  Theory and experiment on the London moment is reviewed. A simple mathematical
model is motivated and then used to study the responses of a spherical
superconductor to an external field and to rotation. It reveals a connection
between perfect diamagnetism (Meissner effect) and the London moment. In the
model neither of these are exact but the deviation from B=0 internal field in
the former and from $B=(2mc/e)\Omega$ in the latter case is described by the
same dimensionless parameter. Apart from its pedagogical values the model might
throw some light on the controversy surrounding the correction to the London
moment.
