668 GEOLOGY OF OHIO. 



individual members outrank in importance the last formation treated. 

 A tabular view of these subdivisions is here appended : 



Subdivisions or the Niagara Group. 



Feet. 



5. Guelph or Cedarville beds 0-45 



4. Springfield beds 30 



3. West' Union beds 10 



2. Niagara shale 30 



1. Dayton stone 0-10 



Total 125' 



The separate elements will be briefly noticed. 



(a.) The Dayton limestone, which forms, wherever it occurs, the very 

 base of the Niagara system, is an exceptional formation. It occupies 

 isolated areas through three or four counties of the Third Geological /Dis- 

 trict. Its place in the series throughout the district generally and the 

 country at large is occupied with widely different kinds of deposits. 

 The typical locality, as the name of the formation denotes, is Dayton, 

 Montgomery county. For a detailed description of the formation, the 

 reader is referred to the Report of the Survey for 1869. 



The Dayton stone is found in great excellence and in considerable 

 quantity in Greene county. Beginning on the western border, we find 

 it capping the outlier of cliff limestone that lies south-west of Harbine's 

 Station, in Beaver Creek township. Owing, however, to the greater ac- 

 cessibility of contiguous deposits — especially those of the Dayton dis- 

 trict — these beds have been but little developed. Neighborhood supplies 

 have been drawn for a long time from the farms of Moses Shoup, Archi- 

 bald Huston, and others ; but within the last two or Miree years larger 

 quantities have been taken out and distributed from Harbine's Station, 

 by the Davton andXenia Railroad. The stone, as here found, has all the 

 characteristic* excellence of the formation in thickness, homogeneity, du- 

 rability, and color ; but its value is somewhat reduced by the abundant 

 crystals of sulphide of iron (known by the quarrymen as sulphur), which 

 weather on exposure, and disfigure the surface by dark-brown stains. 

 The area underlain is considerable, and every foot of the deposit is sure to 

 come into demand with the increasing age and resources of the surround- 

 ing country. 



The next outcrop of it is found on the farm of Mr. James Collins, 

 Xenia township; but though the stone is unmistakable here in its gen- 

 eral character, it is much reduced in thickness and, consequently, in 

 value, and evidently marks the limit of the deposit in this direction. A 



