Early the next morning we were to climb to the top of the steep cliffs behind the old church at the Potrero; that night we slept for the last time in the land of the tropics. Late in the evening I walked over by the home of a Tarahumari Indian. He had a bright fire burning in front of his hut, and on the ground his family were all sleeping peacefully, even down to a very young baby. The house appeared to be deserted, being used probably only during the rainy season. Next morning by four o'clock we began the ascent of the steep mountain. It was before daylight when we left the cañon, and by the time we had climbed for three hours I noticed one of the most singular cliff or cave dwellings I had so far seen. There was a distinct trail leading to it. This trail could be perceived from the very bottom of a deep cañon which branched off from the Batopilas, led along dizzy cliffs, holding to the sides of the steep mountain until it reached a height fully equal to our own, and finally disappeared in an enormous cave. This must have been capable of containing hundreds of people, as it was over a mile distant, and at that distance we could perfectly discern its mouth and even its interior walls. It was the dizziest climb to a home I have ever read of or seen. [Illustration: THE HOME OF A TARAHUMARI INDIAN] That afternoon I came to the farms of some civilized Tarahumaris, built on the very steep mountain side, on which the dirt was held back by terraces or rude retaining walls, so very similar to those seen around the ruins of Northwestern Chihuahua, supposed to be Toltec or Aztec, that I could not help thinking that there was some closer connection between them than that of mere resemblance. I had heard a dozen theories to account for these terraces in the North, as for collecting water in dry seasons, for conducting water, as places for defense, etc., etc., but, with an actual case directly under observation, this seems to be a better explanation: In decades and centuries of rainy seasons of more or less violence, after the people had abandoned these northern houses, or had been killed by their enemies, all the retained loose earth would have been swept away, leaving only rude and dilapidated walls or terraces sweeping around the mountain sides, from which almost anything could be inferred, whether the most peaceful form or the most warlike fortification.