MARSHALL AND ITTXAM COUNTIES. 215 



as no valuable deposits of coal have as yet been discovered. The Peru 

 and LaSalle coal seams, as they extend south, ou the eastern- side of the 

 Illinois river, dip to the southward, and as the superincumbent drift 

 materials increase to nearly a hundred feet in thickness over'the Coal 

 Measures, the coal seams are nowhere exposed above the surface. All 

 the south-eastern part of the county is underlaid by these same forma- 

 tions, except that they have more and more lost surface indications of 

 the coal seams. Natural outcrops do not exist, and no borings have 

 been made so far as I know, and, of course, our knowledge of things 

 hidden beneath the surface cannot be very definite. 



Following the trend of the bluffs from the above starting point to the 

 south line of the county, nothing very definite shows itself. Traces of 

 sandstone along their bases, and of b'mestone higher up, may sometimes 

 be noticed. The former is the coarse, massive, friable sandstone, and 

 the latter the light-colored limestone, described in the reports upon the 

 the geology of Marshall and Bureau counties. The country being rough, 

 and timbered for most of the distance, except the Hennepin prairie, 

 stone is not quarried, and the opportunities to examine outcrops are 

 very scarce. Indeed. I hardly know of a good outcrop in the county, 

 either natural or made by quarrying, and there certainly is no outcrop 

 where a fair section can be made. 



These remarks apply more particularly to the large fractional town- 

 ship of Hennepin, laying immediately adjacent to the Illinois river on 

 the east. The two eastern townships of Magnolia and Granville are 

 dead-level prairie land, devoid of outcropping strata of any kind, ex- 

 cept towards the river on the north. 



West of the Illinois river, the single large township of Snatchwine, 

 which is the only part of the county west of the stream, the geology is 

 similar to that of south-eastern Bureau county, except that no produc- 

 tive coal seams have been discovered. There is also a slight sinking or 

 dip of the strata towards the south. At the north line of the county 

 the bluffs are not remote from the river, and the valley on that side is 

 narrower than in some other places. The trend of the bluffs bear 

 gradually away from the river, at the southern limits of this large town- 

 ship, and the northern extremity of the " Crow Meadows " is reached. 

 The bluffs show some un worked outcrops of the hard, semi-crystaline 

 limestone, noticed about Trenton, in Bureau county, but they are not 

 quarried, and show no fossils where examined. The western end of the 

 township is prairie, without anything of geological interest. 



This is about all that can be said about the geological structure of 

 of this little county. On the map it should be marked as underlaid by 

 the Coal Measures, except the valley of the Illinois river, which should 

 indicate alluvial deposits. The county is quite small, and ite geology is. 



