  We consider constraints on the amplitude of mass fluctuations in the
universe, sigma_8, derived from two simple observations: the present number
density of clusters and the amplitude of their correlation function. Allowing
for the possibility that the primordial fluctuations are non-gaussian
introduces a degeneracy in the value of sigma_8 preferred by each of these
constraints. However, when the constraints are taken together this degeneracy
is broken, yielding a precise determination of sigma_8 and the degree of
non-gaussianity for a given background cosmology. For a flat, Omega_m=1
universe with a power spectrum parameterized by a CDM shape parameter
Gamma=0.2, we find that the perturbations are consistent with a gaussian
distribution with sigma_8=0.49(+0.08-0.07) (95% limits). For some popular
choices of background model, including the favored low matter density models,
the hypothesis that the primordial fluctuations are gaussian is ruled out with
a high degree of confidence.
