Not only pits indicative of the stone tools by which the stones forming the masonry of Sun Temple were dressed appear on all the rocks used in its construction, but likewise many bear incised symbols. Several of these still remain in the walls of the building; others have been set in cement near the outer wall of the eastern kiva. It is interesting to record that some of the stones of which the walls were constructed were probably quarried on the mesa top not far from the building, but as the surface of the plateau is now forested, the quarries themselves are hidden in accumulated soil and are difficult to discover. AGE Sun Temple is believed to be among the latest constructed of all the aboriginal buildings in the park, probably contemporaneous with late building activities in Balcony House, Spruce Tree House, and Cliff Palace. Because of the absence of timbers or roof beams it is impossible to tell when Sun Temple was begun, how long it took for its construction, or when it was deserted. There are indications that its walls may never have been completed, and from the amount of fallen stones there can hardly be a doubt that when it was abandoned they had been carried up in some places at least 6 feet above their present level. The top of the wall had been worn down at any rate 6 feet in the interval between the time it was abandoned and the date of excavation of the mound. No one can tell the length of this interval in years. We have, however, knowledge of the lapse of time, because the mound had accumulated enough soil on its surface to support growth of large trees. Near the summit of the highest wall in the annex there grew a juniper tree of great antiquity, alive and vigorous when excavation work was begun. This tree undoubtedly sprouted after the desertion of the building and grew after a mound had developed from fallen walls. Its roots penetrated into the adjacent rooms and derived nourishment from the soil filling them. Necessarily, when these roots were cut off the tree was killed. It was then cut off about a foot above the ground, the stump remaining. A cross section of this stump was examined by Gordon Parker, supervisor of the Montezuma National Forest, who found that it had 360 annual rings without allowing for decayed heartwood which would add a few more years to its age. It is not improbable that this tree began to grow on the top of the Sun Temple mound shortly after the year 1540, when Coronado first entered New Mexico. How long an interval elapsed for crumbling walls to form the mound in which it grew, and how much earlier the foundations of the ruined walls were laid, no one can tell. A conservative guess of 350 years for the interval between construction and the time the cedar began to sprout would carry the antiquity of Sun Temple back to about 1200 A.D. UNITY OF CONSTRUCTION