Ch. 7: Quartz Group - Opal, Rock Crystals, Amethysts, Rose Quartz, Agate, etc.

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	138	GEMS AND PRECIOUS STONES IN THE

	depth. Over the entire area, trees lie scattered in all conceivable positions and in fragments of all sizes, the broken sections sometimes resembling a pile of cartwheels. A tree 150 feet in length is often found split into as many sections, of almost uniform length, presenting the appearance of having been sawn asunder for shingle-blocks by some prehistoric forester; or broken into countless fragments, ranging from the size of a small pebble to that of a fair-sized boulder, also fractured into perfect-shaped cubes, as if cut by a lapidary. These multiplied fractures are the result of alternate heat and cold, produced by atmospheric changes, acting on the water collected in fissures of the tree. A phenomenon perhaps unparalleled, and the most remarkable feature of the park, is a natural bridge formed by a tree of agatized wood spanning a caflon 45 feet in width. (See Illustration.) In addition to the span, fully 50 feet of the tree rest on one side, making it visible for a length over 100 feet. Both ends of the tree are imbedded in the sandstone. It averages 3 1/2 feet in diameter,—4 feet at the thickest part and 3 at the smallest. Where the bark does not adhere the characteristic colors of jasper and agate are seen. Although the wood is beautiful to the naked eye, a microscope is needed to reveal its greatest charms; not only does the glass enhance the brilliancy of the colors, but it renders visible the structure, which has been perfectly preserved even to the forms of minute cells, and is more beautiful now than before the transformation. Dr. P. H. Dudley examined microscopically some sections of this wood, and found that part of it at least belongs to the genus Araucaria, one species of which, Araucaria excelsa, the Norfolk Island pine of the South Pacific Ocean, according to the same authority, grows to a height of from 100 to 200 feet. Other portions were found to resemble our red cedar, Juniperus Virgin-iana, when grown in the extreme south. The cell-structure of some of the wood indicates growth in a mild, uniform climate, the annual rings being marked only by one, two, three or more slightly smaller hexagonal or rounded, not tabular, cells as is usually the case. The name " chinarump" has been suggested for this substance by Major John W. Powell, this being the Indian name for the material. These trees, according to one of the In-

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