And now great desert plains unfold to view. Upon their confines arise the blue mountain ranges which intersect them, their canyons and slopes, though faint in distance and blurred by shimmering heat arising from the desert floor, yet cast into distinct tracery by the rays of the sun. Towards the azure vault overhead, as we behold the arid landscape, eddying dust-pillars whirl skywards upon the horizon, or perhaps a cloud of dust, far away upon the trail which winds over the flat expanse, denotes some evidence of man--horseman or ox-cart pursuing its leisurely and monotonous way. Upon the edges of the dry stream-beds, or _arroyos_, which descend from the hills and lose themselves in wide alluvial fans upon the sandy waste, a fringe of scant vegetation appears, nourished by the water which flows down them in time of rain. Beneath our horses' hoofs the white alkali crust which thinly covers the desert floor, crumbles and breaks. Gaunt cacti stretch their skinny branches across the trail, which winds among foothills and ravines, and the horned toads and the lizards, the only visible beings of the animal world here, play in and out of their labyrinths as we pass. We are upon the Great Plateau. All is vast, reposeful, boundless. The sun rises and sets as it does upon some calm ocean, describing its glowing arc across the cloudless vault above, from Orient to Occident. Sun-scorched by day, the temperature drops rapidly as night falls upon these elevated steppes, 7,000 feet or more above the level of the sea, and the bitter cold of the rarefied air before the dawn takes possession of the atmosphere. The shivering _peones_ of the villages rise betimes to catch the sun's first rays, and stand or squat against the eastern side of their adobe huts, what time the orb of day shows his red disc above the far horizon. _La capa de los pobres_--"the poor man's cloak"--they term the sun, as with grateful benediction they watch his coming, and stamp their sandalled feet. [Illustration: THE GREAT PLATEAU: NIGHTFALL IN THE DESERT.]