Meanwhile the conquest of the great interior plateaux to the south was rapidly proceeding. The wars with the Dutch rather stimulated than retarded it, for, so long as the Dutch commanded the sea, the widely separated provinces were obliged to communicate by land, and the Indian routes became better known to the Brazilians. Settlers driven from the sugar plantations on the coast took up cattle-raising in the interior of the northern provinces. In the extreme South, as early as 1635 the Paulistas had rooted out the Jesuit settlements from the whole region of the Parana. To the North they traversed the Sao Francisco valley and the plateau of Goyaz. Manoel Correa explored the latter region in 1647, and in 1671 another Paulista, Domingos Jorge, penetrated with a force of subject Indians into the great treeless plains which extend beyond the mountain ranges bounding the Sao Francisco valley on the north. These plains are now the state of Piauhy. At about the same time the cattle-raisers who had established themselves on the lower Sao Francisco in Bahia, crossed over into the same territory of Piauhy. Within a short time the Indians were reduced to submission, and the cattle ranges were extended over the plains of Piauhy, southern Ceara, and the adjacent provinces. This great conquest completed the junction of southern and central Brazil with Maranhao and Para. Long lines of land communication were established, and over them travel was more frequent than would seem likely. Piauhy and Ceara soon produced an enormous surplus of cattle whose export into other provinces brought about a revolution in the alimentation of the coast Brazilians. The Indians along the north-east coast were gradually incorporated, destroyed, or pushed back, though it was not until 1699 that they were finally subdued in Rio Grande do Norte. From this time dates the astonishing development of the population of Ceara, who during this century have furnished nearly all the labour for the gathering of rubber. In the South, settlements multiplied up and down the coast from Rio until nearly the whole of the present state was occupied. Rio and Sao Paulo flourished with the profits of the clandestine trade with the Spanish colonies. The Paulistas continued to spread in every direction. By 1654 they had occupied the headwaters of the Parahyba and west as far as Soracaba.