1911 Encyclopædia Britannica, Volume 21… (1911)
“ Part of the state on the Atlantic coast and along the lower Parnahyba is low, swampy and malarial. South of this the country rises gradually to a high plateau with open campos. This plateau region is watered by numerous tributaries of the Parnahyba, chief of which are the Urussuhy, the Canindé and its tributary the Piauhy, the Gurgueia and its tributary the Parahim, which drains the large inland lake of Parnaguá, the Longa, and the Poty, which has its source in the state of Ceará. The Parnahyba is navigable for boats of 3 ft. ”
