Reproduces of the Dutch, who claimed half the island of New Guinea as part of their East Indies colony, were anxious to explore it for both commercial and scientific reasons and organized a series of expeditions there, among others in 1903, 1907, and 1909-1910. H.A. Lorentz (1871-1944) participated in the first and led the second two. His personal archive of the three expeditions contains correspondence with individuals and institutions in several countries and languages with an index of correspondents in the appendix; information on the organization and infrastructure of the expeditions; and diaries, field notes, draft reports and other documents concerning the local population and the geography, flora and fauna of the regions explored. Also included are several maps, newspaper clippings and articles and manuscripts of his two major publications in which he recounted the first and third of the expeditions: Eenige maanden onder de Papoea's Several months among the Papuans and Zwarte menschen, witte bergen Black people, white mountains.