  The lowest energy configurations for N equal charged particles confined to a
thin conducting disc have been investigated in detail up to N=160 and in
outline for further values up to N=500. For all values of N up to 160 the
particle configurations can be described in terms of concentric shells. The
number of perimeter particles p appears to be simply related to N and to the
mean radius of the outermost internal shell. Justification for these relations
is obtained from a simple model based on the well-known distribution of
continuous charge on a conducting disc.
