Diagram of the Causes of Mortality in the Army in the East - companion plate (David Rumsey 10563.005)
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
Area, not bar length, carries the comparison, and every wedge shares one vertex and one scale, so any month can be weighed against any other month and against the benchmark without reading a single number. The Manchester circle is the persuasive move: it imports a standard the audience already accepts as shameful, then shows the army sitting outside it. Drawing both years at one scale on one sheet turns the fall after sanitary reform into shrinking ink rather than a claim in prose. The key is written as plain explanation in a human hand, which defuses the objection that the reader is being conned by an unfamiliar chart form.
Steal this when
Use this when your number only becomes damning next to an outside yardstick the audience already fears, and when a before and after at one honest scale can do the arguing for you. Import the benchmark as a fixed shape, then show your data overflowing it.