ON THE SCIENCE OF WEIGHING AND 
MEASURING, AND THE STANDARDS OF 
WEIGHT AND MEASURE * 
‘See 
the time when the metric system was originated, the 
& T 
i A French standards of weights were the series known as 
the Pile de Charlemagne, the unit being the Livre poids 
de marc of 16 onces, and double the Jozds de marc. The 
metric equivalent of the fod de marc was subsequently 
determined to be 244°753 grammes, The omce was divided 
into 8 gros (or drachms), and the gros into 72 grazms. 
The old French Livre of 9216 French grains was there- 
fore equal to 489506 grammes, and 7554 English troy 
grains. The French grain was thus equal to 0818 
English troy grain. In determining the new unit of 
metric weight, it was necessary to ascertain the actual 
value in terms of the existing system of the ure and its 
subdivisions, of the provisional weights used ; and from 
accurately comparing them with the old standards, it was 
_ deduced from the ascertained weight of the measured 
cylinder, that the weight of a cubic decimetre of distilled 
water at its maximum density, or at 4° C., which was 
0°9992072 of the provisional kilogram, was equal to 
18827°15 grains of the foids de marc. This, accordingly, 
was definitively adopted as the true weight of the kilo- 
gram, the new unit of metric weight. 
The determination by the French Commission of the 
_ weight of a cubic decimetre of water at its maximum 
density differs somewhat from later authoritative deter- 
minations made in England and other countries, as may 
be seen from the following tabular statement :— 
‘Weight of- cubic 
Date Country. Observer. pacar 
pt4- C 
Grammes 
1795 | France . Lefevre-Gineau. . . 1000°000 
ag England Shuckburgh and Kater 1000480 
1825 | } Sweden. Po Sa 1000°296 
1830 | Austria . Stampfer . 999°653 
1841 | Russia . Kupffer 999°989 
Mean. 1000°084 
- But the latest and most carefully executed determination 
by Kupffer agrees so closely with the French determi- 
nation, that the actual weight of the primary kilogram 
may be taken as nearly identical with its theoretical defi- 
nition, and sufficiently accurate for all practical purposes. 
From the provisional brass kilogram, with its error thus 
ascertained by the French Commission, two new standard 
kilograms were constructed by Fortin, one of platinum, 
the other of brass, and each was determined, after numerous 
comparisons and the requisite corrections, to be of the 
true weight when weighed in a vacuum. The platinum 
weight was constituted the primary metric standard 
kilogram, and is known as the A7zlogramme des Archives. 
Its form is that of acylinder of about 39°4 millimetres in 
diameter, and 39'7 metres high, having its edges slightly 
rounded, being similar to that of the English platinum 
kilogram shown of the actual size in Fig. 12. The density 
of the Kzlogramme des Archives has never been precisely 
determined, as it has been deemed hazardous to weigh it in 
water from a fear of its not being entirely free from the 
arsenic used in preparing the platinum, and of dissolving 
this arsenic, and thus diminishing the weight of the kilo- 
gram. Prof. Miller has assumed the volume of the 
-Kilogramme des Archives when in its normal temperature 
of o° C to be equal to the volume of 48°665 grammes of 
* Continued from p. 389. 
NATURE 
489 
water at its maximum density, as determined by its cubic 
measurement, and consequently its density to be 20°5487, 
Other computations, however, differ slightly from this 
determination. 
The brass kilogram was intended as the commercial 
standard, for regulating all ordinary metric weights in 
air, and was deposited at the Ministére de l'Intérieure 
Paris. One uniform shape is adopted in France for all 
brass kilograms. They are made in the form of a cylinder 
surmounted witha knob. The height of the cylinder 
is equal to its diameter, and the height and diameter of 
the knobs are equal to one half those of the cylinder. 
Like the platinum A7zlogramme des Archtves, the brass 
standard kilogram was never weighed in water, and its 
volume has been computed from its cubic measurement 
to be equal to that of 124'590 grammes of water at its 
maximum density, thus making its density 8206. In our 
standard air, ¢ = 62° F. 6 = 30in,, the platinum standard 
kilogram will thus displace 59°25 milligrams of air, and 
the brass kilogram 151'75 mgr. ; the apparent weight in 
air of the brass kilogram is consequently about 92 mer. 
less than that of the platinum standard. This brass 
kilogram was assumed by the French Commission to be 
88°5 mgr. lighter than the platinum standard, when 
weighed in ordinary air. 
The primary platinum metre and kilogram were pre- 
sented by the Commission on June 22, 1799 to the Corps 
Legislatif at Paris, and were legally constituted as the 
standards of length and weight of the new metric system 
throughout France by the law of Dec. 9, 1799. They 
were deposited at the Palais des Archives. 
A platinum copy of each of the primary metric standards 
of the metre and kilogram was constructed at the same 
time, and deposited at the Paris Observatory. These 
standards, known as the d/étre de l’Observatoire, and 
the Kzlogramme de V-Observatoire, were considered as next 
in authority to the primary standards. 
The unit of capacity of the metric system, the Z¢ve, repre- 
sents theoretically the measure of volume of a cubic deci- 
metre, or the cubic contents of a metallic vessel of this 
capacity when at the temperature of melting ice. But 
practically, there is no material primary standard litre, and 
the legal measure of the litre is determined from the kilo- 
gram ; that is to say, the litre actually is a measure con- 
taining a kilogram weight of distilled water at its maximum 
density. Such a measure can only be verified by com- 
putation, as the vessel itself must be taken at a different 
temperature from the water contained in it, the vessel at 
o° C., the water at 4° C. Authoritative tables are there- 
fore prepared for ascertaining the allowance to be made 
in every case for differences of temperature from the 
normal temperature, as well as for the difference of 
weight of air displaced by the metallic weight and the 
larger volume of water. 
For metric measures of surface, the ave, equal to 100 
square metres in the unit ; and for solid measures, more 
particularly for measuring wood, the s¢eve, or cubic 
metre, is the unit. 
The number and denominations of the metric weights 
and measures actually used in France and other countries, 
for which specific standards are provided, are as follows : 
they include the double and the half of each decimal 
unit, with a duplicate unit to make up the number 9 
units :— 
Double metre 
{ Metre, divided into tenths or deci- 
metres, &c, 
Half-metre, > 3 
6 Metric Measures } Double decimetre, divided into cen- 
of Length . ; timetres and millimetres 
| Decimetre, + - 
(For land) Chain of double deka- 
metre, or 20 metres, divided into 
metres, and links of 2 decimetres 
