Trade Secrets

To the Editors:

Martin Gardner’s review [NYR, March 15] of Steven Smith’s The Great Mental Calculators quotes from a lecture given by Aitken on the art of mental calculation.

I knew Aitken—a most charming and modest man—when he and I were colleagues at Edinburgh University. Round about 1958—i.e., later than his lecture—he gave me an explanation of his remarkable calculating powers which was much clearer than the extract quoted from his lecture. He said that his powers were entirely rational and were based on two factors: (1) a compendious knowledge of the properties of all the natural numbers up to many thousands, and (2) the ability to carry out any necessary interpolation between the natural numbers by doing a rapid Taylor series expansion in his head.

K.G. Denbigh

Chelsea College, London University

London, England