Meyers Konversations-Lexikon was a German encyclopaedia comparable to the Britannica, and the entirety of the fourth edition (1888-1889) is online, all 16 volumes and 16,000 pages. You can browse the volumes here or use the search page. For users of German, this is a great resource.
Nietzsche not mentioned. His books were published, but I guess he was too contemporary.