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Breakdown characteristics in a crossed magnetic field are analysed with the aid of the equivalent-reduced-electric-field (e.r.e.f.) concept. Individual contributions to the secondary ionisation process can be separated, and, in argon, the contribution is mainly due to photons and/or metastable atoms; in ethane, it is wholly due to positive ions; and in hydrogen and nitrogen, a mixture of these two processes exists. For the first time, Somerville's formula for electron recapture by the cathode on account of the crossed magnetic field is shown to work, and also Haydon's suggestion that the secondary ionisation process by photons in subject to the e.r.e.f. principle is substantiated. There is evidence to suggest that secondary electrons leave the cathode under positive-ion bombardment with almost zero energy, whereas, under photon and/or metastable action, the secondary electrons are considered to have a substantial escape velocity which, it is calculated, reduces their probability of being recaptured by the cathode. The use of e.r.e.f. allows successful analysis and prediction of breakdown characteristics in a crossed magnetic field, and the whole subject is shown to be soundly based and to form a harmonious and sell-consistent topic.