The exact dimensions of Fire House (pl. 1) can be obtained only by excavation, but it is approximately 94 by 79 feet in greater and lesser diameter. Some parts of the outside wall are now 10 feet high, and its thickness averages 3 feet, but if the stones accumulated about its base were removed the height would be 4 or 5 feet greater. There are evidences of an external passage-way through the outer wall indicating a central court. Within the enclosure there are many indications of rooms some of which appear to be circular, but the interior is so filled with fallen walls that an accurate ground plan could not be drawn without extensive excavation. The stones forming the wall are, as a rule, cubical blocks, well dressed and accurately fitted, showing good masonry. Two of the largest of the wall stones are 5 feet long and 3 feet wide, with an estimated thickness of 2 feet. As it would take several men to carry one of these stones from the quarry to its place in the wall, they might be called megaliths. The fine spring at the base of the cliff below Fire House was evidently used by the inhabitants for drinking water, and the trail from here to a gateway in the outer wall is still well marked. As one climbs from the spring to the top of the plateau the way passes between the cliff and a flat stone set on edge and pierced with a hole about 5 feet above the pathway. This stone was evidently a means of defense; behind it the warriors may have stood peering down upon their enemies through this orifice. Near it are pictographs of unknown meaning. The circular form of Fire House (fig. 1) and its well-constructed surrounding wall are more characteristic of eastern than of western pueblo masonry. This round type[4] is found from southern Colorado on the north to the neighborhood of the Zuñi settlements on the south; it has not been reported from the region on both banks of the Rio Grande. Roughly speaking, circular ruins correspond, in their distribution, with a line extending north-south midway between the eastern and western sections of the pueblo area—a limitation that can hardly be regarded as fortuitous. Its meaning we may not be able to correctly interpret, but the fact calls for an explanation. The type is old, the modern pueblos having abandoned this form. The area where circular ruins occur corresponds, in a way, to that inhabited in part by the modern Keres, none of whom, however, now dwell in circular towns. Provisionally we shall consider the Keresan pueblos as the nearest of all descendants of those who once inhabited villages of circular or oval form, a generalization substantiated by the existence of words of Keres language in many old ceremonies among all the pueblos. There is a sharp line of demarcation between the zone of circular ruins and that inhabited by the pueblos along the Rio Grande, but on the western border these circular buildings extend as far west as the Hopi country.