Pottles and pecks

Why just the other day I was comparing a US quart with an EU litre: 'tis only 5% more capacious. You could, accordingly, without the sky falling, interchange the two units in many real world situations: filling the tank on your lawn-mower; making custard; buying gloss paint. That Obvs doesn't work for any pair of units though: don't try equating mph and km/hr approaching a speed-camera. My antient copie of Pendlebury's New School Arithmetic (1924) is still in our jacks. I've ranted before about how imperial units require mental gymnastics because they don't do decimal.

But Pendlebury reports [p.194] an agreeable series in capacity measures:  "each of which is exactly twice as large as that which precedes it: noggin - gill - pint - quart - pottle - gallon - peck - tuffet - bushel - strike - coomb - quarter" [quarter being what it says on the tin: ¼ ton]. There is an inconsistency in this statement in that 1 pint is 4 gills not 2: what's missing is "cup". These are imperial not US quarts and cups through; all based on a pint of 20 fl.oz. not 16. How and when those measures drifted apart is a mystery [to me]: inches / miles are the same; pounds weight are the same; seconds / hours are the same [and shared with the rest of the world - decimal time having been dumped early by revolutionary France]. Irish pub [booze] measures were a more generous ¼ gill than those in Britland ⅙ gill; Irish measures are now fixed at 35.5 ml. In UK "Either 25ml and multiples of 25ml, or 35ml and multiples of 35ml (not both on the same premises)". A Baby Powers is a double = 71ml.

I'm glad we've sorted that out.