378 F\ REPORT OF PROGRESS. E. W. CLAY POLE 



hanna and Juniata. Rounded gravel and sand are found 

 in every field. The same is true of Duncan* s island, al- 

 though some of ir, by the deepening of the channel, is now 

 much above the water. 



Before the construction of the canal the Juniata flowed 

 into the Susquehanna, or vice versa, through a channel 

 north of the islands. Once since then, during a great flood 

 in 1846, the Susquehanna rose over its banks, reopened this 

 old channel and swept out the embankment of the canal. 



Much of the land along the east side of the township is 

 alluvial soil consisting of ancient river bottom, now far 

 above the highest floods. On the west side there is no such 

 land. The Juniata flows close under the cliffs. Many feet 

 above this flood-plain may be found rounded and trans- 

 ported stones proving the ancient presence of the river at 

 that height. 



The bearing of these facts on the geological history of the 

 county is easily seen. If the rivers were ever thirty or forty 

 feet higher than now, they may have been 300 or 400 feet 

 higher, for the process which is lowering their channels now 

 has been lowering them for untold ages. 



The Susquehanna thrown more and more to the eastward 

 at Girty's notch lias cut into Dauphin county and left the 

 accumulation of alluvial soil along its western bank, till 

 striking Peter's mountain it again flows westward. The 

 erosion of the Catskill sandstone terrace, or north flank of 

 Peter's mountain, by the river as it slants in to the gap, is 

 finely exhibited. 



The Lower Helderberg limestone, No. VI. 



This limestone makes but a small outcrop in the township 

 in the northwest corner. The point of limestone ridge 

 crosses the river and enters the end of Half Falls mountain, 

 where it has been quarried and burnt for several years. The 

 Limestone extends but a short distance inland, being soon 

 covered by the Bhales and Bandstone of the Hamilton. 



'I'll.- beds are here very much disturbed, and have yielded 

 no fossils. Some of tli<> layers are very sandy, but are 

 nevertheless burnt for lime. 





