The differential elastic scattering cross sections of carbon, magnesium, aluminum, silicon, sulfur, copper, silver, tantalum, wolfram, lead, and bismuth for 340-Mev protons are measured as a function of the angle of scattering. The source of the 340-Mev protons is the external scattered deflected proton beam of the Berkeley 184-inch synchrocyclotron. The scattered protons are detected by a triple coincidence scintillation counter telescope whose detection threshold is set by copper energy attenuators placed between the last two transtilbene scintillators.The observed angular distributions are similar to the pattern observed in Fraunhofer diffraction of plane electromagnetic waves by an opaque disk. The details of the diffraction patterns indicate that the nuclei appear partially transparent to the 340-Mev protons.The observed patterns are found to be consistent with those predicted from elastic scattering of 83-Mev neutrons, indicating that the Coulomb forces are only important in changing the patterns at very small angles.An attempt is made to observe spin-dependent variations in the patterns from neighboring nuclei whose moments are known to differ appreciably. Within the statistics and resolution of the experiment no appreciable variations are detected.