Historical Notes: Jefferson often wrote of his great experience in traveling. Long hours on the road in his legal and public careers made him eager to find the shortest routes to his common destinations. This, and an innate passion for measurement, prompted his desire for a means of knowing the distances he traveled.
During his longest journey, a three-month tour through France and Italy in 1787, he heard of "a pendulum Odometer for the wheel of a carriage."1 The next year he inquired about English odometers, but found them-at seven to ten guineas-too expensive.2 After another long journey to New York and New England in 1791 he purchased his first odometer, for ten dollars, from the Scottish clockmaker Robert Leslie, "the most ingenious workman in America." He attached it immediately to his phaeton and recorded the mileages of his route from Philadelphia to Monticello. This odometer merely counted the revolutions of the wheel.3
The odometer pictured here, made by London instrument makers Nairne & Blunt, may be the one he purchased from David Rittenhouse in 1794.4 This very sophisticated instrument measured the distance in chains, links, and poles as well as miles, so it could be mounted on either a hand-propelled waywiser or a carriage.5
Jefferson, having failed in his own efforts to develop the ideal odometer, received one in 1807 from its inventor, James Clarke of Powhatan County, Virginia. Clarke's odometer had two features that were particularly pleasing to Jefferson. It chimed after every ten miles, and it subdivided the miles decimally, into dimes and cents. Jefferson found "great satisfaction in having miles announced by the bell as by milestones on the road," and as one of the fathers of the American decimal system, he liked being able to use the decimal point in making his itineraries.6 His Clarke odometer also proved the efficacy of the decimal system for measures other than money. "The people on the road," he wrote, "inquire with curiosity what exact distance I have found from such a place to such a place; I answer, so many miles, so many cents. I find they universally and at once form a perfect idea of the relation of the cent to the miles as a unit."7
1787 April 21-22. (Notes of a Tour into the Southern Parts of France, &c.). "The Count del Verme tells me of a pendulum Odometer for the wheel of a carriage."9
1788 February 15. (Memoranda for John Trumbull). "Enquire [sic] if a triangular odometer is to be bought in London, and at what price. it is placed between the spokes of a wheel.10
1788 February 26. (John Trumbull to Jefferson). "The Odometer may be made at Watkins's, Charing cross, but they are not kept ready made because the exact diameter of the wheel to which they are to be applied must be known, as this is the basis of their calculation. If you order one, you must remember this and be attentive likewise to decide the measure, whether it be French or English; that fitted to the Wheel will cost about Eight Guineas. They are likewise made to be fixed on the inside the carriage. But these are extremely liable to get out of order, and cost double that Sum."11
1788 May 18. (Jefferson to John Trumbull). "I find the Odometer too dear, and therefore will not order one."12
1788 July 23. (Jefferson to Benjamin Vaughan). "I have heard that they make in London an Odometer, which may be made fast between two spokes of any wheel, and will indicate the revolutions of the wheel by means of a pendulum which always keeps it's vertical position while the wheel is turning round and round. Thus I will thank you to inform me whether it's indications can be depended on, and how much the instrument costs."13
1788 August 2. (Benjamin Vaughan to Jefferson). "Neither Mr. Cavendish, Mr. Elliot, nor Mr. Nairne are acquainted with an odometer of the kind you mention. We have them fixed to the wheel of carriage, upon other corresponding constructions, and they are said to answer within 1 or even 1/4 P cent of true distances; the cost being from 7 to 10 guineas."14
1791 September 2. "Pd. Leslie for an Odometer 10.D."15
1791 September 12. [Rivanna River ferry]. "Here Odometer failed."17
1794 January 3. "Drew the following orders as paiment [sic] in favor of...D. Rittenhouse for odometer..."18
1807 May 22. (Jefferson to James Clarke). "In coversation [sic] with mr. Stannard a few days ago he informed me that you had invented and made a machine to be fixed behind a carriage for counting the revolutions of the wheel while travelling; he added further that he did not believe yo would be averse to the communication of it...have been encouraged by mr. Stannard to believe you would be willing to let yours be copies, & perhaps to let it come here for that purpose."19
1807 May 27. (James Clarke to Jefferson). "I have just received your letter of the 22d Instant respecting an instrument on my pheaton for measuring distances in traveling, and the pleasure I feel in complying with your request in having it copied and introduced into publick [sic] use, will be greatly increased by your acceptance of it as a present...The first I made had but one index which revolved once in ten miles, and had no bell, yet answered all the purposes of real use; but thinking it no so perfect as it could be, I made the present oen which has two indexes and a bell, such are attached to house doors. The one index points to the figure denoting the number of miles, the other to the fraction of a mile, which is decimally divided, and the bell (which may be heard several hundred yards) gives the alarm at the end of each mile: and the whole machinery...is contaned [sic] in a small brass base about the size of a common shaving box...This instrument was calculated for a wheel five feet one inch diameter, therefore, ti will be necessary to haver your hind wheels brought to that size..."20
1807 June 5. (Jefferson to James Clarke). "I...am very thankful to you for the kind offer of your odometer, on which according to the description of it I should certainly set great value. My wish to receive it here was that i might take the distances on my road to Monticello, to which I shall go about the 20th of the next month, and about the last day of that month proceed on to Bedford."21
1818  September 1. (James Clarke to Jefferson). "By the advise and persuasion of several gentlemen who are anxious to get an odometer like mine, I have at length concluded to take a pattent, and establish a maufactory of them."22
1820 September 5. (Jefferson to James Clarke). "I have duly recieved your favor of the 1st instant requesting my opinion of the merits of your odometer, which I shall give with pleasure and satisfaction having had it in use for 13 years. I think it as simple as we can expect such a machine to be, having only three toothed wheels, entirely accurate, inconsiderable in weight and volume, and of convenient application to the carriage. With respect to it's originality, I can only say I have known no Odometer either in Europe or America, resembling it an any degree, or at all to be compared with it, in all it's characters and merit taken together. I continue still to use it, finding great satisfaction in having miles announced by the bell as by milestones on the road..."23
1821. "I use when I travel, an Odometer of Clarke's invention, which divides the miles into cents, and I find everyone comprehends a distance readily, when stated to him in miles and cents; so he would in feet and cents, pounds and cents, etc."24
1821 January 19. (Jefferson to James Clarke). "On my return from Bedford lately I had the misfortune to lose the rod and ratchet wheel which communicates motion from the wheel of the carriage to the odometer; and I had not been thoughtful enough to note the number of teeth in that wheel, their form, or the size of the wheel. I am obliged therefore to request you to draw for me on paper, or on a card the exact diagram of that wheel. [It] as well as the rod on which it is put, I expect my smith could make, or perhaps you can save me half the doubt by sticking between 2 cards the little wheel itself, which in that way will come safely under a letter cover by the mail."25
1821 April 2. (James Clarke to Jefferson). "I now send herewith, a case containing the rod with wheels (from the same moulds) already fixed, and have directed it to the care of the postmaster at Milton. If the rod should proved not to be precisely of the right length, your Smith with a little of your instructions can very easily adjust it..."26
1821 April 5. "C. Vest stage portage of rod of Clarke's odometer .25."27
1. Thomas Jefferson, "Memorandum taken on a journey from Paris into the Southern parts of France and Northern of Italy, in the year 1787," April 21 and 22, 1787, in PTJ, 11:437.
2. Jefferson to John Trumbull, c. February 15, 1788, Paris, May 18, 1788, in ibid., 12:597 and 13:178.
3. Jefferson, September 2-12, 1791, in MB, 1:831-835; Jefferson to William Short, Philadelphia, September 1, 1791, in PTJ, 22:118.
6. Jefferson to James Clarke, Washington, May 22, 1807. Thomas Jefferson Papers, Library of Congress. Polygraph copy available online; Jefferson to Clarke, Monticello, September 5, 1820, in ibid. Polygraph copy available online.
7. Jefferson to Thomas Cooper, October 27, 1808, in L&B, 12:182.
8. Please note that this list should not be considered comprehensive.
17. Ibid, 2:835. This odometer evidently counted the revolutions of the wheel of Jefferson's phaeton. He had to divide by 360 to determine the mileage, which he recorded in MB on this trip from Philadelphia to Monticello. He wrote beside them, "These measures were on the belief that the wheel of the Phaeton made exactly 360. revolns. in a mile, but on measuring it accurately at the end of the journey it's circumference was 14 f. 10 1/2 I. and consequently made 354.95 revolns. in a mile. These numbers should be greater then in the proportion of 71:72 or a mile added to every 71.