Digitized content includes a frontispiece portrait of Austrian chemist Carl Auer von Welsbach (1858-1929), a key figure in the history of rare earth elements. In 1885 Welsbach showed didymium was not an element, but an alloy of two elements that he named praseodymium and neodymium. He later separated lutetium from ytterbium.

In the 1880s, von Welsbach created fabric impregnated with thorium and cerium, which glowed incandescently when heated by burning gas. Mantels for gas lamps were the first industrial product to use rare earth elements and led to international trade in rare earth ores, especially monazite. Welsbach managed firms around the world that sold gas lamps for lighting streets, homes, and businesses, which shaped the visual landscapes that millions of people inhabited from the 1890s into the 1930s.

In the United States, the Welsbach Incandescent Gas Lighting Company had offices on Walnut Street in Philadelphia, and a factory on the Delaware River at Gloucester, New Jersey. Many of the factory workers were women, who sewed the fabric mantels and packed the mantels into packages for sale across the country.