THE LOWER SILURIAN ROCKS. 573 



Ft. In. 



1. Fine-grained, porous, very friable, light-brown- tin ted; composed of sub- 



angular grains of very glassy quartz; containing numerous small cavities, 

 stained by iron-oxide; weathering with a thin vitrified crust, and occa- 

 sionally with a brown iron- stain; fossiliferous, containing numerous frag- 

 mentary impressions of trilobites and other fossils, the markings being 

 merely thin ferruginous films coating the nearly loose sand; most of the 

 fossils too indefinite and fragmentary to be determined, two species of 

 Conocephalites-]ik.e trilobites r and Triplesia ? primordialis, being the' 

 only ones made out (1365) 1 6 



2. Moderately coarse-grained, much finer than the last, pure white; composed 



of sub-angular to round grains of limpid quartz, the larger grains very 

 much rolled; weathering in places with dark brown blotches, and every- 

 where with a hard quart zitic crust; for the most part a solid layer, though 

 lines of bedding are to be seen on weathered surfaces; forming a narrow 

 crest at the summit of the cliff, only 3 or 4 feet wide (1366) 3 4 



3. Medium to coarse-grained, moderately firm, brown j constituent grains 



much rolled; in, thin irregular layers 1 to 2 inches in thickness; weather- 

 ing with a thin vitrified crust (1367) 1 5 



4. Resembling No. 2 1 4 



5. Medium to fine-grained, moderately firm, brown and reddish-brown; grains 



glassy, sub-angular to rolled; in the interior a massive bed, but weather- 

 ing out in places into thin layers (1368) 7 



6. Fine-grained, friable, yellowish- tinted; composed of much rolled grams of 



dulled quartz; containing little seams and patches of greensand; irregu- 

 lar shaly layers with rough surfaces (1369) 1 6 



7. Medium-grained, rather firm, dirty white; grains glassy and somewhat 



rolled; one layer, subordinate lamination not apparent (1370) 1 6 



8. Medium to fine-grained, brown-and- white-banded; in very thin shaly 



layers of almost loose sand, without hard weathering; occasionally run- 

 ning into firmer material (1371 ) 3 



9. Medium to fine grained, white to yellowish, moderately firm and compact; 



in one heavy uniform mass without perceptible subdivision into layers; in 



places a thick quartzitic crust (1372) 21 3 



10. Medium to fine-grained, close textured; white, dirty white, brownish; 



grains all somewhat rolled; hardened crust; in a massive layer without 

 distinct subdivision; top of the layer ripple-marked on a large scale, the 

 summits of the ridges 2 inches apart (1373) 43 



11. Medium-grained, friable, dark reddish-brown; grains much rolled and 



stained superficially with hydrated iron-oxide; one layer (1374) 2 



12. Medium to fine-grained, very friable, brownish and yellowish; weathering 



into narrow ridgy lines; in some parts, 1 foot thick, cross-laminated; sub- 

 ordinate layers not very well defined, but marked off by different colors. 31 . . 



13. Medium to fine-grained, friable, dirty white to yellowish; grains rolled and 



glassy; in places brown- weathered; upper layers thick, lower ones thin 

 and weathering out in ridges (1375) 27 



14. Very coarse-grained, porous, friable; white with brown- weathering 30 



15. Medium to coarse-grained; dark-brown, reddish- brown, red, white, and 



yellow, in irregular bands 2 inches to 1 foot in width, some layers very 

 ferruginous; grains glassy and much rolled (1378) 20 



16. Very friable, cross-laminated, yellowish layer, constituting a marked hor- 



izon in the series, as seen from below 10 . . 



