The development of the spark discharge. II

Abstract An account has already been given of observations made with a rotating-film camera in the study of the electric spark in air at atmospheric pressure (Aliibone and Meek 1938; Allibone 1938). The object of the present paper is to extend the previous results, and in particular to describe the development of the spark in air at reduced pressures, viz. from 76 to 0.3 cm. fig. The high-speed cathode-ray oscillograph has been used in conjunction with the rotating camera to enable voltage and current oscillograms to be made. Various phenomena, previously observed by oscillographic methods only, have now been shown to be associated with definite processes in the discharge mechanism.