Page:Notes on the State of Virginia (1853).djvu/99

Rh or in its neighborhood, and at Monticello, which is on the most eastern ridge of mountains, called the Southwest, where they are intersected by the Rivanna, have furnished a ratio by which that difference may in some degree be conjectured. These observations make the difference between Williamsburgh and the nearest mountains, at the position before mentioned, to be on an average 6 degrees of Fahrenheit's thermometer. Some allowance however is to be made for the difference of latitude between these two places, the latter being 38° 8′ 11″, which is 52′ 22″ North of the former. By cotemporary observations of between five and six weeks, the averaged and almost unvaried difference of the height of mercury in the barometer, at those two places, was .784 of an inch, the atmosphere at Monticello being so much the lightest, that is to say, about of its whole weight. It should be observed, however, that the hill of Monticello is of 500 feet perpendicular height above the river which washes its base. This position being nearly central between our Northern and Southern boundaries, and between the bay and Alleghaney, may be considered as furnishing the best average of the temperature of our climate. Williamsburgh is much too near the Southeastern corner to give a fair idea of our general temperature.

But a more remarkable difference is in the winds which prevail in the different parts of the country. The following table exhibits a comparative view of the winds prevailing at Williamsburgh, and at Monticello. It is formed by reducing nine months observations at Monticello to four principal points, to wit, the Northeast, Southeast, Southwest, and Northwest: these points being perpendicular to, or parallel with our coast, mountains and rivers; and by reducing, in like manner, an equal number of observations, to wit, 421, from the preceding table of winds at Williamsburgh, taking them proportionably from every point: