Riis had for some time been wondering how to show the squalor of which he wrote more vividly than his words could express. He tried sketching, but was incompetent at this. Camera lenses of the 1880s were slow as was the emulsion of photographic plates; photography thus did not seem to be of any use for reporting about conditions of life in dark interiors. In early 1887, however, Riis was startled to read that "a way had been discovered to take pictures by flashlight. The darkest corner might be photographed that way." The German innovation, by Adolf Miethe and Johannes Gaedicke, flash powder was a mixture of magnesium with potassium chlorate and some antimony sulfide for added stability; the powder was used in a pistol-like device that fired cartridges. This was the introduction of flash photography.