5. Coal Measure

The Chaldron of 36 bushels is used for the sale of coke and in Northumberland for coal.

A ‘keel’ of coal, i.e. the load of the Tyneside lighter known as a ‘keel,’ was, up till the fifteenth century, 20 ‘chaldres,’ the measure of 20 old tons:

The	old	chaldron	of	wheat,	32	bushels	of	62-1/2	lb. = 2000 lb.
„	„	„	„	coal,	25	„	„	80	lb. = 2000 lb.

When the old Chaldron became illegal it gradually gave place to the new ton and to the new chaldron. The Newcastle chaldron was 2 statute chaldrons = 72 bushels. The modern keel of coal is 21·2 tons = 16 statute chaldrons of 36 bushels = 8 Newcastle chaldrons. This double chaldron is then 72 bushels, or, as 1/8 of the keel, = 21·2 tons, it is 53 cwt., and it is divided into 3 Fother of 17-2/3 cwt. = 1966 lb. or nearly the old ton of 2000 lb. Thus the Newcastle fother is nearly the old ton, and the keel of 24 fothers or old tons has taken the place of the sixteenth-century keel of 20 old tons.

In the eighteenth century the coal-bushel was slightly changed from London or Winchester standard. 12 Anne (1714) ordered a special coal-bushel. It was defined as containing a Winchester bushel and a quart, 33 instead of 32 quarts = 2218 cubic inches, and coal was to be sold by the chalder of 36 such bushels, heaped.

This new bushel was 1/8 inch more in diameter and in depth than the old standard; it arose probably from a faulty casting. It is remarkable, inasmuch as its capacity is almost exactly that of the Edinburgh firlot and also of the Imperial bushel instituted a century later.

The Chaldron survives for coke. When coal is coked at the gas-works it swells, so that a ton of coal, = about 3/4 chaldron, yields about a chaldron of coke.

Heaped Measure

It has been seen that in 1392 the bushel was to be measured ‘striked’ and not heaped. Yet the love of extra weight or measure is so ingrained in human nature that it persisted, at least in retail transactions. With a pan-shaped bushel more than twice as broad as deep, heaping increased the measure by not less than one-fourth. With a drum-shaped bushel, its depth equal to its diameter, the increase of heaped over striked measure would be about an eighth, so that a bushel of wheat would weigh about 70 lb. instead of 62 lb. Heaped measure was made illegal in 1835.

It is possible that some long-bushels (as that of Chester = 70 lb.) were originally, or actually, heaped bushels.