Album de Statistique Graphique - Nombre Quotidien de Trains sur le Reseau du Midi (Service a partir du 15 Octobre 1896). 1897-1898. Grave et Imprime par A. Simon, Paris [13188.018]
The pattern
This still is filed under Data as proof.
Define
A chart, map, or count that is the argument, not an illustration next to the argument.
Mechanism
Sighted evidence. The reader is asked to believe their eyes: a bar, a share, a spread on a map.
Verdict
The claim is comparative or quantitative and the figure can be read without a caption doing the sell.
Why it works
Width for volume plus internal stratification for mix is the same decomposition used on the waterway plates, applied to a timetable, and it answers two operating questions with one mark: how loaded is this section, and with what. Erasing the basemap entirely - no coastline detail, no towns beyond the stations - lets the network's own shape carry the geography, which is legitimate because the audience knows the line. The black freight layer reading as a shadow along the underside of each strap is a colour decision that lets goods traffic be seen and ignored at will, since it is the one class an inspector might want to subtract.
Steal this when
Reach for this when you are showing load on a fixed topology - a route, a pipeline, a process with stages - and the mix of what flows matters as much as the amount. Strip the background to nothing, band the line, and put the category key as swatches rather than prose.