= ii 8 808/8Z10 19/1 € wane oe, 1 ten, Pee. ey aaa Alga apd El Kc hahaa Oe Kev AC ate eoerepajtats ete etry lhe kididghils ded a, 4 . ri Pi “ a a i i Beene tet is ann «cs ees aL PAP Pin tah same © EERLM, Wha Arwread ene tee a ST Oke. a en ee Presented to Cbe Library of the University of Toronto bp rs itesenr on Dare. BY THOMAS STERRY HUNT, LLD., Fellow of the Royal Society of London ; Member of the National Academy of Sciences of the United States, the Imperial Leopoldo-Carolinian Academy, the American Philosophical Society, the American Academy of Sciences, the Geological Societies of France and Belgium and of Ireland ; Officer of the Order of the Legion of Honor, . etc,, etc., etc. BOSTON: JAMES R. OSGOOD AND COMPANY, Late Ticknor & Freips, AnD Freips, Oseoop, & Qo. 1875. REA om fans as % fs ibs ae Niel tae fe. RY 8 | oe a ee ee Ener a ee eee a ee ewe 1874, ig i .s 5: E TO JAMES HALL, IN RECOGNITION OF MANY YEARS OF FRIENDSHIP, This Polume is Dedicated BY THE AUTHOR. a eR Digitized by the Internet | Archive in 2007 with funding from Microsoft Corporation PREFACE. —— In choosing from a large number the following papers for tepublication, it may be well to state the considerations which have guided the author in his selection. His researches and his conclusions as to the chemistry of the air, the waters, and’ the earth in past and present times, the origin of limestones, dolomites, and gypsums, of mineral waters, petroleum, and me- talliferous deposits, the generation of silicated minerals, the theory of mechanical and chemical sediments, and the origin of crystalline rocks and vein-stones, including erupted rocks and volcanic products, cover nearly all the more important points in chemical geology. They have, moreover, been by him con- nected with the hypothesis of a cooling globe, and with certain views of geological dynamics, making together a complete scheme of chemical and physical geology, the outlines of which will be found embodied in essays I.—XIII. of the present collection. It was at one time proposed to rewrite for this volume the first seven of these, giving them a more connected , form, and thereby avoiding some little repetition; but it is thought better to reproduce them in the shape in which they originally appeared, and this chiefly for the reason that they seem to the author to have a certain historic value, and serve to fix the dates of the origin and development of views, some of which, after meeting for a time with neglect or with active vi PREFACE. opposition, are now beginning to find favor in the eyes of the scientific world. That such will be the ultimate fate of others herein contained, and not yet generally received, the author is persuaded. It has been his fortune to enunciate, in very many cases, views for which his fellow-workers were not pre- pared, and after a lapse of years to find these views propounded by others as new discoveries or original conclusions. Natu- rally desirous, however, of vindicating his claims to priority in certain of these matters, he feels that the best way of attain- ing this result is to reprint the original essays. It should be said that two of these, namely, IV. and XII., were given as popular lectures, and are thus unlike the others in method and style. The reproduction of the papers on the Geology of the Alps and the History of Cambrian and Silurian requires, it is con- ceived, no explanation, inasmuch as, apart from their general interest, they serve to throw great light upon many questions raised in the essay on the Geognosy of the Appalachians as to the origin and age of their rocky strata. As regards the five papers which are placed at the end of the volume, the author reprints them for the reason that, incom- plete and fragmentary as they are, they have a certain value in the history of chemical theory; and, moreover, contain, in his opinion, the germs of a philosophy of chemistry and miner- alogy which he hopes one day to develop himself or to see developed by others. In preparing this collection for the press, the author has been compelled by the limits assigned to the volume to omit several papers which would else have found a place here, and to abridge others. In some cases, paragraphs have been rewritten and additions made, which are distinguished by being placed in brackets. Explanatory notes are given, and introductory and } a" meh te e / nn ys ai: + al ' 7 a as J ‘2 ei. x ae Ne " i Yaee ty « >, ‘ NG . , As > J Pi '¥ 3 ; 7 Ue 5 be on R ; F ‘ 7, ee ” * 4 iw ; ig ¢ i in this volume and to many which have been omitted. Read _ with these aids, and with the help of the table of contents and _ index, this volume will, it is believed, suffice to give clear and connected notions of the author's views on the various questions a | | T. S. H, Boston, Mass., September, 1874. Fi ies ly { ‘. "historical sketches prefixed, with references both to other papers. = ee se - Ciba 2 mt Oo ge eye, an ta SS ee be” eo > pe , i oan TABLE OF CONTENTS. ee | ee eee L THEORY OF IGNEOUS ROCKS AND VOLCANOES (1858). PAGE The chemistry of a cooling incandescent globe. » + « «© « The primitive ocean and primitive crystalline rock. : ‘ Origin of eruptive rocks; views of Bunsen, Phillips, and Daroaker. BF Softening of crystalline stratified rocks . : : : . ° Poulett Scrope and Scheerer on aqueo-igneous fusion : . tyilnilf ta Daubrée and the author on the origin of mineral silicates. : ° Views as to the condition of the earth’s interior ° ° Aen ie gee 4, Existence of a solid anhydrous nucleus maintained . ‘ : ; 2 Intervention of sedimentary rocks in volcanic phenomena : . . ‘ Origin of the volatile products of volcanoes . .« « «. omg Sir J. F. W. Herschel on the cause of volcanic action . ‘ Brats Its relation to recent sedimentary deposits . . ° . . Fi _ Note on the decomposition of crystalline rocks . ° . : ‘ , Note on the deposition of clays . . . Bt hae Ree a cocouvnmaoanrntoanrr OD ee II. ON SOME POINTS IN CHEMICAL GEOLOGY (1859). Ancient and modern sea-waters compared , : : ° . ny eh Origin and geological importance of alkaline carbonates. ° . 12 Different relations of potash and soda ‘ . ‘ A ° F ¢. Deposits of iron-oxide as evidences of organic life Teer. ee 13 Deposits of alumina; emery and bauxite; their origin . r ‘ «, BB Supposed aqueous origin of basic and acidic eruptive rocks apis 14 Babbage and Herschel on the effects of internal heat A : - 16 Theory of volcanic and plutonic phenomena. . . «© «+ 15 Note on the views of Keferstein . - ‘ “ a ‘ 4 ce ae Geological distribution of volcanoes . aa a IIT. THE CHEMISTRY. OF METAMORPHIC ROCKS (1868). Preface; objections to the name of metamorphic rocks . - 18 Probable relations between the age and constitution of crystalline rocks 19 Sub-aerial and sub-aqueous decay of feldspars , ° . extol « 20 VN ge ee oe hid re e are La oe Pe a) te x 3 TABLE OF CONTENTS. Chemistry of alkaline natural waters . . eae Relations of the soil to potash*salts and phosphates o Sa ihe eee Origin of insoluble metallic sulphides . - a JOR Deoxidation of metals, sulphur, and carbon through vegetation . Twofold origin of carbonates of lime and magnesia . . . . The two types of igneous rocks; their sedimentary origin Rock-metamorphism defined and distinguished from pseudomorphism Relation of alkaline waters to crystalline silicates ° - Local metamorphism; views of Daubrée and Naumann . . = , Progressive change in silico-aluminous sediments Chemical relations of certain mineral silicates . . . . . Various series of crystalline stratified rocks . . Laurentian, Labrador, Green Mountain, and White Meunsaiaa series . The hypothetical granitic substratum; granitic veins . . . Crystalline rocks of Europe and North America compared . . IV. THE CHEMISTRY OF THE PRIMEVAL EARTH (1867). The spectroscope and the nebular hypothesis . . . . . Dissociation defined; terrestrial chemical elements . < Probable existence of more elemental forms of matter in the staré . Chemical and physical constitution ofthesun . . . . . Chemical history of the cooling earth oe eee: ° oa) el ae ete Probable solidification from the centre . 555 Serene 2 eae Primitive atmosphere and ocean; theircomposition. . . . Their action on the primitive crust ‘ ae Mutual relations of carbonic acid, clay, ltmeatonin, sid. son-salt . Waters of the ancient ocean . =. +) o's) ee es Carbonic acid of the ancient atmosphere . . » « «+ « Its relations to life and to climate . : a ete ee fae Formation of gypsums and magnesian limestories Aiea Na th Secondary and aqueous origin of granites . . +. «+ «+ -« Action of internal heat; voleanoes . . . Hopkins, Pratt, and Sir William Thomson on the earth’ s inteidor Controversies of the neptunists and plutonists . CR ihe APPENDIX. The earth’s climate in former ages . oe Tyndall on the relation of gases and vapors to radiant heat PL Former predominance of carbonic acid inthe air . . ‘ Note on the amount of carbonic acid now fixed in Hmmestones oe V. THE ORIGIN OF MOUNTAINS (1861). Hall on palsozoic sediments in eastern North America . «. . Eastern origin of these mechanical sediments ot tn eby . [ee eee SERESEBEESESESAee Ss a TABLE OF CONTENTS. Varying thickness of paleozoic strata . . eral ok Va : . Relation of mountains to sedimentation . ° : ° ° ‘ Continental as opposed to local elevation . ° . . : : : Views of Buffon, Montlosier, and Constant-Prevost : . ° ‘ Views of Humboldt, Von Buch, and Elie de Beaumont . ° é ° Lesley on the topography of mountains. . Me) eee Oe Relations of mountains to synclinals and to erosion . : Ps . . Hall’s views of the origin of mountains . é 7 - : é ; Relations of subsidence to foldings of strata . . a Condensation consequent on the crystallizing of sadinnets ‘ ‘ : The hypothesis of a solid contracting nucleus maintained ° F é Relation of this nucleus to water-impregnated sediments . . ° The softening of these produces lines of weakness inthecrust... . Relation of this process to corrugations . - ‘ z Relations of volcanic and plutonic phenomena to sedimeatadion er WE. THE PROBABLE SEAT OF VOLCANIC ACTION (1869). Discussion of the views of Hopkins and Scrope on volcanoes . . . Views of Lemery and Breislak, of Davy and Daubeny of eg athe Views of Keferstein and Sir J. F.W. Herschel. . . «© «© . Exposition of the author’s view . 8s § 2. «6 “8 6 > Disintegration of the primitive crust . é : . sts ° Hopkins on internal heat and its increase in descending 6 ai Re ty Sorby on the relations of heat and pressure to fusion and solution . Chemical differences in eruptive rocks . . ‘ ° ° oe APPENDIX. Geographical distribution of modern volcanoes en é Distribution of ancient eruptive rocks; their geological relations aft 2 VII. ON SOME POINTS IN DYNAMICAL GEOLOGY (1858). LeConte on the reconstruction of geological theory - + + + + His views compared with those of the author : . Hall’s theory of mountains; the criticisms of Dana, Whitney, and ‘LeConte Views of Hall and the author misunderstood : : . : . LeConte’s theory of mountains considered . ° re NEAR aime id Sa Continental elevation and erosion; Montlosier and Jukes . : . Hall on some North American mountains . é = ‘ < : : Origin and structure of the Appalachians . ‘ ‘ * ° . Their crystalline strata not palzozoic but eozic ° . . ° . Evidences of an eastern pre palseozoic continent . . Aagl Fa ° Dry climate of eastern North America in palzeozoic times Cea ig : Oscillations of continents; their cause . ‘ : ; e ° ° ee Ee ara, ae eee gicah so ee ee xii TABLE OF CONTENTS. Source of heat in plutonic phenomena. . +» « «© «6 The notion of its chemical origin untenable . . . «+ «+ Henry Wurtz on a mechanical source ofheatw. » ». « «+ Experiments and conclusions of Mallet. . ~.« «. «+ .« His views on the origin of volcanic products . . «. + « VII. ON LIMESTONES, DOLOMITES, AND GYPSUMS (1858 - 1866). Introductory note; letter to Eliede Beaumont. . . . . Cordier’s views of the origin of limestones and dolomites . Their identity with those ofthe author . . . . « -« Chemistry of evaporating lakes and sea-basins .. . . - Alkaline waters of rivers and springs . : Separation of lime-salts from sea-water; avpenin isd rook-salt : Origin of sulphuretted hydrogen and native sulphur pi i. See Fa Origin of deposits of magnesian limestones - . «© «© « Their deposition necessarily in isolated basins. . . «. « Hall on the organic remains in magnesian limestones . «. .« Deposits of pure carbonate oflime . . «+« «+. « « -« Generation of dolomite; its crystallization . ° : ° ° Note on chemically deposited silica. ee Conclusions as to the. chemistry of gypsum and dolomite bah Conditions of temperature for the production of dolomite. . . Relative solubilities of gypsum and magnesian bicarbonate’ . Influence of carbonic acid on the formation of gypsum. Geographical and climatic conditions for the production of dolomite Recent conclusions of Ramsay as to magnesian limestones . . IX. THE CHEMISTRY OF NATURAL WATERS. Part I. — GENERAL PRINCIPLES. Atmospheric waters and the result of vegetable decay. . « Action of waters on the soil; researches of Way and Voelcker é Eichhorn on the replacement of protoxide bases in silicates. . Possible relations of saline waters to the soil . ° eae Relations of organic matters to oxides of iron and manganese . Solution and deposition of alumina . ee Origin of sulphuretted hydrogen and sulphurets eee ee Ler Decomposition of silicates; studies of Ebelmann . . + « Kaolinization of feldspars and other minerals Sek ae ee Relation of soda and potash salts tosediments~ -. +. «+ -» Carbonic acid and water as agents in decomposing rocks . . Marine salts in solution in sedimentary strata . +. + «+ -» Porous nature of sandstones and dolomites .— . . Calculations as to the volume of waters held in rocky strata, a x Solid salts and bitterns from sea-water inthe rocks . . «+ BRESSSSSSLLSEARRSRVS SSS58aR ee e TABLE OF CONTENTS, Action of bicarbonate of soda on calcareous and magnesian salts. Origin of sulphates in natural waters. ; : wi . : Indifference of gypsum solutions to dolomite . : : : Decomposition of gypsum by hydrous magnesian Agebonate . . Results of the gradual evaporation of sea-water ‘ . : : Composition of the ancient seas. : . : ‘ ‘ . Separation of the lime salts from sa-suabiee ‘ Fa bia Decomposition of sulphate of magnesia by bigarboniaky of lime . ° Twofold origin of gypsum... ° ks ‘ ar Twofold origin of magnesian wisn. . . fo 2 '« ‘ : Sulphuric and hydrochloric acid in waters . eee Bod Tg - Carbonic acid in waters. 2 f . ~ a a ; Ammonia and nitrogen in rocks sad Water . : ° ° . Simasification of natural waters. . 2. eS lw Part IT.-— ANALYSES OF VARIOUS NATURAL WATERS. Waters of the first class or bitter salines; analyses . . - : Their resemblance to bitterns; absence of sulphates . : : : Predominance of chlorides of calcium and magnesium . . : Probable constitution of the Cambrian ocean : ong Ripe Fy Brines of ancient saliferous deposits . . . .« : aa Note on analyses of saline waters . apt Beas . . : Silicate of magnesia; its formation and chemical sehations ‘ .. Waters of the second and third classes; analyses... oF be Waters of the fourth class or alkaline waters; analyses . «. . Waters of the Ottawa River; analysis . ~. . «+ « « « Variations in the composition of mineral springs . . «. + Comparative analyses of the Caledonia waters . . « « -« Sulphuric-acid springs of New York and Ontario . . . . Neutral sulphated waters; their sources once bie NENeS ten Peake Sulphate of magnesia in waters ee eee ‘ i , Part IIJ.— CHEMICAL AND GEOLOGICAL CONSIDERATIONS. Salts of the alkaline metals in natural waters ¢ ‘ Salts of calcium and magnesium; relations of chlorides and Sacbodaten Results of evaporation; deposition of carbonates of lime and magnesia Solubility of carbonate and bicarbonate of lime ‘ we oe Supersaturated solutiens of carbonates of lime and magnesia grates Salts of barium and strontium in waters . : . . . Tron, manganese, alumina, and phosphates i in waters siiviat stays « Bromides and iodides in waters . ‘ : i . . ° Relations of chlorides and iodides to earthy minerals . ° . ° Sulphates in natural waters; their frequent absence 5 rae Soluble sulphides in natural waters . . « » © «© « Borates; waters of a borax-lake eels Ste as RY welt Cater ho Carbonates; studies of the Caledonia waters. . .«. « - : Waters with a deficiency of carbonic acid be Ms at waattoe Silica; its amount in various waters . . ‘ wees abary i Silicates of lime and rises a deposited from waters Bierbin's 134 135 140 141 142 151 xiv TABLE OF CONTENTS. Organic matters in water; their nature and origin a), Sgt PS eae Geological relations of mineral waters . . . «.« «© « Palsozoic formations of the St. Lawrence basin . . . «. . Relations of mineral waters to the various formations . . . . Contiguity of dissimilar mineral springs Soh ee eRe tt Temperatures of the mineral watersof Canada. . . . « « Results of the evaporation of these waters . . . « « « SUPPLEMENT. Waters with a predominance of chloride ofcalcium. . . . . Waters with soluble sulphides; mode ofanmalysis. . . «. .« APPENDIX. On the porosity of rocks and its significance . eel han Mode of determining the density and porosity of jocks ote, anes eae Table of the density and porosity of variousrocks . . . . . X. . ON PETROLEUM, ASPHALT, PYROSCHISTS, AND COAL. Geological relations of petroleum . . . .« « © « -« Origin and source of petroleum . o Gg te ee The oil-bearing limestone of Chicago; its anilysis eee ieee Large amount of petroleum contained in the limestone. . . Fe Bitumens; their analyses and chemical composition. .- +. «+. «s Wall on the bitumens of Trinidad and Venezuela. . +. « . Conversion of organic matters into coals and bitumen . . «© « Pyroschists or bituminous shales; their nature defined 5S gee Their geological and chemical relations . +. + «+. «+ « -« Chemical similarity of animal and vegetable tissues . - «+ - Note on the constitution and artificial eh tn ofalbuminoids . . Dawson on the origin of coal . PRE eo yy, | ete ree Comparative analyses of epidermal tissues ey Ny On the gaseous hydrocarbons foundin mature . . + «+ « XI. ON GRANITES AND GRANITIC VEIN-STONES (1871-1872). Granite and its varieties defined ANGE ar The relations of granite to gneiss - . a get Seed tae Stratiform structure in various erupted rocks MP Pear tree Me Feldspar-porphyries; their characters and distribution ba: eet ee Granitoid gneisses of New England; true granites . +. + «+ -« Granitic vein-stones; theories as to their origin - + + «+ «+ Views of Scheerer, Scrope, and Eliede Beaumont .- +. + «+ -«» The concretionary origin of granitic veins -. .- pe ett Granitic vein-stones of the White Mountain rocks described res Their banded structure; disturbance of the strataby veins. . .- TABLE OF CONTENTS. Evidences of the progressive formation of such veins er Rare minerals in the granitic vein-stones of New England . Geodes in granites in New Brunswick and Italy - . : Granitic veins distinguished from dikes . . ; ‘ ; Volger and Fournet on the filling of granite veins . . ° Recent age of some concretionary veins . ee nae ° . Note on the salt-wells of Goderich in Ontario .. oe ye On the conditions of the crystallization of quartz . ; aft i's On the emerald-bearing veins of New Grenada . . Recent production of crystalline zeolites ; . . . The Laurentian series; its lithological Ghaeactars:- ; ad Soy Vein-stones in the Laurentian rocks . 5 ‘ ‘ y These vein-stones compared with those of Beandinavia Bilge Minerals of the Laurentian vein-stones . . : . . . Note on the occurrence of leucite . ° ‘ . The concretionary character of these vein-stones — : . Incrustation and skeleton-crystals described . ° . . Crystals with rounded angles; their significance . “ ° . Feldspathic veins of the Laurentian rocks . a Nh ae bee Complex nature of the Laurentian vein-stones . . .. . Vein-stones with apatite and with graphite : ; ° Paragenesis of their mineral species. . . ° ot Concretionary copper-bearing veins of the Blue Ridge. . Supposed eruptive origin of crystalline limestones ye XII. THE ORIGIN OF METALLIFEROUS DEPOSITS. Preliminary statement of the theory of ore-deposits . . . Distribution and diffusion of the chemical elements . . . Separation and concentration of certain elements . ° . Note on the solvent powers of water . . a i Ye The terrestrial circulation compared with that of animela “ History of the diffusion and concentration of phosphates . . Potash and iodine; their elimination from sea-water 4 R Intervention of organic life in all these processes . ar, ° History of the diffusion and the concentration of iron ‘ . ’ Relation of iron-oxides to ancient vegetation. «=. R ‘ : Formation of iron-pyrites and other sulphides . : “ ° Diffusion of copper, silver, and lead in the ocean . R ‘ . Reduction of copper from its solutions < . ° : Ore-deposits in beds and in fissures ool eke . aaa a ie ow The process of deposition in veins. ‘ ° . : : Uniformity of operations in nature ee Lae Paver) Man ee APPENDIX. Sonstadt on the iodine in sea-water . seit hc Te On gold in the ocean; Sonstadt and Heary Wurtz ae th xV 198 200 201 202 - 202 203 - 204 205 205 205 206 208 209 210 210 211 211 212 214 215 216 216 217 218 220 221 + 222 223 224 225 226 226 227 229 230 231 232 233 234 235 237 237 xvi TABLE OF CONTENTS. XIII. THE GEOGNOSY OF THE APPALACHIANS AND THE ORIGIN OF CRYSTALLINE ROCKS. The relations of geology tothe sciences . . «.« «+ « « « 240 Part I. —TuE GEOGNOSY OF THE APPALACHIAN SYSTEM. History of the Appalachian mountainsystem . . . «. . 241 Eaton on the classification of rock-formations . ; ‘ A : - 241 Jackson and Rogers on the rocksof New England . . . . 242 . The Adirondack or Laurentide series; Laurentian . é . 5 - 248 The Green Mountain series; Huronian . A : ; . . r 243 The White Mountain series; Montalban . : ; : . 6 . 244 Rogers on the crystalline rocks of Pennsylvania. . . . . 245 His hypozoic and azoic series probably identical . . . .« . 247 Crystalline rocks of New York and New England oe) es er Crystalline rocks of Virginia, the Carolinas, and Tennessee . ; - 249 Emmons on the crystalline rocks of western New England . . ‘ 250 Note on the decay of these rocks tothe southwest . . . aa The Taconic rocks of Emmons distinguished from the primary . a The Taconic system described and defined : " = . 252 Views of Mather and Rogers on the Taconic rocks in ; . a Rogers and Safford on the primal rocks of Virginia and Tennessee : - 255 Relations of the Taconic to the Champlain division ‘ ‘ é 5 256 The organic remains of the Taconicrocks. . . . «. . « 267 The rocks of the so-called Quebec group E ; . : : 4 259 The Red sand-rock of western Vermont . ‘ ~ Z : - 260 Lower palzeozoic rocks of Labrador and Newfoundland : - aE Lower palzeozoic rocks in the Champlain and Mississippi valleys . « mee Note on the palzeozoic formations in the Rocky Mountains . . . 262 Stratigraphical breaks in the lower palwozoic series. . . - « 268 Continuation of the Taconic controversy . . . . «. « 264 The Upper and Lower Potsdam of Billings . . . .« « « 266 Lower paleozoic rocks of Europe . | 4 = Sn Identity of Taconic with Lower and Middle Cambrian 0 ONS The Huronian or Urschiefer distinct from Cambrian . .« «. «. 269 Crystalline schists of Anglesea andthe Rhine . . +. « « « 270 Crystalline rocks of the Scotch Highlands . -. -. «+ + «+ 2271. Comparative studies of crystalline formations . . ot, Crystalline schists of Lakes Huron and Superior. . « «+ «+ 274 The crystalline schists of the Appalachians, pre-Cambrian . . . 276 Credner on the Eozoic formations of North America . «© + « 277 History of the Norian or Labrador rocks . oy re ke Relations of the various crystalline formations . +. + + « 261 Hitchcock on the geology of the White Mountains . -. . .« « 282 Part II. — Tue Ortcrn or CRYSTALLINE Rocks. Mineralogy of the two classes of crystalline rocks one Me Theories of the source oferuptiverocks . . + + « «+ «» 284 TABLE OF CONTENTS. Mechanical disintegration and recomposition of rocks . . Crystalline silicated rocks of stratified formations . . . Two hypotheses to explain their origin . . ° . . Alleged pseudomorphous change of plutonic rocks . Sth The doctrine of pseudomorphism by alteration . ° : Symmetrical and asymmetrical envelopment of minerals . : Difficulties of the doctrine of pseudomorphous alteration . Scheerer’s doctrine of polymeric isomorphism . . ‘ : Delesse and Naumann on pseudomorphism . . . . Supposed plutonic origin of crystalline stratified rocks . . Views of Naumann and of Macfarlane on primary rocks Hypothesis of the aqueous origin of crystalline rocks : ° Generation of silicates in cases of local alteration. . : Aqueous deposition of feldspathic minerals Ce PEA . Alleged paleeozoic age of many crystalline schists ‘ ‘ The author’s view of their origin defined . ‘ : : Early views of the aqueous origin of crystalline rocks . Evidences of life at the time of their deposition . Evidences of life afforded by meteoric stones. ° Discovery of the Eozdon Canadense Silicates injecting this and various other engeniame Observations of Giimbel, Hoffmann, and Dawson . . . Credner and Giimbel on the origin of crystalline schists Giimbel on diagenesis and epigenesis . Note containing the views of Giimbel on this qusaticn ene ne Note on the crystalline aggregation of finely divided matter . Conditions of early times favoring diagenesis The origin and formation of dolomites . . ° . Influence of carbonic acid on the production of dolomite . Supposed generation of dolomite by Von Morlot and Marignac Two classes of dolomites; their origin . : ‘ Relations of one class of these to gypsum end rook-aalt : Former climate of eastern North America . ° : . Magnesian silicates of Syracuse, New York . . . Supposed organic origin of limestones . : ° ° 5 Their true relation to organic life . «. + ‘ ° é Relations of phosphates to organisms. . ° ¢ “ Phosphatic nature of Lingula, Orbicula, Conularia, etc. . . Relations of silica to organic life . . . ‘ P APPENDIX. Reply to Mr. Dana’s criticisms . . x P . The question of the transmutation of monies stated . . Warrington Smyth’s opinion of epigenesis : rihae d : The views of Delesse on pseudomorphism defined . . Delesse on the eruptive origin of serpentine : : : : He subsequently adopts the view of its aqueous origin . : A revolution in the theory of crystalline rocks . ar . Scheerer’s views explained and defended . . . . - 288 290 » 291 294 - 298 299 801 802 - 802 803 - 810 311 311 - 312 312 + 813 813 814 317 317 818 xv TABLE OF CONTENTS. Dana’s teachings as to psendomorphism . - «+. « « « « 819 He affirms the doctrine of epigenic metamorphism fe ne ee The old doctrine of diagenesis explained and defended . . . .« 821 The views of Naumannexamined . . Bo Ney kt A Various illustrations of the doctrine of transmutation See King and Rowney on the supposed transformations of serpentine - 825 Genth on the supposed alterations of corundum etonie 0 Vihar Dana and Emmons on the Taconic rocks . . . «+ « «+ 826 On the relations of the pre-Cambrian schists . . . « «+ « 827 XIV. THE GEOLOGY OF THE ALPS. The researches of Alphonse Favre . . «+ + «© « « « 628 The crystalline rocks of Mont Blanc . . + « « « « 829 The uncrystalline rocks aroundit . . ‘ bie Te. Association of carboniferous and liassic fossils . -. +. «+ « 882 Difficulties presented by folded and inverted strata. . . «. « 884 Sismonda on the anthracitic systemofthe Alps . .« «-« «.« . 884 Section presented by the Mont Cenis Tunnel - ~ «++ «© « 885 Age of the crystalline schists with anhydrites . . . os an Examples of inverted stratainthe Alps . . .« « «+ «+ « 83% On the supposed recent age of the crystalline schists . . . . 838 The recomposed crystalline rocks of the Alps . . «© «+ «+ « 889 The true crystalline schists of great antiquity . .-. . . « 841 Little or no evidence of metamorphism inthe Alps . . . « ~« 842 The fan-like structure of the Alpsexplained. . .« «© « «+ 848 Grand section across Chamonix and Mont Blanc 6. ee Se 8) Geological history of Mont Blanc . . .« .« .« «© «© « 844 APPENDIX. Antiquity of the crystalline schists of Mont Cenis . . «. « « 84 . Favre on the origin of crystalline schists . . . = in 848 De Beaumont and Pillet on the rocks of Mont Cenis Vaud ‘ ‘ é XV. HISTORY OF THE NAMES CAMBRIAN AND SILURIAN IN GEOLOGY. Part I.— Srtur1an AND Upper CAMBRIAN IN GREAT BRITAIN. The Graywacke formation of the older geologists. . + « «+ 850 Early studies of Sedgwick in North Wales ae eT eae es Early researches of Murchison in Wales en gee Pe eT Ge Cambrian as first defined by Sedgwick ~. ~. «6 + «+ « «© S52 Silurian as first defined by Murchison . ot yy een Examination of the Berwyns by Murchison and Sedgwick :. =e Identity of Cambrian and Lower Silurian fossils . . .»« «+ + 8655 — ee 7 ths TABLE OF CONTENTS. x1Xx *ublication of Murchison’s Silurian System . a ee ifficulty of distinguishing between Cambrian and Silurian Geeks 6 Sie Sedgwick’s views. and position misrepresented . . . «. . - 857 Errors of Murchison’s sections exposed . ‘ é : é : . 358 His Silurian system based upon a series of mistakes . ; ‘ ‘ 362 Sedgwick’s proposed compromise in nomenclature ‘ ‘ ‘ ‘ 363 Unauthorized alteration of Sedgwick’s geological map. bt He AO SA Further history of Sedgwick’s wrongs . ‘ ; ‘ - . ; 364 Part II.— MippLE AND LOWER CAMBRIAN. Ancient fossiliferous rocks of Scandinavia sets eis - 865 The early studies of Hisinger ; curious errors pints a % - 866 Section of the rocks of Kinnekulle . . .». « « «© . 367 : Angelin on the crustacea of Scandinavia... Wee Pet Sk ee 367 F Barrande on the fossiliferous rocks of Bohemia. . . . - 3868 “4 The so-called primordial Silurian . ; . 369 The fossils of the Lingula flags of Wales . ‘ : a8 tel ite te ED Fossiliferous rocks of the Malvern Hills : : . ‘ . ‘ 370 Subdivision of the Lingula flags ; the Menevian beds . ‘ : - 371 Fossils of Lower Cambrian or Harlech rocks . . é ; oe 372 True boundary between Cambrian and Silurian ah sits ‘ . Breaks in the succession of the lower rocks . : ‘ ‘ : : 375 Note on the Tremadoc rocks. ‘ oni : . . ‘ . 3875 Ramsay on stratigraphical breaks. x eit at Ceatgyd hs - 876 General considerations on breaks in geological series a Va on, Re Note on the thickness of British Cambrian and Silurian eae 8 WF Murchison and the Cambrian nomenclature . ’ : . ° - 878 He confounds the Longmynd and Bala groups. . 6H Dae ee The statements of his Siluria criticised . ‘ + ro eee Disagreement as to the Cambrian and Silurian eicneaicleitate . - 381 Distribution of Lower and Middle Cambrian rocks . - ‘ : . 882 Crystalline schists of Malvern and of Anglesea . - «. « « 883 Gold-bearing Lingula flags of North Wales , ‘ irs Hicks on the classification of lower paleozoic rocks . BR Cwichis 0 Se Sedgwick’s latest views on classification . . . ; ° : . 384 Tabular view of lower palxozoic rocks . ‘ . ‘ . . 386 oa ee ee ya i = s st + Seca et a aa eal Part III.— CAMBRIAN AND SrLuRIAN Rocks In NortTH AMERICA. The geological survey of New York . ; ‘ : a} |) “on ae Hall on the rocks of the New York system . ‘ ‘ 387 The Taconic system equivalent to Lower and Middle Ounidietnas p - 888 The paleontological determinations of Hall . . : : ’ : 389 Stratigraphical errors of the Taconic system . . . ° - 890 The Red sand-rock and the primordial trilobites of Vértiiciit : é 391 Contributions of Barrande and Billings to the subject . Logan on the Taconic rocks of Vermont ‘ é Fs ° ‘ 2 894 Hall’s determinations and the errors of Hisinger Bigsby on the fossiliferons rocks near Quebee ° - * Bayfield and Loganonthe same rocks . . , - ‘ . - 3897 XX ? TABLE OF CONTENTS. The graptolites of Point Levis rn 4 Se ee es ee ee Discovery of trilobites at Point Levis. . ie week Gee Logan deseribes and defines the Quebec sous = = ‘ é é 401 He supposes a great and continuous dislocation ° ° . 2) ann Hall accepts Logan’s stratigraphical conclusions . : - : - 403 Potsdam of the Ottawa basin and of Wisconsin . a 6 6 i Its relations to the primordial of Europe : py ite rie Histery of the Paradoxides Harlani of Braintree . . o «0 « £06 The primordial fauna in Newfoundland and New’Brunswick . . 406 Murray on the geology of Newfoundland . . . . . =. « 406 The Lower Potsdam fauna of Billings . . . . « « « 407 Fossiliferous rocks of Troy, New York . 4 o 7 se 2. he”) ea Menevian fauna in New Brunswick . ele) oe Se ee Ln Crystalline schists of Nova Scotia . : ; - > ‘ - 408 Eophyton and its supposed geological relstions - oe Se Hicks and Barrande on the early trilobitic fauna . . . - « 409 Murray on ancient fossiliferous rocks in Newfoundland 0) be) i ot nn Dawson on ancient foraminiferalforms . . . . « «+ « 411 On the Palxotrochis of Emmons . oat gles le Billings on paleontological breaks in the Cdewe basin...) sae The true horizon of the Levis limestone . ‘ ° c° Le Its equivalents in Great Britain and elsewhere. . «. « « « 412 Unconformability of Calciferous and Trenton formations . . . 418 Discordance between the Quebec and Trenton groups . . «. «+ 4138 — Lesley ona similar discordance in Pennsylvania . . . « «+ 414 a The Chazy formation on the Ottawa River . . . «. « « 414 ; Absence of the second fauna to the eastward o>. > ely hae S Distribution of the Lower Helderbergfauna . . «.« « « « 416 7 History of the Oneida conglomerate. Cw 4 Mingling of second and third faunas on the Saguenay ‘ «hoe A Fossiliferous rocks of Anticosti . ‘ 5 . « -4a7 ; Middle Silurian division in Great Britain At Wee +1) he be - 417 i Middle Silurian of Billings different therefrom . . . « « 418 ; Two faunas in the Upper Silurian of Murchison 0 00! te The Onondaga and Water-lime formations . . : : : 418 + Introduction of the terms Silurian and Devonian in Aosta : . . 419 4 Views of De Verneuil andof Hall. . Os ae 419 J ry Names adopted by the geological survey of Canada pte oo. eee ' The geological survey of Pennsylvania. . . « « «+ « 420 The nomenclature adopted by Rogers . o et a See en Rogers on the British equivalents of American rocks ote ee aectqn a Errors of the Silurian nomenclature . ‘ siie o* cor ae The Upper Cambrian or Siluro-Cambrian division ‘ . . . 423 Jukes and Giekie on the Silurian nomenclature : ° ° . - 424 Barrande’s downward extension of Silurian . ¥ Sant : ° . 424 Great importance of Sedgwick’s geological labors . «.« + * . : WAL f A a Rie . \ ‘4 Set ft -- =e — nln ‘ = sa a Ba Sat TABLE OF CONTENTS. XX1 XVI. — OF CHEMICAL CHANGES AND EQUIVALENT VOLUMES (18538). The physical and chemical history of matter RS Ne a uae ae Generation of chemical species considered : F ° ° ‘ - 427 Theory of double decomposition . + + + «© « -« - 428 On the relations of lower to higher species x Sah ae ane - 428 The significance of combination by volumes. - . + + « 429 The nature of chemical union and of solution . : : * : . 429 Relations of chlorine to hydrogen and hydrocarbons . . . . 480 aurent’s law of divisibility in formulas . ‘ ; ‘$ - 481 Reasons for doubling the equivalents of oxygen and dastiois Pi ee ne - Extension of the principle of progressive series . : ° : . - 432 Relations between density and equivalent weightin gases . . . 482 Relations between density and equivalent weight in solids : . - 433 High equivalent weights of solid species . eeerets tk le - 484 Playfair and Joule on equivalent volumes. *. . eas lean - 434 Equivalent volumes of crystalline solids We TEAC AY ess as an Equivalent volumes of liquidspecies. . ~.« +. «© «© «+ «+ 486 XVII. THE CONSTITUTION AND EQUIVALENT VOLUME OF MINERAL SPECIES (1853-1863). Progressive or homologous series inchemistry . «. . a) ae ee General formula for silica and other oxides . «© «+ « «+ «+ 440 Equivalent volume ofcertainsalts. . «.« « «© «© «+ « 440 Probable constitution of the carbon-spars. =. . .« «© «| » 441 Illustrations of isomorphism andf homology . +. . .« « 442 Relations between the various triclinic feldspars . bi sty ~ «448, A similar view subsequently adopted by Tschermak . . . . 444 The feldspathides; scapolites, beryl, andiolite. . . . « « 445 The grenatides; zoisite or saussurite . . . . arte ee lee |S ae Polymerism in mineral species illustrated . $e a thes et Se Relations between the jades and the scapolites . . . . - 447 The allomerism of Professor Cooke . «© «+» + «© «© «© « 447 6 XVIII. THOUGHTS ON SOLUTION AND THE CHEMICAL PROCESS (1854). Views of various chemists as tothe nature ofsolution. . . . 448 Solution maintained to be chemical union. ‘ » M Fe . 449 Chemical union is identification . . . SE ee ee hae aan Chemical decomposition or differentiation. . . ». « « «© 461 Nature of double decomposition . . . «.« « « « + 461 Action by pressure or catalysis . oF ey ee ea ee ae ™ — ss" © os am ee a en eee eee eee | ee XXli TABLE OF CONTENTS. XIX, ON THE OBJECTS AND METHOD OF MINERALOGY (1867). Mincralogy in its relations to chemistry and natural history. . .. Mineralogy the natural history of all unorganized matter . : : ° Objects to be attained in a natural classification . : ° . . Niews of Oken and of Stallo =.) si. 0. oS) ss The nature of chemical species defined . Tee me pe re Varying condensation and equivalents of solid species . . . « Relations of vapors to liquids and solids Se ee ee ay Evidences of polymerism in solidspecies . . . «+ «+ «+ -« XX. THEORY OF TYPES IN CHEMISTRY (1848 - 1861). Kolbe on oxides of carbon as typesinchemistry . . «.«. «+ «+ AG. Wuarte's criticism of Kolbe. 5 iene ise se, ns » we | oe SO Importance of the conception of typesinchemistry . . -. «+. -s Views of Williamson andofGerhardt . . . . «+ Laurent on waterasa type . ere set lige eke re eee The author’s views on the water-type Sears exw oe, glee On anhydrous monobasic acids . Sr tet : Sore hice The conception of condensed or polymeric types . o's sty ) (Cie Pei The nature of sulphur, ozone, and nitrogen «ew tle es Hydrogen the fundamentaltype . . «+. «.« + « -« - Note on the theory of nitrification . : ° : a. te: ae On the value and significance of rational formulas me et ine The hypothesis of radicles and substitution by residues . ° : Ad. Wurtz on polyatomic radicles. . 5) og ee The genesis of the phosphoric acids explainede, of 2 are Gerhardt on polybasic and sub-salts . eae The sulphates.considered as derived from polyatomic radicles . :. Priority of the author to Williamson and to Gerhardt . . . . APPENDIX. The Bion of nitrification. . on ge on Views as to the double nature of nitrogen oes ole Ti See a Its conversion into ammonia and nitrous acid . . . . . . The intervention of ozone in the process 0 8 She paths eae are Experiments of Schénbein on nitrification . ee ee Wn Nicklés on the priority ofthe author . . .« +» «+ « « Schaeffer on the theory of nitrification . +» + «8 «© «# #. SSSRSSE 3S rs SSSSSESS5F ce a a Fy. aa y"4 ] ae m. a e ar ‘i Sra o Bis ae m beieniae ‘i . Re re I. THEORY OF IGNEOUS ROCKS AND VOLCANOES. (1858.) The following Essay, read before the Canadian Institute, at Toronto, March 13, 1858, was printed in the Canadian Journal for May of the same year. It may be regarded as a first contribution to the theoretical notions developed in some of the following papers. In a note in the American Journal of Science for January, 1858, I have ventured to put forward some speculations upon. the chemistry of a cooling globe, such as the igneous theory supposes our earth to have been at an early period. Consid- ering only the crust with which geology makes us acquainted, and the liquid and gaseous elements which now surround it, I have endeavored to show that we may attain to some idea of the chemical conditions of the cooling mass by conceiving these materials to again react upon each other under the influ- ence of an intense heat. The quartz, which is present in such a great proportion in many rocks, would decompose the car- bonates and sulphates, and, aided by the presence of water, the chlorides both of the rocky strata and the sea; while the organic matters and the fossil carbon would be burned by the atmospheric oxygen. From these reactions would result a fused mass of silicates of alumina, alkalies, lime, magnesia, iron, etc.; while all the carbon, sulphur, and chlorine, in the form of acid gases, mixed with watery vapor, azote, and a probable excess of oxygen, would form an exceedingly dense atmosphere. When the cooling permitted condensation, an acid rain would fall upon the heated crust of the earth, de- composing the silicates, and giving rise to chlorides and sul- ; 4 2 THEORY OF IGNEOUS ROCKS AND VOLCANOES. [I. phates of the various bases, while the separated silica would probably take the form of crystalline quartz. In the next stage, the portions of the primitive crust not covered by the ocean undergo a decomposition under the influ- ence of the hot moist atmosphere charged with carbonic acid, and the feldspathic silicates are converted into clays with separation of an alkaline silicate, which, decomposed by the carbonic acid, finds its way to the sea in the form of alkaline bicarbonate, where, having first precipitated any dissolved ses- quioxides, it changes the dissolved lime-salts into bicarbonate. This, precipitated chemically or separated by organic agencies, gives rise to limestones, the chloride of calcium being at the same time replaced by common salt.* The separation from the waters of the ocean of gypsum and sea-salt, and of the salts of potash by the agency of marine plants, and by the formation of glauconite, are considerations foreign to our pres- ent study. In this way we obtain a notion of the processes by which, from a primitive fused mass, may be generated the silicious, calcareous, and argillaceous rocks which make up the greater part of the earth’s crust, and we also understand the source of the salts of the ocean. But the question here arises whether this primitive crystalline rock, which probably approached to dolerite in its composition, is now anywhere visible upon the earth’s surface. It is certain that the oldest known rocks are ~ stratified deposits of limestone, clay, and sands, generally in a highly altered condition, but these, as well as more recent strata, are penetrated by various injected rocks, such as granites, trachytes, syenites, porphyries, dolerites, phonolites, ete. These offer in their mode of occurrence, not less than their compo- sition, so many analogies with the lavas of modern volcanoes, that they also are universally supposed to be of igneous origin, and to owe their peculiarities to slow cooling under pressure. This conclusion being admitted, we proceed to inquire into the sources of these liquid masses which, from the earliest known geological period up to the present day, have been from time * See in this connection the note appended,,page 10. I] THEORY OF IGNEOUS ROCKS AND VOLCANOES. 3 to time ejected from below. They are generally regarded as evidences both of the igneous fusion of the interior of our _ planet, and of a direct communication between the surface and the fluid nucleus, which is supposed to be the source of the various ejected rocks. These intrusive masses, however, offer very great diversities in their composition, from the highly silicious and feldspathic granites, eurites, and trachytes, in which lime, magnesia, and° iron are present in very small quantities, and in which potash is the predominant alkali, to the denser basic rocks, dolerite, diorite, trap, and basalt ; in these, lime, magnesia, and iron-oxide are abundant, and soda prevails over the potash. To account for these differences in the composition of the injected rocks, Phillips, and after him Durocher, suppose the interior fluid mass to have separated into a denser stratum of the basic sili- cates, upon which a lighter and more silicious portion floats like oil upon water ; and that these two liquids, occasionally more or less modified by a partial crystallization and eliquation, or by a refusion, give rise to the principal varieties of silicious and basic rocks ; while from the mingling of the two zones of liquid matter intermediate rocks are formed. (Phillips’s Manual of Geology, p. 556, and Durocher, Annales des Mines, 1857, Vol. I. p. 217.) An analogous view was suggested by Bunsen in his researches on the volcanic rocks of Iceland, and extended by Streng to similar rocks in Hungary and Armenia. These investigators suppose the existence beneath the earth’s crust of a trachytic and a pyroxenic magma of constant composition, representing respectively the two great divisions of rocks which we have just distinguished ; and have endeavored to calculate from the amount of silica in any intermediate variety, the proportions in which these two magmas must have been mingled to produce it, and consequently the proportions of alumina, lime, magnesia, iron-oxide and alkalies which such a rock may be expected to contain. But the amounts thus calculated, as may be seen from Dr. Streng’s results, do not -always correspond with the results of analysis. (Streng, Annales de Chimie et de Physique, 4 THEORY OF IGNEOUS ROCKS AND VOLCANOES. [I. Third Series, Vol. XXXTX. p. 52.) Besides, there are intru- sive rocks, such as the phonolites, which are highly basic, and yet contain but very small quantities of lime, magnesia, and iron-oxide ; being essentially silicates of alumina and alkalies, in part hydrated. We may here remark that many of the so-called igneous ~ rocks are often of undoubted sedimentary origin. It will scarcely be questioned that this is true of many granites, and it is certain that all the feldspathic rocks coming under the categories of hyperite, labradorite, diorite, and amphibolite, which make so large a part of the Laurentian system in North America, are of sedimentary origin. They are here interstrati- fied with limestones, dolomites, serpentines, crystalline gneisses and quartzites, which latter are often conglomerate. The same thing is true of similar feldspathic rocks in the crystalline strata of the Green Mountains. These metamorphic strata have been exposed to conditions which have rendered some of them quasi-fluid or plastic. Thus, for example, crystalline limestone may be seen in positions which have led many ob- servers to regard it as intrusive rock, although its general mode of occurrence leaves no doubt as to its sedimentary origin. We find in the Laurentian system that the limestones sometimes envelope the broken and contorted fragments of the beds of quartzite, with which they are often interstratified, and pene- trate like a veritable trap into fissures in the quartzite and gneiss. A rock of sedimentary origin may then assume the conditions of a so-called igneous rock, and who shall say that any intrusive granites, dolerites, euphotides, or serpentines have an origin distinct from the metamorphic strata of the’ same kind which make up such vast portions of the older stratified formations? To suppose that each of these sedimentary rocks has also its representative among the ejected products of the central fire, seems a hypothesis-not only unnecessary, but, when we consider their varying composition, untenable. We are next led to consider the nature of the agencies which have produced this plastic condition in various crystalline rocks, Certain facts, such as the presence in them of graphite L] THEORY OF IGNEOUS ROCKS AND VOLCANOES. 5 in contact with carbonate of lime and oxide of iron, not less than the presence of alkaliferous silicates like the feldspars in crystalline limestones, forbid us to admit the ordinary notion of the intervention of an intense heat such as would produce an igneous fusion, and lead us to consider the view first put forward by Poulett Scrope,* and since ably advocated by Scheerer and by Elie de Beaumont, of the intervention of water, aided by heat, which they suppose may communicate a plasticity to rocks at a temperature far below that required for their igneous fusion. The presence of water in the lavas of modern volcanoes led Mr. Scrope to speculate upon the effect which a small portion of this element might exert, at an elevated tem- perature and under pressure, in giving liquidity to masses: of rock, and he extended this idea from proper volcanic rocks to granites. Scheerer, in his inquiry into the origin of granite, has ap- pealed to the evidence afforded us by the structure of this rock, that the more fusible feldspars and mica crystallized before the almost infusible quartz. He also points to the existence in granite of what he has called pyrognomic minerals, such as allanite and gadolinite, which, when heated to low redness, undergo a peculiar and permanent’ molecular change, accom- panied by an augmentation in density and a change in chemical properties ; a phenomenon completely analogous to that offered by titanic acid and chromic oxide in their change by ignition from a soluble to an insoluble condition. These facts seem to exclude the idea of igneous fusion, and point to some other cause of liquidity. The presence of natrolite as an integral part of the zircon-syenites of Norway, and of talc, chlorite, and other hydrous minerals in many granites shows that water was not excluded from the original granitic paste. Scheerer appeals, by way of illustration, to the influence of small portions of carbon and sulphur in greatly reducing the fusing point of iron. He alludes to the experiments of Schafhautl and Wohler, which show that quartz and apophyllite may be dissolved by heated water, under pressure, and recrystallized on cooling. * See Journal of Geological Society of London, Vol. XII. p. 326. 6 THEORY OF IGNEOUS ROCKS AND VOLCANOES. [. He recalls the aqueous fusion of many hydrated salts, and finally suggests that the presence of a small amount of water, perhaps five or ten per cent, may suffice, at a temperature which may approach that of redness, to ‘give to a granitic mass a liquidity partaking at once of the characters of an igneous and an aqueous fusion. This ingenious hypothesis, sustained by Scheerer in his dis- cussion with Durocher,* is strongly confirmed by the late ex- periments of Daubrée. He found that common glass, a silicate of lime and alkali, when exposed to a temperature of 400° C., in presence of its own volume of water, swelled up and was transformed into an aggregate of crystals of wollastonite, the alkali, with the excess of silica, separating, and a great part of the latter crystallizing in the form of quartz. When the glass contained oxide of iron, the wollastonite was replaced by erys- tals of diopside. Obsidian in the same manner yielded crystals of feldspar, and was converted into a mass like trachyte. In these experiments upon vitreous alkaliferous matters, the pro- cess of nature in the metamorphosis of sediments is reversed ; but Daubrée foynd still farther that kaolin, when exposed to a heat of 400° C. in the presence of a soluble alkaline silicate, is converted into crystalline feldspar, while the excess of silica separates in the form of quartz. He found natural feldspar and diopside to be extremely stable in the presence of alkaline solutions. These beautiful results were communicated to the French Academy of Sciences on the 16th of November last, and, as the author well remarked, enable us to understand the part which water may play in giving origin to crystalline min- erals in lavas and intrusive rocks. The swelling up of the glass also shows that water gives a mobility to the particles of the glass at a temperature far below that of its igneous fusion. I had already shown in the Report of the Geological Sur- * See for the arguments on the two sides, Bulletin of the Geol. Soc. of France, Second Series, Vol. IV. pp. 468, 1018; VI. 644; VII. 276; VIIL. 500; also, Elie de Beaumont, Ibid., Vol. IV. p. 1312. See also the re- cent microscopical observations of Mr. Sorby, confirming the theory of the aqueo-igneous origin of granite in the L. E. & D. Phil. Mag., February, 1858. I.] THEORY OF IGNEOUS ROCKS AND VOLCANOES, 7 vey of Canada for 1856, p. 479, that the reaction between alkaline silicates and carbonates of lime, magnesia and iron at a temperature of 100° C. gives rise to silicates of these bases, and enables us to explain their production from a mixture of car- bonates and quartz, in the presence of a solution of alkaline carbonate. I there also suggested that the silicates of alumina in sedimentary rocks may combine with alkaline silicates to form feldspars and mica, and that it would be possible to crys- tallize these minerals from hot alkaline solutions in sealed tubes. In this way I explained the occurrence of these sili- cates in altered fossiliferous strata. My conjectures are now confirmed by the experiments of Daubrée, which serve to complete the demonstration of my theory of the normal meta- morphism of sedimentary rocks by the interposition of heated alkaline solutions. But to return to the question of intrusive rocks : Calculations based on the increasing temperature of the earth’s crust as we descend, lead to the belief that at a depth of about twenty-five miles the heat must be sufficient for the igneous fusion of ba- salt. The recent observations of Hopkins, however, show that the melting points of various bodies, such as wax, sulphur and resin, are greatly and progressively raised by pressure, so. that from analogy we may conclude that the interior portions of the earth are, although ignited, solid from great pressure. This conclusion accords with the mathematical deductions of Mr. Hopkins, who, from the precession of the equinoxes, calculates the solid crust of the earth to have a thickness of 800 or 1,000 miles. Similar investigations by Mr. Hennessey, however, as- sign 600 miles as the maximum thickness of the crust. The region of liquid fire being thus removed so far from the earth’s surface, Mr. Hopkins suggests the existence of lakes or limited basins of molten matter, which serve to feed the volcanoes. Now the supposed mode of formation of the primitive molten crust of the earth would naturally exclude all combined or intermingled water; while all the sedimentary rocks are neces- sarily permeated by this liquid, and consequently in a condition to be rendered semi-fluid by the application of heat as supposed 8 THEORY OF IGNEOUS ROCKS AND VOLCANOES. [L. in the theory of Scrope and Scheerer. If now we admit that all igneous rocks, ancient plutonic masses as well as modern lavas, have their origin in the liquefaction of sedimentary strata, we at once explain the diversities in their composition. We can also understand why the products of volcanoes in dif- ferent regions are so unlike, and why the lavas of the same volcano vary at different periods. We find an explanation of the water and carbonic acid which are such constant accompani- ments of volcanic action, as well as the hydrochloric acid, sul- phuretted hydrogen, and sulphuric acid, which are so abundantly evolved by certain volcanoes. The reaction between silica and carbonates must give rise to carbonic acid, and the decompo- sition of sea-salt in saliferous strata by silica, in the presence of water, will generate hydrochloric acid; while gypsum in the same way will evolve its sulphur in the form of sulphurous acid mixed with oxygen. The presence of fossil plants in the melting strata would generate carburetted hydrogen gases, whose reducing action would convert the sulphurous acid into sulphuretted hydrogen ; or the reducing agency of the carbona- ceous matters might give rise to sulphuret of calcium, which would be, in its turn, decomposed by carbonic acid or other- wise. The intervention of such matters in volcanic phenom- enon is indicated by the recent investigations of Deville, who has found carburetted hydrogen in the gaseous emanations of the region of Etna and the lagoons of Tuscany. The ammonia and the nitrogen of volcanoes are also in many cases probably derived from organic matters in the strata decom- posed by subterranean heat. The carburetted hydrogen and bitumen evolved from mud-volcanoes, like those of the Crimea and of Bakou, and the carbonized remains of plants in the moya of Quito, and in the volcanic matters of the Island of Ascension, not less than the infusorial remains found by Ehren- berg in the ejected matters of most volcanoes, all go to show that fossiliferous sediments are very generally implicated in voleanic phenomena. It is to Sir John F. W. Herschel that we owe, so far as I am aware, the first suggestions of the theory of volcanic action PROSE Se St S : ee ee : —— y, I.] THEORY OF IGNEOUS ROCKS AND VOLCANOES. 9 which I have here brought forward. In a letter to Sir Charles Lyell, dated February 20, 1836 (Proceedings Geol. Soc., Lon- don, Vol. XI. p. 548), he maintains that with the accumulation of sediment the isothermal lines in the earth’s crust must rise, so that strata buried deep enough will be crystallized and metamorphosed, and eventually be raised, with their included water, to the melting-point. This will give rise to evolutions of gases and vapors, earthquakes, volcanic explosions, etc., all of which results must, according to known laws, follow from the fact of a high central temperature; while from the me- chanical subversion of the equilibrium of pressure, following upon the transfer of sediments, while the yielding surface reposes upon a mass of matter partly liquid and partly solid, we may explain the phenomena of elevation and subsidence. Such is a summary of the views put forward more than twenty years since by this eminent philosopher, which, although they have passed almost unnoticed. by geologists, seem to me to furnish a simple and comprehensive explanation of several of the most difficult problems of chemical and dynamical geology. To sum up in a few words the views here advanced. We conceive that the earth’s solid crust of anhydrous and primitive igneous rock is everywhere deeply concealed beneath its own ruins, which form a great mass of sedimentary strata, per- meated by water. As heat from beneath invades these sedi- ments, it produces in-them that change which constitutes normal metamorphism. These rocks, at a sufficient depth, are necessarily in a state of igneo-aqueous fusion, and in the event of fracture of the overlying strata, may rise among them, taking the form of eruptive rocks. Where the nature of the sediments is such as to generate great amounts of elastic fluids by their fusion, earthquakes and volcanic eruptions may result, and these, other things being equal, will be most likely to occur under the more recent formations.* [Nore to page 2. —TI have since pointed out that the evidences of a similar process are still to be seen in the granites and crystalline schists * See further in this connection Essays VI. and VII. 10 THEORY OF IGNEOUS ROCKS AND VOLCANOES. LJ] of eozoic ages which in many regions are decomposed to great depths, the feldspar being converted into kaolin, while the hornblende has lost its protoxide bases, the peroxidized iron and the silica remaining behind. This change has affected the crystalline rocks of the southern United States and of Brazil to depths of a hundred feet or more, and doubtless at one time extended to all such rocks as were above the surface of the ocean. The absence of this decayed material from certain regions of crystalline rocks is to be attributed to its subsequent removal by denudation, a process which in the northern parts of Europe and America terminated at the close of the pliocene period, when the remain- ing softened material was swept away by the action of water and ice, and the hard and unchanged rocks beneath were exposed and glaciated, since which time the chemical decomposition of the surface has been insignificant. It is this process which was called by Dolomieu the maladie du granit, and ascribed by him to the influence of carbonic-acid gas from subterranean sources. It was, however, in my opinion a uni- versal phenomenon, and dependent upon the peculiar composition of the atmosphere in early times. These decomposed strata furnished the great deposits of clay and sand of the paleozoic and later periods ; and from them was dissolved the iron which in various forms is found at different horizons in the uncrystalline rocks ; while the silica and the alkaline and earthy carbonates, rémoved in a soluble form from these decaying eozoic rocks, have generated the limestones, dolomites, and various silicious de- posits. (See Proceedings Boston Society of Natural History for October 15, 1873.) . ; In the Proceedings of the same Society for February 18, 1874, I have called attention to the fact that the clay resulting from this decay of rocks remains for many days suspended in pure water, though not in waters even slightly saline, and is therefore readily precipitated in a few hours when the turbid fresh waters mingle with those of the sea, thus forming fine argillaceous sediments. The geological significance of this fact was, it is believed, first pointed out in 1861 by Mr. Sidell in Hum- phreys and Abbot’s Report on the Physics and Hydraulics of the Missis- sippi River (Appendix A, page xi.), where he applied it to explain the accumulations of .mud at this river’s mouth. Many chemical pre- cipitates, in like manner, which may be washed on a filter with acid or saline solutions, readily pass through its pores if suspended in pure water. I have sought to explain these phenomena by the principle that saline matters reduce the cohesion between water and the suspended particles, thus allowing gravity and their own cohesion to come into play. Guthrie (Proceedings Royal Society, XIV.) has shown that the addition of small quantities of saline matters to water diminishes the size of its drops, evidently for the same reason. } FO Ce A) ON We ee et a aa = erg. aT. a Ce all Oly a! ap Bi Il. ON SOME POINTS IN CHEMICAL GEOLOGY. (1859.) A paper with the above title was sent to the Geological Society of London in August, 1858, and read before that body, January, 1859. An abstract of it appeared in the L. E. & D. Philosophical Magazine for February, and it was published in full in the Quarterly Journal of the Geological Society for November, from which it was re- printed, with the addition of a few notes, in the Canadian Naturalist for December, 1859. Such portions of this paper as were but a repetition of the preceding one are here omitted ; what follows may be regarded as a supplement to that. ; . . s ° e . WHEN we examine the waters charged with saline matters which impregnate the great mass of calcareous strata constitut- ing in Canada the base of the palzozoic series, we find that only about one half of the chlorine-is combined with sodium ; the remainder exists as chlorides of calcium and magnesium, the former predominating, — while sulphates are present only in small amount. If now we compare this composition, which may be regarded as representing that of the paleeozoic sea, with that of the modern ocean, we find that the chloride of calcium has been in great part replaced by common salt, —a process involving the intervention of carbonate of soda, and the for- mation of carbonate of lime. The amount of magnesia in the sea, although diminished by the formation of dolomite and magnesite, is now many times greater than that of the lime ; for so long as chloride of calcium remains in the water, the mag- nesian salts are not precipitated by bicarbonate of soda.* When we consider that the vast amount of argillaceous sedi- * See Report Geol. Surv. Canada, 1857, pp. 212-214; Am. Jour. Science (2), XXVIII. pp. 170, 305 ; and further, Essays VIII. and IX. 12 ON SOME POINTS IN CHEMICAL GEOLOGY. [Il mentary matter in the earth’s strata has doubtlessly been formed by the same process which is now going on, namely, the de- composition of feldspathic minerals, it is evident that we can scarcely exaggerate the importance of the part which the alka- line carbonates, formed in this process, must have played in the chemistry of the seas. (Page 2.) We have only to recall waters like Lake Van, the natron-lakes of Egypt, Hungary, and many other regions, the great amounts of carbonate of soda furnished by springs like those of Carlsbad and Vichy, or contained in the waters of the Loire, the Ottawa, and probably many other rivers that flow from regions of crystalline rocks, to be reminded that a similar though much slower process of decomposition of alkaliferous silicates is still going on. A striking and important fact in the history of the sea, and of most alkaline and saline waters, is the small proportion of potash-salts which they contain. Soda is pre-eminently the soluble alkali ; while the potash in the earth’s crust is locked up in the form of insoluble orthoclase, the soda-feldspars readily undergo decomposition. Hence we find in the analyses of clays and argillites, that of the alkalies which these rocks still retain, the potash almost always predominates greatly over the soda. At the same time these sediments contain silica in ex- cess, and but small portions of lime and magnesia. These con- ditions are readily explained when we consider the nature of the soluble matters found in the mineral waters which issue from these argillaceous rocks. I have elsewhere shown that (setting aside the waters charged with soluble lime and mag- nesia-salts, issuing from limestones and from gypsiferous and saliferous formations) the springs from argillaceous strata are marked by the predominance of bicarbonate of soda, often with portions of silicate and borate, besides bicarbonates of lime and magnesia, and occasionally of iron. The atmospheric waters filtering through such strata remove soda, lime and magnesia, leaving behind the silica, alumina and potash, — the elements of granitic and trachytic rocks. The more sandy clays and argillites being most permeable, the action of the in- filtrating waters will be more or less complete ; while finer and I.] ON SOME POINTS IN CHEMICAL GEOLOGY. 13 more compact clays and marls, resisting the penetration of this liquid, will retain their soda, lime, and magnesia, and by sub- sequent alteration will give rise to basic feldspars containing lime and soda, and if lime and magnesia predominate, to horn- blende or pyroxene. The presence or absence of iron in sediments demands es- pecial consideration, since its elimination requires the interpo- sition of organic matters, which, by reducing the peroxide to the condition of protoxide, render it soluble in water, either as bicarbonate or combined with some organic acid. This action of waters holding organic matter upon sediments con- taining iron-oxide has been described by Bischof and many other writers, particularly by Dr. J. W. Dawson * in a paper on the coloring matters of some sedimentary rocks, and is applica- ble to all cases where iron has been removed from certain strata and accumulated in others. This is seen in the fire-clays and iron-stones of the coal-measures, and in the white clays associat- ed with great beds of green-sand (essentially a silicate of iron) in the cretaceous series of New Jersey. Similar alternations of white feldspathic beds with others of iron-ore occur in the Green Mountain rocks of Canada, and on a still more remark- able scale in those of the Laurentian series. We may probably look upon the formation of beds of iron-ore as in all cases due to the intervention of organic matters ; so that its presence, not less than that of graphite, affords evidence of the existence of organic life at the time of the deposition of these old crystal- line rocks, The agency of sulphuric and muriatic acids, from volcanic and other sources, is not, however, to be excluded in the solu- tion of oxide of iron and other metallic oxides. The oxidation of pyrites, moreover, gives rise to solutions of iron and alumina- salts, the subsequent decomposition of which, by alkaline or earthy carbonates, will yield oxide of iron and alumina; the absence of the latter element serves perhaps to characterize the iron-ores of organic origin.t In this way the deposits of emery, * Quar. Jour. Geol. Soc., Vol. V. p. 25. + The occurrence of hydrated mixtures of oxide of iron and alumina, like ane a ge Set 14 ON SOME POINTS IN CHEMICAL GEOLOGY. {Il. which is a mixture of crystallized alumina with oxide of iron, have doubtless been formed. Waters deficient in organic matters may remove soda, lime, and magnesia from sediments; and leave the granitic elements intermingled with oxide of iron; while on the other hand, by the admixture of organic materials, the whole of the iron may be removed from strata which will still retain the lime and soda necessary for the formation of basic feldspars. The fact that bicarbonate of magnesia is much more soluble than bicarbonate of lime, is also to be taken into account in considering these reactions. © = , | The study of the chemistry of mineral waters, in connection with that of sedimentary rocks, shows us that the result of processes continually going on in nature is to divide the silico- argillaceous rocks into two great classes (mentioned on page 3), — the one characterized by an excess of silica, by the pre- dominance of potash, and by the small amounts of lime, mag- nesia and soda, and represented by the granites and trachytes ; while in the other class silica and potash are less abundant, and soda, lime and magnesia prevail, giving rise to pyroxenes and triclinic feldspars. The metamorphism and displacement of such sediments may thus enable us to explain the origin of the different varieties of plutonic rocks without calling to our aid the ejections of the central fire, Mr. Babbage * has shown that the horizons or surfaces of equal temperature in the earth’s crust must rise and fall, as a consequence of the accumulation of sediment in some parts and its removal from others, producing thereby expansion and contraction in the materials of the crust, and thus giving rise to gradual and wide-spread vertical movements. Sir John Her- bauxite, serves to show an intimate relation between the origin of these two bases in an uncombined state. Hydrous alumina, gibbsite, is moreover found » » incrusting limonite, and the existence of compounds like mellite and pigotite, in which alumina is united to organic acids, shows that this base may, under cer- tain conditions, be set free in a soluble condition. * On the Temple of Serapis, Proc. Geol. Soc., Vol. II. p. 73. TE ON SOME POINTS IN CHEMICAL GEOLOGY. 15 schel* subsequently showed that, as a result of the internal heat thus retained by accumulated strata, sediments deeply enough buried will become crystallized, and ultimately be raised, with their included water, to the melting-point. From the chemical reactions at this elevated temperature gases and vapors will be evolved, and earthquakes and volcanic eruptions will result. At the same time the disturbance of the equilibrium of pressure consequent upon the transfer of sediments, while the yielding surface reposes upon a mass of matter partly liquid and partly solid, will enable us to explain the phenomena of elevation and subsidence. According, then, to Sir John Herschel’s view, all volcanic phenomena have their source in sedimentary deposits ; and this ingenious hypothesis, which is a necessary consequence of a high central temperature, explains in a most satisfactory man- ner the dynamical phenomena of volcanoes, and many other obscure points in their history, as, for instance, the indepen- dent action of adjacent volcanic vents, and the varying nature of their ejected products.t Not only are the lavas of different volcanoes very unlike, but those of the same crater vary at dif- ferent times ; the same is true of the gaseous matters, hydro- chloric, hydrosulphuric, and carbonic acids. As the ascending heat penetrates saliferous strata, we shall have hydrochloric acid, from the decomposition of sea-salt by silica in the presence of water ; while gypsum and other sulphates, by a similar re- action, would lose their sulphur in the form of sulphurous acid and oxygen. The intervention of organic matters, either by direct contact or by giving rise to reducing gases, would con- vert the sulphates into sulphurets, which would yield sulphu- retted hydrogen when decomposed by water and silica or by car- bonic acid ; the latter being the result of the action of silica upon earthy carbonates. We conceive the ammonia so often. found among the products of volcanoes to be evolved from the” heated strata, where it exists in part as ready-formed ammonia” (which is absorbed from air and water, and pertinaciously re- * On the Temple of Serapis, Proc. Geol. Soc., Vol. II. pp. 548, 596. _ + For a further development of this theory, see Essays VI. and VII. 16 ON SOME POINTS IN CHEMICAL GEOLOGY. (II. tained by argillaceous sediments), and is in part formed by the action of heat upon azotized organic matter present in these strata, as already maintained by Bischof.* Nor can we hesi- tate to accept this author’s theory of the formation of boracic’ acid from the. decomposition of borates by heat and aqueous vapor.t The metamorphism of sediments im situ, their displacement in a pasty condition from igneo-aqueous fusion’ as plutonic rocks, and their ejection as lavas, with attendant gases and vapors are, then, all results of the same cause, and depend upon the differences in the chemical composition of the sedi- ments, the temperature, and the depth to which they are buried : while the unstratified nucleus of the earth, which is doubtless anhydrous, and, according to the calculations of Messrs. Hop- kins and Hennessey, probably solid to a great depth, intervenes in the phenomena under consideration only as a source of heat. * Lehrbuch der Geologie, Vol. II. pp. 115-122. + Ibid., Vol. I. p. 669. ' + The notion that volcanic phenomena have their seat in the sedimentary formations of the earth’s crust, and are dependent upon the combustion of organic matters, is, as Humboldt remarks, one which belongs to the infancy of geognosy. (Cosmos, Vol. V. p. 443. Otté’s translation.) In 1834, Christian Keferstein published his Naturgeschichte des Erdkérpers, in which he main- tains that all crystalline non-stratified rocks, from granite to lava, are products of the transformation of sedimentary strata, in part very recent, and that there is no well-defined line to be drawn between neptunian and volcanic rocks, sinee they pass into each other. Volcanic phenomena, according to him, have their origin, not in an igneous fluid centre, nor an oxidizing metallic nucleus, but in known sedimentary formations, where they are the result of a peculiar process of fermentation, which crystallizes and arranges in new forms the ele- mente of the sedimentary strata, with evolution of heat as an accompaniment of the chemical process. (Naturgeschichte, Vol. I. p. 109; also Bull. Soc. Géol. de France (1), Vol. VII. p. 197.) : These remarkable conclusions were unknown to me at the time of writing this paper, and seem indeed to have been entirely overlooked by geological rs; they are, as will be seen, in many respects an anticipation of the views of Herschel and my own; although in rejecting the influence of an incandescent nucleus as a source of heat, he has, as I conceive, excluded the exciting cause of that chemical change, which he has not inaptly described as a process of fermentation, and which is the source of all volcanic and plutonic phenomena. See in this connection Essays I. and VII. of the present volume. Ah he ee eS ae a ats tie, soy i hed Oe a ot Pia ai) an’ et ae ‘central heat to be still iietenGig Hs shown by Mr. Bab- ~ age), a process which has long since ceased in the palzozoic regions. Both normal metamorphism and volcanic action are generally connected with elevations and foldings of the earth’s “? E crust, all of which phenomena we conceive to have a common 1g 2 cause, and to depend upon the accumulation of sediments and _ the subsidence consequent thereon, as maintained by Mr. James «Hall i in his theory of mountains.* e e * . . . Ss _* See, for an exposition of the views of Professor Hall, Essays V. and a VIL. of the present volume. is TIT. THE CHEMISTRY OF METAMORPHIC ROCKS. (1863.) This paper was read before the Dublin Geological Society, April 10, 1863, published in the Dublin Quarterly Journal for July, and reprinted in the Canadian Naturalist for the same year. The notions expressed in the first paragraph as to the exist- ence of crystalline strata of all geological ages, the results of a subsequent alteration of palzozoic, meseozoic, and even of cenozoic sediments, are in strict accordance with . those which were then (and are even now) maintained by most of the authorities in geology ; and at that time had scarcely been questioned. Hence it is that the rocks of what are here designated the third and fourth series were, in conformity with the conclusions generally accepted, referred to the paleozoic age. It will, however, be seen that I had at that time no doubt that the rocks of the third (or Green Mountain) series, then regarded as altered Lower Silurian, were, as Macfarlane had already main- tained, the equivalents of a part at least of the Primitive Slate or Urschiefer formation of Norway. He, as is here stated, supposed the Huronian to represent another part of the same formation ; while Bigsby soon after expressed the opinion that the Huro- nian and the Urschiefer are the same. My own extended studies of these rocks in the Green Mountains, in New Brunswick, and on Lakes Superior and Huron, have since convinced me that this view is correct, and that the Green Mountain series is repre- sented in the crystalline strata around the great lakes just mentioned ; and, moreover, that both this series and the crystalline rocks of the fourth or White Mountain series existed in their present crystalline form before the depoSition of the oldest Cambrian sediments. The further history of these crystalline series will be found in an Essay on the Geognosy of the Appalachians (XIII. of the present volume), and in its Appendix. In this connection the reader is also referred to portions of those on Granitic Rocks (XI.), on Alpine Geology.(XIV.), and to the third part of that on Cam- brian and Silurian (XV.). See also a note to the present paper (page 33). These conclusions carry back the origin of these two series of crystalline rocks to a much more remote peridd in geological history than was formerly supposed ; but the chemical principles laid down in this paper I believe to be still true, and of general application, and for this reason it is reprinted with the omission of a few sentences which, by their reference to the supposed paleozoic age of the crystalline rocks above referred to, might serve to mislead the reader. While retaining the original title, I however regard the name of metamorphic rocks, _ 48 applied to crystalline strata, an unfortunate one, which it would be well to banish from the science of geology. Although it is not to be questioned that local and excep- tional agencies, apparently hydrothermal, have occasionally given rise to crystalline silicated minerals in palzozoic and even in more recent sediments, and may thus help III.] THE CHEMISTRY OF METAMORPHIC ROCKS. 19 us to form some conception of processes which were universal in eozoic times, the notion that any of the great series of crystalline rocks are the stratigraphical equiva- lents of formations elsewhere known to us as uncrystalline sediments, will be found to rest on very uncertain evidence. Those crystalline rocks have doubtless, since their deposition, undergone certain molecular modifications (by what has been named diagenesis) which have changed their original aspect ; but something of the same sort is to a greater or less extent true of many sedimentary rocks to which we do not give the name of metamorphic. This term has not only come to be familiarly used as a synonyme for all crystalline stratified rocks, but is associated with the notion of a profound epigenic change (pseudomorphism) extended alike to uncrystalline sediments and to erystalline eruptive rocks; a notion has been embodied in the assertion that “regional metamorphism is pseudomorphism on a grand scale.” See in this connec- tion Essay XIII. and its Appendix. ArT a time not very remote in the history of geology, when all crystalline stratified rocks were included under the common des- ignation of primitive, and were supposed to belong to a period anterior to the fossiliferous formations, the lithologist confined his ‘studies to, descriptions of the various species of rocks, with- out reference to their stratigraphical or geological distribution. But with the progress of geological science a new problem is presented to his investigation. While paleontology has shown that the fossils of each formation furnish a guide to its age and stratigraphical position, it has been found that sedimentary strata of all ages, up to the tertiary inclusive, may undergo such changes as to obliterate the direct evidences of organic life ; and to give to the sediments the mineralogical characters once assigned to primitive rocks.* The question here arises, whether in the absence of organic remains, or of stratigraphical evidence, there exists any means of determining, even approxi- mately, the geological age of a given series of crystalline strati- fied rocks; in other words, whether the chemical conditions which have presided over the formation of sedimentary rocks have so far varied in the course of ages, as to impress upon these rocks marked chemical and mineralogical differences. In the case of unaltered sediments it would be difficult to arrive at any solution of this question without greatly multiplied analyses ; but in the same rocks, when altered, the crystalline minerals which are formed, being definite in their composition, and varying with the chemical constitution of the sediments, * See the remarks on the preceding page. 20 THE CHEMISTRY OF METAMORPHIC ROCKS. [IIL may perhaps to a certain extent become to the geologist what organic remains are in the unaltered rocks, —a guide to the geological age and succession. It was while engaged in the investigation of metamorphic rocks of various ages in North America, that this problem sug- gested itself; and I have endeavored from chemical considera- tions, conjoined with multiplied observations, to attempt its solution. In the Quarterly Journal of the Geological Society of London for 1859 (Essay II. of the present volume) will be found the germs of the ideas on this subject, which I shall endeavor to explain in the present paper. It cannot be doubted that in the earlier periods of the world’s history, chemical forces of certain kinds were much more active than at the present day. Thus the decomposition of earthy and alkaline silicates, under the combined influences of water and carbonic acid, would be greater when this acid was more abundant in the atmosphere, and when the temperature was probably higher (page 2). The larger amounts of alkaline and earthy carbon- ates then carried to the sea from the decomposition of these silicates would furnish a greater amount of calcareous matter to the sediments ; and the chemical effects of vegetation, both on the soil and on the atmosphere, must have been greater during the carboniferous period, for example, than at present. In the spontaneous decomposition of feldspars, which may be described as silicates of alumina combined with silicates of potash, soda and lime, these latter bases are removed, together with a portion of silica; and there remains, as the final result of the process, a hydrous silicate of alumina, which constitutes kaolin or clay. This change is favored by mechanical division ; and Daubrée has shown that by the prolonged attrition of frag- ments of granite under water, the softer and readily cleavable | feldspar is in great part reduced to an impalpable powder, while the uncleavable grains of quartz are only rounded, and form a readily subsiding sand ; the water at the same time dissolving from the feldspar a certain portion of silica and of alkali. It has been repeatedly observed, where potash and soda-feldspars are associated, that the latter is much the more readily decomposed, * yO Ce ee es eee ee ee Pe tiie ve - Sittin od a eae eas ee PT aoe ie ey ae ee ee ee ae _ oe mel ‘s = . a ee aie . ¥ Pt ae OS ee Ro — Pa a eel ae ee IIL] THE CHEMISTRY OF METAMORPHIC ROCKS. a becoming friable, and finally being reduced to clay, while the orthoclase is unaltered. The result of combined chemical and mechanical agencies acting upon rocks which contain quartz, with orthoclase and a soda-feldspar such as albite or oligoclase, would thus be a sand, made up chiefly of quartz and potash- feldspar, and a finely divided and suspended clay, consisting for the most part of kaolin and of partially decomposed soda-feld- spar, mingled with some of the smaller particles of orthoclase and of quartz. With this sediment will also be included the oxide of iron, and the earthy carbonates set free by the sub-aerial decomposition of silicates like pyroxene and the anorthic feld- spars, or formed by the action of the carbonate of soda derived from the latter upon the lime-salts and the magnesia-salts of sea-water. The débris of hornblende and pyroxene will also be found in this finer sediment. This process is evidently the one which must go on in the wearing away of rocks by aqueous agency, and explains the fact that while quartz, or an excess of combined silica, is for the most part wanting in rocks which contain a large proportion of alumina, it is generally abundant in those rocks in which potash-feldspar predominates. So long as this decomposition of alkaliferous silicates is sub- aerial, the silica and alkali are both removed in a soluble form. The process is often, however, submarine or subterranean, tak- ing place in buried sediments which are mingled with carbon- ates of lime and magnesia. In such cases the silicate of soda set free reacts either with these earthy carbonates, or with the corresponding chlorides of sea-water, and forms in either event a soluble soda-salt, and insoluble silicates of lime and magnesia which take the place of the removed silicate of soda. The evidence of such a continued reaction between alkaliferous silicates and earthy carbonates is seen in the large amounts of carbonate of soda, with but little silica, which infiltrating waters constantly remove from argillaceous strata ; thus giving rise to alkaline springs and to natron-lakes. In these waters it will be found that soda greatly predominates, sometimes almost to the exclusion of potash. This is due not only to the fact that soda-feldspars are more readily decomposed than 92 THE CHEMISTRY OF METAMORPHIC ROCKS, [IIL orthoclase, but to the well-known power of argillaceous sedi- ments to abstract from water the potash-salts which it already holds in solution. Thus when a solution of silicate, carbonate, sulphate or chloride of potassium is filtered through common earth, the potash is taken up, and replaced by lime, magnesia, or soda, by a double decomposition between the soluble potash- salt and the insoluble silicates or carbonates of the latter bases, Soils, in like manner, remove from infiltrating waters, ammonia, and phosphoric and silicic acids, the bases which were in combi- nation with these being converted into carbonates. The drain- age-water of soils, like that of most mineral springs, contains only carbonates, chlorides and sulphates of lime, magnesia and soda ; the ammonia, potash, phosphoric and silicic acids being — sabantien by the soil. The elements which the earth retains or extracts froin waters are precisely those which are removed from it by growing plants. These, by their decomposition under ordinary condi- tions, yield their mineral matters again to the soil ; but when decay takes place in water, these elements become dissolved, — and hence the waters from peat-bogs and marshes contain large amounts of potash and silica in solution, which are carried to the sea, there to be separated, —the silica by protophytes, and the potash by alge, which latter, decaying on the shore, — or in the ooze at the bottom, restore the alkali to the earth. The conditions under which the vegetation of the coal-formation grew and was preserved being similar to those of peat, the soils became exhausted of potash, and are seen in the fire-clays of the carboniferous period. Another effect of vegetation on sediments is due to the re- ducing or deoxidizing agency of the organic matters from its decay. These, as is well known, reduce the peroxide of iron to a soluble protoxide, and remove it from the soil, to be afterwards deposited in the forms of iron-ochre and iron-ores, which by subsequent alteration become hard, crystalline and insoluble. Thus, through the agency of vegetation, is the iron- oxide of the sediments withdrawn from the terrestrial circula- tion ; and it is evident that the proportion of this element. IIl.] THE CHEMISTRY OF METAMORPHIC ROCKS. 23 diffused in the more recent sediments must be much less than in those of ancient times. The reducing power of organic mat- ter is further shown in the formation of metallic sulphurets ; the reduction of sulphates having precipitated in this insoluble form the heavy metals, copper, lead and zine, which, with iron, appear to have been in solution in the waters of early times, but are now by this means also abstracted from the circulation, and accumulated in beds and fahlbands, or by a subsequent process have been redissolved and deposited in veins. All analogies lead us to the conclusion that the primeval condition of the metals, and of sulphur, was, like that of carbon, one of oxidation, and that vegetable life has been the sole medium of their reduction. The source of the carbonates of lime and magnesia in sedi- mentary strata is twofold : —first, the decomposition of sili- cates containing these bases, such as anorthic feldspars and pyroxene ; and, second, the action of the alkaline carbonates formed by the decomposition of feldspars, upon the chlorides of calcium and magnesium originally present in sea-water ; which have thus, in the course of ages, been in great part replaced by chloride of sodium. ‘The clay, or aluminous silicate which has been deprived of its alkali, is thus at once a measure of the carbonic acid removed from the air, of the carbonates of lime and magnesia precipitated, and of the amount of chloride of sodium added to the waters of the primeval ocean. The coarser sediments, in which quartz and orthoclase prevail, are readily permeable to infiltrating waters, which gradually remove from them the soda, lime and magnesia which they: contain ; and, if organic matters intervene, the oxide of iron; leaving at last little more than silica, alumina and potash, — the elements of granite, trachyte, gneiss and mica-schist. On the other hand, the finer marls and clays, resisting the penetra- tion of water, will retain all their soda, lime, magnesia, and oxide of iron; and containing an excess of alumina, with a small amount of silica, will, by their metamorphism, give rise to basic lime-feldspars and soda-feldspars, and to pyroxene and hornblende, — the elements of diorites and dolerites. In this 24 THE CHEMISTRY OF METAMORPHIC ROCKS. [IIL _ way the operation of the chemical and mechanical causes which we have traced naturally divides all the crystalline silico-aluminous rocks of the earth’s crust into two types. These correspond to the two classes of igneous rocks, distin- guished first by Professor Phillips, and subsequently by Duro-~ cher and by Bunsen, as derived from two distinct magmas which these geologists imagine to exist beneath the solid crust, and which the latter denominates the trachytic and pyroxenic types. I have however elsewhere endeavored to show that all intrusive or exotic rocks are probably nothing more than al- tered and displaced sediments, and have thus their source with- in the lower portions of the stratified crust, and not beneath it (pages 4, 8 and 14). It may be well in this place to make a few observations on the chemical conditions of rock-metamorphism. I accept in its widest sense the view of Hutton and Boué, that all the crystalline stratified rocks have been produced by the alteration of mechanical and chemical sediments. The conversion of these into definite mineral species has been effected in two ways: first, by molecular changes, that is to say, by crystalli- zation, and a rearrangement of particles; and, secondly, by chemical reactions between the elements of the sediments. Pseudomorphism, which is the change of one mineral species into another by the introduction or the elimination of some element or elements, presupposes metamorphism ; since only definite mineral species can be the subjects of this process. To confound metamorphism with pseudomorphism, as Bis- chof, and others after him, have done, is therefore an error. — It may be further remarked, that, although certain pseudo- morphic changes may take place in some mineral species, in veins, and near to the surface, the alteration of great masses of silicated rocks by such a process is as yet an unprov hypothesis. * | The cases of local metamorphism in proximity to intrusive rocks go far to show, in opposition to’ the views of certain geologists, that heat has been one of the necessary conditions * See further on this subject Essay XIII. and its appendix. III] THE CHEMISTRY OF METAMORPHIC ROCKS. 25 of the change. The source of this has been generally supposed to be from below; but to the hypothesis of alteration by ascending heat, Naumann has objected that the inferior strata in some cases escape change, and that, in descending, a certain plane limits the metamorphism, separating the altered strata above from the unaltered ones beneath, there being no ap- parent transition between the two. This, taken in connection with the well-known fact that in many cases the intrusion of igneous rocks causes no apparent change in the adjacent unal- tered sediments, shows that heat and moisture are not the only conditions of metamorphism. In 1857 I showed by experi- ments that, in addition to these conditions, certain chemical reagents might be necessary ; and that water impregnated with alkaline carbonates and silicates would, at a temperature not above that of 212° F., produce chemical reactions among the elements of many sedimentary rocks, dissolving silica, and generating various silicates.* Some months subsequently, Daubrée found that in the presence of solutions of alkaline silicates, at temperatures above 700° F., various silicious minerals, such as quartz, feldspar and pyroxene, could be made to assume a crystalline form ; and that alkaline silicates in solution at this temperature would combine with clay to form feldspar and mica.t These observations were the com- plement of my own, and both together showed the agency of heated alkaline waters to be sufficient to effect the metamor- phism of sediments by the two modes already mentioned, — namely, by molecular changes and by chemical reactions. Following upon this, Daubrée observed that the thermal alkaline spring of Plombiéres, with a temperature of 160° F., had in the course of centuries given rise to the formation of zeolites, and other crystalline silicated minerals, among the bricks and cement of the old Roman baths. From this he was led to suppose that the metamorphism of great regions * Proc. Royal Soc. of London, May 7, 1857; and Philos. Mag. (4), XV. 68; also Amer. Jour. Science (2), XXII. and XXV. 435. + Comptes Rendus de l’Acad., Nov. 16, 1857; also Bull. Soc. Geol de France (2), XV. 103. 2 26 THE CHEMISTRY OF METAMORPHIC ROCKS. [il might have been effected by hot springs; which, rising along certain lines of dislocation, and thence spreading laterally, might produce alteration in strata near to the surface, while those beneath would in some cases escape change.* This ingenious hypothesis may serve in some cases to meet the difficulty pointed out by Naumann ; but while it is undoubt- edly true in certain instances of local metamorphism, it seems to be utterly inadequate to explain the complete and universal alteration of areas of sedimentary rocks, embracing many hun- dred thousands of square miles. On the other hand, the study of the origin and distribution of mineral springs shows that alkaline waters (whose action in metamorphism I first pointed out, and whose efficient agency Daubrée has since so well shown) are confined to certain sedimentary deposits, and to definite stratigraphical horizons ; above and below which saline waters wholly different in character are found impregnating the strata. This fact seems to offer a simple solution of the difficulty advanced by Naumann, and a complete explanation of the theory of metamorphism of deeply buried strata by the agency of ascending heat ; which is operative in producing chemical changes only in those strata in which soluble alkaline salts are present.t When the sedimentary strata have been rendered crystalline by metamorphism, their permeability to water, and their altera- bility, become greatly diminished ; and it is only when again broken down by mechanical agencies to the condition of soils and sediments, that they once more become subject to the chemical changes which have just been described. Hence, * It should be remembered that normal or regional metamorphism is in no way dependent upon the proximity of unstratified or igneous rocks, which are rarely present in metamorphic districts. The ophiolites, amphibolites, euphotides, diorites, and granites of such regions, which it has been custom- ary to regard as exotic or intrusive rocks, are in most cases indigenous. + See Report of the Geological Survey of Canada, 1853-56, pp. 479, 480 ; also Canadian Naturalist, Vol. VII. p. 262. For a consideration of the rela- tions of mineral waters to geological formations, see General Report on the Geology of Canada, 1863, p. 561, and also Chap. XIX. of the same Report, on Sedimentary and Metamorphic Rocks ; where most of the points touched in the present paper are discussed at greater length. TIL] THE CHEMISTRY OF METAMORPHIC ROCKS. 27° _ the mean composition of the argillaceous sediments of any geological epoch, or, in other words, the proportion between the alkalies and the alumina, will depend not only upon the age of the formation, but upon the number of times which its materials have been broken up, and the periods during which they have remained unmetamorphosed, and exposed to the action of infiltrating waters... .. The proportion be- tween the alkalies and the alumina in the argillaceous sedi- ments of any given formation is not therefore in direct relation to its age; but indicates the extent to which these sediments have been subjected to the influences of water, carbonic acid, and vegetation. If, however, it may be assumed that this action, other things being equal, has on the whole been pro- portionate to the newness of the formation, it is evident that the chemical and mineralogical composition of different systems of rocks must vary with their antiquity ; and it now remains to find in their comparative study a guide to their-respective ages. It will be evident that silicious deposits and chemical pre- cipitates, like the carbonates and silicates of lime and magnesia, may exist with similar characters in the geological formations of any age; not only forming beds apart, but mingled with the impermeable silico-aluminous sediments of mechanical ori- gin. Inasmuch as the chemical agencies giving rise to these compounds were then most active, they may be expected in greatest abundance in the rocks of the earlier periods. In the case of the permeable and more highly silicious class of sedi- ments already noticed, whose chief elements are silica, alumina, and alkalies, the deposits of different ages will be marked chiefly by a progressive diminution in the amount of potash and more especially of the soda which they contain. In the oldest rocks the proportion of alkali will be nearly or quite sufficient to form orthoclase and albite with the whole of the alumina present; but as the alkali diminishes, a portion of the alumina will crystallize, on the metamorphism of the sedi- ments, in the form of a potash-mica, such as muscovite or margarodite. While the oxygen-ratio between the ‘alumina oe che 5 oF. . ‘7 % _ 4 zi ey re ap Ae J fe a i lila a - 28 THE CHEMISTRY OF METAMORPHIC ROCKS. and the alkali in the feldspars just named is 3:1, it becomes 6:1 in margarodite, and 12:1 in muscovite. The appearance of these micas in a rack denotes, then, a diminution in the amount of alkali, until in some strata the feldspar almost entirely disappears, and the rock becomes a quartzose mica- schist. In sediments still further deprived of alkali, metamor- phism gives rise to schists filled with crystals of kyanite or of andalusite, which are simple silicates of alumina, into whose composition alkalies do not enter; or in case the sediment still retains oxide of iron, staurolite and iron-alumina garnet take their place. The matrix of all of these minerals is gen- erally a quartzose mica-schist. The last term in this exhaustive process appears to be represented by the disthene and pyrophyl- lite rocks, which occur in some regions of crystalline schists. In the second class of sediments we have alumina in excess, with a small proportion of silica, and a deficiency of alkalies, besides a variable proportion of silicates or carbonates of lime, magnesia, and oxide of iron. The result of the processes already described will produce a gradual diminution in the amount of alkali, which is chiefly soda. So long as this predominates, the metamorphism of these sediments will give rise to feldspars like oligoclase, labradorite, or scapolite (a dimetric feldspar) ; but in sediments where lime replaces a great proportion of the soda, there appears a tendency to the production of denser silicates, like lime-alumina garnet, and epidote, or zoisite, which replace the soda-lime feldspars. Minerals like the chlorites, dichroite and chloritoid are formed when magnesia and iron replace lime. In all of these cases the excess of the silicates of earthy protoxides over the silicate of alumina is represented in the altered strata by hornblende, pyroxene, olivine, and similar species ; which give rise, by their admixture with the. double aluminous silicates, to diorite, diabase, euphotide, eklo- gite, and similar compound rocks. In eastern North America, the crystalline strata, so far as yet studied, may be conveniently classed in five groups, corre- sponding to as many different geological series, four of which will be considered in the present paper. [IIL IIT.] THE CHEMISTRY OF METAMORPHIC ROCKS. 29 J. The Laurentian system represents the oldest known rocks of the globe, and is supposed to be the equivalent of the Primi- tive Gneiss formation of Scandinavia, and that of the Western Islands of Scotland, to which also the name of Laurentian is now applied. It has been investigated in Canada along a continuous outcrop from the coast of Labrador to Lake Su- perior, and also over a considerable area in northern New York. Il. Associated with this system is a series of strata charac- terized by a great development of anortholites, of which the hypersthenite or opalescent feldspar-rock of Labrador may be taken as a type. These strata overlie the Laurentian gneiss, and are regarded as constituting a second and more recent group of crystalline rocks, to which the name of the Labrador series may be provisionally given. [Since called Norian ; see note to page 31.| From evidence recently obtained, Sir William Logan conceives it probable that this series is uncom- formable with the older Laurentian system, and is separated from it by a long interval of time. III. In the third place is a great series of crystalline schists (the Green Mountain series), which are in Canada referred to the Quebec group, an inferior part of the Lower Silurian sys- tem. They appear to correspond both lithologically and strati- graphically with the Schistose group of the Primitive Slate formation of Norway, as recognized by Naumann and Keilhau, and to be there represented by the strata in the vicinity of Drontheim, and those of the Dofrefeld. The Huronian series of Canada in like manner appears to correspond to the Quart- zose group of the same Primitive Slate formation.* It consists of quartzites, varieties of imperfect gneiss, diorites, silicious and feldspathic schists passing into argillites, with limestones, and great beds of hematite... .. The Huronian series is as yet but imperfectly studied, and for the present will not be further considered.t * See Macfarlane, — Primitive Formations of Norway and Canada com- pared, — Canadian Naturalist, VII. 113, 162. [ + It will be seen above that I have indicated jive groups of crystalline rocks, 30 THE CHEMISTRY OF METAMORPHIC ROCKS. [IIL IV. In the fourth place are to be noticed the metamorphosed strata. of Upper Silurian and Devonian age, with which may also be included those of the Carboniferous system in eastern New England. This group has as yet been imperfectly stud- ied, but presents interesting peculiarities. In the oldest of these, the Laurentian system, the first class of aluminous rocks takes the form of granitoid gneiss, which is often coarse-grained and porphyritic. Its feldspar is fre- quently a nearly pure potash-orthoclase, but sometimes con- tains a considerable proportion of soda. Mica is often almost entirely wanting, and is never abundant in any large mass of this gneiss, although small bands of mica-schist are occasionally met with. Argillites, which from their general predominance of potash and silica are related to the first class of sediments, are, so far as known, wanting throughout the Laurentian series; nor is any rock here met with, which can be regarded as derived from the metamorphism of sediments like the argil- lites of more modern series. Chloritic and chiastolite-schists and kyanite are, if not altogether wanting, extremely rare in the Laurentian system. The aluminous sediments of the second class are, however, represented in this system by a diabase made up of dark green pyroxene and bluish labradorite, often associated with a red alumino-ferrous garnet. This latter mineral also sometimes constitutes small beds, often with quartz, and occasionally with a little pyroxene. These basic aluminous minerals form, however, but an insignificant part of the mass of strata. This system is further remarkable by the small amount of ferruginous matter diffused through the strata ; from which the greater part of the iron seems to have been removed, and accumulated in the form of immense beds of hematite and magnetic iron. Beds and veins of crystalline plumbago also characterize this series, and are generally found with the limestones, which are here developed to an extent while attempting to describe but four ; the fifth being the Huronian series, - which from its close resemblance to the third series (from which it was by Logan regarded as geologically distinct), was to me a source of great per- plexity. For further considerations touching this question, see the remarks on page 18.] er Pew Y os ae a ; : eee a) oT a ae Pg RL ee ee FC i ee ae ee Se a LJ THE CHEMISTRY OF METAMORPHIC ROCKS. 31 unknown in more recent formations; and are associated with veins of crystalline apatite, which sometimes attain a thick- ness of several feet. The serpentines of this séries, so far as yet studied in Canada, are generally pale-colored, and contain an unusual amount of water, a small proportion of oxide of iron, and neither chrome nor nickel; both of which are almost always present in the serpentines of the third series. * | The second or Labrador series is characterized, as already remarked, by the predominance of great beds of anortholite, composed chiefly of triclinic feldspars, which vary in compo- sition from anorthite to andesine. These feldspars sometimes form mountain masses, almost without any admixture, but at other times include portions of pyroxene, which passes into hypersthene. Beds of nearly pure pyroxenite are met with in this series, and others which would be called hyperite and diabase. These anortholite rocks are frequently compact, but are more often granitoid in structure. They are generally grayish, greenish, or bluish in color, and become white on the weathered surfaces. The opalescent labradorite-rock of Labra- dor is a characteristic variety of these anortholites ; which often contain small portions of red garnet and brown mica, and more rarely, epidote, olivine, and a little quartz. They are sometimes slightly calcareous. Magnetic iron and ilmenite are often disseminated in these rocks, and occasionally form masses or beds of considerable size. These anortholites con- stitute the predominant part of the Labrador series, so far as yet examined. They are, however, associated with beds of quartzose orthoclase-gneiss, which represent the first class of aluminous sediments, and with crystalline limestones; and they will probably be found, when further studied, to offer a complete lithological series. These rocks have been observed in several areas among the Laurentide Mountains, from the coast of Labrador to Lake Huron, and are also met with among the * See in this connection the author on the History of Ophiolites, Am. Jour. Science (2), XXV. 117, and XXVI. 234, 32 THE CHEMISTRY OF METAMORPHIC ROCKS. [III. Adirondack Mountains ; of which, according to Emmons, they form the highest summits.* In the third (or Green Mountain) series, which we have referred to the Lower Silurian age, the gneiss is sometimes granitoid, but less markedly so than in the first; and it is much more frequently micaceous, often passing into micaceous schist, a common variety of which contains disseminated a large quantity of chloritoid. Argillites abound, and under the influence of metamorphism sometimes develop crystalline orthoclase. At other times they are converted into a soft micaceous mineral, and form a kind of mica-schist. Chias- tolite and staurolite are never met with in the schists of this series, at least in its northern portions, throughout Canada and New England. The anortholites of the Labrador series are here represented by fine-grained diorites, in which the feldspar varies from albite to very basic varieties, which are sometimes associated with an aluminous mineral allied to chlorite in com- position. Chloritic schists, frequently accompanied by epidote, abound in this series. The great predominance of magnesia in the forms of dolomite, magnesite, steatite, and serpentine, is also characteristic of portions of this series. The latter, which forms great beds (ophiolites), is marked by the almost constant presence of small portions of\ the oxides 6f chrome and nickel. These metals are also common in the other mag- nesian rocks of the series; green chrome-garnets, and chrome- mica occur; and beds of chromic iron ore are found in the ophiolites of the series. It is also a gold-bearing formation in eastern North America, and contains large quantities of copper ores in interstratified beds. .... The only graphite which has been found in the third series is in the form of impure plumbaginous shales, The metamorphic rocks of the fourth (or White Mountain) series, as seen in southeastern Canada, are for the greater part quartzose and micaceous schists, more or less feldspathic; which in certain portions become remarkable for a great * A further description of this Labrador or Norian series is given in Essay XIII. oe See ee a me Nl ee aren 2 ae S ee a III.] THE CHEMISTRY OF METAMORPHIC ROCKS. 33° development of crystals of staurolite and of red garnet. A large amount of argillite occurs in this series; and when al- tered, whether locally by the proximity of intrusive rock, or by normal metamorphism, exhibits a micaceous mineral, and erystals of andalusite ; so that it becomes known as chiastolite- slate in parts of its distribution. Granitoid gneiss is abundantly associated with these crystalline schists. .... The crystalline limestones and ophiolites of eastern Massachusetts, which are probably of this series, resemble those of the Laurentian sys- tem; and the coal beds in that region are in some parts changed into graphite.* ... . Large masses of intrusive granite occur among the crystalline strata of the fourth series, but the so-called granites of the Laurentian appear to be in every case indigenous rocks ; that is to say, strata altered am situ, and still retaining evidences of stratification. The same thing is true with regard to the ophiolites and the anortholites of both series. No evidences of the hypothetical granitic substratum are met with in the Laurentian system, although this is in one district penetrated by great masses of syenite, orthophyre, and dolerite. Granitic veins, with minerals containing the rarer elements, such as’ boron, fluorine, lithium, zirconium, and glucinum, are met with alike in the oldest and the newest gneiss in North America. These, however, I regard as having been formed, like metal- liferous veins, by aqueous deposition in fissures in the strata. The above observations upon the metamorphic strata of a wide region seem to be in conformity with the chemical prin- ciples already laid down in this paper; which it remains for geologists to apply to the rocks of other regions, and thus determine whether they are susceptible of a general applica- tion. I have found that the blue crystalline labradorite of the Labrador series of Canada is exactly represented by speci- [* See in this connection the prefatory note to this essay, and also Essays XIII. and XV. The carboniferous age of the graphite of eastern Massachu- setts has been generally assumed by geologists, though without any good reason. The crystalline rocks of this region, embracing New Hampshire and eastern Massachusetts, include representatives of the second, third, and fourth, and probably also of the first series.] 2* ce) 34 THE CHEMISTRY OF METAMORPHIC ROCKS. (IL mens from Scarvig, in Skye; and the ophiolites of Iona resem- ble those of the Laurentian series in Canada. Many of the rocks of Donegal appear to me lithologically identical with those of the Laurentian period ; while the serpentines of Agha- doey, containing chrome and nickel, and the andalusite and kyanite-schists of other parts of Donegal, cannot be distin- guished from those which characterize the altered palzozoic strata of Canada. It is to remarked that chrome and nickel bearing serpentines are met with in the same geological horizon in Canada and Norway ; and that those of the Scottish High- lands, which contain the same elements, belong to the newer gneiss formation ; which, according to Sir Roderick Murchison, would be of similar age.* The serpentines of Cornwall, the Vosges, Mount Rosa, and many other regions, agree in contain- ing chrome and nickel; which, on the other hand, seem to be absent from the serpentines of the Primitive Gneiss formation of Scandinavia. It remains to be determined how far chemical and mineralogical differences, such as those which have been here indicated, are geological constants. Meanwhile it is greatly to be desired that future chemical and mineralogical investigations of crystalline rocks should be made with this question in view; and that the metamorphic strata of the British Isles, and of southern and central Europe, be studied with reference to the important problem which it has been my endeavor, in the present paper, to lay before the Society. * See in this connection the Essays XIII. and XV. A) & 2 oe ” “4 ~~ b. Ts om IV. THE CHEMISTRY OF THE PRIMEVAL . EARTH. (1867.) The following paper is an abstract of a Friday-evening lecture, given before the Royal Institution of Great Britain, London, May 31, 1867, and here reprinted from the Proceedings of the Institution. As an attempt to bring together in a connected form some of the latest conclusions of chemical and geological science, it attracted at the time considerable attention, having been frequently reprinted, several times translated, and adversely criticised both in the Chemical News and the Geological Magazine. My replies to these criticisms the reader will find in these same journals for February, 1868. As bearing upon the subject of the lecture, an Appendix is subjoined including a note on the relation of the atmosphere of early times to climate, and to the temperature near the sea-level. For further discussion upon the origin and mode of formation of. dolomites and gypsum, and their relation to the composition of the SEDSPHERS, the reader is referred to Paper VIII. in this volume. THE natural history of our planet, to which we give the name of geology, is necessarily a very complex science, including, as it does, the concrete sciences of mineralogy, botany, and zodlogy, and the abstract sciences, chemistry and physics. These latter sustain a necessary and very important relation to the whole process of development of our earth from its earliest ages, and we find that the same chemical laws which have presided over its changes apply also to those of extra-terrestrial matter. Re- cent investigations show the presence in the sun, and even in the fixed stars, — suns of other systems, — the same chemical elements as in our own planet. The spectroscope, that marvel- lous instrument, has, in the hands of modern investigators, thrown new light upon the composition of the farthest bodies of the universe, and has made clear many points which the telescope was impotent to resolve. The results of extra-terres- trial spectroscopic research have lately been set forth in an admirable manner by one of its most successful students, Mr. 36 THE CHEMISTRY OF THE PRIMEVAL EARTH. _ [IV. Huggins. We see, by its aid, mattter in all its stages, and trace the process of condensation and the formation of worlds. It is long since Herschel, the first of his illustrious name, con- ceived the nebulz, which his telescope could not resolve, to be the uncondensed matter from which worlds are made. Sub- sequent astronomers, with more powerful glasses, were able to show that many of these nebule are really groups of stars, and. thus a doubt was thrown over the existence of nebulous lumi- nous matter in space; but the spectroscope has now placed the matter beyond doubt. By its aid, we find in the heavens, planets, bodies like our earth, shining only by reflected light ; suns, self-luminous, radiating light from solid matter; and, moreover, true nebule, or masses of luminous gaseous matter. These three forms represent three distinct phases in the con- densation of the primeval matter from which our own and other planetary systems have been formed. This nebulous matter is conceived to be so intensely heated as to be in the state of true gas or vapor, and, for this reason, feebly luminous when compared with the sun. It would be out of place, on the present occasion, to discuss the detailed re- sults of spectroscopic investigation, or the beautiful and ingen- ious methods by which modern science has shown the existence in the sun, and in many other luminous bodies in space, of the same chemical elements that are met with in our earth, and even in our own bodies, Calculations based on the amount of light and heat radiated from the sun show that the temperature which reigns at its sur- face is so great that we cin hardly form an adequate idea of it. Of the chemical relations of such intensely heated matter, modern chemistry has made known to us some curious facts, which help to throw light on the constitution and luminosity of the sun. Heat, under ordinary conditions, is favorable to chemical combination, but a higher temperature reverses all affinities. Thus, the so-called noble metals, gold, silver, mer- cury, etc., unite with oxygen-and other elements; but these compounds are decomposed by heat, and the pure metals are regenerated. A similar reaction was many years since shown IV.] THE CHEMISTRY OF THE PRIMEVAL EARTH. 37 by Mr. Grove with regard to water, whose elements, — oxygen and hydrogen, — when mingled and kindled by flame, or by the electric spark, unite to form water, which, however, at a much higher temperature, is again resolved into its component gases. Hence, if we had these two gases existing in admixture at a very high temperature, cold would actually effect their combination precisely as heat would do if the mixed gases were at the ordinary temperature, and literally it would be found that “ frost performs the effect of fire.” The recent researches of Henry Ste.-Claire Deville and others go far to show that this breaking up of compounds, or dissociation of elements by in- tense heat, is a principle of universal application ; so that we may suppose that all the elements which make up the sun or our planet would, when so intensely heated as to be in that gaseous condition which all matter is capable of assuming, re- main uncombined, — that is to say, would exist together in the condition of what we call chemical elements, whose further dis- ‘sociation in stellar or nebulous masses may even give us evidence of matter still more elemental than that revealed by the experi- ments of the laboratory, where we can only conjecture the com- pound nature of many of the so-called elementary substances. The sun, then, is to be conceived as an immense mass of intensely heated gaseous and dissociated matter, so condensed, however, that, notwithstanding its excessive temperature, it has @ specific gravity not much below that of water; probably offering a condition analogous to that which Cagniard de la Tour observed for volatile bodies when submitted to great press- ure at temperatures much above their boiling point. The radi- ation of heat going on from the surface of such an intensely heated mass of uncombined gases will produce a superficial cooling, permitting the combination of certain elements and the production of solid or liquid particles, which, suspended in the still dissociated vapors, become intensely luminous and form the solar photosphere. The condensed particles, carried down into the intensely heated mass, again meet with a heat of dissociation ; so that the process of combination at the sur- face is incessantly renewed, while the heat of the sun may be a » ‘ a 5 4 a Bere Be ae > 3 t - +e * | tae i rr i ee | 2 A, ae 4 ues pt aan Oe . ‘ * ¢ ed : 2 ae uf 38 THE CHEMISTRY OF THE PRIMEVAL EARTH. _ [IV. supposed to be maintained by the slow condensation of its mass ; a diminution by y,45,th of its present diameter being sufficient, according to Helmholtz, to maintain the present supply of heat for 21,000 years. This hypothesis of the nature of the sun and of the luminous process going on at its surface is the one lately put forward by Faye, and, although it has met with opposition, appears to be that which accords best with our present knowledge of the chemical and physical conditions of matter such as we must suppose it to exist in the condensing gaseous mass, which, according to the nebular hypothesis, should form the centre of our solar system. Taking this, as we have already done, for granted, it matters little whether we imagine the different planets to have been successively detached as rings during the rotation of the primal mass, as is generally conceived, or whether we admit with Chacornac a process of aggregation or concretion operating within the primal nebular mass, resulting in the production of sun and planets. Mn either case we come’ to the conclusion that our earth must at one time have been in an intensely heated gaseous condition, such as the sun now pre- sents, self-luminous, and with a process of condensation going on at first at the surface only, until by cooling it must have reached the point where the gaseous centre was exchanged for one of combined and liquefied matter. Here commences the chemistry of the earth, to the discussion of which the foregoing considerations have been only prelim- inary. So long as the gaseous condition of the earth lasted, Wwe may suppose the whole mass to have been homogeneous ; but when the temperature became so reduced that the existence of chemical compounds at the centre became possible, those which were most stable at the elevated temperature then pre- . vailing would be first formed. Thus, for example, while com- pounds of oxygen with mercury, or even with hydrogen, could not exist, oxides of silicon, aluminum, calcium, magnesium, and iron might be formed and condense in a liquid form at the centre of the globe. By progressive cooling, still other elements would be removed from the gaseous mass, which would form IV.] | THE CHEMISTRY OF THE PRIMEVAL EARTH. 39 the atmosphere of the non-gaseous nucleus. We may suppose an arrangement of the condensed matters at the centre accord- ing to their respective specific gravities, and thus the fact that the density of the earth as a whole is about twice the mean density of the matters which form its solid surface may be explained. Metallic or metalloidal compounds of elements, grouped differently from any compounds known to us, and far more dense, may exist in the centre ofthe earth. _ The process of combination and cooling having gone on until those elements which are not volatile in the heat of our ordinary furnaces were condensed into a liquid form, we may here in- quire what would be the result, upon the mass, of a further reduction of temperature. It is generally assumed that in the cooling of a liquid globe of mineral matter, congelation would commence at the surface, as in the case of water; but water offers an exception to most other liquids, inasmuch as it is denser in the liquid than in the solid form. Hence, ice floats on water, and freezing water becomes covered with a layer of ice, which protects the liquid below. With most other matters, however, and notably with the various mineral and earthy com- pounds analogous to those which may be supposed to have formed the fiery-fluid earth, numerous and careful experiments show that the products of solidification are much denser than the liquid mass ; so that solidification would have commenced at the centre, whose temperature would thus be the congealing point of these liquid compounds. The important researches of Hopkins and Fairbairn on the influence of pressure in aug- menting the melting point of such compounds as contract in solidifying are to be considered in this connection. It is with the superficial portions of the fused mineral mass of the globe that we have now to do; since there is no good reason for supposing that the deeply seated portions have in- tervened in any direct manner in the production of the rocks which form the superficial crust. This, at the time of its first solidification, presented probably an irregular, diversified sur- face from the result of contraction of the congealing mass, which at last formed a liquid bath of no great depth, surrounding. 40 THE CHEMISTRY OF THE PRIMEVAL EARTH. [IV. the solid nucleus. It is to the composition of this crust that we must direct our attention, since therein would be found all the elements (with the exception of such as were still in the gaseous form) now met with in the known rocks of the earth. This crust is now everywhere buried beneath its own ruins, and we can only from chemical considerations attempt to re- construct it. If we consider the conditions through which it has passed, and the chemical affinities which must have come ‘into play, we shall see that they are just what would now result if the solid land, sea, and air were made to react upon each other under the influence of intense heat. To the chemist it is at once evident that from this would result the conversion of all carbonates, chlorides, and sulphates into silicates, and the separation of the carbon, chlorine, and sulphur in the form-of acid gases, which, with nitrogen, watery vapor, and a probable excess of oxygen, would form the dense primeval atmosphere. The resulting fused mass would contain all the bases as silicates, and must have much resembled in composition certain furnace- slags or volcanic glasses. The atmosphere, charged with acid gases, which surrounded this primitive rock, must have been of immense density. Under the pressure of such a high baromet- ric column, condensation would’ take place at a temperature much above the present boiling point of water, and the de- pressed portions of the half-cooled crust would be flooded with a highly heated solution of hydrochloric and sulphuric acids, whose action in decomposing the silicates is easily intelligible tothe chemist. The formation of chlorides and sulphates of the various bases, and the separation of silica, would go on until the affinities of the acids were satisfied, and there would be a separation of silica, taking the form of quartz, and the produc- tion of a sea-water holding in solution, besides the chlorides and sulphates of sodium, calcium, and magnesium, salts of alumi- num and other metallic bases. The atmosphere, being thus deprived of its volatile chlorine and sulphur compounds, would approximate to that of our own time, but differ in its greater amount of carbonic acid. We next enter into the second phase in the action of the = el oy = ; oa ‘on te s J ; , ; : 1» es Py a ~~ eal pe ee Get te ee ee oe IV.] THE CHEMISTRY OF THE PRIMEVAL EARTH. 41 atmosphere upon the earth’s crust. This, unlike the first, which was subaqueous, or operative only on the portion cov- ered with the precipitated water, is subaerial, and consists in the decomposition of the exposed parts of the primitive crust under the influence of the carbonic acid and moisture of the air, which convert the complex silicates of the crust into a silicate of alumina, or clay; while the separated lime, magnesia, and alkalies, being converted into carbonates, are carried down into the sea in a state of solution. The first effect of these dissolved carbonates would be to precipitate the dissolved alumina and the heavy metals, after which would result a decomposition of the chloride of calcium _ of the sea-water, resulting in the production of carbonate of lime or limestone, and chloride of sodium or common salt. This process is one still going on at the earth’s surface, slowly breaking down and destroying the hardest rocks, and, aided by mechanical processes, transforming them into clays; although the action, from the comparative rarity of carbonic acid in the , atmosphere, is far less energetic than in earlier times, when the abundance of this gas, and a higher temperature, favored the chemical decomposition of the rocks. But now, as then, every clod of clay formed from the detay of a crystalline rock cor- responded to an equivalent of carbonic acid abstracted from the atmosphere, and to equivalents of carbonate of lime and com- mon salt formed from the chloride of calcium of the sea-water. It is very instructive, in this connection, to compare the composition of the waters of the modern ocean with that of the sea in ancient times, whose composition we learn from the fossil sea-waters which are still to be found in certain regions, imprisoned in the pores of the older stratified rocks. These are vastly richer in salts of lime and magnesia than those of the present sea, from which have been separated, by chemical processes, all the carbonate of lime of our limestones, with the exception of that derived from the subaerial decay of cal- careous and magnesian silicates belonging to the primitive crust. The gradual removal, in the form of carbonate of lime, of the carbonic acid from the primeval atmosphere, has been connected ee eae OE SEE oo ge eae a ae 42 THE CHEMISTRY OF THE PRIMEVAL EARTH. [IV. with great changes in the organic life of the globe. The air was doubtless at first unfit for the respiration of warm-blooded animals, and we find the higher forms of life coming gradually into existence as we approach the present period of a purer air. Calculations lead us to conclude that the amount of carbon thus removed in the form of carbonic acid has been so enor- mous, that we must suppose the earlier forms of air-breathing animals to have been peculiarly adapted to live in an atmos- phere which would probably be too impure to support modern reptilian life. The agency of plants in purifying the primitive atmosphere was long since pointed out by Brongniart, and our great stores of fossil fuel have been derived from the decompo- sition, by the ancient vegetation, of the excess of carbonic acid of the early atmosphere, which through this agency was ex- changed for oxygen gas. In this connection the vegetation of former periods presents the curious phenomenon of plants allied to those now growing beneath the tropics flourishing within the polar circles. Many ingenious hypotheses have been pro- posed to account for the warmer climate of earlier times, but are at best unsatisfactory, and it appears to me that the true © solution of the problem may be found in the constitution of the early atmosphere, when considered in the light of Dr. Tyndall’s beautiful researches on radiant heat. He has found that the presence of a few hundredths of carbonic-acid gas in the atmos- phere, while offering almost no obstacle to the passage of the solar rays, would suffice to prevent almost entirely the loss, by radiation, of obscure heat, so that the surface of the land be- neath such an atmosphere would become like a vast orchard- house, in which the eonditions of climate necessary to a luxu- riant vegetation would be extended even to the polar regions. This peculiar condition of the early atmosphere cannot fail to — have influenced in many other ways the processes going on at the earth’s surface.*, To take a single example: one of the processes by which gypsum may be produced at the earth’s surface involves the simultaneous production of bicarbonate of magnesia. This, being more soluble than the gypsum, is not * See Appendix to this paper. ns hae en ey ” > Saree IV.] THE CHEMISTRY OF THE PRIMEVAL EARTH. 48 always now found associated with it; but we have indirect evidence that it was formed and subsequently carried away, in the case of many gypsum deposits, whose thickness indicates a long continuance of the process under conditions much more perfect and complete than we can attain under our present atmosphere. While studying this reaction I was led to inquire whether the carbonic acid of the earlier periods might not have favored the formation of gypsum ; and I found, by repeating the experiments in an artificial atmosphere impregnated with carbonic acid, that such was really the case.* We may thence conclude that the peculiar composition of the primeval atmos- phere was the essential condition under which the great deposits of gypsum, generally associated with magnesian limestones, were formed. The reactions of the atmosphere, which we have considered, would have the effect of breaking down and disintegrating the surface of the primeval globe, covering it everywhere with beds of stratified rock of mechanical or of chemical origin. These now so deeply cover the partially cooled surface that the amount of heat escaping from below is inconsiderable, although in earlier times it was very much greater, and the increase of tem- perature met with in descending into the earth must then have been many times more rapid than now. The effect of this heat upon the buried sediments would be to soften them, pro- ducing new chemical reactions between their elements, and converting them into what are known as crystalline or meta- morphic rocks, such as gneiss, greenstone, granite, etc. We are often told that granite is the primitive rock or substratum of the earth ; but this is not only unproved, but extremely improbable. As I endeavored to show in the early part of this discourse, the composition of this primitive rock, now everywhere hidden, must have been very much like that of a slag or lava; and there are excellent chemical reasons for maintaining that granite is in every case a rock of sedimentary origin, — that is to say, it is made up of materials which were deposited from water, like beds of modern sand and gravel, and includes in its com- * See Paper VIII. A4 THE CHEMISTRY OF THE PRIMEVAL EARTH. [IV. position quartz, which, so far as we know, can only be gener- ated by aqueous agencies, and at comparatively low tem- peratures. The action of heat upon many buried sedimentary rocks, however, not only softens or melts them, but gives rise to a great disengagement of gases, such as carbonic and hydrochlo- ric acids, and sulphur compounds, all of which are results of the reaction of the elements of sedimentary rocks, heated in pres- ence of the water which everywhere filled their pores. In the products thus generated we have a rational explanation of the chemical phenomena of volcanoes, which are vents through which these fused rocks and confined gases find their way to the surface of the earth. In some cases, as where there is no dis- engagement of gases, the fused or half-fused rocks solidify in situ, or in rents or fissures in the overlying strata, and constitute eruptive or plutonic rocks, such as granite and basalt. This theory of volcanic phenomena,was put forward in germ by Sir John F. W. Herschel thirty years since, and, as I have during the past few years endeavored to show, it is the one most in accordance with what we know both of the chemistry and the physics of the earth. That all volcanic and plutonic phenomena have their seat in the deeply buried,and softened zone of sedimentary deposits of the earth, and not in its primi- tive nucleus, accords with the conclusions already arrived at relative to the solidity of that nucleus; with the geological relations of these phenomena, as I have elsewhere shown; and also with the remarkable mathematical and astronomical de- ductions of the late Mr. Hopkins of Cambridge, based upon the phenomena of precession and nutation, those of Archdeacon Pratt, and those of Professor Thompson on the theory of the tides, —all of which lead to the same conclusion, namely, that the earth, if not solid to the centre, must have a crust sey- eral hundred miles in thickness, which would practically ex- clude it from any participation in the plutonic phenomena of the earth’s surface, except such as would result from its high temperature communicated by conduction to the sedimentary strata reposing upon it. ae eae ~~ ee ec a oe w > IV.] THE CHEMISTRY OF THE PRIMEVAL EARTH. 45 The old question between the plutonists and the neptunists, which divided the scientific world in the last generation, was, in brief, this: whether fire or water has been the great agent in giving origin and form to the rocks of the earth’s crust. While some maintained the direct igneous origin of such rocks as gneiss, mica-schist, and serpentine, and ascribed to fire the filling of metallic veins, others — the neptunian school — were disposed to shut their eyes to the evidences of igneous action on the earth, and even sought to derive all rocks from a primal aqueous magma. In the light of the exposition which I have laid before you this evening, we can, I think, render justice to both of these opposing schools. We have seen how reactions dependent on water and acid solutions have transformed the primitive plutonic mass, and how the resulting aqueous sedi- ments, when deeply buried, come again within the domain of fire, to be transformed into crystalline and so-called plutonic or volcanic rocks. The scheme which I have thus sought to put before you in the short time allotted this evening is, as I have endeavored to show, in strict conformity with known chemical laws and the facts of physical and geological science. Did time permit, I would gladly have attempted to demonstrate at greater length its adaptation to the explanation of the origin of the various classes of rocks, of metallic veins and deposits, of mineral springs, and of gaseous exhalations. I shall not, however, have failed in my object, if, in the hour which we have spent together, I shall have succeeded in showing that chemistry is able to throw a great light upon the history of the formation of our globe, and to explain in a satisfactory manner some of the most difficult problems of geology ; and I feel that there is a peculiar fitness in bringing such an exposition before the mem- bers of this Royal Institution, which has been for so many years devoted to the study of pure science, and whose glory it is, through the illustrious men who have filled, and those who now fill, its professorial chairs, to have contributed more than any other school in the world to the progress of modern chem- istry and physics. ——s 46 THE CHEMISTRY OF THE PRIMEVAL EARTH. {Iv. APPENDIX. ON THE OLIMATE OF THE EARTH IN FORMER GEOLOGICAL PERIODS. The following note appeared in the London, Edinburgh, and Dublin Philosophical Magazine for October, 1863. I subsequently found that this consequence of his dis- coveries had not escaped Tyndall, who, in his Bakerian lecture for 1861 (Ibid., October, 1861), after showing that from its influence on terrestrial radiation all variation in the amount of aqueous vapor must produce changes in climate, added, “‘ Similar remarks would apply to the carbonic acid diffused through the air, while an almost inappre- ciable admixture of any of the hydro-carbon vapors would produce great effects on the terrestrial rays, and corresponding changes in climate. It is not therefore neces- sary to assume alterations in the density and height of the atmosphere, to account for different amounts of heat being preserved to the earth at different times; a slight change in its variable constituents would account for this. Such changes, in fact, may have produced all the mutations of climate which the researches of geologists reveal.” A letter from the author to Dr. Tyndall, in which this passage was cited, appeared in the above-named magazine for March, 1864. THE late researches of Dr. John Tyndall on the relation of gases and vapors to radiant heat are important in their bearing upon the temperature of the earth’s surface in former geological periods. He has shown that heat, from whatever source, passes through hydro- gen, oxygen, and nitrogen gases, or through dry air, with nearly the same facility as through a vacuum. These gases are thus to radiant heat what rock-salt is among solids. Glass, and some other solid substances which are readily permeable to light and to solar heat, offer, as is well known, great obstacles to the passage of radiant heat from non-luminous bodies ; and Tyndall has recently shown that many colorless vapors and gases have a similar effect, intercepting the heat from such sources, by which they become warmed and in their turn radiate heat. Thus, while for a vacuum the absorption of heat from a body at 212° F, is represented by 0, and that for dry air is 1, the absorption by an atmosphere of carbonic-acid gas equals 90, by marsh gas 403, by olefiant gas 970, and by ammonia 1,195. The diffusion of olefiant gas of one-inch tension in a vacuum pro- duces an absorption of 90, and the same amount of carbonic-acid gas an absorption of 5.6. The small quantities of ozone present in electrolytic oxygen were found to raise its absorptive power from 1 to 85, and even to 136 ; and the watery vapor present in the air at ordinary temperatures in like manner produces an absorption of heat represented by 70 or 80. Air saturated with moisture at the IV.] THE CHEMISTRY OF THE PRIMEVAL EARTH. 47 ordinary temperature absorbs more than five hundredths of the heat radiated from a metallic vessel filled with boiling water, and Tyndall calculates that of the heat radiated from the earth’s surface warmed by the sun’s rays, one tenth is intercepted by the aqueous vapor within ten feet of the surface. Hence the powerful_influence of moist air upon the climate of the globe. Like a covering of glass, it allows the sun’s rays to reach the earth, but prevents to a great extent the loss by radiation of the heat thus communicated. When, however, the supply of heat from the sun is interrupted during long nights, the radiation which goes on into space causes the precipitation of a great part of the watery vapor from the air, and the earth, thus deprived of this protecting shield, becomes more and more rapidly cooled. If now we could suppose the at- mosphere to be mingled with some permanent gas, which should possess an absorptive power like that of the vapor of water, this cooling process would be in a great measure arrested, and an effect would be produced similar to that of a screen of glass ; which keeps up the temperature beneath it, directly, by preventing the escape of radiant heat, and indirectly by hindering the condensation of the aqueous vapor in the air confined beneath. Now we have only to bear in mind that there are the best of reasons for believing that, during the earliest geological periods, all of the carbon since deposited in the forms of limestone and of mineral-coal existed in the atmosphere in the state of carbonic acid, and we see at once an agency which must have aided greatly to maintain the elevated temperature that then prevailed at the earth’s surface.* Without doubt the great extent of sea, and the absence * [The carbonic acid contained in a layer of pure carbonate of lime or mar- ble, covering the entire surface of the globe, and having a thickness of 8.61 metres, would, if set free, double the weight of the atmosphere. (Canadian Naturalist (2), [1I. 119.) It is probable that the amount of carbonic acid thus fixed in the earth’s crust must surpass this many times, but from the activity of chemical forces then prevailing, the greater part of this was doubt- less fixed in the form of carbonate of lime ata very early period in the history of the globe, so that the atmosphere in the paleozoic age may not have con- tained more than a few hundredths of carbonic acid. It must not be sup- posed that the whole of the vast deposits of limestone which have since been formed are directly and immediately due to the reaction of carbonic acid on the alkaline and earthy silicates of the rocks. A large part of the carbonate -of lime deposited in later times was doubtless derived from the solution of the limestones of pre-existing formations. It nevertheless remains true that a reaction between the carbonic acid of the atmosphere and mineral silicates, similar to that of early times, though small in amount, is still going on at the earth’s surface. (Ante, pages 10 and 20.)] _ sacely oo hai’ Siocctans enema Sonscto'ag climate of later ages, when a vegetation as luxuriant as that found in the tropics flourished within the Arctic circle ;_ bu these causes must be added the influence of a portion of which was afterwards condensed in the forms of coal and carb of lime, and which then existed in the condition of a tran and permanent gas, mingled with the atmosphere, surrounding - earth, and protecting it like a dome of glass. To this effect of ¢ _ boniec acid it is possible that other gases may have contributed. The ozone, which is mingled with the oxygen set free from en i Py ing plants, and the marsh gas, which is now evolved from deci mn | ‘ang vegetation under conditions similar to those then presente by the coal fields, may, by their great absorptive power, have ~ well aided to maintain at the earth’s surface that high tempe: - the cause of which has been one of the enigmas of geology. — V. THE ORIGIN OF MOUNTAINS. | (1861.) The following pages are from a review entitled Some Points in American Geology, which appeared in the American Journal of Science for May, 1861, and was devoted in part to a notice of the remarkable essay which forms the Introduction to the third volume of Hall’s Paleontology of New York, from which numerous extracts are given below. Read in connection with Paper VII. of the present volume, on Dynamical Geology, it will serve to give a notion of the views of Professor Hall and the author _ on the nature and origin of mountains. THE sediments of the carboniferous period, like those of earlier formations, exhibit, towards the east, a great amount of coarse sediments, evidently derived from a wasting continent, and are nearly destitute of calcareous beds. In Nova Scotia, Sir Wil- liam Logan found, by careful measurement, 14,000 feet of car- boniferous strata; and Professor Rogers gives their thickness in Pennsylvania as 8,000 feet, including at the base 1,400 feet of a conglomerate, which disappears before reaching the Missis- sippi. In Missouri, Professor Swallow finds but 640 feet of carboniferous strata, and in Iowa their thickness is still less, the sediments composing them being at the same time of finer materials. In fact, as Mr. Hall remarks, throughout the whole palzozoic period we observe a greater accumulation and a coarser character of sediments along the line of the Appalachian chain, with a gradual thinning westward, and a deposition of finer and farther-transported matter in that direction. To the west, as this shore-derived material diminishes in volume, the amount of calcareous matter rapidly augments. Mr. Hall con- cludes, therefore, that the coal-measure sediments were driven westward into an ocean where there already existed a marine fauna. At length, the marine limestones predominating, the 3 D 50 THE ORIGIN OF MOUNTAINS. (Vv. coal-measures come to be of little importance, and we have a a great limestone formation of marine origin, which in the Rocky Bae ; Mountains and New Mexico occupies the horizon of the coal, and, itself unaltered, rests on crystalline strata like those of the — 2 “a Appalachian range. In truth, Mr. Hall observes, the carbon- iferous limestone is one of the most extensive marine formations of the continent, and is characterized over a much greater area by its marine fauna than by its terrestrial vegetation. “The accumulations of the coal-period were the last that gave form and contour to the eastern side of our continent, from the Gulf of St. Lawrence to the Gulf of Mexico; and as we have shown that the great sedimentary deposits of successive periods have followed essentially the same course, parallel to the mountain ranges, we naturally inquire: What influence this accumulation has had upon the topography of our country, and whether the present line of mountain-elevation from north- — east to southwest is in any way connected with the original accumulation of sediments.” (Hall’s Paleontology, Vol. IIL ; Introduction, p. 66.) The total thickness of the palzozoic strata along the Appala- chain chain is about 40,000 feet, while the same formations in the Mississippi Valley, including the carboniferous limestone, which is wanting in the east, have, according to Mr. Hall, a thickness of scarcely 4,000 feet. In many places in this valley we find the palzozoic formations exposed, exhibiting hills of 1,000 feet, made up of horizontal strata, with the Potsdam sandstone for their base, and capped by the Niagara limestone ; while the same strata in the Appalachians would give from ten to sixteen times that thickness. Still, as Mr. Hall remarks, we have there no mountains of corresponding altitude, that is to say, none whose height, like those of the Mississippi valley, equals the actual vertical thickness of the strata. In the west there has been little or no disturbance, and the highest eleva- tions mark essentially the aggregate thickness of the strata com- posing them. In the disturbed regions of the east, on the con- trary, though we can prove that certain formations of known thickness are included in the mountains, the height of these is V.] THE ORIGIN OF MOUNTAINS. 51 never equal to the aggregate amount of the formations. ‘We thus find that in a country not mountainous, the elevations correspond to the thickness of the strata, while in a mountainous country, where the strata are immensely thicker, the mountain heights bear no comparative proportion to the thickness of the ‘strata. .... While the horizontal strata give their whole ele- vation to the highest parts of the plain, we find the same beds folded and contorted in the mountain region, and giving to the mountian elevations not one sixth of their actual measurement.” Both in the east and west the valleys exhibit the lower strata of the paleeozoic series, and it is evident that, had the eastern region been elevated, without folding of the strata, so as to make the base of the series correspond nearly with the sea- level, as in the Mississippi Valley, the mountains exposed _be- tween these valleys, and including the whole palzozoic series, would have a height of 40,000 feet ; so that the mountains evidently correspond to depressions of the surface, which have carried down the bottom-rocks below the level at which we meet them in the valleys. In other words, the synclinal struc- ture of these mountains depends upon an actual subsidence of the strata alorfe certain lines. “We have been taught to believe that mountains are pro- duced by upheaval, folding, and plication of the strata, and that, from some unexplained cause, these lines of elevation ex- tend along certain directions, gradually dying out on either side, - and subsiding at the extremities. We have, however, here shown that the line of the Appalachian chain is the line of the greatest accumulation of sediments, and that this great mountain- barrier is due to original deposition of materials, and not to any subsequent forces breaking up or disturbing the strata of which it is composed.” We have given Mr. Hall’s reasonings on this subject for the most part in his own words, and with some detail, for we conceive that the views which he is here urging are of the highest importance to a correct understanding of the theory of mountains. In the Canadian Naturalist for December, 1859, p. 425, and in the American Journal of Science (2), XXX. 137, 52 THE ORIGIN OF MOUNTAINS. will be found an allusion to the rival theories of upheaval and accumulation as applied to volcanic mountains, the discussion between which we conceive to be settled in favor of the latter theory by the reasonings and observations of Constant-Prevost, Scrope, and Lyell. A similar view to the former applied to mountain-chains like those of the Alps, Pyrenees, and Alle- ghanies, which are made up of aqueous sediments, has been imposed upon the world by the authority of Humboldt, Von Buch, and Elie de Beaumont, with scarcely a protest. Buffon, it is true, when he explained the formation of continents by the slow accumulation of detritus beneath the ocean, conceived that the irregular action of the water would give rise to great banks or ridges of sediments, which when raised above the waves must assume the form of mountains. Later, in 1832, we find De Montlosier protesting against the elevation-hypothesis of Von Buch, and maintaining that the great mountain-chains of Europe are but the remnants of continental elevations which have been cut away by denudation, and that the foldings and inversions to be met with in the structure of mountains are to be looked upon only as local and accidental. In 1856, Mr. J. P. Lesley published a little Yblume entitled Coal and its Topography, in the second part of which he has, in a few brilliant and profound chapters, discussed the princi- ples of topographical science with the pen of a master. He there tells us that the mountain lies at the base of all topo- graphical geology. Continents are but congeries of mountains, or rather the latter are but fragments of continents, sep- arated by valleys which represent the absence or removal of mountain-land ; and again, “‘ mountains terminate “where the rocks thin out.” The arrangement of the sedimentary strata of which moun- tains are composed may be either horizontal, synclinal, anti- clinal, or vertical, but from the greater action of diluvial forces upon anticlinals in disturbed strata it results that great moun- tain-chains are generally synclinal in their structure, being in fact but fragments of the upper portion of the earth’s crust lying in synclinals, and thus preserved from the destruction V.J THE ORIGIN OF MOUNTAINS. 53 and translation which have exposed the lower strata in the anticlinal valleys, leaving the intermediate mountains capped with lower strata. The effects of those great and mysterious - denuding forces which have so powerfully modified the surface of the globe become less apparent as we approach the equatorial regions, and accordingly we find that in the southern portions of the Appalachian chain many of the anticlinal folds have escaped erosion, and appear as hills of an anticlinal structure. The same thing is occasionally met with farther north ; thus Sutton Mountain in eastern Canada, lying between two anti- clinal valleys, has an anticlinal centre, with two synclinals on | its opposite slopes. Its form appears to result from three anticlinals, the middle one of which has to a great extent escaped denudation. The error of the prevailing ideas upon the nature of mountain chains may be traced to the notion that a disturbed condition of the rocky strata is not only essential to the structure of a mountain, but an evidence of its having been formed by local upheaval ; and the great merit of De Montlosier and Lesley (the latter altogether independently) is to have seen that the upheaval has been in all cases not local but continental, and that the disturbance so often seen in the strata is neither de- pendent upon elevation nor essential to the formation of a mountain. Such was the state of the question when Mr. Hall came for- ward, bringing his great knowledge of the sedimentary forma- tions of North America to bear upon the theory of continents and mountains. These were first advanced in his address de- livered before the American Association for the Advancement of Science, as its president, at Montreal, in August, 1857. This address was never published, but the author’s views were brought forward in the first volume of his Report on the Geology of Iowa, p. 41, and with more detail in the Introduc- tion to the third volume of his Paleontology of New York, from which we have taken the abstract already given. He has shown that the difference between the geographical features of seh ema Da tea Ef i 234 a 54 THE ORIGIN OF MOUNTAINS. iv: the eastern and central parts of North America is aieatay con- nected with the greater accumulation of sediment along the Appalachians. He has further shown that so far from local elevation being concerned in the formation of these mountains, the strata which form their base are to be found beneath their foundations at a much lower horizon than in the undisturbed hills of the Mississippi Valley, and that to this depression chiefly is due the fact that the mountains of the Appalachian range do not, like those hills, exhibit in their vertical height above the sea the whole accumulated thickness of the palzozoic strata which lie buried beneath their summits. .... The lines of mountain-elevation of De Beaumont are, accord- ing to Hall, simply those of original accumulations, which took — place along current or shore lines, and have subsequently, by continental elevations, produced mountain-chains, “They were not then due to a later action upon the earth’s crust, but the course of the chain and the source of the materials were predetermined by forces in operation long anterior to the existence of the mountains or of the continent of which they form a part.” (p. 86.) It will be seen from what we have said of Buffon, De Mont- losier, and Lesley, that many of the views of Mr. Hall are not new, but old; it was, however, reserved to him to complete the theory and give to the world a rational system of orographic geology. He modestly says: “I believe I have controverted no established fact or principle beyond that of denying the influence of local elevating forces, and the intrusion of ancient or plutonic formations beneath the lines of mountains, as ordi- narily understood and advocated. In this I believe I am only going back to the views which were long since entertained by geologists relative to continental elevations.” (p. 82.) The nature of the palwozoic sediments of North America clearly shows that they were accumulated during a slow pro- gressive subsidence of the ocean’s bed, lasting through the palaozoic period, and this subsidence, which would be greatest along the line of greatest accumulation, was doubtless, as Mr. Hall considers, connected with the transfer of sediment and > . " - al —- —N eS tes Sat Pig cee Re “Pps go 7 . = ob Nn ap oo V.] THE ORIGIN OF MOUNTAINS. 55 the variations of local pressure acting upon the yielding crust of the earth, agreeably to the view of Sir John Herschel. This subsidence of the ocean’s bottom would, according to Mr. Hall, cause plications in the soft and yielding strata. Lyell, in speculating upon the results of a cooling and con- tracting sea of molten matter, such as he imagined might have once underlaid the Appalachians, had already suggested that the incumbent flexible strata, collapsing in obedience to grav- ity, would be forced, if this contraction took place along narrow and parallel zones of country, to fold into a smaller space as they conformed to the circumference of a smaller arc, “thus enabling the force of gravity, though originally exerted vertically, to bend and squeeze the rocks as if they had been subjected to lateral pressure.” * Admitting thus Herschel’s theory of subsidence and Lyell’s theory of plication, Mr. Hall proceeds to inquire into the great system of foldings presented by the Appalachians. The sink- ing along the line of greatest accumulation produces a vast synclinal, which is that of the mountain ranges, and the result of such a sinking of flexible beds will be the production within the greater synclinal of numerous smaller synclinal and anti- clinal axes, which must gradually~decline toward the margin of the great synclinal axis. This process, the author observes, appears to furnish a satisfactory explanation of the difference of slope observed on the two sides of the Appalachian anticli- nals, where the dips on one side are uniformly steeper than on the other. (p. 71.) An important question here arises, which is this: while admitting with Lyell and Hall that parallel foldings may be the result of the subsidence which accompanied the deposition of the Appalachian sediments, we inquire whether the cause is adequate to produce the vast and repeated flexures presented by the Alleghanies. Mr. Billings, in a recent paper in the Canadian Naturalist (Jan., 1860), has endeavored to show that the foldings thus produced must be insignificant when compared with the great undulations of strata; whose origin . * Travels in North America, First Visit, Vol. I. p. 78. 56 THE ORIGIN OF MOUNTAINS. v. Professor Rogers has endeavored to explain by his theory of earthquake-waves propagated through the igneous fluid mass of the globe, and rolling up the flexible crust. We shall not — stop to discuss this theory, but call attention to another agency hitherto overlooked, which must also cause contraction and folding of the strata, and to which we have already elsewhere alluded. (Am. Jour. Sci. (2), XXX. 138.) It is the conden- sation which must take place when porous sediments are con- verted into crystalline rocks like gneiss and mica-slate, and still more when the elements of these sediments are changed into minerals of high specific gravity, such as pyroxene, garnet, epidote, staurolite, chiastolite, and chloritoid. This contrac- tion can only take place when the sediments have become deeply buried and are undergoing metamorphism, and is, as many attendant phenomena indicate, connected with a softened and yielding condition of the lower strata. . We have now in this connection to consider the hypothesis which ascribes the corrugation of portions of the earth’s crust to the gradual contraction of the interior. An able discussion of this view will be found in the American Journal of Science (2), III. 176, from the pen of Mr. J. D. Dana, who, in common with all others who have hitherto written on the subject, adopts the notion of the igneous fluidity of the earth’s interior. We have, however, elsewhere given our reasons for accepting the conclusion of Hopkins and Hennessey that the earth, instead of being a liquid mass covered with a thin crust, is essentially solid to a great depth, if not indeed to the centre, so that the volcanic and igneous phenomena generally ascribed to a fluid nucleus have their seat, as Keferstein and, after him, Sir John Herschel long since suggested, not in the anhydrous solid nucleus, but in the deeply buried layers of aqueous sedi- ments, which, permeated with water, and raised to a high temperature, become reduced to a state of more or less com- plete igneo-aqueous fusion. So that beneath the outer crust of sediments, and surrounding the solid nucleus, we may sup- pose a zone of plastic sedimentary material adequate to explain all the phenomena hitherto ascribed to a fluid nucleus. (Quazr. f Hel be aid 1 re ane ts) ok a ae 7 Poel ,: — & V.] ‘THE ORIGIN OF MOUNTAINS. 57 Jour. Geol. Society, Nov., 1859; Canadian Naturalist, Dec., 1859 ; Amer. Jour. Sci. (2), XXX. 136; and ante, page 9.) , This hypothesis, as we have endeavored to show, is not only completely conformable with what we know of the behavior of aqueous sediments impregnated with water and exposed to a high temperature, but offers a ready explanation of all the phenomena of volcanoes and igneous rocks, while avoiding the many difficulties which beset the hypothesis of a nucleus in a state of igneous fluidity. At the same time any changes in volume resulting from the contraction of the nucleus would affect the outer crust through the medium of the more or less plastic zone of sediments, precisely as if the whole interior of the globe were in a liquid state. The accumulation of a great thickness of sediment along a given line would, by destroying the equilibrium of pressure, cause the somewhat flexible crust to subside ; the lower strata becoming altered by the ascending heat of the nucleus would crystallize and contract, and plications would thus be deter- mined parallel to the line of deposition. These foldings, not less than the softening of the bottom strata, establish lines of weakness or of least resistance in the earth’s crust, and thus determine the contraction which results from the cooling of the globe to exhibit itself in those regions and along those lines where the ocean’s bed is subsiding beneath the accumu- lating sediments. Hence we conceive that the subsidence invoked by Mr. Hall (and by Lyell), although not the sole nor even the principal cause of the corrugations of the strata, is the one which determines their position and direction, by making the effects produced by the contraction not only of sediments, but of the earth’s nucleus itself, to be exerted along the lines of greatest accumulation. ... . On the subject of igneous rocks and volcanic phenomena, Mr. Hall insists upon the principles which we were, so far as we know, the first to point out, namely, their connection with great accumulations of sediment, and that of active volcanoes with the newer deposits. We. have elsewhere said: “The voleanic phenomena of the day appear, so far as we are aware, BY * 58 | THE ORIGIN OF MOUNTAINS. and ancient plutonic rocks; these latter, like lected we : in all cases as but altered ea displaced youiens: for v nected with rapid accumulation over limited areas, perhaps disruptions of the crust, through which the semi-flu stratum may have risen to the surface. He cites in this nection the traps with the paleozoic sandstones of Lake Ase , rior, and with the mesozoic sandstones of Nova Scotia and the yi Connecticut and Hudson Valleys. 3; * Ante, pp. 9 and 17. VI. - THE PROBABLE SEAT OF VOLCANIC ACTION. (1869.) The following paper was published in the Geological Magazine for June, 1869, and reprinted, with an additional paragraph, in the Am. Jour. Science, from which it is here reproduced, It is, as will be seen, to some extent a reinforcement of the views advanced in Papers I. and II. ; but, notwithstanding the repetitions involved, it has been thought proper to reprint it entire for the sake of the context. In further eluci- dation of the subject I have appended some extracts from a lecture given in April, 1869, before the American Geographical Society in New York, and published in its Proceedings, in which the distribution of volcanic and plutonic phenomena are con- sidered. TuE igneous theory of the earth’s crust, which supposes it to have been at one time a fused mass, and to still retain in its interior a great degree of heat, is now generally admitted. In order to explain the origin of eruptive rocks, the phenomena of volcanoes, and the movements of the earth’s crust, all of which are conceived by geologists to depend upon the internal heat of the earth, three principal hypotheses have been put forward. Of these the first supposes that in the cooling of the globe a solid crust of no great thickness was formed, which rests upon the still uncongealed nucleus. The second hypothesis, maintained by Hopkins and by Poulett Scrope, supposes solidification to have commenced at the centre of the liquid globe, and to have advanced towards the circumference. Before the last portions became solidified, there was produced, it is conceived, a condi- tion of imperfect liquidity, preventing the sinking of the cooled and heavier particles, and giving rise to a superficial crust, from which solidification would proceed downwards. There would thus be enclosed, between the inner and outer solid parts, a | » We 4 pe ei” Bias Yd 5 tr ee i nD om k J ET Pee ES eee een es or a , ies a <> {f° 60 THE PROBABLE SEAT OF VOLCANIC ACTION. (VL portion of uncongealed matter, which, according to Hopkins, may be supposed still to retain its liquid condition, and to be the seat of volcanic action, whether existing in isolated reser- voirs or subterranean lakes ; or whether, as suggested by Scrope, forming a continuous sheet surrounding the solid nucleus, whose existence is thus conciliated with the evident facts of a flexible crust, and of liquid ignited matters beneath. Hopkins, in the discussion of this question, insisted upon the fact, established by his experiments, that pressure favors the solidification of matters which, like rocks, pass in melting to a less dense condition, and hence concludes that the pressure existing at great depths must have induced solidification of the molten mass at a temperature at which, under a less pressure, it would have remained liquid. Mr. Serope has followed this up by the ingenious suggestion that the great pressure upon parts of the solid igneous mass may become relaxed from the effect of local movements of the earth’s crust, causing portions of the solidified matter to pass immediately into the liquid state, thus giving rise to eruptive rocks in regions where all before was solid.* Similar views have been put eee in a note by Rey. O. Fisher, and in an essay on the formation of mountain-chains, by N. S. Shaler, in the Proceedings of the Boston Society of Natural History, both of which appear in the Geological Maga- zine for November last. As summed up by Mr. Shaler, the second hypothesis supposes that the earth “consists of an immense solid nucleus, a hardened outer crust, and an inter- mediate region of comparatively slight depth, in an imperfect state of igneous fusion.” In this connection it is curious to remark that, as pointed out by Mr. J. Clifton Ward, in the same Magazine for December (p. 581), Halley was led, from the study of terrestrial magnetism, to a similar hypothesis, He supposed the existence of two magnetic poles situated in the earth’s outer crust, and two others in an interior mass, sepa- rated from the solid envelope by a fluid medium, and revolving, * See Scrope On Volcanoes, and his communication to the Geological Mag- azine for December, 1868, VI. THE PROBABLE SEAT OF VOLCANIC ACTION. 61 by a very small degree, slower than the outer crust.* The same conclusion was subsequently adopted by Hansteen. The formation of a solid layer at the surface of the viscid and nearly congealed mass of the cooling globe, as supposed by the advocates of the second hypothesis, is readily admissible. That this process should commence when the remaining envelope of liquid was yet so deep that the refrigeration from that time to the present has not been sufficient for its entire solidification, is, however, not so probable. Such a crust on the cooling superficial layer would, from the contraction cohsequent on the further refrigeration of the liquid stratum beneath, become more or less depressed and corrugated, so that there would probably result, as I have elsewhere said, “an irregular diver- sified surface from the contraction of the congealing mass, which at last formed a liquid bath of no great depth, surround- ing the solid nucleus.” + Geological phenomena do not, how- ever, in my opinion, afford any evidence of the existence of yet unsolidified portions of the originally liquid material, but are more simply explained by the third hypothesis. This, like the last, supposes the’ existence of a solid nucleus and of an outer crust, with an interposed layer of partially fluid matter ; which is not, however, a still unsolidified portion of the once liquid globe, but consists of the outer part of the congealed primitive mass, disintegrated and modified by chemical and mechanical agencies, impregnated with water, and in a state of | igneo-aqueous fusion. The history of this view forms an interesting chapter in geology. As remarked by Humboldt, a notion that volcanic phenomena have their seat in the sedimentary formations, and are dependent on the combustion of organic substances, belongs * The elevated temperature of the interior of the globe would probably offer no obstacle to the development of magnetism. In a recent experiment of M. Tréve, communicated by M. Faye to the French Academy of Sciences, it was found that molten cast-iron when poured into a mould, surrounded by a helix which was traversed by an electric current, became a strong magnet when liquid at a temperature of 1300° C., and retained its magnetism while cooling. (Comptes Rendus de l’Acad. des Sciences, February, 1869.) t Ante, page 39. MS ee eee ee ee eS Se nr ee a ee ot . Te, 2 oe pe 62 THE PROBABLE SEAT OF VOLCANIC ACTION. [VL _ to the infancy of geology. To this period belong the theories of Lémery and Breislak. (Cosmos, V. 443 ; Otté’s translation.) Keferstein, in his Naturgeschichte des Erdkorpers, published in 1834, maintained that all crystalline non-stratified rocks, from granite to lava, are products of the transformation of sediment- ary strata, in part very recent, and that there is no well-defined line to be drawn between neptunian and volcanic rocks, since they pass into each other. Volcanic phenomena, according to him, have their origin not in an igneous fluid centre, nor in an oxidizing meta¥lic nucleus (Davy, Daubeny), but in known sedimentary formations, where they are the result of a peculiar kind of fermentation, which crystallizes and arranges in new forms the elements of the sedimentary strata, with an evolu- tion of heat as a result of the chemical process. (Naturgeschichte, Vol. I. p..109; also Bull. Soc. Geol. de France (1), Vol. VII. p. 197.) In commenting upon these views (Am. Jour. Science, July, 1860), I have remarked that, by ignoring the incandes- cent nucleus as a source of heat, Keferstein has excluded the true exciting cause of the chemical changes which take place in the buried sediments. The notion of a subterranean combus- tion or fermentation, as a source of heat, is to be rejected as irrational. A view identical with that of Keferstein, as to the seat of voleanic phenomena, was soon after put forth by Sir John Herschel, in a letter to Sir Charles Lyell, in 1836. (Proc. Geol. Soc. London, II. 548.) Starting from the suggestions of Scrope and Babbage, that the isothermal horizons in the earth’s crust must rise as a consequence of the accumulation of sediments, he insisted that deeply buried strata will thus become crystallized by heat, and may eventually, with their in- cluded water, be raised to the melting point, by which process gases would be generated, and earthquakes and volcanic erup- tions follow. At the same time the mechanical disturbance of the equilibrium of pressure, consequent upon a transfer of sedi- ments while the yielding surface reposes on matters partly liquefied, will explain the movements of elevation and subsidence of the earth’s crust. Herschel was probably ignorant of the VIL] THE PROBABLE SEAT OF VOLCANIC ACTION. 63 extent to which his views had been anticipated by Keferstein ; and the suggestions of the one and the other seemed to have passed unnoticed by geologists until, in March, 1858, I repro- duced them in a paper read before the Canadian Institute (Toronto), being at that time acquainted with Herschel’s letter, but not having met with the writings of Keferstein. I there considered the reaction which would take place under the in- fluence of a high temperature in sediments permeated with water, and containing, besides silicious and aluminous matters, -earbonates, sulphates, chlorides and carbonaceous substances. From these, it was shown, might be produced all the gaseous emanations of volcanic districts, while from aqueo-igneous fusion of the various admixtures might result the great variety of eruptive rocks. To quote the words of my paper just referred to : “‘ We conceive that the earth’s solid crust of anhy- drous and primitive igneous rock is everywhere deeply concealed beneath its own ruins, which form a great mass of sediment- ary strata, permeated by water. As heat from beneath invades these sediments, it produces in them that change which con- stitutes normal metamorphism. These rocks, at a sufficient depth, are necessarily in a state of igneo-aqueous fusion ; and in the event of fracture in the overlying strata, may rise among them, taking the form of eruptive rocks. When the nature of the sediments is such as to generate great amounts of elastic fluids by their fusion, earthquakes and volcanic eruptions may result, and these— other things being equal — will be most likely to occur under the more recent formations.” * (Cana- dian Journal, May, 1858, Vol. III. p. 207 ; and ante, page 9.) The same views are insisted upon in a paper On some Points in Chemical Geology (Quar. Jour. Geol. Soc., London, Noy., 1859, Vol. XV. p. 594), and have since been hopeniadly put forward by me, with further explanations as to what I have designated above, the ruins of the crust of anhydrous and primitive igneous rock. This, it is conceived, must, by contrac- tion in cooling, have become porous and permeable, for a con- siderable depth, to the waters afterwards precipitated upon its surface. In this way it was prepared alike for mechanical dis- 64 THE PROBABLE SEAT OF VOLCANIC ACTION. "v1 integration, and for the chemical action of the acids, which, as - shown in the two papers just referred to, must have been pres- ent in the air and the waters of the time. It is, moreover, not improbable that a yet unsolidified sheet of molten matter may then have-existed beneath the earth’s crust, and may have in- tervened in the volcanic phenomena of that early period, con- tributing, by its extravasation, to swell the vast amount of mineral matter then brought within aqueous and atmospheric influences. The earth, air, and water thus made to react upon each other, constitute the first matter from which, by mechan- ical and chemical transformations, the whole mineral world known to us has been produced. It is the lower portions of this great disintegrated and water- impregnated mass which form, according to the present hypoth- esis, the semi-liquid layer supposed to intervene between the outer solid crust and the inner solid and anhydrous nucleus. In order to obtain a correct notion of the condition of this mass, both in earlier and later times, two points must be especially considered, — the relation of temperature to depth, and that of solubility to pressure. It being conceded that the increase of temperature in descending in the earth’s crust is due to the transmission and escape of heat from the interior, Mr. Hopkins showed mathematically that there exists a constant proportion between the effect of internal heat at the surface and the rate at which the temperature increases in descending. Thus, at the present time, while the mean temperature at the earth’s surface is augmented only about one twentieth of a degree Fahrenheit, by the escape of heat from below, the increase is found to be equal to about one degree for each sixty feet in depth. If, however, we go back to a period in the history of our globe when the heat passing upwards through its crust was sufficient to raise the superficial temperature twenty times as much as at present, that is to say, one degree of Fahrenheit, the augmen- tation of heat in descending would be twenty times as great as now, or one degree for each three feet in depth. (Geol. Jour- nal, VIIT. 59.) The conclusion is inevitable that a condition of things must have existed during long periods in the history 5 = [ ee ee ee < 2 eucseaea og magnesia . : ‘ SES ekrdisss) evel . baryta and strontia . umdet. © cc... cesseees Pe In 1,000 parts . = : ; 46.3038 68.0423 50.6075 Oe ey eee IX.] CHEMISTRY OF NATURAL WATERS. 117 § 37. The waters of the first class contain, besides chloride of sodium and a little chloride of potassium, large quantities of the chlorides of calcium and magnesium, amounting together, in several cases, to more than one half the solid contents of the water. Sulphates are either absent, or occur only in small quantities, and the same is true of earthy carbonates. Salts of baryta and strontia are sometimes present, while the propor- tions of bromides and iodides, though variable, are often con- siderable. _ In the large amount of magnesian chloride which they con- tain, these waters resemble the bittern or mother-liquor which remains after the greater part of the chloride of sodium has been removed from sea-water by evaporation. The bitterns from modern seas, however, differ in the constant presence of sulphates, and in containing, when sufficiently concentrated, only traces of lime. The reason of this, as already pointed out in § 22, is to be found in the fact that in the waters of the present ocean the sulphates are much more than equivalent to the lime, so that this base separates during evaporation as gypsum.* But as shown in § 23 and § 24, the waters of the ancient seas, which held in the form of chloride of calcium the greater part of the lime since deposited as carbonate, must have yielded by evaporation bitterns containing a large pro- portion of chloride of calcium. Such is the nature of the brines whose analyses are given above, and such we suppose to have been their origin. The complete absence of sulphates from many of these waters points to the separation of large quantities of earthy sulphates in the Cambrian strata from which these saline springs issue; and the presence in many of the dolo- mitic beds of the Calciferous sand-rock of small masses of gyp- sum abundantly disseminated is an evidence of the elimination . of the sulphates by evaporation. The frequent occurrence of crystalline masses of sulphate of strontian in the Chazy and Black River limestones of this region is also to be noted as another means by which the sulphates were separated from the waters of the palzozoic seas. From the proportions of chloride * See further on this point, Bischof, Chem. Geology, I. 413. 118 CHEMISTRY OF NATURAL WATERS. [IX. of sodium, varying from about one third to more than two thirds of the solid contents of the above waters, it is apparent that in most cases the process of evaporation had gone so far as to separate a part of the common salt ; and thus successive strata of this ancient saliferous formation must be impregnated with solid or dissolved salts of unlike composition. The mingling of these in varying proportions affords the only apparent ex- planation of the differences which appear in the relative amounts of the several chlorides in waters from the same region, and even from adjacent sources. § 38. The great solubility of chloride of calcium renders it difficult to suppose its separation from the mother-liquors so as to be deposited in a solid state in the strata.* The same re- mark applies to chloride of magnesium. It is however to be remarked that the double chloride of potassium and magne- sium (carnallite) is decomposed by deliquescence into solid chloride of potassium and a solution of chloride of magne- sium ; and thus strata like those which at Stassfurth contain large quantities of carnallite (§ 22), might give rise to solu- tions of magnesian chloride. This, however, would require the presence of a large amount of chloride of potassium in the © early seas. It appears from the analyses above referred to that the chloride of magnesium sometimes surpasses in amount the chloride of calcium; and sometimes, on the contrary, is equal to only one half or one fourth of the latter salt. While it is not impossible that the predominance of the magnesian chloride in some waters may be traced to the decomposition of carnal- lite, it is undoubtedly in most cases connected with the action of solutions of carbonate of soda ; the effect of which, as already pointed out, is to first separate the soluble lime-salt as carbon- ate, leaving to a subsequent stage the magnesian chloride. (§ 18.) As this reaction replaces the calcium-salt by chloride of sodium, it might be expected that there would be an increase in the amount of the latter salt in the water wherever the magnesian chloride predominates, did we not remember that * [A hydrated double chloride of calcium and magnesium (tachydrite) has since been found at Stassfurth. ] IX.] CHEMISTRY OF NATURAL WATERS. 119 evaporation separates it from the water in the solid form; and that the two processes, one of which replaces the chloride of calcium by chloride of sodium, while the other eliminates the latter salt from the solution, might have been going on simulta- neously or alternately. As the nature of the waters now under consideration shows that the process of evaporation had been carried so far as to separate the sulphate in the form of gypsum, and probably also a portion of the chloride of sodium in a solid state, it is evident that we have not yet the data necessary for determining the composition of the water of the ancient Cambrian ocean, as regards the proportions of the sodium, cal- cium, and magnesium which it held in solution; and we can only conclude from these mother-liquors, that the amount of the earthy bases was relatively very large. § 39. As already remarked in § 22, the mother-liquor from modern sea-water contains no chloride of calcium, but, on the contrary, large quantities of sulphate of magnesia ; the lime in the modern ocean being less than one half that required to combine with the sulphate present. If, however, we examine the numerous analyses of rock-salt and of brines from various saliferous formations, we shall find that chloride of calcium is very frequently present in both of them ; thus supporting the conclusions already announced in § 24 with regard to the com- position of the seas of former geological periods. The oldest saliferous formation which has been hitherto investigated is the Onondaga Salt-group of the New York geologists, which be- longs to the upper part of the Silurian series, and supplies the strong brines of Syracuse and Salina in New York. These, notwithstanding their great purity, contain small proportions of chlorides of calcium and magnesium, as shown by the analyses of Beck, and the recent and careful examinations of Goessmann. In the brines of this region the solid matters are equal to from 14.3 to 16.7 per cent, and contain on an average, according to the latter chemist, 1.54 of sulphate of lime, 0.93 of chloride of calcium, and 0.88 of chloride of magnesium in 100 ; the remainder being chloride of sodium.* * Goessmann, Reports on the Brines of Onondaga: Syracuse, 1862 and 1864; also Report on the Onondaga Salt Co. : Syracuse, 1862. 120 CHEMISTRY OF NATURAL WATERS. . EES The nearly saturated brines from the Saginaw valley in Michigan, which have their source at the base of the carbonifer- ous series, contain, according to my calculation from an analysis by Professor Dubois, in 100 parts of solid matters: chloride of calcium 9.81, chloride of magnesium 7.61, sulphate of lime 2.20, the remainder being chiefly chloride of sodium. Another brine in the.same vicinity.gave to Chilton an amount of chloride of calcium equal to 3.76 per cent.* Ina specimen of salt man- ufactured in this region, Goessmann found 1.09 of chloride of calcium ; and in two specimens of salt from the brines of Ohio, from the same geological horizon, 0.61 and 1.43 per cent of the same chloride. The rock-salt from the lias of Cheshire, accord- ing to Nicol, contains small cavities, partly filled with air, and — partly with a concentrated solution of chloride of magnesium, with some chloride of calcium.t * Winchell, Amer. Jour. Sci. (2), XXXIV. 311. + Edin. Neu. Phil. Jour., VII. 111. The results of the analyses by Mr. Northcote of the brines of Droitwich and Stoke in the same region (L. E. & D. Philos. Mag. (4), IX. 32), as calculated by him, show no earthy chlorides what- ever, and no carbonate of lime, but carbonates of soda and magnesia, and sul- phates of soda and lime. He regarded the whole of the lime present in the water as being in the form of sulphate. If, however, we replace, in calculating these analyses, the carbonate of soda and sulphate of lime by sulphate of soda and carbonate of lime, we shall have for the contents of these brines: — chlo- ride of sodium, with notable quantities of sulphate of soda, some sulphate of lime, and carbonates both of lime and magnesia ; a composition which is more in accordance with the admitted laws of chemical combinations. From these results, it would appear that the earthy chlorides, which according to Nicol are present in the rock-salt of this formation, are decomposed by sulphates in the waters which, by dissolving it, give rise to the brines. ; It is to be regretted that in many water-analyses by chemists of note, the results are so calculated as to represent the coexistence of incompatible salts. Of the association of carbonates of soda and magnesia with sulphate of lime, as in the analysis just noted, it might be said that I have shown that it may occur in the presence of an excess of carbonic acid (ante, page 90). By evaporation, however, such solutions regenerate carbonate of lime and sul- phates of soda and magnesia; and by the consent of the best chemists these elements are to be represented as thus combined. But what shall be said when chloride of magnesium, carbonate of soda, and silicate of soda are given as the constituents of a water whose recent analysis may be found in a late number of the Chemical News ; or when bicarbonates of soda, magnesia, and lime are represented as coexisting in a water with sulphates and chlorides of magnesium and aluminum? These errors probably arise from determining in ; ty os Bitlet es enh oe IX.] CHEMISTRY OF NATURAL WATERS. 121 § 40. The brines from the valley of the Alleghany River, obtained from borings in the coal formation, are remarkable for containing large proportions of chlorides of calcium and magne- sium ; though the sum of these, according to the analyses of Lenny, is never equal to more than about one fourth of the chloride of sodium. The presence of salts of barium and stron- tium in these brines, and the consequent absence of sulphates, is, according to Lenny, a constant character in this region over an area of two thousand square miles. (See Bischof, Chem. Geol., I. 377.) A later analysis of another one of these waters from the sime region, by Steiner, is cited by Will and Kopp, Jahresbericht, 1861, p. 1112. His results agree closely with those of Lenny. See also the analysis of a bittern from this region by Boyé. (Amer. Jour. Sci. (2), VII. 74.)* These remarkable waters approach in character to those of Whitby and Hallowell; but in this the chloride of sodium forms only about one half the solid contents, and the propor- tion of the chloride of magnesium to the chloride of calcium is relatively much greater than in the waters from western Penn- sylvania, where the magnesian chloride is equal only to from one third to one fifth of the chloride of calcium ; the proportions of the two being subject in both regions to considerable varia- tions. | In this connection may be cited a water from Bras d’Or in the island of Cape Breton, lately analyzed by Professor How, which contains in 1,000 parts, chloride of sodium 4.901, chloride of potassium 0.650, chloride of calcium 4.413, and chloride of magnesium only 0.638, besides sulphate of lime 0.134, carbon- ates of lime and magnesia 0.085, with traces of iron-oxide and phosphates; = 10.821. (Canadian Naturalist, VIII. 370.) ‘the recent water, or in water not sufficiently boiled, the lime and magnesia which would by prolonged ebullition be separated as carbonates, together with portions of alumina, silica, etc. In the subsequent calculation of the analyses, these dissolved earthy bases being regarded as sulphates or chlorides, instead of carbonates, there remains an excess of soda, which is wrongly represented as carbonate, instead of chloride or sulphate of sodium. * [For further examples of waters of this class from western Ontario, see the Supplement to this paper.] 6 eS ee ee a ee ie eee ee ae ee er oreo; La eo Se 422 CHEMISTRY OF NATURAL WATERS. [Ix. The analyses of European waters furnish comparatively few ex- amples of the predominance of earthy chlorides.* § 41. We have already shown in § 38 how the action of — carbonate of soda upon sea-water or bittern will destroy the normal proportion between the chlorides of magnesium and calcium by converting the latter into an insoluble carbonate, and leaving at last only salts of sodium and magnesium in solution. A process the reverse of this has evidently inter- vened for the production of waters like that from Cape Breton, and some others noticed by Lersch, in which chloride of cal- cium abounds, with little or no sulphate or chloride of magne- sium. ‘This process is probably one connected with the forma- ‘tion of a silicate of magnesia. Bischof has already insisted upon the sparing solubility of this silicate, and has asserted that silicates of alumina, both artificial and natural, when digested with a solution of magnesian chloride, exchange a por- tion of their base for magnesia, thus giving rise to solutions of alumina; which, being decomposed by carbonates, may have been the source of many of the aluminous deposits referred to in § 9. He also observed a similar decomposition between a solu- tion of an artificial silicate of lime and soluble magnesian salts. (Bischof, Chem. Geology, I. 13 ; also Chap. XXIV.) In repeat- ing and extending his experiments, I have confirmed his obser- vation that a solution of silicate of lime precipitates silicate of magnesia from the sulphate and the chloride of magnesium ; and have moreover found that by digestion at ordinary temper- atures with an excess of freshly precipitated silicate of lime, chloride of magnesium is completely decomposed ; an insoluble silicate of magnesia being formed, while nothing but chloride of calcium remains’ in solution. It is clear that the greater insolubility of the magnesian silicate, as compared with silicate of lime, determines a result the very reverse of that produced by carbonates with solutions of the two earthy bases. In the one * Lersch, Hydro-Chemie, Zweite Auflage: Berlin, 1864; vide p. 207. This excellent work, which is a treatise on the chemistry of natural waters, in one volume 8vo of 700 pages, was unknown to me when I prepared the first part of this essay. oo a ae Be tut IX.] CHEMISTRY OF NATURAL WATERS. 123 case the lime is separated as carbonate, the magnesia remaining in solution ; while in the other, by the action of silicate of soda (or of lime), the magnesia is removed and the lime remains. Hence carbonate of lime and silicates of magnesia are found abundantly in nature; while carbonate of magnesia and sili- cates of lime are produced only under local and exceptional conditions. It is evident that the production from the waters of the early seas of beds of sepiolite, talc, serpentine, and other rocks in which a magnesian silicate abounds, must, in closed basins, have given rise to waters in which chloride of calcium would predominate. [§ 42 of the original paper contains descriptions and anal- yses of eight waters of Class II., the solid contents of which vary from 9 to 20 parts in 1,000; they rarely contain sul- phates. The three given below, which may be taken as exam- ples, rise from the Trenton limestone of the Ottawa and St. Lawrence valleys, the first being that known as the Intermittent Spring of Caledonia. | Waters of Class IT. Caledonia. Lanoraie. St. Léon. Chloride of sodium a : : 12.2500 11.1400 11.4968 nF potassium - ; ‘ .0305 .1460 1832 xi barium 4 . AAT AT ioe Be Bp -0303 .0019 Ee strontium < ¢ foe ds vende .0185 .0019 hs calcium > : ’ .2870 . 2420 .0718 ” Magnesium ., , - 1.0338 .2790 .6636 Bromide of - : Fs P -0238 .0283 0091 Iodide of ss r » ‘ .0021 .0052 .0046 Sarhouste of batyia ve 2) end Se) eandasnes 7 (FT) Rema S ¢ i strontia : . AN ee Ay ty Se pe rhe lime . ‘ . .1264 4520 38493 “ magnesia ‘ ‘ ‘ .8632 4622 .9388 « tren. 8.¥ 3 ; traces traces .0145 Silica : ; mer : ‘ .0225 .0552 .0865 Alumina ‘ - ; . : undet. undet. .0145 In 1,000 parts . . . ° - 14.6393 12.8830 13.8365 Specific gravity . ‘ ‘ ; 1010.9 1009. 42 1011.23 [§ 43 gives the description and analysis of eight waters of Class III. which hold from less than 5 to more than 10 parts mn 44 Be “Y: yy * 3 << . * Te Pee oe 4 124 CHEMISTRY OF NATURAL WATERS. ix of solid water in 1,000. Of the three whose analysis is given below, the first rises from the Chazy formation in the Ottawa valley, and the others from the Utica and Hudson River for- mations in the valley of the St. Lawrence. The alkaline-saline waters of Caledonia, belonging to the same class, which will be mentioned further on in § 47, rise from the Trenton lime- stone in the former region. |] Waters of Class ITI. Fitzroy. Varennes. Baie du Febyre. Chloride of sodium . . . 6.5325 9.4231 4,8234 © * potassium . A peery © 11) .1234 -0610 Bromide of sodium . x ; .0217 -0126 undet. Iodide of 2 eae . . 20082 .0054 undet. Phosphate of soda. ° pe Oe oO. ee skvnes 40 e eee ‘Carbonate of ‘*. ; “ . | 6885 -1705 1.5416 €¢ baryta . : . traces -0226 traces 6 strontia : ; st .0140 ee é¢ lime ; : .1500 .3540 .2180 “s magnesia . > 7860 5433 .4263 és iron . ; traces -O048 : . Sisdeone Alumina ‘ : : 3 » 0040 traces undet. Silica ; ‘. ‘ . ; .1330 .0465 .2129 In 1,000 parts ° . . - 8.3473 10.7202 7.2923 Specific gravity : : . 1006.24 ROG AD i)” odenades § 44. Of the waters of Class IV. the first to be noticed is one occurring at Chambly, on the Richelieu River, in the province of Quebec. Here, on a plateau, over an area of about two acres, the clayey soil is destitute of vegetation and impregnated with alkaline waters ; which in the dry season give rise to a saline efflorescence on the partially dried up and fissured surface. A well sunk here to the depth of eight or.ten feet in the clay, which overlies the Hudson River formation, affords at all times an abundant supply of water, which generally flows in a little stream from the top of the well. Small bubbles of carburetted hydrogen are sometimes seen to escape from the water. The temperature at the bottom of the well was found in October, 1861, to be 53° F., and in August, 1865, to be nearly 54° F, The mean temperature of Chambly can differ but little from Pea Peleg a eee ee ee ee) ~ sae » ree a al - y ae a ‘or, at ee ee NE Ae in a ae (aii IX.] CHEMISTRY OF NATURAL WATERS. 125 that of Montreal, which is 44.6° F., so that this is a thermal water. Another alkaline and saline spring in the same parish has also a temperature of 53° F. The water of the spring here described has a sweetish saline taste, and is much relished by the cattle of the neighborhood. Three analyses have been made of its waters, the results of which are here given side by side. The first was collected in October, 1851; the second in October, 1852 ; and the third in August, 1864, during a very dry season. Waters of Chambly, Class IV. ¥. II. EIS Chloride of potassium . . ; undet. .0324 .0182 = sodium . . ° . .8689 .8387 .8846 Carbonate ‘‘ ‘ ‘ : 5 1.0295 1.0604 .9820 ah lime as. F . 0540 - .0380 .0253 - magnesia . , ‘ .0908 .0765 .0650 is strontia . ; : . undet. .0045 undet. BS iron. : ‘ a ‘ 0024 ¥ Alumina and phosphate . é ; i .0063 “¢ Silica -. ‘ ‘ ‘ é . .1220 - .0730 .0166 Borates, iodides, and bromides . . undet. undet. undet. In 1,000 parts. : . : : 2.1652 2.1322 1.9917 A portion of barium is included with the strontium salt. The water contains moreover a portion of an organic acid, which causes it to assume a bright brown color when reduced by evap- oration. Acetic acid gave no precipitate with the concentrated and filtered water; but the subsequent addition of acetate of copper yielded a brown precipitate of what was regarded as apocrenate of copper. The organic matter of this and of many other mineral springs has probably a superficial origin. The carbonic acid was determined in the third analysis, and was equal in two trials to .903 and .905. The neutral carbonates in this water require .452 parts of carbonic acid. [§§ 45, 46, give the analyses of six more waters of Class IV., none of which are as highly charged with mineral sub- stances as that of Chambly, though holding from 0.34 to 1.55 parts of solid matter to 1,000. All of these waters are found in the valleys of the St. Lawrence and of Lake Champlain, and are believed to rise from the Utica or Hudson River shales. 126 CHEMISTRY OF NATURAL WATERS. (Tx. The analyses of the three given below may be taken as addi- tional examples of this class. That of St. Ours is remarkable for a large proportion of potassium-salts, about twenty-five per cent of the alkalies, determined as chlorides, being chloride of potassium. | Waters of Class IV. St. Ours. Joly. Nicolet, Chloride of sodium . «. «. «© £.0207 # .0347 3920 . potassium . : . - 0496 .0076 -0318 Sulphate of potash ‘ ‘ ° : 60081." °°... SU Carbonate of soda. . . . - 13840 _ .1952 1.1353 - lime . ° . ; ‘ -1740 .0710 undet. ‘+ magnesia. : . - 1287 0278 sig Tron-oxide, alumina, and phosphates . traces ...... " Silica .. ° ; ‘ ; ; . 0161 .0110 . In 1,000 parts. . i ‘ . . 5311 .8473 1.5591 To the above may be joined, for comparison, the analysis of the waters of a large river, the Ottawa, which drains a region occupied chiefly by crystalline rocks, covered by ex- tensive forests and marshes. The soluble matters which it contains are therefore derived in part from the superficial de- composition of these rocks, and in part from the decaying vegetation. The water, which was taken at the head of the St. Anne’s rapids, on the 9th of March, 1854, before the melt- ing of the winter’s snows had begun, had a pale amber-yellow hue, from dissolved organic matter, which gave a dark brown color to the residue after evaporation. The weight of this residue from 10,000 parts, dried at 300° F., was .6975, which after ignition was reduced to .5340 parts. As seen in the table below, one half of the solid matters in this water were earthy carbonates, and more than one third was silica, so that the whole amount of salts of alkaline bases was .088 (of which nearly one half is carbonate of soda); while the St. Ours water, which resembles that of the Ottawa in its alkaline salts, con- tains in the same quantity 4.248, or more than forty-eight times as much. The alkalies of the Ottawa water equalled as chlorides .0900, of which .0293, or 32.5 per cent, were chloride of potassium, The results of some observations on s IX.] -CHEMISTRY OF NATURAL WATERS. 127 the silica and the organic matters of this river-water will be given further on (§§ 70, 71). It will be observed that while the contents of all the other waters in this paper are given for 1,000 parts, those of the Ottawa are calculated for 10,000 parts. Water of the Ottawa River. Chloride of potassium . : ; ‘ é , : ‘ .0169 Sulphate of soda ; ‘ . . ; ‘ : : - .0188 - potassium . ‘ ‘ ‘ . ‘ ‘ : 0122 Carbonate of soda. ‘ ‘ ‘ , F ‘ F . «0410 {: lime . . : ° Sila 8 re ° : . -2680 " magnesia 4 ; ‘ ‘ ‘ . 0690 Iron-oxide, alumina, and phosphates . é . : - traces Silica ‘ . é ‘ ; é 7 é ‘ é . 2060 In 10,000 parts. : : , ‘ Pai ; ; .6116 § 47. It was an interesting question to determine whether the composition of these various waters remains constant. Having collected and analyzed, in September, 1847, the waters of three springs in Caledonia, Ontario, belonging to Class ITI., and not far from the spring of Class II. in the same town, noticed in § 42, I again visited and collected for examination the waters of the same springs in January, 1865, after a lapse of more than seventeen years. The results, when compared as below, show that considerable changes have occurred in the compo- sition of each of these springs, and tend to confirm in an unexpected manner the theory which I had long before put forward, —that the waters of the second and third classes owe their origin to the mingling of saline waters of the first class with alkaline waters of the fourth class. It will be observed that the three Caledonia waters in 1847 were all alkaline, although the proportions of carbonate of soda were unlike. Sulphates were then present in all of them, but most abundant in the Sulphur Spring, which, although holding the smallest amount of solid matters, was the most alkaline. In January, 1865, however, the first and second of these waters had ceased to be alkaline, and contained, instead of carbonate of soda, small quantities of earthy chloride, causing them to enter into the second class. They no longer contained any Ps ee a te ke eee 4 Ly ee ee ee oe ‘a, 4 ¥ 4 Me mt oA 128 CHEMISTRY OF NATURAL WATERS. [Ix. sulphates, but, on the contrary, portions of baryta and strontia. Only the Sulphur Spring, which in 1847 contained the largest proportion of carbonate of soda and of sulphates, still retained these elements, though in diminished amounts, and was feebly impregnated with sulphuretted hydrogen. If we suppose these waters to arise from the commingling of saline waters of the first or second class, like those of Whitby and Lanoraie, con- taining earthy chlorides and salts of baryta and strontia, with a water of the fourth class holding carbonate and sulphate of soda, it is evident that ¢ sufficient quantity of the latter water would decompose the earthy chlorides and precipitate the salts of baryta and strontia present, while an excess would give use to alkaline-saline waters containing sulphate and carbonate of soda, such as were the three springs of Caledonia in 1847. A falling off in the supply of the sulphated alkaline water may be supposed to have taken place, and the result is seen in the appearance of chloride of magnesium and of baryta and strontia in two of the springs, and in a diminished proportion of carbonate of soda in the Sulphur Spring.* These later analyses being directed chiefly to the determina- tion of these changes, no attempt was made to determine potas- sium, iodine, or bromine. For the purposes of comparison, the two series of analysest are here put in juxtaposition ; the © element just mentioned being included with the chloride of _ sodium, and the figures reduced to three places of decimals, The precipitate by a solution of gypsum from the concentrated and acidulated water was regarded as sulphate of strontia, and calculated as such, but was in part sulphate of baryta. * [The Harrowgate springs, in England, have undergone changes not un- like those of Caledonia. Several of the Harrowgate waters, all of which were found by Dr. Hofman, in 1854, to contain sulphate of lime, were examined by Mr. Davis, in 1866, and found, with one exception, to be free from sulphate, and to contain instead salts of baryta, even in the sulphuretted waters. Great differences are there, as elsewhere, observed between closely adjacent springs; and in one of them, a strong saline holding chloride of barium, Dr. Muspratt detected a small amount of protochloride of iron. (Chemical News, Vol XIII, passim. )| + [The complete earlier analyses are given in the original paper. ] a CHEMISTRY OF NATURAL WATERS. 129 Table showing the Changes in the Caledonia Springs. 1. Gas Spring. | 2. Saline Spring. |3. Sulphur Spring. 1847. 1865, 1847, 1865. 1847. 1865, Chlor.sodium . 7.014 | 6.570 | 6.488 | 6.930 | 3.876 | 3.685 ‘¢ magnesium. | ...... ODED oo casts SEEN 95 a50 0] a's nay Sulph. potash . SAUB. 4. sais OB.) Neos 018 | .021 Carb. soda . 4 BUREN tay wes OC Rl Re 456 | .091 ‘slime ; .148 .096 | .117 .095 | .210 077 ‘¢ magnesia . 526 | .455]-.517 | .469 | .294 | .228 se cetpontia® «| s.dse3 QORA Gxacat COTE Pisce | eanns Silica . : : .021 | .020] .042 | .015] .084 | .021 In 1,000 parts . 7.772 | 7.174 | 7.845 | 7.547 | 4.988 | 4.123 In the later analyses of these waters, the carbonic acid in the Gas Spring was found to equal, for 1,000 parts, .671 ; of which .278 were required for the neutral carbonates. The Saline Spring contained .664 of carbonic acid ; of which .290 go to make up the neutral carbonates... The Sulphur Spring, in like manner, gave of carbonic acid .573 ; while the neutral carbon- ates of the water require only .191. All of these waters, in January, 1865, thus contained an excess of carbonic acid above that required to form bicarbonates with the carbonated bases pres- ent; while the analyses of the same springs in 1847 showed a quantity of carbonic acid insufficient for the formation of bi- carbonates with these bases. The questions of the cause of this deficiency, and of the variation in the amount of carbonic acid in these and other waters, will be considered in the third part of this paper. | § 48. The waters of our fifth and sixth classes, as defined in § 34, are distinguished by the presence of sulphates ; the for- mer being acid, and the latter being neutral waters. In the fifth class the principal element is sulphuric acid, associated with variable and accidental amounts of sulphates of alkalies, ’ lime, magnesia, alumina, and iron. Apart from the springs of 6 * I 130 CHEMISTRY OF NATURAL WATERS. (Ix. . this kind which occur in regions where volcanic agencies are evidently active, the only ones hitherto studied are those of New York and western Canada, which issue from almost horizontal Silurian rocks (§ 31). The first account of these remarkable waters was given in the Amer. Jour. Sci. in 1829 (Vol. XV. p. 238), by the late Professor Eaton, who described two acid springs in Byron, Genesee County, N. Y. ; one yield- ing a stream of distinctly acid water sufficient to turn a mill- wheel, and the other affording in smaller quantities a much more acid water. The latter was afterwards examined by Dr. Lewis Beck (Mineralogy of New York, p. 150). He found it to be colorless, transparent, and intensely acid, with a specific gravity of 1.113; which corresponds to a solution holding seventeen per cent of oil of vitriol. No chlorides, and only traces of lime and iron, were found-in this water, which was nearly pure dilute sulphuric acid. Professor Hall (Geology of New York, 4th District, p. 134) has noticed, in addition to these, several other springs and wells of acid water in the adjacent town of Bergen. Farther westward, in the town of Alabama, is a similar water, whose analysis by Erni and Craw will be found in the Amer. Jour. Sci. (2), IX. 450. It con- tained in 1,000 parts about 2.5 of sulphuric acid, and 4.6 parts of sulphates, chiefly of lime, magnesia, iron, and alumina. In this, as in the succeeding analyses, hydrated sulphuric acid, SO,,HO, is meant. The earliest quantitative analyses of any of these waters were those by Croft and myself of a spring at Tuscarora, in 1845 and 1847, of which the detailed results appear in the Amer. Jour. Sci. (2), VIII. 364. This, at the time of my analysis in September, 1847, contained, in 1,000 parts, 4.29 of sulphuric acid, and only 1.87 of sulphates ; while the previous analysis by Professor Croft gave approximatively 3.00 of neutral sulphates, and only about 1.37 of sulphuric acid. Similar acid waters occur on Grand Island above Niagara Falls and at Chippewa. All of these springs, along a line of more than 100 miles from east to west, rise from the outcrop of the Onondaga salt- IX.] CHEMISTRY OF NATURAL WATERS. 131 group ; but in the township of Niagara, not far from Queenston, are two similar waters which issue from the Medina sandstone. One of these is in the southwest part of the township, and fills a small basin in yellow clay, which, at a depth of three or four feet, is underlaid by red and green sandstones. The water, which, like those of Tuscarora and Chippewa, is slightly im- pregnated with sulphuretted hydrogen, is kept in constant agitation from the escape of inflammable gas. It contained in 1,000 parts about two parts of free sulphuric acid, and less than one part of neutral sulphates. This water was collected in October, 1849, and at that time another half-dried-up pool in the vicinity contained a still more acid water. Another similar spring occurs near St. David, in the same township. In con- nection with the suggestion made in § 31 as to their probable origin at great depths, it would be very desirable to have careful observations as to the temperature of these acid springs. When, on the 19th October, 1847, I visited the Tuscarora spring, the water in two of the small pools had a temperature of 56° F.; but on plunging the thermometer in the mud at the bottom of one of these it rose to 60.5°.’ § 49. It appears from a comparison of the analysis of Croft with my own that the waters of the Tuscarora spring under- went a considerable change in composition in the space of two years ; the proportion of the bases to the acid at the time of the second analysis being little more than one third of that in the analysis of Croft. This change was indeed to be expected, since waters of this kind must soon remove the soluble constit- uents from the rocks through which they flow, and eventually become, like the water from Byron, little more than a solution of sulphuric acid. The observations of Eaton at Byron, and my own at Tuscarora, show that half-decayed trees are still standing on the soil which is now so impregnated with acid waters as to be unfit to support vegetation. Reasoning from the changes in composition, it may be supposed that these waters were at first neutral, the whole of the acid being satu- rated by the calcareous rocks through which they must rise. It was from this consideration that I was formerly led to ascribe / 132 CHEMISTRY OF NATURAL WATERS. (IX. to the action of these waters the formation of some of the masses of gypsum which appear along the outcrop of the Onon- daga salt-group (Amer. Jour. Sci. (2), VII. 175). That waters like those just mentioned must give rise to sulphate of lime by their action on calcareous rocks is evident; and some of the deposits of gypsum in this region, as described by good obsery- ers, would appear to be thus formed. So far, however, as my personal observations of the gypsums of western Canada have extended, these appear to be in all cases contemporaneous with the shales and dolomites with which they are interstratified, and to have no connection with the sulphuric-acid springs which are so common throughout that region. (Ibid. (2), XXVIII. 365 ; and Geology of Canada, 352.) § 50. We have included in a sixth class the various neutral saline waters in which sulphates predominate, sometimes. to the exclusion of chlorides. The bases of these waters are soda, potash, lime, and magnesia; which are usually found together, though in varying proportions. For the better under- standing of the relations of these sulphated waters, it may be well to recapitulate what has been said about their origin ; and to consider them, from this point of view, under two heads. First, those formed from the solution of neutral sulphates previously existing in a solid form in the earth. Strata en- closing natural deposits of sulphates of soda and magnesia, sometimes with sulphate of potash (§§ 17, 19), afford the most obvious source of these waters. . The frequent occurrence of gypsum, however, points to this salt as a more abundant source of sulphated waters. Solutions of gypsum may in some case exchange their lime for the soda of insoluble silicates, or this salt may be decomposed by solutions of carbonate of soda (§$§ 7, 19). The decomposition of the sulphate of lime by hydrous carbonate of magnesia, as explained in § 21, is doubt- less in many cases the source of sulphate of magnesia, which, more frequently than sulphate of soda, is a predominant element in mineral waters. In connection with a suggestion made in the section last cited, it may be remarked that I have since Sh Rye: Se Ah Die OS SION a II Ae Es Ps IX.] . QHEMISTRY OF NATURAL WATERS. 133 found that predazzite, in virtue of the hydrate of magnesia which it contains, readily decomposes solutions of gypsum holding dissolved carbonic acid, and gives rise to sulphate of magnesia. ‘In the second place, sulphuric-acid waters, like those de- scribed in § 47, by their action upon calcareous and magne- sian rocks, or by the intervention of carbonate of soda, may, as already suggested, give rise to neutral sulphated waters of the sixth class. It is evident also that waters impregnated with sulphates of alumina and iron from oxidizing sulphates, as mentioned in § 28, may be decomposed in a similar manner, and with like results. Neutral sulphated waters generated by. any of the above processes are evidently subject to admixtures of saline matters from other sources, and may thus become impregnated with chlorides and carbonates. Indeed, it is rare to find waters of the sixth class without some portion of chlorides ; and a tran- sition is thus presented to the waters of the first four classes, in which also portions of sulphates are of frequent occurrence. The presence of sulphates being one of the conditions required for the generation of sulphuretted hydrogen (§ 10), we find that the waters of the sixth class are very often sulphurous. § 51. Waters of the sixth class are very frequently met with in the paleeozoic rocks of New York and western Canada, and are probably derived from the gypsum which is found-in great- er or less abundance at various horizons, from the Calciferous sand-rock to the Onondaga salt-group. It is, however, not improbable that the sulphuric-acid waters which abound in this region (§ 48) may, by their neutralization, give rise to similar springs. In the waters of the district under consideration, the sulphate of lime generally predominates over the sulphates of the other bases, and chlorides are frequently present in consid- erable quantities. For numerous analyses of these waters, see Beck, Mineralogy of New York. ‘The results of an examina- tion by me of the Charlotteville spring, remarkable for the amount of sulphuretted hydrogen which it contaitis, will be found in the Amer. Jour. Sci. (2), VIII. 369. A copious sul- A TI A Tee eA OD Te he Ki ) ey i's he 5 St 134 CHEMISTRY OF NATURAL WATERS. [Ix. phur spring which issues from a mound of calcareous tufa in Brant, in Ontario, overlying the Corniferous limestone, is dis- tinguished by the absence of any trace of chlorides ; in which respect it resembles the acid waters of the fifth class from the adjacent region. BS. POO. ST PS po. Po te OO NT 9 & 6 DD NTO AWASRIANW bo — bo “J _ BD A> Se St I ek BS OD OOS RSS SR SAS ae C9 NCO ATCO ST ° wo S WH MAP WR PDH ON SSSSOOSOOOMH SOO Pwr wo STOO OND EATON reference to the choice of building-stones for the Houses They made use of blocks of an inch cube, which were first soaked in water and then placed under the vacuum of an air-pump, as in my own experi- ments. The following examples are taken from a table in the above re- port, giving the results for thirty-six specignens of building-stones. The value of x in III., or the absorption of water for 100 volumes of rock, as determined by them, is as follows: For three silicious limestones, 5.3, 8.5, of Parliament. eres eee See ae ee TX) a era 4! ee Oe Hae eee oe eS eer re et ree ey POROSITY OF ROCKS. 167 The rocks in the preceding table, with the exception of six, are from the paleeozoic formations of Canada, including, as will be seen, pure limestones of the Trenton formation, dolomites of the Calcifer- ous sand-rock, the Chazy, the Onondaga (or Salina), the Niagara, and the Guelph, a local formation resting upon the Niagara. The sand- stones are from the Potsdam, the Medina, and ‘the Sillery, a mem- ber of the Quebec group, which is associated with the argillaceous shale No. 15, with which are compared the argillaceous shale of the Hudson River group and the compact pyroschists of the Utica formation. I have given in Nos. 12, 13, and 14 determinations with three specimens of a fine gray and very porous sandstone from Ohio, of Devonian or Lower Carboniferous age, and much used for building. Nos. 37, 38, and 39 are three specimens of the well-known soft limestone of Caan, i in France, so much employed in that ORY for architectural purposes. 10.9; for four nearly pure limestones from the oolite, 18.0, 20.6, 24.4, 31.0; for four magnesian limestones, 18.2, 23.9, 24.9, 26.7; and for six sami stones, 10.7, 11.2, 14.3, 15.6, 17.4, and 22.1. These numbers represent the absorption obtained by the aid of the air-pump, without which it is impossible to remove all the air from the pores of the previously dried rock. Thus a cube of two inches of a sandstone which takes up in this way 14.3 of water only absorbed 8.0 by prolonged immersion in water; an Oolitic limestone, capable of holding 20.6, in like manner absorbed only 13.5 ; and a magnesian limestone only 9.1, instead of 24.4. (See, also, On the Porosity of Rocks, Delesse, Bull. Soc. Geol. de France (2), XIX. 64.) X. ON PETROLEUM, ASPHALT, PYRO- SCHISTS, AND COAL. In the following paper on the Oil-bearing Limestone of Chicago, read before the American Association for the Advancement of Science, in 1870, and published in the American Journal of Science for June, 1871, will be found a summary of my conclu- sions on the geological history of petroleum. To it are appended extracts from an earlier paper in the same Journal for March, 1863, On Bitumens and Pyroschists, and some later observations by Dawson and myself on the vegetable tissues forming coal. The reader is also referred in connection with petroleum to my paper on the Geology of Southwestern Ontario, in the same Journal for November, 1868, and to Notes on the Oil-Wells of Terre Haute, Indiana, in that for November, 1871. Wuen, in 1861,* I first published my views on the petro- leum of the great American paleozoic basin, I expressed the opinion that the true source of it was to be looked for in cer- tain limestone formations which had long been known to be oleiferous. I referred to the early observations of Eaton and Hall on the petroleum of the Niagara limestone, to numerous instances of the occurrence of this substance in the Trenton and Corniferous formations, and, in Gaspé, in limestones of Lower Helderberg age. Subsequently, in this Journal for March, 1863, and in the Geology of Canada, I insisted still further upon the oleiferous character of the Corniferous lime- stone in southwestern Ontario, which appears to be the source of the petroleum found in that region. I may here be permit- ted to recapitulate some of my reasons for concluding that petroleum is indigenous to these limestones, and for rejecting the contrary opinion, held by some geologists, that its occur- rence in them is due to infiltration, and that its origin is to be sought in an unexplained process of distillation from pyro- schists or so-called bituminous shalgs. These occur at three * See the Appendix to this paper. a soit I NBA jihiticatota~ gell gt, Miia . e* ‘_ -_ 7 a ae coils “ “a 4 > de ie Oe OP COME A X.] THE OIL-BEARING LIMESTONE OF CHICAGO. 169 distinct horizons in the New York system, and are known as the Utica slate, immediately above the Trenton limestone, and the Marcellus and Genesee slates which lie above and below the Hamilton shales; the latter being separated from the un- derlying Corniferous limestone by the Marcellus state. First, these various pyroschists do not, except in rare in- stances, contain any petroleum or other form of bitumen. Their capability of yielding volatile liquid hydrocarbons or pyrogenous oils, allied in composition to petroleum, by what is known to chemists as destructive distillation, at elevated tem- peratures, is a property which they possess in common with_ wood, peat, lignite, coal, and most substances of organic origin, _ and has led to their being called bituminous, although they are iis not in any proper sense bituminiferous. The distinction is one which will at once be obvious to all those who are familiar with chemistry, and who know that pyroschists are argilla- ceous rocks containing in a state of admixture a brownish insoluble and infusible hydrocarbonaceous matter, allied to lig- nite or to coal, Second, the pyroschists of these different formations do not, so far as known, in any part of their geological distribution, whether exposed at the surface or brought up by borings from depths of many hundred feet, present any evidence of having been submitted to the temperature required for the generation of volatile hydrocarbons. On the contrary, they still retain the property of yielding such products when exposed to a sufficient heat, at the same time undergoing a charring process by which their brown color is changed to black. In other words, these pyroschists have not yet undergone the process of destructive — distillation. Third, the conditions in which the oil occurs in the lime- stones are inconsistent with the notion that it has been intro- duced into these rocks by distillation. The only probable or conceivable source of heat, in the circumstances, being from beneath, the process of distillation would naturally be one of ascension, the more so as the pores of the underlying strata would be filled with water. Such being the case, the petro- 8 170 THE OIL-BEARING LIMESTONE OF CHICAGO. [x. leum of the Silurian and Lower Devonian limestones must have been derived from the Utica slate beneath. This rock, however, is unaltered, and moreover, the intermediate sand- stones and shales of the Loraine, Medina, and Clinton forma- tions are destitute of petroleum, which must, on this hypothe- sis, have passed through all these strata to condense in the Niagara and Corniferous limestones. More than this, the- Trenton limestone, which, on Lake Huron and elsewhere, has yielded considerable quantities of petroleum, has no pyroschists beneath it, but on Lake Huron rests on ancient crystalline _tocks, with the intervention only of a sandstone devoid of organic or carbonaceous matter. The rock-formations holding petroleum are not only separated from each other by great thicknesses of porous strata destitute of it, but the distribution of this substance is still further localized, as I many years since pointed out. The petroleum is, in fact, in many cases, confined to certain bands or layers in the limestone, in which it fills the pores and the cavities of fossil shells and corals, while other portions of the limestone, above, below, and in the prolon- gation of the same stratum, although equally porous, contain no petroleum. From all these facts the only reasonable con- clusion seems to me to be that the petroleum, or rather the materials from which it has been formed, existed in-these lime- stone rocks from the time of their first deposition. The view which I put forward in 1861, that petroleum and similar bitu- _ mens have resulted from a peculiar “ transformation of vegeta- ble matters, or in some cases of animal tissues analogous to these in composition,” has received additional support from the observations of Lesley* in West Virginia and Kentucky, and from the more recent ones of Peckham.t - The objections to this view of the origin and geological rela- tions of petroleum have been for the most part founded on incorrect notions of the geological structure of southwestern Ontario, which has afforded me peculiar facilities for studying * Rep. Geol. Canada, 1866, 240; and Proc. Amer. Philos. Soc., X. 33, 187. : t Ibid., X. 445. ere IRN nt A a a ei anc Soh i X.] THE OIL-BEARING LIMESTONE OF CHICAGO. 171 the question. In this region, it has been maintained by Win- chell that the source of the petroleum is to be sought in the Devonian pyroschists. I however showed in 1866, as the re- sult of careful studies of the various borings: first, that none of the oil-wells were sunk in the Genesee slates, but along denuded anticlinals, where these rocks have disappeared, and _ Avhere, except the thin layer of Marcellus slate sometimes met with at the base of the Hamilton shales, no pyroschists are found above the Trenton limestone. Second, that the reser- voirs of petroleum in the wells sunk into the Hamilton shales are sometimes met with in this formation, and sometimes, in adjacent borings, only in the underlying Corniferous. Exam- ples of this have been cited by me in wells in Enniskillen, Bothwell, Chatham, and Thamesville, where petroleum was only found at depths of from thirty to one hundred and twenty feet in the Corniferous limestone, in all of these places over- laid by the Hamilton shales. It was also shown, that in two localities in this region, namely, at Tilsonburg and in Maid- stone, where the Corniferous is covered only by post-pliocene clays, petroleum in considerable quantities has been obtained by sinking into the limestone.* That the supplies of petro- leum in such localities are less abundant than in parts where a mass of shales and sandstones overlies the oil-bearing limestone, is explained by the fact that both the pores and the fissures in the superior strata serve to retain the oil, in a manner analo- gous to the post-pliocene gravels in some parts of this region, which are the sources of the so-called surface oil-wells. It is, therefore, not surprising that examples of pyroschists impreg- nated with oil should sometimes occur, but the evidence of the existence of indigenous petroleum, which is so clear in the various limestones, is wanting in the case of the pyroschists ; although concretions holding petroleum, have been observed in the Marcellus and the Genesee slates of New York. There is, however, reason to believe, as I have elsewhere pointed out, that much of the petroleum of Pennsylvania, Ohio, and the * American Journal of Science (2), XLVI. 360 ; and Report Geol. Canada, 1866, pp. 241 - 250. 172 THE OIL-BEARING LIMESTONE OF CHICAGO. [x. adjacent regions is indigenous to certain sandstone strata in the Devonian and Carboniferous rocks.* At the meeting of the American Association for the Ad- vancement of Science at Chicago, in August, 1868, in a dis- cussion which followed the reading of a paper by myself on the Geology of Ontario,t it was contended that, although the various limestones which have been mentioned are truly oleifer- ~ ous, the quantity of petroleum which they contain is too incon- siderable to account for the great supplies furnished by oil-pro- ducing districts, like that of Ontario, for example. This opinion being contrary to that which I had always entertained, I re- - solved to submit to examination the well-known oil-bearing limestone of Chicago. ; This limestone, the quarries of which are in the immediate vicinity of the city, is filled with petroleum, so that blocks of it which have been used in buildings are discolored by the exuda- tion of this substance, which, mingled with dust, forms a tarry coating upon the exposed surfaces. The thickness of the oil- bearing beds, which are massive and horizontal, is, according to Professor Worthen, from thirty-five to forty feet, and they occupy a position about midway in ‘the Niagara formation, which has in this region a thickness of from 200 to 250 feet. As exposed in the quarry, the whole rock seems pretty uniformly saturated with petroleum, which exudes from the natural joints and the fractured surfaces, and covers small pools of water in the depressions of the quarry. I selected numerous specimens of the rocks from different points and at various levels, with a view of getting an average sample, although it was evident that they had already lost a portion of their original content of petroleum, After lying for more than a year in my laboratory they were submitted to chemical examination. The rock, though porous and discolored by petroleum, is, when freed from this substance, a nearly white, granular, crystalline, and very pure dolomite, yielding 54.6 per cent of carbonate of lime. Two separate portions, each made up of fragments obtained * Report Geol. Canada, 1866, p, 240. + American Journal of Science (2), XLVI. 355. fe eat ee ee Cares ppt 2 a, - 2 AE link Oly sg se pen malt da dc) oes Gal We Oo ee De ol ait ee he |) AR awe AP Pn Spey Mey Dee ile Pe oY. AA ny wart. Fel pel oe ee ee rire mS ; - X.] THE OIL-BEARING LIMESTONE OF CHICAGO. 173 ' by breaking up some pounds of the specimens above mentioned, and supposed to represent an average of the rock exposed in _ the quarry, were reduced to coarse powder in an iron mortar. Of these two portions, respectively, 100 and 138 grammes were dissolved in warm dilute hydrochloric acid. The tarry residue which remained in each case was carefully collected and treated with ether, in which it was readily soluble with the exception of a small residue. This, in one of the samples, was found equal to .40 per cent, of which :13 was volatilized by heat with the production of a combustible vapor having a fatty odor ; _ the remainder was silicious. The brown ethereal solutions were evaporated, and the residuum, freed from water and dried at 100° C., weighed, in the two experiments, equal to 1.570 and 1.505 per cent of the rock, or a mean of 1.537. It was a viscid reddish-brown oil, which, though deprived of its more volatile portions, still retained somewhat of the odor of petroleum which is so marked in the rock. Its specific gravity, as deter- mined by that of a mixture of alcohol and water in which the globules of the petroleum remained suspended, was .935 at 16° C. Estimating the density of the somewhat porous dolo- mite at 2.6, we have the proportion .935 :2.600::1.537 : 4.260; so that the volume of the petroleum obtained equalled 4.26 per cent of the rock. This result is evidently too low, for two rea- sons: first, because the rock had already lost a part of its oil, while in the quarry and subsequently, before its examination ; and secondly, because the more volatile portions had been dissipated in the process of extraction just described. In assuming 100.00 parts of the rock to hold 4.25 parts by volume of petroleum, we are thus below the truth in the follow- ing calculations. A layer of this oleiferous dolomite one mile (5,280 feet) square and one foot in thickness will contain . 1,184,832 cubic feet of petroleum, equal to 8,850,069 gallons of 231 cubic inches, and to 221,247 barrels of forty gallons each. Taking the minimum thickness of thirty-five feet, as- signed by Mr. Worthen to the oil-bearing rock at Chicago, we shall have in each square mile of it 7,743,745 barrels, or in round numbers seven and three quarter millions of barrels of - oe eee Pe een es eT rx. petroleum. The total produce of the great Pennsylvania oil- region for the ten years from 1860 to 1870 is estimated at twenty-eight millions of barrels of petroleum, or less than would be contained in four square miles of the oil-bearing limestone formation of Chicago. It is not here the place to insist upon the geological condi- tions which favor the liberation of a portion of the oil from such rocks, and its accumulation in fissures along certain anticlinal lines in the broken and uplifted strata. These points in the geological history of petroleum were shown by me in my first publications on the subject in March and July, 1861, referred to on the next page, and independently, about the same time, by Professor E. B. Andrews in this Journal for July, 1861.* The proportion of petroleum in the rock of Chicago may be exceptionally large, but the oleiferous character of great thick- ness of rock in other regions is well established, and it will be seen from the above calculations that a very small propor- tion of the oil thus distributed would, when accumulated along lines of uplift in the strata, be more than adequate to the sup- ply of all the petroleum wells known in the regions where these oil-bearing rocks are found. With such sources exist- ing ready formed in the earth’s crust, it seems to me, to say the least, unphilosophical to search elsewhere for the origin of petroleum, and to imagine it to be derived by some unex- “plained process from rocks which are destitute of the sub- stance. * American Journal of Science (2), XXXII. 85. See also papers on the subject by Andrews and by Professor Evans, Ibid. (2), XL. 33, 334; and one by the author (2), XXXV. 170; also Report Geological Survey of Canada, 1866, pp. 256, 257. 174 THE OIL-BEARING LIMESTONE OF CHICAGO. ene eT eT ce. ee. | ha te nies Ps altar = CO LNT te Ay Cy em EIST i ig 1S SA eS ee ee ie, eh ae aed se Aas A F Nea Hf > 5) BITUMENS AND PYROSCHISTS. 175 APPENDIX. ON BITUMENS AND PYROSOCHISTS. (1861 - 1863.) This paper is reprinted from the American Journal of Science for March, 1863, but many of the facts and deductions which it contains appeared in an earlier paper, entitled Notes on the History of Petroleum, in the Canadian Naturalist for July, 1861, reprinted in the Chemical News, and also in the Report of the Smithonian Institution for 1862. I had for some time previously maintained that the source of the petroleum of the West was not, as was generally thought, to be found in the Devonian pyro- schists, but in the underlying fossiliferous limestones, and had shown the relation of the oil-springs to anticlinals.— See a report of my lecture before the Board of Arts of Lower Canada, in the Montreal Gazette of March 1, 1861. Ir is proposed in the following pages to bring together some facts and theoretical considerations bearing upon the nature, origin, and distribution of bitumens, together with a few remarks on the rocks commonly called bituminous shales. Under the general name of bitumen, as is well known, are included both the liquid forms, petroleum and naphtha, and the solid varieties known as asphalt or mineral pitch. The related substances guayaquillite and berenge- lite, and the substance known as idrialine, seem from the modes of their occurrence to have a similar origin to asphalt, and thus to be distinct from fossil resins. The characters of fusibility and solu- bility in liquids like benzole and sulphuret of carbon, serve to dis- tinguish the solid bitumens from coal and some other matters about to be noticed. It is to be remarked that the chemical composition of these bodies varies considerably ; the earlier analyses of petro- leum and naphtha give a composition which approaches C,H, ; but the later investigations of De la Rue and Muller on the products distilled from the petroleum of Rangoon, and those of Uelsmann on that from Sehnde, show a slight excess of hydrogen, the various hydrocarbons having, for the most part, the formula C,Hn4,. The first formula C,H, may however be adopted, as expressing approxi- matively the composition of the liquid bitumens. The different analyses of asphalt show a diminished quantity of hydrogen, and small quantities of oxygen. Thus the elastic bitumen from Der- byshire gave to Johnston results which may be represented by C,,H,.0,.;* of two varieties of asphalt analyzed by Ebelmann, the * In these formulas, which have been calculated for twenty-four equivalents of carbon, to compare with cellulose, C,,H,.0., I have designed to represent a 176 BITUMENS AND PYROSCHISTS. [x. one from Bastennes gave C,,H,,0,,, while that from near Naples may be represented by C,,H,,,0,, and an asphalt from Mexico gave to Regnault C,,H,,0O,. The analyses of Johnston shows that guaya- quillite and berengelite do not differ greatly from these in the pro- portions of carbon and hydrogen. Passing from the asphalts to idrialine, the results of whose analysis are represented by C,,H,, we have a hydrocarbon with a minimum of hydrogen. It is well in this place to compare the above results with the formula C,,H,,,0,,, which is deduced from Wetherell’s analysis of the so-called albertite — or Albert coal. A “lignite passing into mineral resin” gave to Regnault C,,H,,0,,, and five analyses of bituminous coal by the same chemist yield from C,,H,O,, to C,H,,0,,, while the mean composition deduced by Johnston from several analyses of coal was C,,H,, with from O, to O, From these results it will be seen that some asphalts approach bituminous coals in composition. That of — Naples, which is completely fusible at 140° C., contains less hydro- gen and more oxygen than the albertite, while the idrialine is near in composition to certain bituminous coals, which are thus almost isomeric with some fusible bitumens ; so that it is easy to conceive the same organic matters giving rise either to coal or to asphalt, even without losing their structure. Such appears to be the case in the tertiary strata of Trinidad and Venezuela, the bitumen of which, from Mr. Wall’s researches, seems to have arisen from “a special mineralization of vegetable remains in certain strata, which has resulted in the production of bitumen, instead of coal or lignite.” This conversion, according to him, “is not attributable to heat, nor of the nature of a distillation, but is due to chemical reactions at the ordinary temperature, and under the normal conditions of climate.” Mr. Wall also describes portions of wood from these deposits, which have been partially converted into bitumen, and simply the results of analysis, without attempting to fix the constitution of the matters in question. . In the notation employed, H=1, C=6, andO=8. As it is not generally used in the American Journal of Science, I have not thought necessary to adopt, in this paper, the double equivalent of the latter elements, now em- ployed by so many chemists. I may, however, call attention to the fact that I was, I believe, the first to propose such a change, when, in 1853, I asserted that the even coefficients of oxygen, sulphur, and carbon in ordinary for- mulas seem to furnish a conclusive reason for doubling their equivalents, or for dividing those! of hydrogen, chlorine, nitrogen, and the metals, according as four volumes or two volumes are taken as the equivalent. (Theory of Chemical Changes, Am. Jour. of Science (2), XV. p. 230. [Reprinted as Essay XVI. of the present, volume. ]) X.] BITUMENS AND PYROSCHISTS. 177 leave, when this is removed by solvents, a residue of woody tissue. (Proc. Geol. Soc. London, May, 1860.) These observations have been confirmed by an eminent microscopist and chemist, whose results, lately communicated to me by himself, are not yet pub- lished. . The chemical changes by which the conversion of woody tissue 4 into peat, lignite and bituminous coal is effected, are too well known the hydrocarbons of many asphalts, or to C,,H,,, which represents petroleum. The removal of further amounts of marsh-gas, C,H,, $) 4 to be repeated here. The abstraction of variable proportions of ey | water, carbonic acid, and marsh-gas may give rise either to hydro- + - carbons like C,,H,, which represents idrialine and the basis of most | " bituminous coals, to C,,H,,, which is the approximate formula of | a may even convert bituminous coal into anthracite, as Bischof ‘has ° l) . pointed out ; and we conceive that although heat has in many cases a 4 given rise to this conversion, by a subterranean coking, the change may often have been the result of decompositions going on at ordinary temperatures. Anthracite or nearly pure carbon, on the one hand, and petroleum or carbon with a maximum of hydrogen, on the other, represent the two extremes of a series of which bitu- minous coals and asphalts are intermediate terms. Petroleum, as is well known, impregnates certain rocks, from which it flows spontaneously, and the solid forms of bitumen are often disseminated throughout limestones or sandstones, from which they may be in part removed by heat, and more completely by sol- { q vents such as benzole. To such rocks the term “ bituminous” may : ____ be correctly applied, but it is often inappropriately given to sub- 25 stances like coal and certain combustible schists, which contain little or no bitumen, but yield, by destructive distillation, volatile hydrocarbons, more or less resembling those obtained from asphalt 1 a or petroleum. Analogous products are, however, obtained by the ; 4 distillation of lignite, peat, and even of wood, so that the epi- : thet “bituminous,” applied to hydrogenous coals and combustible i ql schists, raises a false distinction, and perpetuates an error. I . therefore proposed some time since to distinguish these so-called ; 2 bituminous schists, the brandschiefer of the Germans, by the name q of pyroschists. This is the equivalent of the German term, and has a precedent in the name of pyrorthite, given by Berzelius to a sub- stance which appears to be a mixture of orthite with a combustible hydrocarbonaceous matter. Pyroschists are well known to occur in almost every geological group from the Cambrian to the tertiary, 8 * L i | ee al 178 BITUMENS AND PYROSCHISTS. [X. and are often, like coal, employed as valuable sources of volatile hydrocarbons, although like it they contain little or no bitumen. They may be regarded as clays or marls, holding, in a state of in- timate admixture, a variable proportion of a matter approaching to coal in its chemical characters. Although frequently dark brown or black in color, they are sometimes light brown or eyen yellowish- gray, as is the case with the Jurassic pyroschists of the department of the Doubs, and those of tertiary age near Clermont, both in France, Remarkable examples of this are also given by Professor J. D. Whitney in the pyroschists from the Utica formation in Iowa, which were yellowish-brown, weathering to a bluish-ash color. They, however, blackened when exposed to heat, burning with a bright flame, and contained from eleven to twenty per cent of com- bustible matter.* ....A pyroschist of the Utica formation, from Collingwood on Lake Huron, examined by me, gave to dilute hydro- chloric acid from fifty-three to fifty-eight per cent of carbonate of lime, besides a little magnesia and oxide of iron. The insoluble residue was snuff-brown in color, and, when heated, gave off a bituminous odor. When ignited in a close vessel, it lost 12.6 per cent of volatile and combustible matters, and left a coal-black resi- due, which, by calcination in the open air, lost 8.4 per cent addi- tional, making in all 21.0 per cent of volatile and carbonaceous matters, and left an ash-gray argillaceous residue. This schist, however, contained but a very small amount of bitumen ; for, on treating the residue from a dilute acid with boiling benzole, there was dissolved about 1.0 per cent of a brown bituminous matter. The residue, when heated, no longer evolved the odor of bitumen, but rather one like burning lignite, and still gave, by ignition in a close vessel, 11.8 per cent of volatile and inflammable matters. When boiled with a solution of caustic soda, this was scarcely dis- colored. In its insolubility, therefore, the organic matter of this rock resembles true coal rather than lignite. Attempts have been made, on a large scale, to distil this calcareous schist of Colling- wood, which was found to yield from 3.0 to 5.0 per cent of oily and tarry matter, besides combustible gases and water. Overlying the Hamilton formation in Ontario are found black pyroschists, which are supposed to be the equivalent of the Genesee slates of New York. A specimen of these from Bosanquet on Lake * For numerous analyses of pyroschists from this geological horizon, see a note appended to this paper in the American Journal of Science (2), XXXYV. 160. SS = | = 7 my BITUMENS AND PYROSCHISTS. 179 Huron lost, by ignition in a closed vessel, 12.4 per cent, and left a black residue, which was not calcareous. A portion in fine powder was digested for several hours with heated benzole, which took up 0.8 per cent of hrown combustible matter. The residue, carefully - dried at 200° F., then lost, by ignition in a close vessel, 11.3 per cent, and by subsequent calcination 11.6 additional, equal to 23.7 per cent of combustible and volatile elements. The calcined residue was gray in color. By distillation in an iron retort there were obtained from this shale 4.2 per cent of oily hydrocarbons, besides a large quantity of inflammable gas, and a portion of ammoniacal water. : The pyroschists of Bosanquet belong to the Devonian series, and contain the remains of land-plants, so that a partially decayed vege- tation may be supposed to have been the source of the organic matter which is intimately mingled with the earthy base of the rock. Such was probably the case in the abundant pyroschists of the coal period ; but in the pyroschists of the Utica formation (which are Upper Cambrian) the chief organic remains to be detected are graptolites, with a few brachiopods and crustaceans. No traces of terrestrial vegetation are known to have existed at that time, nor do the schists contain the evidences of any marine plants. . The pyro- schists of mesozoic age, in several parts of Europe, contain, on the contrary, numerous fossil fishes, from the soft parts of which, or other animal matters, the combustible substance of these rocks is generally supposed to be derived. (Dufrénoy, Mineralogie, IV. p. 603.) Similar questions arise with regard to the origin of the bitu- mens of the various geological formations already noticed ; for while in some cases, as in the tertiary rocks of Trinidad, they are clearly traced to a vegetable source, bitumens are also met with in Cam- brian, Silurian, and Devonian limestones of marine origin, which abound in shells and corals, but afford no traces of vegetable remains. When, however, it is considered that the lower forms of animals contain considerable portions of a non-azotized tissue analogous in its composition to that of plants, and that even muscular tissue, plus the elements of water, contains the elements of cellulose and ammo- nia, it is easy to understand that vegetable and animal remains may, by their slow decomposition, give rise to similar hydrocarbonaceous bodies.* The various fermentations of which sugar is susceptible * This relation was first pointed out by me in 1849. (American Journal of Science (2), VII. p. 109.) I then endeavored to show that the albuminoid bodies might be regarded as a nitryl of cellulose, or some isomeric hydrate of carbon, and represented by the formula C,,H,,N,O;. I had already pro- 180 ON THE ORIGIN OF COAL. ee suggest analogies: to the different transformations of organic tissues which have resulted in the formation of anthracite, coal, lignite, asphalt, and petroleum, together with carbonic acid and gaseous hydrocarbons as accessory products. (See note on page 182.) [The conclusions of the remaining nine pages of the above paper are briefly summed up in the preceding one on The Oil-bearing Lime- stones of Chicago. As a supplement to the remarks on the origin of coal I may here make some extracts from a paper on Spore- Cases in Coal, by Dr. J. W. Dawson, in the American Journal of Science for April, 1871, including also a note by myself. Dawson has there shown that while some exceptional beds of coal are to a large extent made up of spores and spore-cases, probably of lepido- — dendron, it is by no means true that these are, as some have con- jectured, the principal source of coal. On the other hand, it is clear posed to regard bone-gelatine as an analogous nitryl, CyH»N,O,; which corresponds to one equivalent of glucose and four of ammonia, less 8 HO. These nitryls, it was conceived, might, under certain conditions, regenerate ammonia and a hydrate of carbon. I also adduced evidence that in a case of diabetes, sugar was generated at the expense of ingested gelatine. (American Journal of Science (2), V. p. 75; VI. p. 259; and Silliman’s Elements of Chemistry, p. 517.) The analyses of cartilage-gelatine, or chondrine, in like manner correspond very nearly to a nitryl formed from CH 220z2 (cane-sugar) and three equivalents of ammonia, The formula thus deduced, CauHipNs0y0, requires 14.7 of nitrogen. In 1856, Dusart, starting, as he tells us, from my theoretical views, en- deavored to produce the albuminoid bodies by the action of a solution of ammonia on starch, lactose, or glucose at temperatures of 150° and 200°C. In this way he obtained, after several days, an azotized body, which resembled gelatine. It was precipitated by alcohol in elastic filaments, formed an imputrescible compound with tannin, and, when heated, gave off the odor of burning horn. Its proportion of nitrogen was 14.0 per cent, which is near that of chondrine. (Comptes Rendus de l’Académie, May, 1861, p. 974.) Schoonbroodt has since asserted the possibility of converting sugar into an albuminoid substance, and reiterated my suggestion that the albuminoids are veritable nitryls of the amyloids; under which convenient term he includes those hydrates of carbon which are susceptible of conversion into glucose. (Ibid., May, 1860, p. 856.) In 1861, Messrs, Fischer and Boedeker announced the production of fer- ' mentescible sugar by the action of dilute acids on cartilage, and showed that the ingestion of gelatine increases the amount of sugar in normal human urine. These authors seem, by the abstract before me (Repertoire de Chimie * Pure, July, 1861, from Ann. der Chem. und Pharm., CXVII. p. 111), to ignore alike my own observations and those of Gerhardt, who twenty years since showed that, by long boiling with dilute sulphuric acid, there is formed — from gelatine a sweet fermentescible sugar, together with a large amount of sulphate of ammonia. (Précis de Chimie Organique, II. p. 521.) ; ’ _— - _— P= 4 all l r - - . ~ PP ae reas Vihear er a A re a a Near a ali a ene ats tt a wi 2 . a a : f 7 £ ; } : H : ’ a es re ort oe <. 5 allt a cia ED ee, oe ee Te ae = 1G ; ; 5 1 > a ON THE ORIGIN OF COAL. 181 from the microscopical studies of Dawson and others that, although * it is doubtless true that cellulose may yield bodies having the chemical composition of bituminous coal, and even bitumens, by a process of alteration such as I have described above, the chief source of such coal in the older coal measures has been epidermal tissues, which differ from cellulose in being much richer in carbon. and hydrogen. These tissues, as remarked by Dawson, “are. very little liable to decay, and resist more than-most other vegetable matters aqueous infiltration, properties which have caused them to remain unchanged and resist the penetration of mineral substances more than other vegetable tissues. These qualities are well seen in the bark of our American white birch (Betula alba). It is no wonder that materials of this kind should constitute considerable portions of such vegetable accumulations as the beds of coal, and that _ when present in large proportion they should afford richly bitu- minous beds. All this agrees with the fact apparent on examination of common coal, that the greater number of its purest layers con- sist of the flattened bark of sigillariz and similar trees, just as any single flattened trunk imbedded in shale becomes a layer of pure coal. It also agrees with the fact that other layers of coal, and also the cannels and earthy coals, appear under the microscope to consist of finely comminuted particles, principally of epidermal tissues, not only of the fruits and spore-cases of plants, but also of their leaves and stems.” In this connection I noticed in the same paper the chemical com- position of the epidermal or cortical tissue of plants, to which the name of suberin has been given, and compared it with that of the spores of lycopodium, and at the same time with cellulose and with forms of coal and related bodies. The nitrogen which the first two mentioned bodies contain probably represents a portion of albuminoid. matter, which in lycopodium is considerable in amount. For the purpose of comparison empirical formulas corresponding to twenty- four equivalents of carbon have been calculated for these bodies, as already done on page 176. We have then as follows : — Dien ae AS RE ee ge) at eee H 20 Cork . é : eee ; : F ‘ CH 9-2% 7 Lycopodium . : : : : aN ey ‘: OF NG.. Peat (Vaux) . : wits" : : hd Oe 8 aR Brown coal (Schrétter) : : : : ; eS A: SP FO Lignite (Vaux) Lia 5 OE 8 Bituminous coal (Repnault): es ; i > Con 182 ON THE ORIGIN OF COAL. [x. I further said, ‘It will be seen from this comparison that in ulti- mate composition cork and lycopodium are nearer to lignite than to woody fibre (cellulose), and may be converted into coal with far — less loss of carbon and hydrogen than the latter. They, in fact, approach closer in composition to resins and fats than to wood ; and, moreover, like these substances, repel water, with which they are not easily moistened, and are thus able to resist those atmospheric influences which effect the decay of woody tissue.” The nitrogen present in the lycopodium spores, as remarked by Dawson, “ no doubt belongs to the protoplasm in them, which would soon perish by decay ; and, subtracting this, the cell-walls of the spores and the walls of the spore-cases would be most suitable material for the production of bituminous coal. But this suitableness they share with the epidermal tissue of the scales of strobiles and of the stems and leaves of ferns and lycopods, and above all with the thick corky envelope of the stems of sigillarie and similar trees .... which, from its condition in the prostrate and in the erect, — trunks contained in the beds associated with coal, must have been highly carbonaceous and extremely enduring, and impermeable to water.” The substance known as mineral charcoal is, according to Dawson, derived from woody tissue and the fibres of bark. (See in this connection his paper on the Conditions of the Accumulation of Coal, Quarterly Geological Journal, XXII. 95.) [Nore to page 180. The petroleum of Pennsylvania, according to Pelouze and Cahours, yields by fractional distillation various liquids having the common formula CyrHy»+,(C = 12), the value of » ranging from 4 to 15, (corresponding to C,H,,. . . C,H, in the notation adopted in the preceding pages), and the boiling-point from 0° to 160°C. Of this series, which also in- cludes the paraffines, the first term is marsh-gas or formene, and the second and third belong to the ethylic and propylic groups, being C,H,, C,H, and ©,H, in the above notation. The latter two, according to Ronalds, are found in solu- tion in the crude petroleum. The researches of Foucou and Fouqué (Comptes Rendus, November 23, 1868) show that while the inflammable gases from the so-called Burning Spring near Niagara Falls, and from an oil-well in Wirtz County, West Virginia, are marsh-gas with small admixtures of carbonic acid, the gases from an oil-well in Petrolia, Ontario, and from Fredonia, Chatauque County, New York, are mixtures, in about equal parts, of the second and third hydrocarbons of the above series. The gas at the latter locality is from a well sunk into the Genessee slates, at the summit of the Hamilton formation, which gives no petroleum, but has for many years furnished the supply of gas for lighting a small town. The gas from an oil-well in Venango County, Pennsylvania, contained besides the first three bodies of the series a portion of the fourth, O,H,. Neither acetylene, free hydrogen, carbonic oxide, nor olefiant gas or its homologues were detected. ] XI. ON GRANITES AND GRANITIC VEIN- . STONES. (1871 - 1872.) This paper appeared in three parts in the American Journal of Science for Feb- rhary and March, 1871, and for February, 1872. The license by which the title is made to include a description of certain calcareous vein-stones is explained to the reader under §§ 35-37. PartI., as originally printed, included §§ 1-15; part IL., §$16-31; and part III., §§ 32-49. a ConTENTS OF SEocTIoNS. —1, 2. Definitions of granite and syenite; 3. Structure of granitic and gneissic rocks; 4, 5. Felsites and felsite- porphyries; 6. Gneisses and granites of New England; 7. Granitic dikes and granitic vein-stones; 8. Scheerer’s theory of granitic veins; 9-10. Elie de Beaumont on granites and granitic emanations; 11. Granitic distinguished from concretionary veins; 12. Von Cotta on granitic veins; 13, 14. The author’s views on the concretionary origin of granitic veins; 15. The banded structure of granitic veins; 16. Granitic veins of Maine, Brunswick; 17. Topsham, Paris; 18. West- brook, Lewiston; crystalline limestones; 19. Danville, Ketchum; 20. Denuded granitic masses; 21. Banded veins; Biddeford, Sherbrooke; 22. Veins at various New England localities; 23. Mineral species of these veins; 24. Veins in erupted granites; 25. Geodes in granites; 26. Veins distinguished from dikes; 27. Volger and Fournet on the origin of veins; 28, 29. Certain fissures and geodes distinguished from veins opening to the surface; 30, 31. Temperatures of crystallization of granitic minerals; 32. Laurentian gneisses; 33. Pyroxenites and limestones; 34. Absence of mica-schists; 35. Classes of veins; 36. Granitic vein-stones; 37. Similar veins in Norway; 38. Minerals of _ granitic veins; 39. Evidences of concretionary origin; banded structure; 40. Incrustations of -crystals; 41. Skeleton-crystals; 42. Rounded crystals; 43. Quartz crystals in metalliferous veins; 44. Types of vein-stones; feldspathic; 45. Calcareous vein-stones; 46. Order of suc- cession of minerals; 47. Attitude of the veins; 48. Calcareous vein-— stones in higher rocks; 49. Supposed eruptive limestones. § 1. Tue name of granite is employed to designate a sup- posed eruptive or exotic unstratified composite rock, granular, _ oe ee ee ee ee ee 184 GRANITES AND GRANITIC VEIN-STONES. ee ee a a crystalline in texture, and consisting essentially of orthocla feldspar and quartz, with an admixture of mica, and frequen’ of a triclinic feldspar, either oligoclase or albite. This is he definition of granite given by most writers on lithology, an applies to a great portion of what are commonly called grani rocks ; there are, however, crystalline granite-like aggregates in fiich the mica is replaced by a dark colored hornblende amphibole, and to such a compound rock many authors have given the name of syenite, while to those in which mica and a hornblende coexist the name of syenitic granite is applied. It is observed that in certain of these hornblendic granites the quartz becomes less in ‘amount than in ordinary granites, and finally disappears altogether, giving rise to a rock composed of orthoclase and hornblende only. To such a binary aggregate Von Cotta and Zirkel would restrict the term “ syenite,” which — was already defined by D’Omalius d’Halloy to be a crystalline — aggregate of hornblende and feldspar ; ; by which orthoclase-: feldspar may be understood, since he describes varieties of — syenite as passing into diorite,—a name by most modern — lithologists restricted to a compound of albite, or some more — basic triclinic feldspar, with hornblende. It is apparently by failing to appreciate the distinction between orthoclase and — triclinic feldspar, in this connection, that Haughton has lately described, under the name of syenite, rocks which are composed of crystalline labradorite and hornblende. 4 a § 2. Naumann, regarding orthoclase and quartz as the essen- a tial constituents of granite, designates those aggregates which contain mica as mica-granites, and thus distinguishes them ; from hornblende-granites, in which the mica is replaced by hornblende. These definitions seem the more desirable, as the — name of granite is popularly applied both to the hornblendio © and the micaceous aggregates of orthoclase and quartz. There are not wanting examples of well-defined rocks of this kind in which both mica and hornblende are almost or altogether want- _ ing. . Such rocks have been designated binary granites, a term which it will be well to retain. Chloritic and talcose = P into the composition of which chlorite and tale enter, need _ XI] GRANITES AND GRANITIC VEIN-STONES. 185 only be mentioned in this connection. The name of syenite, so often given to hornblendic granites, will, in accordance with the views already expressed, be restricted to rocks destitute of quartz. While the disappearance of this mineral from horn- blendic granites is held to give rise to a true syenite, the same process with micaceous granites affords a quartzless rock con- sisting of orthoclase and mica, for which we have no name. Great masses of an eruptive rock, granite-like in structure, and _ consisting of crystalline orthoclase or sanidin, without any quartz, occur in the province of Quebec. This rock contains in some cases a small admixture of black mica, and in others an equally small proportion of black hornblende. The latter variety might be described as syenite, but for the former we have no distinctive name; and I have described both of these by the name of granitoid trachytes, a term which I adopted the more willingly on account of the peculiar composition of the feldspar, and also because compact and finely granular rocks in the same region, having a similar chemical composition, pre- sent all the characters of typical trachytes, and apparently graduate into the granitoid rocks just noticed.* In all at- tempts to define and classify compound rocks, it should be borne in mind that they are not definite lithological species, but admixtures of two or more mineralogical species, and can only be arbitrarily defined and limited. § 3. Having thus defined the mineral composition of granitic rocks, we proceed to notice their structure. (Gneiss has the same mineral elements as granite, but is distinguished by the more or less stratified and parallel arrangement of its constitu- ents; and lithologists are aware that in certain varieties of gneiss this structure is scarcely evident, except on a large scale ; so that the distinction between gneiss and granite rests rather on geognostical than on lithological grounds. To the lithologist, in fact, the granitoid gneisses are simply more or less stratiform granites, while it belongs to the geologist to consider whether this structure has resulted from a sedimentary * American Journal of Science (2), XXXVIII. 95. See also Zirkel, Petro- graphie, II. 179. 186 “GRANITES AND GRANITIC VEIN-STONES. deposition, or from the flowing of a semi-fluid heterogene ) mass giving rise to a stratiform arrangement.* ‘a §4. The rocks having the mineralogical composition — [* This process has been particularly described in my Contributions t Lithology, where also the principles of lithological classification are diser = se at length. (American J ournal of Science for March and July, 1864.) A str: of crystals during the movement of the half-liquid crystalline mass, but itn nay in some instances arise from the subsequent formation of crystals, arrang in parallel planes.” In the same paper, in describing the dolerite of Monta & ville, the alternations of a coarse variety, porphyritic from the presence fA large crystals of augite, with a finer grained and whiter variety is noticed; — the two being ‘‘ arranged in bands, whose varying thickness and curving lines _ suggest the notion that they have been produced by the flow and the partial — commingling of two fluid masses.” At Mount Royal also, as there deseri *‘mixtures of augite with feldspar are met with, constituting a granitoid dolerite, in parts of which the feldspar predominates, giving rise to a light grayish rock. Portions of this are sometimes found limited on either side t bands of nearly pure black pyroxenite, giving at first sight an aspect of fication. The bands of these two varieties are found curiously contorted ae interrupted, and, as at Montarville, seem to have resulted from movements in a heterogeneous pasty mass, which have effected a partial blending of an augitic magma with another more feldspathic in its nature.” a Further illustrations of this are given by the author in a communication _ to the Boston Society of Natural History, January 7, 1874. Among these — was a specimen from Groton, Connecticut, in which a large angular fragment j of strongly banded micaceous gneiss is egclosed in a fine-grained eruptive — - granite, the mica plates in which are so arranged as to show a beautiful and = even stratification in contact with the broken edges of: the gneiss, but at right angles to the strata of the latter. Another example is afforded by the erup- tive diorite from the mesozoic sandstone of Lambertville, New Jersey, which —_— is conspicuously marked by light and dark bands due to the alternate pre- % dominance of one or the other of the constituent minerals ; and still another —__ in a fine-grained dark micaceous dolerite dike from the Trenton limestone at _ Montreal, in which the abundant lamine of mica (probably biotite) are ar- ranged parallel to the walls of the dike. A similar banded structureisseen in glacier-ice and in furnace-slags. Some geologists have from facts of this kind been led to suppose that the banded structure of great areas of gneisswas caused by movements of flow in a solidifying mass, and not by successive de- | posits of dissolved or suspended material from a watery medium. While ad- a mitting the frequent occurrence of this structure in eruptive rocks, and the necessity in many cases of a careful geognostical study to determine to which class a stratiform rock should be referred, it was maintained that the great _ areas of gneissic rocks are of aqueous origin, and were deposited in successive — horizontal layers with their associated limestones, quartzites, and iron-oxides. ] XI] GRANITES AND GRANITIC VEIN-STONES. — 187 ordinary micaceous, hornblendic, and binary granites to finely granular and even impalpable mixtures of the constituent min- erals, constituting the rocks known as felsite, eurite, and petro- silex. These racks are often porphyritic from the presence of erystals of orthoclase, and sometimes of crystals or grains of quartz imbedded in the finely granular or impalpable paste. These felsites and felsite-porphyries (orthophyres) are, in very many cases at least, stratified or indigenous rocks, and they are sometimes found associated with granular aggregates of different - degrees of coarseness, which show a transition from true felsites into granitic gneisses. The resemblances in ultimate composi- tion between felsites, granites, and granitic gneisses are so close that it cannot be doubted that their differences are only struc- tural. § 5. Felsites and felsite-porphyries or orthophyres are well known in eastern Massachusetts, at Lynn, Saugus, Marblehead, and Newburyport, and may be traced from Machias and East- port in Maine, along the southern coast of New Brunswick to the head of the Bay of Fundy, with great uniformity of type, though in every place subject to considerable variations, from a compact jasper-like rock to more or less coarsely granular va- rieties, all of which are often porphyritic from feldspar crystals, and sometimes include grains or crystals of quartz. The colors of these rocks are generally some shade of red, varying from flesh-red to purple ; pale yellow, gray, greenish, and even black varieties are however occasionally met with. These rocks are, throughout this region, distinctly stratified, and are closely as- sociated with dioritic, chloritic, and epidotic strata. They ap- parently belong, like these, to the great Huronian system. [Stratiform rocks, seemingly identical with these quartziferous feldspar-porphyries, abound in Missouri, where they are asso- ciated with the iron-ores of Iron Mountain and Shepard Moun- tain. I have also found them over a considerable area along the north shore of Lake Superior, on an island south of St. Ig- nace, and for some distance along the coast to the southwest. The breccia and conglomerate in which is found the native copper of the Calumet and Hecla and the Boston and Albany | 188 GRANITES AND GRANITIC VEIN-STONES. (XL ae mines of the Keweenaw peninsula, on the south shore of the same lake, is made up in large part of the ruins of similar orthophyres. | § 6. Many of the so-called granites of New England are true gneisses ; as, for example, those quarried in Augusta, Hal- lowell, Brunswick, and many other places in Maine, which are indigenous rocks interstratified with the micaceous and horn- blendic schists of the great White Mountain series. To this class also, judging from lithological characters, belong the so- called granites of Concord and Fitzwilliam, New Hampshire. These indigenous rocks are tenderer, less coherent, and gener- ally finer grained than the eruptive granites, of which we have examples in the micaceous granite of Biddeford, Maine, and the hornblendic granites of Marblehead and Stoneham, Massa- chusetts, and Newport, Rhode Island, in all of which localities the contact of the eruptive mass with the enclosing rock is plainly seen, as is also the case farther eastward, on the St. Croix and St. John’s Rivers in New Brunswick, and in the Cobequid Hills and elsewhere in Nova Scotia. The horn- blendic granites of Gloucester, Salem, and Quincy, Massachu- setts, seem also, from their lithological characters, to belong to the class of exotic or true eruptive granites.* The further dis- cussion of the nature and origin of these gneisses and granites is reserved for another occasion, and we now proceed to notice the history of granitic veins. § 7. The eruptive granitic masses just noticed not only in- . clude fragments of the adjacent rocks, especially near the line of contact, but very often send off dikes or veins into the sur- rounding strata. The relation of these with the parent mass is however generally obvious, and it may be seen that they do not differ from it except in being often finer grained. These injected or intruded veins are not to be confounded with a third class of granitic aggregates, which I have elsewhere described as granitic vein-stones, or, to express their supposed * T. S. Hunt on the Geology of Eastern New England, American Journal of Science for July, 1870, p. 88; also Notes on the Geology of the Vicinity of Boston, Proc. Boston Nat. Hist. Soc., Oct. 19, 1870. citeaenitatanen 5 XL] GRANITES AND GRANITIC VEIN-STONES. 189 mode of formation, endogenous granites. They are to the gneisses and mica-schists, in which they are generally enclosed, what calcite veins are to stratified limestones, and although long known, and objects of interest from their mineral con- tents, have generally been confounded with intrusive granites. § 8. Scheerer, in his.famous essay on granitic rocks, which appeared in the Bulletin of the Geological Society of France in 1847 (Vol. IV. p. 468), conceives the congealing granitic rocks to have been impregnated with ‘a juice,” which was nothing else than a highly heated aqueous solution of certain mineral matters. - This, under great pressure, oozed out, penetrating even the stratified rocks in contact with the granite, filling cavities and fissures in the latter, and depositing therein crys- tals of quartz and of hornblende, the arrangement of which shows them to have been of successive growth. Neither Scheerer nor Virlet d’Aout, who supported his views, however (Ibid., IV. p. 493), extended them to feldspathic veins, though Daubrée, at an earlier date, had described certain granitic veins in Scandinavia as having been formed~by secretion, rather than by igneous injection, as maintained by Durocher. § 9. Elie de Beaumont, starting from the hypothesis of a cooling liquid globe, imagined “a bath of molten matter on the surface of which the first granites crystallized.” From the ruins of. these were formed the first sedimentary deposits, but directly beneath were other granitic masses, which became fixed imme- diately afterward. “Some parts of these masses, coagulated from the commencement of the cooling process, but not com- pletely solidified, were then erupted through the sedimentary deposits ” just mentioned. ‘In these jets of pasty matter” were contained many of the rarer elements of the granitic mag- ma, which were thus concentrated in the outermost portions of the granitic crust, and in the ramifications formed by these portions in the masses through which they were forced by the eruptive agents. Those portions of the granitic masses, and their ramifications, in which these rarer elements are con- centrated, are distinguished from the rest of the masses alike by their exterior position and their peculiar structure. They eee Se ae) Se Oe et a a * ia) -. wv 190 GRANITES AND GRANITIC VEIN-STONES. [XI. are often coarse-grained, and include the pegmatites, tourmaline- granites, and veins carrying cassiterite and columbite, frequent- ly abounding in quartz. These mineral products are to be | regarded as emanations from the granite, and are described as 3 a granitic aura, constituting what Humboldt has called the | penumbra of the granite. (Bull. Soc. Geol. de France (2), IV. 1249. See particularly pages 1295, 1321, and 1323.) ; § 10. While Fournet, Durocher, and Riviére conceived the , granitic magma to have been purely anhydrous, and in a state f of simple igneous fusion, Elie de Beaumont maintained, with . Poulett Scrope and Scheerer, that water had in all cases inter- vened, and that a few hundredths of water might, at a low : red heat, have given rise to the condition of imperfect liquidity Mi which he imagined for the material of the injected granites. The coarsely crystalline granitic veins were, according to him, veins of injection, and he speaks of them as examples in which “‘the phenomena essential to the formation of granite had been manifested with the greatest intensity.” The granitic emana- tions, which are supposed to. have furnished the material of these veins, appear to be regarded by him as the result of a process of eliquation from the congealing granitic mass. De Beaumont is careful to distinguish between them and those emanations which are dissolved in mineral waters, or are ex- haled as volcanic vapors (page 1324). To the agency of such ) waters he ascribes the formation of concretionary veins, which : are generally characterized by their symmetrically banded structure. He further adds that granites, as to their mode of : formation, offer a character intermediate between ordinary veins and volcanic and basic rocks. ‘This is conceivable as regards a: granitic veins, since these, according to him, although formed rE by injection, and not by concretion, result from a process of - emanation from the parent granitic mass, which may be de- sf scribed as a kind of segregation. 5 I have thus endeavored to give, for the most part in his own EE words, the views on the origin of granites enunciated by the 4 great French geologist in his classic essay on Volcanic and Metalliferous Emanations, published in 1847. They belong to .: XL] GRANITES AND GRANITIC VEIN-STONES, 191 the history of our subject, and are remarkable as a clear and complete expression of those modified plutonic views which are probably held by a great number of enlightened geologists at the present time. My reasons for dissenting from them, and the theories which I offer in their stead, will be shown in the sequel. : § 11. Elie de Beaumont, while regarding the formation of granitic veins as a process in which water intervened to give fluidity to the magma, was careful to distinguish the process from that of the production of concretionary veins from aque- uous solution, and supposed the fissures to have been filled by the injection of a jet of pasty matter derived from a consolidat- ing granitic mass. Daubrée and Scheerer, in describing the granitic veins of Scandinavia, conceive the material filling them to have been derived from the enclosing crystalline strata, instead of from an unstratified granitic nucleus, but do not, so far as I am aware, compare their formation to that of concre- tionary veins. Their publications on this subject, it should be said, are both anterior to the essay of De Beaumont. § 12. The notion that all granitic veins are the result of some process of injection, and not to be confounded with con- cretionary veins, seems indeed to have been general up to the present time. Even Von Cotta, while strongly maintaining the aqueous and concretionary origin of metalliferous veins in gen- eral, when describing those consisting of quartz, mica, feldspar, tourmaline, garnet, and apatite, with cassiterite, wolfram, etc., which occur at Zinnwald and at Johanngeorgenstadt, is at a loss whether to regard these veins, from their granitic character, as igneous-fluid injections or as concretionary lodes. In sup- port of the latter view he refers to their more or less regular and symmetrically banded structure, and while recalling the fact that mica and feldspar may both be formed in the humid way, considers the nature of these veins to be very problemati- eal, and the question of their origin a difficult one. (Ore De- posits, Prime’s translation, 1870, pages 110 — 124.) § 13. I have for several years taughtythat granitic veins of the kind just referred to are concretionary and of aqueous Pr. et gin TI! Se ee a, ae cr er 192 GRANITES AND GRANITIC VEIN-STONES, [XL origin. In 1863 I described certain veins in the crystalline schists of the Appalachian region of Canada, “ where flesh-red orthoclase occurs so intermingled with chlorite and white quartz as to show the contemporaneous formation of the three species. The orthoclase generally predominates, often reposing upon or surrounded by chlorite ; at other times it is imbedded in quartz, which covers the latter. Drusy cavities are also lined with small crystals of the feldspar, and have been subse- quently filled with cleavable bitter-spar, sometimes associated- with spécular iron, rutile, and sulphuretted copper ores.” A study of these veins shows a transition from those “ containing quartz and bitter-spar, with a little chlorite or talc, through others in which feldspar gradually predominates, until we ar- rive at veins made up of orthoclase and quartz, sometimes in- cluding mica, and having the character of a coarse granite ; the occasional presence of sulphurets of copper and specular iron characterizing all of them alike. It is probable that these, and indeed a great proportion of quartzo-feldspathic veins, are of aqueous origin, and have been deposited from solutions in fissures of the strata, precisely like metalliferous lodes. This remark applies especially to those granitic veins which include ‘minerals containing the rarer elements. Among these are boron, phosphorus, fluorine, lithium, cesium, rubidium, gluci- num, zirconium, tin, and columbium ; which characterize the mineral species apatite, tourmaline, lepidolite, spodumene, beryl, zircon, allanite, cassiterite, columbite, and many others.” (Geology of Canada, pp. 476, 644 ; and ante, p. 33.) In this connection I referred to the occurrence of orthoclase $ with quartz, calcite, zeolites, epidote, and native copper in cer- i: tain mineral veins of Lake Superior, so well described by Pro- i fessor J. D. Whitney. (American Journal of Science (2), ' XXVIII. 16.) The associations, according to him, show the : contemporaneous crystallization of the copper, natrolite, calcite, and feldspar, which last was found by analysis to be a pure potash-orthoclase. a § 14. In 1864 this yiew was still further insisted upon in the Journal just cited ((2), XXX VII. 252), where, in speaking . ee ee, ae ee XI] GRANITES AND GRANITIC VEIN-STONES. 193 of mineral vein-stones “which doubtless have been deposited from aqueous solution,” it is added, “while their peculiar ar- rangement, with the predominance of quartz and non-silicated species, generally serves to distinguish the contents of these veins from those of injected plutonic rocks, there are not wanting cases in which the predominance of feldspar and mica gives rise to aggregates which have a certain resemblance to dikes of intrusive granite. From these, however, true veins are generally distinguished by the presence of minerals contain- ing boron, fluorine, phosphorus, cesium, rubidium, lithium, glucinum, zirconium, tin, columbium, etc. ; elements which are rare, or found only in minute quantities in the great mass of sediments, but are here accumulated by deposition from waters which have removed these elements from the sedimentary rocks and deposited them subsequently in fissures.” In the Report of the Geological Survey of Canada for 1866 (p. 192), I have, in describing the veins of the Laurentian rocks, insisted still further on the distinction just drawn be- tween granitic dikes and granitic vein-stones, which latter I have proposed to call endogenous rocks, to indicate the mode of their formation, and to distinguish them from intrusive or exotic rocks, and sedimentary or indigenous rocks. § 15. The peculiar banded arrangement, which is so charac- teristic in concretionary veins not granitic in composition, is probably not less marked in granitic vein-stones, and often ap- pears in these in a remarkable manner, showing that they have been formed by successive depositions of mineral matter, and generally in open fissures. This structure, and various pecul- iarities to be observed in granitic vein-stones, will be best illus- trated by descriptions of various localities, most of which I have personally examined. It is proposed to notice, first, the veins of the gneiss and mica-schist series of New England ; and, secondly, those of the Laurentian rocks of New York and Canada. In the latter class will be noticed the more or less calcareous vein-stones into which the Laurentian granitic veins are found to graduate. § 16. It is in the series of micaceous schists with interstrati- 9 M 194 GRANITES AND GRANITIC VEIN-STONES. [XI. fied gneisses (§ 6) which I have elsewhere provisionally desig- nated the Terranovan series * [since called Montalban], that I have seen concretionary granitic veins in the greatest abundance and on the grandest scale. This stratified system, which is well seen in the White Mountains, appears to extend south- — ward along the Blue Ridge as far as Georgia, and northeast- ward beyond the limits of Maine. It is in this State that I have particularly studied the granitic vein-stones of this system, whose history may be illustrated by a few examples from notes taken on the spot. In Brunswick the strata near the town are fine grained, friable, dark colored, micaceous, and hornblendie, passing into mica-schist on the one hand, and into well-marked gneiss on the other, and dipping to the southeast at angles of from 15° to 40°. Very similar beds are found in the adjoin- ing town of Topsham, and in both places they include numer- ous endogenous granitic veins. The course of these veins is generally northwest, or at right angles to the strike, though occasionally for short distances with the strike, and intercalated between the beds; the veins vary in breadth from a few inches to sixty feet, and even more. They generally consist in great part of orthoclase and quartz, with some mica and tourmaline, and offer in the associations and grouping of these minerals many peculiarities, which are met with not only in different veins, but in different parts of the same vein. In some Cases, colorless vitreous quartz greatly predominates, and encloses crystals of milk-white orthoclase, often modified, and from one to several inches in diameter. At other, times pure vitreous quartz forms one or both walls, or the centre of the vein, or else is arranged in bands parallel with the sides of the vein, and sometimes a foot or more in thickness, alternating with similar bands consisting wholly or in great part of orthoclase, * American Journal of Science for July, 1870, page 83, and Can. Naturalist, V. p. 198. — The rocks of this White Mountain series are, in the present state of our knowledge, supposed to be newer than the Huronian system noticed in § 5, to which, with Macfarlane and Credner, I refer the crystalline schists, with associated serpentines and diorites, of the Green Mountains. [See further in this connection Paper XIII. and its Appendix; also the third part of Paper XVI. and the Introduction to III.] - Wie, / pe |) wee > ee > a. oe XI] GRANITES AND GRANITIC VEIN-STONES. 195 or of an admixture of this mineral with quartz, having the pe- culiar structure of what is called graphic granite, or else pre- senting a finely granitoid mixture of the two minerals, with little or no mica, and with small crystals of deep red garnet. Prisms of black tourmaline are also met with in these veins, and more rarely beryl and even chrysoberyl. In the rock- cutting on the Lewiston Railroad, just below Topsham bridge over the Androscoggin, there is a fine exhibition of these veins, which present alternate coarser and finer grained layers, trav- ersed by long spear-shaped crystals of dark mica passing from one layer to another. § 17. A remarkable example of a vein of considerable dimen- sions is seen in the feldspar-quarry in Topsham, which occurs in a dark fine-grained friable micaceous schist. At the time of my visit, in 1869, the limits of the vein were not seen, though large quantities of white orthoclase and of vitreous quartz had already been extracted. These were each nearly pure, and in alternate bands, the quartz presenting drusy cavi- ties lined with remarkable tabular crystals. One band was made up in great part of large crystals of mica, and portions of the vein consisted of a granular saccharoidal feldspar. The famous locality of red, green, and blue tourmalines, with beryl, lepidolite, amblygonite, cassiterite, etc., at Mount Mica in Paris, Maine, is a huge granitic vein, which, with many others, is included in a dark-colored very micaceous gneiss. § 18. In Westbrook numerous small veins of this kind, holding coarsely lamellar orthoclase with black tourmaline and red garnet, intersect strata of fine-grained whitish granitoid gneiss. In Windham the dark-colored staurolite-bearing mica- _ schist of this series'is traversed by a granitic vein holding crys- tals of beryl. In Lewiston a large vein of coarse graphic granite, holding black tourmaline, and showing fine-grained bands, cuts a great mass of bluish gneissoid limestone, which forms an escarpment near the railroad, about half a mile below the town. This limestone, which dips eastward about 15%, is interlaminated with thin quartzite beds, which are seen on weathered surfaces to be much contorted. The bluish erystal- 196 GRANITES AND GRANITIC VEIN-STONES. [XL line limestone is mixed with grains of greenish pyroxene, and includes nodular granitic masses of white crystalline orthoclase with quartz, enclosing large plates of graphite, crystals of horn- blende, and more rarely of apatite. These associations of min- erals are met with in the granitic veins of the Laurentian limestones, to be noticed elsewhere. The limestone of Lewis- ton, however, appears to be included in the great mica-schist series of the region ; where similar beds, though less in extent, are met with in various places, sometimes associated with pyroxene, garnet, idocrase, and sphene. A thin band of im- pure pyroxenic limestone, like that of Lewiston, occurs with the mica-schists on the Maine Central Railroad, near’ Danville Junction ; and beds of a purer crystalline limestone were for- merly quarried in the southeast part of Brunswick, where they are interstratified with thin-bedded dark hornblendic and mica- ceous gneiss, dipping southeast at a high angle. § 19. At Danville Junction strata of hornblendic and mica- ceous gneiss, passing into mica-schists, dip southeast at moder- ate angles, and include huge veins of endogenous granite. Two of these appear in the hill just south of the railroad-station, apparently running with the strike of the beds. They are seen to rest upon the mica-schist, and in one of them a mass of this rock, three feet in width, is enclosed like a tongue in the granite, which has a transverse breadth of about seventy-five feet. Notwithstanding the apparent intercalation of these - granitic masses, the proof of their foreign origin is evident in a transverse fracture and slight vertical dislocation of the mica- schist, around the broken edges of which the granite is seen to wrap. The endogenous character of this granite is well shown by its banded structure ; belts of white quartz some inches wide alternate. with others of coarsely cleavable orthoclase, while other portions hold black tourmalines and garnets of considerable size. The evidence of disturbance of the strata in connection with these endogenous granites is seen on a large scale at the falls of the Sunday River in Ketchum. There, mica-schists and gneisses, similar to those already noticed, enclose. great masses XI.] GRANITES AND GRANITIC VEIN-STONES. 197 of endogenous granite, which are seen to be transverse to the strata. On-one side of such a mass more than sixty feet wide, the schistose strata are twisted from their regular northeast strike to the northwest, and so enclosed in the granite as to appear interstratified with it for short distances, The banded structure of the transverse granite veins is here very marked. Some portions present cleavage-planes of orthoclase six inches in diameter ; other parts, which are less coarse, abound in mica. Similar banded granite veins abound in the adjoining towns of Newry and North Bethel, and sometimes present layers of quartz six inches or more in thickness, beside large crystals of mica, and more rarely apatite.* These veins are often irreg- ular in shape and bulging at intervals, and they sometimes run partially across the beds, which seem to have been distended and disturbed ; a fact which was also observed in the thin- bedded schists in contact with some of the veins in Brunswick, and is apparently due to the expansive force of crystallization, as noticed in § 27. § 20. The locality already described at Danville offers an instructive example of a phenomenon often met with in the region now under consideration, where granitic masses, resist- ing the actions which have degraded the soft enclosing schists, stand out in relief on the surface, and seem to constitute the rock of the country. A careful search will however show that they are simply veins or endogenous masses of very limited dimensions, rising from out of the mica-schists, which are often concealed by the soil. This is well seen about the lower falls of the Presumpscott, near Portland, where the mica-schists, with some fine-grained gneisses, dipping southeast at angles of from 30° to 40°, enclose large numbers of granitic veins, which, — though sometimes but a few inches in breadth, often measure twenty or even fifty feet, and are usually very coarse grained, with white mica, black tourmaline, and more rarely beryl. * A good example of a large vein of this kind of intersecting rocks of the White Mountain series may be seen in the Ramble in the Central Park in the city of New York. Its place is marked by a great erratic block perched directly over the vein. a « Suge “alae Je. 6 ne ee ies , a a Cae tea Cus >) Te CeO ee } >. oe } en ee ee r 198° GRANITES AND GRANITIC VEIN-STONES. [XI: They are sometimes transverse to the stratification, but more often parallel, and, standing above the soil, are very conspicu- — ous. § 21. We have already noticed the exotic granites of Bidde- « ford, which are intruded among fine-grained bluish or grayish silicious strata. These latter are traversed by numerous veins of endogenous granite, which are very unlike in aspect to the intrusive rock. One of these veins, near Saco Pool, has a diameter of about an inch and a half, and presents on either wall a layer of yellowish crystalline feldspar about one fourth of an inch in thickness, which includes long plates of dark brown mica. These penetrate the central portion of the vein, which is a broadly crystalline bluish orthoclase, enclosing small portions of quartz, after the manner of a graphic granite. The yellowish and less coarsely crystalline feldspar, with its accompanying mica, had evidently lined the walls of the vein while the centre yet remained open, and had moreover entirely filled a small lateral branch. The same conditions are seen in the filling of other veins in this vicinity, which are often much larger, and present upon their walls bands of an inch or two of the yellowish feldspar, with mica. The successive filling of a granitic vein is still more clearly shown in a specimen from Sherbrooke, Nova Scotia, which I owe to the kindness of Professor H. Y. Hind. The vein, which is seen ‘to be transverse to the adherent fine-grained mica-schist, has a breadth of nearly four inches, about two thirds of which is symmetrical, and is included between two layers, perpendic- ular to the walls, consisting of a fine-grained mixture of white feldspar and quartz, each about one fourth of an inch thick, . and marked by subordinate zones, more or less quartzose. Within these two bands is a coarser aggregate, consisting of two feldspars, with some quartz and muscovite, plates of which, and crystals of pink orthoclase, penetrate an irregular layer of smoky quartz varying from one eighth to one half an inch in diameter. This fills the centre of the symmetrical portion of the vein, on one side of which is the mica-schist, while the other is bounded by a band of more than half an inch of fine- X1.] GRANITES AND GRANITIC VEIN-STONES. 199 grained granite with yellowish-green mica, presenting large crystals of feldspar near the outer margin, where it is succeeded by a layer of pure smoky vitreous quartz of about the same thickness, whose outer surface, against the wall, shows irregular bosses or nodular masses, the. depressions between which are occupied by a finely granular micaceous aggregate unlike any other part of the vein in texture.* This description may be read in connection with the remarks in § 27. Dana has described and figured a similar granitic vein, banded with quartz, observed by him at Valparaiso in Chili (Manual of Geology, 1862, p. 713),+ and has moreover main- tained that such granitic veins, like ordinary metalliferous lodes, are clearly concretionary in their origin, and have been filled by slow and successive deposits from aqueous solu- tions. His testimony to the views which I have advocated in this paper had been overlooked by me, or it would have been noticed in § 12. § 22. The numerous granitic veins so well known to miner- alogists in the mica-schists and gneisses of New Hampshire, Massachusetts, and Connecticut, including, among other famil- iar localities, Grafton, Acworth, Royalston, Norwich, Goshen, Chesterfield, Middletown, and Haddam, seem, from descrip- tions and from their mineral constituents, to be similar to those of Maine, already mentioned. With the exception of Royals- ton and Haddam, however, these localities are as yet only known to me from specimens and descriptions. It is note- worthy that at the former the finely crystallized beryls are directly imbedded in vitreous quartz, and the same is the case with the beryls of Acworth and the blue and green tourmalines of Goshen. A remarkable example of a vein of this character occurs in Buckfield, Maine, described to me by Professor Brush, - * The banded structure is well shown in a granitic vein which I owe to Pro- fessor Haughton of Trinity College, Dublin, got from Three Rock Mountain, near that city. It consists of white orthoclase, with quartz and some mica and garnet, and exhibits near the middle two bands of prisms of black tour- maline pointing towards the centre, which is filled with a coarsely crystalline orthoclase. + From U. 8. Exploring Expedition, Report on the Geology, 1849, p. 570. 200 GRANITES AND GRANITIC VEIN-STONES. [XI. where large isolated crystals of white orthoclase, nearly color- less muscovite, and brown tourmaline occur in a vein of vitre- ous quartz. At Paris and at Hebron, Maine, tourmalines are found penetrating crystals of quartz. The flattened tourma- lines and garnets found in muscovite at several localities in New England are well known to collectors, and a curious ex- ample of enclosure has been observed by Professor Brush at Hebron, where crystals of muscovite are encased in lepidolite. § 23. The following list includes the principal mineral species found in these granitic veins in New England : apatite, amblygonite, triphylline, autunite, yttrocerite, orthoclase, al- bite, oligoclase, spodumene, iolite, muscovite, biotite, lepidolite, cookeite, chlorite, chlorophyllite, garnet, epidote, tourmaline, beryl, zircon, quartz, chrysoberyl, automolite, cassiterite, rutile, brookite, uraninite, columbite, pyrochlore, scheelite, and _bis- muthine. As I am not aware that chlorite has hitherto been mentioned as a constituent of these veins, it may be said that it occurs in one at Albany, Maine. To the above should be added the rare species nepheline, cancrinite, and sodalite, which have long been known in bowlders of a granite-like rock in Maine. According to information given me by Professor Brush, green eleolite with white orthoclase and black biotite occurs in a granitic vein twenty feet in breadth, lately observed in the northwest part of Litchfield, Maine. § 24. We have seen that these endogenous veins are found alike in the gneisses, mica-schists, limestones, and quartzose strata of this region. They are also met with in the eruptive granites, small fissures in which are sometimes filled with coarsely crystalline orthoclase, smoky quartz, various micas, and zircon. Examples of this are seen in the granites of Hamp- stead, New Brunswick, and Mount Uniacke, Nova Scotia. The fine green feldspar of Cape Ann, Massachusetts, and the micas, eryophyllite and lepidomelane, with zircon, described by Pro- fessor Cooke, from the same region, occur in veins in the horn- blendic granites of that locality. Small veins cutting a some- what similar rock at Marblehead contain crystallized green epidote with white quartz and red orthoclase. AB ee Sag F : i ee ee oer ee =5 XI.] GRANITES AND-GRANITIC VEIN-STONES. 201 § 25. The veins which we have described are frequently of very limited extent, and seem to occupy short and irregular fissures, while in other cases the mineral aggregates which characterize them occur in nests or geodes. This is seen near Fall Brook, in the Nerepis valley, in New Brunswick, where the red micaceous granite is in one part very friable, and pre- sents irregular geode-like cavities, sometimes several inches in diameter, which aré partially filled by radiating prisms of black tourmaline, accompanied with quartz and albite crystals, and more rarely small octahedrons of purple fluorite. The en- closing granite is composed of deep red orthoclase, with small portions of a white triclinic feldspar, smoky quartz, and black mica. The conditions seen at this place recall the description of the famous locality of feldspars, etc., at Fariolo, near Baveno, in northern Italy. The rock of that place, described as a granite, resembles, in a specimen before me, some of the intru- sive granites of New Brunswick, and contains a pink and a white feldspar, with a little black mica. It includes veins of graphic granite, and also spheroidal masses, which differ in tex- ture from the mass of the rock, and present geodes of consider- able size, lined with fine large red and white crystals of ortho- clase, accompanied by albite, epidote, quartz, fluorite, and a greenish mica (or chlorite), all of which, according to Fournet, are so mingled and interlocked as to show that they are of con- temporaneous origin. To these are to be added, as occurring in the geodes, prehnite, calcite, hyalite, and specular iron. The orthoclase crystals often have adhering to their opposite faces crystalline plates of albite, which are larger than the planes to which they are attached. The crystals of orthoclase, moreover, frequently present hollowed-out or hopper-shaped faces, which Fournet happily describes as resulting from the forming of the framework or skeleton of the crystals, when the material was ' not sufficient for their completion. A process analogous to this is often seen in crystallization, whether from fusion, solution, or vaporous condensation, giving rise in some cases to external depressions, and in others to internal cavities in the resulting crystals, Fournet ascribes the formation of the geodes in the g* 202 GRANITES AND GRANITIC VEIN-STONES. [XI granite of Fariolo to a process of shrinking, and a subsequent segregation filling the resulting cavities, in which he is forced to recognize the intervention of water, though by no means ad- mitting the aqueous origin of veins, since he holds even those of quartz to have been formed by igneous injection. (Géologie Lyonnaise, *278.) § 26. When we consider the cause which has produced the fissures in the mica-schists and gneisses of New England, which hold the granitic veins already described, it is to be re- marked that their comparative abundance, their shortness and their irregularity, distinguish them from the fissures which are filled with eruptive rocks. Examples of the latter may be seen near Danville, Maine, where dikes of fine-grained dolerite are posterior to the endogenous granitic veins here occurring in the mica-schist. These dikes may be supposed to be dependent upon movements in the earth’s crust opening deep fissures which connected with some softened rock far below. Through . such openings were extravasated the exotic rocks, whether granites or dolerites,— more or less homogeneous mixtures, often widely different in composition from the encasing rocks. The endogenous veins, on the contrary, are distinguished not only by their more or less heterogeneous and often banded structure, but by the fact that their principal constituents are generally the mineral species common in the adjacent strata. § 27. Volger has attributed the formation of the openings containing concretionary veins to the force of crystallization, which is shown to be very great in the congelation of water and the crystallizing of salts in cavities and fissures. Such a process once commenced in an opening in a rock would, he conceived, be sufficient to make still wider the fissure, which might be fed by fresh solutions passing by capillarity through the pores of the rock. If this process were to become concen- trated around several points, the intermediate spaces might be so opened that free crystallization could go on, resulting in the production of goedes in veins thus formed. Fournet, on the other hand, suggests that contraction in the cooling of erupted granites gave origin to the fissures and hr XI.] GRANITES AND GRANITIC VEIN-STONES. 203 geodes now filled or partially filled with crystalline minerals at Fariolo ; we may readily suppose that a process of contraction attendant upon the crystalline aggregation of the materials of sedimentary strata would give rise to rifts or fissures therein. The lesions thus produced in the solid rocks become more or less completely repaired, if we may so speak, by an effusion of mineral matter from the walls, and thus are generated geodes, irregular masses, and many veins. That the process imagined by Volger may in some cases intervene, and may act subse- quently to the one just imagined, is highly probable, though we are disposed to assign it but a secondary place in the pro- duction of vein-fissures. It offers, however, the most plausible explanation of the distortion of the thin-bedded strata already noticed in connection with some of the concretionary granitic veins of Maine, which seem, by a process of growth, to have bent outward the adjacent beds. The vertical transverse veins are, in many cases at least, unsymmetrical, as if they had grown from one side, while the distortion of the beds, some- times attended by irregular concretions in the banded vein- stone, appears at the opposite wall. The notion that the vein- fissures opened as crystallization advanced has been defended by Griiner. § 28. It is not here the place to discuss how far the greater and deeper fissures of the earth are dependent upon the con- traction of sediments, as just explained, or upon the wider ‘spread movements of the earth’s crust, though even of these it may be said that they are more or less directly the results of a process of contraction. It should, however, be noted that while some fissures of this kind are filled with dikes of erupted rocks (§ 26), others hold concretionary veins, which are to be distin- guished from the class of veins just described, inasmuch as the openings in which they were deposited evidently communicated with the surface of the earth. Examples of these are seen in the lead and zinc-bearing veins with calcite and barytine, which traverse vertically the carboniferous limestone in England, and enclose in their central portions material of liassic age, abound- ing in the remains of a marine and a fresh-water fauna, which aa eat ak a ah thal ee i i oy - 204 GRANITES AND GRANITIC VEIN-STONES. [XI show these veins to have been deposited in fissures communi- cating with the surface-waters of the liassie period. For a. description of these veins by Mr. Charles Moore, see the Re- port of the British Association for 1869, and Amer. Jour. of Science (2), L. 365. Similar evidence is afforded by the exist- ence of rounded pebbles imbedded in veins, as observed in Bohemia and also in Cornwall, where numerous pebbles both of slate and quartz were found at a depth of six hundred feet in a lode, cemented by cassiterite and sulphuret of copper. (Ly- ell, Student’s Elements of Geology, p. 593.) Not less instruet- ive in this connection are the observations of Mr. J. Arthur Phillips, on the silicious vein-stones now in process of forma- tion in open fissures in Nevada. (L. E. and D. Phil. Mag. (4), XXXVI. 321, 422 ; Amer. Jour. of Science (2), XLVIL 138.) We cannot doubt that the ancient, like these modern veins have been channels for the discharge of subterranean mineral waters ; and it would seem that while the deposition of the in- erusting materials on the walls of the fissure is in part due to cooling, and in part perhaps to infiltration, in some cases, of precipitants from lateral sources, it is chiefly to be ascribed to the reduction of solvent power consequent upon the diminu- tion of pressure as the waters rise nearer to the surface,* This conclusion, deducible from the researches of Sorby on the rela- tion of pressure to solubility (ante, page 65), I have pointed out in the Geological Magazine for February, 1868, p. 57. See also Amer. Jour. of Science (2), L. 27, § 29. There is evidently a distinction to be drawn between veins which have been open channels and the segregated * Of this a remarkable example was afforded in 1866 at Goderich, in Ontario, . where, in a boring at a depth of 1,000 feet, a bed of rock-salt was met, from ‘which for a time a saturated or rather supersaturated brine was obtained. As an evidence of this, I saw a cube of pure salt, one fourth of an inch in diameter, which had formed upon and around a projecting point of an iron valve in the pump, above the surface of the ground. The liquid beneath a pressure of 1,000 feet of brine, equal to about 1,200 feet of water, or thirty- six atmospheres, having taken up more salt than it could hold at the ordinary pressure, deposited a portion of it as it reached the surface, and actually ob- structed thereby the action of the pump. After a few months of pumping, however, the well ceased to afford a fully saturated brine. XI.] RANITES AND GRANITIC VEIN-STONES. 205 o masses and geodes formed in cavities which appear to have -been everywhere limited by the enclosing rock. In the former case a free circulation of the mineral solution would prevail, while in the latter there could be no renewal of it except by percolation or diffusion through the rock. A comparison be- tween the contents of geodes and fissure-veins, whether in granitic rocks or in fossiliferous limestones, will however show that these differences do not sensibly affect the mineral consti- tution of the deposits. § 30. The range of conditions under which the same mineral species may be formed is apparently very great. Sorby, from his investigations of the fluid-cavities of crystals, concludes that the quartz which occurs with cassiterite, mica, and feld- spar in the granitic veins of Cornwall must have crystallized at temperatures from 200° to 340° Centigrade, and under great pressure ; conditions which we can hardly suppose to have pre- sided over the production of the crystallized quartz found in the unaltered tertiaries of the Paris basin, or the auriferous conglomerates of California. In like manner beryl, though a common mineral of the tin-bearing granite veins, like those studied by Sorby, occurs at the famous emerald-mine of Muso, in New Grenada, in veins in a black bituminous limestone, holding ammonites, and of neocomian age, its accompaniments being calcite, quartz, and carbonate of lanthanum (parisite). Small crystals of emerald are disseminated through this argil- laceous, somewhat magnesian limestone, which contains, more- over, a small amount of glucina in a condition soluble in acids. (Léwy, Annales de Chimie et de Physique, LIII. 1-26; and Fournet, Géol. Lyonnaise, 455.) § 31. To these we may add the production of various hy- drated crystallized silicates, including apophyllite, harmotome and chabazite, during the historic period in the masonry of the old Roman baths at Plombiéres and Luxeuil, and by the ac- tion of waters at temperatures of from 46° to 70° Centigrade (ante, page 25) ; the presence of apophyllite, natrolite, and stil- bite in the lacustrine tertiary limestones of Auvergne ; apophyl- lite incrusting fossil wood, and chabazite crystals lining shells in SL ee ete eee ee en ee a ay lk ites fin A 9h cain a oe ee waa ob bv Stak, : “0 ee 7 206 GRANITES AND GRANITIC VEIN-STONES. [XI. a recent deposit in Iceland. The association of such hydrated silicates with orthoclase, as already noticed (§ 13), and as de- scribed by Scheerer, where natrolite and orthoclase envelop each other, showing their contemporaneous formation, with many other facts of a similar kind, lead to the conjecture that orthoclase, like beryl and quartz, and perhaps some other con- stituents of granitic veins, may have crystallized in many cases at temperatures much lower than those determined by Sorby, and that the conditions of their production include a consider- able range of temperature; a conclusion which is, however, probably true to some extent of zeolites also. § 32. It is now proposed to consider the granitic vein-stones found in Laurentian rocks. The stratified rocks of this ancient gneissic series, as I have elsewhere pointed out, differ consider- ably from those of the White Mountain series, which, with ‘their vein-stones, have been treated of in §§ 16-23. The Laurentian series, the Lower Laurentian of Sir William Logan, as studied by him in a region to the north of the Otta- wa, the only area in which it has yet been examined in detail, appears to consist of an alternation of conformable gneissic and calcareous formations. The latter are three in number, each from 1,000 to 2,000 feet or more in thickness, and separated by still more considerable formations of gneiss and quartzite, a mass of gneiss of great but unknown thickness forming the base. (Geology of Canada, page 45.) The gneissic rocks of the series are very firm and coherent, reddish or grayish in color, often very coarse grained and granitoid, sometimes with but obscure marks of stratification ; and frequently porphyritic from the presence of large cleavable masses of reddish orthoclase, occasionally with a white triclinic feldspar. They are often hornblendic, and sometimes contain small quantities of dark colored mica. A white granitoid gneiss, composed chiefly of orthoclase and quartz, sometimes contains an abundance of red iron-garnet. The latter mineral is often disseminated, or forms subordinate beds in the quartzites of the series. § 33. With the crystalline limestones of the calcareous parts of the series are often found strata made up of other minerals, i. 4 et A F ; 4 XL] GRANITES AND GRANITIC VEIN-STONES. 207 to the entire exclusion of carbonate of lime, by an admixture of which, however, they graduate into the adjacent limestones. These beds generally consist of pyroxene, sometimes nearly pure, and at other times mingled with a magnesian mica, or with quartz and orthoclase, often associated with hornblende, serpentine, magnetite, sphene, and graphite. These pyroxenite rocks are generally gneissoid or granitoid in structure, and sometimes very coarse grained. ‘They occasionally assume a great thickness, and are then often interstratified with beds of granitoid orthoclase-gneiss, into which the quartzo-feldspathic pyroxenites pass by a gradual disappearance of the pyroxene. The limestones often include serpentine, pyroxene, hornblende, phlogopite, quartz, orthoclase, magnetite, and graphite ; so that the same minerals are common to them and to the pyroxenic strata, which may be looked upon as marking the transition between the gneissic and the calcareous parts of the series. These strata, marked by the predominance of calcareous and magnesian silicates, appear, so far_as known, to accompany each of the limestone formations of the Laurentian, sometimes, however, developed to a greater and sometimes to a less extent. § 34. I have elsewhere called attention to the fact that the highly micaceous schists and the argillites of the Green Moun- tain and White Mountain series of rocks are, so far as known, wanting in the Laurentian, and with them the characteristic minerals of the latter series, staurolite, andalusite, and cyanite. There are, however, beds of a highly micaceous rock in the Laurentian which contain an unctuous magnesian mica with a pyroxenic admixture; these are very unlike the mica-schists composed of a non-magnesian mica and quartz, with orthoclase, which abound in the White Mountain rocks. These magnesian beds belong to the calcareous horizons in the Laurentian series, at which also occur the most numerous veins and the principal minerals of economic value. It is also along these . horizons, marked by softer rocks, that the valleys and the arable lands of the Laurentian areas are chiefly found, and for this reason, also, the mineralogy of these parts is better known than 208 GRANITES AND GRANITIC VEIN-STONES. (XI. that of the harder gneissic portions. The above observations on the lithological character of the stratified rocks are impor- tant on account of the relations between these and the included veins, in which the characteristic minerals of the gneissic and calcareous rocks are often found associated. § 35. The history of these veins, as seen in the Laurentian rocks of the Laurentides in Canada, the Adirondacks of northern New York, and the Highlands of southern New York and New Jersey, has been discussed at length by the author in an essay on The Mineralogy of the Laurentian Limestones, in the Report of the Geological Survey of Canada for 1863-66, pages 181 — 223.* In this essay, which will be frequently referred to in the present paper, the vein-stones found in the Laurentian rocks have been noticed under three heads: First, metalliferous veins carrying galenite, blende, pyrite, and chalcopyrite in a gangue of calcite, sometimes with celestine and fluorite ; these, which are of palozoic age or still younger, cut the Potsdam sandstone, the Calciferous sand-rock, and probably also the overlying Trenton limestones. Second, quartzo-feldspathic veins with muscovite, tourmaline, zircon, etc. These veins I have described as passing by insensible gradations into the third class, in which calcite and apatite, with pyroxene, phlogopite, and other calcareous and magnesian silicates predominate, though frequently accompa- nied by quartz and orthoclase. These veins are older than the Potsdam sandstone, which rests upon their eroded outcrops, and sometimes includes worn fragments of apatite derived from them. § 36. It is these last two classes which it is proposed to con- sider in the present paper under the name of granitic vein-stones. In justification of the extension of the term “granitic” to the whole of this series of veins, it must be repeated, that it is not possible to draw a line of distinction between those in which quartz and orthoclase are the characteristic minerals, and those in which calcite, apatite, pyroxene, and phlogopite prevail, * This essay is reprinted, with some additions, in the Report of the Regents of the University of New York for 1867, Appendix E. The reader's attention is called to the note on the Hastings rocks, at the close of that reprint. . ares Se ee en ee XL] GRANITES AND GRANITIC VEIN-STONES. 209 sometimes to the entire exclusion of quartz and feldspar, both of which minerals are, however, frequently intermixed with the preceding species in the same aggregate, In one example, in Burgess, Ontario, the sides of a large vein are occupied by a mixture of calcite and apatite, while the centre is filled by a vertical granite-like layer of reddish orthoclase, with a little quartz and green apatite. Of another vein in the township of Lake, in Ontario, one portion was found to consist of calcite with yellow phlogopite, while an adjacent part consisted of quartz, with brown tourmaline, i etic st native bismuth, and graphite. § 37. The resemblance between the minerals of these Lau- rentian vein-stones and the same species brought from Norway was noticed so long ago as 1827, by Dr. William Meade (American Journal Science (1), XII. 303). Daubrée, in his account of the metalliferous deposits of Scandinavia, published in 1843 (Annales des Mines (4), IV. 199, 282), has given us a careful description of the veins from which these minerals are derived. From this, together with the observations . of Scheerer and Durocher, we are enabled to compare these vein- stones with those of the Laurentian-rocks in North America, and show, as I have —in the essay above referred to — done in detail, and for each principal speciés, the great similarity which exists between the two. In the so-called Primitive Gneiss formation of Scandinavia these veins occur either in gneiss, or in a gneissoid rock consisting of various admixtures of pyroxene, hornblende, garnet, epidote, and mica, the whole associated with crystalline limestones. The veins which abound in the gneiss near the iron-mines of Arendal, in Norway, accord- ing to Daubrée, though occasionally containing calcite, apatite, hornblende, and scapolite,.are sometimes destitute of all calca- reous and magnesian minerals, and become granite-like aggre- gates of orthoclase and quartz. He hence describes these veins, as a whole, though frequently abounding in lamellar calcite, as essentially granitic in character. As already noticed in § 8, Daubrée agrees with Scheerer in regarding these vein-stones as produced by a process of secretion, in opposition to Durocher, | N ee ee a ne ee ne ae ae ee ee een ey er ose Le sre , i) ve -o =~ ae . ee ea ros wa in! : 4 ‘ j bai te Reh ce 4 210 GRANITES AND GRANITIC VEIN-STONES. [XI. who looked upon them as having been formed by igneous injection. ; _ § 38. The principal mineral species known in the correspond- ing vein-stones of the Laurentian rocks of North America are the following: calcite, dolomite, fluorite, apatite, serpentine, chrysolite, chondrodite, wollastonite, hornblende, pyroxene, pyral- lolite, gieseckite, scapolite, petalite, orthoclase, oligoclase, albite, muscovite, phlogopite, sey bertite, tourmaline, garnet, idocrase, ept- dote, allanite, zircon, spinel, chrysoberyl, corundum, quwartz, sphene, rutile, menaccanite, magnetite, hematite, pyrite, and graphite. To which may be added some rarer species, such as tephroite, willemite, franklinite, zincite, warwickite, found in a few localities only, and others of less importance. Of the above list, those species whose names are in italics have been recognized as constituent minerals in the stratified rocks in which the veins occur. The most important species in these vein-stones are calcite, quartz, orthoclase, phlogopite, pyroxene, apatite, and graphite, of which some one or more will generally be found to prevail in the veins in.question. The greater part of the species named in the first list were observed by Daubrée in the veins near Arendal, and to these he adds axinite, gadolinite, and more rarely beryl and leucite;* while in the island of Utoé, asso- ciated with iron-ores, crystalline limestones, and hornblendic rocks passing into gneiss, are similar granitic vein-stones con- taining orthoclase and quartz, with tourmaline, cassiterite, and, in the middle of the veins, petalite, spodumene, and lepidolite. This association is the more worthy of notice, as the only other known locality of petalite (if we except the castor of Elba) is in the crystalline limestone of Bolton, Massachusetts, where it occurs, probably in a vein-stone, with scapolite, hornblende, pyroxene, chrysolite, spinel, apatite, and sphene. * Fora notice of the occurrence of leucite in these veins, and also in veins in Mexico, see the author’s Contributions to Lithology (Amer. Journal Science, (2), XX XVII. 264). According to Garrigou, this rare species occurs both well crystallized and in compact porphyroid masses, in dioritic rocks (ophites), at Lusbé in the valley of Aspé, in the Pyrennees. (Bull. Soc. Geol. de Fr. (2), XXV. 727.) a zm = : 4 4 + ¢ , = y : ~ a 4 " . XI] GRANITES AND GRANITIC VEIN-STONES. 211 § 39. Evidences of the concretionary origin of these granitic vein-stones of the Laurentian rocks appear in their banded structure, their drusy cavities, the peculiar incrustations and modes of enclosure often observed in the crystals, and finally in the rounded forms of certain crystals, which show a process of partial solution succeeding that of deposition. A banded arrangement of the materials parallel to the sides of the vein is often well marked. Thus, while the walls may be coated with erystalline hornblende, or with phlogopite, the body of the vein ~ will be filled with apatite, in the midst of which may be found a mass of loganite, or of crystalline orthoclase mixed with quartz, filling the centre of the vein, as already noticed in § 36. In other instances portions of the vein will be occupied by crystals of apatite, pyroxene, or phlogopite imbedded in calcareous spar, which in some other part of the breadth of the vein, or in its prolongation, will so far predominate as to give to the mass the aspect of a coarsely crystalline lamellar limestone. Prisms of apatite are often observed extending from either side toward the centre of the vein, which in some cases may be filled with calcite or another mineral, and in others is a vacant space lined with crystals. Drusy cavities of this-kind, a foot in breadth and several feet in length and depth, are sometimes met with in these veins in Ontario. § 40. Further evidence of concretionary origin is seen in the manner in which the various minerals incrust each other. Thus small prisms of apatite are enclosed in large crystals of phlo- gopite, in pyroxene, in quartz, and even in massive apatite ; erystals or rounded crystalline masses of calcite are imbedded in apatite and in quartz, and well-defined crystals of hornblende (pargasite) in pyroxene. In another example before me, small erystals of hornblende are implanted on a large crystal of pyroxene, and both, in their turn, are incrusted by small crys- tals of epidote. Crystalline graphite in like manner is enclosed alike in orthoclase, quartz, calcite, phlogopite, and pyroxene. § 41. Another noticeable evidence of the concretionary origin of these veins is the phenomenon already referred to in § 25, where the external skeleton or framework of a crystal is com- FE TR PE Se FECT ar ge NE Be 2 GRANITES AND GRANITIC VEIN-STONES. (XL plete, while the space within either remains empty, or is filled with other minerals, often unsymmetrically arranged. This condition of things is rendered intelligible by the forma- tion of similar hollow crystals during the cooling of certain saline solutions, as for example potash-nitrate. Small hollow prisms of red and green tourmaline, closely resembling the hollow nitre crystals, are common in the well-known gra- nitic vein-stone of Paris, Maine. I have elsewhere referred to the formation of such moulds or skeleton-crystals as having taken place in vein-cavities, and as serving to explain many cases of enclosure of mineral species. (Address to the A. A. A. S., Indianapolis, 1871. Paper XIII. of the present volume.) ~ In addition to the examples there cited, the Laurentian vein- stones afford some curious cases. Thus a prism of yellow idocrase half an inch in diameter from a vein in Grenville, Ontario, composed chiefly of orthoclase and pyroxene, is seen when broken across to consist of a thin shell of idocrase filled with a confused crystalline aggregate of orthoclase, which encloses a small crystal of zircon. In like manner large erys- tals of zircon from similar veins in St. Lawrence County, New York, are sometimes shells filled with calcite. § 42. The rounded forms of certain crystals in the Lauren- tian vein-stones were, I believe, first noticed by Emmons, who observed that crystals of quartz imbedded in carbonate of lime from Rossie, New York, have their angles so much rounded that the crystalline form is nearly or quite effaced, the surfaces - being at the same time smooth and shining. This appearance is occasionally observed in other localities, and is not confined to quartz alone, crystals of calcite and of apatite sometimes exhibiting the same peculiarity. At the same time the ortho- clase, scapolite, pyroxene, and zircon, which are associated with these rounded crystals, preserve all their sharpness of outline, as was observed by Emmons for the orthoclase in contact with the crystals of quartz just described. He suggested that the rounded outlines of these crystals were due to a partial fusion, although he did not overlook a fact which renders — this explanation untenable, namely, that the species presenting —_ a -» 3 i 1 * } 5 : f XL] GRANITES AND GRANITIC VEIN-STONES. 213 rounded angles are much less fusible than those which, in contact with them, preserve their crystalline forms intact. (Geology of the First District of New York, pages 57, 58.) These facts are well shown in the apatite-veins of Elmsley and Burgess, Ontario, where the crystals of apatite rarely present sharp or well-defined forms, but (whether lining drusy cavities or imbedded in the calcite or other minerals of the vein-stone) are most frequently rounded or sub-cylindrical masses, while the pyroxene and sphene, which often accompany them, pre- serve their distinctness of form. This rounding of the angles of certain crystals appears to me nothing more than a result of the solvent action of the heated watery solutions from which the minerals of these veins were deposited ; the crystals pre- viously formed being partially redissolved by some change in the temperature or the chemical constitution of the solution. Heated solutions of alkaline silicate, as shown by Daubrée, are without action on feldspar, as might be expected from the fact observed by him of the production of crystals of feldspar, as well as of pyroxene, in the midst of such solutions. These liquids would, however, doubtless attack and dissolve apatite, which is in like manner decomposed~by solutions of alkaline carbonate, and these latter at elevated temperatures dissolve crystallized quartz. That this solvent process has been re- peated during the filling of the veins is seen by a specimen in my possession, which shows crystals of calcite previously | rounded and enclosed in a large crystal of quartz, the angles of which are also nearly obliterated. From the alternations in the deposited mineral matters in many vein-stones, as well as from what we know of the changing composition of mineral springs, it is evident that the waters circulating in the fissures now occupied by veins must have been subject to periodical variations in composition. § 43. In the Geology of Canada (page 729) I have noticed an example of rounded quartz crystals in the veins at the Harvey Hill copper-mine in Leeds, Quebec. Large terminated. prisms of limpid colorless quartz are there found imbedded in compact erubescite, their angles being much rounded, while 4 as 214 GRANITES AND GRANITIC VEIN-STONES. [XL their faces are concave, and have lost their polish, retaining only a somewhat greasy lustre. A thin shining green layer, © apparently of a silicate of copper, covers the surfaces of the ore in contact with the crystals. From the mode of their arrange- ment in certain specimens, it is evident that these prisms of quartz, lining drusy cavities, were partially dissolved previous to the deposition of the metallic sulphide. § 44. Some of the more important types of Laurentian vein-stones may now be noticed. Those made up of quartz with orthoclase, muscovite, and black tourmaline, often with zircon, are not unfrequent in the Laurentian gneiss, though so far as yet observed less abundant than in the gneisses and. mica-schists of the White Mountain series. It is true, as already pointed out, that, from the greater softness of the en- closing rocks, the veins of the latter series are often weathered into relief (§ 20), and are thus rendered more conspicuous than those in the harder Laurentian gneisses. Among other examples of this first type of granitic veins may be mentioned those in Yeo’s Island among the Thousand Isles of the St. Lawrence, and the well-known vein in Greenfield, near Sara- toga, remarkable for affording crystals of chrysoberyl. A fre- quent type among the Laurentian granitic veins is characterized by great cleavable masses of reddish or reddish-brown orthoclase, with quartz and but little mica. With these are sometimes associated equally large masses of white or pale-colored albite ; these veins are sometimes of great size, one hundred feet or more in breadth. The perthite of Thompson, well known as a cleavable feldspar made up of alternate thin plates of reddish- brown orthoclase and white albite, forms with quartz a large granitic vein; while the peristerite of the same author is an opalescent or chatoyant white albite, with blue and green re- flections, which occurs with quartz in another vein in the same region. Some of the veins of red orthoclase include large cleavable masses of dark green hornblende, occasionally with magnetite. A remarkable vein about eighty feet in width, in Buckingham, Quebec, is composed - entirely of reddish-white orthoclase and cleavable magnetite, the latter in masses some- rf 3 e _ as XI] | GRANITES AND GRANITIC VEIN-STONES. 215 times two or three inches in diameter, scattered through the feldspar. § 45. The veins hitherto noticed occur in gneiss, but.on the river Rouge one consisting of large masses of quartz and albite is found in crystalline limestone. A remarkable vein described by Sir William Logan in Blythefield, Ontario, traverses alter- nate strata of limestone and gneiss, and has a breadth of not less than 150 feet. It consists in great part of a coarsely cleavable pale green pyroxene (sahlite), with a dark green hornblende, phlogopite, and calcite. Portions of the vein-stone, however, consist of an admixture of orthoclase, quartz, and black tourmaline, showing the transition from the calcareous to the feldspathic type of veins. In Ross, Ontario, a vein holds large isolated crystals of white orthoclase imbedded with black spinel, apatite, and fluorite in a base of lamellar pink carbonate of lime. One of the most remarkable of these composite veins is in Grenville, Quebec, and was formerly worked for graphite. It cuts a crystalline limestone, itself holding graphite and phlogopite, and has afforded not less than fourteen distinct mineral species, namely, calcite, apatite, serpentine, wollastonite, pyroxene, scapolite, orthoclase, oligoclase, garnet, idocrase, zircon, quartz, sphene, and graphite. An adjacent vein abounds in phlo- gopite, with pyroxene and zircon. A not less remarkable vein is that described by Blake in Vernon, New Jersey (this Journal (2), XIII. 116), in which calcite, fluorite, chondrodite, phlogo- pite, margarite, spinel, corundum, zircon, sphene, rutile, menacca- nite, pyrite, and graphite occur. Some of these contain bary- — tine, and in one case I have observed natrolite, both seemingly filling cavities, and of later origin than the other minerals. The remarkable zinciferous minerals, franklinite, zincite, dys- luite, and willemite, found in the Laurentian limestones of New Jersey, appear from the descriptions of H. D. Rogers to belong to calcareous vein-stones. Granitic veins are found traversing the magnetic iron ore-beds of the Laurentian series. I have described one in Moriah, New York, which includes angular fragments of the magnetite which forms its walls, and consists of a cleavable greenish triclinic feldspar, with quartz a a oe a ee 216 © GRANITES AND GRANITIC VEIN-STONES. [XL crystals having rounded angles, octahedrons of magnite, al- lanite, and a soft greenish mineral resembling loganite. § 46. As regards the order of deposition of minerals in these veins, we find apatite enclosed alike in calcite, in quartz, in phlogopite, in spinel, in graphite, and in pyrite. On the other hand, apatite sometimes includes rounded crystals of calcite or of quartz ; and graphite, which itself encloses apatite, is found included alike in quartz, in orthoclase, in pyroxene, and in calcite, in such a manner as to lead us to conclude. that its crystallization was contemporaneous with that of all these minerals ; while from the other facts mentioned it would appear that the order of deposition was subject to variation and to alternations. In a vein in Grenville large prisms of a white aluminous pyroxene (leucaugite) penetrate great crystals of phlogopite, while at the same time small crystals of a similar ' mica are completely imbedded in the crystallized pyroxene. Many facts relating to the association of various species in these vein-stones will be found in my essay, but the subject is one which still demands careful study. The banded structure of these veins is well shown in some of those which contain graphite. This mineral, though sometimes irregularly dissemi- nated through the vein-stone, frequently occurs in sheets or layers alternating with orthoclase, quartz, or pyroxene, parallel to the walls of the vein and exhibiting a peculiar structure due to the formation of successive layers of crystalline lamelle more or less nearly perpendicular to the plane of deposition. § 47. The veins hitherto noticed, whether feldspathic or calcareous, are generally vertical, or nearly so, and in most cases traverse the stratification. Of many of them which have been explored to some extent for apatite, mica, and graphite, it is noticed that they are subject to great changes in dimension as well as in mineral contents. They often appear to occupy short irregular fissures, and in some cases are to be described as more or less completely filled geode-like cavities rather than veins. § 48. In the reprint of my essay, already mentioned, several veins are noticed in the county of Hastings, Ontario, in rocks XL] GRANITES AND GRANITIC VEIN-STONES. 217 which were at that time referred by the Geological Survey of Canada to the Laurentian, but have since been found to belong to younger series. Such are the veins containing argen- tiferous fahlerz with mispickel, and that holding native gold with a quasi-anthracitic form of carbon, both from Madoc, and also the vein already noticed as occurring in the township of Lake (§ 36), which contains in one part bismuthine with tour- maline, quartz, and graphite, and in another part calcite with phlogopite. This latter vein occurs in an impure limestone, associated with quartzite and micaceous schists, and belonging to a series unconformably overlying the Laurentian, and re- sembling the rocks of the White Mountain series. It will be noticed that this vein is lithologically similar to those of the Laurentian, which are not improbably of the sameage. Cal- careous vein-stones like those already described are not un- known in the White Mountain rocks in Maine, where are found, on a small scale, aggregates of crystallized pyroxene, idocrase, and sphene, and others of calcite with hornblende, apatite, and graphite (§ 18), closely resembling the Laurentian vein-stones of New York and Canada.* § 49. The various minerals of these calcareous vein-stones are [* In a note in the American Journal of Science for October, 1873, on The Copper Deposits of the Blue Ridge, I have described the occurrence in Vir- ginia, North Carolina, and Tennessee of great concretionary veins in gneisses and mica-schists which I refer to the White Mountain series. These veins are sometimes transverse to the stratification, and at other times inter- bedded. An example of the latter is seen at the Ducktown copper-mine in Polk County, Tennessee, where there is a banded arrangement of the large masses parallel to the walls. The chief part of this vein is filled with pyrite, pyrrhotine, and chalcopyrite, rarely with galena, blende, mispickel, and molybdenite. These massive ores enclose large garnets, and are penetrated with prisms of zoisite, hornblende, and pyroxene, sometimes several inches in length. The hornblende crystals are bent and sometimes partially broken across, the transverse fissures being filled with sulphurets, which are also found between the cleavage planes of large pyroxene crystals. Other portions of the vein are of vitreous quartz, holding metallic sulphides and rarely gar- nets, while large masses of white cleavable pyroxene, and others of finely fibrous greenish or white hornblende, occur, besides masses of white cleava- ble calcite enclosing long prisms .of green hornblende. This vein, with the exception of the abundance of metallic sulphurets, resembles closely in its contents the calcareous veins of the Laurentian rocks above described. ] 10 Se 218 GRANITES AND GRANITIC VEIN-STONES. ‘so q 5 generally described as occurring in crystalline limestones, though C. U. Shepard, H. D. Rogers, and W. P. Blake have each recognized the fact that these mineral species, with their calcareous gangue, belong to true veins. Emmons, however, failed to distinguish between these vein-stones and the stratified limestones of the series, which, as already stated, often contain disseminated many of the same. species, though in a less per- fectly crystallized condition than in the vein-stones. Since the latter are clearly seen to traverse the gneiss, like dikes, Emmons was led to look upon them as eruptive ; and, generalizing from this, he declared that all the crystalline limestones of northern New York were non-stratified rocks of eruptive origin. (Geology of the First District of New York, 1842, pages 37-59.) This view of Emmons was, to a certain extent, adopted by Mather, who, while maintaining the stratified character of the crystalline limestones of southern New York, admitted the existence of eruptive limestones. Von Leonhard had already, in 1833, asserted that limestones have sometimes come from the interior of the earth in a liquid state, like other igneous rocks, and a similar view was at that time maintained by many other geologists. Among others we find Rozet asserting the eruptive origin of the crystalline limestones which are associated with gneiss in the mountains of the Vosges. (Bull. Soc. Geol. de France, III. 215-235.) In support of this view could be urged the dike-like form of the calcareous vein-stones, which other observers, like Emmons, confounded with the bedded limestones. The nature and origin of this misconception were, I believe, first pointed out by me in a communication to the American Association for the Advancement of Science in Au- gust, 1866 (Canadian Naturalist (2), III. 123), and subse- quently more at length in the essay so often referred to. (Report Geol. Survey of Canada, 1863-66, p. 182.) It was there shown that many of these calcareous yein-stones are nearly free from foreign minerals, and so closely resemble in lithological characters the stratified limestones, that the different geognosti- * cal relations of the two alone enable us, in some examples, to distinguish between them. In this connection I called atten- GRANITES AND GRANITIC VEIN-STONES. op to the great dikes of granular limestones found traversing ss near Auerbach in the Bergstrasse, which Bischof has These endogenous concretionary ones are in fact to stratified limestones what endogenous te oe ‘7 LOSE a a ee at ke ey el We ae Ye es. > ret % . era 7% ay, hay ‘4 baie Ibias Se sb is is — ee at XII. THE ORIGIN OF METALLIFEROUS DEPOSITS. This paper, unlike the others in this colle¢tion (with the exception of IV.), was a lecture to a general audience, given before the American Institute of New York, in May, 1872, and reported for their Proceedings. It is reprinted here because it states, - though in a familiar manner, certain views which the author believes to be important, The following extract from areview of American Geology in the American Journal of Science for May, 1861 (a part of which is published as Essay V. of this volume), is prefixed as a concise statement of some of the points in the lecture, “THE metals....seem to have been originally brought to the surface in watery solutions, from which we conceive them to have been separated by the reducing agency of organic matters in the form of sulphurets or in the native state, and mingled with the contemporaneous sediments, where they occur in beds, in disseminated grains forming fahklbands, or are the cementing material of conglomerates. During the subsequent metamorphism of the strata these metallic matters, being taken into solution by alkaline carbonates or sulphurets, have been redeposited in fissures in the metalliferous strata, forming veins, or, ascending to higher beds, have given rise to metalliferous veins in strata not themselves metalliferous. Such we conceive to be, in a few words, the theory of metallic deposits; they belong to a period when the primal sediments were yet impreg- nated with metallic compounds which were soluble in the per- meating waters, The metals of the sedimentary rocks are now, however, for the greater part in the form of insoluble sulphurets, so that we have only traces of them in a few mineral springs, which serve to show the agencies once at work in the sedi- ments and waters of the earth’s crust. The present occurrence of these metals in waters which are alkaline from the presence XII] ORIGIN OF METALLIFEROUS DEPOSITS. 221 of carbonate of soda, is of great significance when taken in - gonnection with the metalliferous character of certain dolomites, which, as we have shown, probably owe their origin to the action of similar alkaline springs upon basins of sea-water.” (Ante, page 88.) 7 ‘‘The intervention of intense heat, sublimation, and similar hypotheses to explain the origin of metallic ores, we conceive to be uncalled for. The solvent powers of solutions of alkaline carbonates, chlorides, and sulphurets at elevated temperatures, taken in connection with the notions above enunciated, and with De Senarmont’s and Daubrée’s beautiful experiments on the crystallization of certain mineral species in the moist way, will suffice to form the basis of a satisfactory theory of metallic deposits.” (Ante, page 25.) There are about sixty bodies which chemists call elements ; the simplest forms of matter which they have been able to extract from the rocky crust of our earth, its waters, and its atmosphere. These substances are distributed in very unequal quantities, and in very different manners. As regards the fre- quency of these elements in nature, neglecting for the present those which constitute air and water, and confining ourselves to the solid matters of the earth’s crust, there are a few which are exceedingly abundant, making up nine tenths, if not ninety-five hundredths, of the rocks so far as known to us. The elements of which silica, alumina, lime, magnesia, potash, and soda are oxides are very common, and occur almost everywhere. There are others which are much rarer, being found in comparatively small quantities. Many of these rarer elements are, however, of great importance in the economy of nature. Such are the common metals and other substances used in the arts, which occur in nature in quantities relatively very minute, but which have been collected by various agencies, and thus made available for the wants of man. It is chiefly of the well-known metals, iron, copper, silver, and gold, that I propose to speak ; but there are two other elements, not classed among the metals, which I shall notice for the reason that their history is ex- tremely important, and will, moreover, enable us to comprehend 222 ORIGIN OF METALLIFEROUS DEPOSITS, [XI more clearly some points in that of the metals themselves, I speak of phosphorus and iodine, You all know the essential part which the former of these, combined as phosphate of lime, plays in the animal economy, in the formation of bones; and how plants require for their proper growth and development a certain amount of phos- phorus. Ordinary soils contain only a few thousandths of this element, yet there are agencies at work in nature which gather this diffused phosphorus together in beds of mineral phosphates. and in veins of crystalline apatite, which are now sought to enrich impoverished soils. Jodine, an element of great value in medicine and in the art of photography, is widely distributed, but still rarer than phosphorus ; yet it abounds in certain min- eral waters, and is, moreover, accumulated in marine plants, These extract it from the waters of the sea, where iodine exists 4#in such minute quantities as almost to elude our chemical ‘tests. (See the Appendix, page 237.) There are probably no perfect separations in nature. We cannot, without great precautions, get any chemical element in a state of absolute purity, and we have reason to believe that even the rarest elements are everywhere diffused in infini- tesimal quantities. The spectroscope, which we have lately learned to apply to the investigation alike of the chemistry of | our own earth and of other worlds once supposed to be beyond the chemist’s ken, not only demonstrates the very wide diffu- sion of various chemical elements here on the earth, but shows us that very many of them exist in the sun. If we accept, as most of us are now inclined to do, the nebular hypothesis, and admit that our earth was once, like the sun of to-day, an in- tensely heated vaporous mass ; that it is, in fact, a cooled and condensed portion of that once great nebula of which the sun is also a part, — we might expect to find all the elements now discovered in the sun distributed throughout this consolidated globe. We may speculate about the condensation of some of these before others, and their consequent accumulation in the inner parts of the earth ; but the fact that we have all the ele- ments of the solar envelope (together with many more) in the XIL] ORIGIN OF METALLIFEROUS DEPOSITS. 223° exterior portions of our planet, shows that there was, at least, but a very partial concentration and separation of these ele- ments during the period of cooling and condensation. The superficial crust of the earth, from which all the rocks and minerals which we know have been generated, must have contained, diffused through it, from the earliest time, all the elements which we now meet with in our study of the earth, whether still diffused, or accumulated, as we often find the rarer elements, in particular veins or beds. The question now before us is, How have these elements thus been brought together, and why is it that they are not all still widely and universally diffused? Why are the compounds of iron.in beds by themselves, copper, silver, and gold gathered ‘together in veins, and iodine concentrated in a few ores and certain mineral waters? That we may the better discern the direction in which we are to look for the solution of this problem, let us premise that all of these elements, in some of their combinations, are more or less soluble in water. There are, in fact, no such things in nature as absolutely insoluble bodies, but all, under certain conditions, are capable of being taken up by water, and again deposited from it.* The al- chemists sought in vain for a universal solvent; but we now know that water, aided in some cases by heat, pressure, and the presence of certain widely distributed substances, such as earbonic acid and alkaline carbonates and sulphides, will dis- solve the most insoluble bodies ; so that it may, after all, be looked upon as the long-sought-for alkahest or universal men- struum. [* It is well known that many chemical compounds when first generated by double decomposition in watery solutions remain dissolved for a greater or less length of time before separating in an insoluble condition. The solubility of recently precipitated carbonate of lime in water holding certain neutral Salts, as already described (ante, page 140), is a fact in the same order. In this connection may also be recalled the great solubility in water of silicic, titanic, stannic, ferric, aluminic, and chromic oxides when in what Graham has called their colloidal state. There is reason to believe that silicates of in- soluble bases may assume a similar state, and it will probably one day be shown that for the greater number of those oxygenized compounds which we call insoluble there exists a modification soluble in water. ] 224 ORIGIN OF METALLIFEROUS DEPOSITS. (xi, "oe Let us now compare the waters of rivers, seas, and subter- ranean springs, thus impregnated with various chemical ele- ments, with the blood which circulates through our own bodies, The analysis of the blood shows it to contain albuminoids which go to form muscle, fat for the adipose tissues, phosphate of lime for the bones, fluorides for the enamel of the teeth, sulphur, which enters largely into the composition of the hair and nails, soda which accumulates in the bile, and potash, which abounds in the flesh-fluid. Allof these are dissolved in the blood, and the great problem for the chemical physiologist is to determine how the living organism gathers them from this complex fluid, depositing them here and there, and giving to each part its proper material, This selection is generally ascribed to a certain vital force, peculiar to the living body. — I shall not here discuss the vexed question of the nature of the force which determines the assimilation from the blood of these various matters for the needs of the animal organism, further than to say that modern investigations tend to show that it is only a subtler kind of chemistry, and that the study of the nature and relation of colloids and crystalloids, and of the phenomena of chemical diffusion, promises to subordinate all these obscure physiological processes to chemical and physi- cal laws. Let us now see how far the comparison which we have made between the earth and an animal organism will help us to understand the problem of the distribution of minerals in nature ; how far water, the universal solvent, acting in accord- ance with known chemical and physical laws, will cause the separation of the mixed elements of the earth’s crust, and their accumulation in veins and beds in the rocks, The subject is one of great importance to the geologist, who has to consider the genesis of the various rocks and ore-deposits, and the relations, which we are only beginning to understand, between certain metals and particular rocks, and between certain classes of ores and peculiar mineralogical and geological conditions. It is at the same time a vast one, and I can now only give you a few illustrations of the chemistry of the earth’s crust, and of the XIL.] ORIGIN OF METALLIFEROUS DEPOSITS. 225 laws of the terrestrial circulation, which I have compared to that of the blood distributing throughout the animal frame the elements necessary for its growth. The analogy is not alto- gether new, since a great French geologist, Elie de Beaumont, has already spoken of a terrestrial circulation in regard to cer- tain elements in the earth’s crust ; though he has not, so far as I am aware, carried it out to the extent which I now propose to do in my attempt to explain some of the laws which have presided over the distribution of metals in the earth. The chemist in his laboratory takes advantage of changes of temperature, and of the action of various solvents and precipitants, to separate, in the humid way, one element from another ; but to these agencies, in the economy of nature, are added others which we have not yet succeeded in imitating, and which are exerted only in growing animals and plants. I repeat it; I do not wish to say that these latter processes are different in kind from those which we command in our labora- tories, but rather that these organisms control a far finer and more delicate chemical and physical apparatus than we have yet invented. Plants have the power of selecting from the media in which they live the elements necessary for their support. The growing oak and the grass alike assimilate from the air and water the carbon, hydrogen, nitrogen, and oxygen which build up their tissues, and at the same time take from the soil a portion of phosphorus, which, though minute, is essential to the vege- table growth. The acorn of the oak and the grass alike be- come the food of animals, and the gathered phosphates pass into their bones, which are nearly pure phosphate of lime. In like manner the phosphates from organic waste and decay find their way to the sea, and through the agency of marine vege- _ tation become at last the bony skeletons of fishes. These are, in turn, the prey of carnivorous birds, whose exuvie form on tropical islands beds of phosphatic guano. A history not dis- similar will explain the origin of beds of coprolites and of some other deposits of mineral phosphates. [By whatever means the phosphates have been first concentrated, it appears. from the recent studies of Sollas that the so-called coprolites of the 10* ) 226 ORIGIN OF METALLIFEROUS DEPOSITS. [XII. green-sand in England result from a petrifaction of sponges by dissolved phosphates, and similar observations have been made by Edwards with regard to the guano of the Chincha Islands. } But again, these plants or these animals may perish in the sea and be buried in its ooze. The phosphates which they have gathered are not lost, but become fixed in an insoluble form in the clayey matter; and when, in the revolutions of ages, these sea-muds, hardened to rock, become dry land, and crumble again to soil, the phosphates are there found ready for the wants of vegetation. Most of what I have said of phosphates applies equally to the salts of potash, which are not less necessary to the growing plant. From the operation of these laws it results that neither of these elements is found in large quantities in the ocean. This great receptacle of the drainage from the land contains still smaller quantities of iodine; in fact, the traces of this element present in sea-water can scarcely be detected by our most delicate tests.* Yet marine plants have the power of separating this iodine, and accumulating it in their tissues, so that the ashes of these plants are not only rich in phosphates and in potash-salts, but contain so much iodine that our sup- plies of this precious element are almost wholly derived from this source, and that the gathering and burning of sea-weed for the extraction of iodine is in some regions an important indus- try. When this marine vegetation decays, the iodine which it contains appears, like the potash and phosphates, to pass into combination with metals, earths, or earthy phosphates, which retain it in an insoluble state, and in certain cases yield it to percolating saline solutions, which thus give rise to springs rich in iodine. (Ante, page 143.) In all of these processes the action of organic life is direct and assimilative, but there are others in which its agency, although indirect, is not less important. I can hardly con- ceive of an accumulation of iron, copper, lead, silver, or gold, in the production of which animal or vegetable life has not either directly or indirectly been necessary, and I shall be- * See the Appendix to this paper. Pg) SD oe Bee eee? XII] ORIGIN OF METALLIFEROUS DEPOSITS. 227 gin to explain my meaning by the case of iron. This, you are aware, is one of the most widely diffused elements in nature ; all soils, all plants, contain it; and it is a necessary element in our blood. Clays and loams contain, however, at best, two or three hundredths of the metal, but so mixed with, other matters that we could never make it available for the wants of this iron age of ours. How does it happen that we also find it gathered together in great beds of ore, which fur- nish an abundant supply of the metal? The chemist knows that the iron, as diffused in the rocks, exists chiefly in combi- nation with oxygen, with which it forms two principal com- pounds: the first, or protoxide, which is readily soluble in waters impregnated with carbonic acid or other feeble acids ; and the second, or peroxide, which is insoluble in the same liquids. I do not here speak of the magnetic oxide, which may be looked upon as a compound of the other two, neutral and indifferent to most natural chemical agencies. The com- binations of the first oxide are either colorless or bluish or greenish in tint, while the peroxide is reddish-brown, and is the substance known as iron-rust. Ordinary brick-clays are bluish in color, and contain combined iron in the state of protoxide, but when burned in a kiln they become reddish, because this oxide absorbs from the air a further proportion of oxygen, and is converted into peroxide. But there are clays which are white when burned, and are much prized for this reason. Many of these were once ferruginous clays, which have lost their iron by a process everywhere going on around us. If we dig a ditch in a moist soil which is covered with turf or with decaying vegetation, we may observe that the stagnant water which collects at the bottom soon becomes coated with a shining, iridescent scum, which looks: somewhat like oil, but is really a compound of peroxide of iron. The water as it oozes from the soil is colorless, but has an inky taste, from dissolved protoxide of iron. "When exposed to the air, however, this absorbs oxygen, and the peroxide is formed, which is no longer soluble, but separates as a film on the sur- face of the water, and finally sinks to the bottom as a reddish 228 ORIGIN OF METALLIFEROUS DEPOSITS. [XII. ochre, or, under somewhat different conditions, becomes aggre- gated as a massive iron-ore, A process identical in kind with this has been at work at the earth’s surface ever since there were decaying organic matters, dissolving the iron from the porous rocks, clays, and sands, and gathering it together in beds of iron-ore or iron-ochre. It is not necessary that these rocks and soils should contain the iron in the state of pro- toxide, since these organic products (which are themselves dissolved in the water) are able to remove a portion of the oxygen from the insoluble peroxide, and convert it into the soluble protoxide of iron, being themselves in part oxidized and converted into carbonic acid in the process. We find in rock-formations of very different ages beds of sediments which have been deprived of iron by organic agen- cies, and near them will generally be found the accumulated iron. Go into any coal region, and you will see evidences that this process was at work when the coal-beds were forming. The soil in which the coal-plants grew has been deprived of its iron, and when burned turns white, as do most of the slaty beds from the coal-rocks. It is this ancient soil which con- stitutes the so-called fire-clays, prized for making bricks which, from the absence of both iron and alkalies, are very infusible. Interstratified with these we often find, in the form of iron- stone, the separated metal; and thus from the same series of rocks may be obtained the fuel, the ore, and the fire-clay. From what I have said it will be understood that great deposits of iron-ore generally occur in the shape of beds; al- though waters holding the compounds of iron in solution have, — in some cases, deposited them in fissures or openings in the rocks, thus forming true veins of ore, of which we shall speak further on. I wish now to insist upon the property which dead and decaying organic matters possess of reducing to protoxide, and rendering soluble, the insoluble peroxide of iron diffused through the rocks; and reciprocally the power which this peroxide has of oxidizing and consuming these same organic matters, which are thereby finally converted into car- bonic acid and water. This last action, let me say in passing, xII.] ORIGIN OF METALLIFEROUS DEPOSITS. 229 is illustrated by the destructive action of rusting iron bolts on moist wood, and the effect of iron stains in impairing the strength of linen fibre. We see in the coal formation that the vegetable matter necessary for the production of the iron-ore beds was not wanting; but the question has been asked me, Where are the evidences of the organic material which was required to pro- duce the vast beds of iron-ore found in the ancient crystalline rocks? I answer that the organic matter was, in most cases, entirely consumed in producing these great results; and that it was the large proportion of iron diffused in the soils and waters of these early times, which not only rendered possible the accumulation of such great beds of ore, but oxidized and destroyed the organic matters which in later ages appear in coals, lignites, pyroschists, and bitumens. Some of the carbon of these early timés is, however, still preserved in the form of graphite, and it would be possible to calculate how much car- bonaceous material was consumed in the formation of the great iron-ore beds of the older rocks, and to determine of how much * coal or lignite they are the equivalents. In the course of ages, however, as a large proportion of the once diffused iron-oxide has become segregated in the form of beds of ore, and thus removed from the terrestrial circulation, the conditions have grown more favorable for the preservation of the carbonaceous products of vegetable life. The crystalline magnetic and specular oxides, which constitute a large propor- tion of the ores of this metal, are almost or altogether indiffer- ent to the action of organic matter. "When, however, these ores are reduced in our furnaces, and the resulting metal is exposed to the oxidizing action of a moist atmosphere, it is again converted into iron-rust, which is soluble in water hold- ing organic matters, and may thus be made to enter once more into the terrestrial circulation.. There is another form in which iron is frequently concen- trated in nature, that of sulphide, and most frequently as the bisulphide, known as iron-pyrites. This substance is found both in the oldest and the newest rocks, and, like the oxide of ” ae eee Se CLP ee le eee See De ES pe Us fo, is eee bs rnp * 7 . i eter wa, >. a - y ety, d : od ae rie 230 ORIGIN OF METALLIFEROUS DEPOSITS. (XI. iron, is even to-day forming in certain waters and in beds of mud and silt, where it sometimes takes a beautifully crystalline shape. What are the conditions in which the sulphide of iron is formed and deposited, instead of the oxide or carbonate of iron? Its production depends, like these, on decaying organic matters. The sulphates of lime and magnesia, which abound in sea-water, and in many other natural waters, when exposed to the action of decaying plants or animals, out of contact of air, are, like peroxide of iron, deoxidized, and are thereby converted into soluble sulphides ; from which, if car- bonie acid be present, sulphuretted hydrogen gas is set free, Such soluble sulphides, or sulphuretted hydrogen, are the reagents constantly employed in our laboratories to convert the soluble compounds of many of the common metals, such as iron, zinc, lead, copper, and silver, into sulphides, which are insoluble in water and in many acids, and are thus conven- iently separated from a great many other bodies. Now, when in a water holding iron-oxide, sulphates are also present, the action of organic matter, deoxidizing the latter, furnishes the reagent necessary to convert the iron into a sulphide ; which in some conditions, not well understood, contains two equiva- lents of sulphur for one of iron, and constitutes iron-pyrites. I may here say that I have found that the unstable protosul- phide, which would naturally be first formed, may, under the influence of a persalt of iron, lose one half of its combined iron ; and that from this reaction a stable bisulphide results, This subject of the origin of iron-pyrites is still under investi- gation. The reducing action of organic matters upon soluble sul- phates is well seen: in the sulphuretted hydrogen which is evolved from the stagnant sea-water in the hold of a ship, and which coats silver exposed to it with a black film of sulphide of silver, and for the same reason discolors white-lead paint. The presence of sulphur in the exhalations from some other decaying matters is well known, and in all these cases a solu- ble compound of iron will act as a disinfectant, partly by fixing the sulphur as an insoluble sulphide, Silver coins brought from XIL] ORIGIN OF METALLIFEROUS DEPOSITS. 231 the ancient wreck of a treasure-ship in the Spanish Main were found to be deeply incrusted with sulphide of silver, formed in the ocean’s depths by the process just explained, which is one that must go on wherever organic matters and sea-water are present, and atmospheric oxygen excluded. . The chemical history of iron is peculiar; since it requires reducing matters to bring it into solution, and since it may be precipitated alike by oxidation, and by further reduction provided sulphates are present. The metals, copper, lead, and silver, on the contrary, form compounds more or less soluble in water, from which they are not precipitated by oxygen, but only by reducing agents, which may separate them in some cases in a metallic state, but more frequently as sulphides. The solubility of the salts and oxides of these metals in water is such that they are found in many mineral springs, in the waters that flow from certain mines, and in the ocean itself, the waters of which have been found to contain copper, silver, and lead. Why, then, do not these metals accumulate in the sea, as the salts of soda have done during long ages? The direct agency of organic life comes again into play, precisely as in the case of phosphorus, iodine, and potash. . Marine plants, which absorb these from the sea-water, take up at the same time the metals just named, traces of all of which are found in the ashes of sea-weeds. Copper, moreover, is met with in notable quantities in the blood of many marine molluscous animals, to which it may be as necessary as iron is to our own bodies. Indeed, the blood of man, and of the higher animals, appears never to be without traces of copper as well as of iron. -In the open ocean the waters are constantly aerated, so that soluble sulphides are never formed, and the only way in which these dissolved metals can be removed and converted into sulphides is by fixing them in organisms, either vegetable or animal. These, by their decay in the mud of the bottom, or the lagoons of the shore, generate the sulphides which fix their contained metals in an insoluble form, and thus remove them from the terrestrial circulation. : ae 232 ORIGIN OF METALLIFEROUS DEPOSITS. JEXIL It is not, however, in all cases necessary to invoke the direct action of organisms to separate from water the dissolved metals. It often happens that the waters containing these, instead of _ finding their way to the ocean, flow into lakes or enclosed basins, as m the case of the drainage-waters of an English copper-mine, which have impregnated the turf of a neighboring bog to such an extent that its ashes have been found a profita- ble source of copper. Under certain conditions, not yet well understood, this metal is precipitated by organic matters in the metallic state, but if sulphates are present, a sulphide is formed. ‘Thus, in certain mesozoic slates in Bohemia, sulphide of copper is found incrusting the remains of fishes, and in the sandstones of New Jersey we find it penetrating the stems of ancient trees. I have in my possession a portion of a small trunk taken from the mud of a spring in the province of Ontario, in which the yet undecayed wood of the centre is seen to be incrusted by hard and brilliant iron-pyrites. In like manner the trees found in the New Jersey sandstone be- came incrusted with copper-sulphide, which, as decay went on, in great part replaced the woody tissue. Similar deposits of sulphides of copper and of iron often took place in basins where the organic matter was present in such a condition or in such quantity as to be entirely decomposed, and to leave no trace of its form, unlike the examples just mentioned. In this way have been formed fahlbands, and beds of pyrites and other ores. The fact that such deposits are associated with silver and with gold leads to the conclusion that these metals have obeyed the same laws as iron and copper. It is known that both persalts of iron and soluble sulphides have the power of ren- dering gold soluble, and its subsequent deposition in the metallic state is then easily understood.* I have endeavored by a few illustrations to show you by what processes some of the more common metals are dissolved and again separated from their solution in insoluble forms. It now remains to say somewhat of the geological relations of * See Appendix to this paper. | : ‘ ; j i - a i t 4 XIL.J ORIGIN OF METALLIFEROUS DEPOSITS. 233 ore-deposits, which are naturally divided into two classes ; the first including those which occur in beds, and have been formed contemporaneously with the enclosing earthy sediments, Such are the beds of iron-ores, which often hold embedded shells and other organic remains, and the copper-bearing strata already mentioned, in which the metal must have been de- posited during the decay of the animal or plant which it incrusts or replaces. But there are other ore-deposits' evidently of more recent formation than the rocky strata which enclose them, which have resulted from a process of infiltration, filling up fissures with the ore, or diffusing it irregularly through the rock. It is not always easy to distinguish between the two classes of deposits. Thus a fissure may in some cases be formed and filled between two sundered beds, from-which may result a vein that may be mistaken for an interposed stratum. Again, a bed may be so porous that infiltrating waters may diffuse through it a metallic ore, or a metal, in such a manner as to leave it doubtful whether the process was contemporaneous with the de- position of the bed, or posterior to it. But I wish to speak of deposits which are evidently posterior, and occupy fissures in previously formed strata, constituting true veins. Whether produced by the great movements of the earth’s crust, or by the local contraction of the rocks (and both of these causes have in different cases been in operation), such fissures sometimes extend to great lengths and depths; their arrangement and dimen- sions depending very much on the texture of the rocks which have been subjected to fracture. "When a bone in our bodies is broken, nature goes to work to repair the fractured part, and gradually brings to it bony matter, which fills up the little interval, and at length makes the severed parts one again. So when there are fractures in the earth’s crust, the circulating waters deposit in the openings mineral matters, which unite the broken portions, and thus make whole again the shattered rocks. Vein-stones are thus formed, and are the work of nature’s conservative surgery. Water, as we have seen, is a universal solvent, and the matters which it may bring and deposit in the fissures of the 234 ORIGIN OF METALLIFEROUS DEPOSITS. [XII. earth are very various. There is scarcely a spar or an ore to be met with in the stratified rocks that is not also found in some of these vein-stones, which are often very heterogeneous in composition. In certain veins we find the elements of lime- stone or of granite, and these often include the gems, such as tourmaline, garnet, topaz, hyacinth, emerald, and sapphire ; while others abound in native metals or in metallic oxides or sulphides. The nature of the materials thus deposited depends very much on conditions of temperature and of pressure, which affect the solvent power of the liquid, and still more upon the nature of the adjacent rocks and of the waters permeating them. The chemistry of mineral veins is very complicated. Many of these fissures penetrate to a depth of thousands of feet of the earth’s crust, and along the channels thus opened the ascending heated subterranean waters may receive in their course various contributions from the overlying strata. From these additions, and from the diminished solubility resulting from a decrease of pressure (ante, page 204), deposits of different minerals are formed upon the walls, and the slow changes in composition are often represented by successive layers of unlike substances. The power of these waters to dissolve and bring from the lower strata their contained metals and spars is probably due in great part to the alkaline carbonates and sulphides which these waters often hold in solution ; but the chemical history of the deposition of the ores of iron, lead, copper, silver, tin, and gold, which are found in these veins, demands a lengthened study, and would furnish not less beau- tiful examples of nature’s chemistry than those I have already laid before you. The process of filling veins has been going on from the earli- est ages; we know of some which were formed before the Cambrian rocks were deposited, while others are still forming, as the observations of Phillips have shown us in Nevada, where hot springs rise to the surface and deposit silica, with metallic ores, which incrusts the walls of the fissures. These thermal waters show that the agencies which in past times gave rise to the rich mineral deposits of our western regions, are still at work there. a a XIL] ORIGIN OF METALLIFEROUS DEPOSITS. 235 Let us now consider the beneficent results of the process of vein-making. The precious metals, such as silver, are so sparsely distributed, that even the beds rich in the products of decaying sea-weed, which we have supposed to be deposited from the ocean, would contain too little silver to be profitably extracted. But in the course of ages these sediments, deeply buried, are lixiviated by permeating solutions, which dissolve the silver diffused through a vast mass of rock, and subse- quently deposit it in some fissure, it may be in strata far above, as a rich silver-ore. This is nature’s process of concentration. We learn from the history which we have just sketched the important conclusion, that amid all the changes of the face of the globe the economy of nature has remained the same. We are apt, in explaining the appearances of the earth’s crust, to refer the formation of ore-beds and veins to some distant and remote period, when conditions very unlike the present pre- vailed, when great convulsions took place, and mysterious forces were at work. Yet the same chemical and physical laws are now, as then, in operation: in one part dissolving the iron from the sediments and forming ore-beds, in another separating the rarer metals from the ocean’s waters ; while in still other regions the consolidated and buried sediments are permeated by heated waters, to which they give up their metallic matters, to be subsequently deposited in veins. These forces are always in operation, rearranging the chaotic admixture of elements which results from the constant change and decay around us. The laws which the First Great Cause imposed upon this material universe on the first day are still irresistibly at work fashioning its present order. One great design and purpose is seen to bind in necessary harmony the operations of the min- eral with those of the vegetable and animal worlds, and to make all of these contribute to that terrestrial circulation which maintains the life of our mother earth. While the phenomena of the material world have been looked upon as chemical and physical, it has been customary to speak of those of the organic world as vital. The tendency of modern investigation is, however, to regard the processes of | ‘sified and vegetable growth a as Sieiekrias oa ch : and physical. That this is to a great extent true in chemical and physical processes the whole secret of 0 life. Still we are, in many respects, approximating | : upon the various eee tS in its air, its waters, and — depths, as processes belonging to the life of our planet. ae ORIGIN OF METALLIFEROUS DEPOSITS. 237 APPENDIX. ON IODINE AND GOLD IN SEA-WATER. Arter the above lecture was delivered, appeared the results of the researches of Sonstadt on the iodine in sea-water, which were published in the Chemical News for April 26, May 17, and May 24,1872. According to him, this element exists in sea-water, under ordinary conditions, as iodate of calcium, to the amount of about one part of the iodate in 250,000 parts of the water. This compound, by decaying organic matter (and by most other reducing agents), is changed to iodide, from which, apparently by the action of carbonic acid, iodine is set free, and may be separated by agitating the water with bisulphide of carbon. The iodine thus liberated from sea- water by the action of dead organic matters, however, slowly de- composes water in presence of carbonate of calcium, and is. re- converted into iodate, the oxygen of the air probably intervening to complete the oxidation, since, according to Sonstadt, iodides are readily converted into iodates under these conditions. He finds that the insolubility of the iodides of silver and of copper is so great that by the use of salts of these metals iodine may be separated from sea-water, without concentration, provided the iodate of cal- cium has first been reduced to iodide. By this property of iodine and its compounds to oxidize and be oxidized in turn, Sonstadt supposes them to perform the-important function of consuming the products of organic decay, and so maintaining the salubrity of the ocean’s waters. Their action would thus be very similar to that of the oxides of iron, as explained in the lecture. : Still more recently the same chemist has announced that the sea- water of the British coasts contains in solution, besides silver, an appreciable amount of gold, estimated by him at about one grain to a ton of water. This is separated by the addition of chloride of barium to the water, apparently as an aurate of baryta adhering to the precipitated sulphate, which yields by assay an alloy of about six parts of gold to four of silver. Other ways have been devised by him for separating these metals from their solution in sea-water. The agent which keeps the gold of the sea in a soluble and oxidized condition is, according to Sonstadt, the iodine liberated by the reaction already described. The views maintained by Lieber, gold in modern alluvial ‘seen. seem to be wal ground am er are led to the conclusion that the circulation of this metal in nature is as easily effected as that of iron or of copper. The transfer of — certain other elements, such as titanium, atin and tin, or at le Tt should here be sibs. that Professor Henry Wurtz of New York, in a paper read: before the American Association for the Ad- _ vancement of Science in 1866, and published in the J ournal Le % his calculations, the total amount of ek hitherto e the earth, and estimated at two thousand million dol tons of water. XUIl. THE GEOGNOSY OF THE APPALACHI- ANS AND THE ORIGIN OF CRYSTAL- LINE ROCKS. ~ The following address was delivered on retiring from the office of president of the American Association for the Advancement of Science at Indianapolis, August 16, 1871. It appears in the Proceedings of the Association and in the American Naturalist for October, and, with some abridgment of the first part, in Nature. A French translation of the entire address was also published in the Revue Scientifique. In reprinting it a few sentences have been substituted for the original references to the Cambrian rocks of Great Britian, and a fuller account of the Norian or Labrador series has been introduced, besides some minor additions in the ‘first part. In the second part of the paper, also, important additions ,have been made. These new portions are distinguished by being enclosed in brackets. In the American Journal of Science for February, 1872, appeared an adverse criti- cism of some parts of the address, by Professor J. D. Dana, to which the author in the same Journal for July, 1872, made a reply, which is here printed as an appendix to the paper ; the short portion relating to geognosy being at the close. Professor Dana’s rejoinder will be found in the same Journal for August, 1872. In accordance with our custom it becomes my duty, in quit- ting the honorable position of president, which I have filled for the past- year, to address you upon some theme which shall be germane to the objects of the Association. The pre- siding officer, as you are aware, is generally chosen to represent alternately one of the two great sections into which the mem- bers of the Association are supposed to be divided ; namely, the students of the natural-history sciences on the one hand, and of the physico-mathematical and chemical sciences on the other. The arrangement by which, in our organization, geology is classed with the natural-history division, is based upon what may fairly be challenged as a somewhat narrow conception of its scope and aims. While theoretical geology or geogeny investigates the astronomical, physical, chemical, and biological oe ee ee ee en ee 240 GEOGNOSY OF THE APPALACHIANS. (XIII. laws which have presided over the development of our earth, and while practical geology or geognosy studies its natural history as exhibited in its physical structure, its mineralogy and its paleontology, it will be seen that this comprehensive science is a stranger to none of the studies which are included in the plan of our Association, but rather sits like a sovereign, commanding in turn the services of all. As a student of geology, I scarcely know with which section of the Association I should to-day identify myself. Let me endeavor rather to mediate between the the two, and show _ you somewhat of the twofold aspect which geological science presents, when viewed respectively from the standpoints of natural history and of chemistry. I can hardly do this better than in the discussion of a subject which for the last genera- tion has afforded some of the most fascinating and perplexing problems for our geological students; namely, the history of the great Appalachian mountain chain. Nowhere else in the world has a mountain system of such geographical extent and such geological complexity been studied by such a number of zealous and learned investigators, and no other, it may be con- fidently asserted, has furnished such vast and important results to geological science. The laws of mountain structure, as re- vealed in the Appalachians by the labors of the brothers Henry D. and William B. Rogers, of Lesley and of Hall, have given _ to the world the basis of a correct system of orographic geol- ogy,* and many of the obscure geological problems of Europe become plain when read in the light of our American experi- ence. To discuss even in the most summary manner all of the questions which the theme suggests, would be a task too long — for the present occasion ; but I shall endeavor in the first place to bring before you certain facts in the history of the physical structure, the mineralogy, and the paleontology of the Appalachi- ans ; and, in the second place, to discuss some of the physical, chemical, and biological conditions which have presided over — the formation of the ancient crystalline rocks that make up so * Jarge a portion of our great eastern mountain system. * Amer. Jour. Sci. (2), XXX. 406; and ante, pages 49-58. XIII] GEOGNOSY OF THE APPALACHIANS. 241 I. Tue Grognosy or THE APPALACHIAN SYSTEM. The age and geological relations of the crystalline stratified rocks of eastern North America have for a long time occupied the attention of geologists. A section across northern New York, from Ogdensburg on the St. Lawrence to Portland in Maine, shows the existence of three distinct regions of unlike crystalline schists. These are the Adirondacks to the west of Lake Champlain, the Green Mountains of Vermont, and the White Mountains of New Hampshire. The lithological and mineralogical differences between the rocks of these three re- gions are such as to have attracted the attention of some of the earlier observers. Eaton, one of the founders of American geology, at least as early as 1832 distinguished in his Geologi- cal Text-Book (2d edition) between the gneiss of the Adiron- dacks and that of the Green Mountains. Adopting the then received divisions of primary, transition, secondary, and tertiary rocks, he divided each of these series into three classes, which he named carboniferous, quartzose, and calcareous ; meaning _ by the first, schistose, or argillaceous strata such as, according to him, might include carbonaceous matter. These three divisions, in fact, corresponded to clay, sand, and lime-rocks, and were supposed by him to be repeated in the same order in each series. This was apparently the first recognition of that law of cycles in sedimentation upon which I afterwards insisted in 1863.* Without, so far as I am aware, defining the relations of the Adirondacks, he referred to the lowest or carboniferous division of the primary series, the crystalline schists of the Green Mountains, while the quartzites and marbles at their western base were made the quartzose and calcareous divisions of this primary series. The argillites and sandstones lying still farther westward, but to the east of the Hudson River, were regarded as the first and second divisions of the transition se- * Amer. Jour. Sci. (2), XXXV. 166. See, for an excellent presentation of this subject, with references to its literature, a paper by Dr. Newberry in the Proceedings of the American Association for the Advancement of Science for 1873, page 185. LiF P 242 GEOGNOSY OF THE APPALACHIANS. [XIIL. ries, and were followed by its calcareous division, which seems to have included the limestones of the Trenton group ; all of these rocks being supposed to dip to the westward, and away from the central axis of the Green Mountains. Eaton does not appear to have studied the White Mountains, nor to have con- sidered their geological relations. They were, however, clearly distinguished from the former by Charles T. Jackson in 1844, when, in his report on the geology of New Hampshire, he de- scribed the White Mountains as an axis of primary granite, gneiss, and mica-schist, overlaid successively, both to the east and west, by what were designated by him Cambrian and Silu- rian rocks ; these names having, since the time of Eaton’s pub- lication, been introduced by English geologists. While these overlying rocks in Maine were unaltered, he conceived that the corresponding strata in Vermont, on the western side of the granitic axis, had been changed by the action of intrusive ser- pentines and intrusive quartzites, which had altered the Cam- brian into the Green Mountain gneiss, and converted a portion of the fossiliferous Silurian limestones of the Champlain valley into white marbles.* Jackson did not institute any compari- son between the rocks of the White Mountains and those of the Adirondacks ; but the Messrs. Rogers in the same year, 1844, published an essay on the geological age of the White Mountains, in which, while endeavoring to show their Silurian age, they speak of them as having been hitherto regarded as consisting exclusively of various modifications of granitic and gneissoid rocks, and as belonging “to the so-called primary periods of geologic time.” t They, however, considered that these rocks had rather the aspect of altered paleeozoic strata, and suggested that they might be, in part, at least, of the age of the Clinton division of the New York system ; a view which was supported by the presence of what were at the time regarded -by the Messrs. Rogers as organic remains, Subsequently, in 1847,{ they announced that they no longer considered these to * Geology of New Hampshire, 160-162. + Amer. Jour. Sci. (2), I. 411. + Ibid. (2), V. 116. =e OU XIII. GEOGNOSY OF THE APPALACHIANS. 243 be of organic origin, without, however, retracting their opinion as to the paleozoic age of the strata. Reserving to another place in my address the discussion of the geological age of the White Mountain rocks, I proceed to notice briefly the distinc- tive characters of the three groups of crystalline strata just mentioned, which will be shown in the sequel to have an im- portance in geology beyond the limits of the Appalachians. I. Zhe Adirondack or Laurentide Series. — The rocks of this series, to which the name of the Laurentian system has been given, may be described as chiefly firm granitic gneisses, often very coarse grained, and generally reddish or grayish in color, They are frequently hornblendic, but seldom or never con- tain much mica, and the mica-schists (often accompanied with staurolite, garnet, andalusite, and cyanite), so characteristic of the White Mountain series, are wanting among the Laurentian rocks. They are also destitute of argillites, which are found in the other two series. The quartzites, and the pyroxenic and hornblendic rocks, associated with great formations of crystal- line limestone, with graphite, and immense beds of magnetic iron-ore, give a peculiar character to portions of the Laurentian system. II. Zhe Green Mountain Series. —The quartzo-feldspathic rocks of this series are to a considerable extent represented by a fine-grained petrosilex or eurite, though they often assume the form of a true gneiss, which is ordinarily more micaceous than the typical Laurentian gneiss. The coarse-grained, por- phyritic, reddish varieties common to the latter are wanting in the Green Mountains, where the gneiss is generally of pale greenish aud grayish hues. [The quartziferous porphyries, which have been noticed ante, page 187, are supposed, in the present state of our knowledge, to belong to this series.] Mas- sive stratified diorites, and epidotic and chloritic rocks, often more or less schistose, with steatites, dark-colored serpentines, and ferriferous dolomites and magnesites also characterize this gneissic series, and are intimately associated with beds of iron- ore, generally a slaty hematite, but occasionally magnetite. Chrome, titanium, nickel, copper, antimony, and gold are fre- 244 GEOGNOSY OF THE APPALACHIANS. (XI. quently met with in this series. The gneisses often pass into schistose micaceous quartzites, and the argillites, which abound, frequently assume a soft unctuous character, which has acquired for them the name of talcose or nacreous slates, though analysis shows them not to be magnesian, but to consist essentially of a hydrous micaceous mineral allied to paragonite. They are sometimes black and graphitic. Ill. The White Mountain Series. —This series is character- ized by the predominance of well-defined mica-schists interstrati- fied with micaceous gneisses. These latter are ordinarily light colored from the presence of white feldspar, and, though gener- ally fine in texture, are sometimes coarse grained and porphy- ritic. They are less strong and coherent than tlie gneisses of the Laurentian, and pass, through the predominance of mica, into mica-schists, which are themselves more or less tender and friable, and present every variety, from a coarse gneiss-like aggregate down to a fine-grained schist, which passes into ar- gillite. The micaceous schists of this series are generally much richer in mica than those of the preceding series, and often contain a large proportion of well-defined crystalline tables belonging to the species muscovite. The cleavage of these micaceous schists is generally, if not always, coincident with the bedding; but the plates of mica in the coarser-grained varieties are often arranged at various angles to the cleavage and bedding-plane, showing that they were developed after sedimentation, by crystallization in the mass, a circumstance which distinguishes them from rocks derived from the ruins of these, which are met with in more recent series. The White Mountain rocks also include beds of micaceous quartzite. The basic silicates in this series are represented chiefly by dark- colored gneisses and schists in which hornblende takes the place of mica. These pass occasionally into beds of dark horn- blende rock, sometimes holding garnets. Beds of crystalline limestone occur in the schists of the White Mountain series, and are sometimes accompanied by pyroxene, garnet, idocrase, sphene, and graphite, as in the corresponding rocks of the Laurentian, which this series, in its more gneissic portions, XIII] GEOGNOSY OF THE APPALACHIANS. 245 closely resembles, though apparently distinct geognostically. The limestones are intimately associated with the highly mi- caceous schists containing staurolite, andalusite, cyanite, and garnet. These schists are sometimes highly plumbaginous, as seen in the graphitic mica-schist holding garnets in Nelson, New Hampshire, and that associated with cyanite in Cornwall, Connecticut. To this third series of crystalline schists belong the concretionary granitic veins abounding in beryl, tourma- line, and lepidolite, and occasionally containing tinstone and columbite. (See Granites and Granitic Vein-Stones, ante, pages 194-199.) Granitic veins in the Laurentian gneisses fre- quently contain tourmaline, but have not, so far as yet known, yielded the other mineral species just mentioned. Keeping in mind the characteristics of these three series, it will be easy to trace them southward by the aid of the concise and accurate descriptions which Professor H. D. Rogers has given us of the rocks of Pennsylvania. In his report on the geology of this State, he has distinguished three districts of various crystalline schists, which are by him included together under the name of gneissic or hypozoic rocks. Of these dis- tricts, the most northern, or the South Mountain belt, to the northwest of the Mesozoic basin, is said to be the continuation of the Highlands of New York and. New Jersey, which, cross- ing the Delaware near Easton, is continued southward, through Pennsylvania and Maryland, into Virginia, where it appears in the Blue Ridge. The gneiss of this district in Pennsylvania is described as differing considerably from that of the southern- most district, being massive and granitoid, often hornblendic, with much magnetic iron, but destitute of any considerable beds of micaceous, talcose, or chloritic slate, which mark the rocks of the southern district. These characters are sufficient to show that the gneiss of this northern district is lithologi- cally, as well as geognostically, identical with that of the Highlands, and belongs, like it, to the Adirondack, or Lauren- tian system of crystalline rocks. The gneiss of the middle district of Pennsylvania, to the south of the Mesozoic, but north of the Chester valley, is described by Rogers as resem- 246 GEOGNOSY OF THE APPALACHIANS. [XIII. bling that of the South Mountain, or northern district, and to consist chiefly of white feldspathic and dark hornblendie gneiss, with very little mica, and with crystalline limestones. The gneiss of the third or southern district (that lying to the south of the Montgomery and Chester valleys) comes from beneath the Mesozoic of New Jersey about six miles north- east of Trenton, and, stretching southwestward, occupies the southern border of Pennsylvania, extending into Delaware and Maryland. It is subdivided by Rogers into three belts. The first or most southern of these, passing through Philadelphia, consists of alternations of dark hornblendic and highly mica- ceous gneiss, with abundance of mica-slate, sometimes coarse grained, and at other times so fine grained as to constitute a sort of whet-slate. To the northwestward the strata become still more micaceous, with garnets and beds of hornblende slate, till we reach the second subdivision, which consists of a great belt of highly talcose and micaceous schists, with steatite and serpentine, and is in its turn succeeded by a third narrow belt, resembling the less micaceous members of the first or southernmost subdivision. The micaceous schists of this re- gion abound in staurolite, garnet, cyanite, and corundum, and are traversed by numerous irregular granitic veins containing beryl and tourmaline. All of these characters lead us to refer the gneiss of this southern district to the third, or White Mountain series, with the exception of the middle subdivision, which presents the aspect of the second, or Green Mountain series. Above the hypozoic gneisses Rogers has placed his azoic or semi-metamorphic series, which is traceable from the vicinity of Trenton to the Schuylkill, along the northern boundary of the southern hypozoic gneiss district. This series is supposed by Rogers to be an altered form of the primal sandstones and slates, and is described as consisting of a feldspathic quartzite, or eurite, containing in some eases porphyritie beds with erys- tals of feldspar and hornblende, together with various crystal- line schists ; including, in fact, the whole of the great serpentine belt of Montgomery, Chester, and Lancaster Counties, with its XIII] GEOGNOSY OF THE APPALACHIANS. 247 steatites, hornblendic, dioritic, chloritic, and micaceous schists (often garnet-bearing), together with a band of argillite, afford- ing roofing-slates. With this great series are associated chromic and titanic iron, and ores of nickel and copper. Veins of albite with corundum also intersect this series near Unionville. We are repeatedly assured by Rogers that these rocks so much resemble the underlying hypozoic gneiss, as to be readily con- founded with them ; and when compared with the latter, as displayed in the southern district, it is difficult to believe that we have in this so-called azoic or metamorphic series of the Montgomery and Chester valleys anything else than a repeti- tion of these same crystalline schists which have been described along their southern boundary, representing the Green Moun- tain and the White Mountain series. We thus avoid the difficulty of supposing that we have in this region two sets of serpentine rocks, and two of mica-schists, lithologically similar, but of widely different ages, —a conclusion highly improbable. It should be said that Rogers, in accordance with the notions then generally received, looked upon serpentine as an eruptive rock, which had altered the adjacent strata, converting the mica-schists into steatitic and chloritic rocks. This so-called azoic series, according to Rogers, underlies the auroral limestone of Pennsylvania, thus apparently occupying the horizon of the primal paleozoic division. We find, how- ever, in his report on the geology of the State, no satisfactory evidence of the identity of the two series of crystalline rocks. On the contrary, a very different conclusion would seem to follow from certain facts there detailed. The azoic or so-called metamorphic primal strata are said to have a very uniform nearly vertical dip, or with high angles to the southward, while the micaceous and gneissic strata of the northern subdivision of the southern district of so-called hypozoic rocks, limiting these last to the south, present either minute local contortions or wide gentle undulations, with comparatively moderate dips, for the most part to the northward.* From this, I think, we may infer that the nearly vertical strata must be, in truth, * Rogers, Geology of Pennsylvania, I. pp. 69-74, and 154-158. 248 GEOGNOSY OF THE APPALACHIANS. [XTIL older underlying rocks belonging, not to the paleeozoic system, but to our second series of crystalline schists. We conclude, then, that while the gneisses to the northwest, and probably those along the southeast rim of the mesozoic basin of Penn- sylvania, are Laurentian, the great valley southward to the Delaware is occupied by the rocks of the Green Mountain and White Mountain series. The same two types of rocks, extending to the northeast, are developed about New York City, in the mica-schists of Manhattan and the serpentines of Staten Island and Hoboken ; while in the range of the High- lands, the Laurentian gneiss belt of the South Mountain crosses the Hudson River. 7 The three series of gneissic rocks which we have distin- guished in our section to the northward have, in southeastern New York, as in Pennsylvania, been grouped together in the primary system, and may thence all be traced into western ‘New England. In Dr. Percival’s Geological Report and Map of Connecticut, published in 1840, it will be seen that he refers to the gneiss of the Highlands two gneissic areas in Litchfield County ; the one occupying parts of Cornwall and Ellsworth, and the other extending from Torrington, north- ward through Winchester, Norfolk, and Colebrooke into Berk- shire County, Massachusetts. Further investigations may confirm the accuracy of Percival’s identification, and show the Laurentian age of these New England gneisses, a view which is apparently supported by the mineralogical characters of some of the rocks in this region. Emmons informs ‘us that primary limestones with graphite (perhaps Laurentian) are met with in the Hoosic range in Massachusetts east of the Stockbridge (Taconic) limestones. The rocks of the second series are traceable from south- western Connecticut northward to the Green Mountains in Vermont, and the micaceous schists and gneisses of the third, or White Mountain series are found both to the east and the west of the mesozoic valley in Connecticut and Massachusetts. They also occupy a considerable area in eastern Vermont, where they are separated from the White Mountain range by XII.] GEOGNOSY OF THE APPALACHIANS. 249 an outcrop of rocks of the second series. To the southeast of the White Mountains, along our line of section, the same mica-schists and gneisses, often with very moderate dips, ex- tend as far as Portland, Maine, where they are interrupted by the outcropping of greenish chloritic and chromiferous schists, in nearly vertical beds, which appear to belong to the second series. I find that the strata of the second series appear from be- neath the Carboniferous at Newport, Rhode Island, in a nearly vertical attitude, and are also seen in the vicinity of Boston and Brighton, Saugus and Lynnfield. Their relations in this region to the gneisses with crystalline limestones of Chelms- - ford, etc., which I have referred to the Laurentian series,* have yet to be determined. We have already mentioned that the crystalline rocks of Pennsylvania pass into Maryland and Virginia, where, as H. D. Rogers informs us, they appear in the mountains of the Blue Ridge. It remains to be seen whether the three types which we have pointed out in Pennsylvania are to be recognized in this region. A great belt of crystalline schists extends from Virginia through North and South.Carolina, and into eastern Tennessee, where, according to Safford, these rocks underlie the Potsdam. It is easy, from the reports of Lieber on the geology of South Carolina, to recognize in this State the two types of the Green Mountain and White Mountain series. The former, as described by him, consists of talcose, chloritic, and epidotic schists, with diorites, steatites, actinolite-rock, and serpentines. It may be noted that he still adheres to the notion of the eruptive origin of the last three rocks, which the observations of Emmons, Logan, and myself in the Green Mountains have shown to be untenable. These rocks in South Carolina generally dip at very high angles. The great gneissic area of Anderson and Abbeville districts is described by Lieber as consisting of fine-grained gray gneisses with micaceous and hornblendic schists, and is cut by numerous veins of pegmatite, holding garnet, tourmaline, and beryl. These rocks, which * American Journal of Science (2), XLIX. 75. 11* ee ee ae Na rte ep ee Oe ee eg ne a Oe ee a ee a : corr - ‘ a 7 3 4 250 GEOGNOSY OF THE APPALACHIANS. [XT have the characters of the White Mountain series, appear, from the incidental observations to be found in Lieber’s reports, to belong to a higher group than the chloritic and serpentine series, and to dip at comparatively moderate angles.* Professor Emmons, whose attention was early turned to the geology of western New England, did not distinguish between the three types which we have defined, but, like Rogers in Pennsylvania, included all the crystalline rocks of that region in the primary system. It is to him, however, that we owe the first correct notions of the geological nature and relations of the Green Mountains. These, he has remarked, are often made to include two ranges of hills belonging to different geological series. The eastern range, including the Hoosic - Mountain in Massachusetts and Mount Mansfield in Vermont, he referred to the primary; which he described as including gneiss, mica-schist, talcose slate, and hornblende, with beds and veins of granite, limestone, serpentine, and trap. He declared, moreover, that there is no clear line of demarcation among the various schistose primary rocks, and cited, as an illustration, the passage into each other of serpentine, steatite, and talcose schist. His description of the. crystalline rocks of this range will be recognized as comprehensive and truthful. [* My own observations have since shown me that the rocks of the White Mountain series are largely displayed, and rarely at high angles, in the Blue Ridge in Carroll County, Virginia, thence southwestward at least as far as Ashe County, North Carolina, and again in Polk County, Tennessee. The lithological study in these regions is rendered difficult by the fact that they are covered, often to a depth of a hundred feet or more, by the undisturbed products of their own decomposition, the protoxide bases having been re- moved by solution from the feldspar and the hornblende, and the whole rock, with the exception of the quartzose layers, reduced to a clayey mass, still, however, showing the inclined planes of stratification. The immense veins of pyritous copper-ores, which these rocks enclose (ante, page 217), have in like manner been changed, to as great depths, into hydrous peroxide of iron. I have already alluded to the significance, both chemical and geological, of this decomposition, and to its great antiquity (ante, page 10). The observa- tions of C. A. White, in the northwest, show that such a decomposition of the Eozoic gneisses was anterior to the cretaceous period, while in Missouri, it appears from the studies of R. Pumpelly, confirmed by my own observa- tions, that the quartziferous porphyries with which the iron-ores of that region occur, were thus decomposed before the deposition of the Cambrian sandstones, ] ; t t 4 if E f Pel wcentl ‘=e ae eA J XIII] GEOGNOSY OF THE APPALACHIANS. 251 To the west of the hills of primary schist, he placed his Taconic system, named from the Taconic hills, which run from north to ‘south along the boundary line of New York and Massachusetts, and form a range parallel with the Green Moun- tains. The lower portions of the Taconic system, according to Emmons, are schistose rocks made up from the ruins of the primary schists which lie to the east of them. Thus the talcose schists of Berkshire are said to be regenerated rocks, belonging to the newer system, but showing the color and texture of the older talcose schists from which they were formed. How far this is true of these particular strata may be a question, for there is reason to believe that Emmons included among his Taconic rocks some beds belonging to the older crystalline series of the Green Mountains ; yet it is not less true that the possibility of derived rocks of this kind is one which has been too much overlooked by geologists.* Emmons elsewhere re- marks that, while the talcose slates of the primary are associated with steatite and with hornblende, these are never found in the Taconic rocks, and also, that epidote, actinolite, titanium (rutile), etc., which are characteristic minerals of the primary, are wanting in the Taconic system.» The statements of Emmons on this point were sufficiently explicit ; he included in the primary system all of the crystal- line schists of the Green Mountains, except certain talcose and micaceous beds, which he supposed to be made up of the ruins of the similar strata in the primary, and to constitute, with a great mass of other rocks, the Taconic system ; which was, in its turn, unconformably overlaid by the Potsdam sandstone and Calciferous sand-rock of the New York system. His views have, however, been misunderstood by more than one of his critics ; thus, Mr. Marcou, while defending the Taconic system, makes it to include the three groups just mentioned, namely, 1. The Green Mountain gneiss; 2. The Taconic strata as defined by Emmons ; and, 3. The Potsdam sandstone ;+ thus * Some observations on this point will be found in Essay XIV. + Proceedings of Boston Society of Natural History, November 6, 1861, and American Journal of Science (2), XX XIII. 282. 252 GEOGNOSY OF THE APPALACHIANS. [XIII uniting in one system the crystalline schists and the overlying uncrystalline fossiliferous sediments, in direct opposition to the plainly expressed teachings of Emmons, as laid down in his report on the geology of the Northern District of New York, and later, in 1846,* in his memoir on the Taconic System. In the geological survey of the State of New York, the rocks of the Champlain division (including the strata from the base of the Potsdam sandstone to the summit of the Loraine or Hudson River shales) had, by his colleagues, been looked upon as the lowest of the paleozoic system. Professor Em- mons, however, was led to regard the very dissimilar strata of the Taconic hills as constituting a distinct and more ancient series. A similar view had been held by Eaton, who placed, as we have already seen, above the crystalline schists of the Green Mountains, his primary quartzose and calcareous forma- tions, followed to the westward by transition argillites and sandstones, which latter appear to have corresponded to the Potsdam sandstone of New York. Emmons, however, gave a greater form and consisteney to this view, and endeavored to sustain it by the evidence of fossils, as well as by structure, The Taconic system, as defined by him, may be briefly de- scribed as a series of uncrystalline fossiliferous sediments reposing unconformably on the crystalline schists of the Green Mountains, and partly made up of their ruins ; while it is, at the same time, overlaid unconformably by the Potsdam and Calciferous formations of the Champlain division, and consti- tutes the true base of the paleozoic column. Although he claimed to have traced this Taconic system throughout the Appalachian chain from Maine to North Caro- lina, it is along the confines of Massachusetts and New York that its development was most minutely studied. He separated it into a lower and an upper division, and estimated its total thickness at not less than thirty thousand feet, consisting, in the order of deposition, of the following members: 1. Granu- * Loc, cit. p. 130, and Agriculture of New York, I. 53. This formed a part of the report by Emmons on the Agriculture of New York, but was also published separately. PEON Ba eis 038 HE 1 si te) ae ey oe ae Cais War cad RR ae LG Wrasse Uae ces nace ete eee deer ir 26: path ory eh Coneeee a a 3 : ay! eT XIIL] . GEOGNOSY OF THE APPALACHIANS. 253 Fe OES A ee lar quartz; 2. Stockbridge limestone; 3. Magnesian slate ; 4, Sparry limestone; 5. Roofing-slate, graptolitic; 6. Sili- cious conglomerate; 7. Taconic slate; 8. Black slate. The apparent order of superposition differs from this, and it was conceived by Professor Emmons that during the accumulation of these Taconic rocks, the Green Mountain gneiss, which formed the eastern border of the basin, was gradually elevated so as to bring successively the older members above the ocean from which the sediments were being deposited. From this it resulted that the upper members of the system, such as the black slates, were confined to a very narrow belt, and never extended far eastward ; although he admits that denudation may have removed large portions of these upper beds. At a subsequent period, a series of parallel faults, with upthrows on the eastern side, is supposed to have broken the strata, given them an eastward dip, and caused the newer beds to pass suc- cessively beneath the older ones, thus producing an apparently inverted succession, and making their present seeming order of superposition completely deceptive. In speaking of this sup- posed arrangement of the members of his Taconic system, Emmons alluded to them as “ inverted strata”; while by Mr. Marcou, the strata were said to be “overturned on each side of the crystalline and eruptive rocks which occupy the centre of the chain, producing thus a fan-shaped structure,” ete.* I have elsewhere shown that this notion, though to some extent countenanced by his vague and inaccurate use of terms, was never entertained by Emmons, whose own view, as defined in his Taconic System (p. 17),t is that just explained. ES =) 7 =e aes * Comptes Rendus de l’Académie, LITI. 804. + See my further discussion of the matter, American Journal of Science (2), XXXII. 427; XXXIII, 135, 281. It is by an oversight that I have, in the latter volume (page 136), represented Barrande as sharing the miscon- ception of Marcou, although his language, without careful scrutiny, would lead us to such a conclusion. In fact, in the Bull. Soc. Geol. de France ((2), XVIIT. 261), in an elaborate study of the Taconic question, Barrande heads a section thus: ‘‘ Renversement congu pour tout un systéme,” and then proceeds to show that the renversement or overturn is only apparent, by explaining, in the language of Emmons, the view already set forth above. 254 GEOGNOSY OF THE APPALACHIANS. . [XIII.. The view of Emmons, that there exists at the western base : of the Green Mountains an older fossiliferous series, underlying the Potsdam, met with general opposition from American ge- ologists. In May, 1844, H. D. Rogers, in his address as presi- dent, before the American Association of Geologists, then met at Washington, criticised this view at length, and referred to a section from Stockbridge, Massachusetts, to the Hudson River, made by W. B. Rogers and himself, and by them laid before the American Philosophical Society in January, 1841. They then maintained that the quartz-rock of the Hoosic range was Potsdam, the Berkshire marble identical with the blue lime- stone of the Hudson valley, and the associated micaceous and talcose schists altered strata of the age of the slates at the base of the Appalachian system ; that is to say, primal in the nomenclature of the Pennsylvania survey. In 1843 Mather had asserted the Champlain age of the same crystalline rocks, and claimed that the whole of the division was there represented, including the Potsdam, the Hudson River group, and the intermediate limestones.* The conclu- sion of Mather was cited with approbation by Rogers, who apparently adopted it, and declared that Hitchcock held a simi- lar view. It will be seen that these geologists thus united in one group the schists of the Hoosic range (regarded by Em- mons as primary) with those of the Taconic range, and referred both to the age of the Champlain division, the whole of which was supposed to be included in the group. In the same address Professor Rogers raised a very important question. Having referred to the Potsdam sandstone, which on Lake Champlain forms the base of the paleozoic system, he inquires, “Is this formation, then, the lowest limit of our Ap- palachian masses generally, or is the system expanded down- ward in other districts by the introduction beneath it of other conformable sedimentary rocks?” He then proceeded to state that from the Susquehanna River, southwestward, a more com- plex series appears at the base of the lower limestone than to the north of the Schuylkill, and in some parts of the Blue * Geology of the Southern District of New York, p, 438. = + bd intense nen acted ay Oc eRe : art ub Woy eee nani e XIIL.] GEOGNOSY OF THE APPALACHIANS. 255 Ridge he includes in the primal division (beneath the Calcifer- ous sand-rock) “ at least four independent and often very thick deposits, constituting one general group, in which the Potsdam or white sandstone (with Scolithus)-is the second in descending order.” This sandstone is overlaid by many hundred feet of arenaceous and ferriferous fucoidal slate, and underlaid by coarse sandy shales and flagstones ; below which, in Virginia and East Tennessee, is a series of heterogeneous conglomerates, which rest on a great mass of crystalline strata. The accuracy of these statements is confirmed by Safford, who, in his report on the geology of Tennessee (1869), places at the base of the column a great series of crystalline schists, apparently repre- sentatives of those of southeastern Pennsylvania. (Ante, page 245.) Upon these repose what Safford designates as the Pots- dam group, including, in ascending order, the Ocoee slates and conglomerates, estimated at 10,000 feet, and the Chilhowee shales and sandstones, 2,000 feet or more, with fucoids, worm- burrows, and Scolithus. These are conformably overlaid by the Knoxville division, consisting of fucoidal sandstones, shales, and limestones, the latter two holding fossils of the age of the Calciferous sand-rock. It is noteworthy that these rocks are greatly disturbed by faults, and that in Chilhowee Mountain the lower’conglomerates are brought on the east against the Carboniferous limestone, by a vertical displacement of at least 12,000 feet. The general dip of all these strata, including the basal crystalline schists, is to the southeast. The primal palzozoic rocks of the Blue Ridge were then by Rogers, as now by Safford, looked upon as wholly of Potsdam age, including the Scolithus sandstone as a subordinate member, so that the strata beneath this were still regarded as belong- ing to the New York system. Hence, while Rogers inquires whether the Taconic system ‘may not along the western bor- der of Vermont and Massachusetts include also some of the sandy and slaty strata here spoken of as lying beneath the Potsdam sandstone,” * he would still embrace these lower strata in the Champlain division. * American Journal of Science (1), XLVIT. 152, 153. 256 GEOGNOSY OF THE APPALACHIANS, _ (Xm. Thus we see that at an early period the rocks of the Taconic system were, by Rogers and Mather, referred to the Champlain division of the New York system, a conclusion which has been sustained by subsequent. observations. Before discussing these, and their somewhat involved history, we may state two ques- tions which present themselves in connection with this solu- tion of the problem. First, whether the Taconic system, as defined by Emmons, includes the whole or a part of the Cham- plain division ; and, second, whether it embraces any strata older or newer than the members of this portion of the New ‘York system. With reference to the first question it is to be remarked, that in their attempts to compare the Taconic rocks with those of the Champlain division as seen farther to the west, observers were led by lithological similarities to identify the upper members of the latter with certain portions of the Taconic. In fact, the Trenton limestone, with the Utica slates and the Loraine or Hudson River shales, making to- gether the upper half of the Champlain division (in which Emmons, moreover, included the overlying Oneida and Medina ‘conglomerates and sandstones), have in New York an aggregate thickness of not less than three or four thousand feet, and offer many lithological resemblances to the great mass of sediments at the western base of the Green Mountains, to which the name of Taconic had been applied. It is curious to find that Emmons, in 1842, referred to the Medina the Red sand-rock of the east shore of Lake Champlain, since shown to be Potsdam ; and, moreover, placed the Sillery sandstone of the neighbor- hood of Quebec at the summit of the Champlain division, as the representative of the Oneida conglomerate; while at the same time he noticed the great resemblance which this sand- stone, with its adjacent limestones, bore to similar rocks on the confines of Massachusetts, already referred by him to the Taconic system.* This view of Emmons as to the Quebec rocks was adopted by Sir William Logan, when, a few years afterwards, he began to study the geology of that region. The sandstone of Sillery * Geology of the Northern District of New York, pp. 124, 125. XIIL] = GEOGNOSY OF THE APPALACHIANS. 257 was described by him as corresponding to the Oneida or Shawangunk conglomerate, while the limestones and shales of the vicinity, which were supposed to underlie it, were re- garded as the representatives of the Trenton, Utica, and Hud- son River formations.* By following these rocks along the western base of the Appalachians into Vermont and Massa- chusetts, they were found to be a continuation of the Taconic system, which Sir William was thus led to refer to the upper half of the Champlain division, as had already been done by Professor Adams in 1847.t As regards the crystalline strata, of the Appalachians in this region, he, however, rejected the view of Emmons, and maintained that put forward by the Messrs. Rogers in 1841; namely, that these, instead of being ‘older rocks, were but these same upper formations of the Champlain division in an altered condition ; a view which was maintained during several years in all of the publications of those connected with the geological survey of Canada. This conclusion, so far as regards the age of the unaltered fossiliferous rocks from Quebec to Massachusetts, was supposed to be confirmed by the evidence of organic remains found in them in Vermont. Mr. Emmons had described, as character- istic of the upper part of the Taconic system, two crustaceans, to which he gave the names of Atops trilineatus and Ellipto- cephalus asaphoides ; the other fossils noticed by him being graptolites, fucoids, and what were apparently the marks of annelids. In 1847 Professor James Hall, in the first volume of his Paleontology, declared the Atops of Emmons to be identical with Zriarthrus (Calymene) Beckii, a characteristic fossil of the Utica slate; while the Elliptocephalus was re- ferred by him to the genus Olenus, now known to belong to the primordial fauna of Sweden, where it is found in slates lying beneath the orthoceratite limestone, and near the base of the palzeozoic series. Although, as it now appears, the geologi- - eal horizon of the Olenus slates was well known to Hisinger, * Geological Survey of Canada, 1847-48, pp. 27, 57 ; and American Jour-.' nal of Science (2), IX. 12. + American Journal of Science (2), V. 108. 258 GEOGNOSY OF THE APPALACHIANS. [XIII. this author in his classic work, Lethza Suecica, published in 1837, represents, by some unexplained error, these slates as overlying the orthoceratite limestone, which is the equivalent of the Trenton limestone of the Champlain division. Hence, as Mr. Barrande has remarked, Hall was justified by the au- thority of Hisinger’s published work in assigning to the Olenus slates of Vermont a position above that limestone, and in placing them, as he then did, on the horizon of the Hudson River or Loraine shales. The double evidence afforded by these two fossil forms in the rocks of Vermont served to confirm Sir William Logan in placing in the upper part of the Champlain division the rocks which he regarded as their stratigraphical equivalents near Quebec; and which, as we have seen, had some years before been by Emmons himself assigned to the same horizon. The remarkable compound graptolites which occur in the shales of Pointe Levis, opposite Quebec, were described by Professor James Hall in the report of the Geo- logical Survey of Canada for 1857, and were then referred to the Hudson River group; nor was it until August, 1860, that Mr. Billings described from the limestones of this same series at Pointe Levis a number of trilobites, among which were sevy- eral species of Agnostys, Dikelocephalus, Bathyurus, etc., con- stituting a fauna whose geological horizon he decided to be in the lower part of the Champlain division. Just previous to this time, in the report of the Regents of the University of New York for 1859, Professor Hall had described and figured by the name of Olenus two species of trilobites from the slates of Georgia, Vermont, which Emmons had wrongly referred to the genus Paradoxides. They were at once recognized by Barrande, who called attention to their primordial character, and thus led to a knowledge of their true stratigraphical horizon, and to the detection of the singular error in Hisinger’s book, already noticed, by which American geologists had been misled.* They have since been separated from Olenus, and by Professor Hall referred to a new and * For the correspondence on this matter between Barrande, Logan, and Hall, see American Journal of Science (2), XX XI. 210-226. XIIL.] GEOGNOSY OF THE APPALACHIANS. 259 closely related genus, which he has named Olenellus, and which is now regarded as belonging to the horizon of the Potsdam sandstone, to which we shall presently advert. Further studies of the fossiliferous rocks near Quebec showed the existence of a mass of sediments estimated at about 1,200 feet, holding a numerous fauna, and corresponding to a great development of strata about the age of the Calciferous and Chazy formations, or, more exactly, to a formation occupying a position between these two, and constituting, as it were, beds of passage between them. In this new formation were in- ~ cluded the graptolites already described by Hall, and the numerous crustacea and brachiopoda described by Billings, all of which belong to the Levis slates and limestones. To these and their associated rocks Sir William Logan then gave the name of the Quebec group, including, besides the fossiliferous Levis formation, a great mass of overlying slates, sandstones, and magnesian limestones, hitherto without fossils, which have been named the Lauzon rocks, and the Sillery sandstones and shales, which he supposed to form the summit of the group, and which had afforded only an Obolella and two species of Lingula ;* the volume of the whole group being about 7,000 feet. The paleontological evidence thus obtained by Billings and by Hall, both from near Quebec and in Vermont, led to the conclusion that the strata of these fegions, so much resembling the upper members of the Champlain division, were really a great development, in a modified form, of some of its lower por- tions. Their apparent stratigraphical relations were explained by Logan by the supposition of ‘an overturned anticlinal fold, _ with a crack and a great dislocation running along the summit, by which the Quebec group is brought to overlie the Hudson River group. Sometimes it may overlie the overturned Utica formation, and in Vermont points of the overturned Trenton appear occasionally to emerge from beneath the overlap.” He, at the same time, declared that “from the physical structure alone, no person would suspect the break that must exist in * See Billings, Paleozoic Fossils of Canada, p. 69. es ee ee Se On AA ees ee m7 . y — eS 260 GEOGNOSY OF THE APPALACHIANS. [XIII. the neighborhood of Quebec, and, without the evidence of fossils, every one would be authorized to deny it.” * The rocks from western Vermont, which had furnished to © Hall the species of Olenellus, have long been known as the Red sand-rock, and, as we have seen, were by Emmons, in 1842, referred to the age of the Medina sandstone, — a view which the late Professor Adams still maintained as late as 1847.¢ In the mean time Emmons had, in 1855, declared this rock to represent the Calciferous and Potsdam formations, the brown sandstones of Burlington and Charlotte, Vermont, being re- ferred to the latter.{ This conclusion was confirmed by Billings, who, in 1861, after visiting the region and examin- ing the organic remajns of the Red sand-rock, assigned to it a position near the horizon of the Potsdam.§ Certain trilobites found in this Red sand-rock by Adams, in 1847, were by Hall recognized as belonging to the European genus C'onocephalus (= Conocephalites and Conocoryphe), whose geological horizon was then undetermined.||. The formation in question consists in great part of a red or mottled granular dolomite, associated with beds of fucoidal sandstone, conglomerates, and slates. These rocks were carefully examined by Logan in Swanton, Vermont, where, according to him, they have a thickness of 2,200 feet, and include toward their base a mass of dark- colored shales holding Olenellus with Conocephalites, Obolella, etc. ; Conocephalites Teucer, Billings, being common to the shales and the red sandy beds.1 Many of these fossils are also found at Troy and at Bald Mountain, New York, where they accompany the Atops of Emmons, now recognized by Billings as a species of Conocephalites. * Logan’s letter to Barrande, American Journal of Science (2), XX XI. 218. The true date of this letter was December 31, 1860, but, by a misprint, it is made 1831, + Adams, American Journal of Science (2), V. 108. t Emmons, American Geology, II. 128. § American Journal of Science (2), XXXII. 232. || Ibid. (2), XX XITI. 374. | Geology of Canada, 1863, p. 281; American Journal of Science (2), XLVI. 224. , X31] GEOGNOSY OF THE APPALACHIANS. 261 A similar condition of things extends northeastward along the Appalachian region. On the south side of the St. Law- rence below Quebec a great thickness of limestones, sandstones, and slates, formerly referred to the Quebec group, is now re- garded by Billings as, in part at least, of the Potsdam forma- tion ; while on the coast of Labrador and in northern New- foundland the same formation, characterized by the same fossils as in Vermont, is largely developed, attaining in some parts, according to Murray, a thickness of 3,000 feet or more. Along the northern coast of the island it is nearly horizontal, and appears to be conformably overlaid by about 4,000 feet of fossiliferous strata representing the Calciferous sand-rock and the succeeding Levis formation. Mr. Billings has described a section from the Laurentian of Crown Point, New York, to Cornwall, Vermont, from which it appears that to the eastward of a dislocation which brings up the Potsdam to overlie the higher members of the Champlain division, the Potsdam is itself overlaid, at a small angle, by a great mass of limestones representing the Calciferous, and hay- ing at the summit some of the characteristic fossils of the Levis formation. Next in ascending order are not less than 2,000 feet of limestones with Trenton fossils (embracing prob- ably the Chazy division), while to the east of this the Levis again appears, including the white Stockbridge limestones.* We have here an evidence that the augmentation in volume observed in the lower members of the Champlain division in the Appalachian region extends to the Trenton, which to the west of Lake Champlain is represented, the Chazy included, by not more than 500 feet of limestone. The Potsdam, in the latter region, consists of from 500 to 700 feet of sandstone holding Conocephalites and Lingulella, and overlaid by 300 feet of magnesian limestone, the so-called Calciferous sand-rock. In the valley of the Mississippi these two formations in Iowa, Missouri, and Texas are represented by from 800 to 1,300 feet of sandstones and magnesian limestones ; while in the Black Hills * T. S. Hunt on the Geology of Vermont, American Journal of Science (2), XLVI. 227. rT eee ee 262 GEOGNOSY OF THE APPALACHIANS. [XIIr. of Nebraska, according to Hayden, the only representative of — these lower formations is about one hundred feet of sandstone holding Potsdam fossils. * In striking contrast to this, it has been shown that along the Appalachian range from Newfoundland to Tennessee these lower formations are represented by from 8,000 to 15,000 feet of fossiliferous sediments. It has been suggested by Logan that these widely differing conditions represent deep-sea accu- mulations on the one hand, and the deposits from a shallow sea which covered a submerged continental plateau. on the other ; the sediments in the two areas being characterized by a similar fauna, though differing greatly in lithological characters ‘ and in thickness. To this we may add, that the continental area, being probably submerged and elevated at intervals, be- came overlaid with beds which represent only in a partial and imperfect manner the great succession of strata which were being accumulated in the adjacent ocean. t In a paper which I hope to present to the geological section during the present meeting of the Association, it will be shown, from a study of the rocks of the Ottawa basin, that the typical Champlain division not only presents important paleontological — breaks, but evidences of stratigraphical discordance at more * American Journal of Science (2), XXV. 489; XXXI. 234. [Later obser- vations show great variations in the thickness of these lower rocks in the West. In the Wahsatch Mountains are found, according to Bradley, from 1,500 to 2,000 feet of sandstones and conglomerates, regarded as Potsdam, overlaid by 3,000 feet of magnesian limestones and shales, holding fossils of the Levis, and, towards the summit, of Niagara and probably of Lower Helderberg age ; the whole followed by 2,000 feet of Devonian sandstones and 3,000 feet of Carboniferous limestones. In the Teton Mountains, however, accord- ing to the same observer, this great thickness of Potsdam and Levis rocks is represented by only 700 feet of quartzites and limestones, overlaid by about 600 feet of magnesian limestones, probably of Niagara age, followed by 2,000 feet of Carboniferous limestones. Inthe Wind River Mountains, in western Wyoming, Professor Comstock has described a remarkable stries, including Potsdam and Levis, followed by strata of Oriskany age, Carboniferous lime- stones, Triassic, Jurassic, and Cretaceous rocks, all apparently conformable, and resting at an angle of about 20° on the crystalline Eozoic rocks. Re- mains of the fauna of the Trenton period (Upper Cambrian) have moreover very recently been made known to us from the West. ] + Ibid. (2), XLVI. 225. dee ab you es wT XIII.) GEOGNOSY OF THE APPALACHIANS. 263 than one horizon over the continental area, which, as the result of widely spread movements, might be supposed to be repre- sented in the Appalachian region. In the latter Logan has already observed that*the absence of all but the highest beds of the Levis along the eastern limit of the Potsdam, near Swanton, Vermont (while the whole thickness of them ap- pears a little farther westward), makes it probable that there is a want of conformity between the two; and I have in this connection insisted upon the entire absence, in this locality, of the Calciferous, which is met with a little farther south in the section just mentioned, as another evidence of the same unconformity.* There are also, I think, reasons for suspecting another stratigraphical break at the summit of the Quebec group,t in which case many problems in the geological structure of this region will be much sim- plified. It should be remembered that the conditions of deposition in some areas have been such that accumulations of strata, cor- responding to long geologic periods, and elsewhere marked by stratigraphical breaks, are atranged in conformable superposi- tion ; and moreover that movements of elevation and depres- sion have even caused great paleontological breaks, which over considerable areas are not marked by any apparent discordance. Thus the remarkable break in the fauna between the Calcifer- ous and the Chazy is not accompanied by any noticeable dis- | cordance in the Ottawa basin ; and in Nebraska, according to Hayden, the Potsdam, Carboniferous, Jurassic, and Cretaceous formations are all represented.in about 1,200 feet of conforma- ble strata. { In Sweden the whole series from the base of the Cambrian to the summit of the Silurian appears as a conform- able sequence, while in North Wales, although there is no ap- parent discordance from the base of the Cambrian to the sum- mit of the Lingula flags, stratigraphical breaks, according to Ramsay, probably occur both at the base and the summit * American Journal of Science (2), XLVI. 225. + See, for the evidence of this, Essay XV., Part Third. + American Journal of Science (2), XXV. 440. 264 GEOGNOSY OF THE APPALACHIANS. [XIII of the Tremadoce slates,* which are considered equivalent to the Levis formation. We have seen that, according to Logan, a dislocation a little to the north of Lake Champlain causes the Quebee group to overlie the higher members of the Champlain division, The same uplift, according to him, brings up, farther south, the Red sand-rock of Vermont, which to the west of the disloca- tion rests upon the upturned and inverted strata of various formations from the Calciferous sand-rock to the Utica and Hudson River shales. These latter, according to him, are seen to pass for considerable. distances beneath nearly horizontal layers of the Red sand-rock, the Utica slate, in one case, hold- ing its characteristic fossil, Triarthrus Becku. This relation, which is well shown in a section at St. Albans, figured by Hitchcock,+ was looked upon by Emmons and by Adams as evidence that the Red sand-rock was the representative of the Medina sandstone of the New York system. When, however, the former had recognized the Potsdam age of the sand-rock, with its Olenellus, which he supposed to be Paradoxides, this condition of things was conceivefl to be an evidence of the existence beneath the Potsdam of an older and unconformable fossiliferous series already mentioned. The objections made by Emmons to Rogers’s view of the Champlain age of the Taconic rocks were threefold : first, the great differences in lithological characters, succession, and thick- ness between these and the rocks of the Champlain division as previously known in New York; second, the supposed un- conformable infraposition of a fossiliferous series to the Pots- dam ; and, third, the distinct fauna which the Taconic rocks were supposed to contain. The first of these is met by the fact, now established, that, in the Appalachian region, the Cham- plain division is represented by rocks having, with the same organic remains, very different lithological characters, and a thickness tenfold greater than in the typical Champlain region of northern New York. The second objection has already * Quar. Geol. Journal, XIX. p. 36. + Geology of Vermont, p. 374. a a a a ee salle sad ‘tot Wo a a nah mis Kad A aviltte vita %, 4) Silene = —_ sp-Geaeiiineetrematicaies tate ' UT) 2) Ca a ra gs Bou eee ame da ine cay —e , ‘+ i" XIII.] GEOGNOSY OF THE APPALACHIANS. 265 @ been answered by showing that the rocks which, as in the St. Albans section, pass beneath the Potsdam are really newer strata belonging to the upper part of the division, and contain a characteristic fossil of the Utica slate. As to the third point, it has also been met, so far as regards the Atops and Ellipto- cephalus, by showing these two genera to belong to the Pots- dam formation. If we inquire further into the Taconic fauna, we find that the Stockbridge limestone (the Eolian limestone of Hitchcock), which was placed by Emmons near the base of the Lower Taconic (while the Olenellus slates are near the sum- mit of the Upper Taconic), is also fossiliferous, and contains, according to the determinations of Professor Hall, species be- longing to the genera Euomphalus, Zaphrentis, Stromatopora, Chaetetes, and Stictopora.* Such a fauna would lead to the conclusion that these limestones, instead of being older, were really newer than the Olenellus beds, and that the apparent order of succession was, contrary to the supposition of Em- mons, the true one. This conclusion was still further confirmed by the evidence obtained in 1868 by Mr. Billings, who found in that region a great number of characteristic species of the Levis formation, many of them in-beds immediately above or below the*white marbles,t which latter, from the recent obser- vations of the Rev. Augustus Wing, in the vicinity of Rutland, Vermont, would seem to be among the upper beds of the Pots- dam formation. Thus while some of the Taconic fossils belong to the Potsdam and Utica formations, the greater number of them, derived from beds supposed to be low down in the sys- tem, are shown to be of the age of the Levis formation. There is, therefore, at present, no evidence of the existence, among the unaltered sedimentary rocks of the western base of the Appalachians in Canada or New England, of any strata more ancient than those of the Champlain division,{ to which, from * Geology of Vermont, 419; and American Journal of Science (2), XX XIII. 419, + American Journal of Science (2), XLVI. 227. ~ See, on this point and on the possibly greater antiquity of the rocks called Potsdam, Essay XV., Part Third. 12 266 GEOGNOSY OF THE APPALACHIANS. [XIII. . their organic remains, the fossiliferous Taconic rocks are shown to belong. Mr. Billings has, it is true, distinguished provisionally het he has designated an upper and a lower division of the Pots- dam, and has referred to the latter the Red sand-rock with the Olenellus slates of Vermont, together with beds holding similar fossils at Troy, New York, and along the Strait of Bellisle in Labrador and Newfoundland ; the upper division of the Pots- dam being represented by the basal sandstones of the Ottawa basin and of the Mississippi valley.* In the present state of our knowledge of the local variations in sediments and in their fauna dependent on depth, temperature, and ocean currents, Billings, however, conceives that it would be premature to assert that these two types of the Potsdam do not represent syn- chronous deposits. The base of the Champlain eee as known in the Pots- dam formation of New York, of the Mississippi valley, and the Appalachian belt, does not, however, represent the base of the palzozoic series in Europe. The Alum slates in Sweden are divided into two parts, an upper or Olenus zone, and a lower or Conocoryphe zone, as distinguished by Angelin. The latter is characterized by the genus Paradoxides, which also occupies a lower division in the primordial palzozoic rocks of Bohemia (Barrande’s stage C), the greater part of which are regarded as the equivalent of the Olenus zone of Sweden and the Potsdam of North America. The Lingula flags of Wales belong to the same horizon, and it is at their base, in strata once referred to the Lower Lingula flags, that the Paradoxides is met with. These strata, for which Hicks and Salter, in 1865, proposed the name of the Menevian group, are regarded as corresponding to the lower division of the Alum slates, and, like it, contain a fauna not yet recognized in the basal rocks of the New York system. [Beneath the Menevian lie the Llan- beris and Harlech rocks (the Longmynd), which constitute the Lower Cambrian of Sedgwick; while above it are the great mass of the Lingula flags and the Tremadoc rocks, his Middle * Report Geol. of Canada, 1863 - 66, p. 236. a a ee Ta ee TY ais ee wie ¢ i 3 XIII] GEOGNOSY OF THE APPALACHIANS. 267 Cambrian. To these succeed the Bala or Upper Cambrian, the equivalent of the Llandeilo and Caradoc rocks, to which Murchison gave the name of Lower Silurian. He at first claimed the Llandeilo as the base of his Silurian system, but subsequently endeavored to extend it downwards so as to include, under the name of Primordial Silurian, the Middle Cambrian of Sedgwick. To this Lyell objected, and while conceding to Murchison the Upper Cambrian as Lower Silu- rian, gave to the middle division of Sedgwick’s series the name of Upper Cambrian. Hicks in a recent paper (1873) has adopted a similar compromise, including, however, in the Lower Silurian the Arenig group, and making the Tremadoe the upper member of the Upper Cambrian. For a discussion of the relations of Cambrian and Silurian the reader is re- ferred to Essay XV. in this volume.| The same classification is now adopted by Linarsson, in Sweden, where, in Westro- gothia, the Cambrian rocks (resting unconformably on the crystalline schists to be noticed further on) are overlaid con- formably by the orthoceratite-limestones, which are by him regarded as forming the base of the Silurian, and as the equiva- lent of the Llandeilo rocks of Wales; The total thickness of these lower rocks in Sweden, including the representatives of the Lingula flags, the Menevian beds, and an underlying fucoidal (Eophyton) sandstone, is only three hundred feet, while the first two divisions in Wales have a thickness of five ‘to six thousand, and the Harlech grits and Llanberis slates (including the Welsh roofing-slates beneath) amount to eight thousand feet additional. Recent researches show that these lower rocks in Wales contain an abundant fauna, extending downward some 2,800 feet from the Menevian to the very base of strata regarded as the representatives of the Harlech grits. The brachiopoda of the. Harlech beds appear identical with those of the Menevian, but new species of Conocephalites, Microdiscus, and Paradoxides are met with, besides a new genus, Plutonia, allied to the last mentioned.* [The Upper * Hicks, Geol. Mag., V. 306; and Rep. Brit. Assoc., 1868, p. 69; also Harkness and Hicks in Nature, Proc. Geol. Soc., May 10, 1871. 268 GEOGNOSY OF THE APPALACHIANS. (XII. Cambrian, as defined by Sedgwick, is represented in North America by the upper portion of the Champlain division of New York, from the top of the Chazy, while the Middle and Lower Cambrian have their equivalents in the Quebec group, the Chazy, Calciferous, and Potsdam, and in the strata holding Paradoxides and other primordial forms in Massachusetts, New Brunswick, and Newfoundland. The precise relation of these to the Potsdam formation of New York is yet to be deter- mined, as well as the question whether there exists in the Appalachians any palzozoic rocks belonging to a lower horizon than the Potsdam. For a further discussion of these questions the reader is referred to Essay XV. in the present volume. } In May, 1861, I called attention to the fact that beds of quartzose conglomerate at the base of the Potsdam in Hem- mingford, near the outlet of Lake Champlain, on its western side, contain fragments of green and black slates, ‘‘ showing the existence of argillaceous slates before the deposition of the Potsdam sandstone.” * The more ancient strata, which fur- nished these slaty fragments to the Potsdam conglomerate, have perhaps been destroyed, or are concealed, but they or their equivalents may yet be discovered in some part of the great Appalachian region. They should not, however, be called Taconic, but receive the prior designation of Cambrian, “unless, indeed, it shall appear that the source of these slate fragments was the more argillaceous beds of the still older Huronian schists. Emmons regarded his Taconic system as the equivalent of the Lower (and Middle) Cambrian of Sedg- wick ; but when, in 1842, Murchison announced that the name of Cambrian had ceased to have any zodlogical significance, being identical with Lower Silurian,+ Emmons, conceiving, as he tells us, that all Cambrian rocks were not Silurian, instead — of maintaining Sedgwick’s name which, with the progress of paleontological study, is assuming a great zodlogical importance, devised the name of Taconic, as synonymous with the Lower (and Middle) Cambrian of Sedgwick. * American Journal of Science (2), XXXI. 404. + Proc. Geol. Soc. London, ITI. 642. + Emmons, Geol. N. District of New York, 162 ; and Agric. of New York, BE. 49, XIII] GEOGNOSY OF THE APPALACHIANS. 269 The crystalline strata to which the name of the Huronian series has been given by the Geological Survey of Canada, have sometimes been called Cambrian from their resemblance to cer- tain crystalline rocks in Anglesea, which have been imagined to-be altered Cambrian. The typical Cambrian rocks of Wales, down to their base, are, however, uncrystalline sediments, and, as pointed out by Dr. Bigsby in 1863,* are not to be confounded with the Huronian, which he regarded as equivalent to the second division of the so-called azoic rocks of Norway, the Urschiefer or primitive schists, which in that country rest un- conformably on the primitive gneiss (Urgnevss), and are in their turn overlaid unconformably by the fossiliferous Cambrian strata. This second or intermediate series in Norway is char- acterized by eurites, micaceous, chloritic, and hornblendic schists, with diorites, steatite, and dark-colored serpentines, generally associated with chrome ; and abounds in ores of cop- per, nickel, and iron. In its mineralogical and lithological characters, the Urschiefer corresponds with what we have designated the second series of crystalline schists. It is, in Norway, divided into a lower or quartzose division, marked by a predominance of quartzites, conglomerates and more massive rocks, and an upper and more schistose division. Macfarlane, who was familiar with the rocks of Norway, after examining both the Huronian of Lake Superior and the crystalline strata of the Green Mountains, had already, in 1862, declared his opinion that both of these were representatives of the Nor- wegian Urschiefer,t thus anticipating, from his comparative studies, the conclusions of Bigsby. The crystalline rocks of Anglesea and the adjacent part of Caernarvon, which have been described and mapped by the British Geological Survey as altered Cambrian, are directly overlaid by strata of the Llandeilo or Upper Cambrian division, corresponding to the Trenton and Hudson River formations. If we consult Ramsay’s report on the region, it will be found that he speaks of the lower rocks as “ probably Cambrian,” * Quar. Jour. Geol. Soc., XIX. 36. + Canadian Naturalist, VIL. 125. 270 GEOGNOSY OF THE APPALACHIANS. [ XIII. ‘and states as a reason for that opinion, that they are connected by certain beds of intermediate lithological characters with strata of undoubted Cambrian age.* These, however, as he admits, present great local variations, and, after carefully scan- ning the whole of the evidence adduced, I am inclined to see in it nothing more than the existence, in this region, of Cam- brian strata made up from the ruins from the great mass of pre-Cambrian schists, which are the crystalline rocks of Angle- sea. Such a phenomenon is repeated in numerous instances in our North American rocks, and is the true explanation of many supposed examples of passage from crystalline schists to un- crystalline sediments. The Anglesea rocks are a highly inclined and much contorted series of quartzose, micaceous, chloritic, and epidotic schists, with diorites and dark-colored chromifer- ous serpentines, all of which, after a careful examination of them in the collections of the Geological Survey of Great Britain, I consider identical with the rocks of the Green Mountain or Huronian series. A similar view of their age is shared by Phillips and by Sedgwick, in opposition to the opinion of the British survey. The former asserts that the crystalline schists of Anglesea are “below all the Cambrian rocks”; + while Sedgwick expresses the opinion that they are of ‘‘a distinct epoch from the other rocks of the district, and evidently older.” ¢ Associated with the fossiliferous Devonian rocks of the Rhine is a series of crystalline schists, similar to those just noticed, seen in the Taunus, the Hundsriick, and the Ardennes, These, in opposition to Dumont, who regarded them as belong- ing to an older system, are declared by Rémer to have resulted from a subsequent alteration of a portion of the Devonian sediments. § Turning now to the Highlands of Scotland, we have a simi- lar series of crystalline schists, presenting all the mineralogical * Geol. of North Wales, pp. 145, 175. + Manual of Geology (1855), 89. t Geol. Journal for 1845, 449. § Naumann, Geognosie, 2d edition, II. 383. XIII] GEOGNOSY OF THE APPALACHIANS, 271 characters of those of Norway and of Anglesea, which, accord- ing to Murchison and Giekie, are younger than the fossilifer- ous limestones of the western coast (about the horizon of the Levis formation of the Quebec group), which seem to pass beneath them. Professor Nicol, on the contrary, maintains that this apparent superposition is due to uplifts, and that these crystalline schists are really older than the lowest Cam- brians, which appear to the west of them as uncrystalline sedi- ments resting on the Laurentian. He does not, however, confound these crystalline schists of the Scottish Highlands with the Laurentian, from which they differ mineralogically, but regards them as a distinct series.* In the presence of the differences of opinion which have been shown in this contro- versy, we may be permitted to ask whether, in such a case, stratigraphical evidence alone is to be relied upon. Repeated examples have shown that the most skilful stratigraphists may be misled in studying the structure of a disturbed region where there are no organic remains to guide them, or where unexpected faults and overslides may deceive even the most sagacious. I am convinced that in the study of the crystalline schists, the persistence of certain mineral characters must be relied upon as a guide, and that the language used by Delesse, in 1847, will be found susceptible of a wide application to crystalline strata: “Rocks of the same age have most gener- ally the same chemical and mineralogical composition, and, reciprocally, rocks having the same chemical composition and the same minerals, associated in the same manner, are of the same age.” t In this connection the testimony of Professor James Hall is also to the point. Speaking of the crystalline _ schists of the White Mountain series, he says :— “Every observing student of one or two years’ experience in the collection of minerals in the New England States knows well that he may trace a mica-schist of peculiar but varying character from Connecticut, through central Massachusetts, and * Quar. Jour. Geol. Soc. ; Murchison, XV. 353 ; Giekie, XVII. 171; Nicol, XVII. 58, XVIII. 443. + Bull. Soc. Geol. de Fr. (2), IV. 786. CT eee ape ee pie ee Oe Ae ee, a r = fi " ae ta ye | nea . 272 GEOGNOSY OF THE APPALACHIANS. [XII thence into Vermont and New Hampshire, by the presence of staurolite and some other associated minerals, which mark with the same unerring certainty the geological relations of the rock as the presence of Pentamerus oblongus, P. galeatus, Spirifer Niagarensis, or S. macropleura, and their respectively asso- ciated fossils, do the relations of the several rocks in which these occur.” * I am convinced that these crystalline schists of Germany, Anglesea, and the Scotch Highlands will be found, like those of Norway, to belong to a period anterior to the deposition of the Cambrian sediments, and will correspond with the newer gneissic series of our Appalachian region. There exists, in the Highlands of Scotland, a great volume of fine-grained, thin-bed- ded mica-schists with andalusite, staurolite, and cyanite, which are met with in Argyleshire, Aberdeenshire, Banffshire, and the _ Shetland Isles. Rocks regarded by Harkness as identical with these of the Scottish Highlands also occur in Donegal and Mayo in Ireland. Through the kindness of the Rev. Professor Haughton of Trinity College, and Mr. Robert H. Scott, then of Dublin, I received some years since a large collection of the crystalline rocks of Donegal, which I am thus enabled to compare with those of North America, and to assert the exist- ence, in the northwest of Ireland, of our second and third series of crystalline schists. The Green Mountain rocks are there exactly represented by the dark-colored chromiferous serpentines of Aghadoey, and the steatite, crystalline tale, and actinolite of Crohy Head; while the mica-schist of Loch Derg, with white quartz, blue cyanite, staurolite, and garnet, all united in the same fragment, cannot be distinguished from specimens found at Cavendish, Vermont, and Windham, Maine. The fine-grained andalusite-schists of Clooney Lough are ex- actly like those from Mount Washington ; while the granitoid mica-slates from several other localities in Donegal are not less clearly of the type of the White Mountain series. Similar micaceous schists, with andalusite (chiastolite), occur on Skid- daw, in Cumberland, England, the relations of which have * Paleontology of New York, Vol. IIL, Introduction, page 93. ee ee ee 2 ee | XII] §° GEOGNOSY OF THE APPALACHIANS. 273 been clearly defined by Sedgwick, who groups the rocks of Skiddaw into four divisions. The lowest of these, succeeding the granite, is a series of crystalline rocks, not described litho- logically, with mineral veins, ‘‘ having some resemblance to the rocks of Cornwall,” and including, towards the summit, “ chi- astolite-schists and chiastolite-rocks.” These are followed in ascending order by two great series of slates and grits, suc- ceeded by a fourth division of schists, sometimes carbonaceous, holding in parts fucoids and graptolites, which are apparently overlaid discordantly by sundry trappean conglomerates and chloritic slates.* The graptolites of the Skiddaw slates are. found to be identical with those of the Levis formation,+ and it is worthy of notice that although Sedgwick places the mica- schists with andalusite (chiastolite) so far below the graptolitic beds, he elsewhere, in comparing the rocks of North Wales and Cumberland, states that the chloritic and micaceous rocks of Anglesea and Caernarvon are not represented in Cumber- land, being distinct from the other rocks of North Wales, and much older. f In Victoria, Australia, the position of the chiastolite schists, according to Selwyn, is beneath the graptolitic slates. Boblaye, it is true, asserted in 1838 that the chiastolite-schists of Les — Salles, near Pontivy in Brittany, include Orthis and Calymene;§ but when we remember that even experienced observers in the White Mountains for a time mistook for remains of crustacea and brachiopods, certain obscure forms, which they afterwards found not to be organic, and that Dana, in this connection, has called attention to the deceptive resemblance to fossils presented by some imperfectly developed chiastolite crystals in the same region,|| we may well require a verification of Boblaye’s obser- vation, especially since we find that more recently D’Archiac and Dalimier agree with De Beaumont and Dufrenoy in placing * Synopsis of British Paleozoic Rocks, p. Ixxxiv, being an Introduction to McCoy’s Brit. Pal. Fossils (1855). + Harkness and Salter, Quar. Jour. Geol. Soc., XIX. 135. t Geol. Journal (1845), IV. 583. § Bull. Soc. Geol. de Fr., X. 227. || American Journal of Science (2), I. 415, V. 116. 12 * R Ld iss “i ai Ss an Ds aia: y 274 GEOGNOSY OF THE APPALACHIANS. (XIII, the chiastolite-schists of Brittany at the very base of the tran- sition sediments, marking the summit of the crystalline schists.* With regard to the crystalline schists of Lakes Huron and Superior, to which the name of the Huronian system has been given, the observations of all who have studied the region concur in placing them unconformably beneath the sediments which are supposed to represent the base of the New York system ; while, on the other hand, they rest unconformably on the Laurentian gneiss, fragments of which are included in the Huronian conglomerates. The gneissic series of the Green Mountains had, however, as we have seen, been, since 1841, regarded, by the brothers Rogers, Mather, Hall, Hitchcock, Adams, Logan, myself, and others; as Lower Silurian (Cam- brian of Sedgwick). Eaton and Emmons had alone claimed ‘for it a pre-Cambrian age, until, in 1862, Macfarlane ventured to unite it with the Huronian system, and to identify both with the crystalline schists of a similar age in Norway. Later ob- servations in Michigan justify still further this comparison; for not only the more schistose beds of the Green Mountain series, but even the mica-schists of the third or White Mountain series, with staurolite and garnet, are represented in Michigan, as appears by the recent collections of Major Brooks of the Geological Survey of Michigan, kindly placed in my hands for ~ examination. He informs me that these latter schists are the highest of the crystalline strata in the northern peninsula, - (Ante, page 18.) | To the north of Lake Superior, as I have already shown elsewhere, the schists of this third series, which, as early as 1861, I compared to those of the Appalachians, are widely spread ; while in Hastings County, forty miles north of Lake Ontario, rocks having the mineralogical and lithological charac- ters both of the second and third series are found resting on the first or Laurentian series, the three apparently unconform- able, and all in turn overlaid by horizontal Trenton limestone.t We have shown, that in Pennsylvania, while some of these * Bull. Soc. Geol. de Fr. (2), XVIII. 664. + American Journal of Science (2), XXXI. 395, and L. 85. i F e - & n! %. i EN MOLI VRAIS lh Se cet eee | eT eS aw: ae XIIL] GEOGNOSY OF THE APPALACHIANS. 275 schists of the second and third series were regarded as altered primal rocks by H. D. Rogers, others, lithologically similar, were referred by him to the older so-called azoic series, which we believe to be their true position. Professor W. B. Rogers has lately informed me that in Virginia a gneissic series, having the characters of the Green Mountain rocks, is clearly overlaid unconformably by the lowest primal paleeozoic strata of the ~ region. Coming northward, the uncrystalline argillites and sandstones holding Paradoxides, at Braintree, Massachusetts,* and St. John, New Brunswick, overlie unconformably crystal- line schists of the second series; and in the latter region, in one locality, rocks which are by Bailey and Matthew regarded of Laurentian age. In Newfoundland, in like manner, a great series of crystalline schists, in which Mr. Murray recognizes the Huronian system as first studied and described by him in the West, is unconformably overlaid by a group of sandstones, lime- stones, and slates, holding Paradoxides. The peculiar gneisses and mica-schists of the White Mountain series appear to be developed to a great extent in Newfoundland, which led me to propose for them the name of the Terranovan system.t From the part which the ruins of these rocks play in the production of succeeding sediments, it is not always easy to define the limits between the ancient mica-schists and the Cambrian strata in these northeastern regions. It is not im- possible that the two may graduate into each other, as some have supposed, in Newfoundland and Nova Scotia ; but until further light is thrown upon the subject, I am disposed to re- gard the relation between the two as one of derivation rather than of passage. We have already alluded to the history of the rocks of the White Mountains, formerly looked upon as primary, and by Jackson described as an old granitic and gneissic axis uplifting the more recent Green Mountain rocks. Their manifest differ- ences from the more ancient gneiss of the Adirondacks, and their apparent superposition to the Green Mountain series, then * Hunt, Proc. Bost. Soc. Nat. Hist., October 19, 1870. + American Journal of Science (2), L. 87. 276 GEOGNOSY OF THE APPALACHIANS, [XI regarded by the Messrs. Rogers as belonging to the Champlain division, led them, in 1846, to look upon the White Mountains as altered strata belonging to the Levant division of their classification, corresponding to the Oneida, Medina, and Clinton of the New York system. In 1848, Sir William Logan came to a somewhat similar conclusion. Accepting, as we have seen, the view of Emmons, that the strata about Quebec included a portion of the Levant division, and regarding the Green Moun- tain gneisses as the equivalents of these, he was induced to place the White Mountain rocks still higher in the geological series than the Messrs. Rogers had done, and expressed his belief that they might be the altered representatives of the New York system, from the base of the Lower Helderberg to the top of the Chemung; in other words, that they were not Middle Silurian, but Upper Silurian and Devonian. This view, adopted and enforced by me,* was further supported by Lesley in 1860, and has been generally accepted up to this time. In 1870, however, I ventured to question it, and in a published letter, addressed to Professor Dana, concluded, from a great number of facts, that there exists a system of crystalline schists distinct from, and newer than, the Laurentian and Huronian, to which I gave the provisional name of Terranovan [since ealled Montalban], constituting the third or White Mountain series, which appears not only throughout the Appalachians, but westward to the north of Lake Ontario, and around and beyond Lake Superior.t Although I have, in.common with most other American geologists, maintained that the crystalline rocks of the Green Mountain and White Mountain series are altered paleozoic sediments, I find, on a careful examination of the evidence, no satisfactory proof of such an age and origin, but an array of facts which appear to me incompatible with the hitherto received view, and lead me to conclude that the whole of our crystalline schists of eastern North America are not only pre-Silurian but pre-Cambrian in age. * Geological Survey of Canada, Report 1847-48, p. 58; also American Journal of Science (2), IX. 19. t+ American Journal of Science (2), L. 83. aga, we a ae Re cet et eigen FSP CS press hm st OP Zt eS eh XIIL] GEOGNOSY OF THE APPALACHIANS. 277 In what precedes I have endeavored to discuss briefly and impartially some of the points in the history of the older rocks, and of the views which during the past thirty years have been entertained as to their age and geological relations, both in America and in Europe. I have said some things which will provoke criticism, and at the same time, I trust, lead to further study of these rocks, a correct knowledge of which lies at the basis of geological science. I cannot, however, conclude this part of my subject without referring to the views put forth in 1869 by Professor Hermann Credner, of Leipzig, in an essay on the Eozoiec or pre-Silurian formations of North America.* With Macfarlane, he refers to the Huronian the gneissic series of the Green Mountains, but includes with it, as part of the Huronian system, the so-called Lower Taconic rocks of Vermont, “with remains of annelids and erinoids.” Credner thus falls into the very error against which Emmons warned American geologists, namely, the confounding in one system the ancient crystalline schists with the newer fossiliferous sediments. Resting unconformably on these, he places, first, the Upper Taconic, corresponding, according to him, to a part of the Quebec group; and, second, the Potsdam sandstone. In this he has copied, for the most part, Marcou, who, however, groups the whole of these various divisions in the Taconic system ; while Credner, rejecting the name, unites a portion of the Taconic of Emmons with the Huronian system, and refers the other portion, together with the Potsdam, to the Silurian. These same views are set forth in a more recent paper, by the same author, on the Alleghany system, which is - accompanied with sections and a geologically colored map.t In this, not content with including in the Huronian both the . fossiliferous strata of the Levis formation and the crystalline schist§ of the Green Mountains, he refers the gneisses and mica- schists of the White Mountains to the same system ; while the broad area of similar rocks from their base to the sea at Port- * Die Gliederung der Eozoischen Formationsgruppe, u. s. w., p. 53. Halle, 1869. t Petermann’s Geographische Mittheilungen. 2 Heft, 1871. 278 GEOGNOSY OF THE APPALACHIANS. [XIIL. land is regarded as Laurentian. This, on Credner’s map, is also made to include, with the exception of the White Moun- tains themselves, all the rocks of the third er White Moun- ‘tain series, which cover so large a part of New England. Those who have followed the historical sketch already given can see how widely these notions of Credner differ from those of Em- mons, and from all other American geologists, and how much they are at variance with the present state of our knowledge. It is much to be regretted that so good a geologist and litholo- gist should, from a too superficial study, have fallen into these errors, which can only retard the progress of comparative ge- ognosy, for which he has done so much. In England, again, Credner confounds the Cambrian and Huronian, referring to the latter system the whole of the Longmynd rocks with their characteristic Cambrian fauna, — a view which is supported only by the conjectured Cambrian age of the crystalline schists of Anglesea, which are pre-Cambrian and probably Huronian, like the Urschiefer of Scandinavia, which Credner correctly refers to the latter system, as Macfarlane and Bigsby had done before him. He, moreover, recognizes in the similar crystalline schists of Scotland, the Urals, and various parts of Germany, includ- ing those of Bavaria and Bohemia, a newer system, overlying the primary or Laurentian gneiss, and corresponding to the Huronian or Green Mountain series of North America; while he suggests a correspondence with similar rocks in Japan, Ben- gal, and Brazil. In a collection of rocks brought from the latter country by Professor C. F. Hartt, I have found, as else- where stated,* what appear to be representatives of the three types of crystalline schists which have been distinguished in eastern North America. | [I have not in the preceding discussion alluded tothe Norian series, otherwise called the Labradorian or Upper Laurentian, for the reason that although largely developed in the southern part of the Adirondack region, it does not occur on our line of section, and, moreover, was not certainly known in the Appala- chians. Subsequent observations of the Geological Survey of e * The Nation, December 1, 1870; and Hartt’s Geology of Brazil, p. 550. XIII] GEOGNOSY OF THE APPALACHIANS. 279 New Hampshire having, however, shown the existence of rocks supposed to belong to this series in the region of the White Mountains, a brief history of it will not be out of place; while for further details the student is referred to a paper by the present writer in the American Journal of Science for February, 1870 ((2) XLIX. 180). The rocks of this series were recognized by Emmons in Essex County, New York, and described by him in 1842, in the geology of the Northern District of that State (page 27). They were by him correctly regarded as identical with the hypersthene rock of the Western Islands of Scotland, described by MacCulloch, and were looked upon as intru- sive. Similar rocks in erratic masses abound in the valley of the St. Lawrence, but were first found in place by Logan, and described by me in the Report of the Geological Survey of Canada for 1852 (page 167). They were shown by Logan to be- long to a great stratified series, which was at first included by him ‘in the Laurentian. Subsequent investigation, however, showed that these rocks rest unconformably on the Laurentian gneiss, and he therefore called them Upper Laurentian. Inasmuch as they are largely displayed in Labrador, and moreover consist in great part of labradorite feldspar, the name of the Labradorian series was also given to them. In 1870 it was shown by me, in the paper above referred to, that these rocks were apparently identical with the norites of Esmark, found in Norway under conditions very like those of the Labradorian rocks of North America, and that this name of norite, given in allusion to that country, has the right of priority. I therefore propose to speak of them by that name, and moreover to designate as the Norian series the great formation of crystalline stratified rocks of which the norites make ‘up so large a part. The typical norites consist chiefly of a triclinic feldspar, varying in com- position from anorthite to andesine, but generally near labra- dorite in composition. The color of these rocks is ordinarily some shade of blue, —from bluish-black or violet to bluish- gray, smoke-gray, or lavender, more rarely passing into flesh- red, and occasionally greenish-blue, greenish or bluish white. The weathered surfaces are opaque white. These norites are 280 GEOGNOSY OF THE APPALACHIANS, (XIII. sometimes nearly pure feldspar, but often include small portions of hypersthene, pyroxene, or hornblende,— the former two being sometimes associated in the same specimen, and in con- tact with each other. A black mica (biotite), red garnet, epi- dote, chrysolite, and menacannite (titanic iron) are frequently present in these rocks ; quartz, however, is rarely seen, and then only in small quantities. Through an admixture of the first- named minerals these norites pass into hyperite, diabase, and diorite. The norites vary in texture, being sometimes coarsely granitoid, and at other times fine grained and nearly impalpable. The coarser varieties often present large cleavable masses, show- ing the striz characteristic of the polysynthetic macles of the triclinic feldspars, and sometimes exhibit a fine play of colors, as in the well-known specimens from Labrador. A gneissic structure is well marked in many of the less coarse-grained varieties of norite, and the lines of bedding are shown by the arrangement of the various foreign minerals. Although norites predominate in the Norian series, they are found in the area of these rocks which is seen to the north of Montreal to be in- terstratified with beds of micaceous orthoclase-gneiss, quartzite, and crystalline limestone, not unlike those met with in the Laurentian and White Mountain series, It was from their dis- tribution in this region that Sir William Logan was enabled to show that the rocks of the Norian series rest unconformably upon the gneisses and limestones of the Laurentian. Further evidence of the same kind was obtained by Mr. Richardson, in 1869, on the north side of the Gulf of St. Lawrence, where rocks of the Norian series were found to lie in discordant stratification, and at moderate angles on the nearly vertical Laurentian gneiss. The norites may be readily studied in Essex County, New York, where they reach the shore of Lake Champlain just above the town of Westport, and include the great deposits of titanic iron ores of this region. ‘The titanic ores of Bay St. Paul, Lake St. John, and the Bay of Seven Islands, in Canada, also occur in Norian rocks. In all of these localities they appear to be directly superposed on the Lauren- tian ; but in the vicinity of St. John, New Brunswick, a small Petite. pte XIIL.] GEOGNOSY OF THE APPALACHIANS. 281 area of norites is found to occupy a position in contact with rocks regarded as belonging to the Huronian and the White Mountain series. The rocks which are referred to the Norian series in the White Mountain region, according to Hitchcock, rest upon the gneisses and mica-schists of the White Moun- tains ; while these overlie unconformably a more ancient series of granitoid gneiss, supposed to represent the Laurentian. The hypersthene rock of Skye was by MacCulloch regarded as an eruptive rock ; and Giekie, in his memoir on the geology of a part of Skye, published in 1858 (Quarterly Journal of the Geological Society, XIV. page 1), appears to include them with certain syenites and greenstones, which he vaguely speaks of as not intrusive, though eruptive after the manner of granites (loc. cit., pp. 11-14). Specimens of these rocks from Loch Scavig, and others in MacCulloch’s collection from that vicinity, which I have examined, are, however, identical with the North American norites, whose stratified character is undoubted. I called attention to these resemblances in the Dublin Quarterly Journal for July, 1863 (ante, page 33); and Professor Haugh- ton, of Dublin, who in 1864 visited Loch Scavig, subsequently described and analyzed the norite from that locality ; which is, according to him, evidently “a bedded metamdrphic rock.” (Dublin Quarterly Journal for 1865, page 94.) The distribution of the crystalline rocks of the Norian, Huronian, and Montalban or White Mountain series would -seem to show that ‘these are remaining portions of great, dis- tinct, and unconformable series, once widely spread out over a more ancient floor of granitic gneiss of Laurentian age; but that the four series thus indicated include the whole of the crystalline stratified rocks of New England is by no means certain. How many more such formations may have been laid down over this region, and subsequently swept away, leaving no traces, or only isolated fragments, we may never know ; but it is probable that a careful study of the geology of New Eng- land and the adjacent British Provinces may establish the ex- istence of many more than the four series above enumerated. When it is considered that we find within the limits of southern 282 GEOGNOSY OF THE APPALACHIANS. [XIIt. ‘New Brunswick alone small areas of palzozoic sediments which are shown by their organic remains to belong to not less than five periods, namely, Menevian, Lower Helderberg, Chemung, Lower Carboniferous, and Carboniferous, all perfectly well dis- tinguished, and each reposing directly upon the ancient erys- talline rocks, we are prepared for a history not less varied and complex for the rocks belonging to Eozoic time. (See the author’s Address before the American Institute of Mining En- | gineers, in their Proceedings for February, 1873.) Professor C. H. Hitchcock, from the results of the Geological ! Survey of New Hampshire, now in progress, announces, in 1873 and 1874, a large number of divisions in the crystalline rocks a of this State. The Norian series there, according to him, rests ; unconformably upon ancient gneisses, which, as he suggests, be- ) long perhaps to the Laurentian, the appearance of which in north- eastern Massachusetts I pointed out in 1870. With the Norian he has however included a great series of granites and of compact felsites, some of which, from specimens, appear identical with the orthophyres of our eastern coasts, of Lake Superior, and Missouri. These, so far as my observations go, are in no way related to the Norian, but probably belong to the Huronian series. (Ante, page 187.) Besides these, he recognizes the White Mountain series of gneisses and andalusite-schists (Montalban). He describes, under the name of gneiss, the so-called granites of Concord and Fitzwilliam, which I had already, in 1870, declared to be gneisses associated with the mica-schists of the Montalban series. (Ante, page 188.) This series he supposes to be more ancient than the well-characterized Huronian rocks of the State ; but admits in addition a ‘second and more recent series of mica- schists with andalusite and staurolite, named the Coéds group. Further researches in this disturbed region will be required to determine whether, besides this series of andalusite and stau- rolite-bearing mica-schists, which (associated with gneisses) oceurs in other regions, as I have in the previous pages of this essay endeavored to show, above the Huronian, there is another and an older series of similar rocks, or whether the two are one and the same series, repeated by stratigraphical accidents. ] ee ae pee: XUI.] ORIGIN OF CRYSTALLINE ROCKS. 283 II. Tue Oricin or CrystaLLine Rocks. We now approach the second part of our subject, namely, the genesis of the crystalline schists whose history we have just discussed. The origin of the mineral silicates which make up a great portion of the crystalline rocks of the earth’s sur- face is a question of much geological interest, which has been to a great degree overlooked. The gneisses, mica-schists, and argillites of various geological periods do not differ very greatly in chemical constitution from modern mechanical sediments, and are now, by the greater number of geologists, regarded as resulting from a molecular rearrangement of similar sediments formed in earlier times by the disintegration of previously ex- isting rocks, not very unlike them in composition ; the oldest known formations being still composed of crystalline stratified deposits presumed to be of sedimentary origin. Before these the imagination conceives yet earlier rocks, until we reach the surface of unstratified material which the globe may be supposed to have presented before water had begun its work. It is not, however, my present plan to consider, this far-off beginning of sedimentary rocks, which I have elsewhere discussed. (Ante, page 63.) ‘ P Apart from the rocks just referred to, whose composition may be said to be essentially quartz and aluminous silicates, chiefly in the forms of feldspars and micas, there is another class of crystalline silicated rocks, which, though far less important in bulk than the last, is of great and varied interest to the litholo- gist, the mineralogist, the geologist, and the chemist. The rocks of this second class may be defined as consisting in great part of the silicates of the protoxide bases, lime, magnesia, and fer- rous oxide, either alone, or in combination with silicates of alumina and alkalies. They include the following as their chief constituent mineral species : pyroxene, hornblende, chrys- olite, serpentine, talc, chlorite, epidote, garnet, and triclinic feldspars, such as labradorite. The great types of this second class are not less well defined than the first, and consist of py- roxenic and hornblendic rocks, passing into diorites, diabases, 284 ORIGIN OF CRYSTALLINE ROCKS. (XI ophiolites, and talcose, chloritic, and epidotic rocks. Inter- mediate varieties resulting from the association of the minerals of this class with those of the first, and also with the materials of non-silicated rocks, such as limestones and dolomites, show an occasional blending of the conditions under which these various types of rocks were formed. The distinctions just drawn between the two great divisions of silicated rocks are not confined to stratified deposits, but are equally well marked in eruptive and unstratified masses, among which the first type is represented by trachytes and granites; and the second, by dolerites and diorites. This fun- damental difference between acidic and basic rocks, as the two classes have been called, finds its expression in the theories of Phillips, Durocher, and Bunsen, who have deduced all silicated rocks from two supposed layers of molten matter within the earth’s crust, consisting respectively of acidic and basic mix- tures ; the trachytic and pyroxenic magmas of Bunsen. From these, by a process of partial crystallization and eliquation, or by commingling in various proportions, those eruptive rocks which depart more or less from the normal types are supposed by the theorists of this school to be generated. (Ante, pages 3 and 23.) The doctrine that. these eruptive rocks are not derived directly from a hitherto uncongealed nucleus, but are softened and crystallized sediments, in fact, that the whole of the rocks at present known to us have at one time been aqueous deposits, has, however, found its advocates. In sup- port of this view, I have endeavored to show that the natural result of forces constantly in operation tends to resolve me- chanical sediments into two classes : the one coarse, sandy, and permeable ; the other fine, clayey, and impervious. The action of infiltrating atmospheric waters on the first and more sili- cious strata will remove from them lime, magnesia, iron-oxide, and soda, leaving behind silica, alumina, and potash,—the — elements of granitic, gneissic, and trachytic rocks. The finer and more aluminous sediments (including the ruins of the soft and easily abraded silicates of the pyroxene group), resisting _ the penetration of the water, will, on the contrary, retain their a a at g owe XIII.] ORIGIN OF CRYSTALLINE ROCKS. 285 alkalies, lime, magnesia, and iron, and thus will have the com- position of the more basic rocks. [We find, in fact, in the sediments of various geological periods, not only beds of clay and marl corresponding to the second class, but strata made up in great part of mechanically disintegrated though chemi- cally unchanged orthoclase, with quartz, the débris of granitic rocks, constituting what is called arkose. Beds of this kind, as will be seen in the following paper on the Geology of the Alps, have even been mistaken for granite and gneiss, and similar recomposed rocks occur in the mesozoic sandstones of New England and New Jersey. Such processes of disintegra- tion and decay have probably been going on from very re- mote times, and the crystalline rearrangement of the resulting rocks may be supposed to give rise to true crystalline schists, or their aqueo-igneous fusion to eruptive rocks. (Ante, pages 14 and 23.)| A little consideration will, however, show that this process is inadequate to explain the production of many of the vari- eties of crystalline silicated rocks. Such are serpentine, steatite, chrysolite, hornblende, diallage, chlorite, pinite, labradorite, and orthoclase, all of which mineral species form rock-masses by themselves, frequently almost without admixture. No geological student will now question that all of these rocks occur as members of stratified formations. Moreover, the man- ner in which serpentines are found interstratified with steatite, chlorite, argillite, diorite, hornblende, and feldspar rocks, and these, in their turn, with quartzites and orthoclase rocks, is such as to forbid the notion that all of these various materials have been deposited, with their present composition, as me- chanical sediments from the ruins of pre-existing rocks of plu- tonic origin. There are two hypotheses which have been proposed to ex- plain the origin of these various silicated rocks, and especially of the less abundant, and, as it were, exceptional species just mentioned. The first of these supposes that the minerals of which they are composed have resulted from an alteration of previously existing minerals of plutonic rocks, often very unlike Pe ep ee ee mee OS et fe Sn ne ore ( 286 ORIGIN OF CRYSTALLINE ROCKS. [xin = 9 in composition to the present, by the taking away of certain elements and the addition of certain others. This is the theory of metamorphism by pseudomorphic changes, as they . 4 are called, and is the one taught by the now reigning school of chemical geologists, of which the learned and laborious Bischof, whose recent death science deplores, may be regarded as the great exponent. The second hypothesis supposes that the elements of these various rocks were originally deposited as, for the most part, chemically formed sediments, or precipitates ; _ and that the subsequent changes have been simply molecular, or, at most, confined in certain cases to reactions between the mingled elements of the sediments, with the elimination of water and carbonic acid. It is proposed to consider briefly these two opposite theories, which seek to explain the origin of the rocks in question respectively by pseudomorphic changes in pre-existing crystalline plutonic rocks, and by the erystal- lization of aqueous sediments, for the most part chemically formed precipitates. Mineral pseudomorphism, that is to say, the assumption by one mineral substance of the crystalline form of another, may arise in several ways. First of these is the filling up of a mould left by the solution or decomposition of an imbedded crystal, a process which sometimes takes place in mineral veins, where the processes of solution and deposition can be freely carried on. Allied to this is the mineralization of organic remains, where carbonate of lime or silica, for example, fills the pores of wood. When subsequent decay removes the woody tissue, the vacant spaces may, in their turn, be filled by the same or another species.* In the second place we may consider pseudomorphs from alteration, which are the result of a gradual change in the composition of a mineral species. This process is exemplified in the conversion of feldspar into kaolin by the loss of its alkali and a portion of silica, and the fixa- tion of water, or in the change of chalybite into limonite by a the loss of carbonic acid and the absorption of water and 3 exygen. x * Hunt on the Silicification of Fossils, Canadian Naturalist, New Series, I. 46, XIII.] _ ORIGIN OF CRYSTALLINE ROCKS. 287 The doctrine of pseudomorphism by alteration, as taught by - Gustaf Rose, Haidinger, Blum, Volger, Rammelsberg, Dana, Bischof, and many others, leads them, however, to admit still greater and more remarkable changes than these, and to main- tain the possibility of converting almost any silicate into any other. Thus, by referring to the pages of Bischof’s Chemical Geology, it will be found that serpentine is said to exist as a pseudomorph after augite, hornblende, chrysolite, chondrodite, garnet, mica, and probably also after labradorite and even orthoclase. Serpentine rock or ophiolite is supposed to have resulted, in different cases, from the alteration of hornblende- rock, diorite, granulite, and even granite. Not only silicates of ’ protoxides and aluminous silicates are conceived to be capable of this transformation, but probably also quartz itself; at least Blum asserts that meerschaum, a closely related silicate of magnesia, which sometimes accompanies serpentine, results from the alteration of flint ; while according to Rose, serpen- tine may even be produced from dolomite, which we are told is itself produced by the alteration of limestone. But this is not all, — feldspar may replace carbonate of lime, and carbon- ate of lime, feldspar ; so that, according to Volger, some gneis- soid limestones are probably formed from gneiss by the sub- stitution of calcite for orthoclase. In this way, we are led from gneiss or granite to limestone, from limestone to dolomite, and from dolomite to serpentine, or, more directly, from gran- ite, granulite, or diorite to serpentine at once,. without passing through the intermediate stages of limestone and dolomite, till we are ready to exclaim in the words of Goethe, — ** Mich angstigt das Verfingliche Im widrigen Geschwiatz, Wo Nichts verharret, Alles flieht, Wo schon verschwunden was man sieht,” * which we may thus translate: “I am vexed with the sophistry in their contrary jargon, where nothing endures, but all is fugitive, and where what we see has already passed away.” Chinesisch-Deutsche Jahres und Tages-Zeiten, XI. 288 ORIGIN OF CRYSTALLINE ROCKS.. [XIIt. By far the greater number of cases on which this general theory of pseudomorphism by a slow process of alteration in minerals has been based are, as I shall endeavor to show, ex- amples of the phenomenon of mineral envelopment, so well studied by Delesse in his essay on Pseudomorphs,* and may be considered under two heads: first, that of symmetrical envelopment, in which one mineral species is so enclosed within the other that the two appear to form a single crystal- line individual. Examples of this are seen when prisms of cyanite are surrounded by staurolite, or staurolite crystals com- pletely enveloped in those of cyanite, the vertical axes of the two prisms corresponding. Similar cases are seen in the en- closure of a prism of red in an envelope of green tourmaline, of allanite in epidote, and of various minerals of the pyrox- ene group in one another. The occurrence of muscovite in lepidolite, and of margarodite in lepidomelane, or the inverse, are well-known examples, and, according to Scheerer, the erys- tallization of serpentine around a nucleus of olivine is a similar case. This phenomenon of symmetrical envelopment, as re- marked by Delesse, shows itself with species which are gener- ally isomorphous or homceomorphous, and of related chemical composition. Allied to this is the repeated alternation of crys- talline laminz of related species, as in perthite, the crystalline cleavable masses of which consist of thin, alternating layers of orthoclase and albite. Very unlike to the above are those cases of envelopment in which no relations of crystalline symmetry nor of similar chemical constitution can be traced. Examples of this kind are seen in garnet crystals, the walls of which are shells, sometimes no thicker than paper, enclosing, in different exam- ples, crystalline carbonate of lime, epidote, chlorite, or quartz. In like manner, crystalline shells of leucite enclose feldspar, hollow prisms of tourmaline are filled with crystals of mica or with hydrous peroxide of iron, and crystals of beryl with a granular mixture of orthoclase and quartz, holding small crys- tals of garnet and tourmaline, a composition identical with the — * Annales des Mines (5), XVI. 317-392. rere . Ba: = | 7 e , . .' i 4 XII] ORIGIN OF CRYSTALLINE ROCKS. 289 enclosing granitic vein-stone.* Similar shells of galenite and of zircon, having the external forms of these species, are also found filled with calcite. In many of these cases the process seems to have been first the formation of a hollow mould or skeleton-crystal (a phenomenon sometimes observed in salts crystallizing from solutions), the cavity being subsequently filled with other matters. (Ante, page 212.) Such a process is conceivable in free crystals formed in veins, as, for example, galenite, zircon, tourmaline, beryl, and some examples of gar- net, but is not so intelligible in the case of those garnets im- bedded in mica-schist, studied by Delesse, which enclosed within their crystalline shells irregular masses of white quartz, with some little admixture of garnet. Delesse conceives these and similar cases to be produced by a process analogous to that seen in the crystallizations of calcite in the Fontainebleau sand- stone ; where the quartz grains, mechanically enclosed in well- defined rhombohedral crystals, equal, according to him, sixty- five per cent of the mass. Very similar to these are the crys- tals with the form of orthoclase, which sometimes consist in large part of a granular mixture of quartz, mica, and ortho- clase, with a little cassiterite, and in other cases contain two thirds their weight of the latter mineral, with an admixture of orthoclase and quartz. Crystals with the form of scapolite, but made up, in a great part, of mica, seem to be like cases of envelopment, in which a small proportion of one substance in the act of crystallization compels into its own crystalline form a large portion of some foreign material, which may even so mask the crystallizing element that this becomes overlooked, as of secondary importance. The substance which, under the name of houghite, has been described as an altered spinel, is found by analysis to be an admixture of véllknerite with a variable proportion of spinel, which, in some specimens, does not exceed eight per cent, but to which, nevertheless, these erystalloids (to use the term suggested by Naumann) appear to owe their more or less complete octohedral form.t * Report Geol. Survey of Canada, 1866, p. 189. + Ibid., pp. 189, 213 ; American Journal of Science (3), I. 188. 13 8 290 ORIGIN OF CRYSTALLINE ROCKS. _[XII. « The above characteristic examples of symmetrical and asym- metrical envelopment are cited from a great number of others which might have been mentioned. Very many of these are by the pseudomorphists regarded as results of partial altera- tion. Thus, in the case of associated crystals of andalusite and cyanite, Bischof does not hesitate to maintain the deriva- tion from andalusite of the latter species by an elimination of quartz ; more than this, as the andalusite in question oceurs in a granite-like rock, he suggests that itself is a product of the alteration of orthoclase. In like manner the mica, which in some cases coats tourmaline, and in others fills hollow prisms of this mineral, is supposed to result from a subsequent altera- tion of crystallized tourmaline. So in the case of shells of leucite filled with feldspar, or of garnet enclosing epidote, or chlorite, or quartz, a similar transformation of the interior is supposed to have been mysteriously effected, while the external portion of the crystal remains intact. Again, the aggregates. of eassiterile, quartz, and orthoclase, having the form of the lat- ter, are, by Bischof and his school, looked upon as results of a partial alteration of previously formed orthoclase crystals. It needed only to extend this view to the crystals of calcite enclosing sand-grains, and regard these as the result of a par- tial alteration of the carbonate of lime, There is absolutely no proof that these hard crystalline substances can undergo the changes supposed, or can be absorbed and modified like the tissues of a living organism, It may, moreover, be confidently affirmed that the obvious facts of envelopment are adequate to explain all the cases of association upon which this hypothesis of pseudomorphism by alteration has been based. Why the change should extend to some parts of a crystal and not to others, why in some cases the exterior of the crystal is altered, while in others the centre alone is removed and replaced by a different material, are questions which the advocates of this fanciful hypothesis have not explained. As taught by Blum and Bischof, however, these views of the alteration of mineral species have not only been generally accepted, but have formed the basis of the generally received theory of rock-metamor- phism. XIII] _ ORIGIN OF CRYSTALLINE ROCKS. 291 Protests against the views of this school have, however, not been wanting. Scheerer, in 1846, in his researches in Polymeric Isomorphism,* attempted to show that iolite and aspasiolite, a hydrous species which had been looked upon as resulting from its alteration, were isomorphous species crystallizing to- gether, and, in like manner, that the association of chrysolite and serpentine in the same crystal, at Snarum in Norway, was a case of envelopment of: two isomorphous species. In both of these instances he maintained the existence of isomorphous relations between silicates in which 3HO replace MgO. He hence rejected the view of Gustaf Rose, that these serpentine erystals were results of the alteration of chrysolite, and sup- ported his own by reasons drawn from the conditions in which the crystals occur. In 1853 I took up this question and en- deavored to show that these cases of isomorphism described by Scheerer entered into a more general law of isomorphism, pointed out by me among homologous compounds differing in their formulas by »M,0, (M = hydrogen or a metal). I in- sisted, moreover, on its bearing upon the received views of the alteration of minerals, and remarked: ‘“ The generally admitted notions of pseudomorphism seem to have originated in a too exclusive plutonism, and require such varied hypotheses to explain the different cases, that we are led to seek for some more simple explanation, and to find it, in many instances, in the association and crystallizing together of homologous and isomorphous species.” + Subsequently, in 1860, I combated the view of Bischof, adopted by Dana, that “regional meta- morphism is pseudomorphism on a grand scale,” in the follow- ing terms : — “The ingenious speculations of Bischof and others, on the pos- sible alteration of mineral species by the action of various saline and alkaline solutions, may pass for what they are worth, although we are satisfied that by far the greater part of the so-called cases of pseudomorphism in silicates are purely imaginary, and, when real, are but local and accidental phenomena. Bischof’s notion of * Pogg. Annal., LXVIII. 319. ¢ American Journal of Science (2), XVI. 218. OT re i a ed is ae oF a a ne “es ee re gts of a i 3) 5 4 292 ORIGIN OF CRYSTALLINE ROCKS. [XIII the pseudomorphism of silicatk like feldspars and pyroxenes pre- supposes dhe existence of crystalline rocks, whose generation this neptunist never attempts to explain, but takes his starting-point from a plutonic basis.” I then asserted that the problem to be solved in regional metamorphism is the conversion of sedimentary strata, “ de- rived by chemical and mechanical agencies from the ocean- waters and pre-existing crystalline rocks into aggregations of crystalline silicates. These metamorphic rocks, once formed, are liable to alteration only by local and superficial agencies, and are not, like the tissues of a living organism, subject to incessant transformations, the pseudomorphism of Bischof.” * I had not, at that time, seen the essay by Delesse on Pseudo- morphs, already referred to, published in 1859, in which he maintained views similar to those set forth. by me in 1853 and 1860, declaring that much of what had been regarded as pseudomorphism had no other basis than the observed asso- ciations of minerals, and that often “the so-called metamor- phism finds its natural explanation in envelopment.” These views he ably and ingeniously defended by a careful discussion of the whole range of facts belonging to the history of the subject. | My own expression of opinion on this question, in 1853, had been adversely criticised, and I had been charged with a want of comprehension of the question. It was, therefore, with no small pleasure, that I not only saw my views so ably supported by Delesse, but read the language of Carl Friedrich Naumann, who in 1861 wrote to Delesse as follows, referring to his essay just noticed : — “You have rendered a veritable service to science in restricting pseudomorphs to their true limits, and separating what had been erroneously united to them. As you have remarked, envelopments have, for the most part, nothing in common with pseudomorphs, and it is inconceivable that they have been united by so many min- eralogists and geologists. It appears to me, moreover, that they commit an analogous error, when they regard gneisses, amphibo- * American Journal of Science (2), XXX. 135. ae a er A ars al i Lee TH? as See Tha ae XIII.] ORIGIN OF CRYSTALLINE ROCKS. —-293 lites, etc., as being, all of them, the results of metamorphic epi- genesis, and not original rocks. It is precisely because pseudomor- phism has been so often confounded with metamorphism, that this error has found acceptance. I only admit a pseudomorph where there is some crystal the form of which has been preserved. There are very many metamorphic substances which are in no sense of the word, pseudomorphs. Had the name of crystalloid been chosen, instead of pseudomorph, this confusion would certainly have never found its way into the science. I think, with you, that the envel- opment of two minerals is most generally explained by a contem- poraneous and original crystallization. Secondary envelopments, however, exist, and such may be called pseudomorphs or crystal- loids, if they reproduce exactly the form of the crystal enveloped, whether this last still remains, or has entirely disappeared.” * It is unnecessary to remark that the view of Delesse and Naumann—namely, that the so-called cases of pseudomorphism, on which the theory of metamorphism by alteration has been built, are, for the most part, examples of association and envel- opment, and the result of a contemporaneous and original crystallization — is identical with the view suggested by Scheerer,-and generalized by myself long before, when, in 1853, I sought to explain the phenomena in question by “ the associa- tion and crystallizing together of homologous and isomorphous species.” | Later, in 1862, I wrote as follows :— “ Pseudomorphism, which is the change of one mineral species into another by the introduction or the elimination of some element or elements, presupposes metamorphism (i. e. metamorphic or crys- talline rocks), since only definite mineral species can be the subjects of this process. To confound metamorphism with pseudomorphism, as Bischof and others after him have done, is therefore an error. It may be further remarked, that, although certain pseudomorphic changes may take place in some mineral species, in veins and near the surface, the alteration of great masses of silicated rocks by such a process is as yet an unprovéd hypothesis.” + * Bull. Soc. Geol. de France (2), XVIII. 678. + Descriptive Catalogue, Crystalline Rocks of Canada, p. 80, London Ex- hibition, 1862 ; also Canadian Naturalist, VII. 262; Dublin Quar. Journal, July, 1863; and American Journal of Science (2), XXXVI. 218. 294 ORIGIN OF CRYSTALLINE ROCKS. [XIIL Thus this unproved theory of pseudomorphism, as taught by Bischof, does not, even if admitted to its fullest extent, advance us a single step towards a solution of the problem of the origin of the various silicates which, singly or intermingled, make up beds in the crystalline schists. Granting, for the sake of argu- ment, that serpentine results from the alteration of chrysolite or labradorite, and steatite or chlorite from hornblende, the origin of these anhydrous silicates, which are the subjects of the supposed change, is still unaccounted for. The explanation of this short-sightedness is not far to seek ; as- already remarked, Bischof, although a professed neptunist, starts from a plutonic basis. [The notion of the plutonic origin of crystalline stratified rocks has in fact found many advocates, as may be seen by reference to pages of Naumann’s Lehrbuch der Geognosie. This learned author himself speaks of them as “those enig- matical deepest-lying rocks which resemble sedimentary strata in possessing more or less perfect stratification, while resem- bling eruptive rocks in mineral composition and crystalline structure ” (oc. cit., Vol. II. p. 8, et seg.). He declares them to be neither sedimentary nor eruptive in the ordinary sense of those terms ; and evidently leans to the notion, of which he speaks with favor, that they are in some way the first-solidified portions of the once molten globe. He elsewhere says that the solidification being from the surface downwards, the lowest. of these rocks must be the newest, except so far as eruptive masses may break up through the crust. Tchitatchef, from his recent researches in Asia Minor, holds to Naumann’s view as to the plutonic origin of the gneissic rocks of that region. The most recent and most explicit statement of this view of the plutonic’ origin of these rocks is that put forth ‘by Macfarlane, in a learned essay on The Eruptive and Primary Rocks, in the Canadian Naturalist for 1864. He conceives that the structure in these rocks may have been generated by currents in the molten mass of the globe; and, further, that the once-formed crust may have had a different rate of rotation from the liquid below ; from which also would result a stratiform arrangement —— —_— ee ee ee ae ee. i Ol a eee all XIII.] ORIGIN OF CRYSTALLINE ROCKS. 295 in the elements of the solidifying layers, such as is seen in many slags, and in certain eruptive rocks. (Ante, page 186.) Add to this notion that of the separation of the fluid or, rather, viscid mass into two or more layers of different composition and density (ante, page 3), and we might have generated from them, by their solidification under the above conditions, the © various types of stratiform feldspathic, hornblendic, and chrys- olitic rocks, which would afterwards be penetrated by injections from the yet liquid portions below. If now we imagine the various plutonic rocks thus formed, both stratified and unstrati- _ fied, to be the subjects of epigenic or pseudomorphous changes, by which some beds or masses were converted in serpentine or into steatitic or chloritic rocks, while others were changed into limestone, quartzite, or iron-oxide, we shall have as clear a con- ception as it is possible to form of the vaguely defined views of Naumann, Bischof, and their school, as to the origin of the crystalline rocks as we now find them. Naumann, while denying the sedimentary origin of the great mass of crystalline schists, admitted, however, the conversion of younger uncrystalline sedimentary strata, in certain cases, into crystalline gneisses and mica-schists, resembling those of the primary formations, and like them subject to epigenic changes. That such crystalline rocks have ever been formed from the alteration of paleozoic or more recent sediments, except locally (pages 18, 298, and 310), is, however, more than doubtful, as will appear from the examination of the supposed examples. of this conversion in the preceding pages of this paper, and also in the following one on the Geology of the Alps. In connection with these two papers are given the views of Giimbel (page 305) and of Favre on this important question. These crystalline rocks, whatever their origin or mode of formation, appear to be in all cases older than the paleozoic sediments. They belong to at least three or four geognostically discordant series, and are moreover occasionally associated with fragmentary rocks, which render it impossible to admit for them any other than an aqueous sedimentary origin, in accordance with the view already defined on page 286. ] 296 ORIGIN OF CRYSTALLINE ROCKS. pxuk Whence, then, come these silicates of magnesia, lime, and iron, which are the sources of the serpentine, chrysolite, pyrox- ene, hornblende, steatite, and chlorite, which abound in these rocks? This is the question which I proposed in 1860, when, after discussing the results of my examinations of the tertiary rocks near Paris, containing layers of a hydrous silicate of mag- nesia, related to tale in composition, among unaltered limestones and clays, I remarked that it is evident ‘such silicates may be formed in basins at the earth’s surface, by reactions between magnesian solutions and dissolved silica” ; and, after some dis- cussion, said “further inquiries in this direction may show to what extent certain rocks composed of calcareous and mag- nesian silicates may be directly formed in the moist way.”* Subsequently, in a paper on The Origin of some Magnesian and Aluminous Rocks, printed in the Canadian Naturalist for June, 1860,t I repeated these considerations, referring to the well-known fact that silicates of lime, magnesia, and iron-oxide are deposited during the evaporation of natural waters, includ- ing those of alkaline springs and of the Ottawa River. Having described the mode of occurrence of the magnesian silicate, sepiolite, in the Paris basin, and the related quincite, containing some iron-oxide, and disseminated in limestone, I suggested that while steatite has been derived from a compound like sepiolite, the source of serpentine was to be sought in another silicate richer in magnesia; and, moreover, that chlorite (unless the result of a subsequent reaction between clay and carbonate of magnesia) was directly formed by a process analogous to that which, according to Scheerer, has, in recent times, caused the deposition from waters of neolite,—a hydrous alumino-mag- nesian silicate, approaching to chlorite in composition,} “ the type of a reaction which formerly generated beds of chlorite, in the same way as those of sepiolite or tale.” Delesse, subse- quently, in 1861, in his essay on Metamorphism, insisted upon the sepiolite or so-called magnesian marls, as probably the * American Journal of Science (2), XXIX. 284; also (2), XL. 49. Tt Ibid. (2), XXXII. 286. t Pogg. Annal., LXXI. 288. XIIL.] ORIGIN OF CRYSTALLINE ROOKS. 297 source of steatite, and suggested the derivation of serpentine, chlorite, and other related minerals of the crystalline schists, from deposits approaching these marls in composition.* He recalled, also, the occurrence of chromic oxide, a frequent ac- companiment of these magnesian minerals, in the hydrated iron ores of the same geological horizon with the magnesian marls in France. Delesse did not, however, attempt to account for the origin of these deposits of magnesian marls, in explanation of which I afterwards verified Bischof’s observations on the sparing solubility of silicate of magnesia, and showed that sili- cate of soda, or even artificial hydrated silicate of lime, when added to waters containing magnesian chloride or sulphate, gives rise, by double decomposition, to a very insoluble magnesian silicate. (Ante, page 122.) To explain the generation of silicates like the feldspars, scapolite, garnet, and saussurite, I suggested that double alu- minous silicates, allied to the zeolites, might have been formed, and subsequently rendered anhydrous. The production of zeolitic minerals observed by Daubrée, at Plombiéres and Lux- euil, by the action of a silicated alkaline water on the masonry of ancient Roman baths, was appealed to by way of illustra- tion. (Ante, pages 25 and 205.) It has been shown by Daubrée that the elements of the zeolites were derived in part from the waters, and in part from the mortar, and even the clay of the bricks, which had been attacked, and had entered into com- bination with the soluble matters of the water to form chaba- zite. I, however, at the same time pointed out another source of silicated minerals, upon which I had insisted since 1857,: namely, the reaction between silicious or argillaceous matters and earthy carbonates in the presence of alkaline solutions. Nu- merous experiments showed that when solutions of an alkaline carbonate were heated with a mixture of silica and carbonate of magnesia, the alkaline silicate formed acted upon the latter, yielding a silicate of magnesia, and regenerating the alkaline car- bonate ; which, without entering into permanent combination, was the medium through which the union of the silica and the * Etudes sur le Metamorphisme, quarto, pp. 91. Paris, 1861. 13 * Pa ORIGIN OF CRYSTALLINE ROCKS. [XIII. magnesia was effected. In this way I endeavored to explain the alteration, in the vicinity of a great intrusive mass of dolerite, of a gray palzeozoic limestone, which contained, besides a little carbonate of magnesia and iron-oxide, a portion of very silicious matter, consisting apparently of comminuted orthoclase and quartz. In place of this, there had been developed in the lime- stone, near its contact with the dolerite, an amorphous greenish basic silicate, which had seemingly resulted from the union of the silica and alumina with the iron-oxide, the magnesia, and a portion of lime. By the crystallization of the products thus generated, it was conceived that minerals like hornblende, garnet, and epidote might be developed in earthy sediments, and many cases of local alteration explained. Inasmuch as the reaction described required the intervention of alkaline solu- tions, rocks from which these were excluded would escape change, although the other conditions might not be wanting. The natural associations of minerals, moreover, led me to sug- gest that alkaline solutions might favor the crystallization of aluminous silicates, and thus convert mechanical sediments into gneisses and mica-schists. The ingenious experiments of Dau- brée on the part which solutions of alkaline silicates, at ele- vated temperatures, may play in the formation of crystallized minerals, such as feldspar and pyroxene, were posterior to my early publications on the subject, and fully justified the im- portance which, early in 1857, I attributed to the intervention of alkaline silicates, in the formation of crystalline silicated minerals.* (Ante, pages 6 and 25.) [ While we may not question the regeneration of feldspars and zeolites (which are but hydrated feldsdars) by the combina- tion of silicates of alumina, like clay, with soluble alkaline or calcareous silicates, it is evident that this process is not the chief nor the primary one; since the existence of clay sup- poses the previous existence and decay of feldspars. The dep- osition of immense quantities, alike of orthoclase, albite, and oligoclase in veins which are evidently of aqueous origin, shows that conditions have existed in which the elements of these :: * Proc. Royal Soc., May 7, 1857. XIIL.J ORIGIN OF CRYSTALLINE ROCKS. 299 mineral species were abundant in solution. The relation be- tween these endogenous deposits and the great beds of orthoclase and triclinic feldspar rocks is similar to that between veins of calcite and of quartz and beds of marble and travertine, of quartzite and hornstone. But while the conditions in which these latter mineral species are deposited from solution are per- petuated to our own time, those of the deposition of feldspars and many other species, whether in veins or in beds, appear to belong only to remote geological ages, and at best are represented in more recent time only by the production of a few zeolitic minerals. See in this connection the paper on Granites and Granitic Vein-Stones, XI. of the present volume, passim, but especially §§ 30, 31, and 49,] While, however, there is good reason to believe that solu- tions of alkaline silicates or carbonates have been efficient agents in the crystallization and molecular rearrangement of ancient sediments, and have also played an important part in that local alteration of sedimentary strata which is often ob- served in the vicinity of intrusive rocks, it is clear to me that the agency of these solutions is less universal than once sup- posed by Daubrée and myself, and will not account for the formation of various silicated rocks belonging to the crystalline schists, such as serpentine, hornblende, steatite, and chlorite. When I commenced the study of these crystalline strata I was led, in accordance with the almost universally received opinion of geologists, to regard them as resulting from a subsequent alteration of paleeozoic sediments, which, according to different authorities, were of Cambrian, Silurian, or Devonian age. Thus in the Appalachian region, as we have already seen, they have, on supposed stratigraphical evidence, been successively placed at the base, at the summit, and in the middle of the Champlain division of the New York system. A careful chem- ical examination among the unaltered palzozoic sediments, which in Canada were looked upon as the stratigraphical equiv- alents of the bands of magnesian silicates in these crystalline — schists, showed me, however, no magnesian rocks, except cer- tain silicious and ferruginous dolomites. From a consideration | 300 ORIGIN OF ORYSTALLINE ROCKS. [XIII of reactions which I had observed to take place in such admix- tures in presence of heated alkaline solutions, and from the composition of the basic silicates which I had found to be formed in silicious limestones near their contact with eruptive rocks, I was led to suppose that similar actions, on a grand scale, might transform these silicious dolomites of the unaltered strata into crystalline magnesian silicates. Further researches, however, convinced me that this view was inapplicable to the crystalline schists of the Appalachians, since, apart from the geognostical considerations set forth in the previous part of this paper, I found that these same crys- talline strata hold beds of quartzose dolomite and magnesian carbonate, associated in such intimate relations with beds of © serpentine, diallage, and steatite, as to forbid the notion that these silicates could have been generated by any transforma- tions or chemical rearrangement of mixtures like the accom- panying beds of quartzose magnesian carbonates. Hence it was that already, in 1860, as shown above, I announced my conclusion that serpentine, chlorite, and steatite had been de- rived from silicates like sepiolite, directly formed in waters at the earth’s surface, and that the crystalline schists had resulted from the consolidation of previously formed sediments, partly chemical and partly mechanical in their origin. The latter being chiefly silico-aluminous, took, in part, the forms of gneiss and mica-schists, while from the more argillaceous strata, poorer in alkali, much of the aluminous silicate crystallized as anda- lusite, staurolite, cyanite, and garnet. These views were reit- erated in 1863,* and further in 1864, in the following lan- guage, as regards the chemically formed sediments : “ Steatite, serpentine, pyroxene, hornblende, and in many cases garnet, epidote, and other silicated minerals, are formed by a erystalli- zation and molecular rearrangement of silicates generated by chemical processes in waters at the earth’s surface.”t Their alteration and crystallization was compared to that of the * Geology of Canada, pp. 577 - 581. + American Journal of Science (2), XXX VII, 266; and XXXVII. 183. a 7 XIIL] ORIGIN OF CRYSTALLINE ROCKS. 301 mechanically formed feldspathic, silicious, and argillaceous sediments just mentioned. The direct formation of the crystalline schists from an aqueous magma is a notion which belongs to an early period in geological theory. Delabeche in 1834* conceived that they were thrown down as chemical deposits from the waters of the heated ocean, after its reaction on the crust of the cooling globe, and before the appearance of organic life. This view was revived by Daubrée in 1860. Having sought to explain ‘the alteration of palzeozoic strata of mechanical origin by the action of heated waters, he proceeds to discuss the origin of the still more ancient crystalline schists. The first precipitated waters, according to him, acting on the anhydrous silicates of the earth’s crust, at a very elevated temperature, and at a great pressure which he estimated at two hundred and fifty atmos- pheres, formed a magma from which, as it cooled, were suc- cessively deposited the various strata of the crystalline schists.t+ This hypothesis, violating, as it does, all the notions which sound theory teaches with regard to the chemistry of a cooling | globe, has, moreover, to encounter grave geognostical difficul- ties. The pre-Cambrian crystalline rocks belong to two or more distinct systems of different ages, succeeding each other in discordant stratification. The whole history of these rocks, moreover, shows that their various alternating strata were de- posited, not as precipitates from a seething solution, but under conditions of sedimentation not unlike those of more recent times. In the oldest known of them, the Laurentian system, great limestone formations are interstratified with gneisses, quartzites, and even with conglomerates. All analogy, more- over, leads us to conclude that, even at this early period, life existed at the surface of the planet. Great accumulations of iron-oxide, beds of metallic sulphides and of graphite, exist in these oldest strata, and we know of no other agency than that of organic matter capable of generating these products. [The presence of graphite, of native iron, and of sulphurets in most * Researches in Theoretical Geology, pp. 297 — 300. + Etudes et expériences synthétiques sur le metamorphisme, pp. 119 - 121. 302 ORIGIN OF CRYSTALLINE ROCKS. [XIII. aérolites, not to mention the hydrocarbonaceous matters which they sometimes contain, tells us in unmistakable language that these bodies come from a region where vegetable life has per- formed a part not unlike that which still plays on our globe, and even leads us to hope for the discovery in them of organic forms which may give us some notion of life in other worlds than our own.” *] Bischof had already arrived at the conclusion, which in the present state of our knowledge seems inevitable, that “all the carbon yet known to occur in a free state can only be regarded as a product of the decomposition of carbonic acid, and as derived from the vegetable kingdom.” He further adds, “liv- ing plants decompose carbonic acid, dead organic matters decompose sulphates, so that, like carbon, sulphur appears to owe its existence in a free state to the organic kingdom.” t As a decomposition (deoxidation) of sulphates is necessary to the production of metallic sulphides, the presence of the latter, not less than that of free sulphur and free carbon, depends on organic bodies; the part which these play in reducing and rendering soluble the peroxide of iron, and in the production of iron-ores, is, moreover, well known. It was, therefore, that, after a careful study of these ancient rocks, I declared in May, 1858, that a great mass of evidence “ points to the existence of organic life, even during the Laurentian or so-called azoic period.” { This prediction was soon verified in the discovery of +i Lozwin Canadense of Dawson, the organic character of which is now admitted by most zodlogists and geologists of authority. But with this discovery appeared another fact, which afforded a signal verification of my theory as to the origin and mode of deposition of serpentine and pyroxene. The microscopic and chemical researches of Dawson and myself showed that the calcareous skeleton of this foraminiferal organism was filled * The Chemistry of the Earth, § 19, in the Report of Smithsonian Insti- tution for 1869. + Bischof, Lehrbuch, Ist ed., Il, 95; English ed., I, 252, 344. + American Journal of Science (2), X XXV. 436. 1 f ) = t y vY XIIL.] ORIGIN OF CRYSTALLINE ROCKS. 303 with the one or the other of these silicates in such a manner as to make it evident that they had replaced the sarcode of the animal, precisely as glauconite and similar silicates have, from Cambrian times to the present, filled and injected more recent foraminiferal skeletons. I recalled, in connection with this discovery, the observations of Ehrenberg, Mantell, and Bailey, and the more recent ones of Pourtales, to the effect that glau- conite or some similar substance occasionally fills the spines of Echini, the cavities of corals and millepores, the canals in the shells of Balanus, and even forms casts of the holes made by burrowing: sponges (Clionia) and worms. The significance of these facts was further illustrated by showing that the so- called glauconites differ considerably in composition, some of them containing more or less alumina or magnesia, and one from the tertiary limestones near Paris being, according to Berthier, a true serpentine.* These facts in the history of Eozoén were first made known by me in May, 1864, in the American Journal of Science, and subsequently more in detail, February, 1865, in a communi- cation to the Geological Society of London.t They were speedily verified by Dr. Giimbel, who was then engaged in the study of the ancient crystalline schists of Bavaria, and soon recognized the existence, in the limestones of the old Hercynian gneiss, of the characteristic Hozoin Canadense, injected with silicates in a manner precisely similar to that observed by Dawson and myself.t{ Later, in 1869, Robert Hoffmann described the results of a minute chemical examina- tion of the EKozodn from Raspenau, in Bohemia, confirming the previous observations in Canada and Bavaria. He showed that the calcareous shell of the Eozoén, examined by him, had been injected by a peculiar silicate, which may be de- scribed as related in composition both to glauconite and to * American Journal of Science (2), XL. 360 ; Report Geol. Survey of Can- ada, 1866, p. 231 ; and Quar. Geol. Jour., XXI. 71. a American Journal of Science (2), XX XVII. 431; Quar. Geol. Jour., XXI. ~ Proc. Royal Bavar. Acad. for 1866; and Can. Naturalist, new series, III. 81. 304 ORIGIN OF CRYSTALLINE ROCKS. [ XIII. chlorite. The masses of Eozoén he found to be enclosed and wrapped around by thin alternating layers of a green mag- nesian silicate allied to picrosmine, and a brown non-magnesian mineral, which proved to be a hydrous silicate of alumina, ferrous oxide and alkalies, related to fahlunite, or more nearly to jollyte in composition.* Still more recently, Dr. Dawson has detected a crystalline silicated mineral insoluble in dilute acids, injecting the pores of crinoidal stems and plates in a paleozoic limestone from New Brunswick, which is made up of organic remains. This silicate, which, in decalcified specimens, exhibits in a beautiful manner the intimate structure of these ancient crinoids, I have - found by analysis to be a hydrous silicate of alumina and ferrous oxide, with magnesia and alkalies, closely related to fahlunite and to jollyte. The microscopic examinations of Dr. Dawson show that this silicate had injected the pores of the crinoidal remains and some of the interstices of the associated shell fragments before the introduction of the calcite which cements the mass. I have since found a silicate almost identi- eal with this occurring under similar conditions in a Silurian limestone said to be from Llangedoc in Wales.t Giimbel, meanwhile, in the essay on the Laurentian rocks of Bavaria, in 1866, already referred to, fully recognized the truth of the views which I had put forward, both with regard to the mineralogy of Eozoén and to the origin of the crystalline schists. His results are still further detailed in his Geognost. Beschreibung des éstbayerisches Grenzegebirges, 1868, p. 833. Credner, moreover, as he tells us,t had already, from his min- eralogical and lithological studies, been led to admit my views as to the original formation of serpentine, pyroxene, and sim- ilar silicates (which he cites from my paper of 1865, above referred to §), when he found that Giimbel had arrived at * Jour. fur. Prakt. Chem., May, 1869; and American Journal of Science asi th . ; Alben Journal of Science (3), I. 379, and II. 57. t Hermann Credner; die Gleiderung der Eozoischen Formationsgruppe Nord Amerikas. Halle, 1869. § That in the Quar. Geol. Jour., XXTI. 67. XIII] ORIGIN OF CRYSTALLINE ROCKS. 305 similar conclusions. The views of the latter, as cited by Credner from the work just referred to, are in substance as follows : the crystalline schists, with their interstratified lay- ers, have all the characters of altered sedimentary deposits, and from their mode of occurrence cannot be of igneous ori- gin, nor the.result of epigenic action. The originally formed sediments are conceived to have been amorphous, and under moderate heat and pressure to have arranged themselves, and crystallized, generating various mineral species in their midst by a change, which, to distinguish it from metamorphism by an epigenic process, Giimbel happily designates diagenesis.* It is unnecessary to remark that these views, the conclusions from the recent studies of Giimbel in Germany and Credner in North America, are identical with those put forth by me ,in 1860.T [* The following is extracted from an essay by the author in the Report of the Smithsonian Institution for 1869, on The Chemistry of the Earth, § 33: ‘The gradual transformation of amorphous precipitates under water into crystalline aggregates, so often observed in the laboratory, appears to depend upon partial solution and re-deposition of the material, which must not be entirely insoluble in the surrounding liquid. If the solvent power of this be reduced, the dissolved portions~are deposited on certain particles rather than others. By a subsequent exaltation of the solvent power of the liquid, solution of a further portion takes place, and this, in its turn, is de- posited around the nuclei already formed, which are thus augmented at the expense of the smaller particles, until these at length disappear, being gath- ered to the crystalline centres. Such a process, which has been studied by H. Deville, suffices, under the influence of the changing temperature of the seasons, to convert many fine precipitates into crystalline aggregates, by the aid of liquids of slight solvent powers. A similar agency may be supposed to have effected the crystallization of buried sediments, and changes in the solvent power of the permeating water might be due either to variations of temperature or of pressure. Simultaneously with this process one of chemical union of heterogeneous elements may go on, and in this way, for example, we may suppose the carbonates of lime and magnesia become united to form dolomite or magnesian limestone.’’] [+ Since the first publication of the above address I have received in a pri- vate letter from Giimbel the following re-statement of his views as to the origin of crystalline rocks : ‘‘ I have seen no occasion to change my opinions, which are, I believe, identical with your own. I do not maintain a metamor- phic origin for the primitive rocks; for, although these are certainly much altered, there are no firm and consolidated rocks which are not so. They were formed like, for example, the limestones of more recent periods; these T 306 ORIGIN OF CRYSTALLINE ROCKS. (XL At the early periods in which the materials of the ancient crystalline schists were accumulated, it cannot be doubted that the chemical processes which generated silicates were much more active than in more recent times. The heat of the earth’s erust was probably then far greater than at present, while a high temperature prevailed at comparatively small depths, and thermal waters abounded. A denser atmosphere, charged with carbonic-acid gas, must also have contributed to maintain, at the earth’s surface, a greater degree of heat, though one not incompatible with the existence of organic life. (Ante, page 46.) These conditions must have favored many chemical processes, which, in later times, have nearly ceased to operate, Hence we find that subsequently to the eozoic times, silicated rogks of clearly marked chemical origin are comparatively rare. In the mechanical sediments of later periods certain crystalline minerals may be developed by a process of mo- lecular rearrangement, — diagenesis. These are, in the feld- spathic and aluminous sediments, orthoclase, muscovite, garnet, staurolite, ¢yanite, and chiastolite, and in the more basic sedi- ments, hornblendic minerals. It is possible that these latter and similar silicates may sometimes be generated by reactions between silica on the one hand and carbonates and oxides on the other, as already pointed out in some cases of local altera- tion. Such a case may apply to more or less hornblendie gneisses, for example, but no sediments, not of direct chemical origin, are pure enough to have given rise to the great beds of serpentine, pyroxene, steatite, labradorite, etc., which abound in the ancient crystalline schists. Thus, while the materials were once pastes, magmas or muds, and so were the primitive rocks at the time of their origin, but during these first ages of the earth the consolidating and crystallizing forces (differing in degree only from those of the present time, and aided by a higher temperature) allowed the magma to assume the form of mineral species, more or less distinct. If we choose to call this change metamorphism, then the rocks thus formed are metamorphic; but so also are the limestones of later periods. The primitive rocks originated by way of sedimentation, the one after the other, constituting distinct forma- tions, and there are no eruptive gneisses.” See, in this connection, the Intro- duction to Essay III. of the present volume, and the statements of Favre in the Appendix to Essay XIV.] XIII] ORIGIN OF CRYSTALLINE ROCKS. Gy for producing, by diagenesis, the aluminous silicates just men- tioned are to be met with in the mud and clay-rocks of all ages, the chemically formed silicates, capable of crystallizing into pyroxene, talc, serpentine, etc., have only been formed under special conditions. [While the generation of various crystalline silicated minerals in rocks since the Eozoie age is theoretically not Impossible, the accumulation of evidence goes to show that although such changes have taken place locally in the proximity of eruptive rocks, and by the invasion of thermal waters, there has been no wide-spread alteration or regional metamorphism, as it has been called, of these more recent sedimentary deposits. | The same reasoning which led me to maintain the theory of an original formation of the mineral silicates of the crystalline schists, induced me to question the received notion of the epi- genic origin of gypsums and magnesian limestones or dolomites. The interstratification of dolomites and pure limestones, and the enclosure of pebbles of the latter in a paste of crystalline dolomite, are of themselves sufficient to show that in these cases, at least, dolomites have not been formed by the altera- tion of pure limestones. The first results of a very long series of experiments and inquiries into the history of gypsum were published by me in 1859, and further researches, reiterating and confirming my previous conclusions, appeared in 1866. (Ante, page 80.) In these two papers it will, I think, be found that the following facts in the history of dolomite are established : namely, first, its origin in nature by direct sedi- mentation, and not by the alteration of non-magnesian lime- stones ; second, its artificial production by the direct union of carbonate of lime and hydrous carbonate of magnesia, at a gen- tle heat, in the presence of water. As to the sources of the hydrous magnesian carbonate, I have endeavored to show that it is formed from the magnesian chloride or sulphate of the sea or other saline waters in two ways :- first, by the action of the bicarbonate of soda found in many natural waters ; this, after converting all soluble lime-salts into insoluble carbonate, forms a comparatively soluble bicarbonate of magnesia, from which a 308 ORIGIN OF CRYSTALLINE ROCKS. (XIII hydrous carbonate slowly separates ; second, by the action of bicarbonate of lime in solution, which, with sulphate of mag- nesia, gives rise to gypsum ; this first crystallizes out, leaving behind a much more soluble bicarbonate of magnesia, which deposits the hydrous carbonate in its turn. In this way, for the first time, in 1859, the origin of gypsums and their inti- - mate relation with magnesian limestones were explained.* — It was, moreover, shown that, to the perfect operation of this reaction, an excess of carbonic acid in the solution during the evaporation was necessary to prevent the decomposing action of the hydrous mono-carbonate of magnesia upon the already formed gypsum. Having found that a prolonged exposure to the air, by permitting the loss of carbonic acid, partially inter- fered with the process, I was led to repeat the experiment in a confined atmosphere, charged with carbonic acid, but rendered drying by the presence of a layer of desiccated chloride of cal- cium. As had been foreseen, the process under these conditions proceeded uninterruptedly, pure gypsum first crystallizing out from the liquid, and, subsequently, the hydrous magnesian carbonate.t This experiment is instructive, as showing the results which must have attended this process in past ages, when the quantity of carbonic acid in the atmosphere greatly exceeded its present amount. (Ante, pages 43, 47, and 91.) As regards the hypotheses put forward to explain the supposed dolomitization of previously formed limestones by an epigenic process, I may remark that I repeated very many times, under varying conditions, the often-cited experiment of Von Morlot, who claimed to have generated dolomite by the action of sul- phate of magnesia on carbonate of lime, in the presence of water at a somewhat elevated temperature under pressure. I showed that what he regarded as dolomite was not such, but an admixt- ure of carbonate of lime with anhydrous and sparingly soluble carbonate of magnesia ; the conditions in which the carbonate of magnesia is liberated in this reaction not being favorable to its union with the carbonate of lime to form the double salt * See the recent conclusions of Ramsay, noticed ante, page 92. + Canadian Naturalist, new series. f : 3h ORIGIN OF CRYSTALLINE ROCKS. 309 which constitutes dolomite. The experiment of Marignac, who thought to form dolomite by substituting a solution of chloride of magnesium for the sulphate, I found to yield similar results, the greater part of the magnesian carbonate produced passing at once into the insoluble condition, without combining with the excess of carbonate of lime present. The process for the pro- duction of the double carbonate described by Charles Deville, namely, the action of vapors of anhydrous magnesian chloride on heated carbonate of lime, in accordance with Von Buch’s strange theory of dolomitization, I have not thought necessary to submit to the test of experiment, since the conditions re- quired are scarcely conceivable in nature. Multiplied geognos- tical observations show that the notion of the epigenic pro- duction of dolomite from limestone is untenable, although its re-solution and deposition in veins, cavities, or pores in other rocks is a phenomenon of frequent occurrence. The dolomites or magnesian limestones may be conveniently considered in two classes: first, those which are found with gypsums at various geological horizons ; and, second, the more abundant and widely distributed rocks of the same kind, which are not associated with deposits of gypsum. The production of the first class is dependent upon the decomposition of sul- phate of magnesia by solutions of bicarbonate of lime, while _ those of the second class owe their origin to the decomposition of magnesian chloride or sulphate by solutions of alkaline bi- carbonates. In both cases, however, the bicarbonate of mag- nesia, which the carbonated waters generally contain, contributes a more or less important part to the generation of the magnesian sediments. The carbonated alkaline waters of deep-seated springs often contain, as is well known, besides the bicarbonates of soda, lime and magnesia, compounds of iron, manganese, and many of the rarer metals in solution ; and thus the metal- liferous character of many of the dolomites of the second class is explained. The simultaneous occurrence of alkaline silicates in such mineral waters would give rise, as already pointed out, to the production of insoluble silicates of magnesia, and thus the frequent association of such silicates with dolomites and 310 ORIGIN OF CRYSTALLINE ROCKS. ae magnesian carbonates in the crystalline schists is explained, as marking portions of one continuous process. The formation of these mineral waters depends upon the decomposition of feld- spathic rocks by subterranean or sub-aerial processes, which were doubtless more active in former ages than in ourown. The subsequent action upon magnesian waters of these bicarbonated solutions, whether alkaline or not, is dependent upon climatic conditions ; since, in a region where the rain-fall is abundant, such waters would find their way down the river-courses to the open sea, where the excess of dissolved sulphate of lime would _ . prevent the deposition of magnesian carbonate. It is in dry and desert regions, with closed lake or sea basins, that we must seek for the production of magnesian carbonates ;. and I have argued from these considerations that much of northeastern America, including the present basins of the Upper Mississippi, Ohio, and St. Lawrence, must, during long ‘intervals in the palzeozoic period, have had a climate of excessive dryness, and a surface marked by shallow enclosed basins, as is shown by the widely spread magnesian limestones, and by the existence of gypsum and rock-salt at more than one geological horizon within that area.* (Ante, page 76.) The occurrence of serpentine and” diallage at Syracuse, New York, offers a curious example of the local development of crystalline magnesian silicates in Silurian dolomitic strata, under conditions which are imperfectly known, and, in the present state of the locality, cannot be studied.t ~ Since the uncombined and hydrated magnesian mono-carbon- ate is at once decomposed by sulphate or chloride of calcium, it follows that the whole of these lime-salts in a sea-basin must be converted into carbonates before the production of carbonated magnesian sediments can begin. The carbonate of lime formed by the action of carbonates of magnesia and soda remains at first dissolved, either as carbonate (ante, page 140) or as bicar- bonate, and is only separated in a solid form, when in excess, * Geology of Southwestern Ontario, American Journal of Science (2), XLVII. 355. + Geology of the Third District of New York, 108-110; and Hunt on Ophiolites, American Journal of Science (2), XXVI. 236. XL] ORIGIN OF CRYSTALLINE ROCKS. 311 or when required for the needs of living plants or animals, which are dependent for their supply of calcareous matter on the carbonate of lime produced, in part by the process just de- scribed, and in part by the action of carbonic acid on insoluble lime-compounds of the earth’s solid crust. So many limestones are made up of calcareous organic remains, that a notion exists among many writers on geology that all limestones are, in some way, of organic origin. At the bottom of this lies the idea of an analogy between the chemical relations of vegetable and animal life. As plants give rise to beds of coal, so animals are supposed to produce limestones. In fact, however, the syn- thetic process by which the growing plant, from the elements of water, carbonic acid, and ammonia, generates hydrocarbona- ceous and azotized matters, has no analogy with the assimilative process by which the growing animal appropriates alike these organic matters and the carbonate and phosphate of lime. Without the plant, the synthesis of the hydrocarbons would not take place ; while, independently of the existence of coral or mollusk, the carbonate of lime would still be generated by chemical reactions, and would accumulate in the waters until, these being saturated, its excess would be deposited as gypsum or rock-salt are deposited. Hence, in such waters, where, from any causes, life is excluded, accumulations of pure carbonate of lime may be formed. In 1861 I called attention to the white marbles of Vermont, which occur intercalated among impure and fossiliferous beds, as apparently examples of such a process.* It is by a fallacy similar to that which prevails as to the or- ganic origin of limestones, that Daubeny and Murchison were led to appeal to the absence of phosphates from certain old strata, as evidence of the absence of organic life at the time of their accumulation.t Phosphates, like silica and iron-oxide, were doubtless constituents of the primitive earth’s crust, and the production of apatite crystals in granitic veins or in crys- talline schists is a process as independent of life as the forma- * American Journal of Science (2), XX XI. 402. 7 Siluria, 4th ed., pp. 28 and 537. 312 ORIGIN OF CRYSTALLINE ROCKS. ~ [XII tion of crystals of quartz or of hematite. Growing plants, it is true, take up from the soil or the waters dissolved phosphates, which pass into the skeletons of animals, — a process which _ has been active from very remote periods. I showed, in 1854, that the shells of Lingula and Orbicula, both those from the base of the palzozoic rocks and those of the present time, have (like Conularia and Serpulites) a chemical composition similar to the skeletons of vertebrate animals.* The relations of both carbonate and phosphate of lime to organized beings are similar to those of silica, which, like them, is held in watery solution, and by processes independent of life, is deposited both in amorphous and crystalline forms, but in certain cases is appro- priated by diatoms and sponges, and made to assume organized shapes. In a word, the assimilation of silica, like that of phos- phate and carbonate of lime, is a purely secondary and acci- dental process ; and where life is absent, all of these sabstanem } are deposited in mineral and inorganic forms. * American Journal of Science (2), XVII. 236. al ed ee Se XIII] ORIGIN OF CRYSTALLINE ROCKS. 313 APPENDIX. REPLY TO MR. DANA’S CRITICISMS. In the American Journal of Science for February, 1872, Professor Dana has criticised certain points in my address, On the Geognosy of the Appalachians and the Origin of Crystalline Rocks, given in August, 1871, at Indianapolis, before the American Association for the Advancement of Science. I am charged by him with rejecting, for many mineral silicates, the view that they are pseudomorphs ; that is to say, crystals chemically altered without loss of external form. I have denied that crystals of serpentine having the shape - of chrysolite, pyroxene, dolomite, etc., and crystals of pinite having the shapes of nepheline or scapolite, are results of a chemical change of these species, nothwithstanding this view is now held by most mineralogists, on the grounds of similarities of geometrical form and the existence of what are regarded as intermediate stages in the process of transmutation ; and I have maintained another and a very different view, which, in my opinion, is more rational. Until we can watch the transmutation of one of these species into another, the argument from supposed intermediate forms is worth no more in the mineral than in the organic world; the reasoning of the trans- mutationists, in the one case and the other, resting upon somewhat similar considerations. In either case we may say, with Professor Warrington Smyth, that in these intermediate forms “lie the ma- terials for a history”; while we venture, with him, to express a doubt whether, from a series of specimens supposed to show a transition from chrysolite to serpentine, or from hornblende to chlorite, “we are obliged to conclude that there has been, histori- cally speaking, an‘actual transition from the one to the other.” (See his anniversary address, as President of the Geological Society of London, in 1867.) Professor Dana says that Scheerer is the only one who shares my peculiar views on this question. I have, however, asserted in my address that Delesse has maintained the views of Scheerer and myself, as opposed to the popular doctrine of epigenesis, and shall endeavor to make good my assertion. In his essay on Pseudo- morphs, published in 1859 (Ann. des Mines (5), XVI. 317-392), 14 314 ORIGIN OF CRYSTALLINE ROCKS. [XIIL. Delesse begins his argument by remarking that since, in some cases, a mineral is found to be surrounded by another clearly resulting from its alteration (as, for example, anhydrite by gypsum), certain mineralogists have supposed that wherever one mineral encloses another there has been epigenesis or pseudomorphous alteration. Such, he says, may sometimes be the case, but it is easy to see that it is not so habitually. A crystallized mineral species frequently includes a large and even a predominating portion of another, and the combination is then considered by many as an example of partial pseudomorphous alteration. In such instances, remarks Delesse, the question arises whether we have to do with the results of envelopment or of chemical alteration ; to resolve which it becomes necessary to study carefully the problem of envelopment, _ He then proceeds to show that the enveloped substance is, in some cases, crystalline (and arranged either symmetrically or asymmetri- cally with regard to the enveloping mass); while in other cases it is amorphous, and enclosed like the sand-grains which predominate in the calcite crystals of Fontainebleau. The difficulty in deciding whether we have to do with envelopment or with epigenesis increases — when the enveloped mineral becomes so abundant as to obscure the enveloping species, or when it becomes mixed with it in so intimate a manner as to seem one with the latter (se fondre insenstblement avee lui). The proportions of the enveloped and the enveloping mineral, we are told, may so far vary that the one or the other is no longer recognizable. “As the forces which determine crystallization have a great energy, the enveloping mineral is sometimes found in so small a quantity as to be entirely masked by the enveloping species.” ‘When minerals have crystallized simultaneously, they have been able to become associated with each other and to envelop each other in all proportions ” (loc. cit., pages 338, 339, 341, 353). . Our author then proceeds to tell us that, haevinge carefully studied in numerous specimens the supposed mica-pseudomorphs of iolite, andalusite, cyanite, pyroxene, hornblende, etc., he” regards them as, in all cases, examples of envelopment, and expresses the opinion that we must omit from our lists a great number of the so-called pseudomorphous minerals, especially among the silicates. The final result of the process of envelopment is, according to Delesse, this, —to give rise to mixed mineral aggregates, owing their external forms to the crystallizing energy of one of the constituents, which may be present in so small a quantity as to be completely obscured by the other matter present. From this condition of things result a se SF inks © a XIII] ORIGIN OF CRYSTALLINE ROCKS. 315 crystalline forms which, though totally different in their origin from the products of chemical alteration or substitution, are emphatically pseudomorphs. From this process of mechanical and more or less heterogeneous envelopment, Delesse next proceeds to consider the crystallizing together of isomorphous or homcomorphous species, in relation to the generally received notion of epigenic pseudomorphism. He declares that “isomorphism explains very well facts which are often attributed to pseudomorphism,” and that many “minerals which are still considered pseudomorphs are in reality examples of isomorphism” (pages 364, 365). Referring to the well-known in- vestigations of Mitscherlich upon the crystallizing together, in all proportions, of isomorphous species, and of the symmetrical crys- tallization of one salt around a nucleus of another isomorphous with it, Delesse suggests that the different forms and varieties of hornblendic and pyroxenic minerals afford many examples of the kind. He then adds, “ If, as Scheerer has remarked, water plays in silicates the part of a base, anhydrous silicates may crystallize at the same time with hydrated silicates, and, moreover, be isomor- phous with them.” In this way, he suggests, we may explain by isomorphism or homeomorphism, the association with pyroxene . of the hydrous species, schiller-spar, as well as that “of various anhydrous and hydrated minerals” (pages 357, 358). In further illustration of the words just quoted from Delesse, we may cite from Scheerer, as examples of what he called polymeric isomorphism, the association (in the same crystals) of iolite and aspasiolite, and of chrysolite and serpentine. If these and similar species crystallize together because they are isomorphous, it is evident that they may each crystallize separately ; and thus the erystals of serpentine with the form of chrysolite, and those of aspasiolite and other so-called hydrous iolites, may be regarded as examples, not of epigenesis, but of isomorphism. We have thus endeavored to set forth, chiefly in his own words, the views enunciated in 1859 by Delesse, according to whom the phenomena of so-called pseudomorphism among mineral silicates are to be explained, for the most part, not by chemical alterations of pre-existing species, but by envelopment and by isomorphism. That the above are really his views, and are, moreover, regarded by himself as contrary to those of the school which I oppose, Delesse does not permit us to doubt ; for, after having set them forth as his own (apres avoir exposé notre maniere de voir), he says, “ We hasten ewe? ey | ee a OD ee eS eee ee eee, > ee eee Mr See es nt a Ce eee a er, See EU Seer Oe a ee RO Tae ye ’< ‘ ‘ = . a ; =a »® OTs a ~ ihe litt. ay.) Tis 316 ORIGIN OF CRYSTALLINE ROCKS. (XIII. to add that these facts may also be explained in a manner altogether different (peuvent aussi s’interpreter d’une maniére toute différente) ; and some savans of Germany, notably G. Rose, Haidinger, Blum, G. Bischof, and Rammelsberg, have sought their explanation in pseudomorphism. Their example has been followed by most min- eralogists, etc.” (pages 358, 359). That the “pseudomorphism” of the authors just named is chemical alteration or epigenesis, it is not necessary to remind the reader, who will now be able to judge whether it is Professor Dana or myself who has misrepresented or misunderstood Delesse. Let us, however, add that the long and somewhat diffuse memoir of the latter, from which we have quoted, is wanting in unity of plan and purpose, and that parts of it, if we may hazard a conjecture, seem to have been written while he still inclined to the views of the opposite school. From the table of pseudomorphs which he has given, and from many passages in the text, it might be inferred that he then held the notions of Rose, Haidinger, etc., which he else- where, in the same paper, speaks of as being entirely different from his own. The views of Delesse, about this time, underwent a great change, which has a historic importance in connection with those which I advocate. When, in 1857 and 1858, he published the first and second parts of his admirable series of studies on metamor- phism, Delesse held, in common with nearly every geologist of the time, to the eruptive origin of serpentine and the related magnesian rocks: Serpentine was then classed by him with other “ trappean rocks”; and he elsewhere asserted that “ granitic and trappean rocks” uridergo in certain cases a change near their contact with the enclosing rock, by which they lose silica, alumina, and alkalies, and acquire magnesia and water, being thus changed into a mag- nesian silicate, which may take the form of saponite, serpentine, tale, or chlorite (Ann. des Mines (5), XIT. 509 ; XIII. 393,415). It would be difficult to state more distinctly the view, which he then held, of the origin of these magnesian rocks and minerals by the chemical alteration of plutonic (granitic and trappean) rocks. This was in 1858, and in 1859 appeared the memoir on pseudomorphs, already noticed, in which, in place of the theory of epigenic pseudo- morphism, or chemical alteration of various mineral silicates, taught by the German school, he brought forward, in explanation of the facts upon which this was based, another theory, which was only an extension of that already maintained by Scheerer and myself. It was not until 1861 that Delesse published the last part of his XIII. ] ORIGIN OF CRYSTALLINE ROCKS. By studies on metamorphism, which appeared in the Memoirs of the Academy of Sciences of France (Vol. X VII.) ; and in it we find that, consistently with the new views adopted by him in 1859, the old doctrine of the epigenic origin of serpentine and the related mag- nesian rocks from the alteration of plutonic rocks is abandoned. In its stead, it is here suggested by Delesse that all these magnesian rocks result from the crystallization of the sepiolites or so-called magnesian clays, which are frequent in many sedimentary deposits. These, according to him, by a molecular rearrangement of their elements, may give rise to serpentine, talc, chlorite, and their various associated and related minerals. The rocks thus generated are still declared to pass insensibly into plutonic rocks ; but, instead of maintaining, as in 1858, that they are derived from the latter, Delesse, in 1861, asserts, on the contrary, that “the plutonic rocks are formed from the metamorphic rocks, and represent the maximum of intensity, or extreme limit of metamorphism.” This recognition of the notion that the great masses of serpen- tine, with their constantly associated hornblendic, talcose and chloritic rocks, have been directly formed from the molecular re- arrangement or diagenesis of aqueous magnesian sediments, and not from the chemical alteration or epigenesis of erupted plutonic masses, marks a complete revolution in our views of the history of the crystalline rocks. The new doctrine did not, however, originate with Delesse, but was previously put forward by myself in a paper, On some Points of Chemical Geology, read before the Geological Society of London in January, 1859, appearing in abstract in the Philosophical Magazine for February, and published at length in the Geological Journal for November, in the same year. I there maintained that serpentines were “ undoubtedly indigenous rocks, resulting from the alteration of silico-magnesian sediments” ; and moreover asserted that the final result of heat, aided by water, on such rocks, would be their softening, and, in certain cases, their ex- travasation as plutonic rocks; which were regarded “as, in all cases, altered and displaced sediments.” When this paper was written, in 1858, I still supposed that the reactions between the elements in beds of silicious magnesian carbonates (which, I had shown, may give rise to certain magnesian silicates in immediate proximity to eruptive rocks) might serve to explain the origin of great areas of serpentine and related crystalline magnesian sili- cates ; but my studies of the silicates deposited during the evapora- tion of natural waters, and of the magnesian sediments of the Paris 318 ORIGIN OF CRYSTALLINE ROCKS. [ XIII. basin, soon led me to seek the origin of these rocks in the alteration of previously formed uncrystalline magnesian silicates. This view was set forth by me in the American Journal of Science for March, 1860 ((2), X XIX. 284), and more fully in the Canadian Naturalist for June, 1860 (also in the American Journal (2), XXXII. 286), where it was pointed out that steatite, chlorite and serpentine were probably derived from sediments similar to the magnesian silicates . found among the tertiary beds in the vicinity of Paris, the so-called magnesian clays. We have seen that these various novel views, put forth by me in 1859 and 1860, though totally different from those taught by De- lesse in 1858, were integrally adopted by him in 1861. These dates are circumstantially given in my address of last year, and yet Pro- fessor Dana, in his review of it, charges me with “ following nearly Delesse” as to the origin of serpentine. He also asserts that J “make Delesse the author of the theory of envelopment,” when I have there declared that the view of Delesse — “ that the so-called cases of pseudomorphism, on which the theory of metamorphism by alteration has been built, are, for the most part, examples of associa- tion and envelopment, and the result of a contemporaneous and original crystallization —is identical with the view suggested by Scheerer in 1846, and generalized by myself, when, in 1853, I sought to explain the phenomena in question by the association and crystallizing together of homologous and isomorphous species.” To Delesse, therefore, belongs the merit, not of having suggested the notion of envelopment in this connection, but of having pointed out the bearing of the envelopment of heteromorphous and —_ species on the question before us. Professor Dana moreover asserts that, while Scheerer is the only one who maintains similar views to myself, I, in common with all other chemists, reject the chemical speculations which lie at the base of his views. On the contrary, unlike most chemists, who have failed to see the great principle which underlies Scheerer’s doctrine of polymeric isomorphism, I have maintained (American Journal of Science (2), XV. 230; XVI. 218) that it enters into a general law, in accordance with which bodies whose formulas differ by nM,0, or nH,O, may (like those differing by nH,C,) have rela- tions of homology, and moreover be isomorphous. (See, further, Paper XVII. of the present volume.) The existence of these same relations was further maintained and exemplified in a paper on Atomic Volumes, read by me before the French Academy of - XIIL.]J ORIGIN OF CRYSTALLINE ROCKS. 319 Sciences and published in the Comptes Rendus of July 9, 1855. This doctrine, which I have never repudiated, is reiterated in my address last year (ante, page 291), and declared to include the poly- meric isomorphism of Scheerer. Professor Dana next says that, in asserting that “the doctrine of pseudomorphism by alteration, as taught by G. Rose, Haidinger, Blum, Volger, Rammelsberg, Dana, Bischof, and many others, leads them .... to maintain the possibility of converting almost any silicate into any other,” I have “grossly misrepresented the views of at least Rose, Haidinger, Blum, Rammelsberg, and Dana” ; and that I “complete the caricature” by this sentence, to be found in my address : “In this way we are led from gneiss or granite to limestone, from limestone to dolomite, and from dolomite to ser- pentine ; or more directly from granite, granulite, or diorite, to ser- pentine at once, without passing through the intermediate stages of limestone and dolomite” ;— “part of which transformations,” says Professor Dana, “I, for one, had never conceived ; and Rose, Hai- dinger, Rammelsberg, and probably Blum, and the ‘many others,’ would repudiate them as strongly as myself.” ‘The “many others,” as he rightly remarks, are “other writers on pseudomorphism,” among whom it would be unjust not to name their progenitor, Breithaupt, Von Rath, and Miiller, at the same time with Volger and Bischof. According to Professor Dana, I “add to the misrep- resentation by means of the strange conclusion that, because such writers hold that crystals may undergo certain alterations in com- position, therefore they believe that rocks of the same constitution may undergo the same changes.” This “strange conclusion” I have always supposed to be Professor.Dana’s own. No one has per- haps asserted it so clearly or so broadly as himself, and I shall there- fore quote his own words in my justification. As early as 1845, in an article entitled Observations on Pseudomorphism (Amer- ican Journal of Science (1), XLVIIT. 92), he wrote: “The same process which has altered a few crystals to quartz has distributed silica to fossils without number, scattered through rocks of all ages. The same causes that have originated the steatitic scapolites occa- sionally picked out of the rocks, have given magnesia to whole rock-formations, and altered, throughout, their physical and chemi- cal characters. If it be true that the crystals of serpentine are pseudomorphous erystals, altered from chrysolite, it is also true, as Breithaupt has suggested, that the beds of serpentine containing them are likewise altered, though often covering square leagues in 320 ORIGIN OF CRYSTALLINE ROCKS. [XIII. extent, and common in most primary formations. The beds of steatite, the still more extensive talcose formations, contain every- where evidence of the same agents.” Again, in 1854, in his Min- eralogy, 4th edition (page 226), Professor Dana, after a complete list of pseudomorphs, compiled from the writers of the school in question, says: “These examples of pseudomorphism should be understood as cases not simply of alteration of crystals, but in many instances of changes in beds of rock. Thus all serpentine, whether in mountain-masses or the simple crystal, has been formed through a process of pseudomorphism, or in more general language, of metamor- phism; the same is true of other magnesian rocks, as steatitic, tal- cose, or chloritic slates. Thus the subject of metamorphism, as it bears on all crystalline rocks, and of pseudomorphism, are but branches of one system of phenomena.” If there could be any doubt as to the mean- ing of the words which I have italicized in quoting them from Professor Dana, it is removed by his language in 1858. Then, as now, adversely criticising my views on this question, he refers to the statements above cited, made in 1845 and 1854, as expressions of his doctrine, mentioning especially the first one, in which he says, “metamorphism is spoken of as pseudomorphism on a broad scale.” (American Journal of Science (2), XXV. 445.) I confess that I do not understand Professor Dana, when in his last criticism of me, fourteen years after the one just quoted, he reproaches me with having charged him with holding the doctrine that “ regional metaphorphism is pseudomorphism on a grand scale” ; and declares that he makes no such remark, neither expresses the sentiment in his Mineralogy of 1854. With these citations before us, and remembering the views of Scheerer, and the later ones of Delesse, together with the language of the latter in his essay on Pseudomorphs, let us notice the words of Naumann, addressed to Delesse in 1861, in allusion to the essay in question : “ Permit me to express to you my satisfaction for the ideas enunciated in your memoir on Pseudomorphs, — ideas which my friend Scheerer will doubtless share with myself” (¢dées que mon ami M. Scheerer partagera sans doute ‘comme moi-méme). Then fol- lows the language which I have quoted. in my address, in which he combats the error of those who hold that gneisses, amphibolites, and other crystalline rocks are “the results of metamorphic epi- genesis, and not original rocks,” and adds, “It is precisely because pseudomorphism has so often been confounded with metamorphism that this error has found acceptance.” (Bull. Soc. Geol. de France (2), 7 ee ee ee ee % f a : Ci ar ." 5 . , ie pee Cn eo 7 ete” q 7 4 ¥ RS ae Lae 4). ma es: ee ee ee Pf s Ly PS et ies fe oo e PP ey te — ay ~ MR i ais hac ie ~— i - a ‘ 7. 7 oa te N .. 5 eens, a ao. —. Le ee ee XIII] ORIGIN OF CRYSTALLINE ROCKS. 321 XVIII. 678.) The reader must now judge whose opinions it is that are here denounced as erroneous, and: whether Naumann was on the side of Professor Dana, or, with Delesse, on the side of Scheerer and myself. I insist the more strongly on this matter, because Professor Dana not only declares that Delesse and Naumann have always avowed the doctrines of the transmutationist school, and do not in any way whatever countenance my views, but implies that I have dealt unfairly with these authorities, Professor Dana says, “If there was any occasion for a notice of my opinions, a critic of 1871 should have referred to the formal expression of them in my Manual of Geology, first published in 1863. The reader will there find the diagenesis of Giimbel, which Mr. Hunt takes occasion to commend, . . . . with but a brief allu- sion to pseudomorphism.” The doctrine of diagenesis, it is hardly necessary to say, I have never attributed to Giimbel, nor does he claim it. It is the old doctrine of Hutton, Playfair, and Boué, is taught by Bischof (Chemical Geology, III. 318, 325, 342), and per- vades my papers of 1859 and 1860, already referred to, But while it has been generally admitted that what, in my address, I have called the first class of crystalline rocks (consisting chiefly of quartz and aluminous silicates) might result from the molecular re- arrangement of the elements of clay and sand-rocks, I maintained ~ in those papers that what I have called the crystalline rocks of the second class (in which protoxide-silicates predominate) have been generated, by a similar process, from aqueous deposits of chemically formed silicates. This view, advanced by me in 1860, having been adopted by Delesse and by Giimbel to explain the origin of the various magnesian silicated rocks hitherto generally regarded as the product of epigenesis, the latter has proposed to designate the process as diagenesis ; a term which I adopt, as one well fitted to denote the generation of all kinds of crystalline rocks through a molecular rearrangement of sedimentary deposits, of whatever origin. Professor Dana, in common with most other geologists, admits in his Manual of Geology the old conception of the pro- duction by diagenesis from mechanical sediments of the rocks of the first class, but in the case of serpentine and steatite declares them to have been formed by epigenic pseudomorphism or chemical alter- ation of pyroxenic and other crystalline rocks ; the origin of which as by him left entirely unexplained. It is true that his allusions to pseudomorphism in that volume are confined to very brief notices on pages 704 and 710 ; a fact which is the more noticeable, when we 14* U OE ee eR Gee age SL, eee Fir cee a eee 322. ORIGIN OF CRYSTALLINE ROCKS. [XU recall that the author had formerly expressed the belief “ that pseu- domorphism will soon constitute one of the most important chap- ters in geological treatises.” (American Journal of Science (1), XLVIII. 66.) That Professor Dana has receded from the extreme views on this subject which he maintained from 1845 to 1858, and which I have constantly opposed, seems probable ; but until he formally rejects them, the student of geology will not unnaturally suppose that he still gives the sanction of his authority to the doctrine which he so long taught without any qualification, but now repudiates, that “metamorphism is pseudomorphism on a broad scale.” {In the Neues Jahrbuch fiir Mineralogie for November, 1872 (page 865), appeared a note from the venerable Carl Friedrich Nau- mann (who has since died at an advanced age), in which he com- ments upon my interpretation of his letter to Delesse. He begins by saying that I have, in my address in 1871, cited some passages from that letter, of which he then proceeds to repeat the substance, and adds: “Although I am still strongly opposed to the excesses of the metamorphic doctrine, I cannot explain how Professor Sterry Hunt can, from the extracts of my letter to Delesse, conclude that I regard those cases of pseudomorphism upon which the theory of metamorphism is grounded as in great part only examples of asso- ciation and development, and also as a result of a simultaneous and original crystallization, and that my view is identical with his own, which he first put forth in the year 1853.” Upon this I have to remark that, instead of citing in my address extracts from his published letter to Delesse, I gave therein a trans- lation of the whole letter, with the exception of the first three lines, which are, however, given above, with some other extracts, in my reply to Dana’s criticisms. From this language I conclude that Naumann knew my address only through these misleading criticisms and my reply thereto. In the next place, it is not clear what were the excesses of the metamorphic doctrine which he still condemned in 1872. He, as we have shown from his Lehrbuch (ante, page 294), regarded gneisses and similar rocks as, for the most part, in some unexplained way, of plutonic origin, though he admitted their pro- duction in certain cases by the alteration of sediments, agreeable to the Huttonian view of diagenesis ; while in the letter above men- tioned he characterizes as erroneous the very different notion that all “ gneisses, amphibolites, etc.,” are “the results of metamorphic epigenesis.” From his language in 1872, however, it would appear XIII.] ORIGIN OF CRYSTALLINE ROCKS. 323 that, in his opinion, such rocks, once formed, may become the sub- jects of epigenic pseudomorphism, and be metamorphosed, as sup- posed by Bischof, Dana, and others, into serpentines, steatites, ete. In this case his implied sympathy, in 1861, with the teachings of Scheerer, who, in denying the epigenic origin of the serpentine asso- ciated with chrysolite and many similar cases, had struck a blow, in the language of Naumann, at “ those cases of pseudomorphism upon which the theory of metamorphism is grounded ” ; and finally, his congratulations to Delesse (who had just declared that often “ the so- called metamorphism finds its natural explanation in envelopment,” and asserted the view of Scheerer and myself that much of what has been regarded as pseudomorphism has no other basis than the observed associations of mineral species) could, in my opinion, ad- mit of no other interpretation than the one which I in 1871 gave toit. There is a confusion, not to say a contradiction, in these expressed views of the venerable teacher, which it is not easy t explain. Nothing has been further from my intention than to misrepresent the views either of Naumann or of Dana; and my error, if I have fallen into one, arises from the difficulty of knowing their real opinions upon the matters in discussion. Let Professor Dana de- fine, as clearly as I have done, his present views as to the origin of magnesian rocks, both those made up of chrysolite and pyroxenic minerals, and those composed of serpentine, steatite and chlorite, which he has supposed to come from an epigenesis of the former ; let him tell us whether he holds the doctrine of pseudomorphic metamorphism which he taught in 1845, 1854 and 1858, and. which, as I have shown, was held by Delesse as late as 1857, or that doctrine so long maintained by me, which the latter adopted in 1861. Such a definition would be eminently satisfactory to those who look to him as a teacher in science, and would prevent any further misconception or unintentional misrepresentation of his views. | Professor Dana, having clearly defined the proposition that the chemical alterations which are recognized in individual crystals are to be conceived as extending to rock-masses, and having, more- over, asserted that the principle of the identity of metamorphism and pseudomorphism “ bears on all crystalline rocks,” is logically committed to all the deductions as to the changes of rocks which the transmutationist school has drawn from the supposed alteration of minerals. By reference to the table of pseudomorphs in the 324 ORIGIN OF CRYSTALLINE ROCKS. (XIII. fourth edition of Dana’s Mineralogy, it will be seen that each one of the metamorphoses of rocks mentioned in the above extract from my address is based upon an asserted epigenic change or conversion of the constituent species. I shall, however, show, in addition, that in each case the application of the principle to rock-masses has been recognized by one or more of the authorities already named, and that the so-called caricature has been drawn by their own hands, It would be easy, did space permit, to extend greatly this list of supposed transmutations. The various associations of rocks and minerals in nature, when interpreted according to the canons of this school, seem, in fact, as remarked by Professor Warrington Smyth, in his address already quoted, “ to offer a premium to the ingenious for inventing an almost infinite series of possible combinations and permutations.” Before proceeding further it is to be noted that no distinction can, in many cases, be established between the results of alteration (or partial replacement) and substitution (or complete replacement) ; since successive alterations may give the same pro- duct as direct substitution. Thus, for example, quartz might be directly replaced by calcite, or else first altered to a silicate of lime, which, in its turn, might be changed to carbonate. The alteration of quartz to a silicate of magnesia, and that of both pyroxene and pectolite to calcite, is maintained by the writers of the present school. Metamorphosis of granite or gneiss to limestone : — Calcite, we are told, is pseudomorphous of quartz, of feldspar, of pyroxene, and of garnet, besides other species; it moreover replaces both orthoclase and albite “by some process of solution and substitution.” (Dana’s Mineralogy, 5th edition, 361.) Since quartz, orthoclase, and albite can be replaced by calcite, the transmutation of granite or gneiss into limestone presents no difficulty. [In the opinion of Messrs. King and Rowney, the crystalline limestones of Tyree in the Hebrides, those of Aker in Sweden, and similar limestones in the - Laurentian of North America, were at one time beds of gneiss, diorite, and other silicated rocks, which have been changed by an epigenie process, (Annals and Magazine of Natural History for 1869, Vol. XIII. page 390.) Volger has also asserted a similar origin for certain gneissoid limestones. ] Metamorphosis of limestone to dolomite : — This change is main- tained by Von Buch, Haidinger, and many others. I am blamed for mentioning in connection with this school the name of Haidinger, who, Professor Dana says, “never wrote upon the subject of the XIII] ORIGIN OF CRYSTALLINE ROCKS. 325 alteration of rocks.” It will, however, be noticed, that his name has been quoted by Delesse with those of Bischof, Blum, and oth- ers as a disciple of this school, and it has never before been ques- tioned that Haidinger was the first, if not to suggest, to clearly set forth, the theory of the supposed conversion of limestone into dolomite by the action of magnesian solutions, aided by heat and pressure,— a theory which I have elsewhere refuted. (Bischof, Chem. Geol., III. 155, 158; Zirkel, Petrographie, I. 246; Liebig and Kopp, Jahresbericht, 1847-48, 1289 ; and American Journal of Science (2), XXVIII. 376). Metamorphosis of dolomite to serpentine : — This change is main- tained by G. Rose (Bischof, Chem. Geol., II. 423), and by Dana (American Journal of Science (3), ITI.'89). Metamorphosis of granite, granulite, and eclogite directly into ser- pentine, chlorite, and tale : — These transmutations are maintained by Miiller, and adopted by Bischof. (Chem. Geol., II. 424, 434.) - Metamorphosis of limestone to granite or gneiss : — This is taught by Blum and Volger. (Chem. Geol., II. 186 ; III. 431.) Having thus given the authorities for the examples cited in my address, I may notice some further illustrations of the doctrine from the pages of Bischof’s work already quoted. Metamorphosis of diorite, hgrnblende-rock, and labradorite to serpentine ; G. Rose, Breithaupt, Von Rath (II. 417, 418): diorite and hornblende-slate to talc-slate and chlorite-slate; G. Rose (III. 312): mica-slate to tale-slate and steatite, and mica to serpentine, steatite, and talc ; Blum, C. Gmelin (II. 405, 468) : quartz-rock to steatite ; Blum (II. 468). [That the extravagant views of the transmutationists, as set forth in the preceding pages, though now denied by Professor Dana, are still maintained by others, is well shown by two recent publica- tions. In one of these, just referred to, Messrs. King and Rowney have gone even further than their predecessors. Not content with teaching the conversion of feldspar, quartz, hornblende, pyroxene, and chondrodite into calcite, they imagine that serpentine, which, according to Dana and others, results in all cases from the alteration of silicated or carbonated species, may itself become the subject of epigenic change, and be converted into calcite. The ophicalce rocks, which are mixtures of serpentine and carbonate of lime, have, according to King and Rowney, been formed in this manner from serpentine ; and they further imagine this process to have been so guided as to leave the unchanged portions of the serpentine with 326 GEOGNOSY OF THE APPALACHIANS. [XID the forms of a foraminiferal organism, the Hozoon Canadense of Dawson. This singular supplement to the hypothesis of epigenic change recalls the notion of the older naturalists, who, rather than admit the organic origin of shells found in the rocks, imagined them to have been generated by a plastic force. It is evident that it makes little difference what mineral species is taken as a starting- point for these transformations, and Dr. Genth has assumed corun- dum. Ina recent paper (Proceedings of the American Philosophi- cal Society, September 19, 1873) he has discussed various facts observed in the association and envelopment of the minerals associ- ated with it, and concludes that there have been formed from corun- | dum, by epigenesis, spinel, tourmaline, fibrolite, cyanite, paragonite, damourite and other micas, chlorite, and probably various feld- spars. According to him, great beds of micaceous and chloritic schists have resulted from the transformation of corundum, and even the beds of bauxite, a mixture of hydrous aluminic and ferric oxides, allied to limonite, which abounds in certain tertiary depos- its, were once corundum or emery, from which this amorphous — hydrate is supposed to have been derived by a retrograde metamor- phosis ; a striking example of the strange conclusions to which this doctrine of epigenic pseudomorphism may lead. The corundum- bearing vein-stones present close resemblance in the grouping and association of minerals to the granitic and calcareous vein-stones described in Essay XI. of the present volume. See, further, the author’s criticisms on this subject, Proceedings Boston Society of Natural History, March 4, 1874.] Coming now to his criticism of the first part of my address, with regard to New England rocks, Professor Dana asserts that “there — are gneisses, mica-schists, and chloritic and taleoid schists in the Taconic series.” I have, however, shown in my address that Em- mons, the author of the Taconic system, expressly excluded there- from the crystalline rocks, which he included in an older primary system ; excepting, however, certain micaceous and talcose beds, which he declared to be recomposed rocks, made up from the ruins of the primary schists, and distinguished from these by the absence of the characteristic crystalline minerals which belong to the Green Mountain primary schists. Again, Professor Dana states that I make the crystalline schists of the White Mountains a newer series than the Green Mountain rocks. Such a view of their geognostical relations has been main- tained for the last generation by the Messrs. Rogers, Logan, and ——~ st Al XIIL] GEOGNOSY OF THE APPALACHIANS. 327 many others, all of whom assigned the crystalline schists of the White Mountains to a higher geological horizon than those of the Green Mountains. In support of this view of their relative antiquity, I have, however, brought together observations from South Carolina, Pennsylvania, Michigan, Ontario, and Maine, all of which point to the same conclusion ; and I might now add similar evidence from New Brunswick and from Nova Scotia. My “ chrono- logical arrangement” of New England crystalline rocks, as it is called by Professor Dana, so far as it is my own, is limited to my affirmation that they are all of pre-Cambrian age ; in proof of which it need only be mentioned that the crystalline schists of both the types in question are, in southern New Brunswick, directly overlaid by uncrystalline shales, sandstones and conglomerates, made up in part of the ruins of these, and holding a Cambrian (Menevian) fauna. As regards the mica-schists with staurolite, cyanite, andalusite, and garnet, I have in my address pointed out the fact that they appear to belong to a great series of rocks, very constant in charac- ter, which have a continuous outcrop from the Hudson River to the St. John, a distance of five hundred miles, and in the latter region are clearly pre-Cambrian. I have, moreover, brought to- gether the evidence of observers in other parts of North America, in Great Britain, in continental Europe, and in Australia, showing that similar crystalline schists, holding these same minerals, always occupy, in these regions, a similar geological horizon. Professor Dana hereupon inquires whether any one has yet proved that these mineral characters are restricted to rocks of a certain geological period. I answer, that in opposition to these facts, it has not yet been proved that they belong to any later geological period than the one already indicated ; and that it is only by bringing together observations, as I have done, that we can ever hope to determine the geological value of these mineral fossils. In no other way did William Smith prove, in Great Britain, the value of organic fossils, and thus lay the foundations of paleontological geology. ri s E a EB. XIV. THE GEOLOGY OF THE ALPS. This review appeared in the American Journal of Science for January, 1872, and serves to throw much light upon many important and still debated points of geology. I have added as an appendix to the present reprint the recent conclusions of Favre, and the statements of Pillet, which serve to confirm certain positions assumed in the review, and elsewhere in this volume.* Since the days of De Saussure, the Alps have been the ob- ject of constant study. No other portion of Europe offers so many problems of interest to the geologist and the physical geographer as this great mountain-chain, whether we consider its lakes, glaciers, and moraines, its curiously disturbed and inverted fossiliferous strata, which seem, at first sight, arranged for the confusion alike of paleontologists and stratigraphists, or the crystalline rocks which form its highest summits. To give a list of the various investigators who have contributed their share to the elucidation of this region would, of itself, be no slight task, and would besides be foreign to our present pur- pose ; which is to call attention to the learned work of Pro- fessor Alphonse Favre of Geneva, in which he has given us the results of more than twenty-five years of labor in the study of Alpine geology, chiefly in Savoy and the adjacent parts of Piedmont and Switzerland, embracing Mont Blane and its vicinity. It is now twelve years since the present writer had oceasion to review, in the American Journal of Science ((2), XXIX. 118), some points in Alpine geology raised by our author in his memoir “ Sur les terrains liassique et keuperien de * Recherches Géologiques dans les parties de la Savoie, du Piémont, et de la Suisse voisines du Mont Blanc, avec un Atlas de 32 planches, par Alphonse Favre, Professeur de Géologie 4 l’Académie de Genéve. 3 Vols. 8vo. Paris. 1867. | XIV.] THE GEOLOGY OF THE ALPS. 329 la Savoie,” published in 1859. Since that time the views then maintained by Favre have, in spite of much opposition, gained ground, and are set forth at length in the present work, sup- ported by an amount of evidence which seems convincing. We shall endeavor from its pages to present a condensed sum- mary of our present knowledge of the structure of Mont Blane and the adjacent regions. The crystalline rocks of the Alps, as first shown by Studer, do not form a continuous chain, but appear as distinct masses, separated from each other by uncrystalline sedimentary de- posits, generally fossiliferous. According to Desor, there are between Nice and the plains of Hungary not less than thirty- four such areas, standing up like islands from out of the sedi- mentary rocks, and presenting for the most part a fan-like structure (en eventail). Of these masses of crystalline rock, Mont Blane is the most remarkable, and is described by Elie de Beaumont as “ rising through a solution of continuity in the secondary strata, which may be compared to a great button- hole.” The length of this area of crystalline rock, measured from the Col du Bonhomme on the southwest to Saxon in the Valais on the northeast, is fifty-nine kilometres, while its breadth, from Chamonix on the northwest to Entréves near Courmayeur on the southeast, is fourteen kilometres. The length of the central mass of protogine is, however, only twenty-seven kilometres. Of the numerous peaks in this area the highest attains an elevation of 4,810 metres above the level of the sea, being 3,760 metres above the valley of Chamonix, and 3,520 metres above the valley of Entréves. This great mass is described by Favre as supported at the four corners by as many buttresses rising from the surrounding valleys, and known as the Cols de Balme, de Voza, de la Seigne, and de Ferret. The distance between the two valleys just named is only 13,500 metres, and the boldness with which the mountain rises from them is strikingly apparent if we take the Col de ]’Aiguille du Midi and the Col du Géant, which are about 3,460 metres above the sea, and distant from each other 5,000 metres, giving a slope of about 30°. A still 330 THE GEOLOGY OF THE ALPS. |. [XIV. greater inclination is obtained if we choose, instead of these, the summits of the Aiguilles which bear the same names, and, although now isolated, represent portions of the former mass of Mont Blanc. The crystalline rocks of this region present two types: first, the protogines which form the centre ; and, second, the crys- talline schists which occupy the flanks and form the Aiguilles Rouges. These schists are also found at a great elevation on the mountain ; at the Grands Mulets (4,666 metres) the rocks ‘ are taleose and quartzose schists with graphite, hornblende, epidote, talc, and asbestus, and similar rocks and minerals are found from thence to the summit. The protogines themselves, according to the evidence of nearly all who have studied them, are stratified rocks, gneissic in structure, and pass in places into more schistose varieties, though Favre regards the distine- tion between these and the crystalline schists proper as one clearly marked. The outlines presented by the weathering of the protogine are very unlike the rounded forms assumed by true granite rocks. According to Delesse, the rock to which Jurine gave the name of protogine is a talco-micaceous granite or gneiss, made up of quartz, generally more or less grayish or smoky in tint, with orthoclase, grayish or reddish in color, and a white or greenish oligoclase with characteristic striae, often penetrated with greenish tale. The mica (biotite), which some previous ‘observers had mistaken for chlorite, is dark green in color, becoming of a reddish bronze by exposure. It is binaxial, nearly anhydrous, and contains a large portion of ferric oxide, The composition of the protogine rock, as a whole, differs from that of ordinary granite, according to Delesse, only in the presence of one or two hundredths of iron-oxide and magnesia. The name of arkesine was given by Jurine to a variety of protogine containing chlorite with hornblende, and sometimes sphene. Among the other crystalline rocks of the Alps are various talcose and chloritic schists, with steatites, chromifer- ous serpentines, diallage rocks, diorites, and euphotides, asso- - ciated with beds of petrosilex or eurite, frequently porphyritic. Highly micaceous schists, often quartzose, and holding garnet, XIV.] - THE GEOLOGY OF THE ALPS. 3oL staurolite, and cyanite, are also met with among the crystalline rocks of the Alps. A great belt of serpentine and chloritic schists, traced for a long distance, may be seen at the base of the Montanvert overlaid by the euritic porphyries, into which they appear to graduate; the whole series, here sup- posed to be inverted, dipping at about 60° from the valley of Chamonix toward Mont Blanc, and overlaid by the more massive gneiss or protogine. The chloritic and talcose schists of the Alps have close resemblances with those of the Urals, and, as Damour has shown, contain a great many mineral spe- cies in common with them. Favre has, moreover, remarked the strong likeness between the chloritic and talcose schists and the mica-schists with staurolite of the western Alps and those found in Great Britain. Granite, though not abundant in the vicinity of Mont Blanc, occurs in several localities, the best known of which is Valor- sine, where a porphyroid granite with black mica forms con- siderable masses, and sends large veins into the adjacent gneiss. These, with others found at the Col de Balme and in the Aiguilles Rouges, appear to be true eruptive granites. Numer- ous ‘small veins met with among the crystalline schists in the gorge of Trient appear, however, to belong to what I have described as endogenous granites. (Ante, page 193.) Favre has himself maintained that they are the results of aqueous infiltration, and has noticed the fact of a joint running longi- tudinally through the middle of many of them as an evidence of this mode of formation. The uncrystalline strata in the region around Mont Blanc include representatives of the carboniferous, triassic, jurassic, neocomian, cretaceous, and tertiary. The existence of an ap- parently carboniferous flora, and its intimate association with a liassic fauna, has long been a well-known fact in Alpine geology. In 1859, Favre pointed out the existence of a zone of triassic rocks in this region represented by red and green shales, with sandstones, gypsum, and a cavernous magnesian limestone (cargneule). These rocks had long before been referred to this period by Buckland and Bakewell, but their horizon was estab- 332 THE GEOLOGY OF THE ALPS. [XIV. lished by the discovery of Favre that their position is inter- mediate between the carboniferous and the strata containing Avicula contorta (the Kossen beds, or the Rhetic beds of Giimbel), which are recognized as forming a passage between the trias and the lias, at the base of the jurassic system. To these, to the northwest of Mont Blanc, succeed the higher members of the system, followed by the neocomian, the ecreta- ceous, and the nummulitic strata of the eocene, with overlying sandstones and shales, the flysch of some Alpine geologists, Few questions in geology have been more keenly debated, or given rise to more often-repeated examinations, than the asso- ciation of a carboniferous flora with liassic belemnites in the districts of Maurienne and Tarentaise, to the southwest of Mont Blane. As seen at Petit-Cceur, the schists, with impres- sions of ferns and beds of anthracite, were so long ago as 1828 described by Elie de Beaumont as apparently intercalated in the jurassic system. Scipion Gras, and Sismonda after him, have agreed in regarding the rocks as constituting one great system, which according to Gras is of carboniferous age, but with a jurassic fauna ; while De Beaumont and Sismonda, on the contrary, regarded it as of jurassic age, but with a carbon- iferous flora, and imagined that by some means there had been in this region a local survival of the vegetation of the palzeo- zoic period. These conclusions were accepted by many geolo- gists, though rejected by not a few. A brief account of the controversy up to that date will be found in the American Journal of Science for January, 1860, page 120; and in the work of Favre now before us the whole matter is discussed at great length in Chapter XXX. The anthracitic system of the Alps, as recognized by Gras, was by him estimated to have a thickness of from 25,000 to 30,000 feet, and included, besides the dolomites and gypsums now referred by Favre to the trias, coal-plants and layers of anthracite, together with limestones holding belemnites of jurassic age. Included in this great system were, moreover, gneissic, micaceous, and talcose rocks, with graphite, serpentine, euphotide, ete., all of which were regarded by Gras as formed by the local alteration of portions XIV.] THE GEOLOGY OF THE ALPS. 333 of the anthracitic system. To this was added in 1860 the discovery by Pillet of nummulitic beds intercalated in the same series near St. Julien in Maurienne. This fact was, however, in accordance with the conclusion previously reached by Sismonda from an examination of Taninge, that “the plants of the car- boniferous period were still flourishing while the seas were depositing the rocks of the nummulitic period.” The question involved in this controversy had more than a local interest, since it touched the very bases of paleontology, by pretending that in the Alps the laws of succession which elsewhere prevail were suspended, and that the same types of vegetation had continued unchanged from the palzozoic to the tertiary period. Already, in 1841, Favre had brought forward the suggestion of Voltz, that these apparent anomalies might be explained by inversions of the strata; but this notion was rejected by De Mortillet and Murchison, as inadmissible for the section at Petit-Cceur. The recognition by Favre, in 1861, of the true age and position of the cargneules and their associated rocks, however, threw a new light on the question, for it was shown that these triassic rocks were interposed at Petit-Coeur between the limestones holding belemnites and the schists with coal-plants. In 1861, the Geological Society of France held its extraordinary session at St. Jean in Maurienne, and there also the succession was made clearly evident, as follows: nummu- litic, liassic, infra-liassic, triassic, and carboniferous ; the last resting on crystalline schists. Attempts had been made to sustain the supposed jurassic age of the so-called anthracitic formation, by maintaining that some at least of the coal-plants were jurassic forms ; but Heer, who had long maintained the contrary, published in 1863 a further study of the fossil flora of Switzerland and Savoy, in which he showed that of sixty species fourteen are peculiar to these regions, while forty-six belong to the-carboniferous flora of Europe, and twenty-seven are common with that of North America. One species only has been identified as of liassic age, namely, Odontopteris cycadea Brongn., and is found in a locality near jurassic belemnites, but associated with no other plant. 334 THE GEOLOGY OF THE ALPS. [XIV. Both Lory and Pillet now admit with Favre that the sup- posed paleontological anomalies of this region have no exist- ence, and that-.this anthracitic system includes carboniferous, jurassic, and nummulitic strata inverted and folded upon them- selves; nor is it without reason that Lory in this connection remarks upon “ the illusions without number to which a purely stratigraphical study of the Alps may give rise.” To this we may add the judgment of Dumont, in discussing the disturbed — and inverted anthracite system of the Ardennes, that for regions thus affected “‘ we cannot establish the relative age of the rocks from their inclination or their superposition.” These conclusions were not, however, admitted by Sismonda, who, in 1866, presented to the Royal Academy of Sciences of Turin an elaborate memoir on the anthracite system of the Alps.* In this, while admitting at Petit-Cceur the existence of evidence of more or less contortion, rupture, and overriding (enchevauchement) of the strata, he still maintains that the an- thracitic system of Maurienne and Tarentaise is one great con- tinuous series of jurassic age, from the fundamental gneiss and protogine, upon which it immediately rests, to the upper mem- ber in which occur thick beds of anthracite, with an abundant carboniferous flora, which he assigns, however, to the middle odlite (Oxfordian) ; the great mass of strata below being re- _ ferred to-the lias, He then particularly indicated the line of the great Mont Cenis tunnel, which, commencing in the upper anthracitic member, should pass downward through the quartz- ites and gypsums, thence through talcose schists and limestones, as far as Bardonecchia. These schists and limestones, accord- ing to him, are in ‘‘a very advanced stage of metamorphism,” and include eruptive serpentines, with euphotide, steatite, and other magnesian rocks. Since the completion of the tunnel, Messrs. Sismonda and Elie de Beaumont have presented to the Academy of Sciences of Paris an extended report on the geological results obtained in this great work. It is accompanied by a description of 134 specimens of the rocks collected at intervals throughout the en- * Memoirs of the Acad., Second Series, XXIV 333. . XIV.) THE GEOLOGY OF THE ALPS. 335 tire distance of the tunnel, which, it will be remembered, passes from near Modane in Savoy to Bardonecchia in Piedmont (about fifteen miles to the southwest of Mont Cenis), a distance of 12,220 metres. The direction of the tunnel is N. 14° W., and the dip of the strata throughout nearly uniform, N. 55° W., at an angle of about 50°. From this we deduce by calculation that the vertical thickness of the strata is equal to nearly 60 per cent of the distance traversed, or in round numbers about 7,000 metres. Of this not less than 5,831 metres, beginning at the southern extremity, are occupied by lustrous and more or less talcose schists with crystalline micaceous limestones, often cut by veins of quartz with chlorite and calcite. Above there are 515 metres in thickness of alternations of anhydrous sul- phate of lime (karstenite) with talcose schist and crystalline limestone. The anhydrite enclosed lamellar tale in irregular nodules, with dolomite, crystallized quartz, sulphur, and masses of rock-salt. This was overlaid by 220 metres of quartzite, occasionally alternating with greenish talcose schists, and en- closing veins and masses of anhydrite. A considerable break occurs in the series of specimens above this, but for the distance of 1,707 metres from the northern entrance to the tunnel, corresponding to a vertical thickness of 1,024 metres, we have principally sandstones, conglomerates, and argillites, occasionally with anthracite. The serpentines and euphotides which ap- pear among the crystalline schists at Bramant, near the line of the tunnel, were not met with, nor was the underlying gneiss encountered. The work terminated at Bardonecchia among the crystalline limestones. According to Sismonda and Elie de Beaumont, there is throughout this entire section no evidence of inversion, dislo- cation, or repetition in the series of 7,000 metres of strata, a conclusion which they support by very cogent arguments. Lory, on the contrary, while he agrees with the observers just mentioned in looking upon the crystalline strata as altered mesozoic, conceives them to include both trias and lias, and to be. placed beneath the true carboniferous by a great inversion of the whole succession. This series of crystalline rocks is 336 THE GEOLOGY OF THE ALPS, [XIv. | very conspicuous along the southeast side of Mont Blanc, ex- tending into the Valais, and is regarded by Lory as a peculiar modification of the trias and lias, so enormously thickened and so profoundly altered as to be very unlike these formations to the northwest of Mont Blane. In this view he is followed by Favre (§§ 666, 753). The serpentines and related rocks of this series are by De Beaumont, Sismonda, and Lory considered to be eruptive. The latter speaks of these as eruptions con- temporaneous with the deposition of the strata, probably ac- companied by emanations which effected the alteration of the sediments. According to Favre, they are clearly interstratified with the lustrous argillo-talcose schists, micaceous limestones and quartzites of the great series, and are by him placed in the trias. He has particularly described those of Mont Joret and those of the Val de Bruglié, near the Petit St. Bernard, where they are immediately interstratified with greenish schists, and associated with steatite, hornblendic and gneissic strata. The serpentines of Taninge in the Chablais, to the northwest of Mont Blanc, he also classes with these in the trias. The conclusions of Lory and Favre as to the geological age of these crystalline schists and limestones appear to us untenable in the light of Sismon- da’s investigations. If we admit with the latter that the whole section of the tunnel represents an uninverted series, and with Favre that its uppermost and uncrystalline portion at Modane is truly of carboniferous age, it is clear that the great mass of crystalline schists which underlie the latter should correspond more or less completely to the pre-carboniferous crystalline strata to the northwest of Mont Blanc. Among these latter, in fact, as observed by Favre, there occur at Col Joli and Taninge crys- talline limestones and talcose schists like those of Maurienne. According to this view, which harmonizes the conflicting opin- ions, and makes the crystalline schists and limestones of the southeast pre-carboniferous, the anhydrites, with limestones, talcose slates, and quartzites seen in the Mont Cenis tunnel, are not the equivalents of the gypsum and cargneule of the trias, but may correspond to the anhydrites which, with gypsum, dolomite, serpentine and chloritic slate, are met with in the primitive schists of Fahlun in Sweden. XIV.] | THE GEOLOGY OF THE ALPS. 337 The existence of great and perplexing inversions of strata in many parts of the Alps is well known. One of the most strik- ing cases is that figured by Murchison in his remarkable paper on the geology of the Alps in 1848 (Quar. Jour. Geol. Soc., V. 246), as occurring at the pass of Martinsloch in the canton of Glarus, 8,000 feet above the sea. Here nummulitic beds, dip- ping S. S. E. at a high angle, are regurlaly overlaid by the succeeding sandstone (flysch), resting unconformably and in a nearly horizontal attitude upon the edges of which are 150 feet of hard jurassic limestone, overlaid in its turn by talcose and micaceous schists, which are by Escher regarded as similar to those which underlie these limestones in the valley below. This mass of flysch appears near by to dip beneath these lime- stones, which, in their turn, are regularly overlaid by neocomian and cretaceous strata. This remarkable superposition of sec- ondary and older crystalline rocks to tertiary is explained by Murchison, in accordance with the suggestion of H. D. Rogers, as the probable result of fracture and displacement along an anticlinal. Many striking examples of inversion are described by Favre in the vicinity of Mont Blanc. The mountain of the Voirons, near Geneva, shows at_its base tertiary overlaid by eretaceous rocks, upon which jurassic strata are superimposed. Similar phenomena are met with along the north side of the Alps from Geneva to Austria, and at various localities on the southern side, in Lombardy. This inversion, moreover, is by no means confined to secondary and tertiary strata. In the val- ley of Chamonix the secondary limestones dip at a high angle toward Mont Blanc, and plunge beneath its crystalline schists, Other examples of the superposition of crystalline schists to the fossiliferous sediments have been pointed out by Elie de Beau- mont in the mountains of Oisans, and confirmed by Lory and Dausse, while similar cases have been recognized by Morlot and Von Hauer in the eastern Alps, and by Ramond, De Bouche- porn, and others in the Pyrenees. All of these cases are by Fayre regarded as examples of the same process of inversion already noticed in so many instances among the secondary and tertiary strata of the region. He proceeds to contrast these 15 3 i / 4 338 THE GEOLOGY OF THE ALPS. [XIv. examples with that of the gneisses with chloritic and micaceous — schists, which in western Scotland, according to Murchison, — a overlie fossiliferous Lower Silurian beds, and are by him re- garded as younger. This, upon the authority of Murchison, Favre regards as a singular and anomalous fact. It should, however, be said that this view of Murchison is rejected by Nicoll, who explains the appearances as the result of disloca- tion and oversliding of older crystalline schists upon the newer fossiliferous beds, in which case the western Highlands will form no exception to the general law of similar ps in the Alps and Pyrenees. (Ante, page 271.) a The fact that the jurassic rocks in the valley of Chamenil 4 pass beneath the crystalline schists of Mont Blanc was first no- ticed by De Saussure, and was afterwards observed by Bergmann and by Bertrand, who argued from this that the limestones were older than the gneiss. Bertrand’s paper, as noticed by Favre, oceurs in the Journal des Mines, VII. 376 (1797-1798). Later, in 1824, we find Keferstein inquiring whether these — = overlying gneisses and protogines might not be altered flysch _ (that is, eocene), a view which he subsequently maintained. Similar views have found favor among later geologists ; we find Murchison asserting the eocene age of certain Alpine gneisses, mica-schists, and granites ; while Lyell has suggested that the protogines, gneisses, etc., of the Alps may have resulted from the alteration both of secondary and tertiary strata. (Anniver- sary Address to the Geological Society, 1850.) . Studer has — a taught that the flysch of the Grisons has been changed into crystalline gneiss, while Rozet and Fournet, with Lory and Sis- monda, have assigned to the jurassic period the great system of gneisses, with taleose and micaceous schists, which make up fe . oO Monts Cenis and Pelvoux, and much of the mountains on the i, frontier of Piedmont and in the Valais. Hutton, as early as 1788, had taught that what he called the primary schists were sediments, the ruins of earlier rocks altered ie 4 by heat, but it does not appear that he attempted to fix the relative age of any such altered rocks, In fact, the notion of — geological periods, based upon the study of fossils, was not as XIV.] THE GEOLOGY OF THE ALPS. 339 yet fully recognized. The suggestions of Bergmann and Ber- trand, that the crystalline rocks of the Alps are newer than the fossiliferous limestones which pass beneath them, seems to have been the first attempt to give to Hutton’s view a definite and special application, and the inception of that hypothesis with which we have since become familiar, which supposes the con- version of mountain masses of palzeozoic, mesozoic, and even cenozoic sediments, in the Alps and elsewhere, into gneisses and other crystalline rocks.* Numerous sections in the vicinity of Mont Blane show the sedimentary strata in their normal atti- tude, resting unconformably upon the crystalline schists, while in some localities the whole succession from the carboniferous to the eocene, both inclusive, is met with. In many parts, however, the carboniferous is wanting, and the trias forms the base of the column, while elsewhere the infra-liassic beds re- pose on the crystalline schists, and in the Bernese Alps no fossiliferous beds lower than the odlite amjaehserved. These variations would appear to be connected with the movement of subsidence which permitted the deposition of marine limestones above the carboniferous strata ; and Favre has further pointed out, in the vicinity of Dorenaz, a want of conformity between these and the succeeding formations. To the carboniferous belongs the well-known conglomerate of Valorsine, which includes pebbles of gneiss, quartzite, talcose, and micaceous schist, and of quartz veins with tourmaline. The paste, which is reddish, taleose, and micaceous, seems identical with many of the pebbles, so that it is sometimes difficult to distinguish these from the matrix. A thin fibrous envelope often surrounds the pebbles (§ 521). Although the alternation of these beds with OthiBes holding plants shows them to be of carboniferous age, it is ‘Often, says Favre, difficult to fix the lower limit of this formation, on account of the great resem- blance between certain of the carboniferous sandstones and [* Already, before Hutton, Von Trebra, in1785, had taught a somewhat similar doctrine. He supposed thataslow change under the influence of heat and water, which he compared to a fermentation, is constantly going on in the interior of the rocks, and may in time convert motintains of granite into gneiss, and of gray wacke into clay-slate. (Erfahrungen von Innern der Gebirge, page 48. )]. 340 THE GEOLOGY OF THE ALPS. [XIV. portions of the older crystalline schists, which, in cases where the former are destitute of pebbles, makes it impossible to dis- tinguish between the two. Necker, in like manner, asserted that it was impossible to draw a line of demarcation, and was hence led to assert a passage from the one to the other. The same close resemblance was noticed by De Saussure, and is testi- fied to by De Mortillet and by Sismonda, who says of the feld- spathic sandstone (grés) near St. Jean in Maurienne, that “ un- less we take care we run the risk of being deceived, and of confounding it with gneiss”; while elsewhere similar rocks assume the aspect of granite from the predominance in them of feldspar. Hence it has happened that observers like Dolo- mieu and Bakewell placed the anthracites of the Alps in the mica-slate formation, and that Berger described as a “ veined granite ” the Aiguille des Posettes, which, according to Favre, consists of nearly vertical beds of carboniferous sediments. In illustration of this condition of things, Favre cites the observation of Boulanger, according to whom the triassic sand- stones of the department of Allier are made up of quartz, feld- spar, and mica, so united as to give rise to a sandstone which would be taken for a primitive rock but for the occasional pres- ence of a rolled pebble of granite.* The paste of this Valor- sine conglomerate, which seems identical with certain of the enclosed pebbles, appears, according to Favre, to have undergone a certain rearrangement, so that the beds of these “ pretendus schists cristallins ” of the carboniferous are with difficulty dis- tinguished from the “ vrais schists cristallins” upon which they rest unconformably. I insist the more upon these details, be- cause in the earlier notice of Favre’s investigations I erroneously represented him as including in the carboniferous a great mass of the older crystalline schists. In this connection we may cite the observation of Sedgwick, who cites similar cases of recomposed rocks in Scotland, “ which it is not always possible to distinguish from the parent rock,” and remarks that “a mechanical rock may appear highly crys- * See Favre, Terrains liassique et keuperien, etc. (1859), pp. 78, 79, to which, in this work, he refers the reader for further explanation on this point, XIV.] THE GEOLOGY OF THE ALPS. 341 talline because it is composed of crystalline parts derived | from some pre-existing crystalline rock.” * Emmons also has called attention to the existence of secondary or recomposed beds of talcose, chloritic, and micaceous schists in the Taconic hills of western New England, which, according to him, have been confounded with the older parent rocks. (Ante, page 251.) It would hardly seem necessary to call attention to facts which are familiar to all field-geologists who have worked much among newer deposits in the vicinity of older crystalline rocks, were it not that their significance is so great in connection with Alpine geology. This deceptive resemblance to the older -crystalline rocks in the Alps, as might be supposed, is not confined to the carbonif- erous. Similar cases are noticed by Favre in the trias, while at the Cols du Bonhomme and des Fours are crystalline aggre- _ gates also noticed by Saussure as closely resembling the older crystalline rocks, which are shown by the fossils of interstrati- fied beds to be of infra-liassic age. Studer, in opposition to Murchison, maintained that the apparently granitic layers in the flysch (eocene) near Interlaken are but the débris of an older crystalline rock, while the crystalline schists of the Bolghen mountain in the eastern Alps, supposed by Murchison to be in some way interposed in the flysch, are both by Studer and by Boué regarded as merely masses of the older crystalline rocks in a tertiary conglomerate.t In discussing the age of the “true crystalline schists” of the Alps, to make use of his expression already-quoted, Favre, as we have seen, places them beneath the carboniferous, and in opposition to the suggestion of Murchison and the opinion of Gueymard, that they may be of Cambrian and Silurian age, concludes that we have no proof of the existence of representa- tives of these systems in the western Alps ($ 808). In this connection we may note with Favre the presence at Dienten, in the Tyrol, of a Silurian fauna, intercalated in beds of gray and green chloritic schists (§ 697 6). The gneiss of Mettenbach, * Geol. Transactions (1835), III. 479. t Ibid., III. 334; Geol. Jour., V. 210. a ee i 349 THE GEOLOGY OF THE ALPS. [XIV. near the Jungfrau, has afforded to Favre a pale green ophicalce resembling that of the Laurentian, in which he has detected Eozoon Canadense (§ 697 a). Having thus declared his convic- tion of the great antiquity of the crystalline schists, whose ruins enter into the composition of the conglomerate of Valor- sine, he proceeds to remark that “the part played by the Alps of Savoy by that mysterious force called metamorphism, to which the formation of the crystalline schists is often attributed, has been greatly exaggerated.” He adds, “I have always been surprised to find in the Alps so few traces of this pretended action,” and suggests that the question has been complicated by the resemblances already noted between the crystalline schists and the recomposed rocks of the coal measures (§ 697 ¢c). In the same spirit he declared in 1859 that there are “ scarcely any evidences of alteration after the Valorsine conglomerate ” ; in the paste of which he admits a crystalline rearrangement, by no means improbable.* It appears inconsistent with these expressions of opinion to find our author admitting with Lory the triassic and jurassic age of the great mass of lustrous schists and micaceous limestones which are overlaid by the carbonifer- ous at Modane, and at various localities, as we have seen, in- clude serpentines, steatites, etc. Our author feels this to be a difficulty, and speaks of these serpentines, unlike those of the Montanvert, the Aiguilles Rouges, etc., as belonging to non- crystalline formations, a character which can hardly be ascribed to them. If, however, Sismonda be correct in placing them below rocks which are, according to Favre, true coal measures, these serpentines and steatites, with their accompanying schists and limestones, are, as we have already shown, in the same horizon with the crystalline schists to the north of Mont Blane. The origin of the fan-like structure attributed to the Alps by nearly all observers since the time of De Saussure, and cor- rectly represented in the sections published by Studer in 1851, and by Favre in 1859, is explained by the latter in accordance with the view put forward by Lory in 1860.¢ He supposes * Terrains liassique et keuperien, page 77. + Lory, Description géologique du Dauphiné, p. 180. pl XIV.) THE GEOLOGY OF THE ALPS. - 343 that the underlying crystalline rocks, forced by great lateral pressure, formed an elevated anticlinal arch, which, breaking on the crown, from the excess of curvature, shows the lowest rocks in the centre of the rupture, flanked on either side by the over- lying strata. These, in their upper part, are subjected to a comparatively feeble lateral pressure, while the deeper portions are forcibly compressed by the smaller folds on either side, from which results the fan-like or sheaf-like structure of the mass. The newer strata in the synclinals are by this process arranged in troughs, and are more or less overlaid by the older rocks, Such a synclinal exists in the valley of Chamonix, between the two ruptured and eroded anticlinals represented by Mont Blanc and the Brevent. In illustration of this structure Favre has given a grand section commencing to the northwest in the mountain known as Les Fiz, which, overlooking the Col d’An- terne, rises to a height of 3,180 metres, and displays all the Alpine formations from the sandstones of Taviglionaz, overlying the nummulitic beds, down to the carboniferous, which :is seen resting on the crystalline schists. These appear in the height of Pormenaz, and in the Brevent, at the northwest base of which the carboniferous rocks are arranged in a sharp fold dip- ping beneath the crystalline strata. The latter, to the northeast, rise in the Aiguilles Rouges, which are steep hills of vertical beds including hornblendic, chloritic, and talcose rocks, with petrosilex, eclogite, and serpentine. The highest of the Ai- guilles rises 2,944 metres above the sea, and consequently 1,892 metres above the valley of Chamonix. This summit, which was visited by Favre, was found to be capped by horizontal strata, consisting at the top of about thirty-seven metres of ju- rassic beds, with belemnites and ammonites, underlaid by infta- liassic strata with cargneules, sandstones, and schists, the whole resting upon vertical strata of unctuous mica-schists, which enclosed a bed of saccharoidal limestone. From thence we pass over the valley of Chamonix, which holds enfolded in crys- talline schists triassic and jurassic strata, and over the summit of Mont Blane, to find the same folding repeated between the base of the latter and the protogines of Mont Chétif. The fan- Te Te ee a ae ge a a 1 ee 2 es eee Rar, we eR, oO . 344 THE GEOLOGY OF THE ALPS, [XIV. like structure attributed to this last is questioned by Lory, according to whom the strata of this mountain dip uniformly — to the southeast, and are overlaid by the great mass of erystal- line talcose schists and micaceous limestones assigned by him to the trias ; but apparently, as we have endeavored to show, a portion of the pre-carboniferous crystalline schists. These rocks are well displayed further on in the mountain of Cra- mont, and are regarded by Favre as identical with those of Mont Cenis.* Lory conceives that the attitude of the rocks of Mont Chétif to the jurassic strata in the trough at the southeast base of Mont Blanc is due to a great fault with an uplift, which has brought these older rocks to overlie the jurassic beds. With the facts before us, we can with Favre trace the history of Mont Blanc from the time when over a partially submerged region of gneiss and crystalline schists the carboniferous strata with their beds of coal and their plant-remains were being de- posited ; many of the strata being made up from the partially _ disintegrated crystalline schists and now scarcely distinguish- able from them. After some disturbance, the secondary forma- tions were laid down unconformably alike over the carbonifer- ous and the older strata, followed by the nummulitic beds and their overlying sandstones; the whole, from the base of the trias, having in this region an aggregate thickness of about 1,250 metres. Subsequently to this occurred the great move- ments which threw into folds all of these strata, enclosing, as in the Tarentaise, the nummulites, with jurassic and carbonifer- ous fossils, among the folds of the crystalline schists. This was followed by great denudation, which removed from the broken anticlinals the secondary rocks, leaving, however, in the horizontal jurassic beds which still cap the Aiguilles Rouges, an evidence of the former spread of these formations, which once extended over what is now the summit of Mont Blane. It is worthy of note that the highest portions of this latter do not exhibit the underlying gneiss, but are capped by crystalline schists, which may be supposed to rest upon it, as do the sec- * See in this connection Hebert, Bull. Soc. Geol. de France (2), XXV. XIV.] THE GEOLOGY OF THE ALPS. 345 ondary strata upon the schists of the Aiguilles Rouges. These elevated points are evidences of the enormous erosion in this region, the results of which have contributed to build up in the lower regions of the Alps, and in the Jura, the great masses of miocene sediment known as the molasse, — a formation partly marine and partly lacustrine, which attains in some parts a thickness of more than 2,000 metres. This period was fol- lowed by other movements which have raised the beds of molasse to a vertical attitude, and in some cases inverted them, so that they appear dipping beneath the nummulitic formation. It is worthy of note that the molasse near Geneva includes in its upper part a lacustrine limestone, followed by marls with - gypsum, and by lignites. That the nature of the fan-like structure of the Alps is cor- rectly represented in the sections of Studer, Lory, and Favre, ean, we think, no longer admit of doubt. Another explana- tion ‘was, however, possible; the dipping of the beds on either side toward the centre of the.mass might indicate synclinal mountains, lying between two eroded anticlinals. Such a mountain-structure appears not to be uncommon in regions where the undulations are moderate ; and is, according to Les- ley, frequent in the anthracite region of Pennsylvania. Snow- don in Wales, according to Sedgwick, and Ben Nevis and Ben Lawers in the Scottish Highlands, according to Murchison, are also examples of this structure, the summits of all of these being composed of newer strata, beneath which, on either side, dip the older formations. When, therefore, geologists of au- thority from Bertrand and Keferstein to Murchison and Lyell maintained that the crystalline rocks of Mont Blanc were newer than the limestones of the valleys on either side, and even declared them to be altered sediments of the tertiary period, it was difficult to regard Mont Blanc as anything else than a synclinal mountain similar in general structure and origin to those just mentioned. Hence it was that in 1860 (American Journal of Science (2), X XIX. 118) I remarked, " “the weight of evidence now tends to show that the crystal- line nucleus of the Alps, so far from being an extruded mass 15 * 346 THE GEOLOGY OF THE ALPS. [XIv. of so-called primitive rock, is really an altered sedimentary deposit more recent than many of the fossiliferous strata upon _ ; a their flanks, so that the Alps, as a whole, have a general syn- clinal structure.” This view of the recent age of the crystal-— line rocks of this region, supported though it has been by the authority of great names, must now, we conceive, be abandoned, and their great antiquity, as maintained by the learned pro- fessor of Geneva, admitted. It however remains true that the extrusion and laying bare of these ancient crystalline rocks is, as we have seén, an event geologically very recent. | It would greatly exceed our present limits to notice our au-— thor’s learned discussion of the superficial geology, including the glacial phenomena, of the Alpine region. His views upon some of the most keenly controverted questions with regard to glacial action will be found set forth in‘his letter to Sir R. L Murchison on the Origin of Alpine Lakes and Valleys, which appeared in the London, Edinburgh, and Dublin Philosophical Magazine for March, 1865. This beautiful work of Professor Favre is accompanied by an atlas of thirty-two folio plates, embracing maps, sections, views, and figures of organic remains, which elucidate the text in a very complete manner. It is a magnificent monument to the industry, acumen, and scientific zeal of one who for a quar- ter of a century has devoted his time and his fortune to the pursuit of science, and has worthily completed the task which his illustrious countryman De Saussure commenced. ? XIV.] THE GEOLOGY OF THE ALPS. 347 APPENDIX. [THE crystalline rocks in the line of the Mont Cenis Tunnel, con- sisting of micaceous limestones, dolomites, gypsums, and anhydrites, with talcose schists, serpentines, and quartzite, have been, as we have seen, regarded by all observers as altered mesozoic strata. According to Elie de Beaumont and Sismonda, they are metamor- phosed jurassic, and the uncrystalline anthraciferous strata in con- tact with them near Modane are unaltered rocks belonging to the same period. Favre, on the other hand, while maintaining the car- boniferous age of the latter, followed Lory in regarding the crystal- line strata as more recent than these, and, in fact, as metamorphosed triassic. These conclusions as to the age of the crystalline rocks I have ventured in the preceding pages to call in question, and have compared them with certain ancient crystalline schists of Scandi-. navia. A letter from Professor Favre, dated February, 1872, admits the justice of my strictures ; he now rejects the notion that they are altered fossiliferous strata, and regards them as of unknown age, citing the recently expressed opinion of Gastaldi that they are older than the carboniferous and are altered paleozoic. The existence of such rocks of paleozoic age is, however, improbable, and those to which I have compared them are eozoic. Professor Favre writes, with reference to my ideas as expressed in the above review and also in my address at Indianapolis (ante, pages 286 — 312), as to the possible alteration of palzozoic and more re- cent strata to crystalline schists: “Je vois avec grand plaisir que vous n’y croyez guere, puisque vous ne voyez nulle part des schistes cristallins dont on puisse dire que ce sont des schistes paléozoiques altérés. Je suis arrivé & croire qu’il n’y a pas de métamorphisme pour les terrains en grand, au moins bien peu, et que tous les ter- rains se sont déposés a peu prés dans l’état ot nous les voyons.”* * “T see with great pleasure that you have little belief in it” (the alteration of palzozoic and more recent strata to crystalline schists), ‘since you nowhere recognize crystalline schists of which it can be said that they are altered paleozoic schists. I have come to believe that there is little or no metamor- phism for the great formations, and that all these formations were deposited very nearly in the state in which we see them.” With the above extract from ; a 348 THE GEOLOGY OF THE ALPS. [XIV. He then proceeds to explain his view that the crystalline schists, the dolomites, and the serpentines have been deposited as such, or have only undergone a subsequent molecular change, such as I have described on pages 300 and 305 of the present volume. It is grati- fying to record such testimony to the views I have so long advo- cated, from the learned geologist of Geneva, who has devoted his life to the study of what is generally regarded as the classic region of rock-metamorphism. The dip of the strata of the whole section of the Mont Cenis Tun- — nel is, according to Sismonda and Elie de Beaumont, to the north- west, but, according to Fayre and to Pillet, the carboniferous rocks at Modane dip to the southward, suggesting (what might here be looked for), a want of conformity between the crystalline and uncrystal- line series. The ancient views of Elie de Beaumont and of Sismonda, according to whom the anthraciferous rocks of this region belong to a single great series of jurassic age, which includes at the same time crystalline schists, a carboniferous flora, a jurassic fauna, and num- mulitic beds, appear to be still maintained by these geologists, and are set forth by De Beaumont in a communication to the French Academy of Science, in 1871, on the rocks of the Mont Cenis Tun- nel. The publication of this in the Comptes Rendus called forth an energetic protest from Pillet in behalf of the Academy of Sci- ences of Savoy, in December, 1871. He there complains of the persistent maintenance of views which he declares to have been set aside by the labors of Favre and others, as shown in the work re- viewed above, and adds: “The opening of the Mont Cenis Tunnel might have been expected to put an end to the discussion, since we see at St. André, near Modane, the primitive granitic rock overlaid by the coal formation with anthracite, by the trias, and by the liassic schists with belemnites, all placed in their normal order and succession.” ] Favre’s letter to me, written in February, 1872, may be compared Giimbel’s conclusions, cited in a note to page 305, from his letter to me, also written early in 1872, XV. HISTORY OF THE NAMES CAMBRIAN AND SILURIAN IN GEOLOGY. The present essay appeared in the Canadian Naturalist for April and July, 1872, and the first two parts of it were reprinted in Nature for May of the same year, and sub- sequently in the Geological Magazine in 1873, while a French translation of the entire paper by Dewalque, with notes and additions, is announced as about to appear in Belgium. Having been desired, in 1872, to prepare for publication a notice of the scientific labors of Murchison, it became necessary for me to examine critically the whole ground of the Cambrian and Silurian controversy, a task which proved much more serious than I had supposed, and brought to light facts which both surprised and pained me. In the interest of truth I determined to write the history as I have here given it, and I had the great pleasure of laying this statement, in its completed form, before the venerable Sedgwick, who, in several letters written to me during the last months of his life, testified his gratitude for the manner in which justice had at length been done to him and to his labors, and, moreover, warmly acknowledged it in the Preface to a new Catalogue of the Cambridge Fossils, dictated by him a few months before his death, which took place in his eighty-eighth year, at Trinity College, Cambridge, January 27, 1873. That Preface contains a more circumstantial and complete account of the personal history of the controversy than had previously appeared. Such a history as this of the Cambrian and Silurian rocks of the Old World was not complete without an account of the progress of our knowledge regarding the similar rocks of North America; and I have, therefore, in the third part, endeavored to set forth in an impartial manner the share of each investigator in the working out of this important chapter in the geological history of our continent. I have, in thé present reprint, made several important additions, and some changes with the view of ren- dering more complete, both for Great Britain and North America, the history of these older paleozoic rocks. The additions and the important changes, whether in notes or in the text, are distinguished by being enclosed in brackets. Ir is proposed in the following pages to give a concise ac- count of the progress of investigation of the lower palzeozoic rocks during the last forty years. The subject may naturally be divided into three parts: 1. The history of Silurian and Upper Cambrian in Great Britain from 1831 to 1854; 2. That of the still more ancient paleeozoic rocks in Scandinavia, Bohemia, and Great Britain up to the present time, including the recognition by Barrande of the so-called primordial paleo- 350 CAMBRIAN AND SILURIAN IN EUROPE. [XV. zoic fauna; 3. The history of the lower palzozoic rocks of North America. I. SrmuRIAN AND Upper CAMBRIAN IN GREAT BRITAIN. Less than forty years since, the various uncrystalline sedi- mentary rocks beneath the coal-formation in Great Britain and in continental Europe were classed together under the common name of graywacke or grauwacké, a term adopted by geologists from German miners, and originally applied to sandstones and other coarse sedimentary. deposits, but extended so as to include associated argillites and limestones. Some progress had been made in the study of this great Graywacke formation, as it was called, and organic remains had been described from vari- ous parts of it; but to two British geologists was reserved the honor of bringing order out of this hitherto confused group of strata, and establishing on stratigraphical and paleontological grounds a succession and a geological nomenclature. The work of these two investigators was begun independently and simultaneously in different parts of Great Britain. -In 1831 and 1832, Sedgwick, aided in the early part of his labors by Mr. Charles Darwin, made a careful section of the rocks of North Wales from the Menai Strait across the range of Snow- don to the Berwyn hills, thus traversing in a southeastern di- rection Caernarvon, Denbigh, and Merionethshire. Already, he tells us, he had in 1831 made out the relations of the Bangor group (including the Llanberris slates and the overlying Har- lech grits), and showed that the fossiliferous strata of Snowdon occupy a synclinal, and are stratigraphically several thousand feet above the horizon of the latter. Following up this investi- gation in 1832, he established the great Merioneth anticlinal, which brings up the lower rocks on the southeast side of Snow- don, and is the key to the structure of North Wales. From these, as a base, he constructed a section along the line already indicated, over Great Arenig to the Bala limestone, the whole forming an ascending series of enormous thickness. This limestone in the Berwyn hills is overlaid by many thousand feet of strata as we proceed eastward along the line of section, oy v : 4 =, a. 4 Ma ‘a a te q B XV.] CAMBRIAN AND SILURIAN IN EUROPE. 351 until at length the eastern dip of the strata is exchanged for a westward one, thus giving to the Berwyn chain, like that of Snowdon, a synclinal structure. As a consequence of this, the limestone of Bala reappears on the eastern side of the Berwyns, underlaid as before by a descending series of slates and por- phyries. These results, with sections, were brought before the British Association for the Advancement of Science at its meeting at Oxford, in 1832, but only a brief and imperfect account of the communication of Sedgwick on this occasion appears in the Proceedings of the Association. He did not at this time give any distinctive name to the series of rocks in question. (L. E. & D. Philos. Mag. [1854] (4), VIII. 495.) - Meanwhile, in the same year, 1831, Murchison began the examination of the rocks on the river Wye, along the southern border of Radnorshire. In the next four years he extended his researches through this and the adjoining counties of Here- ford and Salop, distinguishing in this region four separate geological formations, each characterized by peculiar fossils. These formations were, moreover, traced by him to the south- westward, across the counties of Brecon and Caermarthen ; thus forming a belt of fossiliferous rocks stretching from near Shrewsbury to the mouth of the river Towey,a distance of about one hundred miles along the northwest border of the great Old Red sandstone formation, as it was then called, of the west of England. The results of his labors among the rocks of this region for the first three years were set forth by Murchison in two papers presented by him to the Geological Society of London in Janu- ary, 1834. (Proc. Geol. Soc., Il. 11.) The formations were then named as follows in descending order: 1. Ludlow, 2. Wenlock ; constituting together an upper group; 3. Caradoc, 4, Llandeilo (or Builth); forming a lower group. The Llan- deilo formation, according to him, was underlaid by what he called the Longmynd and Gwastaden rocks. The non-fossilif- erous strata of the Longmynd hills in Shropshire were described as rising up to the east from beneath the Llandeilo rocks ; and as appearing again in South Wales at the same geological horizon, 352 CAMBRIAN AND SILURIAN IN EUROPE. [Xv. at Gwastaden in Breconshire, and to the west of Llandovery in Caermarthenshire ; constituting an underlying series of con- torted slaty rocks many thousand feet in thickness, and desti- tute of organic remains. The position of these rocks in South Wales was, however, to the northwest, while the strata of the Longmynd, as we have seen, appear to the east of the fossilif- erous formations. _In the L. E. & D. Philosophical Magazine for July, 1835, Murchison gave to the four formations above named the des- ignation of Silurian, in allusion, as is well known, to the an- cient British tribe of the Silures. It now became desirable to find a suitable name for the great inferior series, which, accord- ing to Murchison, rose from beneath his lowest Silurian forma- tions to the northwest, and appeared to be widely spread in Wales. Knowing that Sedgwick had long been engaged in the study of these rocks, Murchison, as he tells us, urged him to give them a British geographical name. Sedgwick accord- ingly proposed for this great series of Welsh rocks the appro- priate designation of Cambrian, which was at once adopted by Murchison for the strata supposed by him to underlie his Silu- rian system. (Murchison, Anniv. Address, 1842; Proc. Geol. Soc., III. 641.) This was almost simultaneous with the giving of the name of Silurian, for in August, 1835, Sedgwick and Murchison made communications to the British Association at Dublin on Cambrian and Silurian Rocks. These, in the vol- ume of Proceedings (pp. 59, 60), appear as a joint paper, though from the text they would seem to have been separate. Sedgwick then described the Cambrian rocks of North Wales as including three divisions : First, the Upper Cambrian, which occupies the greater part of the chain of the Berwyns, where, according to him, it was connected with the Llandeilo forma- tion of the Silurian. To the next lower division, Sedgwick gave the name of Middle Cambrian, making up all the higher mountains of Caernarvon and Merionethshire, and including the roofing-slates and flagstones of this region. This middle group, according to him, afforded a few organic remains, as at the top of Snowdon. The inferior division, designated as XVv.] CAMBRIAN AND SILURIAN IN EUROPE. 353 Lower Cambrian, included the crystalline rocks of the south- west coast of Caernarvon and a considerable portion of Angle- sea, and consisted of chloritic and micaceous schists, with slaty quartzites and subordinate beds of serpentine and granular limestone ; the whole without organic remains. These crystalline rocks were, however, soon afterwards ex- cluded by him from the Cambrian series, for in 1838 (Proc. Geol. Soc., IL. 679) Sedgwick describes further the section from the Menai Strait to the Berwyns, and assigns to the chloritic and micaceous schists of Anglesea and Caernarvon a position inferior to the Cambrian, which he divides into two parts ; namely, Lower Cambrian, comprehending the old slate series, up to the Bala limestone beds ; and Upper Cambrian, including the Bala beds, and the strata above them in the Ber- wyn chain, to which he gave the name of the Bala group. The dividing line between the two portions was subsequently extended downwards by Sedgwick to the summit of the Arenig slates and porphyries. The lower division was afterwards sub- divided by him into the Bangor group (to which the name of Lower Cambrian was henceforth to be restricted), including the Llanberris roofing-slates and the-Harlech grits or Barmouth sandstones ; and the Festiniog group, which included the Lin- gula flags and the succeeding Tremadoc slates. In the communication of Murchison to the same Dublin meeting, in August, 1835, he repeated the description of the four formations to which he had just given the name of Si- lurian ; which were, in descending order, Ludlow and Wen- lock (Upper Silurian), and Caradoc and Llandeilo (Lower Si- lurian). The latter formation was then declared by Murchison to constitute the base of the Silurian system, and to offer in many places in South Wales distinct passages to the underly- ing slaty rocks, which latter were, according to him, the HUippee Cambrian of Sedgwick. Meanwhile, to go back to 1834, we find that after Murchi- son had, in his communication to the Geological Society, de- fined the relation of his Llandeilo formation to the underlying slaty series, but before the names of Silurian and Cambrian 7 Ww Ms oe ee SUS TT Re vee ee See ean ee ee pa es ee 354 - CAMBRIAN AND SILURIAN IN EUROPE. [Xv. had been given to these respectively, Sedgwick and Murchison visited. together the principal sections of these rocks from Caer- marthenshire to Denbighshire. The greater part of this region was then unknown to Sedgwick, but had been already studied by Murchison, who interpreted the sections to his companion . in conformity with the scheme already given; according to which the beds of the Llandeilo were underlaid by the slaty rocks which appear along their northwestern border. When, however, they entered the region which had already been ex- amined by Sedgwick, and reached the section on the east side of the Berwyns, the fossiliferous beds of Meifod were at once pronounced by Murthison to be typical Caradoc, while others in the vicinity were regarded as Llandeilo. The beds of Mei- fod had, on paleontological grounds, been by Sedgwick identi- fied with those of Glyn Ceirog, which are seen to be immedi- ately overlaid by Wenlock rocks. These determinations of Murchison were, as Sedgwick tells us, accepted by him with great reluctance, inasmuch as they involved the upper part of his Cambrian section in most perplexing difficulties. When however, they crossed together the Berwyn 'chain to Bala, the limestones in this locality were found to contain fossils nearly agreeing with those of the so-called Caradoc of Meifod. The examination of the section here presented showed, however, that these limestones are overlaid by a series of several thou- sand feet of strata, bearing no resemblance either in fossils or in physical characters to the Wenlock formation, which over- lies the Caradoc beds of Glyn Ceirog. This series, was, there- fore, by Murchison supposed to be identical with the rocks which, in South Wales, he had placed beneath the Llandeilo, and he expressly declared that the Bala group could not be brought within the limits of his Silurian system. It may here be added that in 1842 Sedgwick re-examined this region, accompanied by that skilled paleontologist, Salter, confirming the accuracy of his former sections, and showing, moreover, by the evidence of fossils that the beds of Meifod, Glyn Ceirog, and Bala are very nearly on one parallel. Yet, with the evi- dence of the fossils before him, Murchison, in 1834, placed une fy . . 2 ee ae =e re Ay, 3 Seen -% Phd peti at XV.] CAMBRIAN AND SILURIAN IN EUROPE. 355 the first two in his Silurian system, and the last deep down in the Upper Cambrian; and consequently was aware that on paleontological grounds it was impossible to separate the lower portion of Silurian system from the Upper Cambrian of Sedg- wick. (These names are here used for convenience, although we are speaking of a time when they had not been applied to designate the rocks in question.) This fact was repeatedly insisted upon by Sedgwick, who, in the Syllabus of his Cambridge lectures, published very early in 1837, enumerated the principal genera and species of Upper Cambrian fossils, many of which were by him declared to be the same with those of the Lower Silurian rocks of Murchison, Again, in enumerating in the same Syllabus the characteristic species of the Bala limestone, it is added by Sedgewick: “all of which are common to the Lower Silurian system.” This was again insisted upon by him in 1838 and 1841. (Proc. Geol. Goe., I. 679 ; IIL. 548.) It was not until 1840 that Bowman announced the same conclusion, which was reiterated by Sharpe in 1842, (Ramsay, Mem. Geological Survey, III. Part II. p. 6.) In 1839, Murchison published his Silurian System, dedi- cated to Sedgwick, a magnifieent work in two volumes quarto, with a separate map, numerous sections, and figures of fossils. | The succession of the Silurian rocks, as there given, was pre- cisely that already set forth by the author in 1834, and again in 1835 ; being, in descending order, Ludlow and Wenlock, constituting the Upper Silurian, and Caradoc and Llandeilo (including the Lower Llandeilo beds or Stiper-stones), the Lower Silurian. These are underlaid by the Cambrian rocks, into which the Llandeilo was said to offer a transition marked by beds of passage. Murchison, in fact, declared that it was impossible to draw any line of separation, either lithological, zoological, or stratigraphical, between the base of the Silurian beds (Llandeilo) and the upper portion of the Cambrian, — the whole forming, according to him, in Caermarthenshire, one continuous and conformable series from the Cambrian to the Ludlow. (Silurian System, pages 256, 258.) By Cambrian 356 CAMBRIAN AND SILURIAN IN EUROPE, [XV. in this connection we are to understand only the Upper Cam- brian or Bala group of Sedgwick, as appears from the express statement of Murchison, who alludes to the Cambrian of Sedg- wick as including all the older slaty rocks of Wales, and as divided into three groups, but proceeds to say that in his present work (the Silurian System) he shall notice only the highest of these three. Since January, 1834, when Murchison first announced the stratigraphical relations of the lower division of what he after- wards called the Silurian system, the aspect of the case had materially changed. This division was no longer underlaid, both to the east in Shropshire and to the west in Wales, by a great unfossiliferous series. His observations in the vicinity of the Berwyn hills with Sedgwick in 1834, and the subse- quently published statements of the latter, had shown that this supposed older series was not without fossils ; but on the contrary, in North Wales, at least, held a fauna identical with that characterizing the Lower Silurian. Hence the assertion of Murchison in his work on the Silurian System, in 1839, that it was not possible to draw any line of demarcation between them. The position was very embarrassing to the author of the Silurian System, and, for the moment, not less so to the discoverer of the Upper Cambrian series. Meanwhile, the latter, as we have seen, in 1842 re-examined with Salter his Upper Cambrian sections in North Wales, and satisfied him- self of the correctness, both structurally and paleontologically, of his former determinations. Murchison, in his anniversary address as President of the Geological Society in 1842, after recounting, as we have already done, the history of the naming by Sedgwick, in 1835, of the Cambrian series, which Murchi- son supposed to underlie his Silurian system, proceeded as follows : “‘ Nothing precise was then known of the organic contents of this lower or Cambrian system except that some of the fossils contained in its upper members in certain prominent localities were published Lower Silurian species. Meanwhile, by adopting the word Cambrian, my friend and myself were certain that whatever might prove to be its zodlogical -distinc- i — ver, sue 2 oS ae se ee ee a Sh: a se XV.] CAMBRIAN AND SILURIAN IN EUROPE. 357 tions, this great system of slaty rocks being evidently inferior to those zones which had been worked out as Silurian types, no ambiguity could hereafter arise..... In regard, however, to a descending zodlogical order, it still remained to be proved _ whether there was any type of fossils in the mass of the Cam- brian rocks different from those of the Lower Silurian series. If the appeal to nature should be answered in the negative, then it was clear that the Lower Silurian type must be consid- ered the true base of what I had named the protozoic rocks ; but if characteristic new forms were discovered, then would the Cambrian rocks, whose place was so well established in the descending series, have also their own fauna, and the palozoic base would necessarily be removed to a lower horizon.” If the first of these alternatives should be established, or in other words, if the fauna of the Cambrian rocks was found to be identical with that of the Lower Silurian, then, in the author’s language, “the term Cambrian must cease to be used in zodlog- ical classification, it being, in that sense, synonymous with Lower Silurian.” That such was the result of paleontological inquiry, Murchison proceeded to show by repeating the an- nouncements already made by Sedgwick in 1837 and 1838, that the collections made by the latter from the great series of fossiliferous strata in the Berwyns, from Bala, from Snowdon and other Cambrian tracts, were identical with the Lower Silurian forms. These strata, it was said, contain throughout “the same forms of Orthis which typify the Lower Silurian rocks.” It was further declared by Murchison in this address, that researches in Germany, Belgium, and Russia led to the conclusion that the “ fossiliferous strata characterized by Lower Silurian Orthide are the oldest beds in which organic life has been detected.” (Proc. Geol. Soc, III. 641, et seg.) The Orthids here referred to are, according to Salter, Orthos calli- gramma, Dalm, and its varieties. (Mem. Geol. Survey, II. Part II. 335 — 337.) Meanwhile Sedgwick’s views and position began to be mis- represented. In 1842, Mr. Sharpe, after calling attention to the fact that the fossils of the Bala limestone were, as Sedgwick $4.5 POR ee e ‘ bi CS ee) ey 358 CAMBRIAN AND SILURIAN IN EUROPE. [XV. had long before shown, identical with those of Murchison’s Lower Silurian, declared that Sedgwick had placed the Upper Cambrian, in which the Bala beds were included, beneath the Silurian, and that this determination had been adopted by Mur- chison on Sedgwick’s authority. (Proc. Geol. Soc., IV. 10.) This statement Murchison suffered to pass uncorrected in a complimentary review of Sharpe’s paper in his next annual address (1843). Subsequently, in his Siluria, first edition, page 25 (1854), he spoke of the term Cambrian as applied (in 1835) by Sedgwick and himself “to a vast succession of fossil- iferous strata containing undescribed fossils, the whole of which were supposed to rise up from beneath well-known Silurian rocks. The government geologists have shown that this supposed order of superposition was erroneous,” etc. The italics are the author’s. Such language, coupled with Mr. Sharpe’s assertion noticed above, helped to fix upon Sedgwick the responsibility of Murchison’s error. Although the histori- cal sketch, which precedes, clearly shows the real position of Sedgwick in the matter, we may quote further his own words: “T have often spoken of the great Upper Cambrian group of North Wales as inferior to the Silurian system,....on the sole authority of the Lower Silurian sections, and the author’s many times repeated explanations of them before they were pub- lished. So great was my confidence in his work, that I received it as perfectly established truth that his order of superposition was unassailable. .... I asserted again and again that the Bala limestone was near the base of the so-called Upper Cambrian group. Murchison asserted and illustrated by sections the unvarying fact that his Llandeilo flag was superior to the Upper Cambrian’ group. There was no difference between us, until his Llandeilo sections were proved to be wrong.” (Philos. Mag. (4), VIII. 506.) That there must be a great mistake either in Sedgwick’s or in Murchison’s sections was evident, and the government surveyors, while sustaining the correctness of those of Sedgwick, have shown the sections of Murchison to have been completely erroneous. The first step towards an exposure of the errors of the Silu- XV.] CAMBRIAN AND SILURIAN IN EUROPE. 359 rian sections is, however, due to Sedgwick and McCoy. In order better to understand the present aspect of the question, it will be necessary to state in a few words some of the results which have been arrived at by the government surveyors in their studies of the rocks in question, as set forth by Ramsay in the Memoirs of the Geological Survey. In the section of the Berwyns, the thin bed of about twenty feet of Bala lime- stone, which (as originally described by Sedgwick) they have found outcropping on both sides of the synclinal chain, is shown to be intercalated in a vast thickness of Caradoc rocks; being overlaid by about 3,300 and underlaid by 4,500 feet of strata belonging to this formation. Beneath these are 4,500 feet additional of beds described as Llandeilo, which rest uncon- formably upon the Lingula flags just to the west of Bala ; thus making a thickness of over 12,000 feet of strata belonging to the Bala group of Sedgwick. A small portion of rocks referred to the Wenlock formation occupies the synclinal above men- tioned. (Memoirs, III. Part III..214, 222.) The second mem- ber, in ascending order, of the Silurian system, to which the name of Caradoc was given by him in 1839, was originally described by Murchison under the names of the Horderley and May Hill sandstone. The higher portions of the Caradoc were subsequently distinguished by the government surveyors as the Lower and Upper Llandovery rocks ; the latter (constitut- ing the May Hill sandstone, and known also as the Pentamerus beds), being by them regarded as the summit of the Caradoc formation. In 1852, however, Sedgwick and McCoy showed from its fauna that the May Hill sandstone belongs rather to the overlying Wenlock than to the Caradoc formation, and marks a distinct paleontological horizon. This discovery led the geological surveyors to re-examine the Silurian sections, when it was found by Aveline that there exists in Shropshire a complete and visible want of conformity between the underlying formations and the May Hill sand- stone ; the latter in some places resting upon the nearly verti- cal Longmynd rocks, and in others upon the Llandeilo flags, the Caradoc proper or Bala group, and the Lower Llandovery 360 CAMBRIAN AND SILURIAN IN EUROPE. [Xv. beds. Again, in South Wales, near Builth, the May Hill sandstone or Upper Llandovery rests upon Lower Llandeilo beds ; while at Noeth Grug the overlying formation is traced transgressively from the Lower Llandovery across the Caradoc to the Llandeilo. These important results were soon con- firmed by Ramsay and by Sedgwick. (Ibid., 4, 236.) The May Hill sandstone often includes, near its base, conglomerate beds made up of the ruins of the older formation. To the northeast, in the typical Silurian country, it is of great thickness and continuity, but gradually thins out towards the southwest. There exists, moreover, another region where not less curious discoveries were made. About forty miles to the eastward of the typical region in South Wales appear some important areas of Silurian rocks. These are the Woolhope beds, appear- ing through the Old Red sandstone, and the deposits of Abberley, the Malverns, and May Hill, rising along its eastern border, and covered along their eastern base by the newer Mesozoic sandstone. The rocks of these localities were by Murchison in his Silurian System described as offering the complete sequence. When, however, it was found that his Caradoc included two unconformable series, examination showed that there was no representative of the older Caradoc or Bala group in these eastern regions, but that the so-called Caradoc was nothing but the Upper Llandovery or May Hill sandstone. The immediately underlying strata, which Murchison had regarded as Llandeilo, or rather as the beds of passage from Llandeilo to Cambrian, and had compared with the northwest parts of the Caermarthenshire sections (Silurian System, 416), have since been found to be much more ancient deposits, of Middle Cambrian age, which rest upon the crystalline hypozoic rocks of the Malverns, and are unconformably overlaid by the May Hill sandstone. We shall again revert to this region, which has been carefully studied and described by Professor John Phillips. (Mem, Geol. Sur., IL. Part I.) What then was the value and the significance of the Silurian sections of Murchison, when examined in the light of the —— ee oP on Ole ieee os XV.] CAMBRIAN AND SILURIAN IN EUROPE. 361 results of the government surveyors? The Llandeilo rocks, having throughout the characteristic Orthis so much insisted upon by Murchison, were shown to be the base of a great conformable series, and to the eastward, in Shropshire, to rest on the upturned edges of the Longmynd rocks ; while west- ward, near Bala, they overlie unconformably the Lingula flags, and in the island of Anglesea repose directly upon the ancient crystalline schists. According to the author of the Silurian System, there existed beneath the base of the Llandeilo forma- tion a great conformable series of slaty rocks into which this formation passed, and from which it could not be distinguished either zodlogically, stratigraphically, or lithologically. The sequence, determined from what were considered typical sec- tions in the valley of the Towey in Caermarthenshire, as given by Murchison, for several years both before and after the pub- lication of his work, was as follows: 1. Cambrian; 2. Llan- deilo flags; 3. Caradoc sandstone; 4. Wenlock and Ludlow beds ; 5. Old Red sandstone ; the order being from northwest to southeast. What, then, were these fossiliferous Cambrian beds underlying the Llandeilo and indistinguishable from it ? Sedgwick, with the aid of the government surveyors, has an- swered the question in a manner which is well illustrated in his ideal section across the valley of the Towey. The whole of the Bala or Caradoc group rises in undulations to the north- west, while the Llandeilo flags at its base appear on an anti- clinal in the valley, and are succeeded to the southeast by a portion of the Bala. The great mass of this group on the southeast side of the anticlinal is however concealed by the overlapping May Hill sandstone, — the base of the unconform- able upper series which includes the Wenlock and Ludlow beds. (Philos. Mag. (4), VIII. 488.) The section to the southeast, commencing from the Llandeilo flags on the anti- clinal, was made by Murchison the Silurian system, while the great mass of strata on the northwest side of the Llandeilo (which is the complete representative of the Caradoc or Bala beds, partially concealed on the southwest side) was supposed by him to lie beneath the Llandeilo, and was called Cambrian 16 362 CAMBRIAN AND SILURIAN IN EUROPE. [XV. (the Upper Cambrian of Sedgwick). These rocks, with the Llandeilo at their base, were, in fact, identical with the Bala group studied by the latter in North Wales, and are now clearly traced through all the intermediate distance. This is admitted by Murchison, who says: “ The first rectification of this erroneous view was made in 1842 by Professor Ramsay, who observed, that instead of being succeeded by lower rocks to the north and west, the Llandeilo flags folded over in those directions, and passed under superior strata, charged with fossils which Mr. Salter recognized as well-known types of the Caradoc or Bala beds.” (Siluria, 4th ed., p. 57, foot-note.) The true order of succession in South Wales was, in fact: 1. Llandeilo; 2. Cambrian (= Caradoc or Bala); 3. Wenlock and Ludlow ; 4. Old Red sandstone ; the Caradoc or Bala beds being repeated on the two sides of the anticlinal, but in great part concealed on the southeast side by the overlapping May Hill or Upper Llandovery rocks. These latter, as has been shown, form the true base of the upper series which, in the Silurian sections, was represented by the Wenlock and Ludlow. Murchison had, by a strange oversight, completely inverted the order of his lower series, and turned the inferior members upside down. In fact, the Llandeilo flags, instead of being, as he had maintained, superior to the Cambrian (Caradoc or Bala) beds, were really inferior to them, and were only made Silurian by a great mistake. The Caradoc, under different names, was thus made to do duty at two horizons in the Silurian system, both below and above the Llandeilo flags. Nor was this all, for by another error, as we have seen, the Caradoc in the latter position was made to include the Pentamerus beds of the un- conformably overlying series. Thus it clearly appears that with the exception of the relations of the Wenlock and Lud- low beds to each other and to the overlying Old Red sand- stone, which were correctly determined, the Silurian system of Murchison was altogether incorrect, and was moreover based upon a series of stratigraphical mistakes which are scarcely paralleled in the history of geological investigation. It was thus that the Lower Silurian was imposed on the t XV.] CAMBRIAN AND SILURIAN IN EUROPE. 363 scientific world ; and we may well ask, with Sedgwick, wheth- er geologists ‘ would have accepted the Lower Silurian classifi- cation and nomenclature had they known that the physical or sectional evidence upon which it was based had been, from the first, positively misunderstood.” Feeling that his own sections - were, as has since been fully established, free from error, Sedg- wick naturally thought his name of Upper Cambrian should prevail for the great Bala group. Hence the long and imbit- tered discussion that followed, in which Murchison, in many respects, occupied a position of vantage as against the Cambridge professor, and finally saw his name of Lower Silurian supplant almost entirely that of Upper Cambrian given by Sedgwick, who had first rightly defined and interpreted the geological relations of the group. In a paper read before the Geological Society in June, 1843, (Proc. Geol. Soc., IV. 213— 223) when the perplexity in which the relations of the Upper Cambrian and Lower Silurian rocks were involved had not been cleared up by the discovery of Murchison’s errors in stratigraphy, Sedgwick proposed a com- promise, according to which the strata from the Bala limestone to the base of the Wenlock were to take the name of Cambro- Silurian; while that of Silurian should be reserved for the Wenlock and Ludlow beds, and for those below the Bala the name of Cambrian should be retained. The Festiniog group (including what were subsequently named the Lingula flags and the Tremadoc slates) would thus be Upper instead of Middle Cambrian, the original Upper Cambrian being hence- forth Cambro-Silurian ; it being understood that, wherever the dividing line might be drawn, all the groups above it should be called Cambro-Silurian, and all those below it Cambrian. This compromise was rejected by Murchison, who in the map accompanying the first edition of his Siluria, in 1854, extended the Lower Silurian color so as to include all but the lowest division of the Cambrian, namely, the Bangor group. When, however, the relations of Upper Cambrian and Silurian were made known by the discoveries of Sedgwick and the govern- ment surveyors, this compromise was seen to be uncalled for, 364 CAMBRIAN AND SILURIAN IN EUROPE. [XV. ° and was withdrawn in 1854 by Sedgwick, who reclaimed the name of Upper Cambrian for his Bala group. In June, 1843, Sedgwick proposed that the whole of the fossiliferous rocks below the horizon of the Wenlock should be designated Protozoic, and on the 29th of November, 1843, presented to the Geological Society an elaborate paper on the Older Paleozoic (Protozoic) Rocks of North Wales, with a colored geological map. This paper, which embodied the results of the researches of Sedgwick and Salter, was not, however, published at length, but an abstract of it was pre- pared by Mr. Warburton, then president of the society, with a reduced copy of the map. (Proc. Geol. Soc., IV. 212 and 251 —268 ; also Geol. Jour., I. 5-22.) In this map of Sedg- wick’s three divisions were established, namely, the hypozoic crystalline schists of Caernarvonshire, the ‘‘ Protozoic” and the “ Silurian.” On the legend of the reduced map, as published by the Geological Society, these latter names were altered so as to read “‘ Lower Silurian (Protozoic)” and “ Upper Silurian.” These changes, in conformity with the nomenclature of Mur- chison, were, it is unnecessary to say, made without the knowledge of Sedgwick, who did not inspect the reduced and altered map until it was appealed to as an evidence that he had abandoned his former ground, and had recognized the equiva- lency of the whole of his Cambrian with the Lower Silurian of Murchison. The reader will sympathize with the indignation with which Sedgwick declares that his map was “most un- warrantably tampered with,” and will, moreover, “learn with surprise that an inspection of the proof-sheets of Warburton’s abstract of Sedgwick’s paper was refused him, notwithstanding his repeated solicitations. ‘The story of all this, and finally of the refusal to print in the pages of the Geological Journal the reclamations of the venerable and aggrieved author, make altogether a painful chapter, which will be found in the Philos. Magazine for 1854 ( (4) VIL. pp. 301-317, 359-370, and 483-506), and more fully in the Synopsis of British Paleozoic Rocks, which forms the Introduction to McCoy's British Paleozoic Fossils. Xvid CAMBRIAN AND SILURIAN IN EUROPE. 365 In connection with this history it may be mentioned that in March, 1845, Sedgwick presented to the Geological Society a paper on the Comparative Classification of the Fossiliferous Rocks of North Wales and those of Cumberland, Westmore- land, and Lancashire; which appears also in abstract in the same volume of the Geological Journal that contains the ab- stract of the essay and the map just referred to. (I. 442.) That this abstract also is made by another than the author is evident from such an expression as “the author's opinion seems to be grounded on the following facts,” etc., (p. 448) and from the manner in which the terms Lower and Upper Silurian are applied to certain fossiliferous rocks in Cumberland. Yet the words of this abstract are quoted with emphasis in Siluria (1st. ed., 147), as if they were Sedgwick’s own language recog- nizing Murchison’s Silurian nomenclature. * II. Mipnpie anp Lower CAMBRIAN. Investigations in continental Europe were, meanwhile, pre- paring the way for a new chapter in the history of the lower paleozoic rocks, A series of sedimentary beds in Sweden and Norway had Jong been known to abound in singular petrifica- tions, some of which had been examined by Linnzus, who gave to them the name of Hntomolitht. They were also studied and described by Wahlenberg and by Brongniart, the latter of whom, from two varieties of the Entomolithus paradoxus, Linn., established in 1822 two genera, Paradowides and Agnostus. In 1826 appeared a memoir by Dalman on the Palewade, or so-called Trilobites; which was followed, in 1828, by his classic work on the same subject. (Uber die Palaeaden oder so-genannten Trilobiten, 4to, with six plates, Leipsic.) In these works were described and figured, among many others, two genera, — Olenus, which included Paradoxides, Brongn., * [A letter to the author, written him by the late Professor Sedgwick after reading the above, confirms the opinion here expressed. The abstract in question was furnished by Murchison himself to the Geological Society, the secretary of which declined to receive the abstract offered by Sedgwick of his own paper.] i hae ee 366 CAMBRIAN AND SILURIAN IN EUROPE. [XV. and Battus, including Agnostus of the same author. Mean- while, Hisinger was carefully studying the strata in which these trilobites were found in Gothland, and in the same year (1828) published in his Anteckningar, or Notes on the Physical and Geognostical Structure of Norway and Sweden, a colored geological map and section of these rocks as they occur in the county of Skaraborg ; where three small circumscribed areas of nearly horizontal fossiliferous strata are shown to rest upon a floor of old crystalline rocks, in some parts granitic and in others gneissic in character. The section and map, as given by Hisinger, show the succession in the principal area to be as follows, in ascending order: 1. Granite or gneiss ; 2. Sandstone ; 3, Alum-slates ; 5. Orthoceratite-limestones ; 4. Clay-slates. By a curious oversight the colors on the legend are wrongly ar- ranged and wrongly numbered, as above; for in the map and section it is made clear that the succession is that just given, and that the clay-slates (4), instead of being below, are above the orthoceratite-limestones (5). In 1837, Hisinger published his great work on the organic remains of Sweden, entitled Lethwa Suecica (4to, with forty- two plates). In this he gives a tabular view, in descending order, of the rock-formations, and of the various genera and species described. The rocks of the areas just noticed appear in his fourth or lowest division, under the head of Yorma- tiones transitionis, and are divided as follows :— a. Strata calcarea recentiora Gottlandiz, b, Strata schisti argillacei. * c. Strata schisti aluminaris. d. Strata calcarea antiquiora. é. Strata saxi arenacei. The succession thus given was, however, erroneous, and proba- bly, like the mistake in the legend of the same author's map just mentioned, the result of inadvertence, the true position of the alum-slates (c) being between the older limestone (d) and the basal sandstone (e). This is shown both by Hisinger’s map of 1828, and by the testimony of subsequent observers. In Murchison’s work on the Geology of Russia in Europe, a a ee ee ee es ee eee XV.] CAMBRIAN AND SILURIAN IN EUROPE. 367 published in 1845, there is given (page 15 et seg.) an ac- count of his visit to this region in company with Professor Loven, of Christiania ; which, with figures of the sections, is reproduced in the different editions of Siluria. The hill of Kin- nekulle, on Lake Wener, is one of the three areas of transition rocks delineated on the map of Hisinger above referred to. Resting upon a flat region of nearly vertical gneissic strata, we have, according to Murchison: 1. A fucoidal sandstone; 2. Alum-slates ; 3. Red orthoceratite limestone; 4. Black grapto- litic slates; the whole series being little over 1,000 feet in thickness, and capped by erupted greenstone. Above these higher slates there are found, in some parts of Gothland, other limestones with orthoceratites, trilobites, and corals, the newer limestone strata (a) of Hisinger; the whole overlaid by thin sandstone beds. These higher limestones and sandstones con- tain the fauna of the Wenlock and Ludlow of England ; while the lower limestones and graptolitic slates afford Calymene Blu- menbachit, Orthis calligramma, and many other species com- mon to the Bala group of North Wales. The alum-slates below these, however, contained, according to Hisinger, none of the species then known in British rocks, but in their stead five species of Olenus and two of Battus (Agnostus). In 1854, Angelin published his Palwontologica Scandinavica, Part I., Crustacea formationis transitionis [4to, forty-one plates], in which he divided the series of transition rocks above described by Hisinger into eight parts, designated by Roman numerals, counting from the base. Of these I. was . named Regio Fucoidarum, no organic remains other than fucoids being known therein ; while the remaining seven were named from their characteristic genera of trilobites, which were as follows, in ascending order, certain letters being also used to designate the parts: II. (A) Olenus; III. (B) Cono- coryphe; IV. (BC) Ceratopyge; V. (C) Asaphus; VI. (D) Trinucleus ; VII. (DE) Harpes; VIII. (E) Cryptonymus. -In the Regio Olenorum (II.) was found also the allied genus Para- douxides. With regard to the characteristic genus of Regio IIL, the name of Conocoryphe was proposed for it by Corda in 1847, pe ot aN Pre an Ve Nt eRe ee © AS ey ee ee one 7 368 CAMBRIAN AND SILURIAN IN EUROPE. as synonymous with Zenker’s name of Conocephalus (Cono- cephalites), already appropriated to a genus of insects. Meanwhile, the similar crustaceans which abound in the transition rocks of Bohemia had been studied and described by Hawle, Corda, and Beyrich, when Barrande began his admi- rable investigations of this ancient fauna and of its stratigraph- ical relations. He soon found that beneath the horizon charac- terized by fossils of the Bala group (Llandeilo and Caradoc) there existed in Bohemia a series of strata distinguished by a remarkable fauna, entirely distinct from anything known in Great Britain, but closely allied to that of the alum-slates of Scandinavia, corresponding to Regiones IL and IL of Angelin. To this he gave the name of the first or primordial fauna, and to the rocks yielding it that of the Primordial Zone. Resting upon the old gneisses of Bohemia appears a series of crystalline schists designated by Barrande as Ftage A, overlaid by a series of sandstones and conglomerates, Etage B, upon which repose the fossiliferous argillites of the primordial zone, or Etage C. The rocks of the Etages A and B were by Bar- rande regarded as azoic, but, in 1861, Fritsch of Prague, after a careful search, discovered in certain thin-bedded sandstones of B the traces of filled-up vertical double tubes ; which, accord- ing to Salter (Mem. Geol. Sur., III. 243), are probably the marks of annelides, and are identical with those found in the rocks of the Bangor or Longmynd group in Great Britain, which will be shown to belong to the primordial zone. It is, therefore, probable that the Etage B, which apparently cor- responds to the Regio Fucoidarum or basal sandstone of Scandinavia, should itself be included in the primordial zone. It may here be noticed that it is in the crystalline schists of A that Giimbel has found Zoz00n Bavaricum. To the Etage C in Bohemia, Barrande assigns a thickness of about 1,200 feet, and to this his first fauna is confined, while in the succeeding divisions he distinguished a second and a third. The second fauna, which characterizes Etage D, corresponds to that of the Bala group; while the third fauna, belonging to the Etages E, F, G, and H, is that of the May Hill, Wenlock, and Ludlow formations of Great Britain. (Xv. - ‘ "| ‘ 4 . ™ 5 a % ke oes ve : Pe ee ee a oe ee a / XV.] CAMBRIAN AND SILURIAN IN EUROPE. 369 This classification of the ancient Bohemian faunas was first set forth by Barrande in 1846, in his N otice Préliminaire, in which he declared that the first fauna was below the base of the Llandeilo of Murchison, unknown in Great Britain, and, moreover, ‘new and independent in relation to the two Silu- rian faunas (his second and third) already established in England.” This opinion he reiterated in 1859. These three divisions form in Bohemia an apparently continuous series, and being connected with each other by some common species, Barrande was led to look upon the whole as forming a single stratigraphical system ; and finally to assert that these three independent faunas ‘“‘ form by their union an indivisible triad, which is the Silurian system.” (Bull. Soc. Geol. de Fr. (2), XVI. 529-545.) Already, in 1852, in his magnificent work on the Silurian System of Bohemia, Barrande had given to the strata characterized by his first fauna the name of Primordial Silurian. It is difficult to assign any just reason for thus an- nexing to the Silurian—already augmented by the whole Upper Cambrian or Bala group of Sedgwick (Llandeilo and Caradoc) —a great series of fossiliferous rocks lying below the base of the Llandeilo, and unsuspected by the author of the Silurian System, who persistently claimed the Llandeilo beds, with their characteristic second fauna, as marking the dawn of organic life. . Up to this time the primordial paleozoic fauna of Bohemia and of Scandinavia was, as we have said, unknown in Great Britain. The few organic remains mentioned by Sedgwick in 1835 as occurring in the region occupied by his Lower and Middle Cambrian, on Snowdon, were found to belong to Bala beds, which there rest upon the older rocks: nor was it until 1845 that Mr. Davis found in the Middle Cambrian remains of Lingula. In 1846, Sedgwick, in company with Mr. Davis, re-examined these rocks, and in December of the same year described the Lingula beds as overlaid by the Tremadoc slates and occupying a well-defined horizon in Caernarvon and Me- rionethshire, beneath the great mass of the Upper Cambrian rocks. (Geol. Jour., II. 75; III. 139.) Sedgwick, at the same 16 * x 370 | GAMBRIAN AND SILURIAN IN EUROPE. [XV. time, noticed about this horizon certain graptolites and an Asaphus, which were supposed to belong to the Tremadoc ' slates, but have since been declared by Salter to pertain to the Arenig or Lower Llandeilo beds, the base of the Upper Cam- brian. (Mem. Geol. Sur., III. 257, and Decade IL.) This discovery of the Lingula flags, as they were then named, and the fixing by Sedgwick of their geological horizon, was at once followed by a careful examination of them by the govern- ment surveyors, and in 1847, Selwyh detected in the Lingula flags, near Dolgelly, in Merionethshire, the remains of two crustacean forms, the one a phyllopod, which has received the name of Hymenocaris vermicauda, Salter, and the other a trilobite which was described by Salter in 1849 as Olenus micrurus. (Geol. Survey, Decade II.) A species of Para- doxides, apparently identical with P. Yorchhammeri of Swe- den, was also about this time recognized among specimens supposed to be from the same horizon. It has since been de- scribed as P. Hicksii, and found to belong to the basal beds of the Lingula flags, — the Menevian group. Upon the flanks of the Malvern Hills there is found resting upon the ancient crystalline rocks of the region, and overlaid by the Pentamerus beds of the May Hill sandstone (originally called Caradoc by Murchison) a series of fossiliferous beds. These consist in their lowest part of about 600 feet of greenish sandstone, which have since yielded an Obolella and Serpu- lites, and are overlaid by 500. feet of black schists. In these, | in 1842, Professor John Phillips found the remains of trilo- bites, which he subsequently described, in 1848, as three species of Olenus. (Mem. Geol. Survey, II. Part I. 55.) These black shales, which had not at that time furnished any organic remains, were by Murchison in his Silurian System (p. 416) in 1839 compared to the supposed passage-beds in Caermarthenshire between the Llandeilo and the Cambrian (Bala) rocks ; which, as we have seen, were newer and not older strata than the Llandeilo flags. From their lithological characters, and their relations to the Pentamerus beds, these lower fossiliferous strata of Malvern were subsequently referred 4 cs : ul on ag a7 is I - a ~ ‘ " in eee aren es _— = - —_ ‘woe C. Bo Oe ee a. pees = Se Se eS» Se XV.] CAMBRIAN AND SILURIAN IN EUROPE. atl by the government geologists to the horizon of the Caradoc proper or Bala group; nor was it until 1851 that their true geological age and significance were made known. In that year, Barrande, fresh from the study of the older rocks of the continent, came to England for the purpose of comparing the British fossils with those of the primordial zone, which he had established in Bohemia and Scandinavia, and which he at once recognized in the Lingula flags of Sedgwick and in the black schists at Malvern; both of which were char- acterized by the presence of the genus Olenus, and were referred to the horizon of his Etage C. This important con- clusion was announced by Salter to the British Association at Belfast in 1852. (Rep. Brit. Assoc., abstracts, p. 56, and Bull. Soc. Geol. de Fr. (2), XVI. 537.) [The black schists of Malvern, and the underlying greenish beds known as the Hollybush sandstones, are by Hicks regarded as the equivalents respectively of the Dolgelly and Festiniog divisions of the Lin- gula-flags. (Proc. Geologists, Association, Vol. III. No. 3.)] The paleontological studies of Salter, while they confirmed the primordial character of the whole of the great mass of strata which make up the Middle Cambrian or Festiniog group of Sedgwick (consisting of the Lingula flags and the Tremadoc slates), led him to propose several subdivisions. Thus he distinguished on paleontological grounds between the upper and lower Tremadoc slates, and for like reasons divided the Lingula flags into a lower and an upper portion. For the discussion of these distinctions the reader is referred to the memoirs of the Geol. Survey (III. 240-257). Subsequent researches led to the division of the original Lingula flags into four parts, an upper, middle, and lower, to which the names of Dolgelly, Festiniog, and Maentwrog were given by Mr. Belt in 1867, and a fourth, consisting of the basal beds, which had been already separated in 1865 by Salter and Hicks, with the designation of Menevian, derived from the ancient Roman name of St. David’s in Pembrokeshire.* It was here that, in [* The researches of Mr. Belt on the Lingula Flags appeared in 1867. (Geological Magazine, Vol. IV. 483 and 536, and Vol. V. 5.) He included 372 CAMBRIAN AND SILURIAN IN EUROPE. [XV. 1862, Salter found Paradoxides with Agnostus and Lingula in fine black shales at the base of the Lingula flags, resting con- formably on the green and purple grits of the Lower Cambrian or Harlech beds. The locality was afterwards carefully studied by Hicks, and it was soon made apparent that the genus Para- doxides, both here and in North Wales, was confined to a horizon below the great mass of the Lingula flags ; which, on the contrary, are characterized by numerous species of Ole- nus. These lower or Menevian beds are hence regarded by Salter as equivalent to the lowest portion of the Etage C of Barrande. , Beneath these Menevian beds there lies, in apparent con- formity, the great. Lower Cambrian series, frequently called the bottom or basement rocks by the government surveyors ; rep- resented in North Wales by the Harlech grits, and in South Wales, near St. David’s, by a similar series of green and purple sandstones, considered by Murchison, and by others, as the equivalent of the Harlech rocks. They were still supposed to be unfossiliferous until in June, 1867, Salter and Hicks an- nounced the discovery in the red beds of this lower series, at St. David’s, of a Lingulella, very like ZL. ferruginea of the Menevian. (Geol. Jour., XXIII. 339; Siluria, 4th ed., 550.) This led to a further examination of these Lower Cambrian beds, which has resulted in the discovery in them of a fauna distinctly primordial in type, and linked by the presence of several identical fossils to the Menevian ; but in many respects distinct, and marking a lower fossiliferous horizon than any- thing known in Bohemia or in Scandinavia. The first announcement of these important results was made under the name of Upper Cambrian the Tremadoc rocks with the Lingula flags proper, which he divided in descending order into three parts, Dolgelly, Festiniog, and Maentwrog; while he suggested the union of the basal beds, (previously separated under the name of Menevian,) with the underlying Harlech and Bangor rocks as Lower Cambrian. These divisions of Belt are now recognized by Hicks. It will be recollected that the whole of the Lingula flags were originally included in his Festiniog group by Sedgwick. All of these rocks are inverted in the vicinity of Dolgelly, the apparent ge in descending order being Festiniog, Dolgelly, Tremadoc, and 4 ‘ , a 4 ) XV.] CAMBRIAN AND SILURIAN IN EUROPE. 373 to the British Association at Norwich in 1868. Further details were, however, laid before the Geological Society in May, 1871, by Messrs. Harkness and Hicks, whose paper on The Ancient Rocks of St. David’s Promontory appears in the Geological Journal for November, 1871. (XXVIII. 384.) The Cambrian sediments here rest upon an older series of © _erystalline stratified rocks, described by the geological sur- veyors as syenite and greenstone, and having a northwest strike. Lying unconformably upon these, and with a north- east strike, we have the following series, in ascending order: 1. Quartzose conglomerate, 60 feet; 2. Greenish flaggy sand- stones, 460 feet ; 3. Red flags or slaty beds, 50 feet, containing Lingulella ferruginea, besides a larger species, Discina, and Leperditia Cambrensis; 4. Purple and greenish sandstones, 1,000 feet; 5. Yellowish-gray sandstones, flags, and shales, 150 feet, with Plutonia, Conocoryphe, Microdiscus, Agnostus, Theca,and Protospongia ; 6. Gray, purple, and red flagey sand- stones, with most of the above genera, 1,500 feet; 7. Gray flaggy beds, 150 feet, with Paradowdes; 8. True Menevian beds, richly fossiliferous, 500 feet. The latter are the probable equivalent of the base of Barrande’s Etage C, and at St. David's are conformably overlaid by the Lingula flags ; beneath which we have, including the Menevian, a conformable series of 3,370 feet of uncrystalline sediments, fossiliferous nearly to the base, and holding a well-marked fauna distinct from anything hitherto known in Great Britain or elsewhere. The Menevian beds are connected with the underlying strata by the presence of Lingulella ferruginea, Discina pileolus, and Obolella sagittatis, which extend through the whole series ; and also by the genus Paradoxides, four species of which occur in these lower strata; from which the genus Olenus, which characterizes the Lingula flags, seems to be absent. To a large tuberculated trilobite of a new genus found in these lowest rocks the name of Plutonia Sedgwickit has been given. Hicks has proposed to unite the Menevian with the Harlech beds, and to make the summit of the former the dividing line be- tween the Lower and Middle Cambrian, a suggestion which ee ee Eee et ees 374 CAMBRIAN AND SILURIAN IN EUROPE. (xv. has been adopted by Lyell. (Proc. Brit. Assoc. for 1868, p. 68, and Lyell, Student’s Manual of Geology, 466 — 469.) Both Phillips and Lyell give the name of Upper Cambrian to the Lingula flags and the Tremadoc slates, which together constitute the Middle Cambrian of Sedgwick, and concede the title of Lower Silurian to the Bala group or Upper Cambrian of Sedgwick. The same view is adopted by Linnarsson in Sweden, who places the line between Cambrian and Silurian at the base of the Llandeilo or the second fauna. It was by following these authorities that: I, inadvertently, in my address to the American Association for the Advancement of Science in August, 1871, gave this horizon as the original division between Cambrian and Silurian.* The reader of the first part of this paper will see with how much justice Sedgwick claims for the Cambrian the whole of the fossiliferous rocks of Wales beneath the base of the May Hill sandstone, including both the first and the second fauna. I cannot but agree with the late Henry Darwin Rogers, who, in 1856, reserved the designa- tion of “ the true European Silurian” for the rocks above this horizon. (Keith Johnson’s Physical Atlas, 2d ed.) The Lingula flags and Tremadoce slates have been made the subject of careful stratigraphical and paleontological studies by the Geological Survey, the results of which are set forth by Ramsay and Salter in the third volume of the Memoirs of the Geological Survey, published in 1866, and also, more concisely, in the Anniversary Address by the former to the Geological Society in 1863. (Geol. Jour. (19), XVIII.) The Lingula flags (with the underlying Menevian, which resembles them lithologically) rest in apparent conformity upon the purple Harlech rocks both in Pembrokeshire and in Merionethshire, where the latter appear on the great Merioneth anticlinal, long since pointed out by Sedgwick. The Lingula flags, (including the Menevian) have in this region, according to Ramsay, a thickness of about 6,000 feet. Above these, near Tremadoc and Festiniog, lie the Tremadoc slates, which are here overlaid, in apparent conformity, by the Lower Llandeilo beds. Ata * Since corrected in the reprint of that address in the present volume. Oy ee a hl i al ae ae ll eT ae oe ea XV.] CAMBRIAN AND SILURIAN IN EUROPE, 375 distance of eleven miles to the northwest, however, the Tre- madoc slates disappear, and the Lingula flags are represented by only 2,000 feet of strata; while in parts of Caernarvonshire, and in Anglesea, the whole of the Lingula flags and, moreover, the Lower Cambrian rocks are wanting, and the Llandeilo beds rest directly upon the ancient crystalline schists. In Scotland and in Ireland, moreover, the Lingula flags are wholly absent, and the Llandeilo rocks there repose unconformably upon grits. regarded as of Lower Cambrian’ age. Thus, without counting the Tremadoe slates, which are a local formation, unknown out of Merionethshire,* we have (including the Bangor group and Lingula flags), beneath the Llandeilo, over 9,000 feet of fossiliferous strata, which disappear entirely in the distance of a few miles. From a careful survey of all the facts, the conclusion of Ramsay is irresistible, that there exists between the Lingula flags and the Llandeilo not merely one, but two great stratigraphical breaks in the succession ; the one between the Lingula flags and the Lower Tremadoc slates, and the other between the Upper Tremadoc slates and the Lower Llandeilo, at the base of which were included the Arenig rocks. This conclusion is confirmed by the fact that there exists at each of these horizons a nearly complete paleontological break. * [This statement requires correction, since already, in 1866, Messrs. Salter and Hicks had mentioned the occurrence of rocks supposed to be of that age near St. David’s in South Wales, and very recently, in the Quarterly Geologi- cal Journal for February, 1873, the latter has given a description of the localities of Tremadoc rocks in this region, with figures of the organic remains, a map, and sections. The beds have hereathickness of about 1,000 feet, and rest directly upon the Lingula flags. The apparent want of conformity between the two divisions noticed by Ramsay in North Wales is here not manifest, They are followed in seeming unconformity by the Arenig rocks, which are by Mr. Homfray considered equivalent to the Upper Tremadoc of North Wales, and contain in abundance the graptolites of the Levis formation of Canada. The beds between these and the Lingula flags hold a rich fauna closely allied to the Lower Tremadoc, including an Orthoceras, a new species of Paleasterina, and a Dendrocrinus, various brachiopods and lamellibranchs, trilobites of the genus Niobe and of a new genus, Vesewretus, closely allied to Dikeloceph- alus, to which Hicks refers the supposed species of D. described by Salter from the Upper Lingula and Lower Tremadoe rocks of North Wales; the only true Dikelocephalus in Wales, according to him, being D. furca from the Upper Tremadoc.] 376 CAMBRIAN AND SILURIAN IN EUROPE. [XV. The fauna of the Tremadoc slates is, according to Salter, al- most entirely distinct from that of the Lingula flags, and not less distinct from that of the so-called Lower Llandeilo or Arenig rocks (the equivalents of the Skiddaw slates of Cum- berland). Hence, says Ramsay, it is evident “that in these strata we have three perfectly distinct zones of organic re- mains, and therefore, in common terms, three distinct forma- tions.” The paleontological evidence is thus in complete accordance with that furnished by stratigraphy. We cannot leave this topic without citing the conclusion of Ramsay that “each of these two breaks necessarily implies a lost epoch, stratigraphically quite unrepresented in our area; the life of which is only feebly represented in some cases by the fossils common to the underlying and overlying formation.” In connection with this remark, which we conceive to embody a truth of wide application, it may be said that stratigraphical breaks and discordances in a geological series may, a priori, be expected to occur most frequently in regions where this series is represented by a large thickness of strata. The accu- mulation of such masses implies great movements of subsi- dence, which, in their nature, are limited, and are accompa- nied by elevations in adjacent areas, from which may result, over these areas, either interruptions in the process of sedi- mentation, or the removal, by sub-aerial or sub-marine denuda- tion, of the sediments already formed. The conditions of succession and distribution, it may be conceived, would be very different in a region where the period corresponding to this same geological series was marked by comparatively small accumulations of sediment upon an ocean-floor subjected to no great movements, This contrast is strikingly seen between the conformable series of less than 2,000 feet of strata, which in Scandinavia are characterized by the first three palozoic faunas (Cambrian and Silurian), and the repeatedly broken and discordant sue- cession of more than 30,000 feet of sediments,* which in * The Longmynd rocks in Shropshire are alone estimated at 20,000 feet ; but their supposed equivalents, the Harlech rocks of Pembrokeshire, have a i i i ae = LS —<—- - ——-— ao: Mi — a ee ennuminiecamas - XV.] CAMBRIAN AND SILURIAN IN EUROPE. 377 Wales are their paleontological equivalents. It must, however, be considered that in regions of small accumulation where, as in Scandinavia, the formations are thin, there may be lost or unrepresented zodlogical periods whose place in the series is marked by no stratigraphical break. In such comparatively stable regions, movements of the surface sufficient to cause the exclusion, or the disappearance by removal, of the small thick- ness of strata corresponding to a zodlogical period, may take place without any conspicuous marks of stratigraphical dis- cordance. The attempt to establish geological divisions or horizons upon stratigraphical or palzontological breaks must always prove fallacious. From the nature of things, these, whether due to non-deposition or to subsequent removal of deposits, ~ must be local ; and we can say, confidently, that there exists . no break in life or in sedimentation which is not somewhere filled up and represented by a continuous and conformable suc- cession. While we may define one period as characterized by the presence of a certain fauna, which, in a succeeding age, is replaced by a different one, there will always be found, in some part of their geographical distribution, a region where the two faunas commingle, and where the gradual disappearance of the old before the new may be studied. The division of our strati- fied rocks into systems is therefore unphilosophical, if we assign any definite or precise boundaries or limitations to these. It was long since said by Sedgwick with regard to the whole succession of life through geologic time, that all belongs to one great systema nature. (Philos. Mag. (4), VIII. 359.) We have already noticed that Barrande, as early as 1852, gave the name of Primordial Silurian to the rocks which, in measured thickness of 3,300, while the Llanberris and Harlech rocks to- gether, in North Wales, equal from 4,000 to 7,000 feet, and the Lingula flags and Tremadoc slates, united, about 7,000 feet. The Bala groupin the Ber- wyns exceeds 12,000 feet, and the proper Silurian, from the base of the Upper Llandovery or May Hill sandstone, attains from 5,000 to 6,000 feet ; so that the aggregate of 30,000 feet may be considered below the truth. (Mem. Geol. Survey, III., Part II. pages 72, 222; and Siluria, 4th ed. 185.) [The aggregate thickness since assigned to these rocks by Hicks is ahout 33,000 feet. } EE ee Cos — ar 378 CAMBRIAN AND SILURIAN IN EUROPE. [Xv. Bohemia, were marked by the first fauna ; although he, at the same time, recognized this as distinct from and older than the second fauna, discovered in the Llandeilo rocks, which Murchi- son had declared to represent the dawn of organic life. Into the reasons which led Barrande to include the rocks of the first, second, and third faunas in one Silurian system (a view which was at once adopted by the British Geological Survey and by Murchison himself), it is not our province to inquire, but we desire to call attention to the fact that the latter, by his own principles, was bound to reject such a classification. In his address before the Geological Society in 1842 (already quoted in the first part of this paper), he declared that the discussion as to the value of the term Cambrian involved the question “ whether there was any type of fossils in the . mass of the Cambrian rocks different from those of the Lower Silurian series. If the appeal to nature should be answered in the negative, then it was clear that the Lower Silurian type. must be considered the true base of what I had named the protozoic rocks ; but if characteristic new forms were discov- ered, then would the Cambrian rocks, whose place was so well established in the descending series, have also their own fauna, and the paleozoic base would necessarily be removed to a lower horizon.” In the event of no distinct fauna being found in the Cam- brian series, it was declared that ‘‘ the term Cambrian must cease to be used in zoélogical classification, it being, in that sense, synonymous with Lower Silurian.” (Proc. Geol. Soe., III. 641, et seg.) That such had been the result of paleon- tological inquiry Murchison then proceeded to show. Inas- much as the only portion of Sedgwick’s Cambrian which was then known to be fossiliferous was really above, and not be- low, the Llandeilo rocks, which Murchison had taken for the base of his Lower Silurian, his reasoning with regard to the Cambrian nomenclature, based on a false datum, was itself fallacious ; and it might have been expected that when the government surveyors had shown his stratigraphical error, Murchison would have rendered justice to the nomenclature of EE eT — XV.] CAMBRIAN AND SILURIAN IN EUROPE. 379 Sedgwick. But when, still later, a further “appeal to nature” led to the discovery of “characteristic new forms,” and estab- lished the existence of a “type of fossils in the mass of the Cambrian rocks, different from those of the Lower Silurian series,” Murchison was bound by his own principles to recog- nize the name of Cambrian for the great Festiniog group, with its primordial fauna, even though Barrande and the govern- ment surveyors should unite in calling it Primordial Silurian. He, however, chose the opposite course, and now attempted to claim for the Silurian system the whole of the Middle Cambrian or Festiniog group of Sedgwick, including the Tre- madoc slates and the Lingula flags. The grounds of this assumption, as set forth in the successive editions of Siluria from 1854 to 1867, and in various memoirs, may be included under three heads : first, that the Lingula flags have been found to exist in some parts of his original Silurian region ; second, that no clearly defined base had been assigned by him to his so-called system ; and, third, that there are no means of draw- ing a line of demarcation between those Middle Cambrian formations and the overlying Llandeilo. With regard to the first of these reasons, it is to be said that the only known representatives of the Lingula flags in the region described by Murchison in his Silurian system are the black slates of Malvern and some scanty outliers which, in Shropshire, lie between the old Longmynd rocks and the base of the Stiper-stones. The former were then (as has already been shown) supposed by him to belong to the Llandeilo, or rather to the passage-beds between the Llandeilo and the Cam- brian (Bala) ; while with regard to the latter, Ramsay expressly tells us that they were not originally classed with the Silurian, but have since been included in it. (Mem. Geol. Sur., IIT. Part II. page 9 ; and 242, foot-note.) The Llandeilo beds were by Murchison distinctly stated to be the ‘base of the Silurian system (Silurian System, 222) ; and it was further declared by him that in Shropshire (unlike Caermarthenshire) ‘there is no passage from the Cambrian to the Silurian strata,” but a hiatus, marked by disturbances 380 CAMBRIAN AND SILURIAN IN EUROPE. [Xv. which excluded the passage-beds, and caused the Lower Silu- rian to rest unconformably upon the Longmynd rocks. (Ibid., 256 ; and Plate 31, sections 3 and 6 ; Plate 32, section 4.) But in Siluria (1st ed. 47) the two are stated to be conformable ; and in the subsequent sections of this region, made by Aveline, and published by the Geological Survey, the evidences of this want of conformity do not appear. Murchison at that time confounded the rocks of the Longmynd with the Cambrian (Bala) beds of Caermarthenshire and Brecon. (Silurian Sys- tem, 416.) Hence it was that he gave the name of Cambrian to the former; and this mistake, moreover, led him to place the Cambrian of Caermarthenshire beneath the Llandeilo. It is clear that if he claimed no well-defined base to the Llandeilo rocks in this latter (their typical region), it was because he saw them passing into the overlying Bala beds. ‘There was, in the error by which he placed below the Llandeilo, strata which were really above them, no ground whatever for afterwards including in his Silurian System, as a downward continuation of the Llandeilo rocks (which are the basal portion of the Bala group), the whole Festiniog group of Sedgwick ; whose infra- position to the Bala had been shown by the latter long before it was known to be fossiliferous. It was, however, claimed by Murchison that no line of sepa- ration can be drawn between these two groups. The results of Ramsay and of Salter, as set forth in the address of the former before the Geological Society of 1863, and more fully in the Memoirs of the Geological Survey (Vol. III. Part II.) published in 1866, with a preface by himself, as the director of the Sur- vey, are completely ignored by Murchison. The reader famil- iar with these results, of which we have given a summary, finds with surprise that in the last edition of Siluria, that of 1867, they are noticed in part, but only to be repudiated. In the five pages of text which are there given to this great Mid- dle Cambrian division, we are told that the distinction between the Lower Tremadoc and the Lingula flags “is difficult to be drawn,” and that the Upper Tremadoe slate passes into and forms the lower part of the Llandeilo (under which name a 1 ‘i 4 : : XV.] CAMBRIAN AND SILURIAN IN EUROPE. 381 Murchison included the Arenig rocks), “into which it gradu- ates conformably.” (Loc. cit., 4th ed. p. 46.) In each of these cases, on the contrary, according to Ramsay, there is observed ‘a break very nearly complete both in genera and species, and probable unconformity”; the evidence of the paleontological break being furnished by the careful studies of Salter ; while that of the stratigraphical break, as we have seen, leaves no reason for doubt. (Mem. Geol. Sur., III. Part II. pages 2, 161, 234.) The student of Siluria soon learns that in all cases where Murchison’s pretensions were concerned, the book is only calculated to mislead. The reader of this history will now be able to understand why, notwithstanding the support given by Barrande, by the geological survey of Great Britain, and by most American geologists to the Silurian nomenclature of Murchison, it is rejected, so far as the Lingula flags and the Tremadoc slates are concerned, by Lyell, Phillips, Davidson, Harkness, and Hicks in England, and by Linnarsson in Sweden. These geologists have, however, admitted the name of Lower Silu- rian for the Bala group or Upper Cambrian of Sedgwick ; a concession which can hardly be defended, but which appar- ently found its way into use at a time when the yet unravelled perplexities of the Welsh rocks led Sedgwick himself to pro- pose, for a time, the name of Cambro-Silurian for the Bala group. This want of agreement among geologists as to the nomenclature of the lower paleozoic rocks, causes no little confusion to the learner. We have seen that Henry Darwin Rogers followed Sedgwick in giving the name of Cambrian to the whole palzeozoic series up to the base of the May Hill sandstone ; and the same view is adopted by Woodward in his Manual of the Mollusca. The student of this excellent book will find that in the tables giving the geological range of the mollusca, on pages 124, 125, and 127, the name of Cambrian is used in Sedgwick’s sense, as including all the fossiliferous strata beneath the May Hill sandstone. On page 123 it is, however, explained that Lower Silurian is a synonyme for Cam- brian, and it is so used in the body of the work, 382 CAMBRIAN AND SILURIAN IN EUROPE. [XV. The distribution of the Lower and Middle Cambrian rocks in Great Britain may now be noticed. The former, or Bangor group, to which Murchison and the geological survey restrict the name of Cambrian, and which they sometimes call the Longmynd, bottom or basement rocks, occupy two adjacent areas in Caernarvon and Merionethshire ; the one near Bangor, including Llanberris, to the northeast, and the other, including Harlech and Barmouth, to the southeast, of Snowdon; this mountain lying in a synclinal between them, and rising 3,571 feet above the sea. The great mass of grits or sandstones ap- pears to be at the summit of the group, but in the lower part the blue roofing-slates of Llanberris are interstratified in a series of green and purple slates, grits, and conglomerates. (Some of the Welsh roofing-slates are, however, supposed to belong to the Llandeilo. Mem. Geol. Survey, III. Part Il. pages 54, 258.) The Harlech rocks in this northwestern region are con- formably overlaid by the ‘Menevian, followed by the true Lingula flags, or Olenus beds, of the Middle Cambrian. Upon these repose the Tremadoe slates. The third area of Lower Cambrian rocks known in Great Britain is that already described at St. David’s in Pembroke- shire, about one hundred miles to the southwest; and the fourth, that of the Longmynd hills, about sixty miles to the southeast of Snowdon. The rocks of the Longmynd, like those of the other Lower Cambrian areas mentioned, consist principally of green and purple sandstones with conglomerates, shales, and some clay-slates. They occasionally hold flakes of anthracite, and small portions of mineral pitch exude from them in some localities. The only evidence of animal life yet found in the rocks of the Longmynd are furnished by worm- burrows, the obscure remains of a crustacean (Palewopyge Ram- say), and a form like Histioderma. ‘This latter organic relic, with worm-burrows, and the fossils named Oldhamia, is found on the coast of Ireland opposite Caernarvonshire, in the rocks of Bray Head; which resemble lithologically the Harlech beds, and are regarded as their equivalents. Still another area of the older rocks is that of the Malet + gl, + 4 i“ 4 . ond fe — — 4 4 ? eS Oe . a ee ae a ee XV.] CAMBRIAN AND SILURIAN IN EUROPE, 383 hills, on the western flanks of which, as already mentioned, the Lingula flags are represented by about 500 feet of black shales with Olenus, underlaid by 600 feet of greenish sand- stones containing traces of fucoids, with Serpulites and an Obolella. It is not improbable, as suggested by Barrande and by Murchison, that these 1,100 feet of strata represent, in this region, the great mass of the Lingula flags ; and, we may add, perhaps, the whole series of Lower Cambrian strata, which in Caernarvon and Pembroke underlie them [see page 371]; since these sandstones of Malvern, like those of St. David’s, rest upon crystalline schists, and are in part. made up of their ruins. These crystalline schists of Malvern, which are described by Phillips as the oldest rocks in England, and by Mr. Holl are conjectured to be Laurentian, seem from the descriptions of their lithological characters to resemble those of Caernarvon and Anglesea, with which they are, by Murchison, regarded as identical. The crystalline schists of these latter localities are, by Sedgwick, described as hypozoic strata, below the base of the Cambrian. Murchison, however, in the first edition of his Siluria, adopted the suggestion of De la Beéche that they them- selves were altered Cambrian strata. In fact, they directly underlie the Llandeilo rocks, and-were apparently conceived by Murchison to represent that downward continuation of these upon which he had insisted. This opinion is supported by ingenious arguments on the part of Ramsay. (Mem. Geol. Survey, III. Part IL, passim.) I am, however, disposed to regard them, with Sedgwick and Phillips, as of pre-Cambrian age, and to compare them with the Huronian series of North America, which occupies a similar geological horizon, and with which, as seen in northern Michigan, and in the Green Moun- tains, I have found the rocks of Anglesea to offer remarkable lithological resemblances. It may here be noticed that the gold-bearing quartz veins in North Wales are found in the Menevian beds, and also, accord- ing to Selwyn, throughout the Lingula flags. These fossilifer- ous strata at the gold-mine near Dolgelly appear in direct con- tact with diorites and chloritic and taleose schists, which are 384 CAMBRIAN AND SILURIAN IN EUROPE. [xXv. more or less cupriferous, and themselves also contain gold-bear- ing quartz veins. (Mem. Geol. Survey, Part II. pages 42, 45 ; and Siluria, 4th ed. 450, 547.) The Table on page 386 gives a view of the lower palzozoic rocks of Great Britain and North America, together with the various nomenclatures and classifications referred to in the pre- ceding pages. In the second column, the horizontal black lines indicate the positions of the three important paleontologi- — ; ; q cal and stratigraphical breaks signalized by Ramsay in the British succession. (Mem. Geol. Survey, III. Part IT. page 2.) [Very recently, in 1873, in the Proceedings of the Geolo- — gists’ Association, Vol. III. Part IIL, Mr. Hicks has given a similar tabular view of the lower paleozoic rocks of Great Brit- ain. The Bangor group (to which he applies the name of Long- — mynd or Lower Cambrian),differs from that given in the follow- ing table only in dividing the Menevian into an upper and a lower part. The Middle Cambrian or Festiniog group of Sedg- wick (which Hicks calls Upper Cambrian) presents also the same subdivisions as are here given. In the next, or Upper Cambrian of Sedgwick (called by Hicks Lower Silurian), are in- cluded in ascending order Lower Arenig and Upper Arenig or Skiddaw, followed by Llandeilo, also divided into two parts, and by the Bala group, which he divides into Lower and Upper Caradoc, to which he adds, as we have done, the Lower Llandovery. | [In the new Catalogue of the Cambridge Fossils is an impor. tant preface written from Sedgwick’s dictation late in 1872, and published since his death. In this he unites the Lower Llandovery with the Upper Cambrian, and includes it, together with the Caradoc and Llandeilo, under the name of the Bala group, which he divides into Lower, Middle, and Upper Bala ; while the Arenig or Skiddaw rocks are joined with the Middle Cambrian. Both the Arenig and the Tremadoc rocks, in fact, present a certain intermingling of organic forms belong- ing to the first and second faunas ; but according to Hicks the Tremadoc beds are to be classed with the first, and the Arenig with the second. These two groups of rocks are in fact the XV.] CAMBRIAN AND SILURIAN IN EUROPE. 385 palaeontological equivalents of the Calciferous, Levis and Chazy, which serve in North America to connect the Middle with the Upper Cambrian. As regards the extension to the Upper Cambrian of Sedgwick of the name of Lower Silurian, which, as has been shown, was given to it only through an enormous and now universally acknowledged mistake on the part of Murchison, I am constrained, notwithstanding its adoption by so many eminent geologists, to maintain for the division the name given to it by its true discoverer, Sedgwick. ] In the third column, the subdivisions are those of the New York and Canada Geological Surveys; in connection with which the reader is referred to a table which I prepared and published in 1863, in the Geology of Canada, page 932. Op- posite to the Menevian I have placed the names of its principal American localities; which are Braintree, Massachusetts, St. John, New Brunswick, and St. John’s, Newfoundland. The further consideration of the American subdivisions is reserved for the third part of this paper. With regard to the classification of Angelin, it is to be remarked that although he designates IT. as Regio Olenorum, and III. as Regio Conocorypharum, the position of these, according to Linnarsson, is to be reversed ; the Conocoryphe beds with Paradoxides being below, and not above, those holding Olenus. The Regio Fucoidarum in Sweden has lately furnished a brachiopodous shell, ZLingula monilfera, besides the curious plant-like fossil, Hophyton Linneanum. (Linnarsson, Geol. Magazine, 1869, VI. 393.) 17 Y ; a 3 2 ; ; F ps a ee ee fe my a7 [ CAMBRIAN AND SILURIAN IN EUROPE. | [Xv. 386 ir” sere "wosryoungy “weLiqurery i "SLLIOQUBT’] uuMAeproon gy ‘q oBeqg £ younbpag ‘dnoad 108ug i “qoopey ovou ose A[qeqord pue | io wersquieg JOMO] ‘uTOL “FgpUe saaquTBIg “UBTAOUOT ue ‘ v =i ‘g oe “WOSLYIINT ( ‘Bormquoryy , ; ‘ueLIN ) *Borunysa souorsoxy ‘sung [erpsounag y a ais wrens Piers 10 tenant = em mee. : ‘ ‘dnoid Sorayse,y *SNOIOJIOTVD “QOPVUIAL], TOMO] Tt it ie Sie 10 WRLAQUIeD eTPpryT L *STAQ fal | ‘oopeurary, sedd yg . ee ; “wosLynungy j ‘MUpplyg10 S1uary og oa 0d ata ‘UVLINIG 1aMO'T ; ‘OAT YOvcg ‘oplepueyy SOUL 10 I I oe e hatte einen f younbpog ‘dnoid vpeg ‘ehospiig, uoyuedy, | “leg 10 ooperey AI ‘A TA 1o uetiquiey soddQ | orn “leary uospnyy “AIOAOPULY'T 19M0'T “aq pur "qT "TAD “H sedezq "WOSPYDLN TT ‘eploug ‘euIpoyy ‘Araaopury'y reddy Sauolsoyy 10 Surpnypour ‘uetmypig rodd MOJUTTO ‘BIVTVI NT *“YOoTUo A TIA “TIA ‘euney PIL f younbpog “wermnytg ‘B10q.1Op[PH Jao] “MO[PW'T “SUOTSTAT, "UOTPVOYTSSETD ‘WOSTPOIN, pure “SUOTSTATPQNG ‘SUOTSTATPQNG suypesuy sepuelreg YOMSpoeg Jo soimgepousUto | WeopoUry YRION Whig ao onwrie wet On et oe Oo NA Ft SO Sot Ss Ss het Ue | ‘VOIUANVY HLYON GNV WdOUNA AO SMOOUN OLOZOWTVd AAMOT XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 387 III. Camprran AND SruurRrIAN Rocks In NortH AMERICA. In accordance with our plan we now proceed to sketch the history of the lower paleozoic rocks of North America. While European geologists were carrying out the researches which have been described in the first and second parts of this paper, American investigators were not idle. The geological studies of Eaton led the way to a systematic survey of the State of New York, the results of which have been the basis of most of the subsequent geological work in eastern North America, and which was begun by legislative enactment in 1836. The State was divided into four districts, the work of examining and finally reporting upon which was committed to as many geologists. The first or southeastern district was undertaken by Mather, the second or northeastern by Emmons, the third or central by Vanuxem, and the fourth or western by James Hall ; the paleontology of the whole being left to Conrad, and the mineralogy to Beck. After various annual reports the final results of the survey appeared in 1842. The whole series of fossiliferous rocks known, from the basal or Potsdam sand- stone to the coal-formation, was then described as the New York system. At that time the published researches of British geologists furnished the means of comparison between the organic remains found in the rocks of New York, and those then known to exist in the palozoic strata of Great Britain. Professor Hall was thus enabled, in his Geology of the Fourth District of New York, to declare, from the study of its fossils, that the New York system included the Devonian of Phillips, the Silurian of Murchison, and the Cambrian of Sedgwick; meaning by the latter the Upper Cambrian, or Bala group, which alone was then known to be fossiliferous. From the evidence then before him, he concluded that the Upper Cambrian was repre- sented in the New York system by the whole of the rocks from the base of the Utica slate downward, with the probable ex-— ception of the Potsdam sandstone; while he conceived, partly 388 CAMBRIAN AND SILURIAN IN NORTH AMERICA, [XV. on lithological grounds, that the Utica and Hudson-River groups represented the Llandeilo and Caradoc, or the Lower Silurian of Murchison. (Zoe. cit., pages 20, 29, 31.) The origin of the Cambrian and Silurian controversy, and the errors by which the Llandeilo and a part of the Caradoc had by Murchi- son been classed as a series distinct from the Bala group, were not then known; but in a note to this report (page 20) Hall informs us of the declaration of Murchison, already quoted from his address of 1842, that the Cambrian, so far as then known, could not, on paleontological grounds, be distinguished from his Lower Silurian. : Emmons meanwhile had examined in eastern New York and western New England a series of fossiliferous rocks which, on lithological and stratigraphical grounds, he regarded as older than any in the New York system; a view which had been previously maintained by Eaton. Holding, with Hall, that the lower members of the New York system were the equivalents of the Dpper Cambrian of Sedgwick, he looked upon the fossiliferous rocks which he placed beneath them as the representatives of the Lower Cambrian. By this name, as we have seen, Sedgwick, in 1838, designated all those un- crystalline rocks of North Wales which he subsequently divided into Lower and Middle Cambrian, and which lie beneath the base of the Bala group. When Murchison, in 1842, in his so often quoted declaration, asserted that “ the term Cambrian must cease to be used in a zoological classification, it being in that sense synonymous with Lower Silurian,” he was speaking only on paleontological grounds, and, disregarding the great Lower and Middle Cambrian divisions of Sedgwick, had reference only to the Upper Cambrian. This, however, was overlooked by Emmons, who, feeling satisfied that the sedimentary rocks which he had examined in eastern New York were distinct from those which he, with Hall, regarded as corresponding to the Bala group or Upper Cambrian (the Lower Silurian of Murchison), and probably equivalent to the inferior portions of Sedgwick’s Cambrian ; and, supposing that the latter term was henceforth to be effaced from geology (as indeed was attempted shortly At ; an ae a): 3 a “i “a A bes > ia e te a ee, a ee ae eee ee ee e a : XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 389 after, in the copy of Sedgwick’s map published in 1844 by the Geological Society), devised for these rocks the name of the Taconic system, as synonymous with the Lower (and Middle) Cambrian of Sedgwick. ‘These conclusions were set forth by him in 1842, in his report on the Geology of the Northern District of New York (page 162). See farther his Agriculture of New York (I. 49), the fifth chapter of which, “On the Taconic System,” was also published separately in 1844 ; when the presence of distinctive organic remains in the rocks of this series was first announced. Meanwhile to Professor Hall, after the completion of the survey, had been committed the task of studying and describ- ing the organic remains of the State, and in 1847 appeared the first volume of his great work on the Paleontology of New York. Since 1842 he had been enabled to examine more fully the organic remains of the lower rocks of the New York system, and to compare them with those of the Old World ; and in the Introduction to the volume just mentioned (page ' xix) he announced the important conclusion that the New York system itself contained an older fauna than the Upper Cam- brian of Sedgwick. According to Hall, the organic forms of the Calciferous and Chazy formations had not yet been found in Europe, and our comparison with European fossiliferous rocks must commence with the Trenton group. He however excepted the Potsdam sandstone, which already, in 1842, he had conceived to be below the Upper Cambrian of Sedgwick, and now regarded as the probable equivalent of the Obolus or Ungulite grit of St. Petersburg. Thus Emmons, in 1842, asserted, on lithological and stratigraphical grounds, the exist- ence, beneath the base of the New York system, of a lower and unconformable series of rocks, in which, in 1844, he an- nounced the discovery of a distinctive fauna. Hall, on his part, asserted in 1842, and more fully in 1847, that the New York system itself held an older fauna than that hitherto known in the British rocks. It is not necessary to recall in this place the details of the long and unfortunate Taconic controversy, which I have re- a ea ee es eee) hlUY 1, -) .) aye OS eee ee ' OMe Se enn oe oe eee ee a ee ae y ‘ 390 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. cently discussed in my address before the American Associa- tion for the Advancement of Science in August, 1871. (Ante, page 251.) It is, however, to be remarked that Hall, in com- mon with all other American geologists, followed Henry D. Rogers in opposing the views of Emmons, whose Taconic system was supposed to represent either the whole or a part of the Champlain division of the New York system; which division included, as is well known, all of the fossiliferous rocks up to the base of the Oneida conglomerate (and also this latter, according to Emmons); thus comprehending both the first and the second paleozoic faunas; as shown in the pre- ceding table on page 386. Emmons, misled by stratigraphical and lithological conidia ations, complicated the question in a singular manner, which scarcely finds a parallel except in the history of Murchison’s Silurian sections. Completely inverting, as I have elsewhere shown, the order of succession in his Taconic system, estimated by him at 30,000 feet, he placed near the base of the lower division of the system the Stockbridge or Eolian limestone, in- cluding the white marbles of Vermont ; which, by their organic remains, have since been by Billings found to belong to the Levis formation. A large portion of the related rocks in western Vermont and elsewhere, which afford a fauna now known to be far more ancient than that of the Lower Taconie just referred to, and as low if not lower than anything in the New York system, were, by Emmons, then placed partly near the summit of the Upper Taconic, and partly, not only above the whole Taconic system, but above the Champlain division of the New York system. Thus we find, in 1842, in his Re- port on the Geology of the Northern District of New York (where Emmons defined his views on the Taconic system), that he placed above this latter horizon both the green sand- stone of Sillery near Quebec and the Red sand-rock of western Vermont (which he then regarded as the representatives of the Oneida and the Medina sandstones), and described the latter as made up from the ruins of Taconic rocks (pages 124, 282). In 1844-1846, in his Report on the Agriculture of XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 391 New York (page 119), he however adopted a different view of the Red sand-rock, assigning it to the Calciferous ; and in 1855, in his American Geology (II. 128), it was regarded as in part Calciferous and in part Potsdam. In 1848, Professor C. B. Adams, then director of the Geological Survey of Vermont, argued strongly against these latter views, and maintained that the Red sand-rock directly overlaid the shales of the Hudson- River group and corresponded to the Medina and Clinton for- mations of the New York system. (Amer. Jour. Sci. (2), V. 108.) He had before this time discovered in this sand-rock, besides what he considered an Atrypa, abundant remains of a trilobite, which Hall, in 1847, referred to the genus Conocephalus (Conocoryphe), remarking at the same time that inasmuch as this genus was (at that time) only described as occurring in *‘ oraywacke in Germany and elsewhere,” no conclusions could be drawn from these fossils as to the geological horizon of the rocks in question. (Ibid. (2), XX XIII. 371.) In September, 1861, however, Mr. Billings, after an examination of the rocks in question, pronounced in favor of the later opinion of Em- mons, declaring the Red sand-rock near Highgate Springs, Vermont, containing Conocephalus and Theca, to belong to the base of the second fauna, “if not indeed a little lower,” and to be “somewhere near the horizon of the Potsdam.” (Ibid. (2), XXXIT. 232.) The dark-colored fossiliferous shales which were asserted, both by Adams and by Emmons, to underlie this Red sand- rock, were, by the former, as we have seen, regarded as belong- ing to the Hudson-River group, while by the latter they were described as an upper member of the Taconic system; which ' was here declared to be unconformably overlaid by the Red sand-rock, a member of the New York system. These slates, a few years before, had afforded some trilobites, which, after remaining in the hands of Professor Hall for two years or more, were in 1859 described by him in the twelfth Report of the Regents of the University of New York, as Olenus Thompsont and O. Vermontana. He soon, however, found them to constitute a distinct genus, for which he proposed the 392 CAMBRIAN AND SILURIAN IN NORTH AMERICA, ([XV. name of Barrandia, but finding this name preoccupied, suggested in 1861, in the fourteenth Regents’ Report, that of Olenellus, which was subsequently adopted by Billings in 1865. (Palzo- zoic Fossils, pages 365, 419.) In 1860, Emmons, in his Manual of Geology, described the same species, but placed them in the genus Paradoxides, as P. Thompsoni and P. Vermontana. Hall had already, in 1847, in the first-volume of his Paleontology of New York, referred to Olenus the Hiliptocephalus asaphoides of Emmons, and also a fragment of another trilobite from Saratoga Lake ; both of which were described as belonging to the Hudson-River group of the New York system, or to a still higher horizon. The reasons for this will appear in the sequel. The Llliptocephalus, with another trilobite named by Emmons Atops (referred by Hall to Calymene, and subsequently by Bil- lings to Conocoryphe), occurs at Greenwich, New York. These were by Emmons, in his essay on the Taconic system (in 1844), described as characteristic.of that system of rocks. A copy of the Regents’ Report for 1859 having been sent by Billings to Barrande, this eminent paleontologist, in a letter addressed to Professor Bronn of Heidelberg, July 16, 1860 (American Journal of Science (2), XXXT. 212), called attention to the trilobites therein figured, and declared that no palezon- tologist familiar with the trilobites of Scandinavia would “ have hesitated to class them among the species of the primordial fauna, and to place the schists enclosing them in one of the formations containing this fauna. Such is my profound convie- tion,” etc. The letter containing this statement had already appeared in the American Journal of Science for March, 1861, but Mr. Billings in his note just referred to, on the fossils of Highgate, in the same Journal for September of that year, makes no allusion to it. In March, 1862, however, he re- turns to the subject of the sand-rock, in a more detailed commu- nication (Ibid. (2), XX XIII. 100), and after correcting some emissions in his former note, alludes in the following language to Mr. Barrande, and to the expressed opinion of the latter, just quoted, with regard to the fossils in question and the rocks containing them: “I must also state that Barrande first XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA, 393 determined the age of the slates in Georgia, Vermont, holding P. Thompsoni and P. Vermontana.” He adds, “at the time I wrote the note on the Highgate fossils it was not known that these slates were conformably interstratified with the Red sand- rock, This discovery was made afterwards by the Rev. J. B. Perry and Dr. G. M. Hall of Swanton.” Mr. Billings has blamed me (Canadian Naturalist, new series, VI. 318) for having written in 1871 (ante, page 258), with regard to the Georgia trilobites first described as Olenus by Professor Hall, that Barrande “called attention to their pri- mordial character, and thus led to a knowledge of their true stratigraphical horizon.” I had always believed that the letter of Barrande and the explicit declaration of Mr. Billings, just quoted, contained the whole truth of the matter. My atten- tion has since been called to a subsequent note by Mr. Billings in May, 1862 (Ibid. (2), XXXIII. 421), in which, while as- serting that Emmons had already assigned to these rocks a greater age than the New York system, he mentions that in sending to Barrande, in the spring of 1860, the report of Pro- fessor Hall on the Georgia fossils, he alluded to their primordial character, and suggested that they might belong to what Mr. Barrande has called “‘a colony” in the rocks of the second fauna. This is also stated in a note by Sir William Logan in the Preface to the Geology of Canada (page viii). As the genus Olenus, to which Professor Hall had referred the fossils in question, was at that time (1860) well known to belong, both in Great Britain and in Scandinavia, to the primordial fauna, Mr. Barrande does not seem to have thought it neces- sary in his correspondence to refer to the very obvious remark of Mr. Billings. Mr. Billings further showed in his paper in March, 1862, that fossils identical with those of the Georgia slates had been found by him in specimens collected by Mr. Richardson of the geological survey of Canada in the summer of 1861, on the Labrador coast, along the Strait of Belleisle ; where Olenellus (Paradoxides) Thompsoni and O, Vermontana were found with Conocoryphe (Conocephalus) in strata which were by Billings 394 CAMBRIAN AND SILURIAN IN NORTH AMERICA, [XV. referred to the Potsdam group. (See, for the further history of these fossils the Geology of Canada, pages 866, 955, and Pal. Fossils of Canada, pages 11, 419.) The interstratification of the dark-colored fossiliferous shales holding Olenellus with the Red sand-rock of Vermont, an- nounced by Mr. Billings, was further confirmed by Sir William Logan in his account of the section at Swanton, Vermont. (Geology of Canada, 281.) They were there declared to occur about 500 feet from the base of a series of 2,200 feet of strata, consisting chiefly of red sandy dolomites (the so-called sand- rock) containing Conocephalus throughout, while the shaly beds held, in addition, the two species of Paradoxides (Olenellus) . and some brachiopods. These beds, like those of Labrador, were referred by Logan and by Billings to the Potsdam group. The conclusions here announced were of great importance for the history of the Taconic controversy. The trilobites of pri- mordial type, from Georgia, Vermont, which by Emmons were placed in the Taconic system, lying unconformably beneath a series of rocks belonging to the lower part of the New York system, were now declared to belong to the Red sand-rock group, a member of this overlying system. Much has been said of these fossils, as if they furnished in some way a vindi- cation of the views of Emmons, and of the Taconic system; a conclusion which can only be deduced from a misconception of the facts in the case. Emmons had, previous to 1860, on lithological and stratigraphical evidence alone, called the Georgia slates Taconic, and placed them unconformably be- neath the Red sand-rock. If now both he and Billings were right in referring the Red sand-rock to the Calciferous and Potsdam formations, and if the stratigraphical determinations of Messrs. Perry and G. M. Hall, confirmed by those of Logan, were correct, namely, that the trilobites in question occur not in a system of strata lying unconformably beneath the Red sand-rock, but in beds intercalated with the sand-rock itself, it is clear that these trilobites must belong not to the Taconic, but to the New York, system. We shall return to the ques- tion of the age of these rocks. ee . - sete j ae ee tit i. ots ‘i wf oe, ‘ ; ‘ P ¢ z rive ! Le oe . J [= a. ; : ae ~ nie ao 7 ” ans? a? by » a 5) tie ns Pix (hi iy OS . et ae ey eae gee eee 8 > “ ; ve oy ae ew ee ee a See at Aa) ee cir 6 ee ew) i hina ‘ . " ; AY LS te = how pe ret ai eo TS ae =? F Olas es 9 a eae a ~ a o Sa perce FAL oe Be ae Pa cee ot PIO ee ee Pee hy ie o> ae Ss arr ie is ¥ SO nk Se eee ee ae .An Siler) ae It eke ee ee ee ee . 3:58 , asl : y wer ‘ere ea) a ee *s Cal = Fe % i. 5, = _ 4 ». er, - > i - XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 395 We have seen that Professor James Hall, in 1847, and again in 1859, referred trilobites regarded by him as species of Olenus to the Hudson-River group, or, in other words, to the summit of the second paleeozoic fauna, while it is now well known that they are characteristic of the first fauna. In this reference, in 1847, Professor Hall was justified by the singular errors which we have already pointed out in the works of Hisinger on the geology of Scandinavia. (Ante, page 366.) In his Anteck- ningar, in 1828, while the colored map and accompanying sec- tions show the alum-slates with Paradoxides to lie beneath, and the clay-slates with graptolites, above the orthoceratite- limestone, the accompanying colored legend, designed to ex- plain the map and sections, gives these two slates with-the numbers 3 and 4, as if they were contiguous and beneath the limestone, which is numbered 5. ‘The student who, in his perplexity, turned from this to the later work of Hisinger, his Lethea Suecica, found the two groups of slates, as before, placed in juxtaposition, but assigned, together, to a position above the orthoceratite-limestone. Thus, in either case, he would be led to the conclusion that in Scandinavia the alum- slates with Olenus, Paradosxides, and Conocephalus (Conoco- ryphe) were closely associated with the graptolitic shales ; and, upon the authority of the later work, that the position’ of both of these was there above the orthoceratite-limestones, and at the summit of the second fauna. The graptolitic shales of Scandinavia were already identified with those of the Utica and Hudson-River formations of the New York system. The Red sand-rock of Vermont, containing Conocephalus, had been, both by Emmons and Adams, alike on lithological and strati- graphical grounds, referred to the still higher Medina sand- stone; a view which, as we have seen, was still maintained and strongly defended by Adams. This was in 1847, and Angelin’s classification of the transition rocks of Scandinavia, fixing the position of the various trilobitic zones, did not ap- pear until 1854. | Professor James Hall had therefore at this time the strongest reasons for assigning the rocks containing Olenus to the sum- 1. EW ee 396 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. mit of the second fauna. Before we can understand his reasons for maintaining a similar view in 1859, we must notice the history of geological investigation in eastern Canada. So early as 1827, Dr. Bigsby, to whom North American geology owes so much, had given us (Proc. Geol. Soc., I. 37) a careful de- scription of the geology of Quebec and its vicinity. He there found resting directly upon the ancient gneiss a nearly hori- zontal dark-colored conchiferous limestone, having sometimes at its base a calcareous conglomerate, and well displayed on the north shore of the St. Lawrence at Montmorenci and Beau- port. He distinguished, moreover, a third group of rocks, described by him as a “slaty series composed of shale and graywacke, occasionally passing into a brown limestone, and alternating with a calcareous conglomerate in beds, some of them charged with fossils . . . . derived from the conchifer- ous limestone.” (This fossiliferous conglomerate contained also fragments of clay-slate.) From all these circumstances Bigsby concluded that the flat conchiferous limestones were older than the highly inclined graywacke series ; which latter was described as forming the ridge on which Quebec stands, the north shore to Cape Rouge, the island of Orleans, and the southern or Point-Levis shore of the St. Lawrence; where, besides trilobites and the fossils in the conglomerates, he no- ticed what he called vegetable impressions, supposed to be fucoids. These were the graptolites which, nearly thirty years later, were studied, described, and figured for the geological survey of Canada by Professor James Hall, who has shown that two of the species from this locality were described and figured under the name of fucoids by Ad. Brongniart, in 1828, (Geol. Sur. Canada, Decade II. page 60.) Bigsby, in 1827, conceived that the limestones of the north shore might belong to the carboniferous period, and noted the existence of what were called small seams of coal in the graywacke series of the south shore. This substance which I have since described is, however, entirely distinct from coal, and occurs in fissures, some- times in the interstices of crystalline quartz. It is an insolu- ble hydrocarbonaceous body, brilliant, very fragile, giving a - am koe hone i tas 5 rn « a, ey yy _ ag ae ae: 5, wna % Pes aE Oe ee Ney en ee ee a ay an XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA, 397 black powder, and results apparently from the alteration of a once liquid bitumen. (American Journal of Science (2), XXXV. 163.). In 1842 the geological survey of Canada was begun by Sir William Logan, who in a Preliminary Report to the govern- ment, dated in that year but printed in 1845, says (page 19) : “Of the relative age of the contorted rocks of Point Levis, opposite Quebec, I have not any good evidence, though I am inclined to the opinion that they come out from below the flat limestones of the St. Lawrence.” He however subsequently adds, in a foot-note, “The accumulation of evidence points to the conclusion that the Point Levis rocks are superior to the St. Lawrence limestones.” In 1845, Captain, now Admiral Bayfield maintained the same view, fortifying himself by the early observations of Bigsby, and expressing the opinion that the flat limestones of Montmorenci and Beauport passed be- neath the graywacke series. These limestones, from their fossils, were declared to be low down in the Silurian, and identical with those which had been observed at intervals along the north shore of the St. Lawrence to Montreal (Geol. Journal, I. 455), the fossiliferous limestones of which were then well known to belong to the Trenton group of the New York system. The graywacke series of Quebec, which was still supposed by Bayfield to hold in its conglomerates fossils from these limestones, was therefore naturally regarded as belonging to the still higher members of that system; and, as we have seen, the green sandstone near Quebec, a member of that series, had already, in 1842, been regarded by Emmons as the representative of the Oneida or Shawangunk conglomerate, at the summit of the Hudson River group of New York. It is to be noticed that immediately to the northeast of Quebec, rocks undoubtedly of the age of the Utica and Hud- son River divisions overlie conformably the Trenton limestone, on the left bank of the St. Lawrence; while a few miles to the southwest, strata of the same age, and occupying a similar stratigraphical position, appear on both sides of the St. Law- rence, and are traced continuously from this vicinity to the 398 CAMBRIAN AND SILURIAN IN NORTH AMERICA, [XV. valley of Lake Champlain. These, moreover, offer such litho- logical resemblances to what was called the graywacke series of Quebec and Point Levis (which extends thence some hundreds of miles northeastward along the right bank of the St. Law- rence), that the two series were readily confounded, and the — whole of the belt of rocks along the southeast side of the St. Lawrence, from the valley of Lake Champlain to Gaspé, was naturally regarded as younger than the limestones of the Trenton group. It was in 1847 that Sir William Logan com- menced his examination of the rocks of this region, and in his Report for the next year (1848, page 58) we find him speaking of the continuous outcrop “of recognized rocks of the Hudson River group from Lake Champlain along the south bank of the St. Lawrence to Cape Rosier.” In his Report for 1850, these rocks were further noticed as extending from Point Levis southwest to the Richelieu, and northeast to Gaspé (pages 19, 32). They were described as consisting, in ascending sequence from the Trenton limestone and the Utica slate, of clay-slates and limestones, with graptolites and other fossils, followed by con- glomerate-beds supposed to contain Trenton fossils, red and green shales and green sandstones ; the details of the section being derived from the neighborhood of Quebec and Point Levis, and from the rocks first described by Bigsby. As fur- ther evidence with regard to the supposed horizon of these rocks, to which he subsequently (in 1860) gave the name of the Quebec group, we may cite a letter of Sir William Logan, dated November, 1861 (Amer. Jour. Sci. (2), XXXIIT. 106), in which he says: “ In 1848 and 1849, founding myself upon the apparent superposition in eastern Canada of what we now call the Quebec group, I enunciated the opinion that the whole series belonged to the Hudson River group and its immediately succeeding formation ; a Leptena very like Z. sericea, and an Orthis very like O. testudinaria, and taken by me to be these species, being then the only fossils found in the Canadian rocks in question. This view supported Professor Hall in placing, as he had already done, the Olenus rocks of New York in the Hudson River group, in accordance with Hisinger’s list of i Lx Sc CC rr Crh mC rt™~—~;C~CS XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 399 Swedish rocks as given in the Lethza Suecica in 1837, and not as he had previously given it.” (Ante, pages 366 and 395.) The concurrent evidence deduced from stratigraphy, from geographical distribution, from lithological and from paleonto- logical characters, thus led Logan, from the first, to adopt the views already expressed by Bigsby, Emmons, and Bayfield, and to assign the whole of the paleeozoic rocks of the southeast shore of the St. Lawrence below Montreal to a position in the New York system above the Trenton limestone. While thus, as he says, founding his opinion on the stratigraphical evidence obtained in eastern Canada, Logan was also influenced by the consideration that the rocks in question were continuous with those in western Vermont. Part of the rocks of this region had, as we have seen, originally been placed by Emmons at this horizon, while the others, referred by him to his Taconic system, were maintained by Henry D. Rogers to belong to the Hudson River group ; a view which was adopted by Mather and by Hall, and strongly defended by Adams, at that time engaged in a geological survey of Vermont, with which, in 1846 and 1847, the present writer was connected. As regards the subsequent paleontological discoveries in these rocks in Canada, it is to be said that the graptolites first noticed by Bigsby in 1827 were rediscovered by the Geological Survey at Point Levis in 1854, and having been placed in the hands of Professor James Hall (who in that year first saw the rocks in question), were partially described by him in a communication to Sir William Logan, dated April, 1855, and subsequently at length in 1858. (Report Geol. Survey for 1857, page 109, and Decade II.) They were new forms, it is true, but the horizon of the graptolites, both in New York and in Sweden, was the same as that already assigned by Logan to the Point Levis rocks. Thus these fossils appeared to sustain his view, and they were accordingly described as belonging to the Hudson River group. Up to 1856 no other organic remains than the graptolites and the two species of brachiopods noticed by Sir William Logan were known to the geological survey as belonging to ey ee RR ey ee ee | oe srr 400 CAMBRIAN AND SILURIAN IN NORTH AMERICA, [XV. the Point Levis rocks ; the trilobites long before observed by Bigsby not having been rediscovered. In 1856 the present writer, while engaged in a lithological study of the various rocks of Point Levis, found, in the vicinity of the graptolitic shales, beds of what were described by him in 1857 (Report Geol. Surv., 1853-1856, page 465) as “ fine granular opaque limestones, weathering bluish-gray, and holding in abundance remains of orthoceratites, trilobites, and other fossils, which are replaced by a yellow-weathering dolomite.” In these, which are probably what Bigsby had long before described as fossiliferous conglomerates, the dolomitic matter is so arranged as to suggest a resemblance to certain beds which are really conglomerate in character, and were at the same time described by me as interstratified with the fossiliferous limestones, and as holding pebbles of pure limestone, of dolomite, and occa- sionally of quartz and of argillite ; the whole cemented by a yellow-weathering dolomite, and occasionally by a nearly pure carbonate of lime. (Ibid., 466.) The included fragments of argillite (previously noticed by Bigsby), which are greenish or purplish in color, with lustrous surfaces, are precisely similar to those which form great beds in the crystalline schists of the Green Mountain series of the Appalachian hills, which extend in a northeast and southwest course along the southeastern border of the rocks of the Quebec group. I conceive that these argillite fragments (like those in the Potsdam conglom- erate near Lake Champlain, ante, page 268) are derived from the ancient schists of the Appalachians. This rediscovery of fossiliferous limestones at Point Levis led to further exploration of the locality, and in 1857 and the following years a large collection of trilobites, brachiopods, and other organic remains was obtained from these limestones by the geological survey of Canada. Mr. Billings, who in 1856 had been appointed paleontolo- gist to the geological survey, at once commenced the study of these fossils from Point Levis, and at length arrived at the important conclusion that the organic remains there found belonged, not to the summit of the second fauna, but were to XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 401 be assigned a position in the first or primordial fauna. This conclusion he communicated to Mr. Barrande in a letter dated July 12, 1860 (American Journal of Science (2), XX XI. 220), - and gave descriptions of many of the organic forms in the Canadian Naturalist for the same year. I have already alluded, in describing the rocks of Point Levis, to the peculiarities of aspect which probably led Dr. Bigsby, in 1827, to confound these fossiliferous limestones penetrated by dolomite, with the true dolomitic conglomerates associated with them, and helped him to suppose the fossils to be derived from the limestones of the north shore, now known to be younger rocks. This mis- take was a very natural one at a time when comparative pale- ontology was unknown. Sir William Logan meanwhile made a careful stratigraphical examination of the rocks of Point Levis, and, notwithstanding the peculiarities of the limestones which there contain the primordial fauna, declared himself, in December, 1860, satisfied that “the fossils are of the age of the strata.” In consequence of the discovery of Mr. Billings, Logan now proposed to sepa- rate from the Hudson River group the graywacke series of Bigsby and Bayfield, and ascribed to it a much greater an- tiquity ; regarding it as “‘a great development of strata about the horizon of the Chazy and Calciferous, brought to the sur- face by an overturn anticlinal fold, with a crack and a great dislocation running along the summit,” by which the rocks in question were “ brought to overlap the Hudson River forma- tion.” This series, to which was assigned a thickness of from 5,000 to 7,000 feet, he named the Quebec group, which in- cluded the green sandstones of Sillery, regarded as the summit, the fossiliferous limestones and graptolitic shales at the base, which afterwards received the name of the Levis formation, and a great intermediate mass of barren shales and sandstones, called the Lauzon formation. The first account of this change in the stratigraphical views of Logan occurs in his letter to Barrande, dated December 31,1860. (American Journal of Science (2), XX XI. 216.) This important distinction once established, it was found Z 402 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XY. necessary to draw a line from the St. Lawrence, near Quebec, to the vicinity of Lake Champlain, separating the true Hud- son River group, with its overlying Oneida or Medina rocks, on the northwest side, from the so-called Quebec group, on the south and east. This division was by Logan ascribed to a con- tinuous dislocation, which had disturbed a great conformable palzeozoic series, including the whole of the members of the New York system from the base of the Potsdam to the sum- mit of the Hudson River group, and, throughout the whole distance of one hundred and sixty miles, had raised up the lower formations in a contorted and inclined attitude, and caused them to overlie in many cases the higher formations of the system. This dividing line was by Logan traced north- eastward through the island of Orleans, the waters of the lower St. Lawrence, and along the north shore of Gaspé; and southwestward through Vermont, across the Hudson, as far at least as Virginia; separating, throughout, the rocks of the Quebec and Potsdam groups, with their primordial fauna, from those of the Trenton and Hudson River groups, with the second fauna. This is shown in the geological map of eastern America from Virginia to the St. Lawrence, which appears in the Atlas to the Geology of Canada, published in 1865. In an earlier geological map, published by Sir William Logan at Paris in 1855, before this distinction had been drawn, the region in question in eastern Canada is colored partly as the Oneida formation, and partly as the Hudson River group; while in the accompanying text the Sillery sandstone is spoken of as the equivalent of the Shawangunk grit or Oneida conglomerate of the New York system. (Esquisse Géologique du Canada, Logan and Sterry Hunt: Paris, 1855, page 51.) These rocks were by Logan traced southward across the frontier of Canada, into Vermont, where they included the Red sand-rock and its associated slates; which were thus by Logan, as well as by Adams, looked upon as occupying a position at the summit of the second fauna. When, therefore, in 1859, Professor Hall described the trilobites found in these slates in Georgia in Ver- mont, he referred them to the genus Olenus, whose primordial ti . Pr nt ae ae ee oT . —— ee | ee ae ee a > XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA, 403 horizon in Europe was then well determined, but, in deference to the conclusions of Adams and of Logan, assigned them to a position at the summit of the Hudson River group ; Hall him- self never having examined the region stratigraphically. (Amer- ican Journal of Science (2), XX XI. 221.) In justification of this position he appended to his description the following note (Ibid., pages 213, 221): “In addition to the evidence hereto- fore possessed regarding the position of the slates containing the trilobites, I have the testimony of Sir William Logan that the shales of this locality are in the upper part of the Hudson River group, or forming part of a series of strata which he is inclined to rank as a distinct group above the Hudson River proper. It would be quite superfluous for me to add one word in support of the opinion of the most able stratigraphical geol- _ ogist of the American continent.” Paleontology and _strati- graphy here came into conflict, and it was not till in 1860, when Mr. Billings, in the face of the evidence adduced from the latter, asserted the primordial age of the Point Levis fauna, that Sir William Logan attempted a new explanation of the stratigraphy of the region; declaring at the same time that, “from the physical structure alone, no person would suspect the break which must exist in the neighborhood of Quebec ; and without the evidence of the fossils every one would be authorized to deny it.” (Ibid., page 218.) The typical Potsdam sandstone of the New York system, as seen in the Ottawa basin in northern New York and the adja- cent parts of Canada, affords but a very meagre fauna, includ- ing two species of brachiopods, one or two gasteropods, and a single crustacean, Conocephalites (Conocoryphe) minutus, found at Keeseville, New York. In 1852, however, David Dale Owen found and described an extensive fauna in Wisconsin, from rocks which were regarded as the equivalent of the Pots- dam sandstone ; while the observations of Shumard in Texas, in 1861, and the latter ones of Hayden and Meek in the Black Hills, have since still further extended our knowledge of the distribution and the organic remains of the rocks which are supposed to represent, in the west, the Potsdam and Calcifer- ous formations of the New York system. 404 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. As early as 1842, Professor Hall, in a comparison of the lower palzozoic rocks of New York with those of Great Britain, declared the Potsdam to be lower than the base of the Upper Cambrian or Bala group of Sedgwick. In 1847, as we have seen, he extended this observation to the Calciferous and Chazy, both of which he placed below this horizon; which until a year or two previous had been looked upon as the base of the palozoic series in Great Britain, and was subsequently made the lower limit of the second fauna of Barrande. Al though from these facts it was probable that these lower members of the New York system might correspond to the primordial fauna of Barrande, we still remained, in the lan- guage of Professor Hall, without “the means of parallelizing our formations with those of Bohemia, by the fauna there known. The nearest approach to the type of the primordial — trilobites was found in the Potsdam of the northwest, de- scribed by Dr. D. D. Owen; but none of these had been generically identified with Bohemian forms, and the prevailing opinion, sanctioned, as I have understood, by Mr. Barrande, was that the primordial fauna had not been discovered in this country until the rediscovery (in 1856) of Paradoxides Harlani at Braintree, Massachusetts. The fragmentary fossils published in Vol. I. of the Paleontology of New York, and similar forms of the so-called Taconic system, were justly regarded as in- sufficient to warrant any conclusions.” (Amer. Jour. Sci. (2), XXXI. 225.) Such, according to Prof. Hall, was the state of the question up to 1860. The Conocephalus, detected by him from the Red sand-rock of Vermont, in 1847, and subse- quently recognized in Europe as an exclusively primordial type, seems to have been forgotten by Hall, and overlooked by others, until it was rediscovered in the sand-rock by Billings in 1861. He had previously, in 1860, detected the same genus at Point Levis, together with Arionellus, and other purely primordial types. Associated with these, and with many other trilobites belonging to the second fauna, were found several species of Dikellocephalus and Menocephalus, genera first made known by Owen from the Potsdam of Wis- XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 405 consin. It is by an error that Messrs. Harkness and Hicks, in a recent paper (Quar. Geol. Jour., XX VII. 395), have as- serted that Owen, in 1852, found there, together with these genera, Conocephalus and Arionellus ; the history of the first discovery of these genera in America being as above given. The limestones of Point Levis thus furnished what was hith- erto wanting, —a direct connecting link between the fauna of the American Potsdam and the primordial zone of Bohemia. The history of the Paradoxides Harlant, alluded to by Professor Hall, is as follows: in 1834, Dr. Jacob Green re- ceived from Dr. Richard Harlan the cast of a large trilobite occurring in a silicious slate, which was in the collection of Francis Alger of Boston, and, it was supposed, might have come from Trenton Falls, New York. Dr. Green, who at once pointed out the fact that the rock was wholly unlike any found at this locality, declared the fossil to resemble greatly the Para- doxides T'essint, Brongn., — the former Hntomolithus paradoxus of Linneus, from Westrogothia, — and named the species P. Harlani. (Amer. Jour. Sci. (1), XXV. 336.) In 1856, the attention of Professor William B. Rogers was called to a local- ity of organic remains in Braintree, on the border of Quincy, Massachusetts, where, on examination, he at once recognized the Paradoxides Harlani in a silicious slate similar to that of the original specimen. This was announced by him in a com- munication to the American Academy of Sciences (Proc., Vol. IIL.), as a proof of the protozoic age of some of the rocks of east- ern Massachusetts. Professor Rogers then called attention to the fact that this genus of trilobites is characteristic of the pri- mordial fauna, and noticed that Barrande had already remarked that, from the casts of P. Harlani in the London School of Mines and the British Museum (which had been made from the original specimen, and distributed by Dr. Green), this species . appeared to be identical with P. spinosus from Skrey in Bohe- mia. In 1858, Salter found in specimens sent to the Bristol Institution in England, by Mr. Bennett of Newfoundland, from the promontory between St. Mary’s and Placentia Bays, Oe ne ee BN A a ee on ee ae Ld 406 CAMBRIAN AND SILURIAN IN NORTH AMERICA. ([XV. in the southwestern part of this island, a large trilobite, de- scribed by him as Paradoxides Bennett: (Geol. Jour., XV. 554), which appears, according to Mr. Billings, to be identical with P. Harlani. On the same occasion Salter described, under the name of Conocephalites antiquatus, a trilobite from a — collection of American fossils sent by Dr. Feuchtwanger of New York to the London Exhibition of 1851. This was said to occur in a bowlder of brown sandstone from Georgia, and, as I have been informed by Dr. Feuchtwanger, was found near the town of Columbus in that State. The slates of St. John, New Brunswick, and its vicinity have recently yielded an abundant fauna, examined by Pro- fessor Hartt, who at once recognized its primordial character. This conclusion was first announced, on the authority of Pro- fessor Hartt, in a paper by Mr. G. F. Matthew, in May, 1865. (Geol. Jour., XXI. 426.) The rocks of this region have afforded two species of Paradoxides and fourteen of Conocoryphe, to- gether with Agnostus and Microdiscus, all of which have been described by Professor Hartt. It may here be noticed that, in 1862, Professor Bell found in the black shales of the Dart- mouth valley, in Gaspé, a single specimen of a large trilobite, which, according to Mr. Billings, closely resembles Paradoxides farlani, but from its imperfectly preserved condition cannot certainly be identified with it. (Geol. Canada, page 882.) The geological examinations of Mr. Alexander Murray in Newfoundland, since 1865, have shown that the southeastern part of that island contains a great volume of Cambrian rocks, estimated by him at about 6,000 feet in all. No traces of the Upper Cambrian or second fauna have been detected among these, but some portions contain the Paradoxides already men- tioned, while others yield the fauna which Mr. Billings has called Lower Potsdam. This name was first given in an ap- pendix (prepared by Sir William Logan) to Mr. Murray’s report . on Newfoundland for 1865, published in 1866 (page 46 ; see also Report of the Geol. Survey of Canada for 1866, page 236). The Lower Potsdam was there assigned a place above the Par- adoxides beds of the region, which were called the St. John pt ee en ae 5 iA. ‘at ag 3 TT Se Oe en, ee a ee a ae ws —— XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA, 407 group, — the fossiliferous strata of St. John, New Brunswick, being referred to the same horizon; which corresponds to the Menevian of Wales, now recognized as the summit of the Lower Cambrian. The succession of the rocks containing these two faunas in southeastern Newfoundland is not yet clear; the Lower Potsdam fauna is regarded by Mr. Billings as identical with that found on the Strait of Bellisle, at Bic (on the south shore of the river St. Lawrence, below Quebec), at Georgia in Vermont, and at Troy, New York ; but in none’ of these other localities is it as yet known to be accompanied by a Menevian fauna. The trilobites hitherto described from these rocks belong to the genera Olenellus, Conocoryphe, and Agnostus ; neither Paradoxides, which characterizes the Menevian and the underlying Harlech beds in Wales, nor Olenus, which there abounds in the rocks immediately above this horizon, having as yet been described as occurring in the Lower Potsdam of Mr. Billings. Future discoveries may perhaps assign it a place below instead of above the Menevian horizon. [To the above genera of trilobites occurring at Troy, Mr. Ford has since (in 1873) added Microdiscus, which has also been found at Bic. This genus is common-to the Menevian and the underlying Harlech rocks in Wales, and is also, accord- ing to Emmons, found with graptolites in Augusta County, Virginia. The strata which contain this fauna at Troy, as described by Ford, are of considerable thickness, consisting of limestones with coarse sandstones and shales, which, as the result of a dislocation or of an overturned and eroded anticlinal, are made to overlie, in apparent conformity, the beds of the Utica or Hudson River group, the whole dipping eastward. (American Journal of Science (3), VI. 134.)] The characteristic Menevian fauna in and near St. John, New Brunswick, is found in a band of about one hundred and fifty feet, towards the base of a series of nearly vertical sand- stones and argillites, underlaid by conglomerates, and resting upon crystalline schists, in a narrow basin. The series, the total thickness of which is estimated by Messrs. Matthew and Bailey at over 2,000 feet, contains Lingula throughout, but has 408 CAMBRIAN AND SILURIAN IN NORTH AMERICA, [XV. _ yielded no remains of a higher fauna. The same Menevian forms have been found in small outlying areas of similar rocks, at two or three places north of the St. John basin, but to the south of the New Brunswick coal-field. To the north of this is a broad belt of similar argillites and sandstones, which ex- tends southwestward into the State of Maine. This belt has hitherto yielded no organic remains, but is compared by Mr. Matthew to the Cambrian rocks of the St. John basin, and to the gold-bearing series of Nova Scotia (Geol. Jour., XXI. 427), which at the same time resembles closely the Cambrian rocks of southeastern Newfoundland. This was remarked by Dr. Dawson in 1860, when he expressed the opinion that the auriferous rocks of Nova Scotia were “the continuation of the older slate series of Mr. Jukes in Newfoundland, which has afforded Paradoxides,” and probably the equivalent of the Lingula flags of Wales. (Supplement to Acadian Geology (1860), page 53; also Acad. Geol., 2d ed., page 613.) Asso- ciated with these gold-bearing strata, along the Atlantic coast of Nova Scotia, occur fine-grained gneisses, and mica-schists with andalusite and staurolite ; besides other crystalline schists which are chloritic and dioritic, and contain crystallized epi- dote, magnetite, and menaccanite. These two types of crys- talline schists (which, from their stratigraphical relations, as well as from their mineral condition, appear to be more ancient than the uncrystalline gold-bearing strata) were in 1860, as now, regarded by me as the equivalents respectively of the White Mountain and Green Mountain series of the Appa- lachians, as will be seen by reference to Dr. Dawson’s work just quoted. At that time, however, and for many years after, I held, in common with most American geologists, the opinion that these two groups of crystalline schists were altered rocks of a more recent date than that assigned to the auriferous series of Nova Scotia by Dr. Dawson, who was much perplexed by the difficulty of reconciling this view with his own. The diffi- culty is, however, at once removed when we admit, as I have maintained since 1870, that both of these groups are pre- Cambrian in age. (Amer. Jour. Sci. (2), L. 835 ante, pages 276 and 327.) ~ ee a ee a A ee ee ee ey eS oe XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 409 A notice by Mr. Selwyn of some of these crystalline schists in Nova Scotia will be found in the Report of the Geological Survey of Canada for 1870 (page 271). He there remarks, moreover, the close lithological resemblances of the gold-bear- ing strata to the Harlech grits and Lingula flags of North Wales, and announces the discovery among these strata at the Ovens gold-mine in Lunenburg, Nova Scotia, of peculiar or- ganic markings regarded by Mr. Billings as identical with the Eophyton Linneanum, which is found in the Regio Fucoidarum, at the base of the Cambrian in Sweden. In the volume just quoted (page 269) will be found some notes by Mr. Billings ' on this fossil, which occurs also near St. John, New Brunswick, in strata supposed to. underlie the Paradoxides beds. The same form is found in Conception Bay in southeastern New- foundland, in strata regarded by Mr. Murray as higher than those with Paradoxides, and containing also two new species of Lingula, a Cruziana, and several fucoids. Still more re- cently, Hophyton, accompanied by these same fucoids, has been found by Mr. Billings at St. Laurent, on the island of Orleans near Quebec, in strata hitherto referred by the geological sur- vey, on stratigraphical grounds, to the Quebec group. The evidence adduced by Mr. Billings tends to show that this or- ganic form, whatever its nature, belongs to a very low horizon in the Cambrian. As regards the probable downward extension of these forms of ancient life, I cannot refrain from citing the recent language of Mr. Hicks. (Quar. Jour. Geol. Soc., May, 1872, page 174.) After a comparative study of the Lower Cambrian fauna, in- cluding that of the Harlech and Menevian rocks in Wales, and the representatives of the latter in other regions, he adds :— “Though animal life was restricted to these few types, yet at this early period the representatives of the several orders do not show a very diminutive form, or a markedly imperfect state ; nor is there an unusual number of blind species. The earliest known brachiopods are apparently as perfect as those which succeed them ; and the trilobites are of the largest and best developed types. The fact also that trilobites had attained 18 410 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [KXV. their maximum size at this period, and that forms were present representative of almost every stage in development, from the little Agnostus with two rings to the thorax, and Microdiseus with four, to Lrinnys with twenty-four, and blind genera along with those having the largest eyes, leads to the conclusion that for these several stages to have taken place numerous previ- ous faunas must have had an existence, and, moreover, that even at this time in the history of our globe an enormous pe- riod had elapsed since life first dawned upon it.” The facts insisted upon by Hicks do not appear to be in- consistent with the view that at this horizon the trilobites had already culminated. Such does not, however, appear to be the idea of Barrande, who in a recent learned essay upon the trilobitic fauna (1871) has drawn from its state of development at this early period conclusions strongly opposed to the theory of derivation. The strata holding the first fauna in southeastern Newfound- land rest unconformably, according to Mr. Murray, upon what he has called the Intermediate series ; which is of great thick- ness, consists chiefly of crystalline ‘rocks, and is supposed by him to represent the Huronian. He has, however, included in this intermediate series several thousand feet of sandstones and argillites which, near St. John’s in Newfoundland, are seen to be unconformably overlaid by the fossiliferous strata already noticed, and have yielded two species. of organic forms, lately described by Mr. Billings. One of these is an ~ i C- " “ +, i J a — 3 _ A a See ee ee XX.] THEORY OF TYPES IN CHEMISTRY. - 467 are as truly neutral salts of a particular type. Thus the bibasic and tribasic phosphates are to be looked upon as sub-salts, which sustain the same relation to the monobasic phosphates that the basic nitrates bear to the neutral nitrates. He suc- ceeded in preparing two crystalline sub-nitrates of lead and copper, having the formulas NO,,M,0,,HO (tribasic), and NO;,M,0,,H;03 (heptabasic), both of which retain their water of composition at 392° F. The compounds of sulphuric acid are: 1. The true monobasic: sulphate, 8,0,MO, corresponding to the Nordhausen acid and the anhydrous bisulphates ; 2. The ordinary neutral sulphates, S20¢,M,0,; 3. The so-called disulphates, S,O,,M,O, corre- sponding to the glacial acid of density 1.780; 4. The type $,0,,M,0,, represented by turpeth mineral; 5. The so-called quadribasic sulphates, 8,0,,M,0s. The copper-salt of this octo- basic type still retains, moreover, 6HO at 392° F. (Gerhardt on Salts, Jour. de Pharmacie, 1848, Vol. XII.; American Journal of Science, VI. 337.) Without counting the still more basic sulphates described by Kane and Schindler, we have the following salts, which, in accordance with Wurtz’s notation, correspond to the annexed radicles : — 1. Unibasic Wake a), monatomic. 2. Bibasic Bt. = 5.0, diatomic. 3. Quadribasic §8,H,O,, =S,0, tetratomic. 4. Sexbasic 557,07 =:58, hexatomic. 5. Octobasic 8,H,O;, =S,—O, octatomic. It is easy to apply a similar reductio ad absurdum to the radicle theory in the case of the oxychlorides and other basic salts, and to show that the radicles of the dualists are often merely algebraic expressions. (See further my remarks in the American Journal of Science, VII. 402 —404.)* * Those who are familiar with chemical literature will remember an amus- ing jeu d’esprit of Laurent’s, in which he invited the attention of the advo- cates of the radicle theory to a newly invented electro-negative radicle, eurhizene. (Comptes Rendus des Travaux de Chimie for 1850, pages 251 and 376.) A late writer in the Chemical News (Vol. I. page 326) proposes, as a new electro-negative radicle, under the name of hydrine, the peroxide of hydrogen HOz, the eurhizene of Laurent. ne j Sosa iat Va 468 THEORY OF TYPES IN CHEMISTRY. (XX. The mode of the generation of acids set forth in the case of those derived from phosphoric anhydride, which we conceive to be a simple statement of the process as it takes place in nature, dispenses alike with hypothetical radicles and residues, both of which are, however, convenient for the purposes of notation. In the selection of a typical form to which a great number of species may be referred, hydrogen or water merits the preference from its simplicity, and from the important part which it plays in the generation of species. Water and car- bonic anhydride are both so directly concerned in the generation of the bodies in the carbon series, that either may be assumed as the type; but we prefer to regard C,O,, like the other an-- hydrides, as only a derivative of the — of water, and ulti- mately of the hydrogen-type. — These views were first put forward hp myself in 1848, when ‘I expressed the opinion that they were destined to form “the basis of a true natural system of chemical classification” ; and it was only after having opposed them for four years to those — of Gerhardt, that this chemist, in June, 1852, renounced his views, and, without any acknowledgment, adopted my own. (Ann. de Chim. et Phys. (3), XXXVII. 285.) Already in 1851, Williamson, in a paper read before the British Associa- tion, had developed the ideas on the water-type to which Wurtz refers above, and to him the English editor of Gmelin’s Hand- book ascribes the theory. The notion of condensed types, and et of H, as the primal type, was not, so far as I am aware, brought forward by either of these, and remained unnoticed until re- suscitated by Wurtz in 1855, seven years after I had first an- nounced it, and one year after my reclamation already noticed, which was published in the American Journal of Science, in March, 1854. My claims have not, however, been overlooked a Dr. Wolcott Gibbs. In an essay on the polyacid bases, he re- marks that in a previous paper he had attributed the theory of watér-types to Gerhardt and Williamson, and adds: “In © q this I find I have not done justice to Mr. T. Sterry Hunt, to whom is exclusively due the credit of having first applied the XX.] THEORY OF TYPES IN CHEMISTRY. 469 theory to the so-called oxygen-acids and to the anhydrides, and in whose earlier papers may be found the germs of most of the ideas on classification usually attributed to Gerhardt and his disciples.” (Proc. Am. Assoc. Adv. Science, 1858, page 197.) It will be seen, from what precedes, that I not only applied the theory, as Dr. Gibbs remarks, but, except so far as Laurent’s suggestion goes, invented it and published it in all its details some years before it was accepted by a single chemist. In conclusion, I have only to ask that future historians will do justice to the memory of Auguste Laurent, and will, more- over, ascribe to whom is due the credit of having given to the - science a theory which has exercised such an important influ- ence in modern chemical speculation and research ; remember- ing that my own publications on the subject, which cover the whole ground, were some years earlier than those of William- son, Gerhardt, Wurtz, or Kolbe. — ee fe © —— Se. a « ,= }.. -- en i . a _ e <> a : a -< o- : ‘ 4 v 4 470 ON THE THEORY OF NITRIFICATION. Bh APPENDIX. ON THE THEORY OF NITRIFICATION, In connection with the foot-note on page 465 the following sketch of the theory of nitrification there indicated seems called for, the more especially as it will be seen that the late Professor G, C. Schaeffer of Washington apparently anticipated me in certain points therein. It was in the Amer. Jour. Science for May, 1848 (page 408), that I referred to Gerhardt’s observation that the so-called protoxide of nitrogen corresponds to biphosphamide, PNO, and is NNO, a nitryl derived from nitrate of ammonia by the ronioval of 2H,O, and capable, when heated in contact with an alkaline hydrate, of regenerating ammonia and a nitrate. I then called attention to the similar decomposition of nitrite of ammonia, which by the loss of 2H,O yields nitrogen gas, and remarked that the gas thus obtained, “apparently identical with that of the at- mosphere, is really composed of two equivalents of the element sustain- ing to each other the same relations as in nitrous oxide,” or in other words representing respectively the nitrous and the ammoniacal conditions. This view of the constitution of gaseous nitrogen was again set forth, in September, 1848, in the paper quoted above, as a means of explaining the apparent anomaly in the equivalent volume of nitrogen. The obvious conclusion that gaseous nitrogen might (after the manner of nitrous oxide) regenerate ammonia and a nitrite by assuming the elements of water, 2H:O, was not insisted upon. It was, however, for years so familiar to me and so often set forth in my lectures on chemistry before the medical classes at the Université Laval at Quebec, that I spoke of it in the above paper in — March, 1861, as a view which I had elsewhere suggested, though this was, I believe, the first time that it had been enunciated by me in print. In further explanation of the subject I published in the Amer. Jour. Science for July, 1861 (page 109), a note in which, after describing the generation of ozone or active oxygen by passing air through a solution of permanganic acid, and the production of a ni- trite from air thus ozonized, I referred to the conversion of gaseous nitrogen, as above, into ammonia and nitrous acid, and added : “ From the instability of the compound of these two bodies, however, it becomes necessary to decompose the one at the instant of its forma- XX.] ON THE THEORY OF NITRIFICATION. ATL tion in order to isolate the other. Certain reducing agents which convert nitrous acid into ammonia may thus transform nitrogen (NN) into 2NHs. In this way I explain the action of nascent hydrogen in forming ammonia with atmospheric nitrogen in presence of oxidiz- ing metals and alkalies..... An agent which, instead of attacking the nitrous acid, should destroy the newly formed ammonia, would permit us to isolate the nitrous acid. Houzeau has shown that ac- tive oxygen is such an agent, at once oxidizing ammonia with forma- tion of nitrate (nitrite) of ammonia ; and thus when ozone is brought in contact with moist air, both of the atoms of nitrogen in the nitryl (NN) appear in the oxidized state. From this view it follows that the odor and many of the reactions ascribed to ozone are due to nitrous acid, which is liberated by the decomposition of atmospheric nitrogen in presence of water and nascent oxygen. We have thus the key to a new theory of nitrification and to the experiments of Cloez on the slow formation of a nitrite by the action of air ex- empt from ammonia upon porous bodies moistened with alkaline solutions.” On September 15, 1862, I read before the French Academy of Sciences a note on The Nature of Nitrogen and the Theory of Nitri- fication, published in the Comptes Rendus of that date and trans- lated in the Philosophical Magazine for January, 1863, in which I repeated the points above given, and then proceeded to consider the results announced by Schénbein in 1862. I said: “ The formation of nitrite of ammonia by the combination of the nitryl NN with H,O, must necessarily be limited to very minute quantities by the instability of this ammoniacal salt, which, as is well known, decom- poses readily into nitrogen and water. In order, therefore, to pro- duce any considerable quantity of a nitrite by this reaction, there is required the presence of active oxygen, or of a fixed base to separate the ammonia. The recent experiments of Schénbein have furnished new evidences of the direct formation of a nitrite at the expense of the nitrogen of the atmosphere. According to him, when sheets of paper moistened with a feeble solution of an alkali or an alkaline carbonate are exposed to the air, especially in the presence of watery vapor and at a temperature of 50° or 60° C., the alkaline base soon fixes a sufficient quantity of nitrous acid to give the characteristic reactions. Appreciable traces of nitrite are, according to Schénbein, obtained in this way, even without the intervention of an alkali. He moreover found that distilled water mixed with a little potash or sulphuric acid, and evaporated slowly at a temperature of about 472 ON THE THEORY OF NITRIFICATION. - [XX 50° C., in the open air, fixes in one case a small portion of ammonia and in the other a little nitrous acid. Traces of a nitrite are also formed in pure water under similar conditions. Schonbein explains all of these results by the combination of nitrogen with the elements of the water, producing at the same time ammonia and nitrous acid, As he has well remarked, this reaction serves to explain the absorp- tion of nitrogen by vegetation, and, through the oxidation of nitrites, the formation of nitrates in nature. By these elegant experiments he has confirmed in a remarkable manner my theory of nitrification and of the double nature of free nitrogen. It is, however, evident that since the publication of my note of March, 1861, above referred to, we cannot say, with Schénbein, that the generation of nitrite of ammonia from nitrogen and water is ‘a most wonderful and wholly unexpected thing.” (Letter from Schénbein to Faraday, Philos, Magazine, June, 1862, page 467.)” Referring to the claims of Schén- _ bein, and to my notes of March and July, 1861, the late Professor ‘Nicklés wrote as follows in 1863, in his scientific correspondence for the American Journal of Science ((2) XX XV. 263): “Schonbein has done justice tardily to those who have preceded him in this question. Of this number is T. Sterry Hunt, who, as our readers may remember, long since showed that nitrite of ammonia may be formed by means of nitrogen and water, and thus led the way toa ‘ new theory of nitrification. This is what Béttger arrived at, who first announced that nitrite of ammonia is a product of all combus- tion in the air.” With regard to the production of nitrite of am- monia from nitrogen and water, he further adds, “this point was entirely developed by Sterry Hunt.” The publication of the above called forth a communication from Professor G. C. Schaeffer in the Amer. Jour. Science for November, 1863, page 409, in which he draws attention to the fact that the Re- port of the Smithsonian Institution for 1861 contains an essay on Nitrification by Dr. B. F. Craig (written in 1856), in which the lat- ter puts forth as the suggestion of Professor Schaeffer the .same theory of nitrification as that maintained by the present writer and by Schénbein ; basing it upon the view that nitrogen gas is a nitryl capable of regenerating nitrite of ammonia in presence of water. From this it is clear that Professor Schaeffer had independently at- tained the same conclusion as myself from the conception of the dual nature of atmospheric nitrogen, which I had taught since 1848. He at the same time, as a contribution to the literature of the subject, — called attention to his paper in the Proceedings of the American As- XX.] ON THE THEORY OF NITRIFICATION. 473 sociation for the Advancement of Science for 1850, on the Detection of Nitrites and Nitrates, in which he indicated a delicate test for these salts, showed the frequent presence of nitrites in rain-water, and moreover pointed out that while nitrates are readily reduced to nitrites in solution, these, by oxidation, pass as readily into nitrates. Me x . - ef 4 ne » - . j J - ~ . . ‘ 5 4 4 ; . ; INDEX. ———— AccuMULATION of sediments, effects of, 17, 49, 58, 66. Acid springs, 111; of New York and Ontario, 130, 131. Acids of volcanoes, their origin, 8, 15, 111, 112. Adams, C. B., on the geology of Ver- mont, 391. Adirondack Mountains, rocks of, 32, 241, 243. Aerolites, constitution of, 302. Agalmatolite rocks, 67. Albertite, composition of, 176. Albite, in Laurentian veins, 214; for- mula of, 448. Albuminoids, constitution and arti- ficial production of, 170. Alge. See Sea-weeds. Alkalies, relative proportions in waters, '102; of mineral waters, 135, See Carbonate of Soda and Potash. Alkaliferous silicates, decomposition of, 2, 10, 40, 102, 103. Alkaline silicates, soluble, 7, 21, 25. Alkaline waters, 85, 128, 156. Alleghany River, brines of, 121. Allomerism, 447. Alps, geology of, 328; anthracitic sys- tem of, 332; grand section of, 843. Alteration of rocks. phism. Alum slates of Sweden, 266, 366. Alumina, solution and deposition of, 18, 14, 98, 142; sulphate of, 98, 133; in waters, 142. See Bauxite. Aluminous silicates, origin of, 28, 296, 298. Ammonia of volcanoes, 8, 15, 1138; See Metamor- in rocks and soils, 113; nitrite of, its production, 471. Andalusite rocks, 28, 32, 34, 243, 272, 282, 408. Andrews, E. B., on petroleum, 174. Angelin, Palzontologica Scandinavica, 367. Anglesea, crystalline schists of, 270, 353, 383. Anhydrites of the Alps, 335. Anhydrous monobasic acids, 464. Anorthite, its formula, 443. Anortholite, 31, 32. Anthracite, its origin, 177; of the Alps, 332, 334. Anticlinals, their relations to moun- tains, 53. Anticosti, geology of, 416. Anticosti group, 417. Apatite, 197, 208, 211, 213, 311. Appalachians, geology of, 50, 51, 75, 241. Aquatic vegetation, 2, 22, 95. Arendal, vein-stones of, 209. Arenig rocks, 375, 376, 381, 384. Arkesine, 330. Arkose, 285. Artesian wells of London and Paris, 85. Aspidella Terranovica, 410. Atmosphere, primeval, 1, 20, 40, 42, 47, 301. Atmospheric waters, 94. Atomic hypothesis, 433, 438. Atomic volumes, 488, 435, 440, 455. Attrition of rocks, 20. Auroral rocks, 247, 421; their rela- tion to matinal, 414. Azoic gneisses of Rogers, 246. 476 BABBAGE on internal heat, 14, 71. Bala rocks, 353, 359, 362. Bailey, L. W., geology of New Bruns- wick, 407. Banded structure in veins, 193, 199. Bangor group, 353, 382, 384. Bark, its composition, 181. Barrande on palzozoic geology, 253, 368, 869, 378, 892, 424. Baryta, salts of, in waters, 87, 121, 141, 145, Basic salts, Gerhardt on, 467, Bauxite, 14, 98, 326. Belwil, Quebec, water of, 151. Belt, T., on Lingula flags, 371. Bergmann on Mont Blanc, 338, Bertrand on Mont Blanc, 838, _ Berzelius on silicate of lime, 151, Beryl, 199, 245; kaolin of, 101; a feldspathide, 445. Bessarabia, salt lagoons of, 86, Bicarbonates, See Carbonates, Biddeford, Maine, granitic veins of, 198, Bigsby, J., on Huronian rocks, 18, 269; on Cambrian, 269; on the geol- ogy of Quebec, 396, 400, Billings, E., on the geology of Ver- mont, 260-265, 391-393; on the Potsdam rocks, 266; on Levis fos- sils, 258, 400, 403, 404, 412; on Eophyton, 409; on the Anticosti] group, 416; on Middle Silurian, 417. Bischof, G., 16; on a source of sulphu- retted hydrogen, 87; on decomposi- tion of silicates, 102, 151; on formation of silicate of magnesia, 122; on anthracite, 177; on deoxidation in nature, 302 ; on pseudomorphism, 287, 290, 298, 294, 823, 325; his plutonic basis, 294. Bismuth, occurrence of, 200, 217. Bitterns related to mineral waters, 108, 105, 109, 114, 117, 121, 156, 163, Bitumens, 8, 169, 175, 882, 897. See Petroleum, Bituminous rocks, See Pyroschists. Blake, W. P., on Laurentian veins, 215, 218. Blue Ridge, gneisses of, 217, 249; their decomposition, 250; their copper veins, 217, 250, INDEX. Blum on pseudomorphism, 287, 319, 325. Bohemia, copper slates of, 232; geology of, 368, 7 Borates, their origin, 16, 112, 146. Borax-lake, water of, 146. Bosanquet, Ontario, pyroschists of, 179, Bothwell, Ontario, water of, 159, 162, Bottger on nitrification, 472, Boué on metamorphism, 24, 821. Brainard, J., on silicious deposits, 89, Braintree, Mass., Paradoxides of, 405, Bray Head, rocks of, 382. Brazil, cryatalline rocks of, 278; their decay, 10. uf Breaks in palzozoic series, 263, 875 - 877, 412-415, 418. Breislak on the origin of sulphur, 87. Brines, analyses of, 119-121. . Brittany, crystalline schists of, 278, Bromine in waters, 142. ‘ia Brooks, T. B., crystalline rocks ot Michigan, 274. : Brunswick, Maine, granite veins of, — 194, g Buch, Von, on dolomites, 81, 309, Buffon on mountains, 52, Bunsen on eruptive rocks, 8, 66, 284 3 on aqueous decomposition of silicates, 102, % ’ CAERNARVONSHIRE, crystalline rocks of, 269, 353, 383. Calciferous sand-rock, a dolomite, 117. 155, 415; gypsum in, 117, 155; its re- lations to Trenton and Chazy, 412, 413, i Cagniard de la Tour on vapors, 87. Calcium, chloride of, in waters, 117- 120, 158. Calcium, salts of. See Carbonate of lime, Lime-salts, and Gypsum, Caledonia, Ontario, waters of, 128, 127, 129, 147 - 149. + California, borax-lake of, 146. “s Calumet and Hecla mine, conglomerate of, 187. Me Cambrian series, 266-269; Upper, in Great Britain, 350 - 865 ; Middle snd 28 Lower, 365-3885, 409; in North America, 387 - ~ 425; history of, 349. _ INDEX. Cambro-Silurian of Sedgwick, 363, 381, 423. Canada geological survey, reports of, 420. Cape Ann, Mass., granite veins of, 200. Cape Breton, water of, 121. Caradoc rocks, 353, 359 - 362, 384. Carbon, its primitive condition, 23, 42, 302; anthracitic of Madoc, 217. Carbonates. See Carbonate of lime, Carbonate of magnesia, Carbonate of soda, and Carbonic acid, Carbonate of lime, its origin, 2, 28, ,41, 47, 81, 88, 86, 88, 90, 109; solu- bility and supersaturated solutions of, 139; bicarbonate, its action on sea-water, 82, 85, 90, 109, 308; hy- drous carbonate of, 140. Carbonate of lime and magnesia, Dolomite. Carbonate of magnesia, its origin, 23, 82, 85, 88, 90, 109, 110; action of, on lime-salts, 87, 90, 189; its solubility and supersaturated solutions of, 140, 148; bicarbonate of, its solubility, 91, 109, 148; hydrous carbonate of, pres- ent in some dolomites, 107; sesqui- carbonate of, 138. Carbonate of soda, its origin, 12, 21, 85, 102; amount of, in waters, 85, 124-126; neutral carbonate of, 148; action of, on sea-waters, 2, 11, 12, 41, 85, 88, 90, 105, 189, 148, 307. Carbonic acid, its action on silicates, 2, 10, 102, 150; amount of, in early atmosphere, 41, 47, 308; deoxida- tion of, 23, 42, 302; deficiency of, in certain waters, 149; relations of, to life and climate, 42, 46-48; to the formation of gypsum, 42, 308; sub- terranean sources of, 8, 15, 112. Carboniferous rocks, 228; of North America, 49, 50. Carbon-spars, their constitution, 441, 446. Carlsbad, waters of, 85. Carnallite, 105, 107, 118. Cassiterite, 191, 192, 195, 200, 205; pseudomorphs of, 289, 290. Catalysis, 452. See 477 Chabazite, 442; action of saline waters on, 96. Chacornac on the nebular hypothesis, 38. Chambly, waters of, 125, 149, 152. Champlain division, 252, 258, 264, 266. Chamonix, jurassic rocks. of, 838; synclinal of, 343. . Chatham, Ontario, water of, 145. Chazy formation, 156, 414,415; absent in Herkimer Co., New York, 413; relations of, to Calciferous and Tren- ton, 412; mineral waters from, 124, 156, 157. Chemical change defined, 428, 450, 454, 465; elements, 37, 428; activi- ties in former ages, 27, 42, 306; dis- sociation, 36. Chemistry defined, 454. Cheshire rock-salt, 120. Chiastolite rocks. See Andalusite. Chicago, oil-bearing limestone of, 172. Chloride of calcium in waters, 122, 158; in primeval ocean, 11, 117, 122, 137. Chloride of magnesium, 117, 122, 137. Chloride of sodium, its origin, 2, 11, 41. Chlorine in silicates, 144, 242. Chlorine and hydrogen, union of, 430. Chlorite, its probable origin, 296. Chloritic rocks, 82, 243, 247, 249, 269, 270, 830, 831, 408; supposed pseudo- morphic origin of, 316, 820, 826. Chloritoid rocks, 32. Chromium, its occurrence, 31, 32, 34, 238, 248, 249, 269, 270, 272, 297, 330. Chrysolite and serpentine, 291, 315. Chrysoberyl, 195, 214. Circulation, terrestrial, 22, 225, 235. Classification of the sciences, 35, 458. Clays, origin of, 2, 10, 18, 20, 22, 41, 101, 228; precipitated by saline wa- ters, 10. Climate, primeval, 42, 46-48; palso- zoic of North America, 76, 92, 310. Cloez on nitrification, 465, 471. Coal, its origin, 180, 182, 229; its rela- tion to iron-ores, 229. Collingwood, Ontario, pyroschists of, 178. Colloidal bodies, solution of, 223. Celestial chemistry, 35, 87. Condensed types in chemistry, 468. eR ae eRenp Oe SUReame eent 30% te te 4 ee Sy eee ares eee 478 Concentration of metals in nature, 227, 235. Concretionary structure, £9. Connecticut, gneisses of, 248. Conocephalites in North America, 260, 891, 404. Continent, a pre-paleozoic, 75, 76. Continental elevation, 53, 76. Conularia, a phosphatic shell, 312. Cooke, J. P., on allomerism, 447. Cooling globe, its chemistry, 1, 38, 40, 60, 68, 301, 306. Cods group, 282. Copper-ores, origin of, 282; of Blue Ridge, 217. Coprolites, 152, 225. Cordier on limestones and dolomites, 81. Corundum, 247; its supposed trans- formations, 826. Cotta, Von, on granitic veins, 191. Credner, H., on Eozoic rocks of North America, ‘77; on comparative geog- nosy, 278; on the origin of silicates, 304, 805. Crinoids, fossil, injected with silicates, 804. Croft, H., on various mineral waters, 130, 134, 145. Crust of the earth, 1, 40, 60-64, 223; its flexibility, 8, 15, 57, 72; corruga- tions of, 57, 74; its disintegration, 63. Crystalline aggregation of matter, 305. Crystalline rocks, two great classes, 283; evidences of their plasticity, 4; how formed, 24, 283; evidences of life in, 13, 302. Crystalline schists, relative ages of, 19; are pre-Cambrian, 827; origin of, 283; supposed plutonic, 294; Daubrée on, 301; Giimbel on, 305; Credner on, 805; Favre on, 347. Crystals, rounded, 212; hollow or skeleton, 201, 212. Cumberland, England, schists of, 273. Cyanite rocks, 28, 84, 248, 272. Cycles in sedimentation, 155, 241. crystalline DALMAN on trilobites, 365. Damour, A., action of water on zeo- INDEX. Dana, J. D., on the fluidity of earth’s interior, 56; on granite ve’ 199; on pseudomorphism, 287, 318, 319, 320-323; on regional me amorphism, 291, 820, 322; on equiy= alent volumes, 433. Danville, Maine, granite veins of, 197. Daubeny on volcanoes, 62. Le Daubrée on the action of heated : ters, 6; on the attrition of rocks, 20 on the waters of Plombiéres, 25; on the production of silicates, 25, 297 on silicious deposits, 89; on regen- eration of feldspar, 100; on ony 3 veins, 191, 209; on the origin of crystalline schists, 801; on the pri- meval atmosphere, 301. Davy, H., on volcanoes, 62. A Dawson, J. W., on dissolving of iron- oxide from ‘sediments, 13; on the © origin of coal, 180-182; on Eozoon *‘Canadense, 802; on paleozoic for- aminifera, 411; on the geology of Nova Scotia, 408; on Erian rocks, 419; on Cambrian and Silurian, 424, Dead Sea, water of, 83. Decomposition, double, in chemistry, 428, 451, ie Decomposition of crystalline rocks; its antiquity, 10, 100, 250, . Delabeche on crystalline rocks, 301, Delesse, A., on envelopment of min- erals, 288, 289, 314, 315; on pseudo- morphism, 292, 314-318; his change i of views, 316; on the origin of ser- — pentine, 316, 317; on protogine, 330, se Deoxidation in nature, 23, 280, 302, Deville, H. Ste.-Claire, on dissociation, sia 87; on river-waters, 84; on crystal- line aggregation, 305, ‘ Diabase, 31. Diagenesis in onto 805, 317, 921, Differentiation, chemical, 450. a agune from veins, al Dioetie 23, 26, 82, 196, 243, 247, 240, 269, 270, 830, 881, 408. Disintegration of the primitive crust, 63, Dissociation, chemical, 37. lites, 102; on jadeite, 446. Dipyre, 446 INDEX. Dolerite, 3, 238, 284; stratiform struc- ture in, 186. Dolomieu, decay of granite, 10. Dolomite, origin of, 81, 307; two classes of, with and without gypsum, 87, 88, 309; fresh-water, 88; metalliferous, 88, 809; is not decomposed by gyp- sum, 106; with hydrate and hydro- carbonate of magnesia, 107; organic remains in, 88, 92; artificial forma- tion of, 90, 91, 307; produced by evaporation in closed basins, 76, 85- 88, 92, 101, 310; relations of car- bonic acid in the atmosphere to its formation, 48, 308; supposed epigenic origin of, 81, 92, 287, 307, 325; Cor- dier on, 81; Von Morlot and Marig- nac on, 308; Von Buch on, 81, 309; Haidinger on, 325. Donegal, Ireland, crystalline rocks of, 84, 272. Drops, Guthrie on, 10. Dualism in chemical theory, 428, Dublin, Ireland, granite veins of, 199. Ducktown, Tenn., copper veins of, 217, 250. Dumas on chemical types, 462. Dumont on disturbed strata, 334. Durocher on igneous rocks, 3, 189, 190. Dynamical geology, some points in, 70. EARTH, compared to an organism, 236; interior of, whether liquid or solid, 7, 16, 39, 44,56, 59, 60, 70, 71; its re- lation to magnetism, 60. See Crust of the earth. Eaton, Amos, classification of rocks, 241; on the rocks of Vermont, 241, 252. Ebelman, decay of silicious minerals, 100, Eichhorn, action of saline waters on soils and aluminous double silicates, 95, 96. Elezolite in granitic veins, 200. Elements, chemical, distribution of, 221; in other worlds, 36; possible new ones in stars, 87, Elevation of continents, 15, 17, 53, 76. Elie de Beaumont on water in igneous 479 rocks, 5, 190; on silicious deposits, 89, on granitic veins, 189; on ter- restrial circulation, 225; on Alpine geology, 332, 348. Emerald veins of New Grenada, 205. Emery, origin and occurrence of, 13, 98. Emmons, E., on rounded crystals, 212; on eruptive limestones, 218; on the Green Mountains, 250; on serpen- tine, 250; on the Taconic system, 251-2538, 268, 388-390; on Cam- brian, 268; on hypersthene rock, 279; on recomposed rocks, 341; on the geology of New York, 368. Endogenous rocks, 193, 196 —- 199, Envelopment of minerals, 288 - 290, 314. Eophyton, 385, 409. Eozoic rocks of North America, 75, 277. Eozoon Canadense, 302, 303, 326, 342, 411; E. Bavaricum, 368, Epidermal tissues, their relations to coal, 181. Epidotic rocks, 82, 248, 249, 408. Epigenesis, 286, 318, 317. Equilibrium of pressure, 15, 76. Equivalent volumes, 438, 436, 440. Equivalent weights of oxygen and ‘ar- bon, 176; of compound species, 482, 441; defined, 455, Erian rocks, 419. Erosion as related to mountains, 52, 74. Eruptive rocks, See Exotic rocks. Esmark on norites, 279. q Essex County, New York, norites of, 279. Euphotide, 330, 334, 445. Eurhizene of Laurent, 467. Evans on petroleum, 174. Exotic rocks, 4, 9, 16, 24, 44, 58, 66, 188-190, 284; banded structure in, 186; local alteration by, 298. FAHLERZ, 217. Fairbairn on relations of pressure to fusion, 39. Fan-like structure of the Alps, 342, 843. Fariolo, Italy, granites of, 201. 480 Faults in strata, related to mineral springs, 154, 157. Favre, Alph., on the geology of the; Alps, 828; on metamorphism in the Alps, 342, 347. Favre and Silbermann, thermo-chemi- cal researches, 436. Faye, constitution of the sun, 37, Feldspar-porphyries, 187, 248, 250, 282. Feldspars, their formation, 6, 25, 27, 100; decay of, 101; triclinic, 31, 67, 279, 443; aqueous origin of, 298, 299; constitution and formulas of, 443. Feldspathides, 445, Festiniog group, 353, 371, 379, 384. Fire-clays, 18, 22, 228, Fissures, veins in, 202, 203, 2383. Fitzroy, water of, 124, 142, 152. Flora, fossil of the Alps, 333. Fluid-cavities in crystals, 65, 205. Flysch of the Alps, 337. Foldings in strata, 17, 51, 55-57, 74. Fontainebleau sandstone, 289. Foraminifera, palzozoic, 411. Forchhammer on fucoids, 96; on alka- line sulphurets, 99. Ford, geology of Troy, New York, 407. Formulas in chemistry, 465. Foucou on native hydrocarbon gases, 182. Fouqué on native hydrocarbon gases, 182. Fournet on kaolinization, 100; on granites, 190; on skeleton wi (oa 201; on veins, 202. Fucoids, geological relations of, 2, 22, 96, 144, 226. Fusion, when affected by pressure, 65, 66. GARNET rock, 80. Gaspé, geology of, 406, 415, 418. Gas springs, hydrocarbon, 8, 112, 131, 182. Gastaldi, geology of the Alps, 347, Gay-Lussac, law of volumes, 438. Gelatine, formula and constitution of, 180. Generation of chemical species, 427, 465. Genesee slates, pyroschists, 178. INDEX. Genth, F. A., on gold deposits, 287; corundum, 826. Geognosy, 240; comparative, ~ . 278. Geological relations of mineral 154, 156. “she Geology, its scope and objects, 239, Georgia, Vermont, fossils of, 391, : 402. Gerhardt on types in chennai 468; on basic salts, 467. a Gibbs, Wolcott, on the watertype chemistry, 468. . Giekie on the geology of Skye, ‘ on Cambrian and Silurian, 424. Glaciation of rocks, 10. 1 Glass softened by heated water,6. Glauconite, relation of to potash, 4 ‘a 13, 136; in organic forms, 308. — Glucose and sea-salt, compound of, 441, _ Gheiss defined, 188; granitoid, 185, 188, 206, 248; Laurentian, 206, 243 ; White Mountain, 188, 244, 282; of — the Appalachians, 244-250; of Nova Scotia, 408; primitive of Sones navia, 469. Goderich, salt-wells of, 204. Goethe, 287. Granitic veln-stones; 183, 189-209; ial their aqueous and concretionary ori-— gin, 38, 192, 199; banded structure of, 198 ; mineralogy of, 200, 210; Laurentian, 88, 208; of White Mountain series, 194; of Sherbrooke, Nova Scotia, and of Biddeford, Maine, 198. INDEX. Graphite, its probable organic origin, 18, 301; in Laurentian veins, 210, 216; in various rocks, 32, 33, 248- 245, 248; in aerolites, 301. Graptolites of the Levis formation, 258, 396, 399, 412. Gras on Alpine geology, 382. Graywacke defined, 350; of Quebec, 396, 897, 401. Green Mountain rocks, 18, 29, 32, 241, 248, 249, 274. ‘ Grenatides, 445, Grenville, Quebec, minerals of, 215; section of Chazy at, 414. Groton, Connecticut, granite of, 186. Grove on dissociation, 37. Griiner on filling of veins, 203. Guano deposits, 225. : Guelph formation, 417. Giimbel on Eozoon, 303, 304; on meta- morphism of rocks, 305; on dia- genesis, 305, 321. Guthrie on drops, 10, Gypsum, origin of, 48, 86, 90; two modes of formation of, 110; from bi- carbonate of lime and sulphate of magnesia, 82, 85— 87, 90, 109; inter- vention of carbonic acid in its pro- duction, 48, 808; its action on soils, 97; does not decompose dolomite, 106; is decomposed by hydrous car- bonate of magnesia, 107; its solu- bility in water, insolubility in brines, 83, 85, 91, 107-110, 144; occurrence of, in natural waters, 105, 182 ; its elimination from, by reduction, 99, 145; of fresh-water origin, 87; in Cal- ciferous sand-rock, 117, 155; in Onon- daga formation, 182; iu crystalline schists in Sweden, 836; in tertiary in the Alps, 345. See Anhydrite. HAIDINGER on pseudomorphism, 324. Hall, James, on sources of paleozoic sediment, 49; on mountains, 51, 53-55, 73; on White Mountain rocks, 271; on Potsdam rocks, 889; on New York geology, 387, 389, 404; orf 481 Hallowell, Ontario, water of, 116, 142. Halysites in the Trenton limestone, 417. Harlech rocks, 372, 878, 377, 382. Hartt, C. F., on the geology of Brazil, 278; of New Brunswick, 406. Hastings County, Ontario, rocks of, 216, 274. Haughton on the norites of Skye, 281. Heat, internal, of the earth, 7, 9, 15, 43, 57, 59-66, 71, 72, 77, 78. Heer, O., fossil flora of the Alps, 333. Hegel on the chemical process, 450. Helderberg. See Lower Helderberg. Hennessey on the earth’s crust, 7, 16. Herkimer County, New York, geology of, 413. Herschel, J. F. W., on volcanic phenom- ena, 8, 15, 44, 62. Hicks on Cambrian geology, 372, 373, 375, 384, 409. Hisinger, geology of Scandinavia, 366; errors in his works, 258, 366, 895. Hitchcock, C. H., geology of the White Mountains, 282. Hoboken, New Jersey, serpentines of, 248. Hoffmann on Eozoon, 303. Homologous or progressive series in chemistry, 481, 439, 442. Hoosic Mountain, Emmons on, 250. Hopkins on the earth’s interior, 7, 16, 44, 60, 64. Hornblende, its decay, 100; association of, with pyroxene, 215; rocks of, 244, 246. See Diorites. Houzeau on ozone, 471. How on mineral waters, 121. Hudson River group, 252, 256, 258, 395, 897, 898, 402, 403; mineral waters from, 116, 124, 156. Huggins, his spectroscopic studies, 35. Humboldt on granites, 190. Huronian rocks, 18, 29, 248, 269, 272, 274; their identity with the Urs- cheifer, 269. See Green Mountain series. Hutton on metamorphism, 24; on pri- mary schists, 338. rocks of Georgia, Vermont, 402; on Taconic fossils, 392; on ‘Ameriean palzozic ideanstanine 419. Hydrocarbon gases, 8, 112, 131, 182. Hydrochloric acid, its voleanic origin, 8, 15, 44; in mineral waters, 111. 482 Hypersthene rock or hyperite, 29, 31, 279-281. See Norites. Hypozoic rocks, 245, 246. IDENTIFICATION, chemical, 450. Idocrase, hollow crystal of, 212. Igneous rocks, theory of, 1,3, 4,5. See Exotic rocks. Indigenous rocks, 33, 193. Internal heat. See Heat, internal. Interpenetration in chemistry, 428, 450. Inverted strata in the Alps, 334, 337; at Troy, New York, 407; at Quebec, 413. Iodate of calcium in sea-water, 237. Iodine in mineral waters, 148; its rela- tion to earthy sediments, 143, 226; in sea-water, 143, 226, 237; Sonstadt/ on, 237. Iolite or dichroite, 28; and aspasiolite, 815; a feldspathide, 445. Iron in mineral waters, 128, 142. Iron ores, origin of, 10, 13, 22, 29-81, 97, 227-229, 243; are evidences of life, 18, 302 ; relations of, to mineral coal, 229. See Bauxite. . Iron pyrites, origin of, 230, 232. Isomorphism, 432, 440; its relations to pseudomorphism, 315; polymeric, 291, 315, 318, 442. JACKSON, CHARLES T., on the White Mountains, 241, 275. Jade and jadeite, 445, 446. Jollyte, 338. Joly, water of, 126. Jukes, J. B., on mountains, 74; on Cambrian and Silurian, 424. KAnt on chemical union, 428, 450. Kaolin, its formation, 10, 99-101, 445. Keferstein, C., on igneous rocks and volcanoes, 16, 62, 71, 77; on Mont Blanc, 338. King and Rowney on pseudomorphism, $25. Kinnekulle, Sweden, geology of, 367. | Kolbe on chemical types, 459. INDEX. LA Bate pu Fesyre, waters of, 124. _ Labrador, geology of, 261, 393. Labradorite rocks, 29, 31, 33, 67, 278 - “ 281. See Norian rocks, Lake Elton, water of, 83. Lambertville, New Jersey, cusien rocks of, 186. Lanoraie, water of, 123. Laurent, A., on divisibility of formated 431; on isomorphism, 422; on chem- ical types, 463. Laurentian series, 29, 80, 206; evi- dences of life in, 302; eruptive rocks of, 833; vein-stones of, 208 ~ 218. Laurentian, Upper. See Norian. Laurentides, 243. Lauzon formation, 259, 401, 411, 418. LeConte, Joseph, on dynamic geology, 70- 76. Leonhard on eruptive limestones, 218. Lersch, Hydro-Chemie, 122. Lesley, J. P., on mountains, 52, 58; on an apparent discordance in lower palseozoic, 414. Letheea Suecica, 366. Leucite, 67,101, 210. Levis formation, 259, 401, 418; its fauna, 411, 412, 415. Leymerie on the origin of limestones, 82. : 4 ag Liassic fossils in veins, 203. Lignites, 176, 177, 181. Lime-salts in the modern ocean, 107, re 117,119; in ancient oceans, 2,11,41, 82, 108, 109, 117; in mineral waters, 138. Carbonate of magnesia. Lime, silicates of, 31, 151, 152. Lime-soda feldspars, ‘their pss a o gin, 97. See Feldspars, triclinic. Limestones, Laurentian, 206; of White — Mountain series, 196, 244; supposed eruptive, 218; origin of, 82,811; rela- Be tions of, to organic life, 311. Carbonate of lime. Limonite, organic matter in, 98. ‘Lingula, a phosphatic shell, 312. Lingula flags, 266, 370, 371, 374. Liquids, equivalent volume of, 436. Logan, W. E., on Upper Laurentian, — 29, 279; on the Appalachians, 257; Kopp, H., on equivalent volumes, 433, 434. on the White Mountains, 276; on Bee Carbonate of line BY Amira l J a my ars — Git Cah.... Radek wte.....22 SSD ther fq wh. Title f a Ta Ay OF BORROWER. NAME A, 2 || University of Toronto 4 | Library | — oy 4 Og DO NOT REMOVE THE CARD FROM THIS POCKET Acme Library Card Pocket Ai Under Pat. ‘Ref. 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