The division of the Parana between the Spanish and the Portuguese was a check upon the full development of the river-route. The Portuguese held the upper part of its basin, which now belongs to Brazil. They expelled the Spanish missionaries from the upper Parana about the middle of the seventeenth century, and made themselves masters of the Paraguay north of 20 deg. S. lat. Their forts at Coimbre and Albuquerque prevented any from ascending. D'Azara insists that it would have been Spain's interest to disarm these forts; it would have enabled them to go up the river as far as the Spanish missions to the Mojos and the Chiquitos. On their side, the Portuguese only used the upper section of the river, where it is joined by the Paulist road north of the Coimbre, as a means of access to the gold mines of the Matto Grosso. Even now, although the Parana is open to every flag, the development of the river-route is not independent of political conditions. In making the railway from Saint Paul to Corumba, and so creating on its own territory a means of direct communication with the upper Paraguay, Brazil diverts from the lower districts part of the traffic which ought normally to go there. Again, the ports of southern Brazil and the lines which go to them try to attract to the Atlantic the produce of the basins of the Uruguay and the upper Parana, which would have followed the thread of the river to foster the trade of Buenos Aires if the frontiers had been fixed otherwise. Before the Revolution the river-trade was confined to exchanges between the Misiones and Paraguay on the one hand, and Buenos Aires and the Andean provinces on the other. After the extinction of the missions Paraguay was the chief centre of traffic on the river. At the close of the eighteenth century it had a fairly large population. According to D'Azara, it amounted to 97,000, and 47,000 for the area of the former Missions (Misiones), while Buenos Aires, Santa Fe, Entre Rios and Corrientes had not more than 103,000 inhabitants collectively. Paraguay exported tobacco, _mate_ and timber by the river. The Buenos Aires Estano received 800 tons of tobacco a year. The exports of _mate_ from Paraguay to Peru, Chile and the interior provinces amounted to 1,725 tons, and 2,250 tons went to Buenos Aires. The timber came mostly from the Tebicuary, where the _angadas_ (loads of timber) were formed. The chief constructive sheds also were on the Tebicuary. Boats of twenty to 200 tons were launched there; and they had armed boats, when they went down the river, to detect ambushes of the Indians, who were masters of the right bank north of Santa Fe.