LASALLE COUNTY. 51 



The surface deposits of LaSalle county will furnish an inexhaust- 

 ible supply of sand, clay and gravel. The sand pit in the vicinity 

 of Streator furnishes a clean, sharp sand, that is shipped in large 

 quantities by raihoad wherever a market can be found. The fol- 

 lowing section may be seen at this pit: 



Ft. 



Krown clay 4 



Ash-colored clay 4 



Sand, with streaks of fine gravel 20 



Coars< ' gravel 7 



The clay used in making tile at Streator comes from the bottom 

 of what were formerly shallow surface ponds, that have been filled 

 up mainly by the wash from the higher grounds by which they were 

 surrounded. It is a tough, fine, unctious clay, and at some points 

 is found as much as ten or twelve feet in thickness. It is evidently 

 more modern than the brown clay of the Drift period, and overlays 

 that deposit when both are present. The growth and decay of 

 aquatic grasses, that usually abound in shallow ponds, produce a 

 fine silicious sediment, and this, with the wash from the higher 

 grounds adjacent to them, will fairly account for the occurrence of 

 these tough clays in this position. In other portions of the county 

 the brown clay of the Drift, or, more properly speaking, of the 

 /w.s-.s, is used in the tile factories with satisfactory results. 



In closing these brief notes on the geology of LaSalle county, I 

 desire to express my obligations to Dr. E. Evans, of Streator, for 

 valuable information in regard to the geology of that part of the 

 county, and for hospitable entertainment, and transportation to such 

 localities on the Vermilion river as it seemed desirable to visit ; and 

 also to the Hon. Elmer Brldwin for similar favors while exploring 

 the outcrop on the river in the vicinity of Farm Ridge ; and also to 

 Mr. John B. Duncan, of the Caledonia shaft, Mr. Chas. J. Devlin, 

 of the Union, and the proprietors of the Oglesby shaft, for a de- 

 tailed record of their works. 



It is to be regretted that a detailed record of every coal shaft is 

 not kept, for such records would be of great value, not only to the 

 proprietors and managers of the mines, but to all who desire to 

 obtain reliable information in regard to the value and extent of our 

 coal resources. 



