626 MISCELLANEOUS PAPERS. 



gram was declared to cousist of 18,827.15 Frencb grains, of wbich the 

 livre contained 021G;* or, in other words, the kilogram was declared 

 equal to2.0i28S livres, whence, with the Royal Societifs lvalue of the Uvn; 

 the English equivalent of the kilogram was computed to be 15,444 troy 

 grains. 



During some experiments at the London mint in March, 1820, it was 

 found that the French livre belonging to that institution weighed only 

 7,555 troy grains. This discovery led to an examination of the Royal 

 Society's standards of 1742, which had been carefully preserved, and it 

 was found that their livre agreed with that at the mint, but their Troy 

 pound was nearlj^ 4 grains lighter than the Imperial standard of 1758, 

 and their avoirdupois pound weighed only 7,000 troy grains instead of 

 7,004.t Thus it was rendered almost certain that the accepted English 

 equivalent of the kilogram was about 10 grains too large, and, to remove 

 all possible doubt, a direct comparison of the English and French stand- 

 ards of weight was effected in 1821, | through the co-operation of the 

 respective governments, and then it was definitively ascertained that 

 the weight of the kilogram is only 15,433 troy grains. 



The facts respecting the Royal Society's standards of 1742 are as 

 follows : 



(1) The weighings recorded in the Philosophical Transactions, 1743, 

 pages 553 and 556, give 



R. S. troy pouad = Excli. (8 ounces + 4 ounces) — i grain (5) 



R. S. troy pound = Mint (8 ounces + 4 ounces) — 2f grains (6) 



whence 



Excb. (8 ounces + 4 ounces) = Mint (8 ounces -\- 4 ounces) — 1| grains (7) 



(2) The weighings by Mr. Harris for the Parliamentary Committee 

 of 1758 give § 



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



whence by (6), 



R. S. troy pouad = Exch. (8 ounces + 4 ounces) — 11 grains ■ (9) 



In equations (6) and (8) the weights at the mint were those of the 

 sixth of Queen Anne, 1707. 



(3) In the Philosophical Transactions, 1742, page 187, it is stated that 

 the Paris 2-marc weight weighs 7560 troy grains. As the true weight 

 of 2 marcs is 7554.22 grains, this implies that the Royal Society's troy 

 ])Ound was too light by 5.78 (5760 -^- 7560) = 4.40 grains. 



In the Philosophical Transactions, 1742, page 187, it is stated that 

 the Royal Society's avoirdupois pound weighed 7004 troy grains, while 

 the comparisons made in 1820 show that its weight was then only. 7000 

 such grains. This implies that the Royal Society's troy pound was too 

 light by 4.00 (5760 4- 7000) = 3.29 grains. 



Finally, the comparisons of 1820 showed that the Royal Society's 

 troy pound was "nearly 4 grains too light." 



The mean of these three independent results shows that the Royal 



* Base du System M^trique, T. 3, p. 638. , t 31, pages 19-22. 



t See 40, vol. 1, p. 140, and 31, p. 19. ' $ 13, p. 437. 



