DESCRIPTION OF THE FORMATIONS. P. 67 



south of Sandy hill. But they are usually of less width and 

 much covered with wreckage from the Hamilton sandstone, 

 or Oriskany. or both. 



The Hamilton Montebello sandstone. 



The Hamilton sandstone is one of the most remarkable 

 deposits of Perry county. Lying in the midst of a vast 

 mass of material, consisting almost entirely of shale, it has 

 the appearance of being out of place to the geologist accus- 

 tomed to look on the Hamilton as essentially a soft group. 

 The valleys excavated in the Hamilton shales in most parts 

 of the pakeozoic belt here give place to high, rough, wooded 

 ridges, especially in the southern part of the county. 



Turkey ridge, and Wild Cat ridge in the northeast, Rac- 

 coon ridge, Buffalo hills, Mahanoy ridge, Dick's hill and its 

 geological continuation, Rock hill, in the central portion of 

 the county, with Pisgah hill and Little mountain in the 

 south, are all formed by the outcrop of this sandstone. Some 

 of these are high, rough and untillable, others are compara- 

 tively smooth and accessible. The difference is due to two 

 causes — the hardness and the dip of the sandstone. In 

 Mahanoy ridge the strata are nearly vertical, and the ridge 

 is steep and rugged. In Buffalo hills and Dick's hill the 

 beds dip at about 45°; while in the neighborhood of Sandy 

 hill the dip is very gentle, and the range is cultivated to its 

 top on the south side. Then again the proportion of sand 

 rapidly diminishes toward the north and west, especially in 

 the middle of the bed. This also tends to diminish the 

 steepness and roughness of the ridges. 



At its southeastern exposure near Marysville, this sand- 

 stone attains its greatest thickness and hardness, a thick- 

 ness amounting to about 800'. Prom this point it gradually 

 thins away, the upper and lower beds persisting farthest, 

 and the intermediate shale becoming constantly thicker, 

 until it at length becomes two distinct thin sandstones, with 

 an intervening thick bed of softer material. This change 

 may be detected in Perry county. At Montebello narrows 

 the Little Juniata has cut its way through the lower hard 

 bed and has then flowed for nearly half a mile parallel to 



