It is four hundred miles in length, and at its widest part between two and three hundred. Its superficial area is about equal to the island of Ireland. Its surface aspect differs considerably from the rest of prairie-land, nor is it of uniform appearance in every part. Its northern division consists of an arid steppe, sometimes treeless, for an extent of fifty miles, and sometimes having a stunted covering of mezquite (_acacia_), of which there are two distinct species. This steppe is in several places rent by chasms a thousand feet in depth, and walled in on both sides by rugged impassable precipices. Vast masses of shapeless rocks lie along the beds of these great clefts, and pools of water appear at long intervals, while stunted cedars grow among the rocks, or cling from the seams of the cliffs. Such chasms, called "canons," can only be crossed, or even entered, at certain points; and these passes are frequently a score of miles distant from each other. On the upper plain the surface is often a dead level for a hundred miles, and as firm as a macadamised road. There are spots covered with a turf of grass of the varieties known as gramma, buffalo, and mezquite; and sometimes the traveller encounters a region where shallow ponds of different sizes stud the plain--a few being permanent, and surrounded by sedge. Most of these ponds are more or less brackish, some sulphurous, and others perfectly salt. After heavy rains such aqueous deposits are more numerous, and their waters sweeter; but rain seems to fall by accident over this desolate region, and after long spells of drought the greater number of these ponds disappear altogether. Towards the southern end of the Llano Estacado the surface exhibits a very singular phenomenon--a belt of sand-hills, nearly twenty miles in breadth and full fifty in length, stretching north and south upon the plain. These hills are of pure white sand, thrown up in ridges, and sometimes in cones, to the height of a hundred feet, and without tree, bush, or shrub, to break their soft outlines, or the uniformity of their colour. But the greatest anomaly of this geological puzzle is, that water-ponds are found in their very midst--even among their highest ridges--and this water not occasional, as from rains, but lying in "lagunas," with reeds, rushes, and _nymphae_ growing in them, to attest that the water is permanent! The very last place where water might be expected to make a lodgment. Such formations of drift-sand are common upon the shores of the Mexican Gulf, as well as on European coasts, and there their existence is easily explained; but here, in the very heart of a continent, it cannot be regarded as less than a singular phenomenon. This sand-belt is passable at one or two points, but horses sink to the knees at every step, and but for the water it would be a perilous experiment to cross it.