  We analyze the sensitivity of a network of interferometer gravitational-wave
detectors to the gravitational-wave stochastic background, and derive the
dependence of this sensitivity on the orientations of the detector arms. We
build on and extend the recent work of Christensen, but our conclusion for the
optimal choice of orientations of a pair of detectors differs from his. For a
pair of detectors (such as LIGO) that subtends an angle at the center of the
earth of $\,\alt 70^\circ$, we find that the optimal configuration is for each
detector to have its arms make an angle of $45^\circ$ (modulo $90^\circ$) with
the arc of the great circle that joins them. For detectors that are farther
separated, each detector should instead have one arm aligned with this arc. We
also describe in detail the optimal data-analysis algorithm for searching for
the stochastic background with a detector network, which is implicit in earlier
work of Michelson. The LIGO pair of detectors will be separated by $\sim 3000
\, {\rm km}$. The minimum detectable stochastic energy-density for these
detectors with their currently planned orientations is $\sim 3\%$ greater than
what it would be if the orientations were optimal.
