Thorium and its compounds were used only for academic purposes until 1884, when Auer von Welsbach developed and patented the incandescent gas light mantle in which thorium oxide was the essential ingredient. The mantle industry grew to its peak in the early of the 20th century, but as electricity began to replace gas for general lighting purposes, mantle production decreased and by 1925 thorium was relatively unimportant to commerce. With the advent of atomic energy, thorium jumped back to an important role in nuclear power plants due to its nuclear properties.