MAGNA Carta, signed reluctantly by bad King John in 1215, contained in mediaeval satin a clause which required that "throughout the Kingdom there shall be standard measures of ale, wine and corn dyed cloth, haberject and russet shall also be produced to a width that shall be fixed, and weights are to be similarly standardised."
The barons were less successful when it came to fixing the value of the coinage of the realm until the "Easterlings" arrived. The Easterlings were merchants from North Germany who settled in London a generation later, and their money then, as indeed it is today, was considered to be particularly sound. Two hundred and forty of their silver pennies, or "easterlings", became known as the pound sterling, because in Troy measure that was precisely what they weighed.
This tradition of 240 pennies to the pound continued, as we know, until comparatively recently. There was an overture for decimalisation in 1798 when the ubiquitous Tallyrand invited the London government to send a deputaton to Paris to "deduce an invariable standard for all the measures and for all the weights." Naturally enough, his impertinence was totally ignored. As far as the currency was concerned, it was not until 25 years ago today, on (February 15th, 1971, that the decimal system was finally adopted on these islands.
Meteorologists, however, had gone decimal a little earlier. In the early 1960s they changed almost everywhere except in the United States from using the Fahrenheit scale which has 180 degrees between the boiling and the freezing points of water, to Celsius which has 100.
Apart from the mathematical conveniences of going decimal, many meteorologists felt that the Fahernheit degree roughly half the magnitude of a degree Celsius was rather too precise to use for forecasting. Temperature is, after all, a very variable element on a sunny day it may vary over short distances and times by several degrees Fahrenheit, and the somewhat coarser Celsius degree seemed a more appropriate means by which to specify it. Another advantage seen in the Celsius scale was that it makes a highlight of the freezing point, as the dividing line between positive and negative values of the temperature. The freezing point is off obvious practical importance in the context of the weather and a listener is more likely to be alerted to potential hazards by "minus 2", than he or she might be on hearing the unremarkable figure of "28 degrees Fahrenheit.