(J4 GEOLOGY OF ILLINOIS. 



real gravel deposits can be found. The prairies north and east of Wad- 

 dam's Grove have strewed over them numberless boulders, some black, 

 some flame colored, and some combining the various colors of the meta- 

 morphic rocks. At one place, about half way between Waddam's Grove 

 and Wiuslow, they are rolled into wind rows along the road, and used 

 in part for the lane fences. Many of these are exceedingly beautiful, 

 and many colored. They are the real "lost rocks," and must have been 

 dropped from the slow moving icebergs, as they drifted along towards 

 the south-west. All that part of the county north and east of the Peca- 

 tonica is characterized by these boulders, and by many deposits of 

 gravel and gravelly clays, to be met in almost any of the low ridges of 

 land. The same may be said of the eastern portion of the county, ex- 

 cepting that the deposits are not so extensive. 



Some other formations belonging to the surface geology, such as fire 

 clay, peat, bog iron ore, muck, and the like, will be referred to when 

 we come to speak of the economical geology of the county. 



The Niagara Limestone. The superficial extent of the county covered 

 by this formation is quite small. Waddam's Grove, quite a high eleva- 

 tion of land, two or three miles long and a mile or two wide, and located 

 a little north-west of the town of Lena, is capped by the Niagara lime- 

 stone. At French's quarry, near the top end of this elevation, facing 

 towards Lena, there is an exposure worked to the depth of about fifteen 

 feet. French's well, near the same spot, is forty-five feet deep, the up- 

 per twenty feet being sunk through this formation, and the lower twenty- 

 five feet sinking into the underlying Cincinnati shales. At Blakesley's 

 quarry, twenty-five feet of the same formation is worked into. This is 

 about one mile west of French's, on the north face of the hill. Here 

 they have worked down to the Cincinnati shales. The bottom layers in 

 both these quarries are compact and solid; the top layers are thick, ir- 

 regular, speckled and porous. A species of slender, rottou Cyathophyllum 

 was the only fossil observed in these quarries. From the latter quarry 

 the prospect towards the north and west is beautiful beyond description. 

 The low, level, rich prairie, with its fields and meadows, barns and farm 

 houses, skirted in the distance by the range of mounds, bending around 

 like a distant amphitheatre into- JoDaviess county, presents as fine a 

 prospect, beneath a glowing June sun, as we ever beheld in any State. 



Leaving this elevation, we next find the Niagara outcropping in the 

 south-western part of the county. We would indicate its extent by a line, 

 which should enter the county from the west in the town of Kent, some 

 three miles south of Simmons' Mound, and then follow the general course 

 of Yellow creek, keeping distant from that stream from two to five miles, 

 until nearly opposite to Crane's Grove, then carried southward until the 

 south boundary line of the county was reached, near its bisection by 



