Observations of the Small Magellanic Cloud using the Energetic Gamma Ray Experiment Telescope on the Compton Observatory yield an upper limit (95% confidence) for gamma-ray emission >100 MeV of 0.5×${10}^{\mathrm{-}7}$ photon/${\mathrm{cm}}^2$ s. The expected flux if the cosmic rays are universal rather than galactic in origin, is (2.4-0.5)×${10}^{\mathrm{-}7}$ photon/${\mathrm{cm}}^2$ s, only a third of which arise from cosmic ray electron interactions. Hence, the bulk of the cosmic ray energy density is almost certainly not metagalactic, and therefore galactic in origin.

• Received 4 September 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.127