  We show that if Maxwell's equations are expressed in a form independent of
specific units, at least three Galilean limits can be extracted. The electric
and magnetic limits can be regarded as nonrelativistic limits because they are
obtained using the condition $|\bf{v}| \ll c$ and restrictions on the
magnitudes of the sources and fields. The third limit is called the
instantaneous limit and is introduced by letting $c\to \infty$. The electric
and instantaneous limits have the same form, but their interpretation is
different because the instantaneous limit cannot be considered as a
nonrelativistic limit. We emphasize the double role that the speed of light $c$
plays in Maxwell's equations.
