At those times couriers occasionally pass it swimming, or holding by the tails of their horses, which they drive before them. All carriage intercourse is for the time impossible, and the ordinary traffic between Salta and the lower provinces is therefore as matter of course suspended during the rainy season. To obviate so serious an inconvenience, in the time of the Old Spaniards, a survey was made of this part of the river, and a plan was proposed to the government for throwing a bridge over a rocky pass, which, if executed, would have enabled carts as well as passengers to cross it high and dry at any season. The materials were at hand, and the estimate of the whole expense so small that it was difficult to find an objection to it; on the contrary, it was unanimously approved; but, as nothing is done in a hurry in these countries, it was, like many other most notable projects, postponed, "_hasta mejor oportunidad_," till better times, which, unfortunately for the people of Salta, have never yet arrived.
Ten or twelve leagues below the pass, the river De las Piedras, the last affluent of any consequence, falls in; thence the course of the river is easterly inclining south, as far as Pitos, the frontier fort of Salta in that direction. In the flat saline country through which it afterwards runs, its waters imbibe a brackish taste, from which it takes the name of the Salado, or the salt river, which it preserves the whole way to its junction with the Paranã, near Santa Fé. I have before stated that this river is believed to be navigable as high as Matara, in the latitude of Santiago del Estero.
The Vermejo, the most important of all the affluents of the Paraguay, is formed by two considerable streams, which may be generally called the rivers of Jujuy and Tarija, from those two departments which they respectively drain. At their sources they are at no great distance from each other, but descending from opposite sides of a snow-capped range, the buttresses of which branch out far and wide to the south and east, they are soon hurried away in totally different directions; each, however, finally sweeping round the base of the stupendous platform above, describes, after a long course, the segment of a circle, which is rendered all but complete by the junction of their waters at a point about sixteen leagues below Oran, whence they flow together south in one mighty and navigable stream the whole way to the Paranã. The name of Vermejo, or the red river, is derived from the occasional discoloration of the waters by the red alluvial soil which is washed into them during the periodical floods.