44 GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
Fragments are also found in the detritus from Leroux's fork and other small streams coming 
down from the plains at the north. Several specimens of these fossil trees are in the collection, 
and they exhibit a pleasing variety of color and grain. Some are much more perfectly pre- 
served than others; and the rings of annual growth, the medullary rays, and the cells, are 
distinctly and beautifully preserved, and can be clearly seen by the naked eye. 
One of the specimens, which is very compact, and homogeneous, and as hard as rock-crystal, 
presents a variety of colors, and resembles a beautiful agate. One side is of a deep carne- 
lian-red color, and the other is nearly transparent and colorless, but has a milky or semi- 
opaline whiteness, like specimens of calcedony. Intermediate portions of the mass are yellow- 
ish, and streaks of red, brown, and yellow are found in almost all parts of it. At first sight, 
the specimen appeared to be an agate and devoid of structure, but the parallelism of several 
threads or streaks of dark brown running through one end of the specimen invited a closer 
examination, and in this the beautiful ligneous fibre was found perfectly preserved ; and when a 
plate was polished, the woody structure was most distinctly shown. In some portions of the 
specimen, however,—especially in the white and nearly transparent parts—the structure was 
almost wholly obliterated, and if these parts alone had been collected their vegetable origin 
would not have been suspected. The variety of color presented by this mass, and the exquisite 
preservation of the minutest fibre and cell of the former wood in dense glassy silica, and the 
absence of all open cells or pores, rendered it peculiarly suitable for cutting and polishing, and 
several ornamental stones cut from it for bracelets, &c., are very beautiful. Another specimen, 
also very dense and beautifully preserved, shows the effect of pressure and fracture after the 
silicification was complete, or during its progress. Fragments of the wood are seen separated 
from each other, and firmly imbedded in dense white silica, which was infiltrated, and is dis- - 
posed in concentric layers, agate-like in the larger spaces. The polished surface of this speci- 
men is exceedingly beautiful, every pore and fibre of the wood being well preserved, and the 
angular fragments being set in the white agate base, so as to form a perfect mosaic. Thin 
slices have been cut by the lapidary from all these specimens, in different directions, so as to 
permit the structure of the cells and fibres to be studied under the microscope. These slices 
are ground very thin and are highly polished, so that they readily transmit the light. "They 
have been placed in the hands of Professor Schaeffer, of Washington, for examination and 
description. 
Drift.—Beyond this remarkable locality of silicified trees, the ground in many places was 
found to be strewed with their fragments, and these were mingled with pebbles of agate and 
jasper, the whole forming a mass of detritus or drift which was occasionally very abundant. 
Several specimens of these rolled pebbles are in the collection, and consist of compact red and 
yellowish jaspery rocks, one of them being cut in every direction by a multitude of thin quartz 
veins, from the thickness of paper to one-eighth of an inch, which form a net-work and enclose 
the masses of compact red jasper. This stone when polished exhibits the veins distinctly, and 
yields beautiful ornamental stones. "That the mass was thoroughly solidified before it became 
traversed by the quartz veins, is clearly shown by the sharp angles at the intersection of the 
fissures and by the numerous faults along some of the veins, showing that they are of different 
ages. Mr. Marcou also mentions the occurrence in the drift and in the streams of numerous 
carboniferous fossils, much rolled and worn by attrition. These he supposed to have been 
transported from the mountains in the south—the Sierra Mogoyon or Sierra Blanca. The 
strata also, further on, appeared to dip away from this range towards the north. 
From Lithodendron creek westward, along the valley of the Colorado Chiquito, the red sand- 
stones and red marls were found on both sides, and the upper or lighter-colored strata entirely 
disappeared or were present only here and there in isolated mounds far from the trail. Below 
the point where the stream was crossed, several buttes, supposed to be volcanic or basaltic, were 
seen on the right bank. 
