FISCHER: LENGTH STANDARDS ANp MEASUREMENTS 151 



Bureau of Standards in 1901. The bar is made of iron, with a 

 cross-section of 9 by 29 mm. and its length is defined by the end 

 surfaces, which are remarkably plane when one considers the 

 age in which the bars were made. The bar bears the stamp of 

 the committee, which had charge of its construction, namely, 

 a small ellipse, whereof three quadrants are shaded and the fourth 

 one clear, except for the number 10,000,000, which indicates the 

 number of meters in the length of a quadrant of the earth. It 

 also bears certain prick points which distinguish it from the other 

 meters made at the same time. In Mr. Hassler's report on the 

 construction of these meters, it is stated, on the authority of 

 Mr. Tralle, a member of the committee, from whom the bar was 

 obtained, that all the meters agreed with the true meter within 

 one-millionth part of the toise which is about one-half the 

 accuracy claimed by the committee. 



This bar, which is known as the Committee Meter, served with- 

 out interruption as the standard to which all scientific work done 

 in the United States was referred from about 1807 to 1893, a 

 period of about 86 years, when it was superseded by the present 

 platinum-iridium line standard in the custody of the Bureau 

 of Standards. The new platinum-iridium meter not only super- 

 seded the Committee Meter, but it also superseded the British 

 yard, inasmuch as in 1893 the yard was defined in terms of the 

 meter, according to the ratio: one yard equals 3600/3937 meter. 



In the early development of standards of length, the geod- 

 esist has played an important part and the reason for this is 

 at once apparent. His subject is the study of the size and form 

 of the Earth and, in order to make any progress, work has to be 

 done in different parts of his field. If arcs are measured in Europe, 

 Asia, or America, the length of the standards in which they are 

 expressed must be known before any deductions can be drawn 

 from them. In Prussia it is Bessel in 1823, who had a copy of 

 the Toise of Perou constructed by Fortin of Paris, in order that 

 he might express the results of his determinations of the length 

 of his seconds pendulum at Koenigsberg in terms of what was 

 then the generally accepted standard for geodetic work. The 

 Toise of Bessel was later to take an important part in the history 



