The development of navigation on the Parana during the first half of the nineteenth century was checked by the disturbances and wars of the period of the emancipation and unification of Argentina. The river was blockaded several times and traffic interrupted. Only a few smuggling schooners succeeded in getting through the side branches, which the ships stationed in the river could not watch. Robertson escaped the Spanish vessels in this way. The picture which D'Orbigny has given us of the life of the river belongs to the year 1827. At that time the estuary was blockaded by the Brazilian fleet in the whole area of the delta as far as San Pedro. Piracy was so rife, and the insecurity so great, on the Uruguay and the Parana, that few ventured as far as Buenos Aires, the ships being linked in convoys. Up stream, Corrientes was the limit of navigation. The dictator Francis closed the Paraguay, and even the small boats no longer sailed on the upper Parana, along the frontier of Paraguay. The Correntinos, who spoke _Guarani_, could merely get permission at rare intervals to send a few boats up river. Armed boats convoyed these as far as Neembucu, and they returned with hides and _mate_. Corrientes thus became the market-centre of the upper river and replaced Asuncion in the trade. The flotilla on the Parana included flat-bottomed barges, which were only used in coming down, and strong keeled ships--schooners, sloops and brigs--with their ropes made of leather. Down stream there was a little more diversity in the traffic. The island sent cargoes of firewood and charcoal to Santa Fe and Buenos Aires. The orchards of the delta provided Buenos Aires with oranges and peaches. Hides for export were shipped at Goya and Santa Fe. But the chief freight was lime from La Bajada, which was burned in the kilns on the Barranca, at the outcrops of the beds of conchiferous limestone. [Illustration: CONFLUENCE OF THE YGUASSU AND THE PARANA. _In the foreground is the left bank of the Yguassu, on Argentine territory. The right bank is Brazilian territory. At the back, on the right bank of the Parana, is Paraguayan territory._ PLATE XX. To face p. 236.] The navigation was fairly easy, the journey from Corrientes to Buenos Aires (675 miles) lasting, as a rule, from fifteen to twenty days. Going up, the time was more irregular. They had to stop when there was no south wind, or a little progress was made by hauling (_silgar_). D'Orbigny took a month to travel up.[119] In 1822, before the war with Brazil, there were 651 boats entered at Buenos Aires for coasting trade on the rivers and 1,035 at San Fernando or on the Tigre, the advance port of Buenos Aires. In 1833 Isabelle put at one thousand the number of vessels at work on the Parana and the Uruguay.