Jefferson’s Quest for an Odometer cover

Jefferson’s Quest for an Odometer

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Thomas Jefferson, who liked to count and measure everything, coveted an odometer. While in Paris as the United States minister to France, he learned that he could buy one in London, and asked American artist John Trumbull, who was there, to investigate for him.
Today’s post is guest authored by Julie Miller, historian of early America in the Library’s Manuscript Division.

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Jefferson’s Quest for an Odometer

In Search of Measure

Thomas Jefferson, who liked to count and measure everything, coveted an odometer.

While in Paris as the United States minister to France, he learned that he could buy one in London, and asked American artist John Trumbull, who was there, to investigate for him. Early in 1788 he wrote Trumbull:

“Enquire if a triangular odometer is to be bought in London, and at what price.” (Memorandum for John Trumbull [February, 1788] ).

Trumbull replied, warning Jefferson that odometers were custom-made to fit the “exact diameter of the wheel to which they are to be applied,” and they were expensive (Trumbull to Jefferson, February 26, 1788).

“I find the Odometer too dear,” Jefferson, disappointed, replied, “and therefore will not order one” (Jefferson to Trumbull, May 18, 1788).

Ode to Odometers

Ode to Odometers

Foiled Again

Jefferson must have changed his mind about giving up, since that summer he asked another friend, British diplomat Benjamin Vaughan, to look again, (Jefferson to Vaughan, July 23, 1788).

Vaughan confirmed what Trumbull had already told him (Vaughan to Jefferson, August 2, 1788), and Jefferson returned to the United States the following year without an odometer.

Finally, in September, 1791, while he was living in Philadelphia as Secretary of State, Jefferson bought a pendulum odometer from a Scottish-born Philadelphia clockmaker Robert Leslie. Jefferson learned about Leslie’s work with pendulums as he worked on the “Report on Weights and Measures” that he submitted to Congress on July 4, 1790.

Practical Use

Today an odometer is the instrument in a car that records the distance driven.

In the eighteenth century odometers were mounted on the wheels of horse-drawn carriages, and the pendulum odometer, the type Jefferson bought from Leslie, was commonly used. The pendulum odometer’s triangular shape allowed it to be mounted between the spokes of a carriage wheel, where it counted each of the wheel’s revolutions.

To calculate the distance a carriage had traveled, the driver multiplied the wheel’s circumference by the number of its revolutions. In his July 23, 1788 letter to Benjamin Vaughan, Jefferson explained that the odometer’s pendulum “always keeps its vertical position while the wheel is turning round and round,” and he included a drawing to show what he meant.



To represent the carriage wheel in motion, Jefferson drew several odometers, each attached to a different spoke of the wheel, each with its pendulum dangling downward.

Record Keeping

On September 2, 1791, the same day Jefferson paid Leslie ten dollars for the odometer, he and his friend and fellow Virginian James Madison, then a congressman, set off on a trip home with the odometer strapped to the wheel of Jefferson’s phaeton (a type of carriage).

On the way they stopped at Georgetown to meet with the commissioners who were planning what would soon be the District of Columbia, next Jefferson dropped Madison off at Montpelier, and finally he reached his home, Monticello, near Charlottesville.

As he often did, Jefferson made an itinerary of the trip, in which he recorded his observations of the road and the places where he ate and slept, and, using his new odometer, distances. (The 1791 itinerary is in one of Jefferson’s memorandum books at the New York Public Library.

Measure Twice

Robert Leslie may have been ingenious, but his odometer was not perfect.

Jefferson had to have it mended on the road on September 3, the day after he and Madison left Philadelphia, and then it failed again on September 12, just before he got home. Once at home he discovered a larger mistake, one that he had made himself, the same one that John Trumbull had warned him about in 1788.

Jefferson had calculated that 360 revolutions of the phaeton’s wheel constituted one mile. The distances he recorded as he and Madison traveled from Philadelphia to Virginia, he wrote, “were on the belief that the wheel of the Phaeton made exactly 360 revolns. [revolutions] in a mile, but on measuring it accurately at the end of the journey its circumference was 14 f.[feet] 10 ½ I. [inches] and consequently made 354.95 revolns. in a mile.”

Jefferson had mismeasured his wheel: when he measured it again he found that it was a little bigger than he had thought, and as a result he had miscalculated the number of revolutions it made per mile, and, therefore, the distance he had traveled.

President Thomas Jefferson

President Thomas Jefferson

Fit For a President

In the years to come Jefferson remained interested in odometers, buying at least one more, and working on ways to improve their design.

In 1807, when he was president of the United States, he learned that Virginia inventor James Clarke had designed and made an odometer, and asked Clarke if he could borrow and copy it (Jefferson to Clarke, May 22, 1807).

Clarke, evidently thrilled at such a request from the president, gave Jefferson one of his odometers. Jefferson was happy with this odometer, which he used for many years. He liked the bell that rang after every mile. (Jefferson to Clarke, September 5, 1820). He also liked the way the odometer divided the miles into units of ten, because it justified his enthusiasm for the decimal system, which he had advocated in his 1790 “Report on Weights and Measures.

An Advocate of the Decimal

When he wrote his autobiography years later he was still hoping the United States would adopt a decimal system, and used Clarke’s odometer as an example of its merits:

“I use, when I travel, an Odometer of Clarke’s invention which divides the mile into cents [hundredths], and I find every one comprehend[s] a distance readily when stated to them in miles & cents; so they would in feet and cents, pounds & cents, &c.” (Jefferson, Autobiography, Fragment, 1821).

But even Clarke’s odometer was not perfect; once again, the problem had to do with getting a carriage wheel of the correct size to fit it.

Not Yet Perfect

On September 30, 1807 Jefferson recorded a trip from Monticello to Washington using Clarke’s odometer.

The odometer, he wrote, “is made for a wheel of 16 f [eet] circumference,” but his phaeton had a wheel that measured 16 feet and 5/8 inches. As in 1791, the carriage wheel was too big for the odometer (Itinerary, Monticello to Washington, September 30, 1807).

Jefferson Monument

Jefferson Monument

We forget that Jefferson didn’t work alone, but in collaboration with others.

A Team Effort

Today we celebrate Thomas Jefferson as a scientist and inventor, but we forget the patience and effort he expended on projects over many years.

We forget that Jefferson didn’t work alone, but in collaboration with others, such as Robert Leslie and James Clarke, who combined science with invention and practical mechanics. All of them knew that these endeavors, like many others, are about planning, testing, trying, failing, fixing, trying a different way, failing again, and then, maybe, succeeding – and having a good time along the way.

Inside Adams, Library of Congress