  The conductance through two quantum dots in series is studied using general
qualitative arguments and quantitative slave-boson mean-field theory. It is
demonstrated that measurements of the conductance can explore the phase diagram
of the two-impurity Anderson model. Competition between the Kondo effect and
the inter-dot magnetic exchange leads to a two-plateau structure in the
conductance as a function of gate voltage and a two or three peak structure in
the conductance vs. inter-dot tunneling.
