THE AliT OF WEIGHING AND MEASURING. 



627 



(10) 

 (11) 



(12) 



S 



(5') 



(7') 



Society's troy pound was 3.9 grains lighter than the Imperial standard 

 of 1758; whence 



R. a. troy pound -f :{.9 grains = Standard of 1758 

 but 



Standard of 1858 = Exch. (8 ounces + 4 ounces) -|- IJ grains 



and therefore 



R. S. troy pound = Exch. (8 ounces + 4 ounces) — 2| grains 



Considering the indetiniteness of the data respecting the weighing!- 

 made in 1820, equations (9) and (12) agree fairly well, but equation (5) 

 is very discordant, as are also equations (7) and (8). All the evidence 

 seems to point to an error of about 1^ grains in equation (5) ; and if 

 instead of (5) we write 



R. S. Troy pound = Exch. (8 ounces -|- 4 ounces) — 2 grains 

 (7) will become 



Exch. (8 ounces + 4 ounces) = Mint (8 ounces + 4 ounces) — | grain 



and then all the equations will be reasonably accordant. 



Note 0. [Subsequently added.] 



Assistant O. H. Tittmann, of the U. S. Coast and Geodetic Survey, 

 in charge of weights and measures, has recently shown that the dis- 

 crepancies in the values assigned to the meter in terms of the yard 

 depend mainly upon errors either in the assumed lengths or in the 

 assumed coefficients of expansion of the standards employed.* By a 

 skillful use of the data published by the various observers, combined, 

 with the known coefficient of expansion of the iron committee meter, 

 "CM," of the U. S. Coast and Geodetic Survey, he has succeeded in 

 determining the absolute expansions of the standards in question, and 

 by means of these expansions he has referred all the observations to 

 the said committee meter and to the present British Imperial yard. 

 From the data thus reduced to a common standard he has obtained 

 the very consistent results given in the fourth column of the following 

 table. The values in the third column are those published by the ob- 

 servers themselves, and it is now evident that they really depend upon 

 several different British and metric units. As there is no means of re- 

 ferring the standard used by Prof. W. A. Rogers to the committee meter, 

 his result could not be included in the table. 



LENGTH OF THE METER EXPRESSED IN ENGLISH INCHES. 



Date. 



1817-32 



1818.... 

 1835.... 

 18GG..-. 



1885.... 



Authority. 



H ussier . . 



Kater 



Bailv .... 

 Clarke ... 

 Conistock 



Indiscriminate mean . 



Published 

 value. 



39. 380917 

 39. 37079 

 39. 3G9678 

 39. 370432 

 39. 36985 



Value in terms 

 of Bri tish 

 Imperial 

 yard and of 

 the commit- 

 tee meter, 

 CM. 



39. 36994 

 39. 36990 

 39. 36973 

 39. 36970 

 39. 36984 



39. 36980 



See 73 and 74. 



