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. Recognizing the potential of the flash, Riis informed a friend, Dr. John Nagle, chief of the Bureau of Vital Statistics in the City Health Department who was also a keen amateur photographer. Nagle found two more photographer friends, Henry Piffard and Richard Hoe Lawrence, and the four of them began to photograph the slums. Their first report was published in the New York newspaper The Sun on February 12, 1888; it was an unsigned article by Riis which described its author as "an energetic gentleman, who combines in his person, though not in practice, the two dignities of deacon in a Long Island church and a police reporter in New York". The "pictures of Gotham's crime and misery by night and day" are described as "a foundation for a lecture called 'The Other Half: How It Lives and Dies in New York.' to give at church and Sunday school exhibitions, and the like." The article was illustrated by twelve line drawings based on the photographs. Riis and his photographers were among the first Americans to use flash photography. Pistol lamps were dangerous and looked threatening, and would soon be replaced by another method for which Riis lit magnesium powder on a frying pan. The process involved removing the lens cap, igniting the flash powder and replacing the lens cap; the time taken to ignite the flash powder sometimes allowed a visible image blurring created by the flash. Riis's first team soon tired of the late hours, and Riis had to find other help. Both his assistants were lazy and one was dishonest, selling plates for which Riis had paid. Riis sued him in court successfully. Nagle suggested that Riis should become self-sufficient, so in January 1888 Riis paid $25 for a 4×5 box camera,