The National Academy of Sciences’ Committee to Prescribe & Publish Specifications for the Practical Application of the Definitions of the Ampere & Volt, 1894

[The following narrative is taken from Frederick W. True’s Semi-centennial history of the National Academy of Sciences, A History of the First Half-Century of the National Academy of Sciences 1863-1913, pp. 313-314.]

It will be recalled that the Academy sent delegates in 1884 to the International Congress of Electricians at Paris. At this congress the “legal ohm” or “congress ohm” was established, having for its determination the resistance of a column of mercury 106 centimeters long. It was considered both at that time and subsequently that this length was not the proper one and for further consideration of this and other matters connected with electrical units an international electrical congress was held in Chicago in 1893. On this occasion the ohm known as the “international ohm” was determined upon, having as its basis the resistance of a column of mercury 106.3 centimeters long. The “volt,” “ampere,” “henry” and other units were also fixed.

In the year following an act was passed by the Congress of the United States, defining the various units in accordance with the decisions of the electrical congress. These comprised the ohm, the ampere, the volt, the couloumb, the farad, the joule, the watt and the henry; the last, as is well known, named in honor of Joseph Henry, the first Secretary of the Smithsonian Institution and second President of the National Academy of Sciences.

The act referred to, which was approved on July 12, 1894,[Stat. at Large, vol. 28, p. 101, 53^rd Congress, 2d Session, chap. 131. See also Rep. Nat. Acad. Sci. for 1894, p. 39; also for 1895, p. 7.] contained the following provision:

For some reason which is not apparent, the Act did not come to the attention of the President until the last day of October.[See Rep. Nat. Acad. Sci. for 1894, p. 40.] On November 6, he applied to the Secretary of State for an authentic copy, and received the same on November 9.

The same day he appointed the following committee to investigate and report upon the matter: H.A. Rowland (chairman), T.C. Mendenhall, H.L. Abbot, G.F. Barker, J. Trowbridge, C.S. Hastings, and C. Barus. Professor Mendenhall declined appointment and was replaced by Professor A.A. Michelson. A special meeting was held in New York on February 9, 1895, to consider the report of the committee, in which detailed specifications were given for the practical application of the ampere and volt, which were prepared to meet the requirements of law and were also in accordance with the international agreement. The specifications are quoted in full in the report of the Academy for 1895 (pp. 9-13), with notes and illustrations. The Academy then by a unanimous vote adopted the specifications and prescribed them in accordance with the Act of Congress. “It was also voted unanimously that these specifications be published by the sending, by the president, of a copy of the same to each House of Congress and to the Secretary of State, with the request to the latter that they be issued by the State Department; and, further, by the printing by the home secretary of the Academy of a suitable number of copies for public distribution.”[See Rep. Nat. Acad. Sci. for 1894, pp. 17, 39-42; for 1895, pp. 7-13. The report of the committee constitutes Sen. Misc. Doc. no. 115, 53^rd Congr. 3d Sess. Order printed Feb. 19, 1895.]