GEOLOGY.1

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 Mesozoic red sand stone period. The shales and gravelly soil of this formation spread southward. 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 southeastwardly, 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 aforenamed 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 calls 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 continnous line of about 350 miles in length. It crosses the Delaware between Trenton 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 Medieval time in the Earth's history comprises a single age onlythe 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, passing 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 opened 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 Millersville, 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 fissures 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. Minerals like the epidote and tourmaline result from this baking. The predominant 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 Harbor 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 Paleozoic 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

1 Drawn up by Mr. J. Stauffer, Lancaster.