G. M. Bernstein, M. L. Fischer, and P. L. Richards Department of Physics, University of California Berkeley, California 94720, U. S. A. J. B. Peterson Department of Physics, Princeton University Princeton, New Jersey 08540, U. S. A. T. Timusk Department of Physics, McMaster University Hamilton, Ontario L8S 4M1 , Canada ABSTRACT. Recent measurements of the diffuse background at millimeter wavelengths indicate no departure from a Planck spectrum near the peak of the blackbody curve. Anisotropy measurements indicate no structure, at the 2% level, in the recently detected submillimeter excess. We...