Cambridge.
_The Number Nine_ (Vol. viii., p. 149.).--The property of numbers
enunciated and illustrated by MR. LAMMENS resolves itself into two.
1. If from any number above nine be subtracted the number expressed by
writing the same digits backwards, the remainder is divisible by nine.
2. If the number nine measure a given number, it measures the sum of its
digits.
As the latter is proved in most elementary books on Algebra, I confine my
proof to the former.