At the spot where we crossed the range—starting our ascent from an elevation of 1,100 ft.—were immense holes, vents and cracks in the earth's crust. As we rose slightly higher among many chains of low hills, we were upon a horizontal stratum of laminated granite. Higher still we passed a semicircular hill composed of immense blocks of granite. In the centre of the semicircle was a great round hole, 30 ft. in diameter—an extinct crater. Farther on, ascending upon an inclined plane, we came to another similar semicircle—not of rock that time, but of red earth and cinders. When we reached the highest point (elev. 1,270 ft.) of the divide we had to our left huge pinnacles and pillars of rock of the most fantastic shapes, monoliths from 10 to 15 ft. high, and rocks hollowed by the action of fire. Big boulders, which had become perfectly rounded by having been shot through the air and revolved at a great speed while in a half-solid condition, were to be seen scattered all over the inclined planes of the saddle of the divide. Giant cacti grew in abundance in the interstices between rocks. Although most of the rocks were blackened outside, by chipping off the outer surface one found that they contained inside beautiful white marble or else greyish granite. The latter was striated with thin layers—not more than a quarter or half an inch thick—of crystallized matter, forming veins in the blocks or dividing two strata.
Everywhere could be noticed remarkable perforations of all sizes in the rocks, great spherical or ovoid hollows, or cylindrical tubular channels. In the ground were many volcanic vents with lips baked by fire.
On our right, a kilometre or so farther on, after having gone through an extensive stretch of red sand and lapilli, we came across three hills, the central one of which had the appearance of a cylindrical tower of masonry with windows and doors. It was a wonderful freak of nature. Under this huge tower were several caves and grottoes.
Descending upon the opposite side of the range, at an elevation of 1,200 ft. we found the dry bed of a streamlet, which flowed in a northerly direction when it did flow at all. On emerging from the wide hill mass—about 18 kil. across—we found ourselves among a lot of burity palms on the western spur of the Serra Azul. When we were actually upon them, the Blue Mountains lost their blue appearance and were more of a greyish green, owing to the vegetation which covered most of their slopes. The range was formed of three distinct terraces, the lower one being of greater height than the two upper ones. A number of low hill ranges starting from the main range branched off like spurs towards the south. The uppermost terrace of the main range was supported on a high vertical wall of red rock.
On meeting the Rio Coralzinho we skirted it for some distance through the forest, then marched among a great many domes, small and large; after which we crossed a wonderful field of huge monoliths, superposed boulders, and rocks of all kinds of fantastic shapes.
We had marched 30 kil. that day. We encamped on the River Piraputangas—a tributary on the left side of the Cuyabá Grande River—the Cuyabá Grande being in its turn a tributary on the right of the Cuyabá River.
The Cuyabá River described almost an arc of a circle—in fact, quite a semicircle—its birth taking place in the Serra Azul. Where we crossed it we were only a short distance to the west from its point of origin.
Where we had made our camp we were in a large grassy plain about six kilometres long and nearly two kilometres wide. The rainy season was fast approaching. We came in for a regular downpour during the night, accompanied by high wind, which knocked down all our tents, as the pegs would not hold in the soft, moist ground. We had a busy time endeavouring to protect the baggage. We all were absolutely soaked. The minimum temperature was 52° Fahr. In the morning, after the wind had abated and the rain had stopped, we were enveloped in thick fog.
We had descended to so low an altitude as 750 ft. above the sea level on the north side of the Serra Azul—the lowest elevation we had been at for some considerable time. We had descended altogether from the highest part of the great Central Brazilian plateau. From that point all the waters would be flowing to the north-east or north. We were, in fact, within a stone's throw—to be more accurate, within the radius of a few kilometres—of the birthplace of the Rio Novo, the head-waters of the River Arinos, of the Rio Verde (Green River), and of the several sources of the Rio S. Manoel or das Tres Barras, or Paranatinga; and not distant from the sources of the great Xingu River.
The Serra Azul, extending from west to east, was interesting geographically, not only because it marked the northern terminus of the highest terrace of the great central plateau, but also because from it or near it rose two of the greatest rivers of Central Brazil—the Xingu and the Arinos (Tapajoz), the latter the most central and important river of Brazil, crossing the entire Republic from south to north, as far as the Amazon.