€ ALBERT R. MANN LIBRARY S^ New York State Colleges OF Agriculture and Home Economics .4.2: £ Cornell University Cornell University Library S 591.S86 1895 Rocks and solls:their origin, compositio 3 1924 000 886 980 B Cornell University B Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000886980 ROCKS AND SOILS THEIR ORIGIN, COMPOSITION AND CHARACTERISTICS; CHEMICAL, GEOLOGICAL and AGRICULTURAL. BY HORACE EDWARD STOCKBRIDGE, Ph.D., President of Agricultural College of North Dakota, SECOND EDITION— REVISED AND ENLARGED. FIRST THOUSAND. NEW YORK: JOHN WILEY & SONS, 53 East Tenth Street. 1895. A. 'sn^i Copyright, 1888, By John Wiley & Sons. Dbummond & Nett, ^^ _ 1 to 7 Hague Street, m. i^"fT' . New York. '^ P««' Street, New York. TO %cx>i Stochbri&ge, FARMER, TEACHER, INVESTIGATOR, THESE PAGES ARE AFFECTIONATELY INSCRIBED WITH THE DESIRE OF ACKNOWLEDGING THE ESTEEM AND REVERENCE OF SON AND PUPIL. PREFACE. Five years ago I was requested to prepare a course of in- struction in chemical geology for students in one of the American agricultural colleges. Since then it has been my privilege to deliver a series of lectures on the subject to six consecutive classes, first at the Massachusetts Agricultural Col- lege, and later here in the Imperial College of Agriculture. When I entered into an engagement with the Japanese Govern- ment, the continuation of such instruction was stipulated as a part of my duty. These facts account for the compilation of the material here gathered. The reasons for now presenting the results to a larger audience are chiefly these : As the work has progressed, my students have repeatedly requested the preservation of the lectures in a more permanent and accessible form ; while the magnitude of the field from which I have garnered, and the ex- tremely scattered condition of the literature to which access was found necessary, have convinced me of the desirability of attempting to bring the materials together in a more readily accessible form, — an attempt not previously made, I believe. Hence the book must present some features peculiar to itself, and may, therefore, reasonably seek a favorable, or at least con- siderate, reception by those in whose interests it has been pre- pared. The nature of the work is such that I have no claim for the presentation of new material ; I have neither theories nor opin- ions of my own to force upon the public. Such personal views as are offered are only expressed where such a course was deemed essential to a clear presentation of the facts recorded. I have sought to give a lucid and concise statement of such VI PREFACE. facts as are recognized s,s facts in the light of the most recent and authoritative interpretation of the phenomena considered. With this end in view, every available source of information has been utilized. A list of works of reference for those who desire further details has been placed in the Appendix. The nature of the work, its origin and scope, preclude the possibility of individual reference to each source of information; but wherever facts recorded seem to make such authority desirable, reference is made to the originals. Further than this, I desire to make acknowledgments to all whose labors have been found of assistance, and especially to express my indebtedness to the works of Credner, Dana, Johnson, Gohren, and Mayer. My location so far from the place of publication has rendered personal supervision of proofs impossible ; but I have every confidence in the ability and fidelity of the two friends to whom this task has been confided ; and to them, Dr. Charles Wellington of the, Massachusetts Agricultural College, and Mr. Henry G. K. Heath of New York City, as well as to the pub- lishers, my thanks are due and heartily expressed. I have hoped that the book might be especially acceptable to students and farmers, and with this hope the labor has been performed. Should my professional friends, however, find it a convenient and reliable compend of the subjects treated, my gratification will be proportionally increased. H. E. Stockbridge. Sapporo, Japan, March, i888. PREFACE TO THE SECOND EDITION. More than a year has elapsed since the original edition of this work was exhausted. During this interval publishers and author have been frequently importuned for the issue of a new edition, but other duties and the delays incident upon the collecting of new material have prevented an earlier comple- tion of the work. The author would have preferred to somewhat change the scope of the present edition by rewriting and combining Parts I and II and making them more specifically introductory to the subject-matter of Part III, that the work might be still more distinctly devoted to SOILS. For the present, however, this plan was not feasible, though the hope of its accomplish- ment is not relinquished. The changes introduced are chiefly the correcting of errors incident upon the conditions under which the publication was originally issued. A few changes of statement, necessitated by the progress of the past seven years, have been made. A new Chapter on the USE OF THE SoiL has been added to Part III. In this chapter it is believed the latest develop- ments of science as related to soils are recorded and the most recent applications of the principles involved are elaborated. Several additional tables have been included in the Appendix which it is believed will add materially to the value of the work. These tables are, in their present arrangement, new, part of them are original; but the author desires to acknowledge special indebtedness to the compilations published in the VIU PREFACE TO THE SECOND EDITION. " Handbook of Experiment Station Work " issued by the United States Department of Agriculture. He is extremely glad that the accumulation o( American data has enabled him to make this new portion of the work more distinctly Ameri- can ; it should be borne in mind, Jiowever, that the original edition was not written in America nor entirely for Americans. In its present form it is not only hoped that the book will be accorded the favor granted the first edition, but that the changes and additions will increase the practical utility of the work and bring it into still more intimate and friendly rela- tions to progressive farmers. H. E. Stockbridge. New York, February, 1895. CONTENTS. Part First. ROCK HISTORY. INTRODUCTION. PAGE Rock and Soil, i Mutual relations.— Both mere variations in form of one and the same material. — Geology, the study of rocks. — Diflferent forms of rocks, stratified, unstratified. — Rock strata, dif- ferent kinds of.^ — Fault, Flexure, Denudation. — Order of ar- rangement of strata. — Historical Geology. — Chemical Geology. — Agricultural Chemical Geology. — Authentic history, dawn of. — Kant's hypothesis, world-formation, different phases of. — Fundamental formation. — Sedimentary rocks, a secondary for- mation. — Original rocks not accessible, probable composition of. — Divisions of geological time. CHAPTER I. Arch^an Time 6 First evidences of life. — Primary Gneiss, or Laurentian Formation, distribution of. — Crystallinic Slate, ox Huronian Period. — Rocks, distribution. — Agricultural and economical characteristics. CHAPTER II. Paleozoic Time lo Divisions of. — First indisputable evidences of life. — Silurian For- mation, Age of Invertebrates, divisions of. — Rocks, distribution. Agricultural and ecomical features. — Anthracite coal. — Close of the age. — Devonian Formation, Age of Fishes, life of. — Rocks. — Old red sandstone. — Distribution. — Agricultural and economical features.— Petroleum.— Iron.— Phenomena closing the age. — Carboniferous Age, coal-formation. — Sub-carboniferous. — Silu- rian scorpions. — Rocks, distribution. — Depth of coal. — Coal-mea- X CONTENTS. PACE sures. — Millstone grit. — Industrial accompaniments of the coal. — Mineral deposits. — Origin and process of coal-formation. — Agricultural features. — Close of the age. — Permian Formation, origin of name. — Rocks. — New red sandstone. — Zechstein. — Distribution. — Characteristic phenomena, valley formation. — Agricultural and economical features. — ^^Rock salt. — Close of the age. CHAPTER III. Mesozoic Time, Age of Reptiles 27 Divisions. — Mediaeval time of geologic history. — Triassic Forma- tion. — Rocks, "bonebed." — Eruptive phenomena. — Fossil foot- prints. — Similarity between birds and reptiles. — Agricultural and economical features. — Climate and life. — -Jurassic Formation, life of. — Rocks. — Climate, distribution. — Agricultural and eco- nomical features. — Eruptive phenomena, closing period. — Creta- ceous Formation, or chalk-formation, life. — Distribution. — Divi- sions. — Agricultural and economical features. — Chalk, origin of. — Flint. — Climate, consequent changes in life. CHAPTER IV. Cenozoic Time 37 Recent Period, divisions. — Tertiary Formation. — Characteristics. — Survival of the fittest. — Life. — Subdivisions.^Rocks, distribu- tion. — Closing phenomena of the age. — Agricultural and eco- nomical features, phosphnte deposits. — Coprolites. — Quaternary Formation, Age of M n. — Divisions of. — Glacial Period, drift, characteristic phenomena. — Origin. — Iceberg theory. — Glacial theory, proved by phenomena of present occurrence. — Rocks. — Life. — Distribution. — Man. — Stone Age. — Lake dwellers. — Pro- gressive stages of man's development. — Bronze Age. — Alluvian Formation. — Recent. — Character of deposits. — Agricultural as- pects. Part Second. ROCK COMPOSITION AND DECOMPOSITION. CHAPTER I. Classification and Composition of Rocks, .... 59 Rock and Soil, one to be studied through the other. — Rock-classifi- cation. — Crystalline rocks, acidic and basic, non-crystalline rocks. — Rock-composition. CONTENTS. XI CHAPTER II. PAGE Disintegration through Internal Forces. •. . . ^o Earth-development. — Dynamical Geology. — Volcanoes, forms of. — Causes of eruption. — Results of eruption. — Rock-transformation and decomposition. — Thermal Waters, origin of. — Geysers.— Rock-decomposition. — Contraction of the Earth's Surface. — Change of level. — Elevation, depression. — Changes of former times. — Mountain-formation. — Flexibility of rock-masses. — Con- tinent-formation. — Earthquakes, kind, characteristics. — Causes. — Charleston, South Carolina. — Earthquakes and geological structures. — Earthquake observation. — Rock-metamorphism. — Pressure, heat, moisture. — Hydro-chemical process. — Pseudo- morphism. CHAPTER III. Rock Disintegration through External Forces, . . , 93 Changes of Temperature. — Action of Water, mechanical activity of water. — Deposits of running waters. — Delta-formation. — Glacier- action. — Oceans. — Chemical action of water. — Carbonic-acid wa.ters.^-Action of the Air. — Action of Organic Life. — Animals. Reduction through decomposition of plants. — Chemical action of roots. — Action of decomposing organisms. CHAPTER IV. Products of Rock Disintegration, 1x4 Weathering.— '^\vs\e. required. — Products of weathering. — Crystal- line rocks. — Non-crystalline rocks. Part Third. SOILS. CHAPTER I. Origin and Composition of Soils, 123 Rocks become soil with the addition of organic matter. — Plants as Sources of this Organic Matter. — Humus. — Conditions essential to organic decomposition. — Animals as Sources of Organic Matter. — Burrowing animals. — Earth-worms. — Secretion of acids by viorms.^— Composition of the Soil. — Atmospheric ingredi- ents. — Action of humus compounds on mineral matter. — Nitro- gen. -Ammonia. — Conversion of combined organic nitrogen xn CONTENTS. TACK into ammonia. — Nitrification. — Atmospheric nitrogen and nitrifi- cation. — Other atmospheric ingredients of soils. — Non-atmos- pheric ingredients of soils. CHAPTER II. Classification and Characteristics of the Soil, . . 152 Distinctions based on methods of formation. — Kinds of soil. — Characteristics. — Distinctions based on Physical Characteristics. — Other distinctions. — Soil-analysis. — Physico-chemical Charac- teristics of Soils. — Physical weight. — Specific gravity. — Struc- ture. — Color. — Behavior toward Water. — Imbibition. — Permea- bility. — Evaporation. — Plant-exhalation. — Absorption. — Solu- tion by water. CHAPTER III. Characteristics of Soils — {Continued) 166 Soil and heat. — Color. — Specific heat. — Moisture as affecting heat. — Radiation. — Dew. — Difference between temperature of soil and air. — Experiments on deposition of dew on soil and plant. — Causes and conditions of dew-deposition. — Conditions modify- ing soil-temperatures. — Soil and Electricity. — Soils and Gases. CHAPTER IV. The Soil as Related to the Production of Plants, . 194 Office of the soil. — Soil as Habitat of Plants.^Soi\ as feeder and storehouse of the plant. — Extraction and assimilation of plant- food. — Assimilation of atmospheric food. — Organic ingredients of vegetation. — Formation of carbohydrates. — Albuminoids. — Assimilation of soil-food. — Methods of soil-solution. — Mineral ingredients indispensable to plants. — Proper concentration of plant-food. — Absorptive power of soils. — Results of absorption. — Soil-exhaustion. — Maintenance of soil-fertility. CHAPTER V. Use of the Soil, 215 Purpose of the soil. — Preparing the Soil for the Crop. — Cultiva- tion. — Implements and methods. — Pulverization. — Fineness of division. — Aeration. — Supply of plant-food. — What and when apply. — Form of supply. — Cost of supply. — Manures. — Value of. — Physical action of. — Time and method of applica- tion. — Loss in value of manures and fertilizers. — Amelioration of the soil. — The Crop, as. affected by physical properties of soils.— Crop and moisture. — Methods of conserving moisture. — Chemical conditions influencing soil waters. — Alkali soils. — In- fluence of moisture on soil temperatures. — Effects of Cropping. — Soil renovation. — Rotation. — Inoculation. — Renovation by ■ fertilization. — Crop- producing power. Appendix, . . ^ 249 Index 275 ROCKS AND SOILS. PART I. INTRODUCTION. The solid earth on which we live and from which we draw sustenance consists of material existing in two essentially dif- ferent physical conditions as rock and as soil ; one being more usually the surface decked with verdure, teeming with animal and vegetable life, and supplying us with all the requisites of happy existence ; the other forming the unyielding foiindation on which the great superstructure rests, here and there pro- truding above the surface as cliffs of sea-shore, rocky ledges, or summits of hills and mountains. There is a constant change of condition between these two forms, all soils having been produced by the disintegration of rock, and being capable of reconversion to the former condition again ; and both forms are equally recognized as geologically forming mere variations in form of one material considered as rock, consolidation being regarded as a mere accident of cir- cumstance. Geology is pre-eminently the study of rocks, their forma- tion, transformation, and present distribution. These rocks most frequently repose in beds of more or less nearly parallel layers known as strata, the rocks thus situated having been deposited from material held suspended in water, and being known as stratified rock. The position of strata, though originally horizontal, may now be any degree of variation from this condition through the 2 ROCKS AND SOILS. contortions of nature to which the phable strata have been subjected. The thickness of an individual layer or stratum may vary from a few inches to thousands of feet ; and the total thick- ness of all known strata would be not more than twenty miles. Below these deposited rocks exist unstratified crystalline rocks. Surface rocks may, however, be unstratified, and exist as solid mountains of granite or other crystalline rock, wholly free from all traces of stratification. Dislocations of strata have occurred to most rock deposits, whereby the original horizontal position has been changed, a fact of the great- est importance in facilitating geolog- ical research, in- asmuch as by its means a far greater Fig. i.-Disiocations of Strata. part of the entire series of rock strata is thus made accessible than would other- wise be possible. Should these strata have become fractured and the layers displaced, the displacement is known as a fault. Should no actual fracture have occurred, a fold or flexure is the result ; and if the upper surface or apex of the fold should be worn away a series of dips becomes exposed, the result being known as denudation. It frequently happens that a series of strata become flexed, and that on top of the folds formed new strata of more recent origin may be deposited, producing the phenomenon of uncori- formability of strata. The order of arrangement of strata is of the utmost impor- tance, as it offers the only key with which to decipher these records of earth-history, since the strata were not laid down at one time, but form distinct leaves, each leaf recording the geo- logical events of but a brief span of time. The chronological arrangement of these leaves is, therefore, the only means by which a logical presentation of all the facts of a given era or formation, and ultimately of all formations or eras, may be hoped for. ^j . -r;: tSr?;!-'^?" ^" Fig. 2.— Strata aud Joints. {To/o.cepa^ 2.) INTRODUCTION. 3 Historical Geology is devoted to the study of these records of earth-history. Chemical Geology deals with the phenomena of rock-composition and rock-decomposition. The original rock-crust of the Earth has been constantly sub- jected to disintegrating influences whose ultimate product is a geological formation, no longer solid rock, but more or legs arable soil. The reactions accompanying this transformation of rock into soil form the proper sphere of Agricultural Chemi- cal Geology. With a province extending through all the phases of geo- logic time, this, department of geological science is really a chemical history of the inanimate, inorganic world. A brief outline of this history as recorded in the rocks themselves is, therefore, essential to an understanding of the phenomena to be considered. Authentic geological history begins only with the organized existence of the world, whose rock-formations are the records of its progress ; but an earlier and prehistoric existence was necessitated — ^a period the essential conditions of which are none the less fact because incapable of ocular demonstration. Kant's Hypothesis, the so-called "-nebular theory^' most satisfactorily and logically enunciates the occurrences of this world-formation epoch in cosmic history :^The entire planetary system, of which our Earth forms to-day so infinitesimal a part, had its origin in a misty, nebtilous mass rotating from west to east, in a state of extraordinarily high temperature, about its own nucleus, our present sun. The outermost limit of this system reached far beyond the present orbit of the most dis- tant planet. Through the radiation of heat into space re- sulted a cooling of this vapory mass ; and the accompanying contraction and concentration were followed, of necessity, by an increased rapidity of rotation. So soon as the rapidity of this rotation reached and passed a certain limit, by the laws of centrifugal force there resulted the formation of equatorial rings, which, through unequal conditions and unequal cooling, became broken, each individual segment forming, in time, an independent nebulous sphere still rotating ever from west to east, the precursor of a distinct planet, in each of which, how- ever, the phenomena of ring-formation might be repeated, as 4 ROCKS AND SOILS. proved by the existence of planetary satellites and of the pres- ent rings of Saturn. The period of transition from the original nebulous mist to the resulting world-body has been divided into five phases, as follows : First, the glowing, gaseous condition represented by planetary mist. Second, the glowing, liquid condition repre- sented by the fixed stars with constant light. Third, the slag- formation, or the gradual appearance of a cool, non-luminous surface. The sun is now undergoing the transition from the second to the third phase ; and this third phase is represented by innumerable fixed stars, red in color and not constant in light; stars which gradually but temporarily disappear from view are in the transition stage between the third and fourth periods. Fourth, the phas,e characterized by the violent burst- ing of the solidified crust by the heated, glowing mass within, and the sudden appearance or exudation of the same. This phase is at present witnessed in the sudden appearance of an illuminated star where before darkness alone was visible. Fifth, the progre.ssive thickening of the original crust, on which the watery vapors begin to condense, followed by the complete cooling of the heavenly body. Our Earth has passed successively through the first four stages of cosmic growth ; and exists now in the fifth phase of world-evolution. We have traced the earth's progression, from its original chaotic, nebulous, gaseous form, till the solid earth-crust, the original condition of the geologic world, the time and condition from which and with which geological history begins, appeared. Geologically and chemically considered what was this condi- tion? What were the characteristics of this era? This origi- nal solidification, these first rocks were how formed, and of what did they consist ? Fundamental Formation. The chief geologic forma- tions of to-day are sedimentary in origin. The sea from which the first sedimentary formation was precipitated must have possessed a bottom over which it expanded and on which it rested. Precipitation necessitates a foundation or fundamental material, and whether the occurrence be the result of mechanic cal suspension or of separation from chemical solution, it must INTRODUCTION. 5 have origin in pre-existing material, or in a previous rock- formation. These axiomatic facts admit of but one conclusion, namely : that the entire geological series of sedimentary formations are secondary products of an older and non-sedimentary formation, the fundamental crust. The latter cannot^ be other than the original first product of the cooling of the molten mass of the earth-ball. It is doubtful if this primitive rock still exists anywhere in the modern world sufficiently near the surface to be accessible ; but possibly the gneiss of the archaic formation, the soft- structured but slightly-stratified lowest deposit of the archaic time, may be considered as the product of the surface cooling of the fluid mass. In which case data are at hand for the defi- nite determination of the mineralogical and chemical composi- tion of the first primeval solidification. The mass of our terrestrial sphere, with its surrounding atmosphere included, has not materially changed from the be- ginning to the present ; it is the same yesterday, to-day, and forever. Its material cannot have diminished ; though, perhaps, through the gain of attracted meteoric matter, it may have infinitesimally increased. New rock-formation occurs wholly by the transformation of previously existing rock forms by means of water and atmos- pheric influences, or through the cooling and solidification of molten rock masses. The material of every fresh sedimentary formation depends on the disturbing and rearrangement of older strata. The entire stratification from the most ancient complex to the precipitation occurring in the waters of to-day, has derived its material from the same chief source: the destruction, expansion, and re-formation of the original earth- crust. This latter must, therefore, have contained, and con- sisted of, the same materials from which the more recent, or sedimentary, deposits are formed. The predominating constituent of all sedimentary rocks is silicic acid (SiO^). The occurrence is sometimes in the form of quartz, and then as quartzite, sandstone or sand ; sometimes in combination with bases forming silicates, the most common of all, or more so than all other mineral- forms combined. 6 ROCKS AND SOILS. Both silicates and bases are derived chiefly from the original crust ; and the predominance of the siHcates is due simply to the fact that the affinity of these bases is such that they could not exist in a molten condition in the presence of the acid without combining with the same. It therefore follows that the original rock-crust of the earth must have consisted chiefly of silicates of the more common inorganic or mineral bases. More definitely than this, the chemical composition of a for- mation itself beyond examination, and necessarily judged simply from its products, cannot be determined. Geological like political history is divided into distinct ages, eras, or epochs, each characterized by distinctive features which render it independent and recognizable. Four grand divisions of earth-history are recognized, the chronologic position and geological features of which must be borne in mind. These formation-groups, beginning with the first or most ancient, are as follows : I. ARCHAEAN TIME. II. PALEOZOIC TIME. III. MESOZOIC TIME. IV, CENOZOIC TIME. CHAPTER I. ARCH^AN TIME. This first division of geological history begins with an age preceding the existence of either animal or vegetable life on the Earth. The period was universal in extent, the rocks of this formation being the only onesof so extensive distribution ; and yet, only the more recent deposits of Archaean origin still exist exposed to view, and none of these present indisputable evidences of organic existence. The question of exactly when and where in the Earth's his- tory the first forms of life made their appearance has long of- fered a field for assiduous investigation and discussion. The ARCH^AN TIME. 7 facts of modern biology seem to demonstrate that vegetable and even animal existence became possible when the tempera- ture of the waters condensed on the Earth's cooled rock-crust reached 90° C, yet estimations made, indicate that the tem- perature of the Earth's surface at the close of the Archaean time was not above 38° C. Though the remains of Archaean plants are themselves want- ing, the best of presumptive proof is at hand to establish the fact of vegetable existence during this period. Graphite is a characteristic and widely distributed occurrence among the rock-formations of this time ; and graphite is one of the three allotropic forms of elemental carbon found in nature, and is of undoubted organic origin.* Mineral coal of purely vegetable origin is known to have been transformed into graphite, and in New Brunswick the original coal-producing plants are to-day preserved in the form of graphite. The amount of this form of organic carbon existing in Archaean rocks is often 25^ of the strata, and even traces of anthracite coal are claimed to have been discovered in certain Archaean layers of Norway. These facts seem to demonstrate that the close of the Ar- chaean time was rife with the very lowest forms of plant-life, cryptogams of the marine algae and lichen types. These vegetable forms doubtless preceded the arrival of the first animals, their existence being possible in waters of a higher temperature and earlier date. And the lowest animal organisms are so constituted as to feed on vegetable forms which must thus precede them. The first members of the ani- mal kingdom called into existence were doubtless the lowest of Protozoans. It is even claimed that the remains of Rhizopods exist in the calcareous strata of Canada and Bohemia.f The close of the Archaean time probably found a world whose warm brackish waters were the habitat of hordes of Protozoan life finding sustenance in the abundance of algae, making it their home. I * There is no impossibility in an inorganic origin for graphite as well as for the diamond; but no evidence of such an origin is deducible. f This conclusion is, however, based on analogfy and not on the evidence of act- ual organic remains. 8 ROCKS AND SOILS. Arch^an Rocks are classed in two general groups, known as the — I. PRIMARY GNEISS FORMATION. II. CRYSTALLINIC SLATE FORMATION. I. The Primary Gneiss Formation, or Laurentian Period of America, consists almost exclusively of metamorphic or crys- tallinic rocks, the oldest sedimentary deposits to which geolo- gists have access. They existed originally in the fundamental crust, from which they were dissolved by the action of waters impregnated with silicic acid, and, aided by heat, from the solu- tion or mechanical suspension thus formed deposits of gravel; sand and mud were made, from which the crystalline rocks were evolved by time's transmutation. The rocks thus formed embrace granite, mica-schist, gneiss, crystallinic limestone, quartzite, conglomerate, feldspar and apatite, besides many rocks of the hornblende series, as syenite and hornblende-gneiss. The Distribution of these rocks is universal ; but since only a very small portion of the Archaean world existed in an unsubmerged condition, the accessible Laurentian deposits are confined to a comparatively limited area. In America, the formation is limited practically to the Atlantic slope of the British possessions, though isolated localities of Laurentian rocks occur in, perhaps, all the New England States, in New York in the Adirondack region, along the Appalachian and Rocky mountain systems, and on the borders of Lake Superior. In Europe, the distribution is chiefly in Scandinavia, Scotland, Bavaria and Bohemia. In Asia, the formation is confined to the continent, and there chiefly north of the Stanovoi Moun- tains. II. Crystallinic Slate Formation, or Huronian Period of America. The rocks of this formation are deposited directly on those of the earlier Archaean period. Like their immediate predecessors, they are metamorphic in character, and of sedi- mentary origin. The formation is wholly devoid of organic remains ; and the definite boundaries of its occurrence are not accurately deter- mined. ARCHMAN TIME. 9 The Rocks of this period are chiefly of a slaty character, in conjunction with which occur conglomerate, quartzite, amphi- "bole, jasper, limestone and dioryte, the last-named usually ex- isting in the form of dikes sometimes supposed to be eruptive injections. The Distribution of Huronian rocks is less extensive than that of the preceding Archaean form. They were first studied on the northern borders of Lake Huron; but are now recog- nized on the shores of Lake Superior, in Brazil, Venezuela, northern Africa, Spain, the Swiss Alps, Tyrol, Bohemia, Scan- dinavia and Scotland.* Agricultural and Economical Characteristics of the Archaean Formation. Since soils invariably contain the ingre- dients of the rocks from which they were formed, their compo- sition and characteristics partake of the general nature of the rocks underlying them. As a natural sequence the soils of Archaean regions are pre- dominatingly clays, frequently cold and unworkable, or soils thin and poor in character. The most interesting agricultural feature of the formation is the abundant occurrence in certain localities of apatite, native phosphate of lime which has recently been largely utilized for the manufacture of superphosphate of lime, the chief source of nutritive phosphoric acid. Hornblende, so prevalent a rock-form of this era, invariably contains considerable quantities of iron ore ; and this element is an almost universal occurrence through the , period, and imparts the characteristic reddish color to many Archaean rocks. It most frequently exists in the form of magnetite (FCjOi), hematite (FCjO,), or in the form of titanic iron ore and franklinite, iron ores containing respectively titanium and zinc. The iron deposits of the Archaean formation are thicker and more abundant than in any succeeding age. To them belong the Iron Mountain of Missouri, the iron ores of New * The statement by Credner (£/«»«^»/* der Geologic, Leipsig, 1883, p. 405) that Huronian rocks exist in China and Japan is at variance with facts established by the most recent surveys. lO ROCKS AND SOILS. York and Michigan, and, above all, the famous Swedish iron whose quality is unequalled. Veins of lead, arsenic, cobalt, bismuth, copper, and silver ores of Archaean origin also exist, the veins of the noble metal oc- curring in Bohemia, Silesia, Norway and possibly Canada ; sulphides being the prevailing form in which these metals exist. Aside from the minerals of economical significance, others of Archaean origin are noteworthy, including calc-spar, heavy- spar, fluor-spar, quartz, orthoclase, oligoclase, mica, tourmaline, garnet and topaz. The crystallization of these minerals proves conclusively that the Archaean time was subject to the prevalence of eruptive phenomena, by the intense heat of which the transformation and subsequent condensation and crystallization were rendered possible. CHAPTER II. PALEOZOIC TIME. The geological period and formation-group directly following the Archaean is designated The Paleozoic Time, and is subdi- vided into four distinct formations or ages : I. THE SILURIAN FORMATION II. THE DEVONIAN FORMATION. III. THE CARBONIFEROUS FORMATION. IV. THE PERMIAN FORMATION. This time begins practically with the rocks containing the first undisputed remains of organic life, which are chiefly wacke, slate, sandstone, limestone and conglomerate deposits. I. Silurian Formation, or ^S^ of I^"^^ 'telrates. This formation received its name from Murchison, who first thoroughly studied the rocks of the age in that portion of PALEOZOIC TIME. II Britain formerly inhabited by the Silures. The oldest known fossils are' of Silurian origin, and the number of varieties repre- sented in these rocks, and the number of individuals present, show gradual increase through the age, at the end of which species closely allied to those of to-day, or even still existing, are not unknown. The formations of this age are of a very varied character, giving rise to a widely diversified arrangement and classification in the regions in which Silurian rocks abound. Two general subdivisions of the formation are, however, universal: The Lower Silurian and The Upper Silurian. In the lower strata of the former, usually designated as the Primordial, the earliest fossil remains exist, confined wholly to the lowest vegetable and animal marine types ; while the upper Silurian furnishes the first land plant of geological history, a ground-pine (Lyco- podium), occurring in the limestone of Cape Gasp^. Silurian Rocks, both upper and lower, are mainly sand- stones, conglomerates, shales and limestones, the first-named being in the upper strata often of an argillaceous character. The change here occurring in the character of the rock-forma- tion, that is, in the composition and structure, marks an era in the petrographic nature of the earth's surface, the varieties of rock now appearing in predominating force continuing to be the most frequent formations during all the succeeding ages of geological history or earth-progression, and are the most com- mon deposits of the present era. The sand-beds, fundamental formation of the sandstone, the mud-beds, original form of shales and argillaceous sandstones, and limestone production have been constantly in progress, and are still to-day continuing the process of rock evolution or formation. -And wherever during the world's history sandstone production has occurred, shale or limestone has been brought into existence near at hand ; for the process of rock-pulverization producing the for- mer, also results inevitably in the formation of the letter, sand- deposits and mud-deposits being but different effects produced by one and the same cause. Among the petrographic characteristics of this era are also the appearance in certain localities of quartzyte, silicic slate, 12 ROCKS AND SOILS. marl, and the important carbonate of lime and of magnesia known as dolomite, which not infrequently forms entire moun- tains, or even mountain-chains. The Distribution of Silurian Rocks is of wide extent, though the area covered by them is less than that occupied by succeeding formations. In America the chief deposits are found in Canada, in the angle between the Laurentian and Huronian regions, extend- ■ ing with a south-west trend along the Appalachian region into northern Alabama, and west from Minnesota and Wisconsin, there being important regions also in the central Mississippi basin, in the Rocky Mountains and in arctic North America. In Europe, besides the English deposits, Scandinavia, Russia, the Hartz Mountains, Bohemia and west through Spain and Portugal, important Silurian regions exist ; the Bohemian being particularly rich in both flora and fauna remains. Agricultural and Economical Features. Agricul- turally considered, the regions of Silurian origin are of an inferior nature. The soils are predominatingly clay, and iisually of an unproductive character; while the sandstone regions are not infrequently occupied by barren heaths. In cer- tain Silurian localities, however, usually where the sandstones and calcareous deposits form conjunction, fertile lands occur whose productiveness in the presence of marl may be of a high order. i The peculiarity of the Silurian age, of by far the greatest im- portance, is the prevalence among its rocks of rich mineral deposits of iron, copper, zinc, lead, and less important ores. They exist most frequently in the form of impregnations and isolated enclosures in the surrounding rock-mass, the cavities having doubtless been filled from above. The minerals usually occur in the limestone strata, and exist as sulphides. The American Silurian lead deposits existing in the upper 'Mississippi Vall6y being the chief deposits of the kind in the world. One other peculiarity of the Silurian age is the isolated oc- currence of anthracite coal-strata inserted between the layers of rock;* a noteworthy incident from the fact that coal un- * In " Etage H " of the Bohemian Silurian. PALEOZOIC TIME. I 3 doubtedly of organic origin consists of very nearly pure carbon, and yet exists here as an occurrence of an era at first nearly de- void of all life either animal or vegetable, and the organic re- mains of which are almost invariably of animal salt-water origin. Of a similar nature are the deposits of a poor quality of mineral oil existing in many Silurian regions. From the Silurian age also date a large proportion of the productive rock-salt deposits from which many of the most remarkable salt and mineral springs known take origin. The Close of the Silurian Age found a world mostly submerged beneath the waters of a shallow sea above which only here and there solid land had yet appeared ; and on which only a few of the lowest forms of vegetable growth found a habitat ; and the first land animals, scorpions, recently obtained from the Upper Silurian of Sweden, Scotland and New York.* The waters, however, teemed with life of many forms ; trilo- bites, graptolites, forameniferae, corals, crinoids, and brachio- pods, swam upon its surface, roamed through its depths, or reared their curious structures above the waves. Only at the very end of the Upper Silurian Age did the fishes make their appearance, being the first vertebrates to cross the world's stage, and thus forming a landmark, bounding an era in geological progression. During all the time embraced in the Silurian Age, our entire planet, from pole to equator, possessed a regular and equable temperature, a warm, humid, frostless climate unaffected by change of season — facts abundantly demonstrated by the uni- form distribution of remains of certain species of extinct inver- tebrates, regardless of modern cliniatic conditions, proving the universal existence, during Silurian times, of like conditions of climate and atmosphere. II. The Devonian Formation. This forms the second epoch of Paleozoic Time, and is char- acterized as the Age of Fishes. During this era, the invertebrates of the brackish sea which *Geike, Text-book of Geology (London, 1885), p. 665 ; American Journal of Science, March, 1886, p. 228. 14 HOCKS AND SOILS. covered so great a portion of the world, a fauna represented by the goniatites, snails and nautilus of to-day, though far from disappearing, lost the predominating character they possessed during the Silurian Age, and gave place to vertebrates, mem- bers of the order Pisces, thus marking a long stride in the organic progression traceable through geological history. Here, in the Devonian formation, occur the first ferns and coniferae in nu- merous force, so that the flora of the age is as much character- ized by vascular plants as is the fauna by the predominance of fishes. This age of fishes is remarkable for the abundance of organic life which distinguished it. Its waters were the habitat of myriads of invertebrate animals whose fossil remains form the chief mass, or components, of many rocks traceable to a Devon- ian origin. The name now universally adopted is derived from Devonshire, England, in which locality the formation was first systematically studied. Devonian Rocks. Petrographically considered, the rocks of the Devonian age possess much the same general character- istics manifested by their immediate predecessors of the Silu- rian age. The first rocks of Devonian origin consisted of the corniferous limestone.* Nevertheless, the predominating rock of the age was sandstone, which in frequency of occurrence so exceeds all other formations that the era is still often designated in England as the Old Red Sandstone age. Other rocks of this formation, occurring more or less abun- dantly, are conglomerate, shale, slate and schist, often bitumin- ous in character, yielding even 20 % of combustible material. The limestone of the Devonian period existed invariably in the form of the carbonate^ and was not infrequently of organic origin, large ardas of rock-formations of this age consisting chiefly of the petrified remains of the lower organisms of the Devonian era. The most interesting of these deposits being where the formation consists of the carbonate of lime in the form of vast fossilized coral-reefs. These calcium carbonates * So named from the presence of homstone, a variety of flint, the Latin for " horn" being cornu. PALEOZOIC TIME. 15 are not infrequently accompanied by carbonates of iron, so that many profitable iron mines are located in Devonian regions, where the ore occurs in combination with carbonates, the result of organic petrifaction. The formation is generally characterized as consisting of three distinct deposits, the lower, middle and upper Devonian ; and local variations in each of these subdivisions abound, par- ticularly in America, where local designations are very numer- ous, derived chiefly from the series as named in the State of New York. The Distribution of the Devonian Rocks is wide-spread, there being no continent without them. The American region is confined chiefly to New York, Pennsylvania, Michigan, Ohio, Indiana, West Virginia, Kentucky, Tennessee, Georgia and Alabama; and the portion of Canada lying between Lake Huron and Lake Erie, also in Nova Scotia and New Brunswick. In Great Britain the chief deposits are found in Cornwall, Devonshire, Herefordshire and Ayrshire. On the continent of Europe the most noteworthy localities are in Westphalia, the Prussian Rhine Provinces where the Coblenz strata are especially well defined, in the Hartz Moun- tains, Poland, Russia and Scandinavia, in all of which regions the rocks are rich in petrifactions of both flora and fauna. ?'i Asia, Devonian rocks are distributed over a considerable part of the northern and eastern portion of the continent. In Japan, the oldest discovered rocks are Devonian in character ; the first land of the Archipelago was evidently elevated above the sea during the Devonian age, forming many small islands connected into larger land-areas by continued elevation during subsequent ages. Agriculturally and Economically considered, the Devonian age presents more interesting features than are dis- played by any preceding geological formation. Though the Devonian rocks occasionally become converted into soils too sandy to be productive, they more frequently form the most fertile soils of the regions in which they eicist ; many localities of Devonian origin being famous for their productiveness and agricultural value, as demonstrated in the Rhine Valley, in 1 6 KOCKS AND SOILS. Herefordshire, in the Genesee Valley with its proverbial wheat- lands ; the oak-openings of Ohio and the heavy pine-lands of Michigan 'being largely confined to soils of Devonian origin. The industrial resources of this age are also of unparalleled importance. The shales are of unequalled quality for flag- stones, while the limestones yield, in certain localities, large quantities of mineral oil, and not infrequently natural gas, which is utilized for illuminating, domestic and smelting pur- poses. The great petroleum-producing regions of the world all be- long to the Devonian formation. That this mineral oil is itself of Devonian origin is by no means proved. Indeed, it seems more probable that the oil, being organic in character, and a product of organic existence, chiefly vegetable, origi- nated in an era more prolific in vegetation, namely, in the suc- ceeding carboniferous age ; and that it simply found receptacle, and became reservoired in the caves and caverns of the older and lower sandstone formation of the Devonian age. This supposition seems further justified by the fact that mineral coal, which is also organic in nature, occurs but very seldom during this epoch, while bituminous coal, more nearly yet allied to the oil in character, composition, and conditions of formation, never occurs as a product of the Devonian age. The iron ore, a chief economical product of this age, is not infrequently the magnetic iron, but it most usually occurs as a carbonate in conjunction with limestone, and, like limestone, abounds in animal petrifactions. The Devonian red-iron-ore (Fe^O,) is very frequently of a phosphoritic nature, and the rock in which the ore occurs is not seldom impregnated with deposits of phosphorite, utilized as a fertilizing material, and is a not unimportant addition to the sources of agricultural phos- phoric acid. Other mineral deposits of an eruptive nature, but existing as products of this age, are the deposits of zinc, lead, copper, sulphur and arsenic which usually occur as sulphides, permeat- ing the Devonian limestone strata. Another metal of exceeding value is confined exclusively to rocks of this era. The great tin-yielding mines of Cornwall PALEOZOIC TfME. I J belong to this age, and have supplied the world with most of this indispensable metal ever since the adventurous Phoenicians, unaided by chart or compass, sought the shores of Britain for supplies of this essential ingredient of the implepients of the Bronze Age in human history.* The world which, during the Silurian age, had consisted of little but a surface of brackish water, with here and there solid rock-formations breaking the surface, began, during the Devon- ian age, to assume more the character of dry land, which now appeared with more definite form and complex contour, yet was, in all probability, wholly unoccupied by animals. Toward the close of the age, the land flora became abun- dant, and reached a stage of development characterized by the existence of palms and gigantic ferns, with which indications of a tropical temperature the Devonian soil, though devoid of all animal life, was decked. The sea, above which this land appeared, passed, as the age advanced toward completion, through a gradual change in the character of its inhabitants. The few straggling fishes appearing in the uppermost Silurian rocks increased to become the distinguishing feature of the age; and, though innumerable brachiopods, cephalopods, cri- noids and corals existed throughout the formation, vertebrates, that is, fish of the ganoid type, are the distinctive fauna of the Devonian formation. III. The Carboniferous Age, or Period of Coal Formation. This formation embraces an era directly succeeding the De- vonian, and forms chronologically the longest period of Paleo- zoic time, and is, perhaps, the most interesting and important era of Paleozoic history. Both interest and importance centre in the peculiar and characteristic product of the Carboniferous age, an epoch the remains of which shed so much light on the geologic history * Rodwell, " Birth of Chemistry," p. 39. 1 8 ROCKS AND SOILS. of the world, and to-day play so great a rdle in the political ■and economical history of our time. The formation embraces a time remarkable for the preva- lence of gigantic ferns, palms, lepidodendrous and sigillarian vegetation, in profuseness and luxuriance never again occur- ring. Accompanying this flora was a fauna characterized by the appearance of the first land-animals, amphibians, the only air-breathing creatures existing in the midst of myriads of coral and crinoid life.* The Carboniferous age becomes, there- fore, the era of vascular cryptogams as well as the age of am- phibians ; and marks the advent of air-breathing animals. While the vast deposits of mineral coal distinguishing the age owe their origin to the conditions of which they form a graphic record. The Carboniferous age proper was preceded by a marine period, termed the SUB-CARBONIFEROUS AGE, during which much of the region now occupied by the continents of Europe and America was submerged by a shallow, temperate, brackish sea, from which limestone strata and occasional sand-breds were deposited. It was also during this time that the fragmental rocks forming the shales, conglomerates and sandstones of the Appalachian region, a deposit several times deeper than the limestone, were laid down. The Sub-carboniferous limestones are composed principally of organic remains, chief among them being the formation consisting so largely of crinoids, from which fact the term cri- noidal limestone has been applied to the entire Sub-carbonifer- ous limestone deposit, which like all calcareous rocks of organic origin exists as a carbonate. The Distribution of Sub-carboniferous Rocks seems to have been very general over all continents possessing de- posits of the succeeding Carboniferous formation ; and the era was one universally characterized chiefly as a time of limestone deposit, which product of the age forms the famous " moun- * Unless the Silurian scorpions prove to have been air-breathers, a question as yet unsettled, as there seems to exist a difference of opinion as to the habits of the few individuals recovered. PALEOZOIC TIME. I9 tain-limestone" regions of Kentucky, Tennessee, and other American localities. The States of Michigan, Illinois, Ohio, Iowa, Missouri, Arkansas, Mississippi, Alabama, Virginia and Pennsylvania, all possess extensive areas of this formation ; while in Europe, England, Wales, Ireland, Belgium and Rus- sia furnish the chief localities of this pre-coal-formation era. The true Carboniferous Age, or period of coal-formation, directly succeeded the submerged or the Sub-carboniferous; and its distinctive product exists in a series of coal-beds, or •coal-measures. The Rocks of the Age are chiefly shales, sandstones, limestones, and conglomerates. The limestone stratum is usu- ally an intervening rock occurring between productive coal- measures ; while the conglomerate most frequently exists at the base of a coal-vein, its foundation, as it were ; and is known technically as the millstone-grit. These coal-measures are distributed with considerable regu- larity and evenness over nearly the entire geographical world ; and prove the age of which they were the product to have been of universal extent. They have filled the office of pur- veyor of fuel and light to the world of succeeding ages, from frozen Spitzbergen on the north to New Zealand on the south ; and, encircling the globe from meridian to meridian, are suffi- cient to resist man's depletion for long ages of industrial activ- ity still to come. Some idea of the extent of the world's coal-supply may be gathered from the fact that the explored area of coal land of this period within the United States alone is 190,000 square miles; and on the North' American continent 208,000 square miles. The thickness of the Carboniferous rocks, that is, the entire depth of this formation is exceedingly variable, being in cer- tain localities scarcely more than 100 feet, while in Nova Scotia a formation more than 14,000 feet thick has been traced. The maximum depth of the formation in Pennsylvania is about 9000 feet, though the coal-measure rocks themselves are not defined below 4000 feet from the uppermost stratum. The beginning of the coal-formation era was marked by a 20 ROCKS AND SOILS. great change in the petrographical character of the world. The submarine formations, the sandstones, shales and lime- stones of the Sub-carboniferous age, became hidden by deposits of sand or of gravel, which, in time, hardened into the gritty rocks forming the millstone-grit, the underlying bed on which the coal-measures rest. Though rocks of similar character occur later through the coal strata, they are of more recent origin, and of less exten- sive occurrence, than those which mark the advent of the coal- formation era. For this reason the rocks of the Carboniferous age may be classed in two distinct divisions, each characteristic of an epoch in the history of the formation, the Millstone-grit and the Coal-measure. These two terms signify simply the two divisions of one and the same geological age, the characteristic production of which, the mineral coal, occurs as a phenomenon of only one era or formation of the age. The millstone-grit and the coal-measure are, as it were, two parallel formations, both belonging to one age ; chronologically identical, but petrographically unlike. In other words, the rocks of the Carboniferous age containing mineral coal are of the coal-measure division, while the rocks of the same era which are destitute of productive coal-beds are assigned to the division of millstone-grit. Aside from the rocks and coal of the Carboniferous age, one other occurrence is of importance: the frequent presence of iron ore in combination with the coal-deposits. Indeed, the Carboniferous rocks are very frequently impregnated with iron, always in the form of a carbonate, though often in quantities too small for economical working. Another accompaniment of the productive coal-layers is the bed of clay on which they frequently repose.* The iron is not infrequently mixed with silica, one of the ingredients of the clay, thus forming what is known as clay-iron-stone; though the * This prevalence of coal, iron, limestone, clay and sand as products of one formation is of inestimable industrial importance: the iron to be smelted, lime- stone for its reduction, the coal for fuel, the sand and clay for building the furnace^ The iron region of Pennsylvania is thus favorably situated. Fig. 4. — Carbonized Tree-trunks, imbedded in coal. (After Credner.) Fig. 5,— Carboniferous Tree-trunk from English coal-beds. (After Mantel!.) {To /ace page 21.) PALEOZOIC TIME. 21 pure carbonate is the mineral siderite, and in this mineral ex- ist the most perfect renriains of the organic life of the Carbon- iferous age. The rock-formation of this era is exceedingly irregular in character and composition ; each and every rock ever forming a part of the petrographical arrangement of the era ; at times appearing in combination with every other rock of the age, and under every conceivable modification to be wrought with the given number of factors ; the presence of rock-salt, gypsuin and dolomite not infrequently lending complexity to the form- ation. Mineral Deposits other than the coal and iron are char- acteristic of the age. Gypsum, rock-salt, and dolomite, though existing and increasing the rock-forms of the formation, are, in importance and abundance, surpassed by several minerals of distinctly eruptive origin ; diabase and quartz porphyry being most frequervtly the imbedding rock, usually occupying a posi- tion between the strata of conglomerate, slate and sandstone. Scotland is the chief locality where this eruptive action of the Carboniferous age manifested itself. But the mineral wealth stored in the Carboniferous rocks through this action is found principally in the lead, zinc and copper ores of Northumber- land, Derbyshire, Aix-la-Chapelle, and several localities in the neighborhood of the Great Lakes in the United States. A different product of this same action is the asphalt-de- posit of the Albert Mine in New Brunswick. Origin of Mineral Coal, and the Process of Formation. The fundamental facts of the history of coal-formation are, that the material consists of carbon, hydrogen, and oxygen, in average proportions. of (for anthracite) C 95^, H 2.%%, and O 2.5^; that these ingredients are of undoubted organic origin; and that the organisms whence they were derived were un- questionably vegetable in character. Were evidence other than the chemical composition of the product required, it is found imbedded in the coal itself, where whole tree-trunks, indeed forests of trees, in all the stages of transition, from perfectly preserved wood to wholly trans- formed coal, with delicate leaves and tiny rootlets intact, attest 22 ROCKS AND SOILS. the truth of the hypothesis, and bear witness to historical and scientific facts recorded by Nature herself ages before the first modern mountain was raised above the sea, or the sea itself had assumed definite form. A single glance at the era of which the coal-fields were the product must suffice for the present review of the Carbonifer- ous age. The separation of land from water had at the beginning of the epoch become more distinct ; and the elevation of land above the sea which resulted in the formation of the continents of to-day went steadily forward during the continuation of the era. The first land-inhabiting and air-breathing animals made their appearance on the earth : scorpions, centipedes, thousand- legged worms and lizard-like amphibians ; animals of so low an organism that the heavy carbonic-acid-gas-impregnated atmos- phere of the time sufficed for the aerification of their sluggish blood. And on the earth thus inhabited forests of gigantic, palm-like, morass-thriving trees flourished in a climate poison- ous, warm, and laden with moisture. The rank vegetation of such surroundings, composed largely of the carbon so abundant in the atmosphere in which it grew, completed its growth, and fell into the morass from which it sprang. Here under the partial exclusion of air, by the water present, a slow and imperfect decomposition set in, and a natural char- coal was formed. Upheavals of nature followed ; deluge of water was succeeded by avalanche of sand and mud ; ages succeeded ; heat and pressure did their work; brown-coal became bitumen, the latter became anthracite ; mud and sand were transformed into rock. Convulsion succeeded convulsion ; inundation followed inun- dation ; ages came and went ; the process was repeated and continued till the vast deposits of the Carboniferous age were complete, and the age itself gave way before Time's geologic progression, and its records became a part of geologic history. Agriculturally considered, the Carboniferous age was productive of results, though incomparably less significant than PALEOZOIC TIME. 2 J the great industrial resources called into existence by it, still of an importance equalling, if not exceeding, that attained by any preceding geological era. Hydrous calcium sulphate (CaSO, -|- 2H,0) or gypsum, so universally valued as a fertilizer under the name of " land- plaster," and which when heated till its moisture is expelled becomes " plaster of Paris," so important a factor in many arts, is most frequently found as a product of the Carboniferous age. The soils of coal-formation regions are usually poor when the sandstones or shales form the surface-rocks ; but where the " mountain limestone " of the Sub-carboniferous age is at the surface, soils of remarkable properties are the result, — their grazing qualities, being unequalled. The renowned "blue-grass region " of Kentucky supplies the best possible evidence in support of the fact. Close of the Carboniferous Age. The era of coal- formation was one of great length, and of unceasing change. Intervals of submergence followed the eras of luxuriant coal- forming vegetable growth. Great forests and jungles of acrogens and gymnosperms covered the continents ; but an- giosperms had not yet appeared. Water-insects and marsh- loving articulates teemed on land, vegetation and water; but higher insects were as rare as the flowering plants on which they live. Ganoids and sharks, but no osseous fishes, swam in the waters. A few straggling reptiles foreshadowed the approach of higher vertebrate life soon to appear ; but the iirst represen- tatives of bird and mammalian life had not yet entered the geological arena. The continents were, for the most part, level expanses but slightly raised above the boundless waters. Modern contours were mostly lacking, and the few mountains simply traced the areas of Archaean and Silurian existence. The elevation of surface went gradually on ; new conditions appeared, and the Carboniferous age, with all its phenomena, was at an end ; and the arrival of new conditions ushered in a new era of geo- logic progression. 24 ROCKS AND SOILS. IV. The Permian Formation* This was the final era of Paleozoic time, and marks a tran- sition epoch, a time and formation lying between the coal- building age and the era of higher development belonging to the Mcsozoic time which followed. Permian Rocks. Petrographically considered, the rocks of this formation are, in the eastern hemisphere, much more dis- tinct from the coal-measures directly preceding them than in the western hemisphere. In Europe, two independent divisions of the formation are recognized, namely, the Rothliegendes and the Zechsteinformation ; and from this double or parallel for- mation the term Dyas is given to the German Permian. On the American continent, however, no distinction of epochs is recognizable. The lower and older strata consist mainly of sandstone, soft and crumbly and devoid^ of mineral deposits ; the New Red Sandstone of England, and the Rothliegendes of Germany. These strata are followed by marlites and magnesian limestone, the Zechsteinformation, interspersed with gypsum, copper- bearing shales and the fetid organic-impregnated limestone known as Stinkstein, or bituminous limestone. Aside from the regular rock-formations of the Permian age occur eruptive stone, mostly granitic or porphyritic in character, and occasion- ally accompanied by eruptions of sand and ashes of indisputable volcanic origin. The Distribution of Permian Rocks is in America confined to a comparatively limited area, embraced within the States of Kansas, Nebraska and New Mexico. In England the formation is of considerable extent, particu- larly in the northern portion of the country. It embraces two distinct formations, the New Red Sandstone and the magne- sian limestone. In Scandinavia and Russia the formation is also met * Dana makes the Permian a subdivision or " Period" of the Carboniferous age. But the independent formation is more frequently recognized. PALEOZOIC TIME. 25 with * ; but Germany is by far the region of chief Permian in- terest, the most typical presentation being in the Hartz Moun- tains, and in Thuringia, from the latter place stretching south- ward with outcroppings in Bohemia and the Alps. The Valley- and Basin - forming phenomena of the Permian age are especially worthy of note, and are beginning to ,attract no little attention. The limestone of this era is not infrequently gypsum, and is invariably formed from anhydrite by the absorption of water. This calcium sulphate, so readily soluble in water, becomes worn away, and caverns in the Per- mian formation are the result. These cavities frequently becorne filled with salt-water infiltrations, and, in time, the space originally occupied by the deposits of sulphate of lime become filled with solid masses of sodium chloride. This substitute product, equally soluble in water, also becomes in turn dissolved, and a second hollow exists in the rock-mass, frequently roofed by the soft sandstone of the New Red Sandstone era. This frail covering not infrequently breaks through, and an abyss yawns where solid ground existed but a moment before. These phenomena are advanced as explaining the frequent earth-cavings occurring in the vicinity of Mansfeld in Prussia, and other locahties bordering the Hartz region in north Germany. The territory thus dropping below the surrounding surface is not seldom of considerable extent ; and becomes filled v/ith drainage-water, surrounded by flat shores and moors or marshes, and even fertile meadows. The surrounding walls are usually not complete, and a natural outlet for the accumu- lating waters is thus formed ; and through the bottom-land of the basin or valley into which the cavity becomes transformed a small stream flows, the result of the valley formation, and not its cause as previously supposed ; the erosive action of so insignifi- cant a stream not being equal to the task of such extensive valley-formation as exists, and which is rationally explained only by these known phenomena of Permian origin. * The Russian Permian occupies the extensive plain between the Ural Moun- tains arid the Volga, in the ancient kingdom of Perm, from which fact the present name was given the formation by Murchison. 26 ROCK'S AND SOILS. Agricultural and Economical Resources. Rock-salt is not the only saline deposit dating from Permian times, as salts of the alkalies and alkaline earths are of frequent occur- rence among the rock-stratifications of this era. The famous salt region of Stassfurt, remarkable as the only- known productive deposits of salts of potassium, and to-day the source of most of the potassium compounds of commerce, arts and agriculture, and producing not only sodium chloride and two salts of potassium, but salts of magnesium as well, be- sides supplying more bromine than all other sources of this element combined, is an important feature of the Permian formation. Several metals are also of frequent occurrence in workable quantities in the Permian formation ; among them being some which seldom occur as products of other ages. Notable among these being cobalt, nickel and baryta ; besides which the era was productive of rich deposits of several forms of copper, of lead and of rock crystal. The soils of magnesian limestone origin are most generally of indifferent agricultural value, shallow and unproductive. On the other hand, Permian soils formed from the New Red Sandstone division are invariably of the first quality, fertile, easily workable and productive. The End of the Permian Formation marks the close of a period during which the Earth passed through a remarkable stage of development. Beginning with a submerged epoch, it was characterized by the gradual evolution of continents till the solid land had assumed a form not unlike that which it bears to-day. The progress of organic hfe kept pace with the advance in conti- nental growth, till endogens were supplanted by exogens, and the first lizard-like inhabitants of the solid land began to be displaced by higher vertebrate animals ; the poisonous carbonic- acid-laden atmosphere of the Carboniferous age was succeeded by an atmosphere capable of blood-oxidation, aad the Reptilian Age or Mesozoic Time ; with the advent of which the world entered upon a new era, an epoch of more highly organized ex- istence. MESOZOIC TIME. 27 CHAPTER III. MESOZOIC TIME, or Age of Reptiles. This third grand division of geologic time is divided into three distinct periods: I. THE TRIAS FORMATION. II. THE JURA FORMATION. III. THE CRETACEOUS FORMATION. The firgt of these is, in Europe, further subdivided' into the Buntersandstein, Muschelkalk and Keeper; but, on the American continent, there is hardly an imaginary distinction between the Trias and the Jura formations. The MESOZOIC Time may be properly termed the mediaeval time of the Earth's history, an epoch characterized by the culmination and decline of two great types in the animal world, the Molluscan and the Reptilian ; an age noticeable for the existence of a flora and fauna more nearly allied to the organic life of to-day, and distinguished by the appearance of the first mammals, the first birds, the first modern or osseous fishes, the first true palms, and a vegetation consisting chiefly of dicotyledonous plants. I. The Triassic Formation. This formation, directly succeeding the Permian, derives its name from its triple division in Germany. It marks a most important epoch in organic progress as the period in which the remains of the first mammalian existence occur ; and its rock- formations are among the richest of fossil-yielding deposits. Rocks. In the rock-formation of this period there is great similarity between the American and the European, inasmuch as both continents present a red sandstone as the chief petro- graphic product of the era ;i but with the local complications of 28 ROCKS AND SOILS. the period pertaining to the continent of Europe we cannot deal. The New Red Sandstone formation of America demands more careful consideration ; and next to this, the most import- ant and frequent rock occurrence of the epoch is an impure limestone. There are three separate Triassic regions defined on the North American continent : the Atlantic-border region, be- tween the Appalachian range and the coast ; the Western In- terior region, including most of the Rocky Mountains; and the Pacific-border region, extending westward to the Pacific. To this era belong the sandstones of the Connecticut Valley, the deposits in New Jersey and south through the Carolinas, and the Palisades of the Hudson. The sandstone of the period passes through all gradations, from the fine-grained " freestone," undoubtedly a deposit from calm, shallow water, to the coarse " pudding-stone" conglomer- ate, the latter often occurring far-removed from its native bed, showing evidence of long transportation, and the exertion of mighty force for its accomplishment. Both sandstone and con- glomerate are usually of granitic or gneiss origin ; and fre- quently occur in very irregular stratification, proving the pres- ence of strong water currents during the time of deposition. A peculiar feature of the Triassic rock-formation consists in the singular ripple or rain-drop markings on the upper surface of the strata, due, without doubt, to the extreme shallowness of the water from which the precipitation took place, and the consequent partial surface-exposure of the rock above the water-level. Another peculiar occurrence in the Triassic formation is the so-called " bone-bed " found in England and in Germany, as well as in America : a limestone formation characterized by the prevalence of innumerable fossilized bones of lower animals, es- pecially of members of the orders reptilia and amphibia. Eruptive Phenomena. The entire Triassic region of America is characterized by the remarkable outcroppings of igneous rocks. These ridges or dikes consist of trap of unmistakable vol- canic or eruptive origin, which must have been ejected in a MR so ZOIC TIME. 29 molten condition through extensive fissures made in the Earth's crust. The most remarkable feature of the occurrence is found in the fact that these eruptions seem to have been confined to the Triassic region, and occur but seldom except as accom- paniments of the Triassic formation. The Palisades of the Hudson, and Mounts Tom and Holy- oke in Massachusetts, are superior examples of this igneous formation. The eruption invariably occurred through the sandstone rock ; and not seldom the sandstone was converted by the intense heat into a hard grit, and was torn and rent by the force of the accompanying explosion. Another result of this phenomenon was the evolution of vapors, whose condensation resulted in the tourmaline, hema- tite and garnet crystals so frequently found in these trap-for- mations. Copper, iron and barium ores are also among the re- sults of this eruptive action. Among Triassic phenomena, however, is one so character- istic of the period that it may well be termed the Triassic feature. This is the frequent occurrence of FOOTPRINTS OF BIRDS AND BIRD-LIKE REPTILES in the sandstone formation of this age. These occurrences are nowhere more abundant, more characteristic, or more perfectly preserved, than in the Con- necticut Valley. It remains a still-unsettled question whether any of these footprints were actually made by true aves ; but the probabili- ties tend to prove that they all, or nearly all, owe their origin to the presence on the Earth of animals closely allied to both bird and snake, possessing, in a marked degree, characteristics of both, yet distinct from either. That such animals existed is not a hypothetical conclusion based on the well-known simi- larity between the sub-kingdoms Reptilia zndi Aves ;* nor on * The recdgnized points of similarity between birds and -reptiles are as follows: They are either oviparous or ovoviviparous; the embryo possesses the amnion and allantois; they are devoid of mammary glands; they never possess gills; the skull is joined to the vertebral column by an occipital condyle; each half of the lower jaw consists of several distinct pieces, and the jaw is not united directly to 30 ROCKS AND SOILS the evolution theory that, in the progression from the lower order to the higher, an intermediate existence must have been passed. Beyond all controversy, such creatures are known to have existed ; their fossil remains attest the fact ; and they undoubtedly belong to the epoch of Triassic formation; they were of a lower organization than the birds which succeeded them, and must have chronologically antedated the latter. They unquestionably left their footprints on the sands of their time, while true birds were but just appearing on the face of the Earth, swimming in its waters, and traversing its sands, as the Triassic era drew to a close. Agriculturally and Economically considered, this age is not one of marked features. The soils formed from Triassic sandstone are, however, usually of a fertile nature, and in many localities are of unusual productiveness; the soils of the Con- necticut, Hudson, and Rhine valleys furnishing the best evi- dence of this fact. The " bone-bed " deposits disintegrate into superior soils, and the deposits themselves have been utilized as a source of manurial phosphoric acid. The chief rock-salt deposits of Europe belong to this forma- ation, the purity of the product being a noteworthy feature. Freestone, " landscape marble," gypsum, local deposits of coal, and " pudding-stone marble " are also Valuable products of the Triassic formation. The Climate and Life of Triassic times were those of mild temperatures over the entire Earth's surface ; but the first evidences of zones of unlike climate began to appear and her- ald the change approaching. The poisonous atmosphere of the preceding era had been purified through the assimilation of carbon by the vegetation and its subsequent conversion into stores of coal. A decided step forward occurred in the organic existence of the world ; animals requiring better air and more perfect blood- the skull but to an intervening quadrate bone ; the alimentary canal terminates in a cloaca which receives the secretions and excretions from bowel, kidney, and sexual organs; the red-blood corpuscles are oval and contain a nucleus; the cavi- ties of the chest and abdomen are not separated by a diaphragm; the hemispheres of the brain are not united by the corpus callosum. MESOZOIC TIME. 3 1 oxidation make their appearance. One mammal, a marsupial, the Dromatherium sylvestre, one individual alone of which species has been recovered from its place of preservation in the Triassic rocks, marks the culmination of Triassic life. II. The Jurassic Formation. The middle member of the Mesozoic group most closely re- sembles the preceding formation in the composition of its strata ; but the absence of marine fossils being one of the most characteristic features of the Triassic rocks, so the presence of large numbers of these individuals furnishes the chief and best evidence of the Jurassic character of a formation of Mesozoic time. Indeed, the age is distinguished by the prevalence of new and more highly developed marine animals in innumera- ble varieties, and more closely allied to the representatives of the same orders with which we are to-day acquainted. Ammonites, belemnites, corals of the form of to-day, gastero- pods and mollusks in unprecedented number now appear ; while the shark-like fishes begin to be supplanted by the fish of modern times. Reptiles become less abundant, and birds be- come more abundant ; while the single Triassic mammal, semi- oviparous, is succeeded by several varieties of low-organized, but placental, mammals* Rocks. Aside from the prevalent rocks of the Triassic pe- riod, limestone, slate and clay are frequent occurrences during the Jurassic era ; and the limestone is not seldom in the form of gypsum. Jurassic strata occur in America in the Black Hills, in Colorado, and over considerable portions of the Pa- cific slope. The European Jura is subdivided into the Lias, or black Jura, the Dogger, or brown Jura, and the Malm, or white Jura. But in America no subdivision has been attempted, or can be found to exist. The Climate of the Jurassic period, as is proved by the even distribution of life over the Earth's surface, was one of equableness ; and the predominating forms of life indicate a tropical, or semi-tropical, temperature for the entire Jurassic world. 32 ROCKS AND SOILS. The existence of Jurassic fossils of undoubted marine origin, high above the present sea-level, proves that the water-level of the world was then much higher than now ; or rather, that the continents have undergone a material elevation since the day when salt-water moUusks were stranded high up among the Rocky Mountains. The Distribution of Jurassic Rocks finds chief display in Europe, where the formation bears invariably a triple char- acter. The extensive formation of England extends across the Channel, through France, Germany and the Alps, from a spur of which the name " Jura " is derived. The three subdivisions are each distinctive, and present features typical of European geology. The American region is confined almost exclusively to arctic latitudes, and to locahties in Dakota, Colorado and the Pacific coast. This latter region stretches southward into the Andes. The Agricultural and Economical characteristics of the period are of significant importance. The soils of Jurassic origin are predominatingly clays, and largely heavy and tena- cious ; but marl is of frequent occurrence, in which case the soils are capable of becoming the best of wheat-lands, and of fur- nishing most valuable pasturage. Gypsum is the only mineral product of agricultural value. / But the great deposits of gold- and silver-bearing quartz in Dakota, Colorado, Nevada, and California, the richest gold-pro- ducing regions of the world, are confined to the Jurassic forma- tion. The Eruptive Disturbances which were so noticeable a feature of the Triassic period were but mere trifles compared with the eruptive development which closed the Jurassic era. Whole mountain-ranges date from this time, and were forced above the surrounding surface by internal power which built up barriers of igneous rock in the midst of Jurassic deposits. The entire Sierra Nevada formation is of such origin ; and, like these eruptive strata, is characterized by the presence of exten- sive veins of pure quartz. The heat of the eruption converted the water present at the place of outburst into alkaline solutions of silica, which, filling ME so ZOIC TIME. 33 the crevices and lower levels, solidified and became silicon di- oxide or the quartz reefs. And in these reefs of quartz exist to-day the gold, silver and other metals gathered from the sur- rounding softer formations, and afterwards condensed and so lidified with the mass of the solution. And to this phenome- non is due the existence of these auriferous quartz veins in the midst of the surrounding Jurassic formation, and gives the pe- riod an interest and value it might otherwise fail to attract. With these convulsions oi nature, carried on with such grandeur and on a scale of as significant magnitude as of geo- logical and industrial importance, the Jurassic period came to a .close, and was followed by the final epoch of Mesozoic time. III. Cretaceous Period, or Era of Chalk-formation. This epoch closes the Reptilian age, and is signalized by the extinction and disappearance of innumerable species of mol- lusks and reptiles, and the appearance of many modern types of plants ; so that the period is distinguished by a great revo- lution in the flora of the Earth. Though the palms and coni- fers of the Jurassic period did not disappear, they were now, for the first time, accompanied by members of the great order AngiosPERMS, -which includes the maple, oak and most of our modern fruit and forest trees. The Distribution of the Formation in America is un- important from its extent, and is divided into the so-called ear- lier and later Cretaceous epochs, in neither of which, however, with a single exception located in the State of Kansas, does a true deposit of chalk occur ; though deposits assigned to this formation exist along the Atlantic coast from New Jersey to South Carolina, across the Gulf States, up the Mississippi Val- ley, over the interior portion of the continent, in the Rocky Mountains, and on the Pacific slope. The most typical, the most diversified, and the most thor- oughly studied Cretaceous formation is in England, where the chalk deposits and Cretaceous rocks cover a large portion of the territory; and where the chalk cliffs glistening in the sun, 3 , 34 SOCKS AND SOILS. contrasted against the blue of the sky, and flanked by the green of field and wood, form a most striking, beautiful and charac- teristic feature of the landscape. The English formation is subdivided into the Lower-green- sand, Gault, Upper-greensand, Chalk-marl and Chalk; which names indicate clearly the character of the CRETACEOUS RoCKS which consist chiefly of beds of Greensand, of marlite, clay, and shell-limestone ; while many American deposits contain hornstone corresponding to the flint of England. The Cretaceous formation, petrographically considered, is ex- ceedingly irregular in composition. Its deposits pass through all gradations from fine, pure quartz sand, sandstone, conglom- erate, hard and soft limestone, marl, magnesian limestone, chalk and flint ; so that many localities classed as belonging to this period possess but the slightest possible resemblance to other deposits of the same era. It, therefore, follows that the petrographical features of the formation often fail to determine its geological position, which must depend on its paleontologi- cal characteristics for correct designation. Agricultural and Economical Interests of unusual importance characterize the Cretaceous formation ; the period not infrequently yielding mineral coal, gold, copper, iron, chro- mium ; and, most important of all, the chief quicksilver-produc- ing regions of the globe are of Cretaceous origin. The great natural deposits of cinnabar (HgS) occurring in the metamor- phic rocks of California, Mexico and Spain being of the chalk- formation era. Eruptive stones cannot be considered characteristic of the Cretaceous epoch, but are of occasional occurrence accom- panied by zinc, calc-spar and strontianite, and not infre- quently consisting mainly of basaltic rocks ; while mineral as- phalt is a characteristic accompaniment of Cretaceous eruptive action, the chief asphalt mines of France and Germany existing in districts belonging to this formation. Chalk (CaCO,) of organic origin, the characteristic prod- uct of the Cretaceous formation, is a nearly pure, unsilicious carbonate of lime, consisting almost wholly of the remains of microscopic foraminifera, aquatic by nature, and deposited MESOZOIC TIME. 35 by precipitatipn from the sea-water of the Mesozoic time. A cubic inch of chalk may contain upward of a million of these small Rhizopods. It is generally conceded that the flints so prevalent in forma- tions of Cretaceous origin are not of a metamorphic character, but are the product of the aggregation of silicious infusoria be- longing to the same era as the foraminifera, and, like them, de- posited then as they are to-day in the waters of the deep sea. The Greensand of this period owes its characteristic color to the presence of silicate of iron, and is of considerable agricul- tural value as. a fertilizer known as " marl," and is extensively excavated in New Jersey. Its agricultural value is due to the presence of silicate of potash; and of phosphate of lime of un- mistakable organic origin, as proved by the presence of bones and shells of marine animals. The soils belonging to this period are, as a rule, of excep- tional fertility, especially those in proximity to the upper Greensand, with its supplies of potash and phosphoric acid. The clay soils of this formation, though in themselves heavy, become remarkably productive when in contact with a sub- stratum of chalk, being in England noted as producing barley of rare quality^ and being chiefly devoted to the culture of this grain for malting purposes. Hops and wheat are also remark- ably successful crops grown on this soil. No more interesting or instructive comment can be made on the agricultural properties of Cretaceous soils than the fact that " Rothamstead," the renowned experiment farm of Sir John Lawes, is situated in a Cretaceous region. The soil has now borne forty-five consecutive crops of wheat without ma- nuring, and still, at the end of this protracted drain upon its resources, produces more than twelve bushels of grain per acre, a yield almost equal to the average product of the United States. The soil which has thus, at the end of nearly half a century of constant depletion, shown itself incapable of exhaustion is typical of a large area of soils of Cretaceous origin. It, consists of a tenacious yellow clay, thickly interspersed with nodules of flint. Beneath this surface-formation, at a depth of twelve 36 ROCKS AND SOILS. feet, exists the chalk, containing abundant organic remains of a phosphatic nature, and potassium being present in appreciable quantities. As a result of this fortunate conjunction of circumstances, the gradual but constant decomposition of the mineral constitu- ents present as products of the Cretaceous formation supplies the plant with all the essentials for its growth and maturity, with the single exception of nitrogen. The addition of this one ingredient to the chalk-formation soils of " Rothamstead" would render them practically of exhaustless fertility.* The Climate of the Cretaceous period is characterized by a gradual lowering of temperature from that of the epochs pre- ceding it ; and the regular and even temperature universal on the Earth during the Paleozoic age had now, at the close of the Mesozoic time, assumed more of the zone aspect of to-day, though nowhere is there evidence of anything approaching a frigid temperature ; yet evidences of the occasional existence of floating ice are not wanting. The climatic conditions of the Cretaceous period were those of transition from the warm or temperate condition characteristic of the primeval and mediae- val Earth to the frigid era which ushered in the modern epoch of geologic history. Only a slight transformation was required for the beginning of an era of ice and frigidity, and this change occurred here at the close of the Cretaceous era, when disturb- ances took place which revolutionized the geographical aspect of the world, and swept it free of the organic life which then characterized it. The European continent forced itself above the waters sur- rounding the archipelego of which the Europe of Mesozoic time consisted. The mighty range of the Rocky Mountains reared its peaks thousands of feet above the highest pre-Creta- ceous level. The change of elevation brought frigid, ice- bearing currents down with resistless force upon the temperate lands of the chalk-formation era, sweeping from existence with their frigid, blighting breath almost every vestige of the lower semi-tropical fauna and flora of the Earth. * The relations between nitrogen and mineral matter as food for plants are con- sidered in Part Third. CE NO ZOIC TIME. 37 The characteristic features of Mesozoic time vanished ; new conditions prevailed ; and a new era, the Cenozoic Time, was at hand. CHAPTER IV. CENOZOIC TIME. The primeval stage of organic existence gave way to an era of greater advancement which was, in turn, supplanted by a mediaeval epoch. The lapse of ages continued, progression the watchword, till both these phases were relegated to the past, leaving only their petrified history behind ; and the modern era of geologic evolution, the recent period or Cenozoic time, appeared. Invertebrates, fishes, reptiles, predominated in turn, and characterized each an epoch in the series we are tracing ; and now all retreat to the insignificant position they must occupy in an age marked by the numerical superiority of the order to which the genus homo is assigned. Mammals now predomi- nate, and the arrival of man, for whose reception the world has passed through all this epoch after epoch, and age on age, of preparation, is near at hand. The Cenozoic Time, characterized by the predominance of mammalian animals, is divided into two periods, the distinction between which being marked by the evidences of man's pres- ence on the Earth. These epochs are : I. THE TERTIARY FORMATION, or Age of Mammals. II. THE QUATERNARY FORMATION, or Age of Man. I. The Tertiary Formation. This age was characterized as the period during which the Earth's surface began to assume its present geographical form and appearance, and became the dwelling-place of a fauna and 3^ A'OCKS AND SOILS. flora more closely resembling its modern inhabitants, a con- siderable number of species of which have not become extinct, but live to-day, representatives of races predominating then. The chief characteristics of the Tertiary world, by which it becomes more closely allied to the world of to-day, are as fol- lows : First, a continual increase in distinctness of demarkation between solid land and sea. Gradual elevation and depression of the surface, always, however, with a final gain of elevation on the part of the land, and a constant withdrawal of the waters. A condensation of the sea ; the drying up of marshes ; the draining of lakes whereby rivers flowed where inland seas once had been, and valleys succeeded great basins filled with the fresh or brackish waters of ages of accumulation, — these were distinctive Tertiary phenomena resulting ever in land forma- tion and water-repression within boundaries closely conforming to those with which we are still familiar. Second, the formation of modern mountain-chains. The chief of the lofty mountains of the world date from the Ter- tiary age ; the highest peaks of the Pyrenees and Alps, of the Himalayas, Andes and Rocky Mountains, being of this recent origin. The elevation of such lofty summits inevitably changed the water-sheds and river-courses of the previous era ; and ex- erted no inconsiderable influence on the fauna and flora of the Earth, through the resulting meteorological and climatic modi- fications. Third, the formation of climatic zones. During the earlier periods of the history of our planet, it possessed, from pole to equator, an even temperature, the record of which endures to- " day, and informs us that Silurian corals and the luxuriant vegetation of the Carboniferous world, alike, flourished with equal perfection of growth under equatorial skies and in the midst of polar seas ; for the interior heat of the Earth was still so manifest at the surface, that the uneven distribution of the sun's rays was of little influence on terrestrial temperature. Gradually, but constantly, as the surface-crust became thicker, the external temperature became lower, till now at the begin- ning of the Tertiary age the surface-manifestation of internal heat had nearly ceased, and modern climatic distinctions were CENOZOIC TIME. 39 the result. As a natural and inevitable consequence, the fauna and flora which had before been so evenly and regularly dis- tributed over the Earth became restricted to habitats whose confines they could not pass with impunity; and whole races of animals and plants became exterminated through the action of new climatic influences. The survival of the fittest ensued ; and the existence of those species unprepared for the new sur- roundings in which they were placed became a part of geo- logical history. Fourth, the total extinction of many animal and vegetable forms, and the restricted existence of others. The life so characteristic of earlier ages, of Carboniferous, Cretaceous and later formations, but more particularly the giant Reptilia of the Mespzoic epoch, passed away with scarcely a living repre- sentative to preserve the memory of their existence; and a new order, a higher development, succeeded them ; a modern era began. Fifth, the extraordinary development of animal and vegetable types whose first appearance on the Earth is characteristic of Mesozoic time. The Angiosperms, which first came to notice as remains in the upper chalk-formation, become now the pre- vailing type of forest tree ; mammals, the first feeble and im- perfect representatives of which class date from the upper Triassic period, now first assume the typical mammalian form of monadelphian, placental animals whose young are brought into the world in, a more fully matured condition. The oldest typical mammal dating from the Tertiary age was the so-called Anoplotkerium, which possessed several charac- teristics of the ruminant family, and was followed by true ruminants and carnivora, till the fauna lacked only the genus homo to present all the species of the world of to-day. Sixth. The gradual appearance of innumerable varieties of moUusks identical with the marine fauna of to-day. So near did the youngest Tertiary or most recent period of the age ap- proach the present, that from 60 to 90 per cent of these mol- luscan varieties imbedded in Pliocene formations are identical with the present or living members of the same family. The features, then, by which the Tertiary age may be dis- 40 liOCKS AND SOILS. tinguished are chiefly these: deciduous trees, mammals, bi^ valves and gasteropods become the predominating representa- tives of the organic world; with a gradual separation or di- vision of the Earth into climatic zones, each with its distinctive fauna and flora, and depending for its characteristics upon its remoteness from the equator. These climatic influences ap- proach nearer and nearer those of to-day, and become compli- cated through the rearing of lofty mountain-summits with their various zones of temperature. And as the ancient con- ditions recede, and those of the modern world approach, the number of animal and vegetable forms identical with those of to-day assume ever an increasing ratio. The diversity of ter- restrial conditions and of organic life far surpasses anything that had preceded them, and marks the last stage of progres- sion before the arrival of that still existing. The Tertiary Age has been divided into three separate £pochs or eras, as follows: 1. Eocene (dawn of the r,ecent), with species nearly all ex- tinct. 2. Miocene, whose species are less than half living. 3. Pliocene, the species of which era are more than half still living. The Rocks of the Tertiary period are divided into two kinds : those of fresh-water deposition, and those precipitated from salt or brackish water, the marine deposits. So character- istically different are these two formations in their essential features, that the character of the rocks serves as an accurate register of the extent of salt- as of fresh-water occurrence during the Tertiary formation. Beginning with the first or oldest deposits, we find beds of sand or clay, followed by compact sandstone, beds of loose shells and earth, shell-rocks and calcareous sandstones. These rocks are of a firm texture, suitable for building purposes.* Then follow marls and clays, with carbonate of lime from pul- verized shells, compact solid limestones, greensand identical * St. Augustine, Fla. , the oldest city of European building in America, consists chiefly of edifices built of this stone. CE NO ZOIC TIME. 4 1 with that of the Cretaceous formation, and buljrstone used for millstones.* As is seen by the list, Tertiary rocks are as a formation much softer than those of any preceding era, yet the epoch produces hard slates and sandstones wholly indistinguishable in them- selves from those of earlier strata. Like the Cretaceous age, the Tertiary also contains beds, or deposits, of a silicious Infusoria, and of calcareous Rhizopods.f The Tertiary limestones are largely made up of fossilized Rhizopods, called Nummulites, existing often at great altitudes, forming many Alpine and Himalayan summits ; beds of a kin- dred nature occurring among the Coast Range in California. Distribution of the Rocks., Geographically considered, this age was one of most extensive domain ; and all the conti- nents possess examples, and no insignificant ones, of the for- mation. It was the last epoch of the Earth's history preceding the advent of man; and as such embraces much of the new land-formation bordering the oceans of the world, being to a great extent the formerly submerged surface exposed by the final receding and restriction of the waters. In America, this area includes Cape Cod, the islands off the Massachusetts coast, most of the coast south of New- Jersey, the peninsula of Florida, portions of the Mississippi Valley, where distinctive water-sheds for the Mississippi and Ohio rivers existed, the streams each emptying independently into the sea, and only becoming united at their mouths toward the close of this era. The Rocky Mountain region and the Pacific coast also- present well-defined marine beds of Tertiary origin. In Great Britain, the Tertiary deposits are chiefly Eocene, and are confined to a triangular region, embracing southeastern England, surrounding London, and extending inland nearly to Salisbury. Northern France contains beds of a similar nature. Germany, Switzerland, Italy, Greece, northern Africa, southern Asia, most of Japan, and the islands of the Indian Archipelago, possess Tertiary^ deposits. * South Carolina yielding a famous quality. \ Dana's " Manual of Geology," pp. 493 and 512. 42 ROCKS AND SOILS. The Volcanic or Eruptive Action with which the age came to a close manifested its power over the entire Earth ; and the display of the activity then begun has not yet disap- peared as a real and vital force, present and manifest. For the volcanic and earthquake actions of the present are most in- timately connected with, and in all essential characteristics most closely allied to, the phenomena of Tertiary times. Several distinct epochs of eruptive action seem to have passed over the Earth during the Tertiary age ; or rather, different por- tions of the Earth's surface were undoubtedly subjected at varying intervals to the influences of eruptive action. The chief result of this occurrence, as witnessed to-day, is evidenced by all the great piountain-chains of the Earth, which either date wholly from a Tertiary origin, or by this action were elevated thousands of feet above the highest altitudes previously attained. Long periods often elapsed between these intervals of eruption, so that the formations resulting therefrom are of varying, age ; but always of the same petrographic char- acter, the rocks being igneous in nature, and consisting princi- pally of basalt, porphyry, and other plutonic rocks. Most of the active volcanoes of our day date their periods of activity from Tertiary times, — the lava of modern Vesuvius having its exact counterpart in the formations antedating the era of man. The Agricultu^l and Economical features of this age are in many respects unique. In America, the soils are chiefly of a sandy nature, and frequently of slight agricultural capabil- ity ; but clays also are characteristic of the period, and a con- junction of the two often results in a soil of extraordinary fer- tility, — clay with a sand subsoil being a favorite and productive arable land, while the elays alone form superior pasture-lands. Above the Tertiary clays extensive heaths and marshes abound, wholly sterile, but capable, by drainage, of being converted into valuable meadows. The extensive artificial cranberry-meadows of the Cape Cod region and of New Jersey belong to this class of phenomena, and exhibit the transformation of worthless wastes into unusually valuable land. In England, areas of similar nature are well known ; while in CENOZOIC TIME. 43 Japan such tracts form extensive districts along the coast, and between the highlands of most of the islands. Deposits of phosphate of lime, of animal origin, are unique features of the Tertiary of America and England. South Caro- lina, in the so-called " Charleston basin," possesses the world's largest supply of this essential manurial material. The deposits exist in the form of hard phosphatic rocks, which are exten- sively mined and exported to all the States and to most Euro- pean countries for manufacture into superphosphates for fertil- izing purposes. The rock abounds in fossil remains, but is itself probably of a fossilized guano nature. The crag-formation of England, embracing the larger part of the English Tertiary, is also remarkable as containing vast quantities of hard flinty nodules consisting often of even 60% of calcium phosphate. The subsoils of this region formerly so abounded. in these fossils that extravagant prices were given for the right of digging and removal for use in the commercial fertihzer industry ; but the supply of these so-called coprolites has of late years become much depleted.* An interesting occurrence of the Tertiary age, and one of no little scientific and agricultural importance, is the fact that grasses, to the growth of which more than half of the arable world is devoted, date from the middle of the Eocene ; no gra- minaceous fossils existing in older formations, and the fauna of pre-mid-Eocene times having been wholly unfitted by its dentition for existing on any form of grass.f Coal and lignite abound in most Tertiary regions. The former is invariably either soft or brown coal, and is not uncom- monly of very superior quality. Deposits of this fuel are worked in Colorado and many Rocky Mountain regions, in England, Germany, India and Japan. The last-named country possesses exhaustless resources of superb Tertiary coal in several localities both of Nippon and Yesso. The lignite, sometimes confused with brown coal, possesses its original woody texture. * "Elements of Agricultural Chemistry and Geology,'' Johnston and Cam- eron (13th ed.), p. loi. t American Naturalist, June '86, p. 546. 44 ROCKS AND SOILS. and forms a fuel resembling charcoal, though more durable. Its chief deposits occur in Continental Europe ; Hesse and Bruns- wick both furnishing large supplies of this fuel. Bog iron ore (2Fe,0,+3H,0) exists frequently in Tertiary formations, and often in valuable deposits. The infusorial earth, consisting of the remains of the minut- est infusoria, and so important a factor in the scientific and political world of the present generation as an ingredient of dynamite, is an abundant product of Tertiary life. The chief deposits exist in Germany and in the State of Virginia, though occurring widely as a formation of this era. The Climate of the Tertiary Age was, at the beginning, over at least a portion of the Northern Hemisphere, one of tropical or semi-tropical nature; and this character extended to the regions of the midnight sun, fossil evidences being abun- dant that even Greenland and Spitzbergen possessed during these early times a climate of comparative mildness, being luxuriant in the verdure of the temperate zone, and the home of vast forests of deciduous trees, through which roamed the mammoth and other gigantic mammals which became extinct races by means of the same causes to which are due the death of the forests and the advent of perpetual and impenetra- ble snow. Gradually as the centuries of Tertiary time rolled away, the formation of our modern climatic zones became perfected ; the cycle of formative phases was complete ; preadamic conditions, surroundings and influences were at an end ; man's domain was ready for his occupancy, and the last epoch of geological his- tory arrived. n. The Quaternary Formation, or ^4^^ o/J/a«. The appearance of man on the Earth marks the arrival of a new geologic age ; all efforts to establish evidences of the ex- istence of prerquaternary man having failed when put to the further test of scientific inquiry.* The Quaternary period is *Lyell, "The Antiquity of Man" (London, 1S73); de Nadaillac, Z«/7-«/«Vrf hommes et temps prihistoriques (Paris, 1883). CEXOZOIC TIME. 45 divided into two epochs or formations: i. The Diluvium, or formation immediately following the Tertiary ; and 2. The Alluvium, or period of to-day, which embraces the modern deposits and formations still in process of completion, the peat- bog being a characteristic illustration of this class of phenomena. The American Quaternary is, however, classified more ex- plicitly as — I. The Glacial Period; 2. The Champlain Periob; and 3. The Recent Period, or period of Terrace forma- tion. The intermediate epoch, or Champlain period, is wholly American, and of secondary importance here ; while the Glacial is the characteristic epoch of the Quarternary age. The phenomenon of the age was the gradual moving down from polar regions, over the three northern continents, of enormous masses, fields and mountains of ice, resembling in nature enormously aggravated glaciers, resulting in the so-called Drift formation. Heretofore the phenomena of geological history had pos- sessed a southern trend or tendency ; their field of action having been mostly confined to the southern portions of the conti- nents. But now there is a radical change in the location of active geological progression. The continents which have heretofore been gradually extending themselves toward the south have reached the limit of this expansion ; and the active phenomena of the period approaching are all northern in their origin, and exert themselves most powerfully in regions never since wholly freed from the bonds of ice and snow. the glacial or drift-formation period. This was an era distinguished by the presence of enormous fields of inland ice and glaciers which covered the greater part of the North American and European continents, half of Asia, and large areas in South America ; * moving gradually but irresistibly southwards, burying all nature beneath its frigid * Confined to the higher altitudes, or to the vicinity of the Pacific coast. 46 ROCKS AND SOILS. mantle, passing unresistingly over lofty mountains, and grind- ing rocks to powder and gravel which became deposited in its path, a formation of veritable Drift material. As the term implies, this formation consists of gravel, sand, clay, and boulders existing in an unstra'tificd condition, which have evidently been transported from a distance, usually from localities of higher altitudes. So powerful and resistless was this action, that rocks hundreds of tons in weight were trans- ported many miles, and that, too, independently of grade, surface-slope, or incline. Drift may occasionally exist in a stratified condition, possess- ing the same composition as the unstratified, except that the lower stratum is usually of clay interspersed with enormous boulders which confer the name Boulder clay upon this level. The unstratified Drift is invariably wholly devoid of the remains of marine life, though vegetable material is of frequent occur- rence. The stratified formation occasionally presents marine fossils. The material of the Drift varies with the geological character of the region whence it was transported. The usual distance of transportation seldom exceeded one hundred miles ; and the course pursued was invariably from the north, or in a southerly direction. In Europe, the southern limit of this glacial action was in northern Austria ; while in America a more southern limit was attained, — portions of the States of Maryland, Vir- ginia, Kentucky and Tennessee being of unmistakable Drift origin.* The western limit of this phenomenon was near the Missis- sippi River of to-day. There were also smaller glacial regions in the Rocky Mountains and the Andes. The amount of ice depending on the amount of precipitation, the chief seat of the phenomena must have been confined to the vicinity of the great oceans. The characteristic phenomena of this 'era were of a kind clearly establishing the identity of their cause. Aside from Drift deposits, the abrasion of the surface-rocks was universal, * American Journal of Science, 1 886. 'r.7^^:..'^dH-'?W' 'S^ir:i:-s>' Kic. 6.-Glacial Scratches. (After Hitchcock.) (Tofacep