Anyone who has never made a mistake has never tried anything new.
— Albert Einstein
While I would have to agree with Albert, there are instances of mistakes that I find particularly irritating. While out for a walk in the Cotswolds yesterday I stopped for a while at a hut in Lidcombe Wood to enjoy a coffee on this bright but cold day.
Lidcombe Wood was, at the time of the Domesday Book (1086), only 3 furlongs long and 1 furlong wide, covering a triangle of about 40 acres immediately north-east of this hut.
An area of the stated dimensions could not possible contain an area of 40 acres! For those not familiar with the units, and perhaps this includes the author of the information board, a brief explanation should help.
A furlong is an imperial unit equal to one-eighth of a mile, or 220 yards.
An acre is an imperial unit equal to 1/640 of a square mile, or 4,840 square yards.
The reason for size of an acre goes back to the Middle Ages when the Anglo-Saxon acre was defines as one furlong by one-tenth of a furlong (i.e. 220 yards by 22 yards) which just happens to be 4,840 square yards. This was roughly the area that could be ploughed in one day by a yoke of oxen.
So with these facts at our disposal we can see that even a rectangle measuring 3 furlongs by 1 furlong would only encompass 30 acres and a true triangle with those measurements half of that.