 During the 1840s Feuerbach corresponded and occasionally visited and maintained close personal relationships with several leading German radicals, including, in addition to Ruge and Marx, the publishers Otto Lüning, Otto Wigand, and Julius Fröbel; the revolutionary poet, Georg Herwegh, and his wife, Emma; Hermann Kriege, a freelance activist and early German socialist who emigrated to America; and scientific materialists like Jacob Moleschott and Carl Vogt. The impression made by him on several leading lights of the younger generation is reflected in Gottfried Keller’s Bildungsroman, Green Henry, first published in 1855, and in the dedication (to Feuerbach) of Richard Wagner’s early book, The Art-Work of the Future (1850).