CHEMUNG GROUP. 
255 
evenly over the surface of the water, were distributed widely, and deposited with the sand and 
mud. Similar deposits are going on in the lakes and in the bays of the ocean at the present 
time, and it is a common occurrence to see the water of either covered with a thin scum of 
comminuted particles of wood, extending for great distances. These appearances upon the 
strata in New-York are seen in Ohio, specimens from the two being scarcely distinguishable. 
All facts of this kind are interesting, as showing an approach to that period when terrene 
vegetation flourished on a grand scale, and in its destruction gave origin to the great coal 
measures of the United States. Throughout all the lower rocks of the New-York system, 
there is no evidence of terrene vegetation, and consequently no proximity to coal-bearing 
strata, and it is only subsequently to the deposition of all the limestone formations of this 
system that this kind of vegetation appears. 
The character of strata and materials composing the Chemung group can be illustrated by 
a section or two, much better than by description. Hundreds of sections of the vertical cliffs 
have been noted, but as they present little variation, a repetition would not be instructive. 
The following is a section of the cliff at Chemung Narrows, from above downwards : 
Feet. Inches. 
1. Fissile olive shale, with Aviculse_ 15 0 
2. Compact shale, with Cyathophylli and other corals_ 0 6 
3. Compact shale, with thin courses of sandstone separated by seams of shale. 13 0 
4. Greenish grey sandstone, with seams of shale_ 10 0 
5. Greenish grey sandstone, with the weathered edges stained by oxide of 
manganese and iron_ 7 0 
6. Shale and sandstone, with Aviculas, Atrypce, and other fossils_ 5 0 
7. Soft greenish olive shale_ 3 0 
8. Compact sandy shale, with fossils_ 2 0 
9. Shale in three distinct courses of 2, 4, and 6 feet_ 12 0 
10. Corallines_ 0 2 
11. Olive shale, with abundance of fossils_ 3 0 
12. Compact shaly sandstone_ 2 6 
13. Shale with thin layers of sandstone, containing abundance of fossils- 6 0 
14. Concretionary sandstone_ 3 0 
15. Shale with thin layers of sandstone_ 8 0 
16. Below this to level of river, the character of rock not ascertained- 14 0 
This may be considered a specimen section, and gives the general character of the rocks of 
the group in other places. The fossils of this place are chiefly Avicula pecteniformis, Stro- 
phomenamembranacea, S. interstrialis, Orthis interlineata, Delthyris prolata, Atrypa aspera. 
Another section at Painted-post, in a different part of the group, presents the following 
alternations from above downwards : 
