OGLE COUNTY. HI 



this group. It generally forms the subsoil of a good agricultural region, 

 but .sometimes it is inclined to be a little too sticky and wet. Ever-liv- 

 ing wells of reasonably pure water are found without difficulty where- 

 ever the Cincinnati shales lie near the surface. In some cases, masses 

 of sticks and decayed drift-wood lie between the shales and superim- 

 po>rd clays, separated from the former by only a few feet of marly, 

 blackish clay. In such cases the water of the wells is neither sweet 

 nor pure. 



Tit e Trent o n G r o 11 p. 



The Galena Limestone. Next in the descending series comes the 

 upper division of the Trenton group, known generally in the books as 

 the Galena limestone. It underlies a considerable portion of the county, 

 emerging along the face of the ravines from beneath the concealing 

 drift, and even rising like mural walls along some of the streams. The 

 line of demarkation between this and the nether Blue limestone is not 

 always easily distinguished. Layers, partaking of the characteristics 

 of each of these divisions, are often found intermingled for some dis- 

 tance, although the characteristics of the mass of the two formations 

 are very distinct. This peculiarity is not so marked in this county as in 

 the eastern part of Stephenson. 



The rock here usually preserves its usual coarse-grained porous nature 

 towards the top of the quarries, changing into a denser sub-crystaline 

 mass towards the bottom of the formation. It preserves its usual dull, 

 greyish, cream-colored, chrome-yellow tints. Xo outcrop of it appears 

 along the banks of Eock river, unless it may be near the Winnebago 

 county line. But as we go back from the river, the older formations 

 sink down and run under, and this becomes the prevailing surface rock. 



It is an important member of the series of Illinois strata, both on 

 account of its many economical uses, its historic interest, and the lead- 

 bearing character of certain portions of its basin. 



The superficial area underlaid by the Galena limestone in this county 

 is quite large. South of Rock river the older formations come to the 

 surface a few miles back from the stream, and outcrop along the ravines 

 cut down into this belt of rough, rolling country. But the Galena runs 

 on almost as soon as the level prairie is struck; and all the eastern and 

 south-eastern townships are underlaid by it, and would show it, could 

 the concealing drift clays be removed. The township of White Eock 

 takes its name from a low outcrop of light-colored Galena about the 

 headwaters of Stillman's run, near the center of the township. It is 

 quarried to some extent, and hauled over the surrounding prairie. The 

 .stone is rather soft and crumbly, but is used extensively by the farmers 



