  We attempt to solve the magnetic structure of the gadolinium analogue of
`spin-ice', using a mixture of experimental and theoretical assumptions. The
eventual predictions are essentially consistent with both the Mossbauer and
neutron measurements but are unrelated to previous proposals. We find two
possible distinct states, one of which is coplanar and the other is fully
three-dimensional. We predict that close to the initial transition the
preferred state is coplanar but that at the lowest temperature the ground-state
becomes fully three-dimensional. Unfortunately the energetics are consequently
complicated. There is a dominant nearest-neighbour Heisenberg interaction but
then a compromise solution for lifting the final degeneracy resulting from a
competition between longer-range Heisenberg interactions and direct dipolar
interactions on similar energy scales.
