806 PROF. W. H. MILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND. 
The Commissioners for the Restoration of the Standards of Weight and Measure, 
in their Report dated December 21, 1841, recommended that the avoirdupois pound 
of 7000 grains be adopted instead of the troy pound of 5760 grains, as the new Par- 
liamentary Standard of weight, and that the new standard and four copies of it be 
constructed of platinum. In accordance with this recommendation, five platinum 
weights were made by Mr. Barrow, a little in excess of 7000 grains. The form of 
these pounds is that of a cylinder nearly 1*35 inch in height and 1*15 inch in diameter, 
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 1844 1 lb.; PC 
No. 4 1844 1 lb., respectively. 
The weight of 7000 grains might have been formed from one of 5760 grains, by 
the use of either a decimal or a binary system of weights. In either case, however, 
the number of the weights to be compared with one or the other or both of the 
weights of 7000 grains and 5760 grains would have been large, and the errors of the 
comparisons between themselves might by their accumulation sensibly affect the 
resulting weight of 7000 grains. Moreover, the repeated comparison of weights 
made up of the sum of several others, was a very troublesome process previous to 
the use of the method described in page 764, which had not been thought of at the 
time 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 series of 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 ; II of 360 grains ; K, L, M, N each of 80 grains ; R, S each of 
40 grains, nearly. The platinum of which the five lbs., T and the auxiliary weights 
were made, was prepared by Messrs. Johnson and Cock. 
The numbers of the weights of each denomination, and their values, are given by 
the quotients and divisors obtained in the conversion of into a continued 
fraction. The errors of these weights are found by the following comparisons : — Sp 
and RS with T; T with A-f-B-j-C-j-D-l-F ; each of the weights A, B, C, D with 
F-fG; F with G-{-H ; G with each of the weights H-j-K, H-j-L, H-|-M, H-fN; 
H with K-f-L-fM-f-N-j-R and K-|-L-f-M-l-N-{-S ; each of the weights K, L, M, N 
with R-l-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 as heavy as U nearly, when weighed 
in air of ordinary density, and are therefore lighter than U by about 0'53 grain, the 
weight of the air contained in a space equal to the difference between the volume of 
U and that of Sp or RS. A space equal to the difference between the volume of 7000 
grains of metal of the density of U and 7000 grains of platinum, contains about 0*645 
grain of air. Calling this Q, PS may be compared with each of the weights TH-A-fQ, 
T-l-B-j-Q, T-j-C-j-Q, T-l-D-)-Q. In order to determine the error of the weight of 
0*645 grain with the greatest precision, ten weights Q of 0*645 grain each, so accurately 
