The convenient dry-copying process for printed pages is among the truly revolutionary inventions of the century. In 1937 Chester Carlson, a New York patent attorney, developed the concept of applying an electrostatic charge on a plate coated with a photoconductive material. On November 22, 1938, Carlson dusted powder dyed with evergreen spores across an exposed plate and transferred the imprint to the surface of a paper.
Used to lift molten iron to molds where it was cast into pipe, jib cranes were the sole means of conveyance in the pit-casting process. When pit casting was replaced by centrifugal casting in the 1920s, many pits were filled and the cranes were used to produce cast iron fittings or general maintenance work. Only one jib crane remained at the American Cast Iron Pipe Company in recent years, and it was probably the last pit-cast jib crane to operate, which it did until it was given to the Sloss Furnace Museum in early 1986.