The Same Mortars, a Step to the Right

The second of Cooley's two mortar negatives: the same battery, the same crews, the camera moved a little and the group re-formed — more men in the frame, the standing watcher still on the crest.

Two plates of one subject are how a working photographer insured himself in 1865: wet collodion failed often, and a second exposure cost only another plate. That both survive lets a viewer do what the photographer could not — compare, and see who moved.