Until the 1780s Palau remained mostly isolated from European contact, though trading ships passed near it in route to China. American whalers encountered the islands as early as 1832 and French explorer Jules Dumont d'Urville spent two months in Palau in the winter of 1838–1839, evaluating the potential for whaling. Seventy years of instability in the Spanish empire continued until 1874 with periods of conflict followed by calm only to erupt into insurrection again. The 1812 Constitution of Cádiz was reinstated in 1836 and revoked a year later. Two Carlist Wars followed by the 1868 Revolution, led to a democratic experiment and the drafting of a new constitution in 1869. The constitution called for significant colonial reforms, but before they could be acted upon the Third Carlist War and subsequent restoration of the monarchy ended its authority. During this period, the Pacific colonies in the Caroline, Gilbert, Marshall, and Palau Islands remained mostly autonomous until 1874, when the Spanish attempted to reassert their authority there. That year, German trader Eduard Hernsheim founded a trading station on Malakal Island.