Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States

The seconds pendulum basis

In coordination with scientists in France, Jefferson selected the seconds pendulum at 45° latitude as the basic reference. For technical reasons, he proposed using a uniform rod as the pendulum rather than a traditional pendulum. The pendulum was estimated to be 39.14912 English inches long (in the inches of that time—it wasn't until much later that the inch was defined to be 25.4 mm), or 1.5 times that for a vibrating rod (58.72368 inches).

More traditional proposal

In the evolutionary approach, the foot was to be derived from one of these lengths by a simple integer factor, which would be either three (pendulum) or five (rod), i.e. lengthening it from the traditional value by 1.04970¯6 inches to ca. 331.463 mm or shortening it by 0.255264 inches to ca. 298.317 mm. For practical purposes he wanted the rod to be 58¾ (new) inches long, an increase of less than 0.045%.

Decimal system based on the foot

The revolutionary system was quite similar to the metric system, except the difference of about 5.5 mm between the second pendulum at 45° and the 10,000th part of the distance from the north pole to the equator, which became the first definition of the metre. Also it didn't have the concept of prefixes. A very similar system was a base of discussion in France after the revolution of July 14, 1789, with Jefferson observing.

In distinguishing this from the less radical changes proposed in the first alternative, the report stated:

The original document gives the value of a kental as 16 stones at one point and 10 stones in another point in the document. 10 was presumably the intended value, given the otherwise consistent decimalization.

Depending on exactly which definition of the foot was to have been used, the actual values of the base units would have been:

Foot - 331.4 mm or 298.3 mm (for comparison, the modern US foot is 304.8mm)

Bushel - 36.43 L or 26.54 L (for comparison, a modern US bushel is 35.239072 L)

Ounce - 36.43 g or 26.54 g (for comparison, a modern US ounce is 28.3495231 g)

Subsequent developments

Under the United States Constitution, Article 1 Section 8, Congress shall have power "To coin Money, regulate the Value thereof, and of foreign Coin, and fix the Standard of Weights and Measures". In his first annual message to Congress (what later came to be called "State of the Union Addresses") on January 8, 1790 (a few months before Jefferson's report to the House of Representatives), George Washington stated, "Uniformity in the currency, weights, and measures of the United States is an object of great importance, and will, I am persuaded, be duly attended to."

Washington repeated similar calls for action in his second and third annual messages (after Jefferson's report). Jefferson's decimal proposal had the support of Alexander Hamilton, James Madison, James Monroe, and George Washington. Robert Morris was a powerful opponent of the proposal. In late 1791 the Senate appointed a committee to report on the subject and make recommendations. The committee reported in April 1792, unanimously endorsing Jefferson's decimal system. The Senate was slow to act on the matter and while they delayed events in France complicated the issue. Although French scientists working on a decimal system had originally supported using the seconds pendulum as a scientific basis, and Jefferson had deliberately matched his seconds pendulum proposal to the French one, based on a measurement at the latitude of Paris, the French decided to use the length of a meridian of the Earth instead of a seconds pendulum. This and other developments changed what had promised to be an internationally developed system into a strictly French project. Jefferson wrote, "The element of measure adopted by the National Assembly excludes, ipso facto, every nation on earth from a communion of measurement with them."

The Senate continued to consider Jefferson's two proposals, along with a number of new proposals, for several years. In 1795 a bill titled "An Act directing certain experiments to be made to ascertain uniform standards of weights and measures for the United States" was passed by the House and was approved by committee in the Senate, but on the last day of the session the Senate said it would consider the bill during the next session. The bill was never taken up again. In 1795 the Northwest Indian War, which for years had prevented the surveying and sale of land in the Northwest Territory came to an end. A land rush of settlers, surveyors, squatters, and others rapidly pushed into the region and the federal government had a sudden and intense need to establish a method for surveying and selling land. On May 18, 1796 Congress passed "an Act for the sale of land of the United States in the territory northwest of the River Ohio, and above the mouth of the Kentucky River". This law defined a survey grid system of 6–mile–square townships divided into 1–mile–square sections, with the defining unit being the chain, specifically Gunter's chain. This was the first unit of measurement designated into law by Congress. This law and the way it defined the survey grid ended debate over Jefferson's decimal system.