FEATURE ARTICLE
Revolutionary Minds
Thomas Jefferson and James Madison participated in a small "revolution" against British weather-monitoring practices
Susan Solomon, John S. Daniel, Daniel L. Druckenbrod
Moving Outdoors
Madison appears to have been the first to probe other options. The future president left his home to attend the constitutional convention in late January 1787, but it is clear that he and his family began to wonder about instrument placement shortly before his departure. On December 10, 1786, the Madison family weather diary (see Figure 7) noted that trees were covered in ice and that the thermometer dropped from 30 degrees Fahrenheit to 22 when put "on the porch." On February 16, 1787, the thermometer was moved to the porch and "put in the Box." This arrangement represented a key step forward, beginning to resemble that employed in modern observations.
Figure 2 shows the locations of the Madison Montpelier plantation, Jefferson's Monticello and the closest nearby modern stations where high-quality daily weather records have been routinely kept for decades. Figure 3 compares the difference between 4:00 p.m. and sunrise data observed by Jefferson as well as by Madison for the month of June, to the average values of hourly data from Charlottesville (the nearby modern station that has the most complete hourly series of data).
The siting of Madison's instrument inside the home before 1787 (irrespective of the lighting of fire) clearly greatly reduced the morning-to-afternoon changes in the data compared to outdoor values: The indoor morning data were much warmer than the outside air temperature, and the afternoon data decidedly cooler, so that the range in temperature through the course of the day was greatly reduced by the thermal lag of the home.
After noticing that the data were inconsistent with the occurrence of ice and taking the bold step of moving the instrument outdoors to the box on the porch in 1787, Madison's morning and afternoon observations are dramatically different, and the morning-to-afternoon changes immediately approach modern outdoor data. Thus, in meteorology as in politics, Madison was among the American founders of measures that represented a revolution against British practices.
In the late 1780s, Madison was engaged in the struggle for a Bill of Rights and in decisions over the positioning of his thermometer, while Jefferson was in France, serving as what might today be called ambassador. Jefferson negotiated a close relationship with France as the separation of the newly established United States from Britain took shape, and he was a party to the events that led to the French Revolution. Despite his strong interest in European science, he appears to have been unaware that systematic outdoor meteorological measurements were being collected in France and Germany, organized through the Société royale de médicin and the Societas Meteorological Palatina (Mannheim Meteorological Society). Jefferson continued to take daily measurements of temperature following the Royal Society indoor approach throughout the 1780s and 1790s, as indicated in a January 28, 1790, letter from his personal secretary William Short noting that his "little thermometer which was in the passage is now in the alcove at the foot of your bed."
Jefferson, like Madison, also appears to have begun considering other approaches in the 1780s, but his ideas differed from those of the Madison clan. On December 10, 1788, he wrote to an instrument maker named William Jones to commission construction of two thermometers "graduated from boiling water down to the congelation of spirits of wine … they are intended to be hung on the outside of a glass window, with the face of the plate next to the window so that it may be seen without opening the window."
Jefferson's imagination led to a number of inventions, including a new type of plow offering less resistance and greater efficiency. He had an eye for and a deep appreciation of style, as well as a craftsman's approach to substance and utility. Nowhere are these more apparent than in his many unique designs of his home at Monticello, and positioning of his thermometer directly on a window for easy viewing would have been consistent with a number of other innovations Jefferson built into the dramatic home. The Great Clock could also be viewed from both inside and outside, as could the dial of the weathervane (Figure 4). These indoor-outdoor design features may have been considered elegant by Jefferson, but placement of the thermometer against the window of the stately and massive house can certainly be expected to have affected the data. Some of the brick walls that were made from Monticello's own clay were more than two feet thick, yielding a formidable thermal lag in temperature measurements.
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