no human being, although we had twice heard Indians.  Six weeks had been spent in steadily slogging our way down through the interminable series of rapids.  It was astonishing before, when we were on a river of about the size of the upper Rhine or Elbe, to realize that no geographer had any idea of its existence.  But, after all, no civilized man of any grade had ever been on it.  Here, however, was a river with people dwelling along the banks, some of whom had lived in the neighborhood for eight or ten years; and yet on no standard map was there a hint of the river’s existence.  We were putting on the map a river, running through between five and six degrees of latitude—­of between seven and eight if, as should properly be done, the lower Aripuanan is included as part of it—­of which no geographer, in any map published in Europe, or the United States, or Brazil had even admitted the possibility of the existence; for the place actually occupied by it was filled, on the maps, by other—­imaginary—­streams, or by mountain ranges.  Before we started, the Amazonas Boundary Commission had come up the lower Aripuanan and then the eastern branch, or upper Aripuanan, to 8 degrees 48 minutes, following the course which for a couple of decades had been followed by the rubbermen, but not going as high.  An employee, either of this commission or of one of the big rubbermen, had been up the Castanho, which is easy of ascent in its lower course, to about the same latitude, not going nearly as high as the rubbermen had gone; this we found out while we ourselves were descending the lower Castanho.  The lower main stream, and the lower portion of its main affluent, the Castanho, had been commercial highways for rubbermen and settlers for nearly two decades, and, as we speedily found, were as easy to traverse as the upper stream, which we had just come down, was difficult to traverse; but the governmental and scientific authorities, native and foreign, remained in complete ignorance; and the rubbermen themselves had not the slightest idea of the headwaters, which were in country never hitherto traversed by civilized men.  Evidently the Castanho was, in length at least, substantially equal, and probably superior, to the upper Aripuanan; it now seemed even more likely that the Ananas was the headwaters of the main stream than of the Cardozo.

For the first time this great river, the greatest affluent of the Madiera, was to be put on the map; and the understanding of its real position and real relationship, and the clearing up of the complex problem of the sources of all these lower right-hand affluents of the Madiera, was rendered possible by the seven weeks of hard and dangerous labor we had spent in going down an absolutely unknown river, through an absolutely unknown wilderness.  At this stage of the growth of world geography I esteemed it a great piece of good fortune to be able to take part in such a feat—­a feat which represented the capping of the pyramid which during the previous seven years had been built by the labor of the Brazilian Telegraphic Commission.