No piece of matter can, under ordinary circumstances, contain, in any form, enough energy to provide cosmic ray energies for its particles. However, by evolving a magnetic field, matter can provide a means by which a small amount of ionized matter shot from the region of the magnetic field can, by carrying the magnetic field with it, store up an amount of energy which, estimated per particle, is enormous and of cosmic-ray magnitude. This energy has, in the last analysis, been stolen from a large amount of matter by the small amount. The electromagnetic theorem having to do with the relation between rate of change of electromagnetic energy and rate of doing work on the particles shows that, under suitable conditions, all of the electromagnetic energy, if destroyed, will go into kinetic energy of the particles. The matter is illustrated by considering a ring of gas shot out from a region containing a magnetic field. The ring carries the flux with it, and the corresponding electromagnetic energy becomes destroyed by the subsequent motion of the particles to infinity, to be thought of roughly as a result of the repulsion of the current elements, and more exactly as a result of the electrodynamic forces operating on free particle motion.