CH⁺ vs. CH (left) and CN vs. CH (right). Circles denote LMC sight lines; triangles denote SMC sight lines; all other symbols are for Galactic sight lines (see Fig. 8). The solid lines show weighted and unweighted fits to the Galactic data (omitting "discrepant" sight lines). The dotted line in the right‐hand plot shows the values predicted by "translucent cloud" models T1–T6 of van Dishoeck & Black (1989).