SummaryThe Townsend-Huxley swarm technique for electrons is analysed in detail. Particular emphasis is placed on boundary conditions, and those conditions appro· priate to the Huxley-Crompton empirical relationship are derived and explained. Secondary emission at the electrodes due to both positive ion and photon bombardment is also taken into account. The principal result is an integral expression for the current ratio received at the circumferentially split anode. From this may be deduced the energy factor kl and the secondary emission coefficients. It is shown that it is possible to distinguish between positive ion and photon secondary emission and to determine the associated coefficients simultaneously in the stationary state. Highly accurate conditions for electrical breakdown are also obtained, secondary emission at the anode being taken into account.

The distribution of ions formed by attachment of electrons diffusing through a gas is solved exactly, and the results compared with an approximate calculation given earlier by Huxley. The corrections to the approximate results are inside the present experimental error, and so confirm the satisfactory agreement with experiment already obtained.

SummaryA paradox in the theory of the magnetic effects of stationary currents is discussed and is shown to arise from the neglect of a singular magnetic field which is required to complete the equivalence of magnetic shells and current loops.