Mechanism of the spark breakdown

THE ELECTRIC SPARK was first treated quantitatively by J. S. Townsend in 1903.¹ Since that time, the interpretation of the physical processes that lead to breakdown has been modified radically.^2–7 It is the purpose of this report to trace the development of the present concepts of the physical processes which lead to the d-c electric spark, and to discuss to what extent these processes are understood.