128 GEOLOGY OF ILLINOIS. 



Where unstained by the oxyel of iron, the grains of which it is made 

 up are round and limpid in color, and are a pure quartz. The mystery 

 of its deposition does not seem to be well understood. No fossils, no 

 lines of stratification, have written on it and in it the story of its creation. 

 Horizontal bands or layers, thin and dark iron colored, weather out 011 

 some, of the outcrops, and give the same a pictured appearance, at a lit- 

 tle distance. On the point of one hill a pile of these fragments lay, de- 

 tached from the outcrop, resembling a pile of old, broken, iron pots. On 

 some of these ferruginous fragments I noticed the ripple marks spoken 

 of by Dr. EVERETT, of Dixon, in his description of this rock. These 

 ripple and eddy marks sometimes resemble the forms of organic life iu 

 a remarkable degree. 



Its uses will be spoken of under the head of the Economical Geology 

 of the county. Ascending the scale we next come to the lower division 

 of the Trenton. 



The Buff Limestone. Where in situ and fully developed, this limestone 

 is separated from the St. Peter's sandstone by two or three feet of thin 

 shales, intermingled with a blue and greenish laminated clay. This is 

 especially observable in one or two of the Pine creek outcrops in Ogle 

 county. The best outcrop perhaps in Lee county is in a ravine two or 

 three miles east of Dixon, near the Oregon road. The outcrop is about 

 half way down a hill sloping to the south. In the bottom of the ravine 

 some large detached masses of the St. Peter's sandstone are laying in 

 the bed of the little trickling stream. The top of this formation is prob- 

 ably just below them. The Buff outcrop above and in the hill-side, for- 

 merly quarried largely, shows a compact, heavy-bedded, crystaliue or 

 semi crystaline limestone. The massive layers are about a foot in thick- 

 ness, and separated by thin fossiliferous shales and loose clay. These 

 layers belong to the upper part of the division. The lower part, as ex- 

 amined in situ in Ogle county, is of a dull color, and gives out a dull 

 earthy sound on being struck with the hammer, while these layers ring- 

 out a sharper and more metallic sound. Up Franklin creek in one or two 

 places I detected the Buff limestone above and in close proximity to the 

 underlaying sandstone. These are all the outcrops noticed in the coun- 

 ty. This Buff limestone underlies but a limited area, and that in close 

 proximity to the sandstone outcrops. The base of the bluffs, from the 

 Blue limestone quarries above Dixon to the sandstone bluff opposite 

 Grand De Tour, contain good sections of this rock ; but the outcrops are 

 deeply covered by the talus along the bluff line. 



The Blue Limestone, or Trenton proper. This is very heavily devel- 

 oped, both on Eock river and Franklin creek. About three miles and 

 a half above Dixon, high, perpendicular outcrops begin to appear along 

 the bluffs on the south side of the river ; and from thence almost to the 



