## Abstract

The great secret has already been revealed that this mysterious symbol∫, which is after all only a long *S*, merely means “the sum of”, or “the sum of all such quantities as”. It therefore resembles that other symbol Σ (the Greek *Sigma*), which is also a sign of summation. There is this difference, however, in the practice of mathematical men as to the use of these signs, that while Σ is generally used to indicate the sum of a number of finite quantities, the integral sign ∫ is generally used to indicate the summing up of a vast number of small quantities of infinitely minute magnitude, mere elements in fact, that go to make up the total required. Thus ∫*dy* = *y*, and ∫*dx* = *x*.

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## Copyright information

© Martin Gardner 1998