  A new 8-dim conformal gauging solves the auxiliary field problem and
eliminates unphysical size change from Weyl's electromagnetic theory. We derive
the Maurer-Cartan structure equations and find the zero curvature solutions for
the conformal connection. By showing that every one-particle Hamiltonian
generates the structure equations we establish a correspondence between phase
space and the 8-dim base space, and between the action and the integral of the
Weyl vector. Applying the correspondence to generic flat solutions yields the
Lorentz force law, the form and gauge dependence of the electromagnetic vector
potential and minimal coupling. The dynamics found for these flat solutions
applies locally in generic spaces. We then provide necessary and sufficient
curvature constraints for general curved 8-dimensional geometries to be in 1-1
correspondence with 4-dimensional Einstein-Maxwell spacetimes, based on a
vector space isomorphism between the extra four dimensions and the Riemannian
tangent space. Despite part of the Weyl vector serving as the electromagnetic
vector potential, the entire class of geometries has vanishing dilation,
thereby providing a consistent unified geometric theory of gravitation and
electromagnetism. In concluding, we discuss the observability of the extra
dimensions.
