OP ARTS AND SCIENCES. 379 



XV. 



AN EXAMINATION OF THE STANDARDS OF LENGTH 

 CONSTRUCTED BY THE SOCJETE GENEVOISE. 



By Professor W. A. Rogers. 



Communicated December 10th, 1884. 



Several physical laboratories in this country have recently received 

 from the Societe Geuevoise instruments of precision of various kinds, 

 which appear to have decided merit, both in regard to design and 

 workmanship. The Society has among other things undertaken the 

 construction of standards of length, and of a cathetometer, which is 

 designed to take a high rank as an instrument of precision. Through 

 the kindness of Professor Wright of Yale College, the writer has been 

 permitted the opportunity of a somewhat extended study of one of 

 the standard meters of the Society. Through the courtesy of J. W. 

 Queen & Co. of Philadelphia, the opportunity was at the same time 

 offered of an examination of three other standard meters, and of the 

 meter graduated upon the upriglit bar of a cathetometer. 



On account of the somewhat extended introduction of these stan- 

 dards, it has seemed to the writer worth while to place upon record 

 the results of this examination. 



EXAMINATION OF METERS. 



The meter belonfjintj to Professor Wriiiht is designated W. The 

 meter of similar form and dimensions received from J. W. Queen & Co. 

 is designated Q^. A second meter, in which the graduations are 

 nearly along the centre of gravity of a cross section of the bar, is 

 designated Q.^ The graduations upon W, Q^, and Q.^ are upon silver 

 inlaid in the brass, which is the material of the bars. A third meter, 

 designated Q.^, has the graduations upon the brass. The meter of the 

 cathetometer is designated Q^. 



