  We approximate a 2D Ising spin glass by tiling an infinite square lattice
with large identical unit cells. The interactions within the unit cell are
random. Each such sample shows one or more critical points. We examine the
scaling of the critical temperatures with unit cell size. Due to chaos, the
correlations between unit cells can change sign with changing temperature. We
also examine the scaling of this chaos. This chaos causes many samples to have
multiple phase transitions, because the interaction between adjacent unit cells
changes sign within the ordered phases.
