Prof. Miller on the Imperial Standard Pound. 549 



dated August 22, 1855, I was apprised of the existence of a fourth 

 troy pound of 1 758. This weight was 0*249 graiu heavier than U ; 

 its density =8'3175. •iiirui^ro'vi mn ■.d^'io ■,■n\^i'i 



; If U, the lost standard, be supposed to have the same density dH V, 

 tfce comparisons of Sp and RS with U by Captain v. Nehus in 1829, 

 giyfirj-^rrafoi ^iv/f '^ > w <Sp =U— 0*52959 ■-•'''''' "> ^' y>>'^>' r.x-, 

 TJ nmh mlff:2i( (liirp^ RS=U-0*52444. '>\dt him ,\-mt,\-^=.^ L 



The Commissioners for the Restoration of the Standards of Wefght 

 and Measure, in their Report, dated December 21, 1841, recom- 

 mended that the avoirdupois pound of 7000 grains be adopted 

 instead of the troy pound of 5760 grains, as the New Parliamentary 

 Standard of Weight, and that the new standard and four copies of it 

 be constructed of platinum. ■ 



In accordance with this recommendation, five weights were made 

 by Mr. Barrow, a little in excess of 7000 grains, of platinum pre- 

 pared by Messrs. Johnson and Cock. The form of these pounds is 

 that of a cylinder, nearly 1*32 inch in height and 1*15 inch in dia- 

 meter, with a groove round it, the middle of which is about 0*34 

 inch below the top of the cylinder, for insertion of the prongs of a 

 forked lifter of ivory. They are marked PS 1844 1 lb. ; PC No. 1 

 1844 1 lb. ; PC No. 2 1844 1 lb.; PC No; 3 184411b;; PC No. 4 

 1844 1 lb., respectively. i;Khm(ma:}>l niH \o mniw 



The weights of 7000 grains might havfe be^ii^derited frdn^'^that if 

 5760 grains, by the use of either a decimal or a binary system of 

 weights. In either case, however, the number of weights to be com- 

 pared with one another and with the weights of 7000 and 5760 grains 

 would have been large, and the errors of their compansons among 

 themselves might, by their accumulation, sensibly aifect the resulting 

 weight of 7000 grains. Also, the repeated comparison of weights 

 made up of the sum of several others, was a very troublesome pro- 

 cess, previous to the use of the detached pans, already described, 

 which had not been thought of when the weights were ordered. 



These two evils were in a great measure avoided by the use of a 

 platinum weight T of about 5760 grains, or more correctly very 

 nearly equal to Sp or RS, and of the following auxiliary weights, also 

 of platinum, and all constructed by Mr. Barrow : A, B, C, D each 

 of 1240 grains ; F of 800 grains ; G of 440 grains ; H of 360 grains ; 

 K, L, M, N each of 80 grains ; R, S each of 40 grains, nearly. The 

 numbers of the weights of each denomination, and their values, are 

 given by the quotients and divisors obtained in the conversion of 

 Ifl^ into a continued fraction. The errors of these weights are 

 found by the following comparisons : — Sp and RS with T ; T with 

 A + B + C + D + F; each of the weights A, B, C, D withF + O; 

 F with G + H ; G with each of the weights H + K, H + L, H + M, 

 H + N; HwithK + L4-M + N + RandK+L + M + N + S;eachof 

 the weights K, L, M, N with R + S. 



Sp and RS, instead of being true troy pounds, and, consequently, 

 equal to U in a vacuum, had been adjusted so as to appear nearly as 

 heavy as U when weighed in air of ordinary density, and are there- 

 fore lighter than U by about 0'53 grain, the weight of the air con- 

 tained in the space equal to the difference between the volume of 



