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The mnemonic trap

As an author, it's not uncommon to get emails or letters correcting something in one of my books. Sometimes these corrections are useful, at other times, the correspondent misses the point. But I recently had one from Ronja Denzler that was not only correct, but also highlighted something really interesting about mnemonics.

These phrases to remember something can be genuinely handy - most of us can still recall those for rainbow colours or planets (often still incorporating Pluto) from school, while I distinctly remember a woman called Ivy Watts from my physics class. But the most elegant are the numerical mnemonics, where the numbers of letters in each word represents a digit. This form reaches its zenith in the mnemonics for pi - so much so that the art of producing these has its own, distinctly tortured, name of 'piphology'.

When I wrote Introducing Infinity - a graphic guide in collaboration with the excellent illustrator Oliver Pugh, I asked if he could use a fuller version of the mnemonic I vague recalled from school. The bit I could remember was 'Now I, even I, would celebrate in rhymes unapt the immortal Syracusian...' - Oliver extended this further in the image below:

It was this illustration that Ronja wrote to complain about - because the thirteenth decimal place is incorrect. The reason for this is that the rhyme was originally dreamed up by one Adam C. Orr of Chicago. Being American, his idea of how to spell 'rivalled' was not the same as the British one. Although Oliver is entirely accurate in his illustration that rivalled should have 8 letters, unfortunately the US spelling only has 7 - and that's what the 13th decimal place should have been.

The moral of this story is that if you are designing a numerical mnemonic in English, make sure that you don't use any words such as rivalled, or travelled, or colour, or labour where US and British spellings deviate - otherwise, someone is bound to be misled. 

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