326 OLDER MESOZOIC FLORAS OF UNITED STATES. 
Chalcedony Park. The petrified logs are countless at all horizons and 
lie in the greatest profusion on the knolls, buttes, and spurs and in 
the ravines and gulches, while the ground seems to be everywhere 
studded with gems consisting of broken fragments of all shapes and 
sizes and exhibiting all the colors of the rainbow. When we remem- 
ber that this special area is several square miles in extent some idea 
can be formed of the enormous quantity of this material that it 
contains. 
Although much fossil wood occurs throughout the whole region as 
above delimited, still for several miles to the north of this Chalcedony 
Park it is less abundant, and it is not until the northern end of the 
area is reached that anGther center of accumulation occurs. This lies 
between two mesas, in a valley that opens out upon the general plain 
which stretches north to the Rio Puerco. It ismuch smaller in extent 
than the southern park, but substantially the same general features are 
presented. 
There is still a third center of accumulation, called the ‘* middle 
forest,” which lies some 2 miles southeast of this last and extends to 
the eastern margin of the general region. It occupies the western 
slope of the table-land on the east, and is very extensive, stretching a 
mile or more in a north-south direction and having a width of half a 
mile in places. It presents many interesting novelties. 
All the petrified forests thus far described are, geologically speaking, 
entirely out of place, and the trunks bear every evidence of having 
dropped down to their present position from a higher horizon in which 
they were originally entombed and from which: they have been subse- 
quently washed out. Nor is their original position to be discovered by 
ascending the several mesas included in the area, aithough some of 
these rise 400 feet above the lowest ground. It is not until the still 
higher plateau is reached which bounds the whole region and lies more 
than 700 feet above the valley that the stratum is at last found which 
actually holds the fossil wood. A geologist might therefore traverse 
the entire area from north to south, visit all three of the principal 
forests, and go out with the impression that everything was out of 
place, and with no correct idea of the true source of therfossil wood. 
Even on the east it would be difficult to settle this question, on account 
of the paucity of the trunks in that direction, but it could doubtless 
be done by prolonged and careful search. On the west side, however, 
and directly west of the southernmost area, the plateau is only about 2 
miles wide and has a western escarpment, with another valiey extending 
both south and west of it. This plateau or elongated mesa is highest 
on its western side, rising to the 5,750-foot contour line immediately 
above the escarpment, and here is exposed a fine series of petrified 
trunks fringing the mesa, with many weathered out on the slope or 
rolled down into the valley below. A few feet below the actual sum- 
