These trees did not grow where they lie, or even within many miles of where they are found. They were carried from a long distance to this region by flood waters, and after whirling and drifting around in the inland sea then covering the land, they became waterlogged and finally sank to the bottom, where some eddy or whirlpool carried them. Here they lay for countless centuries, slowly being covered by silt and sand, while yet other logs came to rest above them. Thousands of years elapsed during this drifting and sinking into oblivion under the ooze of this Triassic Sea. And then came Old Ocean, later on in the Mesozoic Age submerging the entire region and adding its weight to the terrific pressure already brought to bear on the burial place of the giants. This pressure packed the sands to stone, and compressed the clays to shale. Already the logs were impregnated with a strong solution of silica, with iron and manganese also present, and the pressure forced it into every fiber. Atom by atom the cells of the wood were dissolved and replaced by the silica, which hardened, taking the exact shape of the cell it destroyed. While the logs were probably partly petrified before the influx of the ocean waters, a great many show that enormous pressure was brought to bear while they were yet flexible. Some logs recently brought to light by the summer floods, are mashed almost flat, cross sections measuring eighteen inches one way and more than five feet the other. [Illustration: Courtesy National Park Service Cross section of log showing natural fracture.] Nature did not slight details in this work of substitution. Even to the most minute particular the structure of the wood was replaced by the intruder. Under the microscope it is possible to identify the kind of wood represented. Dr. F. H. Knowlton has classified the major portion of these trees as belonging to a species of conebearing tree now extinct, related to the Norfolk Island Pine. The logs lay buried for numberless centuries, but natural forces were at work bringing them to the surface again. During the Tertiary Period, a slow upheaval brought the submerged area to light. On and upward it rose, until it now lies more than a mile above the level of the ocean. Freed of its Old Man of the Sea, warmed and comforted by Arizona’s brilliant sun and searching wind, the region lay at rest.