Internal friction measurements were made above 6 mK for a sample of a-SiO2
at 90 kHz using the torsional oscillator method. Since the internal frictio
n is rather sensitive to nonlinear effects, strain amplitudes smaller than
epsilon(A) < 10(-8) were used to remain in the linear regime. Excellent agr
eement with the prediction of the Tunneling Model was observed. (C) 2000 El
sevier Science B.V. All rights reserved.