It was by proceeding up this river that Falkner supposed a hostile naval power might surprise the Spanish territories in the interior and in Chile--a notion founded upon the concurrent accounts given him by the Indians of the possibility of ascending it as far as the Cordillera, and even to Mendoza. If these accounts were to be depended upon, and such a communication were really practicable between the shores of the Atlantic and the provinces of Chile, and Cuyo, it was impossible to foresee to what important consequences it might lead, and how valuable (independently of its advantages as a military position) might become a settlement which would necessarily be the key of that communication. To determine a point of so much interest, in a geographical as well as political point of view, was therefore one of the first objects after the first settlers were fairly established; and an expedition was prepared to explore the river to its sources, and to examine its principal affluents. The command was intrusted to Don Basilio Villariño, a master-pilot in the Spanish navy, who had sailed with Piedra in 1778; and had since been the chief practical officer engaged in the survey originally undertaken by that commander. In the four years which had elapsed since the commencement of that service, he had himself examined and laid down the Bays of Anegada and of Todos Santos, the bar of the River Negro, and the ports of San Antonio, of San Joseph, and that to the south called Porto Nuevo. He had also surveyed the River Colorado for about seven leagues from its mouth. No man, then, in those parts could be better qualified for the task, and no expense or supply was spared, that he might be furnished with everything likely to ensure his success. Four large launches (chalupas) were fitted out, to which masters, carpenters, caulkers, and ample crews were appointed, besides a number of peons with horses, who were to attend them along the banks of the river to assist in reconnoitring the country, and in towing the boats against the stream, when contrary winds might prevent their sailing. On the 28th September, 1782, they started from the settlement of Carmen, and were absent till the 25th of May following; and, although on some points they did not perhaps realize all the expectations of those who sent them, yet they certainly obtained much new and valuable information, and for the first time determined correctly the course of the great river they ascended, and proved the possibility of navigating it to the very foot of the Andes. The heavy Spanish launches unfortunately proved ill-calculated for the service, and could make but little way with the fairest wind against the force of the stream. They were obliged in consequence continually to have recourse to the towing-rope, a tedious and laborious operation, which occupied them a whole month before they reached the great island of Choleechel, about seventy leagues, according to their daily reckoning, from Carmen.