Correlation plots of data for the lines of sight in samples 1, 2, and 4. The error bars show 1 σ measurement errors. The line shown in each panel is an unweighted least‐squares fit that minimizes the residuals in the ordinate. (a) Correlation of 100 μm data with H I column density. (b) Correlation of extinction‐corrected Hα intensity (for samples 1 and 2) or H II column density (for sample 4) with H I column density. (c) Correlation of residuals from the fit of (a) with residuals from the fit of (b).