  This is a preliminary version of a formal proposal by the 3M collaboration to
construct a megaton, modular, multipurpose (3M) neutrino detector for a program
of experiments in neutrino physics. The detector components will be located in
chambers approximately 7000 ft below the Earth's surface in the Homestake Mine
at Lead, South Dakota, to carry out experiments on neutrino oscillations
directed toward the principal experimental goal of the program, viz., the issue
of CP-invariance violation in the lepton sector of elementary particles, an
issue that has been the subject of study in the quark sector for several
decades. The principal physics goal of this program also requires a moderately
intense neutrino beam from an accelerator located a long distance from the
detector array, such as the 2540 km distance of BNL from Homestake. The
construction plan for that neutrino beam is at http://nwg.phy.bnl.gov/.
  Other experimental searches that do not require the accelerator-generated
beam can be carried out with the 3M detector independently of and at the same
time as the neutrino oscillation and CP-invariance violation measurements are
in progress. They are searches for Proton Decay, UHE Neutrinos, and Supernovae
Neutrinos.
