Jefferson's interest in a machine for measuring force went hand in hand with his development of the moldboard plow. Early in 1809, he received a spring-operated dynamometer from France, the invention of Edme Regnier (1751-1825). It was stolen when Jefferson's goods were shipped from Washington to Virginia in March of that year. Some time after April 1810, he was able to borrow a dynamometer from Robert Fulton and to measure mathematically the force necessary to pull a plow fitted with his own "mathematically perfect" moldboard. Not only the plow was tested, as Edmund Bacon states: "He had a machine for measuring strength. There were very few men that I have seen try it that were as strong in the arms as his son-in-law, Colonel Thomas Mann Randolph; but Mr. Jefferson was stronger than he."
1796 May 20. (William Strickland to Jefferson). "I have enquired after and seen the machine for ascertaining the resistance of Plows; and am told it answers with the purpose intended; the plan is extremely simple, consequently the price, which is five guineas is too great...It is invented and sold by Winlaw..."
1808 May 1. (Jefferson to David Baillie Warden). "I read in the Memoirs du societe d'Agriculture de la Seine (but in what part of them I have this moment made a fruitless search to find) some experiments on the resistance, of ploughs by a machine which measured the degree of resistance, of ploughs & consequently the comparative force necessary to draw them."
1808 October 14. (Thomas Mann Randolph to Jefferson). "I have received the French Dynamometer, it is a light & beautiful contrivance depending on a spring, & a good deal in the way of the powder eprouvette which I showed you..."
1809 December 31. (Jefferson to Joel Barlow). "I therefore imported their dynamometer in order to prove mine with Guillaume's. I am now engaged in this work, but have lost my dynamometer. I think you have one. could you do me the favor to lend it to me for this experiment..."
1810 January 24. (Jefferson to Joel Barlow). "...I am disconsolate on learning my mistake as to your having a dynamometer. my object being to bring a plough to be made here to the same standard of comparison by which Guillaume's has been proved..."
1810 April 10. (Jefferson to James Madison). "...I have at the same time recieved [sic] an offer from mr Fulton to lend me his dynamometer, mine having been lost...I have certainly never seen a plough do better work or move so easily, still the instrument alone can ascertain it's merit mathematically..."