Many of these passes afforded obvious points of defence; and the Spaniards, as they entered the rocky defiles, looked with apprehension lest they might rouse some foe from his ambush. This apprehension was heightened, as, at the summit of a steep and narrow gorge, in which they were engaged, they beheld a strong work, rising like a fortress, and frowning, as it were, in gloomy defiance on the invaders. As they drew near this building, which was of solid stone, commanding an angle of the road, they almost expected to see the dusky forms of the warriors rise over the battlements, and to receive their tempest of missiles on their bucklers; for it was in so strong a position, that a few resolute men might easily have held there an army at bay. But they had the satisfaction to find the place untenanted, and their spirits were greatly raised by the conviction that the Indian monarch did not intend to dispute their passage, when it would have been easy to do so with success. Pizarro now sent orders to his brother to follow without delay; and, after refreshing his men, continued his toilsome ascent, and before nightfall reached an eminence crowned by another fortress, of even greater strength than the preceding. It was built of solid masonry, the lower part excavated from the living rock, and the whole work executed with skill not inferior to that of the European architect.1 Here Pizarro took up his quarters for the night. Without waiting for the arrival of the rear, on the following morning he resumed his march, leading still deeper into the intricate gorges of the sierra. The climate had gradually changed, and the men and horses, especially the latter, suffered severely from the cold, so long accustomed as they had been to the sultry climate of the tropics.2 The vegetation also had changed its character; and the magnificent timber which covered the lower level of the country had gradually given way to the funereal forest of pine, and, as they rose still higher, to the stunted growth of numberless Alpine plants, whose hardy natures found a congenial temperature in the icy atmosphere of the more elevated regions. These dreary solitudes seemed to be nearly abandoned by the brute creation as well as by man. The light-footed vicuna, roaming in its native state, might be sometimes seen looking down from some airy cliff, where the foot of the hunter dared not venture. But instead of the feathered tribes whose gay plumage sparkled in the deep glooms of the tropical forests, the adventurers now beheld only the great bird of the Andes, the loathsome condor, who, sailing high above the clouds, followed with doleful cries in the track of the army, as if guided by instinct in the path of blood and carnage.