SlOt 2 . liEPOBT OF PROGRESS. E. W. CLAYPOLE. 



from every point in its edge to the centre. It is thin at 

 Selinsgrove and in Juniata county, and in the northwest of 

 Perry county. In all these directions the sand is gradually 

 replaced by shale. 



Rye township, or rather tire southeastern portion of Rye 

 township, is the locality towards which the Hamilton sand- 

 stone gradually thickens, and consequently the nearest 

 point, at least in Rye township, to the source of the sand. 

 Where then was this source \ We have no right to infer 

 that the original limit of the Hamilton sandstone was at 

 the place of its present greatest thickness. On the con- 

 trary, we must assume its former southward extension for 

 some miles at least. But it is reasonable to infer that that 

 extension will follow the same laws as the existing mass, and 

 we may, therefore, believe that the source of this sediment 

 lay towards the south ; possibty the mouth of some great 

 river, draining a continental area now imperfectly repre- 

 sented by the Azoic country of southern and southeastern 

 Pennsylvania. 



[The outcrop of the Hamilton sandstone crosses the Sus- 

 quehanna river and runs through Dauphin, Lebanon, and 

 Schuylkill counties. The failure of the deposits below it 

 is also a remarkable feature in those counties, as well as in 

 Perry county. It could not be expected that the true cause 

 of a phenomenon, so extensive in its range, and impossible 

 to observe south of the line of the Blue mountain, should 

 be satisfactorily explained at the west end of its area, 

 namely in Rye township, Perry county. But the facts de- 

 scribed in this report make an important addition to our 

 imperfect knowledge of the subject. — J. P. L.] 



The Medina sandstone, No. IV. 



This sandstone makes but small show in the township, 

 in this pari of the county it is thin, not exceeding about 

 loo feet, and the line is drawn so as to throw almost the 

 whole of it into Cumberland county. Its vertical beds 

 (slightly overthrown to the north) are exposed on the rail- 

 way below Mary sville, and may be followed along the south 

 of the Blue mountain. 



