148 GEOLOGY OF ILLINOIS. 



retain the same thickness at Yandalia, their boring terminated 80 feet 

 above the Centralia coal seam. It seems from these shafts and borings 

 that there is a very decided increase in the thickness of the strata asso- 

 ciated with the lower coals in the central portion of the State, and that 

 they will be found at a greater depth here than at points nearer the 

 borders of the coal field. The parties interested in the matter at Yan- 

 dalia should prosecute their boring at least to the horizon of the coal 

 seam at Centralia, to determine, if possible, whether that coal extends 

 into Fayette county. 



A. H. W. 



