  We study the energy and momentum of an isolated system in the tetrad theory
of gravitation, starting from the most general Lagrangian quadratic in torsion,
which involves four unknown parameters. When applied to the static spherically
symmetric case, the parallel vector fields take a diagonal form, and the field
equation has an exact solution. We analyze the linearized field equation in
vacuum at distances far from the isolated system without assuming any symmetry
property of the system. The linearized equation is a set of coupled equations
for a symmetric and skew-symmetric tensor fields, but it is possible to solve
it up to $O(1/r)$ for the stationary case. It is found that the general
solution contains two constants, one being the gravitational mass of the source
and the other a constant vector ${\grave B_\alpha}$. The total energy is
calculated from this solution and is found to be equal to the gravitational
mass of the source. We also calculate the spatial momentum and find that its
value coincides with the constant vector ${\grave B_\alpha}$. The linearized
field equation in vacuum, which is valid at distances far from the source, does
not give any information about whether the constant vector ${\grave B_\alpha}$
is vanishing or not. For a weakly gravitating source for which the field is
weak everywhere, we find that the constant vector ${\grave B_\alpha}$ vanishes.
