  The subject of low energy photon-photon scattering is considered in arbitrary
dimensional space-time and the interaction is widened to include scattering
events involving an arbitrary number of photons. The effective interaction
Lagrangian for these processes in QED has been determined in a manifestly
invariant form. This generalisation resolves the structure of the weak-field
Euler-Heisenberg Lagrangian and indicates that the component invariant
functions have coefficients related, not only to the space-time dimension, but
also to the coefficients of the Bernoulli polynomial.
