Thomas Jefferson and the search for the longitude in America

Jumping off of Becky's recent blog post for the Guardian online about Thomas Jefferson having been a science enthusiast - it bears mentioning that the American President and diplomat was also a long-time longitude enthusiast. He was a keen proponent of the lunar-distance method of finding longitude at sea as well as for mapping the breadth of the United States, writing in 1816 that it is only by 'interrogating the sun, moon, and stars' that we can know the 'relative position of two places on the earth'.

This decades-long interest is reflected in the contents of Jefferson's library, which were sold to the nation in 1815 after the British burned the Library of Congress. Among what he deemed the 'Astronomical' texts in his collection were not only a variety of relevant navigational and astronomical volumes -- including the Connaissance des Temps for 23 years and the Nautical Almanac for 27 years plus associated tables -- but also some publications by projectors. These publications included the two-volume treatise The Theory and Practice of finding the Longitude at Sea or on Land by the Scottish astronomer Andrew Mackay, whom I discussed in my last blog post.

Thomas Jefferson in 1791, while he was Secretary of State

Many American longitude projectors also approached Jefferson as an expert on the subject and as a potential patron for their work. This recalls the ways in which most British projectors approached influential and mathematically or astronomically oriented individuals, from the Astronomers Royal to statesmen and royalty. Jefferson was also viewed as a potential source of financial relief for projectors in dire straits, as was true of the many British longitude actors and institutions. One such man told the politician about his stay in an asylum and addiction to opium and was in turn given fifty dollars and the advice to focus on 'the comfort of your family' rather than on the longitude.

Jefferson apparently rued his status as an unofficial scientific clearing house, writing to a friend after a longitude projector approached him in the street that his 'false reputation [...] has made me a kind of Vortex into which the projects of our country are very much emptied'. Although he responded considerately to most supplicants, he feared 'the sacrifice of the remains of my life in the investigation for others of projects which very often require a great deal of consideration, much research, and sometimes elaborate calculations'. The Astronomer Royal was probably the British official treated most like this, by projectors and other officials alike.

Staff at Jefferson's renowned home, Monticello, compare the longitude letters among his papers to those about perpetual motion, although there are far more of the former than of the latter. This comparison doesn't really hold water, although it was often made in the past as well as in the present. Longitude projectors included learned and earnest men as well as the delusional, dishonest or sorely uninformed individuals who tend to dominate modern perceptions of them.


A number of the American projectors who corresponded with the Board of Longitude during this period also consulted Jefferson, including John Churchman and Captain Matthew Groves. Churchman, a Philadelphia surveyor, wrote to the Board about a magnetic variation scheme from 1787 to 1804. (Magnetic variation continued to arouse interest throughout the eighteenth century.) His Magnetic Atlas of 1790, a copy of which he sent to the British Commissioners, listed Jefferson among its illustrious subscribers. The first letter in the book's appendix of supporting correspondence was also from the diplomat, then the American Minister and Plenipotentiary to the Court of France, who had introduced Churchman's method to the Parisian Royal Academy of Sciences.

In the letter, written in 1787, Jefferson alerted the projector to two things he would likely need to bring his scheme to fruition:

'As far as we can conjecture, we imagine you make a table of variations of the needle, for all the different meridians whatever. To apply this table to use, in a voyage between America and Europe,--suppose the variation to increase a degree in 160 miles,--two difficulties occur: lst, a ready and accurate method of finding the variation of the place; 2d, an instrument, so perfect as that (though the degree on it shall represent 160 miles) it shall give the parts of the degree, so minutely as to answer the purposes of the navigator [...]'

During his presidency, Jefferson also corresponded to some degree with Captain Matthew Groves of Massachusetts. In 1803, Groves wrote to Joseph Banks, a Commissioner as well as the President of the Royal Society, about his method and patented astronomical quadrant for finding longitude at sea by observations of Jupiter's moons. (The Jovian moons were another approach which had not been entirely abandoned by the end of the eighteenth century.) The Captain said that he had contacted the American President about his invention and had reportedly obtained his approval for it. He then asked the Board of Longitude to fund his development and sea trials of it, since the money he had raised for that purpose by subscription in Boston had since run out.

The conclusion of Matthew Groves's handbill of 1803 seeking funding to travel to London to perfect his astronomical quadrant and to put it into general use. Groves promised to return the money if he secured one of the large rewards overseen by the British board of Longitude or a comparable foreign reward.

As we can see through cases like these, Thomas Jefferson belonged to an international circle of actors who were considered experts on and potential patrons of the search for the longitude at sea. Despite his reluctance to engage as frequently as he often did with other projectors, his known interest in the subject and renowned intellect combined with his high political and socio-economic profile to make him seem an ideal contact to cultivate. As a result, many of the American projectors who corresponded with the British Board of Longitude also tried to or succeeded at consulting this revered 'Founding Father' about their schemes, fostering additional interconnections between the networks of individuals who were tackling the issue on both sides of the Atantic from the late eighteenth to early nineteenth centuries.

Image sources: Jefferson and Monticello - Wikipedia; correspondence - Alexi Baker / Cambridge University Library.