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 Williamsburg, and at Monticello. It is formed by reducing nine months' observations at Monticello to four principal points, to wit, the north-east, south-east, south-west, and north-west; 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, four hundred and twenty-one from the preceding table of winds at Williamsburg, taking them proportionably from every point:
N.E. S.E. S.W. N.W. Total. Williamsburg 127 61 132 101 421 Monticello 32 91 126 172 421
By this it may be seen that the south-west wind prevails equally at both places; that the north-east is, next to this, the principal wind towards the sea-coast, and the north-west is the predominant wind at the mountains. The difference between these two winds to sensation, and in fact, is very great. The north-east is loaded with vapor, insomuch, that the salt-makers have found that their crystals would not shoot while that blows; it brings a distressing chill, and is heavy and oppressive to the spirits. The north-west is dry, cooling, elastic, and animating. The eastern and south-eastern breezes come on generally in the afternoon. They have advanced into the country very sensibly within the memory of people now living. They formerly did not penetrate far above Williamsburg. They are now frequent at Richmond, and every now and then reach the mountains. They deposit most of their moisture, however, before they get that far. As the lands become more cleared, it is probable they will extend still further westward.
Going out into the open air, in the temperate, and warm months of the year, we often meet with bodies of warm air, which passing by us in two or three seconds, do not afford time to the most sensible thermometer to seize their temperature. Judging from my feelings only, I think they approach the ordinary heat of the human body. Some of them, perhaps, go a little beyond it. They are of about twenty to thirty feet diameter horizontally. Of their height we have no experience, but probably they are globular volumes wafted or rolled along with the wind. But whence taken, where found, or how generated? They are not to be ascribed to volcanos, because we have none. They do not happen in the winter when the farmers kindle large fires in clearing up their grounds. They are not confined to the spring season, when we have fires which traverse whole counties, consuming the leaves which have fallen from the trees. And they are too frequent and general to be ascribed to accidental fires. I am persuaded their cause must be sought for in the atmosphere itself, to aid us in which I know but of these constant circumstances: a dry air; a temperature as warm, at least, as that of the spring or autumn; and a moderate current of wind. They are most frequent about sun-set; rare in the middle parts of the day; and I do not recollect having ever met with them in the morning.