In 1844, he was appointed professor of art history at Berlin University, and in 1861 he was called to St Petersburg as adviser in the arranging and naming of the pictures in the imperial collection. On his return, he published a book on the Hermitage collection (Munich, 1864). Among his other publications are some essays on Rubens, Mantegna and Signorelli; Kunstwerke und Künstler in Deutschland; and Die vornehmsten Kunstdenkmäler in Wien.