When first Sebastian Cabot and Solis ascended the Paraná, they found that the Guaranís of Paraguay had extended in no instance to the western shore of either of those rivers. The western banks were inhabited then, as now, by the wandering Indians of the still not entirely explored territory of the Gran Chaco. Chaco[9] is a Quichua Indian word meaning ‘hunting’ or ‘hunting-ground’, and it is said that after the conquest of Peru the Indian tribes which had been recently subjugated by the Incas took refuge in this huge domain of forest and of swamp. Be that as it may, the Chaco Indians of to-day, comprising the remnants of the Lulis, Tobas, Lenguas, Mocobiós, and others, are almost as savage as when first we hear of them in the pages of Alvar Nuñez and Hulderico Schmidel. These tribes the Jesuits on many occasions attempted to civilize, but almost entirely without success, as the long record of the martyrdom of Jesuit missionaries in the Chaco proves, as well as the gradual abandonment of their missions there, towards the second half of the eighteenth century. Certain it is that at various places in the Chaco, in the quaint old maps the Jesuits have left us, one reads ‘Mission de Santa Cruz de los Vilelas’, ‘Mission de la Concepcion de los Frontones’, and others; but much more frequently their maps are studded with crosses, and some such legend as ‘Hic occisi sunt PP. Antonius Salinus et Petrus Ortiz Zarate’.[10] It was only when the Jesuits encountered the more peaceful Guaranís that they met with real success. What was the nature of their success, how durable it was, what were the reasons which caused the expulsion of the order from America, and especially from Paraguay, and what has been the result upon the remainder of the Indians, it is my object to endeavour to explain. A long residence in the river Plate, together with two visits to Paraguay, in one of which I saw almost all the remnants of the Paraguayan missions and a few of those situated in the province of Corrientes, and in the Brazilian province of Rio Grande do Sul, have given me some personal acquaintance with the subject.[11]