THE ART OF WEIGHING AND MEASURING. 



G25 



In additicMi to being less exact, the weighings by Mr. Freeman 

 (litter from those by Mr. Harris princii)ally in the sign of the correc- 

 tion to the .'i-J-ounce weight; the former stating that the 32-ounce 

 weight was lighter than the sum of all the smaller weights aud the 

 latter that it was heavier. To ascertain which was right we have 

 only to compare the resulting systems of corrections with those found 

 by Mr. Chisholm iu 1873. Table I shows that according to Mr, Harris's 

 weighings all the weights have grown lighter during the interval from 

 1758 to 1873, while Table II shows that according to Mr. J'"'reeman's 

 weighings some have grown lighter aud others heavier, and that by 

 quantities which cannot be attributed to accidental errors iu the weigh- 

 ings. Iu view of these facts there can be no doubt that the committee 

 of 1758 was right iu using only Mr. Harris's weighings, and it seems 

 equally' certain that the numbers iu Table I should be adopted to the 

 exclusion of those in Table II. 



Table II. — Corrections to the Exchequer Standard Troy \VEHiHT8 of 15>!8, 



DERIVED FROM THE WEIGHINGS MADE BY MESSRS. FREEMAN AND ChISHOLM. 



Denoiuiuatiou of Weislit, 



Ap))areni 



correction in 



17.58. 



Coniniittee's 



correction in 



1758. 



Graiiifi. 



— 0. 03 

 + 0.47 



— 0. 0(i 

 O.ll 

 0. 23 

 0.4G 

 0.42 

 0.83 

 1.(58 

 5. 36 

 8.70 

 2.40 



-43.81 

 -63.62 



Corrections given hy 

 Mr. Chisholm — 



For 1758. For 1873. 



Grains. 



0. 

 + 0.5 



0. 



0. 

 0.0 



— 1.0 

 0.5 

 0.75 



1. 75 

 5.5 



— 9. 

 + 3.0 

 -45.0 

 —61.0 



Grain 



— 

 + 



— 

 

 



1 







1 



3 



3 



— 5, 

 + 4, 

 —53, 

 -65 



s. 

 ()(> 

 10 

 21 

 36 



.45 

 01 

 68 



.09 



.84 

 82 

 04 

 28 

 58 

 46 



From comparisons of their troy pound with their avoirdupois pound, 

 and with the 2-marc weight sent to them by the French Academy in 

 1742, the Royal Society of London found* — 



(1) That the Kuglish avoirdupois pound weighed 7,004 troy grains: 



(2) That the French Uvre, consisting of 2 marcs, weighed 7,500 

 troy grains : 



And for three-quarters of a century the latter value was universally 

 accepted. Further, when the metric system came into being the kilo- 



*7, page 187. It is usual to designate 1742 as the date of tha exchange of stand- 

 ards, but the remark of Cassini de Thury (5, p. 135) shows that the true date must 

 have been prior to April, 1738. In his paper of November, 1742, Graham makes only 

 the indefinite statement that the excliango was "proposed sonic time siuce." 



H. Mis. 142 40 



