Just before the metre, the gram, the litre
Building a Rosetta Stone of Weights and Measures in the
Early Modern World
Last updated: August 31, 2005
On July 23, 1983, two Air Canada pilots found themselves in a tricky situation. Bob Pearson and Maurice Quintal were guiding a Boeing 767 through the Canadian sky more than 40,000 feet above ground when a fuel failure warning light turned on. They were wondering whether there was something wrong with the instruments when a second warning light suddenly went on. The growing suspicion of an actual fuel problem was confirmed when both engines turned off. Flying at 41,000 feet with a 132 tons glider. A tricky situation.
Moments before Flight 143 was supposed to leave Montreal for Ottawa, the mechanics realised the Fuel Quantity Information System Processor (the plane equivalent of a fuel tank indicator) was not working properly, so the crew decided to estimate the fuel load by hand. This involved measuring the depth of the tank, then calculating the contents in litres and, finally, applying a standard and widely known conversion factor to get the weight of fuel, which is the number required by the computer system to determine whether or not they could reach a particular destination. The calculations were made and the conclusion was that there was enough fuel, so they left and made it to Ottawa. As the next stop was considerably farther away, the pilots insisted on repeating the calculations. The plane had now 11,430 litres. Multiplying this by the conversion factor of 1.77, implied there were 20,230 kilograms, enough fuel to make it to Edmonton. What the maintenance crews in Montreal and Ottawa seem to have missed was the fact that the brand new Boeing 767 was set up in the (recently established in Canada) metric system whereas everyone was making calculations with the standard imperial conversion rate. They used the rate of 1.77 pounds per litre, instead of the 0.80 kilos per litre. In reality, the plane took off with only 9,144 kilos of fuel.
Quite luckily, there was no tragedy. The pilots managed to take the plane to the abandoned Royal Canadian Air Force Base of Gimli. After a spectacular landing, Pearson and Quintal became national heroes and the story -now widely know as the 'Gimli Glider Incident'- made the headlines of worldwide media (and even a TV movie was made after it). This dramatic tale illustrates how, even in the current modern world, the conversion and comparability of units of measurement is not a trivial matter. In the past, this problem was probably not that critical, but it was indeed more difficult to solve.
Standardisation is one of the basic trademarks of modernity. Current day travellers sometimes find it quite annoying moving between measurement systems, from metric to imperial and back to metric. Only two hundred years ago that nightmare would have been the dream for many. Before the mid-nineteenth century, when the metric system started to become universal, it was difficult to travel more than a few miles without facing a complete different measurement system, or even the same one, but with different equivalences. For the social researcher involved in dealing with quantitative data, information on the size of measures is both essential and hard to obtain. There are some dictionaries providing comparison between different measures, and quite a few research works on the issue, but they are either not comprehensive (covering, for example, only a particular region of the world) or difficult to obtain (books no longer published and with few remaining copies in the world).
The objective of this project is, then, to build a large (and increasing) database with measures across the world for the early modern period. The task is, of course, daunting. But, unless it is started, it will never be done. And this is the first step into it.
The Ricard tables.
One of the few attempts to clarify this rather complex picture was done in the late eighteenth century by Samuel Ricard, so we took his publication as a starting point. Ricard -a Frenchman- produced, in 1781, a detailed account of different units of length, weight and capacity used in hundreds of cities in the world, and organised them in a series of tables. Most places he describes were in Europe (there was none -for example- in the Americas), but he lists many values for cities or states in Asia and North-Africa. Also, the tables provided some reference values to compare those measures with each other.
We began by entering all these tables in spreadsheets to facilitate access and calculations. As the original publication by Ricard is in French (and a slightly older version at that), we translated the names of places or measures to English or current denomination, and corrected any spelling problem when possible. In general, we tried to use the local name of the measure, but this was not always clear, so we used the English spelling (in future versions of these tables we expect to be able to improve on this by providing local spelling and English spelling).
Of course, none of the original tables is in metric or standard imperial, so another thing we have done was to standardise them in metric denomination. To do that, we took the values appearing in an 1840 book by Horace Doursther, anther Frenchman. Doursther's book is extremely exhaustive (it will be, therefore, the core of the next steps in our project) and, since it was done after the establishment of the metric system, it provides metric comparison for all the measures. Using these values, we calculated the metric equivalents for all measures, indicating in the description of each table (and marked with green in the tables) the reference value we use.
Given the scale of the project carried out by Ricard, it would be surprising not to find any mistakes in his tables, and we do find them. Certainly not as many as one could have expected given the limited resources at the time, but there were some of them. We were able to spot them by making internal calculations that simply did not add up. In all cases were able to find the right value comparing Ricard's data with other sources, and those appear in red in the tables.
Below we provide all the tables we have transcribed so far. As you will be able to see, we labelled them including a 'version' number. Since this is an ongoing project, we wanted to make as clear as possible which is the version that is being used, and when it was last updated. This first release is labelled 05.08, making it clear that is the version that corresponds to August 2005.
The tables are in general self-explanatory. Next to the name of the city we have the name of the measure, including its plural and/or alternative spellings -when known- and comments that describe further characteristics of it -when needed-. The first column with numbers corresponds to the metric value, and the following three are the original numbers from Ricard, followed by the reference in his publication.
The metre is probably the symbol of standardisation and before the metre there was a large variety of measures to evaluate distances and surfaces. Length measures can be broadly divided between those to measure distance in general (e.g, the foot) and those normally used for the lengths of particular goods like fabrics, ropes and so forth (e.g., the ell). Surface, on the other hand, was trickier as in many cases it was not described in terms of physical area, but on how many days, for example, would have taken a man and two oxen to work a particular piece of land.
Weights in the Ricard tables are concentrated in two basic measures: pounds (lb) in most of continental Europe and Britain, and rotolo (and drachma) around the Mediterranean and the Middle East. From the few entries that correspond to other parts of the world, the Asian measure catti is probably one of the most widespread.
Capacity measures, in contrast to weight measures, have varied values and diverse denomination. Two types of measures can be distinguished: those that are used for dry products (normally grains) and those for wet products (wine, beer, oil, etc).
Citation and Feedback
This project is based upon secondary sources and we provide references to these sources in detail. We ask users to reference material taken from this database by citing it as follows:
Allen, Robert C. and Tommy E. Murphy [year of version]; Just before the metre, the gram, the litre: Building a Rosetta Stone of Weights and Measures in the Early Modern World, Table [#, e.g. IV], Version [#, e.g. 05.08] (http://www.nuffield.ox.ac.uk/users/murphy/measures/before_metre.htm)We are, moreover, very interested in watching this project improve and grow with the support and feedback from the academic community. Comments and corrections will be very welcomed. We have, to the best of our knowledge, transcribed the tables accurately and made all calculations correctly. But mistakes do happen. If you find any problem in our database, we will be happy to acknowledge and amend it. Also, if you think the database could be improved in any way, we will be happy to hear from you. Please, simply contact us by email (above).
Acknowledgement of support
This project was made possible through the support of the US National Science Foundation funded Global Price and Income History Group and the Canadian Social Science and Humanities Research Council funded Team for Advanced Research on Globalization, Education and Technology. We are gratful for their support.
Last updated: August 31, 2005