150 GEOLOGY OF ILLINOIS. 



Quarries of the Niagara are also worked near Empire and Como, one 

 of them in the bottom of a little tributary of Elkhoru creek. The out- 

 crops here are low and not very heavy. 



Westward of these latter places and in all that tract of country 

 bounded by the railroad track, Rock creek and Kock river there is 

 scarcely an exposure of any kind ; but this irregular-shaped triangle is 

 nearly all underlaid by the Niagara limestone. 



Eock creek, from the north line of the county to Morrison, and in fact 

 to its mouth above Erie, cuts into the underlaying rock and exposes it at 

 numerous places. All these exposures belong to this formation, except 

 the sandstone at Unionville and Mineral Springs. At Broth well's mill 

 the exposure is sixty feet thick, presenting a perpendicular bluff, cav- 

 ernous, and light-colored on a recent fracture. Just above Jacobs' mill 

 an extensive quarry is opened in the same limestone. In the hill north 

 of Morrison it is again quarried. At this latter place a lime kiln is in 

 successful operation. Some of the layers here have in them many small, 

 curiously shaped cavities, lined with a velv.ety- looking, lead-colored me- 

 talic substance. 



The bluffs along both banks of the Cat-tail, with the exception of a 

 few sandstone outcrops, show the Niagara limestone. 



That high plateau of land bounded by the Cat-tail, the Maredosia and 

 the Mississippi, and consisting of the townships of Newton, Albany and 

 Garden Plain, is underlaid by the same rock. At Albany a high rocky 

 hill, with an old shore line of the Mississippi, fifty feet above present 

 low water mark, rises a short distance back from the river. 



The hill north of Fulton City, and on which it is partly built, is an 

 outcrop of Niagara limestone. At one time it was a small rocky island 

 in the midst of a broader and mightier stream than the present Missis- 

 sippi river. 



But the grandest development of this formation, perhaps, in this part 

 of the State, may be seen along the Mississippi bluffs, near the north 

 line of the county. After viewing these beetling cliffs, the appropriate- 

 ness of the old name "Cliff Limestone," becomes apparent. This bold 

 exposure rises at its highest altitude to the hight of one hundred and 

 seventy-five feet above the level of the bluff road, and this is but the 

 upper portion of the formation at this place. The talus and debris of 

 ages have accumulated along the base, rising in slopes half way up the 

 steep activity. Loose stones, sometimes weighing tons, loosened by the 

 frosts and other atmospheric agencies, have rolled down, and thickly 

 strew the roadside. Sweet, sparkling, deliciously cool water gushes in 

 strong springs from little ravines. Wild grape vines, dense thickets 

 and old monarch oaks oover these talus slopes for the most part ; but 

 sometimes the scene is varied by a slope covered with short tufts of 



