ECONOMICAL GEOLOGY. 63 



Feet. 



6. Limestone (Up. Silurian) 15 



7. Shale, etc., (Cincinnati group) j50 



v Trenton limestone 280 



t. St. Peters sandstone 273 



10. Calciferous limestone 100 



11. Potsdam sandstone 54.5 



Total depth 2 332 



In all the artesian wells of northern Illinois, and they may be 

 counted by the score, not one except the well at. Beardstown 

 already referred to, has yielded any notable quantity of gas, 

 and with .such facts before me I have felt it to be my duty to 

 discourage any large expenditure of money in central or north- 

 ern Illinois, in attempts to develop productive gas wells in 

 those portions of the State. 



In the eastern and southern portions of the State the condi- 

 tions are more favorable, but no experiments have as yet been 

 made that would justify the expression of a decided opinion 

 upon the gas question there. The only deep well bored in 

 southern Illinois of which I have been able to obtain the record 

 is that at Olney. which is given in detail on page 8, of Vol. 

 VII. of these reports. Although this boring was earned to the 

 depth of 2.000 feet, yet it did not reach the base of the lower 

 carboniferous limestone, and therefore affords no evidence in re- 

 gard to the development of the gas producing formations of 

 Ohio and Pennsylvania, which lie from 1.000 to 1,500 feet 

 below the lowest stratum penetrated in the Olney boring. 



The Devonian system is fairly well developed in southern Illi- 

 nois, attaining a maximum thickness of 350 to 400 feet. The 

 following divisions of the system have been recognized : 



Feet. 



Hamilton limestone g<j 



Mair-ellus shale 20 



Corniferous limestone 25 



Onondaga limestone 30 



Oriskany sandstone -jOo 



All these divisions are highly fossiliferous, and some of them, 

 notably the corniferous limestone, possess the dark color and 

 fetid odor which usually characterize the oil and gas produc- 

 ing rocks. These beds thin out rapidly to the northward, and 

 at the mouth of the Illinois river in Jersey county, the only 



