When trying to work out how much grain was produced by crops such as bere, barley and oat in the 1800s, it was necessary to convert the bushel, the unit of measure that was common at that time, to the kilogram, which is the unit of weight in the modern International System (abbreviated to SI).
The bushel is a unit of ‘dry volume’ for measuring things like grain and meal rather than liquids. Farmers and grain traders used a standard basket or barrel which when full would hold 1 bushel, equivalent to 8 gallons. But obviously a bushel of ball bearings weighs more than a bushel of bere grain. So before it can be converted to modern units, the bushel has to be calibrated for each type of filling.
Table, jug and balance
Things used: table, kitchen measuring jug to 0.5 or 1 litre, kitchen balance (e.g. used for weighing out flour), lightweight container and a bag of bere grain, grown in the Living Field garden, harvested and air-dried for some months. The bere grain was cleared of stems and leaves – any long awns still attached to individual grains were broken off. The jug was filled with grain slowly. When a quarter full, the jug was banged gently on the table twice to consolidate the grain. The same was done when half full, three-quarters full and almost full. When full, the container was placed on the balance and the scale brought to zero. The grain was poured into the container and the weight noted.
In this instance, 0.5 litre of bere grain weighed 300 g (not 299 or 301).
A bushel equals 8 gallons or 36.37 litres. So a bushel holds 72.7 of the 0.5 litre measuring jug. Since 0.5 litre of bere grain weighed 300 g, a bushel of bere should weigh 21.8 kg.
The bushel is used in some countries, including the USA and Canada, as a unit of weight and so a bushel has a different weight assigned to it for each type of grain. We are pleased to see that the USA’s standard bushel of barley is 21.77 kg, close to our estimate. Their bushel of wheat and several other small grain crops and beans is 27.2 kg while that of oat is 14.5 kg. It means wheat is heavier and oat is lighter than barley or bere for a given volume. So a person would be happier carrying two bushes of oat than two of bere.
What causes the difference in the weight of a bushel? Provided the cereals are dried to a constant moisture content, the difference lies in the proportion of the (heavier) grain to the surrounding protective husks. Wheat grain commonly falls out of the husks at harvest so the light material may not be included; oat is more husky.
Therefore when converting yields of bere in bushels, we will used the conversion, 1 bushel = 21.8 kg.
University of North Carolina, USA: the source informs that the previous URL (www.unc.edu/~rowlett/units/scales/bushels.html) is no longer ‘live’ and recommends a superior location at University of Georgia – ‘Weights and processed yields of fruits and vegetables‘ .
National Museum of Scotland. Photograph of a bronze bushel measure.
The International Systems of units – Bureau International des Poids and Mesures: http://www.bipm.org/en/about-us/
Note of statistical procedures: the methods reported above can be used in a fun-sized comparison of different cereals and beans. A proper scientific calibration would check the balance with standard weights at the beginning, then repeat the procedure several times with different lots of grain from the same harvest to get an average with a estimate of the variation. If two corn crops were compared, the average plus variation would allow a statistical test of whether the two were really different.
Links on this site
Grain measures in Ancient Greece (measuring tables at Ancient Messene)