# Metric Act of 1866

 14 Stat. 339, July 28, 1866Metric Act of 1866 39th United States Congress Long title: CHAP CCCI. — An Act to authorize the use of the metric system of weights and measures. Authored by: Introduced by: Dates Date passed: House:May 17, 1866 Senate:July 27, 1866. Date signed into law: 1866 Amendments: Related legislation:

The Metric Act of 1866, also known as the Kasson Act, is a piece of United States legislation that legally protected use of the metric system in commerce from lawsuit, and provided an official conversion table from U.S. customary units.[1]

## History

Congressman John A. Kasson from Iowa, then Chairman of the House Committee on Coinage, Weights, and Measures, proposed the act in his report of the Committee on Coinage, Weights, and Measures:

In the schedule of equivalents provided in the bill, extreme scientific accuracy is not expressed. The reasons follow. The exact length of the meter in inches and the weight of the kilogram in grains can of necessity be determined only approximately. The most careful determinations of these quantities now possible are liable to minute corrections hereafter, as more numerous observations are made and better instruments are used. Instead, therefore, of aiming at an accuracy greater, perhaps, than is attainable, it is more expedient to consult the convenience of the people by using the simplest numbers possible in the schedule, and yet such as shall be in fact more nearly exact than can ever be demanded in the ordinary business of life. These numbers are to be used in schools, and in practical life millions of times as multipliers and divisors, and every unnecessary additional figure is justly objectionable.

In a popular sense of the word, however, the numbers in the schedule may be said to be exact. The length of the meter, for example, is given as 39.37 inches. The mean of the best English and the best American determinations differs from this only by about the amount by which the standard bar changes its length by a change of one degree of temperature. Such accuracy is certainly sufficient for legal purposes and for popular use.

The Act was originally introduced as H.R. 596 in the 39th Congress. The House passed it on 17 May 1866; the Senate passed it on July 27, 1866; and it was presented to President Andrew Johnson and signed the next day.

The Act included a now-obsolete definition of the metric system and tables of units.

On August 9, 2007, the Act was amended by Pub.L. 110–69, the America COMPETES Act. It replaced the old definition of the metric system with the modern-day definition of SI.