The attention of Sr. De Gorgoza was called to this route by certain “documents” containing “hints about passages used by the Indians in crossing the Cordilleras.” These documents consisted of “reports by the civil and ecclesiastical authorities about the province of Balboa, which was, at that time, of great importance, from its rich gold mines,” and are probably as reliable as any other civil and ecclesiastical reports of the pious marauders of that period. These reports were accompanied by “a map,” which seems, from a reference upon page 133, to have been that remarkable specimen of puzzling topography, known as Arisa’s map, a copy of which may be found appended to the report of Admiral Davis. The usual reference is made to those unconscious pioneers of interoceanic canal routes, the filibusters, “who carried off quantities of gold, to the great detriment of the Spanish treasury,” etc., etc. This _reliable_ evidence is further corroborated by the flight of birds. Some Pissisi ducks providentially appear to lead our explorer upon the right path, and M. De La Charme is so convinced that the route will be found in the direction taken by these web-footed engineers, that he confidently affirms “there remained to me no doubt but at this place I should find the desired passage. So persuaded,” he “prosecuted his work with confidence.” Many immaterial facts are circumstantially related, but we are not told by what method the survey was conducted, nor whether M. De La Charme was assisted in his work by professional engineers. Without such assistance, his duties must have been complicated and laborious. As mention is made of bogas and laborers only, we must conclude that this arduous duty was performed without any intelligent assistance. He states that strict attention was given to barometric measurements. The notes should have been supplied in proof of the accuracy of his conclusions. The irregularities of the barometer along the dividing ridge of the Isthmus and in South America have been noticed by Moro, Hughes, Herndon, Maury, Michler, and other observers. Used with extreme care, and according to the method recommended by Lieut. Col. Williamson, U. S. A., the results obtained with this instrument are affected by discrepancies and anomalies, which, along the Andes, vitiate the most careful observations, and elude the grasp of the best formulæ. A favorable reconnoissance with the barometer, in this region, should receive a careful verification with more accurate instruments, but it can not be regarded as establishing the feasibility of a route. The map of M. De La Charme, like that of Dr. Cullen, is made up from old maps. The additional topographical information is not laid down.