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NATURE 
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weight in air was made intermediate between that of a 
pound of platinum and a pound of brass, being o'401 gr. 
lighter than P,S,, and 0'232 gr. heavier than W. in standard 
air, 
As the determination of the density of bodies has thus 
been referred to the maximum density of an equal 
yolume of water, it was evidently necessary to determine 
the absolute weight of a normal measure of water at its 
maximum density, in order to determine the true weight 
in air of a given yolume of any substance, the density of 
which has been ascertained. It is claimed to be one of the 
important advantages of the decimal metric system, that 
this relation may be at once ascertained from the circum- 
stance of the unit of weight, the kilogram, having been 
determined by its being the weight of a cubic decimetre 
of pure water at its maximum density. Thus the volume 
of any body expressed in cubic decimetres, or the 
measure of capacity of liquids expressed in litres, the litre 
being the measure of a vessel holding a cubic decimetre 
of water at its maximum density, when multiplied by its 
density, at once gives the weight in kilograms ; or, if ex- 
pressed in centimetres, the weight will be given in 
grammes, There is not the same simple relation between 
the unit of weight and of volume or capacity in the im- 
perial system, the same definite ratio not being established 
between the unit of cubic capacity derived from the unit 
of length and the unit of weight, which is found in the 
metric system. This relation has therefore been deter- 
mined experimentally in England from ascertaining the 
weight of a cubic inch of pure water, and the determina- 
tion by Sir George Shuckburgh in 1798 was accepted by 
scientific men in this country, and has been legalised by 
Statute, by which a cubic inch of water at the temperature 
of 62° F. weighed in air of the same temperature, with the 
barometer at 30 inches, weighs, 252°458 grains of brass. 
From this ratio, the cubic capacity of the standard gallon, 
containing 10 lbs. weight of water, is declared to be 
277'274 inches, and a cubic foot of water is declared to 
weigh 62°321 lbs. avoirdupois. But this ratio does not 
agree with that adopted in France, nor indeed with other 
and different ratios adopted in Sweden, Austria, and 
Russia respectively, as determined from separate experi- 
ments made in each of these countries. As respects the 
metric system, even assuming the weight of a cubic deci- 
metre of water to be exactly a kilogram according to its 
theoretical definition, as to which doubts exist, it is only 
equal to this weight when the water is at the temperature 
of about 39° F. or 4° C, and when weighed in a vacuum, 
When of the ordinary temperature (say 62° F.) and 
weighed against brass weights in ordinary air (say, the 
barometer at 30 inches), it would weigh not a kilogram 
or 1,000 grammes, but about 999'012 grammes, the diffe- 
rence being the loss of weight by the weight of air dis- 
placed by a cubic decimetre of water. According to the 
English ratio, the cubic decimetre of water would weigh in 
air 999°515 grammes. Andif the French ratio were applied 
to our imperial measures a cubic inch of water would 
weigh 252'336 grains, the capacity of the gallon would be 
277'141 inches, and the cubic foot of water would weigh 
62°291 lbs, But in point of fact, a new and authoritative 
international determination of the weight of a standard 
unit of water is very much needed, in order that its true 
weight may be satisfactorily ascertained and uniformly 
adopted in all countries. 
I1.— Standards of Imperial Weight and Measure} 
The English standard units of weight and length, the 
pound and the yard, have come down to us from the 
Saxons, The Mint pound of the Tower of London, which 
continued to be the legal unit of weight up to the time of 
Henry VIII., was the old pound of the Saxon Moneyers 
in use before the Conquest ; whilst the earliest recorded 
standard of length in this country was the yard or gird 
of the Saxon kings, kept at Winchester. re Edgar is 
recorded to have decreed, with the consent of his Wites, 
[Aug. 14, 1873 
the standard.” No change was made by the Normans in 
the system of weights and measures established in Eng- 
land, and bya statute of William the Conqueror it was 
ordained that the measures and weights should be true 
and stamped in all parts of the country, as had before 
been established by law. vl 
The old Tower pound was the ancient pound sterling of 
silver, containing 20s., each of 12d. or pennyweights, It 
was also divided into 12 ounces, and was thus used as the 
apothecaries’ weight. The Tower pound was less than 
the Troy pound by 15 dwt., and contained 5,400 Troy 
grains. It was discontinued by law in the 24th year of 
Henry VIII., the Troy pound, which appears to have been 
first introduced into this country from France at the 
close of the reign of Edward III., being substituted for it. 
The mark of 8 ounces was % of the Tower pound, and was 
identical in weight with the ancient unit of money weight 
in Germany, known as the Cologne Mark. The Tower 
pound was also nearly identical in weight with the ancient 
Alexandrian pound, the 125th part of the Great Talent of 
the Ptolemies, from which it was probably derived. The 
Troy pound is said to have owed its origin to the Arab 
roth or pound of the Caliph Almamoun, of very nearly 
equivalent weight, sent as a present to Charlemagne. 
The earliest English weight for heavy goods was the 
merchants’ pound, declared in a Statute of Henry III. to 
be equal to 25s., or one-fourth more than the Tower 
pound. It must thus have been equal to 6,750 Troy grs. 
Another ancient authority declared the merchants’ pound 
to have contained 15 ounces, and if these were Troy ounces 
this merchants’ pound must have contained 7,200 Troy gers. 
The merchants’ pound seems to have merged insensibly 
into the avoirdupois pound of 7,000 Troy grs,, not later 
than the time of Edward III. It is certain that commer- 
cial pounds nearly equivalent to each of the three weights 
here specified were largely used in different parts of 
France and Germany. Our existing avoirdupois pound 
can be distinctly traced to the time of Edward III. ; and 
there is good ground for believing that no substantial 
difference has occurred in its weight, or that of the Troy 
pound, since either of them was first established as a 
standard in this country, 
There can also be little doubt that the length of the 
English yard has continued unchanged from the earliest 
times. The standard yard of Henry VII., which is still 
preserved in the Standards Department, is hardly ;4pth of 
an inch shorter than the imperial standard yard, and 
being an end-standard, it must have lost a little of its. 
original length. The standard weights and measures 
made in the eleventh year of Henry VII., which are the 
earliest English standards now known to exist, are all de- 
clared to have been taken from the older standards of the 
Exchequer, as were also the later standards of Queen 
Elizabeth, which continued to be the legal standards of the 
country up to the year 1824. Although there is no direct 
evidence of the origin of the Saxon yard, it is highly pro- 
bable, from its {length agreeing very nearly with that of 
double the natural cubit (of about 18 English inches) and — 
from its third part, the foot, being very nearly identical 
with the ancient Egyptian and Greek foot, that these two 
English unit measures of length owe their origin to the 
cubit of a man, the earliest known standard measure of 
length recorded in ancient history. 
The Troy pound was the standard unit of weight in this 
country from the time of Henry VIII. up to the year 
1855, when the imperial pound avoirdupois was made the 
legal standard of weight. The actual primary units of © 
imperial weight and measure are now the standard pound 
avoirdupois and the standard yard in the custody of the 
Warden of the Standards, and deposited at the Standards 
Department, Old Palace Yard, Westminster. They 
were constructed under the superintendence of the Stan- — 
dards Commission, appointed in 1843 for the restoration — 
of the standards of weight and measure which had been 
