 He learned Hungarian and Finnish, and received his doctoral degree in 1869 with a dissertation on Germanic loanwords in Finnic.He taught Greek at the Borgerdyd school in Copenhagen before becoming a professor at the University of Copenhagen; among his students at the university was Otto Jespersen.In 1876 he was invited to give the Ilchester Lectures at the University of Oxford, and they were later published as "The Relations Between Ancient Russia and Scandinavia, and the Origin of the Russian State".