  We study the large $N$ limit of an interacting \td\ matrix field theory,
whose perturbative expansion generates the sum over planar random graphs
embedded in two dimensions. In the \lc\ quantization the theory possesses
closed string excitations which become free as $N\to\infty$. If the
longitudinal momenta are discretized, then the calculation of the free string
spectrum reduces to finite matrix diagonalization, the size of the matrix
growing as the cut-off is removed. Our numerical results suggest that, for a
critical coupling, the \lc\ string spectrum becomes continuous. This would
indicate the massless dynamics of the Liouville mode of \td\ gravity, which
would constitute a {\it third} dimension of the string theory.
