In this paper we consider certain lattice sums which arise when a syst
em of line charges set in a compensating jelly of opposite charge inte
ract via the two-dimensional logarithmic potential. A lattice-limit di
scontinuity phenomenon, similar to that discovered by Borwein et al in
the three-dimensional case, is explored and a high-precision asymptot
ic method is described for the numerical computation of two-dimensiona
l lattice limits.