clear weather; the frequency of a light yellow, but translucent tinge that is strongest at the horizon, and fainter upwards, where it is blended with a sky of a fine light blue, at the height of a few degrees. The number of foggy days is small,[122] and the appearance of clouds, previous to rain, sudden. Indeed, on several occasions, I have observed a clear atmosphere transformed into one abounding with dark clouds and rain, in the space of an hour. Changes of this kind are no doubt produced by sudden transitions of temperature.
Severe gales of wind do not appear prevalent in western America, if the two last winters can be admitted as sufficient examples, as these seasons were much less stormy than those of Scotland. But it is necessary to make an exception of the tornadoes, which occasionally blow down houses, lay waste fields, and open avenues through the woods. One of these tempests destroyed some {220} buildings at Cincinnati, on the 28th of May, 1809. It was preceded by a wind from the south, and a higher current blowing from the west, and was understood to commence in the State of Tennessee. It crossed the Allegany mountains "and made its exit from the continent" on the same day.[123]
Although earthquakes have been frequently felt in the United States, the injury done by them has either been local, or of little consequence. On the 16th of December, 1811, a concussion at Cincinnati threw down some chimney tops, opened room doors that were shut by a falling latch, and caused the furniture to shake. During the
