In 1515 Juan de Solis sailed to the mouth of the River Plate, and landed on the coast of Uruguay. His party were immediately attacked by Charrua Indians, and the bodies of De Solis himself and of a number of his crew were stretched dead on the sands. This ended the expedition, for the survivors left the place in haste and returned to Spain. In 1526 Sebastian Cabot explored the River Plate, and, sailing up-stream, investigated the Parana, and discovered the waters of the Paraguay River itself. In these inland waterways his fleet was met by that of another pioneer, Diego Garcia. This latter, doubtless from chivalrous motives, gave the _pas_ to Cabot, and turned the bows of his vessels down-stream. It was Cabot's intention to establish himself permanently on the shores of this great river system. Near the present site of the town of Rosario he built the fort of Sancti Spiritus. Seeing, however, that his appeals to Spain for assistance remained unanswered, he eventually abandoned his attempt. There seems little doubt that he withdrew practically all his forces from the River Plate; but there are legends of some survivors who remained in the district after the main expedition had left. Some old historians allege that these underwent strange experiences and hardships, but the veracity of such narratives is more than doubtful. [Illustration: ATAHUALPA. The last Chief of the Peruvians.] It was in 1535, the year when Valdivia marched southward from Peru to conquer Chile, that the conquest and actual colonization of the River Plate was first seriously undertaken. Pedro de Mendoza, a soldier of fortune, ventured on the attempt. Mendoza's career as a mercenary soldier had proved quite unusually profitable even for those days, and he had acquired a large fortune at the sack of Rome alone. His purse provided a really formidable expedition. The voyage to the mouth of the River Plate on this occasion was more productive of incident than was usual, even in those days of adventurous pioneers. The halts at Teneriffe and at Rio de Janeiro had resulted in some dissensions among Mendoza's men, and the execution by the orders of the Chief of one of his most popular leaders had all but caused open mutiny at the latter place. Nevertheless, when his forces landed at the site of the present town of Buenos Aires, they constituted a formidable company of men, admirably equipped with everything that the science of the age could devise for the purpose of conquest and colonization, particularly the former.