THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
 LOS ANGELES
 
 The RALPH D. REED LIBRARY 
 -> 
 
 DEPARTMENT OF GEOLOGY 
 UNIVERSITY OF CALIFORNIA 
 
 LOS ANGELES, CALIF.
 
 /) ^ '~i 
 
 &*&*-
 
 Iff?
 
 
 

 
 GEOLOGICAL STUDIES; 
 
 OR, 
 
 ELEMENTS OF GEOLOGY. 
 
 FOR 
 
 HIGH SCHOOLS, COLLEGES, NORMAL, AND OTHER SCHOOLS. 
 
 PART I. GEOLOGY INDUCTIVELY PRESENTED. 
 PART II. GEOLOGY TREATED SYSTEMATICALLY. 
 
 WITH 367 ILLUSTRATIONS IN THE TEXT. 
 
 BY ALEXANDER WINCHELL, LL.D. 
 
 PROFESSOR OF GEOLOGY AND PALAEONTOLOGY IN THE UNIVERSITY OF MICHIGAN, FOR- 
 MERLY DIRECTOR OF THE GEOLOGICAL SURVEY OF MICHIGAN, AUTHOR OF 
 " GEOLOGICAL EXCURSIONS," FOR ELEMENTARY SCHOOLS, ALSO 
 OF ' 4 SKETCHES OF CREATION," "WORLD LIFE,' 1 
 ETC., ETC. 
 
 SECOND EDITION 
 
 CHICAGO: 
 S. C. GRIGGS AND COMPANY. 
 
 188T.
 
 COPYRIGHT, 1886, 
 BY S. C. GRIGQS AND COMPANY.
 
 Geology 
 Library 
 
 * 
 
 m 
 
 "THE diffusion of that which is specially named science has at the same 
 time spread abroad the only spirit in which any kind of knowledge can be 
 prosecuted to a result of lasting intellectual value." PROFESSOR JEBB. 
 
 "All the subjects which the sixteenth century decided were 'liberal' are 
 studies in books; but natural science is to be studied not in books, but in 
 things." PRESIDENT ELIOT. 
 
 "The genesis of knowledge in the individual must follow the same course 
 as the genesis of knowledge in the race." 
 
 "Every study should have a purely experimental introduction." HER- 
 BERT SPENCER. 
 
 "Were I dictator, I would drive all teachers of science out into the great 
 field of dead work; force them to go through all the gymnastics of original 
 research and its description, and not permit them to return to their libraries 
 until their note books were full of their own measurements and calculations, 
 sketch maps, and farm drawings, severely accurate, and logically classified, 
 to be then compared with those recorded in the books." JOSEPH P. LESLEY, 
 
 
 766287
 
 PREFACE. 
 
 rj^HIS work on the elements of geology is intended as a guide 
 -L in the observation of nature, and a synoptical record of the 
 more important tacts and doctrines of the science. The reader 
 is supposed to be desirous of laying substantial foundations for a 
 geological education, and to have attained such mental develop- 
 ment as to require a text book more advanced than the Author's 
 "Geological Excursions." The method, as in that work, is an 
 appeal to the powers of observation; and the facts cited are the 
 most familiar and most accessible. Happily, the widespread 
 Drift of the northern portion of the continent brings to nearly 
 every student's door a body of phenomena so similar as to supply 
 an intelligible common starting point for a very large proportion 
 of the United States and Canada; while for students of the 
 southern states, any inconveniences may be easily overcome. 
 Though this method is believed to be unique, it is, without ques- 
 tion, the method which best comports with the order of develop- 
 ment of the mental faculties, and must prove most easy and 
 gratifying to the student. It is the application to geology of 
 those sound principles which have come into vogue among the 
 best modern teachers of the other sciences of nature. That it is 
 entirely practicable is shown by the personal experience of the 
 Author, and of many other teachers who have used the more 
 rudimental work above mentioned. 
 
 What there is among the universal phenomena of the Drift to 1 
 serve as the elementary data of geological science will perhaps be 
 best understood by turning over the earlier pages of the First 
 Part of the book. The Author does not, however, imagine the 
 pupil a mere recording instrument; but bears in mind the fact 
 that the dawn of reflection is simultaneous with the exercise of
 
 v i PREFACE. 
 
 perception. The observer begins immediately to group phe- 
 nomena to generalize, and to inquire after those uniform 
 antecedents which science denominates causes. The Author 
 encourages this tendency by pausing occasionally to review, to 
 summarize, to induce a general principle, and even to theorize a 
 little. Thus, in the First Part, scientific method is unknown. 
 The science is growing up in the learner's mind simultaneously 
 and symmetrically in all its departments, just as it grew in the 
 intelligence of mankind. 
 
 A little later, after the nearest phenomena have yielded their 
 lessons, the learner is led from home to widen his observations. 
 Well, indeed, if the travel can be real, like the earlier excursions 
 into the neighborhood. But the impracticability of this, as a 
 rule, is offset, as far as possible, by graphical illustrations. In 
 many cases, it may be further offset by specimens, models, and 
 diagrams. These the school, or the teacher, or even the pupil 
 himself, may, to some extent, provide. As, after all, many 
 things can only be known from descriptions, the effort has been 
 made to have them intelligible. 
 
 The purpose to begin with the Drift has led to a more careful 
 study of common minerals and rocks than has heretofore been 
 undertaken in elementary works; but this feature, the Author 
 believes, requires no defence. On the contrary, he is already 
 assured that the tables provided for determinations of minerals 
 and rocks from their most obvious characters will receive a hearty 
 welcome; and will satisfy many longings to know something 
 more about the objects which are absolutely the most obtrusive 
 and familiar which we encounter. 
 
 The same purpose has led to a more particular study of some 
 common types of fossils than has ordinarily been thought appro- 
 priate. But this study has been restricted mainly to examples 
 widely distributed in the Drift, and therefore generally obtaina- 
 ble; and it has been pursued only far enough to illustrate how to 
 study fossils in a scientific way. 
 
 The outcome of the First Part is a somewhat chaotic and 
 undigested mass of facts and doctrines, buried in a considerable
 
 PREFACE. vii 
 
 volume of verbiage. It does not, assuredly, supply the means 
 for a methodized apprehension of the elements of the subject. 
 But it supplies many fundamental facts, many great principles, 
 many impressions, many hints for personal observation, and many 
 impulses to continue. Far better for the student to get so much 
 than to leave school in total ignorance of a science which sus- 
 tains so important relations to industries, to culture, and to civili- 
 zation. 
 
 Part II is the complement of this. Here the whole body of 
 facts and principles is reduced to methodical re-presentation; 
 though the necessity of abridgment has led, in some of the 
 chapters, to mere references to the First Part, instead of recast- 
 ings of the matter. Here, too, the discussions of the several 
 topics are completed, and the various portions are adjusted to a 
 logical relation. The last chapter is a rapid historical sweep over 
 the whole range of terrestrial events. To a limited extent, 
 therefore, the book may be used for elementary reference. But 
 it must not by any means be conceived as intended for a manual. 
 The method of a manual is suited only for advanced students 
 and investigators. A very different method is demanded by be- 
 ginners. This is only to a limited extent even a "text book." 
 That term savors of an educational method which is obsolete and 
 repugnant. The present work is a guide to the study of nature, 
 and a synopsis of the elementary facts and principles of geolog- 
 ical science. 
 
 Because the work is elementary, it has been restricted almost 
 wholly to American geology. But no well beaten path has been 
 pursued. The recent additions to our knowledge of American 
 geology have greatly transformed the science, and the subject 
 has to be treated very much as if no elementary books had been 
 written. Recent investigations have placed us in possession of a 
 large body of information about the remote interior and the 
 Pacific slope, and the vast region north of our national boundary. 
 To this fresh information the author has attempted to give due 
 attention. It will be found a feature of the work, that it sur- 
 passes other elementary books in its presentation of western
 
 PKEFACE. 
 
 geology, especially in its great features and its great historical 
 facts. 
 
 The author's obligations, of course, lie in every direction; 
 they are, indeed, too many to enumerate. But the effort has 
 been made to draw less on the writers of text books than on 
 original sources. To his publishers, his indebtedness and that of 
 the public is great, for that intelligent liberality which has 
 prompted them to demand, regardless of cost, the best style of 
 graphic illustration, and a perfection of mechanical execution 
 which will scarcely be found surpassed. 
 
 The author entertains the hope that he has here brought 
 within reach of his fellow-workers in the advancement of popu- 
 lar education some improved means for placing geological study 
 where of right it belongs side by side with the most esteemed 
 and most favored agencies of material prosperity, of civilization, 
 and of culture. 
 
 UNIVERSITY OF MICHIGAN, Ann Arbor, June, 1886. 
 
 PKEFACE TO A NEW EDITION. 
 
 THE exhaustion of the first edition of this work within six 
 months of its introduction into use is sufficient evidence of 
 its acceptability as an elementary guide to the science of geology. 
 Among the numerous opinions which have reached the author 
 respecting its method and matter, no one is seriously adverse, 
 while commendations are almost unlimited in number. Yet the 
 author begs to request teachers in schools where the time given 
 to geology is quite brief, to remember that the bulk of Part I. 
 results partly from the method of treatment; and that method is 
 chosen for the purpose of rendering the subject entertaining, and 
 building up a knowledge of it in a natural way. For a brief 
 course, Part I. may be taken by itself; and then Part II. may be 
 taken later. Also, the studies of fossil corals and shells in Part 
 I. may be postponed, as well as the palaeontological portions of 
 Part II. ; and these may be taken up subsequently as a course in 
 palaeontology. 
 FEBRUARY, 1887.
 
 CONTENTS. 
 
 PART I. FIELD STUDIES; 
 
 OB, INDUCTIVE GEOLOGY. 
 How WE MAT OBSERVE THE FACTS, AND LEARN THEIR MEANING 
 
 STUDY I. SURFACE MATERIALS, . . 1 
 
 STUDY II. SPRINGS AND WELLS, 7 
 
 STUDY III. BOWLDERS, 12 
 
 STUDY IV. A LITTLE CHEMISTRY 18 
 
 STUDY V. QUARTZ AND FELDSPAR, 23 
 
 STUDY VI. DARK COLORED MINERALS, . 29 
 The Micas and lamellar species; Amphibole, Py- 
 roxene, Hypersthene. 
 
 STUDY VII. LIME, MAGNESIA, AND IRON MINERALS, ... 34 
 Calcite, Dolomite, Gypsum, Haematite, Magnetite. 
 
 STUDY VIII. REVIEW OF THE IMPORTANT MINERALS, ... 39 
 
 Table of Composition, 40 
 
 Table for Determinations, . . . .42 
 
 STUDY IX. QUARTZOSE ROCKS, ... . 44 
 
 STUDY X. MICACEOUS, AMPHIBOLIC, AND PYROXENIC ROCKS, . . 50 
 
 I. Micaceous Rocks, ..... ,50 
 
 II. Amphibolic, and Pyroxenie Rocks, . . 52 
 
 STUDY XI. PELSITIC, HYDROUS MAGNESIAN, AND ALUMINOUS ROCKS, 56 
 
 I. Felsitic Rocks, 56 
 
 II. Hydrous Magnesian Rocks, . . .58 
 
 III. Aluminous Rocks, 60 
 
 ix
 
 x CONTENTS. 
 
 STUDY XII. CALCAREOUS ROCKS, . . . ' . .61 
 
 STUDY XIII. CARBONACEOUS, IRON ORE, AND ERUPTIVE ROCKS, . 67 
 
 I. Carbonaceous Rocks, ..... 67 
 
 II. Iron Ore Rocks, 69 
 
 III. Eruptive Rocks, . - . . . .70 
 
 STUDY XIV. RETROSPECT OF THE ROCKS, 72 
 
 Table of Rock Structure, . . . . .74 
 Table of Rock Composition. . . . .75 
 Table for Rock Determination, .... 76 
 
 STUDY XV. SEDIMENTATION, . . . . . .80 
 
 STUDY XVI. EROSIONS, . 87 
 
 STUDY XVII. STRATA, AND WHAT THEY TEACH, .... 97 
 STUDY XVIII. FOSSILS, AND WHAT THEY TEACH, . . .102 
 STUDY XIX. How THE STRATA ARE DISPOSED, . . . .108 
 STl'DY XX. GEOLOGICAL MAPS. . ' - , . . . . .116 
 STUDY XXI. GEOLOGICAL SECTIONS, . . . "~ . .123 
 STUDY XXII. THKRMAL WATERS, . . . . . .129 
 
 STUDY XXIII. VOLCANOES, 138 
 
 STUDY XXIV. ANCIENT LAVAS, 150 
 
 STUDY XXV. MOUNTAIN PHENOMENA. ...... 160 
 
 STUDY XXVI. MOUNTAIN FORMATION. 169 
 
 STUDY XXVII. VEINS AND ORES, ... .- . . .177 
 
 STUDY XXVIII. GEOLOGY OF SALT .186 
 
 STUDY XXIX. GEOLOGY OF PETROLEUM, 194 
 
 sTI'DY XXX. EXAMINATION OF SOME CUP CORALS, . . .202 
 STUDY XXXI. FURTHER EXAMINATION OF CUP CORALS, . . 210 
 STUDY XXXII. EXAMINATION OF SOME TABULATE CORALS, . . 218 
 STUDY XXXIII. EXAMINATION OF SOME BRACHIOPODS, . . 226 
 
 STUDY XXXIV. FI-RTHER EXAMINATION OF BRACHIOPODS, . 234
 
 CONTENTS. 
 
 PART II. SYSTEMATIC STUDIES; 
 
 OR, OUTLINES OF A LOGICAL ARRANGEMENT OF THE FACTS, 
 WITH THE LESSONS THEY TEACH. 
 
 GENERAL DEFINITIONS AND DIVISIONS OF THE SUBJECT, . . . 245 
 CHAPTER I. LITHOLOGICAL GEOLOGY (Peti-oyr'tphi/), . . .248 
 
 1. Chemistry, 248 
 
 2. Mineralogy, . 248 
 
 3. Kinds of Rocks, 248 
 
 1. Physical Conditions of Rocks 248 
 
 (1) Mineral Constitution, (a) Essential Constitu- 
 
 ents. (V) Accessory Constituents, . . 248 
 
 (2) Physical Constitution, (a) Fragmental. (b) Crys- 
 
 talline, (c) Relations of Rocks to Mechanical 
 and Chemical Actions. .... 250 
 
 (3) Stratified and Unstratified States, . . .252 
 
 2. Methods of Studying Rocks, 253 
 
 3. Most Important Species of Rocks, . . . .254 
 
 CHAPTER II. STRUCTURAL GEOLOGY (Geognosy), . . . 255 
 1. General Definitions, . * 255 
 
 2. Accidents of Stratified Rocks, 256 
 
 1. Accidents of Sedimentation, ..... 256 
 
 2. Accidents of Secondary Origin, 257 
 
 3. Attitudes of Strata, 260 
 
 4. Erosion of Strata, 263 
 
 3. Conditions of Unstratified Rocks, 264 
 
 1. The Erupted Condition, 264 
 
 2. The Intrusive Condition, . . . . . .265 
 
 3. The Vein Condition, 2,65 
 
 4. Classification of Formations, 265 
 
 1. Evidences of Relative Age, 265 
 
 (1) From Superposition, . . . ... . 265 
 
 (2) Evidence from Fossils, . . . . .26(5 
 
 (3) Evidence from Intersections of Vein Matter, . 2(57 
 
 (4) Method of Combining the Observations. . . 267
 
 x jj CONTENTS. 
 
 2. The Cycle of Sedimentation, 268 
 
 3. General Terms Employed in Classification, . . .269 
 
 4. Table of Geological Equivalents, . ... 273 
 
 CHAPTER III. DYNAMICAL GEOLOGY, . . , . . 276 
 
 1. Agency of Water, .... 
 
 1. Running Water, . . . . ... 276 
 
 2. Oceanic Action, . . . ... '. 279 
 
 (1) Ocean Currents, 
 
 (2) Wave Action, ... ... 279 
 
 3. Action of Ice, .... 
 
 4. Assortment of Marine Sediments, 
 
 2. Agency of the Atmosphere, 284 
 
 1. Wear by Wind-borne Sands, . . ' . . .284 
 
 2. Sand Dunes, . . . ' ' . .285 
 
 3. Transportation of Volcanic Ashes, . . . .286 
 
 3. Agency of Heat, . 286 
 
 1. Geological Results of Former High Temperature, . 287 
 
 (1) A Primitive Molten State, . . . .287 
 
 (2) Origin of Erupted Materials, .... 289 
 
 (3) Agency of Steam in Eruptive Action, . . 289 
 
 (4) Metamorphism Filling of Veins, ... . 289 
 
 2. Effects of the Earth's Cooling, . . , . 291 
 
 (1) Contraction and Lateral Pressure, . . . 291 
 
 (2) Evolution of Heat, . . . . .292 
 
 (3) Seismic Results of Contraction, . . , . 292 
 
 (4) Mountain Making 293 
 
 5. Geological Climates, . . 295 
 
 1. Terrestrial Causes 295 
 
 (1) Greater Heat and Greater Uniformity of Primi- 
 
 tive Climates, 295 
 
 (2) Alleged Antecedent Habitability of Northern 
 
 Regions, 295 
 
 (3) Ultimate Total Dissipation of Terrestrial Heat, . 296 
 
 (4) Ultimate Extinction of the Sun, . . .296 
 
 2. Extra-Terrestrial Causes of Climate, . . . .297 
 
 6. Tidal Action in the Earth's History, 297 
 
 1. Definitions, 297 
 
 2. Seismic Consequences of Tidal Action, . . . 298 
 
 3. Tidal Evolution of Heat, . . ... .298 
 
 4. Tidal Influence on Motions of Earth and Moon, . . 299-
 
 CONTEXTS. Xlll 
 
 (1) Lagging of the Tide, 299 
 
 (2) Retardation of the Earth's Rotation, . . 299 
 
 (3) Diminution of Earth's Oblateness, . . .299 
 
 (4) Increase of the Moon's Distance, . . .300 
 
 5. High Primitive Marine Tides and the Consequences, . 300 
 
 6. Ingrained Meridional Trends in the Earth's Crust, . 301 
 
 g 7. Geotechtonic and Scenographic Results, . . . .302 
 CHAPTER IV. PROGRESS OF TERRESTRIAL LIFE, . . . .303 
 
 Definitions Fossilization Horizontal Range Vertical Range 
 
 Colonies, 303 
 
 1. Most Important Types of Plants and Animals, . . . 305 
 
 1. Plants General Classification, 305 
 
 2. Animals General Classification, . . . .306 
 
 Stem I. Protozoa. Stem II. Coelenterata. Stem 
 III. Echinodermata. Stem IV. Vermes. Stem V. 
 Mollusca. Stem VI. Arthropoda. Stem VII. Ver- 
 tebrata, 
 
 2. Nature of the Succession of Organic Forms, . . .314 
 
 1. The Succession a General Progress from Lower to 
 
 Higher, 315 
 
 2. Earlier Animals Generally Comprehensive, . . 316 
 
 3. The Graduation Not Complete, 317 
 
 3. The Dawn Animal, 318 
 
 4. Trilobites, 323 
 
 5. Crinoids, 324 
 
 6. Chambered Shells, 326 
 
 7. Fishes, 331 
 
 8. Reptiles, 335 
 
 9. Toothed Birds, 343 
 
 10. Mammals, 345 
 
 1. Mesozoic Mammals, 345 
 
 2. Tertiary Mammals, 348 
 
 11. Retrospect of Succession of Vertebrate Life in America, 357 
 
 12. Conspectus of Geological Range and Relative Expansion of 
 
 Principal Types of Animal Life, 359
 
 xiv CONTENTS. 
 
 CHAPTER V. FORMATIONAL GEOLOGY, 360 
 
 1. Preliminaries. Geological Maps, 360 
 
 2. The Eozoic Great System, 361 
 
 1. How the Term is Used, 361 
 
 2. Divisions of the Great System, 362 
 
 3. Geographical Distribution and Surface Exposures, . 363 
 
 4. General Constitution of the Great System, . . 364 
 
 5. Kinds of -Rocks and Economic Products, . . .365 
 
 6. Organic Remains, . . . . ... 368 
 
 3. The Cambrian System, . . . . . . .369 
 
 1. Divisions, Subdivisions and Terms, .... 369 
 
 2. Geographical Extension, ...... 370 
 
 3. The Continent at the Beginning of the Cambrian Age, 371 
 
 4. Cambrian Rocks and Minerals, ..... 373 
 
 5. Erosion Features, . . ' 376 
 
 6. Organic Remains, . .. . . . . . 379 
 
 4. The Silurian System, , ... 381 
 
 1. Divisions, Subdivisions, and Terms, .... 381 
 
 2. Geographical Extension, 381 
 
 3. The Continent at the Beginning of Silurian Time, . 382 
 
 4. Silurian Rocks and Minerals, . . . . . 384 
 
 5. Erosion Features, 386 
 
 6. Organic Remains, . . . ' . . . . 387 
 
 5. The Devonian System, . . . . . . . 389 
 
 1. Divisions, Subdivisions, and Terms, . . . . 389 
 
 2. Distribution and Lithological Features, . . .390 
 
 3. Erosion Features, . . ... . .392 
 
 4. Organic Remains, ....... 394 
 
 6. The Lower Cartxmiferous System 395 
 
 1. Divisions, Subdivisions, and Terms, ... . 395 
 
 2. Distribution and Lithological Features, . . .396 
 
 3. Geography of the Continent during the Lower Carbon- 
 
 iferous Age . 399 
 
 4. Erosion Features, . . . . . . . 401 
 
 5. Organic Remains, . .5*' . . . . . 401 
 
 7. The Upper Carboniferous System, 402 
 
 1. Divisions, Subdivisions, and Terms. Table of Coal 
 
 Measures, ........ 402 
 
 Standard Section of the Coal Measures, ... 403
 
 CONTENTS. XV 
 
 2. Distribution, . . 406 
 
 3. Kinds of Rocks, . . . . . . .407 
 
 4. Geological Structure, ...... 410 
 
 5. Coal Mining 413 
 
 6. Organic Remains, ....... 416 
 
 7. Origin of Mineral Coal, 421 
 
 8. Growth of the Land during the Upper Carboniferous, 422 
 
 8. The Mesozoic Great System, 424 
 
 1. Divisions, Subdivisions, and Terms, .... 424 
 
 2. The Triassic System, 424 
 
 3. The Jurassic System, 427 
 
 4. The Cretaceous System, 429 
 
 (1) Distribution and Kinds of Rocks, . . . 429 
 
 (2) Economic Products of the Cretaceous, . . 431 
 
 (3) Fossil Remains of the Cretaceous, ... 433 
 
 5. The Physiognomy of the Interior of the Continent, . 434 
 
 6. Comparative Geology of the Provinces, . . .436 
 
 7. Geological History of the Cordilleran Region, . . 437 
 
 9. The Caenozoic Great System, 441 
 
 1. Divisions, Subdivisions, and Terms, . . . .441 
 
 2. Geographical Distribution of the Tertiary, . . . 442 
 
 3. Organic Remains of the Tertiary, .... 444 
 
 4. Quaternary Materials, ...... 444 
 
 (1) Phenomena of the Surface Materials, . . 445 
 
 (2) Relation of Drift Phenomena to Climatic Causes, 446 
 
 (3) More Critical Observation of the Drift, . . 447 
 
 (4) The Terminal Moraine of the Ancient Glacier, . 448 
 
 (5) Characteristics of the Terminal Moraine, . 450 
 
 (6) Tabular Limestone Masses Imbedded in the Drift, 451 
 
 (7) Champlain Deposits, 452 
 
 (8) Quaternary Lakes 452 
 
 (9) Recent Formations, 454 
 
 (10) Organic Remains of the Quaternary, . . 456 
 
 CHAPTER VI. HISTORICAL GEOLOGY, 463 
 
 1. Presedimentary History, . . . . . . . 463 
 
 2. Inductive History, .465 
 
 1. The Eozoic JEon, 465 
 
 2. The Palseozoic^Eon, 468 
 
 (1) Movements of the Lands 468 
 
 (2) Progress of Animal Organization, . . . 469
 
 CONTENTS. 
 
 (3) The Coal Period, 470 
 
 (4) Close of the Palaeozoic, 471 
 
 3. The Mesozoic ^Eon 472 
 
 (1) Continental History, 
 
 (2) Progress of Mesozoic Life, . . . .475 
 
 4. The Ctenozoic ^Eon, -476 
 
 (1) The Tertiary Age, . .~ 476 
 
 (2) The Glacial Epoch, . . , . .479 
 
 (3) The Champlain Epoch, . . . - . .483 
 
 (4) Effects of Glacier Pressure, 
 
 (5) The Recent Epoch, . . . . . .486 
 
 3. Ulterior History,
 
 LIST OF TABLES. 
 
 COMPOSITION OF THE FELDSPARS, 
 STANDARDS OF HARDNESS, . . . . 
 COMPOSITION OF THE COMMON MINERALS, . 
 FOR DETERMINATION OF MINERALS, . 
 
 ROCK STRUCTURES, 
 
 ROCK COMPOSITION, ...... 
 
 FOR ROCK DETERMINATION, .... 
 
 TYPES OF MOUNTAIN STRUCTURE, 
 CONSPECTUS OF THE GEOLOGY OF PETROLEUM, 
 STRUCTURES OF BRACHIOPODS, .... 
 
 ANALYTICAL TABLE FOR IDENTIFICATIONS, . 
 CYCLES OF SEDIMENTATION, .... 
 
 TABLE OF GEOLOGICAL EQUIVALENTS, 
 
 MOST IMPORTANT TYPES OF PLANTS AND ANIMALS, 
 
 FORMS OF CHAMBERED SHELLS, . 
 
 SUCCESSION OF VERTEBRATES OF NORTH AMERICA, 
 
 RANGE AND EXPANSION OF ORGANIC TYPES, 
 
 STANDARD SECTION OF COAL MEASURES, 
 xvii 
 
 42 
 
 40, 41 
 
 42-44 
 
 74 
 
 75 
 
 76-80 
 167 
 199 
 240 
 240 
 268 
 
 274, 275 
 
 305-314 
 
 329 
 
 358 
 
 359 
 
 403^105
 
 LIST OF MAPS. 
 
 WINDINGS OF THE MISSISSIPPI, ....... 84 
 
 GEOLOGICAL MAP OF THE UNITED STATES (2 pages), . . . 118, 119 
 
 MAP OF ^ETNA AND ITS ERUPTIONS, . . . . . . 141 
 
 MAP OF HAWAII, SHOWING LAVA FLOWS, . . . . 144 
 
 GEOLOGICAL MAP OF NORTH AMERICA, ..... 361 
 
 COAL MAP OF PENNSYLVANIA AND OHIO, . . . . . 407 
 
 MAP OF TERMINAL MORAINE IN THE UNITED STATES, . . . 449 
 
 SUBMARINE CHANNEL OF THE HUDSON RIVER 455 
 
 ^ONIC MAPS. 
 
 NORTH AMERICA NEAR THE CLOSE OF THE Eozoic yox. . . 371 
 
 NORTH AMERICA NEAR THE BEGINNING OF THE SILURIAN AGE, . 383 
 NORTH AMERICA NEAR THE BEGINNING OF THE CARBONIFEROUS AGE, 399 
 
 NORTH AMERICA NEAR THE BEGINNING OF THE COAL PERIOD, . 423 
 
 NORTH AMERICA NEAR THE BEGINNING OF THE MESOZOIC ^ON, . 439 
 
 NORTH AMERICA NEAR THE BEGINNING OF THE CRETACEOUS AGE, 440 
 
 NORTH AMERICA NEAR THE BEGINNING OF THE C^ENOZOIC Mon, . 477 
 xviii
 
 SUGGESTIONS TO THE INSTRUCTOR. 
 
 1. Adhere scrupulously to the method of the book. Vary the facts, 
 illustrations, comments, and inferences according to opportunity or ability. 
 
 2. Do not permit any persons to thrust upon your attention, or that of 
 the pupils, any specimens not yet considered in the book. Most persons 
 have a few treasured minerals from some remote mining region upon which 
 you will be asked to pronounce opinions. Do not be annoyed by them. The 
 specimens at your door are incalculably more important. 
 
 3. Give deliberate attention to the exercises. See that every pupil learns 
 to elucidate every subject presented in them. Occasionally a question is 
 raised which even the teacher may not be prepared to solve. That is 
 intended. It is profitable to have something to study over. 
 
 4. If the class is small say, not over a dozen they may be ordinarily 
 taken into the field. This is always the best course. If the class is large, 
 the subject may be pursued chiefly in the class-room; but illustrations 
 should be abundant. In the study of minerals and rocks, a large supply of 
 specimens, all broken from the same bowlder, may be furnished, and one 
 specimen placed in the hands of each student. The teacher will then direct 
 attention to every character visible in the specimen, pursuing the same 
 method as the teacher of botany. The rock must have been previously 
 selected with reference to showing what is treated in the study appointed for 
 the day. 
 
 When this specimen is well understood, another set may be distributed, 
 and so on. 
 
 5. After a few exercises of this kind, individual students may be re- 
 quired to name such minerals in the specimen in hand as have been pre- 
 viously studied. Then, after the work is more advanced, a mixed lot of 
 specimens may be brought in, and individual students requested to deter- 
 mine them. Reports should be made on slips of paper, and returned with 
 the specimen. These may be examined immediately, if time permits, or 
 after the exercise. The student's report should state all the facts on which 
 the name of the specimen depends: Stratified or not; thick- or thin-bedded; 
 what essential minerals; what accessory minerals; the name. These exer- 
 cises should be continued for many days after the end of the subject of rocks 
 is reached in the book.
 
 XX SUGGESTIONS TO THE INSTRUCTOR. 
 
 6. Get supplies of rock specimens, if the class is large, by having two 
 students volunteer to bring a basket full on the following day, and two others 
 to bring another basket full, and so on. The specimens should be preserved 
 in drawers for future use, both during the present and subsequent terms. If 
 the class is small, a supply should be in store for use when the weather may 
 prevent field work. 
 
 7. Generally, fragments of bowlders broken for building purposes may 
 be found, and further reduced with the small hammers. If not, the collector 
 must use a large hammer for breaking bowlders. This should belong to the 
 school. If necessary, a workman may be taken along. In some cases it will 
 be most convenient to have a large supply of bowlders brought into one 
 corner of the yard, or deposited under a shed. These may all be coarsely 
 broken at once by a workman. Smaller fragments may be produced by the 
 students as needed ; but specimens from the same bowlder should be kept 
 together. This method may be best suited to some girls' schools, to institu- 
 tions in large cities and in other localities where Drift specimens are not 
 easily accessible. 
 
 In a region destitute of bowlders a supply may be obtained from seme 
 bowlder-covered region, by causing to be shipped as freight a number of 
 bowlders of different sorts of rocks, either unbroken and unboxed or broken 
 into hand specimens and boxed. The author has already sent boxed speci- 
 mens to the southern states and to the Illinois prairies. 
 
 9. Encourage the procurement of a good supply of hammers and lenses 
 by the students. They may be regarded as essential to satisfactory work. 
 The lenses are almost indispensable in the examination of rocks. 
 
 10. Encourage the formation of private collections, and see that they are 
 kept properly ticketed. See that a good collection is formed for the school. 
 Procure, if possible, from some dealer a standard collection of common 
 minerals and rocks. 
 
 11. Embrace every opportunity to require drawings. Blackboard draw- 
 ings are useful; but careful sketches on drawing paper are better. Sketches 
 of cliffs, quarries, gravel banks, ravines, fossils, or any other geological fea- 
 tures or phenomena should be required of all. 
 
 12. Dwell long on the subject of geological sections. Nothing is a more 
 useful exercise for the pupil than the construction of sections from the geo- 
 logical map. If the locality permits, have the students also construct sec- 
 tions, with measurements, from the field. 
 
 13. Require each student to construct a tinted geological map. Prefer- 
 ably a map of the United States east of the Black Hills, or better, of the 
 whole country. The maps in the text book may be enlarged; or, for more 
 accuracy, the map of the U. S. Geological Survey may be used. 
 
 14. Require every student to make, also, collections of fossils, and to
 
 SOME PRACTICAL HINTS. XXI 
 
 determine their names if possible. Do not fail to secure exercises in grind- 
 ing, polishing, and investigating, as indicated in Study XXX of this book. 
 15. The production of a neat and accurate geological map may well 
 abate considerably the rigor of a final examination. The same may be said 
 of a well labelled collection of specimens, or a number of well prepared thin 
 sections, or a larger number of polished surfaces of rocks or fossils. In this 
 first stage of the study, the senses and the hands are to be kept in full exer- 
 cise. These will supply motives for the pleased activity of imagination, 
 memory, and the reasoning powers. 
 
 SOME PRACTICAL HINTS. 
 
 Hammers. The best forms of Hammers for general use are shown in 
 Figs. 1 and 2. The palaeontologist's pattern, with pene a tapering and 
 sharp, and transverse to the handle, is by far most convenient in collecting 
 fossils. The face b should be flat, square cornered, and longest in the direc- 
 
 6 
 
 FIG. 1. GEOLOGICAL HAMMER. PAI^E- FIG. 2. GEOLOGICAL HAMMER. QUARRY- 
 
 ONTOLOGIST'S PATTERN. MAN'S, OR STONEMASON'S, PATTERN. 
 
 tion of the handle. The eye should be large ; the handle of hickory, thick, 
 short, and shaped as shown, and fastened in with two iron wedges. Weight 
 may be from half a pound to a pound. For working among very hard rocks, 
 the stonemason's pattern is better. The pene is parallel to the handle, less 
 tapering, and blunter. The temper of all hammers should be that required 
 by the stonemason. Notice, the pene of the palaeontologist's hammer must 
 not be used on quartzose rocks. 
 
 Larger quarryman's hammers, with long handles for use with botli 
 hands, and weighing from two to five pounds, are needed for breaking large 
 bowlders; but one at the service of the class is sufficient. 
 
 Using the Hammer. A blow with the flat face of the hammer in the 
 middle of a fragment shatters it irregularly. A blow with the face a little 
 inclined, or with the pene of the hammer, tends to produce a fracture in the 
 direction of the face-edge, or the pene. If the object is to reduce the size of
 
 xxii SOME PRACTICAL HINTS. 
 
 a specimen, or dress it into form, a quick, sharp blow with the face-edge or 
 the pene, delivered near the margin of the specimen, will cause a break only 
 along the line of contact. If the edge is too thick to break in this way, 
 make it thinner by clipping off with blows along the edge near the angles. 
 
 A steel-faced anvil, weighing ten to twenty pounds, is useful in dressing 
 specimens, and in breaking up masses for the removal of fossils. For the 
 former object, hold the specimen so that the portion to be removed projects 
 beyond the anvil face, and the specimen rests solidly on the edge of the face. 
 Then strike a sharp blow on the projecting part, and it will break off along 
 the line of contact with the anvil. 
 
 To break a large bowlder, strike repeatedly with the pene of a heavy 
 quarryman's hammer along a selected line. Sooner or later the bowlder will 
 split. 
 
 Hardness Tester. A steel rod, wedge-shaped and pointed at one end, 
 
 PIG. &. HABDNI 
 
 TESTER, a, View of the Flattened Side of Point. 
 Taper toward the Point. 
 
 b, View of the 
 
 as shown in Fig. 3, is convenient ; but an old three-cornered file ground to 
 a point is just as efficient. In default of both, a well tempered knife point 
 may be used. Whatever tester is adopted, use the same habitually. 
 
 Magnifiers. A simple pocket magnifier is indispensable in the exam- 
 ination of minerals and rocks. A glass with a single 
 lens will be suitable. A larger size than these figured 
 is preferable. Get nothing but & pocket magnifier. 
 
 Acid. A small glass-stoppered bottle of dilute 
 chlorhydric (muriatic) acid should be at hand in the 
 c l ftss room for testing carbonates. A drop may be 
 taken out on the tip of a blunt stick, and applied to 
 the specimen. In the lack of such acid very strong 
 vinegar will answer in some cases; but do not depend 
 on it. 
 
 Tickets. Small tickets, to be permanently at- 
 tached to specimens to receive numbers, may be cir- 
 cular, oval, or other shape, three-sixteenths of an 
 inch (five millimetres) in diameter, punched from thin white or colored 
 paper that will take ink. A common saddler's or tinner's punch may be 
 used. Fold the paper, and punch through many thicknesses with one blow, 
 
 FIQ. 4. MAGNIFIERS. 
 a, Oval. 6, Bellows 
 Shaped.
 
 SOME PRACTICAL HINTS. XX111 
 
 resting on a block of lead or wood. As the tickets will tend to adhere, lay a 
 quantity in the palm of one hand, and rub them with the finger tips of the 
 other. Square, oblong or triangular tickets may be cut with scissors. 
 Cement. Do not use common mucilage. Take 
 
 Clear Gum Arabic 2 ozs. 
 
 Fine Starch 1^ oz. 
 
 White Sugar ^ oz. 
 
 Pulverize the gum arabic in a mortar, and dissolve in so much water as the 
 laundress would use for the quantity of starch indicated. Dissolve the 
 starch and sugar in the gum solution. Then cook the mixture in a A r essel 
 suspended laundry fashion, in boiling water, until the starch becomes clear. 
 The cement must be as thick as tar, and must be kept so. Use from a wide- 
 mouthed bottle, having a small round bristle-brush passing through the 
 cork. Keep from spoiling by means of a lump of camphor gum, or a little 
 oil of cloves or sassafras. Do not use cement that has grown sour and thin. 
 Some of the fresh-made cement may be hard-dried in greased patty-pans, 
 and then removed and kept indefinitely, to be softened when needed a 
 good expedient for a long journey. This cement may be used to repair min- 
 erals, rocks, or fossils, and to attach tickets. One lot of cement will serve 
 several persons. 
 
 Attaching Tickets. Spread a quantity of specimens on a table, with 
 the side to be ticketed turned up. Spread, also, a quantity of tickets, so 
 separated as to lie singly. With the point of the brush, touch half a dozen 
 specimens in the proper place with the cement. With the moistened tip of 
 the finger, lift a ticket, and press it on a gummed spot. Press firmly, till 
 the ticket takes the shape of the surface, and the cement is forced quite to 
 the edges. Then, as some cement adheres to the finger, rub the finger tip 
 on a damp towel. This removes the cement, and leaves the finger damp to 
 lift another ticket. Thus the process of attaching is expeditious. 
 
 The Numbers. To write the numbers on the tickets, after well dried, 
 use perfectly black ink, and a sharp, good, and fresh steel pen. Make your 
 very plainest figures. These are a permanent record ; illegible numbers are 
 a vexation. The numbers refer to a register, where, against corresponding 
 numbers, may be found columns giving name, locality, how obtained, and 
 other information. Separate labels bearing the names and the same num- 
 bers may also be used. 
 
 Colored Tickets. If each person in a class or company adopts a par- 
 ticular color for his tickets, then all the specimens of the company may be 
 mixed, and may be classified as one lot; and afterward each person can 
 select his own. See that the colored paper is writing paper, and color dis-
 
 SOME PRACTICAL HINTS. 
 
 tinct and fast. Separate ownership may also be indicated by the form o 
 the ticket. 
 
 Map Drawing. To put the preliminary geography on the sheet is, 
 a valuable exercise, but is not a study of geology. The work may be done 
 as an accessory in the study of geography, or an exercise in drawing. For 
 our purpose procure blank (uncolored) printed maps if possible. These may 
 sometimes be had of map publishers. Rand, McNally & Co., of Chicago, 
 have for some years supplied the University of Michigan. They print a very 
 large assortment of maps; but they do not keep in stock blank impressions 
 such as we need ; they have to be specially printed when called for, and the 
 call should be for fifty or more. The writer uses a map of the entire United 
 States; and the best suited is their so-called "standard map," twenty-six: 
 inches by forty-three and one-half inches, 1882; or the later one, thirty and 1 
 one-half inches by forty inches, 1885. Either is a complete railroad map. 
 When geologically colored and mounted, it makes a useful chart for reference, 
 as well as a pleasing souvenir of faithful work. 
 
 Cloth Backing. This is not essential but veiy serviceable. Dampen 
 a piece of fine muslin of requisite size. Stretch it firmly on a smooth board 
 by tacking it down. Paste the back of the map with smooth flour paste applied 
 with a large, stiff, flat brush. Lay the pasted surface on the stretched cloth, 
 carefully excluding all air by holding the edges of the map up and allowing 
 the centre to come first in contact. Press the two surfaces together by rub- 
 bing from the centre toward the sides through the medium of a cloth. It is best 
 to leave the whole attached to the board or table until the map is completed. 
 Then the edges may be trimmed, and the map mounted on rollers. 
 
 Geological Colors. As yet, no set of colors has been agreed upon for 
 general use; but the. following table indicates customary usage: 
 
 FORMATIONS. 
 
 Tertiary. 
 
 Cretaceous. 
 
 Jura-Trias. 
 
 Upper Carboniferous. 
 
 Lower Carboniferous. 
 
 Devonian. 
 
 Silurian. 
 
 Cambrian. 
 
 Eozoic. 
 
 Eruptive. 
 
 COLORS. 
 Yellow. 
 Green. 
 Purple. 
 Brown. 
 Blue. 
 
 Yellowish Brown. 
 Red Purple. 
 Slate. 
 
 Orange Red. 
 Bright Red. 
 
 MATERIALS. 
 
 Gamboge. 
 
 Gamboge and Blue Ink. 
 
 Carmine and Blue Ink. 
 
 Burnt Umber. 
 
 Blue Ink. 
 
 Gamboge and Burnt Umber. 
 
 Blue Ink and Much Carmine. 
 
 India Ink and Blue Ink. 
 
 Carmine Ink and Gamboge. 
 
 Carmine Ink. 
 
 The above is sufficiently detailed for the elementary student, and requires 
 but a very simple outfit, one of which will supply several persons. When 
 subdivisions of these formations are to be indicated, use lighter and deeper
 
 SOME PRACTICAL HINTS. XXV 
 
 shades of the same colors the lighter for the newer formations. For 
 deeper yellow, orange may be used. Put on a blank space a legend explan- 
 atory of the colors. 
 
 These colors may be used on the map published in the text book. They 
 may also be used on sections. 
 
 Avoid colors too deep. Avoid the use of too much paint. Make sharp, 
 clean outlines. Be exact. Use large camel's hair brushes. 
 
 Wall Maps. Get cotton sheeting of requisite width, and cut length in 
 proportion to the width calculating from the dimensions of the map to be 
 enlarged. Use dry pulverized colors mixed in weak glue water. Stretch the 
 cloth on a frame erected vertically in a room. It may be like a quilting 
 frame, in four pieces, with holes and pegs for varying the size. Tack the 
 cloth thoroughly. Prepare the ground with one or two coats of whiting and 
 glue water. When dry, pencil in lines of latitude and longitude, at inter- 
 vals calculated from the map to be copied; and from these pencil in the 
 geography. In the same manner lay down the geological outlines. Then 
 apply the colors, and lastly put in the lettering, rivers, boundaries and what- 
 ever else requires the black which will be made of lampblack and glue 
 water. You cannot put the colors over the lampblack. Do not omit the 
 explanatory legend. Cut the top and bottom straight and mount on rollers. 
 Caution : Use only glue enough to make the colors adhere. 
 
 I I I I I I I I l'l I I [ 1 I I I f , I I / 1 I . I I 1 1 I I I 
 
 .Xn^
 
 GEOLOGICAL STUDIES. 
 
 PART I. 
 FIELD STUDIES; 
 
 OR, HOW WE MAY OBSERVE THE PACTS AND LEARN THEIR 
 MEANING. 
 
 STUDY I. Surface Materials. 
 
 I DESIRE by some natural and pleasant method to introduce 
 my young friends to the science of geology. I trust the 
 study of the subject will prove entertaining, but I shall endeavor 
 at the same time to put them on a truly scientific course. The 
 method which seems most suitable for us in the beginning is that 
 called inductive. We propose to see things for ourselves, and 
 draw our own conclusions from them. For the present we will 
 confine our attention mostly to such things. But when our 
 walks shall have extended over the fields most accessible to us, 
 we will enlarge our information by talks on other fields in which 
 other persons have walked. 
 
 As geology is the science which treats of the earth, we have 
 not far to go before beginning to learn. The earth is under our 
 feet; let us direct our attention to it and see what facts may be 
 observed. These will be geological facts. Every fact learned 
 by observing the earth is part of the science; and the things 
 observed near home are just as real science, and just as impor- 
 tant, as those in distant lands, of which we may read in the 
 books.
 
 2 GEOLOGICAL STUDIES. 
 
 Now, first of all, we see that the surface of the earth is cov- 
 ered by a bed of loose materials consisting chiefly of sand, 
 gravel, small stones, and clay. We will call these materials 
 Drift, for a reason which will be understood hereafter. The 
 uppermost layer, which is known as soil, is generally of a darker 
 color and evidently contains some other substance. We observe 
 the color darkest, and the depth of the soil greatest in places 
 where most vegetable material goes to decay; as, for instance, 
 where many leaves accumulate from year to year, or where 
 grasses or mosses have grown abundantly and decayed, as in low 
 meadows and swamps. In some situations the soil is mostly or 
 wholly composed of substances forming a fine dark mould, with 
 very little gravelly or sandy material derived from the Drift. 
 We also observe that least soil exists in situations where least 
 vegetable matter has decayed, as on dry knolls and along sterile 
 slopes, where the bed rock comes near the surface. It is a fair 
 inference from these observations that the matter which imparts a 
 darker color to the upper layer of the Drift is of a vegetable 
 character. 
 
 Should it happen that our observations begin in a prairie 
 region, like that of central and northern Illinois, we should 
 notice a great depth of dark soil, indicating that vegetation must 
 have grown over the surface with extraordinary luxuriance. 
 What we notice of the native plants or the growing crops quite 
 justifies the inference. We observe, too, that the land is nearly 
 level, and therefore, the matters resulting from vegetable decay 
 have lain on the spot where they grew, and have not been washed 
 away by flowing water. Those who dig wells on the prairies find 
 that underneath the deep soil the material is finer than the sub- 
 soil of most other regions, and has different colors. There are 
 very few pebbles or cobble stones either in the soil or the sub- 
 soil. This prairie deposit must, therefore, have been produced 
 in a different way from the common Drift of other regions. 
 
 But now we visit some locality where a deep excavation has 
 been sunk, and find that the prairie deposit does not continue 
 down to the bed rock. At the depth of thirty, fifty, or a hundred
 
 SURFACE MATERIALS. 3 
 
 feet we reach the bottom of it; and then comes, generally, some- 
 thing like the real Drift of other regions. We examine it care- 
 fully. There are the same sand and gravel, the same rounded 
 stones, as make up the Drift elsewhere. It cannot be distin- 
 guished from the Drift. It is the Drift. So we feel authorized 
 to draw another inference. The real Drift was laid down over 
 much of the prairie region the same as over other regions. 
 Then, afterward, by some means the fine prairie deposit was laid 
 down. 
 
 But by far the greatest number of us who set out to view the 
 surface of the earth must walk over the common Drift. This is 
 something so nearly alike from New England to the Mississippi 
 River, and from Hudson's Bay to the Ohio, that persons every- 
 where will see nearly the same things. So, wherever, within the 
 region indicated, you may begin this study, you will be able to 
 observe the geological facts which I now intend to point out. 
 
 The surface of the Drift, as you have noticed, is generally 
 rolling. There are hills and ridges and valleys. The streams 
 flow along the valleys, and they seem to have been agencies in 
 the making of the valleys. The forms of the hills are rounded, 
 and it is easy to understand that these have been shaped by the 
 rains. We notice, however, that many of the Drift hills are 
 elongated, more or less, and it is a curious fact that in any par- 
 ticular region their longer diameters are all turned in the same 
 direction. There must be some explanation of this, and we shall 
 try and discover it. 
 
 FIG. 5. DRIFT HILLS IN WISCONSIN. (Chamberlin.) See, also, Fig. 357. 
 
 When we examine the materials of the Drift, we notice that 
 it is composed mostly of sand, fine and coarse, with occasional
 
 4 GEOLOGICAL STUDIES. 
 
 beds of clay. There are many stones, large and small, and they 
 are all rounded. We shall call them all bowlders. When they 
 are not over six or eight inches in diameter they are known as 
 cobble stones, and are used for rough paving. ^vVhen they are an 
 inch or less in diameter, down to the size of (/ravel, we call them 
 pebbles. They are used with gravel and sand in road making, 
 and also, mixed with asphaltum or coal tar, in sidewalks. Bowl- 
 ders of all sizes are generally dispersed through the Drift; but 
 the larger bowlders are by no means uniformly dispersed. Many 
 extensive fields are entirely free from them, while in others they 
 form a serious obstruction to cultivation. Here is a view of a 
 bowlder-covered field near Gloucester, Mass. (Fig. 6.) 
 
 PIG. O.-A UOWLDER-COVEUED FIELD NEAR SQUAM, IN GLOUCESTER, MASS. 
 (After E. Hitchcock.) 
 
 In some parts of the country where the bed rock is completely 
 buried by Drift, large bowlders are ' broken up and used for 
 building stones. They present a substantial and pleasing appear- 
 ance. 
 
 The arrangement of the Drift materials will be noted. If we 
 go to any railroad cut through the Drift, we see beds of sand and 
 gravel laid down without any general uniformity. The beds pre- 
 sent a variety of inclinations, and within the limits of a single 
 bed the thinner layers, or laminae, are often seen to pass obliquely
 
 SURFACE MATERIALS.
 
 6 GEOLOGICAL STUDIES. 
 
 across. Fig. 7 presents a view of a gravel bank cut through in 
 the construction of a street. Underneath the soil and subsoil, 
 a a a a, we notice some gravelly beds, b b b, presenting a con- 
 fused and oblique stratification. These are followed by horizon- 
 tally stratified sand, c c c c, and two courses of pebbles, d d d 
 and e e e, separated by a stratum of pebbly sand which is obliquely 
 laminated. Still lower is another bed of gravel,///, distinctly 
 laminated, but in the other direction. This passes, toward the 
 right, into another bed, g a, with laminae inclining to the right. 
 At h h is another stratum of fine buffish sand with lamination 
 inclined steeply to the right. At the foot of the bank is a 
 sloping pile of sand, i i, which has run down from above. 
 
 This fine example of a gravel bluff simply illustrates what 
 may be found on almost every square mile of the northern states. 
 This view is 129 feet above the bed of the Huron River, and 204 
 feet above the bed rock, which has only been reached by boring. 
 On the bed rock the Drift is found to be a heavy mass of unstrat- 
 ified clay, with many large bowlders dispersed through it. At 
 other localities this bottom bowlder clay is found exposed at the 
 surface. Sometimes the materials are so firmly packed together 
 that digging in them is difficult. This is the nature of hard-pan. 
 When a wide extent of hard pan or clay underlies a level region 
 and is near the surface, it arrests the downward escape of the 
 rains, and gives rise to a marshy district. 
 
 Hereafter we shall return to a more careful study of Drift 
 arrangement, and shall try to ascertain how the materials were 
 produced, and how they wer'e spread so extensively over the 
 country. 
 
 EXERCISES.* 
 
 State some geological fact observed by yourself. What other geological 
 facts can you mention? Is there any hill of Drift materials near your resi- 
 dence? Is there any hill not formed of Drift materials? State how the Drift 
 
 * To THE STUDENT. The "Exercises" in this book are not questions on the text 
 but rather applications of the principles, and generalizations from facts stated in the 
 text. They are intended to stimulate thought. Some may be too difficult to answer at 
 presont too difficult even for the teacher. Do not let this produce any feeling of dis-
 
 SPRINGS A XI) AVELLS. 7 
 
 hill appears to be made up. State what cuts or excavations have been made 
 in it. Did you observe any sort of stratification in it? What is the color of 
 the sand? Is the sand coarse or fine? Can you name any hill or place where 
 clay appears? Does the bed rock come to the surface in your neighborhood? 
 Is the bed rock reached in digging wells? If so, does the water come out of 
 the rock or from the Drift? Does the bed rock belong to the Drift? Men- 
 tion some valley which is sunken in the Drift. Mention some steep bank 
 along the valley. Mention a bank or hill not covered by vegetation. Where 
 is sand obtained for making mortar? What is the difference between sand 
 and gravel? Mention some prairie region. Is it level or hilly? What sort 
 of material lies at the surface of a prairie? Why does not Drift lie on the 
 surface ? 
 
 STUDY 11. Springs and Wells. 
 
 I suppose you remember the little pond, where the water rests 
 in a little basin of earth and never leaks out at the bottom. 
 What holds the water? If you dig 1 a hole in the garden and fill 
 it with water, the water soon disappears. It soaks into the ground. 
 But if you cover the bottom and sides with a coat of clay, the 
 water is retained. You may have seen little duck ponds made in 
 this way. It is a layer of clay which holds the water in the little 
 lakelet in the field. Clay is so fine and compact that it is almost 
 impervious to water. 
 
 Suppose the little pond filled with sand and gravel. Now we 
 have a basin of loose materials completely saturated with water, 
 and the clay bed beneath prevents the water from escaping. The 
 surface of the materials is wet; the water is stagnant. After a 
 time some decaying vegetable matter may accumulate on it, and 
 grasses and sedges may take root, and we shall have a marsh. 
 Nearly all marshes and swamps are simply accumulations of sand, 
 gravel, and soil, which are kept saturated with water because a 
 bed of clay or hard pan underlies and prevents the water from 
 soaking away. 
 
 couragemeiit. If you answer half of these questions you do well. With a little reflection 
 you will answer more. It will be all the more useful if some research is necessary, or if 
 the question has to be pondered over several days or weeks. He is the most meritorious 
 student, however, who succeeds in explaining the greatest number of points presented.
 
 8 GEOLOGICAL STUDIES. 
 
 Of course there is a raised rim around this basin. From the 
 level of the marsh the Drift surface slopes upward on all sides. 
 Let us now dig a ditch through the Drift border of the swamp, 
 and give it a slight descent toward the nearest stream of water. 
 Now the water drains from the swamp, and the land becomes 
 sufficiently dry for cultivation. Now the swamp may be plowed 
 and planted to corn. The basin of the swamp still collects the 
 rains, but the ditch continually carries away the excess. If the 
 ditch were covered, we should see the water only at its place of 
 exit, and we might consider it a spring. 
 
 On the hill slope is a spring, which is nothing but the mouth 
 of a covered ditch or drain conveying the water from some 
 saturated bed of porous materials concealed beneath the fields. 
 How steadily it flows! How limpid and cool and refreshing is the 
 stream! It glides down the bank, and is soon joined by several 
 other streamlets fed by other springs along the same hill slope. 
 All together they form a pretty little brook, which flows through 
 the meadows and pasture lands for many a mile. And all along 
 its course the grateful cattle slake their thirst from the cool 
 stream. 
 
 FIG. 8. SPRING ISSUING PROM A BANK 
 
 Let us go back to the hillside spring. Here, Fig. 8, is a 
 cut which shows the various beds of sand, gravel, and clay which 
 form the Drift hill from which the water issues. Here is the soil
 
 SPRINGS AND WELLS. 9 
 
 at the top with its vegetation, and underneath are the common 
 Drift materials presenting their usual imperfect stratification, 
 their oblique lamination, and their abrupt limitations. It is the 
 same thing as seen, in the Drift section in Fig. 7. Only here is 
 a bed of clay. It is from the upper surface of the clay that the 
 water issues. This bed of clay extends back into the hill an 
 unknown distance. It may be a quarter of a mile or more. It 
 may be even a mile or several miles. Generallv, however, all the 
 Drift beds have but very limited extent. Now, in this case, the 
 rain which falls upon the fields percolates downward through the 
 sand and gravel beds, but is arrested by the clay bed. Then the 
 water flows over the surface of the clay bed in the direction of 
 its slope, and that happens to bring it to a place of outcrop on 
 the hillside. The clay bed is like a basin to hold the water, though 
 it may be filled with sand. If the basin is flat, or very shallow, 
 we have a broad sheet of sand saturated with water ready to 
 flow off wherever its margin reaches a hill slope. If the basin is 
 depressed like a trough, the most abundant flow is along the 
 trough. If the hill slope cuts across the trough, then the move- 
 ment of the considerable stream may wash out some of the sand, 
 and leave a real underground passage, along which flows a sub- 
 terranean stream. The case shown in Fig. 8 is much like this. 
 
 Now, evidently, if the water basin extends back under the 
 land, it is possible for the farmer whose house is too elevated to 
 have a spring to dig down to the basin of water which supplies 
 the spring. This is a well. Wherever an excavation is sunk to a 
 bed of sand resting on a clay stratum, there water will be found. 
 But no one can tell certainly the depth at which the clay stratum 
 will be reached. In some places it is so near the surface that 
 even a common cellar reaches the water. In other places it lies 
 at a depth of fifty, eighty, or one hundred feet; and the well ' 
 would be too deep for use. But remember that it is not every- 
 where the same clay stratum which arrests the water. As these 
 Drift beds are of very limited extent, no one can be certain of 
 reaching water at the same depth as in another well but a few 
 rods distant. Nor does the height of the ground indicate any-
 
 10 
 
 GEOLOGICAL STUDIES. 
 
 thing in reference to the depth of the water-bearing stratum. 
 All these things are illustrated in the adjoining cut, Fig. 9. 
 
 
 PIG. 9. DEEP AND SHALLOW WELLS. 
 
 Here a, b, c are clay beds, each of limited extent, and each over- 
 laid by a sandy bed which receives water by percolation from the 
 surface. The descending water which is arrested by c is con- 
 veyed to an outcrop on the hill slope, where it escapes as a spring 
 and continues its descent. That which is arrested by a and b 
 spreads laterally, and after the basins are full it overflows and 
 descends to still lower basins. At 6 the basin b is reached by 
 digging ten or fifteen feet. At d, which is but a few rods dis- 
 tant, and is also at a lower level, the well must be sunk fifty feet 
 to reach the water basin a. 
 
 Probably the water in basins a and b finds outlet somewhere 
 in springs. It may be directly from these basins, or it may be 
 from other basins into which these overflow. The fact that a 
 basin supplies one or many springs does not prevent its supplying 
 wells also. An excavation sunk at f would result in a well, 
 though the spring or range of springs from the basin c may not 
 be far away. 
 
 Spring and well waters are not absolutely pure. Remember 
 that these waters came from the surface of the land, and must 
 have dissolved and carried away as much as possible both from
 
 SPRIXGS AND WELLS. 
 
 11 
 
 the surface and from beneath the surface. You can easily ima- 
 gine that some well and spring waters are notably impure and 
 unhealthy. Some villages and cities have been so poisoned by 
 water which seemed to possess a sparkling purity that deadly 
 epidemics have been occasioned. In many an instance the mys- 
 terious deaths of the inmates of an isolated dwelling even a 
 farm dwelling in the midst of the countrv air have been traced 
 to impurity of well water infected by drainage from the sur- 
 face. Geologically speaking, however, we are most interested 
 in the mineral substances dissolved by subterranean waters and 
 supplied to wells and springs. The most frequently occurring 
 are compounds of lime and iron. The Drift sands abound in 
 them; the waters dissolve them, and escaping to the surface re- 
 deposit them. A common compound of lime thus deposited is 
 of the nature of chalk and limestone. It is deposited because 
 the water escaping to the surface and relieved of its pressure 
 cannot hold as much as while under- 
 ground. When the deposit takes place 
 in standing water, it forms a soft, 
 white substance called marl. When 
 deposited over the surface of dry 
 ground, it builds up a layer of traver- 
 tin, which is like a rock, and in France 
 and Italy has been employed exten- 
 sively for building purposes. When, 
 in flowing over the surface, the deposit 
 incrusts mosses, leaves, sticks, or bones, 
 cementing them in a stony mass, it is 
 commonly called calcareous tufa. 
 
 Iron deposits are formed in a similar 
 way. When the iron compound saturates the materials of a ' 
 swamp, it forms bog iron ore, and may possess any percentage of 
 iron, according to the copiousness and duration of the deposition. 
 Bog ores in some places exist in such abundance and purity that 
 iron is manufactured from them. , Indeed, it is not unlikely, as 
 we shall see, that the great workable beds of iron ore were 
 
 FIG. 10. PETRIFIED Moss.
 
 12 GEOLOGICAL STUDIES. 
 
 originally mere iron-soaked bogs. A similar compound of man- 
 ganese is sometimes deposited in low grounds in a similar way. 
 This product is black, and is known as wad or bog manganese. 
 Both bog ores are employed as paint. The bog iron gives us 
 ochre, and the bog manganese a black pigment much used in 
 carriage painting. Waters holding limestone in solution are 
 "hard." Those holding iron are said to be ferruginous, and 
 often leave a rusty deposit on the surfaces which they bathe. 
 Ferruginous spring waters are often described as chalybeate. 
 Many of them possess valuable medicinal properties. 
 
 EXERCISES. 
 
 Describe the situation of the finest spring known to you. What deposits, 
 if any, does the water leave? Does it produce any rusty stain? State where 
 some travertin or calcareous tufa may be found. When moss is petrified, 
 does the substance of the moss necessarily remain? What becomes of it if 
 not remaining? What is the cause of the white deposit in the bottom of the 
 tea kettle? What sort of water must be used to prevent it? What would be 
 the effect of hard water upon steam boilers? Suppose water holding lime- 
 stone in solution percolates through a bed of gravel, what happens to the gravel 
 after a time? Could iron compounds be used to produce the same result? 
 Name some well which is much shallower than a neighboring well. Suppose 
 the Drift were all sand, how would the existence of springs be affected? 
 Where would the surface water all go? What would be the effect on streams 
 of water? Mention a region where the surface materials are all sand. Are 
 streams of water plentiful there ? Did you ever hear of a river disappearing 
 in the ground? After such a disappearance would it be possible for the 
 river to reappear? Search on the map of Asia or Africa and point out rivers 
 which terminate on the land. Suppose the Drift were all clay, how would 
 the existence of springs be affected? 
 
 STUDY lll.Boiclders. 
 
 Let us return to the bowlders. Except over the prairie 
 regions we find them generally distributed. Multitudes of them 
 may be seen upon the surface, and almost every excavation 
 reveals them buried beneath the surface to depths as great as are
 
 BOWLDERS. 
 
 13 
 
 reached by the Drift formation. In limited districts the Drift is 
 restricted chiefly to sand or to clay; and the uses to which bowl- 
 ders are applied are diminishing the number in sight. Still, it is 
 no uncommon thing to see them clustered as thickly as is shown 
 in Fig. 6. Bowlders, in some instances, retain enormous dimen- 
 sions. Several notable cases have been cited by the geologists of 
 New Hampshire, and 
 one of these is repro- 
 duced in the adjoining il- 
 lustration, Fig. 11. This 
 lies near Gilsum, New 
 Hampshire. It is 46 
 feet long, 24 feet wide, 
 and 26 feet high. It is 
 so large that a country 
 school house is almost 
 hidden behind it. In 
 1817 an enormous piece 
 was split off by the ac- 
 tion of frost. The piece 
 
 was 33 feet long and 10 feet wide. The whole stone, before the 
 splitting, contained 32,000 cubic feet, and weighed 2,286 tons. 
 A thousand miles from here, on the south shore of Lake Superior, 
 are other enormous bowlders, some of which are shown in Fig. 12. 
 The larger one is of porphyry, and lies twenty-five feet high. 
 As with all bowlders, its angles have been rounded off. We 
 must endeavor, in due time, to ascertain the cause of this. 
 One of the largest bowlders known lies in the Northwest Ter- 
 ritory, north of Montana. It is of quartzite, and according to 
 G. M. Dawson, the portion above ground is 40x40x20 feel;. 
 Another one is 40x30x22 feet. 
 
 One peculiar circumstance connected with nearly all bowlders, 
 large or small, is their hardness. This is so notorious that, in 
 allusion to their hardness and roundness, they are very generally 
 known as "hard-heads." Occasionally we find a real bowlder 
 soft enough to be scratched with a knife. Some, also, are in a 
 
 FIG. 11. GREAT BOWLDER NEAR GILSUM, N. H. 
 (C. H. Hitchcock.)
 
 14 GEOLOGICAL STUDIES. 
 
 state of progressive disintegration. In the course of time they 
 will be reduced to sand and mingled with the other constituents 
 of the soil. This suggests that many bowlders must already 
 have been completely disintegrated, and that the finer constit- 
 uents of the Drift have probably been derived from decaying 
 rocks. It suggests, further, that it these bowlders were ever 
 angular, the simple process of decay would have removed their 
 angles, and reduced them to their present rounded forms. We 
 must keep this possibility in mind. 
 
 LAKK SLTKIUOR. 
 
 Everyone has noticed the accumulation of bowlders along 
 certain beaches and points exposed to the action of the waves. 
 This is not because bowlders are transported to such situations 
 and laid down. It is because the Drift abounds in bowlders, and 
 in the exposed situations mentioned, the waves wash out the sand 
 and pebbles, leaving the bowlders to settle together close by the
 
 BOWLDERS. 15 
 
 water's edge. Innumerable bowlder points may be seen along 
 the coast of New England. One interesting example is at Gay 
 Head, on Martha's Vineyard. The Great Lakes exert a wave 
 action almost equal to that of the sea, and similar bowlder beaches 
 may be witnessed at Keweenaw Point, Lake Superior, at Point 
 Waugoshance, Lake Michigan, and a hundred other localities. 
 The curious phenomenon of "walled lakes" finds its explanation 
 here. Many small lakes in the northwestern states exhibit a rude 
 sloping wall of bowlders forming the beach on one or more sides. 
 Human fancy has sometimes attributed these walls to the agency 
 of the Indians or their predecessors, or even to a race of giants. 
 We have only to conceive the original sandy beach filled with 
 bowlders, and the easily movable sand washed out by the action 
 of the waves, to understand that the bowlders would gradually 
 settle together into the position of a rude sloping wall. 
 
 Almost every neighborhood in the northwestern states is in 
 possession of one or more pieces of metallic copper discovered in 
 the Drift. These are real bowlders. They bear the same evi- 
 dences of wear as the stones. They have apparently been sub- 
 jected to the same ordeal as the other constituents of the forma- 
 tion of which they are a part. These are examples of native 
 copper. But native copper is not known to exist in all the coun- 
 try except in the region of Lake Superior. As it would not seem 
 reasonable to regard these Drift specimens as produced where we 
 find them, the theory is suggested that they have been brought 
 from Lake Superior. Now, in the same connection you must 
 have noticed that nearly all our bowlders are unlike any rocks 
 found in place at points nearer than the shores of the Upper 
 Lakes. All these indications point toward the far north as the 
 region whence our Drift materials have been derived. We may 
 further conclude that they would not have been transported from 
 the far north without exposure to much wear, which would have 
 reduced their volume, rounded their angles, and produced an 
 abundance of fine material. These inferences must be borne in 
 mind when we come to theorize about the agency which effected 
 the transportation of so enormous a quantity of stones and sand.
 
 16 GEOLOGICAL STUDIES. 
 
 A more attentive inspection of particular bowlders shows that 
 very few are entirely homogeneous. You must by all means 
 make the examination for yourself. A good many presenting a 
 light-colored or pinkish appearance are nearly homogeneous; 
 but most of these, on close inspection, seem to be formed of 
 grains more or less closely compacted together; and they contain, 
 also, an occasional grain or streak or blotch of a different color. 
 Some dark-bluish or blackish bowlders also appear to the naked 
 eye as almost homogeneous. Close inspection, however, espe- 
 cially with a magnifier, shows that they are finely granular. 
 Most of these reveal, also, a stratified structure; that is, lines or 
 streaks or bands of slightly varying character extend in parallel 
 directions across the surface of the stone. They indicate that 
 the whole stone is composed of layers or strata which slightly 
 differ from each other in color or fineness. 
 
 Most of the bowlders, however, are distinctly heterogeneous in 
 constitution. This is shown by the different colors of the mate- 
 rials. Generally each different color indicates a different mineral. 
 Most bowlders contain two or three different minerals, as you 
 will immediately observe. Some contain even more. Now, the 
 name of a rock depends on the minerals of which it is composed. 
 Hence, to determine the minerals must be our first study. If the 
 minerals are promiscuously and somewhat equally distributed, 
 the rock is not stratified; it is massive. Unequal distribution 
 sometimes exists in a massive rock, but the materials are not dis- 
 posed in parallel planes. When they are so disposed we may 
 know the rock is stratified. But these various layers are not to 
 be taken as strata; they are laminae if they cohere together. 
 Strata are indicated by the separation of a rock into distinct 
 beds. If the strata are nearly a foot thick or over, the rock is 
 thick-bedded. We shall use the term schistose for thin-bedded 
 rocks. The lamination of a rock is often in the same direction as 
 the bedding or stratification; but sometimes it crosses the bed- 
 ding. Besides the minerals which make up the principal bulk of 
 the rock, you will often discover one or more other kinds to a 
 sparing extent. These minerals differ generally in color and also
 
 BOAVLDERS. 17 
 
 in lustre, transparency, hardness, and crystalline form. What 
 we mean by lustre will be understood when you compare a piece 
 of glass with pearl or polished steel. The broken surface of the 
 glass reflects light perfectly, brilliantly. A reflecting surface of 
 pearl is less perfect; the light from it is softer. As to lustre, the 
 glassy, the pearly, and the metallic are the most important dis- 
 tinctions to make. Some minerals, also, are transparent, like 
 glass; others are translucent, permitting light to pass imper- 
 fectly, though nothing can be definitely seen through them. 
 Others are opaque. In ordinary bowlders nearly all the minerals 
 are hard, but with a tester you will readily discover that some are 
 more easily scratched than others, and some cannot be scratched 
 at all. As to crystalline form, nothing can be made out in some 
 cases; but in others we can discern a line or an angle, or a plane, 
 if nothing more. Even so much indicates that a crystalline form 
 belongs to the mineral, and often gives a very important clew. 
 
 There is one other particular in which minerals differ from 
 each other. It is very important, but the distinctions generally 
 cannot be detected without making experiments too nice and 
 elaborate for us to undertake. They differ in chemical composi- 
 tion. The ultimate substances of which they are composed are 
 different in the relative proportions in which they exist. One 
 simple test may always be applied by us; we may observe 
 whether effervescence is caused by an acid; but beyond this we 
 must take the statements of the chemists who have the requisite 
 appliances for making chemical analyses. Accomplished mineral- 
 ogists must themselves be chemists; and it is their practice to 
 employ an outfit more or less portable for making analyses in the 
 dry way; that is, without making a solution of the mineral to be 
 tested. They make use of a blowpipe and mostly dry re-agents, , 
 in the flame of a lamp or gas jet. But though we cannot under- 
 take analyses for ourselves, it is indispensable to understand 
 something of the chemical constitution of minerals; and, there- 
 fore, before we proceed farther we must explain the "rudimentary 
 principles of chemistry.
 
 18 GEOLOGICAL STUDIES. 
 
 EXERCISES. 
 
 What very large bowlder have you ever seen? What is its color as nearly 
 as you remember? Is it homogeneous, or is it composed of different min- 
 erals? Have you ever noticed the distinction between stratified and unstrat- 
 ified bowlders? Here are fragments of rocks obtained by breaking up 
 several different sorts of bowlders; pick out one which is homogeneous. 
 Pick out one which is heterogeneous. How many kinds of minerals in the 
 last? Pick out one having a massive structure. One having a schistose 
 structure. One with a thick-bedded structure. Has the latter any laminae? 
 Pick out a specimen showing laminae. What distinguishes the lamina? from 
 each other? What different colors or forms of minerals can you distinguish 
 in it? Put all the massive specimens in a pile together. Put all the strati- 
 fied specimens together. Are there any homogeneous rocks in the last pile ? 
 [The teacher will frame a large number of similar exercises.] 
 
 STUDY IV. A Little Chemistry. 
 
 It is generally believed that all matter is composed of atoms, 
 or portions so small that they are never divided and cannot be 
 divided. The finest dust floating in the air is coarse in compari- 
 son. The atoms are so minute that they are not only invisible in 
 a beam of light, but also under the most powerful microscopes. 
 An impressive idea of their minuteness may be gained by learn- 
 ing that if a drop of water could be enlarged to the size of the 
 earth, the atoms of which it is composed, each enlarged in the 
 same proportion, would be about the size of small shot. Of such 
 inconceivably minute parts are all substances composed. Iron, 
 stones, water, and air consist alike of ultimate atoms. 
 
 Now let us follow our chemical teachers. Among these bill- 
 ions of billions of atoms there are held to be about sixty-four 
 different sorts. There is one kind of atom in iron, another in 
 gold, another in sulphur. Some atoms appear to be much more 
 abundant than others. If we take an average sample of the solid 
 part of the earth weighing one hundred pounds, it will be chiefly 
 made up of the atoms or elements named below, and in about 
 the proportions stated :
 
 A LITTLE CHEMISTRY. 
 
 19 
 
 Oxygen 
 
 Silicon 
 
 Aluminum 
 
 Iron 
 
 Calcium 
 
 Sodium 
 
 Potassium 
 
 45 pounds. 
 25 " 
 10 " 
 
 8 
 
 Carbon 
 
 Hydrogen 
 
 Sulphur 
 
 Nitrogen 
 
 Chlorine 
 
 Magnesium 
 
 All 
 
 together nearly 
 H pounds. 
 
 In the atmosphere and in water there are larger proportions 
 of Nitrogen, Oxygen, and Hydrogen. A vast number of atoms 
 of the same kind brought together forms a visible amount of the 
 substance. Some substances are solid, others are liquid or gaseous 
 at ordinary temperatures, and under other ordinary conditions. 
 But it has been shown that heat will liquefy, and even vaporize, 
 all solid substances, while cold and increased pressure will liquefy, 
 and even solidify, all gases. 
 
 All the atoms have a tendency to come into close union with 
 other atoms, and to remain so united. This tendency is com- 
 monly known as chemical affinity. The union so formed is a 
 chemical compound. Nearly all the other atoms have affinity for 
 the atom called oxygen. The compound resulting from the union 
 of oxygen with another element is termed an oxide. Thus iron 
 and oxygen form iron oxide, or oxide of iron. Silicon and oxy- 
 gen form silicon oxide / aluminum and oxygen, aluminum oxide. 
 So chlorine, bromine, iodine, and sulphur united with other sub- 
 stances form chlorides, bromides, iodides, and sulphides. Many 
 of these compounds are commonly known by other than their 
 chemical names. Thus, one iron oxide is simple iron rust; hydro- 
 gen oxide is water; calcium oxide is lime; sodium oxide is caustic 
 soda; potassium oxide is caustic potash; silicon oxide is silica, or 
 quartz; sodium chloride is common salt; iron sulphide is pyrite. 
 Some compounds contain two, three, or more times as much oxy- 
 gen, or chlorine, or sulphur as others; but we shall not here ob- 
 serve the distinctions. 
 
 Now, a very important chemical principle is this : Oxygen 
 united with certain substances produces acid-forming oxides / 
 while with other substances it forms basic oxides. The addition
 
 20 GEOLOGICAL STUDIES. 
 
 of hydrogen to an acid-forming oxide makes an acid. The names 
 of the acids most important for us end in ic. Thus, sulphuric 
 acid, or " oil of vitriol," is composed of sulphur, oxygen, and hy- 
 drogen. Nitric acid is composed of nitrogen, oxygen, and hydro- 
 gen. The basic oxides generally have names which end in a. 
 Many of them have also old, popular names, as before stated. 
 
 Another important principle is this : The acids have strong 
 tendencies to form compounds with the bases. Such compounds 
 are salts ; and if the name of the acid end in ic, the name of the 
 salt ends in ate. Thus, sulphuric acid and soda form sodium sul- 
 phate, or according to the old nomenclature, still much used, sul- 
 phate of soda. Silicic acid and lime form calcium silicate, or 
 silicate of lime; carbonic acid and lime form calcium carbonate, 
 or carbonate of lime, which is familiarly known as limestone, 
 chalk, and marl. The latter, however, commonly contains an ad- 
 mixture of clay. 
 
 A third important principle is this: The affinities of different 
 substances for the same substance are not all equal. Sulphuric 
 acid, for instance, has a stronger affinity for lirne than carbonic 
 acid has. Hence, when sulphuric acid is brought into contact 
 with carbonate of lime, the carbonic acid is driven off, and the 
 sulphuric acid takes its place, forming sulphate of lime. All the 
 mineral acids will do the same, forming each its appropriate salt 
 of lime. Even strong organic acids, like pure vinegar or acetic 
 acid, will drive carbonic acid away from carbonate of lime. As 
 carbonic acid is a gas (called also carbon dioxide), it assumes the 
 form of a gas instantly on being compelled to dissolve its union 
 with the lime. The gas is much more bulky than the carbonate, 
 and, accordingly, it forms numerous small bubbles with the liquid 
 acid which remains uncombined. This phenomenon is called effer- 
 vescence. The demonstration of effervescence, as illustrative of 
 this selective action among acids and bases, is quite within the 
 reach of our simple resources. Take a bit of chalk and apply a 
 drop of any strong acid to the surface, and effervescence instantly 
 ensues. The effervescence shows that carbonic acid was one of the 
 constitutents of the chalk. Strong vinegar will produce efferves-
 
 A LITTLE CHEMISTRY. 21 
 
 cence. The same result follows if marl or limestone is employed; 
 hence, these are shown to be carbonates. 
 
 A fourth important principle is this: Heat weakens the strength 
 of the union formed between two or more substances. We have 
 just seen that limestone is carbonate of lime that is, a union 
 between lime and carbonic acid. Now, if we subject limestone 
 to a red heat, the union between the acid and the base is not only 
 weakened, it is destroyed. The carbonic acid rises into the atmos- 
 phere, and the lime remains. Simple lime is known as quick- 
 lime, or caustic lime. But, after cooling, it is eager to regain a 
 supply of carbonic acid, or other acid, and it slowly absorbs that 
 gas from the atmosphere. If we dissolve quicklime in water, and 
 pour off the clear fluid standing over the excess of lime, we have 
 lime-water. This eagerly unites with or neutralizes any acid with 
 which it comes in contact. Hence it is employed to correct 
 "acidity of stomach." If now we breathe into the lime-water 
 through a straw or a glass tube, the carbonic acid from the lungs 
 unites with the lime in solution and forms a white cloud, because 
 the carbonate of lime resulting is not much soluble, and remains 
 as an infinitude of minute white particles. These slowly settle to 
 the bottom and form a white, chalky powder, known as precipi- 
 tated chalk. This also is used by physicians as an antacid. 
 
 Should we pour slowly a quantity of lime-water over a pile of 
 sand, it is obvious that the carbonate of lime would be formed in 
 the interstices between the particles, and might finally fill them 
 up. The grains of sand would then be firmly cemented together 
 by a calcareous cement. We shall find many rocks thus ce- 
 mented. The application of a drop of acid then produces slight 
 effervescence, which reveals the nature of the cement. 
 
 Intense heat is capable of dissolving very many unions not 
 alone between acids and bases, but between oxygen and other 
 substances. It is probable indeed, that a degree of heat is pos- 
 sible which would reduce all substances to their ultimate ele- 
 ments. In such a heat, no compounds could exist. This state 
 of matter is known as dissociation and the facts are connected 
 with theories of the primeval condition of the world.
 
 22 GEOLOGICAL STUDIES. 
 
 Thus it appears that nearly all substances known to us are 
 chemical compounds. Minerals are chemical compounds, for the 
 greater part. Certain metals only, in the native state, are ele- 
 mentary or uncompounded. Gold, silver and copper are samples, 
 but nearly all metals, as well as other substances, have entered 
 into combinations as oxides or chlorides, or sulphides, or carbon- 
 ates and other salts. It is an important fact that every chemical 
 compound tends always to form crystals of the same fundamental 
 form. That is, it will form solids always of the same order (cube, 
 rhombohedron, hexagonal prism, etc.), and always having the 
 sides so inclined to each other as to form the same angle. If 
 then, for instance, we have learned by observation what order of 
 geometrical solids is formed by calcium carbonate, and also the 
 values of the angles, and then find an unknown mineral of the 
 same geometrical form, and having the same angles, it is per- 
 fectly safe to conclude that the unknown mineral is calcium car- 
 bonate. That is, its chemical composition is shown by its cystal- 
 line form. In the determination of minerals, therefore, the 
 detection of the crystalline form is always desirable. By means 
 of the form, the hardness, the color, the lustre and the specific 
 gravity, we may generally make a determination of the common 
 minerals. Knowing the mineral, we know the chemical substances 
 in it. All that we shall at present attempt is the determination 
 of the common minerals entering into the formation of the com- 
 mon rocks; and we. shall attempt this almost wholly by an inspec- 
 tion of their physical characters. 
 
 EXEKCISES. 
 
 What is the acid in carbonate of potash? Of what is chloride of cal- 
 cium composed? What is the composition of lime? Name some substances 
 which are elementary. Name some containing oxygen. Why cannot the 
 atoms of matter be seen under the microscope? Are the atoms infinitely 
 small? Did you ever notice a calcareous incrustation on stones in a pond or 
 lake? How might it be explained? Why is it not a pure white, like chalk? 
 Name some acid which has a strong affinity for lime. Name one having a 
 feebler affinity. What would be a relief to acidity of the stomach? What 
 would result if pulverized marble were thrown into a vessel of vinegar? If
 
 QUARTZ AXD FELDSPAR. 33 
 
 vinegar is acetic acid, what salt would be formed? If you take one hundred 
 grains of the average solid earth, how many grains of silicon might be ex- 
 tracted from it? How many grains of potassium? State, if you can, what 
 elements are most abundant in vegetation. What is the principal source of 
 carbon in plants? 
 
 STUDY V. Quartz and Feldspar. 
 
 We are now prepared to begin the investigation of common 
 minerals. Let us select a common bowlder and break it into so 
 many pieces that each of us shall have one fragment of conven- 
 ient size to hold in the hand and inspect. The collection of these 
 specimens may have been done beforehand; or we may proceed 
 together to the field and procure the specimens as we need them. 
 The best bowlder to begin on will be one containing several min- 
 erals. This will be indicated by the various colors though 
 sometimes various colors result merely from different varieties of 
 the same mineral, as we shall see. 
 
 Now, with our specimens in hand, suppose one or more of the 
 minerals is nearly white; and suppose another reddish, and an- 
 other quite dark colored. Look attentively at the light colored 
 minerals and consider if they seem to be all alike. Test the hard- 
 ness of several samples of the white mineral, or minerals. Can 
 you make a scratch on them ? Yes, you say, your implement 
 leaves a dark metallic mark. That is not a scratch of the min- 
 eral. It shows that the mineral is harder than the implement. 
 Well as soon as we observe this we may pronounce the mineral 
 quartz. This is the hardest of all the common minerals. It is 
 also very abundant. It is not always white, or nearly white. It t 
 may be transparent, pink, red, smoky, or even almost black. But 
 its hardness will always betrav its character. 
 
 It has another character by which you may almost always 
 detect it. Quartz has a vitreous or glassy lustre. This is most 
 conspicuous where the quartz is transparent, but in all ordinary 
 quartz the glassy lustre can be seen.
 
 24 GEOLOGICAL STUDIES. 
 
 The quartz minerals thus detected in the bowlder you find to 
 be generally rounded grains or pebbles. Sometimes, indeed, they 
 are so closely compacted together, that the outlines of the grains 
 can scarcely be traced. One would think that some larger quartz 
 rock had been reduced to small fragments, and the fragments 
 rubbed together until the angles were rounded, and then all com- 
 pacted as we see them. But quartz being a simple mineral, it 
 crystallizes in a definite form. The separate crystalline bodies 
 resulting are crystals. The crystal 
 of quartz is a hexagonal prism. 
 Here, in Fig. 13, you have a view of 
 several crystals, larger arid smaller. 
 Each has six sides, and the end 
 slopes correspond to the sides or 
 faces. This is the termination. Not 
 unfrequently quartz crystals occur 
 with a termination at each end. The 
 crystal appears to have been formed 
 by progressive additions on all the 
 FIG. 13. -A GROUP OF CRYSTALS sides; for almost always we see one 
 side more built out than others. 
 
 But the more a side projects the narrower it is, since the con- 
 tiguous sides must be preserved in true planes. Good quartz 
 crystals may sometimes be found in coarse bowlders, especially in 
 cavities. 
 
 Pure quartz is transparent, like glass, and the crystals pre- 
 sent, therefore, a remote resemblance to diamonds. " Brazilian 
 pebbles" and "Alaska diamonds" are merely crystalline quartz. 
 Quartz, however, is more commonly mixed with some impurity, 
 and it thus loses transparency and acquires color. Violet colored 
 quartz is amethyst. Quartz so mixed as to have a uniform waxy 
 lustre rather than a brilliant, glassy lustre is chalcedony ; while 
 alternating bands of differently colored chalcedony form agate, 
 A chalcedony containing minute mossy patches, of deeper color, 
 is a moss agate. If the impurities greatly dull the lustre of the 
 quartz it becomes flint, and if they produce an earthy lustre it is
 
 QUARTZ AND FELDSPAR. 25 
 
 jasper red, black, or green. Chert is an impure quartz, gen- 
 erally containing lime. 
 
 It is most important to know of what quartz is composed. It 
 is its composition which determines all its properties. The chem- 
 ist tells us that quartz is pure silica, and that silica is composed 
 of silicon and oxygen. There are twenty-eight grains of silicon to 
 every thirty-two of oxygen. So you can calculate from the table 
 in Study IV that one hundred pounds of the solid earth contain 
 about fifty-three and six-tenths pounds of silica, or quartz. 
 
 Now we will carefully examine and test every part of the 
 rock specimen in hand, to ascertain whether it contains more 
 than one variety of quartz. Very likely we shall discover two 
 varieties one with more color than the other. One may be 
 nearly transparent, and the other a little reddish or a little dusky. 
 But we must be sure the glassy lustre is also present. 
 
 Is there a light-colored mineral present which, with consider- 
 able effort, receives a scratch ? Is there a pinkish, reddish, or 
 cream-colored mineral which can be scratched? Any mineral of 
 these colors, if so hard as to be scratched with difficulty, is proba- 
 bly a feldspar. Quartz will scratch feldspar; but feldspar will 
 not scratch quartz. Quartz will always scratch glass. Most glass 
 may also be scratched by feldspar, but not so readily. 
 
 There is sometimes difficulty in deciding whether a small 
 grain of a mineral is quartz or feldspar. We had better select 
 rocks at first which are coarse-grained. But sometimes we are 
 compelled to make the determination in a fine-grained rock. 
 Whether fine or coarse, we may proceed next to examine the 
 lustre. Feldspar has a pearly or subvitreous lustre in most cases. 
 If we detect such a lustre instead of the bright, glassy reflection 
 caused by quartz, the question is decided. If we have a doubtful ( 
 mineral, we must frequently glance at the lustre of an undoubted 
 fragment of quartz, and compare the two lustres. Very often 
 the lustre serves to identify feldspar. 
 
 But there is another method. Feldspar fragments often pre- 
 sent in the rock distinct flat faces or surfaces. Quartz fragments 
 do not. Hence, if, on changino- the position of the stone in ref-
 
 26 GEOLOGIC A L STUDIES. 
 
 erence to the light, we see here and there bright, flat surfaces 
 appearing and disappearing as they reflect and cease to reflect 
 the light from a window, then we may be pretty certain we have 
 feldspar. If, on testing for hardness, one of these appears a very 
 little softer than quartz, the suspicion is confirmed. Still further, 
 if the reflecting plane is bounded by a straight line, and another 
 plane or face can be seen making nearly a right angle with the 
 first one, then we have a final proof, if the other indications 
 agree, that the mineral fragment under consideration is feldspar. 
 Here in the margin is a cut of a feldspar fragment, 
 where a is one of the reflecting faces and b is the 
 other; and these join together at a right angle, or 
 FU 14 nearly that. This is larger than most of the frag- 
 
 FBAOMENT OF ments found in the rocks. A common form under 
 FELDSPAR which feldspar is seen is that of a box partly crushed 
 by pressure applied in the middle of one end at the 
 top and exerted toward the opposite end of the bottom. Here 
 the sides remain at right angles with the top and bottom. But 
 such forms can only be seen in fragments, and generally with a 
 magnifier. 
 
 It is often the case that no right angle can be detected. Still, 
 the reflecting surfaces may be present, showing also the pearly or 
 subvitreous lustre. But if no faces can be found, the pearly 
 lustre may be there, distinctly less brilliant than in a case of 
 broken quartz; and finally, the test for hardness remains to apply. 
 The test of weathering is also valuable. On the weathered sur- 
 face the quartz grains retain their glassy lustre; feldspar grains 
 weather opaque and earthy, with increased whiteness. In spite 
 of these various resorts the learner will sometimes feel in doubt 
 whether certain fragments are quartz or feldspar. This is no 
 good reason for discouragement. Quite possibly the case is a 
 difficult one. He may try another rock, and, if possible, a coarser 
 one; or he may keep on repeating the round of tests, and come 
 to the best decision he can. 
 
 The geometrical form under which common feldspar crystallizes 
 is shown in Fig. 15. Here you see the position of the right
 
 (^L'AKTZ AND FELDSPAU. 
 
 27 
 
 15. LARGE CRYSTAL op 
 ORTHOCLASE, A SPECIES op 
 FELDSPAR. 
 
 angle represented in Fig. 14, since It is at right angles with I i 
 and also with 0. 
 
 We say this is common feldspar; since 
 there exist really several species of feld- 
 spars, all of which are composed chemi- 
 cally of silica, alumina, and an alkaline 
 constituent, while they differ according to 
 the nature of that constituent. If to silica 
 and alumina be united potash, the feldspar 
 is orthoclase, or common feldspar, the spe- 
 cies which gives us most nearly a right 
 angle. This is also called potash feldspar. 
 If the alkaline constituent be soda, we 
 have the feldspar known as albite, or soda 
 feldspar. If it is lime, we get anorthite. 
 If it is soda and lime, we have a soda-lime feldspar, labradorite, 
 or oliyoclase. There are a few other feldspars, but we need not 
 mention them here. 
 
 It is important to notice the proportions of silica in the sev- 
 eral feldspars, because acidic feldspars, or those with much silica, 
 are found in company with other minerals having much silica, and 
 basic feldspars, or those poor in silica, seek the company of other 
 basic minerals. Now the acidic feldspars have silica as follows: 
 orthoclase, 65 per cent ; albite, 68 ; and oligoclase, 62 per cent. 
 The basic feldspars have silica as next follows: labradorite, 52; 
 anorthite, 43. (See the Table of Compositions, Study VIII.) 
 
 You perceive that the feldspars differ in their composition; 
 but we cannot easily test the composition, and therefore we have 
 no certain way for distinguishing them. Hence, sometimes we 
 must simply say the mineral is a feldspar. If we detect the right 
 angle, we may say it is orthoclase. All the other feldspars 
 named may be grouped as planioclase or triclinic feldspars. Of 
 the plagioclase feldspars, albite inclines to snowy white; anor- 
 thite is often glassy and transparent; labradorite inclines to 
 gray, brown or greenish, with sometimes a beautiful play of colors 
 in reflected light; oligoclase is generally white with a greenish
 
 GEOLOGICAL STUDIES. 
 
 tinge and fine striae on the principal faces to be seen with a 
 magnifier. The presence of the colors indicated affords only a first 
 presumption as to the species of plagioclase under investigation. 
 Any plagioclase may show striations. We may safely say: If the 
 right angle is present, the feldspar is orthoclase; if striae are 
 present it is a plagioclase; if the feldspar is glassy it is very 
 probably a plagioclase; if it is cream-colored or reddish it is 
 probably orthoclase; if dusky or greenish, or with internal reflec- 
 tions, it is probably plagioclase. Orthoclase, also, undergoes less 
 change from weathering than plagioclase; and it is found more 
 commonly in the company of quartz. 
 
 Here is a table in which the characters are presented another 
 way: 
 
 Name of Feldspar. 
 
 Alkaline 
 Constituent. 
 
 Leading Colors. 
 
 Transparency. 
 
 Orthocluse. 
 
 Potash. 
 
 White, creamy, gray, flesh- 
 red. 
 
 Translucent, o p a q u e . 
 Rarely transparent. 
 
 Microcline. 
 
 Potash Soda. 
 
 Like orthoclase, or green. 
 
 Translucent. 
 
 *1 
 
 f Albite. 
 
 Soda. 
 
 White rarely bluish, gray, 
 reddish, greenish. 
 
 Transparent to snbtran.- 
 lueent. 
 
 s ! 
 
 Oligoclase. 
 
 Soda-Lime. 
 
 F a i 11 1 1 v grayish-green, 
 white. 
 
 Transparent to subtrnns- 
 lucent. 
 
 'h 
 
 
 
 Labradorite. 
 L Anorthite. 
 
 Lime Soda. 
 Lime. 
 
 Grav. brown, greenish. 
 Play of colors. 
 
 White, grayish, reddish. 
 
 Transparent to snbtrans- 
 lucent. 
 
 Transparent to translu- 
 cent. 
 
 By the decomposition of the feldspars we get kaolin, which 
 consists chiefly of silica, alumina and water. It is white when 
 pure, and is used in the manufacture of porcelain and china 
 ware. 
 
 EXERCISES. 
 
 Have you found any quartz in the specimen in your hand? How many 
 varieties of quartz in the specimen? State the color of each variety. Is there 
 any transparent quartz in the specimen? Point out any feldspar in the
 
 DARK-COLORED MINERALS. 29 
 
 specimen. How do you- know it is not quartz? What indication that it is 
 orthoclase or oligoclase? Point out some reflecting faces of feldspar. Have 
 you met with any striated feldspar? Take another bowlder fragment and 
 point out the quartz. Point out the feldspar. How many varieties of quartz 
 can you find in it? How many varieties of feldspar? Point out plagioclase 
 if any. Practice holding different specimens in such way as to catch the 
 feldspar reflections. Notice again and again the difference between the lus- 
 tre of feldspar and that of quartz. Search many different specimens from 
 different bowlders for varieties of feldspar, and particularly for striated feld- 
 spars. Do you often find orthoclase and plagioclase in the same bowlder? 
 What are commonest colors of feldspar, according to your observation? 
 Does quartz break with smooth faces, like feldspar? Which has the most 
 glistening lustre? Have you noticed feldspar fractures with a didl lustre? 
 
 OBSERVATION. The discrimination of feldspar from quartz is sometimes difficult in 
 email grains. But do not be discouraged, for it is difficult sometimes even for the pro- 
 fessor. Repeat these and similar exercises very many times. Use the same bowlder frag- 
 ments and also different ones. Every time you succeed you will feel fresh delight. 
 Every time you fail, form a new resolve. Always study with specimens. 
 
 STUDY VI. Dark -Colored Minerals. 
 
 Let us examine farther the same rock specimens as before used. 
 \Ve suppose these contain one or more dark-colored minerals. If 
 they do not, we must provide ourselves with specimens from 
 some other bowlder. Among 1 dark minerals disseminated through 
 bowlders, it will be noticed that some occur in thin, mostly shin- 
 ing, scales, and others do not. Let us take specimens containing 
 a scaly mineral. It is probably mica. With a knife point you 
 may lift up a succession of thin scales from the same fragment. 
 There seems no limit to the capability of splitting. Notice that 
 if the surfaces are brilliant, the scales are generally elastic and 
 tough. But examples long exposed to water and air have mostly 
 lost their elasticity, and have become softer, sometimes easily 
 crushing to a greenish -gray, lustreless powder. When the mica 
 is unaltered there is no difficulty in identifying it; but when 
 much altered it approaches the appearance of some other altered 
 minerals. 
 
 Mica, like feldspar, is a generic name; but all the micas are
 
 30 GEOLOGICAL STUDIES. 
 
 composed of silica, alumina, potash and iron, with some other 
 characterizing constituent. Common mica (so-called) is the 
 species muscovite. It splits into thin, tough, flexible, elastic 
 scales. In color it varies from white to gray, brown and pale 
 green. It is sometimes violet, yellow or dark olive green. 
 Bronzy muscovite is sometimes mistaken by the ignorant for 
 gold. The transparent variety is extensively employed in stove 
 doors, and is sometimes ignorantly called "isinglass." By absorp- 
 tion of water, muscovite undergoes the changes alreadv men- 
 tioned, and becomes hydromica, also called margarodite. We 
 find the mineral in all stages of transition to hydromica; and one 
 is often at a loss to decide between the two names. Through 
 the same kind of change it approaches talc and chlorite, as we 
 shall see. 
 
 Deep black mica with splendent lustre is generally the species 
 called biotite. We shall find it more common than muscovite. 
 Phlogopite is yellowish-brown, brownish, red (often with copper- 
 red reflections), green, white or colorless. This, also, is quite com- 
 mon. Lepidolite or lithia-mica is sometimes seen in delicate 
 pinkish scales. You will endeavor to find in bowlders the differ- 
 ent species of mica mentioned. 
 
 While speaking of the scaly minerals in our hands, it is best 
 to mention a few which are not micas. We shall meet with them 
 occasionally. Those which we shall mention are all hydrous 
 silicates of magnesia, except one, with generally other constitu- 
 ents; one of these is talc, which is simply a hydrous silicate of 
 magnesia that is, composed of silica, magnesia and water. 
 The scales are thin and tender, and not elastic, and their color 
 ranges from apple-green to white or silvery. Talc is the softest 
 of the minerals. The scales are very easily reduced to powder. 
 The mineral has a peculiar greasy feel, and this is one means of 
 distinguishing it from some micas; though, as before stated, 
 hydromica approaches it. Another mineral called pyrophyllite 
 is a hydrous silicate of alumina. Thin scales appear much like 
 talc; but the mineral is chiefly known as the constituent of a fine 
 compact rock used for slate pencils. Serpentine, a hydrous silicate
 
 DARK-COLORED MINERALS. 31 
 
 of alumina, magnesia and iron, is sometimes scaly or foliated, but 
 more frequently fibrous. It is far better known, however, in the 
 massive state as a rock. Its color is leek-green or blackish-green, 
 and like talc it has a greasy feel. Under chlorite are included 
 chiefly two foliated minerals which are both hydrous silicates of 
 alumina, magnesia and iron, and both of a greenish color. Of 
 these, ripidolite is transparent or translucent, with flexible, some- 
 what elastic leaves, and prochlorite is translucent or opaque, with 
 flexible and inelastic leaves. Keep a watch for these scaly min- 
 erals. 
 
 This ends the important scaly or foliated minerals. There are, 
 however, two species of dark minerals of much importance, and 
 sometimes we experience difficulty in distinguishing them from 
 dark mica. Arnphibole is one of these. If you take in hand 
 a bowlder fragment containing some dark min- 
 eral which is not mica, the mineral is likely to 
 be hornblende, the common variety of amphi- 
 bole. We can easily provide ourselves with 
 samples of such a rock. We must have them. 
 Now look at this dark mineral, hornblende. It FlG - ^.-CRYSTALS 
 
 j i u iuii Ti i u i i. OF HORNBLENDE, 
 
 is dark greenish or nearly black. It has a bright THE COMMON VA- 
 lustre, and about the hardness of feldspar. If BIETT or AMPHI- 
 you scratch it, the streak is white or whitish. 
 You can generally detect a crystalline face; and sometimes you 
 find a crystalline form which is like a six or four side<i rod, as 
 shown in Fig. 16. Often the surface of the crystal fragment pre- 
 sents a fibrous structure. This distinguishes it from black mica. 
 Another variety of amphibole is white and fibrous, and this 
 is tremolite or asbestos. Asbestos somewhat resembles linen, and 
 may be made into cloth which is incombustible. It is used as a 
 non-conductor of heat to wrap around steam boilers and pipes. 
 Still another variety is actinolite, consisting of coarser and 
 solider, green radiating fibres or blades. Silica, magnesia, lime, 
 iron, and often alumina are the principal constituents of amphi- 
 bole. By combining with water, hornblende changes to a soft, 
 greenish mineral resembling hydromica, though not in scales.
 
 32 GEOLOGICAL STUDIES. 
 
 The other important species of the dark minerals is pyroxene^ 
 It closely resembles amphibole, though inclining' more to green- 
 ish tints. It holds the same constituents, though in different 
 proportions; and has nearly the same crystalline forms and hard- 
 ness and nearly the same specific gravity. It is not easily distin- 
 guished without microscopic or chemical study. In colors, when 
 it varies from green or greenish-black (augite, the common vari- 
 ety), it approaches whitish in one direction (sahlite) and brown- 
 ish in the other (diallaye). It is seldom quite black, while this 
 is a common color with amphibole (in hornblende).* The differ- 
 ent natures of hornblende and augite are shown by 
 the fact that hornblende is very often found, like 
 rnuscovite, in company with quartz, while augite is sel- 
 dom so found. Their resemblance in crystalline form 
 will be seen by comparing Fig. 17 with Fig. 16. 
 FlG 17 Here the faces 1 1 make with each other an angle 
 CRYSTAL or of 87 5', while in hornblende the same faces stand at 
 
 THE^OMMON al1 an S le f 124 30 '' In Fi S' 17 thlS an S le ' S trUn - 
 
 VAHIETY OP cated by the plane i i. It is seldom, however, that 
 ENE ' we can detect the angles in the small fragments 
 found in common rocks. 
 
 There are still two minerals, generally dark, or even black, 
 which possess some importance as rock constituents. One of 
 these is tourmaline. It is seldom sufficiently abundant to deter- 
 mine the name of a rock, but its presence sometimes necessitates 
 a qualifying epithet. Tourmaline may often be seen in the form 
 of straight, stick-like, shining, black, imperfectly three-sided 
 prisms imbedded in crystalline limestones or quartz rocks, and 
 not unfrequently other kinds of rocks. The common prisms 
 range in size from a twentieth of an inch to half an inch and 
 over. Their sides are curved and generally striated or fluted, 
 
 * In addition to this, augite is frequently found altered to hornblende. In spite of 
 these resemblances between amphibole and pyroxene especially between the varieties 
 hornblende and angite it is very desirable for the trained investigator to be able to 
 discriminate between them, since. the determination of certain rocks depends on this. 
 Moreover, there are important and deep-seated differences between them, as is shown by 
 their optical and microscopic properties.
 
 DARK-COLORED MINERALS. 33 
 
 with a hardness equal to quartz. Rarer varieties of tourmaline 
 are brown, green, blue, pink, and even white. The mineral con- 
 tains boric acid, besides silica, alumina, and sundry other constit- 
 uents in various proportions. 
 
 The last of the dark minerals worthy of mention is hyper- 
 stliene. This is sometimes a rock constituent in company with 
 labradorite. It occurs in masses of thin, brittle lamellae of a 
 dark brownish-green, grayish-black, greenish-black, or pinchbeck- 
 brown color, having a hardness nearly equal to orthoclase. It 
 has about the same constituents as amphibole. 
 
 EXERCISES. 
 
 Take in hand a rock fragment containing a dark mineral, and state 
 whether the mineral is scaly. If so. are the leaves elastic? Are they brit- 
 tle? What is their color? What proportion of the rock do they form? If 
 not scaly, is the mineral lamellar? Is it fibrous? What is its color? Is it 
 shining or dull in lustre? If the scales were greenish, what mineral would 
 they probably be? Would they then be elastic or not? If whitish, what min- 
 eral would they probably be? Would they be elastic or not? Would they be 
 harder or softer than mica? If the scales are jet black, what mica have we? 
 What, if they are reddish? What, if they are bronze-like? What points 
 must be mentioned in describing a mineral ? Take another rock specimen, 
 and describe completely the most abundant mineral in it. What light- 
 colored minerals do you see? Pick out a mineral which you think is augite. 
 What particulars lead you to think it augite? Pick out a sample of horn- 
 blende. What differences between them can you discern? Which has most 
 quartz associated with it? If a rock contains biotite, is the other dark 
 mineral, if present, likely to be hornblende or augite? Select a rock contain- 
 ing hydromica. Why will not hydrotnica effervesce? What may hydromica 
 be mistaken for? p]xplain why the surface rock often contains hydromica 
 and the deep quarry rock muscovite. Did you ever know of a man who col- 
 lected bowlders containing bronzy mica, thinking this mineral to be gold? 
 Search for specimens of tourmaline. How does tourmaline differ from 
 hornblende? How will you know it when found?
 
 34 GEOLOGICAL STUDIES. 
 
 STUDY VII. Lime, Magnesia, and Iron Minerals. 
 
 Among' important rock ingredients two yet remain to be 
 studied which belong to the group of carbonates. Some of the 
 properties of carbonates have already been learned, especially 
 their tendency to effervesce when strong acids are applied to 
 them. Chalk, we have seen, is a carbonate, but it does not pre- 
 sent any crystalline form or lustre. It is simply earthy, and con- 
 sists of a mass of fine particles of carbonate of lime compacted 
 together. Marble also consists of a mass of grains and particles 
 somewhat cemented; but marble has some lustre. There are 
 shining faces. In fact, a close inspection, especially with a magni- 
 fier, shows that the rock is composed of small crystal fragments. 
 Some marbles are sufficiently coarse to show the crystalline struc- 
 ture very distinctly. 
 
 Now we frequently find these crystals sufficiently large to be 
 studied. Let us seek for some white vein running through an- 
 other rock. We may at first fall upon a vein of white quartz. 
 The tester will determine. Suppose we have found a white min- 
 eral or fragment large enough to show crystalline form, and soft 
 enough to be easily scratched. Probably this is calcite. You 
 cannot, perhaps, discover the complete form; but if you scruti- 
 nize closely, you will notice some angles, and you will perceive, 
 probably, a number of cracks which run in directions parallel with 
 the faces revealed. Perhaps the cut, Fig. 18, represents part of 
 what you see. Here is one face a, bounded by another 
 face b, forming an angle along the line m n. This is 
 not a right angle, but is greater or less. You see, also, 
 along the fractured border of a several angular sali- 
 ences, which are bounded on one side by planes ex- 
 actly parallel with b, and on another by planes parallel 
 with each other, and in fact parallel with another face 
 of the broken crystal. The directions of these planes 
 are continued in cracks passing through the crystal. 
 It appears that the crystal is made up of many small crystals, all
 
 LIME, MAGNESIA, AND IRON MINERALS. 
 
 FIG. 19. CRYSTAL OF 
 CALCITE. 
 
 having the same shape. If we could get one of these crystals 
 out, it would present the form shown in Fig. 19. This form is a 
 rhombohedron. If you take a cubical box and 
 partly crush it by pressing against one corner 
 toward the corner diagonally opposite, you re- 
 duce the box to the form of a rhombohedron. 
 Notice particularly the difference between this 
 and common forms of orthoclase. 
 
 The hardness of this crystal is much less than that of ortho- 
 clase; and this furnishes a third easy means of separating the 
 two minerals effervescence, want of right angle, and lower hard- 
 ness. 
 
 The cracks generally apparent indicate cleavage planes, as 
 Fig. 18 shows. Every fragment, therefore, presents the same 
 angles as the whole. Calcite is sometimes as transparent as 
 glass, and then known as Iceland spar. It possesses the strik- 
 ing property of double refraction. If you place a plate of Ice- 
 land spar on a printed page, you see every letter beneath it 
 double. Calcite is more commonly almost opaque. Its color is 
 nearly always white, but sometimes we find it yellowish, delicate 
 blue, and various other tints. The fundamental rhombohedron is 
 also frequently modified, and the forms resulting are very numer- 
 ous. The most common, however, is that known as dog-tooth 
 spar, of which a couple of large crystals are 
 shown in Fig. 20. 
 
 We must not conclude too readily that a 
 whitish mineral is calcite, even when soft 
 enough to be cut with a knife. Not unfre- 
 quently we encounter crystals having the lus- 
 tre and hardness of calcite, but with curved 
 faces opposite ones being convex and con- 
 cave. Cold dilute acid applied to these does 
 not cause effervescence, even after they are 
 reduced to powder. But heat applied pro- 
 duces it. The chemist informs us that this 
 mineral is composed of carbonate of lime, 
 
 FIG. 20. DOG-TOOTH 
 SPAR.
 
 36 GEOLOGICAL STUDIES. 
 
 fifty-four parts, and carbonate of magnesia, forty-six parts. A 
 mineral having this composition is called dolomite. This crystal 
 with curved faces is a variety called pearl spar, when the color 
 is white, and brown spar when the color is brown. The brown 
 coloring ingredient is iron. So manganese or cobalt gives a red- 
 dish dolomite. 
 
 But when the crystalline faces are not curved it is difficult to 
 distinguish dolomite from calcite without chemical analysis. We 
 may find "veins" of coarse dolomite crystals closely resembling- 
 calcite veins in color, form, and hardness of the mineral. Our 
 Only expedient then is the dilute acid. We shall see that dolo- 
 mite is a mineral almost as abundant as calcite, and hardly less 
 important. 
 
 A rock ingredient belonging to the group of sulphates is 
 very familiar. It is soft enough to be crushed between the 
 teeth. Everyone knows gypsum; but pure crystallized gypsum 
 is less common. It occurs in distinct crystals, or broad leaves, or 
 plates, sometimes a yard across, and as transparent as glass. This 
 variety is called selenite. One of the crystal plates is shown in Fig. 
 21. Gypsum is composed of sulphuric acid forty-six and one-half 
 
 parts, lime thirty-two and one- 
 half parts, and water twenty- 
 one parts. When subjected to 
 heat the water is expelled, and 
 the gypsum is said to be "cal- 
 cined." When ground gypsum 
 is calcined it constitutes "plas- 
 ter of Paris" so called be- 
 cause the quarries at Montmartre, Paris, supplied gypsum for cal- 
 cination and use in the city. The Paris gypsum, however, con- 
 tained also carbonate of lime. When calcined gypsum is exposed 
 to water it reunites with a certain amount of water, and re- 
 sumes a high degree of hardness. In other words, it "sets." It 
 is, therefore, valuable for many purposes. 
 
 There are three principal ores of iron which in some regions 
 exist to a rock-making extent. Haematite is simply an oxide of
 
 LIME, MAGNESIA, AND IRON MINERALS. 37 
 
 iron, composed of two equivalents (or atoms) of iron and three 
 of oxygen. Taking the mineral by weight, one hundred parts of 
 haematite contain thirty of oxygen and seventy of iron. This 
 mineral is well known as iron rust. In nature it is often beauti- 
 fully crystallized, and occurs also in granular and stalactitic 
 shapes, and in laminae, either thick or thin. The crystals have a 
 metallic lustre, and sometimes are truly splendent. Their color 
 is steel gray, or iron black, but scales thin enough to transmit 
 light are blood red. When the surface is shining and mirror- 
 like, the mineral is called " specular " ore. Haematite sometimes 
 occurs in thin micaceous scales, and frequently in compact Jibrous 
 masses. When earthy, it becomes red chalk and red ochre. 
 Haematite sometimes attracts the magnetic needle. A neat way 
 of distinguishing haematite in any of its varieties is 'by the red 
 color of its powder (called streak). Powdered haematite is, there- 
 fore, red, and is much used as a red paint. 
 
 Limonite is simply haematite which has united with water. 
 It contains sesquioxide of iron, eighty-six parts, and water, four- 
 teen parts, in one hundred. The eighty-six parts of the ses- 
 quioxide contain twenty-six parts of oxygen and sixty parts of 
 iron. We find limonite commonly in stalactitic or botryoidal 
 forms the latter like bunches of grapes and having a fibrous 
 structure. These forms often possess a nearly black, glaze-like 
 exterior. In the mines at Salisbury, Conn., Amenia, N. Y., 
 and in many other localities, the cavities of the rocks often 
 contain groups of brilliant black, icicle-like columns of limonite 
 depending from the roof or reaching quite to the floor of the 
 cavity. In other situations this ore is earthy, and constitutes 
 ordinary yellow ochre. This is the iron deposit of bogs, where it 
 forms bog iron ore, of which we have before spoken (page ll) r 
 Limonite is easily distinguished by its yellow or yellowish-brown 
 streak. 
 
 Magnetite, the third important ore of iron, is known by its 
 black streak. It is a mixture of the two principal oxides of 
 iron protoxide (or one of oxygen and one of iron), and ses- 
 quioxide (or three of oxygen and two of iron). The amount of
 
 38 GEOLOGICAL STUDIES. 
 
 oxygen in one hundred parts by weight is twenty-eight parts, 
 and the amount of iron seventy-two. This ore, 
 therefore, contains more iron per ton than either of 
 the others. It tends to crystallize in black octa- 
 hedrons, or eight-sided forms like Fig. 22, which are 
 sometimes found scattered through crystalline rocks. 
 OcT\nEimAL Magnetite is so named because it strongly attracts 
 CRYSTAL OP the magnetic needle. Occasional pieces possess, 
 MAGNETITE. a j gQ ^ t | ie p O ] ar } t y o f fae magnetic needle, and these 
 are known as loadstone or lodestone. There are several other 
 ores of iron of less importance than these. 
 
 We ought to make mention of a few additional minerals 
 which sometimes give a qualifying character to rocks, even if 
 they are not constitutive, like the others named. Pi/rite or 
 pyrites is bronze yellow, hard as quartz, and occurs in cubes and 
 octahedrons. It is composed of sulphur and iron. Epidote is 
 mostly a pale yellowish-green mineral, as hard as quartz, com- 
 posed of silica, alumina, lime, and iron. It is known principally 
 in a massive or rock condition, as a constituent of crystalline 
 rocks. The crystals are generally elongated, sometimes needle- 
 shaped or fibrous. Garnet is a generic name of minerals con- 
 sisting of silica and various bases. The garnets present a great 
 range of colors, but the common garnet is a deep wine-red. It 
 is an iron-alumina garnet; when transparent, ''precious garnet." 
 It is easily recognized by its twelve-sided or twenty four-sided 
 form. Emery is an impure corundum. The latter exceeds quartz 
 in hardness, and consists almost wholly of alumina. All these 
 minerals may be found in common bowlders, and the student 
 must not cease to search until he finds them. 
 
 EXERCISES. 
 
 What is the nature of the rusty deposit from some spring waters? What 
 is the nature of the white deposit? Suppose haematite combines with water, 
 what does it become? If limonite loses its water, what does it become? How 
 many pounds of iron in 2,000 pounds of limonite? How many in 2,000 
 pounds of hematite? How many in 2,000 pounds of magnetite? How many
 
 REVIEW OF THE IMPORTANT MINERALS. 39 
 
 pounds of lime in 2,000 pounds of calcite? What use has calcite in agricul- 
 ture? Which is most suitable to the soil, calcite or quicklime? What is the 
 difference between farm plaster and plaster of Paris? If a supposed calcite does 
 not effervesce with cold acid, what may be concluded as to its composition? 
 How may calcite be easily distinguished from gypsum? Name all the white 
 minerals thus far described. Which is hardest? Which softest? Which 
 next to hardest? Show a specimen of calcite. Show some other minerals 
 and name them. How can you distinguish mica from micaceous haematite? 
 In a mass of iron ore kept constantly wet, which will we have, haematite, 
 limonite, or magnetite? State where you have seen any of these ores. Which 
 ore was it? How do you know? What are the uses of emery? What is an 
 emery wheel? Have you found calcite in a rock abounding in quartz? If 
 so, was the calcite generally distributed or in a layer? Was it fine-grained 
 calcite or coarsely crystalline? Have you found calcite in company with 
 biotite? In what sort of rock did you find octahedrons of magnetite? Show 
 three specimens giving the three streaks of the principal iron ores. Why is 
 hornblende darker than calcite? Why is it heavier than calcite? What 
 minerals have you now in your collection? 
 
 STUDY VIII. Review of the Important Minerals. 
 
 Of the thirty-five or forty species of minerals briefly noticed, 
 the following are the most important in the study of rocks: 
 Quartz, orthoclase, plagioclase, muscovite, biotite, hydromica, 
 talc, hornblende, augite, calcite, and dolomite. The student who 
 can discriminate these under their various aspects, and especially 
 in rocks not coarse-grained, has accomplished much. The re- 
 maining species, nevertheless, are liable to be met, and many of 
 them constitute important ingredients in certain rocks not gener- 
 ally distributed. This will appear when we come to the study of 
 rocks. 
 
 We have prepared, for the convenience of the student, a 
 tabular exhibit of the chemical composition of these minerals, 
 and have added in the last column figures expressive of the hard- 
 ness of each. The meaning of these figures is understood by 
 reference to certain standards of hardness as indicated on page 42. 
 
 A few species are mentioned in the table for the first time.
 
 40 
 
 GEOLOGICAL STUDIES. 
 
 TABLE OP COMPOSITION OF 
 
 MINERALS. 
 
 OXYGEN. 
 
 SILICA. 
 
 ALUMINA. 
 
 OXIDES 
 or IRON. 
 
 POTASH. 
 
 SODA. 
 
 Binary Compounds. 
 
 
 
 
 
 
 
 Quartz 
 Haematite 
 
 53.33 
 30 
 
 
 
 
 
 
 Limonite 
 
 25 
 
 
 
 
 
 
 Magnetite 
 
 27.6 
 
 
 
 
 
 
 Menaccanite 
 
 
 
 
 
 
 
 Franklinite 
 
 
 
 
 
 
 
 Pyrite 
 
 
 
 
 
 
 
 Halite ("salt") 
 
 
 
 
 
 
 
 Silicates. 
 
 
 
 
 
 
 
 f Orthoclase . . '. 
 
 
 651 ,5 
 
 18 
 
 
 17 
 
 
 ^ 1 Albite g 
 
 
 68 H 
 
 20 
 
 
 
 "ia" 
 
 , Oligoclase 
 
 
 62JJ 
 
 24 
 
 
 
 9 
 
 Labraclorite. ... '| 
 
 
 58 j o 
 
 30 
 
 
 
 4 
 
 Anorthito J ^ 
 
 
 a 
 
 37 
 
 
 
 
 Kaolinite 
 
 
 46.5 
 
 34.4 
 
 ...... 
 
 
 
 ("Muscovite 
 
 
 47 
 
 33 
 
 
 'io' 
 
 '"2" 
 
 1 \ Biotite 
 
 
 36 
 
 16 
 
 20 
 
 8 
 
 ..... 
 
 ^ Phlogopite 
 Lepidolite 
 
 
 40 
 48 
 
 15 
 25 
 
 5 
 9 
 
 9 
 
 
 Pyrophyllite . '.'.'.. '. '. '.'. 
 
 
 5 
 
 '28'" 
 
 
 
 
 Serpentine 
 ^ f Ripidolite 
 
 l] 
 
 
 44 
 31 
 
 "if" 
 
 "3"' 
 4 
 
 
 
 t> [Prochlorite 
 
 
 27 
 
 19 
 
 26 
 
 
 
 ("Hornblende 
 
 
 50 
 
 10 
 
 8 
 
 
 '"2" 
 
 *s! -{ Tremolite 
 
 
 59 
 
 
 2 
 
 
 
 
 
 
 
 
 
 
 ^ [Actinolite ... 
 
 
 57 
 
 
 5 
 
 
 
 s - fAugite 
 
 
 
 48 
 
 7 
 
 
 
 
 1-j Sahlite 
 
 
 54 
 
 
 6 
 
 
 
 ^ {, Diallage 
 
 
 52 
 
 2 
 
 9 
 
 
 
 Hypersthene 
 Tourmaline (black) 
 Epidote 
 
 
 
 52 
 37 
 38 
 
 3 
 
 85 
 
 12 
 13 
 
 
 '"a" 
 
 Garnet 
 
 
 35 
 
 7 
 
 28 
 
 
 
 
 
 
 
 
 
 
 Carbonates. 
 
 CARBON 
 
 
 
 
 
 
 
 ic ACID. 
 
 
 
 
 
 
 Calcite 
 
 44 
 
 
 
 
 
 
 Dolomite 
 
 47. as 
 
 
 
 
 
 
 Magnesite 
 
 52 4 
 
 
 
 
 
 
 Siderite 
 
 37.9 
 
 
 
 02.1 
 
 
 
 Sulphate. 
 
 Gypsum 
 
 
 
 
 

 
 REVIEW OF THE IMPORTANT MINERALS. 
 THE COMMON MINERALS. 
 
 41 
 
 MAG- 
 NESIA. 
 
 IRON. 
 
 WATER. 
 
 OTUER CONSTITUENTS. 
 
 HARD- 
 NESS. 
 
 
 70 
 
 
 Silicon 46. 67 
 
 7 
 5 5-6 
 
 
 60 
 72.4 
 
 15 
 
 Protox. Iron 31.03 + Sesquiox. Iron 68.97. 
 Often with Titanium 
 Approximately, Perox. and Protox. Iron 54 
 + Oxide Titanium 43 
 
 5-5.5 
 5.5-6.5 
 5-6 
 
 
 
 
 Haematite 66 + Sesquiox. Mangan. 14 + Pro- 
 tox Zinc 20 
 
 5 5-6. 5 
 
 
 46 5 
 
 
 Sulphur 53 
 
 6-6 5 
 
 
 
 
 Sodium 39. 3 + chlorine 60. 7 
 
 2.5 
 
 
 LIME 
 
 
 
 f> 7 
 
 
 5 
 
 
 
 6-7 
 6-7 
 
 
 13 
 
 
 
 6 
 
 
 20 
 
 
 
 6-7 
 
 .... 
 
 17 
 28 
 
 
 24.1 
 
 5-io 
 
 Most actual examples 1-5 p.c. water, by al- 
 teration 
 
 Lithia 4 -f Fluorine 5 
 
 1-2.5 
 
 2-2.5 
 2.5-3 
 2.5-3 
 2.5-4 
 1 2 
 
 32 
 
 
 5 
 
 
 1-1.5 
 
 42 
 
 
 5 
 12 
 
 
 1-2 
 2 5-4 
 
 33 
 
 
 13 
 
 
 2-2.5 
 
 16 
 15 
 
 12 
 
 11 
 
 The Iron is a Protoxide - 
 Iron is mostly Protoxide, and ranges to 20 
 
 1-2 
 5-6 
 
 25 
 
 13.4 
 15 
 
 15 
 
 13 
 
 20 
 21 
 
 23 
 
 
 The Iron is a Protoxide 
 The Iron is a Protoxide 
 
 5-6.5 
 5- 
 
 16 
 22 
 
 19 
 2 
 
 
 
 5-6 
 
 2 
 
 '2-2 ' ' 
 
 28 
 
 5fi 
 
 2 
 
 Fluorine 2 + Boron 8 
 Manganese oxide 0-5 
 This is the common Lime-Iron Garnet 
 
 7-7.5 
 6-7 
 6.5-7.5 
 
 2 5-3 5 
 
 21.73 
 47 6 
 
 29.44 
 
 
 Carbonate Lime 54.35+Carb. Magnesia 
 45.B5 7T 
 
 3.5-4 
 35-45 
 
 
 
 
 
 3.5-4.5 
 
 
 32.6 
 
 20.9 
 
 Siilohuric Acid 46.5 ... 
 
 1.5-2
 
 42 GEOLOGICAL STUDIES. 
 
 SCALE OF HARDNESS. 
 
 1. Talc, j Scratched with the finger nail. 
 
 2. Gypsum, ) 
 
 3. Calcite, i Easily cut with a knife. 
 
 4. Fluonte (Fluor Spar), ) 
 
 5. Apatite, Cut with difficulty. 
 
 6. Orthoclase, Barely scratched by steel. 
 
 7. Quartz, 
 
 8. Topaz or Beryl, ^ N ot scratched by steel. 
 
 9. Corundum, 
 10. Diamond, 
 
 The "Table for Determinations" must not be regarded as an 
 infallible guide, but it will probably be an aid to the student. A 
 great deal of exercise should be had on it. 
 
 TABLE FOR DETERMINATION OF MINERALS. 
 
 Hardness 6.5 to 7 or over. 
 Lustre vitreous. 
 Color black: sometimes brown, green, blue, pink or white; 
 
 often in prisms with curved, striated or fluted sides, Tourmaline. 
 Color yellowish-green, Epidote. 
 
 Color deep red, crystalline form conspicuous, 12-24-sided, Garnet. 
 
 Color whitish, dusky, reddish; transparent when pure: 
 
 crystalline faces not shown on fracture. 
 
 No double refraction; crystal, a 6-sided prism, Quartz. 
 
 Double refraction strong (when transparent) ; crystal oc- 
 tahedral or cubical, Andalusite. 
 Lustre metallic ; color brass yellow, Pyrite. 
 Hard ness 4.5 to 6. 
 Streak brownish yellow; lustre silky; often stalactitic or 
 
 botryoidal, Limonite. 
 
 Streak red; often lamellar, columnar or granular, Hmmatite. 
 
 Streak dark reddish-brown; acts slightly on the magnet. Franklinite. 
 Streak submetallic ; powder black to brownish red, Menaccanite. 
 
 Streak black, lustre metallic; crystals often octahedral, Magnetite. 
 
 Streak light. 
 
 Streak white; color mostly light, ranging through white, 
 gray, red, brown and green ; lustre pearly or vitreous- 
 pearly ; texture not fibrous (FELDSPAR). 
 With right-angled crystallization; no surface striations; 
 
 colors mostly white, creamy and pale red, Orthoclase.
 
 REVIEW OF THE IMPORTANT MINERALS. 43 
 
 No exact right angle; striations often present; colors 
 bluish, grayish, greenish, dusky or white, sometimes 
 glassy transparent, Plagioclase. 
 
 Streak pale greenish. 
 
 Color black or greenish black; texture often fibrous; 
 
 having no prismatic right angle (AMPHIBOLE). Hornblende. 
 
 Color green, greenish or greenish-black; often white if 
 
 fibrous. 
 Texture seldom fibrous; having a prismatic angle of 
 
 nearly 90 (PYROXENE), Augite. 
 
 Texture of radiating, prismatic, greenish fibres, Actinolite. 
 
 Texture of fine, parallel, whitish fibres or blades, Tremolite. 
 
 Streak grayish or brownish-gray; color dark brownish- 
 green, grayish-black, greenish-black; lustre some- 
 times a little metalloidal, Hypersthene. 
 Hardness from 3 to 4. 
 
 Effervescence with acids; color generally nearly white; some- 
 limes transparent; lustre vitreous or vitreous pearly. 
 Effervescence with cold acid ; faces not curved ; often trans- 
 lucent or transparent; generally distinctly rhombo- 
 hedral, Calcite. 
 
 Effervescence only with hot acid. 
 Lustre inclining to pearly; color often brownish; faces 
 
 sometimes curved, Dolomite. 
 
 Lustre vitreous. 
 
 Color white, yellow, gray, brown, green, Magnesite. 
 
 Color ash-gray toJarown or red, Siderite. 
 
 No effervescence with acids; lustre greasy, waxy or earthy; 
 
 color greenish ; occuring only massive, Serpentine. 
 
 Hardness below 3; no effervescence with acids. 
 Structure distinctly foiiaceous. 
 Folia elastic when unweathered. 
 
 Colors from black to greenish ; lustre splendent, Biulite. 
 
 Colors gray, brown, greenish, violet, yellowish, olive- 
 green; often transparent, Muscovite. 
 Colors yellowish-brown to brownish, often with copper 
 
 reflections, Phlogopite. 
 
 Colors grass-green to olive-green ; transparent to trans- 
 lucent, Ripidolite. 
 Folia inelastic, greenish, reddish or black. 
 
 Color pink or pinkish, Lepidolite. 
 
 Color apple-green to whitish; folia flexible but inelastic; ( Talc. 
 
 feel greasy, ( Pyroph tjllite.
 
 44 GEOLOGICAL STUDIES. 
 
 Color deep green (CHLORITE). 
 
 Ranging from grass-green to olive-green ; folia some- 
 what elastic; transparent to translucent, Ripidolite. 
 Ranging from grass-green to blackish-green; translu- 
 cent to opaque, Prochlorite. 
 Color black; folia flexible; feel greasy; streak black; 
 
 lustre metallic, Graphite. 
 
 Structure indistinctly foliaceous or compact; green or green- 
 ish ; lustre earthy, Hydromica. 
 Structure not foliaceous; sometimes lamellar. 
 
 Color light; lustre vitreous or silky; crystals transparent, Gypsum. 
 Color black; blackens white paper; in granular masses, Graphite. 
 
 STUDY IX. Quartzose Rocks. 
 
 We return now to the field and resume our intercourse with 
 the bowlders. We should be prepared to study them now as 
 rock specimens. Any accessible rocks " in place " bed rocks 
 will be quite as suitable, and should be especially studied; but 
 taking our country at large, not one tenth of our students could 
 depend on finding a supply of rock specimens without recourse to 
 bowlders. These are almost everywhere throughout our northern 
 states. On the prairies and in the southern states where bowlders 
 do not abound, they should be obtained from some bowlder-cov- 
 ered region. They should be had in large supply. Regions 
 abounding in bowlders are even better situated for lithological 
 studies than other regions, since the number of species to be had 
 on a square mile is much greater than would be supplied within 
 an equal area by rocks in place. 
 
 You have noticed that all the rocks which thus far have been 
 in our hands for mineral study have been hard and made up of 
 grains which are either crystals or fragments of crystals. They 
 are therefore known as crystalline rocks. On the contrary, the 
 bed rocks in most portions of the country are not so hard and 
 crystalline. They consist of limestones, sandstones and shales, 
 having mostly a dull lustre, often containing fossils; and if the 
 constituents are sufficiently coarse to be detected with the mag-
 
 QUAKTZOSE ROCKS. 45 
 
 nifier, they are seen to be rounded as if they had themselves, at 
 some time, been rolled about like bowlders. Many limestones, 
 however, are exceptions to this statement, some of them, and 
 most marbles, being decidedly crystalline. You have remarked 
 then two series of rocks, the crystalline and the frag mental; 
 and you already know that nearly all our bowlders belong to the 
 crystalline series. Of the crystalline rocks you have already no- 
 ticed many sorts or species, and you will find them very much 
 more diversified than the fragmental. 
 
 Probably the first bowlder which we attempt to study will be 
 a quartzite a rock composed wholly of quartz, or nearly so, 
 and either massive or thick-bedded. Glancing over the field, you 
 will probably notice many white or very light-colored bowlders. 
 Inspect one of them closely. Test it for hardness. You make 
 no scratch. Examine its structure. Can you trace the outlines 
 of its constituent fragments or grains? If you can do this easily, 
 the quartzite is granular. But if you find the constituent grains 
 closely pressed together, so that they seem to have indented each 
 other and blended together, the quartzite is vitreous. Sometimes 
 it is so vitreous as to almost constitute something -like a mass of 
 opaque glass. On the other extreme, the grains are sometimes 
 so little adherent that the rock crumbles, and is then a, friable 
 quartzite. All this you can easily demonstrate in the field. 
 Otherwise, the different sorts of specimens can be collected and 
 brought before the class, and placed in your hands. 
 
 There are several other varieties of quartzites. They may be 
 fine or coarse. When they contain pebbles they are quartzose 
 conglomerates. Some are composed chiefly of white porcelain- 
 like quartz; others, of a more glassy quartz. Some have grains 
 or pebbles of jasper red jasper being quite common. These 
 arejaspery. There may be present sparsely scattered crystalline 
 fragments of mica, hornblende, talc, chlorite, or other minerals 
 which give a qualified character to the quartzite. It is then 
 micaceous, hornblenclic, talcose, or chloritic. Quite often the 
 peculiar straight, long, black crystals of tourmaline are seen. 
 With a little patience you may collect twenty or more varieties 
 of quartzite.
 
 4G GEOLOGICAL STUDIES. 
 
 But we have also fraymental quartzose rocks. The common 
 sandstone seen in the bluff or used in some of our buildings is 
 composed merely or mostly of grains of quartz. But when you 
 inspect the rock, the shining lustre of the quartzite is wanting, 
 and the grains are not so closely compacted together. The 
 sandstone, therefore, is more easily broken; and friable kinds are 
 of more frequent occurrence. Moreover, you will notice in e r ery 
 sandstone the presence of foreign particles, sometimes of an 
 earthy character and sometimes of other minerals not quartzose. 
 Among fragmental quartzose rocks there are also conglomerates 
 and grits and materials of various colors, making the general tint 
 of the rock gray, bluish, reddish, purplish, or even nearly white. 
 The character of the sandstone mav also be qualified by the 
 presence of foreign ingredients like mica, clay, calcite, iron-rust, 
 bitumen, petroleum, or coaly matters. It is then micaceous, 
 argillaceous, calcareous, ferruginous, bituminous, petroliferous, 
 or carbonaceous. 
 
 Most of the quartzites show little evidence of stratification or 
 arrangement in layers or "beds." Others are thick-bedded, and 
 still others are thin-bedded, and present a finer and generally 
 more homogeneous texture. These are silicious schists. By 
 the addition of mica, hornblende, or other minerals, they become 
 schists of other sorts, as we shall see. When the bedded quartz- 
 ites contain argillaceous matter, and are extremely fine and uni- 
 form, they constitute novacidite. When they are reddened by 
 an abundance of haematite, they form a jasper schist. The 
 jaspery materials are generally arranged in ribbon-like bands 
 alternating with materials more haematitic or more purely sili- 
 cious. These bands are often so folded and contorted as to con- 
 stitute a curious and instructive study. 
 
 The materials of quartzo-e rocks sometimes occur quite un- 
 cemented. Indeed, all beds of sand are such, and illustrate what 
 is supposed to have been the remote condition of most quartzose 
 rocks. How the sand, in the course of time, has become so 
 consolidated is not fully understood. Among some fragmental 
 rocks, however, we can detect some kind of cement. Oxide of
 
 QUARTZOSE ROCKS. 47 
 
 iron sometimes serves as such cement, and this imparts a reddish 
 or yellowish color to the rock. Carbonate of lime is a common 
 cement, and in such cases can be detected with the naked eye or 
 the lens as a whitish filling of the interstices. Its presence, also, 
 is denoted by a slight effervescence with acids. Some sandstones 
 are so highly calcareous that on breaking the rock sparry reflect- 
 ing faces are visible running through it for short distances. 
 These are faces of the rhombohedral form under which the car- 
 bonate of lime has crystallized. 
 
 Many of you have noticed, scattered over the fields, flattened 
 rounded stones of dark reddish color and considerable weight, 
 apparently containing iron, but also with more or less fine sand 
 disseminated through them. As found in the soil, they are 
 generally composed of concentric layers, one within the other. 
 The outer layers are distinctly reddish, and not very hard, but 
 there is generally a central nucleus which is grayish-black, com- 
 pact, and hard. Quite often the outer, softer layers are detached 
 from the inner mass; and this often takes place before the stone is 
 broken. The nucleus can then be heard rattling within, when 
 the stone is shaken. These stones are the subjects of much 
 curiosity and conjecture among those ignorant of geology. They 
 are often called "iron-stones," "kidney iron-stones," or when 
 clayey, "clay iron-stones," and with a little more correctness, 
 "iron nodules" or "iron concretions." Now, the chemist as- 
 certains for us that they are composed chiefly of carbonate of 
 iron, and are, therefore, impure siderite. Our own inspection 
 reveals a concentric structure, showing that they are ferruginous 
 concretions. That is, the iron matter began at first to collect 
 around a centre in some sand or clay rock, then successive layers 
 collected around the first ones, so that the whole concretion is 
 composed of a succession of concentric layers. It may be sup- 
 posed the carbonate of iron moved through the rock in a state of 
 solution. Arriving at its place, the carbonate was precipitated. 
 When, at some later time, the nodule was left on the surface, 
 exposed to the air, the iron on the exposed exterior united with 
 more oxygen and became a peroxide, causing the carbonic acid to
 
 48 GEOLOGICAL STUDIES. 
 
 escape. As far as this action penetrated, a rusty shell was 
 formed. Deeper within, the original condition remained. This 
 is the state of partial change in which we find it. Now, if we 
 reason correctly, the process of oxidation is continuing, and in 
 the course of time will penetrate to the centre. Also, as the 
 oxidation has penetrated only a certain distance, our thoughts go 
 back to the commencement of the process. It had a beginning, 
 and that was not very far back in time; for if it were, the 
 oxidation would have reached to the centre before our day. 
 Now, if we could ascertain how many years have been required 
 for the oxidation to penetrate one sixteenth of an inch, we could 
 easily calculate how long since the work began, if we might 
 assume that the progress of it has been" uniform. That is, the 
 calculation would show how long a time has elapsed since those 
 geologic events took place which left the nodule exposed to the 
 peroxidizing action. 
 
 The process of concretion is noticed in other kinds of min- 
 erals, as we shall see. In ferruginous sandstone quarries we can 
 
 sometimes observe it going on. 
 A freshly exposed surface of the 
 formation may exhibit a rude 
 concretionary structure extend- 
 ing across two or more strata, 
 as represented in Fig. 23. As 
 the concretionary lines cross the 
 FIG. SS.-COHOBETIOKABT STRUCTURE lineg Q f stratification, they are 
 CROSSING SANDSTONE STRATA. 
 
 more recent than they. The 
 
 arrangement of the material must, therefore, have taken place in 
 the rock. In certain sandstones some of the iron bands become 
 extremely solid. 
 
 Quartzose rocks undergo less change than any others on ex- 
 posure to the weather. They make, therefore, extremely durable 
 building stones. Some of the sandstones, like the Ohio and Nova 
 Scotia freestones, and the Connecticut valley " brown stones," 
 are verv highly esteemed. Even the flinty, quartzite bowlders, 
 in regions where other good building stones are wanting, are
 
 QUARTZOSE ROCKS. 49 
 
 sometimes broken up and dressed into shape for use with other 
 dressed bowlders. Much sandstone is too incoherent for building 
 purposes, and other sandstones after use develop rusty stains, 
 through the peroxidation of the iron which they contain. The 
 disintegration of friable sandstones has often resulted in extensive 
 beds of sand, which are used, as well as the drift sand, in the 
 preparation of mortar. When the sand is white and quite free 
 from iron, it is employed in glass making. Grindstones and 
 whetstones are made from fine and even-grained sandstones. 
 Scythe stones are generally made from a fine-grained mica schist, 
 of which we shall learn hereafter. Many hones are formed of 
 fine homogeneous silicious schist. One well known sort comes 
 from Nova Scotia; but the favorite hones are "Arkansas stones." 
 Others are made from novaculite. These are some of the common 
 uses of quartzose rocks. 
 
 EXERCISES. 
 
 Pick out from this collection of specimens all the quartzites. Select the 
 vitreous quartzites. Separate the granular quartzites. Indicate those some- 
 what intermediate in structure. Point out a quartzose vein. How does a 
 sandstone differ from a quartette? Show a quartzite having two or more 
 varieties of quartz. Point out a jaspery quartzite. One with tourmaline. 
 One with mica scales. One with a little feldspar. Show a stratified quartz- 
 ite. How does this differ from a sandstone? Exhibit a ferruginous sand- 
 stone. What is its color? What does that color result from? Show an 
 argillaceous sandstone. Find some concretionary structure. What are the 
 colors in it? What is the material? Why is one ferruginous sandstone yel- 
 low and another red? What change of color takes place when the yellow 
 one is burned? What is the cause of the change? Why are quartzose rocks 
 used for sharpening purposes? What is sand paper? What is emery paper? 
 Which is most efficient, and why? What is a razor stone? Indicate some 
 building in which sandstone is used. For what parts is it used? Whence 
 was it obtained? State what defect is liable to appear- in a sandstone used in* 
 building. Why do defects reveal themselves after the stone is built in, and 
 not previously? What are flagstones? Mention a locality which affords 
 good flagstones. What defects sometimes appear in flagstones after use? 
 What is the cause of stains? Why do portions scale off? Why do flag- 
 stones sometimes break through the middle? Do the cracks generally run 
 with the walk, or across the walk? What does this indicate? How are arti- 
 ficial flagstones made? What is a 'chalcedonic quartzite? A tourmalinic
 
 50 GEOLOGICAL STUDIES. 
 
 quartzite? Let two students have the task of collecting all possible varieties 
 of quartzose rocks, collecting for some weeks, as opportunity offers. 
 
 STUDY X. Micaceous, Amphibolic, and Pyroxenic Rocks. 
 
 I. Micaceous Rocks. 
 
 No bowlders are more abundant than those containing mica. 
 On every hand its glistening scales may be seen reflecting the 
 sunlight. It exists in all proportions from the scattered scales 
 which characterize a micaceous sandstone or quartzite to such 
 quantities as make it determinative of the character and name of 
 the rock. When a quartzite contains as much as twenty-five per 
 cent of mica, it forms the rock known as greisen (pronounced 
 gri'sen). 
 
 We may return now to the same specimens used when study- 
 ing dark-colored minerals. Here, besides the mica apparent in 
 certain of them, we notice one or more light-colored sorts. Is 
 either of them quartz ? Test its hardness. Is either of them 
 feldspar? Remember, you determine this, first, by hardness 
 inferior to quartz, and superior to calcite; second, by its some- 
 what pearly instead of glassy lustre; and third, by its reflecting 
 cleavage faces, which do not occur in quartz. If you are cer- 
 tain we have in this rock quartz, feldspar, and mica, each in 
 considerable abundance, and no other mineral in much abun- 
 dance, then the rock is granite, if it is massive or unstratified; 
 but if it be thick-bedded, the rock is gneiss (pronounced gnice). 
 If it is thin-bedded, with a large percentage of feldspar, it is also 
 gneiss; but generally, when thin-bedded, the percentage of feld- 
 spar is rather small; the rock is composed chiefly of mica and 
 quartz, and is called mica schist. In all these jocks the mica 
 may be of any species, and so of the feldspar also. 
 
 The proportions of these constituents of granite and gneiss 
 may vary to a great extent, and in this the general complexion of 
 the rock may vary. We have very light granites and quite dark 
 granites. Besides this, the colors of the quartz may vary, as well 
 as those of the feldspar. If either the quartz or the feldspar is
 
 MICACEOUS, AMPHIBOLIC, AND PYKOXENIC ROCKS. 51 
 
 .quite red and is abundant, while the mica is subordinate, then we 
 have a decidedly reddish granite. The rock may also vary in 
 fineness. Fine granites are most durable for building stones. 
 Sometimes you find great crystals of feldspar or great flakes of 
 mica, giving you the constituents of granite, but scarcely suffi- 
 ciently mixed to form a proper granite. 
 
 Some recent lithologists do not separate granite from gneiss; 
 and it is certainly difficult, sometimes, to decide from a hand 
 specimen, whether the rock is stratified or not. We can only say 
 that if the different minerals are equally distributed, the rock 
 may be pronounced massive; but if the mica is ranged across the 
 stone in bands, however indistinct, we may set the rock down as 
 stratified. But these bands and the intervening feldspar or 
 quartz must not be regarded as beds or strata. They are only 
 laminae. They may be of any thinness without making a thin- 
 bedded rock. True beds are marked off by partings. The beds 
 in a gneiss may be one, two, or eight feet thick, each marked by 
 thin laminae. 
 
 Now, here is a rock a very common one, too in which very 
 little mica can be found. It is simply quartz and feldspar. We 
 shall call this rock granulite, if it is massive, and granulite gneiss 
 if it is thick-bedded. Some, not regarding mica a necessary con- 
 stituent of gneiss, call this proper gneiss; and then as a difference 
 of composition needs to be indicated some way, they call this 
 " binary gneiss." We shall use terms uniformly as first explained. 
 If the bedding becomes thin, the rock becomes a granulite schist. 
 Then, if the feldspar fails, the rock is simply a quartzose schist. 
 We study these granular quartz-feldspar rocks here, because they 
 sometimes contain a little mica, and are always associated with 
 micaceous rocks, and behave like them. 
 
 You will recall that altered product hydromica. This gives 
 us a series of rocks parallel with that afforded by mica. Hence 
 we have hydromica granite, hydromica gneiss and hydromica 
 schist. Some hydromica schists are very fine-grained and homo- 
 geneous, having a bluish-gray color. 
 
 Any of these rocks are liable to contain accessory minerals.
 
 52 GEOLOGICAL STUDIES. 
 
 Garnets very often occur in gneiss and mica schist. Other fre- 
 quent minerals are tourmaline, epidote, chlorite, and andalusite. 
 
 II. Amphibolic and Pyroxenic Bocks. 
 
 The foregoing are the rocks resulting in case the dark mineral 
 in our hands is mica. But taking another specimen, in which the 
 dark mineral is not mica, we have to consider whether it is horn- 
 blende or augite. It is probably one or the other, if the mineral 
 is constitutive that is, sufficiently abundant to give character 
 to the rock. Is the dark mineral hornblende ? Well, if we have 
 only quartz with the hornblende, the rock is a hornblendic quartz- 
 ite, if massive or thick-bedded, and a hornblende schist, if thin- 
 bedded whether a little feldspar is added or not. But if the 
 rock is almost wholly of hornblende, it is called hornblende rock 
 or amphibolite. Sometimes such a rock is extremely fine-grained 
 cryptocrystalline and it is then one of the varieties of aph- 
 anite. 
 
 If, however, we have quartz and feldspar with the hornblende, 
 the rock is syenite, if massive named from Syene in Egypt, 
 where the same species of rock was quarried by the Egyptians, 
 centuries ago. As in the micaceous series, the rock, if thick- 
 bedded, is gneissoid; but, as it has not the composition of simple 
 gneiss, we will designate it syenitic gneiss. Similarly, if the 
 rock is thin-bedded, we will call it hornblende schist. If, from 
 syenite the quartz disappears, the rock becomes hyposyenite if 
 the feldspar is orthoclase. 
 
 Many writers apply the name granite to syenite and hypo- 
 syenite; and some use the single term gneiss for these and the 
 true gneiss. If, however, rocks are to be distinguished by their 
 mineral composition, and terms are to be employed to express 
 distinctions, there appears no good reason for suppressing the 
 terms "syenite," "syenitic gneiss" and "granite," from the 
 nomenclature of so-called metamorphic rocks, or those in which 
 the crystallization is a secondary result, in distinction from erup- 
 tive rocks. We shall employ the terms uniformly as indicated 
 above.
 
 MICACEOUS, AMPHIBOLIC, AND PYROXENIC ROCKS. 53 
 
 You must have remarked the great resemblance between 
 granite and syenite, especially when the grains of the black min- 
 eral are very small; more especially if it is black mica which has 
 begun to lose its lustre by absorption of water. In your visit to 
 the stone-cutter, you found him calling them all " granite," but 
 many reputed granites are more accurately syenites. " Scotch 
 granite " is a syenite containing much red orthoclase. Most of 
 the so-called granites, from Maine to Massachusetts, are syenites. 
 The Quincy granite is a syenite. The capitol at Albany is 
 chiefly syenite. In fact the great masses of crystalline granitoid 
 rocks in the northwest, as well as New England, are chiefly syen- 
 ites instead of granites. But good granites occur among our 
 bowlders, and we shall certainly secure specimens. The " Obe- 
 lisk," in New York, is* a micaceous syenite rich in feldspar and 
 with relatively large crystals of hornblende greatly subordinate 
 to the mica. The Mormon Temple, at Salt Lake City, is the 
 same but finer. 
 
 But what are these granite-like rocks which contain no quartz? 
 We have handled many a specimen. Here is one composed of 
 hornblende and orthoclase. Some call it simply " granite "; 
 some "syenite"; some " quartzless syenite"; others, hyposyen- 
 ite. We shall avoid confusion and promote convenience by 
 using the latter name. But here is another rock in which the 
 feldspar is striated it is triclinic, or plagioclase. Hornblende 
 and a plagioclase have generally been called diorite, if the rock 
 is granite-like in texture. But we have to be a little more 
 precise. There are several species of plagioclase. There is 
 one group of them which is acidic, like albite and oligoclase, 
 having a large percentage of silica (see Table); and another 
 group which is basic, having less silica. Now we had better ( 
 restrict the term diorite to mixtures of hornblende and an 
 acidic plagioclase. Then mixtures of hornblende and a basic 
 plagioclase, like labradorite and anorthite, will be called norite 
 (called also gabbro by some, but this name is used in various 
 senses). Some mica is often present in these two species of 
 rocks; but the mica in diorite is generally light colored (musco-
 
 54 GEOLOGICAL STUDIES. 
 
 vite), while that in norite is black (biotite). Some quartz, also, 
 may be present in diorite, and then it is called quartz diorite, 
 Accordingly, if we have a rock containing hornblende and a 
 plagioclase we may consider the plagioclase acidic, if quartz or 
 light mica is present; and basic, if no quartz is present, and 
 especially if some black mica is present. In the former case the 
 rock is diorite; in the latter, norite. Diorites and norites pre- 
 sent all degrees of fineness; and when they are too fine for the 
 constituent minerals to be seen with a magnifier, the texture is 
 microcrystalline or cryptocrystalline the latter term denoting 
 a finer texture than the former. The rock is then a variety of 
 aplianite another variety being almost pure hornblende. Bed- 
 ded aphanite is aphanite schist. 
 
 But suppose the dark mineral in a quartzless granite-like rock 
 proves to be augite instead of hornblende. Now we may remem- 
 ber that augite, as a basic mineral, likes to associate with basic 
 feldspars. Therefore in this case the feldspar is basic; that is, 
 it is not orthoclase nor an acidic plagioclase; it is probably a 
 basic plagioclase like labradorite and anorthite. Now augite 
 and a basic plagioclase form norite and diabase. (For particulars, 
 see Table, Study XIV.) Occasionally, however, we find augite 
 with an acidic plagioclase, like oligoclase; but for this we have no 
 different name; it is a section of diabase. But we do not find 
 augite with acidic orthoclase. Remember then: If you have 
 determined augite, the feldspar with it is a plagioclase and proba- 
 bly a basic plagioclase. 
 
 When any of the foregoing rocks present themselves in a 
 thick-bedded condition, they are gneissoid; and for their descrip- 
 tion we may employ the terms hyposyenite gneiss, diorite gneiss, 
 norite gneiss, and diabase gneiss. Similarly, any of these may 
 also present a schistose structure; but it is not to be certainly 
 concluded from this structure that such rocks have had a sedi- 
 mentary origin, like common stratified rocks. That is still a 
 question. 
 
 The rocks in the quartzless series are generally dark-colored; 
 but not always. We may have a white plagioclase in great abun-
 
 MICACEOUS, AMPHIBOLIC, AND PYROXENIC ROCKS. 55 
 
 dance, and but little hornblende or augite. The mixture of light 
 and dark minerals results in a mottled or speckled, or " pepper- 
 and-salt" appearance. 
 
 The rocks which we have been considering illustrate well the 
 principles of mineral association. The companions of quartz are 
 mica, orthoclase, and hornblende not plagioclase (except albite) 
 and augite. The companions of augite are the more basic pla- 
 gioclases. Hornblende prefers biotite to muscovite; but not al- 
 ways. Thus biotite is found with basic plagioclase in norite, 
 while the more acidic muscovite is found with the acidic plagio- 
 clase in diorite. 
 
 EXERCISE. 
 
 What is lacking in greisen to make it granite? What is lacking in 
 granulite to make it granite? What would result from uniting greisen and 
 granulite? What should we name an unstratified rock composed of quartz, 
 feldspar, mica, and a little hornblende? What, if it is quartz, feldspar, and 
 hornblende with a little mica? If we have quartz and feldspar together with 
 a non-micaceous dark mineral, what, probably, is the latter? If we have 
 quartz, muscovite, and a feldspar together, what, probably, is the feldspar? 
 If we have quartz, hornblende, and a mica, what, probably, is the mica? If 
 we have plagioclase and a mica, is the latter likely to be light or dark 
 colored ? Suppose the muscovite of a granite changes to hydromica, what 
 does the rock become? If the pyroxene of a diabase changes to hornblende, 
 what does the rock become? If the quartz disappears from syenite, what 
 does the rock become? What change would convert hyposyenite to diorite? 
 What would convert diorite to diabase? What would convert diabase to 
 norite? What are the uses of syenite? Wliich is most durable, syenite or 
 granite? Syenite or diorite ? Coarse or fine granite? A basic or an acidic 
 rock? Which weathers most rapidly, feldspar or quartz? Name several dif- 
 ferent varieties of granite. What does feldspar become on decomposing? 
 
 SUGGESTION. The varying composition of the granular rocks thus far 
 studied furnishes an interesting opportunity for a geological game. Prepare 
 a quantity of cubical blocks of hard wood, half an inch or so in diameter. 
 To a number of these attach tickets bearing the name of Quartz. To others 
 attach tickets bearing the names of the other minerals occuring in the granu- 
 lar rocks. Then select two or three minerals (blocks), and lay them side by 
 side, and see which one of a company can soonest tell what rock they repre- 
 sent. Let some umpire, with a supply of checks of any kind, supply the 
 quickest correct respondent in each case with a check. When a given sup- 
 ply of, say, fifty checks is thus exhausted, let the number in each individual's
 
 56 GEOLOGICAL STUDIES. 
 
 counted, and let the one having most checks be declared the 
 winner of the game. On the same or future occasions other games may be 
 played, and the first to win ten games may be declared entitled to a prize 
 whatever may be agreed upon and provided beforehand. In case of appeal 
 from the decision of the umpire, reference may be made to one of the tables 
 beyond. This suggestion relates thus far to massive granular rocks. But 
 when it becomes desirable to make the game a little more difficult, the re- 
 spondent may be required to state also what the rock would be if thick- 
 bedded, and what if thin-bedded. The following minerals are suggested to 
 begin with : quartz, orthoclase, acidic plagioclase, basic plagioclase, musco- 
 vite, biotite, hornblende, augite, talc, chlorite. 
 
 STUDY XI. Felsitic, Hydrous-Jbfagnesian, and Aluminous 
 Rocks. 
 
 I. Felsitic Rocks. 
 
 We have picked up from time to time various round, smooth, 
 and exceedingly fine-grained bowlders, to which we ought now to 
 direct our attention. While the rocks which we have heretofore 
 studied are sufficiently coarse-grained to enable us to inspect their 
 mineral constituents with the naked eye, or at least with a pocket 
 lens, these are too fine for that method of study. The former are 
 phanerocrystalline / these are microcrystalline or cryptocrystal- 
 line, and their texture can only be seen under a compound micro- 
 scope by the use of thin, transparent sections. Their composition 
 may also be learned through chemical analyses. But we do not 
 propose to resort to either of these methods. We must simply 
 see what can be done without them. 
 
 We can at least distinguish colors. Let us separate the black 
 and greenish-black specimens from those of other colors. These 
 are chiefly aphanites ; and we have studied them in connection 
 with other rocks. Some of them can be slightly scratched, while 
 others are as hard as orthoclase. The former are composed chiefly 
 of hornblende, and might be styled aphanitic amphibolite, or 
 amphibolic aphanite. These which are so flinty in hardness 
 evidently contain quartz in intimate union with a dark min-
 
 FELSITIC, HYDROUS-MAGNESIA X, AND ALUMINOUS ROCKS 57 
 
 eral. The principal dark minerals are hornblende, augite, and 
 labradorite. But quartz and labradorite have little to do with. 
 each other ; and of the other two, quartz prefers hornblende. 
 We may presume, therefore, that this flinty aphanite contains 
 quartz and hornblende. But as quartz and hornblende do not 
 much associate, except in company of an acidic feldspar, we may 
 further conclude that the real mineral constituents of this apha- 
 nite are either hornblende, quartz, and orthoclase, or hornblende, 
 quartz, and albite or oligoclase. Now, the former triplet gives us 
 syenitic aphanite, and the latter, dioritic aphanite. This reason- 
 ing is validated by the other modes of study. 
 
 Now let us take up the microcrystalline specimens which pre- 
 sent whitish, grayish, and reddish colors. Give attention, first, 
 to those of nearly uniform color. We shall be able to conclude, 
 after carefully testing the different specimens, that they differ 
 slightly in hardness, like the aphanites. If we can make a dis- 
 crimination of this kind, let us take, first, the hardest. Now, 
 these are as hard as quartz, and there is no mineral but quartz 
 which is likely to be abundant enough to supply these rocks. 
 But these are not pure quartz ; they have not the glassy lustre 
 of quartz. They do, indeed, suggest the jaspers, but there is an- 
 other alternative : they may contain feldspar, intimately mixed 
 with the quartz. But, as before, it must be an acidic feldspar 
 probably orthoclase. Now, other examinations corroborate this 
 induction. This is, then, simply a flinty, amorphous feldspar. It 
 has received the name petrosilex, sometimes also known as liiil- 
 leflinta, or false flint (Swedish, pronounced nearly helleflinta). 
 
 Taking, next, the reddish or whitish specimen, we find that 
 it has the hardness and lustre of feldspar, though it shows no 
 cleavage faces. We can do no more. It seems to be a compact,' 
 amorphous feldspar. Other investigations show it to be chiefly 
 a plagioclase. It is CA\\eA felsite. Petrosilex is sdso felsitic, and 
 by some is not separated from felsite. 
 
 Let us now give attention to the specimens separated as not 
 having homogeneous colors. Our notice is at once attracted by 
 the fact that they consist of a fine, homogeneous base or matrix,
 
 58 GEOLOGICAL STUDIES. 
 
 in which other minerals are imbedded. By testing for hardness, 
 as before, we find that this base by itself is sometimes a felsite, 
 and sometimes a petrosilex. Without regard to this distinction, 
 let us study the imbedded minerals. In one specimen they are 
 clearly crystals of feldspar. Now, crystals of any kind, imbedded 
 in a homogeneous feldspathic matrix, form a porphyritic rock. 
 This is, then, a porphyritic felsite, and this porphyritic rock is 
 the typical porphyry. Notice the colors reddish or grayish 
 base, with white crystals imbedded. 
 
 If we find imbedded crystals or fragments of quartz, the rock 
 is a quartz porphyry / and if we find rounded pebbles thus imbed- 
 ded, the rock is a conglomerate porphyry. This unusual vari- 
 ety of porphyry we shall probably not meet with. It forms, how- 
 ever, the porphyry point at Marblehead, Massachusetts. Other 
 porphyries may be seen at Lynn 
 and Nahant, and they are very 
 common around the shores of Lake 
 Superior. (See Fig. 8.) Other kinds 
 of rocks, also, besides felsites, are 
 often found porphyritic. Figure 
 PIG. 24.- PORPHYRITIC GRANITE, 24 shows a porphyritic granite, 
 
 from Land's End, England. 
 
 II. Hydrous -Magnesian Bocks. 
 
 Let us now direct attention to the Hydrous-Magnesian Rocks. 
 These, as will be inferred, are characterized by the presence of 
 the hydrous-magnesian minerals. If you turn to the table of 
 composition of minerals, on page 40, you will perceive that all 
 these minerals range low in respect to hardness. They must, 
 therefore, impart a moderate hardness to the rooks. You will no- 
 tice further that they are less rich in iron than the dark-colored 
 minerals. Hence the rocks which they form will be of light col- 
 ors and of low specific gravity. Now, in consequence of this 
 comparative softness, we cannot expect bowlders of these rocks to 
 have lasted through the wear and tear of geologic time, like the 
 bowlders of harder rocks. For these reasons the student may
 
 FELSITIC, HYDROUS-MAGNESIAS, AND ALUMINOUS ROCKS. 59 
 
 have to depend partly on descriptions. Still, there are some 
 of this class which, from the quartz contained, have lasted to our 
 time. One of these, protogine, consisting of quartz, feldspar 
 and talc, in a massive state, is not often met in this country ; but 
 it forms the central mass of the high Alps of central Europe, and 
 rounded masses are often seen borne to the lower levels by gla- 
 ciers. Protogine occurs sparingly in the northwestern states. 
 In bedded conditions it gives us protogine gneiss and protogine 
 schist. The last is not essentially different from talcose schist. 
 The latter, however, as we actually find it, consists almost wholly 
 of minute folia of talc. It is a rare rock, though occurring near 
 Marquette, Mich., at various localities in northern New York, 
 and in other regions. But it must no longer be confounded with 
 the sericite schist, or hydromica schist, which was till recently 
 mistaken for talc schist. 
 
 Every one is acquainted with the so-called " soapstone " grid- 
 dles, and the slabs of "soapstone" used for foot-warmers their 
 power of retaining heat being very great. This soapstone is the 
 steatite of the geologist, and consists essentially of grayish, com- 
 pact, amorphous talc. It is soapy to the feel, and is easily cut 
 with a knife. When quite pure it is milk white, and forms the 
 article known as "French chalk." The uses of steatite are quite 
 numerous. Slabs of it are employed for fire stones in furnaces 
 and in stoves. The fine-grained varieties are carved into orna- 
 ments. Inkstands are often made from it, especially the white 
 variety. Ground steatite is employed for diminishing friction, 
 and the manufacture of porcelain and the removal of oil stains 
 furnish other uses. Th*e so-called " soapstone " of the artesian 
 well-borer is merely an unctuous, partially indurated clay. 
 
 Next, there are the chloritic rocks. Chlorite schist occurs in 
 the mining regions of Lake Superior. It is a dark -greenish, 
 greasy looking rock, in which chlorite, in closely aggregated or 
 interwoven folia, is the chief, sometimes nearly the sole, constitu- 
 ent, while quartz is generally the principal ground mass. The 
 feldspars, however, enter into this schist in about the same pro- 
 portions as in mica and hornblende schists. By increase of the
 
 60 GEOLOGICAL STUDIES. 
 
 feldspar, accompanied by a heavier bedding, this schist graduates 
 into chloritic gneiss. In the opposite direction it graduates into 
 chlorite slate, a fine slaty rock, containing some aluminous mat- 
 ter. A rock composed mostly of chlorite is called, also, chlorite 
 rock. 
 
 III. Aluminous Bocks. 
 
 Passing to aluminous rocks, we have first the fine white slate, 
 composed of pyrophyllite, and having the softness, appearance 
 and soapy feel of the talcose rocks, and known as pyrophyllite 
 slate. It occurs in place in North Carolina, and one of the va- 
 rieties is employed in making slate-pencils. But the greater 
 number of aluminous rocks are characterized by a clayey constitu- 
 ent, the basis of which is kaolinite. When the material is un- 
 consolidated and comparatively pure, it forms kaolin, extensively 
 used in porcelain making. When mixed with various impurities, 
 and more or less silica, it constitutes common clay. This is some- 
 times dark, or even black, from the abundance of carbonaceous 
 matter. It is sometimes reddish, bluish or whitish, depending on 
 purity and the nature of the impurities. The burning of clay 
 not only hardens it, but generally imparts a reddish color, 
 through the peroxidation of' the iron. If, however, the iron ex- 
 ists as a silicate, no reddening takes place. This is the character 
 of the " Milwaukee brick," so-called; though this sort of clay is 
 extensively distributed throughout the lake region. Fire clay 
 is a clay free from iron, lime or other substance which would pro- 
 mote fusion; and is therefore capable of resisting intense heat. 
 It generally contains much arenaceous 'matter, which prevents 
 shrinkage and warpiug of the fire-brick. 
 
 When clay with more or less arenaceous or silicious matter 
 has become somewhat indurated, it assumes the character of a 
 shale, a rock which easily splits into somewhat even flakes, and 
 presents many varieties in composition and color. Perhaps the 
 most accessible examples are the dark shale fragments often 
 found mixed with our supply of coal. Most shales are dark, and 
 manv are even black, from the abundance of carbonaceous mat-
 
 CALCAREOUS ROCKS. 61 
 
 ter contained in them. The carbon, under such conditions, pos- 
 sesses a strong predisposition to unite with hydrogen and pass 
 into bitumen. 
 
 When, finally, the clayey rock has been firmly hardened, it 
 constitutes aryillite or clay slate, called sometimes pliyllite. In 
 color it is bluish, whitish, reddish or greenish. It splits into thin, 
 even layers, and is extensively employed for roofing and for writ- 
 ing slates. Argillites are almost microcrystalline; but in some 
 cases we find them graduating into a very fine mica schist or 
 hydromica schist; and in others, by a large accession of extremely 
 fine arenaceous matter, they become novaculite or " oil-stone." 
 
 EXERCISES. 
 
 How does petrosilex differ in composition from felsite proper? How 
 does it differ from aphanite? What is the difference between a porphyritic 
 granitic and a granitic porphyry? Which is most. basic, felsite proper or 
 petrosilex? What is the difference between kaolin and felsite? What is the 
 effect of intense heat upon clay? What is the effect on kaolin? Give an ex- 
 ample of burned kaolin. Is it opaque or translucent? How might it have 
 been made more translucent? What is the difference between porcelain and 
 felsite? Which contains most alkali, kaolin or orthoclase? What causes 
 burnt clay sometimes to be vitrified? What kind of clay would not vitrify? 
 What are unvitrifiable clays used for? What is the effect of limestone peb- 
 bles in brick clay? What causes some bricks to "slack "? What causes the 
 dark color of aphanite? What causes its hardness? If the hornblende 
 should be removed from dioritic aphanite what would it become? What is 
 the difference between pyrophyllite slate and talcose slate? Between talcose 
 slate and steatite? Between protogine and granite? Between syenite and 
 augite-syenite? What class of crystalline rocks is not likely to be found as 
 bowlders? Why not? Why are bowlders predominantly quartzose? Men- 
 tion four or more different rocks or minerals used for making colored 
 marks. What change must be made to convert norite into diabase? 
 
 STUDY XII. Calcareous Kocks. 
 
 Let us get together samples of the common rocks which 
 effervesce on the application of acid, with or without heat. 
 They are composed essentially of calcite and dolomite. We ob-
 
 62 GEOLOGICAL STUDIES. 
 
 tain them at the stone cutter's, from broken articles in marble, 
 from among certain building materials, and occasionally among 
 surface bowlders. If any limestone or marble ledges exist in the 
 vicinity, we shall, of course, obtain specimens from the rocks in 
 place. 
 
 With our assortment before us, we notice at once that some 
 of the specimens are brighter and more lustrous, others are duller 
 and more earthy. The former are cystalline, the latter uncrystal- 
 line. The former are purer, the latter have admixtures of vari- 
 ous accessory ingredients. The former we call marbles; the 
 latter, limestones. The marbles are thick-bedded and have hard- 
 ness and homogeneity, and freedom from cracks and cavities. 
 They can be cut and polished. The limestones are thick- or thin- 
 bedded; but they are not homogeneous, and generally contain 
 fissures and cavities. They cannot be advantageously cut into 
 slabs and polished. Some limestones, however, without being 
 crystalline, are sufficiently thick-bedded and homogeneous to be 
 sawed and polished; and when they contain many fossil shells, 
 encrinites or corals, the polished surfaces are handsome. Such 
 marbles are known as shell marble. 
 
 Of the crystalline, heavy-bedded marbles we have endless va- 
 rieties of color and texture. The granular, white sorts are 
 called saccharoidal. Fine white, even-grained sorts are statu- 
 ary marble, of which the most celebrated quarries are the Pa- 
 rian and Pentelican, in Greece, and those of Carrara, in Italy. 
 By the dissemination of streaks of aluminous matter, clouded 
 marbles are produced, which are common in Vermont. An 
 abundance of bituminous matter makes a black or Egyptian mar- 
 ble which also occurs in Vermont. It may be varied with lighter 
 matter. Some good marbles are calcareous conglomerates. A 
 much admired sort is quarried in eastern Tennessee, and is used 
 for pillars in public buildings. Verd antique marble is a dark 
 green serpentine clouded and varied with lighter calcite. 
 
 Of the uncrystalline, lustreless limestones we find also endless 
 varieties. They are caused chiefly by the variations in the im- 
 purities. Sometimes an inspection of a freshly broken surface
 
 CALCAREOUS ROCKS. 63 
 
 shows a sparry constitution, somewhat approaching that of a 
 marble. Very frequently limestones are more or less saturated 
 with petroleum, which gives them a brown or very dark color. 
 Black limestones contain carbonaceous matter. Bluish and ashen 
 limestones are argillaceous. Yellowish and reddish limestones 
 are ferruginous. Sometimes grains of sand are disseminated 
 through a limestone, which is then arenaceous. If silicious mat- 
 ter not in an arenaceous state is intimately mixed or combined 
 with the calcareous, the limestone is silicious. If alumina is so 
 combined the limestone is aluminous. Distinguish particularly 
 argillaceous and arenaceous from aluminous and silicious. The 
 first two terms imply the material in a somewhat isolated and 
 visible state; the other two imply it intimately commingled, or 
 perhaps chemically combined. 
 
 Many limestones are magnesian. They do not effervesce 
 freely. Let us pick out such from our collection. They do not 
 look very different from the others. Most of the great western 
 limestone formations, so called, are magnesian, or even dolomitic 
 that is, about one-half carbonate of magnesia (see the Table of 
 Compositions, page 40). Though dolomites are not properly sepa- 
 rable by their color, it happens, as a fact, that most of the west- 
 ern dolomites present a buffish hue. This is especially the case 
 with the "lower magnesian limestone" which helps to form the 
 cliffs along the Upper Mississippi. The observation may also be 
 made in Missouri and Michigan. As a fact, it is further observ- 
 able that many dolomites and dolomitic limestones have a finely 
 granular texture. In fact, they have been sometimes reported as 
 sandstones. So the buff color and granular texture may be taken 
 as a preliminary indication of a dolomitic formation. Slowness of 
 effervescence is confirmatory. Beyond this we cannot go without 
 chemical analysis. 
 
 You have, perhaps, noticed some limestone containing small, 
 spherical pellets, like homosopathic pills. Such limestone is 
 oolitic (not pronounced oo-litic). Such pellets sometimes com- 
 pose the entire rock, which is then an oolite. Examination of 
 these spherules broken through the middle reveals a concentric
 
 64 GEOLOGICAL STL'DIES. 
 
 structure. It is then a "concretion," similar to the concretionary 
 " iron-stone " before mentioned. When the concretions are larger 
 the rock is pisolitic. 
 
 Limestones have no standard degree of hardness. All may 
 be easily scratched; but in the Gulf States are limestones which 
 may be cut with the knife. One of these is the widely known 
 "rotten limestone"; another is the so called "white limestone." 
 But they are harder than chalk, and, besides, have "grit" dis- 
 seminated through them. Some chalk is pretty free from grit, 
 though it abounds in nodules of flint. It does not occur in 
 America, but comes chiefly from England and France. " Whit- 
 ing" and "Spanish white" are prepared from it. Marl may be 
 described as unconsolidated chalk. We have already learned (in 
 Study II but see especially Study XV), how it is deposited. 
 We have learned, also, of the origin of travertin and tufa. 
 When calcareous waters drip from the roof of a cavern, the de- 
 posit formed on the floor is stalagmite / and the icicle-like form 
 pendant from the roof is a stalactite. The banded colorations in 
 stalagmite fit it for many ornamental uses. 
 
 All calcareous rocks are slightly soluble in meteoric (or atmos- 
 pheric) waters; hence, when used in architecture or art, in ex- 
 posed situations, they possess a limited durabilitv. The slow 
 decay of limestones and marbles may be noticed in some of our 
 oldest structures. Marble cemetery slabs or monuments, one or 
 two hundred years old, are distinctly weathered. On the dome 
 of St. Paul's Cathedral, London, the weathered, earthy limestone 
 has retreated a quarter of an inch, leaving the silicified fossils 
 projecting to that extent. Yet many of the ancient statues and 
 columns buried in the earth have retained admirable perfection. 
 In the ruined but famous Palace of the Caesars, at Rome, the 
 architectural carvings retain striking sharpness and distinctness, 
 after two thousand years of exposure. On the other hand, most 
 of the caverns of the world are attestations of the solubility of 
 limestone. They began as fissures, through which streams of 
 water passed, dissolving continually and also wearing the 
 limestone surfaces. That such works have been long in progress
 
 CALCAREOUS ROCKS. 05 
 
 is evidenced by the slow yielding of calcareous surfaces during 
 historic times. 
 
 Limestones, considered in reference to their fitness 'for build- 
 ing, should be examined as to their power of absorbing and retain- 
 ing water. A saturated limestone subjected to freezing is liable 
 to crumble, or even to be completely shattered. Hence, argilla- 
 ceous and aluminous limestones are quite unsuitable for situations 
 exposed to the weather. Some of the latter, presenting a fine- 
 grained, massive, and substantial appearance when issuing from 
 (the quarry, may be reduced to a state of ruin by the frosts of a 
 single winter. 
 A hydraulic limestone is one which contains a considerable 
 percentage (fifteen to thirty per cent) of clay or magnesia, or 
 both together. Calcination renders the silica of the clay soluble 
 at the same time that the carbonic acid is expelled from the car- 
 bonate of lime. Contact with water, therefore, dissolves the 
 silica, and this, with the quicklime, slowly forms a hydrous sili- 
 cate of lime, which is firm and insoluble. Another portion of the 
 silica forms a silicate of alumina; and if magnesia be present, a 
 silicate of magnesia also results. 
 
 Gypsum is a calcareous rock of much importance, having 
 most of the properties of the mineral gypsum, already studied. 
 We find it mixed in all proportions with argillaceous matter, and 
 sometimes disseminated richly through argillaceous limestones. 
 It also occurs in stratified beds of great or small extent. Some- 
 times the original bed has been dissolved away, and only some 
 lenticular remnants of it are found. Often, also, the disappear- 
 ance of a gypsum bed occasions "sink holes" at the surface. 
 Such holes, then, seem to indicate the presence of an underlying- 
 soluble stratum, probably gypsum. But they must be carefully 
 distinguished from mere depressions in the drift, sometimes 
 called "potash kettles." Much of the gypsum found in the crude 
 condition contains a considerable admixture of clay, and pos- 
 sesses a bluish color. In other situations as at Grand Rapids 
 and Alabaster, Mich. beds of gypsum exist in a state of 
 great purity, and then it exhibits a crystalline texture. White,
 
 66 GEOLOGICAL STUDIES. 
 
 granular deposits afford snotoy gypsum. Gypsum equally fine 
 and uniform is often tinted with rich colors. Fine gypsum, 
 capable of forming ornaments, is known as alabaster. It may be 
 white or colored. Near Grand Rapids, in Michigan, are extensive 
 beds of pure gypsum, having largely a coarse fibrous structure. 
 Some portions, however, are granular. This formation seems to 
 extend under the central part of the state, for it reappears on 
 Saginaw Bay, where it is also extensively quarried. Other 
 sources of commercial gypsum are on the border of Sandusky Bay, 
 Ohio, and in central-western New York. It is abundant, also, in 
 Virginia, Tennessee and Arkansas. Very fine and extensive 
 deposits exist in Nova Scotia. Gypsum is widely employed as 
 an agricultural fertilizer, also as a plaster for "hard finish," and 
 also in the preparation of "moulds" and "casts." 
 
 EXERCISES. 
 
 What change does calcined gypsum undergo when long exposed to the 
 air? What change does quicklime undergo when so exposed? Which is 
 most impaired by mere dampness? How does dampness affect water-lime? 
 Why might not water-limestone calcined at a white heat make a good 
 cement? Explain how a water-lime might be prepared from pure caus- 
 tic lime. Would caustic lime and pure sand make a cement? Why do you 
 give this answer? Would caustic lime and clay make a cement? Why 
 this answer? How is silica made soluble? What is the use of insoluble 
 silica in a cement? Which most rapidly dissolves, gypsum or limestone? 
 Why did the "Cardiff giant," made of gypsum, possess an ancient appear- 
 ance after a few months' burial? What is the source of rust stains on the 
 surface of some marbles? Have you any specimens from any cavern? 
 Describe them. How might human bones become buried in stalagmite? 
 Have you ever heard of such a case? Have you ever heard of bones buried 
 in travertin? Mention some extensive deposits of travertin. How does 
 travertin differ from common limestone? How would slabs of alabaster 
 serve as an external veneering for house fronts? By what means may plas- 
 ter casts be rendered harder than results from the simple "setting" of the 
 plaster?
 
 CAKBONACEOUS EOCKS. 67 
 
 STUDY XIII. Carbonaceous and Iron Ore Rocks. 
 I. Carbonaceous Bocks. 
 
 Coal is something so familiar that a brief study will make us 
 acquainted with its physical characters and modes of occurrence. 
 Its geological history must, of course, be taken up in another 
 connection. You have seen the "soft coal" burning on the grate, 
 and have noticed the escape of inflammable and other gases; and 
 have also detected the peculiar empyreumatic odor which bitu- 
 minous coal emits. You have seen the gas-making coal put in 
 the retorts at the gas works, and thus received other evidence 
 that common coal contains some constituents which may be 
 driven off by heat. Now, what are these volatile constituents, 
 and what is the coal? Manifestly they are both combustible. 
 The gas burns at the jet, and the coal and gas together burn on 
 the grate. Even the coke which remains in the retort after the 
 gas is disengaged is also combustible. Now, what is that which 
 is combustible in common air, and is also an abundant substance? 
 It is carbon; and this element, therefore, is the basis of all the 
 coals and the inflammable gases derived from coals. 
 
 If we call the chemist to our aid, he informs us that the gases 
 are compounds of hydrogen and carbon; and so are the coals, 
 but with a diminished proportion of hydrogen, and the addition 
 of oxygen. He informs us, also, that coal tar and other liquids 
 derivable from coal, such as naphtha and coal oil, are other 
 compounds of carbon and hydrogen. We observe, also, that 
 the coals called anthracite contain comparatively little of the 
 gaseous and fluid hydrocarbons, while those called bituminous 
 contain larger percentages the fixed constituents of both classes 
 of coals being essentially carbon, or something not very different 
 from charcoal. 
 
 A coal from which all volatile constituents have been expelled 
 is graphite or plumbago; while on the other hand, we find in 
 nature products composed of the liquid constituents occurring in 
 coal, and others composed of the gaseous constituents. The
 
 68 GEOLOGICAL STUDIES. 
 
 liquid product is petroleum, and the other is natural inflammable 
 gas. The petroleum has accumulated in reservoirs in the rocks 
 to an extent which becomes a great natural curiosity some 
 wells having discharged five thousand gallons a day; and the gas 
 is now escaping through artesian borings in such enormous sup- 
 ply as to light cities and furnish fuel for great manufacturing 
 operations. Pittsburgh and its vicinity are especially favored 
 with combustible gas; though enormous outflows exist in Knox 
 county, Ohio, and in various other regions. Though petroleum 
 and gas may be artificially produced from bituminous coal, it 
 must not be inferred that these natural products have been so 
 derived; since according- to the evidences, no connection with 
 coal beds usually exists. A striking proof of this has very 
 recently been brought to light in northwestern Ohio, in a region 
 at least eighty miles from the nearest coal field, where from three 
 wells half a million cubic feet of inflammable gas are obtained 
 daily from a geological position two thousand feet or more below 
 the horizon of the lowest coal (Orton). Probably, however, like 
 coal, petroleum and inflammable gases have had an organic 
 origin, (See, further, Study XXIX.) 
 
 When petroleum is exposed to the air it loses its volatile con- 
 stituents, and the fixed residuum is asphalt. Different varieties 
 of asphaltic products have thus accumulated in deep rock fissures, 
 and they are known by such names as albertite, grahamite, and 
 others. Succinite, or the essential part of amber, is an oxygen- 
 ated hydrocarbon, which may be mentioned in this connection. 
 It is believed to be a fossil resin. 
 
 Peat you may find accumulating around the borders of lakes 
 and ponds. (See Fig. 25.) Often the basins of old lakes are 
 completely filled with peat. Manifestly it is of vegetable origin. 
 It has a dark brown or nearly black color. It is combustible, and 
 emits, like coal, an empyreumatic odor. Some old, deeply buried 
 peats closely resemble that sort of coal known as brown coal, 
 and lignite. These, like peat, have no standard purity. They 
 may be worth more or less as fuel. Peat, however, is extensively 
 employed on the continent of Europe in porcelain stoves for
 
 IRON ORE ROCKS. 09 
 
 warming houses. If we arrange some of these carbonaceous and 
 hydrocarbonaceous substances in serial order, they will stand 
 somewhat as follows : 
 
 1. Gases. Like the light and heavy inflammable gases. 
 
 2. Liquids. Like Naphtha, Petroleum, Benzole, Tuluole, etc. 
 
 3. Waxy Solids. As the Paraffine and Scheererite groups of 
 
 substances. 
 
 4. Firm Solids, (a) Asphaltic, like Asphalt, Albertite, Gra- 
 
 hamite, Torbanite ; (b) Coaly a series including Peat, 
 Lignite, Bituminous Coals, Anthracite, Graphite, Dia- 
 mond (?). 
 
 II. Iron Ore Bocks. 
 
 On visiting any iron ore mine we perceive that the ore occurs 
 as a rock more or less distinctly stratified. We find the ore beds 
 formed from the three principal ores already studied. They form 
 strata like the other rocks with which they are associated. Gen- 
 erally, the stratification of the ore is quite conspicuous. Some- 
 times, however, the beds appear to wedge out in all directions, 
 and thus to terminate. It is so with the beds at Lake Superior, 
 in northern New York, in Missouri, and elsewhere. The ores in 
 these beds are mere masses of hcematite schist, or magnetite 
 schist, and the kinds are distinguished in the same way as the 
 minerals bearing these names. Great beds of titanic iron ore 
 also exist in Canada and other regions, which seem to be substan- 
 tially a mixture of magnetite and oxide of titanium. But titanic 
 ores present various percentages of protoxide and peroxide of 
 iron with binoxide of titanium. The Franklinite ores of New 
 Jersey consist of haematite about two-thirds, and oxide of zinc 
 one-fourth, the remainder being manganese. Sometimes these, 
 great iron-ore masses terminate abruptly against the " country 
 rock" ; but often they disappear by gradual increase of other 
 rock constituents. The accession of silica gives rise to a silicious 
 ore ; then, at a remoter point, to a lean silicious ore ; then, to a 
 highly ferruginous jasperv schist, as previously explained, and, 
 finally, an ordinary silicious schist, or other rock. Mixed with
 
 70 GEOLOGICAL STUDIES. 
 
 clay, haematite forms argillaceous haematite, which is often of a 
 deep red color, varying to brownish black. It has sometimes an 
 oolitic structure. 
 
 Limonite rocks result from the hydration of the haematite and 
 magnetite schists, and, in the regions just named, the process can 
 sometimes be seen incomplete. Extensive beds exist in Salisbury 
 and Kent, Conn., as also at sundry points in Dutchess county, N.Y. 
 At Hinsdale, Mass., it occurs as the cement in a conglomerate 
 quartz rock. The commencement of such a process of cementa- 
 tion of pebbles is often observed in the limonitic deposit from 
 springs. These deposits, as explained in Study II, give rise to 
 extensive beds of boy iron ore, or swamp limonite. One of the 
 most desirable ores of iron is limonite, since, though less rich 
 than haematite and magnetite, it is more easily reduced. The iron 
 yielded by bog ore, however, is cold short, owing to the presence 
 of phosphorus, and hence cannot be employed in the production 
 of wire, or even of sheet iron. For casting it is superior. 
 
 Another important class of iron ores is afforded by siderite, 
 or carbonate of iron. It is generally known as spathic iron. It 
 occurs in gneiss, mica schist, and argillite, sometimes in extensive 
 beds, as in Styria and Carinthia, and at Plymouth, in Vermont, 
 Sterling, Mass., Antwerp and Rossie, N. Y., and the Fentress and 
 Harlem rivers, N. C. Siderite is often found united with argilla- 
 ceous matter in the form of nodules (kidney-iron) and beds (clay 
 iron-stone), especially in the coal regions of the country, though 
 this form of ore exists also in other formations. 
 
 III. Eruptive Rocks. 
 
 That such rocks as sandstones, limestones, and shale have had 
 a sedimentary origin is apparent from the bedded arrangement 
 of their materials in parallel layers; from the identity of those 
 materials with the sediments gathering over modern sea bottoms, 
 and from the presence in them of so many relics of the organisms 
 of the sea but of all this we shall learn hereafter. If traces of 
 stratification are proofs of sedimentary origin, then many of the 
 crystalline rocks are also sedimentary. All the schists and
 
 ERUPTIVE ROCKS. 71 
 
 gneisses are stratified; and granite sometimes passes by contin- 
 uity into gneissoid rocks. But lavas erupted from Vesuvius are 
 not sedimentary. They may, indeed, acquire a parallel fibrous, 
 or even bedded, structure by flow while in a molten state; and 
 some geologists maintain that the bedded structure of gneisses 
 and diorites and many other rocks had its origin in the flow of 
 molten matter: but there are serious objections to this view. We 
 have studied them without any theory as to their origin. We may 
 admit that certain rocks which we have grouped with the sedi- 
 mentary class are sometimes eruptive, or that certain ones have 
 always an eruptive origin. If so, then we may have eruptive 
 granites, syenites, diorites, norites, and diabases, as well as meta- 
 morphic ones of sedimentary origin; or we may regard some of 
 them, like diabase, felsite, and the porphyries, as exclusively 
 eruptive. In any event, we have to admit the existence of cer- 
 tain rocks which bear so much resemblance to modern lavas that 
 we can regard them as nothing else than ancient lavas. 
 
 There are neither modern nor ancient lavas lying within ac- 
 cessible distance of us; and the ancient erupted rocks of Lake 
 Superior and the Canadian regions have not endured the long 
 journey to our doors, as common bowlders have. This simple fact 
 gives one clew to their nature. They are more basic; they con- 
 tain mostly less silica, at least they are not quartzitic; they have 
 dissolved; they have been worn out. So much is certain. But 
 again, we have learned from the other rocks what the chemi- 
 cal elements are, and what are their mineral compounds. The 
 erupted rocks could contain few, if any, new minerals. But, 
 having been molten, the same minerals must exist in a blended 
 condition. Now, though it is impracticable to make a detailed 
 study of the eruptive rocks, we may report that investigation 
 confirms the deductions we have drawn. So we have chiefly a 
 feldspathic series, a hornblendic series, and an augitic series. 
 Beyond this it would hardly be profitable to go without other 
 facilities than we propose to employ. 
 
 The following rocks, already noticed, are included also among 
 erupted rocks: granite, granulite, felsite, syenite, quartz-syenite,
 
 72 - GEOLOGICAL STUDIES. 
 
 diorite, quartz-diorite. The following are named only among 
 eruptive rocks: 1. Feldspathic: phonolite, trachyte, rhyolito or 
 glassy rocks, as pearlstone, pitchstone, obsidian, pumice. 2. 
 Hornblendic and augitic: andesite, quartz-andesite (dacite), va- 
 riolite, augite-andesite, dolerite (basalt), amphigenite (Vesuvian 
 lava). On "volcanoes" and "ancient lavas" see Studies XXIII 
 and XXIV. 
 
 EXERCISES. 
 
 Whatis the material of our so called lead pencils? What proportion ol 
 carbon is in them? How does graphite differ from anthracite? Is graphite 
 combustible? What gem is pure carbon? What is its hardness? Name an- 
 other carbonaceous substance with much lower hardness. How does peat 
 differ from bituminous coal? From what is peat derived, according to your 
 observation? What is paraffine? What are its uses? In what respect is 
 amber like asphalt? Have you ever seen a magnetite schist? What is the 
 color of the dust resulting from the handling of. magnetite schist? What 
 color of dust arises from haematite schist? What color of dust stains the 
 wagons and cars carrying Salisbury (Conn.) iron ore? What color of dust 
 stains the docks at Escanaba and Marquette, Mich.? What is "cold short" 
 iron? What ore of iron most disturbs the magnetic needle? Name the 
 rocks found in both the metamorphic and eruptive series. How can you de- 
 termine to which series a particular granite belongs? 
 
 STUDY XIV. Retrospect of the Mocks. 
 
 A retrospective glance over the rocks which are here studied 
 recalls the fact that different rocks having the same constituent 
 minerals differ chiefly in their structure. They may be crystal- 
 line or fragmental. They may be unstratified, or thick-bedded, or 
 thin-bedded. They may be well consolidated, or imperfectly so, 
 or quite unconsolidated. We notice that most of the rocks are 
 characterized in part by some predominant mineral, such as quartz, 
 mica, hornblende, pyroxene, and so on; and that we thus have 
 several series, each of which runs through the various types of 
 structure. A panoramic presentation of the common rocks, ar- 
 ranged according to structure in the several series, will aid greatly
 
 RETROSPECT OF THE ROCKS. 73 
 
 toward a comprehensive grasp of the subject. Such a presenta- 
 tion is attempted in the "Table of Rock Structure," which fol- 
 lows. 
 
 Again, we may make an arrangement of rocks according to 
 the minerals which they contain, noting at the same time the va- 
 riations of structure for the same mineral aggregates. This is 
 attempted for the common rocks in the appended " Table of Rock 
 Composition." In this, in each compartment, the " massive " 
 rock stands first, and is put in small capitals; the thick-bedded 
 rock next, in "Roman letters"; and the thin-bedded (to which 
 we restrict the term schist) stands last, in " italics." 
 
 Finally, we introduce a " Table for Rock Determination," 
 similar to our previous "Table for Mineral Determination." The 
 intention of this is to enable the student to ascertain the name 
 of a rock as soon as he knows its constituent minerals. This 
 table, as we think, will be found extremely useful; and much ex- 
 ercise should be had on it. But we ought to remark that both 
 the tables for determination contain much more detail than the 
 student of the elements of geology can be expected to acquire. 
 Accordingly, a star is prefixed to names of species regarded im- 
 portant for the elementary student. The further use of these 
 tables is intended for more advanced study.
 
 fl 
 
 alcare 
 
 Series 
 
 I 
 
 1 
 
 S 
 
 A 
 
 ii 
 
 Ill 
 
 PS O 
 
 fill! 
 
 T- 
 i Z&X 
 
 I J O 
 
 ill! 
 
 i an 
 
 e Gneiss. 
 Gneiss. 
 Gneiss. 
 yenite Gneiss 
 Aphanite. 
 leu.Aphanite 
 
 Sy 
 Dio 
 No 
 Hy 
 Di 
 Ho 
 
 artzos 
 eries. 
 
 il 
 
 
 i^ 
 
 gss- 
 
 lif| 
 Sill
 
 f'ii 
 
 ^ 
 
 p 
 
 e 
 
 B- 
 
 III 
 
 2 
 
 s 
 
 g 
 
 ii 
 
 11 I 
 
 = ^: t 
 
 0^ ^ 
 
 B^JS 
 "rt S^ 
 
 EM il 
 
 | 
 
 III 
 
 a 
 
 UQ 
 KI 
 
 8i 
 
 
 i,t<;oci,Asi 
 
 ULITK. 
 ranulitio 
 
 i 
 
 Si: 
 1 
 
 Si: 
 
 S-<j 
 
 11 
 lit 
 
 ill
 
 76 
 
 GEOLOGICAL STUDIES. 
 
 TABLE FOR ROCK DETERMINATION. 
 
 A. Crystalline some of the constituent minerals having shin- 
 ing, lustrous surfaces; or the rock is fine, compact 
 and hard. 
 
 I. PHANEROCRYSTALLINE, consisting of minerals distinguish- 
 able with naked eye or pocket lens. 
 
 1. QUAKTZ the essential constituent of the rock. 
 (1) Massive or thick-bedded (QUARTZITE). 
 
 (a) Composed of fragments compacted but distinct. 
 
 (aa) The constituents are rounded pebbles, Quaitzose Conglomerate, 
 
 (bb) The constituents are small grains, Granular Quartzite. 
 
 (b) Composed of grains completely blended or nearly so, Vitreous Quartzite. 
 (2, Thin- or moderately thin-bedded. 
 
 (a) Composed of separate grains, 
 
 (b) Composed of a somewhat vitreous, silicious mass, 
 
 2. FELDSPAR alone with quartz. 
 (1) Structure massive, 
 
 (3) Structure schistose, 
 
 3. AIicA a leading constituent of the rock. 
 
 (1) Quartz alone with mica. 
 
 (a) Massive or thick-bedded, 
 
 (b) Thin-bedded, arenaceous-granular, 
 
 (2) Feldspar alone with mica, 
 
 (3) Feldspar and quartz with mica either muscovite or bio- 
 
 tite, or both together; texture, coarse or fine ; the 
 feldspar whitish or reddish; the quartz without 
 cleavage planes. 
 
 (a) The feldspar not in definite crystals, but fragments. 
 (aa) Massive, granular, 
 
 (bb) Thick-bedded, or sometimes thin-bedded, 
 (cc) Thin-bedded, mostly with little feldspar, 
 
 (b) The feldspar in defined crystals, or some of it so; 
 
 massive, 
 
 4. HYDROMICA a leading constituent. 
 
 (1) Quartz alone with the hydromica. 
 
 (a) Massive or thick-bedded, 
 
 (b) Thin-bedded, arenaceous-granular, 
 
 (2) Feldspar alone with hydromica, 
 
 (3) Feldspar and quartz with hydromica; texture coarse or 
 
 fine; the feldspar mostly whitish or reddish, ex- 
 hibiting cleavage planes; the quartz without cleav- 
 age planes. 
 
 (a) Massive granular, 
 
 (b) Thick-bedded and sometimes thin-bedded, 
 (C) Thin-bedded, mostly with little feldspar. 
 
 (aa) In conspicuous grains, 
 
 ~bb) Fine, with greasy feel (many former " talcose " 
 schists), 
 
 Quartzose Schist. 
 ( Silicious Schist. 
 } Jasper Schist. 
 
 Granu'ite. 
 Granulite Gneiss. 
 
 < i riimdite Schist. 
 
 Micaceous Quartzite. 
 
 Micaceous Sandstone. 
 
 Minette. 
 
 Granite proper. 
 Gneiss proper. 
 Mica Schist. 
 
 Porphyritic Granite. 
 
 Hydromica Quartzite. 
 Hydromica Sandstone. 
 Hydromica Minette. 
 
 Hydromica Granite. 
 Hydromica Gneiss. 
 
 Hydromica Schist. 
 
 Sencite Schist.
 
 RETROSPECT OF THE ROCKS. 
 
 5. AMPHIBOLE a leading constituent. 
 
 (1) The amphibole occurring as hornblende (commonest 
 
 case). 
 
 (a) Hornblende alone present, Amphibolite or Hornblende Rock. 
 
 (6) Orthoclase alone present with hornblende, Hyposyenite. 
 
 (c) Orthoclase and quartz present, with often some biotite. 
 (<ia) Massive, Syenite proper. 
 
 (66) Thick -bedded, rarely thin- bedded. Syenite Gneiss, 
 
 (cc) Thin bedded with little orthoclase, Hornblende Schist. 
 
 (d)" Plagioclase alone present with hornblende, 
 (aa) The plagioclase acidic, associated often with some 
 quartz or muscovite; color grayish- white to green- 
 ish, or olive green. 
 
 (aaa) Massive, Diorite. 
 
 (bbb) Thick-bedded, Diorite Gneiss, 
 
 (ccc) Thin-bedded, Diorite Schist, 
 
 (bb) The plagioclase basic, generally labradorite. associ- 
 ated with biotite and no quartz: texture coarse or 
 fine : structure massive or thick-bedded, Xoiite. part. 
 
 (2) The amphibole occurring as actinolite. 
 
 (a) Massive and tough, Actinolite Rock. 
 
 (b) Thin-bedded, with some quartz, Actinolite Schist. 
 
 (3) The ampnibole occurring as smaragdite (a light green 
 
 hornblende) with a white or whitish labradorite in 
 
 fine grains mottling the light green muss Euphotide. 
 
 6. PYROXENE a leading constituent. 
 
 (1) Pyroxene alone present, in the form of augite, coarse or 
 
 fine granular, Pyroxenite. 
 
 (2) Orthoclase present abundantly with little augite, Augite Hyposyenite. 
 
 (3) Plagioclase present with pyroxene (angite); texture 
 
 granitoid or fine. 
 
 (a) The plagioclase acidic, ordinarily oligoclase, Diabase, part. 
 
 (b) The plagioclase basic. 
 
 (aa) The pyroxene lamellar (diallagic); the plagioclase 
 a cleavable labradorite; texture granular, color 
 reddish to dark gray and grayish black (Gabbro 
 
 of some), Norite, part. 
 
 (66) The pyroxene granular; the plagioclase anorthite 
 
 or labradorite ; texture fine, Diabase, part. 
 
 (4 Quartz present abundantly, with sahlite and some feld- 
 spar. Pyroxene Schist. 
 
 7. HTPEKSTHENE a leading constituent, generally with cleav- 
 
 able labradorite [physically like Norite. and by 
 
 some so called], Hypersthenite. 
 
 8. EPIDOTE the characterizing constituent. 
 
 (1) I-^pidote alone, or nearly so; texture fine granular; very 
 
 hard; pale green, Epidote Rock. 
 
 (2) Epidote with quartz and feldspar, . Unakite. 
 
 9. HYDKOUS-MAGXESIAN minerals in characteristic abundance. 
 
 (1) Talc alone present, in a massive amorphous state, Steatite. 
 
 (2) Talc with quartz and feldspar.
 
 78 
 
 GEOLOGICAL STUDIES. 
 
 (a) Massive, Protogine. 
 
 (b) Thick bedded, Protogine Gneiss. 
 
 (c) Thin-bedded, with little feldspar. 
 
 (aa) The quartz granular, Talcose Gneiss, Protogine Schist. 
 
 (bb) The quartz fine and nearly wanting, the rock mostly 
 
 a mass of minute folia of talc, Talcose Schist. 
 
 (3) The magnesian mineral is chlorite; quartz and feldspar 
 
 also present. 
 
 (a) The feldspar abundant; structure thick-bedded, Chlorite Gntiss. 
 
 (b) The feldspar scanty; structure thin- bedded, Chlorite Schist. 
 (C) The feldspar not discernible ; texture very fine, struc- 
 ture slaty, Chlorite Slate. 
 
 (4) The magnesian mineral is serpentine. 
 
 (a) Color homogeneous dark green to greenish-black, Serpentine. 
 
 (b) Color mottled, greenish and white, being mixed with 
 
 limestone ("verd antique"), Ophiolite. 
 
 10. ALUMINOUS minerals in characteristic abundance. 
 
 (1) The characterizing mineral pyrophyllite; color white, 
 
 gray, or greenish- white; feel greasy; appearance 
 
 that of a talc rock, Pyrophyllite Schist. 
 
 (2) The characterizing ingredient argillaceous, firmly indu- 
 
 rated, cleaving into thin, even layers [Clay slate, 
 
 Phyllite], Argillite. 
 
 11. CALCAREOUS rocks ; hardness not above 3. 
 
 (1) Effervescence with dilute acid when pulverized. 
 
 (a) Effervescence with cold acid. 
 
 (aa) Rock chiefly calcareous, Marble, 
 
 (bb) Rock a variegated mixture with serpentine, Ophiolite. 
 
 (b) Effervescence only when heated, Dolomitic Marble. 
 
 (2) No effervescence; hardness about 2, Gypsum. 
 
 12. CARBON the characterizing constituent; color black or 
 
 dark -brown. 
 
 (1) Rock distinctly stratified; hardness 2-2.5; lustre bright, 
 
 often sub-metallic; iron black and frequently 
 iridescent; fracture conchoidal; burns with a fee- 
 ble flame of pale color, Anthracite. 
 
 (2) Rock unstratified. 
 
 (a) Lustre resinous; burns freely, Asphattic Substances. 
 
 (b) Lustre metallic; streak black and shining; color iron 
 
 black to dark steel gray ; feel greasy, Graphite. 
 
 13. IRON the character! zing constituent; specific gravity 3.6 to 
 
 5.3. 
 
 (1) Streak black; specific gravity, when pure, 4.9 to 5.2; I Magnetite Schist. 
 
 acts on the magnet, ' Titanic Iron. 
 
 (2) Streak red ; specific gravity, when pure, 4.5 to 5.3, Hcematite Schist. 
 
 (3) Streak dark reddish brown; acts slightly on the magnet; 
 
 contains zinc, Franklinite Schist. 
 
 (4) Streak brownish yellow; specific gravity, when pure, 3.6 
 
 to 4, Limonite Schist. 
 
 (6) Streak white; sp. gr. of siderite 3.6 to 4.5; effervesces 
 
 with hot acid, Spathic I, on.
 
 RETROSPECT OF THE ROCKS. 
 
 79 
 
 II. MICBOCRYSTALLINE and CBYPTOCBYSTALLINE rocks sepa- 
 rate crystals or grains not discernible with a lens. 
 
 A. Texture felsitic partly microcrystalline, distinct miner- 
 
 als discernible only under high powers in thin sec- 
 tions. 
 
 1. Structure massive or indistinctly stratified. 
 
 (1) Color black or nearly black, sometimes greenish. 
 
 (a) Massive or thick-bedded, Aphanite. 
 
 (b) Thin-bedded, but obscurely so, compact. Aphanitic. Schist. 
 
 (2) Color whitish, reddish, or mottled. 
 
 (a) Essentially orthoclastic (see pa<*e 27); silica inti- 
 mately united; hardness quartz-like. 
 
 (act) Without imbedded crystals; color mostly red, Petrosilex. 
 
 (bb) With imbedded crystals (or alternating bands) of 
 
 quartz [Quartz Porphyry], Quartz Petrosilex. 
 
 (co With imbedded crystals of feldspar, Porphyritic Petrosi'ex. 
 
 (dd) With imbedded pebbles. Conglomerate Petrosilex. 
 
 (b) Essentially plagioclastic, basic; hardness between 
 feldspar and quartz. 
 
 (aa) Without imbedded crystals, Felsite proper. 
 
 (bb) With imbedded crystals (or alternating bands) of 
 
 quartz, Quarts Porphyry. 
 
 (cc) With imbedded crystals of feldspar [Porphyry], Porphyritic Felsite. 
 
 (c) Essentially quartzose; felsitic texture not perfect, Jasper Bock. 
 
 2. Structure distinctly bedded or even slaty, Felsite Schist. 
 
 B. Texture colloid ; lustre glassy; constituent minerals com- 
 
 pletely blended or nearly so, Shyolite, etc. 
 
 C. Texture glassy, lustre quite glassy; translucent or trans- 
 
 parent; colorless or white, Vitreous Quartzite, part. 
 
 ilcareo 
 
 distinctly 
 pulverized 
 
 nd 
 
 J. Uncrystalline fragmental 
 stratified. 
 
 I. Effervescence with acids, at least wher 
 
 heated. 
 
 1. Effervescence with cold acids; rock sometimes semi- 
 
 crystalline, sometimes with an earthy lustre. 
 
 (1) Well consolidated, 
 
 (2) Partially consolidated, white or rusty, 
 
 (3) Unconsolidated, putty-like when wet; white, 
 
 2. Effervescence only when heated. 
 
 (1) Having the aspect of a limestone; often finely granular, 
 
 (2) Aspect dark and earthy ; often nodular, 
 
 II. No effervescence with acids, or only very little. 
 
 1. Quartz the predominating mineral. 
 
 (1) The quartz fragments cemented together. 
 
 (a) The fragments consist of rounded pebbles, 
 (6) The fragments consist of fine grains, 
 
 (2) The quartz fragments uncemented, 
 
 2. Clay the predominating ingredient. 
 
 (1) The clayey ingredient somewhat indurated, but the rock 
 fragile and breaking into thin layers, 
 
 Limestone. 
 Chalk. 
 Marl. 
 
 Dolomite. 
 Spathic Iron. 
 
 Conglomerate. 
 
 Sandstone. 
 
 Sand. 
 
 Shale.
 
 80 
 
 GEOLOGICAL STUDIES. 
 
 (2) The clayey ingredient not indurated, 
 (a) Mixed with various impurities; blue, red, dark, or 
 
 white, 
 (6) In a state of purity; color white, 
 
 3. Carbon the characterizing constituent: color black or dark- 
 
 brown. 
 
 (1) Rock distinctly stratified. 
 
 (a) Lustre bright, often submetallic, iron-black and fre- 
 quently iridescent: fracture conchoidal; burns with 
 a feeble flame of pale color; hardness 2 to 2.5, 
 
 (6) Lustre pitchy; fragile; hardness 2 or less; burning 
 with a yellow, smoking flame; surfaces often show- 
 ing vegetable structure [Bituminous Coals}. 
 (aa) Softens and becomes pasty in the fire; has property 
 
 of caking, 
 
 (bb) Burns freely without softening; has no caking 
 property, 
 
 (c) Lustre dull; color generally brownish [Lignite], 
 
 (2) Rock indistinctly or distinctly stratified, with little or no 
 
 lustre; highly bituminous, 
 
 (3) Rock iiiistratifled. 
 
 (O) Lustre resinous; burns freely, 
 
 (6) Lustre metallic; streak black and shining; color iron- 
 black to dark steel gray; feel greasy. 
 
 4. Iron the characterizing constituent (1), (3) and (5) gener- 
 
 ally crystalline). 
 
 (1) Powder black; sometimes as black shore-sand, 
 
 (2) Powder red; lustre earthy; consolidated or pulverulent 
 
 [Red Chalk, Ited Ochre], 
 
 (3) Powder dark reddish brown ; contains zinc. 
 
 (4) Powder brownish yellow; partially consolidated, granu- 
 
 lar or pulverulent [Bog Ore, Shot Ore, Yellow Ochre], 
 
 (5) Powder white; effervesces with acids when heated., 
 
 t/ 
 
 Clay. 
 Kaolin. 
 
 Anthracite. 
 
 Caking Coal. 
 
 yon- Caking Coal. 
 Brown Coal. 
 
 Cannel Coal. 
 
 Asphaltic Substances. 
 
 Graphite. 
 
 Magnetic Iron Ore. 
 Titanic Iron. 
 
 Hamatitic Iron Ore. 
 FranJdinite Ore. 
 
 Limonitic Iron Ore. 
 Spathic Iron. 
 
 STUDY XV. Sedimentation. 
 
 Let us visit a spot overflowed by the last freshet. We go 
 down to the border of the creek and find the flat grimly with the 
 muddy slime deposited while the stream was out of its banks. 
 The level meadow was quite covered by the water; and we can 
 understand that many overflows must make material additions to 
 the land. Indeed, the character of the soil here, and its very 
 level surface, show that during times past this piece of ground 
 tnust have been formed from sediments deposited at times of
 
 SEDIMENTATION: 
 
 81 
 
 overflow. Deposits from rivers are called fluviat He, and the land 
 resulting- is alluvial. In Cincinnati at the time of great floods, 
 the Ohio River, which then abounds in sediments, leaves a thick 
 layer of fine sticuy mud wherever the water stands in streets, 
 yards, cellars and the floors of first stories of the houses. Think 
 of the enormous amount of mud which is thrown down along the 
 whole course of the river wherever the overflow takes place. So 
 the river becomes bordered by alluvial bottoms, except where the 
 banks are too high for overflow. The same is true of the Con- 
 necticut, the Potomac, and all other rivers. 
 
 Let us go down by the pond; here we shall see other results 
 of the process of sedimentation. Perhaps this pond is caused by 
 
 FIG. 25. THE LAKELET SLOWLY FILLING. PKOCESS OF SEDIMENTATION. 
 
 a dam thrown across the stream. Jf so, your father or uncle may 
 remember when the dam was first built; it was not a century, but 
 notice how the pond is "silted up"; it is half filled with mud and 
 sand washed in from the adjacent hill-slopes. Perhaps this pond 
 is a little lake, with or without a slight outlet. You have seen 
 many of them. They abound especially in our New England and 
 Northern States. Suppose ourselves standing by one of these 
 lakelets. It looks a little like the view in Fig. 25. The lakelet 
 is bounded on most sides by elevated ground, but on one side 
 the shore is low and marshy. The land stretches off several rods 
 in a perfectly level marsh or meadow; then we suddenly reach 
 the firm upland. Down by the water the marsh grows less and
 
 82 GEOLOGICAL STUDIES. 
 
 less firm. Even beyond the border of the water, some sedges 
 find a situation suited to their natures, and still beyond, bulrushes 
 and flags rise from water a foot or more in depth. On other 
 sides, the nature of the lakelet border is very different. Now 
 consider on which side the marshy border lies. It is almost al- 
 ways on the side opposite that from which the prevailing wind 
 blows; that is, it is the easterly side ranging from northeast 
 to southeast. The leaves, grasses and twigs which float on the 
 water surface are drifted by the winds toward the marsh, where 
 they become lodged and go to decay. The resulting vegetable 
 matter forms a dark, peaty layer on the bottom, which accumu- 
 lates from year to year. It stretches from the land down and 
 under the water. As the land grows, the marsh-grasses and 
 sedges extend their area, and water-loving plants spring from the 
 submerged portion of the peat. Thus, from year to year, the 
 peat extends further along the bottom, and the land encroaches 
 upon the lake. But suppose this process has been going on a 
 thousand years; the land must have grown lakeward quite exten- 
 sively. Indeed it has; and this level marsh or meadow shows 
 how much land has been made in this way. Let us dig in this 
 marsh. You know beforehand it is formed of black "muck." 
 And now we see why the marsh is exactly level, and why it lies 
 but very little above the surface of the water. 
 
 But here is another phenomenon. Underneath the muck or 
 peat is a bed of marl; how came that there? Well, going down 
 to the lakelet again, you see marl lying- on the bottom; so of 
 course, as the peat bed extends, it covers the layer of marl. An 
 examination of the marl shows numerous dead shells uni- 
 valves or water snails, and bivalves or mussels. These are in all 
 stages of decay, and it is evident that much of the marl thus 
 originates. Living snails and mussels still abound in the water, 
 especially near the shores, crawling on the bottom. But proba- 
 bly some portion of the marl results from precipitation of calcium 
 carbonate from spring waters, as briefly explained in Studies II 
 and XII. 
 
 If sediments are thus accumulating on the bottom from the
 
 SEDIMENTATION. 
 
 83 
 
 deposit of calcareous matter, and from the wash of the land; 
 and if the peat marsh is gradually encroaching 1 , what must be the 
 final result? Evidently, the lake must be filled, and a bed of peat 
 underlaid by marl will occupy its place. Now you understand 
 the origin of those numerous swales and bogs and tamarac 
 swamps which "exist in some regions. They are the sites of 
 ancient lakes. Some of them have become sufficiently drained 
 to be meadows, or even arable grounds. The old swamps, when 
 thus dried, furnish our most productive lands, because they are 
 filled with the very materials which supply the chief food for 
 vegetation. 
 
 The growing swamp is not always on the lee side of the lake; 
 it will be found, however, on the side toward which surface mo- 
 tion sets. Sometimes the position of contiguous hills deflects 
 the prevailing winds from their normal direction; and sometimes 
 a surface drift is imparted by the drainage of the lakelet. 
 
 We must stiuty a little farther the results of river sedimenta- 
 tion. Look on a map of the Mississippi valley from Cairo to the 
 Gulf of Mexico. The region presents but a very gentle slope, 
 and the course of the river is wonderfully sinuous. 
 For the whole distance, one looks out from the 
 deck of a steamboat, over a wide alluvial plain, 
 bounded, at a greater or less distance from the 
 river, by high banks. Toward the gulf it expands 
 in a triangular form, and that part is called the 
 delta. Freqently the whole alluvial plain is so 
 called. This plain is flooded by the high water 
 of certain seasons unless confined by a system of 
 embankments. During ovei flows the sediments 
 subside the coarser first and the finer afterward. 
 This is familiarly illustrated by the subsidence 
 which takes place in a glass of water as shown in 
 Fig. 26. We may suppose this is a glass of Mis- 
 sissippi River water with a little gravel added. 
 
 The alluvial deposit of the Mississippi has thus accumulated 
 to the depth of ten, twenty, or even fifty feet. In Fig. 27 we 
 
 FIG. 
 ASSORTMENT 
 OP SEDIMENTS 
 IN TUBE ID 
 
 WATER.
 
 84 
 
 GEOLOGICAL STUDIES. 
 
 1/yK - - 
 
 '~T^ ^^ I wilKlin s of Hie Mississippi.) 
 
 FIG. 27. WIN DING
 
 SEDIMENTATION. 85 
 
 present a map of a section of the river between Vicksburg and 
 Baton Rouge, with shading to indicate the breadth of the alluvial 
 belt. Through this belt, with its wonderful network of bayous of 
 sluggishly moving 1 water, the channel pursues its sinuous course, 
 frequently striking the high upland, and affording sites for cities 
 and villages, as at Vicksburg, Natchez, and other points. It will 
 be noticed that the stream repeatedly doubles on itself, forming 
 peninsulas. At many points it has completely worn the isthmus 
 across, forming islands, and pursuing a new channel, as seen be- 
 low Fort Adams. At other points, as near Grand Gulf and Port 
 Hudson, the entrances to the old channels have been "silted up," 
 and the old channels then remain as lakes. Thus Bruin Lake 
 was cut off before the river was known to navigators; Lake St. 
 Joseph before 1700, when the river was shortened twenty miles; 
 and Palmyra Lake was formed by the Davis cut-off, D, in 1867, 
 reducing nineteen miles to one. In one memorable instance this 
 conversion of a peninsula into an island was effected by human 
 agency. Notice the position of Vicksburg on the map, Fig. 27. 
 During the late war, in 1862-3, a canal was dug across the U at 
 C, for the passage of the federal gunboats, to enable them 
 to shun the batteries erected on the Vicksburg bluffs. This 
 canal has now become the main channel of the river, and the old 
 channel remains a mere bayou of nearly still water, greatly to 
 the detriment of the trade of the city. Sediment is constantly 
 accumulating in it. Only one expedient seems practicable. The 
 Yazoo river, which empties into the Mississippi a few miles above 
 the city (see map), may be dammed, and its waters conducted 
 through a canal into the Mississippi at the bend of the U above 
 the city. This river then would scour out the bayou, and Vicks- 
 burg would stand on the Yazoo, two miles above its mouth. 
 
 When it is noted that this enormous alluvial deposit extends 
 to the Gulf of Mexico, we gain some conception of the volume of 
 sediments transported by the Mississippi. At its mouth the cur- 
 rent is met by a body of salt water, over which the river dis- 
 charges itself. Here the slackened motion results in the deposi- 
 tion of a vast volume of sediment known as the "bar." But
 
 86 GEOLOGICAL STUDIES. 
 
 another and finer portion of the sediment is borne to sea and 
 taken up by the normal oceanic currents, which carry it to great 
 distances before it finally settles down upon the ocean's bottom. 
 All the rivers which empty into the sea are similarly contrib- 
 uting sediments to be added to the layer accumulating- over the 
 bottom. Thus the oceans are filling, as well as the lakes; and 
 the ocean sediments are burying, also, the remains of the mol- 
 luscs and fishes which lived in the water above their final burial 
 place. The dredge brings up samples of the sediments for our 
 inspection. They are coarser and more abundant nearer the 
 shore, as we should expect; and the continental sediments cease 
 almost entirely before the great abyss is reached. In the zone, 
 from two to three miles in depth, we find a pretty uniform layer 
 of a white marly substance known as "globigerina ooze," from 
 the predominance of microscopic shells of Globigerina, a genus 
 of Foraminifera, of which more will be learned in Part II. With 
 these are numerous fragments of other organisms, especially of 
 Pteropods. This substance when dried presents the appearance 
 of white chalk; and in fact, white chalk is largely composed of 
 similar organisms. At greater depths the admixtures with globi- 
 gerina ooze diminish in quantity. At the greatest depths is 
 found a layer of fine, homogeneous reddish-brown clay, composed 
 of silica, alumina, and oxide of iron. This is supposed to be a 
 residuum left after the solution of Globigerina and Pteropod 
 shells by some peculiar action of the abyssal sea water. 
 
 EXERCISES. 
 
 How does moving water act to separate the finer and coarser particles? 
 In a stream flowing from a steep ravine to a plain, what portion of the 
 transported material will be deposited on the plain? What portion along 
 the slope? Why this assortment? Why is the upper layer of sediment from 
 a pool of turbid water finest? Is the alluvial deposit from the Mississippi 
 fine or coarse? Why is this so? Describe a stream which would deposit 
 pebbles. What do you know about the power of Alpine torrents? What 
 effect is produced on rock fragments transported by water? Has water itself 
 any power to wear the rocks? In what two ways do rocks disappear under 
 the action of water? [See Studies II, III, and XVI.] In a mixture of fine
 
 EROSIONS. 87 
 
 sand, powder, and slime, how may water be used to separate them? Can 
 you think of other moving waters besides streams which also exert an assort- 
 ing action? What movements of the ocean do this? Why are the coarsest 
 pebbles nearest the beach? Why are some beaches pebbly and others sandy? 
 To what depth are the ocean waters stirred by winds and tides? What kind 
 of sediments would be borne to the greatest depths? Why are the most 
 projecting points of the coast rocky? W^ould marine animals generally 
 prefer to live about such points? Why do we not find good shells along a 
 stony coast? Mention some marsh which resulted from the filling of a lake. 
 Ask some of the old citizens if they know any lake or pond which has been 
 filled by sediments. Would you be surprised to find shells in a bed of dry 
 peat? What is filling the Gulf of Mexico? What is getting buried by the 
 sediments? Do you think the deposits are all uniform, or are they arranged 
 in layers? What would cause a coarse layer? What a fine layer ? Have all 
 rivers deltas? What might prevent a river from having a delta? Mention 
 a river without a delta. Mention rivers with extensive deltas. 
 
 STUDY XVL Erosions. 
 
 We have seen, in various situations, a great amount of turbid 
 water. Some of this stands, for a time, almost motionless ; some 
 is hurried onward by running streams, and some is moved by 
 winds and currents in lakes and seas. But in all situations, sus- 
 pended sediments tend to settle, and will eventually settle, unless 
 the agitation of the water is too great. We have seen that some 
 of the material moved by waters consists of pebbles and larger 
 stones. Some consists of sand in a coarser or finer condition. 
 But all is nearly of the nature of the drift materials covering gen- 
 erally the surface of the land. That is, transported sediments are 
 nothing but fragments of rocky formations, broken and ground 
 and pulverized. Let us try and trace some of them to their 
 sources. 
 
 Here, first, is the slime settled in a pool by the roadside. It 
 is quite evident that the last rain washed the material from the 
 roadway and the fields. On this declivity a more powerful cur- 
 rent has cut a deep gully, which renders the highway almost im- 
 passable, and the bowlders, stones, pebbles, sand, and mud are
 
 88 
 
 GEOLOGICAL STUDIES. 
 
 strewn in order along by the fences, and across the flooded fields. 
 The sediments are derived from the drift. Every rain-storm 
 transports portions of the drift from the higher to the lower lev- 
 els. Every rain-storm carries some of the soil from the ploughed 
 fields, and leaves it in the bottom of the lake, or spread over the 
 alluvial flat. 
 
 Let us go to the rocky gorge. Here, in ordinary weather, is 
 a small stream, though noisy ; and it seems to have accomplished 
 a great work. Usually the water is clear, and seems to move no 
 material from its place. But how came this deep ravine into ex- 
 istence ? It is the work of erosion. You have seen the clear 
 brooklet swollen to a torrent. At such time it rises to the level 
 of the crumbling banks, and- tears out stones and" sand, and hurls 
 them down to the foot of the gorge. The finer sediment is carried 
 
 miles beyond into the gentler 
 current of the river, or the stand- 
 ing water of the lake. Sometimes 
 the banks of the gorge are rocky, 
 but the roaring torrent cuts its 
 way through them, and the strata 
 stand in nearly vertical walls on 
 either side. In southern New 
 York, at many localities, are such 
 deep ravines, cut through sand- 
 stones and shales, nearly horizon- 
 tal in position. We give you in 
 Figure 28 a view of one at Wat- 
 kins' Glen, at the head of Seneca 
 Lake. This is a very picturesque 
 region, much frequented by tour- 
 ists. Many other gorges may be 
 seen along the Genesee River, in 
 its course to Lake Ontario. Do 
 PIG. 28. VIEW IN THE GORGE AT WAT- not fail to notice the gorge and 
 KINS' GLEN, N. Y. ("RAINBOW the fa n s at Rochester, when you 
 FALLS"), ILLUSTBATING EROSION i T-, 
 
 BT WATER. pass over the Central Railroad.
 
 EROSIONS. Otf 
 
 In the northwestern states are other examples of erosion equally 
 beautiful and impressive. The Wisconsin River, in its course to 
 the Mississippi, has cut a deep channel through a friable sand- 
 stone, giving rise to a great amount of charming scenery. 
 One of the views is presented in Fig. 29. The student of geol- 
 ogy is greatly favored in this fact, that the very data of his 
 science are the most interesting features of the earth's surface. 
 The greatest of rivers, the Mississippi, has also effected erosions 
 
 FIG. 29. THE "DALLES" OF THE WISCONSIN. SHOWING 
 RIVER EROSION. 
 
 worthy of its greatness, though unimposing, it must be confessed, in 
 comparison with another river whose equal greatness belongs to 
 a past age of the world. Along the upper Mississippi, high cliffs' 
 line the valley most of the way (Fie:. 30). The Niagara, as every- 
 one knows, has excavated a gorge which, with the "falls," its 
 instrument, is the wonder of the world. We shall have to con- 
 sider this in other connections. (See Figs. 305 and 306.) But 
 the most stupendous examples of river erosion are found in the 
 Far West. The Colorado has cut prodigious canons through the
 
 90 
 
 GEOLOGICAL STUDIES. 
 
 horizontal strata to the depth of four, five and six thousand feet. 
 Many of its tributary streams have excavated similar gorges. Thus 
 
 much of the region is scarred 
 and scored in a manner which 
 renders it almost impassable. 
 We cannot conveniently visit 
 this region, but we supply in 
 Fig. 31 a perspective view of 
 the " Grand Cafion " at the foot 
 of the valley of the Toroweap, 
 and of some of the contiguous 
 country. The total chasm pre- 
 sents itself in two stories.. The 
 walls of the outer canon stand 
 five or six miles apart, and about 
 2,000 feet high. The inner 
 canon is 4,000 feet wide and 
 3,000 feet deep. At the bottom 
 flows the diminished river, about 
 300 feet across. The rocky beds 
 which outcrop in the nearly ver- 
 tical walls vary in colors from 
 brilliant red to creamy yellow- 
 ish and gray. But we must not 
 enter here into any detailed 
 statements. For these we refer 
 the student to the glowing pages of Captain Button's descrip- 
 tion in "The Tertiary History of the Grand Canon District," 
 in the Report of the United States Geological Survey for 1881. 
 
 These examples, with others which may be familiarly known 
 to the student, illustrate the destructive action of flowing water 
 in all parts of the world. Aggregating the effects of thousands 
 of years, we begin to understand how enormous has been the 
 transportation of sediment into the sea through the agency of 
 rivers, and how vast has been the destruction of the land. If we 
 stand by any lake or ocean shore, we shall witness a different 
 
 FIG. 30. CLIFF ON THE TPPEK MISSIS- 
 SIPPI NEAB TREMPEALEAU, Wis., 
 ILLUSTRATING RIVER EROSION. 
 (Chamberlin.)
 
 EROSIONS. 
 
 fll
 
 92 GEOLOGICAL STUDIES. 
 
 action of the same agent. Historical records assure us of vast 
 wastage of the land on many an exposed coast ; and we shall 
 learn hereafter that ocean waters have in other ages covered ex- 
 tensive areas now dry land, and have worn down the surface hun- 
 dreds and thousands of feet. The very cafion just mentioned is 
 cut in a plateau which has itself been lowered by erosion to the 
 extent of 10,000 feet; and this plateau occupies an area of 13,000 
 to 15,000 square miles. The student may calculate how many 
 cubic vards the land has lost, and how many have been spread 
 over the bottom of the sea. 
 
 The evidences of the great wastage of the land in times past 
 can everywhere be seen. Sometimes extensive masses are under- 
 mined, and tumble down. This accelerates their final disappear- 
 ance (Fig. 32). In the year 1248 a large part of a mountain in 
 Savoy fell to the plain, under the 
 action of frost. The mountain rose 
 4,000 feet above the plain, and was 
 capped by GOO feet of limestone. The 
 undermining of this mass caused the 
 precipitation of sufficient material to 
 
 cover nine square miles with frag- 
 
 _'.': 'rffib ments, and entirely bury five parishes, 
 FIG 32. MAONESIAN LIMESTONK together with the town and church of 
 UNDERMINED BY THE DISINTE- St Andre. In 1751 a series of ava- 
 ORATION OP A SANDSTONE BE- 
 NEATH. (Chamberiin.) lanches tell during several days from 
 
 a mountain near Servos, in Savoy, 
 
 which sent up a cloud of dust visible twenty-five miles. The 
 amount of material precipitated was 15,000,000 cubic feet. Many 
 similar cases could be cited. 
 
 This underminining process is the method of recession of 
 water-falls, as will be shown hereafter (Figs. 305 and 306). 
 
 The central part of Tennessee that known as the "central 
 basin" -is a vast sunken area more than a hundred miles in 
 diameter ; and this has evidently been produced by the removal 
 of many cubic miles of rocky material through some process of 
 erosion in times past. All around the border of this basin rise the
 
 EliOSlOXH. 
 
 rocky walls of the remaining por- 
 tions of the formations a hundred 
 feet high, or more. In East Ten- 
 nessee is another valley formed by 
 extensive erosion. These are shown 
 in the cut, Fig. 33. See also how 
 the nearly vertical strata of the 
 Unaka range have been worn down 
 to mere stumps. Where have 
 gone the continuations of these 
 upturned strata? 
 
 We direct the student's atten- 
 tion to one more example. In 
 Fig. 34 is shown the evidence of 
 vast erosion in the Appalachians. 
 Here the actual surface is shown 
 along ABC. The slight eleva- 
 tion at A represents truly one of 
 the ranges of the Allegheny 
 Mountains. B represents the range 
 known as Bald Eagle Mountain. 
 Notice the foldings of the vast 
 series of strata. Notice the moun- 
 tain mass represented by E, which 
 once rose 35,000 feet above the 
 present surface, and all has been 
 carried away by erosion. This 
 section is in Centre County, and 
 shows but a fraction of a full sec- 
 tion across the Appalachian chain. 
 But all the mountain elevations 
 have been similarly worn down. 
 
 In very numerous cases singu- 
 lar columns of the eroded rock 
 have escaped erosion. Sometimes, 
 as in Monument Park, Colo- 
 
 31 
 
 ~ Ten ncsnec River 
 
 Nashville 
 
 / /Jfnozville
 
 94 
 
 GEOLOGICAL STUDIES. 
 &> E 
 
 ' X 
 
 8. East 
 
 2V. West 
 
 FIG. 34. ILLUSTRATING ENORMOUS EROSION IN THE APPALACHIAN REGION. (After Les- 
 ley.) A, Allegheny Mountain at Snow Shoe; B, Bald Eagle Mountain; ABC, present 
 surface all above being swept away; D, probably a subterranean mountain of Eozoic 
 rocks; II to in, Cambrian; IV to VI, Silurian; VII to IX, Devonian : X to XII, Lower 
 Carboniferous; XIII, Coal Measures. Compare, for explanation, Study XVII. 
 
 FIG. 35. COLUMNS IN MONUMENT PARK, COLORADO. (Hayden.)
 
 EROSIONS. 
 
 rado (Fig. 35), and in some parts of Wisconsin and Minnesota, 
 they have been protected by a fragment of harder rock, which 
 rests on them like a cap. Sometimes, as in the Plateau Province 
 of Colorado, the rock masses around such columns have been 
 worn away by streams of water. 
 
 We must not forget that mere weathering accomplishes much. 
 This includes the mechanical action of beating rain, hail, and 
 snow, and disintegrating frost, as well as the solvent action of 
 water. On the dome of St. Paul's, in London, the more rapid 
 weathering of the stone causes some of the fossils to project a 
 quarter of an inch, as before stated. This observation, made in 
 1873, was after an exposure of one hundred and sixty-three years. 
 At this rate 7,824 years would be required for the wastage of 
 the stone to exceed that of the fossil to the extent of one foot. 
 As the fossil itself wasted probably half as rapidly as the stone, 
 we may safely as- 
 sume that the wast- 
 age of the rock was 
 not less than a foot 
 in 4,000 years. 
 
 Many instructive 
 examples of atmos- 
 pheric decay may be 
 seen among granite 
 rocks. Here (Fig. 
 36) is a view of the 
 summit of Mt. Hoff- 
 man, Sierra Nevada, 
 showing the bowl- 
 der-like forms re- 
 sulting from atmos- 
 pheric action. A 
 more striking exam- 
 ple is shown in Fig. 
 37, where one of the granite ridges between the Temescal and 
 San Bernardino ranges, in California, is weathered to a state 
 
 FIG. 36. SUMMIT OF MT. HOFFMAN, SIERRA NEVADA, 
 SHOWING DISINTEGRATION OF GRANITE. (Photograph.)
 
 96 
 
 GEOLOGICAL STUDIES. 
 
 which presents the appearance of a bowlder-strewn surface. The 
 weathering of granite is peculiarly apt to result in bowlder-like 
 forms; and it can hardly be doubted that they have sometimes 
 been mistaken for true glacial bowlders, even in tropical countries. 
 Much attention has been given to the wastage of the land 
 generally. Some good authorities conclude that most continental 
 surfaces are lowered by erosion not less than a foot in six thou- 
 sand years. It has lately been calculated by T. Mellard Reade 
 that when we take account, also, of wastage by solution, the sur- 
 
 
 FIG. 37. A RIDGE OF GRANITE WITH BOWLDER-LIKE MASSES RESULTING FROM 
 WEATHERING. (Whitney.) 
 
 face of the basin of the Mississippi is lowered a foot in four 
 thousand five hundred years; and that one hundred tons are 
 removed annually from every square mile of the two Americas. 
 The wastage of the land is called denudation. 
 
 So we may learn that there has been vast destruction of the 
 rocks during the course of many ages. They have been gradually 
 reduced to gravel and mud, and even solutions, and carried off 
 by the streams, to be laid down on the plains, or spread as sedi- 
 ment, if undissolved, over the bottom of the sea. [For other 
 interesting illustrations of erosion see Figs. 85, 86, 95, 55, and GG.]
 
 STRATA, AXI> WHAT THEY TEACH. 97 
 
 EXERCISES. 
 
 From what are sand and mud derived? Was the Mississippi mud ever 
 in a rock condition? How might it be made rocky again? Would it become 
 chalk? Could it be made a granite? What agents produce sand and mud 
 from the rocks? How does frost act? How does a stream of water act? 
 Mention some ravine excavated by running water. Is the excavation in 
 drift or solid rock? Where has the material been carried? How far can you 
 trace it in thought? What is the source of the sediments of the Mississippi? 
 Which is most turbid, the Upper Mississippi or the Missouri? What is the 
 cause of the difference? Whence comes the mud which forms the bar of the 
 Mississippi? What is the color of the water in the lower Mississippi? What 
 is the color of the water in the bayous of Louisiana and Mississippi? Has 
 the Red River any delta? Would the erosions of the Missouri and the 
 streams which feed it have any tendency to lower the Rocky Mountains? 
 Where are the sources of the Ohio? Does New York state contribute any- 
 thing to the bar of the Mississippi? What is the effect of denudation on the 
 depth of the soil? Are the soils generally disappearing? In what situations 
 are soils accumulating? If a hundred tons of material disappear annually 
 from every square mile, to what extent does this lower the surface? [Calcu- 
 late by assuming a mean specific gravity for the material.] Why do bed rocks 
 project above the soil in some places and not in others? Is there any danger 
 of the disappearance of the soil in a hilly country? Which surface lowers most 
 rapidly, that of West Virginia or that of northern Illinois? Can you think 
 of any reason why the plateaus of Colorado and Utah are more denuded than 
 the surface of Louisiana? Suppose the stone on the dome of St. Paul's 
 Cathedral in London is still one foot thick, how thick will it be (on the data 
 given) one thousand years from now, if the cathedral is still standing? 
 
 STUDY XVII. Strata, and What They Teach. 
 
 Most students of geology have been at some time in a stone 
 quarry. There they have seen the quarrymen drilling and blast- 
 ing and prying to remove slabs or layers of the rock. Such slabs 
 are used in the stone walls of houses, sometimes in sidewalks, 
 and sometimes, where they are thin layers of slate, they are em- 
 ployed in roofing. In quarries of granite or other crystalline 
 rocks, the slabs are very thick, as you have already learned, and 
 the stones are worked out in large cuboidal blocks. But in al-
 
 98 GEOLOGICAL STUDIES. 
 
 most every case you will notice that the rocks in the quarry lie in 
 layers, thick or thin. Each layer is a stratum, and two or more 
 layers are called strata. We often also call them beds. If you 
 go back to Watkins' Glen, Fig. 28, you perceive that the strata 
 are quite thin or slaty, or, as we have before said, thin-bedded. 
 The rocks shown in Fig. 29 are also thin-bedded. In both cases 
 the strata are nearly horizontal. Almost everywhere the stratifi- 
 cation or bedding of the rocks can be detected. We must try to 
 ascertain how the bedded structure has been produced. 
 
 You have seen the brooks and rivers at work tearing down 
 the land. You have seen the waves corroding the beach. You 
 have thought on the slow disintegration of all the surface rocks 
 by rains and frosts, and the perpetual wearing of the loose mate- 
 rials of the drift; and you have seen the waters carrying away 
 the sediments to the sea. In thought you have followed those 
 sediments in their distribution over the ocean's bottom. You 
 have seen them lying and accumulating there, while dead shells 
 and bits of coral and bones of fishes have been mingled with the 
 growing deposit. What appearance must the sediments present 
 in case a few acres of sea bottom could be taken out bodily and 
 inspected? The sediments would consist of layers parallel with 
 each other. They would be distinguished by different colors and 
 by different degrees of fineness. Imbedded in the substance of 
 the layers would be the relics of the animals which have lived in 
 the sea. Is this a correct statement of what you would see? 
 Think about it. The depth of the accumulated sediments would 
 correspond to the time spent in their accumulation. You might 
 look at them and reflect: "These layers of mud and sand were 
 once far inland. They were once part of the soil of cornfields 
 and gardens. Crops grew on them. The gully in the road was 
 made by the removal of them. They came down the rivers. 
 Some started on the slopes of distant mountains. The Missouri 
 brought some from the gorges and summits of the Rocky Moun- 
 tains. Some came out of the deep and gloomy canons of the 
 Colorado. Some came from the storm-torn bluffs at Long Branch
 
 STRATA, AND WHAT THEY TEACH. 99 
 
 or Coney Island or Gay Head. Some was yielded by the slowly 
 dissolving promontories of Nahant and Marblehead." 
 
 That is what you might think; and such reflections are sug- 
 gested by our observations on the processes of erosion and sedi- 
 mentation. Now suppose the layers of sediments pressed by 
 thousands of tons of weight. The deeper ones are so pressed when 
 many feet of later sediments are deposited upon them. All are 
 so pressed by the mere weight of deep water. They would thus 
 be condensed into a solid state like the paper pulp which is 
 manufactured into car-wheels. They would be rocks. The rocks 
 would be composed of strata. The thin layers would be laminae. 
 The shells and corals pressed in the rocks would be fossils. This 
 is almost exactly what we have at Watkins' Glen, and in the ma- 
 jority of the rocks underlying the country. All our limestones, 
 sandstones and shales were once just such sea sediments. The 
 limestones, however, contain a very large proportion of matters 
 contributed by the decay of shell-bearing animals. 
 
 You have already learned, however, that many rocks do not 
 exhibit so distinct evidences of stratification as may be seen in 
 ordinary sandstones, shales and limestones. In fact, most of our 
 bowlders are only obscurely stratified, because rocks of this kind 
 resist destruction more successfullv than the rocks more distinctly 
 stratified. These hard or crystalline rocks come to the surface, 
 or outcrop, in most parts of New England and along our northern 
 border. But, as before said, they are really stratified, and must 
 be, therefore, of sedimentary origin like the others. They have, 
 therefore, been altered since they existed in a condition similar to 
 the others. This alteration is known also as metamorphism. The 
 causes of it have been much studied; but there are still some 
 mysteries about it. We understand, however, that great press* 
 ure, great heat, and chemical operations have had much to do 
 with metamorphism. The effect of it is to render a rock less dis- 
 tinctly stratified, harder, more crystalline and less clearly fossilif- 
 erous. So metamorphism impresses characters which are easily 
 observed. 
 
 When we find metamorphic rocks in place, that is, in solid
 
 100 GEOLOGICAL STUDIES. 
 
 ledges instead of bowlders or detached fragments, we generally 
 find them underlying in relative position all the non-metamor- 
 phic rocks. This is plainly seen when we are able to trace them 
 to their contact with other rocks. In Fig. 38, , granite, and b y 
 gneiss, are metamorphic or crystalline, and c, a sandstone, is un- 
 crystalline. Now if we start from the highest point and travel 
 toward the sandstone, we find, on reaching it, that it overlies the 
 gneiss, as the gneiss overlies the granite. Now notice that the 
 granite and gneiss not only underlie the sandstone at the point of 
 contact; they are everywhere stratiyraphically lower than the 
 sandstone, even where their outcrops are topographically higher 
 than the sandstone. This frequent arrangement of strata in 
 respect to positions it is very important to observe and under- 
 stand. An outcrop of one stratum at a higher level than another 
 
 b a 
 
 PIG. 38. CRYSTALLINE AND UNCRYSTAT.MM: 
 
 a, Granite; 6, Gneiss; c, Sandstone. 
 
 does not indicate whether it is stratigraphically higher or lower. 
 We must take particular notice of the dips of the two strata. 
 The dip is the direction in which they incline downward. . In Fig. 
 38 the gneiss and the sandstone dip in the same direction; but as 
 the gneiss has the greatest dip it passes under the sandstone. 
 This is a case of line on for mobility the two dips being different. 
 The position of the sea bottom was different when the gneiss 
 materials were laid down from its position when the sandstone 
 materials were laid down. This single observation shows that 
 the sea bottom has sometimes undergone a tilting or inclination, 
 and that afterward later sediments have been laid down. 
 
 Look again at Fig. 38. Here is also a record of erosions. 
 The gneiss on one side of the granite dips in a direction opposite 
 to the dip on the other side. Suppose the granite could be 
 pushed down so as to lower the gneiss to a horizontal position;
 
 STRATA, AND WHAT THEY TEACH. 101 
 
 the gneiss of the two sides would become nearly continuous, 
 only some portion would be wanting. Now we may fairly assume 
 that the anticlinal position (both ways dipping) of the gneiss has 
 resulted from the uprise of the granite from beneath the for- 
 merly horizontal gneiss. If so, the gneiss may have been origi- 
 nally continuous over the summit of the uplifted granite, and 
 have been subsequently removed by processes of erosion. In 
 such case, the outcropping extremities of the gneiss strata are 
 the mere stumps of a wasted formation, and have been brought 
 to a position higher than the sandstone by an uplift subsequent 
 to the deposition of the gneiss sediments. We might reasonably 
 conclude that there has been another uplift since the deposition 
 of the sandstones; for they are also somewhat tilted. Thus the 
 steep inclination of the gneiss may be the result of two or more 
 uplifts. These things should be much reflected on. 
 
 From the simple stratigraphical observations thus far made, 
 we may draw inferences like the following: 
 
 1. The duration represented by so enormous a pile of sedi- 
 ments as have come to our knowledge, must have been vast. 
 
 2. The sea has covered all the land, for all lands are under- 
 laid by sedimentary rocks. The sea was once universal. 
 
 3. Some special action has been exerted upon the sediments 
 to change them from earthy strata into crystalline rocks. 
 
 4. The land has resulted from an upheaval of the bottom of 
 the sea; and upheavals have occurred more than once in the 
 same region. 
 
 5. The upheaval of the sea bottom bent and fractured the 
 strata, and threw them into inclinations more or less steep. 
 
 6. The work of denudation has removed the upper strata 
 over the higher summits, and left the strata lower in geological 
 position to stand at higher elevations than strata higher in geo- 
 logical position. 
 
 7. The movement of such enormous masses of rocks implies 
 the exertion of force inconceivably great. The nature of this 
 force will be an important subject for future study.
 
 102 GEOLOGICAL STUDIES. 
 
 EXERCISES. 
 
 In what attitude are layers of sediments originally deposited? How, 
 then, do we find them almost always in an inclined position as strata? Did 
 you ever notice strata standing almost on edge? Explain how this could be. 
 Give the history of strata whose edges come up to the surface of the earth. 
 Draw a diagram showing how strata older in age may appear higher topo- 
 graphically. Draw one showing how newer strata may appear higher topo- 
 graphically. Draw a diagram showing conformability of strata. Draw one 
 showing unconformability of strata. Suppose we have several strata, of 
 which the lower is composed of pebbles and the others are progressively finer, 
 what conditions produced this result? Suppose we can trace a stratum for 
 many miles, and find it graduating from a conglomerate to a coarse sandstone, 
 and then to a fine one; explain this. If we could trace it further, what fur- 
 ther change might be expected? In what direction do older strata dip in 
 reference to newer? In what direction do newer strata dip in reference to 
 older? Can you give any reason why inetamorphic rocks are generally more 
 deeply seated than others? 
 
 STUDY XVIII. Fossils, and What Tliey Teach. 
 
 Now, once more let us carry our thoughts back to the bottom 
 of the sea, where the sediments are continually burying the or- 
 ganic relics of the sea. Relics once buried become buried deeper 
 and deeper. By and by some of them are a hundred, or even a 
 thousand, feet beneath the ocean bed, and the sediments are be- 
 coming subjected to an enormous pressure, and are hardening' into 
 solid strata. Now, the amount of sediment in sea water far from 
 land is generally small. The accumulation of successive layers 
 is, therefore, very slow. We can understand that when they have 
 become a thousand feet deep probably many thousands of years 
 must have passed by. In that time the inhabitants of that part 
 of the ocean may have changed greatly. The water is now a 
 thousand feet shallower than it was. The deep-water species 
 which dwelt there at first have migrated to a region where the 
 water is still deep. Shallow-water species are here now. So the 
 remains of the former kind are imbedded in the deep sediments,
 
 FOSSILS, AND AVHAT THEY TEACH. 103 
 
 and those of the latter kind in the later sediments. But the 
 ocean bottom sometimes changes its level. If it has been sink- 
 ing here, the depth may be as great as at first; but if it has been 
 rising, the depth is diminished even more than is due to the ac- 
 cumulation of sediments. Perhaps the nearest land has been more 
 upraised, and the shore is now nearer to this spot; coarser sedi- 
 ments are now deposited here; the mud-loving populations have 
 emigrated, and this place is taken by populations which like a 
 sandy bottom. If, therefore, we could examine an extensive 
 series of strata, we should find them distinguished by their or- 
 ganic contents, as well as by their constitution and color. 
 
 Now let us examine such a series. Every high rock precipice 
 presents one; every deep river gorge presents one; the canons of 
 the Colorado present magnificent examples. Let us put different 
 series together, so that we may inspect a continuous series from 
 the oldest rocks known up to the latest. The column is, say, a 
 hundred thousand feet high (see this in Fig. 39). What is shown? 
 Something even more instructive than would have been antici- 
 pated. The lowest rocks are granites, and gneisses, and crystal- 
 line schists. They contain no fossils. Either there was no life in 
 the ocean when they were formed, or its relics have been oblit- 
 erated by metamorphism. But we must not say there was no 
 life. Very rarely some obscure traces are seen in some of the 
 serpentinous marbles well toward the bottom of the series. They 
 are extremely simple in organization. We shall study them here- 
 after, and learn that they belong to the sub-kingdom of proto- 
 zoans the simplest of all animals. Above the level of the 
 crystalline rocks we find organic remains quite abundant. Some 
 of them are univalve shells; some are bivalves; some remind us of 
 certain crab-like forms, and some are entirely strange and curious. 
 But they are all marine invertebrates. We find nothing with a 
 backbone ; we find nothing which lived on the land ; we find 
 nothing nearly related to creatures which inhabit fresh water in 
 our times. 
 
 The relics of marine invertebrates are found all the way from 
 this level to the top of the series. But somewhat further up we
 
 104 GEOLOGICAL STUDIES. 
 
 encounter the bones, and teeth, and armor plates of fish-like creat- 
 ures. True, they are not much like the remains of modern fishes; 
 but we call them fishes. These creatures were at least bone-bear- 
 ing, and though without backbones, they had something corre- 
 sponding to the backbone. They were vertebrates; but they 
 were marine vertebrates, if we may judge from the remains of 
 other marine animals surrounding them. These very peculiar 
 fishes do not continue to the top of our series; they seem to have 
 lived only during a certain age of the world. (Compare Fig. 39.) 
 
 Next we come to a zone of strata, in which lie the vertebrae, 
 skulls, and other remains of creatures related to our frogs and 
 salamanders. They were of the type of amphibians. We feel jus- 
 tified in concluding that they lived on the land and breathed air. 
 When they perished, their remains were borne into the sea by 
 torrents and floods; and they left for us the record of their exist- 
 ence. With them we find, also, the relics of fishes less abnormal 
 than the earlier ones; and also an abundance of shells and corals, 
 different from the older ones, but still mostly unlike the familiar 
 forms of modern times. (Compare Fig. 39.) 
 
 We are rising now toward the top of the series. For the first 
 time we encounter the remains of reptiles. There are various re- 
 liable means of distinguishing them from the bones and teeth of 
 all other vetebrates. These, of course, breathed air and dwelt 
 mostly on the land. We notice a wonderful diversity among 
 them, and we feel curious to learn what these various reptilian 
 creatures were like. We shall take great delight in studying 
 them by and by. Toward the top of this reptilian zone, where 
 the reptilian remains are less bulky and less numerous, we dete. t 
 some relics which must be ascribed to birds. In the midst of 
 this zone we find also the teeth, bones, and scales of fishes resem- 
 bling modern types. 
 
 Now we reach the upper zone of the long series of strata. 
 Here still are the relics of marine invertebrates, of fishes like the 
 last, together with occasional reptiles and birds. But here is also 
 something very different. Here are the bones and teeth of mam- 
 malian quadrupeds. Here are the unmistakable relics of land-
 
 FOSSILS, AND WHAT THEY TEACH. 105 
 
 dwellers, which must have resembled the modern rhinoceros, pig, 
 :iheep, and horse, and other species of mammals. It is easy to 
 perceive that they were not exactly like our modern quadru- 
 peds, but they resembled them; they were land animals, and were 
 mammals. 
 
 Notice that in all this succession we have not found a bone 
 or a tooth which could be pronounced human. There is no rea- 
 son why human bones alone should have disappeared. We are 
 constrained to believe that man did not exist. AH this succes- 
 sion of organic forms excluded man. He has appeared last of 
 all, and all his remains, and all the remains of his industry lie 
 upon the surface, or buried near the surface, in deposits laid 
 down since the great work of rockmaking was ended, except in 
 the depths still submerged beneath the ocean. 
 
 Arranging this succession in a more synoptical form, and 
 placing the older types at the bottom, so as to stand in the actual 
 order of superposition, it will appear thus: 
 
 7. MAN. Remains found on the mere surface of the earth. 
 
 6. MAMMALS. In the latest system of sedimentary rocks. 
 
 5. REPTILES and BIRDS. In the middle zone of the geolog- 
 ical column. 
 
 4. AMPHIBIANS. The earliest air breathers. 
 
 3. MARINE VERTEBRATES. Fish-like, but not true fishes. 
 
 2. MARINE INVERTEBRATES. Molluscs, crustaceans, corals, 
 etc. 
 
 1. PROTOZOANS (in crystalline strata). Simplest of all ani- 
 mals. 
 
 This succession of organic types, ranging from the bottom to 
 the top of the stratigraphic series, is something very suggestive 
 and very important. Let us think about it. 
 
 1. The variations among these fossil remains, from stratum to 
 stratum, are much greater than would result from simple change* 
 in depth of water or nature of the bottom. They are variations 
 in rank and in class type and even in sub-kingdom. 
 
 2. The general tenor of the variations is an improvement in 
 rank.
 
 106 GEOLOGICAL STUDIES. 
 
 3. There must have been, correspondingly, a continuous and 
 progressive improvement in the conditions of the world in their 
 relation to organic life. 
 
 4. The time demanded for these changes must have been vast, 
 if we may judge from the slowness of changes taking place un- 
 der our observation. 
 
 5. In the earliest ages there was no land; all the species 
 were marine. 
 
 6. If, as we have already inferred, the land resulted from up- 
 heaval of sea bottom, it is probable the first lands were of verv 
 limited extent, and gradually widened themselves with successive 
 upheavals. 
 
 7. Since we know that in modern times, the existence of land 
 elevations interferes with the normal circulation of the waters 
 and the atmosphere, producing extremes of seasons, and abrupt 
 climatic vicissitudes throughout the year, we may infer that 
 when the lands were less developed, the seasons were less extreme 
 _and the climates more uniform. 
 
 8. These things being so, the primitive species of animals 
 must have had a much wider geographical distribution than the 
 later species. 
 
 These conclusions, indicated by our first glance at the records 
 of historical geology, will be found confirmed by all our later 
 studies. 
 
 The progress of life on the earth supplies the ground for a 
 classification of geological time. The facts just stated mark off 
 seven grand eras in the world's history, as shown in the right-hand 
 column of Fig. 39. When these facts are combined with all the 
 known facts of the succession of life, we are afforded a classifica- 
 tion of geological time as shown in the two left-hand columns of 
 Fig. 39. The larger time divisions are designated eras or scons, 
 and these are subdivided into ages. On similar grounds, ages are 
 further divided into periods, as indicated in the fourth column. 
 The rocks receive the same classification as time, and the group- 
 ings bear the same special names. But, for the general designa- 
 tions of the various rock categories, terms have been selected ap-
 
 FOSSILS, AND WHAT THEY TEACH. 
 
 ior 
 
 GREAT SYSTEMS, 
 
 C.EXOZOIC. 
 
 MESOZOIC. 
 
 PALEOZOIC. . 
 
 Eozoic. 
 
 Glacial. 
 
 Pliocene. 
 
 Miocene. 
 
 Eocene. 
 
 Upper Cretaceous. 
 
 iliriilk Cntacwiu. 
 
 Lower Cretaceous. 
 
 Star Peak Group. 
 Koipato Grmip. 
 Permian. 
 
 Coal Measures. 
 Conglomerate 
 
 Carbonif. Limestone. 
 Catskill Group. 
 Chemung Group. 
 Hamilton Group. 
 Corniferous Group. 
 Oriskany Sandstone. 
 Stfrlo-bcrg Group. 
 Salina Group. 
 Niagara Group. 
 
 I Trenton Group. 
 
 Canadian Group. 
 Primordial Group. 
 
 FIG. 39. THE GEOLOGICAL COLUMN.
 
 108 GEOLOGICAL STUDIES. 
 
 propriate to rock groupings, as shown at the heads of the first, 
 second and fourth columns. 
 
 The following scheme illustrates the correlations of terms 
 used in reference to rocks and time, as also, the recognized order 
 of subordination in each category: 
 
 Tune Categories. Rock Categories. Examples. 
 
 ERAS. GREAT SYSTEMS. EOZOIC, PALAEOZOIC. 
 
 AGES. SYSTEMS. LAUBENTIAX, SILURIAN. 
 
 Periods. Groups. Primordial. Canadian. 
 
 Epochs. Stages. Acadian. Potsdam, Chazy. 
 
 EXERCISES. 
 
 Why do limestones afford more fossils than conglomerates? Why do we 
 find different fossils in limestones and shales? What were (he shales when 
 the animal remains were accumulating in them? What kind of sediments 
 accumulate near the shore? Explain how changes of level might change the 
 character of the sea bottom. How might the upheaval of a promontory affect 
 the bottom in a contiguous bay? Would you expect the remains of plants to 
 be found sometimes embedded in the strata? Should these also be called fos- 
 sils? Would they be marine or terrestrial plants? Would terrestrial plants 
 be more abundant in the earlier or the later ages? Why? Should we say 
 'Devonian Period" or "Devonian Age"? Correct the following expres- 
 sions: Primordial System; Hamilton Age; Cretaceous Era; Mesozoic Pe- 
 riod; Palaeozoic Age; ChemungAge; Cambrian Group. 
 
 STUDY XIX. How the Strata are Disposed. 
 
 We find the bed-rock everywhere either at the surface or 
 immediately underneath the unconsolidated surface materials. 
 From what we have seen and reasoned it appears, therefore, 
 that the ocean has rested over every portion of the earth's 
 surface. We have seen reason to conclude, also, that there was a 
 primitive period during which it covered the whole earth at once. 
 The sheet of sediments then deposited must have enwrapped 
 the earth somewhat like a coat of an onion at least we may 
 assume that for the present. But, as we have noted evidences of
 
 HOW THE STRATA ARE DISPOSED. 
 
 109 
 
 uplift and subsidence in the bed of the ocean, the primitive sheet 
 became somewhat irregular. And further, since, as we have con- 
 cluded, land resulted from upheavals of sea bottom, there must 
 have come a time when sea sediments were not deposited over the 
 whole earth, for some portions were above water. And finally, 
 since the extent of the land appears to have been always increas- 
 ing, the area of sea sedimentation has been continually decreasing, 
 Hence we understand that the oldest formations were universal, 
 and later formations have been successively more restricted in 
 
 FIQ. 40. EUUONEOUS SUPPOSITION CONCERNING THE STRATA. 
 
 extent. We may therefore discover the limiting borders of a 
 formation at any place which happened to be the sea shore at the 
 time when the sediments were accumulating out of which it has 
 been formed. 
 
 In addition, it will be remembered that erosion of exposed 
 formations has always been in progress. Some have been eroded 
 quite through, as shown in Fig. 38; their worn edges are pre- 
 sented to view, and thus we discover another important cause 
 why most of the formations, as we find them, are not of universal 
 extent.
 
 110 
 
 GEOLOGICAL STUDIES. 
 
 We must not, therefore, conceive the entire series of rocky 
 sheets as enwrapping tine earth in the style shown in Fig. 40. 
 The arrangements shown in Fig. 41 convey a juster impression; 
 but it will be borne in mind that the stratified portion of the 
 earth is vastly less than here reoresented; and the disturbances, 
 
 EXAGGERATED. THE GREAT SYSTEMS ARE REPRESENTED BY THE SUCCESSIVE BANDS : 
 A, Eozoic; ZJ, Palaeozoic; 6*, Mesozoic; (t, Csenozoic. 
 
 NOTE. The systems of strata do not actually continue under the deep sea with un- 
 diminished thickness. They probably thin out gradually. 
 
 also, greatly less. The diagram is simply intended to render 
 clear the great fact of disturbance of the strata at successive 
 epochs. Here it appears that the dislocations of the strata 
 amount to some distortion of the earth's form. The ocean, s .s- *', 
 rests in the depressions. These are not always, at least under 
 the smaller bodies of water, synclinal basins that is, resulting
 
 HOW THE STRATA ARE DISPOSED. Ill 
 
 from the bending down of the strata. Some depressions result 
 from erosion. Elevations above the ocean level constitute the 
 land. It also appears that rocks of any age may occupy the sur- 
 face. The oldest, or Eozoic, may rise to the summit of high ele- 
 vations, or may lie, or even outcrop, at much lower levels than 
 the later systems of strata. This diagram may be considered a 
 section through the earth. The exterior portion, showing systems 
 of strata, constitutes what is called the crust. Of the interior 
 v/e know nothing from observation. The Eozoic strata which, in 
 some places, as under d and d" , lie many thousand feet deep, in 
 other places rise to the surface, and thus bring us information of 
 the crust to such depths as they attain. The student should com- 
 pare this diagram with Figs. 38, 34, 33, and 31. 
 
 Now we must explain some points which will require much 
 patience and close attention. You will notice that the only sys- 
 tem which completely surrounds the earth is the Eozoic, A. The 
 sediments were deposited when the ocean was universal. In some 
 places the Eozoic comes quite to the surface; in others, as at 
 a a a a, it is overlaid by all the other systems, because in those 
 regions the Eozoic remained depressed below the ocean level. In 
 still other places, as at b b b, it is overlaid only by the Palaeozoic; 
 because either those places were not under the sea after the Pal- 
 aeozoic aeon, or if they were, the later sediments have been re- 
 moved by erosion. In still other places, as c c c c, the Eozoic 
 is overlaid by both Palaeozoic, B, and Mesozoic, Cj because those 
 regions remained sea bottom during the Palaeozoic and Mesozoic 
 eras, and no subsequent erosions have removed the sediments. 
 There are only a few places, like d d' d", where any Caenozoic 
 can be seen, except drift or other Post Tertiary, which covers 
 nearly all the land's surface, and is not represented in this dia- 
 gram. The reason of this is, that the sea still covers nearly all 
 regions covered by it during the Caenozoic aeon. In some places, 
 like d' , the Tertiary (Caanozoic) rests directly upon the Palaeo- 
 zoic, or even the Eozoic. This is because after the older strata 
 were deposited, the region became dry land, and received no more 
 sediments till the Caenozoic aeon, when the region subsided and
 
 112 GEOLOGICAL STUDIES. 
 
 again became sea bottom. Thus a break in the succession of 
 formations generally implies a period of elevation, followed by a 
 period of subsidence. 
 
 If you look closely at this diagram, you will notice an ap- 
 pearance as if the Palaeozoic and Mesozoic strata had at some 
 former time extended further than at present. For instance, the 
 dotted line, c' c', shows -what may have been at some time the 
 upper surface of the Mesozoic. If so, then the dotted line below 
 this shows what may have been at the same time the upper sur- 
 face of the Palaeozoic. In fact, on all sides the arrangement of 
 the strata looks as if they had been once wrinkled up, and then 
 the higher places removed. This is somewhat like the truth; but 
 we must not suppose the Palaeozoic and Mesozoic ever extended 
 quite over all the Eozoic which is now at the surface. We can- 
 not say precisely how far they ever covered the Eozoic, because 
 it is impossible to say how far they have been removed by erosion. 
 We are certain, however, that they have been eroded to a great 
 extent. And we can understand that the sediment produced by 
 such erosions went partly into the sea, and was made over in the 
 patches of tertiary which we observe at d d d' d". 
 
 If the dotted circle, s s s, represents the level of the ocean, 
 you can see that some parts of the crust rise above it and form 
 the continents; and those parts which rise highest are the moun- 
 tains. You see, also, that all the systems of strata extend under 
 the sea. 
 
 Now fix your attention on the d near the lower side of the 
 diagram, a little to the left of the middle. The rocks there are 
 Caenozoic, and you see a section, or cut, right through them and 
 the rocks under them. This section shows what is the surface 
 extent of the Caenozoic area there, in one direction. Here it is 
 the distance from m to n in this little cut, Fig. 42. We do 
 not know how broad this Caenozoic area is in the other direction, 
 but let us suppose it a little oblong in form; then its other diam- 
 eter may be represented by o p; and in p n o will be a map of 
 the Casnozoic area of which a section is shown in Fig. 41 at d, 
 near the lower side of the figure. But then on one side, b,
 
 HOW THE STRATA AKE DISPOSED. 
 
 113 
 
 of this Cjenozoic section is a section of Mesozoic strata. Let us 
 take the length of this Mesozoic section and lay it off from m to 
 r on the side of the map, Fig. 42. 
 As the Mesozoic on the other side is 
 covered by the sea, we may represent 
 the sea as bordering the Caenozoic ? 
 and may lay down as much of it as 
 we please say from n to q, on the 
 other side of the map; and may as- 
 sume that the sea shore leaves the 
 Csenozoic area at s s. Then the dis- 
 tance from r across to n is the whole 
 diameter of the Mesozoic area to the 
 sea, including the portion covered by 
 the Csenozoic. The breadth in the 
 other direction is not known; but 
 we may assume it as extending from 
 t to u. The whole size of the Meso- 
 zoic area not covered by the sea w 
 Lastly, the Palaeozoic when laid down on a map Avill give a belt 
 surrounding the Mesozoic, as shown on x y z. So this is a geo- 
 logical map showing three systems of 
 strata; and Fig. 43 shows the appearance 
 of a section across it. 
 
 Now, once more. Fix your attention 
 on the point Cr in Fig. 41. If we pro- 
 ceed to make a map of the region around 
 this point, it will look something like Fig. 44. Here you see the 
 Eozoic in the middle, and the newest strata around the border. 
 Here, also, the ocean bounds the area on one side. Notice par- 
 ticularly the difference between this map and the other. There 
 the strata dipped from all sides toward the centre; here they dip 
 from the centre toward all the sides. This is shown in the sec- 
 tion as seen at G, Fig. 41, and better in Fig. 45. Here the 
 Mesozoic, c, dips under the ocean, s, on one side, and under 
 the Csenozoic, <?, on the other; the Palaeozoic, b, dips under the 
 
 FIG. 42. MAP OF THE KEGION 
 AROUND b d c, FIG. 41. 
 
 be shown by v t r u w. 
 
 FIGS 43. SECTION ALONG TI 
 LINE y q. FIG. 42.
 
 114 
 
 GEOLOGICAL STUDIES. 
 
 Caenozoic, e', extending on one side under the ocean; the Eozoic, 
 Gr, dips in both directions under the Palaeozoic. From such ob- 
 servations we induce the impor- 
 tant principle that the dip of 
 a formation is always toward 
 neicer rocks and away from 
 older rocks. 
 
 Now, for a more detailed 
 and extensive section through 
 the earth's crust, let us glance 
 at Fig. 46. This is not intended 
 to show what would be seen in 
 any particular region, but what 
 would be seen in a good many 
 different regions. The various 
 geological phenomena which 
 would be seen in many differ- 
 ent regions are here all brought 
 together. So this is not a real 
 but an ideal section. But the section is not imaginary. Every- 
 thing shown is real somewhere. It embraces many features to 
 
 be considered later in our 
 course, and we shall frequently 
 refer to it. For the present, 
 it illustrates in another way 
 the succession of strata, and 
 their modes of superposition 
 
 FIO. 45.-SKCTIO ALONO 
 
 Fro. 44. MAP OP THE TEGIOX AIMHTND 
 (7, Fi. 41. 
 
 EXERCISES. 
 
 In Fig. 42, if we travel from the centre to the circumference, do we pass 
 from newer to older rocks, or from older to newer? If we stand near the 
 circumference, which way do the strata dip? Do they dip toward and under 
 newer strata, or away from them ? If we bore a deep hole at the centre of 
 Fig. 42, what systems of rocks will we pass through? If we stand near the 
 circumference of Fig. 44, which way do the rocks dip? Do they dip toward
 
 FIG. 46. IDEAL SECTION OF TIU; EARTH'S CRUST.
 
 116 GEOLOGICAL STUDIES. 
 
 the older rocks, or away from them ? Must strata always dip toward newer 
 rocks, and away from older rocks? Suppose you bore a deep hole near the 
 margin of Fig. 44, what systems of strata would be passed through? Sup- 
 pose you bore at the middle of Fig. 44, what rocks will be passed through? 
 Must a geological area necessarily be circular? Suppose the ocean should 
 wear away two-thirds from the area mapped in Fig. 44, could you then make 
 a geological map of the region? Try it. Point out places where the Paleo- 
 zoic outcrops in Fig. 41. Show where the Eozoic outcrops. What system of 
 rocks least completely enwraps the earth? How could it be that Caenozoic 
 rocks should rest on Eozoic, with no Palaeozoic or Mesozoic between them? 
 Make a geological map of the region extending from G toward the left, 
 through c, d, and s to b, in Fig. 41. 
 
 STUDY XX. Geological Maps. 
 
 The subject of geological maps is another one requiring 
 thoughtful attention, but one of the very greatest importance. 
 The comprehension of geological maps is a great aid in the com- 
 prehension of geological facts and doctrines. In our last Study 
 you observed small areas, as in Figs. 42 and 44, marked in such a 
 way as to indicate the regions where certain systems of strata 
 come to the surface. You understand, from Figs. 38 and 41, that 
 no formation occupies the surface universally for we except the 
 quaternary, or drift. You understand that each formation comes 
 to the surface in many different places, and in other places is cov- 
 ered by newer formations, or was never deposited. You under- 
 stand, consequently, that the whole surface of the land is com- 
 posed of areas of outcrop of the various formations. We may, 
 therefore, take a map, and color or mark these various areas ac- 
 cording to the formations which come to the surface. Now, most 
 that we can learn about the earth's geology comes from a study 
 of surface formations. If we are seeking for coal, or iron, or fos- 
 sils, we can do but little more than study the formations at the sur- 
 face. Hence, a geological map of the surface conveys most im- 
 portant information. The .geological investigation of a region 
 consists very largely in perfecting a geological map of it.
 
 GEOLOGICAL MAPS. 117 
 
 Now, I wish to offer you a geological map of the United States. 
 The map, Fig. -47, covering two pages, embraces the whole United 
 States except Alaska, though it must be confessed some of the 
 region west of the Black Hills is delineated onlv in a very gen- 
 eral way. This is a real map, which attempts to represent things 
 as they are though not with much detail. In one corner is a 
 "legend," which indicates what systems of strata are mapped. 
 These are the same as the " systems " in the " Geological Col- 
 umn," Fig. 39, with these exceptions: The Laurentian and Hu- 
 ronian are here thrown together as Eozoic; theTriassic and Juras- 
 sic are thrown together as Jura-trias, and the Post Tertiary (or 
 Quaternary) is disregarded, except in some districts west and 
 southwest of Great Salt Lake, since this is understood to be every- 
 where present, covering all other formations. 
 
 Taking up the eastern portion of this map, fix your attention 
 first on the areas marked Eozoic. One large area lies north of the 
 Great Lakes and the St. Lawrence River ; another lies along the 
 eastern flanks of the Appalachian chain of mountains, extending 
 from Pennsylvania through Maryland, Virginia, North and South 
 Carolina and Georgia, into Alabama. These two Eozoic masses 
 pass under all the intervening strata, and meet together. As the 
 Eozoic strata are the oldest known, the strata on both sides of an 
 Eozoic area must be newer than Eozoic, and must overlie the 
 Eozoic. As the dips are always away from the older rocks, it 
 must be that the rocks along the eastern side of the Appalachian 
 Eozoic dip toward the southeast, and those along the western 
 side toward the northwest. And so the rocks along the border 
 of the Canadian Eozoic must dip directly away from it. That is, 
 along the valley of the St. Lawrence River, the rocks next the 
 Eozoic must dip southeast ; in the region north of Lakes Ontario 
 and Huron, the dip must be south ; in eastern Wisconsin, the dip 
 is southeast, and in western Wisconsin it is southwest. 
 
 Southeast from the Appalachian Eozoic, we have very little 
 except Tertiary strata. These, then, overlie the border of the 
 Eozoic, and dip southeastward, extending to the Atlantic Ocean. 
 Northwest of the Appalachian Eozoic, we find strata indicated by
 
 GEOLOGICAL MAPS. 
 
 119 
 
 FIG. 47. CONTINTEU.
 
 120 GEOLOGICAL STUDIES. 
 
 full oblique lines in one direction, and broken oblique lines in the 
 other direction. These are explained in the "legend" to mean 
 that the rocks are either Cambrian or Silurian (Lower Silurian or 
 Upper Silurian, as some geologists prefer to say), but we have not 
 yet ascertained which. These must dip northwesterly, away from 
 the older Eozoic, and toward the newer Upper Carboniferous. 
 Passing under all the Carboniferous, they come to the surface 
 again in Tennessee, Kentucky, Ohio and Indiana, where we have 
 learned them well enough to distinguish both Cambrian and Silu- 
 rian (or, as some say, Lower and Upper Silurian). On the north, 
 Cambrian and Silurian come up along the two shores of Lake 
 Ontario. From this region the dip is southward all the time un- 
 til we reach central Pennsylvania. In southwestern Ohio, the 
 Cambrian, which comes up from the southeast, soon dips down 
 again toward the northwest, and passing under Michigan and 
 Lake Michigan, comes up again in eastern Wisconsin. Now, try 
 and follow the Cambrian and Silurian up and down all the way 
 from the Appalachian Eozoic. 
 
 You must not be content to simply read these descriptions. 
 You must, by all means, follow the systems of strata on the map. 
 When they go under, your thoughts must follow them. When 
 they appear in view again, your thoughts must see them coming 
 from under the newer strata. You must look under the surface 
 of the map and see the solid, thick crust of the earth, with its 
 various strata curved and overlapping, and discontinuing and be- 
 ginning again, disappearing and outcropping, just as I describe 
 them. If you do this, and perform an abundance of such exer- 
 cises as will be given you, the study will soon be easy and delight- 
 ful. If you do not, you will never have a good knowledge of 
 geology. 
 
 Now let us continue the explanation of the map. On the 
 southwestern border of the Wisconsin Eozoic you see Cambrian 
 overlying it, and thence dipping southwesterly under Silurian, 
 Devonian, Lower Carboniferous, and Upper Carboniferous. We 
 can trace it, in thought, under all these systems, into Missouri and 
 Kansas. We might reasonably expect the Eozoic to come to the
 
 GEOLOGICAL MAPS. 121 
 
 surface again in the region farther southwest, but it scarcely suc- 
 ceeds in revealing itself. You will notice one patch in the Ind- 
 ian Territory, and one in southern Texas ; but nearly all that 
 region has been covered by Jura-trias, and then most of that has 
 been covered by Cretaceous. Even upon the top of the Creta- 
 ceous are some patches of Tertiary. 
 
 In New England you will notice considerable areas marked 
 Eozoic; but in some cases we only know that the rocks are crys- 
 talline like Eozoic, while they may be in reality only later rocks 
 hardened and crystallized by metamorphism. You observe, how- 
 ever, a patch of Upper Carboniferous in Rhode Island, and a belt 
 of Jura-trias running through Connecticut and Massachusetts. 
 Farther north you will notice that the valley of the Connecticut 
 is underlaid by Cambro-silurian rocks that is, rocks either Cam- 
 brian or Silurian. 
 
 In the Adirondack region of New York is an interesting 
 Eozoic area. This connects with the Canadian Eozoic by a nar- 
 row neck across the St. Lawrence River. The strata all around 
 this Adirondack area dip away from it. This is a case somewhat 
 like the Eozoic area in Wisconsin. On the other hand, the centre 
 of Michigan is an area of Upper Carboniferous, and since the 
 surrounding strata are all older they all dip toward the centre of 
 Michigan. 
 
 Now let us vary the method of study. Suppose we stand on 
 the southern side of Lake Ontario, the map shows that the dip 
 of the rocks is south; for at that point we have Silurian, while to 
 the south are the (newer) Devonian and Lower and Upper Car- 
 boniferous; and, according to the rule, the dip is toward the 
 newer and away from the older in Canada. 
 
 If we stand at Milwaukee, the dip is eastward, for Milwaukee 
 is on the Silurian, and eastward we have the Devonian and Lower 
 and Upper Carboniferous in Michigan. Lake Michigan must also 
 cover a portion of the Silurian and much of the Devonian. If, 
 on the contrary, we stand at the St. Clair River, the dip is west- 
 ward on the same principle. 
 
 Again, if we stand at Sandusky, Ohio, we are on the Silurian;
 
 122 GEOLOGICAL STUDIES. 
 
 and if we walk straight to Cincinnati, we walk a long distance on 
 Silurian, and then come to Cambrian. Then, if we continue our 
 travel to Nashville, Tenn., we pass again over Silurian, a narrow 
 belt of Devonian, a broad belt of Lower Carboniferous, and then 
 come to a very narrow streak of Silurian again (too narrow to 
 show on the map at this place, though it can be seen south of 
 the Cumberland River), and end our journey on the Cambrian. 
 Should we continne southward to Mobile, we should pass off the 
 Cambrian directly upon the Lower Carboniferous, which extends 
 into Alabama. Then, in the neighborhood of Tuscaloosa, wo 
 should pass upon the Upper Carboniferous, and beyond this, to 
 the overlying Cretaceous, and should find Mobile on the Tertiary. 
 If we should travel from Albany to Boston, we should start 
 on Cambrian rocks and pass to Silurian rocks. Before reaching 
 central Massachusetts we should pass to rocks which are not fully 
 determined perhaps Cambro-silurian and perhaps an outcrop 
 of Eozoic. Crossing the valley of the Connecticut would be found 
 Jura-trias rocks resting horizontally in a trough excavated in the 
 -older rocks. Those on the map are not extended far enough 
 north. Beyond this valley we should find again rocks which are 
 perhaps Cambro-silurian. Beyond these we should have Eozoic 
 rocks for the greater part (all Eozoic on the map) until reaching 
 Boston. All these things, and a thousand others, may be studied 
 out on the map. 
 
 EXERCISES. 
 
 If you travel in a straight line from Detroit to Milwaukee, what systems 
 of strata will you pass over? What if you travel from Mackinac to Cincin- 
 nati? What between Oswego and Plattsburg? What between Charleston 
 and Nashville? State the dip of every system of strata passed between St. 
 Louis and Chicago. Between Duluth and Lake Michigan. Between Sagi- 
 naw and Springfield, 111. Between Springfield and Cincinnati. Between 
 Cleveland and Pittsburgh. What is the dip of the strata at Cleveland? 
 What at Green Bay? What at Binghamton, N. Y. ? What at Utica, N. Y. ? 
 Suppose you bore an artesian well at Lansing, Mich., what systems of strata 
 will be passed through? What if you bore at Charleston, S. C. ? What if you 
 bore at Hartford, Conn. ? What if you bore at Peoria, 111. ? What if you 
 bore at Gralveston, Texas? What if you bore at Montreal, Canada? Would
 
 GEOLOGICAL SECTIONS. 123 
 
 an artesian well bored at Cincinnati pass through the Silurian ? Or the De- 
 vonian? How could you travel from Albany, N. Y., to St. Paul without 
 passing off the Cambro-silurian? How from Cairo to Cape May without 
 passing off the Tertiary? How many great patches of Upper Carboniferous 
 (Coal Measures) are shown on the map? Into what states does the Appalach- 
 ian coal area reach? Into what states the Illinois coal area? Into what the 
 Kansas coal area? Into what the Michigan? Into what the Rhode Island? 
 Which state has the largest area of Eozoic rocks? Which next? Which has 
 the largest area of Tertiary? Which state contains the greatest number of 
 different systems? Which contains the fewest different systems? What 
 states have the largest amount of soft rocks? What ones have most Palaeo- 
 zoic rocks? Give the names of the cities indicated by black dots on the map, 
 and state what system of rocks each is located on. 
 
 NOTE. The student, during his elementary course, ought to construct a geological 
 map of the eastern United States, covering about the same ground as the one here pre- 
 sented. It would be desirable to make it on a larger scale, and also to employ a system 
 of colors as indicated in the introduction. 
 
 STUDY XXL Geological Sections. 
 
 The student cannot take too many exercises on the geological 
 map. He should become familiar as possible with the surface 
 distribution of the formations. This is geographical geology. 
 Such a map is a picture of the geology at the surface. But, at 
 the same time, a careful study of it leads to important inferences 
 in reference to the deeper geology. So you must not be con- 
 tent to look merely upon the flat surface of the map. It is not 
 enough even to learn the location of the different colors lying on 
 the surface. You must think of each color or system of mark- 
 ings as an outcropping of something which goes down beneath 
 the surface to some other region, where it outcrops again. You 
 must think which way it goes beneath the surface that is, what 
 is its dip. The rule already given determines that. So when 
 you look on the geological map, you will learn to look into it, 
 and far beneath the surface. You will see the whole solid frame- 
 work of the rocks which underlie a country. 
 
 Now, we shall undertake some exercises which will give us 
 the power of penetrating into the depths of the solid crust.
 
 124 GEOLOGICAL STUDIES. 
 
 With the geological map before us, we will try to construct 
 some geological sections. That is, if we could cut straight down 
 along the line between two points which may be selected, to the 
 depth of some thousands of feet, and then look at the cut edges 
 of the strata, what form and arrangement would they present 
 to us ? 
 
 To begin with a simple case, let us construct a section across 
 the state of Michigan from Detroit to Grand Haven. We will 
 first draw a line, G J), Fig. 48, to represent the distance along 
 the surface between the two points. We suppose ourselves 
 facing north. We notice that Detroit stands on the Devonian. 
 
 G ^ Take the distance from Detroit to the west- 
 
 p "_ p ING FOB ern Border of the Devonian, and lay it off 
 A GEOLOGICAL SEC- from I) on the line G D. This distance 
 extends to a. Next, lay off from a the dis- 
 tance which corresponds to the breadth of the Lower Carbonifer- 
 ous in the direction from Detroit to Grand Haven. This 
 stretches to l>. Thirdly, lay off the distance which our route 
 passes over the Upper Carboniferous. This takes us to c. Fourth- 
 ly, lay off the distance to the western border of the Lower Car- 
 boniferous; this takes us to d. Finally, lay off the short distance 
 to Grand Haven, on the border of Lake Michigan. This takes 
 us to G. 
 
 Next, we have to consider what is the dip of the strata at 
 each point. On our principles, the dip is toward the Upper Car- 
 boniferous from both ends of the line. Draw lines down oblique- 
 ly, according to the dip, from a, b, c, and d, Fig. 49, the 
 boundary points between the formations. 
 ^v^NvV.-x^x' f Then, knowing that the Lower Carboniferous, 
 which dips down westward in the eastern 
 
 FIG. 49. PROGRESSING . . 
 
 WITH A GEOLOGICAL p art * the state, is the same which comes up 
 SECTION. to the surface from the eastward, in the 
 
 western part of the state, we can connect the lines representing 
 the lower and upper surfaces of this system. That is, the upper 
 line will extend from b to c, passing down under the Upper Car- 
 boniferous; and the lower line will extend from a to d, passing
 
 GEOLOGICAL SECTIONS. 125 
 
 under both Upper and Lower Carboniferous. The dip of the 
 strata from D must pass in the same direction as from a and b. 
 But notice that Detroit is not on the eastern limit of the Devo- 
 nian. The line from the eastern limit wherever it is will 
 pass some distance under Detroit, as at e. We need not know 
 where it comes up to the surface. It is somewhere to the east- 
 ward, but we may cut it off at e, as we are only required to con- 
 struct the section to Detroit. That line, then, ending at e, shows 
 the bottom of the Devonian. Passing westward, it will come up 
 at the west side of the Devonian, wherever that is. But the first 
 system west of Lake Michigan is the Silurian, and the place for 
 the bottom of the Devonian is between it and d, near Grand 
 Haven. The western outcrop of the bottom of the Devonian 
 seems to be in the bottom of Lake Michigan. This belief is con- 
 firmed by observing that on the map, the outcrop of the Devonian 
 strikes the south end of Lake Michigan, and seems to pass under 
 the lake. It comes mostly from under the lake again in the 
 region of Grand Traverse and Little Traverse Bays, and Macki- 
 nac. We will therefore assume that the western outcrop of the 
 Devonian is under the lake. We will also draw a little depres- 
 sion to represent the bed of the lake. 
 
 Instead of seeking for the western outcrop of the bottom of 
 the Devonian, we might say as we did about the eastern outcrop, 
 that it does not concern us to find it; we' know the bottom line 
 passes at some distance under (r, and. in that position wo may 
 draw it, and let fall a perpendicular from G to it as from I) 
 to e. 
 
 So far we have assumed that the surface of the earth is a dead 
 level from Detroit to Grand Haven; but, if we happen to know 
 that the center of the state swells up a little, we should so repre- 
 sent it. We ought, indeed, to know this; because, if you look on 
 any map of Michigan, you see the streams all flowing from the 
 interior into the surrounding- lakes. If, then, we show the sur- 
 face configuration, our section will be a geological profile. 
 Here it is in Figure 50, but on a scale twice as large. In 
 completing the section we may bear in mind that the Silurian,
 
 126 GEOLOGICAL STUDIES. 
 
 which outcrops at Milwaukee, passes under Lake Michigan and 
 the state of Michigan, and we may so represent it, though a sec- 
 
 tion across Michi- 
 
 an does not re ~ 
 
 quire this. It would 
 be proper, also, to 
 represent the Cam- 
 FIG. SO.-COMPLETED GEOLOGICAL SECTION BETWEEN DE- briail under the Silu- 
 rian, since we see 
 
 from the map that on the west of Milwaukee it passes eastward 
 under the Silurian. And, finally, we notice that in central Wis- 
 consin the Eozoic passes southward under the Cambrian; and we 
 may fairly assume that it would appear beneath the Cambrian 
 under Michigan if we were able to make actual examination. 
 So we fill in the lower left-hand corner of our section with the 
 marks indicating Eozoic. Now the section is complete. 
 
 We have, in fact, extended the section farther west than was 
 required. We might have cut it off at Grand Haven. Also, we 
 have carried it deeper than necessary. All that is essential in a 
 section from Detroit to Grand Haven is shown by the broken 
 lines. 
 
 Next, let us construct a geological section from the Eozoic 
 
 north of Lake Ontario to Williamsport, on the Coal Measures of 
 
 Pennsylvania; and let us suppose ourselves facing east. Draw a 
 
 line, E W, Fig. 51, to represent the length 
 
 ^ K-&2-4-27 of the section. This may be the same length 
 
 FIG. 5i. PREPARING as the distance on the map, or any multiple 
 of that distance - However the length of the 
 line chosen compares with the distance, all 
 the intervening distances must be in the same proportion; or, if 
 we know the distances in miles, we may lay them off from a 
 scale. The number of miles may be got from a " scale of miles " 
 given on a good map. When this is done, allow a little space 
 the proper space, if known to the right of E for the distance 
 to the southern margin of the Eozoic; and fix on a point, a, for 
 the border of the Cambrian. The dividing line between the Cam-
 
 GEOLOGICAL SECTIONS. 127 
 
 brian and Silurian is under the lake; let us locate it under 6. 
 The southern limit of the Silurian will be at c. The southern 
 limit of the Devonian, determined from the map, will be at d ; 
 and here the Lower Carboniferous begins. The southern limit of 
 the Lower Carboniferous, which is the northern limit of the Upper 
 Carboniferous, will be at e. Then the southern extremity of our 
 section will be at TF^ just over the border of the Coal Measures. 
 
 Now, we understand that all these rocks dip southward. So 
 we draw lines from the points abed e, 
 Fig. 52, to represent the dip, and terminate 
 downward at such points as to produce a neat ! xx !~X ^-J 
 figure showing all that is required. Then FIG. 52. -PROGRESSING 
 
 we may fill in the lines and characters chosen WITH A GEOLOGICAL 
 . . SECTION. 
 
 to represent the various systems. 
 
 Xotice, that it is customary to represent the dip somewhat 
 greater than the reality, unles the real dip is steep enough to give 
 a convenient breadth to the section. Notice, also, that this makes 
 the thicknesses of the formations too great to be in due propor- 
 tions to the distances along the surface. The section therefore 
 has a " vertical scale " greater than the " horizontal scale," and 
 the section is a distorted one, not a natural one. We always 
 make the two scales the same if practicable. 
 
 We have constructed this section thus far on the assumption of 
 a dead level from end to end. But we ought always to represent 
 the relative elevations of different points as well as we can. In 
 fact, geologists often take very great pains to ascertain the levels 
 of different points. If the region where E is located is some- 
 what elevated, we should so represent it. And if we know that ( 
 a high bluff of strata extends along the south shore of Lake On- 
 tario, we should so represent that. An improved section between 
 the two points would be as shown, Fig. 53. This is made on a 
 scale four times as larsre as the other, which is too small for con- 
 venience. Here we notice a surface slope from north and from 
 south toward Lake Ontario. Also a slope from both directions 
 toward the Chemung River, whose place is shown by e. These 
 things are not all shown on the geological map; but if you can,
 
 128 GEOLOGICAL STUDIES. 
 
 in any way, obtain information about the configuration of the 
 surface, that should be introduced into your section. You will 
 often have to refer to your geographical atlas to learn where 
 places mentioned are located. The directions in which streams 
 run will also show you what regions are more elevated and what 
 are less elevated. The surface, also, always slopes toward streams. 
 The region between streams is always somewhat elevated; but 
 the amount of elevation is less in a country nearly level than in 
 one having considerable slope. 
 
 The following is the way we complete the geological pro- 
 file. Having laid down the necessary points along a horizontal 
 line A 12, draw vertical lines from these points, as shown, Fig. 53, 
 and draw as exactly as you can, a line E P to represent the 
 surface of the earth. The points a c d e, where this line inter- 
 
 FIG. 53. COMPLETED GEOLOGICAL SECTION. 
 E, Canadian Eozoic ; to, Coburg; R, Rochester; 6', Corning: IF, Williamsport. 
 
 sects the vertical lines, indicate the bounds of the different form- 
 ations. From these points we may draw lines to represent the 
 dip and the thickness of each formation. (Those who have ac- 
 cess to the New York State Geological Reports will find in Vol. 
 IV, plate VII, a better proportioned drawing of the above profile; 
 but it is ten feet long.} 
 
 You ought to take a great deal of exercise on the geological 
 map, and especially in the construction of sections. No matter 
 if it requires two or three days to finish one study. 
 
 Let us construct a section or profile from Nashville to Savan- 
 nah. Here it is (Fig. 54). You will notice that the Cambrian east 
 of Nashville is not known to be overlaid by Silurian; and when 
 we trace it to the east of the Appalachians it is so metamorphosed 
 that we are unable to say whether the formation is Cambrian or 
 Silurian, and so it is simplv put down on the map as Cambro-silu-
 
 THERMAL WATERS. 129 
 
 rian. After passing the dome of the Eozoic, we find it overlaid 
 directly by Tertiary strata, and we must so represent it. Not un- 
 likely, however, some strata, intermediate in age between Eozoic 
 anil Tertiary would be found beneath the Tertiary if we could 
 make exploration. The Tertiary passes under the waters of the 
 Atlantic. 
 
 FIG. 54. SECTION FROM N 
 
 LANTIC OCEAN. 
 
 EXERCISES. 
 
 Construct sections as follows: From Madison, Wis., to Chicago. From 
 Chicago to St. Louis. From Sandusky, Ohio, to Nashville, Tenn. From 
 Mackinac to Cincinnati. From Montreal to Albany. From New York city 
 to Oswego. From St. Louis to Cincinnati, From Cincinnati to Newbern, 
 N. C. From St. Paul to Chicago. From Cairo, 111., to Cincinnati. From 
 Kingston, Out., to Chicago. From Detroit to Fortress Monroe. From 
 Cleveland to Cincinnati, and thence down the Ohio to its mouth. The stu- 
 dent may also inspect the section, Fig. 33, and see whether it agrees with the 
 geological map. 
 
 STUDY XXII. Thermal Waters. 
 
 Everyone is familiar with the diurnal influence. of the sun's 
 rays on the earth's surface temperature; and every one has no- 
 ticed that at night the surface cools to some extent. These diur- 
 nal fluctuations of temperature diminish downward in amount, 
 and at the depth of about thirty-two inches disappear altogether. 
 But there are also seasonal fluctuations, and these can be traced 
 to a depth of about fifty feet. The depth, however, varies with the 
 amount of the seasonal fluctuation. It would be less, for instance, 
 in Florida than in Manitoba. But we may assume fifty feet for a 
 mean. This implies that a thermometer buried at that depth 
 would indicate a constant temperature throughout the year.
 
 130 
 
 GEOLOGICAL STUDIES. 
 
 Just above this depth the influence of summer would produce a 
 slight rise, and the influence of winter a slight depression. But 
 the winter and summer influences are each about a year in reach- 
 ing this depth and dying out. Each is about six months in 
 reaching a depth of twenty -five feet. That is, the July influence 
 is felt in January at a depth of twenty-five feet; and the January 
 influence is felt in July at the same depth. Accordingly, water 
 from a well of this depth might really be colder in summer than 
 in winter. 
 
 If we carry our thermometer below the depth of fluctuating 
 temperature, that is, below about fifty feet we find the tem- 
 perature of the earth continually higher. We experience this in 
 mining operations, where the temperature sometimes reaches 
 
 FIG. 55. AN ARTESIAN WELL AT CHICACO. 
 
 C, Chicago. B, Baraboo, Wis. E, Eozoic Quartzite. P, Potsdam Sandstone. J/, Lower 
 Magiiesian Limestone. <S, St. Peter's Sandstone. T, Trenton and Galena Lime- 
 stones. N, Niagara Limestone. (See Fig. 39.) 
 
 eighty or one hundred degrees, or even more; and work would be 
 impossible without means for introducing air from above. We 
 experience it in tunnelling mountains, as Mont Cenis and Mont 
 St. Gothard. We observe it in the temperatures of the water of 
 artesian wells. These are wells bored down to some porous and 
 water-bearing stratum, whose outcrop is some distance away at a 
 higher level than the place of boring. In general, for such 
 depths as we have been able to reach, the temperature averages 
 about one degree higher for every fifty- one feet of descent. The 
 deepest artesian well ever bored is at Sperenberg, near Berlin, 
 Prussia. Its depth is 4,172 English feet (4,042 Flemish), and the 
 bottom temperature is 118 Fahrenheit (38.25 Reaumur). As 
 the temperature at fifty feet was 54.74 Fahrenheit, the mean 
 rate of increase was one degree for sixty-five feet of descent.
 
 THERMAL WATERS. 
 
 131 
 
 There seemed to be a diminishing rate of increase at the greater 
 depths. Indeed, it can hardly be considered probable that a con- 
 stant rate should continue indefinitely. At an assumed rate of 
 one degree for fifty-one feet, it is easy to calculate at what depth 
 the temperature of boiling water would be reached, knowing the 
 mean annual temperature of the place. But it will be borne in 
 mind that under the pressure due to any depth beneath the sur- 
 face, water would retain its liquid state at temperatures above 
 212. At a pressure of ten pounds to the square inch above 
 atmospheric pressure, the boiling temperature is about 239. 
 
 Now, it may be inferred from what we have already observed 
 and reasoned, that many strata which present their edges at the 
 surface, extend down to the depth of hundreds or thousands of 
 feet. This may be concluded, even from Fig. 41, or better from 
 Fig. 46, where an artesian well is shown starting in Lower Jurassic 
 strata and reaching a water-bearing stratum in the Upper Carbon- 
 iferous. Surface water following the course of such a stratum, a, 
 Fig. 56, would become heated. If at such depth a fault or frac- 
 ture of the crust should be encountered, the water might rise to 
 the surface by hydrostatic pressure, precisely as through an arte- 
 sian boring; and thus a warm spring would result, as shown in 
 Fig. 5G. In the 
 case of the springs 
 at Bath, England, 
 a is in the Mendip 
 Hills, the temper- 
 ature of the water 
 is 120, and the 
 depth of B must 
 be about 3,500 FIG 56 _ GEOLOGT OP A WARM SPKING . 
 
 feet, the mean of a, porous stratum receiving water at the surface, and inter- 
 
 thp plimatP hpino- cepted by a fault at j?, at such depth that the temperature 
 
 Bln e of the water is over 100, whence it rises along the fissure, 
 
 50. Many warm and forms a warm spring at S. a' continuation cf a. 
 
 and hot springs 
 
 undoubtedly result in this way. In other places, as at Tuscan 
 
 Springs, Gal., no faulting of the strata exists. Here, Fig. 57,
 
 132 
 
 GEOLOGICAL STUDIES. 
 
 the Cretaceous strata simply present an anticlinal and a fracture 
 through which the water rises from such depth as to have been 
 heated. The steep dip of the Cretaceous sandstone would soon 
 reach the requisite depth. From that they rise eastward, and 
 
 FIG. 57. SECTION AT TUSCAN SPRINGS, SACRAMENTO VALLEY, CAL. (Whitney.) 
 
 a, a, Basaltic Lava; 0, b, Volcanic Ash and Scoriae; c, <, Conglomerate; (/, rf, Cretaceous 
 
 Sandstone; *, Springs 
 
 come to the surface along the ancient shore of the Cretaceous 
 ocean which bathed the western flanks of the Sierra Nevada. 
 Along that outcrop the supply of water is probably received. 
 The water of hot springs has great solvent power, and thus,. 
 
 FIG. 68. - 
 
 CLERMONT, FRANCE. (Scropc.) 
 
 very frequently, the spring delivers mineral water. Calcium 
 carbonate and silica are thus very often brought to the surface. 
 As the water cools, much of the mineral matter is precipitated on 
 the surfaces over which it flows, and we get deposits of tufa or
 
 THERMAL WATERS. 
 
 133 
 
 sinter. Relief of the pressure tends also to cause the water to 
 give up a portion of its mineral, precisely as in the case of com- 
 mon springs, which we considered in Study II. These tufaceous 
 deposits sometimes acquire enormous extent. 
 
 In more numerous cases warm springs are found in proximity 
 to volcanoes. In central France, especially in the departments of 
 Cantal, Haute Loire, and Puy de Dome, is a district of extinct 
 
 FIG. 59. BASINS AT MAMMOTH HOT SPRINGS or GARDINER'S RIVEK. YELLOWSTONE 
 NATIONAL PARK. (Peale.) 
 
 volcanoes, and here the phenomena of warm springs and their 
 deposits are developed on a vast scale. At Clermont the deposits 
 from a calcareous spring have formed an elevated natural aqueduct 
 two hundred and forty feet in length, and terminating in an arch 
 thrown across the stream it originally flowed into, sixteen feet 
 high and twelve feet wide. (See Fig. 58.) Very extensive 
 deposits occur in Italy and other European countries; but the 
 most remarkable are found in the Yellowstone National Park,
 
 13-4 GEOLOGICAL STUDIES. 
 
 where Peale enumerates 2,195 hot springs. These springs are 
 also located in a volcanic district. In Fig. 59 is given, from 
 Hayden's report for 1878, a view of a group of these springs 
 which have built a curious series of basins. Very similar effects 
 are produced by the thermal springs of New Zealand, Asia 
 Minor, and other regions. 
 
 Many of the springs of the National Park present the phe- 
 nomena of geyser action, or periodic ejection of hot water with 
 great force, sufficient in some cases to throw it to the height of 
 one or two hundred feet. Peale enumerates seventy-one geysers. 
 In Fig. GO is presented a view of the "Giant Geyser" in action. 
 The crater has been formed by deposition of a mineral known as 
 (jc-yserite. It rises ten feet above the platform, and at base meas- 
 ures twenty-four feet by twenty-five, diminishing to eight feet at 
 the top. Its depth is twenty-five feet. The temperature of the 
 water is about 198 Fahrenheit. Its eruptions are some days 
 apart, but the volume of water discharged is enormous, and the 
 altitude attained is two hundred to two hundred and fifty feet. 
 The power required to produce this result causes the earth to 
 tremble, and a deep rumbling sound to be emitted. The so-called 
 geyserite is, in other words, a silicious sinter. Silica is held in 
 various proportions in these waters (from eight to fifty-four per 
 cent), and is thrown down, as Peale thinks, in consequence of 
 evaporation; but cooling and relief of pressure probably con- 
 spire. 
 
 A geyser in action is a striking geological phenomenon, and 
 much speculation has been had in reference to its mechanism. 
 The explanation which seems most satisfactory is that proposed 
 by Bunsen. The water accumulating in the geyser tube is a long 
 column, probably more or less tortuous. It is heated below, and 
 a tendency to equalization of temperature throughout exists 
 through the means of a circulation; but the difficulties of circu- 
 lation cause always a higher temperature at the bottom. After a 
 time the bottom temperature exceeds the boiling temperature at 
 the top, but the bottom water does not boil because the pressure 
 is increased. At the depth of thirty-three feet the pressure is
 
 THERMAL WATERS. 
 
 135 
 
 FIG. 60,-GiANT GEYSER IN ACTION. UPPER GEYSER BASIN, FIRE HOLE RIVER, 
 YELLOWSTONE NATIONAL PARK. (Peale.)
 
 136 
 
 GEOLOGICAL STUDIES. 
 
 two atmospheres, and the boiling temperature 250. But by-and- 
 by the increase of heat below brings the water to the boiling tem- 
 perature; or in some cases a momentary relief of the pressure 
 makes the existing temperature a boiling temperature. Then 
 steam is instantly formed, and the column of water above is 
 thrown out. 
 
 A somewhat simpler explanation is suggested by the well 
 
 FIG. 61. GEYSEKITES. FROM UPPEK AND LOWER FIRE HOLE BASIN. (Peale.) 
 
 known behavior of water and steam when attempting to circu- 
 late through the same pipe, and by the analogous case of water 
 and gas in one of the spouting wells of an oil district. Water 
 simply accumulates in the geyser pipe upon the steam formed in 
 the lower part by the bottom temperature. The steam for a time 
 is subjected to compression, and the compression (condensation) 
 increases with the continued development of steam. Finally, the 
 elastic force becomes sufficient to lift the column of water. The
 
 THERMAL WATERS. 137 
 
 commencement of escape now diminishes pressure, and a large 
 volume of steam is instantly formed, which causes the violent 
 action. The heavy thumps sometimes heard before and during 
 the action are due to collapses of steam in contact with the water, 
 and are strictly the same in principle as the sharper sounds fre- 
 quently heard in the steam pipes employed for warming building's. 
 
 EXERCISES. 
 
 The artesian well at the insane asylum, St. Louis, was 3,843| feet deep, 
 the temperature of the water 105, and the mean annual temperature at the 
 sin-face 55; what is the rate of increase of temperature? The correspond- 
 ing data at Charleston, S. C., were 1,250 feet, 87, and 66; what is the rate 
 of increase? Make the calculation for any other well of which you can get 
 the data. At what date will the temperature of July 1 be felt at the depth 
 of twelve feet? If winter cold begins at Christmas, at what date will it pen- 
 etrate through the ground to the bottom of a cellar five feet deep? Will the 
 whole severity of the surface cold be felt at that depth? What should be the 
 temperature of water from the bottom of a well one hundred feet deep at a 
 spot where the annual mean is 40? If the flow of water in this well comes 
 from below, will its temperature be higher or lower than your calculation fr 
 How do we measure the temperature of the water in the bottom of an arte- 
 sian well? Why can we not be sure the temperature there taken is the true 
 temperature due to that depth ? If the strata bored through have a steep 
 dip, is the water likely to have come from a higher or a lower level? How 
 would this affect the temperature? And would this wrong temperature affect 
 your calculation of the rate of increase of temperature? What is the differ- 
 ence between an artesian well and a warm spring? If the temperature of a 
 spring in central Arkansas is 100, from what depth should the water rise? 
 If. the temperature of the Giant Geyser is 198, what is the length of its fun- 
 nel taking no account of the elevation above the sea? Does this tempera- 
 ture of 198 indicate accurately the temperature at the bottom of the funnel? 
 If not, why not? How does the discrepancy affect the result of your calcu- 
 lation? How many atmospheres of pressure at the ,depth resulting from 
 your calculation? Try to ascertain at what temperature steam forms under 
 such pressure. Suppose the temperature of the water is 240 and the press- 
 ure two atmospheres, will the water boil? Suppose now the pressure is sud- 
 denly diminished to one and a half atmospheres, what would happen? Why 
 do warm springs deposit calcareous matter, and geysers silicigus matter? Is 
 the silicious matter the cause of the geyser mode of outflow ?
 
 138 GEOLOGICAL STUDIES. 
 
 STUDY XXIII. Volcanoes. 
 
 We have ascertained, from observations made, that the inter- 
 nal temperature of the earth rises as we descend below the zone 
 of uniform temperature, and to this fact we have not hesitated to 
 ascribe the heat of thermal waters. We have no reason to doubt 
 that the heat continues to rise beyond the possibility of the exist- 
 ence of water, and even till the temperature is sufficiently high 
 to fuse mineral substances. This is an inference; but it is easy 
 to subject it to the test of observation. Visitors to Naples, in 
 Italy, tell us that in the immediate vicinity rises a mountain 4,000 
 feet above the bay, which is seen frequently to emit a volume of 
 steam and smoke, as if its summit were a chimney, and a great 
 fire were nursed within the mountain. This is Vesuvius. They 
 tell us that the surface of the mountain is completely covered 
 with ragged masses and scraps of rocks quite unlike any with 
 which we are familiar, being dark, compact, fine, often glassy, in 
 many cases coarsely cellular and light, and having much the ap- 
 pearance of slags from iron and copper furnaces. We may easily 
 ascertain from the testimony of eye-witnesses that these slags 
 have been ejected, in a molten state, from the chimney of the 
 mountain, and that sometimes copious streams of molten matter 
 have burst through fissures and flowed down the mountain side. 
 These outflows are accompanied by volumes of aqueous vapor 
 and gases and acid fumes, which rise in a vertical column through 
 the crater to the height of several thousand feet in 1779, ten 
 thousand feet, according to Sir William Hamilton. Accompany- 
 ing these are stones and ashes, sometimes in great abundance. 
 The aqueous vapors condense in the upper air and form clouds, 
 illuminated by the glowing lava and by the lightnings generated 
 in the bosom of the vapor. Torrents of rain sometimes descend, 
 converting the ashes into mud, and burying the surface of the 
 earth for many miles around. There are records, indeed, of very 
 destructive eruptions. One which occurred in the year 79 buried 
 three cities Pompeii, Herculaneum, and Stabiae and the work 
 of excavating them is now in progress (Fig. 63).
 
 VOLCANOES. 
 
 139 
 
 FIG. 6:?. M T.VESUVIUS AND THE BAY or NAPLES. (Palmieri.)
 
 140 
 
 GEOLOGICAL STUDIES. 
 
 Vesuvius and Mtna, are the two classical volcanoes of Eu- 
 rope; but many other evidences of the existence of internal 
 
 fires are revealed in 
 the volcanic activities 
 of the Lipari Islands, 
 in the fumaroles and 
 solfataras of the vol- 
 canic districts, and in 
 the occasional out- 
 burst of a volcanic 
 island from the bot- 
 tom of the Mediterra- 
 nean. A f uma role 
 is an escape of steam 
 from the ground. 
 When accompanied 
 by sulphur vapors and 
 other gases it is a sol- 
 fatara. Fumaroles 
 are numerous in the 
 
 Yellowstone National 
 Park, as also in most 
 volcanic regions. 
 
 Let us listen to a statement of what occurred on ^Etna in 
 18G5. This volcano, according to the government survey, is 
 10,868 feet high, and its sides slope at an angle of six to eight 
 degrees. Its crater is a vast abyss, nearly 1,000 feet deep, and 
 two or three miles in circumference. Sometimes it is nearly full 
 of lava; at other times it appears to be bottomless. In July, 
 1803, after a series of convulsive movements, a fissure opened on 
 the south side of the loftiest cone, and molten matter began 
 slowly to issue and descend. Masses of lava and ashes were at 
 the same time ejected from the mouth of the crater. For eigh- 
 teen months the mountain threatened some ulterior convulsion. 
 Molten lava rose in the crater and illuminated the skies. Evi- 
 dently it pressed with enormous force against its walls, and these 
 
 FIG. 63.-THE EXCAVATION OF POMPEII. BURIKD IN AN 
 ERUPTION OF VESUVIUS. \ m Stabiae, new quarter. 
 (Photograph.)
 
 roLc 
 
 VOLCANOES. 
 
 141 
 
 were continually weakened by melting away. At length, on the 
 night of the 30th of January, 1865, the walls yielded, and a rent 
 opened a mile and a half in length on the north of Monte Fru- 
 mento, one of the secondary cones rising on the slope of ^Etna. 
 
 I 23 4 5 <5 7 8 
 
 FIG. 64 MAP OF MTSA AND ITS ERUPTIONS. (After S. von Waltershausen.) 
 1, Ancient Lava; 2, Lavas of the Middle Ages; 3, Lava of 1669; 4, Lavas of 1852 and 1865; 
 5, Lava of 1879; 6, Recent Lavas; 7, Cones and Craters; 8, Non-Volcanic Rocks. A, 
 Aci Reale ; B, Val del Bove ; C, Catania ; R, Randazzo ; S, River Simeto. 
 
 From this molten lava issued for some hours, when communica- 
 tion with the interior supplies seems to have been obstructed. 
 On the following day, new eruptions from the fissure took place,
 
 142 GEOLOGICAL STUDIES. 
 
 and six principal cones, formed of ejected matter, were raised. 
 These gradually blended together, absorbing smaller cones, until 
 a height of nearly 300 feet had been reached. The liquid lava 
 issued from the lower craters, while the upper belched forth only 
 stones and ashes. In two months the cone nearest to Frumento 
 seemed to have become choked up, and only emitted sulphurous 
 and hydrochloric vapors. The cone next lower continued to 
 eject periodically, and with loud explosions, volumes of vapor, 
 ashes, and stones; while the lowest cones continued to rumble 
 and discharge molten matter. By degrees the violence of the 
 action abated. At first the erupted matter rose 5,500 to 5,800 
 feet; then it fell to 300, and gradually ceased to escape. 
 
 During the first six days, the amount of matter escaping- from 
 the fissure, according to Sylvestri, was about 117 cubic yards a 
 second equivalent to a volume twice the size of the Seine at 
 low Avater. Near the outlet it flowed twenty feet a minute; 
 lower down, spreading over a wider surface, its speed was one 
 and a half to six feet a minute. On the second of February the 
 principal stream, now 900 to 1,650 feet broad and forty-nine feet 
 deep, reached an escarpment three miles from the fissure, over 
 which it plunged, a cataract of fire, into the gorge below. This 
 spectacle was ended in a few days by the wearing down of the 
 ledge and the filling of the ravine to the depth of 160 feet. From 
 this the river of fire continued, and by the middle of February it 
 was more than six miles long, well incrusted with cooled lava, and 
 making but slow progress. Farm houses were swept away, and 
 pastures and cultivated grounds were buried beneath slowly 
 hardening rock. Entering the ancient forest, it swept down 
 100,000 to 130,000 trees, and the burning trunks floated along 
 upon the moving stream. Some months after the commence- 
 ment of the eruption, the interior of the stream of lava was still 
 incandescent and moving. Continually the crust was burst by the 
 pressure from behind; new rills would start and freeze, and frag- 
 ments of the crust became implanted in the new rock, so that the 
 exterior was roughened by innumerable sharp edged projections. 
 
 Fearful as was this eruption, it was insignificant compared
 
 VOLCANOES. 143 
 
 with former ones. Since this date the mountain has been quiet; 
 but during twenty centuries, seventy-eight eruptions have been 
 recorded the first in the seventh century B.C., in the time of 
 Pythagoras. (See Fig. 6-1.) In some of them the flows of lava 
 have been more than fifteen miles in length, and have covered 
 areas of more than forty square miles (eruption of 1669), which 
 were once in a perfect state of cultivation, and dotted over with 
 towns and villages. The evidences are seen in the lava patches 
 which still rest on the mountain slopes. In 1669 a stream of 
 lava poured over the walls of Catania, sixty feet in height, and 
 overwhelmed a part of the city. In 1693 ari earthquake accom- 
 panied, which destroyed 60,000 to 100,000 inhabitants, of whom 
 18,000 were Catanians. In 1755 a flood of water, estimated at 
 16,000,000 cubic feet, descended the Val del Bove, carrying all 
 before it. In former days, thousands of other lava flows and 
 cones of ashes have added their contributions to the mass of the 
 volcano, so that there is no spot which has not, sooner or later, 
 been covered by the depositions. In fact, the evidence is that 
 the total bulk of ^Etna, from summit to base, down even to the 
 lowest submarine depths, is nothing but the product of suc- 
 cessive eruptions of molten lava, ashes and cinders. 
 
 From all observations made, it appears that the usual tenor 
 of events attending an eruption of ./Etna is as follows: Earth- 
 quakes are the premonitory symptoms; loud explosions are heard; 
 rifts open in the side of the mountain; smoke, sand, ashes and 
 scorifE are discharged; the action localizes itself in one or more 
 craters; cinders are thrown out, and accumulate around the 
 crater in a conical form; ultimately, lava rises through the new 
 cone, frequently breaking down one side of it, where there is 
 least resistance, and flowing over the surrounding country. Then 
 the eruption is at an end. 
 
 Could we, with Captain Dutton, visit Hawaii, we should find 
 the conditions varied, but essentially the same. This island is 
 composed mainly of three volcanic mountains, Loa, Kea, and 
 Hualalai [give European sounds to the vowels] 7,822 feet high. 
 Mauna Loa is 13,760 feet in height, and has, besides its summit
 
 144 
 
 GEOLOGICAL STUDIES. 
 
 crater, another one, Kilauea, 3,970 feet above the sea level. 
 This is a type of vent so unlike ordinary craters that Button 
 proposes for it the new name caldera. The eruptions of Loa are 
 
 FIG. 65. MAP OF HAWAII, SHOWING LAVA FLOWS. (Button.) H, Hilo; H U, Hualalai; 
 K, Kilauea; K E, Mauna Kea ; K 0, Kohala Mts. L, Mauna Loa. 
 
 quiet. The first indication is a light sent from the crater to the 
 clouds. The liquid lava rises in the crater; sometimes it over- 
 
 Hualalai M. Loa 
 
 FIG. 66. PROFILE OF HAWAII THROUGH HUALALAI AND MAUNA LOA, FROM N. W. TO S. K. 
 Distance 30 miles. Section extends 18,000 ft. below sea level. (Dutton.) 
 
 flows, but generally a fissure opens on the side, and the lava 
 pours forth, accompanied by ejections of stones, cinders, and 
 ashes. The stream of lava has been known to flow sixty miles,
 
 VOLCANOES. 145 
 
 and at times it has reached the sea. Lava streams of various 
 dates are shown in Fig. 65. The eruptions at the summit crater 
 are not generally accompanied by disturbances in Kilau^a. The 
 converse is equally true. Kilau6a is a crater or caldera 16,000 
 feet long, seven and one-half miles in circuit, nearly four square 
 miles in area, and 600 feet deep. The floor is of cooled lava, 
 with one or more pits of molten lava continually in a state of 
 agitation, and at times overflowing the brim and flooding the 
 solid floor. Mauna Kea seems to be extinct. On the island of 
 Maui, the volcano Haleakala is 10,217 feet high, with a crater 
 2,000 feet deep; and lava-flooded valleys one to two miles wide 
 lead from it toward the sea. , 
 
 The red sunsets of 1883 and 1884 arc well remembered by 
 all. It seems, at first view, very far-fetched to assume any con- 
 nection between them and volcanic activities ; but the opinion 
 prevails very generally that they were caused by the fine ashes 
 ejected on the 26th, 27th, and 28th of August, 1883, from a vol- 
 cano on a small island lying in the Strait of Sunda, and com- 
 monly known as Kra-kat'oa. There were three volcanic summits 
 on the island. The northern and lowest, Perboewatan, began to 
 be active in May, after a rest of two centuries; the middle sum- 
 mit, Danan, was the seat of the great eruption of 1883, while 
 the southern and highest summit, Ra-ka'ta, eight hundred and 
 twenty-two metres, did not suffer. The eruption was accompa- 
 nied by several terrific explosions, the greatest of which occurred 
 at five minutes past 10 A.M., August 27, Batavia time. These air 
 shocks travelled no less than three and one-fourth times around 
 the earth. The sounds were heard over an area whose radius is 
 30, or 3,333 kilometres, or whose diameter would reach from the 
 Canary Islands to Jerusalem, and from Novaya Zemlia to the mid- 
 dle of the Soudan. The matter ejected is estimated at eighteen 
 cubic kilometres; and within a circle of fifteen kilometres' radius 
 the thickness of the lavers deposited was twenty to forty metres 
 at the base of the mountain, sixty to eighty metres. The finer 
 ashes fell 1,200 kilometres away, and the finest seem to have 
 floated for months in the upper air. The steam-cloud was seen to
 
 146 
 
 GEOLOGICAL STUDIES. 
 
 rise 11,000 metres. The high southern peak was split through 
 the middle, and the northern half, together with the other two 
 
 FIG. 67. FORM OP THE SUMMIT OF VESUVIUS, IN 1756, SHOWING FOUK CRATERS. (Scrope.) 
 
 mountains, sank out of sight. The soundings over it are now 
 200 to 300 metres. The size of the island was formerly thirty- 
 three and one-half square kilometres; of this only ten square 
 kilometres remain, but the volcanic depositions have added five 
 square kilometres. 
 
 The explosive sounds, the atmospheric shocks, and the great 
 sea waves which destroyed more than 35,000 lives, are believed 
 to be due to the falling in of the crater at successive intervals. 
 This is a common incident of volcanic eruptions. The present 
 
 crater of Vesuvius rises 
 within a much larger 
 crater, Somma, which 
 resulted from the en- 
 gulfment of a former 
 crater during an erup- 
 tion. In 1756 the sum- 
 
 mit presented the ap- 
 pearance shown in Fig. 
 
 FIG. 68. TRIPLE CRATER OP THE TJOENDOENG VOL- TT , 
 
 CANO, SUMATRA. (Hochstetter.) 67. Here were the re- 
 
 mains of four craters, 
 
 one within another. The phenomena of the Sundanese volcanoes 
 illustrate the same thing, as shown in Figs. 68 and 69. This is
 
 VOLCANOES. 
 
 147 
 
 explained by Hochstetter on the supposition of a vast exca- 
 vation in the moun- 
 tain, as shown in Fig. 
 70. By- and -by the 
 
 arch becomes too 
 
 weak to support its FlG - 69. QUADRUPLE CRATER or MERAPI (SUMATRA). 
 
 , , . (Hochstetter.) 
 
 weight, and, falling 
 
 into the abyss, leaves the circle of breakage to contribute the 
 
 FIG. 70. VOLCANIC CONE, WITH INTERIOR MELTED AWAY. (Hochstetter.) 
 
 rim of a new and larger crater, as shown in Fig. 71. Then, after 
 a period of quiescence, the liquid pool freezes over, and a new 
 and small crater, on 
 occasion of subsequent 
 activity, begins to grow 
 in the centre. 
 
 Visitors to California 
 and Oregon are greatly 
 interested in the grace- 
 ful forms of the vol- 
 canic peaks of the Si- 
 erra Nevada and Cascade ranges. Most admired of all is Mt. 
 Shasta, rising a solitary and shapely cone 14,440 feet above the 
 sea (Whitney). It has ceased to be active, but the evidences of 
 great former activity appear in enormous sheets of volcanic ma- 
 terial covering the country around. The fires of Mt. Hood, in 
 Oregon, appear to be dying out, only moderate heat and vapors 
 escaping to the top. But in times past it has covered many hun- 
 
 FIG. 71. VOLCANIC CONE, AFTER THE FALLING-IN OF 
 THE CRATER. (Hochstetter.)
 
 148 GEOLOGICAL STUDIES. 
 
 dred square miles with its ejections. The Columbia River has 
 cut through these in a chasm 4,000 feet deep. Mt. Ranier, in 
 the same range, is 14,444 feet high. Its snow-white summit pre- 
 sents a magnificent spectacle from Seattle, seventy miles distant, 
 on Puget Sound. 
 
 In many portions of the trans-Mississippi region the evi- 
 dences of former volcanic activity are abundant. The whole 
 Nevada range, from Lassen's Peak to Shasta, is volcanic, and 
 so is the Cascade range, further north. Numerous series of vol- 
 canic cones stretch along the western slope of the Sierra. 
 Near Mono Lake is a group extending far south, a view of 
 which is shown in Fig. 72. This is a cluster of truncated cones 
 
 FIG. 72 VOLCANIC CONES. NEAB MONO LAKE, CAL. (Whitney.) 
 
 of very steep sides, chiefly covered with ashes and other loose 
 materials, and having numerous rocky projections rising from 
 their broadly truncated tops. They reach the altitude of 9,200 
 and 9,300 feet above sea level. 
 
 Extinct volcanoes are known in many countries, but the most 
 celebrated region is central France. Here hundreds of cones 
 and enormous sheets of ejected material, worn, in later times, 
 by the agencies of erosion, have given to a wide region an aspect 
 entirely unique and full of interest to the geologist. Here is 
 subjoined a view taken from the work of Poulett Scrope, who 
 has studied and illustrated the region with more detail and thor- 
 oughness than any other investigator (Fig. 73).
 
 VOLCANOES. 
 
 149 
 
 EXERCISES. 
 
 What is the nature of the so-called 
 "smoke" from volcanoes? Is there 
 any "combustion" in a volcano? 
 What is the source of the water which 
 issues as steam? What evidence can 
 you give that this is sea water? Have 
 you ever heard of mud ejected from 
 volcanoes? What analogy can you 
 trace between volcanoes and geysers? 
 Enumerate the principal lines and 
 regions in which volcanoes abound. 
 Enumerate volcanoes situated far in- 
 land. Give some account of any vol- 
 cano not mentioned in the present 
 study. What must be the effect of 
 volcanic action on the internal heat of 
 the earth? If the volcanic cone is 
 formed of ejected materials, what is 
 under the cone? Do you imagine any 
 rocks of sedimentary origin could be 
 there ? Could granitic and other meta- 
 morphic rocks be there? (See Fig. 46, 
 "trachyte" and "basalt.") Profes- 
 sor Whitney found masses of rose-col- 
 ored granite on the tops of the cones 
 shown in Fig. 72; how could they be 
 accounted for? Why not consider 
 them bowlders? Would it be surpris- 
 ing to see rounded stones ejected from 
 a volcano? Should you see them, 
 where and how would you suppose them 
 rounded? Should they afterward be 
 cemented together, what sort of a rock 
 would be formed? Have you ever 
 heard of such a rock as a fact ? Can 
 you suggest why the eruptions of ,33tna 
 and Vesuvius are attended by earth- 
 quakes, and those of Mauna Loa not? 
 Does it appear that different volcanoes 
 have an underground connection? Do
 
 150 GEOLOGICAL STUDIES. 
 
 the summit crater and Kilauea sympathize together? Do ./Etna and Vesuvius ? 
 Do ^Etna and Stromboli? Assuming the two craters of Mauna Loa to be 
 connected, how could lava stand in the summit crater, 9,000 feet higher than 
 Kilauea, without escaping at Kilauea? Supposing the specific gravity of the 
 lava two and eight-tenths, how many atmospheres of pressure would be felt 
 at Kilauea? 
 
 STUDY XXIV. Ancient Lavas. 
 
 The traveller returning southward from a trip to Mt. Shasta 
 may follow the broad valley of the Sacramento River. On his 
 left rise the peaks of the Sierra Nevada, with the foot hills in the 
 nearer distance. For a hundred miles, from Pitt River to Oro- 
 ville, along the eastern side of the Sacramento, he traverses a 
 broad plain of volcanic ashes, destitute of trees and almost 
 destitute of herbage, and as yet hardly eroded into canons. On 
 nearing Bear Creek, more solid lava makes its appearance, and 
 increases as he passes southward. This belt averages about 
 seventy-five miles in width. The materials may be traced chiefly 
 to the great centre of eruptive agency at and near Lassen's Peak, 
 in the Sierra Nevada. The sheets of lava form a regular slope 
 from the Peak to the Sacramento. Through this the more south- 
 ern streams have sunken their channels five hundred to eight 
 hundred feet deep. In some situations crater-bearing cones rise 
 over eight hundred feet, and from these have issued a portion of 
 the materials which flooded the valley. These were laid down on 
 Cretaceous strata. Tuscan Springs, already mentioned (Fig. 57), 
 are in this region. The section shows that the Cretaceous strata 
 were somewhat tilted before the lava was poured out, and further 
 tilted since that event. The conglomerate is not volcanic, and its 
 presence implies the action of a transporting agent over the sur- 
 face after the upheaval of the Cretaceous. To this is probably to 
 be attributed the erosion of the strata. This section also shows 
 a breakage of the strata and the escape of warm mineral waters. 
 
 Near the southern limit of this lava sheet, in the centre of
 
 AXCIENT LAVAS. 
 
 Butte county, the streams have cut _ 
 quite through the lava into the under- 
 lying formations, giving rise to forms = 
 known as "table mountains." Here, = 
 underneath all, are exposed the aurifer- 
 ous slates, tilted up to a steep north- j! 
 easterly dip, and containing intercalated | 
 beds of Carboniferous Limestone. On : 
 the upturned edges of these strata rest = 
 nearly horizontal Cretaceous sand- I 
 stones, with a slight southwesterly dip. g 
 Above these are sandstones interstrati- - 
 fied with shales containing leaves of 
 Pliocene age. Upon these lie accumu- 
 lations of volcanic ashes, scoriae and 
 breccia, and over all rests a heavy bed 
 of basaltic lava. The section, Fig. 74, 
 is taken across the general direction of 
 the streams, and presents, therefore, 
 cuts across a series of lava-topped belts, 
 intervening between the streams. 
 
 The great auriferous region stretch- 
 ing to the south of this has also been 
 the theatre of extensive lava displays. 
 In El Dorado, Calaveras, and other 
 counties are other table mountains, but 
 in Tuolumne county, one hundred and 
 fifty miles south, is the Table Moun- 
 tain which has become so celebrated for 
 its connection with mining operations 
 and the discovery of fossil remains. Its 
 mode of origin is not different from the 
 origin of those in Butte county. The 
 summit of the mountain is occupied by 
 a heavy bed of basaltic lava one hun- 
 dred and forty to one hundred and fiftv
 
 152 GEOLOGICAL STUDIES. 
 
 feet thick. Its width is about 1,700 feet. Underneath is a heavy 
 deposit of detrital material very distinctly stratified and nearly 
 horizontal, composed mostly of fine-grained sandstone or feebly 
 coherent sand, interstratified in which are fine argillaceous shales 
 and clays. With these are beds of gravelly materials strongly 
 cohering together, and called "cement" by the miners. At the 
 bottom is the "pay gravel" or the "channel," a body of coarse 
 gravel exactly like that seen in the bed of an ordinary river, and 
 here gold-bearing. The entire thickness of the detrital beds 
 directly under the centre of the lava is, in one locality, at least 
 fully two hundred feet. But this thickness is much less at the 
 edge of the deposit, owing to the rise of the underlying vertical 
 auriferous slates on each side, as shown in the figure, forming 
 what is known to the miners everywhere in California as the 
 " rim rock." The rim rock rises here fully one hundred and 
 fifty feet above the level of the " pay gravel." The latter, occu- 
 pying the lowest position, is four or five feet thick, and in this 
 
 FIG. 75. TABLE MOUNTAIN IN TUOLUMNE COUNTY, CAL., AT THE BUCKEYE TUNNEL. 
 I, Lava forming the table ; *, Sandstone under the lava ; g. Gravel ; si, Slate ; It, Old 
 river bed; B', the modern river bed; T, Tunnel through the "rim slate" to the 
 "deep placers"; {^Modern Gravel and "shallow placers." The dotted lines indi- 
 cate the probable configuration of the surface when the lava was erupted. (Adapted 
 from Whitney.) 
 
 place is eighty feet wide. To reach this gravel, tunnels are run 
 in through the rim rock, as shown on the right, or sometimes 
 through the cement. When the channel is reached, it is " drift- 
 ed" on, the miners following the paying streaks, or lines of aurif- 
 erous gravel, up and down in the bed of the ancient water- 
 course. 
 
 What else but a water-course could this trough have been? 
 What else but a bed of river gravel, this which lies strewn along
 
 ANCIENT LAVAS. 
 
 153 
 
 the bottom of the channel here excavated in the slates'? There 
 was, in a former time, a stream flowing from the east over the 
 outcropping edges of the auriferous slates, and strewing its bed 
 with gravel from the quartz veins in the slate. On each side was 
 a sufficient rise in the surface to bound a river valley as^ indicated 
 by the dotted lines. By some change in the mode of action, the 
 sands were laid down over the gravel. Then came an enormous 
 flow of lava from the vents of the Sierra, occupying the entire 
 bed of the stream and partly filling the valley. The stream dis- 
 placed wore a new channel along the border of the lava bed. It 
 wore the bounding slope away, and sunk a modern channel deeper 
 than the old one, leaving the lava to cap an elevation in the very 
 place where once was the valley. The modern stream brings 
 auriferous gravel like the ancient one. These are the " shallow 
 placers"; the other gravels are the deep placers. 
 
 The table mountains of Butte county admit of a similar 
 explanation. But the direction of the modern streams in this 
 region crosses the course of the ancient ones. Many impressive 
 
 FIG. 76. BASALTIC PLATEAUX OP THE COIRON, AKDECHE. (Scrope.) 
 
 examples of a similar nature occur in central France, some of 
 which are illustrated in Fig. 76. 
 
 Many remains of mammalian quadrupeds have been found in 
 the deep placers of California. They embrace mastodon, rhino- 
 ceros, and extinct species of horse, species of hippopotamus and 
 camel related to the living species, and, finally, several human
 
 154 GEOLOGICAL SITDIES. 
 
 bones, including an imperfect skull. The question remains as to 
 the precise age of these auriferous gravels; but it appears, at 
 least, that enormous floods of lava have been poured out over the 
 plains and valleys of the western slope of the Sierra since man 
 became an inhabitant of California. 
 
 It is not necessary to enter further into particulars. Not 
 only has so large a part of California been inundated by sheets 
 of molten lava, but even larger areas have been covered in other 
 regions of our Pacific slope. According to Leconte, " the great 
 lava flood of the Northwest covers an area of 150,000 to 200,000 
 square miles, and is 3,000 to 4,000 feet thick in its thickest part, 
 where cut through by the Columbia River at the ' cascades.' " In 
 another place, at least seventy miles distant, where cut into 2,500 
 feet deep by the Des Chutes River, at least thirty successive 
 sheets may be counted. Another great lava flood, according to 
 Gilbert, covers 25,000 square miles of Arizona, and is 3,000 feet 
 thick in its thickest portions. In New Mexico, according to 
 Captain Dutton, the San Mateo Mountains are a volcanic pile 
 11,380 feet high, carved into numerous spurs by magnificent 
 gorges. From this centre the lavas reach out for forty-five miles 
 to the north-north-east, and in other directions for eighteen to 
 thirty miles. The lava forms a superficial sheet over each 
 mesa or table, ranging in thickness from fifty to two hun- 
 dred feet. Many of the vents scattered around the flanks of 
 Mt. Taylor can be easily identified. The "necks" or "chim- 
 neys" which are left standing in the valley plains beyond 
 the farthest verge of the lava-capped mesas are among the 
 most striking features of the country. One is nearly 2,000 feet 
 high. 
 
 Those who have visited the "Giant's Causeway" or Fingal's 
 Cave have seen other great masses of rocky material, having all 
 the essential characters of lava erupted from volcanoes. These 
 are, indeed, the results of igneous eruption, though there be no 
 mountain, and no discovered point where the outflow took place. 
 It escaped through fissures. One travelling along the highway in 
 the valley of the Connecticut south of Hartford may notice at
 
 ANCIENT LAVAS. 
 
 155 
 
 intervals an abrupt ridge running in a straight line across the 
 
 alluvial meadows. Examina- 
 tion discloses the existence of a 
 vertical wall of rock rising from 
 the underlying sandstone and 
 rising out of it. The nature 
 of the rock is essentially lava- 
 like. It seems to have been lava 
 which rose in a molten state 
 through a fissure in the stratified sandstones beneath. This is called 
 a dike. Dikes of melaphyr are shown in Fig. 46, and an actual 
 group of trachytic dikes in Fig. 83. In the Meriden Mountains, 
 not far away, we discover masses of ancient lava which have 
 risen through such dikes. The outflows continue along the val- 
 
 FIG. 77. DIKES. (See also Fig. 83.) A is 
 harder than the contiguous strata, and B 
 is softer. 
 
 
 FIG. 78. BASALTIC COLUMNS ON SEDIMENTARY ROCK. HAVING THE COOLING SURFACE 
 HORIZONTAL. (After Owen.) 
 
 ley of the Connecticut to New Haven, where prominent head- 
 lands are known as " East Rock " and " West Rock." Travelling 
 up the Hudson, our attention is arrested by the " Palisades," 
 which are only another mass of ancient lava erupted, like tlie 
 Giant's Causeway, without the intervention of a volcanic moun- 
 tain. In Fig. 46 is shown a basaltic outflow, intended to illus- 
 trate basaltic formations in various parts of the world. Basaltic
 
 15G 
 
 GEOLOGICAL STUDIES. 
 
 outflows often assume columnar form, and we observe that the 
 axis of the column is always at right angles with the cooling sur- 
 face. In Fig. 78 the columns are vertical because the cooling 
 surfaces were horizontal. In Fig. 79, which shows a dike of 
 basalt, the columns are horizontal because the cooling surfaces 
 wore vertical. If we take a mass of wet starch and allow it to 
 
 Jfe 
 
 FIG. 70. BASALTIC PRISMS FORMED IN A DIKE. HAVING THE COOLING SURFACES VERTI- 
 CAL. (After Owen.) 
 
 cool rapidly, a similar prismatic structure is developed, as is seen 
 in the laundry starch of the markets. The form is perhaps due 
 to general shrinkage. Possibly ancient lavas, while cooling, 
 developed a similar structure from the 
 same cause. 
 
 At Keweenaw Point, or its vicinity, 
 on the south shore of Lake Superior, 
 are the evidences of an enormous out- 
 flow of molten lava, which issued in 
 very remote times, and spread out 
 in numerous sheets, alternating with 
 sheets .of pebbles, which have become 
 cemented into conglomerate. In this 
 
 occur, the native copper. Much of this %! 
 lava presents the character of amygda- 
 loid, Fig. 80. When cooling, it abound- 
 
 DALOID. CENTRAL FRANCE. 
 (Lyell.)
 
 ANCIENT LAVAS. 
 
 157 
 
 ed in bubbles of gases, and became exceedingly vesicular, like 
 some scorire of modern volcanoes. After the gases escaped, the 
 cavities were filled with various minerals, infiltrated in a state of 
 solution. The rock receives its name from the almond-shaped 
 inclusions, and it retains the name even after the minerals have 
 dissolved out. 
 
 The Geological Survey of Italy has lately published sections 
 of the island of Elba, which show a mass of Eocene strata inter- 
 
 FIG. 81. SECTION ON THE WEST PART OF THE ISLAND OF ELBA, 900 METRES. P, Cape 
 Poro; , BaiMella Point; /, Limestone; , Schists; p, Porphyry. (Geol. Surv. Italy.) 
 
 penetrated and interbedded in an extraordinary manner, with 
 dikes and intrusions of porphyry, which materially swell the mass 
 of the island. Fig. 81 is one of the sections. 
 
 Mr. G. K. Gilbert, in a report on the Henry Mountains, of 
 Utah, has made us acquainted with an extreme development of 
 intrusive lavas; that 
 is, igneous rocks 
 forced into the 
 seams separating 
 sedimentary strata 
 (Fig. 82). Such 
 cases have long been 
 known, and Fig. 46 
 shows porphyry so 
 intruded. But in 
 the Henry and other 
 western mountains, 
 the force and volume of the intrusion have been such as to actu- 
 ally lift the overlying masses of strata, as here illustrated. Sub- 
 sequently, erosions have in some cases worn away the overlying 
 strata, and the included porphyritic trachyte is gnawed into 
 
 FIG. 82 IDEAL CROSS-SECTION OF A "LACCOLITE,'' WITH 
 ACCOMPANYING SHEETS AND DIKES. (Gilbert.)
 
 158 
 
 GEOLOGICAL STUDIES. 
 
 many fantastic shapes. The crest of Mt. Holmes (Fig. 83) affords 
 an excellent illustration of dikes. 
 
 Recurring again to Fig. 46, we notice a representation of a 
 vein of granite injected into another mass of granite. It is the 
 general opinion that granite, in vein form, must have cooled 
 from igneous fusion; but there are some who think otherwise. 
 You see, also, that rocks of the eruptive class include also por- 
 phyries and other varieties somewhat different from common 
 lavas. 
 
 The observations which we have made in the last three studies 
 show: 
 
 1. That the internal temperature of the earth increases as 
 we penetrate downward. There is consequently, and necessarily, 
 a constant transfer of heat from the deeper and warmer parts to 
 
 FIG. 83. THE CKEST OF MT. HOLMES, UTAH. (Gilbert.) 
 
 the shallower and cooler parts. In other words there is a contin- 
 ual flow of heat from the interior to the surface, and a final radi- 
 ation and wastage of it from the surface. Thus the simple fact 
 of internal increase of heat proves that the earth is now cooling. 
 2. The numerous evidences of more highly heated conditions 
 at the surface in ages past are proof that the cooling process has 
 been long going on. Our earth must therefore be contemplated 
 as a cooling body. Many of the most important events in its 
 physical history are known to have resulted as incidents of cool- 
 ing. The fact of cooling has been a determinative principle in
 
 ANCIENT LAVAS. 159 
 
 terrestrial progress. It has had something to do with the earth's 
 physical vicissitudes and resultant forms. Through these it has 
 necessarily exerted conditioning influences on the organic beings 
 which have populated its surface. 
 
 From what former high temperature has the cooling pro- 
 ceeded ? Most of those who speculate on this question agree that 
 the whole earth was once in a state of igneous fluidity. Not dis- 
 covering any reason to conclude that even this was the starting 
 point of the process of cooling, they carry the history of terres- 
 trial matter back to a state of molten mist floating in a gaseous 
 medium. 
 
 EXERCISES. 
 
 What is the evidence of the tilting of the cretaceous strata at Tuscan 
 Springs, before the lava was poured out? What is the proof of a subsequent 
 tilting? Which way do the strata dip at Tuscan Springs? Can you draw a 
 diagram indicating the termination of the Cretaceous strata at a higher 
 level than at the springs? What is the evidence of the existence of such 
 higher outcrop? How does the water become warmed ? How does it obtain 
 its mineral properties? How can you reconcile the northeasterly dip of the 
 auriferous slates with the fact that the Sierra lies in that direction? How 
 can the Cretaceous sandstones over them be nearly horizontal? Can you ex- 
 plain why they dip slightly in the opposite direction? What is the source of 
 the "pay gravel" in the deep placers? By what streams transported? 
 What is the difference between these and the shallow placers? After a lava 
 stream displaced the old river, how came a new channel into existence on 
 each side of the lava stream? What is the evidence that the ancient streams 
 of Butte county ran across the direction of the modern streams? Have yoij 
 ever seen a deposit of volcanic rock? What locality of volcanic rocks is 
 nearest to this place? Could vesicular lavas form if the cooling took place 
 under great pressure? Why do you answer thus? Do you think the tra- 
 chyte of the Henry Mountains is vesicular or compact? Why do you answer 
 thus? Are amygdaloids of sedimentary origin or not? Are they metamor- 
 phic? Do they denote any particular kind of eruptive rock? Does the des- 
 ignation relate to composition or to structure?
 
 160 GEOLOGICAL STUDIES. 
 
 STUDY XXV. Mountain Phenomena. 
 
 Let us trace somewhat farther the results of disturbances of 
 the earth's crust. If we turn back to Fig. 38, we notice that the 
 disturbance of the strata results in an elevation of surface having 
 the appearance of a mountain. You have already recognized 
 here the indications of an upheaval of the granite mass which 
 seems to burst through the beds of gneiss once overlying. This 
 figure may be taken as a general section across the Laurentian 
 mountains of Canada or the Adirondacks of New York. The 
 Humboldt, Wahsatch and many other mountains exhibit a simi- 
 lar structure. But we are not certain the central mass becomes 
 exposed to view in consequence of protruding through the over- 
 lying rocks. Perhaps the gneisses or other strata continued to 
 conceal the granite or other central core, after the upheaval, and 
 have been subsequently worn away. It is also quite supposable 
 that a granite summit was originally uplifted above the sea 
 level, and the gneisses when forming as sediments never covered 
 that portion of the granite now exposed to view. It requires 
 sometimes much study to determine in which way it happened that 
 the central mass, whether granitic or not, stands uncovered by 
 later strata. In the case of the Laurentian mountains and the 
 Adirondacks, the third explanation is held to be the true one. 
 
 The section through Tennessee, Fig. 33, which we have used 
 to illustrate erosion, is also a good illustration of two kinds of 
 mountain structure. At the east we see the massive strata of 
 the Unaka ranges standing at a very high inclination, and rising 
 to an average altitude of 5,000 feet, along the entire eastern bor- 
 der of the state. We find at least twenty-two summits which 
 exceed 6,000 feet in altitude. These rocks, according to Safford, 
 are chiefly thick beds of sandstones and conglomerates of the 
 Primordial Group (see Fig. 39), partly in a metamorphic state 
 that is, changed to gneisses and schists. There are two, and for 
 part of the distance, three parallel ranges constituting the Unaka 
 chain, and this is a part of the great Appalachian chain, stretch-
 
 MOUNTAIN PHENOMENA. 161 
 
 ing from New England to central Alabama. The strata of the 
 Unaka ranges are seen to be monoclinal having the dips all in 
 the same direction. This may be distinguished from the anti- 
 clinal structure. 
 
 Recurring again to the section through Tennessee, we observe 
 a fine example of another class of mountains. The Cumberland 
 table land stands at a mean elevation of 2,000 feet above sea 
 level. It is a flat-topped mountain from fifty to seventy-five miles 
 in width, and stretching from Georgia through Tennessee and 
 Kentucky. It can indeed be traced through West Virginia and 
 
 HUDSON RIVER. (Mather.) 
 
 Pennsylvania into southern New York. It subsides in northeast- 
 ern Alabama. As we inspect this east and west section through 
 the table land, it becomes obvious that this is not a mountain 
 mass which has been upheaved, but is a region of relief, result- 
 ing from vast erosions along its eastern and western sides. The 
 contiguous valleys have been excavated. The strata, moreover, 
 remain nearly horizontal. They have not been disturbed. They 
 consist of rocks of Upper Carboniferous age. Lookout Moun- 
 tain and Missionary Ridge, the sites of important battles, are 
 outliers of this great table land. Mountains of relief are styled 
 b}- Powell, " cameo mountains." 
 
 The Catskill Mountains present a similar structure (Fig. 84), 
 consisting of nearly horizontal beds, but having a slight dip south- 
 west, piled up two, three, or four thousand feet above sea level. 
 They belong to the age of the Devonian. The Uinta Mountains 
 are somewhat in the form of a table land; but they are not a
 
 162 
 
 GEOLOGICAL STUDIES. 
 
 proper table land, since upheaval as well as erosion has been con- 
 cerned in the production of the salience. They are one hundred 
 and fifty miles long and fifty broad. In Fig. 85 is presented an 
 idealized section, from Powell, showing a mass of folded strata 
 in the interior, over which passes a broad swell, which has been 
 extensively eroded and flattened along the top. Actual observa- 
 tion has not extended below the level of A JS, C D is the sea 
 level, and Y is the bed of the Green River, which has been ena- 
 bled to cut through the mountain, because it existed before the 
 mountain, and the mountain slowly rose under it, as a log moves 
 on a saw. The river, then, as Powell suggests, has sawed the 
 mountain in two. The actual elevation of this fold was about 
 
 FIG. 85. GENERALIZED SECTION THROUGH THE UINTA MOUNTAINS, FROM NORTH TO 
 SOUTH. (Powell.) 
 
 30,000 feet. The mean depth of the degradation from the sum- 
 mit is three and a half miles, and as the area of the mountain 
 proper is about 2,000 square miles, the total degradation is 7,000 
 cubic miles. The materials were deposited in the bottom of the 
 ocean then contiguous. This took place during the earlier Eocene. 
 On the north the sedimentation partly supplied from this source 
 amounted to more than 6,000 feet, and in some parts to 8,000 
 feet. We thus get new illustrations of doctrines previously 
 generalized. 
 
 From what we have already seen, it is apparent that different 
 portions of the earth's crust have been subject to considerable
 
 MOUNTAIN PHENOMENA. 163 
 
 vertical movements. These could hardly be conceived to take 
 place without extensive fracturing of the strata. In fact, a re- 
 examination of some of our sections, which are simply pictures 
 from nature, will disclose the presence of fractures. In the sec- 
 tion through Tennessee (Fig. 33) we find a break some distance 
 east of the Cumberland table land. Notice that the strata on 
 opposite sides dip in opposite directions, and do not correspond 
 together. On the eastern border of the valley of East Tennes- 
 see is another break, and the strata on opposite sides have differ- 
 ent inclinations, and do not correspond. Such an occurrence is 
 called a fault, or dislocation. Many times the rocks on one side 
 of the fault have been raised or lowered more or less from their 
 original position, and sometimes considerable movements have 
 
 WASATCII PLATEAU 
 Ibults /ran 600 to 1 ,700 feet n ,000/<. high 
 
 E 
 
 c b c c b a 
 
 FIG. 86. SECTION EAST AND WEST IN CENTRAL UTAH, SHOWING NUMEROUS FAULTS. 
 a, Triassic; &, Jurassic; c, Cretaceous; d, Laramie; ef, Tertiary. (Button.) 
 
 taken place. Vast dislocations exist elsewhere in the Appalach- 
 ians, and this is indicated in the diagram, Fig. 34. In several 
 cases the downthrow amounts to 5,000 or 10,000 feet; and Lesley 
 gives an account of a fault not less than 20,000 feet, bringing 
 upper Devonian strata on one side opposite the lowest Cambrian 
 on the other. 
 
 Some of the grandest fractures and faultings known in the 
 world occur in the Rocky Mountains and the regions farther 
 west. The anticlinal of the Park Range of the Rocky Mountains 
 was cleft down the axis, and the eastern half depressed 10,000 
 feet. Colorado Range was severed by an enormous southeast- 
 northwest fault, which dropped the region of the Laramie Hills 
 6,000 or 7,000 feet lower than the southern continuation of the 
 same ridge. The inclined easterly dipping Palaeozoic and Meso-
 
 Paria Plateau, 
 
 Virgen Valley. 
 Pine Valley Mountain. 
 
 Paria Fold. 
 Echo Cliffs. 
 
 East Kaibab Fold. 
 
 Kaibab Plateau. 
 West Kaibab Fold, 
 Kanab Plateau. 
 Kanab Canon. 
 
 Kanab Plateau. 
 
 To-rii-weap Fault. 
 U-in-kar-et Mountains 
 
 Hurricane Fault. 
 Shi-vwits Plateau. 
 
 Grand Wash Fault 
 Grand Wash. 
 
 3* 
 
 if 
 
 I! 
 
 1 
 si 
 
 w 
 
 gn 
 D 
 
 II
 
 MOUNTAIN PHENOMENA. 1G5 
 
 zoic rocks of the Wahsatch, in the region of the Cottonwood, 
 rested against the abrupt, precipitous face of a granite cliff, of 
 which 30,000 feet are now exposed (King). In Fig. 86 we have 
 a section in central Utah, showing seven faults. The great fold 
 of the Uinta Mountains produces, along some parts of its bor- 
 ders, so sharp a flexure that the strata are broken and faulted. 
 A great fracture runs along the axis of the Sierra Nevada for 
 300 miles, accompanied by a dislocation of 3,000 to 10,000 feet. 
 For a large part of this distance the eastern half of the split fold 
 has sunken down to a level with the plain, while the western half 
 remains elevated. The consequence is, that the mountain pre- 
 sents a gentle slope on the west, and a very precipitous one on 
 the east. This appears, consequently, to be a mountain of a type 
 different from any before distinctlv mentioned. It is a mono- 
 
 FIG. 88. GBAYLOCK, A SYNCLINAL MOUNTAIN. (Emmons.) G>, Graylock; H, Hoosac 
 Mountain aurt Tunnel; A, North Adams ; I, I, "Eoliun Limestone" (Trenton); t, Tal- 
 coid Schist; m, Mica Schist; g, Gneiss; *, Steatite. 
 
 clinal mountain, but the continuity of the strata is not inter- 
 rupted by erosion, but by precipitation into the abyss. Similarly 
 the Wahsatch range has been cleft by a fault at least 100 miles 
 long, and the west half has sunken 40,000 feet (King). As the 
 faulting process has had so much to do with the surface config- 
 uration of the plateau region of the West, we reproduce in Fig. 
 87, from Powell, a bird's-eye view of the great Colorado plateau 
 north of the Grand Canon shown in the sketch, Fig. 31. This will 
 be convenient for reference in connection with other points of geo- 
 logical interest. 
 
 In Fig. 88 is shown another variety of mountain. This is a 
 synclinal mountain, or one in which the dips of the strata are 
 from opposite sides toward the centre of the mountain. Corre- 
 spondingly, the contiguous valleys are anticlinal. This results
 
 166 
 
 GEOLOGICAL STUDIES. 
 
 from the more rapid erosion experienced along the exposed and, 
 probably, fractured anticlinal crest. In consequence, the actual 
 original crest has been lowered below the level of the valley, and 
 
 FIG. 89. SECTION THROUGH MT. KEARSAKGE, N. II., SHOWING SYNCLINAL STRUCTURE. 
 (C. H. Hitchcock.) W, Wilmot; W H, Wilmot House; Wh H, White House; P, 
 Plumbago Pt.; o, Porphyritic Gueiss; b, Andalusite Mica Schist; c, Granite. 
 
 the valley stands forth as an elevation. Thus a valley comes into 
 existence where the mountain was, and a mountain remains where 
 
 FIG. 90. THE NEEDLES OF CHARMOZ AND THE MER DE GLACE, SWITZERLAND. 
 (Photograph.) 
 
 the valley was. Mt. Kearsarge, in New Hampshire (Fig. 80), is 
 one of many illustrations. It is one of the various results of the 
 combined action of upheaval and erosion.
 
 MOUNTAIN PHENOMENA. 
 
 16? 
 
 In Figs. 90 and 91 we have views of a type of mountains 
 resulting from a vertical position of schistose rocks sharpened by 
 weathering. These are the well known " needles " (aiguilles) of 
 the Alpine ranges. 
 
 Now let us reduce to a systematic statement the various types 
 of mountain structure to which our attention has been directed, 
 whether in this study or preceding ones. 
 
 FIG 91. CASTLE ROCK RANGE, CAT,. (Whitney.) 
 
 TYPES OF MOUNTAIN STRUCTURE. 
 
 I. Sedimentary. The mountain mass composed of sedimentaiy rooks. 
 1. UPHEAVAL, modified by subsequent denudation. 
 (1) Anticlinal in origin and fundamental form. 
 
 (a) Amphiclinal in actual form. Actual dips both ways. 
 
 Rocky Mountain and Basin Ranges, 
 (a) Central mass an antecedent exposure primordial. 
 
 Laurentian, Adirondac, Humboldt. 
 (/?) Central mass protruded, or revealed by denudation. 
 
 Mill Mountain, Va., Piiion and Diamond ranges. 
 (J) Monoclinal in actual form, 
 (a) Resulting from denudation. 
 
 Unaka Mountains, Tenn. and N. C. ; Wolf Ridge, Va. 
 (ft) Resulting from faulting. 
 
 Elk Mountains, Sierra Nevada, Wahsatch, many Basin ranges. 
 
 Typical structure of Rocky Mountains. (Button.) 
 (c) Orthoclinal, with the strata vertical (generally sharpened by 
 
 erosion). 
 Alpine "Needles." Castle Rock range, Cal.
 
 168 GEOLOGICAL STUDIES. 
 
 (d) Hyperclinal, or ''Fan Structure." Tilting carried beyond the 
 
 vertical. 
 
 Mont Blanc, St. Gothard, San Luis, and Santa Lucia, Cal. 
 (2) Aclinal. Strata horizontal or nearly so. 
 
 (a) Bounded by monoclinals. Uinta mountains. 
 
 (b) Bounded by faults. Kaibab structure of Powell. (Runs into pre- 
 
 ceding.) 
 
 Common in the "Plateau Province." 
 2. RELIEF. Salience resulting from contiguous erosions. 
 
 (1) Tabular. Stratification horizontal. 
 
 Cumberland Mountains, Catskills, House Mountain, Va. 
 
 (2) Synclinal. Strata dipping into the mountain from opposite sides. 
 
 Mt. Kearsarge, N. H. ; Becraft's Mountain, N. Y. ; Mt. Eolus, 
 Vt., Graylock, Mass., Mt. Everett, Mass. 
 
 II. Eruptive. 
 
 1. Material a deposition. Ejected, and brought down by gravity. 
 
 (1) Volcanic cones of ashes and cinders (generally with lava added). 
 
 JEtna, Vesuvius, Shasta, Mauna Loa. 
 
 (2) Volcanic sheets of ashes and cinders, subsequently eroded into 
 
 saliences. Erupted depositions of Oregon. Peperino beds of 
 Italy and elsewhere. 
 
 2. Outflow of molten matter forming sheets, subsequently eroded. 
 
 Lava mesas and mountains. Ridges near Silver City, Col. 
 
 III. Combined. Strata uplifted by intrusions beneath. 
 
 1. Turgescence of crust. Action producing fractures and an excess of 
 
 dykes and veins. Island of Elba. 
 
 2. Laccolites. Action intrusive. Laccolites variously eroded. 
 
 Henry Mountains, Sierra Abajo, El Late, Navajo Mountain, 
 Indian Creek, Wy. 
 
 EXERCISES. 
 
 When we find a region having granitic rocks at the surface, why are 
 there no other rocks over the granite? Can you be certain of the reason why 
 the granite is exposed? Suppose the granite is much higher than the nearest 
 newer rocks, what then would you conclude? What, if the granite exposure 
 is lower than neighboring rocks of later date? How do you know when 
 rocks are of later date than the granite? Suppose we find a mountain with- 
 out granite exposed at the summit, does it probably contain granite? In the 
 section through Tennessee, Fig. 33, point out two types of mountain struc- 
 ture. In what direction do the rocks dip in the Unaka mountains? Is this 
 a case of upheaval ? Is this an anticlinal? How many branches or sides has 
 an anticlinal ? How many are seen in the Unakas? Which branch is present?
 
 MOUNTAIN FORMATION. 169 
 
 Where is the other? What other type of mountain in the Tennessee sec- 
 tion? Is this also a case of upheaval? Is the Uinta Mountain strictly a table 
 land? Has there been any upheaval there? How does this case differ from 
 an ordinary anticlinal? How do we know that the Green River, which has 
 cut through it, is older than the mountain? If the river flowing south had 
 been obstructed by the mountain, where would the river have gone? Would 
 it have been possible for other streams to cut the mountain in other direc- 
 tions? What is the extreme extent to which you could conceive the moun- 
 tain cut up? How might a detached outlier or column have originated? 
 How do we know the formations north of the Uinta were derived partly from 
 the destruction of the Uinta? When several thousand feet of sediments 
 accumulate on a sea bottom, do you think the bottom would tend to sink? 
 Suppose some thousands of feet are removed from the Uinta mountains, do 
 you think the unloading would cause the region to rise? Look at Fig. 87 
 and point out the faults. Show where there has been a downthrow. Show a 
 structure somewhat similar to that of the Uinta Mountains. Point out val- 
 leys of erosion. Do the Uinkaret Mountains look like anticlinals? Does the 
 Pine Valley Mountain? Where is the Grand Canon in this view? Which 
 way does it run? In what direction do these great faults run? Draw a dia- 
 gram to explain how a synclinal mountain might originate. 
 
 V 
 
 STUDY XXVI. Mountain Formation. 
 
 We now present, in Fig. 92, a remarkable section in the Appa- 
 lachian region, worked out by Prof. J. L. Campbell. All the 
 principal varieties of mountain structure are here shown. The 
 strata are Cambrian, Silurian and Devonian, and the particular 
 formations are indicated by numbers and letters corresponding 
 with the general table of formations, Pt. II, ch. ii, 5. For the 
 purpose of showing the relation of the different kinds of rocks to 
 the work of erosion, the conglomerates are distinguished by coarse 
 dots, sandstones by finer ones, shales by closely ruled lines, while 
 limestones are blocked, and those of different periods otherwise 
 distinguished. Here will be noticed two great faults. The mass 
 between them, some four miles long, has been thrown down. 
 TJie dotted lines indicate the former extension of strata. This 
 section must be much studied. It is substantially a real section. 
 Such bendings, altitudes and fractures are facts scientifically 
 worked out.
 
 fi 
 
 I! 
 is 
 
 V;-:,:.;. ; Wolf Ridge 
 N\U V\v.$-:ni<.--l!:u'k 
 
 ^ault 
 
 ftk ; Baths 
 
 I1II
 
 MOUNTAIN FORMATION. 171 
 
 A free glance at the foregoing section conveys the distinct 
 impression that a pile of rocky sheets has been subjected to a 
 folding process, and afterward extensively denuded. The fold- 
 ing process has in some places fractured the strata, and caused 
 dislocations. It is quite possible that the faulting was a subse- 
 quent event. If this section were again flattened out, it would 
 increase considerably in length. In the process of folding, 
 therefore, the original length must have diminished. If this dia- 
 gram were exact, and made to measure, we might lay a thread 
 along one of the formations from end to end, and then measure 
 the length of thread required, and thus ascertain the percentage 
 of shortening in consequence of the folding. King estimated 
 that ten per cent would not more than express the shortening of 
 the strata folded up along the belt of the fortieth parallel. Some 
 of the basin ranges have even undergone a longitudinal shrink- 
 age of over ten per cent. (King, S. F. Emmons.) Claypole 
 measured a section sixty-five miles long, across Huntington, 
 Juniata and Perry counties, in Pennsylvania, and calculated the 
 original length of the strata had been about one hundred miles, 
 giving a shrinkage of thirty-five per cent. We may admit that 
 this is perhaps an exaggerated estimate, and still feel certain 
 that enormous shrinkage of a folded crust must take place. 
 
 A little reflection makes it apparent, also, that the movement 
 of contraction and folding must be the result of pressure from 
 without. A linear shortening, accompanied by folding, results 
 from pressure from the ends. There must have been some enor- 
 mous lateral pressure experienced by all parts of the folded 
 crust. This conviction is strengthened by the appearance of 
 the heavy-topped folds which resulted in the upheaval of the 
 Alps of central Europe. The well known fan structure of the 
 Alps is a remnant of the huge inflated folds, whose extremities 
 appear to have been pressed together by the continuance of 
 the pressure after the folds had been formed. (See Fig. 93.) 
 
 We generalize, therefore, the important principle of lat- 
 eral pressure exerted in the earth's crust. 
 
 Given an enormous lateral pressure, then either the contig-
 
 GEOLOGICAL STUDIES. 
 
 uous parts of the crust will be 
 crushed together and inter- 
 mingled, or the crust will break 
 and certain strata will slide over 
 and between others; or, finally, 
 the crust will suffer wrinkling, 
 as shown in Fig. 94. When 
 once a form like this has been 
 inaugurated, then, evidently, all 
 increased pressure from the di- 
 rections A and _Z? will tend 
 further to elevate a and de- 
 press b and c. When, at length, 
 the weight of the fold a be- 
 comes very great, pressure 
 from the directions A. and B, 
 instead of lifting the fold higher, 
 will develop new folds at H 
 and G. The new folds will not 
 arise until the weight of a be- 
 comes sufficient to overcome the 
 rigidity of the crust at JFTamd Gr. 
 That is, when the crust is more 
 rigid, the fold a will be sus- 
 tained at a higher altitude. So 
 we deduce the principle that 
 the highest mountains will come 
 into existence in the epoch when 
 the crust possesses most rigid- 
 ity; that is, in times geologi- 
 cally recent; because, through 
 terrestrial cooling and contin- 
 ued sedimentation, the crust is 
 becoming thicker and more 
 rigid. A study of mountains 
 confirms the deduction, since all
 
 MOUNTAIN FORMATION. 
 
 173 
 
 the highest mountains are composed chiefly of Caenozoic and Meso- 
 zoic strata. 
 
 To illustrate further the effects of lateral pressure, and to de- 
 monstrate experimentally a probable origin of many mountains, 
 M. Favre, of Geneva, devised the experiment set forth in Fig. 95. 
 He spread a layer of clay on a stretched sheet of India rubber, 
 and allowed the sheet slowly to contract. The sheet may be five- 
 eighths of an inch thick, six and three-fourths inches wide, and 
 sixteen inches long. When stretched to twenty-four inches, it 
 may be covered with a layer of potters' clay from one to three 
 inches thick, made as adherent as possible to the India rub- 
 ber, with a block of wood applied at each end. The slow 
 contraction of the India rubber develops the appearances seen 
 
 
 FIG. 94. FORMATION OF WRINKLES IN THE EARTH'S CRUST, WITH PARALLEL CONTIOTJOI 
 
 FURROWS. 
 
 in the figure. Now, when you carefully inspect this figure, 
 you note several important points of resemblance to the moun- 
 tain corrugations on the earth's surface : (1) There is a set 
 of folds or anticlinals. (2) Some of the anticlinals are frac- 
 tured along the crest. (3) The folds present a tendency to be 
 elongated in a direction at right angles to the direction of 
 the pressure. We note, also, other points : (1) The upper 
 layers are more folded than the lower; the lower, therefore, 
 must have been shortened by squeezing together. Perhaps the 
 lower strata in the earth's crust have been similarly squeezed 
 together, or, instead, have suffered an infinite number of small 
 plications in place of large folds. (2) The corrugations are scat- 
 tered over the entire surface, instead of being grouped like
 
 174 
 
 GEOLOGICAL STUDIES. 
 
 mountain ranges, in a great chain. (3) The longitudinality and 
 parallelism of the folds arise from the 
 fact that the pressure was exerted from 
 two directions. As mountains present 
 similar characters, we may infer that 
 they also receive pressure from two 
 opposite directions. These seem to be 
 facts and valid inferences as far as they 
 
 go- 
 In the results of mountain making 
 we seem therefore to detect the evi- 
 dences of enormous lateral pressure ex- 
 erted from all directions, but especially 
 from directions at right angles with the 
 axes of mountain ranges. What data 
 have we for inferring the origin of these 
 pressures ? 
 
 Now, our attention has been di- 
 rected to some facts which seem to 
 indicate that the earth is a cooling 
 body, and has for many ages been 
 cooling. A cooling process is a shrink- 
 ing process. Hence the earth has 
 contracted in volume; its circumfer- 
 ence has become less. Now, if the mat- 
 ter of the crust or exterior had cooled 
 at the same rate as the interior, the 
 shrunken crust would still fit the 
 shrunken interior, and so no wrinkling 
 would be possible. But the crust is in 
 a position between the heated interior 
 and cold external space, and these con- 
 tending influences hold the temperature 
 of the crust at a point somewhat uni- 
 form; while all the heat emitted by the 
 interior, in this contest, tends continu-
 
 MOUNTAIN FORMATION. 175 
 
 ally to reduce its temperature. While therefore, the interior 
 shrinks, the crust retains its ancient circumference. It is there- 
 fore obliged to wrinkle to dispose of the surplusage. 
 
 But a general shrinkage of the earth would thus result in 
 a process of crustal wrinkling having no relations to parallels or 
 meridians. It would be a wrinkling like that of the skin of a 
 withered apple. There must be, to produce our meridionally dis- 
 posed mountains, some force acting more energetically from east 
 to west than from north to south; or else there must exist in the 
 crust some ingrained predisposition to yield to the action of east 
 and west forces. 
 
 Now, I think it may be shown that both causes have existed, 
 but the exposition of them would carry the elementary student 
 too far. Let us therefore simply state the principles and await 
 the opportunity for their full comprehension. (1) The earth has 
 shrunken more along its east and west circumference than along 
 its north and south circumference. This has resulted from dimin- 
 ishing oblateness due to gradually retarded rotation. (2) In- 
 grained meridional predispositions exist. I have elsewhere sug- 
 gested that the tidal action of the moon while the earth was yet 
 in the incrustive stage, must have implanted a meridional struc- 
 ture which predisposed to wrinkling more considerably in the 
 north-south direction than in the east-west direction. Ocean 
 pressures could have had no agency in initiating the direction of 
 mountain trends, since the axes of the earth's folds existed before 
 the oceans, and the bounds of the oceans were' indeed determined - 
 bv them from the beginning. 
 
 If we glance again at the plateaus of the Grand Canon (Fig. 
 87), we see a vast region shivered by faults. We see great slabs 
 of the earth's crust uplifted on one or more sides, sometimes to 
 mountain altitudes. Now while some fracturing of the crust 
 must have accompanied the actions which upraised mountain folds, 
 we cannot conceive of huge unbent slabs as a product of action, 
 whose characteristic it is to produce bent and crumpled rocky 
 sheets. Here we have the evidences of a force acting vertically, 
 not tangentially. It is as if an ioe-covered lake had been par-
 
 176 GEOLOGICAL STUDIES. 
 
 tially drained. The ice subsides and undergoes fracture along 
 countless sub-parallel and intersecting lines. Should the lake be 
 again filled, and then again drained, and this process several 
 times repeated, the joints in the ice would be opened; there 
 would arise dislocations. Some cuboidal masses would be lifted 
 up. The accompanying lateral motion would throw some into 
 confusion, and the whole would present some resemblance to the 
 actual aspect of these plateaus. Now we have the evidence of 
 a most copious escape of molten matter from beneath the crust 
 of the plateaus during the later stages of the continent's history. 
 In the present state of our knoweldge, perhaps we can do no bet- 
 ter than to connect with these lava outflows such fluctuations in 
 the level of the crust as might explain the great system of fault- 
 ings so characteristic of western geology. 
 
 Thus, our attention has been directed to the most obvious 
 characteristics of mountain forms and mountain mechanism; and 
 we have tried to infer from the phenomena, the way in which the 
 known forces must or may have acted to produce them. The 
 methods of mountain making are not yet fully understood; but 
 as far as we have here gone, our inferences probably represent 
 the truth. The whole subject is too large and too difficult for the 
 elementary student, and he should return to it in an advanced 
 course. 
 
 EXERCISES. 
 
 Look at Pig. 92 and point out the easterly end of the section. Draw a 
 line on the map showing where this section is located. What mountains 
 does it cross? Why is it not drawn exactly east and west? What is the high- 
 est peak? What is its height? What is the lowest point and its elevation? 
 If you were on the summit of the highest mountain, what would he the age 
 of the rocks under your feet? Look at the Table of Types of Mountain 
 Structures and point out the type to which this belongs. Point out others 
 of the same type. How much do you estimate the highest mountain to have 
 been lowered ? By what means was it lowered ? What type is Furnace 
 Mountain ? What type is the Hog Back? What is the length of this section 
 as drawn? Notice the formation marked 7; what is the name of it? Sup- 
 pose it restored from end to end of the section, then measure the total length 
 with scale and dividers; how much is it? What percentage then, did this
 
 VEINS AND OKES. 
 
 177 
 
 section shrink by being folded as it is? Point out here an anticlinal valley. 
 Point out a synclinal mountain. What are the evidences that this section 
 presents a series of folds? Why are the folds not perfect? Why was not 
 the crust mashed into heaps instead of folded, by the great lateral pressure? 
 Did any of the folds turn down? How many folds might be produced par- 
 allel with each other? Why would the central fold be highest? Why might 
 not the sixth fold be highest? Would the folds be narrow in proportion as 
 they are low? Should the rocks mash together what changes of temperature 
 would be produced? Would the sliding of one stratum over another pro- 
 duce any thermal effects? Would the bending of the strata produce any? 
 How high a temperature do you think might be produced by these mechani- 
 cal actions? Might the heat be sufficient to melt the rocks? Suppose there 
 were mere pressure, without motion, would heat be evolved? How might 
 metamorphism result from mountain making? 
 
 STUDY XXVII. Veins and Ores. 
 
 Let us return to the bowlder-strewn fields. We now fix our 
 attention, not on the kinds of rocks, but on their structure. 
 Everyone has noticed 
 thin sheets of certain 
 sorts of rock material 
 cutting through a rock of 
 some other sort. In 
 bowlders these intersect- 
 ing sheets sometimes be- 
 come very conspicuous in 
 consequence of the un- 
 equal weathering of the 
 two kinds of rock. A 
 sheet of this sort is a 
 vein. Here is a notable 
 specimen in the museum 
 of the University of Mich- 
 igan. The projecting part 
 is a portion of a quartz- 
 ose vein intersecting a mass of granite. This was once a fragment 
 
 FIG. 96. A QUARTZOSE VEIN IN A GRANITIC 
 ROCK. (From a specimen in the University of 
 Michigan.)
 
 178 
 
 GEOLOGICAL STUDIES. 
 
 of granite containing a quartzose vein which was probably evei> 
 with the general surface of the granite. Notice now how the vein 
 projects. That seems to be only because the granite, hard as it 
 is, has weathered away so much more than the vein. Many per- 
 sons suppose the granite passes through the quartzose slab, like 
 a plug. This excessive disappearance of the granite must be the 
 effect of weathering ; for any process of wearing which would 
 remove the granite on all sides would also remove the quartz. 
 Here, then, is a confirmation of the doctrine of rock weathering-, 
 to which we were brought by the facts considered in Study XVI. 
 In our wanderings among the bowlders, we often find a rock 
 intersected by many veins. They present 
 various forms. Sometimes they are smooth- 
 sided and sharply distinct from the rock 
 which they cut, as in Fig. 96. Sometimes 
 they blend with the rock. Often they branch 
 and pursue zigzag courses, and, splitting,, 
 unite again, inclosing portions of the rock. 
 Here, in Fig. 97, is an interesting example, 
 full of instruction, but not at all infrequent. 
 Study the forms and ramifications of these 
 veins. In some cases the different veins ap- 
 pear to be but branches of one vein; but 
 what must we say of a rock like this shown 
 in Fig. 98, where the veins are of different 
 sorts of material, and intersect each other in 
 a complex fashion. This shows a surface of 
 syenite on the beach at Salem, Mass. It is 
 thirty- six feet by twenty-seven feet. It was brought to notice by 
 Dr. Edward Hitchcock many years ago. Contemplate it atten- 
 tively. These numerous intersecting sheets are all veins. But as 
 there are numerous intersections, it is obvious that an intersecting 
 vein is more recent than one intersected. So the one which in- 
 tersects all the others is the last. The oldest is the one inter- 
 sected by all the others, or by others which are themselves inter- 
 sected by all the remaining ones, or by those which are finally so- 
 
 FIG. 97. 
 
 INTERSECTING VEINS 
 SEEN IN A BOWLDER, 
 ANN ARBOR.
 
 VEINS AND OKES. 
 
 179 
 
 intersected. These veins are numbered, and you may exercise 
 yourselves in showing that they are numbered in the correct order. 
 Veins 2, 5, and 9 are diabase; veins 3, 4, 10, and 11 are of red- 
 dish granite; vein 6, which is forty inches wide, is a porphyry, 
 and vein 7 is also a porphyry; vein 8 is granitic. Here are ten 
 different epochs of vein formation. The syenite mass has been 
 rent at least ten different times, and after each movement some 
 sort of vein material has filled the fissure. Was the material in- 
 jected from below in a molten state ? Or did it infiltrate in solu- 
 
 FIG. 98. VEINS IN SYENITE ON THE BEACH AT SALEM, MASS. 'E. Hitchcock.) ' 
 
 tion from the contiguous rock? Or was it poured in from the 
 top, either in a state of fusion or solution ? These questions pre- 
 sent themselves for reply; but the answers are not obvious, and 
 we had better postpone their consideration till we get other facts. 
 A little attention will bring to our notice veins having various 
 contents. Besides the materials mentioned, we often find ortho- 
 clase, in large crystalline masses, filling veins; sometimes calcite, 
 beautifully crystallized: sometimes pyrites, or galena, or blende. 
 All these cases, and others, occur among bowlders. In metallif-
 
 180 
 
 GEOLOGICAL STUDIES. 
 
 erous regions it generally happens that several different minerals 
 occur in one vein or gangue. They are, then, sometimes arranged 
 in alternating layers parallel with the rock wall, and each layer 
 is called a comb. In a regular 
 combed vein the combs are sym- 
 metrically arranged on each side 
 of the centre. This is shown in 
 the annexed Fig. 99, where A A 
 represent the country rock, or 
 rock formation, holding the vein, 
 and the bands a, b, c, etc., are seen 
 in a section across the filling of the 
 vein fissure, from wall to wall. 
 Here it appears, that after the fis- 
 sure was opened, the layers, or 
 combs a, a, were first laid on the 
 fissure walls. Then, under changed 
 conditions, the layers b, b were 
 laid upon the first. Subsequently, 
 with further changes, the layers 
 
 c, c and d, d were deposited. Sometimes, as in the "Three 
 Princes- Vein," near Freiberg, the number of combs is much 
 greater. This vein, Fig. 100, presents six different species of 
 minerals, occurring in eleven different combs on each side of the 
 middle four of the sorts being repeated. Examination of this 
 diagram will show the method of arrangement, and also the min- 
 erals of most frequent occurrence in metalliferous veins or lodes. 
 Minerals do not associate themselves together in lodes in 
 a promiscuous manner. When two minerals are present, they are 
 likely to be galena and blende, iron pyrites and chalco-pyrite, 
 gold and quartz, cobalt and nickel ores, magnetite and chlorite, 
 and so on. If three minerals are present, certain rules are also 
 observed; and if more than three, the geologist has learned what 
 to expect together. This association of minerals is known as 
 
 FIG. 99. SECTION ACROSS A VEIN FIS- 
 SURE AND ITS CONTENTS, SHOWING 
 A COMBED VEIN OF SIMPLE SYM- 
 METRY. (VonCotta.) 
 
 To illustrate further, in this connection, some of the principal
 
 VEINS AND ORES. 
 
 181 
 
 sorts of veins, the diagram, Fig. 101, is annexed. 
 , is one which traverses ^K8SSKsM. 
 a formation independ- 
 ently of its texture and 
 position. A. bedded vein, 
 b, traverses the country 
 parallel to its stratifica- 
 tion or foliation; but a 
 sedimentary layer must 
 not be mistaken for 
 such. A bed of coal is 
 not a vein. A bedded 
 vein often sends out 
 branches. A contact 
 vein, c, occurs between 
 two dissimilar forma- 
 tions. A lenticular vein, 
 d, d, thins out in all di- 
 rections. It must be 
 distinguished from len- 
 ticular beds. It bears no 
 
 relation to the stratifi- Flo . IOO ._THE THRKE PBINC 
 cation, and is, in fact, FREIBERG. (Von Weiss 
 
 only a true vein pinched in two in several places. 
 
 A true vein, 
 
 FIG. 101. DIFFERENT SORTS OF VEINS. (Von Cotta.)
 
 182 
 
 GEOLOGICAL STUDIES. 
 
 Most metalliferous ores occur in veins; but there are very im- 
 portant exceptions. Many rich lead mines occur in crevices or 
 caverns in limestones, which are lined by the ores of lead and zinc. 
 (Fig. 102.) Placer mining is a process of washing gravel and 
 
 sand to separate 
 the intermingled 
 metallic particles. 
 (SeeStudyXXIV.) 
 The great beds of 
 magnetite and 
 
 FIG. 102.-CBETICE IK LIMESTONE, SHOWING OCCURRENCE OF hematite OCCUr 
 GALENA AT SHULLSBURG, Wis. (Whitney.) mostly in hugelen- 
 
 a, Cap Rock. 6, Opening, with galena, c, Rock and detritus. ticular masse s con- 
 formable with the stratification of the inclosing schists. The 
 masses shown in Figs. 103 and 104 are portions of such lens- 
 shaped beds in northern 
 New York. In Figs. 105 
 and 106 entire masses are 
 shown. Here it is ap- 
 parent that the ore be- 
 longs to the same system 
 of stratification as the 
 country rock; and in fact, 
 the lines of bedding often 
 pass uninterruptedly from the rock through the ore. (See espe- 
 cially Fig. 105.) This indicates that the ore is segregated, or sep- 
 arated subsequently 
 to the deposition of 
 the original sedi- 
 ments a conclu- 
 sion similar to that 
 before reached in 
 reference to certain 
 concentric struc- 
 tures. (See p. 48.) 
 That the great beds 
 
 FIGS. 103 AND 104. OCCURRENCE or IRON ORE IN 
 ESSEX COUNTY, N. Y. (E. Emmons.) i, Beds 
 of ore/ q, Included masses of quartz or other 
 rock ; 6, Country rock. 
 
 FIGS. 105 AND 106. LENTICULAR MASSES OF IRON ORE 
 INTERSECTED BY LINES OP BEDDING. (After Brooks.) 
 
 105. Slaty, and blending with "country rock." Vulcan 
 Mine, near Waucedah, Wis. 
 
 106. Hard, with hanging wall of quartz, q, and "foot 
 wall " of jasper, ;'. Marquette Range, Mich.
 
 VEINS AND ORES. 
 
 183 
 
 of haematite and magnetite were originally involved in the sedi- 
 mentary process is still more clearly shown in cases where the 
 rocks are less metamorphic and the ore (generally a "lean" ore) 
 presents continuous beds as shown in Fig. 107, Jf, where the iron 
 schists are conformably interstratified in a section from the east- 
 ern portion of the Penokie range. 
 
 Metalliferous deposits are not to be sought for indiscrimin- 
 ately. In general, metamorphic rocks are more productive than 
 others. Certain products, also, are more likely to occur in rocks 
 of certain age. Finally, certain principles of association of min- 
 erals (paragenesis), as before stated, serve as a clew to the dis- 
 covery of particular metals. A few examples will illustrate the 
 distribution of the metals. 
 
 FIG. 107. SECTION THROUGH AN IRON EANGE IN WESTERN MICHIGAN BETWEEN LAKE 
 
 GOGEBIC AND MONTREAL RlVER, SHOWING POSITION OF THE IRON ORE, AND THE 
 
 RELATIONS OF FOUR SYSTEMS OF ROCKS. (Pninpelly and Brooks.) L, Laurentian 
 Granites, Gneisses, and Schists : H, Huronian Slates, Iron Schists, Quartzites, and 
 Diorites; C, Copper-bearing Rocks (Keweenianl, "South Range"; S, Sandstones of 
 Cambrian Age. 
 
 Iron is quite universally distributed. The great beds of mag- 
 netite, haematite, franklinite, and titaniferous iron are located in 
 the metamorphic strata of Eozoic age. In America, the two 
 former occur chiefly in northern New York, northern Michigan 
 and Wisconsin, and southern Missouri. In Sweden nearly all the 
 celebrated iron mines are of magnetite from Eozoic rocks. Titan- 
 iferous iron ore occurs at many localities in the United States, 
 Canada, Norway, and other countries. Franklinite is mined at 
 Hamburg, N. J. Siderite ranges from the Eozoic to the Carbon- 
 iferous strata, and in smaller quantities to later strata. In the 
 coal measures of Pennsylvania, Ohio, and elsewhere, it occurs as 
 an argillaceous ore, in nodules, and beds of clay-iron-stone.
 
 184 GEOLOGICAL STUDIES. 
 
 Limonite occurs in Mesozoic and more recent deposits; and also, 
 as bog iron ore, in modern marshes; also, by hydration of hfema- 
 tite, in rocks of greater age, as in Salisbury, Conn., and thence 
 through Pennsylvania and Tennessee to Alabama. 
 
 Lead, as galenite, and sometimes lead carbonate or cerussite, 
 occurs in pockets and fissures of the Lower Cambrian limestone in 
 Missouri and of Upper Cambrian ("Galena") limestone in Iowa, 
 Illinois, and Wisconsin. Its mode of occurrence is shown in 
 Fig. 102, the cubical crystals of galenite attaching themselves 
 to the limestone surfaces, and sometimes attaining a weight of 
 sixty to seventy pounds. Galenite also occurs in veins, in gneiss, 
 granite, argillite, and crystalline limestone, in various parts of 
 Europe, New York, and New England, and in the Carboniferous 
 Limestone of England and the continent. Galena is often worked, 
 as at Leadville and in the Eureka district, for the silver contained 
 in it. 
 
 Copper occurs in veins in metamorphic rocks of Europe and 
 America. Its principal ores are copper pyrites or chalcopyrite, 
 chrysocolla, malachite, and azurite. Native copper occurs in beds 
 and veins in the vicinity of dikes and beds of igneous origin. In 
 northern Michigan the associated rocks are now thought to be 
 of Keweenian age that is, next older than Cambrian. In New 
 Brunswick, New Jersey, Connecticut, and California, they are 
 Mesozoic. At some localities on Keweenaw Point and in Europe 
 in the " Thuringian copper slates," small particles are collected in 
 large abundance, as a sort of drift copper, deposited in beds. 
 Copper ores are partial to chloritic and hornblendic schists, 
 dolorites, and serpentines. 
 
 Silver is found native with the native copper of Lake Superior, 
 and also elsewhere in veins traversing gneiss, schists, porphyry, 
 and other rocks. In the form of ores, the most valuable are 
 argentite or "silver glance," stephanite (both abundant in the 
 Comstock lode, Nevada), cerargyrite or "horn silver" (chloride) 
 in veins of clay slate in Nevada, Idaho, Arizona, and South 
 America. Argentite is very commonly found with galenite.
 
 VEINS AND ORES. 185 
 
 Silver ores prefer silicious or argillaceous rocks to limestones or 
 dolomites. They also appear to avoid granite and red gneiss. 
 
 Gold is found only native, but it is very frequently alloyed 
 with silver, palladium, or rhodium. Its native place is quartz 
 veins intersecting metamorphic rocks, mostly chloritic, talcose, 
 and argillaceous schists. These range in age from the Eozoic to 
 the Tertiary. Gold avoids lime. The breaking up of the schists 
 has caused native gold to appear in the drifts of many regions; 
 and from these most of the world's supply has been obtained. 
 (Study XXIV.) The exhaustion of the " placers," however, has 
 driven miners very extensively to the quartz lodes in the mother 
 rock. The celebrated Comstock lode, which yields gold and silver 
 in nearly equal proportions, is mostly a sheet of crushed quartz, 
 dipping eastward 33 to 45, with a length of four or five miles 
 and a maximum thickness of about six hundred feet. It has 
 been mined to a depth of three thousand feet, where the enormous 
 outflow of water is found to have a temperature of 170. 
 
 Tin is found, as cassiterite, in rocks of great age mostly 
 eruptive and metamorphic never in limestones or dolomites. 
 The world's supply has come chiefly from Europe; but mines are 
 now worked near Harney, Dak., and deposits which promise to 
 grow valuable are reported from Mexico, Idaho, Montana, Wyo- 
 ming, and New Mexico, as well as from Ouster and other localities 
 in Dakota. 
 
 EXERCISES. 
 
 Correct this expression : Mr. A. has a vein of coal on his farm. If Mr. 
 A. has a bed of coal, lias he probably native silver also? What metalliferous 
 ores might he have? What are the prospects of a man exploring for coal in 
 dark metamorphic slates? What common mineral is most frequently mis- 
 taken for gold? Suppose pyrite and gold are both heated on a shovel, what 
 variations in color do they undergo? What is pyrite composed of? What is 
 the source of the acrid fume when pyrite is heated? Is it probable any gold 
 could be found in your neighbor's garden? Whence comes most of the cop- 
 per of the United States? In what form is it found? Explain how native 
 copper may occur in the drift of Ohio or Illinois. Did you ever hear of its 
 occurrence in those states? Would it be possible for native silver to occur at 
 Columbus. Ohio? What is the age of the rocks at Columbus? Would native
 
 18C GEOLOGICAL STUDIES. 
 
 silver, if occurring there, be found in the solid rocks or in the drift? Look 
 at Fig. 98, and state whether vein No. 3 was the first formed vein there 
 shown. How do you reason on the subject? Have you noticed that granite 
 has been treated as a sedimentary rock, and that here it appears as a vein? 
 Can a vein be also sedimentary? Could this granite vein be dissolved by any 
 means? What substances may we conceive in the water which saturated this 
 syenite at a former time? Can you think how the granite vein could have 
 been deposited through its walls? Do you regard it probable that any veins 
 have been filled by injections of melted matter? 
 
 jgk/v, \. !( i L 
 STUDY XXVIII. Geology of Salt. 
 
 Key West is an island about four miles long and nearly one 
 broad. Through the centre, for two and a half miles, extends a 
 series of ponds, which are one or two feet lower than medium 
 high tides. The ponds seem to have been formerly connected 
 with the sea, and to have been cut off by the ridges of sand 
 thrown on the beach by the waves. The separating ridges, 
 though higher than the ordinary tides, are still lower than the 
 high tides, which occur twice a year in early winter and in 
 midsummer. The high tides, therefore, flow into the ponds. 
 After the ponds have thus been filled, or partially filled, by the 
 winter tides, they remain exposed to the powerful evaporative 
 influence of the sun until the next midsummer. By this time 
 the water is much condensed. Another influx of high tides 
 restores, perhaps, the volume of water, but the resulting brine is 
 salter, since no salt went out by evaporation, though additional 
 salt now comes in. During another period of mean tides a large 
 amount of evaporation again takes place, and the contents of the 
 ponds become denser than before. This process has gone for- 
 ward before our eyes. We know it is a fact. By and by it has 
 been repeated so many times that the brine is completely satu- 
 rated. Then, when the next high tides flow in, arid the next 
 evaporation follows, the oversaturated brine begins to deposit its 
 exc-ess of salt. The next year more salt is deposited. Thus, in 
 course of time, the ponds contain a supply of saturated brine,
 
 GEOLOGY OF SALT. 187 
 
 and the bottom is covered by a bed of salt. Now, this condition 
 was actually reached when the state of things was discovered by 
 the crews of vessels which made a landing, and raked large quan- 
 tities of salt from the ponds and carried it away. These things 
 are matters of observation. Let us think about them. 
 
 Suppose some 'large bay or gulf should become cut off from 
 the ocean, so as to have communication with it only at high 
 tides. Suppose, for instance, it should be the Red Sea. Then, 
 if the evaporation during- the year were greater than the supply 
 of fresh water from the inflowing streams and the clouds, each 
 year's evaporation would increase the density of the water. If, 
 occasionally, through high tides, or extraordinary storms, there 
 should be a fresh influx of sea water, the amount of salt eventu- 
 ally introduced into the basin would become indefinitely great, 
 and, crystallization of salt having at length begun, the amount 
 deposited would increase until the conditions should change. 
 Some sediment, more or less, would find its way, also, into the 
 sea, and would mingle with the precipitated salt. The sea 
 would thus be gradually filled up. It is supposable that the 
 obstruction at the straits might finally increase until all access of 
 the Indian Ocean should be prevented. This might result from 
 an elevation of the region about the straits. The filling of the 
 basin would now be completed, chiefly by fragmental deposits. 
 Or if, before the filling of the basin, a subsidence should be expe- 
 rienced, a new influx of the ocean would bring new beds of sedi- 
 ments over the salt accumulations precipitated and buried in a 
 previous age. If, instead of subsidence, or if, after a period of 
 subsidence and sedimentation, there should be an elevation of 
 the region, then it would become a part of the land. We have 
 already learned that events of this nature have taken place again 
 and again in the history of the world. 
 
 Suppose we stand upon that land. There are beds of salt 
 under us. If we dig down, we shall sooner or later reach them. 
 These salt beds were once the bottom of the sea. We may find 
 more or less pure salt; but we shall certainly find, also, the 
 mechanical sediments which were borne into the sea while the
 
 188 GEOLOGICAL STUDIES. 
 
 salt was crystallizing', and after the salt had ceased to crystallize. 
 We shall find, also, everything which was originally in the sea 
 water. 
 
 What, now, shall we conclude when we see men digging salt 
 from the earth in the county of Chester, near Liverpool ? Here, 
 at Northwich and Winsford, after penetrating through gypseous 
 clav 120 feet, beds of rock salt are found sixty to ninety feet 
 thick. Beneath these are indurated clays for thirty or forty feet, 
 containing beds of rock salt, and below these, 100 feet more of 
 rock salt. Much of this salt is earthy, but some is quite pure. 
 The salt is dissolved, often in sea water, and then evaporated in 
 pans by artificial heat. This is what we see going on at the 
 surface. Are we not led to conclude that here, in Cheshire, is a 
 salt formation quite similar to the one which we supposed formed 
 in the Red Sea ? When we look about, we see Cheshire lying in 
 a geological trough, bounded by the hills of Yorkshire on the 
 northeast, and the highlands of Wales on the southwest. The 
 formation filling the trough is the Triassic. We can understand 
 that that valley was once a bay projecting inward from the At- 
 lantic Ocean, and was probably filled precisely as we have sup- 
 posed of the Red Sea. 
 
 We may subject this conclusion to severer tests. If we take 
 a portion of sea water and evaporate it, we find precipitated suc- 
 cessively peroxide of iron (not in all cases), gypsum, common 
 salt, and epsom salts, or magnesium sulphate. Calcium, mag- 
 nesium, and potassium chlorides remain. If we take the natural 
 brine from a well in Cheshire or Syracuse, and evaporate it, the 
 same succession of precipitates is obtained. The peroxide of 
 iron is thrown down in the " clearing vats." The gypsum forms 
 the first crust on the bottoms of the kettles or pans. The com- 
 mon salt is next crystallized out (in part), and the chlorides 
 remaining form the "bitterns." Examining more closely one of 
 the salt formations for instance, the Salina we find in the 
 lower beds some ferruginous clays; above these, gypseous clays, 
 and clays with masses of gypsum arranged in horizontal courses; 
 still higher, supplies of brine, and in many districts, vast beds of
 
 GEOLOGY OF SALT. 189 
 
 rock salt. Still above are limestones with acicular cavities, which 
 seem to have been once occupied by needles of epsom salts. 
 Here is a close correspondence, and on these evidences we may 
 rest our theory of the origin of salt formations. 
 
 The theory is not intended to apply to cases where salt is con- 
 fined to a vein or dike, as at Bex, in Switzerland. Sometimes, 
 undoubtedly, streams have been fed by brine springs issuing from 
 older formations, and, discharging into inland lakes without out- 
 lets, have undergone evaporation and produced new salt forma- 
 tions. Some of the salt lakes of our western territories probably 
 have an origin of this sort; but their remote origin was in the 
 sea water which salted the salt formations which now surround 
 or underlie them. The Caspian and Aral seas, however, are un- 
 doubtedly remnants of the ancient ocean; and when they disap- 
 pear, salt formations will occupy their sites. The process is 
 already far advanced in many of the bays of the Caspian and the 
 outlying lakes along its borders. 
 
 Turn once more to the geological map, page 118, and fix atten- 
 tion on the formations stretching east and west through central 
 New York. Thev all dip southward, or away from the Eozoic of 
 Canada. We once constructed a section from Canada to Pennsyl- 
 vania (Fig. 53), which shows this dip, but greatly exaggerated. 
 Now, the Salina group, which is the great salt formation of New 
 York, occupies a position in the upper part of the Silurian, as you 
 must remember (see Fig. 39). The Helderberg, which holds a 
 place above it, is almost wanting in central New York, and con- 
 sequently the outcrop of the Salina at Syracuse is close by the 
 lowest Devonian that is, the Oriskany sandstone and the Cor- 
 niferous. Its place may be marked on the section Fig. 53. 
 
 Now let us make a section on a larger scale for the purpose of 
 showing more clearly the geological position of the brines ob- 
 tained at Syracuse and worked under the auspices of the state 
 for about a hundred years (Fig. 108). Here we see the Salina 
 formation excavated at its outcrop. The excavation has become 
 filled with drift materials. A depression remained in the drift 
 which permitted a shallow lake to exist for a geologic period;
 
 190 
 
 GEOLOGICAL STUDIES. 
 
 but this has now shrunken to the present Onondaga Lake which 
 is bordered on the south by a marsh. Beyond the marsh is the 
 hard ground on which Syracuse is built; and beyond this rises a 
 hill underlaid by the Corniferous and Onondaga limestones. On 
 the slope of the hill may be found some outlying fragments of 
 the Oriskany sandstone. Now, the brine which saturates some 
 portions of the Salina strata, overflows at the border of the form- 
 ation, and saturates the bed of drift material filling the excava- 
 tion just mentioned. The rains falling on the surface rest on the 
 top of the denser brine, instead of settling down, and the sur- 
 plus flows into Onondaga Creek. Accordingly, the wells dug in 
 
 Fio. 108. GEOLOGY OP THE SYRACUSE BRINES. SECTION ACROSS THE ONONDAGA SALT 
 BASIN AT SYRACUSE, N. Y. c, Corniferous Limestone; o, Oriskany Sandstone; h, 
 Helderberg Group ; , Brine Wells. 
 
 the saturated drift receive a supply of brine; and the deepest ones 
 obtain the strongest brine. These are about 400 feet deep. 
 
 Notice that the brine supply is merely an overflow from the 
 formation, and must be comparatively weak and limited in 
 amount. But notice that the formation to the south of Syracuse 
 sinks to a greater depth. From this it maybe inferred that arte- 
 sian borings some miles south would reach stronger supplies, and 
 perhaps even a bed of rock salt. Farther west, in Wyoming 
 county, experiments of this kind have disclosed the existence of 
 large supplies of native salt. 
 
 Referring to the map again, it will be seen that the Silurian 
 passes in a basin slope under the peninsula of Michigan and lakes
 
 GEOLOGY OF SALT. 
 
 191 
 
 Huron and Michigan. The Salina which lies near the top of this, 
 outcrops on the east, at Grand River in Ontario; on the west, at 
 Milwaukee; on the north, at Mackinac and on the south, at San- 
 dusky. This basin retains, therefore, all its ancient salinity. 
 Accordingly salt borings carried to the appropriate depths in almost 
 any part of the peninsula, reach either abundant strong brine or 
 a thick bed of salt. The diagram Fig. 109, illustrating these 
 relations, shows a gradual increase in the depth of the salina 
 basin, as we approach the centre of the peninsula. The salina 
 formation is productive on the eastern and western borders, and 
 on the northeast in the Huron peninsula, and at Alpena on Thun- 
 der Bay. 
 
 FIG. 109 GEOLOGY OF MICHIGAN BRINES. (Vertical Scale much exaggerated.) Form- 
 ations indicated by numerals (see Table, Pt. II. ch. ii). 11, Huron Group, consisting 
 of Gencsee Shale, Portage and Chemung; 12, Marshall Sandstone; 13a, Michigan Salt 
 Group; 14a, Parma Sandstone (Coal Conglomerate). Geological Positions of Bri-ne 
 Wells: /, St. Clair Group; II, Port Austin Group; III, Manistee and Muskegon: IV, 
 Original Well, Plaster Quarries; V, Grand Rapids; VI, Lansing (last three unproduc- 
 tive) : VII, Saginaw Valley; VIII, Bay City, shallow wells; IX, Ann Arbor Artesian 
 Boring, 755 feet (no result). 
 
 But the characteristic salt' formation of this state is the 
 " Michigan Salt Group", which constitutes the lower part of the 
 Carboniferous Limestone (see Fig. 39), and whose position is shown 
 in the preceding diagram. This basin underlies the greater part 
 of the peninsula. As the strata are too compact to permit the 
 extensive accumulation of brine, the brine sinks into the underly- 
 ing sandstone, known as the " Marshall Sandstone," and indicated 
 in the " Geological Column " as the probable equivalent of the 
 " Catskill Group " at the bottom of the Carboniferous System 
 or as many think, at the top of the Devonian. The densest 
 brine, as in other cases, is somewhat remote from the out-
 
 192 GEOLOGICAL STUDIES. 
 
 cropping border of the Marshall reservoir, though the line of 
 outcrop is marked by a circle of salt springs. This basin sup- 
 plies the celebrated wells along the valley of the Saginaw River. 
 No native salt is known to exist in the Michigan Salt Group, and 
 it is apparent that the brine will eventually become exhausted. 
 The group contains enormous deposits of beautiful gypsum. This 
 exists in a continuous stratum from side to side of the penin- 
 sula. It shows again the same association with salt as occurs in 
 sea water. 
 
 Still another salt basin is formed in Michigan by the Coal 
 Measures. The brine accumulates in the underlying "Parma 
 Conglomerate." (See Figs. 39 and 109.) The shallow wells at 
 Bay City, on the Saginaw River, are supplied from this source. 
 The generally saliferous condition of the formations in Michigan 
 seems to depend on their dish-like conformation. As a result of 
 this, they have retained most of the soluble constituents left in 
 them by the ancient sea water. There are even indications that 
 a productive salt basin exists between the Salina and the Mar- 
 shall sandstone, in the so-called " Huron Group," which embraces 
 the " Chemung " of Fig. 39. These strata are everywhere satu- 
 rated with brine and "bitterns"; and they supply the numerous 
 " mineral wells " of the state. 
 
 Strata belonging to the horizon of the Michigan salt group 
 are similarly productive of brine and gypsum in Nova Scotia and 
 New Brunswick. The brine accumulations in Ohio seem to be in 
 the Waverly sandstone; those of Kentucky are in the "knob- 
 stones," and those of Tennessee are in the " silicious group." 
 These are all the geological equivalents of the Marshall sand- 
 stone. 
 
 Other salt deposits of the western United States are found in 
 the Cretaceous. The salt and gypsum deposits at and near Salt- 
 ville, in Washington county, Va., are thought by Stevenson 
 to be not older than Tertiary. The salt is from 200 to 500 feet 
 thick, mingled with some red clay; and the gypsum occurs in 
 detached masses, enwrapped in the clay. The basins are exca- 
 vated along a fault which has brought Lower Carboniferous and
 
 GEOLOGY OF SALT. 193 
 
 Cambrian formations into juxtaposition. The singular formations 
 at Petite Anse, La., are probably also Tertiary or Post-Tertiary. 
 Most of the salt formations of Europe are in different members 
 of the Triassic. Those of Russia are in the Permian; those of the 
 Austrian Alps, in the Jurassic; those of the Pyrenees and of Car- 
 dona, in the Cretaceous; while those of Wielicza, in Galicia, of 
 Tuscany and Sicily, are Tertiary. Salt also occurs as a volcanic 
 product. The borings at Stassfurt, Germany, have penetrated 
 1.066 feet of Triassic rock salt, and at Sperenberg, 5,084 feet, 
 without reaching the bottom. The Stassfurt salt manufacture is 
 important. 
 
 EXERCISES. 
 
 If the Mediterranean is salter than the open sea, how can the fact be 
 explained? If the Black Sea were not salter than the Atlantic, how might 
 the fact be explained? Why is it necessary to redissolve the salt found 
 native in Cheshire, England? What caused the clayey state of some of the 
 salt? Was the salt deposited as a sediment? How might gypseous deposits 
 occur above salt beds as well as below ? What is the cause of the rusty stain 
 seen in some inferior samples of salt? What causes the moist condition of 
 some inferior salt? Would pure salt be best obtained by slow evaporation, 
 or by rapid? Will you explain why? What position of the strata is most 
 favorable for retaining their brine? W T hat position is favorable forgetting 
 the salt leached out? Draw a diagram showing how a salt formation might 
 become destitute of brine. In boring a salt well, would veins of fresh water 
 sometimes be passed? How could fresh water be prevented from running 
 down and mixing with the brine? Suppose the Michigan salt basin fall of 
 brine; where would the surface level stand? Could the brine be anywhere 
 higher than the border? Suppose the border deeply notched on one side,' 
 where would the surface level of the brine be? Is the surface of the land 
 above or below the probable surface level of the brine in that basin? If 
 higher, will the brine then rise to the level of the land? (See Fig. 109.) 
 Why could not a brine well be a flowing well? May the water from a flow- 
 ing well be brackish? Draw a diagram explaining your view. In a fresh- 
 water artesian well must we also have a basin arrangement? Would a flow- 
 ing well be possible with a basin arrangement? Suppose the rock arrange- 
 ment for a flowing well such, for instance, as supplies Chicago (Fig. 55), 
 should be filled with brine, would we not have a flowing well of salt water? 
 W T ould it last indefinitely? What would it become, and why? Why must a 
 flowing well be n well of fresh water? Then how can we have a permanent 
 flowing mineral spring? 
 
 V
 
 194 GEOLOGICAL STUDIES. 
 
 STUDY XXIX. Geology of Petrol* ton. 
 
 At the mouth of Thunder Bay, of Lake Huron, is a little 
 island known as Sulphur Island. It rises but a few feet above 
 the level of the water, and its surface is strewn with a deep bed 
 of water-worn fragments of black bituminous shale (see Study 
 XI, and especially XIII). A few years ago some fishermen built 
 a camp fire on the the bed of shale, and the shale itself took fire 
 and burned deep into the ground, and continued to burn for some 
 months. The pieces of shale were not reduced to ashes, but re- 
 tained their form. The bituminous matter burned out and they 
 were left with a reddened appearance. Indeed the bitumen was 
 seen to fry out of the heated fragments and become ignited. 
 Near by, on the main land, is a solid bed of this shale, and there 
 are some fossils in it which we have found nowhere except in the 
 " Genesee Shale" at the top of the Hamilton Group (Fig. 39). 
 Now this Genesee Shale extends from Central New York into all 
 our western states. The observation at Sulphur Island, and sim- 
 ilar ones elsewhere, suggest that the formation contains an enor- 
 mous supply of bituminous matter. Bituminous matter is not 
 always exactly the same. It is everywhere composed of carbon, 
 hydrogen and a little oxygen. Carbon and hydrogen combine in 
 many different proportions to form hydrocarbons. Some of the 
 compounds are solid or tarry, some are liquid and some are gase- 
 ous. Examples of these are asphaltum, coal tar, kerosene, naph- 
 tha, benzole, illuminating gas (Study XIII). The bituminous 
 matter which heat expels from the Genesee Shale is a mixture of 
 several of these. What we call kerosene, then, is contained in 
 Genesee Shale. 
 
 Reasoning in this way, the enterprise was instituted some 
 years ago, of extracting burning oil from black shales. It was 
 successfully done at Dartmoor in England, Autun in France and 
 Bllhl in Prussia. It was much more successfully done in Breck- 
 enridge county, Kentucky, from cannel coal, which is only a black 
 shale peculiarly rich in carbon and hydrogen. It can be done
 
 GEOLOGY OF PETROLEUM. 195 
 
 with greatest success from certain substances known as Torbanite, 
 Albertite and Grahamite. But all undertakings of this class were 
 rendered profitless, about 1859, by the discovery of enormous 
 supplies of natural oil on Oil Creek, in Pennsylvania; and afterward 
 in many other regions. This natural oil, or petroleum, is essen- 
 tiallv a bitumen. It consists of several hydrocarbons mixed. 
 In different localities, it is light, or amber-colored or dark; it is 
 thin, or dense, or tarry, according to the proportions of the 
 lighter and heavier compounds. It closely resembles the sub- 
 stance obtained from black shales by artificial distillation. Is it 
 possible the native petroleum comes also from black shales 
 through a process of natural distillation ? Let us examine the 
 circumstances. In western Pennsylannia, the oil is found accu- 
 mulated in porous sandstones some hundreds of feet below the 
 surface. They are in part, at least, sandstones of the Chemung 
 Group. Below them lies the very same Genesee Shale before 
 referred to (see Fig. III). Should that undergo a process of dis- 
 tillation, the products being lighter than water would rise through 
 the water-saturated rocks to some formation in which it could 
 not escape. Suppose the depth to be 800 feet; is it allowable to 
 assume the temperature at that depth sufficient to promote a dis- 
 tillation, however slow ? In our judgment it is allowable. 
 
 Let us examine the situation in other localities. At Oil 
 Springs and other points in Ontario, oil has long been obtained 
 by boring through surface clays into the Hamilton limestone a 
 depth of one, two, or three hundred feet. This is quite below the 
 Genesee Shale. But there lies at the bottom another and very 
 similar black shale, called the Marcellus. So the same kind of a 
 source is present as in Pennsylvania. But instead of a porous 
 sandstone here to serve as a reservoir, we have the shattered and 
 cavernous limestone; and the clayey covering of drift shuts it in 
 (Fig. 110. II}. 
 
 But we find in Ontario another quality of oil, derived from 
 -another source. In the same township are wells which consist of 
 shafts sunken through the drift to the rock, and these obtain a dark 
 and tarry petroleum, which is used for lubricating purposes (see
 
 196 
 
 GEOLOGICAL STUDIES. 
 
 Fig. 110). The diagram shows the Genesee Shale above the Hamil- 
 ton Limestone extending under the region of these wells. This be- 
 comes the source of oil which rises into the gravel bed at the bottom 
 of the drift and saturates it, and thence flows into the well. But 
 the oil undergoes some evaporation in consequence of the par- 
 tially pervious character of the drift, and hence appears more 
 tarry than the oil from greater depths. Both situations here 
 favor our conjecture. Let us turn to West Virginia. 
 
 Here we find ourselves over the Coal Measures; and find like- 
 wise, two situations in which petroleum accumulates. First, we 
 get the principal accumulation in what probably answers to the 
 Conglomerate (Fig. Ill), and we find below, a series of Sub-Con- 
 glomerate Coal Measures, which are indicated in Fig. 39. These, 
 
 FIG. 110. GEOLOGY OF PETROLEUM IN ONTAKIO. C\ Corniferous Limestone; M, Marcel- 
 IUB Shale; H, Hamilton Limestone; 6, Genegee Shale; 7), Drift, with gravel at 
 bottom and impervious clay above. 7, "Surface Well" at Oil Springs; 77, Com- 
 mon bored wells ; 7/7, Test well, bored 600 feet. 
 
 like the true Coal Measures, contain strata of dark bituminous 
 shale. The Sub-Conglomerate Shales are, therefore, in the precise 
 position to answer the same purpose as the similar Genesee and 
 Marcellus Shales in the other cases. Oil also accumulates in the 
 Conglomerate in southwestern Pennsylvania, southeastern Ohio 
 and northeastern Kentucky. 
 
 Secondly, we find some oil accumulated in the sandstones of 
 the proper Coal Measures. Some of the interstratified black 
 shales lie beneath the horizon of oil accumulation, and are. there- 
 fore, in position to yield oil by distillation, which may rise into 
 the sandstones. 
 
 On the Cumberland River, in southern Kentucky, manv years
 
 GEOLOGY OF PETROLEUM. 107 
 
 ago, in boring for salt, a large supply of oil rushed forth. The 
 situation here is on the Trenton Group of the Cambrian. (Fig. 
 39.) When we come to a detailed examination of this group, we 
 find the upper half of it (Cincinnati sub-group) composed of 
 shales, marls, and limestones. In New York the divisions of this 
 sub-group are named Hudson River Slate above and Utica Shale 
 below; and the latter is described as "a dark -colored slate fre- 
 quently loaded with carbon" (Mather), and, indeed, often igno- 
 rantly explored for coal. Now, wherever this condition of the 
 lower part of the Cincinnati sub-group exists, we have the same 
 provision as before for the evolution of petroleum. On the 
 Great Manitoulin Island of Lake Huron a small amount of oil 
 has also been obtained from the Cincinnati sub-group. 
 
 In the neighborhood of Glasgow, Ky., some petroleum has 
 been obtained. The locality is on the shattered and cavernous 
 Carboniferous Limestone; and the fluid accumulates in the fis- 
 sures, as in the fissures of the Hamilton Limestone of Ontario. 
 Underneath we find some silicious, dark-colored shales, and below 
 these the widespread Genesee Shale full of hydrocarbonaceous 
 matter, as elsewhere. (Fig. 111.) 
 
 In this survey of the facts we find that oil accumulation sus- 
 tains no uniform relation to deposits of coal. The oil is not 
 derived from coal. The situation in every oil region, except 
 West Virginia, is geologically below the coal, and geographically 
 remote from coal. Nor do we find in beds of coal any exudation 
 of oily matter, while in black shales we generally find it. In, 
 Carbonaceous Shales the hydrocarbons manifest a predisposition 
 to form and escape. Mixture of aluminous matter with the car- 
 bon may be the predisposing cause. Beds of carbon nearly free 
 from argillacous matter do not undergo the change. 
 
 We should not overlook the fact that many limestones 
 especially the Corniferous and the Niagara are in some regions 
 densely charged with bituminous matter. This fact has led to the 
 opinion that the source of the oil is in limestones rather than 
 black shales. Accordingly, a "test well" was bored at Oil 
 Springs, Out., six hundred feet deep, and the Corniferous Lime-
 
 ,108 GEOLOGICAL STUDIES. 
 
 stone was penetrated (Fig. 110), but without any additional sup- 
 ply of oil. The same limestone has been many times penetrated 
 in Ohio and Michigan, but no supply was ever reached. The 
 tarry Niagara Limestone was bored into in Chicago, but artesian 
 water was obtained instead of a supply of oil. (Fig. 55.) 
 
 It seems reasonable now to infer, from the uniform relations 
 of the facts, that some carbonaceous, shaly formation is always 
 the source of the petroleum, and that it is eliminated from this 
 by a slow process of spontaneous distillation, under the influence 
 of sUch temperatures as exist within the crust of the earth. 
 
 The following, then, are the conditions of oil accumulation in 
 quantities of commercial importance: 
 
 1. A source below, from which the oil is elaborated. This 
 we find from observation to be always a bituminous shale. 
 
 2. A reservoir above, in which the oil is accumulated. This 
 is a sandstone, or a shattered limestone, or shale. 
 
 3. A slightly anticlinal position of the reservoir, to prevent 
 the lateral spread and wastage of the oil. 
 
 4. An impervious covering, to prevent the escape of the oil 
 to the surface and volatilization there. 
 
 If the reservoir is wanting, the presence of the shale is un- 
 availing. If the anticlinal is crowned by a break, .it may result 
 in the escape of the oil. In the course of ages the volatilization 
 of the light hydrocarbons may leave a fissure filled with the solid 
 residue. Thus is formed the Grahamite of West Virginia, and 
 also the Albertite of Nova Scotia. If the impervious covering is 
 wanting, the oil may rise to the surface, and a residue, like that 
 forming the "gum beds" at Oil Springs, Ont., will be deposited; 
 or, on a larger scale, extensive beds of asphaltum will remain, as 
 in Santa Barbara and Los Angeles counties, Cal. ; on the islands 
 of Cuba and Trinidad, in the West Indies; in Egypt, Palestine, 
 and other countries. The Egyptian asphalt has for centuries 
 been famous for its useful qualities, and is extensively used in 
 Europe for streets. California asphaltum also finds extensive 
 use. 
 
 Let us now bring the facts together in a tabular exhibit:
 
 GEOLOGY OF PETROLEUM. 
 
 199 
 
 CONSPECTUS OF THE GEOLOGY OF PETROLEUM. 
 
 - < 
 
 E-S 
 
 FORMATION'S. 
 
 DRIFT GRAVEL (10) 
 
 SANDSTONES (9) 
 Bituminous Shales (/> 
 
 SOURCE OF OIL. 
 
 to 
 
 OIL REGIONS. 
 
 Oil Springs, Ont. 
 Cal., in Los Angeles County, 
 etc. 
 
 COAL MEASURE SANDSTONES 1.8) () /. 
 
 Coal Measure Shales (e) 
 
 COAL CONGLOMERATE (7) (d) (c) (6) H. 
 
 Shales and Shaly Coals (d) 
 
 CARBONIFEROUS LIMESTONE (6) (c) 
 t WAVERLY SANDSTONE (5) (c) 
 
 CIIEMUNG SANDSTONE (4) (c) 
 
 {GENESEE SHALE (3) 
 Genesee Shale (c) 
 HAMILTON LIMESTONE (2) (b) 
 
 Marcellus Shale (b) 
 
 Corniferous Limestone 
 'Niagara Limestone 
 
 {FISSURED SHALT LIMESTONE (1) (a) 
 Black Utica Shales (a) 
 
 WestVa.; Southwest Pa. 
 
 j Southwest Pa.; W.Va.; North- 
 ( east Ky. 
 
 j Glasgow region, Ky. (part.) 
 ( Contiguous part of Tenn. 
 Central O. ; Venango Co., Pa, 
 
 j Northwest Pa.; Southern N. 
 / Y.; Northeast O. 
 
 E. Glasgow region, Ky. (part.) 
 
 ( D. Bothwcll, Ont. 
 ( C. Enniskillen. Ont. 
 
 Bituminous generally. 
 Bituminous frequently 
 
 B. Manitoulin Island. 
 A. Burksville, Ky. 
 
 Here the various formations concerned are arranged in geo- 
 logical order. Those which serve as the source of petroleum in 
 America are printed in italics; those which serve as reservoirs, ' 
 in small capitals. The letters (a), (b), (c), etc., are used to des- 
 ignate sources; the numerals (1), (2), (3), etc., denote reservoirs, 
 and the letters A, B, C, etc., indicate regions. 
 
 The foregoing facts are otherwise set forth graphically in the 
 accompanying diagram, Fig. 111. Petroleum is known to exist 
 to some extent in all formations from the Eozoic to recent de- 
 posits. 
 
 Other important localities of petroleum, besides those men- 
 tioned, are Baku, on the western border of the Caspian, in Geor- 
 gia, Rangoon, Burmah, and the duchies of Parma and Modena, in
 
 200 
 
 GEOLOGICAL STUDIES. 
 
 Italy. It is also very recently 
 reported from Deli, on the 
 east coast of Sumatra, one 
 well yielding 270 barrels a 
 day. The Baku petroleum oc- 
 curs in a porous, argillaceous 
 sandstone of Tertiary age. 
 In the vicinity are hills of 
 volcanic rocks, through which 
 springs of the heavier sorts 
 flow out. The Rangoon oil 
 is obtained from wells sunk 
 sixty feet in beds of sandy 
 clay, which rest on sandstones 
 and argillaceous slates. Un- 
 der the slates is said to be 
 " coal," but the strata are 
 probably of Tertiary age, and 
 the coal is likely to be an 
 argillaceous lignite or a bitu- 
 minous shale. In Los An- 
 geles and neighboring coun- 
 ties, Cal., the yield from Ter- 
 tiary strata was 5,000,000 
 gallons in 1882, and 262,000 
 barrels in 1884. 
 
 Illuminating oil may be ob- 
 tained from all organic sub- 
 stances by distillation. Petro- 
 leum is probably derived from 
 both animal and vegetable 
 remains. That occurring in 
 limestones may be of animal 
 origin, but that derived from 
 black shales more probably 
 has a vegetable origin.
 
 GEOLOGY OF PETROLEUM. 201 
 
 The production of natural gas in 1885 and subsequently has 
 grown to a wonder not inferior to the yield of petroleum which 
 began in 1859. It escapes from wells bored in certain districts, 
 generally 1,500 to 2,000 feet deep. The gas is a varying mix- 
 ture of light and heavy carburetted hydrogens chiefly, however, 
 marsh gas and escapes generally under the very high pressure 
 of 100 to 700 pounds to the square inch. In the vicinity of 
 Pittsburgh, not less than 150,000,000 cubic feet were produced 
 daily in the latter part of 1885, and 60,000,000 were already 
 introduced into the city. Sixty-five to seventy millions were 
 daily wasting in the Murraysville district alone. Gas fuel has 
 already revolutionized the manufactures of the city. It is 
 reported, also, that pipes are being laid for conveyance of the 
 gas to Buffalo and Cleveland. Meantime, enormous supplies of 
 gas have been reached in northern Ohio from wells which seem 
 to penetrate the Cambrian. One is located at Cleveland. At 
 Fremont, it is said, 2,000,000 feet were (in January, 1886) 
 yielded daily. Gas and oil are reported at Lima, at the depth of 
 1,251 feet. The " Great Karg Well," at Findlay, Ohio, is reported 
 (April, 1886) to yield 10,000,000 feet daily from a depth of 
 1,144 feet. The ignited jet ascends 115 feet. 
 
 It is impossible that such enormous supplies of oil or gas 
 should continue many years. Reproduction is undoubtedly in 
 progress, but it is comparatively slow. We are using and wast- 
 ing the accumulations of millions of years. 
 
 EXERCISES. 
 
 When black shale burns with a flame, why does it not crumble to ashes 
 like coal? What causes the i-eddened appearance of burned shales? Name 
 some localities where oil springs occur. Can you tell why Paint Creek, in 
 Kentucky, is so named? Is the vicinity of an oil spring the best place to 
 bore for oil? If not, why not? Does mineral pitch dissolve in water? 
 What causes the durability of asphaltum when used for pavements? What 
 are the characters of lubricating oil? Can you describe the odor of the 
 Ontario oils? Why is kerosene sometimes called "coal oil"? What is 
 Breckenridge oil? What sort of coal is found in Breckenridge county? 
 How does it differ from a bituminous or carbonaceous shale? Would there
 
 202 GEOLOGICAL STUDIES. 
 
 be a good prospect of success in seeking an oil well at Ontonagon, Lake 
 Superior? Look over this list of localities, and indicate, as nearly as you can, 
 those most favorably situated for oil wells, and those least favorably situated : 
 Potsdam, N. Y. ; Hartford, Conn. ; Waukesha, Wis. ; Mobile, Ala. ; Chatta- 
 nooga, Tenn. ; Bingharnton, N. Y. ; St. Clair, Mich. ; Erie, Penn. ; Wheel- 
 ing, W. Va. ; Frankfort, Ky. ; Montreal, P. Q. : Sarnia, Ont. Have you 
 carefully considered what formations underlie these places? Have you indi- 
 cated the oil-producing formations under them ? Have you indicated forma- 
 tions suited to serve as reservoirs? Some mineral "gum " (asphaltum) occurs 
 on the surface west of Grand Traverse Bay, Mich. ; explain how this happens. 
 How do the formations underlying St. Clair, Mich., compare with those 
 tinder Oil Springs, Ont.? If they are the same, why cannot oil be obtained 
 at St. Clair? What would seem to be the source of the powerful gas wells 
 in Knox county, Ohio? As 12,000 feet of gas are estimated to be equivalent 
 in heating capacity to one ton of bituminous coal, how many tons are repre- 
 sented by a total supply at Pittsburgh of 60,000,000 feet? How many coal 
 miners does this supply of gas represent? 
 
 STUDY XXX. Examination of Some Cup Corals. 
 
 Rocks and minerals are not the only geological specimens 
 brought to our very doors in the Drift. Every one living in the 
 western states, or in southern Ontario, is acquainted with certain 
 organic forms (compare Study XVIII) which the untaught farmers 
 refer with amusing confidence to things familiar to them. Thus 
 we have " petrified honeycomb," " petrified wasps' nests," " pet- 
 rified horns," "petrified butterflies," "petrified snakes" not to 
 mention "petrified hands," "petrified feet," and other petrified 
 things, which are nothing but curious results of the weathering 
 of rocks. We must try to make some acquaintance with these 
 objects. At present we will look into their structure, and here- 
 after we will ascertain what formations they are derived from. 
 It is common to find a promiscuous assemblage of these forms 
 gathered on some shelf or in some box, badly cared for, and yet 
 too curious, and often too beautiful, to permit the intelligent 
 owner to throw them away. Often he longs to know something 
 about them; but there are really few available aids within his 
 reach.
 
 EXAMINATION OF SOME CUP CORALS. 203 
 
 Now, let us look over such a collection. Most of these fossils 
 are worn some too much worn to possess value, but others 
 showing at least some little part in a fine state of preservation. 
 In fact, some of the finest specimens ever found come from the 
 Drift deposits. Large and valuable collections may be gathered 
 from this source, in any part of the region west of the Hudson 
 River. Assorting these specimens according to such knowledge 
 as we possess, we easily divide them into specimens which seem 
 to be shells and specimens which seem to be corals, or which, at 
 least, are not shells. Among those which appear to be corals we 
 readily make again another distinction. Those which present 
 any resemblance to honeycomb or wasps' nests may be separated 
 from those which are more or less horn-shaped that is, short, 
 conical and curved, like a young steer's horn. In picking out all 
 of this division, we must consider that most are somewhat broken 
 and worn, and we must try to conceive the shape of the missing 
 parts. We must also make allowance for some irregularities of 
 form. These corals are not all shaped precisely like bullocks' 
 horns, even when perfect. Sometimes they are rather long and 
 cylindrical; sometimes they are suddenly bent one way or another; 
 and often they swell out and contract at intervals. Sometimes 
 the exterior appears to be covered by a skin; often this has' been 
 worn off, and we see, externally, white lines imbedded in the 
 coral mass, and running from end to end. This is the division of 
 the corals which we wish to study. These are cup corals. A 
 group of them is shown in Figs. 112-116. These are several of 
 the best preserved. 
 
 First, study their external characters. The whole specimen 
 is sometimes called the cell. It is also known as polypary. You 
 notice at the larger end, which we will call the upper end, a 
 depression, giving the coral the appearance of a cup. This is 
 called the calyx, or cup (plural, cal' yces), and this explains why 
 these are called cup corals. (Figs. 113, 114, 116.) The adjec- 
 tive which expresses some relation to the cup is calyc' inal, as 
 calycinal extremity. Sometimes we find a pit in the bottom of 
 the cup on one or two sides, as in Fig. 113. This is a fossa,
 
 204 
 
 GEOLOGICAL STUDIES. 
 
 fossette, or fovea. The exterior of a perfect specimen is gen- 
 erally covered by a skin-like covering called epi-the' ca. This, 
 in some species, is smooth, but more frequently it is transversely 
 wrinkled. (Fig. 112.) Under the epitheca is the wall. Where 
 the epitheca is wanting, or has been worn off, we often see 
 
 FIGS. 112-116. CUP CORALS. 112, Zaphrentis Pioliflca, exterior. 113, Same, showing the 
 Cup. 114, Amplexus Shumardi, general view. 115. Clisiophyllum Oneidaentte, show- 
 ing interior, llfi, Cyathophyllum Cornicuta. 
 
 numerous white lines running lengthwise of the coral (Fig. 124); 
 these are cos' tee, or ribs (adjective, costal). In the cup may be 
 seen a set of radiating raised lines, which look like the upper 
 edges of radial plates. These extend from the outer wall toward 
 the centre. Different species differ greatly in the extent of their 
 development. These are generally called sep'ta (singular, sep-
 
 EXAMINATION OF SOME CUP CORALS. 205 
 
 turn). We shall see that they run lengthwise toward the lower 
 end of the polypary. 
 
 Next, let us study the interior. To do this we may make a 
 transverse section that is, a cut across the polypary at right 
 angles with the axis or line through the middle, from end to end. 
 You will be much interested in this work. Sometimes we find a 
 specimen broken square across, but often we must break it. The 
 surest way, to avoid spoiling the specimen, is first to file a groove 
 around the fossil with a three-cornered, or, better, a " knife- 
 edge," file. But you must select a calcareous specimen; a silici- 
 fied one would ruin your file immediately. Then resting the 
 coral on a solid support, like an anvil, if you have one, place the 
 edge of a " cold chisel" in the groove, and strike a smart blow on 
 it with a hammer or mallet. If the pene of your geological ham- 
 mer is not very dull, you can use that as a cold chisel. Now 
 grind one of the broken surfaces flat and smooth, and polish it. 
 You may use first the smooth flat side of a grindstone; or you 
 may use emery and water on a flat surface of lead, copper or iron. 
 Next, you may polish the surface on a fine hone; or you may do 
 it with emery flour on a piece of plate glass six or eight inches 
 square. The finest polish may be produced with dry emery 
 " slime " on a piece of buckskin tacked to a smooth board. 
 When a transverse section of your cup coral is thus polished, it 
 shows a beautiful internal structure which you can examine with 
 a lens, and of which you may make drawings. 
 
 But it is possible to do even better than this. You may 
 procure a very thin transverse slice so thin that light passes 
 through it, and the whole internal structure will be perfectly 
 shown. File a deep groove around the specimen, a quarter of 
 an inch back from the polished face, and cautiously chip off this 
 thick slice. Attach it to a piece of thick glass, one or two inches 
 square, by melting on the glass, over a lamp or a stove, some hard- 
 ened Canada balsam, pressing the slice, polished side down, in 
 the balsam, till the air bubbles are expelled. When cold and 
 hard, grind the rough side as before, holding by means of the 
 glass, until as thin as paper, or thinner if still too opaque, and
 
 206 
 
 GEOLOGICAL STUDIES. 
 
 polish the surface. Then soften the balsam and cautiously push 
 the slice off into a few drops of softened or liquid balsam resting 
 close by on a microscopic glass slide, taking care to exclude air 
 from beneath the specimen. A microscopic slide is a piece of 
 glass, one by three inches. Next, cover the slice with a drop 
 of balsam, and put on a thin glass cover seven-eighths of an inch 
 square, which may be held down by means of a spring " clothes- 
 pin," until the balsam is hard. If the balsam was liquid before 
 warming, gentle heat will now be required to harden it. Finally, 
 superfluous balsam should be removed with a knife, and the final 
 cleaning of the surfaces of the glass effected with spirits of tur- 
 pentine and bits of cotton cloth. There is nothing in all this 
 beyond the skill or resources of any intelligent student; but the 
 result will be found both gratifying and instructive. Thin slices 
 of rocks and minerals may be similarly prepared; but silicious 
 specimens make more laborious manipulation, and it is best to 
 begin with thin chips struck off with a hammer. If thin slices 
 of corals are not made, many polished surfaces should be prepared. 
 Now, what does a thin section of our cup coral reveal ? Here 
 it is, in Fig. 117. You notice, first, the outer icall. Next, you 
 see a system of radiated structures, 
 extending from the wall toward the cen- 
 tre. Make a transverse section at any 
 distance from the bottom, and similar 
 structures will be seen. These, then, 
 are the septa before noticed in the cup. 
 They are longitudinal radiating plates. 
 Some of the septa, as you perceive, 
 extend well toward the centre, and in 
 this species are a little twisted together. 
 Some extend but a part of the distance. 
 This coral which is shown in Fig. 117 
 has also a fovea in the cup though your specimen may not be 
 sufficiently perfect to show it. 
 
 Now, think over the characters just mentioned. You may 
 
 Fig. 117. TRANSVERSE SEC- 
 TION OF A CUP CORAL 
 (Zaphrentis prolifica), 
 SHOWING THE SEPTA.
 
 EXAMINATION OP SOME CUP CORALS. 
 
 207 
 
 remember that this assemblage of characters forms the genus 
 called Zaphrentis. 
 
 Let us take another, and different, cup coral, and prepare a 
 longitudinal section. This may be done in a manner entirely 
 similar to that before described. Grooves will be filed length- 
 wise of the specimen along opposite sides. Then, after polishing 
 one of the halves and attaching to the glass, 
 it may be best to grind away the whole half 
 down to a thin slice. Sometimes we use a 
 large file for coarse work. Here is the result, 
 in Fig. 118. The outer wall is, of course, 
 shown as before. If the section is precisely 
 central, none of the septa will be cut, and 
 hence none will be seen. Here are no septa 
 shown; but some transverse structures are 
 seen. These are called floors or tabulae,, for 
 they are thin, more or less flat plates. By 
 some they are called diaphragms and septa 
 but we will not so use these terms. Notice 
 that in this specimen the tabulae are broad 
 and conspicuous, extending almost from wall 
 to wall of the body cavity. Here, in Fig. 
 
 119, is a cross section of a specimen of the same species. Notice 
 particularly that the septa are very narrow. Bear in mind this 
 combination of characters. It is known as the 
 genus Amplexm. 
 
 Now we shall find no difficulty in preparing 
 transverse and longitudinal sections of many 
 different specimens. In Figs. 120 and 121 we 
 have sections of a form which shows septa not 
 reaching the centre, and tabular occupying only 
 the middle of the cavity, stretching from the 
 inner margins of the septa on one side to the 
 inner margins on the other. This portion of the 
 interior is known as the central part of the vis- 
 ceral cavity, or simply as the visceral cavity. 
 
 FIG. 118. LONGITUDI- 
 NAL SECTION or A 
 CUP CORAL (Amplex- 
 us Yandelli), SHOW- 
 ING THE TABCL.E. 
 Defects in tabulae re- 
 sult from fossiliza- 
 tion. 
 
 PIG. 119. 
 
 CROSS SECTION op 
 THE SAME SPECIES 
 AS IN FIG. 118, 
 SHOWING VERY 
 NARROW SEPTA. 
 See also Fig. 115.
 
 GEOLOGICAL STUDIES. 
 
 But we notice in the section (Fig. 120) some delicate structures 
 passing from septum to septum, in the region outside of the cen- 
 tral part of the visceral 
 cavity, and dividing it 
 into small cell-like com- 
 partments. This is known 
 as the peripheral region, 
 and these delicate divid- 
 ing lines are sections of 
 FIG. m.-LoNGiuTDi- dissepiments. These run 
 
 NAL SECTION OF A * 
 
 SPECIMEN OF THE obliquely downward and 
 
 SAME SPECIES AS IN 
 
 FIG. m (Cyathophyl- 
 
 lum). 
 
 FIG. 120. TKANSVKRSE 
 SECTION OF ANOTHER 
 CUP COKAL (Cyatho- 
 phyllum), SHOWING 
 SEPTA, CENTRAL 
 AREA, AND DISSEPI- 
 MENTS IN THE PERI- 
 PHERAL REGION. (Di- 
 agram.) 
 
 inward, as shown in Fig. 
 121, and seem to be modi- 
 fications of tabulae. You 
 will notice particularly 
 what characters are asso- 
 ciated together in this form. They constitute the genus Cya- 
 thophyllum. 
 
 Now let us pause to gather these few results together, and 
 make some tentative generalizations. The fundamental structures 
 of cup corals, as we have seen, belong to three categories: (1) 
 The mural system, or outer wall; (2) the septal system, or radi- 
 ating vertical plates or lamellae; (3) the tabular system, or trans- 
 verse plates. Let us conceive these three systems to be essential 
 structures in every cup coral, and to be always present in some 
 state of development, or under some modification; and let us con- 
 ceive a tabula to be, theoretically, a floor extending across the 
 whole body cavity, from wall to wall. Then we shall have some 
 interesting studies in tracing the homologies of these parts in 
 different genera that is, in determining what structures should 
 be referred to septa and what to tabulae, and what is the nature 
 of the modification undergone by these categories respectively in 
 any particular case. If these assumptions are not in accordance 
 with fact, we shall be unable to interpret cup-coral structures on 
 the basis of them. 
 
 We must be prepared to find each of these categories devel-
 
 EXAMINATION OF SOME CUP COEALS. 209 
 
 oped to a complete extent, to a partial extent, or only to an in- 
 cipient extent; or even, in some cases, they may be obsolete, that 
 is, only potentially present. If the tabulse extend, under any 
 modification, quite across the body cavity, they must intercept all 
 the septa, so that the wedge-shaped space between each two 
 septa will be cut into a number of narrow, wedge-shaped spaces 
 arranged in a vertical series. If the outer parts of the tabula? 
 are curved upward, instead of continuing horizontal, then, on a 
 transverse section like Fig. 120, they will be cut, and their cut 
 edges will be seen exposed. From this will result the appearance 
 of cellular tissue seen in the peripheral region of the Cyathophyl- 
 lum, Fig. 120. So we may anticipate other modifications of the 
 several parts. 
 
 EXERCISES. 
 
 If your place of study is anywhere west of the Hudson River, the Adiron- 
 dacs and the Appalachians, and east of the Missouri River, and not on a 
 prairie-covered region, you should make a collection of Drift fossils. In this 
 is included nearly the whole valley of the St. Lawrence River and the penin- 
 sula of western Ontario; but we exclude the Eozoic regions of northern 
 Michigan, Wisconsin, and Minnesota, and southern Missouri. Of course, 
 fossils found in place (in the rock) must be had when obtainable, though 
 really Drift fossils often show structures more perfectly than these. Have 
 you collected any fossils? Have you attempted to arrange them according 
 to their forms and characters? Take this lot of fossils before us and arrange 
 them as completely as possible. Point out the cup corals. Take any specimen 
 and state what part is broken away. What has been the effect of wear on it? 
 Is it silicifled or calcareous? Show where a transverse section might be cut. ' 
 Show the longitudinal section. Does this specimen show the septa? Does it 
 show any tabulae? Is the epitheca present? Does the peripheral part con- 
 tain cellular structure? What genus has this character? Do the septa 
 extend to the centre? Take other specimens and answer the same questions 
 in reference to them.
 
 210 
 
 GEOLOGICAL STUDIES. 
 
 STUDY XXXI. Further Examination of Cup Corals. 
 
 Let us seek further facts by examining a genus of cup corals 
 known as Streptelasma. In Fig. 123 we have a view of the 
 usual appearance of the exterior, and Fig. 123 shows the cup 
 with a fovea on one side, and a series of septa reaching the centre 
 with somewhat of a twist. There is no appearance of cellular 
 tissue in the peripheral part, and there is no indication of tabulae 
 except in the partially cellular mass in the centre, which, in some 
 
 FIGS. 122-124. VIEWS OF SEVERAL CUP CORALS. 
 
 122. Streptelasma corniculum, exterior. 123. Same, showing Cup. 124. Same, showing 
 arrangement of Septa on the exterior. 
 
 cases, we find raised into a dome-like elevation. This central 
 mass may be conceived as resulting from the intersections and 
 slight twisting of tabula? and septa. In Fig. 124 we find an 
 interesting exhibition of an arrangement of the septa often 
 called "feather-form " or pinnate. The lines show where the 
 septa come to the periphery, the external wall in this case being 
 deficient. 
 
 This example will serve to show the mode of increase of the 
 septa. A section across Fig. 124 close to the lower end would 
 reveal only four septa. These are the primary septa, A, J3, C, 
 _>, Fig. 125. Of these, A and C are shown in Fig. 124^. A is 
 the chief septum, B the antiseptum, and C and D the lateral 
 septa. With the growth of the coral, four additional septa
 
 FURTHER EXAMINATION OF CUP CORALS. 511 
 
 appear, in the places marked 1, 1, 1, 1, in Fig. 125. Two of these 
 
 are parallel with , one parallel with 
 
 C, and one with D. Of these four 
 
 additional septa, the one parallel 
 
 with C is skown in Fig. 124. With 
 
 further growth, these septa elongate, 
 
 and others appear parallel with them, PlGS 185 ]2c ._p RIMITIVE SEPTA 
 
 as may be seen at 2, 2, 2, 2, Fig. or A CUP CORAL (MUCH EN- 
 
 126, and in part, also, in Fig. 124. 1! ^^\ fout Primary Septai ^ 
 
 Thus, as growth proceeds, and the B, c, D, with the First Acces- 
 
 circumference of the cup increases, ,J r L Se ^. ta ' *' lf *' 1- 
 
 126. The Second Set of Accessory 
 
 the distance of the septa in the cup septa, 2, 2, 2, 2. 
 
 appears to remain the same. Now let ^ numerical designation of 
 
 Septa is the same as in Fig. 127. 
 
 us conceive the exterior of the speci- 
 men, Fig. 124, to be a skin, and let us slit down along the pri- 
 mary septa, A, J5, C, D, to the apex. Then, removing the skin 
 and spreading it on a flat surface, we shall see the plan of the 
 septa and their mode of growth. The appearance will be some- 
 what as shown in Fig. 127. Here A, B, C, and D indicate the 
 places of the primary septa, as before. It is seen that the whole 
 system is divided into four quadrants or fascicles of septa the 
 two fascicles on the right of the median line A S being sym- 
 metrical with the two fascicles on the left. The plan of the septa 
 is, therefore, fundamentally bilateral. The radiality is subordi- 
 nate and this, it may be said, can be shown of every other so- 
 called "radiate" animal. The break or discontinuity of the septa 
 along the primary septum A is called the apertural gap. The 
 one opposite, along _Z?, is the central gap; the other two are the 
 lateral gaps. The place of the principal fovea in the cup is at 
 A. Giving attention to each quadrantal fascicle in succession, it 
 is easy to perceive the succession of the septa. The older ones 
 are the longer, because they have been growing a longer period. 
 The shorter septa are the newer ones. The succession is indi- 
 cated by the numerals 1, 2, 3, 4, 5, 6, etc. Had the cell grown 
 further, the additional septa would have been introduced at 
 O, O, 0, 0. Since four is the number of primary septa in the
 
 212 GEOLOGICAL STUDIES. 
 
 cup corals, they are also known as TETRACORALLA. By Milne- 
 Edwards they were styled Rugosa. 
 
 Aperlural 
 
 FIG. 127. -PLAN OF SEPTA AND BILATERAL ARRANGEMENT OF A CUP CORAL. 
 
 The external walls of the the four Fascicles of Septa are developed or spread out 
 into one plane. The additions to the number of Septa take place at 0, 0, 0, 0. All the 
 Septa increase in length. 
 
 After examining- the 
 cups of numerous cup cor- 
 
 J/SS&SSUiiff/ft Ez^iS^^ als ' we sha11 find that tlie 
 
 Wiiit/tX< ^k^\ plan O f septa a b ov e de- 
 
 scribed is but imperfectly 
 shown in the cup; yet in- 
 dications of it almost al- 
 ways exist. A very clear 
 illustration of it is given 
 
 FIG. 128. CUP op Meno 
 pkyllum, E & H. 
 
 FIG. 129. PLAN OF SEP- 
 TA IN Zaphrentis Ida, 
 WIN. FROM ROCK- 
 FORD, IND. (From Nat- 
 ure.) 
 
 Fig. 128.
 
 FURTHER EXAMINATION OF CUP CORALS. 
 
 213 
 
 In some of the western states, and even western New York 
 and Ontario, we can hardly make a collection from the Drift with- 
 out finding included some corals of the species represented in 
 Figs. 130, 131. Here we have a widely open cup, showing septa 
 almost strictly radiate, but with the alternate septa shorter than 
 the others. It was probably this beautifully rayed appearance 
 which suggested to Milne-Edwards the name Heliophyllum. 
 The transverse section, Fig. 133, shows a vesicular tissue in the 
 peripheral region, and this is nearly all the evidence of the pres- 
 ence of a tabular system. Both figures, however, reveal certain 
 
 FIG. 131. SAME, VIEW OP 
 THB CUP. 
 
 FIG. 132, PART OF TRANS- 
 VERSE SECTION OF Helio- 
 phyllum Halli. 
 
 FIG. 130. Heliophyllum 
 Halli, HAMILTON 
 GROUP, WIDDER, ONT. 
 (From Nature.) 
 
 appendages to the septa which are conceived to be characteristic 
 of this genus, though, in fact, we find them in several other 
 genera. A longitudinal section, Fig. 133, shows them to be 
 sharply raised, opposite pairs of cctri'nce, or ridges, running along 
 the lateral surfaces of the septa, and curving in such a way as to 
 outcrop in the cup. The carinae are seen in Fig. 133, in places 
 (7, C, where the thin section cuts obliquely across a septum. 
 
 An equally common form of cup coral is the Cystiphyllurn 
 A.'ntericanum t Fig. 134. The cup presents a surface covered 
 with blister-like elevations; and sections in Figs. 135, 136 and
 
 214 
 
 GEOLOGICAL STUDIES. 
 
 137 show the whole interior occupied by a coarse vesicular 
 tissue, without characteristic septa or tabulae. We may suppose 
 
 the mutual intersections of 
 these structures have re- 
 sulted in such mutual dis- 
 placement and distortion 
 that the typically wedge- 
 form compartments have be- 
 come mere vesicles. 
 
 All the cup corals thus 
 far examined are simple. 
 That is, each specimen is the 
 
 FIG. ^-LONGITUDINAL SECTION OF Heliophyl- WQrk of & g j Je individua l 
 lum Halli, SHOWING THE CAKING ON THE 
 
 SEPTA. (From Nature.) C, C, Carina? cut polyp. But many cup corals 
 
 lengthwise, the oblique sections of the Septa are compound, and we find 
 
 giving the clouded patches. T, coarse cellu- . 
 
 lar tissue of central part of visceral cavity, t, them SO in the Drift. 
 
 fine cellular tissue of peripheral part. (The Throughout the Northwest, 
 black blotches are mere opaque rock mate- 
 
 rial ^ one 01 the very commonest 
 
 and most beautiful of these 
 is Acervularia Davidsoni 
 (Figs. 138, 139). Visitors to 
 Petoskey on Little Traverse 
 Bay are made very familiar 
 with this coral through the 
 polished specimens which are 
 offered for sale. But it is 
 found there imbedded in its 
 natural formation. Acervula- 
 ria forms aggregations in 
 elegant spheroidal and cake- 
 like masses. Each mass is a 
 group of small, generally 
 crowded, and polygonal cells, 
 each of which is a real cup 
 coral. They are mostly six- 
 sided by mutual pressure, but sometimes a tube stands sufficiently 
 
 FIG. 134. Gystiphyllvm Atnericanum. 
 
 PER EXTREMITY OP A LARGE SPECIMEN. 
 (From Nature.)
 
 FURTHER EXAMINATION OF CUP CORALS. 
 
 215 
 
 135. PART or TRANS- 
 VERSE SECTION OF Cystiphyl- 
 lum Americanum. (From 
 Nature.) 
 
 FIG. 136. TRANSVERSE SEC- 
 TION OF A Cystiphyllum, 
 SHOWING A DENSE ZONE 
 AROUND THE CENTRAL PART, 
 AND COARSER TISSUE IN THE 
 CENTRE. (From Nature.) 
 
 isolated to retain its fundamental cylindrical form. The com- 
 mon wall between contiguous cells is delicately wavy. The 
 centre of each cup is abruptly sunken. The septa of first order 
 reach the centre; 
 those of the sec- 
 ond order reach 
 only to the cen- 
 tral pit. Indica- 
 tions of carinse 
 are seen on the 
 septa in the pe- 
 ripheral region. 
 In the cross-sec- 
 tion, Fig. 139, the 
 characters of the 
 limiting wall and 
 the septa are still 
 more clearly shown. It appears from this that caringe are not 
 exclusively characteristic of Heliophyllum; but they make here 
 a different group of characters from the 
 group which constitutes a Cyathophyl- 
 lum. 
 
 In Fig. 140 we have another com- 
 pound cup coral. Each cell or tube is 
 by itself nearly a Cyathophyllum. 
 That is, it shows, in longitudinal sec- 
 tion, some very distinct though irregu- 
 lar tabulae in the central portion, and 
 an elegant vesicular tissue in the pe- 
 ripheral portion. But the tabulae rise 
 in a conical elevation in the centre of 
 
 the cup, constituting the distinct genus FlG m ._ LoHGITUD1HAL SEC 
 Lithostrotion. 
 
 Still another elegant compound cup 
 coral appears in Figs. 141, 142 and 143. The genus Diphyphyl- 
 lum is characterized by the presence of an inner wall, which is 
 
 TION OF Cystiphyllum Ameri- 
 canum. (From Nature.)
 
 216 
 
 GEOLOGICAL STUDIES. 
 
 here very distinctly shown. In addition, notice the delicate 
 equidistant tabulae across the small inner tube, and the fine vesi- 
 cular tissue between it and the outer wall. The septa are alter- 
 nately wide and narrow, the former reaching the inner wall. 
 
 FIG. 138. Acervularia FIG. 139. TRANSVERSE FIG. 140. Lithostrotion Canadense. 
 
 Davidsoni. VIEW op SECTION op Acervula- CARBONIFEROUS LIMESTONE op 
 
 A CLUSTER OP CUPS. ria Davidsoni. LARG- MICHIGAN. (From Nature.) 
 ER CELLS. 
 
 The study of these corals is very fascinating; but we have 
 pursued the subject quite far enough for an elementary course. 
 In an advanced course, we shall resume the subject. 
 
 FIGS. 141, 142, 143.Diphyphyllum Arcfiiad. (Billings.) HAMILTON GROUP. (From 
 Nature.) 141, General View. 142, Transverse Section. Showing Double Wall, 
 Septa, Primary Septum in a Fovea. 143, Longitudinal Section. Showing Double 
 Wall, Central Tabnlrc, and two sorts of Peripheral Tissue.
 
 FURTHER EXAMINATION OF CUP CORALS. 21? 
 
 From the details enumerated, let us now gather together 
 definitions of the different genera illustrated: 
 
 AMPLEXUS. Simple, subcylindrical, narrowed toward the 
 lower extremity, covered with epitheca. Septa slender, very nar- 
 row, equal, the chief septum in a fovea. Tabulae horizontal, 
 strong, mostly complete, closing the bottom of the cup. 
 
 ZAPHRENTIS. Simple, horn-shaped or top-shaped, with epi- 
 theca. Cup deep, with a distinct fovea. Septa well developed, 
 reaching the centre, more or less distinctly pinnate. Tabulae also 
 well developed, and reaching to the wall. In the peripheral region 
 sometimes a little coarse vesicular tissue. 
 
 STREPTELASMA. Simple, conical, often curved, with epitheca. 
 Septa radiate in the cup, unequally broad; the broader set some- 
 what twisted together in the centre, and forming, with the modi- 
 fied tabulae, a vesicular eminence. Chief septum and lateral 
 septa distinctly shown externally, as also the pinnately arranged 
 later septa. Tabular completelv developed. 
 
 CYATHOPHYLLUM. Simple or compound, with epitheca. Tab- 
 ulae in the middle of the visceral cavity, cellular tissue in the 
 peripheral part. Septa numerous, regularly radiate, reaching the 
 centre, and sometimes twisted there into a feeble elevation. 
 
 LITHOSTROTION. A compound Cyathophyllum, having the 
 central vesicular tissue condensed into a column which rises in 
 the deep cup as a solid striated cone. Tubes striated externally, 
 sometimes isolated and cylindrical. 
 
 HELIOPIIYLLUM. Simple, top -shaped, seldom compound. . 
 Septa numerous, perfectly developed, their sides decorated with 
 carinaa, or raised lines running downward and inward, and arranged 
 in pairs on opposite sides. Irregular tabulae in the central part, 
 cellular tissue in the peripheral. A Cyathophyllum, with carina?. 
 
 CYSTIPHYLLUM. Simple or compound, with epitheca. Ex- 
 terior deeply wrinkled, and the form often elongate, geniculate, 
 or irregular. Septa and tabulae extremely modified, their normal 
 forms sometimes not appearing, a cellular tissue filling the whole 
 visceral cavity, the cells mostly somewhat crescentic in form, and 
 generally arranged in distinguishable layers from below upward.
 
 218 GEOLOGICAL STUDIES. 
 
 ACERVULARIA. Compound, stems sub-parallel, approximated, 
 often crowded and hexagonal. Cup with an abrupt pit in the 
 centre. Septa well developed, extending alternately to the centre 
 and to the pit. The central part of the visceral cavity with vari- 
 ously shaped tabulae, the peripheral with cellular tissue. 
 
 DIPHYPHYLLUM. Compound, consisting of generally slen- 
 der, cylindrical, epitheca-covered cells, furnished with an interior 
 wall distant from the outer wall. Septa numerous, reaching the 
 inner wall. In the interior, a series of tabulas; in the peripheral 
 part, cellular tissue. 
 
 EXERCISES. 
 
 Make some polished sections of cup corals. In what respect are Strep- 
 telasma and ZapJirentis alike? In what respect unlike? How does Zapli- 
 rentis differ from Cyathophyllum? How does Heliophyllum differ from Cy- 
 athopliyllum? Copy Fig. 127 on a piece of paper, then cut out the four 
 quadrantal fascicles, leaving them connected at the centre, and fold them 
 together like a half ball-cover; do you find an appearance like Fig. 124? 
 Copy Fig. 132. Copy Fig. 139. How does Acervularia differ from Diphy- 
 pJiyllum? Have you been able to identify any cup coral found by yourself? 
 Have you ever collected fossils except from the Drift? Do you know any 
 locality at which fossils may be obtained from the rocks? Have you ever 
 seen Acervularia at Petoskey? Have you polished any coral sections with 
 your own hands? If so, let us see them. To what genera do they belong? 
 Make drawings of some of your polished sections of cup corals. Select one 
 or two of your most perfect specimens of cup corals and draw them. 
 
 STUDY XXXII. Examination of Some Tabulate Corals. 
 
 Our collection of Drift corals was divided, in a former study, 
 into two lots. The cup corals, or liugosa, we have now learned 
 how to study. The other lot, or those commonly called "petri- 
 fied honeycomb," we must next take up and examine. These are 
 quite as common as the rugose corals; and it may as well be 
 stated at once that the proper designation of the group is TABU- 
 LATA, or HEXACOBALLA. From almost any neighborhood within 
 the area before defined we may pick up specimens either identi-
 
 EXAMINATION OF SOME TABULATE CORALS. 
 
 210 
 
 cal with those delineated here, in Figs. 144-148, or at least gen- 
 erically identical with them. 
 
 Beginning with the one represented by Fig. 144, we see a 
 large number of tube ends closely ci-owded together, and pressed 
 
 FIGS. 144-148. VABIOTTS SPECIES op FAVOSITBS. 
 
 (From Nature.) 
 
 144, F. favosus Gf., showing hexagonal cells, septal rudi- 
 ments, and tabulae. 145. F. Alpenensis Win., showing 
 angular apertures. 146, F. tuberosus Rom., showing 
 pores. 147, F. nltella Win.,with cells small. 148, F. clau- 
 sus Rom., branched. 
 
 into hexagonal forms. So far as we can see, 
 
 any two walls in contact are blended into a 
 
 single common wall; but we shall have to 
 
 examine more closely in a thin section. 
 
 Some of the cells show strong tabulae crossing from side to side. 
 
 In some the tabulje near the aperture have been removed, and in 
 
 others no tabulse are in sight. But do we discover any septa? 
 
 There are none well characterized; but we plainly see a number
 
 220 
 
 GEOLOGICAL STUDIES. 
 
 of point-like depressions or indentations around the border of 
 each tabula. Close inspection shows that these alternate with 
 small projections from the inner walls 
 of the cells, and these projections ex- 
 tend, as raised bands or ridges, length- 
 wise of the cells. Fig. 149 is a view 
 of another specimen, showing this 
 character. The raised bands or lines 
 are twelve in number, and are sepa- 
 rated by twelve longitudinal furrows. 
 These raised bands appear like the 
 stumps of septa, and the constancy of 
 
 49.-FArosiTEs FAVOSUS, ti j num ber confirms this interpre- 
 P-ING LONGITUDINAL LINES 
 WITHIN THE CELLS; THESE tation. 
 
 REPRESENT SEPTA. (From If we turn Qur attention to the speci- 
 
 Natnre.) 
 
 men shown in Fig. 145 Favosites 
 
 Alpcnensis, Winchell (afterward described by Rominger as F, 
 Hamiltonensis} we perceive that it is part of an elongated, 
 rudely cylindrical, or tuberose mass, composed of small tubes, 
 which rise from a common central axis, at a small angle, 
 and, after continuing a certain distance, curve toward the sur- 
 face of the mass, and present there their terminations or 
 inouths. These tubes, throughout their whole length, are crossed 
 by delicate transverse plates, which can be nothing but tabula?. 
 Hence, they are of the same nature as those seen in the mouths 
 of the tubes of Fig. 144. Some of these tabulae extend quite 
 across; but some of them join the neighboring ones above or 
 below, and hence are incomplete / and some, after touching their 
 neighbors, continue separately. The tabulae toward the outer 
 ends of the tubes become quite crowded. We notice, also, a 
 system of branching among these tubes. Many tvibes do not 
 originate at the centre, but start from a point in the wall between 
 two tubes, giving the wall an appearance as if split, and thus 
 suggesting that the wall is really double. It ought to be double, 
 if formed by the union of the two walls of the two contiguous 
 cells. This mode of introduction of new cells is called lateral
 
 EXAMINATION OF SOME TABULATE COKALS. 
 
 FIG. 150. THIN SLICE 
 OF Favosites Alpe- 
 nensis. SHOWING 
 
 TABULjE.LoNGI- 
 TUDINAL MCBAL 
 
 STRiJE,(but badly), 
 DOUBLE WALLS, AND 
 LATERAL BUDDING. 
 
 gemmation, or budding from the side. We cannot see here the 
 longitudinal bands and furrows which represent septa. Fig. 150, 
 however, is a thin section of a small globu- 
 lar mass of this species. As the tubules radi- 
 ate from a centre, the section, in passing near 
 the centre, is transverse to the central tubules, 
 and longitudinal to those near the exterior. 
 Now, besides the conspicuous tabulae, we can 
 see here the longitudinal raised lines shown in 
 section, and projecting like spines in the central 
 tubules; and we see, also, a few pores, and a 
 light line along the middle of the common wall 
 in the longitudinal sections, proving plainly 
 their double character. [Pores not engraved.] 
 
 Now, if we take the specimen represented 
 by Fig. 146, we notice, also, a series of slightly 
 divergent tubes, but with only occasional tab- 
 ulae. As in some places they stand close together, it is proba- 
 ble that most of the tabulae once present have been removed. 
 We see nothing different in the nature of the walls, and 
 notice also the evidences of lateral gemmation. But there is 
 one striking character not before clearly seen. The vertical walls 
 are perforated with numerous pores also sparingly detected in 
 Fig. 150. These are arranged mostly in two longitudinal series 
 on each side, but the number of series depends on the width of 
 the side. These pores establish complete 
 communication between contiguous cells, as 
 is shown in places where the light passes 
 through. 
 
 Fig. 147 illustrates a more delicate struc- 
 ture, globoid in form, with small cells radi- 
 ating from a centre. But a thin section, jr IG . 151. THIN 
 
 Fig. 151, shows tabulae and pores quite like op Favosite* nitella. 
 ,,.,., . , X4. SHOWING TABULAE. 
 
 those in the other specimens. The apertures 
 
 of some of the cells incline to be round. There is a type of 
 this group having quite circular cell sections, and it is very
 
 222 
 
 GEOLOGICAL STUDIES. 
 
 abundant throughout the Northwest. A group of the cell 
 mouths is shown in Fig. 152. Here are two sorts of mouths. 
 First, larger, circular mouths, about one 
 millimeter wide, and quite separate 
 from each other; second, small sub- 
 angular mouths, about one-third the size 
 of the others, standing close together, 
 and forming a mass in which the larger 
 cells are imbedded. If we make a ver- 
 tical section, we shall see that both the 
 large and small cells are supplied with 
 tabulae. We shall also perceive com- 
 municating pores. But there are no 
 PIG. \52.-Favosites Canadensis, longitudinal grooves, and hence no indi- 
 BILL. SHOWI** TUBULES OF cations o f septa . In sp it e of the diver- 
 Two SIZES. 
 
 gences of this type, we feel constrained 
 
 to unite it with the other specimens having numerous tabular 
 and connecting pores. These all belong to the great and impor- 
 tant genus known as Favosi'tes (name from 
 favus, a honeycomb, and the conventional 
 termination ites). 
 
 A form slightly different from any of these 
 is also found quite frequently in the Drift of 
 New York, Ontario, and the Northwest, as 
 also, of course, in the rocks of certain forma- 
 tions. This is a rounded, depressed, cake-like 
 mass, composed of numerous flattened tubes 
 radiating from a basal point (not seen in Figs. 
 153, 154), reaching the surface at oblique an- 
 gles, and opening in crescentically three-angled 
 mouths in other words, mouths like small spherical triangles. 
 A section parallel to the tube lengths shows the tube walls lon- 
 gitudinally grooved or striated, and perforated with large pores 
 situated on or near the two lateral edges. It shows also a series 
 of remote, irregular tabula?, and also some longitudinal crests 
 or rows of spinulose projections, which are the homologues of 
 
 153. AHeolUes 
 GoMfussi, BILL.
 
 EXAMINATION OF SOME TABULATE CORALS. 
 
 223 
 
 olites Goldfussi. 
 SHOWING TABU- 
 LA AND POKES. 
 
 septa. This is, therefore, fundamentally similar to Favosites, 
 and belongs in the same Family' but, in consequence of the 
 peculiar form of the tubes and tube mouths, and 
 the positions of the pores, it is set down as a 
 different genus, Alveolites (alveolus, a pit, and ites, 
 as before). 
 
 Another form of this family is Limaria (per- 
 haps from limarius, pertaining to slime or sedi- 
 ment). The surface of a specimen is shown in 
 Fig. 155. It looks much like a small-celled but 
 thick-walled Favosites. The apertures are com- 
 pressed, and open obliquely to the surface. On the outer side, 
 the lip bears two teeth projecting into the cavity; and on the 
 inner side a single tooth projecting 
 between the two outer ones (Fig. 156). 
 A longitudinal section shows that the 
 tubes are connected by lateral pores, 
 and intersected by transverse tabulae. 
 The tabula? arc mostly wanting in the 
 thick-walled portions of the tubes. 
 This you perceive only differs from 
 Alveolites in less compressed tubes, 
 
 thicker walls, and fewer longitudinal crests. There is another 
 genus, Cladopora (x/.ddos, a branch, and xopa, a pore, conven- 
 tional name for certain corals), which only 
 differs from Limaria in having no tooth-like 
 projections in the apertures, and smooth, in- 
 stead of crested, tube interiors. Tabulae exist, 
 but they are rarely seen, the tubes being gen- 
 erally open from end to end. Even longitudi- 
 nal furrows, the vanishing indications of the 
 septal system, are occasionally seen, and are to 
 be regarded as potentially present. Lateral 
 pores in the walls are also present. The 
 species shown in Fig. 157 is branching and reticulating. Other 
 species, like Cladopora Rcemeri, Fig. 158, are simply branched, 
 
 FIG. 155. 
 Limaria crassa, ROM. 
 
 FIG. 156. 
 
 MOUTH AND TEETH 
 op Limaria crassa. 
 X 7. (In the spec- 
 imen figured only 
 one tooth is seen. 
 The opposite two 
 are generally in- 
 conspicuous.)
 
 224 
 
 GEOLOGICAL STUDIES. 
 
 FIG. 157. 
 Cladopora laqueata, ROM. 
 
 and still others form flat, leaf-like expansions. It would be 
 interesting to extend the study of this group of forms, but we 
 fear it would occupy an undue pro- 
 portion of the student's time. The dis- 
 tinctive characters of this order of fos- 
 sils have been shown, as also the 
 method of investigating them. It ap- 
 pears that the septal system is feebly 
 developed, but that the tabular system 
 is generally conspicuous. For this 
 reason they were named by Milne- 
 Edwards TABULATA, or Tabulate Cor- 
 als. We have seen also that the furrows and ridges which rep- 
 resent the septal system are twelve in number. If we should 
 examine all the genera of this group, we would find some with 
 six more or less complete septa. So the number in all cases is a 
 multiple of six. As the number among the Cup Corals is a mul- 
 tiple of four, and they have hence been by Haeckel styled TETRA- 
 CORALLA, so this Order has been by the same designated HEXA- 
 
 CORALLA. 
 
 Let us now bring together the characters of those genera 
 of Favosit'idw which have been illustrated: 
 FAVOSITES. Polypary, compound, massive 
 (globoid, tuberose, pyriform, or elongate), flat- 
 tened, or branching, composed of tubes which 
 are generally crowded and hexagonal, but some- 
 THIN SLICE or Cla- times cylindrical, variable in diameter in the 
 
 dopyra Rcemeri, game species, and opening perpendicularly to 
 BILL. SHOWING J 
 
 the surface. Tabuke generally numerous and 
 conspicuous, in some species irregular or incom- 
 
 THICKENED DOU- 
 BLE WALLS AND 
 DELICATE Trabec- 
 ular STRUCTURES plete. Septa represented by twelve longitudv- 
 
 nal furrows and alternating ridges, which are in 
 some species crowned with spinules in one or 
 more series. Walls perforated by pores in one, 
 
 two, or more vertical rows on each side, but very different in 
 
 number in different species. 
 
 (LIKE SPIDER 
 LINES) WITHIN 
 THE CELLS. X 7.
 
 EXAMINATION OF SOME TABULATE CORALS. 225 
 
 ALVEOLITES. Polypary massive, convex, or flattened, often 
 laminar or branched. Constituent tubules flattened and closely 
 appressed, opening obliquely at the surface with a triangular ori- 
 fice bounded by three curved lines. Septa represented by longi- 
 tudinal furrows. Tabulae more remote and irregular than in 
 FAVOSITES. Pores very large on the two lateral edges of the 
 compressed tubes. 
 
 LIMARIA. Small, branching stems or laminar expansions, 
 composed of thick-walled, conico-cylindrical tubules, with com- 
 pressed orifices opening obliquely to the surface, having a lip 
 bearing two tooth-like projections on one side and one on the 
 opposite. Septa feebly represented by three longitudinal crests 
 on the walls. Tabular restricted to thinner portions of the tubules. 
 Connecting pores present. 
 
 CLADOPORA. Ramose, often reticulating sterns or laminar 
 expansions often these different forms in the same individual. 
 Composed of thick-walled, conical tubules, opening obliquely to 
 the surface, and having dilated orifices. Tubules laterally con- 
 nected by pores. Tabulae very rarely seen. Longitudinal fur- 
 rows mostly obsolete, but occasionally discernible. 
 
 EXERCISES. 
 
 Point out several Tabulate Corals. Are they simple or compound? Are 
 they calcareous or silicified? Were they obtained from the Drift or from 
 strata in place? Are they nearly perfect? Indicate places where defects 
 exist. Are they worn like Drift pebbles? Point out some fracture which 
 passes between two tubules, if you can. Point out some fracture which 
 passes through a tubule. Does this reveal the interior of the tubule? What 
 structures are there revealed? Point out tabulae, if present. Point out 
 longitudinal furrows on the walls. What do these represent? Point out 
 pores, if present. Are they scattered or numerous? In how many rows do 
 they exist on each side? To what genus does this specimen belong? Do the 
 mouths open vertically or obliquely? What is the form of the tube section? 
 Make a drawing of a small portion of the specimen. Make an enlarged 
 drawing of two or three tubules, with all the details. Pick out a Favosites 
 with cylindrical tubules. What was "the form of the specimen when entire? 
 Explain how it differs from the last specimen. How can you most easily 
 detect Alreoh'fes from external characters? Which two of the four genera
 
 22G GEOLOGICAL STUDIES. 
 
 illustrated are least distinguishable from external characters? Which two 
 have thickest walls? 
 
 STUDY XXXIII Examination of Some Brachiopods. 
 
 Of the numerous fossils which any person may collect from 
 the Drift, a large proportion appear to be bivalve shells that is, 
 shells composed of two pieces intended to open and close by a 
 hinge, like a river mussel. Among bivalves, it is extremely easy 
 to make a distinction based on the external form of the shell. 
 Yet it is a distinction of very fundamental value, since it sep- 
 arates two Classes of Molluscs. 
 
 To begin with, we will take the shell of a common river 
 
 mussel, Fig. 159, 
 the hinge side up. 
 The most prominent 
 part, , is called the 
 beak. Now, any ob- 
 serving boy has seen 
 the river mussel in 
 the act of locomo- 
 tion. It raises itself 
 on edge, somewhat 
 inclined, however; 
 separates its two 
 
 PIG. 159.-LEFT V.LVK OF A COMMON RlVER MUSSEL, UKIO. ValV6S 8 % htl 7 ' P' 
 
 a, Beak; h d, External Ligament; be, Hinge Border; O, trudes a soft organ 
 Anterior Border; A Posterior Border; A , Height; ^ d th f ( d 
 C D, Length; 0, Thickness. 
 
 glides over the mud- 
 dy bottom of the pond or stream, leaving a track like the mark 
 of a finger. If our shell, figured above, were in motion, it would 
 move from right to left. It appears, therefore, that C is the 
 anterior end and D is the posterior. It appears that the beak is 
 nearest the anterior end, and is turned in that direction. This 
 valve which is figured is, therefore, the left valve. Next, let us 
 turn our mussel around, so as to look at it hingewise. You notice
 
 EXAMINATION OF SOME BRACHIOPODS. 
 
 227 
 
 that the two valves are equally convex. This is what would be 
 expected. One is a right valve and the other a left; and the law 
 of bilateral, or two-sided symmetry,* which runs through the 
 animal kingdom, and applies, as we have seen, to animals called 
 " radiated," requires that each shall be correspondingly devel- 
 oped. Let us call this bivalvular symmetry. Shells with this 
 symmetry are LAMEL'LIBRANCHS (Lamella, and branchiae, gills, 
 referring to the flat form of the gills. 
 
 FIG. 160. A RIVER MUSSEL VIEWED FROM THE HINGE SIDE, SHOWING EQUAL VALVES. 
 This is an extinct species, Anodonta angustata, from the Catskill Sandstone, New 
 York. 
 
 Now take one of the bivalves picked up from the Drift. 
 There is none more common throughout the Northwest than this 
 which is here figured, and which bears the name Spirifera mu- 
 cronata (spira, a spire, fero, to j 
 bear, and mucronatus, pointed, 
 the latter referring to its extrem- 
 ities). Notice that the beak is 
 exactly in the middle of the shell 
 between its extremities, and that 
 the outline is symmetrical around 
 the valve each way from the 
 back. It must be, then, that one side of the beak is >*he right 
 side, and the other the left; and if so, the two valves are dorsal 
 and ventral, instead of right and left. Let us view a shell from 
 the end, Fig. 162. Here we immediately perceive that the two 
 valves are not equally convex, and have not equally devel- 
 oped beaks. They are not mutually symmetrical. Hence they 
 are not right and left valves; and we conclude as before, that 
 one is dorsal and the other ventral. The law of bilateral sym- 
 metry works, therefore, separately in each valve, and pro- 
 
 Fio. 161. SPIRIFERA MUCRONATA, CON, 
 VIEWED FROM THE VENTRAL SIDE. 
 Showing the Beak and Anterior Bor- 
 der, r, the Right Side: I, the Left.
 
 228 
 
 GEOLOGICAL STUDIES. 
 
 FIG. 102. SPIRI- 
 GERA SPIRIFER- 
 OIDES. VIEWED 
 FROM THE END, 
 SHOWING UNE- 
 QUAL VALVES. 
 V, the So Called 
 Ventral Valve; 
 d, the Dorsal. 
 
 duces what we may call univalvular symmetry. Shells with 
 this symmetry are BRACHIOPODS (ftpa%ia, arm, and TTOU?, ?:<??, 
 foot). The valve which we will call ventral 
 always has the most prominent beak; and it is 
 almost always most convex or swollen. Gener- 
 a ^y> ^ 00 > ^ nas a depression or sinus along the 
 middle, which corresponds to an elevation or fold 
 along the middle of the dorsal valve. 
 
 It is not easy to determine which valve is 
 really ventral or which dorsal. Some of the Ger- 
 man palaeontologists say the smaller valve is ven- 
 tral; while the English say it is the larger. The 
 only means of deciding is an examination of liv- 
 ing specimens belonging to this class. But this 
 examination is not decisive; nor does it indicate 
 clearly which should be regarded the anterior 
 part and which the posterior. In this state of the case, the side 
 opposite the hinge is commonly regarded anterior, though the 
 mouth was actually far back, near the beak. In this view, the 
 right side of the shell will be on the right when the shell lies 
 on the ventral valve, with the hinge side next the observer. 
 This is indicated in Fig. 161, where the dorsal side is down. 
 
 These principles enable us to draw important inferences from 
 small fragments of bivalves. Suppose the line of break of a 
 valve is along a b, Fig. 163. Then, 
 the beak and hinge line being present, 
 it appears that the beak is central, 
 and the valve belonged to a Brachi- 
 opod. If only a part of the hinge line 
 is preserved, that may show symme- 
 trical outlines each side, and thus 
 demonstrate the same thing. If the 
 break is along the line c d, and we have only the small fragment 
 below that line, the symmetry in both directions shows that the 
 break was opposite the middle, and the shell was a Brachiopod. 
 If the break is along the line e f, and we have only the small 
 
 FIG. 163. ORTHIS BIFORATA, 
 VENTRAL SIDE.
 
 EXAMINATION OF SOME BRACH1OPODS. 
 
 piece on the right, if a fragment of both valves is present, their 
 unequal convexity shows the shell a Brachiopod. If we have 
 barely the two beaks broken off at g h, their unequal prominence 
 declares a Brachiopod. 
 
 Now let a Lamellibranch be broken in the same various ways, 
 and the style of the symmetry, or the lack of symmetry, will 
 show each fragment to belong to a Lamellibranch. The student 
 should practise much on these tests. 
 
 Let us give further attention to these Brachiopods. By col- 
 lecting industriously, we find many with the two valves separated. 
 The ventral valve is known by its 
 sinus; and this valve, you will notice, 
 bears a couple of small processes, or 
 projections, t, t, Fig. 164, which are 
 called teeth, one on each side of the 
 middle, on the hinge plate. These 
 are part of the hinge structure, and 
 fit into two sockets, s, s, Figs. 165, 
 166, in the dorsal valve, which is 
 known by the fold. This hinge 
 structure is possessed by all Brachio- 
 pods which have a strong calcareous 
 shell. Between the sockets of the 
 dorsal valve is the cardinal process. This is a projection to 
 
 FIG. 164. INTERIOR OP VENTRAL 
 VALVE OF Spirifera mucronata, tjt. 
 the two teeth ; 6, the beak ; c, c, the 
 cardinal extremities ; a, the trans- 
 versely striated area; /, the trian- 
 gular fissure, showing ledge for 
 reception of deltidium ; 0, occlusor 
 muscular scars ; s,the median sinus. 
 
 FIG. 165. INTERIOR op DORSAL VALVE 
 OP Spirifera mucronata. #, , the 
 two sockets; p, the cardinal process 
 (here not salient); 6, 6, brachial pro- 
 cesses; 0, occlusor muscular scars; 
 a, narrow area; /, the median fold. 
 
 FIG. 166. HINGE PARTS OP 
 Or this subquadrata, EN- 
 LARGED. DORSAL VALVE. 
 , , sockets; p, cardinal 
 process, with pinnate 
 markings; 6, 6, brachial 
 processes. (Meek.) 
 
 which is attached the muscle which opens the two valves. In 
 some other genera this is much more developed. It is generally
 
 230 
 
 GEOLOGICAL STUDIES. 
 
 Fio. 167. INTEBIOB OF DORSAL 
 VALVE or Strophome'na ince- 
 quiradiata, CON. p, the two 
 cardinal or divaricator processes. 
 0, the impressions of the occlu- 
 eor muscles. (Billings.) 
 
 conspicuous in Orthis, as shown in Fig. 166. In the valve 
 shown in Fig. 167, Strophome'na 
 incequiradiata, the cardinal process 
 is divided, and very strong. One 
 extremity of the divaricator, or 
 opening, muscle is attached to this 
 process, and the other to the in- 
 terior of the ventral valve. Then, 
 contraction of the muscle, acting on 
 the cardinal process, as on the end of 
 a lever, lifts the dorsal valve. At the 
 place of attachment of the divarica- 
 tor muscle is a depression, or scar, 
 on the interior of the ventral valve, 
 shown at d, Fig. 168. There are two muscles and two divaricator 
 scars. The valves are closed by two pairs of occlusor muscles, 
 which pass directly across from valve 
 to valve, and leave occlusor scars on 
 the interior of each valve. These 
 scars are shown at 0, Figs. 167 and 
 168. 
 
 The hinge mechanism is more 
 clearly shown in Fig. 169, which rep- 
 resents a section through both valves 
 of a Strophome'na, from hinge to 
 front margin. The structures are 
 indicated in the explanation. It is 
 evident that by the contraction of 
 the divaricator muscle D, the extrem- 
 
 f ront margi 
 
 c,c, the cardinal an- 
 S I 
 
 the beak, with a narrow deltidium ity of the process P, must be drawn 
 
 beneath it; d, the divaricator im- toward the point ft and thus t he 
 pression, or muscular scar; o, the 
 
 occlusor; t>, the vascular impres- dorsal valve must turn on the hinge 
 
 sions; r, the teeth. at ^ ag ft doQr turns on j tg hinges. 
 
 By this movement the valves were separated at the front mar- 
 gin, M. By the contraction of the occlusor, 0, the valves were 
 drawn together.
 
 EXAMINATION OF SOME BKACHIOPODS. 
 
 231 
 
 VALVES FROM BEAK TO FRONT, THE UPPER 
 VALVE THE DORSAL. M, the front margin; A, 
 area of ventral valve ; S, socket in dorsal valve 
 for reception of tooth of ventral valve ; P, di- 
 varicator, or cardinal, process (or lever) ; D, 
 divaricator muscle; 0, occlusor, or adductor. 
 (After Billings.) 
 
 Referring again to the ventral or toothed valve of Spirifera 
 mucronata, Fig-. 164, we no- 
 tice, further, the flat elon- 
 gate-triangular space a, un- 
 der the beak b, and extend- 
 ing the whole length of the 
 hinge line. This is the area' 
 
 and most Brachiopods pos- Fl - 169. DIAGRAM OP THE HINGE MECHANISM 
 , , OF A BRACHIOPOD. SECTION THROUGH BOTH 
 
 sess it only in the ventral 
 
 valve, though some are des- 
 titute of it, and some have 
 an area in each valve. No- 
 tice the notch or fissure in 
 the margin of the area. 
 There is a delicate ledge on the two sides, on which, in the per- 
 fect state, rests a cover, like a stove lid, called deltidium, in allu- 
 sion to its deltoid shape. It consists of two 
 pieces, a right and left. Sometimes the ros- 
 tral portion (nearest the beak) of the fissure, 
 or even the whole of it, becomes covered by 
 an arched pseudodeltidium fixed in position. 
 This is shown in Cyrti'na Hamiltonensis, 
 Fig. 170. But here the hinge portion of the 
 fissure is covered. 
 
 Besides the muscular scars which may be 
 seen in the interior of all Brachiopods, there 
 are always vascular impressions correspond- 
 ing to the positions of the vessels and struc- 
 tures of the internal parts. These are shown 
 in Figs. 167 and 168. In Fig. 171 we have 
 the interior of a ventral valve, showing va- 
 rious structures, and the student may exer- 
 cise himself in pointing out and naming 
 them. 
 
 Referring once more to the dorsal valve of 
 nrifera mucronata, Fig. 165, we see two projections, b, b, 
 
 FIG. 170. Cyrtina 
 Hamiltonensls. DOR- 
 SAL SIDE OF A LARGE 
 SPECIMEN. 6, the very 
 prominent ventral 
 beak ; a, the area ; ps, 
 pseudodeltidium, 
 broken away near the 
 beak; /, fold of dor- 
 sal valve, on each side 
 of which are the ra- 
 dial plications, o r 
 ribs; and these are 
 crossed, especially 
 near the margin, by 
 concentric lines of 
 growth.
 
 232 
 
 GEOLOGICAL STUDIES. 
 
 called brachial processes, the uses of which we must inquire 
 into. In getting together a considerable number of speci- 
 mens with the two valves in place, it sometimes happens that one 
 of the valves is broken away, or weathered away, so as to reveal 
 
 some internal hard 
 structures. It is 
 
 not a very extraor- 
 dinary thing to find 
 a specimen expos- 
 ing an internal 
 
 FIG. lT2.Spirifera mucrona- spire, as shown in 
 FIG. 171 OrtMs subquad- ta, WITH D o R s A L VALVE j, -^ though 
 rata. INTERIOR OF VEN- PICKED AWAY TO EXPOSE &" 
 
 TRAL VALVE, SHOWING THE SPIRES. (From Nature.) not SO completely 
 MUSCULAR IMPRES- The Dental Sockets and other ag nere seen The 
 
 SIGNS, HINGE TEETH, parts may also be seen ; but 
 
 AND VASCULAR MARK- the spires cannot be traced shell has here been 
 
 INGS. (Meek.) completely to the Brachial care f u H y picked 
 
 Processes. * J 
 
 away; and this any 
 
 student can do for himself by using a knife point, or other stout steel 
 implement. These spires cannot be traced completely to connec- 
 tion with the brachial processes, but they can be seen approach- 
 ing them. These processes, shown at b, Fig. 165, are evidently 
 the real points of attachment of the spires to the shell. The 
 spires are arm supports for the spiral, 
 fleshy, fringed arms which existed in the 
 living state, and they are, hence, some- 
 times styled the armature. The two spires 
 are generally connected together by a band 
 (Fig. 173). This, in some genera, is sim- 
 ple, and nearly direct, as here shown, and 
 in other genera becomes remarkably modi- 
 fied. 
 
 It is natural to wonder how the student 
 can know that a spire exists within a shell, 
 since there are many Brachiopods which 
 
 have no calcareous spires some even which resemble in ex- 
 ternal form the most common of those which have spires. For 
 
 FIG. \~&. Spirifera stri- 
 ata, Sow, WITH THE VEN- 
 TRAL VALVE BROKEN 
 
 ' AWAY, SHOWING THE 
 Two SPIRES AND THE 
 SIMPLE CONNECTING 
 BAND. (Woodward.)
 
 EXAMINATION' OF SOME BRACHIOPODS. 233 
 
 instance, a striking general resemblance exists between Orthis 
 bif'ora'ta, Fig. 163, and Spirif'era mneronata, Fig. 161. The 
 former, on account of its form, was long called Spirifera bi- 
 forata, until it was proved to have no spires, but on the contrary, 
 to possess the peculiar muscular scars which characterize Orthis. 
 Now, we need not wait to discover specimens naturally 
 broken or worn so as to reveal the interior. Sometimes with 
 a pointed tool we may pick away the shell sufficiently to re- 
 veal the existence or non-existence of a' spire. In any case, we 
 can grind down one of the valves by the means explained in Study 
 XXX. When we reach the region of the spires, each turn will 
 be ground off, and they will be shown on the ground surface by 
 clear points symmetrically arranged as 
 illustrated in Fig. 174, where the places 
 of the cut spire turns are seen at s, s. 
 It is evident that by continuing to grind, 
 every structure in the shell will be suc- 
 cessively intersected. If, therefore, we 
 
 make frequent examinations as we pro- 
 
 n _ r GROUND DOWN FROM BOTH 
 
 ceed, and mark down in a succession of SIDES, s, , sections of the 
 
 drawings, the positions of the sections JjJ ' wllorls - ( From Xa ~ 
 
 of each structure, we shall have, in the 
 
 end, the means of producing a connected delineation of the whole 
 
 interior. 
 
 The complicated armature of the little Brachiopod known as 
 Centronella Julia, Fig. 187, 188, 189, was worked out by break- , 
 ing in the pincers a large number of specimens, in various longi- 
 tudinal and transverse positions, and marking down each time 
 the places of the various structures broken through. 
 
 In other cases, where the substance of the shell and its filling 
 is somewhat crystalline and translucent, we may grind off all 
 parts of the exterior until the light shines through. Then, hold- 
 ing the specimen between the eye and a window, the internal 
 structures are revealed. It was by such means that the internal 
 spires were discovered in the little shell known as Zygospira 
 modesta, Fig. 178.
 
 234 GEOLOGICAL STUDIES. 
 
 EXERCISES. 
 
 Take a Lamellibranch shell and point out anterior end. The right valve. 
 Take a Brachiopod and indicate the ventral valve. What are the external 
 indications of the ventral valve? What the external indications of dorsal 
 valve? Take various fragments ot Brachiopods and explain what characters 
 show them to be such. Show areas in specimens at hand. Show place of 
 deltidium. Canyon find any pseudodeltidium? Enumerate all the charac- 
 ters which can be seen with the valves closed. Enumerate structures con- 
 cealed by the closed valves. Take a separated valve and show the hinge 
 plate. Does it bear an area? Has it sinus or fold? Is it dorsal or ventral? 
 If dorsal, point out the cardinal process. Point out the hinge sockets. 
 Point out the brachial processes. Point out occlusor scars and any other 
 characters. If it is ventral, indicate the teeth. Show the divaricator scars. 
 To which valve are the arms attached? Construct a model, if you can, 
 showing the mechanism of the hinge action of a Brachiopod; make the 
 valves of wood, and for muscles use pieces of India rubber bands. Take 
 some specimens and investigate them in the various ways described, and see 
 what internal structures can be discovered, and report results at next study. 
 
 STUDY XXXIV. further Examination of Brachiopods. 
 
 The two spire-bearing specimens examined (Figs. 172 and 173) 
 show the spires lying with their apices turned outward. The 
 study of other specimens would show the spires generally in the 
 same position. One of the commonest fossils of the northwest, 
 however, A'trypa reticularis, has the apices of the spires turned 
 toward the centre of the dorsal valve. This 
 is well shown in Fig. 175, where we see, also, 
 a plain connecting band lying in the hinge 
 region, and having its middle part bent for- 
 ward. This species is thin and elegant 
 when young; but with age it grows plump 
 and finally very obese. Different individu- 
 
 Fio m-Atrypa rtticu- als also differ iu smoothness and form. Con- 
 laris, LINN. sp. WITH sequently, inexperienced collectors, having 
 PART OF THE DORSAL & dozen Qr more of thege y common Drift 
 VALVE BROKEN AWAY, . ... 
 
 SHOWING THE APICES specimens, feel some disappointment in be- 
 OPTHE SPIRES. 6, con- j to j d tne a jj belong to one species. 
 
 necting band. (After . . 
 
 Whitfield.) Figs. 176 and 177 are views of exteriors.
 
 FURTHER EXAMINATION OF BRACHIOPODS. 
 
 235 
 
 In the southern part of Ohio and Indiana is found in great 
 abundance, an elegant little shell now known as Zygospira mod- 
 esta, Conrad sp. (Fig. 178). Thousands of them have been 
 picked up at Cincinnati; but they are also widely dispersed 
 through the Northwest. Here you see very loose spires having 
 their apices turned nearly toward the centre of the dorsal valve, 
 as in A'trypa. They are also connected by a simple band; 
 but it arises from the first turns of the spires, after they have 
 reached the anterior part of the shell. 
 
 FIGS. 170, \Tt.-Atrypa relicularis, EXTERIORS. 170, Dorsal side of thin specimen. 177, 
 Hinge margin of an obese specimen. 
 
 FIG. 178. Zygospira modesta. ENLARGED ABOUT Six DIAMETERS. MOST or THE VEN- 
 TRAL VALVE is BROKEN Aw AT TO SHOW THE INTERNAL SPIRES. 
 
 Probably, in our collection of fossil Brachiopods, is a speci- 
 men like Figs. 179 and 1G2, since this species is quite common. 
 It has a circular perforation in apex of the ven- 
 tral beak. The outline is sub-oval, both valves 
 are rather convex, and the surface is marked by 
 concentric wrinkles or lines of growth. It is 
 known as Spirig'era spiriferoi'des, and also as 
 Ath'yris spiriferoi'des. It is a common thing 
 to find one of the valves broken or worn so as 
 to expose the internal spires. It is only a few 
 years since Professor James Hall succeeded for 
 the first time in showing the complicated char- 
 acter of the connecting band _ in this genus. 
 Some conception of it may be formed from 
 Fig. 180. Suppose we take the specimen, 
 Fig. 179, and lay it on the dorsal side, with the 
 beaks to the 'right. Then conceive both valves 
 
 FIG. 179.- Spirig'- 
 era spiriftroides, 
 Hall. VIEW FROM 
 THE DORSAL SIDE. 
 a, beak of ventral 
 valve with circu- 
 lar perforation. 
 For edge view 
 showing commis- 
 sure, see Fig. 162.
 
 230 
 
 GEOLOGICAL STUDIES. 
 
 taken away and the spires left lying. Then imagine the whole 
 of both spires removed, except their first (basal or central) turns, 
 
 and their connections with the 
 brachial plates at , and also 
 the complicated connecting- 
 band. What remains, enlarged 
 about four times, is the part 
 shown in Fig. 180. Consider 
 the nearest, or left hand spire. 
 It is indicated by the shading. 
 
 FIG. 180. -CENTRAL PORTION OP ARMA- I t starts at , from the brachial 
 TURE OF xpirig'era spiriferoides. The n . 
 
 lower side of the figure is the dorsal side. process, extends forward a short 
 
 distance, then turns upward 
 
 and backward as shown at b, and diverging somewhat toward the 
 left margin, passes down into the dorsal valve, and begins the 
 first or basal turn of the spire. At i it is represented as broken 
 off. The connecting band springs up at d, as a flattened process 
 which twists around so that the outside becomes inside and joins 
 its fellow from the other side at e ; then the two turn straight 
 backward, make a right angle upward toward the ventral valve, 
 and, separating at /*, the left hand branch describes a backward 
 1( curve to //, and then bends 
 
 downward nearly parallel 
 with the first turn of the 
 spire, and forward to h, 
 where it joins the spire. 
 
 FIG. \%\.Syringoth'yrls typus, Wiu. D, Dorsal 
 valve. V, Ventral valve. I, I, Dental lamella?. 
 A B, line of section shown in Fig. 182. The high 
 beak is turned down. 
 
 FIG. 182. PECULIAR INTERNAL 
 STRUCTURE OF Syrlngoth'yris 
 typus, Win. Section along the 
 line A B in Fig. 181. /, I, dental 
 lamellae ; mm, transverse plate ; 
 t, fissured tube.
 
 FURTHER EXAMINATION OF BRACHIOPODS. 
 
 237 
 
 FIG. 183. INTERNAL STRUCTURE OF 
 Syringolh'y /is distans, Sow. (Zittel.) 
 From the Carboniferous Limestone 
 of Belgium. D, pseudodeltidium; 
 x, dental lamellae; y, transverse 
 plate; z, fissured tube. 
 
 Various other modifications of the connecting band exist in other 
 genera. 
 
 In central and northern Ohio, and in Iowa and Michigan, is 
 another peculiar modification of the internal structure of spire- 
 bearing shells, which has been 
 named Syringoth'yris. The com- 
 monest species is S. typus, Win- 
 chell. It has, as Fig. 181 shows, a 
 very high beak in the ventral valve, 
 and an enormous triangular area, 
 with a three-cornered opening 
 sometimes partially closed by a 
 pseudodeltidium, Z>, Fig. 183. 
 From the dental lamellae, /, I, 
 Fig. 182, springs, on each side, a 
 transverse plate, m m, and these 
 meeting in the median plane 
 curve downward and are so bent as to form the two sides of a 
 fissured tube, t. Fig. 183 illustrates the modification of this struc- 
 ture in a European species of 
 the same genus. 
 
 All the Brachiopods thus far 
 illustrated are spire-bearing, 
 and constitute, with still other 
 genera, the family Spirifer' idee. 
 How they are to be studied has 
 been shown with sufficient de- 
 tail for a student of the ele- 
 ments of geology. But I must 
 not leave the impression that all 
 Brachiopods are spire-bearing. 
 The highest family, Terebratu'- 
 lidce, is composed of genera 
 which have a loop. This pre- 
 sents many curious modifications, but as most of the species 
 belong to formations and ages (Mesozoic) not represented in 
 
 FIGS. 184, 185. Ter- 
 ebratula Romin- 
 geri, WIN., HAM- 
 ILTON GBOUP: 
 MICHIGAN, NAT. 
 SIZE. 184 View 
 from dorsal side, 
 with most of dor- 
 salvalve removed, 
 showing short 
 loop, I; b f , beak 
 of dorsal valve ; 
 d', deltidium. 
 
 185 VIEW PROM 
 LATERAL COMMIS- 
 SURE, SHOWING 
 
 THE LOOP FROM 
 
 THE SIDE, a, an- 
 terior margin; 6, 
 beak of ventral 
 valve with circu- 
 lar perforation ; 
 d, dorsal valve ; 
 v, ventral valve; 
 L, loop.
 
 238 
 
 GEOLOGICAL STUDIES. 
 
 the rocks occurring near the homes of most who use this book, 
 I shall offer only two illustrations. .The first is Terebrat 'ula. 
 The form of the shell is ovoid very different from most of the 
 spire bearers; the hinge line is short, Fig. 184, and the ven- 
 tral beak has a circular perforation. The exterior is nearly 
 smooth and marked by a few concentric, striations, or it is 
 radially striated and rarely plicated. Examined with a lens, it 
 is seen marked by thousands of minute pwictations, like needle 
 pricks, and this is true of the whole family. The armature 
 consists of a loop, which extends from the brachial processes 
 forward, and is generally turned back into the ventral valve 
 at the anterior extremity. This is shown in Figs. 184, 185, 
 
 FIG. 186 LOOP OP Terebrat'ula 
 (Waldkeim'ia) flavescens. Re- 
 cent. [The name of a sub-ge- 
 nus stands in parenthesis after 
 the name of the genns.] c e, 
 cardinal process; , dental 
 sockets, connected by hinge- 
 plate ; /, loop, the anterior por- 
 tion of which is seen reflected ; 
 a, a, anterior and posterior ad- 
 ductor or occlaeor scars (each 
 in pair), with the median sep- 
 tum between. This sub-genus 
 of Terebrntula has a large and 
 reflected loop. Compare Figs. 
 184, 185. 
 
 FIGS. 1S7, 188, ISQ Centronella Julia, WAVEKLY OR 
 MARSHALL GROUP. 187. View from dorsal side, 
 X3. 188. Dorsal view of loop, X4. 189. Lateral 
 view of loop and vertical plate, X4 
 
 and more in detail in Fig. 186. 
 
 The only other genus to which I 
 shall refer is C entronetta. The loop 
 has been fully worked out in the spe- 
 cies Centronella Julia, which is illus- 
 trated in Figs. 187, 188, 189. The loop 
 is shown in Figs. 188, 189. The geo- 
 logical position is possibly in the Che- 
 mung. 
 
 Many of the Brachiopods found in 
 the Drift are entirely destitute of cal- 
 
 careous armature, either spire or loop. 
 An extremely common form is somewhat semicircular in outline,
 
 FURTHER EXAMINATION OF BRACHIOPODS. 
 
 239 
 
 having the ventral valve very convex and the dorsal concave. 
 Some of these forms were figured for the purpose of showing 
 hinge structures and other internal characters. (See Figs. 
 167, 168, 169.) Here, in Fig. 190, is given a view of the ven- 
 tral valve of Strophome'na incequiradiata, Con. Fig. 191 
 shows the dorsal valve of Strophome'na alternata, Con., as 
 also the area and depressed beak of the ventral valve, and the 
 arched pseudodeltidium. The dorsal valve of Strophomena is 
 
 FIG. 190 Strophome'na in- 
 aquiradiata, DEVONIAN. 
 
 View from ventral side. FIG. 191 Strophome'na alternata, CAM- 
 (Billings.) BRIAN. Dorsal view, showing also 
 
 area and pseudodeltidium of ventral 
 
 valve. (Meek.) 
 
 FIG. 192-LoNGi- 
 TUDINAL SEC- 
 TION THROUGH 
 
 THE TWO 
 
 VALVES OP & 
 incequiradi- 
 ata. (Billings.) 
 
 externally concave, as is shown by the longitudinal section, 
 Fig. 192. 
 
 The further study of Brachiopods belongs in an advanced 
 course. The descriptions and illustrations of internal structures 
 already given are far more than is customary in elementary trea- 
 tises; but they have been given because the illustrative speci- 
 mens can nearlv all be picked up from the Drift, and worked out 
 by the student. They belong to the accessible inductive data of 
 the science; and because the student can reach them by his own 
 manipulation and research, I am sure they will awaken an eager 
 interest. 
 
 The student making actual researches will be aided by the
 
 240 GEOLOGICAL STUDIES. 
 
 following table, in which the characters pertaining to each valve 
 are brought together by themselves : 
 
 VENTRAL VALVE. DORSAL VALVE. 
 
 EXTERNAL CHARACTERS. EXTERNAL CHARACTERS. 
 
 Most prominent Beak. 
 Perforation for pedicle, if any. 
 
 Most conspicrfons Area. Area generally wanting. 
 
 Notch or Fissure in Area. Notch present when area is. 
 
 Deltidium or False Deltidium. 
 
 Sinus, if one exists (save in very few Fold, if one exists (sinus in very few 
 forms). forms). 
 
 INTERNAL CHARACTERS. INTERNAL CHARACTERS. 
 
 Teeth for articulation. Sockets, to receive teeth of opposite valve. 
 
 Divaricator Scars (generally one large one Cardinal Process (for attachment of Di- 
 
 each side of median line). varicator muscles) . 
 
 Ocelusor Scars (generally two crowded be- Occlusor Scars (generally four). 
 
 tween the rear parts of the Divaricators). 
 
 Dental Lamellae. Foveal Plates bearing the Sockets. 
 
 Armature (Spires or Loop). 
 Crura (or basal portions of Armature). 
 Brachial Process (for attachment of Arma- 
 ture). 
 
 Finally, to aid the real working student, I append an ana- 
 lytical table, but only of the genera here illustrated, most of 
 which are by far the commonest, whether in the Drift or in the 
 rocks. Two or three genera are here included, because they pos- 
 sess interesting internal characters. The table is based on the 
 method which the young student will naturally pursue first, 
 observation of external form and other characters; then, study 
 of internal characters : 
 
 TABLE FOR DETERMINATION OF SOME COMMON BRACHIOPODS. 
 
 Hinge line long and straight; often the greatest transverse diameter of the 
 shell. Form of shell somewhat triangular or semicircular. 
 Beak imperforate. Surface plicated or striated. 
 
 Sinus and fold well developed. Form more or less angulated at the hinge 
 extremities; sometimes rounded. Exterior distinctly, often 
 strongly, plicated. 
 
 Area only in ventral valve, which has a triangular notch. Armature con- 
 sisting of two spires having the apices turned to the right and 
 left.
 
 FURTHER EXAMINATION OF BRACHIOPODS. 241 
 
 ^N"o pseudodeltidium. 
 
 SPIRIFERA. Figs. 161, 162, 164, 165, 172, 173, 174. 
 Pseudodeltidium present. Ventral beak very prominent; area very 
 
 large. 
 
 Exterior sharply plicated. Pseudodeltidium complete. Shell struc- 
 ture punctate. 
 CYRTINA. Fig. 170. 
 
 Exterior with medium-sized, rounded plications. Pseudodeltidium 
 partial. Notch with a deep transverse plate, beneath which is 
 a fissured tube. 
 
 SYRINGOTHYRIS. Figs. 181, 182, 183. 
 
 Area in each valve, nearly equal in the two. Triangular notch in each 
 valve. No calcareous armature. Saucer-like pits within for 
 insertion of muscles ; exterior sharply plicated. 
 Delthyroid Section of ORTHIS. Figs. 163, 166. 
 
 Sinus and fold wanting or feebly developed. Outline somewhat semi- 
 circular. Area in each valve, the ventral the broadest, and 
 having a triangular notch, which is sometimes covered by a 
 pseudodeltidium. Ventral valve very convex; the dorsal often 
 concave externally. Surface radiately striated. Cardinal proc- 
 ess bifid and prominent. Calcareous armature wanting. 
 Non-resupinate Section of STROPHOMENA. Figs. 167, 168, 172, 
 191, 192. [The " resupinate " section has the ventral valve con- 
 cave, and dorsal convex.] 
 
 Hinge line short, generally inconspicuous. Exterior plicated, concentrically 
 
 wrinkled, or smooth. Perforation at or beneath the ventral 
 
 beak, either conspiciious or half -concealed. Sinus and fold 
 
 wanting or indistinct. Form ovoid. 
 
 Area beneath ventral beak, and having a triangular notch. Spires 
 
 within. 
 
 Rostral perforation conspicuous. Exterior concentrically wrinkled. 
 Sinus and fold nearly absent. Apices of spires turned outward. 
 SPIRIGERA. Figs. 179, 180. 
 .Rostral perforation concealed or inconspicuous. Apices of spires 
 
 turned toward centre of dorsal valve. 
 
 Exterior with strong, sometimes squamous or even spiny, concentric 
 markings, and strong radial plications. Adult shell tumid. 
 Coils of spires numerous and crowded. 
 ATRYPA. Figs. 175, 176, 177. 
 
 Exterior without conspicuous concentric markings; radial plications 
 small. Adult shell small and lean. Whorls of spires few and 
 loose.
 
 242 GEOLOGICAL STUDIES. 
 
 ZYGOSPIRA. Fig. 178. 
 
 Area beneath ventral beak wanting or scarcely perceptible. Notch usu- 
 ally opening into the large, circular rostral perforation, and 
 generally closed by a pair of deltidial pieces. Exterior smooth 
 or concentrically lined, or radially striate or plicate. Sinus and 
 fold sometimes wanting, generally little developed, and some- 
 times both valves feebly sinuate near anterior margin. Shell 
 minutely punctate. Armature a loop. 
 The loop anteriorly folded back ; not embracing a free, vertical plate. 
 
 TEREBRATULA. Pigs. 184, 185, 186. 
 
 The loop not folded back anteriorly, embracing a vertical, free, longi- 
 tudinal, spiny-margined plate. 
 CENTRONELLA. Figs. 187, 188, 189. 
 
 EXERCISES. 
 
 What results have you reached in the investigations proposed at the last 
 study? Test the "Table for Determinations" with all the Brachiopods you 
 get. Try to make a model of the armature of Spirigera, using cork, paste- 
 board, and mucilage. Make a model of the armature of Centronella. Make 
 a model of the armature of Terebratula flavescens. Make a model of the 
 hinge region of Syringothyris, using white pine, pasteboard, and mucilage. 
 Copy, with lead pencil or with India ink, any of the illustrations of Brachi- 
 opods. Make a drawing of a Brachiopod collected by yourself. Grind down 
 a specimen so as to demonstrate the nature of its armature. Show a speci- 
 men having a pseudodeltidium. Pick out all the specimens differing from 
 any of the genera here described. Take one of these and write out a descrip- 
 tion for yourself, first using the external characters. Make a drawing of the 
 same. Find out all possible of the internal characters. Write a description 
 of them. Which of the genera here described does this specimen most 
 resemble? What prevents its belonging to that genus? Take another speci- 
 men different from any genus here described, and state whether you think it 
 has any calcareous armature. If it has, do you think it a pair of spires? 
 Have you ever noticed a resupinate species? What genera have an area in 
 each valve? 
 
 We have now pursued this method of instruction as far as the 
 time of the elementary student will permit. We have shown him 
 how to take his lesson from nature, and have inspired, it is hoped, 
 some enthusiasm for the science. He has collected; he has ob- 
 served; he has drawn inferences; and from these he has reasoned
 
 FURTHER EXAMINATION OF BRACHIOPODS. 243 
 
 out other facts which could not be observed. This is the method- 
 by which investigators have created the science. It is the natural 
 method of beginning the study. The method might very advan- 
 tageously be extended over various departments of the field not 
 yet mentioned; but our time is insufficient. 
 
 The facts and conclusions reached thus far must necessarily 
 exist for the present in a partially undigested, confused, and un- 
 satisfactory state. The scattered facts and principles reached by 
 the observational and inductive method which we have pursued 
 ought now to be reviewed under some systematic and logical 
 arrangement. A good amount has already been done in the 
 course of these Studies, to bring facts into systematic arrange- 
 ment; but it would be well if the student could now review the 
 whole body of facts in logical order. As this, with most students, 
 would require more time than can be afforded, we are forced to 
 reduce Part II chiefly to a statement of some broader generaliza- 
 tions than have yet been made, and the presentation of some 
 important additional facts and principles which cannot be omitted 
 from the elements of the science.
 
 PAET II. 
 
 SYSTEMATIC STUDIES; 
 
 OR, OUTLINES OF A LOGICAL ARRANGEMENT OF THE FACTS AND 
 THE LESSONS THEY TEACH. 
 
 General Definitions and Divisions of the /Subject. 
 
 EOLOGY, as a term, is derived from fT t , the earth, and 
 
 yoq, a discourse. 
 As a science, it treats of the earth's Constitution, Condition, 
 History, and Adaptations to human wants. 
 
 The following scheme shows the logical subdivisions of the 
 science: 
 
 Constitution, 
 
 Material (I. Lithological). 
 Mechanical (II. Structural). 
 Condition, 
 
 Temperatures, 
 Solidity or Fluidity, 
 Rigidity. 
 
 History, and its Evidences, 
 Grounds of Inference, 
 
 Existing Dynamic Agencies, 
 Records of Former Actions, 
 Thermal, 
 Chemical, 
 Mechanical, 
 Organic. 
 
 (IV. Palaeontological). 
 (V. Formation al). 
 
 Succession of Events (VI. Historical). 
 Adaptations (VII. Economical). 
 
 245
 
 246 GEOLOGICAL STUDIES. 
 
 The terms above appended in parentheses are the general 
 divisions of the subject which will be employed in the following 
 synoptical treatment. They may be defined as follows: 
 
 I. LITHOLOGICAL GEOLOGY. That division of Geology which 
 treats of the elementary arid mineralogical constitution of the 
 Rocks, and their mechanical condition. 
 
 II. STRUCTURAL GEOLOGY. That division of Geology which 
 treats of the Superposition, Succession, Attitudes, Accidents, 
 and Classification of Rocks, both Stratified and Unstratified. 
 
 III. DYNAMICAL GEOLOGY. That division of Geology which 
 treats of the Forces and Modes of Action which have produced 
 the results witnessed. 
 
 IV. PALAEONTOLOGY. That division of Geology which treats 
 of the Organic Beings, vegetable and animal, which lived in 
 former ages of the world. 
 
 V. FORMATIONAL GEOLOGY. That division of Geology which 
 treats of the successive systems of rocks and their subdivisions, 
 and indicates the order of distribution of fossil remains through 
 them. (Divisions IV and V furnish the principal data of Division 
 VI.) 
 
 VI. HISTORICAL GEOLOGY. That division of Geology which 
 narrates the succession of terrestrial events, as induced from the 
 data supplied by the preceding divisions, and as deduced from 
 the recognized principles of the science. 
 
 VII. ECONOMIC GEOLOGY. That division of Geology which 
 enumerates, describes, and locates the various mineral substances 
 possessirig utility for man, and explains the methods of extract- 
 ing them from the earth, and reducing them to an available con- 
 dition. 
 
 In the following sketch, none of the above divisions can be 
 carried beyond a very elementary treatment, and two of them 
 must be dismissed with references to Studies in Part I. 
 
 That part of the earth which is accessible to our investigations 
 is called the crust. Nearly the whole of the earth's crust is in a
 
 GENERAL DEFINITION'S AND DIVISIONS. 247 
 
 mineral condition. A mineral is a definite chemical compound, 
 not depending on the presence of life for its maintenance. A 
 rock is any mass of mineral matter. Most of the matter of the 
 rocks has been arranged through the action of inorganic forces; 
 but some portions of it are of organic origin / though nothing 
 which can be said to form a part of the earth is properly organic. 
 A rock is not necessarily solid.
 
 CHAPTER I. 
 LITHOLOGICAL GEOLOGY (PETROGRAPHY); 
 
 OR, WHAT HAS BEEN LEARNED ABOUT THE MATERIALS OF THE 
 EARTH. 
 
 [The attention already paid to the subject in Part I renders it unnecessary to intro- 
 duce a complete summary in this place, the more so since summaries and tables covering 
 most of the topics may there be found.] 
 
 1. Chemistry. 
 Some rudimentary ideas may be found in Study IV. 
 
 2. Mineralogy. 
 
 See this subject explained in Studies V, VI. See the Gen- 
 eral Review, the Table of Composition of Minerals, and the 
 Table for Determinations, in Study VII. 
 
 3. Kinds of Bocks. 
 
 A rock is a mass of mineral matter, consisting of a single min- 
 eral, or an aggregate of minerals. Rocks are characterized and 
 distinguished by their mineral constitution, their physical struc- 
 ture, and their position or attitude in reference to other rocks. 
 
 1. PHYSICAL CONDITIONS OP ROCKS. 
 
 (1) Mineral Constitution. () ESSENTIAL CONSTITUENTS. 
 Those minerals whose presence determines the specific identity of 
 the rock, and the absence of one of which would make it some 
 other rock species. The particular specifications belong to the 
 definitions of the rock-species which will be cited beyond. 
 
 (b) ACCESSORY CONSTITUENTS. Those minerals which are 
 present in addition to the essential ones. If abundant enough to 
 impart any conspicuous or otherwise important character, they 
 furnish a qualifying term for the name of the rock, as shown 
 below : 
 
 348
 
 LITHOLOGICAL GEOLOGY. 249 
 
 Quartzose, or quartziferous, containing quartz. The qualify- 
 ing constituent may be of such variety as to render a rock ame- 
 thystine, agatiferous, chalcedonic, flinty, cherty, or jaspery. 
 When the quartz is in small grains, the rock is arenaceous. 
 When it is intimately disseminated, or combined, the rock is 
 silicious a term often used, also, as equivalent to quartzose. 
 
 Ferruginous, when stained red or yellow by the presence of 
 oxide of iron. If distinct grains of haematite or limonite are 
 present, the rock is hcematitic, or limonitic. 
 
 Pyritous, or Pyritiferous, containing pyrites. 
 
 Saliferous, containing halite, either crystalline, or in solution. 
 
 Fddspathic, or Felsitic, containing feldspar; but the latter 
 term may be restricted to the presence of feldspar in the state of 
 a matrix, or ground holding other minerals imbedded or inti- 
 mately mixed; but in this sense felsitic is only the adjective form 
 of felsite. 
 
 Kaolinic, containing kaolin. Micaceous, having disseminated 
 scales of mica. Hydromicaceous, having disseminated hydro- 
 mica. Talcose, or Talcitic, having talc in scales or grains. Ser- 
 pentinous, containing serpentine. Chloritic, containing chlorite. 
 
 Amphibolic, containing arnphibole. Varieties of this are 
 hornblendic, tremolitic, and actinolitic. 
 
 Pyroxenic, containing pyroxene. Varieties are augitic and 
 diallagic. 
 
 Tourmalinic, containing tourmaline. Fjpidotic, containing 
 epidote. Garnetiferous, containing garnets. 
 
 Calcitic, or calciferous, containing calcite. But when calcite 
 is present in an impure or amorphous condition, the rock is com- 
 monly described as calcareous. This term is also used when 
 calcite is the essential ingredient. 
 
 Dolomitic, containing dolomite. Sideritic, containing sider- 
 ite. 
 
 Argillaceous, having some clayey matter disseminated. But 
 when mingled in undiscefnible particles, or in a state of intimate 
 union, the term aluminous is preferable. 
 
 Carbonaceous, with carbon disseminated, generally imparting
 
 250 GEOLOGICAL STUDIES. 
 
 a dark or black color. Bituminous, containing bitumen. Petro- 
 liferous, containing petroleum. 
 
 Many of the same terms are employed to express the essential 
 constituents of rocks. Thus a micaceous rock is one, also, which 
 has mica for an essential constituent. A talcose schist is one 
 characterized by talc. Ordinarily, where practicable, the essen- 
 tial constituent is indicated by retaining the substantive form in 
 a compound word. Thus mica-schist, hornblende-schist, having 
 mica or hornblende as essential constituent; while micaceous 
 sandstone, micaceous hornblende-schist, hornblendic mica-schist, 
 and hornblendic gneiss, indicate mica and hornblende as mere 
 accessories. It would, perhaps, be a convenience if the termina- 
 tion -ose (osus, abounding in) were employed to denote an essen- 
 tial constituent, in distinction from an accessory one. We should 
 then have rocks characterized as micose, calcarose, serpentinose, 
 augitose, carbonose, etc., in distinction from others simply mica- 
 ceous, calcareous, serpentinous, augitic, carbonaceous. 
 
 (2) Physical Constitution, (a) FRAGMENTAL ROCKS are 
 such as are composed of fragments of other rocks. Of these, a 
 
 Conglomerate is composed of coarse rounded fragments and 
 pebbles; and when of the size of mustard seed, with some smaller, 
 it is a grit. A cemented mass of angular fragments is a breccia. 
 
 Sandstone, composed of fine rounded grains generally grains 
 of quartz more or less firmly cemented. 
 
 Granular signifies composed of grains. Granite is a granu- 
 lar rock; but most granular rocks are not granite. 
 
 Earthy, lustreless, of indistinguishable particles and not hard- 
 indurated. 
 
 Sand. Fine grains of any sort of mineral or rock, most fre- 
 quently silicious. When of volcanic origin, it is Volcanic sand 
 or Peperino, derived from the " cinders " or " ashes " (commi- 
 nuted lava) produced during an eruption. When the ashes 
 become consolidated they constitute volcanic tufa. None of these 
 substances have any fixed constitution. 
 
 (b) CRYSTALLINE ROCKS. Consisting chiefly of distinct crys- 
 tals or fragments of crystals. Careful observations show that
 
 LITHOLOGICAL GEOLOGY. 251 
 
 this condition sometimes results from solution in icater, as in 
 depositions from springs; sometimes from solidifying from fusion, 
 as in lavas and other erupted rocks; and sometimes through 
 met amor phism of deposits originally fragmental, as in the com- 
 mon crystalline rocks. 
 
 Phanerocrystalline, having the separate crystal fragments 
 visible to the naked eye, or with a simple lens. 
 
 Macrocrystalline, exceedingly fine-grained, requiring a com- 
 pound microscope and thin slices to distinguish the constituents 
 (Rosenbusch). 
 
 Cryptocry&talline, when no magnifying power employed on 
 thin sections discloses the constituent minerals; while at the 
 same time, the whole mass, being composed of doubly refracting 
 particles, has evidently a crystalline texture (Rosenbusch). 
 
 Jtficrofelsitic, partly crystalline, but with an optically iso- 
 tropic or uncrystalline base, used especially for felsites. 
 
 Colloid (like glue), glassy and homogeneous under high 
 powers. When a rock of colloid texture reveals lines suggesting 
 a flow of molten matter, these are styled fluidal, and the texture 
 is fluidal. 
 
 Porphyritic, having distinct crystals disseminated through a 
 mass of some other kind, either phanerocrystalline or cryptocrys- 
 talline. If the disseminated crystals are of feldspar, we say sim- 
 ply, the rock is porphyritic; and if the base is also felsitic, the 
 rock \sporphyry. But if the disseminated crystals are pyroxene 
 or hornblende, we say the rock is porphyritic with pyroxene or 
 with hornblende. 
 
 (c) RELATIONS or ROCKS TO MECHANICAL AND CHEMICAL 
 ACTIONS. Hardness depends on the adhesion of the particles 
 under pressure. Quartz is hard, but gypsum is soft. 
 
 Srittleness is determined by the readiness of the particles to 
 separate under a sudden shock, like a blow with a hammer. 
 Quartz is brittle though hard. 
 
 Toughness is reluctance of particles to separate under a sud- 
 den shock or blow. Hornblende, pyroxene and serpentine are 
 tough, though more or less soft.
 
 252 GEOLOGICAL STUDIES. 
 
 Compactness is closeness of texture; but it does not neces- 
 sarily make a hard or tough rock. Serpentine is compact though 
 soft, and a granular quartzite is hard, though not always com- 
 pact. Porosity is the reverse of compactness. 
 
 Friability is incoherence of parts. The parts, however, may 
 possess any degree of hardness, as in friable sandstones. 
 
 Durability is absence of disposition to change under the 
 influences exerted. Against durability is solubility of the rock 
 (like limestone or gypsum), or of the cementing material of its 
 parts, as the calcite in some sandstones; also porousness, which 
 admits water to augment its solvent action, and permits, also, the 
 entrance of frost to exert its mechanical action. 
 
 (3) Stratified and Unstratified States, (a) The Strati- 
 fied Condition. The materials are arranged in layers or beds 
 called strata. These may exist in any im- 
 aginable attitude or condition. Strata are 
 separated by narrow openings. These 
 constitute seams when filled with some 
 
 FIG.193.-SEAMS AND special sort of matter (Fig. 193). When, 
 STRATA THICK-BEDDED however, a very thin layer between two 
 
 sTJsTrr^eUveen strata is a result of sedimentation it is a 
 
 them. stratum or bed. 
 
 Massive, or Thick-bedded, indicates 
 
 ISI thick or heavy strata. The term has no 
 
 ^--^ ^ _rZ^--= definite limits, but we may say the strata 
 
 FIG 194 LAMINATED are a foot or more in thickness. 
 
 STRATIFICATION on Thin-bedded refers to thin strata, but 
 
 SHALT STRUCTURE. , . . TTT 
 
 has no precise meaning. We may say the 
 
 strata are four inches or less in thickness. 
 
 Shaly, having the materials deposited in very thin layers or 
 leaves as in Fig. 194. 
 
 Laminae are thin subdivisions of strata. The layers of a 
 shale are laminae. 
 
 (b) The Unstratified Condition. This exists when the evi- 
 dences of stratification are wanting. The metamorphic rocks, 
 for the greater part, show but feeble and remote signs of strati-
 
 LITHOLOGICAL GEOLOGY. 253 
 
 fication ; but they may generally be discovered in (ad) the seams 
 which intersect the rock- mass, or (bb), lines or bands in the dis- 
 tribution of the mineral constituents, especially mica, hornblende 
 and pyroxene, or (cc) in some other inequality in the distribution 
 of the constituents as in color or coarseness, or finally (dd) in 
 the fact that the scales and lamellae of the minerals are mostly 
 disposed in one direction. (This disposition of scales, however, 
 is not necessarily the result of sedimentation.) 
 
 2. METHODS OF STUDYING ROCKS. 
 
 (1) Physical Examinations. Study of the mineral con- 
 stituents through their physical characters; study of the physical 
 constitution and condition of the rocks ; whether stratified or 
 unstratified (massive); whether crystalline, uncrystalline, colloid, 
 or porphyritic; and if stratified, whether thick or thin bedded. 
 Here are embraced also, observations of color, lustre and weight. 
 This is the method most available for the elementary student, 
 and hence, the one here employed. 
 
 (2) Microscopic Examinations. Thin, transparent or 
 translucent slices of rocks prepared as indicated on page 205, 
 and examined with a polariscope-microscope, reveal, by the optical 
 and minute textural characters shown, the nature of the con- 
 stituent minerals. This is accomplished either in phanerocrystal- 
 line or microcrystalline rocks. This method of study, introduced 
 within a few years, is constantly growing in importance, and has 
 become indispensable in all thorough work. But we must be 
 content to postpone the employment of it to an advanced course. 
 
 (3) Chemical Examinations. At one period in the his- 
 tory of petrology the chemical investigation of rocks was consid- 
 ered, perhaps justly, as the most exact method available; and 
 classifications were then based on chemical constitution. Various 
 expedients for arriving, through chemical processes, at the mine- 
 ral ingredients of rocks, have been proposed; but we need not 
 explain them here. Aggregate or average chemical characters 
 are still employed, as in the terms acidic and basic, but on the 
 whole, chemical methods with rocks generally have fallen into
 
 254 GEOLOGICAL STUDIES. 
 
 disuse. It may be necessary to add, however, that in the study 
 of minerals, chemistry holds the first place. 
 
 (4) Magnetic Examinations. These have some repute 
 in the study of certain classes of rocks, and magnetic indications 
 are probably useful in explorations for beds of iron ore (see T. 
 B. Brooks in Mich. Geol Rep., 1869-73, Vol. I, Chap. viii). 
 But it is not appropriate to enter upon the subject in this place. 
 
 3. MOST IMPORTANT SPECIES OP ROCKS. 
 
 We again refer the reader to Part I. The principal species and 
 groups of rocks are treated in Studies IX-XIII. In Study XIV 
 we have also a retrospect, embracing a systematic Table of Rock 
 Structure, a Table of Rock Compositions, and also a Table for 
 Rock Determination. The latter indicates the eleven series under 
 which the rocks may be classed. 
 
 V
 
 CHAPTER II. 
 STRUCTURAL GEOLOGY (GEOGNOSY) ; 
 
 OB, WHAT HAS BEEN LEARNED ABOUT FORMATIONS. 
 
 1. General Definitions. 
 
 FORMATION. The term Formation is used in Geology, as 
 elsewhere, to express the abstract conception of process or act 
 of forming. It is also used in a concrete and specially litholog- 
 ical sense to denote that which has been formed. It is the litho- 
 logical result of an action or concert of actions producing some- 
 thing possessing unity and completeness. A particular " forma- 
 tion," though it may be a constituent of something which 
 embraces it, has limits and completeness in itself. A bed of 
 shale is a formation, and so is a bed of sandstone; and these two 
 may be so affiliated together, and so differentiated from other 
 beds of rocks, as to constitute a formation. A doleritic dike is 
 also a formation; and if it intersects the shale and sandstone, the 
 three constitute a formation. The term is thus general or com- 
 mon, without fixed breadth of application. The term terrane is 
 employed in a sense almost identical. 
 
 The most frequent application of the term formation is to 
 stratified beds, and hence ordinarily it refers to beds belonging 
 to one particular interval of time, as the " Cretaceous formation," 
 the "Potsdam formation." 
 
 Sedimentation. The deposition of rock material by subsi- 
 dence in water. 
 
 Stratification. The arrangement of rock material in succes- 
 sive layers. This generally results from sedimentation. 
 
 Layer. A single sheet of sedimentary material. 
 
 Stratum. A series of layers intimately connected. The lay-
 
 256 
 
 GEOLOGICAL STUDIES. 
 
 ers may differ in color or fineness, or, within small limits, in ma- 
 terial. The term bed is often employed in the same sense. A 
 bedded rock is a stratified rock. 
 
 Seam. The parting plane between two strata. It is gener- 
 ally in the nature of a thin, non-sedimentary layer, different from 
 the contiguous layers above and below. The substance of seams 
 is often clay, less or more bituminous, or even pure inspissated 
 bitumen or coaly matter. 
 
 Fossil. The relic or trace of an organic being, animal, or 
 plant, embraced in the substance or open spaces of a rock or a 
 formation. Rocks containing fossils are fossiliferous. 
 
 2. Accidents of Stratified Bocks. 
 
 1. Accidents of Sedimentation. The terms conglom- 
 erate, arenaceous, granular, sandy, shaly, and earthy are briefly 
 defined (p. 250) in explaining terms employed in rock descrip- 
 tions. It is only necessary to add the following : 
 
 Oblique Lamination. This is seen when the lines of lami- 
 nation are inclined to the plane of stratification. The same in- 
 clination of the laminae may persist throughout a considerable 
 
 extent of the stra- 
 tum (Fig. 195), 
 or may change at 
 frequent inter- 
 vals. 
 
 Ebb and Flow 
 Structure. Con- 
 sisting of layers 
 of various kinds 
 
 within one stratum, some being irregu- 
 lar, and others horizontally or obliquely 
 laminated (Fig. 196). 
 
 Drift Structures. This denotes abrupt 
 terminations of laminated beds and ir- 
 regular changes in inclination of laminae, as shown in Fig. 195. 
 
 FIG. 195. OBLIQUE OR CROSS 
 LAMINATION IN POTSDAM 
 SANDSTONE, Wis. (After 
 Strong.) The horizontal 
 strata are separated by the 
 seams s, s, s. The lamina- 
 tion in each stratum (except 
 part of the lower) is un con- 
 formable oblique and irreg- 
 ular. 
 
 PIG. 196. EBB AND FLOW 
 STRUCTUUE. (Foster and 
 Whitney.)
 
 STKUCTUUAL GEOLOGY. 
 
 Besides its occurrence in regularly stratified formations, it is 
 everywhere shown in the " Modified Drift " (see Figs. 7, 8, and 9). 
 
 Ripple Marks. Ridges like miniature waves on the surface 
 of a stratum. They are often seen on the surface of sand drifted 
 by the wind. 
 
 Main Prints. Marks of rain drops, produced when the stra- 
 tum was a soft beach sediment. 
 
 Mud Flow. Appearances like flowing mud on the surfaces 
 of strata. (Compare Fig. 199). 
 
 2. Accidents of Secondary Origin. Many changes have 
 
 taken place in the structure and mechanical condition of strata 
 since the time of their original deposition. 
 
 Mud Cracks. Irregularly intersecting fissures, appearing like 
 cracks produced in drying, and subsequently filled by other sedi- 
 ments. The filling of each crack shows a median joint or fissure, 
 as if the deposit had flowed down each of the opposing walls, 
 forming layers which met in the middle. 
 
 Cone in Cone, A singular and unexplained structure seen 
 in some argillaceous strata, having lines of structure arranged in 
 conical or trumpet- 
 shaped forms in sev- 
 eral series, which 
 seem to be associ- 
 ated together in 
 nests. 
 
 Lignilites, Stylo- 
 
 lites, or Tootfied Structure. Partings in certain 
 limestones which are roughly conformable with the 
 stratification, but have their surfaces studded with 
 tooth-like projections, which interlock from oppo- 
 site sides, and appear as the terminations of stri- 
 ated or furrowed pegs which penetrate the rock 
 vertically, above and below, and at a distance generally less than 
 three inches become confluent with it. The partings and the peg- 
 like forms are generally blackened with bituminous matter. 
 
 FIG. 197. Co 
 
 FIG. 198. 
 
 TOOTHED STRUC- 
 TURE, OFTEN 
 CALLED Lignil- 
 ites.
 
 258 
 
 GEOLOGICAL STUDIES. 
 
 Concretionary Structure. This consists of concentric layers 
 of materials around some centre, at which may be found fre- 
 
 FIG. 199. CALCAREOUS CONCRETIONS. 
 (From the Portage Shales of northeastern Ohio.) 
 
 quently a crystal or some organic fragment. Instead of con- 
 centric layers, the structure is often radiated. Sometimes these 
 
 masses show shrink- 
 age cracks, which 
 have been subse- 
 quently filled, and 
 thus form what are 
 vulgarly called "tur- 
 tle stones," and 
 sometimes " septa- 
 ria." Kidney iron 
 stone consists of 
 FIG. 200. JOINTED STRUCTURE SEEN IN ONONDAGA LIME- concretions (see p. 
 STONE AT "SPLIT ROCK," NEAR SYRACUSE, N.Y. (Van- ^ Some alumino- 
 nxem.) ' 
 
 calcareous concre- 
 tions assume very curious forms, four of which are shown in Fig. 
 199. Many are handsomely spherical or spheroidal. Others 
 present a striking resemblance to flowing mud. The concre- 
 tionary structure can often be traced in strata where no sopa-
 
 STRUCTURAL GEOLOGY. 
 
 259 
 
 rahle concretion has been formed. The lines pass across the 
 bedding planes and inclose spaces which partake of the general 
 stratification, thus showing that the structure was a secondary 
 result (p. 48). 
 
 Where small spherulitic concretions are plentifully dissemi- 
 nated through limestones, the latter become pisolitic (pisum, a 
 pea), or oolitic (wov, an egg). 
 
 Jointed Structure. The presence of one or more sets of 
 divisional planes or .cracks which pass across the stratification, 
 extending to great depths, and divide the rock mass into cuboidal 
 segments. These planes sometimes extend in rigidly fixed direc- 
 tions for many miles, and those in each set are strictly parallel. 
 
 Slaty Structure, or Slaty Cleavage, consists in a system of 
 closely crowded joints which create 
 a tendency in the rock to split in 
 thin sheets, as in roofing slate. This 
 cleavage generally crosses the planes 
 of bedding, but sometimes corre- 
 sponds with them. 
 
 Polished Faces, "Slickensides." 
 Polished surfaces along the faces of 
 a fissure intersecting the stratifica- 
 tion, caused apparently by friction 
 of opposed surfaces resulting from 
 slight movements in the earth's 
 crust. 
 
 Sand Blast Action. The polishing of rock surfaces, especially 
 of pebbles and bowlders, by the friction of dry sand driven by 
 the wind. 
 
 Met amor phi&m. A change in the condition of a sedimentary 
 rock by which the lines of sedimentation are obscured or obliter- 
 ated, the fossils destroyed, and a crystalline condition superin- 
 duced. The work of metamorphism has been accompanied by a 
 softening or aqueous semi-fusion of the materials, the formation 
 of new crystalline combinations, the moulding of certain crys- 
 tals around others (as quartz around feldspar), and sometimes the 
 
 FIG. 201. SLATY STRUCTUBE, AS 
 SEEN IN SLATES IN COLUMBIA 
 Co., N. Y. (Mather.) 
 The strata , b, c, d, etc., are 
 crossed by crowded cleavage 
 planes parallel with each other, 
 but wholly independent of the 
 stratification.
 
 260 GEOLOGICAL STUDIES. 
 
 squeezing of the softened rock into fissures, imparting to it the 
 vein-like condition of a true erupted formation. (See further 
 particulars in Chapter III, 3, (4).) 
 
 3. Attitudes Of Strata. It is probable that most strata 
 were originally horizontal, or nearly so. Observations upon 
 modern sedimentation show that sediments falling upon an un- 
 even bottom tend to the lower levels until the inequalities dis- 
 appear. After that, the successive sedimentary sheets are parallel 
 and practically horizontal. 
 
 The actual attitudes of rocky strata, however, are generally 
 at a wide divergence from undisturbed horizontality. In many 
 instances a whole formation, over hundreds of square miles, pre- 
 sents a regular or gently undulating inclination. In other cases, 
 in addition to the general inclination, the subordinate beds and 
 layers have undergone a complicated disturbance. 
 
 Outcrop is the appearance of a stratum or formation at the 
 surface. Generally the outcrop is the weathered termination or 
 edge presentation of strata which from that point disappear 
 beneath other formations. 
 
 Dip is the direction in which a stratum descends below the 
 horizontal plane. The amount of the dip is the angle made with 
 the horizon. 
 
 Strike, Trend, or Axis is the direction in which the outcrop 
 continues along the surface. If the surface were level, the strike 
 would always be at right angles with the direction of the dip. 
 So, also, if the slope of the surface were in the direction of the 
 dip or the opposite direction. 
 
 Breadth of Outcrop. This is the distance, measured along 
 the surface of the earth, between the upper and under sides of 
 the formation. Its amount depends, in a level region, on the 
 thickness of the formation and the steepness of the dip. More 
 generally it depends on the thickness of the formation and the 
 angle of plunge beneath the surface. This is equal to dip plus the 
 angle of inclination of the surface if it rises in the direction of 
 the dip, and minus this angle if the surface descends in the 
 direction of the dip. The relation is such that
 
 STRUCTURAL GEOLOGY. 
 
 261 
 
 Breadth of Outcrop = 
 
 Thickness of Formation 
 
 Sine of Plunge. 
 Hence, when the plunge is 90, 
 
 Breadth of Outcrop Thickness of Formation. 
 Hence, also, 
 
 Thickness of Formation = Breadth of Outcrop X Sine of 
 Plunge. 
 
 Synclinal Axis. This is a line toward which the strata clip 
 from opposite sides. (See Fig. 50.) A general descent of the 
 strata from opposite sides, across a broad region, regardless" of 
 subordinate flexures, is a Geosynclinal arrangement. 
 
 Anticlinal Axis. The line from which the strata dip in 
 opposite directions (Fig. 45). A Geanticlinal expresses a gen- 
 eral anticlinal tendency of strata over a wide extent, independ- 
 ently of subordinate undulations of the surface. 
 
 Quaquaversal Dip. A dip in all directions from a common 
 point. 
 
 G. 203. A FLEXURE BECOMING A FAULT. (Powell.) 
 
 The disturbances to which the earth's crust has been subjected 
 have not only tilted the strata, but subjected them to extensive 
 fracture. A line of fracture generally pursues a direct course 
 for several miles sometimes even a hundred miles or more. 
 
 A Fault or Dislocation is a displacement of strata along a 
 fracture, which destroys the correspondence of the strata on
 
 262 
 
 GEOLOGICAL STUDIES. . 
 
 opposite sides. They are common in mountainous regions. 
 Faults may attain to displacements of many thousand feet. A 
 fault results from an upthrow on one side or a downthrow on the 
 other. Faults are illustrated in Figs. 86, 34. 
 
 A Fold is a series 
 elevated anticlinal axis. 
 
 FIG. 203. INVERTED SUPERPOSITION. 
 
 A Flexure is a bending of the strata. When the flexure is 
 abrupt, or considerable in vertical extent, it often results in frac- 
 ture and faulting. In many instances a fault may be traced into 
 a shattered flexure, and thence to an unbroken flexure, which still 
 beyond dies out. 
 
 of strata uplifted to a more or less 
 Generally, the steepness of the dip is 
 greater on one side of the fold than on the other. In other 
 
 - words, the fold 
 
 is pushed over. 
 Sometimes the 
 inclination be- 
 comes such as to 
 give the strata 
 on one side a ver- 
 tical position 
 (Figs. 294, 293), 
 or even an in- 
 verted dip (Fig. 
 203). The fold is 
 
 FIG. 204. CONTORTED STRATIFICATION OF SCHISTS IN WEST 
 CHESTER Co., N. Y. (Dana.) 
 
 then said to be 
 overturned. The 
 strata 6, 5, 4, 3, 2, 1 on the left of the figure follow each other 
 in an inverted order, 1, 2, 3, 4, 5, 6, on the right of the axis of 
 the fold ; and the strata in the latter series are bottom side up.
 
 STRUCTURAL GEOLOGY. 263 
 
 Plication, Crumpling, Contortion. In many regions strata are 
 not only tilted and folded, but wrinkled or plicated in an irregu- 
 lar and remarkable manner, as illustrated in Figs. 204 and 205. 
 Such crumplings naturally suggest the exertion of enormous 
 lateral pressure upon softened strata. 
 
 Con for viability is parallelism of the sedimentary planes of 
 strata. When the dip of a formation is different from that of a 
 formation on which it is superimposed, the two are unconform- 
 able. Generally the lower formation has the greatest dip; and 
 this demonstrates that it has experienced at least one more 
 upthrow than the overlying formation (Figs. 293, 107, 298). 
 Sedimentation over a surface rendered irregular by previous 
 
 FIG. 205. CONTORTED STRATA OF POTSDAM SANDSTONE IN ST. LAWBENCE COUNTY, 
 K. Y. (Emmons.) 
 
 wearing results also in a species of unconformability known 
 as a break, or a breach of stratigraphical continuity. (Figs. 
 302, 298.) 
 
 4. Erosion of Strata. All rocks exposed to the action of 
 the elements undergo continued wastage. Their exposed sur- 
 faces disappear through solution or disintegration. The rate of 
 disappearance depends on the intensity of the action and the 
 power of the rock to resist it. Hence the wear is irregular, and 
 in the course of geologic cycles very striking results have been 
 produced. Some of these are illustrated in Figs. 75, 83, 32, 35. 
 
 Denudation is the wasting away of the rocks through the 
 action of the elements, aided sometimes by extraordinary geo- 
 logical action, like earthquakes, floods, and lava torrents. 
 
 Circumdenudation is a wasting on all sides of a mass of 
 rocks, leaving it to stand at or near its original altitude, while 
 the surrounding rock masses have been removed.
 
 264 GEOLOGICAL STUDIES. 
 
 An Outlier is an outstanding mass of rocks resulting from 
 circumdenudation. Figs. 35, 355, 301. 
 
 Erosion, in the more special sense, refers to mechanical action 
 localized along a river valley or sea or lake coast. 
 
 Corrasion is that part of erosion which results from the 
 impact of transported materials against the surfaces undergoing 
 erosion. v x 
 
 3. Conditions of Unstratified Bocks. 
 
 1. The Erupted Condition. The state of rock material 
 which has issued in a molten condition through rents in the 
 earth's crust, like lavas from modern or ancient volcanoes, or 
 lava-like materials from ancient fissures and rents. Descriptions 
 have been given in Study XXIII of several important examples. 
 The basaltic structure belongs to erupted rocks. It consists in 
 closely fitting polygonal prisms of basalt, of which some notable 
 examples exist in the "Giant's Causeway" and " Fingal's Cave"; 
 also on the banks of the Hudson and Columbia rivers. 
 
 Erupted beds are often overlaid by other erupted beds of 
 later origin, giving a truly bedded structure, which must not be 
 confounded with sedimentary bedding. Volcanic bedding occurs 
 especially on the slopes of volcanoes. The bedded structure is 
 also common among the ashes and cinders ejected from volcanic 
 openings, as in California and Washington. Some of the con- 
 glomerate beds of Keweenaw Point, Lake Superior, are thought 
 by some, but not by the latest writers, to be ancient volcanic 
 ejections, though interbedded with strata of undoubted aqueous 
 origin. 
 
 Amygdules. Small almond - shaped or spheroidal cavities 
 filled with infiltrated mineral matter of various kinds. Sometimes 
 one sort fills the cavity, and sometimes various sorts have been 
 introduced in successive concentric layers. Rocks thus formed 
 are amygdaloids. (Fig. 80.) They occur in the more super- 
 ficial parts of anciently igneous formations. The cavities are 
 supposed to have been originally filled with steam. 
 
 Pseud- Amy gdules. The mineral filling of rock cavities which
 
 STRUCTURAL GEOLOGY. 265 
 
 by some means were enlarged beyond the dimensions of an origi- 
 nal vapor vesicle; or even of cavities formed where no vapor vesi- 
 cle existed. Sometimes these cavities run together. 
 
 Metasomatic Change. The displacement on a large scale of 
 the chemical substances of the minerals constituting a rock, and 
 the substitution of other chemical substances. The transforma- 
 tion of augite into uralitic hornblende (having the form of augite 
 and cleavage of hornblende), so commonly observed in the North- 
 west, is part of such a process. Similarly we find chlorite, viri- 
 dite, and other substances appearing as secondary products. By 
 such and analogous changes the whole body of a formation may 
 become changed. All regional metamorphism of stratified rocks 
 is essentially of this character. 
 
 2. The Intrusive Condition. This term is commonly 
 applied to the condition of rock material intruded in a molten 
 state, between strata. This is illustrated in Fig. 46. The tra- 
 chytic intrusions of the Henry Mountains are illustrations on a 
 large scale. See Study XXIV, page 150. 
 
 3. The Vein Condition. A Vein, in the general sense, 
 is a fissure in the earth's crust filled with mineral matter different 
 from that of the fissured rock (Figs. 96, 97, 98). When the fissure 
 is straight and filled with matter injected in a molten state, it 
 forms a dike (Figs. 77, 79, 83). When the filled fissure is 
 more or less sinuous and irregular, it forms a vein in the more 
 restricted sense. Such veins may be filled with granite, por- 
 phyry, or other rocks commonly reputed of the igneous class. 
 (Fig. 4G.) Most commonly, however, the filling of a true vein 
 consists of layers of various mineral matters on the opposite 
 walls, in corresponding succession (Figs. 99, 100). This subject 
 is further elucidated in Study XXVII. 
 
 5. Classification of Formations. 
 
 1. Evidences of Relative Age. (1) From Superpo- 
 sition. Evidently the sediments were originally laid down in the 
 order of age. Unless subsequently overturned, the relative ages 
 of the strata would be indicated by their order of superposition.
 
 266 GEOLOGICAL STUDIES. 
 
 Cases exist, however, in which an upraised fold has been over- 
 turned on a vast scale. Here the ages of the strata on the under 
 side of the fold must be the reverse of their order of superposi- 
 tion (Fig. 203). These circumstances create great difficulties for 
 the practical geologist. 
 
 The faulting of strata, in some cases where the accident is 
 concealed, gives rise to embarrassments in determining the true 
 order of superposition. Here, in Fig. 206, the strata are faulted 
 
 208 
 
 FIG. 206 REPETITION OP STRATA BY FAULTING. Faulted limestone at Barnogat, 
 Dutchess Co., N. Y. (Mather.) 
 
 FIG. 207 DEPOSITION SUBSEQUENT TO FORMATION OF DIKE OR FAULT. Section in 
 Calabria. (Cortege.) Fi, Filadelfla. g, Granitic rock?, rf, Dioritic rocks, p', Plio- 
 cene strata. F, Fault intersecting the Apennines, older than the Pliocene epoch. 
 
 FIG. 208. DIKE AND OVERFLOW WITH SUBSEQUENT SEDIMENTATION, d, Dike, e. Over- 
 flow, a, 6, Later sediments. 
 
 at b m, c m, d m, etc., so that the stratum, a, after dipping 
 beneath the surface, is brought to the surface again at b, c, d, 
 etc., and thus appears to be four or more different strata of the 
 same kind. 
 
 (2) Evidence from fossils. Geological investigation has 
 shown that the stratified formation of each successive period 
 is characterized by particular fossil remains. Having learned by 
 extensive observation what are the characteristic fossils of each 
 formation, the discovery of any of these fossils may be taken as 
 evidence of the age and position of the formation in which they 
 occur. In general, the evidence of age when skilfully deduced 
 from fossils, is considered next in value to that derived from 
 observed superposition. But the value of palaeontological evi- 
 dence diminishes with the increase of distance between the local- 
 ities compared, and with the divergence of the physical condi- 
 tions under which the two faunas existed while living. The
 
 STRUCTURAL GEOLOGY. 
 
 267 
 
 nature of those conditions is indicated in part by the kind of 
 rock holding the fossils. 
 
 (3) Evidence from Intersections of Vein Matter. It is 
 at once intelligible that a vein or dike interrupted or cut off 
 by another vein or dike existed before the one which cuts it off. 
 On this principle, the chronological succession of a considerable 
 number of dikes may sometimes be determined. A remarkable 
 case is illustrated in Study XX'VII, Fig. 98. In some cases a 
 dike or fault may be seen intersecting the lower strata, but ter- 
 minating before reaching the surface. In the case shown in Fig. 
 207, the evidence is that the dike or fault, F, is older than the 
 formations pi, and g and d below pi. The proof of anteriority 
 of a dike is clearer when there remains a mass of overflowed 
 matter, e, Fig. 208, resting on the ancient surface and now 
 included between the older strata and the later a, deposited upon 
 it. In some cases, however, the molten matter e has been 
 intruded between the strata after the deposition of the overlying 
 strata, as in laccolitic mountains, Figs. 82, 83. Compare also the 
 porphyry intrusions, Fig. 46. 
 
 (4) Method of Combining the Observations. Suppose careful 
 determinations of strata have been made in many places. Sup- 
 pose the various formations have 
 
 been so studied and identified that, 
 separately, each may be charac- 
 terized and named. Suppose that 
 in one region (1), as indicated in 
 the annexed scheme, the forma- 
 tions studied may be designated 
 E, F, G, H; in another (2), B, C, 
 E, F, G; in another (3), A, L, M, 
 N, O; in another (4), H, I, J, N; 
 in another (5), B, D, K, M, and so 
 on. Then, correlating these sev- 
 eral series of strata, we should have them stand as shown in the 
 columns headed (1), (2), (3), (4), (5). Obviously, then, the com- 
 plete succession deducible from these collated series is that shown 
 
 (1) 
 
 (2) 
 
 (3) 
 
 (4) 
 
 (5) 
 
 VI 
 
 
 
 A 
 
 
 
 A 
 
 
 B 
 
 
 
 B 
 
 B 
 
 1. c 
 
 
 
 
 C 
 
 ET7 
 
 
 
 D 
 
 D 
 
 E 
 
 F 
 
 XL* 
 
 F 
 
 
 
 
 F 
 
 G 
 
 G 
 
 
 
 
 G 
 
 H 
 
 
 
 H 
 
 
 H 
 
 
 
 
 I 
 
 
 
 
 
 
 J 
 
 
 J 
 
 
 
 
 
 K 
 
 K 
 
 
 
 L 
 
 
 
 L 
 
 
 
 M 
 
 
 M 
 
 M 
 
 
 
 N 
 
 N 
 
 
 N 
 
 
 
 
 
 
 

 
 2G8 
 
 GEOLOGICAL STUDIES. 
 
 in the column headed (VI). Now, wherever any formation, as F, 
 is recognized by its fossils, or otherwise, we know its position in 
 the complete series; and we know what should follow next above, 
 and what next below. And whenever the succession is incom- 
 plete as in (1), we know the four newer formations are wanting; 
 when it is like (2), we know the newest, and also formation D, 
 are wanting; when like (3), we note a wide gap between A and 
 L, and so on. 
 
 2. The Cycle of Sedimentation. The phenomena thus 
 
 designated are also connected with the relative ages of strata. 
 CYCLES OF SEDIMENTATION. 
 
 Palaeo- 
 zoic 
 Systems. 
 
 Coarse Frag-- 
 mental. 
 
 Fine Fragrmen- 
 tal. 
 
 Calcareous. 
 
 Calcareo-Frag 1 - 
 mental. 
 
 : 
 ; 
 
 4 4 
 _j O 
 
 Parma Conglomer- 
 ate. 
 
 Coal Measures. 
 (Broken into many 
 short epochs.) 
 
 Larnmic 
 Limestone. 
 
 Permian Group. 
 
 < 
 
 Waverly Sandstone. 
 (Marshall Phase.) 
 
 Waverly Group. 
 (Chouteau Phase.) 
 
 Mountain 
 Limestone. 
 
 False Coal Meas- 
 ures. 
 
 X 
 
 * < 
 
 E 
 
 Oriskany Sand- 
 stone. 
 
 . 
 Schoharie Grit. 
 
 Comiferons 
 Limestone. 
 
 Hamilton Group, 
 followed by Che- 
 mung. 
 
 k 
 
 < 
 
 a 
 
 Medina Sandstone. 
 Oneida Conglomer- 
 ate. 
 
 Niagara Shale. 
 Clinton Group. 
 
 Niagara 
 Limestone. 
 
 Salina Group. 
 
 
 
 ; B5 
 
 i 
 
 Potsd am Sandstone. 
 
 Calcif erous and 
 Chazy. 
 
 Trenton Group. 
 
 Cincinnati Group. 
 
 It expresses the general fact that the series of strata is made up 
 of repetitions of a smaller series; and the smaller series has below, 
 a coarse f ragmen tal member, followed by a fine fragmental mem- 
 ber, and so on in fixed order, and terminating with a calcareous 
 or calcareo-fragmental member. This order of succession is con- 
 nected, as we shall hereafter see, with the periodical occurrence 
 of greater and less energy in the processes of sedimentation. 
 This order is not to be conceived as always sharply defined; but
 
 STRUCTURAL GEOLOGY. 269 
 
 the general expression of it in the entire series of strata is suf- 
 ficiently striking to be noted as a fact of geological significance. 
 Anticipating the explanations of the names of formations, we 
 here subjoin (page 268) a tabular exhibit of the large cycles real- 
 ized in the succession of geological groups. 
 
 The oldest formation here, the Potsdam Sandstone, is placed, 
 as usual, at the bottom. This is "coarse fragmental." At the 
 right is placed the next following formation, the Calciferous and 
 Chazy, and these together represent the " fine fragmental " 
 member of the Cambrian Cycle. Next to the right stands the 
 Trenton Group (proper), and this is the great "calcareous" 
 member of this cycle. Finally, still further to the right, is the 
 Cincinnati Group, which, as we shall see, is mixed calcareous and 
 argillaceous, and thus stands for the last member of the cycle. 
 The next formation in ascending order is the Oneida Conglom- 
 erate and Medina Sandstone. This is coarse fragmental again; 
 and thus commences a new cycle. On its completion, a third 
 cycle begins with the Oriskany Sandstone. Thus the whole Pal- 
 aeozoic series is composed of five Sedimentary Cycles. The expla- 
 nation of the Cycle belongs to Dynamical Geology. 
 
 3. General Terms Employed in Classification. (1) 
 
 Categories of Time and Strata. On such grounds as have been 
 explained, the whole series of strata forming the stratified crust 
 of the earth may be divided into general and subordinate assem- 
 blages. The object of the classification is to give expression to 
 the history of events in the life of the earth. These events have 
 been both inorganic and organic. There has been a series of 
 transformations of the earth's physical aspect, and a correspond- 
 ing series of transformations of the organic populations which 
 have inhabited the surface. The only records of these great 
 events are preserved in the rocks. They are a part of the rocks. 
 The epochs of more energetic action in the transforming agencies 
 have been marked by coarse fragmental deposits; the long peri- 
 ods of repose and luxuriance of organic production are symbol- 
 ized by the great accumulations of limestone. The same events 
 which changed the aspect of the physical world had some connec-
 
 270 GEOLOGICAL STUDIES. 
 
 tion, at least, with changes in the aspect of the organic world. 
 Thus a classification of the rocks is a marking off, also, of the 
 stages in the history of life. 
 
 At certain epochs the lithological and palasontological breaks 
 are found exceedingly profound. These divide the history of the 
 world since sedimentation began, into a succession of grand Eras 
 or ^Eons. Correspondingly, they give us the greater divisions 
 in the succession of events. There are two conceptions in geo- 
 logical classification, time and events, and the events must corre- 
 spond to the time. The rocks are the records of the events. So a 
 grand division of time gives us a grand division of the rocks and 
 a grand division in organic life. The general designations of 
 these grand divisions are ^fhn (sometimes Era) in reference to 
 time, and G-rfat System in reference to strata. The type of 
 organization corresponding has received no general designation. 
 The divisions of an ^Eon are designated Ages, and the divisions of 
 a Great System are generally known as Systems. So Ages are 
 further divided into Periods, and Svstems are divided into Groups. 
 When we carry the division farther, Periods are divided into 
 Epochs, and Groups into Stages. This, at least, is the general 
 system of nomenclature employed in this work, and conforms very 
 closely with general usage in America. Attempts have been 
 made by an International Geological Commission to unify the 
 usage of different nations, but the recommendation of the Com- 
 mission is unfortunately one not likely to command the accept- 
 ance of American geologists in consequence, partly, of its wholly 
 needless changes in the use of terms. 
 
 We now arrange these general terms in their proper order of 
 subordination for convenience of the student, repeating, for con- 
 venience of reference, the table on page 108. 
 
 Time Divisions. Rock Divisions. Examples. 
 
 vEON. GREAT SYSTEM. PALAEOZOIC, C^ENOZOIC. 
 
 AGE. SYSTEM. CAMBRIAN, TRIASSIC. 
 
 Period. Group. Niagara, Eocene. 
 
 Epoch. Stage. Calciferous, Champlain. 
 
 Each of the different time divisions has its special designation
 
 STRUCTURAL GEOLOGY. 271 
 
 as Eozoic, Palaeozoic. The same special names apply to the cor- 
 responding rock divisions. So we may say "Cambrian Age" or 
 "Cambrian System"; "Niagara Period " or " Niagara Group." 
 But each special name can only be used for a certain category 
 an ./Eon or a Great System; an Age or a System, and so on. We 
 should not say the "Cambrian Period" or "Cambrian Epoch"; 
 the "Palaeozoic Age" or "Palaeozoic Period." This would be 
 like giving the name of a class to an order or family. But this 
 solecism is too frequently perpetrated even by our reputable 
 writers. We shall even observe grosser negligence in employing 
 time designations where rock designations are meant, as " The 
 Trenton Period is composed of calcareous rocks," instead of 
 "Trenton Group." 
 
 (2) Stratigraphical Gaps. It has already been abundantly 
 shown, in Study XIX, that the complete series of formations 
 underlies the earth's surface only in limited regions. In other 
 regions, rocks belonging low in the series occupy the surface; or 
 at least rocks formed long before the conclusion of the work of 
 rock making. It often appears, also, that the series of forma- 
 tions under a particular region is deficient in more than the upper 
 portion of the standard series. Some of the lower ones are found 
 omitted, as illustrated in the columns (2), (3), (4), and (5) in the 
 scheme on page 267. This forms a Stratigraphical Gap. 
 
 (3) Geological Horizon. We may, however, make out a 
 statement of the complete series of formations. Then each form- 
 ation stands in a particular place. That is its horizon. Wher- 
 ever we recognize it, the same formations, save the occurrence of 
 gaps, are always found above, and the same below. 
 
 (4) Geological Equivalents. Whenever we find the same 
 geological horizon in two localities, however separated, the form- 
 ations in the two regions are equivalent. Very likely the char- 
 acters of the strata will be different. They may be even as dif- 
 ferent as sandstone and shale; but chronologically they are 
 equivalent, and lie in the same geological horizon. Owing to the 
 difference in the nature of the sediments, the species of molluscs 
 included may be partially or even wholly different, and thus the
 
 272 GEOLOGICAL STUDIES. 
 
 palaeontological identification be defeated. Many such cases are 
 known. We may then determine equivalency of horizons by a 
 wide-extended study of orders of superposition, as illustrated in 
 the scheme, page 267; or we may identify one or more conspicu- 
 ous fossil types not observed in either locality to range above or 
 below a particular stratum or formation; or finally, the experi- 
 enced palaeontologist may detect a particular expression in some 
 of the fossils or in the collocation of the fossils in the two places, 
 which will serve as an indication that the strata in those places 
 belong in the same geological horizon. 
 
 (5) Geological Synonyms. The geology of the earth has 
 been studied independently in different regions. Each investi- 
 gator has determined the succession in his region; and unless he 
 could certainly determine the equivalences between his formations 
 and those of some earlier-studied region, has, according to cus- 
 tom, bestowed his own names upon them. These are ordinarily 
 geographical designations. The name points to some locality 
 where the formation can be advantageously studied. Now, in 
 the course of time, it becomes certain that a formation named in 
 one region is the equivalent of a certain formation differently 
 named in another region. The two names are now synonyms. 
 Thus, in some cases, we have acquired many names for the same 
 geological horizon. This multitude of synonyms causes confu- 
 sion for the student and the investigator; but it must not be 
 complained of. The synonymy, for the greater part, affects only 
 the subordinate divisions of the rocks and these are not here 
 introduced. 
 
 (6) The Law of Priority. Geologists have agreed, in prac- 
 tice, not only that the most suitable names for formations are 
 geographical, but that the one first proposed shall be accepted 
 generally, and thus become a standard designation. But it is 
 not allowable to take an old name which has been employed to 
 embrace a certain range of strata, and subsequently employ it for 
 a wider or narrower range, as is sometimes done by geologists in 
 their use of the terms " Nashville Group" and " Waverly Group." 
 Against either of these, as a designation of an assemblage of
 
 STRUCTURAL GEOLOGY. 273 
 
 strata wider or narrower than that originally designated, any 
 name later proposed would hold the right of priority. 
 
 4. Table of Geological Equivalents. We will now 
 
 arrange in a Table, the complete series of formations with their 
 accepted classification, descending to the divisions called " peri- 
 ods " and " groups." Then, in parallel columns, we will insert 
 the names of the equivalent formations as known in particular 
 regions. We will select a few states in which investigations 
 began at early periods, or were carried on without the possibility 
 of certain connection with older studied states. To these will be 
 added a column showing the principal English equivalents. The 
 places left blank indicate what formations are wanting in the 
 several regions. 
 
 REMARKS. The student may take notice as follows: 1. The 
 subdivisions of the Jurassic, standing in the column of Ameri- 
 can Standards, cannot be said to have come, as yet, into general 
 use. 2. The Catskill Group is generally ranged under the Devo- 
 nian. 3. The Waverly or Marshall is not generally placed in the 
 horizon of the Catskill. For other remarks see Chapter V.
 
 274 
 
 GEOLOGICAL STUDIES. 
 
 CL2ENOZOIC. 
 
 American Standard. 
 
 Pennsylva- 
 nia. 
 
 Ohio. 
 
 Michigan. 
 
 QUARTERNARY. 
 
 82 
 gl 
 
 M 
 
 1* 
 
 Recent. 
 Champlain. 
 Glacial. 
 
 Recent. 
 Champlain. 
 Glacial. 
 
 Recent. 
 
 Lacustrino. 
 Glacial. 
 
 Recent. 
 Lacustrine. 
 
 Glacial. 
 
 TERTIARY. 
 
 Equus Beds. , t 
 Loup R. Gr. 
 Truckee. ^ a 
 White R. o 
 
 
 
 
 
 
 
 Uinta. * 
 Bridger. | 
 
 Wahsatch. <= 
 
 
 
 
 MESOZOIC. 
 
 CRETACEOUS. 
 
 U 
 
 17 
 
 Laramie. 
 Fox Hills. 
 Colorado. 
 Dakota. 
 
 
 
 
 JURASSIC. 
 
 Flaming Gorge Gr. 
 White Cliff Gr. 
 
 
 
 
 TRIASSIC. 
 
 Star Peak Gr. 
 16 
 ^oipato Gr. 
 
 Red Sandstone. 
 
 
 
 PALAEOZOIC. 
 
 UPPER CARBO- 
 NIFEROUS. 
 
 15 
 
 Permian. 
 
 
 
 lib 
 
 Coal Measures. 
 
 XIII. Coal Meas. 
 
 Coal Meas. 
 
 Coal Meas. 
 
 Ua 
 
 Conglomerate. 
 
 XII. Serai. 
 
 Homewood 8. 
 
 Parma Cong. 
 
 LOWER CARBO- 
 XIFEROUS. 
 
 DEVONIAN. 
 
 IS 
 U 
 
 Carbonif. Lim. 
 
 XI. Umbral. 
 X. Vespertine. 
 IX. Ponent. 
 
 Maxville L. 
 
 Carbonif. Lim. ' 
 Mich. Salt Gr. 
 
 Catskill Gr. 
 
 Waverly Gr. 
 
 Marshall Gr. 
 
 11 
 
 Chemung Gr. 
 
 VIII. Vergent. 
 
 Erie Shale. 
 
 Huron Gr. 
 
 10 Hamilton Gr. 
 9 : Corniferous Gr. 
 
 VIII. Cadent. 
 VmrPost~Merid. 
 
 Huron Shale. 
 Hamilton Gr. 
 Corniferous. 
 
 Little Traverse. 
 Mackinac Gr" 
 
 8 
 
 8 
 6 
 
 t 
 
 Oriskony Gr. 
 
 VII. Meridian. 
 
 Oriskany. 
 
 
 SILURIAN. 
 
 Helderberg Gr. 
 
 VI. Premeridian. 
 
 Waterlime. 
 
 Waterlime. 
 
 Salina Gr. 
 
 VI. Scalent. 
 
 Salina. 
 
 Salina. 
 
 Niagara Gr. 
 
 V. Surgent. 
 IV. Levant. 
 
 Niagara. 
 
 Niagara. 
 
 Trenton Gr. 
 
 III. Matinai. 
 
 Trenton. 
 
 Trenton. 
 
 Canadian Gr. 
 
 II. Auroral. 
 
 (Underlying.) 
 
 Canadian. 
 
 * 
 
 Primordial Gr. 
 
 I. Primal. 
 
 (Underlying.) 
 
 L. Superior S. 
 
 Q^ HtraoNiAN. 
 
 WS|AURKNTIANl 
 
 Keweenian. 
 
 
 
 Keweenian. 
 Huronian. 
 
 
 
 Laurentian.
 
 STKUCTUKAL GEOLOGY. 
 
 275 
 
 Canada. 
 
 Great Britain. 
 
 Europe. 
 
 Miscellaneous. 
 
 Recent. 
 Leda Clay or Erie 
 Clay. 
 Glacial. 
 
 Recent. 
 
 ( Pleistocene. 
 ) 
 
 Recent. 
 
 ^Laterite. (India.) 
 ) 
 
 
 Pliocene or English 
 Crag. 
 
 Pliocene Sub - Apen- 
 nines Antwerp sands. 
 
 Niobrara. 
 
 
 Miocene. 
 
 Oligocene. 
 Eocene. 
 
 Miocene Faluns of 
 Touraine; Upper Mc- 
 lasse. 
 
 
 
 and Tongrian. 
 Eocene Londinian ; 
 Parisian; Nuinmu- 
 
 litic. 
 
 1 Vicksburg. 
 f Claiborne. Tejon, Cal. 
 
 
 *.{$ 
 
 Middle, ) 
 J Green Sand. 
 Lower, J 
 
 iSSnUn. 'l CWC0 ' 1 
 
 SSSSSta,. ; <) Cal - 
 
 g^omian. J^sta. J 
 
 
 Wealden. 
 > Upper, 
 Oolite, \ Middle, 
 ! Lower. 
 
 Portlandian. 
 Oxfordian. 
 Bathonian. 
 Toarcian, ) nik 
 Liasian, ( B }f,^ 
 Sinemurian. $ Jura ' 
 
 Atlantosaurus Beds. 
 Baptanodon Beds. 
 
 
 Rhsetic Beds. 
 Red Marls. 
 Shell L. 
 
 Keuper. 
 Mu^.-lielkalk. 
 Bunter Sandstein. 
 
 Marnes irises. 
 Calcaire coqulllier. 
 Ores bigarre. 
 
 
 Red Sandstones. 
 Coal Meas. 
 
 Rothliengendes. 
 
 Dyas (Europe). 
 
 Coal Meas. 
 
 Terrain houiller 
 Steinkohlen format. 
 
 Upper. 
 1 Lower of Rogers' 
 Lower, \ 
 } Conglom. Meas. 
 
 Bona venture C. 
 
 Millstone Grit. 
 
 Flotzleer Sandstein. 
 
 Calcaire" Carbonif ere 
 Kohlenkalk; Kulm. 
 
 
 Mountain L. 
 
 Mauch Chunk Shale (Pa.). 
 
 
 Petherwin Gr. ~ 
 Dartmouth Gr. a 
 
 Plymouth Gr. | 
 
 3 
 
 
 Kinderhook (111.); Chou- 
 teau L. (Mo.); Yellow S. 
 (Iowa); Silicious Gr. 
 (Tenn.), part. 
 
 Chemung. _ 
 Hamilton. | = 
 
 Cypridina Beds. 
 Eifel L. 
 Spirifer S. 
 
 - 
 
 Corniferous. ^v, 
 
 1 
 
 Liskeard Gr. 
 
 
 Ludlow. 
 Wenlock. 
 Upper Llandoyery. 
 
 
 
 Salina. 
 
 Niagara. 
 TSntoZ 
 
 Lower Llandovery. 
 Caradoc and Bala. 
 Llandeilo Flags. 
 
 Arenig. 
 Trernadoc Slate. 
 Cambrian. 
 
 
 
 Canadian. 
 
 Primordial. 
 
 Up - (Ling^i Fllgs.] i 
 CMenevian. V j."E 
 Low. ^Harlech and |~ 
 ( Longmynd. J o 
 
 Keweenian. 
 
 Fundamental 
 Gneiss. 
 
 Huronian. 
 Laurentian.
 
 CHAPTER III. 
 DYNAMICAL GEOLOGY; 
 
 OB, WHAT HAS BEEN LEARNED ABOUT GEOLOGICAL AGENCIES. 
 
 WE should now make some condensed statements respecting 
 the forces, agencies, and methods of geological work. How have 
 these physical results been accomplished to which our attention 
 has thus far in this Part been turned ? How have rocks origi- 
 nated? How have they been consolidated? How upturned, 
 folded, and plicated ? How metamorphosed ? How have mount- 
 ains been uplifted, valleys sunken, and the basins of the lakes 
 and oceans scooped out ? The explanation of these phenomena 
 belongs to Dynamical Geology. We must restrict ourselves to 
 very summary statements. 
 
 1. Agency of Water. 
 
 1. Running Water. We begin with the action of run- 
 ning water, because its results are most familiar. The mere im- 
 pact of rain drops on the surface disintegrates the soil and even 
 the solid rocks. The dripping from the roofs of caves sometimes 
 wears flutings in the stony walls. But rain water accumulated in 
 torrents works sometimes with amazing energy. The destructive 
 wear of any swollen stream is something which has attracted the 
 notice of all. Most of the erosive work in sediment-bearing 
 streams is by corrasion. 
 
 Every modern river flows in a valley, and the valley is simply 
 a record of the river's erosive work. To what this in many cases 
 amounts has been illustrated in Study XVI and elsewhere. 
 
 Where a stream is precipitated over a " fall," the reaction of 
 the water at the foot gradually undermines the cliff, and it breaks 
 down by degrees. This is more rapid than ordinary erosion. 
 
 276
 
 DYNAMICAL GEOLOGY. 
 
 277 
 
 Most high waterfalls are by such means iu process of recession. 
 As the recession continues, the foot of the fall gradually rises. 
 Unless a fall, therefore, retreats up a rapid stream, its height 
 must continually diminish, and at last the fall will be sloped off 
 to a rapid chute. 
 
 Subterranean streams erode chiefly by solution and by friction 
 of the water. A stream flowing through a fissure constantly en- 
 larges it; but more especially if the fissure is in limestone. By 
 such means caverns have been produced, some of which, like the 
 Adelsberg and the Mammoth caverns, have become wonders of 
 the world. The latter (Fig. 209) has many winding and mutually 
 
 Pis. 209. PLAN OF MAMMOTH CAVE. (Hovey.) 
 
 intersecting passages, which aggregate in length 150 miles. The 
 diameter of the area covered by the cavern is 10 miles, and the 
 main passage extends 4 miles. It is from 40 to 300 feet wide, 
 and from 35 to 125 feet high. 
 
 The amount of sediment transported by great rivers is quite 
 enormous. According to the investigations of Humphreys and 
 Abbot, the silt carried to the Gulf of Mexico by the Mississippi 
 River amounts to l-1500th the weight of the water, or l-2900th
 
 278 GEOLOGICAL STUDIES. 
 
 its bulk. This silt amounts, in other words, to 812,500,000,000,000 
 pounds per year, or a mass 1 mile square and 241 feet deep. 
 Besides this, the Mississippi pushes along to the gulf an addi- 
 tional amount of mud, which, added to that floated, would form a 
 mass a mile square and 268 feet deep. This amount removed an- 
 nually from the whole basin of the Mississippi would lower it 1 
 foot in 4,920 years. Other great rivers accomplish equal or 
 greater results. The Ganges lowers its basin by erosion 1 foot in 
 1,880 years. 
 
 The river sediments which find their way to the sea are widely 
 dispersed over its bottom. The finer are transported to greatest 
 distances; the coarser are deposited nearer the shore. Between 
 the remote distances and the shore all grades of sediments are 
 laid down. If the sediments have such density as to sink 10 
 feet an hour, and the motion of the water is 2 miles an hour, 
 then the sediment would float 200 miles before settling 1,000 feet. 
 Sediments of less fineness would float less distances. But while 
 such suspension occurs in fresh waters, the same sediments in 
 salt water would sink in 1-loth the time. Hence, as a fact, marine 
 sediments would be deposited along a shore belt comparatively 
 narrow, did not the agitation of the water near the surface pro- 
 long the period of suspension of a portion of the sediments. 
 
 River sediments also, at time of overflow, are more or less 
 widely spread over the adjoining flood plain. Thus alluvial de- 
 posits are formed, which fill to a greater or less extent the rock- 
 bottomed valley occupied by the river (Fig. 210). In this cut, f f 
 
 is the level of the alluvial plain at a certain time. If subse- 
 quently the amount of water diminishes, dec' becomes the level 
 of the alluvial plain. By a further diminution, the flood plain is
 
 DYNAMICAL GEOLOGY. 279 
 
 lowered to b a a' b '. These steps in the alluvial slope are ter- 
 races, due to different stages of the water. Sometimes two ter- 
 races occur on one side as the equivalent of a single one on the 
 opposite side. 
 
 If, after a river has become established in its rocky bed, a 
 subsidence takes place, sediment will accumulate underneath the 
 channel, and the river will flow over a mud-formed bed. This 
 has occurred with the river whose valley section is shown in the 
 diagram. If afterward the bottom should be elevated, the mud 
 would be scoured out. 
 
 The bar so commonly formed across the mouths of great 
 rivers results from the sediment pushed into the sea. The devel- 
 opment of the bar causes the extension of the delta. The Mis- 
 sissippi bar advances 338 feet annually over a width of 11,500 
 feet, and the delta has grown into a deep indentation in the shore 
 line of the gulf. The whole area taken by the delta from the 
 gulf is 12,300 square miles. This illustrates the nature of the 
 work performed bv the great rivers. 
 
 2. Oceanic Action. (1) Ocean Currents. These currents 
 exert important agency in transporting any sediments which they 
 float. The fine floating sediments of the Mississippi are borne 
 hundreds of miles, and even to the Straits of Florida. The tur- 
 bid water of the Amazons is traceable northward a very great 
 distance. Generally these currents flow far from land, and con- 
 tribute little to the process of erosion. 
 
 The bottom of the Atlantic, along the Arctic belt, reaching 
 southward to a point 60 miles beyond Nantucket, is covered by 
 a coarse gravel or sand; that of the great depths by a sticky 
 mud. Under the Gulf Stream the bottom is of sand, of so fine 
 a grain that the grains can only be distinguished under a micro- 
 scope. Mixed with it are masses of minute shells. The two 
 form a bed as level and hard as a floor. Bowlders are occasion- 
 ally found, dropped, probably, from cakes of ice floating from 
 shore. 
 
 (2) Wave Action. The waves reach the shore and exert a 
 vast mechanical agency. Not only is the power great, but its
 
 280 GEOLOGICAL STUDIES. 
 
 exertion is incessant. The highest waves are only about 43 
 feet above the bottom of the trough between them; but the 
 force with which they sometimes strike a solid resistance is two 
 or three tons to the square foot. Such force or even the 
 ordinary wave force during a winter (2,000 pounds per square 
 foot) exerted on an ordinary beach, must cause its rapid disin- 
 tegration. . Accordingly we learn that whole towns have been 
 undermined, and many solid acres distributed over the ocean's 
 bottom. Tidal Waves along shore act with similar energy. In 
 straits, small bays, and estuaries, the rise of the tide sometimes 
 amounts to 20, 30, or 50 feet, and it sweeps along with destruc- 
 tive force. The bore of the Hoogley (a mouth of the Ganges) 
 and the piroroco of the Amazons are famous. In the Bay of 
 Fundy the rise of the spring tides is sometimes 60 feet. Under 
 the action of the waves, large continental areas have in times 
 past been wasted; straits like Behring and Gibraltar have been 
 cut; connections of land and water have been modified; climates 
 have been changed, faunas and floras exterminated and replaced 
 by others. Shore action, indeed, has been largely instrumental in 
 that wastage of continental masses which is believed, in some 
 cases, to have resulted in their total disappearance. 
 
 3. Action of Ice. The freezing of water held in the pores 
 of rocks and minerals is a very powerful disintegrating agency. 
 Fine aluminous limestones just from the quarry, when exposed 
 to the action of a winter's frost, split into many pieces. Sand- 
 stones and granites crumble to sand. Crevices are pried asunder, 
 and the most stubborn quartzites are slowly reduced to frag- 
 ments. 
 
 Floating Ice in rivers acts as an efficient agent of corrasion. 
 It carries also, in some cases, large volumes of sediment, and dis- 
 tributes seeds along the valley of the stream. 
 
 In the form of Glaciers, ice seems to have performed impor- 
 tant work in ages past; and our small modern glaciers probably 
 typify the modes of action of the ancient ones. A Glacier is a 
 sheet of ice resting in a mountain valley. It resulted from accu- 
 mulations of snow for years, unmelted by the summer's warmth.
 
 DYNAMICAL GEOLOGY. 
 
 281 
 
 The glacier stretches upward into the region of perpetual snow. 
 Fig. 211 is a view of a couple of modern Alpine glaciers, des 
 Bossons at the left and Tacconnay on the right, with Mont Blanc, 
 the highest summit, in the centre. The glacier moves continually 
 downward, and would encroach on the cultivated fields if the ice 
 were not melted away at the foot. The Glacier des Bossons 
 transported the bodies of the victims of an avalanche 27,500 feet 
 in forty-one years, or about 670 feet a year. The Great Glacier 
 
 FIG. 211. VIEW OP THE GLACIER DES BOSSONS AND MONT BLANC, FROM THE BBEVENT, 
 8,000 FEET HIGH. 
 
 of Alaska moves a quarter of a mile per annum, or twice as 
 rapidly as Bossons. Many rocky fragments roll down on the 
 glacier from the adjoining slopes. These, at last, are landed at 
 the foot of the glacier, and there accumulate a terminal moraine, 
 which is shown in the figure. A lateral moraine is accumulated, 
 also, along each border. These unstratified accumulations of 
 worn and rounded stories remind us of the bowlders in the ordi- 
 nary Drift; and these moraines look like some of the Drift hills
 
 282 
 
 GEOLOGICAL STUDIES. 
 
 scattered over our Northern States. (Fig. 5.) The Alpine mo- 
 raines, however, are destitute of all traces of stratification. 
 (Fig. 212.) 
 
 Moreover, these glaciers by their motion leave scratches on 
 the underlying rocky surfaces identical in appearance with those 
 found on the bed rock throughout the Northern States. One of 
 the anciently striated surfaces is shown in the adjoining cut, Fig. 
 213. This shows that the most flinty materials have yielded to 
 the action which has grooved the ancient rock surfaces. 
 
 The surface of Greenland is completely covered by a modern 
 glacier. A little depression of the summer temperature would 
 
 FIG. 212. TERMINAL MORAINE AND BOWLDER-STREWN AREA AT THE FOOT OF THR 
 MER DE GLACE. Compare the Bowlder- Covered Areas in Figs. 6 and 37. 
 
 extend the glaciated surface over part of North America. It is 
 quite conceivable that without any great severity of cold, an ice 
 covering might become permanent as far south as Chicago and 
 Cleveland. 
 
 Glaciers exert powerful erosive action through the instrumen- 
 tality of the sand and pebbles frozen into the bottom or pressed 
 between the ice and the rock. Where the glacier is 1,000 feet 
 thick, its pressure on the underlying rock is 4,870 pounds to the 
 square foot. Corroborative evidence of the great grinding effi- 
 ciency of glaciers is furnished by the stream of densely turbid
 
 DYNAMICAL GEOLOGY. 
 
 283 
 
 water which issues at the foot. The stream which drains the Aar 
 glacier brings down 280 tons per day, and the Justedal glacier of 
 Norway wears down 60,000 cubic metres of rock annually. 
 
 A glacier mass reaching the sea, protrudes into it, is buoyed 
 up by it, and finally broken off. The detached fragment then 
 floats away as an iceberg, bearing with it mud and other debris 
 from its northern home. The icebergs in the North Atlantic 
 originate on the west coast of Greenland. 
 
 Fio. 213. A STRIATED DOME OF QUARTZITE, FRAZER BAY, LAKE HURON. 
 (Dr. E. Andrews.) 
 
 4. Assortment of Marine Sediments. Water and ice 
 
 are thus agents for the creation and transportation of sediments, 
 and their delivery in the sea. Borne by tides and currents, their 
 unequal rates of deposition result in a complete assortment of the 
 materials. At all times the sediment is coarser near the shore, 
 and grows finer with distance. On this point Darwin has fur- 
 nished some specific data, obtained between Santa Cruz and the 
 Falkland Islands, on gradation in size of transported materials. 
 These are cited below:
 
 284 GEOLOGICAL STUDIES. 
 
 Miles from Depth in 
 
 Shore. Fathoms. Coarseness of Materials. 
 
 2 to 4 . . 11 to 12 . . ... Pebbles size of walnuts and smaller. 
 
 4 to 7 .. 17 to 19 ... Do. size of hazel nuts. 
 
 10 to 11 . . 23 to 25 . . . .8 to .4 inch in diameter. 
 
 12 .. 30 to 40 ... .2 inch in diameter. 
 
 22 to 150 .. 45 to 65 ... .1 inch in diameter to fine sand. 
 
 At any point, however, the coarseness of the deposit depends 
 on the rate of movement of the water. Should any cause increase 
 at any place the transporting power of the water, coarser sedi- 
 ments would be dropped at this place, and the finer would be 
 carried beyond. So the same spot would receive a graduated 
 succession of sedimentary sheets. We should have there, in 
 such case, a real cycle of sedimentation. This would be repeated 
 as many times as the range of variation in the transporting power 
 of the water should be repeated. Hence, probably, the cycle in 
 the succession of rocky strata described on page 268. 
 
 3. Agency of the Atmosphere. 
 
 1. Wear by Wind-borne Sands. Tim only atmos- 
 pheric action important to consider here is its transportation of 
 sands. Incidental to the movement of blown sands is the polish- 
 ing and wearing which result from the impinging of the sand 
 particles against hard surfaces. Quartzose bowlders, and still 
 more other rocks, become polished all over their exposed sides, 
 the actions extending equally to the bottoms of the depressions 
 in the originally irregular surface. This effect is well observed 
 along the sand-covered eastern border of Lake Michigan, and 
 particularly on the sand-strewn plateau slope stretching eastward 
 from Sleeping Bear in Leelanau county. In the pass of San Ber- 
 nardino, California, the granite is scratched like a glaciated sur- 
 face (W. P. Blake). Very marked effects have been reported 
 from the Gila, Amargosa, and Colorado deserts by Newberry and 
 Gilbert. On Cape Cod the driven sands even grind quite through 
 the window panes. In the arts, steam-driven sand is employed in 
 etching and carving.
 
 DYNAMICAL GEOLOGY. 285 
 
 2. Sand Dunes. These are banks or hills of dry sand 
 piled up by the wind. In the temperate zone the prevailing 
 direction of the wind is westerly; hence the drifted sands have a 
 resultant eastward movement, and thus they continue to travel, 
 burving lands and houses and highways in their course. Along 
 the eastern shores of our inland lakes, the sand which is thrown 
 up by the waves is an exhaustless source. When dried, the wind 
 drives it inland, forming banks and hills thirty to over a hundred 
 feet high. At New Buffalo, on the eastern shore of Lake Michi- 
 gan, the dunes measure 93 feet in height, and at Grand Haven 
 they are 215 feet on the north side of Grand River and 205 
 feet on the south side. The track and station buildings of the 
 Detroit and Milwaukee Railway, originally built on the north 
 side, were so persistently encroached on by the sands that they 
 were removed to the opposite side. At Sleeping Bear, the sands 
 are drifting over a promontory 500 feet high. From the summit 
 a wide waste of sand spreads over several square miles. Here 
 and at Grand Haven, the singular spectacle is presented of a 
 dead forest protruding its tree tops a few feet above the surface 
 of the deluge of sand. 
 
 The dunes of England and the northern coasts of France, 
 Denmark, and Russia have, in past times, made serious encroach- 
 ments on human improvements. They have been the study of 
 agriculturists and of scientific commissions, and at present a 
 large degree of control is exercised over them. 
 
 We see no limit to the amount of sand which might thus be 
 drifted, nor to the distance over which it might travel. Von 
 Richthofen maintains that the great loess deposits of China are 
 mere beds of fine sand blown perhaps from the Mongolian desert; 
 and Pumpelly inclines to accept a similar origin for the similar 
 Icess beds of the valleys of the Mississippi, Missouri, Des Moines, 
 and other rivers. Others, however, think them of fluviatile 
 origin. If of asolian, or wind-borne, origin, some adequate 
 source of supply must be pointed out. King has suggested that 
 this may have been in the arid regions of the Cordilleras, where 
 trains of dunes are still moving eastward, and must have moved
 
 286 GEOLOGICAL STUDIES. 
 
 in much greater abundance during the secular dry period of the 
 Quaternary Age. 
 
 3. Transportation of Volcanic Ashes. The atmos- 
 phere exerts a similar agency in the transportation of volcanic 
 "ashes," as alreadv stated in connection with the phenomena of 
 volcanoes (See Study XXIII). Dust from other sources, and 
 even dust probably of cosmic origin, appears to be borne and 
 sustained in the atmosphere almost indefinitely, destined at last 
 to be brought down by precipitations of rain and snow. We 
 present here grains of magnetic iron appearing to have been 
 fused probably the dust of a volatilized meteor. 
 
 FIGS. 214, 215, 216. CORPUSCLES OF MAGNETIC IRON BELIEVED TO BE or COSMIC ORIGIN. 
 X500. (Tissandier.) 
 
 214 From the enow of Mont Blanc at the height of 2710 metres. 
 215 Collected from rain water at Sainte Marie du Mont. 
 216 From the dust collected in the unfrequented towers of Notre Dame, Paris. 
 
 3. Agency of Heat. 
 
 In Studies XXII, XXIII, and XXIV numerous geological 
 facts have been brought to view which point to the agency of 
 heat. The phenomena of thermal springs, volcanoes, and ancient 
 lavas are most naturally explained on the theory of a high inter- 
 nal temperature. The actual increase of heat experienced as we 
 penetrate the earth is direct evidence that a high temperature 
 prevails generally within one or two hundred miles of the earth's
 
 DYNAMICAL GEOLOGY. 287 
 
 surface. As this interior heat is constantly escaping, there either 
 must be some existing source of supply, or else, in ages past, we 
 have ground to argue, a much higher temperature has existed 
 within, and consequently has transmitted a much higher degree 
 of thermal energy to the terrestrial surface. Probably both 
 alternatives represent the facts. 
 
 If the earth is conceived as a cooling body, we must seek for 
 the records of the action of heat at a former high temperature. 
 These records would reveal (1) The consequences of the direct 
 action of heat, and (2) The consequences of the slow abatement 
 of the heat especially the contraction incident to cooling. 
 
 1. Geological Results of Former High Tempera- 
 ture. (1.) A Primitive Molten State. If the primitive tem- 
 perature of the earth was such as to reduce the entire globe to a 
 state of fusion, then there was at some time a first crust a, fire- 
 formed crust. On this the stratified sediments must eventually 
 have accumulated. Later sediments we know accumulated in 
 later ages, until we have in modern times a measured thickness 
 of more than a hundred thousand feet of solid rocks. But 
 these, according to modern views, are all of sedimentary origin, 
 fc-xcept an insignificant amount of erupted and intrusive rocks. 
 What has become of the fire-formed crust ? Can we expect ever 
 to uncover it or penetrate to it as a fact of observation ? We 
 are persuaded it has long since disappeared. 
 
 If ocean sediments accumulated on the fire-formed crust, the 
 first effect was to thicken the envelope within which the earth's 
 internal heat was imprisoned. The previous thickness of the 
 (fire-formed) crust was such as was demanded by the internal 
 temperature and the thermal conducting power of the materials. 
 With the sediments added, there was an excess of thickness, and 
 the heat within would re-fuse the under layer of the igneous 
 crust. So, much of it would disappear. The addition of further 
 sediments would cause the loss of further portions from the under 
 surface. This process would continue. At length the entire 
 igneous crust would have disappeared, the molten central mass 
 becoming inclosed by rocks which had been sea sediments. Nor
 
 288 GEOLOGICAL STUDIES. 
 
 is this the end. The process of eating awav from the under side 
 would continue even to the disappearance of the older portions 
 of the sedimentary crust. How much of the sedimentary crust 
 may thus have disappeared it is impossible to ascertain. The 
 lowest strata ever observed are probably in position far above the 
 oldest ever formed. We are quite at liberty to assume any such 
 disappearance of oldest formed strata as facts of observation may 
 suggest. 
 
 FIG. 217. ASCENT OF ISOGEOTHERMAL PLANES IN THE EARTH'S CRUST. 
 
 The process of subterfusion of primitive portions of the crust 
 is otherwise expressed as an ascent of the isogeothermal planes 
 the planes of equal temperature within the crust. The process is 
 graphically illustrated by Fig. 217. The line c c' represents the 
 bottom of the sea, on which sediments are accumulating. Evi- 
 dences existing, to which reference will be made, that a load of 
 sediments causes subsidence of the bottom, we may for con- 
 venience assume that the subsidence equals the filling, and the 
 line c c' remains fixed. Then let c r, or c' r' , represent the
 
 DYNAMICAL GEOLOGY. 289 
 
 constant thickness determined by the thermal conductivity of the 
 crust materials. A, on the left, represents a section of the fire- 
 formed crust, and M, a portion of the underlying molten matter. 
 Then, as the successive additions, B, C, D, of sedimentary matter 
 are made, successive portions A', A', of the fire-formed crust will 
 be melted off. The total re-fused at successive intervals is shown 
 at A', A', A'; while, in the last case, a portion, B', of the sedi- 
 mentary bed B has also disappeared. 
 
 It will be vain, therefore, to expect to see any of the primitive 
 earth crust. It is equally vain to pretend that its non-discovery 
 is any proof of its non-existence at the beginning of incrustation. 
 
 (2) Origin of Erupted Material. With this conception of 
 a molten interior, it is easy to understand the origin of ancient 
 or modern molten matter. In another connection we shall 
 endeavor to point out the causes of its ascent to the surface. It 
 seems probable, also, that the frequency of the outflows would 
 be greatest in early times, when the crust was thinnest, and the 
 progress of cooling most rapid. 
 
 (3) Ayency of Steam in Eruptive Action. Some force act- 
 ing upward with great energy reveals its existence in the eruption 
 of thermal waters and volcanic ejecta. While steam may exert 
 the eruptive force in the case of geysers, and to a collateral 
 extent in volcanoes, there are reasons for believing that steam is 
 not an adequate explanation of volcanic or seismic action. The 
 presence of water beneath volcanoes is evinced not only bv the 
 usual abundance of steam, and the occasional volumes of mud 
 thrown out, but also by the escape of the various constituents of 
 sea water, such as chlorine, sulphurous acid, sulphur, common 
 salt, iodine, and bromine. Some connection with the sea is 
 implied, also, in the arrangement of lines of volcanic vents around 
 the shores of the continents. The percolation of water to the 
 deep, heated interior would produce results which are quite 
 intelligible; and it is quite probable that some eruptions originate 
 in this way. But the copious fissure outflows of geologic times 
 must be otherwise explained. 
 
 (4) Hfetamorphism. During the ascent of the lower isogeo-
 
 290 GEOLOGICAL STUDIES. 
 
 thermal planes into and through the sedimentary beds, as abov& 
 explained, the latter were subjected to the intense action of heat. 
 This action grew more and more intense in any particular one of 
 the older beds, until it was reached by the plane of fusing tem- 
 perature, when, of course, it became merged in the general 
 molten mass. With the heat was also all the water which could 
 percolate through the rocks. If, at a sufficient depth, the water 
 was converted to steam, and driven toward the surface, it must 
 be remembered that deep-seated water was subjected to enor- 
 mous pressure, and retained its fluid state to a temperature far 
 above 212 Fahr. Without doubt, much of the water saturating- 
 the deep rocks had a temperature of 300 to 800. Here, then, 
 were the conditions of intense chemical action, and of other 
 important molecular changes. The experiments of Daubree and 
 others show that under such conditions rocks become softened 
 and plastic, the molecules of matter enter into new arrangements, 
 and out of the same stuff very different minerals and rock masses 
 come into existence. Thus, earthy shales become slates, or even 
 mica-schists; limestones become marbles. The lines of sedimen- 
 tation become obliterated, and traces of fossils disappear. This, 
 result, in the aggregate, is metamorphism. 
 
 Its progress may be traced in the changes of the mineral con- 
 stituents of the rock. The molecules which, for instance, were 
 so arranged as to constitute a crystal of augite, rearrange them- 
 selves so as to form the mineral hornblende. The place of the 
 old crystal remains a mould, having the crystalline form of 
 augite but the mould is now filled with a substance which, if 
 free to crystallize by itself, would not take the form in which it 
 has become moulded. It is a pseudomorph. It has the substance 
 of one mineral, and the form of another. This hornblende is a. 
 pseudomorph after augite. In a similar way, pyroxene is some- 
 times altered to talc. So, also, the anhydrous magnesian sili- 
 cates, chrysolite, pyroxene, and chondrodite, have been freqently 
 found changed to the hydrous magnesian silicate, serpentine. 
 Other cases are well known. When the pseudomorphism of the 
 constituents of a rock involves the chief mass, so that the rock
 
 DYNAMICAL GEOLOGY. 291 
 
 itself is altered, the change is known as pseudomorphic meta- 
 morphism, or metasomatism. Serpentine rock and the talcitic 
 rock rensselasrite are examples. 
 
 Regional Metamorphistn is that which takes place over a 
 wide area under some general terrestrial influence as just ex- 
 plained. Local Metamorphism is caused by the heat accompa- 
 nying the eruption of molten material through a fissure. The 
 immediate neighborhood of a dike is generally metamorphosed. 
 
 (5) The Filling of Veins. The filling of true banded mineral 
 veins probably depends on the action of heat and water. These 
 are powerful agents of solution. When such solutions find their 
 way into the cooler parts of a fissure, precipitation begins. 
 Layer after layer is deposited, probably at secular intervals, on 
 the fissure walls. The nature of the deposit must vary with the 
 nature of the solution and this will vary with the source from 
 which the solution proceeds. When precipitation takes place 
 it will form simultaneously on the two walls of the fissure; 
 hence the symmetry of the arrangement (see Figs. 99 and 
 100). Possibly some veins are filled by a process of sublima- 
 tion, under the action of dry heat. Many dikes are undoubt- 
 edly filled with matter in a state of fusion. But it is worth while 
 to remember that the action of heat and water must reduce the 
 deep-seated rocks on a large scale to a plastic condition, and 
 that such rocks are necessarily subjected to enormous pressure. 
 If, then, a fissure is opened to them or through them, such plastic 
 substances must be squeezed in. Thus, apparently, many granite 
 veins have originated, and perhaps also, some porphyritic and 
 dioritic veins. An injected material has not therefore, of neces- 
 sity, a molten origin. 
 
 2. Effects of the Earth's Cooling. (1) Lateral Pressure. 
 Heretofore in considering the phenomena of mountains, Studies 
 XXV and XXVI, we have discovered convincing proofs of the 
 exertion of some great lateral pressure. On the theory of a cool- 
 ing and contracting globe, we find an explanation of lateral press- 
 ure which, by the majority of geologists, is held to be the cause 
 of crustal wrinkling and mountain development. It is, however,
 
 292 . GEOLOGICAL STUDIES. 
 
 often objected that the whole possible shrinkage in the circum- 
 ference of the earth due to cooling from the temperature of first 
 sedimentation to the present, would not be sufficient to yield the 
 surplusage worked into the folds and plications which now exist 
 in the crust. This objection acquires weight from the calcula- 
 tions of Fisher and Dutton, and from the studies of Olaypole on 
 the considerable amount of shortening supposed to have taken 
 place in a section through the Appalachians. But it is certain 
 that cooling and consequent shrinkage must have developed 
 enormous lateral pressure, and it is eminently probable that this 
 pressure found relief in wrinkles and plications. If the amount 
 of surplusage afforded by this means is insufficient, we shall 
 presently cite another source of surplusage which may adequately 
 supplement this one. 
 
 (2) Eoolution of Heat. Enormous lateral pressure resulting 
 from the earth's contraction would necessarily produce more or 
 less motion of the parts of the crust. The motion would be ac- 
 companied by friction, and this would evolve very considerable 
 amounts of heat. Mallet has shown that the crushing of small 
 cubes of various kinds of rocks may be made to raise the temper- 
 ature to the melting point. Much more would the crushing press- 
 ure resulting from the earth's contraction. Mallet and others 
 have conceived that the chief part of the earth's internal heat 
 may have a mechanical origin. This suggestion implies the non- 
 existence of a molten core, and, in fact, the diminution of heat 
 toward the centre. But we think that while the crushing action 
 would develop much heat, this cause is not adequate to produce 
 results on such a scale as the facts of geology seem to require. 
 The whole earth has moved forward in all its continental re- 
 gions with a harmonious and synchronous development. This 
 would not be unless all parts were in physical sympathy with 
 each other; and we cannot well conceive a more probable way in 
 which such sympathy could exist than through a state of general 
 plasticity or fusion. 
 
 (3) Seismic Results of Contraction. Different parts of the 
 earth's crust must be conceived as possessing different degrees of
 
 DYNAMICAL GEOLOGY. . '-i93 
 
 strength and rigidity. This would result from different rock- 
 materials, mixed in different proportions, differently metamor- 
 phosed, and eventually resting in different positions. A strain, 
 therefore, under which one part would yield, would be resisted 
 by another part. The stress would be accumulated in the most 
 rigid parts. But no rigidity and no materials could resist all 
 stresses resulting from the action of the earth's mass. Every 
 part must finally yield. In proportion as the stress was great, the 
 final shock must be great. The shock is an earthquake move- 
 ment. It transmits a tremor or vibration through the crust, and 
 this may be felt to a great distance from the seat of the main 
 collapse. The frequent earthquake tremors, therefore, are in 
 part, merely the incidents of the slow contraction of the earth. 
 
 (4) Mountain Making. The principal phenomena of moun- 
 tains which theory must seek to explain are as follows: () The 
 elevation; (b) the folding and plication of the strata; (c) the 
 faulting; (d) the accompanying heat and metamorphism; (e) the 
 great thickening of the mountain strata; (/') the more fragmen- 
 tal character of the strata; (g) the elongation of the mountain 
 uplift; (A) the direction of the elongation. 
 
 Much study has been bestowed on the explanation of these 
 phenomena, and some principles have been generally agreed upon 
 which we will here concisely state. 
 
 There must have been always, since the ocean existed, a sys- 
 tem of ocean currents. There must also have been mineral material 
 held in suspension in the sea water and moved along with the 
 currents. There must also have been coarser materials rolled and 
 pushed along. Some of this matter was simply of chemical pre- 
 cipitation; some resulted from disintegration of shells and corals; 
 but the most bulky part was detrital. As soon as the conti- 
 nental masses rose within reach of the action of the waves and 
 currents, -mechanical sediments existed, and these were trans- 
 ported by the currents. The currents, while originating in astro- 
 nomical causes, were greatly deflected and controlled by con- 
 tinental shores, and even by continental masses while yet in the 
 germ beneath sea level. Supplies of detrital material there-
 
 294 GEOLOGICAL STUDIES. 
 
 fore, furnished from any source, might be moved partly by flo- 
 tation and partly by rolling and pushing for great distances 
 along the line of an ocean current. In the course of ages, the 
 accumulation of sediment along this line would so load the sea 
 bottom that subsidence would result. The accumulation pro- 
 ceeded step by step with the subsidence. Sediments were accu- 
 mulating on other parts of the sea bottom, but not so copiously, 
 nor in so coarsely fragmental a condition; for elsewhere the 
 transporting power of the water was less. 
 
 The downward protrusion of the sinking sea bottom exposed 
 the deepest portion to the fusing and metamorphic action of the 
 internal heat. The semifusion and softening of the deeper por- 
 tion, and perhaps the comparative freshness and unsolidity of the 
 upper portion made the line of subsidence a belt of weakness. 
 We are not in this connection to conceive any actual consider- 
 able downward protrusion along the sinking region. The prog- 
 ress was slow. The protruding portion was progressively melted 
 off. A nearly uniform thickness of the crust was maintained, 
 though along this synclinal the exceptional condition of the ma- 
 terials developed exceptional lack of rigidity. 
 
 Accordingly, when in the progress of contraction, accumulated 
 strains became too great for the crust to withstand, the yielding, 
 the disturbance, the upfolding would take place along the enfee- 
 bled synclinal synclinal in its texture more than in its form. 
 Here a fold would rise. Here a mashing together of the softened 
 materials would take place. Here the lateral pressure would 
 most plicate the plastic sheets of sediments. Here, in this belt 
 of weakness, would be developed the motion due to the contrac- 
 tion that had taken place over broad areas on either side. Here 
 the sea water would find freest access, and here the heat, most 
 readily transmitted from below, and most abundantly generated 
 by most extensive motion, would work most extensive meta- 
 morphism. 
 
 Thus a great synclinal fold became mashed together and up- 
 lifted into an anticlinal mountain elevation. This was the com- 
 pletion of a synclinorium a mountain system originating in a
 
 DYNAMICAL GEOLOGY. 295 
 
 submarine synclinal. During the severe ordeal great fractures 
 must have resulted, and great faultings must frequently have 
 been produced. We have, then, in this account, an explanation 
 which covers all the demands of mountain phenomena, except the 
 linear forms and the direction of the trend; and these we think 
 due to other causes, to be mentioned in another section. 
 
 The weight of the uplifted synclinorium exerted on each side 
 an extraordinary lateral pressure. There existed, consequently, 
 a tendency to the uprise of other ridges parallel with the first. 
 When, in a later age, the crust must yield again, one or more 
 broad but lower folds would rise alongside of the primitive uplift. 
 Thus, from the central and highest crest to the remotest parallel 
 fold on either side, and the plains beyond, a general descent in 
 the extension of the strata constitutes a geanticlinal ; and the 
 meeting of two geanticlinal slopes in the broad valley between 
 two mountain systems forms a geosynclinal. Mountain folds 
 thus raised are destined to be materially lowered in altitude and 
 changed in contour by the erosions of subsequent periods. 
 
 5. Geological Climates. 
 
 1. Terrestrial Causes. (1) Greater Heat and Greater 
 Uniformity of Primitive Climates. The progressive cooling of 
 the earth has resulted, necessarily, in a progressive subsidence of 
 the surface temperature. Heat from the sun and heat from be- 
 neath the crust are two chief factors in terrestrial climates. The 
 solar heat at any point varies with the inclination of the solar 
 rays. The influence of internal heat is the same in all latitudes 
 and at all seasons. When the crust was thinner this influence 
 was greater, and hence climatic uniformity was greater. The 
 greater uniformity extended through the year and over all lati- 
 tudes. When, therefore, the mean surface temperature was 
 higher, it was also more uniform. Tropical climates prevailed at 
 the poles as well as at the equator. This deduction is sustained 
 by the facts of palaeontology. 
 
 (2) Alleged Antecedent Hdbitdbility of Northern Regions. 
 In the earth's cooling from a molten state the diminution of sur-
 
 296 GEOLOGICAL STUDIES. 
 
 face heat would be nearly equal on all sides. But the solar rays 
 would retard the surface cooling to a greater extent in the equa- 
 torial regions than in the polar. Consequently, the polar regions 
 would first attain a habitable temperature. Chiefly on this 
 ground G. H. Scribner has argued that life began at the pole. 
 On this and other grounds President W. F. Warren has recently 
 maintained that the site of Paradise was at the North Pole. Ge- 
 ology points out the fact that the north polar regions were once 
 the site of a luxuriant fauna and flora; that many organic types 
 appear to have emigrated from the north, and that many remain- 
 ing there are degenerate forms; and science and tradition afford 
 other support for this startling doctrine. We cannot yet, how- 
 ever, announce it as a principle in geological history. It may 
 safely be asserted, however, that the principle cited lends no sup- 
 port to the theory that the first representatives of our species 
 made their advent at the pole. At the epoch of man's advent, 
 even if we fix it in Tertiary Time, the earth's geological progress 
 was so far advanced that the polar climate had already become 
 inhospitable; and the location of the Paradise of our first parents 
 at the North Pole is an inadmissible theory. 
 
 (3) Ultimate Total Dissipation of Terrestrial Heat. There 
 is no store of heat in the earth so great as not to be ultimately 
 exhausted. If the earth has not already wasted its original sup- 
 ply, the time will necessarily arrive when external sources must 
 furnish the only supply. As a fact, the present stage of terres- 
 trial cooling is so far advanced that the thickened crust reduces 
 to an inconsiderable pittance all the heat now reaching the sur- 
 face from the interior. Our climates already depend practically 
 on heat from the sun. 
 
 (4) Ultimate Extinction of the Sun. But the sun itself is 
 cooling, and his destiny is just as inevitable as that of the earth. 
 We cannot, indeed, calculate the ages which must elapse before 
 the sun's light and heat will cease to reach the earth. That de- 
 pends on the sun's present temperature and the sun's mass and 
 density. His temperature is not accurately known; but from the 
 most trustworthy assumptions it has been calculated by New-
 
 DYNAMICAL GEOLOGY. 297 
 
 combe that the sun will be as dense as the earth in 12,000,000 
 years. These considerations point out an inevitable limit to the 
 present order of things. 
 
 2. Extra-Terrestrial Causes of Climates. Geological 
 
 observation shows that one or more periods of extraordinary cold 
 have passed, in the history of the northern hemisphere. Much 
 study has been bestowed on efforts to find a cause for such a 
 vicissitude. The following suggestions have been made: (a) The 
 radiating power of the sun has been less at certain periods; (I)} 
 The earth, with the sun and solar system have been transported 
 through colder regions of space; (c) Diminished absorbent power 
 of the atmosphere. These causes would affect the whole earth 
 equally. The next two (not indeed extra-terrestrial) would affect 
 only certain regions: (d) A different arrangement of the conti- 
 nental masses has caused a different distribution of warm and 
 cold currents; (e) Northern elevation. The following would 
 affect the northern and southern hemispheres alternately: (/') 
 Variations in the amount of obliquity of the earth's axis to the 
 plane of the ecliptic; (g) The precession of the equinoxes, or 
 direction of the inclination of the earth's axis in reference to 
 perihelion and aphelion; (A) The periodic increase in the eccen- 
 tricity of the earth's orbit. We cannot afford the space even to 
 explain the three astronomical theories last mentioned, and the 
 others will be at once intelligible, or may be thought out by the 
 student. 
 
 8 6. Tidal Action in the Earth's History. 
 
 1. Definitions. A tide, in general terms, is the change 
 produced in the form of a body by the attraction exerted by 
 another body. Two spheres mutually attracting become mutually 
 prolate. The form of each is a prolate spheroid, with its longer 
 axis in the line passing through the two centres of gravity. The 
 elevations of the prolate poles above the mean surface are the 
 tides. The elevation of the pole opposite the tide-producing 
 body is the antitide. The tide results from the fact that the 
 nearer side of the tide' bearer is more strongly attracted than the
 
 298 
 
 GEOLOGICAL STUDIES. 
 
 FIG. 218. A DEFORMATIVE TIDE. 
 a m is the tidal elevation ; b , 
 the anti-tidal elevation ; c o and 
 d p are the tidal depressions. 
 
 centre; and the antitide from the fact that the centre is more 
 strongly attracted than the farther side. In the annexed dia- 
 gram, the tidal attraction is supposed 
 to come from the side a. Then a m, 
 is the tidal, and b n the antitidal ele- 
 vation, c o and d p are the tidal de- 
 pressions. The tide raised in the 
 ocean by the attractions of the moon 
 and sun are well known. But it is 
 not necessary that a liquid film 
 should exist. It is not necessary that 
 the tide-bearing body should be dis- 
 tinctly plastic. It has been shown 
 that if the earth were as rigid as glass, 
 the moon's attraction would raise a 
 tide in it three-fifths as high as the 
 tide in the water-covered earth; and 
 if the earth were all steel, the tide would be still one-third as 
 high as it is at present. The whole earth then yields to the lunar 
 tidal attraction. There is no matter so rigid as not to be rela- 
 tively plastic and yielding in the presence of the enormous forces 
 exerted upon each other by the heavenly bodies. 
 
 2. Seismic Consequences of Tidal Action. From 
 what has just been stated, it appears that the moon's attraction 
 subjects the earth's crust to strains similar to those resulting from 
 secular contraction. The moon must, therefore, contribute some- 
 thing to earthquake phenomena. There must, then, be a connec- 
 tion in times of occurrence between such phenomena and the 
 phases of the moon. Accordingly, it has been shown, especially 
 by M. Alexis Perrey, that these phenomena are of most frequent 
 occurrence (a) When the moon is in perigee; (b) When the sun 
 and moon are in conjunction or opposition, thus uniting their 
 actions; (c) When the moon is near the meridian. It cannot bo 
 said, however, that tidal agency in earthquakes is fully estab- 
 lished. 
 
 3. Tidal Evolution of Heat. It will at once occur to
 
 DYNAMICAL GEOLOGY. 
 
 299 
 
 the student that motions in the crust caused by tidal disturbance 
 must evolve some heat, like the motions resulting from contrac- 
 tion. But we have not the requisite data as yet for determining 
 whether or not the heat generated in this way is sufficient to ex- 
 plain all the thermal phenomena of the earth's crust, or even any 
 important proportion of them. Here, however, are causes in 
 action, and they must be borne in mind. 
 
 4. Tidal Influence on Motions of the Earth and 
 Moon. (1) Lagging of the Tide. If the terrestrial tide re- 
 sponded instantly to the moon's attraction, the summit of the tide 
 would be always under the moon. But owing to the viscosity 
 even of fluid substances, the tide lags. That is, the moon is 
 always farther west than the apex of the tide. In the accom- 
 
 ;G 
 
 :/AE 
 
 FIG. 219. ILLUSTRATING A LAGGING TIDE. 
 
 panying figure, if Q is the earth's centre and C the position of 
 the moon, then the apex of the lunar tide will be at B instead of 
 A. That is, the rotation of the earth being in the direction of 
 the arrow, it will have carried the point A to B while the tide is 
 completing its rise after the culmination of the moon. 
 
 (2) Retardation of the Earths Rotation. Now, when the 
 earth, the tide, and the moon are in the relative positions shown 
 in Fig. 219, the moon's attraction on the tidal protuberance, in 
 excess of its attraction on the more remote antitidal protuberance 
 D, tends to turn the earth in a direction contrary to that of its 
 actual rotation. That is, the earth's rotation is opposed. The 
 length of the day is increased. Calculation shows that the 
 amount of this increase is quite appreciable. 
 
 (3) Diminution of the Earths Oblateness. This is a neces-
 
 300 GEOLOGICAL STUDIES. 
 
 sary accompaniment of diminished velocity of rotation. This 
 fact implies that the equatorial circumference of the earth has 
 diminished, during long secular intervals of time, more than the 
 polar circumference. Consequently, a greater lateral pressure 
 has been experienced in the latitudinal (east and west) direction 
 than in the longitudinal direction. This excess of latitudinal 
 pressure would produce effects having a meridional trend; and 
 this excess of equatorial shrinkage would supplement the shrink- 
 age due to general contraction. The surplusage in the length of 
 the circumference thus resulting, added to the surplusage result- 
 ing from general cooling contraction, might afford all the sur- 
 plusage wrought into the folds and plications of the earth's 
 crust, and thus obviate a difficulty in the theory of mountain 
 making stated on page 292. 
 
 (4) Increase of the Moon's Distance. Referring again to 
 Fig. 219, we may consider the reciprocal action of the tide B on 
 the moon's motion in the orbit HI. This influence is plainly 
 accelerative. But, if the moon's velocity is increased, its cen- 
 trifugal tendency is increased. It therefore recedes from the 
 earth and revolves in a larger orbit. These actions and reac- 
 tions have existed as long as the earth and moon have existed as 
 separate bodies. We must therefore contemplate a time when 
 the moon was much nearer the earth than at present, and conse- 
 quently revolved with a higher velocity. 
 
 5. High Primitive Tides. On these grounds, it has 
 been suggested by Professor Ball that in early times perhaps 
 during the Palaeozoic JEon the proximity of the moon caused 
 enormously high tides in the oceans, and thus accelerated the 
 processes of erosion and deposition, and shortened correspond- 
 ingly the time required for the geological work accomplished. If 
 such increase of tidal action ever existed, the thickness and 
 coarseness of the strata would testify to it. But the Palaeozoic 
 strata appear to have been quietly deposited, under conditions 
 not very different from those now existing. If we extend our 
 observations back through the Eozoic formations, we discover 
 some evidences of superior energy in the geologic forces, but no
 
 DYNAMICAL GEOLOGY. 301 
 
 such indications of extreme violence as the suggestion of Pro- 
 fessor Ball implies. Still, the reasoning is sound, and we are yet 
 at liberty to conclude that extreme tidal energy left its record in 
 those primordial sediments which have been in later times com- 
 pletely melted away. 
 
 6. Ingrained Meridional Trends in the Earth's 
 
 Crustal Structure. Lunar tides existed on the earth while 
 it was yet molten. They existed during the incrustive stage, and 
 were more considerable than at present in proportion as the cube 
 of the moon's distance was less. The superior density and 
 viscosity of the molten fluid would, however, determine a lower 
 tide than if produced in water. Recurring again to Fig. 219, it 
 is seen that the moon tends to pull the lagging tide around 
 toward the west. In a molten globe there would be some actual 
 slipping westward. This would be greatest, on the average, 
 along the equator. The effect of this slipping, on the forming 
 crust, would be to impart a non-homogeneous structure. Lines of 
 structure running nearly north and south would be ingrained in 
 the crust. So much would result from lunar tidal action on the 
 primitive crust. 
 
 But the slow subsidence of the equatorial protuberance 
 during the secular diminution of the earth's rotational velocity, 
 would produce a result of a similar nature. The excess of lateral 
 pressure in the middle zone of the earth would be analogous to 
 the action of the moon on the retarded tide. Any results pro- 
 duced would have a meridional trend. Meridional lines of struc- 
 ture would determine meridional predispositions to yield and 
 take shape, under the action of any causes affecting the perfect 
 symmetry of the earth's surface. 
 
 The lines of meridional structure and predisposition deter- 
 mined by these two causes were primordial features. Hence, if 
 afterward, the secular cooling and contraction of the earth should 
 tend to develop wrinkles without determinate direction, as 
 would be the case, these meridional ingrained predispositions 
 would give a majority of them a north and south direction. In 
 the equatorial zone, the excess of east and west pressure would
 
 302 GEOLOGICAL STUDIES. 
 
 tend directly to produce meridional wrinkles. Thus we discover 
 causes why the primitive mountains assumed elongated forms; 
 and why the direction of the elongation was approximately north 
 and south. 
 
 This theory is not claimed as one generally recognized among 
 geologists. The suggestions are recent. But some causes 
 operated to produce all the results enumerated on page 293 as 
 mountain features to be explained by a final theory, and these 
 views are submitted as at least plausible and deserving of study. 
 
 7. Geotechtoiiic and Scenographic Results. 
 
 The dynamic actions which have given shape to the earth's 
 periphery are strictly subjects of geological investigation. The 
 results are inseparably bound up with the causes. The descrip- 
 tion of mountains, continents, oceans, and other physiographic 
 features belongs to geology. Such descriptions may be gathered 
 together under a separate head and designated " physical 
 geography "; but so far physical geography is only a branch of 
 geology. It is a grouping of a certain class of structural facts; 
 but without the attempt to interpret them and ascertain their 
 meaning and unity. Physical geography should be taught and 
 understood as an essential part of geology. 
 
 It would be deeply interesting to review here the earth's 
 physiographic features, and trace their connection with the 
 causes that have been passed under review in this Chapter. The 
 method of the First Part of this work, however, has led us con- 
 tinually to an observation of these features as the grounds and 
 suggestions for the principles there induced. For the present, 
 therefore, we shall pass on to other branches of the science which 
 deserve prominent treatment.
 
 CHAPTER IV. 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 DEFINITIONS. Each Age and Period of the world's history 
 has been characterized by its special assemblages of animals and 
 plants. Many of the remains of these have been imbedded in the 
 sediments of the time, and have become fossilized. When we 
 examine to-day the rocks resulting from these sediments, the fos- 
 sil forms are disclosed, and serve as the stamp of the age in which 
 they were alive. Fossils are, therefore, a most important means 
 for the determination of a formation. We shall not, in this 
 course, attempt to lead the student far into this subject. We 
 have shown, in Studies XXX XXXIV, something about the 
 method of studying fossils. In this chapter we propose to give, 
 for convenient reference, an outline tabular exhibit of the classi- 
 fication of fossils, and sketch some of the most prominent fossil 
 types which have appeared and disappeared in the history of 
 life. 
 
 Fossilization. A fossil is whatever reproduces for us any- 
 thing of the form or structure of an organic being no longer 
 living. It may be: (1) The real substance of the organism, like 
 a shell, or bone, so recent as to have been little altered. (2) The 
 perfect form and structure of the organism, but with the original 
 substance replaced by other mineral matter. This is a true pet- 
 rifaction. The replacing mineral is commonly calcite or silica; 
 sometimes pyrites, or other substance. In fossil wood it is fre- 
 quently opal. (3) The fossil may be a mere impression of the 
 exterior of the organism, made originally in the soft mud of the 
 sea bottom. The shell, or coral, may be completely removed; 
 but, with gutta-percha, putty, sulphur, or plaster, the mould may 
 be filled, and the form of the original organism sometimes very
 
 304 GEOLOGICAL STUDIES. 
 
 perfectly restored. In some cases the mould is found filled with 
 stony matter. (4) The fossil may be a mere cast of the interior 
 of a shell or other organism. The soft muddy or sandy filling of 
 the interior became consolidated, and afterward the organism 
 wasted away. Such casts often preserve very perfectly the mus- 
 cular scars or vascular impressions on the interior of a shell 
 
 Horizontal Range of Fossils. This is simply the geographi- 
 cal area over which a fossil species may be found. Some of the 
 older species have been discovered in many different regions and 
 countries. This wide range becomes of great service in identify- 
 ing formations at remote points. The extent of the horizontal 
 range depends on the extent of the uniformity of physical condi- 
 tions when the animals lived. Diverse conditions at distant 
 points necessitated diverse faunas. Thus it happens, sometimes, 
 that equivalent formations hold different assemblages of fossils. 
 
 Vertical Range of Fossils. This refers to the occurrence of 
 the same species, or other type, in formations older or newer, 
 throughout a certain vertical range. It implies that a species 
 survived changes in physical conditions which separated succes- 
 sive periods, and which exterminated most of its fellows. It 
 implies that the physical changes were not great, or that the 
 species possessed great tenacity of life. Hence species with 
 great vertical range are generally, also, species of wide geograph- 
 ical distribution. As a rule, species are confined to a single 
 formation. Sometimes they range vertically into one or more 
 higher formations. Sometimes, after disappearing from overly- 
 ing strata of changed constitution, a species reappears in a still 
 higher stratum formed under a recurrence of the former physical 
 conditions. Its temporary disappearance indicates, therefore, not 
 extinction, but migration to some more congenial region. 
 
 Colonies, so called by Barrande, are incidents of migrations 
 of faunas. A colony is an assemblage of fossils reputed charac- 
 teristic of a certain age, interstratified in a formation containing 
 its own reputed characteristic fossils. Thus Barrande brought to 
 light in Bohemia a colony of Silurian fossils 3,400 feet deep in 
 the midst of a Cambrian group. In such case it is evident that
 
 PROGRESS OF TERRESTRIAL LIFE. . 305 
 
 the included colony is not properly characteristic of a different 
 age. The colony, and the fauna in which it colonized, were con- 
 temporaneous, but living in different regions, separated by some 
 barrier. The removal of this permitted the commingling of the 
 two populations. 
 
 SECTION I MOST IMPORTANT TYPES OF PLANTS AND 
 ANIMALS. 
 
 [Numbers in parenthesis refer to Figures in this work.] 
 
 I. PLANTS. 
 
 SERIES I. CRYPTOGAMS. 
 
 STEM I. THALLOPHYTES.-Consisting wholly of cellular tis- 
 sue. Growing mostly in fronds, or other spreading forms, 
 without proper stems or leaves. 
 CLASS I. ALGAE. Those living in the sea are THALASSOPHYTES (295) ; 
 
 those in fresh water, HYDROPHYTES. 
 
 ORDER I. UNICELLULAR THALLOPHYTES. Including Diatomacea, of 
 microscopic size, and having silicious shields. Other fossil 
 Algae are not thoroughly classified. 
 CLASS II. FUNGI. CLASS III. LICHENS. Not geologically 
 
 important. 
 
 STEM II BRYOPHYTES-(^n^Tis). 
 CLASS I. MTJSCIN^E.- Moss-like. 
 
 ORDER I. HEPATIC/E. Liverworts. ORDER II. BRYOIDExE. Mosses. 
 STEM III. PTERIDOPHYTES (Acrogens).-V^\w Crypto- 
 gams. 
 
 CLASS I. FILICACE.2E. Ferns. The following Families are recog- 
 nized : 
 
 Hymenophyllacece, Sphenopteridce, Paieeopteridce, Netirojiteridm, 
 Cardiopteridce, Alethopteridae, Pecopterida;, Tainiopteridte. 
 Also, from stems we have the genera Caulopteris, Megaphyium, 
 Psaronius. 
 
 CLASS II. BHIZOCARPE^!. Hydropterids. 
 CLASS III. CALAMARIE^E. 
 
 Family 1. Eqnisetece. Horse-tails. 3. Calatnitece. Calamites. 4. 
 Annuiariea-. Annularia, Asterophyllum, Sphenophyllum. 
 CLASS IV. LYCOPODIACE^E. 
 
 Family 1. Lycopodiea;. Psilophyton. 2. X,epidodendrece. Lepido- 
 dendron. Ulodendron, Halonifi. 4. Sigillariece. Sigil- 
 larin, Stigmaria.
 
 306 GEOLOGICAL STUDIES. 
 
 SERIES II, PHANEROGAMS. 
 
 STEM IV. G-YMNOSPERMS.-Seed not inclosed. 
 
 ORDER I. CYCADACExE. Carboniferous Whittleseya and many Meso- 
 
 zoic genera. 
 
 ORDER II. CORDAITE/E. Cordaites. 
 ORDER III. CONIFER/.-Pines, Firs, etc. 
 STEM V. ANG-IOSPERMS.-Seed inclosed. 
 CLASS I. MONOCOTYLEDONS. Bndogens. Mostly parallel- 
 veined leaves. 
 CLASS II. DICOTYLEDONS. Bxogens. Netted- veined leaves. 
 
 II. ANIMALS. 
 
 STEM I.-PROTOZOA. 
 
 Chiefly microscopic, with no definite typical form, without specialized organs, 
 
 and mostly with asexual, as well as sexual reproduction. 
 
 CLASS I. MONEBA. Of completely homogeneous, structureless 
 
 protoplasm. 
 
 CLASS II. BHIZOPODA. Body consisting chiefly of simple sarcode. 
 ORDER I. FORAMINIFERA (Polythalamia). Having a one-chambered 
 or many-chambered shell, calcareous, rarely sandy, silicious, 
 or chitinous. 
 
 SUB-ORDER I. IMPERFORATA. Receptaculites. II. PER- 
 FORATA. Globigerina, Nummulites, Orbitoides, Fusu- 
 lina, Eozoon. (220, 222.) 
 ORDER II. RADIOLARIA(Polycistina). III. LOBOSA. Amoeba. (221.) 
 
 STEM II.-CCELENTERATA. 
 CLASS I. SPONGLffi. (Porifera. Amorphozoa.) Sponges. 
 CLASS II. ANTHOZOA. (Polypi. Zoophyta.) Radiated, mostly 
 with a calcareous skeleton, having radial septa. Skeleton 
 known as coral. 
 
 ORDERI. ALCYONARIA . (Octocoralla. ) With eight radial divisions. 
 ORDER II. ZOANTHARIA. Having twelve or more radial divisions. 
 
 Most Pakeozoic corals belong here. 
 
 SUB-ORDER ANTIPATHARIA. Having an intern&l horny axis. 
 SUB-ORDER A CTINARIA. Without calcareous skeleton. Not 
 
 fossilized. 
 SUB-ORDER MADREPORAR1A (Zoantharia Sclerodermata). 
 
 Having a calcareous skeleton. 
 
 Group 1. Tetracoralla (Rugosa). Cup Corals. Four systems 
 or fascicles of septa. See Studies XXX, XXXT.
 
 PROGRESS OF TERRESTRIAL LIFE. 307 
 
 Family l. Inexpleta. Interseptal chambers empty or with feeble 
 dissepiments tabulae and cellular contents wanting. 
 Septa well developed. Cyathiform, simple. Amplexus 
 (114, 115, 118, 119). 
 
 Family 2. Expleta. Tabulae or cells or both fill the visceral cavity. 
 
 SUB -FAMILY DIAPHEAGMATOPHORA. Tabulae complete; cellular en- 
 dotheca wanting or feebly developed. Septa regularly 
 radiate. Zaphrentis (112, 113, 117), Streptelasma (122- 
 124). 
 
 SUB-FAM. PLEONOPHORA. Tabulae incomplete, present only in central 
 part of visceral cavity; cellular tissue in peripheral part. 
 Cyathophyttum (116, 120, 121), Heliophyllum (130, 132 
 133), Acervularia (138, 139), Diphyphyllum (141-143) 
 Litliostrotion (140j. 
 
 SUB-FAM. CYSTOPHORA. Whole interior filled with vesicular tissue. 
 
 CystipTiyllum (134-136). 
 
 Group 2. Hexacoralla. Septa mostly in multiples of six. 
 Here belong the "honey-comb" corals. 
 
 Family 1. Foritidce. Compound, cells united, small. Septa few, 
 mostly rudimentary. Walls perforated. 
 
 SUB-FAM. FAVOSITIN^;. Massive, without ccenenchyma. Cells long, 
 pi-ismatic, divided by numerous tabulae. Walls pierced by 
 numerous perforations. Septa six or twelve, often reduced 
 to mere longitudinal raised strise on the walls. Favosites 
 (144-149, 152), Alveolites (153, 154), Limaria (155, 156), 
 Cladopora (157, 158). 
 
 GLASS III. HYDROMEDTTS2E (Hydrozoa). Hydras and Sea Net- 
 tles. Fixed, polyp-like, small, undivided by radial septa. 
 Skeleton calcareous, chitinous, or wanting. 
 ORDER HYDROIDA (Hydrophora). 
 
 Family stromatoporida; . [Probably a "comprehensive" type unit- 
 ing characters of Foraminifera, Sponges, Hydroida, and 
 Tetracoralla. Probably also Eozoon belongs in near rela- 
 tion] (223-227). 
 
 SUB-ORDER GRAPTOLITIDJE. 
 
 STEM III.-ECHINODEBMATA. 
 
 CLASS I. CBINOIDEA. Sea Lilies. Crinoids. Supported by a 
 stem. Visceral organs inclosed by calcareous plates sym- 
 metrical in form and disposition. Five to ten arms spring 
 from the border of the cup, and these are fringed with 
 pinnules.
 
 )8 GEOLOGICAL STUDIES. 
 
 ORDER I. ENCRINOIDEA (Palscocrinoidea) (233). Armed Sea Lilies. 
 
 Rliizocrinus (232), Forbesiocrinus (234). 
 ORDER II. CYSTOIDEA. Cystids. Short-stemmed or sessile. Arms 
 
 feebly developed. Pakeozoic. Caryocrinus. 
 
 ORDER III. BLASTOIDEA. Nut shaped or oval, armless, short- 
 stemmed. Cup of thirteen regularly disposed principal 
 pieces. Pentremites. 
 
 CLASS II. ASTEROIDS A. -Sea Stars. Star Fishes. ' 
 CLASS III. ECHINOIDE A. -Sea Urchins. 
 CLASS IV. HOLOTHTJROIDE A. Sea Cucumbers. Holothurians. 
 
 STEM IV.-VERMES. 
 
 The four lower classes of Worms are scarcely known fossil. 
 CLASS ANNELIDA. With cylindrical segmented body and chitin- 
 ous integument. Serpula, Spirorbis? Cornulites, Scolt'thus. 
 
 STEM V.- MOLLUSC A. 
 DIVISION A- MOLLUSCOIDEA. 
 
 CLASS I. BBYOZOA (Polyzoa). Colonies of small animals sur- 
 rounded by a membranous or calcified integument, and 
 forming branched moss-like or membranous compound 
 structures. In general aspect much resembling Hydrozoa. 
 Sub-Class I. Entoprocta. No representatives fossil. 
 Sub-Class II. Ectoprocta. 
 
 Family 4. FeneatelUdce. Fenestella, Polypora, Archimedes. 
 Family 5. Ptilodictyonidce.Ptilodictya, Coscinium. 
 Family 1O. Chcetetidce. In masses resembling diminutive Favosi- 
 
 tidce, but without connecting pores. Monticulipora. 
 CLASS II. BBACHIOPODA (Palliobranchiata). Brachiopods. 
 
 Compare Studies XXXIII and XXXIV. 
 ORDER I. PLEUROPYGIA. Hinge structure and arm supports 
 
 wanting. 
 
 Family 1. Ungulldce, Lingula, Lingulhlla, Lingulepis, Glottidia. 
 Family 2. Obolidce.Obolus, Obolella, Trematis. 
 Family 3. Discinidce.Discina, Orbiculoidea. 
 Family 4. Trimerellidce . Monomerella, Trimerella, Dinobolus. 
 Family 6. Craniadce. Crania. 
 ORDER II. APYGIA. Always calcareous, with hinge structure. With 
 
 or without arm-supports. 
 
 Family 1. Productidce.Producta, Chonetes, Productella. 
 Family 2. Strophomenidce.Orthis (166, 171), Streptorhynchus, Or- 
 thisina, Sirophomena (167, 168, 190, 192), Lepfana, Trop- 
 idoleptus, Skenidium, Vitulina.
 
 PROGRESS OF TERRESTRIAL LIFE. 309 
 
 Family 3. Koninckinidas.Koninckia. None American. 
 
 Family 4. Spiriferida,. Spinfera (161, 162, 164, 165, 172, 174), 
 
 Spiriferina, Cyrtia, Cyrtina (170). Syringothyris (181, 
 
 183), Sprigera (179, 180), Nucleospiru, Merista, Meri- 
 
 stella, Retzia, Uncites. 
 Family 5. Airy place. Atrypa (175-177), Coelospira, Zygospira 
 
 (178) 
 Family 6. Khynchonellidce. Rhynclionella. Leiorhynchus, Di- 
 
 merella, Camerella, Peniamerus, Stricklandia. 
 
 Family 7. Stringocephalidas. Stringocephalus. None American. 
 Family 8. Thecideidce.Thecia. None American. 
 Family 9. Terebratulidce. Terebratula (184-186), Gryptonella, 
 
 Remselceria, Meganteris, Centronella (187, 188). 
 
 DIVISION B.- MOLLUSCA Proper. 
 
 CLASS I. LAMELLIBBANCHIATA (159, 160). Equivalve Bi- 
 valves. See Study XXXIII. 
 ORDER I. ASIPHONIDA. Mantle lobes divided, siphon wanting, pal- 
 
 lial impression without sinus. 
 
 DIVISION A. MONOM YARIA. Only one (hinder) adductor 
 muscle. Ostrea, Gryphcea, Exogyra, Pernopecten, Avicu- 
 lopecten. 
 
 DIVISION B. HETEROHYARIA.'Zwo unequal adductors. 
 Cartilage separated in numerous isolated pits or furrows. 
 Avicula. Pterinea. 
 DIVISION C. HOMOMYARIA.Two equal adductors. Cyrto- 
 
 donta, Nucula, Palceoneilo, Schizodus, Cardmia. 
 ORDER II. SIPHONIDA. Siphon present; mantle lobes more or less 
 
 united. 
 
 DIVISION A. INTEGRIPALLIATA.?s\\i&\ impression with- 
 out sinus. Lucina, Conocardium, Cypricardinia, San- 
 guinolaria. 
 Dl VISION B. SIN UPALLIA TA. 
 
 Solenopsis, Cardiomorpha, Edmondia, Allorisma, San- 
 guinolites. 
 
 CLASS II. GASTEROPODA (Glossophora. Cephalophora). Uni- 
 valves. 
 Sub-Class I. Scaphopoda. Tubular, open at both ends. Den- 
 
 talium. 
 
 Sub-Class IH. Gasteropoda Proper. 
 
 ORDER I. PROSOBRANCHIA. Gills anterior to the heart. Metop- 
 toma, Bellerophon, Cyclonema, Holopea, Platyceras, Pla- 
 tyostoma, Loxonema.
 
 310 GEOLOGICAL STUDIES. 
 
 ORDER II. HETEROPODA. Mostly naked. Unimportant palaeonto- 
 
 logically. 
 
 ORDER III. OPISTHOBRANCHIA. Scarcely known as Pahsozoic. 
 ORDER IV. PULMON ATA. Air-breathing. Pupa, Dendropupa. 
 Sub-Class IV. Pteropoda. Tentaculites, Hyolithes, Conularia. 
 
 CLASS III. CEPHALOPODA (Cephalophora) Cephalopods. 
 
 ORDER TETRABRANCHIATA (236). Having an external chambered 
 
 shell. 
 SUB-ORDER 1. NAUTILOIDEA. Shell straight, bent, or 
 
 coiled. Sutures mostly simple or slightly sinuate. Siphonal 
 
 cornets directed backwards. 
 Family 1. Orthoceratidce. Straight or slightly bent. Orthoceras. 
 
 (235, 237.) 
 Family 3. Cyrtoceratidce. Simply bent. Cyrtoceras (238), Phrag- 
 
 moceras. 
 Family 4. Nautilidce. Coiled ill a plane. Gfyroceras (239). Litu- 
 
 ites, Nautilus. 
 
 Family B. Trochoceratidce. Coiled in a conical spire. TrocJioceras. 
 SUB-ORDER II. AMMONOIDEA (240). Shell coiled variously 
 
 or straight. Suture line undulate, lobed or foliaceous. 
 
 Siphon cylindrical, marginal. 
 Family l. Clymenidce. Umbilicus wide. Siphon internal. Cly- 
 
 menia. 
 
 Family 2. Goniatitidcc . Siphon thick, external. Goniatites. 
 A large Sub-Order, but the remaining genera are post-Palaeozoic. 
 
 STEM VI.- ARTHROPOD A. 
 
 CLASS I. CRUSTACEA. Respiration aquatic. Exoskeleton chitin- 
 
 ous or sub-calcareous. 
 
 Sub-Class II. Cirripedia. Attached when adult. . 
 Sub-Class III. Entomostraca. Carapace horny, composed of 
 
 one or more pieces. 
 ORDER I. OSTRACODA. Carapace of two valves. Leperditia, 
 
 Cythere. 
 
 ORDER IX. PHYLLOCARI DA Feet serving as gills. Ceratiocaris. 
 ORDER X. TRILOBITA (231). Body more or less trilobed. Cephalic 
 shield usually with a pair of sessile eyes. Thorax with 
 movable segments, and caudal shield (pygidium) with con- 
 solidated segments. Paradoxides (228), DiMlocephalus, 
 Phacops, Calymene (229, 230), Proetus, Lichas, Acid- 
 aspis, Asaphus, Illcenus.
 
 PROGRESS OF TERRESTRIAL LIFE. 311 
 
 ORDER XI. MEROSTOMATA. 
 
 Eurypterus, Pterygotus. 
 Sub-Class IV. Malacostraca. 
 CLASS II. ARACHNID A. Scorpions and Spiders. 
 
 ORDER I PEDI PALPI. Scorpions. Abdomen distinctly segmented. 
 ORDER II. ARANEIDA. Spiders. Head and thorax consolidated. 
 CLASS III. MYRIAPODA. Myriapods. Xylobius, ArcMulus. 
 CLASS IV. INSECTA. 
 
 STEM VII.-VERTEBRATA. 
 
 CLASS I. PISCES. Pishes. 
 
 ORDER I TELEOSTEI. Common bony fishes. Not Palaeozoic. 
 ORDER II. GANOIDEI. Endoskeleton generally only partially ossified. 
 Exoskeleton in the form of ganoid scales, plates, or spines. 
 Caudal fin mostly unsymmetrical or " heterocercal ", but 
 sometimes "homocercal." 
 
 DIVISION I. LEPIDOOANOIDEL Exoskeleton of scales of 
 moderate size. Endoskeleton partly ossified. Palceonis- 
 cus, Onychodus (242), Lepidosteus (249-251). 
 
 DIVISION II. PLACOGANOIDEI. He&d and more or less of 
 the body protected by large ganoid plates. Cephalaspis 
 (245), PtericMhys (244), Coccosteus (246), Bothriolepis (247), 
 Scaphaspis, Palceaspis, Dinichthys (241). 
 
 ORDER III. ELASMOBRANCHII (Selachia, Placoidci). Sharks, Rays, 
 and Chimeras. Skull and lower jaw well developed, but 
 no cranial bones. Vertebral column cartilaginous. Exo- 
 skeleton placoid, consisting of grains or tubercles. 
 SUB-ORDER I. HOLOCEPHALL Jaws covered by broad plates. 
 SUB-ORDER II. PLAG10STOML Sharks and Rays. 
 
 SECTION I. CESTRAPHORI (243). Back teeth obtuse. Acrodus, 
 
 Onchus. 
 
 SECTION II. SELACHII True Sharks and Dog Fishes. 
 SECTION III. BATIDES. Rays and Skates. Body transversely 
 
 flattened. 
 
 ORDER IV. DIPNOI (Protopteri). Notochord persistent. Ceratodus. 
 CLASS II. AMPHIBIA. Progs, Toads, Salamanders, Coecilians, 
 
 and extinct Labyrinthodonts. 
 ORDER I. URODELA (Ichthyomorpha). Tailed Amphibians. Notear- 
 
 lier than Permian. 
 
 ORDER II. ANOURA (Batrachia. Theriomorpha). Frogs and Toads 
 or Tailless Amphibians. Not known edrlier than Ter- 
 tiary.
 
 12 , GEOLOGICAL STUDIES. 
 
 ORDER IV. LABYRINTHODONTA. All extinct. Salamandriform. Pro- 
 tected with sculptured bony plates. Teeth with "laby- 
 rinthine " structure. 
 SECTION I. EUGLYPTA Cranial bones strongly sculptured. Lab- 
 
 yrintlwdon. 
 
 SECTION VI. GANOCEPHALA (Archegosauria). Vertebral column 
 notochordal. Archegosaurus, Trimerorachis, Rachitornus, 
 Eryops, Amphibamus. 
 SECTION X. MICROSAURIA. Ossification of limbs incomplete. 
 
 Dendrerpeton, Hylonomus, Hylerpeton, Sauropus. 
 Other American Labyrinthodonts: Tuditanus, Leptophractus, 
 Pelion, JBaphetes, Colletosaurus, Didyocephalus, Cricotus* 
 CLASS III. REPTILIA. 
 
 ORDER I. CHELON I A. Turtles and Tortoises. All post-Palaeozoic. 
 ORDER II. PLESIOSAURIA (Sauropterygia). Head small and neck 
 long. Plesiosaurus (254), Nothosaurus, Simosaurus, Plio- 
 saurus, Elasmosaurus (255), Cimoliosaurus. 
 ORDER III. LACERTI LI A. Lizards. Telerpeton, Centemodon. 
 ORDER IV. PYTHONOMORPHA (Mososauria). Body very elongate. 
 Mososaurus, Leiodon, Tylosaurus, Lestosaurus (256), Gli- 
 dastes, all Cretaceous. 
 
 ORDER V. PH I Dl A. Serpents. .Palceophis, Boavus, Limnophis. 
 ORDER VI. ICHTHYOSAURIA (Ichthyopterygia). Marine. Ichthyosau- 
 rus (252). 
 ORDER VII. BAPTANODONTA. Like Ichthyosaurus, but without teeth. 
 
 Baptanodon (253). 
 
 ORDER VIII. CROCODILIA. Crocodiles, Alligators, and Gavials. 
 ORDER IX. DICYNODONTIA. Jaws beak-like, resembling Turtles. (>u- 
 
 denodon (263), Dicynodon (264). 
 ORDER X. THERIODONTA. Dentition of carnivorous type. Cynodrnco 
 
 (262), Lycosaurus (261). 
 ORDER XI. PTEROSAUR! A. Flying Saurians. Pierodactylus (265), 
 
 Pteranodon, Dimorphodon (266). 
 Sub-Class Dinosauria (according to Marsh). 
 ORDER I. SAUROPODA. Herbivores. Premaxillaries with teeth. 
 
 Plantigrade. 
 
 Families: Atlantosaitridce, Diplodocidw, Morosauridee. 
 ORDER II. STEGOSAURI A. Plated Lizards. Herbivorous. Post-pubic 
 
 present. 
 
 Families: Steyosauridce, Scelidosaurida;. 
 ORDER III. ORNITHOPODA. Feet bird-like. Herbivorous. 
 
 Families: Camptonotidce, Iguanodontida- (258-260), Hadrosau- 
 ridte (258).
 
 PROGRESS OF TERRESTRIAL LIFE. 313 
 
 ORDER IV. THERO POD A. Beast-footed. Carnivorous. 
 
 Families: Xegalosauridte, Labrosaitridte, Zanclodontidas, Am- 
 phisaitridte. 
 
 Also SUB-ORDERS: CCELURIA, COMPSOGXATHA, CERATOSAURJA. 
 CLASS IV. AVES. Birds. 
 
 Sub-Class I. Odontornithes. Birds with teeth [according to 
 
 Marsh]. 
 
 ORDER I. ODONTOLC/E. Teeth in grooves. Hesperornis (269-271). 
 ORDER II. ODONTOTORMxE. Teeth in sockets. Ichthyornis (268), 
 
 Apatornis. 
 ORDER III. SAURUR/C. Teeth. Tail longer than body. Archceop- 
 
 teryx (267). 
 
 Sub-Class II. RatitflB. Sternum without a prominent keel. 
 Sub-Class III. Carinatae. Sternum with a prominent keel. 
 
 Ordinary birds. 
 CLASS V. MAMMALIA. 
 
 Sub-Class I. Ornithodelphia (Monotremata). Oviparous. 
 Sub-Class II. Didelphia (Marsupialia). Pouched Mammals (272 
 
 277). 
 
 DIVISIONS: DIPROTODONTIA, POLYPROTODONTIA. 
 Sub-Class III. Monodelphia (Eutheria). Placental Mammals. 
 ORDER I. EDENTATA. SUB-ORDERS: PHYTOPHAGA, ENTOMOPHAGA. 
 ORDER II. SIRENIA. Manatee and Dugong. 
 ORDER III. CETACEA. Whales, Dolphins, and Porpoises. 
 
 Families: Baltenida?, Catodontidte, Delphlnida;, Ithynchoceti, 
 
 Zeuglodontidte. 
 
 SUPER-ORDER UNGULATA. Hoofed Mammals [according to Marsh]. 
 ORDER I. HYRACOIDEA. Xo canines. Hyracotherium, Ilyracodon. 
 ORDER II. PROBOSCIDEA. Elephantine Mammals. Elephas, Nas- 
 
 todon, Dinotherium (289). 
 
 ORDER III. AMBLYDACTYLA(Amblypoda, Cope). A theoretical type- 
 from which diverged two sub-orders, DINOCERATA and Co- 
 KYPUODONTIA, the former with Uintatherium (284, 285), 
 Dionceras (286), Tinoceras (287); the latter with Corypho* 
 don (Bathmodon) (278-280). 
 ORDER IV. CLINODACTYLA. 
 
 SUB-ORDER I. MESAXONIA (Perissodactyla). Generally odd- 
 toed. 
 
 Families: Rhinoeerida;, Tapiridce, Lymnohyidve, Krontother- 
 idte (288), ralteotherida>, Maehrauchenidce, Equidce (290). 
 XTB-ORDER II. PARAXONIA (Artiodactyla). Mostly even- 
 toed. 
 
 JUVI810N I. OMNIVORA, with Families: Mippopotamidte, Su- 
 idce, HyopntamiilfF, Xiphodontnla-, Anoplotheridce, 
 Oreodontidee.
 
 314 'GEOLOGICAL STUDIES. 
 
 DIVISION II. HUMINANTIA, with Families: Camelidce, Traf/u- 
 Hdw, Cervida;, Camelopardidw, Antilojtidce, Ovidce, 
 Jiovidce. 
 
 ORDER TILLODONTIA. Molarsas in Ungulates. Canines. Plantigrade 
 and pentadactyl. Unguiculate? Families: Tiiiother- 
 ida> (281), Stylinodontidai. 
 
 ORDER TOXODONTIA, Allied to Ungulates, Rodents, and Edentates. 
 ORDER CARNIVORA. 
 
 SECTION I. PINNIPKDIA. Seals and Walruses. 
 
 SECTION IT. PLANTIGBADA. Bears. Walking on whole length 
 
 of foot. 
 
 SECTION III. DIOITIGBADA. Walking on the toes. Families: 
 Mustilidce, Viverridai, Hyafnidte, Canida-, Hy&nodonti- 
 da;, Felidce. 
 
 ORDER RODENTIA. Gnawing Mammals. Families: Leporida;, T^a- 
 gomyidee, Cavidce, Hystricid<B,Cercolabidce,Octodontld(e, 
 Chinchillida>, Castoridw, Muridce, JDipodidre, Nyox- 
 idce, Sciuridte. 
 
 ORDER CHEIROPTERA Bats. Nyctilestes, Nyditherium. 
 ORDER INSECTIVORA, Families: Talpidce, Soricidte, Erinaccidce. 
 ORDER QUADRUMANA, DIVISION I. STREPSIRHINA (Prosi- 
 miae). Lemurs. FamiUes: Zemuridce, Lemuravida>, 
 Limnotheridee. 
 
 DIVISION II. PLATYRHINA. Tfiiled Monkeys. 
 Dl VISION III. CA TARHINA. Including Anthropoid Mon- 
 keys. / 
 
 2. Nature of the Succession of Organic Forms. 
 
 The foregoing tables are a systematic exhibit of the larger 
 types of plants and animals which appeared on the earth in the 
 progress of geological time, and which continue, for the greater 
 part, to dwell in the waters and upon the land, of the modern 
 world. No Class of animals once existing has totally disappeared. 
 Only a very few Orders have become extinct and these chiefly 
 Vertebrates, dwellers on the land, where the vicissitudes of cli- 
 mate and other conditions have been most directly and most 
 severely felt. Scarcely a marine Order is found extinct. A 
 large majority of the marine Families still survive. 
 
 Some further inferences of a fundamental character derived 
 from palaeontological studies should be here enunciated.
 
 PROGRESS OF TERKESTRIAL LIFE. 315 
 
 1. The Succession of Organic Forms has been a general 
 Progress from lower to higher. The lowest position in which 
 organic remains have been found is in the Laurentian. We find 
 here mere traces of organisms related apparently to some of the 
 lowest and simplest creatures now living. We shall presently 
 give them a more particular description. 
 
 Searching through the overlying Huroriian strata, we find no 
 certain evidences of the former existence of life. But immedi- 
 ately on entering the Cambrian strata, such evidences are very 
 abundant, and they never fail through all the higher formations. 
 
 Throughout the Cambrian, the fossil remains pertain exclu- 
 sively to Invertebrates. During the Cambrian were introduced 
 all the leading Clases of Molluscs now known. Also some char- 
 acteristic Class types of Coelenterata, Echinodermata and Arthro- 
 poda. There are also indications of Vermes. So all the Stems 
 or Subkingdoms of animals now known, except Vertebrates, 
 have been upon the earth from Cambrian times. But the Classes 
 were low; the Orders represented were low in their respective 
 Classes; and the Families were low in the Orders to which they 
 belonged. This is a general law. 
 
 Before the close of the Silurian, Fishes existed. These are 
 the lowest Class of Vertebrates; and the Orders represented were 
 low in their Class. They were not well defined and character- 
 istic Fishes. The true Fishes appeared in the Mesozoic Ages. 
 But the Palaeozoic fishes, if we call them such, became very abun- 
 dant and powerful, and constituted what we may style a ruling 
 dynasty until the approach of the Carboniferous JEon. The Silu- 
 rian and Devonian fauna was thus a great advance on that of 
 the Cambrian. 
 
 The time which had now elapsed was enormous beyond com- 
 putation; but only marine animals had been in existence. Next, 
 in approaching and entering the strata of Carboniferous time, we 
 discover remains of Amphibia. Fishes still existed; but Am- 
 phibia were the highest type; and they attained such dimensions, 
 were clad in such armor, and ramified in genera and species so 
 numerous, that they became strictly the dominant type in the
 
 316 GEOLOGICAL STUDIES. 
 
 animal world. This was the easier because the hugest of the 
 armored fishes had mostly disappeared. These air breathers in 
 adult life were a further advance in the grade of organization 
 on the earth. 
 
 Next came the Class type of Reptiles. They expanded enor- 
 mously during the Mesozoic ^Eon. The Fishes and Amphibians 
 became subordinate. This was a reign of Reptiles. Toward the 
 close of the Mesozoic, Birds began to appear first, with long 
 reptilian tails and toothed jaws; then with toothed jaws and 
 shortened tails; then under the typical forms of Birds Hatitce, 
 Cursores, or Running Birds first, and Carinatce, or Perching and 
 Flying Birds next. So here was further exemplified the principle 
 of progress which had been operative from the beginning. 
 
 Next, coming to the study of Tertiary strata, we discover the 
 remains of many Mammals. They had begun already to exist in 
 a feeble way, as far back as the Jurassic Age probably earlier. 
 But here they became dominant. They were not only the highest 
 in rank; they attained, in many cases, gigantic dimensions, and 
 were provided with formidable means of offence. They were the 
 faunal characteristic of the Tertiary. 
 
 Lastly, after all the foregoing histories had been enacted, 
 man came on the scene. He is the last term of a long progress. 
 
 2. The earlier representatives of Class and Ordinal Types 
 were generally Comprehensive. The individual animal was a 
 characteristic example of its Order or Family, but united in itself 
 some characters of other orders and families sometimes of sev- 
 eral orders or families. The associated characters were to be sep- 
 arated in later time, apd organized in an ordinal or family type, 
 or even a class type, more clearly defined. Thus the early fishes 
 retained some of the plated characteristics of Crustaceans, and 
 perhaps more important affinities with certain Tunicates, and also 
 some characteristics which later were to belong to Amphibians 
 and Reptiles. Amphibians breathed like Fishes when young, and 
 like Reptiles when adult. They were, and still remain, a " com- 
 prehensive type." The Reptiles, when they arrived, combined, 
 with proper reptilian characters, some others which were ichthyic
 
 PROGRESS OF TERRESTRIAL LIFE. 317 
 
 as if inherited from the fishes. The earliest birds, in their 
 teeth and long vertebrated tails, still clung to characteristics of 
 a dynasty passed away, and were also a comprehensive type. The 
 same principle is strikingly exemplified in the whole Tertiary 
 history of the Mammals. It was a law in the succession of life. 
 
 Thus, we must not conceive successive types of organization 
 as separated from each other by sharp and fixed lines. They rise 
 into prominence like waves of the sea, blending on their borders 
 with contiguous developments of organization, and then gradu- 
 ally sinking again, to give place to another swell in the ocean of 
 life. 
 
 3. The graduation in the organic succession is not complete, 
 so far as known. Here we must first announce the fact, and 
 then append a reflection. The " missing links " or " gaps " in 
 the organic succession are facts of importance. Let us enumer- 
 ate some of them: (1) Between Eozoon, the first known animal, 
 and the Cambrian forms, next known. (2) Between Cambrian 
 Invertebrates and Silurian Fishes. (3) Between Fishes and Am- 
 phibians. (4) Between Mammals and older Vertebrates. (5) 
 Between Man and lower Mammalia. To these some persons add 
 (6) Between Inorganic Matter and Eozoon. (7) Between Un- 
 intelligent organization and Intelligence. 
 
 Our first knowledge of a type presents it under a somewhat 
 complete development. Our contemplation of the succession of 
 dominant types reveals a series of high wave crests, which give 
 the impression of sharply distinct advents of organic types into 
 existence. Hence the revelation of " gaps " is, at first view, a 
 glaring fact. 
 
 But when we consider the facts of palasontological history a 
 little more closely, we discover: (1) Even if the actual graduation 
 were originally complete, we could expect to acquire only a broken 
 knowledge of it, because (a) only a small fraction of the earth's 
 surface has been explored for fossils, or ever can be; (5) in no 
 locality have the rocks been completely investigated; (c) if all 
 the rocks everywhere were completely investigated, we could not 
 expect to discover a complete record of past life, since the greater
 
 318 GEOLOGICAL STUDIES. 
 
 w 
 
 part of the forms once living have totally perished. Hence, miss- 
 ing links, even if irrecoverable, signify little as a ground for infer- 
 ence. They simplv demonstrate gaps in our knowledge. (2) A 
 closer study shows that the supposed gaps are not so wide as im- 
 agined. The so called Silurian Fishes reveal graduations down- 
 ward toward Crustaceans and Tunicates, and upward toward 
 Amphibians. So of all the great salient types. They are all 
 "comprehensive"; and the characteristic of a comprehensive 
 type is to blend to some extent with neighboring types. (3) The 
 daily progress of discovery brings to view types which fit into 
 the existing gaps. The gaps are becoming filled up. There are 
 already long lines of succession where the graduation from lower 
 
 FIG. 220. WEATHERED SPECIMEN or Eozoon Canadense. From Limestone at Tudor, 
 Ont. (Carpenter.) 
 
 to higher is as gentle and complete as could be demanded to sup- 
 port an extreme inference. The tenor of progress foreshadows 
 the complete closing up of the gaps. It shows, at least, that 
 they would probably be filled if we could recover the complete 
 record. It seems to be more rational in this day to anticipate 
 this result than to attribute high significance 4 to defects in our 
 knowledge which to-morrow may no longer exist. We may, 
 therefore, reason from the chain of organic being, as if no links 
 were missing. 
 
 3. The Dawn Animal. 
 
 We will now glance more particularly at some of the domi- 
 nant types of organization. In doing this, the student should 
 make frequent reference to the table of classification in the sec-
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 319 
 
 ond section of this chapter. First of all was Eozoon. The re- 
 mains of its calcareous skeleton have been found far down in the 
 Laurentian System, in a great bed of crystalline limestone. When 
 exposed on the weathered surface of the rock it appears formed 
 of numerous bent or undulate layers parallel with each other, as 
 shown in Fig. 220. These layers, in most cases, consist alter- 
 nately of serpentine and calcium carbonate. When a thin cross 
 section is made and highly magnified, we are enabled to detect 
 a minute structure bearing considerable resemblance to certain 
 Foraminifera. We should wander too far to enter into details 
 of explanation, and must be content with stating that Eozoon is 
 generally regarded foraminiferal in its affinities. 
 
 We may, then, give some account of its structure and mode 
 of life. At the beginning of its growth it consisted of a small 
 mass of gelatinous substance spread on some support in the bot- 
 tom of the sea. It probably resembled the well known Amoeba 
 living in modern fresh 
 waters, of which one is 
 represented in Fig. 221. 
 This is a minute speck 
 of gelatinous matter con- 
 taining granules, a nu- 
 cleus, n, and a contractile 
 vesicle, c v. Extensions 
 from the mass of the ani- 
 mal's body, called pseu- 
 dopodia, are capable of 
 complete withdrawal, 
 and fusion in the .com- 
 mon mass. Other pseu- 
 dopodia may be extended 
 at the animal's pleasure. 
 This minute creature, 
 without permanent mem- 
 bers, without stomach or 
 other organs, 
 
 FIG. '&. Amoeba Proteus. (After Leidy.) A LIV- 
 ING REPRESENT AT IVE OP THE OLDEST ANIMAL. 
 , nucleus; c v, contractile vesicle; a, posterior 
 portion in a contracted state ; c, c, two pseudo- 
 pods closing around an Inf usorian ( Urocentrum) ; 
 d, diatoms within the animal ; 6, particles of saw- 
 dust. Magnified 100 diameters in the upper speci- 
 men, aud 125 in the lower. Found frequently in 
 fresh waters.
 
 320 
 
 GEOLOGICAL STUDIES. 
 
 all the essentials of animal life. It hungers and feeds; it wills 
 and moves; it is self-conscious and seeks to satisfy its wants. 
 This is nearly the simplest form of organization known. (See 
 page 30G.) It stands as a representative of the oldest type of 
 animal existence. 
 
 But the first animal found its home in. the stormy sea. It 
 must be sheltered from the violence which raged around it. A 
 thin, shelly covering was secreted over it. This was perforated 
 by innumerable minute tubuli, and by some larger pores, and was 
 supported at intervals by calcareous pillars. Over this shell was 
 built a thicker and coarser covering, known as the supplementary 
 skeleton. This Avas perforated by branching canals, through 
 which the gelatinous matter found its way to the exterior. Here 
 new pseudopods were extended, and new gelatinous matter was 
 outspread, and a new roof was built, supported, like the first, by 
 numerous stony pillars. This process was repeated again and 
 again, and the mass grew indefinitely. The accompanying dia- 
 gram is intended to 
 illustrate the mode of 
 growth just described. 
 Organisms of this sort 
 were probably planted 
 in innumerable places 
 along certain favorable 
 tracts of sea bottom. 
 In the progress of their 
 growth many coalesced 
 together, and e n o r - 
 mous reef-like masses 
 came, in the course of 
 
 FIG. 222. DIAGRAM OF STRUCTURE OF Eozoon. (Biltsch- 
 li, after Carpenter.) A", Chambers of two successive 
 
 layers; a, Shelly partitions, perforated by passages; o f ages, into existence. 
 
 K', Proper walls of the chambers, composed of finely . = , , , , 
 
 tubular shell substance-the "nummulinc layer ";JST, Around these the sed- 
 
 Intermediate, or supplementary skeleton, traversed by iments gathered, and 
 
 s t, stolons of communication between two chambers ,, , , . 
 
 of different layers, and by c, a system of canals. a11 that remained ^ of 
 
 Eo zo o n was buried 
 thousands of feet in rock-forming mud.
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 321 
 
 But, though Eozoon disappeared from existence, the type to 
 which it belonged survived. In 
 the Cambrian we have long known 
 a form represented in Fig. 223, 
 and called Stromatocerium rugo- 
 9um. This, in external aspect, 
 resembles Eozoon, but its zoologi- 
 cal affinities remain somewhat in 
 
 FIG. 223. Stromatocerium ruyosum. 
 FKOM THE CAMBRIAN OF NEW YORK. 
 (After Hall.) 
 
 question. 
 
 It will be interesting- to trace 
 the last named type a little fur- 
 ther. It is the type of the Stro- 
 vnatoporidoe. In Fig. 224 is a 
 view of another Stromatoporoid. 
 The typical Stromatopora, when 
 cut through, is seen to consist 
 (Fig. 225) of a large number of 
 concentric laminas, separated by 
 very thin intervals, and connected by innumerable pillars passing 
 from lamina to lamina. This is a simple 
 Stromatopora. Sometimes the pillars be- 
 come more or less obscure (Fig. 22G); some- 
 times they disappear; sometimes the lami- 
 na? are all raised at intervals into little 
 eminences, shown in Figs. 224 and 227; 
 sometimes small, radial, sinuous, and 
 branching canals diverge from one or more 
 perforations in these eminences (Fig. 227); 
 and by these and similar variations, we 
 find established a number of generic dis- 
 tinctions. Stromatocerium is a genus without pillars, and having 
 all the laminse pierced by small holes. Three genera, Stromato- 
 pora, Ccenostroma, and Idiostroma, are extremely abundant in 
 the Devonian limestone of Little Traverse Bay, Michigan. The 
 first is small, from the size of a hickory nut to that of one's fist. 
 The second grows in huge dome-shaped masses, some of which 
 
 FIG. 224. VIEW OF A STRO- 
 MATOPOROID, Stromatopo- 
 ra tuberculata (Nichol- 
 son). FROM CORNIFEROUS 
 LIMESTONE.
 
 GEOLOGICAL STUDIES. 
 
 have been measured over twelve feet across, and recall the reef- 
 like bulk of long extinct Eozoon. 
 The third genus is an enormous 
 tangled mass of branching stems, 
 each a third of an inch in diame- 
 ter, and having a true stromatopo- 
 roid structure. Stromatoporoids 
 are widely distributed through the 
 Devonian, and they are also com- 
 mon in the Silurian. Their near- 
 est affinities are yet undecided. 
 They have by different authorities 
 been referred to the Foraminifera, 
 the Sponges, the Anthozoa, the 
 Hydrozoa, and the Polyzoa. Probably they must be considered 
 one of the comprehensive types (described on page 316), which 
 cannot be assigned precisely to any recognized position. 
 
 FIG. 225. IN'TKUNAL STRUCTURE 
 Stromatopora slriatellu D ORB. 
 (From Nature.) 
 
 FIG. 226. VERTICAL SECTION THROUGH FIG. 227. EXTERIOR OF Ccenostroma mon~ 
 
 Ccenostroma monticuliferum. (From ticuliferum. x 2. (From Nature.) 
 
 Nature.) SHOWING OBSCURE I,. \MIN.K SHOWING MONTICULES AND RADIAL, 
 
 AND PILLARS. CANALS. 
 
 The type of Foraminifera, of which Eozoon and the Stroma- 
 toporoids combined some of the characteristic features, became, 
 in later times, completely eliminated, and underwent, during 
 Mesozoic and Casnozoic times, a remarkable diversification. It 
 survives to-day in a large number of representatives. 
 
 EozoSn played the first role in the drama of life. It was the 
 great lime-secreting and reef-building agent of the early ages of
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 323 
 
 the world. Later, this function was assumed by organisms of 
 another and higher class. 
 
 4. Trilobites. 
 
 At the very opening of the Cambrian Age, Trilobites were 
 present. Their advent and reign form a striking feature in the 
 history of life. Some of their forms are shown in Figs. 228-230. 
 They were Arthropoda, holding a position low in the Class 
 
 Magarensis, FROM 
 
 NlAGABA GROUP. 
 
 PIG. 228. Paraotoaifite.-' Harlani. (After 
 Walcott.) PROM EARLY CAMBRIAN. 
 
 FIG. 230. SAME AS 
 LAST, ROLLED TO- 
 GETHER. 
 
 Crustacea. The body was distinctly trilobed. The anterior por- 
 tion constituted a cephalic shield, usually bearing a pair of ses- 
 sile compound eyes, with a raised, often lobed (Fig. 229) central 
 part, known as glabella. The number of thoracic segments was 
 very variable. The abdominal segments were firmlv united, and 
 formed a caudal shield. Fig. 231 is a diagram showing the prin- 
 cipal parts of a Trilobite, as seen from above.
 
 324 
 
 GEOLOGICAL STUDIES. 
 
 Some of the lowest Cambrian strata 
 are crowded with the fragments of these 
 articulates. They continued abundant 
 during the Silurian; diminished during 
 the Devonian, and became extinct dur- 
 ing the Carboniferous. Their nearest 
 living representative is the King Crab 
 (Limulus) of our eastern coast, the 
 embryo of which presents a strikingly 
 trilobitic aspect. 
 
 FIG. 231.--DIAGRAM or THE STRUCTURE or A Tut- 
 
 LOBITE. 
 
 A, HEAD. 1, External Border of the Limb. 2, Mar- 
 ginal Furrow. 3, Occipital Ring. 4, Glabella. 5, 
 Great Suture, passing in front of the Glabella, and 
 inside of the Eyes. 6, Eyes and Subocular Suture, a, Fixed Cheek, forming along 
 side of the Eye, the Palpebral Lobe, a 5. &, Movable Cheek, g, Genal Point. 
 
 B, THORAX. 7, Ring of the Axis of each Segment of the Thorax. 8, Rib of each Seg- 
 ment of the Thorax. 
 
 C, PTGIDIUM. 9, Continuation of 'the Axis. 10, Continuation of the Ribs. 
 
 5. Crinoids. 
 
 A crinoid consists of body and arms, sup- 
 ported on a stem, which is generally rooted in 
 the submarine soil. It presents the appear- 
 ance of a tree, and hence is embraced in 
 the group formerly known as zoophytes (Fig. 
 232). The parts mentioned are composed of 
 calcium carbonate, and each consists of a num- 
 ber of pieces nicely fitted together. The stem 
 is a pile of circular or pentagonal discs, with a 
 central canal extending the whole length. The 
 calyx, or cup, consists of regularly shaped plates 
 fitted by their edges. The arms, five in number, 
 are ranges of discoid, or imperfectly cylindrical 
 pieces, in one or two series, joined by their flat- 
 tened surfaces, but not, like the stem, perforated 
 for a canal. The arms generally bifurcate near 
 the base, and afterward again. From one or both 
 
 FIG. 232.- Rhizocri- 
 nus Lofotensis. 
 (After W. Thom- 
 son.) A Li VI KG 
 CRINOID. x 2.
 
 PROGKESS OF TERRESTRIAL LIFE. 
 
 325 
 
 sides of each arm generally spring pinnulae, constructed like 
 the arms, but smaller. Over the calyx, in the extinct spe- 
 cies, is generally built, of nicely fitting plates, a dome bearing the 
 passages to and from the interior. Sometimes one of these opens 
 at the' apex of a proboscis which rises from the dome. The plates 
 of the calyx are often elegantly 
 furrowed or sculptured. Their 
 forms, number and arrangement 
 are shown in Fig. 233, which 
 represents the plates of a calyx 
 spread out horizontally. They 
 are grouped as Basal, Radial, 
 Inter-radial, and Azygos plates. 
 The basal, b, b, b, consist gen- 
 erally of a cycle of three plates 
 resting on the top of the stem. 
 Frequently, however, there are 
 two cycles of basals. Whether 
 of one or two cycles, the basals FIG 
 are surmounted by five series of 
 radials, r. Each series consists 
 of the primary, secondary, and 
 (sometimes) ternary, radials 
 (r 1 , r 1 , r 3 ). Between the radi- 
 als are interradials (*', i*, i*) t 
 which generally exist in two or more cycles, having a definite 
 number between each two series of radials, except on one side, 
 called the azygos interradius, where the number is much greater 
 (a 1 , a 2 , etc.). It will be seen that the principle of bilaterality is 
 fully exemplified in this arrangement. A line drawn from the 
 azygos side through the centre of the opposite radial series divides 
 the structure into right and left parts, perfectly symmetrical with 
 each other. 
 
 These elaborately constituted organisms were in existence in 
 the Cambrian Age. The type underwent expansion in number 
 and elaborateness through the Silurian, continued through the 
 
 CALYX or A CRINOID, SPREAD 
 OUT TO SHOW THE FORMS, NUMBER, AND 
 ARRANGEMENT OF THE PLATES. 6, 6, 6, 
 Basal Plates, r', r2, r*, Radials. i r, In- 
 terradials. ai, aa, Azygos Interradials. 
 There are here three radials in each radius ; 
 four interradii, each with five interradials, 
 and one azygos interradiug, with a larger 
 number of pieces.
 
 GEOLOGICAL STUDIES. 
 
 Devonian, and attained its greatest de- 
 velopment in the Lower Carboniferous. 
 Certain genera lived through the Meso- 
 zoic; but the type at the beginning of 
 the Tertiary was nearly extinct. Till 
 recently, but one living species was 
 known. Now, "however, a number of 
 additional species have been dredged, 
 mostly from the Gulf Stream, off the 
 coasts of Florida and Scandinavia, the 
 late Challenger Report enumerating six 
 genera and thirty-two species. It is a 
 very remarkable circumstance that 
 among the genera represented is JRhiz- 
 oc'rinus, Fig. 232, which began its 
 FiI~234.-A CARBONIFEROUS existence in the Cambrian Age. In the 
 CRINOID, Forbesiocrinua com- cold depths of the ocean, changes of 
 m,l.,WA.Y GROUP, OHIO. conditions are glight> and sW We 
 
 judge that the modern conditions have persisted substantially 
 from the dawn of crinoidal life. 
 
 6. Chambered Shells. 
 
 Another of the conspicuous types of organization of which 
 the elementary student should have some knowledge is that of 
 Tetrabran'chiate Ceph'alopods. These molluscs secreted an ex- 
 ternal calcareous shell, in form a hollow, tapering cone, straight 
 or bent, and divided at intervals by transverse partitions called 
 septa. The intervening spaces are chambers, and the last one is 
 occupied by the animal, as shown in cut, Fig. 235. The animal 
 to judge from the Nautilus, the only living genus was fur- 
 nished with many flexible prehensile tentacles, or arms, well 
 developed eyes, a pair of horny mandibles, two pairs of plume- 
 like gills, a funnel, for expulsion of respired water, and a si- 
 phuncle, consisting of a membranous or calcareous tube, which 
 reached from the posterior part of the body through all the septa 
 and chambers. The siphuncle, in some families, passed through
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 327 
 
 the centre of the shell, or near it; in others it was closely mar- 
 ginal on one side or the other (dorsal or ventral). See the 
 upper row of outlines in Fig. 236. 
 
 FIG. 235. RESTORATION OP AN Orthoceras A STRAIGHT, CHAMBERED SHELL or PALAE- 
 OZOIC TIME, a, arms; /, funnel ; c, chamber; , siphuncle. 
 
 The septum was sometimes simply concave, as at ey and in 
 this case the siphuncle was central, or sub-central. Sometimes 
 the suture, or line of junction with the shell, was broadly undu- 
 late, and the siphuncle was on the inner side, as at d. Some- 
 times, with siphuncle close to the outer margin, the suture was 
 
 FIG. 236. POSITION OF SIPHUNCLE AND FORM or SEPTA IN VARIOUS TETRABRANCHIATE 
 CEPHALOPODS. The upper row of figures represents transverse sections of the shells ; 
 the lower row the edges of the septa, a, a, Ammonites; 6, b, Ceratites; c, c, Gonia- 
 tUes ; rf, d, Clymenia ; e, e, Nautilus, or Orthoceras. 
 
 simply lobed (curved or annulate), as at c y or, with the lobe 
 denticulated, as at b y or, with the lobes lobidate and denticulate 
 (often called foliated), as at a. 
 
 The five different styles represent degrees of complication. 
 According, therefore, to the method of nature (page 315), the 
 simplest styles are the more ancient, and began to exist in the
 
 338 GEOLOGICAL STUDIES. 
 
 Cambrian. In the Cambian and Silurian the type underwent its 
 greatest development, though it still survives in Nautilus. The 
 angulated septum belongs to the Devonian; the lobed septum, to 
 the Carboniferous, though it began in the Devonian; the denticu- 
 late-lobed septum characterizes the Triassic, and the foliated 
 septum is known only in the middle and later Mesozoic. 
 
 Again, these chambered shells exhibit all degrees of enrol- 
 ment, from straight to closely coiled. These variations may be 
 advantageously set forth by means of the scheme on the follow- 
 ing page. Here we have, first, an analysis of the form, and op- 
 posite this, in two columns, the names of genera possessing the 
 several forms. In the first column are generic names of Nautil- 
 oidea, and in the next names of Ammonoidea. The names of 
 Nautiloidea which stand a little indented are of the type having 
 a contracted aperture; and the names of Ammonoidea which 
 stand a little indented are of the Ceratites type, having the 
 lobes denticulated. We witness in this table an interesting ex- 
 emplification of nature's tendency to permutation of characters, 
 or repetitions of characters of second order under each of the 
 characters of first order. 
 
 The Tetrabranchs are divided into Nautiloidea and Ammo- 
 noidea, the former having the suture simple and the siphuncle 
 central or sub-central; and the latter having the suture lobed or 
 foliated, and the siphuncle mostly close on the ventral (external) 
 margin. Of the Nautiloidea the three most important families 
 are the Ort/wceraf idee, having the shell straight (Figs. 235, 237); 
 the Cyrtoceratidce, having the rapidly tapering shell strongly 
 bent (Fig. 238), and the Nautilidce, having the shell coiled in 
 a plane (Fig. 239). The Orthoceratidce underwent an extraor- 
 dinary development during the Cambrian and Silurian some- 
 times attaining a length of fifteen feet and were abundant 
 during the Devonian. During all the Carboniferous they were 
 on the wane, and are not known later, except as a local develop- 
 ment in the Trias. The Nautilidce appeared at the beginning 
 of the Silurian, became plentiful in the Carboniferous, and the 
 genus Nautilus still survives.
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 329 
 
 I II! 
 
 
 
 ? ? i i 
 
 
 
 ; * 1 i 
 
 
 
 v & : 
 
 
 
 ?r : 
 
 
 
 1 1 
 
 
 
 III 1 
 
 
 
 x << -. -, 
 
 
 
 . i i i t 
 
 
 | 
 
 '. 1 I I I j 
 
 
 1 
 
 1 ; i r | j 
 
 
 
 
 ; i ! t 1 ! 5 ; 1 1 ! 
 
 :| It III ^ ' : | 1 
 
 
 CHAMBERED S 
 
 : > 'j ': S J i .5^^ o ^ : ^5 
 ! P '' 1 i 1 P : : f P \ P 
 
 |. 
 
 P 
 
 I 
 
 &^ 
 *tft~ 
 
 -3 S3 g ?>" >>O ^ -3 "OS W 
 
 11 HI 1 1 1 1 ! ! H ! ! 1 ! 1 
 
 M itt nnin ? * Mh 
 
 1 1 1 i P 
 
 S a 
 
 t 1 
 
 Ammonoid'ea. 
 
 y'fa -C 
 
 
 c^ 
 
 7^
 
 330 
 
 GEOLOGICAL STUDIES. 
 
 The Ammonoidea were mostly Mesozoic, and underwent a 
 remarkable development in respect to diversification "and num- 
 
 FIG. 'Zyt.Orthoc'eras Carleyi, Devonian, Ohio. 
 FIG. 23S.Cyrtoc'eras Eugenium, Corniferous, New York. 
 FIG. 239. - Gyroc'eras undula'tum, Corniferous, Cherry Valley, 
 N. Y. 
 
 bers. The (JtymenidcB, with internal (dorsal) 
 siphuncle and angulated suture lines, were re- 
 stricted to the Devonian, and never became numerous. The Go- 
 
 niatitidcv were more im- 
 portant. They had a 
 closely ventral (exter- 
 nal) siphuncle, and a 
 suture line bent into 
 lobes and saddles (for- 
 ward pointing and back- 
 ward pointing lobes). 
 They made their advent 
 in the Devonian and be- 
 came an important type 
 in the Carboniferous. 
 Since the Palaeozoic they have been extinct. 
 
 FIG. 240. Ammom'tes eerpenti'mis. a, side view; 
 edgewise view ; c, plan of suture-lobes.
 
 PROGRESS OF TERRESTRIAL LIFE. 331 
 
 7. Fishes. 
 
 The earliest vertebrates were fish-like, and we commonly 
 group them with Fishes; but probably, if their characters were 
 completely known, we should feel constrained to establish one or 
 more separate classes for their reception. TELEOSTEI, or ordi- 
 nary fishes, have the skeleton completely ossified; but sturgeons 
 and sharks have an imperfectly ossified skeleton. The earliest 
 fishes appear to be somewhat allied to these, and they are com- 
 monly arranged under two orders: GANOIDEI, having the exo- 
 skeleton (or bony developments of the surface) in the ganoid 
 scales, plates or spines, and ELASMOBRANCHII, including Sharks, 
 Hays, and Chimcerce, having the exoskeleton placoid consist- 
 ing of grains or tubercles. The Ganoidei are subdivided into 
 
 '""' 
 
 FIG. 241. RESTORATION or Dinich'lhys Herz'eri, A PLATED GANOID FHOM OHIO. 
 (Newberry). 
 
 Lepido ganoids (scale-covered) and Placoganoids (plate-bearing). 
 The last embrace the Sturgeons, which are modern, and the Pla- 
 coderms, which are one of the oldest types of fishes. Until lately 
 the oldest known American fishes were Devonian, though a Silu- 
 rian fish-bed has long been, known in England. In 1884, how- 
 ever, Professor Claypole announced the discovery of American 
 fishes in the middle Silurian of Pennsylvania; that is, as low as 
 the bottom of the Salina Group; while the oldest European fishes 
 are supposed to be of the age of the Helderberg Group. The 
 name of the oldest fish known is Palceas'pis, "ancient shield.". 
 Indications^ however, are found of still older fishes in the Clinton 
 sub-group, and named On'chus Clintoni. This group probably 
 corresponds to the Upper Llandovery of England.
 
 GEOLOGICAL STUDIES. 
 
 The oldest well preserved Placoderms in America come from 
 the Devonian Huron Shale of Ohio, and have been described by 
 Dr. Newberry. One of these is named Dinich'thys, or "terrible 
 fish." D. Herzeri appears to have attained a length of at least 
 twenty feet. Its head was three feet long and two broad, and 
 the under jaws were two feet long. A restoration of this species 
 is shown in Fig. 241. The tail, it will be noticed, like that of 
 most Palaeozoic fishes, was hcterocercal, or "unequal-lobed." In 
 the Devonian flourished also huge Lepidoganoids. One of the 
 Ohio species is named OnycJi'odus siymoi'des by Newberry. 
 The skeleton was cartilaginous, but the 
 teeth were long and formidable. A group 
 of these is shown in Fig. 242. It had jaws 
 twelve to eighteen inches long, and proba- 
 bly attained a length of twelve to fifteen 
 feet. Besides Ganoids, there were huge 
 Elasmobranchs of the sub-order Plag'io- 
 stomes, which includes modern Sharks and 
 Rays, and the type of ancient or Cestraciont 
 Sharks, some of which still live in Austra- 
 lian seas. The back teeth in the latter were 
 
 FIG 242. GROUP op 
 FRONT TEETH OF 
 Onych'odus slgmoides, 
 A SCALED GANOID FROM obtuse, and there was a powerful spine in 
 
 front of each dorsal fin. Fig. 243 shows one 
 of these spines from New York, which, 
 when perfect, was as least ten inches long. The Cestrac'ionts 
 
 THE CORNIPEROUS OP 
 
 OHIO. (Newberry.) 
 
 KSTRACIONT SHARK. MacJuKracan'thus mlcatus. (After 
 Hal!.) 
 
 and still another group, Hyb'odonts, more resembling modern 
 Sharks, became abundant during the Mesozoic ages. 
 
 In Europe, the Pterictithys or "Winged Fish," Fig. 244, 
 has been long a familiar form. This was a companion of Ceph-
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 333 
 
 alas'pis, " Shield Head " and Cocas' tens, " Berry Bone," and 
 several others. 
 
 From Canada, at Scammenac 
 Bay, Mr. Whiteaves described a 
 Pterich'thys Canadensis, Fig. 247. 
 It has, however, no tail, and the 
 sculpturing of the plates resembles 
 Botliriol' epis, of which species are 
 known in Europe, and in the Cats- 
 kill Group of America. Cope points 
 out some remarkable affinities with 
 an Arctic Tunicate, Fig. 248, and in- 
 fers that the Pterichthy'idce are not FlG> ^_ Pleri M h ys miun, FROM 
 a distant remove from an ancestral THE DEVONIAN OF SCOTLAND. 
 type of Tunicates. From the same (After pMdflp - ) 
 locality are described other fish remains, among them a Phanero- 
 
 FIG. 245.- Cephalas'pis Lyelli. (After Brown.) 
 
 pleuron, a near relative of the living Queensland Cerat'odus, and 
 species of the genera Diplacan' thus, Acantho' des, Eusthenop' - 
 
 FIG. 246. Coccos'teus clecip'iens. (After Jukes.) 
 
 teron, Gtyptol' epis, Cheirol' epis, Coccos'teus, Cephalas'pis, 
 Ctenacan' thus, and Homacari thus. 
 
 The types to which these Placoderms and Cestracionts be-
 
 334 
 
 GEOLOGICAL STUDIES. 
 
 longed passed mostly out of existence during Palaeozoic time. 
 
 The Lepidoganoids and ordinary 
 Sharks continued to flourish dur- 
 ing the Carboniferous and the 
 Mesozoic. Teleost Fishes began 
 to appear in the 
 Jurassic, but only 
 became abundant 
 in the Cretaceous 
 and later ages. 
 They remain the 
 dominant type 
 of fishes to-day, 
 though a slender 
 representation of 
 
 ERED TUNICATE some of the older 
 FROM POINT BAR- typeg gtm sur . 
 
 The com- 
 
 Fio. MI.-Botfiriolepis Canadensis, Whit- 
 eaves sp. VIEWED FROM ABOVE. HALF 
 SIZE OF A SMALL SPECIMEN (Cope). FROM 
 THE UPPER DEVONIAN. 
 
 B o w, ALASKA. 
 To ILLUSTRATE 
 AFFINITY WITH 
 Pterichthyida. 
 
 vives. 
 
 mon gar pike, 
 Lepidosteus, is 
 well known in our western and southern fresh waters. It has 
 acquired, however, a bony skeleton, and the tail is less hetero- 
 cercal than that of the allied ancient species. 
 
 FIG. 249. Lepidosteus Httronesis, THE LAKE GAR PIKE. LIVING IN THE GREAT LAKES. 
 
 (From Nature.) 
 FIG. 250. Lepidosteus oculatus, THE SPOTTED GAR PIKE. LIVING IN LAKE ERIE AND 
 
 SOME SMALL LAKES OF MICHIGAN. (From Nature.) 
 
 It will be remarked that the ancient types of fishes possessed 
 in some respects, an embryonic character. Their skeletons were 
 cartilaginous like those of the embryos of Teleosts, and their
 
 PROGRESS OF TERRESTRIAL LIFE. 335 
 
 tails are heterocercal or even vertebrated. The tendency of the 
 embryo tail to a vertebrate structure and hence to a heterocercal 
 character may be well seen in the embryo of Lepidosteus, a 
 
 %rnck 
 
 FIG. 251. EMBRYO OF Lepidosteus FROM THE CUMBERLAND RIVER. NASHVILLE, TEN- 
 NESSEE, SHOWING A VERTEBRATE TAIL. (From Nature, i 
 
 representation of which is given in Fig. 251. This correspond- 
 ence between embryos of modern types and the adults of ancient 
 types is a general principle in the history of life. 
 
 To the period of the Coal Measures, Fishes were the highest 
 type of animals in existence. As in the early history of other 
 types, they were also numerous and bulky. For these reasons 
 palaeontologists have designated the Devonian and Carboniferous 
 the " Reign of Fishes." 
 
 8. Reptiles. 
 
 Reptiles are essentially a post-Palaeozoic type. Telerpeton and 
 Stagonolepis have been reported from the Elgin sandstones of 
 Scotland, and these have been regarded as Devonian, but they 
 may with great probability be referred to the Trias. It is thought 
 also that Eosaurus Acadiensis, a vertebra of which was found 
 by Marsh in the Nova Scotia Coal Measures, may have been a 
 "marine saurian." Generally the place of Reptiles was taken in 
 the Coal Measures by Labyrinthodonts, an Order of Amphibians. 
 Possibly, however, the little Hylonomus was a true reptile. In 
 the Permian, the last group of Palaeozoic strata, occur in Europe 
 the remains of Protorosaurus, a lizard-like reptile, together with 
 other forms. 
 
 But the Mesozoic was the theatre of the chief development 
 of Reptiles. Not only were they numerous and often gigantic in 
 dimensions, but many were heavily armored; and the type, while 
 its forms were comprehensive, became wonderfully differentiated,
 
 336 
 
 GEOLOGICAL STUDIES. 
 
 so that reptilian life became fitted to inhabit all elements, and 
 utilize all conditions of existence. 
 
 FIG. 252. Ichthyosaurus communis. (D'Orbigny.) 
 
 The sea had its reptilian denizens Ichthyosauria, fish-like in 
 their home, their form, their structure. The head of the common 
 Ichthyosaurus, Fig. 252, was enormous, with 
 a huge snout ; neck wanting ; teeth conical, 
 strong, and numerous; orbits of immense size; 
 a long series of ribs extending from the neck 
 to the elongate tail; sternum and sacrum 
 wanting; vertebrae bi-concave; all the limbs 
 paddle-like, composed each of numerous short 
 polygonal bones arranged generally in five 
 longitudinal rows, with a supernumerary row 
 of ossicles on each side, giving' the appear- 
 ance of seven digits, each with many pha- 
 langes. Species of Ichthyosaurus range 
 through the Jurassic and Cretaceous of the 
 Old World. 
 
 In America are found the remains of 
 great reptiles related to Ichthyosaurus, but 
 without teeth. They attained a length of 
 eight or nine feet. The genus Ba.pt an' odon, 
 "toothless bather," and the Order BAPTANO- 
 DON'TA have been established for them by 
 Marsh. Fig. 253 illustrates the foot of Bap- 
 tanoclon discus. Here were six digits. 
 
 The student will notice particularlv the 
 primitive or low condition of the limbs of 
 these Ichthyosauroids. Each limb was a simple fin or paddle; 
 
 000 o 
 
 FIG. 253. LEFT HIND 
 FOOT OF Baptanodon 
 discus, SEEN FROM 
 BELOW, x 1-10. f, 
 femur; F', fibula; i, 
 intermedium ; c, cen- 
 tral bone ; /, fibnlarc : 
 m. metatarsals; T, 
 tibia; t, tibiale. Ro- 
 man numerals indi- 
 cate the digits in or- 
 der. (Marsh.)
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 337 
 
 FIG. 254. Pterosaur us dolichodei'rus. 
 (D'Orbigny ) 
 
 the fore and hind limbs were identical in structure; three bones 
 in the second segment of the limb (as tibia, fibula, and inter- 
 medium, in the hind limb); 
 the mesopodial bones (car- 
 pals or tarsals) simple cir- 
 cular or angularly rounded 
 discs; the number of digits 
 six or more ; the metapo- 
 dial bones (metacarpals and 
 metatarsals) and also the 
 phalanges, mere circular 
 discs, and the phalanges 
 very numerous. These 
 limb-characters, like the general features of Ichthyosaurus be- 
 fore enumerated, point clearly to a close relationship with pree'x- 
 isting and contemporary fishes. The thoughtful biologist cannot 
 avoid the question how such affinities came into existence. 
 
 The PLESIOSAURIA were other sea monsters. The Plesi- 
 osaur'us resembled 
 the Ichthyosaurus, 
 but differed remark- 
 ably in its long neck 
 and snake-like head. 
 A sacrum of two ver- 
 tebra was present, 
 and supernumerary 
 digits were wanting. 
 It attained a length 
 of 18 to 20 feet, and 
 ranged through the 
 Jurassic and Creta- 
 ceous. Elasmosau- 
 rus platyurus of Cope 
 attained a length of 
 
 FIG. IS&.Elasmosaurus platyu'rus. (Cope.) 
 
 50 feet (Fig. 255). Other marine saurians belong to the order 
 PYTHONOMOR'PHA, "sea serpents," of which over forty American
 
 338 
 
 GEOLOGICAL STUDIES. 
 
 Cretaceous species are known fifteen in New Jersey, six or 
 more in the Gulf States, and over twenty in western Kansas. 
 llfosasaums princeps, Marsh, was 75 to 80 feet in length. The 
 body was covered with overlapping bony plates. Each of the 
 four paddles had five digits, but with supernumerary phalanges, 
 like whales. Besides conical saurian teeth in the jaws, there 
 
 FIG. 256. RIGHT PADDLE OF Lestosaurus Mic'romus. x 1-12. 
 
 were two rows of formidable teeth along the roof of the mouth, 
 adapted, as in snakes, for seizing their prey. To give lateral 
 motion to the jaws, an exceptional joint existed in front of 
 the usual articulation, and, as in serpents, the two branches of 
 the lower jaw were unconsolidated in front. The structures for 
 swallowing presented, therefore, a truly snake-like aspect. Our 
 modern snakes appear to be dwarfed representatives of the 
 ancient Mosasaurs, still retaining much of their ancient fondness 
 for the water. 
 
 PIG. 257. RESTOKED JAW or Edentotxiui-us dispar. x 1-6. 
 
 The land also had its reptilian denizens. Of these, the DINO- 
 SAUKIA are by far the most interesting. Though commonly 
 regarded as an Order, the number of modifications of the type 
 has been found so great and so extreme that Marsh proposes to 
 regard the group as a Sub-Class. In one of the Orders, SAU- 
 ROP'ODA (Lizard-footed), the Jurassic Atlantosfmrus immanis
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 339 
 
 attained the remarkable length of one hundred feet. The femur 
 was over eight feet long. Its remains occur in Colorado. The 
 related Hforosaurus grandis was 40 feet long. Apatosaurus 
 Ajax had the vertebras of the neck four feet broad, with a sacrum 
 of three united vertebrae. In another Order, OKNITHOP'ODA 
 (Bird-footed), with only three toes behind, the structure was 
 strikingly bird-like. Among these, Laosaurus altus was about 
 ten feet long, and Nanosaurus was quite diminutive. In the 
 
 FIG. 258. Hadrosaurus Foulki, 
 A BIPEDAL REPTILE PROM THE 
 CRETACEOUS. (After Hawkins' 
 Restoration.) 
 
 FIG. 259. Igitanodon Bernissarten'sis, BOULANGER, AS 
 MOUNTED IN THE MUSEUM AT BRUSSELS BY DE PAUW. 
 Head, a, nostril; b, orbit; c, temporal fossa. Verte- 
 bral column, d, cervical region; e, dorso-lumbar re- 
 gion ; /, sacral region ; g, caudal region ; h, scapula ; 
 i, coracoid ; k, humerus ; I, ulna ; m, radius ; n, ster- 
 num; o, ilium; p, pubia; q, post-pubis; r, ischinm; 
 s, femur; t, tibia; u, fibula; v, third (fourth) trochan- 
 ter; I, II, III, IV, V, digits; X, diagrammatic trans-- 
 verse section of the body between the fore and hind 
 limbs. 
 
 Cretaceous beds of New Jersey are found the remains of 
 Hadrosaurus Foulki, a representative of another family of the 
 bird-footed saurians. This is believed to have been capable of 
 locomotion on its hind feet, or, at least, to have frequently sup- 
 ported itself on two feet while reaching with its fore feet to 
 gather its vegetable diet from the foliage of the forest. Three- 
 toed footprints of some bipedal animals imprinted on the sand- 
 stones of the Connecticut valley are, with much probability,
 
 340 
 
 GEOLOGICAL STUDIES. 
 
 ascribed to some reptile allied to Hadrosaurus. Ornithotarsus 
 immanis of Cope, from the shore of Raritan Bay, was a colossal 
 Dinosaur, whose hind limb, according to Cope, could not have 
 been less than 1,3 feet in length. 
 
 In the Old World, the Ornithopoda were extensively repre- 
 sented by species of Iguanodon. A bed of their remains has re- 
 cently been brought to light at Bernissart, in Belgium, and the 
 settled conclusion of M. Dollo is that Iguari oclon was to some 
 extent a bipedal walker. Fig. 259 represents I. Bernissartensis 
 as recently mounted at Brussels. The head is 14 feet above 
 
 FIG. 260. REPTILES op MESOZOIC TIME. The upper and middle figures are Iguanodon^ 
 after Hawkins. The right hand figure is ffylceosaurus. 
 
 the floor, and the floor space covered is 23 feet 9 inches, the 
 whole length of the animal being over 28 feet. The Iguanodon 
 was an inhabitant of fresh-water marshes, and fed largely on 
 ferns. It was a powerful swimmer, and there are some indica- 
 tions that the toes were webbed. Some years ago a restoration 
 of Iguanodon was made by Hawkins, under the direction of Owen, 
 of London, and Fig-. 260 gives the conception of the reptiles then 
 extant. But it obviously requires some modifications. 
 
 Other, and more characteristically land saurians, constitute 
 the Order THERIODONTA, or "Beast-toothed " saurians, from the 
 Triassic of South Africa. Three sorts of teeth were present,
 
 PEOGBESS OF TERKESTKIAL LIFE. 
 
 341 
 
 conical incisors, long, powerful canines, compressed laterally, and 
 minutely serrated behind, together with conical molars (Figs. 
 
 FIG. 263. Oudenodon Bainii. 
 (Owen.) 
 
 FIG. 261. JAWS OF 
 Lycosaurus. SIDE 
 VIEW. (Owen.) c, 
 c. Canines. 
 
 FIG. 263. JAWS OP 
 Cynodraco serri- 
 dens. FRONT 
 VIEW. (Owen.) 
 
 261 and 262). In the same bed 
 
 occur representatives of another 
 
 order, ANOMODONTIA, or Dicyn- 
 
 odontia, "Dog-toothed," in which the jaws are converted into 
 
 toothless beaks (Fig. 263). In some, however, there was a pair 
 
 FIG. 264.Z>icynodon lacertlpes. 
 (Owen.) SHOWING THE MAX- 
 
 ILLABYTUSK. TRIAS OF 
 
 SOUTH AFRICA. 
 
 FIG. 265. Pterodactylus crassirostris. FROM LITHOGRAPHIC SLATES OP SOLENHOPEN. 
 (D'Orbigny.) Erroneously represented with five anterior digits instead of four. X ? 
 
 of teeth implanted in the upper jaw, growing from persistent 
 pulps, and assuming- the character of great tusks (Fig. 264.)
 
 342 
 
 GEOLOGICAL STUDIES. 
 
 The air, finally, had its reptilian denizens, PTEROSAURIA, 
 " Flying Saurians," having essentially the structural characters 
 
 FIG. 2S&.Dimorphodon macronyx. (After Owen.) 
 
 of a reptile, but with some bird-like modifications, and a pair 
 
 of leathery wings stretched from the greatly elongated outer 
 
 digit, along the side 
 of the body to the 
 tail. We find five 
 modifications of Fly- 
 ing Saurians, all 
 European but one: 
 (1) Pterodactylus, 
 having the jaws 
 toothed to the tip, 
 and tail short, Fig. 
 265; (2) Dimorpho- 
 don (Fig. 266), with 
 jaws toothed, the 
 anterior teeth larg- 
 est, and tail very 
 long; (3) Rham- 
 
 phorhynchus, with tips of jaws edentulous, and tail very long; 
 
 (4) Pteranodon, with jaws toothless and tail short and slender 
 
 FIG. 267. Arcftceoptei'yx macroura. (After Owen.)
 
 PROGRESS OF TERRESTRIAL LIFE. 343 
 
 comprising gigantic forms from the 
 Cretaceous of North America, some 
 having a spread of 23 feet; (5) Or- 
 nithoptents, with a wing-finger hav- 
 ing only two phalanges. 
 
 If to the reptilian forms men- 
 tioned we add the other Permian 
 and Mesozoic forms known true 
 Lizards, Crocodilians, Stegosaurians 
 (plated lizards), and other genera 
 of savage Theropods (beast-footed), 
 like Megalosaurus, and Lcelaps, and 
 other reptiles with hollow bones, the 
 CCELUBIA of Marsh we may easily 
 believe that the "Age of Reptiles " 
 was one of marvellous luxuriance 
 and diversification of the reptilian 
 type. 
 
 9. Toothed Birds. 
 
 While the Age of Reptiles was 
 in progress, true Birds came into 
 existence. One of the earliest forms 
 was ArchcKOp' teryx macrou'ra (Big- 
 tailed Old-flyer), of which a restora- 
 tion by Owen is given in Fig. 267. 
 It comes from the Juras- 
 sic schists of Solenhofen. 
 It had a conspicuously 
 long, vertebrated tail, 
 quill-bearing on each 
 side; and Marsh has re- 
 cently shown that it pos- 
 Pia. 268.-LEFT FIG. 269. -LEFT " Tiiflir sessed teeth. Whether 
 LOWER JAW OF LOWER JAW or Fia.STO.-Tooth more a j^j r( j t h an rept ile 
 Ichthyornis dis- Hesperornis reg- or Hesperor- . 
 par. x2. alls, xi nit. v 4. ls even "*"' a mooted
 
 344 
 
 GEOLOGICAL STUDIES. 
 
 point. Carl Vogt pronounces it a feathered lizard. There are 
 two conical teeth in the upper jaw; eight neck vertebrae, with 
 five pairs of ribs directed backward; ten dorsal vertebrae without 
 
 FIG. 271. SKELETON OF Hegperornis rtgalis, RESTOKKD. (After Marsh.) x 
 
 spinous processes, and supporting ribs without uncinate pro- 
 cesses; five sternal ribs, and very minute sternum. The fore 
 limb, he maintains, is not a proper wing, and there are three
 
 PROGRESS OF TERRESTRIAL LIFE. 345 
 
 digits, resembling those of a clawed lizard. If the feathers had 
 not been preserved, no one would have thought the Archceop- 
 teryx a bird, or capable of flight. Here, then, is a creature in 
 which bird and reptile are so mixed that the best judges cannot 
 agree whether it is one or the other. 
 
 Equally remarkable forms have been described by Marsh, 
 from American Cretaceous strata, on which he has founded the 
 Sub-Class ODONTORXITHES, with two Orders, Odontolcce, having 
 teeth in grooves, and Odontotormce, having teeth in sockets. 
 The tail was not specially elongated. Some of their charac- 
 ters are illustrated in Figs. 268-271. 
 
 These " connecting links " between reptiles and birds pos- 
 sess extreme interest. Whatever conclusions they may sustain 
 respecting the genetic relationship between these two types, ex- 
 ternally so dissimilar, the nature of the structural relations is 
 identical with that which runs through all the numerous and 
 diversified Orders of reptiles, and also allies reptiles with all the 
 other vertebrate classes. 
 
 10. Mammals. 
 
 1. Hfesozoic Mammals. The earliest discovered traces of 
 Mammals occur in the Upper Triassic strata of the Old World,, 
 and in strata of nearly the same age in America. They are single 
 species in each case. The next remains occur in the Jurassic. 
 The Cretaceous passes with the disclosure of only a single relic, 
 found in America. But, with 
 the opening of the Ca?nozoic 
 ^Eon, mammalian life appears to 
 have been abundant. 
 
 The Triassic Mammal of Eu- FlG m _ L ~ B JAW OP Dromatherium 
 rope has been named Jlficroleste* tylvestre, EMMONS. FROM THE JURA TRI- 
 anti?w<;thatof America, Drom- * omH ^^ (After Em ' 
 atherium sylvestre, E rn m o n s, 
 
 from the red sandstones of North Carolina. These have been 
 generally regarded as Triassic; but Professor Fontaine's recent de- 
 termination of the Jurassic age of the Richmond and Deep River
 
 34G 
 
 GEOLOGICAL STL'J)IES. 
 
 coal fields may fix a later epoch for I>romatherium. t The Triassic 
 
 mammal of South Afri- 
 ca is Tritylodon lonyce- 
 vus (Owen), as large 
 as a gray fox, and re- 
 markably specialized 
 for a mammal so an- 
 cient. 
 
 Judging from a sin- 
 gle ramus of the lower 
 jaw of Dronuitherium, 
 Fig. 272, the animal was 
 an insectivorous Mar- 
 supial, related to the 
 Banded Anteater of 
 Australia, MyrmecoM- 
 us fasciatus, Fig. 273. 
 Microlestes is believed 
 to be nearly related. 
 The next horizon of mammalian remains is, in the Old World, 
 
 in the Stonesfield Slate of the Lower Oolite. According to corn- 
 
 FIG. 273. Myrmecobim fasciatus. THE BANDED ANT- 
 EATER OP NEW SOUTH WALKS. X i- (After Gonld). 
 
 FIG. W4.AmphUherium (Thylacotherium} Broderipii. X2. FIG. Wb.-Phascolothe- 
 rium Bucklandi. X 2. 
 
 mon opinion, they all belonged to Marsupials. Arnphitherium 
 (Fig. 274), Amphilestes and Phase olot her ium (Fig. 275) were 
 also, probably, Insectivores. Stereoynathus appears to have been 
 herbivorous. Toward the close of the Oolitic period, the Middle
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 34; 
 
 Purbeck beds supply another deposit of small mammalian re- 
 mains, amounting to 14 species, all considered marsupial and 
 polyprotodont that is, having more than two lower incisors, 
 with canines more or less extensively developed, and the molars 
 either cuspidate or with sectorial crowns. Of these, Playiau'lax 
 is allied to the Kangaroo rats, having large premolars with seven 
 conspicuous grooves on the crowns. The other genera, Spalctco- 
 the'rium, Tricon' odon, and G-alastes are Insectivores, and related 
 to Australian Phalangers. Perathe' rium, from the Paris and 
 American Eocene, was an opossum. 
 
 The Atlantosaurus Beds of the American Jurassic have 
 yielded not less than 17 species of mammals, all of which are 
 probably marsupial or re- 
 lated to marsupials, and 
 most of which are insect- 
 ivorous, and related to 
 European forms. Dryo- 
 les' tes prisons was a small 
 opossum. Four other spe- 
 cies of Dryoles'tes are 
 known. Sty lac' odon, 2 
 
 species, was a near relative of the European Stylodon. 
 odon, 2 species (Fig. 276), was akin to Plagiau'lax, and the two 
 are constituted by Marsh the types of a new order, ALLOTHE'RIA, 
 supposed combining marsupial and other characters, and now 
 extinct. The names of the other genera are Tin' odon, 4 species, 
 Dyplocyn' odon (Fig. 
 277), Tricon' odon, Al'lo- 
 don, and Doc' odon. These 
 Marsh associates in an- 
 other new order, PANTO- 
 T H E ' B i A , to which he 
 thinks most of the Euro- 
 pean Jurassic Mammals 
 
 PIG. 276. Ctenatfodon serratus, MH. 
 LOWER JAW. Prom the Jurassic 
 Territory. 
 
 X 2i- LEFT 
 f Wyoming 
 
 Ctenac' - 
 
 FIG. 277. Dyplocyn' odon victor, MH. x ! <^ '' 
 cisor: b, condyle: c. coronoid process; d, angle. 
 
 belong. With few excep- 
 tions, he says, the Mesozoic Mammals are low, generalized forms,
 
 348 GEOLOGICAL STUDIES. 
 
 without any distinctive Marsupial characters. Not a few of them 
 show features that point more directly to Insectivores. From 
 this Order true Marsupials and Insectivores were probably derived. 
 From the Laramie, or highest group of the Cretaceous, Cope 
 described, in 1884, a single Mammal, Meniscocs' sus conquis' tits, 
 discovered by J. E. Wortman in Dakota. It belongs to the 
 Flag iau' lax f a m i ly . 
 
 2. Tertiaru Mammals. By such beginnings the Mammalian 
 Class was introduced upon the earth. During two entire Meso- 
 zoic Ages they were small and feeble creatures, either low Mar- 
 supial in type or else even lower than Marsupial, and marking 
 Orders from which the Marsupial characters had not yet been 
 clearly differentiated. It must be said, however, that the Marsu- 
 pial, after a few oviparous Monotremes, is the lowest known Mam- 
 malian organization, and an antecedent improbability exists of 
 any older order generalizing marsupial and placental Mammals. 
 
 With the opening of the Tertiary Age a rich mammalian 
 fauna was in possession of the continents at least of America 
 and Europe. We are unable to say whether they generally pos- 
 sessed marsupial characters or not; but there is little evidence 
 that the}- did. They are, however, highly generalized forms. 
 None of our modern Orders had become distinctly differentiated, 
 but several of them were pre-indicated with considerable salience. 
 
 There were characters be- 
 longing to Insectivores, Car- 
 nivores, Rodents, Pachv- 
 derms of different tribes, 
 and even of Proboscidians; 
 but they were variously asso- 
 ciated in the same animals. 
 One of the earliest of these 
 FIG. 278. - Coryph'odon hamatus. From Above, comprehensive types in 
 (After Marsh.) x|. Lower Eoceue. J v 
 
 America and Europe was 
 
 Coryph' odon, Owen (including Bath' modon, Cope), from near 
 the bottom of the Eocene. An outline of the skull is shown 
 in Fig. 278, in which the small size of the brain is indicated.
 
 PROGKESS OF TERRESTRIAL LIFE. 
 
 349 
 
 X*. 
 
 xf. 
 
 This was a large tapir-like quadruped. The limbs were short, 
 and each of the feet was 
 supplied with five function- 
 al digits (Figs. 279, 280). 
 Cope describes 12 American 
 species of Coryphodon and 
 two of Bathmodon. 
 
 Of nearly the same age 
 
 as the Coryph'odon was a FlG . m _ LEFT FoBE FooT . 
 strange animal which Marsh FIG. 280. -LEFT HIND FOOT. 
 has named Tillothd ' rium 
 
 fo'diens, and made the type of a new Order, TILLODONT'IA. 
 It presents a remarkable combination of the characters of 
 Ungulata, Rodentia, 
 
 and Carnivora. The ^ss^-sf^i^^B^^T^SH 
 
 skull (Fig. 281) resem- 
 bles that of a bear, and 
 the skeleton generally 
 is that of Carnivores; 
 but the feet are 5-toed 
 and plantigrade. T h e 
 premolars and molars 
 have grinding crowns, 
 the canines are of small 
 size, and the premaxil- 
 laries carried a pair of scalpriform incisors, like the beaver's in 
 form and in growing from persistent pulps. Anchippodus, Leidy 
 (= Troyosus), was allied to Tillotherium. 
 
 Another interesting form, from the Wahsatch Eocene of 
 Wyoming, is Phenac' odus, Cope, a skeleton of which, in the 
 position in which it was found imbedded in the sand-rock, is 
 shown in Fig. 282. Its nasal bones and several other features 
 resemble the tapir; the tail was as long, proportionally, as that 
 of a cat; the hind feet were semi-plantigrade; the molar teeth 
 were pig-like. Of Phenacodus Cope has described thirteen spe- 
 cies, and has made it the type of a family and of a Sub-order 
 
 FIG. -ISl.TUlotke'rium fo>diens. Mu. M T ITH 
 LOWER JAW DISPLACED DOWNWARD. >< 
 
 (After Marsh.)
 
 350 
 
 GEOLOGICAL STUDIES. 
 
 COJNDYLAR'THRA, which, with Hyracoidea, the Conies, h< 
 in the new Order, TAXEOPODA. 
 
 PIG. 2S2.Pfienac'odus Wortmani, COPE, x rr- WAHSATCH GROUP, WYOMING. (After 
 Cope.) 
 
 Another Wahsatch form, found also in Wyoming 1 , is named 
 Mes' onyx by Cope. The lower jaw is here figured. (Fig. 283, 
 
 a, b.) This animal was 
 distinctly flesh-eating, 
 but in some respects it 
 differed from modern 
 Carniv'ora, and Cope 
 has established a new 
 Order, CREODON'TA, to 
 receive this and numer- 
 ous other extinct flesh 
 eaters,which he arranges 
 in eight families. They 
 
 FIG. 383.- Mesonyx ossif'ragus, COPE. WAH- were also related to Mar- 
 
 SATCH OF BIG HORN RIVER, WYOMING. (After supials and Insectivores. 
 
 Cope.) x |. , side view of mandible; 6, view Qne of them / the 
 
 from above. 
 
 Tillodontia of Marsh) 
 
 was rodent, with lemurine tendencies, and the other, Tvenio- 
 donta, was edentate.
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 :35l 
 
 In the next or Bridger epoch of the Eocene existed in Wyo- 
 ming an assemblage of quadrupeds elephantine in dimensions 
 and striking in organization. These have been made the subject 
 of an elaborate memoir by Marsh, in which an extinct sub-order 
 has received an elucidation unequalled in the history of science. 
 They have also been very thoroughly investigated by Cope and 
 Leidy, and have been embraced within the researches of Osborne 
 and Spier. The DINOCER'ATA of Marsh are constituted of three 
 genera: Uintatherium (= Bathyop' sis, Cope), Dinoc'eras, and 
 Tinoc' eras (= Eo bas' ileus, Cope). With the DINOCER'ATA 
 Marsh unites the CORYPHODON'TA (= PANTODON'TA, Cope) to 
 constitute the Order AMBLYDAC'TYLA, which appears to be pre- 
 cisely identical with Cope's older named AMBLYP'ODA. This, 
 with the orders PROBOSCID'EA, HYRACOID'EA, and CLINODAC'- 
 TYLA (= Perissodactyla + Artiodactyla) form Marsh's Super- 
 Order UNGULATA. It would be 
 out of place here to enumerate 
 the characters of these genera. 
 The student will get an impres- 
 sion of the aspects of these 
 primitive beasts from the skulls 
 and skeletons here figured. It 
 is obvious that the feet resem- 
 ble, except in technical points, 
 those of Coryplt! odon, and also 
 those of the elephant. A cast 
 
 FIG. 284. Uintathe'rium Leidya'num, 
 SKULL. X ^g. BRIDGER GROUP. WYO- 
 MING. (After Osborne.) 
 
 FIG. 285. FEET OF Dinoceras mirabile, MARSH. ( Uintatherium mirabtte of Cope, 
 Leidy, and Osborne.) x | . , Fore Foot; 6, Hind Foot. (After Marsh.)
 
 352 GEOLOGICAL STUDIES. 
 
 of the brain shows the very small size of the hemispheres and the 
 verv large olfactory lobes. The brain is the most reptilian among 
 mammals. In Fig. 286 is a restoration of the skeleton of Dinoc' - 
 
 FIG. 286. Dinoc'eras mirab'Ue, MH. X A- BRIDGER GROUP, WYOMING. (After Marsh.) 
 
 eras. In Fig. 287 is a similar restoration of Tinoc' 'eras or 
 JZobas' ileus. The student will notice in all these a similar struc- 
 ture of the feet, and similar protuberances on the skull. It is 
 uncertain whether these were surmounted bv horns or only cov- 
 
 FIG. 287. Tinocferas ingeng, MH. x J,. BRIDGER GROUP, WYOMING. (After Marsh.) 
 
 ered by thick skin. In either case, they served, probably, as 
 weapons of attack. The enormous canines served a similar pur- 
 pose. 
 
 The Dinocerata, according to Cope, are composed of Eobas- 
 ileus (= Tinoceras, Marsh), Loxolophoclon (included in Tinoc-
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 353 
 
 eras by Marsh), Bathyopsi* ( = Uintatherium, pars, of Marsh), 
 and Uintatherium, Leidy. 
 
 Passing' unmentioned a multitude of remarkable Eocene 
 forms, we reach the White River Beds of the Miocene, and find 
 in existence another type of elephantine quadrupeds. The 
 Urontothe'rium, Marsh (= Symbor' odon, Cope, 4- Miobas 1 ileus, 
 Cope), of which a skull is shown in Fig. 288, had four nearly 
 
 FIG. 288. Bronfofhe'rium ingens. MH. WHITE RIVER BEDS OF THE MIOCENE. 
 (After Marsh.) x tV- 
 
 equal toes on the fore foot and three on the hind foot, thus 
 numerically resembling the tapirs. In size and general conform- 
 ation of the skeleton it resembled 
 the elephant, but with shorter limbs. 
 The nose was probably long and 
 flexible, but without a proboscis. 
 The brain cavity was very small. 
 A pair of horncores rose on the max- 
 illary bones. The canines were short, 
 and separated by a diastema, or in- 
 terval, from the premolars. The 
 student may point out from the 
 illustrations the differences among 
 the great extinct mammals. 
 
 The Tertiary ages of other conti- 
 nents were equally productive of 
 mammalian forms; but we can onlv afford space for mention 
 of two. The Dinothe rium was about the first known of Pro- 
 
 FIG 289.- Dinothe'rium gigan- 
 teum, KAUP. CONTINENT or 
 EUROPE. (After Kaup.)
 
 354 GEOLOGICAL STUDIES. 
 
 boscidians. Its remains have been found in Germany, France, 
 and Greece, in deposits of Miocene age. It had in the lower jaw 
 two enormous tusk-like incisors, directed vertically downward. 
 The molars present a combination of mastodont and tapiroid 
 characters. The animal attained enormous size, and by some 
 it is thought to have been of semi-aquatic habits. The other for- 
 eign mammal to be mentioned is the Sivat/ie' rium of the Sivulik 
 Hills in India, a gigantic four-horned Antelope. The posterior 
 horns possessed two snags or branches, a peculiarity not to be 
 paralleled among existing Cavicor'nia, except in the Prong- 
 buck. Bramathe' riutn was a contemporary of similar organi- 
 zation. 
 
 We must mention, lastly, the succession of horse-like forms 
 that have existed in America during the progress of the Tertiary 
 ages. These have been worked out by Marsh, to whom science is 
 indebted for so many important results. Much, however, has 
 been contributed by Cope and Leidy, and it is not certain that 
 some of their names are not possessed of priority over Marsh's. 
 
 Animals somewhat horse-like were in existence at the begin- 
 ning of the Eocene. Other species appeared in succession, pro- 
 gressively more and more like the modern horse, until, near the 
 close of the Tertiary, the modern genus Equus appeared. It 
 would not be proper to enter here into the details which charac- 
 terize and differentiate these successive equine forms; but the 
 student may refer to the illustrations, Fig. 290, while lie reads 
 the following brief statements: 
 
 In the oldest Eocene deposits of New Mexico are found the 
 remains of a horse-like quadruped, Eohippus ( = Byracothef- 
 riutu?}, about the size of a fox. It had four functional toes 
 before and three behind, thus resembling the tapir. A rudiment 
 (like a "splint bone") remained of the outer or Yth toe behind 
 (since those present were the lid, Hid, and IVth); and since the 
 Vth was present before, there was probably a rudiment of the 1st 
 in the fore foot, making the normal number of five digits in that 
 foot. The "hoofs" were mere thick, broad, and blunt claws. 
 The molars were short and without "cement." There were
 
 PROGRESS OF TERRESTRIAL LIFE. 
 
 355 
 
 Equus 
 
 EOCENE 
 
 Orohippus or *J 
 Hyracottierium j[ 
 
 FIG. 2?0. SUCCESSION OF EQUINE TYPES. (Marsh.) See Explanation, page 354.
 
 356 GEOLOGICAL STUDIES. 
 
 eight carpal bones, resembling those of the tapir. This genus 
 is not illustrated in Fig. 290. 
 
 In the Middle Eocene or Bridger Beds, of Wyoming and 
 Utah, existed Orohippus, also of the size of a fox. This had 
 four functional toes before and three behind. The ulna was com- 
 plete and distinct from the radius. The tibia and fibula were also 
 distinct. The crowns of the molars were exceedingly short, and 
 the enamel pattern simple. Later in the Eocene lived Epihipjms 
 which resembled Orohippus in the digits, but differed in its 
 more developed molars. 
 
 In the early Miocene lived Mesohippus, a horse-like quadru- 
 ped of the size of a sheep. Its functional toes had diminished to 
 three before, nearly equal, and three behind. In the fore limb, 
 however, was a large "splint," the remnant of the Vth digit of 
 Orohippus. The radius and ulna were still distinct, but the 
 latter was considerably attenuated in the lower part. The tibia 
 and fibula were also distinct. 
 
 In the late Miocene of Oregon existed Miohippus, also of the 
 size of the sheep, with three functional toes before and three be- 
 hind, and also a splint of the Vth digit before, but smaller than in 
 Mesohippus. The middle hoof is also larger and the lateral hoofs 
 are shrunken. The ulna is still distinct and as long as the radius, 
 but very slender distally. The fibula is coossified with the tibia 
 at the lower end. The older Miocene Anchitherium, the oldest 
 equine known in Europe, is closely related, but a little more 
 specialized. 
 
 Coming down to the early Pliocene, we find that a horse-like 
 quadruped existed, called froto/iippus, of the size of an Ass. 
 Instead of three serviceable toes it had but one with a dangling 
 hooflet or " dew-claw " on each side. The ulna was as long as 
 the fore arm, but extremely slender. The fibula was rudimen- 
 tary. The crowns of the molars were still longer than in Mio- 
 hippus. Contemporary with this, were the closely related An- 
 chippus in America and Hipparion (= Hippothe'riuni] in 
 Europe; while Merych'ius was probably identical. 
 
 Next, in the Middle Pliocene, existed Ptiohippus, of the pro-
 
 PROGRESS OF TERRESTRIAL LIFE. 357 
 
 portions of a moderate-sized horse, in which was only a median 
 toe, larger than in Protohippus, but with large splints instead of 
 dangling hooflets, on each side. The crowns of the upper molars 
 were longer and the crescentic areas more complicated than in the 
 older types. 
 
 Finally, toward the end of the Pliocene, Equus, the modern 
 horse, existed in America. It differred from Protohippus in a 
 more powerful middle digit, diminished splint bones, upper 
 molar crowns larger and more elongated, and crescentic areas, 
 formed by the enamel plates, more complicated. The horse sub- 
 sequently found its way to the Old World and remained to his- 
 toric times. Meantime it became extinct in America, and was 
 reintroduced on the discovery of the New World by civilized 
 man. 
 
 The historical vicissitudes of the Camel have been similar. 
 These and many other facts indicate that the Old World received 
 some of its Mammalian populations from the New. 
 
 11. Retrospect of Succession of Vertebrate Life in America. 
 
 The following Table, compiled from final publications of 
 Marsh and Cope, exhibits the order of introduction of the princi- 
 pal vertebrate types in America, with a corresponding grouping 
 of formations. The student of geology will find it useful for 
 reference.
 
 358 
 
 GEOLOGICAL STUDIES. 
 
 oiozosaw oiozoarivj
 
 12. Conspectus of the Geological Range and Relative Expan- 
 sion of the Principal Types of Animal Life. 
 
 Foraminifera 
 
 Anthozoa 
 
 Hydromedusco 
 
 Stromatoporidte 
 
 Graptolitidw 
 
 Crinoidea 
 
 Brachioporta 
 
 Bryozoa 
 
 Latnellibranchiata 
 
 Gasteropoda 
 
 Nautiloidea 
 
 Amiuonoidea 
 
 Dibranchiata 
 
 Trilobita 
 
 Arachnida 
 
 Insecta 
 
 Lepidoganoidea 
 
 Placoganoidea 
 
 Elasmobranchiata 
 
 Amphibia 
 
 Labyrinthodonta 
 
 Eeptilia 
 
 Dinosauria 
 
 Aves 
 
 Mammalia 
 
 FIG. 291. TABLE OF RANGE AND EXPANSION OP ORGANIC TYPES.
 
 CHAPTER V. 
 FORMATIONAL GEOLOGY. 
 
 FORMATIONS, THEIR STRATIGRAPHICAL CONSTITUTION, GEOGRAPH- 
 ICAL EXTENSION, AND PAL^EONTOGRAPHICAL 
 CHARACTERISTICS. 
 
 1. Preliminaries. Geological Maps. 
 
 WE must now return to the rocks, and learn more method- 
 ically what are the lithological characters of the various groups 
 into which they are arranged, as heretofore shown (page 274), 
 their thickness and relative importance, the fossil remains which 
 characterize them, and the regions in which they occupy the 
 earth's surface. 
 
 By the aid of the classification which has been already studied 
 to a considerable extent, and the geological map of the Eastern 
 United States, on which numerous exercises have been had, with 
 the general survey of organic life contained in the last chapter, a 
 good preliminary acquaintance has been made with the forma- 
 tions which we are now to study a little more in detail, or at least 
 in a somewhat different manner. 
 
 To prepare the way for a broader and completer comprehen- 
 sion of American geology, we now direct the particular attention 
 of the student to both parts of the Geological Map of the United 
 States on pages 118 and 119. 
 
 To enable the student to acquire a grasp of the method of 
 continental development, we also introduce here a very general 
 map of the geology of North America :
 
 FOR M ATI OX A L GEOLOGY. 
 
 361 
 
 PALEOZOIC 31ESOZOIC C.EXOZOIC Ql'ATERKARY. 
 
 FIG. 292. GEOLOGICAL MAP OF TS'OKTH AMERICA. 
 
 2. The Eozoic Great System. 
 
 1. How the Term is Used. A glance at the geological maps 
 shows that the rocks of this Great System occupy but compara- 
 tively little of the actual surface of North America. But when 
 we reflect that they pass everywhere under the other rocks, we 
 understand that they constitute the great mass of the solid land 1 .. 
 Because they constitute the beginning of the actually observed 
 series of formations, some geologists designate them Archceatt^ 
 from (>.pyr h the beginning. But we know too little about the deep- 
 est and oldest rocks to assert that formations seen at the surface 
 continue down and include the rocks formed in the beginning* 
 We have good reason to believe, as before explained (page 288), 
 that the beginning rocks have been long ago melted away. We 
 do not know that any archsean rocks remain. Assuredly, we have 
 not seen any archaean rocks; and it is certain they are not strati-
 
 362 GEOLOGICAL STUDIES. 
 
 fied, as the oldest rocks known to observation are. We may reason 
 about archeean rocks, as a necessity of our theory of the world. We 
 may even extend the meaning of the term to embrace all the rocks 
 from the beginning of incrustation to the Cambrian. We may some- 
 times use the term in this sense. But we need a term to desig- 
 nate these later archasan rocks, and hence we style them Eozoic 
 a term symmetrical with Palaeozoic, Mesozoic, and Caenozoic, and 
 one which, unlike Azoic (formerly employed), can never become 
 inapplicable through the progress of discovery. The rocks next 
 before the Eozoic were perhaps strata now melted away. Before 
 all strata there must have existed a fire-formed crust a real 
 Pyrogenic formation. Hence, Archcean, in the sense suggested, 
 is comprehensive, and we need to note its divisions. 
 2. Divisions of the Great System. 
 
 { Keweenian System. 
 
 Eozoic Great System, -i. Huronian System. 
 [ Laurentian System. 
 
 The name Azoic was applied to rocks older than the lowest 
 known fossiliferous strata by Messrs. Foster and Whitney in their 
 Government report on the Mineral Region of Lake Superior. By 
 Sir William Logan and his associates rocks holding this position 
 in Canada were divided into Laurentian and Huronian, from the 
 Laurentide Hills and Lake Huron. Very much discussion has 
 been subsequently had, and is still in progress, respecting the 
 classification of these pre-Cambrian rocks; and this has acquired 
 new interest in connection with the public surveys still in prog- 
 ress in Minnesota, Wisconsin, and Michigan. Western studies 
 seem to have established the existence of a Copper Bearing (Ke- 
 weenawan or Keweenian) Series above the proper Huronian and 
 older (as is now thought) than the Cambrian. This System we 
 accordingly introduce here, for the first time, we think, in any 
 text-book. 
 
 At the same time, this arrangement must be regarded as 
 provisional. It will be shown in the next Section that an 
 " Acadian " or " St. John " formation is known on the eastern
 
 FORMATION A L GEOLOGY. 363 
 
 border of the continent, and also in Central Nevada, holding a 
 position beneath the Potsdam formation. This Acadian is not 
 identified in the Upper Mississippi region ; and it may yet be 
 shown that the Keweenian is its chronological equivalent. Again, 
 it has very recently (September, 1885) been shown, by N. H. 
 Winchell, that Cambrian fossils occur in the "Pipestone" of the 
 Upper Missouri River. As the pipestone is embraced in the 
 great Quartzite formation underlying the Potsdam in Minnesota 
 and Wisconsin, the evidence is that this Quartzite is Cambrian, 
 as the present writer long ago suggested, instead of Huronian, 
 as maintained by the Wisconsin geologists. If so, it is in the 
 position of the St. John Slates of the East, and may be their 
 western equivalent. Like the Keweenian, it succeeds downward 
 the Potsdam Sandstone; and the question remains open, What 
 are the relations between the Copper Bearing Series and the 
 Baraboo Quartzite ? 
 
 3. Geographical Distribution of Surface Exposures. Eozoic 
 rocks at present occupy the surface (1) in regions where no later 
 sediments were ever deposited over them in consequence of the 
 uplift of those regions above the sea level; (2) in regions once 
 overlaid by later sediments which have been carried away by 
 erosions; (3) in places where they have been thrust up through 
 breaches in the overlying strata. 
 
 Glancing over the Geological Map, we notice one principal 
 belt stretching from the coast of Labrador to the region north of 
 the Great Lakes, and thence northwest to the Arctic Ocean, 
 covering an area enclosing Hudson's Bay like an arc of a great 
 circular belt. It will be noticed that the Adirondac area is an 
 appurtenance to this, and that an arm stretches southwestward 
 into Minnesota. The considerable area in Michigan and Wiscon- 
 sin may be regarded as simply an outlying patch of the same. 
 This is the great Eozoic nucleus of the continent at least of its 
 eastern and northern parts. It is the Great Northern Eozoic 
 Self. We find also an Appalachian belt stretching from Dutchess 
 county, New York, and, with some interruptions, from New 
 Brunswick to Georgia. This is the Great Seaboard Eozoic Belt.
 
 364 GEOLOGICAL STUDIES. 
 
 Over the Rocky Mountain region, aiid westward at intervals as 
 far as the Sierra Nevada, occur isolated areas and outcropping 
 mountain masses and ranges of Eozoic rocks which have been 
 largely concealed by later sedimentation. This is the Great 
 Cordilleran Eozoic Area. Other detached island-like areas exist 
 in Missouri, Texas, and other regions. 
 
 4 General Constitution of the Great System. The Eozoio 
 rocks, as far as accessible to us, attain an enormous thickness. 
 We have studied probably 95,000 feet of them not all, of 
 course, in one connected series. We find them to be almost 
 wholly crystalline and hard. The greater part are phanerocrys- 
 talline. Nearly all known minerals are embraced in them ; the 
 majority are even restricted to them. Here are found in place 
 those metamorphic rocks whose kinds we have already studied in 
 the bowlder fragments scattered over the Northern States. Here 
 are the great masses of granites, gneisses, diorites, and diabases, 
 whose stratification has become nearly or quite obliterated. 
 Here are most of the different species of schists. Here are the 
 marbles and serpentines. In these old crystalline rocks are 
 enclosed the great deposits of iron ore magnetite, haematite, 
 titaniferous iron, and Franklinite, or zinc-iron ore. Here are our 
 stores of graphite and soapstone (steatite and parophite). 
 
 These rocks show almost everywhere evidences of great dis- 
 turbance. They have sometimes been tilted up at steep angles. 
 Sometimes they are quite vertical. Very commonly later strata 
 rest on the exposed and worn edges of the Eozoic. In Fig. 38 
 we have an illustration. On the left are gneisses, b, dipping to 
 the left, and resting against the central mass of granite, a. On 
 the right are gneisses, b, dipping toward the right at a steep 
 angle, and resting against the other slope of the granite nucleus. 
 On the upper edges of these thick-bedded gneisses rest uncon- 
 formably the strata of sandstone, c. The latter are not Eozoic. 
 The gneisses were tilted before the sandstones were laid down. 
 A geological convulsion here separates two ages and two forma- 
 tions. In Fig. 107 the horizontal sandstones, S, are seen abutting 
 against the slope of the older rocks, C, and the underlying and
 
 FORMATIONAL GEOLOGY. 365 
 
 still older beds, Jf, rest against broken edges of the formation, L. 
 The relation of the Eozoic to the later formations is well shown, 
 also, in Figs. 46 and 84. 
 
 The plication of the Eozoic strata is something as remarkable 
 as their tilting. The section of the Wisconsin rocks, Fig. 293, 
 shows their condition and their relation to the higher rocks. In 
 Mt. Kearsarge, Fig. 89, we find another instructive example of 
 plications. In Fig. 294 we reproduce, from Sir William Logan, 
 a section through the Eozoic strata of western Canada. Here 
 the crumpled condition of the strata is strikingly shown. The 
 dotted lines are intended to indicate the probable connections 
 of the formations. 
 
 Laurentian 
 
 Fio. 293. GENERALIZED SECTION ACROSS THE ROCKS op WISCONSIN. (Chamberlin.) 
 1. Potsdam Sandstone. 2. Lower Magnesian Limestone. 3. St Peter's Sandstone. 4. 
 Trenton Limestone. 5. Galena Limestone. 6. Cincinnati Shales. 7. Niagara Lime- 
 stone. 8. Lower Helderberg Limestone. 9. Hamilton Limestone. 
 
 5. Kinds of Rocks and Economic Products. The Lauren- 
 tian System contains great beds of granite, syenite, and gneiss, 
 with some mica- and much hornblende-schist. Hornblende and 
 pyroxene are very abundant minerals, and with them labradorite 
 is one of the commonest feldspars. Iron is very generally dis- 
 seminated, both as a chemical constituent and also as a min- 
 eral in the forms of magnetite, haematite, and titaniferous iron. 
 There are also, in Canada, three great beds of crystalline lime- 
 stone (Fig. 294), with many intercalated layers of gneiss and 
 rocks consisting largely of pyroxene or hornblende. The Lauren- 
 tian rocks were estimated by Logan at 30,000 feet. 
 
 The Huronian System, as commonly understood, is composed 
 of beds of granular and conglomeritic quartzites, quartz-schists, 
 jasper and chert schists, and several thick formations of diorite 
 and diabase which sometimes pass into granites and syenites; 
 with also a great thickness, higher in the series, of hydro-mica
 
 366 
 
 GEOLOGICAL STUDIES. 
 
 and magnesian schists, and black slate and ferruginous schists, 
 terminated by enormous beds of mica 
 schist, gneiss, and granite. The con- 
 ^ glomerates contain rounded frag- 
 
 2 ments up to a foot in diameter, and 
 ^ with the quartzites, attain a thick- 
 ~ ness of 2,500 feet. The great iron 
 j 3 deposits of northern Michigan and 
 
 Wisconsin are associated with quart- 
 , S zose and dioritic rocks, and are corn- 
 
 s' g monly regarded Huronian. 
 
 The Keweenian System consists 
 ^ g of interstratified igneous and sedi- 
 
 g g . mentary beds. The former are mainly 
 a j^l diabases, with some norites,* mela- 
 ^ P"yrs, and porphyries; the latter are 
 a "^ -| conglomerates, sandstones, and shales 
 - j o derived mainly from the igneous 
 go- 2 rocks. The conglomerates are formed 
 & ", 5 of the debris of felsitic and quartz 
 g I g porphyries, with some from diabases. 
 '8^1 Some of the conglomerate fragments 
 
 3 <' | are one or two feet in diameter. A 
 o J single bed of coarse conglomerate on 
 
 the Montreal River is 1,200 feet thick. 
 The beds are tilted, but not con- 
 
 * These by the Wisconsin and Minnesota geol- 
 ogists, following late German authorities, are 
 termed "gabbros" a name which ought to be 
 allowed to rest in disuse. (See pages 53 and 77, this 
 work.) Gabbro is defined in the Wisconsin Report 
 as follows: il A rock formed of a plagioclase feld- 
 spar and diallage. The feldspar is usually labra- 
 dorite. The diallage is little more than a foliated 
 augite. Usually more coarsely crystalline than 
 diabase. The Duluth granite is a typical exam- 
 . pie." Norite with them is composed of a plagio- 
 clase with hypersthene or enstatlte (similar to hy- 
 persthene, but light-colored). See page 77.
 
 FOBMATIOKAL GEOLOGY. 367 
 
 torted, and metainorphic. Maximum thickness about 45,000 feet, 
 of which over 15,000 feet are sedimentary. Irving separates 
 them into an Upper division wholly sedimentary mostly red 
 sandstone and shale with a mean thickness of 15,000 feet, and 
 a Lower division made up chiefly of basic igneous rocks in many 
 sheets, with a thickness of 25,000 to 30,000 feet. 
 
 Geologists are not united as to the geological position of the 
 great iron-ore beds. Those of northern New York (See Figs. 
 103 and 104) and Missouri are commonly represented as Lauren- 
 tian, and the similar beds in North Carolina, Canada, Sweden, 
 and Norway are believed to be of the same age. But the Pilot 
 Knob and Iron Mountain deposits are not far remote stratigraph- 
 ically from the Lower Magnesian (Cambrian) limestone. The 
 section through the Penokie Iron Range, too, Fig. 107, shows 
 the iron-bearing beds included conformably in the Huronian, ff } 
 while these strata rest quite unconformably against the edges of 
 the Laurentian strata, L. Not unlikely, the rocks inclosing the 
 iron ores of northern New York will be found to be Huronian. 
 
 The mode of occurrence of iron ores and other particulars will 
 be found elsewhere (pages 182, 69). 
 
 The great copper deposits of the Lake Superior region occur 
 in the Keweenian series. They exist partly in the igneous rocks 
 and partly in the sedimentary. In the latter, they appear to be 
 mostly a secondary product, introduced after the sediment was 
 laid down. In some cases the metal appears as an original con- 
 stituent of the conglomerate. In the Calumet and Hecla mine, 
 the most productive in the world, the so called vein is simply a 
 conglomerate 8 to 12 feet thick, lying between massive sheets of 
 trap. The native copper permeates the whole mass, and serves 
 as a cementing material. In the trap rocks the copper is found 
 filling, either alone or with other minerals,, the amygdaloidal cav- 
 ities which abound near the lower and upper surfaces of the 
 sheets, and insinuating itself into the other cavities and fissures. 
 Sometimes the filled fissures assume the characters of true veins. 
 
 From rocks of Laurentian age comes most of the graphite of 
 the world. (See Part I, Study XIII.) They afford, also, apatite,
 
 GEOLOGICAL STUDIES. 
 
 a phosphate of lime used in agriculture; rensseherite or steatite, 
 used for potstone or soapstone, and cut into slabs for chimney 
 
 pieces, furnace linings, 
 and foot warmers, and 
 used also for ink- 
 stands; parophite, an 
 aluminous rock used 
 for inkstands; beds of 
 marble. Formations 
 perhaps later in the 
 contain slates 
 
 FIG. MS.Palceophyciis arthrophycus, WIN. FROM THE 
 KEWEENIAN SANDSTONE, NORTH FLANK OF THE POR- 
 CUPINE MOUNTAINS. (From Nature.) 
 
 and deposits of lead and zinc ores. 
 
 6. Organic Remains. The great deposits of iron ore and 
 graphite have long been regarded as evidence of the presence of 
 organization early in the Eozoic vEon. But no organic forms 
 are known in the Laurentian or Huronian systems except Eozoon. 
 
 FIG. 296. MT. KEARSARGE AMONG THE WHITE MOUNTAINS. SHOWING FORMS ASSUMED 
 BY Eozoic FORMATIONS IN PKOCESS op WEATHERING. BOWLDERS IN THE FORE- 
 GROUND. See section through this mountain, Fig. 62.
 
 FORMATION A L GEOLOGY. 369 
 
 Of this enough has already been said (pages 318-320). In the 
 Keweenian sandstones of the north flank of the Porcupine Mount- 
 ains Dr. D. Houghton collected, many years ago, some remains 
 which appear to belong to marine plants, and these the author 
 has described as Palceophycus arthrophycus and P. articulatus. 
 They are quite as definite in form and characters as any pre- 
 viously described from the Cambrian. A representation of one 
 of these is shown in Fig. 295. 
 
 3. The Cambrian System. 
 
 1. Divisions, Subdivisions, and Terms. 
 CAMBRIAN SYSTEM. [Formations named in natural order of 
 
 sequence downward. Numbering is from below.] 
 III. Trenton Group (4). 
 
 3. CINCINNATI STAGE (4c). The Hudson River shales and slates; 
 Lorrain shales of New York ; Nashville Group of Tennessee. 
 
 2. UTICA STAGE (4&). 
 
 1. TRENTON STAGE (4a): (3) Trenton limestone; Galena limestone of 
 
 Illinois; Lebanon limestone of Middle Tennessee. (2) Black 
 River limestone. (1) Birdseye limestone. 
 II. Canadian Group (3). 
 
 3. CHAZY STAGE (3c). Chazy limestone, New York and Canada. 
 
 2. QUEBEC STAGE (3&). Canada, near Quebec; shales, limestones, 
 
 and sandstones, Newfoundland. Part of Knox Group, Tennes- 
 see. 
 
 1. CALCIFEROUS STAGE (3a). Northern New York. Lower Mag- 
 
 nesian limestones of Mississippi valley; St. Peters sandstone, 
 Wisconsin and Illinois; Knox sandstone, East Tennessee. 
 I. Primordial or Potsdam Group (2). 
 
 2. POTSDAM STAGE (3J) Sandstone of Northern New York, of the 
 
 south shore of Lake Superior east of Keweenaw Point, and most 
 of that of Minnesota and Wisconsin. Chilhowee sandstone of 
 Tennessee. Georgia slates of Vermont. 
 
 1. ACADIAN or ST. JOHN STAGE (2a). St. John Group of New Bruns- 
 wick ; beds of St. Johns and elsewhere in Newfoundland ; slates 
 of Braintree, Mass. ; Ocoee conglomerate and slates of Eastern 
 Tennessee and North Carolina. 
 
 The term " Cambrian " has been employed in various senses, 
 and not unfrequently as equivalent to what is here denominated 
 "Primordial." The sense here employed is that announced by
 
 370 GEOLOGICAL STUDIES. 
 
 the Director of the United States Geological Survey as the one 
 adopted for official use. (Report of the Director for 1881, page 
 xlviii.) It is equivalent to " Lower Silurian " as employed till 
 recently by most American geologists. The name itself comes 
 from Cambria, the ancient name of Wales, and was first used by 
 Sedgwick for fossiliferous rocks older than those by Murchison 
 denominated " Silurian," from Silures, the designation of the 
 ancient inhabitants of Wales. " Primordial " was employed by 
 Barrande for the lowest fossiliferous zone of Bohemia. " Pots- 
 dam " is so named from Potsdam, in New York, and the other 
 terms are geographical in their origin, requiring no explanation, 
 it being as a rule understood that a locality or region giving its 
 name to a formation is one at which the formation was first sci- 
 entifically described and defined with the limitations now employed 
 by geologists. (See Chap. II, 4, 3 (6).) 
 
 2. Geographical Extension. Turning to the Geological Map, 
 we find the Cambrian strata generally resting against the flanks 
 of the Eozoic hills and mountains. Thus, in Canada the valley 
 of the St. Lawrence River is underlaid by Cambrian strata. A 
 large basin, including Montreal and Ottawa, indents the Eozoic 
 area, and a belt of these rocks sweeps around the Adirondac 
 region, crossing the St. Lawrence at Ogdensburg, bordering Lake 
 Ontario on the north, passing under Georgian Bay, rising above 
 the surface on the chain of Manitoulin Islands, sweeping from 
 St. Marie's River to Marquette, thence passing southwestward 
 around the Michigan-Wisconsin Eozoic, and expanding south- 
 ward over southern Wisconsin, and northwestward to Minne- 
 apolis, and beyond. In the valley of the Red River the Cam- 
 brian reappears, and stretches far toward the northwest. A large 
 part of Vermont, New Hampshire, and Maine is occupied by 
 Cambrian and Silurian rocks. These strata come to the surface 
 over a large area, embracing the cities of Cincinnati, Madison, 
 Frankfort, and Lexington (Ky.); also over another area embrac- 
 ing Nashville, Lebanon, Columbia, Franklin, and Murfreesboro 
 in Tennessee. An important belt of Cambrian and Silurian undi- 
 vided is involved in the folds of the Appalachian Mountains. In
 
 FORMATION A L GEOLOGY. 
 
 371 
 
 southeastern Missouri is a considerable area stretching over into 
 Indian Territory. 
 
 3. The Continent at the Beginning of the Cambrian Age. 
 At the beginning of the Eozoic ^Eon that is, when the sedi- 
 ments began to be deposited which were destined to form the 
 rocks of the Eozoic Great System, the regions now occupied by 
 those rocks must necessarily have been under water. If there 
 were any lands existing whose wastage during Eozoic time sup- 
 
 FIG. 297. NORTH AMERICA NEAR THE CLOSE OF THE Eozoic ^EON. Based on the latest 
 publications of the Canadian Survey, and the general views set forth by King in the 
 Report on the 40th Parallel Survey. 
 
 plied materials for Eozoic sediments, we do not know where they 
 were. They seem to have been completely obliterated. If we 
 were to represent America at the beginning of Eozoic time, we 
 could only represent an expanse of water. At the end of the 
 Eozoic ^Eon, however, uplifts took place ; dry lands appeared. 
 More likely, numerous uplifts had taken place during the progress 
 of the Eozoic.
 
 372 GEOLOGICAL ST CD IKS. 
 
 It will be noticed that the continent of Cambrian time con- 
 sisted of three great nuclear areas, corresponding nearly to the 
 great Eozoic areas already pointed out in existing surface geol- 
 ogy. (1) The Great Northern Area. This was arcuate, stretch- 
 ing from the region of the Great Lakes northwest to the Arctic 
 ocean, and northeast to the coast of Labrador, or perhaps far be- 
 yond. (2) The Seaboard Area. This seems to have stretched 
 from New Brunswick southwestward to Alabama, with a breadth 
 varying from 75 to 125 miles, diminished in the latitude of New 
 Jersey. There are reasons to suppose its breadth was much 
 greater on the eastern side, and that it continued over Nova 
 Scotia and Newfoundland. (3) The Great Cordilleran Area. 
 This spread uninterruptedly in width from the western border of 
 Great Plains into western Nevada. It was probably 750 miles in 
 breadth, but its extent north and south has not been ascertained. 
 This land was a great mountain system, displaying lofty ranges 
 made of crumpled strata, enormous precipices, a result of me- 
 chanical dislocations, and finally a type of mountain sculpture of 
 such broad, smooth forms as to warrant the belief that subaerial 
 erosion had never carved and furrowed the mountain flanks with 
 the sharp ravines characteristic of modern mountain topography. 
 The evidences on which these conclusions are based will be par- 
 tially disclosed in describing the results of later geological actions 
 in the same region. This massive belt of Eozoic Cordilleras deter- 
 mined the limits of the modern Cordilleras, and very much of the 
 details of their fundamental structure. 
 
 This was the beginning of the Cambrian Age. This was the 
 extent and configuration of the lands when Cambrian sediments 
 began to accumulate. These were the continental nuclei. The 
 student will particularly notice that the continent of the begin- 
 ning of Cambrian time was formed of Eozoic rocks. In that 
 sense we may speak of it as the Eozoic continent. 
 
 It will be observed that the mapping of an ancient continent 
 is much more than the mapping of the rock exposures of the cor- 
 responding age. If it were not, we might get a map of America 
 at the beginning of any Age the Carboniferous, for instance,
 
 FOKMATIONAL GEOLOGY. 373 
 
 bv simplv taking a geological map and coloring out all the Car- 
 boniferous and newer formations. But, to illustrate the uncer- 
 tainty of such a method, let us suppose the upheaval of the Sea- 
 board Eozoic took place after the Carboniferous Age, instead of 
 at the end of the Eozoic. Such may easily have been the fact, 
 especially as we know that was the epoch of Appalachian up- 
 heaval. The Appalachian Eozoic, therefore, should not appear 
 on a map of the continent as it was at the beginning of the Car- 
 boniferous Age. There are geologists who would leave it off ; 
 but we think evidences exist that a great mass of Eozoic dry 
 land stretched along the place of the present Atlantic seaboard, 
 as represented on our chart, Fig. 297. As it will be necessary 
 hereafter to speak of that land, we may at once designate it the 
 Seaboard Land. 
 
 4. Cambrian Rocks and ^Minerals, By reference to the 
 Table at the beginning of this Section it will be seen that the 
 best known formation at and near the base of the Cambrian is 
 the Potsdam Sandstone. This formation varies from friable to 
 hard. It is generally somewhat coarse-grained, and free from 
 argillaceous matter. Its color is grayish, or reddish, or mottled. 
 The student should fix his attention upon this fundamental mem- 
 ber of the Cambrian. It may be well to refer here to the Cycle 
 of Sedimentation, explained on page 268. Often the Potsdam 
 Sandstone rests directly on the Huronian or Laurentian. This 
 relation is well shown in Fig. 107, where S is the Potsdam Sand- 
 stone ; as also in Fig. 55, where P is the sandstone and E the 
 underlying Eozoic. Fig. 38 illustrates the same; and this may 
 be considered a section across the Aclirondac region, c being the 
 Potsdam Sandstone resting on the eroded stumps of the Eozoic 
 gneisses and schists. Tracing the Potsdam Sandstone thence 
 along the border of the Cambrian lying nearest the Eozoic, we 
 find it in Wisconsin lying horizontally upon the ruggedly eroded 
 surface of the Huronian. Fig. 298 is a very interesting illustra- 
 tion of the contact between the two. The Potsdam Sandstone 
 lines the south shore of Lake Superior from the Sault to Ke- 
 weenaw Point, and forms the celebrated scenery of the " Pictured
 
 374 GEOLOGICAL STUDIES. 
 
 Rocks. On the west of Keweenaw Point most of the sandstone 
 belongs to the Keweenian; but at Bayfield and at the Apostles' 
 Islands the horizontal sandstone is Potsdam. The formation out- 
 crops in the Black Hills of Dakota, surrounding the Eozoic 
 nucleus. It is extensively developed along the Appalachian 
 chain the slates and sandstones attaining a thickness of 3,300 
 feet. In East Tennessee sandstones and shales several thousand 
 feet thick are described by Safford Chilhowee sandstone rest- 
 ing on Ocoee conglomerates, sandstones, and micacous, talcose, 
 and chloritic slates. These enter into the Unaka Range, as shown 
 in Fig. 33. The formation is known in the Big Horn Mountains, 
 at the head of Powder River, along the Wahsatch, Teton, Madi- 
 son, and Gallatin Ranges, also in Central Nevada and other regions 
 of the Far West. The face of a Potsdam cliff on the Upper Mis- 
 sissippi is shown in Fig. 30. 
 
 FIG. 298. SECTION IN SAUK COUNTY, WISCONSIN, SHOWING THE CONTACT BETWEEN 
 THE POTSDAM SANDSTONE AND THE HURONIAN QUARTZITE. (R. D. Irving.) B, 
 Baraboo River; />, Devil's Nose; W, Wisconsin River, separating Sank from Colum- 
 bia County; , North Q.uartzite Range; b, South Qtiartzite Range; d, Potsdam Sand- 
 stone; e, f, upper portions of Potsdam Sandstone; g, Lower Magnesian Limestone; 
 ft, Drift. This is the Quartzite referred to, page 363. 
 
 The Canadian Group represents the approach of limestone- 
 making conditions, but not their full advent. The strata of the 
 East range from a calcareous sandstone below, to an arenaceous 
 limestone above the Chazy. These, in the Montreal basin, un- 
 dergo a large development, and constitute an argillo-calcareous 
 group (the "Quebec") of local importance. In the Mississippi 
 valley, the "Lower Magnesian Limestone" holds position here. 
 This is a buffish, coarse, or granular limestone, well developed in 
 southern Missouri and along the Mississippi north of Dubuque. 
 A common appearance presented by these two formations in the 
 banks of the Mississippi is shown in Fig. 299. The usual erosion
 
 FORMATIONAL GP:OLOGY. 
 
 375 
 
 of the underlying sandstone is shown in Fig. 26, which also shows 
 oblique laminations more clearly shown in Fig. 195. 
 
 In the valley of the Upper Mississippi, the Lower Magnesian 
 Limestone is succeeded by a whitish friable sandstone known as 
 the St. Peters Sandstone, which attains, in places, a thickness of 
 200 feet. Tt is sometimes regarded as a western representative 
 of the Chazy formation. In truth, however, the Calciferous, 
 Quebec, and Chazy, all together, occupy the interval held by the 
 Lower Magnesian Limestone and St. Peters Sandstone at the 
 West. 
 
 FIG. 299. BLUFFS ON THE UPPER MISSISSIPPI NEAR PRAIRIE DU CHIEN. CAMBBIAN 
 ROCKS. The Lower Ledge is Potsdam Sandstone, and the Upper, the Magnesian 
 Limestone. (D. D. Owen.) 
 
 The central and characteristic mass of the next Group is cal- 
 careous the great Trenton Limestone, named from Trenton Falls 
 on the East Canada Creek in Central New York. It stretches 
 along the middle of the Cambrian belt of strata as formerlv 
 traced, into the Upper Mississippi region, and northward past 
 Winnipeg. The Galena Limestone of Illinois, Wisconsin, and 
 Iowa is the upper part of the Trenton. Its thickness in the 
 great Montreal basin is 800 feet; in the Mississippi valley, 100 to 
 200 feet; in the Appalachians it amounts to 2,000 feet. The
 
 376 
 
 GEOLOGICAL STUDIES. 
 
 Cincinnati or Hudson River formation is a caicareo-argillaceous 
 continuation of the Trenton. 
 
 Other regions where the Trenton and Cincinnati limestones 
 are favorably exposed are Watertown, N. Y., in the banks of the 
 Black River; the north shore of the Manitoulin Islands; the west 
 shores of Green Bay and Little Bay de Noquet; southwestern 
 Wisconsin and northwestern Illinois, and some parts of eastern 
 Pennsylvania. The entire Cambrian strata of Nevada are re- 
 ported by Hague 7,000 feet thick, and include, from below, the 
 Prospect Mountain Quartzite and Limestone, the Secret Canon 
 Shale, the Hamburg Limestone, and the Hamburg Shale. The 
 Pogonip Limestone, next in order, probably embraces the Quebec 
 and Trenton formations. The Cambrian strata of the Wahsatch 
 region are reported by King 12,000 feet thick. 
 
 5. Erosion Features. The weathering of the Cambrian rocks 
 
 in Wisconsin and 
 Minnesota has 
 resulted in many 
 remarkable forms. 
 Figs. 30 and 32 
 have been cited. In 
 Fig. 300 the " Hor- 
 nets' Nest," the un- 
 derlying sandstone, 
 as in other cases, 
 has worn away, 
 leaving the Mag- 
 nesian Limestone 
 overhanging. In 
 other cases enor- 
 mous towers are 
 
 left standing in the 
 FIG. 300. THK "HORNETS' NEST," WISCONSIN. EROSION or , , ,. i 
 
 CAMBRIAN ROCKS. (Chamberlin) mldst f a P laln > 
 
 showing how exten- 
 sively formations have been swept away. Fig. 301 is an example 
 of this kind in Dakota county, Minnesota. Here the isolated
 
 FORMATION A L GEOLOGY. 
 
 377 
 
 column is over 19 feet high above the base, which is itself 25 
 feet high, making the whole outlier 44 feet 7 inches above the 
 sandy plain. Much pictur- 
 esque scenery results from 
 erosion of the Cambrian 
 rocks. The "Pictured Rocks" 
 of Lake Superior are in the 
 Potsdam Sandstone. The 
 "Dalles" of the Wisconsin, 
 Fig. 29, are in the same 
 formation. The "Great 
 Chasm of the Au Sable " in 
 northern New York is cut in 
 the Potsdam. The Trenton 
 Limestone is the occasion of 
 numberless waterfalls, some 
 of which, like Trenton, 
 Glenn's and Minnehaha, 
 have become classic. The "High Falls" of the Hudson at 
 Lucerne are partly in the Potsdam Sandstone. 
 
 The examination of a section along the Mississippi River, 
 somewhat like that in Fig. 302, shows that the Cambrian sedi- 
 
 FIG. 301. ''CASTLE ROCK," MINNESOTA. OUT- 
 LIER OF CAMBRIAN ROCKS. (Photograph.) 
 
 Pis. 302. GENERALIZED SECTION ALONG THE VALLEY OF THE UPPER MISSISSIPPI.. 
 CAMBRIAN ROCKS, a, Eozoic rocks. 6, Potsdam Sandstone, c. Lower Magnesian 
 Limestone, d, St. Peter's Sandstone, e, Trenton Limestone. 
 
 ments were deposited on a deeply eroded surface of Huronian 
 rocks, constituting what has been explained as a break (page 
 263). Erosions take place above sea level or a little below it. 
 This Huronian surface seems, therefore, to have been dry land for 
 a long period, after its upheaval, and before the epoch of the Pots- 
 dam Sandstone. During that interval, sediments were accumu-
 
 378 GEOLOGICAL STUDIES. 
 
 lating in other regions. That is, before the Potsdam epoch, and 
 after the close of the Eozoic, some other formation unrepresented 
 in the Northwest unless the Keweenian fill the gap was pro- 
 duced. This intervening formation is found at several points in 
 the East, and is known as the Acadian Stage, consisting chiefly 
 of slates, so far as known. The Acadian Stage is recognized 
 also in the Wahsatch and Great Basin regions. The Potsdam, 
 therefore, was not laid down over the Northwest until after a 
 subsidence. In other words, a map of the continent at the be- 
 ginning of Cambrian time must show more land than the present 
 exposures of Eozoic rocks. 
 
 A similar history appears to have been undergone in the 
 broad Cordilleran region which we have mapped as land at the 
 beginning of Cambrian time. After undergoing vast sub-aerial 
 erosions, during which marine sediments were accumulating else- 
 where, a great subsidence took place, and the region became an 
 archipelago. This was before the opening of Cambrian time, for 
 we find the oldest Cambrian sediments deposited horizontally in 
 the deep valleys of that ancient wasted surface. The entire 
 Cambrian series was built up in horizontal sheets, and the Cordil- 
 leran mountain slopes were slowly buried. The same order of 
 events continued through the Silurian, Devonian, and Carbonifer- 
 ous ages. The horizontal Palaeozoic strata abut against the 
 ancient slopes; and in one case at least, according to King, they 
 rise 30,000 feet along a mountain acclivity. 
 
 The "Cincinnati Swell," so called, is an upsvvelling of the 
 strata causing dips east and west from Cincinnati, as shown in 
 Fig. 303. The oldest rocks are exposed in the bed of the Ohio 
 River and in the amphitheatre of hills surrounding the city. 
 Following the river downward or upward, we reach outcrops of 
 formations successively higher in the series, and soon rise to the 
 Coal Measures. Underneath the Trenton Limestone, beneath the 
 bed of the river, lies the Potsdam Sandstone, which has been actu- 
 ally reached in boring an artesian well at Columbus. The hills 
 about the city are formed of the thin-bedded limestones and shales 
 of the Cincinnati Group. In central Tennessee, rocks of the same
 
 FOKMATIONAL GEOLOGY. 379 
 
 age are similarly brought to light by erosion (see Fig. 33), but 
 with less of a swell in the strata. The fossiliferous limestones, 
 clays, and shales of the suburbs of Cincinnati are reproduced in 
 the hill slopes and river bluffs of Nashville. 
 
 deb ;i bcdeg i 
 
 PIQ. 303. SECTION ACBOSS THE CINCINNATI SWELL. (7, Cincinnati, a, &, Cambrian; c, 
 Silurian; d, Devonian; e, Waverly; /, Carboniferous Limestone; q, Equivalent of 
 Carboniferous Limestone on the easterly side; A, Illinois Coal Field; /, Appalachian 
 Coal Field. 
 
 6. Organic Remains. The Cambrian rocks generally are 
 well stocked with relics of the life of the Age. For the Potsdam 
 Sandstone, the Upper Mississippi valley is the best collecting 
 ground. For the Trenton and Cincinnati formations, northwest- 
 ern Illinois, southwestern Wisconsin, northeastern Iowa, and 
 southeastern Minnesota are prolific regions None, however, 
 have yielded a greater abundance of good fossils than the Cin- 
 cinnati and Nashville areas. The former includes Richmond 
 and Madison, Ind., and Lexington anjl Frankfort, Ky. ; the 
 latter, Lebanon, Columbia, Franklin, and Murfreesboro. At all 
 the points named, the surface of the ground and the banks of the 
 streams are strewn with fossil remains surprisingly well preserved. 
 Scarcely less abundant or excellent are the fossils found along 
 the western shores of Green Bay, and the north shore of Drum- 
 mond's Island, in Lake Huron. Along the Black River, in New 
 York, at Trenton Falls, and in Centre county, Pennsylvania, are 
 also rich deposits. In central Nevada, the Pogonip and Hamburg 
 ridges are found fruitful in fossils. 
 
 The study of these remains shows that with the dawn of the 
 Palaeozoic ^Eon, life was exceedingly abundant in the sea; but 
 neither land animals nor plants are indicated, save some probable 
 tree trunks from the Cincinnati region. In respect to rank, these 
 animals ranged over all the classes of invertebrates. The Trilo- 
 bites, already sketched (page 323), were highest in rank, and most
 
 380 GEOLOGICAL STUDIES. 
 
 conspicuous in the Primordial Period, and continued throughout. 
 Cephalopods of the type of Orthoceras were perhaps equal in 
 importance, and were certainly dominant in prowess. Of these a 
 sketch has also been given (page 326). It is noteworthy that forms 
 indicating much complication and differentiation in structure 
 come from a horizon as low as the Calciferous, implying, perhaps, 
 that simpler forms, still undiscovered, had been in existence dur- 
 ing periods still more remote. Among humbler forms were 
 Crinoids, beautiful creatures which rooted themselves in the sub- 
 marine soil, and grew like tiny animated palms. These have also 
 been sketched (page 324). But besides these types were others 
 which played important roles in the plan of life and the pro- 
 cesses of sedimentation. Coral makers of the type of Polyps 
 were not conspicuous, except Favistella and Streptelasma, Figs. 
 12;i 4, but coral makers of the type of Bryozoa were extremely 
 abundant during the Trenton Period. Individual animals were 
 extremely small, but they combined in large numbers, and secret- 
 ed coral masses from one to eight inches in diameter. Brachio- 
 pods may be particularly mentioned as beginning their geological 
 history in forms related to Lingula, Strophomena, and Orthis 
 biforata. These have been already described and illustrated 
 (Studies XXXIII and XXXIV). Zygospira modesta (Fig. 178), 
 Orthis subquadrata (Figs. 16&, 171), StropJiomena alternata 
 (Figs. 191, 192), and Orthis biforata (Fig. 163), are widespread 
 and characteristic species. The particular features of Paheon- 
 tology, however interesting or important, must here be passed 
 over, to be taken up in a more advanced course. 
 
 The exuberance of marine life at an age so remote that, aside 
 from Eozoon, by some denied, it seems to represent the very first 
 act in life's drama, is a great fact which may well astonish and 
 prompt to speculation. We must remember that remoteness 
 reduces the perspective of the Cambrian to a seeming point of 
 time, while it was undoubtedly measured by hundreds of thou- 
 sands of years. We may bear in mind, also, that the wonderful 
 diversification of Cambrian types, even from the beginning, may 
 possibly have been progressing during that long Huronian /TCon
 
 FORMATIONAL GEOLOGY. 381 
 
 all traces of whose organization have been obliterated by the 
 physical vicissitudes of our planet. 
 
 4. The Silurian System ("Upper Silurian " of Authors). 
 
 1. Divisions, /Subdivisions, and Terms. 
 III. Lower Helderberg Group (7). 
 II. Salina Group (6). 
 
 1. Niagara Group (5). 
 
 3. NIAGARA STAGE (5c). (2) Niagara Limestone; (1) Niagara Shale. 
 
 2. CLINTON STAGE (56). 
 
 1. MEDINA STAGE (5a). (2) Medina Sandstone; (1) Oncida Conglom- 
 erate. 
 
 The Silurian System, named from Silures, the ancient people 
 of Wales, was intended by Murchison to embrace all the fossil- 
 iferous rocks under the Devonian. The progress of discovery 
 having extended downward our knowledge of such rocks, Sedg- 
 wick bestowed the name Cambrian on those which he regarded 
 as underlying the Silurian, as originally known to Murchison; 
 while the latter designated them Lower Silurian. Aside from 
 other considerations, convenience requires a single designation 
 for every group important enough to stand in the relation of a 
 " System." Hence, with good reason, the National Survey has 
 proposed the use of these terms as here employed. 
 
 The other terms employed in the above table are all of New 
 York origin, and require little explanation. The Helderberg 
 Mountains are in eastern New York, south of Albany. The 
 Salina Group, named from its productiveness in salt, was origi- 
 nally the " Onondaga Salt Group," from its supply of brines in 
 Onondaga county. 
 
 2. Geographical Extension. If we start from the Niagara 
 River, which gives its name to the most important mass of the 
 Silurian, Hthologically speaking, we find this system stretching 
 eastward in a broad belt through central New York to the Hud- 
 son River. Northward, it spreads to Lake Ontario; and south- 
 ward, it stretches along the valley of the Hudson, bending in 
 southeastern New York conformably with the trend of the Appa- 
 lachians, which it follows as far as Georgia. Westward and
 
 382 GEOLOGICAL STUDIES. 
 
 northwestward from the Niagara River, the Silurian belt stretches 
 across Ontario to the headland separating Georgian Bay from 
 Lake Huron. It forms the southern and principal part of the 
 Manitoulin Islands, and borders the northern and western shores 
 of Lake Michigan, forming the cape which divides Green Bay 
 from Lake Michigan, and spreading southward beyond Chicago. 
 Green Bay is thus the counterpart of Georgian Bay. Each bay 
 is separated from its lake by a promontory of Niagara Limestone. 
 A belt of importance surrounds the Cambrian area whose centre 
 is at Cincinnati, and this extends northward to include Sandusky. 
 Other Silurian strata are exposed around the Nashville Cambrian, 
 especially on the west. Silurian rocks are known in Maine, and 
 other parts of New England; but in some parts, and in regions 
 farther toward the northeast, they have not yet been completely 
 discriminated from the Cambrian and Devonian. 
 
 Throughout the whole extent of the Silurian, the Niagara 
 Limestone is the great and salient feature. A little acquaintance 
 with the physical features of the country will enable one to trace 
 this formation by means of the quarries, ledges, and escarpments 
 which everywhere accompany it ; and when the place of this 
 limestone is known, it may be understood that the higher groups 
 lie on the side away from the older formations that is, Cam- 
 brian and Eozoic. 
 
 3. The Continent at the Beginning of Silurian Time. Dur- 
 ing the Cambrian Age there occurred in northeastern America a 
 succession of uplifts of the sea bottom; and in consequence new 
 belts of territory were added to the Great Northern Land repre- 
 sented in Fig. 297. Speaking generally, the areas on the geolog- 
 ical map shown as Cambrian rose above sea level during the 
 Cambrian Age, and at its close. As in the East, later geological 
 erosions have removed some portions of the original Cambrian 
 covering the Eozoic nuclei of the land, we represent the land at 
 the beginning of Silurian time as somewhat more extended than 
 the Eozoic and Cambrian surfaces on the Geological Map. 
 
 In the Cordilleran region, on the contrary, the close of the 
 Eozoic was marked by a subsidence of this entire continental
 
 FORMAT1ONAL GEOLOGY. 
 
 383 
 
 limb, for the Cambrian sediments are laid down over the whole 
 of the ancient eroded Eozoic surface, with numerous island-like 
 exceptions. The subsidence continued through the Cambrian, 
 but was greatest toward the west, where the Cambrian strata are 
 now thickest. The portion of the land which supplied the sedi- 
 ments was over western Nevada and the extreme eastern belt of 
 California. The great Cambrian ocean east of the Nevada land 
 was interrupted only by the rugged peaks of the ancient sunken 
 
 FIG. 304. -MAP OF NORTH AMERICA AT THE BEGINNING or THE SILURIAN AGE. 
 
 continent of the earlier ./Eon, some of which are shown on the 
 map, Fig. 304. Similarly the great Seaboard Land appears to 
 have begun a process of subsidence, through which it was over- 
 lapped to an unknown extent by Cambrian and later deposits. 
 
 In consequence of Cambrian elevations in the Northern Land 
 and Cambrian subsidences in the others, the Northern Land is now 
 enlarged on all its borders, and has a belt of Cambrian sediments 
 encircling it on the southern side, and probably to a limited 
 extent around the Hudson's Bay border also. But the Seaboard
 
 384 GEOLOGICAL STUDIES. 
 
 and Cordtlleran Lands having subsided at and since the close of 
 Eozoic time, neither presents as large an area as in the map, 
 Fig. 297. The Cordilleran Land, in fact, was reduced to an archi- 
 pelago at the beginning of the Cambrian Age, and remained such, 
 with even diminishing land areas, to the beginning of the Silurian 
 Age, as represented in map, Fig. 304. 
 
 It is scarcely necessary to say that these maps are merely 
 approximate and suggestive. Where land areas subside they 
 carry out of sight the visible evidences of subsidence; and where 
 they rise it is not always possible to ascertain whether elevation 
 attained was greater or less than the elevation existing at the 
 present time. Movements of the kind here indicated, however, 
 took place; and what is shown by these tentative maps of the 
 growing continent imparts general conceptions which are correct. 
 
 4. Silurian Rocks and Minerals. The Oneida Conglomerate 
 at the bottom properly exemplifies the beginning of a new cycle 
 of sedimentation (see page 268) ; and the progress of it is shown 
 in the succession of the Medina Sandstone. But these two forma- 
 tions cannot be traced westward beyond middle Ontario. The 
 West was too remote from the source of the sediments, which 
 was probably in the decaying Seaboard Land; and coarse mate- 
 rials are replaced by finer, mostly calcareous deposits. The argillo- 
 calcareous strata of the Clinton Stage are seen, however, on the 
 Manitoulin Islands, and farther west in Wisconsin and Indiana, 
 as well as in Ohio, Tennessee, and other regions always not far 
 removed from outcrops of Niagara Limestone. The Medina Sand- 
 stone is a hard, gritty, even-bedded, reddish, whitish, or mottled 
 rock, quite extensively quarried for building purposes, especially 
 in the vicinity of Lockport, N. Y. The Clinton formation em- 
 braces, westward, thick-bedded, fine-textured, aluminous lime- 
 stones, presenting a beautiful appearance, but too retentive of 
 moisture for outdoor architecture. By hard freezing the blocks 
 are shivered to fragments. It includes important beds of lentic- 
 ular iron ore in the lower part, from the Genesee River eastward, 
 and forms valuable deposits in Wisconsin, eastern Tennessee, 
 and Nova Scotia.
 
 FORMATIONAL GEOLOGY. 385 
 
 The Niagara Limestone is generally a light or dark gray, 
 heavy-bedded rock, having a semicrystalline texture. On Drum- 
 mond's Island, and all around the northern and western shore of 
 Lake Michigan, to Chicago, the principal beds are quite crystal- 
 line, but abound in small crystal-lined cavities, which impair its 
 value as a building stone. It is, however, extensively quarried 
 for building and for limemaking, a portion of the formation being 
 free from the defect just mentioned. Beds especially adapted 
 for building are found in western New York and at Joliet, La- 
 ment, and thereabouts in Illinois. The celebrated " Athens Mar- 
 ble," so called, is quarried near Joliet and Lament, and was before 
 the "great fire" a favorite building material in Chicago. It re- 
 mains in excellent repute at the present time. Niagara limestone 
 is extensively quarried at Huntington, Ind. In Chicago and that 
 vicinity some strata of the Niagara limestone are quite saturated 
 with petroleum, and many fruitless expenditures have been in- 
 curred in the attempt to collect this fluid in quantities of com- 
 mercial importance. (But see Part I, Study XXVII.) It is said 
 the first artesian wells of Chicago resulted from the ventures of 
 oil seekers ; though it is certain that geologists had already 
 asserted the practicability of procuring water, and the impossi- 
 bility of getting supplies of oil. 
 
 The Salina Group consists, in Central New York, of tender, 
 clayey marlites and fragile clayey sandstones of red, gray, green- 
 ish, yellowish, or mottled colors, constituting the lower half; and 
 above these, calcareous marlites and impure drab-colored lime- 
 stone, co.ntaining beds of gypsum, followed by hydraulic lime- 
 stone. A vein or bed of dark-green serpentine occurs in the 
 formation, in the city of Syracuse, on James street, and a few 
 rods to the south. The great feature of this group is the salt 
 aud gypsum which it affords. (For geology of Salt and Gypsum 
 see Part I, Study XXVI.) Rock salt is now known to have a 
 wide distribution through the Salina in southwestern New York, 
 Ontario, eastern Michigan, and western Michigan. At Marine 
 City, on the River St. Clair, it is found over 115 feet thick, at a 
 depth of 1,633 feet to 1,748 feet from the surface; and an enor-
 
 386 GEOLOGICAL STUDIES. 
 
 mous manufacture of salt has been established by first dissolving 
 the rock salt by forcing down clear water from the St. Glair 
 River, and afterward evaporating the brine by means of steam 
 pipes. Rock salt is also found of great thickness at Manistee, 
 Ludington, and Muskegon, on the west side of the state. Near 
 Goderich, Ontario, 126 feet of rock salt are found in 520 feet of 
 strata, down to a depth of 1,517 feet. In Ontario rock salt is 
 obtained at a depth somewhat over a thousand feet, at various 
 points stretching from Kincardine on Lake Huron, on the north, 
 to Dawn, near Lake St. Clair, on the south. In Western New 
 York rock salt has been found at depths generally a little over 
 1,000 feet at various localities in Wyoming, Livingston, Ontario, 
 Yates, Seneca, and Cayuga counties that is, from the centre of 
 Wyoming county eastward to Aurora, on Cayuga Lake. The 
 salt bed ranges from 70 to 85 feet in thickness. No rock salt has 
 been found by boring at Syracuse to the depth of 1,969 feet. 
 
 Gypsum, also, is quarried extensively in Cayuga county, New 
 York. It outcrops on the lake shore at Little Point au Chene, a 
 few miles west of Mackinac. The gypsum of Sandusky Bay, of 
 Cayuga, and Ontario, is of the same age. 
 
 The Helderberg Group originally Lower Helderberg con- 
 sists of a series of shales and shaly limestones and proper lime- 
 stones, developed especially in the Helderberg Mountains, but 
 extending westward, with diminished thickness, to Syracuse, 
 Buffalo, and western Ohio. It is known also in Indiana, southern 
 Illinois, and other Western States. The formation extends south- 
 ward along the Appalachians; and is known in Massachusetts, 
 New Hampshire, Maine, Nova Scotia, and New Brunswick. It 
 is famous for its production of hydraulic limestone, which sup- 
 plies the Buffalo Cement Works and numerous other establish- 
 ments in New York and Ohio. The formation also contains gyp- 
 sum. 
 
 5. Erosion Features. Beginning again at the Niagara River, 
 near its mouth, a high escarpment is found, which runs eastward 
 parallel with the shore of Lake Ontario. At Lockport the Erie 
 Canal crosses it, giving occasion for the "locks" which give
 
 FORMATIONAL GEOLOGY. 387 
 
 name to the city. At Rochester it is crossed by the Genesee 
 River at the "Falls." The great gorge of the Niagara River is 
 cut back through this escarpment for about seven miles. A fine 
 section of the Silurian strata may be seen along the walls of this 
 gorge, and they are shown in diagram in Fig. 305. This diagram 
 mostly explains itself. The lower part is supposed to be joined 
 on at the right hand extremity of the upper part. The student 
 will be able to trace the surface of the water from Lake Ontario 
 over the Falls and Lake Erie to Lake Michigan and Chicago. At 
 Cleveland is seen the high bluff on the south shore of Lake 
 Erie; and here is a break in the diagram, in consequence of 
 changes in the direction of the section, and in the direction of 
 the dip of the strata. Other features of the diagram will be 
 referred to in connection with post-glacial history. 
 
 The position of the Falls, now 150 feet high, indicates to 
 what extent the gorge has been excavated back from the escarp- 
 ment. We see the water precipitated perpendicularly over the 
 brink of the thick-bedded Niagara Limestone. The reaction 
 against the underlying shale results in its erosion. The limestone 
 thus undermined breaks off by piecemeal, and thus the Falls re- 
 cede at the rate of about three feet a year. Within thirty or 
 forty years the aspect of the Falls has changed materially. 
 Within the memory of a generation, "Table Rock," as shown in 
 the cut, Fig. 306, was a great curiosity and point of interest at 
 the Falls on the Canadian side. But it has fallen into the abyss. 
 Great encroachments have also been made on Goat Island. 
 
 6. Organic Remains. The life of the Silurian was, in gen- 
 eral, a continuation of the types of the Cambrian. The Silurian 
 genera and species of the Cambrian families showed the progress 
 of those changes which express slow organic advance. The forms 
 were less archaic, and less removed from the aspects of the mod- 
 ern world. Corals and Crinoids became more abundant. The 
 Favosites family was developed under multiplied generic and 
 specific forms. Some of these are illustrated in Figs. 144, 145, 
 146, 148, and 149. Rugose corals also underwent important ex- 
 pansion, but their fullest development was yet future. Cham-
 
 38 ft. above L. Bri 
 
 FIG. 305. DIAGRAM OF THE STRATA ALONG THE NIAGARA GORGE, SHOWING THE GBO- 
 LOGICAL POSITION op NIAGARA PALLS AND THE ANCIENT LEVELS op THE GREAT 
 LAKES.
 
 FORMATIONAL GEOLOGY. 
 
 389 
 
 bered Molluscs diminished in numbers and in size; but the coiled 
 genera became rather more abundant. Other classes of Molluscs 
 increased in relative numbers. Trilobites were shrunken in num- 
 bers and in bulk. One of them is represented in Figs. 229 and 
 230, and is to be contrasted with the Cambrian Trilobite, Fig. 
 228. The Silurian, however, witnessed the introduction of a type 
 entirely new. This was the important type of Vertebrates. 
 According to the established method of succession, they were 
 aquatic breathers; they were low in the Stem or Sub-Kingdom, 
 and were "comprehensive" forms, like all primitive types. Some 
 description of them has been given at pages 231235. Further 
 palaeontological details must be passed by. 
 
 FIG. 306. TABLE ROCK AT NIAGARA FALLS, AS IT WAS. 
 
 5. The Devonian System. 
 
 1. Divisions, Subdivisions, and Terms. 
 
 V. Catskill Group (12), Catskill Red Sandstone [may be Carbon- 
 iferous]. 
 IV. Chemung Group (11). 
 
 2. CHEMUNG STAGE (116), ) _. ~] S W 
 
 [ Erie Shale of Ohio, 
 1. PORTAGE STAGE (lla), ) 
 
 III. Hamilton Group (10). 
 
 3. GENESEE STAGE (lOc), Tennessee Black Shale. Huron Shale 
 
 of Ohio.
 
 390 GEOLOGICAL STUDIES. 
 
 2. HAMILTON STAGE (106). 
 
 1. MARCELLUS STAGE (10a), Marcellus Black Shale. 
 II. Corniferous Group (9). 
 
 3. CORNIFEROUS and ONONDAGA LIMESTONES (9c) (=" Upper Helder- 
 
 berg Group"). 
 
 2. SCHOHARIE GRIT (9&). 
 
 1. CAUDA-GALLI GRIT (9a). 
 I. Oriskany Group (8). Oriskany Sandstone. 
 
 By some the Oriskany is regarded rather as Silurian than 
 Devonian. Palaeontologically it has some affinities with Niagara 
 forms, and also some Devonian relations. The fauna is transi- 
 tional, as it should be. Lithologically, however, the formation is 
 plainly the beginning of a new geological era. 
 
 The Catskill, placed here at the top of the Devonian, in 
 deference to prevailing usage, may very likely prove to be the 
 basal group of the Carboniferous System. It is commonly re- 
 garded as representing the Old Red Sandstone of Scotland, 
 which is Devonian, according to most geologists. Some British 
 geologists, on the contrary, regard the upper beds of the Old 
 Red as Carboniferous; and this is strongly evinced at Dura Den 
 and Arran. If they are so, and the Catskill finds its equivalents 
 in them as the fossils indicate the Catskill becomes Carbon- 
 iferous, and holds exactly the horizon of the Waverly (as qualified 
 by the late Ohio survey) and Marshall of the West, which, on 
 independent palaeontological grounds, may perhaps be parallel- 
 ized with the Catskill. 
 
 The geographical terms here employed are derived from 
 localities in the State of New York. "Corniferous" comes from 
 cornu, a horn, in allusion to the amount of "hornstone" con- 
 tained; or, perhaps, in allusion to the horn-shaped cup corals 
 which abound. " Cauda-galli," signifying cock's tail, refers to a 
 peculiar fucoid which the formation contains. 
 
 2. Distribution and Lithological Features. The Oriskany 
 Sandstone is mostly a purely silicious, friable, rough-looking rock, 
 but is a somewhat inconspicuous formation, although it accompa- 
 nies the other Devonian strata along the Appalachians, and into 
 Ohio, Indiana, and Missouri, and attains a thickness of 250 to
 
 FORMATIONAL GEOLOGY. 391 
 
 300 feet in southern Illinois. A formation commonly known 
 throughout the West as the "Black Shale" a black, bitumin- 
 ous, argillaceous shale is a very persistent and characteristic 
 part of the Hamilton Group. Without much doubt, it is the 
 equivalent of the Genesee Shale of New York. The Marcellus 
 Shale is a very similar formation, with some interstratified lime- 
 stones, and extends as far west as the Detroit River, and perhaps 
 into Ohio. The rocks of the Chemung Group are a bulky and 
 conspicuous mass of greenish, yellowish, and buffish shaly sand- 
 stones and variously colored shales, becoming in Ohio and Michi- 
 gan essentially a series of clays and argillaceous shales. They 
 represent, therefore, a continuation of the shaly conditions begun 
 with the Genesee Shale, and constitute with that formation a 
 stratigraphical series which is physically a unit, and, therefore, in 
 Michigan was designated the "Huron Group." The Chemung 
 rocks (including the Portage) have a very large development in 
 southern New York and Pennsylvania, but are deficient soutli 
 and west of the Ohio. 
 
 The most conspicuous and most persistent lithological feat- 
 ure of the Devonian is the great central calcareous mass. This 
 is made up primarily of the united Onondaga and Corniferous 
 limestones; but in Ohio, Michigan, and other western states, as 
 far as Iowa, the Hamilton formation, predominantly argillaceous 
 in New York and Ontario, becomes predominantly calcareous; 
 and since the Marcellus Shale is generally wanting in the West, 
 the Hamilton and Corniferous limestones unite in one great cal- 
 careous formation. In Ohio and Indiana the formations between 
 the Corniferous and Niagara limestones are also wanting; so that 
 the Hamilton, Corniferous, and Niagara limestones are all brought 
 together, forming what the older writers termed the " Cliff Lime- 
 stone" (Fig. 307). The separation of all these is now easily 
 effected by means of their fossils. 
 
 The great limestone mass of the Devonian forms a conspicu- 
 ous feature in the landscape, traceable by a line of quarries and 
 ledges all the way from central New York to Iowa. Its position 
 is not far from the centre of the belt marked as Devonian on the
 
 392 
 
 GEOLOGICAL STUDIES. 
 
 Geological Map; but west of Ohio the limestones make up the 
 principal part of this belt. 
 
 The economical products of the Corniferous are materials for 
 quicklime and for building purposes. For the latter it is much 
 employed in central and western New York, and in northern 
 Ohio and Ontario. Large accumulations of petroleum are found 
 in the crevices and caverns of the Hamilton Limestone in Ontario. 
 The Corniferous Limestone is very often found saturated with 
 dark petroleum, but no permanent supplies of importance have 
 been obtained from it. The most considerable yields have been 
 found at Tilsonburg, Ont., and Terre Haute, Ind. Petroleum 
 also accumulates abundantly in the Chemung sandstones of 
 southern New York and western Pennsylvania. (See Part I, 
 Study XXIX.) For building purposes these sandstones possess, 
 generally, insufficient coherence. Beds probably the equivalent 
 of the Chemung constitute the "Kidney Iron Formation" of 
 Branch County, Michigan. 
 
 KTEW YOKK 
 
 OHIO 
 
 FIG. 307. CONSTITUTION OP THE "CLIFF LIMESTONE" OF OHIO. 
 
 3. Erosion Features. The Corniferous Limestone has been 
 the theatre of great erosion along the course of certain rivers, 
 and around the shores of the Great Lakes. In central New 
 York many deep valleys like that of Onondaga Creek, south of 
 Syracuse, have been excavated in the Corniferous and Onondaga 
 formations. In the vicinity of the Straits of Mackinac the Cor- 
 niferous limestone has been eroded on a grand scale. A lofty
 
 FORMATIOXAL GEOLOGY. 
 
 barrier once separating the basins of Lake Huron and Lake 
 Michigan has been cut through. Tn the midst of the passage 
 rises the Island of Mackinac to the height of 350 feet. On three 
 sides the island is bounded by precipitous walls about 150 feet 
 high. On the west, on the Upper Peninsula of Michigan, is a 
 headland known as Rabbit's Back, which is the continuation of 
 the limestone of Mackinac Island. On the south, the main land 
 of the Lower Peninsula presents a similar but less elevated prom- 
 ontory, and the exposure of the formation stretches toward the 
 east and the west. The whole 
 island is manifestly a relic and 
 memorial of the destructive pow- 
 er of the elements. The waves 
 have beaten its precipitous walls, 
 and wasted them away at un- 
 equal rates. Fissures, purgato- 
 ries, and caverns have been 
 opened at different stages in the 
 height of the waters. In one place, a veritable natural bridge 
 stands swung at an elevation too high 
 for the eroding agent to reach (Fig. 
 309). On the main plateau of the isl- 
 and rises Sugar Loaf (Fig. 310) 134 feet 
 above the 
 plain. The 
 pinnacle of 
 the island was. 
 the site of Old 
 Fort Holmes. 
 (Compare also- 
 Fig. 305.) 
 
 The axis of 
 
 PIG. 310. Lake Huron 
 
 FIG. 308. 
 
 SECTION SOUTHEAST AND NORTHWEST 
 THROUGH MACKINAC ISLAND, a. Old 
 Fort Holmes; b, Sugar Loaf; c, Robin- 
 Folly; d, Rabbit's Back, on the Upper 
 Peninsula; , Round Island: f. Conglom- 
 eritic stratum; m, surface of the lake. 
 
 FIG. 309. 
 'ARCHED ROCK,'' MACKINAC ISL- 
 AND. Corniferous Limestone. 
 
 'SUGAR LOAF," MACKINAC ISL- crosses diago- 
 AND. Corniferous Limestone. 
 
 of the Corniferous limestones. 
 
 nally the trend 
 The lake shores present many
 
 394 GEOLOGICAL STUDIES. 
 
 cases of bold erosion. Off Thunder Bay Island, in fair weather, 
 one may look down a subaqueous cliff ninety or one hundred 
 feet, into a dark abyss of water. Near Louisville was once a 
 fall in the Ohio River, over a ledge of Corniferous limestone. 
 The retreat of these "Falls" has reduced them to mere rapids; 
 but they still present a fine example of erosion. Other instruct- 
 ive examples may be seen on the Mississippi River at Rock 
 Island, and at the head of Little Traverse Bay of Lake Michi- 
 gan. 
 
 4. Organic Remains. In the invertebrate realm we find the 
 coral type exceedingly augmented during the Devonian. Great 
 coral reefs appear to have been built up somewhat as in modern 
 times. One of these is exposed at the " Falls of the Ohio." 
 This has been a favorite collecting ground for more than a gen- 
 eration. Here abound corals of the types of the Rugosa and 
 Tabulata, the study of which was explained in Part I, Studies 
 XXX-XXXIL A similar reef exists at the head of Little Trav- 
 erse Bay, near Petoskey. Here the type of Stromatoporidce 
 undergoes a remarkable development; and this is repeated in the 
 same formation on the opposite side of the state, at Thunder 
 Bay, and the vicinity. Stromatoporidce make up a large part of 
 the reef-like masses forming 1 the Hamilton limestone of these 
 regions. This interesting type seems to have attained its culmi- 
 nation in the Hamilton and Corniferous periods. We have 
 devoted some space to its exposition and illustration in the last 
 chapter. See Figs. 223-7. 
 
 Examples of Devonian corals are shown in Figs. 130-143; 
 also 147-158. 
 
 Some characteristic Devonian Brachiopods are seen in Figs. 
 161, 162, 165, 166, 168, 170, 172, 174, 177, 179, 180, 184. 
 
 Some characteristic Devonian Fishes are illustrated in Figs. 
 -241-247. 
 
 A majority of the fossils furnished by the Drift of the north- 
 western states are of Devonian age.
 
 FOKMATIONAL GEOLOGY. 395 
 
 6. The Lower Carboniferous System. 
 
 1. Divisions, Subdivisions, and Terms. 
 
 II. Carboniferous Limestone, or Mississippi River Group (13). 
 Mountain Limestone. 
 
 4. CHESTER STAGE (13d). (2) Kaskaskia, or Upper Archimedes Lime- 
 stone; (1) Pentremital Limestone. 
 
 3. ST. Louis STAGE (13c). St. Louis Limestone. Part of Silicious 
 Group, Tenn. 
 
 2. KEOKUK STAGE (136). Keokuk Limestone. Part of Silicious Group, 
 Tenn. 
 
 1. BURLINGTON STAGE (13o). Burlington Limestone (?)=" Michigan 
 Salt Group." 
 
 I. Marshall, or Waverly Group (12). "Kinderhook Group," of 111.; 
 "Yellow Sandstones," of Iowa; " Chouteau " and "Lithograph- 
 ic" Limestones, of Mo.; "Goniatite Limestone," of Rockford, 
 Jnd. ; " Silicious Group " (lowest beds), Tenn. As before stated, 
 the Group may be the western equivalent of the prior-named 
 "Catskill." 
 
 The Lower Carboniferous Series is frequently designated 
 "Sub-Carboniferous"; but as this term necessarily signifies 
 " under the Carboniferous," it is etymologically inadmissible, 
 since the Series is universally recognized as a part of the Carbon- 
 iferous. The term Carboniferous signifies coal-bearing; in fact, 
 however, the great coal-bearing strata in many parts of the world 
 are Mesozoic, or even Ca?nozoic. 
 
 The numerous local designations of the lower Group origi- 
 nated in the fact that for years these rocks, in Ohio, Iowa, Mis- 
 souri, and Michigan, -were regarded as the western equivalent of 
 the Chemung; until, in some regions, they were seen to be so 
 clearly Carboniferous that more thorough examinations were 
 instituted. During the discussion, the formation in each state 
 not yet known to be the same formation received a local desig- 
 nation. 
 
 The great limestone formation of the Lower Carboniferous 
 Series may appropriately be designated the Carboniferous Lime- 
 stone, since in the whole Carboniferous System it is by far the 
 most important and most persistent limestone mass. In the
 
 396 GEOLOGICAL STUDIES. 
 
 United States, it underlies chiefly the great valley of the middle 
 Mississippi; and hence the present writer once suggested for it 
 the " Mississippi River Group." In many parts of Europe it 
 enters into the formation of mountains, and is commonly known 
 as the Mountain Limestone. 
 
 2. Distribution and Lithological Features. The Marshall, 
 or Waverly Group, consists in Michigan and Ohio of rusty, or 
 yellowish, mostly friable, sandstones, becoming, in the lower 
 beds, grayish or bluish, and at bottom, decidedly argillaceous. 
 Locally, some of the beds are quite calcareous and finely cement- 
 ed. In Michigan, the formation outcrops at intervals in a broad 
 belt passing through the central southern counties, and extend- 
 ing northwest into Ottawa county, and northeast to the lake 
 shore (Point aux Barques), in Huron county. In Ohio it stretches 
 from the lake shore, in the vicinity of Cleveland, southward 
 across the state to Waverly and the Ohio River. In eastern 
 Iowa the formation is yellowish or buffish, friable, and in the 
 lower part, argillaceous. In Missouri it is mostly argillo-calca- 
 reous. In southern Illinois, Kentucky, and Tennessee, it is in 
 part a dark, laminated, silicious shale. 
 
 Some of the purely arenaceous beds afford superior gritstones, 
 of which the Berea (Ohio) and Huron (Mich.) grindstones are 
 examples. They are equally in request for building and flagging 
 purposes. The famous bluestone, or freestone, of Cleveland 
 and vicinity, and regions southward to Waverly, belongs here. 
 The fine Nova Scotia freestone is probably of the same age. 
 
 The Carboniferous Limestone Group is almost exclusively 
 calcareous. The St. Louis member, however, is apt to be cherty, 
 especially in Kentucky and Tennessee, where it forms the most 
 characteristic part of the "Silicious Group" of Safford. This 
 cherty limestone is spread out over a large area through central 
 Kentucky, and thence into Tennessee. It forms the rugged 
 " Knob Region " of those states. In Michigan, the limestone is 
 of the St. Louis and Keokuk subdivisions; in southern Ohio it is 
 the Chester and St. Louis. In Michigan, however, is a member 
 of the series underneath the limestone, which is argillaceous, with
 
 FOUMATIONAL GEOLOGY. 
 
 397 
 
 thin intercalated calcareous sheets, and heavy, persistent beds of 
 beautiful gypsum, quarried very extensively near Grand Rapids, 
 and also on the opposite side of the state, near Tawas Bay, at 
 Alabaster. This is the "Michigan Salt Group." It is probably 
 of the same age as the gypsum beds of New Brunswick, which, 
 like the Michigan gypsum, belong to the upper group of the 
 Lower Carboniferous. 
 
 The succession and conformability of the Lower Carbonifer- 
 ous strata are shown in the instructive 
 bluff at Burlington, Iowa, a section of 
 which is shown in Fig. 311. In spite 
 of the complete conformability of the 
 upper and lower strata, the distinct- 
 ness of the two groups is evinced by 
 the strong contrast in the organic 
 remains. 
 
 Limestones of Carboniferous age 
 occur at many points throughout the 
 remote West; but in many cases they 
 belong to the Upper Carboniferous; 
 in other cases, their precise age has 
 not been ascertained. Limestones of 
 the Lower Carboniferous have been 
 identified in the Elk Mountains of 
 western Colorado ; the Wind River 
 Mountains of Wyoming; at Old Baldy, 
 Montana, near Virginia City (Chester 
 Limestone); at Fort Hall, Idaho (St. 
 Louis Limestone); in the Wahsatch 
 and Oquirrh ranges, Utah (St. Louis 
 Limestone), and in the Eureka district F IG . 311. SECTION or THE BLUFF 
 of Nevada, where the Diamond Peak AT BURLINGTON, IOWA. LOWER 
 ... . i i T> i CARBONIFEROUS ROCKS. (C. A. 
 
 Quartzite is 3,000 feet thick, i roba- White .) i to 6, "Yellow Sand- 
 bly some of the western exposures stones"; 7 to 8, Carboniferous 
 
 i * Ail L 11 n Limestone; 9, Drift; R, Mean 
 
 embrace strata of the Marshall Group. He5ghtof the Rivcr . ^ Divislon 
 
 Carboniferous limestone occurs, also, between the two Groups.
 
 398 GEOLOGICAL STUDIES. 
 
 in the Gray Mountains, California, near Ross' Ranch, 1,000 feet 
 thick (? St. Louis), and at Pence's Ranch, eighty miles south, 
 according to Whitney. 
 
 The distribution of the calcareous and fragmental materials of 
 the Lower Carboniferous illustrates the principle heretofore 
 explained, that, with increase of distance from the source of the 
 sediments, the depositions become less fragmental, and more 
 calcareous. The Carboniferous Limestones which, in southwest- 
 ern Illinois, are 1,000 to 1,300 feet thick, become attenuated, 
 eastward, to ten or twenty feet in southeastern central Ohio; 
 while in the Appalachian region, 3,000 feet of soft reddish shales 
 and sandstones (the Umbral Series) occupy the horizon of the 
 Mississippi limestones. On the contrary, the Marshall, or frag- 
 mental group, which is 100 to 200 feet thick in Illinois, and 640 
 feet in Ohio, is represented in the Appalachians by 2,000 feet of 
 coarse, grayish conglomerates and sandstones (the Vespertine 
 Series), passing down into red sandstone, commonly regarded as 
 of Catskill age. Locally, however, this lower group contains 
 from eighty to eight hundred feet of limestone. 
 
 At many places in Pennsylvania and Virginia, the Vespertine 
 Series contains beds of coal, one of which is two to two and a 
 half feet thick, succeeded in Montgomery county, Virginia, at 
 the distance of thirty to forty miles, by another bed six to nine 
 feet thick, consisting of alternations of coal and slate. These 
 deposits are sometimes called False Coal Measures, Lower 
 Carboniferous coal beds occur also in Great Britain. 
 
 In Nova Scotia and New Brunswick, the Lower Carboniferous 
 consists, also, of two epochs. The lower, or Horton Series, is 
 made up of red sandstones, conglomerates, and red and green 
 marlites, intercalated with thin seams of coal. The Albertite 
 (page 68) of the Albert mine is contained in a fissure in this series 
 in New Brunswick. This fragmental group is chiefly developed 
 northward in the vicinity of the Eozoic formations which supplied 
 the sediments. The upper series, called the Windsor Series, is 
 developed chiefly southward, and as might be expected, consists
 
 FOKMATIOXAL GEOLOGY. 
 
 399 
 
 mostly of limestones and marlites, but contains, also, extensive 
 beds of gypsum. 
 
 3. Geography of the Continent During the I,ower Carbon- 
 iferous Age. The distribution of the sediments of the Lower 
 Carboniferous shows that the Mississippi Valley was the site of a 
 great interior ocean, which opened freely southward, but on the 
 east was bounded by the great Seaboard Land which had first 
 risen during or at the end of the Eozoic ^Eon, and which was 
 
 FIG. 312. NORTH AMERICA, NEAR THE BEGINNING OF THE CARBONIFEROUS AGE. 
 
 bordered on the west by a belt of shallow sea, occupying the 
 position in which the Appalachian chain was destined to be 
 uplifted in a future age. This border was the theater of active 
 fragmental deposition. The materials were derived from the 
 wastage of the contiguous Seaboard Land, and perhaps a conti- 
 nental shore lying farther toward the northeast. The slow sink- 
 ing of the sea bottom (perhaps accompanied by a sinking of the 
 Seaboard Land) caused the accumulations to proceed to the 
 extent revealed in the heavy beds of the Umbral and Vespertine
 
 400 GEOLOGICAL STUDIES. 
 
 series of eastern Pennsylvania. The remote interior was, mean- 
 while, the scene of crinoidal life and calcareous depositions. In 
 the Mississippi valley, the fine arenaceous beds of the Marshall 
 Group, resting on the Devonian, stretch toward northern Iowa. 
 The northern limits of the overlying Burlington Limestone are 
 200 miles more southward, and the northern borders of the other 
 divisions of the Carboniferous Limestone are fixed successively 
 more to the south. This shows a gradual southward encroach- 
 ment of the land. During the St. Louis epoch there was a tem- 
 porary subsidence, but, as a rule, the higher members of the 
 Group are southern in position, while the lower are northern. 
 
 In the midst of this interior ocean the groat Cincinnati swell 
 rose as a peninsula, stretching southward from the Michigan 
 border, at which it bifurcated, sending one branch toward Onta- 
 rio and New York, and the other toward Wisconsin in each 
 case to join the mainland. The greater part of the Michigan 
 peninsula was an inland salt sea, like the modern Euxine, in 
 which geological history proceeded somewhat independently, but 
 yet under the same terrestrial conditions as determined the gen- 
 eral tenor of physical and organic progress. 
 
 The Cordilleran region, which was a broad, mountainous belt 
 at the end of the Eozoic, and then subsided to receive the sedi- 
 ments of the Cambrian and Silurian, continued to sink during 
 Devonian and Carboniferous time. The source of the sediments 
 was the Nevada land; and the greatest subsidence was westward. 
 The whole Palaeozoic series attains, according to King, a thick- 
 ness of 1,000 feet in the eastern part of the Cordilleran region, 
 32,000 feet in the Wahsatch region, and 40,000 feet at the extreme 
 western Pakeozoic limit, longitude 117 30'. At the close of the 
 Palaeozoic, the uppermost sheet of the Carboniferous, extending 
 from the Nevada Palaeozoic shore eastward to the Great Plains, 
 was only interrupted by a few island-like granite peaks, which 
 were above the level of deposition the great mass of Eozoic 
 topography having bv that time been completely buried. Tongues 
 and belts of these Carboniferous strata stretched west of the 
 main Nevada shore, as indicated by the positions of gulfs and
 
 FORMATIONAL GEOLOGY. 401 
 
 bays then penetrating even into the limits of the present states 
 of California and Oregon. 
 
 4. Erosion Features. Like all limestones, the Carboniferous 
 limestone has suffered greatly through the agencies of solution 
 and erosion. The silicious or cherty nature of the Warsaw and 
 St. Louis divisions has caused very unequal weathering, and 
 hence a very rugged aspect in the landscape of the so called 
 " Knobs." The St. Louis division is especially abundant in 
 caverns in Indiana, Kentucky, and Tennessee. These may be 
 regarded as dating back to the beginning of the Mesozoic ^Eon. 
 Whatever fissures mav have been produced by movements of the 
 earth's crust, have been continually enlarged in later times by 
 percolating waters. The Mammoth Cave, a plan of which has 
 been given in Fig. 209, is probably the greatest result known of 
 cave-making agencies. 
 
 Many of these caves have contained extensive deposits of 
 various salts, especially of a lime saltpetre, or nitrocalcite. The 
 great limestone formation in the Cumberland Table Land contains 
 hundreds of "nitre caves," which, in the early part of the present 
 century, especially in 1812-1814, were industriously worked for 
 nitrocalcite for the manufacture of nitre. 
 
 5. Organic Remains. The organic remains of the Lower 
 Carboniferous indicate a fauna that differed in important particu- 
 lars from that of the Devonian. The type of corals was less 
 luxuriant, both in respect to the tribes of Cup Corals (Tetraco- 
 ralla) and those of Tabulate Corals (Hexacoralla), but especially 
 the latter. The compound cup coral, Lithostrotion, however, is 
 a common and characteristic species of the widely spread St. 
 Louis Limestone; and simple cup corals, indeed, remained in con- 
 spicuous abundance. But the crinoidal type expanded to a 
 splendid culmination (see description, page 324). The limestone 
 of the upper part of the bluff at Burlington, Iowa (Fig. 311), is 
 in some of its beds composed chiefly of the broken stems and 
 the calices of crinoids. This locality is classical ground for the 
 paleontologist. Mr. Charles Wachsmuth has collected here 355 
 species belonging to 44 genera. Crawfordsville, Ind., is another
 
 402 GEOLOGICAL STUDIES. 
 
 productive locality. The state of preservation of the crinoids is 
 even better than at Burlington, the rock being an argillaceous 
 shale; but the number of species does not exceed 100, according 
 to Professor D. A. Bassett, who states that several thousand speci- 
 mens have been removed. The principal genera are Actinoc'- 
 rinus, Baryc' rimis, Cyathoc' rimts, Dichoc' rinus, Forbesioc'- 
 rinus, Goniasteroidoc' 'riniis, Onychoc' rinus, Platyc'rinus, Scaph- 
 oc'rinus, and Taxoc'rhms (Bassett). The beds here are of Keo- 
 kuk Limestone. The higher divisions, also, from southern Illinois 
 to northern Alabama and the Cumberland Table Land, are gener- 
 ally well stocked with the .remains of crinoidal life. Fig. 234 
 gives a view of a crinoid from the Waverly group of Ohio 
 the epoch of the great expansion of the type under its specially 
 Carboniferous aspect. 
 
 Straight chambered shells were still in process of disappear- 
 ance; but the coiled Goniatites and Nautili were very abundant 
 (see page 326); and Lamellibranchs were increasing in numbers 
 and diversification especially in the earlier periods. Brachio- 
 pods were on the decline. The old genera, /Strophomena, Leptcena, 
 Orthis, and others, were near extinction. Spirifera was repre- 
 sented in numerous species, many of large size, and Syringot h' - 
 yris made its advent into America and Europe. Producta and 
 Chonetes were characteristically abundant. The last of the 
 Trilobites now lived, greatly dwarfed in bulk; but higher Crusta- 
 ceans were taking their place. Fishes were in the high career 
 of advancement; but none belonged yet to the modern type of 
 Teleosts. They were either Ganoids or Selachians; and of the 
 latter, the Cestraciont type was peculiarly prominent. The forms 
 of life here mentioned should be again studied on pages 331-335. 
 
 7. The Upper Carboniferous System. 
 
 1. Divisions, Subdivisions, and Terms. 
 II. Permian Group. 
 I. Coal Measures. 
 2. UPPER COAL MEASURES. 
 
 ( "Lower Coal Measures" of Rogers. 
 1. LOWER COAL MEASFRKS. J 
 
 I Conglomerate Measures.
 
 FORMATIONAL GEOLOGY. 403 
 
 The term Permian is derived from the province of Perm, in 
 Russia, in which a group of strata of this age was described as a 
 " System." It consists, in Europe, of two principal divisions, 
 and hence is often called the "Dyas." 
 
 The details of the stratification of the Coal Measures are not 
 identical at remote points; but a general correspondence exists 
 through western Pennsylvania and Ohio, from which a standard 
 series of formations has been drawn up, as shown below. For 
 the parallelisms of the Ohio coals I depend on Orton's recent and 
 important Report. In Indiana, western Kentucky, and Illinois 
 only a more general correspondence has been traced. In regions 
 still more remote the correspondence is reduced to the existence 
 of a series of shales, sandstones, coal beds, occasional limestones, 
 and one or more considerable conglomerates at or toward the 
 bottom of the series. 
 
 Standard Section of the Coal Measures, Specially Suited to 
 Western Pennsylvania and Eastern Ohio. 
 
 UPPER COAL MEASURES. THICKNESS, 1,700 FEET. 
 
 V. Upper Barren Measures of Rogers, 974 ft., containing 
 6 coal beds, 8 ft., and having at bottom, 
 
 46. Waynesburg Sandstone. 
 IV. Upper Coal Measures of Rogei's = Monongahela Series. 
 
 45. Waynesburg Coal, 6 ft. (I), XXI. 
 
 44. Pittsburgh Sandstone, Shales, and Limestones. 
 
 43. Pittsburgh Coal, 8 ft. (H), Cumberland, Md., Pomeroy 
 
 Bed, Ohio, Primrose bed of Anthracite. XX. 
 
 III. Lower Barren Measures of Rogers = Pittsburgh Series. 
 
 42. Upper Pittsburgh Limestone, 2 ft. 
 
 41. Lower Pittsburgh Limestone, 5 ft. 
 
 40. Morgantown Sandstone, 45 feet = 1st "Oil Sand," Dunk- 
 ard's Creek. 
 
 39. Elk Lick Coal, 3 ft. (F?) (G?), XIX. 
 
 38. Elk Lick Limestone, 2 ft., 
 
 37. Berlin Coal, 3 ft. (F?). XVIII. 
 
 36. Green Crinoidal or Berlin Limestone, 2 ft. 
 
 35. Platt ? Coal, H ft., XVII. 
 
 34. Price Coal, XVI.
 
 404 GEOLOGICAL STUDIES. 
 
 33. Bakerstown Coal, 2| to 4 ft., XV. 
 
 32. Pine Creek Limestone, 2 ft. 
 
 31. Buffalo Sandstone = Upper Mahoning S. 
 
 30. Brush Creek Limestone. 
 
 29. Brush Creek Coal, XIV. 
 
 28. Mahoning Sandstone, 40 to 80 ft., and Shale 50 ft. Lower 
 Mahoning. ? Anvil Rock S.; Kurlew S., Ky.= 2d "Oil 
 Sand," Dunkard's Creek the principal reservoir. A 
 "gas rock." 
 
 LOWER COAL MEASURES. THICKNESS, 642 FEET. 
 
 II. Lower Coal Measures of Rogers. Thickness, 392 ft. = 
 
 Allegheny Series. 
 FREEPORT GROUP. 
 
 27. Upper Freeport Coal, 4 ft. (E), Muskingum County and 
 
 Valley. " Mammoth Bed " of Anthracite, XIII. 
 
 26. Upper Freeport Limestone, 3 ft. White L., Ohio. 
 
 25. Upper Freeport Sandstone, 30 ft. Butler S. 
 
 24. Lower Freeport Coal, 2 ft. (D). Unreliable in Pennsyl- 
 vania, XII. 
 
 23. Lower Freeport Limestone, 2| ft. Butler L. 
 
 22. Lower Freeport Sandstone and Shale, 75 ft. Freeport S. 
 KITTANNING GROUP. 
 
 21. Upper Kittanning: Coal, 14 to 3 ft. (C'). Blacksmith 
 
 Vein, XI. 
 
 20. Middle Kittanning Coal, 3 to 6 feet. Little known in 
 Pennsylvania. Coshocton, Ohio; Great Vein of Hocking 
 Valley, Ohio, X. 
 
 19. Lower Kittanning Coal, 24. ft. (C). "Kittanning" of 
 
 Rogers, IX. 
 
 18. Kittanning Clay, 10 ft. New Brighton Fire Clay. 
 
 17. Kittanning Sandstone, 42 ft. Lower Kittanning S. ; Indus- 
 try S, Ohio. 
 CLARION GROUP. 
 
 16. Ferriferous Limestone and Buhrstone Ore, 1 to 15 and 20 ft. 
 
 15. Upper Clarion Coal, 2 ft. Scrubgrass; Canfield Cannel, VIII. 
 
 14. Lower Clarion Coal, H ft- (B). Clarion Coal, VII. 
 
 13. Putnam Hill Limestone. Not in Pennsylvania. 
 
 12. Brookville Coal, 2 ft. (A). Mahoning Valley Coal. VI. 
 
 I. Conglomerate Measures. Thickness in Ohio, 250 ft. = 
 Serai Conglomerate of Rogers (No. XI) = Sharon Coal 
 Series of Hodge = Pottsville Conglomerate.
 
 FORMATIONAL GEOLOGY. 405 
 
 BEAVER RIVER GROUP. 
 
 11. Homewood Sandstone, 75 to 155 ft. Serai Conglomerate. 
 Tops of Pottsville Conglomerate; Piedmont Sandstone; 
 Tionesta Sandstone ; Upper Homewood Sandstone. 
 10. Tionesta Coal, 3 ft., V. 
 
 9. Upper Mercer Limestone and Ore, 2-J- ft. Mahoning Lime 
 stone. 
 
 8. Upper Mercer Coal, 2 to 5 ft., IV. 
 
 7. Lower Mercer Limestone and Ore, 2| ft. Mercer Limestone; 
 Zoar L. 
 
 6. Lower Mercer Coal, 2i to 3 ft. Lower Porter of Rogers, III. 
 
 5. Conoquenessing Sandstone (Upper), 45 ft. Lower Potts- 
 ville Conglomerate; Lower Homewood Sandstone; Mas- 
 silon Sandstone (part) in Ohio = 1st " Mountain Sand." 
 
 4. Quakertown Coal, 3 ft. (and Shales), II. 
 
 3. Conoquenessing Sandstone (Lower), 25 ft. Massilon Sand- 
 stone (part). 
 
 2. Sharon Coal (and Shales), 4 to 6 ft. Block Coal of Ma- 
 honing Valley; Brier Hill Coal; Massilon Coal, I. 
 
 1. Sharon Conglomerate, 30 feet. In Pennsylvania, Garland 
 Conglomerate and Olean Conglomerate. In Ohio, Ohio 
 Conglomerate part or all =2d "Mountain Sand." 
 
 This series is followed downward, in Pennsylvania, by the 
 " Shenango Sandstone" or "Ferriferous Fish Bed," ( = Sub- 
 Garland = Sub-Olean) and the Meadville Upper and Lower Lime- 
 stones, belonging to the Lower Carboniferous. 
 
 Most of the standard terms in the foregoing table are from 
 Pennsylvania Geology. The capital letters in parentheses, fol- 
 lowing the names of coal seams, were applied by Lesley to the 
 Pennsylvania series above the Serai Conglomerate. Serial num- 
 bers for the entire Coal Measures, based on the latest determina- 
 tions of the Pennsylvania and Ohio Surveys, here follow the 
 names of the coal beds in Roman capitals. 
 
 It has generally been considered that the Coal Measures 
 proper consisted of the formations above what is here designated 
 Conglomerate Measures; and that the "Conglomerate" or " Mill- 
 stone Grit " of the English formed a natural boundary. But it 
 is found that the supposed basal Conglomerate lacks the uni- 
 formity and persistence and constancy of stratigraphical position
 
 406 GEOLOGICAL STUDIES. 
 
 once assumed; and that the system of coal beds, even including 
 limestones, continues below the conglomerate horizon, giving, 
 along the Appalachian belt, some of the thickest and best de- 
 posits sometimes known as " False Coal Measures." It is found, 
 also, that the only coal of Arkansas is subconglomerate. In Ten- 
 nessee the Sevvanee coal bed is 230 feet below the Conglomerate, 
 and 371 feet above the Carboniferous Limestone. For such rea- 
 sons geologists (Lesley, .1. J. Stevenson, Orton) incline to treat 
 as one group the entire series of strata, both above and below 
 the " Conglomerate." 
 
 The " Conglomerate," being an ambiguous term, was replaced, 
 in 1860, by the present writer, with the geographical designation 
 " Parma Conglomerate." Subsequently, for similar reasons, it 
 received, in Canada, the name Buenaventure Conglomerate. 
 
 The student will understand that the Table does not enumer- 
 ate the complete sequence of strata, but only the salient forma- 
 tions, which possess economic or stratigraphical importance, and 
 serve as landmarks in the grand succession of deposits. 
 
 2. Distribution. The coal-producing Coal Measures are con- 
 fined, in America, to the region east of the Rocky Mountains. 
 The locations of the various coal fields will be learned from the 
 Geological Map : (1) The Appalachian Coal Field, having a 
 length of 875 miles, and a breadth ranging from 30 to 180 miles, 
 with an area of 59,000 square miles. (2) The Eastern Interior, 
 or that of Illinois, Indiana, and northwestern Kentucky, 47,000 
 square miles. (3) The Western Interior, or that of Iowa, Mis- 
 souri, Kansas, Arkansas, and Indian Territory, 18,000 square 
 miles. (4) The Michigan, 6,700 square miles. (5) The Rhode 
 Island, 500 "square miles. (6) The Acadian, or that of Nova 
 Scotia and New Brunswick, 18,000 square miles. 
 
 In the Rocky Mountains and beyond, Coal Measure limestones 
 are known to occur in Montana, Wyoming, Colorado, Utah, 
 Nevada, and California; but all the coal west of Omaha to the 
 Pacific coast is Mesozoic or Caenozoic. 
 
 The accompanying Coal map of Pennsylvania and Ohio diows 
 the interrupted attenuations of the six Pennsylvania bituminous
 
 FORMATIOXAL GEOLOGY. 
 
 407 
 
 basins, and indicates the distribution of the anthracite coal of 
 eastern Pennsylvania. Their names are as follows: (1) Southern 
 or Schuylkill Basin and Mine Hill, 146 square miles; (2) Shamo- 
 kin (50), Mahonoy (41), and Lehigh (37) Basins, 128 square 
 miles; (3) Wyoming and Lackawana Basin, 198 square miles. 
 Total anthracite area, 472 square miles. The conglomerates of 
 the lower portion of the Coal Measures generally extend, as in 
 northeastern Ohio, considerably beyond the areas covered by the 
 coal beds. They often lie in huge cuboidal blocks dislocated 
 
 , 313. COAL MAP OF PENNSYLVANIA AND OHIO. Coal Areas in 
 Black. Dotted line shows northern limit of the basal Conglomerate 
 in Ohio. Mesozoic Red Sandstone in broken horizontal lines. 1. 
 Schuylkill.Anthracite Field. 2. Shamokin, Mahonoy, and Lehigh Ba- 
 sins. 3. Lackawana and Wyoming Basin. Z>, Great Dike. F, Fault. 
 NOTE. Several great faults ran parallel with the Appalachian folds. One remark- 
 able fault extends along the Great Valley of Virginia by the ridge called North Mountain 
 see Fig. 92), and into Pennsylvania. Another one, of 20,000 feet, occurs near Chambers- 
 hurg, bringing Cambrian strata up to a level with upper Devonian. 
 
 from the formation, as in the southern counties of New Vork, 
 where they form "Rock Cities" and "Ruined Cities." The 
 same may be seen along the western border of the eastern coal 
 field of Kentucky, and along the brow of the Cumberland Table 
 Land, where masses as large as dwelling houses have been broken 
 off and rolled down the steep escarpment. 
 
 3. Kinds of Rocks. The Conglomerate series presents gen- 
 erally a conspicuous conglomeritic mass, which has in southern 
 New York a thickness of 25 to 60 feet. In the anthracite region 
 it is 1,000 to 1,500 feet thick, thinning westward to 250 feet on
 
 408 GEOLOGICAL STUDIES. 
 
 the Ohio River, including all the associated strata. The nature 
 of this change in thickness indicates the eastern origin of the 
 detrital materials in the great Seaboard Land, as we believe. 
 
 The Coal Measure strata, including the Conglomerate series 
 as well, embrace shales, clays, limestones, sandstones, and beds 
 of iron ore and coal. Something of their arrangement may be 
 learned from the Table on page 403. It must be understood, 
 however, that this is not a full enumeration of the strata. Rogers 
 enumerated, for instance, one hundred important strata and for- 
 mations above the Homewood Sandstone, and left 200 feet at the 
 top of the Measures unspecified. Every bed of coal, as a rule, 
 is understood to be underlaid by fire clay. It is often accom- 
 panied by shales and sandstones. Thus, the Upper Freeport 
 Coal has underneath, 50 feet of sandy shales. The Lower Free- 
 port Coal has above, 4 feet of bituminous shale, and below, 2 feet 
 of fire clay. The Lower Kittanning Coal is followed downward 
 by the Kittanning clay, 8 feet; sandy shales or sandstone, 25 
 feet; buhrstone iron ore, 1 foot; Ferriferous Limestone, 15 feet; 
 Scrubgrass coal, 2 feet; shales, etc., 25 feet; Clarion Lower Coal, 
 3 feet. 
 
 The fundamental order of stratification given in the Table 
 has been traced from western Pennsylvania into Ohio; but the 
 shales and sandstones are subject to great variation. The coal 
 beds and the limestones are the most persistent features, and 
 these are the means of parallelizing the measures at remote 
 localities. The Lower Mercer Limestone, for instance, has been 
 widely used as a geological guide. It is thin, but wonderfully 
 persistent. Its color is dark blue, or almost black, with thickness 
 from one to three feet; contains much iron and silica and an 
 abundance of fossils, and is everywhere overlaid by excellent 
 iron ore. The Upper Mercer Limestone is very similar, but less 
 uniform, and is also accompanied by iron ore and a seam of coal. 
 The Ferriferous Limestone is the centre of a group of strata, 
 comprising, besides the limestone, the best iron ore, the largest 
 clay deposits, and several of the most widely worked coal seams 
 of the Lower Coal Measures. This group of formations serves to
 
 FOKMATIONAL GEOLOGY. 409 
 
 identify the horizon. The limestone is 15 to 20 feet thick, pure 
 light gray above and grayish-blue below, frequently with a de- 
 posit of buhrstone at top, and with this a valuable bed of iron 
 ore. The limestone, also, is full of fossils. This recurrence of 
 similar deposits in relation to successive limestones will be under- 
 stood as an aspect of the cycle of sedimentation (page 268). 
 
 The so called " Mammoth Bed " B has been identified at the 
 following points: Leonard's, above Kittanning, Pa. (3^ feet); 
 Mahoning Valley, Cuyahoga Falls, Chippewa, etc., Ohio; the 
 Kanawha Salines; the Breckenridge Cannel Coal and other mines 
 in Kentucky, the first (or second) Kentucky Bed; the lower coal 
 on the Wabash, Ind. ; Morris, etc., 111.; Murphy sboro ugh, 111.; 
 Clinton, Mo. [250 species of plants]. 
 
 The Pittsburgh Bed, H, at the following points: Cumberland, 
 Md.; Wheeling; Athens, Ohio; the Pomeroy Bed, Ohio; Mul- 
 ford's in western Kentucky, the llth Kentucky Bed. This bed 
 underlies an area of 14,000 square miles. 
 
 The lowest coal beds are most developed in the Appalachian 
 region. In the Schuylkill Basin we have 15 coal seams, each 
 from 3 to 25 feet thick, in all 113 feet of coal, of which 80 feet 
 are marketable. In the second and third basins there are 60 feet 
 of coal. The Upper Coal Measures are more developed in west- 
 ern Pennsylvania, and relatively still more in the states farther 
 west. The coal beds which are anthracite in eastern Pennsylvania 
 are semi-bituminous in middle Pennsylvania, bituminous at Pitts- 
 burgh, and more bituminous in Ohio and Indiana. As we go 
 westward, the Coal Measure limestones grow thicker, and, of the 
 coal beds, the lower coals disappear, and the upper diminish hi 
 thickness and value. 
 
 The characteristics of the different varieties of coal have beeit 
 given in Part I, Study XIII. 
 
 The Coal Measure rocks in the Wahsatch Range consist of 
 Upper Coal Measure limestones-, 2,500 to 3,000 feet; Middle Coal 
 Measure qnartzites, 5,000 to 7,000 feet; Lower Coal Measure 
 limestones (Wahsatch Limestone) amounting, with Lower Car- 
 boniferous and Upper Devonian limestones, to 7,000 feet.
 
 410 
 
 GEOLOGICAL STUDIES. 
 
 In the Eureka district of Nevada, the Lower Coal Measures 
 consist chiefly of heavy -bedded dark blue and gray limestone, 
 3,800 feet; followed upward by the "Weber Conglomerate," 
 2,000 feet. The Upper Coal Measures are light-colored blue 
 and dark limestones, 500 feet. 
 
 4. Geological Structure. Beds of coal, being mere stratified 
 rocks, have been subjected to all the tilting, folding, and meta- 
 morphism which have affected contiguous strata. In most parts 
 
 FIG. 314. SECTION IN A RE 
 
 COAT. MEASURES. 
 
 of the Mississippi Valley, the disturbances of the strata amount 
 seldom to more than gentle undulations. The coal beds, there- 
 fore, are often quite continuous and uniform. The gentle undu- 
 lations, however, frequently bring them within reach of surface 
 erosions, and thus the continuity of a coal bed, or of several beds, 
 is frequently interrupted, as shown in Fig. 314, which represents 
 the general position of the coal strata in the West. Tn Ohio the 
 
 FIG. 315. SECTION FROM CANFIELD TO HAMMONDSVILLE, FROM NORTH TO SOUTH, IN MA- 
 HONING AND COLUMBIANA COUNTIES, OHIO. (Orton.) Coal Seams numbered as in 
 the Table, page 403. 
 
 Coal Measures have undergone very little disturbance, as may be 
 inferred from the section in Fig. 315, taken in the northeastern 
 part of the state. 
 
 In Illinois, the Coal Measures have suffered moderate dis- 
 turbances. The " Shawnee Fault " crosses the coal field from 
 east to west near its southern extremity; and another fault 
 crosses the whole length of the coal field nearly north and south. 
 The former crosses the Mississippi River at Bailey's Landing, in
 
 FORMAT10NAL GEOLOGY. 411 
 
 Missouri. In Jackson county, Illinois, it brings Devonian lime- 
 stone to the surface at the Bake Oven and Bald Bluff, on the 
 Big Muddy, where it stands on an inclination of 25. It con- 
 tinues across the state, and crosses the Ohio River near Shawnee- 
 town, into Kentucky, whence it continues eastward to Bald Hill, 
 in Union county, and as far as the eastern boundary of Hender- 
 son county. The other Illinois axis of disturbance enters the 
 state in Stephenson county, on the north, intersects Rock River 
 at Grand Detour, and the Illinois River at Split Rock, between 
 La Salle and Utica, and continues S. 20 E. to the Wabash 
 River, in Wabash county. It brings the St. Peters Sandstone to 
 the surface on Rock River, and the Lower Magnesian on the 
 Illinois. These, and other smaller disturbances which have taken 
 place since the Coal Period, combine with erosions in breaking 
 up the continuity of the Coal Measures in Illinois. 
 
 FIG 316. SECTION FROM THE GREAT NORTH TO THE LITTLE NORTH MOUNTAIN, THROUGH 
 HORE SPRINGS, VA. (Rogers.) t, t, t, Thermal Springs; 77, Calciferous; 777, Tren- 
 ton: IV, Cincinnati; T 7 , Oneida: VI, Clinton and Lower Helderberg; F77, Oriskany 
 and Cauda-galli. 
 
 A still more disturbed condition of the Coal Measures is illus- 
 trated in Figs. 33 and 34. The great folds of the Appalachians 
 involve the various beds of coal in a complexity of structure 
 whose unfolding has taxed the highest skill of geologists. Fig. 
 316 is an example of the shape into which foldings and erosions 
 have brought strata originally horizontal and continuous. Fig. 
 92 is another illustration of Appalachian disturbance. The 
 anthracite coal basins present a series of valuable coal beds in an 
 extraordinary state of distortion, which brings within a given 
 surface area an amount of coal which would not be suspected 
 from the area and the thickness of the beds. In Fig. 317 we 
 have a section across the east end of the First, or Schuylkill 
 Anthracite Basin, not far from Mauch Chunk, Pa. It represents 
 a depth of about 2,000 feet, and shows two of the grand folds of
 
 41:3 
 
 GEOLOGICAL STUDIES. 
 
 the Appalachians (1 and .2), and three intermediate smaller ones 
 (3, 4, 5). 
 
 It has been said, in speaking of the Lower Carboniferous Sys- 
 tem, that each successive division in the Mississippi Valley has 
 its northern limit, as a rule, a little farther south. This is evi- 
 dence of progressive upheaval northward, while the sedimenta- 
 tion was going on. On the contrary, the succession of beds in 
 the Upper Carboniferous indicates progressive subsidence north- 
 ward while the Coal Measures were in formation. Each succes- 
 sive stratum finds its northern limit a little farther north, so that 
 
 FIG. 317.- SECTION NEARLY NORTH AND SOUTH ACROSS NESQUEHONING COAL BASIN, 
 NEAR MAUCH CHUNK, PENNSYLVANIA. (Macfarlane.) 1, Locust Mountain; 2, Sharp 
 Mountain; 3, Anticlinal, No. 2 (Rothwell >; 4, Anticlinal, No. 3; 5, Anticlinal, No. 4; 
 6, Synclinal B (Rothwell) , 7, Synclinal C ; 8, Synclinal D ; 9, Synclinal E ; 10, Panther 
 Creek; 11, Summit Hill; 12, Old Coal Quarry. 
 
 COAL SEAMS. A (Rogers), 4 f t. ; B (Rogers), 5 ft.; C, />. Small Seams; E (Rjgers), 
 Mammoth Bed, 85 ft. ; F, Red Ash, or Pencil Seam, 15 ft. ; G (Rothwell), Crown Bed. 
 5 ft. ; H, Small Upper Red Ash Seams, a, Red Shale (Catskiir ; b, Vespertine Sand- 
 stone; c, Umbral Shale; d, Serai Conglomerate: e, Slates and Sandstones between 
 Coal Beds. 
 
 not only is the Carboniferous Limestone covered by the Coal 
 Measures in northern Illinois, but also the Devonian and Silurian; 
 and the northern extremity of the coal field even laps over on the 
 Cambrian of northern Illinois. All this is shown on the Geologi- 
 cal Map. If, then, a section were to be constructed through the 
 western part of the Illinois coal field, the northern portion of it 
 would present the general appearance of Fig. 318. Here the 
 older strata, E, 0, S, were slowly rising, while the Lower Car- 
 boniferous sediments were accumulating ; they were sinking 
 while the Coal Measures, J\f, were forming; and at a subsequent 
 epoch they have been reelevated to their present position.
 
 FORMATION A L GEOLOGY. 
 
 413 
 
 5. Coal Mining. Had the coal beds been left in the posi- 
 tions in which thev were formed, our great repositories of mineral 
 fuel would have been practically hidden from observation. To 
 the tiltings and foldings of the rocks we are indebted for the 
 disclosure of the buried stores, and for the cheapest method of 
 extracting them. Beds of coal often outcrop on hillsides and in 
 
 K I) S C 
 
 FIG. 318.- IDEAL SECTION IN ILLINOIS, SHOWING UNCONFORMITY BETWEEN THE COAI, 
 MEASURES AND OLDER ROCKS. #, Eozoic; C, Cambrian: 8, Silurian; Z>, Devonian; 
 A", Kinderhook, followed by Lower Carboniferous Limestones; M, Coal Measures. 
 
 ravines (Figs. 314 and 317), and may be followed into the earth. 
 Their place of outcrop, however, is generally indicated only by a 
 dark band along the surface, or by coal fragments scattered in 
 the vicinity generally southward. When, by excavating, the 
 bed is struck, it is found altered, by weathering, to a depth of 
 thirty to fifty feet. Such coal is pulverulent, or soft, browned, 
 and friable, and not marketable. Fig. 319 shows the method of 
 drifting in on a hillside. If possible, the spot is so chosen that 
 
 FIG. 319. DRIFTING IN ON A COAL BED. a, Month of the Drift. 
 
 the mine water will flow out at the entrance. If otherwise, 
 pumps must be employed. When a region is known to be under- 
 laid by coal, a shaft may be sunk, though no coal appears at the 
 surface. This is illustrated in Fig. 320, which represents the 
 Upper Measures of western Pennsylvania (see the Table, page 
 403); though, in fact, the surface of the country is such that
 
 414 
 
 GEOLOGICAL STUDIES. 
 
 .Surface 
 
 most mines in that region are approached by drifts, or are 
 
 worked by slop e s. 
 The shaft, S, is the 
 means of access to the 
 coal beds, W and P. 
 The sump,u, is sunken 
 to receive the water, 
 which is thence 
 pumped out by ma- 
 chinery. When a coal 
 bed, W, is reached, 
 excavations are made 
 on both sides. Often 
 the same shaft is sunk 
 to a second coal bed, 
 P, and occasionally 
 even to a third one. 
 Thepassages, or gang- 
 ways, are generally 
 extended in straight 
 
 FIG. 320 CONDENSED SECTION IN THE UPPER COAL 
 
 MEASURES OP PENNSYLVANIA, SHOWING METHOD OP lines to the limits of 
 MINING THROUGH A SHAFT. W, Waynesburg Seam ; 
 P, Pittsburgh Seam; S, a Mining Shaft; a, a, Down 
 Cast; 6, Up Cast; , Sump. 
 
 the property, or as 
 far as the coal contin- 
 ues satisfactory; and 
 
 other passages are opened at right angles with these. There are 
 different systems of planning the underground work of a mine, 
 but that most employed is illustrated in Fig. 331, which shows the 
 plan of the mines worked by a powerful and well known com- 
 pany in the Blossburg coal region, of Pennsylvania a region em- 
 bracing, also, the celebrated Morris Run and Fall Brook Mines. 
 
 The plan of working presented shows the condition of the 
 Arnot mines in 1872. Here is a portion of a coal bed about 
 1,500 feet broad and 1,900 feet long, showing where the gang- 
 Ways have been dug out for travel and for ventilation, and also 
 the " rooms " or " breasts ' from which the coal has been taken. 
 It shows also the large amount of coal left for supporting the
 
 FORMATIONAL GEOLOGY. 
 
 415 
 
 roof. These supports will ultimately be taken out also. In some 
 regions the roof rock is so fragile that the gangways have to be 
 timbered. Even then the enormous weight sometimes crushes 
 
 B A 
 
 FIG. 321. PLAN OF THE MINES or THE BLOSSBURG COAL Co., AT AKNOT, PA. SCALE 
 400 FT. TO THB INCH. (After Macfarlane.) A, the Main Gangway: B, the Return 
 Air Course and Ventilating Shaft. The light portions represent the ground worked 
 over to 1872. 
 
 the supports, and disasters happen. The same plan of mining is 
 pursued whether the mine is approached by an adit, as shown in 
 Fig. 319, or by a shaft, as in Fig. 320.
 
 416 
 
 GEOLOGICAL STUDIES. 
 
 In the anthracite, and occasionally in bituminous, coal regions 
 mining is done by slopes, which are simply inclined planes or slop- 
 ing tunnels underground, generally cut in the coal seam to avoid 
 " dead rock." Drifts, which are always most economical, are 
 generally practicable in the bituminous coal regions of Pennsyl- 
 vania, Ohio, eastern Kentucky, Tennessee, Georgia, and Ala- 
 bama; but in the less disturbed and less denuded regions of Illi- 
 nois and Michigan resort must generally be had to shafts. 
 
 6. Organic. Remains. The coal itself affords abundant traces 
 of vegetation, but generally they are obscure and unidentifiable. 
 Spores and spore cases of Lyeopodittm-like plants (Lepidoden- 
 drids) are, however, extremely abundant the spores appearing 
 as minute grains. Vegetable structure may also be detected, 
 even in anthracite, by preparing thin sections and rendering them 
 
 as translucent as pos- 
 sible. The associated 
 shales are often richly 
 stocked with fronds of 
 ferns and fragments 
 of flowerless plants. 
 They are closely 
 pressed on the surfaces 
 of the laminae, and 
 preserve all the deli- 
 cate structures of the 
 plant in such perfec- 
 tion as fully to reveal 
 its nature. Remains 
 of plants are also often 
 disseminated through 
 the sandstones ; and 
 here occur, sometimes, 
 considerable frag- 
 ments of tree trunks. 
 In some remarkable 
 instances such trunks have been found still in an erect position, 
 
 FIG. 822. -IMPRESSIONS OF FERNS ON COAL SHALES, MOR- 
 RIS, ILL. Pseudopecopteris Mazoniana, Lx. a, en- 
 larged pinnules showing nervation.
 
 FORMATIONAL GEOLOGY. 
 
 417 
 
 together with other growths in their original situations, as at the 
 Joggins, in Nova Scotia, Fig. 323. The limestones embraced in 
 
 FIG. 333. ERECT STUMPS IN SANDSTONE OF THE COAL MEASURES AT THE JOGGINS, 
 NOVA SCOTIA, WITH ROOTLETS IN THE VNDERCLAYS. (Dawson.) 
 
 the Coal Measures contain, of course, the relics of marine forms 
 especially Brachiopods, Bryozoa, Crinoids, and Fishes. These 
 
 limestones and their included 
 faunre become largely developed 
 ^^S^^^^^^^j^^^^^. '" Illinois, as at La Salle, and in- 
 
 A synopsis of the classifica- 
 tion of plants is given on page 
 
 Fi<:. 324. LIVING TREE FF.RN. (After 
 Brogniart.) 
 
 . A COAL 
 FERN RESTORED. (AfterDawson.) 
 
 305. The terrestrial types most abundant in the Coal Measures 
 were already well represented in the later Devonian. They were
 
 418 
 
 GEOLOGICAL STUDIES. 
 
 mostly Acrogens or Pteridophytes of the classes Ferns, Cala- 
 inarians and Lycopods ; though some Gymnosperms were also 
 present, especially Cordaites, and possibly also a few Angio- 
 sperms. No remains of Mosses were known until the very recent 
 discovery of several species at Commentry, in France. The steins 
 are found three to four centime- 
 tres long. Only a single Fungus 
 is known in America, and that 
 from Cannelton, Pa. (Lesquereux). 
 No American Palms or other 
 Angiosperms are known. The 
 Ferns were partly Tree Ferns, and 
 the whole group is now nearly 
 extinct. A few species survive 
 on the slopes of high mountains 
 near the equator or on tropical 
 islands in the Pacific Ocean. A 
 living Tree Fern is shown in Fig. 
 
 324, and a fossil species, restored 
 by Dawson, is reproduced in Fig. 
 
 325. The "scars" left on re- 
 moval of the leaves of a Tree 
 Fern are quite characteristic, and 
 are a principal means of distinc- 
 
 P.MW.-CALAABIA. 3.6, cai- tion among the fossil species. 
 
 nmites restored (after Dawson), with The greater part of the Coal 
 
 a spike of Fruit at summit. 327, Sec- Meas ure ferns were herbaceous. 
 
 tion of the stem. 328, The root. 329. 
 
 a Fruit Cone, aso, l, Aster ophylWes. The commonest species belong to 
 332, Annuiana-the last two gen- the tfeuropteris, Pseudopecop- 
 
 era hero regarded as representing . ^ . f 
 
 branches and leaves of Calamites. terM (Fig. 322), bpAenapteriS, and 
 
 Pecopteris families. 
 
 The Calamarians were related to the modern Equiseta or 
 Horsetails. Modern Equiseta are small, herbaceous plants, but 
 the extinct Calamitece attained a height of thirty feet. The 
 principal genera are Calamites (Figs. 326-329), Aster ophyllites 
 (Figs. 330, 331), Annularia (Fig. 332), and HphenopJtyttum.
 
 FORMATIOXAL GEOLOGY. 
 
 419 
 
 Asterophyllites and Anmtlaria, generally treated as distinct 
 from Catamites, are by some regarded as merely stems and 
 leaves of that genus. More recently they are thought to be 
 related to Lycopods. 
 
 FIGS. 333-'M9.-Lepidodendron. 333, Lepidodendron restored (after Dawson). 334, 335, 
 Pieces of Bark, showing the "scars." 336, Branch with leaves. 337, Leaf. 338, 
 Fruit cone. 339, Two scales of the Fruit cone with Fruit (enlarged). 
 
 FIGS. 340-346. Sigillaria. 340, Sigillaria restored (after Dawson). 341, A Leaf. 342, 343, 
 Pieces of Stem of two different species, with Bark adhering, showing Scars of bark 
 and wood. 344, Ideal section of Stem, showing <a> Pith, (6) Vascular cylinder, (c) 
 Inner layer of Wood, (d) Outer layer of Wood, () Bark, (/) Vascular threads going 
 from the vascular layer to the leaves, and (?) Medullary Rays. 345, A Scalariform 
 vessel from the inner layer of wood. 346, Perforated vessel from the outer layer of 
 wood. 
 
 The class of Lycopods includes among extinct forms, Lepido- 
 dendron and Sigillaria. In coal production they hold a place of 
 first importance. Lepidodendron was a genus of large trees 
 related to our humble ground pines and Selaginella. The bark 
 was marked by scars arranged in quincunx order as shown in
 
 420 
 
 GEOLOGICAL STUDIES. 
 
 Figs. 334 and 335. In the accompanying illustrations we have a 
 restoration of Lepidodendron, after Dawson, with separate parts 
 on a larger scale. 
 
 Sigillaria was a closely related genus of large trees. It is 
 at once distinguished from Lepidodendron by having its trunk 
 scars arranged in vertical series instead of diagonal. The parts 
 of Sigillaria are illustrated in Figs. 340340. 
 
 Stigmaria (Figs. 
 347, 348) is merely 
 the subterranean 
 part of a Sigillaria. 
 The types of 
 plants thus noticed 
 have evidently 
 
 Fm. W.-Sligmana AT THE BA OF A SigiUaria STEM. ^^ ^ principal 
 
 part of the coal. 
 
 Lepido de n dr o n and 
 Sigillaria sustain rela- 
 tions to modern Lyco- 
 podium and Selaginella, 
 but differ in the presence 
 of pith ; to Cycadeae, in 
 the fibro-vascular cylinder 
 (Fig. 344, #); to Firs, in their disc-bearing, minute vessels (Fig. 
 346); and to Ferns, in their scalariform vessels (Fig. 345) and 
 scarred stem left by fallen fronds (Figs. 334, 335, 342, and 343). 
 They are, therefore, striking illustrations of comprehensive types. 
 They represent an early stock existing while yet there were nei- 
 ther characteristic Gynosperms, Cycads, nor Angiosperms ; but 
 out of which all these types were to be gradually unfolded. 
 
 The marine life of the Upper Carboniferous comprises mostly 
 the family types descended from the Devonian. Even most of 
 the genera are the same. 
 
 Air-breathing animals now formed a conspicuous part of the 
 fauna. Land Snails, Myriapods, and Neuropterous Insects, with 
 some Orthopters, became comparatively abundant. Crustaceans 
 
 FIG. 348. Stigmaria Jtcoidts (so CALLED), WITH 
 ROOTLETS ATTACHED.
 
 FOKMATIOXAI, GEOLOGY. 421 
 
 increased, but the type of Trilobites now made its last appear- 
 ance. Ganoid and Selachian Fishes continued abundant. The 
 remains of Amphibians proclaim, like the other air breathers, the 
 increasing importance of the land. But they were mostly scaled 
 and plated Amphibians, combining ganoid, amphibian, and rep- 
 tilian characters. 
 
 7. Origin of Mineral Coal. It seems to have been princi- 
 pally from vegetation which grew on the spot. Bituminous coals 
 contain about 81 per cent of carbon, and anthracite about 95 per 
 cent. The former contain, in addition, about 5^ per cent of 
 hydrogen and 12^ per cent of oxygen, and anthracite about 2^ 
 per cent of each. Common wood contains 50 per cent of carbon, 
 6 per cent of hydrogen, and 43 per cent of oxyaren. Ordinary 
 coals, therefore, differ from common woody tissue in diminished 
 quantities of hydrogen and oxygen: and this loss is greatest in 
 anthracite. This is the nature of the change which vegetable 
 matter undergoes when immersed in water. 
 
 Next, the remains of vegetation are found incorporated in 
 the substance of the coal, and disseminated abundantly through 
 the strata associated with the coal. 
 
 Thirdly, beds of peat are coal beds in which the vegetable 
 matter is still in the earlier stages of change, and are evidently 
 coal in process of formation. But we know, from observation, 
 that peat originates from plants growing on or near the place 
 where the peat accumulates. 
 
 This explanation is entirely applicable to the formation of 
 coal, since it is shown that vegetation was growing luxuriantly in 
 the places where the coal beds were forming. The character of 
 the vegetation indicates that it grew on low grounds; its preser- 
 vation from decomposition indicates that standing water was 
 generally present, and the numerous layers of sandy or muddy 
 materials prove that inundations were of frequent occurrence. 
 In proportion as limestones exist, we have proof of deep and 
 lasting inundations by the waters of the oceans. The coal- 
 making areas, therefore, were little elevated above standing
 
 422 GEOLOGICAL STUDIES. 
 
 water, and were very unstable in their position. They were sub- 
 merged and barely emergent in comparatively rapid succession. 
 
 The carbon in the coal has, therefore, been derived chiefly 
 from the atmosphere. It must have existed there in the form of 
 carbon dioxide. Now, we find that the oxidation of a layer of 
 carbon 2^ feet thick over the land would use up all the oxygen 
 in the atmosphere. As the whole amount of carbonaceous mate- 
 rial in the earth's crust would make a layer of carbon over three 
 feet deep, it appears that at a time when it existed as carbon 
 dioxide, there must have been in the atmosphere more oxygen 
 than now exists, though it was all combined with carbon, and 
 none existed free for the support of respiration. But the lime- 
 stones in the earth's crust represent more than 300 times as much 
 carbon dioxide as the coal; and all the carbon dioxide of the 
 post-carboniferous limestones must have existed in the atmos- 
 phere along with that which yielded the carbon of the coal. 
 This, as calculation shows, was sufficient to produce a pressure of 
 224 atmospheres. But a pressure of 80 atmospheres renders 
 carbon dioxide a liquid. It is evident, therefore, that no such 
 amounts of carbon dioxide could have existed in the atmosphere 
 at the epoch of the coal measures, or at any epoch. We must 
 conclude, finally, that the carbon dioxide, represented in the coal 
 and the carbonates of the earth's crust, must have been yielded 
 to the atmosphere progressively, as required. As there is no 
 probability of its derivation from the earth, it seems likely to 
 have been furnished from external space a conclusion of a very 
 suggestive character. 
 
 8. Growth of the Land during the Upper Carboniferous 
 Age. The configuration of the land at the beginning of the 
 period of coal formation is shown in Fig. 349. It follows from 
 what has been said of the progressive northward encroachment 
 of the carboniferous deposition in the Illinois basin, arid the 
 prevalence of the older coal deposits eastward and the newer 
 westward, that a depression was in progress toward the north, 
 which brought the surface progressively to the low level requisite 
 for coal preservation, accompanied, probably, by a corresponding
 
 FORMATIONAL GEOLOGY. 
 
 423 
 
 elevation in southern Illinois and Kentucky, such as to bring the 
 surface too high for coal-making conditions in the later epochs 
 of the period. (Compare Fig. 318.) Correspondingly, there was 
 a moderate rise along the eastern Appalachian region during the 
 later epochs. Westward, coal-making conditions persisted in 
 Ohio, Indiana, and Illinois, until the concluding stages of the 
 period, when there seems to have been a recurrence of marine 
 
 PIG. 349. MAP OF THE CONTINENT NEAR THE BEGINNING OF THE COAL PERIOD. 
 
 conditions in Illinois, Missouri, and Kansas, and farther west a 
 continuance of the marine conditions which had existed during 
 the Lower Carboniferous Age.
 
 424 
 
 GEOLOGICAL STUDIES. 
 
 Interior. Pacific Coast. 
 
 4. LARAMIE (LIGNIT- ' 
 
 ("Cmco GROUP. 
 
 ic) GROUP. [Also 
 
 
 in Gulf Region. 
 See 9.1 
 
 (Hiatus) 
 
 3. Fox HILLS GROUP. 
 
 'I 
 
 2. COLORADO GROUP. 
 
 SHASTA GROUP. 
 
 
 Horsetown Beds. 
 
 1. DAKOTA GROUP. 
 
 1 Knoxville Beds. 
 
 1 j ATLANTOSAURUS BEDS. Jura-Trias 
 
 f 1 BAPTANODON BEDS. or Red Sand ' 
 
 \ "| stone Forma- 
 
 tion of Atlan- 
 
 tic Coast. 
 
 8. The Mesozoic Great System. 
 , Divisions, Subdivisions, and Terms. 
 
 III. Cretaceous System. 
 Atlantic Coast. 
 
 2. LATER CRETACEOUS 
 
 1. EARLIER, CRETACEOUS. - 
 
 II. Jurassic System. 
 
 2. FLAMING GORGE GROUP 
 
 1. WHITE CLIFF GROUP. 
 I. Triassic System. 
 
 2. Star Peak Group. 
 
 1. Koipato Group. 
 
 The Triassic System is so named from its threefold division 
 on the continent of Europe; the Jurassic, from the Jura Mount- 
 ains, and the Cretaceous, from the presence of great supplies of 
 chalk. The Koipato Group commemorates the Indian name of 
 the West Humboldt Range, formed of rocks of this age. The 
 Star Peak Group is so named by King from the mountain of that 
 name. The Group names for the Jurassic are derived from 
 Flaming Gorge on the Green River in Wyoming, and the White 
 Cliffs of Southern Utah on the border of the Grand Canon dis- 
 trict. The Groups of Interior Cretaceous were named by Meek 
 and Hayden from localities in the Upper Missouri region. 
 
 2. The Triassic System. Triassic rocks are unknown be- 
 tween the Appalachians and the eastern slopes of the Rocky 
 Mountains. In the eastern province occurs, in numerous isolated 
 patches, a formation long known as Jura-Trias, in consequence of 
 uncertainty as to its age. One of the principal areas occupies 
 the valley of the Connecticut from New Haven to the northern 
 part of Massachusetts. Another stretches from the southern 
 part of New York across northern New Jersey, to the north of
 
 FORMATION.*!, GEOLOGY. 
 
 Philadelphia, and west of Washington, into Virginia. Other 
 smaller areas occur in western Connecticut, Virginia, and North 
 and South Carolina. The rocks are largely red sandstones, and 
 in New Jersey and Connecticut are extensively worked for build- 
 ing purposes, furnishing the well known "brown stones" of 
 northern cities. The formation near Richmond, Va., and in the 
 Dan River and Deep River districts of North Carolina embraces, 
 in the middle member, valuable beds of bituminous coal The 
 coarse limestone breccia known as the Potomac Marble, seen 
 near Point of Rocks, Md., and elsewhere, lies at the bottom, and 
 outcrops along the western border of the principal area. The 
 thickness of the formation rises to 3,000 feet. 
 
 The eastern Jura-Trias has afforded few organic remains, 
 except foot prints and coal plants. At Portland, and other local- 
 ities on the Connecticut, the surfaces of many of the layers of 
 the brown sandstone are covered with foot prints of animals, 
 many of which are believed to have been three-toed reptiles, such 
 as are known to have lived, a 
 little later, in New Jersey, and 
 in other parts of the world. 
 (See page 339.) Mammals ap- 
 peared during this period, and 
 a jaw found in North Carolina 
 has been represented in Fig. 
 272. The prominent feature of 
 the Age was the commence- 
 ment of the great expansion of 
 the reptilian type. Fontaine 
 has recently subjected to care- 
 ful study the coal plants from 
 this formation, and found them 
 to belong to the age of the 
 
 Lias: and it is quite possible 
 
 r PIG. 350. SLAB OF SANDSTONE FROM TUR- 
 
 that the whole formation is NEK'S FALLS, WITH TRACKS OP THRBE- 
 Jurassic. TOED *""" (E. Hitchcock.) x^- 
 
 (a, a, XfV) , *. <"i Reptilian, d, Am- 
 In the western province, phibian.
 
 426 GEOLOGICAL STUDIES. 
 
 some beds of sandstones, red marlites, and gypsum outcrop along 1 
 the eastern slope of the Rockv Mountains (see the Map, page 
 119), which are either Triassic, or near the bottom of the Juras- 
 sic. In the Elk Mountains of western Colorado, Triassic, or 
 Triassico-Jurassic sandstones and marlites, horizontally stratified, 
 make up a thousand feet of the basal portion. Triassic strata 
 form, also, part of the Uinta and Wahsatch Mountains, attaining 
 a thickness of 1,000 to 1,200 feet. In the West Humboldt 
 Range, two groups are recognizable. The lower, or Koipato, 
 consists of a great thickness of quartzose and argillaceous strata, 
 4,000 to 6,000 feet thick. These, toward the north, become 
 gradually metamorphosed into a porphyroid quite destitute of 
 stratification, and much resembling an erupted felsite porphyry. 
 The upper, or Star Peak Group, consists of a vast series of alter- 
 nating limestones and quartzites, attaining a thickness of 10,000 
 feet. The maximum thickness of the Triassic in the West Hum- 
 boldt Range is, therefore, about 16,000 feet. These two divis- 
 ions are also recognized in the area east of the Wahsatch Moun- 
 tains; but no further correlation of strata can be shown. Triassic 
 rocks are also involved in the Sierra Nevada, and extend into 
 eastern California, where they are sometimes auriferous. 
 
 The Koipato Group, which is represented by dark red beds 
 east of the Wahsatch, is quite destitute of fossils; while the 
 Star Peak Group abounds in marine forms characteristic of the 
 so called Alpine Trias of Europe. 
 
 The Triassico-Jurassic beds of the eastern province rest in 
 long northeasterly trending furrows or depressions between 
 ridges of Eozoic rocks. The latter, not being covered by strata 
 intermediate between the Eozoic and Trias, appear to have con- 
 stituted a part of the dry land during the Palaeozoic ages, as 
 before mentioned, and as shown on all the preceding maps of the 
 continent (Figs. 297, 304, 312, 349). After the Palaeozoic, this 
 region, either through subsidence or erosion, or both, became 
 lowered again below sea level in its eastern part. In the West 
 Humboldt basin, similarly, the Trias rests unconformably on the 
 eroded Eozoic and Cambrian strata. But in the Wahsatch-Uinta
 
 FORMATIONAL GEOLOGY. 427 
 
 basin, it rests conformably on the Upper Carboniferous; and the 
 succession of conformable strata is complete downward to the 
 Eozoic, showing that the presence of the ocean was there unin- 
 terrupted from very early times. [The small scale of the Map, 
 Fig. 47, renders it impossible to represent the small geological 
 areas.] 
 
 A common feature of the Triassic everywhere was the erup- 
 tion of volcanic materials. The trap cliffs of Meriden, Conn.; 
 East and West Rocks, New Haven ; the Palisades, on the Hud- 
 son; Mt. Tom and Mt. Holyoke, in Massachusetts; Bergen Hill, 
 in New Jersey; the ninety-mile trap dike in southeastern Penn- 
 sylvania, Fig. 313, are all features of eruption toward the close 
 of the Triassic Age. Less conspicuous dikes are very numerous. 
 Similarly erupted products are intimately associated with the 
 Trias of the far West ; and the same is true of European Trias. 
 
 3. The Jurassic System. Except so far as indicated in connec- 
 tion with the Jura-Trias of the eastern United States, the Jurassic 
 of North America is confined to the regions west of the Missouri 
 River. The most easterly beds lie along the eastern bases of the 
 Rocky Mountain ranges, and consist of reddish-yellow, friable 
 sandstones, gray, arenaceous marls, reddish-brown bands of clay, 
 and thin bands of cherty limestone, a less compact dolomitic 
 limestone, and thin beds of gypsum. These strata are mostly 
 destitute of fossils; but at Como, fossils are abundant, and fix 
 the age of the formation. The cherty limestone is quite a per- 
 sistent horizon, and the fossils abound in the marls above and 
 below. 
 
 In the Uinta range, in the Flaming Gorge region, the System, 
 as now understood, has a basal, fossiliferous limestone, 200 feet 
 thick, followed by sandstones and shales, 250 feet; a middle 
 limestone, 300 feet, with fossils, followed by cl.ays, shales, and 
 thin sandstones; and at the head of .Burnt Fork, a white sand- 
 stone is seen at the top of the series. The whole thickness is 
 750 feet or over. 
 
 In the Wahsatch range we have heavy-bedded limestone at
 
 428 GEOLOGICAL STUDIES. 
 
 the bottom, with a vast series of silicious, argillaceous, and calca- 
 reous shales above, the whole rising to 1,800 feet. 
 
 In western Nevada, the limestones in the lower part attain a 
 thickness of 1,500 to 2,000 feet, and the shales and slates above, 
 4,V)00 feet. 
 
 Thus the Jurassic strata, which show a minimum thickness of 
 seventy-five feet at the eastern base of the Colorado range, grad- 
 ually thicken up to 750 feet in the Uinta, 1,800 feet in the Wah- 
 satch, and 6,000 feet in western Nevada. This is analogous to 
 the change observed in the Palaeozoic strata in passing from the 
 Mississippi to the Appalachians. The direction of the gradation 
 is reversed; but the principle of diminution in volume with re- 
 cession from the source of the sediments is the same. 
 
 The slates of the upper division of the Jurassic extend into 
 eastern California; and on the Mariposa estate, and in neighbor- 
 ing regions, become the gold-bearing formation. 
 
 On the southwestern border of the High Plateaus, near the 
 37th parallel and 113th meridian, the Jurassic consists of a series 
 of bright-red fossiliferous shales, 300 to 500 feet thick, resting on 
 a very massive bed of white sandstone nearly a thousand feet 
 thick. 
 
 The fossil remains of the Jurassic are characterized by the 
 relative abundance of the Ammonite group of the Cephalopods 
 (see page 326) ; by Belemnites, or Cephalopods of the higher 
 order, Dibranchs; by a great increase of Lamellibranchs; by the 
 advent of the modern crinoidal genus Pentacrimis, and an enor- 
 mous development of the class of Reptiles (see page 335). Ju- 
 rassic Reptiles of gigantic size have been described by Marsh 
 from Morrison and Canon City, Colo., and from Wyoming. 
 
 While the Jurassic is unknown, or at least not certainly iso- 
 lated, in the eastern United States, it is a widespread formation 
 through all the region between the Black Hills and the Sierra 
 Nevada, and as far south as Arizona; and, for its reptilian re- 
 mains, is a formation of extraordinary interest. In European 
 geology the Jurassic possesses foremost importance, and admits
 
 POKMATIONAL GEOLOGY. 429 
 
 of throe main divisions Wealden, Oolite, and Lias with sev- 
 eral subdivisions for the Ob'lite. 
 
 4. The Cretaceous System. (1) Distribution and Kinds of 
 Hocks. The Cretaceous has a moderate development along the 
 Atlantic slope, a larger development in the Gulf States, and cov- 
 ers extensive areas in Texas, and a still wider region over the 
 Great Plains, along the eastern slope of the Rocky Mountains. 
 It is, besides, extensively involved in the general geology of all 
 the interior of the continent, though extensively overlaid by Ter- 
 tiary strata, as appears from a glance at the Map, Fig. 47. On 
 the Pacific border it occurs in the Coast Ranges; and north of 
 the national boundary it stretches far along the eastern flanks of 
 the Rocky Mountains perhaps to the Arctic Ocean, and occurs 
 at Vancouver and Queen Charlotte Islands, and at many other 
 points in the interior. 
 
 In New Jersey the strata consist, below, of bluish and gray 
 clays, micaceous sand with fossil wood and angiospermous leaves, 
 130 feet, and above of dark clays, green and ferruginous sands, 
 and yellow limestone, 300 feet or over, making a total of 400 to 
 500 feet. In Alabama the lowest member, or " Eutaw Group," 
 is a heavy mass of clays, laminated micaceous shales, and irregu- 
 lar layers of green sand, with fragments of dicotyledonous leaves 
 the whole over 415 feet. Above are eighteen feet of loose 
 and concrete sands with Upper Cretaceous fossils, followed by 
 the "rotten limestone," at least 350 feet, uncemented sand 45 
 feet, and a white, marly limestone, 6 feet. Total, about 900 feet. 
 
 The Cretaceous of the Atlantic and Gulf borders may, there- 
 fore, be said to consist of an argillaceous group below, and a cal- 
 careous group above. The strata dip gently toward the Atlantic 
 and Gulf, and pass under the Tertiary. The order of superposi- 
 tion in Alabama is shown in Fig. 351. The vertical lines show 
 the positions of selected artesian wells, which are bored in 
 large number, into the lower beds of the System, where the 
 sandy layers carry supplies of pure, sulphuretted or saline water. 
 The Cretaceous here rests directly on the Coal Measures. The 
 Permian, Triassic, and Jurassic must underlie in the region
 
 GEOLOGICAL STUDIES. 
 
 Coal Mines 
 
 TUSCALOOSA 
 
 Landing 
 Clinton 
 EUIAW 
 Finch's Ferry 
 
 I MOBILE 
 Mobile Bay 
 
 south of the northern limit 
 of the Cretaceous. But 
 it is manifest that a sub- 
 sidence occurred near the 
 beginning of the Cretaceous, 
 and the sea gained on the 
 land. This is true also on 
 the Atlantic border. 
 
 The Cretaceous rocks in 
 Texas consist more general- 
 ly of solid limestones, show- 
 ing deeper water and a re- 
 moter shore. Tracing the 
 formation northward, we find 
 continued accessions of ar- 
 gillaceous and fragmental 
 matters. In the Upper Mis- 
 souri region, the lowest mem- 
 ber is the coarse Dakota 
 Sandstone, often appearing 
 truly conglomeritic, which 
 comes in abruptly above the 
 calcareous beds of the Ju- 
 rassic. It spreads westward, 
 southward to the Uinta 
 Mountains and Kansas, and 
 even into New Mexico, in- 
 creasing in thickness from 
 400 feet in Dakota to 500 in 
 the Uintas. Next above are 
 the clays and limestones of 
 the Colorado Group, attain- 
 ing a thickness of 1,700 feet 
 on the Upper Missouri, and 
 2,000 feet in the Uintas. 
 Then follows the Fox Hills
 
 FORMATIONAL GEOLOGY. 431 
 
 Group of gray, ferruginous, and yellowish sandstones and are- 
 naceous clays, 500 feet thick above Fort Pierre and along the 
 base of the Big Horn Mountains, and 3,000 to 4,000 feet in 
 the Uintas. Finally, the Laramie Group, attaining a thick- 
 ness of 2,000 feet, is found very generally from New Mexico far 
 into British America, over a belt 500 miles wide and more than 
 1,000 miles long. There is evidence that it extends southward even 
 into Mexico. It consists of brackish -water deposits below, and 
 fresh-water above. The rocks are mostly sands, clays, and shales 
 colored with lignitic materials, and containing beds of bituminous 
 or semi-bituminous coal, known as lignite. The Laramie contains 
 plants and marine shells resembling Tertiary species found in Eu- 
 rope, and hence some geologists regard it belonging to the Ter- 
 tiary System. But the Laramie is in some places unconformable 
 with the overlying Tertiary strata, and its land fauna, containing 
 Dinosaurs, was decidedly Mesozoic. Besides, some of the Mol- 
 luscs possessed Cretaceous characters. Dr. C. A. White has re- 
 cently shown that the Chico Group of California is probably of 
 this age. 
 
 (2) Economic Products of the Cretaceous. Cinnabar is 
 found in the Coast Ranges of California in minable quantities. 
 The best known localities are New Almaden, 50 miles southwest 
 of San Francisco, and New Idria, in Fresno county. 
 
 Gold is found, to a limited extent, in the rnetamorphic Creta- 
 ceous of California, and so are copper and chromic iron but 
 none of these are worked. It may be here mentioned, that with 
 the Carboniferous, Triassic and Jurassic, the Cretaceous makes 
 the fourth system of strata found gold bearing in California. 
 The age of the formation, therefore, is not important. It is 
 metamorphism which seems to have separated the metal and 
 gathered it in particles and grains from the rock. 
 
 The Green Sand common in the Cretaceous of New Jersey 
 is mined as " marl " for fertilizing purposes. The green grains, 
 called also glau'conite, contain 8 to 12 per cent of potash and 
 soda, with a trace of phosphate of lime. Some of the limestones 
 of Alabama have recently been found richly phosphatic, as re-
 
 433 GEOLOGICAL STUDIES. 
 
 ported by Prof. E. A. Smith, and may prove of great importance 
 to agriculture. 
 
 Coal is found to a considerable extent in the Dakota Group, 
 at its very base, in the Uinta region. It occurs, also, on Van- 
 couver Island, in beds referred to the Chico [Chee'co] Group of 
 California, which is Upper Cretaceous in the position of the 
 Colorado Group of the Upper Missouri. In California coal is 
 produced from the Te"jon [Ta'-hon] Group in the Coast Ranges, 
 and this has been consfdered to hold the place of the Laramie 
 Group of the Interior; but Dr. White, in a recent memoir, has 
 shown it to be of Eocene age. Back from Se-at'tle on Puget 
 Sound, Washington Territory, coal of excellent quality is mined. 
 Ten miles from Se-at'tle is the so called Renten coal; at twenty 
 miles, the Newcastle coal, of better quality; and at 30 to 40 miles 
 back, on Cedar River, is the Coleman coal, of still superior qual- 
 ity, obtained in a bed reported 40 feet thick. Still farther back, 
 in the Foot Hills of the Cascade Mountains, is said to occur the 
 best of all ; but this is not yet opened. 
 
 The coal supplies of the Cretaceous possess very great impor- 
 tance, since the coal is of good quality, and is widely distributed 
 through regions not supplied with Palaeozoic coal. The Van- 
 couver and Washington coals are shipped to San Francisco and 
 the Hawaiian Islands. The Laramie Group coal is widely em- 
 ployed in Utah at Evanston and Coalville; in Wyoming, at Car- 
 bon and Hallville, at Black Butte Station on Bitter Creek and 
 Bear River, and in the Uinta basin ; in Colorado, at Denver, 
 Golden City, and other localities; in New Mexico, at the Old 
 Placer Mines, in the San Lazaro Mountains. The bed at Evans- 
 ton is 26 feet thick, containing 37-38 per cent of volatile sub- 
 stances, and 4950 per cent of carbon. The Wyoming coal is 
 shipped eastward as far as Omaha. At the Old Placer Mines the 
 rocks are upturned and metamorphic, as in eastern Pennsylvania, 
 and the coal, accordingly, is partially debitumenized containing 
 from 68 to 91 per cent of fixed carbon. This is of Laramie age, 
 and lies in the Trinidad Coal Field of Stevenson, which stretches
 
 FOKMATIONAL GEOLOGY. 433 
 
 along the eastern base of the Rocky Mountains, lying partly ia 
 Colorado and partly in New Mexico. 
 
 Productive coal measures occur in the Cretaceous on the 
 coasts of the islands and main land north of Victoria, British 
 America, at Maple Bar. At Nanaimo, Departure Bay, extensive 
 mines of Laramie age; also at Comox, an extensive field not 
 worked. Coal partly anthracite, associated with plants having 
 Jurassico-Cretaceous affinities, according to Dawson, has been 
 recently reported from Old Man River, Martin Creek, and one 
 other locality farther northwest, on the Suakwa River. Coal 
 outcrops are reported from the Lower Cretaceous, on the line of 
 the Canada Pacific Railway, at the crossing of the South Saskat- 
 chewan, and at Bantry; and from the Laramie at Bassano, Crow- 
 foot, and Coal Creek (long. 114 35'). 
 
 The Cretaceous, therefore, is a great coal-producing System, 
 perhaps not inferior in importance to the Carboniferous. Since 
 it produces no chalk in America, its name appears to be doubly a 
 misnomer. 
 
 (3,) Fossil Remains of the Cretaceous. The Brachiopods 
 are reduced mostly to the Terebratula Family. The Lamelli- 
 branchs increase in numbers and diversification, and approach 
 decidedly toward modern types. The Oyster family is largely 
 developed. Some oysters ( Gryphcea mutabilis) were seven 
 inches in diameter in Alabama, and other species (Exogyra 
 costatd) were five inches across; while Ostrea larva presented a 
 strikingly falcate form, with a deeply and acutely sinuate border. 
 The Ammonite family continued to increase in importance (see 
 the notice, page 326), but completely disappeared at the close of 
 the Cretaceous. The higher order of Cephalopods, Dibranchs, 
 continued to increase. The family of Belemnites was largely 
 represented. The Belemnite resembled a modern squid, but its 
 internal bone, or osselet, was prolonged behind in a cone called 
 the pen. This had a longitudinal cavity (alveolus) opening for- 
 ward, and having at its posterior end a chambered cone called the 
 phragmocone, which had a siphuncle. The ink bag was contained 
 within the cavity of the osselet.
 
 434 GEOLOGICAL STUDIES. 
 
 A highly characteristic reptile of the Cretaceous was the 
 Jtfosasaurus, described page 338, whose vertebras are common in 
 the Upper Cretaceous of the Gulf region. This was an age of 
 sharks, both Squalodonts and Cestracionts. Their teeth lie scat- 
 tered abundantly over the exposed Cretaceous surfaces of Ala- 
 bama and Mississippi by the roadsides, in the fields, and along 
 the river margins. Teleost fishes, or those of the modern type, 
 became quite abundant. Plants of modern dicotyledonous genera 
 prevailed in the forests, besides many modern forms of monoco- 
 tyledons. On the whole, the dawn of the modern aspects of the 
 world was evidently near. 
 
 5. Tke Physiognomy of the Interior of the Continent. The 
 Mesozoic strata enter so largely into the formation of the whole 
 Interior that we turn for a moment to a general consideration of 
 its physiognomy. After passing the " Province of the Great 
 TrMains," which stretch westward from the Missouri River," we 
 reach the first Ranges of the Rocky mountains proper the 
 Colorado and Laramie Ranges the former also known as the 
 Front Range. These are succeeded at intervals of 30 or 40 
 miles by the Medicine Bow and Park Ranges, and the Sah watch 
 Mountains. These are broad massive ranges, serrated with lofty 
 snow-covered peaks, and trending approximately north and south. 
 The valleys between them are fertile expanses known as " Parks," 
 like " North," " Middle," and "South " Parks. Their snows form 
 a perennial reservoir for streams flowing, on one side, into the 
 Gulf of Mexico, and, on the other, into the Gulf of California. 
 These mountains are sometimes known collectively as the Park 
 Mountains; and the whole zone forms the "Park Province." It 
 may be regarded as extending to the 107th meridian. 
 
 West of this comes the "Plateau Province," a broad elevated 
 expanse broken by faults, cut by gorges, wasted by denudations, 
 and dotted with innumerable volcanic outbursts, lone mountains 
 and groups of mountains, and short ranges. It is drained by the 
 Colorado River of the West and its tributaries. It stands on an 
 average 5,000 to 7,000 feet above the sea. Its mountain features, 
 of which the Uinta constitutes the northern boundary, trend east
 
 FORMATION A L GEOLOGY. 435 
 
 and west. Southward, the Plateau Province stretches into Ari- 
 zona. It terminates westward with the Wahsatch Mountains, a 
 north and south range which has been split longitudinally by a 
 great fault, on the west of which the mountain and the whole 
 country has been sunken six to seven thousand feet. 
 
 The steep westerly front of the Wahsatch Range overlooks 
 the next province. It is called the " Great Basin," or " Basin 
 Province." It is 500 miles wide, stretching to the Sierra Nevada, 
 and stands generally at a level lower than that of the Plateau 
 Province. It is characterized by a large number probably over 
 150 of short mountain ranges, which trend north and south. 
 Some of these, in order westward, are the Gosiute, Pequot, East 
 Humboldt, Pinon, Cortez, Shoshoni, West Humboldt, and Monte- 
 zuma ranges. The Union Pacific Railroad passes the northerly 
 extremities of these. On the south are numerous other short, 
 meridional ranges, continuing at least as far as the 37th degree 
 of latitude. These are known as "Basin Ranges." The drain- 
 age of the Basin Province is mostly toward interior salt lakes. 
 
 The Basin Province is bounded by the Sierra Nevada, another 
 great mountain range split longitudinally along its crest, with 
 the eastern half let down 3,000 to 10,000 feet. The steep east- 
 ern face of the Sierra Nevada overlooks the Great Basin toward 
 the east, as the Wahsatch faces it toward the west. From the 
 summit of the Sierra Nevada the country slopes generally toward 
 the Pacific, and forms the " Pacific Province." The Coast Ranges 
 of California, however, interrupt the slope, and cause a longitu- 
 dinal valley along the centre of the state, stretching from Mt. 
 Shasta, on the north, to far beyond Tulare Lake on the south. 
 From the north along this valley flows the Sacramento River; and 
 from the south the San Joaquin. The two bend westward on the 
 38th parallel, and find exit through the Coast Ranges into the 
 Bay of San Francisco. 
 
 The name Rocky Mountains is by some employed to embrace 
 all the mountains from the Colorado Range to the Sierra Nevada. 
 But this seems objectionable. The breadth of country is more 
 than a thousand miles. The mountain features are not conform-
 
 436 GEOLOGICAL STUDIES. 
 
 able to one plan; they do not constitute one system; they were 
 uplifted at various geologic epochs; they are separated by broad 
 intervals ; they are formed of rocks of various ages. We may 
 designate as Cordilleras, after Humboldt, the entire assemblage 
 of mountains, and restrict the name " Rocky Mountains " to the 
 Park Ranges along the eastern border. These constitute the 
 dividing ridge between the waters flowing into the Mississippi 
 and those flowing into the Pacific. 
 
 6. Comparative Geology of the Provinces. The central 
 masses of the Park Mountains are of Eozoic strata, and are en- 
 wrapped, often unconformably, by Palaeozoic formations. All 
 these are involved in the disturbances of the primitive upheavals. 
 Mesozoic and Caenozoic formations abut against the uplifted slopes, 
 and have been themselves tilted by later upheavals, and extensively 
 wasted by denudation. (See the section, Fig. 352.) The old nuclei 
 were extensively plicated with closely appressed folds prior to 
 the deposition of the later sediments. The Park Mountains 
 stood as long islands in the midst of the ocean of Mesozoic and 
 Caenozoic times. This stretched from beyond the Wahsatch 
 Mountains eastward. It covered the whole of the Plateau Prov- 
 ince till late in Caenozoic time, and continued to receive the sedi- 
 ments contributed from the ancient continent farther west. The 
 Plateau Province is almost wholly underlaid by post-Palaeozoic 
 strata, though in places upheaval and erosion bring Carboniferous 
 strata into view. The Basin Province, now so depressed, was, 
 till Casnozoic time, the most elevated region of the Interior. It 
 is underlaid by Eozoic and Palaeozoic rocks, with some Meso- 
 zoic and Caenozoic in the Humboldt Mountain district. It was 
 mostly, during Mesozoic and Caenozoic time, a continental mass, 
 with drainage eastward into the ocean of the Plateau Province. 
 It supplied the sediments which overspread its bottom, and 
 was wasted by the service. Finally, in late Tertiary time, the 
 Plateau region was raised above the level of this ancient land, 
 and the Park region was elevated still higher. Thus the direc- 
 tion of the drainage was reversed. 
 
 The uplift of the Great Plateau was accompanied by an ex-
 
 FORMATIONAL GEOLOGY. 
 
 437 
 
 tensive system of faults, which rent the Plateau 
 Province from north to south. The huge result- 
 ing prismoids present the various attitudes and 
 mutual relations which have been described as 
 Kaibab structure, Uinta structure, and mono- 
 clines (page 160). These features are illustrated 
 in Figs. 85, 86, and 87. Volcanic outflows have 
 contributed to further modify the surface, form- 
 ing sometimes mountain saliences above the pla- 
 teau, and sometimes broad sheets on which 
 erosion has subsequently acted, cutting slit-like 
 gorges and carving high mesas, which rise like 
 titanic tables here and there over the scarred and 
 desert expanse. Some of the most important vol- 
 canic mountains in this Province are Pilot Butte, 
 the Uinkarets, and San Francisco Mountain. Here 
 also are the mountains of the laccolitic type, like 
 the Henry, the Navajo, and Sierra la Sal (see 
 page 157). In southern Utah the Csenozoic and 
 Mesozoic formations terminate in a succession of 
 gigantic steps descending toward the Colorado 
 River, whose " Grand Canon " cuts five and six 
 thousand feet deeper into Palaeozoic and Eozoic 
 rocks. The canon features are illustrated in Fig. 
 31; and a bird's-eye view of the southern part of 
 the Plateau Province is shown in Fig. 87. 
 
 7. Geological History of the Cordilleran Re- 
 gion. It will be remembered that the Cordilleran 
 wing of the continent at the end of Eozoic time 
 stretched in width from the Nevada region east- 
 ward to the 104th meridian; and that it then be- 
 gan to sink, and continued sinking during the 
 entire progress of Palaeozoic time, so that finally 
 only the highest peaks rose through the mantle 
 of sediments. The Cordilleran ocean was now, 
 as it had long been, an archipelago; and the vast 
 
 I;--
 
 438 GEOLOGICAL STUDIES. 
 
 series of Palaeozoic sediments, covering the ancient continent 
 unconformably, were entirely conformable among themselves 
 a state of things quite unlike the frequently occurring un- 
 conformabilities east of the Mississippi. 
 
 Widespread mechanical disturbances now occurred. The land 
 area west of the Nevada Palaeozoic shore became depressed, while 
 all the thickest part of the Palaeozoic deposits from the Nevada 
 shore, eastward to and including the Wahsatch, rose above the 
 ocean and became a land area (King). Between the new conti- 
 nent and the old one which went down, to the west, there was a 
 complete change of condition. The land became ocean, the 
 ocean became land. The new land extended eastward to include 
 the Wahsatch. Eastward of that, to the Great Plains, and in- 
 cluding them, the former ocean bed remained undisturbed. The 
 new-made land, from the Wahsatch to 117 30' west, now yielded 
 the sediments destined to form all the post-Carboniferous forma- 
 tions. That is, the Basin Province was then the continent, and 
 eastward stretched a vast mediterranean sea, as far as Kansas and 
 Nebraska, and southward to the Gulf of Mexico, and northward 
 probably to the Arctic Ocean. (Compare the map of Amerjca at 
 this epoch, Fig. 353.) West of the new land mass of the Basin 
 Province, the successive deposits of the Triassic and Jurassic Ages 
 were laid down in conformable sheets of enormous thickness, di- 
 rectly but unconformably upon the ancient Eozoic floor. East of 
 the same land mass, the Triassic and Jurassic sediments rested con- 
 formably on the top of the Carboniferous. West of the Basin- 
 Province Land, over the Sierra Nevada belt and California, the 
 Mesozoic sediments attained a thickness, by the close of Jurassic 
 time, of 20,000 feet ; in the mediterranean sea, a thickness of 
 only 3,800 feet. The western sea was deep; the mediterranean 
 was shallow. 
 
 At the close of the Jurassic Age, the western ocean, with its 
 original floor of Eozoic ranges, overlaid by twenty odd thousand 
 feet of Jura-Trias sediments, suffered abrupt orographical uplift, 
 resulting in the sharply folded ranges of the Sierra Nevada, and 
 extending the continent 200 miles further west. This uplift
 
 FORMATIONAL GEOLOGY. 
 
 439 
 
 stretched southwaid as far as the 3Gth parallel, and northward 
 probably to Alaska. East of the Wahsatch, however, everything 
 remained undisturbed. The earliest sediments of the Cretaceous 
 were laid down conformably over the Jurassic. But the great 
 event which had marked the history of the Basin and Nevada 
 provinces was signalized over the Plateau and Park provinces by 
 an invasion of coarse and even conglomeritic deposits. These 
 constitute the Dakotah Group of the Cretaceous. They stretch 
 
 FIG. 353. NORTH AMERICA, NEAR THE BEGINNING OP THE MESOZOIC .*EoN. 
 
 from the Wahsatch into Kansas. Thev covered the entire bottom 
 of the mediterranean sea; that is, the entire Province, with the 
 exception of a few Eozoic islands which, from the time of the 
 Cambrian, had stood above the plane of deposition. This phy- 
 sical condition of things continued through the Cretaceous. The 
 greatest thickness attained by deposits of this Age was along the 
 western border of the ocean, where we find about 12,000 feet of 
 Cretaceous. Passing eastward, the thickness diminishes. Along 
 the eastern base of the Rocky Mountains, we find it thinned to
 
 440 
 
 GEOLOGICAL STUDIES. 
 
 4,500 or 5,000 feet; while in western Kansas its development is 
 at a minimum. 
 
 While the Jura deposits had been generally fine and argillo- 
 calcareous, those of the Cretaceous began abruptly in a coarse, 
 silicious conglomerate. Along the borders of the Wahsatch we 
 find many of the pebbles a foot in diameter. Farther east, they 
 continually diminish, and in Kansas no pebbles are to be seen. 
 In the region of the Wahsatch and Uinta ranges, coal beds 
 
 FIG. 354. NORTH AMERICA, NEAR THE BEGINNING OF THE CRETACEOUS AGE. 
 
 appear at the very base of the series, immediately upon the Jura; 
 and they continue to recur at intervals through the whole thick- 
 ness of the Cretaceous. They increase in frequency after the 
 close of the Fox Hill Group, and make their appearance, afso, in 
 the province of the Great Plains. Finally, through the 4,000 or 
 5,000 feet of the Laramie Group, the coal becomes, over the 
 whole Cretaceous area, abundant and characteristic. The western 
 part of the Cretaceous repeats, therefore, the geological history 
 of the Carboniferous Coal Measures, in a region where those
 
 FORMATIONAL GEOLOGY. 441 
 
 measures have no existence. We infer that the water began to 
 shallow early in the Cretaceous, and that the shallowing extended 
 eastward during the progress of that Age. 
 
 The Cretaceous ends the long series of conformable deposits 
 over the Plateau Province, continuing from the Cambrian onward. 
 Its close was marked by an upward and undulatory movement, 
 which was felt from the eastern base of the Rocky Mountains to 
 the eastern base of the Wahsatch. The Uinta, with its broad, 
 flat anticlinal (Fig. 82), now arose. The whole chain of the 
 Rocky Mountains was further uplifted, and the broad, shallow 
 basin of the Colorado was defined. On the Pacific coast, this 
 disturbance was not felt, though there are indications that the 
 region of the Cascade Range was now marked out. The most 
 important result of this post-Cretaceous movement was the eleva- 
 tion of the whole interior of the continent, and the complete 
 extinction of the inter- American mediterranean ocean. The land 
 of the western limb of the continent was now joined to the land 
 of the eastern limb, and the destined completion of the continent 
 was distinctly foreshadowed. 
 
 The Caenozoic history of the Cordilleran region will be given 
 in its proper connection. 
 
 9. The Csenozoic Great System. 
 1. Divisions, Subdivisions, and Terms. 
 II. Quaternary System. 
 3. RECENT, or TERRACE FORMATION. 
 
 2. CHAMPLAIN FORMATION. Fresh water Erie Clays (Logan). Marine Leda Clays 
 
 (Dawson). 
 
 1. GLACIAL, or DRIFT FORMATION. 
 (3) Second Glacial Deposits. 
 
 (2) Interglacial Deposits. 
 (1) First Glacial Deposits. 
 I. Tertiary System. 
 
 3. PLIOCENE GROUP, 
 
 f2) Equus Beds (Postpliocene?) of Pacific slope, 
 
 i Procamelus Beds (Cope), SUMTER 
 
 (1) Loup Rl ver Beds, j T icholeptus Beds (Cope), GROUP. , 
 
 (=Niobrara, Marsh and King, 
 +Humboldt, King + North Park (Hayden and Hague), J }. NKOCKN-B. 
 
 2. MIOCENE GROUP, 
 
 (2) Truckee Formation (in the West), "1 
 
 (= John Day Group, King), contemporary with \ YORKTOWN GROUP, 
 (1) White River Formation (on Great Plains), I
 
 442 GEOLOGICAL STUDIES. 
 
 1. EOCENE GROUP, ] f vicksburg, 175? ft., J Whi te Lime- 
 
 one (Oligo- 
 
 (4) Uinta Formation, 
 
 (= Brown's Creek, Powell), 
 (3) Bridger Formation, 
 (2) Wahsatch Formation, 
 ( = Vermillion Creek, King, 
 or Bitter Creek, Powell), 
 (6) Green River Division, 
 (?=:Elko Group, King), 
 
 sburg, 175? ft., /Whit 
 > stoni 
 son, 60 ft,, ) cene 
 
 Jackson, 60 ft,, j cene). 
 ALABAMA { 
 
 GROUP, 
 
 Claibonif, 150 ft., 
 Buhrstone, 175-200, 
 
 o ( Calca- 
 I reous, 
 
 - 
 
 L cioue, j ? 
 
 (a) Wahsatch Division, 
 (1) PuercoFormationof Cope, j The Tdjon Group, California, is Eocene. 
 
 \ Bluff Lignite, ] o o 
 
 1 ignitic, 1,000 ft., j Orange Sand, or La Grange, \ g 
 ( Porter's Creek, 
 
 The terms, "Tertiary and "Quaternary " are survivals of 
 an old system of nomenclature in which "Secondary" was nearly 
 equivalent to our " Mesozoic," and " Primary " had a somewhat 
 undefined range over rocks older than "Secondary." " Eocene," 
 ''Miocene," and "Pliocene," introduced by Ly ell, are from Greek 
 terms, signifying " Dawn of the Recent," " Less Recent," and 
 "More Recent." Some include the upper part of the Eocene, 
 and the lower of the Miocene, in another group, " Oligocene," 
 which signifies "slightly recent." The Miocene and Pliocene, 
 taken together, are sometimes designated " Neocene," signifying 
 " newer recent." The subdivisions of the Tertiary groups are 
 designated by geographical terms. Those most distinctly limited 
 belong to the Great Plains and the Cordilleran region. The 
 Puerco, though generally regarded as embraced in the Wahsatch, 
 is urged by Cope, with good reasons, as a coordinate group below 
 the Wahsatch. The terms employed for the divisions of the 
 Quaternary refer to the physical conditions prevailing except 
 " Champlain," which alludes to the basin of the lake of that 
 name. 
 
 2. Geographical Distribution of the Tertiary. The Tertiary 
 strata accessible to study embrace only the limited areas which 
 have been raised above water level, or otherwise drained, since 
 the close of Mesozoic time. They are, therefore, of comparatively 
 small extent, and partly in detached interior regions. A belt of 
 marine Tertiary strata extends from Martha's Vineyard over 
 Long Island, southern New Jersey and the Atlantic coast to Key
 
 FORMATIONAL GEOLOGY. 
 
 443 
 
 West, and thence around the Gulf border into Mexico. It grad- 
 ually increases in width to Florida, attaining in Georgia a breadth 
 of 245 miles. In the valley of the Mississippi it spreads out in a 
 deltoid form, reaching, with its apex, to the mouth of the Ohio. 
 A belt of marine Tertiary stretches along the Pacific coast, form- 
 ing, with the Cretaceous, the Coast Ranges of mountains. Sev- 
 eral detached but extensive areas of fresh-water Tertiary occur 
 in the Interior. The Great Plains, up to the bases of the Rocky 
 Mountains, and southward to the Gulf of Mexico, are covered 
 with lacustrine Tertiary, chiefly of Pliocene age, at surface. 
 Another Pliocene basin exists in Nevada, and a third in the North 
 Park. A great basin stretching from the Colorado, or Front 
 Range westward to the Wahsatch is of Eozene age. Northwest 
 it extends to the Wind River Mountains, over the so called Green 
 River Basin, and southward it stretches into New Mexico. Over 
 part of the eastern slope of the Rocky Mountains, along the 
 valley of the White River, are Tertiary deposits of Miocene age, 
 underlying the Pliocene; and others spread through central Ore- 
 gon along the John Day River. The Eocene beds of the Cordil- 
 leran region attain a thickness of 10,000 feet. The Puerco of 
 Cope, which perhaps is not included in the estimate, extends 
 from the sources of the Puerco River in New Mexico, northward 
 and a little east of the Wahsatch Mountains, consisting of green 
 and gray marls, 500 to 
 1, 200 feet thick. Goryph' - 
 odon and other mam- 
 mals of the Wahsatch 
 group are wanting; but 
 Marsh subordinates the 
 Puerco to the Wahsatch. 
 The Tertiary strata 
 are generally little cohe- 
 rent. They have conse- 
 quently been worn by 
 rains into deep ravines, 
 and fluted slopes, and isolated columns. 
 
 FIG. 355. VIEW IN THI 
 MEXICO. 
 
 BAD LANDS OF NEW 
 (Cope.) 
 
 Such areas beinc: desti-
 
 444 GEOLOGICAL STUDIES. 
 
 tute of verdure and soil, are known as mauvaises terres, or " bad 
 lands" a designation first applied to a portion of the White 
 River region. A view in one of these Bad Lands in New Mexico 
 is given in Fig. 355. 
 
 3. Organic Remains of tJie Tertiary. The three great divis- 
 ions of the Tertiary are based on the percentage of molluscan spe- 
 cies belonging to the recent fauna. In the Eocene the percentage 
 of recent species is small; in the Miocene, less than half, and in the 
 Pliocene, more than half. Generally, however, the aspect of the 
 molluscan fauna was decidedly modern. It contained few Bra- 
 chiopods, numerous Lamellibranchs and Gasteropods, and no 
 chambered shells except Nautilus. Sharks of the Squalodont 
 type were very abundant; and Teleost Fishes prevailed as in 
 modern seas. The remains of the latter are of very frequent 
 occurrence in the Green River Shales, in the upper part of the 
 Wahsatch formation. 
 
 The great feature of the organic life of the Tertiary, how- 
 ever, was its Mammals. Dugongs and Whales abounded in the 
 sea. Zeuglodon, a whale-like mammal with an attenuated pos- 
 terior part, attaining a length of over 70 feet, has left its bones 
 in the White Limestone of the Eocene of the Gulf States. Ver- 
 tebra? of whales are found at Gay Head on Martha's Vineyard, 
 together with the teeth of Squaloids. 
 
 The land Mammals, which were far more important, have 
 been already noticed as far as space permits on pages 348358, 
 which the student should now review. 
 
 4. Quaternary Materials. Here we return to the point 
 from which we started on entrance upon this study. In Part I, 
 Studies I-III, attention was directed to the materials cf the Drift, 
 and their method of arrangement. These Studies should be now 
 reviewed. The principal object of the next eleven Studies (IV 
 XIV) was to become acquainted with the materials of the Drift. 
 In Studies XV and XVI we also considered phenomena of the 
 
 'Drift. Thus the simple observation of things nearest at hand 
 led our thoughts to operations performed many ages before man 
 existed on the earth operations of erosion and sedimentation
 
 FORMATION A L GEOLOGY. 445 
 
 which have contributed so greatly to form the vast rock masses, 
 and sculpture the terrestrial surface into the forms which it pre- 
 sents to our eyes. In this place, therefore, we have only to refer 
 to what has been said, and add a few statements of facts not so 
 easily observed. 
 
 (1) Phenomena of the Surface Materials. A line having a 
 general westerly direction from Sandy Hook through Cincinnati 
 marks the southern limit of bowlders. From Cincinnati it con- 
 tinues to the parallel of 38 in southern Illinois and Missouri; 
 but west of the Missouri River it trends in a direction parallel 
 with the river into Dakota. The incoherent surface materials on 
 the south of this line differ in several respects from such materials 
 on the north of it. (a) On the south there are drifted materials, 
 as well as on the north, but bowlders larger than pebbles are 
 wanting, (b) On the north we notice a distinction of unstratified 
 Drift, semi-stratified Drift, and stratified Drift. The first consists 
 of clay with imbedded bowlders, lying generally on the bed rock, 
 but often outcropping at the surface. The second consists of 
 sand, clay, pebbles, and a few larger bowlders, showing oblique 
 and irregular lamination, and holding position above the till or 
 unstratified Drift. This has evidently been moved and laid down 
 by powerful and irregular currents of water. The stratified 
 Drift is composed of horizontal beds of fine materials, mostly 
 along the borders of lakes, or in situations from which lakes 
 have disappeared. It appears to be the result of lacustrine action, 
 and is thus a "lacustrine formation." Its position is above the 
 semi-stratified Drift. Another form of obscurely stratified mate- 
 rials occurs sometimes along river valleys. It is fine, loamy, buf- 
 fish, and calcareous, with occasional remains of vegetation and 
 land animals. It is known as loss, a German term. It may be 
 seen on the Mississippi River at Vicksburg, Memphis, and Daven- 
 port; on the Des Moines at Des Moines, and on the Missouri at 
 Council Bluffs and Omaha. We find, also, fluviatile deposits of 
 recent origin. The term Drift, as ordinarily employed, is not 
 understood to embrace the lacustrine, lo'ss, and fluviatile depos- 
 its, though they are all mostlv modifications of Drift. On the
 
 446 GEOLOGICAL STUDIES. 
 
 south of the boundary line named, the unstratified Drift 'is want- 
 ing; but semi-stratified Drift is generally present, together with 
 occasional lacustrine, and more abundant fluviatile and l5ss 
 deposits. 
 
 (c) On the north of the boundary line the Drift materials 
 extend downward to the bed rock, and end abruptly on a solid, 
 but sometimes shattered, rock surface. The solid surface is gen- 
 erally smoothed and marked by grooves and striae. On the south, 
 the obliquely laminated Drift near the surface mingles gradually 
 with materials resulting from the disintegration of the rock im- 
 mediately underlying, until the latter materials predominate; 
 traces of the original stratification appear; the substance grows 
 less and less changed, and passes downward by degrees into 
 sound, unaltered bed rock. That is, in the south the lower part 
 of the surface deposits seems to have resulted from the decay of 
 the underlying strata, and we can trace the stratification upward 
 from the unaltered rock into the overlying, unconsolidated beds: 
 These lower portions have been formed where they lie; only the 
 higher, gravelly portions have been brought from some other 
 region. The lower portions, therefore, are not properly any part 
 of the Drift. The upper, transported sand and gravel are much 
 less abundant than the proper Drift of the North; but yet, in 
 some localities, they are found one or two hundred feet thick. 
 
 (2) Relation of Drift Phenomena to Climatic Causes. It 
 thus appears that the geological action which in the north re- 
 moved the decayed rock, smoothed and striated the general rock 
 surface, and distributed the bowlders, ceased to operate in about 
 the latitude of Cincinnati. It was an action correlated to climate, 
 since the differences are latitudinal, and the separating line, in 
 mountain regions, is deflected southward, like an isotherm. 
 
 The smooth and striated condition of the bed rocks throughout 
 the northern states (see Figs. 200 and 213) is a condition such as 
 is produced in modern times in all glacier-covered regions (pages 
 280284); the transportation of bowlders is a phenomenon of 
 glacier action ; and thus the two most characteristic features of 
 the Drift are traceable, not only to climatic, but to glacial causes.
 
 FORMATIONAL GEOLOGY. 447 
 
 Again, the deposition of the semi-stratified Drift appears to have 
 resulted from some torrential action, such as might be caused by 
 the rapid conversion of ice into water. Thus, while striae and 
 bowlders are phenomena which suggest a geological winter, mod- 
 ified Drift is a phenomenon suggesting a geological springtime. 
 Comparing the North and South, we see that the ice of the geo- 
 logical winter did not pass the parallel of 39; the floods of the 
 geological springtime rushed to the Gulf of Mexico. 
 
 (3) More Critical Observation of the Drift. Now that we 
 plainly see reasons to regard the Drift as the result of glacier 
 action, much light is shed on the nature of other phenomena. 
 The broad sheet of commingled clay, sand, gravel, and bowlders 
 firmly compacted together, lying immediately on the rock floor, 
 may be regarded as Subglacial Till laid down beneath the thin- 
 ning marginal portion of the ice sheet. The sheet in some places 
 overlying this, similar in character, but less compact, is Englacial 
 or Superglacial Till, formed of materials imbedded in the ice, or 
 accumulated on its surface; while the more homogeneous till, with 
 occasional traces of stratification, and holding a higher position, 
 is Subaqueous or Floe Till, formed under water through the 
 agency of floating ice. (Chamberlin.) 
 
 In the modified Drift we make (following Chamberlin) the 
 following discriminations: The long narrow, sharp ridges of 
 gravel and sand, with some bowlders, stretching out from higher 
 to lower levels, and following generally the courses of the larger 
 valleys, are Osars. The assemblages of conical hills and short, 
 irregular -ridges, with intervening depressions and bowl-shaped 
 hollows, are Kames {Fig. 5). Unlike the osars, they tend rather 
 to stand transverse to the slope of the surface, and to the direc- 
 tion of the glacier movement. 
 
 Among phenomena connected with glacier action, we dis- 
 criminate lateral; median, interlobate, and terminal moraines. 
 Lateral moraines are accumulated along the borders of a glacier 
 (Fig. 211); median result from the union of two contiguous 
 lateral moraines, where two glaciers become confluent; interlo- 
 bate moraines result from the joint action of two adjacent glacier
 
 448 GEOLOGICAL STUDIES. 
 
 lobes or tongues, which push their contiguous lateral moraines 
 together without becoming properly one glacier stream. A ter- 
 minal moraine accumulates in front of the glacier, so that when 
 the glacier retreats, the moraine remains as a curved ridge of 
 confused or locally stratified materials. (See Figs. 211, 212.) 
 
 (4) The Terminal Moraine of the Ancient Glacier. The 
 continental glacier of the United States must not be conceived 
 as one continuous sheet of ice, moving forward with equal pace 
 in all its parts, and accumulating a rigidly continuous moraine, 
 stretching along an unbroken glacier front. The great glacier 
 suited itself to the topographical configuration of the land. It 
 must be viewed as a viscid fluid pursuing the courses of the great 
 valleys, and protruding its front in irregular lobes, in varying 
 directions and to varying distances, according to the direction 
 and length of the valley axes. On the general retreat of the 
 great glacier, therefore, the continental moraine would consist of 
 a scries of crescentic ridges more or less disconnected. So we 
 find it. 
 
 But we must now remark that the glacial period in North 
 America, as in Europe, appears to have been divided into two or 
 more epochs, separated by one or more interglacial epochs. Evi- 
 dences of such division have been detected in so called "dirt 
 beds" in Illinois and elsewhere, intercalated in the glacial Drift. 
 Indications of similar purport are found in New Jersey. We 
 have, accordingly, the phenomena of two or more glacier termi- 
 nations. The older epoch was marked by a glacier which had for 
 its southern limit the line which has already been traced, and 
 which is shown in detail in Fig. 356. The newer epoch appears 
 to have been marked by a glacier leaving-, generally, a more 
 northern moraine. Both moraines have recently been traced 
 across the whole extent of the country from Cape Cod to Dakota, 
 For this work we are indebted chiefly to Messrs. Lewis and 
 Wright for the Atlantic seaboard, Chamberlin for the Interior, 
 Upham for Minnesota, and Wooster for Dakota. Professor 
 Wright's investigations extended also into Indiana, and Cham- 
 berlin's stretched from New Jersey to Dakota. The aggregate
 
 FORMATIOXAL GEOLOGY. 
 
 449 
 
 results possess extreme interest, and are mapped on a small scale 
 in Fig. 356. 
 
 A glance at this map shows a line of morainic crescents extend- 
 ing from Cape Cod along or near the southern boundary of the 
 Drift area, to Indianapolis. This is generally regarded as a line 
 of vestiges of the terminal moraine of the earlier glacier. The 
 more northern morainic system is supposed to pertain to the sec- 
 ond glacier. It is impracticable here to enter into any detailed 
 description of these moraines. We direct attention simply to a 
 few points, (a) The older moraine does not border the Drift- 
 
 Fro. 356. MAP or TERMINAL MORAINE TRACED ACROSS THE UNITED STATES. 
 (From Chamberlin's Report.) B, 2i, B, Southern Limit of Drift; M, M, M, Moraines. 
 
 covered area west of Indiana, (b) It is not coincident with that 
 border west of Pennsylvania, (c) From western Pennsylvania 
 to Michigan the second morainic system is either wanting or co- 
 incident with the first moraine, or quite overlapped it and oblit- 
 erated it. ((/) West of Lake Erie the second moraine consists 
 of a series of great loops rudely concentric with the great lakes 
 and their principal bays. It may be added that the directions of 
 the glacial striations on the rocks indicate that each of these 
 principal and subordinate basins had its separate glacier sheet, 
 which formed its separate loop in the moraine system, (c) The
 
 450 GEOLOGICAL STUDIES. 
 
 remarkable northwesterly trend of the moraine in the valley of 
 the Missouri River follows the isothermal lines. (/) A broad, drift- 
 less area is shown in Wisconsin, (g) Two state universities are 
 located on the second terminal moraine. The University of Min- 
 nesota is located near the junction of the eastern Lake Superior 
 and northern Minnesota moraine. The University of Michigan 
 is on the interlobate moraine, between the Saginaw and Maumee 
 glacial lobes the Kames rising 300 and 400 feet above the bed 
 rock, and the " cat hole " within the city limits of Ann Arbor 
 being one of the morainic "kettles." 
 
 (5). Characteristics of the Terminal Moraine. The Termi- 
 nal Moraine, or more specifically the Second Moraine, consists of 
 an extensive irregular range of confusedly heaped drift ridges or 
 knolls. It sometimes consists of two or more separate ranges, 
 which occupy a width of 20 to 30 miles, while each range is from 
 one to six miles wide. The morainic range is constituted of a 
 series of hills of rapidly but gracefully undulating contour, with 
 rounded domes, conical peaks, winding and occasionally genicu- 
 lated ridges, short, sharp spurs, mounds, knolls, and hummocks 
 promiscuously arranged, accompanied by corresponding depres- 
 sions. The latter are variously known as "potash kettles," "pot 
 holes," "pots and kettles," "cups and saucers" (Fig. 7), "sinks," 
 etc. The characters are shown in the accompanying view of the 
 moraine near Eagle, Wis. (Fig. 357). These characters are not 
 fundamentally different from those presented by the general Drift. 
 They are much more pronounced, and are ranged according to a 
 discoverable system. 
 
 Internally, the moraine is distinguishable into two portions. 
 The one, usually the uppermost, but not occupying the heights 
 of the range, consists almost whollv of assorted and stratified 
 material, resembling the modified Drift under its usual and famil- 
 iar aspects (Fig. 7). The other element of the moraine consti- 
 tutes its basal and central portion, and consists of a confused 
 commingling of clay, sand, gravel, and bowlders, often resembling 
 true subglacial till. It is probably true till pushed up by the
 
 FORMATIONAL GEOLOGY. 451 
 
 glacier, acted on and locally assorted and stratified by waters 
 escaping from the glacier. ' - u*--'^Ct^-i>* " 
 
 (6) Tabular Limestone Ufasses Imbedded in the Drift. In 
 certain regions notably southern Michigan, in the counties of 
 Washtenaw, Lenavvee, Hillsdale, and Jackson, and also in Ber- 
 rien, Van Buren, and Ottawa occur numerous tabular masses of 
 limestone, some of which attain dimensions of 10 to 20 feet 
 square with a thickness of one or two feet, and supply material for 
 numerous limekilns of a transient character. These masses oc- 
 cupy nearly horizontal positions, and lie imbedded near the sum- 
 
 . 357. WESTERN FACE OF THE MORAINE NEAR EAGLE, Wis. (Chamberlin.) Compare 
 also Fig. 5. 
 
 mits of knolls of semistratified sand. They are fragments of 
 Corniferous Limestone, as the fossils prove, the nearest outcrops of 
 which on the north are at Mackinac, and on the south within the 
 distance of 10 to 30 miles. They have not the worn aspect of 
 bowlders; they have been transported gently. The presumption 
 is that they have been derived from the south. The present writer 
 suggested, some years ago, that they were floated by ice floes 
 formed over shallow lakes accumulated in front of the glacier 
 during the period of retreat. Chamberlin, on the contrary, has 
 suggested that they were plowed up and transported by the 
 glacier, and made part of the terminal moraine. Similar frag-
 
 452 GEOLOGICAL STUDIES. 
 
 ments are reported from Wisconsin. The explanation of these 
 exceptional facts is still to be sought. 
 
 (7) Champlain Deposits. These consist chiefly of the inco- 
 herent stratified materials bordering certain lakes. They are well 
 shown about the western end and northern border of Lake Erie, 
 whence they have been named the " Erie clays." They occur 
 also over the western part of the peninsula of Ontario, stretch- 
 ing into Michigan. They consist of layers of clay and sand 
 mingled with some vegetable matter, and ascend the bordering 
 slopes sometimes to the height of one or two hundred feet. The 
 lower sandy layers rising to the surface become saturated with 
 rain water, which is borne along the dip of the stratum, and thus 
 furnishes supplies of artesian water to localities at the lower 
 levels. 
 
 Other extensive Champlain deposits are found in the valley of 
 the Red River of the North. They were laid down in a former 
 great lake, which Mr. Warren Upham proposes to call Lake 
 Agassiz. The shore lines may still be traced at various levels on 
 the east and west. The lake must have received the waters of 
 the Saskatchewan, and had its outflow southward to the Mis- 
 sissippi. 
 
 Evidently the sediments bordering Lakes Erie and Michigan 
 were laid down when the lakes stood at higher levels. As to the 
 drainage and diminution of lakes, it seems to have been general. 
 The climate of America has grown dryer in late geological epochs. 
 But undoubtedly much lake drainage has resulted from a wearing 
 down of outlets. Apparently this cause has operated upon Lakes 
 Erie, Huron, and Michigan, as was explained when treating of 
 the Niagara gorge. Fig. 305 may now be further studied. 
 
 (8) Quaternary JJakes. In the Basin Province of the Far 
 West we find the remnants of ancient Quaternary lakes, which 
 far exceeded present limits. Their former bounds are shown by- 
 old beach lines. These lakes of which Lahontan and Bonne- 
 ville are best known, thanks to the labors of Gilbert and King 
 resulted originally from the subsidence of the east and west sides 
 of the Basin, which took place at the end of the Pliocene. The
 
 FORMATIOXAL GEOLOGY. 453 
 
 bottoms of the depressions formed were 4,000 feet above sea 
 level, and their borders 5,000 feet. Vestiges of Lake Bonneville 
 are seen at present in Great Salt Lake, Utah Lake, and Sevier 
 Lake. This lake was 300 miles long and 180 miles broad. The 
 highest terrace is 940 feet above the present level of Great Salt 
 Lake. Lake Lahontan lay in western Nevada, along the bold 
 front of the Sierra, and was nearly as large as the former; but it 
 was much cut up by mountain ranges. Remnants of this lake are 
 still seen in Pyramid, Winnemuca, Carson, Walker, and Humboldt 
 Lakes. These great ancient lakes began to exist with the begin- 
 ning of Quaternary time though Lahontan was a smaller lake 
 during the Miocene but the progress of their desiccation con- 
 tinued into the Champlain epoch; and some evidences exist that 
 it continued till near the present. The water of Great Salt Lake, 
 however, rose eleven feet between 1849 and 1878. But it was 
 nearly constant till 1866, and the rise is a later occurrence. 
 King is of the opinion that the salinity of these lakes is derived 
 from the influx of saline waters. If, as Gilbert and King have 
 shown, they formerly had drainage to the sea, their primitive 
 salinity derived from the influx of ocean water must have been 
 exhausted; they were fresh-water lakes during their high level; 
 and since the outflow ceased, the only probable source of their 
 present salinity is the slight saline contribution brought by tribu- 
 tary streams. Though these lakes are generally considered coeval 
 with eastern glaciation, it remains to show, with plausibility, that 
 they were not rather a feature of the Champlain Epoch. 
 
 In the northwestern part of the Great Basin, in Oregon, other 
 Quaternary lakes have been described by Russell. These occu- 
 pied the sites of the present lakes, Alvord, Malheur, Warner, 
 Guano, Summer, Abert, Silver, Goose, and Klamath, in Oregon, 
 together with Surprise Valley and the Madeline Plains in Cali- 
 fornia, and Long Valley in Nevada. Some of them attained a 
 depth of 500 and 600 feet', and spread far beyond the limits of the 
 modern lakes. In the old bed of Christmas Lake are found many 
 modern species of fresh-water shells, together with bones of 
 mammals reported by Marsh as Pliocene, and thus possibly
 
 454 GEOLOGICAL STUDIES. 
 
 washed in after fossilization. These lakes lie between the 117th 
 and 121st meridians, and extend from the parallel 41 to 43 30'. 
 Directly north of this group of lakes, between the parallels of 46 
 and 47 30', is the bed of another ancient lake, designated Lake 
 Lewis by Lieutenant Symonds, who regards the lake as of 
 Charnplain age. 
 
 (9) Recent Formations. River terraces and some other 
 phenomena of the latest epoch of geological history have been 
 sufficiently considered in Part I, Study XV. River terraces are 
 illustrated in Fig. 210. 
 
 The geological work of the Recent or Terrace Epoch em- 
 braces much more than the formation of terraces, as commonly 
 understood. Since the dissolution of the continental glaciers, 
 the drainage of the land has become settled in its courses, and 
 all the depositions which rest on the Modified Drift have been laid 
 down. River deltas have been formed in all their extent. The 
 drainage of lakes has continued, and innumerable small lakes 
 have been filled with beds of marl and peat, as previously ex- 
 plained, page 82 and Fig. 25. The beds of rivers have, in many 
 instances, been sunken by erosion, though in others the shrink- 
 age of the volume of water has caused them to rise by accumu- 
 lation of sediment. Cavern erosions have been continued, though 
 more frequently the diminution of water has arrested the work 
 of cavern making. The formation of stalagmites and stalactites 
 dates, generally, from the Glacial epoch, or even an older one. 
 This is true of much of the work which we witness in progress. 
 The erosion of gorges is generally a process of which we witness 
 only the latest stages. The excavation of caverns must have been 
 begun as soon as the land drainage found fissures in limestone 
 formations through which to flow. The removal of soils and the 
 exposure of underlying rocks has been in progress as long as 
 land has existed. In some cases the work was completed and the 
 land obliterated even before the modern epoch. 
 
 The drainage valleys and the deep-cut gorges with which we 
 are familiar in the topography of the present epoch are largely 
 results which have been in progress as long as the land surfaces
 
 FORMATIOXAL GEOLOGY. 
 
 455 
 
 have been exposed. Some of these works extend back, probably, 
 into Palaeozoic time; but some of the greatest, like the canon of 
 the Colorado, have been accomplished since late Tertiary time, as 
 is proved by the age of the strata excavated. The valleys of the 
 Hudson and Connecticut may date from the Palaeozoic; but if so, 
 their courses were both interrupted by the deposits and the oro- 
 graphic movements of the Triassic; to be reopened after the 
 
 FIG. 358. SUBMARINE CHANNEL OP THE HUDSON RIVER AND THE ANCIENT ATLANTIC 
 SHORE. (After Lindenkohl.) 
 
 close of the Triassic. The actual submarine shore line of the 
 coast of the United States, Fig. 358, is a feature in modern topo- 
 graphy. It lies from 80 to 100 miles from the present shore, in 
 about 500 feet of water. Off the harbor of New York, we find 
 what appears to be an ancient channel of the Hudson River con- 
 tinued seaward when the land was some hundreds of feet higher. 
 This may have been excavated as far back as Palaeozoic time, 
 when the Seaboard Land had its higher altitude, and may have
 
 456 GEOLOGICAL STUDIES. 
 
 gone down with the eastern border of that land, when the Appal- 
 achian border reemerged. The submerged Hudson channel, 
 whenever formed, extends 80 miles to sea. At the distance of 10 
 miles its bottom is 48 feet below the general sea bottom. At 20 
 miles it is 90 feet below. At 50 miles it is 66 feet, and continues 
 to diminish. At 80 miles is an ancient bar. The width of the 
 channel is three-fourths of a mile to a mile. Beyond the bar is 
 what appears like an ancient fiord, beginning about 85 miles from 
 Sandy Hook, and extending 25 miles to the edge of the conti- 
 nental slope, with a width of about three miles. For half its 
 length this ravine has a depth of over 2,000 feet. It is inter- 
 rupted by a bar 1,600 feet high. The sides of this submarine 
 river channel slope at an angle of one to three degrees; those of 
 the fiord, 14. 
 
 In the changes progressing under our observation we are fur- 
 nished with clews to the explanation of the grander events of 
 remote geological history. To a large extent these are but ag- 
 gregates of slow operations continued through geologic aeons. 
 So far the method has been uniformitarian. In the elevation of 
 the Uintas we witness, undoubtedly, as Powell has demonstrated, 
 a grand result accomplished by slow movements, since the Green 
 River has cut through the whole altitude of the range. But some 
 cataclysmic events must have taken place, as convulsions like 
 those of Kra-kat'oa, Ischia, and Andalusia, in our own day, would 
 indicate. Much greater ones, but of the same order, must have 
 occurred when the Wahsatch and Sierra Nevada were rent longi- 
 tudinally, and the Basin Province sank a thousand feet along each 
 of its borders. On the whole, however, the geological work in 
 progress may be regarded as mirroring the nature of the methods 
 of the operations which have formed the world. Assuming that 
 the same modes of activity will continue in the remote future, 
 we have ground for anticipating unrealized results as grand and 
 transforming as any which have been realized in the history of 
 the past. 
 
 (10) Organic Remains of the Quaternary. In the ordinary 
 glacial Drift few relics of the organization of the epoch occur.
 
 FOKMATIOXAL GEOLOGY. 457 
 
 Yet pieces of white cedar are found at various depths down to 
 60 feet at least, in the modified Drift. In regions south of the 
 glacial limits life continued to flourish both on the land and in 
 fresh waters. The great Quaternary Lakes Bonneville and La- 
 hontan (whether Glacial or Champlain) on the eastern and west- 
 ern sides of the Great Basin, were stocked with fresh-water 
 species of molluscs, of which the most abundant genera were 
 Limncea, Pomatiopsis, Amnicola, and Siiccinea. The Oregon 
 Quaternary lakes were similarly inhabited. In the Champlain 
 epoch the Gulf of St. Lawrence extended into the basin of Lake 
 Champlain; and some molluscan remains have been left in the 
 valley of the St. Lawrence, in the "Leda clays." The skeleton 
 of a small white whale, Beluga Vennontana, has been discovered 
 on the borders of Lake Champlain. 
 
 Of land mammals numerous species have been found in cav- 
 erns and rock fissures, and in post-glacial surface deposits. The 
 age of remains from caverns and fissures may be glacial or post- 
 glacial; but remains in beds resting on the Drift must, of course, 
 belong to the Champlain epoch, if of extinct species, or to the 
 Recent epoch, probably, if of living species. A limestone fissure 
 at Port Kennedy, Pa., has afforded Cope remains of 34 species of 
 mammals, mostly extinct. Caves in Wythe county, Va.; at Ga- 
 lena, 111. ; and near Carlisle, Pa., have afforded many remains, some 
 of which belong to extinct species. 
 
 In deposits more recent than the Glacial epoch have been 
 found remains of a species of Elephant (Elephas Americanus 
 
 the same as Elephas or Euelephas Jacksoni) as large as the 
 Quaternary Elephant of the Old World. The latter also (Ele- 
 phas primige'nius) is found in the more northern latitudes of 
 America (see Fig. 364). More frequent is the Mastodon Mas- 
 todon Americanus (called also J\I. giganteus and J\f. Ohioticus) 
 
 found generally in peat bogs where, according to prevailing 
 opinion, the creature became mired. But the carcass may also 
 have bee'n borne in by a flood while the bog was yet a lake. The 
 Mastodon was abundant throughout the Northern United States. 
 Three perfect skeletons have been exhumed in Orange countv,
 
 458 
 
 GEOLOGICAL STUDIES. 
 
 New York; one near Cohoes Falls on the Mohawk, one in New 
 Jersey, one in Indiana (destroyed in the great Chicago fire), and 
 one from the banks of the Missouri. Skeletons imperfectly pre- 
 served have been found in very numerous localities, especially 
 western. A nearly complete skeleton was exhumed near Tecum- 
 seh, Mich., and another in Cass county. Dr. Warren's Mastodon 
 from near Newburgh has a height of 11 feet, with a length of 17 
 feet to the base of the tail. The tusks are 12 feet long, of which 
 2 feet are inserted in the sockets. The total height when living 
 
 FIGS. 359-362. PLAN or ENAMEL PLATES ON THE MOLAR CROWNS or PROBOSCIDIANS. 
 359, Molar of African Elephant; 360, Indian Elephant; 361, Mammoth; 362, Molar 
 of Mastodon, perspective view. 
 
 must have been 12 or 13 feet, and the length 24 or 25 feet, The 
 Mastodon probably survived to the recent epoch. The Tecumseh 
 Mastodon was buried in a small bog with only 18 inches of peat 
 over it. In the same county Indian arrow heads are found seven 
 feet beneath the surface of the peat. Mastodon remains are re- 
 ported in Florida, south of the thirtieth parallel. 
 
 The most striking differences between the elephant and mas- 
 todon are found in the molar teeth; and these are illustrated in 
 Figs. 359 to 362. 
 
 The post-glacial deposits of North America have afforded also
 
 FOBMATIONAL GEOLOGY. 459 
 
 the remains of a Horse, larger than the domestic species, a gi- 
 gantic Beaver (Castoroides Ohioensis], of -which an incisor is 
 shown reduced in Fig. 
 363; pig-like and pec- 
 cary - like animals; 
 Oxen, Bisons, and 
 Tapirs ; also Bears, 
 Lions, and Haccoons,- 
 
 Some Edentates, in our tlfl/ftifflff \ A .' 
 
 times almost peculiar 
 to South America, ex- 
 
 , , , . FIG. 363. INCISOK OF THE EXTINCT GIGANTIC BEAVER 
 
 tended their range < cast or aides OMoensis). From Xapeer, Mich. X *. 
 northward to the Ohio 
 
 River. They include several species of Meg <M onyx, and one each 
 of Myl'odon and Megatherium. From Florida are reported re- 
 mains of Rhinoceros, Stag, Camel, Tapir, and Hippopotamus. 
 
 In South America Edendates were the predominant ordinal 
 type, as they still are. The pampean formation of the southern 
 part of the continent is a vast, level deposit, 20 to 100 feet deep, 
 formed largely of materials borne eastward from the slopes of 
 the Andes at a time when the Atlantic covered the country to 
 the foot of the mountains. It stretches over the larger part of 
 Patagonia and the Argentine Republic, embracing one and a half 
 million square miles. This Quaternary formation is a literal cem- 
 etery of strange and mostly uncouth mammalian forms. The 
 great Megatherium Cuvieri (Fig. 364) was larger than the Rhi- 
 noceros, and in some of its proportions exceeded the elephant. 
 The femur was three times as thick as the elephant's. This ani- 
 mal was a huge ground sloth, with massive posterior extremities 
 and post-like tail, which suggests its probable habit of standing 
 erect to browse from the foliage of the forest. Other and asso- 
 ciated Edendates were Megal'onyx, so named by President Jeffer- 
 son ; Myl'odon, larger than the American buffalo ; Scelidothe'- 
 rium, an allied genus, and Grlyp'todon, a huge armadillo, cara- 
 pace-covered like a turtle. 
 
 In Europe, the oldest Quaternary relics are found in caverns.
 
 460 GEOLOGICAL STUDIES. 
 
 They embrace the Cave Bear, Cave Hysiena, and Cave Lion, all 
 somewhat larger than the nearest related modern species, but all 
 regarded, at present, as identical with modern species, or derived 
 from them. With these are found bones of the Mammoth (Ele- 
 phas primiyenius), Rhinoceros, Hippopotamus, Deer, Aurochs, 
 or European Bison, and other species, and often implements of 
 
 FIG. 364.Mtga/he'rium CuvVeri, RESTORED. From the Pampas near Buenos Ayres. 
 
 human production. The most celebrated bone caverns are those 
 of Kirkdale, Kent's Hole, and Brixham, in Great Britain, and 
 Gailenreuth, Perigord, and the Bordogne, on the continent. 
 
 The Mammoth extended into Siberia, and thence into Alaska. 
 The tusks exist in such abundance as to constitute an article of 
 export. The carcass of the Mammoth is sometimes found im- 
 bedded in permanent ice. In some cases the flesh is thus pre-
 
 FOKMATIOSTAL GEOLOGY. 
 
 461 
 
 served, and supplies food for dogs, wolves, and foxes. In one 
 celebrated instance, a carcass taken from ice near the mouth of 
 the Lena furnished a skeleton which was mounted in the Museum 
 at St. Petersburg. From this, and other bones discovered in 
 Europe, Dr. Frass, of Stuttgardt, effected a restoration which is 
 now in Ward's Natural History Establishment, at Rochester, N. 
 Y. Of this, a representation is given in Fig. 365. It will be 
 
 FIG. 365. UESTORAT 
 
 OF THK SIBERO-AMERICAN MAMMOTI 
 (After Fraas and H. A. Ward.) 
 
 Elephax primigenius). 
 
 noticed that this elephant was warmly clad with hair of three 
 kinds. The most abundant was reddish wool, an inch in length. 
 Interspersed through this were reddish-brown hairs, four inches 
 long, and sparser black bristles, twelve to sixteen inches long. 
 It is reasonable to infer from the clothing that the mammoth 
 inhabited a cold, or a cold-temperate climate in the epoch before 
 the advent of continental glaciers. It appears, too, that the 
 invasion of snow and permanent cold was sudden. The mam-
 
 462 GEOLOGICAL STUDIES. 
 
 moth had no time for retreat. There was no returning spring- 
 time. The beast, once buried, remained frozen through a geologic 
 period. 
 
 It has been believed that the mammoth had become extinct; 
 but the mountains of Siam have yielded at least two young spec- 
 imens of a hairy, perhaps dwarf, elephant, which seems clearly to 
 be the descendant of the mammoth of the North. These ele- 
 phants were imported into New York in 1884. 
 
 Human implements and human bones are found in European 
 caverns, in interglacial deposits and in river drifts, associated 
 with the relics of extinct mammals. It appears from the evi- 
 dences that man, in a barbarous state, was a resident in Europe 
 as early as the interglacial epoch. Some indications of his pres- 
 ence during the Pliocene, and even the Miocene, period, have 
 been thought to exist; but the general opinion holds as insuffi- 
 cient the alleged evidence of his preglacial advent,
 
 CHAPTER VI. 
 HISTORICAL GEOLOGY; 
 
 OR, WHAT HAS BEEN LEARNED ABOUT GEOLOGICAL PROGRESS. 
 
 1. Presedimentary History. 
 
 ALL that can be said about the history of terrestrial matter 
 during jeons antecedent to the formation of enduring record- 
 bearing rocks must be a deduction from (1) The ascertained laws 
 of matter; (2) The conditions observed in other worlds; (3) The 
 principles of world making disclosed in the rocky records of our 
 planet. It is intended to offer only a few condensed statements. 
 
 It is generally believed that the matter of the earth and the 
 whole solar system existed, at a very remote period, in a condi- 
 tion analogous to that of modern nebulge. These probably consist 
 of particles and masses accumulated through the action of gravi- 
 tation, from wide realms of space. Through the processes of 
 aggregation, heat and rotation are generated in the nebula. 
 Our solar nebula was once in such a state. Through cooling and 
 shrinkage, its rotation was accelerated, until a succession of rings 
 was detached, each of which, in the course of time, assumed the 
 form of a planet. Each planet was at first in the condition of 
 discrete matter of high mobility, and in a state of rotation. 
 Some of them, in turn, detached rings, which became satellites. 
 
 At some stage in the process of cooling, a portion of th'e 
 matter of a planet, or the whole of it, existed in the condition of 
 "fire-mist," or liquid particles of mineral matter, enveloped in 
 other matter retaining the gaseous condition. Such was once 
 our earth. At a later stage, however, the mineral particles 
 descended toward the centre of gravity, and the planet became 
 a molten globe. Enormous pressure at the centre may have 
 
 463
 
 464 GEOLOGICAL STUDIES. 
 
 reduced the central portion to a solid state; but this solidity was 
 of a very different nature from that which resulted from cooling 
 at the surface. From superficial cooling, a solid crust resulted, 
 and this thickened continually. 
 
 In the course of time, but probably while the crust still 
 retained an incandescent temperature, the vapor of water began 
 to condense in the higher atmosphere. Before this, water could 
 only exist in an invisible gas. Clouds now gathered around the 
 world, and the first rains descended, amid scenes of terrific elec- 
 trical disturbance. The falling rains hastened the thickening of 
 the crust and the cooling of the surface; and in the course of a 
 geologic age, water was permitted to accumulate in a film, which 
 constituted a universal ocean. The descending rains had washed 
 down the atmospheric acids, and the ocean was one of acid 
 waters. These waters were hot. They rested on a crust which, 
 from its mode of origin, was alkaline, and was ready to undergo 
 chemical change as soon as an acid solution was brought in con- 
 tact with it. In this ocean chemical action was intense. The 
 results were soluble substances, like chlorides and sulphates, left 
 in solution, and other substances, like silicates and calcium car- 
 bonate, precipitated. Thus precipitates accumulated over the 
 ocean bottom; and to these were added such detritus as resulted 
 from the mechanical action of the ocean in the shallowest situa- 
 tions. The thickened crust impeded the escape of internal heat, 
 and this acted on the under side of the crust, re-fusing some 
 portions, to restore the equilibrium thickness. 
 
 Thus the cooling, so long in progress, continued. But the 
 crust did not cool in the same proportion as the internal mass; 
 and wrinkles resulted. These assumed general meridional trends 
 in consequence of ingrained predeterminations, caused by tidal 
 actions during the incrustive stage, and by the progressive secu- 
 lar subsidence of the earth's equatorial protuberance, resulting 
 from the slow diminution of rotational velocity. These wrinkles, 
 whether submerged or emergent, furnished the waves new oppor- 
 tunities for detrital production. Thus the crust thickened at an 
 increased rate in the more deeply submerged regions, and the
 
 HISTORICAL GEOLOGY. 465 
 
 removal of subjacent layers proceeded. What amount of the 
 original crust may have been re-fused in this way can only be 
 conjectured. As no portion of the original fire-formed crust has 
 ever been discovered, we may infer that it was all returned to 
 the molten interior. We may even conclude with probability 
 that much of the super-crust, or stratified crust, was also re-fused; 
 since the lowest strata yet explored fail to reveal the evidences 
 of violent oceanic movements which must have taken place when 
 the moon was much nearer the earth, and produced much greater- 
 tides, while, at the same time, the terrestrial day was shorter. 
 When those sediments were deposited which have formed the 
 oldest Laurentian rocks, the tidal and other physical forces 
 appear to have been acting very much as in our times. 
 
 2. Inductive History. 
 
 1. The Eozoic ^HJon. The visible rocks reveal a body of 
 facts from which we may reason by inductive inference, as well 
 as from the principles of nature. The history thus far deduced 
 brings us down to the Eozoic JEon. To this Great System belong 
 the oldest rocks preserved for our study. There must have been 
 sources of sediments then in existence, for these rocks are sedi- 
 mentary in their nature, though the oldest cannot be pronounced 
 characteristically fragmental. If there Avere any emergent lands 
 during Eozoic time, we know not where they were. They have 
 disappeared, consumed by the erosions which were preparing 
 materials for the continental foundations of later ages. Perhaps 
 the ocean was still universal, and the erosions were suffered by 
 the shallower portions of the sea bottom. The rocks which 
 resulted are before us, bearing, however, the marks of subsequent 
 metamorphism, to an uncertain extent. We have passed these 
 rocks in review. They overstrew the drift-covered surfaces. 
 The deepest rocks are also very extensively the surface rocks. 
 
 With the progress of time, the conditions of rock formation 
 changed. We have, in the same regions, gneisses, slates, con- 
 glomerates, and limestones, piled successively above each other. 
 What was the nature of these changes we will not stop to inquire.
 
 46G GEOLOGICAL STUDIES. 
 
 We know, to a certainty, that the Eozoic yEon was inconceiva- 
 bly long; and that the ocean reigned almost or quite universally. 
 
 Of life during the earlier ages, there was none. At length 
 arrived a humble form, which planted itself upon the sea bottom, 
 and opened the drama of organization. Of Eozoon, in its struc- 
 ture and affinities, we have learned in another connection. It 
 was the reef builder of these twilight ages. But when Eozoon 
 ceased to live and work there was a blank, so far as observation 
 goes. In the Upper Laurentian and Huronian, no trace of organ- 
 ization has been discovered. We cannot admit, however, that 
 life, once introduced, was permitted to become extinct, and thus 
 create the necessity of a new beginning. We must conclude 
 that the processes of metamorphism, which so transmuted many 
 of the rocks, have completely obliterated all fossil remains. 
 Probably the Huronian rocks once contained the records of Hu- 
 ronian life. 
 
 But of the physical vicissitudes of Eozoic time we can say 
 more. The crustal wrinkling before mentioned was part of a 
 method which was destined to be continued. Sediments of Lau- 
 rentian age, hardened already by chemical, thermal, and mechan- 
 ical actions, were mashed together by lateral pressure, crumpled 
 where they could not be mashed, and uplifted in huge folds 
 when the surplusage of circumference became too great to be 
 disposed of by these methods. In other words, Laurentian folds 
 of the crust rose toward or above the surface of the ocean. 
 
 Meantime, deposition proceeded. The new folds began to be 
 worn down, arid later deposits, known as Huronian, rested un- 
 conformably on them. There were probably other uplifts of the 
 primal folds. If we reason correctly, it was yet Eozoic time 
 when the Keweenian formations came into existence. In the 
 region which has since been the basin of Lake Superior, igneous 
 ejections occurred on a scale of great magnitude. Probably the 
 region had become land through an uplift at the close of the 
 Huronian. Over this area, great sheets of molten lava, welling 
 through the broken crust, spread out for a distance of 300 miles 
 from east to west, and 100 miles from north to south. The crust
 
 HISTORICAL GEOLOGY. 467 
 
 began to sink, as if a void had been produced beneath it. The 
 sea returned, and covered the region. From the adjoining fel- 
 sitic slopes large quantities of fragments were broken, and rolled 
 as pebbles over the sunken lava sheet, till the surface became 
 again dry land, or a mere shallow. Then the molten eruption 
 recurred, and again a sinking was experienced. These outflows 
 and subsidences, and interposed sedimentary sheets, were many 
 times repeated. 
 
 The close of the Eozoic JEon now approached. Great sub- 
 marine wrinkles, grouped in some cases in wide and massive sys- 
 tems, had been for ages rising to the surface of the ocean, and 
 above its surface. The germinal areas of the North American 
 continent had now emerged. The chief of these were three. (1) 
 The Laurentian or Great Northern Land. This consisted of an 
 irregularly arcuate ridge or broad mountain elevation encompass- 
 ing the area now occupied by Hudson's Bay. Its longer limb 
 stretched from the northern shore of Lake Huron, as it now 
 exists, northwestward between Hudson's Bav and the MacKenzie 
 River to the Arctic Ocean; while the shorter limb stretched from 
 the same region northeastward to the coast of Labrador. (2) 
 The Seaboard Land. This was a broad, crushed, and plicated 
 swell or mass of wrinkles, stretching from Maine southwestward 
 to Alabama, along the slope between the present Appalachians 
 and the Atlantic Ocean. There is considerable reason to believe 
 that in breadth it embraced the region which was destined in 
 later ages to become the site of the Appalachian chain of mount- 
 ains, though in the intervening time destined to undergo a long 
 submergence. There is equal reason to conclude that this land 
 extended eastward beyond the present Atlantic shore, perhaps to 
 the brink of the slope into the deep sea. These conjectural 
 dimensions are represented in the JEonic Map, Fig. 297. (3) 
 The Cordilleran Land. This was the western germinal area. In 
 width it stretched from the eastern base of the Rocky Mountains 
 westward into eastern California, a distance of 750 miles along 
 the parallel of 40. It extended great, but unknown distances 
 northward and southward. This land was a great mountain svs-
 
 468 GEOLOGICAL STUDIES. 
 
 tern, displaying lofty ranges made of crumpled strata; mechanical 
 dislocations effected on a most gigantic scale, but withal a 
 smoothness of surface contour, and an absence of deep cafions 
 and worn gulches which seems to argue an absence of those 
 methods of erosion which have determined the configuration of 
 the modern surface. This massive belt of Eozoic Cordilleras 
 determined the limits of the modern Cordilleras, and very much 
 of the details of their fundamental structure. 
 
 2. The Palaeozoic ^Eou. (1) Movements of the Lands. It 
 was now a new morning in the world's history. The Cambrian 
 Age was dawning. The corner stones of the continent had been 
 deeply laid; yet over the site of North America an ocean ex- 
 panse still brooded. The transition from Eozoic to Palaeozoic 
 time was marked by important orographic movements. While 
 the Great Northern Land stood unmoved, the Seaboard and Cor- 
 dilleran lands underwent great subsidence. The western part of 
 the former and the eastern part of the latter went down beneath 
 sea level; and Pakeozoic sediments began to be spread out over 
 them. Of the Seaboard Land, the Appalachian site became sub- 
 merged. Of the Cordilleran Land, all subsided from the region 
 of the Great Plains to eastern California. Only the granitic 
 mountain summits stood emergent. The broad continent had 
 become an archipelago. Highest stood the Colorado, Medicine 
 Bow, and Park ranges, on the eastern border of the sunken land. 
 The continental mass remaining was on the western border. It 
 was destined to be wasted in yielding the materials to be spread 
 over the ocean bottom, for the upbuilding of the Palaeozoic for- 
 mations. While this sunken Cordilleran surface was receiving 
 its load, it continued to sink. But as the coarsest and most 
 copious deposition was near the wasting Nevada Land which 
 yielded the materials, the subsidence was greatest on the west. 
 By the end of the Palaeozoic /Eon the thickness of the Palaeozoic 
 sediments was a thousand feet around the bases of the Rocky 
 Mountain ranges ; 32,000 feet in the Wahsatch region, and 
 40,000 feet at the extreme western Palaeozoic limit in longitude
 
 HISTORICAL GEOLOGY. 469 
 
 117 30'. So deeply was the grand Cordilleran topography of 
 the close of Eozoic time buried from observation. 
 
 Similar was the experience of the ancient Seaboard Land. 
 The Appalachian border, which sank at the end of Eozoic time, 
 continued to sink during the whole of Palaeozoic time. Sedi- 
 ments accumulated upon it to the depth of 45,000 feet. West- 
 ward toward the modern Mississippi Valley, they diminish to 
 6,000 and even to 3,500 feet. 
 
 Quite the reverse was the movement of the Laurentian Land. 
 Its tendency was upward. Some additional elevation was appar- 
 ent at the end of each succeeding Age. When the close of 
 Palaeozoic time was approaching, its area had been widened so as 
 to embrace most of New England, New York, the Upper Penin- 
 sula of Michigan, Wisconsin, and most of Minnesota. Similar 
 enlargement was experienced along its other borders. 
 
 (2) Progress of Animal Organization. While these great 
 physical transformations were in progress, parallel transforma- 
 tions and parallel progress were going forward in the organic life 
 of the planet. Eozob'n had long since ceased to be a tenant of 
 the ocean ; but its great works were lying imperishable beneath 
 the accumulating masses of the forming continent. As soon as 
 the tumult of the closing action of Eozoic time had subsided, the 
 Palaeozoic ocean was thronged with creatures of grades compara- 
 tively high Trilobites, Chambered Molluscs, Gasteropods, and 
 Brachiopods. Coral animals, Crinoids, Lamellibranchs followed 
 quickly, geologically speaking. In those distant ages were all 
 the experiences which characterize life of our own times hun- 
 ger, fear, pursuit and retreat, slaughters and the pangs of dying. . 
 The very attitudes in which the dead were buried reveal the 
 shrinking which sentient organization experiences when the 
 pains of dying approach. But through all the wide ocean no 
 place was found for creatures conformed to the highest, or verte- 
 brate, type of structure. It was the Reign of Invertebrates. 
 
 As the land extended its borders, and the elements became 
 suited to the requirements of higher types of life, there were, 
 first, premonitions of the advent of vertebrates, and then the on-
 
 470 GEOLOGICAL STUDIES. 
 
 coming of the powerful and cruel dynasty of armored Fishes. 
 They ruled during the later Silurian, the Devonian, and the Car- 
 boniferous ages. Until the last period of the Carboniferous, ver- 
 tebrate life was exclusively aquatic, and, so far as we know, 
 almost exclusively marine. When the atmosphere had become 
 respirable, some humble Amphibian forms might have been seen 
 skulking under the protection of the flowerless herbage which 
 had sprung up. But plated, bony-scaled, and shark-like fishes 
 remained the dominant vertebrates. 
 
 (3) The Coal Period. The last period of the Palaeozoic 
 JEon was marked by its exuberance of vegetal life. Marine 
 plants had existed in the early Laurentian. Their record stands 
 in the beds of graphite which were then formed, and the deposits 
 of magnetite and hasmatite which are believed to have been ac- 
 cumulated through organic agency. Scattered land plants are 
 thought to have flourished along the Silurian and even the Cam- 
 brian shores, since some obscure driftwood has been taken from 
 beds of the Cincinnati Group. During the Devonian ferns and 
 lepidodendroids left their relics in considerable abundance; but 
 during the last period of the Palaeozoic the situation became pe- 
 culiarly suited, in the eastern portions of North America, for the 
 development of an extraordinary volume of vegetation. 
 
 The sinking of the Appalachian geosynclinal had been such 
 that the Palaeozoic sediments accumulated, together, perhaps, 
 with a little subsequent elevation, brought the sea bottom up to 
 the sea level, or a little above. In regions farther west in 
 Ohio, Michigan, Kentucky, Indiana, Illinois, Iowa, Missouri, and 
 eastern Kansas the general tenor of upheaval begun at the end 
 of Eozoic time, had brought the sea bottom up to nearly the same 
 level as it reached in the Appalachian region. Over the broad 
 marsh land, which thus stretched half across the continent, condi- 
 tions uncommonly favorable for vegetable growth existed. The 
 whole expanse, therefore, became clothed with a general type of 
 vegetation in correspondence with the primitive conditions of the 
 world mostly ferns, calamites, sigillarians, and lepidodendroids. 
 
 The growth and prostration of this vegetation through a sue-
 
 HISTORICAL GEOLOGY. 471 
 
 cession of generations resulted in a bed of vegetable material 
 somewhat peat-like in its nature, and, like peat, preserved from 
 decay by saturation in water and exclusion of air. Then followed 
 a subsidence of the whole of the coal-making area. The ocean 
 returned, and sheets of fragmental deposits buried the vast peat 
 bog, to undergo those transformations which should eventually 
 bring it into the condition of bituminous coal. Another uplift 
 succeeded, and new growths covered the new land. Another bed 
 of vegetable matter accumulated, and another submergence re- 
 sulted in its burial beneath strata of sand and mud. Thus emerg- 
 ences and submergences succeeded each other during the entire 
 coal-making period. It is not supposed, however, that all these 
 movements were synchronous over the entire coal-making area. 
 Undoubtedly, some portions underwent, at times, a degree of sub- 
 mergence, while others remained above sea level. The emerg- 
 ences, also, must have been experienced sometimes earlier in one 
 part of the area than in others. The nonsynchronism of these 
 movements resulted in some discontinuity of the beds of coal, 
 shale, and sandstone thus forming. Hence the succession of 
 strata in Illinois is not identical with the succession in Ohio and 
 Pennsylvania. 
 
 While these oscillations of level were in progress in the east- 
 ern part of the continent, the Cordilleran region, as a whole, 
 remained permanently beneath the ocean. The ancient island 
 mountains still stood emergent, and the Nevadan land continued 
 to crumble, in furnishing the sediments which formed the last 
 layers of the Palaeozoic mass. 
 
 (4) Close of the Palceozoic. Great geologic events were now 
 at hand. The broad coal-making region so long oscillating up- 
 ward and downward, as if under the stress of an enormous lateral 
 pressure from which it was seeking relief, at length yielded to 
 the resistless strain. Huge parallel folds of the crust rose along 
 the Appalachian region. A mountain chain came into existence 
 where sea bottom had been during all the Palaeozoic time, save 
 the period of bog lands while the coal beds had formed. The 
 mountains rose to altitudes of twelve to fifteen thousand feet.
 
 472 GEOLOGICAL STUDIES. 
 
 Before human eyes rested on them they had lost by erosion half 
 their original height. The disturbance was felt as far as eastern 
 Kansas. All the intervening region became upland. 
 
 There is reason to conclude that the remnant of the Seaboard 
 Land went down as the Appalachian belt came up. Thus an un- 
 known amount of that land became subsequently concealed by 
 sediments of later date. The Triassic sandstones of Connecticut, 
 New Jersey, and seaboard districts farther south prove that im- 
 mediately after the Appalachian disturbance the border was con- 
 siderably more depressed than at present, and the Appalachian 
 movement may probably have been the counterpart of this de- 
 pression. 
 
 From eastern Kansas westward the great interior ocean re- 
 mained undisturbed, save here and there a moderate upward 
 movement revealed in the broader emergence of the protruding 
 granite masses. But in the Wahsatch region, and westward, 
 enormous alterations of level took place. The long worn Ne- 
 vadan Land now sunk beneath sea level, while, reciprocally, the 
 sea bottom immediately eastward, as far as the Wahsatch, and 
 including that range, rose to a continental emergence. This was 
 now the western continent, lying between the eastern foot of the 
 Wahsatch and western Nevada, in longitude 117 30' the re- 
 gion now known as the "Basin Province." Between the new 
 Basin Continent and the old Nevadan continent, which went down 
 there was a complete change of conditions. The continental see- 
 saw on the west was the counterpart of the continental see-saw 
 on the Atlantic border. The mass in each case which went down 
 was on the side of the ocean; the mass which came up was next 
 the interior. The continental masses were now settled for another 
 age of repose. 
 
 3. The Mesozoic ^Eon. (I) Continental History. East of 
 the Great Plains the land was now extended nearly to its destined 
 dimensions (see Fig. 353). A belt along the Atlantic was still 
 submerged, and also a broad belt on the Gulf border. The latter 
 sent a triangular arm of the sea northward to Illinois, and wid- 
 ened westward into an ocean which stretched over the central
 
 HISTORICAL GEOLOGY. 473 
 
 part of the continent as far, probably, as the Arctic Ocean. Its 
 eastern border was in Minnesota, near the 94th meridian, and in 
 Kansas, near the 96th. Its western border was at the foot of the 
 Wahsatch, near the lllth meridian. It stretched continuously 
 over the Great Plains, was broken into an archipelago in the 
 Rocky Mountain belt, and was diversified with a few island emerg- 
 ences, especially northward, across the intervening distance to 
 the Basin continent. North and south this Intercontinental Sea 
 reached to the Gulf and the Arctic Ocean. Over this area Meso- 
 zoic sediments were spread. They rested conformably at least 
 in the 40th parallel region on the latest Palaeozoic. The source 
 of the materials being on the west, the thickest accumulations 
 were in that direction. Their general thickness at the close of 
 the Jurassic Age was about 4,000 feet. West of the Basin con- 
 tinent was another ocean. All the Nevadan and east Californian 
 part of it had resulted from the post-Palaeozoic subsidence of 
 land which had stood from the close of Eozoic time. The sub- 
 merged surface, therefore, was deeply eroded. Over this the 
 Mesozoic sediments were now deposited unconformably. They 
 accumulated to a depth of twenty thousand feet. The belt along 
 the western border of the Basin continent was destined to form 
 the Sierra Nevada mass. Meantime the Appalachians were wast- 
 ing, and the debris were strewn along the contemporaneous At- 
 lantic and Gulf border, from Sandy Hook to Georgia, and from 
 Georgia to Texas. 
 
 The close of the Jurassic Age was now at hand. It was sig- 
 nalized, especially, by the rise of the vast crumpled folds of the 
 Sierra Nevada. This added 200 miles to the westward extension 
 of the Basin continent, which thus became the Basin-Nevada 
 continent. It stretched southward at least to the 36th parallel, 
 and probably to the 32d. Northward it extended into Washing- 
 ton Territory, and perhaps to the Olympic Mountains. East of 
 the Wahsatch, however, this great disturbance was not felt, save 
 that its rock fragments and finer debris were sent eastward over 
 the ocean's floor as far as Kansas. These coarse materials formed
 
 474 GEOLOGICAL STUDIES. 
 
 the basal or Dakota member of the Cretaceous System. But it 
 was laid down conformably on the Jurassic. 
 
 Along the Atlantic border the Cretaceous Age was marked 
 by a moderate depression. The ocean encroached farther inland 
 than during the Jurassic. The Cretaceous sediments, accord- 
 ingly, covered and concealed nearly all the Triassic and Jurassic. 
 The same statement applies, also, to the Gulf border. 
 
 The close of the Cretaceous was an important era in American 
 geological history. To this epoch, the sedimentary sheets of the 
 central region east of the Wahsatch had been laid down in con- 
 formable superposition from the beginning of the Palaeozoic. 
 Now, however, came the turn of the region at present known as 
 the "Plateau Province." Upward and undulatory movements 
 were experienced. Now rose the broad, flat, east and west anti- 
 clinal range, known as the Uinta Mountains. Not, however, by 
 a sudden movement, for the rise was prolonged through the 
 whole duration of the resulting land surface, and proceeded 
 slowly enough to permit the drainage streams to saw chasms 
 through the entire height of the mountain. Eastward of the 
 Uinta, the whole continental mass was raised; and this brought 
 with it the Rocky Mountain ranges to a higher altitude. The 
 broad, shallow basin of the Colorado now had its limits marked 
 out. On the Pacific Coast, this disturbance was felt only in the 
 denning of the position of the Coast Ranges. On the Atlantic 
 and Gulf, the continent was upraised; and a belt ranging from 
 fifty to a hundred miles was added to the land. 
 
 These changes, however, were not accomplished with abrupt- 
 ness. The Cordilleran sea bottom was slowly rising during the 
 whole Cretaceous Age, reaching the vicinity of sea level at an 
 earlier epoch on the Wahsatch border than in the region of the 
 Rocky Mountains and Kansas. Farther south, however, in 
 Texas, the Cretaceous ocean remained a deep sea till the close of 
 the Age. 
 
 The great feature of the Cretaceous and post-Cretaceous 
 movements was the reemergence of that part of the ancient Cor- 
 dilleran area which is now called the Plateau Province, though,
 
 HISTORICAL GEOLOGY. 475 
 
 indeed, extensive inland lakes continued through the next aeon. 
 The two limbs of the American continent were now joined 
 together. From middle California to Boston Bay was a contin- 
 uous land connection. Only a narrow border remained to be 
 added around the Atlantic, Pacific, and Gulf coasts, and North 
 America would be complete. 
 
 (2) Progress of Mesozoic Life. Vegetable organization 
 reached, in the early Mesozoic, the grade of Cycads and Conifers. 
 Tree Ferns were still abundant. In the later Mesozoic, angio- 
 sperms and palms were common. The marsh borders of the 
 emerging lands of the Dakota period have preserved a great 
 abundance of the leaves of plants belonging to modern and 
 closely related genera. Lesquereux, in a recent publication, 
 enumerates from the Dakota Cretaceous 91 species of flowering 
 plants, belonging to 29 living genera. These include 4 species of 
 Sequoia, 7 of Oak, 5 of Willow, 5 of Poplar, 5 of Plane Tree, 7 
 of Fig, 4 of Magnolia, 8 of Tulip Tree, 9 of Sassafras, 8 of Sar- 
 saparilla. Evidently the forest-covered land presented, in the 
 early Cretaceous, a decidedly modern aspect. American Creta- 
 ceous vegetation was, in fact, more advanced than that of Europe. 
 In the Laramie, or closing period, it had, according to Lesque- 
 reux, an Eocene, or even a Miocene, aspect. That is, the nearest 
 European analogues of Laramie species occur in the Eocene 
 rather than in the Cretaceous. At the same time, the reptilian 
 and molluscan species of the Laramie are indisputably Creta- 
 ceous; and these are best suited to determine the age of a for- 
 mation. Sir W. Dawson, in a very recent note (1885), records 
 the occurrence of Brasenice antiqua in beds of the Belly River 
 series, in the Canadian Northwest. This species MS scarcely dis- 
 tinguishable from the modern Srasenice (Ifydropeltis) purpurea, 
 though it occurs in strata older than those affording remains of 
 Diclonius, a Cretaceous Dinosaur. The horizon is probably 
 Laramie. 
 
 Among Polyp corals, the ancient type of Tetracoralla, having 
 the parts in multiples of four, were mostly extinct, and modern 
 Hexacoralla had taken their place. The type of Crinoids, which
 
 476 GEOLOGICAL STUDIES. 
 
 had culminated in the earlier Carboniferous, was now declining, 
 and the higher Starfishes and Echinoids were succeeding. The 
 old spire-bearing Brachiopods, as also the Orthids and Stropho- 
 me'noids, and other types, had dropped out of existence; and 
 Terebratuloids were now in the ascendent. The waters swarmed, 
 however, with Lamellibranchs and Gasteropods. The higher 
 molluscs were richly represented by Ammonites and Belemnites. 
 But the former showed, toward the close of the Cretaceous, a 
 marked decline. Ganoid and Selachian fishes continued in abun- 
 dance; but the former early dispensed with the vertebrated tail. 
 This is an embryonic character, and accordingly belonged to the 
 early stages of type development. The reptiles were the great 
 feature of the life of the ^Eon. Their modes of life and diversi- 
 fication of type have been elsewhere described. Their graduation 
 into the type of birds presents facts full of curious and philo- 
 sophic interest. Perhaps the most significant event was the advent 
 of Mammals; since this brought organization up to the class- 
 grade of man, and constituted a final renewal of the promise of 
 man's ultimate advent. The first mammals dwelt on the Triassic 
 land, and were feeble and inconspicuous. In the Jurassic Age, 
 they were still feeble, but somewhat more numerous. In the 
 Cretaceous they seem to have gained nothing in bulk, power, or 
 importance. Evidently, the appropriate age for the unfolding of 
 the Mammalian type had not yet arrived. 
 
 4. The Caenozoic JEon. (1) The Tertiary Age. It will be 
 remembered that Mesozoic time was concluded by an uplift of 
 the whole Cordilleran region, and the extinction of the great 
 Plateau or mediterranean sea. But in the basin of the Colorado 
 River, a great depression remained without complete drainage to 
 the sea. There rested, during the Eocene, a great Eocene Lake, 
 extending from the upper waters of the Yellowstone to New 
 Mexico. This, at first salt, became brackish, and, at length, a 
 lake of fresh water. The sediments accumulated in it during the 
 the first epoch constitute the Wahsatch formation (=:Vermillion 
 Creek Group, King; = Bitter Creek Group, Powell). In the 
 progress of time occurred three successive orographic disturb-
 
 HISTORICAL GEOLOGY. 
 
 47? 
 
 ances. The first, during the progress of the Wahsatch, contracted 
 the great lake on the north and south. It stretched now from 
 the valley of the Green River north and south of the Uinta 
 Mountains, and perhaps, also, to the west of the Wahsatch 
 Range, in Utah and Nevada. In it were deposited the sediments 
 forming the Green River division of the Wahsatch formation 
 (= Elk Group, King). 
 
 FIG. 366. XORTH AMERICA, NEAR THE BEGINNING OP C.ENOZOIC TIME. 
 
 The second disturbance terminated the Wahsatch epoch. 
 The great Eocene Lake was now further contracted. It con- 
 sisted, during this epoch, of two or more divisions. One of these 
 rested in the Green River basin north of the Uinta Mountains; 
 another, the Washakie basin, lay east of the Green River, and a 
 third was in western Colorado. The deposits collected formed 
 the Bridger Group. 
 
 The third disturbance restricted the Eocene Lake to the 
 region east and south of the Uinta Mountains, in the valley of 
 the Green and White rivers. In it was deposited the uppermost
 
 478 GEOLOGICAL STUDIES. 
 
 of the Eocene formations the Uinta (= Brown's Creek Group, 
 Powell). During these events the province of the Great Plains 
 appears to have been partly dry land. 
 
 The next orographic movement terminated the Eocene. The 
 Great Plains were now depressed, and a lake stretched from the 
 Missouri River to eastern Wyoming, Colorado, and the Wind 
 River Valley, and from northern Kansas far into British America. 
 A long, narrow depression took place, also, in the far West, 
 along the eastern base of the Cascade Range and Sierra Nevada. 
 It stretched from Washington Territory through Oregon, Nevada, 
 and California. The deposits in the western lake were chiefly 
 the tuffs and rearranged ejecta of volcanic eruption, and attained 
 a thickness of 4,000 feet. The deposits in the eastern lake were 
 the simple detritus from surrounding lands, and attained a thick- 
 ness of 150 feet in Nebraska, 300 feet in Colorado, and 2,000 feet 
 in the Uinta Mountains. The western is the Truckee formation 
 (= John Day Group, King); the eastern, the White River forma- 
 tion; but some uncertainty remains as to their precise synchro- 
 nism. Along the Pacific slope, deposits accumulated to the depth 
 of four or five thousand feet in California and Oregon, which, 
 with the closing disturbance, were upraised in the Coast Ranges. 
 
 This disturbance changed again the bounds of the interior 
 lakes, and inaugurated the Pliocene epoch. The whole interior 
 seems to have experienced a general depression, which interrupted 
 the drainage to the sea. The western Miocene beds were thrown 
 into folds. The resulting lake was divided in two by the archi- 
 pelago of the Rocky Mountains. We find the deposits of the 
 Pliocene or Loup River beds at many points between the Sierra 
 Nevada and the eastern limit of the Great Plains, and from Ore- 
 gon to New Mexico. They reach into Kansas and stretch north- 
 ward, occupying the valleys of the Rocky Mountains. They 
 embrace the Niobrara Group, King and Marsh + Humboldt Group, 
 King + North Park Group, Hague and Hayden. The Pliocene 
 beds of the Great Plains rest conformably on the Miocene, or, in 
 some regions, on the Cretaceous, and attain a thickness of 2,000 
 feet. Those of the Basin and Plateau provinces rest uncon-
 
 HISTOBICAL GEOLOGY. 470 
 
 formably on the Miocene, and are not over 1,000 feet thick. After 
 the shrinkage of the Loup River lakes, deposition continued, form- 
 ing the so called Equus Beds or Upper Pliocene (sometimes also 
 regarded as post-Pliocene) occurring in Oregon, California, and 
 Nevada; and in the eastern United States, in cavern and clay 
 deposits along the Delaware arid Potomac rivers. 
 
 The movement which inaugurated the Pliocene appears to 
 have resulted in an elevation of the Atlantic seaboard north of 
 South Carolina. During the Pliocene, probably the submerged 
 shore land off the present coast marked the border of the land. 
 During the Pliocene, also, the submerged Hudson gorge was 
 principally elevated (Fig. 358). Throughout the Tertiary the 
 Atlantic and Gulf coasts experienced a slow and mostly progres- 
 sive upheaval. But the most considerable emergence on the Gulf 
 and South Atlantic was at the end of the Eocene, and along the 
 North Atlantic, after the Miocene. 
 
 The continental oscillations sketched in the foregoing para- 
 graphs are graphically represented in the accompanying atonic 
 sections, Fig. 3G7. The sections are mere diagrams, representing 
 uplifts and subsidences; but they will greatly aid the memory 
 and imagination in retaining a vivid conception of the locality 
 and order of succession of each of those great orographic move- 
 ments which have made American geology what it is, and have 
 shaped the face of the continent in those forms destined to char- 
 acterize it through the age of human occupation. 
 
 (2) The Glacial Epoch. During the later Tertiary moderate 
 elevations occurred in various regions, completing the drainage 
 of the land, and establishing a tenor of events destined to con- 
 tinue to such extent as to determine the advent of another epoch. 
 The continuance of the elevation became general over the north- 
 ern part of the continent, and more especially the northeastern. 
 The climate, therefore, which had been milder than our present 
 climate, experienced an increase of winter severity, and a pro- 
 longation of the snowy season. The higher elevation of the land 
 increased the corrasive action of the streams and deepened their 
 channels. It also produced an extension of the land alone: the
 
 !L 
 
 
 
 IM 
 
 FIG. 3G7.-^Eouic SECTIONS ACROSS THE CONTINENT ALONG THE FORTIETH PARALLEL. 
 [East of the 87d meridian the Sections follow the 38th Parallel.] Compare with 
 ^Eonic Maps, Pigs. 297, 304, 312, 349, 353, 354, and a56.
 
 HISTORICAL GEOLOGY. 481 
 
 sea border. It is probable that the border of the steep basin 
 slope of the Atlantic, before mentioned, marks the position of 
 the ancient shore in post-Pliocene, if not in Pliocene, time. 
 This, however, could not have formed the continental border 
 along the South Atlantic during Pliocene time, since in South 
 Carolina, Pliocene deposits prove Pliocene submergence. In 
 early post-Pliocene time, Long Island was 150 miles broad, and 
 the western part of Long Island Sound was the lower valley of 
 the Connecticut River. The Hudson River still pursued its 
 course between high banks, 135 miles beyond New York. This 
 supposes the post-Pliocene elevation of the land to have been 
 equal to the highest attained. 
 
 With progressive northern elevation, the rigor of the climate 
 increased. The northern zone of perpetual snow widened to 
 temperate latitudes. Under the influence of the summer sun, the 
 broad snow mass, though not dissipated, was reduced to the con- 
 dition of glacier ice. The snows had fallen over the landscape, 
 and bedded themselves about the trees of the forest. They had 
 gathered themselves about all the rocky saliences, and filled the 
 rugged gorges worn by the long corrading streams. When, 
 therefore, the pervading glacier moved, as all glaciers must 
 move, the forests were prostrated, and the rocky crags were 
 wrenched from their fastenings. The angular fragments were 
 frozen in the glacier's bottom, and like diamonds in their setting, 
 they scored the underlying surface. That surface was covered 
 with sands and clays and rock fragments, the result of the rock 
 disintegration of hundreds of thousands of years. This inco- 
 herent material was moved and mixed by the glacier. With it 
 were mingled the shattered remnants of the forest. By it the 
 old gorges and gullies and river valleys were filled. These debris 
 of former ages were swept clean from the solid surface of the 
 rocks; and the moving glacier mass scoured and scored the solid 
 rocks. It slid over moderate elevations, and crossed many of the 
 valleys which intercepted its course. Eastward, it travelled over 
 Long Island, and out to the ancient shore. In Ohio it reached 
 the Ohio River. Farther west, its limit was reached in latitudes
 
 482 GEOLOGICAL STUDIES. 
 
 considerably higher. It will be understood that the southern 
 glacier limit was coincident with the southern limit of the Drift, 
 as shown on the map, Fig. 356. 
 
 The course of the continental glacier was not independent of 
 the larger topographic features of the land. It tended to move 
 downward from all elevations. The courses of the great valleys 
 determined deflections sometimes for a hundred miles or more. 
 It followed up the valley of the St. Lawrence. It continued 
 along the axis of Lake Erie, and up the valley of the Maumee; 
 but it will be remembered that the slopes were different, some- 
 times reversed by the northern elevation of the epoch. The gla- 
 cier filled the valley of the Connecticut with a broad ice river. 
 It flowed down the valleys of the Mohawk and the Hudson. 
 Pursuing its way along the channel now submerged, it excavated 
 the great fiord which lies now over a hundred miles at sea, and 
 sunken in 500 feet of water. It accumulated to a depth of, per- 
 haps, 5,000 feet. At this depth the heat from the earth's interior 
 would be sufficient to melt the glacier beneath as rapidly as any 
 probable growth above. The sub-glacial melting created copious 
 sub-glacial streams, which transported detrital material, and con- 
 tributed much to the observed arrangements of the Drift. 
 
 In regions beyond the limits of the continental glacier, local 
 glaciers gathered on mountain summits and slopes, and coursed 
 down the mountain valleys, as modern glaciers move in Alpine 
 valleys. Such mountain glaciers clothed the higher slopes of 
 the Appalachians, the Rocky Mountains, the Sierra Nevada, and 
 most other ranges farther north. The remnants of some of these 
 local glaciers survive to our times. (See especially the Memoir 
 of I. C. Russell.) Even the modern Alpine glaciers are but ves- 
 tiges of a wide general glaciation. Under such a sheet of ice 
 lay, for probably thousands of years, the fair continent which in 
 geologically recent times had been clothed with a forest which 
 gave it an aspect exceedingly like that of a modern landscape. 
 The desolate- surface of glacier-clad Greenland remains a vivid 
 picture of northeastern North America only a few thousand years 
 ago.
 
 HISTORICAL GEOLOGY. 483 
 
 It is not necessary to suppose the climate was characterized 
 by excessive cold. Moisture and precipitation are necessary. 
 Where these are abundant, the snow accumulation may outlast a 
 summer of high temperature. The glaciers of the Alps descend 
 to the borders of the fields where crops of grass and potatoes 
 grow. The snow in Tuckerman's ravine, in the White Mount- 
 ains, lasts till August, because it is abundant. In the same 
 climate the general accumulation of snow might be sufficient to 
 last till snow falls again. With the surface widely covered, the 
 temperature could not rise much above 32 Fahr., and less snow 
 would then suffice to withstand the whole summer heat. The 
 continental glacier existed in the eastern United States, where 
 precipitation is now greatest. It was wanting over the Great 
 Plains and the Northwest, where precipitation is still scanty. 
 
 (3) The Champlain Epoch. The epoch of elevation and 
 cold was followed by one of subsidence and warmth. From its 
 extreme limit the continental glacier began to retreat. There 
 must have been left originally a terminal moraine of great mag- 
 nitude. The melting of the ice across half the breadth of the 
 continent resulted in floods, which swept southward, carrying the 
 incoherent products of glaciation, and depositing them in the 
 state of confused stratification which we see in the Modified 
 Drift. To what extent the retreat continued we have no means 
 of learning. It appears, however, that some portions of the un- 
 covered surface, as over central Illinois, had time to develop a 
 considerable amount of vegetation and form a soil. 
 
 Then followed a return of cold, and the glacier again ad- 
 vanced. It does not appear that the second advance was equal 
 to the first. On the final retreat the great terminal moraine 
 was left, which has been traced so continuously across the coun- 
 try, and mapped in Fig. 356. The return of another geolog- 
 ical springtime gave birth to renewed floods, which continued 
 the work begun at the time of the previous thaw. These new 
 floods swept over the old moraine, and probably scattered and 
 levelled to a large extent the accumulation of materials. This 
 may explain the less conspicuous character of this moraine,
 
 484 GEOLOGICAL STUDIES. 
 
 though formed through the action of the severest cold and the 
 most extended glacier. The glacial flood sought, of course, the 
 valleys of the great streams for its main outlet to the sea, 
 and thus bore far southward large quantities of driftwood, and 
 even ice rafts with loads of sand and bowlders. But the flood 
 swept also over the general surface of the land; and thus the 
 states not reached by the action of the ice were reached and 
 benefited by the action of the flood which sprang from the ice. 
 
 It is to be remarked that the aggregate action of the Glacial 
 and Champlain epochs was directly ameliorative, and may be re- 
 garded as a preparation for the needs of the new fauna and flora 
 which were destined to appear. As a general principle, it may 
 be asserted that each renewed terrestrial surface in the whole 
 history of life has been exhausted in supplying the needs of the 
 population introduced to occupy it. The present terrestrial sur- 
 face is visibly deteriorating. The pre-glacial surface had been 
 wasted and scored by the erosions of the ^Eon which supplied the 
 demands of Pliocene populations. By glacier action the old scars 
 were removed the gaping gorges were filled; the rock materials 
 disintegrated through ages were stirred to the bed rock, and dis- 
 tributed in a continuous sheet ; new materials originated from 
 glacial wear; and when the floods came, a beneficent assortment 
 left the finer products at the surface, and extended the reparative 
 action over several degrees of latitude southward. The final 
 result was a land surface specially suited to the needs of an 
 industrial and civilized race of men. 
 
 The course of things thus in progress continued until the 
 northward subsidence carried the land far below its pre-glacial 
 level, and even below its present level. The consequence was an 
 encroachment of the sea on the land. The records of beach 
 action still remain at various altitudes above present sea level, 
 showing the greatest Champlain depression northward. It thus 
 appears that southern New England sank 10 to 25 feet bejow its 
 present level; Sancati Head on Nantucket, 85 feet; parts of the 
 coast region of Maine, 217 feet; the borders of Lake Champlain, 
 350 to 400 feet; the region of Montreal, nearly 500 feet; that of
 
 HISTORICAL GEOLOGY. 485 
 
 the Bay of Fundy, 350 to 400 feet; the Labrador coast, 400 to 
 500 feet; parts of the Arctic regions, over 1,000 feet. On Ben- 
 nett Island De Long found beach deposits at the height of 100 
 feet. Marine shells were found 1,000 feet above the Arctic level; 
 bnt it does not appear that they were not Pliocene or Miocene. 
 Whether this subsidence was felt by the interior of the continent 
 it is impossible to state. The Pliocene of the Great Plains re- 
 mains from 4,000 to 7,000 feet above sea level; and the fact ren- 
 ders questionable any higher Quaternary elevation or any Cham- 
 plain subsidence. 
 
 The subsidence of the land caused a reversal of a portion of 
 the drainage of the Northern States. While the North was ele- 
 vated, Winnipeg Lake, then greatly increased in dimensions, was 
 drained into the Missouri. It has even been suggested that a 
 large stream flowed southward through the present valley of the 
 Minnesota. The great lakes also found various outlets toward 
 the south. With subsidence of the land some of these courses 
 became obstructed, and others even reversed. 
 
 (4) Effects of Glacier Pressure. In thus delineating the 
 events of the Quaternary Age, I have followed the accepted 
 teaching. But I think it may be useful to suggest some conse- 
 quences of glacier pressure over the northern and eastern parts 
 of the continent, which may necessitate some modifications of 
 accepted views. If, as is now commonly held, the accumulation 
 of marine sediments may suffice to depress the earth's crust under 
 the sea, assuredly the accumulation of 5,000 feet of ice upon the 
 land, over half the area of a continent, would cause a depres- 
 sion of the terrestrial crust such as glaciated Greenland, for 
 instance, is actually undergoing. Croll, assuming the crust to 
 remain rigid under such a pressure, has discussed the necessary 
 shifting of the earth's centre of gravity, and consequent flooding 
 of northern regions. But the same flooding would ensue without 
 a shifting of the centre of gravity, if the crust were depressed. 
 If then the northern subsidence and submergence noted were 
 coincident with glaciation, instead of subsequent, the phenomena 
 resulting would be precisely such as we observe. The glacier
 
 486 GEOLOGICAL STUDIES. 
 
 would not persist along shores buried by the sea. The same sea 
 bottom would be there as if the glacier had disappeared from all 
 the land. So the submergence seems to have been coeval with 
 glaciation rather than subsequent. 
 
 Again, a sub-glacial depression over the north and east of the 
 continent must have reacted beneath the crust in other regions 
 and especially in regions bordered by the depression, and most 
 especially if bordered on the east as well as the north. The last 
 was the situation of temperate North America west of the Rocky 
 Mountains. Now the evidence is that the Plateau and Basin 
 Provinces have suffered from powerful vertical actions. That 
 enormous outflows of lava have occurred is another striking fact. 
 These occurrences have been generally synchronized with the 
 close of the Pliocene Epoch; but here are grounds for assuming 
 them to have been coincident with the great submergence at the 
 east. 
 
 (5) The Recent Epoch. The rise of the land from its deep 
 submergence to its present general altitude marks the beginning 
 of the Recent Epoch. As the land did not return to its former 
 elevation, a wide belt along the Atlantic shore northward remains 
 submerged. In the interior the descent of the streams is less 
 than formerly. Hence their rate of flow is less, and their ancient 
 channels remain partly filled with Drift deposits. Most of the 
 larger streams now flow many feet above their ancient beds. 
 
 When the present level of the land was assumed, the water 
 of Lakes Erie, Huron, and Michigan stood many feet above the 
 present level. This was probably due, as has been explained, to 
 an obstruction then existing at the escarpment over which, near 
 Lewiston, the drainage of these lakes had to pass. During this 
 period of high water the so called " Erie clays " were deposited 
 which we now see along the borders of these lakes. The simul- 
 taneous high floods of the rivers, which left their terraces at vari- 
 ous high elevations, were due, perhaps, to the prolonged melting 
 of the ice, and partly, perhaps, to a continuance, at moderated 
 temperatures, of that copious precipitation which at snowy tem- 
 peratures had been the essential condition of glacier formation.
 
 HISTORICAL GEOLOGY. 487 
 
 Thus there may have been a pluvial epoch, beginning during the 
 progress of the Champlain moderation of climate, and extending 
 down into recent times. The diminution of precipitation which 
 then followed appears to be continuing into the present. 
 
 The subsidence of the floods left innumerable small lakes 
 scattered over surfaces having but little slope. The peculiar 
 kettle-like configuration of parts of the surface, especially along 
 the morainic belts, favored the retention of small bodies of water. 
 With the lapse of time, drainage outlets have been worn for some 
 of these, and others have been completely filled with deposits of 
 marl and peat. 
 
 In the present epoch, the land has the appearance of stability, 
 except as occasionally affected by momentary earthquake move- 
 ments. In truth, however, many shores are undergoing slow 
 elevation or depression. These are movements which, in centu- 
 ries, or at least in geological periods, may amount to changes of 
 level as great as any which geological research has brought to 
 light. The coast of New Jersey, for instance, is represented by 
 Professor Cook as subsiding at the rate of two feet in a hundred 
 years. At Uddevalla, in Sweden, the coast is rising above the 
 Baltic level at the rate of four feet in a century; and north of 
 that, the rise is more rapid. Along six hundred miles of the 
 coast of Greenland, a slow subsidence is taking place. Numerous 
 facts of this kind are known. 
 
 When the rivers were at flood on the continent of Europe, 
 man was there. He was present, apparently, during an earlier, 
 interglacial epoch. In America, he found a home during the 
 same epoch, as far north as New Jersey, and, in unglaciated Cal- 
 ifornia, he left his bones buried in the gravels which underlie 
 great lava sheets poured out in early Quaternary, or late Pliocene 
 times. That man existed in remote preglacial times is not im- 
 probable; but he was represented by an inferior race, and lived in 
 some congenial climate. The men who pressed upon the borders of 
 the retreating ice were hardy adventurers, who had already come 
 into the possession of the arts needed to secure comforts under 
 trying climatic conditions.
 
 488 GEOLOGICAL STUDIES. 
 
 But, in any view of the epoch of human origin, man stands as 
 the crowning and consummated event in a series of intelligible 
 preparations and promises which extend back through vast inter- 
 vals of time to Eozoon and the primeval ocean. 
 
 3. Ulterior History. 
 
 We need not remain in complete ignorance of that part of 
 the world's appointed history which is yet future. It is scarcely 
 true that we cannot be certain of any event which yet lacks real- 
 ization. But, if it were true, there are impending events so 
 nearly certain that, like to-morrow's sunrise, their failure can be 
 determined by nothing less than a suspension of the order of 
 nature as known to us; and knowledge, within the limitations of 
 the recognized order of nature, cannot be pronounced destitute 
 of value. 
 
 Certain activities, like the return of summer, and the occur- 
 rence of eclipses, proceed under the laws of matter which, to our 
 cognizance, may be regarded as fixed and invariable. Others 
 proceed in accordance with methods, or laws, made known to us 
 through adequate observation and inference; and these furnish 
 us grounds of anticipation scarcely less solid than the others. 
 
 We know, for instance, that if the earth continues its orbital 
 and rotary motions without great change in the inclination of its 
 axis; if the sun retains its efficiency, and all other conditions 
 determining the present brder of nature remain undisturbed, the 
 seasons will continue to recur; evaporation and precipitation, 
 freezing and thawing, will continue for a thousand or a million 
 years to come, as they have continued through the past. If the 
 principle of gravitation remains undisturbed, and the solvent and 
 mechanical actions of moving water remain as now, it is certain 
 that processes of aqueous erosion will continue to wear away the 
 materials of the earth's crust; and the processes of sedimentation 
 will continue to fill the undrained depressions of the earth'a 
 surface. 
 
 Thus, we may be satisfied that the Niagara gorge will be con- 
 tinued; and, if we use, as a rule, the slopes of the gorge already
 
 HISTORICAL GEOLOGY. 489 
 
 excavated, we may conclude that in the distant future, the bot- 
 tom of the gorge will pierce the bottom of Lake Erie, and thus 
 that lake will be gradually drained, and become a river. We 
 may further reason that since lakes Huron and Michigan stand 
 at nearly the same level as Lake Erie, these will be lowered as 
 much as the latter; and because their depths exceed that of 
 Lake Erie, there will result two or more small lakes, connected 
 by a river, which will flow along the drained basin of Lake Erie, 
 and down the steep, unnavigable slope, continuing" through the 
 Niagara gorge to Lake Ontario. 
 
 We may reason similarly about the general wear and wastage 
 of the land. It has been estimated, from observation, that the 
 surface of North America is lowered by denudation about one 
 foot in four thousand years. This determination immediately 
 suggests that the land is destined to undergo final wastage. As 
 the detritus finds its way into the sea, the latter is slowly filling 
 up, and the sea bottom will continually approach the level of the 
 land. Unless the supply of surface water fails, the sea will 
 eventually overflow the land. It may be supposed the tenor of 
 past history argues for the future higher elevation of the land 
 surfaces and deeper depression of the ocean's bottom. But we 
 shall see that this anticipation is rendered nugatory by another 
 one. 
 
 If the earth has been cooling from a highly heated condition,, 
 and still radiates more heat than it receives from the sun, we 
 have ground for affirming, first, that the time will come, if it ha 
 not arrived, when the thermal energy contained within will be- 
 too feeble for the continued uplifting of continents and deepen- 
 ing of ocean basins; and thus the results of denudation will 
 accumulate indefinitely. 
 
 If the earth still retains residual heat, from the era of primi- 
 tive incandescence, then the cooled crust will continue to thicken,, 
 as this heat escapes into space. With the deepening of the cooled 
 zone, additional water will be received in the pores of the earth. 
 Calculations based on the absorbent capacity of average rocks 
 show that the entire ocean is destined to be absorbed by the crust
 
 49U GEOLOGICAL STUDIES. 
 
 of the earth. It appears, even, that the capacity of the pores 
 will be sufficient to receive the atmosphere also. The earth will 
 hang in space without water or air. When the atmospheric en- 
 velope no longer exists, the sun's heat will no longer be blanketed 
 in. The solar rays will be returned as rapidly as received, and 
 the terrestrial surface will sink toward the temperature of exter- 
 nal space. 
 
 The action of the moon on the lunar tidal protuberance is 
 destroying the earth's rotary motion (page 299). A period may, 
 therefore, be anticipated when the earth will turn constantly the 
 same side toward the moon. If then the moon continues to re- 
 volve in the same period, each side of the earth will be exposed 
 constantly two weeks to the scorching rays of the sun, to be 
 turned during the next two weeks into the shadow, and exposed 
 to the intense cold of planetary space. 
 
 But the moon will gradually recede from the earth, and will 
 suffer a diminution of its tide-producing power, and of its power 
 to impress the earth's rotation. If then the earth's distance 
 from the sun remains about the same, the sun's action on the solar 
 tide will tend to reduce the rotary motion of the earth to synchro- 
 nism with its annual motion. One side of the earth will then be 
 turned continually toward the sun, and the opposite side contin- 
 ually away from it. This train of contingencies might even be 
 traced further; but that is here unnecessary. 
 
 The tendency of the diffusion of heat to a state of equilibrium 
 threatens not alone the final refrigeration of the earth. The sun 
 is inevitably approaching a state of final extinction. His light and 
 heat will eventually become sensibly less; and in the distant asons 
 of eternity the sun will become a dark, cold world. 
 
 Such eventualities might be traced still further. But it is 
 not appropriate here to pursue reflections which verge so nearly 
 on the domain of speculation. The purpose has been simply to 
 illustrate the legitimacy and safety of reasoning from known 
 principles to conclusions which lie even in the depths of the 
 future eternity; and to show that the future conceals eventuali- 
 ties which must terminate the period of human existence on the
 
 HISTORICAL GEOLOGY. 491 
 
 earth. It is useful, also, to be reminded how small a speck of 
 existence we are, and how brief an instant of duration is covered 
 by a human lifetime, or the lifetime of a race. And assuredly, 
 in the presence of such conceptions as those, we may feel a 
 swelling admiration of that spiritual capacity in man which 
 enables him to grasp and comprehend the events of periods past 
 and to come which stretch out into the realm of eternity. It is a 
 belief ingrained in the texture of the human soul, that a being 
 whose thought thus rises superior to all time and space and 
 change is destined, however brief his corporeal sojourn, to out- 
 live in consciousness all the mutations compassed by the horizon 
 of his thought.
 
 INDEX. 
 
 NOTE. An asterisk (*) affixed to the number of a page indicates an illus- 
 tration on that page, of the species or subject mentioned. A dagger (f) 
 indicates a definition or explanation of a term ; but it is used only where 
 more than one reference exists. 
 
 Abyss of Atlantic, 86. 
 
 Acadian, coal field, 406; formation, 
 362, 369, 378. 
 
 Acanthodes, 333. 
 
 Accessory minerals, 51. 
 
 Accidents of stratification, 256, 257. 
 
 Acervularia, 214; Davidsoni. 214, 
 216*. 
 
 Acidic, feldspars, 27*, 53, 54; rocks, 
 71. 
 
 Acids, how formed, 19, 20. 
 
 Aclinal mountains, 168. 
 
 Acrogens, 418. 
 
 Actinolite, 81. 
 
 Adams, Fort, 85. 
 
 Adductor muscle, 231. 
 
 Adirondack Mountains. 160. 
 
 -ffilon, 270. 
 
 ^Eonic, map, 371*, 383*, 399*, 423*, 
 439* 440*, 477*: sections, 480*. 
 
 ^Etna, eruption of, in 1865, 140 seq.; 
 map of, 141*.' 
 
 Affinity, chemical,' 19; elective, 20; 
 weakened by heat, 21. 
 
 Agassiz Lake, 452, 485. 
 
 Agate, 24. 
 
 Age, evidences of, 265. 
 
 Age in classification, 270. 
 
 Air breathers, 420. 
 
 Alabama, iron, 184; rocks, 384; sec- 
 tion through, 430*, fossils, 402, 
 434; coal, 416; cretaceous, 429. 
 
 Alabaster, 65, 66. 
 
 Alaska, diamonds, 24f; glacier, 281. 
 
 Albany capitol granite, 53. 
 
 Albertite, 68f, 69, 195, 198. 
 
 Albeit mine, 398. 
 
 Albito, 27. 
 
 Allegheny Mountains, 93. See "Ap- 
 palachian." 
 
 Allodon, 347. 
 
 Allotheria, 347. 
 
 Alluvial, 81f, 83. 
 
 Alps, structure of, 171, 172*. 
 
 Aluminous rocks, 60; matter, 197. 
 
 Alveolites, 222, 223, 225; Goldfussi, 
 222*, 223*. 
 
 Alveolus of belemnite, 433. 
 
 Amazons River, 280. 
 
 Amber, 68. 
 
 Amblypoda, 351. 
 
 Amenia iron, 37. 
 
 Amethyst, 24. 
 
 Ammonites, 327; serpentinus, 330*. 
 
 Ammonoidea. 328, 329, 428, 433. 
 
 Amoeba, 319*. 
 
 Amphibians, position of, 104; com- 
 prehensive, 316 ; separated by gaps., 
 
 Amphibole, 31. 
 
 Amphibolic rocks, 52, 249. 
 
 Amphibolite, 52. 
 
 Amphigenite, 72. 
 
 Amphilestes, 346. 
 
 Amphitherium, 346*. * 
 
 Amplexus, 204, 207; Shuraardi, 204*'; 
 
 Yandelli, 207*. 
 | Amygdaloid, 156. 
 I Amygdule, 264. 
 
 i Analysis of minerals, 17. 
 , Anchippodus, 349. 
 
 Anchitherium, 356. 
 
 Andalusian earthquakes. 456. 
 
 Andalusite, 52. 
 
 Andesite, 72. 
 
 Animals classified. 306-314.
 
 494 
 
 INDEX. 
 
 Ann Arbor, Drift at, 5*. 
 
 Annularia, 418*. 
 
 Anodonta angustata, 227*. 
 
 Anoinodontia, 341. 
 
 Anorthite, 28. 
 
 Anterior of shell, 228. 
 
 Anthozoa, 322. 
 
 Anthracite, 67, 69, 407, 432. 
 
 Anticipation of discovery, 318. 
 
 Anticlinal, 161f; mountains, 167; 
 
 axis, 261. 
 Antiseptum, 210f. 
 Antitide, 297. 
 Antwerp, N. Y., 70. 
 Apatite, 367. 
 Apatosaurus Ajax, 339. 
 Apertural gap, 211. 
 Aphanite, 52, 56. 57. 
 Appalachian coal field, 406, 423. 
 Appalachians, faults and erosion, 93, 
 
 94, 473*; chain, 160, 467, 469; 
 
 section across, 170*: folds, 292, 
 
 370. 471; strata in, 375, 390, 398; 
 
 glaciated, 482. 
 Aral Sea. 189. 
 Archaean, 361. 
 Archaeopteryx macroura, 34'2*. 343, 
 
 345. 
 
 Arched Rock, 393. 
 Ardiche, volcanoes of, 149*; table 
 
 mountains of, 153*. 
 Area of Brachiopod, 231. 
 Argentite, 184. 
 Argillaceous, 46, 60, 249. 
 Argillite, 61. 
 
 Arizona, 184; lava sheets, 154. 
 Arkansas, 66; stones, 49; coal meas- 
 ures, 4u6. 
 Armature, 232f seq. ; wanting in some 
 
 genera, 238. 
 Arm of Crinoid, 324*f, 325*; of 
 
 Cephalopod, 326. 
 Arm supports, 232. 
 Arnot coal mines, 414*. 
 Artiodactyla, 351. 
 Asbestos, 31. 
 Ashes, volcanic, 72, 286. 
 Asphalt, 68, 69, 194, 198. 
 Association of minerals, 55. 
 Assortment of sediments, 283, 268, 
 
 398. 
 
 Asterophyllites, 418*. 
 Athyris spiriferoides, 235*. 
 
 Atlantosaurus immanis, 338. 
 Atmosphere, agency of, 284. 
 Atoms, size of. 18; kinds of, 19. 
 Attitudes of strata, 260. 
 Atrypa, 234, 241; retictilaris, 234*, 
 
 Augite, 32*, 290. 
 
 Augitic eruptive rocks, 72. 
 
 Austria, 193. 
 
 Autun, 194. 
 
 Axis, structural, 260. 
 
 Azoic System, 362. 
 
 Azygos plates, 325. 
 
 Bad Lands, 443*. 
 
 Baker oil region, 199, 200. 
 
 Bald Eagle Mountain, 93*. 
 
 Ball, R. S., on primitive tides, 300. 
 
 Baptanodon discus, 336*. 
 
 Baraboo quartzite, 363. 
 
 Bar, 279; of Mississippi. 85, 279. 
 
 Barrande, J., on colonies, 304; pri- 
 mordial, 370. 
 
 Basal plates, 325. 
 
 Basalt, 72. 
 
 Basaltic, columns, 155*; lava, 149; 
 structure, 264. 
 
 Basic, feldspars, 53f, 54; rocks, 71. 
 
 Basin, Province, 435, 436, 438, 472: 
 lakes, 452 ; ranges, 435. 
 
 Basins of hot springs, 133*. 
 
 Bassett. D. A., on Crinoids, 402. 
 
 Bathmodon, 348, 349. 
 
 Bathyopsis, 351, 353. 
 
 Beak of shell, 226. 
 
 Bedded vein, 181. 
 
 Bed Rock, 2. 
 
 Belemnite, 428, 433. 
 
 Beluga Vermontana, 457. 
 
 Bennett, I, 485. 
 
 Benzole, 69, 194. 
 
 Bex, 189. 
 
 Big Horn Mountains, 374, 431. 
 
 Biotite, 30 ; associates of, 55. 
 
 Birds, position of, 104, 316; compre- 
 hensive, 317; toothed, 343*, 344*. 
 
 Bitterns, 188. 
 
 Bituminous, sandstone, 46; sub- 
 stances, 194; rocks, 250. 
 
 Bivalves, 82, 226. 
 
 Bivalvular symmetry, 228. 
 
 Black Hills, 374.
 
 INDEX. 
 
 495 
 
 Black Shale, 391. 
 
 Blake, W. P., on sand action, 284. 
 
 Blossburg coal mines, 415*. 
 
 Blowpipe analysis, 17. 
 
 Bog, iron, llf, 37, 70; manganese, 
 12. 
 
 Bonneville Lake, 452, 457. 
 
 Bore of Hoogley, 288. 
 
 Boissons glacier, 281*. 
 
 Bothriolepis, 333 ; Canadensis, 334*. 
 
 Botryoidal limonite, 37. 
 
 Bove, val del, 143. 
 
 Bowlders, defined, 4*; particularly 
 described, 12 seq.; on coasts, 15; 
 of copper, 15; derived from north, 
 15; not homogeneous, 16; result- 
 ing from weathering, 95*, 96*. 
 
 Brachiopods, how to study, 226; 
 structures of, classified, 240; table 
 for determination of, 240. 
 
 Bramatherium, 354. 
 
 Brasenice purpurea, 475. 
 
 Brazilian pebbles, 24. 
 
 Breadth of outcrop, 260. 
 
 Breaks in succession of life, 317; of 
 rocks, 377. 
 
 Breasts, in mining, 4l4f. 
 
 Breckenridge coal, 194, 409. 
 
 Bridge of travertin, 132. 
 
 British formations, 275. 
 
 Brittleness, 251. 
 
 Brixham cavern, 460. 
 
 Brontotherium ingens, 353*. 
 
 Brown coal, 68; spar, 36. 
 
 Bruin Lake, 85. 
 
 Buenaventure conglomerate, 406. 
 
 Buffalo, 201. 
 
 Buhl, 194. 
 
 Building stones, 48. 
 
 Bunsen on geysers, 134. 
 
 Burlington Stage, 395, 397, 400. 
 
 Butte county, 151. 
 
 Caenozoic Great System, 441 ; ^Eon, 
 
 476. 
 
 Caesars, palace of, 64. 
 Calamarians, 418*. 
 Calaveras county, 151. 
 Calcareous rocks, 61, 249. 
 Calciferous Stage, 369, 375. 
 Calcite, 34*f, 35, 61, 303. 
 California, lava beds, 154; geology. 
 
 383, 398, 406, 467; province, 435! 
 
 Calumet and Hecla, 367. 
 Calymene Blumenbachii, 323. 
 Calyx, of coral, 203f ; crinoid, 324*f, 
 
 325*. 
 Cambrian, life, 315, 317, 323, 379; 
 
 System, 369, 377*. 
 Camel, 357. 
 
 Cameo mountains, 161 f. 
 Campbell, J. L., on Appalachians, 
 
 169, 170*. 
 
 Canadian formations, 275, 370; mar- 
 bles, 365; Group, 269, 374, 375. 
 Canals of Eozoon, 320. 
 Canary Islands, 145. 
 Canons of Colorado, 89, 91, 165*. 
 Cape Cod, 448. 
 Carbon, source of, 422. 
 Carbonaceous rocks, 67, 249. 
 Carboniferous, limestone, 197, 395, 
 
 396, 397; life, 315. 
 Cardinal process, 231. 
 CarinaB or carinations, 213. 
 Carinatae, 316. 
 Carinthia, 70. 
 Carlisle cave, 457. 
 Carrara marble, 62. 
 Carson Lake, 453. 
 Cascade Range, 441, 478; volcanoes 
 
 of, 147; coal in, 432. 
 Caspian Sea, 189. 
 Cast of fossil, 66f, 304. 
 Castle Rock, 377*. 
 Castle Rock Range, 167. 
 Castoroides Ohioensis, 459*. 
 Cast, up and down, in mining, 414. 
 Cataclysmic theory, 456. 
 Catania, 143. 
 Catskill, Mts., 161*; Group, 191, 
 
 389, 390, 398. 
 Cauda-galli Grit, 390. 
 Caverns, 277, 454; quadrupeds in, 
 
 457, 460. 
 
 | Cavicornia, 354. 
 Cell of coral, 203f, 219. 
 Cement in rocks, 47. 
 Central gap, 21 If. 
 Centre county, Pa., 93. 
 Centronella, " 233, 241 ; Julia, 233, 
 
 238*. 
 
 Cephalaspis Lyelli, 333*. 
 Cephalic shield, 323. 
 Ceratites, 327, 328, 329. 
 Ceratodus, 333.
 
 496 
 
 Cestracionts, 332*, 402, 434. 
 
 Chalcedony, 24. 
 
 Chalcopyrfte, 184. 
 
 Chalk, 64 ; effervescence, 20 ; precip- 
 itated, 21; red, 37; French, 59. 
 
 Challenger, 326. 
 
 Chalybeate water, 12. 
 
 Chambered shells, 326f, 389. 
 
 Chamberlin, T. C., 365, 374; on 
 Drift, 447, 451, 448. 
 
 Chambers, 326. 
 
 Champlain formation, 441, 452 ; Lake, 
 457; epoch, 483. 
 
 Charmoz, Mt., 166*. 
 
 Chazy Stage, 369, 375. 
 
 Cheeks of trilobite, 324. 
 
 Cheirolepis, 333. 
 
 Chelysoma Maclovianum, 334*. 
 
 Chemical affinity, 19f; study of 
 rocks, 253. 
 
 Chemistry, rudimentary principles, 
 18 seq. 
 
 Chemung Group, 192, 194, 389, 391. 
 
 Chert, 25. 
 
 Chester, salt at, 188. 
 
 Chester Stage, 395. 
 
 Chicago, 198, 382, 385. 
 
 Chico Group, 431, 432. 
 
 Chief septum, 210. 
 
 Chilhowee Sandstones, 374. 
 
 Chimagraa, 431. 
 
 Chlorides, 19. 
 
 Chlorite, 31, 52. 
 
 Chonetes, 402. 
 
 Chromic iron, 431. 
 
 Cincinnati, 81, 382, 445, 446; Stage, 
 369, 470; sub-Group, 197, 376, 
 378. 
 
 Cincinnati swell, 378, 379*. 
 
 Circumdenudation, 263. 
 
 Cladopora, 223, 225; Rcemeri, 223, 
 224*; laqueata, 224*. 
 
 Classification, of formations, 269, 
 274, 275; of fossils, 303, 305-314. 
 
 Claypole, E. W., mountain folds. 171, 
 292V 
 
 Cleavage, 35f. 
 
 Clermont, France, travertin, 132*. 
 
 Cleveland, gas at, 201. 
 
 Cliff Limestone, 391, 392*. 
 
 Climates, geological, 106, 295: ex- 
 tra-terrestrial causes, 297 ; relation i 
 of, to Drift, 446. 
 
 Clinodactyla, 351. 
 
 Clinton Stage, 381. 
 
 Clisiophyllum, 204; Oneidaense, 204. 
 
 Clouded marble, 62. 
 
 Clouds, first formed, 464. 
 
 Clymenia, 327; family, 330. 
 
 Coal, 67; brown, 68; origin of, 421. 
 
 Coal conglomerate, oil in, 196. 
 
 Coal Measures, described, 402 seq., 
 471; standard section of, 403; iron 
 in, 183; brine in, 192; disturb- 
 ances in, 410, 411. 
 
 Coal Period, 470, 471; Fields, 406. 
 
 Coal plants, 416; tar, 67, 194. 
 
 Coal, Cretaceous, 422, 433. 
 
 Coast Ranges, 435, 443, 474. 
 
 Cobble stones, 4. 
 
 Coccosteus decipiens, 333*. 
 
 Coeluria, 343. 
 
 Co3iiostroma, 321 ; monticuliferum, 
 322. 
 
 Coke, 67. 
 
 Cold short, 70. 
 
 Colloid, 251. 
 
 Colonies of fossils, 304. 
 
 Colorado, 94, 98, 397, 406, 426, 428, 
 478; coal in, 432. 
 
 Colorado Range, 163, 434, 468; pla- 
 teau, 165. 
 
 Coloradb River, 434, 441, 476; ero- 
 sion, 89, 91* 455. 
 
 Columbia River, 148, 154. 
 
 Column, geological, 107*, 274. 
 
 Columnar basalt, 155*, 156*. 
 
 Comb in veins, 180. 
 
 Commissure, 237. 
 
 Como, 427. 
 
 Compactness, 252f. 
 
 Composition, of minerals, Table of, 
 40; rocks, Table of, 75. 
 
 Comprehensive types, 316f, 318. 
 
 Comstock Lode, 184, 185. 
 
 Concentric structure, 47. 
 
 Concretionary structure, 258, 
 
 Concretions of iron, 47; sandstone, 
 48*. 
 
 Condylarthra, 350. 
 
 Cone in cone, 257*f. 
 
 Cones, volcanic, 146, 147*; hollowed 
 out, 147*; near Mono Lake, 148; 
 in central France, 149. 
 
 Coney Island, 99. 
 
 Conformability, lOOf, 263.
 
 INDEX. 
 
 497 
 
 Conglomerate, 25; quartzose, 45; 
 
 Carboniferous, 196, 405, 406; Ke- 
 
 weenian, 366; Cretaceous, 439, 
 
 440. 
 
 Conifers, 475. 
 Connecticut, iron in, 184; rocks, 
 
 424, 425, 473. 
 
 Connecticut River, 81, 455. 
 Conspectus of extinct life, 359*. 
 Constitutive ingredients, 38f. 
 Contact vein, 181. 
 Continent, growth of, 371*, 382, 
 
 383*, 399*, 423*, 441, 475; physi- 
 ognomy of interior, 434. 
 Contorted folds, 262f. 
 Contraction of earth, 174, 175; and 
 
 earthquakes, 292. 
 Cook, G. H., on subsidence, 487. 
 Cooling, earth, 158, 174; effects of, 
 
 291, 489; sun, 296. 
 Cope. E. D., on reptiles, 337; mam- 
 mals, 348; Port Kennedy cave, 
 , 457. 
 
 Copper-bearing formation, 362. 
 Copper, bowlders, 15; pyrites, 184. 
 Copper, occurrence of, 184, 367, 431. 
 Corals, Cup, 203, 387; Silurian, 387; 
 
 Devonian, 394. 
 Cordaites, 418. 
 Cordilleran Land, 364, 372, 378, 382, 
 
 383, 384, 467, 468. 
 Cordilleran region, 400, 436, 443, 
 
 476; geological history of, 437. 
 Cordilleras, 436. 
 Corniferous Limestone, 197, 390, 391, 
 
 392, 451. 
 Corrasion, 264. 
 Coryphodon hamatus, 348*. 
 Costfe, 204f. 
 
 Cotta, von, on veins, 181. 
 Cottonwood River, 165. 
 Council Bluff, 445. 
 Country rock, 69, 180. 
 Crater of Vesuvius, 138. 
 Crater of Vesuvius in 1756, 146*; of 
 
 Tjeendoeng, 146*. 
 Crawfordsville crinoids, 401. 
 Cretaceous, System, 424, 429, 439, 
 
 440, 441, 474; &on, close of, 474. 
 Crinoids, 324*, 380, 387, 476; at 
 
 Crawfordsville, 402. 
 Croll, J., on glaciation, 485. 
 Crumpling, 263. 
 
 Crust, lllf, 246; fire-formed, 287; 
 incipient, 464. 
 
 Crustaceans, 402. 
 
 Cryptocrystalline, 54, 251. 
 
 Crystalline form of quartz, 24*; feld- 
 spar, 26*, 27*; calcite, 35*; mag- 
 netite, 38*. 
 
 Crystalline rocks, 45, 70, 250f. 
 
 Crystallization, 22, 56. 
 
 Ctenacanthus, 333. 
 
 Ctenacodon serratus, 347*. 
 
 Cuba, 198. 
 
 Cumberland, Table Land, 161, 407; 
 River, 196. 
 
 Cup corals, 202 sea. ; how studied, 
 203; cup of, 203; table of, 217; 
 Lower Carboniferous, 401. 
 
 Cup of crinoid, 324. 
 
 Currents, oceanic, 279, 293. 
 
 Cyathophyllum, 204*, 208*; corni- 
 cula, 204*. 
 
 Cycads, 420, 475. 
 
 Cycle of sedimentation, 268f, 284, 
 409. 
 
 Cynodraco, 341*. 
 
 Cyrtina, 231, 241; Hamiltonensis, 
 231*. 
 
 Cyrtoceras, 329; Eugenium, 330*. 
 
 Cyrtoceratidte, 328. 
 
 Cystiphyllum, 213, 214, 217; Amer- 
 icanura, 214*, 215*. 
 
 Dakota, 185, 430, 445, 448. 
 
 Dalles of Wisconsin River, 89*, 377. 
 
 Danan, 145. 
 
 Dartmoor, 194. 
 
 Darwin, C., on sediments, 283. 
 
 Daubree on metamorphism, 290. 
 
 Davenport, 445. 
 
 Davis cut off, 85. 
 
 Dawn animal, 318. 
 
 Dawson, G. M., great bowlders, 13. 
 
 Dawson, Sir W., coal plants, 418*, 
 
 419*; Laramie plants, 475. 
 Dead rock, 416. 
 Deformative tide, 298. 
 Delta, of rivers, 279; of Mississippi. 
 
 84. 
 
 Deltidium, 231*. 
 Denudation, 96f, 101, 263; rate of, 
 
 278; finality of, 489. ' 
 Des Chutes River, 154. 
 Des Moines, 445.
 
 498 
 
 INDEX. 
 
 Determination of minerals, 42-4; of 
 
 rocks, Table for, 76-80. 
 Detritus in ocean, 293. 
 Devonian, Life, 315, 322; System, 
 
 389. 
 
 Diabase, 54; eruptive, 71. 
 Diallage, 32, 366. 
 Diamond, 69. 
 
 Diamond Peak Quartzite, 397. 
 Diaphragms, 207. 
 Diastema, 353. 
 Diclonius, 475. 
 Dicynodon lacertipes, 341*. 
 Dicynodontia, 341*. 
 Dikes, 155*, 156*, 427; as bearing 
 
 on age, 266. 
 
 Dimophodon macronyx, 342*. 
 Dinichthys Herzeri, 331*, 333. 
 Dinoceras, 351 ; mirabile, 351*, 352*. 
 Dinocerata, 351. 
 Dinosauria, 338. 
 Dinotherium, 353*. 
 Diorite, 53, 54 ; eruptive, 71 ; quartz, 
 
 Dip,' 100, 260; rule of, 114*, 117, 
 
 120, 121. 
 Dihhllum, 215, 218; Archiaci, 
 
 iphyphyll 
 
 Diplacanthus, 333. 
 
 Diplocynodon victor, 347*. 
 
 Dirt beds, 448. 
 
 Dislocation, 163. See "Faults." 
 
 Dissepiments, 208. 
 
 Dissipation of heat, 296, 490. 
 
 Dissociation, 21. 
 
 Distribution wide in early times, 106. 
 
 Divaricator muscle, 231*. 
 
 Docodon, 347. 
 
 Dog-tooth spar, 35*. 
 
 Dolerite, 72, 184. 
 
 Dolomite, 36, 61. 
 
 Dolomitic limestone, 63, 249. 
 
 Dorsal valve, 227. 
 
 Drainage of lakes, 452. 
 
 Drift 2f, 3*, 5*; formation, 441; 
 
 described, 444 seq.; northern and 
 
 southern, 445-6, and climate, 446; 
 
 at Ann Arbor, 6; fossils, 394; 
 
 limestone masses in, 451. 
 Drift in mining, 413. 
 Drift structures, 256. 
 Dromatherium sylvestre, 345, 346*. 
 Drumraond's Island, 385. 
 
 Dryolestes, 347. 
 
 Dunes, 285. 
 
 Durability, 252. 
 
 Dust, cosmic, 286. 
 
 Dutton, C. E., 90, 91; on Hawaii, 
 143; on San Mateo Mountains, 
 154 ; lateral pressure, 292. 
 
 Dyas, 403. 
 
 Dynamical geology, 246f, 276 seq. 
 
 Eagle, Wis., moraine, 450, 451*. 
 Earthquakes, 292; and volcanoes, 
 
 143. 
 
 Earthy, 250. 
 
 Eastern interior Coal Field, 406. 
 East Rock, 155. 
 Ebb and flow structure, 256. 
 Echo cliffs, 164*. 
 Economic, Geology, 246; products of 
 
 Eozoic, 365. 
 
 Edestosaurus dispar, 338*. 
 Effervescence, 17; of chalk, 20. 
 Egyptian marble, 62; asphaltum, 
 
 198. 
 
 Elasmobranchs, 331, 332. 
 Elasmosaurus platyurus, 337*. 
 Elba, geology of, 157*. 
 El Dorado county, 151. 
 Elements, 18, 19. 
 Elephas Americanns, 447, 458*: 
 
 primigenius, 457,461*; Africanus; 
 
 458*; Indicus, 458*. 
 Elk Mountains, 425. 
 Elongation of Mountains, 293. 
 Emery, 38. 
 
 Emmons, E., on mammals, 345*. 
 Enstatite, 366. 
 Eobasileus, 351, 352*. 
 Eocene, 442. 
 Eohippus, 354. 
 Eosaurus Acadianus, 355. 
 Eozoic, Great System, 361, 465; 
 
 Mon, 465. 
 
 Eozoon, 317, 318* seq., 380, 466. 
 Epidote, 38, 52. 
 Epihippus, 256. 
 Epitheca, 204. 
 Epoch, 270. 
 Equidae, 355. 
 Equine types, 355. 
 Equiseta, 418. 
 Equivalents, stratigraphical, 271 ; 
 
 table of, 273, 274.
 
 499 
 
 Equus, 354, 357. 
 
 Erie clays, 452, 486. 
 
 Erie Lake, '449. 
 
 Erosion of mountains, 160. 
 
 Erosions, 87 seq., 263, 264; rate of, 
 95; some effects of, 109, 488; 
 Cambrian, 376; Silurian, 386; De- 
 vonian, 392 ; Lower Carboniferous, 
 401. 
 
 Erupted conditions, 264. 
 
 Erupted materials, origin of, 289. 
 
 Eruptions of Vesuvius, 138; ^Itna, 
 140, 143; Krakatoa, 145; ancient, 
 150 seq.,- Triassic, 427. 
 
 Eruptive rocks, 70; mountains, 168. 
 
 Eureka district, 410. 
 
 European formations, 275. 
 
 Eusthenopteron, 333. 
 
 Eutaw Group, 429. 
 
 Evanston coal, 432. 
 
 Exogyra costata, 433. 
 
 Expansion of organic types, 359. 
 
 Explosions from volcanoes, 143. 
 
 Extinctions of organic types, 314. 
 
 Eyes, compound, 323. 
 
 Paces of quartz, 24; feldspar, 215. 
 
 Fall Brook coal mines, 414. 
 
 Falls, Trenton, Glen's, Minnehaha, 
 High, 377; Ohio, 394. 
 
 False coal measures, 398, 406. 
 
 Fan structure, 171. 
 
 Faults, 163, 164*, 165; in Colorado 
 plateau, 175, 437; in Appalachi- 
 ans, 407; Illinois, 410; resulting 
 from flexure, 261*, 295; and repe- 
 tition of strata, 266. 
 
 Faunas, why changing, 103. 
 
 Favistella, 380. 
 
 Favosites, 219, 222; favosus, 219*, 
 220*; Alpenensis (Hamiltonensis) 
 219*, 220, 221*; tuberosus, 219*; 
 nitella, 219*, 221*; clausus, 219*; 
 Canadensis, 222*. 
 
 Favositidm, 224, 387. 
 
 Favre on mountain folds, 174. 
 
 Feather- form septa, 210. 
 
 Feldspar studied, 25; angles of, 26*; 
 common, 27; acidic and basic, 27; 
 of, 27; discrimination of, 
 
 Feldspathic, eruptive rocks, 7; 
 rocks, 249. 
 
 Felsite, 57. 
 
 Felsitio rocks, 56 seq. 
 
 Fentress, N. C., 70. 
 
 Ferns in coal measures, 416* ; in 
 Mesozoic, 475. 
 
 Ferns, living tree, 417. 
 
 Ferriferous Limestone, 408. 
 
 Ferruginous, water, 12; sandstone, 
 46; rocks, 249. 
 
 Findlay gas wells, 201. 
 
 Fingal's cave, 154, 264. 
 
 Fire-clay, 60. 
 
 Fire-formed crust, 287; disappear- 
 ance of, 287, 288*. 
 
 Firehole River, 135, 136. 
 
 Firemist, JEon, 463. 
 
 Fisher, O., on lateral pressure, 292. 
 
 Fishes, 331. 470. 
 
 Fishes, comprehensive, 316; separ- 
 ated by gaps, 317. 
 
 Fissure in Brachiopods, 231*. 
 
 Flaming Gorge Group, 424, 427. 
 
 Flexure, 262. 
 
 Flint, 24; in chalk, 64. 
 
 Floating ice, 280. 
 
 Floe-till, 447. 
 
 Floods, Champlain, 484, 486. 
 
 Floors in cup corals, 207. 
 
 Florida, 443, 459. 
 
 Fluidal texture, 251. 
 
 Fluviatile, 81. 
 
 Fold in Brachiopods, 228. 
 
 Folds, in Appalachians, 171 ; moun- 
 tain making, 172*, 173*, 262*; 
 how caused, 175*. 
 
 Fontaine, W. M., on Jura-Trias, 
 345, 425. 
 
 Foot of mollusc, 226. 
 
 Foraminifera, 86, 322. 
 
 Formation, 255f. 
 
 Formational Geology, 246, 360. 
 
 Fort Adams, 85. 
 
 Fossa or fossette, 203. 
 
 Fossils, 99, 102, 256f, 303; condi- 
 tions of, 303; classification of. 
 305-314; what they teach, 102; 
 distinguishing strata, 103; indi- 
 cating age, 266. 
 
 Foster and Whitney, 362. 
 
 Fovea, 203. 
 
 Fragmental rocks, 45. 46, 250f, 268, 
 269. 
 
 Franklinite, 69, 183.
 
 500 
 
 INDEX. 
 
 Praas on mammoth, 461. 
 Freestones, 48. 
 Freiberg, 180. 
 Fremont gas wells, 201. 
 Friability, 252. 
 Friable, 45. 
 
 Frumento, Monte, 141. 
 Fumarole, 140. 
 Fundy, Bay of, 280. 
 Funnel of Cephalopod, 326. 
 Fusion beneath crust, 288*. 
 
 Gabbro, 53, 366. See "Norite." 
 
 Galastes, 347. 
 
 Galena, 184; cave, 457; Limestone, 
 
 375. 
 
 Game, lithological, 55 note. 
 Ganges, 278. 
 Gangue, 180. 
 Gangways, 414. 
 Ganoids, 331f, 402, 476. 
 Gaps in Corals, 211; in organic suc- 
 cession, 317. 
 
 Gaps, stratigraphical, 271. 
 Garnet, 38. 
 
 Gas, inflammable, 68, 69, 201. 
 Gas rock. See Table, 403. 
 Gasteropods, 444. 
 Gay Head, 15, 99. 
 Geanticlinal, 295. 
 Gemmation, 220. 
 Genesee River, 88 ; Shale, 194, 195, 
 
 389, 391. 
 Geognosy, 255. 
 
 Geographical range of fossils, 304. 
 Geological column, 107*. 
 Geology, If, 245f ; subdivisions of, 
 
 245, 246. 
 
 Georgia, 381, 416, 443, 473. 
 Georgian Bay, 382. 
 Georgia oil region, 199. 
 Geosynclinal, 205, 470. 
 Geotechtonic results, 302. 
 Geysers of National Park, 134 seq.; 
 
 action of explained, 134. 
 Giant Geyser, 135. 
 Giant's Causeway, 154, 264. 
 Gilbert, G. K., on Henry Mountains, 
 
 157; sand action, 284; Quaternary 
 
 lakes, 452. 
 
 Gilsum bowlder, 13*. 
 Glabella, 323. 
 
 Glacial formation, 441; epoch, 479; 
 pressure, 485. 
 
 Glaciers, 280; continental, 481 ; pres- 
 sure of, 485. 
 
 Glance, silver, 184. 
 
 Glasgow, Ky., 197. 
 
 Glass, how made, 49. 
 
 Glauconite, 431. 
 
 Globigerina, 86. 
 
 Gloucester bowlders, 4*. 
 
 Giyptodon, 4. t >9. 
 
 Glyptolepis, 333. 
 
 Gneiss, 50, 51; syenitic, 52; species 
 of, 54; protogine, 59; chloritic, 60. 
 
 Gold, 185, 431 ; associates of, 185. 
 
 Goniatites, 327*, 402. 
 
 Gorge of Niagara, 89; Colorado, 90, 
 437; Hudson, 455*. 
 
 Gorges, 454. 
 
 Grahamite, 68f, 6'J, 195. 198. 
 
 Grand Canon, 437. 
 
 Grand Detour, 411. 
 
 Grand Gulf, 85. 
 
 Grand Haven dimes, 285. 
 
 Grand Rapids, 65. 
 
 Grand Wash fault, 164*. 
 
 Granite, 50f, 51, 52; Scotch, 53; 
 Quincy, 53; eruptive, 71, 291. 
 
 Granular texture, 45, 250f. 
 
 Granulite, 51; gneiss, 51; eruptive, 
 
 Graphite, 67, 69, 367, 470. 
 
 Gravel, 4f. 
 
 Graylock Mountain, 165*. 
 
 Great Basin, 435. 
 
 Great Britain, formations, 275. 
 
 Great Northern Land, 363, 372f, 467, 
 
 468, 469. 
 Great Plains, 372, 400, 429, 434, 438, 
 
 440, 443, 468, 478, 483. 
 Great Salt Lake, 453. 
 Great System, 278. 
 Greenland, 282, 482, 485; icebergs, 
 
 283. 
 
 Green River, 162. 
 Green sand, 431. 
 Greisen, 50. 
 Grindstones, 49. 
 Gritstones, 396. 
 Group, 270. 
 Growth, lines of, 231. 
 Gryphasa mutabilis, 433. 
 Gum beds, 198.
 
 INDEX. 
 
 501 
 
 Gymnosperms, 418. 
 
 Gypsum, 36*, 65, 66, 192, 386, 397, 
 
 427. 
 Gyroceras undulatum, 330*. 
 
 Habitability of North Pole, 295. 
 
 Hadrosaurus Foulki, 339*. 
 
 Haematite, 36, 69, 183; stalactitic, 
 37; micaceous, 37 ; ochery, 37; jas- 
 pery, 69; argillaceous, 70; oolitic, 
 70; sedimentary in origin, 183. 
 
 Haleakala, 145. 
 
 Hall, James, on spires, 235. 
 
 Halleflinta, 57. 
 
 Hamilton Group, 194, 195, 389, 391. 
 
 Hard heads, 13. 
 
 Hardness, standards of, 42; of rocks, 
 251. 
 
 Hard water, 12. 
 
 Hawaii, described, 143; map, 144*; 
 profile, 144*. 
 
 Hawkins, B. W., 340. 
 
 Heat, dynamic agency of, 286; evo- 
 lution of, 292, 298; total dissipa- 
 tion of, 296. 
 
 Helderberg, Mountains, 381, 386; 
 Group, 386. 
 
 Heliophyllum, 213; Halli, 213*, 214*. 
 
 Henry Mountains, 157*, 168, 437. 
 
 Herculaneum, 138. 
 
 Hesperornis regalis, 343*, 344*. 
 
 Heterocercal, 332*. 
 
 Hexacoralla, 218, 401, See "Tabu- 
 lata." 
 
 Hexagonal prism, 24. 
 
 Hinge of mussel, 226; of Brachio- 
 pod, 228, 229*, 230', 236*, 237*; 
 mechanism, 231*. 
 
 Historical Geelogy, 246. 
 
 Hitchcock, C. H., Gilsum bowlder, 
 13*. 
 
 Hitchcock, E., on veins, 179*. 
 
 Hipparion, 356. 
 
 Hippopotamus, 153. 
 
 Hippotherium, 356. 
 
 History of earth a cooling history, 
 159. 
 
 Hoffman, Mt, 95. 
 
 Holmes, Mt., 158*. 
 
 Homacanthus, 333. 
 
 Homewood Sandstone, 408. 
 
 Homologies, 208. 
 
 Hood, Mt., 147. 
 
 Hoogly, 280. 
 
 Horizon, geological, 271. 
 
 Horizontal range of fossils, 304. 
 
 Hornblende, 31*; associates, 55. 
 
 Hornblendic rocks, 52, 249. 
 
 Hornblendic eruptive rocks, 71. 
 
 Hornets' Nest, 376. 
 
 Horse, 153, 459. 
 
 Horton Series, 398. 
 
 Hot springs on Gardiner's River, 
 133*: 
 
 Hualalai, Mauna, 143. 
 
 Hudson River Slate, 197; formation, 
 376; valley, 455*, 481. 
 
 Human implements in caverns, 462. 
 
 Humboldt, Mountains, 160 ; Lake, 
 453. 
 
 Huron Group, 192, 389, 391. 
 
 Huronian life. 315; times, 466; Sys- 
 tem, 362, 373, 377. 
 
 Huron River, 6. 
 
 Huron Shale (Newberry), 322. 
 
 Hybodonts, 332. 
 
 Hydraulic limestone, 65. 
 
 Hydrocarbons, 194. 
 
 Hydromica, 30; compounds, 51. 
 
 Hydrous magnesian rocks, 58. 
 
 Hylonomus, 335. 
 
 Hyperclinal mountains, 168. 
 
 Hypersthene, 33, 366. 
 
 Hyposyenite, 52. 
 
 Hyracoidea, 350, 351. 
 
 Hyracotherium, 
 
 Ice, action of, 280. 
 
 Iceberg, 283. 
 
 Iceland spar, 35. 
 
 Ichthyornis dispar, 343*. 
 
 Ichthyosauria, 336. 
 
 Ichthyosaurus communis, 336*. 
 
 Idaho, 184, 185, 397. 
 
 Ideal section of earth's crust, 115. 
 
 Idiostroma, 321. - 
 
 Iguanodon, 340; Bernissarten s i s, 
 339*. 
 
 Illinois, lead, 184; rocks, 385, 386, 
 391, 396, 398, 422, 445; coal, 409, 
 410, 412*; fossils, 379, 402; faults, 
 410, 411; dirt beds, 448, 483. 
 
 Impression of a fossil, 305. 
 
 Improvement in organic types, 105. 
 
 Inclinations of strata, how caused, 
 101.
 
 502 
 
 Indiana, fossils, 379. 401 ; rocks, 384, 
 
 385, 390, 403; petroleum, 392; coal, 
 
 409 ; Drift, 449. 
 Inductive method, 1. 
 Injected matter, 291. 
 "In place" defined, 99. 
 Interglacial epoch, 483. 
 Internal heat, 292. 
 Interradial plates, 325. 
 Intersections of veins and age, 267. 
 Intrusive condition, 265. 
 Invertebrates, marine, position of, 
 
 103 ; reign of, 469. 
 Iowa, lead in, 184; formations, 374, 
 
 391 ; Carboniferous Limestone, 
 
 397*. 
 
 Iron, bog ore, 11; haematite, 36; 
 - limonite, 37; magnetite, 37; in 
 
 Eozoic, 365. 
 Iron ore rock, 69; sedimentary in 
 
 origin, 183. 
 Iron regions. 183, 384. 
 Ironstone, 47, 183. 
 Ischia, earthquake, 456. 
 Isinglass, 30. 
 Isogeothermal planes, 288. 
 
 Jasper, 25. 
 
 , . 
 
 Joggins, coal at, 417. 
 John 
 
 Day River, 443. 
 Jointed structure, 258*, 259. 
 Jurassic, Age, close of, 473; Mam- 
 
 mals, 316; System, 424, 425, 427, 
 
 438, 440. 
 Jura-Trias, 424. 
 
 Kaibab plateau, 164*; structure, 437. 
 
 Kames, 447, 450. 
 
 Kanab plateau and canon, 164*. 
 
 Kanawha salines, 409. 
 
 Kansas, 430, 438, 473. 
 
 Kaolin, 28, 60. 
 
 Kaolinic rocks, 249. 
 
 Karg gas well, 201. 
 
 Kea, Mauna, 143. 
 
 Kearsarge, Mt., 166*, 365, 368*. 
 
 Kentucky, 192. 194, 196, 370, 394, 
 
 396, 403, 407, 409, 416. 
 Keokuk Stage, 395, 402. 
 Kerosene, 194. 
 Keweenaw Point, 374; bowlders, 15; 
 
 lava outflows near, 156. 
 
 Keweenian System, 362, 363, 366, 367, 
 
 374, 466. 
 
 Key West, 186, 442. 
 Kidney iron, 47, 70, 392. 
 King, C., on mountain folds, 171; 
 
 on loss, 285; interior geology, 400; 
 
 Quaternary lakes, 452. 
 Kirkdale, cavern, 460. 
 Knobs, 396, 401. 
 Koipato Group, 424, 425. 
 Krakatoa, eruption of, 145, 456. 
 
 Labradorite, 27, 366. 
 
 Laccolite, 157* 158*, 168, 437. 
 
 Lackawanna basin, 407. 
 
 Lacustrine deposits, 445, 452f. 
 
 Laelaps aquilunguis, 343. 
 
 Lagging tide, 299. 
 
 Lahontan Lake, 452, 457. 
 
 Lakes, Quaternary, 452. 
 
 Lamellibranchs, 226*; how differ 
 from Brachiopods, 226; Jurassic, 
 428: Cretaceous, 433, 476; Terti- 
 ary, 444. 
 
 Lamina, 4f, 99, 252*f. 
 
 Lamination, oblique, 256. 
 
 Land, growth of, 106. 
 
 Land's End, 58. 
 
 Laosaurus altus, 339. 
 
 Laramie, Hills, 163; Group, 431. 
 432; coal, 433; Range, 434; plants, 
 475. 
 
 Lassen's Peak, 150. 
 
 Lateral gemmation, 221 ; pressure, 
 171. 
 
 Lateral pressure, 171 ; illustrated, 
 172*; effects of, 291, 294. 
 
 Lateral septa, 210. 
 
 Laurentian, Mountains, 160; life, 
 315, 317, 318; System, 362, 367. 
 373; times, 465, 466; land. See 
 "Great Northern." 
 
 Lava, Vesuvian, 71, 72, 138; M\- 
 nean, 141*; Hawaiian, 144*; an- 
 cient, 150, 154; tables of, 151*. 
 152*, 153*; sheets of, 154, 485; 
 scoriaceous, 156*; laccolitic, 157*; 
 origin of, 289, 485. 
 
 Layer, 255f. 
 
 Lead, 184. 
 
 Leadville, 184. 
 
 Leconte. J., on western lavas, 154. 
 
 Leda clavs, 457.
 
 INDEX. 
 
 503 
 
 Lehigh basin, 407. 
 
 Lenticular vein, 181. 
 
 Lepidodendrids, 416. 
 
 Lepidodendron, 419*, 420. 
 
 Lepidoganoids, 331. 
 
 Lepidolite, 30. 
 
 Lepidosteus, 334 ; embryo, 335* ; Hu- 
 
 ronensis, 334*; oculatus, 334*. 
 Lesley, J. P., 94; on Coal Measures, 
 
 405, 406. 
 Lesqnereux, I., on Cretaceous plants, 
 
 475. 
 
 Lestosaurus inicremus, 338*. 
 Lewis, H. C., on terminal moraine, 
 
 448. 
 
 Life, progress of, 94, 303, 469, 475. 
 Lignilites, 257. 
 Lignite, 68. 
 Lima gas wells, 201. 
 Limaria, 223, 225; crassa, 223*. 
 Limestone, 62 ; for building, 65 ; hy- 
 draulic, 65. 
 Limonite, 37, 70, 184. 
 Lingula, 380. 
 Links missing, 317 ; connecting, 
 
 345*. 
 
 Lipari Islands, 140. 
 Lithological Geology, 246, 248, seq. 
 Lithostrotion, 215, 216*, 217, 401; 
 
 Canadense, 216*. 
 Little Traverse Bay, 394. 
 Liverpool, salt near, 188. 
 Loa, Mauna, 143. 
 Lobes of septum, 330*. 
 Lode, 180. 
 Lodestone, 28. 
 Logan, Sir W. E., 362, 365. 
 Long Branch, 98. 
 Long Island, 442, 481. 
 Longitudinality in. folds, wanting. 
 
 174; present, 175. 
 Loop of Brachiopods, 237*, 238* 
 Los Angeles, 198, 200. 
 Loss, of China, 285; of America, 
 
 285, 445. 
 Louisiana. 193. 
 Loup River, Beds, 478, 479. 
 Lower Carboniferous System, 395. 
 Lower Freeport Coal, 408. 
 Lower Helderberg Group, 381. 
 Lower Kittanning Coal, 408. 
 Lower Magnesian Limestone, 374, 
 
 375. 
 
 Lower Mercer Limestone, 408. 
 
 Loxolophodon, 352. 
 
 Lunar tides. See "Tides." 
 
 Lustre of minerals, 17; quartz. 
 
 feldspar, 25. 
 | Lycosaurus, 341*. 
 i Lynn, 58. 
 
 Macfarlane, J., 415. 
 
 Machaeracanthus, 332. 
 
 Mackinac, I., 393, 451. 
 
 Madeline Plains, 453. 
 
 Magnesian, rocks, 58 ; limestones, 62, 
 374. 
 
 Magnetite, 37, 183. 
 
 Magnetic corpuscles, 286*. 
 
 Magnetic study of rocks, 254. 
 
 Mahonoy Basin, 407. 
 
 Maine, 382, 386. 
 
 Mallet, R., on internal heat, 292. 
 
 Mammals, position of, 105, 316 ; un- 
 der table mountains, 153 ; separated 
 by gaps, 317; descriptions of, 345 
 j.; Mes 
 
 [esozoic, 345, 476 ; Tertiary, 
 348 seq. 
 
 Mammoth, 457, 458, 460, 461*. 
 
 Mammoth, Hot Springs, 133* ; Cave, 
 277*, 401 ; Coal Bed, 409. 
 
 Man, position of, 105, 316; advent, 
 462, 487; place in nature, 491. 
 
 Mandibles of Cephalopods, 326. 
 
 Manganese bog ore, 12. 
 
 Manitoulin, 1., 197, 376, 384. 
 
 Map. nature of, 113, 114, 372; ex- 
 plained, 116 seq.; of United States, 
 118-119*, 360; interpretation of, 
 117 seq.; to be read beneath the 
 surface, 120: exercises on, 120- 
 122; of North America, 361. 
 
 Marble, 34, 62, 63, 367, 368. 
 
 Marble Canon, 164. 
 
 Marblehead, 58. 
 
 Marcellus Shale, 195; Stage, 390. 
 
 Margarodite, 30. 
 
 Mariposa, 428. 
 
 Marl, llf, 64. 
 
 Marsh, 0. C., on reptiles. 335, 336, 
 428; toothed birds. 343; Allothe- 
 ria, 347; Puerco, 443; Christmas 
 Lake, 453. 
 
 Marshall, sandstone. 191f, 192, 390; 
 Group, 395, 396, 400.
 
 504 
 
 INDEX. 
 
 Marsupials, evolving, 347; Tertiary, 
 348. 
 
 Martha's Vineyard, 15, 442, 444. 
 
 Massachusetts, 386. 
 
 Massive structure, 16, 252. 
 
 Mastodon, 457, 458*; under table 
 mountains, 153. 
 
 Mather, on Catskill Mts., 161*. 
 
 Maui, island, 145. 
 
 Medicine Bow Range, 434, 468. 
 
 Medina Stage, 381, 384. 
 
 Megalonyx, 459. 
 
 Megalosaurus, 343. 
 
 Megaphytum, 417*. 
 
 Megatherium, 459, 460*. 
 
 Melaphyr, 366. 
 
 Memphis, 445. 
 
 Meniscoessus conquistus, 348. 
 
 Menophyllurn, 212*. 
 
 Merapi, volcano, 147*. 
 
 Mer de Glace, terminal moraine, 282. 
 
 Meriden Mountains, 155. 
 
 Meridional, predispositions, 175; 
 trends, 301. 
 
 Meridionality in folds, 293; when 
 wanting, 173. 
 
 Merychius, 356. 
 
 Mesas, 168. 
 
 Mesohippus, 356. 
 
 Mesonyx ossifragus, 350*. 
 
 Mesozoic life, 316, 475; reptiles, 335; 
 mammals, 345, 348; Great System, 
 424; ^Eon, 478. 
 
 Metamorphism, 99, 121, 259f; re- 
 gional, 265; explanation of, 290, 
 291. 
 
 Metasomatic change, 265f. 291. 
 
 Mexico, Gulf of, 85 ; tin in, 185. 
 
 Mica, 29 ; schist, 50. 
 
 Micaceous rocks, 50 seq.,249. 
 
 Michigan, iron in, 183, 392; copper, 
 184; silver, 184; salt, 190, 191*, 
 385, 386, 397, 400; mineral wells, 
 192; formations, 274, 367, 370, 385, 
 391, 393, 396, 469; fossils. 394; in- 
 land salt sea, 400 ; coal field, 406 ; 
 Drift, 449, 451. 
 
 Michigan Salt Group, 191, 192, 397. 
 
 Microcline, 28. 
 
 Microcrystalline, 54, 56, 251. 
 
 Microfelsitic, 251. 
 
 Microlestes antiquus, 345, 346. 
 
 Microscopic study of rocks, 253. 
 
 Migrations of animals, 304. 
 
 Millstone Grit, 405. 
 
 Mineral, 16, 247. 
 
 Minerals, how differing, 17; chemi- 
 cal compounds, 22; some elemen- 
 tary, 22; crystalline forms, 22; 
 reviewed, 39 seq. ; composition of, 
 40-41; determination of, 42-44. 
 
 Mineral, water at Clermont, 132; 
 wells in Michigan, 192*. 
 
 Mining for coal, 413. 
 
 Minnesota, 195, 376. 
 
 Miocene, 441. 
 
 Miohippus, 356. 
 
 Missing links, 317. 
 
 Missionary Ridge, 161. 
 
 Mississippi valley, 83; river, 83, 84*; 
 erosions, 89, 90*; sediment, 277, 
 
 m 
 
 Missouri, 69, 98 ; lead in, 184 ; rocks, 
 
 396. 
 
 Modena oil region, 199. 
 Molten state of earth, 287. 
 Monoclinal mountains 161, 165, 167. 
 Mono Lake, volcanic cones near, 
 
 148*. 
 
 Montana, 185, 397, 406. 
 Mont Blanc, 281*, 286. 
 Montreal River, 366. 
 Monument Park, 93, 94*. 
 Moon in terrestrial history, 298, 299. 
 Moon's distance increasing, 300. 
 Moraines, 281, 282, 447; terminal, 
 
 448, 449*, 450. 
 Mormon temple syenite, 53. 
 Morosaurus grandis, 339. 
 Morris Run coal mines, 414. 
 Mortal', how made, 49. 
 Mosasaurs, 434. 
 Mosasaurus princeps, 338. 
 Moulds, 66; of fossils, 303. 
 Mountain, making, 293; Limestone, 
 
 396; phenomena, 160, 293; slides, 
 
 92. 
 Mountains, Laurentian, etc., 160; 
 
 two classes, 160; of relief, 161; 
 
 synclinal, 165 ; types of, 167 ; high- 
 est, 172. 
 
 Mouths of cells, 220. 
 Muck, 82. 
 Mud, cracks, 257; flow, 257; with 
 
 volcanic eruption, 138. 
 Mural System, 208.
 
 INDKX. 
 
 505 
 
 Murdiison, Sir R., 381. 
 Murraysville gas, 201. 
 Muscovite, 30f ; associates of, 55. 
 Mussels, 82. 
 Mylodon, 459. 
 Myrmecobius fasciatus, 34G*. 
 
 Nahant, 58, 99. 
 
 Xanosaurus. 339. 
 
 Naphtha, 69, 194. 
 
 Natchez, 285. 
 
 Xautiloidea, 328, 329. 
 
 Nautilus. 326, 327*, 328, 402, 444. 
 
 Xavajo Mt., 437. 
 
 Nebraska, 438. 
 
 Xeedles in mountains, 166*, 1G7*. 
 
 Neocene, 441. 
 
 Xesquehoning Coal Basin, 412*. 
 
 Nevada, 184. 374, 376, 406; Coal 
 Measures, 410 ; Jurassic, 428 ; Ter- 
 tiary, 443; Quaternary, 453; fos- 
 sils," 379. 
 
 Nevada Land, 383, 400, 468, 472. 
 
 Xewberry, J. S., on sand action, 284. 
 
 New Brunswick, 184. 192,386,398. 
 
 New Buffalo dunes, 285. 
 
 New Hampshire, 386. 
 
 New Jersey, iron in. 183, 184, 429, 
 442. 448, 472; subsiding, 487. 
 
 New Mexico, lava sheets, 154; tin, 
 185; Cretaceous, 430, 431; coal, 
 432 ; Tertiary, 443*. 
 
 New York, 69, 375, 376, 384, 385, 392, 
 469 ; rock salt in, 386. 
 
 New Zealand hot springs, 134. 
 
 Niagara, erosion, 89, 386, 488; falls, 
 89, 386, 387, 388*; gorge, 388*; 
 Group, 381; Limestone, 197, 382, 
 385, 391. 
 
 Nitre caves. 40. 
 
 Norite, 53, 54, 366; eruptive, 71. 
 
 North America, geological map of, 
 
 North Carolina, 425. 
 
 North, the source of bowlders, 15. 
 
 North pole, habitability of, 295. 
 
 Norway, iron in, 183. 
 
 Novaculite, 46, 61. 
 
 Nova Scotia, 48, 49, 192, 198, 386, 
 
 398; coal, 317. 
 Novaya Zemlia, 145. 
 
 Obelisk syenitic, 53. 
 
 Oblateness diminishing, 175, 299. 
 
 Oblique lamination, 256. 
 
 Obsidian, 72. 
 
 Occlusor muscle, 231*. 
 
 Ocean, action of, 279. 
 
 Ocean pressure and folds, 175. 
 
 Ochre, 37. 
 
 Ocoee formations, 374. 
 
 Odontolca% 345. 
 
 Odontornithes, 345. 
 
 Odontotormae, 345. 
 
 Ohio, iron in, 183; brine, 192; oil, 
 196; gas, 201; gypsum, 386; coal, 
 407, 416; coal section, 410; forma- 
 tions, 274, 370, 378, 384, 390, 391, 
 392. . 
 
 Oil Creek, 195. 
 
 Oil sands. See table, 403 seq. 
 
 Oil stone, 61. 
 
 Old Red Sandstone, 390. 
 
 Oligocene, 442. 
 
 Oligoclase, 27. 
 
 Olympic mountains, 473. 
 
 Omaha, 445. 
 
 Onchus Clintoni, 331. 
 
 Oneida Conglomerate, 381, 384. 
 
 Onondaga salines, 190; Salt Group, 
 
 Ontario, 195; petroleum, 196*, 197; 
 
 fossils, 202: rocks, 384, 392, 400; 
 
 Erie clays, 452. 
 Ontario, Lake, 88. 
 Onychodus sigmoides, 332*. 
 Oolitic limestone, 63. 
 Ooze in Atlantic, 86. 
 Opal, 303. 
 
 Orange county mastodon, 457. 
 Oregon Quaternary lakes, 453 ; tuffs, 
 
 478. 
 
 Ores, 177 seq. 
 
 Organic and inorganic, 247. - *" 
 Oriskany Group, 390. 
 Ornithipoda, 339. 
 Ornithopterus, 343. 
 Ornithotarsus immanis, 340. 
 I Orohippus, 356. 
 ! Orthis, 228, 241, 476; biforata, 228*, 
 
 233, 380, 402; subquadrata, 229*, 
 
 232*, 380. 
 Orthoceras, restored, 327*; siphuncle 
 
 of, 327*; age of, 328; Carleyi, 
 
 330*: in Cambrian, 380. 
 Orthoclase. 26*, 27* ; associates of, 55.
 
 506 
 
 Orthoclinal mountains, 167. 
 
 Orton, E., 68; on Coal Measures, 403. 
 
 Osars, 447. 
 
 Ostrea larva. 423. 
 
 Outcrop, 99, 100*, 260. 
 
 Outlier. 264. 
 
 Overflow and age, 266. 
 
 Overlying, 100. 
 
 Overturned fold, 262. 
 
 Owen, R., 340. 
 
 Oxides, 19f; acid-forming and basic, 
 
 19. 
 Oxygen, some properties of, 19. 
 
 Palseaspis, 331. 
 
 Palaeontology, 246f. 
 
 Palfflophycus arthrophycus, 386*. 
 
 Palaeozoic JEon, 468. 
 
 Palisades, 155. 
 
 Palmyra Lake, 85. 
 
 Palpebral lobe, 324. 
 
 Pantodonta, 351. 
 
 Pantotheria, 347. 
 
 Paradoxides Harlani, 323*. 
 
 Paraffine, 69. 
 
 Paragenesis, 180. 
 
 Paria fold and plateau, 164*. 
 
 Parian marble, 62. 
 
 Park Range, 163, 434, 468; constitu- 
 tion of, 436; section across, 437*. 
 
 Parks in Rocky Mountains, 434. 
 
 Parma Conglomerate, 192, 406. 
 
 Parma oil region, 199. 
 
 Parophite, 368. 
 
 Pay gravel, 152. 
 
 Pearl spar, 36. 
 
 Pearl stone, 72. 
 
 Peat, 68, 82, 421. 
 
 Pebble, 4f. 
 
 Pen of Belemnite, 433. 
 
 Pennsylvania, iron, 183, 184, 194, 
 196; oil, 195 seq. ; gas, 201 ; coal, 
 407, 416; formations, 274, 391, 
 398, 424; fossils, 379; Drift, 449. 
 
 Pentacrinus, 428. 
 
 Penokie iron range, 183*, 367. 
 
 Pentelican marble, 62. 
 
 Peperino, 250. 
 
 Perboewatan, 145. 
 
 Perforation in beak, 235*. 
 
 Period, 270. 
 
 Peripheral region of coral, 208. 
 
 Perissodactvla, 351. 
 
 Permian Group, 402. 
 Perrey on earthquakes, 298. 
 
 Petite Anse, 193. 
 
 Petrifaction, 303. 
 
 Petrography, 248. 
 
 Petroleum, 68, 69; geology of, 194; 
 laws of accumulation, "198; con- 
 spectus of, 199; diagram, 200.* 
 
 Petroliferous, 46, 250. 
 
 Petrosilex, 57. 
 
 Phanerocrystalline, 56, 251. 
 
 Phaneropleuron, 333. 
 
 Phascolotherium Bucklandi, 346. 
 
 Phenacodus, 349; Wortmani, 350*. 
 
 Phlogopite, 30. 
 
 Phonolite, 72. 
 
 Phragmocone, 433. 
 
 Phyllite, 61. 
 
 Physical geography, 302. 
 
 Pictured Rocks, 373, 377. 
 
 Pilot Butte, 437. 
 
 Pilot Knob, 367. 
 
 Pinnate septa, 210. 
 
 Pipestone, 363. 
 
 Piroroco of Amazons, 280. 
 
 Pisolitic limestone, 63. 
 
 Pitchstone, 72. 
 
 Pittsburgh, 68; gas production, 201; 
 coal bed, 409. 
 
 Placers, 152. 
 
 Placoderms, 331. 
 
 Placoganoids, 331. 
 
 Plagiaulax, 347. 
 
 Plagioclase, 27*.; discriminations, 28; 
 as rock-constituent, 366. 
 
 Plagiostomes, 332. 
 
 Plants classified, 303; Cretaceous, 
 434, 475. See " Coal Plants." 
 
 Plaster of Paris, 36. 
 
 Plastic zone, 294. 
 
 Plateau Province, 434*, 441, 474; 
 wastage of, 92; section in, 164*; 
 geology of, 428, 436. 
 
 Plates of crinoids, 325. 
 
 Plesiosaurus dolichodeirus, 337*. 
 
 Plications of shell, 231*; of strata. 
 263. 
 
 Pliocene. 441; inaugurated, 478. 
 479. 
 
 Pliohippus, 356. 
 
 Plumbago, 67. 
 
 Plunge, "angle of, 260. 
 
 Pluvial epoch, 467.
 
 INDEX. 
 
 Pogonip Limestone, 376. 
 
 Polished faces, 259. 
 
 Polishing action of sand, 284. 
 
 Polyp, 214. 
 
 Polypary, 203. 
 
 Pompeii, 138, 140.* 
 
 Porcelain materials, 60. 
 
 Porcupine Mountains, 369. 
 
 Pores in Favosites, 221. 
 
 Pores of rocks and water absorption, 
 490. 
 
 Porousness, 252. 
 
 Porphyritic, 251 ; felsite, 58; granite, 
 58*. 
 
 Porphyry, 251 ; quartz, 58; conglom- 
 erate, 58; Keweemaii, 366; intru- 
 sions, 157; silver bearing, 184. 
 
 Porphyry bowlder, 14*. 
 
 Portage Stage, 389. 
 
 Port Hudson, 85. 
 
 Port Kennedy cave, 457. 
 
 Posterior of shell, 228. 
 
 Potomac, River, 81; marble, 425. 
 
 Potash Kettles, 65, 450. 
 
 Potsdam Group, 369; sandstone, 373, 
 377. 
 
 Powell, J. W., on mountains, 161; 
 Uintas, 162; Colorado plateau, 
 165; Cambrian, 370. 
 
 Prairie, 2f. 
 
 Precipitations, 293; in primitive 
 ocean, 464. 
 
 Preparation of sections of fossils, 
 205. 
 
 Presedirnentary history, 463. 
 
 Pressure, lateral, 171," 172* 291; of 
 glacier, 485. 
 
 Primary septa, 210*, 211*. 
 
 Primordial Group, 369. 
 
 Priority, laws of, 272. 
 
 Proboscidea, 351. 
 
 Prochlorite, 31. 
 
 Products, 402. 
 
 Profile, geological, 125. 
 
 Progress in life history, 315. 
 
 Protogine, 59. 
 
 Protohippus, 356. 
 
 Protorosaurus, 335, 
 
 Protozoans, position of, 103. 
 
 Protuberance of equator, 299f, 464. 
 
 Provinces, 434f, geology of, 436. 
 
 Prussia, 193, 194. 
 
 Pseudamygdules, 264. 
 
 Pseudodeltidium, 231, 237*, 239. 
 Pseudomorph, 290. 
 Pseudomorphism, 290. 
 Pseudopodia, 319, 320. 
 Pterichthys, 332,333*; Canadensis, 
 
 333. 
 
 Pteridophytes, 418. 
 Pterodactylus, 342 ; crassirostris, 
 
 341*. 
 
 Pteropods, 86. 
 Pterosauria, 342. 
 Puerco, 443. 
 Pumice, 72. 
 Punctations, 238. 
 Pyrenees, 193. 
 Pyrite, 38, 303. 
 Pyritous rocks, 249. 
 Pyrophyllite, 30, 60. 
 Pyrophyllite slate, 60. 
 Pyroxene, 32. 
 Pyroxenic rocks, 52, 249. 
 Pythonomorpha, 337. 
 
 Qunquaversal dip. 261. 
 
 Quartz, studied, 23. 
 
 Quartzite, 45 ; hornblendic, 52 ; striat- 
 ed, 283; Baraboo, 363; Prospect 
 Mt., 376; Diamond Park, 397; 
 Wahsatch, 440 ; coal measures, 409. 
 
 Quartzose rocks, 44 seq., 249. 
 
 Quebec Stage, 369. 
 
 Queen Charlotte Islands, 429. 
 
 Quicklime, 21. 
 
 Quincy granite, 53. 
 
 Radial plates, 325. 
 
 Rain, with volcanic eruptions, 138; 
 
 prints, 287. 
 Rains, first, 464. 
 Rakata Mt., 145. 
 Range of fossils, 304; organic types, 
 
 359. 
 
 Rangoon oil region, 199. 
 Ranier, Mt., 148. 
 Ratitae, 316. 
 Rays, 331. 
 Reade, J. M., 96. 
 Recent Epoch, 486. 
 Recession of falls, 92. 
 Red, chalk, 37; ochre and paint. 37. 
 Red sunsets, 145. 
 Reef-building, 322. 
 Re-fusing of crust, 465.
 
 508 
 
 INDEX. 
 
 Reign of Fishes, 335. 
 
 Relief, mountains of, 161. 
 
 Rensselserite, 368. 
 
 Reptiles, position of, 104, 316; com- 
 prehensive, 316; descriptions of, 
 335. 
 
 Resupinate, 241. 
 
 Retardation of earth's rotation, 299. 
 
 Reticulating stems, 223. 
 
 Rhamphorhynchus, 342. 
 
 Rhinoceros, 153. 
 
 Rhizocrinus, 326; Lofotensis, 324*. 
 
 Rhode Island Coal Field, 406. 
 
 Rhombohedron, 35. 
 
 Rhyolite, 72. 
 
 Richthofen on loss, 285. 
 
 Rim-rock, 152. 
 
 Ripidolite, 81. 
 
 Ripple marks, 257. 
 
 Rochester, N. Y., 88. 
 
 Rock cities, 407. 
 
 Rock salt, 385, 386. 
 
 Rocks, 247, 248; classification of, 
 107, 108, 115; physical conditions 
 of, 248; essential and accessory 
 constituents, 248, 249. 
 
 Rogers, W. B., on Coal Measures, 
 402, 403. 
 
 Rossie, N. Y., 70. 
 
 Rotten Limestone, 429. 
 
 Rugosa, 202 seq.; table of, 217. 
 
 Ruined cities, 407. 
 
 Russel, I., on Quaternary lakes, 453. 
 
 Russia, 195. 
 
 Saccharoidal, 62. 
 Sacramento River, 435. 
 Saddles of septum, 330. 
 Safford, J. M., on Unaka Mountains, 
 160, 374; Tennessee geology, 374. 
 Saginaw River brines, 192. 
 Sahlite, 32. 
 Saliferous rocks. 249. 
 Salina Group. 381, 385. 
 Salisbury iron, 37. 
 Salt, geo'logy of, 186 seq.; impurities 
 
 Salt Lake City, 53. 
 
 Salts, how formed, 20; how named, 
 
 20. 
 
 San Bernardino, 95. 
 Sand, 250. 
 Sand blast action, 259, 284. 
 
 Sand dunes, 285. 
 
 Sandstone, 250. 
 
 Sandtisky, 65. 
 
 Sandy Hook, 456, 473. 
 
 San Francisco, Mt., 437. 
 
 Sun Mateo Mountains, 154. 
 
 Santa Barbara, 198. 
 
 Saskatchewan, 433. 
 
 Savoy, 92. 
 
 Scaly minerals, 29. 
 
 Scars on shells, 304; on tree-ferns, 
 418. 
 
 Scelidotherium, 459. 
 
 Scenographic results, 302. 
 
 Scheererite, 69. 
 
 Schist, silicious, 46 ; jaspery and htrin- 
 atitic, 46; mica, 50; granulite, 51; 
 hornblende, 52. 184; aphanitie, 
 54; sericite, 59; protogine, chlo- 
 rite, talcose, 59; chlorite, 84; py- 
 rpphyllite, argillaceous, 60; haema- 
 tite, magnetite, jaspery, 69. 
 
 Schistose, 16f. 
 
 Schoharie Grit, 390. 
 
 Schuylkill basin, 407; section across, 
 412. 
 
 Scotch granite, 53. 
 
 Scribner, G. H., on north pole, 296. 
 
 Scrope on volcanoes, 148. 
 
 Scrubgrass Coal, 408. 
 
 Seaboard Land, 363, 372f, 399, 467, 
 468, 472. 
 
 Seams, 252*, 256. 
 
 Sea over the land, 101. 
 
 Seattle, 432. 
 
 Secret Canon Shale, 376. 
 
 Section, explained, lllf, 112 ; of 
 earth's crust, 115; construction of, 
 from map, 123 seq.; Detroit to 
 Grand Haven, 124*; Ontario to 
 Pennsylvania, 126*; Nashville to 
 Savannah, 128*; through Tennes- 
 see, 93*; in Appalachians, 94*; at 
 Tuscan Springs, 132* ; through 
 Table Mountains, 151*, 152*; in 
 Elba, 157* ; through laccolite, 157* ; 
 Catskill Mountains, 161*; through 
 Uinta Mountains, 162*; central 
 Utah, 163*; across plateau region, 
 164*; across Appalachians, 170*; 
 through Alps, 172*; through Pe- 
 nokie range, 183*; Onondaga sa- 
 lines, 190*"; Michigan basins, 191* ;
 
 INDEX. 
 
 509 
 
 Ontario oil region, 196* ; along Ot- 
 tawa River, 366; along upper Mis- 
 sissippi, 377* ; in undulating Coal 
 Measures, 410* ; Ohio Measures, 
 410; Great North to Little North 
 Mountain, 411; across Sclmylkill 
 basin, 412* ; through Alabama, 
 430* ; across Park Province, 437* ; 
 aeonic, 480. 
 
 Sections, of fossils, 205; Zaphrentis 
 prolifica,206*; Amplexus Yandelli, 
 207*; Heliophyllura Halli, 213*, 
 214*; Cystiphylluin Americanum, 
 215* ; Diphyphyllum Archiaci, 
 216*; Favosites Alpenensis, 221*; 
 F. nitella, 221*; Alveolites Gold- 
 fussi, 223*; Cladopora Rcenieri, 
 223*. 
 
 Sedgwick, Adam, 381. 
 
 Sedimentary rocks, 70. 
 
 Sedimentation, 80f seq,; cycles of, 
 268, 284. 
 
 Seismic phenomena, 292; produced 
 by tidal action, 298. 
 
 Selachians, 402, 476. 
 
 Selaginella, 419. 
 
 Selenite, 36. 
 
 Seneca Lake, 88. 
 
 Septa, of corals, 204, 206; arrange- 
 ment of, 210, 211*, 212*; of cham- 
 bered shells, 326. 
 
 Septal system, 208. 
 
 Serai Conglomerate, 405. 
 
 Sericite schist, 59. 
 
 Serpentine, 30, 184, 385. 
 
 Servos, 92. 
 
 Set, of gypsum, 36, 66. 
 
 Sevier Lake, 453. 
 
 Sewanee coal, 406. 
 
 Shaft, in mining, 413, 414*. 
 
 Shale, argillaceous, 60; bituminous, 
 195. 
 
 Shaly, 252. 
 
 Shamokin basin, 407. 
 
 Sharks, 331, 402. 
 
 Shasta, Mt., 47, 435. 
 
 Shawnee fault, 410. 
 
 Sheets of lava, 150. 
 
 Shi vwits Plateau, 164*. 
 
 Siam hairy elephant, 462. 
 
 Siberian elephant, 460. 461*. 
 
 Sicily, 193. 
 
 Siderite, 47, 70, 183. 
 
 Sideritic rocks, 249. 
 
 Sierra la Sal, 437. 
 
 Sierra Nevada, 95, 435, 438, 473 ; vol- 
 canoes of, 147; eruptions from, 150; 
 fault, 165. 
 
 Sigillaria, 419*. 
 
 Silica, 19, 25, 303. 
 
 Silt of rivers, 277. 
 
 Silurian, life, 315, 317; System, 381. 
 
 Silver, 184. 
 
 Sink holes, 65, 134. 
 
 Sinking sea bottom, 294. 
 I Sinter, silicious, 133, 136*. 
 
 Sinus in Brachiopods, 228. 
 
 Siphuncle of Cephalopods, 326, 237*. 
 
 Sivatherium, 354. 
 
 Skeleton, supplementary, 320. 
 
 Slate pencils, CO. 
 
 Slaty, 98; structure, 258*. 
 
 Sleeping Bear, 284. 
 
 Slopes in mining, 416. 
 
 Smith, E. A., on green sand, 432. 
 
 Soapstone, 59. 
 
 Socket of hinge, 231*, 232.* 
 
 Soil, 2f ; on prairies, 2. 
 
 Solenhofen schists, 343. 
 
 Solfatara, 140. 
 
 Solubility, 252. 
 
 Somma, 146. 
 
 Soudan, 145. 
 
 South Carolina, 425, 479, 481. 
 
 Spalacotherium, 347. 
 
 Spanish white, 64. 
 
 Spar, 350. 
 
 Sparry rocks, 47. 
 
 Spathic iron, 70. 
 
 Species migrating, 102. 
 
 Sperenberg boring, 193. 
 
 Spines of sharks, 332*. 
 
 Spires in Brachiopods, 232*. 
 
 Spirifera, 227. 241, 402; mucronata., 
 227*, 229*, 231, 233*; striata, 232*. 
 
 Spiriferidae, 237. 
 
 Spirigera, 228, 241; spiriferoides, 
 228*. 235*. 236*, 241. 
 
 Split Rock. 111., 411. 
 
 Sponges, 322. 
 
 Spores in coal, 416. 
 
 Springs and wells, 7 seq., 8*. 
 
 Springs, thermal, 131*; at Sacra- 
 mento Valley, 132*; Clermont, 
 132*; National Park, 133*. 
 
 Squalodonts, 434, 444.
 
 510 
 
 Squeezing together, 173. 
 
 Stabi*, 138. 
 
 Stage, 270. 
 
 Stagonolepis, 335. 
 
 Stains, how caused, 49. 
 
 Stalactite, 64. 
 
 Stalactitic haematite, 37; liraonite, 
 
 37. 
 
 Stalagmite, 64. 
 St. Andre, 92. 
 Star Peak Group, 424, 425. 
 Stassfurt, 193. 
 Statuary marble, 62. 
 Steam eruptions, 289. 
 Steatite, 59, 368. 
 Stephanite, 184. 
 Stereognathus, 346. 
 Sterling, 70. 
 Stevenson, J. J., on Virginia salt, 
 
 192; coal, 432. 
 
 Stigmaria, 420*; ficoides, 420*. 
 St. Ignace bowlder, 14*. 
 St. John formation, 362. 
 St. Louis' stage, 395, 400, 401. 
 St. Paul's cathedral, 64, 95. 
 St. Peter's sandstones, 375. 
 Stratification, 6, 16, 252f, 255. 
 Stratigraphical and topographical, 
 
 100. 
 Stratum and Strata, 6, 97, 252f, 255, 
 
 how disposed, 108 seq., 110*. See 
 
 "Sedimentation." 
 Streak, 31*, 37, 
 Streptelasma, 210, 217, 380; corn icu- 
 
 lum, 210.* 
 
 Striation by glaciers, 283. 
 Strike, 260. 
 
 Stromatocerium rugosum, 321. 
 Stromatopora tuberculata, 321 ; stria- 
 
 tella, 322. 
 
 Stromatoporoids, 321. 322, 394. 
 Strophomena. 230, 241, 380, 476; 
 
 inaequiradiata, 230*, 239*; alter- 
 
 nata, 239*. 
 
 Structural Geology, 246. 
 Structure of crust to be read from 
 
 map, 120. 123. 
 
 Structure of rocks. Table of, 74. 
 Stumps in coal. 417*. 
 Stylacodon, 347. 
 Stylodon, 347. 
 Stylolites, 257. 
 Styria, 70. 
 
 Subcarbomferous, 395. 
 
 Sublimation in veins. 291. 
 
 Subsidence, of sea-bottom, 294; dur- 
 ing Coal Measures, 412; Cham- 
 plain, 484. 
 
 Subterf usion of crust, 284*. 
 
 Subterranean waters. 277. 
 
 Subvitreous lustre, 25. 
 
 Succession of organic types, 105, 314; 
 of vertebrate life, 357. 
 
 Succinite, 68. 
 
 Sugar Loaf. 393. 
 
 Sumatra, 200. 
 
 Sump, 414*. 
 
 Sun, extinction of, 296. 
 
 Sundanese volcanoes, 145, 146. 
 
 Supercrust, 465. 
 
 Superior, Lake, 69, 71; geologv of, 
 466, 467. 
 
 Superposition and age, 265, 266. 
 
 Surface materials, 1. 
 
 Surprise Valley, 453. 
 
 Suture of Trilbbite, 324; chambered 
 shell, 327*. 
 
 Syene, 52. 
 
 Syenite, 52; eruptive, 71; quart x, 71. 
 
 Sylvestri on ./Etna. 142. 
 
 Symmetry, bivalvular, 227; univalvu- 
 'lar. 228. 
 
 Synchronistic motions, 490. 
 
 Synclinal basins, 110; mountains, 
 "165*, 166*, 168; axis, 261. 
 
 Synclinorium, 294. 
 
 Synonyms, 272. 
 
 Syracuse, brines at, 188, 189, 190*. 
 
 Syringothyris, 236, 241, 402; typus, 
 '236*, 237*. 
 
 System, 270-f-. 
 
 Table mountains in California. 151*; 
 in Tuolumne county, 152*; in 
 France, 153. 
 
 Table of, chambered shells, 329 ; suc- 
 cession of life, 358; composition 
 of minerals, 40-41; determination 
 of minerals. 42-44; standards of 
 hardness, 42; rock-structure, 74; 
 rock-composition, 75; rock-deter- 
 mination, 76-80; Cup Corals. 217; 
 Tabulate Corals. 224; determina- 
 tion of Brachiopods, 240. 
 
 Table Rock, 387, 389*.
 
 INDEX. 
 
 511 
 
 Tabulae in corals, 207; in Tabulate 
 Corals, 220. 
 
 Tabular limestone in Drift, 451. 
 
 Tabular mountains, 168. 
 
 Tabular system in corals, 208. 
 
 Tabulate corals, 218 geg., 401. 
 
 Tacconay glacier, 281. 
 
 Tteniodonta, 350. 
 
 Tails, vertebrated. of birds, 317. 
 
 Talc, 30. 
 
 Talcose rocks, 249. 
 
 Taxeopoda, 350. 
 
 Taylor Mountain, 154. 
 
 Teeth of Brachiopods, 229, 232*. 
 
 Tejon Group, 432. 
 
 Teleosts, 331 f, 402, 444. 
 
 Telerpeton, 335. 
 
 Temescal, 95. 
 
 Tempei'ature beneath surface. 129. 
 
 Tennessee. 65: central basin of, 92*; 
 valley of east. 92* ; section through, 
 160, 161, 163; iron in. 184; forma- 
 tions, 370, 374, 378, 384, 396: fos- 
 sils, 379; coal. 406,416. 
 
 Tentacles of molluscs, 326. 
 
 Terebratula, 238: Roiningeri. 237*: 
 flavescens, 238*. 
 
 Terebratulidas, 237, 433. 
 
 Terms used in rock classification, 
 108. 
 
 Terrace formation, 441, 454. 
 
 Terraces, river, 278, 454. 
 
 Terrane, 255. 
 
 Tertiary,life,316; System, 441; sub- 
 divisions of. 444. 
 
 Teton Mountains, 374. 
 
 Tetrabranchs, 326. 
 
 Tetracoralla, 202, 475. See "Ciip 
 Corals." 
 
 Texas, 429, 430, 474. 
 
 Texture, 251; granular, 45; aphan- 
 itic, 56. 
 
 Theriodonta, 340. 
 
 Thermal waters, 129 seq. 
 
 Thick- and thin-bedded. 16, 252. 
 
 Thickened strata in mountains, 293. 
 
 Thickness, calculation of, 261. 
 
 Three Princes vein. 180*. 
 
 Thuringian copper slates, 184. 
 
 Thylacotherium Broderipii. 346* 
 
 Tidal, action. 297; wave. 280. 
 
 Tides, high primitive, 300. 
 
 Till, 447. 
 
 Tillodontia, 349, 350. 
 Tillotherium fodiens, 349*. 
 Time and events, categories of, 269. 
 Time, geological, long, 106; classifi- 
 cation of, 107, 108. 
 Tinoceras, 351 ; ingens, 352*. 
 Tinodon, 347. 
 Titanic iron ore, 69, 183. 
 Toothed structure, 257. 
 Topographical and stratigraphical, 
 
 Torba'nite, 69. 
 
 Toroweap fault, 164*. 
 
 Toughness, 251. 
 
 Tourmaline, 82; in quartzite, 45; in 
 other rocks. 52, 249. 
 
 Trachyte, 72. 
 
 Tracks on sandstone. 425*. 
 
 Travertin, 64; at Clermont, 132. 
 
 Tremolite, 31. 
 
 Tremors of earth, 293. 
 
 Trend, 260. 
 
 Trenton Group, 197, 369; limestone, 
 375. 
 
 Triassic, System, 424, 472, 438 ; chan- 
 nel of Hudson River, 455. 
 
 Triclinic feldspars, 27. 
 
 Triconodon, 347. 
 
 Trilobites, 323, 389, 421. 
 
 Trinidad, 198. 
 
 Tritylodon longaevus, 346. 
 
 Tuckerman's ravine, 483. 
 
 Tufa, 11*, 64; at Clermont, 132*. 
 
 Tuffs, volcanic, 478. 
 
 Tulare Lake, 435. 
 
 Tuluole, 69. 
 
 Tuolumne county, .152. 
 
 Tuscany, 193. 
 
 Tuscan Springs, 132*, 150. 
 
 Types of plants and animals, 305- 
 314. 
 
 Uinkaret Mountains, 164*, 437. 
 Uinta Mountains, 162*, 165, 426, 
 
 427, 428, 430, 431, 434, 440, 441. 
 Uintatherium, 351, 353; Leidyanum, 
 
 351*; mirabile, 351*. 
 Ulterior history, 488. 
 Umbral Series,' 398, 399. 
 Unaka Mountains, 93, 160, 374. 
 Unconforrnability, 100. 
 Underlying, 100. 
 Ungulata, 861.
 
 512 
 
 Uniformitarian view, 456. 
 
 Univalves, 82. 
 
 Univalvular symmetry, 227. 
 
 Unstratified rocks, 264. 
 
 Upham, W., on Lake Agassiz, 452. 
 
 Uplifts, 101. 
 
 Upper Carboniferous System, 402 
 
 seq. 
 
 Upper Freeport Coal, 408. 
 Upper Mercer Limeetone, 408. 
 Urocentrum, 819*, 
 Utah, section in, 163* 165; rocks of, 
 
 397, 406, 424, 437; coal in, 432; 
 
 Lake, 453. 
 Utica Stage, 369. 
 
 Valve of shell, 226. 
 
 Vancouver Island, 429. 
 
 Variations from type to type, 105. 
 
 Variolite, 72. 
 
 Vascular impressions, 230*, 231, 232, 
 304. 
 
 Vegetation. See " Plants." 
 
 Vein, condition, 265; filling of, 296. 
 
 Vein intersections and age, 267. 
 
 Veins, mineral, 177* seq. ; quartzose, 
 177. 178; intersecting, 176; kinds 
 of, 181. 
 
 Ventral valve, 227. 
 
 Verd antique, 62. 
 
 Vermont marble, 62; iron ore, 70; 
 rocks, 370. 
 
 Vertebrated tail, 335*. 
 
 Vertebrates, position of, 104. 
 
 Vertical, force, 175; range of fossils, 
 304. 
 
 Vesicle, contracile, 319*. 
 
 Vespertine Series, 398, 399. 
 
 Vesuvian lava, 72. 
 
 Vesuvius, described, 188; crater of, 
 138; crater of, in 1756, 146*; erup- 
 tions of, in 79 A.D., 138; in 1872, 
 139*. 
 
 Vicksburg, 85, 445. 
 
 Victoria coal, 433. 
 
 Virginia, 65, 192, 898, 425. 
 
 Visceral cavity of coral, 207. 
 
 Vitreous lustre of quartz, 23. 
 
 Vogt, Carl, 844. 
 
 Volanic, outflows, 437; tuffs, 478. 
 
 Volcanoes, 138 seq. ; extinct, 148. 
 
 Wachsmuth. C., on crinoids. 401. 
 
 Wad manganese, 12. 
 
 Wahsatch Mountains, 160, 165, 374, 
 
 397, 409, 426, 427, 428, 435, 440, 
 
 443, 468, 474; uprise of, 438; 
 
 formation, 476; coal measures, 
 
 409. 
 
 Waldheimia, 238. 
 Walker Lake, 453. 
 Wall of a coral, 204, 206. 
 Walled lakes, 15. 
 Ward, H. A., on mammoth, 461. 
 Warren, J. C., mastodon, 459. 
 Warren, W. F., on north pole, 296. 
 Warm water, 131. 
 Warsaw limestone, 401. 
 Washakie Basin, 477. 
 Washington Territory, 432, 473, 478. 
 Water as a dynamic agent, 276. 
 Waters of springs and wells, 10; 
 
 often impure, 11; thermal, 131. 
 Watertown, N. Y., 376. 
 Watkins' Glen, 88*. 
 Waugoshance Point bowlders, 15. 
 Wave action, 279. 
 Waverly sandstone, 192, 390, 396, 
 
 402. 
 
 Wave, tidal, 280. 
 Waxy solids, 69. 
 Weathering, effects of, 178. 
 Weber conglomerate. 
 Wells, 9 ; deep and shallow, 10*. 
 Western interior Coal Field, 406. 
 West Humboldt Range, 426. 
 West Rock, 155. 
 West Virginia, 197. 
 Whale in Lake Champlain, 457. 
 White, C. A., on Cretaceous, 431, 
 
 432. 
 
 White Limestone, 444. 
 White River, 443, 499. 
 Whiting, 64. 
 Whetstone, 49. See " Novaculite, " 
 
 46. 
 
 White Cliffs Group, 424. 
 Wielicza, 193. 
 
 Winchell, N. H., on Cambrian fos- 
 sils, 363. 
 
 Windings of Mississippi, 84*. 
 Wind River Mountains, 443; valley, 
 
 478. 
 
 Windsor series, 398. 
 Winnemuca Lake, 453. 
 Winnipeg, 875, 485.
 
 INDEX. 
 
 513 
 
 Wisconsin. 95; river, 89; rocks, ;>0o*, 
 
 370, 376*, 384, 469 ; quartzite, 374* ; 
 
 fossils, 379; moraine, 451*. 
 Wortman, J. E., 348. 
 Wright, G. P., on moraine, 448. 
 Wrinkles, 172, 173; how caused, 174, 
 
 464; disposition of, 173. See 
 
 "Folds." 
 Wyoming, 185, 851, 397, 406, 428, 
 
 478; coal in, 432. 
 Wyoming anthracite basin, 407. 
 Wyoming county, N. Y., 190. 
 W'ythe county caves, 457. 
 
 Yazoo liiver, 85. 
 Yellow ochre, 37. 
 
 Yellowstone, National Park, 133, 
 140; River, 476. 
 
 Zaphrentis, 204, 217 ; prolih'ca, 204*, 
 
 200 *: Ida, 212*. 
 Zeuglodon, 444. 
 Zinc iron ore, 69. 
 Zoophytes, 324. 
 
 Zygospira, 233, 241; modesta, 233, 
 '235*.
 
 
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