manner as it does in receding from the equator; and 600 feet of elevation, De Candolle states, are deemed equal to one degree of latitude, and occasion a diminution of temperature equal to 23ﾦ Fahr.; 300 feet being nearly equal to half a degree. Mountains 1000 fathoms in height, at 46ﾦ of latitude, have the mean temperature of Lapland.
