  The theory on M_4 x Z_2 geometry is applied to the Einstein gravity to yield
the Brans-Dicke theory on M_4 geometry. The geometrical meaning and the
relation between the curvatures and the torsions are clarified. The
cosmological constant is also introduced into the pure Einstein action on M_4 x
Z_2 in order to determine the explicit form of the cosmological term in the
Brans-Dicke theory on M_4 geometry.
