PALZEOZOIC FORMATIONS.
The pakeozoic strata, resting on the metamorphic, insensibly change from the semi-crystalline to the unaltered sedimentary, and are the first rocks in the order of creation which contain the fossil remains of animal life. We have, therefore, in our foregoing sketch of the Mosaic creation, made these rocks the production of the latter part of the third day, or period, in order to conform with the Mosaic account of creation. The fifth day is the period of the creation of the present or existing life, not the fossil creations of a past age. The Mosaic account only presents to the eye such prominent features or pictures of the Creation as the common mind could comprehend. (For a comparison of geology with the Mosaic or Biblical account, see Appendix.) Our palxozoic strata embrace the Cambrian, Silurian, Devonian, and Carboniferous formations of the English geologists, and occupy one-half the area of the United States, or nine-tenths of the State of Pennsylvania, where they range from 10,000 to 35,000 feet in thickness.
The accompanying column or vertical section of the paheozoic strata of Pennsylvania presents a comprehensive view of the entire formation, from the gneissic to the carboniferous, including the coal measures.
We have divided the column, according to the nomenclature of Rogers, into fifteen periods, or formations, and numbered them in the mode adopted by the early surveyors of the State. We have also given the names adopted by the geologists of New York and the English equivalents, in order to present practically to the eye and the mind of all classes of readers the names and positions of the rocks forming the palgeozoic strata of Penn sylvania. The many new names adopted by the geologists of different sections for the various strata tend to confuse the mind; but we hope our present exposition will present them clearly.