44 ECONOMICAL GEOLOGY. 



In the vicinity of Brock's ford, two miles south of Streator, a 

 limestone occurs near the top of the bluff, that closely resembles 

 the limestone south of Petersburg, in Menard county, which there 

 lies some 25 to 30 feet above coal No. 7, and it contains a similar 

 group of fossils. In addition to this, the shales below the Streator 

 coal contain ironstone concretions, completely filled with the little 

 crustacean figured, and described in a preceding volume under the 

 name of Leaia tricarinata, which is regarded as a characteristic fossil 

 of the shales under coal No. 7, from whence it has been obtained 

 at several localities in the State. The following section shows the 

 strata to be seen in the bluffs of the Vermilion, between Brock's 

 ford and Streator. 



Feet. In. 



No. 1. Light gray compact limestone 4 



No. 2. Blue sandy shales and soft sandstone, with concretions of sandy iron ore 35 



No. 3. Bituminous shale Oto 2 



No. 4. CoalNo.7 5 to 7 



No. 5. Shale with discoidal concretions of iron ore 6 to 8 



No. 6. Fire-clay 2to 2 6 



No. 7. Hard conr-retionary sandstone 12 to 15 



No. 8. Shaly sandstone, extending below the river level, exposed 20 to 25 



The limestone at the top of the section contains several species 

 of small BracJdopods, the most common being Athyris subtilita, 

 Spirifer lineatus, Terebratula bovidens, and a small Naticopsis, or 

 Trachydomia, which were mostly in the form of casts, the pustulose 

 shell being removed. 



The hard sandstone, No. 7 of the section, will make a durable 

 stone for rough walls where strength is the main requisite. 



Between Streator and the mouth of Prairie creek, the sandstone 

 under the Streator coal rises so as to form with the sandy shales 

 below, a perpendicular cliff about forty feet in height. Over this 

 sandstone ridge the coal has been carried away by the denuding 

 agencies of the Drift period, but a short distance away from the 

 river it comes in again immediately below the drift. Near the 

 mouth of the creek the sandstone becomes thinner, and the coal 

 appears above it and slopes rapidly down to the river level. 



Several borings have been made in the vicinity of Streator, to the 

 horizon of coal No. 2, but I was unable to obtain any reliable 

 record of the strata passed through. I was informed, however, that 

 the distance between the two seams was about 80 feet. The quality 

 of the coal afforded by No. 2 is generally superior to that of any 

 of the higher seams, but it seldom exceeds a thickness of 3 or 4 

 feet, and lying deeper below the surface, and consequently requir- 



