  A new relaxation mechanism is shown to arise from overdamped two-level
systems above a critical temperature $T^*\approx 5$ K, thus yielding an
explanation for experimental observations in dielectric glasses in the
temperature range between $T^*$ and the relaxation peak at 50 K. Using the
distribution function of the tunnelling model for the parameters of the
two-level systems, both the linear decrease of the sound velocity and the
linear increase of the absorptionup to the relaxation maximum, are
quantitatively accounted for by our theory.
