  We report progress on a program of gravitational physics experiments using
cryogenic torsion pendula undergoing large-amplitude torsion oscillation. This
program includes tests of the gravitational inverse square law and of the weak
equivalence principle. Here we describe our ongoing search for
inverse-square-law violation at a strength down to $10^{-5}$ of standard
gravity. The low-vibration environment provided by the Battelle Gravitation
Physics Laboratory (BGPL) is uniquely suited to this study.
