  We present a new test for a possible Mach-Sciama dependence of the
Gravitational constant G. According to Ernst Mach (1838-1916), the
gravitational interaction depends on the distribution of masses in the
universe. A corresponding hypothesis of Sciama (1953) on the gravitational
constant, $c^2/G = \sum m_i/r_i$, can be tested since the elliptic earth orbit
should then cause minute annual variations in G. The test is performed by
analyzing the gravity signals of a network of superconducting gravimeters (SG)
which reach a precision of $10^{-10} m/s^2$. After reducing the signal by
modelling tidal, meteorologic and geophysical effects, no significant evidence
for the above dependence is found.
