Meteorological Observation in the 18th and Early 19th Centuries
Jefferson’s collection of meteorological data was one piece of a large collective endeavor to expand scientific knowledge in the intellectual movement that has been called the Enlightenment. Beginning in the 17th century in Europe, investigators worked to identify and classify plant and animal species and to make systematic studies of geology, chemistry, and astronomy. With Isaac Newton’s Principia leading the way, they sought to discover the principles or natural laws that governed the universe. Professional scientists and professors of science at universities were not numerous. Much of the research was carried out by physicians and gentlemen amateurs who had the learning, desire, time, and access to information and equipment required to do the work. They shared knowledge through learned societies that formed throughout Europe. In America, their counterpart was the American Philosophical Society, founded in Philadelphia in 1743 with Benjamin Franklin as its first president.
The premier learned society in England was the Royal Society. In the 1660s several of its members, following the lead of an Italian society, the Accademia del Cimento in Florence, began to record meteorological observations. Under the auspices of the Royal Society, Robert Hooke, who experimented in a variety of scientific subjects, published in 1667 a set of instructions and examples called “A Method for Making a History of the Weather.” These were guidelines for creating a weather diary very similar to the records that Jefferson started more than a century later. Hooke advised keeping the information in a bound volume and dividing each page into nine columns “distinguished by perpendicular lines.” The columns would be for: the date; “the Place, Latitude, Distance, Ages and Phaces of the Moon”; the direction and force of the wind; the temperature in degrees from a thermometer; “the Dryness and Moisture” of the air, read from a hygrometer (which Hooke called a hygroscope); the air pressure, from a barometer; “the faces and appearances of the Sky”; “the Effects of the Weather upon other bodies, Thunders, Lightnings, or any thing extraordinary”; and finally “general Deductions, Corollaries or Syllogisms, arising from the comparing the several Phœnomena together.” In the eighth column, intended for the “Effects of the Weather upon other bodies” and other information, the observer should note “the unusual sprouting, growth, or decay of any Plants or Vegetables,” and “the plenty or scarcity of Insects; of several Fruits, Grains, Flowers, Roots, Cattel, Fishes, Birds, any thing notable of that kind.” The arrangement of the record into columns was to enable the information to “be registred so as to be most convenient for the making of comparisons, requisite for the raising Axioms, whereby the Cause or Laws of Weather may be found out.”
Jefferson was familiar with the publications of the Royal Society, although it is not known whether he had first-hand knowledge of Hooke’s guidelines or picked up the methods of keeping a weather diary from someone else. He did not follow Hooke’s directions in all their details—he could consult published almanacs for the phase of the moon, for example, and did not make that one of the regular categories of his weather diaries. Hooke’s guidelines were a model for how to set up a weather record, not necessarily for what would be in it. It is significant that Hooke called for capturing numerical data from instruments for air temperature, pressure, and moisture, but said nothing about standardization of scales; for all the meticulous recording of data, a reading from one person’s thermometer might have no basis for comparison to anyone else’s observations. By Jefferson’s time, the Fahrenheit temperature scale was commonly used in English-speaking parts of the world and the Reaumur scale by the French. Both systems came into general use after Hooke wrote his instructions.
By Jefferson’s time, individuals and societies on both sides of the Atlantic were connected by what historian Anya Zilberstein has called “networks of scientific exchange.” The lines of communication, maintained by correspondence and exchanges of publications, were interrupted by the American Revolution, but then resumed because “they were largely extrapolitical and extra-institutional.” During his residence in Paris, 1784–1789, Jefferson became acquainted with the intellectual community in France, including the Comte de Volney, who when he traveled in the United States in the 1790s gave particular attention to the study of winds in America. Scientific inquiry in France suffered disruption from that nation’s revolutionary upheavals, but then continued.
While international scientific networks could be above politics, at least to a degree, within the United States political affiliations shaped the exchange of information. In the late 18th and early 19th centuries, Harvard, Yale, and other New England colleges fostered interest in natural sciences but could be unwelcoming to those who were not Federalist in politics. Federalists corresponded with British agricultural societies but tended to eschew the kinds of ties that Jefferson maintained with French natural philosophers. Although Jefferson exchanged ideas and information with individuals of his acquaintance in New England, the fissures between him and the region were deep. He had no real lines of communication with its learned societies or institutions of higher learning. American attitudes toward the Enlightenment and scientific progress could be tightly entwined with religious views as well as politics. To a Virginia student in 1799, Jefferson asserted that whereas he saw no limits on the possibilities for human improvement based on scientific inquiry, his Federalist enemies believed “that the human mind is incapable of further advances” and that “we are to look backwards then & not forwards for the improvement of science.”
Jan Golinski, British Weather and the Climate of Enlightenment (Chicago, 2007), 29, 82-4.
Robert Hooke, “A Method for Making a History of the Weather,” in Thomas Sprat, The History of the Royal-Society of London, for the Improving of Natural Knowledge (London, 1667), 173-9.
Henry F. May, The Enlightenment in America (New York, 1976).
Anya Zilberstein, A Temperate Empire: Making Climate Change in Early America (New York, 2016), 54-5, 59, 67-72, 75-85.