682 Ten iisur/ions of the Society. 



XXI. — The Present Status of Micrometry. 

 By Marshall 1). Ewell, M.I). Chicago. 



{Bead November 18, 1908.) 



By the establishment of the International Bureau of Weights and 

 Measures, and more recently of our own National Bureau of 

 Standards, the subject of Metrology has been placed on a sound 

 and satisfactory basis, more so than ever before in its history. 

 Under the able direction of Professor S. W. Stratton, to whom is 

 rightfully due the credit of having created and organised our 

 National Bureau of Standards, this Bureau has become an institu- 

 tion of which all Americans may justly be proud. It has, through 

 its publications and its work, become a great educational force, 

 and by placing the verification of all sorts of scientific standards 

 within easy reach of scientists and artisans of this country, without 

 the delay and expense of sending abroad, it has conferred a benefit 

 upon science and art that can never be measured by any merely 

 pecuniary standard. 



It appears not to be generally understood, though why we are 

 unable to understand, that all American standards of length, area, 

 and cubic measure are derived from the international metre, the 

 legal equivalent being 1 m. equals 39 '37 in.* In 1893, the 

 United States Office of Standard Weights and Measures was 

 authorised to derive the yard from the metre, using for the purpose 

 the relation legalised in 1866, viz. 1 yd. equals §§§f m. 



The customary weights are likewise referred to the kilogram.! 

 This action fixes the values, inasmuch as the reference standards 

 are as perfect and unalterable as it is possible for human skill to 

 make them.| 



The metric system is, therefore, the basis of the entire system 

 of weights and measures in the United States, and in our judgment 

 the Act of Congress, 1866, and the executive orders in pursuance 

 thereof, showed great wisdom in thus finally settling the relation 

 between the yard and metre, and deriving the yard and other units 

 from the metre. Hitherto this relation had been unsettled and 

 ambulatory. At present the British legal (Board of Trade) equiva- 

 lents sustain the following relation : 1 m. equals 39 370113 in., 

 which is very nearly the same value as that found by the late 

 Professor William A. Eogers, of this country. The last relation 

 adopted by Professor Eogers was, as the writer remembers, 1 m. 



* See United States Statute of July 28, 1866 ; Revised Statutes of the United 

 States, 3570. f Executive order approved April 5, 1893. 



% See Tables of Equivalents, Department of Commerce and Labour, Bureau 

 of Standards, S. W. Stratton, Director, 3rd edition, p. 5. 



