We will now leave the inhabited pueblos and the ruins in their immediate vicinity and, going to the north, explore a section of country that shows every evidence of having sustained a considerable population some time in the past. To understand this fact clearly, it will be necessary to fix the location of the places named by means of the map. From time to time confused reports of the wonders to be seen in the San Juan section of Colorado had appeared in the East, but the first clear and satisfactory account is contained in the reports of Messrs. Jackson and Holmes, members of the U.S. Geographical and Geological survey of the territories under Dr. Hayden for 1874 and 1876. In the south-western portion of Colorado is a range of mountains known as the San Juan. Stretching from their base west to the Sierras is a great plateau region, drained by the numerous tributaries of the San Juan River. It would, perhaps, be more in keeping with the facts of the case to say “had been drained some time in the past,” for this is now such an arid, semi-desert country that the majority of the streams are dry, or have but scattered pools of water in them, during a large portion of the year; and yet, at times, great volumes of water go sweeping through them. This whole plateau is cut up with long, cañoned valleys, presenting, in effect, the same surface features that we have already described in New Mexico. Yet this precipitous, cañon-marked section of country is literally filled with the crumbling ruins of a former people. The situation in which they occur is in many cases very singular, and the whole subject is invested with great interest to us, because we see in them the remains of a people evidently the same as the Pueblo people to-day. One of the most extensive ruins in this section is situated at Aztec Springs. This, it will be seen, is about midway between the Rio Mancos and the McElmo. Mr. Holmes found the site of the spring, but it contained no water. He was told, however, by those familiar with the locality that there had been a living spring there up to within a few years. It was evidently a place of considerable importance once. Mr. Holmes describes the ruins as forming the most imposing pile of masonry found in Colorado. They cover an area of over ten acres. This includes only the ruins around the springs. But all about this central portion are scattered and grouped the remnants of smaller structures. So that nearly a square mile is covered with the ruins of this ancient pueblo. Most of the stone used was brought from the Mesa Verde (Green Plateau), a mile away, and must have been a great work for a people so totally without facilities.