PLAIN OF POLISHED PEBBLES—SILICIFIED WOOD. 117 
On ascending from the shallow valley, along one of the side ravines, we found ourselves 
standing on the broad, level expanse of the plain of the Desert. The mountains towards which 
we were travelling rose up from this plain, but were apparently not much nearer to us than 
when we started. The outlines of the nearest ridges were sharp and distinct, and their color was 
a dark reddish-brown ; while the more distant points of the range were various shades of purple 
and blue. From our feet to the base of the mountain the surface seemed unbroken, and almost 
perfectly level; there was not a single swell of the ground, a tree, shrub, or boulder of rock, 
to break the monotony of the level expanse. Pebbles of various colors, like those found at 
Pilot Knob, lay in profusion on the surface. We had not proceeded far before we found that 
the ground was literally paved with them, and that, in fact, but little earth or sand was to be 
seen. "These pebbles were not loose, as upon an ordinary gravel-walk, but seemed laid down 
compactly, as if by art, and all at the same height, as if they had been pressed down by a roller, 
or otherwise. We were, in fact, upon the surface of the layer of conglomerate which caps the 
horizontal strata below, and which was seen in section at the Indian village and beyond Pilot 
Knob. "The size of the pebbles varies from that of a hickory nut to a hen's egg, and larger ; but 
the greater part are not larger than an egg. They consist, as before observed, of various 
colored porphyries, and of basalt and greenstone, mingled with quartz, agates, and jaspers. 
The whole surface of the plain was swept clean by the winds, and the upper layer of pebbles was 
perfectly clean and free from soil, sand, or dust. All the cementing material seemed removed, 
and they were retained to the surface by a narrow but firm bedding on the under side. Every 
pebble had the beautifully polished and glistening exterior, and the diversity of colors was 
increased, and their brilliance heightened, by this singular polish. The glitter of the sun's 
rays on this plain was like that on the water of a lake in a summer's day, when the surface is 
thrown into ripples by a passing breeze. Each pebble seemed firmly placed, and yet could be 
readily detached. The galloping of our mules made a strange clinking or rattling sound, but 
scarcely left a trace of our passage behind us. We, however, crossed several long, path-like 
discolorations of the surtace, extending for miles in nearly straight lines, which were Indian 
trails. The only change which was produced appeared to be the removal or dimming of the 
polish on the pebbles. There was no break in the hard surface, and no dust. That the 
distinctness of the trail was made by removing the polish only, became evident from the fact 
that figures and Indian hieroglyphics were traced, or imprinted, on the surface adjoining the 
path, apparently by pounding or bruising the surface layer of the pebbles. These trails seemed 
very old, and may have endured for many generations. 
While travelling over this brilliantly-paved plain, its surface shining with myriads of pol- 
ished pebbles of agate, jasper, and carnelian, the attention was constantly attracted, at short 
intervals, by some stone of pecular form or unusual color, and it was difficult to resist the temp- 
tation to dismount and examine them. Several masses of a brownish hue, and not rounded 
like the pebbles, but elongated and irregular, were seen. A stroke of my hammer on the end 
of one of these broke it across, and revealed the most exquisite and beautifully preserved organ- 
ization of wood. Each cell and pore could be distinctly traced, ranged within concentric circles, 
Which were the lines of annual growth, and showed that the plant was exogenous. Although 
the exterior was dark-brown, the interior, as exposed by the fracture, was of a light buff color, 
veined with red and brown in varied tints due to the coloration of the silica, which had per- 
meated the pores of the wood by iron or other impurities. The portion contiguous to the 
external surface, for the depth of about one-eighth of an inch, was nearly white and opaque, 
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