CH vs. H₂. Circles and triangles denote LMC and SMC sight lines, respectively; filled symbols indicate detections of both species; open symbols indicate limits for one (or both) of the species. All other symbols denote Galactic sight lines (open squares are for Sco‐Oph; asterisks are for Orion Trapezium; smaller open diamonds are for other "discrepant" sight lines). The solid lines show weighted and unweighted fits to the Galactic data (with ﹩\mathrm{slopes}\,\sim 1.1﹩), for ﹩N( \mathrm{H}\,_{2}) \geq 10^{19}﹩ cm⁻² (omitting various "discrepant" sight lines). The dotted line shows the values predicted by "translucent cloud" models T1–T6 of van Dishoeck & Black (1989).