William Frend (1757–1841) was a British clergyman, an active social reformer, and a sometime mathematician. Frend contributed to some of the algebra tracts published by Francis Maseres and shared his mathematical discomfort on the concept of negative numbers. In his *The Principles of Algebra* (1796), Frend denied the existence of these numbers. The controversy over this claim helped force a more formal, logical examination of the foundations of the real numbers. The established “Laws of Arithmetic” eventually welcomed the negative numbers into mathematics.

The “Table of Contents” for Frend’s *Algebra*.

In 1805, Frend published *Tangible Arithmetic* in which he introduced an “arithmetical toy” to assist in the learning of the subject.

*T**hese** images from its George Arthur Plimpton Collection are presented through the courtesy of the Columbia University Libraries.*

Index to Mathematical Treasures