Every human being on our planet is affected by weights and measures in some way. From the moment we are born and throughout our daily lives, weighing and measuring are an important and often vital part of our existence. Our bodies, the food we eat and all the products we use as an integral part of modern living have all been weighed and measured at some stage in their development.

Weights and measures are undoubtedly one of man's greatest and most important inventions, ranking alongside the wheel in the evolution of civilisation. Commerce would not have progressed beyond the barter system without the invention of a system of weights and measures.

There are three elements to the weighing story and each evolved over the 6,000 years of its history; first, we have the use and development of weights; then the different weighing machines and apparatus; and finally the introduction of weights and measures to control commercial transactions.

From Seed To Electronics
At the height of Egyptian civilisation the weights used were fashioned from bronze and often cast in the shape of animals, some in the shape of a cow, which was an ancient standard of value. This customer of making weights in the shape of animals and other decorative designs was practised in Africa, India and the Far East using brass. Many other materials were used throughout the ages, including porcelain and pottery.

However, the first weights were not fashioned by man but by nature. In order to weigh small amounts precisely, small objects that were easily obtained and of a consistent size were needed. So the grains and seeds of plants were chosen for their elegant uniformity. A grain of wheat became the grain of weight. Mustard seeds were used to weigh gold in India. The seeds of the liquorice plant and of the carob tree were also used. The carob gave us carats, still used today to express the value of gold and diamonds, although it is now a metric carat.

The weights of seeds were eventually transformed into stone equivalents for the weighing of general goods, but other materials such as lead were used as well. Haematite or nephrite were reserved for weighing precious materials like gold.

From Pounds ...
The Romans gave us our pound weight which is derived from the Roman word libra. This explains why our pound has such a strange abbreviation (lb) and why the astrological sign Libra has an equal-armed balance as its symbol.

In England there were, at one time, six different pound weights varying from 5,400 to 7,680 grains. Different pounds were used to weigh different commodities such as coins, gold or wool. Henry VIII began the task of standardising the pound and Elizabeth I completed the work by dividing it into sixteen ounces which totaled 7,000 grains. The Roman pound (or Libra) was divided into twelve uncias, from which we derive our ounces and is referred to as the Troy system. The new Elizabethan pound with its sixteen ounces, known as avoirdupois, was used to weigh general goods, while the twelve ounce pound was reserved for weighing precious metals.

Advances in science are dependent upon accuracy. Every experiment requires superfine measurement so that it can be repeated anywhere in the world and its results independently verified.

The problem for eighteenth century scientists was that no common system of measurement existed.

... To Kilogrammes
In 1789 France had her revolution and the ensuing explosion of new thinking led to the development of revolutionary new system of measurement in which all the different physical properties were linked by interrelated units - the metric system. Imagine a hollow cube with sides measuring one tenth of a metre. Fill it with water and the volume of that water becomes one litre whilst its weight becomes one kilogramme. The master kilogramme, made from platinum, resides in Paris, whilst faithful copies, or witnesses, are held in major cities around the world, ensuring that a kilogramme weighs exactly the same from Kilmarnock to Karachi.

The First Weighing Apparatus
The first weighing machine was probably derived from the yoke, whereby it was discovered that two equal masses would balance if they were suspended from a beam that was supported at its centre. Balances were in use in Mesopotamia as early as 4000 years BC. They consisted of straight pieces of wood suspended by a cord passing through the centre. Holes, pierced in the ends of the beam, carried cords suspending the scale pans.

The accuracy of the beam scale, or balance, relies on ensuring that the distance from the fulcrum to each end of the beam is exactly equal. The holes were difficult to locate precisely and the cords moved about in the holes, so affecting accuracy.

Egyptian Refinement
More than two thousand years later, the ancient Egyptians refined and improved the balance by simply bringing the cords out of the ends of the beam. A little scraping ensured that the arms always remained equal and the cores always lay against the ends of the beam no matter how heavy the load.

The Greeks and Romans used balances struck from metal, usually bronze, with ring-and-hole pivots - a system that made them less accurate than the better Egyptian balances. because of the tendency of the ring to wander in the hole. Probably the earliest picture of a weighing machine was the Egyptian representation of weighing the souls of the dead against a standard of divine truth. This was discovered in what is believed to be the earliest of religious books, the Egyptian book of the dead. The Egyptian balance survived through the centuries to modern times, and wasn't bettered for more than three thousand years.

The Instrument Of Deceit
The first recorded form of a weighing device other than the balance, occurred in 400 BC and was known as the Bismar. It consisted of a rod of wood with a large weight fixed at one end. At the other end was a hook for the goods to be weighed. The user held a rope or metal loop that was slid along the rod until it balanced. The weight was read off a series of notches or nail heads hammered in to the underside of the rod. It wasn' very accurate but traders liked it, probably for the wrong reasons and it became very popular throughout Europe. Aristotle condemned it as an instrument of deceit, but nonetheless it spread across the world under different names. The Normans called it the Auncel, in Russia it was the Bezmen, in India and the Far East it was the Dhari. Banned twice in England in the space of a hundred years, its use did not decline until it was condemned for public weighing by Henry II. However, it is still used today in the Baltic and Eastern European countries and the Far East.

The Roman Steelyard
The Romans invented the steelyard in 200 BC. Originally known as the statera, the English word 'steelyard' comes from the German 'Stalhof', the name of the London base of the Hanseatic merchants of the Middle Ages, who used the instrument extensively in their businesses. The Roman steelyard was another weighing device that has survived to modern times. It consisted of a beam with a sliding poise to counterbalance the load and was generally made from bronze.

Many instruments were particularly attractive, with the poises often fashioned in the shape of heads of gods, men, women or animals. The steelyard was a cheap, compact and accurate instrument. The Roman principle is still used for the steelyards fitted to modern mechanical platform scales. Large suspended steelyards were in use right up to the end of the eighteenth century for weighing carts. The cart was hoisted clear of the ground by means of chains hanging from the steelyard, some of which were about twenty feet (6m) long.

At the opposite end of the scale, there were small steelyards, measuring just three and a quarter inches and were probably used for weighing coins. Although the steelyard offered a practical means of weighing without the use of heavy weights, the balance remained valuable as the most accurate means for weighing precious thing such as gold, certain spices and drugs.

During the Middle Ages the equal-armed balance was refined, the first improvements since those of the Egyptians thirty centuries before. The most important difference lay in the improved fulcrum, which was either a nail or pivot, secured to the beam and working in a fork or 'clevis'.

Leonardo - The Genius
Leonardo Da Vinci (1452 - 1519), one of the most remarkable men of time, designed the first recorded self-indicating scale. He produced two designs, one with a triangular chart, and the other semi-circular, but both worked on the same principle. The object to be weighed is placed in a suspended pan. The chart acts as a pendulum and finds a new position of balance. The weight is shown on the chart by a plum bob crossing its face. Like many of Leonardo's conceptions, including the autogyro, this scale was ahead of its time was not manufactured until three hundred years after his death. During Leonardo's lifetime there occurred a further improvement to the accuracy of the balance that is still in use today - the development of the Swan Neck Beam, so called because of its shape. Knife-edges were cut into the swan neck ends at right angles to the beam.

This enabled the suspension centres of the weighing pans to be accurately located, and provided a true knife-edge, reducing the friction between the knife-edge and suspension ring of the weighing pan.

Knife-Edges Improve Accuracy
Prompted by a need for greater accuracy, particularly in the work of alchemists and assayers, inventors in the sixteenth and seventeenth centuries turned their attention to the evolution of the knife-edge as a pivot for the balance.

One of the earliest recorded representation of the true knife-edge is the famous portrait by Hans Holbein the younger of George Gisze, the Hanseatic merchant. Behind the figure, and hanging on the wall, is a beautiful money weighing scale, so accurately drawn that it has been possible to reproduce the actual instrument. Such an instrument could hardly have been a prototype, therefore there must have been previous efforts in the evolution of this design probably around the year 1500.

Three triangular knife-edges were incorporated into the later balances. One at the centre of the beam, with its apex pointing downwards, acting as a pivot. The other two at the beam ends with the apexes pointing upwards, from which the scale pans were suspended. Friction between the knife edges and their bearings could still reduce accuracy, so the knife-edges were hardened. Later, agate, a very hard stone, was used in their manufacture, and devices to lift the beam clear of the knife-edges when the machine was not in use, were incorporated into balances, to prevent the edges broadening.

In 1857 W & T Avery acquired the rights of Sharkey's patent for a new type of end pivot and bearing for a scale that became known as the brass and agate beam. The rigid construction of the beam, together with the end shackle that housed the agate, gave more protection to the knife-edge against dust and damage. The introduction of this design raised the standard and revolutionised weighing in retail shops.

All of the weighing devices we have examined so far have depended on suspending the goods to be weighed from a rod or beam, but in many business it is usually easier to have the scale pan above the machine without the bother of chains or cords.

The Static Enigma
This means of achieving this convenience was discovered by a Frenchman, Gilles Personne de Roberval. Roberval discovered the 'Static Enigma', that was to defy explanation for the next hundred years. In 1669 he built a model to demonstrate his discovery which comprised a beam, legs and stay, forming a perfect parallelogram. Two arms projected from the legs on which were hung poises of equal weight. His fellow mathematicians were surprised to discover that balance was maintained , even when one poise was moved outwards. No-one realised that this was the basis of a scale design, and Roberval's discovery, like Leonardo's was to wait until the nineteenth century before the principle was used to build counter scales. It is still widely used in the manufacture of weighing machines today. The system must retain a perfect parallelogram so that no matter where the load is placed on the platform , or pans, the machine remains in perfect equilibrium. Today, all weighing machines are still tested for 'cornering' by weights and measures authorities to ensure that the weight of a load is accurately recorded no matter where it is placed upon the platform.

Variations Start To Follow
A variation of Roberval's system was developed by a fellow Frenchman called Beranger, a scalemaker from Lyons, in the mid nineteenth century. The scale pans are supported on pillars and fixed to cradles which hang from the weighing levels.
Yet another great advance in the accuracy of the balance was achieved with the production of the box-ended beam. Although the swan neck had been an improvement, its peculiar shape meant that permanent accuracy of adjustment was impossible. The box-ended beam eliminated the need to make such adjustments and was therefore a great deal more reliable.

Larger Loads To Weigh
Machines to weigh large loads began to develop during the eighteenth century.

The UK Government has recently been examining the idea of charging a toll for the use of motorways. This is hardly a novel idea. In 1741 the Government of the day introduced the Turnpike Act, which decreed that tolls were to be paid for the use of roads according to the weight of the vehicle. The money raised was to be used for the maintenance of the roads, in much the same way as the revenue raised from the present day road fund licences.

This legislation meant increased business for the scalemakers, but the work was heavy and time-consuming. Massive steelyards were installed but the vehicles had to be lifted before their weight could be taken by the scale, and so the inventive geniuses of the day applied their minds to a more convenient solution.

The answer lay in the production of platform scales or weighbridges onto which the vehicles could be driven for weighing. These machines cut the time taken for this operation from six minutes to as many seconds and dramatically reduced the labour required.

Compound Lever System
John Wyatt, a Birmingham mechanic and inventor, achieved success with his Compound Lever Weighing Machine whose design was an ample demonstration of his inventive genius. The machine was based upon a system of levers supporting a platform. The levers were arranged in such a way, that wherever the load was placed on the platform, it transferred that load from the four knife-edges, to the central transfer lever. On the other end of the lever the proportional weights were placed to obtain the reading. Wyatt's machine was simple and beautifully efficient, and reduced weighing errors to approximately one pound per ton, a figure that remained an excellent standard until well into the twentieth century. Wyatt made many of these bridges which were eagerly sought after all over England.

One hundred years after Wyatt, the Fairbanks Brothers of Vermont took out a patent for a compound lever weighing scale. It was claimed at the time that they were the original inventors and poor John Wyatt almost lost his place in history, unit it was pointed out that the principles behind the Fairbanks machine were those employed by Wyatt to build his weighbridges. The Fairbanks Brothers did produce a compact and portable mechanism, which paved the way for rapid developments in both small platform machines, incorporating the principles of the steelyard with compound lever mechanisms, and larger weighbridges for use on railways.

With the industrial revolution now firmly under way, other commercial opportunities began to appear.

New Opportunities
The origins of the present postal system began in 1840 with the passing of the Uniform Postal Act. The regulation of the Royal Mail, whereby weight would determine the cost of postage, provided yet another commercial opportunity for scalemakers to exploit, and large numbers of scales were produced. The most popular designs were based on the Roberval principle, but they were also manufactured using steelyards, helical springs, pendulums and balances. Some were ornately decorated in Victorian Gothic or Art Nouveau styles, with beautiful cases made from wood, alabaster, onyx, porcelain pottery, brass and silver. Many of the machines made before 1915, when a four-ounce letter could be posted for one old penny, carried details of current postage rates. After 1915 postal rates altered much more rapidly, and this practice was abandoned.

Coin-operated equipment began to appear towards the end of the nineteenth and was operated by the weight and size of coin. Apart from person weighers, it included money exchange machines, chocolate and cigarette dispensers and, of course, the 'spending of a penny'.

Towards the end of the 19th century, the technology of weighing machines began to develop into the type of machines we would recognise today. Inventors began to consider designing scales that would indicate the value of goods, as well as the weight.

Indicating Scales
One of the first price-indicating scales to be manufactured commercially appeared in America in 1897. Based on a steelyard supporting a weighing platform, its computer consisted of a flat rectangular chart attached to the steelyard. A weighed cursor, graduated vertically into prices per pound, was slid along the steelyard and the price of the goods could be read off the chart at the point where a balance was achieved. Unfortunately it was very slow to use.

Automatic cylinder scales soon followed, first with a swinging pan supported by two helical steel springs. A rack and pinion device rotated the cylindrical chart that carried both weight and price computations. Later, the swinging pan was replaced by a pan supported by a Roberval lever system, approved by the Board of Trade. This form of scale was to remain in service for many years.

In the late part of the 19th century the development of accurate self-indicating scales for industry revolutionised the weighing process. Loose weights and sliding poises were eliminated in these machines, which gave an almost instant indication of the weight of goods. Pendulums were applied to the Roberval and Beranger designs. The weight from the scale beam, via a cam or pulley, allowed a pointer to traverse the chart and indicate the weight. Yet another innovation, the Avery Dial recorder fitted to industrial weighing machines, printed a fraud-proof record of all goods weighed on the scale. The printed tickets also had the advantage of being much easier to read than hand-written notes.

Electronics Take Over
From the late 1940s mechanical weighing began to combine with electronics. But it was not until the device called a load cell was invented that complex and bulky lever systems and knife-edges were replaced.

Load cells, or transducers, now lie at the heart of every electronic machine. Precision load cells convert weight into electronic signals, and are manufactured for a wide range of products, from a sensitive and delicate scientific balance to a weighbridge for a train. Each load cell contains thin, metal foil electrical resistors, known as strain gauges. When a load is applied, the strain gauge is compressed, changing its electrical resistance, and thereby changing its electrical resistance, and thereby changing the output signal in proportion to the weight put on it. From the cell's electronics, weight information together with other data, such as calibration, are fed via an analogue-to-digital converter to a microchip with the software implanted into it. This processes all of the calculations, descriptions and other information which is then digitally displayed or printed out.

Accuracy in the electronic age means time and distance can now be measured by light, but weight still has to be measured against a known or reference weight, or mass. Today's range of weighing equipment includes balances capable of resolving to one part in five million. Industrial machines which are capable of weighing and counting up to ten thousand different types of parts, and scales that can be programmed to weigh, price and label goods.

Weights And Measures
The third element in the history of weighing are the laws relating to weights and measures. In England these have been incorporated in the statutes of this country since King John signed the Magna Carta in 1215. He decreed: 'that one measure of wine shall be through our realm, and one measure of ale and one measure of corn .... and it shall be of weights, as it is of measures'.

The earliest form of law on uniformity was passed in the reign of King Edgar about 965 AD. However, because of the lack of adequate enforcement in many parts of the country, this ideal was not fully achieved until the end of the nineteenth century.

Officials in Britain began marking weights to attest their accuracy and prevent dishonest dealings as early as 1579. The Worshipful Company of Founders stamped and tested bronze and brass weights, and in 1611 the Worshipful Company of Plumbers were granted rights under a Charter to stamp and test, iron and lead weights. Provincial authorities in towns and cities across the country placed verification marks on their weights, often based on the local coat of arms. In mediaeval times wool carried a tax of one penny on every 28 pounds weight and the tax assessor, or tronator, traveled his district carrying weights across his horse's back. The weights bore the Royal coat of arms, and were to test the wool merchants' scales and ensure that they were not cheating their sovereign king.

Trying to Beat the System
Although many changes have taken place since man first developed a system of weights and measures, one element at least has remained constant. From time immemorial, dishonest people have devoted their energy and imagination to cheating their customers or their employers. In the eighteenth century when guineas and sovereigns were introduced and manufactured in gold, unscrupulous people would often shave or clip small quantities off the coins reducing the amount of metal by as much as 20% of its face value. The penalty for such a practice was death. Pocket coin scales became an essential piece of equipment whenever money changed hands, to ensure you received the true value. Eventually the coins were made with a milled edge which prevented the practice.

In 1907 pottery weights, which had been in use for fifty-seven years, were outlawed because they could become chipped, so altering their weight. Another unscrupulous practice was to place one of the pottery weights in a bucket of water, to make it heavier, with another placed by the fire to make it lighter. The devious shopkeeper used whichever was appropriate, depending on whether he was buying or selling.

Metal weights can also be altered to the disadvantage of the customer by drilling a hole in the bottom. Other forms of fraud involve commodities, like coal, sand and frozen foods, which absorb a certain amount of water and can be made to seem heavier by soaking them before they are weighed.

All trade depends on having a fair system of weights and measures. All our weighing machines and weights have to be inspected and stamped by Trading Standards officers who compare weights to known 'witness' weights. Serious penalties are imposed against those who practise fraud.

Today's modern electronic machines are manufactured to weigh in kilogrammes, or pounds, but they must still conform to the weights and measures regulations of the countries to which they are exported. What is allowed in Britain is not necessarily allowed in Australia.

The document available to download below is one in a set of three museum books which date back to 1945 that were designed to provide a deeper knowledge of the Avery business, the Soho Foundry on which the business has been situated for over 200 years, and of the weighing industry in general.

To download and read the other books in the set, please click here.