So far we have only considered the case of a zero magnetic field. In a weak magnetic field (2lcycl > L) the situation is rather complicated. As discussed in detail in Ref.329, there are two competing effects in weak fields: On the one hand, the deflection of the electron beam by the Lorentz force reduces the direct transmission probability, with the effect of decreasing the series conductance. On the other hand, the magnetic field enhances the indirect transmission, with the opposite effect. The result is an initial decrease in the series conductance for small magnetic fields in the case of strong collimation and an increase in the case of weak collimation. This is expected to be a relatively small effect compared with the effects at stronger fields that are discussed below.