heaped in confusion. In many places the strong
suggestion is that of a log jam left stranded by subsiding floods.
Nearly all the logs have broken into short lengths as cleanly cut as if
sawn, the result of succeeding heat and cold.

Areas of petrified wood are common in many parts of the Navajo country
and its surrounding deserts. The larger areas are marked on the
Geological Survey maps, and many lesser areas are mentioned in reports.
There are references to rooted stumps. The three groups in the Petrified
Forest National Monument, near the town of Adamana, Arizona, were chosen
for conservation because they are the largest and perhaps the finest; at
the time, the gorgeously colored logs were being carried away in
quantities to be cut up into table-tops.

As a matter of fact, these are not forests. Most of these trees grew
upon levels seven hundred feet or more higher than where they now lie
and at unknown distances; floods left them here.

[Illustration: THE PETRIFIED FOREST OF ARIZONA

Showing the formation in colored strata. The logs seen on the ground
grew upon a level seven hundred feet higher]

[Illustration: PETRIFIED TRUNK FORMING A BRIDGE OVER A CANYON

The trunk is 111 feet long. The stone piers were built to preserve it]

The First Forest, which lies six miles south of Adamana, contains
thousands of broken lengths. One unbroken log a hundred and eleven feet
long bridges a canyon forty-five feet wide, a remarkable spectacle. In
the Second Forest, which lies two miles and a half south of that, and
the Third Forest, which is thirteen miles south of Adamana and eighteen
miles southeast of Holbrook, most of the trunks appear to lie in their
original positions. One which was measured by Doctor G.H. Knowlton of
the Smithsonian Institution was more than seven feet in diameter and a
hundred and twenty feet long. He estimates the average diameters at
three or four feet, while lengths vary from sixty to a hundred feet.

The coloring of the wood is variegated and brilliant. "The state of
mineralization in which most of this wood exists," writes Professor
Lester F. Ward, paleobotanist, "almost places them among the gems or
precious stones. Not only are chalcedony, opals, and agates found among
them, but many approach the condition of jasper and onyx." "The
chemistry of the process of petrifaction or silicification," writes
Doctor George P. Merrill, Curator of Geology in the National Museum, "is
not quite clear. Si