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(abridged) Steidel & Sargent (1991a) found that the spectra of the componentsof the close quasar pairs Q1634+267A,B and Q2345+007A,B were in each caseremarkably similar but that individual broad emission lines due to Ly_alpha, SiIV, C IV, and C III] exhibited differences in profile or equivalent widthbetween the A and B components. If the A and B components of these objectsresult from gravitational lensing of a single QSO, the difference in lighttravel time for the two images is roughly 1 year for both pairs. Accordingly,the authors suggested that observations of the spectra of single QSOs wouldreveal similar changes in emission line profiles and equivalent widths on atime 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 selectedfrom the brighter QSOs in the sample of Steidel & Sargent (1991b), which thoseauthors had observed in 1989-90. We find that the spectra from the two epochsare remarkably similar for all QSOs, except for overall changes in fluxes andminor differences in continuum shape which are probably artifacts introduced bythe observing procedures. However, there are also changes in the equivalentwidths or shapes of the stronger emission lines on rest-frame time scales of1-1.5 years in about two thirds of the QSOs. These observations, therefore,support the notion that the spectra of the components in lensed QSOs need notbe exactly identical. Moreover, it should be expected that any differencesbetween the components in such systems should change with time.

Temporal Changes in Quasar Broad Emission Line Profiles and the Gravitationally Lensed Nature of Q1634+267A,B and Q2345+007A,B