Arthur Cayley (1821-1895) was a key figure in the creation of modern algebra. He studied mathematics at Cambridge, qualified as a lawyer, and published about 250 mathematical papers during his fourteen years at the Bar. In 1863 he became the first Sadleirian Professor of Pure Mathematics at Cambridge, where he continued to publish at a phenomenal rate on nearly every aspect of the subject, his most important work being in matrices, geometry and abstract groups. In 1883 he became president of the British Association for the Advancement of Science. Publication of his Collected Papers - 967 papers in 13 volumes plus an index volume - began in 1889 and was completed after his death (while this volume was in the press) under the editorship of his successor in the Sadleirian Chair. This volume contains 70 papers published mostly between 1871 and 1873, as well as a 36-page obituary of the author.