Gaspar the Gaucho

Spread before you a map of South America. Fix your eye on the point of confluence between two of its great rivers the Salado, which runs south-easterly from the Andes mountains, and the Parana coming from the north carry your glance up the former to the town of Salta, in the ancient province of Tucuman do likewise with the latter to the point where it espouses the Paraguay; then up this to the Brazilian frontier fort of Coimbra finally draw a line from the fort to the aforementioned town a line slightly curved with its convexity towards the Cordillera of the Andes and you will thus have traced a boundary embracing one of the least known, yet most interesting, tracts of territory in either continent of America or for that matter in the world.