  A theory containing both electric and magnetic charges is formulated using
two vector potentials, $A_{\mu}$ and $C_{\mu}$. This has the aesthetic
advantage of treating electric and magnetic charges both as gauge charges, but
it has the experimental disadvantage of introducing a second massless gauge
boson (the ``magnetic'' photon) which is not observed. This problem is dealt
with by using the Higgs mechanism to give a mass to one of the gauge bosons
while the other remains massless. This effectively ``hides'' the magnetic
charge, and the symmetry associated with it, when one is at an energy scale far
enough removed from the scale of the symmetry breaking.
