50 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



As far above the leaf-bearing horizon as I was able to ascend, the sili- 

 cified trunks were very numerous and well preserved, and, by the aid of 

 a field-glass, others could be detected in all parts of the clift' to the 

 highest stratum. 



At another point, nearly a mile farther east, I climbed the rugged 

 walls of the mountain for the purpose of examining a number of large 

 trees visible from below. Trunks and fragments of trunks were found 

 in great numbers and in all conceivable positions. In most cases the 

 woody structure is well preserved ; the trunks have a tendency to break 

 in sections, and on the exposed ends the lines of growth, from center to 

 circumference, can be counted with ease. In many cases the wood is 

 quite completely opalized or agatized, and such cavities as existed in 

 the decayed trunks are filled with beautiful crystals of quartz and cal- 

 cite. Our party was so fortunate as to procure some very handsome 

 specimens of amethyst and ferruginous quartz. It is a matter worthy 

 of observation that nearly all of the beautiful crystals occurring so 

 plentifully in this region have been formed in the hollows of silicified 

 trees. The same fact has been noticed in regard to similar crystals in 

 many parts of the West, and notably in the case of the smoky quartz of 

 the Pike's Peak region in Colorado. 



The silicifying agents have been so unusually active in these strata, 

 that not only are all organic remains thoroughly silicified, but all cavi- 

 ties in the loosely bedded rocks and all fracture-lines in the strata are 

 filled with chalcedony or other forms of quartz. 



On reaching the heavily bedded conglomerates of the upper third of 

 the cliff, I found the trees still more perfectly preserved. Many of the 

 trunks are 20 and 30 feet in height. Their roots are in most cases 

 ■imbedded in the layers of finer-grained materials in which they grew, 

 •while the battered and branchless trunks are encased in the coarse con- 

 glomerates and breccias. These latter rocks are composed chiefly of 

 basaltic fragments, many of which are of great size ; there is, however, 

 .always enough tufaceous and other fine-grained material to fill in the 

 interstices and act as a cement. These beds are massive and irregular, 

 .and seem to have accumulated too fast to be thoroughly redistributed 

 by the waters. In most cases where upright trunks penetrate the en- 

 tire thickness of an inclosing bed, the to^js may be seen to terminate 

 with the upper surface of that bed, as if causes had acted at the begin- 

 ning of the deposition of the succeeding stratum to plane down the 

 irregularities of the old surface. In due course of time, this succeeding 

 stratum produced its growth of forest which, in its turn, was buried by 

 the rapidly accumulating conglomerates. 



• The very precipitous character of the cliffs prevented my reaching 

 the upper part of the wall at this point, but I succeeded in making my 

 way to the summit of the mountain at two other points, and found that 

 everywhere the section was practically the same. 



On the opposite side of the valley the same conditions were observed : 

 the fossil trees occur at the highest point reached, 3,000 feet above the 

 river. The ranges forming the rim of this valley on the north and east 

 reach an elevation of 11,600 feet, and as the conglomerates may be seen 

 reaching and forming the loftiest summits without perceptible break or 

 change of character, it is probable that they will be found to inclose the 

 xemains of forests throughout. 



I am totally at a loss to determine just where the truly subaqueous 

 sedimentary rocks end and the subaerial begin, as there is no well- 

 marked break. 



There are probably three distinct groups of the Tertiary formations, 



