| Citation | Distinguished for his contributions to the physics of elementary particles and nuclear interactions at extreme energies such as may be observed in cosmic radiation. Perkins made the first observation of the nuclear capture of a negative pi-meson. He has made a series of brilliant studies of nuclear transmutations in a very wide range of energy, from 10 [to the power of] 2 BeV to 10 [to the power of 6] BeV. In this field his contributions, with Fowler, to the interpretation of electron-photon cascades in lead-emulsion stacks in terms of particle production at ultra high energies are particularly noteworthy. Perkins has also made valuable contributions to technical methods for measuring the ionisation produced by particles in photographic emulsion. |