The various metrical geometries, both Euclidean and non-Euclidean, are discussed, and Euclidean geometry is shown to be a special case of the general projective metrical geometry.

P. O. Bell, A Study of the Projective Differential Geometry of Surfaces by Means of a Modified Tensor Analysis, Transactions of the American Mathematical Society, Vol. 60, No. 1 (Jul., 1946), pp.

THE new edition of this valuable work differs so widely from the older ones, with many changes and additions, and more than twice the original number of examples, that it is almost a new book ...