philologist Jakob Grimm (1865, 2nd ed. 1885); the next, in conjunction with his former teacher Müllenhoff, published Denkmäler deutscher Poesie und Prosa aus dem 8. bis 12. Jahrhundert (1864, ed. 1892). His first major work was Zur Geschichte der deutschen Sprache (Berlin, 1868; 3rd ed., 1890), a history of the German language with special reference to phonetic laws.

He contributed the section on Alsatian literature to Ottokar Lorenz's