LIDKAK.T 
 
 UNIVERSITY OF 
 CALIFORNIA 
 
 CIENCE5 
 BRARY 
 
 UNIVERSITY' OF CALIFORNIA. 
 
 FROM THE LIBRARY OF ^ 
 
 DR. JOSEPH LECONTE 
 
 GIFT OF MRS. LECONTE. 
 EARTH 
 
 Afo. SCIENCES 
 LIBRARY 
 
 

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ELEMENTS 
 
 GEOLOG Y, 
 
 INTENDED FOR THE USE OF S, 
 
 BY I UNIVE: 
 
 SAMUEL ST. JOHN, 
 
 PROFESSOR OF CHEMISTRY AND GEOLOGY IN 
 WESTERN RESERVE COLLEGE. 
 
 Chimborazo. 
 
 "Geology, in the magnitude and sublimity of the objects of which it treats, 
 undoubtedly ranks next to Astronomy in the scale of the Sciences." 
 
 SKr J. F. W. Hersehd. 
 
 NEW- YORK : 
 GEORGE P. PUTNAM, 155 BROADWAY. 
 
 1851. 
 
o 
 
 ENTERED according to Act of Congress, in the year of our Lord 
 one thousand eight hundred and fifty-one, by S. ST. JOHN and J. 
 BRAINERD, in the Clerk's Office of the District Court, for the Dis- 
 trict of Ohio. 
 
 H. SHAIK, 
 HUDSON STEREOTYPE FOUNDET. 
 
H- 
 
 PREFACE. 
 
 THE following treatise has been prepared in ac- 
 cordance with the request of a large number of teach- 
 ers, . who desired to introduce the study of Geology 
 into our higher schools. The work is designed to be 
 strictly elementary, and hence does not embrace pro- 
 tracted discussions on the more abstruse and undeter- 
 mined problems of theoretical geology ; it aims to en- 
 gage the interest of the pupil in the facts of the 
 
 O O J. JT 
 
 science. 
 
 The authorities for the facts cited are principally 
 Lyell, Murchison, Buckland, Ansted, Agassiz, Hitch- 
 cock, Dana, and the State Geological Surveys, par- 
 ticularly that of Professor Hall of New York. 
 
 The engravings- were executed by Professor 
 Brainerd, and in some instances the .subjects were 
 sketched from nature by him. 
 
 An analytical table of contents seemed to the 
 author preferable, for the purposes of examination 
 
 101311 
 
IV PREFACE. 
 
 and review, to a series of questions appended to each 
 page. 
 
 Experience in teaching geology indicates that 
 nothing so much encourages the pupil and facilitates 
 his progress, as frequent use of sections on a large 
 scale, to illustrate both the actual modes of occurrence 
 of geological phenomena, and theoretical views. The 
 map recently prepared by Professor Hall is admira- 
 bly adapted to this purpose. 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 DESIGNED AS A BASIS FOR REVIEW AND EXAMINATION. 
 
 PRELIMINARY OBSERVATIONS. 
 
 Geology defined, . *' . $ 
 Object of Geology, . 
 Descriptive Geology, . 
 Theoretical " 
 Practical " . . 
 
 Adjunct sciences, . 
 
 \Atmospheric agents mechani- 
 cal, chemical, ' . . 14 
 Winds, dunes, . . 15 
 
 CHAPTER I. 
 GENERAL CONSTITUTION 
 
 AND 
 
 STRUCTURE OF THE EARTH. 
 
 Planetary relations of the earth 2 
 Figure of the earth length of 
 
 Frost talus, 
 
 chemical 
 
 16 
 
 Aqueous agency 
 
 mechanical, . . .17 
 Rivers waterfalls Niagara, 18 
 The Simeto, ... 19 
 Example of torrents, . . 20 
 Transport influenced by buoy- 
 
 ancy 
 River deposits, 
 
 21 
 
 22 
 
 Deltas of the Rhone, Nile, 
 Ganges, Rhine, Mississippi, 
 Po, Amazon, . 23 28 
 
 diameters, 
 
 Density of the earth increase 
 of density within, . 
 
 Temperature of the globe of 
 the surface influenced by lat- 
 itude isothermal lines in- 
 crease of temperature be- jlcebergs, 
 low, 5 Agency of the ocean, 
 
 4jlncrusting springs, tufa, 
 Silicious deposits, . 
 Land slides, . '.-, 
 Glaciers^ 
 
 Waves, 
 
 Tides, .... 
 
 Currents, drift and stream, 
 
 Surface outline height of 
 
 mountains mean height of 
 
 the surface of continents 
 
 ocean depths, . .' 6 Gulf Stream, 
 Distribution of land and water, 7i its temperature, 
 Crust of the earth, . . 8' Arctic current. . . ,' 
 Means of Geological investiga- Tides and currents reproduce 
 
 land, 
 
 . 29 
 30 
 
 . 31 
 32 
 
 . 33 
 34 
 
 3537 
 38 
 39 
 40 
 41 
 
 44 
 
 tion, 
 
 Elements their number, 10|General result of atmospheric 
 
 Minerals which compose most I and aqueous agencies, . 45 
 
 rocks, .... \\\Igneous agency . . 46 
 
 Incessant changes, . . 12'Volcanoes submarine, extinct, 
 
 Nature of agents of geological intermittent, solfataras, 
 
 changes, 
 
 13 Their nu tubers in bands, 
 
 4T 
 43 
 
VI 
 
 ANALYTICAL TABLE OF CONTENTS. 
 
 Phenomena of eruptions, . $ 49iCircular atolls, lagoons, their 
 Greatest eruption of modern origin, . . . g 79 
 i times, . . . . 50[Reefs raised^ above the ocean 
 
 iOf Skaptaa Jokul in 1783, . 5l| level, . . . . 80 
 
 Vesuvius, 
 
 Etna, 
 
 Volcanoes of America, 
 
 of Mexico, 
 
 Origin of Jorullo, . 
 
 Kilauea, 
 
 its eruptions, 
 
 52 53;Forrnation of soil on reefs 
 
 54 
 
 Instances of submarine volca- 
 noes, . . . .60 
 Lava, its constitution and va- 
 
 59 Shell fish, mode of life, depth 
 of water, temperature adap- 
 ted to, their exuviae, . 84 
 
 rieties, 
 
 -Earthquakes, kinds of motion, 
 sound, progression, duration, 
 frequency, 
 
 of Lisbon, . . 63 
 
 of Calabria andUllah Bund, 64 
 of South America and Mis- 
 sissippi Valley, . . 65 
 lot springs, phenomena of the 
 
 61 Number of species of 
 
 Geysers, 
 
 Gradual elevation and depres- 
 sion of earth's surface, pil- 
 lars of temple of Serapis, 67 Human 
 
 Rise of shores of the Baltic 
 raised beaches rise of South 
 American coast depression 
 of Greenland, . . 68 
 
 Organic agencies their import- 
 ance, .... 69 
 
 Marine plants, peat, . . 70 
 
 Rafts, driftwood, . . 71 
 
 The most efficient agents, . 72 THB STRUCTURE AND POSITION OP 
 
 Corals their nature, size, po- 
 lyps, zoophytes, their per- 
 petuation, budding, . 73 
 ! Genera of zoophytes, Caryo- 
 phyllia, Meandrina, Astrea, 
 Madrepore, Flustra, ., * . ' 
 
 Color of corals, their beauty, 
 tubipora, ... 75 
 
 Coral reefs, their extent, live 
 in shallow water, . . 76 
 
 shore platform, 
 Infusoria, their 
 
 81 
 
 numbei 
 
 ;heir nature, size, X 
 tripoli, . . 82] 
 multiplication of II 
 
 Rapidity of multiplicat 
 infusoria, red snow 
 
 Remains of vertebrates 
 
 plants, 
 of, no 
 
 85 
 
 animals, extinction 
 introduction of, . . 86 
 62 Distribution of plants, animals, 
 flora, fauna, of different re- 
 gions, ... 87 
 
 Arctic fauna, temperate, trop- 
 ical, .... 88 
 ocal faunas, . . 89 
 
 66 Man's agency in modifying 
 surface on beasts of prey 
 seals, . . .90 
 
 skeletons at Guada-. 
 loupe implements human 
 remains in peat, engulfed, 91 
 Products of human skill pre- 
 served, coins, . . 92 
 General result of modifying 
 agencies ... 93 
 
 CHAPTER II. 
 
 ROCKS. 
 
 Rock defined, stratified rocks, 
 strata,beds, origin of strata, 
 laminae, ripple marks, . \ 
 
 Strata result from mechanical "\ 
 action, ; . 95 
 
 Concretionary structure, sep- 
 taria, ironstones, 
 
 Concentric structure nuclei 
 illustrated in New South 
 
 94 
 
 96 
 
 Fringing reefs, 
 Barrier reefs. 
 
 77J Wales, . 
 
 78|Sand, lime, and clay groups, 
 
 97 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 Vll 
 
 Proportion of the earth cover- jLeibnitz'classification of rocks, 
 ed with strata order of Lehman's, Werner's, . g IK 
 
 ' succession, folded axis, \ 99 The five classes, primary, pa- 
 
 Horizontality of strata their heozoic, secondary, tertia- 
 
 dip, .... 100 ry and quaternary, . . 120 
 
 Clinometer, strike or bearing, .Systems of the classes, . 121 
 anticlinal line, synclinal, 101 Classification of the unstrati- 
 
 Mode of observing dip es- ' j fied rocks, . . 122 
 
 carpment, outcrop, . . 102; PITAPTPP TTT 
 
 Formation defined conform- 
 able; faults; gorge; val- PALEONTOLOGY. 
 ley, .... 103 Fossils characteristic of stra- 
 
 ta, medals of creation, . $ 123 
 | Degrees of preservation; Si- 
 berian mammoth, . 124 
 Casts, moulds and tracks, . 125 
 Petrifaction; aifected by pres- 
 sure, heat, chemical agents, 126 
 
 Thickness of strata, how de- 
 termined ; thickness of Eu- 
 ropean strata; fossiliferous,104 
 . , JJnstratified, igneous rocks; 
 modes of occurrence ; ef- 
 fects upon adjacent rocks ; 
 
 non-fossiliferous, . 105 Plants bituminized ; animal 
 Veins, dikes ; age determined matter converted into adi- 
 
 by their intersection ; of se- pocire, . . . 127 
 
 gregation ; resembling beds; j Metallization of organic bo- " v 
 metaliferous, . . 106| dies, . . .. .128' 
 
 Columnar structure; jointed, 107iPetrifiers, . . -'. . 129 
 Volcanic rocks ; plutonic, 108 Requisite means for determin- 
 Metamorphic rocks, their po- ing fossils ; fundamental 
 
 sition, structure, origin, 109 principle of comparative 
 /Joints ; master joints ; their anatomy, 
 
 direction and origin, . HO.Number of fossils, 
 j Cleavage ; its constancy of I Marine, estuary, fresh water 
 < direction and origin, . lllj and terrestrial relics, . 132 
 Systems of classification iSituation in which fossils were 
 their points of agreement ; j formed ; entire or broken, 133 
 of difference, . . 112 | Species, varieties ; species be- 
 Age of rooks determined by ' come extinct ; genus, order, 
 position, mineral character ' kingdom, family and tribe, 134 
 and organic contents, . 113JDistribution of animate be- 
 
 130 
 131 
 
 Difficulty of observing from 
 
 ings in former periods, . 135 
 
 absence of some strata, . 114jDuration of families, genera, 
 
 Determination by fossils ; spe- 
 cies not identical through- 
 out a formation, . 115 
 
 Identity of mineral constitu- 
 tion does not prove rocks 
 contemporaneous, . . 116[ 
 
 Age of unstratified rocks de 
 
 and species, . . 136 
 Periods when plants arid ani- 
 mals began to exist, . 137 
 Time when most of the chan- 
 ges occur; evidence of ge- 
 ology respecting the devel- 
 opment hypothesis, . 138 
 
 terrnined by their relations j Fossils most unlike as they 
 to the strata, . . 117) are most remote in time, 139 
 
Vlll 
 
 ANALYTICAL TABLE OF CONTENTS. 
 
 Fossil botany; plants, cel- 
 ) lular, vascular, crypto- 
 : gamous, phanerogamous, 
 ; monocotyledonous, dicoty- 
 I ledonous, endogenous and 
 
 exogenous, . 
 
 Plants determined by ana- 
 ' tomical structure ; leaves, 
 flowers, fruits, trunks and 
 secretions, fossil, . 
 Geological position of cellu- 
 lar plants, cryptogamous, 
 coniferae, cycadeee, endo- 
 genous and exogenous, 
 History of fossil vegetation 
 not complete; number of 
 fossil species now known, 
 Origin of the different forms, 
 anthracite, bituminous 
 j -and wood coals ; bitu- 
 minization now occurring, 
 Fossil zoology ; Cuvier's 
 classification ; four divi- 
 sions, .... 
 Radiata, their structure ; 
 echinodermata, sea-ur- 
 chins ; acalephae, jelly 
 fishes ; polypi ; sponges, 
 Mollusca, structure; cepha- 
 lopoda, acephala, gastero- 
 poda ; univalve, bivalve, 
 multi valve and chambered 
 shells ; geological posi- 
 tion of the classes, 
 Articulata, structure ; in- 
 sects, worms, and crusta- 
 cea, their geological posi- 
 tion and number, 
 Yertebrata, structure; mam- 
 malia, birds, reptiles and 
 fishes ; Professor Agassiz' 
 classification of. fishes, 
 ganoid, placoid, ctenoid 
 and cycloid; order of 
 their introduction and 
 prevalence ; rep tiles, where 
 first appear, birds and 
 mammalia, . 
 
 141 
 
 142 
 
 144 
 
 146 
 
 147 
 
 154 
 
 (Coprolites, . . . $150 
 'Classification according to 
 j animate types, protozoic, 
 
 mesozoic and cainozoic, 151 
 jProf. Agassiz' ages of na- 
 140| ture; reign of fishes, of 
 reptiles, of mammalia, 
 and of man, . i 152 
 
 CHAPTER IV. 
 
 THE UNSTRATIFIED ROCKS. 
 
 The igneous rocks consist ot 
 feldspar and hornblende ; 
 differ in structure as they 
 are cooled under slight or 
 great pressure, . . $ 153 
 143 Granitic rocks their struc- 
 ture and position, 
 
 Granite, its characteristic 
 ingredients and colors ; 
 graphic granite ; porphy- 
 
 j ritic, .... 
 
 Syenite; syenitic granite, 
 145|Porphyry, its ancient signi- 
 fication and present use, 
 
 Metaliferous veins, most 
 abundant in the oldest 
 strata; veinstone, gangue 
 or matrix ; their produc- 
 tiveness influenced by 
 their direction, . 
 
 Trappean rocks significa- 
 tion of trap ; origin, dif- 
 ference from granite, and 
 mode of occurrence, 
 
 Greenstone, constituents and 
 
 color; diorite, 
 
 148 Basalt, constituents, color 
 and structure, 
 
 Amygdaloid ; wacke or toad- 
 stone, . . . .162 
 
 Trachyte, its composition ; 
 tuff and clinkstone, 
 
 Serperitine, 
 
 Trap dikes left prominent, 
 or produce fissures, 
 
 *~S) 
 
 158 
 
 159 
 
 led 
 
 161 
 
 163 
 
 165 
 
 Heating effects of trap dikes 
 1 19| ' on adjacent rocks, . 166 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 IX 
 
 Masses of trap intruded be- 
 tween strata resembling 
 beds, . { 
 
 Columnar structure ; giant's 
 causeway, . 
 
 Basalt of Staffa; Fingal's 
 cave, . . . 
 
 Horizontal columns ; " the 
 chimney" in St. Helena; 
 curved columns in New 
 South Wales, 
 
 168 
 169 
 
 170 
 
 /Basalt pillars at Kiama point, 171 
 
 /Examples of trap rocks in 
 
 v the United States, 
 
 Origin of columnar struc- 
 ture in volcanic rocks; 
 Watts' experiments on ba- 
 salt, .... 
 
 .Feldspathic varieties of trap 
 constitute central por- 
 
 \ tions, and basalt the exte- 
 rior of mountains ; cause 
 of it, . 
 
 Volcanic rocks lava, its con- 
 stituents and varieties, 
 
 Lava dikes ; obsidian, pitch- 
 stone, scoria, pumice and 
 peperino, 
 
 Ideal section of the earth's 
 crust, . . . . ^ .' - 
 
 172 
 
 173 
 
 1741 
 
 Talcose-slate, steatite, chlo- 
 
 rite-slate, . 
 
 Serpentine, . . . 184 
 
 Primary limestone, its char- 
 acters and alternations, 
 
 Quartz, its varieties as meta- 
 morphic rocks, 
 
 Clay-slate, constituents, col- 
 ors and texture ; clay, 
 shale, roofing, drawing 
 and whetstone slate, . 
 
 185 
 186 
 
 187 
 
 Cleavage and joints in slate, 188 
 
 Anthracite, plumbago, . 189 
 
 CHAPTER YI. 
 PALAEOZOIC ROCKS. 
 
 haracteristics of the palaeo- 
 zoic rocks, called transi- 
 tion by Werner, . . 190 
 Cambrian system investiga- 
 ted by Murchison and 
 Sedgwick, in Wales ; their 
 extent, thickness, compo- 
 sition, and subdivisions, 
 175 Silurian system characters 
 
 176 
 177 
 
 CHAPTER V. 
 STRATIFIED PRIMARY ROCKS. 
 
 Chronological order of de- 
 
 scription preferable, . 178 Radiata, corals, graptolites, 
 
 Composition of primary 
 strata, thickness, extent, 
 origin, and change; meta- 
 morphic, 
 
 Gneiss, appearance, constit- 
 uents, lamination ; por- 
 phyritic, syenitic ; proto- 
 gine, .... 
 
 Mica-slate, characters ; gar- 
 netiferous, . 
 
 Hornblende-slate, constitu- 
 ents and associations, 
 
 and subdivisions, 
 The rocks of this 
 
 191 
 192 
 
 system 
 
 found in other countries, 193 
 Interesting fossils ; trilo- 
 bites, their structure and 
 compound eyes, . . 194 
 Mollusoa of the Silurian 
 period, Ammonite, Nauti- 
 lus, Terebratula, Produc- 
 ta, Orthoceratite, 
 
 195 
 
 encrinites ; marine plants, 196 
 Igneous rocks of this period, 197 
 Old Red Sandstone, or Devo- 
 
 179 nian system composition, 
 prevalent color, and posi- 
 tion with reference to the 
 coal, . . . ' . 108 
 
 180 Thickness and arrangement 
 
 of the members of the 
 
 181 system, 
 
 Countries in which they are 
 182} developed, . 
 
 199 
 200 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 Ichthyolites, ganoid and 
 placoid orders with hete- 
 rocercal tails, . . 201 
 
 Cephalaspis, . . .202 
 
 Pterichthys, . . .203 
 
 Coccosteus ; holoptychius ; 
 osteolepis, . . . 
 
 Molluscous shells, corals, 
 trilobites, . . . " v . 205 
 
 Plants, .... 206 
 
 Igneous rocks of the period, 207 
 
 Carboniferous system con- 
 stituents, thickness, and 
 subdivisions, . . 208 
 
 Organic remains ; ichthyo- 
 lites, Crustacea, mollusca, 
 insects and encrinites, 209 
 
 Abundance of vegetable fos- 
 sils in the coal measures ; 
 proof of the vegetable 
 origin of coal; number 
 and thickness of coal 
 strata ; coal basins, . 210 
 
 Beauty of the great natural 
 herbaria, presented by 
 coal beds, . . .211 
 
 Species of coal plants found 
 in remote latitudes ; re- 
 semble plants of the pres- 
 ent tropical regions ; the 
 calamite, 
 
 The tree-fern ; still living in 
 Australia ; construction 
 of the names of genera 
 of ferns, 
 
 Characteristics of the Lepi- 
 dodendron, 
 
 Origin of the name Sigilla- 
 ria, characteristics of the 
 genus ; of the Stigmaria, 215 
 
 Trees found erect and in- 
 clined ; mode of account- 
 ing for, . .216 
 
 Modes of accounting for the 
 succession of numerous 
 coal-beds, . . . 217 
 
 Igneous rocks of the carbon- 
 iferous strata, toadstone, 
 
 dikes, troubles, metalifer- 
 ous limestone, petroleum, $218 
 The Permian system origin 
 of the term ; divisions of 
 the system ; terms used in 
 Germany, . . 219 
 
 204 Remains of fishes ; dolomite, 
 comparatively destitute of 
 fossils ; origin of the mag- 
 nesia, . . - . ; . 220 
 
 CHAPTER VII. 
 ROCKS OF THE SECONDARY PE- 
 
 [ndications of a new geolog- 
 ical era, ... 221 
 
 Triassic system upper new 
 red sandstone of England ; 
 its divisions in England, 
 Germany and France, 222 
 
 Fossil plants, fishes, encri- 
 nites, cyathocrinite, 223 
 
 Age of reptiles, Prof. Owen's 
 classification of reptiles 
 extinct and existing, . 224 
 
 Footprints of the cheirothe- 
 rium ; structure of the ani- 
 mal ; called Labyrintho- 
 don ; ichnolites, . 225 
 
 212 Tracks of biped animals in 
 
 the sandstone of the Con- 
 necticut valley ornithic- 
 nites ; their size, . 226 
 
 213 Impressions of raindrops, 227 
 Origin of rock salt, . 228 
 
 214 The Liassic system its pre- 
 
 dominant mineral ; origin 
 of term Lias and its subdi- 
 visions, . . .229 
 
 Fossils, corals, pentacrinites, 
 bivalve shells, gryphite 
 limestone, . . 230 
 
 Ammonite, its structure and 
 resemblance to the nauti- 
 lus, ... 231 
 
 Belemnite ; its shell and 
 
 inlc, 
 
 232 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 Zl 
 
 Fishes and reptiles ; ichthy- 
 odorulites, 
 
 Ichthyosaurus, its general 
 structure; peculiarity of 
 the eye ; length and habits 
 of the animal, ','*' . 
 
 Plesiosaurus, great number 
 of cervical vertebrae, . 
 
 Fossil vegetable matter of 
 this period, . 
 
 The Oolitic system origin of 
 the term ; subdivisions of 
 the system, 
 
 Peculiar features of surface 
 outline produced by this 
 system, . r . 
 
 Fossils, number and variety, 
 corals, encrinites, echini, 
 shells, crustacea and in 
 sects, 
 
 Fishes, saurians and the pte- 
 rodactyle, 
 
 First specimen of mamma- 
 lia in the secondary, be- 
 longed to the marsupials, 
 
 Oolitic flora ; Richmond coal 
 beds, 
 
 Wealden system nature of 
 the deposit, origin of the 
 term, divisions of the sys- 
 tem, .... 
 
 Organic remains, shell-fifih, 
 crustacea, insects, 
 
 Fishes and saurians hylseo- 
 saurus and iguanodon, 
 
 Phenomena of the dirt-bed 
 indicating alternate rising 
 and subsiding of the sur- 
 face, - .; " t . ;.'' 
 
 Cretaceous system its name 
 derived from its leading 
 member (creta ; ) thickness 
 and divisions of the sys- 
 tem ; green sand, gault 
 and chalk, 
 
 Chalk fossils; marsupite, cri- 
 oceratite, hamite, baculite, 
 
 Foraminifera, nummulite, 
 
 abundance of infusoria in 
 chalk, their forms, size, 
 structure and multiplica- 
 tion, -. . g 249 
 Fishes, sharks, ctenoids and 
 cycloids, saurians and 
 bones of birds, . . 250 
 
 235 Sponge silicified and fossil 
 
 vegetables, . . .251 
 
 236 Origin of the chalk, its re- 
 
 semblance to calcareous 
 deposits in coral lagoons, 252 
 
 237 Igneous rocks of the second- 
 
 ary period, . . 253 
 
 238 
 
 CHAPTER VHI. 
 ROCKS OF THE TERTIARY 
 
 239 Their extent and character- 
 
 istics, . . . .254 
 
 240 Sands and clays predominate, 
 
 characters of the calca- 
 reous deposits ; subordi- 
 
 241 nate beds of buhrstone, 
 gypsum and salt, . 255 
 
 242 Extent of the tertiary in 
 
 Europe ; their existence in 
 other countries, . . 256 
 
 Classification of tertiary 
 strata by Lyell and Des- 
 hayes, Eocene, Meiocene, 
 Pleiocene, Pleistocene, 257 
 
 The London and Paris ba- 
 
 243 
 244 
 
 245 
 
 246 
 
 247 
 
 248 
 
 sins, 
 
 258 
 
 Other localities of the Eo- 
 cene, ... 259 
 
 Fossils of the eocene ; char- 
 acter of its plants ; am- 
 ber 260 
 
 Shells and crustacea of this 
 period ; fishes of Monte 
 Bolca, ctenoid and cycloid 
 orders, 
 
 Reptiles and birds, 
 
 Land quadrupeds of the pa- 
 chydermatous order ; the 
 age of mammals, 
 
 261 
 
 262 
 
Xll 
 
 ANALYTICAL TABLE OF CONTENTS. 
 
 Palaeotberium, its-character- [Size of boulders ; rocking- 
 istics ; the Lophiodon, 264| stones, . . 284 
 
 Anoplotherium, origin of 
 name, characteristic spe- 
 cies ; carnivorous quadru- 
 peds ; fossil monkey, 
 
 Fossil insects, state of pre- 
 servation, . , 
 
 Eocene of America, . 
 
 The Meiocene of England ; 
 of Europe, United States 
 
 and Asia; molasse of jOssifero us caverns, 
 Switzerland, . . 268 Kirkdale cave, . 
 
 Plants of the meiocene, zoo- Cave of Gailenreuth, 
 
 Diluvial groves and striae on 
 rocks ; their extent and 
 direction, . . . 285 
 
 265 Roches moutonnees ; streams 
 
 of stones ; glacial beds, 286 
 
 266 Altered drift, . . . 287 
 
 267 
 
 Marine terraces at Glen Roy; 
 river terraces, . . 288 
 
 Ossiferous sands and gravel, 289 
 290 
 291. 
 292 
 
 phy tes and shells ; fossil Origin of the bones in caves; 
 tortoise and salamander, 269| osseous breccia, . . 293 
 Dinotherium, its structure, 270 Fossils, shells and infusoria, 294 
 
 Gigantic herbivorous quad- 
 rupeds, . . . 295 
 The mastodon, its structure, 
 size and range,found abun- 
 dantly at the licks, . 296 
 272 The mammoth, its period, 
 difference from the masto- 
 don and from existing spe- 
 cies of elepha'nts, . 297 
 
 Tertiary fossils of Asia, the 
 Sivatherium, Toxodon and 
 Macrauchenia of South 
 America, 
 
 The Pleiocene of England ; 
 of the sub-Apennines, 
 
 Beds of lignite, paper coal, 
 animal remains, - . 273 
 
 271 
 
 Pleistocene, different uses of 
 
 the term, . . 274 Extinct quadrupeds found on 
 
 its development in South j the shores of the Polar 
 America ; edentate order | sea, , . 298 
 
 of animals; Megatherium, 275ilrish elk, its size; deer and 
 
 Mylodon, 
 
 276 
 
 299 
 
 Megalonyx; scelidotherium, 277 Cetacea; basilosaurus or Zeu- 
 Glyptodon, . 278'glodon, . . .300 
 
 Igneous rocks of the tertia- [Skeletons of birds ; dinornis, 301 
 ry ; extinct volcanoes of Climate of the drift period, 302 
 Auvergne, . . 279' The alluvium, its composi- 
 
 tion ; marine, fresh water, 
 terrestrial ; historic pe- 
 riod, . . 303 
 Raised beaches and subma- 
 rine forests with existing 
 species, " /. . 304 
 Marine silt at Isthmus of 
 Suez, Tyre and Sidon, in 
 Include most recent deposits, 281 the Yellow Sea and Ger- 
 Drift, its composition, . 282,' man Ocean, . . 305 
 Limits of the drift ; elevation JEstuary deposits ; delta of 
 and direction, - - ,- . 233; the Niger, . . 306 
 
 Tertiary volcanoes on the 
 Rhine, in Spain, Hungary 
 and Asia Minor, . . 280 
 
 CHAPTER IX. 
 
 BOOKS OF THE QUATERNARY 
 PERIOD. 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 \Theory of volcanoes regard - 
 | ing the earth, with excep- 
 
 307 tion of a crust of a few 
 miles' thickness in a melt- 
 ed state, . . . 324 
 
 308 Arguments in favor of this 
 
 theory, ... 325 
 Objections, . . 326 
 
 309 Theory of extensive reposito- 
 
 | ries of melted matter, 327 
 3 10, Sir H. Davy's hypothesis of 
 metallic bases of alkalies 
 and earths ; electricity, 328 
 Gradual elevation and de- 
 pression of the surface by 
 expansion and contraction 
 of rocks, . . .329 
 Elevation of mountain chains 
 by collapse of the crust ; 
 plication, . . 330 
 
 313jBeaumont's theory of moun- 
 tain elevations, . .331 
 
 311 
 
 312 
 
 Lacustrine deposits; prai- 
 ries, pampas, lake ridges, 
 ridge roads, . . i 
 
 Chemical precipitates,marls, 
 silicious sinter, alumina, 
 tripoli, salt, . 
 
 Plants of the alluvium, sub- 
 terranean forests and drift 
 wood, 
 
 Peat mosses, extent; anti- 
 septic power, 
 
 Shells and coral reefs of the 
 alluvial period, . 
 
 Extinction of species and 
 genera during the alluvial 
 period ; the dodo and ap- 
 teryx, 
 
 Man found only in the recent 
 alluvium ; skeletons found 
 at Guadaloupe in recent 
 limestone, 
 
 Soil, its varieties ; subsoil, 
 protect surface from wear- 
 ing. -''? ' '-' ''' *' <*"* 
 
 Atmosphere and water modi- 
 fying the surface ; caves 
 and natural bridges, . 315 
 
 Products of igneous agency 
 during alluvial period, 
 
 CHAPTER X. 
 THEORETICAL GEOLOGY. 
 
 Definition of theory and hy- 
 pothesis, . .317 
 
 Theories respecting aqueous 
 and igneous agencies ; 
 uniformity of nature's laws 
 the basis of reasoning, 318 Definition and importance, 
 
 Theories of drift ascribed to 
 
 314 
 
 316 
 
 joint action of ice and wa- 
 ter, . -T -..".. 319 
 
 Iceberg theory, arguments 
 for, and objections to, 320 
 
 Elevation theory, arguments 
 and objections, . . 321 
 
 Glacier theory, . . 322 
 
 No theory perfectly satisfac- 
 tory, . . .323 
 
 Theory of veins by injection, 
 segregation and sublima- 
 tion, ... 332 
 
 Electrical currents influen- 
 cing metaliferous deposits, 333 
 
 Cosmogony ; hypothesis re- 
 specting the earliest condi- 
 tion of matter, . . 334 
 
 Plausibility of the hypothe- 
 sis argued from appear- 
 ances of comets, nebulae 
 and the moon, . . 335 
 
 CHAPTER XI. 
 PRACTICAL GEOLOGY. 
 
 336 
 
 Occupations and habits of a 
 people determined by the 
 geology of the country, 337 
 
 In mining, the most promis- 
 ing fields ; gold, platinum, 
 silver, quicksilver, copper, 
 lead, zinc, iron ; veins, 
 lodes, hade, direction, . 338 
 
 Bituminous coal, anthracite, 
 faults, ... 339 
 
XIV 
 
 ANALYTICAL TABLE OF CONTENTS. 
 
 Diamond, emerald, sapphire, jDrainage, < ', . 362 
 
 topaz, tourmaline, garnet, $340 Scenery of a country affected 
 Importance of Geology to by its geology, 
 
 341 
 
 the Civil Engineer, 
 
 Application of minerals to 
 architecture ; chemical 
 changes in them, . 
 
 Granite, Syenite, porphyry, 
 trap and lavas as building 
 materials, 
 
 Sandstones, color, texture, 
 liability to injury from 
 chemical changes and 
 frost, 
 
 Limestones, varieties, and 
 texture; slates, 
 
 Gypsum, soapstone, salt, 
 
 Clay for bricks and earthen- 
 ware ; fuller's earth, 
 
 Sand for making glass and 
 mortar, . . . 348 
 
 Quick lime, hydraulic lime, 
 Parker's cement, puzzuo- 
 lana, Roman cement, 
 
 Euhrstone, its characters and 
 localities, ..". . 350 
 
 Marls, their colors and situ- 
 ation, : ." .;> , v j 351 
 
 Relation of geology to agri- 
 culture, . . 352 
 
 Inorganic portion of soils ; 
 salts and earth ; hard wa- 
 ter, .... 
 
 Designation of soils accord- 
 ing to predominant earth, 354 
 
 Subsoils, hardpan, 
 
 Organic portion of soils ; 
 amount requisite for the 
 
 34; 
 
 344 
 
 345 
 346 
 
 347 
 
 349 
 
 353 
 
 growth of crops, 
 Origin of soils 
 Alluvial and drift soils, 
 Classification of soils, 
 Characters, of soils derived 
 from granite, gneiss, horn- 
 blende, trap, slates, lime- 
 stones, sandstones, 
 
 The art of maintaining un- 
 interrupted fertility, 361| 
 
 CHAPTER XII. 
 HISTORY OF GEOLOGY. ' 
 
 Recent branch of science ; 
 earlier cosmogonies, 364 
 
 Unprofitable discussions res- 
 pecting organic remains, 365 
 
 Werner's Neptunian theory ; 
 Button's Plutonian theory; 
 Mr. W. Smith's successful 
 labors, . . 366 
 
 Geological society of London; 
 rapid progress of collater- 
 al branches, botany, zoolo- 
 gy, comparative anatomy, 368 
 
 American geology ; Mr. Ma- 
 clure's sketch of Ameri- 
 can geology; Prof. Eaton's 
 survey of the Erie canal 
 rocks ; State geological 
 surveys, . . . 368 
 
 Geology a well established 
 science, 369 
 
 CHAPTER XUI. 
 
 RELATION OP GEOLOGY TO 
 
 RELIGION. 
 
 Office of natural theology to 
 
 treat of specifically ; sus- 
 picions of geology as fa- 
 voring infidelity, . $370 
 
 355 Opinion of Dr. Buckland ; of 
 
 President Hitchcock, 371 
 
 jeology manifests the uni- 
 
 356 formity of Nature's laws 
 
 357 in all periods of the world's 
 
 358 history; power, wisdom 
 
 359 and benevolence of the 
 Creator shown in the struc- 
 ture of animate beings, 372 
 
 Changes to which matter has 
 
 360 been subjected indicate 
 the intervention of a 
 Deity, . . 373 
 
ANALYTICAL TABLE OF CONTENTS. 
 
 Instances of special adapta- [Asia, form and extent of the 
 tion to present races, es- j great continent, moun- 
 pecially to man, . . J374 tains, desert, strata and 
 
 Geology coincides with other metalic products, 
 
 sciences in enlarging our Siberia, its metals and fos- 
 views of the Creator's sils : Tartan/, rocks and 
 
 87- 
 
 plans and works, 
 Discrepancy of geology with 
 the interpretation of the 
 Scripture account of the 
 creation hitherto received; 
 Scripture usage of lan- 
 guage respecting natural 
 phenomena, . . ' 
 
 Use of scientific knowl- 
 edge in the interpretation 
 of ancient writings ; terms 
 used in describing chemi- 
 cal phenomena may im- 
 port very differently to 
 the ancient reader and 
 the modern ; propriety of 
 modifying interpretation 
 by such knowledge, 
 
 First mode of reconciling the 
 apparent discrepancy by 
 interpreting the word day 
 as an indefinite period ; 
 arguments in its favor, and 
 objections to it, 
 
 The most generally received 
 mode of reconciling the 
 discrepancy; extended by 
 Dr. J. Pye Smith, 
 
 If no mode of reconciliation 
 be deemed satisfactory, 
 still it is unphilosophical 
 to presume a collision be- 
 tween the accounts, 
 
 Inti^oduction of death into 
 the world, .. 
 
 Noachian deluge geologically 
 probable ; reasons for 
 supposing it partial, 
 
 CHAPTER XIV. 
 GEOGRAPHICAL GEOLOGY. 
 
 Defined; partially known from 
 
 physical geography, 
 
 volcanoes, . . 385 
 
 Geology of Thibet, Ilindos- 
 tan, India and Ceylon, 
 rocks, fossils and gems, 386 
 eology of China and Japan, 387 
 Persia, rocks, desert, calca- 
 reous deposits and indica- 
 
 376 tions of volcanic agency, 388 
 Arabia, Mount Sinai, valley 
 
 of the Jordan and Mount 
 Lebanon, . . . 389 
 Polynesia, coral reefs ; Neio 
 Holland, its rocks and 
 osseous breccias, . 390 
 European geology more tho- 
 roughly investigated than 
 that of any other quarter 
 
 377 of the globe ; that of the 
 British Islands varied, 
 carefully studied and a 
 standard of reference, 391 
 
 Rocks of Wales; order of 
 the rocks towards London, 392 
 
 378 Geology of Scotland and Ire- 
 
 land, . . 393 
 
 France, stratified and igne- 
 ous rocks, extinct volca- 
 
 379 noes and metalic products; 
 Belgium and Holland, . 394 
 
 Germany, mining districts; 
 Switzerland, its elevated 
 tertiary series, . . 395 
 
 380 Sweden and Norway, drift and 
 
 metals ; Denmark, Iceland 
 
 381 and Faroe Islands, . 396 
 Russia and Poland, strata, 
 
 salt, and gypsum; Austria, 397 
 
 382 Italy, Apennines, tertiary, 
 j volcanoes and marbles ; 
 I Spain and Portugal, strata, 
 
 salt, and quicksilver, 
 
 383 Africa, Atlas mountains, 
 
XVI 
 
 ANALYTICAL TABLE OF CONTENTS. 
 
 strata of the Barbary 
 States ; Egypt, Nubia, Abys- 
 sinia,, dunes from the de- 
 sert, and alluvial of the 
 Nile, 
 
 Western coast, gold coast> 
 central Africa, mountains 
 of the Moon, 
 
 The Sahara, oases, recent- 
 ly elevated bed of the 
 
 Southern Africa, plateau and 
 table mountains ; rocks of 
 the islands of igneous ori- 
 gin, .... 
 
 Form of South America, its 
 mountains, strata, exten- 
 sive plains and volcanoes, 
 its metalic products and 
 gems, 
 
 Cordilleras of Central Ameri- 
 ca, strata, volcanoes and 
 mines ; West Indies, for- 
 mer connection with the 
 continent, volcanic agency, 
 Pitch lake, 
 
 General structure of North 
 America, mountain chains, 
 sandy desert, salt lakes, 
 coal in high latitudes ; au- 
 
 riferous rocks of Califor- 
 nia ; other metals, 405 
 Alleghanies j New England 
 
 geology, . . . 406 
 $399 Atlantic slope, its extent 
 and strata, new red sand- 
 stone, chalk and tertiary, 407 
 400 Tertiary rocks of the South- 
 ern States ; section from 
 the Mississippi river to 
 . 401 the Atlantic ocean, . ^ 408 
 Strata of the Mississippi 
 valley, silurian, devonian, 
 cretaceous and tertiary : 
 
 402 identity with European 
 systems ; subdivisions re- 
 ferred to those of the 
 New York survey, . 409 
 
 Diversity of names applied 
 
 403 to members of the systems, 
 table of equivalence of the 
 lower strata in five States, 410 
 
 Numerous fossils ; some ex- 
 tinct species of the higher 
 mammalia, . . 411 
 
 404 Mineral treasures of the Uni- 
 
 ted States; coal, . . 412 
 iron, copper, gold, silver, 
 lead, salt, gypsum ; no 
 volcanoes ; hot springs, 413 
 
GEOLOGY. 
 
 DEFINITION AND OBJECT OF GEOLOGY. 
 
 1. GEOLOGY is the Science which treats of the consti- 
 tution and structure of the Earth. 
 
 Its object is to observe and describe the mineral masses, 
 and the remains of organized bodies, animal and vegetable, 
 which compose the globe; trace the successive changes they 
 have undergone and discover the various laws that govern^ 
 such changes. 
 
 Descriptive Geology exhibits the facts of the science ; 
 
 Theoretical Geology attempts to account for them ; and 
 
 Practical Geology shows their application to practical 
 purposes. 
 
 Subservient to Geology are Chemistry, which treats of 
 the ultimate particles of matter, and their modes of combin- 
 ation; Mineralogy, which characterises and classifies the va- 
 rious minerals of which the earth is composed ; Botany, and 
 Zoology, which describe plants and animals; and Physical 
 Geography, which relates the facts concerning the general 
 distribution of matter at the surface of the earth the forms 
 and extent of continents and islands, river and mountain 
 systems; together with the changes now occurring in them, 
 
CHAPTER I. 
 
 GENERAL CONSTITUTION AND STRUCTURE OF 
 THE EARTH. 
 
 Fig. 1. The Earth, as seen from the Moon. 
 PLANETARY RELATIONS. 
 
 2. THE Earth is one of the planetary bodies constituting 
 the Solar system the third in order from the Sun com- 
 pleting its circuit of 600,000,000 miles around that lumin- 
 ary in a year, and revolving upon its axis once a day. Its 
 relations to the sun and other members of the Solar system 
 determine its position in space, the amount of heat and 
 Jight it receives, and consequently its vegetable and animal 
 economy. A change in the position of its axis would alter 
 its climate and the distribution of land and sea. 
 
FIGURE DENSITY. 8 
 
 FIGURE. 
 
 3. The/orm of the Earth is 'that of an oblate spheroid. 
 The equatorial diameter is twenty-six and a half miles 
 longer than the polar. 
 
 The equatorial diameter=7925.6 miles, 
 " polar " =7899.1 " 
 
 Difference or flattening, . . 26.5 miles. 
 
 This gives a compression of thirteen and a quarter miles 
 to each hemisphere. If the earth should cease to rotate on 
 its axis, the waters of the ocean about the equator would 
 flow towards the poles, seeking the lowest level, i. e. the 
 position nearest the center of the earth. The direction of 
 rivers running towards the equator would be reversed. 
 
 This form of the globe seems to indicate that its particles 
 have been free to obey the centrifugal force. The other 
 planets exhibit spheroidal forms. The equatorial diameter 
 of the planet Jupiter, exceeds the polar diameter by more 
 than six thousand miles. 
 
 DENSITY. 
 
 4. The density of the Earth is five and a half times that $^ 
 of water. It weighs five and a half times as much as a 
 globe of water of the same size. This is more than twice 
 the density of the most prevalent rocks at the surface, 
 Hence it appears that the density increases towards the 
 center. By the pressure exerted beneath the surface the '' 
 bulk of bodies is compressed, and their density consequent- 
 ly increased. At the depth of thirty-four miles, air would 
 become as dense as water ; at three hundred and sixty-two 
 miles, water as heavy as quicksilver; and at the center the 
 average minerals of the surface would be compressed into 
 
4 STRUCTURE OF THE EARTH. 
 
 less than one-tenth their present bulk. This would make 
 the mean density of the globe much greater than it is. 
 Consequently the materials within must be different from 
 those at the surface, or this compressing force must be 
 counteracted by some expansive power. The density of 
 the Earth is ascertained by astronomical processes ; observ- 
 ing the deflection of the plumb-line caused by a mountain 
 of known dimensions, the attraction of other planets, &c. 
 
 TEMPERATURE. 
 
 5. The temperature of the globe is determined by a 
 variety of influences. The temperature of the surface is 
 influenced by its latitude, being warmer near the equator, 
 and diminishing toward the poles ; by its power of absorbing 
 and retaining, or reflecting the heat of the sun's rays ; by 
 its elevation above the general level, the temperature fall- 
 ing as we ascend; and by the distribution of land and 
 water, the climate of the ocean and of islands being milder 
 and more uniform than that of continents in the same lati- 
 tude. Lines joining places having the same mean annual 
 temperature, are called isothermal lines. These, on the 
 ocean, are very nearly parallel to the equator and to each 
 other, but over continents are modified by the extent and 
 elevation of the land. The following table gives the lati- 
 tude of isothermal lines on the American and European 
 coasts : 
 
 Isothermal Line. Latitude on American coast. Latitude on European coast. 
 
 77 Fahr. 24 21' 18 49' 
 
 68 " 32 20' 81 27' 
 
 59 38 24' 41 33' 
 
 60 " 41 30' 62 3' 
 
 41 " 44 51' 60 7' 
 
 32 61 57' 66 48' 
 
STRUCTURE OF THE EARTH. 
 
 Fig. 2. 
 
G 
 
 STRUCTURE OF THE EARTH. 
 
 The mean temperature of the whole surface of the 
 Earth is estimated to be 58. The surface temperature 
 determines the distribution and growth of plants and ani- 
 mals. 
 
 The heat of the sun penetrates the crust of the earth 
 to a limited extent, rarely exceeding seventy feet. At this 
 limit the temperature remains constant through the year. 
 On descending below this point the temperature uniformly 
 rises about 1 of Fahrenheit for every fifty-four feet of 
 depth. The rate of increase varies with the nature of the 
 rocks passed through, from 1 for thirty feet to 1 for 
 seventy feet. This has been established by numerous ex- 
 periments in mines, Artesian wells,* and mineral springs. 
 
 In the mine at New Salzwerk, near Minden, in Prus- 
 sia, two thousand feet deep, the increase of temperature 
 was at the rate of 1 for fifty-four feet. The mean result 
 of a large number of observations in the Saxony mines, 
 gives an increase of 1 for seventy-six feet at depths of two 
 
 * Artesian wells are borings through, which the water rises 
 nearly or quite to the surface, where no indication of springs ex- 
 isted. They are so called from the French province Artois the 
 ancient Artesium where they were used as early as the 12th 
 century of the Christian era. 
 
 Fig. 3. 
 
 Artesian Well. 
 
 a. porous water-bearing rock between the rocks e and d, which are impervious 
 to water. Through the well at b, the water rises as hi a syphon. 
 
SURFACE OUTLINE. 7 
 
 thousand feet; while in a coal mine in Durham, at about 
 the same depth, it is 1 for fifty-nine feet. The rate of 
 increase observed in sinking the well at the Barriere de 
 Crenelle, Paris, was 1 for fifty-eight feet. In a very deep 
 Artesian well recently sunk at Mondorf, on the frontier of 
 France and Luxembourg, to a depth of nearly two thou- 
 sand three hundred feet, the water at two. thousand two 
 hundred feet had a temperature of 93 Fahrenheit, show- 
 ing an increase at the rate of 1 Fahrenheit for fifty-four 
 feet.* With this rate of increase, at the depth of fifty 
 miles, the heat would be sufficient to melt all known rocks. 
 
 SURFACE CONFIGURATION. 
 
 6. The surface outline of the Earth is very irregular, 
 intersected by mountains and vallies, seas and rivers. The 
 highest mountains exceed five miles. 
 
 Dhawalagiri; in the Himalayas, 28,072 feet. rrj ^ \\rfK 
 
 Aconcagua, " Andes, 23,200 " 
 
 Chimborazo, 21,420 
 
 niimani, 21,149 
 
 Mount Blanc, " Alps, 15,743 " 
 
 Pic Nethou, Pyrenees, 11,168 
 
 The mean height of all the solid parts of the Earth's 
 surface above the ocean, is estimated by Humboldt at about 
 one thousand feet ; that of South America, one thousand 
 one hundred and fifty one ; of North America, seven hun- 
 dred and forty-eight ; of Europe, six hundred and seventy- 
 one; and of Asia, one thousand, one hundred and thirty- 
 two feet. The length of the chain of mountains between 
 Siberia and India is ten thousand miles, and its breadth 
 one thousand five hundred miles. The mountains of Amer- 
 * Ansted. 
 
8 STRUCTURE OF THE EARTH. 
 
 ica, the Andes and Rocky Mountains, extend over 120 of 
 latitude. There are also vast depressions below the general 
 level. The Caspian and Aral seas are situated in such a 
 depression, whose: whole area is not less than one hundred 
 thousand square miles. The surface of the Caspian sea is 
 eighty-three and a half feet below the level of the ocean, 
 and the sea has a depth of six hundred feet. The lake of 
 Tiberias has .its surface four hundred and sixty-six feet 
 below the Mediterranean, while that of the Dead Sea is 
 one thousand three hundred and eighty-eight feet below 
 the same level, and its bottom in some places three hun- 
 dred fathoms lower. But the great deeps of the Earth's 
 surface are occupied by the ocean. Soundings in the At- 
 lantic ocean (27 south latitude 17 west longitude) gave a 
 depth of fourteen thousand five hundred and fifty feet, and 
 four hundred and fifty miles west of Cape Good Hope, six- 
 teen thousand and sixty two feet ; while in latitude 15 
 south, longitude 23 west, a line of twenty-seven ihousand 
 hundred feet, did not reach the bottom. Humboldt 
 tes the mean depth of the ocean at one thousand feet. 
 ftfalffb 7. The distribution of Land and Water upon the sur- 
 | c u fabe^of <the earth is very unequal. 
 
 ) Water occupies 145,300,000 square miles, 
 Land, 51,500,000 " " 
 
 *xt 
 
 Total, .... 196,800,000. 
 
 Nearly three-fourths of the surface is, therefore, beneath 
 water, and there is sufficient water to submerge the whole. 
 
 THE MEANS OF GEOLOGICAL INVESTIGATION. 
 
 8. By the Crust of the Earth, is understood, the exte- 
 rior portion of it, which is accessible to man, a few miles in 
 thickness. The following diagram represents the propor- 
 
CRUST OF THE EARTH. 
 
 9 
 
 tions which the crust, with its mountains and seas, bears to 
 the globe. The point i indicates a depth of one hundred 
 miles ; k five hundred miles. The divergence of the lines 
 at a and h shows the depth of the ocean. The prominences 
 at dj e } f y and g, adequately represent the height of moun- 
 tains. The line I is at forty-five miles above the surface 
 the supposed limit of the atmosphere. The thickness of 
 the heavy line representing the crust is one four hundredth 
 part of the distance to the center i. e. ten miles. 
 
 Fig. 4. 
 
 
 Crust of the Earth. 
 
 This crust, insignificant as it may seem, when compared 
 with the mass of the globe, since it embraces all the strati- 
 fied rocks, enables us to determine the various changes 
 which the Earth has undergone. 
 
 9. The means of investigating Geological phenomena 
 are found principally in the fracture and dislocation of the 
 layers of the crust of the Earth. Artificial excavations and 
 borings, aside from the inclination of these layers, are of 
 little avail. The deepest mine extends but a fraction of a 
 mile below the surface. Had the strata remained, as they 
 
10 STRUCTURE OF THE EARTH. 
 
 were deposited, in a horizontal position, we should have been 
 enabled to investigate only the few superficial ones ; but the 
 slanting position into which they have been thrown, brings 
 the lowest of them to the surface, and presents their edges 
 for examination, as in figure 5, in which the layers a, b, c, d, 
 and e, present themselves to the observer at the surface, suc- 
 cessively from the superficial to the deep seated. Other 
 masses of the Crust of the Earth have been pressed up, in a 
 melted state, from deep recesses to the surface, and are thus 
 subjected to inspection, as lavas of volcanos. 
 
 Inclined Layers of Rocks. 
 CHEMISTRY OP THE EARTH. 
 
 10. Chemists recognize sixty elements, or simple bodies, 
 whose combinations produce all the varieties of matter with 
 which we are acquainted. Many of these occur in small 
 quantities, and are rarely seen. Fifteen or sixteen of these 
 elements enter largely into the composition of rocks. 
 
 These substances, however, very rarely present them- 
 selves in their elementary state ; but, combined with each 
 other, they make the greatest portion of the Crust of the 
 Earth. 
 
 The most prevalent of these is Oxygen, which forms 
 eight-ninths of water, one-fifth of the atmosphere, and con- 
 -~ stitutes one-half of all the matter known to us. With sil- 
 icon it forms silica ; with potassium, potassa ; with iron the 
 oxide of iron, &c. Few minerals occur which do not con- 
 tain oxygen. 
 
CHEMISTRY OF THE EARTH. 11 
 
 Hydrogen forms a portion of minerals, especially bitu- 
 minous coal, and enters into the composition of water. 
 
 Nitrogen is not so abundant, but is found in the bones 
 of animals, living and fossil, in vegetables and in the atmos- 
 phere. 
 
 Carbon is the most abundant ingredient in coal, and 
 enters into the composition of limestone, which is the car- 
 bonate of lime. 
 
 Sulphur exists in the sulphurets of the metals : sul- 
 phuret of iron iron pyrites; sulphuret of lead galena, 
 or lead ore; also in the sulphates, as sulphate of lime 
 gypsum, or plaster of Paris. It is thrown out extensively 
 by volcanos. 
 
 Chlorine is one of the constituents of rock salt (chlo- 
 ride of sodium) and is widely diffused in the ocean. 
 
 Fluorine occurs in fluoride of calcium, (fluor spar,) and 
 other minerals. 
 
 Phosphorus enters into the composition of many min- 
 erals, and of animal bones, as the phosphate of lime. 
 
 Silicon exists in most of the rocks, combined with 
 oxygen, as silica quartz which constitutes forty-five per 
 cent, of the Crust of the Earth. 
 
 The oxide of aluminium alumina forms one-fifth of 
 the mineral feldspar, and abounds in clay and slate rocks. 
 It is estimated at ten per cent of all the rocks. 
 
 The oxide of Potassium also enters largely into the 
 composition of feldspar and clay. 
 
 Sodium forms a part of rock salt and other minerals. 
 
 The oxide of calcium (lime) occurs chiefly as a carbonate 
 (limestone, marble,) which is estimated to form fourteen 
 per cent, of the globe's crust. 
 
 Magnesia, the oxide of magnesium, enters into the 
 
12 STRUCTURE OF THE EARTH. 
 
 composition of many rocks, and abounds in the magnesian 
 limestone. 
 
 Iron is very widely diffused, in the various forms of its 
 ores, oxide, carburet, sulphuret, &c. 
 
 The combinations of manganese, also are common ingre- 
 dients of rocks in small quantities. 
 
 Some knowledge of chemical facts facilitates the researches of 
 the geologist, enabling him to perceive many changes which have 
 taken place in the rocks through the agency of chemical affinity. 
 
 MINERALOGY OF GEOLOGY. 
 
 11. Of the hundreds of simple minerals described by 
 mineralogists, a very few occur in large quantities, making 
 up the great mass of the rocks. The most prevalent are 
 the following : 
 
 Quartz, a hard mineral, striking fire with steel ; and 
 scratching glass and other substances, (a few rare gems ex- 
 ceptcd-) infusible before the blow-pipe, and insoluble in 
 ordinary acids. The transparent grains of granite, and 
 of sandstone, are quartz. 
 
 Feldspar, a reddish white, or flesh-colored mineral; 
 opake, easily scratched, becoming white and glassy by the 
 heat of the blow-pipe. 
 
 Mica, a glistening mineral, tough and elastic, suscep- 
 tible of division into minute laminae, giving to rocks in 
 which it abounds a silvery aspect. 
 
 Hornblende, a black, or dark green mineral, of glassy 
 luster, occurring in granite instead of mica, or associated 
 with it, when the rock is called syenite ; in trap rocks and 
 in hornblende-slate. 
 
 Augite is nearly identical with hornblende in all its 
 characteristics. 
 
MINERALOGY OF GEOLOGY. 13 
 
 Talc, a very soft mineral, of pearly luster, and greasy 
 feel ; the characteristic ingredient of steatite or soapstone, 
 French chalk, and chlorite. 
 
 Serpentine, a green, opake mineral, becoming yellow- 
 ish gray on exposure ; it sometimes presents a mottled ap- 
 pearance. 
 
 Carbonate of Lime, marble, chalk, limestone; effer- 
 vescing with acids, and reduced by heat to caustic lime. 
 
 Dolomite, magnesian limestone ', a compound of the 
 carbonate of lime with the carbonate of magnesia, infusible, 
 and effervescing slowly with acids ; used in the manufac- 
 ture of Epsom salts. 
 
 Sulphate of Lime, gypsum, or plaster of Paris, alabaster. 
 
 Chloride of Sodium, common salt. 
 
 Tourmaline sometimes called schorl a black, or dark 
 brown mineral; brittle, becoming electrical when heated. 
 
 Iron Pyrites, a yellow, hard, cubical mineral, often mis- 
 taken for gold ; composed of sulphur and iron. 
 
 Iron Ores, and Coal. 
 
 While an intimate knowledge of Mineralogy is not indispensable 
 to the Geological student, an acquaintance with those minerals 
 which enter largely into the composition of rocks is necessary, 
 since the structure of the rocks is determined by them. 
 
 AGENCIES USED IN EFFECTING GEOLOGICAL CHANGES. 
 
 12. The study of Nature in all its departments, im- 
 presses upon the mind the idea of incessant change, as well 
 in the solid strata of the earth, as in the more fleeting forms 
 of animal and vegetable organization. Matter and motion 
 seem to be inseparably connected. Changes, however, 
 whether slight and momentary, or so grand as to task the 
 imagination in their conception, and require ages for their 
 2 
 
14 STRUCTURE OF THE EARTH. 
 
 completion,- evince the most enduring permanence in the 
 laws which produce and govern them ; and while our belief 
 in the constancy of natural laws is intuitive, we perceive 
 that incessant change is the means of effecting stability in 
 the whole system. 
 
 13. While Geologists agree respecting the nature of 
 the agents employed in effecting former geological changes 
 that they were identical with those now in operation 
 they are divided in opinion with reference to the intensity 
 with which these agents operated. One class contends that 
 the phenomena require, for their explanation, much more 
 extensive and violent action than we witness at present ; 
 while others claim that existing causes have operated 
 through all periods with the same degree of energy, and 
 when long continued are adequate to the production of all 
 the phenomena. The latter opinion is maintained by Sir 
 Charles Lyell in his Principles of Geology. 
 
 The agencies of geological changes may be classified as 
 atmospheric, aqueous, igneous, and organic. 
 
 ATMOSPHERIC AGENCIES. 
 
 14. Atmospheric agents produce both chemical and 
 mechanical effects. The atmosphere consists of nitrogen" 
 seventy-nine parts, and of oxygen twenty-one parts in a 
 hundred ; of carbonic acid about one part in a thousand ; 
 and of watery vapor a variable quantity. 
 
 Many minerals are acted upon chemically by oxygen 
 and carbonic acid. The sulphuret of iron (iron pyrites) 
 when exposed to moist air, undergoes decomposition ; the 
 sulphur unites with a portion of oxygen, forming sulphuric 
 acid, and the iron with another portion of the oxygen, form- 
 ing oxide of iron ; the two new bodies, thus formed, unite 
 
ATMOSPHERIC AGENCIES. 
 
 with each other, and the sulphuret of iron is converted in 
 the sulphate of iron, (copperas.) Carbonic acid unites withl 
 the oxide of iron, producing the carbonate of iron. It 
 renders water a solvent of limestone, so that water charged 
 with it, falling upon a limestone rock dissolves, and thus 
 removes portions of it, leaving fissures and caverns in the Lj^ 
 rock. These chemical changes are usually followed by a /$<*.. y 
 crumbling disintegration of the rocks. It is, however, li<u***. 
 sometimes the means of consolidation, as when the carbon- 
 ate of lime in solution infiltrates a mass of loose sand, it/ 
 
 cements it, producing a calciferous sandstone. 
 
 \~vv v- 
 15. Winds modify the surface of the earth by drifting! ry^N 
 
 sand, gravel, shells, &c., from exposed to sheltered positions, 
 in deserts and on the sea coasts. 
 
 The sands of the Lybian desert have buried ^ 
 
 cities and temples in Egypt. Many parts of the coasts o 
 England, Holland and France are partially or wholly sub- 
 merged by them. In Brittany, of a whole village over- 
 whelmed by drifting sands, nothing is visible above their 
 surface but the spire of a church. In Cornwall and Suffolk,- 
 England, are sand hills composed partly of comminuted 
 shells, several hundred feet above the level of the sea, ad- . I A ^ 
 vancing upon the cultivated land at the rate of five miles in 
 a century. Ansted states that on the coast of Spain, at 
 Cape Finisterre, they have advanced sixteen miles in half a 
 century five hundred and sixty yards per annum. These \[ 5^ 
 sand hills are called in England dunes or downs j in Scot- 
 land, links. They are sometimes arrested in their progress 
 by the roots of plants, especially of the aruiido arenaria, l< p 
 which bind them into a firm mass. They are also some- 
 times indurated by the carbonate of iron, or lime, or by 
 silica, cementing them, thus forming sandstones. The 
 
16 STRUCTURE OP THE EARTH. 
 
 phenomena of drifting sands are exhibited in our country 
 on the sandy capes as at Cape Cod. 
 
 16. Frost exerts a destructive influence upon rocks. 
 When water which has entered the fissures or pores of 
 rocks freezes, it expands with a force adequate to rend the 
 rocks ; each fragment is again subjected to the same pro- 
 cess until it is reduced to powder. This is most conspicu- 
 ous in rocks of loose texture, but the densest and firmest 
 do not escape. Blocks and ledges of granite, by this pro- 
 cess of exfoliation, lose their angles and edges, and are 
 oftentimes converted into rounded and grotesque forms. 
 The accumulation of fragments at the bases of precipices 
 is called a talus, usually presenting a slope of about 40. 
 
 AQUEOUS AGENCIES. 
 
 17. Aqueous agencies are exerted either chemically, dis- 
 solving and decomposing rocks, or mechanically, abrading 
 them and removing their particles. Water is the most gene- 
 ral solvent known, and few rocks at the surface escape its in- 
 fluence. Its solvent power is enhanced by acids and by heat. 
 
 The amount of common salt, carbonate of lime, and 
 other salts, held in solution in the waters of the Earth, is 
 enormous. The amount of solid matter dissolved in the 
 ocean is estimated to be more than thirty-nine parts in a 
 thousand of water. From this source, shell fishes, coral- 
 polyps and other animals inhabiting the sea, obtain their 
 supplies for their skeletons shells, coral-reefs, &c. The 
 amount thus withdrawn is replaced by the solvent power 
 of the water exerted upon the rocks to which the ocean 
 has access. Water charged with carbonic acid, having dis- 
 solved the carbonate of lime, or the oxide of iron, may 
 lose its solvent power over these bodies by the removal of 
 
AQI;KOI;K AGENCIES. 17 
 
 the acid; in such case tin: eont.-iined Halt i pi 
 Such di-poHtcs of carbonate of lime are called tufa or Jray- 
 ertir^} or, if they occur in water trickling from th: <i 
 of cavern*, they are called xtul.i,/;/, . The d'-po:,it~ in:i.|. : 
 on lh<: floor ben<-ath tin; stalactites, are culled ttqlagmfa*. 
 Similar deposites of the Kills of iron y held in 
 
 solution constitute the ////'//'// of iron, !><><j be* ''' 'II-': 
 waters of hot spring-: oft.eu hold silica in solution, which 
 JepoHite on cooling. 
 
 18. The mei-li'i :,',',, I .ty.in-y of water is still more luani- 
 and is either gradual, as in the wearing down rocks by 
 the rain, or rapid, by torrents, and ocean storms. 
 
 Jtivert arc most efficient agents in transporting mineral 
 masses. When their fall is considerable and their motion 
 rapid, they wear their beds, deepening their channel.-:. 
 They deposit the materials suspended in them along their 
 banks, upon their bottoms, or at their mouths. 
 
 Their eroding power is increased by the friction of the 
 ice, sand, and pebbles conveyed by them, and is exhibited 
 on a grand scale at large waterfalls. The falls of Niagara 
 are one hundred and fifty feet in height, and the average 
 amount of water passing over each minute, is estimuv 
 eix hundred and seventy thousand tons. The position of 
 the foils is not stationary; they have receded about fifty- 
 yards in forty years, and it is difficult to avoid the conclu- 
 sion, that they were originally at QuccriKtown, seven milen 
 below their present position. The length of time required to 
 wear through this space, can not b- > ily determined, 
 
 since they must have passed through several rocks varying 
 in texture, in which the rate of wearing can not now be 
 ascertained. For ft future pr 
 
 can not be predicted. Their present situation is favorable 
 2* 
 
18 STRUCTURE OF THE EARTH. 
 
 to rapid recession. The uppermost rock, over which the 
 water falls, is a hard limestone ninety feet thick ; beneath 
 is a soft shale, which is easily worn away by frost and the 
 friction of the water, leaving the limestone jutting over, in 
 table rocks, sometimes forty feet beyond the shale. From 
 time to time these table rocks fall off. 
 
 Fig. 0. 
 
 
 River Simeto excavating a channel in solid Lava. 
 
 19. The Simeto, one of the principal rivers of Sicily, 
 has excavated its bed from fifty to several hundred feet 
 wide, and forty to fifty feet deep, since A. D. 1603. In 
 the cut given above, A, indicates the lava bed, which des- 
 cending from the summit of the great volcano, has flowed 
 five or six miles, and usurped the old bed of the Simeto, E ; 
 B, the present bed of the river. The lava is not soft and 
 scoriaceous, but is a compact, hard rock, c, indicates the 
 foot of the cone of Etna, and r>, marine and volcanic beds. 
 The general declivity of the river is slight, having two falls 
 of six feet each. The abraded materials of the volcanic 
 rock have greatly assisted the attrition.* 
 
 20. The mechanical force of rivers is exerted in carry- 
 ing forward the sedimentary matter contained in there. 
 When the rapidity of the stream is diminished the heavier 
 portions of the sediment are deposited : but when the rate 
 
 *Lyell's Principles. 
 
 <V*r' 
 
 ^ ~ 
 - <LoX<uuA ttlwrWl Cnx I 
 
 An 
 
AQUEOUS AGENCIES. 19 
 
 of the current is increased by freshets, coarse gravel, peb- 
 bles, and even large blocks of stone, are borne forward by 
 it. Torrents, produced by the bursting of dams, are very 
 destructive in their effects. A remarkable example of 
 this action occurred in the Valais (Switzerland) in A. D. 
 1818. A dam four hundred feet high and six hundred feet 
 wide was formed across the valley during the winter, of the 
 rocks and ice brought down from the mountains by ava- 
 lanches. The water of the river Dranse accumulated 
 in this lake containing more than eight hundred million 
 cubic feet. The inhabitants, anticipating destructive results 
 from its eruption, opened an orifice in the dam near the 
 surface of the water, by which three-fifths of the water was 
 conducted off in three days, without violence. The barrier 
 then gave way, and all the remaining waters were dis- 
 charged in half an hour. The torrent reached the Lake of 
 Geneva, forty-five miles distant, in six hours, destroying 
 houses and trees that were in its path, and strewing the 
 valley with rocks and earth. 
 
 The rapidity with which water excavates a channel was 
 illustrated a few years since in the town of Glover, Ver- 
 mont. A small channel made from Long Pond, which was 
 two and a quarter miles long by one and a quarter wide, 
 with a depth of one hundred and fifty feet, was in a few 
 minutes so enlarged as to discharge all the water into Lake 
 Memphremagog, twenty miles distant, with the usual vio- 
 lent effects of an inundation. 
 
 21. The transporting power of water is rendered more 
 efficient by the loss of weight which minerals sustain in 
 water. Most minerals weigh about one-half as much in 
 water as in the air. It is ascertained by experiment that 
 a velocity of six inches per second will raise and transport 
 

 STRUCTURE OF THE EARTH. 
 
 on a horizontal surface, fine sand; eight inches, coarse 
 sand ; twelve inches, gravel ; and twenty-four inches, rounded 
 pebbles. Fresh water moving with a velocity of one and a 
 half mile per day, raises fine clay, and eight and a half 
 miles per day removes sand. Fine mud settles so slowly 
 in moving water that it is often transported hundreds of 
 miles before reaching the bottom. For this reason the sedi- 
 ment of rivers near their mouths consists mostly of mud. 
 
 22. Deposits of mud are called silt. The thickness of 
 the alluvial bed of the Mississippi river one hundred miles 
 above its mouth, is two hundred and fifty feet. Rivers in 
 this way sometimes raise their beds higher than the adjoin- 
 ing plains, and forsaking their old beds, flow in new chan- 
 nels. The Po has repeatedly deserted its bed, destroying 
 a number of towns. Several churches have been taken 
 down and removed to escape its erratic movements. In 
 one instance, during the fifteenth century, it returned to 
 the bed it had forsaken, but again deserted it during the 
 same century. It is now restrained by artificial banks on 
 an elevated mound, so that its surface at Ferrara is higher 
 than the roofs of the houses in the city. The Mississippi 
 is also confined by levees. 
 
 23. Deltas are deposits of mud, sand, end gravel, 
 made at the mouths of rivers, triangular in form, with the 
 apex of the triangle up the stream. They are called deltas 
 from their resemblance to the Greek letter A. Deltas are 
 fluviatile when formed at the entrance of one river into 
 another; lacustrine when at the entrance of a river into a 
 lake; and maritime when the river empties into the sea. 
 
 These deltas often accumulate rapidly, and mountain 
 lakes are sometimes entirely filled up by them. The Rhone 
 and Arve enter the Lake of Geneva as turbid streams, but 
 
 
 
AQUEOUS AGENCIES. 
 
 21 
 
 the Rhone emerges from the lake perfectly transparent. 
 The delta formed is six miles long a flat alluvial plain of 
 sand and mud. An ancient town, Port Vallais, (Portus 
 Valesice of the Romans,) which anciently stood upon the 
 shore of the lake, has had its harbor silted up, and is now 
 more than a mile and a half inland. Mr. Lyell says, " We 
 may look forward to the period when this lake will be filled 
 up, and then the distribution of the transported matter will 
 be suddenly altered, for the mud and sand brought down 
 from the Alps will thenceforth, instead of being deposited 
 near Geneva, be carried nearly two hundred miles south- 
 wards, where the Rhone enters the Mediterranean." The 
 Rhone after leaving the Lake of Geneva again acquires 
 sediment, and has formed a maritime delta at its mouth of 
 three hundred and twenty thousand acres. The mouth of 
 the river has advanced more than eight miles since the 
 commencement of the Christian era. 
 
 24. The delta of the Fig. 7. 
 
 Nile commences one hun- 
 dred miles from the Med- 
 iterranean, and is two 
 hundred and thirty miles 
 broad. It does not at pre- 
 sent increase much, be- 
 cause the sediment which 
 reaches the Mediterran- 
 ean is swept away by an 
 easterly current, and the 
 detritus brought down by 
 its periodic floods are spread over the plains of Egypt. This 
 fertilizing deposit, consisting of silica, alumina, oxide of 
 iron, and carbonates of lime and magnesia, has accumulated 
 
 Delta of the Nile. 
 
^ 
 
 22 STRUCTURE OF THE EARTH. 
 
 to the depth of more than six feet since the commencement 
 of the Christian era. 
 
 25. The Ganges presents a delta of gigantic dimensions, 
 commencing two hundred and twenty miles from the sea, 
 and having a base line of two hundred miles. It renders 
 the waters of the ocean turbid sixty miles from the coast. 
 The total amount of sediment annually discharged being 
 one four hundred and fiftieth part of the whole weight of 
 the water, is six billion three hundred and sixty-eight mil- 
 lion tons, an amount sufficient to cover a township five miles 
 square to the depth of ten feet. 
 
 The whole coast of Northern Central Europe, from Ca- 
 lais to the Baltic, has been covered with mud brought down 
 by the Rhine, which in some places is several hundred feet 
 thick. Experiments show that the quantity yielded by this 
 river, is about four hundred tons weight per hour. 
 
 26. The delta of the Mississippi comprises an area of 
 thirteen thousand six hundred square miles, projecting into 
 the Gulf of Mexico, with a depth of 1056 feet, and contain- 
 ing 2720 cubic miles. The quantity of water annually dis- - 
 charged by the river is 14,883,360,636,880 cubic feet; 
 quantity of sediment discharged is 28,188,083,892 cubic ^u 
 feet, being the one five hundred and twenty-eighth part of 
 the water. One cubic mile is formed in five years and 
 eighty-one days. The formation of the whole delta would 
 have required, at this rate, 14,203 years. The quantity 
 annually discharged is sufficient to cover a township five 
 miles square with a layer of mud forty feet thick. 
 
 27. The accessions to the land from the sediment 
 brought down by the Po and the Adiye, are one hundred 
 miles long, and vary in width from two miles to twenty 
 miles. The town Adria, a seaport in the time of the Ein- 
 
 e^ *OAA/jvtj<A~e/rrvK - OWJTVC 
 
AQUEOUS AGENCIES. 
 
 peror Augustus, which gave its name (Adriatic) to the gulf, 
 is now more than twenty miles inland. 
 
 28. The detritus of the Amazon docs not form a delta 
 at its mouth, but is swept by ocean currents, and distribu- 
 ted partly in the ocean, where it is discernible three hun- 
 dred miles from the mouth of the river, and partly to the 
 coast of Guiana, where it has formed an immense alluvial 
 
 . deposit. When the matter deposited at the mouth of a 
 river has not accumulated sufficiently to rise to the surface/^fc( 
 of the water, it is called a bar. Such a bar, called " the ~~ 
 Overslough," is formed a few miles below Albany, in the 
 still water caused by the meeting of the waters of the Hud- 
 son with the tide from the ocean. The attempt to remove -4 
 this obstacle to navigation by contracting the river, tended 
 only to increase the velocity of the current and thrust the * t*\ju^ 
 bar farther down the river. 
 
 29. In addition to the materials conveyed mechanically 
 by water, extensive deposits are made by springs. The 
 waters of many springs are charged with carbonate of lime, 
 which is deposited when the water issues from the rocks. 
 Substances deposited in such water become incrusted with 
 limestone. This is not petrifaction, since the substance 
 undergoes no change, but is simply enveloped in the incrust- 
 
 ing mineral. 
 
 Fig. 8. 
 
 Incrusted Twig. 
 
 The preceding cut exhibits a stick thus incrusted. Many 
 
24 STRUCTURE OF THE EARTH. 
 
 such springs in northern Ohio incrust the mosses growing 
 in their vicinity, furnishing beautiful but frail specimens. 
 The loose, porous rock formed by these deposits is called 
 tufa ; the compact is called travertin. Beds of these, some 
 miles in length and several hundred feet thick, are formed 
 by springs in France and Italy. At San Filippo, in Italy, 
 medallions are made by conducting the water into moulds; 
 the deposited matter filling the mould, presents a marble 
 cast of the figure. The beautiful alabaster of Tabreez, in 
 Persia, has the same origin. 
 
 30. Deposits of sih'cious matter are made by hot springs. 
 In the Azores islands hot springs, rising through volcanic 
 rocks, deposit large quantities of silicwus sinter, as it is 
 called, incrusting with beautiful crystalline scales all sub- 
 stances with which their waters come in contact. But the 
 most remarkable hot springs are the Geysers of Iceland, 
 whose circular basins are lined with the silica of their 
 waters. Some springs deposit iron ore, common salt, 
 asphaltum or mineral pitch, (Seneca oil,) &c. 
 
 31. Another mode of action of water is exhibited in 
 land slides. In the year 1806, after a rainy season, the 
 Bossberg, a mountain in Switzerland, was undermined, and 
 a mass of two thousand millions of cubic feet precipitated 
 into the valley, forming hills two hundred feet high, and 
 destroying several villages. Land slides have also occurred 
 from a similar cause 
 
 in the "White Moun- 
 
 tains, and near Troy, ^f 
 
 New York. The 
 
 t- 
 
 banks of the Lake ^ 
 and the Cuyahogn ;^J 
 
 valley in the city of 
 
AQUEOUS AGENCIES. 
 
 25 
 
 10. Land Slides iu ulovclaud. 
 
 Cleveland, are frequently subjected to the same process of 
 degradation, as shown in figure 9. The water which 
 falls upon the surface 
 passes through the 
 strata of gravel and 
 sand D and c, and ac- E 
 cumulates upon the 
 bed of blue clay 
 which is mostly im- 
 pervious to water ; from this it issues, forming springs, and 
 carrying out the sand undermines the upper beds. This - 
 degrading influence is increased by the erosive action of the 
 waves of Lake Erie, E, on the clay bed, as shown at B ; in 
 figure 10. 
 
 32. Glaciers and icebergs water in a solid form are 
 very influential in effecting changes upon the surface of the 
 earth, and their peculiar phenomena have recently attracted 
 much attention on the part of geologists. 
 
 Glaciers are immense bodies of ice formed in the val- 
 leys or on the sides of mountains, extending many miles, 
 and remaining undissolved by the heat of summer. Por- 
 
 Fig. 11. 
 
 Glacier of Grindelwald, Berne, Switzerland. 
 
 3 
 
26 
 
 STRUCTURE OF THE EARTH. 
 
 tions of their mass are granular snow cemented by ioe. 
 They vary in thickness from one hundred to eight hun- 
 dred feet, and have a very gentle slope. Their surface 
 is very rough and often studded with conical masses of ice, 
 called needles. They are traversed by wide fissures pro- 
 Fig. 12. 
 
 Glacier of Viesch, with juodiul and lateral moraines. 
 
AQUEOUS AGENCIES. 
 
 27 
 
 duced by contraction in the winter. Each winter adds a 
 new layer to their surface ; the snow, however, disappears 
 from their surfaces in summer, as regularly as from the 
 surrounding rocks. Expansion, gravity, and the forms of 
 the valleys, cause them to advance slowly down, sometimes 
 even to the borders of cultivation. " The very huts of the 
 peasantry/' says Professor Forbes, " are sometimes invaded 
 by this moving ice, and many persons now living have seen 
 the full ears of corn touching the glaciers, or gathered ripe 
 cherries from the tree with one foot standing on the ice." 
 The surfaces and mass of glaciers abound with fragments 
 of rocks which are often arranged in long lines, and are 
 called moraines. The rocks over which glaciers pass are 
 smoothed, scratched and grooved, by sand and angular 
 
 Fig. 13. 
 
 Striae of Glaciers. 
 
 stones forced forward by their enormous pressure. These 
 striae and grooves are parallel to each other, because the 
 fragments which produced them are fixed in the bottom of 
 
28 STRUCTURE OF THE EARTH. 
 
 the glacier. Sometimes loose stones give rise to irregular- 
 ities of direction and figure. 
 
 33. From glaciers formed in high latitudes near the 
 sea, fragments of various sizes fall into the ocean, and con- 
 stitute icebergs. The polar seas abound with them at all 
 seasons, and marine currents float many of them into lower 
 latitudes. They are sometimes of great size ] one measured 
 thirteen miles in length, and one hundred feet above the 
 water, giving a thickness of seven hundred or eight hundred 
 feet.* Floating into warmer water and atmosphere, ice- 
 bergs melt, depositing their loads of earth and rocks on the 
 bottom of the ocean. Many of them strand upon the New- 
 foundland Banks, and after heavy rolling and disturbance 
 of the bottom, they melt, and mingle the fragments they 
 conveyed with the sands of the Banks.' Similar pheno- 
 mena, on a smaller scale, are witnessed in lakes and rivers ; 
 a fragment of rock is floated to one side and there left by 
 
 Fig. 14. 
 
 Iceberg seen off Cape Good Hope, April A. D. 1829, two miles in circumference and 
 150 feet high. 
 
 * The specific gravity of ice is such as to make it float with one-ninth of its 
 bulk above the surface of the water ; but icebergs are porous, and float with the 
 largest extremity immersed, so that one-seventh or one-eighth is above the water. 
 
AQUEOUS AGENCIES. 29 
 
 the melting ice ; the succeeding season it may be returned 
 by the same agency to the other side. 
 
 34. The geological agency of the ocean is, like that of 
 rivers, twofold. 1st, Erosive, wearing away the coast, 
 undermining and excavating cliffs ; and, 2nd, transporting 
 and accumulating the detritus to form new land. It pro- 
 duces these effects by means of waves, tides, and currents. 
 
 35. The action of waves is incessant, but varies in ex- 
 tent according to the nature of the exposed shore. Since 
 they do not penetrate very deep, and have no progressive 
 motion in the open sea, they do not affect the bottom of 
 the ocean, except where it is very shoal. Cliffs of soft 
 rocks, clay, chalk, or sandstone, are very rapidly under- 
 mined and worn away. The hardest rocks, however, can 
 not resist its never ceasing attacks. Headlands of alter- 
 nately hard and soft rocks, especially if intersected by 
 crevices, are worn away with very great rapidity. The 
 coasts of England exhibit this erosive action of the ocean 
 in a remarkable degree. The cliffs of Yorkshire, it is 
 ascertained by careful measurements, repeated after inter- 
 vals of many years, are worn away six feet in breadth, 
 annually. The average annual loss on the coast of Norfolk 
 is about three feet. When Mr. Lyell, in A. D. 1829, visit- 
 ed Sherringham, Norfolkshire, he found water twenty feet 
 deep, where forty-eight years before stood a cliff fifty feet - 
 high. In the county of Kent, near the mouth of the 
 Thames, stands the Church of Reculver, upon a cliff twenty 
 feet above the sea. In the time of King Henry VIII. the 
 distance between the church and the brink of the cliff was 
 one mile. The following cut represents the appearance of 
 the spot in A. D. 1781, when the encroachments of the 
 sea had attracted notice, though considerable space, with 
 
 3* 
 
30 
 
 STRUCTURE OF THE EARTH. 
 
 other buildings, intervened between the churchyard and 
 the cliff. The walls of an ancient Roman fortification 
 
 Fig. 15. 
 
 Church of Reculvcr in A. D. 1781. 
 
 which was two hundred and forty feet nearer the sea than 
 the church was, had recently been undermined and pre- 
 cipitated into the ocean. In A. D. 1804, a part of the 
 churchyard with some adjoining houses was washed away, 
 and the ancient church with its two lofty spires, a well 
 known land-mark, was dismantled, and abandoned as a 
 place of worship. Figure 16 represents it as it appeared 
 in A. D. 1834. It would probably long since have fallen, 
 had not the incursions of the ocean been checked by an 
 artificial causeway of stones and large wooden spiles driven 
 into the sands to break the force of the waves. The isle 
 of Sheppey, seen at some distance from the main land, on 
 the right hand, in figure 15, which is six milds long and 
 four broad, is continually undergoing abrasion, having lost 
 
AQUEOUS AGENCIES. 
 Fig. 16. 
 
 31 
 
 Church of Keculver in A. D. 1834. 
 
 fifty acres within the last, twenty years.* There are other 
 instances in which islands in this (German) ocean, and im- 
 portant seaport towns, have been entirely obliterated. 
 
 36. The English channel probably owes its origin to 
 the erosive action of the ocean, the geological features 
 of the coasts of England and France, clearly indicating 
 that they were formerly united. During the thirteenth 
 century, a channel half as wide as the English channel, 
 was excavated in the north of Holland, separating Fries- 
 land from the main land. Immense labor is continually ex- 
 pended in Holland to prevent incursions of the ocean, which 
 
 : 
 
 * Lyell's Principles. 
 
32 
 
 STRUCTURE OF THE EARTH. 
 
 threaten to inundate mucli of the country, and destroy the 
 cities of Amsterdam and Ley ''en. The effect of this constant 
 abrasion on exposed coasts, is seen in the production of 
 caverns, bridges, and isolated pinnacles of rock, as exem- 
 plified by the chalk " Needles" of the English coast, and 
 the " Prongs" of the north of Scotland. Figure 17, pre- 
 sents a view of the cluster of rocks seen to the south of the 
 Hillswick Ness, one of the Hebrides. These granite rocks 
 are all that remain of a former island, which may, at an 
 earlier period, have been a promontory of the main land. 
 
 Fig. 17. 
 
 Ilillswick Ness, Hebrides Islands, Scotland. 
 
 37. The coasts of New England and Nova Scotia also 
 exhibit striking instances of the abrading power of the 
 ocean. Boston harbor has been formed by this agency; 
 the outermost islands in it, exposed to the violence of the 
 waves, consist of bare rock ; and the more sheltered ones 
 are continually losing a portion of their covering. At 
 Cape May, on the north side of Delaware Bay, the sea has 
 
AQUEOUS AGENCIES. 33 
 
 encroached upon the land at the rate of nine feet in a year; 
 and at Sullivan's island, near Charleston, South Carolina, 
 four hundred and forty feet in a year. The waves of inland 
 seas and lakes produce similar effects. The indentations 
 of the shores of Lake Erie were caused by this agency. 
 The mode in which it operates at Cleveland, has been 
 already illustrated in 33. The ordinary effects of the 
 ocean' s agency in wearing and transporting rocks, are 
 greatly enhanced by storms. Masses of rock of from ten 
 to thirty tons weight, have been forced by them up an 
 inclined shore. During the erection of the Bell Rock light- 
 house, six granite blocks were thrown over a rising ledge 
 twelve or fifteen paces, and an anchor, weighing two thou- 
 sand two hundred pounds, was thrown up upon the rock 
 from a depth of at least sixteen feet. 
 
 38. The periodical elevations of the ocean waters, called 
 tides, varying from two and a half feet to seventy feet in 
 height, extend the limits of the ocean's power, and produce 
 very marked effects in narrow channels, bays and estuaries. 
 The action of the tide wave is alternate, advancing and 
 receding, destroying as it advances, and bearing away the 
 debris as it recedes ; differing in this respect from currents, 
 which carry the fragments which they produce or meet 
 with, only in the direction of their course. 
 
 " The bore " is a term applied to a sudden influx of the c c 
 tide into a river or strait, which, resisted by the descending 
 water, .and forced into a narrow channel, rises suddenly, r_^_^ 
 and exhibits the phenomena of breakers on a shelving 
 shore. It is most conspicuous at the time of spring or 
 highest tide. Tne bore in the Severn is sometimes nine 
 feet high ; in the Bay of Fundy seventy feet, producing 
 inundations, sometimes sweeping off trees and animals. . 
 
34 STRUCTURE OF THE EARTH. 
 
 39. Another kind of movement in the waters of the 
 ocean is exhibited by marine currents, which perform a 
 most important part in the economy of nature. They are 
 of two kinds, drift, and stream currents. Drift currents are 
 the result of a constant or prevailing wind on the surface 
 of the ocean, penetrating to no great depth, rarely exceed- 
 ing in velocity a half mile per hour, and are easily turned 
 from their course. They are produced chiefly in the regions 
 of the trade winds, and sometimes originate stream currents, 
 which are immense oceanic rivers, covering a space of one 
 to three hundred miles in breadth, and reaching to a very 
 great depth. They are caused by the tendency of water 
 that is displaced to restore the equilibrium of the surface of 
 the ocean. The origin of the displacement is not satisfac- 
 torily ascertained. It has been ascribed to winds, unequal 
 evaporation, difference of rapidity of diurnal revolution in 
 different latitudes, &c. 
 
 The velocity of the currents varies in different parts of 
 their course in some the average is sixty miles, with a 
 maximum of one hundred and twenty miles in a day. 
 Their temperature is either higher or lower than that of 
 the surrounding sea, according to the temperature of the 
 region in which they have their origin. This difference 
 amounts to from 10 to 30 Fahrenheit. Some of these 
 currents extend their course through many thousand miles. 
 The same current has different names applied to it in suc- 
 cessive parts of its course. 
 
 40. The chart, Figure 18, presents a general view of 
 ocean currents, especially of our Gulf stream, which is a 
 continuation of the Mozambique current running between 
 the eastern coast of Africa and Madagascar : doubling tho 
 Cape of Good Hope, it enters the Atlantic ocean as the 
 
AQUEOUS AGENCIES. 
 Fig. 18. 
 
 35 
 
 Chart of Oceanic Currents. 
 
 Cape or Agulhas current. Thence, under the name of 
 southern Atlantic current, it flows north-easterly until its 
 course is turned to the westward by the coast of Africa, and 
 the opposition of the Guinea current from the north. It 
 now forms the Equatorial current, and stretches across the 
 Atlantic, on both sides of the Equator; about midway be- 
 tween Africa and South America it divides, sending a branch 
 southward along the eastern coast of South America, form- 
 ing the Brazil current, while the main stream continues its 
 course by the coast of Guiana, crossing the waters of the 
 Amazon and receiving those of the Oronoco, and enters the 
 Caribbean Sea, as the Guiana current. From the Gulf of 
 Mexico, it issues as the Gulf stream, running north-easterly 
 by the coast of Florida and Cape Hatteras to the St. George 
 and Nantucket Banks, and thence eastward by the Azores 
 to the coast of Europe. The length of the Gulf stream 
 from Florida to the Azores, is three thousand five hundred 
 
00 STRUCTURE OF THE EARTH. 
 
 miles ; which is traversed in seventy-eight days at an 
 average rate of thirty-eight miles per day. The amount of 
 water conveyed in it is more than three thousand times the 
 amount discharged by the Mississippi river, many times 
 greater than all the fresh water in the rivers of the globe. 
 In a part of its course near the Florida Gulf, its velocity is 
 that of a torrent five miles per hour.* 
 
 41. The temperature of the Gulf stream at the Florida 
 coast is 86 Fahrenheit, declining, as it advances northward, 
 to 73 at the Azores. This vast expanse of water, whose 
 temperature is 10 above that of the ocean, must have a 
 great effect upon the climate of adjacent countries. " A 
 simple calculation," says Lieutenant Maury, "will show 
 that the quantity of heat discharged over the Atlantic from 
 the waters of the Gulf stream in a winter day, would be 
 sufficient to raise the whole column of atmosphere that rests 
 upon France and the British islands, from the freezing 
 point to summer heat. It is the influence of this stream 
 upon climate, that makes Ireland the Emerald isle of the 
 sea, and clothes the shores of England with evergreen 
 robes ; while in the same latitude on the other side, the 
 shores of Labrador are fast bound in fetters of ice. In 
 A. D. 1831, the harbor of St. Johns, Newfoundland, was 
 closed with ice in the month of June, although it is 2 far- 
 ther south than Liverpool; and the influence of the Gulf 
 stream is felt in Norway, and on the shores of Spitz- 
 bergen." 
 
 42. On issuing from the straits of Florida, the waters of 
 
 the Gulf stream are of a deep indigo blue color, and the 
 
 line of separation between it and the green waters of the 
 
 Atlantic, is plainly visible for hundreds of miles. The 
 
 * Johnston's Physical -Atlas.' 
 
AQUEOUS AGENCIES. 87 
 
 great eddy in the middle of the Atlantic, caused by these 
 currents, extending from 30 west longitude to the Baha- 
 mas, and between the parallels of 20 and 45 north lati- 
 tude embracing two hundred and sixty thousand square 
 miles is called the Sargazo sea, because its surface is 
 covered with the gulf weed, (in Spanish, Sargazo.) In 
 many places it is so thickly matted, as to retard the prog- 
 ress of vessels through it. 
 
 43. The Arctic current, originating within the polar 
 circle, runs by the shores of Greenland and Labrador form- 
 ing the Hudson Bay current', comes in collision with the 
 gulf stream at Newfoundland, where it divides, and sends 
 a branch southward by the coast of the United States, con- 
 stituting the counter current, between the gulf stream and 
 the coast. It enters the Caribbean sea as an under current, 
 replacing the warm water sent through the gulf stream, 
 and mitigating the climate of Mexico and Central America. 
 The temperature of the Caribbean sea at the depth of 240 
 fathoms, has been found as low as 48 while that of the 
 surface was 85. This current conveys icebergs from the 
 polar seas. Captain Scoresby counted five hundred ice- 
 bergs in it at one time. MeetingJJie gulf stream at New- 
 foundland, they deposit enormous loads of rocks and earth, 
 having thus greatly extended, and probably originated the 
 Banks. The depth, of the great oceanic stream currents has 
 not been generally ascertained, but is in some cases seventy 
 fathoms and probably more. Their mechanical effects, espe- 
 cially when they move rapidly, must be great at consider- 
 able depths, and they transport materials hundreds of miles. 
 
 44. As tides and currents powerfully co-operate with 
 waves in destroying rocks on the shore of the ocean, so also 
 do they conspire in reproducing land, forming banks, and 
 
 4 
 
38 STRUCTURE OF THE EARTH. 
 
 silting up estuaries. Currents assort the materials trans- 
 ported by them, depositing the heavy fragments of rock 
 very near where they receive them, conveying the sand to a 
 greater distance, while the mud settling very slowly may 
 be transported a very great distance. Since the direction 
 and velocity of the current are tolerably uniform, the de- 
 posits will be in a good degree homogeneous. The bed of 
 the German ocean is traversed by sand banks, one of which 
 " the Dogger Bank," is three hundred and fifty-four miles 
 long and eighty feet high. The greatest^ deposits, espe- 
 cially of fine clay, are probably made in the quiet depths of 
 the ocean, beyond our observation. By the agency of tidal 
 waves, sand is forced upon beaches ; and when aided by 
 storms, the sand is carried beyond the reach of succeeding 
 waves. The isthmus ofJSuez, between the Mediterranean 
 and Bed seas, has doubled its breadth since the time of 
 Herodotus. The collection of loose round water-worn peb- 
 ^ , bles, accumulated on beaches by waves, is called shingle. 
 Very many bays and estuaries, are shoaling rapidly with 
 the sediment conveyed into them by the waves of the ocean. 
 The amount of matter brought down by rivers and deposi- 
 ted as deltas, is quite insignificant when compared with 
 ocean deposits. So great is the quantity of detritus held in 
 suspension by sea-water, that extensive tracts of land which 
 have been purposely flooded with it repeatedly, have been 
 raised five or six feet. The ocean also disperses through its 
 vast extent, the saline substances, as common salt and car- 
 | bonate of lime, which it obtains either directly from the 
 * I rocks, or from the rivers which empty into it. 
 IN ^> 45. The general result of atmospheric and aqueous 
 agencies, is the reduction of elevated portions of the earth 
 to lower levels. The loss of land through their influence 
 
IGNEOUS AGENCIES. 39 
 
 greatly exceeds all deposits in the form of jlry land; conse- 
 quently a large portion of the detritus is spread over the 
 bottom of lakes and of the ocean. 
 
 IGNEOUS AGENCIES. 
 
 46. We have seen that the tendency of atmospheric 
 and aqueous agencies is to destroy the inequalities of the 
 Earth's surface, and deposit the materials thus separated at 
 the mouths of rivers and on the bottoms of lakes and seas. 
 An antagonist force, however the igneous agency is as 
 constantly operating to restore and produce these inequali- 
 ties. This agency exhibits itself in the phenomena of 
 volcanoes, earthquakes, hot-springs, and gradual elevations 
 of extensive lines of coasts and continents. 
 
 47. Volcanoes are openings in the earth, through which 
 melted rock, lava, smoke, ashes, gases or vapors are dis- 
 charged. They are usually inverted cones or craters at the 
 summits of conical hills or mountains, which vary in height 
 from the smallest hill to nineteen thousand feet, (Cotopaxi. ) 
 When they exist upon land they are called subaerial ; when 
 under the sea, submarine. Those which exhibit no evi- 
 dence of action since the commencement of the historic pe- 
 riod, are deemed extinct. Of the active volcanoes, some 
 are constant, others intermittent. The periods of inter- t 
 mission vary from a few months to centuries. Monte 
 
 meo, in Ischia, after remaining dormant one thousand seven 
 hundred years, again burst forth in the early part of the 
 fourteenth century of the Christian era. Volcanic vents, 
 which emit only sulphurous, watery, and acid vapors, are 
 called solfataras. 
 
 48. The number of active volcanoes is about three 
 
40 STRUCTURE OF THE EARTH. 
 
 hundred ; of which two-thirds are on islands of the ocean, 
 and the others are usually near the sea. Some, however, 
 are remote from large bodies of water, as Peschan in Cen- 
 tral Asia, which is twelve hundred miles, and some of the 
 Mexican and South American volcanoes, one hundred miles 
 distant from the sea. Volcanoes are grouped as central, in 
 which the disturbing power manifests itself in radii from a 
 central point, as the Peak of Teneriffe and the Isle of Pal- 
 ma (one of the Canary islands) ; or volcanic chains or bands, 
 in which a number of vents occur in a line extending over 
 many miles, oftentimes coinciding with mountain chains. 
 Such a band is presented by the volcanoes of America, those 
 of the Andes and Rocky Mountains being connected by the 
 Cordilleras of Mexico. The same chain may also connect 
 with the remarkable line of volcanoes passing through the 
 Aleutian Islands, Kamschatka, Japan, and the Molucca 
 islands; thence by the Antartic Land (on which Captain 
 Boss observed active volcanoes) to Terra del Fuego, thus en- 
 circling the globe. 
 
 49. The phenomena of an eruption usually com- 
 mence with rumbling sounds in the earth and emission of 
 smoke, sulphurous and acid gases from the mountain ; 
 stones and ashes are thrown with violent explosions from 
 the crater, the earthquake increasing, until the molten lava 
 flows freely down the mountain's sides. Toward the close 
 of the eruption, cinders, red hot stones, and smoke are 
 again thrown out. Impetuous showers of rain, with vivid 
 lightning, and if the mountain is snow-clad, the sudden 
 melting of snow and ice, render the scene still more com- 
 plicate and awful. The lava sometimes does not rise to 
 the brim of the crater, but bursts through the sides of the 
 mountain and flows over the surrounding country. 
 
 
IGNEOUS AGENCIES. 41 
 
 50. The greatest exhibition of eruptive violence on 
 record occurred in the island of Sumbawa (one of the 
 Sunda group), in the year 1815. It commenced on the 
 fifth of April, increased in violence until the twelfth, and 
 ceased in July. The explosions were heard in Sumatra, 
 nine hundred and seventy miles west, and at Ternato, 
 seven hundred and twenty miles east of the island. The 
 ashes were carried three hundred miles in the direction of 
 Java, and two hundred and seventeen miles northward 
 toward Celebes in sufficient quantity to produce darkness 
 equal to what is ever witnessed in the darkest night. The 
 floating cinders westward of Sumatra formed a mass two 
 feet thick, several miles in extent, through which ships 
 with difficulty forced their way. Several streams of lava, 
 issuing from the crater of the Tomboro mountains, covered 
 extensive tracts of land and ran into the sea. The area 
 convulsed by this volcanic paroxysm was one thousand 
 miles in circumference. Out of a population of twelve 
 thousand on the island, twenty-six only survived.* 
 
 51. Of all eruptions of modern times, the most re- 
 markable in respect to the quantity of lava ejected was that 
 of Skaptaa Jokul, in Iceland, in the year 1783. On the 
 eighth of June of that year, clouds of smoke began to 
 collect in the mountain, obscuring the light of day, show- 
 ering down great quantities of ashes and sand. On the 
 tenth, slight shocks of earthquake and flames were per- 
 ceived. On the eleventh, the large river Skaptaa, which 
 had been much swollen, entirely disappeared, and the next 
 day a current of lava rushed down the mountain and 
 overflowed the channel of the river, which was in some 
 places from four hundred to six hundred feet deep, and 
 
 * Ly ell's Principles. 
 4* 
 
42 STRUCTURE OF THE EARTH. 
 
 two hundred feet broad. The lava continued to flow until 
 the twentieth of July, pouring over a lofty cataract, and 
 filling up in a few days an enormous cavity which the river 
 had been for ages hollowing out. On the night of the 
 ninth of August, another torrent overflowed the country to 
 the extent of more than four miles. The eruptions con- 
 tinued, with intervals, till the end of August, and closed 
 with a violent earthquake. One of the streams of lava 
 was fifty miles long by twelve broad, and the other forty 
 miles long by seven broad. Their thickness was, in the 
 narrow channels, five or six hundred feet; but on the 
 plains rarely more than one hundred feet, and in some 
 places only ten feet. Taking the lowest average thickness, 
 the mass of lava can not have been less than twenty thou- 
 sand millions of cubic yards. Thirteen hundred human 
 beings lost their lives, more than one hundred and fifty 
 thousand domestic animals were destroyed, the fisheries on 
 the coast were ruined, and it is afnrrned that Iceland has 
 not yet recovered from the ravages of this eruption of 
 Skaptaa Jokul. The great mass of lava spread over the 
 land by this eruption, distended by gases, cooling on the 
 surface and becoming solid, while the central parts continued 
 liquid and flowing onward, left caverns of great extent and 
 singular appearance. 
 
 The cavern of Surtsheller, or the " black cavern," is a 
 long, winding canal, with several branches, enclosed by a 
 crust of lava six feet thick. It is twenty-five feet wide, and 
 its sides and vaulted roof are studded with stalactites of 
 lava and ice. 
 
 52. The history of Vesuvius and Etna is more com- 
 plete than that of any other center of volcanic action, be- 
 cause their phenomena have been for a longer time intelli- 
 
IGNEOUS AGENCIES. 
 FJ>. 10. 
 
 Surtsheller Cavo in Lava. 
 
 gently observed and recorded. The southern part of Italy 
 has, from the earliest periods of human observation, been 
 subject to violent volcanic action. But previous to the 
 Christian era, no record or tradition of eruptions from 
 Vesuvius existed. The summit of the cone, called Somma, 
 was encircled with vines, and its sides were covered with 
 
44 
 
 STRUCTURE OF THE EARTH. 
 
 luxuriant vegetation. At its base were large towns, among 
 which were Herculaneum and Pompeii. At this period, 
 Ischia, Procida, and the Phlegrean fields were the scenes of 
 volcanic eruptions. 
 
 53. After a slumber of ages, Vesuvius, in A. D. 63, ex- 
 hibited signs of internal agitation in earthquakes, which 
 increased in frequency and energy until the year 79, when 
 an eruption overwhelmed the cities Herculaneum, Pompeii 
 and Stabice. During sixteen hundred years these cities 
 were buried from human observation and memory beneath 
 volcanic ashes and lava. In A. D. 1713, in sinking a well, 
 sonic pieces of marble and statuary were discovered. This 
 led to extensive excavations in Pompeii and Herculaneum. 
 Fig. 20. 
 
 Vesuvius, showing the site of Pompeii and the River Sarno. 
 
 As the former city was buried in ashes and mud, its exhu- 
 mation is comparatively easy, and has furnished an immense 
 store of antiquities paintings and sculptures, linen cloth, 
 household utensils, medicines, loaves of bread with the legi- 
 
IGNEOUS AGENCIES. 
 
 45 
 
 ble stamp of the baker, papyri, &c., in a perfect state of pre- 
 servation. Few human skeletons have been found, most of 
 the inhabitants having fled before the irruption. Since 
 that period there have been forty eruptions of Vesuvius, 
 some of which have destroyed towns as that of 1631 in 
 which lava currents with floods of mud overwhelmed Resina 
 which was built over Herculaneurn, and that of A. D. 1784, 
 in which Torre del Greco was encased in lava. The erup- 
 tion of A. J). 1822, was characterized by violent explosions 
 Fig. 21. 
 
 Crater of Vesuvius, in A. D. 1829. 
 
46 STRUCTURE OF THE EARTH. 
 
 which threw out the lava which had consolidated, altering 
 the shape of the crater, and reducing the height of the 
 mountain from four thousand two hundred to three thousand 
 four hundred feet. The preceding cut presents the appear- 
 ance of the crater in 1829. The amount of lava ejected by 
 Vesuvius in the eruption of 1794, exceeded twenty-two 
 millions of cubic yards. 
 
 54. Etna has been known as an active volcano from th 
 earliest periods of tradition. Its height is ten thousand 
 eight hundred and seventy feet. The base of its cone is 
 eighty-seven miles in circumference, and there are numer- 
 ous subordinate cones or secondary volcanoes upon the 
 sides of the mountain. More than eighty eruptions of this 
 mountain are recorded, several of which are characterized 
 by the great amount of lava ejected ; the whole quantity 
 erupted far exceeding the mass of the mountain. The lava 
 of the eruption of 1669 overwhelmed fourteen towns and 
 villages, with a portion of the city of Catania, running into 
 the sea, and covering eighty-four square miles. Its erup- 
 tions sometimes, instead of occurring at its summit, take 
 place through fissures in its sides, which abound with lava 
 dikes. 
 
 55. The volcanoes of America are generally distinguished 
 by their great height and number. Within two degrees of 
 latitude from the Equator on either side are nine active 
 volcanic vents, including Cotopaxi, Tunguragua, Antisana 
 and Pichincha, all of which are from sixteen thousand 
 to nineteen thousand feet above the level of the ocean. 
 The whole plain on which Quito stands, nine thousand five 
 hundred feet above the sea : with the adjacent mountains, 
 seems to constitute an immense volcanic dome, embracing 
 six hundred square miles, which is almost constantly agi- 
 
IGNEOUS AGENCIES. 47 
 
 tated by internal convulsions, finding vent by eruption at 
 the various craters. Cotopaxi, which rises to the height of 
 eighteen thousand eight hundred and eighty feet, had five 
 great eruptions during the last century, which were heard 
 at distances of from one hundred and forty to six hun- 
 dred miles on the Pacific coast. Molten lava is rarely 
 raised so high as the summit of these volcanoes, but 'cinders 
 
 Fig. 22. 
 
 Cotopaxi. 
 
 and pumice are ejected. The most destructive effects are 
 produced by the torrents of mud and boiling water, which 
 result from the melting of the snow with which the moun- 
 tain is covered, and the bursting of lakes and subterranean 
 cavities. These currents of mud and water fill the valleys 
 to the depth of several hundred feet, and oftentimes contain 
 so many fishes, that their putrescence renders the atmosphere 
 unwholesome for many miles. 
 
 56. In Mexico the transverse band has five active 
 volcanoes, of which Popocatapetl and Jorullo have attracted 
 most attention. Popocatapetl (Smoking Mountain) attains 
 the height of seventeen thousand seven hundred and twenty 
 feet, is snow clad, and continually emits smoke and vapors. 
 
 57. The formation of the volcano Jorullo exhibits an 
 
48 STRUCTURE OF THE EARTH. 
 
 Fig. 23. 
 
 Popocatapetl. 
 
 instance of the origin of a volcanic mountain suddenly ele- 
 vated one thousand six hundred and ninety-five feet above 
 the plain, (four thousand two hundred and sixty-five feet 
 above the ocean,) more than one hundred miles distant from 
 the sea, and quite remote from any active volcano. It oc- 
 curred on the plain of Malpais, west of the city of Mexico, 
 in the year 1759. In the month of June of that year, 
 alarming subterranean noises, with frequent earthquakes 
 commenced and continued about fifty days. After a period 
 of apparent tranquillity, on the night of the 28th of Sep- 
 tember the inhabitants were compelled to leave the con- 
 vulsed plain, in which a tract of four square miles heaving 
 like an agitated sea, was raised to a height five hundred 
 and twenty-four feet ; flames were seen to issue, and frag- 
 ments of burning rock were thrown to great heights. Two 
 rivers were precipitated into the chasms, increasing the 
 fury of the flames.- Thousands of small cones rose up on 
 the plain from six to ten feet high, called by the Indians, 
 ovens (hornitos) emitting sulphureous vapors and smoke. 
 In the midst of these fumaroles, stood six large conical 
 
IGNEOUS AGENCIES. 49 
 
 masses rising from three hundred to one thousand six 
 hundred feet above the plain. The largest of these was 
 Torullo which continued burning and throwing up immense 
 quantities of lava containing fragments of granite rock. 
 
 The annexed diagram presents the outline of the eleva- 
 ted plain j a is the cone Jorullo, and I the plam sloping 
 from the base of the cones at an angle of 6. 
 Fig. 24. 
 
 Jorullo. 
 
 58. Kilauea, in Hawaii, Sandwich Islands, is an ever 
 active, and most remarkable volcano. It is situated, not on 
 the sumnfit, but on the south-eastern flank of Mount Loa, 
 at an elevation of three thousand nine hundred and seventy 
 feet above the sea, while the summit is nine thousand seven 
 hundred and ninety feet higher. Instead of slender walls 
 around a deep crater, liable in most conical craters to be 
 demolished by the explosions of an eruption, the summit of 
 this volcano is nearly a plain, and its crater a deep abrupt 
 pit, seven and a half miles in circuit, of an oval figure, em- 
 bracing about four square miles. At a depth of six hundred 
 and fifty feet below the brim of this pit, a narrow plain of 
 hardened lava, called the " black ledge," projects like a vast 
 terrace or gallery around the whole interior ; and within 
 this gallery, below another similar precipice of three hun- 
 dred and forty feet, lies the bottom, a vast plain of volcanic 
 rock, more than two miles in length. In this plain are 
 pools of boiling lava, which vary at different times in num- 
 5 
 
50 
 
 STRUCTURE OF THE EARTH. 
 
 ber and extent, one of which, in November, 1840, was 
 fifteen hundred feet long by one thousand broad. The lava 
 boils in these pools with various degrees of energy, some- 
 times flowing over, cooling, and thus raising a rim, or pass- 
 ing in glowing streams to distant parts of the crater. At 
 times, the activity of the ebullition is such as to throw up 
 jets of the lava thirty or forty feet high. The overflowing 
 of the pools raises cones, sometimes one hundred feet high, 
 with central cavities, from which vapors issue. 
 
 The adjoining figure represents a singular spire of lava, 
 resembling a petrified fountain. From small vents, the 
 liquid lava, thrown up in jets, falls over, raising a conical 
 
 Fig. 25. 
 
 Lara Spire at Kilauea. 
 
IGNEOUS AGENCIES. 51 
 
 base. The column is built up by the successive drops of 
 lava which fall upon each other, as they are tossed up. 
 These spires vary in height from a few inches to forty feet, 
 and are miniature craters of eruption.* 
 
 59. Four eruptions of Kilauea have occurred since 
 A. D. 1789. That of 1840 was most extraordinary. For 
 several years previous, the lava had been rising in the 
 crater, until it stood about fifty feet above the "black 
 ledge." The immense pressure of the lava and gases 
 opened fissures in the sides of the crater, and the molten 
 flood flowing in a subterranean channel six miles, emerged 
 in an ancient wooded crater, rising in it to the height of 
 three hundred feet; from this again, passing sometimes 
 under ground for miles, and then upon the surface, filling 
 the valleys, melting the hills, and consuming the forests 
 along its path, it poured itself for three weeks with loud 
 detonations into the sea. The length of the stream from 
 Kilauea to the ocean was about forty miles : it accom- 
 plished the passage in three days. The breadth of the 
 stream varied from one to four miles, and its depth from 
 ten to two hundred feet. The coast was extended by it a 
 quarter of a mile into the ocean. The whole area covered 
 by it is estimated at fifteen square miles, and the amount 
 of lava at six thousand millions of cubic feet. The waters 
 of the ocean were so heated that the shores were covered 
 for twenty miles with dead fish. Night was converted into 
 day, its glare being visible more than one hundred miles at 
 sea, and at the distance of forty miles fine print could be 
 read at midnight. The lava in Kilauea fell four hundred 
 
 * Prof. Dana, in the "Geology of the United States Exploring 
 Expedition." 
 
52 STRUCTURE OF THE EARTH. 
 
 feet, showing that the eruption was a disgorgement of the 
 lava of that crater. The Sandwich Islands present re- 
 markable regions of volcanic action, in which several craters 
 occur within a few miles. 
 
 Fig. 26. 
 
 Diamond Hill and adjacent Volcanic Cones in OaHu, Sandwich Islands. 
 
 60. The phenomena of submarine volcanoes are influ- 
 enced by the pressure of the water of the ocean, which 
 may at certain depths entirely suppress any exhibition of 
 volcanic agency exerted at the bottom. History abounds 
 with authentic instances of the rise of islands. The Gre- 
 cian Archipelago is studded with them, and the origin of 
 many of the Aleutian islands is within recorded observa- 
 tion. The structure of others (some of them large, as 
 Hawaii, which covers four thousand square miles, and 
 whose summit is nearly fourteen thousand feet above the 
 ocean,) reveals their history. Teneriffe, St. Helena, and 
 the Azores have the same origin. In the year 1811, an 
 island (Sabrina) arose out of the ocean, near the Azores, 
 to the height of three hundred feet, with a circumference 
 of one mile, and after remaining six months, disap- 
 peared. 
 
 A remarkable volcanic island appeared in the Mediter- 
 ranean sea, in the month of July, A. D. 1831, which re- 
 mained visible above the water about three months. A 
 fortnight previously, shocks were experienced on board a 
 ship passing the spot, which produced an impression like 
 
IGNEOUS AGENCIES. 
 
 53 
 
 the striking of the ship on a sand bar. On the tenth of 
 July a column of water, like a water spout, was seen rising 
 out of the sea, and soon after a dense mass of steam as- 
 cended to the height of one thousand eight hundred feet. 
 On the eighteenth of July, a small island had appeared, 
 with a crater in its center, ejecting volcanic matter. It 
 had, on the fourth of August, attained an elevation of two 
 hundred feet, and a circumference of three miles. After 
 this, it diminished by subsidence and the action of the 
 waves, so that at. the end of October, no vestige of the 
 crater remained. In A. D. 1833, a submerged reef, about 
 three-fifths of a mile in extent, existed in its stead. 
 
 Fig. 27. 
 
 Graham's Island, as it appeared in August, A. D. 1831. 
 
 . 61. The term lava is applied to any mineral sub- 
 stance which has flowed from a volcano in a melted state. 
 Lavas consist essentially of two minerals, feldspar and 
 augite. When the feldspar predominates, the lava is 
 
 UN! 
 
54 STRUCTURE OF THE EARTH. 
 
 called fcldspatliic ; it is light colored, and has specific 
 gravity not exceeding 2.8. Trachyte is such a lava. 
 "When the augite prevails, the lavar is dark colored, has 
 specific gravity exceeding 2.8, and is called augitic 
 basaltic. Lava cooled under great pressure is dense, like 
 the older rocks ; when cooled under pressure of the atmos- 
 phere only, it is porous, distended by gases. Feldspathic 
 lava, flowing into water, is converted into pumice, which is 
 so light as to float on the surface of the water. When 
 silex enters largely into the composition of lava, it pro- 
 duces volcanic glass obsidian, which resembles ordinary 
 glass, and is of a smoky hue. A portion of the lava of 
 Kilauea is vitreous, and is sometimes blown by the wind 
 into minute threads, called by the natives u Pele's hair." 
 The lava of this volcano is more fluid than that of most 
 volcanoes. Lava is a very poor conductor of heat, and 
 consequently the interior portions of a lava stream retain 
 their heat a great length of time. Lava ejected from 
 Etna in 1819 was sufficiently hot and fluid to move a yard 
 a day nine months after eruption. In another instance, 
 lava was in motion ten years after it was ejected. The 
 lava of Kilauea, erupted in June, 1840, was so hot in 
 November that pieces of paper introduced into fissures in 
 it were immediately inflamed. Lava flows within a crust 
 Which is rapidly formed over its surface. On piercing this 
 crust, the fluid within flows out, and its course may in this 
 way sometimes be controlled. In the summer of A. D. 1828, a 
 mass of ice was discovered on Etna, beneath a bed of vol- 
 canic ashes and lava, whose non-conducting property had 
 preserved it for centuries from melting. 
 
 63. Earthquakes are movements, more or less violent, 
 of the superficial crust of the earth, consisting usually of 
 
IGNEOUS AGENCIES. 65 
 
 rapidly succeeding undulations, oftentimes accompanied by 
 sounds, and traceable in particular directions. Three dis- 
 tinct kinds of motion are recognised. 1st, The perpendicu- 
 lar , which acts from below upward, like the explosion of a 
 mine. This was witnessed in the destruction of Biobamba, 
 in A. D. 1797, when many of the bodies of the inhabit- 
 ants were thrown upon a hill several hundred feet high. 
 2nd, The horizontal, which takes place in successive undu- 
 lations, proceeding in a uniform direction. 3rd, The rota" 
 tory or vorticose, which seems to be due to interferences of 
 undulations, causing a whirling movement of the Earth, by 
 which buildings are twisted round, and parallel rows of 
 trees are displaced without being prostrated. The first 
 movement is the most common and harmless, while the 
 third occurs only in the most disastrous earthquakes. A 
 hollow sound, like a mine-explosion, often accompanies an 
 earthquake, which is sometimes heard as distinctly at a 
 great distance from the scene as in its immediate neighbor- 
 hood. The progression of earthquakes is most commonly 
 in a linear direction, with a velocity of twenty or thirty 
 miles in a minute ; but sometimes the concussion proceeds 
 from the center of a circle or ellipse, decreasing in force P 
 toward the circumference. Their duration is very brief; - 
 thousands of lives are sacrificed, and cities and provinces 
 
 are reduced to ruins in a few seconds. No country is , ' 
 
 J x_ at w 
 entirely exempt from their visitations, but particular re- 
 
 ,. x . , . 
 
 gions are subject to severe, continuous, and extensive con- 
 
 cussions, as Central and South-eastern Asia, South America, >*j 
 and Mexico. Slight shocks are so frequent that there i 
 reason to presume that the surface is continually agitated V 
 by concussions on some of its points. There are accounts 
 of no less than three thousand four hundred and thirty-two fc 
 
56 STRUCTURE OF THE EARTH. 
 
 distinct earthquakes which have occurred in Europe since 
 the commencement of the fourth century of the Christian 
 era. 
 
 1 63. The most remarkable earthquake on record is that 
 which destroyed the city of Lisbon, in A. D. 1755. It 
 commenced with a sudden subterranean sound : this was 
 immediately followed by violent shocks, which demolished 
 the greater portion of the buildings, destroying the lives 
 of sixty thousand persons. A large quay, to which hun- 
 dreds of people had resorted for safety from the falling 
 buildings, was instantaneously engulfed in an unfathomable 
 chasm, from which nothing ever rose to the surface. 
 Yessels were thrown violently aground; the bed of the 
 river was raised to the surface, and immediately afterward 
 the ocean came rolling in, fifty feet higher than usual. 
 The walls of some houses were seen to open from top to 
 bottom more than a quarter of a yard, and close again so 
 accurately as to leave but slight trace of the injury. The 
 movement of this earthquake was undulatory, progressing 
 about twenty miles a minute, agitating a surface four times 
 as large as Europe and nearly one-twelfth of the whole 
 superficies of the globe. The water in the lakes of Scot- 
 land rose and fell three feet. The earthquake was per- 
 ceived at Fahlun in Sweden, Barbadoes, and on Lake 
 Ontario. The sea rose on the West India islands, and a 
 ship one hundred miles west of St. Vincent suffered so 
 severe a shock that the seamen were thrown upon the deck. 
 64. The great earthquake of Calabria, Southern Italy, 
 in A. D. 1783, was distinguished by the concentration of 
 its violence, heaving the surface like the waves of the sea. 
 Radiating from the town of Oppido as a center, its violence 
 was manifested over an area of five hundred square miles. 
 
IGNEOUS AGENCIES. 
 
 57 
 
 About two hundred towns and villages were destroyed, and 
 nearly one hundred thousand people perished. The move- 
 ment was rotary, as shown by the twisting of the stones of 
 
 Fig. 28. 
 
 Obelisk of St. fer.uno. 
 
 the obelisks of St. Bruno, which were 
 turned from six to nine inches from 
 their former position. A chasm, a 
 mile long, one hundred and five feet 
 broad, and thirty feet deep, was form- 
 ed; and another, three-fourths of a 
 mile long, one hundred and fifty feet 
 broad, and one hundred feet deep, 
 with numerous elevations and de- 
 pressions : and many disputes arose 
 respecting the ownership of lands 
 which had shifted position. In the 
 year 1819, a large tract of land at 
 the mouth of the Indus, with villages, 
 was submerged, and another tract, called the Ullah Bund, 
 fifty miles long and sixteen broad, was elevated ten feet. 
 
 65. Violent and extensive earthquakes occur in the vicin- 
 ity of the Andes, in South America. A terrible convulsion 
 was experienced in 1822 on the coast of Chili, by which 
 an area of one hundred thousand square miles was perma- 
 nently elevated three feet. In 1812, LaGuayra and Caraccas, 
 in South America, were destroyed by an earthquake of great 
 violence. In December of the previous year, a scries of 
 convulsions commenced along the valley of the Mississippi, 
 from New Madrid to the mouths of the Ohio and St. Fran- 
 cis rivers. The earth rose in great undulations. Lakes., 
 twenty miles in extent, were suddenly formed, and others 
 were drained. Extensive chasms opened in a direction 
 North-east and South-west, and new islands were formed in 
 
58 STRUCTURE OF THE EARTH. 
 
 the river. These agitations of the Mississippi valley 
 ceased, when the South American cities were destroyed. 
 This coincidence, together with the direction of the 
 chasms, indicates a subterranean communication between 
 the localities, which are more than two thousand miles 
 apart. The violent earthquake of G-uadaloupe, which oc- 
 curred in A. D. 1842, extended in a direction North-west 
 to South-east, from Charleston, South Carolina, to the 
 mouth of the Amazon river, destroying several towns in 
 the West India islands. 
 
 66. Hot-sprinys are common in the immediate vicinity 
 of volcanoes. They are found upon the slopes of Etna 
 and Vesuvius, but in great numbers, and with more im- 
 posing features in that remarkable field of igneous agency, 
 Iceland, where they are called Geysers raging fountains. 
 Within a circuit of two miles more than one hundred of 
 them may be found. They are situated in sight of Mount 
 Hecla, in a plain at the foot of a hill of gray trachyte (an- 
 cient lava.) The crater of the great Geyser is a flattened 
 cone of silicious matter; the basin within is of an oval 
 figure fifty-six feet by forty-six, terminating at the bottom 
 in a perpendicular pipe, seventy-eight feet deep. Usually 
 the basin is filled with clear water of the temperature of 
 180. 
 
 At times a subterranean sound, resembling that made 
 by a volcano during an eruption, is heard, and then a 
 slight tremulous motion is perceived on the rim of the 
 fountain ; the surface of the water in the basin becomes 
 convex, and large bubbles of steam rise and burst, throw- 
 ing up the boiling water several feet high : a heavier 
 noise is heard below, and suddenly there shoots up a 
 column of water to the height of one hundred feet, dis- 
 
IGNEOUS AGENCIES. 
 
 59 
 
 persing at the summit into dazzling white foam. After a 
 brief period, a column of steam issues, with a loud, roaring 
 noise ; this is followed by another column of water higher 
 than the preceding ones, mingled with stones, accompanied 
 by loud detonations. The phenomenon lasts a few min- 
 utes, and then the basin resumes its tranquil state. These 
 waters encrust the surrounding soil, and all substances 
 upon which they fall, with silica. 
 Fie. 29. 
 
 Basin of the great Gteyser of Iceland 
 
 Boiling springs are found also in the Azores, Java, and 
 the volcanic regions of Central and South America. 
 
 Thermal springs are not confined to the vicinity of 
 active volcanoes, but are found in the Alps, and Pyrenees, 
 in Virginia, Arkansas, and Oregon. In all cases, however, 
 they arc situated near mountains or rocks which have been 
 subjected to igneous agency. The temperature of the 
 
60 
 
 STRUCTURE OF THE EARTH. 
 
 water varies in different springs; that of the seventy 
 springs in Arkansas ranges from 118 to 148. Thermal 
 waters are charged with salts and gases ; hence they are 
 mineral waters, as those of Bath in England, Wiesbaden 
 in Germany, Saratoga, and the Sulphur Springs of Virginia. 
 67. Another apparent manifestation of igneous agen- 
 cy is the gradual elevation or subsidence of portions of the 
 earth's surface. An interesting example of this is presented 
 by the remains of the temple of Jupiter Serapis, at Puz- 
 zuoli, on the shore of the Bay of Baice, near Naples. The 
 
 building was originally of a 
 quadrangular form, twenty 
 feet in diameter, the roof be- 
 ing supported by twenty-four 
 granite columns, and twenty- 
 two of marble : three of them 
 
 Fig. 30. 
 
 Pillars at Serapis. 
 
 are still standing. The tallest 
 of them is forty-two feet in 
 height; the surface is smooth 
 and uninjured to an elevation 
 of twelve feet, where com- 
 mences a band of perforations 
 made by the Lithodomus (lithos, stone, and clomos, a house,) 
 a shell-fish inhabiting the Mediterranean sea. These per- 
 forations, many of which still contain shells, cover a space 
 of nine feet, and are so numerous and deep as to prove that 
 the pillars were for a long time immersed in sea water ; the 
 lower portions were protected by rubbish and puzzolana 
 volcanic tufa; the upper portions projected above the water, 
 beyond the reach of the lithodomi. The platform of the 
 temple is now one foot below high-water mark, and the sea 
 is one hundred and twenty feet distant. These columns 
 
IGNEOUS AGENCIES. 61 
 
 have been depressed and again elevated more than twenty 
 feet, the relative level of the land and sea having changed 
 at least twice since the Christian era, so gently that 
 these columns have not been prostrated. Professor Bab- 
 bage attributes their tranquil depression and elevation to 
 the contraction and expansion of the rocks on which 
 they stand, in consequence of variations of temperature. 
 A small volcano solfatara and a hot spring exist in 
 their vicinity. The columns are again gradually sub- 
 siding. 
 
 68. The gradual change of relative level of sea and 
 land, on an extensive scale, in regions remote from active 
 volcanoes and violent earthquakes, is exemplified on the 
 coasts of the Baltic sea and Northern 6cean. Beds of ma- 
 rine shells and sunken rocks have been raised above the 
 water-line, and the shells of species now living on the 
 shore are found fifty miles inland and at an elevation, as 
 ascertained by Bravais' measurements, of six hundred feet 
 above the ocean. The northern portion of the coast rises 
 most rapidly ; the average elevation is stated to be four 
 feet in a century. Raised beaches found in England at a 
 height of from twenty to two hundred feet above the 
 existing sea-level, with shells and all the features of the 
 beaches of the present sea-coast, show the same process on 
 that island. Mr. Darwin has also shown that the southern 
 part of South America, at least twelve hundred miles on 
 the east coast, from Rio de la Plata to the straits of Ma- 
 gellan, and a greater distance on the west coast, has been 
 raised from one to four hundred feet. The north-eastern 
 coast of the United States is supposed to be in the same 
 process of gradual elevation. On the other hand, a large 
 portion of the coast of Greenland has been for four centu- 
 
 6 
 
62 STRUCTURE OF THE EARTH. 
 
 ries gradually sinking. Ancient buildings on low islands 
 and near the coasts, have been submerged. The depression 
 of extensive areas in the Pacific and Indian oceans is 
 proved by the existence of banks of dead coral several 
 hundred feet deeper than the limit at which the animal 
 can have lived. On the coasts of Europe and America 
 are found submarine forests, consisting of trees and 
 stumps, together with peat, in the position in which they 
 originally grew, depressed several feet below the level of 
 the sea. 
 
 ORGANIC AGENCIES. 
 
 69. Although organic agencies are less influential in 
 modifying the crust of the globe, than aqueous and igneous 
 agencies, still vegetable and animal bodies not unfrequently 
 make up a large portion of important and extensive rock 
 formations ; and are regarded by the geologist with special 
 interest because they furnish the clearest indications of the 
 physical conditions of the globe at the time and place in 
 which they lived. 
 
 70. Marine plants, which oftentimes cover the surface 
 of the ocean so thickly that ships are impeded in their pro- 
 gress by them, are very perishable, and contribute little to 
 the formation of rocks. But the remains of terrestrial 
 plants enter into the composition of soils, and form exten- 
 sive deposits in the great swamps. Peat consists principally 
 of the fibrous roots of mosses, especially of the Sphagnum, 
 which continually throw up new shoots from the decaying 
 extremities below. When dry it consists of from sixty to 
 ninety-nine per cent, of carbonaceous matter, forming a valu- 
 able fuel. Peat beds, of from four to twenty feet thickness, 
 are common in Ireland and Scotland. The " moss" on the 
 
ORGANIC AGENCIES. 63 
 
 river Shannon extends over one hundred and fifty square 
 miles } and one-tenth of the whole island, it is estimated, is 
 covered with peat, called by the Irish, turf. It is constantly 
 accumulating, with a rate of increase afiected by the 
 amount of moisture and other circumstances; in Europe 
 its increase is estimated at seven feet in thirty years. It 
 is confined to the colder regions of the earth, since the 
 heat of the torrid zone causes very rapid decomposition of 
 organic matter. The process by which it is converted into 
 coal has been, in some instances, observed. In some peat 
 bogs large trees have been found erect ; its antiseptic power 
 over vegetable and animal substances is remarkable, 
 preserving them from decay even for centuries. Peat 
 swamps sometimes burst their barriers and deluge the sur- 
 rounding country with black mud. 
 
 71. The floods of large rivers carry down immense 
 quantities of timber, which meeting obstructions accumulate 
 in rafts, or pass on to the delta, or the ocean. On the Mis- 
 sissippi and Red rivers, rafts have been formed several miles 
 long, bearing soil and growing trees. The delta of the 
 Mississippi contains many layers of wood undergoing the 
 slow process of conversion into coal ; but much of the drift- 
 wood passes out to sea, and is conveyed by marine currents 
 to far distant coasts, or becoming water-logged, sinks to the 
 bottom of the ocean. The Icelander is supplied with wood 
 for fuel and building boats, by the ocean, which brings the 
 drift-wood of the Mississippi and the rivers of Central 
 America to the coasts of his island. The vegetable growth 
 of arctic climates is stunted and slow, while that of the 
 tropics is gigantic and rapid. 
 
 72. The most efficient organic agency in modifying the 
 crust of the earth, is exerted by the most minute and insig- 
 
64 STB.UCTURE OF THE EARTH. 
 
 nificant members of the Animal Kingdom the coral Zoo- 
 phytes and animalcules. 
 
 73. The animals which produce coral are very simple, 
 resembling plants both in their figures and colors. Until 
 the last century they were described as marine plants and 
 flowers. They differ from plants in having distinct mouths 
 and cavities to receive and digest food, and sensibility to 
 pleasure and pain. They have no system of vessels for cir- 
 culation, no glands, no distinction of sex, and no senses but 
 those of touch and taste. Their texture is not that of jelly, 
 but of flesh. They vary in size from a minute fraction 
 hweu.rof an inch, to eighteen inches in diameter. They live 
 t> enr /VK ^ > ^ther solitary, or in masses of hundreds of thousands. 
 Individuals are called polyps; the whole animal structure, 
 whether simple or compound, is termed a Zoophyte. Coral 
 is not a collection of cells in which the polyps may 
 conceal themselves, but an internal skeleton : nor do they 
 exhibit any instinct or industry in forming it. It results 
 from vital processes in their system, which they no more 
 control, than do the more highly organized animals the for- 
 mation of their bones. The species are perpetuated by eggs 
 and buds. The mode of budding is very similar to the 
 budding of plants. A bud swells and bursts on the side or 
 extremity of the parent, acquires tentacles and visceral 
 cavity, and produces other buds and eggs. Polyps may also 
 be multiplied by artificial section, each part having the 
 power of reconstructing a complete animal. 
 
 Every Zoophyte, however large or numerous the colony, 
 commenced as a single polyp ; successive budding may have 
 produced myriads of polyps, which eat and digest separately, 
 but all aid in the growth of the common mass. An injury 
 to one of them is felt by the surrounding ones, but not al- 
 
ORGANIC AGENCIES. 
 
 65 
 
 ways through the whole mass. Some polyps may be turned 
 inside outward with no apparent injury, and the head of 
 one polyp may he engrafted on the hody of another. 
 While the process of budding is advancing at the surface, 
 death is occurring in the central and lower parts of the 
 coral, which, when dead, serve only to support the external 
 living part. 
 
 74. Numerous genera and species of these Zoophytes, 
 have been described by Naturalists. A few of them will 
 serve as illustrations of their general appearance. 
 
 Fig. 31, presents three branches Fig. 31. 
 
 of the Caryophyllia, the polyps of 
 which are of a bright green color, 
 and reside in the radiating cham- 
 bers. 
 
 Fig. 32. 
 
 CaryophyUia. 
 
 The Meandrina, or brain- 
 stone coral, so called from its 
 resemblance to the convulutions 
 of the brain of animals, as seen 
 
 in Figure 32, is of a brown color, F j 33 
 
 and attains the size of several feet 
 
 in circumference. In Figure 33, 
 
 the same coral appears divested of 
 
 its fleshy covering, and exhibits the 
 
 cells within which the polyps par- 
 tially conceal themselves. 
 
 The Astrea is a very common 
 
 and widely diffused Species. It Meandrina without polyps. 
 
 6* 
 
66 
 
 STRUCTURE OP THE EARTH. 
 
 Fig. 34. 
 
 derives its name from its 
 radiated or star-like appear- 
 ance. The polyp is repre- 
 sented in Figure 34, with 
 its tentacles extended. It 
 moves these tentacula, or 
 arms, which are arranged 
 about its head, with great 
 
 1. Star Coral. 2. The polyp magnified. rapi( Jity i n taking its food. 
 
 When the animal is removed, the F - 35 
 
 stellate appearance of the coral is 
 more manifest, as seen in Figure 35. 
 A still more common genus, seen 
 in cabinets, and as mantel ornaments, 
 is the Madrepore, Figure 36. It is 
 branched and studded throughout 
 with distinct cells. 
 
 - The Flustra, Figure 37, is a deli- Astrea without polyp8 ' 
 cate coral, often attached to sea 
 weeds and shells thrown upon the 
 shore. With a microscope, its po- 
 lyps, if examined in the water, may 
 be seen expanded, and retracted in 
 their cells. 
 
 75. Most corals are white, even 
 when the animals secreting them 
 are highly colored. But the Co- 
 " rallium Rubrum red or precious 
 
 Madrepore. coral is of a brilliant red color, 
 
 while the investing animal is blue. It is obtained from the 
 Mediterranean and Red seas, and is extensively used for 
 ornaments. This species is shown in Fig. 38. 
 
 Fig. 36. 
 
ORGANIC AGENCIES. 
 Fig. 37. 
 
 67 
 
 Red Coral. 
 
 The Flustra. 1. Its cells. 2. The expanded polyp. 3. The polyp in its cell. 
 
 An interesting variety of coral is the Tubipora, or 
 organ-pipe coral, (Fig. 39,) composed of parallel tubes, 
 with transverse Fig. 38. 
 
 plates indicating 
 successive gene- 
 rations. It is 
 found growing 
 in the Indian 
 ocean several feet 
 in circumference, and its rich carmine red presents a bril- 
 liant ground-work for its polyp of emerald green color. 
 Fig. 39. Ehrenberg speaks in enthu- 
 
 siastic terms of the exqui- 
 site beauty of forms,. and 
 gorgeous colorings of the 
 corals of the Ked sea. 
 " What paradise of flowers," 
 says he " can rival in beau- 
 ty these living wonders of the ocean." 
 
 76. It is in the extensive coral-reefs, that the Zoophytes 
 evince the power of organic agency in modifying the sur- 
 face of the earth. The great reef along the line of the 
 
 Organ-pipe Coral. 
 
68 STRUCTURE OF THE EARTH. 
 
 northern coast of New Holland is more than one thousand 
 miles long : a link of three hundred and fifty miles of it is 
 1 continuous, with no passage or opening through it. Dis- 
 appointment Islands and Duff's Group are connected by 
 coral reefs so continuous that the natives travel over them 
 from one island to another. Reefs occur in the Pacific 
 ocean from one thousand one hundred to one thousand two 
 hundred miles long, and from three hundred to four hundred 
 miles broad, and of a thickness from thirty to sixty feet, 
 constituting an enormous mass of calcareous matter. These 
 Zoophytes live only in warm seas and near the surface ; no 
 indications of them are obtained from deep sea-soundings. 
 Their growth is slow, but incessant, their numbers incal- 
 culable : they are usually attached to the shores of rocky 
 islands, or to the crests of submarine ridges, rarely at a 
 depth exceeding sixty feet. 
 
 77. Coral reefs are classified as Fringing, Barrier, 
 and Circular reefs : the latter are called, by the natives 
 of the Pacific islands, atolls. 
 
 Fringing reefs are belts of coral attached to 'the coasts 
 of islands or continents. When the coast is precipitous, 
 the belt is narrow; but when it is gently sloping, it is 
 covered with coral until it reaches the depth of about sixty 
 feet, where the animals cease to exist. 
 
 78. Barrier reefs are parallel to the coast, and sepa- 
 rated from it by a deep channel. Figure 40 presents the 
 barrier reef of Bolabola, in the Pacific ocean, encircling 
 the* island, but separated from it. The reef is in this in- 
 stance covered with trees. These reefs vary from three to 
 forty miles in diameter. On the ocean side they termi- 
 nate abruptly in deep water; but within, the slope is 
 gradual. On the outside, the hardier species of Zoophytes 
 
ORGANIC AGENCIES. 
 
 maintain a sturdy growth, resisting a heavy ocean surf, 
 while the frailer varieties nourish in the placid waters 
 
 within. 
 
 Fig. 40. 
 
 Barrier Reef of Bolabola. 
 
 79. The circular reefs, or atolls, are the most common 
 forms of coral islands. The diameter of the circles vary 
 from one mile to forty miles, and their breadth from a few 
 yards to more than a mile. They are not always circular; 
 
 Fig. 41. 
 
 The Coral Isle. Whitsunday. 
 
 one is thirty miles long by six broad. They enclose a 
 space of quiet waters, called a lagoon, which communicates 
 
70 STRUCTURE OF THE EARTH. 
 
 with the ocean by one or more openings through the reef. 
 The origin of these circular isles has been the subject of 
 much discussion. They have been supposed to proceed 
 from the growth of the coral upon the circular rims 
 of volcanic craters beneath the surface of the ocean; 
 and some of their phenomena favor such a view. But 
 the subsidence of the islands, about which the corals 
 accumulate as fringing reefs, furnishes a more satis- 
 factory explanation of their origin. Figure 42 presents a 
 section of the island and reef of Bolabola. When the 
 level of the sea was at the lower line, a fringing reef at- 
 tached itself to the island at A B and B A. As the island 
 sunk in the ocean, the reef grew upward, and formed the 
 barrier reef A' A', the upper line now constituting the 
 ocean level. It is now a vertical section of the reef, island, 
 
 Fig. 42. 
 
 Section of a Coral Island. 
 
 and intervening water of Figure 40. When the island has 
 disappeared beneath the ocean level, we have the circular 
 reef or atoll, enclosing a lagoon as in Whitsunday, Fig. 41. 
 80. But the movement of the islands is not exclusively 
 that of subsidence ; many of them have emerged from the 
 ocean, and are still rising. The evidence of this is found 
 in ancient reefs occurring inland and at great elevations 
 above the sea. Upon the summit of the highest mountain 
 in Tahiti, an island composed almost entirely of volcanic 
 rocks, there is a reef of ancient coral attached to the rocks. 
 
ORGANIC AGENCIES. 71 
 
 This could have grown only in the ocean, and has since 
 been raised to its present position. In the Isle of France 
 also occurs a bed of coral, at a distance from the ocean. A 
 portion of. it is enclosed by two streams of lava, in which 
 the characteristic effects of heat are exhibited in its parti 
 crystalization conversion into compact limestone ormarbl 
 
 81. Coral reefs, having grown up to the surface of the 
 sea, extend laterally, increasing their breadth . The con- 
 stant action of the waves accumulates calcareous 
 shells, sea weeds and drift, upon sheltered portions of the @ 
 reef: in the soil thus formed, seeds, conveyed by 
 ocean or by birds from islands or the continent, spring up, 
 and the reef becomes a habitable island. 
 
 The annexed figure presents a view of the peculiar fea- ^ 
 tures of a Pacific island, with its fringing and barrier 
 
 Fig. 43. 
 
 A Pacific Ocean Island, with coral reefs. 
 
 One of the most singular peculiarities of coral islands is 
 the shore platform around them. It is a flat surface, often 
 several hundred feet in width, but little above low tide level. 
 Upon this lie huge masses of reef rock, worn into fantastic 
 shapes. The platform is the result of the abrading action 
 of the sea, and is not strictly confined to coral rocks, but 
 occurs in sandstone shores similarly exposed, as exemplified 
 in Figure 44.* 
 
 * Dana's Geology of the United States Exploring Expedition. 
 
72 STRUCTURE OF THE EARTH. 
 
 Fig. 44. 
 
 [r It 
 82; 
 
 Shore Platform, "The Old Hat," Bay of Islands. 
 
 The minutest forms of animal life, the microscopic 
 animalcules, commonly called Infusoria, from their occur- 
 ring in great quantities in water infused with vegetable 
 matter, are also important geological agents. Some of 
 them exhibit the simplest conceivable conditions in which 
 animal life can exist ; but others show a complex organiza- 
 tion, with muscular, nervous and vascular systems. Many 
 of them are covered with shields of silica, or the oxide of 
 iron, whose remains, after the death of the animals, consti- 
 tute extensive deposits, although they are so minute that 
 40,000,000,000 of them occupy only one cubic inch. 
 Ehrenberg has demonstrated the existence of monads, 
 which do not exceed the twenty-four thousandth part of an 
 inch in length, and so thickly crowded in the fluid as to 
 leave intervals not greater than their own diameter. 
 Hence he computes that each cubic line of the fluid con- 
 500,000,000 of these monads. A drop of water, 
 dLMf WMHJ ; therefore, may include a number of these infusoria nearly 
 quite equal to the present number of human beings on 
 globe. They are found in the ocean as well as in fresh 
 ^a, water. The beds of marl beneath peat swamps, and at 
 bottom of ponds, are composed chiefly of their shells, 
 and are often several feet in depth. The red scum seen 
 
 
ORGANIC AGENCIES. 73 
 
 floating on the surface of stagnant water consists fre- 
 quently of the shields of oxide of iron belonging to these 
 animals. Ehrenbcrg has obtained several pounds weight 
 of the silicious shields of infusoria, which he reared. In 
 case tripoli, or " rotten stone/' (which is a mass of fossil 
 infusorial shells,) should become scarce, he proposes to 
 supply the market from this source 
 
 83. The rapidity of their multiplication is most aston- 
 ishing, one individual of the Hydatina senta having been 
 known to increase in ten days to 1,000,000; in eleven 
 days to 4,000,000; and in twelve days to 16,000,000. Of 
 another species, Ehrenberg says, one individual is capable 
 of becoming 170,000,000,000,000 in four days. This rapid 
 multiplication is effected by eggs, buds, and spontaneous 
 division into two or more parts, each one of which very 
 soon becomes a perfect animalcule ; this also accounts for 
 their wide diffusion, and sudden appearance in countless 
 numbers. They are found in the waters, upon the land, 
 and in the fluids of living, healthy plants and animals. 
 Only those, however, which have hard shells, leave any 
 trace of their existence after death. Ehrenberg has de- 
 scribed about one thousand living species. 
 
 Snow is sometimes found in New Shetland and on the 
 Alps, of a red color, and occasionally green. This is due 
 to an admixture of F j 45 
 
 an infinite number of 
 microscopic plants of 
 low organization 
 many of them of the 
 
 tribe Of Algae. They Infusoria in Snow. 
 
 are of globular form, celluler structure, and from one one- 
 thousandth to one three-thousandth of an inch in diameter. 
 
 7 
 
74 STRUCTURE OF THE EARTH. 
 
 Their liquid portions contain myriads of animalcules. Fig. 
 45 exhibits a magnified view of these singular beings. 
 Their nature is adapted to a very low temperature, so that 
 they can not bear a temperature above the freezing point 
 of water, but when the snow melts they die. 
 
 84. Molluscous animals, by furnishing extensive accu- 
 mulations of shells, essentially modify the structure of the 
 surface of the earth. Shell-beds are found beneath the 
 waters, and upon the shores of the ocean, lakes and ponds, 
 producing beds of shell marl. Some shell-beds consist of 
 fragments of numerous species mingled indiscriminately, 
 broken and drifted by the waves and currents j while others 
 are made up of a single species that lived in community, as 
 the oyster, which in some places covers the bottom of the 
 ocean, excluding all other genera, several miles in extent. 
 Some species live only in the mud, while others seek sand 
 for their habitations. Certain species live only attached to 
 the shores, others in shallow water, and others still in water 
 varying in depth from one hundred to one thousand feet. 
 The number of families is much the greatest in shallow 
 water, decreasing as we descend, and ceasing entirely in 
 very deep water. Temperature, nature of the bottom, 
 amount of light and food, determine the residence of each 
 species. After the death of the animals, their shells, pro- 
 tected from decay, constitute in some instances a large part 
 of the mineral bed forming by deposits from the water in 
 which they lived. 
 
 85. The remains of fishes, reptiles, quadrupeds, birds, 
 insects, and of men also, are entombed in deposits now 
 forming, but in much smaller quantities, than those of 
 corals, infusoria and shell-fish. Extraordinary occurrences, 
 as the engulfment of cities by earthquakes, the destruction 
 
ORGANIC AGENCIES. 75 
 
 of immense shoals of fishes by submarine volcanic agency, 
 the overwhelming of herds of cattle by sudden inundations, 
 and the drowning of clouds of locusts, produce accumula- 
 tions of their remains, highly indicative of the state of the 
 world at the time in which they lived, just as the fossils of 
 the rocks, formed many ages since, are characteristic of 
 the periods of their formation. But the bodies of most 
 land animals, even the hardest portions of them their 
 skeletons undergo decomposition upon dry land, and leave 
 no trace of their forms. 
 
 86. The number of different kinds species of living 
 plants and animals is very great. Eighty thousand species 
 of plants have been described by botanists, and the entire 
 number undoubtedly exceeds one hundred thousand. Pro- 
 fessor Agassiz estimates the number of living species of 
 animals at two hundred and fifty thousand j mammalia 
 those which suckle their young, two thousand ; birds, six 
 thousand ; reptiles, two thousand ; fishes, ten thousand ; 
 mollusks shell-fishes, fifteen thousand ; insects and crusta- 
 ceous animals, one hundred thousand ; and the star-fishes, 
 coral polyps, &c., ten thousand. While individuals of each 
 of the species are constantly dying, the species is per- 
 petuated through centuries. Some species, however, have 
 become extinct, within the observation of man. We have 
 no proof of the introduction of a species since the creation 
 of the human race. 
 
 87. The distribution of plants and animals upon the ' 
 surface of the earth is very unequal, being influenced by the 
 amount of heat, light, and moisture. Each geographical or 
 climatal region has its own species ; which, in the case of 
 plants, constitute its Flora, and of animals, its Fauna. 
 There are three great climatal regions, the arctic, temperate 
 
76 STRUCTURE OF THE EARTH. 
 
 and tropical. The vegetation of the arctic region is confined 
 to mosses, lichens, and a few trees of stunted growth. The 
 Flora of the temperate region embraces the nutritious grains 
 and fruits, with lofty trees of dense fibre, durable and strong 
 the pine, oak, and cedar. The tropical region greatly 
 excels the others, in the variety and luxuriance of its pro- 
 ductions. The plants of different continents in the same 
 latitude are quite unlike ; those of Africa, for example, bear- 
 ing little resemblance to those of South America or New 
 Holland on the same parallels of latitude, each having been 
 created in its own station. 
 
 '88. The Faunas also are capable of distribution into 
 three principal divisions, in accordance with climate, viz., 
 the arctic, the temperate, and the tropical faunas. The 
 plants and animals found at high elevations on mountains 
 within the torrid zone, resemble those of colder latitudes. 
 
 The principal characteristic of the arctic fauna is its 
 uniformity, embracing few species, but very great numbers 
 of individuals in each species. The same animals are found 
 in it on the three continents, America, Europe and Asia. 
 Some large quadrupeds belong to this fauna, as the moose, 
 the white bear, reindeer and musk-ox. Whales and seals 
 abound in the polar seas, together with star-fishes, jelly- 
 fishes and small crustaceous animals, upon which the whale 
 principally subsists : but very few polyps, and none which 
 secrete coral are found in these seas. Very few insects 
 live in this zone, and no reptiles. The color of the animals 
 of the arctic fauna is frequently white, as shown by the 
 white bear, the white fox, and the ermine, and when of 
 other hues is not brilliant. 
 
 While the number of individuals of the temperate fauna 
 is no greater than that of the arctic the number of species 
 
ORGANIC AGENCIES. 77 
 
 is much greater and more varied. Very numerous orders 
 and genera of animals, with strong contrasts of form and 
 color, are here presented. The members of this fauna on 
 different continents are similar : some of the families, gen- 
 era, and a few species are identical. The arctic and tem- 
 perate fauna are not separated from each other by any very 
 sensible limit, but gradually pass into each other ; a few 
 species of animals range through the entire extent of both 
 of them, as the musk-rat, the ermine and the European 
 field-mouse. 
 
 The predominant feature of the tropical fauna, is its 
 great variety of animals with coverings of brilliant hues. 
 Its members on different continents are quite unlike each 
 other ; they are, however, more nearly allied to each other 
 than to the members of the other faunas. 
 
 15. Besides faunas separated from each other by differ- 
 ence of climate, we have them more or less distinctly lim- 
 ited by geographical features. The interposition of moun- 
 tain chains, deserts and seas separate faunas in the same 
 latitude. The animals of the prairies of America, the 
 steppes of Asia, and the deserts of Africa, are peculiar to 
 those localities. The fauna of Oregon and California is 
 said to be more unlike that of New England, than the Eu- 
 ropean fauna is. Marine animals are distributed in the 
 same way, into local faunas. The codfish does not wander 
 far from the Newfoundland Banks. The fishes of the coast 
 of South Carolina are different from those of the West In- 
 dies. Faunas that differ much are frequently found near 
 each other, while similar faunas are oftentimes widely sep- 
 arated. The range of a species is not affected by its powers 
 of locomotion. The reindeer is no more apt to transcend 
 the limits assigned it, than is the oyster. The distribution 
 
78 STRUCTURE OF THE EARTH. 
 
 of animals is not the result of external influences, for were 
 it so, we should always find in the same circumstances sim- 
 ilar animals ; but it is a law of their being, established by 
 their Creator, analogous to the instincts with which He has 
 endowed them for self-preservation.* 
 
 90. Among the causes modifying the structure of the 
 globe, must be recognized the agency of man. This agency 
 is exerted in controlling to a certain extent the operation 
 of other agencies, aqueous, igneous, and organic, and in 
 contributing to the rocks now forming peculiar mementoes 
 of his existence. Human agency is apparent in the level- 
 ing of portions of the earth's surface j in the direction and 
 restraint of water courses; in the destruction of certain 
 species of plants and animals, and in the substitution 
 of other species. By this means some genera of animals 
 have become extinct, and others are very greatly reduced 
 in numbers. Beasts of prey disappear before advancing 
 civilization, and those animals which are sought for human 
 purposes, without domestication, as the beaver, the seal and 
 the whale, are subject to incessant invasion. Since the 
 discovery of South Georgia, in 1771, one million two hun- 
 dred thousand seals have been annually destroyed, for their 
 skins ; the animal is becoming extinct in that locality. In 
 place of the trees of the forest, man substitutes other plants, 
 particularly the grasses, thus essentially interfering with 
 the natural laws of distribution. 
 
 91. Human skeletons are found in rocks recently form- 
 ed, as in the limestone of the shore of Gruadaloupe. Por- 
 tions of these skeletons are now in the museums of London, 
 
 Principles of Zoology, by Agassiz and Gould, chap. xiii. 
 
ORGANIC AGENCIES. 
 
 79 
 
 Paris, and Charleston. They were found, together with 
 stone hatchets, arrows, and pieces of pottery, in a rock con- 
 sisting of fragments of corals, shells and sand, cemented 
 pretty firmly by the carbonate of lime held in solution in 
 the water. The shells and corals belong to species that 
 now reside in the sea in that vicinity. Figure 46 presents 
 
 Fig. 40. 
 
 Human Skeleton in the Limestone of Guadaloupe. 
 
 a view of the- specimen in the British Museum. Other 
 entire skeletons have been disinterred from the same rock ; 
 some of them found in a sitting posture. The bones have 
 not been petrified, but contain a portion of their gelatine 
 and the whole of their phosphate of lime. Stone hatchets, 
 and a piece of guaiacum wood having rudely sculptured on 
 one side a mask and on the other a frog, have been found 
 in the same bed. Human bodies clad in skins have also 
 been found preserved in peat swamps in England, with 
 coins, arms, and other implements, such as were used by 
 the Britons at the time of the Roman invasion. Great 
 numbers of human beings have been destroyed by sudden 
 catastrophes, as earthquakes and inundations. Thousands 
 
80 
 
 STRUCTURE OF THE EARTH. 
 
 Fig. 47. 
 
 were swallowed up by the great earthquake of Lisbon, ( 63,) 
 and by that of 1780 in Jamaica, which sent a wave of the 
 sea over the city of Savanna la Mar, sweeping off every in- 
 habitant. In 1787, a hurricane drove the sea upon the 
 coast of Coromandel, twenty miles inland, overwhelming 
 ten thousand of the inhabitants with a deluge of mud. 
 
 92. Not only are the bodies of men thus preserved, but 
 the products of their skill, as coins, earthenware and glass. 
 Thousands of ships are annually wrecked upon the ocean, 
 inland seas and lakes : such portions of their cargoes as are 
 not rapidly corroded or decomposed by the water, are soon 
 enveloped by the mud or sand of the bottom, and thus be- 
 come a part of the rock forming there. In figure 47 we 
 have a specimen 
 of conglomerate of 
 sand, glass beads, 
 knives, &c. cemen- 
 ted together by the 
 oxide of iron which 
 was dug up from 
 the bed of the riv- 
 er Dove, in Der- 
 byshire, England. 
 Two silver pen- 
 nies of Edward I. 
 are enclosed in the 
 specimen, which 
 
 are supposed to have been a portion of the treasures of the 
 Earl of Lancaster, lost while crossing the river, more than 
 five centuries ago.* 
 
 * Mantell's "Wonders of Geology." 
 
ORGANIC AGENCIES. 81 
 
 i 
 
 93. An examination of the phenomena of Nature, with 
 reference to the causes now modifying the structure of the 
 globe, exhibits an incessant series of changes, slow and im- 
 perceptible, or sudden and conspicuous, by which the fea- 
 tures of the Earth are essentially altered. The atmospheric 
 and aqueous agencies continually wear down the dry land, 
 and if not counterbalanced by other forces, would ultimately 
 reduce it to the level of the ocean ; while the organic and 
 igneous agencies are accumulating and elevating mineral 
 matter above the ocean's level. What is now dry land was, 
 some thousand years since, the bottom of the ocean, and 
 the present seas cover portions that were then dry land. 
 The geological history of the world is discovered by the 
 study of the deposits thus made, and thus elevated. Some 
 degree of familiarity, therefore, with the operation of these 
 natural causes on a large scale, is indispensable to the geo- 
 logical student, to enable him to interpret the meaning of 
 those past events, the results of which constitute the phe- 
 nomena of geology. 
 
CHAPTER II. 
 
 THE STRUCTURE AND POSITION OF ROCKS. 
 
 94. The term roc7c in Geology indicates any aggregation 
 of minerals, hard or soft, compact or loose. The desert of 
 Sahara is a sand rock ; so in like manner masses of clay and 
 gravel are rocks. The structure and position of rocks de- 
 pend upon their origin. The most obvious distinction of 
 mineral masses is into stratified and unstratified rocks. 
 
 Stratified rocks are such as occur in layers included be- 
 tween nearly parallel planes ; varying in thickness, from a 
 fraction of an inch to many feet. The whole mass of rock 
 is sometimes called a stratum, and the parallel subdivisions 
 of it are termed beds or layers ; the more minute subdi- 
 visions are laminae, which are generally parallel to the planes 
 of stratification. The term bed is also applied to a mass 
 which is wedge-shaped, or lenticular, as a bed of gypsum, 
 salt or coal. Such beds are said to be subordinate to the 
 strata in which they occur. 
 
 As strata originate from deposition in water, the strati- 
 fied rocks are termed aqueous and sedimentary. When the 
 deposit is made upon a level surface and in quiet water, 
 parallel horizontal laminae are formed ; but materials depo- 
 sited upon a steep shore, produce oblique lamination. When 
 the depositing waters are agitated by waves, the laminae are 
 
STRUCTURE AND POSITION OF ROCKS. 
 
 83 
 
 waved, and exhibit what are called ripple marJes, as exem- 
 plified in Fig. 48. 
 
 Ripple marks in the New Red Sandstone. 
 
 Such ripples may be seen in the sand and mud not only 
 on the shores, but at the bottom of rivers, lakes and the 
 ocean. Laminae sometimes occur highly curved, and twisted. 
 They could not have been deposited in these shapes, but havo 
 assumed them after deposition in consequence of the une- 
 qual pressure they have sustained. 
 
 95. The stratified rocks consist of fragments of crystal- 
 line minerals, which are made to cohere by pressure, or by 
 some cement; hence they are called mechanical, to dis- 
 
84 
 
 SEPTARIA. 
 
 Curved Sandstone in Erie County, Ohio. 
 
 tinguish them from those which exhibit a crystalline struc- 
 ture, due to chemical agency. But the subordinate beds of 
 rock-salt, gypsum, &c., are chemical precipitates from solu- 
 tion, and some stratified rocks bear the characters of both 
 
 agencies. 
 
 Fig. 50. 
 
 Septarium. 
 
STRUCTURE AND POSITION OF ROCKS. 
 
 85 
 
 96. A concretionary structure oftentimes pervades 
 rocks. The forms of the concretions are various spheri- 
 cal, ellipsoidal, lenticular, &c. Sometimes, by compressing 
 each other, they become indented and assume various 
 irregular shapes. They are frequently crystalline and con- 
 centric, having a leaf, stick, fish, or other organic substance 
 as a nucleus about which they have accumulated. Some 
 of them have fissures within, dividing the mass into irregu- 
 lar shapes, which sometimes resemble the markings of the 
 turtle's shell; hence they are called turtle-stones. The 
 name commonly applied to them is septaria y (from septum, 
 a partition.) The crevices are often filled with calcareous 
 spar crystallized limestone. From these is prepared an 
 excellent hydraulic cement. 
 
 Fig. 61. 
 
 Septaria in the banks of the Huron river. 
 
 The adjoining cut exhibits the septaria in the slaty 
 
 banks of the Huron river. Many of them are worn out 
 
 of the banks and precipitated into the river : some of them 
 
 are several feet in diameter. Some of the claystones 
 
 8 
 
86 
 
 CONCENTRIC STRUCTURE. 
 
 found in England are so regular in figure and so smooth as 
 to have given rise to the supposition that they were turned 
 in a lathe, and to have been used for money. In this 
 country, they are usually thought to be the work of water 
 or of the Aborigines.* They are caused by molecular 
 attraction, and occur mostly in clay rocks. Similar concre- 
 tions of iron ore occur in regularly ellipsoidal figures in 
 the sandstones associated with the coal, and are called kid- 
 ney iron ore. Concretions are sometimes arranged in layers 
 in a portion of the rock, while other portions are entirely 
 free from them. They sometimes consist of alternating 
 coats of calcareous spar and iron ore. 
 
 97. A concentric structure is of frequent occurrence in 
 the shales and sandstones of New South Wales. Professor 
 Dana gives a remarkable instance of it, illustrated by the 
 accompanying figure. On either side of a vertical fissure 
 
 Fig. 52. 
 
 Concentric Sandstone in New South Wales. 
 
 is a circular area of ten feet, in which the concentric coats 
 of sandstone are from half an inch to two inches in thick- 
 
 * Hitchcock's Geology. 
 
STRUCTURE AND POSITION OF ROCKS. 87 
 
 ness. This structure gradually loses the curvature and dis- 
 appears. Globular concretions also occur here, resembling 
 cannon balls dropped into mud, which are compact and 
 hard, having some foreign bodies, as carbonized wood or 
 pebbles, for their nuclei, though not always at the center 
 of the concretions. In some places they are ten feet in 
 diameter, covering the surface like artificial domes, and 
 looking like a village of rounded huts.* 
 
 98. With reference to their mineral ingredients most 
 stratified rocks are included in the three following divisions 
 the sand group, the clay group, and the lime group. The 
 members of these groups exhibit various degrees of fineness 
 and compactness in their structure, and are designated are- 
 naceous, argillaceous, and calcareous, as sand, clay, or lime 
 is the characteristic ingredient. 
 
 99. Stratification is the most general condition of the 
 rocks constituting the crust of the earth, covering nine tenths 
 of its surface. Stratified rocks always overlie each other in 
 a constant order of succession. A stratum, which in any 
 one situation underlies another, will never, in any other 
 situation, be found above it. Certain strata maybe in some 
 places deficient, but all those which occur together are in- 
 variably in the same relative positions. Thus if six strata 
 be designated by the letters A, B, c, D, E, F, in the order 
 in which they succeed each other, and B, D, be deficient in 
 any locality, the order of the others will always be A, C, E, 
 F. In some instances the strata have been displaced so as 
 to bring them in an order of succession different from that 
 in which they were deposited, as is shown in Fig. 53. where 
 
 Dana's "Geology of the United States' Exploring Expedition." 
 
88 
 
 FOLDED AXIS HORIZONTAL STRATA. 
 
 Fig. 54. 
 
 the strata have been Fig. 53. 
 
 folded in such a way 
 as to cause a repeti- 
 tion of them in an 
 inverse order. Here 
 stratum 6 was the 
 
 lowest, and the oth- i -j y / ///'//'/ /' 
 ers rested upon it in fill ///// / / 
 the ascending order Folded Axis. 
 
 5, 4, 3, 2, 1. The upper part of the curvature has been 
 worn off, so that the strata appear at the surface a, a, in an 
 unusual order of superposition. Such an instance is called 
 a folded axis. 
 
 100. Strata are 
 deposited horizon- 
 tally in obedience 
 to gravity and some 
 of them retain the 
 horizontal position, 
 but most strata are 
 inclined to the ho- 
 rizon, having been 
 elevated to various 
 angles, by subterra- Horizontal strata. 
 
 nean forces, since their deposition. In Fig. 55, we have 
 four strata deposited horizontally. Figure 56 presents the 
 same strata elevated by subterranean forces, with the upper- 
 most ones rent. 
 
 a i Al Fig. 55. 
 
 subsequently at- 
 mospheric and HT^"^ 5 ^' ~: /e -^^ 
 
 aqueous agencies 
 wear off the upper 
 
 m 
 
STRUCTURE AND POSITION OF ROCKS. 89 
 
 Fig. 56. 
 
 portion of the bent strata, which now appear inclined to the 
 
 horizon as in Fig. 57. Fig. 57. 
 
 The dip of a rock is 
 
 the angle which the 
 
 plane of the stratum 
 
 makes with the plane of the horizon ; and is reckoned from 
 Fig. 58. to 90. When the dip is 
 
 90 the strata are, of course, ver- 
 tical. In the Isle of Wight is a 
 series of strata eleven hundred feet 
 thick in this position. The exam- 
 ple in Fig. 58 strata in Wales, 
 on which Powis Castle is built, is 
 
 Vertical Strata. giv(m by Mr Murchison, in his 
 
 el Silurian System." Vertical strata occur on a much larger 
 scale in the cliffs of Savoy. Strata of calcareous shale in the 
 Alps stand vertical for more than one thousand feet in depth 
 and then curve round to their appropriate position. 
 
 101. The dip of the strata is determined accurately by 
 means of an instrument called a clinometer \ but it may 
 ordinarily be estimated with sufficient accuracy by the eye. 
 As a general fact, the deepest strata are most highly in- 
 clined. The direction in which the edge of an upturned 
 stratum appears at the surface is called the strike or Lear- 
 ing. If a ridge runs North and South, the dip of the 
 beds is East and West, and their strike or bearing Nortji 
 8* 
 
90 
 
 CURVED STRATA SYNCLINAL AXIS. 
 
 Fig. 59. 
 
 Curved Strata of the Iselten Alp. 
 
 and South. A pocket compass will enable the observer to 
 determine the strike. The line of dip is always at right 
 angles to that of strike. Horizontal strata have neither 
 dip uor bearing. If we place a book upon the table with 
 the edges of the leaves downward, as in Figure 60, and 
 Fig. GO. remove one cover a short dis- 
 
 tance from the leaves, this cover 
 may represent a dipping stratum, 
 the dip becoming less and less as 
 the cover is raised, until it be- 
 comes horizontal parallel with 
 the table when the dip ceases. 
 The back of the book, a a, exemplifies the strike. The 
 anticlinal line or axis is a line along the summit of a 
 ridge or mountain range, from which the strata dip in op- 
 posite directions. If both covers of the book be thrown 
 partially open, the anticlinal axis will be represented by a 
 line along the back of the book. The synclinal line or 
 
STRUCTURE AND POSITION OF ROCKS. 
 
 91 
 
 axis is the line in a valley toward which the strata dip. 
 To represent this, turn the book over, placing the back 
 upon the table, open it partially and the line between the 
 pages will present the synclinal line. 
 
 102. The dip is usually easily discerned, but as the 
 edges of highly inclined strata may give rise to horizontal 
 lines on the face of a vertical cliff, as seen by an observer 
 in the line of their strike, their dip would not be apparent. 
 A break in the cliff, giving a section of the strata at right 
 angles to their strike, would at once discover their dip. 
 Thus the strata in the headland, Figure 61, would appear 
 perfectly horizontal to an observer in the boat directly in 
 front, while a person on the shore facing a section at right 
 angles to the strike of the strata, would at once perceive 
 that they dip 40. The abrupt termination of strata in a 
 Fig. 61. 
 
 Apparent horizontality of inclined Strata. 
 
 headland is called an escarpment. When the strata dip in 
 all directions from a point, as around a crater of a volcano, 
 the line of strike is circular or elliptical, and the dip is 
 said to be qua-qua-versal When the strata come out at 
 the surface they are said to outcrop. 
 
92 
 
 CONFORMABLE AND UNCONFORMABLE STRATA. 
 
 103. An assemblage of rocks formed under the same 
 circumstances, consequently possessing some characteristics 
 in common, is called a formation. It often embraces dif- 
 ferent substances ] the Lias formation includes the Lias 
 limestones, shales and marls, as does the Coal formation 
 the rocks associated with the coal. The time during which 
 such a group was formed is called a geological period. 
 When successive strata or groups of strata are parallel to 
 each other, they are said to be conformable; when not 
 parallel, they are unconformable. In Figure 62, the strata 
 abed are conformable, as are also efg h ; but the two 
 groups or formations are unconformable. This indicates 
 Fig. 62. 
 
 Conformable and unconforninble Strata. 
 
 that the group efgh had been formed and elevated before 
 the other group was deposited upon them. As the stratifi- 
 cation of different formations is usually unconformable, it 
 is inferred that there have been several different periods 
 during which the various formations were deposited and 
 elevated. The elevation of the strata has not always been 
 perfectly equa,ble ; hence fissures occur, on either side of 
 which portions of the same stratum are found at different 
 
STRUCTURE AND POSITION OF ROCKS. 93 
 
 heights, as at /in Figure 62. These interruptions of the 
 strata are particularly troublesome to miners working beds 
 of coal or ore, and hence they have been called troubles, 
 faults, or slips. The fissures are usually filled with sand, 
 earth, and angular fragments of rocks. When the fissure 
 extends to the surface and has considerable width, it is 
 termed a gorge ; when it is still wider, it is called a valley. 
 
 104. The thickness of strata is determined by measure- 
 ments applied to their edges. If they are vertical, a 
 measure applied horizontally to the edges gives their 
 thickness j but if they are inclined, it is ascertained by a 
 simple trigonometrical process. Having measured the 
 breadth of the upturned edge, and ascertained the dip, we 
 have the hypothenuse and angles of a right-angled triangle, 
 from which the perpendicular side the thickness, is easily 
 obtained. The total thickness of the strata is various in 
 different places. Dr. Buckland estimates the thickness of 
 European strata at ten miles. The stratified rocks usually 
 contain remains of pldn^ and animals, and are then called 
 fossiliferous. 
 
 105. The unstratified rocks exhibit no arrangement in 
 parallel layers, are of crystalline texture, and, having un- 
 dergone the action of heat, are called igneous rocks. They 
 occur in three different positions : beneath all the stratified 
 rocks, granite being the deepest known rock; above the 
 stratified rocks, constituting the summits of the loftiest 
 mountains ; and thrust into the strata, as veins and dikes. 
 The unstratified rocks are found principally in mountains, 
 and are not widely diffused at the surface, of which they 
 constitute not more than one-tenth, but beneath the thin 
 crust of strata are supposed to form the great mass of the 
 globe. They cause extensive changes in the characters 
 
94 
 
 VEINS AND DIKES. 
 
 and position of the strata with which they come in contact. 
 The unstratified rocks are entirely devoid of the remains 
 of animal and vegetable bodies. 
 
 106. Veins are usually masses of igneous rocks injected 
 from below into fissures in both stratified and unstratified 
 rocks; sub-dividing as they advance, and becoming mere 
 Fig. 63. 
 
 Vein 
 
 threads, they disappear. They arc frequently chemically 
 united to the sides of the fissures, but sometimes do not 
 adhere to them. Their contents are sometimes influenced 
 by the characters of the rocks through which they pass. 
 Dikes are large veins of trap-rock, porphyry or lava, ex- 
 tending in some instances seventy miles, with a thickness 
 of several yards. Dikes arc nearly straight, while veins 
 
STRUCTURE AND POSITION OF ROCKS. 
 
 95 
 
 arc very tortuous. As dikes are very compact and hard, 
 the strata through which they pass are often worn away, 
 and they are left standing out like walls. Dikes and veins 
 frequently intersect; in which case that which cuts through 
 the other must be the last erupted, and hence several suc- 
 cessive periods of eruption are proved in the granite, trap 
 and other igneous rocks. Some veins are found entirely in- 
 
 Fig. 64. 
 
 Trap Dike. 
 
 eluded in the rock, and are not traceable to any mass of 
 similar composition but appear to have separated from the 
 rock in which they lie. Theso are called veins of segrega- 
 tion. Veins and dikes cross the strata at various angles, and 
 are sometimes intruded between the strata, and spread out so 
 
96 
 
 JOINTS IGNEOUS ROCKS. 
 
 Fi 65 
 
 as to resemble true beds ; but they have no lamination. 
 The contents of veins are exceedingly varied ; indeed it is 
 presumed that they contain all elementary substances known 
 to chemists. They are divided into two classes the metal- 
 liferous and non-metalliferous. The contents of dikes are 
 much more limited in kind and uniform in character. 
 
 107. A concretionary structure on a large scale is oc- 
 casionally seen in igneous rocks, but a more interesting 
 structure exhibited by them is that which produces regular 
 columns, varying in size from an inch in diameter to seve- 
 ral feet; in length, from one to three hundred feet; and 
 
 in number of sides, 
 from three to twelve. 
 They are so accurately 
 adjusted to each other 
 that no space intervenes 
 between them, and fre- 
 quently consist of joints 
 with alternate convex 
 and concave surfaces : 
 they are usual ly straigh t, 
 but sometimes highly 
 
 curved. 
 
 108. Mr. Lyell distinguishes the igneous rocks into 
 two classes the volcanic, and the plutonic. The volcanic 
 are those which have been produced at or near the surface 
 of the earth, as are the lavas of volcanoes of the present 
 period ; but similar rocks have been poured out upon the 
 land or the bed of the ocean, and have been injected into 
 fissures near the surface, at many different epochs. The 
 plutonic rocks appear to have been formed under enormous 
 pressure at great depths in the earth. They differ from 
 
 Jointed Columns. 
 
MET^.MORPIIIC ROCKS JOINTS. 97 
 
 the volcanic in being more highly crystalline, and free 
 from the pores, or cellular cavities which characterize the 
 volcanic. The granites and porphyries "belong to this 
 class. 
 
 109. There is another class of rocks, which partake of 
 the characters of both aqueous and igneous rocks. These 
 lie upon the plutonic rocks, are highly crystalline in struc- 
 ture, are destitute of organic remains, and yet are divided 
 into beds precisely like the sedimentary formations in form 
 and arrangement. These strata appear to have been de- 
 posited in water in the usual way, and then to have been 
 subjected to such a degree of subterranean heat as to 
 assume a new texture. In some instances a portion. of a 
 stratum has exchanged its earthy for a crystalline texture 
 through a distance of a quarter of a mile from its contact 
 with granite, and has had all traces of its organic remains 
 obliterated, while the remainder of the stratum retains all 
 the characteristics of its sedimentary origin. Thus dark 
 colored limestones filled with shells and corals have been 
 converted into white statuary marble, and clays into slates, 
 or schists. These altered rocks are called metamorphic. 
 
 110. All rocks, whether stratified or not, are divided 
 into masses of determinate figures, by natural fissures tra- 
 versing them in straight lines, and forming planes of vari- 
 able width. These fissures are called joints. Their faces 
 are usually smoother and more regular than the planes of 
 stratification, to which they are vertical, thus dividing the 
 rock into cubical or prismatic blocks. Some joints are 
 more open, regular and continuous than others, passing 
 through several alternations of strata, dividing them from 
 top to bottom, sometimes completely arresting the cross 
 joints. These are called master-joints. The constancy of 
 
 9 
 
98 STRUCTURE AND POSITION OF. ROCKS. 
 
 direction of these fissures is such as to indicate a general 
 and long-continued agency pervading the whole strata. In 
 Great Britain, two-thirds of them run north north-west to 
 south south-east, and the remaining third at right angles to 
 that direction, independently of the dip or strike of the 
 strata. Their origin is attributed to contraction during the 
 consolidation of the strata ; to expansion and contraction 
 by alternations of Fig. 66. 
 
 temperature; and 
 to electricity. In 
 some sandstones 
 and beds of iron- 
 stone, there are 
 numerous and ir- 
 regular fractures 
 or seams dividing 
 the surface into 
 small polygonal 
 areas with a con- 
 centric structure, 
 as exhibited in Figure 66. 
 
 111. Some slate rocks are capable of indefinite subdivi- 
 sion in a direction not coinciding with the planes of stratifi- 
 cation, nor with joints. This is termed cleavage. The direc- 
 tion of the cleavage planes appears to be, generally, parallel 
 to the anticlinal line of the region in which the rocks occur, 
 and is altogether independent of the dip of the strata. The 
 strata on the two sides of a. mountain chain may dip in 
 opposite directions, while the cleavage planes are vertical 
 between them, and parallel to the anticlinal axis, as is the 
 case in the Alps. The phenomena of cleavage in rocks are 
 ascribed to crystallization, or a re-arrangement of the par- 
 
CLASSIFICATION OF ROCKS. 09 
 
 tides of the strata, by which similar materials are collected 
 in planes. 
 
 CLASSIFICATION OF ROCKS. 
 
 112. While little difference of opinion exists among 
 geologists with reference to the general arrangement of the 
 rocks, several systems of classification have been proposed 
 by them. These systems differ in the grouping of particu- 
 lar strata and formations. Their diversity is a source of 
 distraction to the student of geology, on account of the 
 multiplicity and discordance of the terms, which they intro- 
 duce. All geologists agree in the division of rocks into 
 stratified and un stratified fossiliferous and non-fossilifer- 
 ous and in the invariable order of succession of the strat- 
 ified fossiliferous; but it is not practicable at present to 
 determine, in geological formations, the relative places of 
 classes, orders, genera and species, with that accuracy 
 which characterises some other branches of natural science. 
 
 113. The fundamental idea involved in systems of 
 classification is the relative age of rocks, and formations. 
 This, in the case of stratified rocks, is determined by the 
 position of the strata ; by the characters of the animal and 
 vegetable bodies they contain ; and by their mineral con- 
 stituents. 
 
 114. The order of superposition of strata is manifestly 
 indicative of their relative age, since the lowest stratum, 
 upon which the others lie, must have been first deposited, 
 and the others in order upward. But a difficulty attends 
 the investigation of this order of succession, on account of 
 the absence of some of the strata at any one place of obser- 
 vation. There is no place on the globe, where, if a section 
 were made through the rocks, all the strata would be found, 
 
100 STRUCTURE AND POSITION OF ROCKS. 
 
 because the strata are not continuous round the earth, like 
 the coats of an onion. Those parts of the globe that con- 
 stituted the dry land while any deposit was forming in the 
 seas, would receive no portion of the deposit, and as irregu- 
 larities of distribution of land and water have always ex- 
 isted, parts of the surface must have successively consti- 
 tuted continents and islands. This difficulty in observation 
 is obviated by the meeting and overlapping of the various 
 formations. Thus, if six formations be represented by the 
 first letters of the alphabet a, b, c, d, e, f } in their order, 
 and at one place the formations b and e be missing, obser- 
 vation at another place may give the formations a, b, c, d^f, 
 thus supplying the first deficiency b; and further investi- 
 gation at other points, present c, d, e, /, thus enabling us 
 to determine the order of succession of the six formations. 
 115. Since each formation has fossils, remains of ani- 
 mal and vegetable bodies, peculiar to itself, we are enabled 
 by means of them to determine whether strata which are 
 remote from each other geographically, as in America and 
 Europe, were deposited at the same or different periods. A 
 difficulty may seem to arise here, from what has been stated 
 (87) respecting the different animals and plants which 
 live at present in different localities, but the differences 
 between the faunas and floras of different geological periods 
 are much greater than those which exist between the ani- 
 mals and plants of any one period. The difficulty, in the 
 case of the older formations, is also much diminished by 
 the great uniformity which characterised the faunas and 
 floras of those periods ; they were less numerous and more 
 widely extended than at the present period. The relative 
 ages of the more recent formations may be determined to a 
 certain degree, by observing the number of animals and 
 
AGES OF AQUEOUS AND IGNEOUS ROCKS. 101 
 
 plants contained in them which are identical with species 
 living at the present time. This number continually dimin- 
 ishes as we recede from the present geological period, until 
 no trace of the species that live at the present day is found. 
 When two geological formations contain many fossils in 
 common, we infer that they were formed at about the same 
 period. 
 
 116. Some minerals have been deposited, at certain 
 periods more abundantly than at others; still, different 
 minerals have been deposited at the same period, their dis- 
 tribution depending upon local circumstances, as at the 
 bottom of the present ocean, in some places limestones are 
 forming, at others clay-beds, and at others sandstones. 
 Identity of mineral constitution, therefore, does not prove 
 strata contemporaneous, nor does the failure of that idenity 
 necessarily indicate a different period of origin. When the 
 fragments of rocks of one formation are included in those 
 of another, we have evidence that the rocks to which these 
 fragments belonged were formed, consolidated and fractured 
 before the others were deposited. The conglomerates, or 
 pudding-stones, are filled with worn, rounded fragments of 
 other rocks; indeed all the sedimentary rocks "consist of 
 fragments, fine or coarse, of rocks older than themselves. 
 
 117. As the unstratified or igneous rocks occur in no 
 regular order of .succession, their age is not always easily 
 determined. Their relations, however, to the stratified rocks 
 furnish some intimations of their relative ages. When an 
 igneous rock has passed through a stratum, causing disloca- 
 tion or changes of structure, it is manifestly more recent 
 than the stratum. A volcanic rock, as lava, may flow over 
 strata producing its characteristic effects upon them, and 
 subsequently other strata may be deposited upon it, accom- 
 
 9, 
 
102 
 
 STRUCTURE AND POSITION OF ROCKS. 
 
 modating themselves to its form, but experiencing no heat- 
 ing effects from it ; we can, in such case, identify the pe- 
 riod of its eruption, as the one which elapsed between the 
 deposition of the two beds. 
 
 118. In A. D. 1680, Leibnitz divided all rocks into 
 two classes stratified and unstratified in accordance with 
 their origin. Subsequently Lehmann, a G-erman mineralo- 
 gist, classified the stratified rocks, as 1. Primitive those 
 which contain no animal or vegetable bodies; 2. Second- 
 ary those which 'contained plants and animals; and 3. 
 Local those which occurred in limited localities. Werner 
 
 Fig. 67. 
 
 x ^H^^^ftiC!^ 
 
 e 
 
 Section of tho Globe. 
 
CLASSIFICATION OF ROCKS. 103 
 
 made four classes : the primitive, transition, fla&tz (flat- 
 lying,) and alluvial. He proved that the stratified rocks over- 
 lie each other in a constant order of succession. He applied 
 the term transition to the lower rocks which contain organic 
 remains, indicating that the world was, during their depo- 
 sition, passing from an uninhabited to an inhabited state ; 
 his flcctz rocks coincided generally with the secondary of 
 other writers, and in the alluvial he included the most re- 
 cent deposits. In the early part of this century, Cuvier and 
 Brogniart proposed a new class called tertiary, and still more 
 recently a fourth class called the quaternary, has been 
 formed to embrace the diluvial or drift and alluvial deposits. 
 
 119. A section of the globe coinciding with the fortieth 
 parallel of north latitude, shown in Fig. 67, exhibits the 
 positions of the great mountain chains, with the stratified 
 rocks sloping from and extended between them. The pri- 
 mary, transition, and secondary classes of rocks only are 
 indicated, and the proportions of the globe and its " crust" 
 are necessarily sacrificed; for those proportions refer to 8. 
 
 120. A classification extensively used at the present 
 day embraces all the stratified rocks in five classes. 
 
 I. In an ascending order, the first class is the primary, 
 whose strata rest upon the unstratified, igneous rocks, are 
 more or less crystalline in structure, and destitute of organic 
 remains. This class includes the metamorphic rocks, de- 
 scribed in 108. Mr. Lyell designates these rocks, hypo- 
 gene, nether-formed, because they have taken their present 
 form at great depths. 
 
 II. The second class, the transition or palaeozoic, are 
 characterized by the remains of the earliest plants and ani- 
 mals. This class embraces the great coal formation. 
 
 III. The third class, the secondary, commences with 
 
104 STRUCTURE AND POSITION OF ROCKS. 
 
 the new red sandstone above the coal, and extends to the 
 top of the chalk. 
 
 IV. The rocks of the fourth class, the tertiary, are not 
 generally so compact, nor so highly inclined, as the mem- 
 bers of the first three classes. They contain the remains 
 of many plants and animals, identical with living species. 
 
 V. The fifth class, the quaternary, includes the super- 
 ficial deposits, the transported sand, gravel, clay, &c. of the 
 drift, and alluvial, together with the local deposits of peat, 
 marl, bog-ores, and soil formed by the disintegration of 
 rocks in place, including the remains of animals identical 
 with the present species, and some recently extinct, 
 
 121. The following tabular arrangement exhibits the 
 five classes, together with their groups or systems of forma- 
 tions. 
 
 Q DA ,, {Aji Z; .;^.-f;;;;; H '; 
 
 f Pleistocene. 
 
 TERTIARY, J P le . iocene - 
 
 I Meiocene. 
 
 SECONDARY, 
 
 Eocene. 
 
 Chalk. 
 
 Green Sand. 
 
 Wealden. 
 
 Lias. 
 
 Triassic system. 
 
 TRANSITION f ^^ntferous system. 
 
 or -j Old Red Sandstone or Devonian. 
 
 P A _, [ gg**r 
 
 {Clay slate " 
 Mica slate " 
 Gneiss " 
 UNSTRATIFIED ROCKS Granite. 
 
 122. The unstratified rocks do not admit of a system- 
 atic classification in accordance with a strict order of sue- 
 
CLASSIFICATION OF ROCKS. 105 
 
 cession, but may be conveniently arranged in groups, de- 
 pending upon the nature and mode of aggregation of their 
 constituent minerals. Each of these groups is also associ- 
 ated with particular systems of the stratified rocks. 
 
 I. The granite group, comprising granite, syenite, ser- 
 pentine, porphyry ; of dense crystalline structure, and asso- 
 ciated with the primary class, and the Cambrian and Silu- 
 rian members of the transition class, of strata. 
 
 II. The trap group embraces basalt, green-stone, tra- 
 chyte, amygdaloid ; of a compact and less crystalline struc- 
 ture, and occurs in the upper transition or palosozoic, and 
 secondary, strata. 
 
 III. The volcanic group, less compact, vesicular, and 
 associated with the tertiary, and quaternary deposits. 
 
CHAPTER III, 
 
 i PALEONTOLOGY. 
 
 123. MOST of the stratified rocks contain the remains of 
 animal and vegetable bodies, which have been imbedded in 
 them by natural causes. That branch of geology which 
 classifies and describes these relics, is called palaeontology ; 
 (palaios, ancient; ontos, being; logos, a discourse.) The 
 bodies are called fossils, or organic remains. The disco- 
 very that particular fossils characterize certain deposits has 
 greatly contributed to the rapid advancement of the science 
 of geology. t( Hence organic remains acquire a high degree 
 of importance, not only from the intrinsic interest which 
 they possess as objects of natural history, but also for the 
 light they shed on the physical condition of our planet in 
 the most remote ages ; and for the invaluable data they 
 afford as chronometers of the successive revolutions which 
 the surface of the earth has undergone. They have been 
 eloquently and appropriately termed the medals of creation ; 
 for as an accomplished numismatist, even when the inscrip- 
 tion of an ancient and unknown coin is illegible, can from 
 the half-obliterated characters, and from the style of art, 
 determine with precision the people by whom, and the pe- 
 riod when it was struck ; in like manner the geologist can 
 decipher these natural memorials, interpret the hierogly- 
 phics with which they are inscribed, and from apparently the 
 
FOSSILS THEIR PRESERVATION. 107 
 
 most insignificant relics, trace the history of beings of whom 
 no other records are extant, and restore anew those forms 
 of organization which lived and died, and whose races were 
 swept from the face of the earth, ere man, and the creatures 
 which are his contemporaries, became its denizens."* 
 
 124. Fossils differ greatly in the degrees of preservation 
 they exhibit. In a few rare instances animals have been 
 preserved entire, with their flesh and skin. In 1774, the 
 carcass of a rhinoceros was taken from the frozen sand of 
 Siberia, with more hair on the skin than the rhinoceros of 
 the present day has. At the commencement of the present 
 century, the entire carcass of a mammoth was obtained 
 
 Fig. 68. 
 
 Siberian Mammoth found in frozen grayel. 
 
 from an ice-cliff in Siberia, twelve feet high, sixteen feet 
 long, and with tusks nine feet in extent. The flesh was so 
 well preserved that the wolves, bears, and hunters' dogs 
 fed upon it. The skin was covered with a mixture of black 
 bristles, fifteen inches long, and wool of a brown color. 
 
 * Mantell's Medals of Creation. 
 
108 PALEONTOLOGY. 
 
 More than thirty pounds of the hair was collected. The 
 brain and the capsule of the eye were in a good state of 
 preservation. The skeleton, Fig. 68, together with a large 
 quantity of the hair, is in the Museum of Natural History 
 at St. Petersburgh. These animals are assigned to the 
 pleistocene period, when they appear to have been numer- 
 ous in that locality. Dr. Mantell states that thousands of 
 fossil ivory tusks are annually collected there, forming a lu- 
 crative article of commerce, and that the remains of a greater 
 number of elephants have been discovered in Siberia, than 
 are supposed to exist at the present time all over the world.* 
 Insects occur perfectly preserved, sealed up in amber, a fos- 
 sil resin. Parts of the stomach and skin of large reptiles 
 have in a few instances been found in older rocks, preserved 
 by the antiseptic property of certain salts in the rocks. 
 The " eatable earths" which the inhabitants of some coun- 
 tries have eaten mixed with saw-dust, consist of fossil infu- 
 soria. Usually, the harder parts of animals, the bones, shells, 
 and crustaceous shields only, have been preserved. 
 
 125. In some cases no part of the animal or plant is 
 preserved, but the space which the body occupied having 
 been emptied by its decay is filled with mineral matter in- 
 filtered, and thus presents a perfect cast ; or if mineral mat- 
 ter has not been infiltered we have only the mould. In a 
 few instances impressions of only a part of the body, as 
 foot-prints, are found. The tracks of birds occur in the 
 New Red Sandstone above the coal, Fig. 69, though their 
 skeletons have not been found below the chalk. Similar 
 traces of other animals are met with in the same sandstone. 
 
 126. Petrifaction consists in the substitution of mineral 
 
 * Wonders of Geology, sec. II. 17. 
 
PETRIFACTION FOOT-PRINTS. 
 
 109 
 
 for organic matter. In some instances the animal or veget- 
 able substance is almost entirely removed, while the organic 
 structure is retained, so that thin sections examined with 
 the microscope, show the forms of all the fibres and vessels 
 Fig. 69. 
 
 Bird-tracks in New Red Sandstone. 
 
 in their proper places. Limestone fossils placed in acids, 
 have had all the petrifying material dissolved, and yet ex- 
 hibited the animal tissues in a perfect form. The process of 
 petrifaction has been imitated artificially; bones, leaves, &o. 
 
 10 
 
110 PALAEONTOLOGY. 
 
 Fig. 70. 
 
 Tracks of the Cheirotherium. 
 
 have been buried in mud and sand, and after the lapse 
 of a few years have been found petrified. The process is 
 influenced by the presence of salts, as the sulphate of iron, 
 in the mud, and is accelerated by heat and pressure. All 
 fossils, however, are not petrified ; nor does the age of the 
 rock containing the fossil necessarily determine the amount 
 of petrifaction : bones have been obtained from the Wealden, 
 that were light and porous, while some from the most recent 
 tertiary rocks were completely petrified. 
 
 127. Plants are sometimes petrified, but have more fre- 
 quently sustained chemical changes, by which their own 
 elements have been transposed and their vegetable structure 
 destroyed; subjected to moisture and pressure, secluded 
 from the air they ferment, evolve heat, and are converted 
 into bitumen. This change is partially illustrated by a 
 mass of half-dried hay, which ferments, becomes of a black 
 color, and sometimes generates sufficient heat to take fire. 
 Bitumen is a black combustible substance, and liquid as 
 petroleum, naptha ; viscid as asphaltum, mineral pitch ; or 
 solid as jet, cannel and bituminous coals. In like manner 
 animal muscle, buried in wet earth from which the air is 
 excluded, is converted into a fatty wax called adipocere, 
 (adeps, fat, andcera, wax,) retaining no trace of the original 
 muscular fibre. In some of the fishes of the Old Red Sand- 
 stone, their muscles, blood, &c., have been converted into a 
 dark-colored bitumen, which in some places pervades the 
 rock to such a degree as to cau^ it to be mistaken for coal. 
 
METALIZATION PETRIFIERS. Ill 
 
 It resembles black wax, or when fluid, the coal tar of 
 the gas works. This animal bitumen is eminently antisep- 
 tic, preserving in all their elasticity the bones, fins, and 
 scales enveloped in it, better than the oils and gums applied 
 to the old Egyptian mummies.* 
 
 128. The petrifaction of animal and vegetable bodies is 
 frequently accomplished by means of the metals. The me- 
 tallic salts, the sulphate of iron for example, dissolved in 
 the waters of the earth, are decomposed; their oxygen 
 uniting with some of the elements of the organic bodies, the 
 metals are precipitated as sulphurets. Hence fishes are fre- 
 quently found incrusted with iron-pyrites (sulphuret of 
 iron) while their internal parts are converted into stone or 
 bitumen ; not unfrequently, however, their whole substance 
 is changed into metal, all the traces of organic structure 
 obliterated, and their form only preserved. , 
 
 129. The most common petrifiers, are carbonate of lime, 
 oxide carbonate or sulphate of iron, and silica. A fossil 
 petrified in limestone, however, will not necessarily be cal- 
 careous. Many of the fossils of the chalk are flints, and 
 those of clay-slates, calcareous. The cavities, as the interior 
 of shells and hollow-bones, are often filled with crystals of 
 limestone, or of silica, which, dissolved in water, was in fil- 
 tered into these closed cavities through the pores of the 
 shell or bone. 
 
 130. The means requisite for determining the characters 
 of fossils, are furnished by such a degree of knowledge of 
 botany, zoology, and comparative anatomy, as is adequate 
 to the determination of living species. The same modes of 
 investigation apply to both fossil and living species ; they 
 
 * Miller's Foot-prints of the Creator. 
 
 ^^^ 
 
 f UN 
 
 \<v 4 
 
112 PALAEONTOLOGY. 
 
 are the natural complements of each other. Systems of 
 botany and zoology are not complete without these extinct 
 forms. In consequence of the relations which exist between 
 the parts of animal frames, the observer is enabled to de- 
 termine from a single bone the form and position of the 
 other bones, and the entire condition of the animal. Thus 
 the sharp, retractile, curved claws of the lion require that 
 the bones immediately above them on the foot, and with 
 which they articulate, be of such a shape as will allow free 
 motion; the bones preceding these require also to be 
 adapted to the design intended to be subserved by the claws. 
 With these claws are associated the pointed sharp teeth 
 adapted to tearing and cutting flesh. In animals feeding 
 exclusively on flesh we always find the intestines about one 
 fifth as long as in herbivorous animals. Hence a single 
 tooth, or claw, suggests to the comparative anatomist the 
 general form and habits of the animal. A single tooth of 
 the Iguanodon enabled Cuvier to decide that the animal to 
 which it belonged was an herbivorous reptile. The scales 
 of fishes are so highly characteristic that Professor Agassiz 
 has made their peculiarities the basis of his classification of 
 these animals. A single scale found in the intestines of an 
 Ichthyosaurus enabled him to identify the extinct species 
 to which it belonged. In this way, peculiarities of struc- 
 ture reveal to the palaeontologist the characters and modes 
 of existence of creatures that ceased to exist ages before 
 the creation of man, and to the geologist the condition of 
 the world at that period. 
 
 131. The relics of animal and vegetable organization 
 occur in almost every stratified rock, but in much greater 
 numbers, and in a better state of preservation in some strata 
 than in others. Nor are they equally abundant throughout 
 
NUMBER OP FOSSILS. 113 
 
 the same bed, some portions consisting almost exclusively 
 of them, while in others they are sparingly diffused or en- 
 tirely absent. Some limestones many feet in thickness are 
 made up of shells or corals in countless numbers, cemented 
 together by the carbonate of lime. But the greatest numbers 
 of individuals accumulated in a limited space are presented 
 by the most minute animals. Soldani obtained from a frag- 
 ment of rock in Tuscany, which weighed one ounce and a 
 half, ten thousand four hundred and fifty-four marine shells, 
 resembling the Nautilus. One thousand of them weighed 
 one grain. Some of the Wealden strata in England one 
 thousand feet thick, and deposits in Auvergne seven hun- 
 dred feet thick, covering an area eighty miles long and 
 twenty wide, are filled with microscopic crustaceous animals. 
 In G-ermany a bed fourteen feet thick, is made up of fossil 
 animalcules so minute that, according to Ehrenberg, forty- 
 one thousand millions of them occupy but a cubic inch. The 
 total number of organic relics in the rocks is inconceivably 
 great since more than two-thirds of the earth's surface is 
 covered by fossiliferous deposits, many of which are several 
 thousand feet thick. They are found at an elevation of at 
 least seventeen thousand feet above the level of the sea, in 
 strata of the Himalayas and Andes ; and are obtained in 
 excavations more than two thousand feet below the same 
 level. 
 
 132. The medium through which fossils have been de- 
 posited has usually been the ocean ; and by far the largest 
 number are those which lived in the sea, and hence are de- 
 signated marine. Some, however, lived in brackish water, 
 and the strata in which they are found are termed estuary 
 deposits, as was the case in the coal measures, and the 
 Wealden strata. A part of the Tertiary series contains 
 
 10* 
 
114 PALEONTOLOGY. 
 
 fresh water animals and plants. Comparatively few ter- 
 restrial relics occur : but the Wealden, Tertiary, and Dilu- 
 luvial deposits contain some remains of land plants and 
 animals. 
 
 133. Fossils usually occur in the situations in which 
 they were at the time of their death, and hence often have 
 their most delicate parts preserved. Some of the shells of 
 the Wealden retain their epidermis, and ligaments of their 
 valves, showing that they have not been subjected to friction. 
 But there are immense reefs of broken shells and corals, 
 some of which are worn to fine dust, indicating the violence 
 to which they have been subjected. 
 
 134. In order to a full appreciation of the import of 
 fossils, we must be enabled to compare them with each other 
 at different geological periods, and with the existing races. 
 This can be effected only by means of the distinctions and 
 principles of classification used in Natural History. 
 
 A species is a group of individuals that are alike in every 
 character not affected by accidental circumstances. Species 
 are continued from generation to generation without the 
 slightest change of character. Those variable changes which 
 are produced by accidental causes, constitute varieties. Spe- 
 cies are not convertible into each other. We know of no 
 power adequate to the production of a species, short of the 
 direct act of the Creator. Species have been obliterated in 
 thousands of instances in the former ages of the world, and 
 in a few known cases since the creation of man. ( 86.) 
 
 A genus is an assemblage of species having certain char- 
 acters in common. Genera usually embrace a considerable 
 number of species, but a single species differing widely from 
 all others may constitute a genus. 
 
 An order is an assemblage of genera, as a class is of 
 
DISTRIBUTION OP FOSSILS. 115 
 
 orders, while the whole are included in a kingdom. The 
 terms family and tribe are used to designate groups inter- 
 mediate between genera and orders. 
 
 135. We have seen ( 87) that the plants and animals 
 of the present period are distributed in floras and faunas, 
 limited by climate and other circumstances. The examina- 
 tion of fossils in their beds shows that similar laws of dis- 
 tribution prevailed also at former periods. Classes and 
 orders were, as they now are, very widely diffused, and 
 genera often covered extensive areas, but species were re- 
 stricted within comparatively narrow limits. In the periods 
 of deposition of the earliest fossiliferous rocks, the temper- 
 ature of the globe appears to have been higher than at 
 present, and the faunas and floras less numerous, but cover- 
 ing a wider range. A formation existing in different parts 
 of the world, very rarely contains the same species through- 
 out its extent. The fossils of the chalk in England are in 
 very few instances specifically identical with the American 
 chalk fossils : the genera are the same, and the species anala- 
 gous but not identical. 
 
 136. Examination of the successive formations of the 
 fossiliferous rocks, shows that species of plants and animals 
 have been introduced at different periods, continued for a 
 time, then obliterated and their places supplied by others. 
 The periods of duration of families, genera and species, are 
 very variable. Species rarely extend through more than 
 a single formation, but genera are often found in several 
 successive formations, and in a few instances have survived 
 all the mutations exhibited by the fossiliferous strata, 
 having representatives in the existing races. Genera, how- 
 ever, and even orders are sometimes limited to a single for- 
 mation ; in other instances they reappear after having ceased 
 
116 PALAEONTOLOGY. 
 
 through several formations. Those genera and species which 
 survive through several formations, are such as have a wide 
 geographical distribution, and seem to be endowed with a har- 
 dihood which enables them to endure changes of climate 
 and other circumstances. Those species which live in deep 
 water, with a more equable temperature are also more per- 
 manent. Shellfish and crustaceous animals are more endu- 
 ring than vertebrate animals : no species of fish has yet 
 been found in two successive formations. 
 
 137. Geologists presume plants and animals to have 
 been introduced at the period of the deposition of the lowest 
 strata in which their remains are found, though it is admit- 
 ted they may have lived at an earlier period, and all trace of 
 the existence of those first created, may have ceased in con- 
 sequence of their frailty or the action of heat upon the 
 lowest strata. Negative evidence on this subject is by no 
 means conclusive. The failure to find the remains of a par- 
 ticular animal in a formation, does not satisfactorily prove 
 that the anhnal was not living during that period : contin- 
 ued search may yet discover it ; or its mode of life may have 
 been such as to render the preservation of its remains after 
 death, very improbable. But if from the remains found in a 
 formation, we can infer the adaptation of circumstances to a 
 certain class of animals, we do not expect to find in that 
 formation animals whose organization require other circum- 
 stances. Thus in the coal formation whose plants clearly 
 indicate the prevalence of a climate more elevated than that 
 of the tropics at the present time, we do not expect to find 
 indications of the existence of plants adapted to a temper- 
 ate or arctic climate. 
 
 138. The close of geological periods appears to have 
 been the time at which most of the changes in species oc- 
 
SUCCESSION OF FOSSILS. 117 
 
 curred ; in some instances the change obliteration of the 
 old species and introduction of the new is sudden, abrupt, 
 and in others gradual. The introduced species are in no 
 sense modifications of, or descendants from the species that 
 preceded them. The facts of Geology disprove the hypothe- 
 sis which supposes that animated existences were all intro- 
 duced as mere points of vitality monads from which 
 by a natural process of development, without the interpo- 
 sition of creative agency, they advance through continuous, 
 regular grades, to the highest state of perfection and com- 
 plexity. Mr. Hugh Miller has shown, on the contrary, 
 that in certain orders there has been a degradation of spe- 
 cies.* There was a time when reptiles represented the 
 carnivorous and herbivorous quadrupeds, but such magnifi- 
 cent reptiles have not existed since. There was a time 
 when birds seem to have been the sole representatives of 
 the warm-blooded animals, but their foot-prints in the sand- 
 stone show, that in size no birds of the present day can 
 compare with them. Although species remain constant. in 
 their characters, and changes are effected only by creative 
 energy introducing new forms, still progress is discernible 
 in the beings which have successively peopled the surface 
 of the earth progress in their approach to the present races. 
 In the vertebrate animals the order of succession has been, 
 fishes, reptiles, birds, mammiferous quadrupeds, and finally 
 man. The relation between animals and the periods at 
 which they live, appears to be a part of the plan of the 
 Creator, as truly as is their distribution. 
 
 139. By a comparison of the fossils of different forma- 
 tions, we learn that those which are most unlike are most 
 
 * Foot-Prints of the Creator. 
 
118 PALEONTOLOGY. 
 
 remote from each other in time. The organic remains of 
 the Silurian and Carboniferous periods are more like to each 
 other than they are to those of the chalk or tertiary ; and 
 the deeper we descend in the strata, the more unlike to the 
 existing races are the fossils we obtain. In the earliest 
 fossiliferous rocks the simplest forms of organization pre- 
 dominated, but representatives of all the classes are found 
 with them. The relative number of species and genera of 
 these classes has continually varied in the successive for- 
 mations. 
 
 FOSSIL BOTANY. 
 U 
 
 140. All vegetables, fossil or recent, may be arranged 
 under two grand divisions, cellular and vascular. 
 
 I. Cellular plants present the simplest forms of vegeta- 
 tion, consisting of an assemblage of cells of the same kind, 
 without regular vessels, and having no visible organs of 
 fructification. Such are the sea-weeds (confervae, algae,) 
 mosses and lichens. 
 
 II. In vascular plants the cells are elongated into tubes 
 or vessels, called vascular tissue, and form organs of nutri- 
 tion and fructification. Four classes are formed in this 
 division, in accordance with the structure of the organs of 
 fructification. 
 
 1st. Cryptogamise, having neither perfect flowers nor 
 visible seed vessels ; to this belong the fern, equisetum or 
 marestail, and calamites. Great numbers of these occur 
 fossil. 
 
 2nd. Gymnospermous Phanerogamise ? having flowers j 
 but their principal characteristic is the nakedness of their 
 seeds. To this class belong the Oycadece, or piee-ft^pie^tribc, 
 and the Coniferae, or firs. 
 
FOSSIL BOTANY. 119 
 
 3d. Monocotylcdonous Phanerogamic, flowering plants 
 whose seeds have only one cotyledon, or seed-lobe, as the lily, 
 the palm, and the cane. These are also called Endogenous, 
 because they receive their growth wholly within, by the for- 
 mation of new bundles of vessels at the center, crowding out 
 and condensing those which lie toward the edge. They have 
 no pith, concentric circles of woody fibre, nor true bark. 
 
 4th. Dicotyledonous Phanerogamise, flowering plants 
 whose seeds have two cotyledons or seed-lobes, as the bean. 
 These are exogenous, receiving annual deposition of woody 
 fibre, upon the previous growth, and have true bark and pith. 
 A cross section of the oak exhibits the pith at the center, 
 concentric circles of woody fibre, connected by fine straight 
 lines- the medullary rays which radiate from the central 
 pith. To this class belong our forest trees, and shrubs. 
 
 141. As fragments of trunks and branches are often the 
 only specimens we have of a fossil species, we are obliged 
 to resort to the study of their anatomical structure. These 
 Fig. 71. 
 
120 
 
 PALAEONTOLOGY. 
 
 are quite distinctive and are frequently very perfectly pre- 
 served. A fragment of fossil wood cut very thin, will, with 
 the aid of a microscope, show the form and position of the 
 vessels so clearly as to enable the observer to determine 
 the nature of the plant. 
 
 The leaves, either entire, or impressions of them are 
 very common, and enable us to distinguish between endoge- 
 nous and exogenous structures. If the veins of the leaf be 
 all parallel, or connected only by little transverse bars, the 
 plant was endogenous ; but if they are unequal in thickness 
 or arranged in net-like meshes, they belonged to an exoge- 
 nous plant. The flowers of some liliaceous plants have 
 been found with their corollas, and calyxes preserved, but the 
 anthers and pistils could not be recognized. The preceding 
 figure, 71, presents a portion of a coal plant, discovered at 
 Tallmadge, Ohio, by Charles Whittlesey, Esq., which very 
 closely resembles the corollas of some plants. The fruits 
 Fig. 72. 
 
 Fossil Nuts. 
 
FOSSIL BOTANY. 121 
 
 of many plants occur fossil in great profusion, as cones, nuts 
 and seeds. 
 
 Some trunks of trees have been found of great length ; 
 as the Norfolk Island pine, forty feet long, in the carbon- 
 iferous limestone of the Craigleith quarry near Edinburgh, 
 and the "petrified forest' 7 near Cairo in the Egyptian 
 desert, where the silicified trunks of trees from forty to sixty 
 feet in length and three feet in diameter, cover the ground. 
 The resinous secretions of pines and other coniferous plants, 
 are sometimes found fossil, as amber, which has been found 
 in its natural position in trunks of trees. Some specimens 
 of amber are black, showing the process of bituminization 
 they have undergone. This also is supposed to be the ori- 
 gin of the diamond. 
 
 142. The cellular plants, as the algae, occur most abund- 
 antly in the most ancient fossiliferous strata ; in some of 
 the Silurian rocks, entire layers are formed of a large species 
 of sea-weed. Of vascular plants, the cryptogamous fern, 
 equisetum, and calamite are found predominating in the 
 carboniferous rocks, but existed earlier than that period. 
 As we ascend in the series of rocks from the secondary 
 class to the alluvial, the fossil ferns diminish in number, 
 as they do when we travel from the equator toward the 
 poles at the present day, when of the one thousand five 
 hundred species, one thousand two hundred are within the 
 tropics. 
 
 The gymnospermous plants Cycadeae and Coniferous 
 were most abundant in the lias, oolite, and tertiary periods. 
 The endogenous class including the palms flourished during 
 the tertiary period, though they are found to some extent 
 in earlier periods. In the Illinois coal field a group of 
 fossil palm trees has been discovered with their roots in the 
 
 11 
 
122 PALAEONTOLOGY. 
 
 clay, and their trunks in the coal and sandstone above. 
 The geological position of the exogenous plants is in the 
 tertiary and recent deposits. The lignite or brown coal is 
 almost entirely composed of dicotyledonous trees, the poplar, 
 willow, elm, chestnut, and maple. 
 
 trtY "^' ^ e ^ ave reason to P resume tnat tne history of 
 Afossil vegetation is not complete, since probably many 
 P r*^/J families were too frail to be preserved, and many of the 
 j dicotyledonous class were not in situations favorable to their 
 roy^ I fossilization. The grasses, so abundant at the present time, 
 5" 0*/ seem to have been almost entirely absent from the second- 
 ary period, when plants allied to them were flourishing. 
 The exuberant growth of vegetation during the coal period 
 has led M. Brogniart to conjecture that carbonic acid was 
 more abundant in the atmosphere at that time than at other 
 periods. The number of fossil species of plants at present 
 recognised and described, is about eight hundred. 
 
 144. The various forms which the carbonaceous matter 
 accumulated by plants presents anthracite coal, bituminous 
 coal, jet, lignite or brown coal, and peat depend upon the 
 original structure and composition of the plants ; upon the 
 nature of the mineral deposits in which they were imbed- 
 ded ; and upon their more or less complete seclusion from 
 the air. The conversion of wood and peat into lignite and 
 coal, is still occurring. In the state of Maine, true bitumin- 
 ous coal has been found at the depth of four feet from the 
 the surface, in a peat-bog of twenty feet thickness. Sections 
 of the coal show that it is the remains of coniferous trees, 
 immersed in the peat. The timbers of the Royal George, 
 an English ship of war sunk off Portsmouth, and raised 
 after sixty years immersion in the silt of the ocean, resem- 
 bled in texture and color, the wood of submerged forests. 
 
FOSSIL ZOOLOGY. 123 
 
 FOSSIL ZOOLOGY. 
 
 The number of animals fossil, as well as recent, is so 
 great and their structure so diversified, that an outline of the 
 classification of the animal kingdom is indispensable to a 
 due appreciation of the Divine plan manifested in their crea- 
 tion and distribution. 
 
 145. According to Cuvier's Classification, the animal 
 kingdom consists of four great divisions the Radiated, 
 Molluscous, Articulated, and Vertebrated. 
 
 146. I. The -Radiated division is so called because the 
 animals belonging to it have their organs of sense and mo- 
 tion arranged circularly, in radii from a center. They 
 either have no nervous system, or one very indistinctly 
 marked. Some are fixed as the corals ( 74.) ; others move 
 about as the star-fishes, and sea-urchins. The division of 
 Radiata embraces three classes. 
 
 1st. Sea-urchins, whose surface is studded with spines 
 Echinodermata. 
 
 2nd. Jelly-fishes, including the Portuguese man of war 
 nd sun-fishes Acalephse. 
 
 3d. Polyps, attached to the earth like plants ; many of 
 them secrete coral Polypi. 
 
 If sponges belong to the animal kingdom, they should 
 be classed with the animals of this division. The crusts of 
 the Echinodermata are well adapted to preservation and are 
 found in many of the formations, and the secretions of the 
 polyps corals abound in the rocks. The jelly-fishes, 
 having no hard parts, have very rarely been preserved. 
 Agassiz estimates the number of living species of Radiata 
 at ten thousand. About one thousand five hundred extinct 
 species have been recognised : they abound in the pake- 
 ozoic oldest fossiliferous rocks. 
 
124 PALEONTOLOGY. 
 
 147. II. The animals of the Molluscous division, have 
 their nervous systems dispersed through their bodies in 
 irregular masses; their muscles are attached to the skin, 
 which in most of them is covered with a shell, and they 
 have distinct systems of circulation and respiration. This 
 division embraces three classes. 
 
 1st. Those whose arms tentacles are arranged about 
 their mouths, as the cuttle-fish Cephalopoda. 
 
 2nd. Those which creep upon a flat disc or foot, as the 
 snails Gasteropoda. 
 
 3d. Those which have no distinct heads, and are en- 
 closed in bivalve shells, as the oyster and clam Acephala. 
 
 As these animals lived in situations favorable to the 
 preservation of their shells, we find great numbers of them 
 fossil, and they are more frequently used to determine the 
 identity, or relations of strata than any other class of fossils. 
 Shells are either univalve, bivalve, or multivalve, according 
 to the number of pieces which make up the shell. Some 
 univalve shells are divided by tight partitions, and are 
 called chambered shells. The branch of science which 
 classifies and describes shells, is termed Conchology. 
 
 The Cephalopoda abound in the older strata ; and the 
 other two classes in the more recent rocks. The total num- 
 ber of living molluscous species is estimated at fifteen thou- 
 sand. About six thousand extinct species are described. 
 
 148. III. In the animals of the Articulated division, 
 the nervous system is arranged in the form of two parallel 
 cords, which at intervals swell into knots, or ganglions. 
 The bodies of these animals consist of joints articuli each 
 one of which is furnished with a ganglion. This division 
 embraces three classes. 
 
 1st. Insects, including spiders. 
 
CLASSIFICATION OP ANIMALS. . 125 
 
 2nd. Worms, including leeches. 
 
 3d. Crustaceous animals, as the lobster and trilobite. 
 
 Insects are by far the most numerous class of animals, 
 but as they are very perishable, and are devoured by many 
 animals, few relics of them are found in the rocks : still they 
 have been found as low in the series as the coal. Spiders 
 first seen in the oolite, and scorpions in the coal. 
 with the exception of a few which secrete a calcareous cov- 
 ering, have left no trace of themselves in the strata. The 
 entire number of species of the articulate is estimated at 
 two hundred thousand. The number of extinct species now 
 known is about eight hundred. 
 
 149. IV. The highest division of the Animal King- 
 dom is the vertebratedj whose members are characterized 
 by a skull containing the brain, and a spine vertebrae 
 containing the principal trunk of nerves. They have a 
 skeleton, five senses, and red blood. Man belongs to this 
 division. It embraces four classes. 
 
 1. Animals which suckle their young Mammalia. 
 
 2. Birds. 
 
 3. Reptiles, including lizards, snakes, turtles, and frogs. 
 
 4. Fishes. 
 
 The fossil remains of animals of this division are very 
 important, intimating most distinctly the circumstances in 
 which they lived. The members of this division first intro- 
 duced were the fishes, whose remains have been found in 
 the lower Silurian and Cambrian rocks. Professor Agassiz 
 distinguishes them, according to their coverings, into four 
 orders. 1. Those with enamelled scales, like the gar-pike 
 Ganoids (fig. 73.) 2. Those with the skin like sha- 
 green, as the sharks and skates Placoids (fig. 74.) 
 3. Those which have the edge of the scales toothed, and 
 11* 
 
126 PALAEONTOLOGY. 
 
 Fig. 73. Fig. 74. Fig. 76. Fig. 76. 
 
 usually bony-rays in the fins, as the perch Ctenoids 
 (fig. 75.) 4. Those whose scales are entire, and whose 
 fin-rays are soft, like the salmon Cycloids (fig. 76.) The 
 Placoids were first introduced; and the Ganoids succeeded; 
 while Ctenoids and Cycloids were later, commencing at the 
 close of the secondary period, and constituting three-fourths 
 of the existing species. 
 
 The number of living species of fishes is eight thousand, 
 and of extinct species now known, nine hundred. 
 
 Reptiles first appear in the New Red Sandstone, and 
 become predominant in the Oolite. Their remains are 
 among the most remarkable in the strata. Tortoises are 
 found in all formations above the coal. The number of 
 species of Reptiles is estimated at two thousand. Of the 
 extinct species one hundred and twenty are known. The 
 tracks of birds are found in the rocks abundantly, as low 
 as the New Red Sandstone, and their skeletons in the 
 Wealden, Tertiary, and Diluvian. There are supposed to 
 be six thousand living species of birds, and thirty-five ex- 
 tinct species have been recognised. 
 
 The remains of Mammalia first appear in the Oolite, 
 in which some species of Marsupials (animals furnished 
 with a pouch for the protection of their young, as the Opos- 
 sum) have been found, but the remains of animals of this 
 class are found principally in the Tertiary strata, There 
 are probably two thousand living species of Mammalia; and 
 
PAL.EONTOLOGICAL CLASSIFICATION. 127 
 
 two hundred and seventy-five extinct species are described. 
 
 150. The fecal remains of fishes, reptiles, and some 
 other animals, are called Coprolites. They in some in- 
 stances clearly indicate the nature of the food of the animal 
 to which they belonged. Fig. 77. 
 
 The Coprolites of the Sau- 
 rians contain the scales 
 of fishes. The spiral con- 
 volutions of the intestines 
 characteristic of the ear- 
 liest fishes, are distinctly CoproUte - 
 impressed on their fecal remains. Coprolites are found 
 sometimes detached, and sometimes in the intestines of the 
 fossil animals.' 
 
 151. The geological formations have sometimes been 
 grouped and classified, in accordance with the predominant 
 types of animals and vegetables which lived at the time of 
 their depositions. The periods have accordingly been desig- 
 nated, as -protozoic (protos, first ; and zoe, life y) the period 
 in which are found the first forms of animated existence ; 
 mesozoic (mesos, middle ; and zoe, life ;) the period of inter- 
 mediate forms of life j and cainozoic (Jcainos, new j and zoe y 
 life ;) the period of most recent living forms. 
 
 152. The division which Professor Agassiz has proposed, 
 based upon certain classes of animals characteristic of the 
 eras during which they flourished, is more definite.* He 
 distinguishes four Ages of Nature, corresponding to great 
 geological formations. 
 
 I. The Primary or Palaeozoic Age, embracing the 
 Cambrian, Silurian, and Old Ked Sandstone systems : the 
 
 * Principles of Zoology, Chap. XTV. Section 2. 
 
128 PALAEONTOLOGY. 
 
 period during which no air-breathing animals lived ; but 
 Zoophytes, Shellfish, and Trilobites Jhlled the seas. As 
 fishes were the only representatives of the vertebrates, the 
 age is called the Reign of Fishes. 
 
 II. The Secondary Age, comprising the Carboniferous, 
 Trias, Oolite, (including the Lias,) and the Cretaceous for- 
 mations. Insects, Reptiles, Birds, and Mammals, make 
 their appearance during this period, but as reptiles prepon- 
 derate, it is called the Reign of Reptiles. 
 
 III. The Tertiary Age, embracing the tertiary for- 
 mations, in which the animals bear close resemblance to 
 those of the present day, belonging generally to the same 
 families, and very frequently to the same genera. Aquatic 
 animals do not preponderate, as in the former ages, but 
 large terrestrial mammalia abound ; hence this age is desig- 
 nated the Reign of Mammals. 
 
 IV. The Modern Age, comprising all deposits since 
 the Tertiary ; characterized by the introduction of the most 
 perfect animals, with man at their head. Some of these 
 became extinct before the creation of man as the masto- 
 don. This age is denominated the Reign of Man. 
 
CHAPTER IV, 
 
 THE UNSTRATIFIED ROCKS. 
 
 153. THE igneous rocks differ in chemical composition, 
 in modes of aggregations and in position. They often pass 
 into each other by insensible gradations. Two characteris- 
 tic minerals, feldspar and hornblende, enter into the com- 
 position of all of them. When they have cooled under 
 slight pressure they are porous in texture, as modern lavas ; 
 but when they have consolidated beneath great pressure, 
 they are dense and crystalline, as granite. 
 
 GKANITIC ROCKS. 
 
 154. The granite rocks are highly crystalline, destitute 
 of all traces of stratification, and occur as the basis upon 
 which all the systems of strata repose; they are also thrust 
 up to the surface in mountain masses, or injected into the 
 strata in tortuous veins. They are associated, for the most 
 part, with the oldest strata : they constitute the axes of 
 principal mountain chains of the globe. 
 
 155. The characteristic ingredients of granite are quartz, 
 feldspar, and mica, mingled in variable proportions. The 
 prevalent color will depend upon the predominating ingre- 
 dients -, white and flesh-colored are common hues. The rock 
 is either coarse-grained, when the distinct crystalline frag- 
 ments of which it is composed are large ; or fine-grained, 
 when they are very small. 
 
130 
 
 UNSTRATIFIED ROCKS. 
 
 The quartz and feldspar are sometimes so arranged, as 
 to present figures resembling Hebrew or Arabic letters. 
 The rock is then called graphic granite. This structure is 
 frequently exhibited by granite Fig. 78. 
 
 veins, which occur in older gran- 
 ite. When granite contains large 
 distinct crystals of feldspar, it is 
 denominated porphyritic. Gran- 
 ite appears, in some instances, as 
 at Arran in Scotland, to have 
 been protruded through the strata 
 after it had consolidated. Gra P Mc Granite - 
 
 156. In Syenite the three essential constituents are 
 quartz, feldspar, and hornblende. It derives its name from 
 Syene in Egypt, where it was formerly extensively quar- 
 ried. The rock, composed of quartz, feldspar, mica, and 
 hornblende, is called Syenitic Granite. Syenite is of a 
 dark-green, or black color. 
 
 157. The term porphyry (porphura purple) was ap- 
 plied by the ancients to a rock consisting of crystals of 
 
 Fig. 79. reddish feldspar imbedded in a 
 
 base, of which feldspar was also 
 an abundant ingredient. The 
 rock was hard, susceptible of 
 polish, and was used for archi- 
 tectural purposes, sarcophagi, 
 &c. The term porphyry is now 
 used to designate a rock of uni- 
 form compact base, through 
 which are disseminated distinct 
 Porphyry. crystals of any mineral . Crys- 
 
 tals of feldspar occur in basalt and trachyte, constituting 
 
TRAPPEAN ROCKS. 131 
 
 basaltic porphyry, and trachytic porphyry. Instead of feld- 
 spar the imbedded crystals are sometimes of hornblende, or 
 oil vine. 
 
 158. Metaliferous veins, are most numerous in the pri- 
 mary and transition rocks ; they rarely occur worth work- 
 ing above the coal. The ore does not usually occupy the 
 whole vein, but is mixed with quartz, granite, porphyry, 
 sulphate of baryta, &c., which constitutes the vein-stone, 
 gangue, or matrix. Metallic veins differ greatly in thick- 
 ness and extent; the contents of the same vein also vary in 
 its different parts. Metallic veins are most productive when 
 they pass through the junction of the unstratified and strati- 
 fied rocks : their productiveness is also influenced by their 
 direction ; the east and west courses of the tin and copper 
 veins of Cornwall are productive, while the cross courses 
 north and south veins are not worth working. 
 
 TRAPPEAN ROCKS. 
 
 159. Certain crystalline rocks, composed of feldspar, CXJN* 
 and augite or hornblende, are called trap rocks, from the 
 Swedish word trappa, a stair, because they frequently oc- 
 cur in tabular masses rising one above another, as terraces 
 
 or steps. They appear to have been ejected as lava through 
 fissures, and have produced the characteristic effects of heat ; V*-^ 
 upon the adjacent rocks. The trap rocks differ in constitu- 
 tion from the granitic, in containing much less silica, more 
 magnesia, lime, alumina, and oxide of iron ; and in being 
 
 more fusible. The trap rocks occur in dikes, in dome- 
 
 ? o v- v 
 shaped masses covering other rocks, and in regular pillars ; 
 
 they are usually compact, but sometimes are full of pores. 
 There are several varieties of trap rocks. 
 
 160. Greenstone consists of an intimate mixture of feld- 
 
132 UN STRATIFIED ROCKS. 
 
 epar and hornblende of a dark green color, and is either 
 compact or crystalline. When the rock is composed of 
 albite and hornblende in grains it is called diorite. The 
 structure of greenstone is sometimes massive, but more fre- 
 quently tabular. 
 
 161. The constituents of Basalt are augite and feldspar. 
 When the former ingredient prevails, as is usually the case, 
 the rock is of a dark green, or black color, which is due to 
 the iron in the augite. Another metal, titanium, is usually 
 an ingredient, and the mineral, olivine, is often found in 
 grains or nodular masses in basalt. When coarse crystals 
 of feldspar are disseminated in the rock, it is called porphy- 
 ritic basalt. The structure of this rock is usually columnar. 
 
 162. Trap rock, containing almond-shaped cavities, is 
 called amygdaloid, (from amygdalum, an almond.) These 
 cavities are sometimes elongated by the flowing of the 
 melted matter into cylinders several inches long. The 
 cavities of the amygdaloid are filled with zeolites, quartz, 
 calcareous spar, &c. A soft and earthy variety of trap, re- 
 sembling indurated clay, is called wacke or toadstone. 
 
 163. Trachyte is composed of feldspar, with a small 
 proportion of hornblende, titaniferous iron and mica. It 
 derives its name from its roughness, or harshness to the 
 touch trachus in the Greek language signifying rough. 
 It appears frequently in pulverulent masses of pumice, called 
 tufa or tuff in rocks of all ages, invariably indicating the 
 vicinity of erupted igneous rocks. Trachyte usually con- 
 tains distinct crystals of feldspar, and consequently is por- 
 phyritic j it is also sometimes designated trachytic porphyry. 
 A gray variety of basalt, consisting principally of feldspar, 
 produces a clear ringing sound when struck with a hammer, 
 and is called clinkstone. 
 
TEAPPEAN ROCKS. 
 
 133 
 
 164. Serpentine, a greenish rock containing a large pro- 
 portion of magnesia, sometimes traverses the strata in dikes 
 and veins, but occurs more frequently as a metamorphic 
 rock. 
 
 165. Trap rocks very frequently present themselves in 
 dikes, injected into fissures in the stratified and unstratified 
 rocks. Fig. 64, 106, presents a powerful trap dike, pene- 
 trating the strata, in New South Wales. When such dikes 
 pass through soft strata, as shale, they are sometimes left 
 prominent, by the more rapid wearing away of the soft rocks. 
 In some instances, however, they are decomposed more 
 rapidly than the containing rock, in consequence of the 
 oxidation of the iron in their composition ; in such cases 
 they leave open fissures. 
 
 166. The most conspicuous effects produced by trap 
 rocks are the changes which their intense heat has effected 
 on adjacent rocks. A trap-dike in Anglesea, passing ver- 
 tically through shale, has altered the structure of the strata 
 to the distance of thirty-five feet from itself, converting the 
 shale into a porcellaneous jasper, and obliterating the fossil 
 shells of thestra- Fig. 80. 
 
 ta. In the north 
 of Ireland basal- 
 tic dikes traver- 
 sing the chalk 
 have converted 
 it into granular 
 marble to the 
 distance of ten 
 feet. No traces 
 o f the organic re- Trap-dike, 
 
 mains, so abundant in the chalk, are discernible in the rock 
 12 
 
134 
 
 UNSTRATIFIED ROCKS. 
 
 thus crystallized. Fig. 80 represents a trap dike dis- 
 placing and altering the structure of strata. Secondary 
 sandstones have been converted thus into quartz rock. 
 Beds of coal, from their combustibility, exhibit the agency 
 of these melted rocks in a striking manner. A greenstone 
 dike passing through a coal-bed in Ireland has reduced it to 
 cinders, through a space of nine feet on each side. In the 
 north of England a similar effect has been produced by a 
 trap-dike passing through the coal series. At a distance of 
 one hundred and fifty feet, the structure of the coal is 
 changed. At a certain distance it is coked, while in the 
 immediate vicinity of the dike it is burned to soot. This 
 dike extends seventy miles and is fifty feet wide. 
 
 167. Masses of trap rock are frequently met with, in- 
 truded between strata, covering extensive areas, closely re- 
 sembling beds. They take this position when the resistance 
 offered to their progress laterally between the strata, is less 
 than that which they encounter from above. In some in- 
 stances, having spread out in horizontal sheets upon the 
 
 Fii 
 
TRAPPEAN ROCKS. . 135 
 
 bottom of the ocean, they have been subsequently covered 
 by sedimentary deposits. 
 
 168. The structure of the trap rocks, especially of ba- 
 salt, is very frequently columnar, dividing immense masses 
 into regular prisms, and constituting some of the most re- 
 markable features of the earth's scenery. The ll Giant's 
 Causeway " is the legendary name applied to the most regu- 
 lar series of the magnificent basaltic columns which abound 
 in the north of Ireland. The columns vary in the number 
 of angles from three to twelve, but have most commonly 
 from five to seven sides. They are divided transversely 
 into joints, whose upper and lower surfaces are alternately 
 concave and convex, as is shown in figure 65, 107. These 
 joints vary in length and diameter, but from six to eighteen 
 inches are the prevalent dimensions. The surfaces of these 
 
 Fig. 82. 
 
 Basaltic Pillars of Staffa. 
 
 segments are so nicely adapted to each other, that neither 
 between joints nor adjacent columns can a knife-blade be 
 introduced ; and yet each segment is completely dissevered 
 
136 
 
 UNSTRATIFIED ROCKS. 
 
 from the others, so that it may be lifted out of its place. 
 The Causeway extends under the sea. The neighboring 
 headland seen at the left in Fig. 81, consists of alternations 
 of basaltic columns, with beds of ochre interposed. As the 
 ochre is worn away by atmospheric agencies, the columns 
 are left unsupported, and many of them have fallen to the 
 base of the precipice. 
 
 169. The Western Islands of Scotland consist almost 
 exclusively of basaltic or trap rocks, which rise to the 
 height of one hundred and fifty feet above the level of the 
 ocean. The isle of Staffa is distinguished for its basaltic 
 pillars and caves. The Scallop Cave, so called because the 
 sides are formed of curved columns, extends one hundred 
 and thirty feet into the rock, is thirty feet in height and 
 twenty in breadth, at the entrance. But the principal 
 Fig. 83. 
 
 I'ingars Cave, Staffa. 
 
TRAPPEAN ROCKS. 
 
 137 
 
 object of attraction in this island is the Musical Cave, or 
 as it is more commonly known by its legendary name, 
 FingaTs Cave. This cavern is two hundred and twenty- 
 five feet in length, with an average height of sixty-five 
 feet; the breadth at the entrance is a little more than forty 
 feet, and at its farthest recess is about twenty. The sides 
 are columnar and the roof is partially so. The columns 
 have been broken away in many places by the waves, pre- 
 senting lateral recesses and jutting colonnades. 
 
 170. Basal- Fig. 84. 
 
 tic columns are 
 not always ver- 
 tical; they are 
 sometimes hor- 
 izontal, as is 
 the case with 
 "the Chimney" 
 in St. Helena 
 which is a por- 
 tion of a trap 
 dike. In broad 
 flat masses of 
 basalt the pil- 
 lars are upright 
 while in a ver- 
 tical dike they 
 :ire horizontal; 
 
 anJr generally The Chimney St. Helena. 
 
 tlioy are at right angles to the cooling surfaces. 
 
 Figure 85 represents curved columns radiating from 
 raeh side of a bank of basaltic conglomerate. The basalt 
 in contact with the bank exhibits no trace of columnar 
 12* 
 
138 
 
 UNSTRAT1FIED HOCKS. 
 
 structure ; but at a little distance regular columns appear, 
 at first horizontal; after extending thus a few feet they 
 curve gradually upward and at twenty feet distance stand 
 nearly vertical. 
 
 Fig. 85. 
 
 Basaltic Pillars New South Wales. 
 
 The columns are from four to six sided, thirty feet long, 
 and from one to four feet in diameter. The effects of heat 
 upon the conglomerate are well marked. The melted 
 basalt appears to have flowed over a small ridge of conglom- 
 erate in a stream fifty feet thick, and the forms and posi- 
 tion of the columns were determined by the varying sur- 
 face.* 
 
 171. The basaltic scenery of New South Wales delinea- 
 ted by Professor Dana, rivals that of the Scottish Isles. 
 Some of the basaltic ridges rise to the height of four thousand 
 feet above the level of the sea; and fissures or caves occur 
 similar to those of Staffa. Figure 86 presents a view of 
 the basaltic pillars at Kiama point. The sea enters through 
 the channel seen in the cut, which is twenty feet broad and 
 
 * Prof, Dana, Geology of U. S. Exploring Expedition. 
 
TRAPPEAN ROCKS. 
 
 139 
 
 eighteen high; advancing by a subterranean passage for a 
 distance of two hundred feet, it strikes against a wall of 
 basaltic columns with deafening roar, and rises through an 
 orifice to the height of one hundred feet. This is called a 
 blow-hole or spout-hole. 
 
 Fig. 86. 
 
 Kiama Blow-hole in Basaltic Columns. 
 
 172 Numerous examples of trap rocks and basaltic 
 pillars occur in the United States as the "Palisades" of the 
 Hudson River, Titan's Piazza on Mount Holyoke, East and 
 West Rocks near New Haven, Connecticut, &c. Vertical 
 dikes with horizontal pillars in Maine and North Carolina 
 present such regularity of figure and position as to have in- 
 duced the belief that they were products of human skill. 
 Trap rocks are associated with the metaliferous strata of Lake 
 Superior and California, and successive rows of basaltic 
 
140 TJNSTRATIFIED ROCKS. 
 
 columns, constituting mountain masses occur in the vicinity 
 of the Columbia River, in Oregon. 
 
 173. The columnar and globular structure so character- 
 istic of volcanic rocks, especially of basalt, early engaged 
 the attention of Geologists and induced Mr. Gregory Watt 
 to institute experiments in the year A. D. 1804 to ascer- 
 tain its origin. He melted seven hundred pounds of basal- 
 tic rock, in a reverberatory furnace. He was enabled to 
 effect its fusion with a less degree of heat than would have 
 been required by an equal weight of pig-iron. When 
 melted, it appeared as a dark, liquid, tenacious glass ; a 
 portion of it taken out and allowed to cool rapidly, retained 
 its vitreous appearance, resembling obsidian. The remain- 
 der was left in the furnace, and occupied eight days in cool- 
 ing; it was then cold externally, but still retained a consider- 
 able degree of internal heat. The interior of the mass, 
 which had cooled slowly, exhibited a great number of spheres, 
 which as they enlarged pressed laterally against each other, 
 until they were cemented into regular prisms, with seg- 
 ments of alternate convex and concave surfaces. The ar- 
 ticular structure and regular forms of basaltic columns 
 seem therefore to have resulted from the crystalline ar- 
 rangement of the particles while the rock slowly cooled 
 under pressure. 
 
 174. The Feldspathic varieties of trap rocks, as trachyte, 
 constitute the central or axial portions of mountains, while 
 the exterior portions are composed of basalt ; for instance, 
 the summit of Mount Loa is clinkstone, while all its sides 
 are basalt. This has been attributed to the difference in 
 fusibility and specific gravity of the constituents, feldspar 
 and augite. The temperature at which feldspar solidifies 
 is sufficient to keep augite quite fluid. The augite also by 
 
VOLCANIC ROCKS. 141 
 
 gradual cooling crystallizes and is converted into hornblende, 
 for these two minerals differ only in crystallization, and that 
 is determined by temperature and rate of cooling. 
 
 VOLCANIC ROCKS. 
 
 175. The term lava is applied to any rock which has 
 flowed from a volcanic vent, but it is frequently restricted 
 to the melted rocks erupted by active volcanoes or those 
 recently extinct. The constituents of such lava are the 
 same as those of the trap rocks, and we have feldspathic lava, 
 and augitic lava, according to the predominance of either 
 of those ingredients ; but we do not find the compactness 
 and crystalline structure so frequently exhibited, as in the 
 older igneous rocks. Rapidity of cooling and difference of 
 temperature and pressure, adequately account for the diver- 
 sity of forms which igneous rocks present, while their con- 
 stituents are essentially the same. 
 
 176. Lava bursting through the sides of volcanic cones 
 presents itself in dikes similar to trap dikes ; columnar 
 structure also is exhibited by them. 
 
 When thoroughly melted lava cools rapidly, it resembles 
 glass and is called volcanic glass, or obsidian ; it is usually 
 of a dark smoky color. Its fracture presents bright sur- 
 faces and sharp edges ; it has been used by the Mexicans 
 for mirrors, and knives. Lava of less glassy structure, and 
 of a pitch-like luster is called pitcTistone. 
 
 The cellular slaggy matter ejected from volcanoes is 
 called scoria ; when it is composed of feldspar, it is porous 
 and fibrous and is then called pumice. It is so light as to 
 float upon water. Scoria and pumice are the frothy scum 
 upon the surface of melted lava, and become very abundant 
 when hot lava comes in contact with water. Minute par- 
 
142 
 
 UNSTRATIFIED ROCKS. 
 Fiff. 87. " 
 
 tides of lava, light cinders, sand, &c., thrown out by vol- 
 canic eruptions, are called volcanic ashes. These materials 
 cemented together constitute peperino and pozzuolana. 
 
VOLCANIC ROCKS. 
 
 143 
 
 177. The figure on the preceding page presents an ideal 
 section of the Earth's Crust, exhibiting the order of succes- 
 sion in the stratified rocks, and the relative positions of the 
 unstratified. 
 
 B, signifies the classification adopted by Dr. Buckland; 
 and L, that of Mr. Lyell. 
 
 1. Quaternary or modern de- b. 1. Granite and Quartz Veins 
 posits. in Granite. 
 
 2. The deposits of the Terti- b. 2. Granite and Quartz Veins 
 
 ary. 
 
 3. The Chalk formation. 
 
 4. TheWealden. 
 6. The Oolite. 
 
 6. The Lias. 
 
 7. The Triassic system. 
 
 8. The Carboniferous system. 
 
 9. The Old Red Sandstone. 
 
 10. The Silurican. 
 
 11. The Cambrian. 
 
 12. Mica Slate. 
 
 13. Gneiss. 
 
 14. Granitic Rocks. 
 
 15. Volcanic Rocks. 
 
 a. 1. Porphyritic dike overly- 
 
 intersecting the porphyry, 
 gneiss, and mica slate. 
 
 b. 3. Granite Vein passing into 
 the transition rocks. 
 
 c. Greenstone dike of the tran- 
 sition period. 
 
 c. 1. Trap Dike intersecting a 
 
 dike of porphyry. 
 c. 2. Trap Dike of the Oolitic 
 
 period. 
 
 c. 3. Lava Dike of the volcanoes 
 of the Tertiary period. 
 
 d. Lava of active volcanoes. 
 
 e. Cave in the magnesian lime- 
 stone. 
 
 f. Metaliferous veins. 
 
 ing the gneiss. 
 a. 2. Dike of Porphyry passing g. An extinct volcano, 
 through the coal. h. An Artesian well. 
 
CHAPTER V, 
 
 THE STRATIFIED PRIMARY ROCKS. 
 
 178. IN describing the stratified rocks, we may begin 
 with the most recent, in which the circumstances of deposi- 
 tion were very similar to those existing at the present time, 
 and proceed to the most ancient strata whose origin was in 
 a condition of nature widely different from the present, as 
 regards both their mineral structure and fossil contents. 
 But the chronological order appears to be more natural and 
 satisfactory ; commencing with the oldest strata, which are 
 very widely extended, and more uniform in character, fol- 
 lowing the succession exhibited in nature, the facts may be 
 delineated in the order of their occurrence. A knowledge 
 of the phenomena of the older rocks is indispensable to a 
 due appreciation of the characters of the more recent, since 
 the latter are principally derived from the former. 
 
 179. The primary stratified rocks the oldest sediment- 
 ary deposits are composed of the same minerals that con- 
 stitute the plutonic, granitic rocks, upon which they lie, and 
 by the abrasion of which they were produced. As a class 
 they are silicious in mineral character, and crystalline in 
 structure; exhibiting, however, a stratified arrangement. 
 Their particles appear to have undergone less attrition, 
 and subjection to a higher degree of heat than the more re- 
 
METAMORPHIG ROCKS. 145 
 
 cent strata. No organic remains have been found in them ; 
 vegetables and animals either did not live upon the earth 
 at the time of their deposition, or all traces of them 
 have been obliterated by the heat to which the rocks 
 have been subjected. Their thickness is variable, but 
 usually very great; in some instances exceeding twenty 
 miles. They are more widely extended than any other class 
 of strata, and where they form the surface they present bold, 
 rugged, and mountainous outlines. Their order of super- 
 position is not invariable; gneiss, however, usually lies 
 directly upon the granite, and mica-slate succeeds. This 
 class of rocks has been denominated metamorphic (109.) 
 Veins and dikes of the igneous rocks, granite, porphyry, 
 and greenstone, with metaliferous veins are frequently 
 found traversing them. 
 
 Fig. 88. 
 
 Gneiss. 
 
 180. The term gneiss derived from a Saxon word sig- 
 nifying to sparkle is applied to a crystalline aggregation of 
 quartz, feldspar, and mica, distinctly stratified, in which the 
 feldspar is less abundant than in granite, and the quartz is 
 in fine grains. The .mica gives to the rock a glistening as- 
 pect. Gneiss passes insensibly into granite, so that it is 
 often difficult to say where the granite terminates and the 
 
 13 
 
146 STRATIFIED PRIMARY ROCKS. 
 
 gneiss begins. The laminae and strata are usually parallel 
 to each other, and to the surface of the igneous rock upon 
 which they lie, but frequently exhibit remarkable contor- 
 tions, indicating a previous state of great flexibility. Dr. 
 M'Culloch observes: "Imagination can scarcely conceive 
 an intricacy of flexure of which a resemblance could not be 
 found in the gneiss of the Western Isles of Scotland." 
 
 Distinct crystals of feldspar are sometimes found in 
 gneiss; it is then termed porphyritic. When talc takes 
 the place of mica, the rock is called protogine. If horn- 
 blende is added to the ordinary constituents of gneiss, the 
 rock is termed syenitic. A section of Fig. g9. 
 
 graphic granite parallel to its imper- 
 fect laminae, fig. 89, closely resem- 
 bles a transverse section of gneiss. 
 
 181. Mica-slate differs from gneiss, 
 in the absence of feldspar, the greater 
 predominance of mica, and the more 
 perfect slaty structure ; it often, how- 
 ever, passes gradually into gneiss. Perfect crystals of gar- 
 net and staurotide sometimes occur in this rock in as large 
 proportions as either of its constituents, it is then denomina- 
 ted garnetiferous and staurotidiferous. Mica-slate passes by 
 insensible gradations into clay-slate, and into talcose-slate. 
 182. Hornblende-slate is composed principally of horn- 
 blende, with a variable quantity of feldspar, quartz, and 
 mica. When the hornblende and feldspar occur mixed in 
 equal quantities the characters of the rock correspond with 
 those of greenstone. Hornblende-slate occurs in all parts 
 of the primary series, but is most frequently associated with 
 mica-slate and clay-slate, into which it passes by impercept- 
 ible gradations. 
 
SERPENTINE PRIMARY LIMESTONE. 147 
 
 183. The essential ingredient of talcosc-slate is talc, 
 which is sometimes pure, but more frequently mixed with 
 feldspar, quartz, and mica. Steatite or soap-stone is a va- 
 riety of this rock in which talc greatly predominates, is of 
 a grayish green color, greasy feel, and is easily cut. Chlo- 
 rite-slate is another variety, of a compact texture, and green 
 color. Talcose-slate is a metaliferous rock, and frequently 
 the repository of gold. 
 
 184. Serpentine, as stated in 164, occurs both as a 
 stratified and unstratified rock ; in the former case exhibit- 
 ing the characters of strata. As a metamorphic rock it is 
 associated principally with talcose and hornblende slates. 
 
 185. Primary limestone, is a crystalline limestone, fre- 
 quently pure white, and close grained, constituting the 
 marble of sculpture ; but is sometimes compact, and dark- 
 colored. It occurs in thick beds, and in thin leaves. It 
 alternates with gneiss, mica-slate, and clay-slate, and then 
 usually contains some crystals of mica, quartz, and feldspar. 
 It has been found in syenite, hornblende, and granite, en- 
 tirely destitute of any trace of stratification, and even some- 
 times in the form of veins. 
 
 186. Quartz rock occurs interstratified with each one 
 of the primary rocks. When pure it is granular, crystal- 
 line, with little or no tendency to divide in parallel beds ; 
 but when mixed with feldspar, mica, hornblende, talc, or 
 clay slate, it exhibits regular stratification. In some in- 
 stances it is eminently arenaceous a mass of sand, exhi- 
 biting mechanical structure, and apparently made to cohere 
 by the heat to which it has been subjected. 
 
 187. Clay-slate, or argillaceous schist is a rock common 
 to the metamorphic and fossiliferous series. It consists of 
 a very fine mixture of mica or talc with quartz, a large pro- 
 
148 STRATIFIED PRIMARY ROCKS. 
 
 portion of argillaceous matter, a little iron, and some of the 
 alkaline earths. Its prevalent colors are bluish-black, green, 
 purple, and mottled, often accompanied by a glossy luster. 
 Some varieties of slate are soft, and easily worn away, while 
 others are hard and splintery. The slate which is imme- 
 diately in contact with trap or other igneous rocks, has lost 
 its fissile character having become flinty and changed its 
 color. It often occurs interstratified with mica-slate and 
 quartz rock, and in proportion to its nearness to granite or 
 other igneous rocks, it is more highly glazed ; it passes 
 gradually into talcose, hornblende, or mica slates. Passing 
 in the other direction, its luster becoming more dull and its 
 texture less compact, it is called shale, and still farther up 
 in the series it exhibits itself in beds of clay. Roofing- 
 slate is a fine grained variety, of a bluish-black or purple 
 color, splitting into thin, even slates. Drawing slate is a 
 finer and more compact variety, containing some carbon. 
 The Whetstone or hone slate is a fine-grained slate filled 
 with minute grains of quartz, or grit. 
 
 188. Slates exhibit the phenomena of cleavage and 
 joints with greater distinctness and regularity than any 
 other rocks, and it is owing to this structure that they are 
 
 Fig. 90. 
 
 Parallel Planes of Cleavage intersecting Curved Strata. 
 
 capable of being split so evenly and extensively. Figure 
 90 presents the cleavage planes preserving their parallelism 
 through contorted strata, and through alternations of fine- 
 
STRATIFIED PRIMARY ROCKS. 149 
 
 grained and coarse-grained slates, independent of the dip 
 of the strata, (111.) 
 
 Joints are distinguished from cleavage planes by the 
 absence of all tendency in the rock to split between joints 
 in a direction parallel to the joints, while the slate is capa- 
 ble of indefinite subdivision in the direction of the cleavage 
 planes. In Figure 91, the flat surfaces, ABC, represent 
 
 Stratification, Joints, and Cleavage. 
 
 exposed faces of joints, to which the walls of other joints, 
 j j, are parallel : s s, are lines of stratification ; c C, are 
 lines of slaty cleavage intersecting the planes of stratifica- 
 tion at a considerable angle,* (110.) 
 
 189. The clay-slate is sometimes fossiliferous, especially 
 as it occurs higher in the series. Anthracite occurs in pri- 
 mary limestone, mica slate and gneiss ; and Mr. Lyell sug- 
 gests that it is altered coal, since we observe coal in the 
 vicinity of trap-dikes converted into anthracite. Graphite, 
 plumbago or black lead, which is nearly pure carbon, is 
 found in clay-slate and gneiss, and is supposed by some 
 geologists to be coal still farther changed by the action of 
 heat. 
 
 *LyeH's Elements. 
 
CHAPTER VI, 
 
 TRANSITION OR PALAEOZOIC CLASS OF ROCKS. 
 
 190. THE rocks of this class are characterized by their 
 wide geographical diffusion, and great thickness, amounting 
 to many thousand feet. They were originally designated 
 Transition by Werner, but are more appropriately termed 
 palaeozoic, since they contain the most ancient forms of 
 living beings. 
 
 THE CAMBRIAN SYSTEM. 
 
 191. The transition from the crystalline and non-fos- 
 siliferous rocks, to the succeeding stratified fossiliferous, 
 has been investigated in North Wales by Mr. Murchison 
 and Prof. Sedgwick; hence the system is designated Cam- 
 brian, from Cambria or Wales. The rocks of this system 
 are of enormous thickness, and eminently argillaceous in 
 composition, varying from the finest clay-slate to coarse 
 conglomerates. The term grauwacke (grey-wacke) used 
 by German miners to indicate a grey rock, has sometimes 
 been applied to the predominant member of this system, 
 and to the system itself, inappropriately, since greywacke 
 is a general term applied to rocks of different geological 
 periods. The system is subdivided into three groups, 
 taking names from the localities in which they are de- 
 veloped in Wales. 
 
THE SILURIAN SYSTEM. 151 
 
 i " i 
 
 CAMBRIAN SYSTEM THICKNESS ABOUT NINE THOUSAND FEET. 
 
 Plynlimmon ROCkS^-Slates, and conglomerates several thousand 
 feet thick. 
 
 Bala Limestone A dark limestone, associated with slates, and con- 
 taining remains of corals, shells, and fishes. 
 
 SnOWdon Rocks Fine grained, dark colored slates, and conglom- 
 erates, with remains of marine plants, fucoids, shells and 
 zoophytes, several thousand feet in thickness. 
 
 The propriety of separating these groups from the fol- 
 lowing system the Silurian is questioned by some geolo- 
 gists. 
 
 THE SILURIAN SYSTEM. 
 
 192. The Silurian system from the Silures, ancient 
 Britons who inhabited Wales, where the rocks were first in- 
 vestigated and the system established by Mr. Murchison 
 embraces numerous rocks, consisting of sand, clay and 
 limestone, abounding in organic remains, and giving clear 
 indications of marine sedimentary origin. Some of the 
 slates are very fine grained, while others are coarse con- 
 glomerates. The limestones are frequently highly crystal- 
 line. 
 
 UPPER SILURIAN ABOUT FOUR THOUSAND FEET THICK. 
 
 The TileStOUe Hard, finely laminated, greenish sandstones, with 
 reddish shales ; organic remains abundant. 
 
 The Upper LlldloW Rock Fine grained yellowish sandstones ; beds 
 of argillaceous sandstones filled with sea weeds, zoophytes, 
 and scales, fins, jaws, teeth, and coprolites of fishes. 
 
 The AymeStry Limestone A bluish gray limestoraj, mottled with 
 white, containing numerous layers of shells and corals 
 
 The Lower LlldlOW formation Shales becoming slightly calcare- 
 ous ; sandy flagstones. 
 
152 TRANSITION OR PALAEOZOIC ROCKS. 
 
 The WenlOCk Limestone Concretions of argillaceous limestones 
 separated from each other by beds of shale ; extremely fos- 
 siliferous. 
 
 The WenlOCk Shale Dark gray argillaceous beds, with calcareous 
 concretions ; remains of fishes. 
 
 LOWER SILURIAN ABOUT THREE THOUSAND FIVE HUNDRED FEET 
 THICK. 
 
 The CaradoC Sandstone Finely laminated, greenish, fossiliferous 
 
 sandstones ; shelly limestones; remains of corals, mollusca, 
 
 trilobites. 
 ThC LandeilO Flags Hard, dark-colored, sandy flagstones, with 
 
 beds of limestone ; remains of trilobites, and mollusca 
 
 abundant. 
 
 193. Although the subdivisions of the Silurian sys- 
 tem established by Mr. Murchison, as existing in Wales, 
 not recognised in the rocks of that period, in other 
 +. parts of the world, a similar arrangement is discernible in 
 |hem, and his system is the universal standard of reference 
 in comparing them. Silurian rocks, with essentially the 
 same mineral characters and fossil contents, are found in 
 ia, Norway, Sweden, Asia, Africa and Australia. In 
 North America, they are expanded on a scale of extent 
 both lateral and vertical far superior to that of the Welsh 
 rocks. One group of beds of shales and limestones, sup- 
 posed to be contemporaneous with the Ludlow series of 
 / Wales, occupies a surface of more than 10,000 square 
 miles in the valley of the Ohio. The Central and Western 
 districts of the State of New York present these rocks on 
 a magnificent scale, as detailed in the geological survey of 
 that State. Specimens of these rocks have also been ob- 
 tained within the Arctic Circle, and in Terra del Fuego. 
 ~~ T 194. Great interest attaches to the fossils of the oldest 
 
 wy 
 
THE SILURIAN SYSTEM. 
 
 153 
 
 palaeozoic rocks, both because they are the most ancient 
 forms of organized beings of which we have any knowl- 
 edge, and are very unlike the present races. Representa- 
 tives of all the classes of the animal kingdom are found in 
 them. Of the vertebrata, fishes Placoids and Ganoids 
 only have been discovered. 
 
 Trilobites are the principal representatives of the Crus- 
 tacea, which are found in some localities heaped together 
 in vast multitudes. These animals were of an oval figure, 
 protected by a shield, cov- Fig. 92. 
 
 ering the anterior parts of 
 the body, while the ab- 
 dominal portions consisted 
 of segments, which ena- 
 bled them to roll them- 
 selves into balls, so as to 
 present their hard crusts 
 in all directions in self- 
 defense, as do the lobster 
 and woodlouse of the pre- 
 sent day. Their organs 
 of locomotion, if any exist- 
 ed, must have been small, 
 membranaceous or rudi- 
 mentary, since no distinct 
 traces of them have yet 
 been satisfactorily made 
 out. They were destitute 
 of antennae. The back 
 presents two longitudinal furrows, dividing its surface 
 into three lobes; hence the name Trilobite. Their eyes 
 which are in many specimens perfectly preserved, giv- 
 
 Trilobite. 
 
154 TRANSITION OR PALAEOZOIC ROCKS. 
 
 ing us some indications of the condition of the early 
 seas in which they lived, were compound, consisting of a 
 great number of angular fayettes or lenses, similar to the 
 eye of the dragon fly, in which there are twenty-five thou- 
 sand; and of the house fly, in which there are fourteen 
 thousand fa ettes : the trilobite had several hundreds. In 
 Fig. 93. order to extend the field of vision, since 
 
 the eye was immovable, it was elevated 
 above their bodies. The form of the 
 eye was that of a frustum of a cone, in- 
 complete on the side opposite the corres- 
 ponding part of the other eye, enabling 
 the animal to see in all directions hori- 
 zontally. This structure of the eye indi- 
 cates that light bore the same relations 
 to vision then, as it now does, and that 
 these animals lived in water sufficiently 
 transparent to transmit light. " We find 
 in these animals," says Dr. Buckland, 
 " an optical instrument of most curious 
 construction, adapted to produce vision 
 Eye of the Trilobite. O f a particular kind, created in the ful- 
 ness of perfection, and fitted for the uses and condition of 
 the class of creatures to which this kind of 
 eye ever has been and still is appropriate." 
 Trilobites vary from one to twenty inches in 
 length. They were very abundant among 
 the earliest inhabitants of the globe, and con- 
 tinued into the carboniferous period, after 
 which no trace of them is discerned. Two 
 hundred and thirty species, under several 
 genera of the family Trilobite, have been 
 
THE SILURIAN SYSTEM. 155 
 
 described; of which the genus Calymene, fig. 94, is found 
 in the Wenlock division of the Upper Silurian rocks. 
 
 195. Of the Mollusca, the most numerous representa- 
 tives in the Silurian rocks belonged to the class Cephalo- 
 poda ( 147) including the Ammonite and Nautilus, and to 
 the order Brachiopoda of the class Acephala. The latter 
 inhabited bivalve shells, the valves of which, however, were 
 not secured by a hinge, but were confined by a bundle of . 
 muscular fibres attached to one shell and passing through 
 an aperture in the beak of the other ; this gives to the inte- 
 rior of the shell a peculiar appearance. Several hundred 
 species of the Brachiopoda have been discovered in these 
 rocks. Among them was the genus Terebratula ; created 
 among the first, it has survived longer than any others, 
 having several living species in the seas of the present day. 
 The genera Leptsena (Producta,) Delihyris, Orthis. (Spiri- 
 fer^) and Pentamerus, belong to this period. 
 
 The Orthoceratite (prihos, straight; keras, horn,) was a 
 straight shell, divided into numerous chambers by septa or 
 partitions, which were perforated so that a tube (siphuncle) 
 might communicate with all of them. 
 Fig. 95. 
 
 HHriHHHHHHH 
 
 Orthooeratite. 
 
 196. Of the Radiata of the Silurian period, the coral 
 polyps were the most numerous ; their fossils form a very 
 large proportion of the whole mass of the limestones, crowd- 
 ed together as are the corals of coral reefs in the existing 
 oceans. The Chain-coral Catenipora is a beautiful ge- 
 
156 
 
 TRANSITION OR PALEOZOIC ROCKS. 
 
 nus characteristic of the Upper Silurian beds. In the 
 lowest beds, and among the earliest forms of life, are found 
 great numbers of a fossil, called, from their markings upon 
 the rocks, Graptolites, supposed to have been zoophytes, 
 
 Fig. 96. 
 
 Graptolithus Murchisoni. 
 
 Graptolithus Ludensis. 
 
 allied to the sea-pens which inhabit the muddy sediment of 
 the deep waters of the existing oceans. The Graptolites 
 are not found in the limestones, but in the flags or slates 
 of the Cambrian and Silurian rocks, and especially in a 
 mud-stone, which indi- 
 cates tranquil deposi- 
 tion. The Crinoid or 
 Encrinite family is rep- 
 resented in this group 
 of rocks, but was more 
 fully developed at a later period. The fossils of the Silu- 
 rian rocks indicate that they were deposited in deep seas, 
 and in a temperature at least as high as that of the tropi- 
 cal regions of the present period. Marine plants were 
 abundant, but the existence of land plants or animals at 
 that period has not been established. 
 
 197. The igneous rocks associated with the Cambrian 
 and Silurian systems, are granite, porphyry, and greenstone, 
 whose incursions have often given to the strata inclined and 
 contorted positions. But the Silurian beds of Sweden are 
 horizontal, and those of the State of New York are but 
 slightly inclined. 
 
THE DEVONIAN SYSTEM. 157 
 
 THE OLD RED SANDSTONE DEVONIAN SYSTEM. 
 
 198. This system, consisting of conglomerates, sand- 
 stones, marls, and limestones, is intermediate in all respects 
 between the Silurian and Carboniferous systems. The pre- 
 valent color of the marls and sandstones dull red is due 
 to the peroxide of iron. It is called the Old Red Sand- 
 stone, to distinguish it from the New, which lies above the 
 coal. It is extensively developed in Herefordshire and 
 Devonshire in England, and in Scotland, where it has been 
 fully investigated.* Although the beds of Devonshire 
 differ from those of Herefordshire and Scotland, in mineral 
 and mechanical condition, the characters of their fossils 
 clearly show them to be contemporaneous with the Old 
 Bed Sandstone of the other districts ; hence the system is 
 sometimes called Devonian. 
 
 199. Tabular arrangement of the English and Scottish 
 members of the series : 
 
 OLD RED SANDSTONE ABOUT TEN THOUSAND FEET THICK. 
 ENGLAND. BCOTLAND. 
 
 {Quartzose Yellow Sandstone, \ 
 Impure Limestone, LTJppEB. 
 
 Gritty Red Sandstone. J 
 
 Cornstone Gray fissile Sandstone. . . MIDDLE. 
 
 Cornstones and Marl, - 
 
 Red and variegated Sand- 
 stones, 
 
 Bituminous Schists, 
 Coarse gritty Sandstone, 
 Great Conglomerate. 
 
 - LOWER. 
 
 In Scotland the base of the system is an extensive, thick 
 
 * " A New Walk in an Old Field The Old Red Sandstone, by 
 Hugh Miller, Esq.," is a work by a man of self-taught genius, 
 combining the accuracy of scientific research with the fascinations 
 of romance. 
 
 14 
 
158 TRANSITION OR PALEOZOIC ROCKS. 
 
 conglomerate; this is succeeded by coarse red and yellow 
 sandstones alternating with green and red marls; upon this 
 lie very thick beds of calcareous, micaceous and bituminous 
 schists, loaded with fossil nshes, and containing impressions 
 of plants. 
 
 The middle group, corresponding to the Cornstone of 
 England, consists of a bluish gray sandstone and beds of 
 friable stratified clay, while the contemporaneous English 
 beds are principally red and green marls. 
 
 The upper part of the formation presents beds of sand- 
 stone alternating with limestone barren of fossils, and con- 
 taining masses of exceedingly hard chert. 
 
 200. The subdivisions of the Devonian System, in Scot- 
 land and England are local, but serve as standards of com- 
 parison for the rocks of the same system in other parts of 
 the world. They have been investigated as developed in 
 Ireland, Belgium, and Russia; and are known to exist in 
 South America and Australia. In North America, their 
 essential characteristics, mineral and organic, have been 
 shown to be identical with those of the Scottish series ; they 
 are developed in the States of Pennsylvania and New York, 
 and west of the Alleghanies, in some places from one thou- 
 sand to fifteen hundred feet thick. 
 
 201. The organic remains of this period are very pecu- 
 liar, consisting of corals, molluscous and radiated animals, 
 not differing widely from those of the Silurian system ; but 
 the vertebrate animals are here represented by a large num- 
 ber of species of singular fishes, in many instances so well 
 preserved as to exhibit their outlines distinctly. These 
 fossil fishes are sometimes denominated ictithyolites, (ichthus 
 a fish ; lithos a stone,) and although traces of them are dis- 
 cerned in the Silurian rocks, their abundance and perfect 
 
THE DEVONIAN SYSTEM. 159 
 
 preservation in the Devonian system have rendered them 
 characteristic of it. They belonged to the Ganoid and Pla- ^^^ 
 coid orders of fishes, ( 149.) Of the eighty Ganoid spe- 
 cies hitherto described, more than fifty belong exclusively 'Vv- 
 to the Old Red Sandstone formation. The Ganoid fishes 
 are covered with angular scales of bone, coated with enamel, V-jp~ 
 which regularly arranged invest the whole animal. Many <o 
 of these fishes, in the structure of their teeth and other pe- **** J 
 culiarities approximate the reptiles, and hence are called 
 Sauroid. The Ganoid species are nearly extinct ; the stur- ^.^ 
 geon and bony pike are, however, living representatives of 
 the order. Another feature of the fishes of this period 
 approximating them to the Saurian 
 
 lgf * ^^^f type, is the prolongation of the *-* 
 vertebral column into the caudal 
 fin, producing a lieterocercal tail, 
 as represented in figure 98. In all 
 fishes of the existing seas, with the 
 
 exception of the sturgeon, shark, and bony pike, the verte- 
 bral column terminates at the point, 
 from which the caudal fin is given 
 off equally, above and below, consti- 
 tuting a homocercal tail, as exhib- 
 ited in figure 99. All the fishes of 
 the Palaeozoic period had unequally 
 bilobate or heterocercal tails. 
 
 202. The Cephalaspis was a fish, whose most striking 
 feature was an enormous shield forming the head ; hence 
 the name (7cephale, head; aspis, shield.)' This crescent- 
 shaped buckler gave the animal the apgearance of a trilo- 
 bite, and the first discovered specimens were supposed to be 
 crustaceous. The body was comparatively small, elon- 
 
160 
 
 TRANSITION OR PALEOZOIC ROCKS. 
 
 gated, terminating in a heterocercal Fig. 100. 
 
 tail. It was furnished with fins ; the 
 
 dorsal fins are usually conspicuous. 
 
 The body and head were covered 
 
 with bony, enamelled scales. This 
 
 fish seems not to have attained a 
 
 large size ; specimens are about 
 
 seven inches in length. 
 
 203. Another equally singular ge- 
 nus was the Pterichthys the winged 
 fish (Pteron, a wing; ichthus, a fish,) 
 characterized by its two wing-like 
 lateral appendages, which were its 
 weapons of defense, and may have 
 assisted in locomotion. Its body 
 was protected by strong, bony, enam- Cephaiaspis Lyeua. 
 elled plates; its head was small, body flat, and its tail 
 thickly covered with scales. It did not exceed a foot in 
 length. 
 
 Fig. 101. 
 
 Pterichthys Corrmtus. 
 
THE DEVONIAN SYSTEM. 
 Fig. 102. 
 
 161 
 
 Coccostcus. 
 
 204. The Coccosteus resembles the Pterichthys in general 
 structure and covering, but was destitute of wing-like appen- 
 dages. It derives its name from the berry-like tubercles 
 which stud its enamelled bony plates (kokkos a berry ; osteon, 
 a bone.) Its head was large, covered with several plates, and 
 attached to the body by small articulating surfaces. The up- 
 per part of the body was covered with one plate and the low- 
 er part with four. The tail was much longer than the body 
 and furnished with two fins. Many other genera belonging 
 to this period have been described, among which may be 
 named the Holoptychius, whose bony plates are more numer- 
 ous and smaller j and the Osteolepis, in which the bony plates 
 become scales and the figure of the animal approximates 
 that of existing fishes. Some of these attained a large size. 
 205. The brachiopodous genera of shells, Terebratula, 
 Orthis, Spirifer &c., except the Fig. 103. 
 
 Pentamerus, of the Silurian pe- 
 riod are extended into that of the 
 Old Red Sandstone. The corals 
 CyathopTiyllum and Favosites also 
 are common to the two periods. 
 The Favosites consisted of a conge- 
 ries of diverging ascending tubes 
 divided by lamellae and communi- Favosites Poiymorpha. 
 eating with each other by lateral openings. Figure 104 
 presents a polished section magnified to show the interior 
 
 14* 
 
162 TRANSITION OR PALEOZOIC ROCKS. 
 
 Fig. 104. structure. The rocks of New York and Ohio 
 abound in specimens of this genus. The tri- 
 lobites of the previous period reappear in the 
 Devonian, in several species of which the 
 Brontes grew to the length of four feet, and 
 closely resembled the lobster, having similar 
 tuberculated claws. 
 
 206. The plants of the Devonian period appear to have 
 been mostly marine fucoids, which are so numerous in some 
 of the straty, that the slate beds owe their fissile character 
 to the layers of carbonated sea weeds. Ferns and plants 
 allied to the Lepidodendra of the carboniferous period oc- 
 cur; and Mr. Miller has recently proved that Dicotyledon- 
 ous gymnospermous plants with true woody fibre existed at 
 that time.* 
 
 207. The igneous rocks associated with these strata, 
 are principally varieties of the trap, which have invaded 
 and distorted many of the beds. At the close of the Devo- 
 nian period, the true granitic eruptions appear to have ceased. 
 
 THE CARBONIFEROUS SYSTEM. 
 
 208. The Carboniferous system consists of a widely ex- 
 tended series of fossiliferous limestones, alternating with 
 sandstones and dark bituminous shales, containing beds of 
 coal. The subdivisions of the system in England are rep- 
 resented in the following table. 
 
 CARBONIFEROUS SYSTEM. 
 
 C Sandstone, Shale, and Coal, alternating 
 The COAL MEASURES, with beds of clay and ironstone. Land 
 
 { plants in profusion. 
 
 3000 feet thick. Limestone, with fresh-water and marine 
 
 [ shells. 
 
 * Footprints of the Creator, p. 222. 
 
TllK CARBONIFEROUS SYSTEM. 
 
 163 
 
 MILLSTONE GRIT, J Sandstone, Shale, and Conglomerate, 
 600 feet thick. } Shale and thin seams of coal coal plants. 
 
 (" Limestone and flagstone abounding in cor- 
 als and marine shells ; with layers and 
 nodules of chert. Ores of copper, zinc, 
 lead, barytes, and fluor spar. 
 
 CARBONIFEROUS, or 
 MOUNTAIN LIME- - 
 STONE, 1800 feet 
 thick. 
 
 Limestone, with innumerable shells spiri- 
 fer, goniatitc, orthocei-atite, bellerophon, 
 &c. 
 
 Varieties of black, bluish gray, and varie- 
 gated marbles. 
 
 This system of rocks is developed in Ireland, France, 
 Belgium, Spain, llussia, China, and America. 
 
 209. The organic remains of this period are of marine, 
 fresh-water, and terrestrial origin. Ichihyolites teeth, fins, 
 Fig. 105. 
 
 Fossil Fish, Ohio. 
 
 spines, scales and coprolites of fishes, as well as the entire 
 fish abound. The fishes belonged to the ganoid and placoid 
 orders sauroid and in some instances, as in the Megal- 
 ichthys, were of gigantic size. 
 
 Of the Crustacea, the trilobites were still the principal 
 representatives. Shell fish were very numerous and large 
 representatives of all the orders multivalve and univalve, 
 single-chambered and many chambered occur aggregated in 
 masses, as they lived gregariously. Among the bivalves 
 the Terebratula-, Spirifer, and Inoceramus ; and among uni- 
 
164 
 
 TRANSITION OR PALAEOZOIC ROCKS. 
 
 valves, the Goniatite, Orthoceratite, Bellerophon, Euompha- 
 lus and Ammonite, were frequently recurring genera. 
 
 Fig. 106. A few spe- 
 
 cimens of Co- 
 leopterous in- 
 sects beetles, 
 and of the scor- 
 pion have been 
 found in this 
 series. Of the 
 radiata, the 
 crinoid or eri- 
 crinite family, 
 of which the 
 Pentacrinite is 
 a member were 
 most abund- 
 ant; (223) 
 some of the 
 limestones of 
 this group are 
 composed al- 
 most exclu- 
 sively of their 
 remains, and 
 are designated 
 encrinal. The 
 coral polyps 
 formed exten- 
 sive reefs. The 
 marine fossils 
 of this period 
 
 Pentaerinlte. 
 
THE CARBONIFEROUS SYSTEM. 165 
 
 arc mostly confined to the lowest member of the system 
 the carboniferous limestone, in which they are estimated to 
 form at least three-fourths of the whole mass. 
 
 210. In the organic remains of the upper members of 
 the system the coal-measures the great abundance of 
 vegetable fossils, indicating a most luxuriant growth of land 
 plants, is the most striking feature. That coal is of vegeta- 
 ble origin, is abundantly proved by the organic structure 
 which can be seen in it with the aid of a microscope. The 
 differences observed in coals may be due to their origin 
 from difljprent plants. The coal occurs in strata of sand- ... 
 stones and shales, with intervening layers of ironstone and " 
 limestone, some of which appear to be of fresh-water, and some 
 of marine origin. The beds of coal vary in thickness from the 
 
 fraction of an inch to thirty feet ; in one of the English coal- 
 fields their aggregate thickness is one hundred and fifty feel. 
 The number of beds also varies, sometimes exceding one 
 hundred ; the central beds are usually the thickest and purest. 
 The coal-measures are often designated as basins because JN/--\I 
 they present themselves in troughs or basin-shaped cavities. 
 211. The shales which underlie and overlie the beds 
 of coal contain the best specimens of the coal plants, which 
 occur between every succession of laminae. The newly 
 exposed roof of a coal mine presents a beautiful display of 
 interlacing stems and leaves. " The most elaborate imita- 
 tions of living foliage on the painted ceilings of Italian 
 palaces bear no comparison with the beauteous profusion of 
 extinct vegetable forms, with which the galleries of these 
 instructive coal-mines are overhung. The roof is covered 
 as with a canopy of gorgeous tapestry, enriched with fes- 
 toons of most graceful foliage flung in wild irregular pro- 
 fusion over every portion of its surface. The effect is 
 
106 TRANSITION OR PALAEOZOIC ROCKS. 
 
 heightened by the contrast of the coal black color of these 
 vegetables, with the light groundwork of the rock to which 
 they are attached. The spectator feels transported, as if by 
 enchantment into the forests of another world ; he beholds 
 trees of form and character now unknown upon the surface 
 of the earth, presented to his senses almost in the beauty 
 and vigor of their primeval life ; their scaly stems and bend- 
 ing branches, with their delicate foliage are all spread forth 
 before him, little impaired by the lapse of indefinite ages, and 
 bearing faithful records of extinct systems of vegetation, which 
 began and terminated in times of which these relics are the 
 infallible historians. Such are the grand natural herbaria, 
 wherein these ancient remains of the vegetable kingdom are 
 preserved in a state of integrity little short of their living per- 
 fection, under conditions of our planet which exist no more."* 
 212. Several hundred species of coal plants have been 
 discovered which are allied in their generic characters to the 
 ferns, canes, pines, cacti &c., but as species, became extinct 
 before or at the close of the carboniferous period. The 
 same species are mostly found in coal beds in Europe, Aus- 
 tralia, the United States, and in Melville Island in 75 
 north latitude. The plants of the present period which 
 most resemble the coal plants, live within the tropics, and 
 are very much smaller than the corresponding members of 
 the Flora of the carboniferous^era. One of the most common 
 fossils of the coal strata is the catamite, so called from its 
 reed-like appearance. It was cylindrical, gradually tapering 
 to a point, and frequently curved at the extremity ; ribbed 
 or furrowed longitudinally, and surrounded at intervals by 
 horizontal rings or articulations. It was a branching plant 
 with a hollow stem, woody tissue, and distinct bark. It has 
 
 * Dr. Buckland's Bridgewater Treatise, p. 458. 
 
THE CARBONIFEROUS SYSTEM. 
 Fig. 107. 
 
 167 
 
 Tree Fern. 
 
 been supposed analogous to the equisetum or horse-tail 
 of the present day, but was much larger, attaining the size 
 of fourteen inches diameter. 
 
 213. The fronds 
 or leaves of the 
 tree-fern preponder- 
 ate over all other 
 fossils in the shales 
 and sandstones of 
 the coal measures. 
 Their trunks are 
 marked with scars, 
 cicatrices where the 
 
 Fig. 108. 
 
 Lonchopteris. 
 
168 
 
 TRANSITION OR PALAEOZOIC ROCKS. 
 
 Fig. 109. 
 
 Fig. 110. 
 
 Sphenopteris. 
 
 Pecopteris. 
 
 fronds fell off as the trees advanced in growth. More than 
 two hundred species of ferns have been found in the coal 
 series of Europe. 
 Tree ferns are 
 conspicuous ob- 
 jects in the pres- 
 ent flora of Aus- 
 tralia ; a recent 
 traveler describes 
 one of them which 
 rises to a height 
 of fifty feet, ex- 
 hibiting a rich 
 crest of fronds, 
 and rivaling even 
 the princely palm-tree in beauty. The ferns are vascular 
 cryptogamous plants, having their organs of fructification 
 on their leaves, as seen on the leaves of the polypody or 
 the brake. Moisture and a warm climate are favorable to 
 their development. The names of the numerous fossil gen- 
 era of ferns are derived from pteris, a fern, to which is pre- 
 Fig. 111. fixed a term indicative of some pecu- 
 
 liarity, as Lonchopteris (spear leafed 
 fern,) Sphenopteris (wedge leafed fern,) 
 Pachypteris (the thick fern,) &c. 
 
 214. Two genera of lofty forest trees 
 appear to have contributed to the for- 
 mation of coal in large proportion. One 
 of these, the Lepidodendron, (lepidos a 
 scale ; dendron, a tree,) was a branch- 
 ing tree forty or fifty feet in length, and 
 Pachypteris. f our feet in Diameter. Narrow sharp 
 
THE CARBONIFEROUS SYSTEM. 
 
 169 
 
 pointed leaves are found at- 
 tached to it, and scaly cones 
 occur with it which are sup- 
 posed to be its seeds. This 
 tree is regarded by botan- 
 ists as intermediate between 
 the Coniferse and the Lyco- 
 podiaceae or club-mosses. 
 
 215. The other genus 
 Sigillaria, (Sigillum, a 
 seal,) was characterized by 
 Fig. 113. 
 
 Fig. 112. 
 
 Slgillaria. 
 
 Lepidodendron Sternbergii. 
 
 elegant flutings with 
 rows of symmetri- 
 cal scars or impres- 
 sions, disposed with 
 such regularity, as 
 sometimes to have 
 induced the belief 
 that they were en- 
 graved stones. These 
 Mgilla are scars left 
 in the bark by the se- 
 paration of the leaves 
 from the stem or the 
 trunk. These trees 
 are usually found in 
 a horizontal position 
 and much flattened 
 by the pressure to 
 which they have been 
 subjected, but are oc- 
 c asionally found erect 
 
 15 
 
170 
 
 TRANSITION OR PALAEOZOIC ROCKS. 
 
 with their roots in the soil in the positions in which they 
 grew, and their cylindrical forms are then preserved. 
 The Sigillaria grew sixty feet in length, and five feet in 
 diameter, gradually tapering toward the summit. The 
 bark, which is sometimes an inch thick, is frequently 
 converted into coal, while the interior is sandstone or 
 shale. The fossils called Stigmarise (Stigma, a mark,) 
 
 Fig 114> 
 
 formerly sup- 
 posed to consti- 
 tute a separate 
 genus of plants, 
 are now shown 
 to be the roots 
 of the Sigilla- 
 ria; a specimen 
 of the Sigilla- 
 ria has been 
 found in Eng- 
 land in an up- 
 right position, 
 
 Fig. 114, With Sigillaria and Stigmaria. 
 
 its roots still attached and extending in their natural direc- 
 tions. These stigmariae are usually found upon the clay 
 beneath the coal beds. 
 
 216. The fossil trunks of trees are found in many in- 
 stances, erect or inclined in the coal-bearing strata. The 
 mine of St. Etienne, in France, exhibits numerous vertical 
 stems traversing all its strata appearing like a forest of 
 plants petrified where they grew. In the Craigleith quarry 
 near Edinburgh, a coniferous tree fifty-nine feet long was 
 found lying at an angle of forty degrees, and traversing 
 ten or twelve sandstone strata. This would seem to have 
 
THE CARBONIFEROUS SYSTEM. 
 
 171 
 
 been due to sudden subsidence 
 or inundation, by which the sand 
 and mud were brought over the 
 trees ; or in the cases of inclined 
 stems, the greater weight of the 
 roots may have brought them 
 in that position into the sedi- 
 ment of the water in which they 
 floated, as the snags of the Mis- 
 sissippi are known to work their 
 way many feet into the bed of 
 the river. 
 
 217. The origin of the sue- 
 cession of coal-beds with their 
 intervening strata, is not yet 
 satisfactorily ascertained. Some 
 
 geologists suppose that dense 
 
 forests and peat-bogs subsiding beneath the water, were cov- 
 ered with the mud and sand, which constitute the shale and 
 sandstone strata over the coal ; the land rising again and ac- 
 cumulating vegetable growth, was again submerged a sub- 
 mergence and elevation occurring for each bed of coal. The 
 number of alternations thus required renders this mode very 
 improbable. Another mode of accounting for the phenom- 
 ena attributes the coal strata to successive deposits of sand, 
 mud, and vegetables made by rivers in lakes or estuaries, in 
 accordance with the specific gravity of the materials. This 
 mode of action is supposed to be illustrated on a small scale 
 in the deltas of our large rivers, as the Mississippi and 
 Ganges, where immense rafts of vegetable matter are inves- 
 ted by the silt of the rivers, especially during inundations. 
 The perfect state of preservation of many very frail plants of 
 
 Araucaria- 
 
172 TRANSITION OR PALAEOZOIC ROCKS. 
 
 Fig. 116. 
 
 Coal Flora. 
 
 the coal strata however, seems hardly consistent with such 
 violent action. 
 
 218. The igneous rocks invading the carboniferous 
 strata are trap rock and metaliferous veins. The trap is 
 usually dark colored, presenting itself in dikes, and flattened 
 masses resembling strata, appearing to have been erupted 
 at the bottom of p.- 
 
 an ocean. The 
 variety of trap 
 called toadstone, 
 is abundant in 
 the carboniferous 
 limestone with an 
 aggregate thick- 
 ness in some pla- 
 ces of one hun- 
 dred and eighty feet. The dislocations of the coal strata 
 
THE PERMIAN SYSTEM. 173 
 
 by trap dikes are illustrated by Fig. 117, in which the two 
 parts a and c of a coal bed are rent asunder by the dike 6, 
 and the strata on the side a cast up two hundred and sev- 
 enty feet. The texture of the rocks adjacent to the dike 
 has also been changed by its heat. The coal-beds of Bel- 
 gium have been thrown into a zigzag form over an exten- 
 sive district, giving rise to an apparent multiplication of the 
 beds; these "troubles/' however, sometimes render the 
 coal more accessible. 
 
 The carboniferous limestone of this system, is designated 
 metaliferous : it is the great repository of lead ore galena, 
 or sulphuret of lead ; iron also abounds in the system. 
 
 The rocks of this series often contain petroleum, or min- 
 eral pitch, which consists of bituminous matter driven out 
 from the coal by subterranean heat; springs or wells of 
 it exist in many localities. 
 
 THE PERMIAN SYSTEM. 
 
 219. The name Permian System has been applied by 
 Mr. Murchison to a fossiliferous series of rocks, which are 
 most perfectly exhibited in Permia extending over a district 
 of 700 miles in length by 400 in breadth, in Kussia between 
 the Ural mountains and the River Volga. They occupy 
 an intermediate geological position between the Carbonif- 
 erous and Triassic systems ; and consist of magnesian lime- 
 stones, marls, red and green sandstones, with beds of gypsum 
 and rock salt. Their fossil contents animal and vegetable 
 resemble those of the carboniferous period. The subdivi- 
 sions of the system in England are : 
 
 PERMIAN SYSTEM NINE HUNDRED FEET THICK. 
 
 {Gray thin-bedded limestone, 
 Red Marl and Gypsum, 
 Magnesian limestone and Magnesian con- 
 glomerate. 
 
 15* 
 
174 TRANSITION OR PALAEOZOIC ROCKS. 
 
 , TVT T, c< ( Marly beds, with thin bands of 
 
 LOWER NEW ED SANDSTONE S JJ^Jg ^ ^^ ^^^ 
 
 ( Lower new red sandstone. 
 
 These rocks are developed in France, and more distinct- 
 ly in Germany, where they have been thoroughly investi- 
 gated, and classified. The upper or Magnesian member of the 
 series the Germans designate Zech-stein mine stone from 
 its containing copper ore ; and the lower sandstone, they 
 call rothe-todte-liegende red-dead-lier, because it is of a 
 red color, is dead, producing no metal, and underlies the 
 metaliferous deposit. 
 
 220. The lower new red sandstone is closely allied to the 
 upper coal measures, containing some of the same species of 
 extinct vegetables. In mineral composition it differs in 
 being more highly charged with the oxide of iron. The re- 
 mains of fishes are found in it, and in some of the marly 
 beds in such quantities as to render them bituminous and 
 fetid. The characteristic member of this system is the 
 magnesian limestone, which consists of the carbonate of lime 
 and the carbonate of magnesia in different proportions ; the 
 rock is also called dolomite. It occurs usually laminated, 
 but presents some remarkable instances of concretionary 
 structure, sometimes in great masses, which resemble 
 piles of cannon balls. The dolomite is comparatively des- 
 titute of fossils, while other limestones of the system 
 abound with them. This is the only instance in which an 
 extensive limestone deposit has been so largely charged 
 with magnesia, nor is its origin in this case easily account- 
 ed for ; some geologists infer from the structure of the rock 
 and other phenomena, that the magnesia, was infused, ID 
 the state of liquid or vapor, into the limestone after its de 
 position. 
 
[THE PERMIAN SYSTEM. 175 
 
 The prevailing size of the species of fishes found in this 
 formation indicates a diminution from that of earlier pe- 
 riods ; but the most remarkable palaeontological feature of 
 this epoch is the appearance of reptiles, five species of which 
 have been recognized. 
 
CHAPTER VII, 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 221. AT the close of the palaeozoic epoch, a new era oc- 
 curs in the history of 'the globe, marked by violent disloca- 
 tions of the strata then deposited, depression of extensive 
 portions of the earth's surface beneath the level of the sea, 
 obliteration of races of plants and animals, and the substi- 
 tution of others in their places. The class of formations 
 which succeeded the secondary is well developed in 
 England and on the Continent of Europe in five distinct 
 systems, but is only partially represented in America, Asia, 
 and Australia, as far as is yet ascertained. 
 
 THE TRIASSIC SYSTEM. 
 
 222. This system is denominated the Upper New Red 
 Sandstone in England, but is called the Trias on the Con- 
 tinent of Europe, from its appearing in three distinct and 
 well marked formations. They have been investigated 
 principally in Germany and France. The following are 
 the subdivisions in Germany, England and France. 
 
 TRIAS. 
 
 K.VGLAND. GERMANS'. FRANCE. 
 
 Marnesiriaee, 
 
 Deficient. Muschelkalk. Muschelkalk. 
 
 BunterSandstoin. G, 
 
THE TRIASSIC SYSTEM. 
 
 177 
 
 The Bunter (variegated) Sandstein is a fine-grained 
 sandstone, usually of a red color, but sometimes blue, green, 
 or white, and contains some fossil plants and marine shells. 
 The Muschelkalk (mussel-chalk) is a gray or greenish 
 compact limestone, containing the remains of fishes, radia- 
 ted animals, and shells in great abundance : some parts of 
 it are highly charged with animal bitumen. 
 
 The Keuper consists of fine-grained sandstones, and 
 marls of various colors, gray, red, blue, and green, with 
 abundance of rock-salt and gypsum, and few animal re- 
 mains. 
 
 223. The fossil plants of this period were ferns in 
 which even the fructification has been preserved equisefa, 
 coniferse, and cycadex. 
 
 Fossil fishes found in the rocks below the trias, are fur- 
 nished, with heterocercal tails; in the triassic period those 
 with homocercal tails were introduced and have continued 
 to predominate to the present day. The Lily-Encrinite 
 Fig. 118. occurs in the muschelkalk in a beautiful 
 state of preservation. It belongs to the 
 family of Crinoi'dea, which are found in 
 great numbers in the rocks from the Si- 
 lurian system upward. These animals 
 had long jointed stems, attached at their 
 bases to the rocks, supporting a cup- 
 shaped cavity, formed by calcareous 
 plates closely fitting each other. This 
 cup contained the viscera of the animal ; 
 from its margin rose several arms, sub- 
 dividing into branches furnished on the 
 inside with numerous cirri or feelers. 
 Lay Encrinite. This skeleton was covered by soft parts ; 
 
178 ROOKS OP THE SECONDARY PERIOD. 
 
 the mouth was situated over the center of the cup. The 
 number of bones belonging to a single individual amounted 
 to one hundred and fifty thousand. These are found some- 
 times attached, forming a perfect skeleton, but more fre- 
 quently separate j portions of the stems are called entro- 
 . - 1 Q chites, screw-stones, pulley-stones, 
 
 and in the north of England, 
 fairy stones and St. Cuthbert's 
 beads. The stem of the Encri- 
 nite is circular, while that of 
 the Pentacrinite is pentagonal. 
 The Gyathocrinite (cup-like En- 
 crinite) was a genus of remarka- 
 bly light and elegant appearance 
 found principally in the Silu- 
 rian, Devonian and Carbonifer- 
 ous limestones. The Pentacri- 
 nite is exhibited in Figure 106, 
 
 Cyathocrinite. 209. 
 
 224. Reptiles are found in such numbers in the secon- 
 dary rocks, that the period of their deposition has been 
 called the age of reptiles, ( 152, II.) More than thirty 
 new genera have been added to the class by the study 
 of the fossil forms. Reptiles were formerly described 
 under two orders, distinguished by the presence or ab- 
 sence of external feet. The variety and peculiarities of 
 the fossil species render a new arrangement of the mem- 
 bers of the class indispensable. The classification pro- 
 posed by Professor Owen is admirably adapted to its pur- 
 pose, including in natural groups all known species, fossil 
 and recent. 
 
Fig. 120. 
 
180 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 6. Chelonia 
 
 7. Ophidia 
 
 8. Batrachia 
 
 (Serpents.) 
 (Frogs, &c.) 
 
 CLASS III, REPTILIA. Found fossil in. 
 
 OEDKR 1. Dinosauria (Land Saurians.) Oolite, Wealden. 
 
 " 2. Enaliosauria (Marine Saurians.) Muschelkalk, Lias, Oo- 
 
 lite, Wealden, Chalk. 
 
 " 3. Crocodilia (Crocodiles, &c.) Lias, Oolite, Wealden, 
 
 Chalk, Tertiary. 
 
 " 4. Lacertilia (Lizards.) Magnesian Limestone, 
 
 New Red Sandstone, 
 Chalk. 
 
 " 6. Pterosauria (Flying Saurians.) Lias, Oolite, Wealden. 
 
 (Tortoises, &c.) Oolite, New Red Sand- 
 stone, Wealden, Ter- 
 tiary, Chalk. 
 Tertiary. 
 
 New Red Sandstone, 
 Tertiary. 
 
 The reptiles of the Triassic period were of 
 the second order, Marine Saurians ; of the 
 fourth order, Lizards the RliyncJw&aurus, so 
 called from its head resembling the beak of a 
 bird, and the Dicynodon, having only two teeth, 
 which were canine; and of the eighth order, 
 Frogs. 
 
 225. Peculiar markings, bearing striking re- 
 semblance in form and relative positions to tracks 
 made by animals in walking, have long since been } 
 observed in the rocks of this period. In 1834, an 
 account was published of some of these observed 
 in the Bunter Sandstein, in Saxony. They re- 
 sembled the imprint made by a human hand upon 
 any plastic substance, as represented in the ad- 
 joining figure. It was proposed to call the animal, 
 that made the track, G heirotherium (Cheir, the 
 hand; therion, beast.) No bones were then identified 
 as belonging to this animal, its existence being inferred 
 from its tracks alone. The dimensions of the tracks are 
 
THE TRIASSIC SYSTEM. 181 
 
 various, and those made by the hind feet are always much 
 larger than those of the fore feet ; in some instances twice 
 as large. The posterior extremities of the animal appear 
 to hav 7 e been larger and longer than the anterior. Some 
 fragments of skeletons have since been found in the rock 
 with the tracks, which enable Professor Owen to establish 
 a genus of the Batrachian order of reptiles, including 
 several species frequenting the sea shore at the time of 
 deposition of the New Red Sandstone. The jaws were 
 furnished with at least a hundred teeth on each side, di- 
 minishing in size from the middle to the extremities ; in 
 this respect resembling those of the crocodile. An outline 
 of the animal, as restored by Professor Owen, is presented 
 in Figure 121. As a section of a tooth exhibits, by the 
 
 Fig. 121. 
 
 Labyrinthodon Pachygnathus. 
 
 aid of a microscope, labyrinthine convolutions, the animal 
 is called the Labyrinthodon. The tracks of tortoises and 
 crustaceous animals have also been observed in these rocks, 
 and traced in some instances twenty and thirty feet. These 
 fossil foot-prints are called ichnolites (ichne, track ; lithos, 
 stone.) 
 
 226. Numerous remarkable tridactyle impressions have 
 been discovered in the sandstone of the Connecticut Val- 
 ley in Massachusetts, which are universally supposed to be 
 16 
 
182 ROCKS OF THE SECONDARY PERIOD. 
 
 the tracks of biped animals imprinted on the rocks when 
 they were in a soft, forming state. Some specimens ex- 
 hibit very clearly the character of the foot, its rows of 
 joints, claws and integuments. The best impressions are 
 in fine shale, which is incrusted with micaceous sandstone ; 
 the surfaces of the split strata are counterparts of each 
 other; the shales exhibiting the tracks as moulds, and 
 the sandstone as casts in relief. The animals which made 
 these tracks are supposed to have been birds, though none 
 of their bones have yet been found in these strata. Presi- 
 dent Hitchcock distinguishes more than thirty species by 
 differences in the tracks. They are of various sizes; 
 some as small as our sparrows, while some made a track 
 fifteen- inches long, exceeding by five inches the track of 
 the African ostrich. The length of the stride of these 
 largest species was from four to six feet. The doubts 
 formerly entertained respecting these Ornithicnites have 
 been dissipated by the discovery, in the alluvial deposits 
 of New Zealand, of the skeletons of wingless birds as 
 large as those to which the tracks in the New Red Sand- 
 stone are assigned, (301.) These bird tracks have been 
 presented in Figure 69, 126. 
 
 227. The rocks of this period seem to have been espe- 
 cially fitted to perpetuate impressions : the ripple marks on 
 them are very distinct ; but, what is more remarkable, their 
 surfaces often present a pitted appearance, dotted with 
 little hemispherical eminences or depressions which are 
 attributed to rain-drops. These are sometimes elongated, 
 as if the drops were driven by the wind in an oblique 
 direction. President Hitchcock remarks, "It is a most 
 interesting thought, that while millions of men, who have 
 striven hard to transmit some trace of their existence to 
 
THE TRIASSIC SYSTEM. 
 
 future generations, -Fig. 122. 
 
 have sunk into utter 
 oblivion, the simple 
 footsteps of animals 
 that existed thou- 
 sands, nay, tens of 
 thousands of years 
 ago, should remain 
 as fresh and dis- 
 tinct as if yester- 
 day impressed: even 
 though nearly eve- 
 ry other vestige of 
 their existence has 
 vanished : nay, still 
 more strange is it 
 that even the pat- 
 
 tering of a shower * Footprint and impressions of Bain-drops. 
 
 at that distant period, should have left marks equally 
 distinct, and registered with infallible certainty, the dirac- 
 tion of the wind ! " 
 
 228. The origin of rock salt in masses, is usually 
 ascribed to the evaporation of the water in brine springs, 
 or portions of the sea isolated and exposed to a high tem- 
 perature. The salt is in such circumstances precipitated, 
 and accumulates, as is seen in the Great Salt Lake, the 
 Dead and Caspian seas, and the lakes of northern Africa 
 and Arabia. Some phenomena of salt beds, however, 
 indicate a connection with volcanic agency. Salt is not 
 confined to the saliferous deposits of the New Red Sand- 
 stone, but is found in the carboniferous, oolitic, and tertiary 
 rocks. 
 
184 BOOKS OF THE SECONDARY PERIOD. 
 
 THE LIASSIC SYSTEM. 
 
 229. The Lias consists of strata mostly argillaceous; 
 but having a large quantity of calcareous matter also, it 
 embraces many bands of argillaceous limestones. Some 
 beds of marly sandstones alternate with the clays and lime- 
 stones. The term lias is probably a corruption of layersj 
 alluding to the riband-like appearance which a section of 
 the rocks of the system presents. This system of rocks is 
 developed in England, and on the continent of Europe, in 
 France, Switzerland, and Germany ; it is supposed to exist 
 also in Asia and South America, but it is doubtful whether 
 there are any of its deposits in North America. Its subdi- 
 visions are : 
 
 Upper LiaS or Alum Shale soft shales ex- 
 tremely fossiliferous, jet and bituminized 
 wood, hard shales. 
 MarlStOfle colored calcareous clays and sands, 
 
 impure limestone. 
 LOWCF LiaS Shale calcareous flagstones, lamin- 
 
 600 feet thick. 
 
 ated dark-colored shales. 
 
 Lower LiaS a thin bed, of argillaceous lime- 
 stone, containing numerous fossil fishes ; 
 sometimes passing into sandstone. 
 
 230. The Lias formation is surpassingly rich in fossils, 
 embracing representatives of all the great natural families. 
 The Corals are few. and small, but the Crinoidea were ex- 
 ceedingly abundant; whole beds are made up of Pentacri- 
 nites, so perfectly preserved that their minutest anatomical 
 structure is discernible. These ^g^. Fig. 12< 
 animals are supposed to have 
 had the power of attaching and 
 detaching themselves at will ; 
 large masses of them are found 
 attached to the fossil wood of 
 this period. Bivalve shell-fish Gryphca Incurva - 
 
THE LIASSIC SYSTEM. 
 
 185 
 
 are very numerous, some of which are characteristic of the 
 formation, and others of particular beds ; one of the marly 
 limestone beds is called the Gryphite Limestone, from the 
 great abundance of the peculiar fossil Gryphsea incurva, 
 Fig. 123. The Terebratulse were still continued, and the 
 genus Spirifer, which however terminates its existence in 
 this formation, being found in no newer rock. 
 
 231. The Ammonite , though early introduced in the 
 strata, appears at this period to have been greatly expand- 
 ed; more than seventy species of the genus have been 
 found in the British Lias. It was a univalve, many cham- 
 bered shell, whose inhabitant -p. 124 
 belonged to the order Cepha- 
 lopoda. It was allied to the 
 
 Nautilus, which resides in the 
 outer apartment of its shell, 
 communicating with the inte- 
 rior chambers by means of a 
 tube siph uncle and is sup- 
 posed to rise and fall through 
 great depths of water, dimin- 
 ishing or increasing its specific Ammonite, 
 gravity by withdrawing or injecting water into the internal 
 cavity. As the shells of the Ammonite were thin, they 
 were often strengthened by ribs and tubercles. They vary 
 in size from half an inch to four feet in diameter. 
 
 232. The Helemnite, (so called from its resemblance 
 to a dart,) occurs very perfectly preserved in the Lias, 
 Oolitic, and Chalk rocks. It consists of a calcareous, cylin- 
 drical or conical shell, pointed at one extremity, and ter- 
 minating at the other in thin conical chambers. Some 
 specimens are small, amber-colored, and transparent; while 
 
 16* 
 
186 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 others are opake, ten or twelve inches long, and four 
 inches in circumference. The animal 
 belonged to the Cephalopoda, was 
 allied to the Cuttlefish, and was fur- 
 nished with an ink-bag. The shell, 
 (Fig. 125,) was, like the pen of the 
 Cuttlefish, internal. The ink-bag and 
 its contents have been found fossil, 
 and a pigment, india ink, has been 
 prepared from them possessing all 
 the properties of the ink prepared 
 from the recent Sepia. The soft parts 
 of the animal are in many instances 
 so well preserved, that its form and 
 structure are discernible. Its eyes 
 were large and prominent, and its 
 horny beak powerful. Its habits 
 were probably, like those of the family of the present day, 
 extremely voracious. 
 
 233. Fishes and Reptiles were the representatives of 
 the Vertebrata at this period; of the former more than 
 sixty species have been discovered in the Lias of England, 
 belonging almost exclusively to the Ganoid and Placoid 
 orders, and all of them extinct. Numerous fossil spines, 
 or bony rays of the dorsal fins of extinct cartilaginous fishes 
 are found in the Lias rocks, detached and isolated ; they 
 are called Ichthyodorulites. They were not articulated to 
 the vertebrae, but deeply implanted in the flesh. Some of 
 the existing species of shark are provided with the same 
 bony ray, giving to the dorsal fin greater force and preci- 
 sion in its motions. 
 
 234. The Reptiles of the Liassic period belong to the 
 
 Belemnite. 
 
THE LIASSIC SYSTEM. 
 
 187 
 
 marine order Enaliosauria and are principally confined 
 to two genera, Ichthyosaurus and Plesiosaurus. 
 
 The Ichthyosaurus, or fish-lizard so called because ifc 
 combines in its structure the features of the fish with those 
 of the reptile resembled the Grampus or Porpoise in 
 figure, with a much larger head and a long tail expanded 
 
 Fig. 126. 
 
 . , Ichthyosaurus. 
 
 vertically, as are those of true fishes. It was covered with 
 a tough skin, like that of the whale, destitute of scales. 
 The orbit of the eye was unusually large in some speci- 
 mens eighteen inches in diameter and enclosed a series 
 of bony plates, enabling the eye to adjust itself to different 
 distances, and varying intensities of light; an analogous 
 
 Fig. 127 
 
 Head of Ichthyosaurus. 
 
 structure is exhibited by the eyes of turtles, lizards, and 
 especially of the owl. The teeth were conical, like those 
 of the crocodile, and very numerous, amounting in some 
 species to two hundred; in some large individuals the 
 
188 ROCKS OF THE SECONDARY PERIOD. 
 
 opening of the jaws exceeded seven feet. Its organs of 
 p <xo? ftUi locomotion were four paddles composed of numerous bones, 
 surrounded by rays of true fins; the anterior pair were 
 based upon a firm breast bone, which enabled the animal 
 to give rapidity and precision to its motions. The form 
 ^Ut^ an( j arrangement of its vertebrae, which were in some spe- 
 cies one hundred and forty in number, were like those of 
 fishes. Some individuals attained a length of forty feet. 
 They were carnivorous, as is shown by their teeth, as well 
 as by the contents of their stomachs which have been found 
 in a few instances preserved. 
 
 235. The Plesiosaurus (plesion, near; saurus, reptile,) 
 approached more nearly the true reptiles in structure. Its 
 Fig. 128. 
 
 Plesiosaurus. 
 
 head, which resembled that of a lizard, was very small; its 
 paddles were relatively longer than those of the Ichthyo- 
 saurus, and its tail was like that of the crocodile. The 
 most remarkable peculiarity exhibited by this animal was 
 the inordinate length of its neck. Animals have usually 
 not more than five cervical vertebras ; the swan has twenty- 
 four, while the Plesiosaurus had from thirty to forty. The 
 animal seems to have been fitted for rapid motion. It 
 attained a large size ; a perfect specimen has been obtained 
 seventeen feet long, and fragments of larger skeletons have 
 been found. Numerous species of the Ichthyosaurus and 
 Plesiosaurus have been found in the rocks from the mus- 
 chelkalk to the chalk. 
 
THE OOLITIC SYSTEM. 189 
 
 236. Beds of jet, resembling cannel-coal but harder and 
 more lustrous, are found in the Upper Lias, together with 
 large fragments of bituminized wood of coniferous trees and 
 Cycadese. 
 
 THE OOLITIC SYSTEM. 
 
 237. The Oolite is a marine formation of great extent 
 and thickness, consisting principally of alternations of 
 limestones and clays, embracing vegetable remains, and 
 very numerous corals, shells, fishes and reptiles; insects 
 and mammalia also are found in it. The Oolite derives 
 its name (Oon, an egg; lithos, a stone,) from the fact that 
 some of its beds consist of calcareous globules which resem- 
 ble the roe of a fish ; but this structure is not strictly char- 
 acteristic of it. This system is developed in Great Britain 
 and on the Continent of Europe, in France and Germany, 
 (called the Jurassic series,) in Russia, India and America. 
 Its subdivisions in England are : 
 
 Portland BedS limestone of an oolitic struc- 
 ture, abounding with marine shells, ammon- 
 
 _ _ ites, &c. 
 
 UPPER OOLITE. \ , 
 
 immendge Clay blue and yellow clay with 
 
 septaria, gypsum, marine shells and beds of 
 lignite or Kimmeridge coal. 
 
 f Coral OolitC or Coral Rag coarse limestone 
 full of corals and shells beds of yellow sands 
 
 and calcareous grits. 
 MIDDLE OOLITE. *j 
 
 Oxford Clay dark blue clay with septaria and 
 numerous fossils beds of calcareous sand- 
 stone. 
 
190 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 LOWER OOLITE 
 
 coarse gray limestone separated 
 by beds of clay. 
 
 Forest Marble sand, with thin fissile limestone 
 and coarse shelly oolite. 
 
 Great Oolite oolitic limestone and freestone, 
 with beds of clay, and remains of reptiles, 
 corals, &c. 
 
 Stonesfield Slate oolitic limestone, with re- 
 mains of land animals, plants, insects, and 
 mammalia. 
 
 Fuller's Earth Beds marls and clays contain- 
 ing fuller's earth. 
 
 Inferior Oolite coarse limestone, ferruginous 
 sand with shells. 
 
 238. The alternations of limestones with clays and 
 shales, displayed by the Oolitic series, give rise to peculiar 
 features of outline in parts of England and France. Three 
 successive ridges are the hard calcareous beds of the Lower, 
 Middle and Upper Oolites, while the intervening plains 
 and vallies consist of clays and shales. 
 
 Lower Oolite. Mid. Oolite. Upper Oolite. Chalk. L.clay 
 
 Lias. Oxford Clay. Kim. Clay. Gault. 
 
 239. The organic remains of the Oolite are numerous 
 and varied, as might be expected from the variety of min- 
 eral constitution of the strata. 
 
 The corals occur chiefly in the Middle Oolite; the 
 coral rag consists of an extensive coral reef thirty or forty 
 feet thick, composed mostly of a few genera, some of which, 
 as the Gary ophy Ilia, are represented by species in the pre- 
 sent seas. 
 
 Among the Crinoidea, the Pear Encrinite Apiocrinites 
 similar in structure to the Lily Encrinite, grew abund- 
 antly, attached to rocks. 
 
 The Sea Urchins Echini were also numerous. 
 
THE OOLITIC SYSTEM. 191 
 
 Of the mollusca, the bivalve acephalous were very abun- 
 dant ; some beds are almost en- Fig. 129. 
 tirely made up of their remains. 
 The Trigonia Costata, Fig. 129, 
 abounded in the Oxford Clay. 
 Ammonites and Belemnites were 
 as common as in the Liassic pe- 
 riod. Trigonia Costata. 
 
 Crustacea appear in the Oolite with forms closely allied 
 to those of the present day.- Figure 130 presents an ani- 
 mal resembling the Lobster, found in the Oolitic clay. 
 
 Fig. 130. 
 
 Fossil Crustacean. 
 
 Insects also are found, some of which very closely resem- 
 bling the common Dragon-fly, are so perfectly preserved 
 that the most delicate markings, and the nerves of the 
 wings are distinctly discernible. 
 
 240. Of the vertebrate animals, fishes are found in 
 abundance throughout the series, belonging mostly to the 
 ganoid order. The Ichthyosaurus and Plesiosaurus, so 
 abundant in the Lias, extend through the Oolite ; and other 
 saurians of gigantic size are found in these strata Mega- 
 Teleosaurus, tSfeneosaurus and Cetiosaurus. But 
 
192 
 
 ROCKS CJ THE SECONDARY PERIOD. 
 
 the most anomalous saurian of this period, was the Ptero- 
 dactyle, (Pteron, a wing ; dactulos a finger,) an animal, of 
 which Cuvier remarks, " It is undoubtedly the most extra- 
 ordinary of all the beings of whose former existence a 
 knowledge is granted to us, and that which, if seen alive, 
 would appear most unlike anything that exists in the pres- 
 ent world." 
 
 The Pterodactyle bore some Fig. 131. 
 
 resemblance to the bat, but its 
 mouth was very unlike that of 
 the bat, having the jaws and 
 teeth of a reptile. It was fur- 
 nished with powerful membra- 
 nous wings, enabling it to fly 
 with ease and rapidity, and its 
 feet were not so involved in the 
 membranous expanse of the 
 wings as to prevent walking. 
 Its eyes were very large. 
 
 241. The Stonesfield slate Pterodactyle. 
 
 furnishes the only specimens of fossil mammalia yet discov- 
 ered in the secondary rocks. Parts of the skeletons and the 
 Fig. 132. 
 
 Jaw and Teeth of the Phascolotherium. 
 
 teeth of two genera of the marsupial order of mammiferous 
 quadrupeds have been found in this rock. 
 
THE OOLITIC SYSTEM. 
 
 193 
 
 The Phascolotherium was allied to the Opossum and 
 Kangaroo ; and the organic remains of the Oolite generally 
 resemble the present fauna and flora of Australia. 
 
 242. The plants of the Oolitic period consist of coniferae, 
 liliacese, palms and ferns; but the Cycadese, which were 
 introduced in small numbers in the Carboniferous period, 
 are here found abundant. They are intermediate in char- 
 acter, between the Coniferae, palms and ferns. Some of 
 them are short, stout, cylindrical, scaly stems, surmounted 
 by a tuft of elegant leaves resembling a pine apple, while 
 Fig. 133. 
 
 abed e 
 
 a Palm. 6 Arborescent fern, c Cycas. d Pandanus. e Zamia. 
 
 others have trunks thirty feet in length. The Cycadese 
 still grow in tropical regions. Valuable beds of lignite and 
 bituminous coal are found in the Oolite, as the Kimmeridge 
 coal, Brora coal and the Yorkshire Oolitic coal, in England ; 
 but the most important coal beds of the Secondary Period, 
 hitherto discovered, are those of Kichmond, Virginia, which 
 cover one hundred and eighty-five square miles, varying 
 17 
 
194 
 
 BOOKS OP THE SECONDARY PERIOD. 
 
 in thickness from eleven to forty feet. There are three 
 beds exhibiting the same phenomena that are observed in 
 the older coal beds. These beds are extensively wrought, 
 the coal yielding abundant pure gas. The leaves of cyca- 
 deous plants are abundant in these beds. 
 
 THE WEALDEN SYSTEM. 
 
 243. Hitherto, with the exception of a very few thin 
 strata, the whole series of deposited rocks have been of 
 marine origin, as is shown by their mineral constitution and 
 organic contents. The Wealden System exhibits clear 
 indications of being fresh-water deposits, containing numer- 
 ous remains of land plants and animals. This formation 
 consists of a thick series of sandy beds resting on an 
 imperfect limestone, and covered by a bed of clay ; the 
 whole containing fresh-water shells, land plants, fishes and 
 reptiles, which indicate the action of river currents, but not 
 the attrition of the ocean upon them. It resembles the 
 deltas forming at the mouths of large rivers at the present 
 day. The Wealden appears in England, Scotland, France 
 and Germany. The term Wealden is derived from wealds 
 or wolds, the ancient word for woods ; because these rocks 
 form a tract of land occupied by the forests of Kent and 
 Sussex, England. The order of the beds as observed in 
 
 England, is 
 
 WEALDEN SERIES, 
 1000 feet thick. 
 
 Weald Clay, with subordinate limestone and 
 sand fossil fresh-water shells, almost en- 
 tirely composing some beds. . 
 
 Hastings Sand, including the beds of Tilgate 
 Forest bluish gray and ferruginous sand- 
 stones, conglomerate, lignite, fresh-water 
 mollusca. 
 
 PurbCCk Strata compact limestone alter- 
 nating with clay, resting upon the Port- 
 land beds of the Oolite. 
 
THE WEALDEN SYSTEM. 195 
 
 Fig. 134. 
 Me of Wight. Hants. Sussex. 
 
 Section of the Chalk and Wealden. W Wealden. 
 
 The relative positions of the Chalk and Wealden are 
 presented in Fig. 134, in which the Wealden invariably 
 underlies the Chalk. The Oolitic Series is made, by some 
 writers, to embrace these rocks, and by others they are 
 assigned to the Chalk ; but their organic characters espe- 
 cially entitle them to rank as a distinct system. 
 
 244. While some of the organic remains that occurred 
 in the Oolite are found in this formation, most of the 
 Wealden fossils are peculiar, being almost exclusively fresh- 
 water, or terrestrial in their origin. The number of species 
 is not large, but the abundance of remains of a species 
 surpasses what has hitherto been witnessed. The remains 
 of shellfish and crustaceans are in some of the beds ex- 
 ceedingly abundant, and indicate an approximation, in 
 form, to the animals of those classes now existing. Beetles 
 and other insects are often found in these strata. 
 
 245. Among vertebrate animals there are the remains 
 of several species of fish some of which are allied to the 
 lepidotusj bony pike of the North American lakes ; but the 
 reptiles furnish the most remarkable fossils in the Wealden. 
 
 To the Plesiosaurus, Megalosaurus and Cetiosaurus found 
 in the Oolite, are added five genera of Saurians peculiar to 
 the Wealden ; among which are .the Hyloeosaurus, and 
 Iguanodon belonging to the order Dinosauria. 
 
 The Hylseosaurus, or Weald Lizard, was a land reptile, 
 twenty feet in length, covered with elliptical scales. 
 
196 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 The Iguanodonj so called from the resemblance of its 
 teeth to those of the Iguana, a lizard found in the West 
 Indies, was an herbivorous reptile, about thirty feet long and 
 of colossal proportions, having a thigh-bone larger than that 
 of the Elephant. It was furnished with a short horn as 
 are some species of Iguana. 
 
 The remains of a large fresh-water turtle and other 
 Chelonian animals, and fragments of bones belonging to an 
 extinct species of wading bird are found in the Wealden, 
 but no traces of mammalia have been detected. 
 
 246. The general character of the Wealden vegetation is 
 the same as that of the Oolite, with the addition of a few 
 peculiar species. 
 
 Fig. 135. 
 
 Calcareous 
 
 Marine. 
 
 Buhrstone. 
 
 Dirt Bed. 
 
 Portland ^ 
 
 Water. 
 
 Dry Land, 
 
 ^-Marine. 
 
 Subterranean Forest Portland Dirt-bed 
 
THE CHALK SYSTEM. 197 
 
 Between the marine beds of the Oolite and the fresh- 
 water deposits of the Wealden intervenes a bed eighteen 
 inches thick, of black vegetable soil, called the "Dirt-bed." 
 In it are found numerous trunks and stumps of coniferous 
 trees, fossilized where they grew, with their roots still im- 
 mersed in the ancient soil. Here are distinct intimations 
 of elevation of the Portland stone to the surface of the sea 
 in which it was deposited, so as to constitute the soil for the 
 growth of trees ; the growth of vegetation so as to produce 
 eighteen inches of earthy lignite } the subsequent depres- 
 sion so gentle as not to remove the trees from their position ; 
 and finally the deposition of fresh-water and marine strata 
 over the whole. 
 
 Coal beds from one to three feet thick are found in the 
 Wealden of Germany. 
 
 THE CHALK OR CRETACEOUS SYSTEM. 
 
 247. The Cretaceous group is a marine formation com- 
 prising limestones, marls, clays and sands, abounding with 
 remains of marine origin. The name of the system is 
 derived from its leading member, Chalk, (creta.'} This for- 
 mation is extensively developed in England, Ireland, France, 
 Germany, Russia, Spain, Italy, Northeastern Africa, India, 
 South America and the United-States. Its subdivisions in 
 England are 
 
 CRETACEOUS SYSTEM ONE THOUSAND FEET THICK. 
 
 f Upper Chalk, soft, white with flints. 
 
 CHALK FORMATION. \ Lower Chalk, hard white few or no flints. 
 Chalk Marl marl with silicate of iron. 
 
 ChonAin.F.A- " ^lUmnd-sand, chert, ochre. 
 
 TION. Will II blue marl with ferruginous nodules. 
 
 [ Lower Greensaild with occasional limestone. 
 
 17* 
 
198 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 The Greensands consist of silicious sand mixed with 
 the silicate of iron chlorite which gives the green color ; 
 the color is however often yellowish, or gray, from admix- 
 ture with the oxide of iron. These sands alternate with 
 beds of clay and limestone, and contain frequently fuller's 
 earth and chert. 
 
 Gault is a provincial term used in England to designate 
 the brick-clay found in this system. It is a stiff blue clay 
 containing iron-pyrites, and in some portions, the green 
 silicate of iron. It does not occur in the cretaceous system 
 of the United States. 
 
 > The Chalk is a familiar, earthy form of the carbonate 
 of lime, sometimes soft, but frequently sufficiently solid for 
 building purposes. Its stratification is often indistinct, but 
 recognizable by the alternating layers of flint in it. 
 
 Fig. 136. 
 
 Chalk with Flints An Outlier. 
 
 The Upper Chalk is remarkable for its numerous bands 
 of dark colored flints; Kinds from three to six inches in 
 thickness, and from two to four feet apart. These flints 
 
THE CHALK SYSTEM. 199 
 
 have very often an organic body as a nucleus about which 
 they have accumulated, and whose form they have preserved. 
 In the Lower Chalk the flints are rarely found, but the 
 silica is diffused through the mass. The lowest portion is 
 largely mixed with clay constituting the chalk marl, which 
 sometimes is green from the presence of the silicate of iron, 
 or red from the oxide of iron. 
 
 248. The Chalk fossils are numerous, almost exclusively 
 marine, and appear to have been deposited in deep water. 
 
 Among the radiated animals, the Encrinites had dwin- 
 dled to a few species of small size and diminished beauty ; 
 one form of them in this period was the Marsupite, which 
 resembled the lily encrinite deprived of its stem. Sea 
 Urchins echini were very abundant, accompanied by 
 crabs and lobsters whose organization closely resembled that 
 of the members of those tribes of the present day. Bivalve 
 and univalve shells are found abundantly. The cephalo- 
 podous animals to which the ammonite belongs, exhibited a 
 great diversity of forms ; curved in successive whorls like 
 the ammonite, but with the whorls slightly remote from 
 each other, as the Crioceratite ; hook-shaped, as the Sa- 
 mite; or straight like the Orthoceratite, as the Baculite 
 and Turrilite. 
 
 249. Vast numbers of small animals existed at this 
 period living in shells formed of numerous chambers or com- 
 partments, belonging to a group which is still common in 
 the ocean the Foraminifera. These animals occupy all the 
 chambers of their habitation, and not the outer one only as 
 does the nautilus. Their shells are sometimes flat and disc- 
 like, resembling a piece of money : hence we have the Num- 
 mulite, from nummus, a piece of money, Fig. 137. Though 
 .of small size they often constitute almost the entire mass 
 
200 
 
 ROCKS OF THE SECONDARY PERIOD. 
 
 of mountains. Nummulitic limestones Fi g- 137. 
 were used in the construction of the 
 Sphinx and pyramids of Egypt. 
 
 Infusoria also abounded during the 
 deposition of the chalk ; but their beauty 
 and perfect state of preservation in the 
 flints, can be discerned only by the aid of Nummuiite. 
 powerful microscopes; a large proportion of the chalk 
 itself appears to be made up of the fragmentary skeletons 
 of these minute animals. The shapes of the skeletons of 
 these animalcules are various; some consist of parallel 
 tubes arranged transversely upon long fragile ribands; 
 Fig. 138. 
 
 Tossil Infusoria. 
 
 a Gomphonema. b Bacillaria. c Gaillonella. d Xanthidium. e Navicula. 
 
 others are oblong, or globular, with their surfaces studded 
 with hair-like appendages ; while others still are in ramose 
 groups like polyps. Many flint nodules are almost en- 
 tirely composed of the silicious skeletons of these infini- 
 tesimal forms of animal life. Fig. 139 presents one of the 
 
THE CHALK SYSTEM. 
 
 201 
 
 fossil infusoria, closely resembling the living Xanthidi.i. 
 It is here magnified 500 Fig 139. 
 
 times linear. Fig. 140 
 represents the cell of a 
 zoophyte in flint, with the 
 polyp protruded, having 
 been entombed in the min- 
 eral matter while alive and 
 active. This also is mag- 
 nified 500 times linear. 
 The Gaillonellae are an- 
 other family of infusoria 
 
 found in the flint, SO mi- Xanthidium Tubiforme. 
 
 nute that forty-one thousand millions of their skeletons 
 occupy but a cubic inch. Their cylindrical shields are 
 Fig. 140. arranged in a long series 
 
 like a tubular chain. 
 | They multiply by self 
 division with such rapid- 
 H ity that a single individ- 
 ual may produce one hun- 
 dred and forty millions 
 of millions in twenty- four 
 
 Zoophyte in Flint. hours.* 
 
 250. Of the vertebrate animals, the chalk deposits in- 
 clude some sauroid fishes, among which the Macropoma, a 
 voracious fish about two feet long, has been found so weL 
 preserved that its gills and entire stomach with its con- 
 tents are presented to inspection. The teeth and bony 
 spines of sharks are abundant, and the other two orders of 
 fishes the ctenoids and cycloids which so greatly pre- 
 * Mantell's Wonders of Geology, I. |>. 665. 
 
202 ROCKS OF THE SECONDARY PERIOD. 
 
 dominate in the present seas, are also introduced in the 
 cretaceous rocks. 
 
 The reptilian remains of the Cretaceous series compared 
 with the three preceding systems are few, embracing, so 
 far as has been discovered, but one or two forms that were 
 not known before. The Ichthyosaurus and Pterodactyle of 
 the previous system were continued in this, and a new 
 gigantic marine lizard, nearly allied to the Monitor of the 
 present period, was introduced, called the Mosasaurus the 
 saurian of the Meuse, on whose banks its fossil remains 
 have been found. It attained the length of twenty-five feet, 
 and appears to have been the last gigantic form of marine 
 reptiles introduced, before their obliteration at the close of 
 the secondary period. Its teeth are found in the cretaceous 
 deposits of the United States. Several species of marine 
 turtles occur in the cretaceous rocks. 
 
 The bones of birds allied to the Albatross, are recog- 
 nized among the fossils of the chalk, but no trace of any 
 land quadruped, or any member of the whale tribe. 
 
 251. The sponge, a peculiar kind of organism consist- 
 ing of horny fibres, often enclosing spiculae of flint or 
 carbonate of lime, has very frequently served as a nucleus 
 about which the silicious or flinty matter, diffused in the sea 
 at the period of the chalk deposits, accumulated, and the 
 forms of the sponge have thus been perfectly preserved in 
 flint, in chalk and sandstones. Carbonized sea-weeds, drift- 
 wood, and beds of lignite occur in the chalk group of rocks. 
 
 252. The origin of chalk, so different in its texture and 
 appearance from the other limestones, with its included 
 flints, has been the subject of much discussion. It has been 
 supposed by some to be a chemical precipitate : " but there 
 appears no evidence," says Mr. Brande, "of its having 
 
THE CHALK SYSTEM. 203 
 
 been deposited from chemical solution ; on the other hand, 
 it bears marks of a mechanical deposit, as if from water 
 loaded with it in fine division. And upon this principle 
 some gleam of light may perhaps be thrown upon the enig- 
 matical appearance of the flints; for it is found that if 
 finely divided silica be mixed with other earthy bodies, and 
 the whole diffused through water, the grains of silica have, 
 under certain circumstances, a tendency to aggregate into 
 small nodules ; and in chalk some grains of silica are dis- 
 coverable." The flints occur in nodular masses of irregular 
 forms, varying from less than an inch to more than a yard 
 in circumference ; they are quite insulated from each other, 
 each one being entirely enveloped by the chalk. As they 
 almost invariably include some organic body, they appear 
 to be silicious aggregations about nuclei, as septaria are 
 aggregations of calcareous and argillaceous matter. It has 
 before been shown ( 66,) that silica is soluble in water, as 
 it occurs in the Geysers of Iceland. The chalk resembles 
 the calcareous mud that accumulates in the lagoons of coral 
 islets, produced by the ocean wearing corals and shells to a 
 fine powder. ( 79.) 
 
 253. The igneous rocks associated with the chalk and 
 other members of the Secondary series, are basalt and other 
 forms of trap. The basalt of the Giant's Causeway breaks 
 through and overlies the chalk in the north of Ireland, the 
 heat of the igneous rock having rendered the chalk hard 
 and crystalline like primary marble. 
 
 
CHAPTER VIII, 
 
 KOCKS OF THE TERTIARY PERIOD. 
 
 254. THE Tertiary embraces the strata of sand, clay, 
 and limestone, which lie between the chalk and the superfi- 
 cial deposits designated Drift and Alluvium, with which 
 they were confounded previous to the labors of Cuvier and 
 Brogniart in A. D. 1810. They differ from the Secondary 
 
 5> o-trtrvv rocks in mineral constitution and especially in their organic 
 contents ; but are not very distinctly bounded at their upper 
 limit, frequently merging in the recent deposits. In gen- 
 eral they are not so firmly aggregated nor so thick as the 
 Secondary rocks, and are remarkable for exhibiting frequent 
 alternations of marine and fresh-water formations in the 
 same localities. These beds very frequently occur in limi- 
 ted and detached basins, as if deposited in shallow lakes or 
 estuaries; they are however often continuous over very 
 extensive tracts of country, as from Martha's Vineyard 
 southward along the whole extent of the Atlantic coast of 
 the United States. The order of succession of strata is not 
 uniform as in the older rocks; and hence arises the 
 difficulty of framing a description that will apply to them 
 in all localities. Their alternations have, however, been 
 accurately ascertained, especially in the Paris and London 
 basins. 
 
 255. The sands and clays predominate in the Tertiary 
 series ; their colors are various, depending principally upon 
 
CLASSIFICATION OP THE TERTIARY. 205 
 
 the colored compounds of iron, and they are not sufficiently 
 indurated to form firm sandstones and shales. The calcare- 
 ous strata are more varied in structure and appearance, con- 
 sisting of soft marls filled with shells of rough 'masses of 
 coral of fresh-water beds of hard limestone and of ma- 
 rine limestone of coarse sandy texture. They also contain 
 beds of silica, buhrstone, gypsum, and rock salt. 
 
 256. The Tertiary strata occupy a large portion of the 
 surface of Europe, conforming in a remarkable degree to 
 the present outline of the sea; so that if the continent 
 were depressed a few hundred feet, the sea would cover 
 them, indicating that no essential change has occurred in 
 the figure of the land since that period. The Tertiary series 
 has been recognized also, in Northern Africa, in Asia, in 
 North America, and in South America on both sides of the 
 Andes. 
 
 257. These rocks were, at first, classified in accordance ~. 
 with their alternations as marine and fresh-water deposits ; 
 but these alternations are found not to be uniform. The 
 classification generally adopted is that of MM. Lyell and 
 Deshayes, based upon the relative proportion of shells spe- 
 cifically identical with those occurring at the present time. 
 Shells are selected as the test because they are more gen- 
 erally and uniformly diffused in strata than the remains of 
 any other class of animals. 
 
 EOCENE, (Eos, the dawn ; and kainos, recent,) the dawn of the 
 present period with its races of plants and animals ; 
 contains less than five per cent, of living species, in 
 its fossil contents. 
 
 MBIOCENE, (Meion, less; kainos, recent,) though containing 
 more living species than the Eocene, they are still 
 less than half; its per centage of recent species is 
 eighteen. 
 
 18 
 
206 
 
 ROCKS OP THE TERTIARY PERIOD. 
 
 PLEIOCENE, (Pleion, more; kainos, recent,) a majority of whose 
 
 fossils belong to existing species. 
 
 PLEISTOCENE, (Pleistos, most; kainos, recent,) a still nearer ap- 
 proximation to the present period, having ninety-five 
 per cent, of recent shells. 
 
 THE EOCENE OR OLDER TERTIARY. 
 
 258. The Eocene deposits are the most distinct of the 
 series, and occur well developed in France and England. 
 They, however, vary much in local character. The beds 
 of the Paris and London basins are of the same age, but 
 differ greatly in mineral constitution ; in the London group 
 those of a mechanical origin sands and clays almost ex- 
 clusively prevail ; while beds of limestone, silica, and gyp- 
 sum abound in the Paris basin. 
 
 The following tabular arrangement exhibits the order 
 of the beds in the two basins : 
 
 PARIS BASIN. 
 
 Upper Fresh-water group marls, 
 sands, shelly limestone, buhr 
 limestone. 
 
 Upper Marine sands and marls 
 with thin layers of lime- 
 stone. 
 
 Lower Fresh-water marls, sili- 
 cious limestones, gypsum with 
 numerous bones of animals. 
 
 Lower Marine coarse sandy 
 
 limestone ( calcaire grassier ) 
 calcareous marls and green 
 
 sand. 
 
 Plastic Clay blue plastic clay, 
 sand and pebbles, beds of lig- 
 nite. 
 
 LONDON BASIN. 
 
 Bagshot Sand sand containing 
 few fossils. 
 
 London Clay clay, blackish or 
 gray, containing septaria and 
 ferruginous nodules, with nu- 
 merous organic remains. 
 
 Plastic Clay and Sands sands 
 and sandy clay, with shells; 
 beds of lignite, flint pebbles. 
 
Section of the London Basin. 
 
 F represents the London Clay ; E the plastic clay ; D the 
 Chalk -, c the Wealden ; B the Oolite ; the Bagshot sand 
 caps and overlies the London Clay. The position of the 
 City of London is indicated by the building. 
 
 259. There are numerous other localities of the Eocene 
 Tertiary, as in Southern France, Spain, Belgium, Italy, 
 Greece, Asia Minor, Egypt, India and North and South 
 America. 
 
 260. The fossils of this group are very numerous and 
 important, indicating the condition of the earth at the time 
 of their deposition. The general character of the flora and 
 fauna was like that within the tropics of the present day. 
 The species are with very few exceptions extinct, and seem 
 to have been almost exclusively confined to this formation. 
 More than a hundred species of plants have been dis- 
 tinguished, many of which are dicotyledonous, and resem- 
 ble intertropical plants of the present day; a great number 
 of their seeds and fruits have been found in the London 
 clay beds of the Isle of Sheppey. Various fossil resins have 
 been discovered in these beds, the most important of which 
 is amber, occurring in nodules from the size of a nut to 
 that of a man's head ; one specimen weighs 18 Ibs. Speci- 
 mens frequently contain insects whose positions and de- 
 tached legs and wings indicate that they struggled after 
 
208 ROCKS OF THE TERTIARY PERIOD. 
 
 they were involved in the resin which was at that time 
 liquid. 
 
 261. A large number of shells, both univalve and 
 bivalve, occur in the Eocene : the nautilus was retained, but 
 the ammonites and belemnites had become extinct. More 
 than two hundred species of Ceriihium (an elongated shell 
 resembling Fig. 142) living in brackish water, are found in 
 the European Eocene ; and the nummulites, Fig. 137, are so 
 abundant in some localities as to make up al- j,. 
 most the entire mass of rock. The remains of 
 crabs, are abundant in these deposits. About 
 one hundred species of fish have been recog- 
 nized. Their remains at Monte Bolca in North- 
 ern Italy, and at Mount Lebanon are very numer- 
 ous ; the immense quantities which have been 
 found in a beautiful state of preservation at the 
 former locality, have been thought to indicate 
 that the limestone in which they are imbedded was erupted 
 into the ocean in a fluid state, by volcanic action, suddenly 
 suffocating and enveloping them in the calcareous mass. 
 The species offish found in the Eocene are all extinct, and one 
 third of them belong to extinct genera ; but many of them 
 are closely allied to existing species. The ganoid and placoid 
 Fig. 143. orders, characterized by their 
 
 covering of pointed bony 
 plates and enamelled scales, 
 which abounded in the older 
 rocks, had become relatively 
 Placoid scales. rare the placoids, however, 
 
 had representatives in the sharks and rays, whose teeth 
 are found in abundance. The ctenoids and cycloids, 
 which had been introduced just before the close of the 
 
EOCENE. 209 
 
 secondary period, now pre- 
 dominated. The ctenoid 
 order is characterized by 
 scales having the posterior 
 margins finely pectinated 
 
 ,T . , , . ,7 , Ctenoid Scales. 
 
 divided into little teeth 
 
 like a comb ; these scales are imbricated, each lamina being 
 smaller than the one beneath it, and pectinated as repre- 
 sented in Fig. 144. This order is represented by the perch 
 family. The cycloid order is characterized by circular im- 
 bricate scales with smooth margins, of which the mackerel 
 furnishes an example. More than three-fourths of the 
 species of fishes now living belong to the ctenoid and cy- 
 cloid orders. 
 
 262. The reptiles, like the fishes, shells and plants of 
 this period, resemble those now living in warm insular cli- 
 mates ; they include crocodiles, turtles, tortoises, and ser- 
 pents similar to the boa-constrictor attaining sometimes the 
 length of twenty feet. Several species of birds have been 
 obtained from the Eocene resembling the pelican, buzzard, 
 owl, woodcock, quail, &c. 
 
 263. The number and peculiar features of the land 
 quadrupeds, found in the gypseous deposits of the Paris 
 basin attracted the attention of Cuvier, whose accurate de- 
 scriptions of extinct forms have given great importance to 
 palaeontology. These quadrupeds belonged principally to 
 the order pachydermata, or thick skinned animals, repre- 
 sented by the elephant and horse of the present period. 
 The Eocene quadrupeds which have attracted most atten- 
 tion belong to the genera Palseotherium and Anoplothe- 
 rium. This period has been designated the age of mam* 
 mals. ( 152.) 
 
 18* 
 
210 ROCKS OF THE TERTIARY PERIOD. 
 
 264. The palseotherium (palaios, ancient ; therion, wild 
 beast,) resembled generally the tapir of the present day, 
 having a short fleshy proboscis ; in some of its zoologi- 
 cal characters it was like the rhinoceros. Its feet were 
 divided into three toes, instead of four, as in the tapir. 
 The skeletons of the palaeotheria are found so abundant and 
 well preserved in the Tertiary rocks as to leave no doubt 
 respecting their zoological characters. Twelve species have 
 been found, varying in size from that of the rhinoceros to 
 that of the hog. The largest figure in cut 145 represents 
 this animal. 
 
 Fig. 145. 
 
 Eocene Quadrupeds. 
 
 The LopModon was a genus still more closely allied to 
 the tapir ; only imperfect fragments of its skeleton have 
 been obtained, indicating, however, that some of its species 
 attained the size of the rhinoceros. 
 
 265. The name of the Anoplotherium (a, without; 
 oplon, weapon ; therion, wild beast) defenceless animal, is 
 
EOCENE. 
 
 211 
 
 derived from its destitution of tusks or canine teeth longer 
 than the incisors, in which respect it differs from all mam- 
 miferous animals except man ; its feet terminated in two toes, 
 and it had no proboscis. The genus embraces several groups, 
 one species of which resembled the otter, but was much 
 larger ; its peculiarity was the great length of its tail, which 
 surpassed that of the body ; no animal of the present day 
 except the kangaroo has so long and powerful a tail. A 
 species of another group resembled the hare in dimensions 
 and in the proportions of its limbs. But the most charac- 
 teristic species is the Anoplotherium Gracile, called also 
 Xiphodon, whose graceful and elegant form resembled that 
 Fig. 146. 
 
 Anoplotherium G radio (JSphodon.') 
 
 of the gazelle ; it was closely allied in zoological charac- 
 ters to the ruminating animals, (the deer tribe.) The 
 true ruminants, however, as the camel, ox, sheep, goat and 
 deer were absent at this period. 
 
212 
 
 ROCKS OF THE TERTIARY PERIOD. 
 
 Fifty-seven species of mammalia have been recognized 
 in the Eocene, including a number of carnivorous quadru- 
 peds, as the wolf, fox and raccoon. The opossum, bat and 
 monkey are also found in the rocks of this period ; the 
 remains of the monkey, macacus eocsenus, occurs in a bed of 
 sand underlying the London clay, in England. 
 
 266. The fossil insects found in the rocks of this period 
 present remarkable instances of the preservation of the most 
 delicate objects ; the nerves of the wings, the pubescence of 
 the head, and some traces of the coloring are visible. The 
 wings of the beetles are found in some cases extended be- 
 yond the wing-covers, indicating that the insect fell into 
 water while flying. Seventy genera have been found at 
 Aix, in Provence, including some species identical with 
 those inhabiting that locality at the present time. 
 
 Fig. 147. 
 
 FOSSIL INSECTS. 
 
 Lathrobium . 
 
 Penthetria. Liparus. 
 
 267. The Eocene of North America is found in Vir- 
 ginia, Carolina and Georgia, and consists of beds of marl, 
 
AIEIOCENE. 213 
 
 limestone, sands and clays ; about six per cent, of its fossils 
 are identical with the European Eocene fossils, but about 
 one-fourth are very closely allied to them. The Eocene 
 deposits of South America indicate a great difference in 
 fossil contents on opposite sides of the Andes. 
 
 THE MEIOCENE PERIOD. 
 
 268. The Meiocene, nailed also the Middle Tertiary, is 
 imperfectly represented on the east coast of England by the 
 " Coralline Crag " formation, consisting of marine calcare- 
 ous sands, thin limestones and marls ; but in central and 
 eastern Europe it is developed in strata of great thickness 
 and extent. It occupies the great valleys of the Loire and 
 Garonne in France; large portions of Switzerland; the 
 valley of the Danube, including the Vienna basin, with the 
 plains of Hungary and Poland ; the valley of the Rhine 
 and the western coast of Spain. The strata consist of 
 quartzose sandstone, sometimes soft and incoherent, called 
 in Switzerland the Molasse, shelly limestones and marls, 
 with beds of lignite, and thick masses of corals. They are 
 of both marine and fresh-water origin. The Meiocene beds 
 have also been investigated in the southeastern States of 
 the United States. Tertiary deposits on the flanks of the 
 Sewalik hills in Northern India, and in Siam are referred 
 to this period. 
 
 269. Extensive beds of lignite indicate a vigorous 
 growth of plants; among them the palm is recognized, 
 having grown in Central Europe contemporaneously with 
 trees scarcely distinguishable from those still growing there. 
 Among animal remains those of zoophytes were very .abun- 
 dant, making up entire masses of the coral crag, and be- 
 longing mostly to extinct species. Great numbers of shells, 
 
214 
 
 ROCKS OP THE TERTIARY PERIOD. 
 
 marine and fluviatile are found ; many of the latter belong 
 to the genera Limnea and Planorbis, and are identical 
 those of the present day. The palaeontol- Fig. 148. 
 ogy of this period combines the more an- 
 cient characters of the Eocene with the 
 present botanical and zoological features of 
 the same localities. The valley of the Rhine 
 exhibits the most remarkable fossils of this 
 period hitherto discovered. Numerous tur- 
 tles and fishes presenting marked peculiarities of structure 
 have been obtained there. Fig. 149 exhibits an interesting 
 specimen three feet in length, from Oeningen near Lake 
 Constance. This locality furnished also the celebrated 
 relic, a gigantic, extinct, aquatic salamander, which Schewch- 
 zer in 1726 mistook for the skeleton of a man. 
 
 Fig. 149. 
 
 Fresh-water Tortoise. 
 
 270. The most remarkable quadruped of this period is 
 the Dinotherium, (deinos, fearfully large; iherion, beast,) 
 whose remains are found in the valley of the Rhine near 
 
MEIOCENE. 215 
 
 Darmstadt, and in the valleys of the Jura Mountains. " Its 
 
 length was nearly twenty feet ; its body huge and barrel 
 
 shaped, very much resembling that of the hippopotamus, 
 
 Fig. 150. 
 
 Dinotherium. 
 
 being little raised above the ground, although the huge col- 
 umns which formed its legs are supposed to have been 
 nearly ten feet in length. Its head, rarely, perhaps, brought 
 entirely above the water, was like that of a large elephant, 
 and it was provided with a short, but very muscular and 
 powerful proboscis. A pair of large and long tusks were 
 appended to this skull, and curve downward, as in the wal- 
 rus. The tusks do not proceed from the upper jaw, whence 
 they could be made to depend entirely upon the bones of 
 the neck to support them, but are fixed in the lower jaw, 
 and are planted, as it would seem, in this strange position at 
 the greatest possible mechanical disadvantage. There can 
 scarcely be a doubt that an animal provided with appenda- 
 ges so placed, was an inhabitant of the water ; and the 
 tusks, which are very large, were probably useful as pick- 
 axes, enabling the monster to dig for succulent vegetable 
 food by day, while, perhaps, at night they could be attached 
 like anchors to the banks of the river or lake in which the 
 animal habitually dwelt. It was the most gigantic of the 
 
216 ROCKS OP THE TERTIARY PERIOD. 
 
 herbivorous quadrupeds, and was associated with the palaeo- 
 theres of the more ancient Tertiary period, and with the 
 mastodons and elephants which lived on till a far more re- 
 cent date."* 
 
 271. The Tertiary deposits upon the flanks of tne sub- 
 Himalayas or Sewalik hills in India abound with interest- 
 ing fossils, including the monkey, elephant, dinotherium, 
 mastodon, rhinoceros, hippopotamus, horse, giraffe, antelope, 
 and many others resembling the existing animals of the 
 same name. The most singular animal hitherto found in 
 that locality is the Sivaiherium, so called from the Indian 
 god Siva, and iherion, beast. Its size was about that of a rhi- 
 noceros. Its head was large and shaped like the elephant's, 
 and was furnished with a small proboscis. It had two pairs 
 of horns ; one pair, like those of the ox in shape, were situ- 
 ated over the eyes, and the other pair palmated, like those 
 of the elk, were placed on the back part of the head. The 
 structure of the animal shows it to have been intermediate 
 between the pachydermata and ruminantia. 
 
 The Toxodon, (toxon, a bow ; odous, a tooth,) a large 
 quadruped distinguished for the singular shape and arrange- 
 ment of its gnawing teeth ; and the Macrauchenia (makros, 
 long; auchen, neck,) a pachydermatous animal whose neck 
 was nearly as long as that of the giraffe, have been found 
 in the Tertiary of South America. 
 
 THE PLEIOCENE PERIOD. 
 
 272. The only representative of the Pleiocene or Newer 
 Tertiary in England is the Red Crag, consisting of ferru- 
 ginous-colored sand and gravel, with few zoophytes, but 
 abounding in marine fossil shells, many of which are idon- 
 
 * Ansted's Ancient World, p. 282. 
 
PLEISTOCENE. 217 
 
 tical with living species. On the Continent of Europe the 
 extensive beds on both sides of the Apennine Mountains, 
 called the Sub-Apennine deposits, are 2000 feet thick, 
 consisting of calcareous marls and sands, and are extremely 
 fossiliferous. Some of the deposits in Sicily, Greece and 
 Asia Minor belong to this period. The Pleiocene strata 
 cover also extensive regions in southern Russia, central 
 southern Asia, and America. 
 
 273. Remarkable beds of lignite or brown coal y belong 
 ing to this period, found in Germany, exhibit a great mass 
 of vegetable matter. These lignites lie between beds of 
 
 clay and sand, and consist of solid wood, blackened, but in ^ /j M 
 many instances so slightly changed as to admit of being 
 used as timber ; they are similar to the trees now growing in 
 their vicinity. A thin leafy bituminous lignite is called 
 paper coal. The remains of fishes, frogs, insects and quad- 
 rupeds are found in these deposits. 
 
 THE PLEISTOCENE PERIOD. 
 
 274. The Pleistocene embraces the deposits of fossilif- 
 erous sands, marls and gravels, containing fossils which 
 belong almost entirely to living species. They are exten- 
 sive in the Southern parts of Europe, Asia and America. 
 By some writers on Geology they are made to include the 
 drift, while others apply the term to beds of clay, sand and 
 marl deposited subsequent to the drift and previous to the 
 Alluvial. Where the drift does not occur, as in the south- 
 ern parts of Europe and North America, the Pleistocene 
 beds present an uninterrupted series from the Pleiocene to 
 the Alluvial. 
 
 275. The deposits which are spread over those vast . 
 plains in South America, called Pampas, are assigned to 
 
 19 
 
218 ROCKS OF THE TERTIARY PERIOD. 
 
 the latter portion of the Tertiary period. They include 
 a remarkable group of animals, belonging to the order 
 Edentata, of which the sloth, the armadillo and the ant- 
 eater are representatives in the fauna of the present day. 
 The Megatherium (mega, great; iherion, beast,) was a 
 gigantic quadruped exhibiting some very striking resem- 
 
 Fig. 151. 
 
 The Megatherium. 
 
 blances to the sloth. Its length is eighteen feet, its breadth 
 across the loins six feet, while its height was nine feet. 
 Its proportions were singularly massive, its pelvis and hind 
 extremities being three times as large as those of the ele- 
 phant. The fore legs were long, resembling in structure those 
 of the sloth. The fore foot was a yard long, twelve inches 
 broad, five-toed, and armed with long and powerful claws. 
 This animal is taken as the type of the Megatheroid group. 
 276. The Mylodon (mule, a mill; odous, a tooth,) an 
 allied genus found in the same locality, in some respects 
 more closely resembles the sloth. Prof. Owen has given a 
 full description of a perfect skeleton of this animal ob- 
 tained from Buenos Ayres, and deduced its relations and 
 habits. The length of the skeleton is eleven feet, inclu- 
 
PLEISTOCENE. 
 
 219 
 
 ding the tail. Its teeth show that it was a vegetable eater; 
 it probably lived, as do the sloths of the present day, on 
 leaves and buds of trees. 
 
 Kg. 162. 
 
 Mylodon Robustus. 
 
 277. The Megalonyx (megale, great; onux, claw,) re- 
 sembled the mylodon in its size and proportions ; it differed 
 in its claws, and in greater freedom of motion in its fore 
 limbs. 
 
 The ScelidotJierium (scclidos, the thigh ; therion, beast,) 
 though allied to the megatherium, resembled the ant-eater 
 and armadillo. In its hinder extremities and tail, the 
 strength was greater in proportion than in any known ani- 
 mal, living or extinct ; while the length of the animal was 
 
220 
 
 ROCKS OF THE TERTIARY PERIOD. 
 
 not greater than that of a Newfoundland dog, and its fore 
 limbs no larger, its hind extremities were as ponderous as 
 those of the hippopotamus.* 
 
 278. Associated with the megatheroid animals of this 
 period was a colossal armadillo, called the Glyptodon (glup- 
 tos, sculptured; odous, tooth,) from its teeth being sculp- 
 tured laterally with wide, deep grooves. Like the armadillo 
 
 Fig. 158. 
 
 Glyptodon Cluvipes. 
 
 it was covered with a crust or shell, composed of polygonal 
 pieces accurately fitting each other, constituting a massive 
 armour. The structure of its hind foot is very peculiar, 
 presenting a frame work unparalleled in its adaptation to 
 support a great weight, and at the same time allow such free 
 motion in the fore limbs as the habits of the armadillo re- 
 quire. Several species of the genus glyptodon have been 
 determined. The remains of the mastodon have been 
 found in the same localities with the megatheroid animals, 
 
 * Ansted's Ancient World, p. 348. 
 
ROCKS OP THE TERTIARY PERIOD. 221 
 
 279. Igneous rocks are found abundantly in connexion 
 with the Tertiary series ; they are lavas of extinct volcanoes, 
 and are intermediate in character between the traps of the 
 secondary period and the products of active volcanoes. In 
 composition they are principally trachytic, but sometimes 
 scoriaceous, or tufaceous. One of the most remarkable 
 localities of Tertiary volcanoes is an extensive plain in 
 Auvergne, central France, which supports a series of seventy 
 volcanic cones, varying from five hundred to a thousand feet 
 in height, forming a range about twenty miles long and two 
 broad. Many of these cones retain well defined craters 
 several hundred feet deep, and their lava beds can be traced 
 as easily as those of Vesuvius. " There is no spot," says 
 Mr. Scrope, " even among the Phlegracan fields of Italy, 
 which more strikingly displays the characters of volcanic 
 desolation. Although the cones are partially covered with 
 wood and herbage, yet the sides of many are still, naked ; 
 and the interior of their broken craters, rugged, black and 
 scorified, as well as the rocky floods of lava with which they 
 have loaded the plain, have a freshness of aspect, such as 
 the products of fire alone could have so long preserved, and 
 offer a striking picture of the operation of this element in 
 all its most terrible energy." These volcanic vents are of 
 different ages; some of them are manifestly of compara- 
 tively recent origin. 
 
 280. Another interesting group of Tertiary volcanoes is 
 upon the banks of the Rhine, where the graceful forms of 
 the Siebengebirge or Seven Mountains, and the majestic 
 Eifel with its crater covered with scoriae, and its lava cur- 
 rents still visible, are conspicuous features in the pictu- 
 resque scenery of the river. The basis rocks supporting the 
 Tertiary formations are not here, as in Auvergne, granite, 
 
 19* 
 
222 ROCKS OP THE TERTIARY PERIOD. 
 
 but belong to the Silurian formation. Similar evidences of 
 volcanic agency during the Tertiary period are found in 
 Catalonia in Spain, Hungary, Asia Minor in the " burnt 
 district," and in Palestine. The soil in the vicinity of these 
 volcanoes, composed in part of their lavas, is exceedingly 
 fertile. 
 
CHAPTER II, 
 
 ROCKS OF THE QUATERNARY PERIOD. 
 
 281. THE Quaternary series embraces the heterogeneous 
 masses of the Drift and all subsequent deposits up to the 
 present period. English geologists generally discard this 
 division, and extend the Tertiary over this series. 
 
 THE DRIFT PERIOD. 
 
 282. The Drift includes accumulations of sand, 
 gravel, clay, pebbles and boulders, or erratic blocks ; the 
 boulders are fragments of the hard crystalline rocks, usually 
 water-worn, rounded, and scratched, or grooved. The term 
 Diluvium has been applied to this deposit ; drift indicates 
 that the materials have been impelled by currents. 
 
 283. The drift is not universally diffused, but appears 
 to be confined within 40 or 50 from the poles. In Asia 
 it is rarely found lower than 60 north latitude ; in Europe 
 it descends to the southern parts of Poland and Prussia ; 
 and in North America it is found as low as 40, and some 
 of the north and south valleys extend it a little farther 
 southward. Its southern limit in the United States is a 
 line drawn from Long Island through central Pennsylvania 
 to the Ohio, with occasional outliers in the valleys of the 
 Delaware, Susquehanna and Mississippi. It is found also 
 in the southern portions of South America, but not within 
 the tropics. It occurs at elevations above the present sea 
 
224 ROCKS OF THE QUATERNARY PERIOD. 
 
 level, varying from three hundred to five thousand feet. 
 The general direction of the drift in North America has 
 been from north to south, and occasionally southeast ; while 
 in Europe it appears to have been dispersed in various 
 directions from the Scandinavian Mountains. Boulders 
 have been transported in some instances hundreds of miles j 
 the largest of them have, however, usually been deposited 
 within a few miles of the ledges from which they were torn. 
 They diminish in size and number as the distance from 
 their original position increases. Boulders of considerable 
 size are frequently found in Northern Ohio, but are few and 
 small in the central and southern parts of the State. They 
 can be identified with the rocks of the parent ledges by 
 their general constitution and by particular minerals con- 
 tained in them. 
 
 284. Boulders vary greatly in size; some of them 
 weigh thousands of tons. A conglomerate boulder at Fall 
 River, President Hitchcock states, weighs ten million eight 
 hundred thousand pounds ; a granite boulder near Neufcha- 
 tel weighs three million eight hundred and fifty thousand 
 pounds j and the boulder from which the pedestal of the 
 statue of Peter the Great was hewn, weighed one thousand 
 five hundred tons. Some boulders are so poised upon hard 
 surfaces, as to oscillate by the application of a moderate 
 force to them, and are then called rocking stones; others 
 are firmly posited in such a manner as to have given rise 
 to the conjecture that they are artificial structures. An 
 example of this occurs in the State of New York, and is 
 represented in Fig. 154. A boulder of felspathic granite 
 weighing about fifty tons, rests at the height of three or 
 four feet above the ground, upon limestone pillars. They 
 are sometimes poised on the summits of mountains ; others 
 
THE DRIFT PERIOD. 
 
 225 
 
 have been carried over mountain ridges, though they are 
 usually found accumulated in larger numbers on the north 
 sides of mountains. 
 
 Fig. 154. 
 
 Granite Boulder on Limestone Pillars. 
 
 285. The transport of the drift has produced very con- 
 spicuous effects upon the surface of the earth, scratching, 
 grooving, and polishing the rocks. The scratches and 
 grooves are parallel, resembling those produced by glaciers 
 described in 32. They vary from a fraction of an inch 
 to more than a foot in depth and width. Sometimes two 
 or more sets of striae cross each other at a small angle. 
 These striae have been found on the White Mountains five 
 thousand feet above the ocean level. Prof. Locke gives an 
 example of these grooves on the limestone near Dayton, 
 Ohio. u The quarry has been stripped of soil more or less 
 over ten acres, and the upper layer of stone is in most 
 
226 ROCKS OP THE QUATERNARY PERIOD. 
 
 places completely ground down to a plane, as perfectly as 
 it could have been done by a stone cutter, by rubbing one 
 slab on another with sand between them. In many places, 
 in addition to the planishing, grooves and scratches in par- 
 allel straight lines, evidently formed by the progress of 
 some heavy mass, propelled by a regular and uniform mo- 
 tion, are distinctly visible. The grooves, are, in width, 
 from lines scarcely visible, to those three-fourths of an inch 
 wide, and from one-fortieth to one-eighth of an inch deep, 
 traversing the rock in a direction south 26 east, in lines 
 exactly straight and parallel/'* 
 
 It is probable that a very large portion of the earth's 
 surface was affected in this way, as far as the drift extended, 
 since the removal of clay and other substances which cover 
 the rocks discovers the striae ; rocks that suffer disintegra- 
 tion by atmospheric agency, as limestones, which are par- 
 tially dissolved by water holding carbonic acid in solution, 
 do not retain their grooves. The direction of the striae 
 coincides with that of the dispersed drift, and is often mod- 
 ified by the features of the surface ; as when it is diverted 
 from the general direction into a valley. Some sets of 
 striae appear to have been nearly obliterated by others pass- 
 ing over them. 
 
 286. The northern and northwestern sides of the ledges 
 of rocks are more worn by the drift agency, and the hills 
 are elongated in this direction, corresponding in appearance 
 with those denominated by European writers roches mou- 
 tonnees. President Hitchcock has observed very numerous 
 angular fragments of rocks ranged in long narrow lines, ex- 
 tending from the ledges in the same direction with the 
 drift, and overlying that deposit, which he denominate? 
 
 * Ohio Geological Survey, p. 230. 
 
THE DRIFT PERIOD. 
 
 227 
 
 streams of stones. The same geologist adduces as instances 
 illustrative of the prodigious violence of the drift agency, 
 the fracture and overturning of perpendicular strata of 
 slate rocks near the summits of hills. As the materials 
 of the drift are generally supposed to have been transported 
 by the agency of ice, these deposits are called glacial beds ; 
 they have very few, if any fossils. 
 
 287. Overlying the boulder formation occur beds of 
 blue and yellow clay, sand and marl ; these are most abun- 
 dant in lakes, ponds, and river valleys. They sometimes 
 appear to be caused by a new arrangement or assorting of 
 the materials of the drift, producing an inter-stratification 
 of sands, clays, and gravel, and are called altered drift. 
 This appears to have been accomplished beneath the ocean 
 which prevailed over the drift region. 
 
 Fig. 155. 
 
 Parallel Roads and River Terraces 
 
 288. The origin of marine terraces has been assigned 
 to the agency of the ocean exerted at this period. Fig. 
 155 presents a view in the valley of Glen Roy in Scotland, 
 in which two parallel shelves or terraces, level and con tin- 
 
228 ROCKS OP THE QUATERNARY PERIOD. 
 
 uous through the whole glen, are seen. They vary in 
 width from ten to sixty feet, and are covered with boulders. 
 The highest one is one thousand two hundred and fifty feet 
 above the present level of the ocean, and the other is two 
 hundred feet lower. These terraces are stratified deposits ; 
 they are ascribed to the action of water standing at that 
 level, either a lake or the ocean. Similar shelves at these 
 elevations are found in other valleys of Scotland, in Swe- 
 den, and in North America. River terraces present similar 
 phenomena ; they occur in valleys of mountainous districts, 
 where the river flowing over the drift in which it cuts its 
 channel, removes the materials to lower levels. The 
 sudden removal of obstacles gives origin to a new terrace. 
 These are represented in Fig. 155. Ancient lakes have 
 also been reduced by successive stages, and formed broad 
 level terraces. 
 
 289. Various beds of sand and gravel scattered over 
 the valleys and plains are called ossiferous, because they 
 contain bones of the elephant, hippopotamus, bear, deer, 
 horse and other animals which do not now inhabit the re- 
 gions where their remains occur ; the bones of the elephant 
 and rhinoceros are found in England and in Siberia, where 
 they have not been known to exist within the historic pe- 
 riod. These bones are partially petrified by the salts of 
 lime and iron, are harder and heavier than recent bones, 
 but still preserve their bony structure. Many of these 
 ossiferous deposits are local, having been produced by the 
 action of rivers, and the filling up of lakes, but some of 
 them appear to be due to more extensive agencies. 
 
 290. Numerous caverns have been found in Europe, 
 America and Australia, containing deposits of loam, river 
 silt and small boulders. These materials were probably 
 
THE DRIFT PERIOD. 229 
 
 introduced during different periods ; but the animal remains 
 included in them indicate the drift period as the one during 
 which the largest portion of the deposits accumulated. 
 The bones, which are perfectly preserved in many instances 
 in calcareous incrustations, are chiefly those of races of 
 bears and hyaenas which inhabited the caves, together with 
 the remnants of their prey, and occasional fragments of 
 the elephant and rhinoceros. The remains of man, and of 
 animals still living in the vicinity are sometimes found in 
 them. The most remarkable caverns, on account of their 
 organic contents, are Kirkdale Cave near York in England, 
 and the Cave of Gailenreuth in Germany. 
 
 291. The Kirkdale Cave, which Dr. Buckland has 
 very accurately described in his " Reliquiae Diluvianae," is 
 situated about twenty-five miles northeast of York, above 
 the northern edge of the great vale of Pickering, and 
 thirty feet above its waters. Its floor is level and nearly 
 conformable to the plane of stratification of the coralline 
 oolite in which it occurs. In some parts the cave is three 
 or four feet high, and roofed, as well as floored, by the level 
 beds of this rock ; in other parts its height was augmented 
 by open fissures, which communicate through the roof, and 
 allow a man to stand erect. The breadth varies from four or 
 five feet to a mere passage ; at the outlet or mouth against 
 the valley was a wide expansion or ante-chamber, in which 
 a large proportion of the greater bones, as of the ox, rhi- 
 noceros, &c., were found. This mouth was choked with 
 stones, bones and earth, so that the cave was discovered by 
 opening upon its side in a stone quarry. On entering the 
 cave, the roof and sides were found incrusted with stalac- 
 tites, and a general sheet of stalagmite, rising irregularly 
 into bosses, lay beneath the feet. This being broken 
 20 
 
230 ROCKS OF THE QUATERNARY PERIOD. 
 
 through, yellowish mud was found about a foot in thick- 
 ness, fine and loamy toward the opening, coarser and more 
 sandy in the interior. In this loam chiefly, at all depths, 
 from the surface down to the rock, in the midst of the 
 stalagmitic upper crust, and as Dr. Buckland expresses it, 
 " sticking through it like the legs of pigeons through a 
 pie-crust/' lay multitudes of bones of the following ani- 
 mals: 
 
 Carnivora- hyaena, tiger, bear, wolf, fox, weasel. 
 
 Pachydermata elephant, rhinoceros, hippopotamus, 
 horse. 
 
 Ruminantia ox, three species of stag. 
 
 Rodentia hare, rabbit, water-rat, mouse. 
 
 Birds raven, pigeon, lark, duck, snipe. 
 
 The hyaena's bones and teeth were very numerous 
 probably two or three hundred individuals had left their 
 bodies in this cave ; remains of the ox were very abundant ; 
 the elephants' teeth were mostly of very young animals ; 
 teeth of the hippopotamus and rhinoceros were scarce; 
 those of water rats very abundant. The bones were almost 
 all broken by simple fracture, but in such a manner as to 
 indicate the action of hyaenas' teeth, and to resemble the 
 appearance of recent bones broken and gnawed by the liv- 
 ing Cape hyaena. They were distributed as in a " dog- 
 kennel," having clearly been much disturbed, so that ele- 
 phants, oxen, deer, water-rats, &c., were indiscriminately 
 mixed ; and large bones were found in the largest part of 
 the cavern. The teeth of hyaenas were found in the 
 jaws, of every age, from the milk tooth of the young ani- 
 mal to the old grinders worn to the stump; some of the 
 bones were polished in a peculiar manner, as if by the 
 trampling of animals." 
 
THE DRIFT PERIOD. 231 
 
 292. The most remarkable ossiferous cavern of Ger- 
 many is that of Gailenreuth, which lies upon the left bank 
 of the Wiesent. The entrance, which is, about seven feet 
 high, is in the face of a perpendicular rock, and leads to a 
 series of chambers from fifteen to twenty feet high and 
 several hundred feet in extent, terminated by a deep chasm, 
 which, however, has not escaped the ravages of visitors. 
 This cavern is perfectly dark, and the icicles, or pillars of 
 stalactite, reflected by the torches which it is necessary to 
 use, present a highly picturesque and striking eifect. The 
 floor is literally paved with bones and fossil teeth ; and the 
 pillars of stalactite also contain osseous remains. Loose 
 animal earth, abounding in bones, forms in some parts a 
 layer ten feet in thickness. A graphic description of this 
 cave was published by M. Esper, more than sixty years 
 ago ; at that period some of the innermost recesses contained 
 wagon loads of bones and teeth; some imbedded in the 
 rock, and others in the loose earth. The bones in general 
 are scattered and broken but not rolled ; they are lighter 
 and less solid than recent bones, and are often incrusted 
 with stalactite. Cuvier, who enjoyed the opportunity of 
 examining a very large collection of bones from G-ailenreuth, 
 was enabled to determine that at least three-fourths of the 
 osseous contents of the caverns belonged to some species of 
 bear ; and the remaining portion to hyaonas, tigers, wolves, 
 foxes, gluttons, weasels and other small carnivora. By the 
 bones which were referable to the bear, he established three 
 extinct species of that genus, the largest of which is called 
 the Ursus spelaeus. The hyasna was allied to the spotted 
 hyaena of the Cape, but differed in the form of its teeth 
 and head. Bones of the elephant and rhinoceros are also 
 said to have been discovered, together with those of exist- 
 
232 BOCKS OF THE QUATERNARY PERIOD. 
 
 ing animals, and fragments of sepulchral urns of high an- 
 tiquity."* 
 
 293. The phenomena of ossiferous caverns lead to the 
 conclusion that they were the dens of ravenous animals ; 
 that the carcasses of large animals were drifted into them ; 
 and that men have used them as places of abode or sepul- 
 ture. Fragments of bones, mingled with clay, pebbles, 
 shells, etc., cemented together with the carbonates of lime 
 and iron, are frequently found filling fissures in the rocks. 
 Such accumulations are called osseous breccia; they are 
 very abundant in the vicinity of the Mediterranean sea ; the 
 rock of Gibraltar yields fine specimens. The bones of the 
 breccia are referable to both extinct and recent species. 
 The bone breccia of Australia has the same ochreous color 
 as that in Europe has; its bones are all referable to marsu- 
 pial animals, as the kangaroo, wombat, dasyurus, &c. 
 
 294. The fossils of this period are very numerous and 
 various ; shells, both marine and fresh-water, are found in 
 great quantities beneath beds of gravel and boulders, and 
 especially in beds of marl under the muck decaying veg- 
 etable matter of ponds and swamps. The long clam, My a 
 arenaria, and the common oyster, Ostrea borealis, marine 
 shellfish, are found in the deposits of this period far inland, 
 and a very large majority of the shells belong to species 
 inhabiting the ocean of the present day. The immense 
 accumulations of these shells, constituting layers many feet 
 deep, indicate the lapse of a long period of time. Infu- 
 soria abounded at this period ; the silicious marl beneath 
 peat swamps is almost entirely made up of these fossil 
 skeletons. 
 
 295. At this period the most gigantic of the existing 
 
 * Mantell's Wonders of Geology, p. 169. 
 
THE DRIFT OR PLEISTOCENE PERIOD. 233 
 
 groups of herbivorous quadrupeds were represented by 
 allied species, which had a very wide range of diffusion, 
 and some of which had a special organization to enable 
 them to encounter a severity of climate, such as similar 
 animals are not at the present day designed to endure, the 
 elephants, for example, having been covered with hair. 
 The animals which formerly characterized the plains of 
 Siberia and the high latitudes of the North American con- 
 tinent are closely allied to the existing fauna of Northern 
 Europe. 
 
 296. The Mastodon (mastos, nipple ; odous, tooth,) is a 
 genus quite distinct from the elephant and derives its name 
 from the crown of the molar tooth presenting conical tu- 
 bercles covered with enamel. It was a somewhat larger 
 animal than the elephant, with pig. 156. 
 
 a body longer in proportion. 
 It was very widely diffused, 
 its remains having been found 
 in Asia, Europe, and America, 
 from the equator to 66 of 
 north latitude ; it has also an 
 extended range in time, con- 
 necting the Meiocene with the 
 Pleistocene deposits, and con- Tooth of the Mastodon. 
 tinuing down nearly or quite to the epoch of man, concom- 
 itant in the latter periods of its existence with many species 
 of animals which still survive. The temperate zone of 
 the North American continent appears to be the locality in 
 which it flourished ; it is there five times as numerous as 
 the elephant. Its remains abound in the marshes whose 
 waters are saline, called Licks} the skeletons have been 
 found erect with the head thrown upward, as if the anima] 
 20* 
 
234 
 
 ROCKS OF THE QUATERNARY PERIOD. 
 
 had sunk in the mire ; the stomach with its contents of 
 bruised twigs and leaves has been found, confirming the 
 conclusion which the structure of its teeth had suggested, 
 that it was an herbivorous animal feeding upon tough coarse 
 vegetables, as the branches of trees. It is estimated that 
 from the Big Bone Lick in Kentucky, the bones of one 
 hundred mastodons, twenty elephants, two oxen, two deer 
 and one megalonyx have been extracted. Several very fine 
 skeletons of mastodons are now in the cabinets of Europe 
 and America. Fig. 157 presents a likeness of the most 
 perfect skeleton yet exhumed. It was obtained at New- 
 Fig. 157. 
 
 Mastodon found in Newburg, N. Y. 
 
 burg, N. Y., in 1845, and presents nearly every bone per- 
 fectly preserved ; it is about twelve feet high, its tusks are 
 fourteen feet long, and it weighs two thousand pounds. 
 
 297. The Mammoth (from the Arabic behemoth, signi- 
 fying elephant,) was a companion of the mastodon from 
 the Eocene period to the close of the Pleistocene, at the 
 
THE DRIFT OR PLEISTOCENE PERIOD. 
 
 235 
 
 Fig. 158. 
 
 close of which, like the latter, it became extinct. It dif- 
 fered from the mastodon particularly in the disposition of 
 the enamel of its teeth in vertical plates or layers alterna- 
 nating with softer bone. It .differed from the two existing 
 species of elephant the African and Asiatic but was 
 more nearly related to the 
 latter. In the crown of the 
 tooth of the African species 
 the enamel is arranged in 
 lozenge-shaped figures, as rep- 
 resented at a Fig. 158; in 
 the Asiatic species the enamel 
 is in narrow transverse bands, 
 as at 5; while the enamel in 
 the tooth of the fossil species 
 is similarly arranged in broad- 
 er bands, as at c. The remains of the fossil elephant are 
 very numerous, occurring wherever the mastodon is found, 
 but relatively much more abundant on the Eastern than on 
 the Western Continent. Bones of more than five hun-' 
 dred individuals are supposed to have been found on the' 
 coasts of Norfolk and Suffolk in England, and they are very 
 abundant in the shoals of the German Ocean. They have 
 also been found in Ohio, Vermont, and other localities in 
 the United States. But the most singular localities in 
 which these fossils have been found are the frozen grav- 
 els and clays at the mouths of rivers and along the shores 
 of the Polar seas, in latitudes in which the existing species 
 of elephant can not live. The skeleton of the fossil ele- 
 phant found in Siberia, described in 124, closely resem- 
 bles that of the Asiatic species, but its tusks are larger and 
 more curved backward. Its tusks weighed three hundred 
 
236 ROCKS OF THE QUATERNARY PERIOD. 
 
 and sixty pounds, and the bead with the tusks four hundred 
 and fourteen pounds. A large portion of the ivory of com- 
 merce has been derived from the fossils in Siberia. 
 
 Elephas Primigenius. 
 
 298. The remains of other extinct animals are found 
 upon the shores of the Arctic ocean, one of which 
 bears resemblance to the rhinoceros but is quite distinct 
 from any known species of that genus. Von Wrangel 
 states that on an island in latitude 75 and longitude 
 140, in the Polar sea, the hills in the interior were found 
 to contain the skulls and bones of horses, buffaloes, oxen 
 and sheep in such abundance that these animals must for- 
 merly have lived there in large herds. The best bones as 
 well as the greatest number are found at a certain depth 
 below the surface, usually in clay hills, more rarely in black 
 earth. The more solid the clay, the better are the bones 
 preserved, and experience has shown that more are found 
 in elevations situated near higher hills, than along the low 
 coast, or on the flat tundra (moss levels.)* 
 
 299. The bones of ruminating animals nearly allied to 
 
 * Ansted's Geology, II, p. 151, 
 
THE DRIFT OR PLEISTOCENE PERIOD. 
 
 237 
 
 the common species of the ox and deer tribes are very 
 abundant in the deposits of this period; the dimensions 
 of their bones indicate great size, but otherwise they 
 differed slightly from existing species. A remarkable 
 gigantic animal, called the Irish Elk, is found abundant in 
 the east of Ireland and in the Isle of Man. It is found in 
 beds of marl beneath peat-bogs which are the sites of an- 
 cient lakes ; they occur also in the marls of France, Ger- 
 many and Italy. The species is remarkable for the dimen- 
 sions of its antlers, which were palmated. The average 
 weight of the skull and antlers is seventy-five pounds. The 
 
 Fig. 169. 
 
 Megaceros Hibernicufi. 
 
 skeletons are ten feet high, and the antlers spread from 
 ten to fourteen feet. This animal continued to inhabit the 
 earth up to a late period, and by some geologists is supposed 
 to have been in existence after the introduction of the hu- 
 man race. Contemporary with this and other members of 
 
238 ROCKS OP THE QUATERNARY PERIOD. 
 
 the deer tribe were several species of the genus Bos, of 
 which one is supposed to be the great auroch or wild bison, 
 still living in the forests of eastern Europe. 
 
 800. Besides the land mammalia, relics of marine 
 tribes of the class are found in the Tertiary, in the Pleio- 
 cene, and perhaps in the Meiocene, but more abundantly in 
 the Pleistocene, in beds of drift in valleys traversed by 
 rivers. The Cetacea are not fishes ; they breathe not by 
 means of gills, but by lungs, are viviparous and suckle 
 their young. 
 
 Dr. Harlan described the skeleton of an animal of enor- 
 mous size found in the Tertiary in Alabama, under the 
 name of Basilosaurus supposing it to be a reptile; but 
 Professor Owen has shown that it is a Cetacean, allied to 
 the Dugong and Cacholot, and has assigned to it the name 
 Zeuglodon. 
 
 The skeleton of a whale seventy-two feet long has been 
 discovered in a clay bed in Scotland, twenty feet above the 
 present high tide level. 
 
 A portion of the skeleton of a whale which was sixty or 
 seventy feet long, has been extracted from a cliff in Brigh- 
 ton, England, associated with the remains of the mammoth. 
 
 The skeleton of a whale thirteen feet long has been re- 
 cently discovered by a railroad excavation in the blue clay 
 of the valley of Lake Champlain, Vermont. 
 
 301. The skeletons of several species of birds equal in 
 size to those which are supposed to have made the foot- 
 prints upon the New Red Sandstone, have been found in the 
 recent deposits in New Zealand. They appear to belong to 
 a group of which the Apteryx is a living representative, 
 which are more ponderous in proportion than the ostrich, 
 and destitute of wings. They vary greatly in size, 
 
THE DRIFT OR PLEISTOCENE PERIOD. 
 
 239 
 
 Fig. 160. 
 
 some having attained 
 the height of nearly 
 twelve feet, while oth- 
 ers are quite small. 
 The structure of the 
 Dinornis shows that it 
 was, like the Apteryx, 
 well fitted for rapid 
 running. These birds 
 appear to have been 
 continued into the his- 
 torical period; some 
 of them have very 
 recently become ex- 
 tinct ; their bones are 
 found in the state de- 
 nominated sub-fossil. The Dinornig - 
 
 302. The climate of the period immediately succeeding 
 the Drift appears to have been essentially the same as it 
 now is. The deposits of arctic shells in the altered drift 
 which were thought to indicate a low temperature, are quite 
 limited and may be accounted for by the influence of polar 
 currents ; many of them are identical with those of species 
 now living exposed to such currents on the present sea 
 coasts. The existence of elephants, lions, tigers, hyaenas, 
 and similar animals found now only in tropical regions, in- 
 dicates a mild climate in Great Britain and other parts of 
 Europe where their remains are found in abundance. The 
 elephants found in Siberia were clad with wool and hair, 
 showing that they lived in a colder climate than their con- 
 geners are fitted for at the present day ; but the climate 
 must have been milder than it is in those regions at present, 
 
240 ROOKS OP THE QUATERNARY PERIOD. 
 
 to have furnished sufficient food for such large animals as 
 the elephant and rhinoceros, and the supposition that it was, 
 appears to be confirmed by the fact that large birch trees 
 are found embedded in the sandy cliffs, beyond the seventy- 
 fifth degree of north latitude in sufficient quantities to be 
 used by the inhabitants as fuel, while only stunted shrubs of 
 the same genus grow at the present day beyond the seven- 
 tieth degree of latitude. 
 
 THE ALLUVIUM. 
 
 303. The Alluvium embraces the recent and progressive 
 formations, consisting of sands, gravels, clay, marls, vege- 
 table and animal matter, which the rivers, lakes, seas, shell- 
 beds and coral-reefs are constantly accumulating. These 
 deposits are not distinguished from those which immediately 
 precede them by any marked difference of characters, but 
 through gradual, successive steps, they bring the history of 
 the physical changes to which the globe has been subjected 
 to the present time. They may be classified in accordance 
 with their positions as marine, fresh-water, and terres- 
 trial. The period during which they have occurred is des- 
 ignated the historic period the age or reign of man. 
 
 304. The phenomena of raised beaches indicate recent 
 extensive changes of level in the ocean ; such beaches, with 
 their strewn sand, gravel, pebbles, shells, etc., occur in 
 some instances hundreds of feet above the present ocean 
 level. Some of the elevations have been sudden, and were 
 witnessed by living observers, as on the coast of Chili in' 
 1822, and the Ullah Bund, (67, 68;) but others are more 
 ancient, and were probably gradual. Along the coasts of 
 the Mediterranean, ancient beaches covered with the shells 
 of species of shell-fish living at the present time in the ad- 
 
THE ALLUTIUM. 241 
 
 joining sea have been elevated fifty feet, while the coasts 
 of Sweden and Norway have been raised two hundred feet 
 above the present level of the Baltic. Similarly located 
 beaches or terraces are found near the ocean, generally con- 
 forming to its present boundaries, in all parts of the world. 
 Phenomena of a converse kind are presented by subma- 
 rine forests, which are beds of vegetable substances with 
 the roots of the trees in the situations in which they orig- 
 inally grew now depressed several feet below the lowest 
 tide ; as the trees belong to existing species, the depression 
 is shown to be a geologically recent occurrence. 
 
 305. Masses of sand, gravel, pebbles and clay, termed 
 marine silt, have accumulated in many positions on the 
 present shores of the ocean, through the influence of waves, 
 tides and currents. The Isthmus of Suez is said to have 
 gained thirteen miles in width within four thousand years ; 
 the sites of the ancient sea ports Tyre and Sidon are now 
 several miles inland ; and hundreds of square miles of dry 
 land have been formed by the existing seas, in numerous 
 localities, (44.) Of the recent deposits made upon the 
 bed of the ocean but little is known ; soundings, however, 
 show that sand, mud, shells, corals, and vegetable substan- 
 ces have been deposited by sub-marine currents on a scale 
 which rivals some of the ancient strata. The Yellow Sea 
 and the German Ocean have been shoaling at a very sensi- 
 ble rate within the period of human observation ; the for- 
 mer, it is estimated, converts a square mile into solid land 
 in seventy days, or more than five hundred square miles in 
 a century. 
 
 306. Estuary deposits are peculiarly complex, since 
 they are composed of marine and fluviatile silts, and em- 
 brace organic remains derived from the ocean, fresh-water, 
 21 
 
242 ROCKS OF THE QUATERNARY PERIOD. 
 
 and the laud. The delta of the Niger may serve as an exam- 
 ple : its base extends three hundred miles along the coast of 
 the .ocean, and consists of a beach of sea sand, with shells, 
 corals and other marine remains; during the dry season, 
 and at a low stage of the water in the river, these marine 
 deposits extend farther inland. The delta extends up the 
 river one hundred and seventy miles, consisting of vast ex- 
 panses of low lands, swamps, and mud islands, separated 
 by branches of the river and stagnant pools. A rank 
 growth of marsh plants covers much of its surface ; shell- 
 fish and amphibious animals abound, and contribute their 
 remains to its accumulating strata. Like the delta of the 
 Nile it is annually inundated, and deposits of mud and 
 sand are made over the whole surface, mingled with the 
 remains of the elephant, hippopotamus, rhinoceros and 
 other tropical animals, together with a variety of corre- 
 sponding plants. When this delta shall have been elevated 
 beyond the reach of the waters, and become consolidated, 
 its strata of confused and alternating marine, fresh-water, 
 and terrestrial characters, will present appearances similar to 
 those of the Tertiary and Wealden formations. 
 
 Deltas are the most extensive of the accessible alluvial 
 deposits; they furnish a connecting link between forma- 
 tions now in progress and those of former geological eras. 
 
 307. Lacustrine deposits include the mud, sand, marl 
 and organic matter which have accumulated in fresh-water 
 lakes of the present period ; these materials form succes- 
 sive regular layers upon the bottoms of the lakes, indicating 
 quiet, gentle deposition. Lakes have thus been filled up 
 and formed flat alluvial plains ; some geologists ascribe this 
 origin to the prairies, pampas, and steppes. Some lakes 
 have been partially or wholly drained by a more rapid pas- 
 
THE ALLUVIUM. 243 
 
 sage of their waters through the outlets ; when this has been 
 effected hy distinct stages, successive terraces are formed ; 
 this is supposed to have been the origin of the lake ridges 
 ridge roads they having constituted the ancient shores 
 of the lakes. The circumstances of deposition of the fresh- 
 water beds of the Tertiary, Wealden, and Coal series ap- 
 pear to have been similar to those of lacustrine accumu- 
 lations of the present era. Rivers have sometimes deposited 
 their silt upon their beds, and more frequently during 
 freshets upon the adjacent valleys ; such deposits are more 
 heterogeneous and irregular than those made in lakes. 
 
 308. Of the various mineral substances chemically pre- 
 cipitated from water, marl is the most abundant; it is the 
 carbonate of lime held in solution and in mechanical suspen- 
 sion. It occurs in various degrees of purity \ when densely 
 aggregated and sometimes crystalline in texture, *it is called 
 rock marl; when cementing together a mass of shells, 
 shell marl, and when largely mixed with clay, day marl. 
 Marls are found most frequently in the deposits of lakes, 
 ponds and swamps in limestone districts, in which calcareous 
 springs abound. Immense quantities of this material are 
 also conveyed by rivers into the ocean. " A hard stratum 
 of travertin," says Mr. Lyell, "about a foot in thickness, is 
 obtained from the waters of San Filippo in four months ; 
 and as the springs are powerful, and almost uniform iii 
 the quantity given out, we are at no loss to comprehend 
 the magnitude of the mass which descends the hill, 
 which is a mile and a quarter in length, and the third of a 
 mile in breadth, in some places attaining a thickness of two 
 hundred and fifty feet. To what length it might havo 
 reached it is impossible to conjecture, as it is cut off by a 
 stream which carries the remainder of the calcareous matter 
 
244 ROCKS OP THE QUATERNARY PERIOD. 
 
 to the sea." Waters holding silica in solution hot springs 
 have deposited silicious sinter; the hot springs of St. 
 Michael have encrusted surrounding objects, and deposited 
 layers of sinter several inches thick. Alumina is also 
 sometimes similarly precipitated ; a mixture of precipitated 
 alumina, silica and the oxide of iron has been obtained 
 abundantly from Tripoli for use as a polishing powder but 
 much of the tripoli of commerce consists of the silicious 
 shields of animalcules. The oxides of iron and manganese, 
 gypsum, common salt, petroleum or asphaltum, etc., have 
 formed extensive deposits ; they furnish many analogies by 
 which the phenomena of similar beds in the older strata are 
 illustrated. 
 
 309. The plants embedded in the alluvium belong to 
 existing species, and occur as subterranean forests, peat- 
 mosses, and drift-wood. Subterranean forests occur in de- 
 pressed valleys, and low alluvial plains, where trees stand- 
 ing erect or overturned in the situations in which they 
 grew have been invested with mud and sand ; the wood of 
 these trees, though discolored, has been employed in the 
 construction of houses in England. Rivers, ocean-currents, 
 and tides have formed extensive accumulations of drift- 
 wood in estuaries and deltas, and along the sea coast, par 
 ticularly in sheltered bays. An instance of alluvial vege- 
 table accumulation has been discovered by a section of a 
 canal in Scotland. "At a depth of twelve feet from the 
 surface of the fine alluvial sediment/' says Professor 
 Phillips, " a quantity of hazel bushes, roots, and nuts, with 
 some mosses, fresh-water shells, and bones of the stag were 
 met with. In some parts of the sediments an English coin 
 was found, and oars of a boat were dug up. Where a little 
 water entered this peaty and shelly deposit from the adja- 
 
THE ALLUVIUM. 245 
 
 cent limestone, it produced in the wood a singular petrifac- 
 tion ; for the external bark and wood were converted into 
 carbonate of lime, in which the vegetable structure was 
 perfectly preserved. In like manner some of the nuts were 
 altered ; the shells and the membranes lining it were un- 
 changed ; but the kernel was converted into the carbonate 
 of lime, not crystallized, but retaining the peculiar texture 
 of the recent fruit. In this particular case no reasonable 
 doubt can exist that the peaty deposit, full of land-mosses, 
 hazel-bushes, and fresh-water-shells, was water-moved, and 
 covered up by fine sediments from the river and the tide." 
 310. But the most extensive vegetable deposits of the 
 alluvium are peat-mosses, which cover hundreds of square 
 miles, and are sometimes forty feet thick. Peat consists of 
 mosses, especially the sphagnum palustre, rushes and other 
 aquatic plants, together with the trunks, branches, and 
 leaves of trees. Peat swamps occupy the sites of ancient 
 lakes and low woody districts, in which obstructions to the 
 drainage have caused swampy morasses, destroying the for- 
 est trees and favoring the growth of aquatic mosses. The 
 sites of many of the aboriginal forests of Europe are now 
 covered by mosses and fens. Fallen trees by obstruct- 
 ing the drainage of a district have produced peat-bogs ; the 
 prostration of a forest by a tornado about the middle of the 
 seventeenth century produced a peat-moss, which at the be- 
 ginning of the eighteenth century yielded peat for fuel. 
 Peat swamps possess eminent antiseptic power ; the bodies 
 of men and other animals buried in them have been pre- 
 served for centuries. The most ancient peat-mosses belong 
 to the alluvial period ; this is known by their conforming to 
 the present configuration of the land, and by their contain- 
 ing the remains of vegetable and animal bodies belonging 
 
 21* 
 
246 ROCKS OP THE QUATERNARY PERIOD. 
 
 exclusively to existing species. The changes which occur 
 in peat-beds illustrate the formation of coal; a true bitu- 
 minous coal has been found in a peat-bog in the State of 
 Maine, several feet below the surface amidst the remains 
 of logs of wood, ( 144.) 
 
 311. The remains of animals belonging to the species 
 still living or very recently extinct, are characteristic of 
 the Alluvium ; among these remains the exuviae of shell- 
 fish and coral zoophytes are, as they were in the older for- 
 mations, most abundant. Immense banks of dead shells 
 have been drifted together by tides and currents j some of 
 
 Fig. 161. 
 
 Shell Limestone from the Mouth of the Thames. 
 
 them remain loose and are worn by the waves, while others 
 are cemented together by the carbonate of lime into a 
 shelly limestone or sandstone. Fig. 161 represents a por- 
 tion of a block taken from a bank of consolidated shells, 
 in the progress of formation in the English channel near 
 the mouth of the Thames ; it is sufficiently firm to admit 
 of being cut and polished ; the bank consists mostly of one 
 species, having lived gregariously, as do oysters and mus- 
 
THE ALLUVIUM. 247 
 
 sels. Coral reefs with their accumulated debris constitute 
 thousands of square miles of the surface of the earth, 
 ( 76,) and form an aggregate of calcareous matter equal 
 to the limestones of the older formations. The remains of 
 fishes, reptiles, birds and mammalia, which are included in 
 alluvial deposits, though comparatively few in number, are 
 highly indicative of the circumstances in which they lived. 
 312. Some genera and species of animals have become 
 extinct during the alluvial period ; this may have been the 
 case with the great Irish Elk, the Mastodon, the Dinornis and 
 others; but there is one example of extinction which has 
 occurred within the period of authentic history. The Dodo, 
 a bird of the gallinaceous tribe larger than a turkey, 
 abounded in Mauritius and adjacent islands, when first col- 
 onized by the Dutch, more Fig. 162. 
 than two centuries ago. It 
 is now entirely extinct. The 
 stuffed skins formerly in 
 European Cabinets have de- 
 cayed, and the only relics 
 of them are a few frag- 
 ments of the harder parts, 
 as the head and feet, in the 
 British Museums. The 
 bones of the Dodo have 
 been found fossil in a tufa- 
 ceous deposit in the Isle of The Dodo. 
 France. The Apteryx, so called because destitute of wings, 
 is a rare bird living in New Zealand. It differs from most 
 birds in many particulars of its organization. It appears 
 to be almost extirpated, and several of its congeners are 
 thought to have recently become extinct. 
 
248 
 
 ROCKS OF THE QUATERNARY PERIOD. 
 
 Fig. 163. 
 
 The Apteryx. 
 
 313. The remains of man, 
 are found only in the newest de- 
 posits, nor is there any reason 
 for supposing that he existed 
 at an earlier period, since if he 
 had, some vestiges of his exis- 
 tence would have been perpet- 
 uated. Cuvier observes that 
 the bones of men in ancient battle fields were as well pre- 
 served as were those of the horses buried with them ; and 
 much frailer substances than human skeletons have been 
 fossilized in very ancient rocks. The skeletons of men, as 
 well as various works of art, have been found in the allu- 
 vium. The discovery of human skeletons in limestone has 
 been referred to in 91 ; they were found on the north- 
 east coast of Gruadaloupe in a bed of rapidly accumulating 
 limestone, consisting of fragments of corals and shells, 
 
 Fig. 164. 
 
 Cliff at Gaudaloupe. 
 A, the ancient rocks ; B, alhmal limestone containing human skeletons. 
 
 with sand cemented together by the carbonate of lime. 
 The shells and corals belong to existing species, and the 
 pieces of pottery and implements found with the skeletons 
 identify the period of their deposition as historically recent. 
 
THE ALLUVIUM. 249 
 
 The conjecture that man's remains will be found in the 
 older rocks of Asia where the race was first introduced, 
 is shown to be groundless by the fact that the organic 
 contents of Asiatic rocks are known to correspond with 
 those of the rocks of the same age in other parts of the 
 world. 
 
 314. The superficial stratum of the earth's surface in 
 which plants grow is denominated soil; it consists of mi- 
 nute fragments of rock gravel, sand, clay, together with 
 portions of decomposed vegetable and animal matter. It 
 varies in thickness, never exceeding however a few feet. 
 The fragments of which it consists, have either resulted 
 from disintegration of the subjacent rocks or have been 
 transported from the localities in which they were broken 
 up. The mineral mass lying immediately beneath, and 
 destitute of vegetable and animal substances, is called sub- 
 soil. Soils are designated according to their predominant 
 mineral ingredients, as sandy, gravelly, loamy, clayey or 
 calcareous. The soil not only furnishes subsistence to veg- 
 etable and animal bodies but protects the surface of the 
 earth from rapid wearing ; an unprotected surface is wasted 
 by every shower, while even light sands are secured from 
 abrasion by vegetables growing upon them. 
 
 315. Atmospheric and aqueous agencies exerted during 
 the alluvial period, have produced the most recent modifi- 
 cations of the earth's features ; the forms of mountains and 
 valleys have been losing their sharp angles, and become 
 undulating. Caves, which were originally fissures in lime- 
 stone rocks, have been greatly extended by the eroding 
 action of water. The great Kentucky Cave has been traced 
 ten miles in one direction, without finding any termination ; 
 it has also very extensive lateral branches. A similar action 
 
250 
 
 ROCKS OF THE QUATERNARY PERIOD. 
 
 in gorges and valleys occasionally presents the phenomena 
 of natural bridges, of which a remarkable example is found 
 in Virginia. It consists of a magnificent arch of limestone 
 spanning the Cedar craek. Its height above the stream is 
 
 Fig. 165. 
 
 Natural Bridge, Rockbridge County, Va. 
 
 two hundred and fifteen feet j its length ninety-three feet ; 
 its width eighty feet, and its thickness fifty-five feet. 
 
 316. The products of igneous agency during the allu 
 
THE ALLUVIUM. 
 
 251 
 
 vial period are numerous and extensive beds of lava, vol- 
 canic ashes, scoriae, sand, sulphur, etc. New volcanic craters 
 have arisen, as Jorullo, in Mexico; while others have 
 ceased to erupt. Earthquakes have produced great distur- 
 bances of the earth's crust, and various portions of the sur- 
 face have been elevated and depressed. Many mountain 
 
 Fig. 166. 
 
 Chimborazo. 
 
 peaks show, by their forms, and by the lava upon their 
 sides, that they are volcanic vents, though they have been 
 long dormant, and can not be with certainty assigned to 
 the alluvial, or period of active volcanoes. 
 
CHAPTER X, 
 
 THEORETICAL GEOLOGY. 
 
 317. HITHERTO the facts respecting the structure of 
 the earth's crust, the nature of the materials and the order 
 of their arrangement, have been detailed, constituting 
 Descriptive Geology ; but Geology when perfected embra- 
 ces an enunciation of the laws, in accordance with which 
 the successive changes the earth has undergone, and its 
 present condition have been produced. This department 
 of the science is termed Theoretical, or Physical Geology. 
 Sir John Herschel observes, " The first thing that a 
 philosophical mind considers, when any new phenomenon 
 presents itself, is its explanation, or reference to an imme- 
 diate producing cause. If that can not be ascertained the 
 next thing is to generalize the phenomenon, and include it, 
 with others analogous to it, in the expression of some 
 law." * 
 
 A theory is a philosophical explanation of phenomena, 
 deduced from principles which have been established by 
 independent evidence ; while an hypothesis rests solely on 
 the satisfactory explanation of the phenomena, which it 
 furnishes. These terms are, however, frequently used 
 synonymously, and some modes of explanation deemed 
 theories may by the progress of science be shown to be 
 untenable by hypothesis. 
 
 * Herschel's Discourse on the Study of Natural Philosophy. 
 
THEORIES OF THE DRIFT. 253 
 
 318. Geology is an inductive science based upon the 
 observation of facts, and if the theories adduced to account 
 for the phenomena are shown to be untrue or insufficient, 
 the facts still remain unimpeached. Geological theories 
 relate principally to the modes of action of the two 
 great agencies aqueous and igneous. It has before been 
 stated ( 13,) that geologists are divided in opinion respect- 
 ing the intensity with which these agents have operated in 
 different periods ; and while they agree in attributing the 
 stratified rocks to deposition from water, in particular modes, 
 the phenomena of the Drift have given rise to several theo- 
 ries. Diverse modes of explanation have also been pro- 
 posed to account for the phenomena of volcanoes, and the 
 elevation of mountains and continents. All correct reason- 
 ing in natural science is based upon the uniformity of na- 
 ture's laws; a conviction of this uniformity is unceasingly 
 impressed upon the mind by experience and observation. 
 
 THEORIES OF THE DRIFT. 
 
 319. No part of Physical Geology is so unsettled as 
 that which relates to the dispersion of the Drift. It was 
 formerly imputed to the agency of powerful currents of 
 water alone, and by many it was ascribed to Noah's deluge. 
 This was the view entertained by Dr. Buckland when he 
 wrote his Reliquiae Diluvianas. But the short period of 
 that flood and the absence of man's remains and works, 
 with other considerations, have led to the universal aban- 
 donment of that view. The agency of water alone is now 
 regarded as inadequate to account for the phenomena ; they 
 are attributed to the joint action of ice and water. Three 
 theories are advocated by different writers on the subject. 
 
 320. The iceberg theory , supposes that the polar regions 
 
 22 
 
254 THEORETICAL GEOLOGY. 
 
 of the earth were depressed beneath the ocean before the 
 drift, and that during that period icebergs loaded with gravel 
 and fragments of rocks were transported by currents, in- 
 flicting scratches and grooves upon the rocks over which 
 they passed, and melting in lower latitudes deposited the 
 materials they had conveyed. 
 
 It is urged in favor of this theory that such an agency 
 is now witnessed in the phenomena of icebergs bearing 
 thousands of tons of earth and rocks, transported by polar 
 currents, as far as the drift extends. The stranding of the 
 icebergs with fragments of rock frozen in them, is thought 
 to produce striae and furrows upon the bottom of the ocean 
 like those of the drift. 
 
 It is objected to this theory that the boulders of ice- 
 bergs are brought from high latitudes, while those of the 
 drift appear to have been derived from neighboring moun- 
 tains and ledges; the parallelism and uniformity of the 
 striaa are not adequately accounted for ; and the highest 
 portions, as mountain tops, alone should have been furrowed 
 and striated, since icebergs that would float over such 
 heights would not reach to the bottom of the valleys, 
 whereas the scratches are common in the plains and 
 valleys. 
 
 321. The elevation theory attributes the phenomena to 
 numerous elevations of the earth from beneath the polar 
 seas, repeated for successive ages, sending enormous waves 
 toward the equatorial regions bearing icebergs, with their 
 boulders and earth, and urging before them the loose mate- 
 rials lying upon the surface ; the striae were produced by 
 fragments of rocks in the bottoms of immense masses of ice 
 which may have been forced up steep declivities. 
 
 The arguments in favor of this theory are, that such 
 
THEORIES OF THE DRIFT. 255 
 
 upheavals of the bottom of the ocean are known to occur, 
 as in the elevation of Sabrina, Graham's Island, in the 
 Mediterranean sea, and the Aleutian Islands, ( GO ;) that 
 waves caused by earthquakes have great power to prostrate 
 and transport heavy bodies ; and that, as the surface of 
 the continents, the mountain ridges and valleys, were essen- 
 tially the same in form and direction then as now, the origin 
 of the action must be sought for out of the country, and the 
 direction of the drift dispersion indicates that the localities 
 elevated were about the poles. 
 
 It is objected, that so numerous and extensive elevations 
 as the theory requires, are improbable } that the phenomena 
 of the drift indicate prolonged action, while such vertical 
 movements are transient ; and that the parallelism of the 
 striae on the rocks is not accounted for by moving fields 
 of ice buoyed up by water, and conveyed by currents which, 
 instead of passing up mountain sides and over their sum- 
 mits, would have swept around such obstacles. 
 
 322. The glacier theory supposes that the climate, 
 which in the Tertiary period had been so warm as to allow 
 the palms to grow within the temperate zones, became much 
 colder, causing enormous sheets of ice polar glaciers to 
 advance far beyond their previous limits, moving along the 
 surface by alternate advance and retreat, rounding, polish- 
 ing and striating the rocks, and afterward when melted 
 depositing their loads of boulders and detritus, where the 
 drift is now found. ^ In Europe the center of expansion is 
 supposed to have been the Scandinavian mountains, and in 
 North America in the polar regions, from which the glaciers 
 advanced southerly. 
 
 The advocates of this theory contend that the phenom- 
 ena of glaciers as witnessed in the Alps ( 32 ; ) are perfect 
 
256 THEORETICAL GEOLOGY. 
 
 miniature representations of the drift its striae, furrows, 
 boulders and moraines ; that the elevation of extensive re- 
 gions in high latitudes, like those of the Cordilleras in 
 Mexico, and the high plains of Central Asia, would pro- 
 duce such a reduction of temperature as to cause immense 
 glaciers, even thousands of feet in thickness. This theory 
 is advocated by Prof. Agassiz. 
 
 The principal objection to the glacial theory is that gla- 
 ciers are at present entirely confined to valleys, and the 
 origin of such an enormous sheet of ice as it contemplates 
 is altogether hypothetical. 
 
 323. Neither of these theories is deemed quite satisfac- 
 tory - y the proximate cause of the phenomena is very gener- 
 ally supposed to have been the joint action of ice and 
 currents of water, but their origin and exact modes of 
 operation are not determined. 
 
 THEORY OF VOLCANOES. 
 
 324. The cause of volcanic phenomena eruptions, 
 earthquakes, and elevations and depressions of portions of 
 the earth's surface has been the subject of much discus- 
 sion. The prevalent theory on this subject supposes the 
 whole earth, with the exception of a crust fifty or one 
 hundred miles thick, to be in a melted state ; that eruptions 
 are produced by the access of water through crevices to 
 this heated mass, which causes steam and other elastic 
 bodies to force out through craters and fissures, lavas, 
 scoriae, sulphur, and other volcanic products ; and that the 
 whole globe has formerly" been in a state of fusion, the 
 present crust having resulted from the cooling of the sur- 
 face. 
 
THEORY OF VOLCANOES. 257 
 
 325. In favor of this view it is urged 
 
 1. That the temperature of the earth below a certain 
 depth, as tested in mines and Artesian wells, continually 
 increases as we descend ( 5,) at an average rate of about, 1- 
 for fifty feet, which would at a depth of a little more than 
 a mile give the temperature of boiling water, and at a depth 
 of about fifty miles, would be adequate to the melting of 
 any known rock. 
 
 2. The spheroidal form of the earth is thought to indi- 
 cate that it has been in a fluid state ; and, if so, it must 
 have been through the agency of heat. Sir Isaac Newton 
 has shown that a body having the size and density of 
 the earth, revolving on its axis with the rapidity it has, 
 would, if its particles were free to move, assume its oblate 
 spheroidal form. 
 
 3. The numerous extensive volcanoes, whose origin is 
 deep seated, which communicate with each other over vast 
 areas, and the masses of whose lavas thrown out at a single 
 eruption sometimes surpass the bulk of the mountains in 
 which their craters are situated, ( 54,) require an enormous 
 mass of heated matter ; if the interior is in a melted state 
 the materials are abundant, and their extrusion may be 
 produced by the pressure of steam and other elastic bodies, 
 or by the contraction of the crust upon the melted mass. 
 
 4. The phenomena of hot springs, deep Artesian wells, 
 and the increase of temperature generally, as we descend 
 beneath the surface, are adequately accounted for by this 
 theory. 
 
 5. The ultra tropical character of the climate, and its 
 great uniformity during the periods of deposition of the 
 earliest fossiliferous rocks, have been attributed to this 
 origin. 
 
 22* 
 
258 THEORETICAL GEOLOGY. 
 
 6. The rocks constituting the crust of the earth have 
 been melted; the characters of the unstratified rocks show 
 that they have undergone no change since they cooled from 
 a state of fusion, and the stratified rocks consist of frag- 
 ments of the unstratified, and have therefore been melted. 
 
 7. The phenomena of earthquakes, their great extent 
 and violence, are accounted for under this theory, by the 
 undulatory motion of the earth's crust in consequence of 
 the expansion of gases within, or of undulations in the 
 molten mass. 
 
 326. It is contended by objectors to this theory 
 
 1. That the high temperature of the earth as we de- 
 scend in it may be accounted for by chemical action, or by 
 condensation of the air. To this it is replied that the phe- 
 nomena occur where neither of these causes are adequate 
 to their production. 
 
 2. It is objected that the temperature of the ocean is 
 lower at great depths than at the surface. But strata of 
 water arrange themselves in accordance with their specific 
 gravities, the warmest rising to the top, and the crust of the 
 earth is no thinner beneath the ocean than where it consti- 
 tutes dry land. 
 
 3. Again it is objected that if the interior is intensely 
 hot it should melt the crust with which it is in contact, or 
 if not much hotter than the point of fusion at the time the 
 crust consolidated, subsequent cooling should have caused 
 it to solidify ere this. To which the advocates of the theory 
 reply that the perfect non-conducting property of the crust 
 prevents the escape of the heat. Baron Fourier has shown 
 that the effect of this internal heat upon the surface is not 
 the T J f of a degree at present, and that the temperature has 
 not fallen during the last two thousand years more than the 
 
THEORY OF VOLCANOES. 259 
 
 T J ? part of a degree. Currents of lava after accumulating 
 a crust have been known to remain fluid within for many 
 years, ( 62.) 
 
 327. Another theory proposed to account for volcanic 
 action, supposes there are extensive repositories of melted 
 rocks, sufficient for the phenomena of volcanoes, while the 
 great interior mass is solid; but most of the objections to 
 the last theory are equally pertinent to this, and some of 
 them apply with much greater force. 
 
 328. Sir Humphry Davy proposed to account for vol- 
 canic action by the hypothesis that the internal parts of the 
 earth contain great masses of the metallic bases of the 
 alkalies and earths potassium, sodium, calcium, alumi- 
 nium and magnesium which on coming in contact with 
 water decompose it, and produce vivid combustion. This 
 hypothesis, though abandoned by Davy, has been advocated 
 by others, and is not necessarily inconsistent with the doc- 
 trine of central heat ; but the magnitude, universality and 
 perpetuity of volcanic action indicate a more uniform and 
 extensive source. By some G-eologists, electricity is sup- 
 posed to aid in the production of volcanic phenomena, and 
 a remarkable concordance has been discerned between the 
 prevailing direction of strata, and the curves of equal mag- 
 netic intensity, but our knowledge of its modes of opera- 
 tion is as yet quite imperfect. 
 
 329. The gradual elevation and depression of portions 
 of the surface of the earth, as the rising of the coasts of 
 the Baltic and the subsidence of Greenland, ( 68,) are 
 attributed to the expansion and contraction of the rocks in 
 consequence of changes of temperature. It is ascertained 
 by experiment that different rocks are expanded unequally 
 by the same increase of temperature; granite less than 
 
260 THEORETICAL GEOLOGY. 
 
 marble; marble less than slate ; and slate less than sand- 
 stone. An increase of temperature of 600 applied to ten 
 miles thickness of the earth's crust would elevate the sur- 
 face two hundred feet ; and a similar diminution of temper- 
 ature would cause a corresponding subsidence. 
 
 330. The elevation of mountain chains is usually as- 
 cribed to violent volcanic uplifting agency ; but some 
 writers account for it by the collapse of the consolidated 
 crust upon the contracting mass within, some portions of the 
 crust rising in ridges, while others sink beneath its former 
 level, thus increasing the relative height of the ridges. A 
 modification of this view attributes the elevation to a pli- 
 cation, or folding of the strata, in consequence of horizon- 
 tal or lateral pressure. 
 
 331. M. Elie de Beaumont contends that all mountain 
 ranges which are parallel to each other, were elevated at 
 the same time, even when situated remote from each other. 
 The period at which a range was elevated is determined in 
 accordance with principles illustrated in Fig. 62, 103 ; 
 for example, the Chalk series are found inclined upon the 
 flanks of the Pyrenees, showing that they were deposited 
 before those mountains were thrust up, while the lowest of 
 the Tertiary rocks are not thrown out of their horizontal 
 position j the epoch of the upheaval of the Pyrenees was 
 therefore at the close of the Cretaceous, and antecedent to 
 the Tertiary period. By the same test the Apennines are 
 found to date from the same epoch, and. the two ranges are 
 nearly parallel. The same is found to be true of many other 
 ranges at various periods, and hence Beaumont derives his 
 generalization that parallelism indicates contemporaneity. 
 He makes twelve systems of elevations in Europe, the first 
 of which is the system of Westmoreland, in England, and 
 
THEORY OF VEINS. 261 
 
 of the Hunsdruck on the Continent, which was thrown up 
 during the Silurian period, being the oldest upheaval as yet 
 identified upon the globe ; and the last is the system of the 
 Principal Chain of the Alps, which was elevated after the 
 close of the Tertiary period, being the last great convul- 
 sion to which Europe has been subjected. Five or six 
 systems have been assigned to the American Continent, of 
 which that of the Andes is the most recent, its upheaval 
 having occurred, as Beaumont supposes, in the historical 
 period. These views, though generally received with favor 
 by Geologists, require confirmation ; if they can be shown 
 to be correct, their guidance will greatly facilitate geological 
 research. 
 
 THEORY OP VEINS. 
 
 332. It is generally supposed that most veins were 
 injected in a fluid state into fissures in both stratified and 
 unstratified rocks; some veins have been traced to large 
 masses of the same materials, whose former fluidity through 
 the agency of heat is deemed demonstrable. 
 
 It is however admitted that some veins are contempora- 
 neous with the rocks in which they are included, having 
 been separated by chemical segregation, ( 106,) as the 
 flints were separated from the chalk, and the garnets from 
 the mica-slate ; in such cases they are entirely included in 
 the rock. 
 
 The materials of some veins appear to have been sub- 
 limed into fissures, studding the interior with crystals. An 
 experiment has been instituted to test the correctness of 
 this view of the origin of veins. Lead ore (Galena) was 
 sublimed through steam of water in an earthen tube, and 
 condensed in cubical crystals in the colder parts of the 
 
262 THEORETICAL GEOLOGY. 
 
 tube ; boracic acid was sublimed and condensed in the same 
 manner. 
 
 333. By some Geologists veins are supposed to have 
 been formed by the chemical changes that may have taken 
 place under the influence of electrical currents in the inte- 
 rior of the earth ; the experiments of M. Becquerel on the 
 insoluble compounds of copper, lead, and lime, show that 
 many crystallized bodies, hitherto found only in nature, 
 may be artificially formed by the long-continued action of 
 7ery feeble electrical currents, and Mr. Fox accounts for 
 the superior richness of metallic veins running east and 
 west, by the electro-magnetic currents circulating in that 
 direction, decomposing metallic compounds and transferring 
 their elements to a considerable distance in the rocks. 
 
 COSMOGONY. 
 
 334. The Science of Greology does not furnish the 
 means of determining in what state the materials of the 
 earth were when created, nor can it assure us that those 
 materials have not undergone many important changes, of 
 which we have no indications. Conjectures, however, have 
 been formed respecting the earliest conditions of created 
 matter. A prevalent hypothesis supposes matter to have 
 been created in its elementary forms ; chemical attraction 
 caused many of these elements to combine with each other ; 
 this rapid chemical action combustion evolved sufficient 
 heat to vaporize a large portion of the substances ; subse- 
 quent radiation condensed the vapors to a liquid state, and 
 a solid crust accumulated upon which the waters of the 
 atmosphere were precipitated, bringing the phenomena 
 within the province of positive Greology. 
 
 335. The plausibility of this hypothesis is argued from 
 
COSMOGONY. 263 
 
 its accordance with the known laws of Chemistry, and As- 
 tronomical analogies. Comets and some nebulae present 
 matter in an exceedingly attenuated state, so that stars can 
 be seen through the former in some instances with scarcely 
 any diminution of lustre ; and some of them, it is thought, 
 are becoming gradually more dense at their centers. The 
 moon presents the appearance of a globe with its surface 
 shaped by igneous agency. Its mountain peaks rise more 
 than four miles in height, and some of its volcanic craters, 
 which are one hundred and fifty miles in diameter, have 
 their bottoms depressed more than twenty thousand feet 
 below the general surface. These craters very closely re- 
 semble in form, terraces, etc., some of the earth's volcanoes, 
 especially Kilauea, ( 58.) As there is no water upon the 
 moon, and a very rare atmosphere, if any, no stratified de- 
 posits exist, nor are the characteristic effects of volcanic 
 action obliterated, but it presents to us such an appearance 
 as Geologists assign to the earth in the primary period, be- 
 fore the agency of water modified its surface by wearing 
 the igneous rocks and depositing strata of the detritus. 
 
CHAPTER II, 
 
 PRACTICAL GEOLOGY. 
 
 336. BY Practical or Economical Geology is under- 
 stood an exhibition of the facts of the science obtained by 
 observation, and the laws deduced from the facts by gener- 
 alization, with reference to their immediate application to 
 the wants of society. Its importance can not indeed be 
 adequately estimated by monetary tables, since its effects 
 on mind in stimulating intellectual activity, arid inducing 
 wholesome mental discipline, are no less valuable than what 
 it has accomplished for the comforts of society and the in- 
 terests of commerce. But its cash value is distinctly ap- 
 preciable. Mr. Miller states, in his " Old Red Sandstone," 
 that the time and money squandered in Great Britain alone 
 in searching for coal in districts where the well-informed 
 Geologist could have at once pronounced the search hope- 
 less, would much more than cover the expense at which 
 geological research has been prosecuted throughout the 
 world. The Old Red Sandstone, the Silurian rocks, and 
 talcose and mica-slates have been bored for coal, where the 
 author just quoted remarks, " there might be some possi- 
 bility of penetrating to the central fire, but none whatever 
 of reaching a vein of coal." 
 
 337. Not only is the physical condition of a country 
 influenced by its geological structure, but the occupations 
 
MINING METALS. 265 
 
 and habits of its inhabitants are almost exclusively deter- 
 mined by it. A good geological map of a country is the 
 best index of the relative values of its districts for partic- 
 cular economical purposes. 
 
 Practical Geology relates particularly to the processes 
 of Mining, Engineering and Architecture, and Agricul- 
 ture ; it depends principally upon the fact that minerals 
 which are useful for practical purposes are found only in 
 certain geological formations. 
 
 338. In mining for most metals Geology indicates the 
 primary and metamorpJiic rocks, the junction of the strat- 
 ified with the unstratified rocks, as the most promising 
 fields of search. 
 
 Gold and Platinum are found not as ores, but native 
 metals in quartz rock and talcose slate. They are how- 
 ever obtained from the drift and alluvium, which consist 
 of the detritus of these primary rocks. 
 
 Silver occurs as a sulphuret and a chloride in the pri- 
 mary and transition slates; it is also associated with me- 
 tallic copper. 
 
 The principal ore of Mercury the sulphuret is found 
 in mica-slate and in the New Red sandstone. 
 
 The ores of Copper the sulphuret, the oxide, and car- 
 bonate are found in the primary rocks, and in connection 
 with trap dikes in the secondary; copper is also found na- 
 tive in these situations. 
 
 Lead ore is the sulphuret galena ; the unstratified and 
 stratified primary rocks, the metaliferous limestone, and the 
 secondary rocks as high as the lias, are its repositories. 
 
 The sulphuret of Zinc zinc-blende and the carbon- 
 ate of zinc, are found in the Transition and Secondary 
 series. 
 
 23 
 
266 PRACTICAL GEOLOGY. 
 
 Tin, Antimony, Bismuth, Cobalt, Arsenic, Manganese, 
 etc., are found in the oldest rocks. 
 
 Iron occurs in all formations, in quantities and forms 
 adapted to working, but the iron ores of the older rocks are 
 the most valuable. 
 
 The metals are usually found in veins, but sometimes 
 they constitute true beds, and are also diffused in fragments 
 through a rock, as in the drift, or alluvium. Veins follow 
 certain courses relatively to the principal axes of elevation 
 of the country ; they are often interrupted by cross veins 
 and dikes, and thrown either up or down. The veins con- 
 taining metallic ores are called lodes ; those not metalifer- 
 ous, cross courses. The inclination of the vein to the hori- 
 zon is called its underlie, hade or slope; and its intersection 
 with the surface, its direction. The practical Geologist is 
 enabled to determine these, and map them out so as to 
 guide the miner to the readiest and most economical method 
 of developing the ore. 
 
 339. True bituminous coal is found only in the carbo- 
 niferous system of rocks, and in a certain part of the sys- 
 tem only ; all search for it in other positions has proved 
 fruitless. Beds of lignite do occur in the Oolite, Lias, and 
 Tertiary, but they are rarely worth working. Anthracite, 
 which is coal deprived of bitumen, is sometimes found be- 
 low the carboniferous series. Masses of bituminous matter 
 sometimes occur in the Old Red sandstone with markings 
 so similar to the vegetable impressions on the carboniferous 
 sandstones, as to deceive an unpractised eye; but the 
 groups of fossils are characteristic of the formations and 
 enable the Geologist to discriminate them. Dislocations 
 of beds of coal and strata associated with them are singu- 
 larly frequent, and the faults are so complicate as to require 
 
PRACTICAL GEOLOGY. 267 
 
 much geological knowledge and experience to aid the miner 
 in recovering his lost seams. The most successful modea 
 of draining and ventilating the mines are also indicated by 
 the practical Geologist. 
 
 340. The diamond, which is pure crystallized carbon, 
 and is supposed by many Geologists to be of vegetable 
 origin, has been found in the talcose slate, and the New Red 
 sandstone ; the rocks with which it was associated indica- 
 ting the agency of heat. The precious stones, emerald, 
 ruby, sapphire, topaz, carnelian, tourmaline, garnet, etc., 
 are found in the igneous unstratified rocks. The gems 
 are frequently obtained from the drift, together with gold 
 and platinum, having been removed from their original 
 positions by the abrasions of the older rocks. 
 
 341. A knowledge of Geology is highly important to 
 the engineer and architect. "It is in proportion to his 
 acquaintance with Geology and Mineralogy/ 7 says Mr. 
 Cresy, "that the Civil Engineer is rendered skilful in the 
 formation of roads, canals, harbors, building of bridges, or 
 forming foundations of any kind, and draining ; wherever 
 the scene of his labors may lie, he can not be entirely suc- 
 cessful, without a careful consideration of the various strata 
 composing the earth's crust. When Smeaton was called 
 upon to construct the Eddystone Lighthouse, he commenced 
 by examining the structure of the rock on which it was 
 to be based, and as far as possible to endeavor to imitate 
 nature in his arrangement of the courses. Had the build- 
 ers of the Leaning Tower, at Pisa, been equally careful, or 
 had they been acquainted with the composition of the earth 
 on which they laid their foundations, the world would never 
 have had the opportunity of supposing that its inclination 
 was the effect of design, instead of the consequence of an 
 
268 PRACTICAL GEOLOGY. 
 
 insecure base, which might have been consolidated by 
 art ; had the alluvial matter on -which the footings are laid 
 been converted into a mass of conglomerate or artificial 
 rock, this famed Campanile would have stood as upright as 
 the Eddystone Lighthouse. For all the purposes of build- 
 ing, it is necessary that the constructor should be acquainted 
 with the formation and properties of the matter with which 
 he has to deal ; he should understand the cause of the du- 
 rability of a substance, whatever it may be, as well as what 
 disintegrates or destroys it."* 
 
 A litHological map of a country delineating its various 
 strata, their dip and strike, is an efficient guide to the En- 
 gineer in locating public works, estimating their expense, 
 and procuring the materials for their construction. 
 
 342. One of the most important uses to which minerals 
 are applied, is for architectural purposes. The character 
 of the material requires to be adapted to the circumstances 
 in which it is used, in order to secure durability ; some 
 rocks disintegrate rapidly in consequence of expansion 
 and contraction from changes of temperature, and others 
 are destroyed by absorbing water from the atmosphere, 
 which expands in freezing. The importance of the dura- 
 bility of materials has been much neglected in modern 
 architecture. Mr. Ure remarks that, " such was the care 
 of the ancients to provide strong and durable materials 
 for their public edifices that but for the desolating hands 
 of modern barbarians, in peace and in war, most of the 
 temples and other public monuments of Greece and Rome 
 would have remained perfect at the present day, uninjured 
 by the elements during two thousand years. The contrast 
 in this respect of the works of modern architects, especially 
 * Encyclopaedia of Civil Engineering, by Edward Cresy, p. 617 
 
PRACTICAL GEOLOGY. 269 
 
 in Great Britain, is very humiliating to those who boast so 
 loudly of social advancement ; for there is scarcely a public 
 building of recent date which will be in existence a thou- 
 sand years hence/ 7 This frailty of public structures is 
 equally conspicuous in the United States. 
 
 343. Granite, Syenite and Porphyry are valuable ma- 
 terials for building. To adapt them for this use they 
 should be fine and uniform in texture, as the coarser va- 
 rieties are not so coherent. They should be free from 
 metallic bodies, especially iron pyrites sulphuret of iron 
 which, on exposure to moist air, rust, discolor, and disinte- 
 grate the rock in which they are embedded. These rocks 
 usually harden after removal from the quarry and exposure 
 to the air ; their geological position is in the Primary series, 
 but they occur intruded as dikes and veins in the more 
 recent strata. 
 
 The varieties of Trap and Basalt are used for building ; 
 the natural faces of the basaltic pillars require no dressing 
 to fit them for the purpose, and the sombre hue of the fer- 
 ruginous varieties is adapted to some styles of architecture. 
 These igneous rocks are associated with the Secondary series 
 of strata. 
 
 The Lavas of the Tertiary and the Alluvial periods, 
 are also used, but are frequently not sufficiently firm and 
 compact for this purpose. 
 
 344. Sandstones usually consist of grains of quartz, 
 with some admixture of other minerals, as feldspar and 
 mica ; some are cemented together with carbonate of lime, 
 and are called calcareous, others with clay, and are denom- 
 inated argillaceous. Their colors, yellow, brown, red or 
 black, are principally due to the compounds of iron. They 
 occur in strata of all the geological series, and are, there- 
 
 23 * 
 
 UNIVERSITY- 
 
270 PRACTIUAL GEOLOGY. 
 
 fore, widely diffused and easily accessible. They are ex- 
 tensively employed, frequently under the name of free- 
 stones. To fit them for this purpose they should be free 
 from iron-pyrites, iron sand, or any substance which will 
 on exposure to the weather undergo chemical change. 
 Some sandstones, are worthless for ordinary building pur- 
 poses, falling to pieces as soon as they dry, but are very 
 firm while kept beneath the surface of water or in the 
 ground. Sandstones which absorb much water will not bear 
 exposure to frost. This may be tested by immersing them 
 in water and exposing to frost, or in a saturated solution 
 of sulphate of soda Grlauber's Salts and drying in the 
 air ; in the latter case, if much of the solution is absorbed 
 the crystallization of the salt will produce the same disin- 
 tegrating effect as the frost would. 
 
 The Conglomerates and Breccias are not so well adapted 
 to architectural purposes as the rocks which are finer and 
 more uniform in structure. 
 
 345. Limestones have always been highly esteemed for 
 building and various other purposes. They are very abun- 
 dant, occurring in all the series from the statuary marble 
 of the primary to the marls of the alluvial. They are 
 either granular or compact in texture ; the former furnish- 
 ing the firmest and finest marbles. When pure they are 
 white, but they are often clouded with black mica or some 
 metallic compound. These are found in the vicinity of 
 the igneous rocks, to which they are supposed to owe their 
 crystalline texture. The finer varieties of marble are said 
 not to be exceeded in durability by any other rock used in 
 architecture. Some of the compact varieties of limestone 
 are easily wrought, are susceptible of polish, and are well 
 adapted to building purposes. 
 
PRACTICAL GEOLOGY. 271 
 
 Slates are much used for roofing. They "should bo 
 homogeneous and fine in texture, of uniform cleavage, free 
 from pyrites, impermeable to water, and sufficiently tena- 
 cious to allow perforations for nailing them. Such slates 
 are found in the older stratified series of rocks. 
 
 346. Minerals useful for other purposes are found in 
 various rocks. Sulphate of Lime or Gypsum, extensively 
 used for forming stucco, taking casts, etc., is found in the 
 Transition, Secondary, and Tertiary series. 
 
 Steatite or soap-stone, employed as fire-stones to line 
 furnaces and stoves, is soft, may be sawn, and turned in a 
 lathe j a compact variety of it, called pot-stone, is wrought 
 into culinary vessels in Italy. This rock occurs among the 
 oldest strata. 
 
 Salt chloride of sodium is frequently found with 
 gypsum in the New Red sandstone, but occurs also in other 
 strata. The remarkable deposits in Poland and Hungary 
 are in the Cretaceous or Upper Secondary ; the mines in 
 Poland have been worked since A. D. 1251, and are esti- 
 mated to contain sufficient salt to supply the world for 
 many centuries. Hills of salt three hundred to four hun- 
 dred feet high are found in the Cretaceous strata at Cardona 
 in Spain ; but the Catalonian deposits are in the Tertiary. 
 Some salt lakes are at the present day producing deposits 
 by evaporation ; as exemplified by the Dead and Caspian 
 seas, the lakes of Northern Africa, and the Great Salt 
 Lake, which is situated upon the flanks of the Rocky 
 Mountains at an elevation of four thousand two hundred 
 feet above the sea, with an area of two thousand square 
 miles. The brines from which most of the salt in the 
 United States is obtained, come from below the coal. 
 Forty gallons of the New York springs yield a bushel 
 
272 PRACTICAL GEOLOGY. 
 
 of salt. Rock salt has been found in Virginia and in 
 Oregon. 
 
 347. Clay, consisting of alumina and silica, owes its 
 plasticity to the former ingredient ; it results from the dis- 
 integration of feldspar and slate rocks, and is found prin- 
 cipally in the Tertiary and Drift. It is often mixed with 
 the carbonate of lime, magnesia, and the oxide of iron. 
 Clay used for making bricks, generally contains a portion 
 of the hydrated oxide of iron, which is decomposed when 
 heated, forming red oxide of iron, and imparting its color 
 to the brick ; some clays, however, contain no iron, and the 
 bricks made of them are of a light color, as is the case 
 with those made at Milwaukie, Wisconsin. Clay for fire- 
 bricks should contain no iron, magnesia or lime, as those 
 ingredients impart fusibility; such clay is found in the 
 Tertiary and in the Coal formation. Pipe-clay or Potter's 
 clay are pure varieties, and consequently white. Porcelain 
 clay or kaolin is decomposing feldspar, which mixed with 
 silica, lime and unchanged feldspar, produces beautiful 
 specimens of earthenware, some of which are translucent 
 porcelain. The kaolin occurs in extensive beds in granite 
 rocks. The Sevres ware made in France consists of sixty- 
 five parts of kaolin, twenty of feldspar, ten of flint or 
 quartz, and five of chalk. The China ware contains more 
 quartz and is more glassy. 
 
 fuller's earth is composed of silica, alumina, lime, mag- 
 nesia and the oxide of iron ; it has a soapy feel and is used 
 for removing grease from woolen cloths. 
 
 348. Sand is usually grains of quartz, mixed with 
 grains of mica, feldspar, oxide of iron, etc. Sand is ex- 
 tensively used in the manufacture of glass, which is a 
 transparent, fusible compound of quartz silicic acid and 
 
PRACTICAL GEOLOGY. 273 
 
 potash or soda ; the oxide of lead and lime are sometimes 
 added for glass of different kinds. Sand for the manufac- 
 ture of glass should be pure, especially free from the ox- 
 ides of metals, which impart to it deep colors ; the color 
 resulting from one metal may sometimes be discharged by 
 another, as the green color resulting from the oxide of iron 
 is removed by the oxide of manganese. Beds of sand 
 adapted to this purpose are found in the Tertiary, Drift and 
 Alluvium. That which is obtained by pulverizing sand- 
 stones is apt to contain a troublesome amount of iron, or 
 other impurities. Sand used for mortar should be fine and 
 of sharp grit. 
 
 349. Quicklime, used for mortar, for purifying coal- 
 gas and syrups, for fertilizing land, and for various other 
 purposes, is obtained from limestones, by expelling the 
 carbonic acid by heat. The purest marbles furnish the best 
 lime, but some impurities are not detrimental to it for cer- 
 tain purposes. The strength of mortar depends upon the 
 formation of the chemical compound of lime, silica, and 
 water, and is not necessarily impaired by the presence of a 
 small portion of iron, clay, &c. The rich or fat limes 
 double their volume in slaking, and absorb nearly three 
 hundred per cent, of their weight of water ; the poor limes 
 augment their volume slightly in slaking, and absorb about 
 two hundred per cent, of their weight of water. 
 
 Hydraulic lime is distinguished by forming a mortar 
 which sets under water, and consists of silica, lime, alu- 
 mina, magnesia, and frequently the oxide of iron ; the last 
 ingredient is deemed undesirable for most purposes to which 
 this lime is applied. Prof. Beck gives the composition of a 
 variety of this substance extensively used in the State of 
 New York as follows : carbonic acid 34.20, lime 25.50, 
 
274 PRACTICAL GEOLOGY. 
 
 magnesia 12.35, silica 15.37, alumina 9.13, and perox- 
 ide of iron 2.25.* Hydraulic limes are not uniform in 
 their composition. 
 
 ' Parker's Cement, formerly patented in England, consist- 
 ed of fifty-five parts of lime, thirty-eight of alumina, and 
 seven of oxide of iron. It was obtained from the septaria 
 found in the argillaceous strata of the Oolite and the 
 Tertiary. Other septaria forming excellent cements differ 
 in the proportions of their ingredients. Greater caution is 
 requisite in burning hydraulic lime, since it is fusible, and 
 the heat applied to the common lime will vitrify this sub- 
 stance and render the process quite imperfect : common 
 lime will bear a white heat, but the calcination of hydraulic 
 lime is not well effected above a red heat. 
 
 Puzzuolana, a volcanic tufa composed of silica, alumina, 
 lime, magnesia, soda and oxides of several metals, forms 
 with lime and water a strong hydraulic cement. The 
 strong cement used in the construction of the Eddystone 
 lighthouse was made of equal measures of puzzuolana and 
 blue lias lime, slaked into a powder ; it set slowly but very 
 firmly under water. The ancient Romans used puzzuolana 
 in their mortars, but the cement of their structures found 
 in England and other parts of Europe, whose hardness 
 after the lapse of centuries excites the admiration of archi- 
 tects, consists of lime, sand, pounded brick or tile-dust, 
 and wood ashes; it is of a reddish color, and contains cav- 
 ities lined with crystals of carbonate of lime. Artificial 
 puzzuolanas are made by mixing clay with lime ; pipe clay 
 and lime after burning will set into a very firm cement. 
 
 350. Buhrstone, used almost exclusively for millstones, 
 is a cellular variety of quartz, and owes its value for this 
 * Report on the Mineralogy of New York, p. 78. 
 
AGRICULTURAL GEOLOGY. 275 
 
 purpose to the hardness and sharpness of the inequalities 
 of its surfaces. The finest stones have usually been 
 imported from France where they were found in the 
 Tertiary of the Paris basin, but stones of excellent qual- 
 ity are obtained in Muskingum county and other local- 
 ities in Ohio, where it is associated with the carboniferous 
 sandstones. As some of the cavities contain lime, it is 
 conjectured that the removal of that substance by solution 
 has produced the cells. It is found also in Georgia and in 
 Arkansas. 
 
 351. Marls are composed of clay and lime, are very 
 variable in their constitution, and their value for fertilizing 
 soils depends upon the circumstances under which they 
 occur. Their calcareous contents have oftentimes been 
 derived from the shells or other organic bodies embedded in 
 them. They are sometimes colored blue by the protoxide 
 of iron, and red or yellow by the peroxide of the same 
 metal. They are found in all parts of the series of strat- 
 ified rocks ; as the older marls are highly indurated, those 
 which are available are confined to the Tertiary and Allu- 
 vium. The principal deposits are beneath ponds and peat 
 swamps. The name is sometimes improperly applied to the 
 greensand of the Cretaceous formation, which owes its fer- 
 tilizing quality to the alkalies it contains, and not to lime 
 or clay ; but the chalk marl is very largely calcareous. 
 
 352. Geology is second only to Chemistry in the 
 amount and importance of the aid it renders to scientific 
 Agriculture. " The geologist/' says Prof. Johnston in his 
 Lectures on Agriculture, " can best explain the immediate or- 
 igin of the several soils. The cause of the diversities which 
 even in the same farm, it may be in the same field, they not 
 unfrequently exhibit ; the nature and differences among 
 
276 PRACTICAL GEOLOGY. 
 
 the subsoils, and the advantages which may be expected 
 from breaking them up or bringing them to the surface/' 
 Intelligent practice of the art of Husbandry is based upon 
 a knowledge of the constituents organic and inorganic 
 of the crops to be raised, and of the ingredients of the 
 soil, which are also both organic and inorganic. These 
 must be adapted to each other. All plants derive the ma- 
 terials of their growth from the earth and atmosphere ; they 
 have not the power of creating any element, but their 
 chemical composition is a perfect index of their food. All 
 animals obtain their subsistence from vegetables; or from 
 other animals which subsisted upon the products of veget- 
 ation, so that all organic matter is derived from the inor- 
 ganic mineral kingdom, through the medium of veget- 
 ation. After death all animal and vegetable substances by 
 putrefaction return to the earth and atmosphere, from which 
 they originated, to be again absorbed by growing plants and 
 furnish food for animals; thus exemplifying that great 
 principle of instability by which the stability of nature is 
 secured that cycle, the mineral, vegetable and animal, 
 through which particles of matter are incessantly passing. 
 
 353. The inorganic part of soils consists of two classes 
 of substances the salts, which are soluble in water, from 
 which plants obtain their saline matters, and which consti- 
 tute their ashes when burnt; and the insoluble earths, 
 which form the great bulk of most soils. 
 
 The principal soluble saline ingredients of soils, are iron, 
 sulphates of lime magnesia and soda, nitrates of potassa 
 soda and lime, phosphates of lime and magnesia, and chloride 
 of sodium common salt. The carbonates of lime magnesia 
 and iron, are soluble in water charged with carbonic acid. 
 The rarious saline substances are not all found in the same 
 
AGRICULTURAL GEOLOGY. 277 
 
 soil : one soil may contain soda and be deficient in the salts 
 of lime ; another may be supplied with the phosphates and 
 be destitute of the sulphates. If some of these ingredients 
 abound and the others are deficient, the soil will be favora- 
 ble to the growth of certain plants, and unfavorable to oth- 
 ers. The amount of a salt in a soil is oftentimes very 
 small, and might be deemed too insignificant to furnish 
 food to plants, but a single grain of saline matter in every 
 pound of soil a foot deep, is equal to five hundred pounds 
 to the acre. The salt, found in a plant, however minute 
 the quantity, is indispensable to its growth without it 
 the soil is for that plant sterile. These salts are derived 
 from the mineral masses of the soil. The water perco- 
 lating through such soils holds them in solution; they 
 decompose soaps, and hence are said to render the water 
 hard. 
 
 354. The other class of inorganic constituents of soils 
 is the earthy , making ordinarily ninety per cent, or more, 
 of the whole. It embraces three principal ingredients. Sil- 
 ica, in the form of sand; alumina, mixed or combined with 
 sand as clay ; and lime principally in the form of carbonate, 
 as limestone or chalk. Soils are named according to the 
 proportions in which these are mingled. According to John- 
 ston, one hundred grains of dry ordinary soil, containing 
 only ten of clay, form a sandy soil ; ten to forty grains of 
 clay make a sandy loam; forty to seventy, a loamy soil; 
 seventy to eighty-five a clay loam ; and from eighty-five to 
 ninety-five a strong clay, fit for bricks or tiles. Arable 
 land rarely contains more than from thirty to thirty-five 
 per cent, of alumina. If a soil contain ten per cent, of 
 the carbonate of lime, it is called calcareous, and if it has 
 more than twenty per cent, of it, it is designated a marl. 
 24 
 
278 PRACTICAL GEOLOGY. 
 
 The oxide of iron forms two or three per cent, of sandy 
 soils, and in red soils much more. 
 
 Silica presents itself in soils as sand, small fragments 
 of the mineral quartz, one of the constituents of the gran- 
 ite rocks ; or combined with alkaline and earthy bases, as 
 silicates of potassa, lime, alumina, etc. The feldspar of 
 granite yields it in the form of silicates of alumina and 
 potassa. The silicates are slightly soluble, dissolving no 
 faster than the necessities of plants demand, hence they 
 are not rapidly washed out of the soils, as are some soluble 
 ingredients. Silica is found in soils in variable propor- 
 tions, but usually predominates over all the other constit- 
 uents. Silica is contained in the stems of plants, especially 
 of the grasses. 
 
 Clay consists of the silicate of alumina, mixed with 
 uncombined alumina and silica. It is derived from the 
 abrasion of the slate rocks, and from the feldspar of granite. 
 Its most striking property is its adhesiveness; soils are 
 close and compact in proportion to the quantity of clay they 
 contain. When it predominates, it constitutes the heavy 
 cold clay land, requiring under-draining, and sometimes the 
 addition of sand to render it fertile. It retains manures 
 well, being almost impervious to water. Clay soils exhale 
 a peculiar odor called argillaceous, when they are breathed 
 upon. 
 
 Lime exists in soils in very variable quantities, as frag- 
 ments of limestone disseminated with the other materials, 
 or held suspended or dissolved in water, as the carbonate, 
 sulphate, or phosphate of lime. Lime is not found pure 
 or caustic in soils, and if it is applied in this state, it soon 
 loses its causticity by the neutralizing power of the va- 
 rious acids it encounters. 
 
AGRICULTURAL GEOLOGY. 279 
 
 355. The subsoil is of various characters : in some 
 cases consisting of porous sand or gravel, in others of a 
 light loam or a stiff clay. A stratum of these materials, 
 of variable thickness cemented by the salts of lime and 
 iron, and indurated, is called the hardpan. 
 
 356. The organic portion of soils consists of the ani- 
 mal and vegetable substances found in them, which are 
 either the relics of ancient animated forms buried in the 
 rocks, or more frequently the decaying bodies of plants 
 and animals of the present period. Geology leads us to 
 the presumption that in the early history of our globe, 
 mineral matter existed alone, and that subsequently the 
 Creator introduced various races of plants, which drew the 
 elements of their matter from the mineral kingdom. The 
 plants first introduced were simple in their organization, 
 and capable of living upon the elements of air, water and 
 mineral salts, without any previously organized matter 
 for their nutrition. They were cryptogamous, flowerless 
 plants, like the sea weeds and mosses of the present day. 
 These plants having grown and died, furnished by their de- 
 cay the organic matter necessary for the nutrition of the 
 more highly organized flowering plants, subsequently intro- 
 duced. The plants which are cultivated in Agriculture are 
 the flowering ones, for these only bear seeds ; soils therefore 
 must contain some portion of organic matter for their 
 nutriment. The quantity however varies greatly : in peat 
 soils, it forms from fifty to seventy per cent, of the whole 
 weight ; in rich meadows it may amount to twenty per 
 cent., but the proportion is generally much smaller. 
 
 Oats and rye will grow in a soil which contains only one 
 or two per cent, of organic matter ; barley with three per 
 cent. ; while good wheat soils require from four to eight 
 
280 PRACTICAL GEOLOGY. 
 
 per cent. Organic matter alone will not produce a fertile 
 soil ; the inorganic, earthy and saline ingredients must be 
 present. It must also have undergone decomposition : if 
 it is secluded from the oxygen of the air it will not decay 
 and yield up its elements the appropriate nutriment to sur- 
 rounding plants ; a peat bog covered with stagnant water 
 yields very little nutriment to other plants, but exposed to 
 the air and mixed with ashes or other substances yielding 
 alkalies, it becomes a very efficient fertilizer. 
 
 357. The origin of all soils is in the disintegration and 
 decomposition of rocks, produced by the mechanical and 
 chemical agencies of water, air, etc. The amount of soils 
 furnished by groups of rocks depends upon the composition 
 and structure of the rocks. Many slates and shaly lime- 
 stones and sandstones disintegrate rapidly, through the 
 influence of water and frost penetrating between their 
 laminae. Limestones suffer constant loss of materials by 
 the solvent power of rain water holding carbonic acid in 
 solution. The presence of alkalies in the feldspar and 
 mica of granite and gneiss, greatly facilitate the disinte- 
 gration and decomposition of those rocks. Calciferous 
 sandstones are liable to decay by the solution of their lime 
 leaving the sand ; much of the lime passes through the soil 
 and accumulates in the subsoil or hardpan. Rocks which 
 contain metals or metallic compounds which readily suffer 
 chemical change by exposure to the air, are disintegrated 
 with great rapidity : this may be exemplified by pyrites 
 sulphuret of iron which is frequently found in rocks 
 especially the slates ; the sulphur unites with the oxygen 
 of the air, forming sulphuric acid, and the iron with oxygen 
 producicg the oxide of iron, which by combination with 
 the acid forms sulphate of iron or copperas. The sulphate 
 
AGRICULTURAL GEOLOGY. 281 
 
 of iron dissolving in water, the rock becomes porous and 
 crumbles ; flowing over limestone rocks it decomposes 
 them, producing sulphate of lime, or gypsum; or if it 
 comes in contact with the feldspar of granite, it decom- 
 poses that mineral, forming with its potassa the sulphate 
 of potassa, depositing its oxide of iron in the form of iron 
 rust. 
 
 The friction of falling water wears the rocks which 
 are subjected to its agency. 
 
 Vegetables undergoing decomposition generate acids, 
 which act chemically upon the rocks, forming soluble salts 
 with their alkalies and earths : living vegetables also exert 
 a powerful influence upon the rocks ; mosses and lichens 
 growing upon bare granite rocks,- absorbing their soluble 
 parts, decompose and disintegrate them. 
 
 358. Over extensive areas the soil is derived directly 
 from the rock upon which it rests ; it however differs 
 someWhat from the rock in composition ; analysis shows 
 that fragments of rocks exposed to atmospheric influence 
 lose a part of their soluble matter, so that their debris is 
 composed of a larger proportion of insoluble parts. But 
 great masses of soil have been transported from the 
 localities in which they were formed by the agency of 
 currents of water, either alluvial, or exerted on a large 
 scale in the drift, commingling the soils from various rocks, 
 so as to render the earth more uniformly fertile by a 
 mixture of various ingredients, which is known to produce 
 a favorable result. Drift soils are recognized by their 
 heterogeneous character, and by their pebbles, sometimes 
 called cobblestones, consisting of water-worn fragments of 
 the hardest rocks. 
 
 359. Soils are usually classified in accordance with the 
 
 24* 
 
282 PRACTICAL GEOLOGY. 
 
 predominance of some element, as sandy, argillaceous, 
 loam, etc. ; but some writers base their classification on 
 their fitness for certain crops, as wheat districts, corn 
 districts, etc., or on the geological formations, in which 
 case each district is underlaid by characteristic rocks. 
 Prof. Emmons, in his Report on the Agriculture of the 
 State of New York, divides the State into six districts 
 coinciding with six groups of rocks, which impart to the 
 soils, in a good measure, their distinguishing characters. 
 
 360. Soils derived from granite and gneiss contain the 
 earths and salts requisite for a high degree of fertility, but 
 they are often too silicious and porous, and their value 
 depends upon their position and the nature of the subsoil. 
 Syenitic and Hornblende soils contain, in addition to 
 the usual constituents a large proportion of the oxide of 
 iron, magnesia, and the oxide of manganese, and are quite 
 fertile. 
 
 The soils derived from Trap, Greenstone and Basaltic 
 rocks also contain a large per centage of lime, magnesia, 
 and iron, and are highly fertile. The Lava soils, whether 
 trachytic or augitic, owe their remarkable fertility to the 
 large quantity of alkaline salts they contain. 
 
 The slates produce a variety of soils, in many places 
 thin and poor, but in others deep and capable of being 
 made good. 
 
 Calcareous or limestone soils are also very variable in 
 their quality ; those which contain magnesia or iron are 
 fertile. 
 
 Sandstone soils require the admixture of other sub- 
 stances, especially clay, to make them adhesive and fertile. 
 Alluvial soils are generally rich, consisting of finely 
 divided matter thoroughly commingled ; they are found at 
 
AGRICULTURAL GEOLOGY. 283 
 
 the mouths of rivers, and in their valley , and are fre- 
 quently called bottom lands. 
 
 361. The art of maintaining an uninterrupted fertility, 
 or renovating an exhausted soil, consists in supplying those 
 ingredients, mineral and organic, which have been removed 
 in the crops. The earthy and saline substances may fre- 
 quently be obtained by subsoil ploughing, thus forming the 
 earths and salts by the agency of the oxygen of the air 
 upon the insoluble minerals of the subsoil ; or they may 
 be imported from other localities, and applied as mineral 
 manures or fertilizers, such as gypsum, marl, or lime. 
 Many decomposable shales containing iron pyrites, mixed 
 with lime produce gypsum, and constitute excellent ferti- 
 lizers. A deficiency of organic matter must be supplied 
 by turning into the soil green crops which have drawn 
 much of their carbon from the carbonic acid of the air, or 
 by the application of decaying animal or vegetable sub- 
 stances obtained from other sources. 
 
 362. Drainage is indispensable to successful agricul- 
 ture where the water of stiff clay lands or swamps is re- 
 tained by impervious subsoils, inclined strata, or dikes. 
 Geology aids in effecting the drainage either superficial or 
 deep, by indicating the general laws which appertain to 
 dikes and strata, and their permeability to water. 
 
 363. Not only is the physiognomy of a country influ- 
 enced by the different outlines which the various geological 
 formations impart to it, but its scenery is greatly modified 
 by the different kinds of vegetation, whether indigenous 
 or induced by cultivation, which the various soils sustain. 
 
CHAPTER III. 
 
 THE HISTORY OF GEOLOGY 
 
 364. . GEOLOGY is one of the most recent branches of 
 physical science : but little more than half a century has 
 elapsed since it was elevated from the state of absurd 
 hypothesis and wild speculation to the rank of an inductive 
 science, based upon accurate observation of facts. The 
 earlier cosmogonies were altogether fanciful, and in some 
 instances ridiculous. Some of the ancient philosophers, 
 however, appear to have apprehended correctly the origin 
 of many geological phenomena. Pythagoras recognised the 
 operation of the existing causes of change on the earth, as 
 the wearing away of the coasts, and the formation of allu- 
 vial deposits, by marine currents and waves : the geogra- 
 pher, Strabo, was convinced, by finding fossil shells far 
 above the sea level, that parts of the earth had been raised 
 by volcanic agency. 
 
 365. The numerous perfect fossils of Italy early ex- 
 cited a spirit of inquiry respecting their origin. From the 
 commencement of the sixteenth century, two questions 
 regarding them were discussed at great length, viz., first, 
 Whether they ever belonged to living beings, or were mere 
 semblances of animals and plants ; and secondly, If they did, 
 whether they were overwhelmed and imbedded in the rocks 
 by the deluge of Noah. By some writers, fossils were 
 thought to be "lusus naturae," (sports of nature,) the results 
 
HISTORY OP GEOLOGY. 285 
 
 of the operations of a materia pinguis, " fatty matter " 
 found in some parts of the earth, fermented by heat; and 
 others, in an equally unintelligible mode, ascribed them to 
 "tumultuous movements of terrestrial exhalations." These 
 unprofitable discussions were continued for more than two 
 centuries, and in England assumed a theological cast, some 
 writers contending that the Scriptures contain a perfect 
 system of natural philosophy in detail. One of the trea- 
 tises characteristic of the age was Burnet's " Sacred Theory 
 of the Earth ; containing an account of the original of the 
 Earth, and of all the general changes which it hath already 
 undergone, or is to undergo till the consummation of all 
 things/' published in A. D. 1690. Of this work Sir C. 
 Lyell remarks, " Even Milton had scarcely ventured in his 
 poem to indulge his imagination so freely in painting scenes 
 of the Creation and Deluge, Paradise and Chaos." It 
 was, however, at the time regarded as a work of profound 
 science.* 
 
 366. In A. D. 1775, Werner, a professor of mineralogy 
 in the School of Mines, in Germany, commenced teaching 
 that all rocks, unstratified as well as stratified, were deposited 
 by water, that all formations were universal, and that veins 
 were filled by precipitation from aqueous solutions. This 
 was denominated the Neptunian theory, from Neptune, the 
 god of the sea. About the same time, Button, a geologist 
 of Edinburgh, published his theory of the earth, ascribing 
 the origin of all rocks to fire or heat. The melted rocks, 
 after consolidation, he supposed, were abraded by the. action 
 
 * For an admirable sketch of ancient cosmogonies and " Theo- 
 ries of the Earth," consult " Lyell's Principles of Geology," Book 
 I, Chapters 14. 
 
286 HISTORY OF GEOLOGY. 
 
 of water, and deposited as strata, through which igneous 
 rocks often protruded themselves, producing the effects of 
 heat on the surrounding masses. Continents, he supposed, 
 were elevated by volcanic agency, and veins filled by injec- 
 tion of melted matter from beneath. These alternations 
 of fusion, consolidation, abrasion, and deposition, may be 
 repeated, and geology gives no intimation of the time when 
 the series of changes commenced. This view of Hutton 
 was designated the Plutonian theory, from Pluto, the god 
 of fire. While geologists were discussing the merits of 
 these rival hypotheses, Mr. William Smith, an English 
 surveyor, having explored the whole country on foot, with- 
 out the guidance of previous observers, published his 
 "Tabular View and Map of England," in which he ex- 
 hibited the order of the various strata and the relations of 
 their fossils, thus accomplishing more for science than had 
 been effected by centuries of discussions. 
 
 367. The excess of theorizing on the subject induced 
 distrust of all systems, and led the Geological Society of 
 London, formed in 1807, to devote itself to the accumula- 
 tion of accurate observations : the success attending these 
 efforts soon rescued the science from the imputation of 
 being a visionary pursuit. The recent rapid advancement 
 of geology is due in no small degree to the progress of the 
 collateral branches of science botany, zoology, and com- 
 parative anatomy since the palseontological characters of 
 rocks are much more reliable indications of identity or 
 diversity than the mineral characters. 
 
 368. In America, Mr. Maclure, having explored a 
 large part of the United States, in 1810, published his 
 "Observations on the Geology of the United States," 
 giving the first sketch of the distribution of the stratified 
 
HISTORY OF GEOLOGY. 287 
 
 rocks of this country, referred to the European standard. 
 Professor Eaton surveyed the rocks on the line of the Erie 
 canal, through the State of New York, and published the 
 results in 1824. The same year commenced a series of 
 geological surveys of states by legislative sanction, which 
 has progressed until two-thirds of all the states have been 
 completely or partially surveyed. Besides accomplishing 
 the primary design in developing the natural resources of 
 the states, these surveys have accumulated an immense 
 array of accurate observations for the general advancement 
 of science. By comparison and generalization of these 
 results, a highly satisfactory view of the geology of this 
 country may be obtained. The spirit of independence of 
 European classifications, and the determination to develop 
 the rocks as they are, rather than to identity them with the 
 sub-divisions of foreign systems, which have characterised 
 these surveys, have obviated some of the hindrances which 
 retarded the progress of the science in this country. 
 
 369. Although Geology is by no means complete, since 
 in no science are facts more rapidly accumulating, and 
 theories and systems are but expositions of the present 
 amount of knowledge on the subject, still its immense 
 array of facts and legitimate deductions constitute a science 
 as well established as is Chemistry or Astronomy. 
 
CHAPTER XIII. 
 
 RELATION OF GEOLOGY TO RELIGION. 
 
 370. IT is not customary in elementary treatises on 
 branches of physical science to exhibit their relations to 
 morals or religion, since it is the office of other branches 
 of human learning, as natural theology, to treat specifically 
 of those relations in detail. All science has such relations, 
 since it is an exhibition of the laws which the Creator has 
 established over matter, illustrative of his power, wisdom, 
 and benevolence, and religion consists in a knowledge of 
 the Creator and the exercise of those affections which such 
 knowledge enjoins. The science of Geology has, through 
 misapprehension of facts and opinions, been regarded with 
 jealousy, as favorable to infidelity and even atheism, teach- 
 ing the eternity of matter, its self-guiding and renovating 
 power, and dispensing with a Deity in the creation and regu- 
 lation of the world. 
 
 371. On the contrary, those who, with competent knowl- 
 edge of the science of geology and the art of interpretation, 
 have carefully examined this subject, confidently assert 
 that no other science furnishes an equal number of striking 
 illustrations of natural and revealed religion. 
 
 " Shall it then any longer be said," says Dr. Bucklaud, 
 " that a science, which unfolds such abundant evidence of 
 the being and attributes of God, can reasonably be viewed 
 in any other light than as the efficient auxiliary and hand- 
 
GEOLOGY AND RELIGION. 289 
 
 maid of religion ? Some few there still may be, whom 
 timidity or prejudice, or want of opportunity, allow not to 
 examine its evidence ; who are alarmed by the novelty, or 
 surprised by the extent and magnitude of the views which 
 geology forces on their attention, and who would rather have 
 kept closed the volume of witness, which has been sealed up 
 for ages, beneath the surface of the earth, than impose upon 
 the student in natural theology the duty of studying its con- 
 tents ; a duty in which, for lack of experience, they may 
 anticipate a hazardous or a laborious task, but which, by 
 those engaged in it, is found to afford a rational, righteous, 
 and delightful exercise of their highest faculties, in multi-- 
 plying the evidences of the existence, attributes and provi- 
 dence of God." 
 
 " Let not the Christian divine refuse the aid offered by 
 physical science. Let him no longer indulge groundless 
 jealousies against true philosophy, as if adverse to religion 
 Especially let him not spurn the aid of geology, which alone 
 of all the sciences, discloses stupendous miracles of creation, 
 in early times, and thus removes all presumption against the 
 miracles of Christianity and special providence at any time. 
 It is indeed an instructive fact that a science which has been 
 thought so full of danger to Christianity should thus early 
 be found vindicating some of the most peculiar and long- 
 contested doctrines of revelation. And yet it ought not to 
 surprise us, for geology is as really the work of God as reve- 
 lation. And though, when ill understood and perverted, 
 she may have seemed recreant to her celestial origin, yet the 
 more fully her proportions are developed, and her features 
 brought into daylight, the more clearly do we recognize her 
 alliance to every thing pure and noble in the universe."* 
 * President Hitchcock's Religion of Geology, pa 368. 
 25 
 
SJ90 GEOLOGY AND RELIGION. 
 
 372. Geology manifests the uniformity of nature's laws,, 
 carrying back their operation indefinitely into the past, ex- 
 hibiting that unity of design which characterizes the present, 
 extending through all periods of the world's history. It re- 
 recognises the agency of those subtle powers, heat, light, 
 electricity and chemical attraction, regulating all the changes 
 that occurred in the constitution of bodies in all ages. The 
 structure of all the fossil forms of animal and vegetable 
 bodies, shows the prevalence of the present anatomical and 
 physiological laws, in organic systems long since extinct, and 
 links them all into one grand, harmonious system, worthy 
 of the great Contriver. All the proofs of power, wisdom, 
 and benevolence evinced at present, in the adaptation of 
 animate beings to the circumstances in which they are placed 
 by the Creator, are discernible in all periods of fossil botany 
 and zooloffv. Their deviations from the present races in 
 
 O/ 
 
 form or size do not render them anomalous or monstrous. 
 " The animals of the antediluvian world," says Sir Charles 
 Bell, the distinguished anatomist, " were not monsters ; there 
 is no lusus or extravagance. Hideous as they appear to us, 
 and like the phantoms of a dream, they were adapted to the 
 condition of the earth when they existed." This uniformity 
 in' the structure and correlation of parts of animated frames, 
 and the adoption of analogous means for various ends, with 
 such deviations only as the diversity of circumstances in 
 which they were placed required, show the immutable wis- 
 dom and benevolence, as well the unity of design of the 
 Creator. 
 
 373. Although geology does not account for the origin 
 of matter nor aid us in forming a conception of its creation, 
 it does exhibit modifications of it, whose production and regu- 
 lation require the intervention of a Deity. The appearance 
 
GEOLOGY AND RELIGION. 291 
 
 of the various vegetables and animals in successive periods 
 can not be accounted for independently of creative power, 
 and we know of no such power other than the Deity, since 
 the development hypothesis is geologically demonstrated 
 ( 138) to be false. 
 
 374. The instances of special adaptation of means to ends 
 with reference to the welfare of the present races of animate 
 beings, particularly of man, are numerous. Such are the 
 inequalities of the earth's surface, produced by energetic for- 
 ces acting from below, which cause the circulation of water 
 and prevent universal stagnation and death ; the production 
 of soils adapted to sustain vegetable life, by the violent 
 agency which has disintegrated the rocks and commingled 
 their fragments ; the protrusion of metals from deep recesses 
 to accessible positions in veins } and the accumulation and 
 wide diffusion of the useful minerals, rock-salt, coal, 
 marble, &c. 
 
 375. Geology coincides with other sciences in expand- 
 ing our views of the grandeur of the Universe and the plans 
 of the Deity. The microscope discloses to us myriads of 
 living beings in a drop of water, the number increasing with 
 the power of the instrument. The telescope reveals the 
 existence of innumerable suns at such distances from us that 
 their light though traveling at the rate of two hundred 
 thousand miles per second requires thousands of years to 
 come to our world. So Geology, instead of limiting our 
 contemplations of the history of our globe to the past six 
 thousand years, carries us back into the indefinite past, 
 " developing a plan of the Deity respecting its preparation 
 and use, grand in its outlines, and beautiful in its execution."* 
 
 376, The correct interpretation of the Mosaic account of 
 * Hitchcock. 
 
292 GEOLOGY AND RELIGION. 
 
 the Creation has been the subject of much discussion. Until 
 recently, the commonly received opinion respecting it has 
 been, that it taught that the universe began to exist about 
 six thousand years ago, and that its creation was accomplish- 
 ed in six literal days. Geology teaches that the world has 
 existed for an indefinite period, much longer : hence arises 
 an apparent discrepancy, and it becomes eminently desirable 
 to ascertain which interpretation is correct. Much of the 
 difficulty on the subject has arisen from the peculiarities of 
 style and modes of description used in these ancient writings, 
 which are not only not such as are used in scientific treat- 
 ises, but not such as accord with the state of knowledge and 
 prevalent opinion of the present day. The writers of the 
 Old Testament, says Dr. J. Pye Smith, use " language bor- 
 rowed from the bodily and mental constitution of man, and 
 from those opinions concerning the works of God in the na- 
 tural world, which were generally received by the people to 
 whom the blessings of revelation were granted." They de- 
 scribe natural objects and events as they appear to the eye, 
 which is not in accordance with their real nature; they 
 speak, says Rosenmuller, the eminent Ger'man commentator, 
 " according to optical, and not physical truth/' Similar dis- 
 crepancies occur in the scriptures with reference to astronom- 
 ical, physiological, and chemical phenomena. The Creator 
 did not design to anticipate the discoveries of science, and 
 correct the erroneous views entertained on these subjects 
 by the people to whom the revelation was addressed. 
 
 .377. Several attempts have been made to correct the 
 interpretation of the Mosaic account of the creation, so as to 
 make it accord with the established rules of philology and 
 the facts proved by geology. Nor are attempts of this kind 
 confined to this topic. Commentators on ancient writings 
 
GEOLOGY AND RELIGION. 293 
 
 seek all the light which science, history and antiquities shed 
 upon the subject of their investigations; in repeated instan- 
 ces have modern discoveries, in geography, botany, miner- 
 alogy and other branches of science, essentially modified the 
 interpretation of passages in such writings. The same term 
 may convey opposite meanings to different readers. The 
 terms elements and combustion had for the ancient Jew an 
 import different from that which the chemist derives from 
 them. A term is used in the twenty-second verse of the 
 second chapter of Jeremiah and in the twentieth verse of 
 the twenty-fifth chapter of Proverbs, which is translated in 
 the English version nitre ; the nitre of modern chemistry is 
 the nitrate of potassa, which would render the passages 
 cited unmeaning : but if the nitre of the Jews was the car- 
 bonate of soda, the term is apposite and forcible. The pro- 
 priety of such use of science in interpretation is sanctioned 
 by philologists. " If I am reminded, in a tone of animad- 
 version, that I am making science in this instance the inter- 
 preter of Scripture, my reply is that I am simply making 
 the works of God illustrate his Word in a department in 
 which they speak with a distinct and authoritative voice ; 
 that it is all the same, whether our geological or theological 
 investigations have been prior, if we have not forced the 
 one into accordance with the other."* Dr. Harris also, hi 
 his Pre-Adamite Earth, remarks, ".it might be deserving 
 consideration, whether or not the conduct of those is not 
 open to just animadversion, who first undertake to pronounce 
 on the meaning of a passage of Scripture, irrespective of 
 all the appropriate evidence, and who then, when that evi- 
 dence is explored and produced, insist on their a priori inter- 
 pretation as the only true one." 
 * Davidson's Sacred Hermeneutics quoted by President Hitchcock. 
 
 25* 
 
294 GEOLOGY AND RELIGION. 
 
 378. Assuming, as to every geologist seems reasonable, 
 that the period of about sixteen hundred years intervening 
 between the Creation and the Flood was inadequate to the 
 production of the stratified rocks including the remains of 
 extinct races of plants and animals \ and that the deluge 
 was too short and entirely unfitted in its nature, to produce 
 those rocks, we are reduced to two principal modes of recon- 
 ciling the apparent discrepancy between the Mosaic and 
 Geological accounts. 
 
 The first of these interprets the word day in Genesis as 
 a period of indefinite time, during which several geological 
 formations may have been perfected. The advocates of this 
 view urge that such a sense is attached to the word in many 
 languages in use, and that it was so used repeatedly, as is 
 shown by contexts, in the Old and New Testaments, even in 
 the chapter of Genesis, applied to the subject in question : 
 " These are the generations of the heavens and of the earth 
 when they were created in the day that the Lord God made 
 the earth and the heavens, and every plant of the fields." 
 They also argue that the order of creative acts revealed in 
 the sacred record harmonizes with that developed by geo- 
 logical researches. 
 
 It is objected to this interpretation that most of the fossil 
 races had become extinct when those at present existing 
 were introduced, so that if Moses described the fossil races, 
 those that now exist must have been created with man on 
 the sixth day, which does not accord with the sacred records, 
 and no reason is shown why the remains of the existing 
 races, if they were concomitant with the fossil, were 
 not preserved with them. It is also objected that while 
 there is a general resemblance in the succession of events 
 detailed in the two accounts, tKe coincidence in the order 
 
GEOLOGY AND RELIGION. 295 
 
 of introduction of the various animate forms is by no means 
 accurate, since instead of finding the lower half of the fos- 
 siliferous strata containing vegetables only, we meet with a 
 preponderance of animals. 
 
 379. The mode of reconciling the apparent discrepancy 
 which is most generally received, regards the first verse of 
 Genesis as having no immediate connection with the follow- 
 ing verses, but simply asserts that in the indefinitely remote 
 past, " in the beginning," God created the universe ; then 
 passing by an indefinite interval during which all the fos- 
 siliferous strata, up to those of the present period, were depos- 
 ited, the subsequent verses give the account of the introduc- 
 tion of the present races; and that this renovation or 
 remodelling, not creating, of pre-existing materials was in six 
 
 Some of the ablest expositors assert that this interpreta- 
 tion is in strict accordance with the rules of exegesis, and if 
 admitted, the apparent discrepancy disappears. 
 
 Dr. J. Pye Smith has proposed to extend this interpre- 
 tation, on the acknowledged principle that the sacred writers 
 adapted their language to the limited knowledge of the Jews, 
 and consequently did not imply by the term earth, the 
 entire globe, but that portion of it known to the Jews, " which 
 God was adapting for the dwelling place of man and the 
 animals connected with him." This view would obviate to 
 some extent a difficulty which arises from the fact that many 
 of the races introduced in the tertiary period long before the 
 creation of man still survive : some have supposed that these 
 were destroyed and again created, which seems quite im- 
 probable. This hypothesis of Dr. Smith's coincides also 
 with what Natural History teaches respecting the distribu- 
 tion of plants and animals, viz : that they have not dispersed 
 
296 GEOLOGY AND RELIGION. 
 
 from one centre, but have spread from many centres of creation. 
 
 380. If it be admitted that much remains to be accom- 
 plished before a perfectly satisfactory comparison of geolog- 
 ical results with the sacred text is attained, still in the 
 present aspect of the case it is unphilosophical to presume 
 there is any real collision between them. " It is not neces- 
 sary" says President Hitchcock " that we should be perfectly 
 sure that the method which has been described, or any other, 
 of bringing geology into harmony with the Bible, is infalli- 
 bly true. It is only necessary that it should be sustained 
 by probable evidence ; that it should fairly meet the geologi- 
 cal difficulty on the one hand, and do no violence to the 
 language or spirit of the Bible on the other. This is suffi- 
 cient, surely, to satisfy every philosophical mind that there 
 is no collision between geology and revelation. But should 
 it appear hereafter, either from the discoveries of the 
 geologist or the philologist, that our views must be some- 
 what modified, it would not show that the previous views 
 had been insufficient to harmonize the two subjects; but 
 only that here, as in every other department of human 
 knowledge, perfection is not attained, except by long con- 
 tinued efforts/ 7 * 
 
 381. It has been supposed that a change occurred in the 
 constitution of men and animals at the time, and in conse- 
 quence, of the apostacy by which they were rendered mortal. 
 Such an opinion has been based upon the text By one man 
 sin entered the world, and death by sin. Gleology, however, 
 shows that death had occurred in innumerable instances 
 before the creation of man, while physiology demonstrates 
 
 * This whole subject is most fully and satisfactorily discussed 
 in President Hitchcock's Religion of Geology and its connected 
 sciences. 
 
GEOLOGY AND RELIGION. 297 
 
 that mortality is a universal law of organic beings, requiring 
 miraculous interference to prevent its fulfillment. A com- 
 parison of Scripture texts clearly shows that the death re- 
 ferred to in them is limited to man : And so death passed 
 upon all men, for that all have sinned. This limitation to 
 moral agents is also inferred from the text Since ~by man 
 came death, l>y man came also the resurrection of the dead. 
 382. The belief in a deluge is very general among civil- 
 ized nations, and such an event is explicitly described in the 
 Bible. To the flood was formerly assigned the origin of all 
 the stratified rocks, and still more -recently the phenomena 
 of the drift were ascribed to its agency. But Geologists are 
 agreed that no phenomena can at present be identified as the 
 result of the historical deluge, since the nature of the agency 
 exerted differs, in several respects, and the period of the 
 drift was antecedent to the creation of man. Since, however, 
 every portion of the strata has been submerged, and usually 
 many times, geology renders the occurrence of Noah's del- 
 uge eminently probable. Considerations .derived from 
 Natural History, the great number of species probably 
 five hundred thousand and the amount of food requisite to 
 sustain them during the prevalence of the flood, have led 
 most writers who have investigated the subject, to the con- 
 clusion that the deluge was partial, not covering the whole 
 earth, and it is admitted that the design of the penal inflic- 
 tion would have been subserved by such a flood, and that 
 the Scripture writers are accustomed to use universal terms 
 to signify large quantities. 
 
CHAPTER XIV, 
 
 GEOGRAPHICAL GEOLOGY. 
 
 383. BY Geographical Geology is understood the de- 
 scription of the structure of particular districts included 
 within natural or political divisions. The geology of many 
 countries is very imperfectly known, but important deduc- 
 tions respecting it may be obtained from their physical 
 geography, since the connection between the geographical 
 features of a country and its geology is very intimate. 
 The forms and positions of Mountain Chains often furnish 
 a satisfactory means of judging of the probable range and 
 extent of certain formations, which have been carefully 
 investigated in other localities. The geology of a region is 
 usually complicate in proportion as its contour is broken 
 and irregular, indicating that it has been subjected to 
 numerous upheavals. 
 
 384. Asia and Europe form one continent, to which 
 Africa may be considered as a peninsular appendage. The 
 form of this great continent has been determined by the 
 immense zone of mountains and table lands which, com- 
 mencing on the coasts of Portugal and Barbary, on the 
 Atlantic ocean, stretch through a distance of ten thousand 
 miles, to the Pacific ocean, in China and Japan. Adjoining 
 this belt on the north lies a vast plain, extending from the 
 
ASIA. 299 
 
 Pyrenees to the remotest point of Asia, with few interrup- 
 tions by transverse spurs: a similar plain on the south is in- 
 dented by gulfs and arms of the sea. The desert, called the 
 Great Gobi is a plateau of six hundred thousand square 
 miles, elevated more than four hundred feet above the sea. 
 The axis of this mountain chain is granite, though the crest 
 of the Himalayas is gneiss and other metamorphic rocks. 
 The Silurian strata lie at an elevation of sixteen thousand 
 feet above the sea, and much more modern strata are also 
 found in elevated positions, showing that great geological 
 changes have occurred over very extensive tracts of this 
 continent, in comparatively recent geological periods. On a 
 branch of the Altai range, between the rivers Obi and Ye- 
 nissei, are extensive coal beds which, it is affirmed, were set 
 on fire by lightning, and have continued to burn more than 
 a century.* Some of these mountains surpass the Andes 
 in the amount of their metallic products, especially of gold, 
 which is wrought in the metamorphic slates near dikes of 
 igneous rocks, and in the alluvium of these rocks. 
 
 385. In Siberia , the Silurian, Devonian, and Permian 
 strata have been recognised. More than two hundred 
 thousand square miles are covered by the gold alluvium ; 
 and in addition to gold, silver, platina, copper, iron, and a 
 great variety of gems are found. The surface is generally 
 undulating, but much of it is flat and low : interesting 
 organic remains, as the mammoth and extinct rhinoceros, 
 have been obtained from the frozen gravel. 
 
 Tartary is intersected by four systems of mountains 
 with all classes of strata, from primary to tertiary, salt lakes, 
 deserts, and very numerous volcanoes, extinct and active. 
 
 386. In Thibet, Hindostan, and India, the summits of 
 
 * Somerville's Physical Geography page 60. 
 
300 GEOGRAPHICAL GEOLOGY. 
 
 the mountains are of gneiss and mica slate, traversed by 
 granite and porphyry ; these are succeeded by talcose slate, 
 limestones, coal, sandstones of the newer secondary series, 
 and the tertiary strata, including numerous organic remains, 
 among which are those of the mastodon, hippopotamus, deer, 
 gavial, crocodile, sivatherium, and monkey. The unstrati- 
 fied rocks also abound in Hindostan, which is celebrated 
 for its beautiful gems, especially the diamonds of Grolconda, 
 of surpassing brilliancy and hardness, which are found in 
 the conglomerate and alluvium. Ceylon consists chiefly of 
 stratified primary rocks, and is celebrated for its gems. 
 
 South-eastern Asia consists of a range of mountains of 
 plutonic rocks, partially covered by slates, sandstones, and 
 alluvium ; they contain gold, silver and arsenic, and consti- 
 tute the richest repository of tin known on the globe. In 
 Sumatra, Java, and Borneo, volcanic mountains occur, and 
 at their bases secondary and tertiary strata. Their mineral 
 products are diamonds, gold, tin, copper, and sulphur. 
 
 387. The geology of China is varied, embracing all 
 classes of rocks, abounding with metals and precious stones. 
 Its alluvial formations are very extensive. In Japan, coal, 
 amber and sulphur are found, together with metals. Nu- 
 merous volcanoes also exist there 
 
 388. Some portions of Persia are mountainous, while 
 others are level; others still constitute a sandy desert. 
 Unstratified rocks, palaeozoic, secondary and drift deposits, 
 have been identified. The white alabaster of Tabreez is a 
 calcareous deposit made by thermal waters near Lake 
 Oroomiah; the waters of the lake contain one-fifth of 
 their weight of salts. Extinct craters, boiling springs, and 
 deposits of sulphur and asphaltum indicate recent extensive 
 volcanic agency. 
 
EUROPE. * 301 
 
 389. The geology of Arabia also is varied by moun- 
 tains, deserts and fertile plains. The rocks near the Red 
 Sea and Arabian Gulf are granitic. Mount Sinai is 
 syenitic granite. The valley of the Jordan is a fissure 
 through which volcanic agency has been exhibited, and in 
 which there is extensive subsidence below the level of the 
 ocean. Mount Lebanon, which abounds with fossil fishes, 
 belongs to the cretaceous formation. 
 
 390. Polynesia consists of a group or band of islands, 
 volcanic, and coral reefs, which extend from the eastern 
 coast of Asia, with some interruptions, to the west coast of 
 America, intimating the existence of a prolongation of the 
 great continent, but slightly depressed beneath the ocean 
 level. 
 
 The rocky coasts of New Holland present granite, 
 slates, limestones, sandstones, coal, salt, and Oolite. The 
 fossils of its limestone caverns and osseous breccias be- 
 longed to animals closely allied to its present fauna. 
 
 EUROPE. 
 
 391. European geology is more thoroughly investigated 
 than that of any other quarter of the globe, and many 
 designations in the science have been derived from their 
 local application in Europe. 
 
 The seologv of the British Islands is more varied, and 
 
 O D/ 
 
 has been more accurately studied than that of any other 
 area of equal extent in the world. It presents a nearly 
 perfect succession of all the formations, and has been made 
 the type or standard of reference for general geology. 
 
 392. The primary rocks of England are confined to its 
 western portion, or Wales, where also are developed the 
 Cambrian and Silurian formations. In passing from Wales 
 
 26 
 
02 GEOGRAPHICAL GEOLOGY. 
 
 to London, the rocks rise in the series until we reach the 
 center of the London basin, which is tertiary. The car- 
 boniferous system, embracing extensive deposits of coal, 
 extends from the south of Wales to the Scottish border. 
 The Newcastle beds have been most extensively wrought. 
 The Welsh mines yield gold, copper, lead, tin, and iron; 
 rock-salt and gypsum are found above the coaL 
 
 393. Scotland is more mountainous than England, and 
 its rocks are principally primary and palaeozoic : the islands 
 near its coasts are of igneous origin, and present splendid 
 basaltic columns and caves. 
 
 The rocks of Ireland are chiefly palaeozoic, with some 
 secondary formations : trap rocks cover an area of eight 
 hundred square miles in the northern part of the island. 
 Its mineral products are gold, copper, iron, coal and peat. 
 
 394. The geology of France presents nearly all the 
 rocks stratified and unstratified. The secondary, especially 
 the Oolitic limestone, and the tertiary series are con- 
 spicuous, but the carboniferous system is less developed 
 than in England. The great platform of Auvergne was 
 the theatre of violent volcanic action during the tertiary 
 period, and many craters still exist, with perfect forms. 
 The valley of the Rhine yields gold ; while silver, copper, 
 iron, and tin, are obtained in other localities; extensive 
 quarries of gypsum, buhrstone, and flint are wrought. The 
 surface of Belgium and Holland is very flat, and a portion of 
 it is lower than the sea level. No unstratified rocks occur ; 
 the stratified rocks from the clay-slate are found, including 
 some tertiary. Coal-beds and iron mines are wrought. 
 
 395. Primary mountains bound Germany on the east 
 and south-west. All of the fossiliferous formations are 
 represented, including the tertiary ; the drift abounds, as 
 
8 3 
 
304 GEOGRAPHICAL GEOLOGY. 
 
 it does generally in Northern and Central Europe. The 
 mineral products are numerous, presenting some of the best 
 mining districts in Europe. 
 
 The geology of Switzerland is complicate : the central 
 axes of the Alps, which are primary, are covered by the 
 secondary and tertiary series, the latter in some instances 
 at the height of four thousand feet above the ocean, showing 
 that these mountains have been recently elevated. 
 
 396. In Sweden and Norway, the older rocks predomi- 
 nate : chalk and the tertiary are also found, but the drift 
 presents the most striking features. Grold, silver, and 
 copper are obtained, but the iron found in the gneiss is the 
 most important metallic product. The more recent rocks, 
 the wealden, chalk, tertiary, and alluvial, compose the 
 surface of Denmark, while the igneous rocks, greenstone 
 and lava, abound in Iceland and the Faroe Islands. 
 
 397. Russia and Poland are vast plains, bounded by 
 mountains of primary rocks. The silurian, devonian, upper 
 secondary and tertiary strata oocur, covered to a great extent 
 by the drift. Deposits of salt with gypsum are found in 
 the permian and tertiary strata. 
 
 The numerous mountain ridges and vast plains of Aus- 
 tria present all the varieties of geological formations, and 
 mineral products. 
 
 398. Northern Italy consists of extensive secondary and 
 tertiary plains, sloping from the Alps; Mount Bolca is 
 famous for its fossil fishes. The form of the peninsula de- 
 pends upon the Apennines which are of limestone, while the 
 sub-Apennine hills are of tertiary. The Apennines have 
 been elevated several thousand feet since the tertiary period. 
 The traces of volcanic agency are numerous in Italy. The 
 marbles of Italy are celebrated for their beauty and variety. 
 
AFRICA . 305 
 
 The mountainous regions of Spain and Portugal con- 
 sist of primary and secondary strata, the chalk being found 
 at considerable elevation on th'e Pyrenees. Tertiary strata 
 occur together with extinct volcanoes of that period. Rock 
 salt is found in the cretaceous strata, and quicksilver in the 
 clay slate. 
 
 AFRICA. 
 
 399. The Atlas chain of mountains separates the Medit- 
 erranean sea from the great desert ; these mountains are 
 composed of primary rocks, and the strata on their northern 
 slope, m the Barbary States, are secondary and tertiary, 
 into which trap rocks have been frequently intruded, and in 
 which salt and gypsum are found. 
 
 Through upper Egypt, Nubia, and Abyssinia, occur pri- 
 mary rocks, granite, porphyry, syenite (so called from Syene) 
 and limestone ; drifting sands from the desert have en- 
 croached upon these territories, while extensive alluvial de- 
 posits have been made by the Nile in lower Egypt. 
 
 400. The western coast of Africa, for several degrees of 
 latitude on either side of the equator, is composed of granite, 
 syenite and the metamorphic rocks ; the great quantity of 
 gold formerly obtained here led to the designation of Grold 
 coast. 
 
 Central Africa is traversed by the mountains of the Moon, 
 which are primary and basaltic. Much of the gold obtained 
 on the western coast was derived from the metamorphic rock 
 of this range. The secondary series also, including the 
 cretaceous formation, with rock salt, are found upon the 
 Northern Slope. 
 
 401. The Sahara or great desert is a plain, slightly 
 elevated above the ocean, extending from the rocky hills 
 bounding the valley of the Nile to the Atlantic Ocean, two 
 
 26* 
 
306 
 
 GEOGRAPHICAL GEOLOGY. 
 
 thousand six hundred and fifty miles in 
 length and varying from seven hundred to 
 twelve hundred miles in width. Its surface 
 is loose sand, with intervening portions of 
 gravel, pebbles, earth, and salt, and occa- 
 sionally fertile spots oases watered by 
 springs. No rain falls upon the desert. 
 The chalk, tertiary rocks, salt, anji shells 
 identical with species still living in the 
 Ocean, show that this is the bed of a 
 great Mediterranean sea but recently 
 elevated. 
 
 402. Chains of mountains consisting of 
 primary and secondary rocks bound the 
 two coasts of Southern Africa, between 
 which intervenes an extensive plateau or 
 table land, which merges at the southern 
 extremity in the Cape Mountains ; the 
 tabular appearance of these Mountains at 
 the Cape of Good Hope is due to hori- 
 zontal masses of sandstone lying upon 
 granite. 
 
 The islands in the vicinity of Africa, 
 the Azores, Canaries, Cape Verde, St. He- 
 lena and Bourbon are of igneous origin ; the 
 volcanic peak of Teneriffe rises one thou- 
 sand two hundred and seventy-five feet 
 above the ocean. The axis of Madagascar 
 is a chain of mountains, parallel to, and of 
 the same age with the coast chain on the 
 continent, the Mozambique channel only 
 intervening. 
 
SOUTH AMERICA. 
 
 307 
 
 SOUTH AMERICA. 
 
 403. The form of the South American 
 continent is due to the position of the three 
 mountain chains, the Andes running near 
 tho western coast from Cape Horn to the 
 isthmus of Panama, a chain of small width 
 but of majestic height, dipping rapidly 
 towards the Pacific, but sloping on the 
 east into level plains of great extent ; the 
 Brazil chain between the Rio de la Plata 
 and the Amazon river; and the system of 
 Parima and Gruiana between the Amazon 
 and Orinoco rivers. These mountains arc 
 primary and volcanic, covered by slates 
 fossiliferous limestones and red sandstones 
 of various geological ages. Coal and chalk 
 are found at an elevation of thirteen thou- 
 sand and fourteen thousand feet above the 
 Ocean. 
 
 The extensive plains east of the Andes 
 are so low, even near the foot of the Andes 
 that a rise of one thousand feet in the 
 Atlantic Ocean would submerge more than 
 one half of the continent of South America. 
 These plains are divided by the mountains 
 and table lands of Parima and Brazil into 
 three different basins differing in aspect : 
 the Llanos, or grassy steppes of the 
 Orinoco ; the Silvas or woody basin of the 
 Amazon covering an extent of two hundred 
 and eighty thousand square miles ; and the 
 deserts and pampas of Buenos Ayres and 
 
 \ 
 
308 GEOGRAPHICAL GEOLOGY. 
 
 Patagonia. These plains are of recent geological origin, and 
 have furnished very interesting fossils. The tertiary strata 
 are extensively developed in many localities, especially along 
 the terraced coasts of Patagonia, and bordering the plains. 
 Portions of the continent many hundred miles in length have 
 been raised from beneath the ocean within the period of the 
 shell-fish now living, which are found in the plains still 
 retaining their colors. The volcanoes of this continent are 
 among the most magnificent of the globe. 
 
 South America has long been distinguished for its mines 
 of gold, silver and platinum. The diamonds of Brazil are 
 obtained from the alluvium j other gems also are found in 
 the rocks, as the topaz, emerald and sapphire. 
 
 CENTRAL AMERICA. 
 
 404. The Andes continue through Guatimala and Mex- 
 ico in an irregular mixture of table lands and mountains, 
 consisting of granite, gneiss and mica-slate, with a large 
 admixture of lavas ancient and modern; secondary sand- 
 stone and limestone occur together with alluvial deposits 
 along the coasts. Few regions of the globe rival this in in- 
 tensity of volcanic action. The mines of Mexico which are 
 in talcose and mica slates, transition limestones and porphyry, 
 have yielded a large amount of gold and silver. 
 
 The mountains in the West Indies are similar to those of 
 South America of which some of the ranges appear to be 
 continuous ; this fact together with the identity of the fossil 
 remains of extinct quadrupeds, renders it probable that the 
 West Indian Archipelago was once apart of the American 
 Continent, the area of the Gulf of Mexico and the Carib- 
 bean sea having subsided at a recent geological period. 
 Secondary and tertiary strata are also developed upon these 
 
NORTH AMERICA. 809 
 
 islands attended by the drift and alluvium. The islands 
 are still subject to violent volcanic action, especially earth- 
 quakes, and extinct craters are common. The Pitch Lake 
 in Trinidad is three miles in circumference and of unknown 
 depth. 
 
 NORTH AMEBICA. 
 
 405. The general structure of North America is simple ; 
 its form is due to the position of two mountain chains the 
 Rocky mountains running north-west, and the Alleghanies 
 northeast, including one of the most extensive basins in the 
 world, embracing three millions two hundred and fifty thou- 
 sand square miles. The Rocky mountains are composed of 
 primary rocks, covered by sedimentary rocks of various geo- 
 logical ages, intersected by volcanic eruptions, though active 
 volcanoes are principally confined to the northern part of the 
 chain and near the Pacific ocean. At the base of these 
 mountains on the east lies a sandy desert four hundred or 
 five hundred miles wide. Rock salt and salt lakes are found 
 in its vicinity. The coal formation with its fossils of tropical 
 character is found at Melville Island in 74 ? north latitude. 
 
 The auriferous deposits of California are alluvial, the 
 detritus of sandstones, limestones and slates, especially tal- 
 cose slate, intersected by quartz and porphyry. The gold is 
 also found in veins in these rocks. Cinnabar the ore of 
 mercury, silver, platinum, iron, tin and lead are known to 
 exist in this locality. 
 
 UNITED STATES EAST OP THE ROCKY MOUNTAINS. 
 
 406. The Alleghany or Appalachian chain of mountains 
 separates the great Mississippi Valley from the Atlantic 
 slope ; it consists of a series of from three to five parallel 
 ridges with intervening valleys. Extending into New Eng- 
 
310 
 
 GEOGRAPHICAL GEOLOGY. 
 
 land these mountains form the substrata 
 of the geology of that region, of which 
 the unstratified and metamorphic rocks 
 form the principal part ; limited portions 
 qf more recent sedimentary rocks overlie 
 them, among which the new red sandstone 
 is supposed to be recognized in the Con- 
 necticut Valley. 
 
 407. The Atlantic slope is very nar- 
 row at New York, but in its southern 
 portion extends several hundred miles 
 from the ocean. Upon this slope in New 
 Jersey the new red sandstone is found, 
 succeeded by the cretaceous formation, 
 consisting of marls, limestones and green 
 sands; the latter extend to Alabama. 
 The coal in Virginia near Richmond is 
 assigned to the Oolitic period. The ter- 
 tiary series commencing on the coast of 
 Massachusetts extend almost continuously 
 along the Atlantic coast into the Missis- 
 sippi Valley ; in the Carolinas, G-eorgia, 
 and Alabama, they are extensively devel- 
 oped, furnishing many characteristic fos- 
 sils, which are however very rarely spe- 
 cifically identical with the tertiary fossils 
 of Europe. 
 
 408. The tertiary rocks constitute the 
 principal part of the surface in the South- 
 ern states ; they repose upon the creta- 
 ceous, and in the lower portion of the 
 Mississippi Valley, these together with 
 
NORTH AMERICA. 311 
 
 the alluvium overlie the palaeozoic strata, as is shown in the 
 section, Fig. 170 ; in which 
 
 1 indicates the modern alluvium of the Mississippi. 
 
 2. The ancient fluviatile deposit with recent shells and 
 bones of extinct mammalia j loess. 
 
 2* Marine and fresh water deposits with recent sea 
 shells and bones of extinct land animals. 
 
 3. The Eocene with remains of the Zeuglodon. 
 a. b. Terraces. 
 
 4. Cretaceous formation, gravel, sand, and argillaceous 
 limestone. 
 
 5. The Palaeozoic coal measures of Alabama. 
 
 6. Granite. 
 
 409. The stratified formations of the Mississippi valley 
 and the western ridges of the Alleghany Mountains are the 
 older palaeozoic rocks, which are expanded to a vast extent, 
 and of very great thickness, while the secondary formations 
 with the exception of very limited portions of the cretaceous, 
 are deficient. Tertiary and alluvial deposits also extend up 
 the valley of the Mississippi and its tributaries. The strata 
 resting upon the primary rocks over large areas are the 
 Silurian and Devonian. The carboniferous limestone is 
 known to be widely extended in this valley, and the coal 
 formation appears in many localities. These strata have 
 frequently but little inclination, but are of great thickness, 
 and abound in characteristic organic remains. 
 
 The identity of the great systems of the palaeozoic rocks 
 in Europe and in the Mississippi valley is easily recognised ; 
 that of the minor subdivisions is however, in many instances, 
 obscure. The thorough geological surveys made in some 
 portions of the United States whose rocks belong to these 
 systems have led to the adoption of some provisional terms 
 
312 
 
 GEOGRAPHICAL GEOLOGY. 
 
 based upon certain peculiarities of the rocks, or upon tho 
 localities where they have been investigated. The subdivis- 
 ions of the systems made by the New York survey, consti- 
 tute, for the present, a convenient standard of reference. 
 The following tabular arrangement, by Professor James 
 Hall, exhibits the correspondence of these systems in Great 
 Britain and New York. 
 
 TABLE. 
 
 SUBDIVISIONS OF THE BOOKS OF 
 THB NEW- YORK SYSTEM. 
 
 Old Red sandstone 
 
 Chemung group. 
 
 Portage group. 
 
 Genesee slate. 
 
 Tully limestone. 
 
 Hamilton group. 
 
 Marcellus shale. 
 
 Corniferous limestone. 
 
 Onondaga limestone. 
 
 Schoharie grit. 
 
 Cauda-galli grit. 
 
 Oriskany sandstone. 
 
 Upper Pentamerus limestone. 
 
 Encrinal limestone. 
 
 Delthyris shaly limestone. 
 
 Pentamerus limestone, 
 j Water-lime group. 
 
 Onondaga salt group. 
 Niagara group. 
 
 Clinton group. 
 'Medina sandstone. 
 
 Oneida conglomerate. 
 
 Grey sandstone. 
 
 Hudson-river group. 
 ;Utica slate. 
 
 Trenton limestone. 
 
 Birdseye and Blak-river lime- 
 1 stones. 
 
 Chazy limestone. 
 
 Calciferous sandrock. 
 
 r tsdam sandstone. 
 
 SUBDIVISIONS OF THE SILURIAN 
 AND OLD RED SYSTEMS IN 
 GREAT BRITAIN. 
 
 Old Red sandstone. 
 
 Upper and Lower Ludlow rocks, 
 including the Devonian Sys- 
 tem of Phillips. 
 
 Wenlock rocks. 
 
 Caradoc sandstone. 
 
 Llandeilo flags. 
 
 These formations are not as 
 fully recognized in Great Bri- 
 tain as in New York. 
 
NORTH AMi-RIOA. 
 
 818 
 
 The order of succession in 
 these rocks is exhibited in a 
 section from Canada to Penn- 
 sylvania; from the primary to 
 the Old Red Sandstone. Fig. 
 171. 
 
 410. The differences in char- 
 acter and amount of develop- 
 ment which the same strata pre- 
 sent in localities remote from 
 each other, have induced a di- 
 versity of names applied to them 
 in the United States. More ex- 
 tended surveys and comparisons 
 will probably show the identity 
 of some now regarded as di- 
 verse. Since the mineral char- 
 acters of these strata are very 
 fluctuating, their organic re- 
 mains are deemed the most re- 
 liable means of determining 
 their identity or diversity. A 
 table similar to that just used 
 for the comparison of British 
 and American systems has been 
 constructed by the same geolo- 
 gist to show the equivalency of 
 the lower strata in America, 
 bearing different names in five 
 States, New York, Pennsylvania, 
 Virginia, Ohio and Michigan. 
 27 
 
314 
 
 GEOGRAPHICAL GEOLOGY. 
 
 
Wiscon. Eirer. 
 
 s 
 
 Lake Huron. 
 
M.3 1 
 uVg 
 
 I 
 
 
 I 
 
 Ft 
 
 ^ 
 O 
 
 O 
 
 " 
 
 111 6 
 
Green River. 
 
 South Pass. 
 
 North Fork. 
 
 River. 
 
 South Fork. 
 
 Pacific Ocean. 
 
 Fort Tan Courer. 
 
 St. Louis. 
 
X 
 
 * 
 
 <! 
 
 &H 
 03 
 
 fc 
 
 25 
 W 
 - 
 
 m 
 
 
 
 i 
 
NORTH AMERICA. 319 
 
 411. The fossils are said by Professor Hall to be more 
 numerous in the rocks of America than in those of Europe 
 of the same age. Some of the extinct species of the higher 
 mammalia, found in the recent formations of special interest 
 are, the Mastodon, Mammoth, Megatherium, Megalonyx, 
 fossil Elk, several species of fossil Ox, Walrus, Zeuglodoh. 
 
 412. The mineral treasures of the United States are, 
 though imperfectly explored, known to be rich and abundant. 
 The Coal measures of the Carboniferous period are devel- 
 oped on a scale, so far as is known, unequalled in the 
 world, furnishing a supply of mineral fuel amply sufficient 
 for the requirements of the whole civilized world, for thou- 
 sands of years, even should the demand increase rapidly, and 
 the consumption continue to bear reference to the mul- 
 tiplication of all kinds of industrial occupation.* The 
 Alleghany coal field is seven hundred and fifty miles long 
 with an average breadth of eighty-five miles, embracing an 
 area of sixty-five thousand square miles, or more than forty 
 millions of acres, distributed in eight states as follows : 
 
 Pennsylvania, - - 9,500,000 Kentucky, - - - - 6,750,000 
 
 Ohio, 7,500,000 Tennessee, - - - 2,750,000 
 
 Virginia, - - - - 13,500,000 Georgia, .... 100,000 
 
 Maryland, - - - - 350,000 Alabama, - - - 2,250,000 
 
 The Illinois coal field also extends over an area of more 
 than fifty thousand square miles \ of which thirty thousand 
 are in the state of Illinois, and eight thousand in Indiana. 
 This is exclusive of the great coal-area of Missouri whose 
 extent is not ascertained. The varieties of coal in these 
 fields are bituminous, cannel, and anthracite ; the latter is 
 
 * Ansted. 
 
820 
 
 GEOGRAPHICAL GEOLOGY. 
 
 found in Pennsylvania occupying an area of two hundred 
 thousand acres, in three principal districts ; in one of which 
 there are sixteen workable beds of three feet or more the 
 thickest being nearly thirty feet. The beds cease to be 
 anthracitic at a distance from the primary rocks of the 
 mountains. 
 
 The Michigan Fi S- 176 - 
 
 coal basin lies in 
 the central portions 
 of the State, as is 
 represented by the 
 shaded part of Fig. 
 176, and is one hun- 
 dred and seventy 
 miles long by one 
 hundred miles wide. 
 It is underlaid by 
 carboniferous lime- 
 stone, soft, light col- 
 ored sandstones, ar- 
 gillaceous slate, and 
 flagstones. 
 
 413. Iron is found in quantity and quality adapted to 
 working in numerous localities. The deposits of specular 
 iron in Missouri, and near Lake Superior are among the very 
 largest in the world. 
 
 Copper occurs native and as an ore in great quantities 
 on the shores of Lake Superior, in Missouri, and in less 
 amount in Virginia, New Jersey, and New England. 
 
 One of the largest deposits of lead known in the world 
 is wrought in the carboniferous limestone of the north-west- 
 ern and western states ; and is estimated to be capable of 
 
NORTH AMERICA. 321 
 
 yielding more than one hundred and fifty millions of pounds 
 annually. 
 
 Gold is found in the primary rocks of the Alleghany 
 Mountains in quartz rock traversing the metamorphic rocks, 
 particularly talcose slate ; and in greater quantities in the 
 same geological position, and in the alluvium of these rocks, 
 in California. Silver occurs also associated with gold, copper 
 and lead. Rock Salt is found in limited quantity in the 
 strata but is obtained in abundance from the brine springs, 
 which rise from beneath the coal. - 
 
 Inexhaustible supplies of granite, marble, freestone, and 
 other rocks adapted to architectural purposes, are found in 
 the primary rocks, but are as yet little wrought. 
 
 Mineral fertilizers of soils, gypsum, marls, and the 
 phosphate of lime } are found in numerous localities. No 
 active volcanoes exist in the United States, nor are there 
 indications of igneous eruptions east of the Rocky Mountains 
 since the protrusion of the trap. In the Rocky Mountains 
 pumice and other evidences of more recent volcanic agency 
 occur. Severe earthquakes are very rare ; Thermal Springs 
 however are abundant, and in some instances of a high 
 temperature, as the hot springs of Arkansas and Virginia. 
 
/-' 
 
 2r3 
 
 . /) ^ 
 
 3 | T 1JB 
 
 JT-- rfeifffM 
 
GLOSSARY OF TERMS USED IN GEOLOGY. 
 
 NOTE. Such terms as have been defined in the text are not repeated here, but 
 may be referred to by means of the index. 
 
 AEROLITES. Mineral masses that fall from the atmosphere. 
 Albite. A white variety of Feldspar containing soda instead of 
 
 potash. 
 
 Algm. A division of cryptogamous plants, Sea weeds. 
 Alveola. Socket of a tooth. 
 Alveolus. A chamber of the belemnite. 
 Amorphous. Devoid of regular form. 
 Amorphozoa. Animals without definite form Sponges. 
 Analcime. A simple mineral of the Zeolite family, found in trap 
 
 and granite. 
 
 Analogue. A body resembling or corresponding with another body. 
 Anchylosis. A stiff, immovable joint. 
 Anhydrous. Without water. 
 
 Annelides. Worms having the integument formed of rings. 
 Antediluvian. Preceding the deluge. 
 
 Antennce. Articulated horns of insects and Crustacea feelers. 
 Anthracotherium. An extinct quadruped, allied to the paloeotheria 
 
 found fossil in the coal beds of the tertiary. 
 Anthropomorphous. Resembling the human form. 
 Antiseptic. Preventing putrefaction. 
 Argentiferous. Containing Silver. 
 Arragonite. A variety of Carbonate of lime. 
 Asbestus. A fibrous mineral, of which an incombustible cloth ia 
 
 sometimes made. 
 Ashler. A name given to free stone when squared, for building 
 
 purposes. 
 
 Assay. The process of determining the amount of metal in an ore 
 Atom. The ultimate particle of an clement, 
 
324 GLOSSARY. 
 
 Auriferous. Containing Gold. 
 
 Avalanche. A mass of ice, snow, or earth falling into a valley. 
 
 Asterolepis. A large fossil fish found in the Old Red Sandstone- 
 
 BACULITE. A many chambered shell resembling the Ammonite 
 
 unwound. 
 
 Barytes. A mineral so called from its great weight. 
 BassetL Outcrop of strata. 
 Bind. A miner's term for argillaceous Slate. 
 Blende. The Sulphuret of Zinc. 
 Bluff. A precipitous bank. 
 Botryoidal. Resembling a bunch of grapes. 
 Brachiopoda. A group of shell-bearing animals having two long 
 
 spiral arms which assist in locomotion and in procuring food- 
 Byssus. A tuft of hairs by which some shell fishes are attached 
 
 to rocks. 
 
 CALAMINE. Zinc ore the carbonate of Zinc. 
 
 Calc Sinter Calcareous deposits of Springs. 
 
 Calcine. To reduce to powder by heat ; to expel carbonic acid as in 
 
 burning lime. 
 
 Calp. An impure limestone of the palceozoic rocks. 
 Cannel-Coal. A hard bituminous coal burning with a clear flame 
 
 and sometimes used instead of candles. 
 Carapace. The upper shell of some reptiles. 
 Carse. A Scottish term applied to the flat lands in valleys. 
 Cataclysm. A deluge. 
 Cetacea. Whales ; vertebrated mammalia living in the water, but 
 
 not fishes. 
 
 Chalybeate. Water holding iron in solution. 
 
 Chert. A silicious mineral resembling flint, but of coarser texture, 
 Choke-damp. Carbonic acid in mines and wells. 
 Clunch. The hard beds of the lower chalk. 
 Coleoptera. Insects having hard wing cases ; beetles. 
 Conchoidal. Resembling a shell. 
 Conglomerate. A rock made up of rounded, water worn fragments 
 
 cemented together. 
 
GLOSSARY. 
 
 325 
 
 Coombe. - A dry valley. 
 
 Culm. An impure kind of coal. 
 
 Cumbrian. A name applied by Professor Sedgwick to a system of 
 
 of rocks observed in Cumberland, England, now merged in the 
 
 Cambrian or Silurian. 
 Cupriferous. Copper bearing. 
 
 DEBACLE. A great rush of waters, breaking down obstacles and 
 dispersing detritus. 
 
 Debris. Ruins or fragments ; detached from rocks, and accumu- 
 lating in masses. 
 
 Denudation. Removal, by water, of masses overlying rocks, leav- 
 ing them bare. 
 
 Dessicatwn. Drying up. 
 
 Detritus. Sand, gravel, clay, &c., worn off from rocks by water. 
 
 Dolerite. A variety of trap-rock. 
 
 ECHINUS. A marine radiate animal covered with spines called sea 
 
 urchin and sea egg. 
 Ecpyrosis. Destruction by fire. 
 Elytra. Wing-sheaths of beetles. 
 Epoch. A point in time from which a period is reckoned ; also used 
 
 as synonymous with period. 
 Equivalent. A term applied to strata in different regions, whose 
 
 origin was contemporaneous. 
 Erosion. Wearing away by water. 
 Exuvice. What is cast off; a name applied also to organic remains. 
 
 FALUNS. A French term applied to some tertiary strata, resembling 
 
 the English crag. 
 Facette. A little face. 
 Ferruginous. Containing iron. 
 Fiord. A deep, narrow inlet. 
 Fire Clay. A clay containing little alkali, and consequently very 
 
 difficult to fuse. 
 Fire damp. Carburetted hydrogen in mines ; mixed with air is 
 
 very explosive. 
 
 28 
 
326 GLOSSARY- 
 
 Fissile. Easily split. 
 
 Fluviatile. Belonging to a river. 
 
 Flux* A substance used to render minerals more fusible. 
 
 Fuller's Earth. A compact, friable variety of clay, used in cleans- 
 ing clotli. 
 
 Fulgurites. Vitrified sand-tubes which are supposed to have been 
 produced by the striking of lightning on the sand. 
 
 GARNET. A simple red mineral, frequently found in mica-slate. 
 Glacis. A gentle slope, less steep than a talus. 
 Grit. A coarse grained sandstone. 
 
 Gyrgonites. Seedvessels or fresh water plants found fossil, and 
 formerly supposed to be microscopic shells. 
 
 HABITAT. The district within which a species of plants or animals 
 
 is naturally confined. 
 
 Hade. The dip or inclination of a mineral vein. 
 Hamite. A hook-shaped shell of an extinct cephalapod. 
 Homalonotus. A smooth-backed trilobite. 
 Hyphersthene. A variety of the mineral pryoxene, allied to augite. 
 
 IMBRICATE. Laid over each other like scales. 
 Iridescent. Shining with rainbow colors. 
 
 Isomorphous. Having same crystalline form with different chemical 
 constitution. 
 
 KILLAS. A Cornish name for coarse slate. 
 
 LACUSTRINE. Belonging to a lake. 
 
 Leucite. A simple white mineral found in lava. 
 
 Lapilli. Globular volcanic ashes. 
 
 Laterite. Kock found in India, cut in the form of bricks and used 
 
 for the same purpose. 
 Lithological. Pertaining to stones. 
 
 Lithodomi. Shellfishes that perforate and inhabit rocks. 
 Lithophytes. Stone plants ; sometimes applied to corals. 
 Lithographic Stone. A slaty limestone used for drawing and 
 
 printing upon. 
 Littoral. Belonging to the shore. 
 
GLOSSARY. .'.. 327 
 
 Loess. A. tertiary deposit on the banks of the Rhine. 
 
 MARSUPIAL. Animals which carry their young in a pouch as the 
 
 Opossum and Kangaroo. 
 
 Mesotype. A mineral of the Zeolite family often found in traprocks. 
 Molasse. A soft sandstone of the meiocene period found in the 
 
 great valley of Switzerland. 
 Moraines. A Swiss term for the debris brought into the valley by 
 
 glaciers. 
 Moya. A term applied in South America to mud poured out 
 
 from volcanoes. 
 
 NEACOMIAN. A group of rocks in the cretaceous system. 
 
 Nodule. A rounded mass. 
 
 Nucleus. A kernel, or point about which matter accumulates. 
 
 OCHRE. A yellow powder of earth and oxide of iron. 
 
 Oaplized- Wood. Wood petrified with Silica. 
 
 Ornithorhynchus. A genus of quadruped animals having the mouth 
 
 like that of birds. 
 
 Ophite. A rock similar to serpentine. 
 
 Olivine. A simple, olive colored mineral found in basalt and lava. 
 Oryctology. A term formerly applied to the science of organic 
 
 remains. 
 
 Osteology. The science which treats of bones. 
 Outlier. A portion of a stratum detached from the principal mass. 
 
 PACHYDERMATA. An order of quadrupeds having thick skins, as 
 
 the Elephant, Horse, Pig. &c. 
 Pegmatite. A granite in which the three component minerals form 
 
 distinct masses cemented together. 
 Pelagic. Belonging to the deep sea. 
 Phonolite. Clinkstone. 
 Phryganea. A genus of insects, whose larves, called worms, have 
 
 been found fossil. 
 
 Pipe Clay. A plastic clay used in making pipes. 
 Pisolite. A stone possessing a structure like an agglutination 
 
 of peas. 
 
328 GLOSSARY. 
 
 Pit Coal. Ordinary coal ; so called because obtained from pita. 
 
 Plateau. A plain considerably elevated above the sea. 
 
 Puddingstone. Coarse conglomerate. 
 
 Pcecilitic. Variegated ; name given in England to a part of the 
 new red sandstone series. 
 
 Pyrites. A compound of sulphur and a metal so called because 
 the chemical changes produce spontaneous heat ; it is often mis- 
 taken for gold. 
 
 Polythalamous. Many chambered. 
 
 Protozoic. Exhibiting first forms of life. 
 
 Pryrogenous. Igneous ; applied to melted rocks. 
 
 Pryroxene. A species of mineral including several varieties, 
 augile, hypersthene, &c. of silicates of lime, magnesia, and 
 iron. 
 
 QUADRTJMANA. Four handed animals, as the apes. 
 
 RAG. A stone of coarse texture. 
 
 Rake-vein. A group of vertical veins. 
 
 Rubble. A term applied by quarrymen to the fragmentary masses 
 
 of stone surmounting the beds. 
 Ruminantia. A group of quadrupeds including those which chew 
 
 the cud as the ox. 
 
 SACCHAROID. Having the texture of loaf sugar. 
 
 Salifcrous. Salt bearing ; the new red sandstone called the salife- 
 
 rous system because it contains salt. 
 
 Salses. Eruptions of mud from small orifices in volcanic districts. 
 Savannahs. Low plains in North America, generally covered with 
 
 wood. 
 
 Scaglia. An Italian rock of the cretaceous period. 
 Scarped. Having a steep face. 
 Schist. A slate not admitting of such perfect splitting as do the 
 
 slates generally. 
 Seam. A thin bed. 
 
 Selenite. Crystallized sulphate of lime. 
 Silvas. The wooded plains of South America. 
 Sinter. A rock precipitated from water. 
 
GLOSSARY. 329 
 
 Slickensides. The smooth face of a fault ; also one of the Derby- 
 shire lead ores. 
 
 Slide. Miners name for a small fault. 
 
 Spar. A crystallized mineral which gives a ready fracture. 
 
 Stanniferous. Tin bearing. 
 
 Stoss. A Swedish term applied to the side of a rock struck or 
 worn by the drift. 
 
 Suturbrand. A variety of wood-coal or lignite. 
 
 TABLE-LAND. Level land elevated above the seas. 
 Testacea. Molluscous animals having a shelly covering. 
 Turbinated. Shells which have a spiral or screw-form structure. 
 Turrilite. An extinct genus of chambered shells, allied to the Am- 
 monite having the siphuncle near the dorsal margin. 
 
 UNDERLIE. The inclination of a mineral vein. 
 
 WACKE. A German term which has been applied to a soft earthy 
 variety of basalt ; it has been used quite indefinitely. 
 
 Warp. The deposit from muddy waters artificially introduced into 
 lowlands. 
 
 Watershed. The line between two river basins ; it is not always a 
 mountain chain. 
 
 Whinstone. An English provincial term applied to some trap rocks 
 
 ZEOLITE. A family of simple minerals including several varieties 
 usually found in the traps or volcanic rocks; the name is 
 derived from their boiling up when they are exposed to the 
 heat of the blowpipe. 
 
 ', 
 
 28' 
 
ALPHABETICAL INDEX. 
 
 PAGE. PAGE. 
 
 AMPOCIRE, HOlBitumen, 110 
 
 Africa, 305 Bone caverns, 232 
 
 Agassiz, 127 Bore, 33 
 
 Agricultural, 275 Boston harbor, 32 
 
 Age of Rocks, 99 Bowlders, 224 
 
 Alluvium, 240 Breccia, 270 
 
 Alps, curved strata, 90Burnet's theory, 285 
 
 Alumina 11 
 
 Amazon River, 23CALAMITE, 166 
 
 America, geology, 310 Cambrian, 150 
 
 American Volcanoes, 46 Carbon, 11 
 
 Ammonite, 185 Carbonate of lime, 13 
 
 Amygdaloid, 132 Carboniferous, 162 
 
 Animalcules, 72 Caverns, 228 
 
 Animal remains, 246 Caves, 249 
 
 Animals, number of, 75 Cephalaspis, 159 
 
 Anticlinal axis, 90 Cephalopoda, 124 
 
 Antimony, 266 Ceylon, 300 
 
 Anthracite, 149 Chalk, 198 
 
 Anoplotherium, 210 Cheirotherium, 180 
 
 Apiocrinite, 190Chelonia, 180 
 
 Apteryx, 247 Chemistry, 10 
 
 Aqueous agency, 16 Chimborazo, 251 
 
 Araucaria, 171 China, 300 
 
 Arctic current, 37 Chlorine, 11 
 
 Arenaceous, 87 Clay, 272 
 
 Argillaceous, , 87 Clay-slate, 98 
 
 Arsenic, 266 Cleavage, 98 
 
 Artesian well, 6 Clinometer 89 
 
 Articulata, 124 Coal, 266 
 
 Asia, 298 Cobalt, 266 
 
 Astrea, 65 Coccosteus, 161 
 
 Atmosphere, 11 Conformable, 92 
 
 Atolls, 69 Conglomerate, 270 
 
 Augite, 12 Coniferae, 121 
 
 Augitic lava, 54 Copper, 265 
 
 Auvergne, 221 Coprolites, 127 
 
 Aymestry limestone, 151 Coral, 67 
 
 Coral reeft, 68, 247 
 
 BACILLARIA, 200 Cornbrash, 190 
 
 Basilosaurus, 238 Cosmogony, 262 
 
 Basins, 165 Crag, 216 
 
 Beaches, raised, 240 Cretaceous, 197 
 
 Beds, 82 Crinoidea, 164 
 
 Belemnite, 185 Cross courses, 266 
 
 Birds fossil 238 Crustacea, 125 
 
 Bird tracks^ 108 Currents, 84 
 
 Bismuth, ; 266 Cuttle fish, 186 
 
INDEX. 
 
 331 
 
 PAGE. PAG*. 
 
 Cuvier, 123 GALENA,- 261 
 
 Galenreuth, 231 
 
 DATS OP CREATION, 294 Ganges, .....'. 22 
 
 Deltas, 20 Gangue, 131 
 
 Deluge, 297 Ganoid, 125 
 
 Devonian, 157 
 
 Diamond, 
 
 Dikes, 94Genus, 
 
 Diluvium, 223 Germany, 
 
 Dinornis, 239 Geysers, 
 
 Dinotherium, 215 Giant's Causeway, 
 
 Diorite, 132 Glaciers, 
 
 Gasteropoda, 124 
 
 Gault, 198 
 
 114 
 302 
 58 
 135 
 25 
 
 Dip,.... 89 Glacial theory, 255 
 
 Dodo, 247 Glyptodon, 220 
 
 Dolomite, 174 Goniatite, 164 
 
 Drift, 223, 253 Gneiss, 145 
 
 Drift-wood, 63, 244 Gold, 265 
 
 Drongs 32 Gorge, 93 
 
 Dunes, 15 Granite 129, 269 
 
 Graptolite, 156 
 
 EARTH, a planet, 2 Graphite, 149 
 
 form, 3, 257Greensand 198 
 
 crust, 8 jGreenstone, 131 
 
 density, 3 Gres bigarre, 176 
 
 temperature, 4Greywacke, 150 
 
 Earthquakes, 54 Guadaloupe, 79 
 
 Elements, 10 Gulf stream, 36 
 
 Elephant, 235 Gypsum, 271 
 
 Elevation, 254 
 
 Elk fossil, 237 HERCULANEUM, 44 
 
 Eocene...... 206 Ileterocercal, 159 
 
 Encrinites,, 177 Hindostan, 299 
 
 England, 301 Holoptychius, 161 
 
 English channel 31 Homocercal, 159 
 
 Eruption, volcanic, 40 Hornblende, 12 
 
 Escarpment, 91 Hornblende slate, 146 
 
 Estuary deposits, 113 Hornitos, 48 
 
 Etna, 4GHysenas, 230 
 
 Europe, 301 Hydraulic lime, 273 
 
 Extinct Volcanoes, 39 Hydrogen, 11 
 
 Hyheosaurus, 195 
 
 FAULT, 93 Hypogene, 103 
 
 Fauna, 75 Hypothesis, 252 
 
 Favosite, 161 
 
 Feldspar, 12 ICEBERGS, 28 
 
 Ferns, 1C8 Iceberg theory, 253 
 
 Fingal's Cave, 137 Icthyodoru lite, 186 
 
 Fishes, 126 Icthyolites, 158 
 
 Flints, 198 Icthyosaurus, 187 
 
 Floetz, 103 Igneous agency, 39 
 
 Flora, 75 Igneous rocks, 96 
 
 Fluorine, 11 Iguanodon, 196 
 
 Flustra, 66 India, 299 
 
 Footmarks, 108 Infusoria, 72, 200 
 
 Foraminifera, 199 Insects, fossil, 212 
 
 Forests submarine, 62, 241 Ireland, 302 
 
 Formation, 92 Iron, 12, 266 
 
 Fossiliferous, 93 Iron pyrites, 13 
 
 Fossils, 100, 107 Isothermal, 4 
 
 France, 302 Italy, 303 
 
 Frost, . 16 
 
 FucoidB, 151 
 
 Fuller's Earth, 272 Joints,.... 
 
 JET, 
 
 122 
 
 149 
 
332 
 
 INDEX. 
 
 PAGE. p AGI! . 
 
 Jorullo, 47 NATURAL BRIDGE 260 
 
 Jura, 189 Nautilus, 185 
 
 Neptunian, 285 
 
 Kaolin, 272 Neuropteris, 168 
 
 Keuper, 176 New red sandstone, 174 
 
 Kiama, 139 Niagara, 17 
 
 Kilauea, 49 Nitrogen, 11 
 
 Kimmeridge, 189 Nubia, 305 
 
 Nummulite, 199 
 
 LABYRINTHODON, 181 
 
 Lacustrine, 242 OASIS, 306 
 
 Lagoon, 69 Obsidian, 54, 141 
 
 Lam imp, 82 Ocean, 29 
 
 Landslides, 24 Old red sandstone,....!..!!!!.!!.!.!..!!!.! 157 
 
 Land, reproduced, 39 Oolite, , ,.. 189 
 
 Lavas, 53, 141, 269 Ophidia, 180 
 
 Lead, 262 Order, 114 
 
 Lehman, 102 Ore, 131 
 
 Leibnitz, 102 Organic remains, 62, 74 
 
 Lepidodendron, 169 Ornithicnites, 182 
 
 Lias, 184 Orthoceratite, 155 
 
 Lignite, 217 Ossiferous caverns, 232 
 
 Lily encrinite, 177 Osteolepis, 161 
 
 Llanos, 307 Outcrop, 91 
 
 Loam, 277 
 
 Lodes, 
 
 Lophiodon 21 
 
 Lycopodiaceae, 
 
 MADREPORE, 
 
 Magnesia, 
 
 Magnesian limestone, 
 
 Mammalia, 
 
 Mammoth, 
 
 Man, 
 
 Manganese, 
 
 Marine currents, 
 
 Marine plants, 
 
 erslaugh, 23 
 
 c, fossil, 211 
 
 rford clay, 189 
 
 Mastodon, 
 
 Meandrina, 
 
 Megalonyx, 
 
 Megalosaurus, 
 
 Megatherium, 
 
 Mercury, 
 
 Metaliferous veins, 
 
 Metalization, 
 
 Mica, 
 
 Mka Blatei'.. 
 
 Mineralogy, 
 
 Mining, 
 
 Mississippi, 
 
 Molasse, 
 
 Mollusca, 
 
 Monad, 
 
 Monocotyledonous, 
 
 Monkey, 
 
 Moon,.. 
 
 Mosasaurus, 
 
 Mountains 
 
 Multilocular, 
 
 Muschelkalk,.. 
 
 Mylodon, 
 
 .. 169iOxygen, 10 
 
 .. 66 PALEONTOLOGY, 106 
 
 .. 11 Palaeotherium, 210 
 
 .. 174|Palaeozoic, 150 
 
 .. 120 Pampas, 242 
 
 .. 233|Peat, 62, 245 
 
 8, 248 Pele's hair, 54 
 
 2, 266 Pentacrinite, ; . 164 
 
 .. 34!Peperino, 142 
 
 .. 62lPermian, 173 
 
 .. 243Persia, 300 
 
 .. 233 Petrifaction, 108 
 
 .. 65Petroleum, 173 
 
 .. 219 Phaenogamous, 119 
 
 .. 191 Phascolotherium, 192 
 
 .. 218 Phosphorus, 11 
 
 ... 265'Physical Geography, 1 
 
 .. 131 Physical Geology, 252 
 
 .. Ill Pitchstone, 141 
 
 .. 12Placoid, 125 
 
 .. 146 Plants 75 
 
 12 Platinum, ~ 265 
 
 265 Pleiocene, 216 
 
 20 Pleistocene, 217 
 
 213 Plesiosaurus, 188 
 
 124 Plication, 260 
 
 117 Plumbago, 149 
 
 119 Po, 22 
 
 212 Polyps, 64 
 
 263 Pompeii, 44 
 
 202 Popocatapetl, 48 
 
 260 Porphyry, 130, 269 
 
 124 Portland bed,.... 196 
 
 176 Potassium, 11 
 
 218 Pozzuolana, 142 
 
INDEX. 
 
 333 
 
 PAGE. 
 Prairies, .77. 24 
 
 Precious stones, 26 
 
 Primary,.. 
 Producta, 
 
 ..144 Sodium,. 
 "5 Soil,. 
 
 Protozoic, 127 Solftitaras, 
 
 Pterichthys, 16( 
 
 Pterodactyle, 19 
 
 Pumice, 
 
 QUAQUAVERSAL,. 
 
 Quartz, 12, 14 
 
 Quaternary, 22 
 
 Quicklime, 27 
 
 54, 141 Springs, 58, 257 
 
 Stalactites, 17 
 
 Stalagmites, 17 
 
 Steatite, 271 
 
 Steppes, 242 
 
 Stigmaria, v 170 
 
 Stonesfield slate, 19J 
 
 RADIATA, 123 Strabo, 2S4 
 
 Stratum, 82 
 
 Striae of glaciers, 27 
 
 Irift, 226 
 
 Red snow, 7 
 
 Religion, 28f 
 
 Reptiles, 126, 18C 
 
 Rhine, 22 Submarine forests, 
 
 Rhinoceros, 23( 
 
 Rhone, 21 Sulphur, . 
 
 Rhynchosaurus, 18< 
 
 Ridge roads, 243 
 
 Ripple marks, 83 
 
 Rivers, 17 
 
 Rock, 
 
 Rocks, classified,.... 
 
 Rocks, melted, 258 
 
 Rock salt, 183 
 
 Roe stone, 189 
 
 Roman cement, 274 Talcose slate,.. 
 
 Russia, 299 
 
 SALT, 183, 271 
 
 Sand, 272 
 
 Sandstone, 157, 269 
 
 Sandwich Islands, 52 
 
 Saurians, 180 
 
 Scelidotherium, 219 
 
 Scoria, ... 
 
 141 
 
 Scotland, 302 
 
 Scorpion, 164 
 
 Seals, 78 
 
 Secondary rocks, 176 
 
 Septaria, 85 
 
 Serpentine, 133, 147 
 
 Shale, 148 
 
 Shell beds, 74 
 
 Shell limestone, 246 
 
 Shingle, 38 
 
 Shoaling, 241 
 
 PAGE. 
 
 Slates, 271 
 
 Snow, colored, 73 
 
 Species, 114 
 
 Spirifer, 155 
 
 Strike, 
 
 Subsoil, 279 
 
 ... 11 
 
 Sulphate of lime, ........................... 13 
 
 "umbawa, .................................... 41 
 
 Superposition, ......... .. .................... 87 
 
 urtsheller, .................................. 42 
 
 u 
 
 eys, 
 
 Synclinal, 
 
 'alus,. 
 
 Tartary, 
 
 "'eleosaur us, , 
 
 'emperature, 
 
 ""duple at Serapis, .. 
 
 287 
 13!) 
 90 
 
 13 
 
 U7 
 
 191 
 
 4 
 . . ) 
 
 Theory, 252 
 
 n erebratula, 155 
 
 'erraces, 228 
 
 ertiary, 204 
 
 ides, 33 
 
 ilestone, 151 
 
 oadstone, 172 
 
 ourmaline, 13 
 
 ortoise, fossil, 214 
 
 oxodon, 216 
 
 "rachyte, 54, 132 
 
 racks, 108 
 
 150 
 
 ransition rocks,, 
 
 rap, 
 
 rave 
 
 ree-fern,. 
 
 Siberia, 299 
 
 Sigillaria, 169 Trias, 
 
 Silicious deposits, 24Trigonia, 
 
 Silicon, 11 Trilobite, 
 
 gilt, 20 Tufa 
 
 Silurian, 1511 
 
 Silver, 265!UNCONFORMABL,.. 
 
 Sinter, 2i|Unity of plan, ..., 
 
 Siphuncle, 185 United States, 
 
 Sivatherium, 216 
 
 Skaptaa Jokul, 41 VALLEYS, 
 
 131, 269 
 
 ravertin, 17, 243 
 
 167 
 
 176 
 
 191 
 
 153 
 
 17 
 
834 
 
 ^9 
 
 INDEX. 
 
 
 PAGE. PAOI. 
 
 114 Womor . . . 9JU5 
 
 Veins, 
 
 94, 261 
 
 
 . 238 
 
 Yertebruta, 
 
 ; 125 
 
 Whitsunday, 
 
 . 69 
 
 
 52 
 
 \Vi n( j S) 
 
 . 15 
 
 
 39 256 
 
 Xanthidium 
 
 200 
 
 
 52 
 
 tertiary, 
 WATEB . . 
 
 221 
 
 8 
 
 Xiphodon. 
 Zechstein, . 
 
 . 21J 
 
 174 
 238 
 . 265 
 
 Wave<* 
 
 29 
 
 
 Wealden, 
 
 194 
 
 Zinc, 
 
 Wenlock, 
 
 152 
 
 
 . 64 
 
 
 , 
 
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 One volume, 12mo., cloth, $1 00. 
 
 The work is designed to be strictly elementary, and presents the leading facts of the Science 
 In a popular and attractive form. 
 
 5 
 
a. P. PUTNAM'S NEW PUBLICATIONS. 
 
 Alban : A Tale of the New World. 
 
 By the Author of " LADY ALICE." 
 
 "Lady Alicejs decidedly a work of genius. Indeed, we know of few fictions where this first 
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 6 
 
 
G/P. PUTNAM'S NEW PUBLICATIONS. 
 
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 7 
 
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