"Indians they must be," muttered Seguin. "There are no others here. Indians! No! There never were such as them. See! they are not men! Look! their huge horses, their long guns; they are giants! By Heaven!" continued he, after a moment's pause, "they are bodiless! They are phantoms!" There were exclamations of terror from the hunters behind. Were these the inhabitants of the city? There was a striking proportion in the colossal size of the horses and the horsemen. For a moment I was awe-struck like the rest. Only a moment. A sudden memory flashed upon me. I thought of the Hartz Mountains and their demons. I knew that the phenomenon before us could be no other; an optical delusion; a creation of the mirage. I raised my hand above my head. The foremost of the giants imitated the motion. I put spurs to my horse and galloped forward. So did he, as if to meet me. After a few springs I had passed the refracting angle, and, like a thought, the shadowy giants vanished into the air. The men had ridden forward after me, and having also passed the angle of refraction saw no more of the phantom host. The city, too, had disappeared; but we could trace the outlines of many a singular formation in the trap-rock strata that traversed the edge of the valley. The tall groves were no longer to be seen; but a low belt of green willows, real willows, could be distinguished along the foot of the mountain within the gap. Under their foliage there was something that sparkled in the sun like sheets of silver. It was water! It was a branch of the Prieto. Our horses neighed at the sight; and, shortly after, we had alighted upon its banks, and were kneeling before the sweet spirit of the stream. CHAPTER THIRTY FIVE. THE MOUNTAIN OF GOLD. After so fatiguing a march, it was necessary to make a longer halt than usual. We stayed by the arroyo all that day and the following night. But the hunters longed to drink from the Prieto itself; and the next morning we drew our pickets, and rode in the direction of that river. By noon we were upon its banks. A singular stream it was, running through a region of bleak, barren, and desolate mountains. Through these the stream had forged its way by numerous canons, and rushed along a channel at most places inaccessible. It was a black and gloomy river. Where were its sands of gold?