We report the detection of differential gas column densities in three gravitational lenses, MG?0414+0534, HE?1104-1805, and PKS?1830-211. Combined with the previous differential column density and extinction measurements in B1600+434 and Q2237+0305, we probe the dust-to-gas ratio of a small sample of cosmologically distant normal galaxies. We obtain an average dust-to-gas ratio of E(B - V)/NH = (1.4 ± 0.5) × 10-22 mag cm2 atoms-1, with an estimated intrinsic dispersion in the ratio of 40%. This average dust-to-gas ratio is consistent with the average Galactic value of 1.7 × 10-22 mag cm2 atoms-1, and the estimated intrinsic dispersion is also consistent with the 30% observed in the Galaxy.
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