Their route homeward was by the Sierra Amarilla, on the eastern slope of which rises the river Barancas, which they followed some way: before it emerges from the mountains it is joined by the Quetro-leufú, and both together form the Tapalquen. Beyond the Sierra Amarilla was seen that group called by the natives the Huellucalel, from which proceeds the river Azul, the waters of which, running parallel with those of the Torralnelú and Chapaleofú, are lost in the marshes sixteen or twenty leagues distant towards the Salado. Crossing the Tapalquen, they once more found the beaten track to the Guardia del Monte, which they reached in safety on the 28th of May, after an absence of about six weeks. In reporting the results of their mission they recommended that the range of the Vuulcan should be at once adopted as the boundary of the province in that direction, and that a chain of military posts should be established upon it, extending from the sea-coast as far west as the Laguna Blanca, with a sufficient force to overawe the savages and afford efficient protection to such settlements as might be made within that line. The government, at last roused to the conviction of the necessity of some vigorous demonstration of physical force, in order to re-establish something like that salutary fear of the superior military power and discipline of the Christians, which, in old times, had, to a certain degree, restrained and kept the savages in order, adopted the suggestion, and preparations on a considerable scale were made for carrying it into effect. The construction of a fortification on the Tandil was determined upon, and the governor himself prepared to superintend the work, and take the field against the savages with an adequate force. The little army assembled for this purpose was ready to march about the close of February, 1823. It consisted of 2500 men, seven pieces of artillery, with a considerable accompaniment of carts and waggons, and everything requisite for the establishment of a permanent military settlement.