Further journeying brought with it topographical adventures. The country into which they were penetrating is one of the most remarkable in the world for its physical peculiarities. Its scenery bears about the same relation to the scenery of earth in general, that a skeleton's head or a grotesque mask bears to the countenance of living humanity. In no other portion of our planet is nature so unnatural, so fanciful and extravagant, and seemingly the production of caprice, as on the great central plateau of North America. They had left far behind the fertile valley of the Rio Grande, and had placed between it and them the barren, sullen piles of the Jemez mountains. No more long sweeps of grassy plain or slope; they were amid the _débris_ of rocks which hedge in the upper heights of the great plateau; they were struggling through it like a forlorn hope through _chevaux-de-frise_. The morning sun came upon them over treeless ridges of sandstone, and disappeared at evening behind ridges equally naked and arid. The sides of these barren masses, seamed by the action of water in remote geologic ages, and never softened or smoothed by the gentle attrition of rain, were infinitely more wild and jagged in their details than ruins. It seemed as if the Titans had built here, and their works had been shattered by thunderbolts. Many heights were truncated mounds of rock, resembling gigantic platforms with ruinous sides, such as are known in this Western land as _mesas_ or _buttes_. They were Nature's enormous mockery of the most ambitious architecture of man, the pyramids of Egypt and the platform of Baalbek. Terrace above terrace of shattered wall; escarpments which had been displaced as if by the explosion of some incredible mine; ramparts which were here high and regular, and there gaping in mighty fissures, or suddenly altogether lacking; long sweeps of stairway, winding dizzily upwards, only to close in an impossible leap: there was no end to the fantastic outlines and the suggestions of destruction. Nor were the open spaces between these rocky mounds less remarkable. In one valley, the course of a river which vanished ages ago, the power of fire had left its monuments amid those of the power of water. The sedimentary rock of sandstone, shales, and marl, not only showed veins of ignitible lignite, but it was pierced by the trap which had been shot up from earth's flaming recesses. Dikes of this volcanic stone crossed each other or ran in long parallels, presenting forms of fortifications, walls of buildings, ruined lines of aqueducts. The sandstone and marl had been worn away by the departed river, and by the delicately sweeping, incessant, tireless wings of the afreets of the air, leaving the iron-like trap in bold projection.