A generally covariant classical model for gravity, which in the limit of weak fields is essentially equivalent to Fujii's massive dilaton theory, is obtained when the invariance under a group of space-time-dependent geometry-preserving mass-unit transformations of a scalar-tensor theory is broken by ascribing a mass to the scalar field. The experimental consequences are discussed.

• Received 9 May 1972

DOI:https://doi.org/10.1103/PhysRevLett.29.137