Treasure of the Past: I. Recomparison of the United States Prototype Meter
L A. Fischer
U.S. meter No. 27, like the prototypes of all the principal nations, and also like the international meter, is composed of 90 per cent platinum and 10 percent iridium, with minute traces of other metals which compose less than 0.1 percent of the total. It was intercompared at the international Bureau of Weights and Measures, in 1888, with the national prototypes above referred to and with the international meter; and shortly afterwards it was brought to this country by a special messenger, who certified that it had suffered no violent mechanical or temperature disturbance in transportation. Soon after its arrival in this country--or to be exact, on January 2, 1891--the standard was unpacked with considerable ceremony at the Executive Mansion in the presence of the President of the United States, who accepted it as the national prototype meter. It was then immediately repacked, sealed in its metal case, and taken to the Office of Standard Weights and Measures, in the custody of which it remained until the formation of the Bureau of Standards, on July 1, 1901, when it was transferred to the Bureau with the other apparatus belonging to the Office of Standard Weights and Measures. It remained packed and sealed in its case until a few weeks before it was taken to Europe, when it was compared with Meter No. 21, which is exactly similar to No. 27, except that the lines and surfaces are not as perfect as those of No. 27, on account of its having been frequently packed in shaved ice.
Treasure of the Past: I. Recomparison of the United States Prototype Meter, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD
(Accessed September 27, 2023)