  Based on a tentative interpretation of gravity as a pressure force, a scalar
theory of gravity was previously investigated. It assumes gravitational
contraction (dilation) of space (time) standards. In the static case, the same
Newton law as in special relativity was expressed in terms of these distorted
local standards, and was found to imply geodesic motion. Here, the formulation
of motion is reexamined in the most general situation. A consistent Newton law
can still be defined, which accounts for the time variation of the space
metric, but it is not compatible with geodesic motion for a time-dependent
field. The energy of a test particle is defined: it is constant in the static
case. Starting from 'dust', a balance equation is then derived for the energy
of matter. If the Newton law is assumed, the field equation of the theory
allows to rewrite this as a true conservation equation, including the
gravitational energy. The latter contains a Newtonian term, plus the square of
the relative rate of the local velocity of gravitation waves (or that of
light), the velocity being expressed in terms of absolute standards.
