On 2009/01/23, at 11:36 AM, Brian J White wrote:
Not sure I truly understand what you're meaning with this statement
Pat....expand?
At 14:01 2009-01-22, Pat Naughtin wrote:
8 Last, but not least, almost all length measuring is done using
the metric inch (of exactly 25.4 millimetres), the metric foot (of
exactly 304.8 millimetres) and the metric mile (of exactly 1609.344
metres). Meanwhile, almost all mass measurements are carried out
using the metric pound (of exactly 453.5924 grams).
Dear Brian,
The length of the metre has never changed; in fact whenever scientific
advances make it possible to better define the metre, its length
remains the same but the precision with which it is measured is
improved. In contrast, the length of the inch has changed from time to
time and from place to place. Basically whenever the inch, or the
foot, or the yard has been redefined the lengths of all of these have
varied.
The history of the inch
In old traditional measuring systems, some lengths were based on the
human body. For example, the width of a male thumb was used as a
common small measure in many languages. This obviously varies from
person to person so a thumb could never be relied on for accurate or
precise measurement.
In England they chose to use the word ynce instead of the word thumb
for this small distance and the convenient way to do approximate
measuring with it. The word ynce came from a Latin word for a twelfth
and the Roman invaders and occupiers of England commonly used twelfths
to divide their feet into 12 parts and their pounds into 12 ounces.
The words, inch and ounce, both derive from the Latin word for a
twelfth.
1066
In England (before the Norman conquest of 1066), short distances seem
to have been measured in several ways. The inch (ynce) was defined to
be the length of 3 barleycorns. Later the spelling of ynce changed to
inch.
1100
It appears that during the reign of Henry I (1069/1135) the foot again
became the official standard for measuring length rather than using
the barleycorn definition. The inch was defined as 1/12 of a foot.
1215
After the Magna Carta was signed, the English Parliament ordered the
construction of the first set of physical standards for length mass
and volume. These have been lost but it is thought that the inch was
the foundation of the other measures. The inch was defined as the
length of three barleycorns and both the foot and the yard were
established on the basis of the ynce, the foot being 36 barleycorns
and the yard 108 barleycorns.
1280
King Edward I of England ordered a permanent measuring stick made of
iron to serve as a master standard for the entire kingdom. This was
called the 'iron ulna' and a rumour soon spread that it was the length
of the king's arm. He also decreed that a foot measure should be one-
third the length of the iron ulna, and that the inch be one thirty-
sixth of the iron ulna.
1324
King Edward II passed a law that 'three barleycorns, round and dry'
make an inch going back to the old barleycorn definition.
1505
King Henry VII (1485-1509) probably obtained a new standard yard by
basing it on a direct copy of the old standard 'iron ulna' of King
Edward I. By now the word yard had replaced the word ulna.
1588
Queen Elizabeth I issued a new standard yard. This remained the legal
British yard until 1824, when an Act of Parliament superseded it with
a new yard.
1707
At the Act of Union between England and Scotland, English inches were
superimposed on Scottish inches but both continued to be used
alongside each other. There were also different inches in Ireland and
Wales.
1742
The Royal Society commissioned a new yard to be based on the earlier
standard of Elizabeth I. This was the yard that became the basis for
the new yard in 1824.
1824
The Weights and Measurements Act introduced 'Imperial measures' with
the idea of a brass bar that could be preserved in the office of the
Exchequer and that this bar could be the prototype for copies to be
sent to various cities in England, Ireland, Scotland, and Wales. The
brass bar they chose to be the standard had been made in 1760 at the
instigation of the Royal Society. This brass bar had two gold buttons
with a fine engraved dot near each end. The distance between the two
engraved dots was defined as the new Imperial yard.
This meant that the inch was defined as 1/36 of the new Imperial
standard yard and that the English inch, the Irish inch, the Scottish
inch, and the Welsh inch all had to change to suit this new definition.
1832
As there was no legal length standard in the USA, except for several
more or less authentic copies of the British Imperial yard, the
Congress of the USA decided that they would no longer use the British
Imperial standards as the basis of measurement in the USA. They had
noted that the sizes of various inches had begun to vary from the one
used in the UK and even from state to state in the USA. They ordered
that the different weights and measures used in several customs houses
should be averaged and that these averages should be the basis for
standard legal measurement in the USA. As a result of the averaging
survey, the Treasury Department decided that the legal standard yard
for the USA would be the distance between the lines 27 and 63 of a
bronze bar, 82 inches in length, bought in 1813 in England for the
Federal Survey Department. The inch was defined as 1/36 of this length.
1834 October 16
The UK Houses of Parliament in London burnt down and the standard for
length, the Imperial yard, the standard for mass, the Imperial troy
pound, and the standard for volume, the Imperial gallon, were
destroyed. The 1824 yard had a very short official life of 9 years
and 198 days.
1855
New English standards were made as near as possible to the old
standards that were destroyed by fire in 1834. The one exception being
that the new pound was an avoirdupois pound and not a troy pound.
Copies of the new standard Imperial yard were made based on unofficial
standards that had been compared to the 1824 Imperial Yard before it
was damaged so there was only a slight change to the length of the
Imperial inch. One of these new standard yards, Number 11, was sent to
the USA. This then became the legal standard yard for the USA.
1866
The Congress of the USA passed a Bill that permitted the use of the
metric system of measurement in the USA. In this bill the value for
the metre was given as: 1 metre = 39.37 inches or 1 yard = 0.914 401
829 metre. This made the inch 25.400051 millimetres.
1893 April 5
In the USA, the Secretary of the Treasury, Thomas C. Mendenhall,
announced that the international units, metre and kilogram, would be
regarded as the fundamental standards by the Office of Standard
Weights and Measures (which became the National Bureau of Standards in
1901). This became known as the Mendenhall Order and it defined 1
metre as 39.37 inches exactly keeping the inch at 25.400 051
millimetres.
1959
In response to problems that arise because of a range of slightly
different inches being used, several nations (Australia, Canada, New
Zealand, South Africa, the UK, and the USA) agreed to common standards
for the inch and the pound by defining both of these in terms of
international metric standards (except that the USA still uses one of
their old definitions for the USA Survey foot that makes the survey
inch, at 25.400 051 millimetres, a little larger than the
international inch). The agreed inch was made exactly equal to 25.4
millimetres and 1 pound was made exactly equal to 453.592 37 grams.
The result of this agreement is that since 1959 all of the citizens of
all of these nations, Australia, Canada, New Zealand, South Africa,
the UK, and the USA, now use a metric inch and a metric pound every
time they measure in inches or pounds. Many people don't know that
they are using the metric system when they order a 2" x 4" or use a
piece of paper that's 8 1/2 inches by 11 inches.
Cheers,
Pat Naughtin
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
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