  A description is presented of apparatus used to carry out an experimental
search for an electric dipole moment of the neutron, at the Institut
Laue-Langevin (ILL), Grenoble. The experiment incorporated a cohabiting
atomic-mercury magnetometer in order to reduce spurious signals from magnetic
field fluctuations. The result has been published in an earlier letter; here,
the methods and equipment used are discussed in detail.
