If the radius R of curvature of the path of the same rays is observed in a magnetic field of strength H perpendicular to the rays,
e V
--- = ----
m HR
Combining these two equations we get
A difficulty arose in identifying the part of the complex pencil of rays for which the electric and magnetic deviations were determined. Becquerel estimated that the value of HR for the rays deflected by the electric field was about 1600 C.G.S. units. Thus
u = 1·6 × 1010 cms. per second,
and
e