The Kerguelen Islands, known also as the Desolation Islands, lie in the extreme south of the Indian Ocean. By the late nineteenth century they were still relatively unexplored, but they represented a fascinating puzzle: although the Islands were four thousand miles away from South America, they shared the same species of flora. Rodrigues, an island off the coast of Madagascar, was also a point of increasing interest among naturalists. While most archipelagic islands then discovered were volcanic, explorers noted that the caves of Rodrigues were formed of limestone, and that most local species...