  This is a missing chapter from Hans Magnus Enzensberger's mathematical
adventure The Number Devil (Henry Holt and Company, New York, 1997). In the
book, a math-hating boy named Robert is visited in his dreams by the clever
Number Devil, who teaches him to love all things numerical. However, we all
forget our dreams from time to time. Here is one adventure that Enzensberger
overlooked, where the Number Devil introduces Robert to geometry not-of-Euclid,
great circles, parallel transport, the pendulum of Foucault, and the genius of
Euler.
