Plan Showing the Ascertained Deaths from Cholera in Part of the Parishes of St James, Westminster and St Anne, Soho
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
The unit of analysis is the house, not the district, and drawing one mark per death against a real frontage is what makes a cluster impossible to argue with. Stacking the marks perpendicular to the street turns a count into a length the eye can compare along a row without any axis at all. The sheet then does something a plain dot map does not: it draws the competing hypotheses onto the same ground, the dated sewers as distinct line types and the plague pit labelled as erroneously supposed, so the rival explanation is shown failing rather than merely denied. Separating residents from non-residents in the key protects the count from the obvious objection that the dead were passing through.
Steal this when
Use this when a cause is disputed and you need to settle it with placement rather than rhetoric: plot the incidents at their true locations and overlay every candidate explanation on the same ground. Drawing the rival theory in and letting it visibly fail is far stronger than leaving it out.