XXXVl UNITS. 



"On January 2, 1890, the seals which had been placed on metre No. 27 and 

 kilogramme No. 20, at the International Bureau of Weights and Measures near 

 Paris, were broken in the Cabinet room of the Executive Mansion by the Presi- 

 dent of the United States, in the presence of the Secretary of State and the 

 Secretary of the Treasury, together with a number of invited guests. They were 

 thus adopted as the National Prototype Metre and Kilogramme. 



" The Troughton scale, which in the early part of the century had been tenta- 

 tively adopted as a standard of length, has long been recognized as quite un- 

 suitable for such use, owing to its faulty construction and the inferiority of its 

 graduation. For many years, in standardizing length measures, recourse to copies 

 of the imperial yard of Great Britain had been necessary, and to the copies of 

 the metre of the archives in the Office of Weights and Measures. The standard 

 of mass originally selected was likewise unfit for use for similar reasons, and 

 had been practically ignored. 



"The recent receipt of the very accurate copies of the International Metric 

 Standards, which are constructed in accord with the most advanced conceptions 

 of modern metrology, enables comparisons to be made directly with those stand- 

 ards, as the equations of the National Prototypes are accurately known. It has 

 seemed, therefore, that greater stability in weights and measures, as well as much 

 higher accuracy in their comparison, can be secured by accepting the international 

 prototypes as the fundamental standards of length and mass. It was doubtless 

 the intention of Congress that this should be done when the International Metric 

 Convention was entered into in 1875 ; otherwise there would be nothing gained 

 from the annual contributions to its support which the Government has con- 

 stantly made. Such action will also have the great advantage of putting us in 

 direct relation in our weights and measures with all civilized nations, most of 

 which have adopted the metric system for exclusive use. The practical effect 

 upon our customary weights and measures is, of course, nothing. The most care- 

 ful study of the relation of the yard and the metre has failed thus far to show 

 that the relation as defined by Congress in the Act of 1866 is in error. The 

 pound as there defined, in its relation to the kilogramme, differs from the impe- 

 rial pound of Great Britain by not more than one part in one hundred thousand, 

 an error, if it be so called, which utterly vanishes in comparison with the allow- 

 ances in all ordinary transactions. Only the most refined scientific research will 

 demand a closer approximation, and in scientific work the kilogramme itself is 

 now universally used, both in this country and in England.* 



* Note. — Reference to the Act of 1866 results in the establishment of the following : — 



Eqttatio7is. 



3600 



1 yard =^ metre. 



^ 3937 



I pound avoirdupois = ^.^ ^ kilo. 



A more precise value of the English pound avoirdupois is ^.^ ^^ kilo., differing from the above 



by about one part in one hundred thousand, but the equation established by law is sufficiently 

 accurate for all ordinary conversions. 



As already stated, in work of high precision the kilogramme is now all but universally used, 

 and no conversion is required. 



