612 MISCELLANEOUS PAPERS, 



The coinmissiouers appointed in 1818 to establish a more uniforiii sys- 

 tem of weights ami measures repeated the recommendations of the 

 committee of 1758,* and as the avoirdupois pound which had long been 

 used, although not legalized by any act of the legislature, was very 

 nearly 7,000 troy grains, they recommended that 7,000 such troy grains 

 be declared to constitute a pound avoirdupois.t Tbese recommenda- 

 tions were embodied in the act of Parliament of June 17, 1824, and thus 

 one of the troy pounds made in 1758 became the Imperial standard. 

 That standard, like Bird's standard yard, was deposited in the Houses 

 of Parliament and was burned up with them in October, 1834. 



The present English standard pound was made in 1844-'46 by Prof. 

 W. H. Miller, who was one of the members of the commission ap- 

 pointed in 1843 to superintend the construction of the new Parliament- 

 ary standards of length and weight destined to replace those destroyed 

 in 1834. A number of weights had been very accurately compared with 

 the lost standard ; namely, in 1824 or 1825, by Captain Kater, five troy 

 pounds of gun metal, destined respectively for the use of the Ex- 

 chequer, the Royal Mint, and the cities of London, Edinburgh, and Dub- 

 lin; and in 1829, b^' Captain v. Nehus, two troy pounds of brass and one 

 of platinum, all in the custody of Professor Schumacher, and a platinum 

 troy pound belonging to the Eoyal Society. The first step for recover- 

 ing the mass of the lost standard was manifestly to compare these 

 weights among themselves, and upon so doing it was found that for the 

 brass and gun-metal weights the discrepancies between the weighings 

 made in 1824 and 1844 amounted to 0.0226 of a grain,| while for the 

 two platinum weights the discrepancies between the weighings made in 

 1829 and 1845 was only 0.00019 of a grain.§ With a single exception, 

 all the neiv brass or gun-metal weights had become heavier since their 

 first comparison with the lost standard, the change being probably due 

 to oxidation of their surfaces, and on that account the new standard 

 was made to depend solely upon the two platinum weights. For con- 

 venience of reference these weights were designated, respectively, Sp 

 (Schumacher's platinum) and RS (Royal Society). A provisional 

 I^latinum troy pound, T, intermediate in mass between Spand RS, was 

 next prepared, and from two hundred and eighty-six comparisons made 

 in January, February, July, and August, 1845, it was found that in a 



vacuum II 



T = Sp + 0.00105 grain, 



while from 122 comparisons made in January, July, and August, 1845, 



T = RS — 0.00429 grain. 



By combining these values with the results of the weighings made in 



1824-'29, namely, 



Sp = U — 0..S2956 grain, 

 RS =U— 0.52441 grain, 



where U designates the lost standard — the comparison with Sp gave 



T = U — 0.52851 grain, 

 » See 26, 27, and 28. 1 28, pp. 4-5. t 40, p. 772. $ 40, p. 941. || 40, pp. 819-20. 



