334 THE POPULAR SCIENCE MONTHLY. 



There, in Jefferson's own fine hand, stands the record of his obser- 

 vations : 



HOUR. THERM. HOUR. THERM. 



1776, July 1 : 9.00 A. M 8H July 3 : 1.30 p. M 76 



7.00 P. M 82 8.10 P. M 74 



July 2: 6.00 A. M 78 July 4: 6.00 A. M 68 



9.40 A. M 78 9.00 A. M 72J 



9.00 P. M 74 1.00 P. M 76 



July 3 : 5.30 A. M 7li 9.00 P. M 73^ 



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 sur- 

 prise 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 ther- 

 mometer 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 instru- 

 ments would have been spared could the commanding officer have 

 foreseen that in a few years, the war ended and the colonies inde- 

 pendent, this very professor was to go to England and be conse- 

 crated as Bishop of Virginia. 



But notwithstanding interruptions, our meteorologists per- 

 severed, 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 al- 

 most unvaried difference of the height of mercury in the barom- 

 eter 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 pres- 

 sure] of the air to be simultaneous and corresponding in these two - 

 places." Many data were collected regarding the climate of Vir- 



* Notes on Virginia, second American edition, Philadelphia, November 12, 1794. 



