From Caceres onward we were entering the scene of Colonel Rondon’s explorations.  For some eighteen years he was occupied in exploring and in opening telegraph lines through the eastern or north middle part of the great forest state, the wilderness state of the “Matto Grosso”—­ the “great wilderness,” or, as Australians would call it, “the bush.”  Then, in 1907, he began to penetrate the unknown region lying to the north and west.  He was the head of the exploring expeditions sent out by the Brazilian Government to traverse for the first time this unknown land; to map for the first time the courses of the rivers which from the same divide run into the upper portions of the Tapajos and the Madeira, two of the mighty affluents of the Amazon, and to build telegraph-lines across to the Madeira, where a line of Brazilian settlements, connected by steamboat lines and a railroad, again occurs.  Three times he penetrated into this absolutely unknown, Indian-haunted wilderness, being absent for a year or two at a time and suffering every imaginable hardship, before he made his way through to the Madeira and completed the telegraph-line across.  The officers and men of the Brazilian Army and the civilian scientists who followed him shared the toil and the credit of the task.  Some of his men died of beriberi; some were killed or wounded by the Indians; he himself almost died of fever; again and again his whole party was reduced almost to the last extremity by starvation, disease, hardship, and the over-exhaustion due to wearing fatigues.  In dealing with the wild, naked savages he showed a combination of fearlessness, wariness, good judgment, and resolute patience and kindliness.  The result was that they ultimately became his firm friends, guarded the telegraph-lines, and helped the few soldiers left at the isolated, widely separated little posts.  He and his assistants explored, and mapped for the first time, the Juruena and the Gy-Parana, two important affluents of the Tapajos and the Madeira respectively.  The Tapajos and the Madeira, like the Orinoco and Rio Negro, have been highways of travel for a couple of centuries.  The Madeira (as later the Tapajos) was the chief means of ingress, a century and a half ago, to the little Portuguese settlements of this far interior region of Brazil; one of these little towns, named Matto Grosso, being the original capital of the province.  It has long been abandoned by the government, and practically so by its inhabitants, the ruins of palace, fortress, and church now rising amid the rank tropical luxuriance of the wild forest.  The mouths of the main affluents of these highway rivers were as a rule well known.  But in many cases nothing but the mouth was known.  The river itself was not known, and it was placed on the map by guesswork.  Colonel Rondon found, for example, that the course of the Gy-Parana was put down on the map two degrees out of its proper place.  He, with his party, was the first to find out its sources, the first to