From the incredible numbers of wild horses on our Western plains and on the pampas of South America, at a very early period in history, it became a question of some interest with many thinking men as to whether the horse was not indigenous on this continent. It is within the knowledge of everybody that this continent was inhabited by a mysterious and unknown race of people long before it was visited by Europeans. These mysterious people seem to have been driven out by the fierce and warlike savages who occupied the country at the time of its discovery, and even they knew nothing about the people who had preceded them. In very many localities the vanished people left behind them marks, numerous and unmistakable, that they had made considerable progress in the arts of civilized life. Writers have generally designated them as “the Mound Builders,” because they heaped great _tumuli_ of earth over the graves of their distinguished dead, but the real “Mound Builders” did far more than this, for with immense labor they built great, strong defenses for their protection against their enemies. When we go further West and South, into the fertile valleys among the mountains, we find still later traces of these unknown people in the ruins of buildings and dwellings erected, with infinite labor, traces of irrigating canals, etc., but we still fail to come up with them, or any trace of their history. In that region ruins of this type are designated as “Aztec Ruins,” but this title puts us no further on the way of who the builders were. In 1877 a correspondent of a Colorado newspaper, who seemed to write intelligently and candidly, described some of those ruins which he found in the valley of the Las Animas, in Southwestern Colorado. He speaks of a valley fifteen miles long and seven miles wide, on the Animas River, and says this valley was covered with dwellings built of stone, but he gives particular attention to a row of buildings built of sandstone laid in adobe mud. These buildings are about three hundred feet long and three hundred feet apart, as I understand the writer, and extend a distance of six thousand feet. The outside walls are four feet thick and the inside ones from one and a half to three feet thick; there are rooms still left and walls remaining that indicate a building four stories high. In some of the rooms there are writings that never have been deciphered, and in one of them there are drawings of tarantulas, centipedes, horses and men. The word “horses” riveted my attention, and connected with it there were several things to be considered. First, were the drawings really intended to represent horses? Second, if so might they not have been placed there long after the builders had disappeared and in recent years? Third, if placed there by the builders, what was their date, and were they before or after the introduction of the horse into Mexico by the Spaniards? The possibility