They were now leaving the pleasant champaign country, as the road wound up the bold sierra which separates the great plateaus of Mexico and Puebla. The air, as they ascended, became keen and piercing; and the blasts, sweeping down the frozen sides of the mountains, made the soldiers shiver in their thick harness of cotton, and benumbed the limbs of both men and horses. They were passing between two of the highest mountains on the North American continent; Popocatepetl, “the hill that smokes,” and Iztaccihuatl, or “white woman,”[232]--a name suggested, doubtless, by the bright robe of snow spread over its broad and broken surface. A puerile superstition of the Indians regarded these celebrated mountains as gods, and Iztaccihuatl as the wife of her more formidable neighbor.[233] A tradition of a higher character described the northern volcano as the abode of the departed spirits of wicked rulers, whose fiery agonies in their prison-house caused the fearful bellowings and convulsions in times of eruption. It was the classic fable of antiquity.[234] These superstitious legends had invested the mountain with a mysterious horror, that made the natives shrink from attempting its ascent, which, indeed, was from natural causes a work of incredible difficulty. The great _volcan_,[235] as Popocatepetl was called, rose to the enormous height of 17,852 feet above the level of the sea; more than 2000 feet above the “monarch of mountains,”--the highest elevation in Europe.[236] During the present century it has rarely given evidence of its volcanic origin, and “the hill that smokes” has almost forfeited its claim to the appellation. But at the time of the Conquest it was frequently in a state of activity, and raged with uncommon fury while the Spaniards were at Tlascala; an evil omen, it was thought, for the natives of Anahuac. Its head, gathered into a regular cone by the deposit of successive eruptions, wore the usual form of volcanic mountains when not disturbed by the falling in of the crater. Soaring towards the skies, with its silver sheet of everlasting snow, it was seen far and wide over the broad plains of Mexico and Puebla, the first object which the morning sun greeted in his rising, the last where his evening rays were seen to linger, shedding a glorious effulgence over its head, that contrasted strikingly with the ruinous waste of sand and lava immediately below, and the deep fringe of funereal pines that shrouded its base.