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
Amateur Meteorologists
Jefferson not only took measurements himself but also encouraged others to do so, including his close friend and political ally, James Madison. The partnership between Madison and Jefferson as two leading figures in the political events of the American Revolution is well known and amply illustrated by correspondence that includes reflections on early drafts of the Constitution. Jefferson wrote to Madison in 1787 to express his view of the pressing need for "… a bill of rights providing clearly & without the aid of sophisms for freedom of religion, freedom of the press, protection against standing armies, restriction against monopolies, the eternal & unremitting force of the habeas corpus laws, and trials by jury in all matters of fact triable by the laws of the land…." It was just a few years before this that Jefferson made quite a different request to Madison:
I wish you had a thermometer … [to] observe at Sunrise & at 4 o'clock p.m. which are the coldest & warmest points of the day. If you could observe at the same time it would shew the difference between going North & Northwest on this continent. (TJ to JM, February 20, 1784)
The request was more demanding than it might appear. High-quality instruments were very difficult to come by in the late 18th century. Jefferson spared few expenses in pursuit of his interests and seldom purchased anything but the very best in wines, books and scientific instruments. In July of 1776, just as the Declaration of Independence on which he had labored was being signed, Jefferson purchased a Sparhawk thermometer for 3 pounds, 15 shillings—equivalent to at least several hundred dollars today. Madison acquired a thermometer as his friend requested, and he and his family recorded a series of high-quality daily measurements that spanned about 18 years at their Montpelier plantation near Orange, Virginia. (Madison's father's handwriting appears especially often in the record, along with that of the future president and others thought to be his brothers).
Jefferson and his circle of contacts fully appreciated the need for care and attention to calibration. One correspondent wrote that it was important to "ascertain the accuracy of the division by plunging it in boiling water," suggesting that Jefferson and his associates were well aware of the standards prescribing this procedure that had been established by a commission of the Royal Society led by Henry Cavendish.
In 1723, the Royal Society set out recommendations for instrument placement in a paper published by James Jurin, its Secretary: "We judge the most suitable position for a thermometer to be in a closed room, oriented to the North, where a fire is rarely, if ever lit." The Society also invited observers to publish such results in its Philosophical Transactions. Considerable debate about instrument placement ensued in the Philosophical Transactions and elsewhere, with a number of weather observers (particularly in continental Europe) arguing that outdoor measurements would be more useful. Although the need to keep instruments out of the sun was evident, the role of radiative exchange from all sources, including the heat sink of the sky and the emitting temperature of the ground or other nearby objects, was not yet understood. It was not until the period from about 1840 to 1870 that the dual problems of retaining air flow while shielding from the cooling and warming effects of radiation of the surroundings on the air thermometer were managed through the use of louvered boxes or sheds (see Figure 1 for a current system). A well-calibrated indoor instrument might still obtain an accurate daily or multi-daily mean, albeit one with a variable thermal lag induced by its surroundings.
In continental Europe, outdoor measurements, as well as some indoor and outdoor observations, were carried out in a few well-organized observing networks as early as the 1770s, but a number of early observers worldwide dutifully did as the prestigious Royal Society prescribed for many decades, making indoor measurements a major obstacle to the interpretation of many key early meteorological series such as those interpreted by Dario Camuffo, and by Gordon Manley and his colleagues.
Madison informed Jefferson that the temperature on April 27, 1785, "on the second floor and the NW side of the house was on the 24th at 4 o'clock at 77°[F]." Jefferson's notes, for example in December 1802 and February 1803, indicate that data were being taken in a bedroom with "no fire." Thus both men took some data following the Royal Society indoor method, but neither persisted in that mode throughout their lives.
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