Histograms of Q/I (solid) and U/I (dashed) for the 5250.22 Å line, which are sampled along the spectrograph slit for the two Stokes spectra illustrated in Figs. 4 and 5. The measured quantity is the difference between the π component and the average of the two σ components. The error bars for a single pixel are indicated (with asterisk representing Q/I, cross U/I). While the U/I distributions are symmetric around zero, the Q/I distributions are skewed in favor of horizontal fields in the upper panel and in favor of vertical fields in the bottom panel.