[127] A little above its actual position.
[128] In studying the variations of the bed of the Paraná it is necessary to avoid comparing maps drawn at dates separated by long intervals. The differences of such maps are such that they do not enable us to follow the processes by which the actual forms have been derived from earlier forms. The analogies which they show are sometimes due, not to the permanence of the topography, but to the return of a complete cycle of changes, or of conditions analogous to the earlier conditions.
[129] The secondary arms of the right bank, north of Santa Fé, were not explored until 1870. Sullivan's map (1847) only mentions the Riacho de San Jeronimo, which is visible for a short distance below 20° S. lat. The right bank was the domain of the Indians, and the Correntinos would not venture near it. In 1870 ships began to use the San Javier arm, on which many colonies arose. Further north the Paraná Mini has been used since 1890 for exporting quebracho timber.
[130] As between La Paz and Paraná, it seems possible to show some relation between these alluvial stretches at the foot of the cliff and the confluence of the small valleys of the Pampean plain.
[131] The Paso Paraguayo, which has cost the Argentine hydrographic service most work, did not exist at the middle of the nineteenth century. It seems that the channel then kept to the cliff as far as Benavidez, and was continued as far as the source of the Paraná Pavon by a very pronounced buckle, of which the Monriel lagoon is a scar. In 1895 the Paso was only fifteen feet deep.
[132] The granite which outcrops at Martin Garcia also forms the platform of the English Bank in the outer harbour.
[133] The water in the estuary, worked up by waves and tide, contains more sediment than the water of the river.
[134] The current at high tide is stronger than at low tide, and it has shifted to the north-east the streams which find an outlet on this side.
[135] Movement of internal navigation at Rosario (average 1912-1914): entries, 1,108,000 tons, of which 690,000 in ballast; clearances, 580,000 tons. At San Nicolas: entries, 400,000 tons, of which 440,000 in ballast; clearances, 4,000 tons. The difference between the entries and the clearances represents ships starting straight for Europe.
[136] The density is twenty times less in the ranches which use the meagre pastures of the Rio Negro.