  We obtained over 90 hours of spectroscopic observations of four exoplanetary
systems with the Hobby-Eberly Telescope (HET). Observations were taken in
transit and out of transit, and we analyzed the differenced spectra---i.e., the
transmission spectra---to inspect it for absorption at the wavelengths of the
neutral sodium (\ion{Na}{1}) doublet at $\lambda\lambda5889, 5895$ and neutral
potassium (\ion{K}{1}) at $\lambda7698$. We used the transmission spectrum at
\ion{Ca}{1} $\lambda6122$---which shows strong stellar absorption but is not an
alkali metal resonance line that we expect to show significant absorption in
these atmospheres---as a control line to examine our measurements for
systematic errors. We use an empirical Monte Carlo method to quantity these
systematic errors. In a reanalysis of the same dataset using a reduction and
analysis pipeline that was derived independently, we confirm the previously
seen \ion{Na}{1} absorption in HD 189733b at a level of
$(-5.26\pm1.69)\times10^{-4}$ (the average value over a 12 \AA{} integration
band to be consistent with previous authors). Additionally, we tentatively
confirm the \ion{Na}{1} absorption seen in HD 209458b (independently by
multiple authors) at a level of $(-2.63\pm0.81)\times10^{-4}$, though the
interpretation is less clear. Furthermore, we find \ion{Na}{1} absorption of
$(-3.16\pm2.06)\times10^{-4}$ at $<3\sigma$ in HD 149026b; features apparent in
the transmission spectrum are consistent with real absorption and indicate this
may be a good target for future observations to confirm. No other results
(\ion{Na}{1} in HD 147506b and \ion{Ca}{1} and \ion{K}{1} in all four targets)
are significant to $\geq 3\sigma$, although we observe some features that we
argue are primarily artifacts.
