  We investigate the class of ultralocal metrics on the configuration space of
canonical gravity. It is described by a parameter $\alpha$, where $\alpha=0.5$
corresponds to general relativity.
  For $\alpha$ less than a critical value the signature is positive definite,
while for all other values it is indefinite. We show that in the positive
definite case gravity becomes repulsive. From the primordial helium abundance
we find that $\alpha$ must lie between $0.4$ and $0.55$.
