"At its bottom," he says, "a stream of water could be seen winding its way along it, the great depth causing it to appear like a mere riband. As far as time would permit an examination, for a depth of about three hundred feet--I could descend no further, on account of the wall becoming vertical--the formation appeared to be sandstone, horizontally stratified with drift conglomerate. At this depth I found, protruding horizontally from the wall, its end only sticking out, a petrified tree of about a foot in diameter, a fragment of which I broke off as a specimen. How did this tree get there? I also picked up at this point, upon the shelf on which I was standing, a species of iron ore, probably red hematite. The colonel commanding returning to camp, after a cursory look at the _cañon_, in order to put the troops in motion for the day's march, I had not the time necessary to make the full examination which I would have liked. I saw, however, enough to assure me that this _cañon_ is not more worthy the attention of the lover of nature than it is of the mineralogist and geologist." Three days later, Lieutenant Simpson, attended by his assistant engineers and draughtsmen, and escorted by sixty men and several officers, went to reconnoitre the cañon. The account he gives of it is most curious and interesting. At its mouth the walls were low; but as he proceeded, their altitude increased, until, at about three miles from the entrance, they assumed a stupendous appearance. The floor of the ravine, which in some places was no more than one hundred and fifty feet wide--although generally more than double that width--is a heavy sand. "The escarpment walls, which are a red amorphous sandstone, are rather friable, and show imperfect seams of stratification--the dip being slight, and towards the west. Almost perfectly vertical, they look as if they had been chiselled by the hand of art; and occasionally cizous marks, apparently the effect of the rotary attrition of contiguous masses, could be seen on their faces." Having proceeded about three miles, the party turned into a left-hand branch of the cañon. This branch was one hundred and fifty to two hundred yards wide, and its walls of the same towering height as those of the main line of ravine. Two or three patches of corn, with melons and pumpkins growing amongst it, were met with on the way; and then, after following this left-hand branch for half a mile, Mr Simpson turned to his right up a narrow secondary branch, enclosed between vertical walls three hundred feet high, which in some places are without a seam in their surface from top to bottom.