The methods previously described have been applied to a study of the elastic scattering of 4·2 MeV protons by deuterium, helium, nitrogen, oxygen, neon, argon, chlorine and bromine. The results obtained with deuterium and helium as the scattering gases are compared with those of other experimenters working with protons of different energies. The angular distributions of the protons elastically scattered by nitrogen and oxygen, together with the results for carbon obtained in previous measurements, can be simply described in terms of an
S
-component interacting with the Coulomb term in the formula for the scattered wave. Values are obtained in each case for the magnitude of the parameter which defines the amplitude and phase of the
S
-wave. The angular distribution of the protons inelastically scattered by neon has been investigated and evidence obtained for similar collision processes in experiments with argon and chlorine.