WHITESIDE COUNTY. 151 



prairie grass, or the richer ami softer blue glass. The upper part of the 

 exp -mbles dilapidated Cyclopean walls of the mystic times. A 



_ mural escarpment rises from the top of the slopes, and presents its 



Hated face to the broad Mississippi Valley, whose lacustrine waves 

 in older geologic epochs beat against the rocky barrier and wore it into 

 fantastic shapes. Many caverns exist, some of them almost iuacessible, 

 out of which issued, the day I spent among them, the half human cries 

 of wild cats and the growls of a small species of lynx. Some miles of 

 e wall along the road are built, by quarrying the material on the 



- and sides of th - rocks, and letting it go plunging down to 



the very places where it is needed. The little farms thus fenced along 

 the public highway have a fat, rich, sour cold soil, too wet for very sue- 

 ill cultivation, except in occasional mellow localities. As we recede 

 from this bluff line towards the interior of the county the Niagara 

 limestones thin out by erosive and denuding agencies, until the Cincinnati 

 shales and the Galena liinerock s -ly come to the surface. This 



-pecially true along the northern part of the county, where the ex- 

 posure is so much the heaviest. 



In the large area of AYhiteside county underlaid by this portion of 

 the upper Silurian rocks, I noticed considerable difference in lithological 

 character. The exposure just re terred to consists of the upper Cor- 

 aline and Peutamerus beds" of the Cliff or Mound limestone of the 

 earlier western geologists. It is compact, homogeneous in structure, 

 full of minute specks of dendrites, of a light straw-color on a recent 

 fracture, sometimes taking a reddish tinge, nearly the color of brick 

 dust. At Sterling the lower part of the formation is exposed. This is 

 a thinner bedded, rougher, uglier stone, and would hardly be recognized 

 as the same rock just referred to. At Fulton City, the upper part of the 

 quarry, at least, is a friable yellow-colored or ocherons limestone, some- 

 times i>orous or sponge like, and sometimes of a tough crystaline text- 

 ure. Sometimes the color approaches an almost white cream-color. It 

 is identical with the Racine limestone of Mr. LAPHAM. referred to in 

 the Wiseoii>in geological survey. At Lyndon the rock is porous and 

 full of the stems of encrinites. Below Erie, near the point where Rock 

 river leaves the county, the color is still lighter and more delicate, the 

 texture more compact and finer grained, and the stone is in every re- 

 spect, I think, identical with the Leclare limestone, now recognized as a 

 member of the Niagara formation. 



:tanie remains. The characteristic fossil of the upper beds perhaps 

 is the Fentameru* oblongu*. In the speech of the people, masses of it 

 are commonly called -petritied hickory nuts.*" At Broth well's mill many 

 of them are sticking through the rocks ; but at the heavy exposure 

 along the bluffs huge stones are coverrd over so thickly with the c 



