It is impossible from the data available to determine the century in which the towers and great houses of the region were constructed. Thus far a few were seen with great trees growing in them, but none with roofs; the state of preservation of the walls does not point to a great age. Several writers have regarded them as occupied subsequently to the Spanish conquest, while others have ascribed to them a very remote antiquity. It can hardly be questioned that the cliff-dwellers, and by inference their kindred, the tower builders, were superior in their arts to modern Pueblos. It is important to determine first of all the forms of these towers; whether their ground plans are circular, oval, square, rectangular, or semicircular. The northern wall of many is uniformly curved and the last to fall, which might lead to the belief that the southern side, generally straight, was poorly made, but one can not determine that by direct observation, since the latter has fallen. As a matter of fact the south wall was generally low and straight, over 50 per cent of the “round” towers being semicircular, D-shaped, or some modification of that form; but we also have square and rectangular towers. It is also important to determine whether these had single or multiple chambers and the arrangement of the rooms in relation to them. This is especially desirable in towers with concentric compartments. It is also instructive to know more of the association of towers with pueblos and cliff-dwellings or to analyze component architectural features. The tower type often occurs without appended rooms. At Cliff Palace and Square Tower House it is united with a pueblo village under cliffs; in Mud Spring Ruin it has a like relation to rooms of a pueblo in the open. Has its function changed by that union? What use did the tower serve when isolated and had it the same use when united with other kinds of rooms in cliff-dwellings and pueblos? No writer on the prehistoric towers of Colorado and Utah has emphasized the fact that a large number of these buildings are semicircular or D-shaped, but it has been taken for granted that the fallen wall on the south side was curved, rendering the tower circular or oval.[44] In most cases this wall was the straight side of a D-shaped tower. Doctor Prudden, who first recognized the importance of a union of towers with other types of architecture in the McElmo district, says:[45] “Towers of various forms and heights occasionally form a part of composite ruins of various types.” He says also: “Several of the houses are modified by the introduction of a round tower.” And again: “At the head of a short canyon north of the Alkali, which I have called Jackson Canyon ... each building consists of an irregular mass of rooms about 200 feet long, with low towers among them.”