\subsection{History of the Imperial units}
\label{sec:histimpunit}

[from \texttt{www.unc.edu/\texttildelow{}rowlett/units};\\
\textcopyright{} Russ \textsc{Rowlett} and the University of North Carolina at Chapell Hill]

\subsubsection{Distance}
  
In all traditional measuring systems, short distance units are based on the dimensions of the human body. The inch
represents the width of a thumb; in fact, in many languages, the word for `inch' is also the word for `thumb'. The foot
($12$~inches) was originally the length of a human foot, although it has evolved to be longer than most people's feet. The
yard (3~feet) seems to have gotten its start in England as the name of a 3-foot measuring stick, but it is also
understood to be the distance from the tip of the nose to the end of the middle finger of the outstretched
hand. Finally, if you stretch your arms out to the sides as far as possible, your total `arm span', from one fingertip
to the other, is a fathom (6~feet).
  
Historically, there are many other `natural units' of the same kind, including the digit (the width of a finger, $0.75$~
inch), the nail (length of the last two joints of the middle finger, 3~digits or $2.25$~inches), the palm (width of the
palm, 3~inches), the hand (4~inches), the shaftment (width of the hand and outstretched thumb, 2~palms or 6~inches), the
span (width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3~palms or 9~inches),
and the cubit (length of the forearm, $18$~inches).
  
In Anglo-Saxon England (before the Norman conquest of \oldstylenums{1066}), short distances seem to have been measured
in several ways. The inch (\textsl{ynce}) was defined to be the length of 3~barleycorns, which is very close to its modern
length. The shaftment was frequently used, but it was roughly $6.5$~inches long. Several foot units were in use, including
a foot equal to 12~inches, a foot equal to 2~shaftments ($13$~inches), and the `natural foot' (\emph{pes naturalis}, an actual
foot length, about $9.8$~inches). The fathom was also used, but it did not have a definite relationship to the other
units.
  
When the Normans arrived, they brought back to England the Roman tradition of a 12-inch foot. Although no single
document on the subject can be found, it appears that during the reign of Henry~I \Detantatant{1100}{1135} the 12-inch
foot became official, and the royal government took steps to make this foot length known. A 12-inch foot was inscribed
on the base of a column of St.\ Paul's Church in London, and measurements in this unit were said to be `{by the foot of
  St.\ Paul's}' (\emph{de pedibus Sancti Pauli}). Henry I also appears to have ordered construction of 3-foot standards,
which were called `yards,' thus establishing that unit for the first time in England. William of Malmsebury
\pron{£hm£Azb£er£i} wrote that the yard was `the measure of his [the king's] own arm,' thus launching the story that the
yard was defined to be the distance from the nose to the fingertip of Henry~I. In fact, both the foot and the yard were
established on the basis of the Saxon \textsl{ynce}, the foot being $36$~barleycorns and the yard $108$.
  
Meanwhile, all land in England was traditionally measured by the \textsl{gyrd} or rod, an old Saxon unit probably equal
to 20~`natural feet'. The Norman kings had no interest in changing the length of the rod, since the accuracy of deeds and
other land records depended on that unit. Accordingly, the length of the rod was fixed at $5.5$~yards ($16.5$~feet).
This was not very convenient, but $5.5$~yards happened to be the length of the rod as measured by the 12-inch foot, so
nothing could be done about it. In the Saxon land-measuring system, $40$~rods make a furlong (\textsl{fuhrlang}), the length of the
traditional furrow (\textsl{fuhr}) as ploughed by ox teams on Saxon farms. These ancient Saxon units, the rod and the furlong, have
come down to us today with essentially no change.
  
Longer distances in England are traditionally measured in miles. The mile is a Roman unit, originally defined to be the
length of 1000 paces of a Roman legion. A `pace' here means two steps, right and left, or about 5~feet, so the mile is a
unit of roughly $5000$~feet. For a long time no one felt any need to be to precise about this, because distances longer
than a furlong did not need to be measured exactly. It just didn't make much difference whether the next town was $21$ or
$22$ miles away. In medieval England, various mile units seem to have been used. Eventually, what made the most sense to
people was that a mile should equal $8$~furlongs, since the furlong was an English unit roughly equivalent to the Roman
stadium and the Romans had set their mile equal to $8$~tadia. This correspondence is not exact: the furlong is
$660$~English feet and the stadium is only $625$~slightly-shorter Roman feet.
  
In \oldstylenums{1592}, Parliament settled this question by setting the length of the mile at $8$~furlongs, which works
out to $1760$~yards or $5280$~feet. This decision completed the English distance system. Since this was just before the
settling of the American colonies, British and American distance units have always been the same.


\subsubsection{Reorganisations}

Out of the welter\,\footnote{\pron{£hwelt£e£Z}: a state of general confusion; (followed by \emph{of}) a disorderly
mixture or contrast.}  of medieval \pron{£bmed£i£h£Ivl} weights and measures emerged several national systems, reformed
and reorganized from time to time; ultimately nearly all these were replaced by metric. In Britain and its American
colonies, however, the ancient system survived.
   
By the time of Magna Carta\,\footnote{Magna Carta \pron{£bm£agn£e£hk£at£e} \emph{also} Magna Charta \pron{£ht£s£At£e}:
the English political charter which King John was forced to sign by his rebellious barons at Runnymede
\pron{£hr£vn£i£bm£Id} ---~a meadow on the south bank of the Thames at Egham \pron{£heg£em} near Windsor, Surrey.  The
barons were led by Archbishop Langton to frame a charter which effectively redefined the limits of royal power.}
(\oldstylenums{1215}), abuses of weights and measures were so common that a clause was inserted in the charter to
correct those on grain and wine. A few years later a royal ordinance \pron{£h£Od£in£ens} entitled `Assize
\pron{£e£hs£pz} of Weights and Measures' defined a broad list of units and standards \pron{£hst£and£ed} so successfully
that it remained in force nearly 600 years. \coupure
   
The sets of standards, which were sent out from London to the provincial towns, were usually of bronze or brass.
Discrepancies\,\footnote{discrepancy: difference; failure to correspond; inconsistency} \pron{d£is£hkrep£ens£i} somehow
crept into the system, and in \oldstylenums{1496}, following a Parliamentary inquiry, new standards were made and sent
out, a procedure repeated in \oldstylenums{1588}, under Elizabeth~I\,\footnote{(\detantatant{1533}{1603}), daughter of
Henri VIII, queen of England and Ireland \detantatant{1558}{1603}.}.
   
In \oldstylenums{1592}, Parliament settled the question of the mile by setting the length of the mile at $8$~furlongs,
which works out to $1760$~yards or $5280$~feet. This decision completed the English distance system. Since this was just
before the settling of the American colonies, British and American distance units have always been the same.

No revision of law was found necessary for 200 years after Elizabeth's time, but several refinements and redefinitions
were added. E. Gunter\,\footnote{Edmund Gunter \pron{£hedm£end £hg£vnt£e} \detantatant{1581}{1626}.}, a 17th-century
mathematician, conceived the idea of taking the acre's breadth ($4$~perches \pron{p£Et£s}, or $22$~yards), calling it a
chain, and dividing it into $100$~links.

The Act of \oldstylenums{1878} redefined the yard: `the straight line or distance between the centres of two gold plugs
or pins in the bronze bar \coupure measured when the bar is at the temperature of sixty-two degrees of Fahrenheit's
thermometer, and when it is supported by bronze rollers placed under it in such a manner as best to avoid flexure of the
bar.'

From \oldstylenums{1893} until \oldstylenums{1959}, the yard was defined as equalling exactly 3600/3937 meter. In
\oldstylenums{1959} a small change was made in the definition of the yard to resolve discrepancies. Since then the yard
is defined as being equal exactly to $0.9144$~meter.  At the same time it was decided that any data expressed in feet
derived from geodetic surveys within the USA would continue to bear the relationship as defined in
\oldstylenums{1893}. This foot is called the US survey foot, while the foot defined in \oldstylenums{1959} is called the
international foot.
   

\subsubsection{Area}
  
In all the English-speaking countries, land is traditionally measured by the acre, a very old Saxon unit which is either
historic or archaic, depending on your point of view. There are references to the acre at least as early as the year
\oldstylenums{732}. The word `acre' also meant `field', and as a unit an acre was originally a field of a size that a
farmer could plough in a single day. In practice, this meant a field that could be ploughed in a morning, since the oxen had
to be rested in the afternoon. 
% The French word for the unit is \emph{journal}, which is derived from \emph{jour},
% meaning `day'; the corresponding unit in German is called the \emph{Morgen} (`morning') or \emph{Tagwerk} (`day's
% work'). 
Most area units were eventually defined to be the area of a square having sides equal to some simple multiple of
a distance unit, like the square yard.  But the acre was never visualised as a square. An acre is the area of a long and
narrow Anglo-Saxon farm field, one furlong ($40$~rods) in length but only $4$~rods wide. This works out, very awkwardly
indeed, to be exactly $43,560$~square feet . If we line up 10 of these $4 \times 40$ standard acres side by side, we get
$10$~acres in a square furlong, and since the mile is $8$~furlongs there are exactly $10 \times 8 \times 8 = 640$~acres in a
square mile.
  
\subsubsection{Weight}
  
The basic traditional unit of weight, the pound, originated as a Roman unit and was used throughout the Roman
Empire. The Roman pound was divided into $12$~ounces, but many European merchants preferred to use a larger pound of 
$16$~ounces, since a 16-ounce pound is conveniently divided into halves, quarters, or eighths. During the Middle Ages there
were many different pound standards in use, some of $12$~ounces and some of 16. The use of these weight units naturally
followed trade routes, since merchants trading along a certain route had to be familiar with the units used at both ends
of the trip.

In traditional English law the various pound weights are related by stating all of them as multiples of the grain, which
was originally the weight of a single barleycorn. Thus barleycorns are at the origin of both weight and distance units
in the English system.
  
The oldest English weight system has been used since the time of the Saxon kings. It is based on the 12-ounce troy
pound, which provided the basis on which coins were minted and gold and silver were weighed. Since Roman coins were
still in circulation in Saxon times, the troy system was designed to model the Roman system directly. The troy pound
weighs $5760$~grains, and the ounces weigh $480$~grains, which is the traditional weight of the silver coin called the
shilling. The shilling was equal to $20$~pence (pennies), and therefore a pennyweight is $480/20 = 24$~grains. The troy
system continued to be used by jewellers and also by druggists until the nineteenth century. Even today gold and silver
prices are quoted by the troy ounce in financial markets everywhere.
  
Since the troy pound was smaller than the commercial pound units used in most of Europe, medieval English merchants
often used a larger pound called the `mercantile' pound (\emph{libra mercatoria}). This unit contained $15$~troy ounces,
so it weighed $7200$~grains. This unit seemed about the right size to merchants, but its division into $15$~parts, rather
than 12 or 16, was very inconvenient. Around \oldstylenums{1300} the mercantile pound was replaced in English commerce
by the 16-ounce avoirdupois pound. This is the pound unit still in common use in the USA and UK. Modelled on a
common Italian pound unit of the late thirteenth century, the avoirdupois pound weighs exactly $7000$~grains. The
avoirdupois ounce, $1/16$~pound, is divided further into $16$~drachms. Unfortunately, the two English ounce units don't
agree: the avoirdupois ounce is $7000/16 = 437.5$~grains while the troy ounce is $5760/12 = 480$~grains. Conversion
between troy and avoirdupois units is so awkward, no one wanted to do it. The troy system quickly became highly
specialised, used only for precious metals and for pharmaceuticals, while the avoirdupois pound was used for everything
else.

Since at least \oldstylenums{1400} a standard weight unit in Britain has been the hundredweight, which is equal to
$112$~avoirdupois pounds rather than $100$. There were very good reasons for the odd size of this `hundred': $112$~pounds
made the hundredweight equivalent for most purposes with competing units of other countries, especially the German
\emph{Zentner} and the French \emph{quintal}.  Furthermore, $112$ is a multiple of $16$, so the British hundredweight can be
divided conveniently into $4$~quarters of $28$~pounds, $8$~stone of $14$~pounds, or $16$~cloves of $7$~pounds each. The ton,
originally a unit of wine measure, was defined to equal $20$~hundredweight or $2240$~pounds.
  
During the nineteenth century, an unfortunate disagreement arose between British and Americans concerning the larger
weight units. Americans, not very impressed with the history of the British units, redefined the hundredweight to equal
exactly $100$~pounds. The definition of the ton as $20$~hundredweight made the disagreement carry over to the size of the
ton: the British `long' ton remained at $2240$~pounds while the American `short' ton became exactly $2000$~pounds. (The
American hundredweight became so popular in commerce that British merchants decided they needed a name for it; they
called it the cental.) Today, most international shipments are reckoned in metric tons, which, coincidentally, are
rather close in weight to the British long ton.
  
\subsubsection{Volume}
  
The names of the traditional volume units are the names of standard containers. Until the eighteenth century, it was
very difficult to measure the capacity of a container accurately in cubic units, so the standard containers were defined
by specifying the weight of a particular substance, such as wheat or beer, which they could carry. Thus the gallon, the
basic English unit of volume, was originally the volume of eight pounds of wheat. This custom led to a multiplicity of
units, as different commodities were carried in containers of slightly different sizes.

Gallons are always divided into $4$~quarts, which are further divided into $2$~pints each. For larger volumes of dry
commodities, there are $2$~gallons in a peck and $4$~pecks in a bushel. Larger volumes of liquids were carried in barrels,
hogsheads, or other containers whose size in gallons tended to vary with the commodity, with wine units being different
from beer and ale units or units for other liquids.
  
The situation was still confused during the American colonial period, so the Americans were actually simplifying things
by selecting just two of the many possible gallons. These two were the gallons that had become most common in British
commerce by around \oldstylenums{1700}. For dry commodities, the Americans were familiar with the `Winchester bushel,' defined by
Parliament in \oldstylenums{1696} to be the volume of a cylindrical container $18.5$~inches in diameter and $8$~inches deep. The
corresponding gallon, $1/8$ of this bushel, is usually called the `corn gallon' in England. This corn gallon holds
$268.8$~cubic inches.
  
For liquids Americans preferred to use the traditional British wine gallon, which Parliament defined to equal exactly
$231$~cubic inches in \oldstylenums{1707}. As a result, the US volume system includes both `dry' and `liquid' units,
with the dry units being about $1/6$ larger than the corresponding liquid units.
  
In \oldstylenums{1824}, the British Parliament abolished all the traditional gallons and established a new system based
on the `Imperial' gallon of $277.42$~cubic inches. The Imperial gallon was designed to hold exactly $10$~pounds of water
under certain specified conditions. Unfortunately, Americans were not inclined to adopt this new, larger gallon, so the
traditional English `system' actually includes three different volume measurement systems: US liquid, US dry, and
British Imperial.

On both sides of the Atlantic, smaller volumes of liquid are traditionally measured in fluid ounces, which are roughly
equal to the volume of one ounce of water. To accomplish this in the different systems, the smaller US pint is divided
into $16$~fluid ounces, and the larger British pint is divided into $20$~fluid ounces.


\subsection{Metrication in the UK}
\label{sec:uksys}

[from \texttt{www.metric.org.uk}; UK Metrication Association]

{\slshape
Parliament first debated the metric system on \oldstylenums{13}th April \oldstylenums{1790}. This was when parliamentarian Sir John
Riggs Miller [Britain] and the Bishop of Autum, Prince Talleyrand [France] put to the British Parliament and French
Assembly respectively, the proposition that the two countries should cooperate to equalise their weights and measures,
by the joint introduction of the metric system.

There was no immediate progress although there were many positive debates in the second half of the \oldstylenums{19}th
Century. For example, \oldstylenums{1}st July \oldstylenums{1863} the Bill for a compulsory change to the metric system
was approved by 110 votes to 75 votes.

The following year, \oldstylenums{9}th March \oldstylenums{1864}, the House of Lords debated a Bill to permit the use of
metric weights and measures in trade. One supporter noted that Englishmen were notorious for liking old terms and old
habits and he hoped that the new nomenclature would not be diverted by attempts at ridicule. Parliament passed the Bill
and this became the Metric Weights and Measures Act \oldstylenums{1864}.  On the \oldstylenums{24}th February
\oldstylenums{1868} a parliamentary proposal to set Imperial cut-off dates was withdrawn on promise of a Royal
Commission of enquiry.  The Enquiry Report was positive, and on the \oldstylenums{26}th July \oldstylenums{1871} Britain
almost became a metric country. The government lost the Bill to make metric compulsory after two years, by only 82 votes
to 77 votes. An argument that might have influenced opponents was a plea that Britain would be `letting down America and
our colonies' who had harmonised their systems with the ones in use in Britain\footnote{At that time the American
  Congress had emulated Britain by allowing contracts in metric.  A particularly strong USA advocate for metric was John
  Quincy Adams.}.

There were further debates, and near misses, in the UK Parliament in \oldstylenums{1872} and \oldstylenums{1896}, before
a comprehensive debate [ \oldstylenums{21}st June - \oldstylenums{6}th August \oldstylenums{1897}] concluded by
legalising the use of metric for all purposes. There were no contrary votes.

Metrication continued to be debated for the next 10 years. In \oldstylenums{1904} The House of Lords unanimously voted
to make metric compulsory after two years. It was claimed that the Austrian and German nations had successfully made
metric compulsory with a changeover time of only `one week'! The Government said they would not obstruct the proposal,
but the Bill was never adopted in the Commons. Two similar debates in \oldstylenums{1907} failed.  Conflicts in Europe
put further political consideration of metrication out of mind until the publication of a Government White Paper on
Weights and Measures \oldstylenums{10}th May \oldstylenums{1951}.  The \oldstylenums{1951} White Paper was in fact the
28th Report put to Parliament during the preceeding 100 years. This latest report was in response to the the Hodgson
Committee Report published in \oldstylenums{1949}.  Eventually we had the Weights and Measures Act \oldstylenums{1963};
a long series of Parliamentary questions to Ministers and the Federation of British Industries [now the CBI\/\footnote{
  \textsc{Confederation of British Industry}}] lobby in favour of metrication in \oldstylenums{1965}. These initiatives
culminated with the creation of the Metrication Board in \oldstylenums{1969} by Anthony Wedgewood Benn, Minister of
Technology. The target date for completion was end \oldstylenums{1975}. The transition to metrication and the role of
the Board were given positive support and encouragement by Geoffrey Howe the responsible Minister of the new Government
in \oldstylenums{1972}. Indeed at that time, and until circa \oldstylenums{1977}-\oldstylenums{1978}, there was good,
sensible and steady progress.

Prepackaged food changed but the really difficult issue to emerge affected retailers of `loose weight' products. The
retail problem was that metric prices would always appear to be more expensive than their nearest Imperial equivalent.

The product which brought all voluntary retail initiatives to a full stop was the experience of the floor covering and
carpet retailers. Their \oldstylenums{1975} change to sales by the sq. metre started well, but in \oldstylenums{1977}
one of the major High Street retailers found enormous commercial advantage in reverting to sales by the square yard.
Consumers could not be persuaded to believe that goods costing, for example, \pounds10 per square yard or \pounds12 per
square metre were virtually priced the same.  Consumers bought, in very significant volume, the apparently cheaper
priced imperial version.  Metrication of carpet sales entered into full scale reverse and the Chambers of Trade and
retail associations pressed for firm Government leadership, \idest\ compulsory cut-off. Then the political nerve began
to fail.

The necessary Order, drafted by the Board of Trade in \oldstylenums{1978}, was agreed by a huge range of retail trade, industry,
engineering, consumer, trade union, elderly person, sporting and educational organisations and \dots the overwhelming
number of parliamentarians. A small number of critics, in each political party, did voice opposition to the element of
compulsion but this seemed to come from a relatively small minority within the Eurosceptic movement.

However, the initiative was in the hands of Secretary of State for Trade, Roy Hattersley and a General Election was
expected in \oldstylenums{1979}. Labour lost the election and Margaret Thatcher became Prime Minister.

One Conservative backbencher, Sally Oppenheim had been almost the lone but persistent critic of the metric programme.
Ironically she was appointed junior Minister of Consumer Affairs at the DTI and then metrication was added to her
portfolio. In letters to MP's and associations she made it clear [a] she was not opposed the metrication in principle,
[b] metrication was not the result of Britain's accession to the EEC but [c] she did object to measures which would
compel people to adopt metric against their will. Proponents of metrication, trade and consumer organisations,
officials and the Metrication Board explained and argued that a voluntary change at retail level was absolutely
impossible \dots it could never happen. It was a recipe for confusion, waste and duplication.  Government had to lead over
the last hurdle. It did, it led backwards. In \oldstylenums{1980} the Metrication Board was abolished.

In truth the Metrication Board had little else to do. Every possible programme had been agreed, consumer information
campaigns composed and there was nothing to do until or unless a date was fixed for the completion of the transition. We
little knew then the die was set for a further 20 years of waste, confusion and argument. Successive DTI Ministers did
nothing to inform consumers or public opinion. They did nothing to refute the new `big lie' namely, that Britain was
being forced to change because of the European Commission. In fact, during the past 20 years most Commission Officials,
European Politicians and businesses in Continental Europe `couldn't have given a damn' whether Britain changed to the
metric system or not. They seemed to quite like the idea of Britain shooting itself in its economic foot, by imposing
upon itself the extra costs and waste of maintaining a dual system. For twenty years not one single British Minister has
attempted to explain the advantages of metrication. Most tried to pretend or imply they were protecting our British
culture from the European bully.  
}

\hspace*{\stretch{1}}Jim \textsc{Humble} \textsc{obe}\footnote{Officer of the Order of the British Empire}, Director of
the Metrication Board \Detantatant{1978}{1980}

However, the government had already signed up to the European Directive \texttt{71/354} to harmonise our units of
measurement by requiring SI. This resulted in several further Directives which set out transition dates for
phasing out most non-metric units. UK legislation was then amended to enact these changes. \oldstylenums{1995} saw the
removal of the pound (weight) and pint for labelling pre-packed goods.

Perhaps the most significant change took place at the end of \oldstylenums{1999}; as of January \oldstylenums{1}st
\oldstylenums{2000} it has no longer been legal to sell loose products (vegetables, fruit, cheese, meat, nails, ground
coffee, etc.) by reference to the ounce, pound, pint or gallon (with the exception of draught beer). Pints of beer
are usually spoken about in the same breath as the pint of milk in returnable containers, but there is one significant
difference, in that it is now perfectly legal to sell milk in metric sizes.

Although a great deal has happened in the UK over the past 30 years, there is still a lot of ignorance of the current
situation. Some people think it's already gone too far, others don't seem to be aware of what has actually happened. One
school of thought is that SI (metric) is OK for some fields, \parex\ scientific and engineering endeavours, but it is not
suitable for others. For example, as Britain is an island, and the design of our road signs doesn't affect how we do
trade with the rest of the world, it is not necessary for road signs to convert to metric. However, SI is a coherent
system of units, and including non-metric units defeats the point. We buy our petrol by the litre, so it's easier to
calculate consumption using kilometres; coaches and trucks have odometers recording kilometres, and speedometers showing
km/h (not kph, please!) in prominent form. The argument also ignores the fact that the UK shares a border with Ireland,
which has largely converted its distance signs, and is planning to change its speed limit signs in \oldstylenums{2001}.

%%% Local Variables: 
%%% mode: latex
%%% TeX-master: "units"
%%% End: 

%%% correction 2002-08-12


