Informal report describing a suggestion for a way to detect secondary particles produced by the collision of protons at high center-of-mass energies: The present note has as its purpose to suggest a new 4π geometry concept for detecting the reaction products, which eases some of the problems of high-multiplicity events. The device could be used as a stand-alone detector in some experiments, but basically is conceived as a useful adjunct to a calorimeter type device. I call it the Porcupine for reasons soon to be apparent" (p. 1).