  In this paper we consider the billiard flow in the exterior of several (at
least three) balls in $\R^3$ with centres lying on a plane. We assume that the
balls satisfy the no eclipse condition (H) and their radii are small compared
to the distances between their centres. We prove that with respect to any Gibbs
measure on the non-wandering set of the billiard flow the two positive Lyapunov
exponents are different: $\lambda_1 > \lambda_2 > 0$.
