Observed oscillations of the sun with five to ten minute periods are a predicted source of gravitational radiation with a strain at the earth of approximately 10^-26. In the transition zone (2 pi r approximately lambda ; inner part of the solar system) the dynamical character of the gravitational field emerges as a phase shift of the oscillatory tidal force relative to the phase of the solar oscillations. The phase shift is sensitive to the spin of the gravitational field, suggesting a test of the spin composition of relativistic gravity. The author investigates and compares the transition-zone phase shift for three pure-spin theories: Nordstrom's theory (a spin-0 theory), a vector theory analogous to electromagnetism (spin-1), and general relativity (spin-2); and for Jordan-Brans-Dicke theory in which gravity is a mixture of spins 2 and 0. The solar gravitational waves might be detectable, near the turn of the century, by optically linked gravitational antennae flown in space. Such detection would permit a direct measure of the spin composition of relativistic gravity.