WE much regret to record the death on March 10, at the age of fifty-six years, of Prof. John F. Hayford, whose passing has been the occasion of appreciative accounts of his life and work in several American scientific journals. John Fillimore Hayford was trained as a civil engineer at Cornell University and was appointed computer to the United States Coast and Geodetic Survey. During this time he served on the International Boundary Commission of the United States and Mexico. In 1895 he went to Cornell University as an instructor in civil engineering, but in 1898 he returned to the Coast and Geodetic Survey, where he remained as inspector of geodetic work and chief of the computing division until 1909. In that year he went to Northwestern University, Illinois, as director of the newly organised College of Engineering. While there he investigated on behalf of the Carnegie Institution of Washington the problem of the surface levels of the Great Lakes and the causes of their fluctuations. Hayford is best known, however, for his computation of the dimensions of the earth, or the Hayford spheroid, based on the theory of isostasy, which was accepted at the recent Madrid meeting of the International Geodetic and Geophysical Union. His work on isostasy was also acknowledged last year by the award of the Victoria Medal of the Royal Geographical Society.