Aug. 21, 1873] 
NATURE 
327 
ON THE SCIENCE OF WEIGHING AND | 
MEASURING, AND THE STANDARDS OF 
WEIGHT AND MEASURE * 
, III. 
IMPERIAL STANDARD POUND 
THE standard unit of imperial weight is the avoirdu- 
pois pound of platinum, constructed under the 
superintendence of the Commission for Restoration of the 
Standards. The mode of constructing this new standard 
Fic. 4.—Form and size of the lost Standard Troy Pound. 
of weight, together with full details of all the scientific 
processes employed, have been described by Prof. W. 
H. Miller, to whom its construction was more imme- 
diately entrusted. A drawing of the imperial standard 
pound has already been shown in Fig. 1. 
For constructing this standard, the first point to be 
Fic s5.—Queen Elizabeth's Standard Troy Pound of eight and four ounces 
determined was the exact weight of the lost standard 
Troy pound, from which the weight of the new standard 
Avoirdupois pound was to be derived. Upon investiga- 
tion, this proved to be the most difficult problem to be 
solved by the Commission. The old standard had been 
constructed in 1758, together with two similar pounds, 
under the direction of the Parliamentary Committee of 
* Continued from p. 309. 
that year. Itis stated to have been composed of gon 
metal, but unfortunately no record exists of its volume or 
density, and it is not probable that it was ever weighed 
in water. An accurate drawing of the lost standard pound 
had been made in 1829 by Captain Nehus, who measured 
its dimensions with the greatest care. (See Phil. Trans, 
1836, p. 361) Itvery nearly resembles a Troy pound now 
in the Standards Department, which was constructed at 
the same time, and is said to be the original from which 
the lost Standard was made, Its form and size are shown 
in Fig. 4. 
_When the Troy pound was constructed under the 
direction of the Committee of the House of Commons in 
1758, it was made as nearly as possible of the genuine 
weight of the Troy pound according to the ancient 
Standard. For this purpose comparisons were made of 
the Exchequer Troy Standards with each other, and with 
other Troy standards belonging tothe Mint and the prin- 
cipal scale-makers. At the period when the Troy pound 
of 1758 was constructed, there existed no distinct Stan- 
dard Troy Pound at the Exchequer. The Exchequer 
Troy Standards of Queen Elizabeth, which were the legal 
standards in 1758, consisted of a binary series of Troy 
Fic. 7.—Platinum Troy Pound, 
T, of the Standards Department. 
Fig 6—Platinum Troy Pound, 
RS, of the Royal Society. 
The form and size of the two platinum Standard Troy Pounds, RS and T, 
are as follows :—RS being a truncated pyramid surmounted by a knob, T 
cylindrical with a groove. The length of the side of the base of RS is o 95 in., 
the total height 2 66 inches; the diameter of the base of T is 1125 inch, the 
height 1'07 inch. 
ounces from 258 0z. to 40z.,in the form of cup weights, 
fitting into each other. To obtain a Troy pound it was 
necessary to take the two Exchequer Standard weights 
of 8 and 40z., represented in Fig. 5. 
The two other Troy pounds constructed in 1758 were 
found by the Commission to be in existence, as well as 
two similar Troy pounds made at the same time and 
bearing similar marks, though all differed slightly in their 
dimensions, as well as in volume and weight. They were 
all in good preservation and were carefully examined by 
Prof. Miller, but there was no satisfactory evidence of 
their having been accurately compared with the lost 
standard’ so as to identify its weight, and thus to render 
them available for determining the proper weight of the 
new standard. One of the two last-mentioned pound 
weights (denoted as O by Prof. Miller) is shown in Fig. 4. 
This weight was purchased by the Commission, and is 
now deposited in the Standards’ Department. It differs 
very slightly in its dimension from the lost standard, as 
shown above, and its,weight in air was computed by Prof. 
Miller to be 5759°85625 grains of the lost standard. 
For ascertaining the exact weight of the lost standard 
