The Pharmaceutical Journal
Vol 269 No 7229 p909-911
21/28 December 2002

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Weights, measures, medicines and the calendar

The modern pharmacist works with the metric system of weights and measures. The student pharmacist of today has no problem, for example, in making up a 1 per cent solution of an active ingredient. Just take one gram and make up to 100ml with water. Simple!

For older colleagues life, in their own student days, was not so easy. "Oh, no!" said the lecturer in pharmaceutics. "You cannot make up 1 grain to 100 minims to provide a 1 per cent solution." The reason, it was explained, was that one imperial fluid ounce of water, that is to say eight fluid drachms or 480 minims, actually weighed 437.5 grains. So the volume of a grain of water was actually 480 divided by 437.5 equalling 1.097 minims, so 100 grains of water measured 109.7 minims.

The British Pharmacopoeia graciously allowed this last figure to be approximated to 110 minims for practical dispensing purposes, so a 1 per cent w/v solution in the imperial system of weights and measures was produced by making up 1 grain of solid to 110 minims of solvent, or 4.375 grains to 1 fl oz. At this point the young student realised that this pharmacy game was not going to be quite so straightforward as he or she had imagined. What was this strange system in which 20 grains equalled a scruple and three scruples made one drachm? If eight drachms made 1oz then that made 480 grains so where did this 437.5 come from? Why were things so complicated?

Weights and fair trade

Until the official acceptance of the metric system we had inherited a system of weights and measures which had evolved over many centuries. It had developed to facilitate fair trade, using units which were reasonably readily understood by ordinary people who had access to basic methods of weighing and measuring. Every schoolchild knows, or used to know, that Julius Caesar mounted an expedition to Britain in 55 BC. It was not until 43 AD, in the time of Claudius, that the Romans invaded Britain, with four legions under the command of Aulus Plautius. Within a generation Roman domination extended north to Scotland and the great highways of Ermine Street, Watling Street and the Fosse Way were helping communications and trade. The new roads now connected many parts of Britain with much of the European mainland, greatly facilitating both national and international trade. Standard methods of weighing and measuring goods were essential. Existing Celtic measures were no doubt based on simple standards such as the pace, foot, palm or grain of wheat. The Roman system involved more precise standards. The Roman foot (pes) was divided into 12 inches (pollici) and the palm (palmus) was one quarter of the standard foot, which measured 11.65 imperial inches or 296mm. This was almost identical to the earlier Egyptian foot and slightly shorter than the Greek foot, which measured 308mm. The cubit (cubitum) was one-and-a-half feet.

The thousand paces

For measuring distances there was the Roman mile, the mille passus or one thousand paces. Why one thousand paces, when our imperial mile, which is similar in length, consists of 1,760 yards, each yard being approximately one pace? The answer is that the Roman military pace involved a double step, so each time the left foot met the ground made one pace (passus) which measured five Roman feet. Possibly the average legion member had rather shorter legs than his Anglo-Saxon successors. The stade (stadium) was 125 paces or one-eighth of a Roman mile. The Roman mile of 1000 military paces or 5,000 Roman feet was equivalent to 4,856 British imperial feet and so, rather shorter than our own mile of 5,280 feet.

For weighing solid materials the standard Roman weight at the time of the conquest of Britain was the silver denarius or pennyweight. Six pennyweights made one ounce (uncia) equivalent to 27.41 grams and 12 oz or 72 denarii made one Roman pound (libra) of 328.9 grams, a good deal lighter than our imperial pound of 454 grams which contained 16oz rather than 12. For liquid measure the sextarius had a volume similar to our own pint and 48 of these made one amphora.

The fall of Rome

In 406 AD, Constantine III withdrew the legions from Britain and four years later Rome was sacked by Alaric the Goth. Appeals from Britain for military support went unheeded as the Empire faced barbarian invasions. The national and international trade which had been such a feature of Roman life collapsed in the face of deteriorating roads and lack of security for tradesmen, travellers and merchant caravans. Trade, instead of involving 100 million people using a common currency, re-adopted to pre-Roman local activity and, in the absence of officially backed weights and measures, slowly returned to traditional units and systems, largely at local level. With colonisation by the Anglo-Saxons, Germanic systems and traditional measures intermingled with earlier units. The North-German foot, reflecting, presumably, their larger feet, measured 13.2 imperial inches or 335mm and was divided into 12 "thumbs" or four "palms". The cubit was two feet and the rod of 15 feet was equivalent to marginally over five metres. The German foot became the basic unit of measurement and land was measured in lots of 40 rods in length and four rods in width. This produced an acre of 160 square rods or 36,000 square German-feet, which was the same area as our modern acre.

Coinage was erratic during the Anglo-Saxon period but Offa, King of Mercia (757–796), introduced a new silver penny, the sterling, weighing 32 wheat grains. Twenty of these pennyweights made an ounce and 12 ounces made a pound. It is believed that the Saxon kings kept their standard weights and measures in Winchester, headquarters of the kings of Wessex. Unfortunately none of those standards appears to have survived, although the term "Winchester measure" became established.

The Norman conquest

Life in Britain changed with the conquest of 1066 but the Winchester measure survived under the new regime and its use in agriculture and commerce continued. The Winchester standard weights and measures were transferred by the Normans to Westminster Abbey and became the Norman standard also. At the end of the 13th century it was decreed that an inch was the length of three barleycorns, 12 inches made one foot and three feet one yard. Five-and-a-half yards made one rod and the acre of 160 square rods was unchanged. In the time of Henry V (1413–1422) troy weight was recognised, the term believed to be derived from the French town of Troyes. The troy pound weighed about 373 grams divided into 240 pennyweights of 24 grains each, or 12oz of 480 grains each, numbers still familiar to the older generation of pharmacists. In Tudor times a statute of 1496 defined the troy ounce as 20 sterlings of 32 wheat grains each. Twelve ounces made the troy pound and the gallon was the volume measure of eight troy pounds of wheat, eight gallons making a bushel. So the troy pound weighed 5,760 grains. During the 16th century the avoirdupois pound emerged, which weighed 7,000 grains divided into 16 ounces, so the avoirdupois ounce weighed 7,000 divided by 16, or 437.5 grains, which takes us back to our pharmacy student mentioned above, struggling with his 1 per cent solution.

The imperial system

Following some years of committee work the Imperial Weights and Measures Act of 1824 standardised the avoirdupois system using the weights and measures most of us are familiar with. The troy pound of 12oz was abolished and all prior enactments rescinded. Troy weight remained in use for precious metals, involving 480 grains or 20 pennyweights to the troy ounce. Pennyweights are still in use for certain traditional activities in the horticultural area, such as annual competitions to grow the largest gooseberry. The apothecaries' system remained in use in pharmacy, with 480 minims or eight fluid drachms making one fluid ounce and 20 fl oz making one pint. In weight, 480 grains, 24 scruples or eight drachms made one apothecaries' ounce. Thus, the apothecaries' ounce of 480 grains weighed 31.104 grams in modern metric measure, whereas the avoirdupois ounce of 4.375 grains weighed 28.349 grams. This sufficed until the introduction of the metric system. Local traditions continued. For example, a gill of ale was widely regarded as a half-pint measure and I well recall numerous requests over the pharmacy counter during my apprenticeship in the early 1950s for a gill of vinegar. The customer always expected to receive half a pint of vinegar for his "gill", despite the fact that every school exercise book used in the City of Sheffield bore, on the back cover, a table of imperial measures which invariably commenced: 4 gills=1 pint. Another old term familiar in apprenticeship days was "Winchester" to describe the 80 fl oz (half gallon) bottles used for storing dispensing stock-mixtures.

The metric system

Regarded by many as an alien system introduced by Napoleon Bonaparte, the metric system has not been welcomed in Britain. A description of the system would be superfluous here, but its adoption has been slow and, in many areas, unpopular, as the recent cases of "metric martyrs" in the retail sector demonstrate. The public undoubtedly finds the adoption of the system, for household purchases, confusing. My own recent experiments in shopping indicate that requests to purchase loose goods such as fruit and vegetables in metric quantities from small shops are met with raised eyebrows and surprised comments that this is an unusual request, despite dual pricing and metric weighing systems. On 24 May 1965 the Board of Trade announced in the Commons that it would be supporting industry's wish for a planned adoption of the metric system and that an extended period would be required for the change. By the mid-1970s the change was proceeding and the pharmaceutical industry was the first to make the conversion. I well remember numerous meetings and discussions in the industry to bring it about. Some thought that "outers" of 10 bottles or packs would need to replace "outers" of 12 for wholesale distribution. This made cartons of inconvenient shape and there was some relief when it was recalled that metric France still shipped huge quantities of wine in dozens. Yet, almost four decades after the Board of Trade statement, and two centuries after French scientists advocated it, the metric system is still not fully accepted in Britain and certainly not in the United States.

Metric time

Objections to the metric system would certainly not have surprised Napoleon. Apart from metric weights and measures the First Republic sought to introduce metric time. The French Academy of Sciences set up a committee to develop a decimal calendar. The chemist Antoine Lavoisier was one of the members. Its report was presented to the National Convention on 20 September 1793. The year would still comprise 12 months, but each month would consist of 30 days divided into three weeks, or "decades", of 10 days and the year would begin at the autumn equinox. This conveniently reflected the fact that 22 September 1792 had seen the foundation of the Republic and abolition of the monarchy. Each day would be divided into 10 hours and each hour into decimales. Division of time into sixtieths, an inheritance from the Babylonians, would disappear. At the end of each year there would be a period of five days (or six in the case of a leap year) to complete the 365 day year. This period would be a holiday, which became known as the sansculottide, when ordinary people (the sans culottes, who could not afford to wear expensive culottes) could celebrate. The new months of 30 days each would be named to reflect the seasons of the year. Commencing in autumn, Vendemaire, Brumaire (foggy) and Frimaire, followed in winter by Nivose, Pluvoise (wet) and Ventose (windy). In spring, Germinal, Floreal and Prairial, followed in summer by Messidor, Thermidor and Fructidor. A public instruction committee was set up to explain and introduce the new systems of weights, measures and time. Decimal time was the most difficult to establish. Objections to the new names of the months reflected the fact that although they were descriptive in Paris, the climate was different in the south. More particularly, it did not take the sans culottes long to realise that they would only have one weekend every 10 days instead of every seven, an unattractive proposition to the peasant in the field or the man in the street. The authorities struggled on but many difficulties became apparent. Napoleon became First Consul in 1800 and crowned himself Emperor in 1804 and, recognising that the old system was still in use, abandoned the decimal calendar and announced that from January 1806 the Gregorian calendar would be universally adopted in the French Empire. Apart from a brief revival during the Paris Commune, the Revolutionary Calendar vanished for ever in 1871. In 1812 the French government also announced that the former traditional weights and measures would be re-adopted in place of the metric system. At the time Napoleon was occupied with his Russian campaign, resulting in the destruction of his Grand Army. Perhaps critics of the metric system are unfair in laying it at the feet of the Emperor himself. It was introduced before he came to power. France did not adopt metric weights and measures until 1840.

Calendars and lost days

The Gregorian calendar to which France returned in 1806 was the result of the efforts of Pope Gregory XIII to correct the accumulated error of the Julian calendar, introduced in 46 BC by Julius Caesar. A Papal Bull of 1582 introduced the new calendar, deducting 10 days so that 5 October 1582 became the 16 October. The main catholic countries, France, Spain, Portugal and parts of what is now Italy came into line and in France, Monday 20 December followed Sunday 9 December. The new calendar, devised by the German Jesuit Christopher Clavius, was regarded in protestant countries as a theft of days by the Papacy. Scotland adopted it in 1600 but it was only in 1752 that England came into line, when 11 days between 2 and 14 September were omitted and the calendar year began on 1 January instead, as previously, on Lady Day, 25 March. The change resulted in riots in the streets of London and a demand for the return of the "missing days".

Resistance was even greater by the orthodox church and Russia did not fully adopt the Gregorian calendar until the October revolution of 1917 with Greece finally coming into line, the last European country to do so, in 1923. No doubt the religious associations of the Gregorian calendar were one reason for the efforts of revolutionary France to adopt the ill-fated and short lived decimal calendar.

Acknowledgement
The author is grateful to Professor T. G. Booth for assistance in the preparation of this article.