William Kingdon Clifford published the paper defining his "geometric
algebras" in 1878, the year before his death. Clifford algebra is a
generalisation to n-dimensional space of quaternions, which Hamilton
used to represent scalars and vectors in real three-space: it is also a
development of Grassmann's algebra, incorporating in the fundamental
relations inner products defined in terms of the metric of the space. It
is a strange fact that the Gibbs- Heaviside vector techniques came to
dominate in scientific and technical literature, while quaternions and
Clifford algebras, the true associative algebras of inner-product
spaces, were regarded for nearly a century simply as interesting
mathematical curiosities. During this period, Pauli, Dirac and Majorana
used the algebras which bear their names to describe properties of
elementary particles, their spin in particular. It seems likely that
none of these eminent mathematical physicists realised that they were
using Clifford algebras. A few research workers such as Fueter realised
the power of this algebraic scheme, but the subject only began to be
appreciated more widely after the publication of Chevalley's book, 'The
Algebraic Theory of Spinors' in 1954, and of Marcel Riesz' Maryland
Lectures in 1959. Some of the contributors to this volume, Georges
Deschamps, Erik Folke Bolinder, Albert Crumeyrolle and David Hestenes
were working in this field around that time, and in their turn have
persuaded others of the importance of the subject.