It was this survey, with the soundings afterwards taken by Oyarvide (who lost his life in completing them), that furnished the materials for the chart of the river Plate, officially published at Madrid in 1810: nor was this all that Buenos Ayres owed to Malaspina: upon his return to Valparaiso from the north-west coast, he detached two of his most intelligent officers, Don José Espinosa, and Don Felipe Bauza, well known in this country, to map the road across the pampas; and by them the true positions of Santiago in Chile, of Mendoza, San Luis, the post of Gutierres on the river Tercero, and other points along the line, were, for the first time, determined. Their map, so far as it extends, is the best, and the only one of that line of country, I believe, ever drawn by any one capable of taking an observation.[28] Whilst they were thus engaged in fixing one part of the geography of the interior, the Viceroy turned to account the temporary sojourn at Buenos Ayres of some of the officers attached to the commission for laying down the boundaries under the treaty of 1777 with Portugal, and employed them in mapping other portions of the territory under his immediate jurisdiction. In 1794 M. Sourreyere de Souillac, the astronomer of the third division of that commission, laid down the line of road from Buenos Ayres to Cordova, and fixed the latitude of that city in 31° 26´ 14". In 1796 Azara, with Cerviño and other officers employed on the same service, made a detailed survey of the frontiers of the province of Buenos Ayres, in the course of which they fixed the positions of all the towns and forts of any importance between Melinqué, its north-western extremity, and the most southern bend of the river Salado, beyond Chascomus. That river they found to have its origin in a lake in latitude 34° 4´ 45", longitude from Buenos Ayres 3° 36´ 32"; it is an insignificant stream, of trivial importance till joined by the Flores. Thus materials were collected for laying down a considerable portion of country upon the very best authorities; but, like the surveys of the coast, many years were suffered to elapse ere they were made available to the public. Bauza's map was not published till 1810, and it was only in 1822 that the positions fixed by Azara in 1796 appeared for the first time as his in the "Statistical Register," published that year at Buenos Ayres. De Souillac's might have remained unknown for ever, had not Señor de Angelis lately brought them to light; as well as Malaspina's "Fixed Points on the Shores of the River Plate."