We are indebted to the Arabs for preserving and extending the knowledge of earlier civilisations they took over. Their weights and measures also, realising that these facilitated trade by having utility and purpose. Coins of precious metals also served as weight for purchases, using the same names. Circulating within the Arabic domain was a silver Dirhem of 45 full grown barley grains, which was a quarter of a Persian Khorine or a third of a Greek Attic Stater. Ten Dirhems made a Wukryeh of 450 grains which we call an ounce from the Latin "uncia" or twelfth, which name is used genetically for such a class of weight or volume.
This unit of weight, and value, was widely used in the Mediterranean area, and entered Europe mainly through land routes to become key measures of weight and money. In the northern German City States there was the Mark of Cologne in value eight ounces of silver, 3600 grains, matching a pound weight of sixteen ounces, 7200 grains. For the southern states, being more influenced by the Greek Attic Mina (50 staters) of 6750 grains, had a pound of fifteen x 450 grain ounces which is the same.
In England, King Offa accepted the "silver" ounce but a shortage of this metal obliged smaller coins. The Dirhem was halved to 222 grains for the penny, twenty of which made the ounce as before, and twelve ounces the moneyer's pound. So it was termed until the conquest, when William allowed the natives to keep their measures but had the standards moved from Winchester to the tower of London so that he could put his finger on them. Weights and measures were always held in temples, along with other sacred objects. This 5400 grain pound was then called the Tower pound, and continued to be used only for minting coins. Hopefully at twenty to the pound. inflation permitting!
The Arabs also had a gold Dirhem of 48 grains, which was half the Egyptian gold Bequa. It was used exclusively for bullion and external trade mostly sea-borne, and reached Europe from the Mediterranean via the French town of Troyes - an important trading centre from which the Troy weight system is thought to have been named (the best of several suggestions). Again, the gold Dirhem was halved and this weight of 24 grains became known as a Pennyweight or dwt, but not, be it noted, not the weight of a silver penny. This similarity of names was to cause trouble later. Twenty pennyweights made the "gold" ounce and twelve of these the Troy Pound of 5760 grains. This pound was generally reserved for goods of high intrinsic value and importance from gold to "brede" and has had a long eventful history. It replaced the Tower pound for mint purposes in 1527 under Henry VIII.
Not surprisingly, France remained aloof from all this, but there was a period when French and English money became aligned. Under Charlemagne, they also had their measures through the Arabs but, more directly, from Persia. The Pied du Roi was half a Persian Cubit 25·56 inches. The livre of 7653 grains was a bit heavier than the Persian Daric of 7554 grains whose direct ancestry was the Sumerian Mina of 60 Shekels. "An assize of Bread and Ale" was issued by Henry II which. amongst other matters, regulated the quality and price of such vital commodities to ensure that the peasantry did not add complaints over these to their other grievances. It was accepted by Henry III and Edward I, and augmented with a "Tractus de Ponderibus et Mensuris", by whom is not certain, but being referred to early in the fourteenth century, to be much transcribed and quoted since. This Tractus was intended to specify which of the various pound weights and many other specialised measures were to be used for what material and how.
Some were called "Libra Mercatoris" - Merchant's Pounds - because they were intended for exchanges of goods internally. and to provide a numerical fit to arrangements of weights and currency on the continent particularly the North and South German City States. As explained, the first had a commercial weight of sixteen x 450 grain ounces = 7200 grains, matched by two Marks of Cologne each with eight ounces of silver coinage = 2 x 3600 grains, However the Tractus . . seems to be describing two differing pounds one of twelve ounces, the Troy pound. and another of fifteen, but "the ounce in either case is in weight twenty pence".
Professor Connor (ref. 3) agrees this is a vague statement which does not distinguish between the pennyweight of 24 grains and the weight of a silver penny, 22 1/2 grains. The tractus clearly states that the twelve ounce pound was to be used for high-value goods. Further he reminds us the moneyer's or Tower pound with twelve 450 grain ounces was never used commercially. Since all ounces were to be the same, a fifteen ounce Merchant's pound on this assumption 15 x 480 = 7200 grains as required above.
F. G. Skinner (Ref 2) takes a literal interpretation of "the ounce consisteth of twenty pence", i.e., 20 x 22 1/2 = 450 grains. So, fifteen of these would be 6750 grains which was the weight used by southern German states. For trade with the northern States there was a simple relationship whereby sixteen 450 grain ounces equalled fifteen 480 grain ounces = 7200 grains.
Perhaps a vagueness of the Tractus could have been rather more than the uncertainty of the compilers, but a ploy to let the two weight systems have cavalier use by those who did understand them? There is an analogy with a revision of the foot and a definition of its inch as three barley corns under Edward I without specifying from which part of the ear they were to be taken. The new foot was in fact a craftsmanÕs measure that was already in use for building before being legalised, and could be formed at any time by twelve thumb widths; this inch should have been stated "that average barley cornes". It was intended to supplant the Saxon measures. which were strongly entrenched for land measurement. This foot was based on an inch of three full grown barley cornes "taken from the middest of the ear", making a foot of 13·2 present inches. Hence the 16 1/2 feet (new) to the real Rod, Pole or Perch!
Changes of measuring and monetary system are always taken full advantage of by nimble witted merchants, There was an inflationary step created by the roundings up (never down) due to the change from dozenal/binary to decimalised coinage and the loss of definite named steps allowed it free rein. At present in the new Millennium (appropriately) a restriction of all retail trade to an inflexible scale has resulted in a rounding down from pounds and ounces to whole numbers of cm and three-figure grammes, but no corresponding reduction in price.
It is difficult to quantify, but an estimate is that a "Product Shrinkage" (in the jargon used) of five percent represents a hidden price rise for the consumer of one percent. Examples show that shrinkage is well above this, so a metrification rip off of some £3,000 million annually is likely. Again, without named steps such as ounces, inches or simple fractions there are no ready indications as to where you are in a string of numbers. It needs a sharp eye and a good memory to note any change in the number of grammes on a packet of food!
The Merchant's pound of fifteen Troy ounces became well established, to become known as the London pound. However, the lighter fifteen Tower ounce pound was also used internally, with the 22 1/2 grain coins being treated as weights. An opportunity to use a weight some 6% less than the pennyweight (dwt) of the actual weight scale, which an illiterate public could assume it represented, would be irresistible. As Connor put it gently "The fact of it being lighter than the pennyweight would do little to discourage its use by merchants".
Some of the confusion and opportunities for fraud, were due to the integral relationship via the 450 grain ounce between money and weights. However, an ongoing debasement of coinage "to help the Exchequer" would have made the connection with weight uncertain. By Henry VIII, the silver penny had become reduced to twelve grains! Besides this two other factors were operating to render weights and coinage Independent of one another.
The Hanseatic League of North German Cities were, initially, the major purchaser of English wool, recognised as the best available They were granted facilities to set up a trading post in London but, despite this, they refused to allow reciprocal arrangements to English merchants within their area up to Elizabeth I. By then, other trading routes had been established and their organisation was weakened by internal dissension.
The other cause was that sea-going vessels were becoming larger so direct voyages to and from the Mediterranean area could be made with greater capacity and safety. This improved exchange favoured the Troy weight system with its 480 grain ounce, and the German Cities, forming a 450 grain area were bypassed. The Troy system Long established amongst gold and silver smiths, became more used commercially here. Under Henry VII there was a sixteen troy-ounce MerchantÕs pound of 7680 grains, and a range of troy-ounce capacities for wheat.
By the mid fourteenth century most of our wool was being exported for use by Florentine weavers and dyers. To encourage this trade Edward Ill adopted a new aver de-pois-system of weights based on the Florentine ounce of 437 grains which was virtually the Roman ounce of 436 grains This sixteen ounce pound of 6992 grains developed alongside the fifteen troy-ounce merchant's pound, and was regarded as interchangeable with it.
By having the better divisibility of sixteen, the aver-de-pois pound would be more suitable for small scale transactions. It also shared in the four pound cloffe additions which took the hundredweight up to 112 pounds. Edward III put a stop to this with a series of weights that were this figure's binary divisions, from a half of 56 lb to a sixteenth - the clove of 7lb, intended to be used for the wool clip. Export of this product accounted for nearly three quarters of the country's revenue, Hence the Chancellor's Wool Sack as a reminder of the fact.
So, despite the injunction in Magna Carta: "Let there be one measure and one weight throughout England", there was a proliferation of the latter for various reasons and purposes, with differing interests vested in them all. The twelve x 450 grain-ounce Mint pound, together with its fifteen ounce Merchant's pound, was abolished by Henry VIII in favour of the twelve x 480 grain-ounce Troy pound for mint purposes. There was still the Merchant's pound of fifteen troy ounces, with its equivalent of sixteen tower ounces, 7200 grains, required for the German trade, and a Troy Merchant's pound of sixteen troy ounces, 7680 grains, for no clear reason, Then there was the modest Plantagenet aver-de-pois pound the result of many considerations in the wool trade, waiting in the wings for its place in history.
It is opportune now to invoke this last pound as a means of resolving the disagreement over the Merchant's pounds mentioned at the start. There was an instruction in the Tractus: "and VIII pounds do make a gallon of wine," which seems to have been a rule for all major pounds, particularly those used for external trade. Certainly, a simple relationship between weight and quantity was helpful for import duties, also as a unit of drink.
Up to the eighteenth century, wine had been sold, and duty levied. by a gallon of 231 cubic inches without any knowledge as to how or why this quantity had been determined. It certainly had no legal status, so was successfully challenged by an importer who declared his cargo by a larger ale gallon which was lawful.
An enquiry discovered a measure in the Guildhall of 224 cubic inches which had been there "Since time out of mind". Since this container held eight of the then official aver de pois pounds, some claimed it to be the true wine gallon for the time, but recognised the difficulty of imposing an even smaller gallon on an unwilling public The 231 cubic inch measure was eventually legalised, thus breaking the link between weight and volume until a revision of 1824. It was this "Queen Anne" wine gallon, with its binary divisions and multiples, that was taken to the American Colonies to become the official measures for all liquids of the United States.
However, the interest here is to check a reasonable assumption that a gallon of 231 cubic inches was one based on the Merchant's pound of fifteen Troy ounces = 7200 grains. The 224 measure undoubtedly held eight aver-de-pois pounds of wine, and we have specimens to prove that these were, in early days, 6992 grains. So, scaling up 224 by the ratio 722 / 6992 we get 231, which confirms the opinion of Professor Connor.
Such was the situation described, before this digression, that was inherited by Elizabeth I, with merchants complaining "that the weights being used throughout this realm are uncertain and varying one from another to the great slander of the same Our realm and decency of many, both buyers and sellers". It was decided to cut out the Gordian tangle, and declare that the Aver-de-pois weight system would be the only one that was legal for all purposes. Using Edward III's Wool weights as a start, with particular attention to the half hundredweight, 56 pound one, 58 sets of elegant brass weights in binary sequences were made for distribution to important cities. These were bell shaped from 56 lb to 1 lb and nesting discs from 8 lb to 1 lb, to 1 oz, to 2 drams (1/32) oz).
The Troy weight system was also reviewed by examining specimens held by several authorities. and found that they agreed "very well". Sets of nesting cups were made from 256 oz to 1/8 oz (60 grains), the grain being the same as for aver-de-pois. Although Troy weight has a nominal pound, all measurements are stated in ounces only to be distinct from the other mundane use. Troy weight was still reserved for the Mint and precious materials. These our measures remained the same until the last revision under George IV in 1824, when the only change was to an all-purpose gallon of ten pounds of water - a Tudor ale gallon, and to give them an accolade of "Imperial" which is somewhat dated now. "Customary", "Traditional", or "Natural" are preferred since They have become and used world-wide, with no need of compulsion but for their ability to provide a perspective on, and a link to, our material world and dealings with it.
Rather more than world-wide since their origins in Mediterranean measures which, in principle if not exactly, take us back to Sumeria and Egypt. They were used by Isaac Newton to elucidate the relationships between matter, force and motion, hence the movements of the Earth and other planets round the Sun. Our Foot and Pound took us to the Moon, but there was an unfortunate dispute with an interloper when trying to land on Mars. They have now departed the Solar system on their way to another Sun as integral parts of "Voyager", which they were used to construct and direct. Does the "Greetings!" plaque that the vessel carries provide a means of deciphering its measures?
Technical and Social metrologies have differing requirements and purposes. The first postulates abstract concepts which need not relate to anything but one another, to be operated on by multi- figured calculations, the second should employ units that match our physical abilities and perceptions, also provide a perspective onto the objective world and assist in dealings with it.
They should be dealt with by small numbers, and contain the elementary divisions that distributions may require, or to form the simple proportions instinctively used when making comparisons of size, weight, distance, value. etc. All of the above facilities are embodied in our present measures because they have been evolved down the ages for the understanding and convenience of their users.