Abridgment of studies on sparking in air

Sparking voltages and gradients in air between spheres of unequal diameters and between two cylinders placed with their axes perpendicular to each other in space (called cross-cylinders) have been determined. Complete tables giving the coefficients of gradient corresponding to any given spacing and radii, have been tabulated, the formulas used being those of Kirchhoff and Russell. For cross-cylinders, an approximate formula has been developed. In the theoretical discussions, the more definite form of the theory of ionization by collision as given by Bergen Davis has been extended to the spheregap and a relation has been deduced to account for the variation of the sparking gradient as investigated in the first part of this work, which is in substantial agreement with those found by F. W. Peek, A. Russell and others.