tttl€tt,'tlie*li5^thCsiB tliAt all three wereniade df thfe' sttmi^tAefift^fife 

 evidently erroneous ; and nothing can be inferred from the density of 

 either of the two remaining. - ("^ •" ^'» 



/'^Mr. Vftndome readily consented to allow his troy''j)(5>Bfcidit<iIbe 

 etperimented upon by the Committee. Denoting this weight b^ 

 the letter V, by weighing in air and in water it was found thaJt 

 AV=8- 15084, and that it was about 0':309 grain lighter than U. 

 K j Air* Bingley had in his possession two troy pounds j both daited 

 175S. One of these, O, said to be the original weight from wMch 

 the standard was made for the House of Commons in 1758, has 

 since been purchased by the Committee ; the other, M, has been pre- 

 sented to the Mint by Mr. Bingley. As Mr. Bingley was unwilling 

 to permit either of these weights to be weighed in \vatc'r, Mossrsi 

 Troughton and Simms were commissioned to construct an instru- 

 ment on the principle of the Stereometer invented by M, Say for the 

 purpose of finding the density of gunpowder (Ann. deChimie, 1797; 

 ti. xxiii. p. 1), but with some improvements wliich I had describea 

 in the Philosophical Magazine for July and December, 1834, vol. Vi 

 p. ,203. Let V prefixed to the symbol of any weight denote the 

 yolume of that weight at 0° Cent., the unit of volume being the 

 volume of a grain of water at its maximum density. Then, by 

 means of the Stereometer, it was found that i?V—-t'0= 22*68, 

 t>V— t>M= 1 7*38. These dififerences show that the volume of the lost 

 standard cannot be inferred with any high degree of probability from 

 a comparison of the remaining pounds. The only resource now 

 remaining was indicated by Professor Schumacher's remarks on the 

 figure of the lost standard : — " As soon as the Imperial standard 

 troy pound was brought to Somerset House, Captain Nehus's first 

 care was to make an accurate drawing of its shape and marks, 

 measuring all its dimensions with the greatest care. The annexed 

 drawing represents this pound in its actual dimensions ; and is now, 

 since the original has been destroyed by the calamitous fire that con- 

 sumed the two Houses of Parliament in 1834, the only thing remain- 

 ing which can preserve an idea of it." By a comparison of the figure 

 of U in the Philosophical Transactions for 1836, with a profile of V 

 traced mechanically, the axis and the extreme diameter of the knob 

 and cylindrical portion of U, appeared to be a very little greater than 

 the corresponding dimensions of V. On comparing the profiles of 

 JJ and V, it did not seem possible to suppose that the volume of U 

 iras less than that of V. But the volume of O, as well as tliat of M, 

 being less than that of V, it appeared that of the three weights V, 

 O, M, V approximated most nearly to U in volume. As the exist- 

 ing data were utterly insufficient to determine how much, if at all, 

 U exceeded V in volume, it appeared safest to assume the volumes of 

 U and V to have been equal. This eourse vf^ also recommended 

 by Professor Schumacher. 



It was afterwards found that O was 0-144 grain lighter than U, 

 AO=8-4004; and that M was 0*047 grain lighter than U, 

 AM=8*34^1. 

 ,„.J^i,^ l^^^^;,fi;^ :Wil)wn.AWler*.Epqw,,pf fte P^.^of JEfi^di 



