Xi APPENDIX. 



sibly in some cases exactly where they are now found. Of course 

 there were many subsequent oscillations of level, by which much 

 of our continent was sunk deep enough beneath the ocean level, 

 to receive thousands of feet in thickness, of later deposits, and 

 again raised to its present elevation. 



The walls of the excavation at the bottom of which these plants 

 were found, are composed of the same fine-textured, more or less 

 hard, gray and bluish-gray, argillaceous, slightly gritty beds, as 

 some of those containing the plants, for ten or twelve feet above 

 the bottom of the cut; and farther up, apparently much the same 

 kind of rocks continue for thirty or forty feet, alternating with 

 beds of softer, crumbling, brownish-red material, disposed to form 

 red clays by disintegration. The nature of the rocks composing 

 the mountains here, above this last-mentioned horizon, was not 

 determined by examination ; and no organic remains, excepting 

 those of the plants collected here, were seen at this locality. 



About two hundred yards to the northeastward from the point 

 where the plants already mentioned were taken out at the bottom 

 of the cut, excavations were in progress in the tunnel, by means 

 of a vertical shaft sunk on an elevation more than one hundred 

 feet above the actual horizon of the point where the plants 

 alluded to above were found. The rock thrown out of this shaft 

 is a very hard, compact, rather coarse-grained, massive grit, of a 

 light bluish-gray color, differing from any of the beds exposed 

 in, or directly over, the cut at the plant locality. It is brought 

 up from the shaft generally in large, irregular massive blocks, as 

 blasted from the beds. In these I saw many fragments of stems 

 and branches of trees, most of which are small, but I obtained 

 several specimens of moderate size, one of which consists of a 

 fragment broken at both ends, measuring twenty-two inches in 

 length, and three to four inches in diameter. Some crushed ex- 

 amples seen in the rock appear to have belonged to individuals 

 of considerably larger size. All of these specimens are coated, 

 as it were, by a bark-like covering of shining coaly matter, while 

 inside of this nothing but the same hard, gritty material compos- 

 ing the surrounding matrix occurs. Generally no well-defined 

 markings are seen either on the surface of this coaly matter, or 

 on the rock within. On one of the specimens, however, obtained 

 here, there are pits closely resembling, in size, form, and arrange- 

 ments, those of the genus Stigmaria. 



The absence of surface markings on most of these specimens is 

 perhaps due, in part, to the fact that they were drifted and con- 

 sequently abraded before being deposited here, and in part to the 

 tremendous pressure to which they have been subjected during 

 the consolidation of the rock, or its subsequent movements. The 

 evidences of pressure are seen on nearly all the specimens, which 

 are usually found crushed and broken, with the surface of the 



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