  We present measurements of the magnetic moment and specific heat of single
crystals of the spin-chain insulator, Pr3RuO7. The susceptibility indicates
that three-dimensional antiferromagnetic order sets in at TN = 54 K, with spin
polarization approximately along the chain direction, but the susceptibility
anisotropy above TN indicates that the intrachain interactions are
predominantly ferromagnetic while the interchain interactions are
antiferromagnetic. This competition presumably gives rise to the observed
metamagnetic behavior for applied fields along the polarization direction. The
specific heat anomaly at TN is unusually mean-field in shape, with magnitude
indicating that the transition involves mostly ordering of the ruthenium
moments. A Schottky-like anomaly at low temperature may be due to praesodynium
ions ordering in the effective field established at TN.
