Page:Popular Science Monthly Volume 45.djvu/350

 There, in Jefferson's own fine hand, stands the record of his observations:

The fourth of July, 1776, was, then, relatively cool. I think statements to the contrary have been made, and the day described as hot and sweltering. More than one historian may have drawn upon imagination in describing the weather of those first days in July when the signers of the Declaration were gathered together in Philadelphia. Strange that from the same hand that penned the Declaration should come at this late date a true statement of the weather of that period. One can not help a feeling of surprise that Jefferson, with so many duties pressing, should have found time to make these detailed observations.

The Colonial Weather Service experienced all the vicissitudes of war. Madison writes to Jefferson somewhat pathetically as follows:

"I wish we had a barometer; but there is no possibility of getting one here at present. The British robbed me of my thermometer and barometer." This must have been a serious loss to the colonial meteorologists, although to us there is a touch of the ludicrous in the very idea of British soldiery relieving the college professor of his thermometer and barometer. Perhaps the instruments would have been spared could the commanding officer have foreseen that in a few years, the war ended and the colonies independent, this very professor was to go to England and be consecrated as Bishop of Virginia.

But notwithstanding interruptions, our meteorologists persevered, and their long-continued correspondence is full of wherefores and whys which even at this day are of interest and meaning. They ascertained "by contemporaneous observations of between five and six weeks" that "the averaged and almost unvaried difference of the height of mercury in the barometer at these two places was 0·784: of an inch; the pressure at Monticello being so much the lightest—that is to say, about a thirty-seventh of its whole weight.

Furthermore—and this is truly remarkable—they proved in their own words "the variations in the weight [meaning pressure] of the air to be simultaneous and corresponding in these two places. "Many data were collected regarding the climate of