INTRODUCTION 

 CONVERSION OF UNITS OF LENGTH AND MASS 



United States usage. — No general agreement yet exists on the factors 

 to be used in the conversion between the metric and the English systems of 

 units. In the United States, an Act of Congress of July 28, 1866 (14 Stat. 

 339; 15 U.S.C. 204) established the metric system as lawful throughout the 

 United States and ordered the units of weights and measures in common 

 use to be defined in terms of this system. A schedule annexed to this Act 

 established 39.3700 inches as the equivalent of the meter and 2.2046 pounds 

 (avoirdupois) as the equivalent of the kilogram. In 1893 T. C. Mendenhall, 

 Superintendent of Standard Weights and Measures, issued an order * stating 

 that his office would regard the International Prototype Meter and Kilogram 2 

 as the fundamental standards and affirmed the equivalents of the Act of 1866. 



In actual practice, the National Bureau of Standards still uses the length 

 ratio annexed to this Act, which yields 1 inch = 2.540005 centimeters. How- 

 ever, in the case of the pound, the National Bureau of Standards has adopted 

 the results of a comparison of the British Imperial Standard Pound and the 

 International Prototype Kilogram made in 1883, 1 pound = 453.5924277 

 grams, rather than the ratio annexed to the Act of 1866, which yields 1 

 pound = 453.597+ grams. 



British usage. — In Great Britain, the English standards of length and 

 mass are legally defined by the Imperial Standard Yard and the Imperial 

 Standard Pound, respectively, and the relation of the English to the metric 

 units are experimentally determined by direct comparison. 3 The conversions 

 now legally sanctioned in Great Britain are: 



1 inch = 2.539998 centimeters 

 1 pound = 453.59234 grams 



Recent comparisons. — According to the most recent comparisons : 4 



1 Imperial Yard _ 3600000 > which yields 

 1 meter ~ 3937014 ' 



1 inch = 2.539996 centimeters 



1 U. S. Coast and Geodetic Survey, Bull. 26, 1893. 



2 Prepared by the International Bureau of Weights and Measures, Sevres, France. 

 This bureau was established by the International Metric Convention, 1875, and is sup- 

 ported by the contributions of many nations, including the United States. 



8 For a discussion of the problems involved, see Darwin, C, et al., Proc. Roy. Soc. 

 London, ser. A, vol. 186, p. 175, 1946. 

 4 Nat. Bur. Stand., private communication, July 1949. 



1 



