-NRLF 2 SbT 13E &$ \ e THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA PRESENTED BY PROF. CHARLES A. KOFOID AND MRS. PRUDENCE W. KOFOID EAWTH SCIENCES ' '3RARY \ X THE GEOLOGY OF PENNSYLVANIA p 2 s? . 7 A* t ^0t ^*, /fc~^^*s ** THE GEOLOGY OF PENNSYLVANIA A GOVERNMENT SURVEY BY HENRY DARWIN ROGERS STATE GEOLOGIST OF NATURAL HISTORY IK THB UNIVKRSrT\ r OF OI.ASflOW [ HON. F.8.S.K., F.O.S. ; MFMI OP THE AMERICAN VHILOSOPHICAL UK II i -. ; FELLOW OF THE BOSTON ACADBMY Or ARTS AND SCIENCKS; UFHBER QT THE BOSTON NAT. HIST. SOCIETY, FTC. BTC. IN TWO VOLUMES VOL. I. M DC COL VI II PALEONTOLOGY LIBRARY Gift of C. A. Kofoid Af v. / PREFACE. THE GEOLOGICAL SURVEY OF PENNSYLVANIA, the chief results of which are embodied in this Work, was commenced early in the year 1836, in obedience to an Act of the Legislature authorising " A Geological and Mineralogical Survey of the State, &c;" and the State Geologist was directed "to make annual reports to the Legislature of the progress of the Work ; and cause to be represented on the State Map, by colours and other appropriate means, the various areas occupied by the different geological formations ; and on the completion of the Survey, to prepare for publication a full account of the Geology and Mineralogy of the State." " By virtue of this Act the Author was appointed to conduct the Survey, which he actively prosecuted with a corps of able assistants for six years, until the appropriations were expended." " At the time of the organisation of the Survey, it was estimated that it would occupy at least ten years ; but the financial embarrassments of the Commonwealth made it expedient to withhold further appropriations after the sixth year, and to bring the Survey abruptly to a close before it could be completed in all its parts. The State Geologist, anxious to make the Work as full and symmetrical as possible, continued the exploration, and devoted himself to the preparation of the general final Report for three years longer, labouring for the chief part of this period without salary, and at his own expense." " The mass of information and material collected by the Survey, and thus systematised and prepared for the press, was deposited in the Office of the Secretary of the Commonwealth early in the year 1847, to await publication by the Legislature." In that position it was allowed to remain until the spring of 1851, when, on the recommendation of a joint Committee of the Senate and House of Representatives, from whose Report the above statements are ex- tracted, funds were appointed and measures taken " for the revision of such portions of the field-work as, from the rapid development of the mining districts of the State, required re-survey, and for the publication of the Report itself, with VOL. i. a ii PEEFACE. the accompanying maps, plates, cuts, and sections, in a style suitable to the exigencies of the Work and the reputation of the Commonwealth." In the . language of another Committee a Select Committee of the Senate appointed early in 1855 to inquire into the progress and condition of the Survey, and the steps necessary to complete its publication " A joint committee, consisting of two members of each branch of the Legislature, with the then Secretary of the Commonwealth, was authorised to issue proposals for a contract under which the publication of the Work might be made." This contract, which embraced a provision for further field-researches, was awarded, ill - advisedly, to wholly incompetent parties, who, on the eve of bankruptcy, dissolved copartner- ship. The contract was allowed to pass " to their successor, who soon after suspended payment." " The publishing firm which succeeded that with which the Committee originally contracted, was finally dissolved by the death of the senior partner ; and another firm took its place, which, after a short-lived exist- ence, soon likewise disappeared. No commercial firm then remained, even in name, to represent the parties with whom the Commonwealth had contracted. Although the publishers had drawn, on account of their contract, the sum of four thousand dollars over and above the amount paid to the State Geologist (for his field-work, &c.), they do not appear to have made any progress towards the pub- lication of the Work." " The funds so advanced to the publishers, and for which the State has received no equivalent, are totally lost, as no sufficient security was taken to cover these advances." The Committee of the Senate making this recital, adverting to the want of proper management which resulted in this loss, and the delay in the publication of the W T ork, proceed to say, that " the State Geologist meanwhile commenced his field-work early in the spring of 1851, and continued, with a small band of assistants, actively engaged in it until the close of the season." " Having con- sumed his own means in the expectation of immediate reimbursement, he appealed to the Legislature for redress, which he procured." Next year " a large amount of material was ready for the press," and "the Geological Map was placed in the hands of the publishers for engraving ;" but, for the causes already recited, no progress was made. Notwithstanding the many impediments in his path, arising mainly from delays in procuring his quota of the funds, the Geologist persevered in his field and closet labours until the spring of 1855, the limit allowed by the Act of 1851. At that date he presented a memorial to the Legislature, calling attention to the bad management which had retarded tlio production of the large mass of PREFACE m information collected by the Survey, whereupon the Select Committee of the Senate already mentioned, sketching the advanced condition of the Work Under its revised and greatly-expanded form, and presenting a Schedule of its materials, for the most part re-drawn and almost entirely re-written., recommended " to confide the whole Work, in its supervision and publication, to the State Geologist him- self." In accordance with this suggestion, it was so enacted in March 1855 : the conditions of the contract between the Commonwealth and the Author being, that for the publication of the final Geological Report of the Survey made by him on behalf of the State, with the accompanying maps, plates, cuts, and engravings, including the enlargement of the Geological Map of the State to twice its scale, and the furnishing to the State of one thousand copies thereof within three years, he was to receive the sum of sixteen thousand dollars and the copyright of the Work. Fourteen thousand dollars of this fund was the amount originally allotted to the publication upon an estimate in 1851, made before the revision was under- taken, and the other two thousand were added for the enlargement of the chief Map. To save from loss a portion of the large amount of useful information col- lected, and to meet the expectations of the public, the Author has deemed it his duty to expand his Work, both in the illustrations and the text, considerably beyond the amount of material he proposed to print in the Schedule submitted to the Senate's Committee in 1855. The actual cost of the Work has, therefore, exceeded by several thousand dollars the amount to which he is legally entitled. The enlargement of the General Geological Map of the State a task of great labour, amounting to a total reconstruction of it, and the introduction of much additional and fresh material has itself entailed a far larger expenditure than was assigned it. Intended to represent, with close and faithful minuteness of detail, a country of excessive topographical and geological intricacy, it required its geographical features to be executed on copper, in the very best style of map-engraving, and the geological ones to be done by the beautiful modern process of colour-printing from stone. Both it, and the minor maps, and other illustrations executed in this manner, will, the Author trusts, meet the approval of his fellow-citizens and of his readers generally. A statement of these facts has seemed due, first, to the public, who have long looked for the fruits of the Survey ; and secondly, to the Author himself, who has encountered, in the performance of his duty, unusual obstacles and hardships. At the time the Geological Survey was organised, it was not contemplated to construct any new maps for the elucidation of the Geology, but simply to represent, iv PREFACE. " by colours and other appropriate means, as the law expressed it," the areas occu- pied by the different geological Formations on the Map of the State, then the pro- perty of the Commonwealth. The Survey had not proceeded far before it was discovered that that Map, full of errors, was wholly unsuitable for the purpose, and it became apparent that a correct delineation of the Geology demanded either the construction of a wholly new Geographical Map, or a thorough revision and correction of its most defective parts, embracing the entire Mountain-chain of the State. This voluntary addition to the arduous labours of the Geological portion of the Survey was undertaken and persevered in, until a wholly new Map was formed compiled in part from original Surveys, in part from the numerous explo- rations ordered by the State, in connection with her internal improvements and was presented in 1847 as an accompaniment to the general description of the Geology then handed in for publication. In the preparation of that Map, all the larger features of the Mountain-chain, and of the plains a.nd hills to the south of it, and of the table-lands to the north, were critically examined and laid down with approximate truth, though not with the refined accuracy of a trigonome- trical survey, upon a scale of one inch to the mile, upon two preliminary maps ; one embracing the region south-west of the Susquehanna, the other the country of the Anthracite Coal-fields between that river and the Delaware. Upon the revival of the Survey in 1851, reorganised more expressly for a closer study and exhibition of the previously less explored parts of the State, especially the Anthracite Coal-fields, it was discovered that the Map embracing these, though exact enough for the general purpose which it had fulfilled, of improving this part of the State Map, was too inaccurate a topographical foundation for the reception of the very intricate geology of the region to be depicted. It became necessary, there- fore, to construct a new Map of the whole Anthracite country ; and this proved to be a very laborious and costly part of the Survey. Without any separate appropriation for the object, an independent instrumental Topographical Survey was carried on side by side with the Geological one, and the results of both embodied in a series of local Maps, some of them on a scale nearly as large as four inches to the mile. From these Field Maps the Geological and Topographical Map of the Anthracite Region has been carefully constructed. Butfor the geographical labours incidental to the Survey, the whole Work might have been in print years ago, and at a mate- rially less cost to the Commonwealth. Had the Geologist been provided, as he usually is in such investigations, with sufficiently truthful and large maps ready engraved to his hand, there would have been not only this important saving of time, toil, and expense, but a corresponding economy in all these particulars in the PREFACE. v preparation of the Work for the press, and in the supervision of it while in the hands of the artists. The reader will observe that all the maps which accompany this Work are what are called in the United States " Topographical;" they picture, that is to say, by appropriate shading, the physical relief or inequalities of the surface. In this feature they embody a far larger amount of information, both geological and geographical, than can possibly be conveyed through geological charts destitute of hill- work; indeed, no map can be said to meet the wants, either scientific or practical, of a geological survey, which does not picture, approxi- mately at least, the vertical element as well as the horizontal. Every Physical Geographer, every Engineer, indeed every working Miner, will testify to the correct- ness of this assertion. Partly for this reason, and partly through the necessity for making new and more accurate maps of some sort, whereupon to present the Formations of the State, the Author thought it best, while conducting the two- fold Survey, to knit together the Geology and the Topography as intimately as the means at his disposal would permit. In the Palseontological portion of this Work two principal objects have been kept in view ; first, to exhibit the most characteristic organic remains of the fossiliferous formations of the State ; and secondly, to ascertain, describe, and figure all the more prominent new species found in the Carboniferous Rocks, especially in the Coal-formation proper. The fossils of the various deposits have been carefully examined and compared, and due weight has been assigned them in the classification and grouping of the strata ; but as a thorough Palseontological exploration did not enter into the plan of the Geological Survey of the State, being precluded by the stintedness of the funds appropriated, the Author has contented himself with introducing only so much of the subject as will fully illus- trate the typical nature of the ancient forms of life entombed within the diiferent formations, except in the instance of the extinct vegetation of the Coal. Even had he been allowed the funds to conduct an independent Palseontological investi- gation, a large portion of the labour might have seemed superfluous, from the circumstance that the neighbouring State of New York, far richer than Pennsyl- vania in well-preserved organic remains, including, moreover, most of the same species, has for many years past been conducting, at great expense, a thoroughly minute investigation of its Fossils extending, indeed, to other States by the ablest Palaeontologist of the country, Professor James Hall. I am indebted to my accomplished Assistant, Leo Lesquereux, Esq., for the valuable essay and beauti- ful figures illustrating the new species of Coal Vegetation, discovered chiefly by himself in the Anthracite Coal-fields of the State. vi PKEFACE. The intimate relations of the Geology of Pennsylvania to that of the whole Appalachian Basin, or the region between the Atlantic Slope of the Continent and the Central Plains west of the Mississippi, and the importance of co-ordi- nating its strata, especially its Coal-rocks, with those of other districts, the better to illustrate its true position industrially as well as physically, have induced me to introduce a somewhat full Essay on the General Geology of the United States. It is intended to fulfil the office of a key to the more minute descriptions contained in the main body of the Work to be to the Geology of the State what a general map on a small scale is to a local one greatly amplified ; or what a " Finder Telescope," embracing a wide field of view, is to the chief instrument directed upon a special star, the general place of which the other shows. A like motive a desire to indicate the positions occupied by the several widely-diffused Formations of Pennsylvania and the United States in the general scale of the strata best known to the geological world (I mean the scale of the European Rocks) has impelled me to add an Essay, originally presented in abstract to the British Association, " On the Correlation of the American and British Palaeozoic Strata." It is only through such wide comparisons, cautiously instituted, that we can learn with what portions of the world our country is in nearest affinity. In the Appendix to this Work there appears, amid other miscellaneous matter, a description of the methods of research employed in the Geological Survey of Pennsylvania, with some suggestions in relation to geological explorations gene- rally, adapted to other countries. The nomenclature of the Palaeozoic Formations employed in this Work demands a word of explanation here. After a mature analysis of the whole system of Ancient Secondary (Palaeozoic) Rocks embraced in the Appalachian Chain, conducted in accordance with their organic remains and mineral com- position, it became apparent to the State Geologists of Virginia and Pennsyl- vania, Professor W. B. Rogers and myself, that none of the existing systems of nomenclature neither the imported British ones, nor the narrowly local geo- graphical ones of New York were applicable to our strata, under the average types they manifest in the mountain-chain and the broad basin of the States to the West of it. It was found that these Appalachian Rocks were far from being suffi- ciently co-ordinate with the European Palaeozoic strata, under their British types, to bear their names ; while, on the other hand, the special titles assigned to them in New York were deemed too local and too inexpressive, either of their position in the scale of Formations, or of their ruling characters, to be usefully applicable. PREFACE. vii The fifteen Formations, or series of deposits, defined by their prevalent organic remains, and of the physical horizons which separate them as sediments, extending from the lowest deposited in the dawn of animal life to those formed at the end of the Coal Period, are called by names significant of their relative ages, the words employed suggesting metaphorically the different natural periods of the day. These names are Primal, Auroral, Matinal, Levant, Surgent, Scalent, Pre- meridian, Meridian, Post-meridian, Cadent, Vergent, Ponent, Vespertine, Umbral, and Serai, meaning respectively the Formations of the Dawn, Daybreak, Morning, Sunrise, Mounting Day, Climbing Day, Forenoon, Noon, Afternoon, Declining Day, Descending Day, Sunset, Evening, Dusk, and Nightfall. Some such nomenclature, based on time, is, for many reasons, preferable to the inexpressive ones which rest for the most part on geographical terms, only locally correct, or on narrow and inconstant palseontological characters. I avail myself of this opportunity to express my ever-grateful and affectionate acknowledgments to my brother, Professor William B. Rogers, for the valuable assistance he has generously rendered the Survey in every department at various stages of its progress. The staff of Assistants on the Survey of the State necessarily fluctuated with the vicissitude of its history, and the changing demands of the work. Small at the commencement, it was rapidly augmented to a corps of twelve, which it remained till towards the suspension of the appropriation in 1842 ; after which, until 1845, whatsoever aid I required was chiefly employed on my own account. Upon the resumption of the field-work in 1851, a new staff was organised, consisting of two Geological Assistants, a Topographer, Assistant Topographer, and a party of Surveyors. In the campaign of 1836 the assistants were John F. Frazer (now Professor Frazer), and James C. Booth (since Professor Booth). In that of 1837 they were Messrs Samuel S. Halderman, Alexander M'Kinley, Charles B. Trego, and James D. "Whelpley, Geologists ; and Dr Robert E. Rogers, Chemist. In that of 1838 they were Messrs Harvey B. Holl, Alexander MKinley, Charles B. Trego, James D. Whelpley, James T. Hodge, Dr Robert M. Jackson, John C. M'Kinney, Peter W. Shaeffer, and Townsend Ward, Geologists ; and Dr Robert E. Rogers, and Martin H. Boye, Chemists. In that of 1839 the corps was nearly the same, Mr Peter Lesley and Dr Hen- derson being added, and Messrs Whelpley and M'Kinney resigning. In 1840 the corps consisted of the same assistants, with the addition of an able Draftsman, George Lehman. viii PREFACE. In 1841 the number of the Geological Staff was reduced, the Geologists being Mr M c Kinley, Mr Holl, Dr Jackson, Mr Lesley, and Mr Boye ; and the Chemist, Dr Rogers. After the revival of the field-work in 1851, the Geological Assistants were Pro- fessor E. Desor and William B. Rogers, junior. The Topographers were Peter Lesley, and subsequently Augustus A. Dalson ; and the chief Surveyors, Peter W. Shaeffer (performing also geological functions) and Henry W. Poole. The neat one-sheet Map of the Coal-fields is by Mr Lesley. The beautiful large Map of the Anthracite Region is by Mr Dalson, chiefly from his own surveys. Since the cessation, in the autumn of 1854, of the active revision of the Min- ing Districts, and of the Topographical Surveys, my sole assistant in geological field-research, in completing unfinished topographical work, and in preparing for the press the final Drawings of the extensive mass of Geological Sections and Diagrams introduced into this book, has been my nephew, William B. Rogers, junior. Besides the gentlemen here mentioned as scientific assistants, the Survey has employed many other persons, some of them of much skill and merit, in sub- ordinate capacities. One of these, Patrick Daly, merits especial mention for the value of his services and fidelity to the Survey. For full mention of the special parts performed by the individual members of the corps in the various successive stages of the Survey. I beg to refer to the widely- circulated Annual Reports of its progress. To attempt a precise history of the labours of each, in a field where their duties were so multifarious, would, besides being somewhat invidious, lead me into too minute and tedious a narrative. I beg, in concluding this Preface, to testify in general terms my high appre- ciation of the zeal and ability of my Assistants, my admiration of their energy in confronting difficulties, and their fortitude in meeting the privations and hard- ships incident to the life of a Geologist in the United States ; and my grateful thanks for the personal devotion displayed by all of them, with one or two exceptions, in aiding me to the fulfilment of my duties. HENEY D. EOGEES. PHILADELPHIA, April 1858. TABLE OF CONTENTS, INTRODUCTION PHYSICAL GEOGRAPHY. PAGE Physical Geography of Pennsylvania, ' . . 1 Boundaries and area, .... 1 Position of the state, .... 2 General watershed and main slopes, . '. - 2 Chief natural divisions, . . , . 3 Orography and scenery of the first district, . 4 Orography and scenery of the second district, . 5 Appalachian ridges, ..... 7 Mountain ridges, . . . . 10 1. Anticlinal ridges, . . . .11 2. Synclinal ridges, . . . . 12 3. Monoclinal ridges, . . . . 13 Valleys, ...... 15 1. Anticlinal valleys, . ... 16 2. Synclinal valleys, .... 17 3. Monoclinal valleys, . . . 18 Different classes of scenery in the mountain-chain, and their relationships to the physical geography and geology of the region, ... 19 Scenery commanded by anticlinal mountains, . 19 Scenery from synclinal mountains, . . 22 Views from the ends of the exterior basins, . 23 Views from the ends of the interior troughs or coal basins, ..... 24 Scenery and structure of the mountain crests, . 25 1. Anticlinal crests, . . . .-25 2. Synclinal crests, .... 26 3. Monoclinal crests, .... 26 Aspects of the mountain sides, ... 27 Passes or notches in the mountains, . . 28 General character of the scenery in the valleys of the Appalachian zone, .... 30 Anticlinal valleys, .... 30 Synclinal valleys, .... 30 Monoclinal valleys, . . .31 Scenery characteristic of the broad valleys of com- plex structure, . . . . 31 Orography and scenery of the third district, . 32 1. South-eastern belt of the bituminous coal region, ..... 33 2. Northern belt of the bituminous coal-field, . 34 3. Basin of the Alleghany and Ohio rivers, . 36 Orography and scenery of the fourth district, . 36 Lakes, ...... 37 Orography and scenery of the fifth district, . 39 Hydrography, ..... 39 Atlantic drainage, . . ... 40 Its general periphery, .... 40 Its chief river basins and their dividing water- sheds, ..... 40 VOL. I. PAGE Areas of the chief river basins, . . . 41 Mexican Gulf, or Ohio river drainage, . 42 The lake drainage, .... 42 Eiver system of the Delaware fiver, . . 43 Kiver system of the Susquehanna river, . . 44 Eiver system of the Potomac river, . . 45 River system of the Alleghany river, . . 46 Scenery along the principal rivers, . . 47 The Delaware river, .... 47 The Susquehanna river north branch, . 48 West branch of Susquehanna, ... 49 The Juniata river, .... 50 The Alleghany river, . . . .51 Climatology of Pennsylvania, ... 52 Temperature average of the year, . . 53 Mean temperature of the spring months, . 53 Summer mean temperature, ... 53 Autumn mean temperature, ... 54 The winter mean temperature, ... . 54 Summary, ..... 54 Extremes of temperature, ... 54 Tabular statement of greatest degrees of heat and cold, over a term of nearly 60 years, . 55 Rain averages for the year, ... 56 Extreme quantities of rain, ... 56 Prevailing winds, .... 57 GEOLOGY. GENERAL INTRODUCTORY CHAPTER. Classes of rocks embraced in Pennsylvania, . 59 The gneissic or hypozoic rocks, . . . 60 The palaeozoic rocks, . . . . 60 PART I, METAMORPHIC STRATA OF PENNSYLVANIA INTRODUCTORY CHAPTER. Classification of the metamorphic strata of the Atlan- tic slope of the middle and southern states, . 62 BOOK I. GNEISSIC ROCKS OF PENNSYLVANIA. General distribution of the gneissic or ancient meta- morphic strata, ..... 66 The three gneissic districts, ... 66 TABLE OF CONTENTS. CHAPTEE I. SOUTHERN ZONE OF GNEISS. PAGK Or Gueissic rocks south of 'the Montgomery and Chester valley, . . . 67 DETAILS OF THE SOUTHERN GNEISSIC DISTRICT. Gneissic rocks of the valley of the Schuylkill, between Philadelphia and Spring Mill, ... 67 First belt, ...... 68 Granite veins, ..... 69 Unstratified or true igneous rocks, . . 69 Syenite, ...... 69 Trap dykes, ..... 70 Falls of Schuylkill quarry, . . .70 Second or middle belt, . . . .71 Wissahickon Creek section, ... 72 . Third or northern belt, .... 73 Description of the northern or upper belt of gneiss, 73 Structure of the upper or northern belt of gneiss, . 74 Subdivisions and details of the northern belt of gneiss on the Schuylkill, .... 75 Limits of the three belts of gneiss of the southern gneissic district, . 305 Local details, . . ... 306 CHAPTEE IV. Structure and local details of the western division of the fourth district, .... 307 Topography, ..... 307 Anticlinal axes, ..... 307 Local details, ..... 309 The Narrows of the Susquehanna, . . .310 Limestone boulders, . . . .310 Strata East of the Tioga river, . . . 310 Tioga river and country westward, . . . 310 Vergent shales, ..... 310 Iron ore stratum, . . . . .311 Eoseville on Mill creek, .... 311 Ponent red shale, . . . . .311 Limestone of the Vespertine series, . . 311 Mountain escarpment S. of Wellsborough, . 312 Singular lake, ..... 312 BOOK V. Fifth or Lower Juniata district, being the South- eastern half of the Appalachian chain between the Susquehanna and Maryland, . . 313 DIVISION I. First and second synclinal, and included anticlinal belts, embracing Perry and the North-western portion of Franklin county, . . . 313 CHAPTEE I. Structure of Perry and western part of Franklin county Sherman's valley, . . . 313 Flexures in the strata of Sherman's valley, . . 314 Anticlinal axes, . . . . 314 North Horse valley, .... 317 Burns's valley, . . . . .318 Path valley, ..... 318 Amberson's valley, .... 318 Structure of Path valley, .... 318 Fault in Path valley, .... 319 Auroral limestone in Path valley, . . . 320 Composition, . . . ' * . . 320 Geographical distribution, .... 320 Matinal slates in Perry and Franklin counties, . 321 Composition, ..... 321 Geographical distribution, .... 321 Matinal slate in North Horse valley, . . 321 Matinal slate in Burns's valley, . . . 321 Matinal slate in Path valley, . . .321 Matinal slate N.W. of the fault, . . .322 Iron ore in the matinal slate along the fault, . 322 Carrick ore bank, ..... 322 Mount Pleasant ore bank, . . . 322 Matinal slate N.W. of Dividing mountain, . 322 Matinal slate in Amberson's valley, . . 323 Matinal slate S.E. side of Path valley, . . 323 Bear valley and its anticlinal axis, . . 323 Matinal slate in Bear valley, . . . 323 Auroral and matinal rocks of M c Connellsburg cove, 323 Auroral limestone and anticlinal axis, . . 324 Fault along the N.W. side of the cove, . . 325 Fault in McConnellsburg cove, . . . 325 Lowry's knob, ..... 325 S.W. of Lowry's knob, . '. - . . 326 Matinal slates of the cove, . . . 326 Levant sandstones of the Cove mountains, . 326 Little Scrub ridge, .... 326 Dickey's mountain, .... 326 Cove mountain, . . . . 327 Little Cove mountain, .... 327 CHAPTEE II. LEVANT AND SURGENT AND SCALENT ROCKS OF PERRY AND FRANKLIN COUNTIES Levant series composition, . . . 328 Kittatinny mountain, . 29. Nevins's Quarry, ..... 226 30. Broken Saddle of Gneiss in Auroral Limestone on Bailey's Farm, ..... 227 31. Close Foldings in the Matinal Slate at Harrisburg, . 246 32. Cleavage in Slate Quarry, Delaware Water-Gap, . 248 33. Section S.W. of Walpack Bend, . . .281 34 & 35. Section, Gbdfrey's Ridge, S.W. of Stroudsburg, . 284 36. Section through Stroudsburg across Walpack Axis, . 285 37. Flexures at Wind Gap and at Lehigh Water-Gap com- pared, . . . . . 287 38. Section of Stone Ridge at the Lehigh, . . . 288 39. Section on the Little Schuylkill through Port Clinton, 290 40. Section near the Schuylkill, through Summer Hill, . 292 41. Section of the Blue and Second Mountains, . . ib. 42. Section showing the Strata E. of the Tioga River, . 310 LIST OF ILLUSTKATIONS. XXVI 1 FIO. 43. Section at Roseville, . . . . . 44. Mountain Escarpment S. of Wellsborough, . . 45. Section at Fannettsburg, . . . . 46. Fault opposite the End of Dividing Mountain, . . 47. Section near Carrick Ore-Bank, . . . 48. Fault near S.W. end of Sandstone Wedge, . . 49. Fault S.W. of the Sandstone Wedge, . . . 50. Section of the Fault opposite Cowan's Gap, . . 51. Section of Fault at the Old Mount Pleasant Ore-Bank, 52. Fault at Carrick Ore-Bank, . . . . 53. Section 5 miles E. of M c Conuellsburg, . . . 54. Section of Fault opposite M c Connellsburg, . . 65. Fault 1 mile S.W. of the end of Little Scrub Ridge, . 56. Fault 1 mile N.E. of Hunter's Mill, 57. Section through Lowrey's Knob, 58. Fault ]J miles S.W. of Lowrey 'a Knob, 59. Section S.W. of Lowrey's Knob, 60. Section of Kittatinny Mountain, E. side of the Susque- hanna River, ...... 61. From Pfout's Valley to base of Peter's Mountain, 4 miles N.E. of Millerstown, ..... 62. From Shade Mountain, 3i miles N.E. of Lost Creek, to Millerstown, ...... 63. From N.E. eud of Tuscarora Mountain to Blue Moun- tain, at 4 miles E. of Sterret's Gap, . 64. From Limestone Ridge to Pisgah Hill, . 65. From Shade Mountain, 5 miles S.W. of Freeburg, to Mouth of Mahantango Creek, 66. From Shade Mountain, 5 miles N.E. of the Juniata, to Tuscarora Mountain, 4 miles S.W. of Thompsontown, 67. From Shade Mountain through Mifflintown to Tusca- rora Mountain, ..... 68. From Tuscarora Mountain, 4 miles S.W. of Run Gap, to Blue Mountain, S.E. of Kennedy's Valley, 69. From Shade Mountain below Lewistowu to Tuscarora Mountain, 34 miles S.W. of Run Gap, . . 70. From Blue Ridge, 64 miles S.W. of Lewistown to Blue Mountain, ...... 71. From Blue Ridge to Blue Mountain, 1 mile S.W. of Three Square Hollow, .... 72. From Jack's Mountain, through Orbisonia, to Blackleg Mountain, ...... 73. From Blackleg Mountain to Blue Mountain, 24 miles S.W. of Roxburgh, ..... 74. From Blacklog Mountain S.W. of Meadow Gap to Blue Mountain, 3 miles S.W. of Strasburg, . 75. From Sideling Hill, past Werefordsburg, to Little Cove Mountain, ...... 76. Knolls of Pre-meridian limestone near Beavertown, . 77. Section across the Lewistown Valley near Kishaco- quillas Creek, ..... 78. Topography of Forge Ridge, .... 79. Anticlinal Flexure in Dry Valley, . . . 80. Strata of the Muucy Hills, . 81. Section of Montour Ridge at Danville, . . 82. Section of Montour Ridge at Hemlock Creek, . 83. Section of Montour Ridge at Fishing Creek, . . 84. Surgeut Upper Calcareous Shales at Danville, . 85. Section across the Seven Mountains by the Turnpike Road, ...... 86. Section across the Seven Mountains, 5 miles E. of the Turnpike, . ... 87. Section across the Seven Mountains from Hartmau's northward, . . . . . 88. Short Mountain and Terrace, seen in profile, . . PAGE no. 311 89. 312 319 90. ib. ib. 91. ib. ib. 92. 320 ib: 93. 322 94. 324 325 95. ib. 96. ib. 97. ib. 98. tUt 326 99. 100. 328 101. 102. 345 103. 104. ib. 105. 106. ib. 107. 354 108. 109. ib. 110. ib. 111. 112. 355 113. ib. 114. 362 115. ib. 116. 362 117. 364 118. 119. ib. 120. 366 121. ib. 405 406 408 409 439 441 ib. ib. 442 481 il>. ib. 484 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. Sketch of Brush Mountain from the N. side of Brush Valley, ...... 484 Nittany Mountain and Terrace, as seen from Bald Eagle Mountain, ...... 485 Section of Nittany Mountain opposite the E. end of Nittany Valley, . . . . .488 Section along the Anticlinal Axis through Nittany, Nip- penose, and Musquito Valleys, . . . ib. Drift Mound in Anti's Gap of Nipponese Valley, . 489 Perspective Sketch of the Ravines in the S. Barrier of Nippenose Valley, ..... i6. Section of Sugar Valley and adjacent Mountains, . 491 Section of Brush Valley looking W., . . . 493 Tussey Mountain Terrace, cut down by erosion, . 504 Section of Dunning's Mountain, and High. Barrens, Morrison's Cove, ..... 507 Section of Martin's Hill, Bean's Cove, . . 510 Section of the Warrior Ridge at the Pulpit Rocks, . 519 Pulpit Rocks, ...... 520 Standerfer's Knob, and Side-view of Jack's Mountain, 522 Woodcock Valley at MConnellstown, . . 523 Woodcock Valley at Trough Creek Gap, . . 524 Section of Black Oak Ridge, . . . 625 Section of Trough Creek Valley, . . . 532 Typical Section of the Great Bald Eagle Valley, . 534 Strata near Cumberland on the Potomac River, . 541 Section along Pine Creek near Jersey Shore, . . 544 Sketch showing different vegetation upon different rocks in the Bald Eagle Mountain, . . . 545 Section at Eagle Furnace, Bald Eagle Creek Valley, . 546 Section of Rocks on Larry's Creek near the Susque- hanna River, ..... 550 Section of Short Mountain Synclinal, and Anticlinal of Canoe Run, with Vergent Iron-Ore, . . ib. Bald Eagle Mountain N.E. of Hannah Furnace, . 553 Profiles of the Crest and Terrace of Bald Eagle Mountain, ...... ib. Oblique Meeting of Anticlinals of Lock and Canoe Mountains, ...... 554 Section of Scalent Grey Marls and Limestones on the Juuiata above Bell's Forge, . . ib. Displaced Summits of Canoe Mountain near the Juniata, 556 View of Frankstowu Knob (Anticlinal) from the top of Blue Knob in the West, &c., . . .557 Section 4 miles S.W. of M'Kee's Gap, . . 558 Anticlinal of Pine Ridge, with Scalent and Pre-meri- dian Limestone and Chert, ib. Section N.E. of Buckstown, showing flexures and blocks of Meridian Sandstone, . . . ib. Section of Scalent and Surgent Strata opposite the end of Buckstown Mountain, .... 561 Section of the End of Lime Ridge near Bedford, . 562 Section on Bob's Creek at Buckstown, . . 563 Section on Bedford and Greeusburg Turnpike, . 565 Form of the Escarpment of the Alleghany Mountain, ib. Map of the Vicinity of Bedford, showing the Outcrop of the Fossiliferous Iron-Ore and Pre-meridian Limestone, 566 Section on Hollidaysburg Turnpike, . . . ib. Section on Dedding's Creek and 1 mile S., . . 567 Section on Dedding's Creek and 1 mile S., . . ib. Section at Bedford, ..... 568 Section 1 mile S.W. of Bedford, . . .669 Section of the Cumberland Valley at the Maryland line, 570 Section on Cladding's Run, .... 572 Section of Savage and Wills' Mountain, . . 574 ERRATA. Page 174, line 32, for FIG. 25, read 23 a, page 181. 216, line 15, for Marble Hill, read Marble Hall. 383, line 21, for Pre-Meridian Sandstone, read Meridian Sandstone. 476, line 1, for Baird'i, read Betty's. 505, last line, for Williamsport, read Williamsburg. 543, line 11, for Levant formations, read Swrgent formations. 554, line 19, for Levant ore calcareous shales, read Surgent, : V .vi'if L ''t>; ^^fflmn 1* m ' ANTICLINAL VALLEYS. 9 Many other instances of very long, slender, regular ridges might be adduced, as the Mahoning or Second Mountain, north of the Kittatinny ; the Tuscarora Mountain in Juniata County ; Jack's Mountain, in Mifflin ; Bald Eagle Mountain, running from Lycoming, through Clinton and Centre into Blair and Tussey Mountain, in Blair and Bedford; but nearly all of these are members of groups of ridges, to be described in detail hereafter. Annexed is a Sketch showing the Kittatinny Mountain in the distance, and the Mahoning or Second Mountain in the middle space. The foreground is the stony crest of the Sharp Mountain, near the Lehigh Summit Mines. This picture will convey a good conception of the features of our monoclinal ridges, with their level crest-lines, their occasional notches, and steep forest- covered slopes. The instances of long and narrow valleys of anticlinal structure, or where the strata dip away from the central line of the excavated trough, and not towards it, are, as in the cases of a synclinal structure, very numerous. An interesting example is that of Path Valley, in the north- western corner of Franklin County. Another more symmetrical one is Kishicoquillas Valley, in Mifflin. Both these are of simple anticlinal structure at their western ends, but contain several waves of the strata at their eastern, causing them to subdivide into long slender prongs. Kishicoquillas Valley has three such very regular prongs, like a fork, separated by high single- crested synclinal ridges. Penn's Valley is another instance of the same structure, forking eastward. The largest of all is Nittany Valley, enclosed eastward by the table-land which joins Bald Eagle Mountain to Nittany Mountain, and westward by the coalescing of Bald Eagle Mountain with Brush Mountain. Only the lesser anticlinal valleys, such as Nippenose Valley, Sugar Valley, and Black Log Valley, which contain no more than one regular anticlinal flexure, are of strictly symmetrical form. Some of these are extremely slender, being excavations in the backs or crests of long narrow and steep waves of the strata ; others, such as Nippenose and Mos- quito valleys, are more oval in form, the denuded crust-waves out of which they are scooped being broad and flat. These anticlinal valleys, even the most slender and regularly terminated, bear much less resemblance to a narrow tapering canoe than do the synclinal troughs, unless we liken them to a narrow boat turned bottom upwards, with the bottom or keel carved out. Instead of their mountain rims or crests ascending towards their ends to unite in a peak, like the prow and stern of a skiff, they run level to near their junction, and the terminal single ridge sinks slowly tapering off, like the cutwater of a slender inverted bark. The mountain-sides enclosing the anticlinal valleys present quite different contours from those embracing the synclinal. The latter, for the most part, descend with very regular flattening curvature of slope, or if they are terraced, as they frequently are in the anthracite coal-basins, the benches are narrow, and too obscure to form a feature in the landscape, except in rare cases ; they are, moreover, seldom gashed by numerous and deep ravines ; whereas the slopes of the anticlinal valleys are usually conspicuously terraced and carved by sharp gullies commencing sometimes in the crests of the ridges, but more frequently in the edges of the broad shelves running horizontally round the valleys at different levels on the mountain-flank. Beautiful cases of this terraced structure are to be seen in all the middle and north-western anticlinal valleys of the chain west of the Susquehanna. It occurs conspicuously in Black Log, Kishicoquillas, Peun's and Nittany valleys, and their branches, and also in Morrison's, Friend's, B 10 OROGRAPHY AND SCENERY OF SECOND DISTRICT. and Millikin's coves, in nearly all of which there is a broad and nearly level bench or terrace high on the slope of the bounding mountains, which from a distance looks singularly like a wide elevated beach formed by pent-up waters. Such, however, was not its origin, as we shall prove hereafter. In those valleys of anticlinal structure, or outward-dipping stratification, such as Nittany Valley and Morrison's Cove, where the inclination of the rocks is very steep, the terrace is proportionately high towards the main crest ; and where the dip is nearly or quite perpendicular, and the rocks are equally hard and massive with those in the chief ridge, it becomes a secondary summit as lofty as the primary one, and the mountain is then strictly double-crested, with a long shallow grove or depression between its two sharp ridges. Wherever these anticlinal valleys subdivide, the mountain-spurs which separate their forks being terraced like the more continuous enclosing ridges, and the terraces or benches being composed of resisting strata, lower in position than those forming the upper main-crests, the latter are obliterated for a greater or less distance short of the terminations of the shelves ; and thus high synclinal ridges are seen rising centrally out of the tops of lower, broader ones, which themselves ascend many hundred feet above the level of the valleys below. These mountains, seated upon mountains, are curious and impressive features in the orography and scenery of Kishicoquillas and the other forking anticlinal valleys. A clearer conception of their aspect will be gained by inspecting the geological map, and the picture of Kishicoquillas Valley here presented. A glance at the map will suffice to show how much more extensively the mountain flanks facing the anticlinal valleys are slopingly trenched and guttered, than those looking into the synclinal troughs. It will materially assist our conceptions of the topographical features, or external structure of this mountain-zone of the State, if, in this place, we devote a little attention to the several kinds of mountains and valleys of which it is constituted. The elongated, narrow form of the ridges, their general steepness, sharpness, and levelness, have been already adverted to, and mention also has been made of the synclinal and anticlinal valleys, and of the table-lands ; but as there are several kinds of ridges, plateaus, and valleys, each class having a distinctive configuration or orographic character dependent on its geological structure, it is expedient that we should define them, and show with what conditions of stratification they are connected. Mountain Ridges and Valleys. The ridges or elongated, narrow, continuous tracts of high ground, both those of mountain elevation and the lesser ones, entitled to the name of long, slender hills, are of three orders, resulting from three different forms of the strata composing them. In geological language they are of anticlinal, synclinal, and tnonoclinal structure. When it is considered that every part of this zone of the Appalachian Chain owes its relief to a diffused and powerful cutting or wearing action of waters upon a broad group, or series of groups of great parallel undulations of the strata, or more or less compressed waves in the earth's outer crust, it is apparent that there can exist but three forms of ridges and valleys : 1st, Those consisting of strata bent convexly upward, or dipping anticlinally ; 2d, Those consisting of strata bent concavely upward, or dipping synclinally ; 3d, Those consisting of strata not recurved in either of these modes, but dipping only in one direction, or monoclinally, and forming the flanks of the waves. These three types of geological structure, shared by the valleys as well as by the ridges, are each of them accompanied by distinctive external forms, or special orographic characteristics, only modified more or less by the relations of the strata in regard to hardness, thickness, angle, I m W ANTICLINAL KIDGES. H or dip, and other conditions affecting the amount of resistance they presented to the excavating or erosive agency of the waters. 1. Anticlinal Ridges. In their external form, the anticlinal ridges, whether straight or curved, are strictly wave-shaped. Widest and loftiest at the centre, they taper away, contracting and sinking to either extremity, not with a straight, descending crest-line, but with a convex, curving one ; indeed, they are most symmetrically and softly arched in longitudinal profile. Their transverse profile is likewise an arch steeper or flatter ; but the incurvation, except in the very flattest ones, is seldom symmetrical, one brow and slope of the ridge curving and descending more abruptly than the other. In their lower slopes, and near their base, the curvature flattens off, so that the profile is bell-shaped, though distorted from the unequal steepness above spoken of. In some instances the anticlinal ridge embraces above the level of the valleys around only the upper or crest portion of a wave of the strata ; in others it takes in all the convex half of an undulation ; and in others, again, it includes, besides this, towards either base, the commencement of the concave dips of the adjoining troughs in the strata outside of it. To speak more generally, it depends entirely upon the relative prominence of the crust-waves, or relative depths to which the waters have pared away the strata from the synclinal troughs, at what level the neutral plane, or plane cutting through the straight parts of the flanks of the waves where the convex curves just cease and the concave begin, will be placed in relation to the general valley-level of the country. Upon its position, in an anticlinal ridge, will much depend the style of profile of the mountain, especially towards its base. Of course the foot and lower slope in all cases owes a portion of its flatness to the accumulation of rubbish collected there ; but in the Appalachians of Pennsylvania this is a thin mantle, and does not sensibly alter the shapes of the hills even where they pass into the valleys. The simple anticlinal ridges display upon their flanks and summits various degrees and kinds of erosion from water, dependent upon the nature of the strata denuded. In some cases the crest is grooved longitudinally into a little shallow valley ; in others, this grooving extends deeper, reaching soft interior rocks, and then the crest is double, and we behold the first stage of an anticlinal valley enclosed between two monoclinal ridges. Wherever the uppermost hard stratum, lapping over the summit of the mountain, has not been thus longitudinally scooped, the crest is smooth, presenting few notches ; but wherever the scooping has formed two narrow monoclinal ridges at the summit, each of these is gashed by many ravines, wide at the top, and contracting as they descend the flank of the ridge. The picture given of the Lewistown Valley, and Blue and Shade Mountains in the back- ground, illustrates how different the amount of erosion has been on a single-crested and double- crested anticlinal ridge. It displays, furthermore, in the Shade Mountain, the long tapering point, and gently convex descending crest-line, so distinctive of the extremities of the simple anticlinal ridges. Another even more perfect example of this gradual pointing down of these ridges is in the north-east end of the Blue Ridge, as it may be seen from any high spot just above the village of Mifflintown. The Bald Eagle Mountain, as seen from Fair- View Inn, a]so shows it (see Plate) ; but the obliquity of the view conceals much of the slenderness of the point of the mountain. Instances, Many interesting examples of anticlinal ridges, single, double, and triple-crested, occur in the mountain-chain. Among the more prominent may be mentioned Montour's Eidge, 12 OROGRAPHY AND SCENERY OF SECOND DISTRICT. between the two branches of the Susquehanna and Tuscarora Mountain, near the Juniata, both single-crested ; the Blue Eidge, south of the Juniata in Mifflin, double-crested ; and the Shade Mountain, east of that river in the same county, triple-crested for the greater part of its length. Many of the anticlinal spurs projecting from the mountains surrounding the anticlinal valleys are simple or unbroken in outline at their extremities, but further along them their crests divide, and in some cases, where two hard massive strata form the ridge, they carry not two, but four secondary crests. It is recommended to the reader to inspect with care that part of the geolo- gical and topographical map which represents the mountain-chain south-west of the Susque- hanna, where he will detect all the above-described and many other curious phases in the topo- graphy. Where an anticlinal wave of hard resisting strata is so far eroded along its summit as that the ridge formed by it carries a groove or shallow valley along its crest (and such is the case with the Tuscarora Mountain and the Blue Ridge on the Juniata), the crest-line of the mountain is not a gradual curve or flat arch, but a nearly straight line, terminating in two gently-descending curves ; it is the longitudinal profile of a truncated wave. A fair conception of the side view from a distance of an anticlinal ridge, deeply excavated into a valley, may be got from the picture given of Millikin's Cove, as it appears from Dry Ridge. 2. Synclinal Ridges. Ridges and hills of the synclinal structure are almost equally numerous with those of the anticlinal form, existing, in fact, wherever energetic denuding waters, acting on alternately -resisting and easily-worn strata, have cut away the harder masses from the convex waves of the crust, and left them only in the troughs or the concave parts. There they often stand forth in bold relief above the anticlinal valleys, composed of softer materials, trough-shaped in the curvature of their strata, yet mountains in their elevation above the general level. Previous to the denuding action, such ridges and plateaus were the valleys of the waves into which their strata were undulated ; but the ridges of those waves having been all swept away, and the soft materials beneath them cut into valleys, these more protected remnants of the harder upper rocks project above the general level. In some instances these synclinal ridges have narrow and sharp crests ; but this is only when their strata dip inwards from both sides at steep angles. Mount Pisgah, near Mauch Chunk (for a view of which, with its inclined plane, see the picture in this work), is a good instance of the narrowness in the terminating crest of a synclinal ridge or basin. Wherever the synclinal dip is only moderately steep, and the hard rocks are in sufficient thickness, the ridge is flat-topped ; and if the synclinal trough is broad, and comparatively flat in the bottom of the wave, and its flanks steep enough to oppose the resisting edges of the strata to the waters, we have the ridge spread out into a plateau. In many cases synclinal plateaus, or table-lands of hard formations, occupying the depressions of broad flat undulations, terminate in several subordinate, synclinal spurs or fingers, originating precisely in the same manner as the detached synclinal ridges, from the denudation of the harder strata from off the anticlinal portions of a belt of waves or flexures. The side aspect or longitudinal profile of a synclinal ridge or mountain is essentially unlike that of an anticlinal one. While the latter is gently convex, unless where its crest is truncated, and even then its ends are this species of mountain has a crest-line slightly concave, especially towards its extremities. The anticlinal ridge terminates in a slowly-declining, tapering iC<- V . fS ;: ^ Sill >mJ ~ Ss\ " f ', . 1; - ; Aj** " "' v- **&_ ^te'v% I *., : i? --, * 5rtC%Cv'./'rr3 1 ,O' . . '- j.a**T. '*J V: -yi : - 1 -S'': - . - If { ffl :. Ill 1 , 1 W' > 1 ; f^^l ba3i ; i a: 03 bd , ' SYNCLINAL RIDGES. 13 point ; the synclinal one rises near its end into a softly-swelling hump, and then falls rapidly away with a bold concave sweep into the plain. Even where a synclinal mountain or plateau is deeply excavated along its summit, or is but the extremity of a trough-shaped valley, we may still discern this slight rise at the end, and abrupt external slope. It is well seen in the picture of the end of Canoe Mountain in Sinking Valley, the feature appearing not merely in the upper crest but in the terrace below it. Instances. All the districts of the mountain-chain present us with examples of synclinal ridges and plateaus. The anthracite basins terminate by the converging of their bounding monoclinal ridges in synclinal spurs ; the long and attenuated Dauphin Basin terminates in a very conspicuous one. West of the Susquehanna the synclinal mountains are numerous. Kishi- coquillas Valley contains three such spiirs, and indeed the whole remarkable mountain-group between the Lewistown Valley and the Valley of Bald Eagle is full of them. Nittany Mountain is an interesting example of one, Brush Mountain is another, and so also is Canoe Mountain, with its conspicuous encircling terrace. Two pictorial views, one representing the spurs in the eastern end of Kishicoquillas Valley, the other showing the termination of Canoe Mountain, are introduced to give the reader a clearer conception of the peculiar physiognomy of some of the synclinal ridges of the Appalachian Chain viewed endwise. The picture from Warrior Ridge, of Huntingdon and the mountains adjacent, indicates the very different modes of ending of anticlinal and synclinal mountains. Jack's Mountain in the distance is seen sinking slowly towards the right hand ; while Terrace Mountain, the high knob in advance of it, ends abruptly, throwing up a slight hump. The features of erosion belonging to synclinal ridges and plateaus differ distinctly from those characteristic of the anticlinal mountains. In the one instance the excavation or wash has been across the edges of the strata, or approximately perpendicular to their dip, this being into the moun- tain, the watery currents from it ; in the other, or anticlinal condition, the push of the waters down the slope has coincided partially with the outward dip of the beds. In the first case the rocks have been comparatively protected from erosion, and therefore the ravines and gutters, though relatively numerous, are seldom of great magnitude ; in the other, they have been in the attitude to be most easily ploughed up at their outcrops, and hence we find such enormous gashes in those crests and slopes of anticlinal and monoclinal mountains, whose strata thus dip coincidently with the course of the eroding waters. The S.E. edge of the great table-land which margins the bituminous coal-field of the State, and is called the Alleghany Mountain, is a good example of that excessive erosion visible in all the higher synclinal plateaus and ridges, consisting of nearly horizontal strata. As seen from near Hollidaysburg (see Picture), it displays a remarkable amount of deep trenching from its summit to its base. The Pennsylvania Railroad has its track through one of the ravines here shown, with a grade of 1 04 feet per mile. 3. Monoclinal Ridges. Monoclinal ridges, or those whose strata all dip in one direction, are numerous in all parts of the mountain-chain. For the most part they are the sides or barriers confining synclinal or monoclinal valleys, and each therefore finds its counterpart in a second ridge on the opposite side of the valley, containing the other outcrop of its own strata dipping to an opposite quarter. Viewed as isolated masses, these ridges are nevertheless 14 OKOGEAPHY AND SCENERY OF SECOND DISTRICT. monoclinal, or possess a one-way dip. It is only where the two counterpart crests unite that the resulting spur is synclinal or anticlinal, as the case may be. In all the mountain-chain there is but one narrow-crested monoclinal mountain or ridge of any magnitude which has not its counterpart, or the oppositely dipping outcrop of its strata, within the State, and that is the Kittatinny, the features and great length of which have been sketched already. To make the rule of the basin, or rather the wave -structure of strata, universal except in districts of original obliquity of deposition it can be shown that the formations of the Kittatinny Mountain, even to some of their subordinate individual beds, rise again to the surface in the State of New York, in the direction of Lake Ontario, passing beneath our whole mountain-zone, or only rising once to disappear again, as a small anticlinal wave, in Montour's Ridge. The transverse profile of a monoclinal ridge depends essentially upon two circumstances the relations as to hardness and thickness of the several beds of rock entering into it, and the inclination at which these dip. The hard rocks will form crests, and the edges of shelves and terraces, and the soft ones, depressions between the crests, and also the floors of the terraces themselves ; a steep or perpendicular dip is accompanied by a narrowness of base and a sharp- ness of summit ; and by an approximation of the crests, if there be more than one, and it causes the terraces to be slanting and narrow ; a gentle dip, on the contrary, spreads the mountain both at base and crest, converts all but the primary summit into the margins of terraces, and causes these shelves to be broad and approximately flat. From considerations already presented, it must appear that the marks of erosion upon the two opposite flanks of a monoclinal ridge must greatly differ. This may readily be seen by inspecting the map, and some of the plates of scenery. The terraces or benches on the outcrop or basset side of the ridge are usually well defined, wherever the dip is neither too flat nor too near the perpendicular ; whereas on the other, or dip side of the ridge, they are more vague and rounded. It is chiefly in coal-fields, where there is a great inequality in hardness between the sandstones and the coals, and especially in those where the strata have a moderately steep slope, that the benches are clearly discernible on the synclinal aspects of the hills. Wherever they are, they furnish, as in some of the anthracite coal-basins of Pennsylvania, an invaluable key for detecting and tracing the outcrops of the seams of coal. The downward carving or grooving of the opposite slopes of such ridges is likewise very different ; so different indeed, in certain districts, that a shrewd eye, practised in reading the geology by aid of the topography, will oftentimes infer the important condition of dip of the strata by these features of the denudation. Instances. Besides the remarkable instance of the Kittatinny Mountain, we may cite as among the well-characterised examples of large monoclinal ridges, all those long, narrow crests next exterior to the moimtain-rims, enclosing the anthracite coal-basins, from which they stand, usually, not a mile distant, insulated by a deep valley of soft red shale, and bounded outside by other valleys of equally soft rocks. They are to the inner citadels of fuel like so many outer protecting ramparts. All of these monoclinal ridges are continuous with each other, constituting, in fact, but one line of outcrop encircling all the coal-fields. This is readily seen. We may trace the monoclinal crest from the Kettle Mountain east of Mauch Chunk, through the Mahoning or Second Mountain to Sherman's Knob or Cove Mountain, west of the Susquehanna ; thence through Peter's Mountain eastward, and Berry's Mountain back again westward to the Buffalo Mountain near the Juniata ; and thence again eastward by the Mahantango Mountain to its MONOCLINAL KIDGES. 15 junction with the Line Mountain, and back westward to the synclinal knob which it forms with the Mahanoy Mountain at the Susquehanna, and again eastward through the latter to the Catawissa Mountain, and from the synclinal knob of this still eastward by the Nescopeck Mountain to the anticlinal table-land, where this unites with the Wyoming Mountain ; and so by this latter crest entirely round the Wyoming and Lackawanna coal-field, from whence we may bring it across in a flat and tortuous outcrop through the table-lands at the sources of the Lehigh, until we enter the Nesquehoning Mountain, and then finally turn eastward and southward round the Kettle to the point we started from. West of the Susquehanna numerous long and narrow monoclinal ridges encompass the anticlinal valleys and coves of that region all the way to Maryland. These lie in groups, which are more or less complex, and the monoclinals of each group may be seen to thread into each other in a manner very similar to the above-described winding about of the outer ridges of the coal-basins. Those of the great north-western belt of anticlinal limestone valleys, including the Kishicoquillas Valley, constitute one of the most remarkable examples to be met with in the world, certainly the finest case in the Appalachian Chain of this winding into each other of the monoclinal ridges due to the symmetrical disposition of the anticlinal and synclinal undulations of the strata. Commencing with the Bald Eagle Mountain, say opposite Williamsport, we may thread the monoclinal mountain - crest through ten successive anticlinal spurs, and nine alternating synclinal knobs, by a beautifully regular zigzag progress S. to the spurs of Jack's Mountain, in Union and Snyder counties ; thence trace it S.W. as the crest of Jack's Mountain of Kishicoquillas Valley, and back again N.E. into the Seven Mountains ; and thence meander it through these into Tussey Mountain, and follow it as the crest of Tussey Mountain to Bean's Cove, at the Maryland State line, and back again N. through Evit's, Dunning's, Lock, Canoe, and Brush Mountains into Bald Eagle Mountain, and along this to the point of setting off. In this belt of anticlinal valleys it will be observed that the outward projecting spurs are anticlinal, and the re-entering ones synclinal ; whereas in the anthracite coal-region, where the interior valleys are of synclinal structure, the salient spurs are synclinal, and the re-entering ones anticlinal. And all these reciprocating, topographical features are the simple consequences of the planing down to one general low level of mighty systems of crushed waves, or parallel flexures of the strata ; the waves of the one, or anticlinal region, have had their hard upper rocks worn through into lower softer ones ; the waves of the other, or synclinal coal-district, have had their soft upper rocks cut away into lower harder ones. Valleys. As already intimated, the valleys of the Appalachian Chain are of all the three classes which belong to a region of undulated strata ; namely, Anticlinal, Synclinal, and Monoclinal. They are, indeed, but the superficial depressions caused by extensive grooving by water of the same waves of the crust which include the ridges. It is obvious that, as the formations consist of alternately hard and soft, or resisting and removable deposits, a mere difference in the general depth to which the denuding watery currents were able to plane down the crust-waves, into which these strata were undulated at their elevation, would determine for each individual convex and concave flexure whether it would become a valley or a ridge. If at the time of their last retreat, or at that stage when their cutting power ceased, the moving waters were in contact with soft mud rocks, or as yet unconsolidated limestones, they would leave a permanent valley, whether they were just deserting the back of an anticlinal or convex wave, 16 OROGKAPHY AND SCENERY OF SECOND DISTRICT. or the bed of a synclinal or concave one ; and if, on the contrary, they were in contact with less removable materials, sandstones and conglomerates, they would leave a permanent ridge or plateau, whether the flexure were an anticlinal or a synclinal one. Anticlinal Valleys. Anticlinal valleys are of two classes 1st, Those which terminate in coves, or are enclosed at their ends as well as sides by mountain barriers or ridges ; 2d, Those which are open at both extremities, and are insulated at their sides only, by ridges of synclinal or monoclinal structure. Nearly all the larger valleys of the mountain- zone of Pennsylvania belong to the first class. After what has been already stated concerning the erosion of anticlinal flexures, and the scenery of anticlinal valleys, no further description of them is here needed, beyond a men- tion of an interesting difference between them and the synclinal valleys in the contour or profile of their beds. While the synclinal basins are strictly trough- shaped, or have their line of greatest depression of surface in their middle or near the synclinal axis of their strata, these anticlinal valleys are for the most part raised in the centre, and have two lines of depression one at the foot of each bounding ridge. They constitute the class of excavations termed by Buckland and other geologists, Valleys of Elevation, and when elliptical and not too much elongated, the visibly dome-shaped contour of their beds entitles them to this appellation. Being excavations in the summits of Qpnvex or anticlinal waves, they may not unfitly be called Valleys of Elevation and Erosion, as the denuded synclinal troughs, or those in concave flexures, may be styled Valleys of Depression and Erosion. This bulging of the more central tracts amounts, in some instances, where the denuding waters have encountered a resisting underlying stratum at the anticlinal axis, to a positive ridge. All gradations of profile, from gently arching to prominently ridged in the centre, are to be met with in the anticlinal limestone valleys of the mountain-chain west of the Susque- hanna. Being well defined by name on the geological map of the State, and by the pale-blue tint employed, it is not expedient in this place to do more than call the attention of the reader to their topographical structure. Their physical features will be fully sketched in connection witli the geological descriptions to be given of them in future chapters of this work. The arched form of surface distinctive of the larger anticlinal valleys of Clinton, Centre, Mifflin, Blair, and Bedford counties, and the cavernous structure of the great magnesian limestone formation of which they chiefly consist, combine to divert a large proportion of the atmospheric water they receive, from their higher middle tracts towards their sunken margins. By a drainage chiefly subterranean, these central tracts in Nippenose, Nittany, and Penn's valleys, in Morrison's Cove, and indeed in several others, are seriously deprived of superficial streams, and their soil is dry and barren, while their borders, on the contrary, are most copiously supplied with gushing springs and large brooks of filtered, sparkling water. So deficient in irrigation, and therefore unsuitable to agriculture, are the central high grounds, that they usually go under the name of " The Barrens." Their soil is for the most part sandy, being derived from the disintegration of the very arenaceous lower beds of the magnesian limestone, and no doubt this quality concurs with the underground drainage above adverted to, to give them their prevailing sterility. It has been proposed to seek a remedy for this by sinking artesian wells, and in one or two instances sufficient supplies of water have been thus procured to render farming profitable, where previously it was not practicable. It is manifest, however, from the facts here stated, that the geological conditions are adverse to the procuring easily of a full supply of the subterranean water by such artificial means ; the anticlinal or arching dip of the strata, and their cavernous nature, being most inimical to the success of VALLEYS. 17 artesian wells. Positions may be found, however, on the slopes of these barrens or central ridges, where the water will rise nearly to the surface by its own hydrostatic pressure ; and in some anti- clinal tracts there is a flatness, or actual basining of the rocks at the summit of the anticlinal arch, which, where it exists even locally in these valleys, may sometimes, despite the multitudes of fissures and caves in the limestone, render artesian borings profitable. The picture of Millikin's Cove, from Dry Eidge, displays at a glance the extent to which the waters were able to scoop out a valley in the crest of an anticlinal wave. Synclinal Valleys. Like the anticlinal valleys, the synclinal are of two classes ; those which are encompassed by a rim of hard strata, and those which are open at one or both extremities. The several anthracite basins are good examples of the class of closed synclinal valleys both straight and curved, and both simple and complex in structure. The basin enclosing the coal- field of Broad Top Mountain, in Huntingdon and Bedford, is another good instance of a sym- metrical yet complex valley of this class. Many lesser ones will be mentioned in the detailed description of the geology. A curious example is the mountain-basin of Scrub Eidge, in Fulton County ; this valley being a shallow depression within an insulated mountain-plateau, ruptured at one side by a deep ravine. Of the other class of synclinal valleys, or those not enclosed at either end, there are several striking examples within the mountain-chain. ' One of the largest of these is the long valley or narrow plain which commences at the Susquehanna, opposite the western end of the Mahauoy Mountain, and ranges across the Juniata, as the valley of Tuscarora Creek, to the end of Scrub Eidge, above referred to. This may be regarded as a prolongation of the same synclinal trough, which embraces the Shamokin Coal-basin. Another very similar valley of the same structure is traceable through even a longer distance from the Catawissa Mountain, in Columbia County, across the Susquehanna, at the junction of its two great branches, and thence through Snyder, Huntingdon, Mifflin, and Fulton counties, even into Maryland, between the Black Log and Shade group of anticlinals on its one side, and the anticlinal ridges of Montour's Eidge and Jack's Mountain on the other. Its central portion is called the Lewistown Valley ; and as it is there obstructed by several local ridges, the whole may be as properly viewed in the light of a chain of valleys as in that of one single continuous trough. There is nothing especial in the scenery of this class of valleys to call for particular description. There is a subordinate class of valleys allied to these valleys which are open only at one end, and usually forking there into two branches, and closed at the opposite extremity by ridges, or the summit of some anticlinal plateau. These may appropriately be called Synclinal Coves. A brief inspection of the topography shown on the geological map of the State will display the positions of a number of such half-shut-in valleys of all dimensions. Several large ones will be seen opposite the western terminations of the anthracite coal-basins, and the reader will note a series of them in Union County, penetrating westward from the general plain of the district, be- tween the beautifully symmetrical anticlinal spurs, in which the mountains of Mifflin and Centre counties there terminate. The scenery of these coves is usually striking and attractive, from the exquisite regularity of the curves by which the bounding ridges slope down into the bed of each glen, or further out into the plain that forms the middle distance of the picture. VOL. I. C 18 OROGRAPHY AND SCENERY OF SECOND DISTRICT. There are two kinds of these open synclinal valleys, one terminating, as in Union County, in a level country ; the other subdividing or forking by the introduction, near their mouth, of a synclinal ridge or mountain, which itself is sometimes but the terminal knob of another synclinal cove of similar structure. Our map displays near the Susquehanna three interesting examples of this arrangement of spoon within spoon, opposite the terminations of the three first coal-basins those of Dauphin, Wiconisco, and Shamokin. The two branches into which each synclinal cove, thus divided in its middle by a mountain basin, bifurcates, are both of them monoclinal valleys, or valleys, all the strata of which dip in one direction that is, towards the synclinal axis of the parent valley prolonged. Monoclinal Valleys. The third class of valleys consists, according to our joint topographical and geological classification, of those in which, as above stated, all the strata dip in one direction. In a region so regularly undulated as the Appalachian Chain, they are almost invariably very long and slender, and of uniform average width ; they are, indeed, merely excavations or deep trenches on the sides of the anticlinal or synclinal waves, and not on their summits or in their troughs, as are the other two kinds. Wherever the formations are greatly contrasted in their capacities for resisting the scooping power of moving water, these valleys are proportionately deep below the parallel crests which confine them, but in the same group of formations they are relatively narrow or broad, according to the steepness or flatness of the dip of the rocks, while their height or level above the average plane of the country is the greater in proportion as this dip is less. The chief variety of feature to be met with in these valleys is in the carving of the slopes of their bounding ridges. In many instances this is very beautiful and picturesque, espe- cially where the valley is large and very long, and confined by mountains, whose crests possess a gentle curve. If, in such cases, the observer stands on some buttress or more projecting station midway up either slope, he may often feast his eye upon a long superb perspective of indented mountain-sides. For a reason already intimated, the ravines and terraces of the two enclosing barrier-ridges will offer essentially different profiles : the one set, belonging to strata dipping away from the valley, will be sharply escarped and trenched ; the other, pertaining to beds of rock dipping into the valley, or with the slope of their own side of it, will be more delicately and faintly grooved and modelled ; and thus a rich diversity of contour is frequently to be seen, where the topography is of the simplest kind, and the geological structure, or dipping of the strata, undergoes no change. We get a good view of a monoclinal valley, that of the Mauch Chunk Creek, between the Mahoning and Sharp mountains, from a buttress of the latter, called Mount Jefferson, at the head of the inclined plane of the Mauch Chunk Eailroad. Instances. -By far the longest valley of the monoclinal class is that which lies immediately N.W. of the Kittatinny Mountain. In strictness it stretches the whole distance from the Hudson River at the end of this mountain, which in New York is called the Shawangunk Range, to Perry County, west of the Susquehanna. Throughout its N.E. half, where it is bounded N.W. by the Pokono Mountain, and the whole way thence to the Schuylkill, it is a somewhat broad belt, and contains generally at least one subordinate anticlinal flexure, so that rigidly it is not a monoclinal valley. Toward its western end, however, it contracts, and runs to its termination without any deviation in its strata from their usual steep north-west inclination. This valley contains much fine scenery of the kind characteristic of its class, additionally diversified by the CLASSES OF SCENERY. 19 presence, on the one hand, of bold spurs entering it from the Kittatinny Eidge, and, on the other, by great bastions of the Pokono. Next in magnitude is the long curving valley immediately at the S.E. base of the Alleghany Mountain. This begins in Lycoming County, with the rising of the Bald Eagle Moun- tain, which confines it on one side. There, and in Clinton County, it is watered by the broad and placid Susquehanna, and by several large tributary streams entering it through deep passes in the plateau on its north. Further forward to the S.W. it leaves its graceful curvature of line, and runs almost absolutely straight between the Alleghany Escarpment and the sharp crest of the Bald Eagle Ridge, nearly to the termination of the latter in Blair County. Throughout this central part of its course it possesses the monoclinal structure on a scale of grand simplicity. Turning more southward in Blair, the valley widens by a curious offset in its mountain barrier at the ridge called the Lock Mountain, and further on it dilates again by another offset of the same ridge near Bedford. The rising of Wills' Creek Mountain presently reduces it, however, to its average dimensions, and approaching the State boundary of Maryland, it divides into two branches, losing its monoclinal structure by the admission of the synclinal basin of the Potomac Coal-field. In Lycoming and Clinton this grand deep trench in the strata embraces a few trivial undulations which modify its topography, diversifying its northern and central tracts, with a few small picturesque ridges of limestone. Again, in Bedford County, the introduction of one or more short waves of the strata, near the foot of the Alleghany Mountain, causes the presence of more than one knob and stony-crested ridge. Besides these more marked exceptional features, the valley exhibits throughout its entire N.W. border, a multitude of low hills, carved from out the base and lower slope of the Alleghany Mountain. These are well shown in the picture of the front of the Alleghany and the country at its base, taken from near Hollidaysburg. It is not necessary to enumerate here the many long and slender monoclinal valleys which begird the anthracite basins, like so many moats enclosing walled cities. The geological map exhibits them in all their curious symmetry, and the descriptive details hereafter to be given will set forth their more special features. Wherever there exists a basin within a basin, or one anti- clinal valley within another, two such monoclinal valleys, one on each side, will be seen to occupy the spaces between the rims of the inner and the outer ridges. DIFFERENT CLASSES OF SCENERY IN THE MOUNTAIN-CHAIN, AND THEIR RELATIONSHIPS TO THE PHYSICAL GEOGRAPHY AND GEOLOGY OF THE REGION. The kinds of scenery most characteristic of the larger anticlinal and synclinal valleys have been already alluded to, but it will be instructive to sketch succinctly the several classes of natural pictures to be met with in the Appalachian Chain, with somewhat more of geological method, avoiding a repetition of what has been already described. Scenery commanded by Anticlinal Mountains. Beginning with the views distinctive of the anticlinal belts mountains and valleys we will, in the first place, conceive ourselves standing on the summit of a simple or unbroken, long, narrow, anticlinal ridge. Stationed anywhere near the central swell of its crest, and commanding an unobstructed sweep of vision, we may usually behold a very interesting panorama of mountains. Looking across the chain in either direction, the eye descends the long, beautifully-curving, flattening slope of the mountain-side from a craggy 20 OROGRAPHY AND SCENERY OF SECOND DISTRICT. foreground, over gnarled and wind-distorted trees of stunted growth, to timber growing progres- sively denser and richer, till low towards the foot, and in the valley, the forest spreads away in broad and dense luxuriance. Beyond the adjacent valley or narrow plain rises a counter-slope of another mountain-ridge similarly clothed with woods, and ending in a stony crest of nearly equal elevation with the summit we are upon. Our position is, however, somewhat higher than the crest-lines of the monoclinal and synclinal ridges around us, and the eye travelling across them, and through the notches which here and there indent them, or beyond their points, sees ridge suc- ceeding ridge, and valley behind valley, grouped in a far-receding perspective, like majestic waves on a storm-tossed ocean. The upper slopes of the mountains being for the most part clothed with forest, this resemblance to some vast sea, heaved into enormous billows, is rendered all the stronger from the monotony of the colour which clothes the wide scene. It is only in the nearer distances, especially in the valleys beneath us, that this monotony of tone is relieved by other brighter tints, by clearings, cultivated fields, the rich browns of the ploughed earth, and the gayer green of the meadows. It is delightfully interrupted by a feeling akin to surprise when the eye catches sight, through some deep notch or opening, of a patch of cultivated valley, with its farms and dwellings smiling in the sunshine amid the dusky green of the seeming wilderness. Let us now suppose that the beholder, sated with these broad mountain-top views, turns to gaze in the direction of the trend of the crest upon which he is standing, or towards the north-east or the south-west. To open these longitudinal views from foreground obstructions, he will usually travel along the summit and station himself somewhere upon the long drooping end of the moun- tain, though at as high a level as possible. There he will be greeted by a scene which seldom fails to interest and delight him. Very different from the previous, it is a picture of long receding valleys instead of opposing mountains. Centrally in the nearer parts of the landscape is the regularly-tapering forest-clad ridge upon which he stands, and beyond it a wide noble panorama, formed by a girdle of mountains, converging to the distant vanishing-point of the picture in a swelling peak, or gracefully rounded summit, the highest object in view ; and all between this background and the hill on which he is stationed, the more or less cultivated plain or valley stretches before him, and dividing at the lower point of the ridge, passes to the right and left of him. He is looking, in fact, towards the head of a great anticlinal cove between the mountains,along an anticlinal valley many miles in length, which, bounded by symmetrical mountain-slopes, opens towards him, and divides at his feet. In some instances, as in Centre and Mifflin Counties, these coves are simple, and we look along but one slender valley closing up in the distance ; but this style of scene has many modifications, and there are numerous examples where, besides the prin- cipal valley stretching in front of us, we look forward past the ends of synclinal ridges, right and left, into other parallel plains. Of this character are the beautiful semi-panoramic pictures to be seen whenever we are at the trouble to ascend to some high clear spot on the N.E. point of Shade Mountain, in Snyder County, or to a similar position on the Tuscarora Mountain, in Juniata. A little study of the 'topographical features represented on the map, will suggest many other choice points of view of this description ; indeed, there is scarcely an elevated anticlinal ridge within the portion of the chain west of the Susquehanna which does not, from one or both of its extremities, command a superb view of valleys and their bounding ridges, seen in the direction of their length in prolonged perspective. The interest belonging to this class of scenes is frequently much enhanced by a singular ANTICLINAL MOUNTAINS. 21 structure in the ends of the anticlinal mountains, from whence the beholder is supposed to be looking. Through geological causes, hereafter to be explained, the point of the mountain, instead of tapering off simply and smoothly, sinks with a beautiful crest-line to a certain spot, and there ceases, plunging, as it were, into the centre of a little crescent-shaped or horse-shoe valley, which closes around it, and projects its two horns or prongs backwards, to coalesce with either base of the mountain. Where the mountain ends somewhat bluntly, as the Shade Mountain in Snyder, and Jack's Mountain in Huntingdon, do, this crescent-like rampart in the foreground of the picture, steep and often craggy on its inner slope, and smoothly declining on its outer, is a beautiful addition to the scene. Where the mountain terminates acutely, as the Tuscarora Mountain does at its S.W. extremity, or as the Black Bog and adjacent Blue Ridge do at both ends, the appended ridge has, in its ground-plan, almost the form of a long and slender dart, projecting a keen point into the valley, and its two barbs, backwards, towards the main ridge. There is another interesting class of scenes commanded by the anticlinal mountains, in which long anticlinal valleys or coves terminate. These points of view are the peaks or swelling knobs before spoken of, as occupying the middle points of the pictures, beheld by looking from the ends of anticlinal spurs up the anticlinal valleys. Let the reader, studious of interpreting the relations of the scenery of the mountain-chain to its topography, imagine himself standing at the head of either of the anticlinal coves which intervene between the western ends of our anthracite coal-basins. Let him, for example, stand at the junction of the monodmal ridges, Peter's and Berry's Mountains, or at the union of Mahantango Mountain with Line Mountain. He will observe two very different scenes, as he gazes eastward or westward. Eastward, he beholds a picture very similar to those before described, as seen from the ends of the insulated anticlinal ridges, only much more circumscribed, for he looks into a short anticlinal cove forking to his right and left into two narrow monoclinal valleys. But westward he gazes over a landscape of far wider scope ; he sees the two monoclinal ridges, at whose elevated point of junction he is standing, diverge and recede before him in gentle curvature, like the bulwarks of a great ship viewed from the end of the forecastle ; while subsiding in front of him there stretches a long, expanding valley, hilly, and covered with wood in its nearer, narrower end, but smooth, cultivated, and gay with farms and villages in the distance ; and he catches here and there the silvery surface of one or both of the main streams which flow from him along its margins, or perhaps that of the main Susquehanna River itself. Centrally, in the background of the scene, appear the ends of high-swelling anticlinal mountains, on the extremity of one of which we have before supposed him stationed, and gazing towards the very spot from which he is now looking. If our traveller, still restricting his attention to the commanding points of view afforded by the high anticlinal ridges and knobs of the country, chooses, in the same district, one of the points of junction of the monoclinal ridges which immediately invest the anthracite coal-basins, shifting his station from the outer to the inner barrier of the coal-field, if he chooses, for example, a spot on the high anticlinal plateau west of Tremont, or any similar geological locality, he will have before him a very curious and interesting scene. At the head of a crescent- shaped rim of mountain, he gazes into a deep crescent- shaped valley called " the Kettle," and across the middle of this beautiful valley, looks upon a broad, swelling, anticlinal mountain, the 22 OEOGEAPHY AND SCENERY OF SECOND DISTRICT. very same upon which he had his previous station. The deep moon-shaped valley before him throws forward its two horns to embrace the broad mountain in front of him, each running indefinitely into the distance, as a straight and narrow monoclinal valley between two sharp- crested monoclinal ridges, into which the anticlinal knob soon diverges. If his perch is high enough, he can look along their narrow summits, and into the valleys between them, counting four mountain-ridges and three enclosed valleys. In the middle of the wide picture he catches a distant view of the expanding anticlinal plain or valley, which nearly filled the scene at his previous station, and right and left of it he beholds the narrower side- valleys prolonged from the crescent-shaped " Kettle " below him. If, instead of selecting a series of stations on the broader anticlinal waves of the surface, our traveller chooses his points of look-out at the head of one of the slender limestone coves west of the Susquehanna, he will meet with a series of views very similar in their general features to some of those just described, but differing in the comparative slenderness of the valleys along which he will gaze. Planting himself back from the immediate head of one of these coves upon the next ridge, as he did in a previous instance, he sees before him, not a deep crescent-shaped Kettle or valley, but a very interesting crescent-shaped plateau, or mountain-floor, or upper cove, beyond which he looks into the lower principal one. Some of these mountain-coves in Centre and Union counties are indeed somewhat depressed at their ends, and therefore approach a little the anticlinal " Kettles " in their scenery and topography ; and in truth the industrious explorer of these features of the chain may find them of every gradation, from deep " Kettles " to high level crescent-shaped mountain table-lands, as the conditions of stratification permit. If the soft stratum forming the excavation is very thick, and the dips moderately steep, a wide deep valley is the consequence ; if it is thin relatively to the hard formations embracing it, and the anticlinal flexure is gentle, an elevated crescent-shaped plateau is invariably met with. Scenery from Synclinal Mountains. The kinds of scenes visible from the summits and sides of the straight-backed and level synclinal and monoclinal ridges of the Appalachian Chain are, for the most part, so identical with those already described, as seen from the tops of the anticlinal ridges, that it would be superfluous to attempt to depict them. Nor is it necessary to sketch the features of those which are beheld from the terminal synclinal knobs or basins, looking outwards into the valleys and plains, further than to indicate wherein they differ from the scenes beheld from the points of the anticlinal ridges. We have seen that the latter, embracing great longitu- dinal views of the anticlinal valleys, are bounded by the ridges which enclose and terminate these coves ; they of course take in the most terraced slopes of the adjacent mountains. The other class of scenes, or those of the synclinal belts, likewise sometimes terminate in cove-shaped valleys, though they more frequently look out into plains and valleys which are not closed in the dis- tance by any converging ridges. The terminal knobs of the synclinal basins being loftier than the drooping points of the anticlinal ridges, these first-named stations offer altogether the widest and most panoramic mountain-pictures to be grasped by the eye ; and they have this further superiority over the other class of summits, that they control unobstructed views in all directions outward from the basins to which they belong, into the longitudinal plains included between the receding anticlinal summits in one direction, and inward in the other, to embrace the features of the mountain-troughs at the ends of which they are seated. The outward view, or that which we get upon gazing off from the synclinal basin, whether it embraces a cove or an unclosed valley receding SYNCLINAL VALLEYS. 23 to the horizon, shows the anticlinal mountain-slopes in their least indented and terraced aspects, unless where these slopes belong, as in the case of the Tuscarora, Shade, and Blue Mountains, to ridges grooved along their crests, when they are deeply notched and ravined. In such instances the perspective is very fine, as the reader may infer from inspecting the picture of the Lewistown Valley, and such others as show the indented flanks of the ridges of this order. Another characteristic feature of these scenes is the deepness of the valley in the front of the picture, or that in which the synclinal knob terminates. Ending more abruptly than the anticlinal spurs, these synclinal mountains usually overlook steeper slopes and deeper valleys on their outer sides. Some of the most commanding points of view of this class are the terminal knobs of the several Anthracite Coal-basins ; but precisely as we found, in the anticlinal stations connected with these basins, two different classes of commanding summits one set belonging to the exterior rini of mountains, the other to the interior rim, or that immediately enclosing the Coal Valleys, so here, we find among the synclinal knobs two similarly related kinds. Each description of summit commands, of course, two classes of scenes, one in the direction from the Coal-basins, the other in that towards them. Views from the Ends of the Exterior Basins. Let us, for the sake of more clearly under- standing the scenery connected with the great synclinal belts or basins of the mountain-chain, conceive ourselves standing on any one of the five terminal knobs in which the outer mono- clinal ridges encircling the coal-fields unite towards the west namely, upon the ends of the Cove Mountain, the Buffalo Mountain, the Mahanoy Mountain, the Catawissa Mountain, or the Shickshinny or Knob Mountain ; or suppose ourselves in a corresponding position to the Broad Top Coal-field on a knob of Terrace Mountain, or that of the Harbour Mountain. From either of these high stations we can command one view from and another towards the coal- field to which the mountain -barrier is related. The outward view is wide and panoramic, embracing, in the middle of the picture, a long synclinal plain, extended, with gradually- narrowing borders, almost indefinitely before us, or finally closing by the approximation of the anticlinal ridges which confine it. To the right and left of the picture lies a broad valley, formed by the forking of this broad synclinal plain, at the base of the knob upon which we stand. All the mountain features, enclosing the main valley and these its two branches, have the soft curving lines, and graceful smooth slopes, distinctive of anticlinal ridges or convex undulations of the strata. The inward or other view is wholly different : usually far less comprehensive, it is much more curious and striking. In nearly each of the localities mentioned, the station is sufficiently elevated to enable us to embrace, at one glance, the entire structure of the mountain trough, upon the extremity of which we are perched. From our very standing-place, the high mountain- knob slopes down in a majestically flowing curve, first softly convex, and then concave ; and on either side it expands, throwing out two wings, which, descending and contracting in breadth, sweep, bending away, till they become two sharp, craggy, monoclinal crests. As the bed of the valley descends, these enclosing ridges sink also, but more slowly, and grow narrower, straighter, and more parallel ; and now we behold a structure which may be aptly likened to the bow of a stupendous boat, or to a huge cradle built for holding and launching some colossal ship ; the difference in the dimensions being, that here miles answer to fathoms. This ability to scan with 24 GEOGRAPHY AND SCENERY OF SECOND DISTRICT. one look the vast natural trough ; to gaze downward along the high mountain-walls which enclose it, to behold all the planking of the ship's great hull ; the graceful divergence of her bul- warks, the beautiful convergence of her sides towards the central line or keel, and her far-stretch- ing length, never fails to fill the beholder with a sense of elation and surprise. But the scene here sketched carries this curious resemblance no further than to the middle distances ; for within a few miles, and in some instances at a less space, there rises in the centre of our fancied boat a mountain-knob, the synclinal termination of the enclosed coal-basin, and from this spot forward the outer trough is parted into two contracted monoclinal valleys, the same which have been already described as branches of the beautiful crescent-shaped anticlinal valleys designated " Kettles." The inner basins, or those immediately embracing the coal strata, containing no such central features, but being trough-like throughout, present, when seen from their terminal syncli- nal knobs, this resemblance to a ship or boat far more exactly. To the description of these we shall come presently. Views from the Ends of the Interior Troughs or Coal-Basins. Shifting our position along any of the synclinal belts, including the narrow coal-basins from the termination of the outer mountain-barrier to the end of the inner one, or that belonging to the immediate rim of the coal- field, we enjoy, as in the previous case, a view of two remarkable but very different scenes. One of these we behold when we look from the coal-field into the synclinal cove which encompasses the mountain summit upon which we stand ; the other opens itself on gazing in the opposite direc- tion into the coal-basin itself, which stretches away, descending and expanding, almost from the spot we occupy. The first or external picture is that of a symmetrical cove, bounded and closed by two con- verging mountain-crests. Stationed in the centre of the trough, we look along the valley and see its bed gradually contracting and rising as it recedes from us, until it lifts itself like the stem of a sharp canoe into the high peak which bounds our view in the distance. The scene is very analogous to that already described, as visible from an anticlinal ridge, when we look lengthwise into an anticlinal cove, with this difference, that we are standing on a loftier point, and behold a much more boat-like contour in the bed and slopes of the valley before us. The whole carving or modelling of the valley is different ; it has the softness and delicacy of curve characteristic of the synclinal structure, due to an accordance between the slope of the strata and the slope of the waters which cut them ; whereas the valleys and coves of anticlinal structure are more boldly seamed and distinctly terraced, through the reverse relation of the dip of the strata to the course of the scooping waters. One of the finest of this class of views is that from the end of the Dauphin Coal-Basin; another is that of the Valley of Zerbe's Run from the end of the Shamokin Basin, and a third is from the top of Mount Pisgah into the Lehigh Kettle. The other or interior scene, that of the inner valley or coal-basin, is, in its simple grandeur, perhaps the most impressive of all. Standing on any of the mountain-summits in which, by the closing together of their narrow barriers, either the Schuylkill, the Shamokin, or the Wyoming coal-field terminates, and looking into those valleys, the beholder sees a structure singularly like the deck and bulwarks of a gigantic ship scanned lengthwise from the bow- sprit ; his point of view is relatively as high above the crests of the ridges which diverge right and left from him, and then trend away nearly -parallel for miles towards the waist f ( ' 1 % <\ I . .am-'t I' - ... . : . ^-'iifcV'Vwi 1 I f! i i \M N*S t : * ' * i -fj" vr ^nr > , \^- \\ % ^,^PO ^t^B -- EH MOUNTAIN CEESTS. 25 of the symmetrical skiff -built valley, as when upon the stem of an actual vessel he plants himself on the butt of the bowsprit, and overlooks the taffrail, the forecastle, and the deck. Of this class of scenes none are finer than that from Mount Pisgah, near Mauch Chunk, into the Lehigh Basin ; that from the end of Bear Mountain into the Wiconisco Basin ; that from the knob of the Mahanoy Mountain, looking into the Shamokin Basin, and that from the Shickshiuny Mountain, gazing into the Wyoming Coal-field. In some cases a shoulder or platform on the inner side of one of the bounding ridges of the trough-shaped valley projects sufficiently forward into the valley, and is high enough, to afford a fine general picture of its interior. Such a view of the eastern half of the Pottsville Coal-basin, or first Great Coal Valley, is procurable from the Lehigh Summit Mines looking westward. It is especially instructive in displaying the slenderness of the mountain barriers of the valley and the narrowness of their crests. The Locust Mountain and the Sharp Mountain are well seen in profile at the notches or gaps through which the Little Schuylkill enters and passes out of the basin. (See the Plate.) SCENERY AND STRUCTURE OF THE MOUNTAIN CRESTS. Having in the foregoing paragraphs sketched the general features of the several kinds of scenery visible from the anticlinal and synclinal summits, it will be instructive, before leaving these and descending into the valleys and the passes through the ridges, to look at the crests of the ridges themselves. I. Anticlinal Crests. The mountains of anticlinal formation, when not truncated, have their crests usually very smoothly and regularly rounded. They are wider for the most part than those of the monoclinal ridges, but narrower than those of the synclinal, and they are commonly less flat than either ; indeed, every portion of the top may be said to have some curvature. Their local topography is therefore not interesting, though the distant views they command are unobstructed by any inequalities in the foreground. But when truncated or trenched along their crests, their local scenery is oftentimes pleasing and curious. If the tourist wishes to explore such a mountain, with a view to a knowledge of its topography and its geological contents, he will set out at one extremity, ascend the crest-line along the anticlinal axis to the high point where the crest divides, and the long oval valley or spoon-shaped mountain-basin begins, and there pause and scan the exquisitely beautiful curvature of the lines of the surface of the shallow mountain- vale. If the anticlinal structure is symmetrical, in other words, the two slopes of the anticlinal curve of the strata nearly equal, he will perceive a remarkable evenness and equality in the soft slopes of its two borders. If the ridge is denuded of its timber, he may, from his high station, see along its entire length, and grasp the beautiful oval curve of the narrow crest or ledge which encircles it. In some instances it will have the regularity of a most accurately carved, shallow skiff ; in others, one or both of its sides will be notched, and opposite to each opening will occur a depression in its bed. Not unfrequently the converging slopes of this trough in the top of the mountain will descend towards each other by successive stages, and not continuously, and the terraces corre- sponding in height, and looking like the benches in a boat, will suggest the similitude to a skiff still more strongly. The explorer may follow the central line or anticlinal axis through the middle of the high valley, and there examine the lowest strata which the denuding waters have been able to cut into upon the back of the uplifted wave ; and to seek the very lowest, he will go to VOL. I. D 26 OROGRAPHY AND SCENERY OF SECOND DISTRICT. the depressions opposite the lateral notches. Again he may walk along either of the narrow crests enclosing it, and obtain superb views of the external country, and, by merely turning his head, find relief from the fatigue of a vast and complicated picture, in the simplicity, quietness, and home-like nearness of the little mountain-valley at his side. Following the more unbroken of the two crests, if one of them is notched, he will pass in succession the points opposite the openings in the other, when his eye, previously hemmed in by the rim of the valley, which is seldom more than two or three hundred yards distant, will catch with surprise and pleasure the far-off plains and hills, with their brightly tinted farms and houses, and frequently a shining river. Such are the con- trasts which refresh the geologist while toiling along the summit-ledges of the anticlinal ridges which so abound in the Appalachian Chain. 2. Synclinal Crests. The tourist finds the ascent of the synclinal ridges more abrupt and arduous than that of the anticlinal ones. He meets with some, retaining a simple, narrow, straight crest-line for many miles. There is one such, called the "Dividing Mountain" between Path and Anderson's Valleys in Franklin County. The slender terminating ridge of the Dauphin Coal-basin is another ; and the Hole Mountain, in Lebanon, a third ; though few of them are like the latter, insulated from other ridges. In the great majority of instances, the single-crested hills of synclinal structure are merely long spurs, separating anticlinal valleys, and expanding into basins by the division of the crest into two monoclinal ones. The styles of scenery visible from both the terminal knobs, and from the points of bifurcation of these high synclinal spurs, have been already sketched. But some of the synclinal ridges have the form of long and very narrow mountain-troughs ; that is to say, they have been truncated, or hollowed at their crests into slender oval basins, bounded by two adjacent, parallel, monoclinal ledges. A good example of this structure is to be found in the ridge in Franklin County, terminating in ParneU's Knob. The local scenery of such a trenched synclinal summit is very analogous to that already depicted as belonging to the similarly truncated, anticlinal mountains. The slender, elevated, oval valley has the same spoon-shaped terminations, and the same notches in one or both of the barriers confining it. It differs chiefly in showing no platforms or benches on its slopes, and presenting altogether smoother and softer concave lines. 3. Monoclinal Crests. The mountain summits of the monoclinal ridges, when longitudinally explored, are fully as interesting as those of the other classes. They indeed abound in a richer variety of immediately local pictures. This diversity mainly depends, however, upon geological conditions, that is to say, upon steepness in the dip of the strata, and especially upon a wide difference in the relative hardness or susceptibility to erosion of the materials of the mountain. Where these are nearly homogeneous, the crest is for the most part monotonous in its features, being simply rounded like that of an unbroken anticlinal summit ; but where they are in strong contrast, the mountain-top is full of variety. To picture more clearly the appearance of these crests, let us suppose ourselves tracing one of those which bound the southern or middle anthra- cite coal-basins, where an extreme difference of hardness exists between the massive conglomerates and sandstones, and the thick coal-beds and clay-rocks, all composing the Lower Coal-measures. We will imagine ourselves proceeding westward, along either the Sharp Mountain or one of the ridges enclosing the Wiconisco or the Shamokin Basin. The average width of the actual top of the mountain is seldom more than 100 yards. It is frequently much narrower. This top is approximately level, but it is picturesquely broken up into a succession of long narrow floors or MOUNTAIN SIDES. 27 strips of smooth surface, each seldom more than 30 or 50 feet broad, standing at slightly different levels, and separated by long, narrow, jutting crags, or ribs of hard and naked sandstone or conglomerate, broken at their outcrops into enormous blocks. Pursuing a zigzag course across the summit from one smooth floor over a strong reef to another floor, we soon ascertain which is the highest ledge, and gazing thence, we are able to mark the exact profile or configuration of the mountain-top. Stretching before us and behind us, are usually three, or four, or five of these nearly horizontal floors or terraces, each with its supporting craggy rib of conglomerate. The perspective is extremely curious and picturesque. If a sparse growth of gnarled chestnut oak, black oak or chestnut, shades as usual the summit and sides of the mountain, we behold long vistas or alleys among the trees, marked out by these alternating smooth and rocky strips. Shifting our position to a ledge on the outer verge of the mountain, we overlook an extremely steep and stony slope, and may discern one or more similar, but less level and well-defined benches or terraces at different levels below us, and beyond these a progressively smoother surface, growing steadily flatter, and covered with a denser forest all the way to the base. If now we cross the crest to the brow or shelf, looking into the basin, we behold a much less steep and rugged flank ; the benches are more numerous ^each marks the outcrop of a bed of coal but they are slanting, and comparatively indistinct, and the bushes and trees are thicker upon them. Advancing along the top of the ridge, and choosing for our path either the highest smooth floor or the top of the most projecting stony rib, we follow it for a distance, perhaps of some hundreds of yards, when it changes its relative elevation above those adjoining it, or disappears to permit some other bench or ledge to form the actual comb of the mountain. Thus our journey offers a con- stant succession of new local pictures, the path we are tracking leading us from a smooth floor, clothed with soft herbage, to reefs and cliffs, and back again alternately, sometimes to one verge of the mountain, to open one broad landscape to our view ; sometimes to the opposite verge, to substitute another, and even wider picture ; or again, along a high central crest, from whence we command both scenes, and can unite them into a perfect panorama. Aspects of the Mountain Sides. Mention has been already incidentally made of some of the prevailing features of the slopes of the Appalachian Eidges, their benched outline, faint on their dipward sides, conspicuous on their escarped ones, and their general vesture of forest, stunted and sparse towards the crests, but luxuriant and dense low down. It is now in place to speak concisely of one or two other features. Nearly all the higher ridges, particularly those of mono- clinal structure, have their flanks thickly strewn with a stony rubbish, the wreck of the disrupted materials of the mountain, dislodged from the outcrops of its strata, and left dispersed in wild confusion from its very summit to its outer base in the valley below. This fragmentary matter, which is of all sizes, from sand and comminuted shale to vast angular blocks of the bulk occasionally of a small house, is coarsest and in greatest quantity where the strata which have supplied it are alternately massive and soft. It would appear to prevail in greatest plenty near and within the deep clefts or notches of the mountains through which the floods tore their violent passage, and along the beds of which the comparatively puny and quiet rivers now find their easy channels across the chain and towards the ocean. In such localities the covering of loose blocks of stone above the strata and the soil is so thick, the pieces are so large, the vast pile so steep and pervious to the rain, that neither tree nor shrub gets foot-hold, and, as a conse- quence, the mountain is utterly naked of foliage. These great "stone-slides," as they are called, 28 OKOGKAPHY AND SCENERY OF SECOND DISTRICT. face in some places the entire mountain from its summit to rts base, but more commonly they occur in enormous patches. The sandstone blocks of which they consist are usually coated with a dark grey lichen their surfaces being too dry for even a green moss and this lichen, black- ened by decay, imparts a singularly austere and savage aspect to the mountain-passes. We shall discuss in another place the question of their origin, and that of the period of their production. Passes, or Notches in the Mountains. Among the local scenes characteristic of the Appala- chian Chain, none, perhaps, are so impressive and picturesque as the deep notches or defiles in the ridges. They are of two classes : indentations or clefts, which do not descend to the level of the adjoining valleys ; and more profound gorges, intersecting the mountains to their very base. The former are called " Wind-gaps," from the almost constant presence of a breeze in one or other direction through them ; and the latter those at least which afford passage to the larger rivers are called " Water-gaps." They are various in their forms, both as respects their profile and their ground-plan. In their simplest type, these notches are mere wide clefts, the sides of which slope at inclinations rarely exceeding 45, until they reach the base of the mountain, where, in some cases, they approximate so closely as to leave space for only a narrow stream ; in others, they are still so wide apart as to let the broadest rivers flow between them. Numerous deviations from this regular profile are to be met with, all of which are traceable to geological conditions in the dip and composition of the strata intersected. I have elsewhere in the pages devoted to the discussion of the effects of local erosion upon strata classified the several forms of our mountain-gaps, and explained the origin of the many curious modifications of shape which they exhibit. For the present we shall refrain from so close an analysis ; and viewing them only as specimens of scenery, confine our attention to such features as give them distinctive pictorial characters. In this light they may be regarded as of two classes : 1st, Simple, straight, transverse notches, cut squarely or at a large angle across the ridges ; 2d, Complex, or wind- ing passes, often curving like a goose's neck. Those of the first class generally prevail where the intersected mountains, if monoclinal, possess but a single crest, or contain but one hard stratum, or where they are of anticlinal or synclinal structure. Those of the second class occur in those ridges which include two or more thick ribs of hard rock, separated by some easily-wasted soft material, and which, therefore, possess compound or double crests. The gaps in the Kittatinny Mountain, and those in most of the barrier ridges of the anthracite basins, are of the first descrip- tion ; while some of those cutting the monoclinal ridges of the great limestone valleys west of the Susquehanna, and also the ridges next exterior to the coal-fields, appertain to the second class, or possess the more picturesque winding outline. The scenery connected with the simpler straight notches is rather tame, unless where the mountain is unusually lofty, and where its two ends, exposed to view in the gorge, are covered, in whole or part, with the dark "stone-slides" previously described, and then it sometimes pos- sesses a degree of savage grandeur. There is, however, one form of the straight notch which is extremely impressive. It is when the mountain contains one great convex wave of some hard formation, which spans it from base to base, and exposes its own edges in the form of a majestic arch on each side of the gap in shattered mural precipices. Then, when the scene is large, the width and elevation of the rainbow-like curving cliff impresses the sense with something approaching the siiblime. Pennsylvania possesses a number of these arch-enclosed passes, but o W o b ta w M H in CO :S , 1 ;/ V B tSS&'SWC** ' [ H-W ^ApniBI 1 m : M O JZ5 LAKES OF PENNSYLVANIA. 37 valleys having very, low water-sheds, constitute admirable thoroughfares for the commerce and intercourse of Pennsylvania with New York. The southern and western border of the tract has a deeply indented margin connected with the feature already adverted to, the existence, namely, of long, slender anticlinal valleys, carved out of its softer strata, penetrating south-westward between the high finger-shaped plateaus terminating the bituminous coal region. This district is not without its fair share of striking scenery. Some of the views within the valleys of its chief rivers, the Delaware and Susquehanna, are grand and picturesque, par- ticularly those visible from certain points on the edges of the table-lands overlooking those streams ; and the same may be said of the valleys of their larger tributaries. Indeed, few of the Appalachian rivers can boast a greater amount of attractive valley-scenery than the North Branch presents throughout its whole course, from the great bend near the State line through New York, and thence through Pennsylvania to the Wyoming Valley. It owes this eminence, in part, to the beautiful manner in which its terraces of northern drift or gravel have been strewn and shaped at the last retreat or rush of waters across the continent. A sketch, elsewhere introduced, of Spanish Hill, near Athens, in Tioga County, will convey some notion of the style of the hills, and of the remnant terraces of drift skirting their base. Lakes. It is a curious fact that nearly all the lakes and natural ponds within the State, excepting those of a similarly constituted district between the Alleghany River and Lake Erie, are embraced within the country contained between the Delaware River on the one side, and the Lehigh and the North Branch of the Susquehanna, or, more correctly, the lower part of the West Branch, on the other. This circumstance in their distribution is the more remarkable, when we reflect on their almost total absence from every part of the Atlantic slope between the Hudson and Georgia, and from every portion of the Appalachian Chain, notwithstanding its numerous valleys, S. W. of the Susquehanna. This deficiency, which is painfully felt by every tourist in search of the picturesque, extends also to the whole of the western slope of the Ohio-Mississippi Basin, and is a distinctive feature of the drainage of the whole country south of 41 of latitude. In contrast with so wide and complete an exemption from this beautiful feature, there is an unusual profusion of ponds and lakes throughout the greater part of the country lying north of the above-named boundary. What can be the cause of so singular a difference in the conditions of the flowing off of the waters 1 Simply the absence from the southern half of the continent of the great superficial stratum of gravel, sand, and clay, called by some geologists Diluvium, by others Drift, and by others, again, the Glacial Deposit. North-eastern and North-western Pennsylvania are just within the southern border of this great drift-formation, which extends indefinitely northward, even to the shores of Hudson and Baffin Bays, and of the Arctic Sea. The broad, high table-land, in which the Appalachian Bituminous Coal-field terminates on the confines of New York, has evidently stopped the southward course of the nearly-spent sheets of water which transported the drift, and turned them south-eastward and south-westward over the two northern corners of Pennsylvania. A careful investigation of the distribution of the boulder- matter has shown me, that whereas it has scarcely reached the high primary water-shed of Potter and M c Kean counties, to enter the valleys of the Sinnemahoning or the other northern streams of the West Branch, it has been strewn much more freely over Bradford, Susquehanna, and Wayne counties on the east, and Warren, Crawford, and Elk on the west. In both of these districts the drift, as we shall see hereafter, thins down to a sheet of gravel, so shallow and 38 OROGRAPHY AND SCENERY OF FOURTH DISTRICT. sparse as scarcely to be discernible on the table-lands of Monroe and Lucerne, and of Butler and Lawrence. But while this is so, it is traceable much further south, in both these quarters, along the immediate river-valleys which extend from the plains of New York into or through the Appalachian Plateau. Though we discern the last or most southern sprinkling of it on the upland, no further south in the Appalachian Valley than Northampton and Lehigh counties, it is packed in a thick sheet, carved here and there into bold terraces, all the way down the valley of the Delaware to the level of the tide-water. And again in Western Pennsylvania, while it ceases on the hills in Mercep and Butler counties, it follows all the valleys which enter the Ohio River from the north, not only those of the Alleghany and the Beaver rivers, but many more, debouching much further south in the State of Ohio. The prevalence of lakes and ponds within the drift-covered tracts of the country would appear to be connected with the partial blocking-up of the valleys and ravines by this material choking the outlets of the waters. It may be partly due, also, to the extreme levelness which it has imparted to the surface ; the original inequalities of the rocky floor of the country having been smoothed by the filling-up of the lesser depressions with this loose superficial coating. It has thus produced wide level plains in localities where, but for its presence, continuous irregular slopes would exist to drain away the waters in slender streams. In districts not covered with drift the water-sheds or summits separating the different systems of ravines and valleys are almost invariably too narrow to contain any large collections of water, as the opposite slopes are in close proximity. This is particularly true where the strata are anticlinal, or dip opposite ways from the summit, or even where they are monoclinal, or dip all in one direction. But in regions where the foundation-rocks of the country are overspread with a smooth mantle of drift, these water- sheds are apt to be extremely level plains, into which the lateral brooks descending from the hills collect and produce small lakes. Certain it is, that the most lake-bestudded districts of the United States and British territories of the continent are just those where these two conditions, namely, wide flat water-sheds and deep coverings of drift, prevail together. The Lacustrine tracts at the sources of the northern feeders of the St Lawrence and its Upper Lakes, but especially those at the sources of the Mississippi, where it interlocks with the waters of the St Lawrence and with those of Hudson Bay, are striking exemplifications of this general law. Other circumstances, however, besides the existence of the drift-stratum, conduce to the prevalence of lakes in the country N., N.E., and N.W. of Central Pennsylvania. From the Susquehanna River south-westward, the strata of the Appalachian Chain and the Atlantic Slope are scarcely anywhere basin-shaped, or even flat in their dips over large areas ; but they undulate and incline at high angles. As a consequence, the ground above them slants in one or other direction too rapidly to support large tracts of still-water. . But N.E. and N. of the Anthracite Coal-fields, and throughout Middle and Western New York, they incline very gently, and permit a far more frequent occurrence of horizontal plains or nearly level valleys, whose beds have been further smoothed by the introduction of the drift. The large lakes of Central New York evidently owe their origin to long transverse trenches or valleys, scooped out of the gently-south-dipping strata of that district, by the powerful force of a heavy sheet of moving water passing over the terraced surface of the State in a direction transverse to the outcrops of the rocks, or from N. to S. The softer formations have been excavated into long wide ravines, or great shallow valleys ; while the harder ones have been left at higher levels on the edges of the great terraces, contracting HYDEOGRAPHY. 39 and partially closing the northern ends of these vast ravines. It is to the flattish southward dip of the strata, their alternation of hard and soft, and the transverse rush of the eroding currents, that we must ascribe the production of the basins of these beautiful sheets of water. OEOGEAPHY AND SCENERY OF THE FIFTH DISTRICT. After the descriptions already given of the other portions of Northern Pennsylvania, it is not necessary to dwell long upon the physical structure and aspect of that natural area which lies between the northern escarpments of the Lower Coal- rocks in Warren, Crawford, and Mercer, and the shore of Lake Erie. This is a somewhat diversified, undulated district, full of moderately deep ravines, intersecting and insulating innumerable low hills, which grow flatter and tamer as we approach the water-shed, which traverses the belt longitudinally in a meandering course from New York to Ohio, at an average distance of 10 or 15 miles from the lake-shore. Between this water-shed or flat summit, dividing the streams flowing towards the Ohio Eiver from those enter- ing Lake Erie, and the edge of the table-shaped hills, containing the lowest coal-rocks, the general surface, disregarding the local hills and hollows, is approximately a level plain. It is overstrewn with a thin sheet of drift, which is accumulated, however, in thicker masses, in terraces within its deeper valleys. This plain has a mean elevation above the sea of somewhere between 1100 and 1200 feet. Owing to a combination of geological conditions already mentioned, namely, a flat dip in the strata and a surface-covering of gravel or boulder-drift, it possesses several lakes near the sources of its streams. The largest of these is Chatauque Lake, in New York, the surface of which is 1272 feet above tide-water. The chief lakes in Erie and Crawford counties are Oil-Creek Lake, Lake Pleasant, Lebceuf or Waterford Lake, Conneautte Lake, and Conneaut Lake. To these might be added Pymatuning Swamp, a long tract of wet, peaty marsh, covering the water-shed between Crooked Creek and an eastern tributary of Chenango Creek. The-other much narrower division of the district or that which lies between the water-shed of the Ohio and Lake streams and the shore of Lake Erie has a somewhat different configura- tion of its surface. It descends rather rapidly from the water-shed to the lake by a succession of obscure, alternately gentle and steepish slopes. The declination of the ground may be inferred from the difference in the elevation of its two margins ; that of the water-shed, in which it begins, being nearly 1200 feet, and that of the lake, in which it ends, being only 565 feet above the level of the sea. This tract is cut transversely by numerous sharp ravines and long tortuous valleys, carrying its waters to the lake ; and the borders of some of these afford many small, pleasing bits of scenery. But the characteristic, and altogether the most impressive pictures, are those of the lake itself. The first view which the traveller gets of this broad inland sea as he passes the water-shed, especially when the surface of the lake, crisped into gentle waves by a light western breeze, reflects the deep blue of the upper sky, never fails to charm and surprise him. HYDROGRAPHY. Turning our attention from the Orography of Pennsylvania, or the relief of its surface, to the Hydrography, or the features of its drainage, we perceive it to consist of three principal slopes, divided by two chief water-sheds the Primary Appalachian Water-shed already traced, dividing 40 HYDROGRAPHY. the Atlantic streams from those of the Ohio Eiver, and the Lacustrine Water-shed, separating the latter from the tributaries of Lake Ontario and Lake Erie. The Great Hydrographic divisions and sub-divisions of the State may be appropriately classified in tabular form in the following manner : f Basin of the Delaware Eiver. Basin of the Delaware Bay, which consists of the J " Brandywme I and a few other small streams. Atlantic drainage flows into Basin of the Susquehanna. Basin of the Chesapeake Bay, which embraces Mexican Gulf drainage flows into <( ^ m of the Ohio River, which includes in the Ohio River. 1 Pennsvlvania an( ^ numerous l esser streams entering Potomac, part only of which lies within the State. Basin of the Alleghany River. Beaver Monongahela Lake drainage flows into / Basin of the Genesee River at its Basin of Lake Ontario in Pennsylvania, which "j (^ source. embraces ( Conneaut Creek, and numerous short Basin of Lake Erie, embracing "j streams. ATLANTIC DRAINAGE. Its general Periphery. The Atlantic drainage of the State comprises about 28,526 square miles of its surface. The water-shed, enclosing the streams descending towards the Delaware and Chesapeake Bays, traced in its entire sweep round the sources of the Delaware and Susque- hanna in New York, is an irregular elliptical girdle ; it begins near the mouth of the Delaware Bay in New Jersey, ranges northward through that State to near its northern corner, thence north- ward into the Catskill Mountain, dividing the drainage of the DelaAvare from that of the Hudson and of the Mohawk, and thence north-westwardalong the HelderbergMountain, between the streams of the Mohawk and those of the Susquehanna. Becoming now the primary water-shed, it turns to take a tortuous course south-westward between the waters of the North Branch of Susque- hanna and those of Lake Ontario, until in Potter County, Pennsylvania, it begins to divide those of the West Branch of Susquehanna from those of the Ohio Eiver, and continues thus southward to Cambria County, where it becomes the crest of the Alleghany Mountain, and separates the sources of the Juniata branch of the Susquehauna, from those of the Conemaugh of the Ohio Basin. Near the Maryland line, and in Maryland, this water-shed divides the head-streams of the Potomac from those of the Youghiogheny, another western water. Its chief River Basins and their dividing Water-sheds. The waters of the Atlantic drain- age in Pennsylvania, belonging to the three large river-basins of the Delaware, Susquehanna, and Potomac, are separated into these receptacles by two important water-sheds, extending from the tide- water to the primary water-shed of the Appalachian Chain, or transversely to the mountains. That which insulates the streams of the Delaware, commences below Trenton, and extending north-westward through Bucks, Lehigh, and Schuylkill counties to the sources of the Catawissa, AEEAS OF THE CHIEF EIVEK-BASINS. 41 there deflects northward through Lucerne, round the sources of the Lehigh, and thence through Wayne County, between the Delaware and the Susquehanna waters into New York. The other, which divides the waters of the Susquehanna from those of the Potomac and other streams entering the Chesapeake Bay, commences near Havre-de-Grace in Maryland, enters Penn- sylvania in the western corner of York County, runs thence north-westward to the Kittatinny Mountain in Franklin, and pursues an exceedingly tortuous course among the crests of the Appala- chian Eidges, through Franklin, Perry, Juniata, Huntingdon, Fulton, and Bedford counties, to a point where it meets the great primary water-shed of the State in the crest of the Alleghany, in the south-eastern corner of Somerset County. This is the southern boundary or rim of the Susque- hanna Basin ; its eastern boundary ranges from the head of the Chesapeake Bay northward through Chester, Berks, and Schuylkill counties to the sources of the Catawissa, where it falls into the water- shed confining the Delaware Basin. Between it and the lower part of the Delaware water-shed lies the basin of the Schuylkill Eiver, and also that of the Brandy wine, with one or two smaller ones, tributary to the Delaware and Chesapeake bays. Areas of the Chief Eiver Basins. The portion of the hydrographic basin of the Delaware Eiver, lying within the State, contains about 3895 square miles of surface. It is a long comparatively narrow strip of country, widest in the middle, and stretches across the whole Mountain-zone of the State, from New York to the head of tide-water. The large division of the Susqxiehanna Basin belonging to Pennsylvania covers an area of not less than 17,018 square miles. It is much the largest of all the primary hydrographic basins of the State. The area of the Schuylkill Basin, carefully estimated, contains about 1884 square miles. This, which may be regarded as only a secondary basin of the Delaware Eiver, extends from the tide-water into the mountains, but not across them, and does not span quite one-half of the breadth of the State. That part of the Potomac Basin which extends into Pennsylvania, occupying portions of Adams, Franklin, Fulton, Bedford, and Somerset counties, has a surface of about 1581 square miles. The small remaining area, tributary to the Atlantic tide-water, is the triangular basin of the Brandywine and its adjoining streams in Delaware and Chester counties. This we may estimate to cover not more than 720 square miles. The several chief river-basins of the Atlantic system here sketched, are in close hydro- graphic contact both with each other and with the exterior river-basins of the country. Their bounding and dividing water-sheds are in many places so depressed as to afford, especially in the valleys which they traverse, the most facile communication across them. One is astonished, indeed, to find by how many low summits, easily traversable by railroad and canal, they are con- nected with each other. Thus, however important a knowledge of these water-sheds or summit- lines of the drainage of the country is to the civil engineer in planning or constructing canals and other highways, they constitute no serious obstacle to free communication in all directions. They no doubt deflect the currents of inland trade, but it is only in a few districts that they can be said to arrest them. It is a fortunate feature in the Atlantic Eiver Basins of Pennsylvania that they are thus connected, by wide frontiers and through singularly flat summits, with the two other great river-systems of the country, the Lake Basins in the north, and the great receptacle VOL. I. F 42 HYDROGRAPHY. of the Ohio drainage in the West. Thus Pennsylvania, though traversed nearly from end to end by a broad zone of mountains, is in no way cut asunder by it. On the contrary, its river- valleys rather link its distant parts together, and by their stretching beyond its borders into the neigh- bouring States, open channels to a wide external commerce. Mexican Gulf, or Ohio River Drainage. The large river-basin of the Ohio-Alleghany River, comprising all that district which lies west of the Primary Water-shed of the State, excepting merely the narrow strip composing the Lake Erie slope, contains, upon a careful estimate, about 12,632' square miles of surface. From a mean elevation above the sea in its north-eastern and south-eastern corners of about 1800 feet, it falls towards the Ohio River to a level of about 1000 feet, and in the beds of the streams to about 700 feet. This river-basin has on its N.E. that of the Genesee, and on its E. those of the Susquehanna, the Juniata, and the Potomac. On its N.W. it is separated by a very easily passed water-shed from the Basin of Lake Erie. The Basin of the Juniata River, by far the largest tributary of the main Susquehanna below its two northern branches, covers a surface of about 3428 square miles. By this basin and that of the West Branch, the Susquehanna River expands itself entirely across the mountains, spreading to a far greater distance westward than it does eastward. The North Branch, however, which must be regarded as the main stream the others being affluents has its area of greatest expansion towards the north, where in New York it waters a wide extent of country. The Pennsylvanian portion of the basin of the Ohio River is divisible into three sub-basins of drainage that of the AUeghany River, that of the Monongahela, and that of the Beaver River. The hydrographic valley of the Alleghany River within Pennsylvania occupies an area of about 9546 square miles. The portion of the Monongahela Basin included within our borders covers the less space of 2800 square miles. The district, drained by streams entering the Ohio directly, including that part of the Beaver River Valley which belongs to our territory, may be assumed to contain about 3086 square miles. The Lake Drainage. A very small area of the Genesee Basin of Lake Ontario enters Pennsylvania ; it probably contains not more than 90 square miles. The Lake Erie Slope, occupying a part of Erie and a small portion of Crawford counties, may be estimated to cover about 352 square miles. It is very difficult, in the absence of a perfect map of the streams of Pennsylvania, to reach exactitude in the estimation of the areas occupied by these several river-systems and their subdivisions. THE DELAWARE RIVER-SYSTEM OF THE DELAWARE RIVER. 43 Has its source in the N.E. corner of Delaware County, at an elevation of about 2000 feet above the sea. It traverses Delaware County, New York, flows between Pennsylvania and New York as far as Carpenter's Point, thence between Pennsylvania and New Jersey as far as the State-line below Chester, and thence between the State of Delaware and New Jersey to its estuary the Delaware Bay. THE DELAWAKE the Laekawanna Creek, the Lehigh River, It from the right >. the Schuylkill River, from the left the Pawpacton, the Neversink River, which rises in Moosick Mountain, on the Eastern bor- ders of Wayne County, and flows Eastward through Wayne and Pike. The towns washed by it and its branches are Belmont, Mount Pleasant, Bethany, Honesdale, and Hawley. It empties into the Delaware between Mount Hope and Barryville. which rises in the table-land of the Pokono Mountains, in the swamps called the " Shades of Death," in Mon- roe and Lucerne counties. It traverses thence between Lucerne and Carbon, and across the latter, and between Lehigh and Northamp- ton, and through the latter. The towns seated on or near it and its branches are Stoddartsville, Whitehaven, Pennhaven, Mauch Chunk, Lehighton, Weissport, Parryville, Allentown, Bethlehem, and Easton. It empties into the Delaware just below Easton. wliich rises in the Southern Anthracite Coal-field in Schuylkill County. It traverses Schuylkill, Berks, Montgomery, and Phila- delphia counties, flowing towards the S.E. The towns seated on or near it are Tuscarora, Middle- port, Port Carbon, Pottsville, Schuylkill Haven, Or- wigsburg,Port-Clinton,Hamburg,Reading,Pottstown, Phcenixville, Norristown, Manayunk, and Phila- delphia. on the right from Broad Mountain Mill Creek, West Branch, Tulpehocken, and French Cr. on the left from Broad Mountain Little Schuylkill, Maiden Cr., Manatawny, Perkiomen, and Wissahickon ; and empties into the tidal portion of the Delaware a . few miles below Philadelphia. f which rises in the plateau of the Catskill Mountain ; / traverses Delaware Count y, N. York, flowing westward ; 1 and empties into the Delaware at Hancock. It receives |Tl 1" : which rises in the North part of Ulster County ; traverses Ulster and Sullivan, flowing southward. The chief town seated on or near it is Montecello. empties into the Delaware at Carpenter's Point, below Port Jarvis. several large streams in New Jersey, the chief of which is the Rancocos, which rises in Monmouth and Burlington counties, New Jersey ; and traverses Burlington County. Its towns are Pemberton, Mount Holley, Vincent-town, Eayrstown, Lumberton, &c. It empties into the Delaware a few miles below Bur- lington City. It passes by or near the towns of Narrowsburg and Port Jarvis in New York ; Milford in Pennsylvania ; Belvidere in New Jersey ; Easton and New Hope in Pennsylvania ; Trenton, Bordentown, and Burling- ton in New Jersey ; Philadelphia and Chester in Pennsylvania ; and Wilmington in Delaware. It empties into the Delaware Bay. HYDROGRAPHY. THE SUSQUEHANNA It receives from the right, the Shenango River, the Chemung River, the Great West Branch of the Susquehanna, its rival in size, the Juniata River, Rises in Otsego County, New York, in and near Otsego Lake, on an elevated table-land. It traverses Otsego, Broome, and Tioga counties, in New York, and entering Pennsylvania in Bradford County, passes through it and Wyoming, Luzerne, Columbia, Montour, and Northumberland, and flows between the last and Snyder, and between Dauphin and Perry, and Cumberland, and thence between Lancaster and York to Maryland, where it presently enters the head of the Chesapeake Bay. which rises in Madison County, New York ; traverses Shenango and Broome counties, N. Y. ; washes the towns of Sherburne and Norwich ; and empties into.the Susquehanna at Binghampton hi N. Y. [ which rises in Stenben County, N. Y. ; ) traverses Steuben and Chemuug counties, N. Y. ; } washes the towns of Bath and Elmira ; ( and empties into Susq., below Athens. which rises in Cambria County, Pennsylvania ; traverses Clearfield, Clinton, and Lycoming, and divides Union from part of Northumberland to its junction with the North Branch of the Main Susq. ; washes the towns of Clearfield, Lockport, Jesseyshore, Williamsport, Muncy, Milton, Lewisburg, and Northum- berland ; and empties into the Susq. at Northumberland ; 'from the right Clearfield Cr., Mushannon Cr., Bald Eagle Cr., Whitedeer-hole Cr., Buf- p falo Cr., and several lesser ones ; receives ( * rom tne le ftfae Sinneinahoniug Cr., Kettle Cr., Pine Cr., Lycoming Cr., Loyalsock Cr., Muncy Cr., Chillisquaque Cr., and several >- lesser ones. which rises on the Eastern slope of the Alleghany Moun- tain in Blair and Bedford counties ; traverses Bedford, Huntingdon, Mifflin, Juniata, and Perry counties ; passes the towns of Bedford, Huntingdon, Newton Hamil- ton, Lewistown, MifHiutown, and Millerstown ; and empties into the Susq. at Duncan's Island, above Petersburg ; "from the right Trough Cr., Aughwick Cr., Tuscarora Cr., Buffalo Cr., and several lesser It I ones ; receives} from the left Frankstown Cr., Kishicoquil- las Cr., Cocolamus Cr., and several lesser ones. such as Cayuga River, Sugar Cr., Tawanda Cr., Mahoo- peny Cr., Fishing Cr., Penn's Cr., Sherman's Cr., Cone- dogwinit Cr., Yellow Breeches Cr., Conewago Cr., Codorus Cr., and Deer Cr. which rises on the border of Wayne and Susquehanna counties ; the Lackawanna Creek, \ traverses part of Susquehanna and Luzerne Counties ; I passes by Carbondale, Scranton, and Pittston ; l^and empties into the Susq. at Pittston. ("which rites in Schuylkill County in the Southern Coal Basin ; I traverses the Western part of Schuylkill, also Lebanon and \ Dauphin counties ; I passes the towns of Tremont, Pinegrove, and Humel's Town ; Land empties into the Susq. at Middletown. f which rises in the Southern corner of Berks County, on the border of Chester ; / traeerses Lancaster County; \ passes Morgantown, Churchtown, Lancaster, and Safe Harbour ; ^and empties into the Susq., near Safe Harbour. {which rises near the Eastern side of Lancaster County, South of the Copper Mine Ridge ; traverses the Southern part of Lancaster County, and a small part of Cecil County, Maryland ; and empties into the Susq. a few miles above Port Deposit. such as the Wyalusing Cr., Tunkhannock Cr., Nescopeck Cr., Catawissa Cr., Shamokin Cr., Mahanoy Cr., Mahan- tanga Cr., Wiconisco Cr., Chiques Cr., and Conewiugo Cr. also numerous second- rate, but important streams, from the left, < the Swatara Creek, the Connestoga Creek, and Octorara Creek, besides many smaller ones, It passes by or near the towns of Unadilla, Great Bend, Binghampton, Owego, Athens, Tawanda, Tunkhannock, Pittston, Wilkesbarre, Berwick, Bloomsburg, Danville, Northumberland, Sunbury, Dauphin, Harrisburg, Marietta, Columbia, Port Deposit, and Havre-de-Grace. It empties into the Chesapeake Bay in Maryland, about 12 miles South of the State line of Pennsylvania. EIVER- SYSTEM OP THE POTOMAC RIVER THE POTOMAC Rises in Hardy County, Virginia, at an elevation of about 2500 feet above the sea. It traverses Hardy County, Virginia, and Alleghany County, Maryland, and flows thence Eastward and South-eastward, between Maryland and Virginia, the whole way to its entrance into Chesa- peake Bay. '. , . , ( several rivers and important second-class streams, which, belonging wholly ( to Virginia, need not be here described. no important river, but several large streams, called " Creeks," namely- It receives Wills' Creek, Sideling-hill Cr., Licking Cr., 'which rises in Somerset County, at the East base of the Alleghany Mountain ; traverses the South-east corner of Somerset, North-west corner of Bedford, and the narrow part of Maryland ; passes no important town ; and empties into the Potomac at Cumberland. (which rises on the East slope of Tussey Mountain, in the South part of Bedford County ; and empties into the Potomac below Old Town. which rises in the valley West of Townhill, in the South- east corner of Bedford ; and empties into the Potomac above the mouth of the Cacapon River. ! which rises in Fulton County, East of M c Connellstown Cove; and empties into the Potomac several miles East of Hancock. (which rises in Franklin County in Anderson's Valley East Branch rises in the North-west corner of . , , Adams county ; and empties into the Potomac at Williamsburg. All these streams traverse the narrow part of Maryland, after flowing out of Pennsylvania. THE ALLEGHANY 46 HYDROGRAPHY. THE ALLEGHANY the Conewango Creek, the French Creek, Rises near the centre of Potter County, at an elevation of about 1700 feet above the sea. It traverses the west part of Potter, N.E. corner of M"Kean, then enters New York, and returns into Pennsylvania in the N.E. corner of Warren County, which it traverses diagonally, and passes through Venango, Clarion, and Armstrong, and between Butler and Allegheny, where, at Pittsburg, it drops its name and takes that of the Ohio, passing between Butler and the rest of Alleghany County, and then across Beaver County, to become the dividing limit between the States of Ohio and Virginia. which rises in Cattaraugus County, New York; traverses Cattaraugus County, New York, and the North part of Warren County, Pennsylvania; empties at Warren into the Alleghany. which rises in Chatauque County, New York, not far from Cha- tauque Lake; traverses the S.W. corner of Chatauque County, New York, and Erie, Crawford, and part of Venango counties, Penn- sylvania; pastes at or near the town of Mcadville ; and empties into the Alleghany at Franklin. which rises under the name of Chenango, the main Pennsylvanian stem, in the N.W. corner of Crawford County, West of Coii- neautville ; from the right, J traverses West sides of Crawford, Mercer, Lawrence, and Northern half of Beaver counties ; passes at or near the towns of Lawrence, Newcastle, Sharon, and Greenville ; 'from the riyhl the Mahoning River, which rises in the Lake Water-shed in Ohio, traverses Summit, Portage, Warren, and Mahoning counties of that State, and empties into the Beaver or Chenango in Lawrence It County, below Newcastle ; receives ^ from the left Neshannock Creek, which traverses Mercer County, and empties into it below Newcastle and Slippery-rock Creek, which traverses Butler, a part of Lawrence, and empties into the Beaver near the North line of Beaver County ; and empties into the Alleghany at Beaver. / which rises in Warren County ; ) traverses the S.E. portion of Warren, and Eastern part of Ven- j ango Counties ; V and empties into the Alleghany at Tionesta. I which rises in the South part of M c Kean County, at an elevation of nearly 2000 feet; It the Beaver River, from the left, the Tionesta Creek, the Clarion River, the Red-bank Creek, the Mahoning Creek, the Crooked Creek, the Conemaugh, or Kiskiminctas River, traverses Elk, S. edge of Forest, and middle of Clarion counties ; tses at or near the towns of Ridgeway and Clarion ; / tra \pa. \ ani the Monongahela River, the Chartiers Creek, :d empties into the Alleghany at Foxburg. (which rises in the Western border of Clearfleld County ; , traverses centre of Jefferson and Northern border of Armstrong N counties ; I passes at or near the town of Brookville ; ' and empties into the Alleghany near Vanburen. which rises in the Western border of Clearfield County ; traverses Southern side of Jefferson, and Northern side of Arm- strong counties ; passes at or near the towns of Punxatawney and Nicholsburgh ; and empties into the Alleghany some miles above Kittanniug. ( which rises in the interior of Indiana County ; < traverses West part of Indiana, and Eastern half of Armstrong ; \ and empties several miles below Kittanning. ("which rises in the Eastern border of Cambrian County, in the Alleghany Mountain ; I traverses the breadth of Cambria County, and the whole Northern \ border of Westmoreland ; 1 passes at or near the towns of Johnstown, Bolivar, Blairsville, Salts- burg, and Leechburg ; V-and empties into the Alleghany at Freeport. which rises in Virginia, in Lewis County ; traverses Lewis, Harrison, and Monongalia counties in Virginia, and divides Fayette and Westmoreland from Green and Wash- ington, North of which it traverses Alleghany County to Pitts- burg ; passes at or near the (owns of Morgantown, Greensburg, Browns- ville, Williamsport, Elizabethtown, and MKee's Port; receives from the riant the Cheat River, which rises in Virginia in the backbone of the Alleghany Mountain, and empties into it a short distance North of the Stateline, and the Youghiogheny, which rises in the Backbone Mountain, traverses Hampshire county, Virginia, northward, and Somerset, Fayette, and Alle- ghany counties, Pennsylvania, north-westward, emptying into it at M c Kee's Port ; and empties into the Alleghany at Pittsburg. which rises in the centre of Washington County ; traverses the Northern half of Washington, and Southern half of Alleghany Counties ; passes at or near the town of Washington ; and empties into the Alleghany three miles below Pittsburg. \ and empties into the Alleghany three miles below fittsburg. It passes by or near the towns of Coudersport, Olean, Warren, Franklin. Kittanning, Freeport, Pittsburg, and Beaver; It empties, or more properly, it changes its name at Pittsburg into the Ohio River, which empties into the Mississippi River at Cairo, the Southern point of the State of Illinois. RIVER SCENERY. 47 SCENEEY ALONG THE PRINCIPAL RIVERS. The Delaware River. This noble river, the eastern boundary of Pennsylvania, throughout its entire breadth exhibits, along its immediate valley, a considerable variety of topographical feature and scenery. From its head-streams in New York, to where it emerges from the Pokono or Catskill Mountain, it flows in a tortuous course through a deep narrow trough in that elevated table-land. The mean level of the plateau remaining nearly constant, and the valley growing pro- gressively deeper, the river-hills, which are all that the traveller at the river-side usually beholds, grow higher and steeper as he descends. Meandering much more than the valley containing it, the river sweeps sometimes close by the base of the bounding hills, the lower parts of which are, in many cases, faced by high naked cliffs, exposing the reddish brown shales and sandstones of the district, in beautiful contrast with the mixed green hues of the foliage. The perspective of jutting and retreating hills, clothed for the most part with a combination of coniferous and decid- uous forest to their summits, and washed at their base by long bending reaches of the broad river, are very attractive, notwithstanding a prevailing sameness in general feature. After leaving the plateau in Pike and Wayne counties, the river emerges into a broad open valley, wholly different in aspect and structure from that which it has left. The waters which carved a way for it seem to have been impelled in their momentum southward, with great energy, against the strong stony barrier of the Kittatinny or Shawangunk Mountain, and to have scooped their deepest trench near the base of that high ridge. The river, therefore, turns abruptly at Carpenter's Point, from a S.E. to a S.W. course, and follows the foot of the mountain, sometimes hugging its base, some- times sweeping a moderate distance from it into the plain, until it finds a passage through it by the great breach called the Delaware Water-gap. The scenery along this stretch of the river is eminently beautiful. Low within the valley, the river is bordered by fertile cultivated flats, variously carved in one or more terraces ; and behind these, particularly on the N.W., rise numer- ous rolling hills, some under the plough, some covered with timber, all deeply cut by ravines, in the steeper of which are many beautiful waterfalls, while still beyond the hills we see ascend- ing the long slopes or bold escarpments of the plateau of the Upper Delaware. All the way along on our left the view is bounded by the forest-covered flank and straight crest of the Kitta- tinny Mountain. Turning at the Water-gap, the Delaware, in issuing through the main ridge of the mountain, passes between steep, nearly perpendicular, mural cliffs of grey sandstone, rising on either side to its very crest. The sketch of this scene from the S. will give some notion of its character. Leaving the Water-gap, the river descends gently southward, obliquely across the entire breadth of the Appalachian Plain or Valley, to where it enters the hills called " The South Mountains," below Easton. This portion of its course is marked by no striking features, the surface of the country being elevated only 100 or 200 feet above it, and being, from the softness of the slates and limestones, smoothed down into rather inexpressive lines. Below the mouth of the Lehigh, the Delaware is bordered by an alternation of hills and narrow intervening valleys, the river-hills being but the ends of the intersected ridges of the low chain of the Highlands of New Jersey ; but from the southern edge of these hills, at Durham, the scenery for many miles southward wears a wholly different character. It is that of a table-land, 48 HYDROGRAPHY. elevated 300 or 400 feet above the level of the river, cut on one or both sides of the valley into long ranges of perpendicular precipices, or extremely steep slopes. One stretch of precipice on the Pennsylvania side, known by the name of the Nockamixon Eocks, is an exceedingly striking and picturesque range of beetling cliffs, rising sheer for 200 or 300 feet from the brink of the river, with only a narrow roadway between them, through a length of nearly 3 miles. Some of the views from the base of these crags are almost grand ; and the pictures they make with the river below are beautiful. Tufts of bushes and trees, and climbing vines, heighten by their green hues the rich brown tints of the rocks, to the bold faces and narrow ledges of which they lend a grace which no cliffs without vegetation ever possess. There are few more attractive drives or walks by the river borders of Pennsylvania than this one at the foot of the Nocka- mixon Rocks. Further down its valley the Delaware passes, in the vicinity of New Hope, some bold ridges of trap-rock, which impart a pleasing variety to banks, elsewhere, in this part of its course, comparatively tame. Passing Trenton, its borders presently put on a totally changed aspect. Ceasing to be a gay running stream, full of bushy islands, and rocky reefs, and rapids, it becomes a wide tidal river, rising and ebbing between shores which are in many places only low banks of sand and gravel, and in others, broad slimy marshes, covered with reeds and grass. Turning at Bordentown south-westward, the river maintains these features all the way to its wide estuary, the Delaware Bay. The Susquehanna River North Branch. That portion of the Susquehanna Eiver which flows near the northern boundary of the State, passes from its sharp elbow, called " The Great Bend," to the mouth of its affluent, the Chemung Eiver, through a charming broad valley, bounded by soft slopes, terminating in wide table-shaped hills. It is a fertile and very beautiful district : and with its westward extension, the plain of the Chemung Eiver is rapidly becom- ing one of the most attractive agricultural districts of New York. From the mouth of the Chemung Eiver to Pittston, where the river suddenly turns at a right angle on entering the Wyoming Coal-field, it flows, with many bendings, along a deep and picturesque valley, almost identical in its features with that of the corresponding sketch of the Delaware, the main differ- ence being, that the bed of the valley is wider, and the hill-sides confining it less mountainous. From the mouth of the Lackawanna at Pittston, where it enters, to Nanticoke, where it leaves the beautiful Wyoming Valley, the scenery along the river is wholly different. It flows through a broad and almost perfectly level smooth plain the Wyoming and Kingston Flats composed of a deep bed of diluvium or drift. On either side of this plain rise the rolling hills of the coal- basin, and behind these the long gentle slopes of the high mountain-barriers which frame in the whole scene. At Nanticoke the river turns abruptly northward out of the coal-basin, through its steep barrier, by a highly picturesque pass, and then sweeps again as suddenly westward, to run for several miles in a closely-confined trench, between the outer and the inner ridges of the basin. It does not, however, run round the western end of this, but at the ravine of the Shick- shinny turns suddenly southward, and cuts across its point, leaving a high insulated hill of the coal strata on its western or right-hand side. Disengaging itself by a fine pass from the southern barrier of the coal-basin, it passes out into an open valley, and makes another rectangular bend, to run once more towards the W., parallel with the Nescopeck Mountain, which it follows to the neighbourhood of Catawissa. Beyond this point it maintains its general course westward, some- SUSQUEHANNA RIVER 49 what S., parallel with the southern base of Montour's Eidge, all the way to Northumberland, where it is joined by its great tributary, the West Branch. In some portions of this long reach of the river, the scenery adjoining it is uncommonly, rich and pleasing. A remarkably fine view up the river is presented from the hills on its west bank, a little below the mouth, of Fishing Creek. Between Northumberland and the Kittatinny Valley the river leads us through many strik- ing scenes. It is studded with many little islands, most of which are covered with trees or bushes to the water's edge ; and it is here a wide and majestic river, flowing alternately for long reaches, across highly cultivated belts of country, and past the ends of steep and rugged moun- tains. (The View of the river at the gap of the second mountain will convey some notion of the appearance of its banks.) (The Scene, embracing the Blue Hill at Northumberland shows the junction of the North and West Branches, and gives a just conception of the style of the hills bounding its immediate valley.) Passing out from the mountains, it traverses a beautiful country in the Kittatinny Valley, dividing Dauphin from Cumberland County. There are superb views of this reach of the river from Harrisburg, from the dome of the Capitol, and also from the southern slope or summit of the Blue or Kittatinny Mountain ; and again from the high hills on the edge of York County. Quitting the Limestone Valley, the river next traverses the Red- shale Belt, between the villages of Highspire and Bainbridge, crossing a rather monotonous country, except at the Conewango Falls, or Rapids, where numerous hard trap-dykes impede its course, and cause it to rush in wild tumult, by deep and dangerous sluices, for a long distance between black and jutting reefs. At Chiques Ridge, one mile above Columbia, the river leaves the smoother country, and passes between a range of high and picturesque crags. "With two or three intermissions, caused by the softer limestone valleys which it next crosses, it runs the whole way thence to the vicinity of Port Deposit, or nearly to the head of the Chesapeake Bay, between steep, naked, and half-naked hill-sides, rising from 200 to 400 feet above its channel. In some parts of this long reach, as at the mouth of the Conestoga, the river is greatly dilated, and is filled with rocky islands and projecting reefs. In other localities its rugged banks approach, and the river rushes with tremendous force, especially during freshets, through these deeper gorges. The traveller, who finds only- a rough *,nd very toilsome path along its eastern shore, from Turkey Hill to Port Deposit, a distance of more than thirty miles, will choose to descend it by its right bank along the tow-path of the Canal. He will pass an almost unbroken succession of interesting rocky scenes, affording much geological instruction ; and he will witness many beautiful bits of river perspective, but he will find himself pent in all the way between the bold river-hills. West Branch of Susquehanna.- The upper part of the West Branch of the Susquehanna, and also its tributaries, the Sinnemahoning, Kettle Creek, Pine Creek, &c., draining the high plateau N.W. of the Alleghany Mountain, flow through deep trenches in the horizontal strata, very analogous in their features to those which give passage to the Delaware, and the Main, or North Susquehanna, in the north-eastern part of the State. From the mouth of the Sinnemahoniiig, out into the Bald Eagle Valley, the river-hills are very high and steep, and admit extremely narrow strips of level ground between their feet and the river, except near the openings of the lateral streams. The trough through which the lower half of Pine Creek flows is equally pro- found. A notion of the appearance of this high table-land, where- the larger streams intersect VOL. i. o 50 HYDROGEAPHY. . i it to its base, may be gleaned from the little outline Sketch, showing the hills near Young Woman's Creek. Entering the valley between the Alleghanj'- Mountain and the Bald Eagle Ridge, the river pursues a beautiful winding-course the whole way from Lock Haven to the neighbourhood of Muncy, alternately sweeping towards the middle of the cultivated valley and back again, close into the base of the steep and wood-covered ridge. Near Muncy it turns with a broad majestic curve round the end of the Bald Eagle Mountain, and in a few miles deflects from a S.W. to a S. course, through a highly fertile, richly cultivated, open country, till it strikes the base of the Blue Hill, or range of Red Sandstone Cliffs above Northumberland. S.W. of Muncy the river crosses a singular belt of deeply-eroded country, full of .conical hills. Our Picture (see Plate) represents these Muncy Hills, the river, and the point of the Whitedeer Mountain. All this lower reach of the West Branch abounds in charming scenery, if the observer is at the pains to ascend one of the mountain-spurs or hills, high enough to open sufficiently expansive views. The Juniata River. This second great tributary of the Susquehanna has two chief upper divisions, the Frankstown and the Raystown Branches, both of which, like the main stream be] ow their junction, traverse much beautiful scenery. We will trace the Frankstown Branch as that which is most accessible. After gathering its head-waters from the eastern slope, and the foot- hills of the Alleghany Mountain, it begins to assume the volume of a small river near Frankstown. Below this point it first passes the Cove of the Lock Mountain, a curious district of conical hills, in structure very like the Muncy Hills of the West Branch. Its course is now by a wild and rocky gorge through the Lock or Canoe Mountain, into Canoe Valley. Winding north-eastward through this valley, it next goes through Tussey Mountain into Hartslog Valley by an interesting curving pass of the form of the letter S. The mountain, which consists of two ridges, is trenched along its centre for the passage of the river, and the western ridge is moreover breached at Water Street by a lateral notch, which gives passage to a small tributary stream, and heightens much the picturesqueness of the place, which is further enhanced by a great stone-slide covering the ends of the mountain. Crossing Hartslog Valley, it next traverses Warrior Ridge, passing by the Pulpit Rocks, one view of which is exhibited in the frontispiece to this volume. Emerging from the Warrior Ridge, and deflecting rg'ore towards the east, it crosses the Huntingdon Valley and passes by the northern end" or knob of Terrace Mountain and Sideling Hill, receiving first the Raystown Branch, which nearly doubles the volume of its waters. Here bending southward, it follows a picturesque gap through Stone Ridge a sketch of which, at the Canal, is given in this work and turning more eastward, it presently enters the deep cleft in Jack's Mountain, called " Jack's Narrows," upon the western side of which the mountain is covered with a great stone-slide, or field of naked angular blocks of sandstone, which imparts a most desolate aspect to the pass, especially when the forest is not in leaf. On emerging from Jack's Narrows, the river crosses a succession of open valleys divided by narrow ridges, until it meets the base of Blue Ridge in Sugar Valley. There it makes a great loop, turning in an ox-bow backward, till it reaches Newton Hamilton, whence it flows with many large sinuosities, longitudinally, through the Juniata or Lewistown Valley, to the deep synclinal ravine called the " Long Narrows," formed by the near approach of the Blue and Shade Mountains. The Picture of the Lewistown Valley, as it appears from the ridge west of Lewistown, which is given in this work, will sufficiently exhibit the character of its scenery. ALLEGHANY KIVER 51 The Long Narrows of the Juniata is a narrow trough between mountain-ridges, deeply trenched on their flanks, and thickly clothed with timber on their lower slopes and at their base, and overspread nearer their summits with extensive sloping sheets of dark-grey angular blocks. The pass is seven miles long, and is one of the wildest and most impressive within the mountains. At the eastern end of the Long Narrows, the river turns south-eastward, and winds between hills and valleys across the country, to the base of the Tuscarora Mountain, passing Mifflintown, Mexico, and other villages. This is one of its most beautiful districts ; but the finest views are not imme- diately upon the river, but from the higher hills which overlook it at a moderate distance. Below New Mexico it sweeps the base of the Tuscarora Mountain for several miles, until it turns abruptly across its eastern end, a mile N.W. of Millerstown. The pass by which it traverses the end of the mountain is a simple notch, much less grand 1 than some of the other water-gaps; but the long straight reach of the river, before it enters the notch, furnishes a fine view of the beautifully sym- metrical form of the Tuscarora Mountain stretching for a great distance. Below Millerstown the river drosses the Wildcat and Buffalo Valleys, washing the end of the Buffalo Mountain. We get superb views of the terminal knob of this ridge, which in shape is like the curving hump and neck of the Bison that once frequented the region, with the river and its tree-covered banks in the foreground. Pursuing its course, the Juniata, after making two or three bends, goes through a belt of hills called the " Half-fall Mountain," where, as at nearly all its passes through the larger sandstone ridges, it is impeded by ledges of hard strata, and thrown into ripples or rapids. From the Half-fall Eapids it flows between steep but low cliffs and hills, for about four miles further, to its entrance into the main Juniata, at Duncan's Island, having followed a winding course entirely across the central zone of the Appalachian Chain, through a distance of nearly 200 miles. THE ALLEGHANY KIVER. I shall complete this sketch of the chief rivers of Pennsylvania with a concise description of the Alleghany, but shall omit any specific account of its local scenery, as the topographical and pictorial features of the wide region watered by it, and by its tributaries, have been already suffi- ciently delineated. The Alleghany, from its sources to where it becomes the Ohio Eiver, flows through a deep and comparatively narrow trench, excavated in the north-western plateau, and western coal-basin of the State. From the centre of Potter County, where it takes its rise, it runs with a somewhat swift descent westward, and then northward in a curving course, till it enters New York. There it takes a wide sweep north-west ward- into Cattaraugus County, passing Olean, to pursue from near Valley Creek a long sinuous south-westward course, to its great bend at Franklin. Edging its way gradually into the coal-basin, the north-western margin of which it enters near Warren, it takes an abrupt turn at the mouth of French Creek, and runs across the coal-field south-eastward to the mouth of the Mahoning, traversing entirely the sixth or last sub-basin, and entering the fifth or that of Brookville and Kittanning. Near the mouth of the Mahoning, the River Valley suddenly departs from its previous south-eastward trend, to resume its normal S.W. direction, or to follow the length of the coal-basin. This it does by a succession of convex and concave sweeps to Pittsburg, where, upon receiving its noble tributary, the Monongahela Eiver, it deflects north- 52 CLIMATOLOGY. westward at right angles, and stretches to -the mouth of the Beaver Eiver, where it makes another rectangular elbow, flexing to the S.W. to leave Pennsylvania, and pass into the State of Ohio. A little attention to the relations of the present drainage of the country, to the general scooping of the surface by the primeval waters which shaped it, will show us why the Alleghany River assumes ,the remarkable rectangular changes of direction which we have above noted ; first flowing S.W. ; thence from French Creek to Mahoning south-eastward ; thence to Pittsburg south-westward again ; thence to Beaver north-westward ; and once more from Beaver south- westward into Ohio. It is evident that, while the main discharge of the denuding wave was south-westward, or down the broad trough of the bituminous coal-field, one large influx of eroding waters swept the basin north-westward from the Appalachian Mountains, and another south-eastward from the region of the lakes. Titus it has arisen that all this western district of Pennsylvania is trenched by three main systems of valleys, as respects their directions ; chief valleys stretching south-westward, other valleys opening into these at right-angles, or north- westward and northward, and a third set also opening at right-angles into the same first system south-eastward and southward. The streams of the north-western slope, or those draining into Lake Erie, are relatively too insignificant to merit here the kind of description called for by the Delaware, Susquehanna, Juniata, and Alleghany Rivers. We pass, therefore, now to a brief sketch of the Climatology of - the State. CLIMATOLOGY OF PENNSYLVANIA. As respects its climate, Pennsylvania is very fortunately related to the rest of the United States. Owing to its midway station in the Appalachian Chain, between the cold region of the Gulf of St Lawrence and the tropical heats of the Gulf of Mexico, it enjoys, in point of tempe- rature, a climate nearer to the medium of that of the whole country than any other district on the Atlantic side. This temperate condition is also partly due to the softening influence of proximity to the Atlantic Ocean on one side, and Lake Erie on the other, for unlike any other State except New York its one slope rests upon the tide, and its other upon the Lawrentian Lakes. Like all the wide belt of country S.W. of New England, which is centrally traversed by the Appalachian Chain, and has the Atlantic Slope on the one border and the slope into the Ohio Basin on the other, Pennsylvania possesses three climates ; but from the cause already, assigned the proximity of the Ocean and the Lakes these climates are tempered from the more extreme types they exhibit in the other parts of this zone. The Atlantic Slope, including the tide-water plain at its base, is much wider throughout the Southern States, and both it and the mountain-chain behind it are therefore further removed from the influence of the ocean ; and, again, the Western Slope of the State, by its inland position, is so far withdrawn from the hot plain encircling the Gulf of Mexico, that the S.W. wind of the continent, a most important element in our climates, is materially tempered in both its heat and humidity. To these sources of a comparatively equable climate, should be added the relatively lower elevation in Pennsylvania of the mountain-chain, the mean height of which increases towards both the N.E. and the S.W. My object here is to present merely a general outline of the climatal features of the State, there being no room in this work for local details on this subject. I shall therefore best succeed TEMPERATURE. 53 by presenting the chief climatal elements of temperature and moisture, in their average and extreme amounts. Temperature, Average of the Year. The mean or average temperature of the entire State is very nearly 47, or about that of the Island of Great Britain. When we contrast the latitudes of the two countries, the mean of the one being scarcely as high as lat. 41, that of the other being lat. 54 20', this coincidence of mean temperatures is not a little remarkable. It is inter- esting as indicating why this portion of the United States seems more congenial than any other to the British, German, and other populations emigrating to America from the north temperate climates of Europe. The Northern Border of the State kas a mean temperature, with a certain fluctuation due to height, of about 45, but the north-western corner or western part of this northern belt possesses a mean annual heat of about 47, the difference being evidently due to the ameliorating action of the broad surface of Lake Erie. The Southern Border, or rather the belt S. of a line stretching from Easton to Pittsburg, has a mean temperature of about 50. So marked a difference in the temperatures of the northern and southern sides of the State, equivalent to a change of 1 of Fahrenheit for every 25 or 30 miles difference of latitude, contrasts strikingly with the more gentle gradations of climate in Western Europe and on the Pacific side of North America, where the average rate of variation is at the least 60 miles, or 1 of latitude to 1 of temperature. It is plain, therefore, that Penn- slyvania, in common with all the country north of it as far as Hudson Bay, contains, for its breadth in a N. and S. direction, a remarkably wide range of climates. In other words, it has its different climatal zones very closely compressed. A given mean annual temperature will not be found to range due E and W. across the State; but the Isothermal Lines, or those marking identical average heat, are deflected southward where they cross the mountains. This arises from the circumstance that elevation above the sea, especially where the mountains are near it, is a main cause of coolness. So that we must go S. along the mountains a certain distance to find the same temperature which we have been tracing towards them over the plains. In crossing the Appalachians of Pennsylvania, the mean annual heat, under the same latitude, appears to decline about 3, and therefore the Isothermal Lines must swerve to the southward in the highest portions of the chain about 75 or 100 miles, resuming their latitude when they descend into the plain of the Alleghany and Ohio River. These are the conditions of the average heat of the whole year ; let us look next at the relations of temperature for each of the four seasons. Mean Temperature of the Spring Months. According to the temperature charts and tables, published recently by Mr Lorin Blodget, our best authority on the climates of the United States, the average temperature for the three spring months of the southern edge of the State is about 50, while that of its northern border, excepting the Lake Slope, where it is 45, is very nearly 44. Thus the spring mean temperature of the entire State is about 47, or the same as that of the whole year. The Mountain Zone is cooler by 2 or 3 than the South-eastern and North- western Slopes. But elevation appears to exert a less sensible influence in reducing the tempera- ture in the spring than during either of the three other quarters of the year. , Summer Mean Temperature. The mean temperature of summer of the southern half of the State is about 70, and that of the northern half about G7; but at this season the Mountain-zone 54 CLIMATOLOGY. is so much cooler than the Atlantic and Western Slopes, that to get a clear notion of the summer climates we must divide the State, for this period at least, into its three Belts, a south-eastern, a middle, and a western. Thus the mean summer temperature of the district between the tide-water and the first range of mountains is about 72^ ; that of the Mountain Belt is about 67 ; and that of the western side of the State, very nearly 69 ; in other words, the cooling influence of the moun- tains, contrasted with the Atlantic Slope, is equivalent to a mean difference of 5^, or more than twice their effect in the spring season. The difference of 3^ between the eastern and the western slope or plain, is evidently somewhat more than is due simply to a difference of elevation, and must be ascribed in part to the proximity of the Atlantic Slope to the low, warm plain of the tidal sea-board of the Southern States. The mountain climate of the State, as might be inferred from its average summer temperature of 67, is eminently tonic and salubrious to constitutions debilitated by the greater and more protracted heat of the lower country. Autumn Mean Temperature. The average temperature of the whole State in the autumn seems to be about 50, that of the Atlantic Slope approximately 54, and that of the Ohio Slope about 52. At this season the cooling influence of height is very sensibly felt in the mountains ; it is indicated in the much earlier arrival there of frost and snow than in the south-eastern and western plains. The Winter Mean Temperature. Elevation exerts at this season of the year so marked an influence in the distribution of temperature, that it is expedient again to consider the climatal zones as coinciding nearly with the three great Orographic divisions of the surface the two slopes and the intervening mountain-chain. So viewed, the Atlantic Slope has, for this season, a mean temperature of about 30, the Mountain Belt approximately 2 4, and the Western Slope nearly 28. It is an important feature in the climate of the southern border of the State that the mean winter temperature of 32, or the point of freezing and melting, lies along a line just coincident with the edge of tide- water, touching Trenton, Philadelphia, and the Susquehaana; near Port Deposit. Summary. From the above data, it would appear that the Atlantic slope exhibits a range from mean winter to mean summer temperatures of 42^, namely, from 30 to 72.5 ; the Mountain Chain a like range of 43, namely, from. 24 to 67 ; and the Western Slope a similar one of 41, namely, from 28 to 69. The corresponding mean annual range for the climate of Great Britain is about 20. Extremes of Temperature. The climate of Pennsylvania exhibits, like every portion of the United States east of the Rocky Mountains, very wide extremes of temperature, both periodic, or annual and diurnal, and non-periodic, or casual, namely, sudden rises and falls of heat con- nected with the shiftings of the weather. These oscillations are, however, less extreme in the Middle States than in perhaps any other district of the eastern half of the continent, certainly less extreme than in New England and the States west of the Mountains. The Mean Maximum Temperature for the summer season, averaging the whole of Pennsyl- vania, is about 74, and the Mean Minimum Temperature for the same is about 65. These are important data for indicating the adaptation of the climate for certain crops, for it is the summer of the year, more than any other portion of it, which has a critical relationship to agriculture. The summer. temperatures and the summer moisture control all vegetable life, and even animal life, to a large extent ; and upon them depend many of man's most important interests. The extremes of summer and winter temperatures are the most important of the limiting conditions of life, TEMPERATURE. 55 determining what plants and animals can, and what cannot, flourish naturally or through artificial culture, and a correct statement of them is fully as essential to the thorough definition of any climate as the mention of its annual, seasonal, and monthly mean temperatures. It is to be regretted that the casual or non-periodic oscillations of weather have hitherto received from meteorologists, in their descriptions of climate, so little attention. Up to the present time there is almost no temperature-chart before the public which indicates, in addition to mean isothermal temperatures, the known or possible extremes of heat and cold for each district or zone of country. In the present incompleteness of the published records of temperature, I find it diffi- cult to procure a statement of the extremes of heat and cold to which the interior localities of Pennsylvania are liable. Mr Blodget's excellent treatise on the Climatology of the United States furnishes ample data concerning the thermal fluctuations at Philadelphia, and I must content myself with presenting, in the most condensed shape, a simple statement of these. In place of exhibiting the vicissitudes of temperature for every month of the year, I prefer, for the sake of brevity, to introduce only those of the five warmest months and the three coldest, since these contain nearly all the elements which are useful for the comparison of the extremes of one climate with those of another, and all the conditions influential to agriculture, horticulture, and the other arts especially affected by climate. The following Table exhibits not only the greatest degrees of heat and cold felt in each of the eight months referred to, over a term of nearly sixty years ending with 1856, but it also states the lowest or coolest maximum temperature experienced, and the highest or warmest minimum in each month : < Highest maximum, or greatest heat known, 94 I Lowest minimum, or greatest cold known, 32 ( Highest maximum, . . . . 98 t Lowest minimum, 42 f Highest maximum, .... 98 1 Lowest minimum, .... 65 ( Highest maximum, .... 96 \ Lowest minimum, .... 5.0 f-, \ .tiiffiicstj uiQiXiiTiii.nl. .... 93 SEPTEMBER, < , (_ Lowest minimum, . . . . 35 DECEMBER, I Highestmaximum > .... 72 ( Lowest minimum, . . . . 2 JANUARY, j Highest maximum, . . . . 66 (. Lowest minimum, .... 10 'FEBRUARY, j Highest maximum, .... 70 j. Lowest minimum, . . . . 7 MAY, JUXE, JULY, AUGUST, Lowest maximum, or least heat known, Highest minimum, or least cold known, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, Lowest maximum, Highest minimum, ... 71 55 '81 62 86 65 85 69 78 55 44 25 40 24 44 17 The above record of temperatures, remarkable as it 'is, fails to show the extreme degrees of heat and cold, especially the latter, which belong occasionally to the climate of Philadelphia. It is stated by Blodget, on the authority of Pierce, that in 1780, which was the coldest winter known until the two last, 1856 and 1857, " the Delaware River was closed from the 1st December to the 1 4th March, and that during the month of January the mercury was several times between 1 and 15 below zero, and only once during the month as high as 32." The winter of 1783-1784 seems to have been almost as intensely cold. Philadelphia, seated on the tide- water, does not offer, however, a fair specimen of the climate, 56 CLIMATOLOGY. or rather climates, of Pennsylvania. Its winter extremes of cold are less by many degrees than those experienced in higher and more interior localities ; while its extremes of heat are only a little if at all greater. Thus at Lambertsville, on the Delaware, a station which represents very fairly the climate of the Atlantic Slope of New Jersey and Pennsylvania, the highest maximum tem- perature during nineteen years, ending with 1855, is recorded at 1QO; while the lowest minimum is given at 16.5. This exhibits a range of 116.5 ; or 5 or 6 greater than the range at Philadelphia. The ordinary or mean annual range for this city is 85. This is the difference between the average of the extreme coldest temperatures of all the winters for sixty years, and the average of the extreme warmest for the same term. As an illustration of the difference between Philadelphia and the interior in their degrees of extreme winter cold, the winter of 1835, an uncommonly severe one, showed a cold of 22 at Lancaster, and of 24 at Pottsville ; while at Philadelphia it was only 6. Again, in 1856, while the lowest temperature at Phila- delphia was 7, that at Pittsburg was 1 8. Rain Averages for the Year. Few districts of the United States, or indeed of the world at large, are more fortunately circumstanced as to rain than Pennsylvania. Lying within the belt of the non-periodic rains, it is blessed with a singularly equable distribution of moisture throughout the year. The State is seldom visited by a drought of more than- six weeks' duration, generally occurring, when it does take place, in the latter half of the summer. ( These dry periods, hardly more frequent than once in four or five years, are rarely so severe as those which visit the west and some other parts of the country. It is, in like manner, comparatively exempt from protracted and flooding rains. The rains of Pennsylvania, New Jersey, and Eastern New York take the form of brief, light, rain-storms of one, two, or at most three days' duration, and of intermitting showers ; and these, excepting during the occasional summer and autumn droughts, are spread with remarkable impartiality over the several seasons, and even over all the several months of the year. At Philadelphia and along the Atlantic Slope of the State, the average annual rain-fall amounts to 42 or 43 inches. In the Appalachian Chain and on the Ohio Slope, it is materially less. Thus, at Carlisle, the average for six years has proved to be only 34 inches ; and at Pittsburg, the average for eighteen years is a little short of 35 inches. This difference in the atmospheric precipitation on the Atlantic Slope and in the mountains, is a curious exception to the general law of rain in many countries, where the mountains receive much more than the plains, even though the plains lie close to the sea. It would seem to imply, that the mountain rains of Pennsylvania are derived in considerable amount from the far-removed Gulf of Mexico, the S.W. wind from which has parted with a large share of its moisture on its journey, while the Atlantic Slope, or sea-board, receives an additional supply from the more local winds of the ocean. At Philadelphia, the fall of rain for each of the four seasons averaged, during nineteen years ending with 1856, for spring, 10.97 inches ; summer, 12.45 ; autumn, 10.07 ; winter, 10.06. At Pittsburg the respective amounts, during eighteen years ending with 1854, were, spring, 9.38 inches ; summer, 9.87 ; autumn, 8.23 ; winter, 7.48. Extreme Quantities of Rain. The total annual supply of rain fluctuates considerably in all parts of Pennsylvania, in accordance with the general non-periodic character of all the elements of its climate. Thus at Philadelphia, during twelve years, the fall in shape of rain and snow was EAIN AND WINDS. 57 one year only 35 inches, while another it was nearly 55 inches. At Pittsburg, during eighteen years, one year had 25.6 inches, while another year had 47.8 inches ; and Gettysburg, near the mountains, had, in different years, 30.2 inches, and 52.2, in a term of seventeen years. Still more remarkable are the yearly variations in the rain-fall at New York. In a term of nineteen years, ending in 1854, one year (1837) produced 65.5 inches, while 1840 gave rather less than 30 inches. It is stated by Mr Blodget, that in the Central States of the Union, about two and a half times the least observed quantity of water falls during certain years, that in some years less than half the average descends, and in others nearly double the average quantity. At Lambertsville, the greatest number of rainy days for eighteen years has been 118 ; the least number 85. At Fort Mifflin, on the Delaware, below Philadelphia, the greatest number of rainy days recorded is 110, and the least number 86 ; while the greatest number of snowy days is 17, and the least number 11. At Carlisle, the highest number of rainy days recorded is 93, the lowest number 68 ; and the highest number of snowy days 26, the lowest number being 19. At Pittsburg, the greatest number of rainy days for any one year has been 153, the least number 101 ; while the greatest number of snowy days has been 35, and the least number 13. The average number of the latter being 25. Comparing the conditions of rain near the Tide-water with those at Pittsburg, we find that, while the former enjoys 7 inches, or 20 per cent more actual rain and snow than the latter, the relation is reversed as to the number of rainy and snowy days, the western locality exceeding the eastern in nearly as great a ratio. Prevailing Winds. The dominant winds in Pennsylvania, as in so many other parts of the United States, are the westerly ones ; but its several regions differ materially in the proportionate amount of the winds from the various quarters of the compass. Adhering to our division of the State into its South-eastern, Middle, and Western Climatal Zones, we have the elements for comparing the winds of each in the excellent summaries of observations on wind and weather, contained in the Meteorological Tables of the Medical Statistical Eeport on the Army of the United States, prepared under the direction of the Surgeon-General. Collecting the data there recorded for the localities of Alleghany Arsenal at Pittsburg, Carlisle Barracks at Carlisle, and Fort Mifflin on the Delaware, during the twelve years from 1843 to 1854 inclusive, I find that the winds were as follows ; the circle of the horizon being divided into eight equal segments of 45 each, the number of days within the year on which the wind blew from each of these direc- tions was N. N.K. E. S.B. S. S.W. W. N.W. Fort Mifflin (average of only six years), . . . 24 50 25 30 32 75 51 65 Carlisle Bai-racks (average of seven years), 16 17 73 26 24 18 126 53 Alleyhany Arsenal, Pittsburg (average of twelve years), 49 42 26.5 16 27 59 55.5 46 It will be seen from the Table, that on the sea-board the most frequent wind of all is the S.W. This is likewise somewhat the most abundant wind at Pittsburg, but at Carlisle Barracks the W. wind greatly predominates over all the others ; though a part of the 126 days recorded as west wind is evidently the S.W. current undergoing a local deflection from the dying away of the lofty chain of the Blue Eidge, near this place, and the sudden opening thereby of the low Atlantic Plain to this somewhat pent-up breeze. All the three divisions of the State display VOL. I. H 58 CLIMATOLOGY. a marked superiority of the winds of the north-westerly over the south-easterly half of the compass- circle. At Fort Mifflin,the three westerly winds namely, S.W.,W.,and N.W.,blow 191 days; while all the other five blow for only 161 days. At Carlisle Barracks, the predominant winds are the W., N.W., and E., occupying together 252 days ; but it is evident that this locality, the only one within the Mountain Chain whose winds have been reported on, is not happily situated for the purpose. Its N.E. winds amount to but 1 7 days, while its E. winds blow for 73 days. These latter are plainly, in part, the N.E. currents, deflected by the topography of the country. At Pittsburg, all the five winds, S.W., W., N.W., N., and N.E., are of nearly equal frequency, the S.W. and the W. somewhat preponderating. The three other winds, the E., S.E., and S., are comparatively infrequent, and in this feature the region resembles closely the tide- water front of the State. Situated just far enough to the south to escape the severity of the cold and humid N.E. wind of the New England coast, and the savage energy of the intensely cold parching N.W. blasts of the northern interior of the continent, and just far enough N. to avoid the full heat and sultriness of the humid and relaxing S.W. and S.E. winds from the Gulf of Mexico and the warm Atlantic, this happily placed region is endowed with a climate possessing fewer of the noxious qualities of the general climate of the eastern half of the continent, than any other equal territory seated between the Atlantic and the Eocky Mountains. GEOLOGY. GENERAL INTRODUCTORY CHAPTER. CLASSES OF BOOKS EMBRACED IN PENNSYLVANIA. AN inspection of any good geological map of the United States, and the British Provinces, will show that Pennsylvania embraces only the more ancient systems of strata of this portion of the continent. It includes no deposits of the Tertiary or Kainozoic age ; none belonging to the Cretaceous or Greensand, nor any referable to the somewhat older Oolitic period. Tertiary and cretaceous strata border the State upon the S.E., in New Jersey, but they do not cross the Delaware River into Pennsylvania. The strata upon which the surface-wash and soils of Pennsylvania repose, belong to the three oldest classes of the sedimentary rocks namely, to the GNEISSIC, the PALAEOZOIC, and the earliest MESOZOIC ; each, but especially the PALAEOZOIC, being developed upon a scale of great magnitude. No large masses of igneous or volcanic rocks of any description appear within the borders of the State, the only intrusive materials being a few bold dykes of trap-rock, and innumerable lesser veins of the granitic rocks, all confined to the south-eastern district. Of the three groups of strata above- mentioned, the gneissic, or ancient metamorphic rocks, and the rnesozoic red sandstone formation, occupy about an equal extent of territory, and are limited to the south-eastern counties. The palaeozoic rocks cover about nine-tenths of the surface of the State ; they possess an enormous aggregate thickness ; divide themselves into many series, which again subdivide into numerous formations ; they include a great profusion of organic remains, and exhibit in their undulations every diversity of structural feature to be met with in the Appalachian Chain, and they enclose an extraordinary amount and variety of the mineral deposits most useful to the wants and purposes of civilised man, particularly coal, and the chief ores of iron. A large proportion, therefore, of this work will be devoted to a description of these Appala- chian Palaeozoic formations. Resting upon these three great groups of solidified or rocky strata are sundry loose super- ficial deposits, some of which are invested with sufficient interest to demand a general descrip- tion. These are chiefly certain soils, the ferruginous loams of the hematitic iron ores, and the northern Drift or Diluvium. 60 EOCKS OF PENNSYLVANIA. The Gneissic or Hypozoic rocks of the State include nearly all the more common varieties of felspathic, hornblendic, and micaceous gneiss and mica-slate. Closely associated with these, yet belonging to a wholly different system of strata, are extensive formations of talcose and micace- ous slates, indurated clay-slates, chloritic and steatitic slates, referable in strictness to the palaeo- zoic system, but so thoroughly metamorphosed through diffused igneous action, as not to be easily separated in detail from the true gneissic class. To this group of the crystalline strati- fied rocks have generally been referred the altered Primal slates, and Primal white sandstone, and also the crystalline limestone, or white and bluish marble of Montgomery, Chester, and Lancaster counties ; but I shall show that these great strata do not truly date with the proper gneissic group, or so-called primary rocks, but are of palaeozoic age, and identical, in fact, with the widely- spread primal and auroral rocks of the fossiliferous or secondary period. The Palaeozoic Rocks, the full classification and detailed description of which will be intro- duced in a subsequent chapter, constitute a vast succession of fossiliferous strata, commencing (in ascending order) with the lowest fossiliferous deposits resting on the gneissic class, and termin- ating with the last or highest of the coal strata. A comparison between their numerous organic remains and those of the palaeozoic strata of Europe has satisfactorily shown that these rocks were deposited, with certain interruptions, during all the four earliest periods of the five great Euro- pean divisions of palaeozoic time, namely, the Cambrian, Silurian, Devonian, and Carboniferous ages. Neither in Pennsylvania, nor in any other quarter of North America yet explored, have rocks of the fifth or latest palaeozoic period, called the Permian, been discovered. The prolonged succession of sedimentary actions, producing these enormous strata of the Appalachian system, ceased with the close of the Carboniferous era, the whole formative process being terminated by the upheaval of the ocean, in whose broad bed and around whose margin the deposits had been collected. In the region of the palaeozoic basin of Europe there was a similar upheaval at the end of the Coal period ; but it was more partial, leaving a reduced but still wide area of waters for the reception of the next subsequent group, the Permian. Though the Appalachian palaeozoic strata represent, therefore, a somewhat less extended scale of geological time than the European, they compensate for this deficiency in their extraordinary thickness, in the abundance and variety of their organic remains, and in the number of the separate, well- defined fossiliferous horizons, or independent platforms of extinct life which these display. As developed in Pennsylvania, the aggregate thickness of these ancient deposits is not less, according to measurements carefully executed, than about 35,000 feet, and the scale upon which some of the constituent formations were produced was proportionately grand. Some of these formations, well defined by their organic remains and their lithological composition, measure individually between 3000 and 5000 feet. The strata of the Appalachian system of Penn- sylvania (and the description applies equally to those of other regions) exhibit a remarkable variety of mineral character. They may, however, be all embraced under the three prevailing generic classes of the sedimentary rocks, namely, Sandstones, Slates, and Limestones ; enclosing as subordinate layers, lesser deposits of coal, chert, and iron ore. The coarser mechanically-produced strata consist in a large degree of silicious fragments, partly forming thick and massive Conglomerates of quartz pebbles, partly grey and whitish quartzose Sandstones. Other formations of great thickness, and wide, horizontal expansion, have an argillaceous composition, and are of the class called Argillaceous Sandstones and Sandy Shales. ROCKS OF PENNSYLVANIA. 61 Many of these solidified sandy clays are brown and reddish ; others, of less thickness, are grey, greenish, and even yellow. The more purely argillaceous rocks of the system are certain enor- mous formations of clay-slates and shales, of very various aspects and textures. Some of these are grey and bluish ; others are red ; while certain others, again, consist of clay and sand stained by the red oxide of iron. Besides these, there is another important class deficient in the silicious ingredient, and abounding in clay and the carbonate of lime, in those proportions which consti- tute marls or calcareous shales. These are frequently variegated, showing many tints in com- paratively thin alternating strata. Not the least interesting and important class of the Appalachian rocks are the true Limestones. They consist for the most part of an union of carbonate of lime and carbonate of magnesia, though some of them contain only a small amount of the latter ingredient ; others, again, include much argillaceous matter, and some are very sandy, and should be called Shaly and Silicious Limestones. All of these deposits are more or less fossiliferous. Their distinctive peculiarities of composi- tion, their characteristic organic remains, and their constituents generally, will be dwelt upon in the subsequent parts of this work. PART I. METAMOKPHIC STEATA OF PENNSYLVANIA. INTRODUCTORY CHAPTER. CLASSIFICATION OF THE METAMOEPHIC STEATA OF THE ATLANTIC SLOPE OF THE MIDDLE AND SOUTHEEN STATES. BEFORE entering upon a special description of the older rock-formations of Pennsylvania, with which our detailed account of its geology must commence, it will be expedient, for a clearer understanding of their relations to each other, to present a concise sketch of the geological composition of the Atlantic Slope of the Middle and Southern States, of which the Formations in Pennsylvania are a portion. Discarding from o\ir present survey the* newer deposits of the region, or those long, narrow, superficial troughs of unconformably overlying red and grey shales and sandstones of Mesozoic or middle-secondary age, which partially cover the older or crystalline and semi-crystalline strata, and restricting our attention to these, we shall find that, when carefully studied, they rank them- selves so far as they admit of subdivision at all into three natural physical groups. All the sedimentary mineral masses, without exception, are in a condition of more or less metamorphism or transformation from the earthy to the crystalline state by heat, and therefore, in using the term in a critical sense, all of them are metamorphic rocks. In the more current conventional application of this word, however, only some of them pertain to the usually recognised meta- morphic or gneissic series ; others belong unequivocally to the Palaeozoic or ancient life- representing system ; while others, again, constitute an extensive intermediate group, not typically gneissic or granitoid in their degree of crystalline structure or metamorphism on the one hand, nor yet fossiliferous on the other, so far as the closest scrutiny reveals. For a long while indeed, from the commencement of geological research in this district of the Atlantic Slope until the geological surveys of Pennsylvania and Virginia had disclosed the composition and structure of the region- all of these ancient and more or less altered strata, between the summit of the Atlantic Slope in the Blue Eidge and South Mountain and its base at the margin of Tide-water, were regarded and designated alike as Primary Eocks, and were supposed to constitute but one group, the oldest known to geologists. Early, however, in the course of those surveys, it came to light that by far the larger portion of the rocky masses of at least the METAMOEPHIC STRATA. 63 middle and north-western tracts, including much of the Blue Ridge and of the Green Mountains, were of a different type and age from the oldest metamorphic or true gneissic system. The evidence in support of this conclusion was, first, an obvious and very general difference in the composition of the two sets of strata ; secondly, a marked difference in their conditions of metamorphism ; and thirdly, and more especially, a striking contrast in the direction and manner of their uplift, the plications and undulations of the less metamorphic series dipping almost invariably south-eastward, while the gneiss in many locali ties has no symmetrical foldings, but only a broad outcrop dipping to a different quarter. These structural dissimilitudes imply essential differences in the direction and date of the crust-movements which lifted and transformed the respective groups, and they led the geologists of Pennsylvania and Virginia to a conviction that, over at least many tracts, there would yet be discovered a physical unconformity both in strike and dip. It was not, however, till a relatively late date in the prosecution of the geological survey of Pennsylvania, that the geologist of that State detected positive evidences of this physical break and of a lapse of time between the two groups of strata, and established, by ocular proof, the correctness of the previous induction. This unconformity, reflecting so much light on the whole geology of the Atlantic Slope, was first clearly discerned in tracing the common boundary of the two formations from the Schuylkill to the Brandywine and the Susquehanna, but it was quickly afterwards recognised on the borders of the gneissic district N. of the Chester County Limestone Valley, and again soon afterwards in the Lehigh Hills at their intersection by the Delaware River. Prior to the suspension of the geological survey from 1843 to 1851, the true Palaeozoic age of the non-fossiliferous crystalline marbles, and semi-crystalline talcoid slates, and vitreous sand- stones of the Chester and Montgomery Valley, had been clearly demonstrated by the State geologist through a comparison of the strata with their corresponding formations in a less altered condition further north ; but it was not until the resumption of field research, upon the revival of the survey in 1851, that any distinctive fossils were detected in these greatly changed rocks, which, even in their original state, seem to have been almost destitute of the usual organic remains. Assembling all the evidence which we now possess, we have in the Atlantic Slope, by actual demonstration, but one physical break or horizon of unconformity throughout the whole immense succession of altered crystalline sedimentary strata, and within this region but one Palseontological horizon that, namely, of the already discovered dawn of life among the American strata. This latter plane or limit, marking the transition from the non-fossiliferous or azoic deposits to those containing organic remains, lies within the middle of the primal series or group of the Pennsyl- vania survey, that is to say, in the primal white sandstone, which, even where very vitreoiis, and abounding in crystalline mineral segregations, contains its distinctive fossil, the Scolithus linearis. The Primal slates beneath the sandstone, and in intimate alternation with it, possess not a vestige of organic life, nor has any such been yet discovered anywhere within the limits of the Atlantic Slope, or on the northern or western borders of the Great Appalachian Basin of North America, either in this lower primal slate or in the other semi-metamorphic grits and schists physically conformable with it, and into which the true Palaeozoic seqiience of our formations physically extends downwards. We have thus, then, two main horizons subdividing the more or less metamorphic strata of the Atlantic Slope into three systems or groups : the one, a physical 64 METAMOEPHIC STEATA. break or interruption in the original deposition of the masses ; the other, a life-limit or plane denoting the first advent, so far as yet discovered, of organic beings. As these two planes are not coincident, but include between them a thick group of sedimentary rocks, separated from the lower physically, from the upper ontologically, we are fully authorised, in the existing state of research, to employ a classification which recognises a threefold division of all these lower strata. To the most ancient or lowest group, it is proposed in this work to continue the name of Gneiss, preferring, however, to call this division generically the Gneissic Series, employing some- times the technical synonyme Hypozoic, proposed by Professor John Phillips for the lowest of the metamorphic strata. To the great middle group, less crystalline than the gneissic, and yet destitute of fossils, the descriptive terms Semi-metamorphic or Azoic are applicable. And to the third uppermost system, or entire succession of the American Appalachian strata, from the Primal containing the earliest traces of life to the latest true Coal rocks or last deposits of the Appalachian Sea, it is here proposed to affix, as for many years past, the well-chosen title conferred on corre- sponding formations in Europe, of the Palaeozoic, or ancient life-entombing system or series. Thus we have the Hypozoic rocks, or th6se underneath any life-bearing strata ; Azoic, or those destitute of any discovered relics of life ; and Palaeozoic, or those entombing the remains of the earth's most ancient extinct forms of once living beings. The Atlantic Slope of Pennsylvania includes all these three systems of strata, but our first concern is with the lowest, or most ancient, the Hypozoic or Gneissic Eocks. It will be seen further on in our description of these, and of the Azoic strata, where the latter display their maximum amount of crystalline structure or metainorphism, that the members of the two groups often simulate each other so closely, and are indeed so identical in mineral aspect and structure, as to baffle all attempts at distinguishing them lithologically ; nevertheless, it will clearly appear from the evidence embodied in the sections illustrating this country, that they are distinct systems occupying separate zones, susceptible of delineation on the geological map. At the time of the first construction of the general Geological Map of the State, the true limits separating the Hypozoic or Gneissic from the Azoic or Semi-metamorphic rocks were but vaguely understood, and the State geologist did not venture to define them on the map, but shaded the one system into the other ; indicating, however, what he has since proved, that the true gneissic rocks, in their south-westward course, pass out of the State at its southern boundary, a short distance E. of the Susquehanna, while the Azoic or talco-micaceous group, as a genuine downward extension of the Primal palaeozoic series, widens progressively, going westward, until, from a very narrow outcrop at the river Schuylkill, it occupies at the Susque- hanna the whole broad zone S. of the limestone valleys of the Conestoga and Codorus streams in Lancaster and York counties. Since the revival of the field-work of the survey, the dividing limit of these two sets of metamorphic strata has been traced and mapped with precision. To the S.W. of the Susquehanna, it has never, it is believed, been pursued through Maryland and the other Southern States, though one may readily discern it in going northward or westward from Baltimore, or ascending the Atlantic Slope in Virginia. In Maryland, it crosses the Balti- more and Susquehanna railroad about 12 miles N. of Baltimore, and it is intersected by the Baltimore and Ohio railroad a little E. of Sykesville ; it crosses the Potomac about 40 miles above Georgetown and the James Eiver in Virginia, 40 or 50 miles W. of Eichmond. The line of METAMORPHIC STEATA. 65 boundary is, however, not a simple one, but is intricately looped, in consequence of numerous nearly parallel anticlinal foldings of the strata, sending promontories or fingers of the older rocks within the area of the newer or semi-metamorphic, to the W. of their average boundary, and causing, of course, corresponding troughs, or synclinal folds of the newer, to enter, eastward of the average boundary, the general area of the older. The Atlantic Slope has received hitherto so little exact geological study, that we are as yet without the data for determining, with any precision, either the succession of its much-broken and closely-plicated strata, or the geographical limits which separate even the larger sub-groups. It is sufficient, however, for our present purpose, to show the existence, and the approximate range, of two great metamorphic systems, separated by a physical break, and the conformable relations of the later, or upper of these, to well-known lower Palaeozoic formations of the Appalachian Chain. VOL. I. BOOK I. GNEISSIC EOCKS OF PENNSYLVANIA. \ GENEBAL DISTRIBUTION OF THE GNEISSIC OE ANCIENT METAMORPHIC STRATA. The three Gneissic Districts. Within the limits of the State there are three distinct tracts, or zones, of the Older Crystalline Gneissic Strata. The First of these, which I shall call the Southern District, ranges from the Delaware at Trenton to the Susquehanna, south of the State line, and lies wholly S. of the Limestone Valley of Mont- gomery and Chester counties, except near its eastern end, where a spur of the gneiss encompasses it on the N., and extends thence eastward to Trenton, along the margin of the Mesozoic Red Shale. This, the largest of the gneissic tracts, breaks off to the W. of the Brandywine, in a succession of narrow tongues. Near the State line of Delaware it sends forward, however, through the S.E. corner of Chester County and the State of Maryland, a continuous and widening belt to the Susquehanna. It is widest in the meridian of Chester and Ridley creeks, where it spreads from near old Chester to within a mile and a half of the Paoli. The Second Zone lies N. of the North Valley Hill, extends lengthwise from near Valley Forge to the West Branch of Octorara Creek in Lancaster County, and expands northward from the foot of the North Valley Hill to the southern edge of the Red Sandstone district, or Valley of French Creek and south base of the Welsh Mountain, in Chester County. The Third Zone or District of the Gneissic Rocks is confined to the belt of hills ranging from the Delaware below Easton to Reading on the Schuylkill, known as the South Mountains. This tract, prolonged from the Highlands of New Jersey, follows this range of hills to where they subside near the Schuylkill, the gneiss being flanked on the S.E. by the upper margin of the Mesozoic Red Sandstone, and on the N.W. by the Primal White Sandstone, and Auroral Limestone of the lower border of the Great Appalachian Valley. Within these general limits, the Gneissic rocks occupy, for the most pVt, the higher ridges and their slopes, while the Palaeozoic strata repose in the included valleys, and at the northern base of the Chain. CHAPTER I. SOUTHERN ZONE OF GNEISS, OE GNEISSIC ROCKS SOUTH OF THE MONTGOMERY AND CHESTER VALLEY. OBSERVING the prescribed order of description, we shall begin our account of these ancient metamorphic strata with the Southern district, or that south of the first limestone- valley. But in order to exhibit fully at the outset its structure and composition, it will be expedient to depart from our usual rule of tracing each tract from E. to W., and begin in the middle, where the belt is broadest and most fully developed. Here we have the benefit of the fine natural section and series of artificial exposures furnished by the River Schuylkill. Boundaries. This most southern belt of our crystalline strata makes its first appearance at a spot in New Jersey, about six miles N.E. of Trenton, where it emerges from beneath the margin of the overlapping Mesozoic Eed Sandstone. From thence it gradually expands in its course south-westward, keeping the southern border of Pennsylvania to Delaware and Maryland. Its lower or south-eastern margin crosses the Delaware River a short distance below the bridge at Trenton, and passes by Bristol, Philadelphia, Chester, and Wilmington, being separated from the river by a narrow strip of Diluvial and Alluvial deposits, which only in a few places exceed one mile in width. The northern boundary, commencing at the same point in New Jersey, crosses the Delaware about a mile and a half above Trenton, and ranges in a somewhat undulat- ing line to Sandy Creek, about a mile E. of the Wissahickon. W. of the Wissahickon, the northern edge of this zone of the gneiss ranges just S. of Barren Hill ; crosses the Schuylkill a little below Spring Mill, passes about a mile and a half S. of the Paoli, and terminates near Boardsley's Run of the West Branch of the Brandywine, and not far from the Chester County Poor-House. W. of the Brandywine, the gneissic rocks sink under the altered Primal strata, in a succession of anticlinal fingers, on slender promontories, the boun- daries of which will be given when we come to trace their distribution in detail. DETAILS OF THE SOUTHERN GNEISSIC DISTRICT. Gneissic Rocks of the Valley of the Schuylkill, between Philadelphia and Spring Mill.* Commencing at Fairmount on the Schuylkill, and following the E. Bank of the river in a general north-westerly direction, our geological section intersects the strata nearly at right angles to their strike. It presents the formation under a great variety of features and of composition ; the several kinds of gneiss alternating in considerable frequency with each other. It is not possible to divide the whole of this broad belt of Gneissic country, and the Palaeozoic belt of Montgomery and Chester, into any very sharply-defined subordinate ranges, for the many differ- ently constituted bands of the crystalline rocks either so fade into each other, or are of such limited * The reader should here consult the Geological Map and the Illustrative Sections of the Schuylkill and neighbouring valleys. 68 SOUTHEKN ZONE OF GNEISS. length, that to trace and map them in detail would be a work of herculean labour. The strata are too generally obscured by a deep covering of loose earth, largely derived from their disinte- gration, and the rocks themselves are too deeply rotted and softened by surface action, to permit that abundance of salient exposures which would be essential to the recognising and picturing, with minute exactness, of their innumerable local bands. Nevertheless, the whole of the gneissic system of the Schuylkill may be approximately and conveniently subdivided into the three large groups of strata, occupying, where they are intersected by the river, three broad Belts. The first, or most southern general Division or group, may be approximately defined as extend- ing from the lowest exposures on the river, or those near Gray's Ferry, to the upper end of Manayunk ; the second, or middle Belt, extending from Manayunk past the Serpentine and Soap- stone range to a line a little N. of the upper boundary of the County or City of Philadelphia ; and. the. third, or northern, extending thence to the northern edge of the whole Gneiss formation, as it is overlaid and limited by the older Primal rocks in the vicinity of Spring Mill. FIRST BELT. The southern or Philadelphian Belt contains the following chief descriptions of ordinary gneissic rock, with many sub-varieties. The most common or typical variety of all is a grey, bluish, rather finely-laminated triple mixture of quartz, felspar, and mica ; the quartz, for the most part, white or transparent ; the felspar usually white, and very generally somewhat chalky from incipient decomposition ; and the mica, most commonly black or dark brown, and in small plates. This rock occasionally includes small insulated garnets. The next most common species is a dark, bluish-grey, sometimes greenish-black gneiss, com- posed of hornblende and quartz, with sometimes a little felspar, the hornblende always greatly predominating. This rock is very usually fine-grained and thinly bedded, its fracture and struc- ture being controlled by the general parallel crystallisation of the prevailing hornblende. A third common variety of the gneiss of this group is a micaceous quartzose rock, generally of a light grey colour. Some beds of this species contain such a predominance of the crystalline quartz, in minute granular division, and such a subordinate amount of minutely disseminated mica, as to have a character of ordinary grey whetstone ; but this species of the gneiss is much more abundant in the middle belt than in the southern one. A much coarser kind of grey micaceous gneiss, consisting of a predominance of rather large flakes of mica, with a subordinate quantity of felspar and quartz, occurs interstratified with all these other species, as a very usual transition variety between the standard grey gneiss and the highly micaceous kinds verging towards mica-slate. It is very usual to find the typical gneiss, of a threefold constitution, alternating with the hornblendic species, and both of these alternating with the quartzose micaceous variety. As a general fact, not without exceptions, however, the more micaceous the rock is, the greater is its abundance in insulated crystals of common garnet. Interposed among the above varieties of true gneiss are beds, more or less thick, of kinds so abounding in mica as to be entitled to the designation of true mica-slate. This rock prevails in two or three outcrops, both above and below Columbia Bridge, and it may be stated generally, that the further north we advance across the southern division of the gneiss, the larger is the pro- portion of the more micaceous varieties of the ordinary gneiss, and the greater the frequency of these bands of mica-slate. An interesting variety of the ordinary or more felspathic kind, is one containing large, more Pictorial Section of East Bank of the SchirylMll' from Spring Mill to Manayunk, A ' ' V A p [> ti r A n, t i u, n- c, b u o rv of G n- e v a s v c a, n d> rttlseozoLc $ t r cu t- a/ ^ Pictorial Section of East Bank of Sohulkill- Continued . ]-ica,ce.ous (r n, e v s s , Mica, Slate. Garnets. Q w cu r t z o ,t ! Coarse/ G w e v o u. s Mica, o r TL- b I e & M n u n ^fe4^^^r%'' ^ : : : z ^^^SSiJc^7te^Tr^ a, r n, t v f e r o w s CT TL 6 I/ S G n/ i a s . Grey Micaceous G neiss Sorn/bl/e>n>d't' a TL d. F e 7, spa. TL c i --. ~- . . . .". ._ - ,--- ~ -- ,- C o a/ r t, t * i * t c. d, FIRST BELT OF GNEISS. 69 or less insulated, segregations of crystalline felspar, the longer axes of whose crystals lie generally parallel with the lamination of the rock. This variety may be designated a porphyritic gneiss, having that feature of an excess of crystalline felspar which is accepted by geologists as a dis- tinctive character of the porphyritic rocks, and being, moreover, essentially similar to those well- known and beautiful granites which geologists agree to call Porphyritic. A band of this porphyritic gneiss occurs at the Falls of Schuylkill, just below the Quarries, and ranges towards Nice-Town in one direction, and towards the Toll-gate, on the Lancaster Eoad, five miles W. of Philadelphia, in the other. Another outcrop of the same felspathic variety of the gneiss may be seen crossing the West Chester Plank-Road, just E. of Darby Creek. The Gneiss rocks, especially the more felspathic varieties, exhibit throughout this southern belt an extensive disintegration, pervading them in some localities to a depth of many feet below the soil. When in this condition, the felspar is either wholly or partially converted into kaolin (or China earth), and softened ; the mica is itself also sometimes decomposed, staining the mass, from the oxide of iron set free. Such is likewise the case with the hornblende, where this is an ingredient. To this susceptibility of decomposition under long-continued atmospheric agency, we must ascribe the great prevalence of mica in the soil of this region, and the general absence of superficial fragments and boulders of the gneiss, these having, in part at least, wasted into soil. By the slow but increasing disintegration of the felspar, a certain small portion of potash is constantly furnished to the soil to sustain its natural fertility, and the mica loosened from the rock becomes also a valuable ingredient, by giving it a peculiar spongy texture, admirably suit- ing it for the retention of moisture. A practical application of this rotted gneiss is occasionally made near Philadelphia, the loose materials of the rock being sifted, to procure a sand which is of remarkable sharpness, and well suited for the purposes of masonry. Granite Veins. In this southern zone of the gneiss formation occur numerous injections of true granite. These are for the most part narrow, obscure dykes, or more truly intrusive veins, penetrating and branching into the gneiss rocks, which are very generally contorted in their vicinity. Frequently these veins expire within the gneiss, only the larger ones having been injected with force enough to cut entirely through it. These granite dykes possess a remarkable general uniformity of composition and mineral character. The constituent minerals are felspar, quartz, and mica, all coarsely, independently, and confusedly crystallised. The predominant mineral is white felspar, and the next most abundant constituent is the quartz ; the mica, indeed, being frequently almost wanting. The prevalence of felspar imparts to these veins a predominant whiteness, which usually enables them to be immediately recognised. It is likewise the cause of their generally very rotten condition, for throughout all this district the felspar and other easily decomposible minerals are, from some cause, universally and deeply decayed. Unstratified or true Igneous Rocks. Several rocks of the igneous class present themselves in the district before us. Of these, one of the most frequently seen is a peculiar felspathic syenite in thick dykes, also a white coarse-grained granite composed of felspar and quartz, in tortuous and sometimes ramifying veins, and greenstone and other forms of trap-rock in dykes, and also quartz, chromiferous iron ore and other minerals, occurring singly or associated in the shape of elongated thin dykes or narrow veins. To these should, perhaps, be added some of the masses of serpentine, for the unstratified character of these last named is no longer doubtful. Syenite. Of the above-mentioned intrusive rocks, the most largely developed is the species 70 SOUTHERN ZONE OF GNEISS. which I have called a Felspathic Syenite. This is for the most part a confused crystalline mixture of translucent smoky felspar and quartz, with sometimes a little mica, and more rarely a small proportion of hornblende. The felspar frequently forms almost the entire mass of the rock, and is always the predominant ingredient. Where it occurs alone, the crystallisation is usually very coarse and perfect. In the central portions of the dykes or beds, this rock presents few or no traces of any parallelism in its internal structure, much less any genuine stratification, but upon the sides where it approaches contact with the strata of gneiss enclosing it, an imperfect strati- fication is discernible. This feature is only such, however, as belongs to many dykes of genuine igneous granite, and by no means indicates it to appertain to the stratified metamorphic class. The rock before us is well adapted to certain purposes of architecture, being much more cohesive than the ordinary gneiss rock of the region, and less liable to disintegration under atmospheric action. Its chief localities are in the south part of Delaware County, from whence it passes south- westward into the State of Delaware, the dykes augmenting in frequency and size as we trace them in that direction. This rock has been extensively employed in the construction of the Delaware breakwater. The largest quarries of it are on Naaman's, Brandy wine, and Christiana creeks, in the State of Delaware. The localities of the more important trappean and other dykes will be mentioned in another place. Trap Dykes. Where the road from Davisville to Huntingdon intersects the county line, there is an extensive trap dyke running nearly E. and W. in a straight line for three miles. The gneiss in its vicinity assumes very much the character of a syenite, and some of it might be use- ful as a building-stone. The River Schuylkill presents a series of excellent exposures of the different divisions of the gneissic belt, from Philadelphia to Spring Mill. The general structure of this part of the region is exhibited in No. III. of the larger sections. At Fainnount, near Philadelphia, the gneiss projects above the Diluvium, and is quarried to some extent in this vicinity, and also on the west bank of the river in several places. The grain or lamination of the rock is exceedingly contorted, implying the occurrence, at some period, of an immense compressing force. In all the quarries from Fairmount to the Falls of the Schuylkill, the rock is intersected by numerous cross joints, which appear, until closely examined, to represent its divisional plains or true stratification, and which, at Fairmount, are nearly horizontal. These joints divide the mass into blocks of convenient shape and dimensions, and when they dip in the proper direction, greatly facilitate the operations of the quarry. The belt of felspathic gneiss which passes Philadelphia is well developed on Darby Creek, Crum Creek, Ridley Creek, Chester Creek, and the other adjacent streams. On nearly all of these it has long been wrought, supplying Philadelphia and other places with a large amount of very excellent working-stone, and material for the foundations of houses, and for other purposes. At the Falls of the Schuylkill there is a large quarry of very excellent gneiss of a light grey aspect, which has long contributed its supply of good building-material to Philadelphia. In this quarry there is a vein of large-grained granite, with red felspar ; the strata dip to the N.W. Falls of Schuylkill Quarry. The quarries at this locality expose the thick-bedded variety of gneiss, consisting of felspar, quartz, and black mica, with an occasional sprinkling of solitary crystals of garnet. The felspar and garnets show a tendency, especially in the upper layers, to partial decomposition. The stratum is traversed by numerous great joints, running approxi- SECOND BELT OF GNEISS. 71 mately N. and S. The direction of the dip is about 15 20 to N. 20 E. It tends to quarry in large irregular trapezoidal blocks. The mica in this rock is in minute scales, and small in quantity in proportion to the quartz and felspar. The lower quarry exposes a massive gneiss, of alternating mica and felspar bands, with tendency to a porphyritic structure from excess of felspar. SECOND OR MIDDLE BELT. The middle zone of the Gneiss of Southern Pennsylvania, as it crosses the Schuylkill, consists of an alternation of four principal varieties. Perhaps the most abundant of these is a very micaceous species of the ternary or mica quartz and felspar rock, holding garnets in greater or less profusion. A very common feature in this rock is a wavy or minutely undulated lamination, arising apparently from a contorted or wavy structure in the coarsely crystallised mica, its predominant mineral. This would seem to proceed from the interference of the innumerable planes of cleavage, or what is the same thing of crystalline lamination with the original planes of deposition of the strata. The twisted form of the flakes of mica is frequently seen to be due to the displacing effect of grains, or crystalline bunches of included quartz. It would seem as if these minerals had crystallised or segregated, from their parent sedimentary materials, under a conflict of forces, the newly-awakened crystallising energies being not always parallel to the original bedding of the deposit, but more frequently oblique to it. Perhaps the next most common subdivision of the gneiss of this middle tract is a variety consisting almost exclusively of the above-described wavy mica. This rock graduates into the more micaceous sorts of gneiss, by containing a less or greater mixture of finely-granulated crystalline quartz, felspar, and hornblende. The southern half of the gneissic zone before us is characterised, on the Schuylkill and the Wissahickon, by containing an alternation of the above two varieties of micaceous gneiss or mica -slate, with beds of hornblendic gneiss the last- named rock being, from its thin lamination, sometimes entitled to the name of Hornblende Slate. The northern half of the zone consists largely of a fourth variety of the more schistose class of the gneissic rocks. This is a grey fine-grained binary mixture of granular quartz and minutely crystallised scales of mica, the quartz being the prevailing element. It is a species of whetstone, and some of the more quartzose bands would furnish masses well suited for employment as whetstones for scythes. A very common, indeed a characteristic feature of this quite remarkable and extensive division of the micaceous gneiss group, consists in its peculiar fracture ; the rock breaking into long narrow chunks, comparatively smooth on their sides, but excessively ragged on their ends ; a style of fracture strongly resembling that of half-rotted fibrous wood. This peculiar rock is in greatest force towards the northern side of the middle gneissic belt, or between the serpentine and steatite, and the hard felspathic gneiss of the southern margin of the third or Northern Gneissic Belt. It is interstratified towards its southern side, with more or less frequent and thick bodies of the other variety of mica-slate, possessing the mica in large and twisted scales, with an abundance of garnets. On its northern side it alternates to some extent with a greenish talcose slate, or, what is the same thing, -the talc in this quarter replaces the mica in whole or in part in certain divisions of the group. It is here that we meet with the interesting belt of Steatite and Serpentine, which extends from E. of the Wissahickon on the brow of Chestnut Hill, across the Schuylkill to Mill Creek, beyond Merion Square. Viewing the steatite as a stratified rock of the mica-slate group, we may reasonably regard it as having been metamorphosed to its present composition and structure, 72 SOUTHERN ZONE OF GNEISS. by infusion of magnesian matter from the dyke of intrusive Serpentine which everywhere adjoins it. Wissahickon Creek Section, comprising the Talc-Slate, Steatite, and Serpentine. This section, intended to illustrate the Middle Belt, commences at the most northern exposure of the mica-slate S. of Thorpe's Paper-Mill. The rock is a mica-slate, exceedingly full of garnets. Besides the mica, which is the principal constituent, and the garnets, it contains a little minutely disseminated quartz, but not much. The dip is 80 to S. The mica is everywhere more or less minutely wavy, and in the very micaceous kinds it is coarsely crystallised and remarkably waved. It weathers a ferruginous brown. The exposure of talc-slate, steatite, and serpentine, commences opposite the bridge over Wissahickon Creek, near Thorpe's Mill. The first rock which here succeeds the garnetiferous mica- slate above described, is a stratum of green talcose slate, estimated to be 40 feet thick ; this dips about 70 to N., about 20" W. Eeposing upon it at the same angle is the Steatite Group, which is an alternation of talc-slate and talcose steatite ; the former material apparently predominating. This occupies an estimated breadth or thickness of 120 to 140 feet. In the northern half of this group the talcose chloritic beds contain numerous octahedral crystals of oxide of iron. Next in order N., and adjoining the Talc-Slate and Steatite, is the Dyke, or Bed of mixed Serpentine and Steatite. The thickness of this is not great, apparently not more than from 12 to 20 feet. A steatitic Talc-slate adjoins the Serpentine on the N., extending for 30 feet. Then succeeds a Garnetiferous Mica-slate, dipping about 85 to N., 20 W., quite garnetiferous, precisely similar to that below this. It dips as do the others, and extends for 75 feet. This is succeeded by a close-grained Quartz-slate or Scythe-stone, the thickness of which is about 100 feet. Following this is the ordinary very garnetiferous Mica-slate mica in large flakes, and crinkled. This bed has a thickness of 50 feet. Next in order, extending for 500 feet, is a group of beds composed chiefly of a hard Quartzose Mica-slate, or thin-bedded Quartzose Gneiss, including alternating thin beds of the ordinary garnetiferous mica-slate. This brings us to a bold dyke of Bluish-grey Granite, from 50 to 60 feet in width. Then succeeds a hard Blue Micaceous Quartzose Gneiss or thin-bedded Flagstone. This alter- nates with the more rough mica-slate ; it has a thickness of about 200 feet. On the N. edge of the Quarry it seems to dip S. 85, but towards its northern limit its dip is about 85 to N. Succeeding this rock is a belt of close Hornblendic Gneiss and Quartzose Mica-slate, having a thickness of 200 feet, its northern limit coinciding with a marked depression in the hills. These are the uppermost or terminal beds of the great gneissic formation. A spring of remarkably pure well-aerated water occurs in the Flagstone Group, a little N. of the Granite Quarry. Passing the depression in the hill, we enter immediately upon the Primal Older Slates in their usual metamorphic condition, with characteristic white streaks of imperfectly crystallised felspar and dark hornblendic mineral, and with the roundish specks of semi-crystallised felspar. One band in this formation is excessively hornblendic, very ferruginous, and may possibly include some workable iron ore. These rocks possess precisely the type which they exhibit on the Schuylkill. Their thickness on the Wissahickon Creek cannot be less than 300 feet ; dip about N. 20 W. THIRD BELT OF GNEISS. 73 No outcrop of the Barren-Hill White Felspar Eock could be detected at the base of the hill. That the Barren Hill opposite this point has an anticlinal structure, seems evident from the fact that the overlying limestone occurs on the S. slope of the ridge, close to the turnpike-gate on the city line, at the intersection of the Germantown and Perkiomen Turnpikes. Good brown iron ore is found in the Little Valley between the main hills of Gneiss and the Barren-Hill Eidge. I am inclined to infer, that upon the Wissahickon Creek this highest group occupies a narrower belt than upon the Schuylkill. THIRD OR NORTHERN BELT. The third and most northern of the divisions into which we have found it convenient to separate the Gneiss of the Schuylkill district, extends from the somewhat abrupt cessation, or edge of the above-described micaceous belt, to the base of the Primal altered slates of the South Valley Hill, at Spring Mill. This zone is here, at the river, not more than about half a mile in breadth ; and what is curious, it runs to a point, before reaching the Valley of the Wissahickon, only two and a half miles to the eastward, being overlapped obliquely by the margin of the Palaeozoic rocks. From its tapered point near the Eidge Turnpike, this zone of hard gneiss expands regularly in its course westward, until at Darby Creek, and beyond it, or in the vicinity of the Delaware and Chester County line, it has a breadth of about four miles. The materials constituting this northern tract are very similar to, if not identical with, those which compose the southern or Philadelphian one. If they differ from that, it is by possessing a less proportion of the more micaceous varieties of gneiss, and almost no mica-slate. The prevailing varieties in this tract are, first, a massive felspathic gneiss, some of it micaceous, and some of it like a stratified syenite ; and, secondly, a dark hard hornblende felspar gneiss, thinly laminated and strongly striped, when viewed in transverse section. The first-named, or more felspathic kind, is in some beds porphyroidal, and strongly resembles the gneiss above Philadelphia, and that at the Falls of Schuylkill. A remarkable feature in the northern or uppermost bands of gneiss on the Schuylkill, or those which next adjoin the base of the Primal series, is the possession of a less than usual completeness of crystallisation in the constituent minerals, the felspar, more especially, appearing to be less perfectly developed- than common, and more in the condition of roundish or lenticular segregated lumps. In this circumstance, the gneiss here approximates somewhat to the structure of the lowest beds of the Primal series, which are also porphyroidal, but exhibit their metamorphism in a far lower degree. The following somewhat more detailed description of this Northern Belt of the Gneissic Rocks will serve to exhibit more fully the differences between it and the middle Zone, and its general agreement with the lower or more southern one. Description of the Northern or Upper Belt of Gneiss. The northernmost belt of gneiss, or that commencing near the Quarry, half a mile S. below Spring Mill, and extending to the northern brow of the hills overlooking that locality, is distinguished from the next division of the Gneissic Formation to the south of it, by the prevailingly massive character of its bedding, its large excess of felspar, and comparative deficiency of quartz, mica, and hornblende. The mica seems to be next in abundance to the felspar ; it is generally black, and in very minute scales. The horn- blende element predominates most in the upper members of the group adjoining the William Penn Furnaces, where beds of true hornblendic gneiss alternate with micaceous felspathic layers, and with others more purely felspathic. This entire group contrasts strikingly with that next south VOL. I. K 74 SOUTHERN ZONE OF GNEISS. of it, in the total absence of garnets, and of that excess of mica, or of mica and quartz, which so generally characterises the garnetiferous varieties. From the massiveness of many of its beds, and the regular parallelism of its structure, this rock is admirably adapted for quarrying ; the less contorted and disturbed parts of the formation being fit to afford an abundance of noble blocks of building-material of almost any dimensions. Two sets of joints traverse the strata, one perpendicular to the horizon, but nearly at right angles to the strike, no matter what the inclination of the dip ; the other approximately coincident with the strike, and for the most part nearly perpendicular to the plane of stratification. This rock displays a marked gradation of abatement, as we ascend from the lower to the upper members of the group, in the extent of segregation or crystalline separation of its constituent minerals. These, in the inferior beds, are almost invariably the felspar and mica, especially in separate parallel laminae ; and where the felspar is in excess, it occurs in large porphyroidal crystals. But in the middle and superior portions, while the general parallelism of the lamination is still retained, the lamiuse are finer and more commingled. The several mineral constituents are less coarsely crystallised, and any isolated felspar has the form of lenticular or ovoidal knots, showing a lower, less advanced, stage of segregation. It would seem as if these highest members of the whole gneiss formation have experienced a less perfect and thorough metamorphisrn than the middle and lower masses. Structure of the Upper or Northern Belt of Gneiss. Near the bend of the Schuylkill, the lower strata of this upper group, in a bluff hill one-third of a mile below the William Penn Furnaces, displays a true anticlinal flexure, and it is here, just on the anticlinal axis, that the more northern of two considerable veins of granfte intersect these strata. From this axis northward for 350 feet, the beds dip very regularly at angles declining from 55 to 40, towards N. 20 W. ; and for the next 800 feet their inclination is so gentle, that they may be described as horizontal. Such dip as they do possess is from the river towards the N.E. At the limit here mentioned, they exhibit a distinctly marked synclinal structure, rising with a gradually increasing inclination for the next 300 feet, and then immediately displaying for the following 600 feet across their strike a succession of remarkable contortions, presenting, on a small scale, several beautiful anti- clinal and synclinal folds. This brings us to within some 200 feet of William Penn Furnace, No. 2. Here the contortions appear to terminate ; and with the exception of a few very subordinate twists in the bedding, the strata stand almost perpendicularly throughout the next 1400 feet. This brings us to the northernmost limit of the whole Gneiss formation, or to a line about 1400 feet N. of the Old William Penn Furnace, No. 1. It is possible that one or two plications may exist in this space ; but with one exception, which is at the northern end of the Upper Furnace (No. 1), the prevailing dip is nowhere less than about 80 to either the N. or S. As an argument for the general unconformity of the Lower Primal Rocks to the Upper Gneissic group, I would call attention to the folded and contorted condition of the latter, and the very uniform, nearly vertical, dip of the first-mentioned. Another even more cogent reason for assuming such unconformity is the striking contrast which prevails in the law of flexure, of the two formations. The undulations of the gneiss do not belong to the Appalachian system of south-east-dipping axes planes, but exhibit a wholly different character, being either minute and local contortions, or wide gentle undulations, with comparatively moderate dips, which are for the most part to the N., and not, as in the other system, to the S. DETAILS OF THE GNEISS. 75 Subdivisions and Details of the Northern Belt of Gneiss on the Schuylkill. Commencing at the point below the Granite Quarry, S. of Spring Mills, at about 100 feet S. of the end of the long tangent in the Norristown Railroad, occurs the most northern good exposure on the side of the railroad. It begins with a small injection of pinkish granite composed of felspar and quartz. Immediately adjoining the granite on the N. side, we find a variety of massive gneiss, con- sisting of rather coarsely crystallised felspar, quartz, and hornblende, with some mica. Certain bands of it tend to the porphyroidal structure, from excess of felspar. It is evenly bedded, and shows the parallel lamination of gneiss, but this is not minute or very continuous. It dips about 80 to N. 20 W. A similar massive gneiss appears to occupy the hill on the opposite side of the river, at the cuts in the Eeading Railroad. About 160 feet N. of the first dyke is a second vein of granite, or more properly a syenite, producing, on the gneiss in contact with it and S. of it, a S. dip of 70. This syenite is composed, chiefly, of coarsely crystallised felspar, both pinkish and white ; it holds a much less proportion of 'quartz, and a considerable amount of large specks of imperfectly crystallised or finely granu- lar hornblende. The injection is about 1 feet thick. Succeeding the dyke of syenite, is a repetition of the kind of gneiss occurring to the southward, massively bedded, porphyroidal in many of its layers, of a bluish-grey colour, and consisting, for the most part of a triple mixture of felspar, quartz, and mica, and occasionally some hornblende the felspar frequently appearing in large insulated blotches. This rock is now extensively quarried ; it occupies the bold point of the hill, causing a bend in the river. From the vein of syenite, for 250 feet across the strike, it dips very evenly at an angle of 45 or 50 to N. 20 W. But at that distance the dip changes pretty suddenly to a very small angle. On the side towards the syenite it is penetrated by a few injections of granite. It would thus seem that there is here a true anticlinal flexure in the gneiss a large vein of syenite being protruded very nearly in the axis. The slight northward dip is succeeded at about 900 feet from the Quarry by a gentle dip to the S. Some 387 feet N. of the Small Quarry, at the S. end of the New Furnace (William Penn Fur- nace, No. 2), the rock is seen in a cut made for pumps ; the dip is almost perpendicular, about 87 S. It is a good exposure of a quite peculiar gneiss, massive, dark-blue, streaked, and lenticularly spotted white. It consists chiefly of felspar and dark-blue mica, in alternate slightly wavy bands or laminae, with lenticular concretions, or crystallisations of pinkish-white felspar. Some of the beds are porphyroidal, from abundance of lumps of felspar, others minutely or closely laminated in delicate parallel, slightly wavy, bluish-black and pinkish-white streaks, produced by the two predominant minerals. This rock contains some quartz, and occasionally some hornblende. Its vertically dipping beds support the large New Iron Furnace, No. 2. At the N. end of the New Furnace is a felspathic micaceous gneiss, somewhat minutely banded, without the lenticular crystallisations of felspar. 266 feet from the N. end of the New Furnace is a trap-dyke, very hornblendic, about 8 feet thick. About 421 feet N. of the north end of the New Furnace is the same kind of gneiss, minutely streaked or laminated, some beds still containing lenticular segregations of felspar, but these fewer and smaller, the whole rock more minutely and evenly laminated, and more closely resembling an altered argillaceous sandstone, yet still claiming the appellation of a gneiss. The felspar has a mealy chalky aspect on the weathered surfaces. 76 SOUTHERN ZONE OF GNEISS. About 100 feet N. of the north end of the Old Furnace, No. 1, is an exposure of a felspathic micaceous gneiss, which continues for 170 feet. At the north end of this furnace the dip is 60, but 100 feet farther on it is 85. Nearly 330 feet N. of the north end of No. 1 Furnace, there is a ledge of a somewhat different rock, Avith almost perpendicular and regular bedding. Decidedly less gneissic in its crystallisa- tion, it has lenticular lumps of felspathic mineral, and is finely streaked ; the whole has an earthy sedimentary aspect, and the felspathic specks and concretions are rounder than in the true gneiss; the strike of the rock is nearly S. 70 W., or parallel with the prevailing strike of the genuine gneiss ; to the southward its course is such as to range straight for the shore of the river at the Ferry House, opposite Spring Mill, and it must range thence along the north base of the belt of hills bounding the river, between the Ferry House and Merion Furnace, opposite Conshohocken. This rock has a more earthy and less crystalline aspect. I incline at present to regard it as the lowermost member of our Secondary or Palaeozoic system of strata. If it be really such, it is not here locally separated from the gneiss beneath it, by any marked unconformity in respect to either their strike or dip, but the two sets of rocks are contrasted in a very marked manner, both in their external aspects and their mineral composition. The passage from one into the other is so abrupt as regards their composition and crystallisation, as to require us to place them in wholly different systems. The visible thickness of the vertically-dipping beds of this upper doubtful group is about 100 feet. This stratum forms the N. point and face of the hill, immediately S. of the Spring-Mill Valley. Limits of the three Belts of Gneiss of the Southern Gneissic District, more precisely defined. It is not possible to trace, at least at present, with close precision, the boundaries eastward and westward which separate the southern and northern belts of harder gneiss, from the middle tract of softer, or more micaceous strata ; but their approximate limits may be indicated somewhat as follows : Limits of the Southern Belt. The Southern, or Philadelphia Belt, can be traced from the Delaware, below Trenton, to the Neshaminy, constituting the whole of the gneiss S. of the southern edge of the red sandstone. West of the Neshaminy, its northern border, or that which separates it from the micaceous middle belt, leaves the southern trough of Primal white sand- stone, and, trending south-westward, passes between Shoemaker Town and Mill Town, and crosses the Schuylkill near the northern side of Manayunk. To the S.W. of the Schuylkill the limit is less precise, partly from a deficiency of exposures of the rocks, and partly perhaps chiefly from the existence of a succession of undulations, which may cause a repetition of out- crops, or separate belts of the two divisions of the strata. On the Brandywine, the northern limit of the more massive gneiss would appear to be somewhere N. of Chadd's Ford. It would seem that, after crossing the Brandywine, the rocks of this group run forward for several miles, into Chester County, and through the northern side of Delaware into Maryland, in a succession of gradually contracting ranges or slender fingers, the more northern of which terminate in the neighbourhood of the Eedclay and Whiteclay Creeks, while the middle ones extend forward to cross the Little Elk Creek, and to pass to the south of the eastern end of the great Southern Belt of the Serpentine. It is very obvious, from the structure of this zone on the Brandywine, from Chadd's Ford, southward, and through the country to the west of that stream, that the gneiss is here undiilated in a series of wide anticlinal waves. This is indicated, not only in the alternately N. and S. dips of the strata on the Brandywine, but in the occurrence of those several synclinal NORTHERN LIMIT OF SOUTHERN GNEISS. 77 troughs of Primal and Auroral palaeozoic rocks, which in the south-eastern corner of Chester County, and the north-eastern corner of the State of Delaware, are folded in between the uplifts of the gneiss. Besides these anticlinal fingers, this southern gneissic belt sends forward to the S.W. a long unbroken zone or line of outcrop, through Northern Delaware and Cecil County, Maryland, to cross the Susquehanna Kiver between a point some two miles below the Pennsyl- vania State line and Havre-de-Grace. This is a grey granitoid gneiss, composed largely of quartz and felspar, and occurs on the Susquehanna in very massive beds. Limits of the Mica Slate or Middle Gneissic Belt. Viewing the middle micaceous belt as terminating eastward, somewhere in the neighbourhood of the Neshaminy, and S. of Edge Hill on the southern ridge of Primal sandstone, we can define its northern limit to be formed by that outcrop of Primal rocks passing Moretown and Chestnut Hill, to a point a little "W. of the Wissahickon, at which latter place the mica-slate seems to leave the belt of Primal rocks, and to be bounded thenceforward on its north-western side by the south-eastern margin of the northern tract of older felspathic gneiss. Thus limited, it crosses the Schuylkill, as already defined, about one mile S.E. of Spring Mill. From the Schuylkill the line of contact of the two groups, pursu- ing first a course somewhat W. of S.W., passes through the eastern corner of Haddon Township, and the lower edge of Newtown, to take a range somewhat more to the W., coincident nearly with the north-western edge of Delaware County. It then proceeds through Westtown, in Chester County, and crosses the Brandywine somewhere within a mile below the E. and W. branches of the junction of that stream. East of Unionville the tract of hard felspathic and hornblendic gneiss, to the N. of the more micaceous gneiss, appears to run to a point, and here, therefore, the common boundary of the two groups re-curves rapidly backward towards the N.E. Whether the rocks bounding this belt of harder gneiss, W. of the Brandywine, appertain all of them to the ancient Gneissic slate formation, or whether they are not in reality the lower Primal slates under a highly metamorphic and crystalline condition, is a question which remains open to future research ; but I incline to the belief that, within the general synclinal trough of the micaceous gneiss, where the Brandywine intersects it, we shall ultimately discover smaller synclinal waves, containing unconformable troughs of those older Primal slates. The western general limit of the middle gneissic belt may be vaguely defined, then, as occurring somewhere near the Brandywine, across which it is probable there extend some narrow anticlinal fingers, expiring, like those of the southern harder gneiss, under the overlapping, very undulating, margin of the altered Primal series. Whether, indeed, there may not occur,. even in the more central tracts of this micaceous zone, between the Schuylkill and the Brandywine, some small insulated troughs of the Primal older slates, is a point which likewise remains for future investigation. Limits of the Northern Belt of the Southern Gneissic District. -We have just defined, in a general way, the southern boundary of this northern tract of gneiss, and it remains to describe now its northern edge, or that which separates it from the long continuous belt of Primal talcose older slates which border it on the N. From a little W. of the Wissahickon, where this northern tract of gneiss seems to emerge from under the Edge Hill trough of Primal strata, the common limit of the gneiss and talcose slate can be readily traced along the northern brow of the Chestnut Hill range, to the Schuylkill just below Spring Mill. West of the Schuylkill, the line of contact of the older Primal, with the Gneissic strata 78 SOUTHERN ZONE OP GNEISS. ranges along the brow of the range of hills overlooking the river, and thence through the summit of this ridge, as it borders the limestone valley of Merion Furnace. It thus passes G. W. Fisher's, and P. Pechin's, and W m . Morgan's, N.E. of Morgan's Corner. Thence its course takes it about half a mile S. of the Spread Eagle Tavern. On the back road from the Paoli to the Spread Eagle, S. of the turnpike road, we find the limit of the two formations, about one-third of a mile E. of the cross-road leading from Eeeseville to the Leopard Inn, a dyke of close-grained bluish trap-rock occurring a little N. of the line of junction. Here the older rock is a dark bluish grey felspathic micaceous gneiss, very similar to that S.E. of Spring Mill on the Schuylkill. In this vicinity, further eastward, the gneiss is very quartzose and massive. It dips 85, to N. 10 E. In the deepest of the railroad cuts, near the Toll-gate, W. of Morgan's Corner, the rock is a massive granitic gneiss, of greenish felspar, white and garnet-coloured quartz, and brown mica. These varieties are here cited, for the purpose of comparison with the very different kinds of gneiss, which we will presently find to prevail in contact with the Primal slates further westward. Tracing the edge of the gneiss, it may be seen to pass about one mile and a half S.E. of the Paoli, or half a mile N.W. of the Leopard Inn, on the Darby Eoad. Here the rock is a more hornblendic gneiss than further eastward, and the change from this hard material, to the softer talcose micaceous Primal slates, is plainly visible in. the transition from a somewhat uneven surface to one of a lower level, having smoother outlines and softer undula- tions. Our line now crosses Crum Creek, near Mavis's Grist Mill ; and here the gneiss is in close proximity to the southern margin of the long belt of stratified serpentine, which originates in the talcose primal slates, about one mile S.E. of the Paoli, and more than one-fourth of a mile N. of the gneiss at that point. From Crum Creek, where a very hornblendic gneiss commences and ranges for many miles south-westward, its northern or north-western edge, coincident nearly with the southern border of the serpentine as far as Taylor's Run, passes about one mile N. of Sugartown, and the same distance N.W. of West Chester. Following the southern side of the valley of Taylor's Run, till it approaches the Brandywine, it crosses this stream below Taylor's Ford, and preserves its course westward to the vicinity of Marshallton, keeping near the road leading from West Chester to that village. In the vicinity of Marshallton and Trembleville this line seems to terminate, or to deflect rapidly southward ; for the north-western, or here, western boundary of the true gneiss, appears not to reach as far to the westward as the village of Union- ville, in East Marlborough Township. Of the Geological Structure of the Gneissic Region of the Schuylkill (See the Section.} A remarkable feature in the structure of the whole southern gneissic district, is the prevalence of a northward dip in the strata. This inclination prevails along the Schuylkill, with very few local and trivial exceptions, throughout all the three great subdivisions of the zone of gneiss, until we approach the upper or northern side of the third or northern belt. There the rocks for the first time, for any considerable width of outcrop, are contorted, folded, and lifted into a generally almost perpendicular dip. The ordinary or average angle of inclination of the strata may be stated to vary between 30 and 50, and the prevailing point of the compass to which this dip is directed is somewhere between N. 20 E., and N. 30 E., though occasionally it is nearly N., and in one or two instances it is N.E. From Philadelphia, the whole way to the Wissahickon, there exists no interruption to this general northward dip, and not until we approach the lower edge of Mana- yunk is it much undulated or contorted, and even there the undulations are within very narrow STRUCTURE OF GNEISSIC REGION. 79 limits, and produce very little reduction in our estimate of the thickness of the formation. At Fairinount the true dip of the rocks is very steep, approaching, indeed, to the vertical. The strata there are traversed by numerous conspicuous joints, presenting at a little distance a decep- tive appearance of a nearly horizontal stratification, in thick and almost parallel beds ; but this is not to be confounded with the genuine stratification or grain of the rock, as marked by the structural distribution of its mica and other minerals. Advancing northward, this steep inclination of the strata soon subsides, for along the shore of the river, from Lemon Hill to the Quarries below the Columbia Bridge, the ruling dip is in only one or two local spots steeper than 40, or even than 30. In the Quarries spoken of, it is in one or two places 50, and even 70. From the Columbia Bridge to the Wissahickon, and even beyond it, the rocks dip with remarkable steadiness at angles seldom lower than 20, and seldom higher than 30. Passing the Wissahickon, they begin to exhibit a series of local contor- tions, though but few of these contain a dip to the southward for more than a few yards. At two or three spots below Manayunk, the inclination is as steep as 50, or even 70, but at the town, and indeed as far up as the Sinnaminson Creek, a quite gentle slope prevails, the highest angle not exceeding 20 or 25, excepting at one locality of very narrow contortions . Above the Sinnaminsen, as far as the Greentree Run, the dips are a little more variable, and generally steeper, but nearly all are embraced between the angles of 30 and 50. In this part of the section the strata are more waved in their dip, though never thrown out of their prevail- ing northward declination. Approaching and passing the Greentree Run, we find them through a space of nearly 300 feet in an almost perpendicular attitude ; they soon, however, resume their dominant northward dip ; but from this point to the vicinity of the Soapstone Quarry, they pre- sent, for the first time, a succession of synclinal and anticlinal undulations. In this division of the section, the inclination of the strata still to a large extent towards the north is at all angles from 30 up to 70. It is worthy of note here, that the steatite belt itself gives evidence of containing a synclinal wave in the dip ; for the talc-slates and mica-slates to the south of it, for several hundred yards, dip steadily towards the north, at an angle of about 30, while those of the northern side of the Quarry show a steeper inclination to the south. Passing the Steatite Range, the northward dip is quickly resumed, and in this part of the Mica Slate Belt, both at the Schuyl- kill and on the Wissahickon, the slope is steeply towards the north. Entering now that division of our section which belongs to the Northern Belt of harder Felspathic Gneiss, we encounter the most irregularly dipping or undulating portion of the whole gneissic zone. Approaching the Quarries of Blue Porphyroidal Gneiss, at the lower limit of this tract, we meet with a steeply-compressed anticlinal axis in the strata, the line of the axis marked by a strong dyke of syenitic granite. Here the south dips are 70, and even steeper, while the north ones vary from 45 to 55. Passing the Quarries, we immediately encounter a wide space of more than a fourth of a mile, in which the rocks are almost horizontal, and towards the northern edge of this we perceive an axis or turn in the dip, marking a broad, regular, syn- clinal trough or basin. From the northern edge of this trough, to the upper limit of the whole gneiss formation, past the William Penn Iron-Furnace, No. L, the gneiss is closely folded, and compressed into very steep, or nearly perpendicular dips, with numerous short plications. If now we review these interesting features in the structure of this broad zone of gneiss, we can hardly resist the conclusion, that in the three belts passed over by our section, there are 80 SOUTHEEN ZONE OF GNEISS. really but two groups of rocks, a lower and a higher, and that the entire zone, viewed broadly, constitutes but one wide synclinal wave or basin, the harder felspathic and hornblendic gneiss dipping northward, throughout the whole southern belt or outcrop, and reappearing in steep and multiplied contortions on the other side of the trough, and the upper or more micaceous group of rocks filling the synclinal centre of the trough, and compressed into the lesser foldings which it exhibits, by the lateral force of the wide crust undulation, within which it has been caught, and folded. Of the Belt of Gneiss North of the Mooretown and Attleborough Range of Primal Sandstone. Between the southern edge of the Middle Secondary or Mesozoic red sandstone formation, in Bucks and Montgomery counties, and the southern range of Primal white sandstone, extending from Edge Hill to Morrisville, there is a nearly continuous long and narrow tract of Gneiss rocks, which in their composition seem to be identical with those of the northern belt, west of the Schuylkill. Indeed, from the fact of this identity, and from their lying in the same line of strike, the rocks of the two tracts must be regarded as belonging to one continuous zone of strata, interrupted at the surface only by the basins of the older Palaeozoic strata, which lie obliquely across the belt. It is not necessary to define it minutely in this place, further than to add to what has been now indicated, the statement, that at the western end of this area the gneiss runs forward in three points. The first and longest projecting finger of the belt is a con- tracting anticlinal outcrop, which is insulated from the middle finger by the narrow synclinal trough of Primal rocks, which passes the Pennypack Creek at Shelmire's Mill. From the Penny- pack, where it is rather more than a mile wide, this promontory of the gneiss ranges contracting in width, between the southern foot of Edge Hill and the northern border of the Mooretown and Attleborough range of Primal strata, until, south of the village of Edge Hill, it has a breadth not exceeding one quarter of a mile. Within a mile to the W. of this place it runs to a point, being saddled by the Primal slates and white sandstones of Edge Hill, or the eastern extension of Barren Hill. This is evidently an anticlinal elevation in the gneiss, and the axis is a very straight one, and of considerable length, being prolonged even to the Schuylkill, a distance of several miles beyond the point at which the gneiss itself sinks out of sight. The middle branch or finger of this area of gneissic rocks is much shorter than either the southern one, just traced, or the most northern, presently to be mentioned. It extends for about two miles westward of the Huntingdon Turnpike, to a point about one mile west of the Penny- pack, or to within three-fourths of a mile of Willow Grove. It is an anticlinal belt, embraced between the southern and northern synclinal ranges of the Primal sandstone, into which the eastern end of the limestone basin of Montgomery County forks. This gneiss may be seen on the Pennypack for about half a mile above Shelmire's Mill, and is again intersected, near its western termination, by the road leading south-eastward from Morgan's Mill to Blaker's Store. It terminates in a point about due south of Morgan's Mill. The most northern branch of the belt of gneiss rocks before us is in reality not continuously connected with the main tract, but is cut off from it by the encroachment of the southern edge of the red sandstone against the northern prong or basin of Primal white sandstone, in the vicinity of the Pennypack. The denudation of the red sandstone, W. of the Pennypack, and N. of Willow Grove, has exposed this patch of the gneiss through a length, bordering the northern side DETAILS WEST OF THE BRANDYWINE. 81 of the Camphill outcrop of Primal rocks, for as much as four miles, and through a breadth, on the Doylestown Turnpike, amounting to about one mile. Throughout these three western branches of the northern belt of gneiss, the strata are of the same hard massive character as those which constitute the northern tract W. of the Schuylkill, and S. of the Chester County Valley, and there can be no doubt that they are a prolongation of that range. The predominant varieties are hornblendic and felspathic gneiss, with a subordinate proportion of beds of the more micaceous kinds. Old Plumbago Mine, Buck's County. Near the Buck Tavern, on the New Hope Turnpike, there is an old mine of plumbago on the farm of Isaac Hogeland. A tradition states that black- lead was procured here more than a hundred years ago. After lying long neglected, the mine was recently reopened, but it is again in a state of dilapidation, atid no accurate observations respecting the vein or bed are at present practicable. NARROW RANGES AND LOCAL OUTCROPS OF GNEISS WEST OF THE BRANDYWINE CREEK. Southern Belt. Commencing our description of the more detached tracts of the harder horn- blende and felspar varieties of gneiss, constituting the general Southern Belt of the Southern Gneissic Eegion, where they begin to separate into anticlinal fingers, W. of the Brandywine Creek, the first band we have to notice is one which crosses that stream in the vicinity of Chadd's Ford. This runs towards the western end of Pennsbury Township. The principal variety of the rock at Chadd's Ford is a dark blue and speckled hornblendic gneiss. This anticlinal outcrop seems to end within two miles of the river, but, in the same line of strike, a rock of the same composition is uplifted through the newer strata, in two or three detached broken ridges, all the way to the East Branch of Redclay Creek at Pierce's Paper-Mill. It is probably an extension of the same anticlinal range. As already mentioned, the Gneiss Rocks basin a little below Chadd's Ford, and in the line of this basin, rests, further westward, a trough of crystalline Auroral limestone, with some Primal sandstone. South of this trough, a much broader tract of the gneiss branches forward toward the W., bounding the Kennet Square Basin of Limestone and its eastern branch, on their south. This belt embraces both hornblendic gneiss and the ordinary grey felspar and mica rocks, the latter being sometimes quite micaceous and full of large garnets. Approaching the East Branch of Whiteclay Creek, this tract of gneiss begins in turn to subdivide, and at the intersection of that stream it breaks up into three narrow tapering fingers, apparently subsiding anticlinal outcrops, which terminate at, or a little to the westward of, the Middle Branch of Whiteclay. The most northern of these bands crosses this stream a little below Moor's Grist-Mill, the middle Fork reaches it about Wickersham's Mill, and the southern crosses it to the southward of Pennock's Factory, to extend apparently nearly one mile further westward. Between these narrow siibsiding belts of the gneiss lie narrow troughs of micaceous and talcose slate, identical, in crystalline and other characters, with similar rocks further N., which I have unhesitatingly referred to the Primal Slate series. The predominant rock in these narrow outcrops of gneiss is the hornblendic variety. VOL. I. L 82 SOUTHEEN ZONE OF GNEISS. South of the detached fingers of gneiss above described, runs a much more extended and broader tract of the same rock, across the Whiteclay Creek above its forks. The northern edge of this passes the little manufacturing village of Chandlerville, on the East Branch of Whiteclay, and its southern border adjoins the narrow basin of crystalline limestone which includes Nevin's Quarries. This belt stretches towards Kemblesville. At the main fork of Whiteclay Creek, and for half a mile N.W. of this, we have the broken outcrop of the gneiss, some of the beds of which are of the prevailing hornblende variety. This bounds the trough of limestone on the S.E., and it ranges south-westward into the N.E. corner of Maryland. Middle Belt of Gneiss on the Brandywine. Turning next to the middle tract, or that of more micaceous gneiss, we may state briefly, that wherever it displays itself on the Brandywine above Brinton's Ford, or between Brinton's Ford and the main fork of the stream, it is a somewhat decomposable rock, consisting of the ordinary triple mixture of quartz, felspar, and mica, with some strata of thinly-bedded hornblendic gneiss and numerous layers of very micaceous gneiss, full of large garnets. In this group occasionally occur thin bands of a granite-like gneiss, disposed in very regular parallel beds, and having a square fracture, which confers on it an aspect and structure resembling the white Primal sandstone when greatly altered. This gneiss much resembles some members of the formation between Fairmount and Manayunk. Many contortions occur in this zone on the Brandywine, but the prevailing dip is chiefly to the S.E. Northern Belt of Gneiss near the Brandywine. A very similar rock to that just described as occurring below the forks of the Brandywine, occurs in the vicinity of Taylor's Ford, and Avest- ward from the river towards Marshallton and Trembleville. I conceive it to be not at all improbable, that the northern zone of more massive gneiss, in passing West Chester, subsides towards or beyond the Brandywine, and is there saddled over and swept round by the newer group of more micaceous felspathic gneiss, here interposed between the hornblendic variety and the talcose Primal slates. This, at least, is the most feasible view we can adopt, from the defective data afforded, after a diligent and careful study of the district. The stratification and composition of the strata are necessarily so obscure from extensive metamorphism, and from the occurrence of many imperfectly traceable anticlinal and synclinal \inclulations, that it is next to impossible to define sharply the respective limits of the formations. CHAPTER II. MIDDLE ZONE OF GNEISS, OE THE GNEISSIC ROCKS BETWEEN THE NORTH VALLEY HILL OF CHESTER COUNTY AND THE SOUTHERN MARGIN OF THE MIDDLE SECONDARY RED SANDSTONE. Boundaries. Having described the Gneiss, S. of the limestone basin of Montgomery and Chester, and of the red sandstone in Buck's County, in its several belts and outcrops, and under its different aspects, we come next to the interesting area of the same rocks W. of the Schuylkill, and between the North Valley Hill, as a southern boundary, and the southern margin of the Mesozoic red sandstone and the base of the Welsh Mountain as its northern. From a spot about half a mile west of Valley Forge as its eastern point, the southern edge of this broad belt of gneiss ranges continuously, along the northern base or side of the North Valley Hill, in a direction about S. 70 W., the whole way to the Western Branch of the Octorara in Lancaster County. The northern, or rather the north-eastern boundary, formed by the southern overlapping edge of the red sandstone, is a gently curving line, commencing at the eastern point near Valley Forge, already designated, and terminating at the eastern end of the Welsh Mountain near the county line, between the counties of Chester and Berks. Traced in detail, it passes Wheatley's Lead-Mine near Pickering Creek, crosses that stream at Kenzie's Mill, and then, with a gentle sweep convex south-westward, it passes immediately by the little village of Kimberton. From this point its course is nearly straight to Coventry Village, opposite the junction of the two branches of French Creek. It crosses, in this course, the main French Creek about two miles N.W. of Kimberton, and follows thence to Coventry the north side of the French Creek Valley, except at one bend of the stream opposite Pughtown, where the line for half a mile takes the southern side. From Coventry Village, the boundary between the gneiss and red sandstone, trending first a little N. and then slightly southward, runs nearly due westward for more than seven miles, to the north-eastern point of the main ridge of Welsh Mountain near the village of Springfield. But there is an insulated belt of the gneiss situated a short distance to the N. of this boundary, on the North Branch of French Creek, and this may be more strictly viewed as the northern extension of the formation. The north-western limit of the wide tract of gneiss before us, is traceable from the sources of Pine Creek, a tributary of the North Branch of French Creek, south-westward along the south- eastern base, first of the eastern spur of Welsh Mountain to Springfield, and from thence along the base of the main AVelsh Mountain, over the Lancaster County line N. of the little village of Cambridge, to within two miles of the western end of the ridge. Viewed broadly, this whole area of the gneissic rocks divides itself westward into two main spurs or broad fingers, the shorter and more northern one terminating at the point just indicated, some two miles E. of the western end of the Welsh Mountain ; while the southern, and much longer, extends forward between the North Valley Hill, and the southern base of Mine Eidge, to the North-west Branch of the Octorara, already stated as the westernmost limit of the whole 84 MIDDLE ZONE OF GNEISS. tract. This division of the gneissic area into two western branches is the result of two wide anticlinal undulations, and the reception between them of a broad synclinal belt of the Primal strata, penetrating the gneissic region eastward from the head- waters of the Pecquea in a gradually contracting basin, extending as far as the North Branch of the Brandywine in West Nantmeal Township. This synclinal belt of Primal rocks, a prolongation from the limestone basin of the beautiful and fertile Valley of the Pecquea, is itself a complex trough, penetrated from the eastward by two narrow anticlinal spurs or fingers of the gneissic rocks, causing it to branch into three subordinate troughs. The gneiss may therefore be described as throwing, towards the W., two large and long anticlinal belts, and between these, two others, much shorter and narrower. These latter start off from the main southern division in the neighbourhood of the West Branch of Brandywine, and extend for a few miles a little S. of W., the southern one to a point about one mile E. of the little village of New Italy, and the northern one to about two miles E. of Compassville. The relations of the geological structure of this district to its topography are such, that the gneissic rocks for the most part constitute the valleys, while the Primal strata form the ridges between them ; the one material being easily eroded, and the other, consisting mainly of hard, firmly cemented, and even semi-vitreous sandstone, opposing a superior resistance to the exca- vating action of the waters which shaped the surface. To define now somewhat more exactly the limits of the two principal ranges of the gneiss, or what is the same thing, the southern limit of the Northern belt, and the northern limit of the Southern one, we may state that the first line commences at the West Branch of Brandywine, near Ackland's Grist-Mill, and running almost due westward, follows the south side of the South Branch of Indian Run, leaving the Manor Presbyterian Church to the S. of it about half a mile. Thence, after crossing the West Branch of Brandywine, near M c Duff's Grist-Mill, the boundary between the formations coincident, nearly with the north base of the barren ridge of Primal white sandstone, extends along the south edge of the valley of Twolog Run, beyond which it crosses the county line about one mile and a half S. of the village of Cambridge ; and now deflecting northward, and in one mile more, turning again westward across the Pecquea, it runs for three miles further towards the W. end of the Welsh Mountain, to unite with the north- western boundary of the same area of gneiss, already indicated as ending at this point. This wide finger of the gneissic district is bounded, in its western portion on its southern side, by a narrow belt of Primal sandstone and slate, separating it from the limestone of the basin of the Pecquea. Turning now to the northern limit of the Southern or longer belt of the gneiss rocks, we may approximately define it as crossing the West Branch of the Brandywine, near Waggon Town, and as extending thence towards the W.S.W. along the northern side of the valley of Rock Run, till it crosses Buck Run north of Morris's Grist-Mill, or more than half a mile N. of the E. Sadsbury Friends' Meeting-House. Thence it ranges more nearly westward, to the vicinity of the Mine Hill Gap, passing near the Black Horse. From the Mine Hill Gap, the line, coincident throughout nearly its entire length with the southern base of Mine Ridge, pursues a direction somewhat more southward, till it passes Copper Mine Run in the vicinity of the old copper mine, from which the Mine Ridge derives its name. Beyond this point, to the western extremity of the visible zone of gneiss, the northern boundary observes a course very nearly towards the S.W. GNEISS NOKTH OF CHESTER VALLEY. 85 It unites with the southern limit a little W. of the North-west Branch of Octorara Creek, where the belt of gneiss thus bounded ends in an acute point, enclosed by the North Valley Hill and the southern spurs of the Copper Mine Ridge. There remains to be described only one other subordinate tract of these gneissic rocks, that of the Northern Branch of French Creek. This is insulated superficially from the main area of the gneiss by a long narrow tongue of the Mesozoic red sandstone, and its dykes and ridges of trap-rock extending from Rock Run, where it forks away from the main area of red sand- stone, and runs westward to the County line just N. of Springfield. The narrow strip of gneissic ground thus cut off from the main country of gneiss, by the above-mentioned tongue of sandstone, commences in a point near Rock Run, spreads to a width of nearly a mile N. of the Warwick Iron-Mines, and then contracts again, passing the Hopewell Iron-Mines, till it ends in its western point N. of Springfield. This insulated outcrop of ancient gneiss is an exceed- ingly interesting mineral zone. It includes those well-known, remarkable, mineral localities familiar to the mineralogists of the State, as the Knauer Town Copper-Mine, Steel's Iron Pits, and the Iron-Ore Mines of the Hopewell Furnace, all of which will receive a sufficiently detailed description in a future chapter. Character of the Gneiss Rocks N. of the Chester County Valley. A marked difference is presented between the gneissic region N. of the Chester County Valley, and that already described lying S. of it. In the latter district there occurs, as we have seen, a great diversity in the composition of the rocks of the older metamorphic class ; there being an abundance, if not a prevalence, of the softer micaceous varieties, and a general deficiency of the more massive granitoid kinds. Here, on the other hand, we encounter chiefly the granite-like varieties of white felspathic gneiss, with hard hornblendic gneiss, such as constitute the typical gneiss rock of the central ridges of the South Mountain, or Highlands between the Delaware and the Schuylkill. By far the most prevalent variety is a felspar-quartz rock, of a greyish white colour, holding only a subordinate amount of mica, and disposed in comparatively massive beds. Certain of the more minutely granulated sorts, of a whitish aspect, resemble so nearly some portions of the Primal white sandstone when excessively crystalline from metamorphic action, that to discrimi- nate between the two formations is by no means easy, but demands the closest care. Nor is this to be wondered at, for the composition of the white Primal sandstone is often just such as would be derived from a white felspar and quartzose gneiss of this description. Micaceous gneiss does occur in the area before us, but nowhere in outcrops of any considerable breadth ; and true mica-slate except merely in thin subordinate layers has been nowhere met with. Towards the northern side of the region there would seem to be a larger relative amount of massive hard hornblendic gneiss, while centrally, and along the southern border, the white felspathic sort is by much the most abundant. Of the Undulated Structure of the Gneiss District, N. of the Chester County Valley. That the wide area of gneiss now under description is undulated in a succession of anticlinal and synclinal waves, is obvious to any practised geological observer who studies its structure with due care. Indeed, the evidence furnished by our map and sections is even more conclusive, as regards this feature, than it is for the gneiss region south of the Limestone Valley, for in that district the closely folded and convulsed condition of the strata renders the detection and tracing of the anticlinals of the gneiss extremely difficult, while here the undulations are, in the main, more 86 MIDDLE ZONE OF GNEISS. open, symmetrical, and susceptible of continuous tracing. Along the northern or north-eastern "border of the district, especially S. of the Valley of French Creek, the topographical features, of themselves, plainly suggest the presence of a succession of anticlinals. The present margin of the red sandstone marks pretty evidently the approximate ancient shore-line of that wide estuary, which floated the sediments to form the red sandstone ; and this shore-line was determined by the northern sides, and eastern ends, of a succession of hills or anticlinal ridges, which kept off the waters from the country further south. It is only necessary to travel down the Valley of French Creek, from Knauer Town to Kimberton, to recognise the probable truth of this picture. The notion of an undulated or folded structure in the gneiss, finds corroboration in the parallel arrangement of the hills and valleys, and in the sudden changes in the dip of the strata, where- ever we make a transverse section through the region ; but it receives its most positive demon- stration when we study the topography and distribution of the gneiss on the western side of the county. There, as we have already seen, several long tapering tongues of the Gneiss formation project forward towards the W., including between them actual troughs of the Palaeozoic rocks, a feature not attributable to any other mode of elevation of the gneiss than that of an undu- lation of its general floor, in the manner of long anticlinal waves. Some of these waves, no doubt, are so closely compressed, or folded, and others are so irregularly dislocated, as to render the analysis of them obscure or even impossible, yet the geology of the country clearly estab- lishes their presence. Faults. Even in the more central tracts of the district, we are presented with some interest- ing evidences of these crust-undulations. I allude now to a succession of parallel dislocated syncli- nal axes, running through West Pikeland and West Vincent townships. Though externally the presence of these faults with a synclinal clipping of the strata is not recognisable in any exposures of the strata, the artificial development of the ground, in a series of excavations for valuable deposits of iron ore, has recently enabled me to discover their existence and true structure, and to show that all the principal accumulations of ore are seated upon them. These faults are all connected with the trough-like or synclinal position of the strata supporting the ores. But the most conclusive proof of undulations in the gneiss, and one which accounts for the presence of these deposits of iron ore, is the occurrence at almost every dislocation of an insulated patch of the Mesozoic red sandstone. The iron ore usually rests in a cleft or deep narrow trough, confined between steeply-dipping beds of gneiss, or a wall of granite on the one side, and moderately steep south-east dipping strata of the red sandstone, within or behind which no ore is ever found, on the other. These strata of red sandstone are invariably highly altered and crystalline, for they contain frequently minute crystals of mica, specular iron ore, graphite, and even felspar. Yet, in other layers of mottled and half-baked red shale, in close alternation with these more altered ones, we see proof of their unquestionable identity in composition and origin with the red sand- stone formation, from the general southern margin of which, some of them are separated by an interval of four miles. It seems highly probable that, at the completion of the red sandstone deposit, there were several very narrow troughs of it, reposing within some of the deeper valleys lying between the hills of the basin of Pickering Creek ; and that at the time of the elevation of the formation, or possibly, contemporaneously with the movements which accompanied the injection of the mineral veins of the Phcenixville and Perkiomen district, these troughs were dislocated longitudinally, and all the superficial red sandstone washed away, except those narrow IRON ORES. 87 strips which were caught or nipped within the broken synclinals between the sides of the faults. In this manner we may readily account for the existence of these outlying narrow belts of the red sandstone, and for the presence of the deep and rich deposits of hematitic iron ore which they contain, and which have evidently been derived by percolation from thin strata, by the long-continued trickling of the surface-waters in the lines of fracture. Above the Friends' Meeting-House, a bed of a singular, hard, hornblendic rock crosses the road, appearing also on the road leading from the Yellow Springs to the Eed Lion, two miles above the latter place- Pipe-clay occurs in Uwchlan Township, in considerable abundance. Graphite is said to occur in West Nantmeal, disseminated through blue quartz, but none was met with. IRON ORES OF THE GNEISS. Brown Iron Ore, or Hematite, of the Basin of Pickering Creek near the Yellow Springs, and the Geological Conditions under which it occurs. Allusion has already been made to the deposits of brown hematitic iron ore in West Pikeland and West Vincent townships in the Valley of Pickering Creek ; and it was stated that these, with very few exceptions, are in cl6se relation with lines of sudden fracture, or parallel longitudinal faults, ranging along the lesser valleys of the district ; it was intimated, also, that these dislocations are only so many ruptured synclinal troughs, enclosing narrow belts or outcrops of a material which, by all lithological analogy, can only be referred to the Middle Secondary red sandstone, altered more or less by some igneous metamorphic agency. I shall now offer to the reader some sketches of the three or four principal deposits in the neighbourhood of the Yellow Springs, which have been developed by mining, and which serve best to disclose the law which seems to regulate the distribution of the ore. Commencing with the most north-eastern principal excavation the first which we meet with is one about a mile and a half N.E. of the Yellow Springs on the new road to Kimberton, and on land owned by Mr Lewis. Leivis's Ore Bank. This deposit, of which a considerable quantity of good brown hematite is now sent to the Ironworks at Phoanixville, rests in a triangular cleft or narrow trough between steeply-dipping gneiss rock on its S.E., and more gently-pitching altered red sandstone and shale, declining south-eastward at an angle of 45 on its N.W. White felspathic granite occurs near the southern wall of the fissure. The ore itself is confined almost entirely to the loose earthy matter occupying this long open trench, very little of it penetrating the adjoining rocks. It is a somewhat sandy variety of ordinary brown iron ore. The excavations here, all of them open to the day, extend to a depth of between 30 and 50 feet below the level of the soil, and their longitudinal distribution is N.E. and S.W., for this is the direction of the trough which includes the ore. Some of the more altered, or highly crystalline fragments of the red sandstone, contain numerous flat plates or spangles of plumbago, besides crystals of specular oxide of iron. The more argillaceous layers of this oiitlying fragment of the red sandstone formation, exhibit a less degree of alteration from the normal aspect of the red shale, though they are generally mottled and much discoloured, and even sub-crystalline, and speckled with minute centres of segregation. The topographical relations of this gulf between the strata, con- taining ore, are just such, it should be observed, as we might look for upon the assumption of a synclinal flexure in the strata, with or without a disruption. In other words, the line of the 88 MIDDLE ZONE OF GNEISS. fault or fissure is centrally along the bed of a narrow but quite extended valley ; and it should be mentioned, that such are the external conditions under which we find nearly all the larger deposits of iron ore in this district. It may not be amiss to state here, that it is in this same line of valley that we find another collection of hematitic ore a little more than one mile to the N.W. of the Yellow Springs ; and it is an interesting fact that the bed of ore, a little S. of Kimberton, lies almost exactly in the same line. I would not, however, here wish to intimate, that either of these two last-mentioned deposits can be recognised as occupying the line of fault in the strata in which we recognise the loose ore. It seems probable, indeed, that the western deposit is not connected with any synclinal trough in the rocks, but is the result of an extensive decomposition of very ferruginous beds of the gneiss. Possibly, however, this part of the valley, like that at the Lewis Mine, may once have been overspread by a narrow thin capping of fer- ruginous red shale and red sandstone. Fegeley's Ore Beds, near Yellow Springs. About half a mile N.E. of the Yellow Springs, two rather extensive excavations have developed a large deposit of the brown iron ore ; one of which is known as Fegeley's Mine. They occur in the bed of a little narrow valley which runs just N. or back of the high hill, at the S. base of which the Yellow Springs are situated, and which is separated from the valley containing the Lewis Ore Bed by a narrow belt of gneissic hills. Both of the ore pits at Fegeley's, lie within one long trough or trench in the strata. This is embraced by steeply-dipping and twisted beds of micaceous gneiss on one side, and by a narrow outcrop of altered red sandstone on the opposite or N.W. side. This sandstone dips south-east- ward, at an average inclination of about 40, to abut apparently against the wall of gneiss rock, making with it a long, deep, narrow trough or trench, 100 feet or less in width at the surface, and in many places perhaps as deep. Irregular injections of half-decomposed felspathic granite penetrate the gneiss of the southern wall of the basin. Ore occurs, confusedly mingled in with the rotted materials of the gneiss and granite, but the main body of the ore is in loose earth resting against the N. sloping wall of red sandstone. The principal excavation at Fegeley's Mine is about 200 feet long, 100 feet wide, and 50 feet deep ; but ore is known to exist in many places in the bottom of the pit. The irregular bed of ore itself is about 40 feet wide. The outcrop of red sandstone which bounds this line of iron ore on the N.W. forms a low ridge, not more than 200 yards broad, traceable, at intervals at least, by the soil and surface fragments for half a mile or more N.E. and S.W. All topographical indications suggest, that exploration should be made for ore in the line of prolongation of this ore-deposit of Fegeley's. A short distance to the N.E. of Fegeley's chief ore-pit, there is a yet larger one in the next field, accompanied by corresponding geological features, and where likewise the ore dips to the S.E., reposing against a slanting wall of altered red sandstone. In the bottom of this pit the bed of ore has a thickness or width of about 12 feet. A careful inspection of the ore and all the attendant phenomena disclosed in these excava- tions, cannot fail to suggest the notion, that the ferruginous red sandstone is the source of the iron ore, and that it has yielded it up by a process of filtration and percolation of the surface waters, by which it has been carried down into the cleft between the rocks, and left there to concrete. The average annual yield of Fegeley's Mine is about 2400 tons. It is conveyed to the furnaces at Phcenixville. The mine adjoining Fegeley's, yields yearly about 2000 tons. IRON ORES. 89 ORE-DEPOSITS SOUTH-WEST OF YELLOW SPRINGS. Latschaw Mine. A third line or narrow belt of iron ore occurs to the S.W. of the Yellow Springs, commencing probably in the meadows of the Valley of Pickering Creek. S.E. of this attractive place of public resort, two principal mines are seated along this line : one about three- fourths of a mile S.W. of the Springs, known as the Latschaw Mine ; the other, about three- fourths of a mile further S.W., called generally the Steitler Ore Bank, owned by Reeves, Buck, & Co. of Phcenixville. These are seated apparently on one line or fault, which brings in contact in a narrow trough, a long narrow outcrop of Middle Secondary red sandstone and steeply- dipping beds of Gneiss. Nearly the same geological conditions prevail at both of these mines, namely, crushed beds of red shale or sandstone dipping to the S.E., and abutting against nearly perpendicular strata of gneiss, with, generally an intervening vertical wall of white felspathic granite in a more or less decomposed state. In the Latschaw Mine, the stratum of red sandstone seems to have been caught in a deep fracture in the gneiss, and>greatly squeezed and crushed. The iron ore reposes on the slanting face of this compressed mass of sandstone and of shale, and is even dispersed or mingled through its fragmentary materials along the line of the fault. So crystalline is the red shale and sand- stone, and so full of scales of segregated mica and plumbago, that the observer is sometimes at a loss to decide, from hand specimens, whether the rock is really an altered sandstone or a variety of gneiss. The Steitler Ore Bank. This valuable deposit of iron ore, evidently lying in the same great fissure in the gneiss which contains the Latschaw deposit, fills a deep triangular trough between beds of crushed red sandstone on the N. side dipping S., and a perpendicular dyke of white felspathic granite, which bounds the gneiss and forms the southern wall of the fissure. Except in the existence here of a more regular and massive dyke of granite, the geological conditions under which the ore occurs are almost identical with those which prevail at the Fegeley and Lewis Mines in the Basins N.E. of the Yellow Springs. The annexed Sketch represents the relations of the ore, and of the different strata to each other. The Steitler Ore Bank has been wrought for the past eight years without interruption, yield- ing annually from 3000 to 5000 tons. It was first worked some fifty years ago by a Mr Van- leer. The ore from this mine is rich, and generally of excellent quality. A little black oxide of manganese, and also a little sul- phuret of iron, are occasionally found with the ore. Very beautiful masses of fibrous haematite, some of them delicately stalactitic, are frequently met with in this mine, which contains a more than usual abundance of those hollow geodes, which are sometimes called Bomb- shell Ore. It is not uncommon in this and other kindred deposits to meet with beautifully white plumose mica, enclosed within these and other cavities of the ore. The source of such mica, so insulated, is a point of much interest in the theory of the origin of crystalline veins and minerals, and every occurrence of this sort may furnish food for chemico-geological speculation. Jones' Mine, near Yellow Springs. This small excavation for iron ore is near the Latschaw VOL. I. M FIG. 1. Steitler Ore Bank. 90 MIDDLE ZONE OF GNEISS. Mine, but not upon the same line with it, being seated upon another rupture in the strata, about one-eighth of a mile S. of that. At this pit there seems to be a line of fault in the strata, filled with fragments of gneiss, of intrusive white granite, and of highly-altered crystalline red sand- stone. The iron ore, in a crude and sandy state, is interspersed through this confused mass, which it serves more or less to cement. On the South side of the trench containing the ore, we meet, as usual, with steep strata of gneiss, and on the North side with South-east-dipping beds of a rock which, from its highly crystalline condition, and its abounding in mica and in specular iron-ore, greatly puzzles the observer to determine whether it also is gneiss, or a highly-metamorphosed form of the argillaceous re( i sandstone. This mine is not at present deep enough to exhibit the geological phenomena in that distinctness under which we witness them Fio. 2. Jones' Mine. r at the Steitler and the Fegeley Mines, and some doubt must remain whether we have here another outlying narrow belt of the red sandstone or not. Here is a little sketch, which is deemed to represent correctly what is actually visible at this opening in the strata. Iron Ore in Uwchlan Toivnship. Iron ore occurs on the West Chester and Pottsgrove State Road, one-fourth of a mile N. of the Little Eagle Tavern in Uwchlan Township. It occurs in gneiss, and evidently at a fault in the strata, and some of the fragmentary rock adjoining. The ore resembles much the altered red sandstone of other ore localities. This ore has not been much explored, and the two or three pits here dug are very superficial. On nearly the same line or strike, similar iron-ore may be recognised near the Morgantown Road, on a farm of Morgan Hoffman, and a small ore pit has exposed good ore in a field, owned by William Parker, nearly in the same line, which coincides almost precisely with the strike of a narrow belt of sparry limestone, which ranges through Morgan Hoffman's farm to George Downing's. AVhether this limestone is a true igneous dyke or vein of carbonate of lime, or a closely-compressed synclinal trough of sedimentary limestone metamorphosed by heat, I will not undertake to say. It extends about a mile and a half in a straight line. It is an interesting fact, having some bearing perhaps upon the question of the origin of the iron ores I have been describing, that several of these deposits adjoin, if they are not closely connected with, outcrops or outbursts of limestone. This is the case at the Lewis Ore Bank, where, it is said, a narrow strip of limestone has been uncovered in the excavations for ore. It is likewise true of the locality of Kimberton, where a small exposure of highly-crystalline sparry limestone, with spangles of plumbago, occurs within 100 or 200 feet of the limestone, and we have seen that it obtains also in regard to the ore at William Parker's, which is evidently adjacent to the limestone belt of Morgan Hoffman's farm. CHAPTER III. NORTHER'N ZONE OF GNEISS, OR GNEISSIC EOCKS NORTH OF THE MESOZOIC RED SANDSTONE. GNEISSIC KOCKS OF THE SOUTH MOUNTAINS. Boundaries. The South Mountains between the Delaware and Schuylkill Rivers, though of comparatively humble elevation, constitute part of a great mountain system, which extends through New Jersey and New York under the name of Highlands, and through Maryland and Virginia under that of the Blue Ridge. Entering Pennsylvania at the Delaware River, they occur as a broad tract of nearly parallel but irregularly- connected ridges, ranging in the direction of their length from the N.E. towards the S.W., and having an average breadth of from seven to nine miles, until we approach, the Schuylkill. These ridges rarely possess a height of more than 400 or 500 feet above their adjoining or included valleys ; though their bold undulating outlines, and the rugged steepness of their slopes, clothed usually with forest, give to their scenery a prevailing mountain character. Enclosed among these hills, as in so many basins, lie several soft and fertile little valleys, the soil of which reposes on the beds of our Appalachian Auroral limestone. The materials, not only of the well-defined ridges, but of the elevated portions of the tract generally, are either rocks belonging to massive and thick-bedded varieties of gneiss, or they consist of the Primal white sandstone, the lowest in geological position' of our older or Palaeozoic secondary strata. To the nature of these materials, and to the violence of the uplifting action to which they have been sub- jected, we must ascribe the rugged and sterile character of these hills. Owing partly to the greater intensity in the quarter next the Delaware of the subterranean disrupting forces, partly to the less thickness in this direction of the white sandstone overlying the gneissic strata, these latter are here much more extensively developed than they are further Westward towards the Schuylkill. Before entering upon a more detailed account of the areas occupied by the several formations constituting the range of hills before us, let us trace the general boundaries of the whole belt, and show how it is related in geographical and geological position to the other tracts which confine it on the N.W. and S.E. We shall then be prepared to delineate hereafter with precision the situation of the irregular insulated patches of limestone, sandstone, and other materials embraced among these hills. Geographical Range of the Rocks of the South Mountains. Tracing, in the first place, the South-eastern limit of the tract, we find it to coincide pretty accurately, along its whole extent from the Delaware to the Sclmylkill, with the North-western margin of the Mesozoic red shale and sandstone rocks, which spread to the S. so extensively through Bucks and Montgomery counties, and which here overlap and conceal the group of rocks we are about to describe. At the Delaware River, the boundary in question passes close to the little village of Monroe, 92 NORTHERN ZONE OF GNEISS. being more exactly marked by a small stream which flows at the base of the hills. Taking a course somewhat W. of S., the line runs about three-quarters of a mile N. of Bursonton ; then crossing Durham Creek, ranges westward to the vicinity of Opp's Tavern, beyond which it bears to the N.W., approaching Leitz's Tavern about two miles S. of Hellertown. From this point the line of division between the two classes of rocks ranges in a direction a little S. of W., until it meets the South Branch of Saucon, about half a mile N.W. of Cooperstown. Here turning rather abruptly, and assuming a nearly South-western course to the head of Hasacock Creek, which it pursues for some distance, it sweeps more to the W. and passes out of Lehigh into Berks, crossing the line not far from the Northern corner of Montgomery. Entering Berks County, the line crosses the Sumanytown Eoad a short distance to the N.W. of Eitz's Inn ; then taking a course about 50 S. of W., and nearly parallel with the Montgomery County line, it ranges N. of the northernmost of the two Meeting-Houses in Hereford Township, keeping a little S.E. of Mount Pleasant Iron-Mine, and crossing Swamp Creek about a mile above the county line. It next ranges through Boyerstown to Ehoads' Mill on Ironstone Creek, keeping S. of the road to Kline's Tavern, and curving at the same time Westward and then North-westward, it passes the Manatawny Creek a little below the line of Amity Township. From this point the margin of the tract ranges N. of W. to the intersection of the Limekill Creek and the Township Road of Oley and Exeter. Here it turns again South-westward to follow a somewhat undulating line to the Schuylkill, crossing in its route Monokesy Creek a quarter of a mile, S. of Snyder's Mill, then passing near a little church, crossing Eauch Creek, and finally curving round the base of the Neversink Hill to the river. Along the whole of the line just traced, the Gneissic rocks and the Auroral limestone, where this occurs, are overlaid unconformably by the edge of the Middle Secondary red sandstone. In several neighbourhoods, however, the precise line of junction of the two sets of rocks is difficult to trace, owing to the quantity of soil, gravel, and fragmentary matter lodged near the base of the hills ; this is the case, for example, between the South Branch of the Saucon and the Hasa- cock. In other places, which will be alluded to hereafter in detail, the overlying rock is not the ordinary red shale and sandstone of the middle secondary series, but a coarse, variegated, and more or less calcareous Conglomerate, identical in geological situation and in aspect with the rock commonly called Potomac Marble. The North-western boundary of the belt of hills before us corresponds very nearly with the South-eastern edge of the great limestone formation of the Kittatinny Valley. Taken as a continuous line, it begins at the Delaware Eiver, about two miles below the town of Easton. From this point it forms a somewhat undulating border, stretching to the W.S.W. to within two miles of Maiden Creek, a tributary of the Schuylkill, where it suddenly curves to take a direction nearly due S. to Eeading. In the earlier part of its range, this line coincides almost exactly with the Northern base of the Lehigh Hills, maintaining thus, from the Delaware to Allentown, a course parallel to the Southern bank of the Lehigh, from which it nowhere far recedes. South-westward from the vicinity of Allentown, the edge of the limestone bounding the tract may be traced by Emaus, Millerstown, Metztown, and Walnut-town, to the curve near Maiden Creek already alluded to, where, sweeping S., it passes Solomon's Temple, and takes thence the road leading to Eeading. GNEISS OF THE SOUTH MOUNTAINS. 93 Though the line just traced marks the general North-western boundary of the South Moun- tains, there occur several small detached hills, lying beyond it to the N.W. The longest and most elevated of these is Chestnut Hill, near Easton. This, which is properly a spur of the general chain in New Jersey, consists chiefly of the gneissic rocks. Another small ridge, consisting also of gneissic rocks, lies in a bend of Monokesy Creek, about three miles N. of Beth- lehem. A third still smaller elevation occupies the bend of the Lehigh immediately E. of Allen- town, keeping for some distance the Northern side of the river. Mittbaugh Hill. "Westward a few miles from Beading there is an insulated tract of gneiss, forming, with the sandstone of Millbaugh Hill, an elevated district, the last of the chain of the Highlands. Between the Schuylkill and Cumberland County, this is the only representative of the South Mountains of our State. The tract is about nine miles long and two wide, and extends from the Cacoosing into Millbaugh Hill. Its structure is displayed in the General Section No. V. I shall now exhibit in detail the geological composition and structure of this chain of hills, following the general plan of description already laid down, and tracing the belt from the N.E. towards the S.W. Composition and Structure. The rocks which compose this belt of hills between the Delaware and Schuylkill Eivers, appertain to three formations : one group belonging to the Gneissic system, another to the Palaeozoic Primal sandstone, and a third to the Palaeozoic Auroral limestone. The gneiss and the sandstone enter cliiefly into the ridges and hills, while the limestone, the upper- most of the three, partially occupies the synclinal valleys. As the sandstone and limestone formations are members of the great Appalachian Palaeozoic system of strata, the delineations of their boundaries and features will be reserved for a future chapter, and my present descriptions will relate only to the rocks of the Gneissic or older metamorphic class. The gneiss of this Northern Belt differs considerably, in its features and constitution, from that of the southernmost tract already described. It is for the most part a massive rock in thick beds, bearing much analogy in appearance to common felspathic granite, except that it is distinctly stratified. Its prevailing character is that of a mixture of felspar and quartz, with but little mica. Sometimes it is a triple mixture of felspar, quartz, and hornblende, and not unfrequently the magnetic oxide of iron is disseminated among these constituents. In certain belts of the Highlands in New Jersey, this last-mentioned mineral is so common an ingredient that it might almost be termed one of the characteristics of the rock. In this felspathic or granitoid gneiss there is present very little mica, talc, or chlorite, or any of the laminated minerals of this order ; nor does the chain contain any extensive beds of micaceous, talcose, or chloritic slates, such as occur in the Southern Belt. In the arrangement of the materials of the gneiss there is an obvious tendency to a certain parallelism of the crystals, especially the felspar and hornblende, which are frequently of a flattish form, and occupy thin alternating layers in the rock. This marked difference in the composition of the predominant rock of the two gneissic ranges must be ascribed to an original difference in the chemical nature of the strata, from which each of these sets of crystalline rocks was formed by metamorphic agencies. Besides the essential want of correspondence between the two regions in the gneiss itself, I have stated that this Northern range contains little or no talcose slate. This is to be explained by the circumstance that in the 94 NORTHERN ZONE OF GNEISS. Eastern part of the South Mountains, and throughout the chain of the Highlands in New Jersey, there is a general absence, in the lower portion of the Appalachian series, of those slates which, further towards the S.W., adjoin the Primal white sandstone, and which, through igneous action, have been metamorphosed into the talcose and chloritic rocks of those districts. In its geological structure, the chain of the South Mountains or Highlands, between the Dela- ware and the Schuylkill, presents us with a beautiful example of a belt or group of parallel and somewhat closely-compressed anticlinal and synclinal flexures. A glance at the three general Sections, Nos. II., III., and IV., and at the local sections of this chain, will suffice to show the nature of these bold undulations. It will be seen that from one end of the range to the other, the gneiss, and the older Appalachian strata in contact with it, are bent into a series of folded or inverted flexures, having, that is to say, the strata in the N. leg of each anticlinal turned over, and dipping steeply to the S., or rather to the S.E., in accordance with the law so universal through- out our whole Appalachian Chain. Near the Delaware, as shown in both the general and the local sections, there are three distinct ridges of the gneiss, separated by two synclinal troughs of the Auroral limestone. Here the entire breadth of the chain is about 7^ miles. At the Eastern corner of Berks County, where Section III. crosses these hills, their breadth is about six miles. Here they consist almost exclusively of the gneissic rocks. But near the Schuylkill, as exhibited by our sections, the whole belt is much contracted, consisting chiefly of the spurs of the Neversink Mountain, and the ridges are composed almost exclusively of the Primal white sandstone, in an altered and much indurated state. We do not advance far eastward from the river, however, before the Gneiss crops out on the Southern slope of the spur of Penn's S. Mountain, South of the town of Reading. MOEE DETAILED DESCRIPTION OF THE GNEISS AND ITS MINERALS IN THE SOUTH MOUNTAINS. At the North-eastern extremity of the chain is the insulated ridge called Chestnut Hill. This, which is but the South-western prolongation of Marble Mountain, a spur of the chain lying on the Eastern or New Jersey side of the Delaware, commences at the river, and passing immediately to the N. of the town of Easton, crosses the Bushkill above Hester's Dam, and then subsiding into a long and narrow point, sinks under the limestone near Seip's, about four miles from its origin. Its rocks, which are well exposed at the passage of the river round its Eastern end, con- sist chiefly of gneiss, its Southern flank alone containing other materials, the more interesting of these being a belt of talc-schist, serpentine, and various associated minerals, among which are zircon, actynolite, augite, silvery mica, soft woolly asbestos, and fine pseudomorphic crystals of serpentine. The gneiss belongs to the massive granitoid variety, so common throughout the whole chain. Its strata dip at a steep angle towards the S.S.E., but exhibit in many places much contortion, implying the violence of the forces which have uptilted them. The same dip is visible in the beds of the talc-slate. The blue limestone of the valley encircles the base of this hill on every side, except just at the passage of the river. Chestnut Hill presents the mineralogist, at several localities, with beautiful specimens of various mineral species, especially of the maguesian class. The Northern part of the ridge exposes, on the river at " the Weygatt," high, overhanging cliffs of a rock of quartz and felspar, containing veins EOCKS OF THE SOUTH MOUNTAINS. 95 of epidote. To the S. of this, ranging along the Southern slope of the hill, is seen a band of ser- pentine and other magnesian rocks, imbedding a great variety of interesting minerals. Next the Delaware, the serpentine is mostly of the yellow sort, containing in places rhombic carbonate of lime, with indurated asbestos, and also grey carbonate of lime in serpentine. Far up the Southern slope of the hill occurs a mass of semi-crystalline greenish-grey augite, including flesh-coloured carbonate of lime. Near the serpentine are several varieties of tremolite, some of it in bladed crystals, some greenish. A little to the westward, near Wolf's Old Quarry, the serpentine abounds with nephrite, some of which is of a beautiful bluish tint, some of a delicate pink hue, and containing smap shining crystals of tremolite. A little S. of the nephrite, indeed apparently intermixed with it, are several varieties of talc, as slaty, greenish, whitish, and a scaly green kind. Some of the talc is compact, and is mingled with serpentine, and pervaded with white fibrous carbonate of lime. To the S. of this locality, there extends another band of coarse quartz and felspar rock, in which some of the felspar is reddish. This portion of it contains crystals of tourmaline and sphene. A belt of this rock occurs at the edge of the river, where it is overflowed at high water ; it contains a quantity of soft asbestos, filling the joints. About one mile to the W. of this point, being on the same Southern slope of the hill, and a little W. of the Easton and Wind-Gap road, a beautiful silvery mica was formerly found in abundance, but is now nearly exhausted. Near this occurs a scaly talc, in which good crystals of zircon have been met with. Close to this spot, and near the spring that supplies the town with water, is found a white tabular, crystalline tre- molite, some of which is minutely dotted with specks of plumbago ; a variety of greenish, tabular tremolite is also here. To the westward of this, in a little cleared meadow, were found specimens of a serpentine rock, containing flesh-coloured and light carbonate of lime, and also irregular masses of tourmaline in a crystalline serpentine. Here, near an old distillery, augite occurs in light-green and earthy-looking crystals, with well-developed terminating faces. Still further westward, toward the Gap of the Bushkill, and a little S. of a syenite rock, which ranges through the ridge, we find a large band of tremolite rock, in the fragments of which are seen crystals of grey tourmaline. AVdst of the Bushkill, on the Eastern sloping face of the hill, we meet with a beauti- ful dark-green variety of serpentine, some of which has delicate streaks of white, probably carbonate of lime and asbestos. This band of rock is in solid beds, some of them several feet thick, and as it promises to prove susceptible of a fine polish, it may perhaps become valuable as an ornamental stone. It is obviously a stratified rock, overlying regularly the syenitic belt of the ridge, which here consists chiefly of sahlite, and dips S.S.E., towards the overlapping limestone of the valley. Between the solid beds of dark serpentine, lie thinner beds of a more slaty sort, with distinct bands of micaceous rock, dividing the serpentine and marking the plane or angle of stratification. Though upon crossing these crystalline rocks to the Northern side of the ridge, we find them, near the Bushkill, in such close proximity to the limestone as to imply the absence of the generally interposed stratum, the Primal white sandstone, yet to the westward of this a slate is seen, having the appearance of the slaty member of the Primal series, near which occur asbestoid and talcose slates, probably portions of the same low Palaeozoic rock. Higher up the hill the blue limestone occurs in place, and adjoining it we find the gneiss. At the first of the above localities, the limestone in contact with the crystalline rocks forms only a narrow tongue or point, running in from the 96 NORTHERN ZONE OF GNEISS. westward, between the main ridge of Chestnut Hill, and a smaller spur which runs out to the Bush- kill, a little above the new stone mill. This smaller ridge consists chiefly of serpentine and talcose rocks, bounded at a short distance on the N. by the blue limestone. Some of the talc contains cubic crystals of sulphuret of iron, and some of it is interspersed with fine green serpentine, in which crystals of zircon are said to have been found. The true direction of the gneissic belt of Chestnut Hill is a little S. of W. Its more elevated por- tion terminates a little W. of the Bushkill, beyond which the rocks are much concealed by diluvium, cropping out, however, at Seip's Tavern. The high land represented on the Northampton County map as the Western prolongation of the ridge, is not strictly a part of it, but a line of limestone knobs, occurring south of the true range. Before proceeding to the main belt of the Lehigh Hills, a small insulated ridge, met with about three and a half miles N. of Bethlehem, claims attention. It commences a little W. of the road leading from Bethlehem to Nazareth, and follows the South side of the Monokesy Creek, in the form of a narrow elliptical hill, crossing the stream, and terminating near the road which leads from Bethlehem to Mauch Chunk, a short distance W. of which road its gneissic rocks sink away under the limestone of the valley. This ridge, formed of the same rocks as Chestnut Hill, in the prolongation of which, moreover, it seems to lie, owes its elevation very probably to one and the same uplifting force. A third detached ridge, consisting chiefly of gneissic rocks, lies between Allentown and Beth- lehem, immediately N. of the Lehigh, and parallel with it. The principal rock in this hill is a compound of quartz and felspar, in which, however, are occasional seams of hornblende and epidote. Its northern side is strewed with fragments of yellowish white Primal sandstone, the strata of which appear in place, dipping gently northward, at the Eastern end of the hill, about -a mile and a half West of Bethlehem. Ridges South of the Lehigh. The chain of the South Mountains, consisting of nearly parallel, though often irregularly-united ridges, will be best described by tracing each belt separately. The first group of ridges extends from the Delaware to Saucon Creek, where along narrow.valley, running in a transverse direction entirely across the tract, separates this from the other belts further to the S.W. Eestricting our attention, in the first place, to the group of hills E. of the Saucon, they naturally divide themselves into three ranges : the northernmost, known as the Lehigh Hills, com- mencing at the Delaware below Easton, and terminating near Hellertown ; the middle one, beginning also at the river above Bieglesville, and terminating N. of Cooperstowu ; and the southernmost, lying S. of Durham Creek, and running from the river to Springtown. The first 'of these, the Lehigh Hills, bounding for some miles the valley of the Lehigh Eiver on the S., and commencing in a loop of the Delaware about two miles below Easton, ranges towards the S.S.W., and gradually approaches the Lehigh, until the gneiss rocks show themselves on the river-bank, about a mile and a half below the mouth of Saucon Creek. Near the East Branch of this stream the chain separates, enclosing small tracts of limestone between its spurs. The gneissic rocks occupy the margin of the river for only a short distance, the limestone, their usual boundary, resuming soon its place on the Southern side. This belt of the gneiss terminates near the bridge over Saucon Creek, between Shinersville and Freemansburg, the limestone folding round the base of the hill, and extending up the East Branch of Saucon. Between this East Branch and the Main Creek lie two other ridges or spurs, nearly in a line with the chain just THE LEHIGH HILLS. 97 mentioned, the Southern one terminating E. of Hellertown, and the other further northward. Between them is a narrow limestone valley, which contracts in breadth towards the E., and heads near the Little or East Saucon. Though a separate chain of elevated rocks, the Northern belt here described is not entirely detached from the middle range already referred to, a tract of crystalline rocks lying round the head of the Little Saucon, serving to connect them geologically. In the general prolongation of the chain, but disconnected from the previous set of ridges by the transverse valley of the Saucon and its South Branch, we have the Metamorphic or gneissic rocks extending towards the S.W., through the lower townships of Lehigh and Berks, in a series of nearly parallel spurs, almost to the Schuylkill. In describing the general South-eastern and North-western boundaries of the whole chain through Lehigh, we have already given very nearly the true limits of these rocks in that county. This part of the belt is separated longitudinally for several miles, into two parallel sets of ridges, by the upper part of the valley of the Saucon. One of these tracts, lying W. and N. of that creek, commences at the Lehigh, near Bethlehem, and ranging S. of Allentown, and past Emaus and Millerstown, passes into Berks, losing there its character as a distinct zone of hills ; the other originating W. of the South Branch of Saucon, ranges South-westward to the head-waters of Perkiomen Creek, where it merges westward into the general belt. On both sides of the county line, dividing Lehigh and Berks, the Gneiss Hills compose an unbroken tract having a breadth of about six miles. Passing still further to the westward, the general chain expands in width, but becomes subdivided by valleys entering it from the S. and W. ; the broad gneissic tract being broken into about five spurs or ranges, and the intervals between them occupied by belts of limestone and sandstone, the latter often forming hills as elevated as those of the gneiss. The northernmost subdivision of the gneiss, starting from the general belt in Rockland Township, terminates about three miles E. of the mouth of Maiden Creek, near the head of Dry Run. It is bounded on the N.W. by a narrow undulating belt of the Primal sandstone, which, from the neighbourhood of Metztown to Solomon's Temple, separates the gneiss from the limestone of the Kittatinny Valley. This tract of the gneiss is bordered on the S. by a long narrow tongue of the same sandstone, starting off from the main mass of that formation E. of Solomon's Temple, and running eastward past Pricetown as far as Shiffert's Inn. W. of Penn's Mountain, which consists of the sandstone, and S. of the Pricetown range of the same rock, lies another nearly-detached tract of the gneiss, bounded on the E. and S.E. in Oley and Exeter townships by the Primal slates and the Auroral Limestone. The margin of this large patch of strata is made so excessively irregular, by the protrusion into it of the spurs of sandstone, as to render it impossible to describe it intelligibly in words. A third spur of the general chain occupies the Southern half of Rockland Township, between the two head-streams of Maiiatawny Creek. A fourth smaller spur projects to the S.W., forming the Northern corner of Pike Township. It is bounded by Pine Creek on the N.W., and by another parallel stream, also a tributary of the Manatawny, on the S.E. A fifth and much larger tract of the crystalline rocks fills the South-eastern part of Pike, the North-western two-thirds of Colebrookdale, and the Northern half of Earl townships. It is limited on the N.W. and W. by a long, narrow, curving belt of the sandstone, which follows the Eastern side of the tributary just mentioned, and then the Main Creek. Its Eastern border passes through Cole- brookdale Township, from Perkiomen to Ironstone Creeks, making here a gently-undulating line, nearly parallel with the Montgomery County line. This South-eastern edge of the gneiss is VOL. I. N 98 NORTHERN ZONE OF GNEISS. \ 3 f 2 3 I M \ \ ^ \i \l formed by the margin of the overlapping red sandstone of the Middle Secondary period, except at a few points, where small patches of the limestone and white sandstone intervene. Between the head of Ironstone Creek and the main Mana- tawny, near Spang's Furnace, there extends a small ridge of the Primal white sandstone, which separates the Gneiss tract along its southern limit into two divisions. A line drawn from a point on Ironstone Creek, about a mile S.W. of Boyerstown, westward to the end of this sandstone ridge, will mark with toler- able accuracy the general limit of the Gneiss on the S. STRATIFICATION OF THE SOUTH MOUNTAINS, AS SEEN IN TRANSVERSE LOCAL SECTIONS. Section (A.) Along the Delaware River W. side (looking S.W.) The best natural exhibition of the structure of the Delaware and Schuylkill division of the South Mountains, indeed the only good one, is that along the first-named river from Easton to Monroe. Reserving for a future chapter the longitudinal tracing of the synclinal belts of the Palseozoic strata, their positions and features in the sections will be noted here, as essential to a clear understanding of the constitu- tion of the chain. Commencing at the mouth of the Lehigh, we first encounter the Auroral limestone of a dark blue colour and ferruginous aspect. Near the Lehigh Bridge its strike is irregular, for it dips to S. 20 to 45 W., at an average angle of 25. The rock shows some metamorphism, is massive and free from joints, but displays a transverse cleavage dipping 60 to S. 40 E. The S. dip continues for two- thirds of a mile below the Lehigh, but is steeper when it changes to a gentle N. dip of 20. Approaching the foot of the Lehigh Hill it becomes more altered and slaty, the partings between the beds being covered by a thin micaceous film ; here the cleavage planes are more conspicuous than the planes of bedding. It is worthy of note that in this locality the strike of the cleavage is not coincident with the strike of the Palseozoic rocks to which it belongs, nor yet with the strike of the Gneiss upon which they unconformably repose. The strike of the Gneiss in this district varies from N. 50 E. to N. 45 E. ; that of the Palseozoic rocks is usually about N. 65 E. But the strike of the cleavage planes of the latter, though approximately conformable to that of the beds, is generally more E. and W. by several degrees. In the general direction of their dip, the cleavage planes observe the usual law, declining steeply to the S.E. Quitting the limestone, and crossing a space of 500 feet without exposures, we come upon the Primal rocks of the Northern flank of the Lehigh Hills in a highly- altered condition ; the first met with are numerous fragments and masses of the Primal silicious slates, and the Primal white sandstone, but not in place. From beneath these, rise massive beds of a grey quartzose conglomerate, greatly altered by igneous agency. Its pebbles, of pea and nut size, are in fused contact with a syenite or syenitic gneiss of felspar and augite, the whole rock so altered that UNCONFORMITY OF PEIMAL AND GNEISS. 99 its sandy paste contains regularly-formed crystalline felspar. It is at once a conglomerate and a porphyry. These beds dip 75 to N. 40. W. From below the Primal rocks rises an arch or anticlinal wave of granitoid gneiss with thin injections of syenite. On the S.E. side of this anticlinal ridge of gneiss, the Primal sandstones and slates again appear all highly altered, some layers of the slates being porphyroidal. Here the dip is about 35 to the S.E. Between these two exterior belts of Primal strata flanking the ridge, there occurs a narrow compressed trough of the same rocks, involving a synclinal fold of the lowest beds of the Auroral limestone. The Lehigh Hill appears, therefore, to contain two folded anticlinals. Unconformity of the Primal Strata to the Gneiss. The precise angle of dip of the underlying Gneiss is not well exposed, but it seems at the N. base of the hill to be steeper than that of the Primal conglomerate, implying a movement of the older rock before the deposition of the materials of the newer. In other localities, embraced within this line of section, the want of parallelism between the two systems of strata is better displayed. Between the Southern foot of the Lehigh Hill and the Northern base of Bucher's Hill, there intervenes a comparatively wide and smooth valley of limestone. This trough rapidly contracts and descends south-westward, terminating about two miles from the river ; it is not a simple synclinal belt, but contains some two or more anticlinal undulations in the limestone. Between the Northern limit of this basin at Eaub's Ferry, and the immediate Southern base of the Lehigh Hill, we detect another small trough of the limestone, separated from the main one by a mere narrow point or spur of the older crystalline rocks. Along our line of section there are several large quarries of the limestone at eligible localities facing the river. One of these displays Eipple Mark on a truly superb scale. This quarry is close to Uhlersvilla The next belt crossed by our section is the tract of Gneiss known as Bucher's Hill. Generally the strata are seen to dip to the S.E. at an average angle not exceeding 45 ; they are undulated in at least two or three folded flexures, the axis planes of which observe the prevailing law, dipping South-eastward. The gneiss here is the prevailing greenish and white felspathic variety. Between Bucher's Hill, which is the middle ridge, and the Durham Hill, or most Southern of the three anticlinal belts, lies another synclinal trough of the Auroral limestone, skirted in one or two places by exposures of the Primal sandstone. This belt occupies the valley of Durham Creek, as far to the S.W. as Springtown, being on the river, rather more than a mile wide. At Durham Furnace the rocks are well exposed. Between the furnace and Durham Creek they exhibit a regular anticlinal flexure. This is the locality of the well-known Durham Cave, remarkable for the Mammalian Bones which were discovered in it, and which I shall hereafter allude to when enumerating the fossil remains of our Bone-bearing Caverns. The cave is situated on the North side or steeper flank of the anticlinal arch, which will be found, I think, to be the prevailing position of these limestone caverns in the valleys of the Appalachian Chain. Durham Hill. The last belt which the section crosses is that extending between Durham Creek and Monroe. The gneiss forming the ridge between the Durham and the Monroe valleys, is at the river only about one mile broad ; it is indeed merely a spur of the Musconetcong Mountain sinking down. Its structure is that of a double anticlinal, embracing a very shallow synclinal band of Primal strata and Auroral limestone between the two flexures. On the N., 100 NORTHERN ZONE OF GNEISS. towards Durham Creek, this gneissic belt is flanked by a narrow outcrop of the Primal strata succeeded by the limestone. Here we detect one of the most interesting instances of uncon- formity of dip between the Palaeozoic and the Gneissic or Hypozoic rocks, anywhere to be met with in the South Mountains, or indeed in the Appalachian Chain. The appended little section and diagram will illustrate the discordant relation of the two systems, both in dip and strike, and serve to bring out distinctly the magnitude of the crust-movement which occurred between the periods of deposition of the two sets of strata. FiQ. 4. Unconformable contact of the Primal Rocks and the Gneiss. At the North base of the hill, the Gneiss, syenitic in its composition, dips 50 to S., 40 E., being probably the inverted leg of a folded anticlinal. The Primal rocks lean upon the denuded edges of its beds dipping in a nearly opposite direction namely, 35 to N., 30 W. The whole Primal group is here about 100 feet thick, and consists of a lower, member, a dark silicious conglomerate, and an upper, composed of alternating beds of altered white sandstone and altered silicious slate. Upon these repose the lower beds of the Auroral limestone, conforming in dip and strike with the sandstone. On and near the road we discern an equally remarkable discordance of strike, that of the Gneiss being S. 50 W., while that of the Primal and Auroral rocks is S. 60 W., or 20 away from parallelism. (See Ground Plan.) On the South flank, or rather at the South base of the Durham Hills, reclines a narrow outcrop of the Auroral limestone, consisting of white magnesian limestone, greenish talcose slate, and blue limestone. Abutting abruptly against the latter, we come suddenly on the conglomerate, which terminates the unconformably overlying Mesozoic red sandstone. This rock is here a true puddingstone, being composed of pebbles of all the adjacent older uplifted rocks, Gneiss, Primal sandstone and slate, and Auroral limestone, imbedded in a paste of red shale. The conglome- rate dips 30 to N., 30 W., while the limestones, somewhat twisted, lean to the S. 25 E., at a varying angle of from 30 to 60. This interesting spot marks one point along the Northern shore of the broad red sandstone estuary, skirted by a bold range of hills with comparatively deep water at their base, where the crust-disturbances which lifted and drained the district shook down a large body of fragmentary matter, to be rolled and imbedded by the waters along their base. FIQ, 5. Section across the South Mountains between Allentown and Cooporsburg, looking S.W. Our next local section designed to exhibit the structure of the chain, extends south-eastward from Allentown on the Lehigh, to Cooperstown near the South Branch of the Saucon, a distance of about seven miles. The chain as here exhibited is of simpler features than where it is cut by SECTIONS ACEOSS SOUTH MOUNTAINS. 101 the Delaware, for the southern and central ridges having both expired south-westward, before reaching the neighbourhood of our section, the only divisions of the chain presented are, the main Northern anticlinal belt in westward prolongation of the Lehigh Hill of the Delaware, and a lesser Southern ridge which rises in the forks of the Saucon, and extends south-westward towards the Manatawny. The first belt of rock included in the section is the Auroral limestone of the valley of the Lehigh Creek and Eiver, and the strata dip and undulate almost precisely as they do S. of Easton, in a corresponding position at the base of the hills : that is to say, they display an anticlinal axis, which a little further eastward, or just S. of the acute bend of the Lehigh, lifts to the surface even the Primal sandstone. Whether the sandstone is directly in contact with the Gneiss, or separated from it by a narrow outcrop of the Primal rocks, we are unable, from the absence of exposures, to state. The general structure of the ridge dividing the valley of the Little Lehigh Creek from that of the Saucon, is apparently the same as that of the Lehigh Hill near Easton, or in other words, it contains a cotnpound anticlinal, with steep or even inverted north-westerly dips, and more moderate south-easterly ones not exceeding 60. The rock of the Southern slope of this ridge is for the most part a hornblendic gneiss, that near the crest is a binary granitoid gneiss of quartz and felspar. An obscure slaty cleavage pervades certain portions of the Gneiss, the plains dipping generally at a steep angle, about 75 towards the S.E. Between the South-eastern base of the Lehigh Ridge, and the Northern foot of the subsiding gneissic ridge of the Saucon, there spreads a smooth open valley of limestone occupied by the Saucon Creek. Branching southward it receives the South Fork of that stream, flowing through another smaller limestone basin. Our section-line passes over the Eastern point of the ridge of Gneiss, which separates the main Saucon Valley from its southern lateral branch. The Gneiss near the end of the ridge dips at a gentle angle towards the S.E., though further to the S.W. this ridge, like that N.W. of the Saucon, is anticlinal in its structure. The limestone belt of the main Saucon appears to be undulated ; a steep anticlinal axis ranging between the village of Friedensville and the Zinc Mine. This inter- esting mine of Calomine, or the silicious oxide of zinc, occurs in a close synclinal fold of the Auroral limestone, near the South base of the Gneissic Hills. Passing the spur of Gneiss of the Saucon Ridge, we enter a narrow belt of South-east -dipping limestone near the South Branch of the Saucon. This limestone may be seen almost in contact with the gneiss which supports it, its own beds dipping at an angle of 45, those of the Gneiss dip 30 to the S.E. ; thus presenting us with another instance of unconformity between the two systems of strata. In this case, besides the want of parallelism, there is an absence of the whole Primal series, the result either of a dislocation in the strata, or of a suspension pf sedimentary action in the Primal period at this place, or possibly it has arisen from the overlapping of the limestone past the original margin of the sandstone, as both were deposited unconformably upon the Gneiss. Crossing the South Branch of the Saucon, our section immediately enters the wide area of the Mesozoic Red Shale and Sandstone, there terminating in the upper conglomeritic beds of that formation, which abut, with a gentle North-westerly dip, against the more steeply South-east- dipping beds of the Auroral limestone, under conditions of contact very analogous to those pre- sented at Monroe. The red shale formation is well seen half a mile northward from Coopers- burg, where its beds show a dip of only about 10. Here the rock exhibits distinct ripple- 102 NORTHERN ZONE OF GNEISS. marks. No capping stratum of conglomerate is visible, though the debris of that rock occurs near the Hellertown Road ; it has probably been swept away by denuding waters. FIG. 6. Section across the South Mountains, nine miles east of Beading, through Friedensburg, looking S. W. , **" s:r-<'f--7fS /Tr^;^><>^7\Nfc>--^ir\ J u * v-i-y s/j-z-CV- This section, like the two already described, commences in the Auroral limestone of the Kitta- tinny Valley beyond the North base of the Gneissic ridges of the South Mountains. Passing one or two flexures in the limestone, the section crosses a branch of Maiden Creek, and soon meets the material of the Primal sandstone, showing a wide, gently-ascending plain to the margin of the Gneiss at the foot of the hills. Some portions of the sandstone are pebbly. Entering upon the Gneiss, our section crosses an undulating belt of moderately high hills, some five miles in width, to the Slate Valley of Friedensburg, which it first touches near Monokesy Creek. This wide belt of hills consists in part of Gneiss, in part of Primal "White Sandstone ; the latter formation, though seldom seen in place, occurring evidently in narrow synclinal basins included between the anticlinal undulations of the Gneiss, which, for the most part, occupies the higher ridges. (See Fig. 6 Section, 9 miles E. of Reading.) From the foot of the Gneiss Hills, west of the Monokesy, the section traverses a smooth gently-undulating plain, the whole way to the Northern margin of the Mesozoic Red Sandstone. In the space of about four miles, the first two miles, following the Friedensburg road parallel to the section, cross Primal Upper Slate, occupying a broad outcrop before it dips beneath the Auroral limestone basin of the Manatawny and Monokesy. The remainder of the distance is across the Auroral limestone, which exhibits several undulations. The Gneiss of the hills traversed by our section is identical in constitution with that of the Lehigh ridge further north- eastward. The Primal series, besides containing much white sandstone, embraces beds of a coarse conglomerate. Cleavage abounds, especially in the Palaeozoic strata crossed by this section, and dips almost invariably at a steep angle towards the S.E., obedient to the prevailing law of cleavage- dip in the Appalachian Chain. This structure is plainly shown in the limestone S. of Maiden Creek, the planes dipping S.E. ; the Gneiss itself in the first hill shows cleavage, dipping very steeply to the same quarter, the strata themselves dipping 45 southward. On the Mana- tawny the bluish upper Primal slates display cleavage, dipping eastward 45 or 50, the beds dipping 10 to the N.E. : south of the stream the cleavage-dip is still S.E., but at as low an angle as 35. Further on in the limestone, the true dip of which is often obscure, the cleavage- dip maintains its usual direction. Our section terminates in the red sandstone formation, which contains, as its uppermost deposit, a calcareous conglomerate apparently dipping in the very unusual direction of S.W. at an angle of 45. At another locality near the section, its dip is to the W. 30 ; and one and a quarter miles from the Yellow Tavern the conglomerate, well exposed on the road, seems to dip a little S. of W. as steeply as 50 or 60. These irregularities in strike and dip imply some local disturbance, an inference which is rendered probable from the occurrence of many joints intimating partial metamorphism. SECTION NEAE BEADING. 103 This section, designed to exhibit the structure of the Neversink Hill near its termination at the Schuylkill, commences a little below Reading in the Auroral limestone, embraces the excellent Fio. 7. Section across the Neversink Hill of the South Mountain near Reading, looking N.E. /,//////// ^^^gsau^^/^^a^^ax ^^^-^ ^K^^^^^^j^^^ c r succession of exposures of the rocks afforded by the cuttings along the Reading Railroad, and terminates in the Mesozoic conglomerate at the South-eastern base of the hill about three miles below the town. It displays none of the older Metamorphic strata, but only the Primal rocks and the Auroral limestone reposing on them. Even in this depressed termination of the chain we may detect the presence of the two main anticlinals which undulate the strata of the hills for several miles thence to the N.E. Passing from the Auroral limestone of the North-western base of the hill, dipping with considerable irregularity at a steep angle, towards the first main flexure of the Primal White Sandstone which ranges under its central crest, the section crosses a belt of undulated and crushed sandy ferruginous slates, highly indurated and much intersected with cleavage. These are the Primal upper slates resting upon the Primal sandstone. This latter exhibits a double or compound flexure, the steep limb of the arch being towards the N.W., in obedience to the more prevailing rule. Towards the lower end of the section, exposed in another deep cut of the railroad, another normal arch or flexiire of the Primal sandstone displays itself, the steeper or North-western side dipping perpendicularly, and the gentler South-eastern, at an angle of 60. For some distance N. of this, the Primal White Sandstone, succeeded by the Primal newer slate, highly indurated and crushed, exposes a prevailing dip to the N.W. of about 30. Between the two main anticlinals of the mountain there is evidently a deep synclinal trough rising rapidly north-eastward into the hill, but at the railroad containing a basin, or rather a cove, of the Auroral limestone, evidently much contorted by pressure and metamorphosed by the action of heat. On the South-eastern flank of the Southern anticlinal, we detect a narrow outcrop of the same limestone, leaning at a steep angle upon the Primal rocks. Throughout this section these Auroral strata and the Primal slates and sandstone supporting them, display a very decided amount of meta- morphism, and it is interesting to notice that the cleavage one of the more conspicuous symptoms of this change observes the usual law, and dips steeply to the S.E., or parallel to the average direction and angle of the axis planes of the flexures, manifesting at the same time its usual fan- like divergence where it is in immediate proximity to the lesser anticlinal and synclinal curves. The section illustrates the fine exposure of the Mesozoic Conglomerate, or uppermost stratum of the great Red Shale formation visible at the Railroad. It is here more than usually calcareous, but contains, besides its numerous pebbles of the Auroral limestone, others referable to all the contiguous formations of older date than itself. The conglomerate, dipping about 15 to N. 20 E., abuts directly against the steeply -southward-dipping beds of the Auroral limestone. It is evident that the conditions attending its origin were precisely identical with those which witnessed the production of the same deposit in the region of the Delaware, as already explained ; namely, a wild strewing of pebbles, the fragments of the earthquake-shaken hills which composed at the time the northern shore of the Mesozoic waters. PART II. PALEOZOIC, OR ANCIENT FOSSILIFEROUS STRATA OF PENNSYLVANIA. INTRODUCTORY BOOK. CHAPTER I. A SYNOPSIS OF THE APPALACHIAN PALAEOZOIC STRATA OF PENNSYLVANIA IN THE ASCENDING ORDER. PRIMAL CRYSTALLINE SCHISTS (or Azoic Group). This is a very thick and widely-diffused group of semi-crystalline strata, indurated clay -slates, talcose, micaceous and hornblendic schists, and grey silicious grits, without visible fossils, but in close physical relation with the overlying fossiliferous Primal rocks, and apparently a portion of the Palseozoic system. PRIMAL SEEIES. PRIMAL CONGLOMERATE. A heterogeneous conglomerate composed of quartzose, felspathic, and other pebbles, imbedded in a silicious or talco-silicious cement. This rock does not appear in Pennsylvania, but is largely developed in Virginia and Tennessee, where it has a thickness of 150 feet. This formation and the preceding seem to lie below the lowest ascertained fossiliferous horizon. PRIMAL OLDER SLATE. A sandy slate of a brown and greenish-grey colour, containing much felspathic and talcose matter. It has hitherto disclosed no fossils. The thickness of this rock has not been ascertained in Pennsylvania, the beds being too much folded. In Virginia it is 1200 feet thick. PRIMAL WHITE SANDSTONE (Potsdam Sandstone of New York). A compact, fine-grained white and yellowish vitreous sandstone, containing specks of kaolin. This stratum is dis- tinguished by a cylindrical stem-like fossil, the Scolythus linearis, which crosses the beds in a perpendicular direction. Probable thickness about 300 feet. PRIMAL UPPER SLATE. A greenish-blue and brownish talco-argillaceous slate, sometimes very soft and shaly. Its only fossil a peculiar fucoid. It is probably about 700 feet thick in Pennsylvania. AURORAL SERIES. 105 AURORAL SERIES (BLUE LIMESTONE OF THE WESTERN STATES). AURORAL CALCAREOUS SANDSTONE (Calciferous Sandstone of New York}. A coarse grey calcareous sandstone, containing drusy cavities, enclosing crystals of quartz and calcareous spar. Within the limits of Pennsylvania this occurs chiefly in Northampton, Centre, and Huntingdon counties. It is about 60 feet thick at Easton. AURORAL MAGNESIAN LIMESTONE. (The Chazy and Black River Limestones of New York are parts of this formation). A light-blue and bluish-grey massive limestone, containing generally from ten to thirty per cent of carbonate of magnesia. In the south-western portion of Pennsyl- vania it contains thick beds of chert. Its thickness is from 2500 to 5500 feet. MATINAL SERIES. MATINAL ARGILLACEOUS LIMESTONE (Trenton Limestone of New York). A dark-blue and bluish-grey, soft, argillaceous limestone, alternating near its upper limit with blue calcareous shale. This whole formation is very fossiliferous, being characterised by the Chcetetes lycoperdon, Leptcena sericea, Bellerophon bilobata, Isotelus gigas, and many other fossils. In Northampton, Mifflin, and Centre counties, it is from 300 to 550 feet thick. MATINAL BLACK SLATE (Utica Slate of New York}. A blackish and dark-blue fissile slate, usually very carbonaceous, distinguished by Graptolites, Orbiculce, and other characteristic fossils. It appears in Northampton County and in Kishicoquillas Valley. Its thickness is from 300 to 400 feet. MATINAL SHALES (Hudson River Slates of New York}. Bluish-grey shales and sandy slates, containing, especially in their upper portion, many beds of argillaceous sandstone, and some layers of dark-grey silicious conglomerate. In the western parts of Berks and Lebanon, the formation contains much red and reddish-brown slate, alternating with yellow layers. The middle portion, in certain localities, yields a tolerably good roofing-slate. It has many characteristic fossils, especially a species of Graptolithus, of Heterocrinus, of Orbicula, of Modiolopsis and other Acephala, and of several Trilobites. It contains some species common to it and the Matinal argillaceous limestone. Thickness in Centre County, 1200 (?) feet. LEVANT SERIES. LEVANT GREY SANDSTONE (Oneida Conglomerate of New York). A compact greenish-grey massive sandstone, containing, in many places, thick beds of silicious conglomerate. From 250 to 400 feet thick in many ridges in Centre and Huntingdon counties. LEVANT RED SANDSTONE (Division I., or Lowest Member of the Medina Sandstone of New York}. A soft argillaceous red and brown sandstone and red shale. It contains few or no fossils. In Centre and Huntingdon it is from 500 to 700 feet thick. LEVANT WHITE SANDSTONE (apparently Divisions II. ,111., and IV. of the Medina Sandstone of New York}. A white or light-grey sandstone, rather fine-grained, very hard and massive, alternating at its upper limit with greenish shales, and containing there thin-bedded and mottled- VOL. i. o 106 SYNOPSIS OF PALEOZOIC STRATA. grey and red sandstone. These upper beds are often covered with a network of the impressions of large articulated marine plants, especially the Arthrophycus Harlani. The freshly fractured surfaces of the lower beds are generally dotted with yellow ferruginous specks. In some out- crops the whole mass is 450 feet thick. SUKGENT SERIES. SURGENT LOWER SLATE (probable equivalent of Lower Green Shale of Clinton Group of New York). Olive-coloured and yellowish slates, containing but little calcareous matter, and including thin sandy beds. Some of its layers acquire, by exposure, a peculiar claret colour. Characterised by the little branching fucoid Buthotrephis gracilis, and other fossils. This formation is in some places 200 feet thick. SURGENT IRON SANDSTONE. An alternation of red and ponderous ferruginous sandstone, red argillaceous sandstone, and green sandy slate. The red sandstone very usually contains two or three thin beds rich enough in iron to be valuable as an iron ore. In the Kittatinny Moun- tain, on the Susquehanna, it is 80 feet thick. SURGENT UPPER SLATE. A green fissile slate, changed at its outcrop into a buff-coloured, and sometimes a claret and brownish, slate. It contains thin layers of argillaceous sandstone, and abounds in the small branching fucoid Buthotrephis gracilis. Its thickness frequently exceeds 250 feet. SURGENT LOWER ORE SHALE (part, perhaps, of the Upper Green Shale of Clinton Group, New York).- A greenish fissile shale, with thin layers of limestone. This formation sometimes contains a band of the red fossiliferous iron ore. It has a thickness near Jack's Mountain, on the Juniata, of 760 feet. SURGENT ORE SANDSTONE. A tough grey calcareous sandstone, with thin partings of shale. It is from 10 to 30 feet thick. SURGENT UPPER ORE SHALE (probably on horizon of Upper Green Shale of Clinton Group of New York). This formation consists, in Pennsylvania, of an alternation of bluish and greenish shales and fissile slates, with thin beds of argillaceous and sometimes pure limestone, and occa- sionally thin beds of calcareous sandstone. Its lower portion is characterised by the well-known red fossiliferous iron ore, in one or more thin layers. It abounds in Beyrichia and other fossils. On the Juniata it is 300 feet thick ; in some places even more. SURGENT BED MARL (Clinton Group of New York}. A red, slightly argillaceous shale of very uniform composition. It contains scarcely any fossils. Its thickness on the Juniata is in some places 350 feet. SCALENT SERIES. SCALENT VARIEGATED MARLS. An alternation of blue, green, and red marly shales and fossili- ferous limestones ; the red shale more abundant towards the bottom. It contains Cytherina alta, Avicula alta, and other shells. Thickness on the Juniata, about 400 feet. SCALENT GREY MARLS (probably this and the Scalent variegated Marls represent the Onon- dago Salt Group of New York). Ashy, greenish blue, and grey calcareous marls and shales, with SCALENT SEEIES. 107 occasional beds of impure argillaceous limestone. It graduates upward into the Cement Eock. Thickness on the Juniata, 800 feet. SCALENT LIMESTONE (Water Lime Group of New York). A blue flaggy limestone, sometimes containing bands of chert. Certain portions have a thinly-bedded, wavy stratification. It is frequently highly magnesian, and is extensively employed, especially in New York, for making hydraulic cement. This rock contains the Cytherina alia, Tentaculites ornatus, and a few other distinctive fossils. Thickness on the Juniata, 250 feet. PRE-MERIDIAN SERIES. PRE-MERIDIAN LIMESTONE (Lower Helderberg Limestone of New York). A diversified calca- reous formation, usually of some shade of greyish blue. It is argillaceous and flaggy in its lower beds, and shaly towards the middla It frequently contains layers and nodules of chert, espe- cially near its upper limits. It has many characteristic fossils, the Pentameris galeatus, and other shells, with corals. The average thickness of this rock is between 50 and 100 feet. MERIDIAN SERIES. MERIDIAN SLATE. A dark ash-coloured and blackish slate, passing upwards into a dark ashy grey sandy calcareous rock. It has its greatest thickness on the Upper Juniata, near Franks- town, where it is 1 70 feet. MERIDIAN SANDSTONE (Oriskany Sandstone of New York}. A coarse, yellowish, calcareous sandstone, graduating near its upper limit into a fine-grained quartzose conglomerate, and becoming in its lower beds a coarse arenaceous limestone, characterised by the Atrypa elongata, Spiriftr arenosus, and other remarkable large Brachiopodous shells. Its greatest thickness on the Juniata is about 150 feet. POST-MERIDIAN SERIES. POST-MERIDIAN GRITS (Canda-Galli andSchoharie Grits of New York}. A formation contain- ing two members hitherto only met with in a limited district in New York. The lower member is a dark-greenish argillaceous rock, recognisable by a peculiar plant, resembling somewhat a cock's tail. The upper member is a more calcareous grit. This formation is largely developed in New Jersey, north-east of the Delaware Water-Gap, where it has a thickness of 300 feet. POST-MERIDIAN LIMESTONE (Upper Helderberg or Corniferous Limestone of New York, part of Cliff Limestone of Western States).- In North-Eastern Pennsylvania, New Jersey, and New York, a blue, and in some portions a sparry limestone, including bands and nodules of chert. In Upper Canada and the Western States it is light-grey and straw-coloured, and sometimes oolitic, still retaining the chert. Among its many fossils are numerous large corals, as Favo- sites Gothlandica, Favistella, &c., and characteristic shells, as the Pleurorhynchus trigonalis. Its thickness east of the Delaware Water-Gap is about 80 feet. CADENT SERIES. CADENT LOWER BLACK SLATE (Marcellus Slate of New York). A black and highly bitumin- 108 SYNOPSIS OF PALEOZOIC STKATA. ous slate, graduating upwards into a dark-blue argillaceous shale. In some districts these are overlaid by greenish-grey sandy shales. In Pennsylvania, Virginia, and Tennessee, a thin argil- laceous limestone generally occurs near the bottom of the black slate. The fossils, with few exceptions, are of diminutive size, most of them identical with those of the Cadent upper black slate. Thickness in Huntingdon, 250 feet. CADENT SHALES (Hamilton Group of New York}. Bluish-grey, brownish, and olive-coloured argillaceous shales, including in some districts thin beds of dark-grey and brown sandstone. It has many fossils, particularly bivalve shells. Thickness in Huntingdon, 600 feet. CADENT UPPER BLACK SLATE (Genessee Slate of Neiv York}. A brownish-black, and in some regions bluish-black, very fissile slate, characterised by its small and delicate fossils ; many of them, as Leptcena setigera, identical with those of the Cadent Lower Black Slate. It is the lowest known horizon of Carboniferous plants. Thickness in Huntingdon, 300 feet. VERGBNT SERIES. VERGENT FLAGS (Portage Flags of New York}. A rather fine-grained grey sandstone in thin layers, parted by thin alternating bands of shale. It abounds in marine vegetation. Thickness in Huntingdon, 1700 feet. VERGENT SHALES (Chemung Group of New York}. A thick mass of grey, blue, and olive- coloured shales, and grey and brown sandstones. The sandstones predominate in the upper part, where the shales contain many fossils. Thickness in Huntingdon, 3200 feet. PONENT SERIES. PONENT RED SANDSTONE (Catskill Group of New York}. In its fullest development this is a mass of very thick alternating red shales, and red and grey argillaceous sandstones. It has very few organic remains. Among them is the Holoptychius, and one or two other remarkable fossil fishes, of genera distinctive of Old Red Sandstone. This formation has its maximum thickness in its south-eastern outcrops, where it measures more than 5000 feet. VESPERTINE SERIES. VESPERTINE CONGLOMERATE AND SANDSTONE. White, grey, and yellowish sandstone, alter- nating with coarse silicious conglomerates, and dark-blue and olive-coloured slates. It frequently contains beds of black carbonaceous slate, with one or more thin seams of coal. The only organic remains are fragments of coal plants ; some of these are specifically, and even generically, different from those of the Serai coal series. It has its greatest thickness near the Susquehanna, where it measures 2660 feet. TJMBRAL SERIES, OR CARBONIFEROUS SHALES AND LIMESTONES. UMBRAL RED SHALES AND LIMESTONE. In Pennsylvania this series consists almost entirely of soft red shales and argillaceous red sandstones, gradually becoming, in Virginia and Tennessee, a triple mass, the lowest member of which is a mass of buff, greenish, and red shales, with sand- UMBRAL SERIES. 109 stones ; the middle a thick body of light-blue limestone, often oolitic ; and the upper, blue, olive, and red calcareous shales, embracing massive strata of grey and brownish sandstones. The limestone is the principal rock in the Western States. When it is a red shale it is without fossils, but as a limestone it is full of organic remains. The maxinmm thickness of the united Red Umbral Shale, south of the Southern Anthracite Basin, is 3000 feet. SEEAL SERIES, OR COAL STRATA. SERAL CONGLOMERATE (or Lowest Division of the Coal-Measures}. A grey and whitish quartz- ose conglomerate, in massive beds alternating with grey sandstones. It frequently contains one or more thin seams of coal. It is thickest in the Sharp Mountain, where it measures 1100 feet. LOWER PRODUCTIVE COAL-MEASURES ; LOWER BARREN COAL-SHALES ; UPPER PRODUCTIVE COAL-MEASURES ; UPPER BARREN COAL-SHALES. An exceedingly diversified group, consisting of these four subordinate formations. It comprises argillaceous and silicious sandstones, silicious conglomerates, shales of almost every colour and texture, and limestones both pure and argilla- ceous ; all of these alternating with coal-slates and fire-clays, and numerous seams of coal. The organic remains are many species of terrestrial plants distinctive of the true Goal period; likewise marine shells, corals, and fishes. CHAPTER II. SUBDIVISIONS OF THE PALEOZOIC BEGION, AND BRIEF SKETCH OF THEIE STEUCTUEAL FEATUEES. IN describing the extensive and complicated region of the Palaeozoic rocks of Pennsylvania, embracing nearly the entire State, it will be essential, for the sake of clearness, to subdivide the whole area into a number of subordinate districts, having natural boundaries, and to observe a definite order in the investigation of their details. I propose, therefore, to portion off the region into the following tracts : The Divisions of the Palaeozoic region are, First, The South-Eastern District. This embraces all the tracts of Palaeozoic rocks in the south-eastern counties, including those of the South Mountain. Second, The Kntatinny Valley District. The long regular belt of the Kittatinny or Great Appalachian Valley. Third, The Orwigsburg and Stroudsburg District. This is the long and narrow zone of strata between the southern base of the Kittatinny Mountain and the southern base of the Pokono, and its prolongation, the Mahoning or Second Mountain, extending from Carpenter's Point to the Susquehanna. Fourth, The North-Eastern District. This embraces all the country N.W. of the division last mentioned, and N.E. of the Upper Lehigh, and of the North Branch of Susquehanna above the Lackawanna, omitting the Coal Basin, and includes the several valleys in Bradford and Tioga, which head south-westward between the detached table-lands of the bituminous Coal Basins. Fifth, The Lower Juniata District. This complicated belt of ridges and valleys is embraced between the Kittatinny Valley on the S.E., .and the North Branch of Susquehanna below Berwick, Jack's Mountain, and Sideling Hill on the N.W. It includes the valleys east of the Main Susquehanna, known as Armstrong's Valley, Mahantango Valley, and the Valley of Roaring Creek, and that S.E. of the North Branch. Sixth, The Upper Juniata District. The scarcely less intricate parallel belt included between the North Branch, Jack's Mountain, and Sideling Hill on the S.E., and the foot of the Alleghany Mountain on the N.W. Seventh, The North- Western District. The tract to the N.W. of the bituminous coal district, embracing Crawford and Erie, with parts of Warren and Mercer counties. Eighth, The Anthracite Coal District.- This includes not merely the interior of the several anthracite basins, but the mountain-belts encircling each, extending generally to the external base of the second or outer barrier. Ninth, or Bituminous Coal District. In this tract is embraced the whole of the bituminous region, including its insulated northern patches, and all the country to the N.W. of the Alleghany Mountain, excepting the portion already assigned to the Fourth and Seventh Districts. FIKST DISTRICT. HI GENEEAL COMPOSITION AND STRUCTURE OF THE SEVEEAL DISTRICTS. FIRST DISTRICT. It has been already fully shown in the first Part of this Work, that the only rocks of the Palaeozoic system which appear in the south-eastern district, are those which apper- tain to the two lower series, the Primal and Auroral. These rocks appear in six separate belts. The First Belt lies south of the Montgomery and Chester Valley ; it is narrow at the Schuyl- kill, but expands south-westward, and from the Brandywine to York counties occupies nearly all the space between the valley and the State line. It contains the Primal slates and Auroral lime- stone, under conditions of excessive metamorphism. They are closely plicated with inversions, especially in the southern half of the belt ; but it is possible to recognise and trace all the principal anticlinal and synclinal folds. This tract includes a succession of narrow oblique troughs of the Auroral limestone altered into crystalline marble. These are indicated on the Map. All the Palaeozoic rocks are much intersected by cleavage planes and" joints, and their true dip is therefore oftentimes obscure. They are, moreover, so transformed in many instances from their original sedimentary type, and resemble so closely the more ancient Gneissic or Hypozoic strata, with which they are in contact, that, from the vagueness of the dip, it is impossible to define their boundaries with due precision. The Geology of this diversified belt is discussed in detail in the text allotted to it ; and for a general notion of it, the reader has but to study the Map and Sections. The Second Belt is that of the long and narrow Valley of Chester and Montgomery counties, where the ridges immediately bounding the valley consist of the Primal slates and Primal white sandstone, and the bed of the valley itself of the Auroral magnesian limestone, all greatly altered by diffused igneous action. This belt begins at Trenton, includes only the altered Primal rocks as far as Willow Grove ; but thence to Bart Township, Lancaster County, it embraces both this series and the limestone. The whole is a narrow synclinal basin, with the strata closely folded together, those of both sides of the trough dipping with much regularity to the S.S.E. at an angle ranging between 60 and 70. (See the general and local Sections.) The Third Belt is a short and slender tract of the Auroral limestone in Buck's County, near New Hope, where denuding action has cut through the comparatively shallow Mesozoic red sandstone, and exposed this small portion of its Palaeozoic floor. The Fourth Belt is the rather complicated one known as the Limestone Valley of Lancaster and York counties. Its boundaries are delineated on the Map ; but the altered Primal slates, and the still older Gneissic rocks, are in some places so blended in their outcrops, and so similar in aspect, as to render their separation somewhat indefinite. This belt exposes the Primal slates, Primal white sandstone, and Auroral magnesian limestone, in a number of closely-compressed oblique anticlinal and synclinal flexures. (See the general Sections.) The prevailing dip is to the S.S.E. ; only on the larger anticlinals do we meet with a dip to the N.N.W. ; and in many of these the strata, in descending, steepen, and presently become inverted, dipping like the rest to the S.S.E. Within the belt there are four conspicuous anticlinal ridges, exposing the Primal white sandstone and a portion of the Primal slates : these are, Mine Ridge, AVelsh Mountain, Chiques Ridge, and the Pigeon Hills. The Auroral limestone of this belt in the fertile region of the central part of Lancaster County has been extensively uncovered along its northern border by the denudation of the southern side of the shallow overlying red sandstone. Both the 112 SUBDIVISION OF PALAEOZOIC REGION. Primal rocks and the Matinal limestone have undergone throughout many portions of this whole belt a partial metamorphosis, but their alteration has been less excessive than in the more southern belt of the Chester County Valley, and the district south of it. The Fifth Belt is that of the South Mountains between the Delaware and Schuylldll, includ- ing Millbaugh Hill, near Womelsdorf. As shown by the Sections and by the Map, the Primal and Auroral rocks along this range occur in a succession of insulated tracts, the Primal sand- stone forming, for the most part, the flanks and even crests of many of the hills, sometimes with a monoclinal outcrop reposing on the Gneissic rocks, sometimes in swelling anticlinals ; while the limestone rests in the included synclinal valleys, and flanks, in some places, the belt on the S.E. The anticlinal and synclinal flexures affecting these rocks are, with few exceptions, of the oblique or inverted order, and therefore their prevailing dip is towards the S.E. The strata show fewer marks of extreme metamorphosis than those in the preceding belts. The Sixth Belt is that of the South Mountains of Cumberland, Adams and Franklin counties. It includes only the Primal series, exposing extensively the Primal older slates, especially in the south-eastern ridges, for the most part greatly indurated, altered to a sub-crystalline texture, and affected by cleavage. The whole of the Primal series is here much thicker, and is more extensively expanded over the surface by numerous parallel flexures, than in the eastern South Mountains. The sections exhibit clearly the composition and structure of the belt, and show the anticlinals and synclinals to be of the oblique and much-compressed class, and the prevailing dip to be therefore towards the S.E. SECOND DISTRICT. Kittatinny Valley. The only formations which appear within the limits of this naturally-defined division of the Palaeozoic region are those of the Auroral and Matinal series ; nor are all of these continuously or extensively developed, the principal masses being the Auroral magnesian limestone and the Matinal newer slate. The Auroral calcareous sandstone at the bottom of the series is but seldom seen, and it is only occasionally that we observe at the junction of the limestone and slate along the middle of the valley the other two formations, the Matiual argillaceous limestone and Matinal black slate. They would seem not to have been everywhere deposited so far to the S.E. The Matinal black slate occurs in a very narrow outcrop in Northampton and Lehigh, and the Matinal argillaceous limestone is occasionally in contact with it in the same region, and appears again in Franklin County. This latter is almost the only formation of the whole belt which is obviously fossiliferous, the others being very scantily supplied with organic remains. In its geological constitution the Kittatinny Valley displays remarkable uniformity. Excepting in the south-western part of Franklin County, the whole belt is composed of two great lithological zones, the Auroral magnesian limestone forming its south-eastern side, and the Matinal upper slate its north-western. In the part of Franklin just referred to, these two formations repeat themselves in several short and narrow parallel anticlinal and synclinal outcrops. Through the entire length of the valley the strata are folded into a very uniform steep south-eastern dip, in a series of compressed flexures. This structure is distinctly illustrated in all the numerous general sections which cross the district. It is only by a careful and minute inspection of the phenomena of the dips that the geologist detects in this greatly plicated belt the lines of anticlinal and synclinal flexure. These he cannot, however, ultimately fail to recognise, after clue practice. They are readily SECOND DISTEICT. 113 discernible on the Delaware, Schuylkill, and Susquehanna, and on the Cumberland Valley Rail- road. In the zone of Matinal slate the flexures are more obscure than in the limestone, in con- sequence of the excessive amount of cleavage which, though it affects the limestone, is a more prevailing feature of the slate. The almost universal direction of dip in the cleavage planes is S.E., or parallel with that of the stratification, or more strictly with the dip of the imaginary planes bisecting the anticlinal and synclinal curves or flexures. These cleavage planes in the slate, more especially, often efface all marks of the original bedding, and render the detection of the few organic remains of the strata very difficult. Along the north-western border of the valley the beds of slate have their normal dip, inclining north-westward beneath the sandstones of the Kittatinny Mountain ; but along its south-eastern margin, so general is the inversion of the folded limestone,^this formation appears almost everywhere to pass under the Primal rocks of the South Mountains ; and were we not familiar with this striking and general fact of the close compression and obliquity of the more south-eastern Appalachian flexures, and had we not fully established the true infra-position of the Primal to the Auroral rocks, we might imagine the latter to be the lower or older groiip. THIRD DISTRICT. Orwigsburg and Stroudsburg Valley. This long and very narrow tract consists of the Levant, Surgent,Pre-meridian, Meridian, Post-meridian, Cadent,Vergent, and Ponent Eocks, embraced between the south-eastern base of the Kittatinny Mountain and the foot of the Pokono and Second Mountain. Between Carpenter's Point and the Walpack Bend of the Delaware, we have only the Cadent and higher strata on the Pennsylvania side of the river; but between the Walpack Bend and the Water-Gap, the Post-meridian, Meridian, and Pre-meridian Rocks enter the State from New Jersey, and near the Water-Gap the whole of the Levant series gradually crosses the river. From this point to the Susquehanna, all the formations enumerated are included within the belt. The structure of the tract is by no means intricate. From Carpenter's Point to the Wal- pack Bend, the strata have all a gentle N.W. dip ;. but south-westward from that locality, the belt contains in most places one principal anticlinal flexure, and in certain localities there are lesser ones parallel with it ; but even the main anticlinal does not range the whole length of the tract, for that which is the chief axis between the Delaware and the Little Schuylkill, leaves it, and passes into the Pottsville Coal-basin, south of Middleport, while another takes a nearly corresponding place, entering it from the side of the Kittatinny Mountain. This last dies out near the Swatara, and from thence to the Susquehanna the dip is monoclinal and very nearly perpendicular, becoming even inverted as we approach the river. The general sections exhibit sufficiently the structure of the belt in each different segment of its length. FOURTH DISTRICT. The North-Eastern Counties. Throughout this extensive district we are presented with very little variety, either in the strata, their mode of dip, or the features of the sur- face. Between the south-eastern escarpment of the Pokono Mountain, and the northern line of the State, nearly the whole region, if we except the Lackawanna Coal-basin, and the mountains enclosing this trough, is a high and much undulated table-land, the south-westward expansion of the plateau of the Catskill Mountains, with only a few defined ridges and chains of hills upon it. Its strata belong chiefly to the Ponent series, one of the least fossiliferous, least useful, and least interesting of all our Appalachian formations. They are spread out in a succession of very VOL. i. p SUBDIVISIONS OF PALAEOZOIC REGION. flat and wide synclinal and anticlinal waves, as exhibited in Section I., and are therefore approxi- mately horizontal. This district includes the four anticlinal valleys in Bradford and Tioga, which divide the several narrow plateaus in which the bituminous coal-basins terminate towards the N.E. These anticlinal belts expose no strata lower in the scale than the Vergent flags and Vergent shales which saddle each axis. The other rocks are of the Ponent series, and have their outcrops around the borders of each valley. The general sections exhibit the broad undulations of this region. FIFTH DISTRICT. The Mountain-belts of the Lower Juniata. The rocks exposed in this very complicated division of the Appalachian Chain, included between the Kittatinny Mountain on the S.E. and Jack's Mountain on the N.W., consist of all the great series of strata from the Auroral to the Ponent inclusive. A sufficiently correct general conception of the structure of the district will be derived from a comparison of the Map with the general Sections, and by observing that the whole region is made up of three great anticlinal belts, each consisting of a group of several lesser undulations, and of four synclinal tracts, likewise compound, but showing fewer flexures. The First Anticlinal Belt is that of Perry County. It commences in the Pottsville Coal-field, on the Swatara, divides the two western prongs of the basin, and is the anticlinal, separating Berry's and Peter's mountains. It lifts, within the limits of our present district, the Ponent and Vergent rocks in Powell's and Armstrong's valleys, and crossing the Susquehanna, elevates the Cadent rocks in the Half-Fall Mountain. Soon after crossing the Juniata, it ceases to be a nearly simple anticlinal belt, and becomes a group of parallel flexures, rapidly widening by the successive introduction of new anticlinals. These, as we trace the belt in its gradual sweep south-westward, diverge and elevate to the day in the central part of the general tract of Cadent strata, first the Pre-meridian, and next the Surgent rocks, showing lower and lower strata as we advance, and imparting to each formation a complicated but beautifully winding line of outcrop. The more south-eastern of these anticlinals pass out early into the Kittatinny Valley, the more north- western range through Amberson's Valley, but also enter the Kittatinny near London. The First Synclinal Belt is the broad trough of Vergent, Ponent, and Vespertine rocks west of the Susquehanna, and embraced between this anticlinal zone and the southern basin of the Kitta- tinny Mountain, and called Sherman's Creek Valley. It is the trough of the Dauphin Coal-basin. The Second Anticlinal Belt is that of Mahantango Valley, Tuscarora Mountain, and Path Valley. This originates as a group of flexures in the north-western part of Broad Mountain, and within the district before us lifts to the surface the Ponent, Vergent, and Cadent Eocks in Mahantango, and crossing the Susquehanna, brings to view in the great anticlinal of the Tuscarora Mountain, the Meridian, Pre-meridian, Surgent, and Levant strata to the Levant White Sandstone. Advanc- ing and curving south-westward, the belt develops other parallel anticlinals in Liberty Valley which, passing through the knobs of the Southern Tuscarora Mountain, and the " Locking of the Mountains," enter North Horse Valley, and expose the Matinal slates. As these decline others rise, and a chief one ranges along Path Valley, bringing up the Auroral limestone. Connected with this belt is the anticlinal of M c Connellstown Cove. The Second Synclinal Belt is that of Wildcat and Buffalo Creek Valleys. It is the westward prolongation of the trough of the Bear Valley Coal-basin. It is a nearly simple synclinal trough, containing, west of the Susquehanna, the Vespertine, Ponent, Vergent, and Cadent strata. By the coalescing of the first and second anticlinal belts it terminates near the head of Buffalo Creek. FIFTH DISTRICT. 115 The Third Anticlinal Belt is that of Shamokin Valley, and Shade and Black Log Mountains. It is a more simple anticlinal zone than either of the preceding. The flexures which compose it begin near the Lehigh River, and are traceable between the basins of the Eastern and Middle Coal Region, and through the Catawissa Valley into Roaring Creek Valley in the district before us. In the valley of Roaring Creek and Shamokin Creek, the rocks exposed in this zone are the Ponent, Vergent, and Cadent. Soon after passing the Susquehanna, the Pre-meridian, and next the Surgent and Levant strata, rise to the day upon the expanding anticlinal of the Shade Mountain, which, for some distance, is the only flexure of the belt. Approaching the Juniata, as this anti- clinal begins to subside, another conspicuous one, that of Blue Ridge, rises, and parallel with it a second, still greater one, that of Black Log Valley. The first lifts the Levant White and Red Sand- stones into a mountain-ridge with a double crest, while the last-named elevates first the whole Levant series, and then the Upper Matinal Rocks in the anticlinal valley of Black Log. This latter grand wave upon the crust continues further south than that of Blue Ridge, and dies away soon after entering Fulton County, the whole belt there terminating by the closing over of the Ponent strata. The anticlinal of Pigeon Cove, at the Maryland line, may be referred to this belt, or the second, indiscriminately. The Third Synclinal Belt is the long and regularly-curving valley bounded by the second and the last-described anticlinal belts. Where it is crossed by the West Mahantango and Cocolamus creeks, it is a broad valley of the Vergent and Cadent rocks ; but approaching the Juniata, anticlinal undulations elevate the Surgent and Scalent marls and shales, and the zone of Vergent and Cadeiit strata is contracted to the narrow central valley of Tuscarora Creek. The belt continues through the little Aughwick Valley of the same narrow dimensions. To this synclinal zone we may refer the trough of Scrub Ridge, in Fulton County. The Fourth Synclinal Belt is embraced between the third anticlinal and the foot of Jack's Mountain, Montour's Ridge, and Sideling Hill, the north-western limits of the district. This long and narrow trough in the strata is traceable from the knob of Catawissa Mountain, as a hilly zone of the Ponent rocks following the North Branch, and extending westward towards New Berlin. Curving with an ample sweep more and more to the south, the valley, now confined between Jack's Mountain, Shade Mountain, and Blue Ridge, includes a series of small anticlinals, which lift the Surgent rocks, so that this part of the belt exposes a chain of several parallel outcrops of the Vergent, Cadent, Pre-meridian, Surgent, and Levant strata, as far to the S.W. as the Great Bend of the Juniata. Beyond this point the belt is of simpler structure, the minor anticlinals subside, and the trough contains little else than the Vergent and Cadent rocks to the termina- tion of Jack's Mountain. From this latter locality to the southern line of the State, this zone becomes monoclinal along the foot of Sideling Hill, showing the Vergent and Ponent rocks dip- ping gently westward, first from the Jack's Mountain anticlinal, and then from that of Pigeon Cove. In relation to the character of the flexures in this diversified Fifth District, very few words of general description will suffice. Nearly all the undulations, both the greater and the lesser ones, are bold curves of the normal type, that is to say, have their north-western sides steeper than their south-eastern, but not inverted, as in the district of the Kittatinny Valley, nearer the source of the pulsations of the crust which caused the flexures. The special features of each zone will be found distinctly delineated in the numerous general and local sections which cross the whole district ; and their geology will be treated of in detail in future chapters. 116 SUBDIVISIONS OF PALAEOZOIC REGION. SIXTH DISTRICT. The Mountain Belts of the Upper Juniata and West Branch of the Susque- hanna. In the complicated division of the Palaeozoic region, to which we next proceed, we have repeated and extensive outcrops of all the strata from the top of the Ponent to the bottom of the Auroral series. The general sections from IV. to IX., inclusive, cross the district, and, if studied in connection with the Map, will much assist the reader in comprehending the following outline. Looking at the structure of the whole district, we perceive it to consist of six natural lesser belts or tracts, but not disposed in an order as regular and parallel as those of the district just described. The First Belt is embraced between the southern part of Montour's Ridge and the base of the Alleghany Mountain, and extends lengthwise from east of Harvey's Creek to the western ends of Buffalo, Whitedeer, and Whitedeer Hole valleys. The rocks comprised within the tract are those of the Levant, Surgent, Pre-meridian, Cadent, Vergeut, and Ponent series. On the S.E. the interesting anticlinal zone of Montour's Ridge shows all the Surgent and Upper Levant strata. North of it runs the long synclinal of the Vergent and Ponent rocks, investing the western end of the Wyoming Coal-basin ; and north of this again there is a long anticlinal tract, crossing the upper waters of Harvey's and Fishing creeks, and elevating the same series. In the central portion between Montour's Ridge and the end of the Bald Eagle Mountain, the Surgent and Pre-meridian rocks appear in the region around Milton, with a belt of the Cadent and Vergent both north and south of them. West of the Susquehanna this belt is limited by a succession of symmetrical anticlinal mountain-spurs, the terminations of as many great anticlinal waves, which there lift in gentler undulations the Middle and Upper Levant, Surgent, and Pre-meridian strata through the Cadent and Vergent, and impart to the Surgent a very winding line of outcrop, fold- ing this series round the points of the mountains and into the coves, or intervening synclinal valleys. The Second Belt is the well-characterised region embraced between Jack's Mountain and the Bald Eagle Mountain. It includes a very remarkable group of grand anticlinal flexures, the top of each principal wave forming a long and narrow fertile valley of the Auroral limestones and Matinal slates, divided by bold synclinal mountain-ridges of the massive Levant sandstone. The larger valleys are Kishicoquillas, Penn's, Brush, Sugar, and Nittany valleys. These close at one or both ends by the gradual coalescing of their mountain-barriers, brought together by the declension of the crests of the anticlinal waves. Ten long symmetrical mountain-spurs of the Levant white sandstone, curiously arranged in echelon, form the eastern termination of this belt. Its western end is near the Juniata, in the two anticlinals of Jack's Mountain and Bald Eagle Mountain, not far from Hollidaysburg. The Third Belt is an interesting synclinal zone nearly in the prolongation of the former, commencing on the N.E. between the two southern terminating anticlinals, and having Tussey Mountain for its north-western boundary, and Stone Mountain and the base of Sideling Hill for its south-eastern. In this deep and broad trough in the strata, which consists in the main of but one ample synclinal basin, with a few lesser undulations, there are contained the whole of the Palaeozoic strata of the State, from the Levant sandstones to the Coal strata inclusive, excepting only the Post-meridian series, universally absent to the S.W. of the Delaware River. In the limited Coal-basin of Broad Top Mountain, we have an outlying patch of bituminous coal-measures, denoting not only the depth of this great synclinal wave, but in its remoteness SIXTH DISTRICT. 117 from the main coal region "W. of the Alleghany Mountain, the enormous extent of the denuda- tion which the intervening anticlinal belt of country has experienced. The Fourth Belt is the narrow anticlinal zone in Huntingdon and Bedford, bounded on the east by the eastern base of Tussey Mountain, and on the west by the north-western foot of Dunning's and Wills' Creek mountains. This tract embraces a chain of fertile anticlinal valleys of the Auroral limestone, namely, Morrison's Cove, Friends' Cove, Bean's Cove, and Milliken's Cove ; the three first forming the back of a great anticlinal wave, or perhaps more strictly of a group of waves. In the central parts of Morrison's Cove, as in the corresponding parts of the Kittatinny Valley, the crest of the anticlinal wave exposes the very lowest sandy strata of the Auroral series, the equivalents of the Auroral calcareous sandstone (Calciferous Sandstone of New York). On the other hand, rocks as high in the scale as the Meridian sandstone rest in the synclinal trough between Evit's and Wills' Mountain. The Fifth Belt is the very long and narrow and continuous valley enclosed between the Bald Eagle, Dunning's, and Wills' mountains, on the S.E., and the escarpment of the Alleghany Mountain on the N.W. This zone possesses, except where a few local undulations occur, a very regular monoclinal structure, its strata dipping towards the N.W., at an angle which grows pro- gressively less as we advance in that direction and ascend in the general series. Its rocks, com- mencing with those on the north-western flank of the Bald Eagle range, and terminating near the summit of the escarpment of the Alleghany, appertain to the Surgent, Pre-meridian, Meridian, Cadent, Vergent, and Ponent formations. Only in the western side of Bedford County are the simple monoclinal features of this long valley locally interrupted by the introduction of two or three small anticlinal tracts. Throiighout the extensive and varied Sixth District, the anticlinal and synclinal flexures of the strata are of great length and striking parallelism, and in many quarters so singularly regular, as to suggest irresistibly their analogy to a group of stupendous waves or billows in a flexible crust. It will be seen by a glance at the sections which illustrate this district, that the flexures are, with scarcely an exception, of the normal order, but have, like those of the Fifth District, a large arc of curvature, and therefore a prevailing steepness in their dips. In a few instances, a longitudinal dislocation of the strata is discernible along the crest, or on the north side of the anticlinal waves ; and usually in such cases there is a sudden change in the dip, with a loss of regularity in the form of the anticlinals. SEVENTH DISTRICT. The Country N.W. of the Bituminous Coal Region. This division of the Palseozoic region of the State is, as the Map shows, of an irregular, triangular form, being but a portion of an extensive natural geological belt, which ranges from southern New York into north-eastern Ohio. In stratification and structure, it is by far the simplest portion of the State. The only formations which underlie it are the Vergent shales and the Vespertine sandstones, for it is an interesting fact that both the Ponent red sandstones and shales, and the Umbral red shale, are entirely thinned away before they reach this north-western outcrop of the general basin, enormous as their thickness is in the south-eastern valleys of the Appalachian Chain. By the general section (VIII.) it will be seen that across this whole tract the strata exhibit, with little or no variation, an extremely gentle dip towards the S.E., passing finally under the Bitu- minous Coal Region. From the north-western outcrop of the Lower Coal Eocks, the surface gradually slopes north-westward to Lake Erie, descending about 1000 feet. EIGHTH DISTRICT. The Anthracite Coal Region. This is a division of the Appalachian Chain, 118 SUBDIVISIONS OF PALAEOZOIC EEGION. of great apparent complexity of structure, but of remarkable and beautiful symmetry when understood. I include in it not only the Coal strata or Serai series, but the Umbral and Vespertine formations also, and therefore its curiously inflected boundary will be traced by fol- lowing the outer base of each external or second mountain encompassing the Coal-basins and valleys of Umbral red shale. In the aggregate, it may be viewed as a broad synclinal tract enclosed between the anticlinals of the Kittatinny Valley on the south, and the wide anticlinal at the foot of the Alleghany Mountain on the north ; but regarded more in detail, we find it composed of an extensive succession of moderately steep anticlinal and synclinal flexures or waves arranged in several groups or belts. The First Belt is that of the Pottsville or southern coal-basin. This is a long synclinal zone beginning E. of the Lehigh in the Kettle Mountain, and terminating W. of the Susquehanna in the two troughs of the Cove and Buffalo mountains. This synclinal belt forks into two at the knob of Berry's Mountain, where a great anticlinal flexure elevates lower rocks. In the interior of this great trough, or the part occupied by the coal strata, there are several subordinate undulations of the strata producing important local effects in the distribution of the coal-beds, but unconnected with any very conspicuous features of the surface. The Coal-basin itself reposes in the middle of the general synclinal zone of the Umbral red shale, and Vespertine conglomerate. It begins at the Lehigh, gradually widens to a breadth of four miles at Pottsville, and at Good Spring Creek divides into the two basins of Dauphin and Bear Valley. A more detailed descrip- tion will be given in the chapters on the Anthracite Coal strata. The Second Belt is a shorter parallel anticlinal tract extending from the Lehigh westward, next north of the Pottsville Basin. It comprehends, first, the Nesquihoning Broad-Mountain, composed of Vespertine conglomerate ; next, the Locust Valley of Umbral red shale ; and, lastly, Broad-Mountain, a table-land consisting of the Serai conglomerate, with a few subordinate narrow basins of the Coal-measures. This belt ends westward in the concave sweep of the Mahan tango Mountain. Broad-Mountain is an elevated plateau, including several lesser anticlinals, which pass out into the low valleys of the Umbral red shale, both eastward and westward, by a series of loops which separate its synclinal mountain-spurs. The structure of the Nesquihoning Mountain is that of a wide, flat, regular anticlinal wave, w ith a number of insignificant gentle undulations on its summit and northern flank. The Third Belt is the important synclinal tract or basin north of Broad-Mountain, which con- tains the rich coal-fields of Mahanoy and Shamokin, or the Western Middle Coal-basins. It com- mences in the Head Mountain, and terminates westward at the Susquehanna, in the synclinal knob of Mahanoy Mountain. The inner trough, or that of the Coal strata, comprehends several lesser basins divided by well-defined anticlinal ridges. The Fourth Belt is the broad table-land including the Eastern Middle Coal-basins. It lies between the anticlinal belt of Nesquihoning Mountain on the S., and that of the Wapwallopen and North Branch on the N., and extends from near the Lehigh westward, to the western foot of the Catawissa Mountain. Its central plateau of the Serai conglomerate comprises five con- tinuous and well-marked anticlinal flexures of gentle curvature and dip, forming six small and shallow troughs of the Coal-measures. The terminations of some of these minor basins are discern- ible in the flat mountain-spurs, which protrude eastward and westward from the general plateau. EIGHTH DISTEICT. 119 The Fifth Belt is that of the beautiful and well-defined Wyoming Coal-basin. As all the other belts are severally in contact with each other, so is this one linked to the last described by the high table-land of the Vespertine conglomerate between the sources of the Lehigh and Wapwal- lopen. This belt is a very regular synclinal trough, tapering to a point at each end, and sweeping with a bold crescent curve, convex towards the S.E. The Coal-measures, as in all the other synclinal tracts, are encompassed by a double mountain-crest, the interior consisting of the Serai conglomerate, the exterior of the Vespertine sandstone. Within the Coal-basin there are several secondary undulations imparting no prominent features to the tract, but affecting materially the local outcropping of the coal-beds. The belt, including the Vespertine strata, originates a few miles N. of Carbondale, and gradually curving south-westward and westward, terminates in a synclinal mountain-ridge at Fishing Creek. A general survey of the relative positions of these several belts of the Anthracite districts, as they are depicted on the Map, discloses a curious oblique arrangement. Each more northern zone is situated further east than its neighbour. In other words, all the principal anticlinal and synclinal flexures of the region are grouped in echelon. By consulting the general sections which cross the district, it will be seen that only in the first, or Southern Coal-basin, do the flexures approximate to the folded or inverted type. Advancing northward, the undulations take on the normal form, and decline progressively in curvature or steepness as we proceed. In the Western Middle Coal-basin the strata dip at a moderately high angle ; while in the more northern tracts of the Eastern Middle, and the Northern or Wyoming belts, they undulate much more gently. This striking gradation is but one instance, among many, of conformity to a law which is very general throughout the entire Appalachian Chain, namely, that the undulations of the strata open out and decline in steepness as we recede from the quarter of maximum disturbance or rupture of the crust, precisely as we see occur in the more advanced waves of a broad group of billows suddenly generate^ upon the surface of a fluid by some local force. NINTH DiSTpacT. The Bituminous Coal Region. In its composition and structure, this last, and much the largest, of all the divisions of the general Palaeozoic region of the State, is extremely simple. It comprises only the Vespertine, Umbral, and Serai series, the former in very narrow lines of outcrop, bordering and dividing some of the coal-basins, except in the north-eastern part of the district, where the Vespertine conglomerate, or sandstone, occupies an extensive irregular area between the escarpment of the Alleghany Mountain on the S., the State line on the N., the valley of the North Branch of Susquehanna on the E., and the waters of the Sinnemahoning on the W. Throughout the rest of the region, the Coal-measures bordered by the Serai conglome- rate occupy the whole surface. The beautifully symmetrical structural features of this vast region are illustrated in the general Sections. Viewed broadly, the whole territory is to be regarded as only the north-eastern end of an enormous coal-basin, which, commencing in our northern counties, has its southern termination in Middle Alabama. The portion which is embraced within the limits of Pennslyvania, covers more than 10,000 square miles. It has for its south- eastern margin, the narrow table-land of the Alleghany Mountain ; and for its northern border, the much wider plateau of the northern counties. From these two limits, the surface slopes south-westward, sinking gradually towards the middle of the vast but nearly horizontal trough. 120 SUBDIVISIONS OF PALAEOZOIC REGION. Traversing nearly tlie whole length of this district are five very long and comparatively low or flat anticlinal undulations, which subdivide the general area into six subordinate narrow coal- basins. The First of these lesser basins is bounded in Somerset by the anticlinals of Negro Mountain and Laurel Hill. It thence follows the table-land of the Alleghany Mountain, and ends at the North Branch in the narrow plateau of the Mahoopeny Mountain, the trough gradually ascending and flattening until finally it is greatly denuded of its coal-measures, as it approaches its north- eastern termination. The Second Basin, or that of Ligonier Valley, is in its southern parts a deep trough, between the anticlinals of Laurel Hill and Chestnut Eidge. It rises and shoals towards the N.E., and as a continuous coal-basin terminates on the West Branch of the Susquehanna, below Karthaus. Further on it becomes a table-land, ending in a narrow elevated spur near Towanda, and sustain- ing, like the eastern end of the first basin, only a few detached small patches of the coal-rocks. The Third Basin begins near the Kiskiminetas, and rises toward the Sinnemahoning, until at Trout Run it ceases to contain a continuous belt of the Coal-measures. It there merges into the general northern plateau, and is prolonged into Bradford as a third narrow mountain-spur, sustaining a few insulated tracts of the Coal strata. South of the Kiskiminetas there are three sub-basins in the prolongation of this third synclinal belt. The Fourth Basin likewise commences near the Kiskiminetas, and ceases to hold any but a few small patches of Coal strata beyond the sources of Trout Run. It ends in a long narrow plateau or flat spur in the northern part of Tioga County. The Fifth Basin originates as a defined trough of the Coal-rocks in the neighbourhood of Freeport, by the rising of the anticlinal axis which forms its north-western limit. This basin contains an unbroken belt of Coal-measures as far as Clarion River. Following the valley of that stream toward its sources, il^becomes a part of the general northern table-land. Though it retains the synclinal form, only its higher summits hold any tracts of the Coal strata, and even these scattered patches cease after the belt enters Potter County some distance. Its north-eastern prolongation is rather a chain of low, flat, sandstone hills, than an unbroken spur or plateau. South-westward it merges into the larger basin of the Ohio River. The Sixth Basin is the last or north-western trough, formed by the general south-eastward dip of all the strata from their north-western outcrop, and by the fifth anticlinal. It is of great breadth in Butler, Beaver, and Mercer, but contracts and grows shallow in Clarion and Elk, and becomes a mere chain of detached coal-bearing summits resting on an elevated plateau of the Serai and Vespertine sandstones and conglomerates, as it ascends the Tionesta into Warren and M c Kean counties. In the opposite or south-western direction, this trough enlarges by the merg- ing into it of some of the narrow adjacent basins on its S.E., and it becomes the main coal-field of the Ohio River for a great distance along the western border of Virginia and the south-eastern side of Ohio. Besides the above six long subordinate troughs included in the general Coal-field, there is one to the east of the first enumerated, occupying the south-eastern side of Somerset County, between the anticlinal axis of Negro Mountain and the crest of the Alleghany Mountain. The northern end of the Potomac Basin of Virginia and Maryland penetrates a few miles into Pennsylvania. NINTH DISTRICT. 121 There is a small high synclinal belt, containing, however, little or no available coal, in the table-land of the Alleghany or Bowman's Mountain, in Luzerne County. This may be viewed as a portion of the first or Mahoopeny Basin. Taking a comprehensive view of the whole broad bituminous Coal region, we are struck with the extraordinary length, parallelism, evenness of breadth, and progressive declension north-west- ward of its several beautiful belts of symmetrical, anticlinal, and synclinal waves, and with their strong resemblance, in all the features here named, and in their grand crescent-like sweep, to a group of subsiding billows. When we enlarge our survey still farther, and embrace the entire width of the Appalachian flexures from the south-eastern to this north-western side of the State, we are still more forcibly impressed with this resemblance, and with the appropriateness of the general theory of crust- undulations elsewhere given. In the south-eastern division of the State, the strata are, for the most part, closely folded or plicated, the north-western sides of the anticlinals being entirely inverted : in the middle or mountain region, this feature is somewhat subdued ; the waves are more expanded, though still steep and of the unsymmetrical form ; while in this north-western district, the undulations are low, and much dilated, and the two slopes of each wide wave are approximately equal. VOL. I. Q CHAPTER III. DISTRIBUTION OF THE PALAEOZOIC STEATA IN PENNSYLVANIA, AND THEIR CHANGES OF TYPE AND THICKNESS. BEFORE entering on the detailed delineation of the Palaeozoic Eocks, in their many successive outcrops within the State, it will be expedient, for the sake of completing our general picture of them, to show their broader features, with the changes of type and thickness which they undergo. Beginning with the lowest, and pursuing each formation in the geographical order laid down, or from S.E. to N.W., we shall commence with the Primal series. PEIMAL SERIES SOUTH OF CHESTER VALLEY. PRIMAL LOWER SLATE. This formation is developed in great thickness from the Brandywine to the Susquehanna, and thence south-westward, but is too much disguised by metamorphism, and close plication of its beds, to admit of measurement. It is, indeed, nowhere susceptible of exact estimation, but may be conjectured to be, where most expanded, ............. 2000 feet. PRIMAL SANDSTONE. This rock, the equivalent of the Potsdam Sandstone of New York, is distinctly visible, though not in much thickness, around some of the small limestone basins of Chester County. It is prominent on the Street Eoad, and in Dochranaman Hill; but its thickness is not accurately ascertainable. It occurs on the Susquehanna, the most southern outcrops being near Peach Bottom, where it measures . 90 PRIMAL UPPER SLATE. This formation is not recognisable around the limestone troughs of the southern part of Chester County. THE PRIMAL LOWER SLATE, On the Schuylkill, consists of two divisions : 1st, T/ie Lower, a semi-porphyroidal altered sandy slate, is . 300 2d, The Upper, an imperfectly crystallised talcose micaceous slate, is . 200 In Edgehill, near Attleborough, the formation measures PRIMAL SANDSTONE. This frequently consists of two sandstones and an interposed slate. Thicknesses On Schuylkill and Wissahickon, 35 to . East of Willow Grove (including quartzose conglomerate), Edgehill, near Attleborough, ..... Coatesville, North Valley Hill- Lower Sandstone, . . ..... Slate, ..... Upper Sandstone, ..... 125 Parkesburg, North Valley Hill Lower Sandstone, ...... 50 Slate, .... ... 300 Upper Sandstone, . 20 370 Susquelwnna, above Columbia Lower Sandstone (with included bands of slate), . . 300 Slate, . . . . . . . . 300 Upper Sandstone, ....... 27 627 PRIMAL SEEIES. ^ 123 PRIMAL UPPER SLATE in lino of Chester Valley. At Willow Grove, and east of it, this rock does not exist. In Barren Hill, and on the North Pennsylvania Railroad, it is talcose and thin. At the Diamond Rock, and in Paoli Section, it is thin, possibly between 200 and . 300 feet. Near Coatesville it is .... ... 700 At Parkesbwrg, where probably all is not seen, it shows 300 On the Susquehanna, above Columbia, it measures about . . 1000 From the above data it would appear that this division of the Primal series augments even more rapidly than the White Sandstone as it stretches westward. Survey of the Formation The Primal Wliite Sandstone fluctuates much as to its thickness within the region where it occurs, though it is singularly retentive of its character as a rock. It would seem on the whole to augment towards the S.W. or W. ; and this agrees with its general absence in New Jersey, and its full dimensions on the western slope of the Blue Kidge in Virginia. The Primal Upper Slate likewise increases westward and north-westward, as the preceding statements fully indicate. We know, moreover, that it is in great force in Maryland and Virginia. PRIMAL SERIES IN THE SOUTH MOUNTAINS. On the Delaware River The PRIMAL SANDSTONE is the principal formation of the series, very little slate being discernible. In Durham Ridge, at Myer's Quarry, its whole thickness is about . . . . 1 00 feet. In Chestnut Hill, north of Easton, the sandstone is well developed, but its thickness is unknown ; probably it does not exceed ...... 100 On the Schuylkill, below Reading Its thickness is much greater than at the Delaware. It is folded and crushed, and cannot be measured. The PRIMAL SLATES possess some development in the South Mountains near the Schuylkill, but cannot be measured. In Adams County Both of the Primal Slates, particularly the Lower, are evidently largely developed in the South Mountains, between the Susquehanna and the Potomac. The PRIMAL SANDSTONE is also thick throughout this belt, probably as thick as on the Susquehanna, or 300 The Primal series nowhere rises again to the day N. W. of the South Mountains. AURORAL SERIES. Auroral Calcareous Sandstone. A rock apparently identical with the true Calciferous Sand- stone of New York, is visible near the Delaware, and at a few points further W., along the south margin of the Kittatinny Valley, as at Columbia, but nowhere throughout this belt in much thickness. Assuming that the lowest sandy Magnesian Limestone of the Auroral series at Columbia represents this formation, it has there a thickness, between the underlying Primal slate and another overlying slate, of 250 feet. No fossils having been discovered in it, we have only lithological characters to guide us, and its identification is therefore doubtful. A calcareous friable sandstone, unlike the Primal sandstone, rises from beneath the Auroral limestone in the more elevated tracts of Nittany Valley and Morrisons Cove, and I have less hesi- tation in referring it to the Auroral calcareous sandstone. Still no fossils have been found in it, though no favourable outcrops have occurred. 124 TYPES OF PALEOZOIC STRATA. AURORAL MAGNESIAN LIMESTONE. This great formation, which seems to constitute the most extensive floor of the Appalachian Basin east of the Missouri River, is nowhere in Pennsylvania susceptible of entire measurement. In its south-eastern synclinals, as the Chester and Conestoga valleys, we have its lower part, but not its upper. In the Kittatinny Valley, though the whole formation is present, it is too much plicated and obscured to admit of satisfactory mensuration ; and in the great anticlinal valleys of Centre, Blair, and Bedford, though its entire thickness outcrops in certain neighbourhoods, it is impossible, from the extensive wash from the sandy barrens against which it rests, to ascertain, within a few hundred feet, its lower limit. In these last districts we may, however, make an approximation to its total bulk. On the Schuylkill its upper and lower portions are not visible, or are so concealed as to make estimation of thickness impossible. It is, however, practicable to obtain proof of great thickness, by measuring across the limbs of the synclinal basin from its contorted central area. The measurements thus made serve to check each other, and give a thickness of 3000 feet, comprising evidently the middle and a large part of the lower beds of the formation. The limestone is of the Magnesian type, somewhat argillaceous in the upper beds. In Kishicoquillas Valley the lower beds are not visible for perhaps many hundred feet. 1. The lowest seen are alternations of light-blue, fine-graiued, and darker magnesian rock, -with knots of white dolomite, ....... 300 feet. 2. Fine-grained light-greyish blue magnesian limestone, a little chert in lower layers, COO 3. Dark crystalline magnesian limestone, with kernels of dolomite, . . 100 4. Light-blue limestone, weathers mealy, conchoidal fracture, . . 600 5. Slightly magnesian limestone, some beds very pure ; fine texture, purplish blue, massive and ribboned, ...... 200 6. Pure light-blue conchoidal and massive limestone, . . . 150 Total thickness visible, . 1950 feet. Nittany Valley, Bellefonte, ascending 1. Grey crystalline rough magnesian limestone, underlaid by much of same con- taining chert, visible, ...... 600 2. Pure blue limestone no fossils, . , ^00 3. Grey crystalline limestone, no fossils, .... 1500 4. Light-blue fine-grained, like bird's-eye marble, a very few characteristic fossils, 300 5. Alternation of light and dark-grey rough crystalline rock, weathers with sandy surface (not silicious), corals and other fossils, . . . 1000 6. Magnesian, massive light-blue grey no fossils, . . . 500 7. Alternation of blue coralline and argillaceous dull-blue magnesian limestone, 200 8. Dark-blue massive rubbly limestone, with many fossils, . . 400 9. Clear blue, massive, like bird's-eye marble, with fossils, . . 150 10. Massive, blue, fine-grained limestone, with obscure corals, . . 20 11. Blue, thin-bedded limestone, encrinal and coralline, . . 30 Total thickness, . 5400 feet. f MATINAL SERIES. The Matinal series is evidently thick wherever it appears in Pennsylvania, and has apparently its maximum dimensions at its great south-eastern outcrop, in the Kittatinny or Appalachian Valley. There, however, its thick uppermost mass, the Matinal shale, is unfortunately so folded and so intersected with cleavage-planes as to baffle every attempt at measurement. The whole series cannot be of much less depth than the Auroral limestone, and we shall not err widely if we assume it, in the Kittatinny Valley, at from 3000 to 4000 feet. The Matinal shale manifestly declines in thickness as it spreads north-westward, but the other members the black slate and the argillaceous limestone appear to retain their bulk. MATINAL SERIES. 125 MATINAL LIMESTONE (TRENTON L. OF NEW YORK). No traces of this formation have been met with in either of the great limestone basins S. of the Kittatinny Valley. Within that long limestone belt it appears and disappears, at intervals, from the Delaware River to Maryland, though probably it is absent through more than two- thirds of this distance. Delaware River. The formation has been measured only on Martin's Creek, near the road leading from Easton to the Delaware Water-Gap. There it is well exposed, and exhibits its characteristic composition and fossils. Its thickness is about ........... 350 feet. Kishicoquillas Valley. The next outcrop of the formation admitting clear measurement is Kishicoquillas Valley, about half-way across the Mountain Chain. Here, under its usual type of alternating thin layers of smooth dark-blue limestone and blue shale, and with its usual fossils, it has a thickness of . 550 Nippenose Valley. Advancing to the furthest north-western outcrop, the Matinal limestone appears through- out nearly the whole length of the Great Nittany Anticlinal, where the elevation is sufficient to bring it to the day. In Nippenose Valley, with numerous characteristic fossils, the rock graduates at its upper limit into the Matinal black slate. It measures . . . . 300 Nittany Valley. In the neighbourhood of Bellefonte, a more south-western locality on the same belt, the Matiual limestone, in the condition of a bluish-grey, thin-bedded, but somewhat rubbly limestone, has a total thickness of ............ 360 The lowest 60 feet is dark-blue, thin-bedded, and of the Trenton type. Milliken's Cove. Far to the S.W. the Matinal limestone is discernible in Milliken's Cove and the other limestone coves of Bedford County. ' It wears its usual type, and has the characteristic fossils, but is obviously of reduced thickness, when compared with its development N. of the Juniata. MATINAL SLATE (UTICA SLATE). Kittatinny Valley. The first or most S.E. appearance of the Matinal black slate is in the Kittatinny Valley, where it occurs chiefly between the Delaware and Lehigh. On Martin's Creek, where it is finely exposed, it measures about .......... 300 It grows thinner proceeding westward. Near Nazareth it is very carbonaceous, and at its outcrop is so soft as to be convertible into a pulverulent, dark pigment. Kishicoquillas Valley. This formation is well developed around the borders of nearly all the anticlinal limestone valleys of the Mountain Chain west of the Susquehanna. It is of full dimensions in Kishicoquillaa Valley, where it is of its usual composition, but much intersected with cleavage. It measures, apparently, 400 It is recognisable by its Graptolites and other distinctive fossils. Nippenose Valley. In this anticlinal uplift the Matinal black slate abounds in its usual fossils, retains all its lithological characters, and exhibits a thickness of . . . . . . 300 Nittany Valley. Near Bellefonte, and elsewhere along the N. W. border of the last great anticlinal, the Black slate, with its characteristic fossils, measures nearly ....... 300 Milliken's Cove. It occurs as far S. in the State as Milliken's Cove, with its usual fossils and in its full dimensions. The passage between its lower limit and the top of the underlying limestone being, as elsewhere, quite abrupt. i MATINAL SHALES (HUDSON RIVER SLATE). As already stated, this, by far the largest formation of the Matinal series, is not susceptible of accurate measurement anywhere along the Kittatinny Valley, its main south-eastern outcrop. Reappearing all round the anticlinal limestone valleys between the Kittatinny and Alleghany Mountains, S.W. of the Susquehanna, it there displays itself in numerous good exposures. Kishicoquillas Valley. In Kishicoquillas Valley, the locality selected as being about half-way across the chain, the 126 TYPES OF PALEOZOIC STRATA. formation occurs under its usual Pennsylvanian type of a blue shale and slate, alternating with thin grey calcareous sandstones, and containing many distinctive fossils, especially towards its upper limit. It has a total thickness of about . . .......... 1200 feet. Nittany Valley. Crossing north-westward to its last outcrop in the State, we find this rock ranging along the south-eastern base of the Bald Eagle Mountain, under an average thickness of about . . 700 An imperfect measurement in Nippenose Valley indicates its thickness there to be a little less, and in Bedford County it is perhaps somewhat greater. Summary. The whole formation presents a marked reduction in thickness as it spreads west- ward, or more properly north-westward ; but in crossing the Mountain Chain of Pennsylvania, it exhibits no approach to the highly calcareous type which it wears where it next re-emerges to the day in the distant anticlinal of Southern Ohio and Northern Kentucky. LEVANT SEEIES. The Levant series, naturally divisible into three groups or distinct formations, is largely developed in the Appalachian Chain of Pennsylvania, from the Kittatinny Mountain, its most south-eastern outcrop, to the Bald Eagle Mountain, Dunning's Mountain, and Wills' Mountain, its most north-western. Each of the subdivisions undergoes a greater or less change of type in advancing across the Chain ; indeed, the middle member, or red shale and sandstone, does not show itself at all in the Kittatinny Mountain and other south-eastern outcrops ; and the lower and upper formations, likewise thin towards the S.E., acquire their maximum development near the opposite side of the Mountain Zone. These Levant sandstones constitute, with the exception of the carboniferous sandstones enclosing the Broad Top Coal-field, all the mountain- ridges, and higher spurs, of the entire Chain west of the Susquehanna between the Kittatinny Valley and the valley at the base of the Alleghany Mountain. Within this space a remarkable series of long, parallel, anticlinal undulations of the strata lift these rocks into the mountain-crests alluded to. In the part of the Chain occupied by Perry, Juniata, Mifflin, Union, and Centre counties, the chief anticlinal mountain outcrops of the Levant series are about nineteen in number ; while in the district south of the Upper Juniata, or that of Franklin, Huntingdon, Fulton, Bedford, and Blair, their outcrops amount to seven or eight. With a view to avoid a too detailed tracing of the changing characters and dimensions of the three members of the Levant series, they will be described in this general sketch as they occur only in their south-eastern, middle, and north-western outcrops in the Chain. LEVANT GREY SANDSTONE (ONEIDA CONGLOMERATE OF NEW YOBK). Kittatinny Mountain or South-Eastern Outcrop Delaware Water-Gap. At this locality the inferior group of the Levant series is very thick. It consists of two members. The lower is a grey sandstone and conglomerate, the pebbly beds most abundant near its base ; the upper strata are formed of finer-grained light-grey sandstone, with part- ings of light fissile slate. Whole thickness about .... . 300 feet. The second member is a softer sandstone, chiefly thin bedded, and in colour greenish-grey. Its thickness is about . . . . . . . . . . 400 Neither of these rocks contains any fossils. Total thickness, ... 700 LEVANT SERIES. 127 Lehigh Water-Gap. The next good exposure of the formation is at the pass of the river Lehigh. There the mass consists 1st, Of very coarse quartzose conglomerate, ....... 2d, An alternation of fine white sandstone and a nut coarse conglomerate, capped by a still coarser, 3d, A coarse quartzose conglomerate, with beds of sandstone, ..... 4th, Fine-grained white and grey sandstone, fine conglomerate, and layers of shale, 50 feet. 75 75 200 , Total thickness of the formation, 400 Susquehanna Gap. The strata referable to this member of the Levant series at the Pass of- the Susque- hanna are, near the base, a very coarse heterogeneous red conglomerate, not more than 5 feet thick ; and in contact with this, a compact white conglomeritic sandstone, in thickness not more than 40 feet. The sand- stone exhibits oblique slips or faulty joints, and may originally have been somewhat thicker than it now measures. There is likewise a blank space between the southern limit of the conglomerate and the northern visible limit of the Matinal shale, amounting to between 40 and 50 feet more, and possibly a portion of this is occupied by beds of the Levant series. But making every allowance, we cannot attribute to this grey sand- stone formation a greater total bulk than from 60 to . . . . . . 70 Comparing the three exhibitions of this stratum in the Kittatinny Mountain, it presents a remarkable reduction of size as it extends south-westward. But this feature is perfectly in accordance with what we know of the relations of the formation to the series upon which it reposes further to the N.E. in New York. There it rests unconformably upon the upturned edges of the Matinal strata ; a fact which, taken in connection with its coarse, pebbly heterogeneous composition, shows that to have been the quarter of greatest disturbance of the sea-bed, at the time of the strewing in of its materials. It is easy, therefore, to understand how those materials should have been accumulated more abundantly than in the remoter localities to the S.W., where the agitations of the earth's crust were gentler. Jack's Mountain, or Middle Belt, Kishicoquillas Gap. Advancing now about half-way across the chain to the middle belt of outcrops, the first good exposure of the formation admitting of measurement is at the Kishicoquillas Gap in Jack's Mountain. The position of Montour's Kidge in Columbia County would make a comparison between the formation at that locality and the Kittatinny Mountain interesting ; but unfor- tunately it is inaccessible to observation, the lowest rock visible in the anticlinal axis being an upper member of the Levant white sandstone group. Contenting ourselves with the developments in Jack's Mountain, we have, at the Kishicoquillas Gap, the Levant grey sandstone, in the condition of a fine-grained, light-grey, massive sandstone, abounding in yellow ferruginous specks. It has here a total thickness of . . . . . . 300 Juniata Gap, or Jade's Narrows. At this locality the stratum is a greenish white, hard, silicious sandstone, with a total thickness of . . . . . . . . . . 250 Comparing the two exposures in Jack's Mountain, we observe the same reduction of the formation south- westward that we have previously noticed in the Kittatinny Mountain ; a further confirmation of the view adopted, that the materials of this deposit were swept in from the N.E. or E., and not from the S.E., as was the case with some of the other Appalachian rocks. The formation displays, however, an obvious augmenta- tion of thickness, when we contrast it in this middle belt with its diminutive bulk in the Kittatinny Mountain opposite. Said Eagle and Wills' Mountains, or North- Western Outcrop, Belief onte Gap. There is no sufficiently complete exposure of the Levant grey sandstone admitting of measurement, in the Muncy and Bald Eagle Mountain, until we advance as far to the S.W. as the Gap near Bellefonte. At this spot there are two groups of strata, the lower, a hard grey sandstone without pebbles, but full of the characteristic yellow specks, its thickness being 170 feet; and an upper, composed of greenish-grey slightly micaceous sandstone, with the ochreous specks, and divided by thin layers of a fissile greenish slate, under a thickness of 38Q feet. Possibly the upper member should belong to the Levant red sandstone, or middle formation of the series; but its characters place it rather in the grey sandstone. Thus constituted, the formation measures . . . 550 Canoe Mountain Gap, Juniata River. This locality is not quite on the line of the most north-western out- crop, but is near enough for general comparison. All the Levant formations are well exposed here. The grey sandstone wears its usual character of a grey-greenish and pinkish hard silicious sandstone, in massive beds. Its thickness amounts to nearly . . . . . . . . 500 128 TYPES OF PALAEOZOIC STEATA. The next outcrop eastward exhibits the formation at Water Street in Tussey Mountain, under a thickness of ............. 450 feet. Wills' Mountain, Milliken's Cove. The last locality at which this rock is to be seen, to the S.W. along its north-western outcrop, is in the main gap entering Milliken's Cove of Wills' Mountain. There the rock, as visible, measures only about . . . . . . -v . . 100 Looking at the very notable difference in its thickness here, when compared with that on the Juniata, one is dis- posed to suspect an obscuration of the lower portion of the mass, from a possible fault along the western edge of Milliken's Cove ; a conjecture suggested by the vertical and shattered condition of the strata in Buffalo Ridge, the western barrier of the Cove. Should this not be the case, the formation has undergone an unusually sudden diminution in its bulk. We are nevertheless warranted in looking for some abatement of thickness towards this south-western quarter. General Survey of the Formation. It will be seen, upon scanning the facts here recorded of the Levant Grey Sandstone, that while it displays a marked declension of size from the Delaware to the country west of the Susquehanna, or in the direction of its first outcrop, and exhibits a corresponding, but less notable declension in the same south-west direction along its middle and north-western belts, it presents, in a transverse or north-west direction across the Chain, an almost equally rapid augmentation of its bulk. We may look upon the successive anticlinal and synclinal outcrops and undulations of the stratum as but portions of a deposit originally con- tinuous, from some unknown limit south-east of the Kittatinny Mountain to an undefined north- western or western boundary, where the oceanic waters of the Levant period ceased to deposit their materials. Within the mountain-range, where alone this broad sheet of matter has been lifted to view, or where lifted, preserved in the general denudation, we discover a progressive enlargement of its mass within the Chain, both eastward and north-westward, indicating some north-easterly quarter as the direction of its maximum average expansion. There can be little doubt that, after the tremendous crust-movement which partially upheaved and drained the bed of the Matinal ocean, the trend of the newly-established shore of the contracted waters was NsE. and S.W., and the sea-shore itself at no great distance S.E. of the Shawangunk and Kittatinny Mountain. And it is a fair deduction from all the assembled facts, that the first strong currents at least of the Levant period, or that strewing the grey sandstone, came from the N.E., and spent themselves south-westward and westward. We have evidence in the stratification of Virginia that it carried its materials far south of the Potomac ; but how far in a westerly direction it swept them out into the mid-sea, which existed where we have now the great coal-basin of Western Pennsylvania and Ohio, it is beyond the power of man to divine. The wide anticlinal uplift of Ohio, Middle Kentucky, and Tennessee, brings the Matinal shales conspicuously to the surface, but shows them immediately overlaid by the Scalent rocks, and in some places by yet higher formations, enabling us to perceive that there was not a vestige of the sediments of the Levant period deposited so far towards the W. And this conclusion is confirmed when we pass still further across the floor of the ancient Palaeozoic sea, and discover a similar total absence of the Levant materials at the upper limit of the Matinal shales in Wisconsin and Missouri. LEVANT RED SANDSTONE (MEDINA RED SHALE or NEW YORK). It has been already intimated that the Levant Eed Sandstone has no existence, so far to the S.E. as the Kittatinny Mountain. It first shows itself in the south-eastern part of the Mountain Chain to the west of the Susquehanna, in Perry and Franklin counties. The formation becomes LEVANT SERIES. 129 for the first time conspicuous in the Tuscarora Mountain, being cut into on the anticlinal axis, at the pass called Run Gap. It is feebly developed in the ridges enclosing Path Valley. In the long complex anticlinal belt, or group of anticlinal mountains, the Shade, Blue, and Black Log mountains, this formation is still more expanded, forming there, wherever the denuding waters have cut the series deep enough, a distinct bench or terrace below the level of the higher crest. But no good exposure offers itself in this zone for measuring the thickness. We must, therefore, select the nearly central outcrop, or that of Jack's Mountain, for the first distinct development, admitting of satisfactory observation of the type and thickness of the stratum. It has been already intimated that this rock does not show itself in Montour's Ridge, the elevation and erosion of the strata there not having proceeded quite far enough. Jack's Mountain, Kishicoquillas Gap. At this most north-eastern exhibition of the Levant Red Sandstone, it consists of three members, the lowest a pale, red sandstone, imbedding pebbles of quartz, Matinal slate, and other older Appala- chian rocks, 400 feet in thickness, surmounted by a coarse, friable red sandstone, sprinkled in some layers with small pebbles, and full of large ferruginous spots, 100 feet thick ; and this overlaid in turn by a dark-red, flaggy, and in part argillaceous sandstone, containing in some layers pebbles of red shale ; thickness 500 feet. The total thickness of this well-characterised formation is thus, at this locality, about ...... 1000 feet. Juniata Gap, or Jack's Narrmvs. Here the rock is a red argillaceous sandstone, speckled yellow with hydrated peroxide of iron, and alternating with red shale. The sandstone beds abound in oblique laminse, or false bedding. Thickness .......... 650 North-western Outcrop, Bald Eagle Mountain, Bellefonte. The most north-eastern locality along its north- western outcrop, at which the Levant Red Sandstone has admitted of measurement, is the Bellefoute Gap. There it is a thin bedded grey and red argillaceous sandstone, alternating with a fourth part red, grey, and greenish shale. High in the mass are found stem-like vegetable forms resembling an irregular Scolithus. This appears to be the Scolithus verticalis of Hall, a fossil of the Medina Sandstone of New York. The thickness of the rock here is about ........... 500 Canoe Mountain Gap, Juniata River. At the gap of Cauoe Mountain this rock is a reddish brown, rather argillaceous sandstone, with beds of grey sandstone, all alternating with much red shale. Here its thickness is expanded to ........... 1050 In the next south-eastern outcrop of Tussey Mountain, at the gap called Water Street, the whole mass, possessing the same general composition, measures ...... 700 Milliken's Cove. At this locality, which is upon the same general line of outcrop, the rock holds its prevail- ing north-western characters, except that it includes a larger amount of grey sandstone than on the Juniata. Its thickness is ........... 800 General Survey of the Formation. Comparing the data afforded by the above records, we perceive that this formation, while it dilates rapidly in thickness as we meet it going northward, exhibits at the same time, at its successive outcrops, a. fluctuation in its dimensions. The direc- tion of its maximum increase would seem to be nearly westward on the parallel of the Juniata River ; but we are not in possession of a sufficiently numerous and widely-dispersed series of measurements to deduce any general inferences respecting the direction of its more permanent development, or the quarter from whence its sediments have entered this portion of the ancient Appalachian Sea. LEVANT WHITE SANDSTONE (PART OF MEDINA GBOCP OF NEW YORK). The upper formation of the Levant Series, a somewhat complex group of white sandstones and olive-coloured slates, ranges, as already indicated, with the lower or grey sandstone through the entire breadth of the Appalachian Chain, from the Kittatinny Mountain to the Bald Eagle and Wills' mountains. Of the three Levant formations, it is altogether the most fluctuating VOL. i. K 130 TYPES OF PALAEOZOIC STRATA. as respects its subdivisions or general type, though in regard to its thickness it is apparently the most constant. The fluctuations it undergoes result from the coming in and thinning out of some, or nearly all, of its sandstones and slates. Perhaps the most persistent of its members is a mottled red and white hard sandstone, in comparatively thin layers high in the formation, well characterised by impressions of the Arthrophycus Harlani. This appears to be the typical rock of the Medina Sandstone of New York. Kittatinny Mountain, or South-Eastern Outcrop Delaware Water-Gap. Selecting the same localities as those previously chosen for exhibiting the other formations of the Levant Series, we shall commence with this at the Delaware Water- gap. It here consists of a light-grey and olive-grey compact sandstone, in some beds sparsely pebbly. This member, forming a prominent 'rib of the mountain, is about 200 feet thick. Overlying this are some alternating beds of sandstone and slate, but whether these are properly referable to this formation, or to the lower part of the overlying Surgent series, is somewhat uncertain, the outcrops being obscure. Lehigh Water-Gap. At the Lehigh Water-Gap there is a thick succession of alternating white sandstones and olive shales, the upper sandstones being mottled red and white, and containing the characteristic Marine vegetation. There is a deficiency of exposures in the lower part of the formation through more than 200 feet, though the fragments indicate both grey sandstone and the olive-coloured shales. There then succeeds a white and grey pebbly sandstone, 80 feet thick. Above this repose alternating greyish white sandstones and brownish sandy shales, about 100 feet thick, overlaid by white sandstone and brownish and green slates, vaguely marked by fucoids 50 feet thick, succeeded by sandy shales, brown, olive, and yellow, 30 feet thick. Capping these are olive and buff, green and brown shales, with grey and greenish flaggy sandstone, 300 feet thick. These bring us to the uppermost bed of the formation, which is a massive red and grey quartzose sandstone, intercalated with olive and yellowish shales, the whole group having a thickness of 100 feet. The aggregate bulk of the formation is therefore about . . . . . 760 feet. Susquehanna Gap. It is impossible, from the lack of clear exposures of the strata, to determine with preci- sion the other different members or the total thickness of the Levant White Sandstone formation at the Susque- hanna. It is sufficiently obvious, however, that it consists there, as elsewhere, of an alternation of white sand- stones, with greenish and yellowish slates, and that it has reddish sandstones, with marine plants among its upper layers. Its total thickness may be estimated at from 300 to ..... 400 This formation, so obviously below its average size in the south-western part of the Kittatinny Valley, augments steadily as we meet it rising in its successive anticlinals through Perry, Juniata, and Mifflin counties, in crossing north-westward. As only its uppermost members are visible in Montour's Ridge, at the Danville Narrows, it is impossible to estimate its bulk in the middle belt of the chain to the east of the Susquehanna j but westward of the river it has been measured at all the localities already given as exposing the other two lower Levant formations, except the Kishicoquillas Gap. Jack's Mountain, South-East Flank Juniata Gap, or Jack's Narrows. At this interesting locality the Levant White Sandstone is composed, 1st, Of two principal massess, the inferior a white and greenish-grey silicious sandstone, generally massive and very compact, with scarcely a trace of organic remains, its thick- ness being 420 feet ; and, 2d, Of a red sandstone, alternating with grey and pinkish sandstone, and green and red shale, only 30 feet thick. The uppermost, or thin member, has some of its sandstone layers covered with a network of the Arthrophycus Harlani. Total thickness of formation ..... 450 North-Western Outcrop Bald Eagle Mountain Bellefmite. Here the Levant White Sandstone has its usual composition, and though not measurable with perfect precision, its thickness is evidently between 400 and 500 Canoe Mountain-Gap of the Juniata. Here the formation is a rather homogeneous mass of white and grey fine-grained sandstone in ponderous beds. Its thickness, carefully measured, is ... 550 At the Gap of Water Street, in Tussey Mountain, with a similar composition, the thickness of the mass is 500 At both localities the Arthrophycus Harlani abounds near the top of the formation. Milliken's Cove. In the Buffalo Ridge, the western barrier of this anticlinal valley, the Levant White Sandstone exists, well exposed under its prevailing north-western homogeneous type. Its thickness here is about . ........... 400 General Survey of the Formation. At the Susquehanna, and also at the Delaware Water-Gap, SURGENT SERIES. 131 the Levant White Sandstone is too vaguely denned in composition and limits to permit us to trace its changes in the Kittatinny Mountain. We are able, however, to recognise it, especially at the Lehigh Water-Gap, as possessing in this its south-eastern outcrop its most complex type. Contrasting the aspects of the rock here, and in the central belt, it manifestly becomes more aren- aceous as it spreads north-westward, from a diminution of its shales, which at the Lehigh greatly preponderate over the sandstones, and from a positive and rapid augmentation of the latter. The upper part of the formation retains its mixed type of olive shales, and close-grained white sand- stones, as far even as Jack's Mountain ; for in the belt next to the S.E., or that of the Shade and Black Log ridges, the alternation of these is conspicuous. The Pennsylvania Canal is excavated in this alternating upper division of the formation through the Long Narrows of the Juniata. It is an interesting fact that this series is nearly constant in its thickness throughout its middle and north-western outcrops. It is to this uniformity of bulk, and to its equally remarkable permanency of composition and hardness, that we must ascribe the extraordinary evenness of height and width in the sandstone crests of all this portion of the mountain-chain. While speaking of the Levant grey sandstone, it was shown that none of the formations of the Levant period reach westward to the anticlinal of Ohio and Kentucky ; but casting a glance northward to the geology of the basin of Lake Ontario, we can discern the western limits of each of the three formations, under the names of the Oneida Conglomerate, Medina Shale, and Medina Sandstone, the Oneida Conglomerate extending no farther than the eastern end of Lake Ontario, the Medina Red Shale and its overlying sandstones running on across the Niagara Eiver, and thence north-westward nearly to the Straits of Mackinac. From these statements it is obvious that the Middle and Upper formations, deposited in more tranquil waters, were much more widely diffused, both south-westward and north-westward, than the coarser, more heterogeneous grey sandstone beneath them ; the red shale, the finest sedi- ment of all, spreading the farthest distance. SURGENT SERIES. The Surgent group of formations, like the Levant series, with which it is intimately con- nected, is in great force throughout the Appalachian Chain of the State, from the north-west flank of the Kittatinny Mountain to the similar slope of the last Main Ridge east of the foot of the Alleghany Mountain. It consists of seven formations or sub-groups of strata, and each of these varies in its type and thickness within the space described, independently of the others. Some of them, indeed, are altogether wanting in the Kittatinny Mountain, and other south- easte rn outcrops. As these Surgent rocks adjoin those of the Levant series immediately beneath them, they observe almost precisely the same topographical distribution ; the chief difference being, that whereas the Levant usually form the crests of the syncb'nal ridges, these constitute one flank and base of the monoclinal ones, and both slopes of the anticlinal. They likewise stretch away in tapering belts, from the terminal spurs of the mountains, some distance forward into the plains. SURGENT LOWER SLATE (BASE OF CLINTON GEOUP or NEW YORK). SOUTH-EAST BELT, or Kittatinny Mountain .and Perry County. At the Delaware Water-Gap this formation is too obscurely visible to admit of measurement or description. 132 TYPES OF PALAEOZOIC STRATA. At the Lehigh Water-Gap it may be distinctly recognised and measured, having a thickness of about 100 feet. In Perry County it exhibits its usual type of a fissile, olive-coloured slate, becoming claret and liver-coloured by exposure. It measures from 150 to . . . 200 MIDDLE BBLT. At Mifflintmwi the Surgent lower slate, olive-coloured and fissile as usual, measures . 150 At Danville it is a greenish slate, weathering yellow, and containing bands of a block iron ore. It measures apparently ....... 700 At the south-east base of Jack's Mountain, Jack's Narrows, &c., this formation is not separable from the Surgeut upper slate, owing to the absence of the iron sandstone, the two together consisting of, A, green slate, with a few thin calcareous layers ; B, yellow and olive slate, with very little calcareous matter, but some thin, sandy beds; measures from 500 to . . 550 NORTH-WEST BELT. Milton, and north-west of the Muncy or Bald Eagle Mountain. Along this outcrop all the three members of the Surgent slate group are present ; but the exact posi- tion and thickness of the Surgent iron sandstone are not easily ascertainable. The whole group measures ........ 700 Survey of the Formation. This member of the series appears not to fluctuate much in the north-east and south-west direction, but it undergoes a marked increase of thickness towards the N.W. Beyond the Appalachians, however, it is again, upon its reappearance at the surface in New York, much thinner, being seldom more than 50 feet. SURGENT IRON SANDSTONE. SOUTH-EAST BELT. At the Delaware Water-Gap this rock has escaped notice, if indeed it exists. At the Lehigh Water-Gap its thickness is . . . . .4 feet. In Perry County, in the Kittatinny Mountain, it is . . . . . 80 It is thinner further N.W. MIDDLE BELT. Near Mijjlintown it is a ponderous red and brown ferruginous sandstone, with partings of slate. It contains trails or tracks of some animal. Its thickness is from 20 to . . 25 Near Danville it is an alternation of olive sandy slate, and brown heavy sandstone, containing the block iron ore. It measures . . . . . . 58 At Jack's Mountain it is absent. On the Potomac it is 3 or . . . . . . . 4 In Wills Creek Axis it is . . . . 30 NORTH-WEST BELT. This rock is present in the north-west outcrop, but its thickness is unknown. Survey of the Formation. This rock, seldom more than 50 feet in thickness, appears to observe no law of regular development in any given direction, but, like many other of the Appalachian sandstones, fluctuates variously. SURGENT UPPER SLATE. SOUTH-EAST BELT. At the Delaware this rock exists apparently in much force, but cannot be easily measured. Near the Lehigh Water-Gap this slate passes so insensibly into the Surgent lower shale, that the two must be measured together. Their thickness amounts to about . . 166 feet. In Perry County, under the form of a dingy olive slate, it measures . . 100 MIDDLE BELT. Near Mifflintown it is a green and claret-coloured slate. Its only fossils are faint fucoids. It measures from 200 to . . . . ' 250 Near Danville the formation is a green fissile slate. Thickness . 50 SURGENT SERIES. 133 In Jack's Mountain it is not separable from the Surgent lower slate, through the absence of the iron sand- stone. NORTH- WEST BELT. Here, though separated from the Surgent lower slate, it is not independently measurable. Survey of the Formation. Like the Surgent lower slate, of which it is but a repetition, this stratum augments towards the N.W. through the mountain-chain. On the Potomac the two slates measure together about 400 feet. SDRGENT LOWER SHALE. SOUTH-EAST BELT. It is doubtful if the lower and upper shales exist at the Delaware Water-Gap ; their fossiliferous iron ores have never been discovered. Near the Lehigh Water-Gap the lower shale, though present, is so united with the upper slate as not to admit of separate measurement. In Perry County this formation is imperfectly developed ; the calcareous fossiliferous layers are but little seen, even at Millerstown. The fossiliferous ore is barely recognisable. The whole measures, probably, ........ 100 feet. MIDDLE BELT. Near Mifflintown it is a liver-coloured calcareous slate, imbedding thin layers of sandy fossiliferous limestone. Thickness uncertain. Near Danville it is composed of green fissile shale, fossiliferous limestone, and fossiliferous iron ore. Total thickness, ......... 60 feet. In Jack's Mountain it is an olive and claret-coloured fossiliferous shale, with occasional thin layers of calcareous and argillaceous sandstone. It measures 200 to ... 250 NORTH-WEST BELT. In the northwest outcrop this formation is a greenish shale, with sandy calcareous layers thickness 110 Survey of the Formation. It would seem that this stratum first enlarges somewhat in spread- ing towards the N.W. across the mountains, and then contracts again to about its original thickness. SURGENT ORE SANDSTONE. SOUTH-EAST BELT. At the Lehigh Water-Gap this formation is easily recognised. It measures . . 110 feet. In Perry County it is a close, hard, white sandstone thickness, . . . 15 In the south-east part of the county the iron ore underlies, in the north-west it overlies, and in some places it lies both below and above, the ore sandstone. MIDDLE BELT. Near Mifflintown the ore sandstone measures 20 to . . . . 25 Near Danville it is a tough calcareous sandstone thickness, . . . . 8 In Jack's Mountain the ore sandstone measures . . . . . 25 NORTH-WEST BELT. Here this formation is absent Survey of the Formation. Thickest towards the east ; this rock, west of the Susquehanna, gradually thins away north-westward, but with fluctuations. On the Potomac it is 30 feet. SURGENT UPPER SHALE. SOUTH-EAST BELT. At the Lehigh Water-Gap it measures ...... 120 feet. 134 TYPES OF PALAEOZOIC STRATA. In Perry County this formation is a calcareous olive shale ; it weathers buff, and contains the fossiliferous ore. It measures in the S.E. 30 to 50 feet, in the N.W. 150, and has an average thickness of . 50 feet. MIDDLE BELT. Near Mifflintovm. Here it is composed of grey calcareous shale, with thin layers of fossilferous lime- stone thickness 200 to . . . . . . 225 Near Danville it is a sandy, argillaceous, green fissile slate, with layers of fossiliferous limestone, and fossiliferous ore near the base thickness, . . > . 160 In Jack's Mountain it is composed of altered olive calcareous shales, and thin beds of limestone. The lower beds of the latter are fossiliferous, while the upper beds are not so ; it measures . 250 NORTH-WEST BELT. The upper calcareous shales consist, ascending, of 1. An alternation of slates and ferruginous limestones, with some fossiliferous iron ore, GO feet. 2. Olive and buff shales, . . . . . . 65 3. Limestone with Beyrichia, . . . . . . 65 4. Grey and greenish shale, full of fossils, . . . . . 40 Total, . 230 Survey of the Formation. This Upper Calcareous Shale group appears to enlarge gradually towards the N.W. Both it and the Lower Shale are, however, much thinner at their distant outcrop in Clinton County, New York, than in Pennsylvania, both masses there being seldom more than 20 feet thick. On the Potomac the two shales together measure about 340 feet. SURGENT RED SHALE MARL. SOUTH-EAST BELT. At the Lehigh Water-Gap this formation is abundantly developed. It has a thickness of about 975 feet. In Perry County, at the Susquehanna Gap, it measures . . . . 400 MIDDLE BELT. Near Mifflintoivn, where it contains the Clinton fucoid, or Buthotrephis gracilis, its thickness is . 340 Near Danville it is a uniform red shale, without fossils, and measures . . . 380 In Jack's Mountain the red shale exists in full development, but its thickness is undetermined. It measures at Newton Hamilton, ...... 250 And at Lewiston, about . . . . . . . 1 60 On the Potomac, at the Capon Axis, it is about . . . . 100 NORTH-WEST BELT. Here the Surgent red shale maintains its usual constant characters. It is without fossils. Its thick- ness is . . . . . ' . . 350 In Blair and Bedford it is much thinner, and at the Potomac, near Cumberland, it is wanting entirely. General Survey of the Formation. It would seem, from the above local measurements, that the Surgent red marl or shale steadily thins towards the south-west, and at the same time towards the north-west, but much more gradually. In the latter direction it appears in New York, near Lake Ontario, but reduced to a very slender deposit. SCALENT SEEIES. This series, the representative, in a general way, of the Onondaga-Salt and Niagara groups of New York, consisting, in Pennsylvania, of three subdivisions or formations, is in some districts of the Appalachian Zone in very great force. Its usual topographical position is in the valleys at the feet of the high monoclinal and anticlinal ridges of the Levant sandstones, and on the adjacent sides of the neighbouring limestone ridges. The Niagara limestone, so important a formation in New York and the North- Western States, is absent from the series in Pennsylvania; but the Water-lime exists, and is very persistent throughout the Chain. SCALENT SERIES. 135 SCALENT VARIEGATED MARLS. SOUTH-EAST BELT. At the Kittatinny Mountain it is not seen. Near the Tuscarora Mountain, where the stratum first appears in force, its thickness is about . 100 feet. MIDDLE BELT. Near Newton Hamilton, where it consists of an alternation of red, bluish, and greenish shales, and thin layers of argillaceous limestone, it measures ..... 285 On the Potomac at the Capon Axis, it is about .... 300 At Mifflintmm it exceeds ....... 440 At Lewistown about ........ 450 NORTH-WEST BELT. Near Muncytown this stratum is an alternation of red and green marl. It is only . 20 Survey of the Formation. This deposit exhibits a rather remarkable increase of thickness from the S.E. to the Middle Belt of the Appalachian Zone, and an equally remarkable decrease thence north-westward. SCALENT OBEY MARLS. SOUTH-EAST BELT. At base of Kittatinny Mountain very feebly developed. Near Tuscarora Mountain it is a mass of grey, greenish, and bluish calcareous shales, in thickness about . . . . . . . . 600 feet. MIDDLE BELT. Near Mifflintown, it measures about ...... 600 Near Lewistown, about . . . . . . . 500 Near Newton Hamilton, consisting, in the lower part, of green and blue calcareous shales ; in the middle, of the same, with flaggy limestone ; and in the upper, of flaggy limestone, alternating with grey, blue, and olive calcareous marls. It measures . . . . 945 On the Potomac it is about ....... 350 NORTH-WEST BELT. Near Milton this formation consists of blue shales and thin layers of limestone, with thicker beds of blue fissile slate, underlaid by a thick succession of greenish and bluish marls, alternating with flaggy, argillaceous limestones. It contains few or no fossils. Its thickness is . 1200 From Muncy south-westward, the formation grows gradually thinner and less diversified. Survey of the Formation. West of the Susquehanna the Surgent grey marls seem to enlarge in bulk steadily towards the N., and more slowly towards the N.W., or they gradually decline south-westward. SCALENT LIMESTONE. SOUTH-EAST BELT. At the Kittatinny Mountain this rock is absent altogether. In the centre of Perry County its average thickness is . . 50 feet. At the Tuscarora Mountain it is . . . . . 200 MIDDLE BELT. At Mifflintown it exposes, perhaps, more than . . . . 30 At Newton Hamilton, where it is a flaggy blue limestone, supporting 25 feet of chert, it measures 85 At Lewistown it is thicker. On the Potomac the thickness is about . . . . . ." 350 , NORTH-WEST BELT. Near Milton, this rock, a thin-bedded blue limestone, with Cytlierina alia and other fossils, has a thickness of . . . . ... 100 Between Munaj and Jersey Shore it is from 40 to . . . 60 136 TYPES OF PALAEOZOIC STRATA. At Frankstown, where it is a blue flaggy limestone, imbedding chert between its upper layers, it measures more than ........ 215 feet. Survey of the Formation. With considerable fluctuation this limestone appears to augment gradually south-westward, for in Blair and Bedford it is frequently thicker than 200 feet, and we have seen that it is still thicker on the Potomac. PRE-MERIDIAN SERIES. This remarkably persistent calcareous group of shaly and massive Limestones, with more or less Chert, is almost everywhere present west of the Susquehanna, where the undulations of the strata lift the middle Palaeozoic rocks to the surface. Its orographic position is usually near the crests of the monoclinal ridges which next adjoin the mountains of the Levant sandstones, the very crests themselves carrying the overlying Meridian sandstone. Its distribution and changes of type will appear from the following details : PRE-MERIDIAN LIMESTONE. SOUTH-EAST BELT. Along the Kittatinny Mountain the formation is in some places quite thick ; in others very attenuated, or gone altogether. At Broadheads Greek, near the Delaware Water-Gap, it is a dull, blue, hard, and massive limestone, imbedding chert in its upper part. It abounds in corals. Thickness, . . 105 feet. At the Susquehanna Gap there appears to be no trace of it. At Millerslown it measures . . . . . 100 At the Tuscarora Axis, the limestone is . . . . 140 The overlying chert, . . . . . . 25 It occurs here in two divisions, both fossiliferous A lower massive one, . . . . .' . . 60 An upper thin-bedded one, . . . . . 80 ., In Fulton County, its average thickness is about ... . 250 MIDDLE BELT. Along this line the formation expands south-westward, but with fluctuations. In Montour's Ridge it is . . . . . 60 Between Lewistown and Newton Hamilton, where it is a blue massive encrinal and coralline lime- stone, it is . . . . . . . . . 107 At the Potomac, above the mouth of the Capon, it is . . . . . 24 The Pre-meridian chert varies from nothing to 30 feet, or more, being in Montour's Ridge thin and absent ; west of Adamsburg, 30 feet ; at Newton Hamilton, 0; and on the Potomac, 20 to 30 feet. NOHTH-WEST BELT. Near Muncy this rock is in its lower part a massive encrinal limestone, containing corals and other fossils, and is from 140 to . . . . 150 On the Juniata at Frankstown it is a massive blue and knotty limestone, with a bed of shale in the middle : its thickness is . . . . . . 1 35 Survey of the Formation. With many fluctuations of thickness, but great general constancy of type, this rock rather augments in mass as we approach the Potomac. North-westward it is not thick, ranging from 20 to 50 feet in the valley N.W. of the Bald Eagle Mountain. At its outcrop in the Helderberg Mountain, in New York, its thickness varies from 100 to 140 feet. South-westward along the Appalachian Chain this rock maintains its full bulk of 200 or 250 feet. MERIDIAN SERIES. 137 It seems not to spread to the western outcrops of the Appalachian strata in Middle Kentucky, Ohio, or beyond Western New York. MERIDIAN SERIES. This coarse and fossiliferous sandstone, with its frequently attendant shales, is one of the most constant of all the Palaeozoic strata in Pennsylvania. It is rarely altogether absent ; for even where, from its feeble cohesion and comparative thinness, it exposes no conspicuous out- crop, we may usually detect its presence at the places appropriate to it in a yellow sand derived from its disintegration. When in force, it usually occupies the crest of the narrow, sharp, stony ridges which next adjoin the high sandstone mountains of the Levant series. MERIDIAN SLATE. SOUTH-EAST BELT. At the Tuscarora Axis, on the Susquehanna, this rock is chiefly the dusky, calcareous, sandy shale, and its thickness is . . . . . 80 feet. In the middle of Perry County it is about . . . . 40 At the base of the Kittatinny Mountain it is . . . . wanting. From the Delaware to the Susquehanna, along the base of the Kittatinny Mountain, it fluctuates from to . . . . . 100 feet. MIDDLE BELT. In this zone these sandy slates and shales, though variable, are thickest towards the N.E. Thus Near Danville, they are . . . . . . . 30 Near Newton Hamilton, as friable sandy shales, from 40 to . . . . 50 On the Potomac they are . . . . . . wanting. NORTH- WEST BELT. In Whitedeer Valley these dusky shales, passing upward into argillaceous sandstone, measure about 70 feet. Near Huncy the type is that of a dusky shale, weathering buff, the upper beds sandy and cherty, the thickness . . . . . 60 Between Muncy and Lockhaven, . . . . . 50 At Frankstown, on the Juniata, the formation embraces two divisions 1. Dark ash and black slate, without fossils, . . . .80 feet. 2. Dark grey, sandy, calcareous shale, with fossils, . . . 90 170 Survey of the Formation. This interesting formation expands very slowly northward rather than north-westward. It does not appear to exist in New York, nor in any of the Western States, but it seems to run on south-westward into Virginia. MERIDIAN SANDSTONE. SOUTH-EAST BELT. This formation, conspicuous and easily traceable wherever it possesses even a moderate thickness, is occa- sionally discernible N.W. of the Kittatinny Mountain, as near the Lehigh Water-Gap, in the crest of the first stony ridge. At the Lehigh, where it is a pebbly sandstone, its thickness is 80 or . . . 90 feet. At the Susquehanna it is . . . . . . . wantin" In Perry County, where it is frequently a pea-conglomerate, it is nowhere more than . 20 feet. MIDDLE BELT. Along this zone the formation augments in thickness south-westward, but unsteadily. In Moiitour's Ridge it is in some places hardly visible ; in others it is . .35 feet. From the Susquehanna to Lewistown it expands to . . . .70 VOL. I. g 138 TYPES OF PALEOZOIC STRATA. Near Newton Hamilton, where it is a massive, coarse calcareous sandstone, imbedding layers of chert in its lower portion, it measures ...... 150 feet. On the Potomac its dimensions are about . . . . 350 NORTH-WEST BELT. In Whitedeer Valley it is . . . .>;. . very thin. Traced along this belt, the sandstone increases in thickness south-westward from Muncy to Franks- town, and thence declines to the Potomac. Near Frankstown, where it is a calcareous fossiliferous sandstone, internally bluish, externally yellow, it measures ....... 125 feet. Survey of -the Formation. As already stated, this formation fluctuates, but it is in the main thickest westward and south-westward. It does not range into Western New York, but stretches along the Appalachian Chain far through the State of Virginia. It is not seen in Eastern or Middle Tennessee, nor anywhere west of the Appalachian Coal-field. POST-MERIDIAN SERIES. The formations of this series nowhere appear in Pennsylvania, except in the valley north-west of the Kittatinny Mountain, between the Walpack Bend of the Delaware and the Lehigh River ; it is unnecessary, therefore, to trace their distribution in this place. CADENT SERIES. The Cadent formations, some of which are among the most astonishingly persistent of all the Appalachian Palaeozoic deposits, occur in superb development in many portions of the Mountain- chain of the State. Topographically considered, they occupy the sides of the long synclinal and monoclinal valleys south-west of the Susquehanna, and the more central parts of some of the anticlinal valleys or plains outside of the outer ridges confining the Anthracite Coal-fields. These three formations, the Lower and Upper Black Slate, and an interposed Olive Shale, undergo but few changes of type, except that of thickness ; but this being a material element, its varia- tions in regard to each must be noted separately. CADENT LOWER BLACK SLATE. SOUTH-EAST BELT. Along the valley N.W of the Kittatinny Mountain this formation is, for the most part, very thin, or alto- gether wanting. At the Susquehanna, Gap its thickness is quite insignificant. In Perry County, it consists, at the Half- Fall Mountain, of 1. Buff and grey Calcareous Shale, imbedding a minute plant, . . 25 feet. 2. Pale-green Argillaceous Limestone and Green Shale, . . , : 20 3. Black fissile Carbonaceous Slate, full of the usual fossils, . . . 180 Total thickness, .. . 225 feet. MIDDLE BELT. Along this zone the deposit is somewhat inconstant in its thickness, though very persistent in its composition, excepting as to its iron ore. Near Selinsgrove, on the Susquehanna, it measures . . . . 665 It is there a black fissile pyritous slate with layers of impure limestone. At Lewistown it is several hundred feet thick. On the Potomac, near Sideling Hill, it is au ash-coloured and black slate, passing upward into black fissile slate and impure clayey limestone. Its thickness is . . . 590 CADENT SERIES. 139 NORTH-WEST BELT. In the Whitedeer Valley this formation is a fissile black slate, with large lenticular cakes of blue limestone and septaria in its lower half. These become more continuous further S.W. Its fossils are few. The thickness here is from GOO to .... 800 feet. Near Frankstown it is a black fissile slate, with cement layers near its base. Its thickness is more than . . . ' . . . . . . 300 On the Potomac it measures upwards of . . . . . 400 Survey of the Formation. It undergoes a marked expansion northward in the Appalachians, and a much less rapid augmentation south-westward along the Chain, as far at least as the Poto- mac and interior of Virginia, beyond which it steadily diminishes, to disappear in Eastern Tennessee. It is probably wanting altogether in the Western States, the Black Slate of the west appearing to be the Cadent Upper Slate. The thick layer of impure argillaceous limestone accompanies this slate near its base, in Fulton and other neighbouring counties. CADENT SHALES. SOUTH-EAST BELT. This formation ranges parallel with the Kittatinny Mountain, from the Delaware Kiver to Perry County, as a mass of grey and olive shales, growing gradually sandy until, between the Schuylkill and the interior of Perry, they become an argillaceous sandstone, with even some silicious conglomerate. This sandstone character, however, fades rapidly north-westward, and ceases between the Tuscarora and Shade mountains, the rock assuming its normal compo- sition of a true shale or fine sandy mud. Along the south-east side of Perry this rock is . . . 800 feet. In the Half-Fall Mountain on the Juniata, where the formation is a hard fossiliferous sandstone, it measures between 600 and . . . . . 700 MIDDLE BELT. On the Potomac the formation is at its maximum, or . . . . 1100 NORTH-WEST BELT. In Whitedeer Valley, where the rock is an argillaceous and calcareous blue sandy shale and sand- stone, with numerous fossils, its thickness is from 600 to . . . 800 Between Frankstown and the foot of the Lock Mountain it is . . . . 400 From Hollidaysburg, south-westward, the formation grows very thin. At Cumberland, on the Potomac, it is . . . . . . wanting. Survey of the Formation. This formation, the Hamilton Group of New York, increases in its average thickness to the Potomac, and ranges thence south-westward along the Appalachian Chain, until it expires near the James River in Virginia. In the Western States this middle deposit of the Cadent period appears to have no existence. CADENT UPPER BLACK SLATE. SOUTH-EAST BELT. On the Lehigh, north of the Kittatinny Mountain, the Calcareous Upper Black Slate is seen under a thickness of from 220 to . . . . . 250 feet. In Perry County the rock is altogether . ..... wanting. MIDDLE BELT. On the Potomac this rock measures . . . . . . 415feet. NORTH-WEST BELT. Throughout this belt the deposit is usually a bluish-black fissile slate, with minutely-divided par- ticles of mica, and a small sagitate fossil. In Whitedeer Valley it measures 200 to . . . . . 300 140 TYPES OF PALJEOZOIC STRATA. In the Muncy Hills, and north-eastward, 250 to . . . . 300 feet. Near Frankstown, it is from 300 to . . " . .. . . . 350 On the Potomac, near Cumberland, it is not less than . . ; . 700 Survey of the Formation. This very widely-diffused deposit of ancient black Carbonaceous Mud appears to augment pretty steadily in a westward direction across the Chain. In Virginia it appears to attain its maximum near the James River, having a thickness on Dunlap's Creek of 850 feet. It thins away altogether in Eastern and Middle Tennessee. Westward along the northern outcrop of the great Appalachian Basin, it stretches through New York, Ohio, and Indi- ana, into Northern Illinois, where it comes gradually to a thin feather-edge. From the best authorities it reappears, however, far to the N.W., in British America. VERGENT SERIES. This series, consisting of two closely-related formations, a group of flaggy Sandstones and Shales, and a group of Fossiliferous Shales, occurs at every large outcrop of the middle Palaeozoic strata within the State. The two formations observe somewhat opposite directions for their maximum development, and must therefore be traced separately. They occur, for the most part, ranging centrally along the synclinal and monoclinal valleys embraced between the Mountain Ridges, composed of the Levant sandstones on one or both sides. VERGENT FLAGS. SOUTH-EAST BELT. These rocks may be recognised on the Lehigh under a somewhat more than usually argillaceous type. Some of the thin flaggy layers are imprinted with the trails of molluscs and other marine creatures. The thickness of the formation here has not been ascertained. - In Perry County this group is . . . . . wanting. MIDDLE BELT. Near Catawissa the formation, with its characteristic fucoids or marine plants, appears under a thickness of . . . . . . . . 1000 feet. Near Huntingdon it is a little thicker, being about . .... 1700 On the .Potomac it is again less developed, being about . . . 1200 NORTH-WEST BELT. Along this line of outcrop, at the base of the Alleghany Mountain, the thickness of the group, as well as its characters, are very constant. At the West Branch of the Susquehanua it is about ..... 1200 At Hollidaysburg it is a little thicker. At the Potomac it is . . ' . . . . . 1400 or 1500 Along this line the mass consists of dark-grey flaggy sandstones, parted by thin layers of blue shale. Large marine plants, and a Nucula, are its chief fossils. FOURTH BELT. In Bradford and Tioga counties the Vergent Flags are , .. . . 1000 On the Genesee River, in New York, it measures about . . . . 1000 There the deposit consists of thin-bedded, fine-grained, silicious grey sandstones, intimately alter- nating with blue and greenish shales. Survey of the Formation. This formation appears to augment slowly towards the N., theW., and the S.W. VERGENT SERIES. 141 VERGENT SHALES. SOUTH-EAST BELT. On the Lehigh, the whole Vergent series, consisting chiefly of this group, measures about . 1750 feet. In Perry County the Vergent shales consist of two members, 1st, A lower, composed of olive-grey and blue shales and grey sandstones, with a dark slate at the bottom : this is about . . . . 1 700 2d, An upper, of brown shale and sandstone, alternating with grey shale and sandstone, . 700 MIDDLE BELT. At Catawissa this deposit an alternation of grey, red, and olive sandy shales, with grey and red argillaceous sandstones has a thickness of . . 3050 Near Huntingdon this formation, not very fossiliferous in type, has a thickness of . . 3200 NORTH-WEST BELT. On the Portage Railroad, and extensively along the base of the Alleghany Mountain, the average thickness of the formation is not far from ... . . 2200 On the Potomac, a few miles east of Cumberland, its thickness is between 2100 and . . 2400 FOURTH BELT. Between Mahoopeny and Tioga Point it is apparently . . ... 2500 FIFTH BELT. On the Genesee River, New York, it is . . . . . 1500 Survey of the Formation. This very thick formation, remarkable for its general uniformity of composition, appears from the above statements to have its maximum development in the region of the Juniata, or half-way across the Appalachian Chain. Though it gradually thins towards the W., it is a rock of wide extension in that direction, spreading into Ohio, Kentucky, and Middle Tennessee, and along the Appalachian Chain. It stretches in full force through Virginia, and reaches East Tennessee, and probably Alabama. PONENT SERIES. The Ponent strata of the Appalachian Chain constitute a thick and remarkably uniform deposit, which does not admit of subdivision, either by its fossils or its mineral composition. Unlike some of the great groups, which gradually assume new phases, by the loss or the acquisi- tion of subordinate members, or by mutations in the members they retain, this series undergoes almost no important modification but that of thickness. Adjoining, as it does, the overlying Vespertine sandstone, which, from its bulk and superior hardness, almost invariably occurs in the shape of a high ridge, this Ponent group occupies generally the slope and foot of the Vespertine mountains. Thus it forms the south-eastern flank and base of the main Alleghany Mountain throughout its entire course across the State. And it everywhere falls into a like position in the exterior or Vespertine Mountain ridges which encircle the whole anthracite Coal region. The formation exhibits a very interesting gradation in its dimensions as it spreads through the State, which the following details will show. SOUTH-EASTERN BELT. It has its thickest development at its first or south-eastern outcrop, or in the valley N.W. of the Kittatinny Mountain. At the Lehigh River it measures ....... 5000 feet. At the Susquehanna it is about ....... 6000 MIDDLE BELT. Throughout this belt the character of the deposit which may be accepted as a fair type of the formation 142 TYPES OF PALAEOZOIC STKATA. generally is that of a red sandstone and red shale, containing, in their superior portion, grey and buff sandstones, alternating with grey and yellow shales, all surmounted by a conglomeritic rock, of a fine-grained red sandstone paste, imbedding pebbles of white quartz. No good exposures for measuring the Ponent rocks occur between Catawissa and the Potomac. At Catawissa the formation measures . . . . . .4172 feet. On the Potomac, in Sideling Hill, its thickness is about < . - . . 4500 NORTH- WEST BELT. Its average thickness along the Alleghany Mountain may be assumed at about . . 2000 Around the Wyoming Basin it is approximately . . ... 2500 Near Tunkhannock, where it preserves its middle type, being free from very coarse grits, and con- sisting of fine and argillaceous sandstones, with an increase of red and green shales, and with some calcareous layers, it measures about . . ... 1500 On the Loyal Sock Creek its thickness is nearly . . . . 1000 FOURTH BELT. Near Ralston it is between 550 and . . . . . . 600 In the Armenia Mountain, on the Williamsport and Elmira Railroad, it is . . 400 On Towanda Creek, above Canton Corner, an approximate measurement shows it to be nearly 400 FIFTH BELT. In the Tioga Valley, near the State line, according to the Geological Survey of New York, its thick- ness is . . . . . . . . 400 Near Ettisburg, between Coudersport and Wellsville, New York, it measures only . . 90 It consists in this district of greenish, sandy shale, red marly shale, and very thinly bedded mica- ceous and shaly sandstone. Near Smethport its probable thickness is somewhere near . . . . 170 In this district the deposit consists of red marly shale, and a bright green ferruginous sandy shale and argillaceous sandstone, forming a red soil. A curious dark, rough, pebbly rock occurs in the red shale. Near Olean, N. Y. In the valley of the Alleghany Eiver, south of Olean, the Ponent mass chiefly a red shale has an apparent thickness of . . . . . . 50 At Warren. No trace of the Ponent formation is visible around Warren, nor any red shales refer- able to the series. Here the Alleghany .River flows outside, or west of its western margin. Survey of the Formation. From the foregoing statements it is obvious that this great homo- geneous deposit thins away steadily and rapidly towards the N.W., from its maximum develop- ment at its south-eastern outcrop, near the Susquehanna River. This abatement of the mass is regular and not fluctuating, a fact which confirms the inferences to be deduced from its unifor- mity of composition ; namely, that it was deposited all from one quarter, and during one long uninterrupted condition of the physical geography. From Pennsylvania the formation may be traced south-westward along the Appalachian Chain, with a gradual declension of size, until it finally thins out in eastern Tennessee. Dipping westward from the Appalachian Chain under the first great bituminous coal-field, it nowhere reappears at its western margin, but evidently ceases somewhere in the interval ; nor does the formation, nor any equivalent of it, reappear any- where in the Western States. VESPERTINE SERIES. The Vespertine group of strata, the first of the carboniferous formations of the Appalachians, has a very wide distribution in Pennsylvania, encircling with a sort of outer girdle all the coal- fields, both the anthracitic and the bituminous ones, of the State. It undergoes gradual but VESPERTINE SERIES. 143 important changes of type, growing thinner and assuming a finer and finer texture in its materials as it spreads westward. Its orographic position is in the mountain-ridges and external escarp- ments of the table-lands which enclose or support the coal-fields ; but, except in the north-western district of the State, it does not immediately adjoin the conglomerates and sandstones of the coal- measures, but is separated from them by a greater or less thickness of the soft, umbral rocks, which fill either an intervening valley or an intermediate space on the coal-bearing table-lands. SOUTH-EAST BELT. This great formation is thickest and most varied in its composition along its south-eastern outcrops, or where it surrounds the first anthracite coal-basin. At Mauch Chunk, on the Lehigb, its thickness is . . . . 1300 feet. Near PottfVtlle the mass is about ....... 1800 In the Second Mountain, on the Susquehanna, and in the Fourth, or Peter's Mountain, opposite Dun- cannon, it measures nearly ....... 2000 Throughout this belt it consists largely of coarse grey sandstones and silicious conglomerates, with grey shales imbedding coal plants. MIDDLE BELT. In the Nescopeck Mountain, north of the eastern Middle Coal-basins, the formation measures . 1100 At Catawissa, in the same line of outcrop, it is . . . . . 1044 WYOMING BASIN. Surrounding the northern or Wyoming Coal-field, the Vespertine series consists of a succession of grey sandstones, imbedding some pebbly layers and some beds of shale. It has everywhere a thickness of several hundred feet. At CobVs Gap, where it is made up chiefly of greenish-grey sandstones, it measures . . 310 At Solomon's Gap, where the greenish-grey sandstone is more argillaceous, and subdivided by more numerous and thicker layers of shale, and where the whole terminates upward in a stratum of coarse pebbly and micaceous sandstones, the entire mass possesses a thickness of about 560 At Hertzotfs Gap, north of Kingston, the Vespertine series consists chiefly of olive and reddish sand- stones and shales, with occasional layers of a coarse grey sandstone ; the uppermost 80 or 100 feet include a mass of thick-bedded grey sandstones, passing towards the centre into a coarse conglomerate. The entire series measures here nearly . . . 600 NOKTH-WEST BELT. In the Alleghany Mountain, on the Loyal Socle, its thickness is . . . . 900 East of the North Branch it is much thinner. In this North-west Belt, and along the north side of the State, it is a somewhat argillaceous, micaceous flaggy sandstone. Near Wellsborough the Vespertine deposit amounts to . . . . . 700 FOURTH BELT. At the Conemaugh Gap, S.E. base of Laurel Bill, the Vespertine formation is a grey sandstone with beds of shale, terminating upwards in a grey calcareous sandstone ; its thickness is 400 to 500 On the Conemaugh Gap, at the western slope of Chestnut Ridge, the rock is a grey argillaceous and micaceous sandstone, with a few beds of dark shale. Its thickness is . . . 349 Near Astonville this formation is a greenish, flaggy sandstone, with beds of grey sandstone and blue slate. Its thickness is . . . . . 475 At the Hill at Cartersville, 1J miles above Ralston, only the top of the Vespertine is seen. At Blossburg the Vespertine sandstone consists of greenish and grey argillaceous sandstones, with a thin calcareous concretionary bed about 30 feet from the bottom. The whole formation pos- sesses a thickness of . . . . . . . 150 FIFTH BELT. In the vicinity of Coudersport, retaining its prevailing north-western type of greenish and grey sandstone, it seems to have a thickness of about . . 300 144 TYPES OF PALEOZOIC STRATA. It is very probable that a portion of this, perhaps the upper half, is to be ranked as umbral. An absence of fossils and a close assimilation in the types of the two series, render it difficult to define their com- mon boundary. Olean. In the hills, three miles and more S. of Olean, the Vespertine Series, consisting of evenly- bedded greenish-grey sandstone, with partings of olive shale, measures about . . 100 feet. It contains a Scolithus, or vertical worm-like form. Warren. Around this locality the group of rocks reposing directly upon the easily recognisable Vergent series, and overlaid by the Serai White Sandstone, and therefore referable to the Ves- pertine series, consists of four members : the lowest is a group of thin-bedded sandstone and olive-grey shale, the sandstone containing a perpendicular, bifurcating stem-like fossil, and also a true Scolithus. This member is . . . . . thin. The second is a massive quartzose conglomerate, of smooth ovoid pebbles, about . . 10 feet. The third member is a thick mass of olive-grey shale and thin-bedded sandstone, probably the Tionesta Coal-measures, though of the aspect of the Vespertine. It is about . . 175 The fourth, or uppermost, is a fossiliferous grey sandstone. Its thickness is 10 to . 15 The Vespertine conglomerate caps the hills north-west of the Alleghany River. It is often mistaken for the Serai conglomerate and sandstone of the Coal-measures. Survey of the Formation. It is apparent from the measurements here given, that the direc- tion of the maximum rate of diminution of this deposit is nearly due west. UMBRAL SERIES. The Umbral Series contains, in Pennsylvania, but one formation the Umbral Red Shale. Though widely distributed, this is not coextensive with all the coal-fields, but thins out, as we shall see, under the bituminous coal region. Its prevailing character, which is that of a dark- brownish red shale and red sandstone, it steadily maintains throughout its range, except in Cam- bria and Somerset counties, where some greenish and blue calcareous shales or marls, and fossili- ferous limestone, intrude themselves in the mass, to become, further towards the S.W. and W., an important independent formation. The Umbral Rocks very generally occupy, in the anthracite region, the valleys between the ridges of Vespertine sandstone, and those of the Serai conglome- rate, or lowest coal-measures, and, in the bituminous coal region, the edges of the mountain table-lands between the same two formations. The following details will show a remarkable gradation in the thickness of this interesting deposit : SOUTH-EAST BELT. Bordering the Pottsville Coal-basin, the thickness of the formation on the Lehigh at Mauch Chunk is about ........ 3000 feet. At Mount Carbon, on the Schuylkill, it measures . . ' . . . 29,50 Near the Susquehanna it is rather less than this. MIDDLE BELT. Wyoming Basin. Around the Lackawanna Valley, or north-eastern division of the Wyoming Basin, the type which the Umbral formation wears is that of a mixed group of shales and fine sandstones the inferior portion containing red shale ; the middle, grey sandstones and buff slates ; and the upper, a very close-grained calcareous sand- stone, like hone. Near Scranton the red shale is extremely thin, and in some places entirely absent. From Scrantou, south-westward, the relative proportion of this material augments, until, at Solomon's Gap, it greatly predominates in the mass, while the close sandstone of the middle and upper portions somewhat abates its thickness. TJMBRAL SEEIES. 145 On the borders of the "Lackawanna division of the basin, the average thickness of the whole formation is about 350 feet ; but in the Western or Nanticoke district, the whole is two or three times as bulky. At Gobi's Gap the entire series measures ..... 440 feet. At Solomon's Gap its thickness is . . . . . 569 At Hertzogs Gap, north of Kingston, this Umbral formation consists of olive-coloured and red shales, alter- nating with red and grey sandstones. The whole possesses a thickness, below the egg and nut-conglome- rate of the coal, of about ....... 360 feet. At Nanticoke, only the middle and upper portions are visible, the rest being concealed by the river. This visible part consists of soft calcareous red shale and sandstone, through a thickness of 260 feet, surmounted by thin-bedded grey sandstone, in alternation with olive-coloured shales, capped by the hone-like beds. Total thickness visible, about . . . 400 At Broad Top Basin the Umbral limestone is a rather silicious, slightly foetid limestone, of a cloudy greenish white colour. In Trough Creek Valley it measures 3 to . . . . . 4 In Ground If off Valley its thickness is . . . . . 12 In Brush Creek Valley it is . . . . . . . . 20 THIRD BELT. Near Astonville the Umbral series is composed largely, especially in its middle portion, of grey and greenish coarse sandstone, the thickness of which is . 350 feet. This is underlaid by red and greenish shales and ferruginous sandstones, with Lepido- deudron : thickness . . . . . . 87 And overlaid by a thin white conglomerate, . . . . 20 Surmounted by blue, and a blue and red shale, about . . . 130 Total thickness, . . 587 In the Hill at Cartersville, 1 J miles from Ralston, the Umbral consists, in its lower part, of micaceous flaggy sandstone, in alternation with red and blue shales, in a thickness of about . . . . . . . 300 Next a thin pebbly sandstone, and over this coarse white and greenish-grey sandstones, alternating with thinner beds of red and blue marly shale, nodular iron, as usual, occurring at the upper limit. Its thickness is about . . 234 Total thickness, . . 534 At Ralston Old Mines the upper part only is seen. It is . . 122 It consists of two soft marly shales, each between 40 and . . . 50 The lower red, the upper chiefly bluish and greenish, and between them argillaceous sand- stones, including a layer of balls of iron ore, . . . . 24 The upper shale two or three feet of nodular carbonate of iron. On Fall Creek, Towanda Basin, south side, the Urnbral, as usual, in this region, is a triple group. Its lowest member is a soft red shale 18 to . . .20 Its middle, a mass of yellowish fine-grained argillaceous sandstone, imbedding near its centre about 4 feet of ferruginous shale, with massive mottled grey concretionary iron ore the whole . . . . . .134,, Its upper bed is a ferruginous bluish shale, containing a little red shale, . . 14 Total thickness, . . 168 East of Tioc/a River the Umbral is very thin. FOURTH BELT. Blossburg. Beneath this basin the Umbral series is a mixed group, composed of a large body of greenish grey sandstone throughout more than the lower half, and of red and green shales alternating with argillaceous sandstones in the upper part. The middle and upper portions contain several courses of nodular iron ore, consisting of carbonate of iron, with much extra- neous matter, and in some layers partially oolitic. The thickness is . 238 VOL. I. T 146 TYPES OF PALAEOZOIC STRATA. At the Conemaugh Gap, south-east base Laurel Hill. The Umbral series consists of red shale, including, near its base, beds of light-blue sandy limestone, and near its superior limit grey and white argillaceous sandstone and iron ore. Its thickness is ..... 370 feet. On the Conemaugh Gap, at the Western Slope of Chestnut Ridge, the Umbral consists of the red marly shales, containing little grey sandstones in its upper half, centrally a thick bed of sandy limestone, and composed in its lower part of olive shale. Its total thickness is . 195 It would seem not to be overlaid by any conglomerate, but is succeeded immediately by coal- measures. FIFTH BELT. At Coudersport there is a greenish flaggy micaceous and argillaceous sandstone, including thin bands of red sandstone of similar composition. This rock, though possibly pertaining to the Vespertine series, is more probably the representative of the middle arenaceous member of . the Umbral. It is overlaid by Umbral red shale, here very thin. The Umbral rocks appear to thin away altogether between Coudersport and Smethport. Smethport. The Umbral appears not to extend so far westward. Survey of the Formation. From the foregoing data, it would appear that this Middle Car- boniferous deposit thins faster towards the north, but changes to a calcareous type farther towards the south-west. SEEAL SERIES. The Serai conglomerate, the only portion of the Coal formation whose changes of type and c listribution admit of a general survey, exhibits the following modifications : At Mauch Chunk its thickness is about . . . . . 950 feet. It is here composed of hard grey silicious conglomerate in ponderous beds, coarse grey sandstones, sandy clay-shales, and a few thin layers of fissile black coal, slate, and fire-clay. At Nesquehoning, on Rhume Run, its thickness is . . . 792 At Tamaqua its thickness is about . . . . . . 803 Here it is an alternation of very coarse silicious conglomerate in massive beds, the pebbles of the size of an egg or orange down to that of a nut or pea ; also of interposed coarse and fine grey sandstones, and here and there a sandy shale. There are also two or three thin imperfectly- developed beds of coal in it. At Pottsville its thickness is about . . . . . . 1030 Here the rock contains a less amount of coarse conglomerate, a larger proportion of rough argilla- ceous sandstone, two or three bands of coarse shale, two or three beds of coal slate, and a very thin, imperfectly-formed layer of very slaty coal. At Lorberry Gap, it is about . ' . . . . . . 675 Here the group consists of five or six thick strata of coarse egg and uut-conglomerate, forming as many bold ribs in the Sharp Mountain, with interposed beds of coarse sandstone and sandy shale. It embraces three thin impure scams of coal, and possibly a fourth, with their coal slates. At Yellow Spring Gap Dauphin its thickness is about . . . . 660 It is a compact sandstone in the lower and middle portions ; an alternation of sandstone and con- glomerate in the upper the latter small in quantity. At Bear Gap, Wiconisco Basin, it measures . . . . 460 At this locality, and indeed in the outcrops of the base of the Coal-measures throughout the west- ern part of the Wiconisco Basin, the group consists wholly of coal-measures, having lost entirely that preponderance of conglomerates and coarse sandstones which it contains throughout the Sharp Mountain, and indeed in both borders of the Pottsville Basin as far SEEAL SEEIES. 147 west as Dauphin. It possesses here even less of the Sharp Mountain or conglomerate type than it exhibits in the Shamokiu Basin still further north-westward. At Klinger's Gap, Wiconisco Basin, there is an alternation of conglomerates, from pea to egg in coarseness, with fine and coarse sandstones, under a thickness of about . . . 230 feet. To this succeeds a group of four coal-beds, divided by pea, and pea and nut-conglomerates, and fine and pebbly sandstones, the whole possessing a thickness of . . 400 ., These two groups, in 630 feet of strata, represent the main lower group as it is developed at Bear Gap. Eastern Middle Coal-Jield, Hazleton and Beaver Meadow Plateau. Here the conglomeritic group possesses a considerable thickness, though this is not susceptible of accurate determination. As seen at several points on the southern margin of the plateau, it is estimated to be not less in thickness than . . . . . . . . 700 Mahano;/ Basin, Ashland Gap. In the gap of the Mahanoy Mountain at Ashland there is a great development of the conglomerate rocks. The pebbles are silicious, and of sizes ranging from pea to egg. Estimating its thickness from the top of the red shale to the lowermost coal-bed, it is not less than ...... . 600 If a ponderous bed of egg-conglomerate immediately overlying the bed of coal be included in our estimate, the total thickness will be . . . . . 800 In Shamokin Gap. In the Shamokin Mountain, at the village of that name, the lower or conglo- meritic group of coal-measures restricting its limits, as we have done elsewhere, to the top of the hard rocks below the fifth seam of coal ascending, which is very generally the commence- ment of the softer coal-measures consists of an alternation of ribs of nut, coarse conglome- rates, pebbly and fine-grained sandstones, with coarse shales and coal-slates in about equal proportions. It is made up of five of the hard silicious strata and four of the softer argilla- ceous, each of the latter including a bed of coal : some of these are of good quality and thick- ness. The whole group has here a thickness of .... 630 In Zerbes Gap, at Trevorton, we see the most western natural section of the conglomeritic coal- measures in the Shamokin Basin. Here the group has a thickness of about . . 500 ,. The mass consists of five ponderous strata of silicious conglomerate and coarse sandstone, and four thick beds of argillaceous shale and slate in regular alternation with them the two kinds of rocks in about equal quantity. Each argillaceous member encloses a thick and valuable bed of semi-anthracite. In this western end of the Shamokin Basin these coals of the con- glomerate group are far thicker and of higher average purity than anywhere else in the corresponding part of the coal-measures around the anthracite region. In the Northern Anthracite, or Wyoming and Lackawanna Coal-fields, the formation consists of two strata, the lower chiefly a nut, coarse conglomerate of quartz and grey sandstone pebbles ; the upper a mass of dark-grey sandstones, sometimes pebbly. The average thickness of the lower stratum on the south-east side of the- basin is 70 to 80 feet ; on the northwest side it is not more that 40 feet. The upper bed measures from 60 to 90 feet. At Scranton the coarse lower rock is .... 80 feet. The upper fine-grained is . 70 150 At Plane 7, Roaring Brook, CobVs Gap, the nut conglomerate is . 45 The sandstone, . . . . . 45 yu At Solomon's Gap, the lower is . . . 80 The upper, . . . . . . 90 170 On the north side of the valley, at Hertzog's Hollow, back of Kingston, The upper rock is 60 The lower, . . . . . . 40 100 , 148 TYPES OF PALAEOZOIC STRATA. In Troy Gap, back of Troy, the upper is 50 to . _ . . 60 feet. The lower, . . . . . 50 110 feet. At Warrior Path Gap, west of Solomon's Gap, the lower (conglomerate) is 75 The upper (sandstone), . '. . 60 135 ., At Nanticoke, Susquehanna Gap, the nut conglomerate is . . : . . 30 NORTH-WEST BELT. Near Astonville, the lower or true conglomeritic rock, consisting in part of sandstone, in part of pebbly rock, has a thickness of ... 45 feet. Upon it rests a coarse pebbly sandstone, which is . . 25 But between them is a coaly and bituminous slate, of the thickness of 2 72 In the Hill at Cartersville, the Serai conglomerate consists of a pea conglomerate of 45 And a pebbly sandstone, which is 15 60 At the PMlston Old Mines this interesting stratum has scarcely a thickness of 11 to . . : 12 The conglomerate itself is hardly . . . . 8 In Broad Top Mountain, near the Juniata River, the thickness of the Serai conglomerate is not 100 FOURTH BELT. At Blossburg, the Serai conglomerate group consists of a very white sandstone, measuring ...... 20 feet. Surmounted by a pea conglomerate, which is . 7 27 Survey of the Formation. None of the land-derived or mechanically-formed sediments of the Appalachian Basin exhibit so remarkably regular a gradation of declining thickness, or quantity of material in a definite direction, as this great sheet of gravelly matter underlying and includ- ing the lowest coal-beds of the main or Serai coal series. It seems to thin faster towards the W.N.W., rapidly at first, but beyond the anthracite region very gradually. BOOK I. PRIMAL AND AURORAL STRATA OF THE ATLANTIC SLOPE. IN the South-eastern District, or Atlantic Slope, the only Palaeozoic formations are, as I have already indicated, those of the Primal and Auroral series, which I shall now proceed to describe, pursuing the general order adopted throughout this work that is to say, commencing with the most southern hills, and passing through each tract from the N.E. to the S.W. DIVISION I. PRIMAL SERIES. INTRODUCTION. The three great divisions or formations of the Primal Series the Primal Older Slate, Primal White Sandstone, and Primal Newer Slate, which appear within the limits of Pennsylvania, are not all present in each belt where the series is exposed. In the more south-eastern zones especially, the Primal Upper Slate, and in some localities the Primal White Sandstone, would seem not to have been originally developed, or to have been deposited interruptedly. Even where present, the distinct recognition of the slates is rendered, in many cases, very difficult, as already shown, from their close approximation, in aspect and composition, to the more ancient metamorphic schists. Some uncertainty must, therefore, remain in regard to the exact position of the lines of boundary between the two systems of strata in the more altered belts, that especially which is in contact with the southern Gneissic tract in Lancaster and York counties. It is obvious, from evidence already adduced, that the primal strata once overspread the southern Gneissic region much more extensively than they do at present, those portions only along the southern border having been preserved from the general denudation, which were protected by lying in the synclinal troughs of the more ancient rocks. CHAPTER I. PRIMAL SERIES. THE SOUTHERN BELT. THIS southern outcrop of the Primal white sandstone has been already described, as it is trace- able from the vicinity of Trenton to that of the Schuylkill, along the northern side of the Gneissic belt. It was stated to occur in a closely-folded synclinal flexure, and to lap round the end of the altered Auroral limestone in the neighbourhood of Willowgrove, the southern and longer line extending through Barren Hill to the Schuylkill. This outcrop exhibits the stratum in a more thoroughly metamorphosed condition than it anywhere else presents. Though it has not lost the regular and parallel bedding distinctive of the formation, it has undergone an almost total alteration of its lithological aspect and character, bearing less resemblance to a fine- grained sandstone than to some varieties of quartzose felspathic gneiss. Its structure is decidedly crystalline, and we frequently recognise in it a large proportion of well-developed felspar, not however so entirely insulated from the quartz as in typical gneiss or granite. It would seem, indeed, to have experienced just that degree of semi-fusion requisite to develop an imperfect felspar, but insufficient thoroughly to melt the silicious sand which is in a measure diffused through the felspathic mass, without much influencing the crystalline condition of this latter, very much as the sand occurs in the Fontainbleau carbonate of lime. So gneissoid is the aspect of this rock, as it appears at Barren Hill and other localities, that it has generally been regarded by geologists and mineralogists as a true Primary rock, and has even been regarded as a variety of Eurite. It is traversed by innumerable joints, which divide it into small rhombic masses. In the Barren Hill range, as far indeed as the Delaware, the stratum in the main consists of thin-bedded altered sandstone, and, in the upper portion, much altered slate ; the Primal Newer Slate having a talcose and felspathic character. The massive thick-bedded more purely silicious part of the Primal white sandstone appears not to enter into the formation in this south-eastern belt, and hence the absence of the vitreous quartzose beds seen in other regions where that type of the rock has undergone the same extent of metamorphosis. It is an instructive fact connected with the change of constitution in this stratum, that it is in contact with very few trappean dykes or granitic veins of any kind. Like many other instances of meta- morphosis on a large scale, it seems rather to have been caused by a general or diffused heat most probably by the escape from within the crust, through innumerable joints and crevices, of a copious and perhaps often-repeated stream of intensely-heated volcanic gases and vapours. That we discover in this altered rock no traces of organic remains should not surprise us, since so few species of fossils have been as yet detected in the whole Primal series anywhere, even in those districts of the United States where the strata have been least affected by igneous agency. The disappearance of the narrow Primal zone at the Schuylkill, in its course towards the west, is probably the result of an actual thinning away of the formation, which throughout this line is of very limited dimensions. Upon the northern border of the limestone, the Primal white sandstone and Primal newer slate occupy the western and southern slopes of the North Valley Hill, the whole distance from Valley Creek, near the Schuylkill, to Back Township in Lancaster PRIMAL SERIES. 151 County, the lower beds of the sandstone being in contact with the gneiss which skirts it on the north. Between the point at which the northern branch of the eastern belt disappears, about half a mile west of Willow Grove, and its reappearance at Valley Forge, it is nearly hid by the unconformable overlapping of the Mesozoic red sandstone, beneath which it is probably con- tinuous. Along the North Valley Hill, the sandstone contains a larger proportion than further eastward, of purely silicious beds ; it is even here much indurated and altered by heat, some of its layers containing minute needle-shaped crystals of hornblende, and a little crystallised talc, the evident products of segregation. The general dip of the strata is at an angle of about 70 to the south, identical with that of the immediately overlying limestone. The whole mass may be distinctively recognised in the notches which give passage to both the East and West Branches of the Brandywine, and also at the pass by which the Philadelphia and Columbia Eailroad turns northward from the valley towards Mine Hill. At some of these natural sections, the thickness of the sandstone disclosed is about 100 feet, and that of the overlying Primal newer slate perhaps a little greater. These rocks appear to have covered, at one time, nearly the whole of the northern Gneiss region of Chester County, for isolated hills of it occur in several localities. It is thus found in small outlying patches near Valley Forge and between Downingtown and Mainesburg, and other places between the North Valley Hill and the Welsh Mountain. Between the township of Honeybrook and West Cain, commencing near the Lancaster turn- pike, above Werner's Mill, and extending westward nearly as far as the county line, there is a steep hill consisting of this formation. On the road from Downingtown to the Red Lion, in the lower part of Uwchlan Township, the same rock occurs, in a small isolated hill running north- east and south-west for about a mile. We have already mentioned the occurrence of a similar detached hill of this sandstone near London Grove. Another, called the Buckingham Mountain, occurs near Centreville in Bucks County. RANGE OF THE SOUTHERN TROUGH OF PRIMAL ROCKS IN BUCKS AND MONTGOMERY COUNTIES. There exists a long, narrow, very straight, and closely-compressed trough of the Upper Primal Rocks, or the white sandstone, and the more slaty beds immediately beneath it, in a com- pressed synclinal flexure of the gneiss, extending the whole way from the Delaware below Trenton to the neighbourhood of the Wissahickon. The hardness of the Primal sandstone especially when highly altered by heat, as in the Belt before us, compared with the less cohesive Micaceous Gneiss, has caused this synclinal outcrop or trough to stand above the general plain of the country, especially of the district south of it, in the form of a low and very regular ridge. In Bucks, and even Montgomery County, this is very generally called " Edge Hill Ridge," under a mistaken but common impression that it is a prolongation of the hill bearing that name, which constitutes the southern boundary of the limestone basin E. of the Wissahickou. But this latter, as will be seen by a glance at the Map, or a perusal of succeeding paragraphs, terminates near the Pennypack, a mile or more to the north of the belt now under description. The two ridges are, in fact, not connected except at their origin E. of the Wis- sahickon, where the anticlinal ridge of Barren Hill subdivides, by the intrusion into it from the E. of an anticlinal tongue of gneiss, sending forward its north-dipping outcrop in the sharp mono- 152 PRIMAL SERIES. SOUTHERN BELT. clinal north-dipping Primal rocks flanking Edge Hill, and forming with this the compressed synclinal trough of the long belt which we are tracing. From this point of divergence of the. two ranges, which is about 2 miles E. of the Wissahickon, this belt of rocks, trending less toward the N. than the true Edge Hill, passes about one-fourth of a mile S. of Edge Hill village, and just S. of Mooretown, and ranges thence across the Pennypack near Walton's Mill. From this point it maintains its course E. about 16. N., and runs on to Brownsville in Bucks County, this village being situated just at the southern base of the ridge. Crossing the Neshaminy at Mather's Mill, it passes S. of the village of Attleborough, the crest of the ridge, or probable synclinal axis, being just about one-half of a mile from the village. Thence it extends through Oxford, and a little N. of Fallsington, and reaches the west side of the Delaware Eiver just below Morrisville, where its strata are well exposed in a quarry near the river-side. From this point it pursues the same straight course through the wide channel of the Delaware, in which it forms a ridge or ripple, and receding from the river-bank in New Jersey, loses itself from view under a covering of drift and sand. The general structure of this long and regular belt is everywhere very simple, being that of a nearly perpendicular synclinal fold, in which the strata of the two sides of the trough are compressed into approximate parallelism with each other, dipping at very steep angles, and in some places even in the same direction. An inversion of the southern side of the trough, though a frequent, is not an invariable feature, some of the sections across the ridge exhibiting these beds dipping steeply to the N. ; but in such cases, always at a higher angle than that at which those of the northern side of the axis dip southward. In other words, the axis plane is not perpendicular to the horizon, but invariably dips steeply to the S.S.E. The composition of this most southern of all our outcrops of the Primal strata is well seen on the road leading into Attleborough from Bristol. Passing from the Gneiss at the soiithern foot of the Sandstone Ridge, the Primal strata present themselves under the following aspects and dimensions : SECTION of Primal Sandstone S. of Attleborough. Scale, 1 inc/=1000 feet. 4 ^ r fctfi ..-'' '"'' " WWMimW'.'jtiJfi'/L'/. _ / Vxa BOO . K- " ,/" >*" < o>" o-" Immediately succeeding the gneiss, there occur, on the southern slope of the ridge, a group of highly altered slates of the older Primal division. These are semi-crystalline, and contain much segregated felspar and mica. The group is between 200 and 300 feet thick. Over these, which may be seen in the trenches at the road-side, dipping very steeply towards the N., is the Primal white sandstone formation, which, as usual throughout this belt, indicates an extreme degree of metamorphism. The rock is very quartzose, and in some layers even semi-vitreous, and it contains mica, talc, and schorl in the thin partings which separate its beds. Surmounting these sandstone strata, or succeeding them in the centre of the ridge at the synclinal turn of the dip, are intercalated beds of white quartzose conglomerate, the pebbles generally not exceeding the size of a boy's marble. These hardest layers occupy the crest of the ridge. The visible thickness of the white sandstone from the slate on the one side, to the synclinal axis on the QUAKEIES. 153 other, is about 3 00 feet, and this may be given as the approximate depth of the formation generally in its course through Bucks County. It becomes perceptibly thinner as it ranges westward towards the Wissahickon, for on the Limekiln Turnpike, S. of Edge Hill village, the whole formation, well exposed in a deep cut, shows a thickness not exceeding 150 feet. Owing to the amount of metamorphic action to which this belt of sandstone has been sub- jected, its strata possess a firmness of cohesion, and a tendency to lamination, which, combined with the original thinness and parallelism of its bedding, allow it to split up in quarrying into slabs or flagstones of unusual size, regularity, and strength. The rock is therefore extensively employed throughout the adjoining rural districts as a flagstone for steps, walks, and especially for dairies or milk-vaults. A prevailing structural feature throughout all this zone of altered Primal strata, is a system of cleavage planes, which dip invariably at a steep angle, 70 or 80 to the S.S.E., whether the strata themselves dip in that direction or not. This, be it observed, is the almost universal direction of the cleavage-dip throughout the Atlantic Slope. The following is a list of some of the principal quarries of flagging and building stone at present resorted to in this Ridge. None, it would seem, have been opened to the W. of the Pennypack, in consequence, apparently, of a reduction in the hardness of the rock, from abatement of metamorphic action in that direction. The two or three quarries E. of the Neshaminy, including that at Morrisville on the Delaware, are not here embraced. PRINCIPAL QUARRIES IN THE SOUTHERN BELT OF PRIMAL SANDSTONE BETWEEN THE NESHAMINY AND THE PENNYPACK. 1. Franklin Vansant's, near the Neshaminy, on the south side of the Ridge. This is a large quarry. 2. Maiden Hicks's, three-fourths of a mile west of Vansant's, also on the south side of the Ridge. It contains a harder stone than that quarried by Yansant. The flags are thin and smooth. 3. Maiden Itidge's quarry is situated 300 yards west of Hicks's quarry. It is a large one, yielding larger flags than any of the others. Stones can be procured measuring 6 feet by 8, and 4 by 6, and having a thickness frequently of from 2 to 6 inches. This quarry is half a mile east of Brownsville. 4. Capt. E. Groom, Beuj. Knight, and Mr Lerdom, all have quarries about half a mile west of Brown's Mills. All three yield a stone quite similar to that of Vansant's, of a yellowish white colour, and thicker flags than those from Hicks's, there being much good building-stone. 5. Silas Rhoads and Samuel Acops have two quarries on the south side of the Ridge, near the Bustleton Turnpike. These quarries yield stone like those next east a good building-stone, but a less proportion of large flagstone. The best building-stone is from the quarries of Groom, Knight, and Lerdom. There are no other quarries opened in Bucks County to the westward. All the flagging-stone produced is immediately bought up. It sells at the quarry for $1 per horse-load. The building-stone is sold at about 12 cents per perch. The best description of building-stone at the quarry costs 20 cents per perch. GENERAL GEOGRAPHICAL LIMITS OF THE PRIMAL STRATA WEST OF THE SCHUYLKILL, AND SOUTH OF THE CHESTER COUNTY LIMESTONE VALLEY. In describing the geographical distribution of the older Primal Slates south of the Chester County Valley and west of the Schuylkill, no difficulty presents itself in defining their Northern limit, which coincides very nearly with the Northern base of the South Valley Hill, or, in other words, with the Southern margin of the limestone of the valley, the interposed Primal white sand- stone being, as already mentioned, very thin. Nor is there any obscurity in the boundary between VOL. i. u 154 PEIMAL STKATA OF MONTGOMERY. this slate belt and tlie gneissic rocks to the south of it from the Schuylkill to the Brandy-wine, this line having been already defined as that of the Northern edge of the gneiss. But to the west- ward of the Brandywine a difficulty does present itself, from the introduction of a number of troughs included between the series of narrow tapering anticlinal belts, or fringes of gneiss, by which the Primal series is spread prodigiously to the southward, almost to the Southern line of the State. If the actual limit between the lowest Primal rocks and the gneiss could be minutely followed, it would be found to wind in and out, in a zigzag manner, between the uplifted spurs of gneiss, each successive trough to the S. lying somewhat further towards the W. than the preceding one. The general line of boundary is represented on the Geological Map ; it is designedly somewhat vague. Looking at the entire area occupied by these Primal rocks, between the Schuylkill and the Susquehanna, and between the Pecquea and Conestoga valleys and the Maryland State line, we are reminded of the form of a hatchet or cleaver, the long slender belt between the Schuylkill and the Western Branch of the Brandywine representing the handle, and the wide slate district of the South-western townships of Chester, and of the Southern ones of Lancaster, representing the blade. The Southern limit of the Primal slates within the State is the Northern edge of the long tract of Serpentine, under the State line in Lancaster ; but other narrow ranges occur in Mary- land, before we reach the main district of gneiss. Progressively expanding in its range south- westward, the belt of older Primal rocks is even broader in York County than it is in Chester and Lancaster ; and in Maryland it is wider still. COMPOSITION OF THE PRIMAL STRATA AS THEY ARE DEVELOPED IN THE MONTGOMERY COUNTY VALLEY, EAST OF THE SCHUYLKILL RIVER. It. is only on their Northern outcrop, or that extending eastward from the Wissahickon towards the Pennypack Creek, that we find the Primal rocks wearing a resemblance to their ordinary sedimentary aspect, undisguised by metamorphism. There the principal mass is an alternation of thin beds of bluish grey sandstone and still thinner layers of brownish sandy slate, very much the type which the older Primal rocks exhibit on the Susquehanna above Columbia. A partial metamorphism is observable, however, even in this Northern outcrop, for the most argillaceous, or slaty partings, present oftentimes the aspect of an incipient talcose crystallisation. Along the Southern border of the Limestone Valley, all the Primal rocks wear a greatly more altered character ; the lower beds, or those adjoining the gneiss, presenting indeed so advanced a condition of crystallisation as to be entitled to the name of Semi-Porphyroidal Rocks. On a first inspection, especially of the weathered and disintegrated outcropping frag- ments of these lowest Primal beds, the observer is very liable to confound the formation with the uppermost hornblendic felspathic layers of the adjacent genuine gneiss ; and until my own researches enabled me carefully to study and trace the several strata of this zone, the propriety of referring these porphyroidal beds to any system of rocks newer than the Gneissic formation, was never, I believe, entertained. In the district of the Schuylkill and Wissahickon, the three members, of which the Primal series there consists, present the following aspects and dimensions. PRIMAL ROCKS ON THE SCHUYLKILL. 155 The lowest, or semi-porphyroidal group, evidently an altered sandy slate, or argillaceous sandstone, is remarkable for the regular parallelism of its lamination and bedding ; the laminae, alternately light and dark, being exceedingly thin, many of them usually packing within the thick- ness of an inch. These laminae consist, where the rock wears its most metamorphosed form, of white earthy, imperfectly-developed felspar, and perfectly- developed earthy hornblende. Besides these alternate whitish and dark streaks, the cross fracture of the rock displays a multitude of ovoidal concretionary crystallisations, generally only specks in size, but sometimes of the dimen- sions of bullets, the larger and better formed concretions being frequently genuine crystals of felspar. In some of the layers certain laminae are studded with isolated crystallisations of hornblende. The maximum thickness of this group at the Schuylkill is about 300 feet ; but not more than 100 feet can be seen immediately at Spring Mill. The next rock ascending, or the second member of the Primal series, is a species of imper- fectly-formed talcose and micaceous slate. When most metamorphosed, it consists of wavy, nearly parallel laminae of quartz, mica, and apparently some talc, with innumerable crystals of dodecahedral garnet. It exhibits this composition near the mouth of the ravine of Aramink Creek, opposite Conshohocken. The twisted or wavy form of the plates of mica seems due, as in the coarse mica-slates of the true gneissic series, to the interference of the garnets and of the segregated quartz. When less altered, these strata have the characters of an impure sandstone, pervaded with particles of imperfectly-developed mica and talc. This rock is very liable to disintegrate from exposure to weather ; it decomposes into an unctuous talcose earth, of a mottled deep-red and bhie colour, forming a highly ferruginous soil, a chief source from whence the percolating waters extracting the oxide of iron have formed those large deposits of brown heematitic iron-ore that adjoin the outcrops of the Primal and lower Auroral formations. The very abundant fragments of white quartz, resembling a pale chert, which strew the surface near the outcrop of this second member of the Primal series, are not fragments of genuine injected quartz veins penetrating the strata, but merely large segregations of the quartzose matter of this rock consequent upon its alteration by heat. Such plates of fine-grained cherty quartz, sometimes including imperfectly-developed felspar, may readily be mistaken at first glance for the more quartzose felspathic layers of the altered Primal white sandstone of the range of Barren Hill. The apparent thickness of this middle member of the Primal series is here about 200 feet. The third and terminating rock of the Primal series near the Schuylkill is the white sandstone above mentioned, so conspicuously exposed in the anticlinal ridge of Barren Hill. It is a thin- bedded, yellowish white, very compact rock, presenting in composition much imperfectly- developed felspar, and showing a tendency to a rhombohedral fracture. The more solid layers seldom exceed two inches in thickness. Other more schistose bands, consisting of the same quartzose felspathic matter in intimate fusion, contain likewise many minute partings of crystal- line mica and talc, and the surfaces of the more solid felspathic beds exhibit very frequently at these partings innumerable minute crystalline specks of pure black schorl. This rock possesses a thickness in Edge Hill, Barren Hill, and near the Wissahickon, of 35 to 40 feet ; but further eastward the group is far more massive, being, in the vicinity of Willow Grove, not less probably than 100 feet thick, and in Bucks County, in the southern trough, not less than 300 feet. 156 PRIMAL ROCKS LOCALITIES WHERE THE PRIMAL ROCKS MAY BE BEST STUDIED. On the Southern side of the basin, tfte lowest, or semi-porphyroidal group, is well exposed for observation in the ravine of the Aramiuk, and thence at the base of the river-hills eastward to the Ferry House opposite Spring Mill ; again in the point of the hill at Spring Mill, just North FIG. 9. Section on Aramink Creek. o f the William Penn Iron-Furnace. It has been laid open to view by quarrying, at the entrance of the Wissahickon mto tne gneissic hills, and again at the foot of Chestnut HiU) on tne Germantown and Perkiomen Turnpike. It is J6S.E. a material very well adapted for macadamising the turnpike roads, being tough and durable, while it is easily quarried. The Second Division of the Primal Series, or the Mica-Talcose Group, is best exposed along its Southern outcrop, at and near the mouth of the Aramink Creek. Elsewhere upon this line it is generally covered by surface matter. Its fragments are abundant in the soil upon it. Ranging as it does immediately at the foot of the Gneiss Hills, it is very generally concealed by the rubbish of the rocks higher on the slopes behind it. The same obscurity attends this southern outcrop of the upper Primal rock the White Sandstone ; but a fair exposure of this exists in the vicinity of Spring Mill, immediately on the road at the base of the Furnace Hill, where a large and old excavation for iron ore has revealed the stratum and its steep Northern dip. But the best exposures of the Primal white altered sandstone are at the several cuts through the Barren Hill ridge, formed for the passage of the turnpike roads. Perhaps the completest of all is at Edge Hill village, where the whole formation is finely developed in a deep cut on the northern Pennsylvania or Water-Gap Eailroad. Some of the upper beds of this rock are beau- tifully developed in an excavation on the South side of the anticlinal of Barren Hill, adjacent to the village of Spring Mill. It may be well seen, under the modifications induced in it by cleavage, in the end of the Church Hill at White- marsh. Along the Northern side of the basin, the lower groups, in their unaltered aspect of sandy slates and argillaceous sandstones, are best beheld near Sandy Run, especially in the deep cut in that vicinity for the Northern Pennsylvania Railroad. Further to the eastward the Primal white sandstone sheets the Southern slope of the same Northern boundary of the valley, and is fairly exposed on two or three of the cross-roads of the country. COMPOSITION OF THE PRIMAL STRATA IN THEIR DISTRIBUTION WEST OF THE SCHUYLKILL. When the Primal rocks W. of the Schuylkill and S. of the edge of the red sandstone, are carefully studied, they exhibit as remarkable a constancy in the characters of the white sandstone member, as they present aberration in the lithological type of the other or slaty groups. Primal White Sandstone. The sandstone retains throughout its entire distance to the Susquehanna, almost identically, the features which distinguish it in Montgomery County. It presents, that is to say, in those outcrops where it has undergone the greatest amount of rneta- morphism, a semi-vitreous texture, specks of imperfectly-developed felspar, partings delicately coated with white talc, and surfaces imbedding minute segregated crystals of schorl. In its less altered belts, especially those north of the Chester County Valley, as the north Valley Hill and the Welsh Mountains, the sandstone is ordinarily less firmly cemented, and therefore more extensively crumbled and eroded along its outcrops, more porous and softer, and less divisible into thin flags ; it contains, moreover, but little segregated talc or schorl. Primal Slates. But when we trace the slates of the Primal series, in our progress to the W. or S.W., we find that they are not so persistent in their characters, but put on some new and WEST OF THE SCHUYLKILL. 157 interesting features, losing others which are distinctive of the group to the eastward of the Schuylkill. Thus the peculiar speckled and semi-porphyroidal group of beds, at the very base of the whole Primal series, in contact with the gneiss at the Schuylkill, is less distinctly recognised as we follow the boundary between the two systems of rocks westward for a few miles. We may still detect it, though more obscurely, S. of the Paoli ; but we cannot recognise it when we reach the Brandy wine. This change may be due either to the running out of this division of the formation by loss of material, or it may result from a change in the conditions of meta- morphism arising either from a modification in the original composition of the stratum, or from a more intense and prolonged exertion of subterranean heat. The form of rock which replaces the dark semi-porphyroidal beds at the base of the Primal series, and therefore of the whole vast Palaeozoic system, is one which well deserves to be critically studied and noted. It is a variety of silicious, talco-micaceous slate. In certain districts W. of the Brandywine, especially towards the Susquehanna, where the metamorphic action seems to have been in its highest energy, the crystalline character of these rocks is at its maximum, and it is there sometimes difficult to dis- tinguish the strata from certain forms of the more micaceous beds of the true Gneissic or Hypozoic system. An extensive comparison, however, of the materials of the two formations, enables one almost invariably to determine definitely between the real micaceous slate and that which only simulates it. It is impossible to subdivide into its several component members the Great Lower Primal Group of Southern Pennsylvania, W. of the Schuylkill Eiver, for the more we study it in detail, the more nugatory become our efforts to trace the separate strata or determine their strati- graphical relations. This difficulty proceeds from several causes : first, a pervading transverse cleavage, which extensively effaces all clear traces of the original bedding ; secondly, the presence of innumerable plications, often so closely compressed as to appear as only one uniform dip, the anticlinal and synclinal foldings in many cases escaping detection through the obscuring influ- ence of the cleavage ; and, thirdly, mutations in the composition, or at least in the now prevailing crystalline or metamorphic constitution of the beds. Defining, then, the entire succession of slaty rocks embraced between the upper limit of the genuine Gneiss and the bottom of the Primal white sandstone, as one natural group, it will be best represented as an alternation of talcoid silicious slate, talco-micaceous slate, and quartzose micaceous rock, usually also schistose, or thinly laminated. Along the Northern side of the tract occupied by these older Primal rocks that is to say, adjoining the great limestone of the valley on the south the principal form which the stratum assumes is that of a talcoid slate,full of lenticular lumps of granular quartz, apparently the silicious material in excess, in a state of segregation. This form of the fragments prevails especially where the cleavage, always dipping to the S.E., is not coincident with the bedding. In the rarer instances where these two sets of planes do concur, the laniination is more parallel, and the silicious granules more dispersed among the talc. Alternating with the talcose slates are beds of the more micaceous variety ; but the more highly micaceous, silicious schists, prevail chiefly in the lower half of the formation, or, as respects the belt in question, in its central and southern portions. Besides the talcose and the micaceous varieties of the metamorphosed Primal slates, there exists a third species of rock under the form of a nearly pure clay-slate of the character of roofing slate. This seems to occupy a horizon comparatively low in the series, for it is never inter- 158 PRIMAL STEATA OF MONTGOMERY. stratified with the talcose or upper division, but with the highly-crystalline micaceous rocks, which seem to prevail most in the central and lower. DESCRIPTION OF THE SECTION ALONG THE BEANDYWINE. (SEE ENGRAVED SECTION.) A careful examination of the " Section along the Braudywine Creek " will render more evident than any general description can, the conditions under which the older Primal slates appear, as respects their crystallisation, cleavage, and dip, within this middle portion of the Southern Primal Belt in Pennsylvania. Restricting our attention to the portions of the section south of the Chester or Downingtown Valley, it will be observed that talc-slate, with a steep northward dip of 80, and an equally steep South-dipping cleavage, immediately succeeds the limestone a few hundred feet south of the railway station. From this point to the road leading to West Chester, about a thousand yards below the Bridge at Taylor's Ford, we have a succession of talc-slates and talco- micaceous slates, more or less quartzose, dipping for the most part southward, and full of South-dipping cleavage with, however, occasional steep North dips, implying the presence of acutely-folded flexures. In one instance the cleavage also dips towards the north. This whole belt manifestly belongs to the older Primal slates. Between Taylor's Ford and Brinton's Run, or the vicinity of Chadd's Ford, the section crosses a complex belt, embracing much micaceous and hornblendic gneiss, with soft felspathic gneiss, under various conditions of dip, and irregularly alternating with mica- ceous and talcose slates, occasionally containing garnets. This alternation of the harder, more massive gneiss, with the softer, more loosely aggregated, and, to appearance, less perfectly developed, seems to mark the presence of two systems of rocks, an older or Hypozoic gneiss, and a more modern or Azoic series, probably the lower Primal slates in conditions of extreme metamorphism. I conceive that the most natural interpretation of the geological features of this district will be found in the hypothesis of a succession of narrow parallel anticlinal folds of the older gneiss, enclosing between them folded troughs of the newer metamorphic group, precisely as we recognise a similar series of anticlinal fingers and synclinal basins of the two respective formations in the region of the East and Middle Branches of the Whiteclay Creek further to the S.W. Grasping the whole of this part of Chester County in one general survey, I suppose it to contain a series of closely-compressed anticlinal and synclinal flexures the anticlinal lifting the older rocks, the syn- clinal holding within them the newer, and disposed in echelon, or in oblique order ; the more southern, as a general rule, terminating further to the west than the more northern. This conception satisfactorily explains the presence of the numerous parallel synclinal valleys of the still higher Auroral limestone, with their bounding outcrops of the Primal white sandstone, dipping conformably with the semi-gneissic or micaceous schists. It likewise accounts for the rapid horizontal expansion of the whole slaty Azoic region, from the Braudywine westward. THE PRIMAL STRATA, AS EMBRACED IN THE SYNCLINAL VALLEY OF MONTGOMERY AND CHESTER COUNTIES. These rocks lying in a trough of the great Gneiss formation, but unconformably upon its more contorted beds, consist of all the three older Primal strata which this part of Pennsylvania pos- sesses, together with the chief part of the Auroral or ma~gnesian limestone series. The Primal rocks form the border of the valley, the South side of which they fringe with a continuous belt, while they skirt the Northern side more interruptedly, ranging from the Eastern point of the trough, near the county line of Bucks and Montgomery, to the Wissahickon ; and again, from Valley Forge continuously westward through Chester and Lancaster counties, the interruption in the region of the Schuylkill being by an unconformable overlap of the Southern edge of the Middle secondary red shale or Mesozoic red shale and sandstone. In the district E. of the Schuylkill, the Southern fringing belt ranges along the base of the Giieissic hills to beyond the Wissahickon ; but from thence eastward they occupy a narrow ridge of their own, called Edge Hill. The Northern outcrop forms, from the Eastern head of the valley westward to the AVissa- EASTERN END OF BASIN. 159 hickon, the bounding ridge of this portion of the limestone valley. All the Eastern end of the trough, from a point about half a mile W. of the Willow Grove Turnpike, to near the Hunt- ingdon Turnpike E. of Pennypack Creek, is underlaid by the Southern belt of the Primal rocks, the Auroral limestone terminating at J. C. Tyson's, E. of the source of Sandy Kim, a mile to the S.W. of Willow Grove. STRUCTUEE OF THE EASTEEN END OF THE LIMESTONE BASIN OF MONTGOMEEY AND CHESTEE, FEOM THE WISSAHICKON TO THE PENNYPACK. Some interesting features exhibit themselves in the structure of our great Southern limestone- basin towards its Eastern termination. Its most Eastern division, extending from the Wissahickon to the Pennypack, is regularly bounded by a Southern and a Northern ridge or belt of hard Primal rocks ; but these ridges do not coalesce, as would be the case if the basin was one of the most simple synclinal form, but they run on separately past the termination of the limestone in two independent and slightly-approaching crests, till they terminate about a mile apart in the vicinity of the Pennypack, the outcrops of the Primal strata being prolonged indeed across that stream nearly to the Huntingdon Turnpike. The whole trough ends in the form of a swallow's tail with the two prongs collapsed, as when the bird is darting. The included bed of limestone itself forks, but not into points as acute as those presented by the belts of Primal strata which confine it. One prong of the limestone valley prolongs itself eastward to within half a mile of Willow Grove, past the source of Sandy Run ; while the other more Southern one, following the Northern base of Edge Hill, extends almost to the Willow Grove Turnpike. This forking of the end of the whole basin is the consequence of a complex anticlinal flexure of all the strata of the region prolonged from the eastward, across the Pennypack, between the two Primal spurs, and dying down in the eastern end of the trough of limestone. Its effect is to form two subordinate independent troughs in the eastern end of the one general basin, as exhibited on the Geological Map. Willow Grove is situated in the Northern synclinal valley on the Primal sandstone ; while the Southern trough crosses the turnpike about half a mile S., the upper rocks at the crossing being the same white-sandstone group. Between these two branch basins of the Primal series, we find in reality a double and not a single anticlinal axis ; or in other words, the wave is concave on its crest. This is evident from the existence of two separate anticlinal belts or points of the gneissic rocks penetrating westward between the spurs of sandstone in the vicinity of the road con- necting Blaker's Store and Morgan's Mill. These two anticlinal points of the gneiss enclose a synclinal ridge of the Primal rocks, the highest or capping stratum being the conglomeritic bed which terminates the white-sandstone group. Advancing westward as the two anticlinals sub- side, we discern at the turnpike only one broad flat arching of the upper Primal slates, lifted to the surface by the more southern and important of the two flexures. It is this line of elevation apparently which causes the broad swell of upper Primal sandstone, in which the limestone valley abruptly ends at Hollowell's and Tyson's farms. The more northern and feebler axis does not show itself in the topography to the westward of Willow Grove. The extreme synclinal point or last visible trace of the more southern basin of Primal strata, or that of the true Edge Hill, is at the Huntingdon Turnpike near the Sorrel Horse Inn ; and the further exposure of the northern or Camp Hill belt, or trough, is on the same meridian, or road 160 PRIMAL STEATA OF MONTGOMERY. leading N.W. from the Sorrel Horse Inn. About half a mile to the eastward of this road, this belt of the Primal rocks is overlaid by the southern conglomeritic margin of the Middle secondary red sandstone ; but the belt itself very probably terminates near this point. The following sections display the changing structure of the Primal belt in its progress Westward. Mimmc Bed Sd,l. FIG. 10. Section E. of Pennypaok at Sorrel Horse Inn. (Scale, 1 inch = 2000 feet.) Fid. 11. Section from Moron's Mill to the west of Yerke's Factory. (Scale, 1 inch = 600 feet.) FIG. 12. Section of Primal rocks at Willow Grove Turnpike. (Scale, I inch= 1500 feel.) Fio. 13. Section at Forking of Basin near Tvson west of Willow Grove. (Scale, 1 inch = 2000 feet.) DETAILS RESPECTING THE PRIMAL ROCKS IN THE DISTRICT OF WILLOW GROVE. On the Willow Grove Turnpike near Willow Grove, we may discern the structure of the whole Primal Zone as it is represented in our section. Just north of the forking of the Turnpike, we detect on the sides of both the roads the Primal rocks, leaning at a moderate angle upon the gneiss, dipping towards the little valley in which Willow Grove is situated. Crossing this valley to the road leading to Newtown, and ascending the hill forming the southern boun- dary of the same small valley, we find this hill sheeted over with the Primal sandstone, dipping to the opposite quarter, or to the north, and forming thus with the other outcrop the Northern Branch Basin. Here, upon the northern slope and end of this hill, the fragments of the sandstone contain numerous vestiges of Scolithus linearis, the fossil char- acteristic of the White Primal Sandstone. If now we advance along the turnpike southward, we may readily perceive the synclinal structure of the southern valley, or that at the northern foot of Edge Hill, by noting first the southward gentle dip of the upper layers of the Primal slates by the roadside, and presently a similar dip in the overlying white sandstones at the brow of the hill as we descend into the valley. Crossing the valley and the crest of its southern ridge, or Edge Hill, we may plainly see the same Primal rocks recur in the inverse order under an opposite and steeper dip to the northward. Further eastward the relative positions of the several belts of strata are disclosed to careful study in the line of our section, crossing the whole belt from Morgan's Mill to Yerke's Mill or Factory. At Morgan's Mill we find the lowest layers of the Middle Secondary Red Sandstone, under their usual condition of a very coarse conglomerate. A few hundred feet southward from Morgan's Mill on the road to Willow Grove, we have the gneiss emerging from beneath this margin of conglomerate ; while across a meadow south-eastward, and by the road to Blaker's Store, we detect the northern synclinal belt or trough of the Primal sandstone dipping gently southward near Newport's BAEREN HILL. 161 house, and beyond this, on the road near his gate, dipping very steeply northward, constituting a narrow trough. If we advance south-eastward along this road, we will detect a second belt of the gneiss occupying a breadth of several hundred yards, until, near the intersection of this road with that leading to Shelmire's Mill, we encounter the eastern point of a synclinal hill of the Primal sandstones. Near this intersection of roads is a second anticlinal axis, which, between the Pennypack and this point, lifts to the surface the older Gneissic rock, but which here, and to the west- ward, only elevates the overresting Primal slates. At this part of our section, where it crosses the road running from Edge Hill to Shelmire's Mill we come upon the conglomerate beds which in this neighbourhood terminate the Primal series. These cap the synclinal hill already mentioned, and likewise the two spurs to the south of it, which are only the two outcrops of the hard Primal rocks that here form the Southern or Edge Hill basin. Both these latter ridges are abruptly cut down at their eastern ends by transverse erosion, the point of the basin of upper hard Primal rocks being here nipped off. Tracing the northern synclinal line of the Primal rocks eastward from near Morgan's Mill, we follow it through a hill lying eastward of Newport's house, and detect it at several points till it crosses the Pennypack, and leads along the northern brow of a ridge half-a-mile to the north-west of the Sorrel Horse Inn. In this ridge we may detect the lower or slaty Primal rocks in a highly metamorphic condition, approximating in their aspect and crystalline condition to a rather finely-laminated gneiss, with some beds of which they are in contact. In the centre of a close synclinal fold of these slates the white Primal sandstone is seen densely cemented and very vitreous, and only about twenty feet in thickness, all the upper beds having been cut away. In this synclinal fold the strata dip about 60 to S. As already mentioned, the red sandstone conceals the termination of the strip of Primal at a short distance beyond this spot to the east, or before it reaches the county line of Bucks and Montgomery. PRIMAL STRATA WITHIN THE AURORAL LIMESTONE VALLEY OF MONTGOMERY AND CHESTER COUNTIES. First Anticlinal lifting the Primal Rocks. Besides the Northern and Southern fringing out- crops, and a long contracting Eastern belt, in which the trough terminates, there occur two or three anticlinal uplifts of the Primal rocks within the outer limits of the limestone of the valley. The most southern of these insulated tracts is the narrow belt of Barren Hill, a prolongation of Edge Hill, which range is but a monoclinal outcrop of the Primal white sandstone and its under- lying slates lifted into a perpendicular dip by an anticlinal flexure in the gneiss immediately behind it to the S. The axis of this anticlinal wave is prolonged all the way to the Schuyl- kill, gradually subsiding westward till it permits the upper Primal white rocks to bury them- selves near Spring Mill under the overlying Magnesian limestone. It is a closely-compressed or sharp anticlinal, elevating the gneissic rocks to the surface as far westward along the sinking crest of the Edge Hill ridge as the vicinity of Heydrick's Mill, on the road leading from the Bethlehem Turnpike towards Willow Grove. Westward of this point of depression in the ridge, no gneiss is visible in its axis, but only the uppermost layers of the older Primal slates, which are here more or less talcoid from metamorphosis by heat. Even these talcoid layers sink out of view before we reach the village of Barren Hill, from a point E. of which, to the village of Spring Mill, the only rock exposed along the summit and flanks of the ridge is the white Primal sandstone in a highly felspathic condition, with talcose Fid. 14. Section at Middleton's. partings. A section of this compressed flexure is exposed in a cut on the turnpike road at Middleton's. It is interesting as showing a bending of the outcrops of the strata both ways down-hill, from the pressure of retreating waters. Barren Hill presents us with some striking examples of overturned outcrops, from the mere VOL. i. x 162 PRIMAL STKATA OF MONTGOMERY. Flo. 15. Overturned outcrop of Primal Sandstone in a quarry in Barren Hill, on the Eidge Road. effect of the pressure induced by the denuding waters during their diffused rapid subsidence at the time the land was uplifted. It is both there and in many other parts of Pennsylvania on far too great a scale to be attributable to the softening action of rain and hill-side pressure. Between this anticlinal of the Primal rocks and the base of the Gneissic hills to the south, there lies a narrow parallel trough full of exqui- sitely-beautiful local scenery, its soil a deep covering of fertile earth derived from the Gneissic and Primal strata. This little synclinal valley appears to contain here and there patches of the lower beds of the Auroral magnesian limestone; but the outcrops of this rock are difficult to detect in the earthy covering above mentioned ; and it is more than probable that the trough is too shallow to contain any long continuous belt of it. The limestone is detected resting on the Primal white sandstone, in a south dip close by the Toll Gate on the Wissahickon and Perkiomen Turnpike at Middleton's. Second Anticlinal of Primal Rocks. The next anticlinal belt of insulated Primal rocks within the Limestone Valley east of the Schuylkill Eiver, is a long narrow range of the Primal older slates in a more or less talcoid condition, which, commencing at this river at Conshohocken, and extending eastward, contracts, and finally subsides at the Perkiomen turnpike south of Marble Hall. This uplift of the Primal strata through the Magnesian limestone is simply a prolongation of the bold anticlinal fold of the lower rocks of Bethel Hill, west of the Schuylkill, opposite Conshohocken. It evidently originates in the plateau of gneiss to the westward. Sinking to the eastward across the Schuylkill, it insulates a trough of the Magnesian limestone between it and the belt of the gneissic hills bounding the river between Conshohocken and Spring Mill ; and beyond the Western head or termination of this limestone basin, insulates between the gneiss which the anticlinal there uplifts, and the main Southern gneiss, a similar contracting trough of the Primal slates. It is along this trough of the slates that the upper part of the Gulf Creek flows, until it breaches the anticlinal, and passes northward through the deep gorge called " The Gulf." The axis, or back of the wave, is probably prolonged to the eastward across the Wissahickon, for apparently a couple of miles beyond the Perkiomen Turnpike, near which the talcose slates seem to sink under the limestone. Even on the Bethlehem Turnpike a ridge in the limestone, directly in the prolongation of this axis, betrays in its structure and soil the presence of this anticlinal wave. It is worthy of remark, that all the marble of the limestone basin of Montgomery County is confined to the synclinal trough adjoining the anticlinal axis now described, upon the N. ; the genuine marble not extending more than half a mile from the uplifted belt of slate, nor eastward in its line of strike beyond the neighbourhood of the point of sinking down of the Primal slates, or past the Meridian, where the anticlinal rapidly loses its force. As the marble is evidently only a highly metamorphic variety of the ordinary Magnesian limestone, crystallised and changed in tint by igneous action from within the earth, it is quite natural that it should run thus parallel with and adjacent to this line of uplift, produced as this has been by the protruding forces of the interior. The whole of this belt of marble is in fact but the vertically upturned, and occasionally inverted, Northern side of this anticlinal wave, the side along which the maximum ANTICLINALS. 163 amount of igneous influence is invariably manifested. In offering this explanation of the origin of the marble by metamorphism, it is proper to observe that we must not ascribe the whole of the change to its proximity to the line of anticlinal uplift of the Conshohocken axis. There is a tendency in the whole of the limestone of the Southern half of the general valley to a much greater degree of alteration than belongs to the same rocks in the Northern half. Throughout this entire synclinal belt the metamorphism from heat, of course, has been far greater along its Southern than upon its Northern margin, partly because the strata of the former side are nearer the principal injections of igneous rocks of the whole region, and partly in consequence of the perpendicular or even inverted position which has permitted the subterranean volcanic vapours to pervade them more freely, and exert their maximum influence. Analogous with this general tendency to a higher degree of metamorphism along this South side of the basin, we have the effect of the powerful anticlinal uplift of the Bethel Hill axis, causing a similar greater change along the narrow belt immediately adjoining it on the N., where the limestone is likewise in the condition of marble. Third Anticlinal of Primal Rocks. A short and relatively insignificant flexure of the strata ranges near the northern margin of the Limestone Valley, and throws up a ridge of the Primal rocks from a little N. of Frea's Corner, where it is encroached upon by the edge of the red sand- stone, to the point S. of Reuben Cox's Limekilns. Near the Western end of this ridge the rocks composing it are well exposed in two or three small quarries ; while a road leading a certain distance along its summit enables us to detect the Primal white sandstone capping the talcose slate quite near its crest. The Primal rocks are exposed in this ridge through a length of a little more than one mile. On its Northern flank the white sandstone appears to be inverted, or to dip Southward. Between the North base of the ridge and the next or fourth anticlinal, there runs a narrow trough of the Magnesian limestone, about one-third of a mile broad. This at its Western end is shut under by the overlapping edge of the red sandstone, which here crosses the limestone obliquely from near the, Western end of this third to the Western point of the fourth anticlinal of Primal rocks. In this trough the limestone is quarried near the road leading N. from Frea's Corner, and again more extensively at the limekilns at Reuben Cox's. Fourth Anticlinal of Primal Rocks. A fourth and comparatively feeble anticlinal flexure lifts the Primal rocks to the surface through the limestone of the valley in the Church Ridge, crossing the Wissahickon Creek near the village of Whitemarsh. East of the Wissahickon this axis at the Bethlehem Turnpike exposes only the uppermost of the Primal rocks, or the white sandstone. On the south side of the anticlinal axis line, or fold, these strata dip at a moderate angle to the southward." On the North side they dip perpendicularly, making this a flexure of the true normal form. The Episcopal Church at Whitemarsh crowns the summit of this regular anti- clinal ridge. In the exposure at the Turnpike, the altered sandstone is pervaded with cleavage- planes, dipping according to the prevailing law of cleavage-structure throughout all Southern Pennsylvania, at a rather high angle to the S. Near the very axis of the flexure the dip of the cleavage-joints is towards the axis plane, or steeply to the N., making, with the South- dipping cleavage of the beds N. of the axis, that fan-like arrangement of these fissures which is so characteristic of anticlinal folds in strata highly susceptible of cleavage-structure. (See the Section.) To the Westward of the Wissahickon this anticlinal belt of the Primal rocks is prolonged 164 JUNCTION OF PEIMAL AND AUEOEAL STEATA. into a ridge considerably higher and longer than that crossed by the Turnpike at the Church, extending for about three miles ; it terminates in a low point near the extension of the Plymouth road. It is flanked, and is even saddled for much of its length, by the white Primal FIG. 16. Section along the Bethlehem Turnpike from Sandy Run to Chestnut Hill. * -. Pr. Sd.1. '-... Laml - .. ..... " X . ?* * sandstone. The Primal slates, somewhat talcose, but in a less metamorphic condition than on the Southern side of the valley, emerge to the day in several places along the crest of the ridge. They are much affected, as usual, by cleavage ; and though the anticlinal structure of this long narrow hill is obvious, no exposures permit us to detect the actual place of the turn of the dip westward of the turnpike at the Wissahickon. A trough of limestone that, namely, in which Hains's Inn is situated is embraced between this axis of the Church Hill and the Fort Washington Ridge, or northern general boundary of the valley ; but though doubtless prolonged far to the westward of the Wissahickon, this rock soon vanishes from view, being buried under the margin of the Middle secondary red sandstone. That overlapping stratum extends obliquely across the trough from the Wissahickon opposite Fort Washington to the Northern base of the anticlinal ridge of the Primal rocks, meeting this about half a mile west of that stream, and there bringing the accessible limestone to a point. PASSAGE FROM THE PRIMAL TO THE AURORAL STRATA AT SPRING MILL AND CONSHOHOCKEN, ON THE SOUTH SIDE OF THE LIMESTONE BASIN. DESCRIPTION OF SECTION PAST SPRING MILL ACROSS THE SOUTHERN SIDE OF THE LIMESTONE BASIN OF MONTGOMERY, BEING A CONTINUATION OF THE SECTION ALONG THE SCHUYLKILL FROM PHILADELPHIA TO SPRING MILL. The accompanying Section is intended to illustrate the relations of the Primal strata at the Schuylkill to the Gneissic rocks beneath them, and to the Auroral limestone overlying them. FIG. 17. Section of the Primal and Gneissic Strata, and of the Auroral Limestone and its Ore-Ground, near Spring Mill. _+ 0< * ** r- * It commences on the point of the Furnace Hill, just east of the William Penn Furnace, at the northern or upper limit of the gneiss. Here the passage from the harder gneiss to the softer porphyroidal talcoid slates is marked by a decided change to a gentler slope on the flank of the hill. A portion only of the lower Primal rock is seen in the point of the hill as it stretches towards the Schuylkill. From the position of the outcrop of Primal sandstone at Lentz's old ore-digging, it may be inferred that the section crosses the same outcrop nearly at the road at the base of the hill. There is a blank of about 400 feet between this road and the base of the Barren Hill Ridge, but this blank occupied by the surface materials of the little valley is evidently underlaid by the Primal strata, no Auroral limestone having ever been detected here in wells or excavations. The section now crosses the ridge near a MATSAN'S EUN. 165 quarry of the upper beds of Primal white sandstone, which here dips to the S. at an angle of 35". Just north of the crown of this narrow ridge, the same white rock has been recognised in sundry wells sunk in quest of ore, dipping perpendicularly, or even turned under to a S. dip of 85, proving that the anticlinal axis of the ridge lies between these wells and the quarry before mentioned on its south slope. In immediate contact with these perpendicularly-dipping beds of Primal sandstone occur steeply-inclined beds of dusky ferruginous magnesian limestone pervaded with cracks, giving the rock a brecciated aspect. At this junction of the Primal and Auroral strata is the southern limit of the deep deposits of ferruginous clay and loam which imbed the large accumulations of brown htematitic iron-ore, which constitutes already such a prominent source of wealth to the whole southern half of this great limestone belt. Our section crosses about 50 feet of recognisable outcrop of the Auroral limestone, seen sometimes in the deeper ore-diggings, sometimes in the valley of Spring Mill Brook. Wherever exposed, these limestone beds dip a little to the south of the perpendicular. Beyond the limit here stated no rock is exposed for about 400 feet, until we approach the road leading from Spring Mill to Marble Hall ; but in that vicinity we detect steeply-dipping talcoid slates, elevated by the anticlinal axis further north. Our section now crosses the talcoid Primal slates on the south side of this anticlinal for about 600 feet. These slates dip like the limestone at a very steep angle to the south. Here on the northern side of the summit of this ridge, which is the pro- longation of Bethel Hill of Conshohocken, our section encounters the large trap-dyke which extends from the south slope of Bethel Hill through the village of Conshohocken and the crest of this slate ridge past the point we are upon to the Perkiomen Turnpike, which it crosses between Marble Hall and Barren Hill. This dyke is here about 30 feet in width. Northward from the trap-dyke we pass over in the line of section between 500 and 600 feet more of talcoid slates, till we approach the northern foot of the hill, where we detect the lower upturned beds of the Magnesian lime- stone. At the base of the hill we come upon the blue and shaded marble ; and here the marble belt is between one- third and one-half of a mile broad. Our section displays a wide trough or depqsit of ore-ground between the two anticlinal uplifts which it intersects. This ore-ground beginning on the south just north of the summit of the White Sandstone Ridge, reaches to the foot of the higher ridge of Primal talcoid slate. Neither on the White Sandstone Eidge nor the Talcoid Slate Hill is there any depth of ferruginous soil sufficient to include a notable amount of iron ore ; but in the trough between them, the ore, containing loam and clay, rests in a very deep deposit, measuring in some longitudinal gutters not less probably than 100 feet. It is in these deeper collections of the ferruginous earth that the largest deposits of the richest ore should be obtained. The iron contained in this ore-bearing soil has been in part derived from the lower beds of the Magnesian limestone, some of the strata of which are excessively ferruginous ; but in larger part it has proceeded, no doubt, from the disintegrated talcose slate, a rock abounding in iron, as the red colour and composition of its clays demonstrate. The line of our section crosses another narrower belt of ore at the foot of the Furnace Hills. This deposit pertains to a deep lodgment of ferruginous earth and decomposing slate-rock, just at the contact of the talcoid slates and the Primal White Sandstone. The ore is for the most part more sandy than that which overlies the limestone and talcoid slates further removed from the Primal white sandstone. PASSAGE BEDS AT THE MOUTH OF MATSAN'S EUN OPPOSITE CONSHOHOCKEN, A transverse section at Caldwell's Furnace, from the Primal Slates into the Auroral Limestone, displays, 1. Talc-slate on the north slope of the bounding ridge, dipping perpendicularly. Fio. 18. Section at Caldwell's Furnace. 2. North of the slate, a narrow band of mottled blue-and- white crystalline limestone and marble. 3. A bed of talcoid or nacreous altered slate, apparently about 100 feet thick. 4. A band of impure altered limestone, about 50 feet thick. This passes under the southern edge of the Engine House. 5. A talcoid and garnetiferous altered slate, extending to within 100 feet of the brook. This underlies the Furnace. 6. The lower beds of the Auroral magnesian limestone, as a continuous mass, visible on both sides of Matsan's Eun and in its channel. 166 PKIMAL EOCKS WEST OF SCHUYLKILL. On the north side of Matsan's Eun, or about 200 feet south of the Conshohocken bridge, there is a good exposure of the lower beds of the Auroral magnesian limestone near the railroad ; here the rock is sub-crystalline, and mottled whitish and blue ; it weathers of a ferruginous yellow, and dips without contortion 77 to N. 25 W. The alternating or passage beds, above described, range westward up the valley of Matsan's Run, on its south side nearly to its head, some of the limestone bands having been quarried to furnish a flux for the Furnace. THE PEIMAL WHITE SANDSTONE BOUNDING THE CHESTER COUNTY VALLEY WEST OF THE SCHUYLKILL. Having defined the outcrops of the Primal white sandstone bordering the main basin of limestone of Montgomery County, and traced them to their terminations E. of Willow Grove, and having shown the several narrow anticlinal belts in which they appear within this basin, we will now follow them along both margins of the same great trough, as it stretches in a nearly straight line through Chester into Lancaster County. THE SOUTHERN OUTCROP OF THE PRIMAL SANDSTONE. It is an interesting fact disclosed in the attempt to trace continuously the Primal white sandstone along the Southern side of the Chester County Valley, that it ceases almost entirely on this border of the basin in the neighbourhood of Spring Mill, or E. of the Schuylkill, and that no effort to discover it in a regular outcrop of any length or appreciable thickness has yet disclosed it on the West side of the river, or even for several miles westward, until we reach points opposite the Spread Eagle and the Paoli. North of the latter place the outcrop of this sandstone may be recognised at two or three spots just at the base of the South Valley Hill ; in some instances by the character of the soil, and the angular fragments of the sandstone imbedded in it ; and in one case in a house-well at the country-seat of Mr Thomas Biddle. In these spots the thickness of the whole stratum cannot exceed a very few feet, nor can we suppose it con- tinuous ; for if it were, we should almost certainly detect it in the numerous lanes, and in the railroad cuts, which so abundantly intersect this border of the basin. The next point further westward at which we recognise unequivocally the outcrop of this interesting rock is on the South Eoad, about one and a half miles E. of Downingtown, or one- third of a mile W. of the Railroad Viaduct. Here the rock is exposed in the gutter of the road, and it has been dug into in a well near by. A soft sandy material, the decomposed stratum, is yet distinctly discernible at the spot. It presents its ordinary, somewhat talcose, aspect. The dip of the strata, both here and generally along this margin of the valley, is very nearly vertical. We cannot discover any vestiges of the formation, either S. of Downingtown or for a few miles W.S.W. of it, though it is very probable that it appears and disappears in the same obscure manner as it does further eastward ; but in the vicinity of Coatesville, and westward of that village, this well-marked rock possesses a sufficient thickness to project conspicuously in rugged outcrop at the entrances of the numerous ravines and gorges which there cut the South bound- ary of the valley. Even there, however, it seems not to possess a thickness of more than 30 or 40 feet, and is sometimes thinner ; and yet, from the superior hardness of its semi- vitreous mass, and its silicious nature making it invulnerable to the chemical influences of the elements, it is a very prominent feature in the stratification, even where thus thinly developed. The rock SEEPENTINE. 167 in nearly perpendicular dip thus holds its course to the westward, skirting the border of the valley until the limestone itself terminates, and the two sides of the basin ultimately unite. This union of the two lines of the Primal sandstone occurs near the Conewango Creek in Drumore Township ; yet the long and remarkably straight synclinal trough within which they lie stretches on in precisely the same course for a few miles towards M c CaH's Ferry ; but before reaching the Susquehanna River the synclinal structure ceases, and a monoclinal South dip alone remains. Only the lower Primal rocks, or the micaceous crystalline slates, reach the river. Indeed, it is doubtful if the sandstone extends even to the Conewango. In another Chapter it is shown that other outcrops of the Primal white sandstone occur some miles to the S. of this long line, and entirely insulated from it, proving that the forma- tion has at one time spread itself very extensively to the southward. BELTS AND LOCALITIES OF SERPENTINE SOUTH OF THE LIMESTONE VALLEY OF MONT- GOMERY AND CHESTER COUNTIES. 1. The Serpentine and Steatite Range of the Schuylkill in the Sout/tern Edge of Montgomery County. This, the most eastern zone of the magnesian rocks in Southern Pennsylvania, lies entirely within the middle or micaceous belt of gneiss, or highly metamorphic Azoic rocks, but near its northern border. It is a long and straight line of outcrop of steatite or serpentine, extending from the northern brow of Chestnut Hill between the two turnpikes, across the Wissa- hickon Creek and the Schuylkill to near the Baptist Meeting-house Road, about a mile west of Merion Square. Along the eastern and central parts of its course, the southern side of this belt consists chiefly of a talcose steatite. The northern side, containing much serpentine in lumps, dispersed through the steatite ; but towards the western side this separation seems to disappear. The serpentine division, or band, is conspicuous on the line leading from Chestnut Hill down to Thorpe's Mill, where enormous blocks, without any distinct traces of stratification, cover the surface along the line of the bed or dyke. The same rock is similarly exposed on the west side of the Wissahickou, opposite Thorpe's Mill, and thence westward along the north side of a lane leading up to the Ridge Road. The whole belt is vaguely exhibited at the summit-level of the land between the Wissahickon and Schuylkill valleys ; but, descending towards the Schuylkill, we again discern, on the north side of the line of outcrop, the huge blocks of mingled serpentine and steatite, until, near the Schuylkill river, they choke the bed of the ravine next north of the Soap-stone Quarry. On the west side of the Schuylkill, this serpentine and steatite rock is still visible in large blocks, a little above the soap- stone of that bank of the river ; but between this point and the vicinity of Merion Square, the rock, though discernible at a few points, is nowhere conspicuous. About one-third of a mile west of Merion Square, it is quite prominent again, the surface being strewn with huge masses. It may be distinguished at once from any other mineral aggregate of the region, not merely by the enormous dimensions of its loose blocks, but by its rugged, frowning, dark aspect, and also by the general coating of dark lichens and other cryptogamous plants. The serpentine seems not to follow the steatite the whole distance to the western termination of the belt. Only in a few neighbourhoods does the steatite, constituting generally, as already said, the southern half of the tract, present itself in sufficient purity and mass to be profitably quarried. On the east bank of the Schuylkill, however, about two miles below Spring Mill, at the spot called the Soapstone Quarry, it has long been successfully wrought : and on the west side of the river, in one place on the bank, and at another about one-third of a mile west, the rock has been quarried, though upon a less extensive scale. In former years it was excavated to a small extent on the west bank of the Wissahickon, just opposite Thorpe's Mill ; but the band of steatite at this place appears to be too thin to warrant its being pursued at present. Both at the Wissahickon and the Schuylkill, the steatite, which is regularly stratified, dips steeply to the N. 35 W., agreeing in its inclination with the subjacent beds of mica-slate ; but on the west side of the Schuylkill, at the points where it has been exposed in quarries, it dips at a more moderate angle to the south-east, thus indicating a pro- bably synclinal structure in this central portion of the belt. The material is used chiefly for the lining of stoves, fire- places, and furnaces. The principal market for it is the city of Philadelphia. Towards the end of the last century and the beginning of this, before the introduction of the marble of Montgomery 168 BELTS OF SEEPENTINE. County for street-door steps in Philadelphia, this easily-dressed stone was in some demand for that use ; but it proved badly adapted to the purpose, because of the very unequal hardness of its different constituent parts, there being a difficulty in getting blocks free from knotty lumps of imperfectly-crystallised serpentine, which make it to wear unevenly under the attrition of the feet. We may sometimes see, in an old and much-worn door -sill of this rock, these knots of the serpentine mineral projecting above the steatite like hob-nails in a plank. 2. Second Outcrop of Serpentine in our progress westward. The next outcrop of the serpentine in our progress west- ward, occurs on the western brow of the table-land of Gneiss just south of the narrow limestone trough of the upper part of Gulf Creek. It is within half a mile of Morgan's Corner. The exposure there has a length of only a few hundred feet, but it is at least 300 feet wide. It is bounded on the south by genuine gneiss, and immediately on its north by talcose and steatite slate. Between this belt and the narrow strip of limestone in the valley north of it, there is an uplift of hornblendic gneiss, distant from the serpentine about 100 yards. Immediately north of this last outcrop of the gneiss we encounter a repetition of the talcose-slate formation, or older Primal rocks under that highly altered gneissoid aspect which they wear so conspicuously on the Schuylkill between the Aramink and Spring Mill. The belt of serpentine comprises both true injected or igneous serpentine, and serpentinous steatitic talc-slate. In the two quarries in which it is best exposed, stratification is visible in some places, but ill others there is none. In a quarry east of the road, the dip is steeply northward, while in that on the opposite side of the road it is 70 southward. FIG. 19. Section of South Valley Hill, east of Morgan's Corner. 3. Third Belt of Serpentine, or that of tlie neighbourhood of the Paoli. We come next in order to the most extensive serpentine range of Chester County. This has its eastern extremity on the farm of General Wayne, of Revolutionary memory, about one mile south-east of the Paoli Hotel, and just at the line of East Town and VVillistown. Its western termination is near the western line of East Goshen, and about two and a half miles N.N.E. of West Chester. These limits give a total length of about six miles. Its course is W. about 25 S., coincident nearly with that of the strike of the gneiss and talcose slate which border it for the greater part of its length. Commencing in a narrow point of the General Wayne farm, it widens rapidly as we trace it westward, until, at a distance of a mile at and beyond Maris's Grist Mill, its total breadth is nearly 2000 feet. In this central part of its course it runs for nearly three miles almost parallel with the old State Road to West Chester, at an average distance of one-third of a mile, gradually approaching the road until it crosses it about four miles from the Paoli, or three-fourths of a mile north-east of East Goshen Friends' Meeting-house. It is here reduced to a breadth of no more than 400 or 500 feet. Under this average width it ranges on, passing the Barren Hill School-house and across Ridley Creek, and thence for one mile further to its termination beyond the old blacksmith's shop at John Gheen's farm. Throughout its entire range, this serpentine appears chiefly as a stratified rock, and in its widest central portion we may distinctly perceive that it has a synclinal or undulated structure. It is, indeed, rather an impure talcose slate, largely impregnated with serpen- tinous matter, than a zone of genuine intrusive serpentine. Dykes of this mineral it does, however, embrace, and these on a small scale are very numerous, but they bear in the aggregate a small proportion to the whole belt. Its stratified structure is well exposed at the crossing of the State road, where it dips 70 N. ; also in the ravines which cut it near the Barren Hill School-house, and still more convincingly near the old smithy at John Gheen's, in which latter locality it has a nearly perpendicular dip, but discloses under close inspection innumerable minute contortions and plications of the thin lamiuse of the rock. The eastern end of this zone of serpentine is bordered both south and north by the talcose-slate formation, in which it seems to lie as a folded synclinal trough ; but from the vicinity of Maris's Grist Mill to its western termination, its southern margin is in contact with a massive hornbleudic gneiss, its northern touching in some places upon ordinary talcose slate, but in others, especially towards the western end, upon quartzose and garnetiferous micaceous gneissoid rock, of the group I have called Azoic. This gametiferous micaceous gniess may be seen dipping steeply northward, conformably with it, close to John Gheen's dwelling. The prevailing dip of the hornblende gneiss, bounding it on the south is northward 70 80. WEST CHESTER BARRENS. 169 Along the northern edge, or a little outside of the northern margin of this line of serpentine, trap-rock occurs in greater or less abundance, and apparently as a succession of narrow elongated dykes. These seem not to be strictly parallel with the serpentine and other strata, but to observe a more North-east and South-west direction. Narrow dykes of this rock intersect, indeed, this range of Serpentine Barrens in many neighbourhoods, and this is a feature which may be noticed in nearly all the outcrops of serpentine within the State. The crystalline minerals of this tract, few in number, will be mentioned in a future Chapter in connection with those of the other serpentine belts. 4. Fourth Tract of Serpentine. There is a small and apparently insulated development of serpentine about three- fourths of a mile S., 45 W., from the old smithy near Gheen's dwelling. It is evidently not in the prolongation of the long belt just, described, but is almost exactly in the range of the Serpentine Barrens, one mile north of West Chester, with which it is possibly united, though no external indications of such connection present themselves, there being an interval of half a mile between the small patch and the eastern extremity of the Main West Chester Line of Barrens. Though small, this area of serpentine is readily discerned, forming a little elliptical mound. 5. Fifth Serpentine Tract, or that of the West Chester Barrens. In the same general line with the long range of serpentine traversing Willistown and East Goshen, though strictly about one-third of a mile further S.E. than its line of strike, is the Serpentine belt of the West Chester Barrens. The N.E. point of this appears to be just S.W. of the East Branch of Chester Creek, or one-fourth of a mile N.E. of the West Chester Railroad. It crosses the railroad nearly two miles from the centre of West Chester, exposing impei'fectly its stratified structure in the railroad cuts ; whence it ranges about one mile further between the forks of Taylor's Run. The mean width of this belt is at least 1000 feet. Though chiefly an impure and stratified serpentinous talcose slate, the tract includes many injections of genuine igneous serpentine. Like all the middle and western portions of the Paoli belt, this tract is bordered on the South by massive hornblendic gneiss, while it is fringed on the North by the earlier talcose slate and micaceous slate of the South Valley Hill, into which it appears somewhat abruptly to graduate. The more compact varieties of this serpentine have been used for building-stone in West Chester and its vicinity, and the material proved to be well adapted for many architectural uses. It has a very pleasing effect when newly built into walls, as it has a quiet tone of greyish green ; but exposure to the elements for a few seasons causes it to fade, or to become more dull and greyish. Several neat structures have been built of it. The chief minerals of this range hitherto discovered are mentioned in the general list already referred to. 6. Sixth Serpentine Outcrop. To the S.W. of the Main West Chester Belt of serpentine, there occurs near Hoope's Saw Mill a small outcrop of serpentine and steatite, which is evidently in the same line of strike with the large serpentine tract north of West Chester, and the small detached one to the east of that. 7. Seventh Outcrop. Another trivial exposure of Magnesian rock, chiefly steatite, occurs on Taylor's Run, on the land of Caleb Cob, close to an outcrop of granular limestone. These are about half a mile S.W. of the previously-mentioned locality of serpentine. 8. A still more trivial locality of steatite is at the Black Horse Tavern, on the road to Taylor's Ford. It is in the same general line with the three previously-mentioned localities of magnesian rocks. 9. Again, on the same line, both serpentine and steatite present themselves about three-fourths of a mile S.W. of the Brandywine, on the farm of Mr Wurth. All the above six exposures of serpentine and steatite occur so nearly in one line, and this is so probably a line of dislocation connected with the synclinal fold of the older strata, that we can hardly doubt that these outcrops derive their existence from one chain of injections of true serpentine mineral along the southern margin of the talcose Primal slates. 10. An entirely insulated exposure of associated steatite and serpentine occurs near Marshall's Mill, on the West Branch of the Brandywine, on the farm of Humphreys Marshall. This does not seem to be connected with any of the other serpentine injections of the district, for it is too far South to be in line with the six outcrops previously described, and too far North to be related to the large serpentine ridge east of Unionville. It is more strictly in bearing with a small exposure of the same rock, which occurs in the neighbourhood of West Maryborough Inn. 11. The last-mentioned locality, West Marlborough Inn, possesses a small exposure of stratified serpentinous rock, containing injections of serpentine ; and this is the most Western of all the outbursts of this rock until we come to the great one, which commences at the Little Elk Creek and extends for many miles to the Susquebanna Eiver, which it crosses. VOL. I. Y 170 BELTS OF SERPENTINE. 1 2. There succeeds now a more Southern line of insulated exposures of serpentine, the most Eastern of which ia encountered half a mile S.E. of the Willistown Inn, in Willistown Township. This includes both serpentine and steatite. 13. The next locality of the serpentine rock of this belt is near Darlington's Corner, and here occur carbonate of magnesia and crystalline chlorite, besides the interesting mica mineral Klinoclore. 14. Near Strode's Mill, in East Bradford Township, there occurs a large outburst of serpentine, with lithomarge and fine talc connected with it. 15. Another exposure of the same magnesian rock exhibits itself N.W. of Strode's Mill, near the Prospect Hill Academy. This is nearly in a line with a large belt of the same rock east of Unionville. 16. One or two detached knolls of serpentine occur in Lower Oxford Township, the furthest west of the small insulated patches known to us. 17. Serpentine Belt of the Unionville Barrens in Newlin Township. We have arrived now in our progress towards the S.W. at a conspicuous belt of serpentine, about equal in magnitude to that north of West Chester, and one of the most interesting of the whole series for the crystalline minerals which it contains. It lies in the south-eastern corner of Newlin Township, about one mile N.N.E. of the village of Unionville. It has a mean breadth of some 800 feet or more, and its total length is about one mile. It lies altogether within the micaceous talcose slate, many portions of which rock wear here a very quartzose and sandy aspect. This belt consists of stratified ser- pentinous talcose slates, with much injected or infused true igneous serpentine. It is intersected by several narrow dykes of fine-grained basaltic trap, which trend N.E. and S.W. Besides these, there occur some interesting mineral veins. One of these, which has attracted the notice of mineralogists, is a narrow vein of very hard white albite, including many crystals of corundum, some portions of the vein being indeed almost an emery or corundum rock. An attempt was made some years ago by a skilful and most zealous mineralogist of Chester County, D. Lewis Williams, to mine regularly this very hard and intractable but valuable material ; but the undertaking was not long persevered in. Loose chunks or blocks of the corundum rock strewing in one place the north slope of the ridge of serpentine, derived either from the above-mentioned vein or from other injections, were collected at one time to the amount, it is said, of between six and seven tons, and exported to Europe. Besides the albite with corundum, there occur several veins or dykes of granite, consisting almost exclusively of felspar. This mineral is here in such purity, indeed, as to be in much request for the purposes of dentistry. Owing to the demand for felspar entirely free from extraneous associations, a successful quarry has been opened, and has already furnished a considerable quantity for the market. Associated with the pure orthoclase, which is in very large crystals, there is also occasionally much oligoclase or soda spodumene, another felspar mineral. There are several other insulated small localities of serpentine west of the Brandywine, but they are not of sufficient importance to be entitled to a special description. Long Serpentine Belt of the State Line on the Southern Edge of Chester and Lancaster Counties. A very extensive belt of stratified and injected serpentine rocks ranges near the State Line from the Little Elk Creek in Chester County across the Octorara Creek to Maryland, and thence across the Susquehanna. Its length from the Little Elk to the Susquehanna exceeds 17 miles, and the tract is prolonged beyond the river through the northern edge of Maryland for several miles further. Its mean width may be given at about one mile. This is a range of wild and stony barrens scarcely tilled, except in a few spots on its two margins, and overgrown with stunted black oaks, and other trees characteristic of the magnesian soils of all these serpentine belts. Along its southern border this magnesian formation is in contact with black hornblendic gneiss, but apparently without conformity of dip. On the Susquehauna a different rock, a micaceous talcose slate, bounds it on the S. ; along it northern edge it is every- where bordered by the micaceous talcose slate of the Primal series ; and this latter formation seems to lap round its eastern extremity, near the valley of Little Elk River. Much trap-rock presents itself just west of the Little Elk along the southern edge of this range of serpentine, and dykes of that material occur within and adjacent to the belt, especially throughout its southern half, and apparently along its whole course. One of these may be seen on the main road leading to Carter's Ferry at the crossing of Buck Run. The zone of serpentine rocks now before us is especially remarkable for containing large quantities of chromiferous iron-ore. It is indeed one of the chief sources of chromate of irou in the United States, having already furnished large supplies of this mineral for both the home and the European demand. The chrome ore penetrating the serpentine rocks in true lodes or veins, with more or less regularity, has likewise been met with in great abundance in a fragmentary IRON ORES. 171 state upon the surface of the barrens, and to a small depth amid the disintegrated materials of the serpentine. It has, therefore, been mined both by regular mine-shafts, and by superficial pits or holes, and trenches. The scattered surface ore, locally called " Sand Chrome," has been extensively gathered from the beds of the ravines and valleys which intersect the barrens, and after being washed on the spot has been shipped away to market. When, for a succession of years after the first development of this mineral, the high price of $45 per ton stimulated the discovery and pre- paration of it, many thousand tons of the stream or " sand chrome " were transported to the sea-board, especially to Baltimore. More lately, since the richer deposits of the more accessible surface ore have been in chief part exhausted, resort has been had to mining in some of the more regular solid veins. Only two such subterranean excavations are now, however, systematically prosecuted, owing partly to the circumstance, that the present market for the mineral is easily glutted, and partly to the fact, that nearly all the most promising localities of the region are at present monopolised by one individual. Both of these mines are situated a little westward of the East Branch of the Octorara Creek. It will suffice to present here the chief features of one of them, namely, Wood's Chrome Mine. This is situated not far from the Horse-shoe Ford of the Octorara, the vein of chromi- ferous iron-ore observing a nearly N.E. and S.W. direction, and dipping 45 to N.W., or with the local slope of the ground. It has been mined throughout a length of about 300 feet. As a lode it is quite irregular, varying from a width of 20 feet to nothing, or expanding into large pockets of ore, and then contracting until the walls meet. It also throws off several branches, some of which return into the main vein. The shaft at present (1854) has a depth of about 150 feet, and an open drain meets the shaft about 20 feet below its mouth. This mine produces at present between seven and eight tons of excellent chrome ore daily, the fruits of the labour of three hammers and the attendant aid. The present price of the chrome ore is about $25 per ton. The gross yield of this mine is therefore nearly $200 per day. The finer pieces of the ore are packed in barrels on the spot as they come out of the mine, and are thus sent to Europe without re-handling. The rest of the ore, after dressing and washing, is transported to Baltimore and other home markets. The Line Mine. The other chief mine situated immediately on the boundary line of Pennsylvania and Maryland, and called therefrom " The State Line Mine," is not now actively wrought. Its shaft is about as deep as that of Wood's Mine. The aggregate former yield of the Line Mine amounted to several thousand tons. There are several interesting minerals associated with the chromiferous iron-ores and serpentine of this range of magnesian barrens, and nearly all the species occur equally at the two mines here spoken of. These minerals are enumerated in the general chapter on the mineral localities of the Primal district of the Atlantic Slope of Penn- sylvania. There is another shorter tract of serpentine barrens containing both the stratified and the unstratified intrusive varieties of the rock, situated about two miles north of the State Line in Lancaster County on the waters of the Cone- wango. The southern edge of this is near the little village of New Texas. The whole belt is about three miles long, and more than half a mile wide, and it has somewhat the form of a crescent, its convex curve being to the N.W. Its north-east end is about one and a half miles E. of the Conewango Creek, which it crosses about two miles N. of the State Line, extending westward of the stream about a mile until its south-west extremity is within two miles of the Susquehanna, and a mile and a half N. of the State boundary. From this locality much silicate of mag- nesia has been taken, and transported to the chemical works of Baltimore and elsewhere, for the manufacture of Epsom salts and other preparations of magnesia. The excavation of this mineral is no longer pursued ; it was dug only in superficial pits. Titaniferoits Iron Ores. There are in the main serpentine belt of Lancaster four or five localities of titaniferous iron-ore, commencing near the Horse-shoe Bend of the Octorara, and ending about three miles E. of the Susque- hanna River. At one of these, on the farm of Mr Jenkins, some of this ore has been mined, but only to a trivial extent. A small amount of the same refractory variety of iron ore has been also dug on the shorter tract of serpen- tine barrens N. of New Texas. A more productive locality occurs near the Baptist Meeting-house, where several hundred tons of the variety called Bird-eye Iron Ore have been successfully mined. A careful examination of these two belts of serpentine near the State Line of Lancaster County cannot fail to convince any observant geologist that the material, ordinarily termed serpentine, as presented in these barrens, com- prehends both a stratified and an unstratified rock. Pure serpentine is here found only in the form of dykes intruded through a stratified serpentinous talcose rock, evidently a metamorphic clay-slate the mica and talc-slate formation of the Susquehanna. The stratified serpentinous rock seems to have been impregnated with the magnesiau 172 BELTS OF SERPENTINE. minerals during the intrusion of these veins of igneous serpentine. The evidences in support of this view are abundant in the ravines which intersect the barrens north of the village of New Texas. The genuine serpentine rock is itself a material of quite diversified aspect, some of it being of a dark-green colour, and very tough ; other varieties less dense and heavy, and much more easily fractured, and of a pale or yellowish green. This latter kind usually abounds in contact with the chromiferous iron-ore at Wood's Mine and the other chrome localities. Certain small patches of the rock wear a slightly pinkish colour, but the predominant hue is some variety of green. The strata crossed successively in proceeding northward from the southern side of the more southern or main zone of serpentine near the Susquehanna, is as follows : 1. Hornblende gneiss and trap-rocks. 2. Serpentinous talcose slates, with dykes of serpentine. 3. Gneissoid, micaceous, and talcose slates, yielding a ferruginous soil, containing bands of whetstone or mica- slate. 4. Serpentinous stratified talcose sedimentary rocks, full of intrusive serpentine. 5. An alternation of talcose, micaceous, and argillaceous slates, embracing the roofing-slate of the Peach Bottom Eange. This latter group belongs to the older Primal slates, which extend all the distance to the Limestone Valley under various remarkable conditions of metamorphism, some of them even simulating the ancient Gneissic rocks. At the State Line, five miles W. of the Susquehanna River, we find a small ridge of serpentine. It is about a mile long, and lies principally in Maryland. In this belt the mineralogist may obtain fine specimens of green serpentine, actinolite, chlorite, and asbestos, tintaniferous iron-ore and magnetic iron-ore. A band of chlorite slate, near the northern base of the ridge, contains, in abundance, beautiful octahedral crystals of the last-named mineral. About one mile northward is another smaller ridge of serpentine, like the serpentine belts of Chester and Lancaster counties ; that above described occurs in a lenticular form in the talcose and chlorite slates. The following cut is introduced in illustration of a remarkable feature connected with the cleavage of the Primal slates described in this Chapter. It exhibits an instance of the segrega- tion of talc and quartz, in thin lenticular laminae, in planes coincident with the planes of cleavage, and obliquely transverse to the bedding of the rock. It is interesting as proving crystallisation to be the result of the, same metamorphic influence, only more energetically exerted, which has caused the cleavage. The locality whence the drawing was taken, is at the N. foot of Bethel Hill. The strata dip steeply N. from the anticlinal axis of the Hill ; the cleavage obeys the usual law, and dips steeply S., and approximately parallel to the axis plane of the flexure, on the flank of which it occurs. FIG. 20. Cleavage, N. foot of Bethel Hill, looking N.E. CHAPTER II. THE PEIMAL SEEIES BOUNDING THE MIDDLE GNEISSIC DISTEICT. WE may now trace the Primal white sandstone and slate as we find them developed N. of the Chester County Limestone Basin, and S. of the edge of the red sandstone. In doing this we shall have occasion to follow, first, the conspicuous and continuous zone, bordering the Chester County Limestone Valley on the N., under the name of the North Valley Hill ; in the second place, the Mine Eidge and its spurs, all of which are formed of this rock ; and in the third place, the Welsh Mountain and its dependencies. PRIMAL SERIES, WHITE SANDSTONE AND SLATES IN THE NORTH VALLEY HILL. Commencing W. of the Schuylkill about one mile E. of Valley Forge, the Primal white sand- stone of the North Valley Hill, so called, emerges into view from beneath the overlapping margin of the Middle Secondary red sandstone at the Eastern point of the hill known as Mount Sorrow, or that upon which Washington and his forces were encamped, amid great sufferings and privations, in the memorable winter of 1777-8. Here the Primal rocks, consisting chiefly of the older semi-crystalline slates, cross the East Valley Creek in a broad contorted belt, not less than half a mile in width. As we trace the formation westward, it would seem to expand rapidly, and to embrace a much larger portion of the white sandstone, and a less relative amount of the underlying Primal slate group. This change seems to take place in that section of the ridge which is called Mount Joy, for when we reach the Western point of Tredyffrin Township, or the vicinity of Ayer's Store, the chief rock visible is the white sandstone ; indeed, this is the case in the vicinity of Diamond Rock, though the north flank of the ridge at this latter point includes also a considerable thickness of Older Primal talcose slate. Throughout this part of its length, the belt of the Primal rocks is disturbed in dip by two or three closely-folded undulations, and it is in consequence of these that the sandstone at the Diamond Rock is spread over the Southern slope and summit of the ridge in so broad an outcrop. The lesser contortions and fractures connected with these undulations are the evident causes of the numerous veins and cavities, filled with crystals of quartz, which occur in the compressed and fractured masses of the sandstone at Diamond Rock, and which have conferred upon this cliff its name. A partial interruption in the continuity of the North Valley Ridge occurs at the depression above Ayer's Store, and it would seem that the outcrop of the Primal rocks takes here a sudden offset northward, the result, apparently, of the cessation of the undulations prolonged thus far from the Eastern end of the ridge, and the introduction of one or more new anticlinal waves in the strata extending from this point westward. It is pretty obvious that near Ayer's Store, almost the whole of the broad outcrop of the Primal rocks has been swept from off the gneiss, and only a single monoclinal line of the sandstone left at the base of the hill in contact with the limestone of the valley. From this jog or local change in its course, the Primal belt ranges with remarkable straightness towards 174 NORTH VALLEY HILL. the W.S.W., and with no actual interruption, until in Lancaster County it coalesces with the range bounding the Limestone Valley on the S. It presents, however, several decided fluctua- tions in its breadth, due to changes in the dip, and especially to the introduction of a less or greater number of narrow anticlinal undulations in it. The structure of this zone is pretty well exposed in all the principal gorges through which the tributaries of the Brandywine and the Octorara drain through it in their progress southward. In these natural sections, though the edges of the strata are generally much obscured by fragmentary rubbish and soil, it is easy to detect the presence of usually two, and sometimes even three, closely-folded anticlinal plications, the dip being generally at a high angle to the S.E. From the changes which arise in these flexures, the breadth of the whole belt varies from a quarter of a mile in some places to at least three-quarters in others. In sundry cases we may detect sharp saddles, or anticlinal uplifts of the subjacent gneiss rocks, subdividing the whole belt, at least at the level of the beds of these transverse valleys, into a succession of parallel, closely-folded, synclinal troughs. In some instances the lower strata of the Primal series, thus brought up on the back of the gneiss, is so crystalline and gneissoid from metamorphic action, especially where it is contiguous to dykes of intrusive granite, that to determine always the boundary which separates the two sets of rocks is by no means easy. For several miles E. of the East Branch of the Brandywine, there seems to be but an insignifi- cant thickness of Primal talcose slate associated with the white Primal sandstone ; but approaching the West Branch of that stream, or the vicinity of Coatesville, both the upper and lower Primal slates appear in the series in rapidly and steadily augmenting force. There is no feature connected with the Primal rocks of this district of Pennsylvania so remarkable as their appear- ance and disappearance within the narrow limits of a few miles. This fluctuation is perhaps most conspicuously exhibited in the striking contrast presented in the composition of the North and the South Valley Hills between Valley Forge and Downingtown, in which district it has been already shown that there is on the South side of the limestone even a total absence of the white Primal sandstone, or a bed of it so thin as generally to escape detection ; while on the North side of the valley the formation is developed under a thickness of at least 50 feet at Diamond Rock and elsewhere. Again, to the S. of the basin there appears to be a vast expansion of the lower Primal slates in their metamorphosed condition of talco-micaceous slates ; but to the N. of this great trough, at a distance no greater than two or three miles, there is a great deficiency of this schistose group. (See Fig. 25, Section through Coatesville to mouth of Buck Run, at the end of this Chapter.) It would seem that both the sandstone and the argillaceous or slaty members of the series had in this part of their original area been thrown down in irregular patches, and in beds of quite inconstant thickness. When we reach the West Branch of the Brandywine, and examine the constitution of the Primal series there, or study it in sections still further W., we are struck with a marked difference of type compared with that which it possesses at or E. of Downingtown. Near the latter place, at the pass of the Brandywine, through the North Valley Hill, the Primal slate is almost wanting ; and the white sandstone, folded in several successive waves, seems at first, until these are recognised, and their influence estimated in multiplying the thickness of the belt, to be a formation of enormous depth, whereas it nowhere in reality surpasses 100 feet. The first outcrop of the rock, or that which bounds the valley, presents the sandstone in its usual indurated or slightly vitreous condition, and in this characteristic state it DIAMOND ROCK. 175 contains in the thin partings separating its remarkably parallel layers, delicate coatings of pure white talc ; while imbedded in the surfaces of the sandstone are numerous very small needle- shaped crystals of black schorl, always more or less broken, as if from a difference in the law of shrinkage, or cooling of the rock and the mineral. The other outcrops or folds of the stratum which lie further N., and nearer to the border of the gneiss, and which are more injected with igneous granite, show a still more advanced stage of metamorphism. There the rock consists of an excess of granular quartz, involving specks of crystalline felspar, the presence of which, and of the included talc, renders it sometimes difficult to distinguish the altered stratum from some fine-grained white granites. The schorl is, however, a sure guide to the recognition of the sand- stone, however altered. Fio. 21. Section, Diamond Rock to Paoli, looking N.E. .X' An inspection of the Sections across the Chester County Valley and its north and south bounding hills, one extending from Phrenixville to the Paoli, another along the East Branch of Brandywine through Downingtown, and the third through Coatesville by the West Branch, will serve to show the relative development of the different members of the Primal series in these different districts, and by comparison, exhibit those remarkable fluctuations in their dimensions to which we have alluded. This comparison will show that, while in the two Eastern sections very little Primal talc-slate occurs on the North side of the valley, the series embraces at Coatesville an enormous preponderance of the slates over the white sandstone, the upper Primal slate having a thickness of at least 700 feet, while the chief bed of the white sandstone measures no more than 30 or 35 feet. (See Sections.) Fio. 22. Section North of Coatesville, lookingN.E. Following the formation westward along the same outcrop N. of the valley, we find it well exposed near Parkesburg, at the passage of Buck Eun through the ridge. Here the belt appears to contain three outcrops, in a denuded, anticlinal, and synclinal flexure, its whole width from FIQ. 23. Section, Hill North of Parkesburg, looking N.E. i the limestone to the gneiss being a. little less than one-third of a mile. In the vicinity of Parkesburg the strata, in descending order, are as follows : 176 PRIMAL BOOKS, MINE RIDGE. 1. The upper or newer Primal slates, possessing a total thickness of about 700 feet, are subdivided by an inter- calated thin bed of yellow sandstone, situated here very near the middle of the group, which may be regarded as the upper Primal sandstone of Coatesville and Chiques Eidge. Above this upper sandstone there are 300 feet of thinly- laminated micaceous slaty strata internally, olive brown externally, very brown and ferruginous. These contain in their lower part thin layers of white sandstone. The yellow sandstone is itself about 200 feet thick, and between it and the micaceous slate occurs an alternation of thin and slaty layers of sandstone with the ordinary Primal slate. Underneath the yellow sandstone there succeeds another group of laminated slaty strata, some 350 feet in thickness, resting upon the upper beds of the main deposit of white Primal sandstone. 2. The middle or white Primal sandstone member of the series is in this neighbourhood about 50 feet thick. In its southern or first outcrop, north of Parkesburg, it is quarried in one or two places, and being very evenly and thinly bedded, it affords large slabs, well adapted for building and for flagging. On the surface of some of these we discern the characteristic broken crystals of black schorl in more than usual size and abundance. 3. The lower member of the Primal series, a thick group of brown silicious slates, more or less talcose and micaceous, is generally too much obscured at its outcrop by a covering of fragmentary matter, derived from the sand- stone crest of the ridge, and from the adjoining gneiss, to enable us accurately to estimate its thickness ; but this cannot be less than 300 or 400 feet. These strata, especially the upper and the middle groups, are well exposed on the Strasburg Turnpike, immediately north-west of Parkesburg ; and the middle member, or the white sandstone, conspicuously so in the gorge of Buck Run, one mile east of the village. Under about the same type, the Primal rocks range forward to the Westward into Lancaster County, and we meet them in approximately the same relative development in their next out- crops to the N., namely, in the Mine Ridge at its Eastern spurs. This narrow regular belt of the Primal strata in the North Valley Ridge keeps its course insulated between the Auroral limestone on its S., and the gneiss on its K, the whole way to the Westernmost Branch of the Octorara Creek ill Bart Township, where, by the cessation of the gneiss, it coalesces with another and broader belt of Primal rocks, that of the Mine Ridge. To the description of this belt we next proceed. Fossils. The only fossil known to exist in the Primal rocks in Pennsylvania, the Scolithus linearis, is to be met with abundantly in the Primal white sandstone in the line of outcrop we have been tracing, especially in that portion of it which is embraced between Downingtown and Valley Forge. At the foot of the ridge, for a mile east of Ayer's store, specimens of this simple cylindrical form, arranged perpendicularly to the bedding of the sandstone, are numerous by the roadside. MIDDLE BELT OF PRIMAL EOCKS NORTH OF THE LIMESTONE VALLEY, OR THAT OF MINE RIDGE AND ITS SPURS. Between the synclinal trough of Auroral limestone terminating westward in Drumore, or the same basin prolonged through the Primal rocks to the Susquehanna, near M e Call's Ferry as a Southern limit, and the South edge of the limestone of the Pecquea and Conestoga Valley, there spreads a broad undulated tract of the Primal rocks, embracing a number of short, narrow, insulated basins of Auroral limestone, divided from each other by anticlinal waves, which elevate the lower Primal slates to the surface, but nowhere bring to view the subjacent gneiss rocks. In this district the more prominent stony ridges consist of the Primal white sandstone, but by far the largest extent of the surface eastward of Big Beaver Creek, a tributary of the Pecquea, belongs to the Primal slates. There we may recognise a series of little limestone basins. This MINE EIDGE. 177 general anticlinal zone rapidly contracts as it extends Eastward between the range of gneiss, which now bounds it on the S. and the limestone of the Pecquea basin on its N. It there begins to take the name of the Mine Ridge, and under this title extends until it is opposite the Eastern end of the Pecquea Basin. The narrowest and lowest part of this ridge is at the notch called the " Gap," through which the Columbia Railroad passes, and where its summit is not quite 500 feet above the level of the ocean. The width of the ridge, or rather of the belt of Primal rocks, in this vicinity, does not much exceed half a mile. There, and to the Westward for some distance, the structure of the Mine Ridge is very simple ; it is composed of the three members of the Primal series already described, the white sandstone being in considerable relative force, and the whole undulated into one synclinal with one anticlinal wave ; or, in other words, into three moderately gentle dips. That margin which reposes against the gneiss, dips rather steeply from it, or Northward ; but this dip is succeeded near the gap, or central crest of the ridge, by an anticlinal flexure making a South dip and a second North one, the beds affected b ythe latter descending beneath the limestone at the foot of the" hill. Advancing Westward, the only difference in the structure of this elevated zone of the Primal rocks is, that additional anticlinal flexures introduce themselves from the Westward into the belt, until in the longitude of Big Beaver Creek we may count at least six of these waves. In the opposite direction, or Eastward from the " Gap," the structure of the Mine Ridge becomes complicated in a different manner by the appearance of a succession of anticlinal spurs N. of the main crest. If we trace this out to its Eastern termination, we shall find it ending W. of the West Branch of Brandywine in a long trough or synclinal point, and N. of this we may notice a long narrow anticlinal belt of the Gneiss rocks coming in from the E. to divide this spur of the Mine Ridge from another basin of Primal strata lying yet further N. in the centre of West Cain Township. Nearly W. of this uplift of the Gneiss rises an anticlinal spur of the Primal sandstone, N. of the true Mine Ridge, and projecting forward into the South-eastern corner of the limestone basin of the Pecquea, enclosing a little synclinal cove of that limestone between it and the main ridge. Still advancing Northward to the North boundary of Cain and West Brandywine townships, we reach another and much longer synclinal belt, prolonged from the Mine Ridge, but quite out of line with it. This is divided in part, or towards the E., by a narrow strip of uplifted and denuded Gneiss, penetrating across the West Branch of Brandy- wine, some three miles, to within a couple of miles of the limestone in the neighbourhood of Compassville. It is probable that the anticlinal wave which uplifts this second belt of Gneiss is the same with that which arches into a ridge or spur of the Primal rocks a little N. of the above-named village. In any case, it is obvious, from the structure and topography of the district, that the two or three successive spurs which protrude themselves Westward into the Limestone Valley, to enclose as many lesser valleys or synclinal coves of the Auroral strata, are the results of the gradual declension in that direction of so many undulations that further East- ward are in sufficient force or elevation to lift out the Gneiss. The most Northern of the three synclinal ranges, into which that of the Mine Hill may be said to expand itself in its progress Eastward, terminates in a low point W. of the North Branch of the Brandywine, near Springtown Methodist Church. Traced thence Westward by the Manor Presbyterian Church, it extends in a widening belt, and, crossing the West Branch of the Brandy- wine, becomes the broad and but little cultivated belt known as the Barren Ridge, the crest line VOL. i. z 178 PRIMAL ROCKS NORTH OF CHESTER VALLEY. of which follows nearly the boundary between West Cain and Honeybrook townships. The Northern edge of this belt is defined by the Southern margin of the Gneiss from Indian Run Valley to the Pecquea. Between the Western end of this belt, which may be viewed as terminating near the line which separates Chester and Lancaster counties, and the South-western end of Welsh Mountain, there extends, nearly in its line of prolongation, a narrower outcrop of the Primal rocks intervening between the Gneiss on the W. and N., and the limestone of the Pecquea basin. It is probable, however, that this strip of the sandstone along the margin of the valley is not every- where discernible, for the district presents indications of a succession of faults, extending West- ward from the Gneiss into the limestone, and bringing these two formations into contact by engulfing and hiding from view the interposed Primal series. NORTHERN BELT OF PRIMAL ROCKS NORTH OF THE CHESTER COUNTY VALLEY, WELSH MOUNTAIN, &c. The third and last principal belt of the Primal strata N. of the Limestone Basin of Chester County, is that of the Welsh Mountain and its Spurs. It commences about four miles E. of Morgantown, where the Mesozoic red sandstone overlaps the end of the ridge, and extends in a direction a little S. of W. to a point about two miles south of the village of New Holland. In this belt the white sandstone is not as firmly cemented a rock as it is in the North Valley Hill. Advancing Westward, the ridge assumes a more systematic anticlinal form (see general Section V.), the sandstone dipping in both directions beneath the Matinal limestone ; and as the axis sinks, the upper slates, which are of a dark-brown colour, occupy the surface, and hide the sandstone. Where the axis is high, as near the Sorrel Horse Inn, two and a half miles from Churchtown, the sandstone formation exhibits marks of much more igneous action than in other parts of the range. It is partially vitrified, very compact, and traversed by innumerable planes of cleavage, with imperfect crystallisation. This is not the result of contact with any igneous rocks, for the nearest trap-dyke is distant more than half a mile, and has produced but little alteration in the limestone in its immediate neighbourhood. In this belt we meet with all the three divisions of the Primal series which characterise it in the North Valley Hill, and in Chiques Eidge at the Susquehanna ; but the Primal white sand- stone member appears to be in yet greater force than in any of the outcrops situated to the S.E. The general structure of the main Welsh Mountain seems to be very analogous to that of the Mine Eidge near the " Gap." In other words, it consists of an anticlinal and a synclinal wave, and, towards its Western end, appears to be still further complicated by the rising of another shorter anticlinal, entering it from the Gneissic district to the E., to form its Westward spur. The upper or newer Primal slates, reposing upon the white sandstone, are in some places excessively ferruginous at their uppermost limit, where they alternate with the lower beds of the Auroral magnesian limestone, so that large accumulations of iron ore may be looked for at the North base of this ridge, where the limestone of the Morgantown or Conestoga Valley is in contact with its strata. It is precisely under these relations, both as respects the geology and the topography, that the large mine called Jones's occurs near the head of that limestone valley, two and a half miles N.E. of Morgantown. I have intimated in another chapter, that there exists a prolongation of this band of Primal BLACK HORSE HILL. 179 rocks, not quite in line with the axis of the Welsh Mountain, but nearly a mile to the N. of it. This belt extends from near Jones's Mine eastward for about three and a half miles to Pine Creek, terminating about one and a half miles N. of the Warwick Iron Mines. Like the Welsh Mountain, it has a stony surface, a sandy and sterile soil, and is covered almost entirely with forest. These two Primal ranges are probably connected by a neck of the same strata between Springfield and Jones's Mines ; but the surface there being low and much obscured by the untilled swampy tracts which form the water-shed between the Conestoga and the South Branch of French Creek, the continuity of the Primal strata cannot be easily made out. The extreme Western point of the Primal strata of the Welsh Mountain is at Mill Creek, near the Old Peters Eoad. The Welsh Mountain is the N.W. boundary of the Gneissic district of Chester County. From its Western spur, the view over the fertile and highly-cultivated plains of the Conestoga is, in the month of June, when the crops are ripening, extremely attractive, for this is one of the most fertile and best-tilled of all the grain-fields of the United States. The charm of the landscape, in which the middle distances abound in all the features of agricultural beauty, is not a little enhanced by the contrast between the fertility of the plain and the wilder- ness-like aspect of the background of forest-covered hills, or mountain-spurs, by which the scene both S. and N. is bounded. INSULATED ANTICLINAL RIDGES OF PRIMAL SANDSTONE. There is a low insulated hill of the Primal rocks a little N. of the Welsh Mountain, and rather more than one mile W. of Churchtown. It is somewhat more than one mile in length. Its structure is anticlinal, and the limestone on both sides dip from it. It marks the position, therefore, of a flexure of some magnitude. Another rather longer tract of very similar form is situated about three miles N. of Lancaster, near Neffsville. This is likewise anticlinal in its structure, is surrounded by the lime- stone, and is the crown of a short axis, of which there are many in the adjacent limestone which do not thus protrude the Primal series. INSULATED BASIN OF SEDIMENTARY STRATA WITHIN THE NORTHERN GNEISSIC AREA OF CHESTER COUNTY. That there should occur in the interior of the Gneissic district of Northern Chester County one or more insulated synclinal belts or troughs of the Palaeozoic strata, ought not to surprise us after what has been already disclosed of the existence of a succession of anticlinal and synclinal undulations in the Western part of the district, and of the series of synclinal dislocated basins in the very heart of the region, containing long lines of iron ore. The most conspicuous detached basin of newer rocks, resting within the Gneiss, is one in the West corner of West Vincent Town- ship. It is a long belt of Primal white sandstone, which here forms a regular ridge elevated above the general rolling plain of the Gneiss rocks, and known in the neighbourhood as the Black Horse Hill. Its length is about two miles, and its breadth is not less than 2000 feet. From the crumbled condition of the sandstone at its outcrops, and the absence of any quarries or good natural exposures, it is impossible to recognise the dip of the strata ; but that these con- stitute a synclinal belt or outlying trough is very obvious. It is worthy of note that this tract 180 PRIMAL ROCKS, NORTH VALLEY HILL of Primal sandstone lies nearly in the range of the long synclinal trough of that rock, forming the hilly belt known as the Barren Ridge west of the North and West Branches of the Brandywine. COMPOSITION AND LIMITS OF THE PRIMAL SERIES OF THE NORTH VALLEY HILL NEAR VALLEY FORGE AND WESTWARD. That section of the North Valley Hill which extends from its Eastern termination E. of Valley Forge to Lancaster County, contains all the three upper formations of the Primal series in full development, though, from metamorphic action, under a greatly-altered aspect. The main central crest of the ridge marks for the most part the outcrop of the sandstone or middle member of the series, while the lower Primal slate occupies the Northern flank, and the upper Primal slate the Southern. These slates have each a thickness of several hundred feet, but the sandstone embraced between is nowhere of great bulk, indeed seldom exhibiting a diameter of a few yards, and nowhere 100 feet. The slates are chiefly silico-argillaceous rocks, as may be easily seen, where they are in their normal condition in the belts further to the N.W. There they are ordinary sandy slates, with included beds of argillaceous sandstone ; but along these more metamorphic Southern ranges bordering the Chester County Valley, their structure and aspect display almost the extremest degrees of metamorphism of which argillaceous strata are susceptible. The visible boundary of the Auroral limestone, as marked by the overlapping edge of the Mesozoic red sandstone, is traceable from Port Kennedy to near the Eastern point of the North Valley Ridge ; but at the foot of Mount Sorrow the slates of the Primal series emerge to view in contact with the margin of the red sandstone, and from this point forward to the W., as far as the point of first appearance of the Gneiss, the border of the Primal slate is defined by the undu- lating boundary of the red rocks namely, over the Northern flank of Mount Sorrow, and across Valley Forge Creek at the Dam. But from the Eastern apex of the belt of gneiss near the Baptist Church, the margin of altered Primal rocks defined from this point onward by that formation, trends off somewhat more South-westward, assuming a higher position on the Northern slope of the main ridge. The precise place of the line of contact of the Primal and Gneissic rocks is not susceptible, in many parts of the ridge, of exact determination ; yet the boundary can be sufficiently well inferred from the external features, the change in the soil, and the surface frag- ments. Guided by these signs, and by occasional outcrops of both formations, we can follow the limit along the Northern slope the whole way to the point in the spur of the ridge where this first breaks down at the passage of the road which leads down its flanks into the valley, and also at Ayer's Store. From the Valley Forge Creek to this gap or depression, the ridge is very straight, even, and continuous, and is everywhere crowned by the outcrop of the hard, altered Primal sandstone, which appears to have been trenched away by a rush of waters through this depression. Here, and at the crossing of the road from Pickering Creek towards the Paoli, it is easy to recognise, on the Southern slope of the ridge, the upper Primal slate in the condition of a talco- chloritic crystalline slate ; but it is more difficult to detect the lower Primal slate of the Northern slope of the hill. This is beautifully exposed at Valley Forge Creek, is cut in the Pennsylvania Mining Company's shaft, and is visible frequently in fragments on the Paoli and the other roads over the ridge ; but it is not generally discernible in place, being extensively covered by the IKON ORES. 181 fragments and the sand of the Primal sandstone of the crest of the ridge, swept over it by retreating waters. The actual constitution of these Primal schists is that of talco-chloritic slates, in which the talco-chloritic and quartz constituents are distinctly segregated, and in many portions thoroughly crystallised. Indeed, so completely are these masses converted to the structure and composition of the talco-chloritic schists of the genuine Gneissic family of rocks, that they have hitherto been invariably referred to that group ; and it is with much difficulty that a geological observer, not intimately acquainted with the phenomena of metamorphism in the rocks of our Atlantic Slope, can persuade himself that these are genuine Palaeozoic masses, or beds of a fossiliferous age, converted by mere igneous agency to the antique aspect they present. But a study of the gradations or alterations assumed by these strata, as they may be traced from the zone of maximum change to the districts of least transformation further N.W., puts the correctness of this conclusion beyond all doubt. The Primal sandstone, as it presents itself along the two lines of outcrop bordering the Chester County Valley, exhibits nearly all the varieties which belong to it where it is thickest and most largely developed elsewhere, whether we compare it with the Potsdam Sandstone of New York, or with the mountain masses flanking the North-western slopes of the Blue Ridge in Virginia and the States further S. Here in Chester County it contains, besides its typical beds of pure white and yellowish white quartzose sandstone, some other members, especially coarse loosely- aggregated sandstones, and fine-grained silicious conglomerates. Notwithstanding the excessive heat to which these rocks have been subjected, they have not been at all fused, nor have their obscure organic relics been obliterated. Indeed, the Primal sandstone of the summit of the North Valley Hill contains in great abundance, even where it has been baked and indurated, the curious stem-like fossil, the Scolithus linearis, so distinctive of this formation. Though con- vinced for many years past, from structural evidence, that this crest rock is the true Primal or Potsdam sandstone, yet my recent discovery (in July 1853) of this organic form, the earliest type of living organism in any American formation, affords a satisfactory confirmation of the soundness of the deduction. FIG. 23 a. Section from North Valley Hill through Coatesville, to mouth of Buck Run on Brandywine. 1 inch =2500/ee. Tofc. 4- Talc. Mica. Slata IRON ORES OF THE PRIMAL STRATA. Jones's Iron Mine in the Southern Corner of JBerks County. This extensive and valuable iron-mine belongs to the Warwick Iron Company. It is near the eastern extremity of that branch of the Conestoga Limestone Basin of Lancaster County, which extends into the southern angle of Berks, under the name of the Morgantown Valley, N. of the Welsh Mountain. The mine is about two and a half miles north-east of Morgan- town. Its geological position is in the upper Primal slates, just at the base of the Auroral magnesian limestone. More correctly, this ore is the upper Primal slate itself, or its highest beds rather, in a very ferruginous condition. In this and several other respects its relations are strictly the same as those of the great iron-ore deposit of the Cornwall Mines in Lebanon County. 182 IRON ORES OF THE PRIMAL STRATA. The chief mine is an open excavation, covering rather more than five acres ; and there is another to the south of it occupying about one acre. Magnesian limestone bounds the ore on the northern edge of the principal excavation. Here there is a mine-shaft 1 80 feet deep, with a competent steam-engine. The shaft enters the limestone at a depth of 50 feet from the surface, and a boring, descending 20 feet from the bottom of the shaft, is still in this rock. A dyke of trap-rock cuts the ore-bearing strata near the southern side of the pit, and produces phenomena pre- cisely identical with those caused by the trap-dykes in the Cornwall Lebanon Mines, converting the ore to a more highly crystalline form, and endowing it partially with magnetism. As in every such instance, the ore is richest and purest adjacent to the trap-dyke. This is equally the case in the southern or smaller mine. The strata dip to N. 30 W. at about 20 ; and in the northern bank of the large mine, we may perceive the Auroral limestone regularly overlying the upper beds of the Primal slate, containing or consisting of the ore. This mine has been wrought with more or less activity for the past seventy years. Its product in 1853 was about 7000 tons, and this is stated to represent the average yield for the last twenty years, while for the previous fifty years the annual amount furnished is given at about half as much. In this mine, as in that of Cornwall in Lebanon, some of the ore contains a small amount of copper, in the form chiefly of sulphuret, carbonate, and silicate of copper. To extract this copper ore has been a favourite thought with some metallurgists for several years past, and about five years ago, an elaborate and expensive experiment was under- taken with this object by the American Mining Company of New York. They erected at the mines machinery for crashing and grinding the ore, and a costly apparatus, consisting of cylinders bearing a multitude of magnets and brushes for withdrawing the pulverised magnetic oxide of iron from the copper ore, and other constituents. This enterprise has proved to be unprofitable, partly from the difficulty of effecting a thorough separation, partly from the want of a sufficient abundance of the essential element, the copper ore. Including the cupreous iron-ore mined within the four years of this undertaking, the whole annual product was not less than 10,000 tons. Iron Ore Bank of Cfwstnut Hill, near Columbia. This large mine is situated about three and a half miles north- Flo. 24. Chestnut Hill Ore Bank, 3 miles N.E. of Columbia, Lancaster County. 1 inch = 500 feet. east of Columbia, in a high trough-like valley or basin on the slope of Chestnut Hill, a spur of Chiques Kidge. The structure of the valley is apparently synclinal, the dips gentle, and in the central portions nearly flat. The ore lies in the lowest layers of the Primal newer slates, the very same formation which contains the ore in the Cornwall, Jones's, and Safe-Harbour mines. As the mine is now developed, it is perhaps the clearest illustration the region affords of the geological relations of the Primal ore. It is worked by benching or open quarrying, the whole material enclosing the ore being in many parts cut down perpendicularly in steep banks. The depth in the centre of the big mine, from the soil to the bottom rock supporting the ore, is about 100 feet, and ore of greater or less richness prevails throughout this entire thickness. The present excavation (1856) covers nearly the whole of the tract of ground belonging to this one estate namely, about eleven acres ; but undoubtedly this is not the full extent of the ore-bearing ground. Indeed, the existence of a rich large mine, owned by the Messrs Grubb, almost half a mile to the eastward, shows that the ferruginous deposit has a wide range. The ore-embracing stratum has been dug through to the supporting rock in several places. In each such instance the floor is the upper surface of the Primal white sandstone. In some places the first layers of this rock are a pale yellowish sandy slate ; but, penetrating a little farther, the hard white sandstone invariably appears. It would seem, therefore, that the ore all lies within the first 80 or 100 feet of the newer or upper Primal slate. This slate, throughout the upper 40 or 60 feet or more the thickness varying with the amount of the formation is now in a thoroughly disintegrated condition, being in the condition for the most part of a bluish, yellowish, and white laminated unctuous clay; but it still retains, more or less distinctly, the stratification or intimate foliation of the original slate. Though CHESTNUT HILL. 183 approximately horizontal, the layers display a wavy bedding, the result seemingly of an undulation of the strata primarily impressed, and not a consequence of any washing in of ore or clay deposits. Beneath this rather regularly bedded ore-containing slate, there lies throughout a large part of the mine an irregu- lar deposit or bed of rich solid concretionary ore, extending under a variable thickness of 10, 20, and 30 feet, down to the top of the Primal sandstone. (See Fig. 24 a.) It is evident that this ore, which is a brown cellular fibrous haematite or limonite, has been derived from the filtra- tion of the oxide of iron, from out the ferruginous slates above, which show in their condition of meagre clays, that they have been thus completely leached by water. The surface of the Primal sandstone is even now a water-bearing plain, for it is only here that water is met in sufficient quantities for domestic use, in and near the mine. Consoli- dated layers of the brown ore are also seen overlying certain of the more impervious layers of the clay-slate, as if this also at one time arrested the descent of the ferruginous particles. Possibly a part of the undulation of the strata may be due to the upward bulging action of the ore, as this was accumulating and concreting from above, such as we know took place in the gypseous strata of Western New York from the collection of great cakes of plaster on an impervious floor of shale. An interesting inquiry is here suggested as to what can have been the geological atmospheric condition which pro- duced the remarkable percolation which carried down so large an amount of ore out of these ferruginous beds. Was it tepid rain, charged with carbonic acid, in an early Palaeozoic period 1 or could it have been a long filtration of surface waters, such as now soak the earth ? or are we to surmise an action of internal steam issuing upward through crevices in the strata, in a period of crust-movement and disturbance 1 ! I am inclined to the first conjecture. It is worthy of note, that only in one spot in the mine do we meet with a crystalline magnetic ore. In the old or large mine there is a band of this ore, three or four inches thick, containing small but beautiful octahedral crystals ; everywhere else the ore is the common brown peroxide of iron. From this fact it would appear that this Chestnut Hill deposit was invaded by a less energetic metamorphic action than that which attacked the Cornwall and Jones- town strata, where the crystalline and magnetic condition, due to heat, is the prevailing state, and not the exception. At what stage or period did this metamorphism of the ore take place ? Was the oxide of iron of the Cornwall and the Jones's Mine primarily deposited as a part of the slate, and crystallised at the time of the metamorphism of all the Palaeozoic rocks ? or did the ore originate from out of the ferruginous slate by a process of percolation, bringing together its particles, previously intimately diffused there, the heating, altering action arising afterwards ? I am dis- posed to think that the ore was collected from the substance of the rock, and then metamorphosed. But this is at the present a somewhat obscure inquiry. Probably the Palaeozoic masses underwent more than one action of upheaval, undulation, denudation, and metamorphism ; one perhaps at the end of the Matinal age, and a final one at the close of the Coal period. Fio. 24 a. Section of Iron Ore at the base of the Primal Slate, Chestnut Hill Mine. CHAPTER III. PRIMAL STRATA ON THE SUSQUEHANNA AND IN YORK COUNTY. THE Primal rocks occupying the Southern townships of Lancaster County, and the whole South-eastern angle of York County, are admirably exposed for geological study in the deep and cliff-lined valley of the Susquehanna, from Marietta to the Tidewater at Havre-de-Grace. I pro- pose, therefore, to illustrate this portion of the Southern zone by a detailed description of these strata, as they are displayed along the West bank of the river, where the fine natural section has been aided by numerous cuttings for the Tidewater Canal, appealing to the elaborately con- structed profile of the rocks for future elucidation of the structure and features of the region. One such carefully-compiled continuous section furnishes a better conception of the geological composition of the district, than any multitude of unconnected notes drawn from detached localities. This has been surveyed and drawn up with care, and will therefore supersede the necessity of much detailed description of the surface phenomena of the Slate country E. and W. of the river, where, in truth, there is extremely little variety in either its geology or mineralogy. DESCRIPTION OF THE SUSQUEHANNA SECTION. The Susquehanna River, throughout its entire length from Marietta to where its waters merge into those of the Chesapeake Bay at Havre-de-Grace, occupies a deep broad valley, varying in width from a few hundred feet to more than a mile. On either shore it is for the most part bounded by rocky bluffs supporting table-lands, at an elevation of from 1 00 to 500 feet above its waters. These bluffs exhibit a grand natural section of the whole group of the Primal series, constituting the base of our Palaeozoic system. Leaving the Auroral Limestone Valley of York and Wrightsville at Creitz Creek and proceeding South- ward, we pass a belt of hills about two miles in width, which elevate Primal rocks high above the river-level. They indicate the presence of at least two folded anticlinals, which, coming in from the South-west corner of York County, cross the Susquehanna below Columbia, and droop away at the West Branch of the Little Cone- stoga Creek, where the limestone laps around the base of the hills. In a little cove between these two anticlinals exists a narrow trough of impure limestone, seen on both banks of the river. In the hill N. of this cove, there is no appearance of Primal sandstone, the strata consisting exclusively of the Primal upper slates. Under conditions of partial metamorphism, they present themselves as dark-blue silicious slates, with the cleavage surfaces glazed, and in some places speckled with crystals of sulphuret of iron. The wider belt of Primal strata below the cove, like the former, is chiefly slate. There are two bands of Primal white sandstone, neither of which exceeds one hundred feet in thickness. If our construction of dips is correct, they form the two limbs of the folded anticlinal. It should be observed that the planes of true bedding are very obscure, being almost entirely obliterated by the cleavage, which intersects the rocks by an infinite number of parallel planes. The planes of cleavage are nearly or quite parallel in strike with the planes of bedding, though they dip at a high angle, ranging from 70 to 90 S., 15-20E. This wide anticlinal belt of slate stretches southward in an almost straight course, with a slight increase in its breadth, entirely across York County, into the extreme South-east corner of Adams County, and thence into Maiy- PRIMAL ROCKS, SUSQUEHANNA RIVER. 185 land. It is bounded N.W., throughout its whole length, by the York and Hanover Limestone Valley, or that of the main Codorus and Creitz Creeks, and S.E. by the narrow limestone trough of Cabin Branch Run, and the other shorter limestone basin of Jefferson. The structure of this belt is that of a broad flattened anticlinal arch, with one or even more synclinal depressions in its middle. Only in a few localities does it expose Primal white sandstone. A somewhat promising locality of roofing-slate occurs in this ridge about two miles south of the York and Wrightsville Railroad. One mile south of Hanover, we meet the line of contact between the limestone and slate ranging N.E. and S.W., and, passing half a mile south of Littletown, bringing the margin of the slate to the Maryland line near Arnold's Mill. The limestone belt of the York Valley, lying on the N.W. of the slate, terminates near this spot in a wedge-shaped point, by the folding round of the overlapping middle secondary red sand- stone, which, after concealing the limestone, encroaches upon the slate. From the belt just described, which has its southern limit on the west bank of the river at Cline's Run, and on the east bank at Charlestown, we enter upon a limestone valley about two and a half miles broad. This somewhat corrugated basin constitutes the south-western prong or branch of the great Conestoga limestone. It tapers westward in a very slender folded belt, terminating in a point at the Eastern Branch of Codorus Creek; but it is extremely narrow only three miles west of the river, at the old Margaretta Furnace. It is quarried in two or three places near Cabin Branch Run. It contains a rather interesting stratum of somewhat coarse, calcareous conglomerate, consisting of lumps of grey limestone, imbedded in a dark slaty cement. This band is about one hundred feet thick, and occurs about a mile and a half above Beig's Mills. The furnace was supplied with ore from the northern margin of the slaty limestone at its junction with the Primal slate. At the river the limestone exhibits a high degree of metamorphism ; it is silicious and magnesian, imbedding thin layers of talc-slate and segregated quartz. The flexures, so far as they can be clearly made out, are gentle. The cleavage dips uniformly Southward at a high angle. The synclinal trough of altered Primal slates, embracing this fold of the limestone, somewhat expands to the S.W. and near the South Branch of the Codorus, or about a quarter of a mile west of the York and Baltimore Railroad ; and ten miles nearly south of York, admits another narrow trough of limestone. This rock is quarried on the farm of Mr Daniel Diehl. South-westward from Diehl's, towards Jefferson, it is excavated at several other localities, and converted into linie for the fields. At Christian Knull's, east of Jefferson, we meet with indications of iron-ore in it. We now enter upon that extensive area of barren rocks which first appears a little west of the Schuylkill, forms the southern boundary of the Chester Valley, and covers the southern portion of Lancaster and York counties. These rocks we are forced, after close study, to regard as constituting the base of the Primal system, though so altered as to have been hitherto mistaken for true Hypozoic metamorphic rocks of the Gneissic group. The reasons for this conclusion will be given elsewhere. They sustain the high table-lands through which the river flows, and constitute the rocky bed of the stream, above which the harder masses project, forming multi- tudes of little islands. Descending the river, the boundary shores approach each other, and their dark, wood- covered and rocky sides give to the scenery a wild and picturesque character. The precise line of contact of the limestone with the talcose slates is not clearly visible on the west side of the river ; indeed, there seems to be no line of sudden transition. The lower bands of the limestone, naturally more slaty than the higher strata, have themselves undergone so much metamorphism as to be scarcely dis- tinguishable from the Primal slates. For convenience in description, we shall first consider the belt of rocks included between the limestone on the N., and the mouth of the Conestoga on the S. The first and most notable fact is the great apparent unifor- mity in the direction of the dip, which throughout this entire distance is towards the N.W., varying from 15 to 45 W. of N. On the east side of the river the high table-land of Turkey Hill, formed of the rocks now under consideration, sends forth several spurs or fingers towards the East, all of which droop away only a few miles from the river, VOL. I. 2 A 186 PRIMAL ROCKS, SUSQUEHANNA RIVER. permitting the limestone to take its place at their extremities. These fingers are evidently of anticlinal structure. From examination of the Section, it will be seen that several close folds may be constructed from the dips in this belt. It is interesting to observe that the axis planes of these folds all dip towards the N. W. ; in other words, in a direction opposite to that which the Appalachian system of flexures usually observes. The cleavage throughout this belt is very distinctly denned. From the limestone to Green Branch Run, two miles below, it fluctuates from one side of the perpendicular to the other, but not more than 10 either way. Its strike is S. 50 60 W. The strike of the cleavage thus changes to S. 75 W. ; but approaching Lockport the planes of bedding become more conspicuous than those of cleavage, and in the flatter dips the scales of mica predominate in the bedding. The cleavage thus becomes less and less obvious, and at Lockport has entirely disappeared as a distinctive phenomenon. Starting from the lower limit of the synclinal valley of Cabin Branch Run, which, on the eastern side of the river, is nearly coincident with the south bank of Wistler's Run, and examining the composition of the strata of the slate belt forming Turkey Hill and its extension westward, we may define the whole tract, as far as Lockport, to consist of the Primal slates under the condition of Micaceous, Talco-micaceous, and Gneissoid Schists of a pre- vailing greenish-grey hue. Throughout this space the north-westward dip exhibits no change to the S.W., but only varies its inclination, sometimes fluctuating suddenly as if from a close fold in the strata, but display- ing on the whole a progressive declension in its angle from an average of 75 or 80 on the northern side of the belt, to 30 as we approach Lockport. On the cleavage planes, which for the most part, as already stated, are very steep, we see in some places numer- ous small lenticular plates of segregated quartz. These obey the general law of parallelism to the cleavage structure, and not to the original bedding, and they afford an instance of that mode of molecular crystallisation of the elements of the rocks which, carried further, has produced, I conceive, the foliation or grain in all mica- slates, gneiss, and other completely metamorphic rocks. Pursuing the line of section southward, down the west bank of the river, it will be seen that, passing Lockport, the mica-slates grow more gneissoid, or become more coarsely crystalline, with a more distinct development of their constituent minerals, and this semi-gneissic character prevails as far as Shenck's Feny. In some portions of the mass, the foliee of the mica-slate enclose plates of segregated quartz. The same dip which prevails above . Lockport, continues to within a few hundred feet of Shenck's Ferry, the angle varying from 45 20, the direction N.W. Near the Ferry commences a series of low undulations, to be specified presently. As already intimated, the true cleavage structure disappears a little above Lockport, and therefore no portion of the belt now under review displays this phenomenon ; nor indeed do we meet with it, unless once or twice very locally, anywhere to the S. of this neighbourhood within the broad metamorphic zone crossed by one section. This disappearance of slaty cleavage, and acquisition of a more highly crystalline structure in the rocks, is in strict accordance with that view of the origin of both, which ascribes them to a crystallising polarity among the mineral particles excited by a high subterranean heat, the difference between the slaty structure and crystalline foliation being merely the result of a difference in degree of the rearranging force among the mineral particles. A little more than half a mile below the dam near Lockport, there is a slender dyke of trap-rock visible, both in the canal bank and the river. It seems to dip steeply southward, intersecting the dip of the slates. This trappean dyke is very probably but a prolongation of the long curving injection of trap-rock which ranges from N. of the Conestoga, S.W. of Millersburg, and intersects the hills and valleys east of Safe Harbour, meeting the east bank of the river about a mile above Shenck's Ferry. Passing now to the belt of country embraced between the vicinity of Shenck's Feriy and that of M c Call's Ferry, we find ourselves still in the same group of talco-micaceous schists occasionally gneissoid, which have been already passed over from above Lockport. Indeed, there is but little essential variation either as to aspect or composition in the strata throughout the whole wide tract passed over by the Susquehanna from the lime- stone valley of Cabin Branch Run to the slate belt of Peach Bottom or Slate Point, the chief change being to a more gneissic character between Lockport and Shenck's Ferry. M C CALL'S FERRY. 187 The special belt before us, or that from the Ferry to M c CaH's, differs from the remainder of the region in containing several distinctly-marked broad undulations of the strata. There are, indeed, three anticlinal waves, all of which cross the Susquehanna towards the S.W. They are wide and flat, or show only gentle dips, the inclination on both flanks being nearly equal. The first of these flexures is visible in the hill just north of Shenck's Ferry ; its dips are about 20, the northern towards the N.W., the southern towards the S.W., showing that the wave itself is rapidly expiring westward. The next is a rather bolder, wider arch, occupying the whole breadth of the hill just south of the valley at the mouth of which the Feny is situated. In this instance, likewise, both the N. and S. dips are deflected from westward, and at the very axis or summit of the wave the dip is nearly westward at an inclination of about 15, that of the two slopes being about 20. The valley of Shenck's Ferry is simply the synclinal trough formed by these two anticlinals. Some of the layers of talc-slate in the most southern of these anticlinals contain garnets. The third, or most southern, is a gentle broad wave occupying the hill, terminating on the river at Duncan's Point. In it, the dips on both flanks of the arch are also nearly equal, not exceeding 15. The whole anti- clinal, like the other two, sinks towards the West. The middle of the synclinal wave embraced between the last-named anticlinal of Duncan's Point, and that below Shenck's Ferry, is situated about two-thirds of a mile south of Otter Creek. Its S. dip is about 15, its N. about 20. In the south bank of Otter Creek, one hundred yards from the river, is situated York Furnace, near to which there exists a band of limestone, not more than two feet thick, enclosed between talc-slate. It is impure, and not suitable for a flux for the smelting of iron-ores, though the more compact portions might make a lime fit for agriculture should the bed be discovered thick enough to admit of being profitably quarried. It appears to be merely a calcareous layer in the talcose Primal slate, and not a fold of the Auroral limestone. Octahedral Iron occurs as a constituent of the talco-micaceous slates, in more or less development through- out the whole district, from Turkey Hill to Peach Bottom ; but it seems to be more than usually abundant between the vicinity of Safe Harbour and Shenck's Ferry. It occurs abundantly in minute but beautiful crystals near Cooper's Point, below Peach Bottom, not far from the State line. Purple Sulphuret of Copper, with a little blue and green carbonate of copper, enclosed in irregular veins of white quartz, were met with in excavating the canal at one of the deep cuts near Duncan's Point. These indi- cations of copper ore were, however, very faint, and there was nothing to imply the existence, either at this or any other locality along the river, of a possibly profitable lode of copper ore. Continuing our survey down the river, we pass over, between M c CalTs Ferry and Muddy Creek, very nearly the same class of micaceous schistose rocks already traversed higher up, the chief difference being that they are somewhat more gneissoid and abound less in octahedral iron. Throughout this belt there prevails but one general southerly direction in the dip. This is at all angles, from 20 near M c CaH's Ferry, to 50 in the vicinity of Muddy Creek, and is towards all points between S. 20 E., and S. 20 W., the former prevailing. This southerly dip continues, in fact, with one or two local interruptions, the whole way across the Slaty district, from the anticlinal at Duncan's Point to the zone of true ancient massive gneissic rocks and granite dykes south of the State line. There can be little doubt, however, that this is not a genuine monoclinal belt of strata, but one containing many closely-compressed inclined foldings, the axis planes of which, if detected, would be found to dip at low angles southward ; for it is inconceivable that the strata here seen to dip so uniformly, should be of the enormous thickness implied by the supposition that they contain no flexures or repetitions of their outcrops. From the above-mentioned last visible anticlinal, to the first genuine plutonic or eruptive rocks, is a distance of at least eleven miles perpendicularly across the strike ; while the average dip is as steep as 45 or 50. The data imply a thickness of seven and a half or eight miles. The supposition of so huge a depth of regularly sequent deposits, is incompatible with the well-ascertained comparative thinness of the whole formation on the Brandywine, and more remarkably still on the Schuylkill. But the existence of actual flexures, folded ones apparently, does not rest on inference ; it is established by observation, as the portion of our Susquehanna section below Muddy Creek will clearly show. That such compressed folds do thus repeat the same strata many times over at the surface, is plainly indicated by a feature 188 PRIMAL ROCKS, SUSQUEHANNA RIVER. of the tract, well exhibited on the Map ; I mean the running forward towards the N.E. of ridges and tongues of the slate, like that N. of Cabin Branch and Turkey Hill, into the limestone tract of Lancaster County, N. of its general southern boundary. These projecting tongues are but the terminations of the anticlinals which have thus lifted and spread out the slates below the limestone. When we follow this belt of metamorphic slates south-westward, through Maryland and into Virginia, this progressive expansion at the surface^ and from the cause here presented, becomes still more conspicuous. Returning to the special belt we have been describing, it will be seen by the section to exhibit much slaty cleavage or an abundance of foliation-planes. These fissures, seldom coincident with the planes of bedding, but for the most part steeper, dip like the bedding towards the S. Their prevailing inclination from M c Call's to Muddy Creek, where the average inclination of the bedding is low, is as steep as 45. From Muddy Creek southward, it is seen to become much steeper, until, in the vicinity of Slate Point, it mounts to 80 or 85. Below Hough's Run, S. of Slate Point, it ceases to be conspicuous. This prevailing southward dip of the cleavage-planes, coinciding as it does with the very general southward inclination of the strata, is certainly a striking confirmation of the law, several times already enunciated, of the parallelism of cleavage-structure with the planes of plication. To one convinced, as the author is, of the generality of this law, where the zone of cleavage-structure is a broad one, the phenomenon is of itself a satisfactory indication of the existence of a system of inclined foldings, even where the metamorphism has completely obscured these. The law here enunciated of the relation of cleavage to plication of strata, is not merely one of scientific interest, it is of great practical importance, as every person may perceive who reflects that in districts really much convulsed, but which exhibit superficially but one direction of the dip, the miner or mineral explorer who might be deluded into costly outlays from the seeming uniformity and assumed depth of his mineral bed, will take warning at the indications which the cleavage may give him of shallow foldings and perplexing repetitions of the seams he may be pursuing. From Muddy Creek to the vicinity of Peach Bottom, the river intersects the same talco-micaceous schists seen above, but growing finer grained as we approach Peach Bottom. In this space there appears to be an anti- clinal flexure, the axis of which crosses the river a few hundred feet above the canal lock. Slate-belt of Peach Bottom. The next subordinate belt which the section crosses, is the slate range of Peach Bottom and Slate Point. The rock here is a dark-blue indurated clay-slate, much of which has the structure of roofing-slate, extensive quarries of which have long been successfully wrought at the Peach Bottom Cliifs on the eastern side of the river, and also at numerous points west of the river, in York County, and in Maryland. The workable slate-belt here is about half a mile wide. The slaty cleavage and the bedding appear throughout to be nearly coincident in their dip, which at the quarries is nearly perpendicular a little southward. The quality of the Peach Bottom slates is very good, and their exportation is slowly augmenting. The belt runs north-east- ward through Slate Hill from the river, a distance of about two miles, and south-westward through York County from Slate Point, a distance of about six and a half miles to the State line. Slate-quarries have been opened N.E. of the river, along nearly the whole distance mentioned, but never extensively wrought, and in the same detached manner through York County. At Slate Hill on the river, the slate is quarried in steps or benches, and not in one general breast, though the material is so uniformly pure as to admit of being nearly all wrought. On the east side of the river there are seven quarries near the shore, and four others of smaller size back on the hills, which are at the present time unwrought. On the York County side there is only one quarry at the river, but in the interior of the county there are seventeen more, embraced between a point two and a half miles back, and the end of the range six miles from the river. The workable slate appears not to extend in Lancaster north-east of the limit given, but in the other direction there are indications that it is prolonged beyond the distance of the six miles named. One of the quarries on the river, Brown's Lower Quarry, yields slates which will bear strong stove heat without cracking, and the workmen use flags of it for frying their meat upon. So uniform is the composition of the material, and so diffused and regular the metamorphism, that the original planes of sedimentation or bedding are too indistinct at these river quarries to be discernible. The cleavage- planes, the only visible ones, dip about 80 to S., 30 E., and this condition prevails throughout. SLATE OF PEACH BOTTOM. 189 Statistics. During the year 1853 the quarries of J. and S. Brown yielded 1000 tons, and in the two pre- ceding years 1500 tons. Caldwell's quarry, on the same north-east side of the river, yields annually about 400 tons. Cox's quarry, on the opposite side of the river, has afforded but a small amount ; but much slate is wrought in York County, where one quarry, that of Eoland Perry, the largest in the belt, produced, in 1853, about 2000 tons. The price of slate for the last six years has ranged between $14 and $17 per ton. Slates of the largest size, of 24 by 14 inches, were $69 per thousand; ditto 16 inches by 8 inches, $22 per thousand ; ditto 12 inches by 6 inches, $12 per thousand. In the extension S.W. of this general belt of Primal slates, there are five or more quarries wrought in Frederick County, Maryland, near the railroad eight miles from Fredericktown. The next belt of strata cut by the river, and indicated on our section, extends from below Slate Point to the second canal-lock below the State line, a distance of about four miles. The rocks here exposed are various forms of mica-slate and talcose-slate, alternating with talcose white sandstone, certain outcrops of which bear the unmistakable characters of the Primal white sandstone. One or two outcrops of chlorite-slate occur, and occasionally the mica-slate graduates towards a micaceous quartzose gneiss. Much of the finer-grained talcose slate is undistinguishable from rock, so-called, which near the Schuylkill, and along the South Valley Hill, both east and west of it, and also in the anticlinals of the Montgomery and Chester Limestone Valley, is seen in intimate alternation with the Primal white sandstone. Either from the more frequent presence in this district of the middle part of the Primal series, the White Sandstone group, or from a less excessive degree of metamorphism, the strata here exhibit a far lower condition of crystalline change than in some of the tracts further Jf., having fewer of the features of true micaceous schists, and more of the characters of genuine sedimentary sand- stone. Indeed, at several places between Slate Point and the State line, we meet with a rock which, in its composition, lamination, colour, fracture, and whole lithological aspect, is absolutely undistinguishable from the main bed of the Primal white sandstone, as it is seen in Edge Hill and other notorious localities of this readily recognised rock. One of the localities is just below Slate Point, the sandstone forming, in fact, the south flank of the Slate Hill, and reposing, regularly bedded, immediately upon the slate itself, which near the contact is highly nacreous, and in that minutely wavy or crinkled lamination which usually denotes a metamorphism approaching the rock usually called Talc-slate. About 1700 feet further down the river, there is another outcrop of Primal white sandstone immediately north of Hough's Run at the canal lock. Here the rock is between 90 and 100 feet thick. It dips at the canal level 45 to S., 30 E. ; but rising into the hill it grows flatter until it becomes nearly level, as if bending to form an anticlinal arch ; indeed, it is difficult to resist the conclusion that these two South-dipping belts of sandstone are simply the two abutments of a wide fold or flexure, the northern flank of which is inverted into a somewhat steeper South dip than the southern. This view is confirmed by the crushed and contorted con- dition of the dark slates which fill the space between the outcrops of the sandstone. It is further confirmed by the presence in this neighbourhood, both within the supposed arch and at Slate Point above it, of a steep South-dipping cleavage, a feature quite iisual in the slaty rocks throughout the district. At other points further down the river, especially between Eock Run and the State line, a material having all the aspect of the Primal white sandstone under a more extreme condition of metamorphism reappears. We meet it again, though materially more altered and crystalline, about two-thirds of a mile below the State line, and here, as we should expect, it is in contact with a dark crystalline slate, precisely such as we find the talcoid slates of the South Valley Hill, Chester County, where, in alternation with the sandstone, they are more than usually metamorphosed. In truth, we encounter repetitions more or less frequent and distinct of this altered white sandstone and its contiguous slates all the way along the river to the mouth of the first stream in Mary- land, more than a mile and half below the State line. In other words, we may recognise these outcrops of the Primal white sandstone throughout a belt nearly three miles and a half broad, from the south flank of the Slate Point Hill to near the crossing of the great belt of serpentine. Serpentine Belt. Passing out of the talcose and micaceous slates which, as already stated, extend for about 190 PRIMAL ROCKS, SUSQUEHANNA RIVER. two miles below the State line, we meet a narrow belt of Serpentine rock having all the distinctive features of the Serpentine of the southern border of Lancaster County, of which, indeed, it is but the prolongation. As in all the other localities where this formation has been met with, it is in contact with the talcoid or altered older Primal slates, immediately adjacent beds of which are frequently so impregnated with the magnesian mineral, and so changed thereby, as to seem at first sight like a stratified serpentine. This rock contains much green actinolite. The full width of the dyke is not at present visible, but is is manifestly very narrow when com- pared with the space occupied by the belt under the State line in Lancaster. Even here, however, its breadth, including the serpentinous slates associated with it, seemed at the time the canal was excavated to extend two hundred yards. Whether this slender outburst is connected with the extensive and broad tract of chromiferous serpentine barrens of Deer Creek in Maryland, or whether that is an independent and somewhat more southern range, we have not ascertained ; but it is notorious that the maguesian rocks abound extensively throughout this zone to the S.W. Almost immediately adjoining the outcrop of the serpentine at the river upon its south side, there is a slender band of gneissic chlorite rock. This is too imperfectly exposed to enable an observer to ascertain whether it is stratified or not, but the masses visible exhibit an indistinct irregular foliation, more suggestive, however, of slaty cleavage than of sedimentary bedding. Gneiss and Granite Belt. The last subdivision of the ancient rocks traversed by the Susquehanna is a broad belt consisting mainly of massively-bedded gneiss under its several varieties, and of mica-slate and horn- blende slate cut by dykes of genuine intrusive syenite, granite, and greenstone 'trap. Perhaps the predominant rock of all is a thickly-bedded granitoid gneiss of the typical composition and structure assigned to that forma- tion. It consists, in other words, of the three characteristic minerals, quartz, felspar, and mica ; the quartz and mica predominant, and completely and widely detached, streaking the rock in light and dark wavy bands and blotches. This is the rock which is so extensively quarried on the east side of the river, north, and also south, of Port Deposit, and used by the Federal Government for the Delaware breakwater and other national works. Besides this prevailing variety, there is a broad outcrop near Havre-de-Grace of a more felspathic granitoid Gneiss of a yellowish and pinkish tint ; it also is an admirable building-stone when large and coarse blocks of a durable material are wanted. Hornblendic gneiss, graduating into hornblende slate, likewise prevails. On the east side of the river, the southern limit of the crystalline rocks is one mile below Port Deposit, the shore farther south being Tertiary or Diluvium. Of the Intrusive Rocks, the principal varieties are syenite and granite, the former more abundant than the latter. Wide dykes of a fine-grained grey granite are quarried near the canal about half a mile above the old Cone- wango Bridge, and a little further north there is a thick dyke of white igneous quartz. These granite dykes dip steeply south-eastward. An augitic syenite displays itself in several thick dykes about two miles lower, and this and other varieties of syenite abound in the neighbourhood of the mouth of Deer Creek. Near the vein of quartz above the Conewango Bridge there is a dyke of greenstone, but this rock is not abundant along the river. Above Havre-de-Grace there are noble exposures of the yellowish felspathic gneiss, not merely in the banks of the river but back upon the plain, where the edges of the strata are imperfectly covered by the attenu- ated margin of the horizontal tertiary sands and clays. Here the river, already a tidal estuary, expands into the Chesapeake Bay, the abrupt enlargement of which denotes the disappearance, deep below the ocean level, of all the older crystalline rocks, and the presence of the far more easily excavated strata of the uncemented and horizontal deposits of a tertiary or post-tertiary age. Reviewing the phenomena of cleavage throughout this southern zone of the Primal rocks as they are revealed on the Susquehanna, we discover an interesting exception to the prevailing law of a south-eastward cleavage dip, attended, however, with no interruption to the universal law of the parallelism of the cleavage structure to axis planes of the flexures, or the direction in which the strata have been obliquely compressed. First, The northern tract of the Primal slates exhibits over their whole breadth, from the limestone near Wrightsville to the limestone of Cabin Branch Run, the normal or south-eastward dip, and under conditions which imply at least two anticlinal folds with axis planes, dipping, of course, to the same quarter ; and through- out this belt the cleavage fissures invariably dip at a steep angle in the same normal direction. CLEAVAGE. 191 Secondly, The wider middle tract between the synclinal of the Cabin Branch Kun and the anticlinal district of Sheuck's Ferry, displays, with scarcely any interruption, an abnormal or north-west dip of the strata ; but here the cleavage is nearly vertical, sometimes very steeply southward, but more prevailingly northward, or in the direction approximating to parallelism with the steep abnormally-dipping axis planes. This is the state of things from a little S. of Cabin Branch Run to the vicinity of Lockport, where the cleavage, previously fading, disappears. Thirdly, Crossing' the narrow belt of more open and visible anticlinal waves, between Shenck's and M c Call's Ferries, we enter, above the latter locality, upon one great sequence of south-east dips of the strata, extending the whole way to the State line, and indeed to the southern limit of the metamorphic rocks at the mouth of the river. From M c Call's Ferry to Slate Point the selfton presents us with a third zone of cleavage ; but this observes invariably its normal direction, dipping to the S.E., and, as usual, at a steep angle. Below Slate Point, where the degree of metamorphism, even in the Primal slates, becomes once more excessive, the cleavage again vanishes, or gives place to that condition which is called foliation, and which does not permit, except in rare instances, the distinct recognition of the original lamination of the strata. It would thus appear that even where the cleavage assumes an abnormal direction of dip, it is in obedience to an equally abnormal direction in the plication of the strata ; and we may further remark, that wherever the rocks exhibit evidence of excessive metamorphism, or, in other words, show an approach to the maximum con- ditions of crystallisation or separate segregation of their constituent minerals, the cleavage ceases, and foliation, or that structure which is derived from the parallel arrangement of the component crystalline minerals, takes its place. PRIMAL SERIES, OR SLATE-BELT IN THE SOUTHERN PART OF YORK COUNTY. As already intimated, very little need be said in detail of the altered Primal slates S.W. of the Susquehanna in York County, no connected section being possible after leaving the bank of the river. Even on the line of the York and Baltimore Railroad, the natural and artificial sections of the rocks are infrequent, and so shallow that it is not possible to trace out the changes in the dip of the strata, detect their foldings, or recognise their lines of contact. As the Susquehanna section furnishes a far more complete exhibition of these, it will suffice to say of the western half of this slaty belt, that quitting the range of the synclinal limestone trough called the York Valley, and proceeding southward by the Codorus Creek and its South Branch, we cross nearly at right angles to the strike a wide succession of bluish-grey fine-grained micaceous and talcose slates intimately set with cleavage planes, the flakes of mica- being invariably arranged upon the cleavage surfaces. Some bands of a very pale or whitish green tint are extremely silicious, with delicate micaceous and talcose partings, and are identical in aspect and composition with the highly -altered and shaly portions of the Primal white sandstone of the vicinity of the Schuylkill, for example, at Barren Hill. As far S. as the Hanover Junction, the apparent dip of the strata is steeply southward ; though within this space there are indications, especially between the third and fourth mile-posts on the railroad, of an anticlinal flexure in the strata, broad and low, corresponding very nearly with one of the flexures in the same slate-belt at the river. The cleavage-dip likewise agrees with that at the Susquehanna, being everywhere south- ward at a high angle. These conditions imply one or more flexures of the prevailing character, steep or inverted on the north-west side, extending to the synclinal trough or little valley just S. of the Hanover Junction, which appears to be seated in the basin which embraces the lime- stone belts of Cabin Branch Run and of Jefferson. Passing S. of this natural boundary, we 192 PRIMAL ROCKS, YORK COUNTY. enter at once on a succession of exposures of micaceous slates, very similar to those traversed by the section further north, with the exception that they are more crystalline. These continue with a steep north clip as far as the village of Glen Rock. There the strata begin to assume a more highly metamorphic character, and lithologically would be called green quartzose micaceous gneiss, or gneissoid mica-slate, and they retain this crystalline type the whole way hence to the State line. It is worthy of note, that the northward dip seen in the district north of Glen Rock con- tinues, with only local interruptions and trivial contortions, throughout the remaining part of the section. It is toward the central portion of this more gneissoid division, especially in the neigh- bourhood of the Shrewsbury Station, about three miles by railroad north of the State line, that the contortions or little flexures most predominate ; and it is interesting to observe that these correspond very nearly in their latitude of transverse distance across the slate-belt, with those noticeable at the Susquehanna, in the vicinity of Otter Run. Another circumstance harmonisino- the two sections, is the absence of any distinctly-pronounced South-dipping cleavage after we pass the village of Glen Rock, but in place of this a wavy foliation seemingly coincident with the stratification. The section at the State line does not enter the belt of South-dipping stratifi- cation, with steeper South-dipping cleavage, which the Susquehanna Valley exposes from M c CalTs Ferry southward the whole way to the serpentine belt at the State line. Reviewing these facts of dip and structure, we find in this comparison of the two sections, a striking confirmation of the general principles of the relations of cleavage to the crust undula- tions so frequently enforced in this work. The whole topographical geology of southern Lancaster and York demonstrates a progressive sinking of the flexures, or anticlinal and synclinal waves, as they advance north-eastward to the Susquehanna, and across it to the limestone tracts of the Conestoga and Pequea, where the slates finally sink out of sight in flattening anticlinal spurs. Now it is in this district of subsidence, or at the Susquehanna, in the belt prolonged from Turkey Hill, that the cleavage-dip approximates to the perpendicular, leaning almost as often to the North as to the South, parallel to the axis planes of the flexures, many of which, as already intimated, observe a northward instead of a southward dip. Further towards the S.W., where the flexures are manifestly more closely compressed, "and therefore more oblique, but where their axis planes, in place of dipping to the south-eastward, descend north-westward, contrary to the usual rule, the cleavage is less perpendicular and more constantly towards the same abnormal quarter. In a rather wild and sequestered neighbourhood among the Barren Hills, thirteen miles S.E. from York, we come upon Susan Ann Furnace, not recently in operation, but undergoing repairs. The iron ore procured near it was found to make an inferior metal, and was abandoned for a purer variety obtained about seven miles to the W., at a point seven and a half miles S. of York, where the mineral occurs between seams of disintegrated slate, in nests and loose deposits. It is rather silicious, but is said to yield a tolerably .good iron. Near the Maryland line, at Essex Hall, on the farm of Mr Clark, a small deposit of iron ore was worked some years ago. In the fields between this and the State line, are found loose crystals of red oxide of titanium. CHIQTJES RIDGE. 193 CHIQUES EIDGE. A broad and conspicuous chain of hills, known as Chiques Eidge, is the next principal belt of the Primal strata. It originates about three miles N.W. of Lancaster, and after ranging almost due northward for eight miles, crosses the Susquehanna a little above Columbia, and extends parallel with the southern side of the river, until it passes Codorus Creek, and is overlaid by the south-eastern edge of the Mesozoic red sandstone. This belt is in many parts more than one mile in breadth, and near its eastern extremity, where it is widest, it contains two or three anticlinal flexures. The general structure of this ridge, as seen at the Susquehanna, is that of a 'very much com- pressed or folded anticlinal flexure, on the northern side of which the strata lie in an inverted altitude ; that is to say, the rocks, originally uppermost, are seen dipping apparently beneath others inferior to them in the order of stratification. The consequence is that the limestone lying N. of the ridge dips southward, to underlie the rocks of the ridge. Above the bridge at Wrightsville, the most southern member is a slaty sandstone evidently one of the upper strata. It dips 70 S. Approaching the main axis of the ridge, we meet high perpendicular cliffs, consisting of the Primal White Sandstone, and indurated Primal upper slates. The colour of the rock is whitish, sometimes of a bluish tinge. About a mile below the mouth of Codorus Creek, to the N. of the folded axis, the sandstone is underlaid by a tolerably thick belt of striped slates, this again by a succession of thick strata -of sandstone and slate, the latter predominating, until we reach the limestone at New Holland. Sometimes the slates dip slightly N. from the axis, and sometimes they are inverted, or dip towards it. Half a mile above the furnace on Codorus Creek, the compact white sandstone dips N. 60. From this to Brillinger's, we see no more of the sandstone, the rock being the upper silicious slate similar to that at the mouth of the Codorus. The belt of white sandstone terminates westward at a point at about two miles N.E. of York, where the Codorus flows round it. The belt of silicious slate, lying further N., passes westward from the mouth of the Codorus and New Holland, ranging S. of Liverpool, until it is covered by the red sandstone at Shultz's, four miles north of York. At Chiques, on the Susquehanna, we have a very distinct and bold exposure of nearly all the Primal strata of this belt, as shown in the enlarged section. SECTION FEOM COLUMBIA TO THE CHIQUESALUNGA CREEK AT HALDEMAN'S, THROUGH THE CHIQUES EIDGE. This fine natural section gives us a view of the whole constitution and structure of the Chiques Eidge. By it we learn the precise conditions into which the strata have been altered by igneous agency. The rocks embraced here are in the descending order, or that in which, looking eastward, we shall review them. 1. The alternating or passage beds of slate and limestone, connecting the bottom of the great Auroral lime- stone series with the top of the Primal ; 2. The Primal newer or upper slates ; and, 3. The Primal White Sand- stones. 1. The alternating group extends from the town of Columbia, past the railroad engine-house to the furnace. Between the street at the engine-house and the furnace, a distance of about 1100 feet, we cross two thick bands of the limestone and an interposed bed of slate, all clipping at an average angle of 50" to the S.S.E. The first bed of limestone, magnesian in its composition, is exposed for a little more than 250 feet in the bank. It is VOL. I. 2 B 194 PRIMAL ROCKS CHIQUES RIDGE. very crystalline, mottled, and partially intersected with steep South-dipping cleavage fissures, and altogether exhibits evidence of much metamorphism ; indeed, the cleavage in places renders the recognition of the bedding quite obscure. The band of slate, also about 250 feet across, is of a dull olive-colour, very ferruginous, highly indurated, and intimately cleft with cleavage-joints. These dip about 75 southward, or steeper than the strata do ; nor do they coincide in strike with the bedding, but range more E. and W. Passing the slate, the last or lowest band of the limestone is seen exposed for about 400 feet. This is also highly magnesian, but more sandy than the other bed. It is quite as highly altered, being crystalline, white and mottled, and full of cleavage. 2. From the furnace to the first exposure of the Primal sandstone, a little north of the second ravine, there is a fine natural section of the whole thickness of the Primal upper slate, though very possibly a folded flexure near the Tunnel may repeat a portion of the beds under three parallel dips. The apparent dip is nionoclinal until we pass the second ravine, where a low narrow anticlinal wave is discernible. If we assume no fold or repetition of the strata between the furnace and the ravine, a distance of 2500 feet, and accept 45 as the average dip of the beds, we must suppose the thickness of this upper Primal slate to exceed 1 800 feet ; a bulk far exceeding that which it possesses further eastward in the North Valley Hill of Lancaster and Chester. This slate appears to be even more transformed in its texture by igneous action than the beds above it. It is very hard, internally of an olive green, externally of a dingy brown, from presence of much oxide of iron, and has a baked aspect. It exhibits, moreover, in every part of the mass, an excessive amount of the cleavage fissures. These dip in all cases southward, and at angles varying from 80 to 65, declining as we go north- ward towards the anticlinal flexure in the underlying Primal sandstone, with the axis plane of which those most adjacent are almost strictly parallel. Even in the low small arch N. of the second ravine, the cleavage planes are true to this law of parallelism, unaffected by any tendency to the fan-tail arrangement which such an arch would have induced had it been more remote from the overpowering influence of a great folded flexure. 3. Passing the base of the upper Primal slate, we cross next an irregular oblique arch or anticlinal fold of the Primal sandstone, occupying a width of about 500 feet. The southern flank of this arch contains two gentle waves ; the northern is completely inverted, so that the sandstone beyond the axis dips almost parallel with that south of it. Between these two similarly inclined legs of the curve, a mass of slate, about 150 feet across its strike, displays itself in the very axis of the flexure. This is manifestly the uppermost bed of slate of the Primal sandstone group ; this formation here containing as its chief members two white sand- stones, and an interposed bed of slate about 300 feet in thickness. Between the anticlinal axis, lifting this middle slate to view, and the northern base of the Chiques Ridge at Haldeman's, a distance of nearly 3000 feet, occur three other exposures of the Primal white sandstones : the first of these is some 250 feet above the Henry Clay Iron-Furnace ; it is the same sandstone as that of the compressed anticlinal just passed over, here brought again to the surface with a southern dip of 60. Between it and the anticlinal fold there is there- fore an oblique compressed basin of the lower members of the upper Primal slate, at least such is a reasonable construction of the strata as they are seen. The slates embraced in this supposed synclinal trough show the slaty cleavage dipping 70 to S., 20 E. ; whereas the planes of stratification dip at 60 to S., 10 E., a deviation in strike of 10. This upper sandstone of the Primal sandstone group has, at its outcrop N. of Henry Clay Furnace, a thickness of about 27 feet. The slate, or middle member of the same group, about 300 feet thick, as already stated, next rises, leaning southward at an angle of 50, and immediately beyond it there appears the upper portion of the lower or main Primal white sandstone, most curiously doubled into a beautifully- rounded oblique saddle, the north side of which is perpendicular, the south dipping at 50. It rises above the level of the road about 20 feet, and con- sists wholly of the white silicious sandstone, without joint or fracture, or trace of cleavage fissure, and with the lines of original bedding only barely discernible. Here the pure massive sandstone has undergone a most excessive, yet regular folding, or doubling together, at a time when the materials must have been PIGEON HILLS. 195 in a partially movable or semi-plastic state. It is one of the most striking instances risible within the whole Appalachian Chain, of this plasticity of the sedimentary matter of the ancient Palaeozoic strata. The slaty mass overlying this much bent and compressed sandstone, has been doubled into a much more acute curve at the anticlinal axis, and is, moreover, greatly cut in the sharp synclinal fold, just N. of the anticlinal, by cleavage- joints. Indeed, all the beds from this middle anticlinal sandstone to the third or northern one, are pervaded with the cleavage fissures : those in the slate, separated by very short intervals ; those in the beds of sandstone occurring at an average distance of about half an inch. Approaching the third anticlinal, or that of the main northern crest of the ridge, we meet the lower or chief member of the Primal white sandstone group, elevated in a grand waving arch, forming a superb mass of cliffs south of and behind the mansion of Professor Haldeman. Facing the ends of these strata, which span in all a distance of about 1000 feet, we discover that the sandstone exhibits, when closely scrutinised, not a sym- metrical, normal wave, but one containing two synclinal curves upon its crest. The southern flank of the general wave dips southward at a gentle angle, increasing from 30 to 45. The northern flank plunges from the last rapid turn, almost perpendicularly out of sight, to fold most probably backwards beneath the arch, and finally to abut, with dislocation, at a depth of '2000 feet or more against the south-dipping limestones visible just beyond it in the stream. In this main terminal arch the cleavage, which elsewhere dips invariably southward, deviates from this prevailing rule at one point on the S. slope of the wave, and dips at a steep angle northward. Elsewhere throughout the flexure it slants southward at an angle of 80. The thickness of the lower sandstone member cannot be accurately estimated, but, including its thin beds of slate, we may assume it at not less than 300 feet. The fault or dislocation alluded to evidently extends a great distance E. and W. along the northern base of the Chiques Kidge. Some of the beds of the middle and lower members of the Primal white sandstone exhibit, in the Chiques Ridge, a great multitude of specimens of the stemlike fossil, the Scolithus linearis. This is nearly straight, and would seem to have a small knob or swelling at one of its terminations. Its position in the rock is invariably perpendicular to the plane of the beds, and therefore where cleavage disguises the direction it is a good guide. Pigeon Hills. About eight miles south-westward from York there occurs the range called the Pigeon Hills, rising through the limestone of the York Valley. These hills have an elliptical form, are between seven and eight miles long and three broad, terminating south-westward near the turnpike, at a point four miles north of Hanover. The strata comprising different portions of the Primal sandstone and Primal newer slate, consist usually of a dark slate and a light- coloured sandstone, of different degrees of fineness and compactness. The whole belt, though carefully explored, develops little of interest in a scientific or an economical point of view. About four miles N.N.E. from Hanover, occur green chlorite, and a beautiful variety of foliated oxide of iron. The slate in the neighbourhood shows small traces of copper ore. A belief exists throughout this neighbourhood that the slates of these hills are of the coal formation, and that coal perhaps exists in them, whereas they belong to the very lowest fossiliferous formation of our State ; while the workable coal is exclusively confined to a wholly different group of rocks, lying much higher in the order of stratification, and occupying an entirely different geographical range. The junction of the slate and limestone rocks is seen on the S. of the Pigeon Hills, about four and a half miles N.E. from Hanover. CHAPTER IV. PRIMAL BOCKS OF THE SOUTH MOUNTAINS BETWEEN THE DELAWARE AND SCHUYLKILL. THAT the Primal series is not continuous in the belt of the South Mountains, where they traverse Northampton and Lehigh, is rendered highly probable by the infrequent and local manner in which it shows itself. Still we are entitled to consider it as not confined merely to the few scattered points where it emerges to the day, but as resting in many places at the base of the Gneissic ridges, buried under a deep covering of loose Diluvium. I shall hereafter refer to various places where it rises to the surface in sketching the limits of the limestone, which, whenever it is present, it immediately underlies. There are many exposures in this part of the chain where the limestone is seen resting directly in contact with the gneiss. At the Delaware the Primal sandstone flanks the gneiss in the Lehigh Hill, and also near Durham. Going west- ward, it shows itself on Durham Creek, a little E. of Springtown, in the ridge bounding the limestone E. of Hellertown, and in the end of the spur immediately E. of the South Branch of the Saucon. Ascending the Lehigh, the first point where it appears in place is on the south side of the river about a mile S. of the Bethlehem Bridge, where it occurs in a thin band, resting on the gneiss, and dipping northward 20. It rims in a narrow belt from the road east- ward to the Saucon, where it adjoins the lower termination of the limestone of that stream. The sandstone occurs on the northern slope of the small ridge of gneiss rocks occupying the north side of the Lehigh, E. of Allentown. It shows itself again not far from this, on the southern side of the river, about a mile below the Allentown Bridge, the piers of which have been con- structed of it. Here it constitutes but a thin stratum, the limestone in some places lying nearly in contact with the gneiss. There are but two other localities in Lehigh and Northampton counties. The first of these is near the top of the mountain E. of Emaus, where a rather coarse . variety of the sandstone is seen dipping with the slope of the mountain, rather steeply towards the W.N.W. The mountain itself is Gneiss. The other locality is at Millerstown, and exhibits the sandstone as a low ledge at the foot of the mountain, dipping 1 towards a point 75 W. of N. Westward of this, especially in Berks, it increases in thickness and abundance as we approach the Schuylkill. In Berks County the white sandstone, which appears in a few detached localities along the north- western _line of the South Mountains in Lehigh County, begins to show itself as a more continuous formation, rising even into high irregular ridges in the south-western part of the chain. A very usual position of the sandstone is upon the flanks and around the extremities of the spurs of the gneiss, where it often indeed overtops the crystalline rocks, which then appear only on the crest of the hills as low dykes difficult to trace. Even where the sandstone is best developed, some difficulty attends our tracing it as a continuous formation. This arises from its immediate proximity to the greatly-convulsed gneissic strata, and from its lying so frequently on the declivities of the hills, where its outcrop is much obscured by fallen fragments. The sandstone, where it is subordinate to a larger ridge, often either encircles, at a little distance, the LEHIGH AND BERKS. 197 extremity of the spur, or lies more or less obliquely across it. Sometimes, even in the middle of a high track of the sandstone, where no regular belt of older rock protrudes itself, evidence is perceived that this has reached the surface at certain spots, from the quantity of angular frag- ments. The sandstone itself offers often great difficulty in determining its stratification and the true direction of its dip ; whole hills looking like mere piles of huge angular blocks, innumerable fissures and cleavage-joints traversing the beds so as greatly to perplex the observer. Passing from Lehigh into Berks, the first exposure of the sandstone is at a hill lying S. of the Little Lehigh, and about two miles S.E. of Metztown. Here the rock is chiefly in loose pieces, covering the foot and lower declivity of the hill. The sandstone also shows itself in place, about one mile S. of Metztown, immediately W. of the church. Between the visible edge of the limestone, which passes by Metztown and the foot of the hills further S., there is a considerable tract of country where no rock appears upon the surface, with the exception of the isolated tract of sandstone at the church just referred to ; a deep covering of diluvium hiding everything from view. Approaching the mountains from the N., the first rock seen in place is a white variety of gneiss. This is on the road leading to Hoof's Inn. West of this, in Maxa- tawny Township, the limestone is seen where a road crosses the Sacony Creek. The sandstone, which shows itself N.E. of the creek, disappears a little S. of Grim's Mill, the gneiss showing itself on the W. side of the stream, between the mill and Hunter's Furnace. The general margin of the limestone passes about a quarter of a mile N. of "Walnut-town. About a mile south of this place, to the N.E. of the road, occurs a sandstone ridge, running in a N.E. direction. A little further S., upon the same road, we observe the outcrop of the gneiss. This gneiss, part of a long belt, averaging about a mile in breadth, terminates at Miller's Mill on Dry Run. A belt of the sandstone, as already described, flanks it both upon the N. and S., the sandstone uniting round the point of the gneiss, a little east of Solomon's Temple. South- ward from this last-mentioned place, towards Reading, the sandstone lies on the E. of the road the whole way to within three miles of the town, where a belt of slate, the upper member of the Primal series, crosses the road. If we here turn aside to the N.E., taking the road to Barnard's Mill (Rothermel's Mill on the county map), we encounter, just at the mill, a low protruding mass of igneous rocks. A little to the N.W. of this point, a small body of limestone has been dis- covered, S. of which, in the sandstone, we may trace a low dyke of syenitic rocks running towards the N.E. E. of its north-eastern end, and W. of its south-western, occur two other small patches of limestone. The line dividing the limestone of the Schuylkill Valley from the sandstone and slate bounding it on the E., after following the road which leads from Solomon's Temple south, suddenly curves to the eastward about two miles north of Reading, reaching, but not crossing, the road from that city to Pricetown. Here, at Rothinberger's Inn, turning very abruptly to the S.W., and gradually receding westward from the road last mentioned, it next runs to the Schuylkill, passing through the western side of Reading, leaving thus a triangular tract of the limestone included in the general area of the sandstone. Hills East of Reading. Penn's Mountain, commencing E. of Reading, and running in a N.N.E. direction nearly five miles, consists, on its summit and western side, of the Primal white sandstone, dipping to the W.N.W. Descending the eastern slope of the mountain, we soon encounter the gneiss rocks, which maintain this position as far to the S.W. as Kesler's Mineral Spring. This is the termination of the wide belt of gneiss and syenite, coming off from the general 198 SOUTH MOUNTAINS EAST OF THE SCHUYLKILL. t chain with a prevailing south-west and north-east direction of the strata. At Spie's Church there occurs a high sandstone ridge in the midst of the gneiss, being detached from any other tract. Penn's Mountain, at its northern extremity, sweeps suddenly to the eastward, jutting between the main belt of the gneiss around Spie's Church, and a narrower tract which crosses the Reading and Pricetown road. N. of this last tract, and N.W. of the prolongation of Penn's Mountain, are some high sandstone ridges, probably concealing dykes or beds of crystalline rocks between them. Pursuing the road north-eastward to Miller's Inn, we have the sandstone on the N.W., while on the S.E. the hills consist principally of gneiss. Between Miller's Inn and Pricetown the road separ- ates a hill of gneiss on the S.E. from a high short ridge of sandstone on the N.W. Gneiss occurs also about one mile from Pricetown, south-east of the road going towards Sterner's Inn (of the old State map). A sandstone ridge rises at Sterner's Inn, on the north-west side of the road, and extends nearly to the tributary of Manatawny Creek, in Rockland Township, beyond which, until we pass Roth's Mill, all the rocks are crystalline. Going E. of S. from Roth's Mill to Pine Creek, we encoun- ter none but gneissic rocks forming a wide tract. The sandstone, however, shows itself at the spot marked Shiffert's Inn on the county map, appearing on the slope of the hill N. of the road. The rock here is somewhat coarse and of a purplish colour. Passing to the S.W. it seems to cross the road. Descending the creek we meet another ridge of similar sandstone, occupying the west side of the stream, at a mill designated on the Map as Mineder's. Further S., about a quarter of a mile N. of Snyder's Upper Forge (Udree's Forge of the old map), the sandstone again shows itself on a small hill E. of the creek, and again on its W. side. The hill immediately to the S.E. of Sterner's Inn consists obviously of gneiss, the surface being wholly covered with their fragments, though no regular outcrop is seen. Still pursuing the road to Oley Furnace, we pass diluvium, containing much fragmentary sandstone, until at the creek, close to the furnace, we behold the sandstone in place, dipping steeply on the east side of the stream to the N.N.W. The rock here is coarse and reddish, and occasionally very talcose. Immediately W. of the creek lies a large hill of syenite, and about half a mile nearer Fredens- burg, we come upon the margin of a wide tract of slate, apparently the upper member of our Primal series, of which the sandstone hitherto most commonly encountered is the lower. Nearly two miles N.W. from Fredensburg, on the north-east side of the road to Miller's Inn, occurs a belt of sandstone, dipping steeply to the N.N.W. Here is an old mine of iron ore to be described here- after. Beyond this a sandstone ridge is seen running parallel with the road, about a quarter of a mile on its north-east side. Between this and Miller's Inn, an interval of about a mile, the prevailing rock is gneiss. Let us now trace the line which divides the gneiss from the Primal slate and sandstone, and the Auroral limestone in the northern and western parts of Oley Township. About three-fourths of a mile S.W. of Lobach's Mill, on Pine Creek, we come upon the margin of the limestone, crossing the stream in an eastern and western direction, through the lands of Jacob Keim. The dip here is due S. 60. To the N.E. and E. of this the sandstone shows itself in a belt, to be presently described. North of St Peter's Mill (marked Maul's on the old map) runs the edge of the gneiss, which here exhibits no sandstone interposed between it and the limestone. The margin of the limestone is well seen half a mile W.S.W. of the mill, the rock dipping steeply to the S.S.E. Immediately above this limestone, on the creek, we have the slate crossing the stream just at the road leading to Sterner's Inn. The true dip of this last rock is difficult to discover, owing to the obscurity of HILLS EAST OF READING. 199 the divisional lines of the strata, and the abundance of cleavage planes, wholly independent of the lines which mark the dip, the dubious direction of which leads to some uncertainty respect- ing the precise formation to which the stratum belongs. Could its beds be seen passing unequi- vocally under those of the limestone, it would plainly prove itself to be the Primal newer slate ; if, on the other hand, it should be seen to dip away from the limestone at the line of contact, no doubt would remain as to its being part of the Matinal slates. The margin separating the slate from the gneiss passes about half a mile N.W. of Fredensburg. Taking the road leading out of Fredensburg to the S.W., we pass over the slate for nearly a mile and a half, until we cross a little stream, the dividing-line of Alsace and Oley townships, where we pass directly upon the gneiss. Ascending the creek by a steep ravine, we pass the eastern termination of the spur of sand- stone at Spie's Church, already spoken of. East of this spot the boundary of the slate and gneiss is near Knabb's Mill (Reiff's on the old map). The hills immediately W. of the mill (marked Knabb's on the map), and of the road separating Oley and Exeter townships, are strewed with fragments of gneiss, as far down the creek as the first exposure of the limestone, which is half a mile north of the road running westward from Oley Forge. Following this road, which deflects towards the S.W., we pass across a corner of the limestone tract, and at a short distance W. of the Manokesy Creek encounter the common margin of the limestone and the gneiss. These two formations rest apparently in contact, from the upper point of the limestone, on the Manokesy, below the mill marked Knabb's, throughout a mile and a half towards the S.W. About two miles E. of Maurer's Inn, the sandstone shows itself in place, between the lime- stone and the gneiss, on the southern slope of a hill, some distance N. of the church. Under this sandstone is an argillaceous slate, probably the Primal older slate, in very thin laminae. Between this and Maurer's Inn the rock is exclusively sandstone, the large double hill N.E. of the tavern being entirely of this formation. Here a quarry has been established for getting building-stone ; the dip of the rock is obscure. This ridge of sandstone extends in a north- easterly direction, about two miles and a half towards the insulated sandstone hill, near Spie's Church, from which, however, it is separated by more than a mile of gneiss. East of the ridge the rocks are a white variety of gneiss, consisting of quartz and decomposing felspar, and a syenite composed of felspar and hornblende, in frequent alternation with the gneiss. Where these rocks abound the surface is marked by small rounded hills, covered with fertile soil, giving a pleasing aspect to the country. A similar topography is particularly striking in some parts of Colebrookdale Township, hereafter to be mentioned. The limestone belt, bounded, as we have already said, for the first mile and a half by gneiss, runs afterwards the whole way to the Schuylkill, below Eeading, crossing Bishop's Creek about a mile below Maurer's Inn, and folding round the southern point of the Neversink Hill. From the Manokesy, westward to the Schuylkill, the limestone belt, bordered on the S. by the middle secondary rocks, contracts into a narrow zone, a few hundred yards in breadth. On its narrow limit it dips to the S. Where it crosses the Perkiomen turnpike, three miles from Reading, it shows in a quarry near the road many beds of a crystalline granular structure. Much of the rock at this place is of a dull yellowish white. It dips a little W. of S. It strikes the western reach of the Schuylkill, about a mile and three-fourths S. of Eeading, where it is overlapped on the S. by the coarse calcareous conglomerate of the Middle Secondary series. North-eastward this narrow belt opens into the wide tract of limestone, which occupies much of 200 SOUTH MOUNTAINS EAST OF THE SCHUYLKILL. the eastern half of Oley Township. From its southern point on Manatawny Creek, a fourth of a mile below the line dividing Amity from Earl townships, the eastern edge of this large tract passes up the Manatawny, and then up its eastern tributary, as high as the line which separates Oley from Pike. Its northern margin crosses Pine Creek, about a mile below Lobach's Mill. Its north-western corner is at the place marked on the map, Peter's Red Ochre. Mine. Its western limit is the eastern boundary of the slate, which occupies a large tract in the western half of Oley. The limit between these rocks runs southward, nearly through the middle of the town- ship, until it strikes the Exeter line a little E. of Manokesy Creek. The slate, which we have already mentioned to be most probably the Primal newer slate, spreading from the western edge of the township (Oley), eastward beyond Kemp's Inn, shows generally a dip to the S.S.E. About half a mile S. of Kemp's Tavern the slate is bordered by slaty limestone, which apparently overlies it. The slate E. of Fredensburg graduates into slaty sandstone ; but S. of Eieff's Mill the slate is soft and sectile, approaching in texture to pipe- clay. At this and several other places its strata are intersected by veins of quartz. I have already referred to the belt of sandstone which occupies the valley of Pine Creek. This extends from the neighbourhood of Pott's Forge to the edge of the limestone, a mile below Lobach's Mill, where, doubling round the point of a wide spur of the gneiss, it runs eastward, to join the much longer tract of sandstone which follows the Manatawny and its eastern tributary in Pike Township, for many miles. This latter range of the sandstone, commencing near the western corner of Hereford Township, crosses the narrow part of District Township, and then the whole of Pike, following the eastern side of the Manatawny nearly as far down as the line dividing Amity and Earl. Mention has already been made of another tract of sandstone in the form of a ridge or spur, commencing about a mile E. of Spang's Furnace, and running in a N.E. direction into the region occupied by the gneiss. At Hill's Inn the limestone is found on the E. side of the Manatawny, dipping to the N.W. The sandstone immediately E. of this dips steeply in the same direction. A little N. of the Amity Township line, the sandstone, on the other hand, crosses to the west side of the creek. At the bridge on the Township Road, over the Manatawny Creek, the limestone, in its upper beds, is striped by reddish ribbons. A calcareous slaty sand- stone here occurs, precisely similar in appearance to the red sandstone of the Middle Secondary or Mesozoic rocks, of which it may be a detached or outlying patch. About a quarter of a mile below this, on the creek, is the general margin of the Middle Secondary red shale and calcareous conglomerate. The southern half of Earl Township includes chiefly long hills of syenite and other crystalline rocks, running in a N.N.E. and S.S.W. direction, having coarse Primal sandstone flanking them on their north-west slopes. Taking the road from Kline's Tavern, near the Manatawuy, eastward to Boyerstown, the sandstone of one of these spurs, approaching from the N.E., shows itself on the road dipping 35 S.S.E. At the intersection of the road and the township line of Earl and Douglas, we enter on the margin of a small tract of limestone, overlapped further S. by the red sandstone. It crosses to the N. of this road. The limestone peeps out at a house laid down on the county map as Keely's Tavern, and shows itself again in a quarry a few hundred yards E. of the tavern kept by Mr Gresh. Near Keely's Old Stand the sandstone occurs on the N. side of the road, and it again appears N.W. of Gresh's. The limestone to the S. of this HILLS EAST OF HEADING. , 201 is overlapped by the Middle Secondary rocks. East of the limestone, and before reaching Rhoads's Mill, we come, in succession, upon white gneiss, syenite, sandstone, and limestone, the latter appearing at the mill. From this point eastward to Boyerstown, the whole space is occupied by crystalline rocks, covered on their Southern margin by the Middle Secondary. All that part of Colebrookdale Township lying to the N.W., N., and N.E. of Boyerstown consists exclusively of gneiss. This forms innumerable hills, covered by a deep and rather fertile soil, the whole district presenting, in a succession of undulating outlines, a highly pleasing series of landscapes. The limit of the gneiss and overlapping Middle Secondary sandstone, passing through this township, from Rhoads's to the West Branch of Perkiomen Creek, I have already defined. A locality of crystalline limestone occurs in the centre of Colebrookdale Township, on the North- east side of a road. The spot is about three-fourths of a mile N.W. of the edge of the Middle Secondary red sandstone. Between this place and Swamp Creek He several high hills, covered entirely with diluvium and fragments of sandstone. Hills of this description are common along the line separating the Middle Secondary region from the gneiss of the South Mountains. At Swamp Creek we enter a valley bounded on the N.W. by rounded knolls of the gneiss, and on the S.E. by the Mesozoic red sandstone. This valley contains several exposures of limestone. The first of these is on the West side of the stream, and belongs to Peter Motha. A little N.E. is the quarry of Jacob Oberholz, and beyond this, in the same direction, the limestone occurs on the premises of Henry Stauffer. At the first place the strata dip N.E. ; at the second, nearly S. A narrow belt of the Primal white sandstone commences just E. of the West Branch of Perkiomen Creek, and runs to the N.N.E., through Hereford Township, to the line of Lehigh County. It is bounded on the S.E. by the overlapping red sandstone, and on the N.W. by the gneiss. The white sandstone shows itself on the main road, passing through the centre of the township ; the rock dips towards the S. It is again well exposed on the East side of the main Perkiomen Creek, where the Sumneytown road crosses. We find a small insulated patch of the white sandstone in District Township, about a mile and a quarter N.W. of Hoofs Inn, where it occurs surrounded by an elevated table-land of gneiss rocks ; the sandstone is of a coarse texture. Passing from Hoofs Inn south-westward along the West Branch of the Perkiomen, we meet another spot where the sandstone undoubtedly exists in place ; this is about half a mile from the inn, on the S.E. side of the road. A little W. of this commences on the stream a narrow valley, extending down to John Rush's forge, where the mountains approaching close it in. The Old Mount Pleasant forges are situated near the lower end of this valley. Limestone shows itself a short distance above Rush's Mill (Hunter's on the old State Map), dipping S.S.W. It is again exposed in two fine quarries, one on each side of the creek, at David Schall's forge (Thompson's on the old Map). In the more western of these quarries the limestone considered the best is of a dark-blue colour. According to our analysis, the rock in both localities is highly magnesian, the composition being in other respects also precisely similar ; the lighter-coloured variety containing, if anything, rather less foreign matter. The dip in both quarries is to the N.AV. Iron Ores of the Primal Strata. Before closing this description of the Primal rocks of the State, it is expedient to mention that large deposits of brown hscmatitic iron-ore are not unfrequent in the soil and detrital matter which VOL. I. 2 C 202 SOUTH MOUNTAINS. rest upon the Primal newer slates. This is the geological position of the great mine on Chestnut Hill, four miles east of Columbia, the ore occurring in a sort of basin of the disintegrated slate. Throughout the Appalachian Chain much valuable iron-ore is discovered in connection with the same formation. The localities of these Primal ores of iron will be discussed in the general Chapter upon the Iron Ores. OUTLYING BELT OF PRIMAL BOOKS OF MILLBOUGH HILL. There is an insulated belt of the Primal strata skirting the Northern side of the solitary oval tract of gneissic rocks W. of Reading and S. of Womelsdorf, which appears to extend from a point nearly S. of Sinking Spring westward, a little N. to the county line of Berks and Lebanon, thence south-westward, terminating in the western spurs of Millbough Hill, ISLE, of Shefferstown. It is narrow when intersected by Cacoosing Creek, but broad near its western termination, from the presence of two or three anticlinal flexures. The strata consist of both the Primal slates and Primal white sandstone, fragments of which rocks are strewn abundantly in many places along the base of the ridge, hiding the southern edge of the limestone of the Great Valley. CHAPTER V. SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. THE irregular chain of hills west of the Susquehanna Eiver in Adams, Cumberland, and Franklin counties, called the South Mountains, is a broad zone of low ridges, consisting almost exclu- sively of the Primal strata. It is the North-eastern termination of the first continuous mountain- range of the southern Atlantic States, called in Maryland and Virginia the " Blue Kidge." Tracing it South-westward, this tract originates near Dillstown in a narrow point, expands rapidly towards the head-waters of the Conecocheague, beyond which it grows narrower again, and curves swiftly Southward. It has the Cumberland Limestone Valley for its Northern and Western boundary, and the red sandstone plain of Adams County for its South-eastern ; Green Ridge and Jack's Mountain on the Western border of Adams County are eminences in this hilly belt. In its geological constitution this tract is without much variety, for it contains scarcely any rocks except those of the Primal' series. It is doubtful if the true Gneissic rocks anywhere reach the surface within its borders, and only in one or two localities have even the lowest members of the Auroral limestone been met with covering the upper Primal slates. Even of intrusive igneous rocks it embraces a singularly small amount, those met with being chiefly greenstone and trap-rock. The geological structure, or mode of stratification of this belt, is equally simple. The whole tract consists of two or three groups of high, narrow, nearly parallel anticlinal ridges, expanding and subdividing toward the S.W. These are composed of the Primal white sandstone. Between them are high parallel valleys and plateaus of the Primal upper slates, which, from being softer and more fissile, have been worn and trenched by the ploughing force of waters to somewhat lower levels than the more resisting, better cemented sandstones. The crests of the ridges are therefore stony and rugged, their flanks usually smoother, being formed chiefly of the slate. To trace somewhat more in detail the several leading subdivisions of the belt, the first, or most eastern, is an anticlinal ridge, the rising of which N. of Dillsburgh, forms the very com- mencement of the chain. Commencing there, close to the Yellow Breeches Creek, which for many miles flows near its Northern base, it rises and expands until nearly opposite Shippens- burg, where, already divided into two anticlinal prongs, it begins to subside, and finally sinks to the level of the Limestone Valley, about five miles E. of Chambersburg. A rather deep valley, that of Mountain Creek, follows this sandstone range on its South, side, the whole distance out to the Cumberland Valley. It consists of the Primal upper slates, much intersected with slaty cleavage. At one locality, Pine Grove Furnace, there occurs in the middle of this range of slate a narrow band of limestone, marking the position of the synclinal axis, or keel of the trough, into which the formations have here been folded. To the S.E. of this slate valley of Mountain Creek there is a second long continuous range of the Primal sandstone, commencing to the S.W. of Dillstown, and running forward, with little i 204 SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. interruption, towards the State line, ending in a series of spurs N.E. and E. of Waynesburg. For some few miles from its point of origin, this hilly tract appears to include but one anticlinal flexure, and it probably continues of this simple structure to within three or four miles of the Gettysburg and Chambersburg turnpike road ; but further S. it spreads, takes in a second, and then a third wave, subdividing into separate anticlinal ridges, until three of these branch off in succession, and die away in prongs projecting into the limestone of the Waynesburg Valley. A fourth, called Green Ridge, runs more continuously forward, with one or two hitches in its course, until it is intersected by the State line. The North-eastern termination of the mountain, near Dillsburg, consists entirely of the lower sandstone, the altered slaty belt on the Southern side having disappeared between the Petersburg and Carlisle turnpike and the end of the mountain, in consequence of the subsiding of the axis of elevation. It ends in two principal ridges. In a rough valley between these occurs a yellow porous sandstone, often indicative of iron ore, some of which was found on the surface near the end of the Southern ridge. A little N. of Dillsburg the limestone of the Cumberland Valley folds round the Eastern end of the mountain, and appears on Dogwood Run, S. of Yellow Breeches Creek, where it is covered by the overlapping rocks of the Middle Secondary series, consisting here of the calcareous pudding-stone, or Potomac marble, and altered red shale and red sandstone. Another section across the mountain, more to the S.W., extends from S. to N. along the Baltimore and Carlisle turnpike. The first important stratum of the hills is the usual grey silicious altered rock so common along their Southern side. North of this, about three miles from Petersburg, occurs the dark green slate, with its epidote and white intrusive quartz. Succeeding this is an extremely compact silicious altered slate ; and beyond this, a reddish grey rock, of the same series, containing specks of reddish felspar and small veins of epidote ; and near this the fissile talcose rock, several times mentioned before. North of these we pass a tract of low ground, and then a high rough ridge of sandstone, ascending which we come to Mountain Creek, at Holly Furnace, not now in operation. Beyond this to the N. is another bold ridge, the northernmost of the chain, consisting also of the Primal white sandstone of the lower division, which here resembles closely the same rock as it occurs in Chiques Ridge, on the Susquehanna. The beds here have a steep southern dip of about 70. This dip is evidently,- however, an inverted one, as these are the lower rocks of the formation, and lie N. of a folded anticlinal axis. Between the Northern base of this ridge and the margin of the limestone of the Cumberland Valley, a deep deposit of diluvial matter hides from our view nearly the whole of the slaty or upper division of the Primal rocks ; which, in consequence of its easy denudation, is commonly found in the valley at the foot of the mountain, thus covered by transported matter. Crossing the mountain by another section still further to the S.W., we find the following order of things. Beginning at Cumberland Furnace, and passing to the head-waters of Opossum Creek, the North-western ridges of the mountain, near Cumberland Furnace, consist entirely of the Primal white sandstone. In the ridge N. of Pine Grove the rock is a more talcose sandstone, belonging probably to a higher part of the formation. Large veins of white quartz are here abundant. A whitish talcose slate rests conformably upon the talcose sandstone, dipping with it to the S.E. This latter rock forms an admirable material for the in-walls of a furnace, SECTIONS OF THE STRATA. 205 and is used in that at Pine Grove. Immediately S. of Mountain Creek, near the furnace, occurs a thin interposed belt of limestone, used as a flux, and also taken across the mountain, into Adams County, for lime for the fields. This rock contains disseminated crystals of Fluor- spar. Associated with this limestone is a valuable deposit of iron ore, which has supplied the furnace here for a long time. It is of the kind usually found in our limestone soils, being technically the brown hydrated peroxide, having a variety of structures. The analyses to be given will display the composition of one variety of the ore of this mine. The limestone is evidently one of the beds at the alternation of the Primal slate and Auroral limestone. Passing the low ridge containing the limestone, we encounter a bold mountain of a somewhat talcose sandstone, two miles in breadth, containing probably an axis of elevation with the rocks on its Northern side inverted. On the Southern flank of this ridge occurs a belt of altered silicious rock, including a narrow band of talcose slate ; and S. of this, a zone of green altered slates, charged with epidote and quartz ; and overlying this again, another belt, of a more silicious altered slate. It is interesting to observe the importance which a single belt of limestone will give to a locality. It has here given rise to a rich deposit of iron ore, rendering productive a most beautiful and sequestered spot in a chain of hills, elsewhere remarkable for their forbidding features and sterile soil. The calcareous rock is only developed to any extent near the furnace, though it is said to be visible at Dull's Saw Mill, three miles higher up Mountain Creek. A fourth traverse of the chain by the line of the Chambersburg and Gettysburg turnpike road, displays the following succession of outcrops and exposures of the rocks, and though these are not sufficiently connected to afford data for a structural section, they furnish some instruction as to the materials of which the tract is composed. Leaving the limestone near Fayetteville, and going Eastward across the belt, we meet for the first three miles only fragmentary matter, chiefly of the white Primal sandstone, fine-grained, and weathering flesh colour and yellow, swept down from the hill-sides. Approaching Steven's and Paxton's furnace the prevailing rock is a conglomerate, with pebbles of the size of a pea. The rock becomes finer-grained E. of the furnace, and assumes more the typiftal characters of the formation. Passing Grsefienburg Springs, a little E. of the furnace and the Toll-gate, we encounter the first clear exposure of Primal white sandstone, here in the condition of a bluish conglomerate with pebbles, ranging in size from that of a pea to that occasionally of a large nut. At this spot the strata dip 60 to S. 60 E. A little further on there is a second exposure, where the dip is more uncertain, but where the cleavage is distinctly 80 to N.W. ; the apparent dip is 35 to the same quarter ; the rock is a fine-grained sandstone. Fragments of the coarse bluish conglomerate are next met with, and still further on, in a shallow pit, one may see the Primal slates full of micaceous and talcose partings of a pale sea-green colour ; here the strata dip 85 to N. 30 W., and the cleavage planes 75 to S. 10 E. The summit of the ridge exhibits a dark-blue and greenish-blue indurated rock, weathering a dark brown, and evidently very ferruginous. It appears to be a band of the Primal slate in a highly metamorphic condition, approaching jasper. Its beds dip 45 to N. 70 W. ; its cleavage 60 to N. 70 E. This rock is succeeded by Primal slates, under their more ordinary forms, and 206 SOUTH MOUNTAINS, SOUTH-WEST OF THE SUSQUEHANNA. . the Primal white sandstone, much altered, and with a peculiar fracture ; here the cleavage dips 20 to S. 20 E., the strata apparently dipping at a high angle westward. Approaching Willow Grove Tavern, we meet a more favourable display of the rocks. The white sandstone forming the face of a hill a few hundred yards S. of the road, exhibits, as it sometimes does in Montgomery County, thin laminae, differing in tint, and separated by sur- faces or films of well-crystallised mica. Here the dip is 70 to S. 80 E., the cleavage dipping in the opposite direction. From this point to Cashtown the strata display no outcrops deserving a record here. At Cashtown the rock is partially a conglomerate of a grey colour. Here we meet the margin of the unconformably overlying mesozoic red sandstone. The mountain-gap of the Gettysburg and Chambersburg turnpike divides the altered slaty rocks on the S. from the unaltered sandstone on the N., until in our progress East ward Ve reach the summit, E. of which the altered rocks cross the road, to range North-eastward along the Southern ridges of the mountain. The sandstone ridges which constitute the North-western spurs of the mountain, near Caledonia Furnace, jutting towards Green Village and Shippensburg, ranging North-eastward, become the main body of the mountain, the altered rocks lying on the Southern side. The same bed of altered rocks which lies between Caledonia Furnace and Cold Spring, and which crosses the turnpike South-east of the summit, is seen on the Southern side of the mountain, crossing one of the head-waters of Conewango Creek. Crossing the mountain between Caledonia Furnace and Cold Spring, a distance of seven miles in a S.S.E. direction, no vestige of the white arenaceous sandstone is to be seen, until the foot of Green Eidge, at Cold Spring, is reached. The section displays rocks precisely similar to those on the East side of the mountain, on the railroad at Maria Furnace and at Holm's Creek, showing everywhere marks of alteration by igneous action. In the ridge W. of Caledonia Furnace occurs a talcose sandstone ; and a fourth of a mile S. of the furnace, a highly- altered jaspery slate. Half a mile S. of the furnace, we meet a grey, spotted, silicious rock, evidently an altered sandstone ; two miles S. of the furnace, a grey, altered, silicious rock, with dark blotches ; and two miles N. of Cold Spring, a greenish slate, spotted with epidote, and charged with much white quartz. One mile N. of the same place, a reddish slate, speckled with white, occurs; and half a mile nearer Cold Spring is a red, jaspery, altered rock ; all belonging, probably, to the thick system of slates composing the upper member of the Primal series, but greatly modified in texture by the intrusion of quartz, and by other igneous action. Throughout this section the strata dip invariably to the S.E. Though no anticlinal axis is visible, there is convincing evidence that the rocks have been upheaved along such an axis, and folded together, so as to make those on the N.W. dip in an inverted altitude to the S.E. a feature very common throughout the whole range. FIG. 25. Section across the South Mountains along the Gettysburg EE. 1 inch =3 miles. . czV S. 50 E. A fifth section across the chain is furnished by the exposures of the strata along the Waynes- SECTION GETTYSBURG RAILROAD. 207 burg and Emmetsburg Turnpike, and the cuttings of the old Gettysburg Railroad. Leaving the Auroral limestone of the valley, and entering the hills, the first actual exhibition of the strata met with is a South-dipping mass of Primal upper slates supporting Primal sandstone. These are probably inverted, forming the North-western leg of a wide complicated anticlinal flexure, the South-eastern limb of which would seem to be in the ridge containing the tunnels, several miles to the S.E., where the Primal sandstone and Primal upper slate dip at a moderately low angle South-eastward. Within this anticlinal belt there would seem to be three other anti- clinal flexures, all lifting to the surface different portions of the Primal lower slates, and all showing a prevalence of moderately steep South-east dips, with rather steeper South-east-dipping cleavage. These lower Primal slates are highly indurated, and even decidedly crystalline, con- taining in some of their layers segregated specks, and even half-formed geodes of epidote, and other minerals. They bear strong general resemblance to the half-crystallised older Primal slates, just S. of Spring Mill. Passing now to the Eastward of the Green Ridge Axis, we cross a high slope of slate, apparently the upper Primal in a synclinal fold, and then traverse a succession of outcrops of the Primal white sandstones and slates, to the Eastern base of the high land called Jack's Mountain, at the foot of which the older rocks disappear under the mesozoic red sandstone of the plain of Adams County. The exposures in the sandstones near the Tunnel opposite Jack's Mountain, indicate a probable thickness of 1000 feet. Near the Tunnel at the North-west side of the mountain there is a hard epidotic rock, and not far from it highly-altered greenish slate, a rock found in several other localities further W., and containing layers of grey slate spotted with epidote. Further W. occurs epidote with asbestos. Near Miney Run search was made many years ago for copper ore, but nothing was found to justify the expectation of finding a productive vein of that mineral. A small quantity of copper ore was once obtained, and a furnace built for smelting it, in a small ridge N. of Jack's Mountain, but the exploration was abandoned. The metal occurs in the form of a green and blue carbonate, with a little native copper. Evidently the ore is not abundant. DIVISION II. AURORAL SERIES. IN the South-eastern district, the principal Auroral strata are those of the magnesian lime- stone. The Auroral calcareous sandstone (Calciferous Sandstone of New York) is in a few locali- ties seen emerging from beneath it ; but this formation would appear not to have been continuously deposited in this region. The other rocks of the series, the Auroral argillaceous limestone (Tren- ton Limestone of New York), generally so rich in fossils, as well as the overlying Matinal slates (the Hudson River group of New York), have evidently been removed at an early period, before the deposition of the Mesozoic red sandstone, by wasting waters that spared only the very lowest formations of the Palaeozoic series. In some parts of the district the portion of the Auroral magnesian limestone which has escaped denudation is nevertheless of great thickness, not less probably than 2000 feet. It belongs, however, to the inferior part of the formation, everywhere comparatively destitute of organic remains, even in the more fossiliferous districts ; and to this fact, arising from some general cause, and to the prevailing scarcity of fossils in all the formations throughout the region S.E. of the Kittatinny Valley, we must impute their non-appearance in the belts about to be described. In the region before us there are three principal belts or tracts of the Auroral limestone ; that of the Chester County Valley, that of Lancaster and York, and that of the South Moun- tains, between the Delaware and Schuylkill. A fourth, but much smaller outcrop, appears in the midst of the generally overlying tract of the Mesozoic or Middle Secondary red sandstone, in Bucks County, near New Hope. I shall describe, in the order in which they are here mentioned, these several areas' of the formation, all of which I consider to have been originally connected by portions since washed away. CHAPTER I. GENERAL DESCRIPTION OF THE LIMESTONE VALLEY OF MONTGOMERY AND CHESTER. THIS interesting belt of the Auroral limestone, the borders of which have been already indicated in a previous Chapter devoted to the southern outcrops of the Primal sandstone, is worthy of a more full and connected description than it has yet received. Externally the tract, with its highly cultivated farms, numerous thriving villages, factories, furnaces, and mills full of prosperous industry, presents a scene unsurpassed in the United States. The soft, pictur- esque beauty of the plain or bed of the valley is much enhanced by the two ranges of slate hills, still clothed with the remnants of the natural forest. It lies between these like the deck of a slender shallow boat between its sloping sides. Its surface is in almost every part irrigated with running brooks of pure transparent water, and it is crossed by several swift-flowing, sparkling streams, as large as the rivers of some countries. The grandest of these is the Schuylkill. It is here a broad current, and bears deservedly the title of river. The enclosing hills, or two edges of the general upland, between which this valley lies, at an average depression of nearly 300 feet, are superbly carved into innumerable wooded ravines and narrow dells. This is especially true of the slope overlooking the valley on the South. From any point on the southern table-land near the head of one of its ravines, the view is truly enchanting : broad slopes of foliage and a shady dell fill the foreground of the picture ; wheat-fields and pastures, orchards and snug tidy farm- houses, many of them of the dignity of country mansions, occupy for miles the middle distance ; and the extended background is a rich succession of fading hills and far-stretching mountains. Breaking what might otherwise approach to monotony in the curves of the landscape, are here and there deeper gorges in the north and south barriers of the valley, furnishing waterway for the larger streams, the Schuylkill, the Wissahickon, the Brandywine in both its Branches, and the Octorara. The narrower parts of some of these are precipitous, and so shut in and wild as to present a most grateful contrast, in their tangled foliage, rough rocks, and mossy clifis, with the neighbouring scenes of open pastures and sunny corn-fields. NORTHERN AND SOUTHERN BOUNDARIES OF THE LIMESTONE. This belt of limestone, which forms the Great Valley, and extends through the western half of Montgomery County, through Chester County, and Sadsbury and Bart townships, in Lan- caster County, commences about a mile and a half S.W. of Willow Grove. Tracing it along its southern margin, we find it entering the northern corner of Cheltenham Township, crossing the Bethlehem Turnpike near the Running Pump Tavern, a mile below Flowertown, and thence passing to Spring Mill on the Schuylkill, where it crosses the river and follows Gulf Creek, through Upper Merion Township, into Chester County. After passing the county line, a little less than a mile S. of the Baptist Meeting-house, it follows the foot of the South Valley Hill VOL. I. 2 D 210 VALLEY OF MONTGOMERY AND CHESTER about the same distance N. of Glassley and N. of the Paoli, to within a couple of furlongs of the Warren Tavern, and from thence half a mile S. of the Steamboat Tavern, and some- what more to the N. of the Indian King. Near Downingtown the belt has decreased much in width, being little more than three-fourths of a mile broad. The belt passes about two furlongs S. of the town. From Downingtown, the foot of the hill indicates the margin of the limestone, which passes rather less than a quarter of a mile below Coatesville to Freeman's Mill, on Buck Run ; thence to Cloud's Mill, near Phillip's Tavern, on the Gap and Wilmington Turnpike ; and to the Octorara Creek, near the junction of Cloud's Run. In Lancaster County it follows Cooper's Run as far as the dam near the Valley Mills, but continues along the valley a furlong S. of the stream. We thence trace the same southern margin across the West Branch of the Octorara, about a fourth of a mile below Buckman's Tavern, and thence to Kunkle's and Eckman's Run, at which place the limestone terminates. On Eckman's Farm the line doubles back towards the E., and pursues nearly a straight course, by the Reform Meeting-house, to Buckman's Tavern ; thence running straight to the Octorara, a fourth of a mile above Noble's Factory. The greatest width of the limestone in Lancaster County is not much more than half a mile. Returning into Chester County, the northern boundary continues direct to Parkesburg. At Coatesville it passes one furlong and a half N. of the village. Two miles E. of Coatesville the belt widens, and the northern edge passes a fourth of a mile S. of East Cain Church. Still expanding, the northern margin passes one-third of a mile N. of Downingtown to West Whiteland Township line, where it is within a furlong and a half of the Valley Turnpike ; and thence continues N.E. for about three and a half miles. The width of the limestone, taken along the eastern township line of West Whiteland, is a little more than two miles ; and the northern margin is a nearly straight line from thence to the Valley Creek, which it crosses half a mile from its junction with the Schuylkill. As the belt passes into Upper Merion, it is over- laid on the N. by the red sandstone a portion of which, jutting forward as far as the King of Prussia Tavern, conceals that part of the formation which lies to the N. of Reesville. From thence the northern line continues direct to within half a mile of Norristown, and, turning down towards Swede's Church, crosses the Schuylkill one mile below the bridge. Doubling S. a short distance from the river, it forms, in Plymouth Township, another loop, and then crosses the Ridge Turnpike at the fourteenth milestone from Philadelphia, and the Germantown Turnpike a little more than a quarter of a mile below the fifteenth milestone. It then passes into White- marsh Township, crossing the Wissahickon at Mather's Mill, a short distance below Sandy Run, following the run until it reaches the eastern extremity of the belt in Abington Township, near Willow Grove. Chemical Composition. In its chemical composition this limestone is, with the exception of an occasional stratum, highly magnesian, and many layers contain the carbonate of magnesia in the full proportion (namely, about 45 per cent) requisite to constitute the rock the peculiar definite chemical combination called Dolomite. More usually, however, the amount of carbonate of magnesia is somewhere between 10 and 30 per cent. As a general rule, the lower part of the formation is the most magnesian. This portion contains likewise a larger share of silicious and talcose matter than the beds higher in the series. The lime which this limestone yields, though invariably more or less magnesian, produces, on the whole, a very superior cement, the magnesia present in it giving the mortar the property of concreting with more rapidity than belongs to a Pictorial Section., along Left Banlf of Sdnrvlkill , shewing Malinal Limestone from. Red Sandstone "below Xorristown. to Conslmhocken Dam . Massive, P a, 1 t- I Whte. -fine g-r^ 1 3Ca.g T 1 ' I,-iTrve,s t T A- -i c fe T) & 3, d, e- db Pale 3 I S T, a, fr y L . \eo' W lit ~L t e> a. n A, P cu I e> .B Z- "U. f P r o b ,i ,' t e g of T a ~u- Z a- r Zn-verji/OTt n f ' a ll a TL ' ^ t . 77 Li m, i t i o n- of & r e. '. > THOUGH OF AURORAL LIMESTONE. 211 i cement of lime alone. Many of the more highly magnesian limestones can be made to furnish very excellent hydraulic cements. Geological Structure. The general geological structure of this populous and rich limestone belt, though curious, is extremely simple. Measured from one extremity to the other, the lime- stone, coincident very nearly with the bed of the valley, has a total length of about 58 miles. Its eastern end is just N. of Abington in Montgomery County, and its western at the source of Big Beaver Creek in Lancaster. In form, it resembles very much a long slender fish ; and this likeness is increased when we include as part of it the two spurs into which the bounding narrow sandstone ranges of' Edge Hill and Mount Washington terminate, near the Pennypack, E. of Willow Grove. As pictured in the Map, it resembles a slender gar-fish, fins and all, with its tapering jaws asunder. The widest portion of the valley is between the Wissahickon and Valley Creek, where, from the southern barrier of the Primal slate to the northern margin of over- lapping Red sandstone, the maximum distance is nearly three miles, and the average distance about two and a half miles. From the East Branch of the Brandywine it tapers very gradually and slenderly to its western termination. From the Wissahickon eastward it closes up much more rapidly, ending bluntly from the intrusion of the low anticlinal wave S. of Willow Grove, which spreads it into the broad snout already noticed. Trough-like Dip of the Limestone. The general structure of this first main belt of the Auroral limestone is that of a long and slender basin or synclinal trough, the southern side of which is much more steep than the northern. From the neighbourhood of the Gulf Mills, a little west of the Schuylkill, to its western end, this oblique symmetry prevails with scarcely any interruption. The strata of the southern side of the valley dip perpendicularly, often a little overturned into a steep south dip, but sometimes inclined steeply in the normal direction, or northward ; and it is only towards the western extremity, where the whole trough grows shallow, and rises as it flattens up and thins away, that the north dip ceases to be steep. The strata of the north side of the valley, or from the synclinal axis northward, dip at an average inclination of about 45 southward, or more strictly S. 20 E. But even this inclination is not absolutely constant, for in the wider central division of the valley this northern part of the trough contains in some places one or two short, low, and narrow anticlinal waves. Between the Schuylkill and the eastern termination of the basin, the general simplicity of the synclinal structure is much more frequently interrupted by the presence of included anti- clinal flexures, the more prominent of which as, for example, those of the Conshohocken Ridge, or Bethel Hill, Barren Hill, and that of the Church Ridge, with others already described lift to the day conspicuous local outcrops of the Primal upper slate and white sandstone. This eastern end of the basin is obviously much more undulated than its central and western portions, and the greater frequency of compressed waves in the strata is evidently connected with that longitudinal prolongation of the still sharper folds which corrugate the narrow zone of Gneiss embraced between the Attleborough sandstone range and the southern edge of the red shale. It is indeed but a local exemplification of a very general fact, that of the westward declension and cessation of the stronger crust-plications entering Pennsylvania from New Jersey. The position of this great synclinal trough between two sets of flexures, one set entering and enclosing it from the N.E., the other from the S.W., proves its relation to the same general cause which has preserved the troughs of coal, converting them to anthracite in a part of the Appalachian Chain 212 VALLEY OF MONTGOMERY AND CHESTER just opposite. Indeed the whole tract of the Atlantic Slope and the Appalachians, embraced between the Delaware and Lehigh on the N.E., and the Susquehanna on the W., is a tract of general depression of the crust lying between the two more uplifted districts, that of the mountains of New Jersey and New York on the one hand, and that of the Blue Kidge and the Juniata on the other. If, while inspecting the geological map of the State to assist our conceptions, we lift away in imagination the superficial deposit of Mesozoic red shale and sandstone concealing a part of the older rocks of the Atlantic Slope, we shall perceive this sinking and dying-out of the north-eastern and south-western groups of anticlinals much more obviously. It is to this fortunate abatement in amount of vertical uplift of the crust in the district between the Delaware and the Susquehanna, that Pennsylvania is indebted for the inestimable advantage above her sister States to the N.E. and S.W., of so remarkable an extension southward, or towards the tide, of her fertile and iron-yielding Auroral limestone ; and it is to the same cause that she owes her inexhaustible basins of anthracite nearer to the sea- board markets by very many miles than any of the other Appalachian Coal-fields. CONDITIONS OF METAMORPHISM OF THE LIMESTONE. Throughout this limestone basin, the southern steeply upturned outcrop exhibits a far higher degree of metamorphism by heat than the northern, and this alteration appears greater where the strata approach most nearly the vertical position, and is greater still where they are inverted, that is to say, between the Wissahickon and the Brandywine. It is chiefly within these limits that the elsewhere bluish and yellowish limestone is in a condition of crystalline and granular marble, white, shaded, or mottled, from the dispersing and segregating action of a high temperature upon its changeable ingredients. An examination of the Map and Sections will show that all the marble quarries hitherto opened are included within this steeply upturned or overturned outcrop, the best of them lying within half a mile of the southern edge of the formation, or of some sharp inverted anticlinal like that of the Conshohocken Ridge. It is likewise along this most convulsed and cleavage-intersected side of the trough that, from the same cause, as will hereafter be explained, nearly all the largest, deepest, and richest deposits of brown iron-ore or haematite have hitherto been met with. Throughout the northern half of the basin, especially where the limestone observes its usually very regular southward dip of seldom more than 45, the rock is in the condition of a sub-crystalline, and even earthy or purely sedimentary magnesian limestone, and its bedding is for the most part very uniform and rather thick. Its colour is a pale greyish blue, except in neighbourhoods like that on the Schuylkill below Norristown, where a partial metamorphism has approached the northern border, and it is then, very frequently, a pale straw-yellow and bluish white. The interleaved thin layers of argillaceous matter which so frequently separate the beds of the limestone are in the condition of an indurated clay -slate, but seldom show even incipient crystallisation. In many instances wide bands of the limestone, along its northern outcrop, exhibit numerous cross- joints intersecting the beds in nearly all directions, and causing the rock in certain quarries to break into a mere rubble of small angular fragments, assisting much the labours of the quarry- man and limeburner; but these joints, and the before-mentioned semi-crystalline texture, are the METAMOEPHISM. QUARKIES. 213 limits to which the metamorpliism of the rock has reached, a true parallel slaty cleavage being seldom or never, discernible. But the state in which the very same beds exist, where they rise perpendicularly or with inver- sion to their southern outcrop after passing the synclinal turn in the centre of the basin, is very different from all this, and in striking contrast. The faintly crystalline and earthy limestone is here a distinctly crystallised, often a granular marble. Its colour is changed to a brilliant white, or to a mottling of purely white and dark blue, from the presence of segregated or half-developed graphite ; and the dispersed ferruginous matter is here in a state of mimite solitary crystals of sulphurate of iron disseminated through the body of the stone. The rock, instead of lying in thick, often massive beds, is cleft into thin plates by innumerable natural fissures or cleavage- planes, not parallel with the stratification, but dipping steeply southward or acutely across it, and these fissures are filled and lined with distinctly crystalline flaky talcose and micaceous matter, sometimes talc and mica fully developed. The partings of slate between the limestone layers have been converted to laminae of talc-slate, in which there is often a cleavage-structure distinctly dis- cernible, much more intimate than that in the altered limestone, but dipping in parallelism with it. Viewed edgewise, a fresh exposure of the most altered limestone, such as is visible on the River Schuylkill near Conshohocken, has the aspect of a blue and mottled marble, streaked with films of talc, and shivered by innumerable cleavage-joints ; but viewed face-wise, the layers and fragments have the aspect of a talcose or micaceous slate, so copious is the covering of talc and mica upon their surfaces. (See Sketches of the Quarries.) QUARRIES IN THE LIMESTONE, AND OTHER PRACTICAL DETAILS. The portion of the formation which enters Abington Township is more slaty and fractured than that further to the W., and it also contains a larger amount of silicious or sandy matter. Those portions of the rock which are exposed, or are nearest to the surface, have in many places undergone partial decomposition, and have the appearance of a white calcareous sand. This sandy aspect of the limestone may be observed in all the quarries in the neighbour- hood of Sandy Run, and also at many other localities. Unless the rock has undergone partial decomposition, the limestone is crystalline and granular. It varies in colour from blue to white, as a greater or less amount of carbonaceous matter chances to enter into its composition. Each of these colours is not confined to a particular stratum, but changes repeatedly in the same bed ; and, indeed, the area occupied by one particular colour is usually very small. The dip throughout the whole formation is remarkably uniform. Near Sandy Run it is towards the S. and S.S.E. Quarries and pits have been opened on almost every farm along Sandy Run. One of the largest in this vicinity is on the farm of Mr Fitzwater, near Fitzwatertown. The limestone is chiefly blue, the dip S.S.E., at an angle of about 60. On the turnpike opposite Sellerstown, a limestone quarry of some size is wrought, the rock making an excellent lime. An extensive quarry of the same nearly white variety of the limestone exists on Mather's farm. There the beds are crossed by very regular joints, giving the appearance of a stratification in another direction ; the true dip is towards the S. Near the Germantown Turnpike, about a fourth of a mile above the Plymouth Meeting-house, are good lime- stone quarries. Much of the stone in this neighbourhood is beautifully white, though some layers occur having a more or less bluish tint. The weathered surface of many beds is rough and sandy, showing some silicious matter in the rock. Spring Mill. North of the Furnace 200 yards there is a large quarry in the limestone near the southern edge of the formation, in which the dip is 85 to S. 10 E. The southern side of the quarry is massive and jointed, and the dip planes are almost effaced ; the northern side is more thin-bedded and talcose, of a bluish-white colour, and its struc- ture very crystalline. In that portion of the Limestone Valley which occupies the southern part of Upper Merion Township, especially 214 VALLEY OF MONTGOMERY AND CHESTER. in the immediate vicinity of the Schuylkill, there are numerous and extensive quarries, furnishing a large supply of the rock, a portion of which is transported to Philadelphia, and other places, by the several railroads and the Schuyl- kill navigation ; but a large amount is converted into lime on the spot, designed for the same markets. A large quarry of the limestone is wrought on the west side of the Schuylkill, two or three miles below Valley Forge, where the rock is tolerably thick-bedded, and of a light colour. The quarried stone is conveyed to the river by a railroad, and thence taken by boats to the various limekilns. Extensive quarries have also been opened near the Valley Church, where the limestone is very similar to that of the last locality, dipping steeply south, being of a light tint, and furnishing an excellent lime. On the road from Glassley to Valley Forge, near the county line, there is a small bed of slaty talcose calcareous rock extending E. and W. about three furlongs in length towards Valley Creek. It constitutes a small hill, over the east end of which the road passes. Near Valley Forge occurs a stratum of felspathic rock like that seen at Barren Hill. It is exposed in the Creek, and occasionally appears overlying the Primal white sandstone at the foot of the North Valley Hill, a little East of the North Valley Church. The limestone near the White Horse Tavern in East Whiteland Township is occasionally talcose and slaty. Nearer the Steamboat Tavern the more usual granular structure prevails : throughout all this range, however, the rock yields an excellent lime. At Downington the limestone is chiefly of a light colour, and compact. Several quarries of compact and granular limestone have been opened in this vicinity. The width of the formation near the East Cain Church is reduced to about three-fourths of a mile. It is somewhat variable, being dependent, probably, upon the angle of the dip, which, however, is pretty constant. At Coatesville it does not exceed three furlongs. At Bell's Quarry, Midway, the rock is of a light colour. About one mile east of Trueman's Mill, we find a small bed of white clay, derived from the decomposition of an altered felspathic slate, lying between the limestone and the talc slates. In the vicinity of Buck's Run and Parkesburg the limestone becomes darker and more slaty. Passing Cloud's Mills into Lancaster County, it gradually declines in thickness, being at Cooper's Fulling Mill, in Strasburg Township, not more than two furlongs wide. At its termination in Bart Town- ship it becomes more than usually sandy, especially near its margin. The main belt seems to terminate on Eckman's Run ; but another small lenticular belt shows itself a mile and a half further to the west, on the premises of Mrs Bare, where the rock is quarried. The practice of the landholders is to let out the right of working the quarry for a certain period, and the tenant during that time may excavate as much stone as he may require. Many quarries also are opened and worked by the proprietor for his individual supply. No record is therefore kept to enable us to ascertain the number of perches annually quarried. TRAP-DYKES. Near the Meeting-house, about a mile above Flowertown, a trap-dyke crosses the Bethlehem turnpike in a N.E. and S.W. direction. It appears to contain labradorite. It is about two and a half miles long, commencing near the north-west line of Springfield Township, and ranging past Bickell's Mill, on the Wissahickon, to the School-house half a mile further "W. The protrusion of the dyke has not disturbed the adjoining strata to any serious extent. A marble quarry has been opened S. of the dyke, near Beck's Mill. The rock is granular, and its predominant colour is bluish. Crystals oifluate of lime occur in this quarry. About half a furlong N. of the dyke there is another quarry on Bickell's Farm, in which the beds are somewhat contorted. Another dyke of trap crosses the Schuylkill near Conshohocken : commencing a little E. of the Perkiomen Turnpike, about half-way between Barren Hill and Marble Hall, it crosses the Norristown or Ridge Turnpike, ranges nearly along the crest of the Conshohocken Slate Eidge, goes through the village, and passing the river, in the bed of which it may be seen, it follows the summit of Bethel Hill into Delaware County, terminating near the road leading from the Lan- caster Turnpike to the King of Prussia Village. This is by far the longest and widest trap-dyke of the valley or its borders, its length being a little more than six miles. MAKBLE. 215 OF THE MARBLE OF THE LIMESTONE BASIN OF MONTGOMERY COUNTY. The quarrying of marble iu this district was commenced about 75 years ago, by Daniel Hitner. For the last 15 or 16 years the average quantity sent from the quarries of Marble Hall, owned and wrought by the present proprietor, Daniel 0. Hitner, has been about 25,000 cubic feet. The belt of marble is nearly three-fourths of a mile wide. Marble Hall, on the Perkiomen Turnpike, is the east- ernmost point at which good building-marble is wrought, though the belt is known to continue further. It extends thence to the Schuylkill nearly to the Chester County line. The largest quarry of all is that of Marble Hall ; here the strata dip to S. 20o, E. about 85, presenting in one or two places a flatter inclination. This quarry is not less than some 400 feet in length, and at the top is 60 or 70 feet wide. The greatest depth to which the quarry has been sunk is 265 feet. At this depth were procured the blocks of beautiful white marble sent by direction of the State of Pennsylvania, and by the City of Philadelphia, to the great monument at Washington. At this depth the stratum of white marble, for which this quarry is chiefly wrought, has a thickness of 5 feet ; but the usual thickness of this bed of pure white stone is 8 feet, that of the pure and clouded white together being generally about 20 feet. Mr Hitner has quarried blocks 6 feet in thickness, though the general thickness of the blocks readily procurable does not exceed 2| feet. The only saccharoidal or statuary marble in this or any of the quarries, is found here at a depth of 120 feet, in a layer of only 6 inches in thickness. It is of a yellowish white colour and remarkable evenness of grain. The white marble is used for monuments, and for the finer architectural purposes. It now sells for about one dollar per cubic foot. To the south of the large quarry of Marble Hall, which, besides the white marble, yields much beautiful clouded or shaded stone, there is a quarry of blue and black marble, distant about 300 yards. This is owned by Mr Leutz, but now wrought by Daniel 0. Hitner. This blue and black marble now sells for about 40 cents per cubic foot. It is used chiefly for fronts of buildings, for monument bases, &c. The thickness of the good blue marble in this quarry is 22 feet, and that of the black variety 8 feet. Besides these quarries in the vicinity of Marble Hall, there are others about three-fourths of a mile north from Spring Mill ; one set owned by Robert T. Potts, another adjoining his by Mr Peter Fritz. The marble of Potts' Quarry is chiefly of the clouded variety, besides a little white and some plain blue. The annual yield of this quarry is about 12,000 cubic feet. The quarry owned by Fritz is at present but little wrought. Next in position to the westward, but still seated in the same belt, are two quarries westward of the Schuylkill ; these are Henderson's and Brook's, in Upper Merion Township. Henderson's, the nearest to the Schuylkill, affords a plain blue marble, besides a little white. Both of these quar- ries are wrought at present to only a moderate extent. A little south of the Valley Turnpike, about three and a half miles E. of Downingtown, is the extensive quarry of superior white marble which has for many years supplied Philadelphia with the beautiful article employed in so many of its public and private edifices. It is on the farm of Mr John R. Thomas. The beds on this quarry are slightly contorted. The portion worked for the marble separates into two bands. The rock occurs in massive beds, chiefly white, with sometimes a bluish tinge, and is quarried with great facility. It has been much used in the construction of the Girard College and other public buildings which adorn Philadelphia and the neighbouring towns. This marble is converted into a good lime, but its crystalline or granular structure causes it to crumble in the kiln, making it a little difficult to manage. The lime from this variety is much esteemed by masons, being sold in Philadelphia under the name of Fish-eyg Lime. The blue-mottled limestone or marble of Whitemarsh, occurring at the quarries not more than three-fourths of a mile north of the northern limit of the Primal Strata, is evidently on the south side of the trough, or folded synclinal axis of the district. This is further proved by its great steepness of dip, about 80. It is, moreover, of the maximum degree of metamorphism or crystallisation ; contains talcose or micaceous lamina), and crystals of sulphuret of iron, V call-, mica Slate sandstone, probably the Primal white sandstone altered. It dips 45 to N. 15 W. North of this sandstone there is a band of ore at the South foot of the River Hill, or in a straight line about one-half of a mile from the river. But the main range of the ore is just at the South foot of the tract of high ground occupied by the sandstone. The ore lies in decomposed sandy LOCAL LIMESTONE BASINS. 219 talco-micaceous slate between the sandstone, and an outcrop of limestone South of it. This important range of ore has been proved, and opened for a length of about half a mile. Its strike is N. 70 75 E. The accom- panying section exhibits the relations of the three ranges of ore of this vicinity to each other, and to the strata with which they are connected. Mylin's Ore-Pit is an open excavation for ore at the junction of the limestone and black slates, in the little insulated limestone basin which crosses the Pecquea, at the mouth of the Big Beaver Creek. It is among the alternating beds which connect the two formations. This was a recently opened bank in 1854, and the product in ore that year did not exceed 3000 tons ; but the succeeding year it yielded about 1 00 tons per week. The ore itself is of only moderate richness. It is conveyed at present to Lancaster. The Conewango Ore-Bank occurs likewise at the junction of the Auroral limestone and the Talco-Micaceous slates of the Primal series. Magnesian limestone outcrops within 100 yards South of the Mine Shaft, which has a depth at present (1854) of 54 feet. There is an open pit with an inclined plane for elevating the ore, the shaft and engine being used for pumping. The ore itself exhibits here a rather solid mass not very regularly bedded ; it is in fact the ferruginous slate disintegrated, and re-cemented by the action of the surface-waters, the whole mass consisting of more than one-third part of earthy matter. The ore itself has a richness of about 40 per cent metallic iron, and it is said to produce a metal of excellent quality. It is smelted at the Conewango Furnace, and also at York Furnace. The same year the product of the mine was 150 tons per week; the bottom of the mass of ore had not been reached in the pits. A small insulated patch of the limestone has escaped denudation on the Little Beaver Creek, near the Fulling Mill, about two miles from Strasburg. No ore has been found in its vicinity. CHAPTER II. AURORAL LIMESTONE OF LANCASTER AND YORK COUNTIES. IT is unnecessary to define in this place the very irregular boundary of this extensive tract of the Auroral limestone. Its Southern margin has been already traced in describing the Northern border of the Gneissic region, and its Northern limits will be given when we come to specify the outlines of the overlapping Red sandstone. Meanwhile an inspection of the Geological Map will convey a sufficiently exact idea of its shape and position. Except in a few localities, the strata of this belt exhibit a less degree of metamorphism than belongs to the great altered tract last described. Though evidently much acted on by heat, their transformation has not amounted to a crystallisation, and a change of its blue hue to the white or mottled tint. In some places, however, the igneous action has accomplished this, and imparted to the more argillaceous seams the composition and aspect of a talcose slate. It has been already mentioned, that this tract of limestone is traversed in an East and West direction, by a number of anticlinal axes. Many of these are closely-compressed folds of the strata, and such are not continuously traceable without great difficulty. The general Sections, from V. to VIII. inclusive, will sufficiently explain its structure with the aid of the Map. In con- sequence of the inversion of the beds, forming the Northern side of each anticlinal flexure, the whole district shows a prevailing Southern or South-eastern dip, but at the same time, much inequality in the degree to which the rock is broken in different localities. In a district like that of the valleys of Lancaster and York, where the limestone is very extensively employed for building, and for conversion into lime for the soil, it is of the utmost practical importance, in seeking for a suitable site for quarries, to give close attention to the situation of the places in relation to the anticlinal flexures. It will be found to be almost invariably the fact, that the strata lying to the S.E. of each anticlinal axis, and possessing a rather moderate inclination towards that quarter, are more free from irregular joints, and less crushed and shattered, than those upon the turn of the axis, or belonging to the inverted or northern side. Where sound rock is desired, the first position should be sought, and where broken stone is wanted, the latter. In its chemical composition, there is no difference between the rock of this tract and that of the Chester County Valley. Investigations in the laboratory have shown it to contain quite as much magnesia in the corresponding parts of the formation. Many of the inferior layers, those, for example, which are exposed on the Lancaster and Harrisburg Railroad, upon the prolongation of the anticlinal of Chiques Ridge, are so magnesian as to be regarded as almost a true Dolomite. The lower portions of the Auroral magnesian limestone are perhaps nowhere in this district better exposed than on the Susquehanna River below Columbia, near Strickler's Run, where they are seen passing, by a gentle gradation, with alternations, into the upper strata of the Primal series. An anticlinal in the ridge N. of Charlestown lifts the Primal sandstone to the level of the river, and from this point for half a mile N. to Strickler's Run, the Primal newer slate is exposed with a steep inverted and somewhat contorted dip, and an excessive amount of cleavage. TRAP DYKES. 221 At Stickler's Run we meet with the lowest members of the Auroral limestones. Commencing with it, and proceeding northward, the strata are as follows, in the ascending order : 1 . Limestone, apparently very magnesian, sub-crystalline, of a light blue colour, with white spots and streaks. Dip nearly vertical and parallel ; thickness, 150 feet. 2. Blue talcoid slate, about 200 feet thick. 3. Limestone, mottled blue and white, and coarsely crystalline ; thickness, 15 feet. 4. Dark blue slate ; 20 feet. 5. Limestone, crystallised and brecciated ; the fragments flat, white, and coarsely crystalline, cemented by blue and less crystalline limestone. The occurrence of altered fragmentary limestone so low in the formation is not a little curious. 6. Bluish talcoid slate, 200 feet. 7. Limestone, crystalline magnesia, blue With whitish blotches. Dip nearly vertical, rather towards the South. It is intersected by irregular cleavage- planes, dipping generally 75 S. This outcrop is at the head of the sluice-way of the Columbia Dam. On the Northern side of the synclinal trough contained between the anticlinal below Strickler's Run and that of Chiques Ridge, some of the same beds reappear. The lower members of the limestone, those in alternation with the higher Primal slates just above Columbia, have been already treated of. These lower beds are seen in the corresponding part of the formation opposite the ends of Welsh Mountain and of Chiques Ridge. In relation to the cleavage, so conspicuous in the strata in this vicinity, a marked difference is observable between its dip on the two sides of the synclinal basin of Columbia, that of the steeply-dipping inverted rocks of the Southern anticlinal having, as we have seen, an inclination of 75 S., and that of the more gently-dipping beds of the Southern side of the Chiques anticlinal, a steepness of only 45 S. This is one instance among many proving that the original planes of deposition have exerted some degree of control over the subsequently-formed cleavage-fissures, tending to approximate them to parallelism with themselves. The most Eastern appearance of the limestone in the large tract before us, is in the narrow valley of the Eastern Branch of Conestoga Creek, at a point three miles E. of Morgantown. Here the formation emerges from beneath the Mesozoic red sandstone, at the foot of the Welsh Mountain. The limestone along this valley has a general dip to the N.N.W. It varies in colour from blue to white and pink, and in some places is much mottled. These deviations from the ordinary blue tint, indicate more or less igneous actions, and a greater or less proportion of magnesia and other extraneous ingredients. Some of the striped and mottled layers would yield a marble of a pleasing aspect, susceptible of a moderately good polish ; but the difficulty is to discover among the north-dipping strata, an outcrop of beds sound enough to be quarried successfully, so generally is the rock, in this position, seriously shattered and jointed. Trap Dykes, &c. Near Morgantown, the strata are contorted. Layers of chert are here met with, embedded in the limestone. In this valley there are three dykes of trap-rock, all observing nearly a N.N.E. and S.S.W. direction. 1st, The first of these occurs a little E. of Churchtown. It has not perceptibly affected the texture of the limestone with which it is in contact. 2d, The second originates at the Conestoga Creek near Pennytown, and extends for more than one mile in a S.S.W. direction. 3d, The third crosses the Waynesburg and Lancaster Turnpike, about half a mile above the Sorrel Horse Tavern. Approaching New Holland, the 222 AUROKAL LIMESTONE, YOEK COUNTY. 4 limestone becomes silicious, and is much intersected by veins of igneous quartz, the fragments of which strew the surface. About a mile N. of the end of the anticlinal of Welsh Mountain, there is a belt along which the strata are nearly horizontal, marking the centre of the basin N. of that ridge. The city of Lancaster is situated upon a tract of deep blue limestone, containing thin seams of talcose slate, all dipping 60 S. This belt is the prolongation of the south-dipping zone of the Southern side of the anticlinal of Chiques Ridge. The rock contains much sulphuret of iron in cubical crystals, the decomposition of which has imparted to the soil in many places a dark brown ferruginous hue, and has been the obvious source of the iron ore disseminated in numerous small deposits throughout the neighbourhood. Near Millerstown, and also about three miles W. of Lancaster, there are several small dykes of trap-rock, which appear to have influenced, though very locally, the dip of the limestone in contact with them. Around Litiz the prevalent dip is towards the S. and S.S.E. Near Euphrata a quarry was opened a number of years ago, from which were obtained some good pieces of marble of a very light blue tint, and some of it decidedly shaded. A considerable quantity of chert occurs at this locality. Auroral Limestone in the Valley of York. Passing to the Western side of the Susquehanna, we observe that the belt of limestone is there much contracted in its width. Its Southern margin is near Creitz's Creek, below Wrightsville. Here it is quarried on the South side of the creek ; another large quarry occurs on the North side of the same stream ; while a third, in which we find some beds of variegated limestone, is wrought a little N. of the bridge. The Northern- most exposure of the rock near the river, is in a quarry a quarter of a mile above the bridge. The limestone here is nearly white, and has the aspect and texture of a marble, but is much traversed by cross joints, and is hence difficult to procure in large blocks. From this vicinity towards York, we notice several varieties of the limestone, some belts of which are highly magnesian. The town of York is scarcely a mile from the Southern border of the limestone ; and the excavation for the railroad, a little S. of the town, shows it to be slaty, denoting its passage into the slate on the S. North of the Codorus it is extensively quarried and converted into lime. One mile N.W. of the town are extensive quarries, in one of which occurs a beautiful flesh-coloured marble, but not in beds thick enough to be profitably wrought. On a hill half a mile W. of the town, a variegated, silicious, and calcareous rock is quarried for a building-stone. That part of the limestone belt S. of the Pigeon Hills ranges between their Eastern end and the slate ridge to the S., and passing by Spring Forge, advances towards Hanover. S.W. of the forge, the belt becomes quite narrow and interrupted by bands of slate ; but it may be traced continuously between the Slate Eidge, or " Barren Hills," on the S., and Pigeon Hills on the N. Iron Ore. A belt of iron ore is traceable along the Southern edge of this limestone, near the slate, for several miles. It passes a little S. of Hanover, and thence towards Littlestown. This ore was mined many years ago, but lay long neglected, owing to the inferior quality of the iron which it produced when smelted with charcoal, in consequence, chiefly, of its containing a considerable portion of the oxide of manganese. It occurs in quantity in a small hill two miles S.W. of Hanover, and at many other localities, and of late years has been successfully mined on a large scale. LIMESTONE, ADAMS COUNTY. 223 The red sandstone passing from the West end of the Pigeon Hills, encroaches upon the lime- stone as it advances S., until, near Arnold's Mill, at the State line, it overlaps the whole of the formation. Along the Southern base of the Pigeon Hills, in the slates N. of the margin of the narrow zone of limestone already traced, we find another belt of iron ore, of less length than that on the South side of the limestone. At Moul's, five miles N.E. from Hanover, the ore was dug about forty years ago. Much of it is scattered about the fields. Huge rocky concretions of ore pro- trude themselves at the base of a spur of the Pigeon Hills, about three-fourths of a mile to the N.E. The thickness of this deposit of ore is very great, not less perhaps than 100 feet ; but the mineral is extremely silicious. Limestone, The Northern border of this division of the limestone, after ranging along the Southern side of the Pigeon Hills, folds round their South-western termination, and meets the overlying red sandstone on their Northern declivity. Extensive limestone quarries, producing a valuable lime, occur near the end of the hills. A limestone quarry exists on a farm near Cone- wango Chapel. Some of the beds yield a fine, compact, light-coloured variety, promising to be susceptible of a good polish as a marble. It affords a good lime. The Northern division of the limestone is overlapped, as we have said, along the Northern base of the Pigeon Hills. It appears, however, a little E. of King's Tavern, ten miles from York. The course of the Southern margin of the overlapping red sandstone from this point is nearly N.E., passing within two and a half miles N.W. of York. Between York and the spot at which the limestone disappears at the base of the hills, it is much traversed by small ranges of slate. The anticlinal ridge, consisting of the white Primal sandstone and slate prolonged from Chiques Eiclge at the river, ranges along the Northern edge from Wrightsville nearly to York, within a mile and a half of which it terminates. The limestone folds round its Western end, and extends North-eastward between this ridge and another of silicious slate, running Westward from the Codorus. These uniting, the limestone ends in a point N. of the belt of silicious slate just mentioned, which belongs, apparently, to the upper portion of the Primal slate. We find another small wedge-shaped tract of the limestone crossing the river below Bainbridge, and extending Westward about a mile, when it is overlapped by the red sandstone, about a mile N. of New Holland. About half a mile W. of the river, near its Southern margin, we find lumps of iron ore in the soil. Auroral Limestone, at the Southern Base of the South Mountain in Adams County. There is a narrow outcrop of the limestone near the foot of the South Mountain in Adams County, which, being of some economical importance to the agriculture of the neighbourhood, merits a brief description in this place. The most North-easterly point at which we observe it is about a mile and a half north of Petersburg, where a beautiful white and compact variety is opened in a quarry. About half a mile S. of this, on the opposite side of a trap-ridge which intersects the formation, are other quarries. The rock is here of a light grey colour and remarkably soft, having been further removed from the influence of the once heated trap-rock. Another extensive quarry occurs in the same neighbourhood, two miles N.W. from Petersburg. Much search has been unavail- ingly made for limestone among the hills near the base of the mountain, ten or twelve miles Westward of Petersburg. The lime at present used is all brought from this latter place. 224 INSULATED TRACTS OF LIMESTONE. The next point at which we notice the limestone is about two miles N. of Fairfield. The rock here is of several shades of colour purplish, greenish, and some of it nearly white ; it is also crystalline. On the West side of the Middle Creek, below Myers' Mill, it again shows itself, but is not quarried. The paucity of the exposures of limestone through this belt of country is due, unquestionably, to the extensive manner in which the older rocks are overspread by the Middle Secondary red shales and sandstones overlapping everything as far as the base of the hills. SMALL INSULATED BELTS AND QUARRIES OF LIMESTONE SOUTH OF THE MIDDLE SECONDARY RED SANDSTONE. In the district S. of the Middle Secondary red sandstone, there occur scattered, especially through Chester and Lancaster, a multitude of small patches closely-folded basins I conceive them to be of the Auroral limestone, bordered in some instances', though not in all, by the Primal white sandstone. S. of the Chester County Valley they lie almost invariably within tracts of the semi-metamorphic rocks, or crystalline Primal slates, but N. of that Auroral basin many of them are in the midst of what appears to be gneiss. Proceeding in our description of these from E. to W. as usual, it will be convenient, for the purposes of classification, to note and trace those first which belong to the districts S. of the synclinal troughs of the Montgomery and Chester Valley and the Lancaster Valley, and then to review those that appertain to the Gneissic region of the Western part of Chester County. It will be seen, I think, that by far the greater number of these insulated outcrops and small basins of limestone, though probably not the whole of them, are, with whatever rocks they are in contact, only outlying patches of the great Auroral limestone of Southern Pennsylvania, folded, metamorphosed, disguised, and mineralised by intense igneous action, or that transforming agency which invaded all the older formations of the district in which they occur. Many of the lesser and more insulated of these outcrops of limestone show them- selves only in solitary quarries, but even in the great majority of such instances the topographical and geological structure of the adjoining ground strongly imply the existence of smaller or larger basins, or true synclinal troughs, resting sometimes on the gneiss, but in most cases embraced as folds within the talcose micaceous slates, which, upon the view I have adopted of the metamorphism of our rocks, are only the upper and lower Primal slates of the base of the Palaeozoic system altered and crystallised. The limestone of these tracts exhibits all gradations of metamorphism, from the first change from earthy limestone to compact crystalline clouded marble, on to granular limestone and dolomite, and even to the most coarsely-crystallised calc-spar, with segregated crystalline graphite. In some cases the rock is almost pure carbonate of lime ; in others, it is a ' true dolomite, or double carbonate of lime and magnesia. In some instances, again, it is free from any foreign minerals ; while in sundry other cases there abound numerous mineral species in all stages of segregation or development, from the most vaguely-formed crystalline nuclei to the most perfectly definite crystals. In certain examples we may distinctly trace the minerals through all these gradations of evolution, while in other instances we can ascribe their presence only to intrusive veins of true igneous or volcanic matter, bringing the foreign substances into the limestone, or commingling them with it. The most Eastern locality of crystalline limestone in the district of the State we are now studying, is that of G. Vanartsdalen in Bucks County, about three miles W. of Attleborough. This should properly be enumerated among those in contact with the Gneissic rocks, for it is surrounded by hard crystalline hornblende gneiss. It stands aloof, at a distance of one mile, from the Edge Hill zone of Primal white sandstone which traverses Bucks County South of Attleborough. A hornblende gneiss is in contact with the limestone both N. and S., and even splinters and small blocks of the dark gneiss are involved in the crystalline limestone, as if ruptured from the walls of a fissure, through which the carbonate of lime of the quarry and the included minerals may have gushed up. Some of the thinner of these flakes of gneiss are excessively contorted and folded, indicating the whole mass to have been at one time in a pasty state, and so heated and squeezed as to have softened and QUAERIES SOUTH OF CHESTER VALLEY. 225 folded the included gneiss. The limestone itself is a white crystalline mass, consisting of true granular lime- stone, granular dolomite, and calc-spar, full of specks of perfectly and imperfectly crystallised pure graphite, and replete with a variety of other interesting minerals. Some of these extraneous minerals exist as solitary crystals invested by the limestone, but the chief part occur in bunches and irregular veins through the general calcareous mass. It would seem as if some of these bunches and vein-like included masses had been elaborated from the materials of the gneiss caught in and melted up with more or less of the elements of the limestone. We are naturally led to this inference when we find that we can trace a regular gradation from the percep- tibly stratified gneiss into these contorted strings and bunches of the crystalline minerals surrounded by or dispersed through the limestone. Some of these veins or strings of mineral matter present themselves in one part as true veins of felspar, modified at its edges by the presence of much crystallised mica and graphite. These felspar injections consist of tolerably pure labradorite. In some places the limestone includes large bunches of serpentine, associated with talc and other magnesian minerals. The presence of these naturally suggests a possible origin by segregation, either in full or in part, from the dolomitic layers of the originally magnesian limestone. The quarry also includes blotches and little nests of calc-spar and serpentine, and again of calc-spar and coccolite, sahlite, scapolite, and sphene. Mica occurs in several beautiful varieties, and graphite both in large regular hexagonal crystals and in curved irregular plates, and also in fibrous bunches. It is worthy of remark that neither brucite nor spinel seems to occur here, though some of the conditions and associations are such as to suggest at first a hope of finding them. The whole exposure of the limestone is between 200 and 300 feet long, and about 50 feet wide, and the quarry is opened on the South side of a small valley at the base of a low bordering hill. This valley may possibly be the remnant of a trough or basin of stratified magnesian limestone invaded by igneous injections along its Southern margin, and the fused and metamorphosed portions, as exposed in the quarry, may be almost the sole remnant of the mass reserved to us from a wasting denudation. LIMESTONE QUARRIES OF CHESTER COUNTY SOUTH OF THE GREAT VALLEY. BELT FIEST. Giving our attention now to the limestone basins and quarries of Chester County S. of the Great Valley, we find that they nearly all lie to the W. of the Brandywine, and are so related as to constitute or to suggest the existence of at least 6 or 7 long and narrow limestone troughs or basins. Brown's Quarry. The most Southern of these within the State is a narrow trough ranging S.W. length of more than two miles, from near the Delaware State line to near the forks of Whitely, or Whiteclay Creek. This narrow belt is bordered on both sides by gneiss, chiefly of the hornblende kind. Three principal quarries occur in the tract. The first encountered in going S.W. is Brown's Limestone Quarry, on a tributary of the East Branch of Whitely, near the Delaware line. It contains but little of the pure white limestone, the rock being much metamorphosed, and rather full of mica. It is, however, regularly stratified, and the lime furnished is well adapted for agriculture. I). Nevins's Quarry. This is situated to the S.W. of the preceding about three-fourths of a mile, being on the E. side of the East Branch of Whitely Creek. The strata dip at a gentle angle South-eastward, and a low anticlinal undulation or saddle lifts the talcose slates underlying the limestone to the level of the bed of the quarry, proving the total thickness of the limestone not to exceed 40 or 50 feet. This quarry likewise contains a small amount of white limestone, much brown mica occurring throughout the upper beds. It yields, however, a pretty good lime. The limestone is overlaid by the ordinary very micaceous rock, dipping on South side of quarry gently S., and there is a dyke of granite at the S. margin, J. Nevins's Quarry. This is the furthest opening South-westward within this belt, and seems to be near its termination. It is between the two branches of Whitely Creek, one mile above their junction. It has been wrought for 30 years by Mr J. Nevins, and includes both the blue and white varieties of the crystalline lime- stone. The white variety is a coarsely crystallised dolomite, producing an excellent lime for building. This occurs in massive beds in the lower part of the quarry, through a thickness of 20 feet. Above it there lies, in VOL. I. 2 F 226 INSULATED TEACTS OF LIMESTONE. equally massive layers, a variety streaked with bluish and brownish bands, deriving its colours from the presence of an abundance of bronze-coloured mica. This coloured rock produces a grey lime. An anticlinal axis or saddle runs longitudinally through the quarry in a direction about N. 60 E. FIG. 29.-Nevins' 8 Quarry. ^ ^ n Vmrt cMn of this gaddle the ^p ig looking rock. The dip on the South side of the quarry is to the S. about 30. A contortion along the Southern edge of the quarry, and in the gneiss-like rocks which border it, presents an unequivocal indication of an inversion or fold by which the Gneissic rock is brought to lean over or rest upon the limestone which it elsewhere supports. Fragments of altered white sandstone occur in the vicinity of the quarry, to intimate that this is really a compressed trough of the Primal and first lowest beds of the Auroral strata. The whole breadth of the valley embracing the trough of calcareous rocks is not more than 200 yards. There is a quarry of limestone in the State of Delaware, about three miles S. of the State line, distant about four miles from the above-described one of J. Nevins, in a direction not far from S. 30 E. BELT SECOND (or that of Kennet Square.) A line of detached limestone quarries extends from a point one mile S.W. of Chadd's Ford, on the Brandywine, to the East Branch of Whiteclay Creek, near Avondale Post Office. A branch of this trough, apparently a narrow or compressed fold in the strata, commences at Nickle's Quarry, includes MendenhalTs, which is likewise in Pennsburg Township, and embraces Goss's Quarries near Eedclay Creek. It passes or unites with the Southern side of the main Kennet Square Basin in the vicinity of Pierce 's Paper Mill. In the quarry of Mr Mendenhall the limestone is scarcely at all exposed, for, as Mr Mendenhall alleges, it lies very deep. It is overlaid by sandstone, which exhibits an apparent dip of 35 to the S. on the South side of the Quarry. The main Kennet Square limestone-basin, divided from the foregoing narrow trough by a ridge of dark hornblende gneiss, extends from a point nearly N. of Goss's Quarry, to the East Branch of Whiteclay Creek, near the Avondale Post Office, as above mentioned. This trough is itself divided at its Eastern end by a wide low anticlinal hill of the Primal white sandstone, upon which the village of Kennet Square is seated, separating it into two branches or subordinate shallow basins. These coalesce into one wide basin a little W. of Kennet Square at the West Branch of Eedclay Creek. Here the valley has a width of more than three- fourths of a mile, but the limestone does not apparently everywhere underlie it. This rock is quarried at Hoopes's, near the Creek. From this neighbourhood the belt steadily contracts to its Western termination beyond the East Branch of Whiteclay. The trough is bounded on the S. by hornblende gneiss towards its Eastern end, and by the lower Primal slates in the condition of micaceous and talcose slate towards its Western. On its Northern side the Primal white sandstone, underlaid by highly-crystalline Primal slate, everywhere borders the limestone at the foot of the Toughcanem Hill. The uncomformable relation of the Primal rocks and limestone to the gneiss is nowhere better shown than along the Southern side of this basin in the vicinity of Eedclay Creek, and nowhere have we more convincing proof that the white sandstone and micaceous slates associated with it, bordering this trough, are of the true Primal series ; for here they not only dip beneath the limestone all along its Northern margin, but rise in a regular anticlinal saddle through the limestone to divide the basin into two regular troughs. Throughout this belt the limestone, wherever it is exposed, has a highly crystalline structure, and the greater part of it is more or less magnesian or dolomitic. The Branch Basin south of Kennet Square exhibits a deep deposit of sand in the bed of the valley, extensively concealing the limestone. As already stated, the village of Kennet Square itself rests on Primal white sandstone. BELT THIRD. Next in order, proceeding Northward, is the longest and most continuous of all these limestone troughs. This commences on the E., near the Eed Lion Inn, on the old street road, half a mile W. of the E. boundary of East Marlborough Township, audit ranges, curving gently Southward a distance of about nine miles, nearly to the Middle Branch of Whiteclay Creek ; the trough is broadest between the West Branch of Redclay Creek and the East Branch of Whiteclay Creek, having there an average breadth of more than half a mile. The Western half of the whole basin is subdivided into three subordinate narrower valleys, all of them containing the limestone, more or less continuously, and all of them ending Westward in the vicinity of West Grove Friends' Meeting-house. UPLIFTS OF GNEISS. 227 (1.) The first or most southern branch leaves the main basin about midway between the West Branch of the Kedclay and East Branch of Whiteclay, and runs as a narrow, somewhat irregular trough for more than three miles, to a point a little E. of West Grove Friends' Meeting-house. There are several quarries of good crystalline limestone included in this lateral valley. One of these is near Hume's Grist Mill on Whiteclay Creek, and two others are at William Jackson's, towards the Western end of the trough. The point of junction of this small valley, sometimes called Pleasant Valley, with the main basin, is in the neighbourhood of Joshua Pusey's Mill. The furthest Westward point at which limestone has been detected in this narrow belt is a little S. of West Grove Meeting-house, where a tradition of the neighbourhood alleges it was met with many years ago in a well, and the topography seems to testify that the rock may prolong itself thus far. Excellent crystalline limestone, well adapted for agricultural and other uses, is quarried at William Jackson's ; some of the beds being pure white carbonate of lime, while others consist more or less of dolomite. Brownish mica occurs in these beds, as in nearly all the limestone quarries of this class throughout the county. Adjacent to this quarry there occur scattered chunks of altered white Primal sandstone imbedding small crystals of Rutile. In the mica-slate bordering the limestone of Pleasant Valley, there have occasionally been found segregated nodules containing a compact Kyanite. Iron ore, but apparently not in large deposits, occurs S. of West Grove Meeting-house. A tooth of Mastodon giganteus, apparently the fifth molar, was found some years ago in Pleasant Valley, about one mile E. of William Jackson's, on the East Branch of Whiteclay Creek. (2.) The main trough of limestone throws off another and shorter branch, diverging, like the last described, from the Southern side, at a point between the two branches of the East Whiteclay Creek, not far W. of Hicks's Grist Mill. This smaller valley runs for about one mile and a half to a point a little N. of West Grove Meeting-house. The limestone has, as yet, been very little opened, or quarried, in this smallest branch of the general basin. Though the limestone of this branch-basin, N. of Pleasant Valley, ranges apparently in a continuous belt, it has been quarried hitherto at only two points : the most Eastern one is where it was wrought some years ago by Eobert Michener ; and the more Western, at present wrought by Henry Story, is one-fourth of a mile N. of West Grove Meeting-house. (3.) The main or Northern fork of the basin stretching towards the Middle Branch of Whiteclay Creek approaches to within half a mile of Kuisey's Clover Mill. Between the East Branch of Whiteclay and the Western end, it contains three or four considerable quarries of the crystalline limestone. The chief of these are known as Bailey's and Philips 's. This last-named quarry, being situated farthest to the South-west of all the lime- stone deposits in this part of Chester County, supplies stone and lime for agricultural uses to a circle of country to the S. and W., extending to twelve or even twenty miles. Though it is evident from the topographical features of the whole limestone trough, from the Red Lion Inn on the E. to Philips's Quarry on the W., that it is a true synclinal basin, yet, from the appearance in its more central parts of occasional exposures of the upper Primal slates, and even of the subjacent gneiss rocks, it is probable that the bed of the valley is more or less undulating, and that the limestone is not everywhere absolutely continuous. Uplifts of Gneiss, and Dykes of Granite, In fact, there seems to extend an anticlinal axis of gneiss parallel with the Southern margin of the trough, the whole way from Joel Bailey's, a little West from the West Branch of Redclay, to Hicks's Grist Mill on the East Branch of Whiteclay, a distance of more than three miles. Connected with this line of uplift we may occasionally detect an obscure outburst of granite. The gneiss is itself massive and granitic. The anticlinal structure of this narrow protruded belt of older rock is well seen on the farm of Joel Bailey. , . The following little sketch exhibits its features as exposed near his house. This anticlinal is said to range FlQ. 30. Broken Saddle of Gneiss in Auroral Limestone on Bailey's Farm. for nearly two miles to the Eastward, and to approach the East Branch of Redclay ; but I have not traced it there. 228 INSULATED TRACTS OF LIMESTONE. Granite Dykes. Just N. of Hicks's Grist Mill white granite shows itself in a low ridge, with contorted materials of the Primal white sandstone, borne through the limestone apparently by the intrusion of the granite. There is a third dyke of granite, possibly a branch of that which ranges by Hicks's Grist Mill, which passes S. on the South side of Baker's Quarry, between the Branch Basin containing this quarry and that at William Jackson's. This dyke extends from near Baker's Quarry to a point about one-fourth of a mile N. of West Grove Meeting-house. Another but shorter anticlinal uplift of granitic gneiss passes through the farm of William Jackson in Pleasant Valley, and appears to range for a mile or more North-eastward, passing under the knoll upon which the Locust Grove School-house stands. This protrusion of the ancient gneiss rocks in anticlinal undulations through the overlying limestone, some- times with traces of the Primal white sandstone and Primal micaceous crystalline slates, sometimes without any vestiges of them, is a feature confirming the evidence derived from various other phenomena, of the original unconformity in deposition of the Primal and Auroral strata upon the gneissic rocks. Besides the quarries already enumerated, there are two or three good ones in the vicinity of Joel Bailey's. In all of these artificial exposures the general character of the limestone is very similar. It is generally a crystalline dolomitic limestone, sometimes very granular, disposed in massive beds, and contains, for the most part, more or less segregated mica, talc, and other minerals, the mica being rarely absent. In consequence of these extraneous substances, it seldom yields, when burnt, a perfectly white lime, though in nearly all the quarries some layers may be found so free from these foreign minerals as to produce, if care be observed in quarrying it, a stone convertible to lime of the very finest quality. An interesting geological feature connected with this long and shallow trough of Auroral limestone, is the marginal outcrop of Primal white sandstone, and Primal crystalline slate, which almost everywhere borders it. These rocks are best seen along the old street road, and the lanes leading out from it, upon the Northern side of the basin. The conformable dip of the sandstone under the edge of the limestone, or towards the centre of the basin, is well exhibited at the street road opposite Joel Bailey's, and again at Taggart's cross-roads farther E. In some of the quarries the limestone, especially near the Southern margins of the trough and its branches, is overlaid by micaceous and other crystalline slates, identical almost in composition with the micaceous crystalline schists of the Primal series. These are evidently but the intercalated argillaceous beds which almost every- where belong to the lower part of the Auroral limestone formation. In truth, it would seem as if nearly all the limestone of this and the other small valleys of the district belonged to the very base of the formation, or that portion which presents a type of passage from the Primal or Schistose into the Auroral or Magnesian limestone series ; and this view is in consonance with the obvious shallowness of all the limestone masses embraced within these troughs. Between the Southern border of this Street Road basin and the Northern edge of the Kennet Square limestone trough, or that bounded by the Toughcanem ridge, extremely little genuine gneiss shows itself at the surface, and that which does appear is the hornblende variety. It is obvious that the anticlinal belt which divides these two zones of Auroral limestone is here composed mainly of the older Primal slates, under the highly- crystalline micaceous type, which they wear so generally throughout all the Southern district of Pennsylvania. The true Gneissic or genuine Hypozoic metamorphic rocks, elevated only in narrow and broken fingers to the Westward of the Brandywine, here hardly lift themselves to the surface. The Primal white sandstone on both the N. and S. sides of the Street Road Limestone Basin, possesses all the features distinctive of this rock under its most metamorphosed form. Thus, where it dips gently Southward under the limestone on the North side of the valley near the Red Lion Inn, it contains the same minute broken crystals of schorl, the same thin partings of highly crystalline talc, and wears the same felspathic and semi-vitreous aspect which so strongly characterise it throughout all its outcrops bordering the great limestone valley of Montgomery and Chester counties. It is not practicable to make out in strictly correct sections the undulations and dips of the strata, either in this or any other of the more complicated of these limestone troughs ; but their structure is evidently identical with that of the Appalachian basins generally. The inclination of the rocks on the S. or S.E. side is either QUARRIES. 229 steep or inverted, unless where an actual dislocation forces the approximately level limestone to abut against uplifted walls of older gneiss or granite, while the dip on the N. or N.W. side is almost universally Southward at a gentle angle. Both in Baker's Quarry in the Middle Branch of the Street Road Basin, and at Jackson's in the Southern Branch, the dip of the limestone is for the most part very gentle ; that at Baker's flatly undulating, while that at Jackson's is at the low angle of 20 Southward into the base of the hill which bounds it. In William Jackson's Quarry well-developed crystals of phosphate of lime have occasionally been found ; and the same mineral has been met with one mile WS.. of Chatham in a soil derived from the Primal mica-slate. Asbestos, in flexible sheets like paper, has also been found in Jackson's Quarry. Neither in this nor in any other of these local isolated tracts of Auroral limestone and Primal white sand- stone, do we meet with these rocks under a fossiliferous type. Obscure traces of the Scolithus, the sole fossil of the Primal white sandstone yet discovered in Pennsylvania, have been once or twice met with upon loose fragments of the rock ; but this is the only instance of organic remains yet discovered. But this absence of fossils from these the most ancient of all the Palaeozoic deposits of our country, need not at all surprise us, since their occurrence is extremely rare even in those basins of the same formations farther N., where the strata are much less. altered and crystalline. Indeed, we know of no discovery of organic remains in the lowest beds of the Auroral limestone equivalent to the rock of these valleys in any part of the middle States. Nearly in a line prolonged Eastward from the Street Road Basin, but some three and a half miles Eastward from its Eastern termination at the Red Lion Inn, there is an insulated outcrop of both the Auroral limestone and the Primal white sandstone just W. of the Brandywine a little below Brinton's Ford. This is at Good- wood's Quarry (formerly Harvey's). The quarry has not been wrought for several years. The limestone is for the most part sandy. Sandstone is scattered on the surface in the immediate vicinity of the limestone, but does not exhibit itself in place. Very probably this patch of limestone is an outstanding remnant of a more continuous belt which may once have connected it with that of the Street Road Basin, for it seems to lie in the same general synclinal wave in the older strata. In like manner, there can be veiy little doubt that the Eastern prong of the Kennet Square Basin, now embracing the detached quarries of Passmore, Mendon Hall, and Nichol's, was once prolonged across the Brandywine at Chadd's Ford ; for we have the plainest proofs in the synclinal dipping of the hornblende gneiss of that vicinity, that a great natural trough or basin, competent to contain, until denuded, a belt of Primal and Auroral rocks, does here exist. BELT FOURTH. N. of the long basin of the Street Road above described, and distant from it about two miles, there lies a much smaller trough or synclinal fold in the strata, containing a more or less continuous band of crystalline Auroral limestone, extending for about three miles from near the Drover's Inn, W. of Unionville, to nearly the N. line of London Grove Township. This narrow belt, marked by a narrow irregular valley, passes less than half a mile to the N.W. of West Marlborough Inn. In this vicinity, and likewise nearer to the Drover's Inn at Logan's Quarry, the limestone has been quarried to some extent. The most western quarry of this tract is J. C. Bailey's, situated about one mile S. of W. from the West Marlborough Inn ; but the features of the country and the soil indicate that the limestone belt is prolonged considerably further South-westward in the direction of Cook's Grist Mill, though the rock has nowhere been opened. Traces of the Primal white sandstone are to be met with on the margin of this small trough. Between West Marlborough Inn and London Grove Post-office, and even further to the S., the older Primal rocks, here in the condition of true micaceous slates, occupy a broad anticlinal belt, their south-dip towards the Street Road Limestone Basin being obvious in all the neighbourhood around London Grove Meeting-house and Post-office. Between the Friends' Little Meeting-house and Pusey's Grist Mill, we pass over the South-east-dipping outcrop of this Primal sandstone, the same which forms the Northern boundary of the Street Road Basin. In Eli Logan's Quarries, about one mile W. of Unionville, the limestone .dips to the S.E. about 30, but irregularly, and with some remarkable folds. Resting apparently upon the limestone, there is a white gneissoid rock, possibly only a highly-altered or crystalline form of the upper Primal slates, in alternation with the lime- stone. It is a conceivable supposition, however, that this rock pertains to the true gneiss formation, and that all the strata in this quarry are inverted. 230 INSULATED TRACTS OF LIMESTONE. In the anticlinal belt which separates the Street Eoad trough of limestone from that of West Marlborough Inn, there would seem to be very little or no genuine gneiss W. of the Meridian of Unionville ; but between the Brandywine Creek and Uuiouville, that rock does appear in occasional narrow uplifts. What seems to be genuine hornblende gneiss occurs near the Marlborough Meeting-house, some two miles E. of Unionville. The rock here contains some epidote. BELT FIFTH. The next and most Northern principal belt of the crystalline Auroral limestone occupies a long and narrow trough in the strata extending from Boardley Kun, one mile W. of Marshallton, to near the South- west corner of West Marlborough Township, a distance of about nine miles. It is not certain that we have here a simple continuous synclinal trough ; for though the natural exposures and the quarries of the limestone all lie in one very straight and narrow line, parallel with the other basins, and with the general strike of the strata of the country, yet these developments are too far asunder, and the topographical features of the belt are too irregular, to allow us to assert positively that the limestone is strictly connected along this whole tract. The probabilities are great, however, that it is. Commencing with the most Eastern exposure, we meet the rock first in a quarry owned by Moses Bailey, on the East side of Boardley Run. The rock here yields a tolerably good lime for agricultural uses. The next opening is in the quarry belonging to the Chester County Poor-house, about one mile further S.W. Here the rock is a highly-crystalline dolomitic limestone, containing in some, especially the upper layers, much segregated brown mica ; in fact, certain of the upper beds include so much mica and quartz as to be entitled, from their composition, to be called calcareous gneiss. These upper beds are regularly interstratified with a micaceous gneiss-like rock ; and even between the more massive beds of the true magnesian limestone, the parting layers are almost invariably either pure mica and talc, or a mixture of these with quartz, entitling them also to the name of Gneiss. The whole mass dips 35 to 45 to S., 20 E. Much as these overlying strata resemble genuine gneiss of the micaceous-slate variety, it is difficult, from the analogy of the limestone to that of other localities, unquestionably superposed upon the Primal crystalline rocks, to regard it as a merely inter- calated mass between strata of the genuine old gneiss formation ; it is more in accordance with all the results of our researches, to view this limestone and the associated gneiss-like beds as the passage-rocks between the Primal and the Auroral series, and to conceive that they hold their existing position, either from an inversion of the strata, or from a dislocation of the South side of the limestone valley of the Poor-house Farm, causing them to dip South-eastward against the uplifted older rocks which border them in that quarter. In this quarry occur several interesting minerals, the most remarkable being the Chesterlite, once regarded as a variety of felspar ; also Rutile and feathery Talc. Next in order South-westward, among the quarries belonging to this belt of limestone, is that near Hoopes's Grist Mill, in an ox-bow bend of the Brandywine, in Newlin Township. Nearly two miles to the S.W. of this locality occur the quarries of Pierce and Edwards ; these are about two miles to the N.W. of Unionville, on the road from Embreville to Doe Run Village. One mile and a half further to the S.W., and in the same exact line, is Connor's Quarry, on the road from Unionville to Doe Run. These three last-named quarries yield an excellent lime. The rock is very crystalline, and more or less dolomitic. In Connor's Quarry the strata dip at a moderate inclination to the S.E. ; and to the N. of the quarry there is a band of South-east-dipping Primal white sandstone; and still further to the N. are the older Primal slates in the condition of quartzose mica-slate, likewise dipping to the S.E., or beneath the Primal sandstone, at an angle of 45. Micaceous sandstone, and occasionally Primal white sandstone, border the synclinal valley on its N.W., throughout its whole length ; but the white sandstone is to be detected only occasionally. The older Primal slates, highly crystalline in their structure, likewise bound the valley on the S.E. ; but in some of the exposures of the limestone we are at a loss to determine whether the rocks of this character, leaning upon the dolomite, are the true Primal slates inverted upon the limestone, or overlying schistose beds belonging to the alternating portion or base of the Auroral limestone series. It is pretty evident that these rocks, as they occur on the South side of the lime- stone at Connor's Quarry, are really the Primal slates inverted against the limestone. The furthest opening in the limestone in this synclinal is that of Baker's Quarry, half a mile E. of the W. line of West Marlborough Township. INSULATED TRACTS OF LIMESTONE. 231 It is more than probable, from the remoteness of the localities at which the limestone has been discovered, and from the irregular features in the topography of this belt, interrupting the continuity of the valley, that limestone does not occur in one unbroken trough, but has been lifted and washed out of the shallow basin in several sections of its length ; and it is indeed natural to suppose that the synclinal structure itself is not per- fectly regular ; the more probable view being, that the whole tract is a chain of short and narrow basins, rather than one long, continuous, straight trough. About two miles N.W. of West Chester, in the valley of Taylor's Eun, and therefore E. of the Brandywine, there is a small outcrop of limestone on land belonging to Caleb Cope. This is so nearly in the line of the long chain of quarries of the Poor-house synclinal, that we are almost induced to conjecture that it may belong to the same trough with them, and that it is an outstanding remnant of the Auroral rocks preserved from denudation. BELT SIXTH. The last and shortest of all the synclinal tracts of the crystalline magnesian limestone S. of the Great Valley of Chester County, is that in the vicinity of Doe Run Village. This extends for rather more than a mile in a S.W. direction, parallel to the Valley of Doe Run, from near the village to the vicinity of Passmore's Mill. Near the first-named locality, the limestone is exposed in a quarry owned by a Mr Hayes, and it is again developed S. of the Doe Run stream, near the South-western end of the belt, in quarries owned by Hoopes and Jones. No true gneiss shows itself N. of the Poor-house Chain of Quarries, but all the strata embraced between that long synclinal line and the great limestone valley of Chester County, pertain to the Primal series. This series is here evidently of great thickness ; it is made up of micaceous and talcose slates, embracing a large proportion of fissile clay-slate of the nature of roofing-slate, and it apparently belongs to the same place in the formation which embraces the Susquehanna zone of roofing-slate, making so conspicuous a feature near the State line. The comparatively rare occurrence of white Primal sandstone outcropping from beneath these lower beds of the Auroral magnesian limestone, which have just been described, should not surprise us when we reflect that that rock is extremely thin, and is sometimes altogether wanting along the Southern margin of the deeper and more continuous limestone-trough of the main Chester County Valley ; and when we also remember that this formation, nowhere very constant in its thickness over wide districts of county in the middle States, exhibits in Chester County a progressive general increase of its mass as we advance to the Northward. This fact alone makes it very probable that the non-appearance of the sandstone round some of these Southern basins results from their lying outside of its continuous area, and it may serve furthermore to explain the absence of its characteristic fossil the Scolithus, even where the rock itself occurs. INSULATED LOCALITIES OF CRYSTALLINE LIMESTONE WITHIN THE GNEISSIC DISTRICT NORTH OF THE CHESTER COUNTY VALLEY. 1. Turning now to the localities North of the Chester County Limestone Valley, and noting them in the usual order from E. to W., the first which we meet with is a small outcrop about three-fourths of a mile W. of the village of Charlestown, and a little N. of Pickering Creek. It is near Clevenstine's Foundry. The bed or mass appears to be but a few feet in thickness, and resembles more the layer in gneissoid micaceous rocks, or' even an intrusive vein of impure calcareous spar, than a folded bed of limestone at the passage of the Primal and Auroral series. It was at one time quarried to a small extent, and burned in a limekiln, but the lime was dark and impure. 2. The next outcrop of limestone occurs near the village of Kimberton. This is a small bed of altered crystalline limestone, chiefly in the condition of calcareous spar, with scattered crystals of plumbago, epidote, and two or three other minerals. It occurs very near the contact of the Gneissic rocks and overlapping fed sandstone, and adjoins a dyke of syenite, to which it ewes, most probably, its highly crystalline structure. 3. Another locality is near the Northern road leading from Kimberton to the Yellow Springs ; it adjoins the large ore-pit on Mrs Lewis's farm. This limestone has been quarried, and converted into good lime. Ascending 232 LOCALITIES OF LIMESTONE NORTH OF CHESTER VALLEY. French Creek, the next is at Schuyer's Quarry, near Bachardt's Oil Mill. This outcrop extends Westward into the next farm. 4. There is another on the South side of French Creek at Vanlear's, half-way between Pughtown and Coventry, but S. of French Creek. This also has been quarried and converted into good lime. 5. A little to the W. of Vanlear's is a small exposure of the limestone at Christman's, which has been converted into an excellent lime. 6. There is another small exposure S. of Coventry Village. 7. Following the South Branch of French Creek occurs another isolated bed in Nautrcul Township, S. of Miller's Grist Mill. 8. A little W. of Warwick Furnace we meet with another small bed in contact with micaceous Gneiss. 9. A dyke or vein of sparry limestone forms the Northern wall of the iron ore-pits at Crossley, one mile N. of Knauertown. It is in contact with a wide dyke of granite, and includes several crystalline minerals, and exhibits every indication of having been at one time in a state of fusion. ' 10. There is a long and narrow strip of limestone in Uwchlan Township, W. of the Little Eagle Tavern ; its total length, as indicated by a succession of sink-holes, and one or two small quarries, and by two or three wells sunk into it, is probably one and a half miles. The rock is a very coarse, crystallised, white sparry lime- stone, abounding in numerous little flakes of plumbago. It has been found to produce, when properly burned, an excellent white lime. It lies chiefly in low meadow ground, and under a deep covering of soil, and being- very narrow, is obscurely seen. It is therefore very difficult to pronounce whether it is an igneous vein or a bed in the metamorphic gneissoid strata, or again a closely-folded narrow trough, doubled between, but yet overlying these. CHAPTER III. AURORAL LIMESTONE OF THE SOUTH MOUNTAINS BETWEEN THE DELAWARE AND SCHUYLKILL. IT remains to describe the several narrow belts of the Matinal limestone of the Eastern division of the chain of the South Mountains. Commencing on the N., we have the limestone of the Lehigh, a part of the great Kittatinny Valley. Passing down the Delaware, from the mouth of the Lehigh, this belt of the limestone, measured obliquely in the direction of the river, has a breadth of about two miles, showing first a Southern dip of about 45, which diminishes, then passes into horizontal, and then into a gentle Northern dip, forming a synclinal basin. Between the Northern dip last mentioned, and the uplifted gneiss to the S., there are indications of a narrow anticlinal elevation of the limestone, connected probably with a high narrow ridge of the gneiss which appears in New Jersey. Passing round the end of the first ridge on the Pennsylvania side, consisting chiefly of gneiss and syenitic rocks, we come to a narrow belt of limestone which extends Westward from the river, about two miles, occupying a little recess between two spurs of the chain. This limestone is quarried near the river, at Ihrie's, and at Harman's. A large amount of lime is made at the latter place, which is four miles below Easton, and some of the stone goes down the canal to various points in Bucks County, where large quantities of it are used. Much jaspery chert, with chalcedony and quartz, derived from the limestone, strew the fields about a mile from the river. The prevailing dip of the gneiss in the Lehigh Hill is to the S.S.E. at a steep inclination. Between these strata and the Northern belt of limestone, we find indications, near the Delaware, of the presence of the Primal white sandstone. This formation, if really present as a continuous stratum, must be of inconsiderable thickness. Resting, as it does, directly on the violently uplifted Gneissic rocks, its unfrequent appearance at the base of the hills may, however, be explained in part by the crushing it has undergone, and by the mass of transported fragments concealing it from the sight. The Southernmost of the two spurs of the Lehigh Hill, mentioned above as bounding the little narrow tract of limestone, forms the Northern limit of another larger limestone valley, the Southern boundary of which is Frey's Run. The limestone of this valley, dividing the Northern belt of primary rocks from the middle one, terminates on Frey's Run, about two miles W. of the Delaware, the last exposure of the rock being at Stout's Quarry, where its dip is Northward. The breadth of this tract, measured along the river, is very nearly two miles ; here at Uhlersville, about five miles below Easton, it is extensively quarried and converted into lime. The strata, which have been tilted into a nearly vertical position, differ much in the quality of the rock in the different layers. Bounding this limestone valley on the S., we have the broad belt of crystalline rocks, which I have designated as the middle ridge of the whole mountain-chain. The rocks of this range, comprising chiefly massive strata of gneiss and beds of syenite, cross the Delaware into New Jersey, forming a ripple called Rocky Falls. South of this middle belt, and N. of the Southern VOL. I. 2 G 234 AURORAL LIMESTONE, SOUTH MOUNTAINS. or Durham Eidge, which is a prolongation of the Musconetcong Mountain of New Jersey, there lies another narrow but rather longer tract of the limestone, occupying the valley of Durham Creek. The breadth of this tract of limestone, measured along the river from a point opposite the mouth of Musconetcong Creek to the mouth of Durham Creek, is about one mile ; the upper edge of the limestone, N. of the village of Eiegelsville, being much obscured by a covering of diluvium, and the lower bordered by the Creek, along which it is well exposed, from its mouth to the neighbourhood of Springtown. A little W. of the old Philadelphia Eoad, and N. of that to Springtown, the limestone appears on the South side of the creek, dipping 60 nearly S. The dip is also Southward in several places east of Springtown. The existence of a steep Southern dip along the South side of this valley is in strict analogy with the position of the rocks generally in the valleys of the whole South mountain-chain, and implies an overtilting of the strata to the N. This folding of the beds upon themselves in the synclinal axes of our first great mountain- chain, though remarkable, is a prevailing feature from Vermont to Tennessee. East of Springtown there is a low ledge of Primal sandstone lying N. of the road, and following the course of the creek in a North-eastern direction. South of the Durham Eidge of Gneiss, there occurs another smaller strip of the limestone, bounded on the S. by the conglomerate and red sandstone of the Middle Secondary formation. This small tract shows itself a little W. of the river, near Monroe, occupying the South side of a little stream. It is well seen in a quarry, inclining 75 to a point a little E. of S., and in another, where it dips to the S.E. at an angle of 30. Its last appearance towards the W. is at the old Philadelphia Eoad, where the red sandstone overlaps it. The next detached tract of limestone which claims description is that of the Little Saucon, along the valley of which it may be traced, though with rather obscure exposures. The rock shows itself in the creek about half a mile N. of Lower Saucon Church, near a blacksmith's shop. Further up the creek, it is said to have been dug, but found too slaty for use. Its last occurrence along the stream is near the intersection of the road and the creek, where it is well exposed, and of a good quality. At this place its strata dip 40 North-westwardly. Ascending the creek beyond this, the Gneissic rocks show themselves, and the country becomes wild and rocky. The next tract of limestone is that of the main Saucon Creek, in the valley of which it is the prevailing rock, from within a mile of the Lehigh, almost to the very source of the stream. This belt, ranging in a N.E. and S.W. direction, separates the group of ridges terminating on the Delaware from the rest of the chain, stretching towards the Schuylkill. Conforming to the general curvature of the valley of the Saucon, the limestone occupies, throughout the greater part of its course, both sides of the creek, and ascends, for a little distance, some of its tributaries. The lowest point at which it shows itself is about a mile and a half N. of Hellertown, and by the channel of the creek, nearly two miles above its mouth. Expanding soon in breadth to embrace both channels of the Saucon, which here divide to form an island, one part of the tract sweeps Eastward, running up between two spurs of the gneiss, until it terminates in a point about two miles E. of Hellertown. Half a mile E. of the town, the limestone is seen dipping to the N.W. A little to the E. of this, between two small hills of gneiss, a short belt of the Primal sandstone appears, the rock resting directly on the gneiss, and dipping towards the W.N.W. DELAWARE TO SCHUYLKILL. 235 Beginning with the termination of the limestone, E. of Hellertown, the Southern edge of the formation will be found running thence, in a general South-western course, along the Southern side of the valley of the Saucon. About the Lehigh County line, a spur of the gneiss, running down between the main creek and a small Southern tributary, insulates the limestone in the valley of the latter, in the form of a little cove, where it is opened in two quarries, belonging to Abel and Flexer. The general margin of the formation follows the Northern foot of this spur as far W. as the South Branch of Saucon, where it doubles round it ; the limestone here running Eastward to form another little cove between the spur already mentioned and a second small belt of primary to the S. of it. The North-western point of the spur includes a small tract of the Primal sandstone. The edge of the limestone now crosses over to the Western side of the South Branch of Saucon, extends in that direction about half a mile, and then curves back by the S. and E. until it again meets the stream, where the limestone disappears beneath the overlapping Middle Secondary rocks. Within the curved edge just traced, is included, therefore, a third small cove of the limestone, lying, like the others, between two jutting points of the gneiss. Coming back now to the general Southern margin of the limestone, we trace it from the South Branch of Saucon, first Westward and then South-westward, along the main creek nearly to its source, about a mile and a half N.E. of Shimer's. From this point, the whole way down the Northern side of the valley of the Saucon, the other, or North-western margin of the limestone nowhere departs far from the border of the stream, following the curvatures in its course, with consider- able regularity, to the point where we commenced our description, about a mile S. of the Lehigh. The limestone of the main belt of the Saucon is quarried E. of Hellertown, as already mentioned ; also at a point about half a mile S. of it, dipping at both of these places towards the N.W. It is opened also at Upper Saucon Church in a quarry on both sides of the road, where the dip is towards the S. South of the creek, about half a mile from the intersection of the Allentown Eoad with that leading S. from Upper Saucon Church, occurs Toger's Quarry, where the rock dips to the S., as it does at a point N. of this, near the creek. Crossing the creek on the road to Allentown, we find another quarry, the strata dipping to the S.S.E. ; and another about two miles higher up the stream, a little W. of the road which leads Eastward from Emaus. Here the dip is gentle and a little N. of E. Still further up the creek, beyond the Upper Saucon Township line, there is a large quarry, owned by several persons. The pre- vailing dip just here is to the N.E. The last exposure of the limestone is about a mile and a half above this in a quarry. The dip is gentle, and to the S.W. Upon the South Branch of Saucon, the limestone is opened at a quarry, and at Berger's Mill. Wherever the limestone on this tributary rests in contact with the overlapping red shale and sandstone, it loses its usual clear blue, and acquires a light, bluish pink colour. In this vicinity the rock is highly magnesian. The rock is crashed, consisting of innumerable small square fragments. Besides the continuous belts of limestone now traced, there occur, in the region of these hills, several small isolated patches, remnants, as it were, of a once widely-diffused tract of the forma- tion, the main body of which has been broken up and swept away. Commencing with the Easternmost, we meet with one of these at the Bucks County line, at a point about a mile and a half W. of Springtown ; and about a mile further Westward another, where the rock has a dip of 35 to the S.E. and is quarried. These two patches lie embraced in the gneiss. In Upper Saucon Township, S. of the creek, and a little W. of the Allentown Road, we meet with 236 AUROEAL LIMESTONE, SOUTH MOUNTAINS. a third, near the top of a ridge of gneiss, where the rock is exposed at Erdman's Quarry. The limestone is of the common blue variety, but it abounds in fissures filled with white carbonate of lime. Its proximity to the agricultural district S. of it, where no limestone occurs, and its elevated position, which facilitates hauling, cause it to be somewhat resorted to. The only other detached localities of the limestone in Lehigh County occur in Upper Milford Township. One of these is about one mile S.W. of the uppermost exposure of the lime- stone on the Saucon. It is near the source of one of the main branches of Perkiomen Creek. Another lies in the Western corner of the township, half a mile S.W. of Hampton Furnace, being also on a tributary of the Perkiomen ; and a third is on the Hasacock Creek. The rock here is in close proximity to the Middle Secondary red shale and sandstone. There remains one other tract of the limestone to be spoken of as occurring S. of the Lehigh. It occupies a recess in the Gneissic belt immediately S. of Bethlehem. Commencing on the Southern bank of the river, about a mile above the town, the line which divides it from the gneiss runs in a crescent until it meets the river again some distance below the town. Thus enclosed, it forms properly but a part of the great belt of the Kittatinny Valley. The greater part of the limestone of the several tracts above described belongs to the blue varieties of this rock so familiarly known. It is by no means, however, invariable in its com- position, very many bands being more or less magnesian, and some so highly so as to furnish, when properly treated, an excellent hydraulic cement. Occasionally we meet with a somewhat rare and interesting variety, possessing an oolitic structure. Bands of this description are met with above South Easton, and also on the Bushkill, and again N. of Chestnut Hill. These oolite beds of the Auroral magnesian limestone are not unfrequent in other parts of the State ; their common position seems to be near the bottom of the formation. DURHAM CAVE. Before quitting our description of the limestone, we may devote a few words to a cavern which occurs in this rock on Durham Creek. Its position is a little N. of the stream, and not far from the Delaware. It has a length of about three hundred feet, an average height of twelve, and a breadth varying from four to forty feet. The floor of the cave is not level, but descends as we penetrate to the interior. Its rough walls are adorned with few pendants or stalactites. Much of the bottom of this cave is covered with water, the level of which is influenced, it is said, by that of the Delaware. About half-way down occurs a narrow lateral cavern, terminating in the form of the letter T. The general direction of the main gallery is S.W., becoming S. towards the remoter end. The rocks show an anticlinal axis about twenty yards S.E. of the entrance of the cave, the direction of the axis and the cave nearly coinciding. This cave was found many years ago to contain some interesting fossil bones, an account of which will be found in another Chapter. ZINC MINE OF THE SAUCON. Immediately N. of Friedensville is the zinc mine of the Pennsylvania and Lehigh Company. It is a superficial excavation or open quarry, the entrance being by a slope way. The principal ore is calamine, or a silicious oxide of zinc : it appears to be abundant, and has been somewhat extensively mined. It appears to occur irregularly injected into the limestone, which dips perpendicularly on the North side of the mine, and as steeply as 85 on the South side. The limestone is much injected with thin veins of quartz. It would seem that the vein of ore coincides very nearly with a closely-compressed, perpendicular, synclinal fold in the limestone, possibly with a synclinal fault. This mine was commenced about 1853, and wrought for three years. The ore is smelted at Bethlehem, and con- verted into white paint. The vein would seem to range South-westward, or along the synclinal axis or possible fault. BOOK II. THE KITTATINNY VALLEY, OR THE SECOND PALEOZOIC DISTRICT. CHAPTER I. BOUNDARIES AND FEATURES OF THE VALLEY, AND CHARACTER OF THE STRATA. PERHAPS no subdivision of the State exhibits better-defined natural boundaries than the Kittatinny Valley. It is limited on the S. by the chain of the South Mountains, which is not, however, a continuous barrier, but consists of one range of hills from the Delaware to the Schuylkill, and another from Dillstown in York to Maryland, with an intermediate space, presenting a more broken boundary. Its Northern limit is the Kittatinny Mountain, separating it by a very regular natural wall from the mountain districts on the N.W. Dimensions. The entire length of this belt from the Delaware to Maryland is about 165 miles. Its mean breadth in Northampton, Lehigh, Berks, and Franklin, is 15 miles ; and in Lebanon, Dauphin, and Cumberland, between 10 and 11 miles. Throughout its whole extent it presents a gently-undulating surface, approximating to a level plain, with here and there a belt of low hills. The inequalities of its surface are greatest along the Northern side, near the foot of the Kittatinny Mountain. Some detached hills of slate appear in the middle of the valley near the Schuylkill. A high degree of fertility characterises the soil of all the Southern half of the district. Embracing only the Auroral and Matinal rocks in their South-eastern type, the geological composition of this belt is necessarily simple, nor do the several formations undergo any very marked changes in their longitudinal range. The structural features of the valley, though peculiar, and well deserving of attention, are almost as uniform. The strata are everywhere bent into oblique and closely-folded flexures, with South-eastern dips. But few T organic remains are to be recognised, the more highly fossiliferous formations, the Matinal limestone, Trenton limestone, and Matinal black slate (Utica slate), hardly appearing in more than one or two neighbourhoods. Cleavage. -In nearly every part of the district the strata display an excessive amount of cleavage, the divisional planes or joints dipping almost invariably towards the S.S.E., or parallel with the planes which bisect the anticlinal and synclinal flexures. The direction of the cleavage is therefore approximately constant, whatever may be the local dip of the rocks. This cleavage has originated subsequently to their elevation and contortion, 238 KITTATINNY VALLEY. but seems to be intimately related in its direction with the position of the anticlinal and synclinal axis planes. These latter were obviously the planes of maximum temperature in the crust, while the strata were as yet newly upraised, being the portions most crushed and fissured, and the channels of escape for the intensely-heated elastic vapours which we must suppose accompanied the energetic lifting and folding of the rocks. Conceiving the cleavage to be a species of crystallisation effected through molecular polarities excited in a definite direction, it is not difficult to comprehend how these forces might be awakened throughout the entire rocky mass of a given district by the action of innumerable alternately-disposed planes of maximum and minimum temperature, and to imagine such a region to represent, as it were, a stupendous thermo-electric series, capable of engendering the corpuscular forces or polarities, and of pro- ducing parallel alternating planes of maximum and minimum cohesion resulting in cleavage. A glance at the general sections which cross the Kittatinny Valley, will convey a correct notion of its structure, and show the singularly constant South-eastern dip of all the strata, with the oblique direction of their compressed flexures. Character or Type of the Formations. The Auroral calcareous sandstone occurs as a thin formation in the vicinity of the Delaware, presenting very nearly the type which it exhibits under the name of Calciferous sandstone in New York. It seems not to have been everywhere deposited, for we meet with only occasional indications of it further towards the S.W. along the valley. The Auroral Magnesian Limestone. The formation which underlies the entire Southern half of the valley, though a stratum of enormous thickness, is not susceptible of accurate measure- ment in any part of the district, from the frequency and obscurity of the flexures that traverse it. Except in Cumberland and Franklin, and a few localities E. of the Susquehanna, it does not embrace the higher fossiliferous beds of the formation. It consists for the most part of two varieties of limestone, one highly magnesian, the other less so ; and these form an extensive alternation. The magnesian variety constitutes by far the largest portion of the mass, especially in the lower and middle divisions. Many of the inferior strata are very crystalline, and present, when weathered, a harsh granular surface. These freqiiently contain the full proportion of the carbonate of magnesia essential to the constitution of the rock called Dolomite. Some of the lower beds are very sandy and ferruginous. To the disintegration of these I impute in part, at least, the very ferruginous quality of the sandy loam which fills the depression in the surface in so many places in the Southern side of the valley, and in some localities includes such valuable deposits of haematitic iron-ore brown hydrated peroxide of iron. In Lehigh, Northampton, and elsewhere, there occur in this belt, low in the formation, layers of a decidedly Oolitic limestone. These are well exposed near Allentown. A similar rock occupies the same place in the series in Centre and Huntingdon counties, and is extensively met with in Virginia, and also in East Tennessee, in the prolongation of the Kittatinny Valley. So wide a geographical range manifests a remarkable extension of that peculiar condition in the waters which gave rise to the oolitic structure. Alternating with the lower limestone masses of the formation, are beds of sandy talcoid slate without fossils ; these link the Auroral with the underlying Primal series. They are especially conspicuous on the Susquehanna at Columbia, in the more Southern belt already described. In the middle and upper parts of the formation, which have their outcrop chiefly in the Northern half of the limestone belt, there is a large MATINAL EOCKS. 239 proportion of a purer limestone, which may be recognised by its dull blue colour, and the freedom of its weathered surfaces from any incrustation. This is the variety best adapted for the making of lime, and for use in the smelting of iron. The Matinal Limestone (the equivalent of the Trenton Limestone of the Geological Survey of New York) is distinctly recognisable near the Delaware, also on Martin's Creek, and at a few other localities within the belt of the Kittatinny Valley, but chiefly E. of the Lehigh. It is a more North-western rock, however, so far as respects ita fullest development in Pennsylvania, appearing in the anticlinal valleys of Mifflin and Centre counties, and other central portions of the Appalachian Chain. South-west of the Susquehanna we occasionally meet with a few organic remains in the uppermost portion of the limestone, as near Carlisle, and again near Chambersburg, but these are referable apparently to the higher fossiliferous members of the Auroral magnesiau limestone, known to contain several species in common with the Matinal limestone. Matinal Black Slate and Matinal Limestone on Martins Creek. On Martin's Creek the passage from the limestone to the Slate formations exposes at least 300 feet thickness of the Matinal Black Slate (Utica Black Slate) without fossils, and from 300 to 400 feet thickness of fossiliferous Matinal limestone (Trenton), all dipping at 30 on an average to N. 30 W., and all thoroughly cut up by cleavage-planes, which for the most part are almost absolutely horizontal, except where they curve in a sort of waving or sigmoid bending between the planes of bedding. In the Matinal limestone are to be found Chcetetes lycoperdon, and two or three other characteristic well-known fossils of the formation. Beneath this argillaceous limestone (Trenton) may be seen, in the first anticlinal S. of the boundary of the limestone and slate, the smooth massive marble beds visible on the Mohawk, and characteristic of the higher member of the Auroral series. The Matinal Black Slate (the equivalent of the Utica Slate of New York) is also seldom or never present in the region of the Kittatinny Valley ; at least, it has not been recognised by its distinctive organic remains. I regard the thin bed of brownish carbonaceous slate met with at the junction of the Auroral limestone with the Matinal slate in the neighbourhood of Nazareth and on the Bushkill, as probably representing the margin of the formation. A black slate, identical to all appearance with that which overlies the Auroral argillaceous limestone (Trenton) on Martin's Creek, and which is undoubtedly the equivalent of the Matinal Black slate (or Utica), occurs in all the hills ranging N. of the margin of the limestone through a belt some two or three miles broad. We meet it on the road between Easton and the Water-Gap as far as 10 miles from Easton. At the hill 7^ miles from Easton, it displays beautiful oblique rhombic prisms, produced by the intersections of the planes of bedding, the cleavage and the cross joints. Here the dip of the cleavage has an unusual direction, which, instead of being towards the E., or even E. 20 N., is generally in this belt towards the Highlands, or the igneous range of New Jersey ; that is to say, about S. 30 E. The Matinal Newer Slate (corresponding to the Hudson River Slate of New York) exhibits throughout the North-eastern portion of the valley very nearly the type which it wears on the Hudson, embracing, in addition to a large preponderance of grey argillaceous slate, many beds of arenaceous slate, and some masses approximating in the coarseness of their fragments to true conglomerates. Further to the S.W. the formation acquires a somewhat more exclusively 240 KITTATINNY VALLEY. argillaceous character, not, however, to the exclusion of all the coarser layers, many of which are visible on the Susquehanna at Harrisburg. Along the North-western side of Lebanon and Dauphin, the lower and middle members include numerous beds of red and yellow slate, which impart to the soil an aspect not usual in other parts of this belt. These coloured layers, especially distinct in the region N. of the Swatara, are more seldom met with either E. of the Schuylkill or W. of the Susquehanna. They represent a very common type of the formation as it occurs in the central parts of Virginia in the range of the same great valley. At the Delaware River, and in several localities between it and the Lehigh, the more purely argillaceous portions of this rock have the composition and cleavage-structure of roofing-slate. One outcrop of this roofing-slate lies near the base of the Kittatinny Mountain. Organic remains are rarely visible in this Matinal newer slate of the Kittatinny Valley, partly from their actual sparseness in the rock, and partly from the effects of the cleavage-fissures which almost everywhere traverse it, and impart to all its fragments surfaces not coincident with the planes of original deposition, upon which alone the fossils are arranged, or could be more readily detected. Geological Structure. Little need be said in detail of the structure of the Kittatinny Valley, as an examination of the general sections cannot fail to render perfectly intelligible the character of its numerous flexures, and the cause of the almost universal prevalence of a South- eastern dip. It is extremely difficult to recognise, and especially to trace along the surface, the individual lines of anticlinal flexure within the slate-belt of the Northern side of the valley, in consequence of the imperfect exhibition of the true dip, disguised as this is by the more promi- nent feature of the cleavage-planes all dipping in one direction. Within the outcrop of the limestone the recognition of the axes is more easy, on account of the less thorough obliteration of the dip by the cleavage -fissures, and the greater conspicuousness and individuality of particular layers in the strata. Some of the more conspicuous anticlinal and synclinal flexures in the limestone are readily discernible on the Delaware River, where the rocks are less closely folded than further Westward ; but on the Schuylkill and Susquehanna a very close inspection of the edges of the strata is frequently requisite before we can detect the place of the abrupt change in the direction of the dip. In most cases the space occupied by the actual curve or flexure is very narrow, often not more than a few yards, while the dip on both sides is approxi- mately parallel, or towards the same South-eastern point, and at nearly the same angle. It may be stated as generally true, that the inclination of the less disturbed, or South-eastern leg of the arch, is from 45 to 60 ; while that of the North-western inverted side is from GO to 80. There is seldom, indeed, a difference of more than 20 in the dip of the two sets of strata, and in some cases they have been compressed into almost perfect parallelism. In the quarries, which are becoming numerous upon the Eastern bank of the Susquehanna below Harrisburg, an opportunity is afforded in two or three instances of detecting the anticlinal curve and abrupt inversion of the strata on the Northern side of it. Other more numerous examples are visible in the cuttings of the railroad between the Susquehanna and Chambersburg, more particularly in the Western part of Cumberland County and in Franklin County. CHAPTER II. AUBOKAL LIMESTONE OF THE KITTATINNY VALLEY, FROM THE DELAWARE TO THE SCHUYLKILL. THE North-eastern division of the Kittatinny Valley, or that included between the Delaware and Schuylkill Rivers, is separated somewhat unequally by the line of boundary between the Auroral limestone and Matinal slate. Commencing at the Delaware a little above the mouth of the Pequest, it recedes very gradually from the river until it reaches Martin's Creek, near its mouth, leaving but a narrow belt of limestone on the Pennsylvania side. From Martin's Creek the Northern limit of the limestone pursues the base of the Slate Hills, crossing the Bushkill near the intersection of the road from Easton to the Wind-Gap. Thence sweeping a little more to the Westward than in its former course, it ranges to Nazareth and Bath, passing through the centre of these villages. From Bath its course is to Siegfried's Bridge on the Lehigh, the line previously passing S. of Kreidersville. Crossing the Lehigh, the junction of the limestone and slate inflects more to the Southward, passing Gordon's Creek near Sieger's, and leaving Toglesville about half a mile to the S. It intersects the Berks County line near Haus's, and thence taking a less Southerly course, passes half a mile N. of Kutztown and S. of Moslem Church, approaching Maiden Creek about half a mile N. of the Friends' Meeting-house. Here it curves Southward, and ranges parallel with the valley of Maiden Creek, which it leaves, and crosses the Schuylkill at Althouse's Bridge, nearly two miles above Maiden Creek, and about nine miles from Reading. The line of junction of the two groups just traced is rendered somewhat irregular in certain neighbourhoods by the intrusion of narrow belts or tongues of slate into the limestone, and of limestone into the slate, the results of anticlinal and synclinal flexures. We meet with such N. of Trexlerstown. Besides this interlocking of the formations, a few local tracts of the slate appear within the general limits of the limestone, involved in the synclinal folds of the latter, and on the other hand, small anticlinal belts of the limestone occur inside of the area of the slate. Such are the natural results of the folding and subsequent denudation to which the strata have been subjected. At tlie Delaware River. Beginning the more detailed description of the Auroral limestone at the Delaware River, 1 shall allude, in the first place, to the comparatively narrow belt embraced between the general boundary of the South Mountains and the narrow spur of gneiss called Chestnut Hill, N. of Easton. This trough of the limestone, which terminates in a synclinal point a few miles E. of the Delaware in New Jersey, between two ridges of the Gneissic rocks, seems to possess the true basin-like structure, without the usual inversion along its Southern side. The strata resting against the foot of Chestnut Hill show where they are exposed on the Delaware, a Southern dip of about 4.5 diminishing to a very gentle one at the mouth of the Lehigh, and becoming a true Northern dip near the base of the Lehigh Hills. The lower beds are silicious, and many of them highly magnesian, and included in them are many layers and nodular bands of dark -grey chert, portions of which are reddish. Fragments of this chert are abundant in the soil N. and N.W. of the town of Easton. The limestone, especially the middle part of the formation, is quarried in a number of places ; for example, ou the N. side of the Bushkill, about one mile and a half from Easton, where it is extensively excavated, and converted into lime. There are other large quarries below the mouth of the Lehigh, along the Delaware Canal, which supply much lime- VOL. I. 2 H 242 AUROEAL LIMESTONE, KITTATINNY VALLEY. stone to Bucks County, where the farmers use anthracite coal for burning it into lime for fertilising the soil. The iron ores along this Southern belt of the limestone near the Lehigh have been already alluded to in the Chapter upon the Rocks ^of the South Mountains. North of Chestnut Hill. Much of the surface of the wider belt of the limestone embraced at the Delaware between Chestnut Hill and the foot of the Slate Hills, is covered superficially, in the vicinity of the river, by drift and river alluvium ; but when we proceed Westward to within two miles of Martin's Creek, the limestone appears abundantly exposed. Near the river-side, about two miles above the mouth of Martin's Creek, hsematitic iron-ore, apparently of good quality, was at one time dug, but the mine is no longer wrought. From the general shallowness of the earth over the limestone, there would appear to be but little probability of the existence of a large deposit of ore in this locality. At the mouth of Martin's Creek the belt of limestone is very narrow. The rock, which is here nearly horizontal, is quarried on the river-bank. A little below the stream the dip is North- Westward, and somewhat further down there is a small anticlinal flexure. Advancing S. we meet with S.E. dips five miles above Easton, at Sandt's, and some distance lower down with a N.W. dip, about 45, proving another more considerable normal axis. The lime- stone of this neighbourhood is more silicious than that nearer the slate, and the lime derived from it is less esteemed. It belongs evidently to a lower position in the formation. Still descending the river, we cross another anticlinal axis, and lastly a synclinal trough, on the Northern side of which the South-eastern dip is 45 ; while on the Southern, at the base of the steep anticlinal of Chestnut Hill, it is nearly perpendicular. It is a fortunate circumstance that the purity of the limestone adjacent to the Northern edge of the belt adapts it so well for agricultural use, since the soil of the slate country to the North is particularly benefited by the appli- cation of lime, and there is a rapidly growing desire among the farmers for this valuable fertilising agent. Several quarries are now wrought along this border, especially S.W. of Bath, and the limestone is conveyed into the slate tract, and there burned into lime. SECTION FROM EASTON NORTH ALONG THE DELAWARE, INCLUDING THE MINERAL AXIS OF CHESTNUT HILL. Examining more closely the rocks along the Delaware northward from Easton, the Auroral limestone is seen well exposed in the hill N. of Easton, nearly to the axis of Wolfs Hill. Probably there are two anticliuals in the limestone in this space. On the South side of Wolfs Hill (Chestnut Hill) we come upon the massive altered rocks, Primal slates, and sand- stones. This ridge consists, in the axis or centre of the arch, of a coarse, highly crystalline porphyritic granite, and both the North and South flanks contain a great variety of remarkably altered rocks. Both on the South and North sides of the axis the Primal sandstone is very well exposed. On the South side it seems to constitute a separate low arch. It is here largely displayed on the river-side, and is very vitreous, much fused, and generally of a reddish hue ; but a white sandstone of the more normal character is associated with this. The slates and limestone which overlie this are entirely metamorphosed. The former is a crystalline dolomite, including much serpentine and various beautiful magnesian minerals. The slates have been rendered magnesian and talcose, and in some instances highly micaceous. In contact with a vein or dyke of coarse granite near the South side of the gap, the slaty rocks, with bedding and dip still clearly perceptible, are seen changed into chloritic, and micaceous, and hornblendic slates, looking much like members of the Gneissic or older metamorphic series ; and yet among the coarser grits, thus altered, we may discern the quartz pebbles unchanged. Towards the North end of the gap, after passing a great thickness of very massive, coarse, felspathic granite, such as already described, we come upon a massive-bedded rock, having all the appearance of regular stratification, and dipping steeply North. This has externally the aspect of a thick-bedded sandstone, but is a peculiar micaceous and hornblendic grit, looking, when fractured, precisely like some of the old horublendic and micaceous slates. Beyond this point, and just at the North end of the gap, there is a considerable mass of Primal white sandstone, forming a stone-slide or talus. In the North-west flank of the ridge, the sandstone may be seen in place dipping vertically. CHESTNUT HILL. 243 There can be no doubt that the micaceous and hornblendic slates and grits are lower members of the Primal series, in a highly altered or metamorphosed condition. A little further North beyond these exposures of Primal white sandstone, are calcareous slates and sandstone of the base of Auroral limestone, presenting extraordinary chemical alteration. These are speckled throughout with greenish serpentine, &c., or converted into white crystalline dolomitic marble. The slaty parts contain also beautiful crystals of mica and talc. It would thus seem that the great agent of metamorphosis in this belt has been the intense heat effused during the intrusion of the great dyke of granite which forms the main body of the ridge, and that while this has developed in the slates of the Primal series a hornblendic character, and has vitrified the pure silicious sandstone, it has dolomitised the adjacent magnesian limestone, and in these and the contiguous slates has developed the serpentine, silicate of magnesia, and, in fine, the talcose and other magnesian minerals which so greatly abound on both flanks of this remarkable igneous axis. Near the centre of the Gap there occurs a considerable mass of this dolomite, and of serpentine marble and slate, which may be explained by merely regarding the ridge as a double anticlinal flexure, including near its middle a small fold or synclinal trough of the Auroral limestone. There can be little doubt of the presence of two chief lines of eruptic matter, each composed principally of granitic rock. On each side of these, and therefore between them, are stratified serpentinous beds, with various associated magnesiau minerals and dolomitic limestones. It is probable, therefore, that there exists between the two granitic dykes a synclinal fold or squeeze of the Auroral limestones, which have undergone alteration and impregnation with serpen- tine and other minerals, as on the outside of the dykes they unquestionably have. Near to each of the granitic belts we meet the massive gneiss in places much altered, and some of it impregnated with serpentine or converted into it. The bedding and internal stratification of much of the massive serpentine and serpentinous gneiss is too obvious to be doubted. Upon each external flank of the ridge there occurs a belt or outcrop of the Primal sandstone, much injected with granitic matter, but still an unmistakable sandstone. The Primal slates are converted, not into but towards a gneiss, with specks of fine crystalline hornblende and mica, mingled with the granules of sand. The belt on the S.E. is seen at the river's edge with a flattish anticlinal roll in it. The rock here weathers a reddish brown. It is a coarse sandstone, very hard, and injected with felspathic granite, some of which seems to be segregated. This outcrop, ten feet above low-water-mark, is smooth from erosion, and exhibits the feature called Eochgs Moutonnais in Switzerland. Two views may be entertained of the geological origin of the serpentines and associated magnesian minerals : one, that they are altered forms of the magnesian silicious limestone of the base of the Auroral series ; the other, that they are true igneous injected materials. The fact that one zone of these minerals is on the flank of the ridge, and seemingly outside of the Primal rocks, is friendly to the first of these hypotheses ; but two other belts of the serpentine occur nearer the axis of the ridge, amid the true gneiss, and with granitic injected rocks near. If we suppose that the whole uplifted zone embraces a compressed synclinal fold of the Auroral limestone and the structure of the hill strongly indicates this we may impute the magnesian minerals in part to the metamorphosis of the magnesian calcareous rocks. The serpeutinous rocks even of the more central parts of the ridge exhibit a sort of stratification, and this implies that a portion at least of the material called serpentine here, was originally a sedimentary rock, but altered, the trans- formation consisting, most probably, both in a segregation of its own elements and an intrusion of true igneous mineral matter. Beyond the North side of the gap of Wolfs Hill, for about three-fourths of a mile, no exposures are seen ; we then enter upon a series of undulations or flexures in the limestone, which continue with but little interruption to Martin's Creek, where, as already stated, the slaty limestone and slate of the Matinal argillaceous limestone (Trenton limestone) formation are admirably exposed. This part of the section displays the following conditions : 1. For | mile North of gap no exposure ; then at limekiln, magnesian limestone, dip North 85. 2. At 200 yards we have South dip, which continues until, 3. At 500 yards, we have North dip, about 70. Then, 4. At GOO yards, we have South dip. 244 ATJKORAL LIMESTONE, KITTATINNY VALLEY. 5. At 800 yards North, dip 60, which continues to 6. 1000 yards, where we meet South dip about 50, becoming more gentle, 40, 30, and 20. This low South-dipping flaggy limestone continues exposed along the river-shore, until it is seen gradually to turn over into a North dip at the great bend of the river (convex to the West). This is a beautifully regular broad anticlinal. The rocks of the Northern flank of the axis are well seen at the Mineral Spring Hotel, five miles north of Easton. 7. Passing about one mile very obliquely across the strike, without any exposure, we come upon another broad anticlinal of the limestone. Here are two limekilns. The rock of this axis is dark-blue and argillaceous, and more thin-bedded and slaty than the preceding, and is greatly cut by cleavage. This, in its upper beds, has the aspect of the Trenton limestone. A little further on (500 feet) we come upon the Matinal argillaceous limestone (Trenton limestone) in a high escarp- ment on the North side of Martin's Creek. The dip of the rock is about 30, but rolling, and the cleavage nearly horizontal. The mass consists of calcareous blue slate, with courses of blue argillaceous limestone aud fissile blue slate of very even texture. This latter has the smooth cleavage and nature of roofing or writing slate. Here occur many Trenton fossils. The whole thickness of the formation exposed cannot be less than 150 feet; and there is no doubt a portion of it not visible. Anticlinals. From what has been noted above, it appears that there are four anticlinals actually discovered between the first exposure of the limestone and the margin of the slate, and assuming one in the interval between the flank of Wolf Hill and this first exposure, we may put down five anticlinals. Several anticlinal flexures are discoverable in the limestone belt where it is intersected by the Lehigh River, between Allentown and the margin of the formation. Some of these are com- pressed South-east-dipping folds, others more open curves of the normal type. From below Allentown to within two miles of Easton, the Lehigh flows near the base of the South Mountains, apparently in the trough of the first synclinal flexure. The general dip of the limestone, as it here rests against the foot of the Gneiss Hills, is not inverted but steep towards the N.W. I have already alluded to the occurrence of strata of oolitic limestone near Allentown. These are to be seen near the bridge which here spans the Lehigh. At Porter's Quarry, one mile and three-fourths below Easton, the following structural features may be noted in the limestone Dip of the strata, 45 to N. 25 W. Dip of main joints S. 45 E. Dip of cleavage -planes at right angles to bedding. Dip of second or great smooth joints, 85 to S. 40 W. CLEAVAGE IN THE REGION OF THE DELAWARE EIVER NEAR EASTON AND THE SOUTH MOUNTAINS. No district in Pennsylvania, nor indeed in the Middle States N.W. of the general South- eastern boundary of the Appalachian Valley, displays the cleavage structure in the rocks so con- spicuously and pervasively perhaps, as the country between Easton and the Delaware Water-Gap. The whole belt of rocks from Easton to beyond Stroudsburg and this includes nearly all our forma- tions from the Primal to the Vergent is remarkable for the amount of the cleavage fissures which everywhere, in nearly parallel direction, intersect the more argillaceous and calcareous masses. Even in the belt of anticlinal and synclinal ridges called the South Mountain (locally, the CLEAVAGE. 245 Lehigh Mountains), this feature, so curious in a scientific point of view, and practically so important, prevails very extensively. Commencing the following brief sketch of the phenomena with this Southern zone, it will be well to call attention first to the cleavage in the Auroral limestone of the synclinal troughs exposed on the Delaware south of the mouth of the Lehigh. Here, as the Section will show, the cleavage in the limestone, which, from the extreme thinness of the Primal series, is almost the only Palaeozoic mass preserved, observes, very generally, the law prevalent throughout all the South-eastern Appalachian region. It exhibits a steep South-easterly dip ; but it is interesting to note that the strike of the cleavage seems not to coincide with either the strike of the Palaeo- zoic strata to which it belongs, nor yet with the strike of the previously disturbed and somewhat unconformable syenitic gneiss. In the Auroral limestone of the synclinal before us, the abundance of the cleavage-planes is decidedly less than in the Matinal slates of the Kittatinny Valley, a fact quite in accordance with the very general observation that these massive magnesian rocks, like all our massive thick- bedded homogeneous strata, excepting the purely argillaceous ones, have been far less affected by the transforming igneous influence derived from within the crust, than the ancient mud-rocks. Everything else in the geology of this disturbed and contorted zone, leads us to infer that here the metamorphic action was at a maximum, or was at least more intense than in the tracts further north. The higher degree of cleavage in the slate rocks further up the Delaware must, then, be fairly attributed to some special relations between the mineral natures of the strata, and their susceptibilities to assume this peculiar structure. Into the consideration of this somewhat subtle connection I shall enter in another place, where an attempt will be made to give a theory of cleavage and metamorphic action generally. The strike of the Gneiss in this district varies from N. 50 E. to N. 45 E. That of the Palaeozoic strata is generally about N. 65 E. But the strike of the cleavage-planes of the latter the limestone is frequently, by several degrees, more E. and W., though sometimes it is very nearly conformable to that of the strata. In the greatly disturbed and altered igneous and metamorphic mineral axis N. of the town of Easton, there called Chestnut Ridge, and in New Jersey, the Marble Mount, the Auroral mag- nesian limestone highly affected by contact and intrusion of injected or infiltrated volcanic matter, displays the cleavage structure very conspicuously. The talcose and serpentine rocks, whether we regard them as altered forms of the magnesian limestone or not, are unquestionably stratified rocks, and even these display the cleavage structure. Disturbed as the bedding is in this much- convulsed anticlinal belt, the cleavage-planes, though far from regular, and often nearly perpen- dicular, have a prevailing steep South-eastern dip. CHAPTER III. MATINAL SLATE OF THE KITTATINNY VALLEY, BETWEEN THE DELAWAKE AND SCHUYLKILL. Boundaries. It has been already stated that the Northern side of the Kittatinny Valley is occupied almost exclusively by the Matinal newer slate spread out in a broad belt like the lime- stone, by a series of anticlinal and synclinal undulations. The Southern margin of this slate was traced from the Delaware to the Schuylkill in defining the Northern limit of the limestone. The Northern boundary coincides very nearly with the Southern slope of the Kittatinny or Blue Mountain, the junction of the upper layers of the slate with the lower beds of the Levant grey sandstone being in some places lower, in others higher, on the mountain-side. Geological Structure of the District. By a reference to the general Sections, Nos. II. and III., it will be seen that throughout this portion of the valley the anticlinal flexures in the slate have less of the closely-compressed or inverted form than belongs to those S.W. of the Schuylkill. On the mountain-side of the belt especially, the more open or normal style of undulation is every- where discernible near the foot of the mountain. The Kittatinny Ridge itself, from the Delaware to the Schuylkill, exhibits no inversion of the strata, the dip being at a moderate angle towards the N.W. ; it is therefore but the Northern abutment of a huge normal arch. Further to the S.W. the rocks of this mountain, and the ridges N.W. of it, are more nearly vertical, and in some places, as at the Sus- Fio. 31. Close foldings in Matinal Slate, Harrisburg. g. quehanna, actually overturned beyond the perpendi- cular ; and connected with this greater steepness, we observe in the corresponding portions of the Matinal belts of the Great Valley a proportionately greater amount of compression and obliquity in the flexures, and therefore a more general preva- lence of the South-eastern dips. Within the limits of the Slate tract, the Auroral limestone is lifted to the surface in two localities by anticlinal flexures, but it is very evident that in other places this formation lies at no great depth, though concealed by the overlapping slate. One of these insulated outcrops of the limestone is at the Delaware River in the Little Valley of Cobus Creek ; the other in or near Kreidersville, not far from the Lehigh. The Cobus Creek Belt of the Matinal limestone is but the South-western termination of the long and narrow anticlinal of the Valley of Paulinskill in New Jersey. With the gradual sub- sidence of the axis, the limestone contracts to a point, and passes under the slate about two miles West of the Delaware. The flexure is nowhere very steep, even the North-western dip not exceeding 45. On the Delaware the belt is rather more than one mile in width, the Southern limit being somewhat more than half a mile below the mouth of Cobus Creek. This limestone produces excellent lime, and is quarried to some extent. The most Western quarry is near the Tott's Gap Road. The much smaller outcrop of the limestone near Kreidersville is about two and a half miles SLATY CLEAVAGE. 247 North of the Southern edge of the slate. Its extent is limited. The dip there is very irregular, but the predominant direction is Eastward about 40, and the strata seem to have been contorted and broken by a more than usual degree of subterranean action, for the rock is rilled with intru- sive veins of white quartz of all dimensions up to a foot in width. This little tract of the lime- stone, so far within the general margin of the slate, is therefore most probably the result of a local dislocation on an anticlinal, rather than the effect of a regular unbroken flexure. This limestone is quarried and converted into lime on the spot for agricultural use. Between the Northern edge of the limestone tract, and the anticlinal of Cobus Creek, the slate exhibits an apparent general dip to the S.E., but much of this is due to the cleavage fissures, all of which incline in that direction. It is probable that this belt constitutes one wide syncli- nal trough with lesser undulations in the middle of it. Along its Southern border runs a chain of slate hills, traceable with interruptions to the Lehigh. At the junction of the two formations the limestone displays a gentle dip North-westward, passing under the base of these hills. Near this line of contact there occur in the slate several calcareous layers, some of which approximate to the composition of an impure limestone. Some of these contain casts of fossils of the usual characteristic species, but they are imperfectly preserved. Veins of white rhombic carbonate of lime, with white quartz, occur in this line in several localities ; and further Northward in the slate tract, injections of white igneous quartz are not unfrequent. In the vicinity of Martin's Creek, and again near Kreidersville, fragments of igneous quartz are numerous in the soil, and some of these are of large size, showing the veins to be one foot and more in thickness. Slaty Cleavage. A remarkable peculiarity in the position of the cleavage-planes is visible over quite a wide belt in the centre of the Appalachian Valley, all the way, indeed, from the Delaware to the Lehigh, and extending even N.E. and S.W., beyond the rivers. It is that of a near approach to horizontally. This flatness of the cleavage-dip is well seen on Martin's Creek, at the junction of the Matinal limestone and Matinal black slate, and characterises, I believe, the entire outcrop of these two rocks in their range South-westward to the Lehigh. But the zone over which it prevails is even broader, for the same flat cleavage is met with to the N.W. of the contact of the two strata over a space of at least two or three miles. It may be seen along Martin's Creek for nearly three miles above its mouth. Further to the S.W. we behold the cleav- age with this gentle dip, or even flat position, to the N. of the villages of Nazareth and Bath, and near Kreidersville. Indeed it occurs in various places, though along belts less continuous and broad, the whole way to the Southern base of the Kittatinny Mountain. About eight miles from Easton, on the watersheds between Martin's Creek and Richmond Creek, the Matinal slate exhibits both cleavage-planes and trans verse joints in remarkable regu- larity, but directed to rather unusual quarters of the horizon. Roofing-Slate Quarries near Delaware Water-Gap. The portion of slate belt included between the Delaware and Lehigh presents several localities of excellent roofing-slate. While the formation, as a whole, contains much coarse arenaceous rock, and even some beds of conglomerate, certain strata, especially in the lower part of the mass, possess the qualities of the roofing-slate of commerce. That part of the formation which contains the roofing-slate lies in a narrow zone, distant from one to three miles from the Kittatinny Mountain, running from a point in New Jersey a few miles E. of the Delaware Water-Gap, across the Delaware and the Lehigh, to a few miles W. of the latter river. It is, however, only in a very limited number of places within this belt that the rock presents that fortunate union of conditions which must exist to produce good slates. Not only must the rock be sound, uniform, and compact in texture, easy of cleavage in one direction, and tough in every 248 MATINAL SLATE, KITTATINNY VALLEY. other, and free from any bands (called ribbons) containing sulphuret of iron, which cause its rapid decomposition, but it must lie in a favourable manner for being quarried, with a stream of water passing over the stratum to preserve it moist, and cause it thereby to split with ease and regularity. These conditions are very happily combined in the two quarries, which are at present wrought near the Delaware Water-Gap. That on the West side of the Delaware, worked by the Pennsylvania Slate Company, presents some very interesting features. The Quarry at present is in the form of a beautiful amphitheatre or circle of cliffs, about 100 feet in diameter, and at least 60 or 70 feet high. The strata, fine bluish slate with ribbons of bedding, dip about 30 to N. 30 W., with remarkable regularity. In all the portions below a certain plane, apparently that of a slip or fault, the FIG. 32. Cleavage in Slate Quarry. Delaware , , . . , , . Water-Gap. cleavage is very nearly horizontal; but immediately above that plane, the cleavage-planes of the first course curve down steeper and steeper towards the S.E., or S. 45 E., and in all the still higher ones the tendency is to a S-.E. dip, but only very gently, except in the North-western parts, where it is more obvious. The annexed Sketch shows the cleavage in its different phases. The texture of this slate, in the absence of any defining fossils, suggests that it may belong to the Utica Slate Formation, and it is quite conceivable that an 30 K. 30 w. ax j g a j tn j g dj s t ance f rom tij e outcrop of the Levant Sandstone of the Kittatinny Mountain may lift the Matinal Slate to the day, but this needs confirmation. The true stratification of the rock is only detected here by the difference in colour caused by numerous very thin layers, from a few lines to an inch or two in thickness, traversing the rock in bands parallel to each other, and at various distances, not generally exceeding two feet. These ribbons denote the direction of the dip of the strata, being seams of a somewhat different composition from the rest of the mass. Between each two of these ribbons the layer of slate is homogeneous, or of uniform texture and composition ; but a difference in the quality of the slate on the two sides of one of these thin layers is quite common. When we examine a new surface of the slate, the usual and permanent colour of which is a dark bluish grey, the hue of these ribbons is nearly black ; but on exposure to the atmosphere, they show after some time signs of spontaneous decomposition, and display a whitish efflorescence, which indicates that this part of the slate contains the sulphuret of iron. These ribbons are therefore carefully excluded from the slates when they undergo the operations of cleaving and trimming, in their preparation for the market. At one place in the quarry, the dip of the strata, as indicated by that of the ribbons, is towards the W.N. W., at an angle of about 30. In the same part of the quarry the dip of the cleavage-planes, or in other words, of the slates, is towards the South, and at an angle of nearly 50. Here, however, is the same dislocation or fault traversing the quarry as in the spot first described. This is a slide of one part of the stratum upon the other, and is from six to twelve inches wide, being filled with white calcareous spar and fragments of slate. The rock below it has not only a different actual dip from the portion of the stratum above it just alluded to, and a different direction also in the cleavage of the slates, but a different quality in these slates themselves, those beneath being much superior to those over the dislocation. From this lower part of the quarry, nearly all the roofing and writing slates are derived. The best school-slates are got from belts that lie directly beneath the sparry seam or fault. The direction of the cleavage-planes in this portion of the mass is nearly horizontal, while the planes of stratification dip towards the N.W., but at a very moderate angle. The differ- ence between the directions of the cleavage-planes above and below the fault, renders it possible that the dislocation and slide in the stratum took place after the mass had acquired this remarkable tendency to cleave in a direction oblique to the stratification ; for had the cleavage originated subsequently to the disruption of the rock, we ought to find it main- taining the same direction, and observing the same features on both sides of the fault. These facts concerning the change in the quality and the position of the slates caused by the dislocation, indicate how numerous and minute the circum- stances are which must be attended to by those who enter on the business of quarrying this rock. About a mileS.E. of the quarry just described, another has been opened, but it has not been vigorously wrought. That on the opposite side of the river, in New Jersey, is worked, though rather inactively, notwithstanding the excel- lent quality of the roofing-slates procured in it. In the hills along Martin's Creek, about four miles above its mouth, are indications of good roofing-slate. Slate Quarries near the Lehigh Water-Gap. The only other considerable quarry, besides those near the Delaware, in operation within the slate-belt of this part of the State, is the Union Slate Quarry, about one mile W. of the Lehigh LEHIGH SLATE QUARRIES. 249 and about nine miles N.W. of Allentowu. The most remarkable feature here is the parallelism of the cleavage-planes of the slates to the plane of the stratification. The dip is towards the S.S.E., at a somewhat variable angle, averaging 15. Owing to this coincidence of the cleavage with the stratification, the surface of the slates is slightly undulating. They are esteemed well adapted for roofing, but being hard, they are not sold for writing-slates. The hardness of the rock in this quarry I attribute to the high temperature originally imparted to it by a mass of intruded quartz, which has entered it from a deep source within the earth. The force which injected this material has heaved up a portion of the strata into the form of a small anticlinal elevation in the quarry, and has in other respects deranged the dip of the rock. The slate quarries around the town of Slatington are situated near the base of the Kittatinny Mountain, about two mile S. of the Lehigh Water-Gap, embraced in forty acres of land, owned by a company. Five quarries are now opened, called the Washington, Trout Creek, Franklin, Bangor, and Douglas. The first is the largest, 120 feet from base to top, and 300 feet exposure. The Douglas is the smallest, 60 feet high, with a front face of 75 feet ; from this school-slates are taken; and from the other four, roofing-slate. (Mining Magazine, 1856.) There is a small quarry which has been occasionally worked, lying about one mile and a half W. of the town of Nazareth. Roofing-slate was also formerly procured on the East side of the Lehigh, near Kreidersville. It is by no means improbable that other points along the same belt of country would reward diligent search by pre- senting eligible situations for quarries. In the neighbourhood of Nazareth, which is on the line dividing the slate from the limestone formation, a material is procured, which answers well the ordinary purposes of black paint. This appears to be simply a more than usually carbonaceous, black, and soft variety of the Matinal black slate, occurring near the base of the formation a little above its contact with the limestone. It occurs also further E. on the Bushkill, and has been found likewise on the Union Canal, in a corresponding situation in the stratum. It requires to be ground in a drug-mill, and levigated in troughs, by passing over it a stream of water. Thus prepared, it constitutes, when mixed with oil, a very excellent pigment for the exterior of houses, fences, and other structures exposed to the weather. Evidences of Erosion of the Surface. In no part of the Kittatinny Valley are the evidences so striking of an energetic rush of waters across the surface from the Northward, as in this region between the Delaware and Lehigh. Transported boulders of sandstone and conglomerate traceable to the Levant rocks of the Kittatinny Mountain, and to the Vesper- tine and Serai conglomerates still further North, strew the soil in almost incredible numbers. This drift appears to be most abundant opposite the gaps and depressions in the Kittatinny Mountain. Hydraulic Lime. Some of the calcareous layers in the inferior portions of the Slate formation seem by their com- position to be well adapted for producing an excellent variety of hydraulic cement. A manufacture of this article was begun a few years since on the Eastern side of the Lehigh, above Siegfried's Bridge, the rock being near the junction of the slate and limestone. The cement made proved to be well suited to the purposes of hydraulic architecture. Slate Hills. In pursuing this slate formation Westward from the Lehigh, we find towards the line between Lehigh and Berks counties, a large area of country very uninteresting to the geologist from its sameness. An endless succession of slate hills, containing rocks of the same character as those already described, leave little to say concerning this region. About the head- waters of Antelanna, or Maiden Creek, those hills attain a height almost entitling them to the name of mountains. From the neighbourhood of New Tripoli, westward, the slate-hills and ridges increase in height : some of their more conspicuous peaks, visible from a great distance, have received the names of Spitzberg, Round Top, &c. The ridges passing across the line into Berks County range near the churches N. of [Schaffer's Tavern, and rise E. of Round Top and Spitzberg, to nearly the same elevation, being entirely cut down by denudation in the valley of Maiden Creek and Pine Creek. W. of the latter stream they again rise into high points, and a ridge of great height continues West- ward, until it almost unites with the Blue Mountain N.E. of Hamburg. Above the mouth of Pine Creek, and near the Church, a little above the Old Union Furnace (Reagan's), is a slight calcareous band in the slate, which has been tried for making lime, but without much success. Some of the limekilns here are upplied with stone brought across the mountain from the Pre-meridiau formation. Indications of calcareous strata appear in the low ground near the foot of the mountain ; but the nature of the country is such as to offer scarcely any good exposures of rock in place. Lime has become much prized by the farmers in the slate region as a manure, and is extensively prepared by many who bring the limestone with great labour over a hilly road from the neighbourhood of Kutztown, ten or fifteen miles. Red Slate. About Klinesville, seven miles Eastward from Hamburg, we find a band of red slate, which seems to die out a little to the Eastward of that place. As we shall hereafter see, this variety is of very common occurrence in the VOL. I. 2 I 250 MATINAL SLATE, KITTATINNY VALLEY. formation further Westward. W. of the Schuylkill, and along the Tulpehocken Creek, alternations of red slate, with the dark-grey slate, are very common, and seem to be connected with the calcareous bands, which are more common there than in the district before us. Band of Limestone. About four miles N.W. from Kutztown, a little N. of Saconing Creek, at Kemp's Mill (Kiemer's on the County Map), there is a band of limestone in the Slate formation, which is quarried on the farm of Mr Eocher. It is seen in the quarry about 20 feet in thickness, mixed with slates, some of the strata being very thin, others one foot or more in thickness, the dip about 30 S.S.E. It is used for burning into lime for a manure. The same band is also seen at Sontag's, above Lesher's Mill, near the mouth of the Saconing, and at other places further Westward ; but it is not known to extend Eastward much beyond the quarry at Kocher's. This is evidently a prolongation of a calca- reous band, which we shall have occasion to notice as occurring at Winter's, on the West side of the Schuylkill. At Hoch's, two and a half miles West from Kutztown, in the Southern edge of the slate, there occurs well-crystal- lised Arragonite. CHAPTER IV. AURORAL LIMESTONE OF THE KITTATINNY VALLEY BETWEEN THE SCHUYLKILL AND SUSQUEHANNA RIVERS. THE Northern boundary of the Auroral limestone from the Schuylkill to the vicinity of Stouchtown is very irregular, in consequence of the presence of a number of anticlinal undula- tions, which cause the limestone and slate to interlock by a succession of long narrow tongues, or tapering belts. I shall therefore not attempt a minute tracing of the line of separation, but refer to the Geological Map for a general exhibition of its course. After many undulations in the vicinity of the Tulpehocken, the line passes about two miles Northward of Stouchtown, in a more nearly straight direction West-south-westward, ranging half a mile N. of Myerstown, and thence parallel with the turnpike leading to Harrisburg, preserving a nearly uniform distance from it of about half a mile, as far as Hummelstown. Crossing the Swatara Creek or River north of this village, it extends parallel with the stream for nearly two miles ; and about a mile W. of the point at which the turnpike road crosses this, it intersects the turnpike road, and thence ranges a little S. of this to the Susquehanna at Harrisburg. North of the Southern Slate Ridge, which forms the Northern boundaiy of the main belt of limestone from the Swatara to the Susquehanna, there is a narrow strip of the limestone extending Eastward from the river below Harrisburg. This lies on both sides of the turnpike road near the Dauphin County Poor-house, where it is but little more than one-fourth of a mile broad. Between it and the chief mass of the limestone to the S. there is here a narrow belt of the slate, which, widening Eastward, merges into the general slate tract near the Swatara below Hummelstown. Trap Dyke. About four miles W. of Reading there occurs a dyke of trap, crossing the limestone Northward from the Primary hills. It may be seen on the turnpike a little E. of Sinking Spring, and thence down the Cacoosing Creek, showing itself on the W. of the stream, and crossing the Tulpehocken at the mouth of Cacoosing, where the trap-rock in place is finely exposed near Van Reed's Mill. Thence still further N.E. the boulders of trap appear on the slate near Epler's ; but the dyke does not seem to reach so far N. as the Schuylkill. Iron Ores. Brown iron-ore lies on the surface in many places Westward of the Schuylkill, especially about Cacoosing and Sinking Spring ; though for many years sufficient search seems not to have been made for it. More recently considerable quantities have been mined, and sent to the Schuylkill at Reading. One mine is situated about nine miles from Reading, and about a quarter of a mile S. of the turnpike. The ore was disseminated through clay. It is of mixed quality, though much of it seems to be capable of making a good iron. S. of the road from Womelsdorf to Stouchtown, ore is seen on the surface ; and about half a mile S. of the place last named it has been mined. This ore lies on the rising ground S. of the Tulpehocken, on the limestone, where that rock is very silicious and cherty. The ore is of a hard, compact quality, much of it being found in large solid masses, some of which weigh more than 100 pounds. It has the external aspect of a cold short ore. There are indications that iron ore might be found at several points from Womelsdorf S.W. along the Southern margin of the formation. CHAPTER V. MATINAL SLATE OF THE KITTATINNY VALLEY BETWEEN THE SCHUYL- KILL AND SUSQUEHANNA. THE upper portion of this formation, as exposed on the West bank of the Schuylkill below the mountain, for several miles contains some thick bands of tolerably compact sandstone, inter- stratified with the slate. The more solid beds are in several places quarried, and have been used in the construction of culverts, bridge abutments, &c., on the Reading and Pottsville railroad. About two miles below Hamburg these sandstone strata become less frequent, and the slate more uniform, though it is still very silicious. Further down the river the slate becomes thinner in its laminae, and darker coloured, some of the bands bearing a resemblance to roofing- slate, though none of it has a sufficiently regular cleavage to be valuable as such. At Althouse's Bridge, as already observed, occurs the point of junction of the slate with the limestone. We find no calcareous bands of any importance in the railroad cuttings near the river, the excavations being mostly through the harder projecting ridges of silicious and slaty rocks ; the limestone, if its narrow bands reach the river, being usually in a position occupied by low ground or diluvial soil, owing to its greater tendency to decomposition and denudation. Nearly Westward from Shoemaker's (about 12 miles above Eeading), we find on the high lands W. of the river a band of limestone 20 or 30 feet thick, in thin layers, including some slate. This is quarried at Winter's, and other places in the neighbourhood, for burning into lime for manure. Thence it extends Westward towards the head-waters of Irish Creek, and is probably the same band as that which is quarried at Straus's, Mast's, Himmelberger's, &c., crossing the Northkill near Hawk's Mill, and passing N.W. of Bernville to the Northern edge of the main limestone formation near Kauffman's, three miles N. from Stouchtown. N. of this band of calcareous slate are some veins of red slate, but not of great thickness. On the Main North Kill, perhaps half a mile above the Little North Kill, there occurs a thick bed of limestone dipping 35 S., exposing an outcrop of more than 300 feet in breadth. The composition of the rock is peculiar, and well deserves the attention of the geological inquirer as suggesting some- important theoretical inferences. It is a true calcareous conglomerate, composed of pebbles of the Auroral magnesian limestone firmly cemented by a limestone paste. Some of these pebbles are but imperfectly rounded or worn upon their edges, but the greater proportion of them are apparently completely water- worn. This stratum extends several miles, appearing more than two miles W. of the Little North Kill. It is not the only instance in the Auroral series of a conglomeritic limestone consisting of pebbles derived from the inferior part of the formation, of which it is itself one of the upper members. Near the little village of Hope, in New Jersey, there is a similar stratum not far below the junction of the limestone and slate. It is obvious, from the occurrence of so thick a bed of limestone pebbles, that at the period of the formation of the stratum, the previously -deposited limestone must not only have been SCHUYLKILL TO STJSQUEHANNA. 253 already solidified, but sufficiently uplifted to be exposed to destructive currents. Each such' stratum has been evidently the result of a paroxysmal movement, probably of the nature of an earthquake, not sufficiently energetic permanently to elevate or incline the newly-formed sedimentary mass, or to interrupt the general progress of the deposition, yet violent enough to set the waters into active motion, and thus break up and strew afresh in form of pebbles the more exposed upper strata. The limestone matter which occupies the interstices between the pebbles may have originated either from materials in a state of suspension in the waters at the time of the sudden movement, or more probably as a wash from the newly-deposited and still soft and pulpy carbonate of lime of other tracts still submersed. One of the most interesting circumstances attending this conglomerate is the terminal position which it occupies in the formation. It is at or near the higher limit of one of the thickest and most widely-expanded limestone deposits of the continent. The violent agitation of the sea-bed which it indicates must therefore have been that which preceded or attended the extensive revolution in the physical geography in the Appalachian ocean, by which the growth of the Auroral calcareous sediments, their wide shell-beds, and vast coral reefs, were for ever suspended, and a new state of the waters established, hostile to nearly all the old forms of life, but friendly to others freshly created, and with new adaptations. This revolution, as the geological exploration of the Palaeozoic Basin of the continent shows,' banished the conditions favourable to the deposition of lime from nearly its entire area, and substituted a state of things compatible only with the precipitation of mud and sand, to endure as long, seemingly, as the immense antecedent period of the calcareous depositions. It could have been nothing short of a total reconstruction of the bed and shores of that ancient sea ; and from various evidence, the nature of the revolution was partly a sudden, partly a gradual, stupendous lifting of the sea-bed from comparatively deep to shoal water. Near Wagner's, four miles Westward from Hamburg, a slight exposure of slaty limestone appears, but the material is not now used. Westward from this, four miles further, at Shartel's, eight miles from Hamburg, we find some considerable bands of red slate, which appear to die out Eastward. S. of Irish Creek we find steep slate hills, and a little N.E. from Bernville rises a high ridge, which is called " Scull's Hill," and which is prolonged past Bellman's Church towards the Schuylkill, near the mouth of Irish Creek. This ridge is chiefly slate, with some thin bands of silicious rock, all dipping steeply S.S.E. To the S. of this ridge, about the head of Plum Creek, we again find calcareous strata in the slate in the neighbourhood of Himrnelberger's Mill, and S. of this a red slate, interspersed with the bands of dark and yellow slate common to the formation. From this point South-eastward are barren slate hills (containing red slate bands), with a few sandstone strata, extending hence to the Northern border of the limestone near Eeeser's Mill, six miles N. from Beading. On the road from Reading to Bernville we pass from the limestone to the slate, about one mile S.E. of the bridge over the Tulpehocken, or about five and a half miles from Reading. Hills of the slate continue along the bank of Tulpehocken to Heister's Mill, near which are beds of limestone mixed, and alternating with slate ; and above Heister's the calcareous bands increase in frequency and thickness, varying from a few inches to 50 or 60 feet in dimensions. The dip here is much confused and undulating ; but this condition continues for a very short distance, the general dip being 45 to 70 S.S.E. Red slate occurs abundantly on both sides of the calcareous belts. The main calcareous band extends Eastward to the neighbourhood of Bern Church, and disappears a short distance beyond it. These calcareous beds near the base of the slate probably represent the Auroral argillaceous limestone. From Heister's on the Tulpehocken to a mile beyond Bernville, on the road to Rehrersburg, we find thin bands of limestone in the slate. All these bands, when of sufficient thickness and purity, are quarried iu many places for 254. MATINAL SLATE, KITTATINNY VALLEY. burning into lime, which is used as a manure ; but the lime produced from them is not considered so good for building as that from the main limestone formation on the S. Crossing from Womelsdorf to Bernville, we pass first a belt of the slate, about half a mile wide, then limestone a quarter of a mile in width, dip 30 to 45 S.S.E. ; then a slate ridge, two miles from Womelsdorf. Half a mile N. of this are some bands of limestone, but slate prevails as far as Tulpehocken at the mouth of North Kill Creek. Near the Tulpehocken we find many belts of red slate. From the mouth of North Kill up the tow-path of the canal, dark and red slates are chiefly apparent for about two miles, then bands of slaty limestone 10 to 50 feet thick. These latter continue mixed with dark and red slates to a little above the old forge (formerly Ege's), where the slate becomes more and more mixed with calcareous strata. At about half a mile above the forge the slate ceases, and the limestone continues to Womelsdorf, though somewhat thin and slaty, opposite the end of the slate hill half a mile N.E. from that town. The dip about Beruville is steeply S.S.E. 60 to 80, diminishing Southward towards Womelsdorf to 30 and 40. From all this it would seem that the slate suddenly widens out W. of the Schuylkill by deflecting its Southern margin Southward, very nearly to the turnpike at Hain's Church, eight miles W. from Heading, and thence to within less than half a mile of the Primal sandstone near Womelsdorf is penetrated by belts from the wider portion of the limestone region N.W. of Womelsdorf, and that the two formations mutually pierce each other by innumerable tongues or small pointed belts, which gradually thin out, the limestone bands on the E., and the slate bands on the W. This irregularity ceases from the neighbourhood of Kauffman's, N.W. from Womelsdorf, and N. of Stouchtown, for here the limestone having spread out on the N. to its usual breadth, and the slate having contracted to a narrower range, the line of union between them, trending W.S.W., is nearly straight, and is well defined. Near the Southern border of the slate S. of Rehrersburg, the formation embraces several bands of the red slate. Northward from that village to the base of the mountain, the only rock is the grey slate of the upper half of the formation. It appears to be destitute of any beds of limestone. The prevailing dip is to the S.S.E., and steep ; in some places it is perpendicular. W. of Eehrersburg narrow bands of the limestone show themselves. One occurs on the road to Jonestown, three miles from Eehrersburg, and another about three miles E. of Jonestown. Along the Tulpehocken the slate ridges contain much intrusive quartz in the form of narrow veins. Indeed, all the higher ridges of the central tracts of the valley appear to be traversed by innumerable thin injections, and to owe their elevation above the general plain to the superior resistance locally presented by these ribs of indestructible material, over that offered by the slate under the excavating action of the denuding currents. In the tracts so replete with igneous quartz, we usually find the strata dipping at a steeper angle than elsewhere, a natural consequence of the more complete folding together of the beds under the lateral compression connected with the intrusion of so large an amount of material. Iron Ore. About two miles N.E. of Jonestown large masses of a rough and cellular silicious iron ore appear upon the surface. These strew the Southern slope of a low ridge of slate, and seem to be derived from a band of yellowish and red slate of the kind very common in this neighbourhood. Limestone. N. of the red slate there exists a narrow band of slaty limestone, and a similar thin bed appears S. of the iron ore. About half a mile E. of Stumpstown, iron ore closely resembling that above mentioned was dug many years ago, but the supply proving deficient, the excavations were abandoned. Near this old mine occurs a calcareous and ferruginous stratum in the slate, very susceptible of decomposition ; and it seems probable that this ore is derived from a somewhat similar band of rock. On the Rehrersburg road, about three miles E. from Jonestown, a little S. of a small limestone band, a small excavation was once made for iron ore, which was found in very limited quantity. Bunker's Hill. S. of Jonestown there is a high and rocky ridge called " Bunker's Hill," which rises steeply on the Eastern side of the Swatara, and ranges along the Southern side of the Little Swatara for between two and three miles, sinking away Eastward near the road from Stumpstown to Lebanon. Towards the Western end of this hill there is a depression, over which passes the road from Jonestown to Lebanon. East of this indentation its higher parts consist of sandstone closely resembling the Primal sandstone, though it is difficult to conceive how it can have been uplifted here. It lies in huge broken masses on some parts of the hill, and on others is more disintegrated. The Western part of the hill, next the Swatara Creek, shows none of this sandstone, being composed of curiously altered rocks, with some boulders of trap. Along the Northern and Southern bases of this ridge we find a limestone evidently very different from the calcareous slaty bands so common in this part of the slate formation. From its position and character it HOLE MOUNTAIN. 255 seems to belong to the Auroral limestone. It is visible along the Little Swatara south of Jonestown, where it is quarried, and appears to extend about two miles up that stream Eastward. On the Southern side of Bunker's Hill it is quarried on the bank of the Swatara, a little below the aqueduct, and at other places on the S. of the hills farther Eastward. On both sides of the ridge this limestone evidently overlies the sandstone. On the S. we find the limestone overlaid by slate, with some red bands ; and about half a mile S. of Bunker's Hill, as we approach another trap ridge, the slate exhibits the influence of the once heated trap in its highly-altered aspect and structure. Half a mile further S. there is another ridge of trap-rock, the interval between this and the last-mentioned being occupied chiefly by the slate, which here includes some bands of argillaceous sandstone. This dyke crosses the road from Jonestown to Millerstown, about two and a half miles from Jonestown, and terminates on the Eastern bank of Swatara, about a mile above the Waterworks. Eastward it does not extend much beyond the Eastern road from Lebanon to Stumpstown, and is seen abundantly on the middle road, S. of Little Swatara, and also on the road from Lebanon to Jonestown. Between this Southern trap ridge and the Northern margin of the limestone, half a mile North of Lebanon, the whole space is occupied by the slate of the usual character of the formation. North of the limestone on Little Swatara, S. of Jonestown, we find the slate in its ordinary characters ; but on the N. of the town it includes calcareous bands, and also much interposed red slate. A little above the Swatara Bridge west of the town there is a quarry of the slaty limestone, the layers being from an inch to a foot in thickness, the whole dipping nearly perpendicularly. Ascending the Swatara from this point we find a band of red slate of considerable width, and others narrower, mixed with the common dark slate, which continues to nearly two miles above Jonestown, where we find calcareous strata that have been quarried and used for making lime. About a mile further (i. e. one mile below Weidman's Forge) there is a silicious conglomerate 30 or 40 feet thick, an upper member of the Matinal slate. On the E. of the Swatara it forms a hill or ridge. Above this point, in the neighbourhood of the forge, we have the slate exposed along the canal bank, with a general S.S.E. dip, though in some places curiously twisted and contorted. The Hole Mountain is a narrow ridge rising E. of the Swatara, extending nearly parallel with the Blue Mountain for four and a half miles, and subsiding Eastward before reaching the road which connects Millersburg with Pine Grove. The included valley of Hole Creek, about one mile in width, between the two mountain-summits, contains only the Matinal newer slates, with some thin bands of very slaty limestone. In the narrow crest of the Hole Mountain we meet with massive beds of the Levant grey sandstone, dipping to the S.S.E. at an angle of 80. The very summit itself consists of a silicious conglomerate, adjacent to which are beds of a fine-grained whitish grey sandstone. Both flanks of the ridge expose the slate. It is manifest that a steep and closely-compressed synclinal fold has here preserved the lowest of the hard Levant rocks from denudation, and formed this long narrow ridge. The anticlinal flexure connected with this synclinal occupies the middle of Hole Valley. As usual in such closely-folded synclinal flexures, the strata are much contorted near the centre of the trough. This is displayed at the Western end of Hole Mountain, near the feeder of the Union Canal, where the beds of slate are greatly crushed and twisted. At Harper's, near the mouth of Indian Creek, five miles W. of Jonestown, limestone is quarried from the calcareous bands of the slate. These seem thicker and more abundant here than they usually are in this range. The calcareous layers are, however, only from one to six inches in thickness, being much mixed with slate. They yield a lime of inferior purity. Two miles S. of Harper's, other calcareous strata appear, which are probably a prolongation of those a little N. of Jonestown, while those at Harper's, on Indian Creek, may belong to the strata on the Swatara about two miles above Jonestown. It is, however, very difficult to trace accurately such very thin bands of limestone through a country composed of friable slate, and where the exposures of the limestone are comparatively rare and ill defined. On a singularly sliarp and abrupt slate. hill near the creek above Harper's, there occurs a peculiarly fine-grained compact rock, resembling a hone-slate or novaculite. About two and a half miles N.W. from Harper's, a little iron-ore was once mined. A shaft was sunk, eighteen or twenty feet, through earth and rotten slate, to a peculiar conglomerate rock, containing innumerable rounded masses of sulphuret of iron, the cement being calcareous matter. This rock was said by the miners to be two or three feet thick, and much decomposed on the outside. .Below it lies the ore, which is evidently derived from the decomposition of the calcareous and ferruginous stratum above, but which is probably too highly impregnated with sulphur to be usefully employed in a furnace. 256 MATINAL SLATE, KITTATINNY VALLEY. A very similar region to that above described, embracing the ordinary Matinal slate, interspersed with narrow- bands of calcareous rock, ranges Westward, and is well seen on Monday Creek, from the Swatara to the mountain. The calcareous bands appear both on the S. and N. of the road from Jonestown to Harrisburg, one being quarried near the creek, about half a mile N. of that road. Further up the creek, about a mile from the mountain, there is a cal- careous stratum a little below the furnace. This is visible near a spring in low ground, but is not used ; further Eastward, however, it is more apparent. This is probably the same band as that seen in Hole Valley, and which ranges along the Southern base of the mountain, at the distance of from half a mile to a mile from it. It is doubtless a prolongation Eastward of the same calcareous stratum seen to the Westward of the Susquehanna, near the mountain. It passes not far from Linglestown, and is visible in occasional spots throughout this range Eastward as far as Hole Valley. Indications of other calcareous strata in the slate are apparent near the mountain, much further Eastward, but do not seem to be connected with any important beds of limestone. These calcareous beds are seldom fossili- ferous. From Monday Creek Westward to the Susquehanna, the same upper portion of the Matinal slate presents precisely the same features as further Eastward, The hill to the Eastward of Harrisburg contains a conglomerate, with strata of slate and sandstone, much resembling that noticed as occurring in a hill E. of the Swatara, above Jonestown. The slate hills S. of the narrow belt of limestone which passes near the Dauphin County Poor-house, and along the turn- pike from Harrisburg towards Hummelstowu, have been sufficiently noticed already. CHAPTER VI. AUEORAL LIMESTONE OF THE KITTATINNY VALLEY BETWEEN THE SUSQUEHANNA AND THE MARYLAND STATE LINE. ALONG the South-western bank of the Susquehanna, we find the Southern margin of the limestone overlapped by the red shales of the Mesozoic or Middle Secondary series, about two miles below New Cumberland, at the mouth of the Yellow Breeches Creek, the limestone rising in a moderately elevated cliff near the river. Near its contact, it has derived a reddish tinge from the overlying red shale ; but a little further N., in Musser's Quarry, it loses this stain, some layers presenting the aspect of a fine white marble, which, if thick enough to work, would be a valuable rock. The prevailing dip of the limestone here is towards the S.S.E., at an inclination of 30 35. Near the mouth of the creek, the limestone contains a narrow belt of slate, visible occasionally for several miles up the stream, and extending, indeed, along the Southern border of the formation, the whole way to Maryland. Above New Cumberland, the Lime- stone is discernible along the water's edge, preserving its usual character, but exposing changes of dip implying the existence of an anticlinal fold. Immediately above, the dip diminishes to 15 S., and gradually grows less, until at a little more than a mile below the railroad bridge at Harrisburg, the strata become horizontal, indicating this as the position of a flat anticlinal arch. North, for about a fourth of a mile, the strata incline Northward, at an angle not exceeding 20. We then find a flat synclinal axis, beyond which, for three-quarters of a mile, to the bridge, the steeper southern dip is resumed, gradually increasing, until at the bridge it is about 45. The steep Southern dip continues to the boundary of the limestone and slate, which is seen in the ravine at the bridge, along which the railroad passes. The slate here, dipping to the S., or under the limestone, is evidently inverted by a folding of the limestone, somewhere between this point and the synclinal axis above mentioned. The natural or original position of the great slate for- mation of the Kittatinny Valley is, of course, above the limestone. (See Section of West Bank of the Susquehanna, opposite Harrisburg.) Boundary of Auroral Limestone and Matinal Slate. From this point of junction near the bridge, the line dividing the two formations ranges nearly Westward to the most southern bend of the Conedogwinit Creek, following thence the general course of that stream, the Southern bends of which reach but do not penetrate the limestone, while its Northern loops lie all within the slate. The limestone, towards its northern margin, contains thin belts of the slate, similar to that noticed as ranging near its Southern side. Near Newville, the boundary leaves the course of the Conedogwinit, to bear somewhat more Southwardly. It here makes a double turn, taking a zigzag course, in consequence of an irregular anticlinal axis near Newville, which elevates the limestone in a long projecting point, penetrating the slate North-eastwardly. Eesuming its regular course, it passes S.W. from Newville, leaving Shippensburg three miles to its S.E. ; and then deflecting still more towards the S., it passes a little W. of Green Village, and reaches the Conecocheague north of Chambersburg. It follows this stream past the town, and VOL. I. 2 K 258 AUEOKAL LIMESTONE, KITTATINNY VALLEY. after pursuing it about four miles, stretches away in a S.S.W. direction to Greencastle, and thence on to the Maryland line, which it intersects about a mile E. of the Conecocheague. Boundary of* Auroral Limestone and Primal Slate. The Southern margin of the limestone, quitting the Susquehanna two miles below New Cumberland, runs first North-westward, and then Westward for several miles, leaving a narrow belt of the rock on the South side of Yellow Breeches Creek. The overlapping Red Shale crossing the creek about two miles N. of Lisburn, follows its border to Bryson's, west of Lisburn, where the Red Shale leaves the limestone, the formation beyond this point being bounded on the S. by the Primal sandstone. Making the general course of the creek its boundary, the limestone passes by the Southern side of the stream, at Williams's Mill, about three miles N. of Dillsburg, and extends some distance along Dogwood Run, folding round the end of the South Mountain. Further towards the S.W., the edge of the limestone lies near the North-western base of the mountain, though it is frequently concealed by a covering of diluvium. In some places, owing to a fault or sudden folding together of the Primal slate, immediately at the base of the moun- tain, the limestone approaches the sandstone ; and indeed in some of the ore banks, situated low down on its declivity, limestone shows itself beneath the ore. In these instances, however, it is probably not the main body of the formation, but a narrow belt in the Primal slates. The limestone, generally, is much interstratified with greenish and reddish slate along the base of the mountain. Having thus defined, with sufficient accuracy, the two boundaries of this broad tract of the limestone, I shall next give some details connected with the formation. South-westward from Montalto, much ore strews the surface along the North-western side of the mountain. In the neighbourhood of Tomstown it occurs in large blocks, but is very silicious, being associated with fragments of the yellow silicious rock already alluded to as frequently accompanying the iron ore along the mountain. The limestone folding round the Southern end of this mountain-ridge extends some distance up the little valley of the Cold Spring Branch, appearing on the North side of Green Eidge below the rolling mill. Iron ore, in moderate quantity but of inferior quality, has been dug to some extent on the North-west side of the stream. A considerable amount of ore is visible in the soil on the farm of Mr Middauer, three miles N.E. from Waynes- burg. It is rather too silicious to make a superior iron. Sulphate of Baryta. On the Southern part of the same farm, and also on another adjoining one, loose masses of tolerably pure white sulpliate of baryta occur. It probably occupies a position between the narrow belts of limestone and slaty sandstone which traverse the hills of this neighbourhood. Proceeding from the foot of the mountain towards Waynesburg, we first meet, after leaving the low grounds, with slaty limestone, alternating for some distance with slate, until we reach the second ridge, three miles S.E. from Waynesburg, where a band of white limestone crosses our section. This latter rock is quarried, and shaped into tomb- stones, about three miles further S.W. On the top of the ridge the limestone is of a dark colour, alternating over a breadth of a mile with bands of slate. In the next ridge, two miles S.E. of Waynesburg, the limestone is interstratified with a thinly-laminated green slate. Near Waynesburg the slate becomes more silicious, some of it being reddish, and nearly all of it containing minute scales of mica. The line of iron ore seems not to extend South-westward much beyond Middauer's ; for in crossing its range in several places between Waynesburg and the foot of the mountain, few indications of it were visible on the surface. White Limestone. On the Southern Branch of Antietam Creek, near the Maryland line, we encounter a band of white limestone at Eoyer's. The bed is here several feet thick, but somewhat divided by thin sheets of a greenish slate. It is a beautiful rock, of a white aspect and fine texture, and where large blocks are not required, might be advantageously employed as a marble. Cave. A rather extensive cavern occurs in the limestone at the North-eastern end of a ridge, a little lower down DETAILS. 259 on the same branch of Antietam Creek. Still lower down the stream, at David Funk's, occurs a grey calcareous and silicious rock, in thin layers, from which excellent flagstones are quarried. Again, still further down, and near the State line, there is a belt of limestone, said to yield a lime which will not slack after being burned. Travertin. Near the West Branch of Antietam Creek, one mile N.W. of Waynesburg, we meet with a deposit of travertin, or calcareous tufa, of considerable superficial extent. A similar deposit is visible near the mill E. of Chambers- burg, and in several other places along the streams of the limestone region, where the water is highly charged with car- bonate of lime. This material, when in a sufficiently pulverulent condition, is an admirable manure, particularly when applied in the form of compost. Limestone, Fossiliferous. The North-western border of the great limestone belt passes through the borough of Cham- bersburg, in the neighbourhood of which some bands of the rock are fossiliferous a character which the formation only rarely assumes anywhere in the Kittatinny Valley north-eastward of Franklin County. These fossiliferous beds belong to the Matinal limestone, or Trenton formation of New York. About seven miles Southward of Chambersburg, in a ridge called " Grindstone Hill," we find a bed of sandstone interstratified with the limestone, yielding a material suitable for rough grindstones. Advancing from Waynesburg towards Greencastle, we cross alternating belts of limestone, and interstratified greenish slates ; and beyond these the limestone spreads in a nearly uniform belt, over a considerable breadth of surface, diversi- fied as usual, however, in colour, composition, and qualities. Four miles N.W. of Waynesburg occurs a dark bituminous variety ; and in a ridge two miles further, a band nearly white. Immediately N.W. of Greencastle we encounter the line of contact of this wide belt of the Auroral limestone and the Matinal slates. This latter rock, which we shall next proceed to describe, ranges along the North-western margin of the above zone of limestone the whole distance across the State, from the Delaware River to this point, and Southward into Virginia. CHAPTER VII. PRINCIPAL BELT OF THE MATINAL SLATE OF THE KITTATINNY VALLEY BETWEEN THE SUSQUEHANNA AND THE MARYLAND STATE LINE. Boundary. The very uniform character and composition of this wide formation, together with its general deficiency in interesting and useful minerals, will render a detailed description of it unnecessary. Its South-eastern margin has been indicated in defining the North-western boundary of the limestone. From the Delaware Water-Gap to Strasburg, in Franklin County, its North-western limit coincides with the base or flank of the Kittatinny or North Mountain, where the formation supports the massive Levant sandstones occupying the summit of the ridge. From Strasburg to the Maryland line, the principal slate-belt recedes from the mountain, and is bounded on the W. by a wedge-shaped tongue of limestone, the boundary between the two rocks passing the villages of Strasburg and St Thomas, or Campbeltown, and intersecting the Maryland line about a mile W. of Conecocheague Creek. About a mile and a quarter from the base of the mountain, at the Susquehanna River, the slate contains a thin belt of limestone, imperfectly visible at the river-side. Either the same or another bed is seen about a fourth of a mile nearer the mountain. This belt seems to extend Westward several miles, growing, however, gradually thinner and more -slaty, and ceasing, probably, S.E. of Sterrett's Gap. In no part of this belt of the slate formation have the strata the structure and cleavage requisite to produce roofing-slate. The nearest approximation to that useful variety yet seen occurs in the bed of the Conedogwinit, above Alter's Mill, where the rock is traversed by cleavage-planes of tolerable regularity, but its usefulness is destroyed by its containing sulphuret of iron. At " Dublin Gap," N. of Newville, there occurs a spring highly charged with sulphureted hydrogen gas. Some bands of the slate, particularly those lying adjacent to the limestone, are highly car- bonaceous, and of a dark colour somewhat resembling the slates of the coal-measures. This analogy in their appearance, notwithstanding the conclusiveness of all geological evidence to the contrary, induces many persons, not familiar with the geology of the country, to suppose that the formation may actually include coal. For the last fifty years, excavations have, from time to time, been made at various places in the valley, in the confident belief that coal will be discov- ered, and though in every instance unsuccessful, they are still occasionally renewed. This dark carbonaceous slate, the Matinal black slate of our classification, is nowhere a thick formation in the Kittatinny Valley, from many parts of which it is altogether absent. We have already seen that it possesses a very thin outcrop, near Nazareth, and elsewhere in Northamp- ton County. In Centre and Huntingdon counties it is more expanded. CHAPTER VIII. BELTS OF AURORAL LIMESTONE AND MATINAL SLATE IN THE SOUTH-WESTERN PART OP FRANKLIN COUNTY. First Limestone Belt. The South-western portion of Franklin County contains three mode- rately broad belts of the Auroral limestone, alternating with three belts of the Matinal slate, occupying the interval between the margin of the great slate belt above described and the Eastern slope of the Cove Mountain. An anticlinal axis ranges nearly centrally along each zone of limestone, imparting to the intervening belts of overlying slate a regular synclinal structure. The relations of these belts to each other are shown in the Section through Bedford to the South Mountain. The most Eastern, and by far the largest range of limestone, is that already alluded to as terminating in a long tongue near Strasburg. It is broadest at the Maryland line, and does ,not materially diminish in width until we trace it about three miles N. of the Greencastle and Mercersburg road, where it is about three miles wide. West of St Thomas, it is but little more than a mile from its Eastern to its Western border, which is within three-fourths of a mile of Parnell's Knob. Here it curves a little Eastward, taking a direction about N.N.E. to Strasburg, following the foot of the mountain until it disappears in a narrow point under the overlying slate. The anticlinal axis which runs somewhat centrally along this belt, prolonged beyond Roxbury, seems to extend for many miles towards the N.E., being probably the same axis which separates the North Mountain, at Dublin Gap, from the spur lying S. of it, and which is thence pro- longed through Perry County. The usual aspect of this rock is rather uniform. The beds belong to the upper half of the Auroral limestone ; some of those in the Southern part of the tract, near the anticlinal axis, are magnesian. First Slate Belt. The belt of slate which bounds this tract of limestone on the W. embrac- ing both sides of Claylick Mountain, at the Maryland line, ranges a little E. of N. to the foot of Parnell's Knob, where it again separates by receiving the mountain in its synclinal axis, one portion passing along the Eastern and the other along the Western base and slope. The overlying Levant sandstone occupying the tops of Claylick and Parnell's mountains, in the middle of this trough of slate, have nearly a perpendicular dip, implying that they have actually been folded together along the synclinal axis, by an action like that of closing a book with its back or cover downwards. Second Limestone Belt. West of this belt of slate, the average width of which somewhat exceeds a mile, there ranges a narrow zone of the limestone, traversed longitudinally by an anti- clinal axis, which has given to the rocks E. and W. of it the steep inclinations they possess. This anticlinal belt of limestone, passing out of Blair's Valley, between the Claylick and Two-Top Mountains, at the Maryland line, ranges to the mouth of Bear Valley, separating Parnell's from Jordan's Knob. Its average breadth is about half a mile. The rock exhibits the usual variety in its several beds, some of these being silicious, while others again are pure, and adapted to 262 BELTS OF LIMESTONE AND SLATE. produce an excellent lime by burning. Certain bands of it are evidently of the kind suitable for hydraulic cement. About a mile and three quarters from Parnell's Knob, the soil above this limestone contains a deposit of iron ore, which was at one time smelted in a small furnace at Loudon. Second Slate Belt. West of the last-described belt of limestone ranges another parallel zone of the slate, also about half a mile in width, which, like the previously-mentioned slate tract, con- tains a synclinal trough ; in the middle of this lies the Two-Top Mountain on the S., and Jordan's Knob on the N. Third Limestone Belt. To the W. of this slate, there ranges another anticlinal belt of limestone, emerging from between the Two-Top and Little Cove Mountains south of the Maryland line, and passing along the foot of the latter to Loudon, and thence for several miles along the middle of Path Valley, vanish in a narrow point N.W. of Fannettsburg. The elevation of this belt of limestone has caused the Eastern inclination of the rocks in the Two-Top and Jordan's Mountains, and the Western dips in the Little Cove and Tuscarora ridges. We thus perceive that all the valleys subordinate to these axes of elevation contain the limestone or its next superior rock, the slate, having in every case anticlinal dips ; while the mountain-ridges included between these valleys, consisting of the higher Levant rocks, rest invariably in the synclinal troughs embraced between the lines of elevation. Third Slate Belt. The narrow belt of slate which overlies the last-mentioned range of lime- stone occupies the base of Little Cove and Tuscarora mountains, and rises nearly to their summits where it supports the Levant sandstone. Passing W. of Loudon and Fannettsburg by Concord, it extends into North Horse Valley, between the Tuscarora and Conecocheague Mountains in Perry County. The valley called the Little Cove, bounded by the Cove or Tuscarora Mountain on the W., and the Little Cove Mountain on the E., presents the strata in the form of a synclinal trough, the two enclosing mountains consisting of the Levant sandstone. Both margins of this valley are occu- pied by the Surgent red slates, seen near the foot of the bounding ridge. The Pre-meridian lime- stone encircles the Cove, inside of the red shale, and supports in its turn the Meridian sandstone in two belts, the North-western one forming a considerable ridge. The centre of the basin is occupied by the Cadent slates, the strata on the West side of the synclinal axis dipping gently E., while those on the East side are nearly perpendicular. Among the lowest layers of this Cadent slate occurs a highly important bed of iron ore used at Warren Furnace. It is a grey proto- carbonate of iron, precisely identical in chemical composition with the nodular and plate ores of the shales of the Coal-measures. The discovery of the true nature of this ore, and of the exact place which it occupies in the strata, constitutes one of the most interesting and useful of the develop- ments of a practical kind connected with the Geological Survey. In describing the rocks of Huntingdon and Bedford counties, this important deposit will be again alluded to. CHAPTER IX. IRON ORES OF THE KITTATINNY VALLEY. POSTPONING to another Division of this Work the discussion of the general geological and chemical relations of the iron ores of the State, and such statistics of quantity and composition as I have to offer, I shall, in accordance with a plan already commenced, present in this place some details respecting the iron ores of the great natural area now described the Kittatinny Valley. The greater part of these notes, it should be observed, relate to observations made as long ago as 1840, the date of our more minute researches into the geology of the district. Unfortunately time was not allowed me to extend the re-surveys imperatively called for by the progress of development in the coal regions, and some other tracts, to this important zone of country, and therefore some of the statements, especially those relating to the more variable features of the deposits, and to the mere statistics of mining, are partly obsolete ; but even these possess a certain permanent value, in showing, if not the exact present condition of things, at least all the real phases which our surface ores assume, under their different localities and different stages of development, by mining. I indulge a hope of being yet able, before the com- pletion of this work, to supplement this account with a description of the chief and most characteristic mines of the surface brown iron-ores, as they now appear. But should this purpose miscarry, enough is here presented to show the distribution, even with local precision, of nearly all the more valuable deposits, and to display the unfailing wealth in iron of this part of the State. BETWEEN THE LEHIGH AND THE SCHUYLKILL. Leaving the vicinity of the Delaware River, and approaching the Lehigh near its great bend at Allentown, we find iron ore near the Philadelphia road, two and a half miles S. of that town, in its favourite geological position near the junction of the Auroral limestone and the Primal slate. The deposit seems to be most abundant at the com- mencement of the steeper slopes of the hills of the Primal formation. In the low ground S. of the ridge containing the quarries, near the road from Bath to Bethlehem, about one mile from the first-named village, the soil displays indications of iron ore. This spot holds very nearly the position in the limestone belt occupied by the ore-deposit near the Delaware, already spoken of, and by other still more important accumulations W. of the Lehigh. About four miles N.E. of Bethlehem, between Hecktown and Butzville, iron ore of excellent quality was dug upon the farm of Michael Myers, but the quantity obtained at the date of our observations was not great. About five miles, a little W. of N., from Bethlehem, there begins a range of valuable deposits of iron ore, which extend in a W.S.W. direction across the Lehigh, and are prolonged, with some interruptions, for a very great distance. Previous to our investigations, a shaft was sunk on the farm of Henry Goetz, five miles from Bethlehem, terminating in iron ore at the depth of forty-five feet. To the Westward of this, on the farm of Jacob Rice, much ore has been obtained. The deposit here lies beneath a deep accumulation of common earth. The ore is of variable quality and texture. No limestone had been reached in these excavations, and a well S.E. of the mine reached a depth of ninety feet before it encountered the rock. About 100 yards E. of this mine another was subsequently established. Derby's Mine lies Westward from Rice's one and a half miles. In the same range was Rohn's Mine, affording, like the two last named, chiefly small ore, mixed with much earth, from which it is detached by washing and screening. A few other less important deposits have been met with along this line E. of the Lehigh, and the aspect of the surface is such as to 264 IRON ORES OF THE KITTATINNY VALLEY suggest a strong hope that persevering explorations within the belt will issue in the discovery of yet more important accumulations of ore. Iron ore is abundant on the surface along the Northern base of the hills, South-westward as far as Emaus. About three-quarters of a mile S.W. from this village a mine was opened at Mr Daniel Schwartz's, and subsequently other shafts were sunk a little W. from the old opening. Further S.W. the ore is abundant on the surface, and excava- tions have revealed it in some quantity. From Emaus towards Millerstown there is also much surface ore, and fine specimens of fibrous hsematite may be found among it. West of Millerstown there extends a tract of low level land along the North side of the mountain, and the ore is here less abundant. From Millerstown towards Trexlerstowu, one mile from the former, much ore was seen on the surface of the fields. If we now take a position on the Lehigh, 3 miles above Allentown, where the range of the iron ore noticed as occurring at Rice's farm, and other places on the East side of the river, crosses to the West, we find it to be very exten- sively dug about half a mile W. from Hartman's Dam, near the Furnaces. This deposit lies on the corner of three farms, and is mined on each. The ore lies in the ferruginous clay in the interstices of the limestone rock, and, as might be expected from such a situation, contains much pipe ore, which is evidently of excellent quality. Associated with this are large masses abounding in the red oxide of iron, and apparently of excellent quality. But little hard or compact ore was found here, and much of that formerly obtained by Richards and Smith was prepared by washing the smaller particles from the soil. This washing is performed at the dam on the Lehigh by a machine. The ore deposit seems to range at first North- ward, but gradually to turn to the Westward, forming a kind of semicircular curve. It has been wrought in some places to a depth of about 60 or 70 feet, the limestone rock appearing along the side of the ore. Rather more than a mile N.W. from this belt of ore, and about four miles N.N.W. from Allentown, successful diggings were made for ore by Major Moyer. The surface-soil is here diluvial matter, with many pebbles of quartz and sandstone, and it exhibits scarcely any signs of ore. The upper surface of the ore was discovered in ploughing the fields, and a shaft was sunk about 30 feet deep. Like most other ferruginous deposits of the limestone region, it consisted of irregular nests and bunches of ore dispersed in loose earth, though the main direction of the ore could be traced dipping Southward. Some of the masses here unburied were of large size. Two principal varieties were met with, large lumps containing much oxide of iron, and between these ferruginous clay, holding a large mixture of true pipe-ore of excellent quality. The surface in this neighbourhood, and S. of it, is chiefly formed of a diluvial deposit, consisting of boulders and pebbles of the compact Levant sandstones of the Blue Mountain, and of white quartz coated with ferruginous matter. This Diluvium or drift probably conceals the outcrop of much iron ore. Southward from this locality, and about three miles from Allentown, ore was dug at Kratzer's, but the work was not prosecuted to any great extent. This ore lies near the point of a Slate ridge, which extends into the limestone from the Westward, coming in from the main Slate formation near Jordan Creek at Sieger's. The quality is variable, some being compact and hard, while other portions are of more open texture, and better adapted for smelting. Passing the end of this Slate ridge Northward, we again come upon the limestone, which extends N.W. between this ridge and the main belt of the Slate formation, but which grows narrower, and finally terminates by the closing together of the Slate ridges at a point a little W. of Sieger's Tavern, on Jordan Creek. In this limestone, a little N. of the first- mentioned Slate ridge, on lands of Mr Guth, about five miles from Allentown, iron ore has been dug for some years. It is on the ascending ground a little S. of Jordan Creek. Immediately S. of these old excavations, shafts were sunk developing a large quantity of a black unctuous clay, said to be 30 feet thick, evidently a decomposed slate, much charged with sulphuret of iron. If rich enough in this material, it may prove of some value for the manufacture of copperas. Opposite to this place, on the North side of Jordan Creek, iron ore is abundant on the surface, and so continues to the neighbourhood of Sieger's Tavern, near which a mine was in operation, and yielded a considerable quantity of ore. This mine is very near the junction of the limestone and slate ; the shaft was about 50 feet deep ; and the ore, though said to make a good iron, was too much mixed with slaty and earthy matter to yield a large per-centage. This place is about six miles and a half W.N.W. from Alleutown. Balliofs Mines. Between two and three miles North-eastward from this point, in the same range, and also near the Northern border of the limestone, are situated the much-noted mines belonging to Stephen Balliot, Esq., where ore has been obtained for many years in large quantity. This ore seems to be chiefly of two kinds : first, the " honey-comb ore," occurring frequently in large masses, a loose open variety, usually found nearest the surface, working freely in BETWEEN THE LEHIGH AND SCHUYLKILL. 265 the furnace, and said to yield a good iron ; and, secondly, a variety found generally below the honeycomb ore, though sometimes mixed with it, more compact in texture, and containing much oxide of iron. This bank was worked chiefly by uncovering the ore, though several shafts were sunk, and drifts run from them. The deposit appears to be very extensive, the workings already embracing many acres of ground. A little Westward from Balliot's the same body of ore was mined by Richards and Smith. In one of the North-western shafts at Balliot's diggings, a deposit of the oxide of manganese was found. It was said to be about four feet thick, which probably means that the manganese was scattered through a thickness of four feet of earth and iron ore. Another shaft, E. of the main workings, exhibited a dark-coloured clay, mixed with small fragments of white quartz. This clay seems to be highly charged with sulphur, but does not contain iron enough to make it a suitable material in an unconibined state for the manufacture of copperas. This range of iron ore may be traced by surface specimens a mile further Eastward towards the Lehigh, and also occasionally to the S.W. as far as Xander's, where it seems to terminate, the limestone itself ending here by a folding round of the slate hills to the S. of Jordan Creek, near the churches S.W. of Guth's and S. of Sieger's. Trexkrstown Mints. The range of ore which has been mentioned as crossing the Lehigh, and passing from three to four miles Northward and North-westward of Allentown, where it has been already noticed at the diggings of Everhart, Miller, Moyer, and Kratzer, may be traced South-westward by the surface specimens in the direction of Trexlerstowu. About two miles N.E. from Trexlerstown lies Shoemaker's Old Mine, long unwrought ; and three-fourths of a mile further S.W. occur other openings, on a farm of Mr Grammer. The ore found here was, at the depth at which we saw it, of a rather open and cellular structure. Near the church at Trexlerstown a mine was opened, exposing a considerable quantity of ore, which was covered with about 20 feet of earth, and was of variable depth, lying in nests and large masses, some of the lumps weighing several hundred pounds. It was in general rather compact and silicious, the limestone here being much mixed with quartz and chert. Several curious varieties of haematite occurred in this mine. From this vicinity towards Millerstown, and also South-westward, and Westward towards Breinigsville, the surface indicates the presence of much iron ore. Near the " Big Spring," a little W. of Trexlerstown, there is a bed of impure black oxide of manganese, appearing in the soil itself near the road-side. Copperas Mine. A mile W. of Trexlerstown, and half a mile N.E. from Breinigsville, occurs the noted mine of copperas earth and iron ore, worked, at the period of our first surveys, by Nathan Whiteley. Some borings had been made here by the proprietor, the results of which may serve to illustrate this interesting and singular deposit : RESULT OF BOEINGS AT THE IRON AND COPPERAS MINE NEAR No. 1. West of present Workings. Feet. 30 Clay and gravel. 4i Iron ore. 1\ Clay. 2 Black clay. 12 Sulphuret of iron. 5 Iron ore. Bottom of boring. No. 2. further Westward. Feet 15 Gravel and clay. 1 Iron ore. 15 Clay. 5 Slate. 6 In clay. 9 Pipe ore and clay. 4 Clay. Bottom. TBEXLERSTOWN. No. 3. Eastern Boring. Feet. 14 Clay. 8 Iron ore and clay. 9 Iron ore. 3 Clay. 2 Copperas earth. 2 Do. and black clay. 2 Do. and white clay. 8 Brown clay and iron ore. 2 Rock-iron ore. 8 Clay. Bottom. The black oxide of manganese is found in the upper portion of the iron ore, on the West side of the mine. The sili- cious slate is somewhat gypseous, evidently from a chemical reaction of sulphate of iron on carbonate of lime in the rock. The origin of this large deposit of sulphuret of iron is to be traced probably to a small shallow bed of Matinal black slate, which appears to have once rested on the limestone, and to have undergone disintegration. The iron ore, or brown peroxide of iron, in contact with the sulphuret of iron, is carefully separated from the rest, and laid in heaps, in order that the oxygen of the atmosphere and the rains may decompose and wash out the sulphurous portion ; but such ore never makes a superior iron. Westward from Breiuigsville the soil presents abundant indications of iron ore, and on a farm belonging, at the date VOL. I. 2 L 266 IRON ORES OF THE KITTATINNY VALLEY of our visit, to Mr Breinig, about one mile N.W. of the village near the base of a slate ridge, openings were made, which yielded ore in moderate quantities. The ore had generally a rather silioious aspect, and some pieces contained a consi- derable amount of white quartz. South of Metztown is Trexler's Furnace. Its ore, at the date of our investigations, was obtained from various places viz. Moselem, Breinig's, Shoemaker's, the Old Diggings near Kutztown, &c., with some magnetic ore from three miles Southward, at Landis's, and other localities. About a mile S. of Kutztown, good iron-ore was at one time obtained in some quantity, though subsequently the works were neglected, on account, it is said, of the influx of water. This is in the low ground near the South side of a limestone ridge, which lies between it and Kutztown. The surface-soil between this locality and Kutztown is abun- dantly strewed with blocks of chert of various colours, but generally dark bluish or black, in masses of considerable size. On the ridge S. of Kutztown there are extensive quarries of limestone from which much stone is transported into the slate country on the N., and there burned into lime for manure. The dip of the strata at these quarries is about 20 S. A white clay is also found at the iron mine. The Moselem, Iron Mines lie near the Northern border of the limestone within about 900 feet of the foot of the slate hills, five miles W.S.W. of Kutztown, corresponding in geological position with Balliot's Mines in Lehigh County. The ore is obtained by sinking shafts through the soil, and is commonly reached at a depth of from 20 to 40 feet. The diggings are very extensive, covering an area of several acres, and have been wrought for veiy many years, yielding a large amount of ore. This is said to occur in nests and irregular layers, varying in thickness from 1 to 8 feet ; it is of good quality. Some of it has a bluish tint, and contains a little man- ganese. On the top of the ridge S. of these mines the limestone is visible with a very gentle Northern dip. Large quan- tities of a dark-coloured chert are scattered over the surface, some of the masses weighing several hundredweight. Iron ore is indicated on the surface near the two-mile stone on the turnpike N. of Beading. About one mile N. of this town there is a narrow insulated belt of Primal Slate, constituting a ridge which runs Westward, and half a mile N. of the town there occurs another narrow outcrop of the Primal sandstone, barely visible in the Southern slope of the hill. Between the Schuylkill and the Susquehanna. The few notes relating to the less important localities of Hsematitic ore within the Kittatinny Valley, between the Schuylkill and at Susquehanna, have been already given in Chapter V., describ- ing the geology of that tract, and the reader is referred to the general Chapters on the Ores of the State for an account of the only one great ore mass of the district that of the great Cornwall mine. BETWEEN THE SUSQUEHANNA EIVEE AND THE MARYLAND STATE-LINE. Proceeding Westward from the Susquehanna, we meet with a large deposit of good iron-ore, about two and a half miles from the Harrisburg Bridge, called the Gorgas Ore Bank. The ore is imbedded in the ferruginous soil which over- lies the limestone. It occurs in bunches and irregular veins, the general course and dip of which coincide somewhat with those of the underlying rock. It is extensively mined, and is conveyed by railroad and canal to the smelting furnaces along the Susquehanna, especially to those of Governor Porter at Harrisburg, and under skilful treatment produces an excellent metal. A trap-dyke crosses the Yellow Breeches Creek about two miles N. of Lisburn, altering more or less the adjacent limestone. In the vicinity of Sheperdstown, three miles S. of Mechanicsburg, the limestone encloses a considerable tract of slate, rather more than half a mile in breadth. This is probably a belt of Matinal Slate folded in between the lime- stone in a compressed synclinal axis. About a fourth of a*mile N.W. of Sheperdstown, iron ore, apparently of good quality, has been obtained. It has not proved abundant, though little has been done towards developing it. At the Carlisle Iron Works, six miles S.S.E. from Carlisle, a trap-dyke, traceable from the mountain, crosses the Yellow Breeches Creek immediately at the furnace, and extends N. 20 E. entirely across the valley, meeting the base of the Kittatinny or North Mountain, about two miles E. of Sterrett's Gap. It forms a sharp, very narrow, rocky ridge, from 10 to 17 feet high a useful natural boundary employed to designate the Township lilies. The limestone is consi- derably affected by it in its texture and colour, though not much disturbed in its prevailing South-eastern dip. In a quarry near the furnace, a little removed from the trap, the rock has the aspect of fine-grained, whitish, and dove-coloured marble. This trap-dyke, and the contiguous beds of the limestone, are well seen in the cutting on the Harrisburg and Chambersburg railroad, where the dyke is about GO feet wide. Another lesser trap-dyke penetrates the limestone a little Westward of the former. BETWEEN THE SUSQUEHANNA AND MARYLAND. 267 The iron ore which supplies the Carlisle Iron Works is obtained at several points. The variety denominated " mountain ore," occurs along the Northern slope or base of the first sandstone ridges, near the junction of the limestone. Another variety, known as limestone or pipe ore, belongs to the ferruginous soils overlying the limestone itself. The iron obtained from the mountain ore is generally " cold - short," hard and brittle ; while that derived from the limestone ore is softer, tougher, and more tenacious. The mountain ore is in some furnaces employed alone for the manufacture of foundry pigs and castings, but a mixture of the two kinds is generally deemed necessary for the produc- tion of good cast-iron for forging or puddling. One principal reason of this is, that in the mountain ore, derived originally from the Primal strata, the oxide of iron is associated with a larger proportion of the oxide of manganese, and other dele- terious constituents, than generally accompany it in the ores originating from the limestone. Both of these varieties belong to the general species, called by mineralogists brown hydrated oxide of iron, though they assume a considerable diversity of aspect and structure, arising from their greater or less degrees of richness and purity, and the manner of their concretion. The " mountain ore " obtained a mile and a half South-west of the Carlisle Works is of several descriptions. In the upper portion of the deposit, much of it is compact, passing under the name of " hard ore." The " honey-comb ore," lying beneath this, or imbedded between it, is a softer and more porous variety, more readily reduced in the furnace. Half a mile S. from the furnace, a small body of a somewhat different ore has been met with. The " limestone ore " employed at this furnace was obtained from a belt about two miles N.N.W. from the works, where ore had been dug, in different places, for several years. The supply in 1840 was chiefly from a deposit about eight feet thick. Much of it belongs to the fine variety denominated " pipe ore," consisting of a congeries of parallel stalac- titic tubes or stems, from whence it derives its name. One part of this ore is mixed with two parts of mountain ore in the manufacture of forge pigs. For the chemical composition of these several varieties, see the general Chapter on the Iron Ores. Between the deposits of limestone ore above-mentioned and Carlisle, ore has been found in several places ; an exten- sive digging, now abandoned, occurring near the Hanover road. Half a mile S. of this, on a farm belonging to Mr Holmes, a very good-looking ore was found, and subsequently mined. Between this spot and Carlisle, other excava- tions exist, from whence the ore was conveyed across the North Mountain to a furnace S. of Landisburg, where it was mixed with ores of that neighbourhood. In the neighbourhood of Carlisle there occurs much good limestone ; both the ordinary kind, adapted for making lime, and the magnesian variety, suitable for the manufacture of hydraulic cement. About four miles Westward from Carlisle, near the State road, there occurs a neglected excavation where iron ore to some extent has been procured. About four and a half miles S. of the town, near the turnpike, there is a deposit of appa- rently good ore, formerly wrought to some extent, to supply Holly Furnace, not now in operation. On the Walnut Bottom road, aboxit five miles S. W. from Carlisle, ore is abundant on the surface of a little hill. Southward of this, at Peffer's, between the foot of the mountain and the creek, ore was formerly obtained for Holly Furnace, and more recently for Cum- berland Furnace. Though not far from the sandstone of the mountain, some of it is of the variety called pipe ore ; parts of it, however, are manganesian. Along the low ground, near the foot of the mountain, ore is abundant on the surface for a considerable distance Westward. Cumberland Furnace has been smelting chiefly the ore obtained near the base of the sandstone ridge of the mountain about three miles S.W. from the furnace. This ore appears to lie in bands, and large bunches or nests in the loose soil near the bottom of the declivity of the mountain. The mine generally wrought is an irregular excavation, from forty to fifty feet deep, in the sides of which the ore is scattered in lumps throughout a large extent of the deposit, but is best and most abundant nearest the bottom. The ore from this bank is mixed with another ore from the limestone tract obtained a mile and a half north of the furnace. For an analysis of each of these ores, see the general Chapter on the Iron Ores. Iron ore occurs on the surface about seven miles west of Carlisle, on the farm of Mr William Kerr, in considerable quantity. Near the Big Pond at the head of Yellow Breeches Creek is Pond Furnace. The ore smelted at this furnace is procured from the Primal slate, on a low spur of the mountain, S.W. of the Pond. The old excavations on the Eastern side of the hill have been abandoned, and another deposit opened on the Western side. The limestone employed as a flux in Pond Furnace is collected from the surface fragments of the neighbourhood, and is therefore of every diversity of character. Mary Ann Furnace lies about three miles West of the Pond ; near it is Augusta Furnace. These furnaces are situ- 268 IRON ORES OF THE KITTATINNY VALLEY ated close to the foot of the mountain, about three miles S.E. of Shippensburg. Mary Ann Furnace is supplied with ore from two banks, opened many years ago, one called the " Helm Bank," three miles N.E. of the furnace, and another called the " Clippinger Bank," two miles towards the N.W. The Helm Bank ore overlies that part of the limestone which is much interstratified with slate, being near its margin. The ore dips steeply to the N.E., but varies much in quantity in different parts of the excavation. The Clippinger Bank yields an ore of the very best description, much of it being stalactitic, or of the kind called pipe ore. The analyses will display the prevailing composition of the ores of both these banks. The Clippinger ore occurs in regular nests in the interstices of the limestone rock, surrounded by a very tenacious reddish clay. The quantity fluctuates much in different spots, and the water incommodes more or less the deeper dig- gings. These circumstances attend nearly all the deposits of the limestone ore in the valley. Where the ore occupies the interstices between the beds of limestone, it is almost invariably pure and of the pipe-ore kind, though the quantity in these situations is apt to be precarious. The mountain ore obtained near the junction of the Auroral limestone and the Primal slate of the mountain is procured with greater certainty, but is frequently quite unfit for making forge iron, without an admixture of the pure ore of the limestone, being used by itself only for foundry metal. The flux used in Mary Ann Furnace is a limestone procured in the vicinity of the Clippinger Bank. Southampton Furnace is situated about three miles further to the S. W., or four miles S. of Shippensburg. These two furnaces when in blast were supplied with ore from three different banks. One called the " Hill Bank," lying about three hundred yards W. of the upper furnace, contains the mountain ore in its usual varieties. That in the upper part of the mine is cold-short, while a honey-comb ore lying beneath it is of much better quality. The ore of this bank sup- plied the upper furnace which used the hot blast, and made foundry iron and castings. The lower furnace was furnished with ore from a mine at Kressler's, three-fourths of a mile to the N. W., and also from the " Railroad Bank," lying in the limestone formation, four miles W. of the furnace. The ore at Kressler's has been extensively wrought for many years. It occurs in nests and irregular layers in the soil and the rotten slate, the deposit having a dip nearly coinciding with the direction of the underlying strata. This ore is^ esteemed to be well adapted for making good bar-iron, but is less productive in iron than some others in the neighbourhood. Much loose ore is visible on the surface, N. of the present excavation. The " Railroad Bank " formerly yielded a valuable supply of good ore, but the encroachment of the water, and a reduction in the quantity of ore, subsequently caused it to be less actively wrought. The ore exists rather in bunches or nests than in regular layers, and is hence very variable as to quantity. A small ridge of limestone bounds the ore immediately on the N. The lower furnace, smelting these ores, made forge pigs for bar- iron. The composition of these ores will be found in the Tables of Analyses. Proceeding Northward to the neighbourhood of Shippensburg, it appeared that a moderate amount of excellent ore had been procured in a spot called the " Pilgrim Bank," near the Northern margin of the limestone, three miles and a half from the town. A good ore was formerly obtained on the farm of Mr Hamills, a mile and a half S.E. from the town. Ore was also procured about a mile and a half W. of Shippensburg, at the old Roxbury bank. It was the stalactitic or pipe ore, and made a bar-iron which was much esteemed for its soft and tough qualities, but, as usual with ore of this description, the quantity was limited. For analyses, see the Tables. About two miles S.E. from Green Village, and half a mile N. of the railroad, a deposit of beautiful pipe ore of excellent quality was wrought for the supply of Caledonia Furnace, to which it was conveyed a distance of eight miles in waggons. It produced a good iron, and with great facility, agreeing in these respects with the pipe ore generally. It occurs in bunches, which together form an irregular layer, conforming with the direction of the adjacent limestone. Its position is between two little ridges of the limestone, one of which immediately bounds it on the N. It is deeply covered with earth, and is somewhat expensive to procure. Caledonia Furnace is situated on the Gettysburg and Chambersburg turnpike, ten miles from the latter place. It is supplied with ore from several deposits, besides the Green Village bank already noticed. A belt of ore-ground extends for apparently several miles nearly along the line of contact of the limestone of the valley and the sandstone of the ridges, which jut forward in advance of the main body of the mountain. On this line of ore, coinciding with the position of the Primal slates, which intervene between the limestone and the sandstone, the Pond Iron banks occur about three miles from Caledonia Works. They consist of extensive diggings, in which the ore is met with at various depths, in nests and irregular layers, in a ferruginous soil. Much of this ore has a hollow reuiform structure. About three hundred yards S. of this spot, a bed of ore was formerly wrought for the supply of Montalto Furnace. It overlies the sandstone, and yields a metal of very indifferent quality. The flux employed in Caledonia Furnace is procured a little N. of the Pond diggings. BETWEEN THE SUSQUEHANNA AND MARYLAND. 269 Another excavation furnishing ore for the same furnace occurs three miles further to the S.W., at Hiefner's. This bank, situated further from the mountain than the former, yields an open and crumbly ore, which smelts with facility, but produces a somewhat cold short iron. The chemical composition of these ores will be found among the analyses in the Tables. In one of the openings at Hiefner's, an impure limestone was encountered thirty feet from the surface. A little Eastward of the openings some pipe ore occurs in the soil, for an analysis of which, see the Tables. Another belt of ore-ground seems to exist on the summit of a little ridge of limestone N. of the former excavations. This ore is different in quality from the other, and promised to be abundant twenty feet below the surface. The ridge extending South-westward, the ore seems to continue along it, and about three-fourths of a mile from the Hiefner bank occupied the surface in an abundance seldom seen. It had been partially opened here, but making a highly cold-short iron, was abandoned. These deposits of ore seem to range nearly along the line of contact of the limestone, and a narrow interposed belt of silicious slate and sandstone. About a fourth of a mile S.E. of Beattie's, on the turnpike, occurs a dark-coloured limestone, an unsuccessful trial of which as a flux was made in the furnace. The analyses, showing its composition, will be seen in the Tables. Iron ore of very inferior quality occurs between two ridges of sandstone, three miles N.N.E. of Caledonia Furnace, affording another evidence of the impure nature of the ores derived from the rocks of the South Mountain, when com- pared with those which occur in the limestone of the belt immediately N.W. of it. Montalto Furnace is situated on a branch of Antietam Creek, about seven miles N.E. from Waynesburg, and near the foot of the outer sandstone-ridge of the mountain. Though iron ore appears upon the surface, in more or less abundance, the whole way along the North-Western base of the mountain from Ege's Carlisle Works to this place, yet nowhere does it occur in such profusion as between the Caledonia Ore Bank at the Pond, and a point two or three miles S.W. of Mont- alto. This furnace was supplied from extensive excavations lying about a fourth of a mile N.E. of it, on the declivity of the first sandstone-ridge. The ore occurs, as in other similarly-situated mines, in the loose soil of the mountain-side, in nests and irregular layers, varying greatly in their dimensions ; but the whole deposit seemed to be of prodigious mag- nitude. The lower portion of the ore "was the purest. This ore, though abundant in quantity, does not, however, yield a large proportion of iron. The composition of these two ores is recorded in the Tables. In one of the deeper diggings of Montalto, a band of limestone was reached, being probably a layer in the Primal slates. It is interesting thus to observe the prevailing connection between the limestone and large deposits of iron ore. On the West side of the most Western tract of limestone, in Franklin County, about four miles W. of London, a deposit of iron ore occurs, formerly smelted in the old Mount Pleasant Furnace near it, but now taken to Carrick Furnace, four miles towards the N. The ore ranges, in greater or less abundance, for six or eight miles, in a narrow line along the S.E. base of the Tuscarora Mountain, being procured in considerable quantity N. of Carrick Furnace. Its position is near the contact of the limestone and overlying slate. It is of two varieties : one a hard ore, occa- sionally iridescent, making a rather cold-short iron ; the other a "honey-comb ore," esteemed to be of much better quality. The analyses, showing their chemical nature, may be found in the Tables. The limestone employed as the flux in Carrick Furnace is procured in part from a quarry adjacent to the works, and in part from the loose pieces scattered through the neighbouring fields. A little pipe ore has been occasionally found. About five miles N.E. of Mercersburg, and two and a half miles from St Thomas, not far from the anticlinal axis, lies a deposit of iron ore, no longer wrought. It is stated to have yielded a good, soft iron ; it was, however, red short, or brittle, at a welding heat. When roasted or smelted, it gave off a strong odour of garlic, a circumstance indicative of its containing arsenic. The presence of arsenic in this ore I have ascertained by analysis, the results of which may be seen in the Table showing the Composition of the Iron Ores. BOOK III. DISTRICT OF THE ORWIGSBURG AND STROUDSBURG VALLEY. CHAPTER I. LIMITS OF THE DISTEICT, AND CHAEACTEE OF THE FOEMATIONS. THE division of the State which is now to be described may be regarded as a single valley, enclosed between the Shawangunk, Blue, or Kittatinny Mountain on one side, and the Cats- kill, Rocky, Pokono, Mahoning, or Second Mountain (for by all these names it is known) upon the other. Twelve or fifteen miles broad, where it enters the State from New York at Carpenter's Point, this valley becomes scarcely two miles wide at its intersection with the Susquehanna, six miles above Harrisburg. The alterations of form where it expands and contracts in width, are sudden but regular, and due in every instance to the appearance and disappearance of numerous anticlinal flexures, some of which arise within it, while others enter it from the great Kittatinny Valley. These latter crossing obliquely through the Kittatinny Mountain, form synclinal knobs or spurs on the Southern side, and anticlinal knobs or promontories on the Northern side of that high ridge the one class projecting Eastward into the Kittatinny Valley, the other advancing Westward into the Stroudsburg Valley. These closely-folded flexures occur at intervals along the whole course of the Kittatinny Mountain, and confer upon its generally monotonous crest almost its only features of diversity. By a reference to the Map, one of these anticlinal spurs may be observed at Milford, another at the Walpack Bend, a third at the Delaware Water- Gap, another at the Wind-Gap, and a group of four or five together at the Little Schuylkill. One law regulates their occurrence in all cases. The anticlinal axis or flexure, approaching the mountain Westward from the Kittatinny limestone valley, where it is in maximum force, ascends through a long, narrow cove of Matinal slates, then passes through the mountain as an arch, in the Levant grey and white sandstones, and issues on the other side in the form of a long, pointed, gently-declining spur of Surgent slates and shales, around and over the end of which, curve and arch successively the Pre-meridian, Meridian, Post-meridian, and Cadent rocks. After passing through the mountain in this very oblique manner, each anticlinal axis con- tinues its Westward course, nearly parallel with the medial line of the valley for several miles, and many of them pass out from the valley through the next mountain-ridge bounding it on the N., in a similar manner, forming analogous knobs and curves in the mountain on that side. DELAWARE WATER-GAP. 271 Thus the Milford axis forms the cove behind the Pokono Knob, N.W. of Stroudsburg ; the Wai- pack Bend axis is another that may be looked \rpoii in its prolongation Westward, as that of the Cove behind the Kettle Mountain east of Mauch Chunk ; and an axis originating where the Water- Gap anticlinal dies away, after traversing the valley for forty miles, passes out of it through the curve of the Wildcat or Mahoning Mountain, deflects the Sharp Mountain, and enters the Pottsville Coal-basin at Middleport ; and the final contraction of the valley at Pinegrove is due to an almost similar entrance of another anticlinal flexure from the E. near the Little Schuylkill. At every point, therefore, along its whole extent, a section across this belt exhibits the presence of one or more important flexures. Such a section also displays, on the Southern side, the older rocks, the Levant sandstones, slates and shales, forming the Kittatinny Mountain, and dipping steeply Northwards ; in the middle, the Cadent and Vergent rocks ; and on the Northern side, the almost horizontal Ponent and Vespertine series, cropping out along the grand escarpment of the great Catskill or Pokono Mountain plateau, or in the country W. of the Lehigh : these latter rocks nearly vertical, and forming the double -crested summit of the Mahoning or Second Mountain. The Meridian series, which occurs along the Shawangunk Mountain in New Jersey, cannot be traced continuously to the Westward beyond the Lehigh. The Pre-meridian limestone series forms also a thin and waning outcrop, and finally ceases within this belt W. of the Swatara. The sections across this zone at the Delaware and Lehigh, and at the Susquehanna, will amply explain the conditions in which the several strata occur in its Eastern, Middle, and Western divisions. CHARACTER OF THE STRATA IN THE DISTRICT. Though narrow, the Third District embraces a considerable number of formations namely, those of the Levant, Surgent, Pre-meridian, Meridian, Post-meridian, Cadent, Vergent, and Ponent series. These are best developed in the region of the Delaware, for some of the strata thin out towards the S.W. The sections at the Delaware, Lehigh, and Susquehanna will give a clear idea of the composition and dimensions of the several groups in the types which they there exhibit. With the aid of these diagrams a very brief account of the rocks will suffice to present a perfect key to the geology of this district. (See Sections of Delaware, Lehigh, and Susquehanna Gaps, in the Kittatinny Mountain.) DESCRIPTION OF THE STEATA FEOM THE DELAWARE WATER-GAP NORTHWARD TO BROADHEAD'S CREEK. The Levant rocks on the New Jersey side, in the Kittatinny Mountain, show a strike N. 70 E., with dip 35 or 40 to N. 20 W. On the Pennsylvania side, the strike is N. 00 E., the dip about 35 to N. 30 W. 1. Levant Rocks, Kittatinny Mountain. The lower main rib consists of grey conglomerate and sandstone ; the conglo- merate is most abundant towards the base, and is composed of quartz pebbles of nut and pea size, with scattered pebbles of black slate, some of them one and a half inches long. This is evidently the equivalent of the coarse conglomerate of the Lehigh Gap ; but here the pebbles are smaller, and a large proportion of the mass is sandstone. Thin partings of black fissile slate, two to four inches thick, occur iu it. Light grey sandstone constitutes the upper portion of the stratum. The whole thickness of this member is about 300 feet. 2. The second member is a soft sandy rock, including a thin rib of hard material. The chief part of this mass 272 STRATA NORTH OF DELAWARE WATER-GAP. consists of thin- bedded dark grey sandstones, inclining to olive. Many of the layers contain scattered quartz pebbles. Thickness about 400 feet. 3. The third member forms a prominent thick rib of the mountain, and consists of light grey and olive grey, very compact sandstone, some of it pebbly, and occasionally between the beds are partings of grey flaggy sandstone. It has a thickness of about 200 feet. 4. Surgent Strata. The fourth group consists of dark-greenish grey, and brownish and light-grey sandstones, with hard semi-vitreous, reddish sandstones, occurring near the middle of the mass, the light-grey being near the top. The whole mass passes upwards into a hard, arenaceous reddish shale and shaly sandstone. The entire thickness of this member is about 400 feet. This group appears to begin the Surgent series, its upper grey sandstone representing perhaps the Surgent iron sand- stone ; this is indicated by a comparison of the section with that at the Lehigh Water-Gap, where there is a similar absence of the lower Surgent slates. 5. The next division is a deep red argillaceous sandstone or highly indurated sandy shale, including thick bands of an olive-green argillaceous sandstone and shale ; the more sandy beds are often quite pebbly. There are layers of light- greeuish-grey flaggy sandstone, but the red sandy shale greatly predominates. Towards the top of the mass the greenish shale becomes intercalated with red shale. The thickness of the whole is about 350 feet. 6. A mass of indurated sandy shales succeeds, composed of red, olive, and greenish-grey beds alternating, the red being confined to the lower half. This portion of the series lies in several broad flat undulations, upon one of which is perched the Water-Gap Hotel, in a position commanding a fine view of the pass and valley. All this portion of the formation displays cleavage-structure very conspicuously, dipping invariably to the S.E., but at all inclinations, from steeper than 60 nearly to horizontality ; the flattest dip being always on the North-western side of the anticlinal curve. In this vicinity namely, to the N.W. of the Hotel the strata exhibit a curve in their strike which sweeps more South-westward than the mountain-crests, or the great anticlinal lines of the country. This bending round of the rocks is due to the sinking South-westward of an important anticlinal flexure, which, coming out from the Kittatinny Mountain east of the Delaware River, here subsides not far W. of the road leading from the Gap to Dutotsville. The anticlinal shows itself in the form of the hill on the Jersey side, and is the principal flexure N. of the Gap. Eastward it swells into a mountain-ridge, vying in elevation with the main monoclinal crest of the Kittatinny. 7. North-west of the variegated group above described succeeds the true red shale member of the Surgent series plainly exposed on the hill to the W. of the village of Dutotsville. It dips 25 to 30 N.W., composing the hill to its base, where the diluvium of the valley commences and conceals for a space all the overlying formations of the Surgent series. This red shale exhibits distinct cleavage-plapes, dipping as usual to the S.E. The thickness of the red shale is apparently 200 or 300 feet, but in this vicinity it is not susceptible of accurate estimation. Prolonging our section, we cross the broad Diluvial flats of the valley to the base of the limestone and sandstone ridge called Fox Hill, a blank space of about 2000 feet measured across the strike of the strata of the district. It is impossible to say whether the prevailing N.W. dip continues under the whole of this interval, or whether there enters one or more gentle flexures ; but the smoothness of the valley implies the absence of any considerable undulation, and this is further indicated by what we know of the structure of the country N.E. and S.W. of these flats. Assuming the dip to be all in one direction and to average 20, the thickness of the strata covered up will be about 700 feet. The portion adjoining the red shale must be the Surgent variegated shales, the highest division of the series, and probably these fill the entire interval, since we have no evidence of the existence in this region of any strata of the Scalent series the Niagara group of New York and the Western States which intervene between the Surgeut shales and the Pre-meridian limestone, the first rock here met with on the North-western margin of these flats. Pre-meridian Limestone Series. Along the base of Fox Hill, but best seen for measurement a little S. of the bridge across Broadhead's Creek, we detect these rocks, and thence crossing the ridge or following the line of natural exposure in the back of that stream, we are able to extend our section from near the base of the Pre-meridian limestone to the Cadent rocks, and even far beyond. Enumerating the formations we encounter 1. A little S. of the bridge, nearly horizontal surfaces of Pre-meridian limestone full of Pentamerug galeatm. This is for the most part a thinly-bedded argillaceous limestone with limestone shale ; thickness about GO feet. 2. Next succeeds a shaly limestone, the Pre-meridian shales, abounding in Delthyris macropleura. Its thickness is some 30 feet. 3. Next follows a calcareous sandstone somewhat pebbly, 15 feet in thickness. This is not the Meridian sandstone, but a member of the Pre-meridiau limestone. STRATA NORTH OF LEHIGH WATER-GAP. 273 4. Meridian Sandstone Series. Upon the sandstone reposes an impure limestone, or rather a calcareous shale, con- taining layers of chert. This rock has a thickness of 50 feet. It is apparently an upper member of the Pre-meridian limestone, but more properly it belongs to the Meridian series, and is the equivalent of the Meridian dusky shale of other localities. 5. Resting on this calcareous rock is an ash-coloured shale embracing beds of chert and several calcareous bands 30 feet thick in its upper portion. This group is about 80 feet thick in all. This stratum is to be regarded as the second member of the Meridian shales frequently seen in this position on the upper Juniata. 6. The next which succeeds is an arenaceous limestone, with courses of blue chert predominating in the lower layers, the upper portion being in part a coarse and pebbly sandstone. This is about 30 feet thick, here wearing the usual attenuated condition it has along this first South-eastward outcrop N.W. of the Kittatinny Mountain. Though destitute in this locality of fossils, it bears all the indications of being the Meridian sandstone, or F. VII. of the Annual Reports, the Oriskany sandstone of the New York Geological Survey. 7. Post-Meridian Series. Following the sandstone is a sandy shale, containing many impressions of the peculiar fucoid called the Cauda galli, from its resemblance to a cock's tail. This rock by estimation is from 120 to 150 feet thick. The last formation is much intersected by planes of cleavage, which dip with great regularity rather steeply to the S.E. Cleavage near the Delaware Water-Gap. At the Kittatinny House, N. of the Water-Gap, the Surgent variegated marls and indurated shales exhibit cleavage very distinctly ; its dip is a little W. of S., which appears to be its prevailing direction in all this district N. of the Gap. At the Kittatinny House the strata dip S. 40 W. The cleavage pervades all the more argillaceous beds in planes extremely close together, while in the more arenaceous rocks, alternating with the shales, the fissures are usually some inches asunder. It is an interesting fact that, not only here but throughout the districts of cleavage gene- rally, this feature abounds much more on the Northern dips than on the Southern ; or, in other words, it predominates on the most incurved sides of the anticlinal and synclinal flexures. It appears to me that this fact is of itself conclusive against the hypothesis which ascribes the cleavage-structure to a lateral mechanical compression, for it is obvious that, at the formation of the undulations in the strata, there must have been as much stretching or dilatation at the convex curves as squeezing or compression at the concave. DESCRIPTION OF THE STRATA FROM THE LEHIGH GAP NORTHWARD. The following is a description of the strata as they are exposed in the Lehigh Water-Gap or pass of the River Lehigh, in the Kittatinny Mountain. Observing the ascending order, the first formation met with in the Lehigh Gap is the Matinal slate. Starting from the top of this we have, composing the LEVANT SERIES, 1. An egg conglomerate of grey-sandstone paste holding pebbles of quartz, Matinal chert and slate, and Primal slate and sandstone. Thickness, 50 feet. 2. An alternation of fine-grained white and pinkish sandstone and nut conglomerate, containing pebbles of quartz, slate, and chert in a grey paste. This is capped by about 10 feet of egg conglomerate similar to that above described. The whole stratum has a thickness of 75 feet. 3. Nut conglomerate, pebbles consisting chiefly of quartz, which in some beds repose on quartzose sand. Thickness, 75 feet. 4. Fine-grained white and grey sandstone 10 feet thick, followed by an alternation of grey sandstone and pea con- VOL. I. 2 M 274 SECTION ON THE LEHIGH. glomerate, the sandstone mingled with argillaceous matter, predominating in the higher beds, and not so thickly bedded as the conglomerate strata beneath. Whole thickness, 200 feet. This brings us to the synclinal trough, whence to the anticlinal roll N. of it is 225 feet horizontally. After passing these flexures, we have a wide space of 450 feet horizontally of apparently soft rocks, presenting no good exposures except near the middle where there occurs a thick bed of sandstone. 5. Whitish and grey sandstone containing pebbles, the partings argillaceous. Thickness, 80 feet. 6. Greyish-white sandstone alternating with indurated brownish sandy shales, not well exposed. Thickness about 100 feet. 7. Whitish sandstone having argillaceous partings overlaid by brownish and greenish slates, exhibiting vague fucoidal markings or blotches. 50 feet thick. 8. Indurated sandy shales tinged brown, olive, and yellow, vaguely marked by fucoids. 30 feet thick. 9. Indurated shales, brown, olive, and buff green, interstratified with beds of grey and greenish flaggy sandstone ; about 200 feet thick. This brings us to the Lehigh-Gap Hotel. 10. Indurated olive and yellowish shales, and massive, ponderous, red-and-grey quartzose sandstone; the partings are thin bands of shale marked by reticulated fucoids. Over these is a thick mass of ponderous grey quartzose sand- stone. Thickness of the group, 100 feet. SURGENT SERIES. Aquanchicola Creek, which meets the Lehigh, conceals about 100 feet of these strata. 11. Indurated red and greenish shales. Near the base of these is a band, five feet thick, of iron sandstone overlaid by alternating bands of olive and red ferruginous indurated shales full of fucoidal markings of the Surgeut newer slates and iron sandstone. Thickness of this group, about 170 feet. 12. A grey and rather vitreous sandstone, somewhat thin-bedded, with partings of slaty sandstone 100 feet thick. This appears to be the equivalent of the Ore Sandstone of the Juniata country. 13. A thin-bedded greenish-grey sandstone, with olive and buff-coloured argillaceous and sandy slates, the argillaceous slates predominating in the higher portion, where also reddish sandstones and shales begin to appear. Thickness, 120 feet. 14. Bed shale and red sandstone of the prevailing type of the Surgent red shale. Section on the Lehigh from South Side of Stone Eidge Northward. Proceeding Northward from the Southern base of Stone Eidge through a good series of exposures, the lowest group of the strata developed belongs to the higher part of the Scalent series. From the termination of the Section of the Lehigh Water-Gap which ends about the upper limit of the Surgent red shale, to the beginning of these exposures of variegated shales, is a space across the strike of about 2250 feet, with an average dip of 45, all of which would appear to be occupied by the Scalent variegated and grey shales. At the base of Stone Eidge we meet a thin development of the Scalent limestone, somewhat argillaceous and full of Beyrichia and other characteristic fossils. Succeeding the limestone is a belt of variegated shales apparently of the Scalent age. A bed of chert follows these, apparently the sole representative of the Pre-meridian limestone series. Upon it is a thin stratum of dusky shale, and over this about 175 feet of pebbly sandstone, then 30 feet of shale, and again 25 feet of sandstone surmounted by a thin layer of chert, all these four rocks constituting the Meridian series. Upon the last sandstone rests a dark slate, seemingly the black slate at the base of the Cadent series. From the deficiency of exposures, the section skips an interval of more than 3000 feet from the North base of Stone Eidge to a point further Northward. The first exposures consist of the upper members of the Cadeut shale formation under the form of olive shales and black slates. They dip at an angle of about 40 Northward, and are somewhat intersected by cleavage planes-dipping at the same angle South-eastward. These are succeeded by the Cadent upper Uack slates in their usual form of fissile black slates, easily distinguishable from the more shaly members below. The thickness of this formation here, on the Lehigh, is about 250 feet. The Vergent series is well exposed, overlying the Cadent slates. It presents itself as made up of alternating bauds of grey sandstone and olive shale of the Chemung type. The dips are fluctuating throughout the mass ; at its contact with the slates beneath, the inclination does not exceed 40 towards the N., but it soon steepens into 70, and then declines again into 45, after which the strata undergo several small undulations, and finally are lifted upon an anticlinal arch, the opposing dips of which are 25 Southward, and 70 Northward. Passing this arch, the grey rocks of the SECTION ON THE LEHIGH. 275 formation become more prominent, but are soon seen in alternation with the lower members of the next overlying series, or Ponent rocks, throughout a flatly undulated tract just S. of the mouth of Pogopogo Creek. The total thickness of the Vei'gent series as thus exposed is from 1700 to 1800 feet. At Pogopogo Creek the dip is gently Northward, but it soon turns, and 300 feet above the creek the upper grey bed of the alternating rocks is seen spanning a low arch. From this anticlinal it is only 500 feet to the main central synclinal axis of the valley. This axis forms a pro- minent ridge occupied entirely by rocks of the Ponent series, which dip 15 N. on the South side of the basin, and 20 Southward on the North side, flattening gradually down to 10 as we recede from the axis. The centre of the basin only is occupied by true homogeneous red shale ; passing Northward, these soon alternate with olive shales, and then with the sandstones of the Vergent, as we have seen was the case on the South side of the synclinal axis. In the Pouent rocks, cleavage is a somewhat conspicuous feature. It dips uniformly Southward at the high angle of 70. The alternating measures cease about a 1000 feet N. of the axis, and we enter upon Vergent rocks. These exhibit themselves in a long series of exposures on the Lehigh. They consist for the first three-fourths of a mile of flaggy, greenish-grey sandstones, alternating with thin layers of argillaceous sandstone, and olive and blue clay-slate ; the shaly beds augmenting in thickness and proportion towards the top of the formation. Fossils are few, but those to be seen are chiefly vegetable, as stems of ferns. Fucoides velum,, and a few Nuculce, are also found. The flaggy beds exhibit well- preserved ripple and shore marks, and trails of marine creatures,