"The works ... which here appear in English have all but one (the last) been published before in Danish periodicals or as books. Most of them were written in Danish; two were in French, and one in German ... The works in Danish have been translated by Mr. H. Gilbert-Carter ... with the exception of the last (unpublished) paper, which was translated by Miss A. Fausbøll. The translation of the three papers written in French and German has been done by Professor A. G. Tansley."--Prefatory note.