Colonel Cabrer, the only surviving officer of all those employed on this important survey, was living during the time I was at Buenos Ayres, and for many years had, to my knowledge, been engaged in drawing up an elaborate account of the whole progress of the survey from first to last; in his possession I saw a complete set of all the beautiful maps executed by the Spanish officers, the originals of which are deposited at Madrid. He is lately dead, and I understand that the authorities of Buenos Ayres have been in treaty for the purchase of his papers, which will be of the greatest importance, not only to them, but to the governments of the Banda Oriental, of Paraguay, and of Bolivia, whenever the time comes, as it must ere long, for definitively fixing their respective boundaries with Brazil. I considered myself fortunate in obtaining copies of several detached portions of these surveys, and particularly of an original map, drawn from them by Colonel Cabrer himself for General Alvear, when commanding-in-chief in the Banda Oriental in 1827. There is no doubt that, so far as the Spanish frontiers extended, these maps are the best existing data respecting the countries which they delineate: on the other hand, we must look to the Portuguese authorities for materials for the adjoining provinces of Brazil. The most perfect map of that part of the continent perhaps ever made was drawn at Rio de Janeiro in 1827, for the use of the Marquis of Barbacena, when appointed to command the Emperor's army in the war with Buenos Ayres, and was taken with his baggage at the battle of Ituzaingo, and afterwards given to me. It comprises, on a large scale, all the country lying east of the Uruguay, from the Island of St. Catharine's to the River Plate. On my return to England I placed it in the hands of Mr. John Arrowsmith, with the rest of my geographical materials. As regards the greater part of the interior provinces west of the Paraguay, the information obtainable is very imperfect; indeed of some vast portions of those regions, it may be said that nothing but the general courses of the principal rivers is as yet known. The immense tract called the Gran-Chaco is still in possession of aboriginal tribes, and other extensive districts are inhabited by people who, though of a different race, seem little beyond them in civilization.