  We present the results of a GHRS program to monitor the absorption lines in
the spectrum of the Seyfert 1 galaxy NGC 4151 caused by outflowing gas from the
nucleus. Although we see subtle changes over the four year period in the GHRS
spectra of the broader of the absorption features, the wavelength constancy of
all the features is remarkable. The limits on the secular acceleration suggest
that either (1) The absorbing clouds are well beyond the broad emission line
region, or (2) The clouds are experiencing significant drag from an intercloud
medium. The exception to this constancy occurred during one of the epochs of
our monitoring when a broad shallow C IV trough appeared at an outflow velocity
of 3750 km/s and then subsequently disappeared.
