  (abridged) Steidel & Sargent (1991a) found that the spectra of the components
of the close quasar pairs Q1634+267A,B and Q2345+007A,B were in each case
remarkably similar but that individual broad emission lines due to Ly_alpha, Si
IV, C IV, and C III] exhibited differences in profile or equivalent width
between the A and B components. If the A and B components of these objects
result from gravitational lensing of a single QSO, the difference in light
travel time for the two images is roughly 1 year for both pairs. Accordingly,
the authors suggested that observations of the spectra of single QSOs would
reveal similar changes in emission line profiles and equivalent widths on a
time scale of a year or less. In order to test Steidel & Sargent's hypothesis,
we obtained in 1992 high quality spectra of 30 quasars with z(em) ~ 1 selected
from the brighter QSOs in the sample of Steidel & Sargent (1991b), which those
authors had observed in 1989-90. We find that the spectra from the two epochs
are remarkably similar for all QSOs, except for overall changes in fluxes and
minor differences in continuum shape which are probably artifacts introduced by
the observing procedures. However, there are also changes in the equivalent
widths or shapes of the stronger emission lines on rest-frame time scales of
1-1.5 years in about two thirds of the QSOs. These observations, therefore,
support the notion that the spectra of the components in lensed QSOs need not
be exactly identical. Moreover, it should be expected that any differences
between the components in such systems should change with time.
