The Roncador River.
Continuing in a north-westerly direction we again obtained a gorgeous view of the treble portal—by which word the Brazilians describe a monumental entrance of any kind. That is just what those three immense gaps in the plateau looked like: an immense wall of rock forming a high barrier, with three gigantic natural gateways.
After finding a stream of good water on the west side of the plateau we rose again higher, obtaining a splendid bird's-eye view of the picturesque depression we had just crossed. The effects of erosion following those of volcanic activity were evident enough upon the entire landscape. On the west side we had a horseshoe-shaped vertical wall—seemingly containing an extinct crater—and yet another on the north side of the western end of the elongated ellipse which was there formed.
With some difficulty we managed to get the animals up to the summit of the plateau (elev. 2,580 ft.). From there we obtained a sumptuous view beyond. An immense dyke of brilliant red rock, flat-topped, lay majestically to the west. At its foot the Rio Pedra Grande had its birth, and then flowed westward into the Rio Roncador. Four gigantic flat table-lands stood impressively in a line. Three more, equally impressive, loomed in the south-west. Other minor ones, quite wall-like—rectangular in vertical section—appeared in the blue distance, while the horizon was barred by a long flat plateau.
Looking north as we descended from the table-land, we found on our left another extinct crater—semicircular in shape, with several superimposed strata of lava, each about one foot thick, capping its lip, which was broken up into three sections. The valley below that crater formed a cuvette, the bottom of which (elev. 2,200 ft.) showed deep erosion by water in one or two places. Sand covered the lava-flow which had travelled northward. Quantities of heavy, spherical, bullet-like blocks of hard-baked rock were scattered all about—evidently shot out of the crater when active.
We had travelled 80 kil. from Cayambola in three days, and we had reached a spot of slight, well-rounded undulations where grazing was fair. I decided to halt early in the afternoon—more particularly as this spot appeared to me to have been at one time or other submerged—probably it had been a lake bottom. I had, since the beginning of my journey, been searching everywhere for fossils—but in vain. I had not seen the vestiges of a single one. Personally, I was persuaded that Central Brazil could well be geologically classified in the archaic group—the most ancient of the terrestrial crust, and consisting (in Brazil) chiefly of gneiss, mica schists and granite, solidified into their present form by intense eruptive phenomena and dissolved—not by immersion in ocean waters, as some suppose, but by deluges of such potentiality as the human mind can hardly conceive.
It was quite enough to visit the central plateau of Brazil to be persuaded that that continent had never been submerged under a sea; on the contrary, it must have been the oven of the world. The volcanic activity which must have taken place in that part of the world—it was not a separate continent in those days—was quite, as I have said, beyond human conception. This does not mean that at later periods there may not have been temporary lakes—as, for instance, in the spot where we encamped that night—or portions of country which had become flooded, upon the cooling of the earth, and subsequently became drained and dry again.
A wonderful surprise awaited me that day. To the north of my camp was a peculiar round mound. I climbed it, and what was my astonishment in the short ascent to find near the summit, among a lot of lava pellets, marble fragments, crystals, and great lumps of iron ore, a number of vertebræ from the tail and spine of a giant reptile! The vertebræ had been disjointed and scattered somewhat about by wind and water—but there they were; the smaller ones on the side of the hill, the larger on the summit—which led me to believe that the animal had crouched on the top of the hill when dying. Some of the fossil vertebræ were so large and heavy that I hardly had the strength to lift them up. The bones—petrified—were of a beautiful white. Many of them had, unfortunately, become so fractured as to make identification difficult. On following the line of the dorsal vertebræ—somewhat scattered about—I came upon some vertebræ which appeared to me to be cervical vertebræ; and then, behold my joy! in searching around the summit of the mound I perceived the skull. The skull was so big and heavy that I could not carry it away, but I took several photographs and careful drawings of it from all sides.