The Colliery Chaldron System
Two chaldrons, one commodity, and a factor of two between them.
Origin
Established through the Tyne coal trade from the medieval period, with the London chaldron fixed by statute in 1421 and the Newcastle measure set by local custom.
The catch
A Newcastle chaldron was nearly twice a London one, and the two were not even the same kind of measure. The northern chaldron was a weight, fixed at 53 hundredweight in 1694 and built around what a keelboat could carry down the Tyne. The London chaldron was a volume of 36 heaped bushels, set for sale and taxation at the wharf. Coal was loaded by one and unloaded by the other, which guaranteed an argument at each end.
| Measure | Bushels | Litres | Reckoned for |
|---|---|---|---|
| London chaldron | 36, heaped | 1,308 | Retail sale and duty at the wharf; about 28 cwt of coal |
| Newcastle chaldron | 72, nominally | — | Fixed by weight at 53 cwt in 1694 |
| Keel | 8 Newcastle chaldrons | — | One barge load, about 21 tons |
| Corf | variable | — | One basket from the coal face, the hewer’s pay unit |
| Score | 20 corves | — | How a hewer’s output was tallied |
Coal was measured by volume rather than weight for most of its history, because volume could be checked by eye in a wagon or a hold while weighing required apparatus nobody had. The consequence was endless argument, since a chaldron of large coal weighs less than a chaldron of small. London finally moved to sale by weight in 1831, which is why the coal sack was fixed at one hundredweight and why weights and measures inspectors spent so much time on street vendors.