OF LANCASTER COUNTY. 605 



GEOLOGY.i 



Lancaster County presents three prominent geological features. -which it may be well 

 to notice separately, Commencing on the northern boundary, the Conewago range of 

 hills separating the county from Dauphin and Lebanon Counties, belongs to the Meso- 

 zoic red sand stone period. The shales and gravelly soil of this formation spread south- 

 ward. A glance at Scott's County Map, will show the range of hills commencing at 

 Bainbridge, on the Susquehanna, extending in a line curving northwardly, then soutb- 

 eastwardly, with a general eastward course, embracing the greater portion of surface 

 of the northern tier of townships. The limestone valley, constituting the central portion 

 of the county, extends by a narrow inlet between two Gravel hills, in Penn township, 

 not over a mile apart, (southeast of Manheim, ) which opens into a limestone basin, 

 around the borough of Manheim, widening out and embracing a large portion of Penn, 

 Warwick, Clay and Ephrata townships, and portions of West and East Cocalico. The 

 red shale or gravel formation east of Reamstown, and on the south-eastern side of the 

 Cocalico creek, and north of the Conestoga creek, in a narrow strip, extends westward, 

 crossing the southern portions of Ephrata, Warwick and Penn townships, to the afore- 

 • named inlet. The Reading and Columbia Railroad passes nearly through the centre 

 of this isolated valley. This Mesozoic red sand stone, is a portion of what Dana chills 

 the Palisade range, which extends from Rockland, .on the Hudson river, southward 

 through New Jersey, Pennsylvania and Virginia, east of the Blue Ridge, in a contin- 

 uous line of about 350 miles in length. It crosses the Delaware between Ti-enton and 

 Kintnerville ; the Schuylkill about 12 miles below Reading, and the Susquehanna river 

 between Highspire in Dauphin, and Bainbridge in Lancaster county. In York county 

 this belt inclines southward, in conformity with the Appalachian flexures, or mountain 

 ranges on the N. W. 



The Mesozoic or Mediaeval time in the Earth's history comprises a single age only — 

 the Reptilian. It is remarkable, however, that very few fossils or signs of life of any 

 kind are found within the county. The rock is in general a red sand-stone, pass- 

 ing into a shale or conglomerate, and occasionally including beds of impure lime-stone. 

 The brown building stone, often called freestone, used in the erection of our County 

 Jail and Court House, were quarried in the Black Oak Ridge, in Clay Township. Other 

 quarries of sandstone are 6pened along the range of hills. Millstones are also made 

 from a hard millstone grit found in Cocalico Township, and other points. Extensive 

 dikes of trap or greenstone are met with in the Conewago hills, as also below Bainbridge 

 near Millers ville, and crossing thence towards Safe Harbor and at various other points. 



This Trap rock is of igneous origin, and belongs to the class of rocks met with in 

 volcanic countries, like lava, being in fact the melted material of older rocks, ejected 

 through fissui-es in the sand stone. In some places the sandstone is baked into a hard 

 grit by the heat, and at times blown up by steam so as to seem scoriaceous, or the 

 clayey sandstone is changed into very hard rock, similar to Trap itself. IMinerals like 

 the epidote and tourmaline result from this baking. The predonunant red color in the 

 soil, arises from the oxidation of magnetic iron grains present in it. 



The calcareous formation, or the Limestone Valley, extends from the Gravel Hills, or 

 Red Sandstone formation, to the Gneiss and Talc Slate Hills, commencing at Safe Har- 

 bor east of the Conestoga creek, inclining towards Willowstreet, thence eastward below 

 or south of Strasburg, in a westwardly course along the boundary between Salisbury 

 and Sadsbury Townships. This Limestone Valley as well as the Gneissic portions, 

 belong to an age or period prior to the shales. The Palaeozoic age is represented by a 

 hard quartzite named the Postdam sandstone by the geologists of New York, a rock 

 which is remarkably compact and rather fine grained, and consists almost exclusively 

 I Drawn up by Mr. J. St lufler, Lancaster. 



