GEOLOGICAL SURVEY OF PENNSYLVANIA. FINAL REPORT ORDERED BY LEGISLATURE, 189L A SUMMARY DESCRIPTION OF THE GEOLOGY OF PENNSYLVANIA, IN THREE VOLUMES, A NEW GEOLOGICAL MAP OF THE STATE, A MAP AND LIST OF BITUMINOUS MINES, And many Page Plate Illustrations. By J. P. LESLEY, State Geologist. VOL. I. DESCRIBING THE LAURENTIAN, HURONIAN, CAMBRIAN AND LOWER SILURIAN FORMATIONS. HARRIS BURG: PUBLISHED BY THE BOARD OF COMMISSIONERS FOR THE GEOLOGICAL SURVEY. BOARD OF COMMISSIONERS. His Excellency ROBERT E. PATTISON, Governor, and cf-officio President of the Board, Harrisburg. ARIO PARDEE, Hazleton. WILLIAM A. INGHAM, Philadelphia. HENRY S. ECKERT, Reading. HENRY McCoRMiCK, Harrisburg. CHARLES A. MINER, Wilkes-Barre. JOSEPH WILLCOX, Philadelphia. Louis W. HALL, Harrisburg. SAMUEL Q. BROWN, Pleasantville. CHARLES H. NOYES, Warren. W. W. H. DAVIS, Doylestown. SECRETARY OF THE BOARD. WILLIAM A. INGHAM, . . Philadelphia. STATE GEOLOGIST. PETER LESLEY, Philadelphia. Entered for the Commonwealth of Pennsylvania, in the year 1892, according to acts of Congress, By WILLIAM H. INGHAM. Secretary of the Board of Commissioners of the Geological Sun-rii. In the office of the Librarian of Congress, at WASHINGTON. D. C. UNIVERSITY OF CALIFORNIA > f SANTA BARBARA Ptl in I LETTER OF TRANSMITTAL. To His Excellency Governor ROBERT E. PATTISON, Ex- officio Chairman of the Board of Commissioners of the Geological Survey of Pennsylvania : SIR : I have the honor to submit to your approval this First Volume of the Final Report ordered by act of Legis- lature, approved in June, 1891 ; being a Summary of the results of the Survey from its beginning in June 1874 to the close of its field work, June 1, 1890 ; since which date office work has been continued for the completion of its publications ; chiefly the last sheets of the Anthracite sur- vey, the maps and sections of the survey of the New Red belt of Bucks and Montgomery counties, the completion of the Bituminous colliery map of Western Pennsylvania, and a new Geological State Map. These will be published in the coming summer, together with the Second and Third volumes of this Final Report. In writing this Summary I have quoted from more than a hundred volumes of reports published by the Board since 1875, a complete list of which, with an Index to their subjects, will be found at the close of the third volume. In every case I have given credit to and thrown respon- sibility upon the assistant geologist who made the obser- vation, or reported the fact quoted, by a reference in text or foot note to date and page of his report. Most of the illustrations are photo-electrotype reduc- tions, and therefore fac-similes of the drawings made by the assistant geologists, or in the office of the Survey from their sketches, or from data in the text of their re- ports, published in their reports during the course of the Survey. The smaller illustrations are grouped on page plates to iv GEOLOGICAL SURVEY OF PENNSYLVANIA. diminish the cost of the publication and to hasten its com- pletion. They form in fact an illustrated index to the maps and sections to be found (on a larger scale) in the series of reports. The names and districts of all the assistants on the sur- vey will be found in a list at the end of the third volume. I have endeavored to confine the text of the book to general and systematic statements; and have therefore placed all the detailed local and ancillary matter in foot notes. I trust that this will accommodate the reader as much as it has lessened the size of the book. I have written it also in Saxon English, as far as a work of physical science can be so written, as it is in- tended for the use of the people of Pennsylvania, in whose vocabulary Norman English has never been domesticated, who greatly prefer before and after, or before and behind, to anterior and posterior, and overlaid and underlaid to superimposed and subjacent, as I do myself, and who are mostly or wholly ignorant of Latin and Greek. Although the personal element can never be entirely suppressed from any work of man, I have endeavored to avoid dogmatic statements not made by a consensus of the geological opinion of to-day, and to place the many differences of that opinion still remaining unsolved in such a light as to show that our science is not an oligarchy but a democratic republic, in which every voice has a right to be heard, and that even after the vote has been taken there remains the right of calling for a re-consideration of it. The book is almost wholly a practical description of facts discovered or verified by the observation of the members of the corps of the Geological Survey in their several dis- tricts, not at all influenced by geological theories, but sim- ply seen and measured, and placed in their true relations to one another. The arrangement of the book will be seen by consulting the Table of Contents. The order of description is chrono- logical from oldest to newest, but the representation of of each formation is made as in a columnar section from LETTER OF TRANSMITTAL. V the top to the bottom, by which the mental conception of the pile of strata is enforced by the eye. A descriptive section with the bottom bed on top is an old-fashioned abomination repudiated now by all good geologists. The page plates of fossils, placed in all cases at the end of the chapters of the several formations, are half -sized re- productions of the figures of fossils given in Report P4, Dictionary of the Fossils of Pennsylvania and the sur- rounding States, published in 3 volumes in 1889-1890.* The Dictionary has been so successful that the demand for it has long since outrun the edition ; and the office of the survey is in receipt of requests for it which cannot be answered because the edition is exhausted. It has been a completely successful experiment. But there has been a call for the classification of the figures under the head of the formations to which the fossils properly belong, and I have endeavored to meet this call by grouping the figures of each formation in a series of page plates, which will sufficiently index the Dictionary for geological purposes. In the case of each series the grouping begins with plants, and proceeding upward in the order of life through species of bryozoa and corals, brachiopod, gasteropod, cephalopod, phyllopod and lamillibranch shells, annelids, crustaceans, insects, and vertebrate fish and reptiles, so far as the for- mation in question contains these. Where references to authority and locality are wanting the reader must consult the Dictionary. These page plates are for popular instruc- tion and not for the use of experts. J. P. LESLEY, 1008 CLINTON STRBET, PHILADELPHIA, February IS, 1892. * P4, Vol. 4, Appendix, was forbidden by the Board to be published until after the final report and other publications of the survey had been printed, for fear of delaying these. In consequence of this action, I have been pre- cluded from inserting in these page plates many of the fossil forms found in Pennsylvania and elsewhere recently, many of them of the most inter- esting character. VOL. I. TABLE OF CONTENTS. I. Our Geological Knowledge, 1 II. Geological Time, how measured, ... . 5 III. Geological Dimension; area, outcrop, dip, thickness, 22 IV. General sections; typical sections; local sections; columnar sections, .... 30 V. The Appalachian sea, 35 VI. The Names of the Formations, 39 VII. Archaean, Azoic, Highland, Laurentian, Fun- damental gneiss, Crystalline schists, . 53 VIII. Archaean Highland Belt in Pa. and N. J , 63 Archaean Types in New Jersey, .... 71 IX. Archaean rocks of Pa., Reading and Dur- ham hills, 74 In northern Chester county, 75 In Bucks, Montgomery and Delaware counties, 79 On the Schuylkill river, 91 X. Are the Archaean rocks sedimentary ? . . 95 The argument from Olivine, 98 The argument from Serpentine, .... 101 Delaware Co. serpentines, 102 Chester Co. serpentines, 103 Lancaster Co. serpentines, 104 Northampton Co. serpentines, .... 105 The argument from Labradorite, . . . 107 The argument from Marble, 109 The argument from Apatite, 113 The argument from Iron ore, 115 viii GEOLOGICAL SURVEY OF PENNSYLVANIA. Chapter. Page> XL The Newer Gneiss of the Philadelphia belt, 118 Its three sub-divisions, 120 1. The Philadelphia(lower) sub-division, 121 2. The Manayunk (middle) sub-division, 122 3. The Chestnut Hill(upper)sub-division, 123 The Chestnut Hill fault, 125 XII. The Philadelphia rocks in Chester, Lancas- ter and York counties, 127 The Newer Gneiss in York county, . . 128 The Newer gneisses in Maryland, . . . 130 XIII. Hydro-mica slate formation; phyllite belts of York and Lancaster counties ; South Valley Hill slate of Chester Co., . . 133 Main York Co. phyllite belt 134 Southern or Peach Bottom belt, ... 136 Peach Bottom roofing slates, 137 XIV. Geology of the South Mountains, .... 142 XV. The Huronian System, so called, 152 XVI. For. No. I, Chiques sandstone, Hellam quartzite, North Valley Hill sandstone of Chester Co., Potsdam sandstone, Upper Cambrian quartzite, Sugar Loaf sandstone of Md., 165 No. I on the Susquehanna, 168 The Chiques Ridge fault, 171 No. I, east of the Lancaster plain, . . . 173 Rogers' Primal in the Chester Valley, . 175 No. I in the Highland range, 179 No. I in Southern Chester Co., . . . 181 No. I in Southern York Co., 182 No. I in the Pigeon Hill, 182 No. I along the South Mountains, ... 183 No. I in Middle Pennsylvania, .... 186 XVII. On Scolithus linearis, 187 XVIII. On Cambrian fossil life, . . 192 XIX. South Valley Hill slate belt, 199 XX. Iron mines in the Primal Upper Slate, . . 205 York county limonite banks, 211 TABLE OF CONTENTS. IX Chapter. Page. Banks north of York, 214 Banks west of York, 215 Banks of the Pigeon Hills, 216 Banks near Hanover, 217 Banks south of the York Valley lime- stone, 219 Banks in the York Co. phyllite belt. . 220 Banks in the hydromica belt S. of York, 222 Adams county limonite banks, . . 225 Lancaster county limonite banks, . . . 226 Welsh Mountain banks, 228 Northampton county limonite mines, . 229 Ranges of Northampton banks, . . . . 231 Lehigh county limonite mines, .... 233 Berks county limonite mines 235 In Oley valley, 236 Cumberland county limonite mines, . . 238 Mountain Creek limonite banks, . . . 241 Banks along Yellow Breeches creek, . 246 Franklin county limonite banks, . . . 248 Mont Alto bank, 249 Path Valley mines, 252 The two Virginia ranges, 253 Grubb'sCodorus ore in quartzite, . . . 253 Lehigh Mtn. Min. Co.'s mine, .... 254 XXI. Magnetic limonite mines doubtfully re- ferred to the Primal slates, or to the Gneiss, or to the Trias, in York, Ches- ter and Berks counties, 256 In York county, 256 In Chester county, 262 The Warwick group 265 In Berks county, 267 XXII. On the Great Valley, 270 Levels above tide of water ways, . . . 271 The two belts, limestone and slate, . . 274 Synclinal mountains of IV in III, . 278 Anticlinal belts of II in III, 279 viii GEOLOGICAL SURVEY OF PENNSYLVANIA. Chapter. Page> XI. The Newer Gneiss of the Philadelphia belt, 118 Its three sub-divisions, 120 1. The Philadeiphia(lower) sub-division, 121 2. The Manayunk (middle) sub-division, 122 3. The Chestnut Hill(upper)sub-division, 123 The Chestnut Hill fault, 125 XII. The Philadelphia rocks in Chester, Lancas- ter and York counties, 127 The Newer Gneiss in York county, . . 128 The Newer gneisses in Maryland, . . . 130 XIII. Hydro-mica slate formation; phyllite belts of York and Lancaster counties ; South Valley Hill slate of Chester Co., . . 133 Main York Co. phyllite belt, 134 Southern or Peach Bottom belt, ... 136 Peach Bottom roofing slates, 137 XIV. Geology of the South Mountains, .... 142 XV. The Huronian System, so called, 152 XVI. For. No. I, Chiques sandstone, Hellam quartzite, North Valley Hill sandstone of Chester Co., Potsdam sandstone, Upper Cambrian quartzite, Sugar Loaf sandstone of Md., 165 No. I on the Susquehanna, 168 The Chiques Ridge fault, 171 No. I, east of the Lancaster plain, . . . 173 Rogers' Primal in the Chester Valley, . 175 No. I in the Highland range, 179 No. I in Southern Chester Co., . . . 181 No. I in Southern York Co., 182 No. I in the Pigeon Hill, 182 No. I along the South Mountains, ... 183 No. I in Middle Pennsylvania, .... 186 XVII. On Scolithus linearis, 187 XVIII. On Cambrian fossil life, . . 192 XIX. South Valley Hill slate belt, ..... 199 XX. Iron mines in the Primal Upper Slate, . . 205 York county limonite banks, .... 211 TABLE OF CONTENTS. IX Chapter. Page. Banks north of York, 214 Banks west of York, 215 Banks of the Pigeon Hills, 216 Banks near Hanover, 217 Banks south of the York Valley lime- stone, 219 Banks in the York Co. phyllite belt. . 220 Banks in the hydromica belt S. of York, 222 Adams county limonite banks, . . 225 Lancaster county limonite banks, . . . 226 Welsh Mountain banks, 228 Northampton county limonite mines, . 229 Ranges of Northampton banks, .... 231 Lehigh county limonite mines, .... 233 Berks county limonite mines, .... 235 In Oley valley, 236 Cumberland county limonite mines, . . 238 Mountain Creek limonite banks, . . . 241 Banks along Yellow Breeches creek, . 246 Franklin county limonite banks, . . . 248 Mont Alto bank, 249 Path Valley mines, 252 The two Virginia ranges, 253 Grubb'sCodorus ore in quartzite, . . . 253 Lehigh Mtn. Min. Co.'s mine, .... 254 XXI. Magnetic limonite mines doubtfully re- ferred to the Primal slates, or to the Gneiss, or to the Trias, in York, Ches- ter and Berks counties, 256 In York county, 256 In Chester county, 262 The Warwick group 265 In Berks county, 267 XXII. On the Great Valley, 270 Levels above tide of water ways, . . . 271 The two belts, limestone and slate, . . 274 Synclinal mountains of IV in III, . 278 Anticlinal belts of II in III, 279 GEOLOGICAL SURVEY OF PENNSYLVANIA. Page. Limestone coves in the slate belt edge, 283 Synclinal belts of III in II, 286 Southern edge of No. II, 289 Relation of South Mts. uplift toll, . . 291 XXIII. Why is there no coal in the Great Valley ? 294 XXIV. No. II. The Great Valley limestone, ... 298 Sub-division of No. II, 299 XXV. No. II in the Lehigh region, 301 The folded stratification, 306 XXVI. Limestone quarries of the Great Valley be- tween the Schuylkill and Snsque- hanua rivers, 309 Berks county quarries, 311 Lebanon county quarries, 314 Lebanon city group, 315 Annville group, 317 Dauphin county quarries, 319 Swatara quarries, 319 Hummelstown group, 320 Beaver station group, 321 Paxtang group, 322 XXVII. Limestone quarries of the Great Valley in Cumberland and Franklin, 324 XXVIII. MagnesianbedsinNo.il, 327 Section of beds opposite -Harrisburg, . 331 Negative deductions from facts, . . . 334 Amount of magnesia present, .... 334 XXIX. Hydraulic cement quarries on the Lehigh, 337 In Mifflin and Centre counties 340 XXX. Limonite mines near the top of II, . . . . 341 Ironton and other mines in Lehigh Co., 345 Moselem mine in Berks Co., 350 Cornwall mine in Lebanon Co., .... 351 Path Valley mines in Franklin Co.. . . 357 Henrietta mines in Blair Co., 361 XXXI. No. II. Nittany Valley limestones, ... 365 Centre county anticlinals, ...... 365 Centre county cross sections, 369 TABLE OF CONTENTS. XI Chapter. Page. XXXII. Centre Co. limonite mines, 372 Two varieties of ore, 372 Pennsylvania Furnace mine, 378 XXXIII. Nittany Valley, Huntingdon county, mines, 387 Pennington range, 390 Warrior Mark and Lovetown range, . . 391 Dry Hollow range in Huntingdon Co., . 391 Cale Hollow range in Huntingdon Co., 394 Huntingdon furnace banks, 398 Sinking Valley mines, 399 XXXIV. Canoe Valley and Morrison's Cove, ... 401 The Springfield mines 404 Leathercracker Cove ores, 409 Morrison Cove ores ; Bloomfield mine, . 414 XXXV. Friends Cove 419 Milliken'sCove, 420 Kishicoquillis Valley, 421 Black Log Valley, 422 McConnellsburg Cove, 423 Horse valley, 424 XXXVI. Caverns and Sinkholes in II, 425 Rate of erosion of II, 430 Precipitation of limonite in caves, . . . 433 Depths of limonite deposits in caves, . 434 Precipitation from pyrites, 435 XXXVII. Zinc, Lead and Barium in No. II 436 Saucon zinc mines in Lehigh Co., . . . 436 Bamford zinc mines in Lancaster, ... 44 Sinking Valley zinc mines in Blair, . . 444 Barytes in No. II, 447 Gypsum absent from No. II, 450 XXXVIII. Trap Dykes in No. II, 451 Grand Horseshoe Dyke in Perry, . . . 458 Little Horseshoe Dyke, 460 Mid Cove Dyke, 460 Duncannon Dyke. 461 Effects of trap, 464 Serpentine in No. II 464 Xii GEOLOGICAL SURVEY OF PENNSYLVANIA. Page. XXXIX. White limestone and marble of II, ... 467 In New Jersey, 469 In York county, 473 In Chester county valley, 477 In Centre county, . 479 XL. Black marble in No. He., 482 XLI. Thickness of formation No. II, 485 In Lancaster county, 485 In Middle Pennsylvania, 488 In New York'State, 489 XLII. Oil and Gas in No. II, 492 Why no Trenton oil or gas in Pennsyl- vania, 494 XLIII. Mechanical deposits of No. II, 497 A peculiar sandstone, 497 Parkesburg artesian well, 498 XLIV. The Fossils of No. II, 501 Fossils of the Calciferous, Ha, . . . 511 Fossils of the Quebec group, 511 Fossils of the Chazy, lib, 513 Fossils of the Black River, He., . . . 513 Fossils of the Birdseye, He. 515 Fossils of the Trenton, He, 517 XLV. No. Ill, Utica and Hudson River forma- tions, 525 The Sea in which the Deposits were made, 529 Nonconformability, 531 Origin of the pyrites, ........ 537 Fossil abundance 538 Fish discovered under Trenton, .... 541 Black slates 542 Limestone intercalations, 543 The roofing slate belt, 543 Stratification and foliation of slate, . . 547 Rolls in the slate, 550 Thickness of the formation, 551 Peach Bottom roofing slate, 555 XLVI. Thickness of No. Ill, .... .557 TABLE OF CONTENTS. xitt Chapter. Page. XLVII. Character of No. Ill, 562 Fossils in the formation, 565 Quartz veins ; their origin, 566 Flagstone layers, 569 Mineralogical poverty of III, . ". . . . 570 Neither oil nor gas in III, 571 Iron ore in III in New York, 572 XLVIII. The Roofing Slate Beds of No. Ill, ... 574 Westward extension of the belt, . . . 589 Notes on the Bangor belt by R. M, Jones, 582 XLIX. The slate quarries in 1882, 588 In Northampton Co., Washington town- ship, 590 Lower Mt. Bethel township, 592 Plainfield township, 593 Bushkill township, 595 Upper Nazareth and Moore, 596 East Allen township, 599 Allen and Lehigh townships, 600 In Lehigh Co., Washington township, . . 604 N. Whitehall and Heidelburg, .... 608 S. Whitehall and Lynn, 607 In Berks Co., Albany township, 609 Weisenburg and Albany, 611 In Perry township, 615 L. Fossils of No. Ill, 617 Peach Bottom fossils for comparison, . 618 LI. No. IV. Oneida and Medina formations, 625 Thickness of No. IV., 627 At the gap above Harrisburg, 637 Comparative tables in the gaps, .... 641 Thins southward and northward, . . . 649 No. IV described in Logan gap, . . . 651 No. IV at Orbisonia, 653 No. IV in Spruce Creek gap, 655 No. IV in Tyrone gap : section, .... 657 No. IV in Mill Hall gap, 659 No. IV, in Williamsbnrg gap, .... 661 GEOLOGICAL SURVEY OF PENNSYLVANIA. Page. No. IV in the Bedford gaps, 661 Oneida, IVa, not deposited there, ... 663 No. IV in Clinton, Centre, Lycoming, . 667 No. IV along the Great Valley, .... 669 No. IV at the Susquehanna Water Gap, 669 No. IV at the Schuylkill Water Gap, . 673 No. IV at the Lehigh Water Gap, . - 674 No. IV at the Delaware Water Gap, . 675 No. IV in New Jersey, 676 No. IV in New York, 677 Lead ore veins in No. IV, 678 LII. Topographical features of No. IV, .... 681 Three groups of mountains of IV, . . 682 Parallelism of mountains of IV, ... 686 Convergence of mountains of IV, . . . 688 Mountain spurs of FF, ....... 689 Anticlinal and synclinal knobs, .... 692 Crests, single and double, 695 Difference in heights, 696 Keel mountains of IV, 697 Oneida Terrace, ravine system, .... 698 Anticlinal vaults restored, ...... 699 Model of the plications of Middle Penn- sylvania, representing the upper sur- face of Medina, IVc., 703 Methods of constructing a model, . . . 704 Conformity of IV upon III, ..... 707 LIU. The mineral worthlessness of the mountains of IV, 711 Foot notes on gold, silver, etc., .... 712 LIV. The fossils of No. IV, 714 May Hill sandstone in England, . . . 716 The earliest echinus, cockroach, 'fern, . 716 Lesquereux's L. Silurian land-plants, . 717 Drifted plants show changes of the rela- tions of land to sea, and changes of vegetation on land, 718 VOLUME I. LIST OF ILLUSTRATIONS. 276 (PI. I). Map of the bends of the Conedoguinit creek in Cumberland Co., to show their relation to the out- crop contact line of II and III. 277 (II). Cross section of the Great Valley on the meridian of Harrisburg, to illustrate Chapter 22. 280 (III). Map of the Great Valley west of Carlisle, to show the coves of II in the outcrop edge of III. 281 (IV). Cross section of the Great Valley, to show the hypothetical character of the Path Valley faults. 284 (V). Pig. 1, Exposure of waves in beds of II; Fig. 2, Local map of a limestone cove of II in III near Orrstown, Cumb. Co. 285 (VI). Fig. 1, Cross section of the Hole, at Swataragap; Fig. 2, A similar cross section of Path Valley and Bear Valley at Loudon, Franklin Co. ; Fig. 3, Map of southern Franklin, showing the parallel zigzag outcrops of No. IV, the parellel alterations of III and II at Mercersburg, and the crenulated edge of the limestone belt. 331 (VII). Vertical detailed section of 115 limestone beds in the McCormick quarries opposite Harrisburg. with thickness, and the percentage of carbonate of mag- nesia designated by tint. 348 (VIII). Figs. 1, 2, Maps of Moselem limonite mine and vicinity, Berks Co. Fig. 3, map of the Lebanon city and Cornwall part of the Great Valley. 349 (IX). Figs. 1, 2, 3, Cornwall mine cross sections. 352 (X). E. V. d'Invilliers' map of Cornwall mine. 353 (XI). Nine illustrations of the Cornwall mine. XViii GEOLOGICAL SURVEY OF PENNSYLVANIA. 616 (LXX). Fossil seaweeds of Peach Bottom slate. P. Frazer. 618 (LXXI). Others drawn by J. P. Lesley. 622 (LXXII). Photograph of Jack's mountain anticlinal arch. 624 (LXXIII). (1) Seven Mtns., 6 cross sections. Sketch map of mountains of IV from Bald Eagle across to Tuscarora mountains.. (3) Views, map and cross section of an eddy hill in Big Fishing Creek Gap in Centre county. 626 (LXXIV). (1) Bald Eagle (Bellefonte) gap, contour map. (1) Canoe Valley narrows of the Juniata, Hunt- ingdon Co. (3) Map of zigzags of IV in Perry Co. 628 (LXXV). Greenwood Furnace fault ; two sections, and a map. 630 (LXXVI). Bald Eagle faults. Map by E. B. Harden. 632 (LXX VII). Port Clinton gap section. H. M. Chance. 634 (LXXVIII). Delaware gap section. H. M. Chance. 636 (LXXIX). Lehigh gap contour map, by H. M. Chance. 638 (LXXX). Delaware gap section. H. M. Chance. 640 (LXXXI). Logan gap section, Mifflin Co. 642 (LXXXII). Lewistown section, Mifflin Co. 644 (LXXXIII). McVeytown section, Mifflin Co. 646 (LXXXIV). Long Hollow section, Mifflin Co. 648 (LXXXV). (1) Kishicoquillis valley section. (2) Mc- Kee mine section. (3) Mount Union section. 650 (LXXX VI). Orbisonia section No. 1, Huntingdon Co. 652 (LXXXVII). Orbisonia section, No. 2. 654 (LXXX VIII). Delaware Water Gap contour map. 656 (LXXXIX). (1) Jack' smtn. anticlinal crest section, to show its sudden decline in Huntingdon Co. (2) Map of the same. (3) Port Clinton map, showing fault at the Schuylkill. (4) Warp of dips, E. and W. side of Delaware Water Gaps. 658 (XC). (1) Seven mountains, Huntingdon and Union counties ; 7 cross sections by d'Invilliers. (2) Perry Co. synclinals ; four illustrations. (3) Map of the same two grand synclinals. LIST OF ILLUSTRATIONS. xix Page. 660 (XCI). Perry county faults and folds ; 2 cross sections nnd a map of Centre township. 662 (XCII). Perry Co. fault, four illustrations. (2) Little Germany fault map. (3) Spring * township zigzag belts. 664 (XCIII). Blue mountain map, by G. Lehman. 666 (XCIV). The same continued east to include Port Clin- ton and the Little Schuylkill river. 668 (XCV). Seven Mountain sections, Nos. 8 and 9. 670 (XCVI). Seven mountain sections, Nos. 10 and 11. 672 (XCVII). Seven Mountain sections, Nos. 12 and 13. 680 (LIII). The Arch Spring in Sinking Valley, Blair Co., picture by Lehmann, from Geol. Pa. 1858. (2) Catioe mountain terrace (Oneida, IVa.), as seen from head of Sinking Valley. 700 (LVII). Model of the surface of the Medina No. IV in middle, northern and northeastern Pennsylvania, as it existed after elevation and plication, and before ero- sion ; constructed by J. P. Lesley. Photograph in slant light from the S. E. 702 (LVIII). The same photographed in light from N. W. 714 (CXI). Fossils of IV, Oneida and Medina. INTRODUCTORY CHAPTERS. CHAPTER I. Our Geological Knowledge. A summary description of the geology of Pennsylvania implies a condensed account of all the work done by the ge- ologists of the state survey for fifty years, together with the knowledge produced by some thousands of private explora- tions. It is a task made difficult, not so much by the ex- tent and diversity of the territory to be described, as by reason of the great number of rock formations which ap- pear at the surface, and the erratic courses which their out- crops pursue ; by the local variations of character exhibited by them ; by the complicated structure of the underground ; by the multitude of mineral beds having an economical value ; by the eruptions of volcanic rocks in different places, and the extensive rnetamorphism of the older formations in the southeastern counties; and by the concealment of a con- siderable portion of the rock surface of the northern and western counties beneath a covering of glacial drift. So great is the variety of objects of geological interest which present themselves to the eye of a skilled observer at every point, that we may justly consider the number infi- nite which offer themselves for investigation in an area of 50,000 square miles ; that is, within the limits of our state. A small spot upon the surface of the whole globe Pennsyl- vania is nevertheless a world in itself, to the just contem- plation of which the liveliest imagination can rise only by a great effort ; one of those objects of contemplation pre- sented to the mind of man before which it bows with all its faculties of logic and rhetoric in reverence, imperfectly comprehending what it sees, and hopeless of framing an adequate salutation to it. For, the longest and most in- timate conference with these phenomena of Divine operation 2 GEOLOGICAL SUKVEY OF PENNSYLVANIA. will not enable the greatest genius to do justice to their description. The geology of such a territory is a history of the works of nature through a lapse of time, which, if compared to the life of a man, or even to the existence of the human race, is little less than an eternity. Events of the greatest magni- tude and complexity have followed each other in uninter- rupted sequence, without known beginning, and without yet reaching an end. Geologists spend their lives in de- ciphering the hieroglyphic records of this history, only a part of which are legible, and the largest part is concealed entirely from view. One fact at a time may easily be noted ; a group of facts may be compared and discussed with pleasure and safety ; but the geological drama has been played out upon an imperial stage, by combined and con- flicting natural forces in company, according to a plot not yet revealed, beginning in ages previous to the creation of any living being. The drama was played without an audi ence. Therefore, the geologist who makes himself its re- porter is soon lost in amazed bewilderment ; and when he takes his pen in hand will pray for the pardon of innumer- able mistakes before he yields to the necessity of commit- ting them. The great English historian of the last century, Gibbon, 'has left for our instruction a luminous description of the difficulties to be overcome and of the successes to be achieved by a narrator of human events when twenty years of zealous preparation is followed by twenty years of patient execution. He tells how many languages had to be ac- quired, how many previous works of genius mastered, how many original documents deciphered, what toil, what doubts, what discouragements had to be endured. He paints a touching picture of the mingled pain and pleasure with which he ended his task, and closing his book bade a lingering adieu to the occupation of his life. The geologist is a historian in every sense of the word ; subject to the same disabilities and exposed to the same de- ceptions ; handling a mass of fragmentary records ; cross- examining unintelligent and unsympathetic witnesses ; OUR GEOLOGICAL KNOWLEDGE. 3 judging conflicting testimonies ; following trains of events which pursue parallel lines separated along shifting boun- daries but mutually affecting each other's characters. But while the historian of human affairs writes under the safe guidance of well-known and well-understood prin- ciples of human nature, the motives of which he has him- self experienced, and by which he may interpret with a near approach to truth the actions of his historical characters, so as to rill out the rude and slender sketches of tradition, or detect and amend the mistakes of ancient documents, it is the ill fortune of the geologist to be compelled to write the physical history of the globe, or a part of it, in almost com- plete ignorance of those fundamental principles of his science on which he should rely for all his explanations. It is true that the collection of geological facts has become in- credibly great, but it is also true that from this very wealth of facts springs the impossibility of any description of them which shall satisfy the common mind, while the geologist himself, if not completely lost in the wilderness of details, either becomes a slave to his own favorite theories, or stands uncertain between the views of jarring schools. None of the greater questions in geology have yet been answered. We know nothing of the interior of the earth beyond a depth of about five miles and that only at a few points. We are ignorant as yet of the exact cause of earthquakes, and of the origin of volcanoes. The history of the crystalline formations remains mysterious. We cannot yet explain the elevation of a continent, with its systems of faults and folds; nor the submersion of the- ocean bed. The relative distribution of land and water has. been changed in every age, but how, how much, or why r we do not know. Consequently no geologist has succeeded yet in even plausibly mapping the surface of the earth 'as it was at any past time, with river drainage on land, and its deposits in the sea. The courses of those ancient ocean currents are unproved which distributed the river sedi- ments. Ancient lakes, with or without outlets, are known to have existed, but their limits have been destroyed and their extent is a matter of guess work. The connection of 4 GEOLOGICAL SURVEY OF PENNSYLVANIA. even great formations in distant countries has been broken and cannot be' restored. The migration of living creatures from one region of the globe to another, under the stress of a change of temperature, or the prevalence of enemies, introduces an element of deception into the arrangement of any lime-table for the globe, or even for a subordinate division of one continent. We know not if the sun has always shone upon the earth with the same energy of light and heat. We know not if the tides in past ages have or have not been more efficient at their work. The composi- tion of the atmosphere may have greatly changed, nor have we any means for settling that question. The geologist then must examine and describe his special region in a deceptive twilight of science. Detailed reports of business properties are not affected by such fundamental difficulties, but a description of a region like Pennsylva- nia pretending to display a summary of our knowledge of it, must cautiously handle all the generalities and be con- tent to leave great questions unanswered and a thousand facts unexplained. CHAPTER II. (Geological Time. Time and space are the two eyes with which man looks upon the world, the two lenses which he uses for examin- ing-, defining and measuring whatever has attracted his attention or excited his thirst for knowledge. In every branch of science, in every business, in every handicraft, in the tine arts, well-defined and common standard measures of time and space have been invented, and in the present century refined to the utmost precision by delicate instru- ments. The science of geology has its own apparatus, and no description of the geology of a place or of a region can be either written or comprehended unless both the writer and the reader are inspired by the sincerest respect for an accurate application of the standards of time and space to all and each of the whole series of observed facts. The idea of time is the most fundamental of all geolog- ical ideas, and at the same time is to most minds the vaguest. To count the minutes in an hour, the years in a century, or the centuries in the Christian era has become a familiar and easy mental operation for all educated per- sons, and the few] who have pursued historical studies possess clear notions of dynasties for two or three thousand years before the time of Christ. But to the majority of mankind any statement respecting previous ages in the geo- logical history of our planet is unreadable because written in a time-language which they cannot appreciate. The great operations of nature have been so exceedingly slow and have been carried on through so many ages, each of vast duration, that untrained minds become confused and weary with them. Nevertheless the geologist is compelled to describe rock formations in an order of their successive deposits; and he can make their nature clear in no other way than 6 GEOLOGICAL SURVEY OF PENNSYLVANIA. explaining the comparative quietness, or the comparative commotion of the age of each. Going backward in time and downward through the rocks, he is compelled to give time-names as well as mineral-names to the formations or groups of beds which he describes. Bat his time-names can only be comparative, such as new and old, newer and older, recent, ancient and archaic. And his mineral-names also can only be comparative : upper, middle and lower. These terms, however, can present no well-defined idea to any mind but that of a geologist, for they are the terms in daily use among men for events which run their course in a few days, or years, or centuries of human time, or for things which are measurable by inches, yards or miles in the country where those who use them live. A single one of the principal rock formations of Pennsylvania required more time for its deposit than the duration of the human race from its first appearance on the planet until now. The age of our primeval forest can hardly compare with the age which one large coal bed reached before its life was destroy- ed by the invasion of the overlying sands. If the limestone deposits of the Cumberland valley could be measured not by feet and yards but by years and centuries, and com- pared with events of human history, we should merely get a vague notion of enormous time, expressed by the old phrase "a thousand years is as a single day." Nevertheless, however ineffectual will prove the effort to frame a clear idea of the whole course of geological time, or even to define with any distinctness its major sub-divisions, it is absolutely indispensable for the understanding of the geology of any region to suspend our habitual estimates of human events, and substitute for them the largest possible conceptions of geological time, upon the grandest scale which we are capable of imagining. To the human individual who seldom lives beyond three- score years and ten, and whose short life is crowded with business affairs, time is considered a precious commodity to be spent with economy, its loss and its waste lamented, and its use converted into a religious duty. But these ideas are products of the latest age of human GEOLOGICAL TIME. 7 history, and are essentially ideas of the modern factory and counting-room. Disembodied immortal spirits would value time by a different standard. Science, especially the science of geology, 'dispenses time as the commonest drug in the market of the universe. The idea of precise time is the product of the routine of civilized human existence. It is unknown in the vegetable and animal worlds ; it is disregarded by nomadic races. The idea took root when the home was organized by woman, and meals were cooked at fixed hours of the day. It be- came" "confirmed when superstition organized priestcraft, and religious ceremonies demanded a calendar. The moon was the first clock. The invention of the water-clock by the ancients was made for the benefit of the wealthy and cere- monious. The first mechanical clock in Europe was one sent as a royal present by the Caliph Haroun-Al-Rashid of Bagdad to Charlemagne. Even now, with all the chro- nometers of Christendom, it is still a fact that nineteen- twentieths of the human race have never seen a clock, and have no.practical need of one. The idea of absolutely precise time came with the inven- tion of the steam engine, the locomotive, and the telegraph, and with the erection of modern observatories. It bears the same relation to the crude instinct of time in the mental constitution of the race that the few and costly ingots of aluminium bear to the sum total of common clay with which the world is full. But, with the spread of civiliza- tion, and the multiplication of machinery, popular educa- tion will in the end fix it in the minds of all. Whatever moves with regularity, continuously, by steps or stages equal to each other, and therefore countable with- out being accountable, or disturbed by perturbations, is a clock is a measurer of time a scale by which the rate of the course of events can be recorded. A locomotive, a power loom, a printing press, any engine adjusted by a gov- ernor to invariable motion, a sewing machine driven by a well-directed foot, is a clock. All reciprocal motion, all rotary motion can be set to keep time. The melting snow water dropping from a roof will furnish a geologist with a 8 GEOLOGICAL SURVEY OF PENNSYLVANIA. measure for calculating the annual rate of growth of stalag- mites in a limestone cave. The essential nature of a clock is its regularity ; and that depends on the energy which moves it ; while the rate of its own particular motion depends on its construction, a short pendulum ticking seconds, a long pendulum ticking minutes. But while the geological world is full of natural time- markers, they are of every variety of construction, and therefore furnish no common standard of time. The geol- ogist who seeks to investigate the age of the globe stands like a purchaser in a clock-makers shop, surrounded by a thousand time-keepers all ticking at once but not together, independent of and indifferent to each other's rate of going, and waiting for their turn to be adjusted to a common rate ; the little ones, like children out of school, rollicking in an ecstasy of quarter seconds ; larger ones soberly stating their movement in seconds ; here and there a great pendu- lum disdaining to record its relations to universal time oftener than once a minute. In the world of physical science entomologists, concho- logists, ornithologists apply to use only the little patent levers and repeaters ; while the mineralogists, the geologists the astronomers, in their several calculations work only with cathedral clocks. But in all branches of physical science without exception the differentiation of time is accomplished naturally and is illustrated scientifically by natural phenomena in one way or in another, on a smaller or on a grander scale, and at rates so immensely different that, while whole series of thousands of one kind complete their cycles of existence within the lifetime of a man, others require a thousand centuries to substantiate one item ; and this is what happens in geology. Now, for such phenomena geology has as yet failed to find any precise measuring time-machine, any clock, and must still content itself with rudely divided scales of rela- tive proportion without knowing the actual sizes of their aliquot parts. But geologists, being now emancipated from the superstitious belief that God created the world in GEOLOGICAL TIME. 9 six days, or in six ages, are free to gaze back along an interminable vista of events, having modern human history with its accurate chronology of days and years in the fore- ground, through the middle distance of classical and monu- mental history measured by [olympiads, centuries and dynasties, into a background of pre-historic and glacial times unchecked by any measurable records ; beyond which is dimly seen an infinite extent of geological times, ages and formations, vanishing in the extreme distance toward some absolutely unimaginable beginning. In contemplating this grand picture from day to day, as the geologist is obliged to do, two sentiments take posses- sion of him : an admiration for the variety and multi- plicity of the things which have happened ; and a profound conviction of the slowness of time, the infinite patience with which the world has been made. And these senti- ments are the product of observation ; are neither a fancy nor a faith. It is evident to observation that the clock of nature has ticked regularly; that the same physical forces have oper- ated through all time in the same way as they are seen operating at the present moment; that in every age rivers have been delivering leisurely their burdens to the sea in obedience to the varying rainfall of the seasons; that the forests have spread and disappeared again, successively occupying for centuries the soil; that living creatures of a million kinds have made their appearance on the planet in an orderly series, the rule of which we do not understand, but the order of which is plainly although not completely revealed by fossil remains imbedded in the rocks. For it is impossible for any sane man to doubt that the rate of life with which we are familiar now was in every geolog- ical age the rate at which animated creatures were gener- erated, grew, propagated their kind and perished. No reason can be given for supposing that the cockroach whose form is imprinted on a shalyroof of a coal-bed lived either a shorter or longer life than the cockroach of the modern dwelling ; or that the Eurypterids in the Darlington shales of Beaver county had a different life experience 10 GEOLOGICAL SURVEY OF PENNSYLVANIA. from that of any modern lobster on the New England coast. The great pachyderms whose skeletons have been transferred from the clays of the Rocky Mountains to the museums of New Haven, Philadelphia and Washington, by Leidy, Cope and Marsh, no doubt lived each one as long a life as a modern elephant, rhinoceras, tapir, horse or elk. The ancient coral reefs of which the limestone beds behind the Blue Mountain at Stroudsburg, Danville, Lewistown, Tyrone City and other places in middle Penn- sylvania, must have grown as slowly as grow now the Mad- repore reefs off the Florida coast. But beyond this general conviction that the ordinary events of nature in the mineral, vegetable and animal worlds have been pursuing the even tenor of their way through all geological ages, we cannot go. We cannot divide geological time into centuries, much less into years; but we can and must apply the conviction thus obtained that geological events have slowly come about to explain how they came about and in what order they occurred. When this fundamental idea of immense stretch and suc- cession in geological time has become familiar to the public mind the greatest difficulty will have been removed from the path of the geologist in his efforts to describe the' geology of any district or region like Pennsylvania ; and only for this reason is it insisted upon here. To make it still more plain the following illustrations of its truth will be adduced and specimens will be given of the calcula- tions of geological time attempted by recent writers. The annual growth of trees, interrupted by the winter, is marked by their rings of bark, so that the age of a tree can be discovered by the number of these rings. In like man- ner the deposits of a river are more abundant and of a coarser quality after long-continued rains ; so that a section of a sand bank or mud flat at the mouth of a river should mark the course of time by thin layers of fine clay and coarser sand alternately. This fact has been taken ad- vantage of by those who have investigated the history of Egypt. The regular inundation of the Nile, commencing at midsummer and lasting a hundred days, covers the valley GEOLOGICAL TIME. 11 and the delta with a sheet of fertile mud. The turbid waters then fall, the land emerges, the winter passes. In March the hot dry khamzin blows, and clouds of sand sweep across the surface, depositing a layer of yellow desert dust upon the previous layer of Nile mud. This takes place year by year with the regularity of clock-work. Shafts have been sunk through these alternate layers to the floor on which some monument of antiquity was erected four thousand years ago, and the counting of the alternate layers has verified its recorded date. In some of these shafts sunk to a greater depth fragments of human pottery have been discovered, and by the number of layers of mud and sand it has appeared that human beings pursued their handicraft at least fifteen thousand years ago. It is evident that, were a proper site on the shore of the Mediterranean between Rosetta and Damietta selected by the Egyptian government, 'and a shaft sunk deep enough to reach the original bed on which the delta of the Nile began to be de~ posited, it would be possible, either by counting the alter- nate layers of sand and mud, or by simply estimating their average number in each foot or yard of the descent, to cal- culate with considerable accuracy the geological time at which the drainage of old ^Ethiopia adopted the present valley of the Nile for its most convenient route to the sea. The Nile indeed in this respect stands alone among all the rivers of the world ; the only river which receives no side streams for fifteen hundred miles of its course, re- sembling thus the unbranched date palms which spread their annual plumes at the top along its bank ; the only river which deposits all its burden during half a year, and waits to give the atmosphere an equal chance for depositing its special burden of a different kind. But all the rivers of the world have seasons of copious outflow and increased deposit ; therefore all the river sediments of the world are composed of alternate layers of coarse and fine material ; and as we go back in geological time, making sections of older and older river sediments, more and more packed and consolidated, hardened, dried and converted into shale and sandstone rocks, the geologist observes in all of them this 12 GEOLOC4ICAL SURVEY OF PENNSYLVANIA. fundamental character of alternation ; the incontestable proof of their origin as river sediments ; affording an irre- sistible conviction that they grew, layer upon layer, annu- ally, through ages of immense duration rudely measurable by their several thicknesses. The same lesson is taught in other ways ; as, for example, by the annual layers of autumn leaves which have been blown upon the surface and sunk to the bottom of still water ponds and little lakes in the forests, with the eggs of insects attached to them, and the wings or bodies of dead insects imbedded with them. A deposit of this kind i-n Switzerland is described by Heer as thirty feet thick, and shows thousands of such alternate layers of black vegetable matter and fine white clay, each no thicker than a sheet of paper, marking the quiet alternation of annual seasons for many thousand years. The influence of wet and dry seasons in tropical countries marks the annual stalactite growth in limestone caves. For in the rainy season an abundance of water falling on the surface finds its way to the roof of the cave charged with carbonate of lime, and the dropping in the cave goes on with great rapidity. But in the following dry season the growth of the stalactite stops, just as the life of a tree sleeps during the winter; and thus the stalactite has its annual rings of growth like a tree, from which its age can be esti- mated. The stalagmite floor of such a cave consists of suc- cessive sheets ; and in the case of one Brazilian cavern, thirty thousand of these annual sheets have been counted. There is a little brook in Switzerland called the Tiniere, which has its springs in the mountains of Berne, and de- scends through a narrow ravine which it has cut for itself down to the bank of the Lake of Geneva near Vevey. Fed by rains, cloud- fogs and melting snows it wears away the rocks through which it passes and spreads sheet after sheet of sand and clay over a little fan-shaped mound which it has accumulated at its mouth. A railroad has been cut through this mound, showing its dome-shaped structure, and the slow and gradual way in which it has been made. In the sides of the railroad-cut three long black streaks are GEOLOGICAL TIME. 13 visible one above the other. They make three long arched lines. They consist of vegetable matter mixed with frag- ments of charcoal, pottery, and the implements of man. They represent three times at which some tribe of Swiss aborigines selected the mound as habitable ground, resid- ing upon it awhile until destroyed or driven away by some unusual violence of the little river descending from the mountains, or by some pestilence or invasion of hostile foes. Although the three arched streaks are separated from one another by only a few feet, the intervals must needs represent great lengths of time ; for, the three settlements were made by different races ; for, in the lowest arch no tools were found except stone axes, and chisels, and needles of bone. In the middle streak were found beside these instruments made of brass ; and in the Upper streak, manufactured tools of iron were discovered. Therefore centuries probably elapsed, the mound always growing higher and higher very slowly, new tribes coming into the region with advancing civilization seeking places to live on. As no alternate layers in the mineral constitution of the mound could be made use of for calculating this rate of growth, the Swiss geologists resorted to another method, which is one of universal ap- plication in the geology of sedimentary rocks of the globe. They measured the amount of water annually flowing down the Tiniere ; they measured the quantity of solid matter held in suspension by the little river at various seasons of the year. From these two data they calculated the thick- ness of stuff spread over the whole extent of the mound in a single year, taking this thickness as a unit of measure- ment for the depth of the lowest streak beneath the present surface of the mound. It resulted from the calculation, that the people who left their stone axes in the lowest streak lived about seven thousand years ago; and the ap- proximate accuracy of the calculation was confirmed by a similar process of thought applied to the case of human habitations buried in a little delta at the mouth of one of the rivers of the Jura, by the gradual enlargement of which the lakes of Neufchatel and Bienne, originally one lake, has been separated into two. In this case also the age of 14 GEOLOGICAL SURVEY OF PENNSYLVANIA. the human remains was found to be about seven thousand years. But in both these cases, which are exceptionally favorable for estimating the time of the occupation of the mounds by man, no knowledge is obtained respecting the far greater lapse of time previous to their first occupation during which the two rivers mentioned had been doing the same work in the same way, work the beginning of which goes back into the last geological age. A bridge was built by the Romans from one vertical wall to the other of a deep and narrow ravine in the center of France. For unknown ages a river of Auvergne had been working its channel down through a lava bed, undermining and throwing down one after another of its basaltic columns, grinding them up into black mud and delivering the- mud to the Loire to be deposited in the Bay of Biscay. The Roman bridge is broken, but its arches still cling to the walls of the chasm, showing that this has not been sen- sibly widened in two thousand years. A flagrant proof of the extreme slowness with which the erosion of the surface of the earth has ever been going on ; and we may turn from the basaltic columns in Auvergne to the great canon of Colorado or any of the gaps in the mountains of middle Pennsylvania with a sentiment of profoundest conviction for their vast antiquity. The process of destruction is evident ; it goes on before our eyes daily and annually; "but unless we have a sound conviction of its infinite slow- ness we shall fall into the popular superstition which prat ties about convulsions of nature which never occurred, and fails to realize the true character of the events which the geolog- ist has to describe. The lesson of geological antiquity is taught with equal clearness by the series of volcanic eruptions which mark the whole history of the earth from the beginning to the present day; and although evidence of the exercises of the eruptive forces on an exceptionally grand scale at certain times is not to be mistaken, corresponding to the greater and the more widespread earthquakes which have some- times varied the importance of calamities in human history, they cannot be considered in any other light than as excep- GEOLOGICAL TIME. 15 tions to the regularity of the whole series of volcanic phen- omena, which in the gross has undoubtedly been as regu- lar, and has proceeded as leisurely as -any other function of nature. Vesuvius at the Christian era had been asleep from beyond the earliest traditions of the inhabitants of Italy; its old crater was a cattle ground of Umbrian cow-herds, and accounted so safe from all commotion that Spartacus encamped his army in it as an impregnable fortress. When the rirst eruption awoke the mountain to renewed activity, pouring a sheet of lava over Herculaneu m and covering Pom - peii and the surrounding country with ashes, men were as much astonished as we should be were the old vents in York and Adams county to be again re-opened and fresh streams of lava pour from them over our cultivated fields. Since Pliny's day the activity of Vesuvius has been continuous, its eruptions recurring every few years, yet without sensi- bly increasing the size of the cone. Therefore, the con- struction of the cone must date back in ages previous to the appearance of man. Every volcanic mountain in the world has grown like a vegetable bulb, skin over skin, through wastes and wildernesses of time of whfch the human imag- ination can form but a vague idea, and which the science of geology can only indicate by reference to the geological age of that particular formation in which the lirst appearance of such cones can be recognized. Every geological age had its own volcanoes, its own outflows of lava and its own tufa beds. The backward vista is interminable ; the cause is unknown ; their phenomena have pervaded the ages from the beginning. It is a seductive temptation to the speculative geologist to translate the vague ideas of geological time into figures. But whether the results of any calculation thus mathe- matically stated increases our knowledge or clarifies our ideas may well be doubted ; for after all, when the product of multiplying large numbers reaches into the millions it merely generates the idea of vastness. To write the sum of a hundred million years helps us. no better than to write the words infinity or eternity. Yet the effort at such a cal- culation is a useful exercise of the mind and furnishes an 16 GEOLOGICAL SURVEY OF PENNSYLVANIA. opportunity for examining the facts which must be used in making the calculation. With this end in view one or two such calculations will now be given. The western coast of South America has been lifted from the ocean to a great height in the air by successive earth- quakes, one of which suddenly lifted it three feet since the settlement of Chili by the whites. Marine shells can be broken out of the rocks at a height of 16,000 feet above the sea. The average rate of this upheaval is of course unknown; but should we base a calculation upon the observed rise of the land of northern Scandinavia, namely, live feet in a century, the rocks containing these fossil shells would be 320,000 years old. From the character of the shells we k-now that the rocks which hold them were deposited in what is called the Jurassic age. But if all known geological time were represented by the twelve hour divisions on the dial of a clock, the Jurassic age would be at about nine or ten o'clock, and therefore the highest antiquity we could give to the mountains of South America would represent but a portion of geological time. While parts of the crust of the earth are slowly elevated other regions are slowly sinking into the sea. In middle Pennsylvania we have a series of great formations lying one upon another, all of them originally deposited in succession in a great water basin which in early times occupied the area of the United States. Some of these formations were spread upon the bottom in deep water; some of them in water so shallow that they exhibit mud cracks, ripple marks and foot-prints such as travelers notice everywhere on sea beaches. They hold both shore-living shells and coral reefs. These facts compel us to believe that the bottom of the Pennsylvanian sea kept on sinking through all the ages during which these deposits of limestone, sand and clay were made in it ; and probably at a rate proportionate to the inflow of the solid materials from the rivers around it. The rate of sinking is of course unknown, but must have been as slow as the wearing away of the surrounding lands. The total thickness of these deposits, measured from the top of the coal measures down to the bottom of the great lime- GEOLOGICAL TIME. 17 stone of the Nittany valley at Birmingham in Blair county, is not less than 40,000 feet. If the geologist prefers to take the Scandinavian rate of elevation as a measure for his cal- culation, five feet in a century, he gets 800,000 years. This result is indeed a most uncertain approximation to the truth, and is of no scientific value whatever, but it will serve admirably well to impress upon the mind the reality of the vast antiquity of that part of the surface of the globe which we are competent to examine. Considering the fineness of nineteen- twentieths, say ninety-nine-hundredths of the 13 formations which appear at the surface in middle Pennsyl- vania, the'rate of their deposit must have been lower than five feet in a century, and consequently the length of time required much greater than the result of the calculation. The tidal layers of red mud in which were found at Potts- ville by Dr. Lee and Professor Rogers the "foot-prints of shore-feeding animals, measure 2,000 feet in thickness. The fine dark mud and sand formation through which the belt of roofing slate in Lehigh and Northampton counties runs is at least 6, 000 feet thick. The Carboniferous formation at the top of the series, with its slow-growing coal-beds, and its slowly deposited limestone, fireclay and shale beds is 3,000 feet thick. Taking these three formations together, apart from the other ten, we have 12,000 feet of sediments which might have had a rate of deposit no greater than a few feet in a century, requiring a million years. In another part of this book will be described the folding of the Paleozoic formations of middle Pennsylvania, with basins five miles deep, and arches five miles high; Al- pine ranges which once traversed our State ; now reduced by the frosts and waters of ages to within a thousand or two thousand feet of the level of the sea. A whole world of rock has been dislodged, ground up and carried by the Juniata, the Susquehanna, the Schuylkill and the Delaware into the Atlantic. All southern New Jersey, Delaware, Maryland and the general Tide Plain of the southern states have been constructed by the rivers which have been engaged since the age of the coal measures in eroding the great rock folds of the Appalachian belt. Can we find in 2 18 GEOLOGICAL SURVEY OF PENNSYLVANIA . I what goes on before our eyes to-day a measure for this erosion. Certainly not one of any accuracy. Yet one is at hand which will give some good idea of it. The Juniata river is said to pass at Millerstown in Perry county about 24, 000, 000 cubic feet of water per hour ; hold- ing enough sediment in suspension to represent in the course of a year about 1,000,000 cubic yards of the rock waste which its innumberable branches are robbing from the mountains. Considering the whole water basin of the upper Juniata, the erosion going on must lower its general surface about one foot in 1,500 years. The original surface of the region was on an average say 9,000 feet above the present surface of the country. This gives us 13,560,000 years as the length of time during which the Juniata has been carry- ing the rock waste of its own special upper country into the sea; and all the other rivers of the Atlantic coast have been doing the same work at the same rate during the same length of time. No wonder we have the great lowlands of the Atlantic coast, now cultivated by man ; and the vast sloping sea-bottom which has its continuation under water from the line of coast far out to the submerged precipice which the soundings of the Coast Survey have shown to be the border of the gulf stream. The work done by the Mississippi river has been ascer- tained with considerable accuracy by the United States Army Survey under Humphreys and Abbott. At its present rate of work (which alone can be studied) it removes from the face of the immense region between the Allegheny and Rocky mountains one foot of surface depth in 6,000 years. It is impossible to state the original height of the general surface of the Mississippi water-basin in the coal era when the great river began its operations. From some districts like middle Kentucky and Ohio it has removed all the formations from the top of the coal measures nearly to the bottom of the series, a thickness of say 10,000 feet. In other parts, as at Pittsburgh, the erosion amounts to only 2,000 feet. If an average of only a thousand feet be as- sumed the age of the Mississippi would be 6,000,000 years. The science of geology in its present stage is like a river GEOLOGICAL TIME. 19 bearing variable 'quantities of solid matter which can be seen and felt, and quantities of invisible chemical solutions. It consists of an abundance of indisputable facts, mixed with innumerable fugitive suggestions, hypotheses and" theories, changeable in their nature and subject to present and future criticism. The accumulation of facts which re- main the permanent body of the science increases continu- ally and at an accelerated rate from year to year. The study of one mineral bed after another and one geological locality after another is gradually procuring a sound and useful knowledge of the structure and mineral wealth of regions. Thus the beneficial work of good geologists is in favor of the business community, which troubles itself little about questions of cause and effect, and is well content with definite statements of quality and quantity, seeking only to learn where the useful can be found and how it can be cheaply got. Yet the discussion which forever goes on in the geological profession respecting the origin and age of minerals appeals strongly to the intelligent curiosity of ed- ucated men of all classes, and, in so far as they can be understood by laymen, make an important part of the gen- eral education of the community. The race of man differs from the races of animals in pos- sessing not only a more powerful reason, but the faculty of imagination, by which man sees the invisible, and can ap- preciate the past. In science the business of the imagina- tion under the guidance of mathematics is as important as the business of the judgment under the guidance of the senses. Without imagination men would be like savage tribes before the horse was tamed. The prosaic mind goes afoot and travels in a narrow circle around its dwelling place, knowing so little of the world beyond that it cannot comprehend its own vicinity. The geologist finds such minds everywhere. They are incapable of seeing what he sees both in the distance and in the depth, because the im- agination which they possess has not been cultivated like his own. He rides his imagination like a winged horse in all directions, far and near, collecting knowledge from every quarter. In telling his science he speaks from horseback to 20 GEOLOGICAL SURVEY OF PENNSYLVANIA. men on foot. His steed may be better or worse. He has his own adventures with it. It sometimes stumbles, some- times he is thrown, and sometimes he is run away with. When the imagination is of the finest quality it must be ridden with a curbed bit and a strong rein. The tendency to exaggeration in geology is especially great. It gathers force and velocity by indulgence, like a rock descending a mountain slope. So, exaggeration in the estimate of geo- logical time has been carried by the vivid imagination of some geologists to a wholly unreasonable excess, yet always under the form of mathematical calculation, dealing with absolute facts which the most sober reasoner cannot deny, and which are the products of the most careful observation and the most skilful investigation by geographers and chemists. A single illustration of such exaggeration will suffice. An English geologist of eminence has recently discussed with great ability the quantity of soluble and insoluble sub- stance carried into the sea by rivers. Combining Herschel's estimate of 2,494,500,000,000,000,000 of tons of water in the world ocean, with Frankland's analysis of 100,000 tons of sea water holding 1,017 tons of the sulphates of lime and magnesia, and 49 tons of the carbonates of lime and mag- nesia, he gets 1,222,000,000,000,000 of tons of carbonate of lime and magnesia in the world ocean, a quantity sufficient to cover 50,000,000 square miles of land with a layer 13 feet deep, and 25,000,000,000,000,000 of tons of sulphate of lime and magnesia, a quantity sufficient to cover the same num- ber of square miles with an additional layer 265 feet thick. He estimates that the rivers of the world remove annually, on an average, from each square mile of continental surface 100 tons of rock matter ; and that the proportionate amount of its various substances would be as follows : Of car- bonate of lime, 50 tons ; sulphate of lime, 20 tons ; silica, 7 tons ; carbonate of magnesia, 4 tons ; sulphate of mag- nesia, 4 tons ; per-oxide of iron, 1 ton ; chloride of sodium, 8 tons ; and 'alkaline carbonates and sulphates, 6 tons. Taking first the carbonates of lime and magnesia, re- moved from the land surface and deposited in the sea at the GEOLOGICAL TIME. 21 rate of 54 tons per square mile per year, it must have re- quired 480,000 years to charge the ocean water with the amount of these salts which Frankland says it holds. Taking next the sulphates of lime and magnesia he gets 25,000,000 years. Treating the chlorides in the same way he gets 200,000,000 years. Estimating the amount of mechanical sediments or solid matter carried by a river to the sea at six times greater than the chemical solution, that is, 40,800,000,000 tons per annum ; and considering the total surface of the globe 197,000,000 square miles (one cubic mile weighing 10,903,- 552,000 tons) he concludes that it would require for cover- ing the whole globe with a rock formation of every kind one mile thick, 52,647,052 years ; and, therefore, if the geologists estimate all known formations taken together as measuring 10 miles in depth, we must suppose that the first rocks were deposited 526,000,000 years ago. All that can be said respecting any such calculation is that it has no scientific value whatever, although based upon acknowledged facts ; but, as has been already said, it will help to make far lower estimates of the age of the world in- telligible and credible. 22 GEOLOGICAL SURVEY OE PENNSYLVANIA. CHAPTER III. Geological Dimension. The second fundamental element of geological thought is the idea of space in its three dimensions of length, breadth and thickness. Any transcendentally imagined fourth dimension must appear to be absurd. Astronomy deals with unimaginable and infinite distances, as its sister science, geology, deals with unimaginable if not infinite operations of time. In both cases the common mind is subject to a thousand deceptions. Who can believe that the moon when it rides in a clear night through the atmos- phere to all appearance no higher than balloons could mount or an eagle soar, is in reality 240,000 miles distant from the spectator, sixty times the radius of our globe. And yet this distance is the smallest of the heavenly spaces. The sun's mean distance from us is 92,000,000 of miles; while the light of the nearest fixed star traveling at the rate of 200,000 miles a minute does not reach us until after a journey of eight days. Such ideas would seem to be useless to the practical geologist. But no truth is useless; all knowledge is practical either in its direct application to facts or in its education of the finer qualities of the mind. No man can rightly understand the descent of a coal bed or ore vein from the surface into the depths of the underground unless his imagination is disciplined to estimate properly the dimensions of space, and by habituating himself to the measurement of distances of all grades, long and short, he acquires the power of calculating those lengths and breadths and depths which are within the scope of mining opera- tions. To the practical astronomer our globe seems as small to the surrounding solar system as a grain of sand compared with the mass of a mountain. To the practical geologist GEOLOGICAL DIMENSION. 23 who compares the whole globe with the spot on its surface which he is studying for practical purposes, it seems infi- nitely great. It is hard to conceive the depth at which the center of the earth lies beneath our feet; it equals the dis- tance from San Francisco to Newfoundland or from Phila- delphia to Berlin.. Only those who travel extensively can estimate the size of the continents and oceans of the world; those who circumnavigate the globe; he who travels round it in 80 days. Were a continuous first-class railway laid like a hoop of iron on a great circle, an express train running at a schedule rate of 40 miles an hour would require 24 days to come around to its starting point. Of this great globe nothing is known by the geologist except its thinnest skin. The deepest boring has pene- trated it only to the depth of little more than one mile. If all known sedimentary and crystalline formations at their greatest thickness were added together, the sum total would not amount to 20 miles. These 20 miles in depth of rock carry us back through all the known ages of geolog- ical time. The rest of the globe, unknowable and unimag- inable, must represent an infinite lapse of previous time. In describing an area of the earth' s surface like the State of Pennsylvania, the first thing to be done is to get a right idea of its actual size, not so much in relation to the whole surface of the earth as in relation to the whole area of the North American continent, over which its rock formations spread and in which they may be studied far beyond the limits of the state. Pennsylvania is about 300 miles long and 150 miles wide, a mere spot on the surface of the globe. Its geological formations extend into surrounding states with areas as large or larger than its own; arranged in the same order of super- position one upon the other; exhibiting similar characters and structure, and carrying the same mineral wealth. As geological truth depends upon the comparison of all like facts affecting a given case, the geologist of Pennsylvania must make himself familiar with the geology of the whole Atlantic seaboard and the whole Mississippi valley; and he will often find the solution of his own local problems five hundred or a thousand miles beyond the border of his own 24 GEOLOGICAL SURVEY OF PENNSYLVANIA. state. On the other hand the geology of New York, of Ohio, of Maryland, of Virginia, of West Virginia, of Ken- tucky, gets a still stronger reflected light from investigations pursued for fifty years in Pennsylvania, where all the great formations between the fundamental rocks and the coal measures are in a more complete series, and at their greatest known thickness. In this respect our state, small as it is in relative area to the whole Appalachian region, is in fact a standard of comparison, and occupies in geology as in politics the position of the keystone in an arch. The reason for this will be explained hereafter; at present it is only needful to eni'orce the fact, and to stim ulate the imag- ination to its proper comprehension, namely, that our geo- ology is not local but general; that the rock formations of one county of our state are not confined to that county, but extend in immense sheets, with practically the same char- acter, and lying upon one other in the same order, beneath the surface of many of the other counties of the state, and also of extensive regions of neighboring states; forming in fact successive floors beneath nearly the whole United States; sometimes rising to the surface, so that their edges can be examined along lines and belts of greater or less length; and sinking again to depths of several miles, where it is to be presumed that their nature is unchanged; and this presumption is the sole basis, but a practically sound and reliable basis, for the little knowledge which we possess of the earth's interior. The three dimensions of length, breadth and thickness then applies in practical geology to every rock formation. (1) To the length of its outcrop, which (in Pennsylvania) runs in a northeast and southwest direction; (2) to the dis- tance which it extends underground from southeast to northwest before it rises again to the surface in New York or in Ohio; and (3) to the number of feet, or yards, or hundred yards of its thickness as measured from its bottom bed to its top bed, wherever it appears at the surface. These are its three elements of size and quantity; and with these three elements all the measurements and calculations of practical geology are accomplished. If the slope (or GEOLOGICAL DIMENSION. 25 angle with the horizon) at which a formation sinks into the underground and rises again to the surface be carefully observed, it becomes possible, and is usually an easy matter, to estimate with truth its bulk or solid contents, the num- ber of square yards or tons which it contains, and its dis- tance beneath the surface at any given point where it may be desirable to bore a well or sink a shaft to work it. This is the first business of the geologist, and it is more successfully pursued than people imagine, for it proceeds upon the well-established application of geometrical rules for the treatment of the length, breadth and thickness of all solid bodies, rules that are invariable. If rock formations were absolutely regular in their shape, of equal thickness everywhere, this practice of geol- ogy could be conducted without the least chance of mis- take, and business men might depend with absolute re- liance on the assertion of a competent geologist that a cer- tain rock formation would be struck at such and such a depth. But the case of a perfectly regular rock formation is one of the rarest in nature. Not only every bed of limestone, sandstone, shale, clay, coal or iron ore varies in thickness within its own particular limits of variation, but every group of beds, and every formation composed of groups of beds, thickens in one direction and thins in another, or thickens and thins alternately and irregularly throughout its whole extent. So that, were it not for the many times and places at which rock beds rise to the sur- face to be measured again and again, these irregularities would present an insuperable obstacle to the accurate prac- tice of geology. In this respect the folded structure of all middle Pennsylvania gives to our study of its geology an immense advantage, and makes our knowledge of it ex- tremely accurate. But where the whole series of forma- tions lie entirely flat, and only the highest members of the series can be seen at the surface, as throughout western Pennsylvania and the greater part of the Mississippi basin, tjiey completely conceal their underground irregularities of thickness and quality. The only knowledge we can then obtain of such irregularities must come from a comparison of the records of well borings. 26 GEOLOGICAL SURVEY OF PENNSYLVANIA. The exact number of wells bored in western Pennsyl- vania is not known, but it must exceed 50,000. Many of them have gone down only a few hundred feet, many more are 1,000 feet deep, few reach 3,000, and the deepest, the experimental borehole of Mr. Westinghouse, at Pittsburgh, and the wells at Erie, Franklin, and Wheatland are respec- tively 4,685, 4,460, 3,880, and 3,484 feet deep. Had the re- cords of all the wells bored since 1859 been carefully kept and the character and thickness of every rock stratum been ac- curately observed, our knowledge of the underground geo- logy of western Pennsylvania might be considered perfect. As it is, nine-tenths of this knowledge has been lost. But the one-tenth which has been rescued, taken in connection with the innumerable outcrop exposures along river cliffs and in ravines, is quite sufficient to make the geology of that half of our state more accurate and reliable than the geology of any part of the known world ; that is to say, to the depth of about a mile. All the underlying formations which only outcrop in middle Pennsylvania, and the great crystalline floor-rocks which outcrop in southeastern Penn- sylvania, are absolutely unknown in western Pennsylvania. The expression absolutely unknown is true indeed only in its precise sense. Probabilities are of every grade of force, and sometimes rise nearly to the level of cer- tainties. When eye-witnesses cannot be obtained, circum- stantial evidence will in many cases prove sufficient for conviction. If the head of a nail is seen on one side of a board and its point projects from the opposite side, no reasonable person would think it necessary to split the board to see if the nail went through from the head to the point. If the Gorniferous limestone formation, No. Villa, which runs along the foot of the Bald Eagle mountain for a hundred miles, from Muncy, past Williamsport, Lock Haven, Milesburg, Tyrone City, AltoonaandHollidaysburg, to Cumberland, in Maryland, and so on south, as a contin- uous formation, descending vertically, or dipping steeply north west ward, as if to go under the Allegheny mountain if this limestone makes its appearance in a similar outcrop along ihe Mohawk valley, in the State of New York, and GEOLOGICAL DIMENSION. 27 keeps on in a nearly straight line westward to Niagara Falls, reappears on the southern shore of Lake Erie near Cleveland, and runs south through the State of Ohio to the Ohio river above Cincinnati, and so on across Kentucky into Tennessee, no reasonable man can refuse to believe that it underlies, in a practically unbroken sheet, the whole region enclosed between these two lines, and must surely be struck by every oil well if the drilling goes deep enough.* It is for the geologist to calculate what that depth would be at any given point in the region ; and this he could do with math- ematical certainty were the overlying formations perfectly regular in thickness. Since they are not thus regular, some law of irregularity must be discovered, and this can only be done by measuring the interval between the Cor- niferous limestone and some coal bed or limestone at the surface, on the two edges of the region, the one in middle Pennsylvania, the other in central New York and central Ohio. Such measurements have been made and repeated until a pretty accurate average interval has been obtained on each of these lines of outcrop. The difference between them is so great that no better example of the irregularity of our formations could be selected. The Devonian and sub-Carboniferous formations in Ohio measure, all told, only 1,175 feet; in Erie and Crawford counties, 3,000' ; in Clinton county, 9,274' ; in Blair county, 10,909' ; in South Huntingdon, 11,546' ; at Cumberland, in Maryland, 11,510' ; at Catawissa, in Columbia county, 12,212' ; on the Susquehanna river, above Harrisburg, 16,285' ; on the Schuylkill river, between Pottsville and Schuylkiir Haven (they stand vertically) 20,000' (?) ; on the Lehigh river, in Carbon county, 15,970' ; at Broadheadville, 13,550' ; at Stroudsburg, in Monroe county, 13,000', and at Port Jarvis, along the Delaware river, in Pike county, 12.750'. *It has actually been struck by three wells, the Presque Isle well at Erie, at a depth of 1,400 ; the Wheatlaud well in Mercer county, at 3,384, and the Con way well, nine miles below Franklin, at 3,880? But its southward dip carries it down below the bottom of the Westinghaus well at Pittsburgh. (See I 5, Carll's last Report, 1890, pages 72, 185, 188, 230.) 28 GEOLOGICAL SURVEY OF PENNSYLVANIA. It is thus easy to see that formations VII, VIII, IX, X, XI and XII, which occupy the interval, are thicker in Pennsylvania than in Ohio, and as they are all deposits of sand and clay in sea water, and are not only thicker, but of a coarser character at the east than at the west, four con- clusions may confidently be drawn, namely, (1) that the de- posits came from the east and were floated out toward the west ; (2), that the finer material was carried farthest out to sea westward ; (3) that the difference of thickness had little or nothing to do with the depth of water; and (4) that the westward thinning must be gradual, if not regularly graduated. If now we could be sure that the westward thinning was not only gradual, but regularly gradual, its rate would be easily obtainable, and then the thickness of the interval could be calculated with great precision, say for every ten miles on a line drawn from Altoona to Pittsburgh, and from Pittsburgh to Columbus in Ohio. On such a supposition the depth of the limestone under- neath Pittsburgh would be almost exactly 7,600 feet. But here a disturbing element enters into the calcula- tion. The outcropping edges of formations IX, X, XI and XII can be followed up the West Branch Susquehanna for many miles and all the way around into Ohio. They are also brought up to view and can be measured in the mount- ain gaps at Johnstown, at Confluence, at Blairsville, Latrobe and Connellsville in southwestern Pennsylvania. We can see how they all diminish in thickness from the Allegheny mountain westward. We see also that the red formations IX and XI diminish in thickness more rapidly than the others, and become so thin before reaching the Ohio line that they can hardly be recognized. This com- plicates the calculation, so that we are forced to conclude that the Corniferous limestone must lie at a depth beneath Pittsburgh considerably less than the 7600' above stated. The law of irregularity of ocean deposits illustrated by this example on a grand scale holds good for all the sedi- mentary formations of the world and makes itself felt in the case of every individual bed in every formation, pro- GEOLOGICAL DIMENSION. 29 ducing local thickenings and thinnings of every conglome- rate, sandstone, shale or limestone bed; obliging the careful geologist to repeat his measurements everywhere, and restraining him from making too confident predictions of what the boring tools are to find, or the precise depth at which any desired bed will be struck. This will be ex- plained more fully in describing the oil regions. Returning to the subject of the westward thinning of our formations, and reversing the direction, they are seen to increase in thickness from the Allegheny mountain east- ward to their final outcrop along the Blue mountain which borders the Cumberland valley. In this middle belt of the State we have uncommon opportunities for studying irreg-' ularities of rock thickness. The strata rise to the surface and sink again several times in a breadth of 50 miles; and every time they rise for examination going southeast they show themselves coarser and harder and thicker. If we took in our examination only the direction from Altoona to Chambersburg we might suppose these sediments to have been produced by the destruction of the South mountains of Fayette and Adams county; but the formations thin away southward through Virginia into Tennessee, as they do westward into Ohio; but in the other direction, north- eastward, they increase in thickness toward the Catskill mountains. Comparative measurements made at Altoona, at Hunting- don, in Perry county, along the North Branch of the Susque- hanna in Montour county, along the Lehigh river in Carbon county, and along the Delaware in Monroe and Pike counties, must remove from every intelligent mind the popu- lar and mischievous opinion that what is called a general section of a series of rocks can be used for the practical purposes of exploration by anybody who has it in hand, whether he be a geologist or not. 30 GEOLOGICAL SUEVEY OF PENNSYLVANIA. CHAPTER IV. On General Sections. It is necessary to explain clearly what this term "general section " means, and it will then be seen that the common practice of writers of geological reports and text-books in placing a general section of the series of rocks which they 'are about to describe on the first page of their description to enable their readers to keep in mind the order, character and thickness of the rocks, while in one way it facilitates the understanding of the description, leads in another way to the most serious practical errors, whenever that de- scription is taken as a guide to the special study of a re- gion or locality. A vertical section of a formation or series of formations means a representation or drawing of a deep cut in the earth from the surface downward, like the cut made by a knife through a pile of buckwheat cakes at the breakfast table. The character and thickness of each cake is thus revealed and the order in which the cakes lie one upon the other. If the various layers lie smooth and flat the section shows it. If the layers be crumpled the section shows it. If they differ in thickness anywhere the section shows it. And if they have a general slope or inclination in one direction, the lower layers rise toward one end of the sec- tion, and the upper layers sink at the other end. It is called a vertical section because it is made from the surface directly towards the center of the earth. A columnar section is merely a small portion of a verti- cal section, showing the same facts of order, character and thickness, by a narrow column placed at one side of the printed page, drawn without any regard to the slope or wrinkles of the rocks, and representing them as if they were lying Jlat. The measurements are made at right ON GENERAL SECTIONS. 31 angles to the beds, and are intended to express the exact thicknesss of the several beds. It is evident that a hundred such columnar sections may be made along the line of any one vertical section; but that where the beds of a general section are very regular one columnar section will be enough to show their character, order and thickness along the whole line. If, however, the rocks of a vertical section be variable in character and thickness then a dozen or more columnar sections will be required to exhibit these varia- tions. Yet many geologists are satisfied with one, and the readers of their reports and consulters of their text-books are left to gather the nature of such irregularities from descriptions of them in the text. Now, what is true of one vertical section is true of all. The line along which any vertical section is made is selected by the geologist where it can be best studied in his district; where a river has exposed the rocks for a mile or miles; where railroad cuttings, lines of quarries, ore banks, mine shafts or oil borings furnish him data for his measurements. Such sections are of the greatest value, and are in fact the foundation of all accurate geology. But these natural lines of section do not often run in the most convenient direction; run sometimes diagonally across the strike and dip of the formations. The} 7 must be swung around to cross them at right angles, if the true structure of the district is to be exhibited. Consequently the geologist must make as many such sections as possible in all parts of the district. Some will be short and some long according to circum- tances. To represent the whole geology of the district he must put them together. He constructs thus what he calls a general vertical section, and gives that as expressing a summary view of the geology of the whole district. This summary view will certainly give some general idea of it. But a general idea of the geology of a district, however good it may be, will be mischievously bad in one respect, in that it will lead people who are not judicious field geol- ogists to believe that that general section represents accu- rately the geology of each and every portion of the district. They will act on that assumption. They will apply that 32 GEOLOGICAL SURVEY OF PENNSYLVANIA. general section to the discovery of minerals in parts of the district where local facts do not correspond at all to the general section. In fact nothing has tended more to bring into popular disfavor the work of field geologists than the serious embarrassments to which laymen have been sub- jected in trying to apply the general section of a district to some special locality in which they are personally in- terested. What has just been said has greater force in respect to general columnar sections, which are intended to furnish a quick and easy key to the order, character and thicknesses of the rock-beds of a district. Even in the hands of an ex- perienced geologist such general columnar sections are dangerous tools to work with. They impose upon the im- agination, and through the imagination upon the reasoning faculty. They seem to reveal clearly what in fact they conceal ; they mystify it, distort it, and change the truth into positive error. They give the impression of regularity in geology; whereas irregularity is the only law of geology which can be called absolutely universal. Even the experienced geologist is strongly tempted to recognize a general columnar section as true at every lo- cality. Only with an effort can he keep in mind that it is a fiction, a construction, not a reality; a generalization; a sort of dressed up official representative of thousands of facts for which it speaks, but the various natures of which it cannot correctly express. If one of the beds of any such columnar section happens to be 20 feet thick at one end of his district and 100 feet thick at the other end ; or, if it be found to measure 20 feet at one point and 100 feet at an- other even if these two figures be known to represent the thinnest and thickest sizes of that bed within a given dis- trict the columnar section will either say that the bed varies from 20 to 100 feet, or it will say that its average thickness is 60 feet. These are the two plans ordinarily adopted in constructing a columnar section ; but they do not relieve it of its mischievous character. For in the first place there may be places underground to which no one has had access where the bed may not exist at all. or where it ON GENERAL SECTIONS. 33 thickens to 200 feet. Should a shaft be sunk or a borehole drilled at such a point the general section is at once dis- credited, and even whatever value it has will be denied. But even if the geologist has been able to discover the greatest thickness which the bed has anywhere, and its thickness at that place amounts to 100 feet, it may be an exceptional and purely local fact. Perhaps the bed throughout the district varies little from 20 feet. To say then in the columnar section that the bed varies from 20 feet to 100 feet gives a wholly false and unpractical de- scription of it. If the second plan be adopted and the average of 60 feet be marked on the edge of the column, it becomes a false guide everywhere in the district, for there may not be a single locality where this average of 60 feet is realized. What, then, is to be done? Shall there be no attempt made to exhibit in the form of a column the order, char- acter and /thickness of the rock formations of a district \ Shall the reader be left to manufacture his own ideas of it from a confused mass of detailed descriptions in the text of the report ? If he be thus left to his own devices he will undoubtedly construct some general columnar section for himself, and it will probably be a worse one than that which the wise geologist has discarded. There is a plain road out of the difficulty. A typical columnar section should be substituted for the so-called general columnar section. Among the many local columnar sections which the geol- ogist constructs (along his numerous lines of vertical sec- tion), each one giving the precise facts at the place where they present themselves to the eye for examination and to the hand for measurement, there will always be one or an- other more precise and more complete than the rest, show- ing more distinctly the order, character and thickness of the beds of the district, arid as accurate in its statement of the facts as any of the rest. 'Such a columnar section, vouched for in all of its details, and marked with the name of the locality where it was studied by the geologist and can be studied by any number of observers who choose to verify 3 34 GEOLOGICAL SURVEY OF PENNSYLVANIA. the accurateness of his observations such a columnar sec- tion, rightly called typical, is at the same time good authority and of practical value. It leaves nothing to the vague imagination. It is a reality to be depended upon. It will serve as a useful guide. It stands only for what it is worth. It makes no pretensions to general truth. It says nothing respecting the stratification or structure at other localities in the district, being only one of many, all differ- ent from each other; and it can be referred to in explanation of similar appearances not so well exposed to examination. Above all, it will enforce upon -the mind of everyone who uses it for comparison with other local columnar sections that law of irregularity or variability on which the genius of geology must forever insist, as the first to be recognized and profoundest to be felt of all the laws of our science a law that cannot be too often or too earnestly inculcated a law both of the highest theoretical and the most real prac- tical character, governing both our calculations respecting the outspread of continental formations and the minutest details of our mining operations. THE APPALACHIAN SEA. 35 CHAPTER V. The Appalachian Sea. The arrangement of land and sea upon the surface of the globe, with which geography makes us familiar, appears to the human mind to be fixed and unchangeable. The relig- ious traditions of mankind have taken this for granted and explained the creation accordingly. But this is not a fact. By the fossil forms of many extinct animals and vegetable creations embedded in the rocks of all ages, it appears that all continents have been formed beneath the sea, and have emerged from it into the air. By the way the continental fossiliferous formations lie one upon another it appears with equal plainness that the lands have emerged and been submerged alternately many times in the course of the history of the world. But when the bottom of the sea is lifted into the air the water which covers it flows away from it, lifting the general sea level of the world in propor- tion to the amount of land which has become uncovered. The lifting of the general surface of the sea resubmerges lands which were previously out of water. The crust of the earth has been subjected in all geological ages to such movements, and such movements are going on still; move- ments both upward and downward. They are not upward movements of the land and downward movements of the sea bottom, but alternate upward and downward move ments of both the dry lands 'and of the ocean bottoms. The upward movement of a continent draining its edge, lifts the sea level and submerges the edges and low-lying plains of other continents. The downward movement of one continent drawing the ocean over its low-lying lands, lowers the sea level and causes an apparent elevation of other continents; but the elevation is only apparent; the ocean coast is extended outward by the fall of the sea level;. 36 GEOLOGICAL SURVEY OF PENNSYLVANIA. submarine banks like those of Newfoundland and off the Alaskan coast, are left like great islands exposed to the air and ready to receive the seeds of a new vegetation, and the immigration of new races of animals to feed upon them. For the same reason, whenever the bottom of the sea has been lifted there has been a rise of the sea level and an overflow of the lowlands of all continents. On the other hand every downward movement of the earth crust beneath the ocean has lowered the sea level and drained the coasts of the continents. It is a geological speculation unsup- ported by sufficient evidence that the oceans have always been oceans, and that the ocean bottoms have always been descending. There is sufficient evidence to the contrary; and such evidence is afforded in the clearest manner by the geology of Pennsylvania. For many ages the crystalline floor kept going downward, draining the sea water from the rest of the surface of the world and exposing to the air more and more of the - coasts of then existing continents. At first the downward movement, if not sudden, was relatively swift, and a deep ocean was early established along that part of 'the earth's surface now occupied by our Atlantic states ; but this is not certain. This ocean first received the Cambrian sediments, and afterwards the Silurian, Devonian and Carboniferous. Its original depth may be imagined from the fact that on top of 15,000 feet of Cambrian beds lie in middle Pennsylvania 6,000 feet of lower Silurian limestone (regarded by most geologists as a deep sea deposit)* and 6,000 feet of fine sand and mud-slate, on top of which lie 30,000 feet of Upper Silurian, Devonian and Carboniferous strata. Now if this Appalachian ocean had been established at once, by a sudden drop of the crust of the earth to a depth sufficient to receive all these Cambrian, Silurian, Devonian and Carboniferous strata, that is to a depth of 7 or 8 miles, the general sea level of the world would have been lowered many hundreds of feet. But we are forbidden to suppose a sudden movement on so grand a scale. But whether *Bnt of this assumption I ain very doubtful, as will appear in the Chapter on Formation No. II. THE APPALACHIAN SEA. 37 quick or slow, such a downward movement of one part of the earth's crust should in all probability have entailed as a consequence a corresponding elevation of other parts of the surface of the globe, parts of the then existing ocean bottoms, as well as parts which were already dry land. There is nothing but a theory to oppose the supposition that what is the Atlantic ocean now (or a portion of it) was in all Palaeozoic time a continent exposed to the erosion of the rainfall, supplied with rivers, and bestowing the waste of its rocks in the Appalachian sea. Its smaller rivers, de- scending rapidly from its highlands, would supply conglo- merates; its larger rivers meandering from its back countries, with longer and more gentle currents, would supply the slates and clastic limerocks. It is, of course, impossible to decide between the oppos- ing probabilities of a faster or a slower rate of the down- ward movement which established the Appalachian sea basin. All we can say is that the great limestone deposits are very early ; and supposing them deep sea deposits, we must conclude that the establishment of a deep Appala- chian sea basin was of early accomplishment; that the downward movement was at first comparatively rapid; and that it continued (perhaps more and more slowly) to the end of the coal age. The two thoughts which are here fundamental to the knowledge of our Pennsylvanian geology are these: (1) that what was the continental area of crystalline rocks became by the downward movements of the earth's crust an Appalachian sea basin of unknown depth, and was in the course of the Cambrian, Silurian, Devonian and Car- boniferous ages so completely filled up as to become at last a great marsh or archipelago of marshes, bearing the vege- tation of the coal; and (2) that this whole area was then lifted high into the air; that a corresponding contempo- raneous down ward movement established the Atlantic ocean or parts of it, as the thrust which elevated the Appala- chians came from that direction; and that submergence of other lands of the world must have been occasioned by the general rise of the sea level. 38 GEOLOGICAL SURVEY OF PENNSYLVANIA. All this took place in the Palaeozoic times, that is in the first great geological age of the world of animal and vege- table life. The coal measures, which were the last deposits in the Appalachian sea, taken as a whole, is inconceivably ancient and remote from the present day. A second division of geological history then succeeded : the Mesozoic or Middle age of animal and vegetable life. Then came the Kainozoic (Cenozoic) or New world of animal and vegetable life, ending with the appearance of man. Each of these three ages of the world's geological history has had its own series of continental elevations and depres- sions; its invasions of the continent by the ocean and the reappearance of land surfaces on the retreat of the water into the sea basins; its own peculiar sequence of sediments brought by rivers {and deposited in the sea, all of them preserving in their mud and sand layers the waste of suc- cessive forests, and the dead remains of genera and species of animals. All the greater mountain ranges of the world are com- posed of such sedimentary rocks, which have been lifted out of the ocean into the air in successive ages since the de- posit of our coal beds, and mostly in Mesozoic and Kainozoic times. Movements on so grand a scale must have altered mate- i;ially the relation of lands to seas, modifying more or less the geography of the whole earth's surface. Therefore, I find it hard to believe that oceans have always been oceans, and continents, continents, even if other facts than those alluded to above were not known to prove the opposite. THE NAMES OF THE FORMATIONS. 39 CHAPTER VI. The Names of the Formations. Everything has to have a name. It makes very little dif- ference what name is bestowed upon it, provided that name be generally accepted and is different from the name of anything else, so that the name shall always stand for that one thing and for nothing else. In science great pains have been taken to invent names which signify the character, or some characteristic feature, of the nature of the thing named. But in a science like geology, which includes sev- eral sciences, structural geology, chemical geology, fossil geology (paleontology) and economical geology (mining engineering, etc.) different geologists will each one look upon a rock formation with that particular interest which it has for his special studies or work, and will wish to name it accordingly. Geologists in different regions will give dif- ferent names to the same formation, each affixing to it the title of some locality where he finds it best exposed to view, most easily studied, of greatest size, or most valuable for the community. Geologists of different countries, speak ing different languages, have given many different names to the same stratum or series of strata. All this is inevitable. No international congress of geologists can either hinder or help it. The confusion arises out of the multiplicities and irregularities of nature itself. Those who wish to profit by geological investigations and discoveries must submit to the burden of geological nomenclature and learn all the names, even if they choose to use qnly some. It is impossible, to macadamize or asphalt the highways and byways of knowledge. All our state geological surveys have invented names for some of their formations, and for others have borrowed names already given to them in neighboring states. Geo- 40 GEOLOGICAL SURVEY OF PENNSYLVANIA. logical formations care nothing for geographical lines established by king's charter or acts of congress. They pass underground from one state into another. The geology of southern New York is exactly the same as that of north- ern Pennsylvania. The geology of northern New Jersey passes on across middle Pennsylvania into Maryland and Virginia. Eastern Ohio and western Pennsylvania share with West Virginia the same beds of coal, limestone and iron ore, the same oil and gas sands. The formations ex- posed on the Juniata are exposed on the Potomac, and their outcrops extend to Alabama. The Brown sandstone and red shale belt of Bucks, Montgomery, Chester, Lancaster, York and Adams counties is continued to the Dan and Deep rivers of North Carolina in one direction, and up the Connecticut valley into Vermont in the other direction. The Philadelphia gneisses and mica schists pass on without break through Delaware, Maryland and east Virginia as far as Georgia. The South mountains of eastern Pennsyl- vania are the same as the Highlands of New Jersey and New York ; the South mountains of southern Pennsylvania are the same as the Blue Ridge of Virginia. These facts are positively known to all geologists now ; but they were only suspected to be possibly or probably true by geologists sixty years ago, when the principal state surveys were set on foot. Hastily to give the same name to a series of rocks in two different states which might turn out on examination to be two distinct series would have made a great embarrassment ; and an example of this is af- forded by the employment in our Pennsylvania reports of the name "Potsdam sandstone" borrowed from Dr. Emmons' survey of the Champlain district in northern New York, to designate the "White Spot" rock overlooking Reading, Chicques rock at Columbia, the quartzite beds at Mt. Holly Springs and Mont Alto in Cumberland and Franklin counties, and the North Valley hill rock at Downingtown and Norristown; for it is now doubtful if all or any of these have right to that name. A still more flagrant instance is afforded by the old and standing controversy over the name Taconic System, a THE NAMES OF THE FORMATIONS. 41 name which may justly be called the Nightmare of Ameri- can Geology, from which, however, we are happily almost awakened. For fear of thus hampering their surveys with names that might become popular and yet' be absolutely false and worse than useless the state geologists of Pennsylvania and Virginia, the distinguished brothers Henry D. and William B. Rogers, refused to accept the names of the formations adopted for New York by the four principal geologists of that state, Mather, Emmons, Vanuxem and James Hall, and adopted a plan of numbering the great formations ac- cording to their order of superposition from below up- wards; a series of numbers which of course would never change, and for which distinctive names might be after- wards substituted. These numbers, from I to XIII (after wards increased to XVII) only applied to the rock forma- tions of three-fourths of the state, Silurian, Devonian and Carboniferous. The earlier rocks of the Crystalline region, and the later rocks of the New Red or Brownstone region, all of them in southeastern Pennsylvania, were left unnum- bered. This numbering was accomplished in 1836 and 1837. Between that time and 1858, when the " Geology of Penn- sylvania" was published, the brothers Rogers, who were poets as well as geologists, devised a series of names which they proposed to substitute for the series of numbers, and for all other names applied by foreign and domestic geolo- gists to the Palaeozoic formations, considered as successive deposits made in one long, great geological day of time ; a day divisible into four portions, before and after sunrise, before and after sunset; the day in which the Lower and Upper Silurian, Devonian, Carboniferous systems of the English geologists were deposited. But the Coal Measures belonged to the night and received no name ; or, rather, were allowed to retain that popular appellation, being sim- ply Coal Measures. No. 1, at the base, also, was simply named the Primal sandstone; Nos. 2, 3, Auroral and Matinal ; Nos. 4, 5, 6, Levant (sunrise), Scaletut and Premeridian; No. 7, M&ri- 42 GEOLOGICAL SURVEY OF PENNSYLVANIA. dian or noon; Nos. 8, 9, Cadent an&Ponenl (sunset) ; Nos. 10, 11, 12 Vespertine, Umbral and Serai. All these names, except three, are long since forgotten. No geologist has accepted them as useful. But, curiously enough, the people of western Pennsylvania, led by the coal prospectors of the Allegheny mountains, adopted the three exceptions, and still speak of the Vespertine sand- stone No. X, the Umbral red shale No. XI, and the Serai conglomerate No. XII. Some geologists have, therefore, em- ployed them in local reports; and they will continue to be used occasionally instead of the newer 'names: Pocono sandstone, Mauch Chunk red shale, and Pottsmlle conglo- merate. When the geological survey of the state was reorganized in 1874, and county reports began to be published, it was needful to adopt names for the rock deposits. The old numbers were not precise enough; the fanciful names of 1858 had been universally ignored; the New York names had come into universal use. These last therefore were applied to the formations in Pennsylvania, and others of the same geographical character were added at the end of the list where Pennsylvania had higher strata than any in New York. No. 1 was called Potsdam sandstone. No. 2 included the Calciferous sandstone, Chazy and Trenton limestone. No. 3 included the Utica and Hudson river slates. No. 4 included the Oneida conglomerate and Medina sandstone. No. 5 included the Clinton, Niagara and Salina shales. No. 6 was the Lower Helderberg limestone. No. 7 was the Oriskany sandstone and Caudagalli grit. No. 8 extended from the Corniferous and Marcellus up through the Hamilton, Genessee, Portage and Chemung. No. 9 was the Catskill or Old Red sandstone. No. 10, not being named in New York, although it forms the peaks of the Catskill plateau, received the name Po- cono gray sandstone. No. 11, Mauch Chunk red shale. THE NAMES OF THE FOKMATIONS. 43 No. 12, Potts ville conglomerate. No. 13, Allegheny river coal measures. No. 14, Pittsburgh (Lower Barren) measures. No. 15, Monongahela river coal measures. No. 16, Washington county group. No. 17, Greene county (Upper Barren) measures, the highest Palaeozoic strata to be found in Pennsylvania, and possibly belonging to the last or Permian age of that era in geological time. Names given by the assistant geologists of the state survey to sub-divisions or important local beds in these formations will appear in the chapters devoted to their description. The terms Azoic, Eozoic, Palaeozoic, Mesozoic, Kainozoic, have been already alluded to as designating the successive grand geological ages of vegetable and animal life on the planet. It is not intended in this book to use the first two with any dogmatic sentiment, in view of the current con- troversies on what I consider a very unimportant subject, namely, the precise unification of geological nomenclature. One name is quite as good as another provided it be known to what it applies, and provided that it implies no false description of character. Azoic or No-Life rocks was a good term, first applied by Foster and Whitney to the crystalline and semi-crystal- line rocks of the Lake Superior region, to express the fact that no relic of either vegetable or animal life had yet been discovered in them. It was not intended to assert that these rocks never had had fossil seaweeds or shells in them, but merely that nonesuch had ever yet been discov- ered in them. It is not only probable but proved that fossil bearing sediments crystallize, and in doing so obliterate the fossil forms which before crystallization must have been visible enough. The term Azoic simply tells the fact that no fossils have been found in them. The objection made to it, that rocks of later ages may suffer this change and lose their fossils is not practically a good one, and for this reason, viz : that ninety-nine-hundredths of the Azoic rocks belong to the oldest geological age we know anything 44 GEOLOGICAL SURVEY OF PENNSYLVANIA. about; therefore Azoic is a very convenient name for the oldest formations, whether they appear at the surface in our southeastern counties, or lie at great depths beneath the rest of the state. Archcean is however a much better terra, invented by Professor Jas. D. Dana, and adopted very generally, almost universally, by the geological craft, because it simply means the oldest rocks known, and passes by the question whether they ever contained fossils or not. Fundamental gneiss was the term preferred at first by English geologists because it expressed the general character of the crystalline consolidated floor on which all other formations have been built up. But Dana's name Archcsan has been gradually replacing the English name even in England. Laurentian, Sir W. E. Logan's name for the Azoic, Archaean, Fundamental gneiss floor of the known geological under- world, has been very generally adopted by American geologists, and has been used in many of the reports of the survey of Pennsylvania, especially in Prof. Prime's reports on Northampton and Berks counties, Mr. C. E. Hall's reports on southern Bucks, Montgomery and Delaware counties, and Dr. Persifor Frazer's reports on Chester, Lan- caster, York and Adams counties. The mountains of the Lower St. Lawrence, Labrador, Canada, and the Adiron- dack region of northern New York, show the floor rocks of the world on the grandest scale. Pre-Cambrian is another term for the same azoic, archsean, fundamental, Laurentian rocks, adopted by conservative geologists who recognize how little we know of them, and how uncertain are the identifications of them in the isolated and far-separated regions where they appear at the present surface of the globe. For this term merely states that they were in existence when the first Cambrian or Eozoic sedi- ments were deposited upon them in the earliest seas. In this sense Pre-Cambrian means all rocks older than or be- neath the lowest Cambrian beds which contain fossils. But by other geologists it is used in another sense, namely, to signify formations which show themselves rising to the sur- THE NAMES OF THE FORMATIONS. 45 face from beneath the Cambrian, and which yet may not be as old as the Laurentian, but intermediate between the Laurentian and the Cambrian. If they contain fossils they should be included in the Cambrian. If they do not, they are Azoic rocks, but yet may not be Laurentian. The Huronian system, lirst studied by Murray on the north shore of Lake Huron, and so called by Logan and Hunt, of the Canada survey, was supposed to hold such in- termediate place. But Irving and A. Winchell have appar- ently proved that only the lower portion of it is Pre-Cam- brian, and the upper portion may be Cambrian, although no fossils have yet been found in it by which alone its Cam- brian age can be established. In Report E of the Pennsyl- vania survey Dr. T. S terry Hunt has used this name Huronian in describing rocks in Adams county; and Dr. Frazer's sections of the South mountains of Cumberland and Fayette counties give them a Huronian aspect. On the other hand, Walcott's Cambrian quartzites seem to be well represented in the Mt. Holly (Papertown) gap, and else- where between that and the Maryland line. But no fossils (except ScolitTius) have as yet been found in the South mountains ; probably, or perhaps, for want of observers suf- ficiently disciplined by the study of Cambrian areas else- where to detect them. The Green Mountain rocks of Ver- mont are called by T. S. Hunt Huronian. Of the White Mountain hornblendic gneisses and mica schists he makes his Montalban system, and identifies it with the Philadel- phia belt ; Montalban being after and above Huronian. See Report E, page 241. Eozoic rocks are those which show by fossils the dawn of life on the planet. It is a convenient phrase which means nothing definite and it is synonymous with the term Cambrian, although the Eozoon canadense is called a Laurentian fossil. But C. E. Hall asserts that he can prove that the strata which contains this oldest of all supposed animal remains in the rocks of the'earth really belong to post-Laurentian times. At all events, with the possible ex- ception of the Canadian Eozoon canadense, the earliest ani- mal remains are the trilobites and shells of the Lower Cam- brian (once called Taconic] rocks. 46 GEOLOGICAL SURVEY OF PENNSYLVANIA. Cambrian is Sedgwick's English name for a great series of deposits in Wales, Scandinavia, Bohemia, Spain and elsewhere, which have been admirably studied by Walcott and others in eastern New York, eastern Massachusetts, New Brunswick, Newfoundland, Georgia and the Rocky mountains. Its three divisions of Lower, Middle and Upper are characterized by what are called the Olenus, Paradoxides, and Olenellus faunas, or groups of trilobites mixed in with sea shells of many kinds, sponges, worms, sea weeds, etc. With the old controversy between Sedg- wick and Murchison respecting the limits of the Cambrian and Silurian systems, practically settled by the publica- tions of the geological survey of Great Britain, we have nothing to do. And as little now with the equally pro- tracted and ill-natured controversies over Dr. Emmons' Taconic system, now happily ended by discoveries which turn that unfortunate system upside down and distribute its members among the Silurian and Cambrian formations. The same fate has befallen Logan's Quebec group. Neither of these too famous names appear in the reports of the Pennsylvania survey, as far as I can now recollect, except that certain fossils in P. 4 are quoted as occurring in the latter. Palceozoic ropks are those which contain the remains of the ancient living beings of the world, vegetable and ani- mal, from the Cambrian sea weeds, sponges, worms and trilobites up to the land plants, shells and reptiles of the Coal age. If anyone pleases he may merge the Eozoic in the Palceozoic, and begin the system at the bottom of the Cambrian sediments, calling the whole Palceozoic. Cam- brian is a more definite term than Eozoic, and quite as con- venient. The fewer names the better. Until their discov- ery by Walcott three years ago in the Trenton limestone of the Colorado, fishes were supposed to have come into ex- istence in the Upper Silurian times. New discoveries are constantly carrying back the first appearance of one or an- other family of living things to remoter and remoter times. No one has a right to say how early in geological history vegetables and animals appeared. "The dawn" of life re- THE NAMES OF THE FORMATIONS. 47 cedes, farther and farther into the past. The word Eozoic is becoming useless ; the term Palaeozoic will always be sufficient to embrace it. Silurian rocks, originally studied by Murchison in Wales, whence their name, and since then in most of the countries of the world, were early recognized in New York, and there classified (in ascending series) as Potsdam, Cal- ciferous, Chazy, Trenton, Utica, Hudson river, Oneida, Medina, Clinton, Niagara, Salina (at first Onondaga] and Lower Helderberg, corresponding to the Pennsylvania num- bers I to VI. Devonian rocks, first studied by De la Beche and Mur- chison in southwest England, and afterwards in Scotland and other parts of the world, received in New York the sub-division names (upwards) Oriskany, Upper Helder- berg, Marcellus, Hamilton* Genesee, Portage, Chemung and Catskill, corresponding to the Pennsylvania Nos. VIII and IX. The Carboniferous formations in Pennsylvania are (in ascending order) Pocono ( Waverlyin Ohio), Mauchchunk, Pottsville, Allegheny, Pittsburgh, Mono7igahela, Wash- ton county and Greene county groups, the last two being awkward names for the highest palseozoic rocks in the state. An unknown additional quantity of beds having been re- moved by erosion, the original topmost or last deposits of the Carboniferous series are unknown. This is the same as saying that the exact date at which the Appalachian sea was dried by the elevation of the Palaeozoic continent into the air is not indicated by any now remaining layer or layers of rock in the region of southwest Pennsylvania, or elsewhere in the state. If the upward movement took place within the limits of the Permian age of Europe, then the highest strata of Greene county may be called rem- nants of the Permian formation. But geologists on both sides of the Atlantic are disposed to classify the Permian strata as the last of Paleozoic age, and to begin the great Mesozoic age with the Trias. The Mesozoic or middle life time of the world's geological history, as we know it on the surface, began with that vast 48 GEOLOGICAL SURVEY OF PENNSYLVANIA. catastrophe which produced the United States as a contin- ental area. He that is best acquainted with the phenomenon will be the best convinced that it was a sudden or rapid movement, a genuine cataclysm. The overthrust faults are of themselves alone sufficient to prove it. A belt of par- allel mountains, as high as any that now exist in South America or Asia, rose into the air along a line extending from the St. Lawrence to the Q-nlf of Mexico, passing through Pennsylvania. The whole Appalachian sea was drained off and became dry land, a continental area of coal measures, much of which has since then been carried away, but much still remains, constituting the extensive coal fields of the present time. The whole rain water drainage was reversed. The Palaeozoic river system which came from the east disappeared, and a new Mesozoic river system began to dissolve the raw continent and carry its undried strata piecemeal eastward into the newly-created basin of the present Atlantic ocean. The Mesozoic age has three divisions, during which were successively deposited the Triassic, Jurassic and Creta- ceous rocks. These again are subdivided in Europe into Bunttr, Middle Trias, Keuper, RhcBtic and Lias; Oolite, &c.; Wealden, Oreensand and Chalk. With most of these names Pennsylvanian geology has nothing to do. Some are local English or German names. And many more names have been invented for use in other countries of Europe, Asia and Africa, where peculiar fossil plants and animals of Mesozoic times have been collected and described; ferns of a new style; trees quite different from those that made the coal forests; crocodilian land reptiles; winged lizards, the prototypes of birds; reptilian sea serpents; superb whorled shellfish (Ammonites)^ small land mammals like kangaroo- rats and ant-eaters; fish with pointed teeth of twisted fibre; the earliest oysters, &c. The Mesozoic age was probably as long as the Palaeozoic, judging by the thickness and variety of its sediments, and the succession of its living creatures. In Bucks and Mont- gomery counties Mr. B. S. Lyman's survey makes out more than 22.000 feet of regularly super-imposed strata, all de- THE NAMES OF THE FORMATIONS. 49 posited in its earlier and middle divisions. To this must be added the Cretaceous or greensand marl deposits of southern New Jersey, which only appear in Pennsylvania at the bend of the Delaware below Trenton. New Red was the name (borrowed from the English) at first given to the Mesozoic belt crossing the Delaware, Schuylkill and Susquehanna rivers, and the Maryland state line. Trias is the name usually given to it in the survey re- ports; and by this name the system, as studied by the Hitchcocks in Massachusetts, by Cook in New Jersey, and by Fontaine in Virginia, is now commonly known. RlKKtic is the term adopted by Fontaine (in his U. S. Geological Survey monograph report on the. fossil Mesozoic plants of Virginia) by the use of which he wishes to make more precise the sub-division of Mesozoic time in which that vegetation flourished. Newark formation is the name used by the New Jersey Geological Survey, and adopted by the assistants of the U. S. Geological Survey, for the Trias sandstone formation of Pennsylvania. The Lias and Oolite of Europe are not recognized in the Atlantic seaboard region of North America. The Cretaceous, on the contrary, is well represented, but no chalk beds are known this side of the Mississippi river. It contains the lower two of the three greensand marl beds of New Jersey and Delaware, the third or uppermost being placed in the Tertiary. Its lowest member (the English Wealden] is called the Potomac formation, and its upper or greensand member the Severn formation, by the U. S. geol- ogists working in Maryland and Virginia. The KAINOZOIO (Cenozoic) TERTIARY, Third, New Life age of geological history, produced an equally vast and varied series of deposits, named by Lyell Ei.cene, Miocene and Pleiocene (to which was afterwards added Pleistocene] to express the fact that the species of plants and animals now living, all of them new, made their debut upon the scene in tliedawn of this new third great day (Eo-cene tertiary}; be- came more numerous in Mio-cene tertiary times ; most 4 50 GEOLOGICAL SURVEY OF PENNSYLVANIA. numerous in Pleio-cene; and most of all numerous in the Pleisto-cene. These names, except the last, are still in common use, but only for purposes of vague and general description, or in references where knowledge is not locally precise enough. They do not much concern Pennsylvania, a region out of water since Mesozoic times, and therefore destitute of those Tertiary sediments which (with the Creta- ceous) make the tide water plain of southern New Jersey, Delaware, Maryland and other Atlantic and Gulf states. Pamurikey (Eocene), Chesapeake (Miocene), Appomatox (Pliocene ?), and Columbia (early Pleistocene), are names given to Tertiary sub-divisions in Maryland and Virginia by the U. S. Geologists. The PamunJcey represents the uppermost (or third greensand marl) beds of New Jersey. The Chesapeake diatom beds at Fort Monroe are 1,000 feet thick. The Appomattox gravel loam formation is the same as the Bryn Mawr (400' level) high gravel of the Delaware county Report C 4. The Columbian terraces pass up the river valleys of Pennsylvania and are connected with our glacial deposits, which are usually designated, not Tertiary, but Quarternary. In the Tertiary age appeared shrubs and trees that flower and fruit, and animals of sea and land that suckle their young, herbivorous and carnivorous, man among the number. When first mankind appeared is not known; nor when the dog, the ox, the sheep, the horse, the elephant. It has just become known that Leidy's fossil horse of Caro- lina was not a modern horse. Mammoths and Mastodons were not the modern elephant. No fossil ape agrees en- tirely with man. Yet discoveries year by year have been pushing back the proven existence of man into Tertiary times. There is therefore less and less propriety in sep- arating the age of man from the Tertiary (or Kainozoic)age and calling it, as is so often done, the QUAKTERNARY or Fourth age of the world. Yet this will still be used as a con- venient term for expressing the state of things which now exists, and be especially applied to alluvions, or river sands and gravels and clays such as Philadelphia is built upon. THE NAMES OF THE FORMATIONS. 51 The Glacial Age, or Age of Ice, is a term which fre- quently occurs in this and other geological literature of a recent date. Its use began when, half a century ago, the great Swiss explorer of the Alps, Louis Agassiz of Neuf- ohatel, announced his theory that Europe had been covered with a sheet of ice just previous to the creation of mankind. When he settled as a teacher in Harvard College, Cam- bridge, Mass., he showed that all New England had been under ice. Since 1847 the phenomena of the glacial epoch have been studied by Upham, Carll, Wright, Lewis, Cham- berlin, Dawson, Whitney and a host of other glacialists, over all North America ; and the southern edge of the ice sheet, the terminal moraine of the continental glacier, has been traced for over 2,000 miles from Cape Cod to Mani- toba. Its course through Pennsylvania is mapped and described with many illustrations in H. C. Lewis' Report of Progress Z. The age seems to have been double, the first ice sheet receding and the second ice sheet advancing, with an interval of vegetation between the two. In Cali- fornia man seems to have been living before the first advance of the ice. In other parts of America man and the mastodon lived together as in Europe and Asia man and the mammoth lived together in glacial times. The cause of the prevalence of ice in the glacial age is still a matter of contention; but the facts have been verified beyond controversy and are accepted by all. Many of the details are still to be worked out; but the general theory is well established. Now granting that such physical operations as the evaporation of the sea water and the condensation of snow upon highlands, to form ice in favorable situations, have been regular from the beginning of geological time, it is reasonable to search for evidences of previous and far more ancient glacial epochs ; and such evidences, in the shape of moraine blocks and scratched rock surfaces, have been found in England, in India and in South Africa. Prof. Kerr thought he found such in his survey of North Carolina. All these evidences are localized in the last Permian or first Triassic rocks. None have been found in Pennsylvania; 52 GEOLOGICAL SURVEY OF PENNSYLVANIA. and foe good reason. There must have been a glacial age im- mediately following the rise of the great anticlinal mountains of our state out ol the Appalachian sea into the upper regions of the atmosphere to a height of more than five miles above present sea level, and to a height of perhaps eight miles above the bottom of the alternate synclinal valleys. Even if the climate of the 40th parallel of north latitude in the coal age was tropical, the tops of the uplifted anticlinal ridges must have been immediately covered with perpetual snow, like Killimanjaro under the equator in eastern Africa, the volcanoes of Peru, and Mount Whit- ney overlooking the valley of death in Arizona, where the thermometer stands at 110 F. in the shade. The heads of the synclinal valleys doubtless made good circuses for the manufacture of neve ; and of course glaciers flowed down the synclinal valleys, and produced mountain-meal and moraines. The meal was not white like that made now from Jurassic, Cretaceous and Tertiary slopes of the Alps, but dark grey and red from the Carboniferous and Devon- ian ; and therefore the deposits of Triassic age in Pennsyl- vania, brought down by the Susquehanna and Delaware from that ancient highland, are mostly red or reddish. But the long continuance of erosion has reduced the highland to its present level of only 1,500 to 2,500 feet above tide level, and swept away every trace of that local glacial state of things. Alluvial deposits are those river gravels, sands and clays which have been deposited in the now existing valleys, mostly since the retreat of the ice, and up to the present date. HIGHLAND GNEISS. 53 CHAPTER VII. The Earliest Archcean, Azoic, Highland, Laurentian, Fundamental gneiss or crystalline schists. In the beginning of time as known by the science of geology, the heavens were as they are to-day; the planets encircling the sun, comets coming' and going, the moon a trifle nearer to the earth, the sun a little farther off but shining with somewhat more fervor and brilliancy. The earth was already in extreme old age, having long before then shrunk almost to its present size and globular shape, by slow condensation, from a gaseous to a liquid state, and got itself encrusted with a rind of solid rock, which no longer shone with a dull red light of its own, but reflected into space the white radiance of the sun. The surface of the earth was no longer hot enough to keep all the water of the planet in a state of vapor in the surrounding atmosphere; descending in local deluges of sour rain to boil upon the rocks and dissolve apart their mineral elements, sweep them into hollows, and there leave them, while it sprang aloft as steam to rejoin the universal canopy of cloud. All this had taken place before the flrst age of which we have any geological monuments, and is only known to God and Dr. Sterry Hunt, who has de- scribed it magnificently in his Chemical Researches. When the monumental history of geology commences, the crust of the earth had become as fixed and rigid as the attraction of the sun and moon and Jupiter would permit. It still bent and groaned and quaked indeed, as the globe turned on its axis beneath thier irresistible influence; but now only enough to strain open great vol- canic vents, from which flames and smoke and ashes were ejected, to fall in beds of tufa over large areas ; and from 54 GEOLOGICAL SURVEY OF PENNSYLVANIA. other apertures great streams of lava poured themselves upon the surface of the lands, or spread themselves upon the bottom of the sea. Earthquakes were then in the common order of events, and changes of sea level rapidly accomplished. The air was moist and murky, the ocean warm, the continent a bare and rocky desert, ridged and rugged, with no sign of future life. No sound disturbed the silence of the air, except the noise of water-falls, of rain, or breaking waves, the roar of a volcano, the crash of a crumbling cliff, or the explosion of a descending meteor. But snow had begun to cover the peaks of Alpine mount- ain ranges, and old thousand- branched rivers raged through chasms between them, fretting their sides into valleys, and sweeping the rabble-rout of that perpetual destruction into all low places where the waters lay eager "to receive and spread it out in beds. There was no more hurry nor appearance of confusion then than now ; only a anore earnest, rapid and efficient operation of tearing down t)n land and building up at sea ; for Nature was leveling her grounds and getting ready to plant and house her future progeny. Nor can we find out with all our search- ing and calculation how many centuries or milleniums of human and solar years that first great No-life age of purely physical preparation lasted. Of that Archaean, oldest, Azoic, or No-life age we know nothing except the kinds of rock which bear its date. These appear at the present surface of the earth only here and there, in limited districts, far apart from one other, in Canada and New England, in the Blue Kidge, in the Rocky mountains, in Brazil, in Scotland and Scandinavia and Bohemia, in the Ural mountains, in Upper Egypt, the pen- insula of Mt. Sinai and elsewhere ; but so surrounded and overlaid by the deposits of aftercoming ages that no con- nected account can be given of their origin and general dis- tribution; nor can the geography of that time be mapped out ; not even where was land and where sea ; nor where the mountains rose, nor where the rivers ran, nor the di- rection of the great sea currents, nor the location of vol- canic vents. So that nearly all that has been printed in HIGHLAND GNEISS. 55 geological books respecting these things may be safely regarded as pure speculation, and uncommonly daligerous for any one to believe who wishes to gather only the knowledge that is real, and prefers expectant ignorance to any satisfaction to be drawn from unsubstantial opinions. What is certainly known about the oldest rocks may be set down in a few sentences. First, that they underlie all the formations in which appear traces of vegetable and animal life, and therefore, that they constitute the underground bottom floor of all countries wherever life-rocks occupy the surface Secondly, that they differ from the life-deposits of suc- ceeding ages by being crystalline instead of granular; as loaf-sugar differs from ground sugar, or wheat from grist or flour, or wood fibre from paper pulp, or a stone-slide at the head of a river from the sand banks at its mouth. For the life-rocks of subsequent times have been made out of the frost-fractured and water-worn no-life rocks of the ground floor of the world; and show this derivation in the fact that the original crystals may still be detected, with their points and edges worn off, and their prisms changed into globules or rounded grains. Thirdly, that they differ among themselves by the cir- cumstance that some are coarsely crystalline (like the porphyries and graphic granite), while others are so finely crystalline (like many of the quartzites, felsites, diorites, dolomites and micaceous gneisses) that their crystalline constitution must be looked for with a magnifying glass. Fourthly, that they differ among themselves in another particular, namely, that some are plainly stratified or bedded, others foliated or split into millions of thin leaves, and others subdivided only into masses by occasional cracks; and these three principal varieties seem to repre- sent, 1st, those which were deposited in water and after- wards crystallized; 2d, those which were ejected from vol- canoes as dust or ashes and afterwards crystallized; and 3d, those which flowed up from the interior of the earth as lava and crystallized on cooling. But there'is such variety in each kind, and so much discussion among microscopical 56 GEOLOGICAL SURVEY OF PENNSYLVANIA. geologists over these different varieties, as to leave the whole subject still in doubt and confusion. Fifthly, that they may all be broadly grouped under two heads in respect of their chemical constitution. For the crust of the earth is almost entirely made out of three ele- ments, two metals and one gas ; the two metals being sil- icon and aluminium, and the gas being oxygen. The other elements known to chemists play subordinate parts. First, the union of oxygen with silicon makes silica (quartz, rock crystal, opal, <&elt of highlands. 6. The Tiornblendic rock is full of grains of magnetic oxide of iron; and a good deal of what appears on first glance to be hornblende is in reality magnetic oxide of iron. The quantity of iron held by these strata must be immense; and, therefore, it excites no wonder to see many of the beds rich enough in iron to be mined as beds of mag- netic iron ore. Where all this disseminated iron came from is a mystery; but is no greater mystery than where the grains of quartz sand came from which make up so large a part of the granulite variety. Both these constitu- ent elements of azoic strata furnish very strong evidence in favor of their sedimentary origin. But if this be granted it still remains an unanswered question where were the more ancient land areas from which these quartz and iron sands were washed down into the azoic sea ; and what kind of country could that have been to furnish such stupendous quantities of iron ? 7. The granulite strata consist of grains of quartz, mixed with pinkish- white feldspar, and also with some grains of magnetic oxide of iron. The amount of quartz, however, is seldom in excess of the feldspar; that is, the quartz usually occurs in small glassy grains, and not in chunks. The rock is therefore, usually, as fine-grained as it is massive, and in this respect reminds one of the massive THE ARCHAEAN HIGHLAND BELT. 69 sandstone strata of later ages and undeniable sedimentary origin. The feldspar varies in color between dull white and flesh-pink, greenish and bluish tints being rarety seen. The feldspar also varies in its relative percentages of potash, lime and soda. The strata in which the potash feldspar abounds are hard, resist the weather and show their stratification plainly; but those in which the soda feldspar, the soda-lime feldspar and the lime feldspar abound are softer, weather into rounded bowlders, and get so covered with the soil which they make in mouldering as to conceal their stratification, and this give a soft and rounded aspect to the hill slopes. 8. On the whole, the ridges which are made chiefly by the hornblende gneiss are higher and rougher, and their crests are rocky; but the ridges which are made chiefly by fjranulite rocks have rounded summits. The ridges on the northern side of the belt, where the iron mines are, show the hornblende character of topography more plainly than the southern side of the belt; and this geographical fact may have an important geological significance. The soils also indicate the difference; for the hornblende districts are covered with earth stained by the decomposition of the iron element to a deep brownish red; whereas, the granulite districts are covered with light-colored, sparkling, sandy earth. 9. That the iron ore beds are original parts of the strati- fication and not ejections from below is- plainly shown in these highlands ; for they lie in lens-shaped plates between the gneiss rocks; fining off to an edge all round; or rather fading away into gneiss rocks so gradually that one cannot say where the bed ceases to be an ore and becomes an un- profitable rock.* It seems conclusive logic that if the magnetic ore beds lie thus between the gneiss rocks, the whole azoic mass must be a sedimentary formation. 10. The absence of any noteworthy mica schist forma- *Report D3, Vol. II, page 239. Along the southern edge of the azoic belt some limestone has been deposited with the magnetic ore ; and there is a. hand specimen in the Pennsylvania collection, which shows three parallel layers of ore averaging an inch in thickness, separated by two layers ot" Hmestone each three or four inches in thickness. 70 GEOLOGICAL SURVEY OF PENNSYLVANIA. mation,* of any remarkable crystalline limestone beds,f and especially of any magnesian formation (chlorite, talc, ser- pentine,:}: &c.), in the Pennsylvania highlands between the Schuylkill and Delaware rivers, shut in as they are on both the north and south sides by sedimentary fossiliferous sandstone and limestone formation, patches of which lie upon the very summits or are preserved between the ridges, makes it useless for us to seek for a Huronian formation here. To imagine that it once existed, but has been swept away, or that it lies buried many thousands of feet deep to the north and south of the highland belt, is a mere conjec- ture, worthless because unsupported by any known facts. The Archaean rocks of the highlands of New Jersey pass across the Delaware river into Northampton county, Pa. and extend in parallel ridges through southern Lehigh and Berks as far as the Schuylkill river at Reading, where they sink (westward) beneath the Great Valley limestone, not to rise to the surface again (as a mountain range) short of York and Adams counties. The South mountains of York and Cumberland, Adams and Fayette were formerly supposed to be a geological con- tinuation (or revival, geographically, going southwest) of the highlands of New Jersey and the Easton- Reading, or Durham hills ; but it is nearly certain that the South mountains are for the most part composed not of Archrean (Laurentian) but Cambrian (Huronian?) strata. *Both muscovite and biotite mica has been found in fine scales and in large plates in several places. See D3, Vol. II, page 53. fThe crystalline limestone bed in the report of the first survey, as running through Colebrookdale, was sought for carefully but not found by the second survey. D3, Vol. II, page 56. JGreenish talcose slates appear along the southern edge of the belt at one or two places and will be described in another place. A narrow outcrop crosses the Schuylkill below Reading and runs a mile or two west. A lew miles further west they appear again in Mulbaugh hill- But with these exceptions there is a gap of about sixty miles in the direct Highland-Blue Ridge range which may be said to extend from Massachu- setts to Georgia. But in northern Chester, south of the direct line, they oc- cupy the surface in the Welsh mountain region, and still further south there is a Philadelphia-Baltimore belt of them to be described further on. THE ARCHAEAN HIGHLAND BELT. 71 Archxan types in New Jersey. The Archaean (Laurentian) rocks of Pennsylvania have been studied as closely, but in some respects under less favorable circumstances than those of New Jersey, where they have been subjected to repeated examinations and are exposed in a bolder manner and in connection with mining operations at many places. The New JerSey report of 1889 is of special value. It distinguishes four types or characteristic masses of highland strata, without positively affirming what their re- spective ages are, how they underlie or overlie each other, or what their mutual geological relationships may really be, but very particularly describing their geographical ranges and their mineral constituents.* I. The Mount Hope type (FeldspatMc gneiss of Smock; in part the Hornblendic gneiss of Britton) is a nuartz-feld- spar-magnetite rock, varying from massive to coarse and to fine-grained and beautifully foliated, often obscurely foli- ated on a fresh unweathered surface ; the quartz generally in shot-like grains pressed into the cleavage face of the feldspar, which, under the pocket lens, gives a character- istic unmistakable spotted (poicilitic) appearance to a broken specimen ; the feldspar both orthoclase and plag- ioclase ; the magnetite usually in rough, irregular little grains, occasionally in octrohedral crystals, and sometimes largely replaced by hornblende and scattering flakes of black mica (biotite}. These massively-bedded and usually well-foliated strata have numerous interstratified layers of hornblende-feldspar rock without quartz, some of them only a few inches thick, others many feet thick, and usually quite destitute of magnetite. The typical Mount Hope rocks usually occupy the highest ground or summits of the ridges flanked by the Second or Oxford type of rocks; which would make them older than or underlying the Ox- ford ; but there are important exceptions to this general *New Jersey An. Rt 1889, part 2, page 12, Geological Studies of the Archaean Rocks, by Frank L. Nason. See Geol. Rts. of Pa., by Persifor Frazer, Fred. Prime, C. E. Hall and.E. V. d'lnvilliers, C, C2, C3, C4, C5, D, D2, D3, Vol. 1 and 2. 72 GEOLOGICAL SURVEY OF PENNSYLVANIA. statement which perhaps weaken somewhat the correctness of that conclusion. The Mount Hope type rocks may be separated into three classes: 1, Light-colored quartz and feldspar rock. 2, The same, darkened with magnetite. 3, The same, darkened with hornblende, or biotite, or both. Texture and general appearance the same in all. Dark (non-eruptive diorite- looking) feldspar-hornblende layers are often interstratilied with them, and beds of solid iron ore occur in all three. II. The Oxford type (Syenite gneiss of Smock; in part Honiblendic gneiss of Britton), always well foliated (even in fresh broke specimens) and not so heavy-bedded as the Mount Hope type, consists of feldspar (both kinds) and hornblende, with grains of quartz frequently rounded and imbedded in the feldspar; always only a small proportion of magnetite (sometimes octohedral) ; the hornblende usually distributed in strings so as to give the rock a striped appearance; and the longer axes of feldspar often oblique to foliation. The railroad tunnel at Oxford tunnel shows all the various phases of this type; but no contact with the other type can be seen; the change however seems abrupt and radical. The Oxford rocks are, however, almost everywhere seen on the flanks of those ridges the central mass of which is of the Mount Hope type. The Mount Scott range which reaches the Delaware is a suffi- cient example and introduces the distinction of types into Pennsylvania. III. The Franklin type (probably the Biotite gneiss of Smock and Britton); foliation less distinct; texture more uneven ; crystals of biotite, &c. at angles to each otlier ; eyes of quartz and feldspar singly or mixed frequent (augenstructuf); rocks rather thin bedded; frequent inter- strata of biotite and hornblende schist; essentially a quartz- orthoclase -biotite rock (plagioclase rare); quartz and feld- spar grains usually sharply angular, in striking contrast with other types. IV. The Montmlle limestone type; not certainly known to belong to the Archaean; possibly of later age. Southeast belt (A); bluish gray, rarely white; crystalline ; holding THE ARCHAEAN HIGHLAND BELT. 73 great quantities of serpentine, more or less chrysolite; also diopside, in some places small crystals of muscomte mica; never tourmaline, no zinc, no iron. Northwest belt (B) sparkling white; holding graphite, tremolite, tourmaline, pyrite, great quantities of zinc, and also beds of iron. 74 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER IX. The ArcJicean rocks of Pennsylvania. 1. In the Reading and Durham Jiills. Prof. Prime and Mr. C. E. Hall have described the high- land rocks in Lehigh and Northampton counties in the same general terms;* but there is mention made not only of hornblendic and feldspathic gneisses, but occasionally of mica-schists, rocks composed of white mica and decom- posed white feldspar. f Mr. Hall says, that the crystalline rocks are composed chiefly of quartz and feldspar; that mag- netite is disseminated throughout the rock in all parts of the region, and that the magnetic iron beds are distinctly interstratified; that in some places the rock contains small amounts of dark mica and pyroxene (hornblende) and that occasionally particles of mica and magnetite are found to- gether; but that many rocks are wholly of quartz and feld- spar. One vein (?) of corundum has been found.J The Delaware river cuts through five ridges of these rocks, separated by valleys filled with sedimentary lime- stone. Some of these ridges seem to be rock arches pressed over northwards. In the third ridge at least 800 and perhaps 1,200 feet of strata show themselves. This anticlinal structure, however, cannot be made out in the ridges of the belt as a whole. Some of the ridges seem to be monoclinal and others synclinal. It is quite impossible to be sure of the correctness of any kind of structure anywhere. Nevertheless, there are places where plenty of opposing dips can be observed, although it can seldom be decided that they lie on two sides of an arch, or *Reports D, D2, D3, Vol. I. |D2, page 7. $D3, Vol. I, pages 254-255. The difference being due to the possible existence of a roll. OLD GNEISS IN CHESTER COUNTY. 75 on two sides of a basin. One example will be sufficient to illustrate the difficulties. The Hexerikopf ( Witch s head) is the highest point of land southwest of Easton where two of the azoic ridges converge. On its north slope gneiss rocks dip to the S. E. 54; at its south brow 29; on the south slope they dip to the N. W. 36, 60 and 50. There is certainly a basin on the south slope, even if there be an overturned arch at the crest; if there be no such arch then the whole mountain is a basin with at least 1,200 and possibly 2,000 feet of azoic strata visible on each of its sides.* #. In northern Chester county. The Welsh mountain azoic district of northern Chester county is nowhere more than 500 feet above present sea level; is surrounded by sedimentary sandstone and lime- stone (although the northeastern rim is concealed by still later deposits); and was once covered by them, as is shown by the patches of sandstone left upon it. It does not lie in the W. S. W. prolongation of the highland belt of Berks county, but to the south of it; the present interval between their edges being ten miles. This interval represents an ancient valley, of great but unknown depth, now filled up with Palaeozoic white sandstone and limestone, covered in turn by a thick mass of Mesozoic brown sandstone and shale. The azoic rocks of both districts undoubtedly meet beneath this valley and form its floor, covered entirely by the white sandstone and limestone which rise to the pres- ent surface on both sides of it; the sandstone being about 100, and the limestone about 2,000 feet thick, and perhaps covered in places by a third deposit of slate; but of this we know nothing; only, it is certain that the limestone in the valley suffered erosion before the Trias sand and shale was deposited upon it in much later times. The thickness of these later brown sands and shales is also unknown; but, judging by the dips and distances, they must be nearly *See the accompany page plate, showing both alternative constructions; also the description of the locality and its rocks on pages 75 and 251, of Report D3, Vol. 1, 1883. 76 * GEOLOGICAL SURVEY OF PENNSYLVANIA. 4,000 feet thick along their northern edge. The ancient buried valley, then, must be about as deep beneath the present mountain surfaces to the north and south of it as the valley of the Rhone between the two enclosing ranges of the Alps. Originally this could not have been the case; for the brown sandstone strata all dip northward at the rate of at least 500 feet to the mile; so that if they were de- posited horizontally, either the Highlands were 5,000 feet higher than they are now, or the Welsh mountain district has been elevated 4,000 feet. The Welsh mountain azoic rocks are, as we might suppose from their underground connection with the High- lands, the same dark hornblendic and light gray feldspathic gneisses which have been described in the foregoing pages. Being more easily destroyed by the weather than the white sandstone which was afterwards deposited upon them, their outcrops lie in shallow vales between ridges of white sandstone;* but this is owing to the fact that the softer white feldspathic gneisses, interbedded with the harder dark hornblendic gneisses, make up the greater part of the form- ation as it appears at the present surface. By far the most prevalent variety, is a feldspar-quartz rock (granulite) of a grayish-white color, holding only a subordinate amount of mica, and deposited in comparatively massive beds. Some of the finer-grained kinds can hardly be distinguished from the white sandstone afterwards deposited upon the azoic rocks. f Micaceous gneiss strata, however, are also some- times seen; but nowhere in outcrops of considerable breadth ; and true mica slate only in thin interstratified layers. It is very noteworthy, that in this Welsh mountain azoic h'eld, as in the Highland belt, the hornblendic rocks prevail along its northern portions, and the feldspathic rocks along the middle and southern portions.:}: No reason for this can, in our present knowledge of the azoic formations, be given. Eor even if it be true that two grand rock waves and *Dr. Frazer's Report C4, page 163. fPages 164-165. tCM, p. 165. OLD GNEISS IN CHESTER COUNTY. . 77 several smaller ones traverse the district from east to west, it cannot be proved that the hornblendic gneisses are lower in the series than the feldspathic gneisses ; or, that they are brought up only by the northern arch. Such a suppo- sition is merely a tempting conjecture. Plumbago beds have been found in at least three places in the district. One 3 feet thick lies between gneiss strata dipping 45 to the S. E.* Another is a gneissoid stratum 12 to 15 feet thick containing about 4 per cent, of dissem- minated graphite, which is shown to be merely an element in the rock by the fact that the stratum includes horses of whitish rock without graphite, f An outcrop, traceable for a long distance, is that of a curious conglomerate (so- called) containing graphite ; but, although the rock looks like a conglomerate, it is more likely to be a decomposed por- phyritic crystalline rock if judged by the fresh character of its feldspar, the unworn- angles of its quartz crystals, and the even distribution of the "graphite through it.J Although exhibitions of plumbago in these azoic rocks suggest a relationship to the Canadian azoic rocks, they can have no time value for settling the order of the series, even were the relative age of the Canadian plumbago beds estab- lished ; for the origin of the graphite is wholly unknown. For, while it is looked upon by some as a proof of fusion, like the graphite in cast iron, others rely on it as a confir- mation of the sedimentary character of the rocks which hold it, as if it represented the consolidated and recrystal- lized remains of living creatures, the first and lowest kinds of plants or animals. And, in fact, graphite is found both in lava and in limestone. Porphyries occur with the hornblende syenite ; and these consist of a mixture of large crystals of potash feldspar and white (sometimes amethyst-colored) quartz, sometimes enough mica being present to make the rock a coarse por- phyritic granite. The syenite layers are a dark compound of hornblende and white feldspar, and weather into round boulders and clay, and show iron stains. *C4, p. 222. fc4, p. 251. JC4, p. 254. Dr. Frazer, C4, p. 215. Dr. Genth's analysis of such syenites exhibits labradorite and andesite with pyroxene. 78 GEOLOGICAL SURVEY OF PENNSYLVANIA. The absence of limestone and serpentine beds from the azoic district of northern Chester is as noteworthy as their absence from the Highlands of Berks, Lehigh and North- ampton counties. The Welsh mountain proper is the westward extension of the northern part of the district into Lancaster county; a prong of gneiss, covered partially with sedimentary white sandstone, sinking beneath the great limestone plain of Lancaster, and not rising again to the surface, although the sandstone reappears on the Susquehanna river, above Col- umbia, and again in the Pigeon hills, on the Adams county line. (Chiques or Hellam quartzite.) A southern prong of gneiss, covered with sandstone, and known as the Gap hills and Mine ridge, extending much further through Sadsbury and Bart townships, sinks beneath the limestone, and does not rise again to the present sur- face. At one point on the Susquehanna river, at the mouth of Tocquan creek, in the center of a flat arch of great breadth, the gneisses which have been described in the Highlands and in the Welsh mountain region,* should make their appearance ; but they do not neither the horn- blendic nor feldspathic gneisses but the vast arch is made up of micaceous gneisses and mica schists, apparently many thousands of feet in thickness, as will appear here- after in the course of this history. West of the Susquehanna river, in Pennsylvania, the highland rocks nowhere reach the present surface, for the rocks of the South-Mountain-Blue-Ridge range belong to a different system, as will be described further on. We will therefore turn back here and describe them as they ap- pear along the Philadelphia belt in southern Bucks, Mont- gomery, in Delaware and in southern Chester counties, where we will find them supporting the white sandstone and limestone sedimentary formations, but also in contact with another great azoic system of an entirely different char- acter and of as yet unsettled age. *Prof. Frazer's report on Lancaster county, C3, p. 71, 128. See, also, the third line of the Susquehanna river section, sheet 3, in the Atlas to C3. OLD GNEISS OF BUCK RIDGE. 79 3. In Bucks, Montgomery and Delaware counties. At the Delaware river, opposite to the city of Trenton, a low range of old azoic gneiss is seen rising from beneath the mesozoic brown sand and shale formation and running in a straight course west southwestward thirty miles to the Schuylkill river above Philadelphia. For the first few miles it is more or less concealed by the earliest Delaware river gravels. From the gorge of the Neshaminy to the gorge of the Pennypack, it makes what is locally known as the Buck ridge, with a constant width of 2^ miles.* At Willow Grove, in Montgomery county, it splits the northern fork soon disappearing beneath the edge of the mesozoic country to make its underground connections with the Welsh mountain region of northern Chester its southern fork keeping on, as a narrow thread, into Dela- ware county, where it spreads out into three separated areas, the northern one passing on into southern Chester and the southern one into the State of Delaware. Between the two forks commences the range of white sand stone and overlying limestone, of the Chester county valley, which runs straight W. S. W. for sixty miles, past Con- shohocken, Downingtown and Coatesville, into Lancaster county. The valley is evidently a long and narrow basin, at least towards its eastern end, where the limestone is seen lying in a spoon of sandstone, and the sandstone lies in the spoon-shaped depression which splits the ridge of gneiss. There can be no mistaking the fact that here the Chiques sandstone reposes directly upon the old azoic gneiss floor of Pennsylvania, without the intervention of any other azoic rocks, just at it rests upon the old azoic gneiss of the Reading hills. So also,for miles along the North Valley Hill in Chester county, this " North Valley Hill sandstone " or quartzite is seen lying directly upon the older azoic gneiss of the Welsh Monntain country But it is equally evident that the age of the older gneiss and the age of the sandstone were separated by some great interval of time, for the sandstone lies comparatively flat *See map on page 39 of Report 06, and large sheet mapln C6. 80 GEOLOGICAL SURVEY OF PENNSYLVANIA. upon the nearly vertically upturned edges of the gneiss. The sandstone basin is real ; the basin of gneiss is false a mere valley worn out of a much older surface of uplifted, compressed and complicated rocks. How many ages were required for working down the ancient range of gneiss into hills and hollows before the sand of the sandstone was drifted into the water around the gneiss spurs is the most important question to be asked of our geology, and the most difficult to be fitted with a proper and probable answer. For during those intermediate ages the rain had been al- ways falling, and the rivers running to the seas, and the seas adjusting their deposits. But where were the lands overhung with clouds and traversed by streams? And where were the seashores along which the tides were rolling gravel and spreading out the new formations of sand and mud ? And where shall we seek for the rocks which rep- resent those gravels, sands and muds ? And in what con- dition should we expect to find them, crystalline or uncrys- talline, fossiliferous or non-fossiliferous ? The Buck, ridge gneiss (always called syenite in Mr. Hall's reports C5 and C6) has the character of the prevail- ing rocks of the Highlands and Welsh mountain district. The rocks are composed chiefly of quartz, feldspar and hornblende. The beds are often massive, but usually have thin bands of black mica or of hornblende. They are syenites, gneissic granites, or granite gneisses. A. peculiar bluish quartz is a remarkable feature of the formation.* Small particles of magnetite are in some places scattered through the rock ; but nowhere in sufficient abundance to make a magnetite iron ore bed. Graphite occurs ; and in one place enough of it in the rock to warrant an attempt at mining, which however was abandoned. f Crystalline limestone occurs near Rockville, at Van Artsdalen quarry, so well-known to mineralogists.:}: A gray and red granite appears between Somerton and Feasterville. *Report C6, page 4. fThe old mine on A. Johnson's farm, near Feasterville, Bucks county. See 06, page 57. tC6, page 47. NOTE. After his long survey of the Philadelphia belt Mr. Hall made a careful re-survey of the Highlands. See D2. OLD GNEISS OF BUCK RIDGE. 81 Now the rock which lies upon it is usually a fine-grained, thinly-laminated, whitish sandstone, changed by infiltra- tion of silica into a quartzite, and full of small scales of light -colored mica ; but some of the beds are occasionally coarse enough to be called a fine conglomerate; and east of Willow grove there are massive beds of conglomerate made up of rolled pieces of the Buck ridge syenite gneiss and the blue quartz, overlaid by finer sandstone beds and beds of sandy slate.* This shows that the old azoic (syenite) land was not very far off, and was bare of any newer azoic form- ations, mica-schists, micaceous gneiss, &c.; for not a frag- ment of any such rocks can be found in the sandy conglo- merate, f Furthermore, in places where the sandstone was not de- posited, and where the limestone strata therefore rest directly upon the old azoic gneiss (as at the furnace quarries at West Conshohocken on the Schuylkill) the limestone beds contain similar fragments of syenite which shows the neighborhood of an old azoic seashore.;}: But how far the land extended back from the shore (towards the present Atlantic ocean), or how high into the air it rose, must be left to the imagination, unguided except by a single fact, namely, that in a long subsequent time in the history of the earth, at the end of the Palaeozoic ages and the beginning of the Mesozoic ages, the azoic syenite land was out of water just as it was out of water at the begin- ning of the Palaeozoic ages when the white sand and lime- stone were deposited. For, at the southern edge of the Mes- ozoic brown sand and slate country in Bucks and Mont- gomery counties the bottom beds not only lie directly upon the azoic range of Buck ridge, but are conglomerates largely made up of rolled syenite rock fragments. But whether this particular belt of azoic land remained exposed to the air through all those Palaeozoic ages, during which 40,000 feet of strata of all sorts were deposited to the north- west of it, is a question to be discussed more in detail here- *Exposed in the N. E. Penn. R. R. cut below Willow Grove. C6, page 45. fC6, page 5. JC6, page 36. 6 82 GEOLOGICAL SURVEY OF PENNSYLVANIA. after. But surely Buck ridge could not have remained through all those ages exposed to aerial destruction unless it had been at the outset of them a high mountain range. On the other hand, it could not have been an Alpine mountain range facing the Palaeozoic sea through all those ages without doing more than dropping a little gravel into the white sand-beds here and there, into the lowest beds of Palaeozoic limestone, and into the lowest beds of the Meso- zoic sand and shale. Were it the mountainous northwest edge of an Atlantic continent it must have been somewhere or other broken by mighty rivers draining such a con- tinent. Where are the deposits which such rivers must have made in all that lapse of ages? We will see in due time. But surely no such rivers opened their mouths in Bucks or Montgomery counties; for the sandstone (which is indeed a vast delta deposit, extending far and wide in the United States, as we shall see hereafter) is so thin in eastern Penn- sylvania that it can stand for but a transitory operation at an early period of the Palaeozoic age ; being immediately followed by the great oceanic magnesian limestone forma- tion (at least 2,000 feet thick in the azoic regions, but more than 6000 feet thick in middle Pennsylvania) representing a totally different relationship of continental and oceanic circumstances. In the face of all these difficulties we might assume that the Buck ridge azoic district was a long narrow island at the time when the sandstone was deposited around it. But if so, this island must have been the crest of a moun- tain ridge belonging to a much larger extent of azoic land which had sunk and become submerged at least 50 miles broad namely, from Trenton up the river Delaware to the gap in Chestnut ridge above Easton; for over the whole of this breadth, as we have seen, the sandstone and limestone were deposited. And it looks as if the Buck ridge was the only azoic island at that time. For the sandstone patches on the Welsh mountain region and on the tops of the Berks county highlands remain in evidence that these were all submerged. Yet this seems a very strange fact on noticing that the Highland summits now stand 1,000 feet OLD GNEISS OF BUCK RIDGE. 83 above tlie present sea level, and Buck ridge only about 400 feet. We should be obliged then to suppose one of three things, either that Buck ridge has sunk additionally since then; or that the Highlands have been lifted additionally since then; or that the whole azoic underground country on which they both stand has been tilted or warped to produce the difference of height. How idle are all such conjectures to account for the im- aginary fact that Buck ridge remained an island, while the higher Highlands were beneath the sea level, when the only reason for supposing it an island is furnished by syenite pebbles in the sandstone and limestone beds, which- pebbles may have come from some more distant azoic land no longer to be seen ? The impotence of the structural geologist to encounter such a problem with success becomes more and more ap- parent as new facts present themselves to be adjusted into place. Since those remote days in the history of the planet movements of many kinds, in shape, direction and degree, have followed each other at shorter or longer inter- vals, disguising and distorting or obliterating each others' traces; while the perpetual shifting of the ocean level up and down in all ages, often produced 'by foreign catas- trophes, and originating even on the opposite side of the globe, takes from us the only index and measure of move- ment which might otherwise be at our command. We know not when the excessive plication of the Buck ridge gneisses took place, whether wholly before or partly after the deposit of the sandstone. As we see them now, the old azoic strata stand nearly vertical. But it looks as if two principal folds, both tightly compressed, run along the ridge, one producing the short north spur at Willow Grove, the other following the narrow belt or thread, scarcely a tnile wide, past Chestnut Hill to the Schuylkill just below Conshohocken. Whether or not these -are true rock arches is much more than doubtful. But if they be, it is plain to see that two such arches in a breadth of two miles, if re- stored by ideal projection upward, compels us to believe 84 GEOLOGICAL SURVEY OF PENNSYLVANIA. that Buck ridge was once a mountain 10,000 feet high ; and that it has been torn and worn and washed away down to its present lowness. There is no difficulty in believing the fact of its great height, seeing that we have absolute proof of the former existence of mountains 20,000 feet high in middle Pennsylvania, where now in the place of them spread smiling limestone valleys not 800 feet above the level of the sea. The difficulty lies in finding reasons for deciding whether the elevation of this mountain range took place before or after the deposit of the sandstone and lime- stone of the Chester county valley. For, in the first case, they should lie more horizontally around it and be mixed with itsdebris to a vastly greater extent than they are : and in the second case, they must have covered the mountain, been pushed up to an almost vertical posture, been eroded away along with it, and their eroded outcrops be found now on both sides of it . To test the question let us look at their present attitude. On the north side of the Buck ridge proper from Trenton to Willow Grove, and on the north side of the short north- ern prong west of Willow Grove, the sandstone and lime- stone cannot be found; their edges lie concealed under- ground beneath the Mesozoic brown sands and shales. But that they are there we know by an accident. Among the many probable faults in the mesozoic, one is so great in its vertical displacement the one that runs from the Del- aware river at Centre bridge (15 miles above Trenton) south westward to Forestville near Doylestown as to bring the ground-floor of sandstone and limestone up through the mesozoic to the present surface. This happy accident, taken in connection with their appearance again, 15 miles further north, alone: the south flank of -the Highlands is quite sufficient to justify us in asserting that they extend beneath the mesozoic the whole distance (30 miles) between Buck ridge and the Highlands ; ofcourse everywhere lying upon the azoic ground floor ; but whether flat and undis- turbed, or compressed into folds, or simply shifted by faults, we cannot tell. From Willow Grove westward to the Schuylkill, along OLD GNEISS OF BUCK KIDGE. 85 the northern side of the south prong of the Buck ridge, there is a continuous outcrop of sandstone and limestone (as has been already said) turned up at various steep angles from 60 to 90.* These are the north dips on the southern side of the Chester county valley basin east of the Schtiyl- kill ; and if the curves of the basin be properly drawn they show that the bottom sandstone beds must descend to depths of many thousand feet beneath the present sur- face. But if the argument from structure be good for depth, it is equally good for height ; and we are compelled to believe that these beds once ascended into the air with these steep dips to an unknown elevation above the present surface. What is the limit of this their uprise into the air ? What is to prevent us from believing that they ascended upon the northern flank of the azoic mountain to its top, and descended its southern flank to an equal depth beneath the present surface? In fact, if they can be found along the southern edge of the azoic ridge, and in a nearly vertical posture (descending southward beneath the present surface) must not this be accepted as proof that they arched entirely over the azoic mountain when it was at its highest ? No, not quite ; for it will still remain a possibility that the azoic arch in rising and pushing up a still higher arch of over- lying sandstone and limestone, broke the upper arch and left two edges separately projecting (at any supposable height) between which its own arch (broken or unbroken) rose still higher naked in the sky.f But the main point is. are such outcrops of sandstone and limestone to be found on the south side of the azoic ridge ? And, if found, can we be sure that they are the very sandstone and limestone of the north side ? Does the sandstone lie upon or next to the azoic, and the limestone upon or outside of the sandstone? In answering these questions the following statements can be made : *As shown in Mr. Hall's cross sections, Figs. 18, 19, 20, 21 and 22, on page 43 of Report C6. fin discussing the Mesozoic belt of Bucks and Montgomery counties, the elevation of the Asoic mountains of the Philadelphia belt will be offered as explanation of the northward dip of the 22,000 feet of Mesozoic sediments. It is evident that the Buck Ridge syenite was once 22,000 feet or more be- neath its present position. 86 GEOLOGICAL SURVEY OF PENNSYLVANIA. 1. There is no sandstone, no limestone to be found in the Atlantic coast country southeast of the Buck ridge gneiss except just at its southern edge. The country between it and the Delaware river is occupied by a great series of azoic- rocks, (which will come under discussion in due time) among which not a single stratum of sandstone or lime- stone can be found. And beyond the Delaware river the whole breadth of New Jersey is made of quite recent for- mations, lying upon a mesozoic floor. If Palaeozoic sand- stones and limestones exist beneath the mesozoic floor we must be content to remain ignorant of the fact for many years at least until the legislature of New Jersey shall order borings profound enough to reach them to be made, and for such purety scientific knowledge only. 2. An outcrop of steep sandstone beds actually does run along the south side of Buck ridge, in an unbroken line from the Trenton city bridge, 16 miles, to Huntingdon valley (the Pennypack creek) in Montgomery county. For the next 6 miles, as far as Abington station on the N. Penn. R. R. it makes no show. Then (at Waverly Heights) it re- appears and runs for 3 miles to near Chestnut Hill, beyond which it is no more seen.* It forms a low ridge, , and is known as the Edge Hill sandstone (eurUe, quartzite, ita- columite) ; many yards in thickness ;f standing vertical; with the surface edges of the beds often pressed, crushed or "creeped" over at an angle always towards the south, (as seen in fig. 17, 06, page 41) ; so that the surface ex- posure has given the false impression that the formation dipped northward under the azoic ridge ; but it is the same formation as the sandstone on the north side of the ridge. 3. An outcrop of vertical beds of limestone also runs for some distance along the south side of the sandstone east of the Pennypack, making the little valley or gentle vale of Huntingdon creek. West of the Pennypack, where there appears no sandstone, the limestone is seen running on alongside of the gneiss. *See the sheet maps of 06, and the small map, Fig. 14, on page 39, C6. fit is impossible to find its southern edge anywhere, see C6, page 41, therefore it cannot be accurately measured. jSee fig. 25, C6, page 45. OLD GNEISS OF BUCK RIDGE. 87 4. The west end of the sandstone outcrop at the Penny- pack seems (from the strike of the beds) to be sharpened to a point. The same is noticeable at the east end of the sandstone outcrop at Waverly Heights. Some would account for the non-appearance of the sandstone in the interval, by suggesting that the sandstone had not here been deposited on the gneiss, which would account for the limestone resting against the gneiss. But an irregular line of crush faulting would afford an equally good explana- tion; and such a. line of faulting seems called for by the thinness of this belt of limestone, and by its shortness also; for otherwise why should not the limestone run as far as the sandstone does? And, as the limestone is, say, 2,000 feet thick in the Chester valley, why should it not make a much greater show on the south side of Buck ridge? Other considerations (hereafter to be presented) add testi- mony to the existence of a great fault. The Buck ridge range of syenite gneiss, then, has been pushed up since the deposits of the sandstone and lime- stone were made ; and through them as overlying deposits. The syenite gneiss strata were, of course, under water when the deposits upon them were made. It follows, then, that any syenite fragments in those deposits could not have come down from the Buck ridge strata, but must have been brought from some syenite land at that time out of water. Where, we know not ; certainly not the Welsh mountain district, nor the "range of the Highlands, for they also were under water. Perhaps from Delaware county, where the syenite areas are large and we have no positive testimony to the fact of their being then submerged, although it is hard to imagine them otherwise. It is idle to look far afield elsewhere. The Buck ridge range of syenite gneiss, however, could hardly have been pushed up thus in a quiet manner, by simply sharing in the general elevation of a 50 or 100 mile broad region of which it was ojae of the mountain ridges. For, in that case, the sandstone and limestone deposits would have been lifted also in a quiet manner upon it with their hor- zontality or seabottom-slope-dips preserved. The steepness 88 GEOLOGICAL SURVEY OF PENNSYLVANIA. of their present dips and their frequently vertical posture shows that the Buck ridge was not lifted but squeezed up; squeezing also the sandstone and limestone beds in its own folds. Therefore, we must suppose that to some extent its own folds correspond to their folds; or, in geological terms, that they lie to that extent conformably upon the gneiss strata. This, however, a long and elaborate study of the whole ground (represented by the arrows, &c. on Mr. Hall's sheet map) shows plainly enough that they do not. The sandstone and limestone folds sometimes correspond to folds in the gneiss, and sometimes they do riot; and many of the strike and dip details in the gneiss are evidently inconsistent with the folds in the sandstone and limestone. We must conclude, therefore, that the azoic country had been subjected to movements previous to the age of the sandstone deposits, folded, elevated and depressed, weather-beaten and eroded by streams, and sculptured into a region of hills and valleys, which had to be resubmerged in order to receive the sandstone and limestone deposits upon its worn and irregular surface. The eastern portion of the Buck ridge, i. e. in Bucks county, shows no sign of an anticlinal arch structure. All the dips are towards the south, at high angles (75, 78, 80) all across from the sandstone on its southern edge to the border of overlapping mesozoic at its northen edge. On the Neshaminy, however, the belt (two miles wide) is a regular arch, with steep south dips at its southern edge, a 25 south dip near its middle, and vertical north dips at its northern edge. Three miles further west, a section through Feasterville shows just the reverse, 63 and 65 N. dips on its southern edge and 75 S. dips on its northern edge; so that one would think that Buck ridge was here an azoic basin. Four miles further west, along the Pennypack, where the belt is 2 miles wide, the gneiss is vertical or (overturned ?) 80 N. at its .south edge, and then has 56, 70 and 65 S. dips for 1 miles, with nothing visible along its northern edge ; and this is within half a mile of the end of the sandstone basin ; so that we have south dips in the OLD GNEISS OF RUCK RIDGE. 89 gneiss in direct prolongation of the north dips in the sand- stone. It is needless to illustrate further the fact that the sand- stone does not He conformably upon the gneiss, in the sense of the earliest history, but only in the sense of the later history. And here it is necessary to point out a geograph- ical fact which seems to remove the movements of this later history far away from the azoic ages and bring them down to the very end of Palreozoic time, to the close of the Carboniferous age, the date as we know of that general movement which produced all the folds of middle and western Pennsylvania and the whole belt of Appalachian country from New York State to Alabama. This geo- graphical fact is the extraordinary straightness and peculiar direction of the south edge of the Buck ridge belt from the Delaware river at Trenton to the Delaware county line, as shown on Mr. Hall's sheet map. The south edge of the Buck ridge (marked by the vertical or steep south-dipping sandstone and limestone, and further west at the Schuylkill by serpentine beds) runs first S. 80 W. 2J miles, then S. 62 W. 6 miles, then S. 79 W. 18 miles (to within one mile of the Schuylkill), then S. 61, W. 5 miles (to the Delaware county line). Nothing in Pennsylvania is more remarkable than this long line of 33 miles, divided into four parts, two of which have a common strike of 61, 62, and the other two a com- mon strike of 79, 80, especially when we consider that it represents a sudden plunge vertically downward and southward (with or without fault) of one great system of rocks beneath another ; for one of these strikes is almost exactly parallel with that of the great plunge of the whole Palaeozoic system of formations vertically downward and northward into the Pottsville coal basin, sixty miles dis- tant to the north, along a line (of even greater length) in a direction S. 62 W. The significance of this line is intensified by another, which is undoubtedly in some way connected with it, viz : The long straight line of the vertically-plunging limestone (marble) beds at the south edge of the Chester county 90 GEOLOGICAL SURVEY OF PENNSYLVANIA. valley, the strike of which is S. 74 W. for 45 miles west of the Schuylkill river. Generalizations become more dangerous as they become larger ; but it is impossible to shut the eyes to the fact of a grand parallelism of the anticlinal and synclinal folds throughout Eastern Pennsylvania, produced by a hori- zontal movement from the southeast ; or to the fact that the system of parallel folds as a whole is itself parallel to the special uplift of the azoic belt of Buck ridge which we have been describing in the detailed manner which its import- ance justified. The historical azoic question raised by all this parallel- ism is this : Were the Palaeozoic sediments shoved north- westward on the Azoic floor, adjusting their gigantic pli- cations upon it without regard to its own previously pli- cated condition ; or, did this azoic floor consist of a system of parallel mountain ridges which decided the par- allel direction of and located and increased the Palaeozoic folds ; or. was the real folding accomplished in the azoic floor itself, the Palaeozoic formations merely sharing in the -movement ; or, was the whole movement a complica- tion of additional azoic crumplings below, with new pal- CBZOIC foldings above ? These alternative hypotheses must be discussed more fully when we come to the history of the palaeozoic ages ; but it was necessary to allude to them in advance in drawing attention to the remarkable line of the Edge Hill or south border of the Buck ridge azoic belt, and especially the most remarkable part of it, viz: the 16i-mile straight S. 80 W. line, against which abuts diagonally the Philadelphia gneisses. The Buck ridge old azoic (syenite) belt crosses the Wis- sahickon at the complicated bend of the creek a mile west of Chestnut Hill; not as a ridge, but mouldered away to the level of the stream, and only 400 hundred yards wide. Thus it runs on a mile and a half further west to Barren Hill; then a mile and a half farther west to the Schuylkill river at Spring Mill, where it is just one mile wide. The river after crossing the limestone valley strikes the hill belt OLD GNEISS ON THE SCHUYLKILL. 91 of syenite, turns east and flows for a mile at its foot to Spring Mill, and then turning at a right angle southward cuts through it between bluffs of nearly vertical syenite rocks for a mile. Here the dark hornblendic rocks are pretty plainly arched, although most of them are vertical, or dip very steeply northward (as the sandstone and limestone strata do which face the north side of the ridge); but obscure south dips are seen on the southern side of the belt, where the Philadelphia system abuts against it along a line of fault, at the first brook above Lafayette station. All the ex- posures from here down the river past Manuyunk and Phil- adelphia belong to the Newer Azoic system of mica-schists and micaceous gneisses to be described in the next chapter. In Delaware and southern Chester counties the old syenite azoic areas are so irregular in shape that they can only be described by reference to the geological colored county map.* As defined by Mr. Hall they appear as on the accompanying sketch map, by which it will be seen that their irregular outlines are produced by the partial removal of the overlaying Philadelphia system of micaceous gneiss. The whole district is a low rolling hill country no- where more than about 500 feet above tide level ; and the older gneisses being more easily decomposed, their areas are somewhat sunk beneath the general surface, and sur- rounded by the indefinite, gently sloping escarpments of the borders of the micaceous gneiss areas. Only one syenite area has a well determined east and west extension, between Bryn Mawr and West Chester, with an outlying area further on, crossing the Brandy wine. Chester creek makes long exposures of the syenite, which appears also on the Delaware state line and in the northernmost county of that state 4. On the Schuylkill River. Prof. Rogers' description of the syenite belt where it crosses the Schuylkill river is given on page 76 of his geol- ogy of Pennsylvania, 1858. *See them represented, as defined by Mr. Hall, in a plate on page vii of the preface to Report C4, on Chester Co., 1883. 92 GEOLOGICAL SURVEY OF PENNSYLVANIA. The "harder feldspathic gneiss " is first seen (ascending the Schuylkill) north of the soapstone quarries, dipping southward 70 and even steeper; and then northioard 45 to 55, making a sharp anticlinal arch, up through the broken center line of which has flowed a strong dyke of syenite gneiss. Passing the blue prophyroidal gneiss quarries the strata are lying nearly flat for say 1,500 feet, and then turn up and stand nearly vertical, being closely compressed into numerous narrow folds, all the way past the Wm. Penn iron furnaces, nearly to Spring Mill, at the sharp bend of the river, where the valley limestone appears. He describes in detail (on page 75) the character of the strata from the dyke northward; commencing at a small dyke, 100 feet south of the end of the long tangent of the Norristown railroad, which follows the east bank of the river. His description may be divided into the following parts : (a) Dyke of syenite, small, composed of pinkish feldspar and quartz; next north of which come (b) Gneiss rocks, dipping 80 > N. 20 W., composed of feldspar, quartz and hornblende (with some mica), coarsely crystalline, evenly bedded with parallel lamination (not minute or very continuous) dipping 80 > N. 20 W. (Some beds have feldspar in excess and may be called por- phyries.) Similar massive gneiss cut by the Reading rail- road on opposite river bank. Distance along railroad 160 feet. (c) Dyke of syenite (about 100' north of first dyke). coarsely crystallized pinkish and white feldspar, with a much less proportion of quartz, and a considerable amount of large specks of finely granular (imperfectly crystallized) hornblende. Dyke 10' thick. Contact with gneiss makes a plane dipping 70. (d) Gneiss, massively bedded, bluish gray (feldspar, quartz, mica, occasionally some hornblende), many beds prophyroidal, feldspar appearing in large insulated blotches. Granite injections in gneiss near the syenite dyke. Extensive quarries. Bold nose of hill at bend of river. OLD GNEISS ON THE SCHUYLKILL. 93 Dip of gneiss for the first 250' regular, 45 to 50 > N. 20 W. Then rather suddenly flattens to a small angle. Dip of gneiss at 900' from the quarry, gently south. (e) Interval between " the small quarry" and the south end of Wm. Penn furnace No. 2, 387'. Here (/) Gneiss massive, dark-blue, streaked and spotted (with lens-shaped white blotches) ; composed of feldspar and dark blue mica, in alternate slightly wavy laminae, with lens-shaped concretions of pinkish feldspar. In some of the bands these lumps are so abundant as to make the rock porphyroid. Other bands finely laminated, the laminae being in delicate, parallel, slightly wavy, bluish black and pinkish white streaks, according to the relative proportions of the dark mica and pink feldspar. The rock contains some quartz, and occasionally some hornblende. Dip (under furnace) 90. (g) Gneiss (at N. end of furnace No. 2) feldspar mica ; some of it minutely banded ; no feldspar lumps. (k) Trap dyke (266' north of north end of furnace No. 2), very hornblendic; thickness, 8'. (i) Gneiss (421' north of north end of furnace No. 2) same as (/); some beds with feldspar lumps, but fewer and smaller than in (/); all more minutely and evenly lamin- ated than (f)\ a real gneiss, but more like altered clay- sandstone. The feldspar weathers mealy, chalky. (/) Dip at north end of Old furnace No. 1. 60 >. (k) Gneiss (100' north of north end of Old furnace No. 1\ feldspar- mica; exposed for 170' ; dip at south end of exposure, 80 >. (I) Gneiss (?) (330' north of north end of Old furnace No. 1; with feldspar lumps and specks rounder than those of (/); finely streaked; looks less gneissic and more sedi- mentary; strike S. 70 W. (pointing across the river to the ferry house opposite Spring Mill); dip, 90 >; visible thick- ness (in exposure) 100' ; ranges along the base of the hill slope from ferry house up the river bank to Merion furnace opposite Conshohocken. The rock mass (1) conforms to the vertical gneiss (&) in strike and dip, but is more earthy and less crystalline, and, 94 GEOLOGICAL SURVEY OF PENNSYLVANIA. in fact, looks so different that Prof. Rogers feels author- ized to place it at the base of the palaeozoic system, lying immediately upon the gneisses (&) all in vertical posture. The difficulties of structure are great, perhaps insupera- ble. If the gneisses be closely folded and the folds pressed together, sp^as to make one dip, and there be no clue to the character of the last or northernmost fold, it becomes im- possible to tell whether (I) lies upon or beneath (&) ; for, if the last beds of (&) are rising northwards, then (Z) under- lies ; if falling, then (I) overlies. Mr. Rogers regards the horizontal middle part of the belt as a basin, but it may be the flattened top of a grand arch ; in which case, all the vertical gneisses of the northern side of the belt are going down together, and this is the only view to be taken of them in harmony with their extension eastward and their encircling at Willow Grove the sandstone and the limestone of the valley. Another difficulty arises from the abundance of mica in the masses (/) (g) (i) and (#) and especially (d) in which hornblende is only an occasional element. In fact, only di- vision (5) of the whole belt is distinctively a hornblende- syenite. This difficulty will be felt when we come to de- scribe the Philadelphia azoic belt lying alongside and south of this Buck ridge belt and supposed to be a differ- ent system, chiefly if not exclusively on the ground of its exceptionally micaceous character. As for the two "dykes" of syenite (a) and (c) containing little or no hornblende, they may be integral members of the series. But if they be true igneous dykes they are merely additional examples of what we meet with in the Highlands and Welsh mountain regions. The trap dyke (7^), very hornblendic, belongs to a very late time of disturbance during and at the close of the deposit of the Mesozoic brown sand and shale, when all our largest trap dykes were ejected from the interior as black lavas, and the whole region of middle New Jersey and southeast- ern and southern Pennsylvania, in fact the whole wide belt of the Atlantic seaboard, was shattered and rifted by continental earthquakes on the grandest scale. ARE THE ARCHAEAN ROCKS SEDIMENTARY ? 95 CHAPTER X. Are t?te Archcean rocks sedimentary? The alternations of feldspar-gneiss beds with hornblende- gneiss beds is as easily explained as the alternation of hard sand-rock beds and shale beds among the sedimentary rocks; or as the. alternation of limestone and magnesian- limestone beds in great limestone formations. The feldspars are combinations of the silicate of alumina r with silicates of lime, soda and potash,- and a little magne- sia and iron. The hornblendes are combinations of the silicates of magnesia, lime and iron, with more or less silicate of al- umina, and little or no soda. The chemical analyses of both the feldspars and horn- blendes show an infinite variety of these combinations ; which means an infinitely various mixture of the six sili- cates of alumina, lime, soda, potash, magnesia and iron ; as might be expected when rivers bring down sand and mud from a country of all sorts of rock, mixing them on the way in all possible proportions, and laying them down in beds of all possible thicknesses, shapes and order of super- position. Where the pure quartz sand was in great excess, the rock became a quartzite. Where the alumina was in excess, a massive feldspar rock was afterwards produced. Where the quartz was simply in excess of the alumina, a quartz- feldspar syenite gneiss was the consequence. Where there was a considerable charge of potash and a small charge of iron, the deposit became a quartz-feldspar mica granitic gneiss. Where magnesia and lime were abundant, horn- blende crystals were formed, if the deposit did not origin- ally consist of rolled hornblende crystals, obtained from some weathered country composed largely of hornblendic rocks. 96 GEOLOGICAL SURVEY OF PENNSYLVANIA. In a word, given sediments of sand and mud, composed of coarse and fine particles of quartz and feldspar, some of them from a country poor in magnesia, others from a country rich in magnesia, there must result alternations of felsitic, micaceous and hornblendic gneisses, in beds of every thickness and thinness, and in every variety of grouping. If, in the upper part of a great formation feldspathic gneiss beds predominate, while in its lower part hornblendic gneiss beds predominate, such an arrangement ought to indicate that the drainage of the country which supplied the materials was at first more magnesian or dolomitic, and became less so afterwards. And if a great formation with few micaceous beds be succeeded by a great formation of mica schists, such an arrangement Ought to indicate another change in the drainage system, viz., an increase in the quantity of potash with iron in the river waters. Throughout the Cambrian, Silurian, Devonian and Car- boniferous ages such changes in the drainage system of the continent which furnish the numerous palaeozoic sedi- ments of middle and western Pennsylvania certainly took place, or else we should not now have that remarkable pile of dissimiliar formations, arranged in no assignable logical order, and composed of an infinite variety of combinations of coarse and fine grains of quartz, of the different feld- spars, and of limestones with more or less magnesia and iron. We have a right, therefore, to suppose such changes of drainage to have occurred in pre-Cambrian time. On this supposition, and granting the possibility of the partial or complete re-crystallization of sediments with a total destruction of all traces of organic life (if such existed), it- becomes an easy matter to explain the alternations of syenitic, hornblendic, granitic, micaceous and garnetiferous gneisses and schists, with clay slates, mica slates, talc slates and even with such serpentine beds (hydrated sili cates of magnesia and iron) as cannot be proved to have had a volcanic origin.* *Even Professor Bonney admits this distinction. THE ARGUMENT FROM THE MICROSCOPE. 97 The argument from the microscope. There is a new school of geologists who trust to the microscope for deciding whether an apparently bedded mass of crystalline rocks were originally sedimentary strata, or whether they were ancient outbursts or out- flows or overflows of molten rock-glass taking on the ap- pearance of stratification in the course of their lava-like movement.* Such geologists take a totally different view of the order of the old gneiss system rocks, and reject its chro- nological subdivisions into Lower, Middle and Upper Laur- en tlan. Their point of view is strengthened by the acknow- ledged fact, that the whole Laurentian country from Lake Superior to the shores of Labrador, northern New York and much of New England is traversed by vast dykes of massive (unstratitied) syenite and granite cutting the bedded rocks and each other in all directions both vertical and horizontal. Such masses or dykes of unstratified rock in the highlands of New Jersey have already been re- ferred to.f At Kennedy's granite quarry, in Delaware county. Radnor township, near Wayne station (a good photo- graphic view of which is given on plate XXXVIII of Re- port of Progress 05). no stratification can be made out by the eye, and the syenite mass looks like an eruption from below. In strong contrast to this is the fact that at the Leiper "granite" quarries, so called, in Ridley township (shown in plates 16 to 22 of the same report.) the original sedi- mentary stratification is unmistakable. But here we are in another system of rocks which has no certain connection with the Laurentian, as will be seen hereafter. How much of the Laurentian system is sedimentary and how much of it volcanic may never be exactly defined; but the mere fact that one kind of rock can be seen cutting or penetrating the other is the strongest argument for the gen- niness of both, in spite of opposite theories of the general *Rhyolitic, from the Greek verb rhein, to flow. fThe granite of Richmond, Va., is of this kind. 7 98 GEOLOGICAL SURVEY OF PENNSYLVANIA. origin of the whole, and in spite of any revelations which have been or may hereafter be made by the microscope ; with regard to which last, it may be also said, that the microscopic examination of a transparent slice of azoic rock may lead two observers to opposite conclusions under the influence of two opposite prejudices, the one believing at the outset that his specimen comes from a volcanic rock, the other that it is from an original sediment subsequently metamorphosed. The argument from olivine. A case in point occurs in Mr. F. D. Adams' report to the Canada survey (in 1885) on microscopic inspection of thin sections of a labradorite rock from the Upper Saguenay river, flowing through the typical Norian region. In the sections he could see grains of olivine, each having two skins, an inner of pyroxene (?) and an outer of actinolite (or hornblende), the whole being encased in a matrix of lime-soda feldspar. The rock at large, from which the sections were made, was composed of lime-soda feldspar, olivine and some scattered grains of titaniferous (?) iron ore. Now since olimne* is one of the universally recog- nized volcanic glasses, abundantly expelled from modern volcanoesf ; and since it is of frequent occurrence also in older lavas, basalts and trap dykes, both in the form of grains and small masses, long crystals and balls; and since its golden-colored transparent crystals (chrysolite) also is found in modern and recent lavas, \ the conclusion has been drawn that the Saguenay rock formations taken as a whole have been originally in a molten condition, and that the olivine grains were the lirst to solidify while the envelop- ing feldspar mass was still in the condition of molten glass; in other words, that the silicate of magnesia solidified in *A pale olive green opaque silicate of magnesia and iron (^3 sil., ^ mag. and ^ iron. fSee especially accounts of the Hawaiian islands, and of the Challenger dredgings in the Pacific. jThose found in sand at Expailly in France (Dana) probably came from the Auvergnese basaltic beds. THE ARGUMENT FROM OLIVINE. 99 grains first, and the silicates of lime and soda as the sur- rounding rock afterwards. The enveloping zones or skins of each olivine grain seen under the microscope would then be the products of a slow subsequent process, by which the surface of each grain (silicate of magnesia and lime) lost some magnesia and became ^.pyroxene or augite ; while the surface of the enveloping feldspar gained some magnesia and became an actinolite or hornblende (silicate of mag- nesia, lime and iron); both the inner zones of pyroxene and the outer zone of actinolite being minutely crystallized in tibers crosswise. Similar grains with double skins (the outer hornblende) were described by Tornebohm,* as seen in Swedish gabbro rock (an ancient crystalline, granite-like, magnesia-lime-soda lava) the feldspar of which is usually taken to be labradorite, and some varieties of which contain an abundance of olivine. f It is easy enough to see how a grain of strongly mag- nesian silicate might act on and be affected by its en- velope of lime-soda silicate to produce in time intermedi- ate skins or shells of magnesia-lime-soda silicate by the gradual mixing of the three elements along the contact surfaces. But it is a risky thing to dogmatise an opinion, 1, as to how the grains were first formed, and 2, as to the nature of the action and reaction between the grain and its envelope. While it may be safely accounted probable that the magnesia was concentrated by the fiery fusions of the mass; and while it seems almost positively certain that the fibrous zones could not have been cross crystallized around the grains until after they had been fully formed; we know too much of cold aqueous concretionary structure in sedimentary rocks (e. g. oolites in the magnesian lime- stones of No. ItJ:) not to make the aqueous formation of the olivine grains a possibility. And then, the aqueous alterations of minerals seen going on at a low tempera- ture in the hardest crystalline rocks, at all depths of per- meation, suggests the possibility of the cold aqueous for- mation of the skins of the olivine grains. *Neu. Lehr. fur Min., 1877, page 303, Adarns. t A. Geikie's Text Book of Geol., page 150, 1882. JCambro Silurian. 100 GEOLOGICAL SURVEY OF PENNSYLVANIA. The granular condensation of the overcharge of magnesia in a magnesian silicate mass is illustrated by Dr. F. A. Genth's discovery in 1874 that grains of chrysolite are dis- seminated throughout the whole mass of bronzite (iron- bearing enstatite) forming Castle Rock in Delaware county.* The bronzite mass is a silicate of magnesia and iron (57, 36, 6). But the grains of chrysolite have twice as much magnesia and iron to the silica as the rock has which en- velops them. In studying Castle Rock repeatedly I could not quite convince myself that it is stratified, and there- fore do not deny that it may be a volcanic dyke. Bur on the other hand it is an integral part of the long belt of ser- pentine strata which crosses the county; therefore it ought to be sedimentary. But this belt of Delaware county ser- pentine rocks does not belong to the older gneisses; it be- longs to the mica schist series to be discussed hereafter; therefore, the question of the volcanic origin of Castle Rock does not directly affect any question respecting the stratification of the older syentte belt which passes just north of it. The point to keep in view is this, that the genuineness of the stratification of the older gneiss rocks is not impugned by any amount of volcanic disturbance and intrusion to which they may have been subjected; nor by any number of massive granite dykes, bosses or layers of gabbro;t nor by any amount of olivine discoverable in the area of coun- try which they occupy. The scarcity of olivine in the older gneisses can be appre- ciated from the fact that in the long course of the history of the geological survey of Canada its accomplished chem- ist and mineralogist, Dr. Hunt, never saw (or at least never reported finding) olivine in the Norian gneisses, although he found it in some (Norian ?) boulders in New Hampshire which were supposed to have come from Canada in the ice age.:}: When Mr. Adams says that it "occurs abundantly *Report of Progress B, page 163. fSuch as the Gabbro formation of Lake Superior, which, however, is placed above the gneiss by western geologists. JAdams, Am. Nat, Nov., 18a5, page 1088. THE ARGUMENT FROM SERPENTINE. 101 in the anorthosite of many parts of the Sagnenay area," and that he has found it also in a hand specimen from old rocks near Dolin's lake in New Brunswick, such discoveries leave the question of the aqueous or igneous origin of the great gneiss formation as a whole still unanswered; for it is supposable, and will be to many minds probable, that the observed occurrences of olivine are referrable in all cases to dykes or layers or bosses of igneous rock ejected through and between the recrystallized sedimentary gneiss beds, and not to the constitution of the gneiss itself. The argument from serpentine. It is needless to discuss the vexed question of the origin of serpentinous rocks if we recognize the fact that they may be of various kinds and have more than, one origin ; some of them being sedimentary, others volcanic, and yet imitating each other in the same way as the granite gneisses and granites imitate each other. In Pennsylvania we have no notable serpentine beds in the Highland, Welsh mountain, Buck ridge, Delaware county older gneisses. A discussion of the serpentine beds of the mica schist series on the Schuylkill and west of it would properly find its place in describing that series. But as Mr. T. D. Rand has argued in the most forcible manner for the assignment of these serpentines to a place in the older gneiss series, not only in Delaware county, but also in Northampton county, it is better to give the facts here. In the proceedings of the Academy of Natural Sciences of Philadelphia, November 24, 1886, pages 393, 407, and in the annual report of the geological survey of Pennsylvania for 1887, Mr. Rand's views may be found with illustrative maps and sections. Of the two parallel serpentine belts that cross the Schuylkill river (1) above and (2) below Lafayette station, the (2) belt (with steatite} cannot be traced (west) beyond a bend in the Black Rock road (one-half mile north of the P. R. R.) The first belt is conspicuous at Rosemont station (P. R. R.), but no farther. A (3) belt commences LIBRARY UNIVERSITY OF CALIFORNIA SANTA RARRARA 102 GEOLOGICAL SURVEY OF PENNSYLVANIA. on Meadow brook f mile east of Darby creek and runs on westward. It was always doubtful to which belt (1) or (2) this should be assigned. In 1885 Mr. T. D. Rand* "found a distinct outcrop on the Roberts road, on the property of Colonel Joseph F. Tobias, or of Dr. E. H. Williams, with fragments in the soil of the former to the northeast. The belt is very narrow, arid the valley of a small creek seems to occupy nearly the same line." The outcrop is about half-way between the Rosemont (1) exposure and the Meadow brook (3) exposure and seems to settle the ques- tion, f The Edgehill (eurite) rock seems to outcrop 100' to 200' from the serpentine on the Roberts road. The two occupy here the same relations as they do near Radnor station, on the other (N.) side of the Laurentian axis. The Delaware county serpentines. Castle rock, four miles north of Media, in Delaware county, is a confused mass of plates of that species of enstatite rock:}: which contains iron (bronzite) and which, after imbibing water (chemically) turns into serpentine rock (composed chiefly of silica and magnesia. ) On the eastern side of a brook flowing south there are outcrops of serpentine which indicate the continuance of the mineral towards the Schuylkill ; but at the west end of the Castle *Strike N. 30 E., dip 50 S. 60 E. ; mica schist, adjacent, strikes N. 40 E., dip 6508.50 E. fThis outcrop is somewhat south of the Kosemont outcrop line and indi- cates some change in strike, or a throw, or an echelon structure. Jin Bucks county, near the Neshaminy, between Scottsville and Rock- ville, at Vanarsdalen's quarry of crystalline limestone (interbedded with hornblendic gneiss and charged with plumbago) among the numerous species of crystals some contain percentages of magnesia, but none come under the head of magnesian silicates proper. (Report B). Near the mouth of the creek, at Flushing is an outcrop of enstatite rock, bedded and dipping 10, the relations of which are not understood. (Report C6, p. 60.) Mr. Salom, when Dr. Genth's pupil, found that between 5 and 10 per cent of the Castle rock was soluble in dilute chlorhydric acid, and composed of silica, 45 ; mag., 31.6 ; ferrous oxide, 19.4 ; lime, 3.9, representing dissemi- nated grains of chrysolite; the insoluble 90 to 95 per cent was composed of silica, 56; mag., 29; ferrous ox., 12; lime, 1.2, closely agreeing with the composition of bronzite. Genth's Rep. B, 1875, p. 64. THE ARGUMENT FROM SERPENTINE. 103 rocks a cultivated outspread of gneiss land soil shrouds the geology of this singular place in mystery.* There is a range of abandoned quarries extending from Media W. S. W. past Lenni for miles, f Other ranges tra- verse the county. C. E. Hall's sketch map in C4, preface page v, shows more than 50 spots marked serpentine. It is noteworthy that no'ne of them are in the Older (syenitic, liornblendic) gneiss regions. All of them are in the interval regions of Newer (micaceous) gneiss, the equivalent of the Philadelphia belt. Nor are any of them in the South Valley Hill belt of mica slate. :{: The Chester county serpentines. Serpentine outcrops are very numerous in Chester county. Thirteen are enumerated in Report 04, pages 62, 63. Brin- ton* s quarry is a grand exhibition of serpentine, and from this quarry 500,000 cubic yards of the rock had been taken before 1880, the largest being 3 feet square and 16 feet long. In 1880 6,000 cubic feet of rock were moved, valued at $10,000. Dr. Frazer makes the general remark that "the serpen- tine under no consideration has any direct connection with the series of hypozoic and palaeozoic strata, or strata of pri- mary origin. The serpentines near Baltimore are said to furnish under the microscope ample evidence that originally they were *Mr. E. B. Harden has made for me photographic pictures of the mass as it appears on all sides and in various lights. I have myself made a careful contour line map of it, with pencil sketches ; but I could come to no certain conclusion whether its apparrent bed-plates were or were not cleavage planes. It may be synclinal, or it may be a dyke. fSee also notes on the minerals of the county by Col. Joseph Willcox, in C4, p. 346. {Mr. Hall and Mr. Rand are thus directly opposed in their structural views respecting the Serpentine. Dr. Frazer agrees with Mr. Hall in iso- lating the Serpentine from the Archaean, but he advocates its connection with the hydromica and chlorite series. Report 04, page 289. Prof. Rogers notes serpentinous geodes in the Welsh mountain gneiss, at Warwick mines, Report C4, page 238. Fine specimens of serpentine have been found in the mines on Fritz's island near Reading, at Topton, and at the Wheatfield, Boyerstown, Ruth and Jones mines in Berks county; but no serpentine beds. See Reports D2 and D3. 104 GEOLOGICAL SURVEY OF PENNSYLVANIA. trap dykes, holding a rhombic pyroxene, with or without olivine. * A similar conclusion was reached by Prof. F. D. Chester, of Dover, Delaware, in studying the large belt of serpen- tine on the state line in Chester county;f and he was led to regard all the serpentines of Chester county as alterations of rocks containing a rhombic pyroxene, either enstatite or bronzite. The great mass of Castle rock, unchanged enstatite rock in Delaware county can be seen passing on eastward as a serpentine outcrop. The Lancaster county serpentine. The two remarkable belts of serpentine in southern Lan- caster, passing over into Maryland, are described in detail by Dr. Frazer in his Report C3, pages 26, 89, 177, 190. Wood's celebrated chrome mine is in the southern belt in an oxbow of Octoraro creek just within Little Britain township. In Fulton township the serpentine ridges are called "barrens." Up to 1877 about 90,000 tons of chrome-iron ore had been taken. The mine was then 720 feet deep and yielded 500 or 600 tons of the ore annually. The serpentine country through which the ore vein runs is unstratified and about three quarters of a mile in breadth. The ore strikes S. 78 W. The sandy chlorite slates to the north of the mine dip S. 50. The rocks southeast of the mine are hornblendic, and " a region of syenite commences on that side "(Glenn). The same kind of difficulty here encounters the geologist as in Northampton county, whether he is disposed to connect the serpentine structur- ally with the older hornblendic gneiss (syenite) system, or with the newer gneiss (mica schist) system, or with the still later chloritic (phyllite) system. *Dr. G. H. Williams, of the Johns Hopkins University, on the Peritodites and Serpentines of Baltimore. t Letter, Oct 23, 1886. The mother rock of this belt appears to consist of a rhombic pyroxene, probably bronzite, associated with a variable amount of diallage, both minerals largely altered intolightamphibole aggregates, gen- erally tremolite, partly actinolite ; and these are found in all stages of alter, nation into a true chrome-serpentine, the direct product of alteration of pyroxene, as described by Drasche in the Tyrol. THE ARGUMENT FROM SERPENTINE. 105 The Northampton county serpentine. The serpentine of the old Wolf quarry of Chestnut Hill, Northampton county, seems to be not an originally bedded deposit, like limestone, but an alteration product in the white tremolite* quarry-rock (belonging to the hornblendic or amphibole gneiss series), composed chiefly of silicate of magnesia and lime. The silicate of magnesia after im- bibing water has separated from the mass into veins and lumps and scattered pseudomorph crystals of pure serpen- tine. The lime has also separated in the iorm of veins and masses of snow-white crystalline carbonate of lime (calcite). It is possible to trace on the face of the quarry, in the space of a few inches, the gradual transformation of the pure white tremolite rock into a mixed stone, composed mainly of serpentine, tremolite and calcite. The steps of the process is observable in the thin slices under the micro- scope, the tremolite crystals being broken up into bundles of fibres traversed by irregular canals of serpentine.^ It was always an interesting question whether the ser- pentine beds of Chestnut hill belonged to the Highland gneiss or to the limestone of the valley ; \ but Mr. Rand seems to have set the matter at rest by his observations in the gap of the Delaware above Easton and in the gap of the Bush kill west of the river. Five soapstone (steatite} outcrops are exposed and four of them have been quarried, all dipping steeply southward enclosed between solid ribs of gneiss one or two hundred feet thick. | *See Genth's Report B, 1874, page 67. On page 64 he notes that the " Wal- lastonite " of Easton is tremolite. |G. P. Merrill, in Proc. U. S. National Musenm, Vol. VII, 1890, page 600, where an analysis of the tremolite by Eakins is given : Sil. 58 ; Mag. 26 ; Lime 12 ; Alum., Potash, Sod 4. jSee Rogers' Geol. Penn., 1858, Vol. 1, p. 94, and Report D3, Vol. 1, 1883, p. 79. T. D. Rand. Notes on the genesis and horizons of the Serpentines of S. E. Pa. in Proc. Acad? Nat. Sci., Phila., March 25, 1890, page 95. II South-dipping rnagnesian limestone outcrops border the river for a mile above Easton to within 200 feet of the first exposed steatite or talc-slate bed, which is not thick, has no visible hanging wall, but a foot- wall of gneiss. The second one is immediately below the first and in the gneiss ; one mass 106 GEOLOGICAL SURVEY OE PENNSYLVANIA, Chestnut hill is the western end of one of the Highland ranges of New Jersey, severed by a steep and picturesque gap cut through it by the river. Its beds of gneiss dip all one way, southward, as the limestone beds do to the south of it. There is no appearance of anticlinal structure in the ridge.* Its crest, straight and sharp, is made by a massive rib of gneiss, dipping at the river .31; at its highest point (700' A. T.) 59, on the road 30, at the Bushkill gap 40, 43, 48, 60, further west 28, all southeast ; no northwest dips anywhere, until its western point sinks beneath the around-lapping limestone country, the nearest outcrop of which dips 12 S. W. That the whole ridge is a mono- clinal uplift is confirmed by the first limestone dip (28, N.) seen at the Bushkill gap abutting against the lowest visible gneiss dipping 48, S. E. f The talc-schist or soapstone beds, and the serpentine (picrolite) beds are not of the age of valley limestones (magnesian though many of these be) but belong to the more ancient gneiss formation of the South of it among many (5'-6' long) nearly pure talc schist at one end, at the other apparently unaltered qartzose gneiss. Two hundred feet north of the second appears the third, quarried for 100' up the slope ; both walls gneiss, fallen blocks of the hanging wall showing change from granulite to steatite. The fourth and much larger one is 300'-400' further north ; inter- val, all (?) gneiss. The fifth 200'-300' further north ; interval all gneiss, ank is 3 miles northeast of Co- lumbia in Lancaster county, in a shallow synclinal (?) vale on the south flank of Chiques ridge. f The ore is at the bottom measures of the slate, next over the quartzite which * Dr. Frazer discusses the origin of the limonite deposits in Report C, 1874, page 137, and thinks it most probable that it is to be lound in "the pyrite crystals_of the brown slates. Even the slates which are not so situated as to permit the percolation of water through them exhibit a porous structure, the pores being filled with brown ochreous limonite ; and this occurs to an unknown depth, and the slates seem to merge by imperceptible degrees, in a direction normal to the plane bedding, first into completely metasomatized pseudomorphs of limonite after pyrite (but still retaining the form of the latter); then the same with a kernal of pyrite; then the pyrite itself, first with a shell and then with a mere stain of ferric hydrate ; and finally the same slates are revealed porphyritic from the pyrite, and not at all decomposed." This suggests that the limonite was manufactured by percolating waters in the body of the slate mass and merely set free by erosion and gathered together into low grounds or cavities of the surface, or caverns in the neighboring limestone, by running waters carrying the mud of the triturated slates together with the limonite of the cavities as fast as exposed, and both dumped together (slowly) into the reservoir to settle. On page 139 Dr. Frazer makes his own calculation of quantity. A speci- men of slate from under the York limestone taken on the railroad five miles southeast of York, 3|"x2", showed to the naked eye 350 pits left by decayed crystals of pyrites, varying from ^ to ^\ of an inch, or 40 to the square inch. Nine layers of such pits were visible in the thickness of \ inch. This would amount to 12.27 cubic inches of pyrites in a column one square inch five feet long, or 32 pounds in five cubic feet of slate. Every running mile of outcrop five feet thick and 1,000 feet high (eroded from the present surface) must have yielded 75,000 tons of pyrites, or 48,700 tons of iron, or 80,000 tons of limonite. He carries the calculation further on page 140, but the above is enough to justify him in saying that allowing for all contingencies we have more than enough to account for the largest ore banks. f Dr. Frazer does not accept the simple synclinal structure. Ore beds at mouth of a drift 250 long sink N. W. beneath the floor of the drift. In the middle parts of the mine the ore's lie flat. One or more anticlinal waves are therefore probable. On page 213 he makes a curious, novel, but by no means useless, suggestion that possibly the weight of the high walls of the open mine has helped to convert a shallow synclinal into a very low anticlinal. His numerous close observations to settle the question of anticlinal wave structure of the mass in this and the neighboring mine occupy several in- structive pages of his book. 208 GEOLOGICAL SURVEY OF PENNSYLVANIA. has been exposed in the mine floor. The dips are gentle; bottom flat; an open quarry, 100 feet deep, ore from top to bottom of the slope walls; area in 1856, about 11 acres, in 1877, 1400' wide by 3350' long. The old Grubb mine half a mile east is in the same slate and merely a continuation of the formation towards Lancaster.* The decomposition of the slate mass into limonite is evi- dent to the eye. The upper half or more of the walls are of a bluish, yellowish and white greasy clay, laminated as it was before the change. Underneath is a mass of solid ore, 10 to 30 feet deep, lying on the quartzite floor; brown, cellular fibrous hematite (limonite) precipitated from above as the heavier element of the wet clay which filled the hollow. The present drainage passed beneath the slate over the face of the quartzite ; and this has always been the agent of de- composition. Layers of such ore however occur in the slates above, resting on tight clay strata which formed subordinate drainage planes. In only one place was the ore changed to magnetite; a band from one to three inches thick is full of beautiful small octahedral crystals of magnetic iron ore. Dr. Frazer says that the general appearance of the Chest- nut Hill mine is that of all the banks of York county along the slate belt, but on a much larger scale; the ores being in all of them of two kinds : (1) Wash ore, distributed through the upper part in planes but without the regular- ity of a bed of sediment, i. e. concretionary shot, balls and chuncks embedded along rude planes of clay ; (2) Solid concretionary ore, usually low in the mine, hard, massive, usually darker and more botryoidal or bunched like grapes. Quartz fragments are seen sticking out of the slope walls. *"A11 the ores which lie above the Chikis quartzite from the mouth of the Chikiswalunga through Silver Spring and to the German settlement and the works of the New York Company should be included are parts of the same system." Frazer, Report C3, p. 203. The. /Shirk bank is north of Chikis ridge 3 miles N. of Columbia and E. of Marietta. It produced 8000 tons a year for ten years, afterwards less ; at first 4 tons of ore to one of wash, later 1 ton of ore to four of wash. It was an exceptionally rich pot, very wet, slate clay mass, required heavy timbering. No quartzite seen. Limestone exposed in the wall. Grade of ore 40% to 48%. Stopped 1874. Coppen- hoffer's and Garber'sare small banks along the same north foot of Chiques ridge, following the fault. IRON MINES IN THE PRIMAL UPPER SLATE. 209 Hollow bombs of ore, sometimes tilled with very soft fine clay or simply with water and lined inside with black oxide of iron,* are common. Until the introduction of the Lake Superior Marquette and other red hematite ores Pennsylvania easily held its preeminence as the great iron smelting state of America by reason of the great number and remarkable size of its brown 1 hematite (limonite) iron deposits ; and by importing the richer magnetic and specular ores for mixing with its own stock of limonite and fossil iron ore it still re-mains the principal iron state, furnishing always about one-half of all the iron produced in the United States. She was the first to adopt Bessemer' s process of making low steel in 2, and afterward 5 and 10 ton flasks, f Most of the great limonite beds are, as has been said above, in the Upper Primal slates. Others are in the lime slates above the Trenton limestone No. lie. Others are in the slates interbedded in the great limestones. Others are in the slates over the Oriskany sandstone No. VII. These will be described in their proper places. The Upper Primal Slate limoidtes range along the north side of the Chester county valley ; along the hydro- mica belt in York and Lancaster; along the north foot of the Highlands from Easton to Reading, and along the north- west foot of the South Mountains from Boiling Springs to Mont Alto. It is probable that this is also the geological horizon of Pine Grove mines on Mountain creek in the heart of the South Mountains ; and possibly of the Rich- mond ore bank in Path Valley north of Mercersburg in Franklin county, although this last range is along the *This lining is often oxide of manganese, a metal constantly accompanying iron in limonite deposits ; often beautifully crystallized in fibers or needles. The bombs and balls show plainly enough that the peroxide of iron was dis- tributed as fine particles throughout the plastic clay, and that these particles slowly concentrated around points of mutual attraction, probably in most cases towards minute quantities of organic matter which have disappeared by oxidation. f A process virtually invented and practiced by Wm. Kelly at his furnace in Kentucky, when he boldly blew air into the molten metal in his furnace hearth. See my Iron Manufacturers' Guide, 1858. 14 210 GEOLOGICAL SURVEY OF PENNSYLVANIA . Path Valley fault, on the contact of the limestone with the Hudson River slates ; as described in a future chapter. Chester valley Umonite mines. The mines of the Chester county valley have never been of first-class importance. Prof. Rogers' description of them in 1858 was condensed and re-published in C4, 1883, pages 141, etc. It has hardly more than a historical value, since the change in the iron industry has concentrated the iron works and destroyed local small mining by the importation of dis- tant richer ores. But it has a geological value for those who study our formations. Some of the old banks are on the edge of the valley, and evidently in the Upper Primal slates, above the sandstone and beneath the limestone. Others are as evidently wash- ings from these iron-bearing slates into ancient caverns in the limestone, the roofs of which have been removed by erosion, leaving great pots of clay filled with wash and ball ore. Of this kind are the deserted Hitner banks near Marble Hall, Montgomery county r from one of which were taken 10,000 tons in 1852, and 12,000 in 1853. From all the pits dug east of the Schuylkill up to 1858 probably 60,000 tons were taken, in a belt seven miles long and a mile wide. The ore deposits ranged in long narrow strips, as deep troughs of iron soil sunk in the limestone outcrop ; the two most productive being one just north of the Barren Hill range ; the other just north of the belt of marble. But outliers were found ; as, Wood's pit, one mile north of Marble Hall, where shallow ore soil rested on limestone so thin that the North Valley Hill sandstone was struck beneath it.f West of the SchuylTcill several pits were made south of Bethel Hill (Whitehall's pit, Fisher's pit) for Merion fur- nace use. The Baptist Church old shaft, 75' deep, got superior ore, resting on white marble. Another pit was sunk 200' feet further east. t See C. E. Hall's Report, C. 6. CHESTER VALLEY LIMONITE BANKS. 211 Fisher (Geo.) bank, 300' N. E. of Henderson's marble quarry in U. Merion, is large, and until 1854 yielded good ore ; afterwards more of an earthy wash ore. Another pit, 1250' N. E. of the last, and a later pit for the Phoanixville works gave $ ore. Widdart's bank, 800' S. of last, was reopened before 1854. Millerton's bank near the school house sent ore to Jones' furnace above Conshohockin. Otto's bank, newly opened in 1854, had ore. Supple' s & Hampton's pits were small. Hughes & Jones' 1 pits were also small, but made a large group. Howellville, Tref. town, had its group of pits from which good ore was got. Wilson's, N. W. of village. Wood- man'' s had ore f, dirt ; sent to Phcenixville. Jones', Beavers' , & Bucks and King's, near the Baptist Church m. from Centreville, were all three large banks. 8. Bea- ver's bank, mile S. E. of head of Valley Forge dam, lay along the north side of the valley, and got its ore-wash (Rogers thought) from the lower magnesian part of the great limestone formation. Holland' s bank, 1 m. N. W. of Howellville, 43' deep in 1854, sent excellent ore to Pho3- nixville. West of Paoli was another group of diggings : Buchan- an's, 1200' N. of Oakland hotel, f ore, sent to Jones' fur- nace. Jacobs' , 2 m. E. of Oakland, and two others m. S. of Ship tavern. McGuire' s, 1 m. N. of tavern ; much good ore. E cans' , f m. E. of tavern; much good ore. Neat's three pits. An untried pit was opened 1 m. N. W. of Downingtown. West of Coatesville several small pits on the south side of the valley.* York county Umonite banks. The mines of York and Adams county in the hydromica (Upper Primal) belt are described by Prof. Frazer in his * Rogers' Geol. Pa. 1858, pp. 217 to 219, gives some very interesting details of Lancaster Co. limonite banks in evidence of his belief that the South Valley Hill mica slates (bearing iron) underlie the Chester Valley limestone formation. 212 GEOLOGICAL SURVEY OF PENNSYLVANIA. Report of Progress C, 1876. On pp. 5 to 9 is given a list of 158 mines in all the formations of the two counties, in alpha- betical order, many of them small openings, others old, large and deep mines.* Golin bank (67) 2 miles W. of Wrightsville, at the N. edge of limestone belt, S. edge of slate belt ; opened 1854 ; in 1874, 400' long, 25' deep at west end, in sandy clays; B. StricJcler bank. 1 mile west of the Gohn, on the same line ; 1854 ; worked by Mnsselman ; then by Haldeman till 1864 ; 1874 abandoned ; half an acre ; 30' deep to water. Stoner bank, half a mile further west on same line ; 1850 to 1873, 40,750 tons to Musselman and Watts ; partly by shafts ; open f acre, 25' deep. D. Rudy 's banks, half a mile further west on same line ; 1862 to 1870, 9,872 tons ; H acres, 25' deep ; abandoned. Ruby 1 s bank, half a mile (4 m. from Wrightsville) on same line ; 1862 ; worked 4 years ; 400' long E. and W. or % acre ; abandoned ; much loose qnartzite. Keller's bank, half a mile further west; acre ; 10' to water ; ore exhausted. Heistand's bank, a mile further west on same (midway between Wrightsville and York ;) 1864 ; Musselman & Haldeman ; 2 acres, 600' long, 20' deep to water ; abandoned 1871 ; walls, clay and gravel. Blessingef s bank, one mile further west ; and 1000' N. of limestone limit; acre; trench 750' E. and W. ; exhausted; sandstone fragments and sandy slate. Norses bank, half mile further west, and J m. N. of limestone ; f acre, 300' long, 25' deep ; abandoned. Miller's bank, one-third mile further west, and 2000' N. of limestone ; i acre, 15' deep ; has only yielded 300 tons ; ground strewn with sandstone and slate blocks. * Of these are described 126, arranged in nine lines running N. E. and S. W. and numbered from N. E. to S. W. Nos. 1 to 6, from Shrewsberry to the Maryland line ; 7 to 14, S. of Margaretta furnace, from Red Lion to 8. of Jefferson and Loganville to Red Lion ; 15 to 66, from S. of Wrightsville by Hanover Junction to Littlestown in Adams ; 67 to 109, from Wrightsville through York to N. of Hanover in Adams ; 111 to 118, a group north of York ; 110, near the river N. of Wrightsville ; 119, 120, S. of Wellsville ; 121, W. of Wellsville : 122 to 126, near Dillsburg. In this chapter only those in the hydromica slate belts will be noticed. YORK COUNTY LIMONITE BANKS. 213 S. and 1. Deitz's two banks, m. apart, further on, 1500' N. of limestone ; about 1864 ; abandoned 1870 ; yielded 2000 tons ; 8' stripping over ore lying in pockets in white and yellow clay ; in all \ acre, 20 ' deep ; water scarce. Susanna Fritz' s bank, a mile west of Norse bank (.or 3 m. east of York) and \ m. N. of limestone border ; 1865, to June, 1874 ; principally wash ore, in pockets and nests in blue clay which prevailed in the walls beneath the strip- pings ; abandoned, but large quantity of ore at north end reaching nearly to the surface ; 40' deep, partially filled with water (1874.)* HeidelsbacTi 's bank, f mile further west and 500' north of the limestone ; small ; 600 tons ; exhausted by 1868 ; acre, 10' deep.f Ifibert banks, If miles north of York (the most northern is sometimes called the Corr bank). Operated by Benson & Cottrell, owners from 1866 to October, 1873 ; |+1| acres, 30' deep ; principally wash ore ; 10 tons daily ; part filled with water (1874)4 D. Louck's banks, li miles northeast of York and ^ mile north of limestone ; two, 100' apart, with a smaller bank between ; 1867 ; wash ore, some lump ; water not quite sufficient to wash ; acre, 20' deep, and acre, 25' deep.g Thus far the limonite deposits have been either on or just N. of the northern edge of York Valley limestone belt, which edge crosses the Codorus a mile north of York, swings west and north and east to recross the creek two miles lower down, and recrosses a third time 5 miles north * Many samples taken for analysis yielded in McCreath's laboratory : Insol. res. 19.750; iron sesquiox., 63.285 ; alum. 0.765 ; manganese sesquoix., 2.210; phos. acid, 2.986; sulph. acid, 0.068; lime, 0.196; mag., 0.216; water, 10.880=metaljic iron, 44.300; inang., 1.540; sulp., 0.024; phos., 1.303. f Here a compact bed of quartzite crosses the road, dipping 60 northwest, but there is room for concealed southeast dips between it and the limestone belt. J An interesting bed of compact quartzite, dipping 30, north 15 west cuts out the ore in the Corr bank. Slates carrying ore much contorted, with cleavage planes dipping 70 southeast If these be original bed planes then the slates dip beneath the limestone. Rock beds cut are crystalline schists much intersected by veins of quartz. 214 GEOLOGICAL SURVEY OF PENNSYLVANIA. of York. From this third crossing the limestone edge runs west 2f miles to Ewingsville, and so keeps on to the north side of the Pigeon hills. It then returns east, south, south- west around the south foot of the hills and runs on into Adams county. Returning now to the Codorus creek there are several banks in the slate country north of York: Lightner's, Louck's, Benson & Cottrell's, Hake's, west of the Codorus ; and Benson & Cottrell's and Smyser's east of the Codorus ; all of them either on the limestone border or not more than 1500' from it. Taking them in the order named will be to follow the edge of the limestone around Pleasureville. (See Report C, 1875, p. 69.) Banks north of York. Lightness bank, 1 m. W. N. W. of York, on the lime- stone border; leased by an English company, Sept., 1874. LoucTc 1 s bank, If m. N. of York, \ m. from the limestone; open cut 60' long, 15' wide, 18' deep in bluish clay; stripping 5'; yellow clay with ocreous iron, 7'; white clay and chlorite, thin; clay and ball ore V; dip of slate 46 N. 23 W.; dip of ore the same. Benson and CottreWs bank, near last; 1870; 1000 tons a year; ten per cent, lump; water scarce; ore contains a little sulphur and a little phosphorus; magnetic sand and much specular iron intermixed with the ore. Hake's bank, % m. N. of last; clay; not at work in 1874. Smyser'sbank (SmaW s bank), 3 miles N. of York, on the south edge of the limestone a mile N. of PleasureviJle; leased for 20 years (1864-1884) by Ashland Iron Co. 2 acres, 40' walls; 15 tons per day of both wash and lump ore of two kinds, one a sandy manganese limonite; the other a smooth greyish blue compact ore full of small cavities stained on the edges with limonite; also a white ore looking like a cherty limestone, in fact a spathic or carbonate iron ore, suggesting interesting reflections upon the genesis of the limonites. There is on the east side of the bank a lime- stone bed which dips 18 to the west, i. e under the ore de- BANKS NORTH OF YORK. 215 posit, and Dr. Frazer suspects it of a greater antiquity than the York valley limestone. (See C, p. 68.)* Cottrell & Benson 1 s bank, across the road from Smyser's bank ; 1871 ; 10 tons per day, all wash ore, hauled to Emigsville, railroad to Marietta. In 1874 acre, 40' deep. (C, p. 66.) Banks west of York. Eisenhart(Jac.}, on the Gettysburg turnpike, 2 m.W. of York, has surface wash ore on slate ground ; and not far from here near the Carlisle road fork to Emig's Mill in the debris of an old pit was seen a large specimen of magnetic limonite. The Beelor trap dyke runs across the neighbor- hood towards the old Kauffman bank, 3 m. S. W. of York on the narrow belt of slate which from here west to Pigeon hills splits the limestone belt into two ; 300 tons were taken out ; ore so magnetic as to disturb the surveyor's compass ; ore, mostly anhydrous, lay in scales along with mottled red and blue limestone ; a mass of ore in place dips 25 S. 10 E. ; but the associated slates dip 70 S. 10 E. Beelor' s trap dyke runs close by on the east. Ey ester s (M.}~bank(Smysers's, Brillinger 's 3 m. further S. W. along the N. W. edge of the slate belt, along aban- done shaft 64' to upper ore, 4'. M. Brotzman (No. 46), open cut, no regular bed; alternate beds of dark brown and light yellow decayed damourite slate ; flint with the clays ; dip, 17, N. 72 E., perhaps conformable to surface over which the clays have washed. M. Brotzman (No. 48), small open cut ; little ore in partially decomposed slate ; W. end ore in bottom ; thin streaks of manganese oxide in the face prettily crystallized. (N. B. The miners were carefully picking this out to throw away, and were much astonished to learn that it was valuable.) T. Richard, 3 m. S. W. of Easton ; open cut : ore interstratified between white clays ; shaft 107' down through slate and clay to ore " 27' to 40' thick " on a floor of " black dirt" (D3, Vol. 1, p. 194. ) f Raub & Lerch (No. 54), 5 m. S. of Easton ; shaft sunk 15' to ore, and 100' to ore; 3 beds of ore reported, middle one only minable; partings damourite clays. Joy (No. 55), 2 shafts, 50' and 75' deep, to ore in damou- rite slate and clay. &t Stout & RiegeVs abandoned mine, 5^ S. W. of Easton, magnetic ore occurs near the limonite pit. a : LEHIGH COUNTY LIMONITE MINES. 233 All the mines thus far mentioned are on outcrops of the ower damourite slate formation at the bottom of the great imestone series. Mines north of the Lehigh river and in damourite slates )f various horizons in the middle and at the top of the imestone series are thus named and described in D3: Biery(Jas.); George (Ab.); Chapman; Lerch; Shinier (No. | )) ; Ritter (Simon) ; Goetz ; Gernert ; Merwin & Shortz ; \ohler; Ritter (W.); Schortz (Nos. 12 and 14); Hummel; 3eck (W. G.); Beck (J.); Lawall ; Woodring; Gernert & leller ; Messinger & Woodring ; Moser ; Fogel ; Young ; 5chimer (No. 24); Walter; Richard (T., Jr.); Messinger. Lehigh county limonite mines. There appear to be four lines of ore deposits across Lehigh Bounty. (7) A southern range along the foot of Lock Ridge, on a general N. W. dip like the rocks on which the )re (and damourite slate) rests. In this range are the mines :>f Wagenhorst ; Wescoe ; A. Hertzog ; H. Kaiser ; Meitzler ; Ludwig, Hertzog and Liess ; Kreishman (2) ; Gaumer ; erschner (2) ; Schwankweiler ; Crane I. Co. ; Allentown I. Jo. ; Wiand ; Laros ; Marck ; and those at Hunsingerville, tfhich are so grouped together as to constitute one great rregular excavation, viz : Maple Grove pits ; P. Kline's nines ; J. Barber & Co.'s ; Hensinger mines leased by the A.llentown I. Co.; Thomas I. Co.'s; Hensinger & Saul's; Mickley's ; Hensinger Heirs'; Keifer's ; Desh's.* This southern range is continued eastward across North- ampton county along the north foot of the Lehigh mount- ain as far as the Delaware river opposite Easton, as already described. The second range lies in the limestone country to the north of the first range, and embraces the mines of Ludwig (2) ; Butz ; Yager ; H. Kaiser ; Blank ; Smoyer (4) ; B. *Many of these mines were stopped in 1874 on account of the depression in the iron trade. Some had been abandoned ; some had their machinery standing, ready to be exploited again. They are all located by numbers on the sheets of the Lehigh survey map, executed by Mr. Clark under Pro- fessor Prime's direction, and published with Report D, 1875. Their descrip- tions appear on pages 17 to 24 of that report. 234 GEOLOGICAL SURVEY OF PENNSYLVANIA. Smoyer ; J. Smoyer ; B. P. Smoyer ; Judith Smoyer ; T. Smoyer ; A. Smoyer ; Reub. Romig (2) ; P. Romig ; Werner & Reinhart ; and Lauer. The third range, further north, comprises the mines of Weiler ; Crane & Thomas I. Co. ; Lichtenwallner ; Smoyer ; Geruart ; Sholl ; J. Bastian ; E. Bastian ; and F. Guth. The fourth range, further north, comprises the mines of F. Breinig ; Moser ; T. Breinig ; Whitely ; Fogel ; Schwartz ; Bortz ; Koch ; Grammis ; Gackenbach ; Fischer ; J. & D. Smith ; Haines ; Miller ; Scholl & Co.; Steininger ; Moyer ; Stein ; J. Laros ; Levi Lichtenwallner ; Krcemlich and Lich- tenwallner ; and the trial pits at Chapman's station ; and the mines in the Fogelsville Cove, although these lie really further north next the slate region. Ninety-eight (98) mines, mostly open quarries, large and small, shallow and deep, are named, enumerated and located on the first map of Lehigh county, published with Prof. Prime's first report of topographical work done in 1874 (D, 1875). One hundred and three (103) others were in 1875, 1876, named, enumerated and located on the four-sheet colored map of the county published with Report D2 in 1878. These are classified geographically thus : In the first range, along the foot of the South mountain: Reder ; Desh ; Shelly ; Daney ; Schwartz (Dan.); Emaus I. Co.; Bader; Trexler & Kline; Kline (H.) three; Kline (Jessie); Kemmerer ; Keck & Ritter ; Kline (G.); Stein; Hottenstein ; Apple; Kipping & Holsbach; Seam; Whit- man ; Spinner. North of the Little Lehigh : Reinhart ; Jobst ; Wenner; Kemry & Carbon I. Co. ; Smoyer ; Steiner & Kehm ; Woodring ; Roth ; Glick (L. and C.) two; Acker ; Reinhart. In the middle of the limestone country: Schadt; Rush ; Ritter ; Sheirer ; Mclntire ; Miller ; Biery ;.Wennor ; Roth ; Butz & Belden ; Singmaster ; Butz ; Walbert ; Descher. Northern edge of limestone : Barber & Aimy ; Marck ; Scherer ; Jobst ; Kratzer ; Crane I. Co. ; Wenner ; Guth (D. A.); Thomas I. Co.; Weaver; Klein; Sieger; Crane I. Co.; Gackenbach ; Blank ; Guth(C.); Guth (H.); Henry ; Boyer ; Balliet ; Levan ; Henninger ; Schadt ; Baer. BERKS COUNTY LIMONITE MINES. 235 Mines at Ironton: Kennel (Ironton RR. Co.); Mickley; Ironton Co.; Balliet Bros.; Balliet heirs; Brown; Bitter; Steckle (P.); Steckle (D.); the last two east of Ironton.* Berks county limonite mines. The Lehigh ore belts are continued westward towards the Schuylkill ; but most of mines named, enumerated and lo- cated on the map of Mr. d'Invilliers' Report D3, Vol. 2, 1883, chapter 10, are next to or not far from the Lehigh county line. The limestone valley (between the South mountains and Hudson River slate edge hill) is narrowed down in Berks county to about 2 miles, then widens to about 4 miles and so continues to the Schuylkill. The narrow- ness of it just at the Berks-Lehigh line is brought about by a jog in the South Mountains and two extensions of the slate hills southward toward the jog ; the slates, of course, overlying the limestone. It is remarkable that just here have been made nearly 40 excavations, and that scarcely any ore has been found, or at least mined, in the limestones for the 15 miles west to the Schuylkill ; the two Moselem banks being the solitary noted exceptions, and these lie at the edge of the slate. These facts make it likely and in fact almost certain that the ore deposits on the limestone surface near the county line owe their origin to the damourite slates at the top of the limestone series, which once bridged the * The great Ironton, or old Balliet mine, is one of the geological wonders of the State, an excavation 2000' long, 800' broad and 90' deep, worked for more than half a century. But as the damourite slates of this mine are of an entirely different, higher horizon and later age, namely at the top of the limestone series, it does not properly come into this chapter on the lower damourite slate belt {primal) of limonite ores at the bottom of the series. I have found it impossible to avoid reference in this chapter to all the limo- nite mines of the valley, because of the difficulty of selecting out those which are exclusively confined to the lower outcrop of slate. Some of those in the very center of the valley may be in the lower, or in the upper slates, or in slates of some intermediate horizon. The valley limestones are ex- cessively compressed and crimpled ; so that on lines of anticlinal the lower slates may appear at the present surface (although that is not at all probable except in rare cases); while on lines of synclinal the upper slates may be and probably sometimes are preserved at the present surface. I was also anxious to give in this chapter a general view of the iron ore wealth of the region. The description of the Ironton mines is therefore postponed to a following chapter. 236 GEOLOGICAL SURVEY OF PENNSYLVANIA. valley, and still bridges it half way. And, if this be so, then it is possible that all the 200 and more mines in the limestone belt of the three counties must be referred to the top damourite slates, and not to the Primal^ the bottom. It is an additional testimony to this, that the two greatest limonite mines of the region, the Ironton in Lehigh and the Moselem in Berks, are in the upper damourite between the limestone belt and the slatebelt.* The lower damourite (Primal Upper hydro-potash-mica slate) lying upon the Chiques quartzite, follows the north- ern foot slope of the South Mountains around to Reading. A group of ten limonite banks are located in the cove at the head of the Little Lehigh. south and west of Sham- rock (S. E. of Topton). A mine is just south of Topton ; another, 1 mile S. E. of Bower's station ; two more a mile S. W. of Lyons station ; five more S. of Fleetwood station ; another (Shaefer's) i m. S. E. of Blandon station. In Oley Valley. In the Oley Valley, Hunter's & Weaver's mines are 2 m. S. W. of Friedensburg ; and these are the only limonite banks in the body of the highlands in Berks county except the Bittenbender and Gehman banks 5 m. S. of Alburtis. But. there are indications of a siliceous hematite connected with the Chiques quartzite beds in many other places. The ores of this formation where exploited have been found not only silicious, but so phosphatic and with so little alumina, magnesia and lime as to make cold short iron invariably. These ores however seem in all cases to be the product of the overylying damourite slates, the iron of which set free has found a home in the quartzite, especially where this is in a sandstone condition. f The Udreeore ~ba,rik in Ruscom Manor on the N. flank of Furnace Hill, 1 m. S. W. of Pricetown, was the largest producing bank in the mountains in 1882 ; belonging to *In a following chapter this famous Ironton mine will be described in de- tail (from D2, p. 39, &c., as examined and mapped by the survey in 1875;, because it is the best and most typical deposit of limonite in this region of the state, and the most instructive for the elucidation of the structural rela- tionship between the limestone and slate formations of the Great Valley. t See D3, p. 361. OLEY VALLEY LIMONITES. 237 the Clymer I. Co., and located in the sandstone close to the gneiss ; worked since 1871 by the Clymer I. Co. for Mt. Laurel Furnace ; mostly wash ore ; some bombs ; hand- some specimens of concretions and stalactites ; varieties of gothite, lepidocrocite. turgite, red and yellow ochre ; too cold short for the neighboring Oley furnace ; cheaply mined as an open cut, 70' deep ; ore dipping 70, N. 20 E., 20' thick ; 300' along outcrop ; horses of clay ; 18 to 20 tons per day ; analysis by McCreath : Iron 40.05 ; manganese 3.314; sulp. .003; phos. .522; sil. matter, 22.44. The Warner mine, \\ m. S. E. of Friedensburg. at the junction of Oley slates and limestone, the line of contact crossing the open cut ; Clymer I. Co. for Oley furnace ; damourite slate (turned to white and buff clay), largely used for excellent building brick ; wrought for 18 years ; 10 to 15 tons per day ; ore dips 30 to 50 N. W. (away from slate hill), as a bed 2' to 8' thick underlaid with clay ; shaft sunk (1878) 49' to 2' hard ore bed ; at 56' another 8 foot ore bed (50 per cent, lump); clay between the two beds, but second bed nearly flat, etc. See interesting description of efforts to get water at this dry mine on page 365.* The Hunter mine, 300 yards N. W. of the last (Weaver), was abandoned when visited in 1882, and is accounted almost if not quite exhausted, being wholly in the lime- stone One shaft was sunk 90' through yellow clay, to a 1' bed of white kaolin, under which lay V or 2' of limo- nite ore ; under this a. little black clay holding concretions of carbonate of iron (siderite); under this a thin bed of mixed black, clay and limonite.t * Carbonate of iron (siderite) has been seen here, but apparently in no great quantity. It is important for the genesis of limonite. f This shaft section is extremely interesting, as there can be no doubt that the black clay must have held pyrites and siderite, and by the decompo- sition of these the limonite was produced, precisely as in the case of the Devonian Marcellus ore mines of Mifflin county on the Juniata river, which will be described in a future chapter. The kaolin in this mine has been a good deal mined. The best quality, No. 1 white, used to be sold at from $7 to $15 a ton to Connard's paper mill at Pleasantville,and Burgess's paper mill at Spring City. Opposite Royer's Ford, No. 1 was a deposit 30' by 20' under 6' of cover, pinching out all round. Of the three grades there were about 800 tons. (See four compara- tive analyses by McCreath, D3, p. 368.) 238 GEOLOGICAL SURVEY OF PENNSYLVANIA. The Manwiller mine, 1 m. W. N. W. of Griesermers- ville, Oley township, entirely in the limestone, was started in 1873 and abandoned in 1878 ; there was a fair showing of lump, but the whole was merely a pocket like so many of the smaller limonite banks of the region. About 2000 tons were got. Ore can be seen cropping out in the little Dale Forge limestone valley in Washington township. 5000 tons were taken from the J. Rush bank in Hereford township, now filled with water. 5000 tons were got from one of the Bittenbender banks (in the same township) during 5 years work ; greatest depth of open cut 50'. in limestone and clay ; great quantity of flint mixed with the bottom ore. 1000 tons were mined from the adjacent Gerham bank, but con- demned for its excess of silica.* Schweitzer & Kurtz bank, \\ m. N. E. of Pricetown, and Schaeffer' s at Fleetwood, were new mines in (1882), in limonite which belonged to the quartzite beds. (D3, p. 371.) The Muhlenberg (Beidler] bank, W. of Reading, in lime- stone, an open cut 30' deep, shows much siliceous limonite, with slate and clay holding the ore. Seitzinger bank, a mile nearer Reading, has limestone outcrops east and west of it. The Eureka bank, 3 m. W. of Reading, a 40' cut, yielded cleaner cellular ore, with little or no pyrites, but some oxide of manganese. Cumberland County limonite mines. The limonite mines of Cumberland and Franklin, along the foot of the South mountains, as far as Mont Alto, are described in a special report of the Iron Ores and Limestone Quarries of the Cumberland Valley by Mr. E. V. d'lnvil- liers. f Beginning at the east end of the South mountains, 12 *These banks run parallel to and 800' S. of the magnetic, ore workings higher up the hill in the gneiss, and have nothing to do with that ore. The mag- netite mines of Berks will be described elsewhere. f Annual Report of the Geological Survey for 1886, part IV with two maps. They were also described by me in a private report, with illustrations, published in the proceedings of the American. Philosophical Society of Philadelphia, Jan. 3, 1873. Mr. McCreath's analyses will be found in Report M3, 1881. CUMBERLAND COUNTY LIMONITE MINES. 239 miles west of Harrisburg, we have (going west) the follow- ing limonite mines :* Leidig & Hoffer (30); Beltzhoover (29); Ege (28); Pepper (27); Strickler (26); King (8); Pepper (7); Grove, or Peach Orchard (6); Big Pond (4); G. H. Clever (5); Clever Mam- moth (3); Muslin (39); Chestnut (38); J. H. Cressler (37); J. Bridges (36); all in Cumberland county and south of the Yellowbreeches creek and Harrisburg and Potomac rail- road. Then in Franklin county Ahl (27); McHose (28) on the railroad ; Cressler (29); Koser (30); Southampton (23); Ruby (24); Gochenauer & Rohrer (25); Means (26), all in the ravine of Furnace Run. Then along the Mont Alto railroad Stephen's Pond (8); McNeal (7); Roth (5); Pond No. 1 (9); Pond No. 2 (10); and the group back (E.) of the Pond banks, viz: English (11); Promise (13); Hope (12); Wiesling (15); Limekiln (16) ; White Rock (18); Calliman (17); Guilford (14); then again on the railroad. J. Rock (6); No. 32 ; George (20); No. 8 ; No. 5 ; l$o. 4 ; No. 3 ; No. 2 ; No. 1, of the Mont Alto (1); Mill Bank (3?); Smith and Avery (2); Wythe Douglass (22); Pass Orchard (21); G. Rock (20); and lastly R. McCreary (19); on the Baltimore and Cumberland Valley road. Leidig & Hojfer's bank is a. small abandoned digging in the cove between two of the end spurs of the South Mount- ain, 3 m. S. E. of Boiling Springs. Beltzhoover 'bank, 1350' long, 180' wide and 80' deep, on the north west side of the spur ; open cut to south separated from main ore by 200' of yellow clay ; ore body not more than 40' thick ; 60,000 tons won.f * On the small maps in Ann., 1886, part IV, p. 1437, the mines are num- bered, and the names are given in the columns at the bottom of the maps ; but on the larger maps in the Atlas to the volume (part IV) the names alone are given. It is a pity that no geographical arrangement of mines according to numbers was possible ; but I here endeavor to diminish some- what the embarrassment thus produced for the reader by taking the mines along the foot of mountain in order first, especially as these are certainly in the Primal hydromica or lower damourite slates beneath the limestone. t Here the ore dips distinctly 40 to 50 N. and N. E. away from the mount- ain. Variegated clays overlie the ore on the north, and are manganiferous Ore rests on reddish sandy slate, beneath which no ore is found. The old Crockett bank is further west up the hollow. The Siplinger bank is also long abandoned. Trial pits sunk westward found no ore. at least for 30 240 GEOLOGICAL SURVEY OF PENNSYLVANIA. Ege bank (Big bank) of Phila. & Reading I. Co. 2 m. S. of Boiling Springs, an immense excavation, practically abandoned (in 1886) and the shafts and faces fallen in ; 1500' long, 250' wide, 70' deep at south end. At the west end the ore was drifted on and found always dipping steeply S. E. into the mountain, thickening and thinning but " with an average thickness of 25 to 40 feet." Pockets of manganese-iron ore edge the main body, and weathered into sooty clay masses or large spots in the white clay mass. The wash ore is mostly removed ; the remain- ing solid bottom ore is of poorer quality, and expensive to mine. The greatness of this mine may be judged from the fact that the lease called for 50,000 tons per annum ; but it never actually yielded more than 35,000 tons in any one year. Pepper, or Old bank, near the head of a little limestone valley extending around a ringer of the mountain 2 m. S. W. of Boiling Springs ; trench 375' long, 150' wide, 45' deep ; east end wall, buff clay and sand, wash ore ; west of plane, white clay streak 12' wide ; balance, good and poor ore ground mixed ; many black manganese blocks ; abandoned (1883). In 1873 I saw a stope 70' high, showing 25' wash ore above, 45' solid ore below, arranged in fine anticlinal arch;* shafts from the floor down went through 35' more of solid ore, making 100' of ore ground in all. At least 100,000 tons beneath the surface. A low tunnel was driven in white clay along the N. edge of the ore body to keep it in sight, and the tunnel doubled on itself N. W. showing an anticlinal structure, such as I saw in the heading. See foot note to d'Invillier's, p. 1468. Toward the east end the ore body swelled to 400' broad. No. 3 tunnel 775' long, from the RR. to the ore, was cut to avoid a plane. It was driven 650' before the ore was reached, proving again the strange S. E. dip of the damourite slate formation here. See many other interesting details in d'Invillier's report; among them that the manganese deposits limit the ore in this as in other banks in this vicinity. Eastward the ore shelves up and covers a wedge of limestone 160' thick. Trial shafts eastward have not been very satisfactory ; but it is supposed that the ore is practically continuous to the Beltzhoover bank, 3700' distant. There is a considerable amount of shot ore largely mixed with quartz. The trial pits were usually in a greenish talcose slate (soapstone) of the miners. *See my pen and ink sketch of it in Amer. Phil. Soc. Proc., Jan. 3, 1873, page 9. I estimated a possible 9,000,000 tons along the little valley leading up to the Strickler mine ; but it must have been an overestimate. MOUNTAIN CKEEK LIMON1TE BANKS. 241 of ore were taken out prior to its abandonment ; ore excellent for gun metal ; used at Boiling Springs furnace 75 to 85 per cent, to 15 'to 25 per cent, limestone ore, hematite or magnetic.* Strickler bank, on the high divide back of the finger mountain and at the head of the vale of the Old mine (f m. W. S. W. of it). It is a mile E. of Mt. Holly Springs (paper mills). The bank in 1883 was 200' long by 120' wide and W deep to level of water ; the mine having been long abandoned after yielding possibly 40,000 tons.f The ravine descending from the high divide at the S trickier bank west down to the Mt. Holly banks corres- ponds to the ravine descending from the Streckler bank east to the Old bank ; and the line continued west past Mt. Holly banks is straight up Mountain Creek valley to the Pinegrove Furnace banks, in the heart of the moun- tains. Why Mountain creek did not keep on and issue at the Old bank is an interesting structural (and erosion) question. No ore has been found in the test pits along the ravine. Mountain Greek limonite banks. The first two banks ascending the valley are the Mt. Holly mines, 1 m. S. of Mt. Holly Springs, on the south side of the creek, 150 yds. up the slope at the foot of the mountain. They were both abandoned when visited by * Carlisle Iron Works property on which all these banks stand is 10,000 acres. Furnace recently (1883) improved, with hot blast, > &0 1 s GO 02 3 a i 3 1 North Mountain, 300' 300' 450' 400' 370' 300' A. T. South Mountain, 250' 250' 180' 150' A. T. * For all these levels see Report on Levels, N, 18?a 272 GEOLOGICAL SURVEY OF PENNSYLVANIA. It is plain to see that the three great rivers which drain a large portion of four states, Virginia, Maryland, Penn- sylvania and New York, have cut the deepest channels ; and that all three enter the Great Valley at exactly the same level, 300' A.T. ; while the smaller intermediate rivers, Lehigh, Schuylkill and Swatara, have cut down only to 370', 400' and 450'. From the Delaware to the Susquehanna water gaps in the North mountain the distance (in a straight line) is just 100 miles. From the Susquehanna to the Potomac water gaps (in a straight line) is 75 (but by the curve of the North mountain 85) miles. From the Potomac to the James river water gaps, the valley of Virginia is straight for 160 miles, and instead of being crossed by intermediate rivers, is drained lengthwise, northward, into the Potomac, by the Shenandoah river 120 miles long. The various sections of the Great Valley are drained by large streams flowing from divides both ways to the trans- verse river channels ; thus : (1) The Little Lehigh eastward into the Lehigh and so into the Delaware ; (2) Antilauna (Maiden) creek westward into the Schuylkill ; (3) Tulpe- hocken creek eastward into the Schuylkill ; (4) Swatara creek westward into the Susquehanna ; (5) Connedogwinit and Yellow Breeches creek eastward into the Susquehanna ; Conecocheague creek westward into the Potomac. ylk ek Divi Li 250' 783' 310' 501' 200' 270' 485' 230' 150' THE GREAT VALLEY. 273 The divides at the heads of these lateral or in-valley streams represent the general level of the whole floor of the valley across the state ; and the levels of these divides are indicated by the summit stations of the various railroads which, together, make a continuous line of traffic from end to end. See table at the foot of last page. By this showing the floor of the Great Valley is lower between the Delaware and Susquehanna, than between the Susquehanna and Potomac. But it must be remembered that railroads follow depressions, and seek the lowest place on a divide ; and that from Harrisburg to Newville (30 miles) the Cumberland Valley railroad grade reads : 322', 357', 436', 427', 458', 477' (at Carlisle) and 533', mostly on a pretty level limestone plain. In the next eleven miles it rises to 654', and suddenly then to the "summit" 783'; falling again at Chambersburg to 618' and at Greencsstle to 585'. So that in reality we may feel safe in assuming a gen- eral level of the floor of the valley across the whole state, as traversed by the lines of railroad, at about 500' A. T.* * A line of levels carried along railway lines from Sandy Hook via Hagers- town, Md., Gratton, Va., Athens, O., Mitchell, lad., to St. Louis (published in Coast Survey Report for 1882, page 521-f, with a map of the route, page 557), fortunately for our present purpose, follows the Great Valley from Easton, through Allentown, Reading, Lebanon, Harrisburg, Carlisle and Chambersburg to Hagerstown, and then ascends the valley of the Potomac on its way west Easton. (No. XIX) Cut on one of the central piers of the RR. bridge across the Lehigh river, 214' above mean sea level. Easton. (XX) Cut W. corner of jail, on foundation stone, 357.5'. Easton. (U) Sill of blind window, E. side of court house, 363.5'. AHentown. (I) Cut on sill of basement window S. side of front entrance of jail, 321'. One and a half miles W. of Allentown. (XXI) Cut on N. W. corner RR. bridge over wagon road, 295 5'. One-half m. W. of Macungie station. (XXII) Cut on top stone, N. side RR. bridge over small run, 383.5'. Reading. (J) Cut on coping stone, E. abutment of N. E. RR. bridge at RR. depot, 264'. One-quarter m. E. of Shamrock station. (XXIII) Cut on N. E. corner RR. bridge, 424.5'. One-eighth m. E. of Robesonia station. (XXIV) Cut on pier of small bridge, 432.5'. 18 274 GEOLOGICAL SURVEY OF PENNSYLVANIA. But the lines of railroad connect the principal towns of the valley ; and these have all been built on the most fertile and smoothest'part of the valley floor, viz : its southern belt composed of limestone soil ; and it is to this belt alone that the above average of 500' A. T. applies ; its northern belt is rougher and higher. The two belts. The Great Valley is divided geologically lengthwise, from end to end, into two belts of country ; one, next the North mountain, a slate belt; the other, next the South mountain, a limestone belt. The line of separation in some places runs for miles remarkably straight ; in other places it is remarka- bly crooked ; but along the whole course it may be called the middle line of the valley ; the slate region being to the north and west of it ; although occasional streaks of limestone ap- pear in the slate belt, and occasional patches of slate in the limestone belt ; but the relative proportions in width vary, the slate belt being nearly every where the wider of the two, and in parts of the valley twice or even three times as wide as the limestone belt. In Cumberland county, however, the limestone belt is a little wider than the slate belt. One and a halfm. W. of Womelsdorf station. (XXV) Cut at E. end of base of N. wall of overhead bridge RR., 483.5'. Lebanon. St. Mary's Catholic church. (XXVI) Cut on S. side of south- ernmost front entrance ; centre of cross, on white marble block, 474.5'. Lebanon. (K) Bottom of square hole in top of marble post in ground oi Mr. P. L. Weiner, S. E. corner Eighth and Chestnut streets, 465.5'. One and a quarter m. W. of Annville. (XXVII) S. W. corner RR. bridge over Joe Crider's dam, 405'. Swatara bridge (RR.) (XXVIII) Cut on stone parapet between Beaver and Hummelstown station, 367.5'. Harrisburg. (XXIX) Centre of top surface of monument in capitol grounds, marking astron. stat. coast survey, 356.5'. (L) Cut at base of pillar at S. E. corner capital building, 367.5'. Carlisle. (M) Cut on base of column at W. side of jail entrance, 472.5'. Shippensburg. (XXX) Cut on water table of house and store of W. C. J. Reddig, N. W. Corner Main and Railroad streets, 654'. Chambersburg. (N) Cut on pedestal at base ofN. pillar of court house front, 620.5'. Greencastle. (XXXI) Center of cross cut in stone in front wall of RR. depot, 7" above sidewalk, S. of entrance, 588 5 . Hagerstown. (A) Cut on water table of court house, corner Washington and Jonathan streets, on Jonathan street side, 552.5' = 168.3402 meters, THE GREAT VALLEY BELTS. 275 The Slate belt has an average general level about two hun- dred feet higher than the limestone, say 700' A. T. This is strongly marked all the way from the Delaware river at Belvedere, to the Schnylkill river at Leesport, by a steep hill-slope down from the higher slate floor of the valley to its lower limestone floor; and this step in the surface is made more remarkable by narrow openings or ravines from which issue numerous small water courses heading in the recesses of the slate land, and at the foot of the North mountain. This elevated terrace-like edge of the slate belt contin- ues, although in less regular style, through Berks into Lebanon county ; can be recognized in Dauphin and Cum- berland counties ; but gradually becomes less conspicuous in Franklin county. There is no mistaking, however, the greater relative height of the slate belt everywhere along the Great valley. The distinction is emphasized moreover in all cases where limestone coves invade the slate belt, and where slate ridges traverse the limestone belt. It is evident to the most in- different spectator that the surface of the limestone land lies naturally lower than that of the slate land,* but a clear exhibition is made of it by the contour-line maps of Lehigh and Northampton counties published with Reports of Progress D, D s and D s . These maps show the relative levels of the whole limestone belt of the valley, of the edge of the slate belt, and of the slopes of the South Mountains, all the way from the Delaware to the Schuylkill rivers, f No contour -line surveys of the Slate belt have been made anywhere along the valley ; and until such surveys have been made and a continuous contour- line map of it has been * The reason for it will be given further on, in connection with the under- ground cavernous condition of the limestone belt. t It is evidently desirable that the Legislature should provide means for continuing this topographial survey westward across the Susquehanna river to the Maryland line. In Franklin and Cumberland counties the South Mountains have been elaborately surveyed in the same manner, and down their western slopes to the south border of the limestone belt ; but the means of the survey were to olimited to bear the expense of carrying the work across the limestone land to the edge of the slate land. 276 GEOLOGICAL SURVEY OF PENNSYLVANIA. C/i.XXII,p/ate/T Conedoguincl Creek in Cumberland Co. fa. THE GKEAT VALLEY BELTS. 277 I.&S'S 278 GEOLOGICAL SURVEY OF PENNSYLVANIA. executed, no entirely accurate knowledge of its geological structure can be obtained. We know, however, that it is everywhere very much crumpled into narrow folds ; and that some of these folds are so sharp that the limestone for- mation everywhere underlying it comes occasionally to the surface. The north edge of the Slate belt is high up on the slope of the North mountain ; in fact the outcrops of the top layers of the formation run only one or two hundred feet beneath the crest of the mountain. Synclinal mountains of IV in III. The upper part of the Slate formation is coarser or more massive than the lower part, and in some places contain pebbles in such abundance as to become conglomerate rock. Therefore, as in some places along the south edge of the slate belt the underlying limestone comes to the surface along the middle line of an uncommonly sharp and strong up/old so in some places along the north edge of the slate belt the upper and coarser slates have been preserved along the middle line of an uncommonly -sharp and deep down- fold. In two notable cases even the Medina sandstone No. IV has been thus preserved ; and this is the explanation of Hole mountain in Lebanon county, and ParneWs Knob mountain in Franklin county both of them standing out in front of the North mountain. (Plate, page 285.) Hole mountain in Lebanon county is a ridge five miles long ending at the Swatara river. Its top is a V-shaped pinched stripe of the sandstone No. IV, held in a vice of upper slates. Along the banks of the Swatara the slates can be seen going down in front of it and coming up behind it, and then going down again under the North mountain. ParneW s mountain, in Franklin county, is of precisely the same character, but longer, and produced by a deeper down-fold (synclinal) of the slate belt. It is 10 miles long and entirely cut off from the North mountain behind it by the narrow straight upfold (anticlinal) of Bear valley. The down-fold is so deep that a regular canoe of the sandstone THE GREAT VALLEY BELTS. 279 No. IV has been preserved, its two crests being separated by a middlegroove in which lie some of the lowest soft layers of the Clinton red shale formation No. V. In studying Hole mountain we make a first step towards understanding the geology of all Middle Pennsylvania ; in studying ParneTC s mountain we make a second step ; and if we consider Jordan's Knob behind it, we take the third step. For the North mountain here (at London) doubles back upon itself (see page plate) and after zigzaging around Horse valley, Amberson's valley and Path valley, comes back to Loudon and runs on, as if nothing had happened to divert it from its course, into Maryland. But all these zigzags represent high upfolds and deep downfolds in the slate formation No. Ill which underlies the mountain every- where ; and not only in the slate formation No. Ill, but in the limestone formation No. II which lies still deeper everywhere under the slate ; for along the middle of Am- ber son' s valley and Path valley the underlying limestone has been brought up and bared at the surface ; while the steep, dipping slates are confined to the side hills and to the steep mountain slopes.* Anticlinal bells of limestone in the slate. The great upfold (anticlinal) of Path valley runs on from Loudon southward bringing to the surface in front of Cove mountain a narrow belt of limestone. The upfold of Bear valley runs on also, by Bridgeport, Mercersburg and Simpstown, and brings to the surface another long narrow belt of limestone. Between these two parallel limestone strips runs a strip of slate, preserved in the downfold (synclinal) of Jordan's Knob. The Loudon and the Mercersburg strips of limestone termi- nate in two coves at the Maryland line, the Punchbowl (or Corner), and Blair's valley; and these two coves lie between Cove mountain and two mountain spurs in Mary- land (Two Top mountain and Casey's knob) which ex- actly correspond to Jordan's knob and Parnell's knob * Along the north side of Path valley runs a great fault, so that the under- lying limestone has slipped, up against the upper slates on the mountainside. 280 OEOLOGICAL SURVEY OF PENNSYLVANIA. Ch.XXH, plate 3. THE GREAT VALLEY BELTS. 281 Cross section of the Great Valley from near Cowan's Gap south through Scotland to the South Mountain in Franklin County, ?a. 282 GEOLOGICAL SURVEY OF PENNSYLVANIA. towards which they look, the distance being about 14 miles. Blair's valley is the easternmost of the two coves, and corres- ponds in all respects to Bear valley between the Jordan and Parnell's knobs. The geology of this part of Fayette county is beautifully simple, symmetrical and instructive. It is rendered still more instructive by the following particular : A third upfold (anticlinal) runs in front of Parnell's mountain, and brings to the surface in the slate belt the underlying limestone in a third long narrow slip, which starts at a point at Strasburg, and is crossed by the Cham- bersburg pike just west of St. Thomas, where it is 1% mile wide. After passing St. Thomas southward this strip of limestone becomes nearly 5 miles wide at the Greencastle- Mercersburg pike, and so passes on into Maryland. The slate belt, which is seven miles wide at Newville in Cumber- land county, 6 miles wide at Chambersburg in Fayette county, is thus narrowed to 3 miles at Welsh run and the Maryland line ; the main limestone belt 13 miles wide bor- dering it on the east, and the Welsh run limestone belt 4 to 5 miles wide bordering it on the west. This widening of the Welsh Run limestone belt south- ward from St. Thomas might have been produced in two ways ; it was actually produced in a third way exactly con- sistent with all that has just been said. (1) It might have been produced by a swelling upward of the Strasburg anti- clinal after passing south by St. Thomas ; or (2) it might have been produced by a flattening out of its dips on both sides ; but it actually was produced (3) by two other addi- tional anticlinals running alongside of (in front or east of) the Strasburg upfold; one, which may be called the St. Thomas anticlinal, brings up a strip of limestone south of St. Thomas ; the other, the Rock Spring anticlinal, which brings up a little prong of limestone 3 miles S. of St. Thomas, and after crossing the slate belt obliquely produces the Rock Spring limestone cove 3 miles N. of Chambersburg. These three up-folds in the slate belt of middle and northern Franklin combine to keep the limestone up to the surface along the Wetsh run belt near the Maryland line. THE GREAT VALLEY LIMESTONE COVES. 283 Limestone coves in the slate belt edge. The limestone indentation in the edge of the slate belt at Rock Springs is about 3 miles deep. (Plate, page 285.) Another similar indentation of limestone in the south- east edge of the slate belt occurs at Fairview and Middle Spring on the Cumberland county line (page plate). Both these indentations point southwest, showing that the anti- clinals which upheave the underlying limestone through the slate sink in that direction. Another indentation is shown upon the map at Newville in Cumberland county, but it points northeast. Newville is built in this little limestone cove and has slate hills all round it except to the west. The outlines of slate show a downfold (synclinal) running just south of the village. Another very little indentation in the south edge of the slate belt is made at Plainfield, 4 miles west of Carlisle, and the arrows on the map along the creek here show that the prong of slate is a true synclinal. Another very pretty indentation of limestone in the slate belt, two miles long and pointing (like the last two) east- ward, lies back (north) of Kingston, six miles east of Car- lisle. Here the arrows on the map instead of explaining the facts are very confusing, all of them pointing south at various angles. The cause of this will be explained here- after, but it may as well be mentioned here that most of these upfolds (anticlinals) and downfalls (synclinals) are not only squeezed tightly together, but so bent over north- ward (as if by a pressure from the South mountains) that the strata which ought to dip north dip south, and cannot therefore be easily separated from those which ought to dip south. In other words, one-half of the south dipping strata are in reality overturned and lie with their upper faces downwards. Another limestone cove in Cumberland county runs up into the south edge of the slate belt in the opposite direc- tion (northeast) behind the long prong of slate which points out half a mile west of Kingston along a deep downfold (synclinal) in the limestone belt. (Plate, page 276.) No such interruptions of the south edge of the slate belt 284 GEOLOGICAL SURVEY OF PENNSTLVANIA. Ch.XXU, plate 5~. Specimen section ofwaveA in 7o tiluttrcdc anticlinal Coves of JT, and. synclinal Prangs cdong-tke center line cfthc ^eaJ;Yaflcy, Cumber/and MOURSVILLE ,tt TOx FAIRVIEW ; t^ ( -25' 90 I ,40 so; \20 diagonal and 'transverse- limes-Tone tL'jj,). ,. THE GREAT VALLEY LIMESTONE COVES. 285 limestone and Slate belts- (M^HT) of the, 9reat Yallcy. 7o illustrate Chap, XXII of Ttnal Report IWf, T / 4'" ' NV ' / ^N * '' ji Chamber s'&ury *$ ^ ( * r& ** ' X . .jV 286 GEOLOGICAL SURVEY OF PENNSYLVANIA. occur in Dauphin and Lebanon counties. In Berks county, approaching the Schuylkill, they become very numerous, but produce a state of things geographically so curious and important as to require a special description. East of the Schuylkill the edge of the slate alternately advances upon the limestone and retreats from it in a series of small irregular curves which scarcely disturb the straight line of the contact; but there is a decided cove at Moselem, and another at Kutztown, both pointing west; and together they broaden the limestone belt and contract the slate belt a trifle. At Monterey near the Lehigh county line, a cove points northeast. In Lehigh Co. limestone coves back of slate prongs play a great role in the geography. One is produced by an an- ticlinal passing Trexlerville ; another deeper one lies north of it ; a third and very large one is that of Jordan creek ; a fourth is the Ironton cove. All these point west, and have the effect of reducing the breadth of the slate belt on the Lehigh river to one-half of the breadth it has on the Berks-Lehigh county line. In Northampton county the many irregularities in the face line of the slate belt are all of the nature of coves ; but in no case are they shut in behind synclinal prongs of slate. But on the other hand we have here smajl circuses of lime- stone completely enclosed in the slate belt, back of* its edge, anticlinal in their structure, and teaching the same lesson as the coves, viz : that the limestone formation No. II passes down (northward) underneath the slate formation No. Ill, and is here and there brought up through it to the present surface by upfolds or anticlinal waves. Synclinal belts of III in II. Prolong two limestone coves (one pointing east the other pointing west into the edge of the slate belt) until their opposite points meet, and you will have a strait of limestone between the mainland of slate and a long narrow island of slate in front of it ; the strait of limestone being an anti- clinal or upfold, and the island a synclinal or downfold, or basin. SYNCLINAL BELTS OF III IN II. 287 Such basins of slate in the limestone belt are numerous enough to prove that the slate formation No. Ill originally entirely covered the limestone formation No. II. In Franklin county one commences 3 miles South of Chambersburg and runs 4 miles, crossing the South Penn RR. mile from the Marion junction. The arrows near Marion point the limestone going down very steeply under the east edge of the slate strip. This slate strip is un- doubtedly a closely folded downfold (synclinal). The other is a similar little strip of slate half a mile west of Greencastle, a few hundred yards wide, a mile or so long, and separated from the edge of the slate belt by a strip of limestone only a few hundred yards wide. An arrow at its north end pointing east and three others along the rail- road pointing west show that this little strip of slate also lies in a closely folded trough in the limestone. Returning now to the eastern end of Cumberland county, the map shows the slate belt suddenly widening from 3 miles at Kingston and Hogestown to 5 miles at the Susque- hanna river. Its edge makes a beautiful curve to the river at Bridgeport and Harrisburg. Part of this curve is a great fault, of which more will be said hereafter, the limestone country has been etevated and the slate country depressed ; so that the Connedogwinet creek, however often it tried to break through the wall, was never able to do more than scoop little semi-circles from it at various points along the line ; and this explains the remarkable loops of the creek. In Dauphin county the edge of the slate belt runs on east nearly straight for seven miles to Beaver station on the Lebanon Valley railroad, the railroad between Harris- burg and Beaver keeping on the limestone. From Beaver across to the North mountain is all slate, and the belt is 8 miles wide and continues of that width into Lebanon county, its south edge being a very even line and nearly straight. But between Beaver and the Swatara river towards Hum- melstown there is a space of about a mile where the slate belt throws a projection southward over the limestone ; and 288 GEOLOGICAL SURVEY OF PENNSYLVANIA. this projection turns west and forms a belt of slate land in the heart of the limestone belt, a mile or two wide, extend- ing back 6 miles past Church ville to the Susquehanna at New Cumberland. The river flows across this slate belt 3 miles below Harrisburg. At New Cumberland (on the west bank of the river) this slate belt is scarcely half a mile wide ; but it keeps on west, in a trough of the limestone, 8 miles, and ends in two blunt prongs one to the north and the other to the south of Shepherdstown. Before coming to an end it broadens out to a width of two miles, with such varieties of dip as to baffle all explanation. Only it is evident that this belt of slate overlies the limestone, and runs east and west about 12 miles, splitting the limestone belt into two ; just as the three slate belts of Southern Franklin county split up the limestone belt into four. In Lebanon county the slate belt is unbroken by the ap- pearance at the surface of any large appearances of the un- derlying limestone. Its width from Lebanon to the Swatara gap in the North mountain is 9 miles. Its south edge is quite straight as far as Lebanon ; there bending a little it runs almost straight into Berks county. The Union canal on the north side of Lebanon marks the contact of the lime- stone sinking beneath the slate. The Ime passes one mile north of Myerstown. The limestone belt is 1 miles wide on the Dauphin-Leba- non county line ; 5 miles wide at Lebanon ; G miles wide at Shafferstown; and 6 miles wide at the Lebanon-Berks county line. No strips of slate have been preserved on the limestone belt, except at its southern edge, where large tracts of slate may be supposed to overlie the limestone where everything is covered up by the comparatively recent Mesozoic Trias red shale formation, to be described further on. The edge of one of these slate tracts extends for 4 miles at Cornwall, and is visible for a mile in width along the rail- road to the mines.* *There may be some doubt about these slates being No. III. They may be tbe slates beneath the limestone. SYNCLINAL BELTS OF III IN II. 289 Another semi-circular slate tract 2 miles long (E. and W.) and 1 broad (N. and S.) appears, at Shaefferstown. The limestone dips beneath it all around its eastern, north- ern and western sides, there can be no doubt about its being a preserved portion of the slate belt, now separated from it by an eroded interval of just 5 miles. The south border of this patch is overlapped by the edge of the great Mesozoic (Trias) red shale formation of Lancaster county. How far south the slates extend under the red shale is not known ; but no slates appear on the limestone in the Manheim, Ephrata and Conestoga valleys in Lancaster county south of the red shale. In Berks county the slate and limestone belts of the Great Valley are so intermingled that no general description would be understood.* While the northern or main part of the slate belt runs to and across the Schuylkill, long prongs and strips of slate cross the limestone belt in the triangular enlargement of the Great Valley between- Womelsdorf, Leestown and Reading ; and long strips of limestone traverse the slate belt north of Womelsdorf and Bernville on the Union canal. Southern edge of No. II. Having thus traced the contact of the limestone and slate belts along the middle line of the great Valley from the Maryland state line to the Schuylkill river in Berks county, and pointed out the streaks of limestone coming up through the slate, and the prongs and ridges of slate still left un- eroded on the limestone, in all four counties, it will be proper to describe the southern edge of the limestone belt, and show how essentially different it is in Franklin and Cumberland, from what it is in Dauphin and Lebanon. The southern edge of the limestone belt in Franklin and Cumberland counties runs along the foot of the South mountains to their eastern termination 11 miles west of the Susquehanna river. Here it turns round the end of the * It can only be understood by an examination of the colored geological map of Berks county, made to accompany Report D3, Vol. Ill, which re- mains unpublished, except as one of the maps in the Hand Atlas Report X. 19 290 GEOLOGICAL SUKVET OF PENNSYLVANIA. mountain southward and is immediately lost beneath the Mesozoic Trias red shale. It is evident that the limestone of eastern Cumberland county and the limestone of middle Lancaster county are connected underneath the Trias red shale belt which sepa- rates them at the present surface by a breadth of more than 10 miles measured along the river. Whether the Cumberland county limestone and the York county limestone are also connected underneath the Trias red shale directly across a distance of 17 miles, is less cer- tain. The doubt arises from the possible underground con- nection of the South mountain rocks beneath Dillsburg, Rosstown and Liverpool with Chiques rock at Columbia. If such be the case, we must draw the edge of the under- ground limestone belt from Yellow Breeches creek (2 miles north of Dillsburg) to New Holland at the bend of the river, and so on towards Lancaster city. But, on the other hand, as we do not know what has caused the depression in which the Trias red shale was de- posited, we cannot tell how deep it may be ; consequently, we cannot tell whether or not the limestone in York county covers the South mountain rocks under the Trias red shale. The main point is that, when the South mountains come to an end, the limestone belt becomes covered with Trias red shale, the north edge of which is of course the south edge of the surface limestone belt in eastern Cumberland, across Dauphin and nearly across Lebanon county. Not until we reach the eastern corner of Lebanon does the south- ern edge of the surface limestone belt rest again against South mountain rocks. Here a small isolated mountain mass called South mount- ain in Lebanon county and Mulbaugh s Jiill in Berks county, separates the limestone belt to the north of it, from the red shale belt to the south of it in Lancaster and Ches- ter counties. East of Mulbaugh's hill the red shale laps around and again covers the south edge of the limestone as far as to the Schuylkill river below Reading. East of the Schuylkill river the South mountain gneisses THE GREAT VALLEY. 291 rise in the range of highlands, with the great valley of lime- stone at its north foot, and so continues through New Jersey and New York into New England. Mulbaugh 's hill at the corner of Lebanon, Berks and Lancaster counties is therefore an isolated piece of the highlands about 2 miles broad and 10 miles long, surrounded on the north by limestone and on the south by red shale ; but underground no doubt entirely surrounded by lime- stone ; for the limestone is seen going down under the red shale at both ends of it ; and there is every reason to believe that the Trias belt south of it, which is not more than 6 miles broad at the west and 10 at the east, occupies a buried limestone valley of unknown depth. We have then in Cumberland, Dauphin, Lebanon and Berks counties an extraordinary phenomenon, which has a most important bearing upon the river drainage of the whole Atlantic coast. The great range of the South mountains which otherwise extends continuously for many hundred miles, from its southern end in Georgia to its northern end in New England, is here broken by a gap 60 miles wide, I. e. from Dillsburg in York county to Reading in Berks county. A great gateway through which the greatest river of the coast (the Susquehanna) drains the back country into the greatest bay of the coast (the Chesapeake) ; and the breadth and depth of the bay correspond to the area and volume of the river, which has been filling it during all the ages since the Coal. And in this gateway stands a pillar (Mulbaugh s hill) to mark the continuance of the range un- derground. Relation of the South Mountain, uplift to No. II. Had it not been for this remarkable break in the South mountain-Blue Ridge-Highlands range of the Atlantic sea- board region of the United States, it might have been sup- posed that the limestone formation No. II was deposited in a sea, the southeastern shore of which lay at the north- western foot of the South mountain range, then in existence. But the South mountain range was not then in existence. 292 GEOLOGICAL SURVEY OF PENNSYLVANIA . The sea extended to that part of the surface of the globe now covered by the Atlantic ocean. This fact is made known in several ways : (1) By the great thickness of the formation at the foot of the mount- ain range ; (2) by the existence of faults along the foot of the mountain range ; and of course faults presuppose the spread of the formation southeast of the faults ; (3) by the appearance of the limestone formation in valleys between the parallel ridges of the mountain range ; for such lime- stone valleys can only represent fragments of the general limestone outspread preserved in deep troughs ; (4) by the appearance of the limestone along the southeastern foot of the mountain range ; as, for example, in southern Berks and Northampton counties, in New Jersey and New York; (5) by large areas of the limestone formation between the South mountain and the present Atlantic coast ; as, for example, in York, Lancaster, Chester and Montgomery counties ; but chief (6) by the great expanse of the forma- tion (both covered and not covered by Trias red shale), through the 60 mile opening in the range above described, far away towards Maryland. The numerous relics of the limestone formation No. II, preserved as small isolated areas, in southeastern Pennsyl- vania, taken in connection with the isolated areas remain- ing in the heart of the mountain range, suffice to prove that it originally extended in an unbroken sheet, and probably in a nearly horizontal attitude, over all the United States and Canada ; and that it probably now underlies the Creta- ceous and Tertiary belt of the Atlantic and Gulf States, and perhaps the whole of the Atlantic ocean, the Gulf of Mexico and the Caribean Sea, covered of course by less ancient Palseozic, as well as by Mesozoicand Kainozoic formations. It follows that the uplift of the South mountain must be later than the limestone and slate formations of the Great Valley. The date of the birth of the range can even be fixed with a near approach to truth. Its upheaval seems to have been in some sense the cause of the folding of all the formations of middle Pennsylvania of the more gentle waves in western and northern Pennsylvania, and southern NewYork, and of the great faults of Virginia and Tennessee. THE GREAT VALLEY. 293 Now, as these foldings and faults affect the Coal measures No. XIII at the top of the series, just as seriously and in precisely the same manner as they affect the lowest forma- tions of the series, the sandstone No. I, the limestone No. II, the slate No. Ill, the sandstone No. IV, &c.,' the fold- ing action must have taken place after the Coal measures had been deposited. On the other hand, the Mesozoic (Trias) red shale formation next following in age the Coal measures lies quietly, as we have seen, over the upturned edges of the older series, and therefore the folding action must have begun and ended in the interval of time between the deposite of the last Coal measures (Permian of Green county) and the first or bottom beds of the Mesozoic strata which we see lying sometimes upon the gneiss, sometimes on No. I, sometimes on No. II, along a line east and west of Norristown in Montgomery county and elsewhere. If the folding action was produced by a push of the whole Atlantic coast region northwestward as it evidently was for there is a general overturning of the tops of the folds in that direction the push must have been connected with the rise of the whole range of the South mountains from its northern to its southern end ; for the folded country is a thousand miles long by five hundred broad ; and the im- mense height of the upfolds (anticlinals) and. depth of the downfolds (synclinals), amounting variously to 5 miles vertical, shows that nothing less happened than a shifting back of the whole Atlantic belt of the earth's crust north- westward a distance of at least 4.0 miles. The mountains thus created were evidently as grand as any more recently produced in any part of the world, the Andes and the Himalayas for example. But these consist of the last deposits of the ocean, and have so lately ascended into the air that, although their destruction is going o n with great rapidity, many of their summits are still more than five miles high. Whereas, a like process of destruc- tion has been diminishing our old Pennsylvania mountains for many geological ages, so that not a trace is left of their original magnificence ; the edges of a few of the harder formations make continuous ridges and these not more than 1000 or 2000 feet above the general surface of the low lands. 294 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER XXIII. Why is- there no coal in the Great Valley f The answer to this often asked question is easy, short and practical : No coal beds can be found in the Or eat Valley because the Coal Measures which once covered the region have all been swept away into the Atlantic Ocean. The geological structure of the Great Valley, taken as a whole, is simple and easy to understand. It has large features not to be misunderstood ; in fact visible at a glance upon the colored geological map of the State, where a band of blue (limestone) and a band of gray (slate) run side by side its whole length across the State. I will recapitulate in a few short sentences the principal points of the last chapter so that they may be kept in mind. 1. The South Mountain sandstone (No. 2) is older than the limestone formation in the valle} 7 , and passes down under it to make a foundation for the whole valley and for all Pennsylvania, New York and Ohio to the northwest of it. 2. The limestone strata (No. II.) are older than the slates of No. Ill, and of course underlie the slate belt ; except where the slate belt is thin and worn away, letting the underlying limestone appear in the coves. The whole lime- stone belt was once covered by the slate formation. As the cleaning away of the slate from off the limestone belt has been always going on, and is still going on, only isolated patches of the lowest part of the slate formation remain here and there on the limestone belt. 3. The slate formation (No. III.) is older than the North mountain sandstone and passes under it northward. 4. The North Mountain sandstone (No. IV.) descends in its turn, northward, beneath the formations of Pike, Monroe, Carbon, Schuylkill, Perry and Fulton counties. We shall see in succeeding chapters how formations II, III, IV rise several times to the surface in middle Penn- sylvania ; every time making a limestone valley surrounded THE GREAT VALLEY. 295 by a slate belt and by a mountain like the North mountain. Then we shall see them plunging vertically to a great depth beneath the Allegheny mountain, along the top of which runs the first bituminous coal basin. Here we see all the formations from IV to XIII piled upon them. In Huntingdon county all the formations from IV to the Broad Top Coal measures (XV) are piled upon them. Even close by the Great Valley, in Dauphin, Schuylkill and Carbon counties, all the formations from IV up to the top of the Anthracite Coal measures (XVII) remain piled upon them ; the limestone No. II lying at- the enormous depth of 30,000 feet beneath the city of Pottsville. Just as we see along the Little Juniata all the formations from XIII in the Allegheny mountain to IV in Bald Eagle mountain rising (southeastward) one after the other to make an arch h've miles high in the air over the Nittany limestone and slate valley, and then descending (southeastward) one after the other in Tussey and Terrace mountains beneath the Broad Top coal field just so we see the whole pile of formations from XII to IV coming straight up from the underworld in the Sharp mountain, Second mountain and North mountain to make a similar great arch in the air over the slate and limestone belt of the Great Valley . But as the great arch over Nittany Valley has all been swept away, and it is useless to seek for coal at the present surface anywhere between the Cambria and Clearfield coal mines and the Broad Top coal mines, so the arch over the Great Valley has been swept away and it is useless to seek for coal south of Sharp mountain in Schuylkill and Dauphin counties. The coal measures have been swept away from the Great Valley many geological ages ago ; and we know by long experience that there are no workable beds of coal in any of the pile of formations beneath the coal measures, except one bed in No. X at Duncannon, and that is worthless, and has been swept away (with the rest of the rocks) from the Great Valley. To illustrate what has been stated above in a few words I insert two cross sections which will speak to the eye better than any words : 296 GEOLOGICAL SURVEY OF PENNSYLVANIA. Section through Harrisburg (page 277, plate 2) from Dun- cannon at the mouth of the Juniata, down the Susquehanna to Columbia ; and Section across Franklin county (page 281. plate 4) from Path Valley mountain, through Scotland to the South mountains.* The practical importance to the farmers of the Great Valley of knowing these facts and understanding the above statement is evidently considerable. Why should they waste time and money in digging for coal where it cannot possibly exist ? There is not a trace of a coal bed left at any point in any county along the whole course of the Great Valley between the Hudson and the Potomac; nor in Amberson's valley and Path valley which lie behind the North mountain in Franklin county ; nor in the Fishing creek Trout run Pine Grove valley in northern Dauphin and Lebanon counties. All reported discoveries of coal beds are mistakes which a few words will suffice to explain. Along the center line of the Great Valley, between the limestone belt and the slate belt, the black Utica slate formation, Ilia, crops out, always thin, and often absent. In other words, the bottom rocks at the southern edge of the slate belt are often as black as the black slate of a coal bed, and have deceived many persons into digging for coal. When weathered down they make the jblack clay which is so conspicuous in the great Ironton iron mines of Lehigh county, and the Moselem mine of Berks county. They make a black soil at other places along the lines of junction of the slate and limestone lands. But no impressions of coal plants are ever seen in these Utica black slates. But occasionally impressions of graptolites may be observed on them, looking like lead pencil marks on paper; some of them are merely forked lines ; some of them look like the * These sections have been carefully constructed on a scale of 4 miles to 1 inch from observed outcrop dips in the Great Valley and to the north of it so numerous that no material error can be imagined in the general shape of the arch in the air over the Great Valley. THE GREAT VALLEY. 297 edge of an open umbrella ; others like holly leaves. They are the remains of curious little animals which swarmed at the surface of the ancient sea ; and they were. so numerous that their dead bodies darkened and even blackened the mud which afterwards was hardened into slate rock. These graptolite slates are exposed to view in the horse shoe bends of Connedogwinnet creek in Cumberland county. Discoveries of coal are reported from time to time by people living in front of tJie North mountain, on its foot slopes. Pieces of so called coal are frequently found lying on the surface or are knocked out of the exposures of dark slate ; for example, near Mercersburg and London in Frank- lin county. But these pieces are not indications of the existence of a workable coal bed. They are merely black shale layers in the upper part of the slate belt (Hudson river slate formation Illb,} charged with the animal carbon of dead graptolites and trilobites (water bugs) which lived in immense numbers in the waters of that age.* Discoveries of coal have also been reported from behind the North mountain in Lebanon county, along a narrow belt of the Marcellus formation (VIIK) which runs entirely across the state into the southern states, and zigzags through many of the valleys of our middle counties. It is a narrow belt of outcropping black-slates very much resembling the black-slates which cover coal beds in the coal regions. But it is slate and not coal. People who see it in a hillside in the form of a regular bed, and very black, looking a good deal like the outcrop of a coal bed, think that it is merely the bad edge of a good coal bed. They who try to burn a piece of it in a blacksmith's fire find that it will blaze a little at first and then remain red hot and throw out a good deal of heal;; but when they take the piece out of the fire, it is nothing but a stone. This however does not discourage them ; there are plenty of wandering miners seeking a job who assure them that if they will "go down on the bed" it will turn to good coal. In almost every county in the. state * The chemical analysis of a specimen of this deceptive kind of coal, found back of Mercersburg in Franklin county, will be given in a subsequent chapter, where the rocks of the slate belt are described. 298 GEOLOGICAL SURVEY OF PENNSYLVANIA. lying between the North mountain and the Allegheny mountain considerable sums of money have been wasted in sinking shafts and drifting tunnels into this belt of Mar- cellus black slate during the last fifty years, but no valuable coal bed has ever been obtained.* CHAPTER XXIV. The Great Valley Limestone No. II. Having described in the last chapters the general topo- graphical and geological features of the Great Valley, I shall give in this and following chapters descriptions of its two principal formations in sufficient detail to make them understood : (1) the limestone beds in the Lehigh region ; the quarries between the Schuylkill and Susquehanna ; the quarries west of the Susquehanna ; (2) the slate belt with its roofing slate quarried in the Lehigh region ; and its clay-limestone beds on the Susquehanna. The reader will thus be prepared for a description of these formations where they have been preserved in synclinal basins in Chester, Lancaster and York ; and where they are brought up to the present surface by anticlinal waves in Fulton, Perry, Juniata, Mifflin, Bedford, Blair, Hunting- don, Centre, Clinton and Lycoming counties. The exhibition is so great, the wealth of observations so over-abundant, that the most condensed summary of the facts published in the reports of the survey will seem to need ,ome apology for its length. But it is an embarass- * In Perry and Juniata counties thin streaks of very slaty Marcellus coal cross the bed of the Juniata river, and much money was formerly wasted in following them into the hillside ; all money thrown away. Peoples' experience of Marcellus black slate mining in other states has always been the same. I have added this instance of deceptive coal pros- pecting, because it is of importance to the citizens of Lebanon and Dauphin Bounties in the Great Valley. It will find its place again in a future chapter on the Marcellus formation. THE GREAT VALLEY. 299 ment of riches. I can only strive to classify the subjects .properly, and avoid repetitions.* Subdivision of No. II. In New York state No. II is subdivided into (1) Trenton, Black river and Bird? s-eye limestone at the top ; (2) Chazy limestone in the middle ; and (3) Calciferous sandstone at the bottom, resting on the Potsdam sandstone, f In Pennsylvania along the Great Valley belt the only distinct division of it that can be made is into upper purer limestone beds, ancj lower magnesian cherty and sandy beds ; that is, if the New York names are to be used, into Trenton limestone on top, and Calciferous sandstone for all the rest of it down to the bottom 4 *The detailed descriptions of quarries may seem needless ; but they are only specimens on a large scale of the economical geology of the state, and teach the structural geology in a better manner than it could be taught by verbal general statements. It is a kind of object teaching. It shows the difficulties and the successes of field work. It points out localities for study. Above all, it has a business value. The quarries of the Great Valley are selected because they are a numerous, connected and tj'pical series, and have played a master role in the history of the growing wealth of Pennsyl- vania. fThe discussion on the "Quebec group" of the Reports of the Canada Survey do not concern us in Pennsylvania ; but any geologist who desires to know the last word on it will find, it in two short communications in Science, Dec. 26, 1890, page 359 ; one by R. W. Ells, repeating his opinion (published in the Canada Survey Report of 1887-8, pp. 83, 84, K) viz.: "That these [Quebec] rocks represent a peculiar development of strata of Trenton age, and probably even down in that formation," sustaining Logan's old view ; the other, by Alfred R. C. Selwyn, the Director of the Canada Sur- vey, opposing W. Ami's views, and repeating his own opinion (as against Logan) published in 187(>-7, that the Quebec city rocks are certainly of Hud- son river (Lorraine, Cincinnati) age, overlying the Trenton. I may be per- mitted to add here that neither my conversations with Logan while he lived, nor the study of his written statements of the case, removed my objections to what I regarded his extraordinary and improbable theory of an expan- sion of a part of formation ^o. II eastward into a great local formation named by him "the Quebec group." f Writing of the magnesian part of the formation in the Lehigh region, Prof. Prime says : " Lithologically it seems to be impossible to make any distinc- tion between the limestones which must belong to different geological hor- izons ; for limestones from the top of the series, close to the Trenton lime- stone, look quite as much like those from just above the Potsdam [C'hiques] 300 GEOLOGICAL SUEVEY OF PENNSYLVANIA. Even in the back valleys of Middle Pennsylvania no better sub-division of the whole formation can be made ; . although the unbroken, uncrumpled condition gives a chance to put its beds in vertical order which is not possible in the Great Valley. For we there see only a gradation from the purer beds at the top downward into middle cherty beds and lower sandy and cherty beds, without any strongly marked general horizons of change. Prof. Stevenson's railroad section of 4519 feet of it in Bedford county, Snake Spring township (Report T2, p. 93) will illustrate the fact. 420' of Trenton blue flaggy limestones, He; succeeded downwards by thicker beds of light blue or bluish grey ; mostly not silicious ; many yielding superior lime.* 1351' of Chazy beds, in part 116 ; highest beds hardly silicious ; white chert balls begin to appear (descending) 600' below the top ; next 400' cherty limestones ; further down more and more silicious ; black chert appears at 1200' from top ; streaks of chert so numerous that the weathered surface is fretted with ridges. f 420' of concealed measures. 419' of limestone, mostly silicious. 400' (estimated) concealed measures. 175' (exposures imperfect) limestone, silicious. 150' concealed measures. 300' (Calciferous in part, Ha) beds of cherty calcareous grit ; fretted weather surfaces show the abundance of thin 'chert layers. 90' concealed measures. sandstone (No. 1) as do specimens taken from two beds in the same quarry not ten feet vertically apart. No traces either lithological or palseontological have been found by which the Calciferous sand rock (said by Rogers to occur near Easton) can be recognized or differentiated from the other formations." (Report D2, page 11.) *The line of separation of the Ulica slate No. Ill from the underlying Trenton limestone No. II, is almost abrupt where well seen in Milligan's Cove (T2, p. 93). Fossils rare; Calymene senaria and Strophomena alter- nata, obtained from one of the highest beds. Columnaria alveolata was seen in Morrison's cove (p. 94). f Cyathophylloid fossils got near the base of this subdivision along the Juniata. THE GREAT VALLEY. 301 620' of limestone beds sandy but with very little chert ; most of them might be called a calcareous sandstone. 175' concealed measures Total, 4519 feet.* No one can doubt that the uppermost beds of the lime- stone belt represent the Trenton outcrop on the Mohawk river. We can therefore safely use that term in Pennsyl- vania; and typical Trenton fossils occur in sufficient numbers to justify its use. Chazy fossils occur sparingly in the middle magnesian beds, and I see no objection to retaining that name. But Calci/erous sandstone was from first to last an un- fortunate New York term and ought to abandoned. The_ beds are limestone, riot sandstone beds, although they are often sandy, and have an abundance of silica in the form of chert ; but many of the lowest beds are nearly pure magnesian limestone, layers. f CHAPTER XXV. No. II in the LeMgh region. $ The beds of limestone along the Lehigh river, where they have been exposed to special view in very extensive quarries worked for the Allentown, Crane and Thomas furnaces, are seen to vary much in texture, color, hardness, structure and chemical composition. Some beds are compact, others crystalline. Blue and dove colors prevail ; but some beds are almost white, others nearly black ; and the blue limestones are of all shades from lightest to darkest blue. * It is quite probable that towards the northern edge of Bedford county a greater thickness of this formation is brought to the surface ; but no details were obtained there. (T2, p. 94. ) 1 1 am unwilling to add another name to our already copious nomenclature by calling them the Allentown, or the Easton, or the Reading, or best of all the Bethlehem formation, which last would be unexceptionable, if distinct limits could be assigned to it, which cannot be done. I prefer therefore to distinguish vaguely the lower, middle and upper portions by the old num- bers, Ha, life, He. JI take the substance of this chapter from Prof. Prime's report, D, D2, D3. 302 GEOLOGICAL SURVEY OF PENNSYLVANIA. The hardest beds are commonly those of dark blue color ; others are soft, disintegrating to | or % of an inch on a weathered surface so that they can be rubbed to loose sand between the fingers. Groups of the harder beds make little ridges which determine to some extent the direction of brooks and streams on the surface.* The softer beds give lines of sink-holes leading down to caverns through which subterranean streams flow, some- times reappearing at the surface in large springs, at other times emptying into the larger river valleys. Many of the longitudinal vales are ancient caverns which have lost their roofs. Two different kinds of structure are well known to the farmers : rock limestone and slaty limestone. The massive beds of rock limestone are accounted to make a better farm lime, or stronger manure ; and this is probably a correct opinion, for the slaty limestone owes its structure to its greater percentage of silicate of alumina, which does not act as a manure. Some very pure lime or lime-magnesia (dolomite) beds with a very slight percentage of silica are extremely thin-bedded, slaty looking, and ringing when struck. Some shaly beds have so large a percentage of alumina that they decompose to clay. A very strange, peculiar and entirely mysterious feature of some beds is a structure resembling a mass of clam shells closely packed together with their round sides uppermost. The chemical composition varies between a pretty pure carbonate of lime, and a nearl}'- correct dolomite (half lime, half magnesia), but always with some amount of silica, alumina, iron, phosphorus, carbon and water of crystalliza- tion. And it seems that the lower (more southern) beds of the formation are more magnesian (on the whole) than the upper (more northern) beds.f *Well exemplified in the steep bluff of hard limestone, bounding the Jordan, | m. N. W. of the Thomas I. Co.'s mine, No. 149 of the map. Ex- tensive quarries of good curbing and crossing stones are worked on the N. bank of the Jordan, f m. E. of Orefield. f Such is the opinion of Prof. Roepper of Bethlehem, and Mr. W. Firm- stone of the Glendon I. Works, whose analyses have been numerous and intentionally directed to the discrimination of the beds as fluxes. It is cer- THE GREAT VALLEY. 303 The dolomite beds, however, are distributed among the limestone beds in a curiously capricious manner, showing no kind of order or system anywhere throughout the form- ation.* This is the case high up in the series ; as appears from analyses of 10 of the beds of Grove quarry in Black Log Valley, made for Orbisonia furnace in Huntingdon county ; where the Trenton formation is exposed, about 500' thick, dipping about 60, and composed of dark blue- and gray soft argillaceous limestones alternating with blue lime shales (more abundant toward the top); the quarry be- ing opened in lower beds, measuring 22, 20, 10, 24, 18, 21, 20, 32, 30, and 72 inches thick respectively ; and the re- spective percentages of carbonate of lime being (in whole numbers) 90, 85, 90, 74, 81, 83, 81, 82, 85, 47, the last and lowest a dolomite. (F, p. 260.) Damourite (hydromica) layers only half an inch or more in thickness part the limestone beds from one another all through the formation, and in such numbers that a hun- dred of them have been counted in a single outcrop. They are regularly interstratified with the limestone beds, and are decomposed by the weather into clay.f But the damourite is sometimes seen as leaves thinner than paper, completely intermingled with the limestone and so thoroughly incorporated as to make a separation of the two impossible. The flakes of the mica in this latter case cross the body of the limestone in all directions.^ tain that the cement beds, so rich in alumina, are at the top of the magnesian series, or in the Trenton formation II c. *Of this more will be said in describing the McCormick quarries at Har- risburg. Here I will merely give Mr. J. B. Britton's analyses of viine beds in Troxell's quarry, Jordan Bridge of the C. rong of slate (III) more than a mile long ; the real syn- clinal of the district ; the trough in the cove being a mere local roll, although a large one,* The Ironton RR. CoSs Kennel mine, and the H. Mickley abandoned and exhausted, lie to the south of the slate prong and 1000' from it. Damourite white clay and Utica black clay in the latter. The former mostly yellow plaster clay, but some white, and a little black clay overlying the white; a little ore visible in contact with and under the black clay.^ The great Siegersville limestone cove, further south, con- tains many mines, none of them less than half a mile from the edge of the slate belt, and most of them a mile or two from it. They are all described in D2, pp. 34 to 39 ; many abandoned; some mere wash ore; most of them showing white clay. 8. Sieged s mine at Siegersville, worked at E. end. has a 6 inch ore layer under the sod ; then 12' barren ; under which ore bed 2' to 4' ; ore in shaft in floor reported 40' thick ; *But, as an illustration of the difficult geology of the limestone belt, ob- serve on the map the long (N. E. and S. W.) line of observed limestone dips obliquely crossing the point of the slate prong, and reading only 32, 23, 28, 320, 120 ( a t the point), 11, 22, 25, 32, 24, 8. JE. Even the violent theory of a collapsed overthrown and flattened down synclinal will not ex- plain so puzzling an exhibition. It almost justilies the theory of the non- eonformability of III upon II. To increase the embarassment there are dips of N. E. 17 and 28 in the slate pronrj along the high road. (See the fine colored map of the Ironton mines in D2, pocket.) t A remarkably beautiful colored geological sheet map of the Ironton group of mines and slate prong which separates them may be found in a pocket to Report D2, 1878. The limestone in the mine floors, the ore masses, the red, white, yellow, and red clays, and the undecomposed slates are all distinguished by separate colors. The depths are shown by contour lines, which are also extended over the whole sheet. It is a rarely perfect exhi- bition, on a scale of 300' : 1" of an unusually complete piece of difficult field work. It is dated 1875, and is the work of Mr. Ellis Clark, Jr., aid to Prof. Fred. Prime, Assistant Geologist in charge of the Survey of the Lehigh region. 346 GEOLOGICAL SURVEY OF PENNSYLVANIA. much lump ore and blood red clay ; in one place limestone over the clay, the limestone "thorough!} 7 permeated by damourite.* Jas. Kline's mine, at Orefield, m. S. of Siegersville, is within m. of the N". edge of the long syrcelinal slate prong which runs out eastward four miles, eastward N. of Wen- nersville. Most of the ore is extracted. AtN. E. corner soil 20' deep ; then red ore bearing clay 10', then yellow and white clays streaked with ore ; very little lump ore found. Damourite slate sticks so closely to much of the ore that it cannot he separated by washing. White clay both above and beneath the ore. At W. end, soil M^feet ; then all white clay down to standing water, with a good deal of only partially decomposed damourite slate in the clay. Yield of mine has been great. B. Weaver's mine, I m. E. of Orefield and Guthsville, and. just on the north edge of the slate prong ; 40' deep ; near top damourite slate with white ore clay underneath ; atN. end damourite slate holding thin strings of ore, but the ore mass is beneath it ; slate resembles No. III. The Thomas I. Go. and Crane I. Go. and D. A. Guth 1 s and the two Wanner mines range eastward along the north side of the slate prong. They have furnished large quanti- ties of ore, but are exhausted. At Guth's mine limestone is seen dipping S. E. towards and under the slate prong ; but the Utica slate (?) seems to dip N. W. Toward the end of the slate prong are six mines : Kratzef s, Jobsfs (2), and Scherer' s, on the north edge of the slate prong ; Marck's at the extreme point ; and Barber and Al- ney' son the south edge near the point. In these are seen pinkish damourite slate, and sometimes a black slaty rock which may stand for the Utica. The whole range are abandoned. In the next limestone cove 3 m. IS". W. of Trexlerville, there are about 15 mines, mostly abandoned^ all but one within *This either shows a cavern deposit of clay, or proves the decomposition of damourite layers far down the stratification beneath an insoluble roof of limestone beds. LIMONITE MINES NEAR THE TOP OF II. 347 i m. of the edge of the slate : LichtenwallnerX Loros' (two), Stein's (two), Moyer s, Steininger's (two), Scholl &Co.'s, Miller's (two), and Haines' and Smith's (Schlong's), the last two in front of the east point of the slate prong which shuts in the cove.* In the centre of the Cove a mile from the slate edge Krsemlich & Lichtenwallner'smine (D. p. 42), 50' deep, not worked since 1873, has its ore mass lying on horizontal blue Limestone, probably the flat crown of the anticlinal of the cove. There is evidently a large amount of damourite slate and white clay underlying the ore and in some places inside of it. If we could tell the shape of the arch, this would settle the question whether or not some of the Le- high limonites were made from damourite sub-formations in the body of No. II. But if the arch is flat, or subdi- vided by a synclinal, the damourite clays in this mine may also belong to the slates at the top of II. At the head of the next shallow limestone cove and close against the edge of the slate belt, l^m. N. W. of Breinigs- ville, is Fr. Breinig* s large exhausted mine, 50' deep ; but a small pit on the east of it was still worked in 1874 ; ore streaks in damourite slate and white and yellow clays ; ore and clays pitching 18 to 25, S. 80 E. away from the slate belt! And yet a glance on the large sheet map of D2 is sufficient to show a bridge of slate (III) thrown across *In Lichtenwallner's pits (one 40' deep) the ore lies both on and under white clay over damourite slate ; blue limestone reported at the bottom of a well 130' deep. At Loros's mine a gravel of clay, quartz and slate (all in small pieces) 15' deep covered the west end. Stein's oldest mine must have had a great output. The other leased to the Thomas I. Co. shows no slate ; the ore lies in and over white and pink damourite clays 47' deep ; limestone at 40' in one place dips 42, S. 41 E. (top layers drab slaty 4', laying on common blue limestone water worn); ore clays over the limestone dip 42, S. 40 E. A hole 10" square in the floor drains the mine into some un- known cavern. Moyer'' s, a new stripping (1875). Steininger's old mine ; very productive ; 600' x20' deep ; exhausted. The other leased by Lani- gan, 25' deep ; ore in damourite slate overlying white clay, dipping 22, S. 40 E. In one place under 12' of solid white clay is ore 6', then clay 12'. Scholl & Co. 's ore in rolling clay ; general average dip 10, S. 5 E.; local dips, to S. W. (one of them 55, S. 25. W); output 25 tons per day (1883) Miller' 1 s, abandoned, described by Rogers (1858) as ore interstratified irre- gularly with clay. Haine's, abandoned Smith's, 40' deep, described by Rogers as Schlong's, in damourite slate. 348 GEOLOGICAL SURVEY OF PENNSYLVANIA. LIMONITE MINES NEAR THE TOP OF II. 349 Section along Cornwall Railroad from Isebanon to Miners' Village. Section acraalSig Hill combined wdk Seclwn cdang Furnace creek. them Iraf dUUrla itt relaiiantkip io Creek section. CnvyXU OR i-MA5S Seal*. rtHical and Jinriifntal alUa . &OO fe*t, lo 4 inch. """ J.U& 350 GEOLOGICAL SURVEY OF PENNSYLVANIA. the limestone of the cove (II) and isolating the head of the cove as an enclosed limestone circus in the body of the slate belt. This abnormal dip must therefore be a sag of the decomposed ore-mass into some cavern in the limestone. The Trexlertown Copperas mine deserves mention here for the bore hole records preserved in Rogers' Geol. Pa., 1858, p. 265 ; 1 m. W. of Trexlerville ( m. N. E. of Brein- igsville) ; worked in 1836-1840 ? by N. Whitely. Boring No. 1 recorded : Clay and gravel, 30'; iron ore, 4|'; clay. 7'; black clay, 2'; sulphur et of iron (pyrites], 12'; iron ore, 5'. Boring No. 2: clay and gravel, 15'; iron ore, 1'; clay, 15': slate, 5'; clay, 6'; pipe ore in clay, 9' / clay, 4'. Boring No. 3 : clay, 14'; iron ore in clay, 8'; iron ore, 9'; clay, 3'; copperas earth, 2'; copperas in black clay, 2'; cop- peras in white clay, 2'; brown clay and iron ore, 8'; solid iron ore (pipe?), 2'; clay, 8'. Manganese oxide appeared in the west wall. The slate mentioned in No. 2, was made somewhat gypseous by the reaction of the sulphate of iron on its lime element. "The origin of this large deposit of sulphuret of iron," says Mr. Rogers, "is to be traced probably to a small shallow bed of Matinal [Utica] black slate which appears to have rested on the limestone and to have undergone disintegration." But if this opinion is correct we may extend the expla- nation to most of the other limonite mines in the central area of the limestone belt. The Moselem mine in Berks Co. This famous old mine, 5 m. W. of Kutztown, is within 1000' of the edge of the slate belt, and corresponds exactly to the great Ironton mine. The ore was reached at first by shafts through surface stuff 20' to 40' deep. Immense quantities of good ore were mined from nests and irregu- lar layers varying from V to 8' thick ; some of it bluish and slightly manganesian. Limestone beds in the ridge south of the mine dip northward, as they should, under the ore, and (if continued] under the slate belt. Large quantities of dark chept, some of them hundreds of pounds inweight r THE MOSELEM MlNE. 351 lay scattered over the soil. (Rogers' Geol. Pa., 1858, p. 226.) In 1878 the mine was surveyed by A. P. Berlin, in common with the whole valley between the Schuylkill and the Lehigh county line. It was then 2000' long and 100' deep, with five inclined planes. (See Fig. 1, on plate VIII.)* It is certainly a surprising circumstance that this great Moselem deposit should stand alone ; that nothing like it appears for so many miles along the edge of the slate belt in Berks and the counties to the west of it. One is tempted to suspect great local variations in the thickness or rich- ness of the upper damourite slate formation. Or perhaps a mechanically produced non-conf or mobility has shoved the damourite slates beneath the slate belt edge. But more probably the only and sufficient explanation is, that only here and at Ironton and a few other places caverns have been eroded to receive the iron drainage. Vague as this suggestion may seem it is borne out by such exhibi- tions as the Pond banks of Franklin county ; and by the cavern deposit of Penns valley in Centre county, to be de- scribed in another chapter. The Cornwall mine. This summary description of the Lower Silurian Forma- tion No. II would be incomplete without a special mention of one of the most important mines in Pennsylvania, the great magnetic iron ore mine of Cornwall, in Lebanon county, unique in its character, standing alone in the geology of *Fig 2 on the same plate is a reduction from Sheet XIV, of the great topo- graphical map of the South Mountains (Reading and Durham highlands) published in the Atlas to Report DH, Vol. 2, 1883. The survey of the lime- stone belt was made by Mr. A. P. Berlin in 1878. The small portion of it given in Fig. 2 illustrates the flatness of the limestone belt; the steep hill- side edge of the slate belt, through small gorges in which its back drainage issues upon the limestone belt; and the close proximity of the great limo- nite deposit to this outcrop wall. At the the east edge of the figure the reader will notice the normal 36 northwest dip of the limestone descend- ing beneath the slate belt in the ravine; also northwest and southeast (anti- clinal roll) dips in the quarry east of the ravine ; also an 18 northwest dip in the little quarry west of the ravine; and other northwest dips around Leibensperger's ; so that the geological place of the ore slates is unmistakably at the top of II under the slates of III, with no evidence of non-conform- ability between the two formations. 352 GEOLOGICAL StJRVEY OF PENNSYLVANIA. THE CORNWALL MINE. 354 GEOLOGICAL SURVEY OF PENNSYLVANIA. the State, arid pouring year after year its flood of wealth into the business world. Worked for more than fifty years, it shows no sigh of exhaustion ; on the contrary, its annual output continually swells in volume. Three hills of ore three hundred feet high, are ranged in a line a mile long and a third of a mile wide. Walls of solid ore 80 feet in vertical height are stoped down by dyna- mite ; and the fragments, broken up to portable sizes, are loaded in cars and distributed to the iron furnaces of the region. A floor of the solid iron ore at water level conceals an underlying ore-mass, into which test holes have been bored varying in depth from 50 to 300 feet. A great vol- canic trap-dyke, like the half of a cup, supports the ore- mass at its northern edge, and has been proved by some of the bore-holes to be its floor. Along the southern edge runs one of the few great faults of the State, limiting the ore- mass on that side. Against this fault descends (northward) at a gentle slope the Mesozoic beds of northern Lancaster, their sheared-off edges making the southern side of the cup which holds the ore-mass. It is this unusual occurrence of Mesozoic red sandstone faulted against the limestone formation of the Great Valley, with an outburst of ancient lava rising through the crack thus produced and making its way sidewise between the limestone strata, lifting them and holding them isolated, as in a vat in a chemical laboratory it is this unusual combination of circumstances which has given its unique character to the Cornwall iron mine. The mine has been a puzzle to geolo- gists ; and a satisfactory explanation of it has been only recently obtained by a laborious research upon the ground. It is now made evident that the whole ore-mass was orig- inally a set of lime-shale strata belonging to the very top of Formation No. II, which we may call the passage beds between No. II and No. III. These beds, held between the two walls of Trap and Trias, have been attacked by hot acid waters flowing into them, dissolving away the carbon- ates of lime and magnesia, and leaving behind in a concen- trated mass the insoluble silicates and hydrated peroxide of iron, converted much of it into the magnetic oxide. THE CORNWALL MINE. 355 The whole mass of ore is distinctly stratified, and shows the process of concentration. The original insoluble matters in the lime-shale still remain in the ore. The stratification of the ore-mass is perfectly regular ; but almost unchanged white crystalline limestone beds lie interstratified in the midst of it, showing that some of the original strata had a mineral composition not susceptable to a change into ore. These limestones lie in their original places among the other strata which have been changed into ore. But they have been subjected to merely enough change to convert them into an inferior kind of crystalline marbie. The rest of the ore strata were no doubt first charged with hydrated peroxide of iron (brown hematite) ; but the change went on one step further; the water was driven off, and the oxide of iron was crystallized into magnetic iron ore ; still retaining all the impurities of the original lime-shale beds. The remarkable features of this ore mass are : First, the quantity of sulphur which it contains ; and, Secondly, the universal distribution of a small percentage of copper through the whole mass of ore ; and its concentration into strings and plates of native copper only in the upper part of the mass where attempts were made at one time to ob- tain it in sufficient quantities to make it marketable ; but the richest pockets of it at the top of the hill were soon ex- hausted, and none others have been met with lower down.* *The origin of the copper, and of the sulphur also, has been connected with the outburst of trap, and also with the neighborhood of the Triassic sandstones, but the subject is still entirely obscure. Nor is it of practical importance, for all attempts to mine copper in Pennsylvania have signally failed. But to geologists the question of the origin of the copper in the Corn- wall ore is one of high interest. At present the only facts which we can bring to bear upon it are those connected with the old copper operations at the edge ol the Mesozoic sandstone in Chestercounty westof Norristown; and these are not sulllciently understood to throw much light upon the subject It is remarkable that the mines near Dillsburgin York county furnish the same kind of copper-bearing magnetic iron ore as that at Cornwall ; that they are surrounded by Mesozoic red sandstone near its present northern edge; and that outbursts of trap similar to the trap enclosure at Cornwall are also in contact with the Dillsburg ore. Similar ores are also mined on Fritz's is- land in the Schuylkill near Reading, and at Boyertown and at Seitzholtz- ville further east in Berks county, where copper and trap again accompany the ores. All this suggests, although it does not prove, that the copper has come in some form, perhaps as vapour, with the fluid lava from the interior 350 GEOLOGICAL SURVEY OF PENNSYLVANIA. I do not propose to repeat in this summary of the geol- ogy of the State the very full description of the Cornwall mine published as a separate memoir in the Annual Report of the Survey for 1885, pages 491 to 565, with maps and sections and page, plate diagrams, showing stope-faces, the structure and the construction of the ore-mass. In lieu of verbal descriptions I give the more important of these illustrations, greatly reduced, but legible enough to make the whole thing comprehensible.* The geological situation of the Cornwall mine and its railway connections with Lebanon are shown by Fig. 3 on Plate IX. The reason for placing it geologically at the top of II in- stead of at the bottom, although it is on the southern in- stead of the northern edge of the limestone belt, is made clear by Fig. 1 on Plate IX, which represents a cross-section of the belt (looking east) from the edge of the slate belt to the edge of the Trias country. The vertical rise of the top beds of II at Lebanon, their flattened rolls across the belt, and their descent at Cornwall, require no commentary, f of the earth ; and it is possible that the sulphur accompanied it On the other hand we have copper shales in the Devonian formation of the northern counties of the State a hundred miles from any trap, and several miles above the plutonic floor. But one of the most conclusive proofs that the Cornwall and Dillsburg copper has no necessary connection with either the Trap or the Trias is found in the facts mentioned on a previous page, namely, that similar leaves and strings of native copper are found in stripping the black clay from the limonite ore mass at Ironton, which is not at all magnetic, has no trap near it, and is in fact a simple leaching from the upper damourite slates at the edge of the slate belt It looks as if the sea-water of that age was heavily charged with soluble salts of copper, as the water of the Medi- teranean Sea is now. As for the abundance of sulphur, it is only necessary to allude to the many red-short ores of our back valleys, far from any source of heat ; but especially to the account given on a previous page of the Copperas mine between Breinigsville and Trexlersville in Lehigh county. *The reader may find a condensed statement of all the facts, and a num- T>er of their illustrations, in Mr. E. V. d'Invilliers' paper read before the In- stitute of Mining Engineers at its Pittsburgh meeting, Feb., 1886, and pub- lished in its Transactions. I assisted Mr. d'Invilliers by a personal examina- tion of the mine, and am responsible for the theoretical conclusions to which he did not yield an unqalified assent, and at which other competent geolo- gists may demur. Cornwall must continue to be for many years a theme for discussion. f I have in a previous chapter described similar descents of the slates of III along the south edge of the limestone belt in Cumberland and Dauphin PATH. VALLEY MINES IN FRANKLIN COUNTY. 357 Cross-sections of the ore mass and trap are given in Fig. 2, Plate IX, and Fig. 1, Plate XI ; and a section lengthwise through the three ore hills is given in Fig. 3, Plate IX. A reduction of D'Invilliers' topographical map of the whole mine (in part) is given in Plate X. The most strik- ing feature of this map is the trap liook at its eastern end. I can imagine no other explanation for this most interesting structure than that suggested in the memoir in the Annual Report, viz : that the ore-mass really represents a body of limeshales thrown into a sharp and deep synclinal, and that the out* and up-flowing trap followed the synclinal bedding. This south side of the synclinal trough was sheared off by the fault, and, therefore, the trap hook stops at the fault. But this leaves unexplained why the trap did not follow up the fault to the present surface, and pre- ferred rather to rise sidewise (N.) between the beds. The curious tongued structure of the trap on the north edge of the Big Hill shown in Fig. 3, Plate XI suggests that we are thece not far from the extreme limit of the trap ejection upwards. The outcropping unchanged limestone beds in the body of the ore mass are shown in Fig. 2, Plate XI. Patli Valley mines in Franklin County. Path valley is an anticlinal limestone cove in the north- western side of Franklin county, extending for about ten miles in a 1ST. E. and S. W. direction along the eastern base of that portion of the North mountain locally known here under the name of the Tuscarora mountain. It ends on the S. W. in a cove between this mountain and an outlying spur known as Bear Knob, while to the N. E. the anticlinal counties. Another occurs in Lebanon county east of Cornwall. But the most extraordinary instance is to be seen at Reading, where a north and south belt of III is colored on d'Invilliers' map as intervening between the Schuylkill and the mountains back of Reading. How the structure here is to be explained I can only conjecture by supposing a westward slip of the valley rocks from over the mountain gneiss. At the beginning of Chapter XXVI, I have described the east dips of the limestone in the quarries at Reading, but I omitted to notice this belt of overlying slate, which Mr. d'Invilliers has no doubt of being No. Ill, and not primal slates. 358 GEOLOGICAL SURVEY OF PENNSYLVANIA. lies about midway between the Round Top and Dividing Mountain spurs. The limestone of No. II is exposed in this valley between Doylesburg on the IS". E. and the Rich- mond furnace on the S. W. and is nowhere over two miles wide, tapering toward each end. The north dips toward the mountain flank are usually somewhat steeper than those on the south side of the axis, especially for a distance of six or eight miles in Metal township, owing largely to the presence of a fault along the base of the mountain, which swallows up a large portion of the No. Ill slate formation, and opposite Fannettville brings the limestones of the val- ley within close proximity to the mountain sand rock No. IV. Along this line the dips are often vertical, if not overturned to the S. E. and it is mainly in this portion of the limestone area, near the junction of Nos. II and III, that the iron ores of this region are exposed and developed for a distance of about eight miles between Richmond fur- nace and Fannettville. The South Pennsylvania branch of the Cumberland Valley railroad was originally con- structed to reach these deposits, which were then thought to be of great extent and purity, but which after a consid- erable development, have proved a source of expensive dis- appointment to the projectors of the road and those inter- ested in the resources of that region.* Richmond bog ore bank at the S. W. end of the range, 3000' N. of Bear Knob ; long abandoned, 20'x20'xlo' deep 5 uniformly good rich non-phosphatic ore, but not much of it. Mount Pleasant bank, the oldest and largest of this range ; two open cuts separated by barren clay partition at S. W. end and uniting in one large open cut at N. E. end towards Cowan's Gap. Southern cut still 250' x 100' x 60' deep, although a good deal filled up since its working was abandoned. A 60' high steep barren red-sand-wash wall on the S. E. in which a few decomposed layers of sandstone, with steep (overturned ?) S. E. dip, appear above the con- formably dipping limonite. On the N. W. side, the divid- ing partition is largely of white, bine and yellow clays. *DTnvilliers in Annual Report 1886, part IV, page 1490. The following description of the banks is greatly condensed from pages 1401 to 1501. PATH VALLEY MINES IN FRANKLIN COUNTY. 359 Behind the partition dense close-grained limonite under sooty-black clay ; left in wall a N. W, dipping lens-shaped bed 10' to 20' thick, interrupted by barren clays. Total length 450'. On the mountain side 8' to 20' of stripping stopped work in that direction. Total output said to be 100.000 tons. Analyses: Iron, 47.5; manganese, 2.3; sulp., 0.05; phos., 0.34 ; silicions matter, 11.7. Beaver bank, 2500' N. E. of last; 200' x 150' x 20' to 40' deep ; bed of limonite 20' thick said to be left along E. wall. A rib of barren iron stained sandstone extends through the middle of the oval open cut ; and another shows in the N. W. (mountain) wall, through which a drift reached some good ore. No black clay ; all the barren stuff is red. Whole output 10,000 tons ; ore very irregularly scattered ; well 80' deep in floor, said to have gone through good wash ore. McGowan pit, 1000' N. E. of last ; small, irregular ; all wash ore ; no black clay ; less red than white and yellow clay. Worked long ago. Other small pits, abandoned ; one 20' deep said to have been all good lump ore.* Well up the mountain side, N. W. of the banks at the foot of the slope just described, is another range of banks : Old Johnson bank ; furnished say 500 tons of ore mixed through a sand and clay wash. Lessig pits ; the one furthest (N. E.) yielded say 200 tons of slaty cold-short ore. From the other pits, 10' to 18' deep, clean good limonite, say 50 tons in all. The outcrop runs straight across both tracts and would yield some ore here and there if opened. Car rick 1 furnace has a run of 1^ miles on the outcrop further N. E. First pit 50'x'30'xlO / , yielding considera- ble good ore ; shaft 10' deep in floor stopped in ore. Porous wash ore making tough iron shows in the bank wall under 7' stripping. Two other pits (600' N. E. of last), 50'x25'x 15'. gave say 500 tons of ore condemned at the furnace. f *The banks described above are on S. Pa. M. & R. R. Co.'s tract of 6000 acres. The company holds leases on several thousand acres more ; but the field is practically abandoned. f This is a curiously interesting illustration of the variation in quality in limonite along one and the same outcrop line. 360 GEOLOGICAL SURVEY OF PENNSYLVANIA. After many smaller pits comes a large one, lOO'xSO'xSO': a 25' shaft in the floor produced excellent lump ore. No water here ; water scarce in all the pits ; pits therefore often abandoned even when good ore could be got. Another cut (a little lower down the slope) 300' N. E. of last ; 150'x50'x 20' ; slope (very old) put down 20' on N. W. side in good lump ore. Old Carrick bank, % m. further on N. E. and just in front of the Wind Gap by which the road passes over into Hunt- ingdon county. Here only the top of No. Ill crops out, all the rest of the slate formation being swallowed, up in the fault * and the ore mine 300'x40'x25' runs along the fault and close to the limestone. A shaft 125' deep sunk in the mine floor is said to have passed through a steeply dip- ping 30' to 35' ore bed. Another shaft (at W. end) is said to have gone 75 feet through this ore and stopped in solid lump-ore. Yet the whole place is abandoned and dilapi- dated. Most of the output came from gallery workings N. E. and S. W. of the ravine. All the wall towards the mountain shows soft sooty black clay, like that which caps so manv of the mines along the foot of the South mount- ain. Four sets of lessees have worked the mine ; output estimates vary so as to be worthless. Analyses of samples of ore used by Carrick furnace in 1880: (1) lump ore: Iron, 45.3; mang., 1.1 ; sulp., 0.05; sil. mat., 16.3 ; phos., 0.36 (2) wash ore : 36.4 ; 1.7 ; 0.06 ; 26.0 ; 0.27. Railroad bank (Carrick Fur. Co.) 1200' further N. E. than last ; 400 / x40 / xl6 / ; not much ore visible in 1886; strip- ping very heavy; shaf t 'under S. E. wall 40' (reported) en- tirely in ore, and in drifts to N. and W. Bank must have had a very large output. Analysis of a sample picked up: Iron, 43.6; mang., 0.24; sulp., 0.005; sil. m., 18.5; phos., 1.482 (unusally large). A few more pits are seen further on N. E. beyond the Fannettville road ; outcrop distinct for more than a mile ; G. Umbril's abandoned pit being the last. A short distance E. of Mercersburg are three small banks, *Henderson's fault, as we used to call it, because discovered and described by A. A. Henderson of the First Geol. Survey of the State 1839-40. THE IIENRIETA MINES OF BLAIR COUNTY. 361 Leib's, Stauffef '?, McFarland 1 s, now abandoned, which yielded some good bog ore. Stinger's old pits at the mouth of Bear valley, 1 m. E. of London, and on or near the II-III line ; long abandoned ; analysis: Iron, 39.5; mang.,4.8; sulp., 0.04; sil. m., 18.8 ; phos., 0.61. Garlic BankE. of last (2 m. S. W. of St Thomas) ; 200'xlOO'x20'; walls of red clay carrying fine ore and a little lump; not worked for 15 years (1886) ; too far from RR. ; good ore; analysis: Iron, 52.9; mang., 0.08; sulp., 0.15; sil. m., 6.89 ; phos., 0.06. In the other direction 2 m. W. from Mercersburg, the Webster bank is on a II-III contact line ; abandoned. The Henrleitamines of Blair Co. These limonite deposits are the only others to be described in this chapter as appearing to have a geological horizon at the top of II, in contact with the slates of III, and along lines of fault like the Path Valley mines in Franklin county last described.* Leather cracker Cove is made by an anticlinal of No. II limestone, faulted on both sides, so that the arch is thrown up 2000' and rests against the slates (III) and the sand- stones (IV) of Tussey mountain to the east, and of a small slate ridge (III) to the west. The big fault (the eastern one at the foot of Tussey) is about a mile long, and approxi- mately parallel with the strike of the country. The anti- clinal runs on N. 20 E. to and through Canoe Valley in Huntingdon county. See Fig. A in Report T, p. 91. * I am loth to mix these up with the great mines of the Great Valley, and to separate them from the regional mines of Nittany Valley and Morrison's cove ; but they are the only notable mines in middle Pennsylvania behind the Great Valley referable to the top of II, when I made my last survey of that iron region ; all the other limonite deposits of II being re- ferable to various horizons in the body of the formation. But it will ap- pear in a subsequent chapter (XXXIV) that I now place a different inter- pretation on that fact, and believe that the Henrietta ore horizon is only ac- cidentally connected with the slates of III by reason of a great upthrow fault 362 GEOLOGICAL SURVEY OF PENNSYLVANIA. lALap cft/te SaticonZinc TTtlnes cuici vicinity. ~Pl. XII . THE HENRIETTA MINES OF BLAIR COUNTY. 363 The line of contact limonite ore deposits runs from the Henrietta bank due south. At the south end of the line of ore the Oneida terrace (IVa) and the Hudson river slates (UK) are swallowed by the fault.* It seems a logi- cal conclusion that this line of limonite ore has been pro- duced in some way by the fault. The contact of II and III is sharply defined along Tussey mountain its whole length across four counties, and along Dunnings, Lock, Loop, Canoe, Bald Eagle and Nittany mountains, for about a hun- dred miles of outcrop. Almost every ravine cutting through the terrace of slate into the limestone valley affords as good an opportunity as could be desired for finding any ore deposits existing at the contact of the two formations, or produced by the decomposition of lime-shale beds of pas- sage from limestone to slate. In most cases the cultivated fields at the base of the mountain would betray the pres- ence of such ore deposits. In spite of all this however not a single such discovery of any importance has been reported, except in Leathercracker cove. The conclusion is obviously good that the Henrietta ore mines occupy this geological horizon exceptionally, by accident, and solely in virtue of the Leathercracker faults. But this conclusion has a wider range and applies forc- ably to the Great Valley, where we see the Path Valley deposits of Franklin county lying along just such another fault ; and then we must go 140 miles along the middle con- tact line II and III before we reach the Moselem mine in Berks county, where we have seen there is some reason for suspecting a faulted structure. In the Ironton region of Lehigh county there is scarcely a single mine which can be assigned with certainty to the contact of II and III ; and from Ironton eastward no deposits of limonite can be proved to overlie the Trenton. Even at Cornwall there is solid limestone (Trenton ? ) at the very top of the ore shale mass. Remembering that no limonite appears with the passage beds in the bends of the Conedogwinit in Cumber- land county, and keeping always in mind that we have as *A11 the arguments for the fault are given successively in detail in T, p. 90, to which the reader is referred. 364 GEOLOGICAL SURVEY OF PENNSYLVANIA. yet no assistance from fossil forms in determining the true position of any limestone or lime shale beds faulted against the slates of III at Henrietta mine or elsewhere, it must be regarded as quite possible that all our Great Valley limo- nites are cavern deposits of very recent date derived from the decomposition of a series of damourite lime shales be- longing to various horizons in the Magnesian limestone for- mation, that is, the Chazy and Calciferous. In the next chapter such horizor^s will be exhibited. NITTANY VALLEY LIMESTONES NO. II. 365 CHAPTER XXXI. Nittany Valley limestones, No. II. Centre County anti- clinals. Nittany Valley cross -sections. The ore horizons of the Great Valley have been seen to be obscured by the folded and crumpled condition of lime stone and slate belts. In Nittany, Brush, Penns, Canoe and Kishicoquillis valleys, and in Morrison's, Friend's and McConnellsburgh coves, a simple anticlinal structure, dis- turbed by only a few faults and hardly at all crumpled, makes the order of the limestone beds an easier study, sufficient to establish the different horizons by approxi- mately parallel ranges of ore banks.* The great rock waves of Middle Pennsylvania are splen- didly exhibited in the McConnellsburgh Cove in Fulton county, with its 8000' fault on the western side ; in Kishi- coquillis valley in Mifflin county, with its surrounding ter- race and eastern keel-shaped mountain prongs ; and most of all in Nittany valley and Morrison's Cove (united by Canoe valley) where the grandest anticlinal of the State brings to the surface the whole of the magnesian limestone (capped by 400' of Trenton limestone) with immense de- posits of iron ore. A description of the Nittany anticlinal, and of the subordinate waves which broaden and spread out its southern slope, is a necessary preliminary to the descrip- tion of that oldest and richest iron ore region of middle Pennsylvania. Centre county anticlinals. The great Nittany valley anticlinal, which brings to the surface the top layers of No. II in Mosquito valley in *Mr. D'Invilliers in Report T4, p. 137-8, says that the popular belief in continuous belts of ore-producing territory along fixed outcrop belts or horizons was not confirmed by his survey of Centre county ; but this does not invalidate the statement that limestone horizons are demonstrable, and ore horizons approximately so. 366 GEOLOGICAL SURVEY OF PENNSYLVANIA. Ft. XIII. &WM Section* tfJfoJl in Jfittaivy Valley, GemtivGo. Chestnut ndge taledwy'rirfye-.. zfetD CENTRE COUNTY ANTICLINALS. 367 Lycoming, and Nippenose valley in Clinton, rises in Cen- tre county so as to expose on the Centre-Huntingdon line, west of Bellefonte, at least 6000' of the formation, without however bringing the bottom beds to the surface.* Continuing S. W. across Huntingdon into Blair at a still higher elevation it exposes more than 6000' of No. II down to (or nearly to) the bottom beds at Birmingham on the Little Juniata. Then it sinks rapidly to the head of Sink- ing Creek valley, where the slates of III close over it, and the mountain rocks of IV, the Frankstown fossil ore red- shales of V, and the Hollidaysburg limestones, etc. cover it; and so it runs on south through the Devonians into the coal measures of Somerset county. The Gatesburg ridge anticlinal in Centre county runs parallel and 1J miles to the S. E. of the Nittany (Chestnut ridge) anticlinal ; and becomes the Hickory ridge anti- clinal of Huntingdon county, crossing Half Moon creek 2 m. N. of its junction with Spruce creek. f Dry Hollow synclinal lies between the Chestnut ridge and Hickory ridge anticlinals. Sand ridge (Tadpole ridge} anticlinal in Centre county, runs parallel and 1 m. S. E. of the Gatesburg ridge anti- clinal, and its S. E. dips pass beneath Spruce creek down into the roots of Tussey mountain. It is the Spruce creek anticlinal of Huntingdon county. On the county line, opposite Pennsylvania furnace, it brings to the surface * D'Invilliers in T3, p. 443 : East of Bellefoute the axis beds are the " Bar- ren " sandrocks of Sand ridge ; west of Bellefonte the axis runs along Chest- nut ridge. Its S. E. dips are rather gentle here, but its N. W. dips (in the Stormstown valley, 1^ miles wide, between Chestnut ridge and Bald Eagle mountain) are steep, vertical, or even overturned so as to dip S. E. f This arch is quite subordinate to the great Nittany arch, and is in fact a roll on the grand S. E. slope of the formation from the Nittany arch crest towards Tussey mountain. One result is that the Hickory ridge barrens are not the Sand ridge barrens of Centre county, but are much higher in the series ; giving us two quite distinct horizons of Calciferous sandstone strata in No. II. This roll appears to die down rapidly N. E. and S. W. from Half Moon run, and probably flattens out before reaching Warrior run ; at all events there is no trace of it in the long exposures of the Little Juniata. It seems to bring up the particular horizon of shales from which the Old Seat, Huntingdon furnace, and Dorsey ore deposits were generated. (D'Invilliers letter of May 18, 1885, in T3, p. 445.) 368 GEOLOGICAL SURVEY OF PENNSYLVANIA. 3500' of No. II ; and it is in this upper half of the for- mation that most of the pipe ores of the region are mined.* The Brush valley anticlinal runs along at the S. E. foot of Nittany Mountain, between it and Brush mountain. f It passes north of Rebersburg and Madison ville, with N. W. dips of 65 to 70, and S. E. dips of 15 to 20. Just north of the Penns Valley cave, pure soft gray Trenton limestone beds dip 70 N. W. and 45 S. E. It reaches its greatest height near Centre Hall, where it brings to the surface beds 2500' beneath No. TIL:}: Sinking and flattening S. W. it car- ries the Watson, Ross, Stover and other ore deposits. On Spring creek. 1 m. S. of Lemont, its dips are 48 N. W. and 12 S. E., flattening to 8 at Boalsburg. Then it rap- idly dies out before reaching the foot of Tussey mountain. The Penns Valley anticlinal runs south of Brush mount- ain, between it and Stone mountain, in the slates of III in Pine Creek Hollow ; lifts the top Trenton beds at Hoster- man's saw mill, and rims into a cove of Tussey mountain. TJie Penns Narrows anticlinal barely lifts to the surface in the Narrows and in George's valley the top Trenton *This Sand ridge anticlinal axis runs from Pennsylvania furnace (N. E.) to Johnston's ore bank in College township, lapping past the dying Brush Valley anticlinal ; and between the two begins the Nittany mountain syn- clinal which deepens (N. E.) and takes in the slates of III, the sandstone of IV, and the red shale of V, which make the canoe-shaped Nittany mount- ain. At Pennsylvania furnace the Sand Ridge dips vary from 25 to 60, N. W. and 25 to 40 S. E. At Johnston's bank its S. E. dips vary from 15 to 30. (T4, 35.) f Eastward this axis makes Sand mountain in Union county and crosses the Susquehanna near New Columbia. Westward it curves from W. toS. W. just as the Nittany valley anticlinal does, entering Centre county in Miles township at the head of the narrow Hudson river slate cove with which Brush valley commences. It brings up the top Trenton beds near Rudy's mill. JThis accounts for the ore-poverty of Brush valley; the uppermost ore horizons on steep dips affording no good opportunity for concentration and preservation ; and the rest being buried. It crosses the Susquehanna north of Lewisburg. On e mile east of Aaron s- burg its limesand beds dip 68 N. 25 W. and 40<-' S. 35 E. It bends sharply southwards and crosses the pike i m. S. of Millheim, where dips of 70, 640, go N. W., and 12, 20, 30 S. E. are seen. Then it bends and runs due west to the church, 1 m. N. E. of Penn Hall ; here|m. N. of edge of III in Egg Hill. North of Spring Mills its dips are 60 N. W., 20 S. E, Gentle arch at Penns creek ; greatest height 2m. further west on the Bellefonte- Lewistown pike ; then turns S. W. and dies into the Tussey mountain cove. CROSS SECTIONS IN CENTRE COUNTY. 369 beds, with dips of 70 N. W. and 60 S. E. Its highest point is 2 m. W. of the MiJlheim pike with dips of 70 N. W. and 50 S. E. At Potter's mills are dips of 85 N. W. and 70 to 80 S. E. It sinks west in the slate "Loop" 4 m. west of Potter's mills, and issues S. W. from Tussey mountain at the Bear Meadows in Huntingdon county.* It will be seen from the above sketch of the structure and from the figured cross-sections why almost all the limo- nite ore deposits are confined to the Nittany valley proper, the great arch of which brings up nearly the whole of for- mation No. II, exposing to erosion and concentration all its iron-bearing limeshale and limesand horizons. Cross-sections in Centre Co. Figs. 1, 2, 3, 4, 5, 6, on Plate XIII show the structure of the region by a series of cross sections described in Mr. D'lnvilliers' report on Centre county, T4, 1884, pp. 34 to 41. The rest appear as plates p. 668 &c. below. The Madisonburg Gap cross-section, at the Clinton- Centre county line, shows the Nittany axis barely a mile distant from the Bald Eagle mountain in which the slates of III are vertical or overturned (S. E. 80 to 86). Against these rest the thin-bedded shaly Trenton limestones (He) ; against these rest the white, hard crystalline, magnesian, sandy Chazy limestones ; and under these on the arch the limy sandstones of Sand ridge, making "The Barrens." At the Washington Furnace and. Beck ore banks (2 m. N. W. of the old Washington furnace) the measures are over- turned, and the ore horizon is about 3000' beneath the Slates of III. South of the arch the same ores lie at the Snavely, Sallow and Day, and Huston banks, dipping 30, S. 85 E. (towards Nittany mountain) between beds of cherty lime- stone (Chazy, or Calciferous) ; the slates of III at the base of the mountain dipping 40, and the Medina sandstone 50, S. E. * The Confer anticlinal only exposes III in Decker valley, and in the small oval Lick valley (Lechenthal). The Poe Valley anticlinal, passing from Union into Mifflin county, also only exposes III along the north foot of Paddy's mountain and south foot of Bald mountain. 24 370 GEOLOGICAL SURVEY OF PENNSYLVANIA. The Howard and Jacksonville cross-section, 4 m. S. W. of the last, shows the sand-lime strata (containing some good pale blue beds) at Jacksonville overturned 68 to 80, S. E. without any appearance of a break or fault in the arch. Fossiliferous blue limestone quarries are N. W. of the village ; and black shiny Utica slate, polished by slid- ing pressure, within 300' of the Bald Eagle mountain, has been prospected for coal ! Near the Butler ore bank inter- stratified magnesian limestone and common sandstone beds are overthrown to 50 or 60, S. E. Sand ridge has a double, crest, the northern crest being made by very hard blue flaggy sandstone beds; the southern covered with loose sand. The sandstone beds are regularly inter strati- fied with the magnesian limestone beds. The higher southern ridge shows 20 to 25 dips to S. E. The ore hori- zon in Madison Gap cross- section above here runs through the Hecla, Voneda, and Schwartz mine limestones dipping 30 to 40, S. E. Then come the overlying dark blue Trenton beds (He) making a reddish soil ; then the Utica black slates, extensively prospected for coal, on the H. Brown tract, dipping 40, S. E. The Hecla Furnace cross- section, 3m. W. of last. In Little Fishing Creek Gap IV dips 52, 40, 40, S. E. Be- tween Nittany mountain and Sand ridge a shallow valley. Blue very slightly calcareous sandstones, dipping 22, S. E. were once quarried for paving flagstones (40, S. 30 E.) near the McKinney ore bank. At the Darrah bank, N. W. of the Sand ridge, the same blue silicious magnesian lime- stones in bold ledges and cliffs dip 20 to 25, 8. E. into the ridge.* Along the north road, magnesian limestones are overturned to 85, 83, 70, 83, 80, 88 to S. E., but others dip 85, 88, 60, 65, 76 normally N. W. The anticlinal begins to get its normal shape after passing S. W. into Spring township. The Belief onte cross-section is the best that can be got N. E. of the Little Juniata. The Barrens (sand ridge), sinking 4m. E. of Belief onte, do not show the sandstones *This is a mile from Bald Eagle mountain and must mean an excessive overturn. CROSS SECTIONS IN CENTRE COUNTY. 371 on the section. The Medina sandstones, IV, in Bald Eagle mountain dip 80 to 70, N. W. The slates of III on the mountain side, 50, N. W. The Trenton blue fossiliferous limestones, IIIc, 600' thick, both massive and thin bedded, fine grained and laminated, dip 50, N. W., as in the Alex- ander and Morris quarries on Spring creek north of Belle- fonte. Then at the Presbyterian church appear the upper- most magnesian (Chazy) beds, banded, broken by cleavage holding masses of chert, and decidedly whiter than those above them ; all of them more or less sandy and cross- cracked ; dipping on an average 50 (with local variations of 30 to 60) N. W. to the anticlinal axis, a mile S. of Bellefonte, were they only dip 9 N. W. and S. E. Then the same beds descend in the same order, with S. E. dips of 30, 20, 12 and 10, toward Nittany mountain. The Fillmore-Boalsburg cross-section, 6 miles further S. W. crosses the whole valley ( m. W. of the end of Nit- tany mountain) from the Bald Eagle mountain to Tussey mountain, 8 miles, across the Nittany valley anticlinal, the Nittany mountain synclinal, and the Brush Valley anticli- nal. Here the bottom slates of III dip. 70, N. W. The blue Trenton beds, at first 70, lower their dips so rapidly that at Fillmore they dip only 20 to 15, N. W. Half a mile further, on Crust farm, the arch of lime-sandstones is flat- tened to 6 dips both ways (10, 12, well exposed on Spring Creek, 1 m. S. of Roopsburg). South of the axis in Big Hollow, N. W. of Houserville, purer limestones descend at 10, 15, 18, 16, 30, S. E. into Paddington ore banks. On Slab Cabin run, 15, 20*, S. 60 E. (showing the shoaling of the Nittany mountain synclinal). Here the long syncli- nal prong of III is crossed. Then the Trenton limestones rise steeply (50, 60, N. 20 W.). Then the lime sandstones rise (48, N. W.) on the Brush Valley anticlinal, and sink again (8 to 12, S. E. )covered by the Trenton beds descend- ing at 20 to 30 under the slates of III in Tussey mountain. 372 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER XXXII. Centre county limonite mines. Pennsylvania Furnace ore banks. Mr. E. V. d' Invilliers' elaborate report on Centre county, T4, was published in 1884, when the iron industry of the state was depressed, when only three of the four small char coal furnaces were in blast and the supply of water for washing the limonite ores of the county was very limited. Since that date there has been an active movement in de- veloping the iron ore resources of the district. Two large coke furnaces, with the latest improvements, have been erected at Belief on te by the Robert Valentine Company, and the Philip Collins Company, and operated under various changes of name. Brown hematite banks have been opened up all along the ore belts, especially in the middle mem- bers of the limestone series. Branch railroads have been constructed to reach the mines near the State College and along the foot of Bald Eagle mountain. The use of jigs to separate the ore from the Hint and sandstone of the ore masses is now common and will soon be universal. Water for washing away the clay and sand is procured either from the surface streams or, in the dry limestone districts, by sinking artesian wells to the drainage level ; some of them being several hundred feet deep, and at least one of them west of the Huntingdon county line, a thousand feet. The market for the ores is found at the numerous furnaces along the main line of the Pennsylvania railroad and its branches. The fuel used is coke from the Clear-field and Connellsville coal districts. Two varieties of ore. * The two chief varieties of ore occurring in the county are : 1st. The wash and lump hematite ore of the " barrens." 2d. The pipe ores. *This paragraph and those that succeed it as far as to the end of the list of mine groups are taken nearly verbatim from Mr. d'Invilliers' report on Cen- tre county, T4, 1884, pp. 133 to 138. His detailed descriptions of the mines of these groups occupy 117 pages of that volume (pp. 139 to 256) of which no summary can be made with any success. I will confine myself to a de- scription of the great Pennsylvania furnace mine and refer the reader for the rest to his excellent work. CENTRE COUNTY LIMONITE MINES. 373 1. Of the first class it may be stated that the appearance and character of the ore in all the banks, as well as the ac- companying waste material, show evidence of their being waste deposits, caught in vast caverns of irregular shape, showing mixed sand, tough clay and rolled ore, and though intimately associated with sandy measures in the limestone formation of II have really a still lower limestone bottom. In the chief mines of the district notably at Scotia and Tow hill after a superficial covering of 15 to 30 feet of mixed clay, sand and fine ore has been removed, the under surface reveals solid rock-ore in large lumps, mixed with clay in a confused arrangement, of great richness and va- riety. An integral difference in the clays of these ores and the limestone pipe ores (one to be expected probably from their different horizons) is the much greater stiffness and toughness of the former. The clay of these lower ores fre- quently occurs in non-ferruginous bands or dykes, running through the length of the banks, barren, and hard .to pass through the washers, but by no means cutting off the ore. This non-ferruginous clay has usually a white to pink color ; while the yellow clay of the pipe ore deposits is inti- mately mixed with the ores and offers no material resistence to their thorough cleansing in the washing-machines. Moreover, it may be noted that in every case the ore of the barren needs jigging in addition to washing to free it from the mixed sand and flint that accompany it. All the analyses of these ores show an absence of bisul- phide of iron, and the occurrence of all the iron as sesqui- oxide at once suggested a different chain of effects in the production of these as compared with the pipe ores, to be presently described, where this salt of iron is frequently present. The sand rocks which originally held these ores occupy a position low down in the sandlime series of II. By having their lime leached out, these loosely aggregated sandstones have fallen into sand, and it is probable that this same leaching action has concentrated their iron salts, which would be deposited as insoluble peroxide. What changes may have followed this process of deposition to 374 GEOLOGICAL SURVEY OF PENNSYLVANIA. bring about the irregular and confused appearance of the banks to-day and the grading of the ore body from fine to coarse lumps is a matter of speculation still. The deposits do not look like formations in situ, nor would such a theory explain the rounded character of ore and flint balls and occurrence of barren spots beside nests of great richness. While no distinctively pipe ores have been reported from the ore banks in the "barrens," some persons detect in the compact needle ore (occasionally met with) a form of pipe, and illustrate their opinions of the common origin of pipe and hematite ores by this fact. Physically and chemically they appear to be quite different ; but the general resem- blance of all ores from different banks, divided only as to two classes, is not as remarkable as the local variations which give rise to the occurrence of bessemer, neutral and cold-short ores lying quite close to each other, and appar- ently along the same range. 2. The pipe ores have varying horizons in the limestone, and though generally above the essential ''barrens" limo- nites, it is by no means certain that some of them do not occur also in the 1000 feet of limestone beneath these. The frequent connection of damourite slate beds with the chief ore bodies in the southeastern district of the State is not observed in Centre county. It is true that most of the pipe ores are accompanied with a white and buff-colored clay, which may be the result of the decomposition of such slate bands ; but it may also represent the disintegration of the magnesian limestones themselves. While the chemical explanation of these facts is still a matter of speculation, repeated examinations of the ore banks in various parts of Nittany and Penns valleys leads me to believe that the pipe ores are deposits probably due either, first: To the decomposition of iron pyrites, origi- nally contained in the limestone or slate bands, and after oxidation as sulphate, filled into interstices in the limestone, and changed into peroxide by contact with vegetable mat- ter or other organic substances ; or, second : To the prior pro- duction of ferrous carbonate, by reaction between the fer- rous sulphate and the calcium carbonate of the limestone, CENTRE COUNTY LIMONITE MINES. 375 afterwards converted into limonite by oxidation and hydra- tion. The manner of occurrence between walls of regularly- bedded limestone, sometimes as thin shells of ore and again as large pipes in masses 8 to 10 feet thick, would confirm one or the other of these views, while the presence of iron pyrites in perfectly undecomposed pipes surrounded with thoroughly oxidized ore in the Sinking Creek mine in Penns valley, lends probability to the theory. The presence of pyrites in hematite is not new, and the many analyses show- ing bi-sulphide of iron in the succeeding pages will illus- trate its frequency in this district. Crystallized brown hematite, a pseudomorph after pyrite, has been gathered in the Cumberland valley, as well as specimens of bombr shell ore holding a clay inside filled with loose crystals of pyrites. In other banks showing a low percentage of sulphur many of these ores may have occurred as carbonates in the slates, which upon the dissolution of their lime matter have deposited these iron salts as now found. In those banks where a considerable surface deposit has escaped from the general erosion, this oxidation has been so com*- plete as to show but a low percentage of sulphur ; whereas, in the case of the Sinking Creek mine before mentioned, the ore occurs in places between limestone beds, and has not yet had a chance to become thoroughly changed. The outcropping of these pipe ores is spread out to a much greater extent than they occupy lower down be- tween limestone layers. The width of these outcrops is affected by the topography of the country. This surface ore is greatly disintegrated, and occasionally is indeed so fine as to be hardly distinguished from so much reddish brown loam or earth ; but a close inspection of it will re- veal the presence of small stems or pipes, making usually a cubic yard of ore for each 4 or 5 cubic yards of material, and often better. The work of the season did not confirm the popular be- lief in continuous belts of ore-producing territory along miles of surface outcrop. At best, while assigning approx- imate horizons to these pipe ore deposits, they have their 376 GEOLOGICAL SURVEY OF PENNSYLVANIA. Section ofPenn's Valley through BoaLsburg. /. XIV. Section through the Henderson farm S.W.ofBoalsburcj. * , Map ffftfie anJcA. 406 GEOLOGICAL SURVEY OF PENNSYLVANIA. the arch to the east of it strata more than 5600' beneath III. How much more lie concealed in the arch can only be guessed by the little Juniata section, which measures be- tween 6000' and TOGO' feet and still does not expose the bot- tom beds of the great formation. Mine No. 1 (Dams mine), is an open cut, 600'x500'x30' to 65' deep. It is surrounded by a well denned ore ground limit, 2600' N. and S. by 300' to 1450' wide, outside of which the surface is a sandy waste without ore, as both surface show and trial pits combine to prove. The ores are of every grade of color, character and value. Fig. 14 of pi. XXII shows how little of the ore mass has been removed, chiefly wash ore. Shafts 1, 2 and 3, respectively 65', 100 and 161' deep, show the depth of ore mass, as they strike the sandstone floor on which the ore mass lies and crops out to the surface on theE. side of the mine, disintegrating to a sharp clean sand. The upper sandstone layer is heavily incrusted with ore, and its small cavities and irreg- ularities are filled with ore. The first 60' of wash ore was mined in open cut ; then a 60' shaft went down in lump and wash ore, pitching west against the sandstone. The wall of the pit must be ex- cessively steep since this 120' shaft is only 35' from the solid rock wall. The mine is therefore a cavern deposit, one of the very few cases wherein a demonstration can be obtained.* Shaft 3 has the following record : Loose wash ore very lean in places, clay layers, 40' ; block and lump ore, 2' to 3'; worthless wash sand and clay masses, 112'; ore in white and yellow clay, 6'; sandstone, massive to bottom (161'). But this record disagrees with every other section in the mine and may, perhaps, be accounted for by the fact that the miners were in search of large lump and pipe ore only, and considered all small- wash ore-ground worth nothing to them. For on the W. side of the bank, wall and shaft prove wash ore 120' deep. Elsewhere also the whole mass is solid but variable wash ore. It is interesting that loose pieces of sandstone, ferrugi- *It is possible that it is a small synclinal on the crown of the arch. (F. Platt, in T, 162). THE SPRINGFIELD MINES. 407 nous slate, and pieces of sand rock greatly resembling spe- cimens of IV and V. and conglomerated sandstone frag- ments held fast by an iron ore cement, are all found in the ore mass. Between the Davis and Lykens pits, say 2000', is barren ground. Mine No. 2 (Lykens'), is 600'x400'x80' deep (once 100') encircled by a limit of ore ground. 2200'xlOOO', on the sur- face. It is worked for the Cambria Iron Co. The Lykens' shaft at its N. end has a great output. No bottom to the ore has been reached in the cut ; but the shaft strikes the sand rock floor at 215'. It works solid ore, that is, great lumps packed close together in the clay ; usually in two layers, the upper one reddish ore, then I/ to 4' sand or sand- stone, then the lower one heavy black lump ore in clay, resting on the true sandstone floor. Both the ore layers and the sandstone parting vary much and rapidly in thick- ness, but in the main rising and falling together conforma- bly to the irregularities of the sandstone floor. This mine is remarkable for the quantities of bombshell ore in it, and for the scarcity of honey comb ore. The bombs are some- times of great size, some filled with soft white lime clay, others with more or less decomposed sandstone or sand, many quite hollow/* Mine No. 3, is of a totally different character, on a geo- logical horizon only 2600' beneath III, separated by more than a mile of barren limestone outcrops, and in limestone hollows. Its wash ore body contains mostly only small rounded water worn ore balls. f The open pit 6' to 20' deep shows only wash ore in caves in the limestone separated by promontories and ribs of limestone. Fine grained waving purple or brown or white clays all carry varying amounts of the ore balls. Dark limestone walls in the whole pit, and an occasional layer of slate parts two limestone beds. The floor also is limestone. But at a place where nearly solid ore made the tempo- *See other details and numerous ore analyses in T, 163, 167. f Occasionally some rounded pieces of sandy limestone and limestone are noticed in this mine also. 408 GEOLOGICAL SURVEY OF PENNSYLVANIA. rary floor of the pit a horizontal drift followed the ore (S. E.) for WO' under solid limestone cover, and soon a solid limestone floor was got also. A 45' shaft from the surface struck the end of the drift. The ore layer, thus inclosed in the limestone, when mined averaged 5', but varied between V and 19'. This is very remarkable as it shows the possi- ble production of limonite between almost horizontal strata of unchanged rock. It also shows a sort of broad shallow synclinal, (or shelf ?) on the western limb of the Canoe valley anticlinal. All this agrees very well with the description of the ore production at the Pennsylvania banks in Centre county, which are also on the same geological horizon, viz : 2600' beneath IIT.f The Prussia mine, small, abandoned, 1500' S. W. of Springfield No. 2. Tar Hole bank 600' N. W. of the Prussia. McPheese bank 3000' S. W. of Springfield No. 2, but separated from its ore-area by barren ground ; a small pot of wash ore. Canoe valley, at Williamsburg, and at Springfield, is 4 miles wide, [measuring between the two edges of the lime- stone floor, and 5 between the crests of its bounding mountains. At Rebecca furnace mines (10 m. S. of Wil- liamsburg its width is but 3 miles. Here Canoe (or Lock) mountain swings round to the west, and projects as a broad round synclinal knob southwards into Morrison's Cove. The slate on its flank runs on south, in the synclinal as a narrow belt, past Martinsburg two or three miles. At Martinsburg and Fredericksburg the limestone land is 3 m. wide ; this is 12 m. S. of Williamsburg. Millerstown is \ See further description and numerous analyses in T, pp. 171 to 177. No limonite mines are more extensive, valuable, or better worked than these and that is my excuse for so largely extracting from the Report. It seems that traces of cobalt appear also in these ores, T, 172, 173. See accounts of plant, machinery, etc., T, 177. LEATHERCRACKER COVE ORES. 409 14 ; Henrietta furnace mines, at the entrance to Leather- cracker Cove, 15 ; and the head of the cove 17 m. S. of Williamsburg. Between Fredericksburg and Millerstown a belt of slate 2 m. long and m. wide splits the lime- stone land into two belts ; the eastern one lying along the foot of Tussey running S. to the head of Leather- cracker cove ; the western one running on S. past Curry, Woodbury, Waterside and Enterprise, to the south end of Morrison's cove. The slate belt is a sharp and faulted synclinal between the Henrietta (Leathercracker) anticlinal and the Curry- Woodbury anticlinal.* Leather cracker Cove ores. The Henrietta mines in Leathercracker Cove have been described in a previous chapter on the Limonite ores of the top of II, but only in such general terms as might state their possibly very exceptional horizon at the contact of II-III. This was once considered by others as well as by myself the true theory. But I am more and more confirmed in the belief that this is a mistake, and that they belong to middle horizons of. the formation brought by the faults into contact with III, as in the case of the Path Valley mines in Franklin county. It only remains to notice here the character of the Hen- rietta ores, referring the reader to Mr. Platt's full details in T, 183 to 202. PL XXIV, f. 20 maps the main pit, 600'x200'x60' deep, all in ore clay. Projecting boulders of limestone, much rounded by chemical decomposition, stand up irregularly on the floor, from around which (as also from around masses of barren clay) the wash ore has been removed, f *On the great map sheets of the Morrison's Cove Survey, in Atlas to T, this is improperly named the Morrison's Cove anticlinal, and the other the Canoe Valley anticlinal. In fact, however, both represent the great Canoe Valley anticlinal in its southern course where its crest is split by a synclinal roll. The Bloomfield anticlinal is a great wave of the western half of Mor- rison's Cove. The Woodbury-Curry half of the Canoe Valley anticlinal becomes the great wave of the eastern half of Morrison's Cove ; the two be- ing separated only by the wide shallow synclinal of Lock Mountain. f Some of the main features of the mine are similar to features found in nearly all the brown hematite deposits of the lower Siluro-cambrian lime- 410 GEOLOGICAL SURVEY OF PENNSYLVANIA. and <&eatnerc>racfce, p. 77, and the map of Miftiin county in the same Atlas, No. 41. t DescribecTin detail and with special maps in Report T3. The valley is de- scribed hy d'Invilliers in his report F3 and the fault on p. 239. It will be hereafter described in the chapter on Oneida and Medina sandstone forma- tion N. IV. 422 GEOLOGICAL SURVEY OF PENNSYLVANIA. mining was long ago abandoned. No doubt there is this good geological reason for a scarcity of ore, viz: that the valley erosion had not been carried down deep enough into the magnesian (Chazy) part of the formation.* The fact is, the Trenton is so thick and the dips are usu- ally so low, that the Chazy has but little chance to reach the present surface. On the other hand the limestone quarries of the valley are all excellent, and the Trenton beds furnish also hydraulic limestone, on which at Milroy a large plant is now (1891) being established, f Black Log valley. Slack Log valley in Huntingdon county (its N. E. end in Mifflin) is 20 miles long, by 1 mile wide, and on a gentle curve4 It is a fine specimen of the class of valleys and coves of limestone and slate produced by the erosion of the high steep compressed rock waves of Pennsylvania. In this case the anticlinal had a double crest, which it shows at the present surface ; but it is probably a single simple sharp anticlinal underground. The breadth of limestone at Orbisonia gap is only 2600' feet ; and the thick- ness of Trenton limestone about 500'; from under which rise only the upper beds of the Chazy (lib) on the two crests of the wave. | The fact that no limonite ore has been found in Black Log Valley goes far to support the view that there is really * D'Invillier's Report F3, 1891, p. 237. t There are, however, steep dips in some places. On the creek road from Belleville to Union Mills the beds dip 65 and 68, S. 55 E. At the quarry on Yoder's farm the stone looks more like slate than limestone; and this is the characteristic feature of the Trenton beds in middle Pennsylvania. The Trenton is in fact a transition formation from the magnesian II to the argil- laceous III. The Utica slate here dips 60, N. W. (T3, 238). JSee Geol. Atlas of Counties, Report X, 1885, Map of Huntingdon No. 31, and preface descriptions, p. 57. A cross-section will be given in a future chapter. j| The Grove quarry seems to show the limit of the Trenton beds down- ward, and the top bed of the Chazy, by the following analyses in Ashburn- er's Report F, 1876, p. 260. Carbonate of lime in top bed (22" thick) 90.16. Then follow downwards 84.68, 89.68, 74.18, 81.18,82.60,80.68,82.18, 85.18, and then the bottom bed, only 46.68, which may be assumed as the top of the Chazy. VALLEYS AND COVES OF NO. II. 423 no limonite horizon at the junction of II and III ; that is, at the top of the Trenton, and at the bottom of the Utica. McConnellsburg cove. TheMcConnellsburg cove in Fulton county, is a canoe- shaped valley with pointed N. E. and S. W. ends, enclosed in mountain walls of Medina sandstone(IV), with slopes of Hud- son river slates (III), and a fertile floor of limestone (II), 13 miles long by 2 miles wide. It differs from all the other coves in having along its N. W. side a profound fault, the limestone (II) being upthrown 80CO' against Devonian strata (VIII). This fault swallows up the slate (III) and sand- stone (IV) and consequently destroys the mountain wall on the N. W. side of the cove.* The limestone beds at McConnellsburg and between that village and the school house dip 55 towards the fault (W.) and are mostly silicious, with much honey-comb chert, and so red a soil in some places as to suggest a good deal of limonite iron ore. At Sargent's Rocks, in the southern end of the Cove, are the extensive old limonite banks of the Hanover Iron Works, worked for about 25 years, and abandoned in 1847. The annual yield of ore is said to have varied between 1200 and 2000 tons, and much ore is sup- posed to remain. Its horizon is high in the formation.! The furnace got also some ore from the Patterson place, on the eastern road towards the pike, and trial pits were sunk on the Nelson farm, but all such work was abandoned forty years ago; and the development of the ores of the Cove is still to be made. The underground erosion of the limestone strata is vari- ously illustrated in the Cove. Its south end is drained by Esther's run, heading in the high vale between Cove and Dickey's mountains. In about 4 miles it sinks, and rises again in the Big Spring ; then cuts through the Me- *A description of the fault is given by Stevenson in his Report T2, p. 55, 56 ; and details of its exhibition in his subsequent chapter XIII on Ayr, Todd and Dublin townships, T2, p. 291 et seq. t Analysis by McCreath: Iron, 46.1; sulphur, 0.115; phosphorus, 0.083; sil. mat, 21.5 (T2, p. 296). 424 GEOLOGICAL SURVEY OF PENNSYLVANIA. dina ridge, and joins Cove creek between the Lutheran Church and Elysian Mills.* Horse Valley. Horse Valley at the S. W. end of Perry county, con- tains a narrow belt of limestone land, with two points or prongs at its north end, where the anticlinal has two crests, and only one point at its south end, where the anticlinal is simple. It is one of the branches of Path Valley in Frank- lin county, and almost its whole floor is made by the slates of III. Occasional pieces of limestone have been found near the gap.f * The drainage of the Cove is very curious as shown on the colored map of Fulton county in Report T2. The natural course of Esther's creek would have been around the N. end of Lowrie's Knob instead of through a gap in the ridge (IV). So also at the northern end of the Cove, the drainage ought all to flow south past McConnellsburg into Cove creek. Instead of that, it gathers itself by streams that flow N. as well as S. and W. into Licking creek, which breaks a gap through the Medina mountain (IV) at Knobsville. f See Geol. Hand Atlas, Report X, 1885, Map No. 45, and Preface p. 85. Dr. Henderson made the top beds of II reach the surface. But Prof. Clay- pole could not satisfy himself of the fact, and drew his cross-section as if the limestone did not See his Report F2, page 352, and his section on page 350, which I reproduce in a future chapter. CAVERNS IN NO. II. 425 CHAPTER XXXVI. Caverns and sinkholes in II. The whole surface of the limestone belt of the Great Val- ley is pitted with sinkholes in the farmers' fields. By these holes the rainfall escapes into caverns, which ramify in all directions both along and across the stratification, and re- appears in springs in the beds of the deeper valleys. This explains the scarcity of brooks and creeks on the maps of the limestone belt in the Great Valley ; and on the maps of Kishicoquillis and Nittany valleys and their branches, and the limestone coves of Fulton and Bedford counties. Many ancient caverns are now dry, the drainage having opened for itself new ones. Others have been deserted be- cause completely choked .and filled with lime-iron clays and ore. Others have been exposed to the sunlight by the fall- ing in of their roofs, and converted into vales by the solu- tion of their walls. Those which were filled with deposits arid then uncovered form the limonite iron mines of the present day.* *A most instructive case is described by Prof. Ewing in his special report embodied in Report T4 on Centre county, at page 418. I give his descrip- tion verbatim, as follows : ''Cavern deposit of iron ore. On Sinking creek, as it rounds Egg hill, in Potter township, on the Wagner place (A. Kerr, in county atlas), is an ex- posure of ore quite unique in many respects. The ore occupies caverns eroded out of the limestone. In this exposure most of the limestone is left intact. The ore that has been removed has been taken from openings into the solid mass where erosion has removed the material from one side. Even there it is necessary to remove large quantities of limestone in order to get the ore. Large masses of pipe ore are found, with lump ore, bomb shell ore, and wash ore. Most of the ore taken out has been removed from one large triangular space, having sides about 20 feet in extent, and a depth of 15 feet, one side forming an opening from the bank of the creek-bed. Besides this, several small test-holes, drift, and slant openings have been made. Those within a range covering not more than 20 or 25 feet in thickness of rocks strike ore of the same character ; those out of this range show but little ore. The ore is found in the worn joints imbedded in a tenaceous red or yellow clay. "As pipe ores are undoubtedly formed by the evaporation of chalybeate 426 GEOLOGICAL SURVEY OF PENNSYLVANIA. Shifting creek in Blair county offers a fine example of the extensive underground chemical erosion of limestone beds in the upper part of No. II. Its Arch spring became famous among the white settlers at an early date.* The waters, which percolate through the mass, one might expect to find in a place like this evidence as to the time of the formation of these pipes. The fact that all are broken off none being attached to the limestone implies that they were formed at a sufficiently remote period for subsequent waters to dissolve away the attachments. The fact that the pipes are straight and generally parallel, implies that they were formed while the rocks were sta- tionary, and not during a gradual upheaval. It is inconceivable that they were formed while the rocks were in their original horizontal position ; hence, it is altogether probable that they were formed after the Appalach- ian upheaval, and while the rocks were in their present position, that is, dipping 45 S. E. "One very interesting specimen from this region has one of the pipes at an angle of 40 with the rest. I think it probable that in this case the pipe had broken in falling, and had been cemented by subsequent depositions of the same material, as there is abundant evidence of later depositions in thread- like pipes at right angles with the larger ones. "As previously remarked, the probable condition of the ore while in so- lution, and at the time of deposition, was that of a ferrous carbonate. It is probable that oxidation began at the time of, or soon after, deposition. When the deposition was rapid, masses of carbonate and semi-carbonate were doubtless formed, which have subsequently been oxidized. Evidence of this is seen in the larger masses found, especially here, of ore containing cavities, giving it a porous appearance, often called bomb-shell ore ; for as the carbonate of a low specific gravity changes to the oxide of a higher spe- cific gravity thei-e is a loss in volume. The change naturally beginning from without forms concentric layers of the oxide and leaves cavities within. Even the pipe ore is more or less porous." * Captain John S. McKiernan, who moved from Blair into Clearfield, sent to the Tyrone Herald, March 11, 1886, the following slip from a very old newspaper : "Among the other curiosities of this place, is the swallows which absorb several of the largest streams of the valley, and after convey- ing them several miles under ground, in a subterraneous course, return them again to the surface. These subterraneous passages have given rise to the name 'Sinking Spring Valley.' Of these the most remarkable is called Arch Springs, and runs close upon the road from the town to the fort. It is a deep hollow, formed in the limestone rock, about thirty feet wide, with a rude natural stone arch hanging over it, forming a passage for the water, which it throws out with some degree of violence, and in such plenty as to form a fine stream, which at length buries itself in the bowels of the earth. Some of these pits are near 300 feet deep ; the water at the bottom seems in rapid motion, and is apparently as black as ink, though it is as pure as the finest springs can produce. Many of these pits are placed along the course of this subterraneous river, which soon after takes an opportunity of an opening at a declivity of the ground and keeps along the surface among the rocky hills for a few rods, then enters the mouth of a large cave, whose ex- CAVERNS IN NO. II. 427 creek rises on the high ground of the Kettle at the south end of the valley, and flows along the exis of the anticlinal for 3 miles ; then works over to the east side of the valley and flows in the upper limestones at the foot of the mount- ain for two miles ; disappears in a large sink hole and flows underground a mile, its "hollow" or surface channel being dry. Another creek, heading near the Bald Eagle mountain, on the west side of the valley, and flowing square across it to the hollow, meets a brook descending from the east mountain terrace and flows one or two miles further along the hollow, according to the wetness or dryness of the season, and disappears gradually through a succession of sinkholes. A third creek starts in the center of the val- ley five miles north of the last mentioned, flows across east- ward 1^ miles, enters a large cave, flows under its roof 4200 feet, issues from a picturesque arch at the N. E. end of the cave, and thence flows through a flat to the river at Union Furnace. Elk run follows the opposite or N. W. outcrop of the same limestone beds at the foot of Bald Eagle (Brush) mountain, cutting a deep narrow trench to the river at Tyrone forges ; and this trench merely represents a similar series of sink-holes and caves which have lost their roofs. All the brooks descending from the terrace further south than the head of Elk run, fora distance of two miles, sink as soon as they pass the edge of the slate belt and enter the limestone land. Of course their waters rise somewhere to terior aperture would be sufficient to admit a shallop with her sails spread. In the inside it keeps from 18 to 20 feet wide. The roof declines as you ad- vance, and a ledge of loose, rugged rocks keeps in tolerable order on one side, affording means to scramble along. In the midst of this cave is much timber, bodies of trees, branches, etc., which being lodged up to the roof of this passage, shows that the water is swelled up to the very top during freshets. This opening in the hill continues about 400 yards when the cave widens, after you have got round a sudden turning point (which prevents its being discovered till you are within it) into a spacious room, at the bot- tom of which is a vortex. The water falls into it, whirling round with amaz- ing force ; sticks, or even pieces of timber are immediately absorbed and carried out of sight, the water boiling up with excessive violence, which subsides by degrees until the experiment is renewed." 428 GEOLOGICAL SURVEY OF PENNSYLVANIA. augment Elk run ; just as all the waters of the Sinking creek system issue at Arch Springs.* A cave in Gregg township, Centre county, is described by Prof. Ewing as typical of the many which ramify be- neath Nittany and Brush valleys. It is about a mile west of the end of Brash mountain ; on the 43 S. E. dip of that synclinal ; in dark blue limestone, possibly near the middle of formation II. f The "Hollows" of our limestone country are not ordi- nary valleys of erosion but unroofed ancient caverns. This is apparent from their peculiar shape, and the fact that many of them are dry, that is, have no flowing streams, but are studded with sink-holes into which the rainfall dis- appears to caverns beneath them which have been subse- quently formed. Prof. Ewing describes one known as the Big Hollow, in Centre county.:}: *Fine pictures of these arches and caves were made by Prof. Rogers' ac- complished Swiss artist, Mr. Lehman, and published in the Geology of Penn- sylvania, 1858, Vol. I. They will be found (reduced) in a future plate. f In Report T4, p. 442. " The entrance is from a deep sink. It extends along the strike of the rocks and contains deep clear water. It is suffi- ciently large to allow navigation in a large row-boat Its height in places is 20 or 30 feet, and its breadth about the same. The roof of the cave is formed for the most part by one thick stratum of limestone. In places, however, this has fallen away, leaving exposed the strata above. The cave extends 1200 feet beneath the surface. At the far end the rocks dip in a more easterly direction, so that the roof comes down to the surface of the water. About 300 feet in, the cave divides into two parts, one wet, the other dry, the same stratum forming the roof ot both. The side toward which the rocks dip contains the water, the more open side apparently having its bottom filled by the d&bris fallen from above. The two arms are separated by a natural partition of uneroded rocks. The dry cave may be reached by another sink in line with the opening alluded to. Within the cave are stal- agmites and stalactites of every variety of form. "About 80 feet from the far end of the cave is a deep ravine, and the Fathomless /Spring known as the source of Penn creek. As the water in the spring stands at the same level as that in the cave, the two are probably connected ; and the cave is no doubt only one section of a much larger sys- tem of underground drainage ; for, a short distance nearly west of the cave a stream sinks beneath the surface, and is probably identical with that which appears as Penn creek." JT4, p. 442. "Several beds of ancient streams are noticeable in this lo- cality. One of the most extensive of these appears to originate near Johns- ton's ore bank. Here several indistinct depressions converge into one ravine which crosses the road passing northeast of Struble's bank. The Bellefonte and Buffalo Run RR. grade follows this ravine to thecurve near Thompson's, CAVERNS IN NO. II. 429 Of the innumerable limestone caverns of Pennsylvania very few have been explored, most of them are inaccessi- ble, and the existence of a great number of them is only indicated by sink holes in the farm fields. One of the most interesting is the Hartman cave (now the Crystal Hiil cave) in Monroe county, which was explored in 1880, and found to be floored by 10' of clay, on which was spread a thin layer of stalagmite, and on this again a foot of black earth containing the teeth and bones of ani- mals of both extinct and living species, mostly broken, splintered and gnawed by large and small carnivorous beasts which at one time made the cave their home, dragging into it their prey to be devoured.* where a branch ravine joins it ; which the grade follows upward, diagonally, through the Barrens. This ravine is traceable to the vicinity of the Pond bank. "The main ravine, known as Big hollow, continues in a sinuous course northeastward until it reaches Spring creek, one mile below Houserville. Big hollow has a distinct course of about five miles ; its banks are in places from 50 to 100 feet high, here sloping and gradual, there steep and precipi- tous. As in the case of real river channels, the steep banks are on the inside of the curves. " The whole topography of Big hollow indicates that it is the bed of an an. cient stream. An extensive area slopes toward this ravine. Several smaller ones join it on its course, yet I know of no evidence that water has flowed through it since the first settlement of Centre county ; but I have found numerous sink-holes along the channel ; and gravel deposits and other de- bris in the vicinity of some of them indicate that large quantities of water have flowed into them in times of freshet ; and this makes it probable that there exists beneath the Big hollow an underground channel joining Spring creek." *The report of the exploration, made by Mr. Paret, Prof. Porter and Dr. Joseph Leidy, was published in the Annual Report of the Geo. Sur.Pa. for 1887, pp. 1 to 20, with two plates by Dr. Leidy, who identified the remains of the living lynx, gray fox, wolf, skunk, weasel, raccoon, mole, dusky bat? little brown bat, woodchuck, porcupine, beaver, musk rat, gray squirrel, ground squirrel, meadow mouse, white footed mouse, wood rat, gray rab- bit, deer, elk ; no domestic animal, except perhaps a pair of imperfectly de- veloped teeth of a horse ; many bird bones, especially of the wild turkey several kinds of turtles and snakes ; snail shells, a valve of the river mus- sel, and two other shells ; some small fragments of charcoal ; many seeds of dogwood, pignut, walnut ; works of man, a bone fish hook, harpoon head, 5 bone awls, a bone needle, a bored cone shell, a chipped spear head of argillite, a black flint knife and a piece of brown pottery. But with all the above were found remains of the extinct peccary (Dicoty- 430 GEOLOGICAL SURVEY OF PENNSYLVANIA. A vertical cavern in the limestones of II was exposed by quarry work in the Chester county valley near Port Ken- neday, and explored by Mr. Wheatley, of Phoenixville ; the animal remains being described by Prof. Cope. These were all of a comparatively recent geological age. This fact, taken in connection with the Tertiary lignite beds of the Pond bank in Franklin county, and the Ironton mine in Lehigli county, prove that all our caverns are of geologic- ally modern construction, and belong not at all to the re- mote dates of the limestone formations which they pene- trate ; that they are in fact the last descendants of an infi- nite series of caves excavated in successive ages, and un- roofed and swept away as the unceasing erosion by atmos- pheric waters lowered the original surface of the globe to its present level. The rate at which this erosion has gone on deserves consideration. The rate of erosion. The rate at which the surface of our limestone valleys has been lowered is hard to calculate. It depends (1) on the amount of rainfall from year to year and from age to age ; (2) on the way the rain falls, whether in a perpetual drizzle, or in violent downpours ; (3) on the slope of the beds of the water channels, whether more or less steeply inclined ; (4) on the solubility of the rocks, both in general and in par- ticular, determining the shape and size of caverns, the sta- bility of their roofs, and consequently the amount of me- chanical erosion which is in addition to the amount of chemical solution. Undoubtedly a part of our limestone formation passes off to the ocean as lime water ; but another part passes off as broken matter, floated limestone pieces, limestone sand, limestone mud. And when the new oceanic deposit is made it must represent both these forms ; as we see that it does ; for the microscope shows mechanical fragments cemented by a chemical precipitate. les pcnnsylvanicus) ; of another larger extinct peccary (Platygonus vctus}; and of the extinct gigantic beaver (Castoroides ohioensis.*) This cave, not being in No. II, but in the lower Helderberg limestone No. VI, will be more properly described in a future chapter. CAVERNS IN NO. II. 431 The chemical solution of the limestone strata of Centre county was studied by Prof. A. L. Ewing in 1883*, at the upper end of the Old Bellefonte dam, below the entrance of all visible tributaries of Spring creek. (1) The cross-sec- tion and velocity of the stream were here measured ; (2) the amount of solids in the water was determined by evapo- ration ; (3) the area of the whole water basin was calcu- lated geographically. 1. The average width, 75' ; average depth (six measure- ments), 2.7' ; average velocity (got by bottles floated at va- rious depths), 3263' per hour = about 24, ,500 cubic yards of water passing a given point every hour. 2. By evaporation (two tests), 2400 grains of solid matter were got from one cubic yard of water ; according to which (24,500x24x365x2400-5-7000=) 73,584, 000 Ibs., or 328,500 long tons of solid matter carried away per annum. 3. The area drained by Spring creek is rudely estimated at 100 square miles, three-fourths of which is mountain slope ; the rest limestone valley. By evaporating mount- ain water it was found that nine-tenths of the solid matter in Spring creek came from the limestone valley. Prof. Ewing calculated the annual waste of the region at 282 tons per square mile ; and the waste of the limestone valley by solution at 275 tons per square mile. Taking the specific gravity of limestone at 2.75 (Traut- wine, p. 386), a layer one foot deep over a square mile would weigh 2,140,540 gross tons. A layer of 275 tons would be only one-eight thousandth (^oW) f an mc ^ thick. In other words the surface of Nittany valley is lowered at the rate of one foot in eight thousand years by the loss of what is constantly running off past Bellefcnte, so far as that can be calculated in the manner described above. Other things, however, have to be taken into considera- tion which should vitiate the correctness of that result without substituting for it another more reliable. The loose stones in the main channel and in all its branch water ways show that annual floods play a role of great import- *Proc. Am. Ass. Adv. Science, 1884; copied into Report of Prog. G. Sur. of P., T3, 451. 432 GEOLOGICAL SURVEY OF PENNSYLVANIA. ance in the operation ; frost loosening the limestone slabs, and water breaking them into pieces, grinding them to- gether, and sweeping them away into the Susquehanna river and so onward into the sea. The rate of this mechan- ical destruction of the surface is unknown, and probably cannot be in any manner calculated. It' it be assumed equal to the rate of chemical solution, the surface of the country may be said to lower itself one foot in 4000 years. But even this more rapid rate cannot be adopted for cal- culations extended backward many ages ; for, while the chemical solution is a constant quantity, provided the an- nual rainfall be a constant quantity^ the rate of mechanical erosion depends on the velocity of streams, i. e. on the slope of the water-basin. But this was much greater in past ages than it is now. When the top limestones on the Belle- fonte and other anticlinals were first laid bare the general surface of the region had a topography exactly resembling that of the Shade and Black Log region at the present day ; but it had an elevation above the sea at least 5000 feet higher. Of course erosion went on at its usual high rate in Alpine regions ; but as we have no data for calculation, it is left to the imagination of the student of nature to adopt a mean rate between the extremes of excessive me- chanical erosion at the outset and of excessive chemical solution now. At present the water fall from the head of Spring creek (1290' A. T.)* in Penn's valley to the dam at Bellefonte is only about 57C', and from Bellefonte to tide water in Chesa- peake Bay about 720' At the birth of Nittany valley the fall of the Spring creek which then traversed it lengthwise (as Black Log creek traverses its valley) was say 500', and of the Susqnehanna river which then existed say 5000'. The rate of surface erosion may well have been then 400 or even 100 years per foot. All such calculations are therefore fruitless, seeing that the age of Nittany valley can be made at will either 40, 000,- 000, 20,000,000, 2,000,000 or only 500,000 years. If we go back beyond the uncovering of the top limestones of No. *T4, 419. CAVERN DEPOSITS IN NO. II. 433 II on the Bellfonte anticlinal to the coal age, we greatly increase the time, but not in proportion to the thickness of the overlying formations ; for, the erosion must have been vastly more rapid when the surface stood 20,000' or 25,000' above the sea. In fact this part of our science is nothing but a fairy tale ; and the best geologist is merely the most lively ra- conteur. Precipitation of limonite in caves. The rate of deposit of limonite (hydrous peroxide of iron) in cavities is sometimes, under favorable circum- stances, quite rapid. For example, at the Bennington shaft near the Allegheny mountain summit tunnel of the P. RR. in Blair county "the pump column" receives from the mine water one inch of such deposit each year, supplied by the decomposition and oxidation of carbonate iron ore balls in the roof shales of the Miller coal bed. And again, at Johnstown, in the Slope mine, an area of half an acre (near New Furnace No. 5) is now being filled with limonite mud from the same source (viz : decomposition of ore balls in roof) so rapidly that a layer 18 inches in depth has been made in the course of the last eight years ; so that it looks as if the whole space once 'occupied by the coal bed would in a few years more be occupied by a consolidated bed of limonite iron ore.* *The process is facilitated in this instance by the fact that some warm water from the large furnace works passes through the roof of the mine. (Report T, p. 171.) The deposit of iron rust in the municipal purifying revolvers at the Ant_ werp water works is accompanied by physical details of the greatest inter- est for geologists studying the theory of the formation of limonite deposits, including organic matter, clays of various colors from white to black, and concretions. "In March, 1885, three of these revolvers were started at Ant- werp, and the original iron and gravel beds were converted into ordinary sand filters ; by this change the capacity of the works was at once doubled. The total weight of iron in use at one time was reduced from 900 tons to 3J tons, and all the expenses connected with digging over and washing the purifying materials were done away with. "When pure water is passed through a revolver, a certain amount of iron is dissolved, and then the water flows out a light gray color. After two or three hours, the color changes to a reddish brown, and a deposit of rust 28 434 GEOLOGICAL SURVEY OF PENNSYLVANIA. Depth of limonite deposits in caves. The depth of a limonife ore-clay mass therefore depends on the depth of the cavern floor ; and this in turn depends upon the deepest drainage level of its district. Theoretically such a deposit of ore ought not to be deeper than the place where its ancient water course came out on the Lehigh or Schuylkill river, but, considering the chem- ical action of the water on the floor of the cavern, and in fissures descending beneath the floor, some slight additional depth must be allowed. It is a practical geological rule, however, that an owner of ah iron bank in fterks county cannot expect to find ore below the plane of 200' above tide, which is the level of the bed of the Schuylkill at Reading, and the level of the bed of the Lehigh at Allen town. An allowance must also be made for the grade of the descent of the underground water from the mine to the outlet. An iron bank near Reading maybe deeper, therefore, than one at Kutztown or at Womelsdorf can be. Topton Junction, for example, stands at 485' A. T. Subtract 200' from 485' takes place at the bottom of the vessel. If filtered at once on escaping from the revolver the liquid will generally be clear at first, but after a time it will sometimes get cloudy and the deposit of rust will take place, showing that the iron existed in the first instance in solution, and was afterward precipitated by the action of atmospheric oxygen. If the water be impure, colored and charged with dissolved organic matter, it will issue from the revolver of a dark gray color, and this will increase to an inky black in the case of very bad water. So that it is possible to judge of the quality of the water by the color assumed during its treatment. If the impurities are not more than the iron can deal with, the liquid, on stand- ing for some three or four hours, becomes lighter and lighter in color, a black precipitate forms, and sinks very slowly to the bottom, the color be- comes a dirty gray, and then the water will filter quite clear and bright. If the impurities overpower the iron, or are of a nature which the iron cannot effectually attack, a purplish color remains, and the liquid will not filter col- orless. As in the case of the Bischof filter, the time of repose and exposure to the air before filtration is obtained by providing a sufficient depth of water over the sand of the filter beds. "In addition to its chemical action, iron possesses the property of causing the very finely-divided particles of matter, which cause opalescence and cloudiness, to coagulate to such an extent that they can be removed by fil- tration. The waters of the Nile, for example, which will not subside clear' in any reasonable time, and which cannot be filtered bright by sand filters, yield a beautiful clear water if agitated with iron before filtration through sand." Sci. Amer. Supp., No. 580, p. 9260, Feb. 12, 1887. CAVERN DEPOSITS IN NO. II. 435 and we have 285' as the possible depth of a cave or sink- hole. But Topton Junction is 18-J miles from Reading. If we only allow a fall of 5' per mile for the cavern waters we must take off 92', leaving only 193' for the possible depth of a cave, or of an iron ore deposit at Topton Junction. Beyond some such properly calculated depth sinking for iron ore of this kind is a hopeless affair. The filling of the caverns, however large and numerous they may be, is easily comprehensible when we remember that an average of 93 per cent, of the magnesian limestone formation rock is soluble, and when dissolved by the rainfall passes off entirely into the sea. Of the remaining 7 per cent, of insoluble clay-iron sand, a portion would be carried away by rapid waters, but a portion would settle and remain in quiet pools in the large cavern chambers, and would en- tirely fill such galleries as were kept full of water by the choking up of their lower exits. Limonite precipitated from pyrites. Enough is said on this subject on preceding pages lo suggest inquiry, for no sufficient knowledge of it has yet been obtained. Dr. T. S. Hunt has expressed his opinion strongly that all our limonite deposits have had this origin. But the frequent finding of crystals and pipes of pyrites in the ore banks is not of itself a broad enough basis for so large a generalization, and many of the facts narrated in preceding chapters seem to have no direct connection with such a process. The presence of magnetite, however, is a detail which may be connected with that of pyrites.* *Mr. W. B. Devereux, of Colorado, has published in Trans. A. Inst. Min Engineers, Feb., 1884, an interesting paper on the Pitkin county iron ores- which he concludes with the following paragraph : " While in doubt as to the relation this ore-body bears to the limestone, I hazard the opinion that the magnetite is a direct product of the decomposition of iron pyrites, and that the ore-body at no great depth is massive pyrites instead of massive magnetite. I base this opinion upon the following facts : Crystals of mag- netite are common in this locality, which are pseudomorphs, showing the common hemi-hexahedral form and characteristic striations of pyrites. Efflo- rescence of ferrous sulphate is also common ; and in the bed of the ravine the ore is a mixture of pyrite and magnetite, the latter appearing as a fine- grained gray matrix, and, when pulverized or broken off, being strongly 436 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER XXXVII. Zinc, Lead and Barium in No. II. New Jersey has its great Franklin zinc mine, famous throughout the mineralogical world as well as the world of commerce and the arts. Pennsylvania has its one great Saucon mine of zinc ore, also ; and two other zinc mines of no commercial importance, but equally interesting from a geological point of view ; all three being precipitations of salts of zinc in the same old limestone formation of No. II. The Saucon zinc mines of LeMgh county. The location of these mines is shown on plate XII, page 364, above. They have riveted the curious attention of geol- ogists for many years, as they have given occasion to some of the most splendid exhibitions of mining engineering genius, in its efforts to overcome extraordinary difficulties in the way of drainage. The mine pumps are among the greatest in the world. The most powerful apparatus that could be constructed was required for keeping the great excavation dry enough to work. The limestone formation in the Saucon valley lies in a deep trough into which, and to the bottom of which, flows the rainfall of the surround- ing mountains. The beds are uptilted and broken, the innumerable fissures which traverse them and the caverns which have been excavated in them permit the accumulation attracted by the magnet. This rapidly increasing percentage of pyrite, the occurrence of the two minerals in intimate juxtaposition, and the fact that no intermediate stage of hematite occurs, taken together with the testimony of the pseudomorphs, all oppose the application to this case of the ordinarily accepted theory that magnetite is a metamorphic derivative from hematite. Having enjoyed a somewhat extensive observation of iron-ore deposits, and accepting, as satisfactory in many cases the theory just mentioned, yet in this case I can see nothing which will permit its use as an explanation of the i'acts. This ore contains a trace of silver also, but no copper. It may be in- teresting to note that pieces of the limestone referred to, when struck with a hammer, emit the odor ofsulphureted hydrogen." ZINC MINES IN NO. II. 437 of great quantities 'of water; the dissolution of the lime rocks has produced concentrated masses of zinc ore ; and the phenomena of our great brown hematite iron ore de- posits are here repeated, zinc being substituted in the place of iron. The geological cause of this substitution of zinc for iron may be said to be quite unknown, or at all events has not yet been satisfactorily explained on any theory ; nor can we suggest a reason why some of the beds of No. II in Saucon valley are as heavily charged with zinc as are the iron-bearing beds of No. II elsewhere in the State with iron. If it be suggested that the zinc has come from a dis- tance, whether from above or below, it is only necessary to point to certain thin beds of limestone, carrying zinc which have been mined to a small extent and without profit in the neighborhood of Penningtonville in Lancaster county, and of similar beds of limestone carrying both lead and zinc which have been repeatedly mined without profit in Sink- ing valley in Blair county. In the last mentioned district of the State two sorts of unwise notions have been expressed regarding these zinc- bearing beds. (1) They have been looked upon as merely veins descending into the interior of the globe. Similar veins of zinc ore do in fact exist in Sinking valley, opposite Birmingham, but they are concen- trations of the zinc and lead from the limestone beds of the valley, and (2) there is no good reason for believing that they are connected in any way with the underground depths. They have nothing to do with the anticlinal struc- ture of Sinking valley any more than the zinc ores have with the monoclinal structure at Penningtonville, or than the zinc ores have with the synclinal or basin structure of the Saucon valley. The fact is, that zinc and lead seem to be inherent constituents of all limestone formations the world around. It is probable that they were deposited with the limestone in far grater abundance in ancient ages, and were originally brought into the Appalachian sea as soluble salts, together with the lime and magnesia waters of prim- eval rivers. It only remains to add, that the zinc and lead ores of Pennsylvania correspond in all respects to the No. II zinc ores of Wythe county, Virginia, and to the great 438 GEOLOGICAL SURVEY OF PENNSYLVANIA. lead and zinc deposits in the fissures and caverns of the ancient limestone country of Wisconsin and Missouri. They all belong to the same remote age, and have been con- centrated into their present form in the same limestone formations and by a similar process. The Saucon zinc mine at Friedensburg is said by Rogers to be in a close synclinal fold.* He describes it as merely a surface quarry ; but it had only been started in 1853, and worked three years by a slope when he saw it. Its calamine ore or silicate of zinc, appeared then irregularly injected into the limestone, which stood vertical in the N. wall, and dipped 85 in the S. wall. The limestone was also injected with thin veins of quartz."f Prof. Prime in his Report D3, 1883, p. 239, says the ore, zinc blende, associated with iron pyrite, is disseminated through a limestone which seems broken up, and its crevices filled in with the ore. The mass has somewhat the appearance of a breccia. The zinc blende is not confined to one bed or horizon, but ex- tends through a vertical thickness of 30 or 40 feet in some places, while at other points of the mine the infiltration seems confined to a vertical thickness of 10 to 20 feet. The mine has been worked (1877) to a depth of 250' on the slope of the bed. The excavations are very large and ex- tend along the strike more than 1000'; the dip of the lime- stone being 30 to 35, S. 5 to 10 E. It is evident that the source of the ore was above, and not beneath ; that the term "infiltration" is as justly used in this case as in that of our limonite or brown hematite iron ore deposits. That the zinc was an original constitu- ent of the limestone is extremely doubtful. And yet the fact that the zinc of Pennsylvania and New Jersey, as well as of the western states occurs in No. II. seems to link the metal with limestone of Lower Silurian age. The notion of a deep-seated source expressed by Mr. F. L. Clark in his *Geol. Pa. 1858, p. 101. On page 236 he suggests that the synclinal may be faulted. f The ore was smelted at Bethlehem and converted into white paint. The vein seemed to range along the axis of the synclinal or fault, 1856. ZINC MINES IN NO. II. ' 439 paper on the Mining and Metallurgy of Zinc in the U. S., published in the "Engineer and Mining Journal" of Sep- tember 8, 1883, I cannot concede to ; but his description of the mines is perhaps the best we have, and I give it in a foot-note.* * The zinc deposits in the Saucon valley, Lehigh county, Pennsylvania, which were once extensively worked, now produce but little ore. Their history, however, has a special interest from their connection with the in- troduction of spelter-making into this country, and from the fact that they belong to a class of deposits which seems to warrant a belief in their con- tinuance to a considerable depth, and because they are a good illustration of the general effect of the characteristic feature of the ore market above re- ferred to. Tbree principal deposits have been discovered, known respectively as the Ueberoth, Hartman and Saucon mines : they occur in magnesian limestone of the Lower Silurian formation, and have many points in common, while they also present some striking differences. They were all at one time owned or controlled by the Lehigh Zinc Company, whose works were at Bethlehem, four miles distant. The Ueberoth mine, which is, so far as developments have shown, the largest, was worked continuously from 1853 up to the fall of 1876. It was for many years the main dependence of these works, and produced in the neighborhood ot 300,000 tons of ore. The strata of limestone are here very much disturbed and tilted up almost to the vertical, apparently by the ob- trusion of the syenite ridge of the neighboring South mountain. The ore came close to the surface, and a very rich pocket was found in the clay above and around limestone boulders, which is estimated to have produced 100,000 tons of ore. When this body of ore was exhausted, the ore was fol- lowed down in crevices between the boulders. These crevices lie in planes parallel to the bedding of the limestone, or in planes perpendicular to it, and preserve great regularity in their position, an i a parallel course for several hundred yards in a northeast and southwest direction ; they are nearly ver- tical, and at the depth of 225 feet, to which the mine was worked, showed no signs of closing up. The ores at first were exclusively calamine and smith- sonite ; but at greater depth blende made its appearance, coating the walls of the crevices, and in some cases penetrating into them several feet ; in other cases, segregated as rich seams, which nearly filled the cross-openings. At first, it was confined to the northeastern end of the mine; but at the low- est depth reached it could be traced almost continuously to the extreme southwestern end. The dip of the ore body appeared to be regular, and to the southwest. Six of these parallel crevices were worked, and about as many crossings ; and where they intersected, rich bunches of ore were found, some of which were as much as 60 feet across and 20 feet thick. All the indications seemed to point with increasing certainty to the existence of a backbone or underlying deposit of blende, out of the reach of the action of meteoric waters, from the continuation of which the oxidized ores have been derived. Timbering the mine was always a serious difficulty, but the greatest ob- stacle to be overcome was the water. Even at a depth of 40 feet, the flow 440 GEOLOGICAL SURVEY OF PENNSYLVANIA. Bamford zinc 'mines in Lancaster County. In the northern part of East Hempfield township, Lan- caster county, limestone beds impregnated with almost in- was already very strong ; at the depth of 150 feet, it was found necessary to put in what was then the largest pumping engine in the world. This en- gine, which is a single cylinder, double-acting, condensing, walking-beam engine, with a pair of fly wheels, has a 110-inch cylinder and a 10-foot stroke, and is calculated to work four 30-inch plunger pumps and four 30-inch lift pumps, with 10-foot stroke, and to take water from a depth of 30 feet. At the time it was stopped, it was running from six to seven strokes a minute, and was working three pairs of 30-inch pumps and one pair of 22-inch pumps, and was easily handling all the water that came to them. The pump-shaft and foundation for the engine were no less remarkable in their way. The latter was built up from the solid rock, 60 feet below the surface of the ground, of hewn blocks of Potsdam sandstone ; the former, which measured 30 feet by 20 feet in the clear, was started on a small crevice, and timbered with 12-inch square yellow pine sticks, and divided into three compart- ments, and further strengthened by two open brattices of the same heavy timber. When the pitch of the vein carried it out of the shaft, the rest of the depth was sunk through solid rock. The Hartman mine distant about half a mile, was worked at first ex- clusively for calamine. Its exploitation gradually exposed a central horse of blende, which the method of mining adopted made it necessary to leave for the support of the timbers which carried the roof. The increasing im- portance of this blende at the lowest level worked, 150 feet, caused a change to be made in the method of mining. The mine was operated for a year after the large engine was stopped, and the last work that was done was the putting in of a slope to develop this deposit of blende. The water in the Hartman was always less strong, the pitch of the crevices less steep, and the surrounding rock less disturbed than in the Ueberoth mine ; the strike of the crevices was more to the west, and the blende came nearer to the sur- face. The Saucon mine, however, affords the simplest and best illustration of this form of deposit. It is distant about a quarter of a mile, and was origi- nally leased by the Passaic Zinc Company, by whom it was sub-let to the Lehigh Zinc Company on high royalties. When the rich deposit of calamine first discovered was apparently exhausted, this sub-lease was surrendered by the latter company, and in 1875 the original lease passed to the Bergen Point Zinc Company, by whom the mine has been worked ever since. A face of blende was uncovered at the western extremity of the open pit, and the ore followed under a heavy cap of limestone for a distance of 250 feet up to the property of the Lehigh Zinc Company on the west. On this pro- perty, it was reached at a depth of 110 feet, under 100 feet of solid limestone, and was followed 150 feet farther on the course of its strike. On both pro- perties, it was followed to a depth of nearly 200 feet. In the fall of 1879, all the property of the Lehigh Zinc Company passed into the hands of its bond- holders under foreclosure of its mortgages, and in the spring of 1880 all the mining property was sold to the proprietors of the Bergen Point Zinc Works. The workings of these two mines, taken together, show a remarkable ZINC MINES IN NO. II. 441 visible zinc blende, dipping about 70, N. 15 W. at the surface and S. 15 E. in the deep, are described in Dr. regularity of width, pitch and course, and the deposit is clearly shown to be a large chimney or chute of ore of irregular cross-section, which, how- ever, preserves a lenticular shape, the longer axis of which is about 60 feet, and pitches to the south at an angle of about 30 degrees ; the transverse axis measures about 30 feet. The axis of the ore-body dips to the west-south- west with a slope of about one foot in four. The weathered outcrop has evidently given rise to the pit of oxidized ores ana to certain irregular de- tached deposits which lie in the same course, several hundred yards beyond it. Here, then, are three similar deposits of zinc ore, with their nearly parallel chimneys of blende and their corresponding beds of calamine, which have evidently been brought up from below, by solution in thermal springs, through crevices formed in the limestone by the gradual upheaval of the neighboring South Mountain, and have undergone subsequent alteration from the action of meteoric waters. Nearer the mountain, where tbe strata are most tilted and the ground most disturbed, the water is strongest and the largest deposit of calamine is found. In the Hartman mine, the strata are more nearly flat, the blende is sooner met with, and the water is much less strong ; and in the Saucon mine, the blende is met with at the edge of the pit, and only moderate-sized pumps are required in working it at a depth of 200 feet That the water in these mines comes from the same surface springs which supply the Saucon Creek, is evident from the fact that, when the big mine was abandoned, this creek shrank at once to a small fraction of its former volume, and only gradually recovered it as the mine filled up. Very careful surveys of the bed of this stream failed to discover any point at which it showed any diminution of its volume or seemed to sink into the ground. It is, therefore, very improbable that the water, having once come to the surface, found its way back into the mine. It was probably tapped in under-ground courses connected with the springs which give rise to thecreek. This is the more probable, as the mine which has the most water is on the highest ground and is farthest from the creek, and the mine having the least water is nearest the creek. It is therefore reasonable to suppose that nearly the maximum quantity of water likely to be encountered was already handled, and that, if a solid body of underlying blende were developed, it could be profitably worked with the machinery already in place. The Saucon mine is still the main dependence of the Bergen Point Zinc Works, but its continued working must be attended with increasing cost and uncer- tain risks. The ores of this region are remarkably free from lead, arsenic and antimony, and it is this circumstance that gives them their principal value and interest, and has been the basis of the very high reputation of the metal and oxide obtained from them. Only the richest of the ores are, in the present state of the ore market, available as spelter ores, but even the leanest of the oxidized ores produce a very fine quality of oxide. The blende is very peculiar. It is massive, and rarely shows even traces of crystallization ; when pure, it has a bluish slate color, has a very characteristic conchoidal fracture, is translucent on thin edges, and gives a clear ring when struck. As generally sent to the works, it resembles broken limestone ; is somewhat mixed with iron pyrites, and assays from 35 to 40 per cent of zinc. It is not 442 GEOLOGICAL SURVEY OF PENNSYLVANIA. Frazer's Report C3, p. 55 At the west end of open cut No. 1, a shaft was sunk cutting two or three belts rich in easy to concentrate, both on account of its non-crystalline structure and of the pyrite it contains. The causes which led to the extinction of the Lehigh Zinc Company and the abandonment of the first two-named mines were briefly these ; the im- possibility of competing successfully in the oxide market with the owners of the big mine in Sussex county, New Jersey, after the expiration of the patents covering the oxide process left them free to take the trade, or in the sheet-zinc and metal market with the Western smelters, using cheaper and richer ores, at a time when a general depression. of all manufacturing enter- prises made it unusually burdensome to carry the heavy bonded indebted- ness incurred during a period of high prices and general inflation in acquir- ing mines and putting up machinery to work them. Under more favorable circumstances, it is probable that these mines could have been profitably worked for years to come ; for although the pumping expenses were heavy> they were not excessive, considered as a royalty on the ore, and these charges per ton would diminish in proportion to the amount of ore mined. Now, however, it will probably be left for another generation to discover what value they still have. Other deposits of zinc ore have been discovered in the same Silurian for- mation in Pennsylvania, Maryland and Virginia, which have been worked from time to time, but have produced very inconsiderable amounts of ore. Small oxide works were built at an early day near Birmingham, Blair county, and at Landis station, in Lancaster county, Pennsylvania, but they were soon abandoned. At the latter point, shallow beds of rich carbonate of zinc were first discovered, but were worked out. About 1876, expensive concentrating works and two blocks of spelter-furnaces were put up, to treat the grains and kernels of c^stallized blende scattered through the underlying limestone, before sufficient exploration was made to warrant such an outlay of money ; they have for years been lying idle. Mr. J. Eyerman, furnished the same journal December 15, 1883, the follow- ing interesting particulars: As the ore (calamine,smithsonite and sphalerite) in this mine is near the surface, it is not, at present, difficult to work. The calarnine is found in large quantities disseminated through the limestone. It is found mostly on the north side of the mine, where it is worked by a small force of men. This mine has furnished, and will continue to furnish, the finest speci- mens of calamine (or silicate of zinc) known to the world. It is very often found in botryoidal and stalactical forms. It is not seldom that sheets or plates of calamine from two to three feet square and from one-eighth to one- fourth of an inch thick, and containing thousands of little crystals on the surface, are found between the crevices of the limestone. Again, it is found as a thin coating to the inside of a quartz geode. This ore is quite scarce at the Endy mine. It seems to have been replaced by the blende. The smith- sonite or carbonate of zinc is found in white scales and in granular masses, coating calamineand blende. It is also more commonly found as a brownish earth, which hardens when dry. It is found near the center and along the west side of the mine. It has often been mistaken for clay. This is also mined at present by a small number of men. The sphalerite or zinc-blende ZINC MINES IN NO. II. 443 zinc. The east end of cut No. 2 showed the vein striking N. 85 E. In a small open cut m. W. of RR. bridge over Little Conestoga creek 80 tons of sandy limestone impreg- nated with calamineand blende, and seamed with calcite, were taken out ; dip apparently 50, N. 10 E. ; but on the RR. the limestones dip 8, N. 5 W. The Bamford mine was worked for a white oxide between 1850 and 1860. Streaks of silver lead are found in the lime- stone, which is about 12' thick.* Mr. E. G. Spilsbury's letter respecting the mine (C3, p. 198) describes two parallel beds of the limestone, near the slate, but not at the contact of the two formations, as in Blair county, " unmistakably bedded veins, and not fissure or gash veins ; conformable both to the stratification and dip of the inclosing rocks ; " striking N. 74 E. and dip- ping 72, N. 15i W. The hanging wall limestone is a breccia (or crushed) par- tially decomposed, whitish gray, and highly silicious ; full of seams, cavities, and small caves (15' to 20' long and as many broad, by 4' to 6' high), all completely filled with a dark red sandy loam, and not with mineral as in Missouri and Illinois. In none of these loam-filled "cavities have I ever found a trace of mineral." The broken condition of the roof limestone extends from the surface to the bottom of the pump shaft 110'. The foot wall is not uniformly smooth but has offsets, like layers, shelving downward over and past each other and into the ore body ; or, in other words, the ore passes up between these shelving layers of dark blue limestone sometimes to a distance of 8 or 10 feet. (See figure in C3, p. 199.) The foot wall limestone is less silici- ous, dark blue, in places almost black, and very close and is not mined. It is found throughout the mine, with pyrite disseminated through it. It is not met with in as large quantities here as at the Endy mine. Greenockite (sulphide of cadmium), hydrozincite, and goslarite (sulphate of zinc) are met with in smaller quantities. The sulphate of zinc is scarcely ever found. A considerable quantity of greenockite has been mined. It is found as a yellowish powder coating blende and limestone. It was formerly separated at the LJethlehem works. * Notes by P. Frazer, July, 1876, C3, p. 196, give details of crushing and roasting. 444 GEOLOGICAL SURVEY OF PENNSYLVANIA. compact, with occasionally small holes lined with ealcspar and frequently filled with specular iron ore. The minerals in the vein matter consists of the two sul- phides of zinc and lead ; changed for about 18' beneath the surface to calamine and carbonate of lead ; unchanged sul- phides below. The vein matter or gangue itself is a lime- stone very like that of the foot wall, but crystalline in spots. The galena (sulp. lead) is found in bunches or little strings running along on or near the hanging wall ; but the Jjlende (sulp. zinc) impregnates the whole vein matter, more or less thoroughly. The percentage of silver in the galena varies wonderfully from $2 per ton in one bunch to $2,000 in the bunch next to it ; a general average may be perhaps $22.* Sinking Valley zinc and lead mines in Blair county. These are described by Mr. F. Platt in chapter XV of his Report on Blair county, T, 1881, pages 247 to 277, only a short summary of which can be given here, the reader being referred to the original report. Sinking valley is the triangular south end of Nittany valley, south of the Little Juniata river ; 10 miles long by 5 wide at the river ; anticlinal in structure, the axis sinking southward, as shown by Figs. 33 and and 34.f The lime- stones dip about 30, S. E. on the east side of the axis, and *The bright golden "rosin blende" is very pure; only slight traces oi iron and cadmium, and a small mechanical admixture of lead ; average of 14 samples: zinc, 65.9; sulphur, 32.3 ; iron, 0.8; lead, 0.3; cadmium, 0.07. Average of a year's work showed about 18 per cent, of blende in the vein. Run of vein one mile; another, covered with 15' soil, 1| m. further on. reins proved to depths of 75' and 110'. North vein' worked out for 300', to a depth of 50', with an average width of 12'. South vein worked out 400', to a depth of 75' ; more regular ; width from 14' to 18' ; zinc in vein never ex- ceeded 12 p. c.; richest ore from 50' down to 75' ; "at the 110' level, although the vein is well defined, there is little or no ore in it, at any of the points where it has been opened, and what little ore is in it appears in strings and not disseminated as above." (For details of history, machinery, cost of mining, manufacture of spelter, &c., see Mr. Spilsbury's letter in C3, pp. 202, 203.) fThe axis sinks at the rate of 600' per mile from the vein at Birmingham to the head of the Kettle; so that the zinc mines are very low down in the magnesian limestones of II. ZINC MINES IN NO. II. 445 about 80 E. S. E. (overturned), on its west side. The Keystone Zinc Co.'s mine near Mr. Kinch's house, and the deep shaft on the Borie farm are both near the axis. Fissure veins occur in various parts of the valley, and were tried for as long ago as the War of Independence, as the old pits on the Fleck farm bear witness.* But most of the work has been done by the Keystone Zinc Co., which was incorporated in 1864, and abandoned mining in 1870. In 1875 the Tathams tried to find good working ore with a deep diamond drill hole east of the Fleck farm. In 1876 W. Arms tried to develop a vein on the Isett farm. Still later prospecting has been done, and the citizens of that district are subject to periodical excitements by vague or incorrect reports of mineral wealth hitherto concealed, or "never properly developed," as the favorite phrase is worded. But certainly enough has been done to disprove the probability of extensive deposits underground, and to sustain the geo- logical theory that the metals were originally distributed through the limestone strata, set free by erosion, and con- centrated in small quantities in fissures. It is impossible to examine the closed up and decayed workings ; but much can be learned from the reports of ex- perts like Dr. Roepper of Bethlehem ; Mr. Williams of Philadelphia ; Mr. IHckerson, Mr. Spilsbury and others.f The Keystone Zinc Co.'s shafts, about \ m. S. W. of Bir- mingham, were sunk from the top of a knoll 80' above the road, and drained by an adit level, driven on 347' S. W. One line of shafts followed the limestone strike on a vein so variable as to open out into spacious chambers, and con- tracting again to a mere crack. This fact alone suffices to stamp the " vein " as no true vein, but a cavern deposit, like any limonite bed. Were there a true vein it might be traced to the river and be found in the bank ; but no trace of ore has rewarded diligent search in that direction, and *SeeGen. Roberdean's letter to President Reed, dated April 17, 1778, in Pennsylvania Archives, Vol. 6, p. 422. Smelted lead was sent down the river in flat boats. Another attempt was made by John Musser r"- Rapliistom* planrstria. FOSSILS OF THE CALCIFEROUS, lid. 511 their arrangement. Huxley saw a resemblance to the hag fish (Myxine), but could indicate no living fish with a simi- lar assemblage of teeth and plates. Owen at first suggested that they might possibly be toothed crustaceous claws ; af- terwards, that they might rather be spines, booklets, den- ticles of naked shell-fish or worms. They seem to have been the only preservable part of the animal whatever it was ; and they may possibly be the only evidence we have for the early existence of the soft circle-mouthed family of fishes. Dr. Woodward suggested that they might be the tongue-armor of the shell-less gasteropods (Nudibran- chiata) which have therefore never been found in the rocks.* Fossils of tJie Calciferous, Ila. Some of the most characteristic and most widely dis- tributed forms of this formation, are, according to S. A. Miller's N. A. Geology and Palaeontology, f Ophileta com- planata, Ophileta U7iiangularis, Holopea turgida^ Hol- opea dilicula, and Pleurotomaria primigenium. From the Potsdam ascend into this Calciferous division, Pleurotomaria canadensis and Leptcena barabuensis. The following have been assigned to this formation (or to supposed equivalents of it in the Quebec group) Pluro- tomaria calcifera, Pleurotomaria postumia, Helicotoma perstriata, Maclurea matutina, Maclurea sordida, Eccy- liomphalus canadensis, Camarella calcifera, Lingulella mantelll, Lingulella iren.e, Amphion salteri, Bathyurus cordai, Bathyurus conicus, and Asaphus canalis; but the identifications of Quebec and Calciferous strata are always to be distrusted. Fossils of tlte Quebec group. Of these the less said the better until the controversy over the Quebec group has been settled. The species Lingulepis maera, mlnuta, andmanticula, Acroteta gemma, Agnostus communis, bidens, and neon, Crepiceplialus Tiaguei, and *Q. J. G. S. XXXV, p. 389. t Second Edition, Cincinnati, 1889, page 34. 512 GEOLOGICAL SURVEY OF PENNSYLVANIA. XXXf Orthocerata figured by Em i Orthoceras multillneatum. Calymene FOSSILS OF THE CHAZY, II b. 513 unisulcatus are confidently assigned to equivalents of the Quebec group in the Rocky Mountains. The family of Graptolites is said to reach its highest development in the Quebec group. Thirty genera and 170 species of Grapto- lites have been named thus far in North American rocks. Maclurea atlantica and Asaphus canalis are said to range up through the Chazy and higher.* Fossils of the Chazy, 11 b. The characteristic form of this age is considered to be the line whorl-shell Maclurea magna. With this are as- sociated others which continued to live even into Hudson River times : Stropliomena alternata, and incrassata, Orthis perveta, Leperditia canadensis, loucTcana, and amygdalina, Orthoceras multicameratum, and Mlineatum and the lamellibranch shell Modiolopsis nasuta. Scolithus is abundant in the formation as recognized in some regions; and Lingulepis morsel is described from the St. Peter's sandstone of the west.f Fossils of the Blac'K River limestone, II c (in part). These were defined by Vanuxem in 1842 in the bluffs of Birdseye and Trenton beds at Boonville, N. Y., but there has always been a doubt of the propriety of separating the Black river and Birdseye beds and giving two names to what seems like one formation, distinguished on the Black river by its abundance of Cephalopod shells, and on the Mohawk river by an abundance of the Birdseye fucoid Phylopsis tubulosa. The vast and varied population of the sea at the begin- ning of the Trenton age, as shown in the Black river beds, produced by its decay the dark color of the rocks, the black marbles of Vermont and Pennsylvania. Many of the species died out however before the normal Trenton limestones were deposited. But the family of straight * This paragraph is a condensation ot statements made by S. A. Miller on his page 35. t S. A. Miller, 1889, p. 38. 33 514 GEOLOGICAL SURVEY OF PENNSYLVANIA. Phytopsia tubulosa P (Fucoidet demittu*.) V 3$ircLei/& and ^Blaclc^&ivw*: . __ 7al.Oh, B .Val.Z. Olyptocrinus decadactylue. omatopora densum. (Syringoitroma^ ^\j/ffifa ^ omntopora (Aleeto) frondosa. Nicholo. (Av III a. Graptolithus divaricatus. Hall. Pal. N. Y., Vol. HI, Graptolith >v< I. in* Graptolithua gncilit. Hall. Pal. N. Y., Vol. Ill, p. jli. Ilr.ll. Canada Rt., 1858, Pal., N. Y NO. III. UTICA AND HUDSON RIVER. 531 sea limestone deposits to reputed shallow-water shale and slate deposits. But it still leaves to he considered the im- portant fact that 6000 feet of the shale formation No. Ill was laid down in reputed shallow water. If we adopt that explanation we must conclude either that a shallow sea can be nevertheless as much as 6000 feet deep, and still receive near shore deposits ; or else that any rapid upward move- ment at the end of the limestone age must have lasted but a. comparatively short time, and was followed by a long slow downward movement of the sea bottom to receive the 6000 feet of slate. It will be seen hereaftei*, in describing the successive formations from No. IV to No. XVII, that such a downward movement did in fact take place, contin- uously, or by successive instalments, and at varying rates, through the whole series of Palaeozoic ages to the end of the Coal age. The darkness which covers this whole subject is still further increased by our insufficient knowledge of the effects pro- duced long afterwards upon the condition of the Palaeozoic formations by the great earth movements in the Mesozoic ages ; for many of the phenomena usually considered as falling under the head of originalnon-conforinability\&.\v been produced by the crushing and faulting of formations beneath, against and over each other. It has been rather too rashly asserted that the limestone beds of No. II in Pennsylvania along the Great Valley were plicated and lifted out of water, and subjected to the erosion of atmos- pheric agencies, and then resubmerged and covered over non-con formally by the slate beds of No. III. The old and recent surveys of the Great Valley show that there is no sufficient ground for such an assertion. On the contrary, wherever the contact of the upper beds of II with the lower beds of III are exposed to observation they are seen to overlie each other in uninterrupted sequence as if they were beds of one formation. Along the middle line of the Great Valley however, from the Delaware to the Susque- hanna, the contact is obscured by the crushed, folded and overturned condition of the rocks. But from the Susque- hanna to the Potomac the contact line can be studied with GEOLOGICAL SURVEY OF PENNSYLVANIA. JfoJUI&tuxt XXXXJ. Diplograptus (Graptolithus) anpistifoiius, Diplograptus (Graptolithui) spinulosns. """ 1 H *Dal!. D1 PloPaptus (Graptolithus) marcldus **^lfcr Diplograptus (Graptolithus) whltfleldi. -" K A Till', Diplograptns prUUs. Orptolithu multifaMiculat Thamnograptus capillaris. Graptolithua divergen Ehynchonella capax ( Atrypa capo, ; Conrad. . Ehynchonella P modesta, Rhynchonella antlcosti (? ^"""y"") neglect* ahecuba, Bill strophomena (aJ(rna(a, Mr.) nauta IB ::: ....... I J * 3F ** a IW3.. "^llBfc NO. III. UTICA AND HUDSON RIVER. 533 comparative ease ; and in the bends of Conodoguinet creek the upper limestones of No. II are seen changing, by a sys- tem of alternations nearly a thousand feet thick, into the lower beds of No. III. These alternations of thin lime- stones, lime shales and clay shales are called the passage beds of No. II and III ; and they occupy in that region the place in the series which the Utica shale division of No. Ill occupies elsewhere. In Franklin county the superposition of No. Ill on No. II can be studied to great advantage by means of the 'four anticlinal belts of II sustaining synclinal belts of III, as more fully described in Chapter XXII, page 288, above. In Berks county the same fact is made clear in another way, as the limestone belt west of the Schuylkill is set with parallel synclinal slate ridges lying in long narrow troughs of the limestone. In Lehigh county we have the best of these exhibitions in Huckleberry ridge. Here the front edge of the slate belt at Foglesville runs forward 6 miles to a sharp point within 2 miles of the Lehigh river at Allen- town, while a great cove of limestone behind it encloses the Ironton mines.* All these isolated streaks and spurs of the slate No. Ill in the limestone valley of No. II are so many separate proofs that the slate formation overlies regularly, and conformably the limestone formation No. II. This condition of things becomes still plainer when we leave the Great Valley to study the two formations in the interior valleys of Middle Pennsylvania. Path valley in Franklin county serves as a link of con- nection between the interior mountain country and the Great Valley, into which Path valley opens at its southern end. The McConnellsburg cove in Fulton county is the first completely isolated uprise of the limestone back of the North mountain and is surrounded by a border of overlying slate. Horse valley in Perry county is almost entirely floored with slate. A border of slate entirely surrounds the central limestone floor of KisJiicoquiUis valley with its three parallel slate prongs towards the east. A similar border of No. Ill slate entirely surrounds the irregular *See description in Chapter XXX, page 347, above. 534 GEOLOGICAL SURVEY OF PENNSYLVANIA. . Ilia, fyfjUCd, and III I, ^i Lyrodesma poststriatum. ( Xueulana pothriata. ) E. "Uo' T r r^>. ! " 'i o '" yNw- 1 -' 2 Ct ^>^<^. 110^^4 NO. III. UTICA AND HUDSON RIVER. 535 limestone area of Penn, Brush, Nittany, Sinking Spring, Canoe and Morrison valleys. Similar slate rings surround the limestone of Nippenose and Mosquito valleys in Ly- coming, and Friends and Milligari's coves in Bedford. All these outcrops of No. Ill show the slate to be about 1000 feet thick, resting conformably upon the top beds of Trenton limestone, and descending conformably beneath the surrounding sandstone mountains of No. IV. It may be af- firmed with confidence that in no part of the world is there a more satisfactory exhibition of regular conformity in the superposition of one great formation upon another over an extensive region. The attention of the reader is directed to the fact that all the valleys floored with No. II and surrounded by a contin- uous outcrop of No. Ill, as described above, are in counties of middle Pennsylvania lying west of the Susquehanna river; for neither the limestone nor the slate reaches the present surface of the State anywhere east of the Susque- hanna river, except in the Great Valley. When No. Ill goes down for the last time along the south foot of the Bald Eagle mountain in Centre county, and Dunnings mountain in Blair county, it does not rise again until we reach Cin- cinnati on the Ohio river, where the slare formation has re- ceived from the Ohio geologists the name of the Cincinnati group. Its northern outcrop, exposed in Canada, but con- cealed beneath the waters of Lake Ontario, appears at the western foot of the Adirondack mountains in northern New York, and in the lower Mohawk valley, where it received nearly fifty years ago the name Loraine s7ial.es and Utica slate. From Albany south it was named the Hudson River slate, a name by which it has been commonly known in American geology, and by which it has been habitually designated in all the reports of the Pennsylvania Geological Survey since 1874. The name of Naslimlle group was given to it by the Geological Survey of Tennessee, around the central area of which its outcrop describes a great ring. Along the southern extensions of its outcrop No. Ill exhibits a remarkable change of color soon after passing out of Pennsylvania into Virginia, becoming so red by ex- 536 GEOLOGICAL SURVEY OF PENNSYLVANIA. F777 S.Itta. Qttica, and .Ulb.^&usUon riveiiconJM. Modiolopsis anodontoides Cyrtolites ornatus. Rogers, page 821, fig. 61 Bucania rugos Cyclonema bilix hisonia turricula. Murchisonia gracilts. Murchisonia gracilis f.o -.-rz. -' ~~\ in t,. EM. Microdiscuo quadricostatus, Proetus spurlocki Proetus parviuscu Menocephalus globosus, "' ''^~ Triarthrus glaber, Triarthrus spinosu NO. III. UTICA AND HUDSON RIVER. 537 posure to the atmosphere as to give the slopes of the mount- ains into which it sinks a reddish soil; indicating a much larger percentage of disseminated iron pyrites throughout the mass than in Pennsylvania. From the Hudson river northward through Vermont into Canada the slate beds also exhibit an extra percentage of sulphide of iron; but in that region the pyrites instead of being distributed microscopically through the slate is concentrated into mil- lions of separate beautifully perfect individual cubes, of all sizes from a half inch down to the tenth of an inch. Long exposed surfaces of these Vermont slates are pitted with square holes from which the crystals of pyrites have been re- moved by solution. In the roofing slate belt of eastern Penn- sylvania such crystals are frequently seen; and some of the beds are rendered worthless to the quarrymen by the quan- tity of microscopic pyrites which they contain; others seem to be almost perfectly free from this noxious adulteration. One of the sources of the pyrites was no doubt an infu- sion of sulphate of iron poured into the sea by primeval rivers. But we must ascribe the special abundance of py- rites in certain parts of the formation, in certain beds, and at certain localities, to some more restricted cause ; and we know of no other special cause than that of the secretion of sulphur in the tissues of animals and plants, especially of sea weed vegetation. The accumulation of sea weed on a shore will always furnish a considerable amount of iron pyrites to the shore sands ; and consequently to the deposits of the sea bottom in the neighborhood. We have a right to suppose that the general distribution of iron pyrites through the slates of No. Ill testify to the existence of marine plants in great abundance in that age, even were no traces of the existence of such plants preserved as col- ored impressions on the surface of the slates. We are, however, not left to any vague speculation on this subject. The remains of plants have been collected from the New York outcrop of No. Ill and described and figured by Pro- fessor Hall under the names Sphenothallus , Buthotrephis, and Pal&opJiycus* It is true that other imprints on the ^Palaeontology of New York, Vol. 1, 1847, pi. 68, 69 and 70. 538 GEOLOGICAL SURVEY OF PENNSYLVANIA. slates have been described and figured as plants which are now believed with good reason to be merely markings left by wriggling worms, crawling crustaceans, and locomotive shellfish ; yet this does not invalidate the plant character of the remainder ; and we cannot imagine a sea inhabited by animals, even of the lowest grade, without the co-exist- ence of a world of marine plant life on which these ani- mals could feed. One of the most curious facts connected with the expo- sures of No. Ill is the occurrence in some places of streaks and nuts of a sort of anthracite coal. Such nuts of coal, as large as a hen's egg, have been picked out from between the slates of No. Ill on the side of Cove mountain in Franklin county. Their composition will be given in another place. Their origin is quite unknown ; they have no connection whatever with beds of coal ; they have not been transported, but were made in the place where they were found ; they are disconnected also from each other ; they appear to be concretions or small accumulations of nearly pure carbon ; and their genesis is probably connected in some manner with that general distribution of carbon through the slate- mud which has given so many of the beds of the formation a black or blue-black color. Besides the markings made by animals and the impres- sions left by plants there is a third kind of fossil forms in No. Ill of the greatest interest to the geologist. Some of the slate beds are made up of innumerable paper-like layers of slate connected together ; and on the surface of these black films of mud appear millions of markings resembling scattered straw, and bits of black thread. Most of them are fragments of some living organisms which at first sight would be taken for the thin stems of plants. Others are arranged together in regular forms radiating from a center or with a center line forked at both ends, the end-forks forking again. Some of these kinds have all their forks connected by a delicate almost invisible membrane, like an old umbrella with its ribs sticking out beyond the edge of the silk. Others are like oval leaves pointed at both ends and with radiating nerves, the ends of which project all NO. III. UTICA AND HUDSON RIVER. 539 round beyond the edge of the leaf. Most of those which are single fragmentary threads or narrow ribbons have one edge delicately toothed from end to end ; some are toothed on one edge toward one end and on the opposite edge toward the other end. Some have both edges set with fine saw teeth ; and it becomes evident that many which seem to be toothed only on one edge have been folded along the mid- dle so as to bring all or some of the teeth of both edges to one side. Large collections of these Graptolites have been made both in Europe and America, and subjected to the closest examination and comparison. It is quite certain that these little creatures were a peculiar kind of floating animal, but nearly as low in the grades of life as plants ; that they grew from living specks, as the leaves of a tree grow from buds ; and that they produced at first a foot stalk, which expanded and multiplied itself and became gradually furnished with the necessary organs of nutrition and reproduction. A great number of separate genera and species of these graptolites existed in that very early age of the world ; some of which continued to exist for two or three ages following, and then this whole family of living creatures disappeared from the waters of the world. In the age of No. Ill the Appalachian ocean and its extension through northern Europe was alive with them, incredible multitudes floating and feeding on the surface and sinking to the bottom to be fossilized in the slate-mud. It is pro- bable therefore that the prevailing dark color of our roofing slates and other beds of No. Ill should be ascribed to the vast amount of carbon secreted by the graptolites, and at their death transferred to the slate-mud which was all the time accumulating at the sea bottom. It is barely possible (perhaps if we knew more about it we would say it was quite possible) that colonies and conglomerations of grap- tolites in some places were dense enough to account satis- factorily for the thin streaks and nuts of coal mentioned above. We may imagine that the graptolites floated mainly at the surface of the water and received the principal part of their sustenance from the carbonic acid which in those early ages loaded the atmosphere more heavily than now ; 540 GEOLOGICAL SURVEY OF PENNSYLVANIA. and that this manner of feeding brings the graptolite life into close analogy with the plant life of all ages, the leaves of trees receiving their sustenance in like manner from the air ; but we must not forget that microscopic life has al- ways pervaded the world, furnishing the chief food of all lower orders of creatures. The relations which existed between these curious ani- mals, the graptolites, and other animated inhabitants of the Appalachian sea the solid shells of which are also abund- ant at some of the outcrops of Formation No. Ill is a sub- ject of mere speculation. Whether the graptolites had any intercourse, friendly or hostile, with the multitudes of free- floating crinoids, or with the submarine meadows of stone lilies waving their calcareous heads upon long-jointed stalks rooted in the mud, and spreading their locks of calcareous hair abroad in search of microscopic food, we cannot tell. Nor do we know what intercourse there was between these crinoidal animals and the innumerable shell-fish of various classes, kinds and species which then lived. A great vari- ety of species have been figured and described. Most of them persisted through the whole slate age, then perished to be seen no more in higher formations; so that a collection of fossils of No. Ill is quite sufficient to distinguish this forma- tion from all preceding it and from all that followed it in geological history; and quite sufficient to identify the out- crops of No. Ill wherever they may be encountered in Europe or America. The amount of coralline life in the Utica and Hudson River age was very great and a variety of beautiful forms are figured by Hall in plates 75 to 78 of his first New York volume, and by Newberry in plates 1 to 4 of the first volume of the Palaeontology of Ohio. A considerable variety of shells have also been preserved in these two formations. Among BR ACHIOPODS were species of Lingula, Leptaena, Or this, Atrypa, OrMcula, Slropho- mena, Zygospira. Wiynchonella, Retzia, Nuculites, Cypri- cardites, Megambonia. Of LAMELLIBKANCHS were species of Avicula, Ambonycliicb, Modiolopsis, Orlhonola, Lyro- desma. Of GASTEROPODS there were species of Murcliisonia, NO. III. UTICA AND HUDSON RIVER. 541 Pleurotomaria, Bellerophon, Cyrtolites. Among CEPIIALO- PODS were species of Endoceras, Orthoceras, Ormoceras. Of TRILOBITES there were various species of Dalmaniles, Acidaspis, Ceraurus, Proetus, Asaphus, Calymene. Previous to Dr. Walcott's publication in 1890 of his dis- covery of fisli remains on the Colorado river it has been the opinion of all geologists that no vertebrate animal yet existed. Not a trace of any kind of fish has elsewhere been detected in the first four formations of the Palaeozoic series; the earliest known fish-spine was found by Professor Claypole in one of the beds of Formation V, in Perry county (to be noticed hereafter); nor is there any certain evidence of the existence of land plants. As the corals of the present day pervade the trophical belt of the earth, and as a change oi' temperature of a few degrees is known to produce wide- spread destruction among the finny tribes of our present sea, the abundance of coral life and the absence of fish in the early ages conspire to testify to a high temperature of the ancient ocean water; and this agrees with our supposi- tion of the gradual cooling of the globe. The black Utica slate, and many darker layers of the Hudson River slate, especially in the western States, have been so heavily charged with carbon from the decayed bodies of the creatures which filled the sea, that hand speci- mens will smoke andtiame in a blacksmith's fire. This has given them the mineralogical name of fire slate (pyroschists). Dr. Sterry Hunt in his Tenth Chemical Essay, 1875, page 178, gives analyses of Utica slate composed of 53 to 58 per cent of carbonate of lime with a little magnesia and ox- ide of iron; the insoluble part of the rock lost 12.6 per cent of volatile and combustible matters, leaving a coal black residue. AVhen this was heated in the open air it lost 8.4 per cent additional, making in all 21 per cent of volatile and carbonaceous matter in the rock. Very little of this however was bitumen; the most of it was of the nature of a true coal. Attempts to distill oil on a large scale from this rock resulted in the production of only from 3 to 5 per cent of oily and tarry matter, besides combustible gases and water. 542 GEOLOGICAL SUKVEY OF PENNSYLVANIA. It is not likely that the black slates of any part of this great formation No. Ill will ever be used by the business world for the distillation of oil, or the production of illumi- nating gas. Such pyroschists or black slates have been deposited in all ages. It will be shown in a proper place that they are not only sometimes very rich in carbon, but interleaved with thin beds of coal, deceiving people into the belief that they can be profitably mined. Such is the case especially with the black slates near the botton of Formation No. VIII on the Janiata and elsewhere in the State. It will also be seen that such pyroschists usually form the roof of every true coal bed and furnish the material from which the dis- tillation of coal oil was carried on previous to the discovery of petroleum. But in the upper or later formations the carbon distributed through the black shales was certainly derived in large part from water plants growing in pools surrounded by a land vegetation. We may, therefore, take it for granted that the carbon of the black slates of forma- tion No. Ill was obtained also from the destruction of some- kind of water plant vegetation, but mixed with the decayed animal tissues of shell-fish, corals, water-bugs and worms. It will be shown in describing the Oil Measures, that the quality of petroleum obtained from formations of different ages differs greatly, especially in odor; and this is part of the evidence that the older petroleums are of animal origin more than vegetable ; and that the newer petroleums (in Pennsylvania) had a vegetable rather than animal origin. In speaking of worm tracks as abundant in No. Ill no mention was made of the forms of the worms themselves ; for it can be readily understood that such soft creatures, destitute of internal skeletons and external hard coverings would die and vanish without leaving any trace except casts of their barrows, and impressions of their movements. This is true of the whole family of sea slugs. But there were in the Hudson River Age, and also in ages subsequent, vast numbers of leeches, with horny plates in their mouths set with little tooth-like conical projections. Multitudes of the shining little cones (Conodonts, see Chapter XLIV, JSTU. III. UTICA AND HUDSON RIVER. 543 page 507, above) have been found, not only scattered sep- arately, but in small groups, and in some instances attached to fragments of the horny plates on which they were set. What these leeches lived on is an interesting question. They are found scattered over surfaces of slate on which appear worm tracks which were probably made by the animal that owned the teeth. But the size of the animal and the efficient character of its biting apparatus would lead us to suppose that there existed then sea animals of a considerable size clad in succulent flesh ; yet no remains of that kind have been discovered. The few limestone beds which are locally interstratified with the slates, as in Dauphin county, are too thin and muddy to make them deserving of serious mention in economical geology ; especially seeing that they crop out within two or three miles of the north edge of the limestone belt of the Great Valley. In the outcrops of No. Ill around the isolated limestone valleys and coves of Middle Pennsylvania also such interstratified thin limestones have been occasionally observed. As for example on the slopes above Spring Mills in Southern Centre county (426, T4). As there are no iron ore beds in No. Ill, nor any other metalliferous beds, this formation is of no mineral value throughout the greater part of the State. Its soil is dis- posed to be cold and wet ; but otherwise sufficiently fer- tile ; so that the No. Ill slopes of Bald Eagle, Tussey, Shade, Black Log, Tuscarora, North and Blue mountains are farmed by a large number of landholders, the fields ex- tending half way up the mountain side (T4, 425). The roofing slate belt. In one part of the State, however, Formation No. Ill is of great mineral value, furnishing the finest quality of roofing, table, and school slates. The roofing slate belt of No. Ill runs from the Delaware to the Schuylkill, through the northern townships of Northampton, Lehigh and Berks, where large settlements of slate workers have opened extensive quarries, and built GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. III.' I PICA AND HUDSON RIVER. 545 nal ^Report, Vol.1, 1831 Slalingtoii section. pL L , (D 3 page 13o.) Small bed* (containing some Large beds.) 400 Inrlndrx l/ir uuarrij beds around Hcinbftck.f, and around Slatedale; exact position unknown. 08 3) 3D. 5ont6 ' roofing slate quarries 100' (jo 7 WeUhtQOtn rooting slate quarries. i$LJ J J / 100 uarries 1L / 114 franklin roofing slate quarri gn ;i 100 ,,' Scimesffiess % Cos slate (Blue vein. Washington cLuarri 210 rcmjinq slate The liio* /3l/M> mountain (junrnj. 35 546 GEOLOGICAL SURVEY OF PENNSYLVANIA. considerable towns connected by railroads. This district is to Pennsylvania what North Wales is to Great Britain ; and in the course of time the quarries of Slatington on the Lehigh and Bangor on the Bushkill will become as worthy of the pilgrimage of geologists and tourists as the Welsh slate quarries of Tremadoc. Dr. Chance, in Report of Pro- gress D3, Vol. I, 1883, describes more than a hundred slate quarries, old and new, some abandoned, many vigorously worked, illustrating his descriptions with photographic views of the older and deeper quarries, and giving many sec- tions of the beds in which the workings are carried on. The section along the Lehigh at Slatington (D3, page 147) shows the folded structure of the formation and the order in which the principal valuable beds of slate occur. The measured thickness of the roofing slate part of the forma- tion amounts to 1529 feet, divided up into small and large slate beds, separated by groups of beds which are not fit to quarry (page 135). See plates L and LI. The groups of beds that are worked may be thus de- scribed. Group A (at the bottom), 12 feet ; Group B, 25 feet ; Group C, 12 feet ; Group D, 60 feet ; Group E, 50 feet ; Group F, 12 feet. Groups A and B are only 16 feet apart ; C is 222 feet above B, and separated from D by only 15 feet ; D from E by 12 feet ; E from F by 73 feet. But these only represent beds that have been successfully worked on the Lehigh river. Many others have been opened and tested but not worked. In a general way it may be said that the upper beds of slate run parallel with the foot of the Blue mountain, at a distance of from half a mile to a mile from it. The out- crop of the lowest beds runs rudely parallel with the other at a distance of from half a mile to a mile further south. These variable distances from the Blue mountain and from each other are in consequence of the folded condition of the formation, bringing up the same beds to the surface in small and large waves again and again. The slate quarries furnish fine opportunities for studying the character and quantity of the earth movement which has thrust the whole country northward. In no other part of the slate belt No. NO. Til. UTICA AND HUDSON RIVER. 547 III from the Delaware to the Potomac can the exact quan- tities of its folding be obtained ; but the openings in Lehigh and Northampton are so large and numerous, and so close together, that transverse sections can be constructed with- out much difficulty, and the shape of the plications can be represented to the eye (as in plate L). It must not be supposed that the slates sent to market are the original laminae of the beds deposited one above the other and split asunder. The beds of the formation will not thus split. Although originally deposited in leaves or thin sheets of mud these original layers have been com- pacted into a solid mass and cannot now be separated by human tools. Even if they could be so separated they would be useless to man, because they are bent into curves. Fortunately for our arts of life the pressure which folded the beds produced another and very remarkable effect upon them. Being a great and uniform pressure from the south toward the north, it subdivided the whole formation into millions of thin plates, perpendicular to the direction of the pressure ; and these are the plates which are split asunder by the quarrymen and sold for various purposes. Thus we have curved planes of original stratification, and straight smooth planes of pressure-foliation. The most striking feature of the slate quarry to the eye of a spectator is this double-banded structure of the rocks. He sees the face of the quarry crossed by the foliation in straight lines, seldom vertical, but usually dipping steeply toward the south ; and the quarry operations follow these bands and pay no attention whatever to the original stratified beds of the formation. Across the bands of foliation the curved ribbons of the folded strata are seen passing from one side of the quarry to the other in a series of waves, each stratum distinguished from the strata above and below it by either strong or delicate differences of color. Every one must have noticed in rooting slates, and some- times in writing slates, bands of a lighter or darker tint crossing them ; these reveal the original sedimentation. Every one must have noticed on dark writing slates, whitish spots, and that the slate pencil when it leaves the black 548 GEOLOGICAL SURVEY OF PENNSYLVANIA. ,'sm i Xuadn Quarry. M.S Z. KJlaiinuS Quarry, X, . 3. SSayaf Quarry, X. Si. 4. Tallin ftm Quary, 76 fc NO. III. UTICA AND HUDSON RIVEIl. 549 , Matec/uam^ on 550 GEOLOGICAL SURVEY OF PENNSYLVANIA. surface and crosses such a white spot will not bite. These white spots are small pellets of clay in the original sedi- ment mashed flat and enlarged, and reduced to an exceed- ing thinness by pressure. See plates XXXVIII, XXXIX. Another interesting phenomenon connected with the planes of foliation is their frequent fan-shaped structure, especially where the original beds are sharply bent upon themselves ; for, since the foliation was produced by pres- sure, and in planes perpendicular to that pressure, when- ever the mass was sharply bent the direction of the pres- sure was modified on the two sides of the fold, causing the planes of foliation to diverge. This will be sufficiently ex- plained in a more detailed description of the slate region. As the development of the cleavage planes or slate foli- ation was produced by the pressure expended by an earth- movement from the south, and as the amount of this move- ment must have been measured by the number and sharp- ness of the anticlinal and synclinal rock-folds which re- sulted from it, we should expect the greatest amount of foliation, that is, the greatest number of workable slate beds to be in districts where folds are most numerous. At the first glance this would seem to explain the fact that there are only two workable slate beds on the Delaware river, for there the whole mass of Formation No. Ill slopes north- ward in a very regular way, with dips of 20 increasing to 35 at the top (in the Delaware Water Gap) where the upper- most Hudson River beds are seen going down beneath For- mation No. IV. On the Delaware river there is an almost total absence of the sharp small rolls and basins which are so prominent a feature on the Lehigh river; and this has given an oppor tunity for a fair measurement of the thickness of the forma- tion north of the great anticlinal which crosses the river about 2 miles south of the Gap. Its upper series of beds' measured from the base of No. IV down to Williams' old slate quarry count up say 1540 feet; the lower series meas- ured from Shocks down to Belvidere counts up say 3700 feet; the total of 5240 feet ought probably to be increased to 6000. NO. III. UTICA AND HUDSON RIVER. 551 The upper series consists of beds which are commonly more than one foot thick; and the lower series, of beds which are usually less than one foot thick (Sanders' report in D3, page 85). An independent set of measurements along the Delaware river gives an equally large estimate, and places the two slate quarry beds at 1000 feet and 2350 feet respectively beneath the base of No. IV (Chance's re- port).* These five or six thousand feet of rocks consist of beds of slate varying in thickness from only one hundredth of an inch up to a maximum of at least 30 feet; being nearly all of them of a dark grey bluish black color; some of them of very fine-grain ; others coarser ; and some coarse enough to be considered sandstone, but not continuous. It has already been said that No. Ill in its frequent ap- pearances in Middle Pennsylvania west of the Susquehanna river exhibits nothing like this thickness. At Orbisonia in southern Huntingdon it measures only 1870 feet (Ashburner F, 160). At Logan's gap in Mifflin county it measures 2304 feet.f In Blair county gaps the whole formation was esti- mated at only 900 feet. In Penns valley, Centre county, it is estimated at 800 feet or upwards (T4, p. 425) without any distinction being made between Hudson and Utica. In Friends cove and along the Jnniata in Bedford county it seems to be about 700 feet.:}: Seeing that the roofing slate beds are confined to the east- ern end of the Great Valley in Pennsylvania, it looks as if they constituted a separate formation and were not deposited to the westward; the thinning of No. Ill toward middle Pennsylvania being possibly explained by that fact. The belt of roofing slate, however, runs on through northern New Jersey and southern New York toward Newburgh on the Hudson; and important quarries have been opened in later years along this line. * In Munroe township, Lebanon county, Mr. Sanders got by construction 6000 feet for the probable total thickness of No. III. But in the geological reports rf the New Jersey Survey an estimated thickness of only 3000 feet is assigned to the whole Formation No. Ill along the Delaware river. f Hudson River 937, Utica, Upper Gray 210, Utica, Middle Black 302, Utica Lower Gray 855 feet (F, p. 55). t Utica being 200 feet. 552 GEOLOGICAL SURVEY OF PENNSYLVANIA. The continuation of the belt beyond the Hudson along the New York-Massachusetts line through Vermont into Canada, has given rise to the most protracted, the most vehement, and undoubtedly the most important discussion which has ever agitated the American geological world. It is called the discussion of the TAOONIC SYSTEM.* *It commenced upon the publication in 1844 of the report of the New York geologist, Dr. Emmons, upon the rocks of northern and eastern New York ' and it has been participated in by almost every geological field worker in the United States, and by several of the most distinguished geologists ot Europe. It has not ceased yet ; and in fact the controversial literature on the subject has been largely increased in the last few years. The hinge of the controversy is the question whether the great slate formation of the Taconic mountains in New York and of the plain between the Green mount- ains of Vermont and Lake Champlain is really Formation No. Ill of Penn- sylvania and the Southern States ; or whether it represents the older and underlying Cambrian system of formations. The place where the most perfect cross-section has been made is in Georgia county, Vermont, where broad outcrops of four formations, two of slate and two of limestone, alternate, and run side by side. Some look upon these two slate belts as repetitions of each other and the two limestone belts as repetitions of each other. If there be no repetition, we have at the bottom 1000 feet of fossiliferous limestones ; then 3750 feet of slate (the lowest 200 feet, Georgia shales crowded with fossils and the uppermost 50 feet a quart- zite); then 1700 feet of limestone (many of the beds broken into breccia); then from 3500 to 4500 feet of slate. (Bulletin U. S. G. Survey No. 30, C. D. Walcott, 1886). If there be a repetition we have a state of things greatly resembling the geology of Lehigh and Northampton counties in Pennsyl- vania, namely, a limestone formation measuring 1000 or 2000 feet in thick- ness like No. II, overlaid by a slate formation between 3000 and 5000 feet thick, No. III. Resemblance is rendered the more striking by the presence of beds of roofing slate quarried along the outcrop. Those who claim no repetition, that is, who refuse to believe in the existence of a fault bringing up again the lower limestone and slate to the surface to make the upper limestone and slate, have constructed the extraordinary theory, that the upper limestone is a lenticular or local deposit in the body of the slate for- mation. A lenticular limestone formation at least 1700 feet thick seems to me a physical impossibility ; and it is evident to those who have studied the Appalachian faults that a great fault must run through Georgia county, Vt.' which swallows up the upper limestone at its north end, and a large part of the upper slate in the same direction. The discussion is, however, at pres- ent in the hands of palaeontologists, who are not deterred by structural laws when these present extraordinary obstacles to their classification of the rocks by the fossil forms which they contain. It is evident that, if the Cambrian age of the Vermont limestone and slate be forced upon us as it seems to be ; and especially if the two great limestone and two great slate formations of Georgia, Vermont, be insisted upon, then it becomes impossible to explain their absence in New Jersey and Pennsylvania. It throws doubt upon the identification of the Potsdam NO. II r. UTICA AND HUDSON RIVER. 553 As the slates of >No. Ill are seen going down beneath the northern edge of the Mesozoic formations along the Leba- sandstone along the foot of the South mountain under the Lehigh valley limestones ; and it breaks all connection between the well-established geology of the Great Valley from Alabama to New York with its evident continuation through Massachusetts and Vermont into Canada. If the roofing slates of Georgia county Vt. underlie the Potsdam then they can- not be in the same formation with the roofing slates of No. Ill ; and it be- comes necessary to repeat again and again the great fact that at the bottom of our roofing slates of No. Ill lie the black Utica beds, and underneath these lie the uppermost beds of No. II containing Trenton fossils. Tt would be a most astonishing thing if 10,000 feet of slates and limestones in Vermont and eastern New York should be wholly wanting in New Jersey and Pennsylvania ; and at the same time at least 8000 feet of slates and limestones on the Delaware river should be entirely absent east of the Hudson. It may be objected, that the 6000 feet of No. Ill on the Lehigh and Dela- Avare fades away to 700 or 800 feet on the West Branch Susquehanna and upper Juniata rivers. But we must remember that the direction of this thinning is across the measures northwestward; and that the gi eat thick- ness of No. Ill reasonably maintains itself along the line of strike from northeast to southwest. Therefore it is to be expected that No. Ill will be as thick in Massachusetts and Vermont as it is in the Great valley of New Jersey and Pennsylvania. It is a conclusion of equal validity that if- No. Ill diminishes in thickness from its Great Valley outcrop northwestward toward the Allegheny mountain it must have been of equal or greater thickness in its original area southeastward toward the Atlantic Ocean ; and although the destruction of this great formation over all that part of its original area has been almost if not quite complete, yet we ought to find fragments of it in southeastern Pennsylvania which have escaped such des- truction. We may not be able to recognize 'it with absolute certainty in such preserved patches, because of the universal metamorphosis which all the rocks of southern Pennsylvania have evidently undergone. In other words, if the limestones of No. II preserved in Lancaster county, in tue Chester county valley, and in similar basins still further and as far south as the Delaware State line, gradually change iheir aspect and become beds of white crystalline marble, we ought to expect that the slates of No. Ill if preserved anywhere south of the Great Valley should also present a similar difference of aspect, and show themselves as crystalline slates or schists, perhaps even as chlorite slates, talc slates or mica slates. But it is well known that limestones are always much more changed than mud rocks are; except when the mud contains an unusual percentage of magnesia andiron. Unfortunately too little attention has yet been paid to the chemical analysis of the beds of No. Ill ; and therefore we are not in condition to speculate safely upon the degrees and varieties of crystallization which the slate beds of No. Ill might assume in the highly metamorphic region of southeastern Pennsylvania. Without this chemical knowledge we cannot argue to conclusion the moot question whether the South Valley Hill slate belt in Chester and Lancaster counties is a preserved part of No. Ill, or whether it is an older (Cambrian) formation brought to the surface by a great fault running along the southern edge of the Chester county valley. 554 GEOLOGICAL SURVEY OF PENNSYLVANIA. , Onddci LIIJ water gap; coat dida. yap. NO. III. UTICA AND HUDSON EIVER. 555 nori county southern line, and at the south foot of the South mountains between the Schuylkill and the Dela- ware ; and as slates, apparently No. Ill, are brought up to the surface through the Mesozoic by the Doylestown fault, we have a right to suppose that the slates of No. Ill form, at least in some places, the floor of the Mesozoic belt along parts of its range ; although there are good reasons for believing that the principal part of that floor consists of the eroded outcrops of the limestones of No. II, which are seen rising from beneath it, without any slate, at Norristown. It is not surprising, therefore, that Dr. Frazer, in his sur- vey of Lancaster county, observed at several places, a slate formation, very black and lustrous, which may be inferred to be Titled slate^ because overlying the limestone forma- tion No. II. This is rendered the more probable when, as at Brickerville, in Elizabeth twp, the black slates appear emerging from beneath the south edge of the Mesozoic, as if they were connected underground with the No. Ill slates of Lebanon county. They are so black that excavations have been made in them in the hope of finding coal ; but their principal interest to the geologist arises from their re- semblance to the Peach Bottom roofing slates which have already been mentioned as crossing the Susquehanna river at the Maryland line. The Peach Bottom roofing slate belt projects northeast- ward into Lancaster county and southwestward through the corner of York county into the State of Maryland. It ap- pears to be a closely folded basin about 9 miles long, the beds dipping nearly vertical. Eight principal quarries have been worked, some of them for many years, to a maximum depth of 200 feet. As in the Slatington region, so here, the quarries are not continuous, the roofing slate quality varying lengthwise of the basin. It is described in more detail in Chapter XIII, page 141 above, but it requires mention here because it has been sup- ])osed to be a far south outlier of III, and its quarries have been compared with those on the Lehigh, on the strength of numerous undescribed seaweed-like fossil markings on the faces of some of the slates, which our great master in 55(5 GEOLOGICAL SURVEY OF PENNSYLVANIA. Palaeontology, James Hall, pronounced to be possibly a species of ButhotrepMs, a genus of Hudson River age.* This is a slender support for so important a theory. The fact of a roofing slate foliation of some of the beds goes for nothing; or rather is in favor of a Cambrian age, when the great slate quarries of Wales, and Vermont, and the quarries now being opened in the South Mountains of York and Adams counties are considered. It is hard to imagine the Peach Bottom slates to be III, and the great limestone formation II to be wholly absent from the district; and in its place the Chiques quartzite (see page 183 above); while the surrounding region consists of mica and chlorite schists. It hardly seems worth while to conjecture that the Peach Bottom slates represent the upper member of No. Ill, and the mica schist country the lower division metamorphosed regionally. It is still less worthy a conjecture that the Lehigh slate belt is a separate formation deposited where the rest of III and the whole of II were not deposited. In Pennsylvania such non-conformability of deposition is scarcely possible, however probable it may be elsewhere, in Canada for instance, f *Prof. JohnS. Stohr, of Franklin and Marshall College, Lancaster, Pa., read a paper before the Linmean Society, in 1886, to draw public attention to the Peach Bottom fossils. Subsequently, in a letter to me dated May 20, 1886, he says that one of the specimens in his possession "seems to have a woody stalk, with pinnae extending from both sides, but not distinct enough to determine their character. What seems to be pinn 82 4Q 14.40> 5.40 2.68] !:Sh O.llj 2.30 2.70 99.10 The pyrites (sulphide of iron) so universally disseminated through the slate formation must have been one of the original constituents of the oceanic mud ; for there are no traces anywhere to be found of either ancient or modern volcanic action in the Great Valley, to supply sulphur.* The amount of sulphur also, in any specimen of slate is so small that we must suppose it derived from the sea water Silica, .... 55.880 1. 60.530 2. 3. 59.630 59.260 Alumina, Oxide of iron, Lime, Magnesia, Water, Alkalies, 19.400 10.570 .080 1.710 8.170 3.760 17.400 9.290 .080 1.920 5.510 5.270 18.560 19.877 .8.571(a) 10.071(6) .672 .250 2.252 1.917 4.560 3.600 5.109 4.855 Sesquiox. manganese, . Sulphuric acid, .... Phosphoric acid, .... .290 .123 .012 .279 .058 99.570 100.000 100.046 (a) and (6) are sesquioxide of iron. Dr. Genth's analysis of the blackish Peach Bottom roofing slate, the red dish white and the greyish white damourite slates of Lehigh county (Re- port B, page 126) show that the green specimens had more iron than the reddish. * The two trap dykes which cross the valley, one in Cumberland county and one in Berks county, are of so local a character that they need not be considered. CHARACTER OF FORMATION NO. III. 565 above, rather than from the earth-crust beneath the oceanic mud. But if it came from the sea waters it must be as- cribed to sea vegetation ; about which however we know very little, because the marks which that vegetation has left on the slate rocks are few and indistinct, especially so along the slate belt of the Great Valley. In New York state however great numbers of what seem to be sea-weed forms are found in the Hudson river slate formation No. III. At all events, we know that the ocean waters in that age swarmed with innumerable living things called grap- tolites ; and if these were more animal than vegetable, still it is not to be supposed that the waters were not quite as prolific of other kinds of more strictly vegetable life, and in sufficient quantity to furnish all the sulphur required to explain the analyses. Much of this vegetation was prob- ably of microscopic size and infinite fecundity. We can- not otherwise account for the sustenance of the innumer- able swarms of animals which then populated the sea; es- pecially the free-swimming trilobites^ 6f all sizes from an inch to a foot in length. But besides trilobites there was the greatest abundance of other kinds of animals chain corals, star fish, shell fish of many kinds as well as flesh- eating cuttle fish * in other regions of the ocean, if not in the part of it which is now Pennsylvania. And a few frag- ments of land plants have been found, which compels us to believe that rivers brought plenty of decayed vegetation into ths sea, and therefore a percentage of sulphur. And of course the same rivers must have brought down to the sea the mud out of which our great slate formation was made. The continent must have been large from which so much mud was manufactured ; and the rivers must have been huge which brought so much stuff to the sea. Its fineness shows that the mouths of these rivers were at a great dis- tance ; and probably there were vast deltas, mud-flats. If so, it is impossible not to imagine them covered with some sort of salt water vegetation, and that will help to account for the abundance of such shell fish as liked the shallows. * A rather dangerous term for popularizing the designation Cephalopod ; but one can do no better. 566 GEOLOGICAL SURVEY OF PENNSYLVANIA. That the deltas and shallows must have been at a great dis- tance from the present site of our Great Valley is evident ; for it is impossible to suppose 5000 or 6000 feet of mud to have been deposited in any but a deep sea basin ; for if the shores had been near, some of the earlier and middle beds would have been of coarse sand and gravel ; but none such were deposited until the basin had become well filled and the shores approached nearer by some change of the world's ocean level ; then indeed, the upper flagstones of No. Ill were deposited over the older fine muds ; and finally the off-shore shingle of No. IV (Oneida conglomerate and Medina sandstone) was spread overall. These considerations are offered here not for the purpose of settling scientific questions still under discussion among geologists ; but to familiarize the minds of readers of this report with the extent and complexity of our geological phenomena ; and to illustrate the value of the practical rule to keep all the facts in view for explaining each one. Quartz veins are very numerous in many parts of the slate belt. They are seldom more than an inch or so thick and usually cut across the beds, but often insert themselves between the slates. The substance matter of these veins, which is now so glassy and brittle, was originally fluid, and deposited itself in any open crack or fissure in the rocks, however small. This fact was practically discovered by Dr. Graham of Lon- don about 20 years ago, when he succeeded in separating silica in a jelly-like state from other elements with which it is commonly combined as a hard rock. Graham's gel- atinous silica (or fluid quartz) can now be made by any chemist and kept in bottles for a long time before it will harden into quartz. Nature has been manufacturing it in all ages and in immense quantities, and has put it to sev- eral particular uses, one of which is to make gems like the precious opal, etc.;* but chiefly to heal the wounds of the *A beautiful example of the use which Nature makes of gelatinous silica is the production of a kind of opal above a bamboo joint These lens-shaped stones, called tabasheer, are sold for "madstones" or "snakestones" in India. See G. F. Kunz's paper on " Madstones and their Magic " in Science, Vol. XVIII, No. 459, Nov. 20, 1891, page 286. CHARACTER OF FORMATION" NO. III. 567 rock formations after earthquakes, to fill up all the cracks opened in the strata (when compressed and folded and foliated like those of the slate belt) with vein quartz. The material out of which nature manufactured the fluid quartz is indicated by the analyses on page 564 above. The specimen of Delaware gap roofing slate (A), when analyzed, was found to be more than one-half silica. The other specimen (B) was about two-thirds silica. In fact, taking the whole slate belt of the great valley together, if we could analyze it as a single specimen, we should proba- bly get from it about 60 PER CENT of silica, 20 PER CENT of alumina and the remaining 10 PER CENT would be lime, magnesia, soda, potash, iron, carbon, sulphur, oxygen, hy- drogen, with traces of other rarer elements. Thus we see that the original mud deposit was mainly silicate of alumina derived from the wear and tear of feld- spar rocks on some distant continent. But a certain extra amount of silica came from the wear and tear of silicate rocks not feldspar ; and this extra amount was an availa- ble reserve for the natural manufacture of vein quartz after a long lapse of time.* For the veins had to be opened be- fore they could be filled. The original mud had no fissures in it. When the bed of the sea was lifted into the air, dried, hardened, folded and fissured, the deposit of vein quartz took place. The whole mass was still warm as well as wet, not merely warm but hot,+ and must have remained so for an indefinite number of ages since the cooling could take place only at the surface of the whole mass, now elevated 30,000 feet above its former level. The sea water still resident throughout the mass shared the high temper- ature of the mud deposits, dissolved a portion of their silica, and filled the cracks with vein quartz. * Of course the above statement is too short and simple to be in any sense complete. Chemists and geologists will fill it out for themselves. But some true and easily-seized notion of the genesis of quartz veins ought to be given to the uninitiated. f The law of increase of heat downwards from the surface, at the rate of 1 F. per 60' depth (added to the local invariable annual mean temperature ten feet beneath the surface) would give the rocks of No. Ill before eleva- tion a temperature of melting lead, 635 F. 568 GEOLOGICAL SURVEY OF PENNSYLVANIA. This operation, taking place throughout the whole 3000 feet of uplifted deposits, would have different results in the different formations. In the sand and gravel deposits (Potsdam, Medina, Oneida, Oriskany, Pocono, Pottsville) the silica would be deposited between the grains and pebbles, cementing them into a solid sheet or stratum of quartzite, sandrock, or conglomerate.* The mud deposits would not only be cemented, but cut with transverse and longitudinal quartz veins. The lime muds would receive quartz veins in abundance (as we see in the present surface sections), but an infinitely greater number of calcite veins the supply of silica being limited, and the supply of carbonate of lime unlimited. Meanwhile the tearing down of the elevated mass in the regions of eternal frost went on, and formation after forma- tion was washed away, continually producing a lower and lower upper surface, until the present surface level has been reached; and still the waste goes on, and still the surface gets nearer and nearer to sea level. The quartz veins of the swept away upper portions of the mass, have been carried off with the rest, into the Atlantic. But the tops of the quartz veins which are at the present sur- face strew the ground with fragments underneath where they once existed as solid veins. This accounts for the quanti- ties of quartz fragments which are found lying on the pres- ent surface in many places along the slate belt. For ex- ample, on the Jordan in Low Hill township Lehigh county the ground is covered with pieces of quartz (See D3, p. 124, No. 187). A few miles south of this the veins of quartz show in the slates (No. 190, p. 124). In most of the slate of that region, quartz veins are abundantly numerous, and some of them are quite large, like the one noted in D3, page 105, No. 96, at the Northampton Slate Quarry. The inser- tion of the quartz between the laminae of a slate beds, that is, following its lines of cleavage, is noted in D3, p. 122, No. 175, at the North Peach Bottom Company's quarry. * This is a fair way of accounting for the general quartzite aspect of the lowest, hottest and most compressed formation No. I, as compared with the higher, cooler and less compressed coarse strata of the Coal measures, No. XIII. CHARACTER OF FORMATION NO. III. 569 Flag stone layers occur in the Slate formation No. Ill, and many small quarries have been opened along the slate belt both in New Jersey and Pennsylvania; some of them in connection with the roofing slate quarries (to be described farther on) some of them having apparently nothing to do with the roofing slate strata. The sand deposits which made these flagstone layers, were in some few places so coarse as to deserve the name of gravel beds, or conglomerate rocks, although the pebbles in them are all small. For instance, there is a pretty high ridge of land two miles long south of Slatington in Lehigh county, made rocky by loose fragments of a conglomerate.* But where the rocks are exposed on the Lehigh river, they con- sist of fine-grained sandstone, in a series of beds, none of them more than four feet thick, 40 feet of them being visi- ble and the rest concealed (See D3, p. 114, No. 142). As a rule the sandstone beds in the slate belt are fine- grained and thin-bedded. That they are very numerous, and are separated by slate beds can be seen wherever the belt is not too much folded. A very good exhibition the purpose is made in Berks county, Albany township, where the rocks are vertical. Here 500 feet of fine sandstones and dark gray slates can be measured (see D3, p. 126). f Sometimes both the sandstone and the slate beds all have a greenish hue. Such a belt crosses the Schuylkill river at Hamburg (D3, p. 128 to 133)4 Sometimes the slates are olive colored or red, as already mentioned. Red slates at various places along the Hamburg belt strike so as to come between the sandstone outcrops. || The flagstone strata quarried in the northeast corner of Perry township, Berks county, roll so as to connect them with the red slate exposures (No. 244). On the other hand the quarries about * Dr. T. Sterry Hunt was so much impressed by this exhibition of coarse and massive strata in the midst of the slate belt, as to imagine it a proof of the far greater age of the formation, oil grounds which it is not necessary here to discuss. t See also p. 113, No. 133, on the Lehigh ; also, the Emanuel Church hill in Northampton county covered with thin sandstones, p. 105 D3. JSee also north of Seeberlingville, page 126, No. 198. || No. 236. 570 GEOLOGICAL SURVEY OF PENNSYLVANIA. Shoemakersville do not seem to have a connection with the red slate belt (No. 250, 251). It looks as if the upper part of the slate formation No- Ill furnishes most of the flaggy sandstone strata. There are quarries in Berks county where the strata dip 65 to- wards the south, in a line which would carry them west into the spur of the North mountain. It is hardly possible therefore to assign them a position more than 1000 feet or so below the top of No. III. The flags taken out here (at J. Gilt's, D3, No. 205) have rough faces, but dress up well. It is not safe to conclude however that the flagstone strata are confined to the upper part of the formation. They may probably be found in all parts of it. The massive flaggy sandstone outcrops south of Smiths ville in Berks county are in the line of the red slate belt ; and yet there are argillaceous limestone beds near them (No. 222, 223). The mineralogical poverty of No. III. The mineral wealth of the Great Valley is concentrated in its southern or limestone belt. The northern or slate belt is a farming district, of a fertility varying with the more or less sandy quality of the different layers of slate which come to the surface along narrow lines parallel to the sides of the valley. As the slate formation is several thousand feet thick everywhere along the Great Valley ; it might be expected that at least some of this huge series of layers would be valuable to the mining interests of the country. Not so, however. A few thin layers of poor limestone, or limy slate alone appear to attract attention. Not a single min- eral ore is to be found in the whole extent of slate belt of the valley. Not even a bed of iron ore of any kind what- ever worth shafting on has ever been seen or is likely to be ever seen. The whole formation seems to have been de- posited in deep oceanic waters, and what metallic salts were deposited with the mud and fine sand remain disseminated through the whole so as to be practically worthless in a strictly mineral sense. CIIVKACTKK OF FORMATION NO. III. i)71 Neither Oil nor Gas in No. HI. Of late it has become necessary to give warning that neither oil nor gas is to be found by any amount of boring anywhere in the Great Valley. Since the wonderful development of gas and oil at Lima and other towns of Western Ohio and Indiana from the Trenton limestone a thousand projects have been formed to exploit the Trenton in Middle Pennsylvania by boring down to it through the overlying slates. Some of these vain projects have disregarded the commonest rules of pros- pecting. For example, a well was bored north of Harris- burg where the slates stand vertical ! No attention was paid to the fact that the bore hole if vertical itself must neces- sarily keep down always in the same rocks in which it started, at least until they turned to take a north dip. It would probably require a depth of between 10,000 and 20,000 feet for that well to strike the Trenton limestone which crops out at Harrisburg ; where moreover it raises no suspicion of oil or gas. A little science is a dangerous thing. It usually resides in words and names. The Trenton limestone has yielded vast quantities of gas and some oil in Ohio and Indiana; why not in Pennsylvania? Simply because the Trenton in Ohio and Indiana lies on almost a dead level, and far enough under ground (1000-2000 feet) to preserve its gas from es- caping until bore-holes are provided. In the Great Valley, on the contrary, as every farmer must know who opens a quarry on his farm, the limestone beds have been upturned, even overthrown, crushed, crumpled and broken into frag- ments, and in that condition they reach the surface. Why is the limestone belt scarce of water? Because the up- turned and broken beds easily permit the rainwater to de- scend to caverns which ramify beneath the valley in all di- rections. Of course the ascent of oil, and still more of gas, must be equally easy. If the Trenton in our State ever had any store of the precious mineral it has lost that whole store long ago. There can be none left. We have no evi- dence that it ever had any. 572 GEOLOGICAL SURVEY OF PENNSYLVANIA. No one but an expert geologist can compare two fields so as to say that they are alike, or if they differ how they differ ? Twin sons of one father may resemble each other so closely that they pass for one another in common so- ciety ; yet one may be ignorant and the other learned ; the one a poor man and the other a millionaire. These are mat- ters of original constitution, and still more of circumstance. Just so with rocks of the same name, age and character, but either deposited under different conditions, or subse- quently subjected to different adventures. The flat lying Trenton of the west is like the titled nobleman heir to princely estate which has remained unspoiled and still abounds for him. The Chambersburg Trenton is like a younger son who has spent his patrimony, whatever that was, in riotous living, and there is no more of it.* Iron ore in the body of the Hudson river formation No. JIJ, in its 500 miles extent of outcrop in Pennsylvania, is almost unknown. The great limonite deposits of Ironton, Moselem, and Leathercracker Cove are below the base of the formation. And yet in Eastern New York beds of carbon- ate of iron, partly crystallized into spathic iron ore, partly weathered into limonite, are extensively mined, f * "CHAMBERSBURG, PA., July 25, 1887. An effort is now being made in this place to secure subscriptions for boring for natural gas. A number of Chambersburg people who have visited the gas-producing districts of Ohio believe that gas can be found underneath the surface here, because of the marked similarity of some sections of this county to the gas fields in Ohio. Subscription books are now being circulated over the town, and it is thought the necessary amount needed for the experiment, about three thousand dol- lars, can be obtained. Much interest is displayed in the project, for if gas should be found manufactories would undoubtedly spring up in large num- bers, and the future of Chambersburg would be almost beyond estimate." fSee Siderite basins of the Hudson River Epoch, by James P. Kimball, in Amer. Jour. Science, August, 1890, p. 155. They lie about a mile east of the Hudson river, between Catskill and Germantown RR. stations, Avest of Copake, in a range parallel with Taconic hills, and are plicated, some of the anticlinals being overthrown and compressed westward (giving E. dips). One section reads : Dense fissile slate, weathering white, 200'-f ; brecciated sandstone (ferro-calcareons) 161' ; sandstone passing into conglomerate (ferro-calcareous) 120' ; black slate and sandy shale (interbedded) 50' ; grits (ferro-calcareous, seamed with calcite) 48'; carbonate of iron (clay iron- CHARACTER OF FORMATION NO. III. 573 stone, siderite, sometimes spathic) 44' ; grey slate (weathering into drab shale in the river bluffs) 662, to the bottom of boring No. 1 ; 1300 in all. These lower slates, which, as Hall and Mather maintained (against Em- mons) are Hudson river slates, have afforded Hudson river fossils to Mr. T. Nelson Dale near Poughkeepsie. (Am. Jour. Sci. XVII, 1979, page 377.) The ore body is a group of clay iron stone layers separated by more or less ferruginous and calcareous shaly layers, the whole group varying from 8 to 60 feet, and evidently deposited in separate sea side lagoons, into which riv- ulets from the hornblende gneiss country brought magnesian deposits. 574 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER XLVIII. The roofing slate beds of No. 111. These are what give an economical value to the forma- tion, and redeem the slate belt of the Great Valley (geo- logically speaking) from almost utter barrenness. Were it not for its roofing slate quarries, one-half of the Great Val- ley would be merely farming land, without mineral wealth of any kind beneath the soil. At present, however, there are no roofing slate quarries in the Great Valley except at its eastern end in Lehighand Northampton counties, and in New Jersey. It is even doubtful whether or not the beds of roofing slate continue to range through the formation west of the Schuylkill river. The signs of their existence in Lebanon, Dauphin, Cumberland and Fayette counties are very scanty, al- though, here and there, what look like well laminated slate beds do crop out ; as for example on Conodoguinit creek ; where, however, the slate is spoiled with pyrites.* It is, therefore, of considerable importance to ascertain all the geological facts which bear upon the place of the roofing slate beds in the formation where we know them to exist, in order that their outcrops may be traced along the valley where their existence has not yet been certified. 0??, the Delaware rive?' Formation No. Ill appears divisi- ble into two series: an upper, and a lower. TJie upper series, mostly consisting of thicker beds (from one foot to many feet thick each) may be considered as oc- cupying say 1540 feet of the whole thickness of the forma- tion, f The lower series, mostly consisting of thin beds (less than *At Alton's mill. See Rogers, Geol. Pa., 1868, Vol. 1. f Measured by Dr. Chance, and Mr. Sanders, from the base of No. IV in the Delaware water gap down to Williams' old slate quarry. THE ROOFING SLATE BEDS OF NO. III. 575 one foot in thickness) occupies the remaining say 3700 feet, down to the limestone of No. II. * But this subdivision of the formation is not founded upon any other distinction than the one apparent fact that there is a general tendency to heavy beds in the upper, and thin beds in the lower parts of the formation. As for the mate- rial itself there seems to be no good ground for the distinc- tion. The whole mass, 5240 feet (and probably more) in thickness, consists of beds infinitely various in thickness, from 30 feet down to the hundredth of an inch beds of slate, nearly all of the same uniform dark grey or bluish-black color, both coarse-grained and fine-grained with occasional beds of sandstone, which are not persistent but either run out in a short distance or change into ordinary slate beds.f In the section along the eastern bank of the Delaware river (see page 554) two slate quarries are shown, one on beds which come 1000 feet below the bottom sandstone of No. IV; the other 2350 feet below it4 The interval of 1350' would represent the extreme thick- ness of the roofing-slate zone in the formation if no other quarry beds exists still lower, that is in the remaining 3000 feet of the formation down to the limestone. But of this we cannot be sure, and in fact have reason to doubt, as will presently appear. On the Leliigfi river the section is not so simple, and measurements are not so easy.|| Here a broken arch in the slates has given rise to a fault, of unknown upthrow, half a mile in front of the center of the gap, which cuts off all * Measured from opposite Belvidere, up the west bank of the Delaware to R. Shock's. See Report D3, Vol. I, p. 85. f Dr. Chance remarks (D3, p. 150) that the foreman of the quarry on the Xew Jersey side informed him that the diamond saiv used there for sawing out slabs showed that the diamonds were more rapidly worn away by the fine-grained than by the coarse-grained slate. These saws cut through the slate at the rate of 1 inch in 5 minutes, 50 strokes forward per minute (D3, p. 103). % This section, constructed by Dr. Chance from data obtained by him in making his contour map of the Water Gap, will be found on page 159 of Report D3 ; the section along the west bank of the river on page 157; the map in Report G6. i| See Dr. Chance's section on page 554 above, and map in G6. 576 GEOLOGICAL SURVEY OF PENNSYLVANIA. measurements down from No. IV after the first 1000 to 1500 feet.* Other rolls of considerable magnitude traverse the slate belt between the fault and theSlatington quarries, which are between 2 and 2| miles from the center of the gap.f Then we get the crumpled roofing slate belt 810 feet thick; which, although crumpled, can be measured with much cer- tainy4 But the country south of Slatington, between the quarries and the limestone is so full of folds that no meas- urement of strata is possible; therefore the real height of the lowest Slatington quarry-bed above the limestone, can- not be made out. All that we can say then is (1) that the uppermost part of the great slate formation at the Lehigh water gap con- sists of hard sandy slate beds, alternating with steel colored fine-grained sandstones, beneath which come soft, shaly, bluish-black slates; (2) that more than 1000' down from the top of the formation lies a zone of roofing slates at least 1500' thick; and (3) that underneath this comes a vast rib- bon-slate series. The Slatington roofing slate zone is itself made up of groups of beds of very various qualities, each group con- sisting of irregularly arranged thick and thin beds, some of which (both- of the thick and thin beds) have the roofing- slate character. This section could never have been made out but for the extensive exploitation of many of the beds, several of which are brought to the surface again and again by the rolling * Even the thickness of the slate between No. IV and the fault is uncertain owing to small rolls at the base of the mountain; but it cannot be less than 1000', nor more than 1500'. f Mr. Sanders has endeavored to adjust these rolls in his long section, underneath the Slatington section. J See the Slatington section on plates L and LI, p. 554 above. Dr. Chance expresses the opinion that between the fault at Slatington the crumpling is so great as to suggest a possibility that the rooting slate belt may be near the bottom of the formation (No. Ill) and therefore not far above the limestone (No. II). But the continuation of the Slatington belt westward near the foot of the mountain to be described directly, and the measurements at the Delaware water gap already given, seem to make it quite necessary to place theSlatington beds in the upper half of the forma- tion (D3, Vol. I, p. 151). THE ROOFIXG SLATE BEDS OF NO. III. 577 of the measures, as shown in plate L, on p. 544 above, the most important consecutive section in the Great valley.* Its great value consists in its proving conclusively, (1) that the roofing-slate zone of the formation is (here at least) 1500 feet thick ; (2) that in this zone lie many different beds of workable slate, some small, others of great size ; (3) that although the zone is crumpled the roofing-slate beds hold their special character over a space sufficient to allow them to appear again and again at the present surface ; (4) that the top of the zone is more than 1000' down from the top of the slate formation No. Ill ; and therefore (5) that the bottom of the zone must be a long way up from the top of the limestone formation No. II. The section has moreover a peculiar value for geologists since (6) it shows what a small percentage of the whole thickness of No. Ill its roofing-slate beds make, even where those peculiar deposits make their best show. But to the business world this is an unimportant consideration. Just as a few five and ten foot coal beds in 3000 feet of coal meas- ures, if accessible over an extensive region, can make the fortune of a whole commonwealth, so a few ten and twenty foot roofing-slate beds in 5000 feet of slate formation may suffice to supply an extensive commerce; although all com- parisons between the two cases in the matter of supply and demand must necessarily be omitted. f The roofing slate beds differ from the slate strata among which they lie (1) by the special fineness of mud out of which they were made ; and (2) by the special closeness and evenness of the cross cleavage. All the slates of No. Ill are more or less foliated ; but the roofing slates are so delicately and evenly foliated (not parallel to the bed planes, but across them at various angles) that they can be split apart into school-slates, roof-slates, billiard-table slabs, mantle pieces, and fine flags of various market values. ^ *And yet it is imperfect, inasmuch as its continuity is broken by three concealed intervals of 100', 60' and 100' ; besides the indefiniteness of its up- permost 400' "which includes large known workable beds." 1 30, 000 tons of slates is a fair annual shipment from the Slatington district ; 50,000,000 tons of coal from the anthracite region. JSee the commercial tables in D3, p. 144 to 146. 37 578 GEOLOGICAL SURVEY OF PENNSYLVANIA. The belt of quarries extends 30 miles across Northampton and Lehigh counties. Numerous towns and villages have sprung up along the belt between East Bangor within 5 miles of the Delaware river, and Slatedale 3 miles west of the Lehigh river. Branch railroads have been made for their service ; and new localities are being all the time ex- plored. The belt is wide and the outcrops numerous. Some of the quarries are within a mile of the North mountain ; others (Chapman's for instance) are five miles from the mountain, and two miles from the edge of the limestone of No. II. Isolated quarries have even been opened within a mile from the edge of the limestone belt. But all the successful quarries seem to belong to the Slatington zone, the outcrops of which repeat themselves in parallel lines, with alternate north and south dips, over a geographical belt of surface varying in width from one to three miles according to the number of the rolls and the flatness or steepness of the dips. But as yet there is no proof that any one of the quarry beds extends for 30 miles or for 10 miles along the zone. The continuance for any distance of the special roofing slate quality of any layer or group of layers in the slate formation is only determined for the individual quarries, or immediately adjoining quarries. It is not certain there- fore that a fine quarry bed may not exist along a line of ordinary and worthless layers. Every exposure should therefore be tested for itself. The place of a coal bed in the coal measures is a good guide for the coal prospector ; but there is as yet no satisfactory proof of the fact that the place of a slate bed in the section (if discoverable) is a sure guide for the slate prospector. Even the continuance of the Slatington zone as a whole along the Great Valley westward beyond the Schuylkill is a matter of doubt. Roofing slate quarries have been opened in the northeastern part of Berks county which undoubt- edly belong to the Slatington zone ; but no roofing slate quarries have been opened in western Berks, in Lebanon, Dauphin, Cumberland or Franklin counties. The expla- nation of the fact may be a geological one, viz : that the THE ROOFING SLATE BEDS OF NO. III. 579 Slatington zone thins away and vanishes in Berks county, going west. Or the explanation may be a financial one, viz : that exploration confines itself to the neighborhoods in which capital has been planted along the lines of already constructed railroads, etc., within near and easy reach of the principal markets. Thus far, no inducement for ex- ploring the slate belt of the valley has been sufficiently strong to divert capital invested in the roofing slate manu- facture into new channels and to distant districts. The cost of testing the value of a new coal opening is inconsiderable. The cost of testing the real value of a slate outcrop for roofing slate quarry purposes is a serious consideration. It requires the eye of an experienced slate miner to pass judgment upon a slate outcrop as to whether there is a likelihood that the bed will furnish roofing slate at a considerable depth underground ; and the actual profitableness of a slate quarry is never known until extensive quarrying has been done. This the great number of abandoned quarries sufficiently demonstrates. Even where the qualities of fineness and foliation (split- ability) is possessed by a roofing slate bed, it is sometimes made worthless by a want of evenness. The excessive crumpling of the slate belt applies sometimes to the mi- nutest details of a quarry, and quarries have been aband- oned because the slates are twisted or warped, and there- fore worthless.* The ribbon structure of the roofing slate beds is their most striking peculiarity. The ribbon pattern seems to cross the beds ; but in fact it shows the real bedding of the original deposits, and has been itself subsequently crossed by the cross-cleavage, or slaty foliation, produced by the tremendous side pressure at the time of the folding of the formation. f The ribbon pattern is made by the different colors of * The Flynn quarry is said to have been abandoned for this reason (see D3, p. 104, 109). See also the bent slates in the Blue Vein quarry, p. 117, No. 1566. On the Jordan the cleavage is described as curly (p. 124, No. 184). fSee D3, p. 85; and Rogers' Geol. Pa. 1858, Vol. I, p. 248. 580 GEOLOGICAL SURVEY OF PENNSYLVANIA. the original muddy deposits, some gray, some black.* The ribbons at the Newville slate company's quarry are " tight and some of them jet black" (D3, No. 119). Those at the Blue Vein quarry when they get under 30' or 40' of cover become tight (No. 1566). An expert slate miner judges of the value of slates partly by its ring.-\ Westward extension of the roofing slates. West of the Lehigh river the Slatington roofing slate beds run on towards the Schuylkill. The old Diamond slate quarry 4 miles west of Slatington (3 miles from the North mountain) was worked to a depth of 250 feet and abandoned. A quarry near Pleasant Corner (7 miles) is abandoned. The Laurel hill quarry and Lynnport quarry (11 miles) are each 60' deep4 Near the Berks county line (15 miles) are the New Slate- ville quarries, on the two sides of a roll, both on a bed 4' thick and both abandoned. On the other side of the county line in Berks county the Centennial quarry is 80' deep ; and near it an abandoned quarry on a 20' bed. West of this no roofing slates have been found, but flagstone quarries have been opened. || There arises then a practical question : how is the roofing slate sub-division of the slate belt to be recognized along the valley ? (1) First, by its distance from the top or bottom of ths for- mation, as described above, /. e. 1000' to 2000' beneath the sandstone No. IV of the mountain crest, 2000' or 3000' above the limestone. As the latter measurement is almost * The best at the West Washington quarry is called "the grey bed" (D3, 98). f Thin-bedded slates, dark blue, with a good ring (p. 113, No. 135). The slates have a good ring, dark color and even cleavage (p. 114, No. 146). The slates lei't on the pile are thick and have a poor ring (p. 109, No. ] 14) etc. J The one lies one mile from the mountain the other two miles ; at the first the dip is vertical which if it lasted all the way to the mountain would make the bed 5000' below the sandstone; in fact the distance is much less. These are 6000' from the sandstone outcrop. [| In Albany township west of Kempdou ; in Perry township (half-way between Leonhartsville and Virginsville) where 3' flags 10 feet long are obtained ; and near Shoemakersville. THE ROOFING SLATE BEDS OF NO. III. 581 an impossibility on account of the folds in the middle slate limestone zone of the valley the former measurement (i. e. from the sandstone No. IV down) is the only one avail - ble. When the dips in the foot hills of the mountain are 10 to 20, the roofing slate belt must be looked for a mile or so from the mountain ; when the dips are 50 to 60, it must be looked for close to the foot of the mountain slope. But it must be remembered that the whole breadth of the slate belt is so folded, that the roofing slate zone (if it exists) will come to the surface several (or even many) times be- tween the mountains and the edge of the limestone. To show how important this consideration is we must go back for a moment to Lehigh county. There are three places west of the Lehigh river where roofing slate quarries have been worked nearer the edge of the limestone than the Slatington quarries are to the mountains; thus, in N. Whitehall township (2m. S. W. of Laury's, P. O.) the North Peach Bottom quarry (250x200' long and 90' deep) is only f mile from the edge of the slate. Here the beds are flat, but in a downfold, and therefore cannot lie more, than 2000' above the limestone. Again in S. Whitehall township between Orefield and Crackenport is an abandoned quarry on Huckleberry ridge, a long downfold (synclinal) of slate between two areas of limestone and only f mile wide. Although the slates are here vertical, there is only room for 1320' on both dips or 760' on each dip. It seems as if we must insert a roofing slate zone near the lower limit of the foundation. Again, east of Seipstown, and 4 miles west of the last, there is an old quarry not far back of the limestone edge, dip 70. But here there is room enough for perhaps 2000' of distance from the limestone up to the slate, The truth seems to be that the main belt of roofing slate runs along more than half-way up in the formation ; but that there exists beds of roofing slate in the lower half of the formation, some of which, in some neighborhoods, may possess commercial] value. And this explains a fact first noticed by the First Geological Survey of Pennsylvania, and published by Prof. Rogers in his final report, Vol. 1, 582 GEOLOGICAL SURVEY OF PENNSYLVANIA. page 260: After saying that "in no part of the slate for- mation" from the Susquehanna to Maryland " have the strata the structure and cleavage to produce roofing slate, he adds : ' ' The nearest approximation to that useful variety yet seen occurs in the bed of the Conedoguinit, above Alter' s Mill, where the rock is traversed by cleavage- planes of tolerable regularity, but its usefulness is destroyed by its containing sulphur et of iron." As the Conedoguinit runs along the southern edge of the slate belt, and some- times cuts a little into the limestone belt, these cleaved slates must belong to the lower part of the slate formation No. III. So in Franklin county 1 miles southeast of Orrstown on the road from Orrstown to the railroad, there is a fine road- cutting 30 feet long by 15 feet high which showed the folded slates with a roofing slate cleavage at right angles to the folds and the accompanying local map shows how close the locality is to the southern border of the slate belt, and therefore in the lower part of the formation. Red slate, which is not rooting slate, has not been ob- served in Northampton county ; nor in Lehigh county ex- cept within a few miles of the Berks county line 1 m. N. E. of Seiberlingsville in Weisenburg township No. 197, D3, p. 155); but in Berks county it is frequently noticed by Mr. Sanders, e. g. in Albany township, west o f Kemp- don (No. 206) red slate spotted with green ; half a mile S. of Kempdon (No. 208). Notes on the Bangor slate belt. By R. M. JONES. At my request Mr. Jones addressed me the following letter, embodying in his own way valuable information, which it is natural that he the pioneer of this important industry alone knows, or knows better than any one else. BANGOR, October 10, 1S8J. "According to my promise, I write to you concerning the slate interests of our country, and particularly of Northamp- ton countv THE ROOFING SLATE BEDS OF NO. III. 583 "The slate belt of Fail-haven and Paultney, Vermont, runs through Middle Granville and Granville Corners in Wash- ington county, N. Y. to Pawlet Wagen. In all the above named places there are large and extensive quarries in full operation. In this part of the belt the slates are of various colors, viz: purple, green and red. This belt thence runs through North Hoosick and Hoosick Falls in Rensselaer county into Columbia county, N. Y. In this county the stratum makes a large dip which runs under the bluestone of the Hudson river division below Kingston, N. Y. This dip is over sixty miles in extent. The slates are nothing in all this distance but a conglomerate slate of no value what- ever as slates. The finest slate of any value we will meet in this stratum is in Sussex county, N. J., which is of an in- ferior quality, properly belonging to the Chapman division, what is called the wavy or ribbon slate adapted only for local trade. In the north part of the stratum what are called the Bangor slates are considered in England and the Conti- nent (where they know what to look for in slates) the trade mark of America, so much so that all slates shipped from this country are called Bangor slates to gain credit and reputation. The slates of Sussex and Warren counties N. J. do not amount to much. We have made a close ex- amination of the strata between the Delaware Water Gap on the Jersey side through Warren and Sussex counties, N. J., into Orange county, N. Y., and we find the article of poor quality, more of the earthenware nature than slates, lacking the principal quality of the right kind of slates for roofing or school slates, which is toughness. There is an old quarry at the Delaware Water Gap, one on the Jersey side of the river, opened over sixty years ago by a gentleman named O. Evans, a native of Carnarvonshire, North Wales. He worked the quarry successfully for a number of years until his death, and accumulated considerable property and money through the working of this quarry. On the west side of the Delaware river near the gap, nearly opposite the Evans property, is another slate quarry near the village of Slateford, in Northampton county, Pa. This is supposed to be the oldest slate quarry in America, the quality of the 584 GEOLOGICAL SURVEY OF PENNSYLVANIA. slate is the same as in the Jersey part of the stratum ; the stratum makes a southwest dip here of over live miles in length, appearing and outcropping at the Boyer farm and other places in that locality in that neighborhood. The quality of the article in those places for roofing or school slate is only ordinary. This stratum runs southwest through the Brushy Meadows Valley, East Bangor, Bangor, Pen- argyle and the Wind Gap. And right here I would say that the great slate center of our state is destined to be be- tween East Bangor and about one mile southwest of the Wind Gap ; a belt of slates near ten miles in length from northeast to southwest, and about one mile in width or thick- ness from north to south. We have a number of quarries opened and in course of opening in this section. The prin- cipal quarries are the following: First, in East Bangor the celebrated Seek-no-further property, the old Delp property the Meyers, Bray and Short property, the Star slate quarry, the Standard slate property, the Bangor Central, the Howell property, the New Bangor quarries, the Old Bangor quar- ries, the Bangor Royal, the Bangor Unison, the North Bangor and the Washington slate property. All of these quarries except the little Washington are in full operation ; and there is more slate made in this section of the country than in any other one part of the United States. And then we must take into consideration that all these improvements are of a very recent date. R. M. Jones started nearly all these quarries since July, A. I). 1865. When he started the Old Bangor quarry on the first of August, 1866, Bangor under the name of the New Village contained less than twenty inhabitants. Now it is made into a borough of near three thousand souls ; and if all who work in the borough of Bangor would live in it we would have a population of over nine thousand inhabitants. Bangor was named after old Bangor in Wales, and is considered by all the finest mining town in the State of Pennsylvania. "Two miles and half northwest of Bangor on this slate belt is the town of Penargyl ; there is a very geart body of large beds of slate in this locality. The cleavage in this place is mostly horizontal, the ribbons pitching from 35 to 45 THE ROOFING SLATE BEDS OP NO. III. 585 degrees southeast. When we talk about a bed of slates we mean that portion of the rock that lays between ribbons or black streaks that run across the cleavage and grain of the slates. These streaks only occur in this stratum in the slates of New Jersey and Pennsylvania ; there are no rubbons or black streaks in this stratum in the States of New York, Vermont or New Hampshire, nor Virginia ; but we find the ribbon in part of the State of Maryland near the Point of Rocks. There is much difference in the quality of these ribbon slates. In some parts of the belt, especially in the north part of this stratum the ribbon slates will not do for roofing slate ; but the south part of the belt is well adapted for roofing as a second quality of slates ; and the fact of the matter is that all ribbons or wavy slates are nothing more than second grade of roofing materials. Still there is a large quantity of this kind of slate recommended by architects in your city and some parts of the adjoining counties. Some do it from ignorance of the true quality of slates ; but the most of our architects specify this article of roofing because it pays them to do it ; and th only way a second quality of slates of this kind has succeeded so well is by having percentage paid to that class of men who specify what material shall be used for the buildings. When such stuff is sent to England where they want first quality of slates they are not accepted. "At Pen Argyl two and one-half miles from Bangor there are some very fine slate quarries opened by Jung & Co., John & Rich, Jackson & Co., Stean, Jackson & Co. and the Albion Slate Company, and Henry Fulmer. All these quarries contain large beds of slates ; and slates can be pro- duced in this section of the slate belt at from thirty to forty per centum cheaper than at other localities on this stratum ; because from a large bed of slate we can make large sizes of slates. For instance, it only takes 98 slates of 24 x 14 to make a square of slates (that covers 100 feet of roofing); while it will take 533 slates of 12 inch by 6 inch slates to make a square (or 100 feet) ; and while the mechanics are making one square of 12x6 they will make five and one-half squares of 24 X 14 inch slates. Hence the importance of selecting slate 586 GEOLOGICAL SURVEY OF PENNSYLVANIA. properties containing large beds of slate. In this part of the stratum the slates are not adapted for school slates ; but in the south part of this the mountain strata is where the school slates can be procured. About one-half a mile south of Pen Argyl on the Bangor and Portland Railroad a large deposit of a very fine quality of school and roofing slates was discovered by R. M. Jones of Bangor, Pa. at a place called the Grand Central quarry which are of a fine texture and very dark color. Also Mr. Jones has discovered a large plant in the north part of the slate stratum of the Pen Argyl division, which is about three miles southwest from Pen Argyl. This is a large field for enterprise. The slate stratum pitches like the waves of the sea. The general dips are about three miles. And right here I would like to draw your special attention to the fact that the same bed of slate loses its strength and toughness in its outcropping. On the down dip the article will split from the side across the grain or cleavage readily, but on the outcropping it will not split across the grain or cleavage at all. About one mile from the Wind Gap southwest, the position of the ribbon changes to nearly a vertical position, and keeps on that way princi- pally all through Northampton county to the Lehigh river at Walnutport ; and the cleavage dipping about seventy- five degrees southeast. The stratum is much conglomerated from the first mentioned points to the Lehigh river. There are a few places in and between the aforesaid points where good quarries are and may be opened. At the Little Gap Hower & Son have a good slate property. About one and a half mile southwest of the Howard quarry a good quarry may be opened on the same beds. At Berlinsville there are several quarries opened and in course of being opened. At a place called Himbach several good quarries within about two miles from Walnut Port are well adapted for both school and roofing slates, but there is considerable con- glomeration in the slate belt from the Wind Gap to Walnut- port, and investments should be made with great care and close examination of the premises. ''The whole width of the slate belt from about one mile above Siegfried's bridge on the Lehigh river to the Lehigh THE ROOFING SLATE BEDS OF NO. III. 587 Gap is near ni;ie miles, but in all that distance there is not over three quarters of a mile of what might be termed a No. 1 article of slates adapted for school and roofing slates. This commences about a quarter of a mile below the Queens hotel at Walnutport and runs up the river towards the Lehigh Gap less than half a mile north of Walnutport as we proceed northeast from Walnutport. Beyond Berlinsville the good stratum is about a quarter of a mile wider. From the Little Gap to the Wind Gap the belt is much conglomerated and full of posts and crystals, which makes it a very dangerous field to operate in."* *Mr. Jones' letter is brought to a close with a beautiful verse of poetry in the Lower Silurian language of Wales, the age of which is not quite so remote as that of the slate belt, but nevertheless has this in common with it, that the vowel foliation crosses and obscures the original consonantal stratification. I would gladly give it here had I any friend at hand learned enough to verify the orthography. 588 GEOLOGICAL SURVEY OF PENNSYLVANIA. CHAPTER XLIX. The slate quarries of Northampton and Lehiqh counties in 1882. In 1883, Mr. Sanders' notes on the quarries of the slate belt were published in report D3, Vol. I, pages 86 to 133. No subsequent resurvey of the belt could be made, as the corps were fully occupied in other counties. New opera- tions, especially upon the Lehigh river above Slatington, deserve description for which I have no data. The follow- ing list and short mention of the quarries as they were be- fore 1883 will suffice to show the character of the belt.* In Northampton Co., Upper Mount Bethel township. 1. Washington Brown's Quarries, on the slope of the mountain overlooking the Delaware, recently opened ; 75 X 75x40 feet; 600' below the Oneida sandstone; dip 25 N. 40 W. cleavage flat. The slates have a good color and are smooth. 2. John Morrison's Quarry, at the foot of the steep slope of the mountain, 800 to 900 feet below the Oneida ; opened in 1877 ; 150x100 feet ; five to fifteen of Drift on top of the slates, which are decomposed under the drift ; dip 20, N. 40 W., cleavage flat. The beds are four feet and under in thickness. ?. J. W. Williams' Quarry, half a mile northwest of Slate- ford ; 150x150x100; 30 to 50 feet of Drift on top, with boulders 2 feet in diameter ; thickest bed 4 feet ; dip 20, N. 10 W. ; cleavage 2, S. 10 E. At the factory the ribbon slate is seen in the bed at the creek fifty feet below the quarry. f *The numbers are those in D3, and are found on the county maps of the D3 atlas. They begin at the Delaware river and run in a general westward order across Lehigh county into Berks. fThis was the first slate quarry opened in Pennsylvania viz: by Mr. Williams auout the year 1812. It is described in Prof. H. D. Rogers' Geol- ogy of Pennsylvania, Vol. I, p. 248 as follows ; but the/cm^ is not now vis- ble, being buried under water and debris. SLATE IN NORTHAMPTON AND LEHIGH COUNTIES. 589 4. Emory Pipher quarry, a few hundred yards west and slightly below Morrison's quarry; abandoned; 200x100 feet ; beds seen small ; dip in the south and central part of the quarry flat ; at the north edge 20, N. 40 W. ; cleavage 20 south. J. Snowden quarry. (Fig. 1 p. 548) This quarry owned by H. P. Jones is 500 yards northwest of Williams quarry ; 150x150x40 ; 15' of drift on top. Two of the largest beds are 14 and 12 feet thick ; cleavage 26 south. At the north side of the quarry there is a fault showing, probably the same fault as described by Prof. Rogers in the Williams quarry ; beds south of the fault dip 40 north. Product in 1882 about 150 squares a month. Started in 1870. 6. The quarry (Fig. 2) worked by William Manus of Scran ton, on Peter Fry's farm ; 300x100 feet and full of water ; no large beds to be seen. 7. L. Or one" s farm, \% miles north-east of East Bangor, a small abandoned quarry, 50x50x15; dip 20 N. 40 W., with flat cleavage; largest bed 2 feet thick; cleavage twisted. 8. J. Oyer's farm, li miles north of East Bangor; 100 x 100 feet, full of water ; beds 3 feet thick and less ; 10 feet of Drift; dip 10. N. 40 W. ; cleavage 20. S. 20 W. 9. Opposite Belvedere. The contact of the slates and limestones on the Delaware river shows by a high ridge. The dip is 70, S. 20 E. and the cleavage 25, S. 20 E. The same dip shows for three quarters a mile up the river. The slates are thin bedded, compacted together, making solid beds, in some cases 10 feet thick, between loose rib- bons. From the river road up north until the road lead- ing from Centreville to Porterville is reached, nothing but ribbon slates show. 11. C. Wolfs farm on Martin's creek half a mile east of the township line, a small excavation ; dip 15, N. 40 E. ; cleavage 60, S. 40 E. ; ribbon slates. 12. East Bangor quarry No. 3, Bry & Short; north side of the railroad, east of the wagon road leading north from East Bangor ; 150x50x50 ; dip 5, S. 40 W. ; cleav- age 20, S. 10 W. ; beds rather small. 13. Old East Bangor quarry. Fisler & McKean ; across 590 GEOLOGICAL SUKVEY OF PENNSYLVANIA. the road from East Bangor No. 1 ; 250x150x50, with water in the bottom; dip flat; cleavage 20, S. 10 W. ; largest bed 3 feet thick. 14. East Bangor No. 2. Bry & Short, 300 yards west of the old East Bangor quarry; 200x450x60; dip 10, N. ; cleavage 20, south ; largest bed four feet. 15. East Bangor No. 1. Bry & Short, between East Bangor No. 2 and the railroad ; 250x200x100 ; dip 20, N. 20 W. ; cleavage 20, S. 20 E. ; beds 16, 10 and 11 feet in length along the cleavage. 16. Star quarry. Major Aims, 500 feet west of the East Bangor No. 2; 200x200x50; cleavage 20, south. There is an old quarry (not being worked) just south of this, on the same beds as the East Bangor No. 1. Washington township. Colon Aims' quarry, close to the township line, on the north side of the creek ; 100x50x40 ; with 10 to 20 feet of Drift on top ; dip 25, N. 40 W. ; cleavage 20, S. 4 E. ; beds all small. Some of the slates are made from single beds, while others have two or more beds in them. The slates made from the ribbon slate are mostly bent ; others are good except a few which are slightly bent. 17. Bangor Central quarry, % mile west of the township line on north side of creek; 200x100x40 feet deep; dip 25, N. 40 W. ; cleavage 10, S. 40 E. ; make slate out of single beds, and from two or more beds ; some of them slightly bent ; beds all small, 18. Bangor Old quarry, 500 feet west of the Bangor Cen- tral ; side hill cut, 50 feet deep at the face, with from 15 to 30 feet of gravel on top ; dip 25, N. 40 E. ; cleavage 15, S. 40 W. ; slates made from single beds and from two or more beds ; some much bent. 19. Powell's quarry, on south side of railroad, f mile east of Bangor ; side hill cut, 300 feet long, by from 50 to 100 feet broad, and 80 feet deep ; dip 25, N. 40 W. ; cleavage 15, S. 40 E. ; 5 to 15 feet of *Drift on top ; largest bed 4 feet. The slates on the dumps are made from one or more SLATE IN NORTHAMPTON AND LEHIGH COUNTIES. 591 beds ; all of these with two beds in them were bent, some few of the others were also bent. 20. Bangor Valley quarry, a few hundred feet west of Powell's quarry; 200x150x50 feet; dip 20, N. 50 W. ; cleavage 10, S. 50 E. ; 5 to 10 feet of Drift on top ; largest bed 3 feet ; quarry on top of the Bangor axis ; slates above the Bangor slates. 21. Bangor quarry (Fig. 3), mile east of Bangor ; 600 x 400x130. A synclinal axis passing through the center of it, about 70 feet below the surface ; the plane of the axis dips 5 to the north, the cleavage also dips 5 north. There is 30 feet of Drift on top of the south side of the quarry ; largest bed 9' 6" ; synclinal axis pitches to the west, being the same synclinal that shows in the Washington quarry and the Bangor Union. The slate in the north end of the quarry would come to the surface at the railroad, on a line between the Washington and Bangor Union quarries. The slate on the south side of the quarry probably shows in the Washington quarry. There are 60 men engaged in quar- rying, besides the drivers, engineers and splitters. The quarry is worked by horses and carts and also by three cable derricks run by separate engines. There are 42 shanties in operation. (1882.) 82. Washington, quarry (Fig. 4), Fulmer & Wagner, just west of the Bangor quarry ; 150 X 100 ; reported 70 feet deep ; 20 feet of Drift on top ; cleavage 12, N. 30 W. 23. Bangor Union quarry is some 250 x 250 x 130 feet deep at the deepest place, with from 11 to 20 feet of Drift on the surface ; largest bed 4 feet thick. The synclinal axis which shows in the Bangor quarry also shows in this one, but the plane of the axis dips slightly to the south instead of to the north as in the Bangor. The quarry is worked by 5 cable derricks, which supply material to 20 shanties. The derricks are run by one engine, which, working a line of shafting, connects with the cable derricks by conical friction wheels. The quarry is running on roofing and school slates. Those slates made just below the turn of the axis are bent ; the others are good. The beds in the quarry are tight and some of the slates are made across the beds. (1882.) 592 GEOLOGICAL SURVEY OF PENNSYLVANIA. 24- North Bangor No. 1 ; south-east corner 200 feet west of the north-west corner of the Bangor Union ; 200x200x 40 ; 20 feet of Drift, and they make slate one foot below it ; cleavage 10, S. 30 E ; dip 45, S. 30 E. ; two largest beds 4 feet ; there is a bed measuring 10 feet along the cleavage ; at the south end of the quarry this 10 foot bed has two feet of rock on the top of it, making only 8 feet of it workable. The beds show all the way across the floor of the quarry ; all of them are under 4 feet in thickness. .25. North Bangor No. 2, a few hundred feet north of No. 1 ; 150x100, 40 feet deep ; dip 35, S. 30 E.; cleavage 15, S. 30 E. ; beds under 4 feet ; I was told there were two measuring 12 feet in the quarry, but could not see them as it was full of water. 26. North Bangor No. 3 (Fig. 5 p. 548 above), 200' north of No. 2; side hill cut 150x200x100; of irregular shape and worked at the centre of the synclinal axis ; plane of axis dips 15, S. 30 E. ; cleavage dips the same. 27. Jacob O. Pystef 1 s quarry, one and a half miles S. E. of Bangor, 50x50x20 feet ; cleavage 30, S. 30 E. 88. Two miles S. E. of Bangor, on the east side of Mar- tin's creek, on P. Pysher's farm, is a small cut 50x30x30 ; dip 10 N, ; cleavage 30 S. ; slates all thin bedded ribbon slates. 29. True Blue slate quarry (Fig. 6, p. 548), on Martin's creek 1 m. E. of Factoryville; irreg'ular, averaging about 150 X 150x80 ; at the face the structure is shown as in the fig- ure ; in the cut the cleavage is 25 S. parallel to the plane of the two axes. At the bottom of the cut a quartz vein shows one foot thick dipping 25 S., spoiling the cleavage for a short distance on each side of it. On the south-east corner of the quarry a few small quartz veins show. The slates are all thin bedded ; have a good metallic ring, but those that have been exposed on the dump show signs of bleaching. The quarry not being worked in 1882. Lower Mt. Bethel township. 30. On Little Martin's CreeJc^ half a mile above the school-house, ribbon slates show dipping 70 N.. with a SLATE IN NORTHAMPTON AND LEHIGH COUNTIES. 593 cleavage of 25 south. A quarter of a mile below the school- house ribbon slates show with a flat dip and cleavage of 25, S. 10 E. 32. In the bottom of a small hollow half a mile north- west of Martin's Creek Post Office, there is a small aban- doned quarry of ribbon slate ; dip 45, N. 20 W. ; cleavage S. 20 E.* Plainfield township. 3f. Hull's quarry, A. & O. T. Hull, 1 m. N.E. of Pen Ar- gyl; 250xl50x- q O; 15' loose slate on top; dip at surface 68, S. 10 E. but steeper in the lower part of the quarry ; cleavage 15, S. 10 E. ; two largest beds 10 and 7 feet thick ; blocks come out even and split and sculp well ; not as much waste as in the average run of quarries. 38 Pennsylvania quarry, at north end of Pen Argyl ; 250 X200 feet ; dip at N. end 55, N.3<) W., gradually flattening southward ; cleavage 25, S. 30 E. Seventy feet from the north end is a 20 foot bed ; some distance below this a 6 foot bed ; rest of the beds smaller ; most of the ribbons tight. 39. Jory quarry, N. A. Jory &Co., 400x200x80 ; worked in the center of a synclinal; dip slight in center of axis ; plane of axis vertical ; cleavage horizontal.^ *Just above the mouth of Martin's creek the contact of the slates and limestones shows. The slates foi half a mile up the creek are seen dipping slightly towards the north, and are very much contorted. The cleavage ia Hat, the beds are small but not ribbon slate. Just east of where the road. from Martin's creek crosses Mud run, vertical black slates show with a horizontal clearatje. The largest bed is two feet thick. On the road lead- ing down Mud run between Hutchinson . Moore township. 16. Daniel Beef s quarry, on the east side of the town- ship, half a mile south of the railroad : 150x100; full of water ; on the same beds as the St. Nicholas ; dip 10 S. 40 E. ; cleavage 65, S. 40 E. *There are about 50 squares on the pile, most of them have iron pyrites in them at the junction of the ribbons; the slates on the end of the pile have changed color. Some of them also have thin veins of quartz in them. On the east side of the creek 100 feet north of the Daniel's quarry, the thin bedded slates are seen turning to the north, the dip being 20 north. The cleavage is 20 south. 500 feet further north the dip is 20 to the east ; 50 feet further north it is 10 north. 800 feet north of this there is a small aban- doned cut 60X60 feet showing the slates flat. Half a mile north of Daniel's quarry a small opening 10 feet deep in thin bedded slate shows, with a dip of 10 to the south and a cleavage of 15 south. Half a mile north of the above there is another abandoned quarry 50x75 feet, full of water. The slates are all thin bedded, bleached and iron stained. The dip is flat and cleavage 20 south. SLATE IN NORTHAMPTON AND LKHIGH COUNTIES. 597 79. Chapman quarry; 500x300x139; has 6 cable der- ricks run by independent engines ; 30 shanties in opera- tion ; splitters make from 2 to 6 squares a day, averaging about 4 ; hoisting apparatus very complete ; can hoist a stone of two tons 150' vertical and 300' horizontal'in about 2 minutes ; large factory for making and planing slabs and other sawed material ; with 3 diamond saws, 4 planers, 1 jig saw and 1 smoothing table ; diamond saws cut by re- ciprocating motion, at the rate of an inch in 5 minutes, 50 stroke a minute. The slates are all thin bedded, split well and are tough ; the blocks come'out of the quarry in large even pieces, some of them 20 feet long ; sculp and fracture well.* 82. ^Empire quarry, on the Manocacy creek, 1 m. E. of Chapman's; 100x100; full of water; cleavage 10 south; slates thin bedded ; iron pyrites in some of them ; also a few small quartz veins running through the slates. 83. Richard Moser* s quarry, 300 yards up the creek from the Empire ; full of water ; cleavage 20 south ; slates thin bedded ; weather to a slightly different color ; some show iron pyrites. 84. MaucJi Chunk quarry, at Chapman's Station; 200 x 150, full of water ; dip vertical ; cleavage 22, S. 40 E. ; slates tHin bedded. j^ So. Bethlehem quarry \ 200x150x80; dip on the surf ace vertical, then south a short distance and again vertical ; cleavage 10 south ; slates all thin bedded ; distances be- tween the loose ribbons along the cleavage of the workable beds are 7', 7', 3', 9', 3' and 3' ; one cable derrick run by a 15 horse-power oscillating engine ; six shanties in opera- tion (1882). On the south side of the quarry t'ley had to go down 60 feet before getting to good slate. On the north they went down only 20 feet. There is a quartz vein dip- ping to the south through the quarry 20 feet from the stir- * A few hundred yards east of Chapman's there is an abandoned quarry 250X250. East of Chapman's, across the creek, another 50X50 full of water ; cleavage 20 E. ; slates thin bedded. 598 GEOLOGICAL SURVEY OF PENNSYLVANIA. face on the north side and 60 feet on the south. The slate above the vein has not a good cleavage.* 88. Thomas Ryan's quarry, 100x50x40; slates thin bedded ; joints vertical ; cleavage horizontal ; dip towards the south averaging about 60. Some few slates have iron pyrites in them. 89. Jacob Flin'rf s abandoned quarry, 1,000 feet north- west of Ryan's quarry ; 100x40x30; dip 30, N. ; cleavage flat. Quarry said to have been abandoned because the slates were twisted. 90. Abandoned quarry, 1,000 feet north of Chapman's, 60x60, full of water; dip vertical; cleavage S. 10 E. ; slates all thin bedded. 400 feet west of this another quarry 100x40 full of water, with vertical dip and cleavage of 10, S. 20 E. 91. Abandoned quarry, 1 m. W. of Chapman's, 100x50, full of water ; slates thin bedded. 92. Helmari's quarry, 1% miles S. W. of Chapman's ; 100x100 feet, full of water; dip 45 south ; cleavage flat ; joints vertical ; slates thin bedded ; those on the dump bleached and iron stained. 93. McKee's quarry, 600 feet north of Helman's ; 100 x 100, full of water ; dip 22, S. 25 E. ; cleavage 15, S. 25 E. ; joints vertical, running east and west and north and south ; slates thin bedded, f 96. Northampton quarry, 1 m. S. W. of Chapman's ; two, both full of water; the southern one 150x150, the other about the same size ; separated by about 25 feet of slate ; 15 feet from the top a heavy vein of quartz dipping slightly to the south ; cleavage 20, S. 40 E. ; slates all thin bedded ; those left on the dump appear very rough and thick ; some of them have iron pyrites in them, and they have changed color. (See page 548 above.) * Abandoned quarry west of the last and 300 feet on the strike from it ; 200'X200' ; cleavage 10, S. 10 E. ; joint vertical. A quartz rein shows in this quarry as in the Bethlehem. 200 feet north of this there is another abandoned quarry 100X100 full of water. fOn the ridge a mile east of the Emanuel church, loose thin bedded sand- stone covers the surface of the ground. 300 yards north of Emanuel church slate dips 90 to the north with a cleavage of 45 south. SLATE IN NORTHAMPTON AND LEHIGH COUNTIES. 599 97. Abandoned quarry (Fig. 7), \ in. S. of Chapman's, 150x150, full of water; slates thin bedded; vertical dip. The horizontal section in the figure shows the contortions in the strike of the rock at the northwest corner of the quarry. East Allen township. 98. Chester county quarry is 200x250x130 feet deep. The slates dip 20, S. 40 W, Cleavage horizontal. At 10 to 40 feet from the top of the cut, veins of quartz show parallel to the bed plates. The slates are all thin bedded and the beds differ slightly in color. Some few of the slates have a small amount of iron pyrites in them. The blocks coming out of the quarry are large and even in size. Some of them are 20 feet long, 4 feet wide and 2 feet thick, but do not seem to split well. There is a little water in the quarry. It is worked by two cable derricks, run by one forty- horse power engine. At the corner of the road, just north of the quarry, there is an abandoned quarry full of water.* 100. A. Koch 1 s quarry, on Catasauqua creek, 3 miles W. of Bath ; 200x100 ; full of water ; dip 15 to N. ; cleavage 5 to S. ; slates thin bedded ; some iron pyrites. * The contact of slate and limestone enters the township from Upper Naz- areth east of Bath, takes a westerly direction, crossing the railroad half a mile south of Bath, continues on to the south-west for a mile, turns to the south for J of a mile, then turning to the west passes through Jacksonville and then along to the west, keeping south of the road leading west from Jacksonville. There are three outlying patches of limestone in the north- western part of the township shown on the map. They are probablybrought to the surface by the anticlinal which enters the slate south-west of Bath. Their shape cannot be accurately defined owing to the surface being covered with loose slate. A limestone quarry, 1,000 feet west of the Chester slate quarry. The dip of the limestone is 20 to the west. On top of the quarry there is a body of slate which is non-conformable to the limestone. The slate is somewhat broken and has probably fallen down on the eroded lime- stone. One quarter of a mile S. of Koch's quarry the limestone crops out, dip flat, with loose slate on top of it. 1,000 feet south of this more limestone outcrops, and about 50 feet lower the slates show. There is a small cut in the bottom of the hollow at this place, hut it is full of water, and nothing could be seen. At the saw mill dark blue, thin-bedded limestone crops out with a dip of 30 to the S. 30 E. There is a small amount of graphite on the bed plates. Just south of this outcrop of limestone, gray slates show, dipping 30 to the north, and at the road leading west from Jacksonville is gray cement stone dipping 35 to the south. 600 GEOLOGICAL SURVEY OF PENNSYLVANIA. Allen township. 106. Abandoned gnarry, lies a few hundred yards east of the railroad near S. B. Hoffman's house, having about 5, 000 cubic yards taken out of it ; dip 10, S. 10 E. ; cleavage parallel to bedding ; a few quartz veins. 107. Abandoned quarry, If miles north of Siegfried's bridge, on the Central Railroad of New Jersey, 75x50, full of water ; dip flat ; thin bedded slates.* Lehigli township. 108. S. Reple 's quarry, across the road from the hotel at Rockville, 100x200, full of water. For 500 feet north along the foot of the hill there are several small openings showing the slates flat and dipping 20, S. 10 E. ; cleavage 65, S. 10 E. ; main opening, slates flat ; one bed 7 feet thick, f 111. Old Harper's now Henry's quarry, % m. S. E. of Danielsville ; dip steep N. 45 W. ; cleavage 45, S. 10 E. ; beds small, with small tight ribbons4 11%. J. Henry's quarry (Fig. 8), m. S. of Harper's quarry; 200x150x30; regular synclinal axis; cleavage at center and north side vertical, but on south side about 60 south. 113. Eagle slate quarry, F. M. Hower, i m. S. of Har- per's ; two openings in a line 100x200x60, separated by 50 feet of rock ; dip 80, S. 10 E. ; cleavage 60, S. 10 E. ; * South of Kreidersville the slates dip 20 S. and the cleavage 20 S. On R. R. at N. W. corner of the township the slates have a slight dip to the south, averaging about 5 with rolls and twists and a few small vertical faults ; cleavage indistinct, about 40 to the south ; at center and north end of cut slates flat with rolls and twists ; everything contorted. f Three quarters of a mile south of Rockville outcrop of large bed of apparently good roofing slate ; cleavage 60 south. East of Harper's grist- mill outcrop of small slate beds; dip 20, S. 50 W. ; cleavage 60 S. J The cleavage in this quarry is not parallel to the strike, but the strike of the rocks is not parallel to the mountain ; if it were continued it would strike the mountain at from a mile to two miles and a half. The slates look good, some of them are of a different color, separated by a wavy line but no rib- bon. 200' S. of the quarry is an old opening now being filled up. NO. III. ROOFING SLATE BELT. 601 no large beds ; cleavage nearly parallel with bedding ; blocks of 20 to 30 feet in length sometimes obtained. They make about 80 squares a day and also a few school slates. 114. McChunk and National quarries, i m. E. of the Eagle quarry and close together ; one 100 x 150, the other 250x250, both full of water. In the southern one the rocks appear to dip 80 S., the cleavage 40 S. ; largest bed not over 5 feet, but only 50 of the 250 feet in the quarry is ex- posed ; slates left on the pile thick and have a poor ring. 115. Uplinqer & Griffith' 1 s quarry and Uplinger & Henry's quarry (Fig. 9) ; two quarries 150 feet apart ; 500 feet south of the Eagle quarry is Uplinger & Harper's quarry ; dip 80 N. ; quarry full of water. 150 feet south, at the north end of Uplinger & Griffiths' quarry, slates lie flat ; for 800 feet more an occasional outcrop shows a flat dip ; at the south end of the quarry (where they were working in 1882) a synclinal axis. None of the beds large ; slates look good and are darker than at most of the other quarries. 116. Continental quarry, \\ miles S. of Daniels ville ; full of water ; 200' square ; dip 80 S. ; cleavage 45 S. ; one bed 10 feet thick.* 118. Col. B. Mauref s slate factory is one mile north of Poplar Grove, where they make about 2,000 school slates a day. 119. Newcille Slate Co.' s quarry, 1 m. N. of Poplar Grove on the south bank of Bertsch creek; 75x125x90 deep ; dip 42, S. 10 E. ; cleavage 75, S. 10 E. ; ribbons tight ; some jet black; bottom bed 15 feet ; then 4 feet of small beds ; one bed 15 feet thick ; 25 feet of small beds, and on top one bed 10 feet thick. 120. New York and Pennsylvania quarry, li m. IS", of Poplar Grove ; full of water ; reported cleavage imperfect and slate rocky. * An abandoned quarry, | of a mile east of Danielsville and 200 feet north of the strike of the Continental quarry, shows a flat synclinal, with the cleavage dipping 60 to the south. 602 GEOLOGICAL SURVEY OF PENNSYLVANIA. 121. Kestef s Meadow quarry, leased by John Pauls and Peters; 150x100x60; 10 to 15 feet loose slate on top; largest bed 24 feet ; blocks come out in large, even pieces ; split well and the slate looks good. In 1882, working on the large bed, on the south side of the synclinal axis ; cleavage about 45 S. 122. Doddridge quarry, leased by Joseph Roberts; 500 yards north of the Kester Meadow quarry ; just (1882) started; cut down 30 feet, showing one bed 11 feet thick, with a few small beds on top ; dip 70, S. 10 E. ; cleavage 65, S. 10 E. 123. J. Remley 's quarry, 1 m. E. of Walnut Port, small, 15 feet deep, full of water ; dip 60, S. 10 E. j cleavage 50, S. 10 E ; two large beds reported in this quarry, the largest one 10 feet thick (probably 10 feet along the cleavage) ; slates on the dump look good. 12 4. HeiribacKs quarry (Fig. 10), H m. N. E. of Wal- nut Port, leased by Caskie & Emack. The section of the eastern face of the quarry shown in Fig. 10, gives the struc- ture. The quarry is 100x200x60 ; main cut originally 150 feet deep, now partially filled by waste. It is now (1882) worked by two tunnels, one driven east and the other west. The main opening shows the rock about vertical, but Mr. Caskie says that in the bottom they bent towards the north. Joints mostly horizontal and quite persistent, but some dis- tance apart, allowing large blocks to be taken out. In each of the tunnels there is a joint at thereof. The largest beds are from 10 to 15 feet thick, making a total (along the cleav- age) of about 25 feet. The whole 150 feet of the breadth of the quarry is used for making roofing slate. There is a factory at the quarry for making school slate with a capac- ity of 10,000 cases a year. 126. Owen Williams & Co.' 1 s quarry, J m. W. of Hem- backs ; 200X100X80 ; 60 feet of slate, used for roofing and school slates ; largest bed 8 feet thick ; other beds 6', 3' and 4'. The note (1882) adds : 100 feet west of this quarry Mr. David Williams has opened a quarry. He has only the NO. III. ROOFING SLATE BELT. 603 gravel stripped off, which is about 20 feet deep. The beds he expects to strike are the same as in Owen Williams & Co.'s quarry. 127. Williams & Jones' quarry, just west of Owen Wil- liams' quarry; 200x100x90; dip in the bottom vertical; at the south side near the surface a roll in the rocks ; clea- vage 60, 15 S. E. In this quarry there is a bed of slate from which they make slate pencils. 128. Abandoned quarry just N. of Walnut Port, 200 x 200 feet, full of water.* 135. Beach, Barge & Co.'s quarry, 1 m. below Treich- ler's, in the hill side east of the railroad, is 50 feet deep at its face ; dip 15, S. 10 E. ; cleavage the same ; slates thin bedded, dark blue with a good ring.f *On the railroad above the dam, the dip of the slates is 30, S. 10 E. ; cleavage 60, S. 10 E. 100 feet further north the dip is 25, N. 20 W. ; cleavage 60, S. 10 E. Just above this an anticlinal shows with aflat clea- vage ; then 100 feet further north the slates dip vertically. A few hundred yards south of the wagon bridge the slates dip 50 to the south. A short distance from where the wagon road goes under the railroad a massive gray conglomerate (dipping 30, N, 30 W.) is made up of white and black pebbles averaging one inch in diameter ; also tine grained gray sandstones. The junction of III and IV is not visible ; but the slates 50 feet below are seen gradually turning into sandstone. A hundred feet N. of the road crossing is the last place the slates are seen, 50 feet below the sandstone of IV. Further south, 250 feet, an anticlinal in the slates appears in the side of the road. The axis of the anticlinal is about vertical, and the cleavage is par- allel to it Two-thirds of a mile south of Walnut Port the slates dip 75 south. There are some small beds of interbedded sandstone at the same place. fOn the railroad, at the township line there are three peculiar curves showing in the slates. The cleavage is parallel to the axis of these curves. In the first one the axis dips 5 to the south. 500 feet north and under the above there is another flat turn with the axis horizontal, then 300 feet further north there is a flat turn with the axis dipping 10 to the south. 604 GEOLOGICAL SURVEY OF PENNSYLVANIA. Quarries in Lehigh county. Washington township. 140. Abandoned quarry, 1 m. N. of Slatington 25x100, a side hill cut 25 feet deep ; dip 25 to the north ; cleavage 60 to the south.* 146. Captain D. D. Jones' new quarry, on Welch run k m. N. of Slatington ; (1882) ; dip 10 S. and pitch 12 W. with cleavage vertical; big bed of slate .outcrops several hundred feet to the east, 30' thick ; twenty feet above big bed another 7' ; good ring, dark color, even cleavage. 14-7. Welchtown quarry, John T. Robinson & Co. ; opened in 1844 ; two large beds, one 27 feet along the cleavage, and another on top 18 feet, separated by 25 feet of smaller beds ; in 1882 making 8 squares a day ; worked by a tunnel on the 27 foot bed. llfi. Williams' railroad quarry, a few hundred yards north of the Slatington depot, 100x100x100 feet deep. 149. Old Keystone quarry, 200' N. of the Williams RR. quarry ; side hill cut 200 feet square, 60 to 80 feet deep at the face ; one large bed 16 feet, then 10 feet of small beds, then a bed underneath 25 feet ; dip 30 to the S. 10 E. cleavage vertical ; dip the same all the way to the Wil- liams quarry ; 150 feet south of the Williams quarry slates dip 70 south, cleavage 30 south. 150. Tunnel quarry, on Trout run, 300 yards from river ; one large bed back of the tunnel ; two smaller cuts along side the tunnel had fallen in. 152. Abandoned quarry, just above the borough bridge on the south side of Trout run; side hill cut 100x50x40 feet at the face ; dip 32 S.; cleavage 64 S.; five to twenty * At the southern end of Slatington the slates in the river are vertical. 200 yards S. of C. Zellman's on the railroad fine-grained sandstone out- crops; dip 20 to S. ; largest layers 4 feet thick ; 40 feet of sandstone shows. 50 feet further south a synclinal shows with the sandstone on the south side of it vertical. 300 yards N. of Rockdale slates dip 45 to the south ; cleavage parallel. At the water station slates are flat. Just south of the run the dip is 25 N. ; rocks slaty sandstone and slate. Then for over a quarter a mile southward the slates are flat. They then change gradually to a dip of 25 to S. In the next 200 yards the dip changes gradually to 15, N. 45 W., making a synclinal axis between these two points. 500 yards further down the railroad Ihe dip is 20, S. 45 W. NO. III. ROOFING SLATE BELT. 605 feet of loose slate at the surface ; beds showing all under four feet thick. 153. Penlynn quarry, 150x150x100 feet deep; dip 60, S. 10 E; cleavage 40, 8. 10 E. There is a 20 foot bed in the quarry. The other beds are smaller and most of them workable. North of the quarry 100 feet dip 90; 200 feet further north flat. 154. Old quarry No. 1, 500' N. 40 E. from the Penlynn quarry, on the north bank of Trout run, E. of Washington quarry ; slates vertical ; cleavage 60 south ; two 10 foot beds with smaller beds between. 155. Old quarry No. *2 (Fig. 11), around the curve in the hill from quarry No. 1. It shows a synclinal axis with the plane of the axis dipping 70 to the south. The cleavage also dips 70 to the south parallel to the plane of the axis. It also shows tJie bed thickening as it curves around the axis from 27 feet thick to 35 feet. Just after the curve the distance from where it is 27 to where it is 35 feet is 50 feet* 156. Old quarry No. 3, a short distance down the creek from No. 2 ; one bed 20 feet thick dipping 28 S. ; cleavage 75 S. The quarry not worked in 1882. All three quarries belong to James Hess & Co. 156a. Washington quarry, James Hess & Co., 300 x 200x75 deep ; at the south side the slates, flat at the middle of the quarry, turn sharply downwards, the dip becoming vertical; cleavage 60 S. ; upper bed 15'; then twelve feet of small beds ; lower bed 12'. 15Gb. Blue Vein quarry, 200 feet south of the Wash- ington quarry; on the same beds; 200x 150x75 ; a synclinal, its axis dipping 60 S. ; an anticlinal between this quarry and the Washington. f Under the twelve foot bed there is a school-slate bed. The lower four feet of the big bed has rock in it. The ribbons when they get under thirty or *This is a flagrant proof of the effect of the earth movement on the whole formation No. Ill, in changing its thickness. f This synclinal axis passes north of the t enlynu quarry through Slating- ton, and shows in the Tunnel quarry. It does not show at the river, prob- ably owing to a want of exposure, 606 GEOLOGICAL SURVEY OF PENNSYLVANIA. forty feet of cover become tight. In the south wall the slates are bent. 157. Blue Mountain quarry (Fig. 12), 600' long east to west, 250' at its widest part, 120' deep ; surface loose for 10 to 15 feet down ; two beds 16 and 27, separated by 12 feet of smaller beds ; started 35 to 40 years ago ; originally worked by Williams & Moser ; 4 spar derricks and 1 large cable derrick. They are making 55 squares a day (1882). 158. Columbia, quarry, N. side of Trout run N. of the Blue Mountain quarry ; 300 feet long ; dip vertical ; clea- vage 20, S. 20 E. ; 10 to 30 feet of loose rock on top.* 159. American quarry, No. 1 and 2 (Fig. 13), W. of Co- lumbia. Quarry No. 1, 250x100 feet; beds 30', separated by 6 feet of small beds, one being 2 feet thick. No. 2 shows the section Fig. 13. 160. Girard quarry, m. W. of Columbia on the N. side of Trout run ; 250x100x50 ; full of water ; one bed 15 feet thick, 161. Star Slate quarry, 300x100x60 ; dip 70, S. 10 E.; cleavage 50, S. 10 E. ; two beds 27' and 18' ; 10' of clay on top, and 4' of blue slate underneath the clay. 162. Williams, Owen & Jones' quarry, 40 feet deep, 100 feet square, in line with Star quarry ; shows the slate turn- ing over towards the south ; one derrick, working on the 27- foot bed. 163. Franklin quarry (Fig. 14). H m. W. of Slatington depot and N. of Trout Run. (There are several old openings south of it towards the Star quarry.) On aflat synclinal ; 4 spar derricks and one cable derrick ; greatest deph 150'. 165. Junction quarry, opposite the junction of the Slate- dale branch railroad, full of water, 200x100' feet square; one bed 15' ; the rest all small ; dip steep S. ; cleavage about 50 S. 200 feet north of it a small quarry 50x50, full of water. On the Lehigh and Berks RR. S. E. of the junc- tion quarry aflat synclinal shows vertical cleavage. 166. Industrial slate quarry, 300 N. of the Junction *500 feet south of the Columbia is an old abandoned quarry ; the dip of the slate is 70, N. 20. The cleavage 50, S. 20 E. 150' S. E. of thi% the dip is 10 N. NO. III. ROOFING SLATE BELT. 607 qnarry ; working on the 20 foot bed ; (1882) making about 15 squares per day ; dip vertical at the surface, curving to- wards the south at the bottom of the quarry ; cleavage about 45, S. 10 E. 167. Abandoned quarry 1000' W. of the Industrial, full of water, 200x290x40. There are three other openings be- sides this, the largest 300x100, all full of water ; one large bed 15 feet thick. 168. Abandoned quarry 1500' from the end of Slating- ton. Its section is shown in the section of the Blue mount- ain quarry. 169. Blue Mountain slate quarry (Fig. 15), 250' N. of east; 200x40x60; largest bed 27' ; dip~60 N. ; cleavage about 60 S. ; at bottom of large bed cleavage slightly curved ; section of the two quarries shown in Fig. 15. 170. Monarch quarry, owned by Mr. Hersh, on the south side the creek from the Blue Mountain quarry shows the same beds with a dip of 15 N. ; not worked (1882). Across the road another abandoned quarry ; dip 70 N. ; beds ap- parently the same. Two other quarries in the same field, the largest 150x150x50' deep. 171. Lock slate quarry (Fig. 16), m. W. of Slatedale. At the southeast end of the quarry there is a small open- ing 50x50x50 feet showing a bed 15 feet thick, dipping 85, N. 10 W., with a cleavage dipping 70, S. 10 E. The main quarry is 400' long. In 1882 the work was under ground by means of two slopes going down on the large bed ; cable derricks worked by one engine ; inclines three feet apart ; structure shown in Fig. 16. 17%. Standard quarry, i m. S. E. of Slatedale, 300x50x 114' deep ; beds 20', 8' and 16' ; 3 of gravel and 6' of loose slate over the quarry ; the 16-foot bed worked ; a large bed at west end did not work well ; rocks sculp and split nicely and come out of the quarry in good sized blocks.* *Grey slate shows in the southwest corner of the township, dipping 30, S. 20 W. The sandstone strata seen on the railroad one mile below Slat- ington makes a high hill which extends west more than two miles back fronj the river. No solid outcrop shows, but the ground is covered with loose pieces, 608 GEOLOGICAL SURVEY OF PENNSYLVANIA. JVorfk WJiitehall township. 175. North feach Bottom Slate Co.' s quarry, 2m. S. W. of Laury's Post Office; 250x200x90 at the deepest place ; slate beds horizontal, with slight rolls ; cleavage about horizontal ; joints vertical, but make different angles with each other ; blocks 20' square got ; largest bed be- tween loose ribbons 8' thick. About 30 feet from the sur- face there are segregated veins of quartz that split the cleavage for some distance around the veins. At the top of the quarry there is a bed of sandy slate which does not split well, bat the slates made are black, with a good ring and smooth surface ; the second quality slates have a very uneven surface and look poor. A factory connected with the quarry was engaged on an order for flooring for the Patent Office in Washington, 1882.* Heidelburg towns/tip. 182. Diamond Slate quarry (Fig. 17), leased by Hartley & Bar ; opened 1854 ; 250x150 ; two large beds, one 24 and and the other 30 feet thick, separated by 5 feet of small beds ; on top of the 24-foot bed a few quartz veins / a few also in the slates above it ; beds rise slightly E. along the strike. At 500' N. of the main quarry is an old abandoned quarry ; dip 45, S. 10 E.. and nothing to be seen.t * There are very few exposures in the township at which the dip can be obtained. On the small creek that empties into Jordan creek in the south- west part of the township, there are two dips to be had just east of the school house, the slate dips 10 to the south and a quarter of a mile above the mouth of the creek the slates are flat, with a few small rolls in them for half a mile on each side. f At S. end of Germanville slates dip 55 S. On Jordan creek 1 in. E. Pleasant Corner, a sharply folded anticlinical shows dipping 60 to the south. On the south side dip 50 S. ; north side 70 S. This shows a tight compression and overthrow. Half a mile south slates dip 50 south. 1| miles up a small creek that runs into the Jordan at this point, there is an abandoned slate quarry with nothing to be seen. \\ m. E. of Pleasant Cor- ner slates dip 30 S. 20 E. NO. III. HOOFING SLATE BKLT. 609 South Whitehall township. 183. An abandoned slate quarry on the Huckleberrv ridge synclinal % m. S. of Guthsville, 200x100, full of water; slates vertical ; cleavage 45 S. ; slates all thin bedded.* Lynn township. 192. Laurel Hill Slate Co.'s quarry, 1m. IS. E. of Lynn- port ; 75x50x60 ; dip vertical ; cleavage steep toS. 40 E. ; beds worked are 26', 10', 8', 6' and 2' in length along the cleavage 193. Lynnport Slate quarry, at Lynnport, north of the railroad, 150x100x60 feet.* 194. Two abandoned quarries at Slateville ; the one beside the road shows the northern half of the anticlinal axis, with one bed 4 feet thick ; the other quarry shows the slate dipping about 45 S., with one bed 4 feet thick. 195. Star Slate quarry (Fig. 18), George W. Griesheimer ct Bro., at New Slateville, one mile northwest of Stein- ville ; started about 1868 ; worked by the present owners silica 1876 ; make about 7500 squares a year. The cross section Fig. 18 shows one large bed 30 feet thick.- Quarries in Berks county. Albany townshiy. 195. Centennial quarry, 1 m. W. of Steinsville, Faust, Heinly & Bros., 150x50x80; 80, N. 20 E. The section *Low Hill township has no quarries. At its X. E. corner slates dip 15, S. 60 W. ; i in. further down a small run the dip is 45 N. with cleavage 45 S. curled. Just below Low Hill on the Jordan slates dip 30 S., cleav- age curly. A few hundred yards further down the dip is 30 S. 1| m. down the creek slates dip 50, N. 10 W., dark blue, thin bedded, with no regular cleavage. \ mile further down the dip is 50, S. 20 E., slates massive, cleav- age irregular. In the road across the Weidasville bend in the creek the ground is covered with pieces of quartz. 1| miles down the creek from Weidasville the slates are flat. Half a mile S. of Low Hollow P. O. slates dip 50, S. 10 W. ; cleavage parallel to dip. At the northwest corner of the town- ship slates dip 80 S. One mile N. E. of Lyons Valley P. O, slates are flat. One mile S of Claussville slates are flat ; and on the creek in the southwest corner of the township veins of quartz show in the slate. *1| m. E. of Lynnport slates dip 55 S. 610 GEOLOGICAL SURVEY OF PENNSYLVANIA. M.ffA tu&eAter {flak Phyllo^ptu. typn.. A grap.clite .gured by H.II, Pa. NO. III. ROOFING SLATE BELT. 611 cut shows the quarry and a small opening made on the large bed to the south. 196. An abandoned quarry, east of the Centennial, nearly on the county line; bed 20 feet thick, dipping 70 N.. cleavage vertical. Weisenburg town.sliip. 199. Old quarry, east of Siepstown, near the township line ; dip 70, S. 20 E ; cleavage 20, S. 20 E., tolerably perfect ; slates look like good roofing slates.* Albany township. S05. John GiW s flagstone quarry is two miles from Kempdon station. The sandstone dips 65 south. The strike of the rocks would carry it directly into the point of the mountain. The sandstone conies out of the quarry with rough faces, but after being dressed it looks good. Just north of the quarry slates dip 35 south. f *One mile south of this slates dip 10 N. ; and | m. further south, in upper Macungie township, slates dip 20 to the south. H miles N. of Seiberlings. ville an outcrop of red slate shows in the road, but it is not roofing slate- One mile north of Seiberlingsville, along the curve of the hill, there is an outcrop of thin bedded grey sandstone ; also some light green slate. This outcrop shows for about a mile. f At Trexler's station the slates dip 20, S. 20 W. | a mile west they dip 45 to the south. Just east of the Mountain Post Office the dip is 64O, s. 10 E. | a mile west of the Post Office it is 80, S. 20 E. 1* miles west of the Post Office the dip is 63, S. 10 E. Going on west into the cove at Digby Miller's the dip is 80, S. 10 W. At S. Knesler's it is 52, S. 10 E. At William Bo- lick's it is 90, S. 10 E., and, also, near the same place it is 75, S. 10 E. At John Berg's it is 90. At this place there are thin bedded dark gray slates, with inter-bedded sandstones. The sandstone is fine grained and in thin layers. The outcrop shows 500 feet of slates and sandstones. At the new Bethel church the slates are vertical. Just north of the church they dip 45 to the south; One mile east of J. Gilt's quarry there is red slate with dip of 20, S. 10 E. The slate has patches of green in it. On the road just below the grist mill slates and inter-bedded sandstones dip 45, S. 20 W. 200 yards south red slates show 40 feet thick ; dip about 60, S. Opposite the school house, light greenish sandstone makes the high ridge to the east called Round Top. 1000 feet further down red slate shows. J m. south of the grist mill thin bedded olive slates dip 80 N. A shaft on Stone run 1| miles above its mouth was sunk on red slate, 20 feet deep ; red slate 20 feet thick, some ol it has spots of green in it ; also, some green slate ; no roofing slates ; cleav- age not good, i m N. of this, a gray sandstone dips 90, S. 10 W. 5 m. N. of 612 GEOLOGICAL SURVEY OF PENNSYLVANIA. JfiMl. Orthis (Platystrophia) biforata, Var. dentata. Orthis dicho /// / 3. ! g;>5-t^v.i Orthis (PlatystropMa) biforata, Var. acutilirata. (Del So /":m*~~Sl, XTW^ St. Orthis jamesl, Hit. If* A,* , Ui JSNf U LV.l Orthi3 clytie, Hall, 14th Annual Orthii (Platyitrophia) biforata. ( Terebra Orthis orthambonltes, II. cerata ' H - 13 "> * I860, p. 12, ; 00 \ Orthis emacerata. v ar. multisecta, OrthU occidentals, Hall. Pal. N. Y. Vol. 1, 1841 fill Orthis Insculpta, Hall, Pal. N. Y. Vol. 1, 1847. frl MfVMf Orthis retro sa f Salter, (ieol. Survey of NO. III. ROOFING SLATE BELT. 613 Wessnersville slates dip 45, S. 10 W. Half a mile south of Wessnersville red slates dip 90 S. 2 m. S. E. of Wessnersville olive slates dip 50, S. 30 E. 1 m. W. of last is a red slate outcrop. Greenwich township has no quarries. On the railroad \ m W. of town- ship line, slates dip 58, S. 20 E. Opposite Lenhartsville, slates and thin bedded sandstone dip 55, S. 20 E. At the road crossing red slates show. On the small creek 2 in. N. E. of Lenhartsville red slates dip 55 S. 1| m. E. of Smithsville, a fifty foot outcrop of red slate in the road. | m. N. of Smithsville red slates crop out. 2 m. W. of Smithsville, 15 feet of red slate dip 55, S. 20 E. At Klinesville, red slate outcrop. The hill 1 m. S. of Klinesville is made of fine grained, thin-bedded sandstone. On the south side of the hill red slates show in layers as far as the school house and along the road to the east for a mile and a half, i m. S. of Smithsville slates dip 200, S. 400 W. Half a mile further there is an outerop of massive flaggy sandstones. There aie two small outcrops of limestone in the township ; the northern is on S. D. Kohler's farm ; length of outcrop unknown owing to loose slate covering it. Just north of this outcrop the slates dip 35, S. 2QO E. The other limestone outcrop is half a mile south of W. Heffner's grist mill ; dip 10 N. ; limestone blue and thin bedded. Maxatawny' 'township has no quarries. 1| m. N. of Kutztown the slates are flat : also \ a mile north of this, on top of the hill above the j unction of the slate and limestone, the slates lie flat, but at the lower side of the same cut dip 45 west Richmond township has no quarries. E. of Virginsville one mile, lime- stone outcrops ; the most northern dips 30 N. A quarter of a mile south (with slate showing between) the limestone lies flat with rolls in it. Half a mile south of this, with slate between, the limestone dips 30 north ; it is dark blue, thin bedded, and shows 100 to 200 feet, and has the appearance of the Trenton. Along the small creek half a mile east of this there is no lime- stone to be seen ; therefore the outcrop is probably that of a sharp anticlinal. Two and one-half miles E. of Virginsville thin bedded sandstone dip 30 S. m. E. of Merkel's saw mill slates dip 90 W. ; also some fine grained sand- stone. Just below Merkel's saw mill slates dip 35, S. 30 E. On the hill north of Moselem furnace slates dip 15, S. 60 W. m. S. of Moselem furnace slates dip 20 north. 1 m. W. of the furnace the dip is flat. Windsor township has no quarries. At school house No. 4 slates dip 90, S. 30 E. with some slaty sandstone. 300' S. red slate shows for half a mile east | m. S. of St. Paul's church red slates show for GOO feet acrossthe out- crop; no dip visible; m. E. the same dip S. 60, S. 30 E. 1^ m. E. of Hamburg slates dip 50 south. 1 m. E. at the old railroad grading alter- nate beds of slate and sandstone dip 52 S. 20 E. At the east end of Ham- burg sandstone outcrops in the road. 1 m. N. of Hamburg alternate beds of slate and sandstone dip 75, S. 10 E. waving. m. below the lock- house sandstone dips 10 E. (massive sandstone of IV). 500' further up the river dark gray slates dip 50, S. 20 E. 200 feet shows underneath gray slate, slaty sandstone and thick bedded sandstones. 1 m. E. of Hamburg slates dip 60 S. | m. further east fine grained olive sandstone, 15 feet thick, thin bedded, dips 80, S. 10 E. South of the run red slate, 30 to 50 feet, dip 50, S. 10 E. 1 m. N. of Windsor Castle slates dip 60 south. ^ m. N. of Windsor Castle slates dip 35 south. 1| m. E. of Windsor Castle slates dip 60 south. 614 GEOLOGICAL SURVEY OF PENNSYLVANIA MMl. LV/. Crthia oinnata, HaM. Pal. N. Y. Vol. 1, 1847, Ifud. lit un *r*fe rieurotomona '.Scalituf) tropldophora, "get. Pholidop. Cincinnati Orthodesma parallelum. ( Orikmota parallel*. OrthodeBma corvatum, H & W 1'al. Ohio, , |tg ^^^^^^^I4 "' ! ' *fP^ m Orthoceras capitollnum. Sfford Geol. Tenn. 1869 Sal-ford. Orthoceras dnseri, Gfol.Tenn.rU NO. III. ROOFING SLATE BELT. 615 Perry township. 244- A flagstone quarry, at the northeast corner of the township, worked by Jacob Derby. The stones make good flagging, and are taken out generally 2' X 3' X 3" in size. Some are 10 feet long. They are dark gray and come out regu- larly. The sandstones roll to the north and south and dip to the northeast.* 850. W. Collier's flagstone quarry, f m. N. E. of Shoe- makersville, is 150 feet long. 10 feet of flagstone exposed has from 5 to 10 feec of broken slate on top. Stones, from 2' to 4'x5' to 8', show dark gray generally, 2 inches thick, with smooth faces. The joints are not regular, making a loss of about one-third in squaring them up. Half a mile southeast of this quarry the slates dip 80 south. 51. A small flagstone quarry, two miles east of Shoe- makersville, 20x30x10 feet. The stones on the pile are 6x6x3 feet; quarry full of water. One mile south the slates dip 50, S. 10 W.f * Half a mile west slates dip 50 south. 500 feet south limestone outcrops ; 30 ieet; shows west for three miles. Just west of the Zion church it is flat with rolls in it { m. N. of the church slates dip 50 south. 1000 feet south of the limestone red slate outcrops. One mile south of the above limestone outcrop is another about parallel to it. On Peter Folk's farm the limestone dips under the slate at an angle of 20 to the south. At the corner of the roads the slate dips 18, S. 70 west. 1 mile further west the limestone dips 32 U south ; light blue and broken. lj in. further west the limestone dips 20, S. 20 E. Is light blue with some siaty limestone on top. Limestone shows again at the creek above the grist mill. t At the north end of Mohrsville the slates are flat 1| m. N of Shoe- makersville on the canal slates dip 45, S. 30 W. 200 feet further north, dip 90, N. 30 E. ; probably an anticlinal brings up the limestone further east. 1 m. further up the canal slates dip 60 S., 30 W. In Ontelaunee township, 1 m. N. of Evansville, limestone outcrops show 100 feet wide. 1J m. E. of Leesport slates dip 55", S. 20 K. 1 m. N. of Leesport, slates and some slaty sandstone dip 40, S. 20 E. The Crane Iron Co. J s ore bank, 2| m. N. E. of Leesport consists of two open cuts now- full of water. At one place could get a slate dip of 45 south. The surface is covered with loose slate, and pieces of slate coated with hematite. From the looks of the dump I should say that the mine had a great deal of slate in it. 616 GEOLOGICAL SURVEY OF PENNSYLVANIA. JotiH Aeaweejk Copied cund reduced, to /*jroin,jiyivreA NO. III. FOSSILS. 617 CHAPTER L. The Fossils of No. III. The Utica Slate (Ilia) formation is very fossiliferous in Newfoundland, Labrador, the island of Anticosti, Can- ada (as far west as Lake Huron, where it thins out), Ver- mont, New York, New Jersey and middle Pennsylvania, its characteristic fossil everywhere being a beautiful little qnaker-like trilobitethe Triarthrus (three jointed) becMi of Green*. On the Ohio river this fossil is abundant, asso- ciated with Leptobolus lepis and other Utica forms, not in black slate but in blue lime shales and marls, which are beds of passage from the Trenton limestone beds up into the Hudson River slates, as in Lebanon and Cumberland counties Pennsylvania ; and also in the Western States. None of its characteristic fossils are found in the Galena limestone, and none of the characteristic Galena forms nre found in the Utica. f In Centre county, Professor Evving cites Matternville as a good locality for seeing the sandy slates at the base of the Hudson River formation graduating downward into the Trenton through a series of limy layers which carry "fossils common to the Trenton and Utica.* * Monograph of Trilobites, 1832. Other species of this genus are T. cana- densis, Smith; T. glaber, Billings; and T. spinosus, all in the Utica and the last very abundant in Canada. S. A. Miller, p. 44. The figures of these trilobites are given life-size in my Dictionary of Fossils in Pa. Report P4, Vol. 3, 1890, pp. 1208, 1209 ; and reduced to one-half linear on plate 38, p. 526, and plate 43, p. 536, above. fS. A. Miller, p. 44. JThe whole of No. Ill, Utica and Hudson River combined seems to be only 800 feet thick. At Egg Hill in Penn's valley, and Spring Mills, tran- sition (Utica) shaly limestones holding Trenton fossils are well seen. Me- tween Jacksonville and Howard near the base of Bald Eagle mountain a tough black lime shale crops out (overturned to 60) ; and near Hoy's house, at the base of the mountain (that is, high in III) fossils are seen like those at Egg Hill. 618 GEOLOGICAL SURVEY OF PENNSYLVANIA. ,a&ffiafy6 t 1/orJr county NO. III. FOSSILS. 619 Prof. Ewing makes no attempt to separate the Utica from the Hudson River, but names the following list of fossils of No. Ill as a whole as being in his collection : Stems of Glyptocrinus decadactylus ; Orthis lestudin- aria; a cast of OrtTiis subquadrata(\) ; OrlJiis / Stro- phomena alternata ; Leptcena sericea ; BelleropJiou bilo- batus ; Murcltisoniagracilis ; Modiolopsis modiomorpha ; Modiolopsis curta ; Ambonychiaradiata; OrtJionota, ; Trinucleus concentricus ; Callimene ( Triarthrus) becJcii ; Callimene ; Orthoceras .* The Utica fossils catalogued in C. Hall's special collec- tion for the Survey (O3, p. 190 to 192) consist of 44 indi- viduals of Triarthrus (Calymene) beck ft, got by him at Bellefonte, with crinoid stems, fragmental and poor ; also 47 hand specimens collected by W. A. Fellows, along the Bellefonte outcrop, some of them slabs showing on their surfaces numerous fragments of that trilobite, mostly heads, comparatively few bodies, and these nearly all more or less crushed or distorted ; tail pieces comparatively rare. Also 85 other specimens of the same trilobite. These suffice to show the vast abundance of this charac- teristic trilobite life in that .part of the Utica sea which covered middle Pennsylvania. No doubt any collector could fill his cabinet with^individual specimens at any place along the numerous and very extensive outcrop lines. In Bedford county, the Utica black shales, about 200' thick, containing a few compact slate layers an inch or so thick, show a few graptolites. They pass gradually up- ward into brown shales, and then into non- fossil if erous yellow shales which make up the mass of the Hudson River formation, some thin sandstones being seen near the top. The whole of III is only about 700' thick, f * Report Centre county, T4, 1884, page 427. He adds that most of these forms are found also in the Trenton limestones. So far as the fossils can guide us in the identification of strata at a distance it would seem as if in middle Pennsylvania only the lower half of No. Ill was deposited, the upper or roofing slate division being wanting. Yet the distance between Allentown and Bellefonte is only about 150 miles. t Stevenson, T2, 1882, page 93. 620 GEOLOGICAL SURVEY OF PENNSYLVANIA. Clisiophyllum oneidense. (Billings Canad. . VIH a-. Cornift/reuS 7/ UngTila cuneata, Conrmd. (He. Tren/on in Pa. NO. III. FOSSILS. 621 The Hudson River formation, Hlb, a marine deposit from the Gulf of St. Lawrence west to the Red River of the North, and south to Tennessee and Texas, varies in thick- ness from 6000' on the Delaware and 2000' in eastern Canada, to 1100' at Toronto, 250' in Missouri, and 100' in the far northwest. It is very fossiliferous around the Falls of the Ohio, where it consists of 800' of blue lime shales and limestone layers. The seas swarmed with animal life and seaweed, and many of the strata are composed wholly of their remains.* Some fossil forms lived through the whole age, and occur from bottom to top : Callimene callicephala / A saphus gigas, and megistus ; Bey rich ia chamber si ; Leptcena sericea / Bellerophon bilobalus ; Zygospira modesta ; Stropho- mena alternata ; and Orthis testudinaria / and all of them (except the Beyrichid) have been found in older strata (No. II). L. sericea continued to live into a later age. Other forms (at least in the Cincinnati country) seem to have had but a short range of life : Streptorhynchus hal- lianum has a limited range in the lower part ; Streptor- hynchus planoconnexum and sinualum are limited to strata below the middle ; Streptorhynchus nutans and sul- catum are confined to the middle zone of the upper division ; Streptorhynchus subtentum and filitextum are confined to the upper part. Of five species of Lichenocrinus three, crater if ormis, dyer I, patter soni. are confined to the lower half ; two, tuberculatus, affinis, to the upper part. Of species of the trilobite Acidaspis one, crossota, occurs below ; two. anchoralis, Cincinnati ens is, in the middle ; one, coralli, above. RhynclioneUa capax and dentata, Streptelasma corniculum, Favistella stellata, Tetradium fibratum, Cypricardites, &c., are confined to the upper *S. A. Miller's N. A. G. and P. Cincin. 1889, p. 46. He describes the out- crop from Cincinnati west, 50 miles, to Osgood in Indiana, N. to Dayton, and X. E. to Xenia. The hills at Cincinnati expose the lower half (400'). In Kentucky it makes a circular clay crop around the Bluegrass country. It is rare to find a layer of solid limestone (in the 50' of clay) more than one foot thick. The stone is a mass of more or less ground up shells, corals and crinoids. GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. III. FOSSILS. 623 part. Grinoids as a rule have a limited vertical range, each species holding by its own separate horizon. Characteristic and widely distributed species of No. Illb are : Aulopora arachnoidea, St^matopora inflata, Ortliis occidentalis, Or this subquadrata,0rtkisretrorsa, Pterinea demissa, Pterinea insueta, Cyclonema bilix, and Glyplo- crinus decadactylus .* At Henrietta station, in Blair county, Mr. R. E. Sanders in 1875 obtained from the Hudson River slates ten speci- mens of brachiopods of undetermined species. (O3, p, 191.) From the same slates, 1 miles S. \V. of the Henrietta mine, he got Glyptocrinus decadactylus, and other crinoid stem impressions. (O3, p. 191.) From the same slates in Leathercracker cove, besides the crinoids, he collected ScJiirod.us cequalis ; Triari/trus (Calymene) beckii , a head of Dalmanites limulurus fairly well preserved : GraptolilTius mucronatas (?) ; and poor, faint, indistinct impressions of other graptolites. (O3, p. 192.) A collector of Hudson River fossils in Middle^Pennsyl- vania must devote a long time and close attention to the business, and if successful, will find most of his specimens injured and distorted by the excessive pressure and shear- ing movement of bed upon bed which took place when the anticlinal and synclinal waves were produced Peach Bottom roofing slate fossil seaweeds are figured on plates LXX, LXXI, on pages 616, 618, above, for com- parison with the seaweeds figured on plate XXVI, page 502, and on plate CXI, page , Chapter LIII on the fos- sils of Oneida and Medina, No. IV : and to illustrate what is said on page 183, above. *S. A. Miller's N. A. S. and P., p. 47. See also a lull synopsis anil discus- sion of the relationship of the Cincinnati rocks to No. Ill and No. II in the east, in Jos. F. James' paper "On the age of the Point Pleasant, Ohio, beds," in Journ. Cincin. Soc. Nat. Hist, July, 1891 ; in which the conclusion is arrived at that no beds as low as Trenton appear on the Ohio river within the limits of the State of Ohio. 624 GEOLOGICAL SURVEY OF PENNSYLVANIA. I it i NO. IV. ONEIDA AND MEDINA. 625 CHAPTER LI. Formation No. 1 V. Oneida and Medina. Middle Pennsylvania west of the Susquehanna river is a labyrinth of parallel mountains, with straight sloping sides and sharp horizontal crests, none of them elevated more than a thousand feet above the valleys which they include. These mountains interlock in zigzags, sending out spurs and knobs into the large valleys, and enclosing longer or shorter narrow parallel coves. (See pi. 73, 74, &c.) With three exceptions, to be noted directly, all these mountains are composed of Formation No. IV, subdivided into three sets of sandstone and sandy shale beds; the lowest one (IV a) known as the Oneida conglomerate; the middle set (IV b) known as the Medina red sandstone; and the upper (IV c) as the Medina white sandstone. The Oneida conglomerate (IV a) was so named by the geologists of New York because of its coarseness, being a pudding stone or pebble rock ; but in middle Pennsylvania its beds are mostly a gray sandstone interleaved with a few beds of conglomerate. Professor Rogers therefore called it the Levant gray sandstone, because the aspest of the rock is that of ordinary sandstone. The Medina or Levant red sandstone (IV b} contains so many interstratified softer shaly beds, and is so charged with iron, turning red when exposed to the air, that it makes a. visible division between the lower and upper parts of the whole formation. The uppermost subdivision, the Medina or Levant white sand- stone (IV c] is not only characterized by its purer color, or rather absence of all color, but by its greater massiveness, so that it constitutes the real backbone of the mountains, cropping out along their crests. Formation IV has been a boon to Appalachian geolo- gists. It gave them at the very outset, fifty years ago, a key 40 GEOLOGICAL SUEVEY OF PENNSYLVANIA. BALD EACLE CAP AT BELLEFONTE contours of 100 feel. %y %.H Sanders. NO. IV. ONEIDA AND MEDINA. 627 to the structural geology of the whole region from Tennes- see to New York. It marks the maps of Pennsy vania, Mary- land, Virginia and Tennessee with topographical lines not to be overlooked or misunderstood. It furnished a safe basis for that enthusiastic investigation which resulted long ago in the establishment of the science of geological topo- graphy or Topographical Geology. By means of these numerous bold mountain outcrops the plication of the earth-crust along the Appalachian belt was at once com- prehended and could be estimated at its full value ; could be measured, sectioned, mapped, and modelled in solid form ; and a number of such models have been made by the Penn- sylvania Geological Survey. In the latest of these models the formations which cover No. IV have been lifted off, and the great arches in the air (long since destroyed and carried into the Atlantic) have been restored ; so that the complicated structure of the region is now as well known as the internal anatomy of the human body. And this is due, chiefly, to the great thickness of Formation No. IV, and to the extensive outspread of its sandy sediments over the bed of the Appalachian sea. For a description of this model, and two photographs of its surface, see the close of Chapter LIT. I will first consider the thickness of the formation ; sec- ondly the variations which obtain in its internal constitu- tion in different parts of its outspread ; and, thirdly, the effect which these variations have had in producing differ- ent topographical "aspects of the country, and the lessons which they teach respecting the formation of mountains in other parts of the world. The thickness of No. IV. First : As to the thickness of the formation as a whole ; and then, as to the variation in thickness of its subdi- visions. In measuring the thickness of any of our greater forma- tions there is almost always some uncertainty as to where the measurement at the bottom is to begin, and as to where 628 GEOLOGICAL SURVEY OF PENNSYLVANIA. thro ug THE THICKNESS OF NO. VII. 629 the measurement is to end at the top ; for, as I have already sufficiently set forth, there never has been stop or pause in the tribute of the rivers to the sea ; and there never has been uniformity in the nature of that tribute ; sand being de- posited in one place at the same time that mud was being deposited in another ; and innumerable alterations of sand and mud of every possible variety have taken place through the entire process. The bottom of a formation in one place may not exactly correspond to its bottom in another place ; and the same is true of its top. Nature has never written its historical memoir of geological operations in distinct and well-rounded sentences; has never numbered and headed its chapters ; has seldom drawn strong black lines between its paragraphs. The formations grade and fade away into each other ; and that, both downward and up- ward ; and the geologist who attempts to measure any for- mation at any place must simply do his best to select some bottom rock to begin it with and some top rock to end it with. But in doing this he is always liable to mistake. He must make his selections on his own responsibility. He can never confidently assert that the bottom and the top of his formations are established facts of science. When he multiplies his measurements of a formation in various places in order to obtain by comparison a knowledge of its variations in thickness he subjects himself to the risk of multiplying his errors. Sometimes, indeed, a special bed at the bottom or at the top of a formation is so flagrantly different in constitution, in color, or in its fossil forms, from all the other beds near it, that he can adopt it as a key rock with considerable confidence. But this is rarely the case ; and even when such a key rock presents itself in one part of his district, and another such key rock almost or exactly like it presents itself in another part of his dis- trict, there is always a possibility that the two are not con- tinuous ; that they were not deposited at exactly the same time throughout the region ; and that perhaps nature has repeated the deposit locally and subsequently. In measuring No. IV therefore we have been obliged to assume as its bottom limit the first massive sandstone to be 630 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. VII. 631 seen lying regularly upon the upper or roofing slate division of Formation No. Ill ; and we have been obliged in like manner to assume as the upper limit or top of No. IV, the highest massive white sandstone bed which presents itself at any given locality overlaid by the softer although still sandy reddish shale beds of No. Y hereafter to be de- scribed. Very exact instrumental measurements of No. IV have been made in accordance with this plan, that is, be- tween such assumed bottom and top limits, in many parts of Pennsylvania : at the Delaware, Lehigh and Schuylkill Water Gaps ; at the Susquehanna gap above Harrisburg; at Logan gap near Lewistown; at Rockhill gap near Orbi- sonia ; at the Bald Eagle gaps near Bel lefonte and Tyrone City ; and at the gaps near Bedford. But as these meas- urements were made by different assistants of the Geolog- ical Corps they can be compared together only by making allowance for the inevitable differences of personal opinion respecting the best top and bottom limits of the formation. Yet, after all, these differences are so moderate as not to vitiate the conclusions drawn from the comparison ; and we have moreover on record for comparison the equally intel- ligent and conscientious measurements of the assistants of the First Geological Survey under Professor Rogers, which serve in a measure to check, and in fact help to verify their accuracy. The measurement of No. IV by Mr. Sanders in Blair county sums up 2896' ; that of Mr. Dewees at Logan gap in Mifflin county, 2722' ; that of Mr. Billin in the south of Centre county, 2440'; that of Dr. Chance in Clinton county, 2301' ; that of Professor White at Spruce Creek tunnel in Huntingdon county, 2000' (made uncertain by a fault); that of Mr. Ashburner in southern Huntingdon county, 1808' ; that of Professor Stevenson, in Yellow creek gap, Bedford county, 2035' (diminishing toward the Maryland line to less than 1000'); and in Fulton county about 1600'; (according to Professor Rogers' estimate in Cove mountain 2100', and in Tussey mountain 1650'). In the Lycoming county gaps Mr. F. Platt estimates it at 1375'. Dr. Chance's measure- ment at the Schuylkill Water Gap was 1400' ; at the Lehigh 682 GEOLOGICAL SURVEY OF PENNSYLVANIA. /LXXV// THE THICKNESS OF NO. VII. 633 Water Gap (complicated with a fault) 1125' ; and at the Delaware Water Gap 1565'. It will be seen by the above statement that the greatest observed thickness of No. IV is in the center of the State, and that it evidently diminishes in all directions from that central district. When followed southward through Vir- ginia it thins, at first gradually, and then rapidly, to such an extent that the whole formation appears to be only about 40' thick at its outcrop west of Knoxville, in Tennessee.* Westward, under western Pennsylvania and Ohio, it has not been reached by the deepest borings ; but that it dimin- ishes in that direction also, is evident from the fact that its outcrop is too small to be recognized in the Columbus and Cincinnati region. Under northern Pennsylvania and cen- tral New York it is also completely concealed ; but it must diminish in that direction also, for its outcrop along the Mohawk valley amounts to only 400', diminishing toward Albany ; and it makes no appearance at all around the eastern foot of the Catskill mountains. This is a remarka- ble phenomenon not to be easily explained. To most geo- logical minds it will seem'quite sufficient to say, that dry land existed there while two or three thousand feet of sand and gravel were being floated into a deep sea in middle Pennsylvania. The difficulty of this explanation is in- creased when one follows the lofty crest of the Kittatinny mountain along the north line of Berks, Lehigh and North- ampton counties in Pennsylvania, crosses the Delaware at the Water Gap into New Jersey, and follows the equally high crest of the Schawngunk mountain into New York, to see it suddenly cut off a few miles east of the hotels at Lake Mahunk, to appear no more until the western border of New England is reached. Now, when 'a mountain ridge, the bold outcrop of a great sandstone formation 500 miles long suddenly terminates, not as an anticlinal nose descend- ing underground, not as a cynclinal knob rising into the air, but as if the end of a slanting board had been sawn off, *In the White Oak mountains of East Tennessee, however, it measures between 800 and 900'. 634 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. VII. 635 the structural geologist cannot do.ubt that the formation has been swallowed by a fault.* *Dr. Mather, Geologist of the First District of the New York Survey, in his quarto report of 1843, pages 355 to 361, describes this shattered condition of the mountain. He says that the Indians called the mountain Swang- gum, that is "white rock." The sandstone mass he called "Schwangunk Grit," and gives its thickness as variable between a maximum of 500 feet and a minimum of 60, "its usual thickness being between 60 and 150." It is traversed by two systems of faults, one parallel to the strike (N. 20, E. ), and the other transverse (N. 60 W.). The cross faults are lew between the Delaware river at Carpenter's Point (Port Jervis) and Ellen ville and Wa- warsing in Ulster county, where the mountain is traversed by great breaks and faults. "The ridge then sinks and rapidly disappears beneath the val- ley, while several wrinkles or parallel axes of elevation spring up on the east at the same height, run eastward between the Stony Kill, Mule Kill, Sanders' Kill, etc.; sink down gradually towards the mouths of these streams, and finally disappear below the valley in Rochester and Marble- town, or show their continuation only by low broken ridges of upheaved lime- stone. These axes of elevation are terminated apparently on the south by the high cliffs along the transverse lines of fault. On the cast of these minor axes the main axis of elevation takes its rise from High Point, which is a high cliff of grit rock on the main fault, and ranges thence northeastward, more or less broken and dislocated by minor transverse and oblique faults, and diminishing in height until the Shawangunk mountain and its grits, which envelope most of its higher parts, entirely disappear below the lime- stone and quarternary deposits at and near Rosendale. Several high points with mural fronts and ends are seen between High Point and Springtown, as Sam's Point, Great Mogunk, Puntico Point, etc., all of which are caused by faults along the main features of the mountain. It has been mentioned that the wrinkles or subordinate axes of elevation seem to terminate at these rocky points on S. E. side of the mountain, but the termination is only ap- parent, caused by transverse fractures. The ridges almost all slope down to the N. and N. E. from where the main fractures cross each other, and the rocks disappear below the more recent formations, while their southward extremities almost always present high precipitious and often vertical cliffs.." Although these statements of Mather are not A'ery lucid, they are substan- tially correct, as any geologist may observe who makes one of the great sum- mer hotels, the Mohunk or the Manawaska, his headquarters. Overlooking lakes which lift on top of the mountain, surrounded by vertical cliffs of sandstone and conglomerate, and dammed by glacial moraines, these com- fortable and hospitable places furnish unrivaled iacilities for exploring one of the most interesting and instructive fields of geological research in Amer- ica. Mather's illustrations of the Shangunk grit and its fractures on plates V, f. 13 ; VI, f. 7 ; VIII, f. 2, 3, 4 ; VIII, f. 4 ; XV, f. 3 ; XXVI, f. 4, 5, 6, 7, and XXXIX, f. 1, 2, 3, are so bad as to serve no purpose but that of contrast- ing the slovenly and absurd drawings of his day with the precise and math- ematical sections of our own. Yet even then the best geologists like Hall, Logan, Lyell and Murchison illustrated their lucid English text with wood cuts hardly since surpassed for correctness and beauty. 636 GEOLOGICAL SURVEY OF PENNSYLVANIA. LXX/X. AT THE GAP ABOVE HARRISBURG. 637 At the Gap above Harrisburg. From the list of localities above mentioned where For- mation No. IV has been measured to obtain its total thick- ness, one locality has been omitted because it requires a separate and special consideration, namely, the gap of the Susquehanna above Harrisburg. Three separate measure- ments have been made in this gap by Professor Rogers by Mr. Sanders, and by Professor Claypole, without, however, reaching absolutely sure results, owing to the overturned and somewhat crushed condition of the formation. Every- where else along the line of the Kittatinny, Blue or North mountain, from the Delaware to the Potomac, the beds of No. IV slope northward and westward at various angles from 20 up to 80 and even 90. But where the Susque- hanna breaks through, the earth movement from the south has done more than press up the beds into vertical attitudes ; it has pushed them over 20 beyond the vertical, overturning them to a south dip of about 70. It will be shown in the next chapter that this overturn or inversion affects not only Formation No. IV, but all the overlying formations up to No. XI ; and that the squeeze produced by folding 20,000' of rock into a sharp synclinal basin has resulted in a large amount of sliding and slipping of one group of beds upon another, in the production of minor irregularities of dip and strike, occasional rolls, small faults, etc., and perhaps in the lessening of their original thickness. How much No. IV has suffered in this respect is uncertain ; but it is evident that under such circumstances the measured thick- ness of any formation, whether hard or soft, cannot be im- plicitly accepted as the real or original thickness. At all events it would be unsafe to draw the same conclusions from measurements made at such a place that we can safely draw from measurements made of it at places where no such violent upturning and overturning has occurred. The measurement of No. IV in the Susquehanna gap sums up less than 500'. This is at the southeast corner of Perry county ; but in the western and northern parts of that same county No. IV appears to be about 2000' thick. 638 GEOLOGICAL SURVEY OF PENNSYLVANIA. AT THE GAP ABOVE HARRISBURG. 639 Following the mountain only a few miles eastward from the Snsquehanna, to where the beds of No. IV lean in their natural attitude (dipping north) the formation becomes of its usual thickness ; and following the mountain westward from the Susquehanna not more than 15 miles, the usual thickness of the formation is again resumed. We have, therefore, some right to ascribe its abnormal thickness at the Susquehanna to the overturn. Another explanation tyowever has been suggested and will be described in the next chapters, since it affects still more seriously Formations No. V and No. VI in this locality. The thickness of Formation No. IV as a whole is of course the sum of the thickness of its three subdivisions, (lower, middle and upper) Oneida, Medina red, and Medina white. If the relative thickness of these divisions remained constant, and if the_hardness and softness of the beds of the three divisions were everywhere the same, it is evident that the shape of a mountain of No. IV would be always the same. But the law of universal geological irregularity operates upon all three subdivisions. In fact each sub- division of No. IV has as much right to be considered an individual r and distinct formation as if it had no topo- graphical relationship with the other two ; and the only reason why the three subdivisions of No. IV have been grouped together into one formation is the fact that the three together always make one mountain ; the shape of which, however, necessarily varies with the Variations in solidity and thickness of the subdivisions, as will be shown directly. For the present we will regard simply the thick- ness of the subdivisions; repeating, however, and insist- ing still more earnestly upon it, what has already been said respecting the indefiniteness of the bottom and top limits of all formations and groups of beds. If the three sub- divisions of No. IV had been made by a stone cutter out of three slabs of rock placed one upon another there would be no uncertainty as to their thickness ; but seeing that they are three artificial groupings of an immense number of sand and mud deposits, each varying in its individual character and thickness, white and gray sandstones alter- 640 GEOLOGICAL SURVEY OF PENNSYLVANIA. LXXX/ THE THICKNESS OF NO. IV. 641 nating with gray and reddish muds, it is extremely diffi- cult to decide upon any fixed planes of division between them. All that we can do is to group the lower gray sands togther as the Oneida, the upper white sands together as Medina white, and call the softer and more or less reddish beds between them as the middle division, or Medina red; and arrange their thicknesses at the various places where they have been measured in a table like the following : At the Delaware Water Gap. H. M. Chance /* Medina upper sandstone, 200' " upper shales, etc., 530, . " white conglomerate, 200' " lower shales, etc., 110' Oneida gray sandstone, 75' "j roe " lower shales, etc., 240' ^ " white conglomerate, 210' J 1565' At the Lehigh Water Gap. H. M. Chance :f Medina upper sandstone, 85' \ " upper shale, 180' I " gray sandstone, 70' f " lower shale, 330' J Oneida cong. sandstone, 290' ) 460' " conglomerate, 170' i . , * H. D. Rogers gives different measurements of No. IV at the three water gaps, in Geol. of Pa., 1858, Vol. I, p. 126 to 130. At the Delaware : Levant White sandstone (some sparsely pebbly beds) making a prominent rib of the mountain, 200', (overlying sandstone and slate alternations, may be added, or may be thrown into the formation V.) 2. Levant Red, wanting. 3. Levant Gray (Oneida) , upper division thin bedded, soft sandstones, 400' ; lower pebbly member, 300'. Total, 900', in- stead of Dr. Chance's 1565, the latter being the result of instrumental meas- urements of subdivisions. |H. D. Rogers, at the Lehigh: 1. Levant White; top division, massive grey and red sandstone with shale partings, 100' ; shales and flags, 300' ; sandy shales, 30' ; sandstones and shales, with fucoidal mar kings, 50' ; sand- stones and shales, 100' ; white and gray pebble rock, 80' ; concealed (sand- stone and shale) beds, 200' ; total 760'. 2. Levant Red, wanting. 3. Levant Gray (Oneida) fine sandstone, small conglomerate and shale, 200' ; coarse pebble rock and sandstone, 75' ; fine sandstone and coarse conglomerate, 75 ; very coarse pebble rock at bottom, 50' ; total, 400'. Total thickness of IV, 1160', agreeing remarkably with Dr. Chance's instrumental measure above, 1125'. 41 642 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. IV. 643 At the Schuylkill Water Gap. H. M. Chance ;* Medina upper sandstone, 90' "j " upper iron shales, 480' I " white sandstone, 60' j 1230/ " lower iron shales, 600' J Oneida white conglomerate, 200 1430' At the Susquehanna Gap. H. D. Rogers. f Medina upper, 300' to 400' \ " lower (red), 0' J> max. 470' Oneida, 60' to 70' J In the Juniata gaps of Perry county. E. W. Claypole : Medina sandstone and shales 1500' ) 2000* Oneida conglomerate and sandstone, 500' > * Rogers gives no measurements at the Schuylkill and Swatara Water Gaps. The bottom coarse red pebble rock of the Oneida, only 5' thick, with white coarse sandstone, full of fault slips which suggest a greater thickness than 40', is separated from the visible upper limit of No. Ill slate by a con- cealed interval of 50' more or less. Prof. Claypole in his report on Perry Co., F2, 1885, p. 310, describing Rye township, makes the Medina rock rib of the mountain to be only 100' thick, and says nothing about the Oneida. He places 500' of " soft material" between the top of the Medina and the bot- tom of the Clinton Iron Sandstone rib which makes the other crest of the North mountain at Sterrett's gap, the Medina crest being the lower of the two and in Cumberland county. In Carroll township, he says, the Medina makes little or no show, running along south of the county line on the crest (F2, 159). The same in Spring township (p. 333). Tyrone township, next west, gives vertical Medina at McClure'sgap (p. 370). I have expressed my belief and the reasons on which it is based, that this excessive thinness of No. IV and the total disappearance of one or two thousand feet of over- lying measures in Perry county, west (and east) of the Susquehanna Water Gap, described by Prof. Claypole in F2, p. 303 (see illustration p. 304), and assumed by him as good evidence of the existence of a district of dry land in Upper Silurian times in that district of the State, is rather to be explained by the upturned and overturned condition of the south side of the Cove synclinal and Dauphin county coal basin, producing not only the oblique fissuring of the Oneida outcrop in the Gap, but, as I believe, great slip-faults paralled with the strike, swallowing up and pressing underground the softer formations. I do not believe that No. IV was originally any thinner at the Susquehanna than at the Schuylkill or Delaware, or than it seems to be in the gaps of the Juniata river, even in Perry county, where in the Tuscarora mountain, etc. Prof. Claypole gives it a total thickness of 2000' (F2, page 36). 644 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. IV. 645 Logan's gap, Mifflin county. C. A. Ashburner: Medina white sandstone, 820' ) 21(xy Medina red sandstone, 1280' $ Oneida red conglomerate, . 300' ) 622 , j 2722 '* Oneida gray sandstone, 313' > Jack's Narrows, Mifflin county. H. D. Rogers: Levant top red sandstone,! 30' ) 45)) , 1 Levant upper white sandstone, 420' ) [ Levant red sandstone and shale, 650' ' Levant lower white sandstone , 250' Rockhill gap, Orbisonia, Huntington county. Ashburner : Medina white sandstone, 400' ) JOQ/W Medina red sandstone, 930' J Oneida red conglomerate, 158' ) ,-gg, Oneida gray sandstone, 410' 3 Canoe Mt. gap, Huntingdon Co. H. D. Rogers : Levant (upper) Avhite sandstone, 550' "l Levant (middle) red beds,|| 1050 i 2100' Levant (lower) gray sandstone, T 500' J Bald Eagle Mt. gaps in Blair Co. R. H. Sanders : Medina white sandstone (north crest), 1068' Medina red alternations,** 520' Oneida gray sandstone (south brow), 1319' * Rogers does not measure the Upper division of IV here (Geo. Pa. I, p. 130), but subdivides the Middle division into (at top) dark red flags with some red shale pebbles, 500' ; coarse friable red sandstones, iron-specked, 100' ; pink sandstones with layers of quartz, slate and other older pebbles, 400' ; total 1000'. The lowest ( Oneida) division, fine massive gray sandstone, iron-specked, he makes 300'. Total only 1300'. fSome of the layers are covered with a net-work of the sea weed, Arthrophycus harlani. J These and other asigned thicknesses given by Rogers in his Geo. Pa. 1858, have been proved incorrect by the close instrumental field work of Bil- lin and Ashburner, Sanders and Chance since 1874. " Measured with precision." Ponderous, homogeneous, fine grained white and gray sandstone beds." Geo. Pa. I, 130. || " Reddish brown, rather argillaceous, with beds of gray sandstone, all alternating with much red shale," p. 129. 1 " Wears its usual character of grey-greenish and pinkish hard siliceous massive sandstone beds, p. 127. **The detailed section of these alternations will be found in Report T, on Blair county, by Franklin Platt, 1881, p. 17, discussed on p. 47. The de- scription is minute and very interesting. The division made in the text is liable to a great modification, inasmuch as the north crest of the Bald Eagle 646 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. IV. 647 Bald Eagle, Bellefonte gap. H. D. Rogers : Levant white sandstone, 400' to 500' Levant red sandstone and shale,* about 500' I, 1550' Levant upper green sandstone,! 380' > 55() , Levant lower gray sandstone,} 170' ) Bald Eagle, Mill Hall gap. H. M. Chance : Medina upper (north crest), 695' Medina middle (vale), 705' < 2301' Oneida (southern crest), 901' is really made by 100' of white sandrocks at the top of the section, sup- ported by 255' of red sandstone beds parted by layers of red slate from 6 inches to 5 feet thick. Underneath this 355' the rocks are concealed for 540', and the detailed alternations begin and go down for 1000', leaving the bottom division to be 1309' thick. In fact only 400 or 500' of the upper division of 1068' answer to the description of the White (upper) Medina; the Red (middle) Medina is really 500+520=1020' thick. All this is merely a matter of classification and does not at all invalidate the correctness of the detailed section. The Medina White is made up of hard white and greenish gray flinty sandstones, fine grained, compact, homogenous, with almost none of the pebbles which make it so coarse a pebble rock in the North, Blue or Kittatinny mountain outcrop. Its top beds are thin, mottled red and grey, and often covered with sea weed impressions. They are parted by or alter- nate with soft greenish non-fossiliferous shales. They are much specked with yellow pits of decomposed iron. The Medina red upper member is made up of red clay flagstones, with (toward the bottom) some other layers of small quartz pebbles, flattish fragments of red shale occur throughout the pile of sandstone beds. Such is its general character in Mifflin county. The Oneida in Mifflin county has pebbles of quartz and slate and sandstone apparently derived from some antient land or coast of No. Ill and No. I. But in Blair county the Oneida shows obscure vertical plant stems. Steven- son does not recognize the Oneida in Bedford county. The Oneida is char- acteristically speckled and pitted by the decomposition of minute granules of some iron ore, perhaps pyrites. Its upper subdivision is a clayey sand, greenish gray, slightly micaceous, ochre-pitted, and its rock beds parted by thin fissile yellow shales. The lower is an ochre-pitted hard gray sand- stone! (T, 48. ) *Thin grey and red clay sandstone layers, alternating with a fourth part red, grey and greenish shale partings. High in the division are found ver- tical plant stems like Hall's Scolithus verticalis at Medina, N. Y. t Greenish grey slightly micaceous, specked with ochre, with thin fissile greenish slate partings. In Pleasant Gap, Center county, it is quarried for flagstones. (T4, 428. ) t Hard gray sandstone without pebbles, but full of yellow specks. See detailed section in Report G4 on Clinton county, 1880, p. 120. The subdivisions are empirical. The upper hard, massive, red, grey and white sandstones are not well exposed. The middle softer sands and shales make the little trench between the crests. Then come hard, massive, white (with a few speckled) sandstones, 188' : concealed, 118' ; hard, massive, siliceous dark grey and greenish grey speckled beds, 155' ; and at the bottom a mass not well exhibited, but principally hard massive sand rocks, 410'. 648 GEOLOGICAL SURVEY OF PENNSYLVANIA. THE THICKNESS OF NO. IV. 649 Bald Eagle gaps in Lycoming county. F. Platt :* Medina upper hard sandstone, 100' "| Medina middle red beds, 1200' i> 1375' Oneida hard sandstone, 75' j Wills' Mt. gap, Milligan's cove. H. D. Kogers. Levant white sandstone, 400' ] Levant red sandstone,! 800' 1 1300' Levant grey sandstone, 100' j No. IV thins southward into Virginia and Tennessee. On the James river the whole Medina measures only 300' and whole Oneida only 90' ; together 390'4 Stevenson calls the Medina in Waldron's ridge, Lee Co. Va., " evidently more than 300'." West of Knoxville, in Tennessee, I saw it represented by only 40' of sandstone. Towards the west it entirely disappears from the Ohio and Kentucky column. Northward it thins away in an equally remarkable man- ner. At Niagara the Medina is 300' or 400' ; and the Oneida, in Oneida county, N. Y., only 100' to 120'. But going eastward along its northern outcrop it increases. Prof. Prosser's general section of Western Middle New York State gives Red Medina sandstones and shales, 942'. | * Mr. Platt says in Report G2, p. 29, that no exact measurements were made for want of satisfactory exposures, and that the figures given above are only probable. t Includes here a larger amount of grey sandstone than on the Juniata. Rogers says that in this main gap through Wills' mountain into the cove the Oueida is last seen going south. He suspects a fault swallowing up a part of the formation, "a conjecture suggested by the vertical and shattered con- dition of the strata in Buffalo ridge the western barrier of the cove." Geo. Pa. 1858, p. 128. JJ. L. Campbell, Geol. Rich Patch in "Virginias," Vol. I, No. 12, Dec., 1880, illustrated with sections. Proceed. Am. Philos. Soc. Phila., Aug., 1880. || "Thickness of Devonian and Silurian Rocks, etc." Amer. Geologist, Oct., 1890, p. 205. His section is made up from well-borings. Under his Medina the Oswego sandstone, 210', is placed in No. III. In the Walcott well on Lake Ontario, red shale and red siliceous sandstones alternating, meas- ure 690' ; but they may be Clinton ; under them Oswego sandstone, 210'. In the Clyde well, Wayne Co., N. Y., Medina red shales, etc., 24', 3', 915= 942'. At the bottom of the Seneca Falls well, Medina red shales and sand- stones, 150' ; how much more unknown. At Rochester Logan made the Me- dina 600'. Geo. Sur. Canada, 1863, p. 310. 650 GEOLOGICAL SURVEY OF PENNSYLVANIA. NO IV. AT LOGAN GAP. 651 No. IV at Logan Gap. PL LXXXI, p. 64.0. The best place perhaps for studying No. IV is at the Gap through Jack's mountain in Mifflin county. Here the white Medina sandstone beds measure 820' ; most of them consisting of massive lawers of exceedingly hard rock varying from 2' to 4' in thickness ; some of them fine grained ; some of them slightly argillaceous, that is the grains of sand are imbedded in a matrix of clay. They slope up from the floor of the gap at the south end and make the upper part of the mountain and its high, bold rock-covered crest, running eastward toward the Susque- hanna, and westward toward the Juniata ; and it is the great thickness of these Medina while sand rock beds that makes Jack's mountain one of the highest in middle Pennsylvania. The weather acting upon the slight cement, dissolves it, and sets free the sharp grains of sand, producing along the top of the mountain collections of glass sand. Some of the more solid beds, resisting dissolution, break up into great blocks which slide down and cover the upper part of the northern slope. The Medina red middle division of No. IV in the heart of the gap is 1280' thick. It consists of laminated reddish sandstone layers, too soft and friable for building purposes, interstratin'ed with red sandy shales. On the surface of these shales ripple marks and the impressions of sun cracks like those seen on a modern sea shore abound, leading one to suspect that the waters of that ancient time were shal- low, and the sea bed in places exposed to the air and sun. But at the same time, many of the strata are obliquely cross-bedded, as if deposited in swiftly flowing currents. Beneath these lie the Oneida rocks, divided into an upper and a lower group, called the Oneida red conglomerate and the Oneida gray sandstone. The upper group consists of massive sandstone strata, reddish in color, very coarse, full of small pebbles which in some places become as large as hens' eggs ; the layers varying from V to 6' in thickness, so that large stones are quarried from them in the gap. This mass of pebble rock 652 GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. IV. AT ORBISONIA. 653 rising at an angle of 55 to the brow of the famous terrace which surrounds Kishacoquillis valley is 310' thick. The lower group measures also 310', and is made up of very hard greenish gray sandstone, the grains of sand coarse and strongly cemented together, mixed with pebbles of quartz, none of them as large as those in the group above. Some of the beds are five grained, equally hard and massive, and contain small scattered pebbles. Some of the beds show a good deal of disseminated oxide of iron.* About 25 miles west of Logan Gap the Juniata breaks through the mountain at Jack's Narrows. Here the Medina white sandstone is only 450' thick, the 30' of beds at the top being a group of alternating red, pink and gray sandstone layers and red and green shales ; some of the sandstone layers being covered with a net-work of sea weed markings (ArtTirophycus Jiarlani). The remain- ing 420' consists of strata, massive and compact, of white and greenish gray sandstone, with scarcely a trace of any organic life. Under these lie 650' of soft clay sandstone generally red, and speckled yellow with iron, current bedded to a great degree, and interstratified with beds of very soft red shale. Under these lie 250' of greenish white, hard, sandstone, down to the bed of the river in the gap, be- neath which nothing can be seen, as the exposure is anti- clinal. No. IV at OrUsonia. PL LXXXV1, p. 650. At Orbisouia, 10 miles further south, Black Log mount- ain shows No. IY in Rockhill Gap in its three divisions. The Medina white, 400' thick, consists of massive white and gray, fine-grained, hard sandstone beds alternating in the upper part with red and grayish shales. The Medina *Professor Kogers estimated the middle division of No. IV in Logan Gap, at 1000' ; of which the uppermost 500' consists of dark red flaggy beds of mixed sand and mud, some of which contains curious pebbles of red shale of unknown origin. Under these lie 100' of coarse red sandstone, loosely cemented together, friable under the weather, some of them sprinkled with small pebbles and showing a great number of iron stained spots. Under these lie 400' of pale red sandstone beds containing pebbles of quartz and fragments of slate apparently like No. III. These 1000' of reddish and more or less pebbly soft rocks constitute the middle division of No. IV. 654 GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. IV. AT SPRUCE CREEK GAP. 655 red, 930', consists of soft brown and red clay sandstones and shales ; the sandstones in the central part softer and more friable and specked with iron. The Oneida is divis- ible here also into two groups, the upper (158') consisting of hard red and greenish gray, broken up sandstones with conglomerates ; the lower (410') of hard massive greenish sandstone and gray conglomerate strata. No. 2 Vat Spruce Creek Gap. In the gap of the Little Juniata through Tussey mount- ain 20 miles northwest of Jack's mountain narrows, the Medina white sandstone, 1000' thick, showing few pebbles, but many impressions of the sea weed above mentioned, descends from the crest of the mountain to the bed of the river southward on a slope of 20. Under this lies 700' of Medina red sandstones and shales. The next underlying 200' are concealed but probably belong to the middle divi- sion, making it 900' thick. Under these concealed rocks, the Oneida conglomerate appears with its massive coarse and pebbly beds, apparently only 100' thick ; but the Spruce creek tunnel fault at this place obscures the section. Frag- ments of the Medina white, sliding from the crest of the mountain, cover its southeastern slope and also the upper part of its northwestern side ; for the thin beds broken up by the weather into innumerable flagstones slide upon each other down that slope ; and in this respect the surface show of Medina formation in this part of the region is peculiar. The best place to see this operation of gradual destruction is in Jack's Narrows before mentioned ; where the formation is thrown into a double anticlinal arch cut through by the river. The two walls of the gap are slopes of about 30, entirely covered from the crest of the mountain to the bed of the river with a smooth and regular universal stone slide, composed of millions of broken flags slipping over each other farther and farther in their slow but never ceasing descent. The material thus provided by nature has been thankfully accepted by man ; and railroad engineers find in this great stone slide an inexhaustible provision for the finest railroad ballast that can be conceived. 656 GEOLOGICAL SURVEY OF PENNSYLVANIA. LXXX/X- Langtudifial Section ofJacts Mountain miavmy between Three Springs and Saltillu shotting the subsidence at the Anticlinal at the end of the Mountajn.hyCha$.AAshbur r.p.n*. NO. IV. AT TYRONE GAP. 657 The ravine which descends into Spruce creek gap has been excavated in the Medina middle; and the Juniata river makes its very remarkable bend below the Spruce creek station in order to use the lower part of this ravine for a water way. The long hog-back in the bend (through which the Pennsylvania tunnel has been driven) is made by the Oneida conglomerate ; the outcrop of which slopes up the mountain side and becomes the brow of the terrace which surrounds Nittany and Canoe valleys. This terrace is the prominent feature of the northwest slope of Tussey mount- ain for many miles eastward. No. IV at Tyrone Gap. In the gap of the Little Juniata through Bald Eagle mountain at Tyrone City, Formation No. IV stands verti- cal, affording a fine opportunity for the study of its beds. But all the beds are not visible, being concealed by the ma- terial which has slidden from above. The section pub- lished in Report T, page 17, and Report T3, page 144, is as follows : Sandstone, white Medina, 100 rb Sandstone, red, with layers of red slate from 6" to 5' thick, 255' Concealed interval, 540' Sandstone, red massive, 84' Sandstone, green slaty, 1' 8' Sandstone, red, with a few layers of red shale, 87' Slate, green, 0' 6" Sandstone, red, 10' Shale, red, 5' Slate, green, . . 5' Sandstone, red, 5 Sandstone, gray, 20' Shale, red, 1' Sandstone, gray, 10' Shale, red, . f 0' 6" Sandstone, red, 10' Sandstone, grayish red, 15 Slate, red, Slate, green, ... 16" Sandstone, gray, 15 Slate, gray, 1 Sandstone, brown, 20 Slate, gray, 1 Sandstone, brown, 8 Shale, red, 6' 42 658 GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. IV. IN MILL HALL GAP. ( Sandstone, reddish brown, 75' Slate, red, ... 1' Sandstone, red and gray, 200' Sandstone, red, 9' Shale, red, 4' Sandstone, red, 2 Slate, red, 3 Slate, green, 1 Slate, red, 4 Slate, green, ... 2 Sandstone, red, 6' Sandstone, red, some little of it gray, 15' Sandstone, red, 10' Slate, gray, 2' Sandstone, red, 18' Slate, gray, 0' 5" Sandstone, grayish brown, 12' Shale, red 0' 3" Sandstone, brown, 20' Shale, green, 0' 2" Sandstone, brown, 4' tehale, red, 1' Sandstone, brown and gray, and concealed, 150' Sandstone, gray, and concealed, 409 Sandstone, gray, 320' Sandstone, gray, and slaty sandstone, 440' 2906' 6" In Tyrone gap, according to Mr. Sanders, the Medina white measures 1068', the Medina red 668', and the Oneida 1160' making a total of 2896'. A crush fault (apparently of no great magnitude) makes the statement a little doubt- ful. It is evident from the section above given, that the whole formation has a very different character along this its westernmost Bald Eagle outcrop, from its character along the Jack's mountain outcrop, 25 miles to the southeast. Many of the beds of the upper Medina, although massive, have a red color and might justly be thrown into the mid- dle division (Medina red). No. IV in Mill Hall Gap. In the Bellefonte gap through Bald Eagle mountain, 30 miles to the northeast of Tyrone gap, the Medina white may be said to have a thickness of 400' or 500'. The Me- dina red here consists of thin bedded gray and red clay sandstones, constituting three parts of the whole mass. 660 GEOLOGICAL SURVEY OF PENNSYLVANIA. ~~ XcT Section tine J-% OCTOM Centre tomukip. NO. IV. IN THE BEDFORD GAPS. 661 separated by and alternating with beds of red, gray and greenish shale. In the uppermost beds have been found stem-like vegetable forms (Scolithus vertical-is) which are probably the casts of the burrows of worms going down and coming up in the sand'on the shore of the sea ; its total thickness say 500'. The Oneida is here again divisible into two groups, the upper (380' thick) composed of greenish gray slightly micaceous sandstones, specked with iron ochre, and separated from each other by thin layers of finely lami- nated greenish slates ; the lower (170' thick) a mass of hard gray sandstone beds, entirely without pebbles, but com- pletely covered (where exposed to the weather) with yellow ochre specks produced by the decomposition of iron pyrites disseminated through the whole rock, in what original form has not been investigated. This iron speckled aspect of the Oneida division of Formation No. IV is characteristic of it throughout the central region of the State, and is a peculiarity which marks it quite as plainly as the flagstone slides mark the Medina upper division. No. IV in Williamsburg Gap. In the gap'of the Juniata river through Canoe mountain in Blair county, the Medina white is a mass of white and gray, line grained heavy sandstone beds, 550' thick. The Medina red consists of softer, reddish brown, clay sand- stone beds, a few beds of gray sandstone, and a great many beds of red shale, subdividing a total thickness of 1050'. The Oneida is as usual composed of massive greenish gray and pinkish, iron speckled, very hard sandstone beds, in all 500' thick. No. IV in the Bedford Gaps. In Bedford county the Medina white, still making the crests of the mountain, is a mass of almost snow white, line-grained, very hard and gritty rocks, 860' thick in the Yellow creek gap through Tussey mountain, but growing thinner southward, so that it is only 300' thick in the Rays- town Juniata gap through Tussey mountain, near Bedford, 662 GEOLOGICAL SURVEY OF PENNSYLVANIA. ?'m(wy ftudt in, Spring M?) limed fane <3>erry Co NO. IV. IN THE BEDFORD GAPS. . 663 and 200' in the gap through Evitt's mountain (T2, p. 91) ; no fossils but the sea weed Arthrophyous being seen in it at any exposure. The Medina red in the Bedford dis- trict contains comparatively little soft shale ; its beds being chiefly hard fine-grained red sandstone grits ; containing innumerable pellets of ochreous clay, which when exposed to the weather are dissolved out, leaving the rock in a curiously pitted, or finely honeycombed condition. Flat- tened lumps of red clay may be found by breaking the rock of many of the beds ; and these suggest an explana- tion for the universal iron speckled condition of the Oneida beds.* As for the Oneida or lower division of No. IV in Bed- ford county, Dr. R. M. S. Jackson of the First Geological Survey could find only 100' of beds which he could so call in the gap of Will's mountain into Millikin's cove. He suggested that the lowe'r part of it might be concealed by a fault along the western edge of the cove, seeing that the strata in Buffalo ridge are much broken and turned up ver- tical. But Professor Stevenson, in report T2 on Bedford county, could not recognize any Oneida rocks south of Morrison's cove. Gray sandstones indeed appear in Raver's creek gap through Tussey, on the Henrietta road in Wood- *How these balls of clay enclosed in fine sand originated is a curious ques- tion. It is also a matter of some moment to get any answer to the enquiry, whether they were originally round, or whether they were deposited in their present flat shape. For if they were originally round their flattened con- dition now must be ascribed to pressure, that is, to the consolidation of the Formation No. IV under the burden of all the formations up to the Coal measures, which were afterwards laid down upon it. And this would in- troduce a subject which has hardly yet received attention from geologists, namely, the amount of compression and loss of bulk vertically which all our formations have suffered in the lapse ot time, partly by the closer pack- ing together of their sand and mud grains, but chiefly from drying out of the original sea water with which they must have been for many ages com- pletely soaked or water logged. For if this diminution of bulk could be shown to bear a considerable proportion to the original thickness of sand and mud deposits, the calculation, if made upon a sound basis of fact, would materially modify the. speculations now so popular, oftentimes so rash, and in all cases so unsatisfactory, respecting the mutations of the sea level in various geological ages. For if our formations in drying have lost only 5 per cent of their thickness, the total shrinkage in thickness of say 40,000' of Palaeozoic strata would amount to 2000'. 664 GEOLOGICAL SURVEY OF PENNSYLVANIA. XCfif tcJ^irom twc&ifoal ortion o foe g^TT-rE? K / I L L NO. IV. IN THE BEDFORD GAPS. 665 berry township, and obscurely at two places on Banning' s mountain ; but Oneida beds are certainly absent along the Raystown Juniata in both Tussey and Evitts mountain gaps. In fact Oneida sandstone beds were seen by him at no locality in Bedford county more than 35' thick. At the two places last mentioned there can be no question of con- cealment by faults, for the top layers of No. Ill are regu- larly overlaid by Medina red or brownish red shales con- taining two fossils which unmistakably belong" to that divi- sion(Ambonyc7im radiata and Rliynclionellacapax}2c&& th Hudson river slates pass without any break of sequence upward into Medina shales ; so that there can be no doubt that the Oneida formation was not deposited in the bed of the sea in this locality, even in the condition of tine sand. Yet it must not be rashly concluded from this fact, that dry land existed here. For had dry land existed it must have been land of No. Ill raised above the sea level and afterwards submerged to receive the deposit of No. IV. But the moment a portion of sea bottom is lifted above water level rain-erosion commences, and continues until re- submergence ; and rain-erosion must leave its marks in the shape of hills and hollows however small or low. Some break in the continuity of the deposit must take pi ace, and must remain visible ever after wherever the consolidated rock strata are now exposed to examination. If no such break appears we ma} 7 be sure that the sea bottom has not been lifted to the air. Therefore if the Oneida format! on, thick and pebbly further northeast, grows thinner and finer and at length disappears going south, allowing the Medina above it and the Hudson river below it to come quietly together, it is certain that its disappearance is really and surely due to the fact that the sediments were floated fur- ther out into deep water according to their fineness, until at length the finest material was exhausted, or, mingled with equally fine material floated in from other directions. 666 GEOLOGICAL SURVEY OF PENNSYLVANIA. Ml ylkil Wafo^ap, (mdjie/ne, reduc<o ft. ivneaf NO. IV.- IN CLINTON, CENTRE AND LYCOMING. 667 No. IV in Clinton, Centre and Ly coming. Following the Bald Eagle outcrop of IY eastward into Clinton count}', the gaps at Lock Haven, Jersey Shore and Williamsport furnish sections of it along a stretch of 40 miles. In the gap at Millhall, near Lock Haven, the Medina upper hard massive white, gray and red sandstones, not very well exposed measures 695'. The middle division of in- terstratified softer sandstones and shales measures 705'. Under these lie hard massive sand rocks mostly w r hite; with a few beds of gray, mottled with iron rust, 188'. Under these, partly concealed, softer sandstones and shales, some of them red, 118'. Under these, massive, hard, dark gray and greenish gray, iron specked, flinty sandstones, 155'. Under these are hard and massive sandstones with con- cealed intervals of softer rocks, 440' ; which makes a total thickness of 2301'. (G-4, 129). It is evident that no useful classification of the beds of the whole formation into three divisions can be made out of the mere terms of this sec- tion ; but it will be shown in its proper place that where the eye of the geologist is at fault, the hand of nature works with unerring certainty, and carves the shape of the mount- ain in accordance with the larger groupings of the hard and massive beds. In the gaps issuing from Nippenose valley and Mosquito valley in Lycoming county the rocks of No. IV are not well exposed. The Medina upper hard sandstone is esti- mated by Mr. Platt at only 100' ; the middle red division he makes 1200' ; arid the Oneida hard sand rock only 15' ; the total being only 1375' (G-2, 29). The contrast between the section at Mill Hall carefully measured by Dr. Chance and this roughly estimated section of Mr. Platt at Jersey Shore and Williamsport is very striking, and not easily explained. It certainly affords no safe basis for generaliz- ing on the extent, thickness or method of the deposits. 668 GEOLOGICAL SURVEY OF PENNSYLVANIA. NO. IV. ALONG THE GREAT VALLEY. 669 No. IV along the Great Valley. Passing now to the long outcrop of No. IY, which bor- ders the Great Valley, we have, first, at the gap of the Susquehanna above Harrisburg an expression of the for- mation totally different in character from anything observ- able in the outcrops northwest of it toward the Allegheny mountain. The Medina upper division consists of a series of comparatively thin white sandstone beds, alternating with greenish and yellowish slates ; some reddish sand- stones occurring among the upper layers showing impres- sion of marine plants ; altogether making only 300' or 400'. The absence of massiveness here in the upper division of No. IV is quite remarkable. The consequence is that in- stead of making the crest of the mountain, these upper beds crop out below the crest on the southern side, over the outcrop of the Oneida ; the crest being made by the Iron sandstone of the Clinton formation No. V. that is, in Perry county. The Medina middle soft red division of No. IV is here entirely wanting ; and the geologist must travel along the mountain westward toward Franklin county to find it again appearing in the ridges which enclose Path Valley, but only feebly developed. Or he must cross Perry county north- westward to find it coming into the series in the gaps of the Tuscarora range. If he continues further northward to the Shade mountain, Blue Ridge and Black Log mount- ain gaps, he will find it much increased in thickness. Be- yond these to the northwest are the sections in Jack's mount- ain, Tussey mountain, and the Bald Eagle range, which have already been described, where it attains its maximum thickness. No. IV at the Susquehanna Water Gap. But, in the Susquehanna gap above Harrisburg the Oneida makes a great mark rising steeply to the top of mountain, along which its rocky outcrop runs, on the southern slope. It is about 70' thick, 40' of which consists of white sand- stone beds containing pebbles ; under this an exceedingly 670 GEOLOGICAL SURVEY OF PENNSYLVANIA. Xcvi. NO. IV. AT THE SUSQUEHANNA WATER GAP. 671 coarse, heterogeneous, red pudding-stone, 5' thick. Under this, between it and the uppermost layers of Hudson River slate, there is a concealed space of 40' or 60'. How much sliding and faulting has taken place in this interval, or how much of it is occupied by concealed sandstones cannot be made out. The wall of Oneida exhibits so many oblique slips and fault joints that its present thickness may be dif- ferent from that which it had when it lay horizontally at the bottom of the sea. The most interesting feature of this famous exposure (apart from the fact already men- tioned that the formation is here pushed over the vertical to a reversed south dip of 70) is the five foot 'coarse pud- ding-stone. As this lies at or near the bottom of No. IV, and more or less directly upon the slates of No. Ill, it is certainly an indication of some disturbance having taken place in some other and perhaps distant district of the earth's surface. But it is useless to speculate upon the origin of a bed, composed of pebbles and fragments of all kinds, since we are entirely ignorant of the depth of water which then and there existed, of the nature of the tide- runs or other currents which could transport the material, and of the shape, character or location of the shore lines which bounded the then water basin. It serves no good purpose to suggest that we have here a shingle on a sea beach. It would be equally useless to suggest an isolated gravel bank in the midst of the sea. Towards the west, for a thousand miles, no land could have existed at that time ; nor for less than three or four hun- dred miles towards the north. Our South mountains, and in fact all southeastern Pennsylvania was then not only under water, but covered by the limestone and mud for- mations No. II and III. If the great mountain mass of North Carolina was at that time out of water, which is very doubtful, it was nearly 500 miles distant to the south. All the highlands of New Jersey were at that time sub- merged. The Adirondack mountains in northern New York, and perhaps parts of New England, may possibly have been out of water, and possibly the Oneida pebbles were derived from those sources (but were certainly subsequently 672 OEOLOGICAL SURVEY OF PENNSYLVANIA. #/ / XCVH . fffi'/fy of If 4 ^-!> M i . . '.I h^ NO. IV. AT THE SCHUYLKILL WATER GAP. 673 submerged, as the Barnardston fossils show). But it would defy the keenest genius to make out the case, or paint the picture of the transaction in colors which would not fade into an ^indistinguishable gray under the light of precise enquiry. And the hopelessness of the attempt is accented by a fact which seems to be never alluded to by those who generalize on such subjects ; namely, the fact that our for- mation No. IV while being deposited in the Appalachian sea of America was at the same time being deposited in the prolongation of that sea which reached Europe ; being re- cognized in England under the name of the May Hill sand- stone ; and it will be shown in discussing Formation No. VII that this critical fact was repeated in the case of the OrisJcany sandstone which was deposited in the United States at the same time that it was being deposited in France ; specimens from that formation, full of the same ani- mal forms and presenting exactly the same aspect, having been collected from the outcrops on both sides of the present Atlantic. No. I Vat the Schuylkill Water Gap. A topographical contour map of the Schuylkill Water Gap at Port Clinton made by Mr. Chance, with careful measurements of the five groups into which No. IV is there subdivded, gives us the following description of it : Three prominent ribs of sandrock rise vertically from the bed of the river to the north slope of the crest of the mount- ain. No distinction can be made in the Medina between an upper white and a lower red division. At the top rest 90' of Upper Medina gray sandstone beds, supported by 480' of iron stained shales ; under which are 60' of Lower Medina white sandstone beds supported by 600' of iron stained shales ; and at the bottom, 200' of Oneida white sandstone and gravel beds, which make the crest.* *This is a rare occurrence, due to the great thickness and massiveness of this rib. The terrace on the north slope is made by the outcrop of the com- paratively thin and unsupported Upper Medina rib. See cross-section, ng. 4, plate LIT, on p. 554 above. 43 674 GEOLOGICAL SURVEY OF PENNSYLVANIA. At this interesting locality the bottom of No. IV is wholly separated from the slates of No. Ill by a vertical fault, on the north side of which the sandstones of IV rise vertically into the air, making the crest and north slope of the mount- ain. On the south side of the fault the slate formation No. Ill is sheared off like a cake of cheese, the edges of the slates abutting nearly horizontally square against the upturned bottom plate of Oneida conglomerate. It is im- possible to affirm that it is actually the bottom layer of the Oneida ; but there is very little reason to doubt it ; seeing that when the break took place, and the whole mass of No. IV was turned up at right angle, it is probable that it was turned up as a solid mass ; and that the lower surface of the bottom bed acted as a grinding surf ace against the edges of the slates. As no verbal description can give a clear idea ^of this phenomenon the section is presented in the figure cited in the last footnote. The Schuylkill Water Gap is 50 miles east of the Sus- quehanna water gap ; and in these 50 miles the character of the formation has evidently changed in an extraordinary degree ; and this change goes on becoming more and more striking eastward. No. 1 V Lehigli Water Gap. At the Lehigh Water Gap (25 miles east of the Schuyl- kill Water Gap) Dr. Chance's measured section gives the following details : Upper sandstone rib 85' ; upper ferru- ginous shales 180' ; Middle gray sandstone rib 70' ; lower ferruginous shales 330'; (total Medina 665';) Oneida sand- stones, some of them pebble-rocks, 290' ; Oneida massive conglomerate 170' ; (total Oneida 460') ; total of Forma- tion No. IV, 1125'. We see that the pebble-rock, which at the Susquehanna gap was less than 100' thick and at the Schuylkill gap 200', is at the Lehigh gap nearly 500' ; constituting everywhere from the Susquehanna to the Lehigh the central rib of the mountain and sometimes its crest ; while the middle and NO. IV. AT THE DELAWARE WATER GAP. 675 upper sandstone ribs crop out as terraces and benches along the northern slope.* No. IV at tlie Delaware Water Gap. At the Delaware Water Gap (25 miles. still further east) the gradual change in the constitution of No. IV produces another feature, namely, the subdivision of the Oneida into three, the Medina continuing to be sub-divided into four. We now have seven distinct subdivisions of the formation No. IV as follows ; Upyer Medina sandstone'rib 200' ; upper ferruginous shales with some sandstone beds 530' ; Lower Medina sandstone rib (here a white conglomerate) 200' ; lower ferruginous shales with the sandstone beds 110' ; (total Medina 1040') ; Upper Oneida gray sandstone rib 75' ; intermediate shales with sandstone beds 240' ; Lower Oneida white conglomerate rib 210' (total Oneida 525'} ; total thickness of No. IV, 1564'. f At the Lehigh Water Gap there is some doubt about the relation of the bottom bed of Oneida to the slates of III on which it rests ; but at the Delaware Water Gap there is no confusion or concealment whatever ; the under surface of the bottom bed of the lower division of the Oneida con- glomerate rests quietly and regularly upon the uppermost sandy slates of No. III. And, what is more important * At the Lehigh the Upper Medina sandstone makes the crest, but as it is comparatively thin the crest is not sharp ; and as it is supported by the sec- ond rib, with only 170' of hard shales between them, the two ribs act like one, and as if 235' thick, making a very high gently rounded crest See figure 3, LII, page 554. The south slope of the mountain becomes steeper and steeper across the 330' of hard shales ; and becomes 35 across the 290' of Oneida sandstone and 170' of Oneida conglomerate, more than two- thirds of the way down to the foot Here the slates of III commence, and the slope suddenly becomes gentle. It is a remarkable contour for the mountain of IV, well worthy of careful study. The outcrop which was at the very crest at the Schuylkill is here at the Lehigh nearly at the south foot of tbe mountain ; not on account of dip, but on account of the differ- ent arrangement of the rock ribs and parting shales in the body of the mountain. t Here the Oneida upper sand rock rib, thin as it is, makes the crest, be- cause it is so closely supported (within 110') by the huge Lower Medina sand rock rib, and by the very sandy character of the Oneida middle shales. The Oneida conglomerate makes precipices along the southern slope half way down the mountain. See cross-section, PI. LXXX, p. 638. 676 GEOLOGICAL SURVEY OF PENNSYLVANIA. still, the uppermost beds of No. Ill are here so sandy as to contain thin beds of sandstone, showing a regular proces- sion of deposits, and a sort of passage from the slaty kind (III) to the coarser sandy and gravelly kind (IV). And yet the transition is in fact instantaneous ; as if avast quantity of grav.el was deposited upon a level sea bottom of dark sandy mud. We are again left in total darkness as to the cause of this remarkable operation. But after all, it is no more extraordinary than the way the May Hill sandstone of England rests upon the shales and limestones of lower Silurian Age. No. IV in New Jersey. The Kittatinny mountain (called Shawangunk mountain) after crossing the Delaware river at the Water Gap runs on for 35 miles to the north corner of New Jersey at Port Jervis. Oneida conglomerate (Shawangunk grit) is de- scribed in the Geology of New Jersey (1868, p. 146) as a mass measuring (at Otisville) 800' or 900' thick, composed en- tirely of beds of conglomerate and sandstone. The lower part is a mass of quartz pebbles, from one quarter to three quarters of an inch in diameter, in a light colored quartz cement. In the beds above, the pebbles become smaller ; and near the top they can hardly be distinguished from the paste in which they are imbedded, the whole rock being a massive compact quartzite. No fossil forms have been found. Some of the beds contain crystals of iron pyrites which have yielded to chemical assay as much as $11 of gold to the ton, This occurs at the bottom of the formation next the slates of III. The lead ore veins which traverse the rock will be mentioned directly. I The Medina beds outcrop along the northern slope of the mountain descending to the Delaware river. Their esti- mated thickness where the Erie railroad crosses the mount- ain east of Port Jervis is 800'. The two formations Me- dina and Oneida are here seen to pass into each other by a series of alternations, white and red, fche white being Oneida, the red Medina. These colors strongly contrast and distinguish the two formations. The Indians called NO. IV. IN NEW YORK. 677 the mountain "Shamgum" the white rock. It is evident from the change of color that the sea water at the begin- ning of Medina time, began to receive large accessions of iron ; but there was not at any time deposits of iron ore. The red Medina sandstones are interstratified with reddish shales ; and these are so abundantly traversed by trans- verse cleavage planes as to give the rock in some places the appearance of a red roofing slate, dipping steeply across the bedplates towards the southeast ; but the coarser and harder brownish red sandstones do not show this cleavage and exhibit the true northward dip. Occasionally a gray- ish green shale occurs. The bottom Medina beds (next over the Oneida) are all sandstone, made up of grains of quartz, some of them containing small pebbles of white quartz, interstratified with soft shales ; while the upper Medina beds are nearly all reddish shale (much split by cross cleavage) interleaved with thick red and grayish sand- stone beds. No fossil of any kind except a sea weed has been found ; and this is the more remarkable because, ex- cellently well preserved ripple marks are common, in fact almost universal. No. IV in New Yoik. The Shawangunk mountain in New York runs on north- east about 45 miles, to within 10 miles of the Hudson, and abruptly ends at Rosendale where the Rondout and Wai- kill valleys come together. Leaving New Jersey "the mount- ain has a crest of white Oneida, and a northern slope of red Medina. But advancing northeastward the Medina rocks disappear and at last the mountain consists exclu- sively of Oneida beds, estimated by Mather at 500' running down to 150' and even as thin as 60'. Some red beds at the top would seem to indicate that the Medina is slighly rep- resented ; but no division between the two formations is possible ; and it will be seen hereafter that the next supe- rior formation No. V thins away in the same direction, let- ting the limestone of No. VI rest upon the beds of No. IV. These details respecting the geology of New Jersey and New York are given here merely for the purpose of show- 678 GEOLOGICAL SURVEY OF PENNSYLVANIA. ing that the variations in Formation No. IV throughout Pennsylvania are not to be compared for magnitude with its variation in this New York district. The mountain in New York is broken by great cross-faults which traverse also the formations above it and below it. In fact the re- gion bordering the Hudson river valley has been shattered by the earth movements which elevated New England; and probably it is to the greatest of these faults that the mount- ain owes its sudden termination. Lead ore veins in No. IV. The remarkable lead veins which traverse No. IV in New York are among the consequences of the shattered condi- tion of that region. Such lead veins are not to be expected in Pennsylvania where the outcrop mountains of No. IV exhibit few cross fractures. In the early settlement of America, Indians and hunters searched everywhere for galena to furnish themselves with bullets. Hundreds of traditions of Indian lead mines have been handed down, most of which are pure fictions. Indians and hunters cer- tainly did find lead in certain places and carefully con- cealed their discoveries as long as it was possible to do so ; but probably every such actual lead locality is now known, and are few in comparison with the great number of fic- titious places. Most, if not all of the actual veins have been repeatedly explored, and some of them mined at con- siderable cost, none of them to profit. Forty years ago the Ellenville mine at the base of the Shawangunk mount- ain, the Ulster mine near Red Bridge 600 or 700' up the side of the mountain, and the Shawangunk mines near Wurtsboro in Sullivan county, N. Y., 600 or 700' up the mountain, were all in operation. They were all abandoned. In the Ellenville mine some lead and zinc were obtained. In the Ulster mine masses of zinc, lead, copper, and iron pyrites were obtained. In the Shcwangunk mine three masses of lead ore were taken out weighing from 800 to 1400 pounds. But the lead veins were only 2' or 3' thick, and the ore very irregular. The abundance of finely formed LEAD ORE VEINS IN NO. IV. 679 rock crystals, together with the mixture of ores, show that they were deposited from solution in the cracks which tra- versed the region after it had been shattered by the great earth movement which took place at the end of the coal age. It is idle to look for such veins in No. IV in middle Pennsylvania. The same may be said of gold. Although the lower beds of the Oneida are largely made up of gold- bearing quartz, of course they cannot be considered in any sense ancient glacial placer gravels ; and free gold has never been reported. What gold exists is in the quartz pebble itself. It is perfectly certain that no gold mining can be successful in any of the mountains of No. IY in Pennsvlvania. 680 GEOLOGICAL SURVEY OF PENNSYLVANIA. J/ltJd-c/i Spring on Sinking Cr. Lin. Canoe Mounkwn terrace and linking valley. TOPOGRAPHICAL FEATURES OF MIDDLE PENNA. 681 CHAPTER LII. Topograplucal features of middle Pennsylvania. The facts presented in the foregoing chapter introduce the subject of the topography of the central belt of Penn- sylvania, especially of that half of it which stretches from the Susquehanna river to the Maryland state line : for this topography has for its most striking features the bold ridge- outcrops of Formation No. IV. It has already been said that all the Pennsylvania mount- ains from the North mountain of the Great Valley to the Bald Eagle mountain facing the Allegheny, in the country west of the Susquehanna river (with only three excep- tions) are mountains of Formation No. IV*. The mountains of No. IV may be classified in three groups of zigzags, so complicated in their shape that they can only be described by a map. To the inhabitants of the various counties in which these groups stand they seem like separate mountains, and so each has received some separate local name. Names of Mountains of IV. The number of local names is very great ; the prominent ends of the zigzags being usually named after some settler, like Parnell's knob and Jordan's knob in Franklin county, *Two of these exceptions are in Perry county, namely; Cove mountain, ten miles and Buffalo mountain twenty miles above Harrisburg, which are mountains of No. X, and belong to the anthracite region of eastern Penn- sylvania. The third exception is that of Sideling hill and Terrace mountain in Huntingdon county, surrounding the Broad Top coal basin, and continu- ing under various local names, like Harbor mountain and Town Hill, into Maryland, all mountains of No. X. The Broad Top mountain enclosed by them is made by No. XII capped with coal measures. A fourth exception might be mentioned in the case of Great and Little Savage mountains, in Somerset county, surrounding the Cumberland coal basin in Maryland ; but this outcrop of No. X and XII is nothing but a zigzag of the Allegheny mountain and belongs properly to the general bituminous coal region of western Pennsylvania. 682 GEOLOGICAL SURVEY OF PENNSYLVANIA. Sidney knob in Fulton county, Jacks mountain in Union county, Tussey's mountain, Dunning' s mountain and Evitt's mountain in Mifflin, Blair and Bedford counties. Others have been named after the animals that haunted them in early times ; Bear Meadow mountain in eastern Huntingdon ; the Buffalo mountains in Union ; White Deer and Bald Eagle mountains in Ly coming. Tuscarora mount- ain, ranging through Juniata county, was named after the principal tribe of Indians in middle Pennsylvania.. Stand- ing Stone mountain on the borders of Huntingdon and Mifflin, was named after a remarkable monolith or solid stone pillar 70' high, which once stood on the bank of the Juniata, at the mouth of the creek, near the present town of Huntingdon. Around it the grand council fire of the tribes was lighted. Sometimes a name was repeated ; as, for instance, Path Valley mountain, along which the south- ern county line of Centre runs, which has no connection whatever with the mountains surrounding Path valley in northern Franklin county. Several projecting spurs are called Dividing ridge, or Dividing mountain, because they separate two parts of an enclosed valley. German settlers from the Rhine, familiar with the name Siebengebirge, called the knot of ridges between Kishicoquillas valley and Brush valley the Seven mountains ; but their ends toward the Susquehanna, in Snyder and Union, retained their Indian name of the Buffalo mountains ; a proof that the bison roamed through Pennsylvania, when the beaver made its dams on many of our streams, and herds of elk ranged through the Allegheny uplands. Three groups of mountains of IV. 1. The southernmost group of mountains of IV lies be- tween the North mountain of Cumberland and Franklin and the Tuscarora mountain which ends at the Juniata at Millers town. The eastern zigzags are represented in lig. 3, pi. LXXIV, p. 626. They enclose the fertile valleys of Perry county, Greenbrier, Kennedy's. Henry's, Shafer's, Little Illinois, Sherman's, and Horse valleys, with Path valley, Burn's valley, and Amberson valley in Fulton THREE GROUPS OF MOUNTAINS OF IV. 683 county, issuing southward upon the Great Valley at Mer- cersburg. This group is extended southward through Fulton as Sidney knob, Tuscarora mountain, and Cove mountain surrounding McConnellsburg Cove in Fulton county, into Maryland. It includes also the isolated mount- ain which ends in ParnelPs knob ; and the two mountains which project from Maryland toward Mercersburg. 2. The middle group of mountains of IV., is of a pecu- liar character. Tt resembles three long narrow canoes moored side by side, but projecting beyond each other ; or rather three canoes floating bottom up, each one with its bottom knocked out. They are in fact the eroded tops of three long closely folded anticlinal arches of No. IV, sep- arated from each other by equally long narrow and closely compressed basins filled with Formation No. V. (a)The southern anticlinal, having West Shade mountain for its south dipping and Black Log mountain for its north dip- ping outcrop, extends from Fort Littleton on the Fulton county line to within ten miles of the Juriiata at Mifflin- town. (5)The middle anticlinal, called Blue ridge, ex- tends from the Horse Shoe bend of the Juniata at Newton Hamilton to the Juniata river above Mifflintown. (c)The third extends from the Juniata river at Lewis town to within 8 miles of Sslinsgrove, on the Susquehanna, in Snyder county. The shape and arrangment of these three is shown in the Vignette Map of the State at the beginning of this volume. Nothing in topography is more beautifully symmetrical ; nor can anything illustrate to greater advan- tage the plication of the formations in middle Pennsylvania. 3. The third group of mountains of No. IV is of so com- plicated a character as to defy description in words, and is- therefore given in outline in the Vignette just mentioned. In this figure a black line represents the Medina white sandstone outcrop which everywhere in this group, extend- ing from the Susquehanna at Muncy in Ly com ing county to the Maryland line, makes the mountain crest; while the broken line alongside of it represents the Oneida gray sandstone outcrop which everywhere in this group forms a bold terrace on the mountain flank. The southern 684 GEOLOGICAL SURVEY OF PENNSYLVANIA. border of this group is the noble ridge of Jack's mountain, which borders the Lewistown valley on the north and for 50 miles, shuts in behind it the fertile Kishicoquillis lime- stone valley, bordered on the northwest by the Standing Stone mountain, and on the north by the Seven mountains, which spread (northward) as Short mountain, Brush mount- ain, Nittany mountain, Buffalo, White Deer and Bald Eagle mountains as far as the Williamsport valley. From the western end of the Seven mountains projects Tussey's mountain which runs on uninterruptedly about 100 miles to the Maryland line, shutting in behind it the fertile lime- stone valleys of Penn's creek, Brush creek, Spruce creek, Canoe valley and Morrison's cove. The Bald Eagle out- crop is the second finest in the State, extending along the West Branch of the Susquehanna for 30 miles, from Muncy to Lock Haven; than onward along the Bald Ea- gle creek for 50 miles, from Lock Haven to Tyrone City; thence onward along the upper Little Juniata for 15 miles, to Frankstown; then returning to the Little Juniata (13 miles) as Brush mountain ; bending back and running south (20 miles) as Canoe mountain; turning and running north (6 miles) toward Hollidaysburg as Lock mountain; resuming its south course as D tinning' s mountain (25 miles) it bends round Dutch corner and runs south (30 miles) as Evitt's mountain into Maryland. Isolated geographically from this outcrop on the west is the anticlinal of Will's mountain and Buffalo Ridge, extending from Bedford (25 miles) to the Maryland line. This long and perhaps tedious enumeration of the mount- ains of IV in middle Pennsylvania, west of the Susque- hanna river, will interest the people of that part of the State who will now understand the geological identity of the labyrinth of mountain ridges among which they live. But its principal value arises from a single geological idea, namely : that this continuous series of mountain crests and slopes are all made in one and t the same way, out of one and the same set of rocks, exhibiting every- where the same internal constitution and differing only, (1) in the thickness of the beds or groups of beds at one THREE GROUPS OF MOUNTAINS OF IV. 685 place and another, as has been fully explained in the last chapter ; and (2) in the various angles to the horizon, at which their strata have been tilted up. It now remains to show, first, why these mountains some- times run in straight lines parallel to each other for many miles; secondly, why these parallel lines sometimes come together at both ends, as do the gunwales of a boat at the prow and stern; thirdly, why in other districts they unite in a series of zigzags; fourthly, why the opposite points of such a series of zigzags have two totally different charac- ters, one long and sloping gradually into the plain, the other high, sharp and abrupt, projecting like a knob into the air ; fifthly, why the mountains of the first or southern group have only one crest and two slopes, whereas the mountains of the middle and northern groups have a crest, a long continuous slope on one side, and a bold terrace half way up the slope on the other side; sixthly, why the Bald Eagle mountain in Centre county has two crests of e'qual height and no terrace ; seventhly, why the terraces are cut through at short and regular intervals by double headed ravines; and, eighthly, what all this teaches us respecting the great rock arches which once rose high in the air, but have long since been removed and swept into the Atlantic, furn- ishing collateral evidence that the surface of Pennsylva- nia is still being slowly but continuously fretted down toward the level of the sea. Before taking up these several items it is essen tial to the un- derstanding of the subject that the reader first imagine For- mation No. IV as originally lying in a continuous and nearly horizontal sheet, deeply buried beneath Formations V, VI, VII, VIII, IX, X, XI, XII, and all the coal meas- ures from XIII to XVII. He must then picture to himself this continuous sheet Formation No. IV, with all the forma- tions beneath and above it pressed sideways and folded into arches and troughs also under western and northeastern Pennsylvania, just as we see it at the surface in middle Pennsylvania west of the Susquehanna. Beneath the anthracite coal basins it lies at various depths from 10,000' to 20,000'; but between the basins the tops of its 686 GEOLOGICAL SURVEY OF PENNSYLVANIA. great arches approach much nearer to the surface; and one of them actually comes to the present surface in Montour's ridge at a single point between Danville and Sunbury, where, in a ravine descending to the North Branch of the Susquehanna, 37' of its upper beds are actually exposed (See G7, p. 114). The mountainous exhibition of it at the present surface west of the Susquehanna is the conse- quence of a gradual upward slope of the whole formation from beneath the anthracite country, westward. Going west- ward the arches rise first, like the backs of whales issuing from the surface of the sea, covered with soft red shales of Formation No. V, and gradually lifting themselves higher and higher into the air. This is why all the eastern ends of all the mountains of IV, facing the Susquehanna valley, have one and the same character of long gently sloping mountain noses. Parallelism of mountains of IV. A. The first point mentioned above is the parallelism of the mountains of IV. This parallelism is perhaps the most remarkable feature of the topography of middle Pennsyl- vania. It is a consequence of the extraordinary symmetrical shape of the anticlinal arches, which can be compared to nothing better than the long even folds in heavy woolen carpets when pushed sidewise over a floor. The formations composing each fold may be well explained by the annual layers of wood in a fallen tree trunk which arch over each other, flat along the top, and steeply sloping on the sides. Now let a lumberman adze off the upper part of such a tree trunk, reducing it to a flat surface, he will expose the edges of the wood-layers in two sets of parallel lines, one set to the right and the other to the left ; exactly corresponding to each other ; the uppermost layers being the farthest apart, and the lowest layers to which his work reaches occupying a middle line over the center line of the log. This it precisely what nature has done in her carpentry work upon the long prostrate anticlinal folds of the Palaeo- zoic formations ; only with a difference of tools. Instead PARALLELISM OF MOUNTAINS OF IV. 687 of the carpenter's adze, she has employed frost, the thaw- ing heat of sunshine, and the transporting power of rain water. With these tools everlastingly at work she has planed off all the anticlinal arches of middle Pennsylvania nearly to a common level. But the difference in the tools employed by the carpenter and by nature makes a signal difference in the neatness of work done in the two cases. The adze and jack plane make no account of variation in hardness or softness of the several layers of wood ; the edges are all reduced to the same plane surface ; for such tools have no selective power and care nothing for either the resistance or the compliance of the wood which they remove. But the tools of nature ex- ercise a kind of selective judgment ; or, rather, they are sensitive to the slightest differences of hardness or softness in the rocks upon which they operate. If we could ascribe intelligence to nature we should be obliged to say, that she has no intention to produce an even smooth topography, that is, to reduce the surface of the State to a perfectly level plane. Her water work has gone further into the softer rocks, leaving the harder outcrops elevated, and the hard- est and most massive formations standing out as mountain ridges. But her manner of working has been essentially the same as that adopted by the carpenter who, instead of the rapid action of adze and plane, should content him- self with the slow and tedious operation of sandpaper, would himself produce the same variety of parallel ridges separated by creases on his log of wood. The parallelism of any two mountains of IV on two sides of any anticlinal which extends for many miles teaches us two facts : 1. We learn that to have exact parallelism in long straight outcrops the crest of the anticlinal must be level for a long distance ; for it is evident that if the crest of the anticlinal slope upward the opposite outcrops must diverge ; if it slope downward they would approach each other. (2) We learn that the characteristic form of our anticlinal arches cannot belong to one formation, but to a whole and very thick series of formations, all folded together. This can 688 GEOLOGICAL SURVEY OF PENNSYLVANIA. be easily understood by crumpling two substances even as different in thickness as silk and woolen ; or by com- paring the short irregular angular crimpling of one thin sheet of paper with the ample and regular fold of an entire ream of paper. The Palaeozoic formations, lying upon each other like a pile of Canada blankets, could not have been pressed by the earth movement into any arches and troughs not of magnificent length, height and depth, and of beautiful symmetry. Therefore it must be kept in mind that we are dealing not with a few layers of sandstone, but with 40,000' of superimposed sediments ; and that when they were thrust into anticlinals and synclinals they all moved together, yielding and adjusting themselves to each other, especially the softer to the harder, but yielding to the earth movement as if they all constituted one single formation. Convergence of mountains of IV. B. The second point to be noticed seems at first sight a violation of the principle just stated ; for the parallelism is not perfect and universal ; it has its variations ; but these variations, when explained, will be seen to be essential to the principle. However many miles two mountains of IV may run parallel, they are sure sooner or later to approach and unite at one end or at both ends. If this occurs at both ends it shows that the anticlinal fold dies down in both directions. The student of our geology must be careful to make a strong distinction in his mind between the end of an anti- clinal mountain and the end of its anticlinal fold. The mountain comes to an end because two parallel outcrop mountains have converged and sink together beneath the present surface. But the anticlinal fold itself keeps on, carrying the formation deeper and deeper In this way one formation disappears in a loop at the surface and is replaced by another further on, also in the shape of a loop. Following the axis of an anticlinal fold we have say first an arch of No II in the valley coming to a point ; then, a loop of No. Ill, filling up the end of the valley; then a loop of No. IV mak- MOUNTAIN SPURS OF NO. IV. 689 ing the end of the double mountain; on the outside nose of which is a loop of No. V settling into the plain ; then a loop of the limestone formation No. VI descending be- neath a looped ridge of Oriskany sandstone No. VII ; which descends beneath a rolling hill country of No. VIII, ending in a grand mountain cove of red sandstone No. IX capped with white sandstone X; sinking as an anticlinal nose into a deep loop valley of the red shales of XI, en- closed between opposite dipping mountains of the Conglom- erate XII, separating two coal basins. This is the rule in all cases where the anticlinals are of the first order of magnitude. Mountain spurs of No. IV. C. A third point to be explained is the production of groups of mountain zigzags. This requires a little more strenuous effort of the imagination, but it is merely a com- plicated form of what has just been described. When the earth-movement pressed the whole series of Palaeozoic for- mations into folds it obeyed a thousand variations of local stress and strain, and produced therefore not merely a few grand arches of the first order one or two hundred miles in length, but scores of folds and wrinkles of the second and third order of far inferior height and length. These sub- ordinate folds may properly be considered mere parasites of the great anticlinals ; they are, in fact, wrinkles on the descending sides of the grand arches. But these smaller arches bring the outcrop of No. IV to the surface and re- turn it underground in the same way, but more rapidly and locally. They produce the same topography, but on a smaller scale. Each minor fold has its two opposing outcrops of No. IV, coming together in the direction in which the fold dies down. Where there are six such minor folds side by side, all dying down in one direction (say eastward, as in Snyderand Union counties) there are neces- sarily as many pairs of outcrop mountains of IV one on each side of each fold, producing a group of mountains in zigzag, with six points in one direction, and as many in the other. Perhaps the best way to comprehend this phenom- 44 690 GEOLOGICAL SURVEY OF PENNSYLVANIA. enon, would be to take a sheet of corrugated zinc roofing, and hold it slanting in a basin of water. The edge of the water will make similar zigzags against the surface of the tin. The more erect the zinc plate is held the shorter will be each zizzag. If the plate be held nearly flat, one end scarcely below the water and the other scarcely above it, the zigzags will be long and sharp pointed. By varying the shape of the bends in the tin plate, that is, by represent- ing anticlinals and synclinals of different height, breadth and sharpness, all sorts of variations in the zigzag water line can be got, and all the variations of our No. IV. mount ain zigzags may be imitated. The inelasticity of sand and mud deposits greatly helps us to explain their present folded condition. It cannot be too of ten repeated, that, when the earth movement took place the whole 40,000' of Palaeozoic formations were still in a moist and plastic state. Had they been of any dry, hard, elastic material they would have been bent into a very few perfectly regular folds, each formation sliding upon the sur- face of the one beneath it, and none of them wrinkled. But the actual mass of mud and sand deposits being wet and plastic, was necessarily, when thrown into folds as a whole, compressed into ten thousand subordinate folds and wrinkles. The great anticlinals are none of them mathemat- ically perfect vaults. Their opposite sides do not descend in smooth unvarying curves into the synclinal troughs, but wave and halt and pitch irregularly in their descent. In geological language, the dip is constantly changing to steeper or less steep, and is occasionally reversed ; so that on the long slope of a grand anticlinal there are always seen to be one or more subordinate rolls'and basins. When the bottom of the long anticlinal slope is at last reached, we are in the middle of a great synclinal basin, and begin to ascend the long wavy slope of the next parallel grand anticlinal. Thus, anticlinals and synclinals virtually oc- cupy the same ground ; each anticlinal measuring in breadth from the center line of one synclinal across the arch to the center line of the next synclinal ; each synclinal measur- ing in breadth from the crest line of one anticlinal across MOUNTAIN SPURS OF NO. IV. 691 to the crest line of the next. From the very nature of the curves it is impossible to avoid embarrassment in the use of these terms ; and it is unfortunate that the double mean- ing of the terms employed makes their representation to the mind of the student somewhat vague. If it were pos- sible to assume points half way down 1he slope we might confine the term anticlinal to the arch above these lines, and the term synclinal to the trough below these lines ; but in practice this cannot be done ; the reader must exercise his intellect to understand the facts of the case, and keep the distinction between the upward curves or arches and the downward curves or troughs as distinctly as possible be- fore his mind's eye. Nothing in geology is simple ; noth- ing in any branch of science is easy ; to understand the true nature of the commonest fact of the world requires a strenuous endeavor of the judgment and the imagination working harmoniously together. And this is especially true in geology, most of its facts being concealed from the naked eye, and therefore to be mentally conceived, and cautiously reasoned upon. Illustrations of the complicated character of the anti- clinals and synclinals of No. IV are given in fig. 1, pi. LX XIII, p. 624, and fig. 1, pi. XC, p. 660. See also pi. XCV, XCVI, XC VII, p. 670. One of these represents a series of sections at intervals apart of about a mile across the Seven mountains in eastern Huntingdon county. The other represents a series of transverse sections, taken at greater intervals across the main anticlinal of Perry county which crosses the Susquehanna and runs on eastward between the two arms of the Schuylkill county anthracite coal basin the Dauphin basin on the south and the Wiconisco basin on the north. In the first section the large white band repre- sents the folds of No. IV, mostly along the plane of the present surface. In the second section No. IV is every- where underground, but waved in the same manner ; at the sections on the Juniata and Susquehanna rivers it is covered by 10,000' or 15,000' of higher formations. How is it possible then, it may be asked, to draw cor- rectly the shape of the waves of the deeply buried forma- 692 GEOLOGICAL SURVEY OF PENNSYLVANIA. tion. The answer is, that they can be geometrically con- structed on the supposition that the thickness of the over- lying formations remain unchanged throughout the region ; at least that any irregularities of thickness in each will practically be compensated for in all ; and that the dips observed at the surface will give a good practical idea of the basins and arches concealed underground. Nearer than this to the exact truth the geologist cannot come, unless he employs boring tools, which is of course not to be thought of for such great depths. Enough is plainly observable at the surface to make the complicated structure of middle Pennsylvania completely evident. Wherever formation No. IV comes to the surface in mountain ridges a thousand feet high, cut through to their bases by rivers exposing the strata, there the character of the anticlinals of the first order reveals itself with admirable clearness. The difference between the anticlinal and the synclinal Knobs of IV. D. The fourth question must now be answered ; why the opposite points of a series of zigzag mountains of No. IV are so totally different in shape and character? It must be remembered that zigzags of No. IV are pro- duced only in districts where the plicated formation is de- scending beneath the surface eastward and consequently rising into bhe air westward or vice versa. If now we im- agine such a set of zigzags pulled out to a straight line in other words, the formation not waved, but still descend- ing underground in one direction and rising into the air in the other it is evident that in the descending direc- tion, it will be first thinly veneered and then more and more thickly covered with the next soft red shale forma- tion No. V. In the other direction the bare sand -rock edges will be abruptly broken off in a line of cliffs, from un- derneath which will crop out the soft dark shales of No. Ill, making a steep slope from the foot of the cliffs down to the floor of the valley ; and in the valley will crop out the limestones of No! II. Let us now restore the zigzags. The only difference will ANTICLINAL AND SYNCLINAL KNOBS OF IV. 693 be, that instead of a long straight range of cliffs at the crest of the mountain there will be as many pointed pro- jections as there are zigzags, each projection being a peak of cliffs, around which the slope of underlying slate will bend. Between the peaks, and running up into the zigzags, will be long narrow vales of slate, No. III. By merely looking from a distance at the shape of the eastern and western ends of a zigzag mountain of IV a geologist can tell with certainty in which direction the an- ticlinals which make the zigzags are dying down, whether eastward or westward ; for if the anticlinal is rising west- ward and descending eastward, the east end of the mount- ains must be a long and gentle slope covered with the red shale of V ; and the west end of the mountain must be a high peak, rocky and precipitious, with a steep slope of slate No. Ill into a valley of limestone No. II. The geolo- gical county maps furnish plenty of examples of both kinds ; that is cases where the rocky point is at the west end and the red shale slope at the east end of the mountain; and cases where the rocky point is at the east end and the red shale slope at the west end of the mountain. To assist the reader some prominent examples may be pointed out. Taking the southern outcropof No. IV, and following it from the Delaware Water Gap west ward, Off set knob appears as a synclinal cliff-tipped projection looking east, while the red shale end of the zigzag sloping to the west is behind the Wind Gap. The zigzags.'of the little Schuylkill in northern Berks are produced by ten small anticlinals sinking west- ward ; consequently it is the eastern points of the zigzags which have the Knob cliffs. In Cumberland county the two projections of the North mountain into the Great Val- ley are towards the west ; their corresponding red shale zigzags pointing east are in Perry county. Parnell's knob and Jordan's knob are similar synclinal end cliffs pointing southward. The mountains of No. IV in Perry county, all end northeastward in long slopes of red shale ; their southwestern ends, projecting into Franklin county, are high and rocky. The triple central anticlinal group of No. IV, in Shade, Blue and Black Log mountains die down at 694 GEOLOGICAL SURVEY OF PENNSYLVANIA. both erids^ eastward and westward, in long red shale slopes. So does Jack's mountain at its southwest end in Hunting- don county, and its northeast end in Snyder county. The Buffalo. White Deer mountains slope their east ends be- neath the red shale country of Union county, but project westward into Kishicoquillis, Penn's, Brush and Nittany valleys in long high rocky ridges, with ranges of cliffs on each side and broken off sharply at their western end.* Let us take the case of the west end of the Nittany mountain in Centre county. Thousands of years ago the mountain did not end where it now does, but extended fur- ther west; and ages before that old time it extended still fur- ther west, indeed all the way to the Juniata river. In fact, Nittany mountain at that time extended to and was merely an extension of Canoe mountain in Blair county. In like manner Brush mountain once extended westward and united with Tussey mountain. Short mountain once ran past Aaronburg, Millheim and Spring Mills to join Tussey mountain, and Egg hill was part of it. The same is true of the two beautiful mountains which project westward into Kishacoquillis valley. There was once a time when the northern knob was extended to meet the Standing Stone mountain atMilroy ; and the southern knob continued on through the center line of the valley towards Reedsville. The proper way to express the fact, then, is to say that the cliff knobs of No. IV show how far the destruction of the formation by sunshine, frost and rain in the synclinals up to the present time has gone. In each instance a rocky knob marks the exact center line of a synclinal basin ascend- ing into the air ; and on the other hand every long sloping red shale nose of a mountain of No. IV marks the. exact center line of an anticlinal arch descending into the under- ground. With this clue in hand the student of our geology *The term broken off, is that which an artist would use, or a mere topo- grapher, or railroad engineer ; but the student of geology ought not to use it if he can find any substitute for it ; for there is no geological break at the ends of these craggy mountains. Let this be well remembered and under- stood, for otherwise the most important geological idea of this subject will be lost CRESTS, SINGLE AND DOUBLE. 695 cnn find his way through the hilly labyrinth of middle Pennsylvania. The elaboration of this subject has been intentionally carried to an unusual length and minuteness in the foregoing pages, because the laws of Structure and Erosion, expressed on so grand a scale by the outcrops of IV, hold good in the million details of structure and erosion on a smaller, and on the smallest scale, in all the other Palaeozoic formations, whether regarded in mass, in groups of strata, or in one single layer. Therefore further allusion to the subject will not be necessary in other parts of this book beyond occa- sional references to what has been written in this chapter. Crests, single and double. E. The fifth question to be answered, namely : Why the southern mountains of No. IV have a single crest and two slopes, while the northern mountains of IV have but one crest and a terrace, and the northernmost of all, the Bald Eagle, two crests and no terrace, can be easily an- swered by merely pointing to the fact, stated in the last chapter, that Formation No. IV is practically a single sheet of sandrock at the southern side of the district, and a double sheet of sandrock at the northern side of it. To state the fact more precisely : In the Kittatinny mountain facing the Great Valley the Onieda conglomerate, the bottom member of No. IV, is coarser, and more massive, and has resisted erosion best ; while the Medina strata are not only comparatively thin, but are weakened in their resistance to erosion by large intervals of softer rocks ; so that the whole northern slope has been worn down by the weather without leaving any very bold terraces. In Perry, Fulton and Franklin counties the Oneida is thin and has a mass of harder massive rocks above it which make the top of the mountain, with a pretty regular slope, showing slight in- dications of terraces. But in the middle and northern groups of mountains of IV the formation consists of very massive Oneida at the bottom, and still more massive Medina at the top, the two separated by a thick, soft, red mass. The Medina therefore makes the crest of the mount- 696 GEOLOGICAL SURVEY OF PENNSYLVANIA. ain, protected by the softer but still pretty massive middle division; while the Oneida, undermined by the soft sin re ormation of No. Ill on which it rests, unable to rival the Medina in its resistance to the weather, and therefore in its height, is necessarily left as a bold terrace on the outcrop slope, about two-thirds as high as the crest of the mount- ain. In the majority of cases the dip of the formation as a whole, whether toward the south or toward the north, ranges between 40 and 60 ; so that the Medina upper slants upward through the mountain as its central rib or plate from base to crest, its cliffs overhanging the terrace of Oneida below. Difference in tlie height of mountains of IV. F. The sixth point of topographical interest to be ex- plained geologically is the fact of the Bald Eagle mountain having two crests of equal height and no terrace ; and the additional fact that this mountain with two crests is in- ferior in height to the opposite Tussey mountain, which has but one crest and a terrace. In Tussey mountain the upper Medina is thick and the Oneida thin ; whereas in Bald Eagle mountain the upp^r Medina and the Oneida are of about equal thickness. In Tussey mountain therefore the upper Medina makes a high crest and the Oneida a terrace ; whereas in Bald Eagle mountain each makes a separate crest. The inferior height of the Bald Eagle mountain is due to the fact that its stratification is vertical. This leads us to the consideration of another law of topo- graphy, namely that (other things being equal) the relative heights of mountains is determined by the angle at which their rocks lie to the horizon ; the flatten the rocks the higher the mountain; the steeper the dip the lower the mountain ; the steepest dip (90) makes the lowest mount- ain. Surface erosion, that is, the gradual destruction of strata at their outcrops, comes about as a double process of undermining, and toppling down. However hard and massive a formation may be, and therefore in itself consti- KEEL MOUNTAINS OF IV. 697 tuted to resist erosion, its powers of resistance will not avail it, if it lies, at a moderate slope, upon a soft, easily weather- ing formation underneath. For, as the underlying softer rocks are removed by the weather, the overlying, massive, hard rocks tumble down in blocks separated by the cleavage planes. But if the underlying softer formation has in it numerous interstratih'ed beds of hard rock, its own rate of erosion is made slower thereby, and the overlying forma- tion is less rapidly undermined ; consequently its height above the valleys remains always relatively greater. But when the stratification is vertical, a lower massive formation (like the Oneida) can no longer give a protective support to an upper massive formation (like the upper Me- dina}. Each must take care of itself separately. It is a case of "divide and conquer." The sunshine, frost and rain have the mountain at a disadvantage, and reduce its relative height to a secondary rank. This interesting law of erosion illustrates itself by producing various features of topography which are inexplicable to minds not familiar with the character of the war which is perpetually waged between the attacking and defending parties, the elements of erosion on the one side, and the rock constituents on the other. One beautiful illustration of the way in which the rocks support each other against the assault of the weather may be found in the synclinal knobs ; for, in these knobs two outcrops come together and are therefore united in self-de- fense. In addition to their union they lie horizontally along the center line of the basin. The anticlinal knobs are still better protected, and are therefore relatively higher than the synclinal knobs, as shown in the sketch of Tussey mountain as seen from the top of Terrace mountain, back of Stonerstown, in Huntingdon county (Fig. 42, p. 143, of Manual of Coal). Keel mountains of IV. Before leaving the subject of the crests and terraces of No. IV, the most beautiful phenomenon in the topography of middle Pennsylvania must be mentioned. When two GEOLOGICAL SURVEY OF PENNSYLVANIA crests converge and become one. projecting as a single high narrow ridge, between two limestone vales, and end- ing in a synclinal point, their two terraces curve and unite around the end of the point.. If the curve be a semi-circle, that shows that the synclinal is rising rapidly into the air. But if the synclinal rises very slowly the combined terraces project miles beyond the end of the crest, and then come to a similar, but lower synclinal point of their own in the limestone valley. This is the case with the two synclinal terraced mountains at the east end of Kishicoquillis valley; and it is the case with Short mountain, Brush mountain and Nittany mountain in Clinton and Centre counties. A spectator regarding these mountains from the floor of the valley, sees them end on in perspective, or as if in section, arid is struck with surprise at their symmetrical shape, re- sembling ships that have been turned over with their keels uppermost (Figs. ). For this reason they received from the geologists of the First Survey the name of Keel mount- ains of IV. Ravine system of IV. Gr. The seventh and last item of topographical interest relates to the two entirely different modes in which the two sides of a terraced mountain of IV is drained. Tussey mountain, for example, with rocks dipping south into Huntingdon county, and outcrops overlooking northward the great limestone valley in Centre. On the Huntingdon side there is a long slope of the red rocks of formation No. V, down which the rainfall delivers itself by innumerable rivulets, flowing in straight and shallow channels from crest to base. On the other or Centre county side the uppermost slope next the crest is a sheet of fallen fragments of upper Medina, stopped in their descent by the Oneida terrace, the rainfall cannot deliver its waters in straight lines to the base of the mountain on account of the massive Oneida strata which out-crop along the brow of the terrace. Consequently it cuts deep ravines sideways, right and left, in the soft lower Me- dina ; and these ravines meeting in pairs, break out through the Oneida terrace and its supporting slates of III, in deep THE ANTICLINAL VAULTS RESTORED. 699 short gorges debouching upon the limestone valley. The regularity of this system of terrace ravines is wonderful. The ravines are all alike in depth, narrowness and steepness of sides. The distance from ravine to ravine is almost ex- actly the same from one end of the mountain to the other. Each ravine has a double head, one to the right the other to the left, its branches being usually of equal length.* It is impossible to repress one's admiration at this flagrant proof, first, of the regularity of the mountain constitution ; secondly, of the equal action of the elements upon it at all points ; thirdly, at the total absence of violent, paroxysmal or irregular conduct in the processes of nature. In fact it may be said, that a student who wishes to investigate the subject of Erosion, that is, the perpetual destruction of the earth's surface by the surrounding atmosphere, and the ways in which this destruction is accomplished, could not do bet- ter than to start his investigation with a close study of the terrace ravines of No. IV; for he would tind out in his subsequent experience that this special physical phenome- non will suggest the true explanation of every detail of the features of an eroded region. The Anticlinal vaults restored. It only remains to say, that when one has familiarized him- self with a limestone valley shut in between two mountains of IV, with their even rocky crests, and ravine cut ter- races, the strata dipping always away from the valley in both directions, he cannot hesitate to drawing the conclu- sion, that as the two mountains come together at the two * See also the map of the south flank of Jack's mountain in Mifflin county, given on page plates CIV, CV, CVI, CVII in the next volume. These plates present (on a scale of |) the eastern half of the unpublished MS. map of the south flank of foot hills of Jack's mountain from Logan's Gap west to McVeytown. The map stretches westward to Mount Union and Jack's Narrows, exhibiting similar features. It was one of the earliest pieces of topographical work of the Survey (1874-75), and was intended to illustrate Report F on the fossil ore belts of the Lewistown valley, but was not finished in time for the publication ot that Report. It is now used as an illustration in the chapters on the Clinton formation, No. V. The terrace ravines are shown in fig. 2, plate XIV, p. 376 ; in plate XVII, p. 389; plate XXII, p. 400 ; and especially by the great map sheets of Morrison's Cove, in Report T, Atlas. 700 MODEL OF PLICATIONS OF IV. ANTICLINAL VAULTS RESTORED. 701 ends of the valley, so their strata were formerly united in the air above in an immense arch or vault of unbroken sand- stone miles high. This effect upon the judgment and imagination com- bined is irresistible in the case of the larger valleys. In the case of a long and narrow anticlinal valley like Black Log, a casual visitor might not be led to this conclusion, but to a very different one. His first impression would probably be that the strip of limestone land along the center line of the valley had been pushed up, splintering asunder the overlying slate and sandstone formations (III and IV), and thrusting the broken edges of the fracture to the right and left. In the beginning of the present century such was the theory of the Swiss geologists, Thurman, Desor, and others, respecting the valley formations of the Jura ; and such was the theory respecting all the mountains of the world entertained by one of the fathers of German geology, Leopold Yon Buch. Quite recently has this old and false conception ceased to mingle intimately with correcter views in many minds. The principles enunciated in this chapter nevertheless cannot be called new, for they were fully ex- plained and sufficiently illustrated in my "Manual of Coal and its Topography," published in 1856, and in Professor Rogers' Geology of Pennsylvania published in 1858. But even then they were not new ; for the whole subject of Pli- cation and Erosion was placed permanently on its proper basis of demonstrated theory fifty years ago, by the assis- tant geologists of the First Survey of Pennsylvania ; and both facts and principles were known and used by Whelp- ley, Henderson, Jackson and McKinley in their daily field work, and in the construction of the maps and sections with which they illustrated and embellished their reports. It has been recently stated as a new discovery that there is an or- ganic connection between anticlinal folds and down-throw and up-throw faults ; and the credit of this supposed dis- covery has been given to the able geologists of the United States Survey in the Rocky mountain regions. But like other applications of principle to fact in this whole sub- ject, the passage of arches into f units was so fally explained MODEL OF PLICATIONS OF XO. IV. THE ANTICLINAL VAULTS RESTORED. 703 by the early surveys of Pennsylvania and Virginia that nothing essentially new or different has in recent years been added to it, except in the one point of the distance to which Onerthrust faults have been carried horizontally, as in Western Scotland, the Alps, and the Rocky mountains. Model of the upper surface of the Medina, No. IV, after its plication and before its erosion. Page plates LVII, LVIII were made from two photo- graphs of the surface of a model constructed by me in 1886, to show the crumpled geology of Middle Pennsylvania, as contrasted with the gently waved structure of the whole country back of the Allegheny mountain (the western and the northern counties) and the almost wholly undisturbed condition of things in the Pocono and Catskill mountain region on both sides of the upper Delaware river.* *I planned this model In 1841 while I was drawing the thirteen long sec- tions across the State which Prof. H. D. Rogers published in 1858 along the bottom border of my State Map. But the data obtained by the First Survey did not seem to me sufficiently precise. When the Second Survey was organized in 1874 I waited until the surveys of the middle counties could be mapped, with local sections abundant enough to cover the whole area. By 1886 most of the county maps had been published on a scale of two miles to the inch, with well-defined limits to the formations. In 1885 1 published, in Report X, count3 r maps of the whole State on the scale of six miles to an inch. Of these I selected enough to cover a sufficient area, and afford a sat- isfactory basis for a model. There are but two methods of making such a model ; one is to cut it down to fixed limits ; the other is to build it up from a base plane. With hypso- metrically surveyed contour line maps of the surface the simplest method is to jig out the contours in paper, card board, or veneer wood ; pile them on one another ; paste, glue or tack them fast ; cover them with wax ; tool the whole to a smooth surface ; cast a mold ; from the mold cast a positive ; and finally tool it to satisfaction. In 1856 I made such a model of the Johnstown district in Cambria and Somerset counties, from Edward Smith's contour map of the country for the Pennsylvania railroad. Sheets of paper repre- senting Smith's 10-foot contours were scissored by myself and my wife in the evenings, and the result was a very beautiful model, the photograph of which was made into a relief plate and published in 1877 in Report H2, page 92. But it was a tedious and laborious job. Most of the models of the Second Survey have been made in this manner, chiefly by Mr. E. B. Harden, topographical assistant of the survey. The process requires nothing but accurate, patient labor. Another method is to construct cross sections at various intervals across the area to be modeled, and as nearly as possible at right angles to the 704 GEOLOGICAL SURVEY OF PENNSYLVANIA. The model is limited on the south by the Maryland and YV. Virginia state line, from Adams county to Fayette county ; on the southeast by the range of the South mount- ains, the Reading and Durham hills, and the Highlands of New Jersey and New York : its lower left hand corner is strike ; draw them on slips of paper, wood, lead, zinc, or block tin ; leave the bases of the strips straight cut the upper section surface lines ; arrange the strips on a solid basis at their true geographical distances from one an- other ; nil in the intervals with plaster or wax ; and tool the whole model to the upper section lines. This, however, requires the eye and hand of an artist ; but it has the advantage of a more delicate and truthful treatment of the intervals between the section slips, governed and guided by the topo- graphical features of the survey map of the region modeled. The geological artisst is not encumbered with the solid plates of the first method, and can work freely in correcting and bringing out to clear view the characteristic fea- tures of the topography, provided he has studied them himself and appre- ciates their character. This method can safely be adopted only by the geolo- gist who has done the field work himself, and it cannot be safely delegated to office hands. I used a modification of this process for a model of Morrison's Cove, in 1853, for the Pennsylvania Railroad Company, to show the iron ore horizons. I took prisms of soft wood 18" long, 3" wide and 2" thick, and drew on their contiguous sides duplicate geological sections ; then tooled down the surface of each block. When laid side by side in a series, the surface of the country was exhibited topographically. By separating the blocks the geological structure on the cross lines between block and block could be consulted. The surface of the whole series was painted to show the outcrop belts. In constructing other local geological models I have found this method much more satisfactory than the method of jigging and building up. But in making my model of the corrugations of middle Pennsylvania I was compelled to use the method first described, on account of its rapidity of execution, since I accomplished in six weeks what would probably have cost me as many months of labor by the method of cross sections. A descrip- tion of the details will be useful to geologists who are not familiar with such work. I first laid the colored geological Hand Atlas county maps together to cover the field. I divided the field into four parts by equal N. W. interval lines to make four models which could afterwards be cast in one. Then I drew on tracing paper the outcrop limits of the formations above and below the Medina. The known thickness of the overlying formations gave the depth of the top of Medina in reference to sea level. Sea level was the nor- mal datum of the model. The deepest sea level of the top of the Medina was adopted as the plane base of the model. The contour lines of the top of the Medina were determined by measuring down from the contour limit lines of all the upper formations. Account had to be taken of the known thin- ning of all the formations northwards and westwards. The columnar sec- tions governed the whole process. When the dips were steeper a reduction for angle had to be made. When the dips were gentle, no such reduction was necessary, as the error would be trivial. In the end I obtained an un- UPPER SURFACE OF MEDINA, NO. IV. 705 in Butler county. The area exhibited is about 230 miles long by 130 broad. The scale adopted was that of the small county maps in the Hand Atlas, Report X, 6 miles to the inch. The photograph plates reduce the scale to about 33 miles to the inch. It was essential to my design of a true representation of the amount of plication that the vertical scale of relief should be the same as the horizontal geographical scale, a principle which has been kept in view in the construction of all cross sections published in the Reports of the Survey from the beginning. No matter how gentle the gradients they must conform to nature. The human eye is a perfectly competent instrument and may be safely trusted to notice and estimate accidents of relief of the minutest size and most delicate variation from the horizontal. Nothing should be left to the imagination. Science gains nothing and loses much by any exaggeration under any circum- stances. There is no such thing as meeting nature half- way. Absolute truth in relationships is as necessary for knowledge as correct understanding of individual things. For plate .L/VII the model was photographed upside down, with a slant light from the left (S. E.) to bring out the master feature of the structure, the Nittany Valley or Bald Eagle Mountain Anticlinal, which occupies in crescent shape the center of the area. As its western slope is very steep, in parts vertical, the shadow cast is heavy. The prevalence of steeper western than eastern slopes in the case of most of the other anticlinals is marked on this plate ; especially in the case of the three great anticlinals which lap each other and make the southern border of the First Anthracite coal field from Mauch Chunk, Tamaqua and Pottsville to the end of the Dauphin county basin, and so onwards through Perry and Cumberland county into Franklin. The echelon arrangement of this combined over- derground contour line map of the top of the Medina approximately correct. It was only necessary afterwards to take the curves of dip in the air to re- store the aticlinals destroyed by erosion, and the model was complete. The scale being 6 miles to the inch horizontal and vertical alike, an inch of height represents 31,680 feet. 45 706 GEOLOGICAL SURVEY OF PENNSYLVANIA. thrown anticlinal is very remarkable and could be well ex- hibited only by a model seen under a S. E. slant light. For Plate LVIII the model was photographed erect under a slant light from the left (N. W.) to bring out other fea- tures ; especially the Anthracite synclinals and their con- tinuation southwestward into Maryland. The reader will notice that from Carbondale (an inch below the center of the top line of the plate) there is a continuous synclinal trough, much crumpled in the center of the plate (Seven Mountains), with a local deep hole (Broad Top), shallowing into Maryland. It will be noticed that the Nescopec anti- clinal of Luzerne county, which separates the Middle and Northern Anthracite basins, keeps on as the anticlinal of Kishicoquillis valley and Jack's mountain, dying down in Bedford county. The crescent shape of the corrugations of the region is visibly explained by Plate LVII, which brings into relief the great Nittany anticlinal. By taking its crescent as an arc of a great circle, and drawing a radius from its middle and highest point (in Centre county), southeastward towards the head of Chesapeake bay, it will be made evident that along that radius was exerted the maximum force of the horizontal thrust which displaced the formations and piled them together in folds. By laying a string upon the model along this radial line, I found that the forward thrust of the earth crust (so far as the Medina can indicate it) was at least 40 miles. It is worth noting also that the Bald Eagle Mountain and Black Log Mountain faults are southwest of said radius, and have their right hand (N. E.) side walls thrust forward. Conformity of IV upon 111. \ 1 have expressed my opinion on this interesting geolog- ical topic in the third report on Lehigh and Northampton Counties, D3, Vol. 1, 1883, pp. 32 to 35. A non-conformity of the Oneida conglomerate, No. IVa, upon the top of the Hudson river slates, No. Ill, has fre- quently been asserted. In Pennsylvania they appear to be quite conformable ; no erosion of the uppermost slates of CONFORMITY OF IV UPON III. 707 III previous to the deposit of the conglomerates and sand- stones of IV having been noticed. At the Rondout quarries in New York the Helderberg limestones seem to lie upon the upturned edges of the Hud- son river slate. At Catskill village they appear to lie di- rectly but conformably upon the slate. Mr. Davis in his recent beautiful memoir (quoted in G 6 ) states in his text and shows in his sections an apparently perfect conformdbility of the Lower Helderberg limestones (JVo. VI) upon Hudson river sandstones and slates (No. Ill] in the vale of the Catskill, a mile or two back from the Hudson river; with an apparent absence of the Clinton ( V) and Medina and Oneida (IV) which usually intervene. Although the district of country in which these phenom- ena present themselves is small, yet, out of these local phe- nomena an hypothesis has been framed and made to apply to a thousand miles of the continent, viz : that the Hudson river age closed not merely with a disturbance of the re- lations of land to sea, resulting in the shifting of coasts and the deposit of gravels and sands (which might be easily admitted), but with huge elevations and upturnings of the sea-bed, extensive erosion, and the deposit of horizontal upon vertical strata.* * S. A. Miller in his N. A. Geol. and Pal. 1889, p. 48, says : It always rests unconformably upon the Hudson river group, and bears the internal evi- dence of having been derived from land immediately north and east, and of having been deposited in shallow water, subject to waves and currents which transported only short distances. The conglomerate indicates a shore-line and rapid deposition, and is almost non-fossiliferous, although a few frag- ments of fucoids and shells, generally too imperfect for definition, ba^e been found in it The sandstone too bears the evidence of having been deposited near the land in shallow water, not only in wave-lines, rill-marks about shells, and ripple-marked slabs, but in mud-cracks produced by sun-drying. In all these respects it compares with the Potsdam, which separates the Ta- conicfrom the Lower Silurian." Certainly a sand deposit that extended from May Hill in England to Lake Huron and Tennessee in America, must exhibit the character of a shore de- posit in some places, but could not possibly have done so everywhere. Cer- tainly in its many hundreds of miles of outcrop in Pennsylvania itshows noth- ing of that character. The fine grain of almost all of the sandstone layers of its upper and lower divisions and the loamy nature of its whole middle di- vision, is satisfactorily good evidence that the great Medina sea was not shallow, but deep ; and the pebbles of its conglomerate beds are so small 708 GEOLOGICAL SURVEY OF PENNSYLVANIA. To this I object : 1. the almost universal conformability of the Oneida upon Hudson river formation ; 2. the ab- sence of pre-oneida plications; 3. the impossibility of ob- taining the principal materials of the Oneida conglomerate, out of any known Hudson river strata ; 4. the fact that Oneida deposits still remain far south of the Hudson river belts (as at Greenwood lake in New Jersey) ; 5. and above all, the fact that at the Schuylkill Water Gap, where the Oneida rests at right angles on the apparently eroded edges of Hudson river slate, there is in reality a snapped anticli- nal and downthrow of the slates, and no unconformability. Mr. Davis shows the Lower Helderberg conformably over- lying the Hudson rioer "sandstones," in a synclinal. At first glance this would seem to settle the question of land elevation and subsequent subsidence ; and he there- fore speaks of a long interval of time (Oneida, Medina and Clinton ages) during which no deposits took place. But a little consideration will serve to show the uncer- tainty of this kind of evidence. For, during all these ages it no doubt rained as often as it rains now ; and if so, all land surfaces must have suffered erosion ; and yet the Hud- son river slates in his Catskill section are not eroded ; they could not therefore have been rained on i. more ridiculous than the report of silver veins in any mountain of IV. As gold goes with quartz silver goes with limestone. If there were faults filled with lead ore in the Medina Mountains more or less silver, if only a trace, would be found in the lead ore. But no lead ore vein is known in Pennsylvania in any of its mountains of IV. The lead ore is con- fined to the limestone valleys. The remarkable cross fault lead veins of [the Schwangunk Mountain of IV east of the Delaware have already been noticed. None such have been MINERAL WORTHLESSNESS OF MOUNTAINS OF IV. 713 in these mountains. All the old Indian stories about lead ore, and all the lying assurances of wandering miners that they have discovered gold and silver ores in the mountain amount to nothing at all. As for iron ore the only show of it is in the slates just under the sandstone near the summit. These top slates con- tain enough iron to coat the stones, and to make little iron ore bogs lower down the slope where the springs of water issue. The iron-coated sandstones are of course worthless. The bog ore is good enough, what little there is of it, and mixes nicely with other ores ; but the farm clearings where these bogs lie can hardly be said to be a dollar more valuable for them. There is no iron ore bed which could be found by searching for it. The iron is distributed through the slate and cannot be mined.* On the backside of the mountains of IV run outcrops of the valuable iron ore beds of the Clinton formation No. V, noticed in that mountain from Port Jervis westward in New Jersey, nor in any mountain of IV in Pennsylvania. When I was surveying the Strouds- burg country in 1839, I learned that a geological tramp from Germany had been deluding the people into preposterous mining operations in the Pocono Mountain. There were traditions of sixteen different Indian silver ore veins in the Kittatinny Mountain east and west of the Wind Gap. This impostor told the people that he had found one of these veins, had traced it across the Aquanchicola Creek valley, across Godfrey's ridge, across Broad- head's creek near Stroudsburg, across the Devonian hills to the foot of the Pocono Mountain escarpment and up the escarpment to a place where it could be successfully mined. He collected one or two thousand dollars in small sums from the farmers and village storekeepers, and kept him- self and one or two hands at work for eighteen months making a large hole in the face of the mountain, and then disappeared leaving the hole behind him. Such is a history of fraud many times repeated in the last fifty years. * One remarkable exception to this statement must be noticed. There is a gash fault across Black Log Mountain west of Orbisonia in Huntingdon county, which was filled with limonite iron ore long before the mountain and valley surface of that country was established at the present level. Nothing of that sort escapes the keen eye of the hunters and farmers of any region. The search for iron ore keeps men and boys on the qui vive ; and this curious and exceptional deposit was exploited by furnace men and ex- hausted. No other such instance is known in our state, and probably no other exists. It is strictly analogous to the lead veins of the Schawngunk Mountain east of Port Jervis ; for the Black Log Mountain is shivered by cross faults in the same manner ; as exhibited in the Rock Hill Gap and in the gangways of the fossil ore mine southwest of Orbisonia. 714 GEOLOGICAL SURVEY OF PENNSYLVANIA. block ore aud fossil ore. These beds have been foun dand opened here and there along the North Mountain, but with- out financial success. In 1839 I discovered the block ore just behind the mountain on the bank of the Little Schuyl- kiJl opposite Port Clinton. Since then the bed has been opened ; but the attempt to mine it was abandoned ; the ore was poor and the bed thin. And this appears to be the case along the whole line for a hundred miles. Back of Cowan's Gap in Fulton county it was tried. In the Lit- tle Cove southwest of Mercersburg it is of little value. But this has nothing to do with the Oneida and Medina. If any religious mind asks why God made the mountains of IV without a single valuable mineral in it a question which has been more than once put to me respecting other mountains mineralogically worthless the answer is a plain one and should be satisfactory to any reasonable man. Mineral value is not the only kind of value. The true worth of mountain land is to cool the air and condense its mois- ture into rain, to feed the streams which supply the valleys, and to preserve the forests. For such benefits as these the inhabitants of the Great Valley should be ever thankful to the North Mountain without looking so fine a gift horse in the mouth or pining for gold or silver mines, which after all are not half so desirable as fertility and water power. FOSSILS OF ONEIDA AND MEDINA NO. IV. 715 CHAPTER LIV. Fossils of Oneida and Medina No. IV. The whole formation is remarkably destitute of remains of animal and vegetable life. The abundance of molluscan and crustacean forms in the preceding Trenton and Hudson River ages seem to have given place to a barrenness of all living existence. Nothing but the stony casts of macerated seaweeds are to be found in the two or three thousand feet of rock strata of Oneida and Medina age in Pennsylvania. These are so abundant in some places as to cover extensive surfaces of the sandstone beds. Their forms are repre- sented on plate CXI, page 716. They are most abundant in the upper division.* This species of seaweed is called Arthrophycus Tiarlani. The surfaces of great slabs torn from the Tussey Mountain outcrops on the Juniata and floated by ice down the bed of the river, are completely covered with a network of its stony casts in high relief. In New York State James Hall describes from the mid- dle division of IV two small lamellibranch shells Cypricar- dia orthonota, and Modiomorpha alata (Conrad's Unio primigenius), and two small gasteropod shells, BelleropJion trilobatus (Conrad's Planorbis trilobatus) and EnompTia- lus (Cyclostoma, Pleurotomaria} pervetustus. the earliest known appearance of this kind of shell. Dana says that one of the most common Medina brachiopod shells is the *Prof. W. B. Rogers, Geo. Va., 1884, p. 175, says that "near the upper limits of the group, as well as in the shaly bands beneath, organic impressions are often abundantly discovered. The thin slabs of buff and olive sandstone lying near the top are particularly rich in these remains, among which may be noted as abundant a small globose terebratula, and at least two well characterized species offucoides [sea weeds]. Cylindrical markings, simi- lar to those of No. I, are often exhibited in great numbers in the more com- pact and fine-grained white or pinkish white strata. 716 GEOLOGICAL SURVEY OF PENNSYLVANIA. HarUnla halll. (Go.pp.rt. Fo. Klor. de. Ueberg, 1. ~ Conrmd. (tic. Trfn/bn in Pa. Collect*? from /to, at Pert C2w ton; and front IVi.c, ' Omitted from "&*nf*fou * /U/a/At above