  We obtain estimates for the number of integral solutions in large balls, of
inequalities of the form $|Q(x, y)| < \epsilon$, where $Q$ is an indefinite
binary quadratic form, in terms of the Hurwitz continued fraction expansions of
the slopes of the lines on which $Q$ vanishes. The method is based on a coding
of geodesics on the modular surface via Hurwitz expansions of the endpoints of
their lifts in the Poincare half-plane.
