^912.] STEVENSON— THE FORMATION OF COAL BEDS. 499 



Not long after deposition of the Putnam Hill, but long enough 

 for deposition of 40 to 80 feet of inorganic materials, the formation 

 of two coal beds and the erosion of broad valleys, another sea inva- 

 sion is recorded in the Vanport limestone of I. C. White. This 

 underlies in most of its extent an ore deposit, which in the earlier 

 days was so important that the rock below was termed the Fer- 

 riferous limestone. Like its predecessors, it is confined to the west 

 side of the basin. A fossiliferous limestone is present in the Lower 

 Allegheny at some places in western Maryland, but one cannot 

 determine whether or not it is contemporaneous with the Vanport, 

 as no fossiliferous limestone has been found at the horizon within 

 80 miles toward the west or northwest. The Vanport appears to be 

 wanting in the whole of West Virginia as well as in Pennsylvania 

 south from the line of the Ohio River. The deposit is recognized 

 first at about 70 miles north from the West Virginia line and at an 

 equal distance west from the crest of the x-\llegheny Mountains. 



The most easterly locality in Pennsylvania, from which this 

 limestone has been reported, is in Indiana county at 75 miles east 

 from the Ohio line — apparently the tip of a prong; it appears at 

 many places in the next county north, but its distribution indicates 

 that the area is broken into prongs ; and this is the mode of occur- 

 rence along the northern border where its limits are very well de- 

 fined. From western Jefferson, the area is continuous to the Ohio 

 line where the bed is 15 to 20 feet thick. The deposit is less regular 

 in Ohio, being represented in many places by fossiliferous shale, 

 calcareous sandstone and occasionally by limestone. These condi- 

 tions prevail in Mahoning, Columbiana, Stark and western Tus- 

 carawas, the limestone being of frequent occurrence in the last. 

 Thence southward into Elliott county, Kentucky, the limestone with 

 its ore seems to be continuous ; beyond that the ore bed is traceable 

 for many miles. The western boundary of the deposit is reached 

 at a few localities in northern Ohio but, for the most part, it is 

 beyond the present outcrop. While the extent of the Vanport in 

 Ohio may have been less than that of the Mercer, its extent in 

 Pennsylvania was far greater. The sea-invasion reached 60 miles 

 farther east into Indiana county and 70 miles farther north into 



