Lewis Carroll in Numberland

Review by Andrew Crumey

Published in Scotland on Sunday

Lewis Carroll in Numberland
Robin Wilson
Allen Lane, £16.99

Everyone knows Lewis Carroll as the author of the Alice books, but in his day job he was an Oxford maths lecturer, and most of his publications were about geometry, logic and numerical puzzles. It is this side of his output that Wilson explores in a book that will interest Carroll afficionados and delight fans of recreational mathematics.

We also learn about Carroll himself, though Wilson sticks to the facts, never trying to delve too deeply into Carroll’s psyche. Speculation about his unhealthy interest in children is dismissed as “nonsense” (probably rightly), but we are still left with the impression of a man at odds with normal society, finding solace through playing the role of teacher. As well as making up stories for children, Carroll loved setting them conundrums – not always with happy outcomes. One girl, faced with the familiar puzzle of getting a fox, a goose and a bag of corn across a river, promptly burst into tears. Another child (son of the actress Ellen Terry) recalled being given the same problem, which Carroll demonstrated using matches and a matchbox, and found himself completely bored by the lengthy explanation. Carroll’s vice, it seems, was not paedophilia but pedantry. His talent was for combining it with whimsical humour.

Even in serious books about logic, Carroll could not resist crazy examples such as, “No fossil can be crossed in love; an oyster may be crossed in love; therefore oysters are not fossils”. He memorised strings of numbers by turning them into coded verse: “Two jockeys to carry made that racer tarry” stood for the logarithm of 2. Carroll considered writing a book called Logarithms by lightning to explain his technique, by means of which he extracted the 13th root of 87654327 in his head in nine minutes flat – but like so many of his projects, it never materialised.

Intriguingly, Carroll seems to have had an obsession with the number 42, long before Douglas Adams got hold of it. Alice’s Adventures in Wonderland has 42 illustrations, and Alice’s incorrect multiplication after she falls down the rabbit-hole makes sense in a sequence of number bases ending with 42.

For the general reader, this book may delve just a little too deeply into the mathematics of voting systems and matrix determinants, but teachers might find ideas for the classroom, perhaps after translating Carroll’s nineteenth-century prose into the language of Harry Potter. They should bear in mind, though, what Carroll himself wrote, after reducing the little girl to tears. “That was a lesson to me about trying children with puzzles.”